LCL filtering-based circuit topology structure of high-power PWM (pulse-width modulation) rectifier

Abstract

The invention discloses an LCL filtering-based circuit topology structure of a high-power PWM (pulse-width modulation) rectifier. The circuit topology structure of the PWM rectifier comprises a single-phase PWM rectifier and a PWM rectifier adopting a three-phase and four-wire system; a better filtering effect is achieved by replacing the traditional L filter with an LCL filter; a PWM rectifier control method is based on the pulse width modulation technology of an SPWM (sinusoidal pulse width modulation) mode, and a control mode for a voltage outer loop and a current inner loop is adopted; a PI control mode is adopted by the common voltage outer loop and the independent current inner loop, and P and I parameters are respectively set for the common voltage outer loop and the independent current inner loop. According to the LCL filtering-based circuit topology structure disclosed by the invention, current and voltage cophasing at the grid side can be realized, so that the harmonic content of the grid side is reduced, and the harmonic pollution is reduced.

Description

technical field [0001] The invention belongs to the technical field of power electronics application, and relates to a circuit topology structure of a high-power PWM rectifier based on LCL filtering, and specifically relates to a distributed power supply, which is applied to renewable energy generation and grid connection, charging and discharging, and energy storage systems. power electronic rectifiers. Background technique [0002] Among all power conversion devices, the rectifier circuit appeared the earliest. Common power conversion circuits include rectifier circuits, inverter circuits, AC-AC frequency conversion circuits and DC buck-boost circuits. In addition to the equipment that directly uses the mains power, most of the power consumption equipment is obtained by corresponding DC or AC conversion of the electric energy of the grid, that is, first converting the mains power into the AC or DC power required by the power consumption equipment, Then the converted elec...

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Problems solved by technology

However, the dual boost circuit must use two inductors. The inductor is the core component of the boost circuit. The inductor has a large volume. The selection of its value determines the size of the rectifier and is also an important part of the raw material cost.

[0004] Inductors are used as magnetic components. Due to the dual Boost parallel structure, the two inductors work in the positive and negative half cycles of the power grid. It is easy to be saturated, and the change of the flowing current will not cause energy transfer, and the energy will be consumed on the coil. In the case of long time and high power, the coil winding will heat up, which will inevitably affect the accuracy of the inductance value. Therefore, the controller's Design poses serious challenges

[0005] And because the PWM rectifier adopts the PWM modulation method, the grid current contains high-order harmonics near the switching frequency, which will affect other EMI sensitive equipment in the grid. Therefore, a filter must be installed between the grid and the rectifier to suppress the current. High-frequency harmonics, while isolating the sinusoidal grid voltage and the pulse-shaped AC side voltage

The traditional PWM rectifier grid side filter uses an L-shaped filter to limit the high-order harmonic current within a certain range

Although the L-type filter is simple and practical, in high-power applications, the switching frequency is relatively low (1-2kHz), so that the inductance value required for the grid-side current to meet the corresponding harmonic standards is too large

This will bring the following problems: the rate of change of grid-side current will decrease, and the dynamic response performance of the system will be reduced

[0006] The existing three-phase PWM often adopts the connection method of three-phase three-wire system, and there is mutual coupling between the three phases, so its control often requires vector transformation to achieve three-phase decoupling, that is, transforming the three-phase abc static coordinate system to two-phase rotation The complexity of modeling and control in the dq coordinate system is self-evident, and the actual implementation is also more complicated

[0007] When the PWM rectifier is started, the grid voltage will charge the bus capacitor from zero voltage through the inductance, which may cause circuit resonance, or transient saturation of the inductance, resulting in a large inrush current, which may damage the circuit components and affect the circuit. The safe working state of the PWM rectifier poses a threat to the safety and reliability of the PWM rectifier

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