A control system and its strategy method for solving low voltage ride through

Abstract

The invention discloses a control system for overcoming the low voltage ride through. The control system comprises a photovoltaic cell array, a three-phase inverter, a power grid and a controller, the three-phase inverter comprises a power switch circuit and a filtering circuit, the power switch circuit and the filtering circuit are sequentially connected between the photovoltaic cell array and the power grid in series, and the signal input end of the controller is respectively and electrically connected with the output end of the photovoltaic cell array, the output end of the power switch circuit and the output end of the filtering circuit to collect current or voltage signals. The signal output end of the controller is electrically connected with the switch tube signal end of the power switch circuit to conduct repetitive control, PI adjustment and net side voltage front feed on the collected current or voltage signals to output pulse width modulation signals for controlling communication of a switch tube, the current can smoothly pass through the photovoltaic inverter when low voltage (including zero voltage) faults of the power grid occur, and the synchronization current is output to the maximum degree.

Description

technical field [0001] The invention relates to a photovoltaic power generation system, in particular to a control system and a strategy method for solving low-voltage ride-through. Background technique [0002] When single-phase, two-phase, or three-phase faults occur on the grid-side voltage of the photovoltaic power station for some reason, the grid-side voltage of the inverter will drop to varying degrees. According to the requirements of relevant specification documents, each inverter needs to be able to pass through this fault area within a certain period of time. The current common control method is: the photovoltaic inverter is controlled by software. The implementation scheme is often to adopt a double-loop control strategy under the positive and negative sequence rotating coordinate system to smooth the output current as much as possible. The existing positive and negative sequence double-loop control strategy has strict requirements on the judgment and response ...

AI Technical Summary

Problems solved by technology

The existing positive and negative sequence double-loop control strategy has strict requirements on the judgment and response of power grid faults; due to the addition of a 100Hz filter in the control strategy, the control lag is caused; there will be a relatively large impact on the product at the moment of power grid drop and recovery. Spikes, especially at high power, seriously affect the life of product components, and the reliability is not high; the requirements for control technology are very high; during the fault period, the output current needs to be derated; abc / dq coordinate transformation is required ( The three-phase static symmetrical coordinate system is transformed into a two-phase synchronous rotating coordinate system), the calculation method is cumbersome, and the DSP implementation takes up a lot of memory, etc.

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