Modeling and control of a five-level Diode-Clamped Converter based StatCom

This paper presents a state model of a three-phase, four-wire five-level diode-clamped converter (DCC) employed in a Static Compensator (StatCom) for medium power applications. Two auxiliary circuits are used to equalize the voltages across the DC-bus capacitors. A detailed controller design procedure is presented. The proposed controller is composed of a DC-link voltage sub-controller to keep the DC-bus voltage constant, a Terminal voltage sub-controller to maintain the StatCom output voltage closed to a predefined value, a Neutral-point subcontroller to stabilize the neutral point and two Auxiliary subcontrollers to equalize the voltage across the capacitors. The StatCom controller is validated in simulation and results show the effectiveness of the proposed balancing method. The static compensator is capable of regulating its terminal voltage with a controllable droop characteristic.