Grid Fluctuations · Solar Operations Excellence

Grid Fluctuations

Hello Guys

I’m currently dealing with an issue where one of our solar parks is causing continuous power fluctuations to the grid, which has led the grid operator to shut down the plant when this occurs.

The plant has a total installed capacity of 14 MW. At the time of commissioning, the grid infrastructure was not fully ready, so the plant was limited to 50% capacity. This limitation was applied directly at inverter level, where all Sungrow SG250HX inverters were capped at 50% output.

In addition, the plant is controlled by a PPC (Power Plant Controller), which performs curtailment based on market signals (e.g., negative pricing).

After approximately one year, maintenance was completed on the grid export infrastructure, and the plant was allowed to operate at 100% capacity.

Following this change, we started to observe serious instability whenever the plant was actively curtailed by the PPC. We noticed that the inverters were generating large amounts of reactive power, and the cause was initially unclear. This issue persisted for several months.

In summary, the inverters receive curtailment and control signals from the PPC, and we strongly suspect that the PPC control parameters (active and reactive power setpoints, control gains, ramps, or droop settings) were tuned when the plant was operating at 50% and were never updated after the plant increased to full capacity. This appears to be causing unstable inverter behavior and oscillations seen by the grid.

A key observation is that when we disable the PPC/loggers and turn off both active and reactive power control, the fluctuations stop immediately. This strongly suggests the issue is related to PPC control logic and configuration rather than the inverters or the grid itself.

I’d appreciate your thoughts on this.

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