A Control Strategy of Neutral-point Clamped Three-level Grid-connected Inverter Current Hysteresis SVPWM

According to the topology of neutral-point clamped (NPC) three-level static var generator (SVG), this paper presented a new control way about hysteresis currents with space vector pulse width modulation (SVPWM). In this method, the interphase current was taken as the control target, and a new decoupling method was obtained. In the corresponding phase command voltage region, one phase switch state was fixed first, according to the relationship between the DC side midpoint voltage and phase current. Then the other two phase switching states were controlled independently so as to control two corresponding phase current errors, and the third phase current error was also controlled. This method implemented the requirement of midpoint voltage control, high response speed and low switching losses. Experiments proved that the way has a good dynamic and static characteristics.