Phase-splitting control method and system of star chain statcom

Abstract

The present disclosure relates to a phase-splitting control method and system of a star chain STATCOM. Among them, the method includes: calculating the neutral point voltage of the star chain static synchronous compensator based on the preset three-phase voltage modulation signal and the three-phase grid voltage; The positive and negative sequence components of the current are compensated and the load reactive power and negative sequence current are calculated; the single-phase AC current is controlled separately based on the preset resonant controller; the phase-locked loop based on the second-order generalized integrator obtains the single-phase AC voltage phase respectively; The direction of the single-phase AC output current adjusts the output voltage to realize the balance control in the phase and complete the phase-splitting control of the star chain STATCOM. The present disclosure does not need complex coordinate transformation and current decoupling control, and does not need complex calculation of zero-sequence voltage or negative-sequence voltage, and can automatically adapt to the unbalanced voltage and load conditions of the power grid, and better realize the control of each chain through phase-separated control. The equalization of the capacitor voltage of the cell.

Description

technical field [0001] The present disclosure relates to the field of power electronics, and in particular, to a phase-splitting control method and system of a star chain STATCOM. Background technique [0002] Static synchronous compensator (static synchronous compensator, STATCOM), as one of the effective means to solve the power quality of power system and power user end, is more and more widely used at present. Among them, the chain static synchronous compensator has the advantages of no need for transformers, high modularity, easy expansion, strong fault tolerance, good output waveform, wide operating range, and fast adjustment speed. It is especially suitable for reactive power compensation of medium and high voltage high power systems. According to different connection modes, there are two topologies: star and delta. Under the same voltage level, the star topology requires low phase voltage, and the number of cascaded units is small, which has certain advantages in co...

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Problems solved by technology

Under normal working conditions, the voltage feed-forward decoupling control under the dq rotating coordinate system is adopted. In order to maintain the balance of the capacitor voltage between phases, the phase-to-phase control adopts PI control to achieve phase-to-phase balance, but this method is easy to unbalance the three-phase output current; another This form of phase-to-phase control uses two-phase coordinate system transformation to calculate the zero-sequence voltage, but this control method is not suitable for unbalanced conditions

In the case of unbalanced load, the balance of capacitor voltage between phases is achieved by injecting negative sequence voltage, but this method will inject negative sequence current into the grid current; under the condition of unbalanced grid, the balance of capacitor voltage between phases is achieved by injecting zero sequence voltage , but the calculation of zero-sequence voltage is complicated; two control strategies of zero-sequence voltage and negative-sequence voltage are integrated, and switching is performed according to actual working conditions, which increases the complexity of the system

[0004] It can be seen from the above-mentioned existing technologies that the control of "voltage-oriented decoupling control + phase-to-phase control + phase-to-phase control" requires coordinate transformation, and phase-to-phase and phase-to-phase control are complex, especially under unbalanced conditions, it is necessary to inject zero-sequence voltage or Negative sequence voltage, the calculation is more complicated

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