Research On Capacitance Voltage Control Method When Cascade Statcom Output Zero Reactive Power

With the improving of the power supply reliability and power quality requirements,dynamic reactive power compensation is a primary method of stabilizing the voltage level,Among them, the static synchronous compensator has become the hotspot of the research at home and abroad and become development trend with many advantages.Cascade STATCOM is to connect multiple H-bridge modules in series with the DC output side, which improves the voltage level and increases the capacity of the device. Due to the difference between the parameters of each H bridge, making the DC side of the capacitor voltage imbalance, a direct impact on the device output voltage and current waveform quality.Therefore, the DC-side capacitor voltage balance problem is one of the research priorities and difficulties of cascade STATCOM.This paper analyzes the causes of the unbalanced DC side voltage of the STATCOM and the commonly used solutions ,we can take voltage balance control method to maintain the DC side capacitor voltage balance according to current size when device normally issued reactive current. When the reactive current emitted by the device is zero or particularly small, that is,zero output reactive power state, using that balance control method will reduce the voltage balancing capacity for cascade STATCOM, or even lose balance control capability,Aiming at this problem, a method of injecting the third harmonic current into command current of STATCOM is proposed,The relationship between the amplitude of the third harmonic current and the adjustable maximum power is analyzed, the regulation ability is analyzed. the method of determining the minimum amplitude of the third harmonic current is given,Build simulation model in MATLAB/Simulink ,The simulation results show the feasibility of the method.This paper designs the software program of cascade STATCOM experiment platform.Compared with the traditional DC side capacitor voltage control method on this experimental platform, The experimental results show the effectiveness for the cascade STATCOM zero output reactive power injection third harmonic current to maintain voltage balance...