Novel Control for Active Power Compensation using DSCC-MMC based ES-STATCOM

In recent years, modular multilevel converters (MMC) have gained popularity for high-power applications such as in flexible AC transmission systems (FACTS) and High Voltage DC (HVDC) applications, due to their scalability and modularity along with high efficiency in handling high-power and high voltage needs of the power grid. In the same domain of applications, one such usage of the MMC-based system is the integration of energy storage with static synchronous compensator (STATCOM) technology (known as ES-STATCOM) for providing active power compensation along with reactive power support to the grid. This paper introduces a novel dynamic model-based control approach to the MMC-based ES-STATCOM for the integration of energy sources with the power grid. The design of various controller elements is based on detailed harmonic evaluations for both dynamic and steady-state operation modes. The design of the circulating current control adds second-harmonic computation of the modulation indexes for the suppression of second-harmonic circulating current. This approach further improves the converter's performance by reducing the fluctuation in the capacitor voltages and eventually the losses. Finally, the operating range of the MMC-based ES-STATCOM system is being discussed, which lays down the operating limit for active power compensation with reactive power compensation given the priority. The functionality of the proposed control architecture is validated through a Real-Time Digital Simulator (RTDS) and Virtex 7-based FPGA controller in a Controller Hardware-in-Loop (C-HIL) environment.