Direct power control method for current negative sequence component restraining under network unbalance

Abstract

The invention discloses a direct power control method for current negative sequence component restraining under network unbalance. The direct power control method comprises the steps that three-phase voltage and three-phase current of a transformer are detected and transformed into a two-phase static coordinate system, T / 4 delay positive-negative sequence decomposition is carried out on two-phase static voltage and two-phase static current, active power and reactive power of a system are calculated, and the active power and the reactive power are predicted; compensation power in the two-phase static coordinate system is calculated when negative-sequence current needs to be zero, the negative-sequence current is made to be zero, and given active power and reactive power of the system are calculated; a conditional function is set up, an SVPWM positive-sequence voltage component is solved, an SVPWM negative-sequence voltage vector is determined, and an SVPWM voltage vector is output to a PWM rectifier. The direct power control method has the advantages that during a network unbalance fault, it can be guaranteed that the system is stable, response speed is high, design of a power filter is facilitated, the requirement for system sampling frequency is not high, and high robustness and good adaptability are achieved.

Description

technical field [0001] The invention relates to a grid power control method, in particular to a direct power control method for current negative sequence component suppression under unbalanced grid conditions. Background technique [0002] In the case of small-value grid voltage unbalance, when the DC side voltage bus stability is taken as the control target, the negative sequence component of the current will inevitably be generated, which will cause the unbalance of the grid-connected current. The current contains a large number of negative sequence components. If the transmission line operates under such working conditions for a long time, it will cause various protections with negative sequence components as the starting elements to malfunction, directly threatening the operation of the power grid; for generators and transformers, when When the three-phase load is unbalanced, if the maximum phase current is controlled to be the rated value, the other two phases will not ...

AI Technical Summary

Problems solved by technology

The current contains a large number of negative sequence components. If the transmission line operates under such working conditions for a long time, it will cause various protections with negative sequence components as starting elements to malfunction, directly threatening the operation of the power grid; for generators and transformers, when When the three-phase load is unbalanced, if the maximum phase current is controlled to be the rated value, the other two phases will not be fully loaded, so the utilization rate of the equipment will decrease. On the contrary, if the rated capacity is to be maintained, the one phase with the larger load will be overloaded, and There will also be waveform distortion caused by unbalanced magnetic circuit, and additional loss of equipment will increase.

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