Open loop and closed loop control schemes for capacitor voltage equalization in DSTATCOM application

DSTATCOM is widely used custom power device for shunt connected applications. DSTATCOM with split capacitor voltage source inverter (VSI) is popularly used topology for load compensation. Using hysteresis control currents in the system are made to track the reference currents, generated by instantaneous symmetrical component theory. The split capacitor inverter topology suffers from a major problem of capacitor voltage imbalance, which degrades the tracking performance, resulting into improper compensation of source currents. Thus to observe complete compensation effect, it is important to maintain voltages of both capacitors at their respective reference values. This paper suggests two methods, open loop and close loop balancing, with the use of two quadrant chopper as a auxiliary circuit. These methods are studied in details and their comparative analysis is also shown. The effectiveness of both the schemes is verified using MATLAB simulation environment.