Research On High Frequency Harmonic Suppression Technology Of PWM Rectifier And Its Application

The PWM rectifier can not only realize the adjustable power factor,but also the high frequency harmonic current is easily filtered when the switching frequency is high.However,with the increase of the power level of the PWM rectifier,the switching frequency is limited by the performance of the device,which leads to the high frequency harmonics cannot be easily filtered by the inductor.It is worth systematized research.In this paper,the suppression technology of switching frequency level and high frequency harmonic of voltage source full bridge PWM rectifier is studied for medium and high-power applications.In this paper,starting from the mathematical model of SPWM pulse wave,taking two level SPWM as an example,the analytical expression is obtained by introducing two dimensional Fourier analysis tool.The highfrequency harmonic characteristics corresponding to switching frequency are analyzed,and a feasible way to suppress high-frequency harmonics and a new idea of designing main circuit filter parameters are obtained.The main work of this article is as follows.First,the design method of the conventional L rectifier is improved.In the design of main circuit,a new idea of parameter design is proposed to determine the lower limit value of the filter inductor based on the analytical expression of voltage harmonic,which can determine the upper limit of the inductance by the rectifier of the rectifier and the capacity of the DC side to determine the lower limit of the DC side capacitance.A more perfect design scheme is put forward based on the existing capacitance upper limit calculation method.The power exchange process between power supply and rectifier is also considered in the design process.In the design of controller parameters,a set of accurate design scheme for computer aided design is proposed in view of the inaccuracy and failure of the existing methods.It can save the artificial repeated calculation.After introducing the parameters of the system,the Matlab control system toolbox can be used to complete the automatic design,and the parameters can be reached without adjustment.The original scheme of parameter designing and the new one of this paper are compared and analyzed.The results show that the design process of this scheme is simpler and the results are more accurate and reasonable,so that the control effect and stability are better.The high frequency harmonic suppression technique for PWM rectifier is studied.The limitations of the traditional three phase LCL PWM Rectifier's structure,model and parameter design method are analyzed.A new type of simplified three phase LC PWM rectifier is proposed.The basic structure and model of the system are put forward,the parameters of the main circuit and control circuit are designed,and the basic control block diagram is given.On this basis,low frequency harmonic suppression and grid side voltage support additional control algorithm are proposed.The control effects of L filter +PI controller,LC filter +PI controller,LC filter +PI controller + resonant controller are studied in three modes.On the basis of the network side voltage additional control algorithm,a new design and control method of the LCL rectifier is proposed to avoid the complex model of the traditional LCL rectifier and the stability problem of its controller.The results show that the proposed scheme achieves the desired effect and has obvious suppression effect on the harmonic current on the mesh side.In this paper,the application of the new simplified LC type PWM rectifier in many fields is studied.The results show that the scheme can be applied to many fields such as distribution network converter,static var generator and APF,traction converter and so on.