Chopper Controller Based DC Voltage Control Strategy for Cascaded Multilevel STATCOM

Abstract

-The superiority of CMI (Cascaded Multilevel Inverter) is unparalleled in high power and high voltage STATCOM (Static Synchronous Compensator). However, the parameters and operating conditions of each individual power unit composing the cascaded STATCOM differ from unit to unit, causing unit voltage disequilibrium on the DC side. This phenomenon seriously impairs the operation performance of STATCOM, and thus maintaining the DC voltage balance and stability becomes critical for cascaded STATCOM. This paper analyzes the case of voltage disequilibrium, combines the operation characteristics of the cascaded STATCOM, and proposes a new DC voltage control scheme with the advantages of good control performance and stability. This hierarchical control method uses software to achieve the total active power control and also uses chopper controllers to enable that the imbalance power can flow among the capacitors in order to keep DC capacitor voltages balance. The operating principle of the chopper controllers is analyzed and the implementation is presented. The major advantages of the proposed control strategy are that the number of PI regulators has been decreased remarkably and accordingly the blindness of system design and debugging also reduces obviously. The simulation reveals that the proposed control scheme can achieve the satisfactory control goals.

Coordination control of positive and negative sequence voltages of cascaded H‐bridge STATCOM operating under imbalanced grid voltage

“…The three‐phase cascaded STATCOM comprise of cascaded multilevel inverter (CMI) in series with a linking inductor L μ ( μ = a , b , c ) [22–24], as illustrated in Fig. 1.…”

“…The typical current decoupling feedback control shown in Fig. 2, which is well designed for the three‐phase balanced system [23–25], is selected as the basic control frame of the developed coordination control strategy here.…”

A Novel Single-Phase Reactive Current Detection Algorithm Based on Fast Orthogonal Signal Generator and Enhanced Moving Average Filter

“…Equation (22) is the necessary and sufficient condition that an EMAF can eliminate the nth harmonic. In (23), the window length L EMAF is the lowest common multiple of the window length of corresponding MAF blocks.…”

“…The current reference contains the detected reactive current i q and the active current i p given by the DC voltage control. The equivalent DC-side voltage U CMI yields [22]:…”

Frequency Trajectory Planning Based VSC Control Strategy for Power System Frequency Regulation

“…significantly affects the frequency control performance. Current FR strategies exploit the energy from DC capacitors of VSCs [16], rotors of motors and turbines [17], PV and wind generations with operating reserves [18], grid loads with demand response, and energy storage devices [19] including batteries, supercapacitors, flywheels, etc. These energy sources for FR service are extremely limited or costly.…”