Current separation compensation-based cascaded H-bridge distribution static synchronous compensator (DSTATCOM) device and separation compensation method

Abstract

The invention provides a current separation compensation-based cascaded H-bridge distribution static synchronous compensator (DSTATCOM) device. The device is characterized by comprising cascade structures of three phases of power units, wherein the cascade structures of the three phases of power units are connected by adopting Y-shaped structures so as to realize the split-phase decoupling control of three phases of currents; each power unit adopts a converter structure of alternating current (AC)-direct current (DC)-alternating current (AC); each power unit comprises a four-quadrant rectifier, a DC capacitor and an H-bridge inverter, wherein the left side of the DC capacitor C is provided with the four-quadrant rectifier which is connected with an AC electric network through a multi-winding transformer in an isolation way; the four-quadrant rectifier is combined with the DC capacitor C to play the role of a DC regulated power supply and fulfill the aim of performing balancing control on the DC voltage of each power unit; the four-quadrant rectifier provides part or all fundamental wave positive-sequence reactive compensation current; the right side of the DC capacitor C is provided with the H-bridge inverter; the H-bridge inverters are cascaded and then are connected with the electric network through reactors Ls; the H-bridge inverters only take a negative-sequence, harmonic or part reactive compensation task; and when the device compensates a negative-sequence current, the four-quadrant rectifier provides two-way active energy flow channels for the H-bridge inverters.

Description

technical field [0001] The present invention relates to a cascaded H-bridge type DSTATCOM device based on current separation compensation, especially for the topological structure and Current compensation control method. Background technique [0002] Cascaded H-bridge multilevel converters are widely used in high-power converters such as DSTATCOM due to their simple structure, easy modular design, switch load balance and low output voltage harmonics. However, this structure has the problem of unbalanced capacitor voltage on the DC side caused by the difference in the capacitance energy of each power unit and the loss of the power unit itself, which seriously affects the quality of the output waveform of the device. For this reason, people have developed many DC side capacitor voltage equalization control schemes, among which the external energy exchange method is widely used in practical engineering because of its advantages of simple and independent algorithm, fast respons...

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Problems solved by technology

In this way, on the one hand, the complexity of device selection will be increased due to capacity differences; on the other hand, the price of switching devices usually increases exponentially with the increase in capacity

In addition, for the fundamental positive-sequence reactive power compensation current, when the current flows through the H-bridge inverter, it will cause 2 pulses of energy on the DC side

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