A feeder is only as compliant as its worst phase.

Low-voltage planning has long been able to treat a feeder as a balanced three-phase circuit. For most of the network’s history that was a safe assumption. High penetrations of single-phase distributed generation and single-phase load are ending it, and they do so in a way an aggregate check doesn’t catch.

Voltage compliance is assessed per phase. In Australia, the nominal is 230 V with a range of +10% / −6% (AS60038 and AS61000.300.1), and each phase at the point of supply has to sit inside that range, not the average of the three, each one independently.

Single-phase connections are where this bites. A rooftop inverter or an EV charger connects to one phase, not three. At low penetration the connections diversify across phases and across the day, and the feeder behaves close to balanced. At high penetration that diversity fails. PV exports on the phases it happens to sit on through the middle of the day; EV charging loads other phases through the evening. One phase is pushed toward the upper limit at midday while another is dragged toward the lower limit at the evening peak.

The trap is that the three-phase average can look compliant while an individual phase is in breach. A planner working from aggregate feeder loading, or from a balanced load-flow assumption, sees headroom that isn’t there.

This is not only a high-solar story. Any concentration of single-phase power-electronic load does the same thing from the other direction. EV charging, and increasingly induction cooking, draws hard on whatever phase it happens to be wired to. A network with modest rooftop PV but rising electrification will see the same per-phase divergence, driven by load rather than generation. The mechanism is the connection being single-phase, not whether it imports or exports.

The instinct is to reach for conductor augmentation. Larger conductor lowers impedance, and lower impedance does reduce the magnitude of voltage excursions. That part is real. But it reduces them symmetrically. It does nothing about the asymmetry between phases, and nothing about the time-of-day variation that drives the swing. Conductor is a fixed impedance: it cannot pull a phase down at midday and hold it up at the evening peak. To bring a single over-voltage phase back inside the limit by impedance alone, you would oversize the conductor well beyond the thermal load — paying for capacity you don’t need to address a problem conductor was never the right tool for.

Behind-the-meter batteries are sometimes offered as the answer. For a network planner they are not, because they cannot be centrally controlled, and they are also usually a single phase device, doing which does not fix feeder balance. A customer’s battery cannot be dispatched to hold a phase within limits, and it cannot be counted on for compliance.

A STATCOM put in now is not interim spend to be written off when the larger upgrade arrives.

What corrects a per-phase, time-variable problem is per-phase, dynamic control. An LV D-STATCOM regulates each phase independently and continuously: absorbing reactive power on the phase running high, supplying it on the phase running low, and rebalancing load across the three phases. It tracks the daily cycle rather than being tuned to a single condition.

There is a second consequence worth naming. Because a feeder is limited by its worst-loaded phase, unbalance leaves real capacity stranded, two phases can sit well under their limit while the third sets the constraint. Rebalancing recovers that capacity and lets a network use conductor it already owns to its actual rating. That is what defers augmentation, rather than simply delaying it.

None of this replaces augmentation, and augmentation does not replace it. They sit on the feeder as two layers doing two jobs. New conductor adds thermal capacity and lowers impedance; it does not balance phases, filter harmonics, regulate voltage through the day, or report the power-quality conditions where it sits. Those functions do not arrive with copper, and they do not stop being needed once copper is installed. The capacity an upgrade unlocks tends to fill with more of the single-phase load and generation that drove the divergence in the first place.

So a STATCOM put in now is not interim spend to be written off when the larger upgrade arrives. It is the control layer that keeps a feeder balanced and compliant before augmentation, through it, and after it. Where the constraint is genuinely thermal and the conductor cannot carry the current, augmentation is the right answer. The STATCOM stays in service, doing the work the new conductor was never going to do. The two are complementary by design.

The per-phase compliance trap is not a future problem. It is already visible on high-penetration feeders that pass an aggregate check and fail a per-phase one. Worth checking which of yours do.

Why a 40 kVAr device supports voltage on a feeder carrying far more than 40 kVA, and how much correction to expect

A common question from distribution engineers assessing a low voltage D-STATCOM is how a 40 kVAr device can support voltage on a feeder that carries far more than 40 kVA. The question almost always traces to one assumption: that the device sits in series with the feeder and must carry the full load current, the way a line voltage regulator does.

A shunt-connected D-STATCOM does not work that way. It connects in parallel, carries only its own reactive current, and supports voltage through the reactance between its connection point and the source. This note sets out the mechanism and works a representative example.

Series and shunt connection are different problems

A series voltage regulator is installed in line with the feeder. All feeder current passes through it, so it must be rated for the full through-current, often several hundred amps. Measured against that benchmark, 40 kVAr looks too small to matter.

A shunt D-STATCOM connects across the feeder at a single point. Feeder current does not pass through it. The device carries only the current corresponding to its own rating:

I = Q / (√3 × V) = 40,000 / (√3 × 400) ≈ 58 A
where Q = 40 kVAr, V = 400 V phase to phase

That 58 A is independent of feeder loading. The device is sized to its own reactive current, not to the feeder it supports.

How reactive injection raises voltage

The network behind any connection point can be represented as a source with a series impedance, R + jX, back to it. Current flowing through that impedance produces a voltage difference. The familiar low voltage drop relationship is:

ΔV ≈ (P·R + Q·X) / V

A shunt D-STATCOM supplies reactive power locally, so that reactive power no longer has to be imported through the upstream reactance X. Removing Q from the upstream path removes the Q·X voltage drop it was causing, and the local voltage rises. For a reactive-only device the support reduces to:

ΔV ≈ Q·X / V

Worked example

Consider a 1 MVA distribution transformer feeding a 1 km low voltage feeder on 95 mm² overhead conductor, with the D-STATCOM connected 750 m along the feeder. Representative values:

Transformer reactance	Xtx ≈ 0.008 Ω
Line reactance to the connection point (0.29 Ω/km × 0.75 km)	≈ 0.218 Ω
Total upstream reactance	X ≈ 0.225 Ω

Applying the relationship:

ΔV ≈ Q·X / V = 40,000 × 0.225 / 400 ≈ 22.5 V ≈ 5.6%

The same result follows from the device current and the upstream reactance, which is worth showing because the two routes are the same physics:

ΔV_LL ≈ √3 × I × X = √3 × 58 × 0.225 ≈ 22.5 V

On this feeder, a 40 kVAr device applies about 5.6% voltage correction at its connection point.

It’s important to remember that the STATCOM can both source and sink VARs, so it can move the voltage in either direction, either up or down 22.5V in this simplified case. This allows it to respond to voltage rise from solar, or voltage drop from load, in real time.

The connection point sets the result

The feeder in the example is 1 km long, but the device sits at 750 m. The final 250 m plays no part in the calculation, because the device’s reactive current flows back to the source through the upstream reactance only. Voltage authority is set by the impedance between the device and the source, not by the total feeder length. This is why siting matters: the device belongs where the upstream reactance, and the voltage problem, are greatest. It is also the clearest distinction from a series device, whose effect depends on what lies downstream of it.

Where the relationship applies

The Q·X / V relationship depends on the feeder having meaningful reactance. Overhead open-wire conductor, with an X/R ratio near 1, meets that condition. On low-reactance cable the same kVAr produces little voltage movement, and a D-STATCOM earns its place through phase balancing rather than bulk reactive support.

It is also worth separating the correction the device applies from the total feeder voltage drop. On a feeder with X/R near 1, the real-power drop (P·R) from load current is comparable to the reactive drop, and a reactive device does not act on it. The 5.6% figure is the correction available at the connection point, not the elimination of the feeder’s full drop under load.

In practice. A shunt D-STATCOM provides voltage correction at the point where it is needed, sized to its own reactive current rather than to feeder loading. The EcoVAR adds two capabilities relevant to low voltage feeders: independent phase balancing, which addresses the per-phase voltage problem that symmetric reactive injection cannot, and installation without a feeder outage. On a weak overhead feeder these allow voltage to be corrected at the connection point in place of, or ahead of, conductor augmentation.

EcoJoule’s EcoVAR regulates voltage in parallel — sized below feeder current, installed without an outage, and responding within a single cycle.

As rooftop solar, batteries and electric vehicles push low-voltage networks beyond the conditions they were designed for, distribution businesses are re-examining how they manage voltage.

These distribution businesses are increasingly turning to low-voltage distribution STATCOMs (D-STATCOMs), like EcoJoule Energy’s EcoVAR, to address constraints that are inherent to traditional series voltage regulators, and do so without taking feeders out of service to install.

Traditional voltage regulators are connected in series with the feeder. The whole feeder current passes through the device, which sets its rating, size and the work required to install it. A STATCOM takes a different approach: it connects in parallel. The feeder current flows past the unit, and only the corrective current flows through it.

How a STATCOM differs from a traditional voltage regulator

• Parallel connection, not series. A series regulator carries the full feeder current. The EcoVAR connects in parallel, so feeder current flows past it and only the corrective current flows through the unit.
• Rated below feeder current, so smaller. Because it carries only the corrective current, a STATCOM can be rated for a fraction of the feeder current it supports. The result is a compact unit that suits an existing pole or enclosure.
• Installed without an outage. The parallel connection means the EcoVAR can be added to a live feeder and commissioned in hours, without the planned supply interruption a series device requires.
• Sub-cycle response. Power-electronic switching corrects voltage within a single cycle — a response far faster than the step changes of mechanical tap-changing regulators.
• Corrects imbalance between phases. A regulator that moves all three phases together cannot fix a feeder where some phases sit above the target voltage and others below — stepping the high phase down drags the low phases further down. The EcoVAR regulates each phase independently and shifts load between phases, bringing all three within limits at once and releasing feeder capacity for more solar.
• Holds its reference under two-way power flow. Traditional regulators reference the “line side voltage” for regulation. When rooftop solar exports and power flows back up the feeder, that reference is lost and the regulator can step the wrong way. A STATCOM sits in parallel, measures the local voltage directly, and injects or absorbs reactive power to hold it, so two-way flow does not disorient it.
• Active harmonic filtering too. Alongside voltage support and phase balancing, the EcoVAR filters harmonics, helping maintain power quality as more inverters and electronic loads connect.

“The network problems behind voltage limits and curtailed solar are real, and they need a device-based fix.
The question for distributors is which fix. A parallel STATCOM does the same regulation work without carrying the feeder load,
without an outage to install, and fast enough to follow conditions in real time.”
Dr Mike Wishart, Chief Executive Officer, EcoJoule Energy

In service across six markets

EcoVAR units are in service addressing voltage problems in the United Kingdom, Belgium, Lithuania, Australia, Malaysia and New Zealand.

In the United Kingdom, UK Power Networks is operating the EcoVAR on its network through an innovation project, with pole-mounted units installed in Kent. Details are published by UK Power Networks at ukpowernetworks.co.uk.

About EcoJoule Energy

EcoJoule Energy is an Australian energy technology company, established in 2014 and based in Brisbane. It develops technologies for the future grid, including low-voltage distribution STATCOMs (EcoVAR) and battery energy storage systems. EcoJoule’s technology relieves grid congestion and allows solar generation to reach more customers, maximising the use of existing poles and wires so the benefits of the energy transition can flow to all users of the distribution grid.

A plain-language guide to the device that holds voltage steady on the low-voltage grid — and lets existing poles and wires carry more solar.

A distribution STATCOM (D-STATCOM) is a power-electronic device connected to the low-voltage (LV) network to regulate voltage. It does the job of a voltage regulator, but instead of switching taps or capacitor steps, it exchanges reactive power with the grid continuously and adjusts within a fraction of a mains cycle. That speed, and the resolution it brings, is what separates it from conventional correction equipment.

An Advanced Voltage Regulator

At its core, a D-STATCOM is a voltage-source converter. By controlling the magnitude and phase angle of its output voltage relative to the grid, it either sources reactive power to raise local voltage, or sinks reactive power to lower it. There are no discrete steps. The output is variable across its full range, so the converter can hold voltage at a target rather than bracketing it between tap positions.

Advanced LV units control each phase independently. This matters on the LV network, where single-phase rooftop solar, EV charging and uneven load routinely pull the three phases apart. A per-phase controller corrects each phase to its own target instead of applying one average correction across all three.

Sub-Cycle Response and Active Harmonic Filtering

A D-STATCOM samples and adjusts its output many times within a single 50 Hz cycle. This sub-cycle response lets it track fast voltage variations that step-based equipment cannot follow.

The same capability allows it to act as an active harmonic filter. Non-linear loads inject harmonic currents that distort the voltage waveform. Because the converter can shape its output within the cycle, it synthesises a waveform that drives a compensating current — equal in magnitude and opposite in phase to the harmonic content already on the network — so the two cancel at the point of connection. The result is a cleaner voltage waveform without the tuned, passive filter banks that conventional approaches rely on.

Connected in Parallel, Not Series

A D-STATCOM is connected in shunt (parallel) with the network, not in series with the load. It injects current at its point of connection rather than carrying the line current through itself.

This is the reason a relatively low-power STATCOM can have a large effect on voltage. On an electrically weak network — long feeders, small conductors, high source impedance — a modest injection produces a meaningful voltage change. A small shunt device therefore moves voltage far more than its rating alone would suggest, precisely where the network is least able to support itself.

High renewable penetration is changing where instability shows up on the grid. Voltage rise from clustered rooftop solar, imbalance from single-phase connections, and harmonics from inverters now originate inside the LV network, close to the customer. Two factors are driving adoption:

1. Cost. Compared with conductor upgrades, additional transformers, or large centralised compensation, a distributed LV STATCOM is a lower-cost way to manage these conditions — and the EcoVAR installs with no outage required.
2. Location. A shunt LV device applies regulation and reactive power at the source of the problem, on the feeder where the issue arises — rather than generating reactive power upstream and pushing it down the line alongside real power, loading the very conductors it is meant to relieve.

By correcting voltage, balancing phases and filtering harmonics locally, the LV STATCOM frees up capacity on existing poles and wires. That lets more solar generation reach more customers without the cost and disruption of rebuilding the network.

As rooftop photovoltaic (PV) penetration rises across residential and commercial low voltage (LV) networks, distribution planners increasingly face the question of whether smart inverter volt-var functions are sufficient to maintain voltage stability and power quality. This article examines the fundamental limitations of PV inverter reactive power capability and explains why a dedicated distribution-level Static Synchronous Compensator (D-STATCOM) — grid-connected and independent of local solar generation — is required to provide reliable, continuous voltage and power quality support.

1.  The Inverter Apparent Power Constraint

A grid-connected PV inverter is a current source converter rated to a fixed apparent power (S, measured in kVA). The relationship between active power (P), reactive power (Q), and apparent power is governed by:

S² = P² + Q²

Because S is fixed by the inverter’s hardware rating, any reactive power the inverter delivers comes directly at the expense of active power output. When a PV system is generating at or near its rated capacity — exactly the conditions under which voltage rise and overvoltage events are most acute — the inverter has minimal remaining capacity available for reactive compensation.

Research published in Scientific Reports (2025) quantifies this constraint precisely: the inverter must manage its limited apparent power capacity between delivering active power and supplying reactive support, and this trade-off becomes especially important during peak solar output, when the inverter may prioritise active power and limit reactive contribution [1].

The practical consequence is that grid support from PV inverters is weakest precisely when the grid needs it most — at midday under high irradiance and high reverse power flow.

2.  No Support When Solar Generation Is Absent

Voltage and reactive power demand on the distribution grid do not follow a solar schedule. Evening peak loads driven by air conditioning, cooking and electric vehicle (EV) charging create reactive demand that is structurally disconnected from daytime solar generation.

Conventional customer-owned grid-tied inverters are inactive at night and produce negligible output under heavy cloud cover or during winter months. When an inverter is not generating, it cannot provide reactive power unless it is specifically designed and configured to operate in a standby STATCOM mode — a capability that is not standard in residential or small commercial inverters, and one that requires a connected DC source to maintain the DC link voltage.

Research cited by Oxford’s Clean Energy journal (2022) confirms that while PV inverters can technically be operated at night to provide reactive support, there are no standard policies or incentives to operate them in this mode, and the operational frameworks to do so are not in place for distributed residential assets [2].

A dedicated D-STATCOM, by contrast, draws its reactive power from the AC line itself. It requires no local generation source. A voltage source converter (VSC) uses a small DC capacitor to synthesise leading or lagging reactive current — it neither consumes nor generates active power — and is therefore available on a 24/7 basis, regardless of irradiance, cloud cover, season, or time of day.

3.  Phase Imbalance and Neutral Voltage Displacement

The majority of residential solar installations in four-wire LV distribution networks are single-phase connected. Where uptake is uneven across the three phases of a feeder — which is the typical real-world condition, not the exception — the result is a phase imbalance that displaces the neutral voltage from its reference point.

This neutral point shift is not a benign condition. Research published in IEEE-indexed literature has documented that single-phase DG units in LV networks cause neutral-point shifting, with a side effect that voltage in phases adjacent to the high-generation phase can decrease, creating the potential for undervoltage events on other phases [3]. A separate study published in IEEE Transactions on Smart Grid confirms that unbalanced and resistive LV networks can exhibit positive inter-phase voltage sensitivity terms, acting as destabilising positive feedback loops after individual inverter tripping events [4].

The critical failure mode is a cascade: when neutral voltage shifts, the phase-to-neutral voltage seen by single-phase inverters on the affected phases moves outside the limits specified in inverter protection standards (such as AS4777 in Australia and equivalent IEC standards internationally). Inverters detect an apparent overvoltage or undervoltage condition and disconnect. Each disconnection reduces generation on that phase, which may worsen the imbalance on others. The result is potential rapid shedding of multiple inverters across the feeder, further destabilising voltage and leaving the grid with a substantially reduced generation fleet at no notice.

A three-phase D-STATCOM connected at the feeder level addresses this failure mode directly. By drawing unequal reactive currents from each phase to compensate for the uneven generation and load across phases, the STATCOM actively restores neutral voltage to its reference. It provides a fixed, stable phase-to-neutral reference for all single-phase inverters connected downstream — a reference that does not shift with load or generation imbalance. This stabilises the operating environment for every customer-owned PV inverter on the feeder, allowing them to remain connected and productive.

Field data from Endeavour Energy’s DER Integration Strategy supports this analysis. Their LV analytics tools identified high daytime DER-related phase unbalance as a primary network stress condition, and noted that single-phase voltage rise caused by PV is amplified by the influence of the neutral conductor [5]. Endeavour are in a multi-year deployment of a fleet of LV STATCOMs as proven, business-as-usual solutions for voltage management on constrained feeders, forecasting a population of 240 units by the close of the 2029 regulatory period [5].

4.  High Power Single-Phase Loads: The Compounding Problem

The challenge of neutral voltage management is not limited to PV generation. The same distribution feeders that are absorbing rooftop solar are also experiencing growing loads from air conditioning, induction cooking and, increasingly, residential EV charging. A household running a 6 kW split-system air conditioner simultaneously with a 7 kW EV charger on a single phase represents a 13 kW load imbalance contribution from one connection point.

These high single-phase loads draw both active and reactive power. Air conditioning compressors are inductive loads with power factors typically in the range of 0.7–0.85, meaning they draw significant reactive current in addition to their active demand. This reactive demand cannot be addressed by PV inverters: they may be on a different phase, they may be offline at night, and even if active they have no mechanism for measuring or responding to a neighbour’s reactive demand.

A D-STATCOM monitors the aggregate reactive current on each phase at its point of connection and injects equal and opposite reactive current to compensate — whether the reactive demand originates from air conditioning, motor loads, EV chargers, or the reactive losses in the feeder cables themselves. This compensation is instantaneous, continuous and independent of the source of the reactive demand.

5.  AS4777 and the Australian Regulatory Context: “Do No Harm” vs. “Fix the Problem”

The regulatory framework governing grid-connected inverters in Australia is AS/NZS 4777.2, administered through the National Electricity Rules and enforced via the Clean Energy Council’s approved inverter list. AS4777 has been progressively updated — most recently to the 2020 version — to incorporate volt-watt and volt-var response modes, ROCOF withstand requirements, and tighter export limit controls [8].

These improvements are meaningful, but they reflect a fundamental design philosophy that can be described as “do no harm.” The standard’s primary objective is to ensure that inverters connected to the LV network do not actively worsen grid conditions — they must disconnect under abnormal voltage or frequency, ramp up softly on reconnection, and curtail output before causing overvoltage. The volt-var response mode, where enabled, asks an inverter to modulate its own reactive output in response to the voltage it sees at its own terminals.

This is a reactive and localised response. An inverter operating under AS4777 volt-var compliance is reacting to the voltage at its own connection point. It has no visibility of conditions on other phases, no awareness of neutral displacement developing elsewhere on the feeder, and no mechanism to inject corrective current in response to a neighbour’s inductive load. It is designed to avoid making its own situation worse — not to actively correct the network condition.

The distinction becomes critical under the conditions that are now becoming common across Australian LV networks: high concentrations of single-phase solar on unevenly loaded feeders, combined with growing single-phase loads from electrified appliances and EV charging. Localised voltage control techniques such as inverter volt-var control require no coordination but have limited effectiveness when PV penetration is high — a finding that holds regardless of how well individual inverters comply with AS4777 [9].

Neutral displacement — the condition in which unequal phase loading shifts the neutral point away from its reference — is not something any single-phase inverter can detect or correct under AS4777. Each inverter sees only its own phase-to-neutral voltage. When that voltage moves outside the standard’s thresholds, the inverter disconnects, which is precisely the compliant response. The standard provides no mechanism for the inverter to identify that the root cause is a network imbalance, nor any obligation to remain connected to stabilise the neutral.

A D-STATCOM operates under a fundamentally different design mandate. Rather than compliance with a connection standard, its purpose is active network correction. It continuously monitors all three phases and the neutral simultaneously, and injects unequal reactive currents across phases as required to restore balance. It does not wait for a voltage excursion to occur at its own terminals — it suppresses the conditions that would cause excursions at every inverter downstream. Where AS4777 asks: “are you connected safely?”, a D-STATCOM asks: “what does this network need right now?”

The compliance record under AS4777 reinforces this gap. As documented by Endeavour Energy, only 1% of inverters sampled in an earlier audit were confirmed to have volt-var settings correctly configured under the 2015 version of the standard [5]. Even where compliance rates improve with the 2020 version, the structural limitation remains: a fleet of individually compliant inverters, each acting on its own local voltage signal, does not constitute a coordinated reactive power resource. The aggregate behaviour of thousands of independent volt-var responses is not equivalent to a single deterministic compensator with full network visibility.

6.  The AC Line-Connected Architecture: Why It Matters

The fundamental difference between a PV inverter operating in volt-var mode and a dedicated D-STATCOM is the source of the reactive energy.

A PV inverter derives its reactive capability from its inverter hardware, but the reactive power headroom is always constrained by, and in competition with, the active power generated by the connected solar panels.

A D-STATCOM is connected directly to the AC distribution network. Its VSC synthesises reactive current by shifting the phase of its output voltage relative to the grid voltage — the DC link capacitor provides only the small amount of active power needed to cover switching losses. There is no trade-off between active and reactive power; the full rated reactive output of the STATCOM is available at any load level, any time of day, and under any generation condition.

As summarised in a comprehensive STATCOM review in Wiley’s International Transactions on Electrical Energy Systems (2021), the incorporation of a STATCOM eliminates the need for reactive power control loops in PV inverters and provides superior voltage regulation capability, particularly during night-time and under fault conditions when PV reactive support is unavailable [6].

7.  The Network Operator’s Perspective

Distribution network service providers (DNSPs) are responsible for voltage quality across the entire feeder, at all times, for all customers — including those without solar. Relying on customer-owned inverters to deliver network voltage support introduces dependencies that are not within the DNSP’s control: inverters may be updated, replaced, configured incorrectly, or disconnected. Compliance rates for volt-var settings, as documented by Endeavour Energy, have historically been low — only 1% of inverters sampled were confirmed compliant with volt-var requirements under the 2015 version of AS4777 [5].

A D-STATCOM, owned and operated by the network, delivers a deterministic, auditable, and controllable reactive power resource that is not subject to the compliance variability of thousands of independently owned and configured customer assets.

Conclusion

PV inverter volt-var functions are a useful supplementary tool for managing daytime voltage excursions on lightly loaded feeders. They are not, and cannot be, a substitute for dedicated reactive power compensation infrastructure.

The constraints are structural: PV inverter reactive output is bounded by its apparent power rating, is absent at night and under low irradiance, is single-phase and does not address neutral displacement, cannot respond to reactive loads on other phases, and is subject to compliance variability at scale.

A D-STATCOM connected at the LV distribution level provides continuous, grid-referenced reactive compensation that is independent of solar generation. It stabilises the neutral reference, supports balanced operation for all connected inverters, compensates reactive demand from high-power loads, and provides these functions 24 hours per day, 365 days per year.

For distribution networks managing increasing DER penetration, a STATCOM is not a replacement for smart inverter functions. It is the precondition that allows those inverter functions — and the solar generation they support — to perform reliably at scale.

Bibliography

• M. Alzahrani et al., “Control strategy evaluation for reactive power management in grid-connected photovoltaic systems under varying solar conditions,” Scientific Reports, vol. 15, 2025. https://doi.org/10.1038/s41598-025-08918-y
• Y. Lavi, “Use of solar PV inverters during night-time for voltage regulation and stability of the utility grid,” Clean Energy, vol. 6, no. 4, pp. 646–660, 2022. https://doi.org/10.1093/ce/zkac038
• C. Wengert et al., “Neutral-point shifting and voltage unbalance due to single-phase DG units in low voltage distribution networks,” IEEE PowerTech, 2009. https://www.researchgate.net/publication/224601814
• K. Dehghanpour et al., “Statistical Modeling of Networked Solar Resources for Assessing and Mitigating Risk of Interdependent Inverter Tripping Events in Distribution Grids,” IEEE Transactions on Smart Grid, 2020. https://arxiv.org/pdf/1908.01129
• Endeavour Energy, “DER Integration Strategy and Business Case — Regulatory Proposal 2024–2029,” December 2022. Available at: https://www.endeavourenergy.com.au
• M. Sadiq et al., “A review of STATCOM control for stability enhancement of power systems with wind/PV penetration: Existing research and future scope,” International Transactions on Electrical Energy Systems, vol. 31, no. 9, 2021. https://doi.org/10.1002/2050-7038.13079
• M. Pinthurat et al., “Dynamic Power Balancing Algorithm for Single-Phase Energy Storage Systems in LV Distribution Network with Unbalanced PV Systems Distribution,” arXiv preprint, 2020. https://arxiv.org/pdf/2011.06181
• Global Solar Energy Systems (GSES), “AS/NZS 4777.2:2020 Updates — What You Need to Know,” 2022. https://www.gses.com.au/as-nzs-4777-2-2020-grid-connected-inverter-updates-what-you-need-to-know/
• A. Nouri et al., “Resilient Decentralized Control of Inverter-interfaced Distributed Energy Sources in Low-voltage Distribution Grids,” arXiv preprint, University College Dublin, 2019. https://arxiv.org/pdf/1911.11420

The Grid Has Changed. Reactive Compensation Must Follow.

Distribution networks were designed around a straightforward premise: power flows from a substation to passive loads, and fixed reactive compensation devices — principally capacitor banks — manage voltage along the way. That premise no longer holds.

Rooftop solar, battery storage, electric vehicles, and variable industrial loads have fundamentally altered the direction, magnitude, and predictability of power flow on low-voltage networks. In this environment, fixed capacitor banks — devices that deliver a predetermined block of reactive power, regardless of real-time grid conditions — are structurally limited in what they can address.

EcoJoule Energy develops and supplies the EcoVAR, a Low Voltage Distribution Static Synchronous Compensator (D-STATCOM), purpose-built for the operational demands of the modern distribution grid. This bulletin sets out the technical distinctions between fixed capacitor banks and D-STATCOM technology across the parameters that matter most to network operators.

Dynamic Response vs. Fixed Correction

A capacitor bank delivers reactive power in discrete steps, determined by the switching of fixed capacitor elements. The correction is basic, in discrete steps and generally cannot compensate for high voltages associated with high renewable generation and reverse power flow.  Furthermore where load or generation varies continuously — as it does wherever solar PV, EV chargers, or variable industrial plant is present — a capacitor bank has to switch frequently, compromising its design life.

The EcoVAR operates as a voltage-source converter. It measures grid conditions on a sub-cycle basis and adjusts reactive power output continuously, from full capacitive to full inductive, within a single electrical cycle. This response characteristic is not an incremental improvement on capacitor technology — it is a categorically different operating mode.

Where a network carries solar PV, cloud-driven irradiance changes can drive voltage from below statutory minimum to above maximum within seconds. A capacitor bank, limited by switching frequency and fixed step size, cannot track this. The EcoVAR does so automatically, without operator intervention and without equipment wear associated with mechanical switching.

Voltage Boost and Reduction: Both Directions of Control

A conventional capacitor bank provides one direction of voltage correction: it raises voltage by injecting reactive power. It cannot absorb reactive power. This means a capacitor bank is of no utility — and can be actively harmful — when overvoltage is the prevailing constraint.

Overvoltage is increasingly the binding constraint on distribution feeders with embedded solar. As generation ramps up during the middle of the day, feeder voltage rises. Without the ability to absorb reactive power and suppress that voltage rise, a capacitor bank has nothing to offer at the moment the network most needs assistance.

The EcoVAR provides both boost and reduction. It raises voltage at times of high import demand and suppresses overvoltage during periods of high solar export. This bidirectional voltage control capability is what enables the EcoVAR to be the primary reactive compensation device on a feeder, rather than a partial solution requiring supplementary equipment.

Additional Functions: Harmonics, Phase Balancing, and DC Integration

Reactive power compensation is one of three primary functions the EcoVAR delivers. The other two — active harmonic filtering and independent per-phase reactive compensation — address constraints that capacitor banks not only cannot resolve but can worsen.

Harmonic distortion from variable-speed drives, switched-mode power supplies, EV chargers, and grid-tied inverters is a growing operational challenge on distribution networks. Capacitor banks present a low-impedance path at certain harmonic frequencies and can create resonant conditions that amplify, rather than attenuate, harmonic voltages. The EcoVAR includes active harmonic filtering, measuring distortion and injecting compensating currents in real time.

Phase imbalance from single-phase loads and generation creates neutral current, increases feeder losses, and degrades the voltage quality experienced by three-phase customers. The EcoVAR operates independently on each phase, redistributing reactive current to minimise imbalance. No capacitor bank configuration delivers this capability.

The EcoVAR architecture includes an 864 VDC secondary bus, which provides a direct integration interface for battery energy storage systems. This allows reactive compensation and energy storage to share a common power conversion stage, reducing total equipment footprint and capital cost for operators deploying both technologies.

Network Augmentation Deferral and DER Hosting Capacity

The financial case for D-STATCOM deployment rests substantially on two outcomes: deferring capital expenditure on network augmentation, and increasing the volume of distributed energy resources that can be connected without constraint.

Distribution network augmentation — reconductoring, transformer upgrades, substation expansion — is triggered when one or more network parameters exceed their operating envelope. Under voltage, over voltage, thermal loading, phase imbalance, and harmonic distortion each represent a separate augmentation trigger. A capacitor bank addresses only one of these: undervoltage, and may exacerbate harmonics. The EcoVAR addresses all four simultaneously.

The practical consequence is that the EcoVAR can defer augmentation that a capacitor bank cannot. Where a feeder has a thermal constraint and a harmonic constraint as well as a voltage constraint, only a device that addresses all three delivers meaningful augmentation deferral. Deploying a capacitor bank in this scenario removes one constraint while leaving the others intact.

Hosting capacity for distributed energy resources is limited by whichever network constraint is reached first. Increasing that capacity requires addressing the binding constraint. On most heavily loaded feeders with material solar penetration, the binding constraint during high-export periods is overvoltage — a constraint a capacitor bank is structurally incapable of addressing. The EcoVAR, with its ability to absorb reactive power and suppress voltage, directly increases the volume of solar and storage that a feeder can host without statutory exceedance or equipment damage.

EcoJoule technology enables the energy transition to benefit all grid users: generation that would otherwise be curtailed reaches more customers, and network capacity already built into existing poles and wires is used to its full extent before new capital investment is required.

Installation: No Planned Outage Required

Network operators and field crews consistently identify planned outage requirements as a constraint on the deployment of new equipment. Each outage requires notification, coordination, and customer impact management.

The EcoVAR is designed for live installation. Deployment does not require a planned de-energisation of the feeder or the connection point. This characteristic reduces the total cost and elapsed time from procurement decision to operational commissioning, and removes a material barrier to the scale of deployment that distribution network service providers need to achieve across their asset base.

Capability Comparison: Fixed Capacitor Bank vs. EcoVAR D-STATCOM

Capability	Fixed Capacitor Bank	EcoVAR D-STATCOM
Voltage Response	Fixed step correction only; capacitors switched in or out in discrete banks	Continuous, stepless correction from full capacitive to full inductive within one cycle
Voltage Regulation	Boost only; cannot absorb reactive power or suppress overvoltages	Boost and buck; raises undervoltages and suppresses overvoltages including PV export surges
Harmonic Filtering	None; can amplify harmonics at resonant frequencies	Active harmonic filtering built in; reduces voltage distortion from non-linear loads
Phase Balancing	None; three-phase devices cannot address single-phase imbalance	Per-phase independent control; corrects current and voltage imbalance in real time
Response to PV Variability	Cannot track cloud-driven fluctuations; switching frequency limited	Responds within milliseconds; tracks rapid irradiance changes without hunting or oscillation
EV Load Response	Stepped correction cannot match fast-ramping EV charger demand	Continuous reactive compensation matches dynamic EV charging profiles automatically
DER Hosting Capacity	Limited by inability to manage overvoltage from generation	Increases hosting capacity by managing export overvoltages and reactive current flows
Network Augmentation Deferral	Partial; voltage boost only, limited thermal relief	Defers augmentation by addressing voltage, thermal, imbalance, and harmonic constraints simultaneously
Installation Requirement	De-energisation typically required for switching equipment	Live installation possible; no planned outage required for EcoVAR deployment
DC Bus Architecture	N/A	864 VDC secondary bus; supports direct integration with battery storage
Grid Code Compliance	Passive device; limited programmable response	Programmable to comply with evolving grid codes for reactive power, voltage, and harmonics

Summary

Fixed capacitor banks were fit for purpose on the distribution grid that existed twenty years ago. On the grid that exists today — and on the grid that will exist in five years — they address a subset of the reactive power problems network operators face, and introduce failure modes that did not exist in the unidirectional, load-only network for which they were designed.

D-STATCOM technology, as delivered in the EcoVAR, is not a premium upgrade to a working solution. It is the appropriate device for a grid environment characterised by bidirectional flows, embedded generation, dynamic loads, and tightening power quality standards. Network operators evaluating reactive compensation assets should assess fit for purpose against the grid they operate, not the grid they operated.

About EcoJoule Energy

EcoJoule Energy designs and supplies Low Voltage Distribution STATCOMs and Battery Energy Storage Systems for electricity distribution networks worldwide. The EcoVAR delivers reactive power compensation, active harmonic filtering, and per-phase voltage balancing without requiring network outages for installation. EcoJoule operates through a global distributor network and direct market presence in selected regions.

Efficient deployment of the EcoVAR begins before the unit leaves the warehouse. Utilities that have built repeatable installation programmes have converged on a practical site selection methodology that balances electrical performance with installation practicality. 

Start with the voltage problem, not the substation 

The EcoVAR is a point-of-connection device. Its reactive power compensation, phase balancing, and active harmonic filtering act locally — so placement relative to the voltage problem matters. 

Utility field experience with the EcoVAR suggests the optimum investment-to-benefit placement on most low voltage feeders is between the halfway and two-thirds point along the feeder length. That zone is the starting point for site assessment, not the substation end where access is easiest. 

Smart meter data has made this assessment considerably more precise. Utilities with advanced metering infrastructure can identify specific spans and phases where voltage deviations are most frequent and most severe, reducing the selection process to a short list of candidate poles rather than a manual survey of the full feeder. 

Practical constraints shift the selection, but rarely far 

Once the electrically preferred location is identified, the assessment turns to what is already on the pole. Streetlighting attachments, distribution fuses, telecommunications equipment, and vegetation encroachment each add time, cost, or safety risk to installation. Where the optimal pole carries a heavy load of existing equipment or access is constrained, utilities move to the next viable pole in either direction along the feeder. 

This trade-off is manageable because the EcoVAR’s installation footprint is small. A standard installation does not require a supply outage and can be completed in under two hours. The cost of shifting one or two spans from the theoretical optimum is low relative to the cost of managing a congested pole or scheduling vegetation clearing. 

An action bias is often the right economic decision 

Because the EcoVAR can be relocated if a better site is later identified, over-engineering the initial site selection carries its own cost. Utilities that treat the first installation as a testable hypothesis — rather than a permanent capital commitment requiring exhaustive pre-work — generally reach resolution faster and at lower total cost. 

The practical rule that has emerged across experienced deployment programmes: identify the voltage problem zone, find the cleanest pole in that zone, install. Refine if the data warrants it. 

Australia’s 10 million energy consumers are missing out on $1.1 billion a year in savings due to underinvestment in voltage management technologies on the energy distribution grid, according to Australian-based global power electronics manufacturer EcoJoule Energy.

Voltage control issues are also destroying about $317 million worth of appliances each year. 

While governments and network operators are investing billions in infrastructure like synchronous condensers across Australia to enhance transmission-level grid stability, this investment will do little to help consumers affected by energy waste and appliance damage caused by inefficiencies in low-voltage distribution networks.

Analysis by EcoJoule found implementation of a nationwide Conservation Voltage Reduction (CVR) program would save the average customer about $110/annum¹ on their electricity bill, while increased appliance life would result in savings of about $35/annum² per customer.

EcoJoule Energy Founder & CEO Mike Wishart said the continued growth of rooftop solar, electric vehicles, and home electrification was expected to add further pressure on the distribution grid over the next decade.

“We’re investing heavily in transmission infrastructure, but the reality is most Australians experience the grid at the distribution level. If we don’t address voltage inefficiencies there, households will continue to miss out on significant savings while absorbing unnecessary costs. Without targeted investment in voltage management, these inefficiencies will compound and become even more costly for consumers.”

“This isn’t just about energy waste, it’s about real dollars lost by households every year and avoidable damage to appliances. Smarter voltage management is one of the most immediate and cost-effective ways to return those savings to consumers.”

The problem of overvoltage on distribution grids is increasingly recognised worldwide, with EcoJoule recently completing several installations of its EcoVAR STATCOM in the UK, Europe, and Asia. EcoVAR is a static compensator mounted on existing power poles using power electronics and software to correct grid voltages.

EcoJoule last year secured a $15 million investment, led by Ellerston Capital and the Clean Energy Finance Corporation (CEFC), to expand the rollout of its platforms across Australia and the world. EcoVAR STATCOMs have now been installed on four different continents.

EcoJoule Strategic Advisor and Director of the Energy Futures Network at the University of Wollongong, Ty Christopher, said more efficient use of scarce energy resources would contribute to the energy transition.

“The cheapest and cleanest energy is the energy that never has to be used in the first place,” he said. “Managing overvoltage means less energy is wasted and more clean solar energy can be exported.”

“Many of the challenges affecting reliability and renewable uptake are occurring on the distribution system,” he said.

“If we do not start approaching stability issues on the distribution grid with the same enthusiasm as the transmission grid, reliability will continue to decline.”

“While large-scale assets provide essential inertia and support the bulk power system, they are not designed to resolve the highly localised issues that arise on distribution feeders.

“These include voltage rise from rooftop solar, imbalances between phases and fluctuations that occur in real time as demand and generation shift.

Distributed STATCOM technology is increasingly being deployed to provide that capability. EcoJoule Energy’s EcoVAR system, a pole-mounted STATCOM, delivers real-time voltage control and reactive power support at the feeder level, helping stabilise networks and improve overall performance.

“EcoVAR allows utilities to manage voltage and reactive power dynamically, right where the problem exists,” Dr Wishart said. “It complements transmission level investments by extending stability across the entire network.”

EcoJoule Chief Commercial Officer Martin van der Linde said the shift in grid dynamics was driving a need for more balanced investment across both transmission and distribution.

“Network operators are seeing growing constraints at the edge of the grid,” van der Linde said. “If we want to continue connecting solar, EVs and new loads, we need to invest not just in the transmission backbone, but in the distribution network that connects directly to customers.”

He said distributed solutions provide a practical and cost-effective way to address these challenges while maximising existing infrastructure.

“Targeted deployment of distributed STATCOMs can improve power quality, unlock additional capacity and reduce the need for large-scale upgrades,” Mr van der Linde said. “It is about getting more value from the network we already have while supporting future growth.”

A coordinated approach that combines transmission-level assets, such as synchronous condensers, with distribution-level technologies will be essential for maintaining a stable and reliable grid.

“Grid stability is a whole system issue,” Dr Wishart said. “Investment needs to reflect that by supporting both the transmission network and the distribution network, where much of the change is happening.”

The company, which was established over a decade ago, currently has both local and international customers, including Endeavour Energy, UK Power Networks (UKPN), CLP Power (Hong Kong), Essential Energy, Ausgrid, SA Power Networks and AusNet Services.

EcoJoule has also developed EcoSTORE, a battery energy storage system (BESS) that absorbs excess solar energy and releases it when needed, while also improving the grid power quality for consumers using the same voltage stabilisation technology.

ENDS

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Media enquiries to:

Ben Ready
RGC Media
0415 743 838
ben@rgcmm.com.au

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References

1. AER RIN data excluding HV connections and using AEMC analysis of national average residential retail electricity price ($0.28c/kWh)
2. https://documents.uow.edu.au/content/groups/public/@web/@eis/@secte/documents/doc/uow278855.pdf

EcoJoule Energy’s EcoVAR Low Voltage D-STATCOM delivers utility-scale power quality outcomes from distributed installations — addressing voltage instability, phase imbalance, and harmonics at the point of cause, rather than attempting centralised correction downstream.

A common assumption in network planning is that system-scale problems require system-scale equipment. EcoJoule Energy’s EcoVAR challenges that assumption — and the evidence from operating deployments supports a different conclusion: distributed power quality correction, applied at the source of grid stress, is more effective, more cost-efficient, and more resilient than centralised approaches.

The EcoVAR is a Low Voltage Distribution STATCOM (D-STATCOM) installed on the LV distribution network by the utility. A single unit serves all customers downstream on a feeder segment, from typically 5 to 200 residential connections, or a combination of residential and commercial loads including three-phase commercial buildings.

The device is not a customer-premises solution. It is utility infrastructure, approved, owned, and operated by the network business.

The Case for Distributed Correction

Distribution networks are not uniform. Voltage instability, phase imbalance, and harmonic distortion each originate at specific points on the network. They are at the customer connection, at the inverter, at the motor load. Centralised solutions, whether at the substation or at transmission level, address these problems after the fact, working against the impedance of the network itself.

The physics favour distribution. Reactive power, which governs voltage stability, cannot be efficiently transported over long distances. Every kilovar of reactive support sourced locally avoids the losses associated with delivering that support from a remote point. An EcoVAR installed at the end of a feeder provides reactive compensation where the voltage drop is greatest, with no transmission losses and no dependency on upstream infrastructure capacity.

“Centralised solutions address power quality problems after they have already propagated through the network. The EcoVAR eliminates them at the point of origin,  which is where they do the most damage.”
Dr Mike Wishart, CEO EcoJoule Energy

The same principle applies to harmonics. Distortion generated by inverter-based loads, variable speed drives, and EV chargers propagates upstream through the network. Filtering that distortion at or near the source, before it reaches the substation transformer, reduces impedance stress throughout the network. Centralised harmonic management addresses the symptom; distributed filtering addresses the cause.

Stacked Economic Benefits: How Utilities Build the Business Case

The EcoVAR’s value is not derived from a single performance metric. Its business case is built by stacking measurable outcomes across the performance categories that regulators and utilities already track: voltage compliance, loss reduction, asset life, and capital deferral. Each benefit is independently quantifiable; together they produce a compelling investment case even at the individual feeder level.

Scale Through Distribution: Many Units, One Outcome

The objection that distributed solutions cannot achieve system scale impacts misunderstands how distribution networks function, they are in fact distributed systems themselves. It makes intuitive sense that a distributed solution is the best solution for distribution networks.  A utility deploying EcoVARs across a portfolio of feeders achieves network-wide power quality improvement through coordinated distributed correction. This is the same principle that underpins modern distributed energy resource management. The EcoVAR is not a substitute for system planning; it is a tool that makes existing infrastructure more capable, deferring the need for system-level intervention.

KEY INSTALLATION ADVANTAGE
The EcoVAR requires no network outage for installation. It connects to existing LV infrastructure and eliminates the switching costs and customer disruption associated with alternative network upgrades. This reduces the total cost of deployment and simplifies scheduling for network operators.

Critically, each EcoVAR installation is independently valuable. The business case does not depend on network-wide deployment. A single unit on a constrained feeder delivers measurable, reportable outcomes from day one. Voltage compliance, loss reduction, asset life extension, all while the utility builds confidence in the technology before broader rollout.

This deployment model reduces investment risk significantly compared to large, centralised infrastructure projects, which require full commitment before any benefit is realised.

About EcoJoule Energy

EcoJoule Energy designs and manufactures Low Voltage Distribution STATCOMs (EcoVAR) and Battery Energy Storage Systems (EcoSTORE) for electricity distribution networks worldwide. EcoJoule’s technology is deployed by utilities across Australia, Asia-Pacific, and Europe. The company’s mission is to ensure that the benefits of the energy transition reach all users of the distribution grid — by relieving grid congestion, enabling solar generation to reach more customers, and maximising the capacity of existing network infrastructure. EcoJoule is headquartered in Brisbane, Australia.

MEDIA ENQUIRIES

Martin van der Linde
Chief Commercial Officer
sales@ecojoule.com

Global operator of Distribution STATCOMs across four continents brings field-proven grid management expertise to the Australian engineering community.

EcoJoule Energy today announced it has joined the Electric Energy Society of Australia (EESA) as a Bronze Sponsor. The membership reflects EcoJoule’s commitment to contributing global operational experience in low voltage distribution management to Australian power engineers as the sector navigates the challenges of widespread distributed energy resource (DER) integration.

EcoJoule’s EcoVAR Distribution STATCOM is currently in service across four continents, making it one of the most operationally validated low voltage STATCOM platforms available to distribution network service providers worldwide. The company joins EESA at a time when Australian networks face mounting pressure from rooftop solar penetration, load imbalance, and power quality degradation across low voltage feeders.

A core principle guiding EcoJoule’s deployment approach is that Distribution STATCOMs are most effective when applied close to the point of voltage excursion — at the low voltage lines where solar generation, excess load, and power quality issues interact directly. This distinguishes the EcoVAR from upstream voltage management approaches, which address symptoms rather than causes and leave low voltage customers with limited relief.

The EcoVAR delivers simultaneous reactive power compensation, phase balancing, and active harmonic filtering in a single field device. Its 800 VDC secondary architecture and installation process that requires no network outage reduce deployment cost and customer disruption. These are both material considerations for networks managing increasingly tight maintenance windows.

EcoJoule positions the EcoVAR as the commercially demonstrated, field-proven alternative to network augmentation for managing the modern distribution environment. Augmentation carries a structural disadvantage that is widely understood but rarely quantified in investment decisions: the stochastic nature of network demand means new assets routinely enter service years ahead of their utilisation curve, creating capital that earns no return until load growth catches up. The EcoVAR allows networks to extract maximum capacity from existing infrastructure now, deferring augmentation expenditure until it is genuinely warranted — and in many cases avoiding it entirely.

The installed cost of EcoVAR deployment is a fraction of augmentation, and the device operates dynamically, responding to real-time network conditions rather than being sized for a future peak that may arrive later than modelled, or not at all. Through its EESA membership, EcoJoule intends to contribute to the Society’s technical program with content grounded in operational data from live network deployments, supporting Australian power engineers with practical, evidence-based guidance on low voltage STATCOM application as DER penetration continues to grow.

About EcoJoule Energy

EcoJoule Energy develops and deploys Low Voltage Distribution STATCOMs and Battery Energy Storage Systems for electricity distribution networks. The company’s EcoVAR platform is in service across four continents, enabling distribution network operators to manage voltage excursions, phase imbalance, and power quality issues at the low voltage level — maximising the capacity of existing network infrastructure and enabling greater solar generation to reach more customers. EcoJoule believes the energy transition should deliver benefits to all electricity users, and designs its technology to ensure the benefits of distributed generation flow equitably across the distribution grid.

Martin van der Linde 
Chief Commercial Officer
EcoJoule Energy
sales@ecojoule.com