Current source type rectifier and grid-connected control method based on virtual resistor

Abstract

The invention discloses a current source type PWM (Pulse-Width Modulation) rectifier and a grid-connected control method based on a virtual resistor. A grid-connected rectifier consists of commercial power, an alternating-current filtering inductor, an alternating-current filtering capacitor, a three-phase current source type rectifier, a direct-current inductor, a direct-current capacitor and a digital controller. Sampled alternating-current filtering capacitance voltage is transmitted to a microprocessor to perform digital phase locking, and after phase locking is finished, the alternating-current filtering capacitance voltage and phase are transmitted to an alternating-current controller. The alternating-current controller consists of a coordinate converter, a virtual impedance regulator and a divider. The coordinate converter converts the three-phase alternating-current filtering capacitance voltage into the voltage under a two-phase static coordinate system, after the voltage is regulated by the virtual resistance regulator, current passing through a virtual resistor is obtained, control amount of the alternating-current side is obtained through the divider, the control amount is superposed on the control amount on the direct-current side, a driving signal obtained through a PWM generator is transmitted to a driving plate, and after the signal is amplified by the driving plate, the connection and disconnection of a three-phase current source type rectifying bridge switch are controlled. The control effect of the virtual resistance regulator in the alternating-current controller is equivalent to the control effect that a resistor is directly connected in parallel on an alternating-current capacitor, so that oscillation can be effectively damped, loss is not caused, and ultraharmonics in grid-connected current can be effectively inhibited. The rectifier is high in dynamic response speed, stable in dynamic response and high in power factor, the total harmonic distortion rate of the grid-connected current is low, and the method can be applied to an uninterruptible power supply.

Description

technical field [0001] The invention relates to a control method for stably controlling a current source rectifier and realizing a low total harmonic distortion rate of grid-connected current, belonging to the field of rectifier control methods. Background technique [0002] The traditional UPS power supply usually uses a phase-controlled rectifier, and the DC bus voltage is about 400V. However, due to its low power factor and heavy pollution to the power grid, it has been gradually replaced by high-frequency PWM rectifiers based on full-control devices. High-frequency PWM rectifiers are divided into two types: voltage source type and current source type. Among them, the DC bus voltage required by the current source type PWM rectifier is lower than the peak-to-peak voltage of the AC side voltage. Therefore, when the DC bus voltage is about 400V, use the current source The type PWM converter can complete the upgrading of UPS at a lower cost under the premise of maintaining t...

AI Technical Summary

Problems solved by technology

[0003] Since the AC side of the current source rectifier uses inductance and capacitance filtering, it is easy to generate resonance on the AC side, which affects the waveform of the grid-connected current and may cause shutdown

Compared with the voltage source rectifier, the transient model of the current source rectifier has high order, strong coupling, and has nonlinear characteristics. It is difficult to use the direct current control and indirect current control of the voltage source rectifier in the current source rectifier. direct application

The nonlinear control method solves the problem of strong nonlinear coupling of the current source rectifier in theory. The AC side can be damped through closed-loop control, but the control performance is highly dependent on the system parameters and is sensitive to parameter changes. achieve complex

[0004] In theory, connecting a resistor in parallel with the AC filter capacitor is the simplest and most effective way to suppress oscillation, but it cannot be practically applied because the resistor will generate power consumption

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