Research On Control Method Of Three-Phase Rectifier Based On Virtual Synchronous Machine

The virtual synchronous machine(VSM)is a kind of emerging power electronic technology that models and controls the power electronic converter according to the mathematical model of the synchronous machine.The power electronic equipment will have a certain virtual inertia and virtual damping with VSM technology,and thus shows similar characteristics of synchronous machines.Power electronic converters with virtual synchronization characteristics can independently adjust the power output to achieve friendly interaction with the grid.In order to realize the virtual synchronization function in the three-phase rectifier,the control method of the three-phase rectifier is investigated based on the virtual synchronous machine.Firstly,the theory of virtual synchronous control is demonstrated,which includes the mathematical model of synchronous generator and the equivalent method of synchronous generators and inverters.Then the mathematical model of synchronous motor is established,and the equivalent method is employed to realize the model equivalent of synchronous motors and rectifiers.Secondly,with the equivalent model of synchronous motor and rectifier,the specific control method of three-phase rectifier based on virtual synchronous machine is proposed.Effective control of output power and DC-bus voltage is achieved by controlling the virtual torque control.Thirdly,the droop control of the three-phase rectifier based on virtual synchronous machine is studied.Considering the requirements of grid frequency/voltage adjustment,the principles of active power-frequency droop and reactive power-voltage droop in inverters and rectifiers are investigated.The droop control method and a low voltage ride through control strategy are designed for the three-phase rectifier based on virtual synchronous machine.Finally,aiming at reducing the large current harmonics on the AC side of three-phase rectifier based on virtual synchronous machine,a current harmonic suppression method is proposed.The suppression of the current harmonics on the AC side of the three-phase rectifier is realized with current harmonic injection.The three-phase rectifier system is built with MATLAB/Simulimk,and 10/60kVA experimental platforms are built to verify the proposed method.The simulation and experimental results verify the rationality and effectiveness of the proposed methods.