A diode-clamped cascaded H-bridge STATCOM for voltage balancing of individual capacitors

This paper firstly proposes a novel topology for static synchronous compensator (STATCOM) based on diode clamped cascaded H-bridge (DCCH) circuit. The proposed topology guarantees the voltages across each capacitor in the same phase are clamped and equal to each other through the diode-clamped circuits. The balancing process through the diode-clamped circuits is bidirectional and it is realized by diode-clamped circuits only. The amount of calculation is thus reduced and the complexity of algorithm is also lowered. The parameter of clamping inductor has a great impact on voltage balancing effect. So, this paper further proposes the parameter selection principle of inductor in diode-clamped circuit. Compared with traditional software individual voltage balancing strategy, the balancing speed of the proposed topology is improved dramatically and the balancing effect is also strengthened. Simulation and experimental results verify the parameter selection method of clamping inductor and validate the effectiveness of proposed topology in Var generation and voltage balancing of individual capacitors.