Research On Second Harmonic Problem Of Single - Phase Voltage Source PWM Rectifier

With the continuous development of economy and the gradual improvement of the level of power switch device, more and more automation equipment is used for the industrial production, In actual operation, there are many dc source as the power supply equipment, PWM rectifier technology is widely used at present for high power factor, less input current harmonic, reversible and excellent performance of energy. So it is currently widely used in areas such as new energy power generation and ac drive.The mathematical model of single-phase voltage source PWM rectifier and the cause of dc voltage pulse are introduced in this thesis, in order to guarantee the single-phase PWM rectifier dc side voltage stability and the ac side work in the unit power factor, the existing power decoupling control strategy under the dq coordinate transformation is analyzed at first. The second harmonic at ac side is not considered when the PWM rectifier works under the control of dq coordinate transformation, so there is error in control link. To deal with it, according to the relationship of the energy, the voltage and current loops of nonlinear control algorithm are designed respectively based on Lyapunov energy function, mean filter is developed for the AD sampling; also space vector pulse width modulation PWM and dead zone compensation are used to improve the precision of the control algorithm.The method of active filtering is also studied in this thesis. LC resonant circuit is added in DC side in Traditional solution. By this way, second ripple of DC bus can be reduced. However, this solution also brings some problems such as lowering system’s power density, increasing power loss and shortening system’s operating time. To deal with it, a new topology in this thesis is firstly proposed which some auxiliary components such as additional power switches are added to the existing circuit. Then three harmonic compensation schemes are compared and analyzed, two of which are based on energy-storage capacitance in DC side and another is based on energy-storage capacitance in AC side. At last, different control strategies are designed respectively, so as to ensure the system running normally without distortion, also track the expected value fast at the same time, these kinds of schemes are based on PSIM9.0 circuit simulation, the correctness of the theoretical analysis is demonstrated by the simulation structure.The system of hardware and software, which the hardware circuit principle diagram and the writing of the program flow diagram, are designed at the end of the thesis, the circuits of single-phase PWM full bridge rectifier with IGBT as switches are tested, the experiment results show that the scheme can guarantee the system tracking error asymptotically converges, eventually make the system asymptotically stable. These experiment results also show the system design is correct and effective, compared with other control method; this system can be better eliminate current steady-state error, improved the dynamic response effect and get more practical value.