Single-phase PWM rectifier direct current control design

Overview:

Through the control idea of ​​single-phase PWM rectifier, several control strategies of direct current control of single-phase PWM rectifier are analyzed and summarized. The working principle, advantages and disadvantages of each strategy are analyzed, and the single-phase PWM rectifier is summarized and prospected. The development trend of direct current control technology. 1. Introduction With the development of power electronics technology, the application of power electronic equipment has become more and more widespread, causing a large number of non-linear loads to flow into the power grid, bringing more and more serious harmonic pollution to the voltage and current of the power system. . The PWM rectifier improves the power factor of the system and reduces the harmonic pollution to the power grid, which has received people's attention. According to the input inductor current state, the PWM rectifier can be divided into current interrupted operation mode (DCM) and current continuous operation mode (CCM). Since CCM mode has small input and output current ripple, easy filtering, small device conduction loss, suitable for large The advantages of power occasions have gained more attention. In the CCM mode, depending on whether the transient inductor current is directly selected as the feedback amount, it can be divided into direct current control and indirect current control. The indirect current control structure is simple and does not require a current sensor, but its biggest disadvantage is that the current dynamic response is slow, and even the AC side current contains a DC component, and is sensitive to system parameter fluctuations. Compared with indirect current control, direct current control uses the input current of the rectifier as feedback and controlled quantity to form a current closed-loop control, which improves the current dynamic and static performance, and also makes the grid side current control insensitive to system parameters. The robustness of the current control system is enhanced. Therefore, direct current control technology has a very broad application prospect and use value. 2. Single-Phase Voltage PWM Rectifier Block Diagram The topology of the single-phase voltage-type PWM rectifier is shown in Figure 1. It consists of three parts: AC loop, power switch bridge, and DC loop. The AC circuit includes an AC electromotive force UN, a grid side resistor RN, and a grid side inductor LN. The DC loop includes a series resonant circuit composed of an inductor L2 and a capacitor C2 for filtering the second harmonic component of the power grid, the filter capacitor Cd, and the load. RL, etc.; the power switch bridge is composed of four anti-parallel diode IGBTs. The control idea of ​​the single-phase PWM inverter is to keep the current and voltage on the AC side as in phase as possible while ensuring the stability of the DC side voltage, so that the power factor of the AC side is 1. (For details, please read PDF document)