Control method of pulse-width modulation (PWM) rectifier and static synchronous compensator combined operation system

Abstract

The invention discloses a pulse-width modulation (PWM) rectifier and static synchronous compensator combined operation system and a control method thereof. The PWM rectifier and static synchronous compensator combined operation system is formed by a plurality of PWM rectifiers, a static synchronous compensator and an upper computer monitoring platform. Each PWM rectifier is formed by a three-phase bridge type inverter circuit, a connecting reactor, a direct current side capacitor, direct current side load and a controller. The static synchronous compensator is formed by a three-phase bridge type inverter circuit, a connecting reactor, a direct current side capacitor and a controller. On the condition that three-phase network voltage is unbalanced, the PWM rectifiers input negative-sequence current to restrain double frequency existing in direct current side voltage to fluctuate. The static synchronous compensator inputs negative-sequence current opposite to the negative-sequence current inputted by the PWM rectifiers and ensures three-phase equilibrium of grid-side current. The PWM rectifier and static synchronous compensator combined operation system can restrain the double frequency in the direct current side voltage of the PWM rectifiers to fluctuate and can also maintain the three-phase equilibrium of the grid-side current on the condition that three-phase network voltage is unbalanced.

Description

technical field [0001] The invention relates to a combined operation system of a PWM rectifier and a static synchronous compensator and a control method thereof. Background technique [0002] Affected by unbalanced loads and three-phase grid faults, the voltage of the three-phase grid is often in an unbalanced state. In order to enable the three-phase PWM rectifier to operate normally under the unbalanced state of the three-phase grid voltage, many scholars have done research on the control strategy of the PWM rectifier under the unbalanced voltage condition. According to the different control objectives, the control strategy of PWM rectifier under the condition of unbalanced voltage is divided into two categories: the first type of control strategy is to maintain the three-phase balance of the input current of PWM rectifier as the control objective, and it is necessary to make the output voltage of PWM rectifier contain the three-phase The negative-sequence voltage compone...

AI Technical Summary

Problems solved by technology

However, when multiple PWM rectifiers are connected in parallel, the power quality problem generated by the PWM rectifier cannot be ignored. A large amount of negative sequence current flows into the three-phase power grid, which will increase the loss of the distribution network and threaten the normal operation of other equipment in the distribution network.

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