Research On Finite Control Set Model Predictive Control For Single-phase Cascaded H-bridge Converters

Finite Control Set Model Predictive Control(FCS-MPC)technology has the advantages of flexible control mode,good dynamic performance,strong robustness compared with the traditional PI control.It has been widely used in cascaded H-bridge(CHB)converters.Firstly,this paper describes the control methods of CHB converters(including inverters and rectifiers)at home and abroad,and reviews the current research situation of power converter model predictive control method in detail from the aspects of improving steady-state performance,reducing calculation load,eliminating weight coefficient,diagnosing switch fault and balancing switch loss.In order to solve the problem that the FCS-MPC control method of CHB converter,such as heavy burden,poor steady-state performance and the need for weighting coefficient,this paper proposes a Hierarchical FCS-MPC method and applies it to single-phase CHB rectifier.The basic principle of the proposed method is similar to space vector modulation.However,this method is a hierarchical control structure.The first layer is used to track the AC current,and the second layer is used to adjust the DC voltage.The control method has the advantages of low calculation burden,good steady-state performance and no weight coefficient.Aiming at the problem of switch fault diagnosis of CHB rectifier,this paper presents a method of switch fault diagnosis based on voltage error.The first step is to locate the fault module and the second step is to locate the fault switch.The method can detect the fault switch in the shortest time without adding additional hardware.Aiming at the problem that FCS-MPC method is difficult to realize the switch loss equalization of CHB rectifier,this paper proposes an improved PI switch loss equalization method.The basic principle of the proposed method is to balance the switching loss by adjusting the DC side voltage imbalance.In addition,the proposed switch loss equalization method can effectively reduce the switch loss.Finally,the FCS-MPC method is extended to CHB photovoltaic inverter.Based on FCS-MPC method,CHB photovoltaic inverter can realize independent MPPT control and grid side current sinusoidal control with power factor of 1.