CHITEK controls harmonic interleaving, flicker and reactive swing at PV, wind and battery-storage interconnect points using combined SVG and AHF equipment. Several inverters switching on one bus interleave their emissions, and charge-to-discharge transitions produce a reactive step. Compliance is assessed where the grid operator measures it: the point of common coupling.
PV inverters, full-power wind converters and battery PCS units all switch at high frequency. Several units on one interconnect point interleave their harmonics, and the charge and discharge transition produces a reactive step and a flicker event. The compliance question is what the grid operator measures at the point of common coupling.
Reviewed by the CHITEK power quality engineering team · Last updated
At a PV, wind or storage interconnect the two problems arrive together, because the same inverters produce both switching harmonics and reactive swing.
| Aspect | AHF (Active Harmonic Filter) | SVG (Static Var Generator) |
|---|---|---|
| What it does | Injects a compensating current that cancels the harmonic current drawn by non-linear loads. | Supplies or absorbs reactive power continuously to hold power factor and support voltage. |
| Primary target | Current distortion (THDi) and harmonic spectrum at the point of common coupling. | Power factor, voltage fluctuation and reactive demand across the load cycle. |
| Typical trigger | VFD banks, rectifiers, welding sets, induction furnaces, LED drivers, UPS rectifiers. | Low or swinging power factor, voltage sag and rise, weak or long feeders, EV load steps. |
| Behaviour at light load | Compensation scales with the measured harmonic current, so output falls as load falls. | Holds output as required to reach the target power factor even at near-zero active load. |
| Use in this sector | Harmonic correction where multi-inverter interleaving or LCL filter interaction pushes emission past the grid limit. | Reactive support and voltage hold as irradiance or state of charge changes, and to avoid leading power factor at low output. |
Compliance is assessed at the point of common coupling, so the survey should be taken there rather than at the inverter terminals.
Utility-scale / Distributed / Agri-PV
Wideband oscillation from multi-inverter
>8%
THD
Fluctuation from irradiance variation
PF Low
Reactive Diff.
AC side reflection from DC ripple
DC Bias
Xfmr Overheat
Onshore / Offshore / Distributed
Low-order distortion from full-power converter
>10%
THD
Reactive surge from gust/turbulence
Reactive
Swing
Phase imbalance from auxiliary load
>5%
Unbalance
Grid-side / User-side / Source-side
Harmonic stack from multi-PCS
>6%
THD
Lag regulation at low load
< 0.9
PF
Voltage flicker at interconnect
> 0.8
Pst
Each case below is written up the same way: what the site was, what the survey measured before anything was specified, what was installed, and what the acceptance test showed afterwards. Projects marked Typical Configuration are illustrative — sizing for those always starts from a site survey rather than from the table.
Typical Configuration · Solar PV
Illustrative configuration — sizing starts from a site power-quality survey
An illustrative arrangement for a utility-scale or distributed PV plant: SVG at the step-up bus, AHF on the inverter AC feeders.
For utility-scale and distributed PV, the usual arrangement is an SVG at the step-up bus plus AHF on the inverter AC feeders. Multi-inverter resonance and cloud-edge reactive swings are the two failure modes — both need a measurement campaign before ratings are fixed.
Illustrative configuration — not a specific delivered project. Reference projects in this sector are available on request.
Wideband harmonic emissions from many inverters switching together, reactive swing as irradiance or state of charge changes, and voltage flicker at the interconnect. Multi-inverter LCL filter interaction can also produce resonance.
Inverters and PCS units are rated for active power. At low output their reactive capability is a smaller share of what the plant needs, and cable and transformer capacitance can push the measured power factor leading or lagging depending on the hour.
A combined SVG plus AHF arrangement is the usual answer. The SVG holds power factor and voltage, the AHF removes switching harmonics, and the ratings are split according to what the survey finds.
The grid agreement and the local standard, measured at the point of common coupling. Emission limits, flicker and reactive capability are all assessed there, so the survey should be taken at that point rather than at the inverter terminals.
Every project on this page started with a measured survey. Send us your single-line diagram and load list and we will tell you what we would measure first.
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