外文翻譯--三相電壓型pwm整流器建模和仿真研究-wenkub.com
2024-08-29 17:13 本頁面
【正文】 simulation Introduction Diode and phasecontrolled converters constitute the largest segment of power electronics that interface to the electric utility system today. These converter circuits are simple but the disadvantages are large distortion in line current and poor power factor. To bat these problems the PWM rectifier various power factor correction(PFC) techniques based on active wave shaping of the line current have been proposed.The PWM rectifier offers several advantages such as: control of DC bus voltage,bidirectional power flow unity power factor and sinusoidal line current. Many control techniques have been adopted for these rectification devices to improve the input power factor and shape the input current of the rectifier into sinusoidal waveform. In actual implementations the direct current control scheme is widely adopted. The conventional rectifier model is a multiinput multioutput nonlinear system. The difficulty in controlling the rectifiers is mainly due to the nonlinearity. As reported in the excellent survey traditional control strategies in the direct current control scheme establish two loops: a line current inner loop for power factor pensation and an output voltage outer loop for voltage regulation. The most uses system parameters dependent Proportional Integral (PI) regulator: for the output voltage control loop which can generate the modulation index or the amplitude of the reference current for the inner PWM input current control loops. The main task of the current inner loop is to force the currents in a threephase ac load to follow the reference signals. This paper focuses on the modeling and control of the new equation based on power balance is introduced to replace the original nonlinear equation. Then,nonlinear input transformation is applied to make the improved model linear. A simplified algorithm is proposed for space vector PWM rectifier. This algorithm avoids the lookup tables of sine or arctangent and plex calculations needed in the conventional methods by directly calculating the duty cycles of space voltage vectors which track the reference voltage vectors in each sector in the space vector.1 Modeling and Control of VSR The mathematical model of VSR in dq coordinates The main circuit diagram of the threephase voltage source rectifier structure is shown in power semiconductor switch consists of an IGBT connected in parallel with a diode. Where ua ,ub and uc are the phase voltages of three phase balanced voltage source and ia ,ib and ic are phase currents vdc is the DC output voltage R and L mean resistance and inductance of filter reactor respectively C is smoothing capacitor across the dc bus RL is the DC side load and iL is load current. The following equations describe the dynamical behavior of the boost type rectifier in Park coordinated or in dq:Where,urd=Sdvdc, urq=Sqvdc,urd,urq,and Sd,Sq are input voltage of rectifier,switch
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