A Method for Suppressing Zero Crossing Distortion of Line Current of Unidirectional Three-phase Star-connected Controlled Rectifier

Abstract

The invention provides a control method for suppressing zero-crossing distortion of a line current of a three-phase star-connected controllable rectifier with one-way flow of all energy. The method comprises: step one, according to conditions met by midpoint voltages uAN, uBN, uCN between the input terminal connected to an inductor of a three-phase rectifier circuit and a three-phase power sourcein a non-distortion state of a three-phase input current, corresponding given value u*AN, u*BN, u*CN are provided; step two, on the basis of determination conditions, whether a certain phase of inputcurrent enters a zero-crossing distortion zone is determined; step three, if all phases of input currents work in a normal working zone, give values u*AO, u*BO, u*CO of input terminal voltages of thethree-phase star-connected rectifier are equal to the u*AN, u*BN, u*CN; and step four, if a certain phase of input current isK enters the zero-crossing distortion zone and K is equal to A, B, and C, acorresponding phase of rectifier bridge input terminal voltage uKO of the current becomes zero and given values of another two phases of rectifier bridge input terminal voltages are corrected, wherein u*HO=u*HN-u*KN, the H is equal to A, B, and C, and H is not equal to K, and fundamental components of the other two phases of rectifier bridge input terminal voltages change with a new given value.Therefore, the zero-crossing distortion of the input current of the three-phase star-connected controllable rectifier is suppressed.

Description

technical field [0001] The invention belongs to the research fields of power electronics technology, new energy power generation and smart grid, and in particular relates to the suppression of zero-crossing distortion of input current of a three-phase star-connected controllable rectifier with unidirectional energy flow. Background technique [0002] In quite a lot of practical industrial applications, electric energy does not need to be transmitted in two directions, such as fan, pump motor energy-saving speed control power supply, communication power supply, power closing power supply, electric vehicle charging power supply, etc. Therefore, in recent years, controllable rectifiers with unidirectional energy flow have received extensive attention in the field of power electronics technology. Compared with the controllable converter with bidirectional energy flow, the rectifier with unidirectional energy flow can use fewer fully-controlled devices, has a relatively simple co...

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Problems solved by technology

[0003] However, in many controllable rectifiers with unidirectional energy flow, whether it is a single-phase circuit (such as a single-phase bridgeless rectifier and its cascaded circuit), or a three-phase circuit (such as a three-phase VIENNA rectifier, a three-phase star-connected bridgeless Rectifiers and all star-connected cascaded three-phase controllable rectifier topologies), due to the existence of input side inductance, essentially cannot achieve true unity power factor operation, and the inductor current can only lag the power supply voltage at a suitable angle (the Angle depends on the inductance value and the magnitude of the load current), it can run in a sinusoidal waveform, so when the current is running with leading power factor, lagging power factor (the lagging angle is not equal to the lagging angle of the original sinusoidal current) or unity power factor, the current is at Distortion will occur near the zero crossing point. For the above problems, there is currently no effective solution

Therefore, the harmonic pollution of the power grid, the decline of system stability and the reduction of operating efficiency have seriously restricted the development and application of controllable rectifiers with one-way energy flow, and the current distortion problem is in the one-way flow of energy. It is especially prominent in three-phase controllable rectifiers, because the zero-crossing distortion of each phase current will cause the corresponding distortion of the other two phase currents at the same time, thus multiplying the damage of current distortion

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