Resonant and Hybrid Voltage Control of an HVDC Terminal based on Modular Multilevel Converter

The Modular Multilevel Converter has become a flexible solution for the integration of renewable energy systems due to his modular design, high power capacity, and control of active and reactive power in high power applications. It is necessary to keep an adequate sub-module (SM) voltage and output voltage to ensure global stability during disturbances; in order to achieve these control goals, this paper presents a Proportional Integral Resonant (PIR) control technique and a Hybrid voltage controller based in a Band Pass Filter (BPF) in the control stage to the selective elimination of undesired harmonic components that improves the performance of the voltage capacitor in the SMs. Time-domain simulations on a 200 MW MMC terminal operating as an inverter, with seven submodules per-arm, is used to validate the controller under different operating conditions. Results show that the implementation of the PIR and Hybrid Voltage control presents good performance to control the output voltage and capacitor's voltage in each submodule during power changes. A comparison with the traditional PI approach is made in this paper to presents the advantages of the proposed method. Analytical results show that the PIR approach has a slight difference in the oscillations of the SM capacitor's voltage, around 0.42 %, whereas the PIR has around 3.5 %.