Design and Implementation of a Resonant Controller to Balance the Capacitor Voltage on a HVDC Terminal Based on MMC

Abstract

In recent years, the High Voltage Direct Current (HVDC) based on a Modular Multilevel Converter (MMC) has become an attractive solution for the integration of Renewable Energy Sources (RES), especially wind energy, located at long distances from consumption centers. The operation of MMC terminal needs to accomplish stability in the main parameters of the electrical grid, such as voltage, phase, and frequency. To maintain these parameters in their typical values, the MMC needs to control the circulating currents, each voltage in the capacitor of the submodules, output current, and output voltage. This paper proposes a control scheme for a leg of the MMC to make the balance of the Submodule Voltage Capacitor (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SM</inf> ). The proposed control scheme includes a Proportional Integral Resonant (PIR) Controller, which uses a Band-pass filter (BPF) to make the selective attenuation of undesired harmonic components. The control scheme is validated in Hardware in the Loop dSPACE and a scale-down MMC prototype. Results show that the resonant controller controls the output voltage and capacitor’s voltage in each submodule during normal operation. A comparison of time-domain simulations and experimental results is made in this paper. Analytical results show that the output voltage is a sinusoidal waveform rated at 150 V and 60 Hz, and the submodules’ balance is achieved.