Controlling And Switching Strategy Research Of Bidirectional Rectifier-inverter

With the continuous development of micro-grid, bidirectional rectifier-inverter which can possess the bi-direction flowing ability of energy, and switch freely between rectifier state and inverter state was widely applied. Based on the current-controlling, a series of studies to the control method and switching methods of bidirectional rectifier-inverter was conducted, from the analysis of dynamic response and stability.First, under the purpose of achieving bi-direction flowing ability of energy, the dq model of bidirectional rectifier-inverter was set up in the dq synchronous rotating coordinate system, and a SVPWM modulation wave generating method was proposed.Secondly, a detailed study was conducted to current control methods, and the double-loop control method was used for the designing of the corresponding rings.Focused on the ramp response of the inner slope transfer function, the references between inner slope performance indexes and filer inductance, PI controller parameters were obtained, which provide the basis to improve filer inductor and PI controller. In addition, the stability of the designed current loop and voltage loop was verified from the perspective of the frequency domain analysis.Then combined the voltage current characteristics of bidirectional rectifier-inverter with double-loop control method, two dual mode switching methods were put forward: “Variable DC source switching method” and “Variable power switching method”, and a MATLAB model for simulation and verification was built.Simulation waveforms show that both two dual mode switching methods can achieve bidirectional rectifier-inverter mode-switching control, but the length of time each method taken to finish the switching process and the smoothness of each switchover process were different.Finally, as the TMS320F2812 was used as main chip, an experimental platform was built for the verification test. Rectifier state and inverter state two working modes of the bidirectional rectifier-inverter were experimentally tested, and the “Variable DC source switching method” was simulation verified. All the testing results showed that the bidirectional rectifier-inverter can work at unity power factor in both rectifier mode and inverter mode and possess the bi-direction flowing ability of energy, at the same time, the harmonic content of the AC phase current can be less than 1.3%. Thesimulation result showed that the “Variable DC source switching method” can effectively achieve the switching between rectifier state and inverter state of the bidirectional rectifier-inverter.