Soft starting method improved based on H-bridge cascade STATCOM (Static Synchronous Compensator)

Abstract

The invention relates to a soft starting method improved based on an H-bridge cascade STATCOM (Static Synchronous Compensator). The method is characterized by comprising the main steps of: accessing a current-limiting resistor in series during starting of the STATCOM, controlling pulse signals of all unit switch devices so as to absorb active power provided by a power grid to the greatest extent, and pre-charging a device; removing the current-limiting resistor after pre-charging is completed, and forwarding the device into an idle running period; providing a voltage given value of a DC side by a voltage gradually-increasing method during idle running period; and stably increasing the voltage of the DC side into the given value; forwarding into a load running period and completing the starting process. According to the soft starting method of the device, provided by the invention, the pulse signal of all unit switch devices are controlled from a pre-charging period, harmonic distortion rate of the output current of the device during the pre-charging period is greatly reduced, and the voltage steady-state value of the DC side is also effectively improved during the pre-charging period; and the voltage given value of the DC side is provided by a voltage gradually-increasing method, so that the capacitor voltage of the DC side can be stably increased into the given value without overshoot.

Description

technical field [0001] The invention relates to an H-bridge cascaded static synchronous compensator, in particular to an improved soft start method based on the H-bridge cascaded STATCOM. Background technique [0002] The H-bridge cascaded STATCOM has the advantages of modularization and easy expansion, and has broad application prospects in the field of medium and high voltage reactive power compensation. The H-bridge cascaded STATCOM main circuit topology is as follows: figure 1 As shown, each phase of the device has n inverter units cascaded, and each inverter unit has an independent capacitor on the DC side for energy storage, providing DC voltage support for STATCOM. The STATCOM three-phase commutation chain is connected in star form, and connected to the grid through connecting reactors. figure 1 L is the connecting reactor of the device, u dc1 , u dcn are the DC side capacitor voltages of A-phase unit 1 and unit n, respectively. [0003] Soft-start technology is ...

AI Technical Summary

Problems solved by technology

After the pre-charging process is over, the output voltage and current phasor diagram when the device is transferred to no-load operation is as follows: image 3 As shown in (a), since the capacitor voltage on the DC side of the uncontrolled rectification stage is not enough to rise to a higher level, the output capacity of the device is limited when it is transferred to no-load operation. A large amount of reactive current, at this stage, the inner loop of the current will form a large inrush current, and STATCOM may start protection measures and exit operation due to this

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