Implementation of Active and Reactive Power Control in a Novel Solar Power Plant Controller Solution

The increasing penetration of variable renewable energy resources connected to the distribution grid creates a number of challenges for system operators and utilities, in particular in the areas of voltage and frequency management. In order to mitigate some of these challenges, regulators have introduced grid codes that impose some level of controllability on the power output of renewable energy plants. In this paper, the authors present a power plant controller solution designed to meet the active and reactive power control grid code requirements for PV plants in India. The control solution coordinates the real-time active and reactive power output of the plant inverters to meet aggregate target values measured at the plant's point of interconnection with the grid. After presenting the overall solution architecture, the authors detail the different control modes that were implemented (direct active/reactive power control, droop-based control based on frequency or voltage) and how operational constraints such as inverter availability, inverter thermal limits, permissible grid frequency and power plant voltage were accounted for. The performance of the control algorithm is presented and discussed based on offline simulation results. The performance of the overall solution where the algorithms are embedded in a real-time runtime environment is also evaluated. To assess the solution performance, real-time hardware-in-the-loop (HIL) tests are performed and presented. The overall results are discussed, and future enhancements are proposed.