Model Predictive Power Control Strategies For Single-Phase PWM Rectifiers

As an important part of power electronic devices for energy conversion, single-phase PWM rectifiers have widely used in railway, power system, and energy conversion due to these advantages:low current harmonic, unity power factor and bidirectional power flow. With the development of power electronics technology and devices, the single-phase rectifiers require faster dynamic response and better harmonic resistance to satisfy the improvement of power quality requirements. Therefore, it is significant and important in theoretical research and practical engineering application that this paper focuses on the control algorithms of single-phase PWM rectifier.In order to obtain faster dynamic response, reduce the line current total harmonic distortion (THD), and keep constant switching frequency for single-phase PWM rectifiers, this paper focuses on the research of control algorithm optimizations, the circuit parameter sensitivity analysis, and the inductance parameters on-line identifications. Specific contents are shown as follows:Firstly, the mathematical model of single-phase PWM rectifiers is established. And various construction schemes for the rotating vectors of the main voltage and line current are compared and discussed to estimate single-phase instantaneous power. Combing with the single-phase instantaneous power theory, two classical predictive power control schemes are discussed.Secondly, in order to improve the disadvantage of variable switching frequency in traditional predictive power control scheme, based on the effective combination of an active vector and a zero vector in each control horizon, a model predictive power control algorithm with constant switching frequency is proposed, which can improve the control precision of the adopted rectifiers. In order to reduce the huge calculation consumption and complexity of the algorithm, a model predictive direct power control (MP-DPC) algorithm with power error minimization is proposed. A cost function with respect to power errors is described, and the optimal modulation function is deuced from minimizing the cost function. Then, PWM signals are generated by constant frequency modulation algorithm.Meanwhile, a computer simulation comparison of the proposed MP-DPC and traditional DPC schemes verifies the effectiveness and correctness of the proposed scheme.Thirdly, as the fact that the predictive power control algorithms are sensitive to circuit model parameter mismatches, the impacts on system power factor, active and reactive powers of model parameter mismatch are analyzed in this paper. Theoretical analysis shows that the inductance parameter mismatch will reduce power factor, increase the reactive power. And there is no effect on the active power. On basis of this, a inductance parameter on-line identification method based on steady-state power deviation is proposed.the proposed identification method is verified and tested by computer simulation. Simulation results show that the proposed method can identify the inductance parameter, effectively. As a result, the proposed MP-DPC with inductance identification method is not sensitive to the inductance value.Finally, a single-phase PWM rectifier experimental platform with TMS320F2812 controller is designed. The hardware and software design solution is shown. An experimental comparison of the proposed MP-DPC, traditional instantaneous current control, and finite-control-set DPC schemes is adopted. The experimental results verify the feasibility and effectiveness of the proposed MP-DPC scheme and the inductance identification method.