General Control Scheme for a Dual-Input Three-Level Inverter

This paper proposes a general control scheme for the dual-input three-level inverter, which comes from a neutral point clamped three-level inverter. It can be used for photovoltaic (PV) systems or battery storage systems with two dc sources. The dual-input three-level inverter can be connected with two PV arrays, which are able to realize maximum power point tracking independently. First, the dynamic model of the dual-input three-level inverter is established, which describes the relationship between the dual-input voltages and the duty cycle. After discussing the control theory of the dual-input voltages, a typical control scheme is proposed. The design of a control loop is introduced in details. Afterward, modulation and restriction of the proposed method are discussed. Finally, experiment on a 125 kW dual-input three-level PV inverter is implemented to verify the validity and feasibility of the proposed method.