Inverter power current limiting method after short circuit fault of distribution network

Abstract

The invention provides an inverter power current limiting method after a short circuit fault of a distribution network. The method comprises the steps of setting a current limiting device comprising a current limiting mode selector, a controller and a PWM (Pulse Width Modulation) generator in the distribution network, acquiring voltage and current information of the distribution network, performing normal control on inverter power output current by the controller via the PWM generator, acquiring the inverter power output current, performing comparative judgment on whether the inverter power output current exceeds the limit, correspondingly determining to adopt PWM current limitation and / or controller current limitation according to the judgment result, and the like. A new method is provided for inverter power current limitation after the short circuit fault of the distribution network, and the method can effectively limit the instantaneous shock current value and the steady-state current value after the short circuit fault of the distribution network, thereby preventing line protection misoperation on the distribution network and ensuring the safety of an inverter power supply and relevant equipment.

Description

technical field [0001] The invention relates to a current protection method after a fault in a distribution network containing a photovoltaic power source, in particular to a current limiting method for an inverter power supply after a short circuit fault in a distribution network. Background technique [0002] At present, solar photovoltaic power generation is developing rapidly, and photovoltaic power generation has been widely used in traditional power grids. The most common grid-connected photovoltaic power supply is the inverter power supply with inverter (inverter power supply for short). When a short-circuit fault occurs in the distribution network containing distributed inverter power supply, in order to avoid burning out the inverter Inverter power supply, it is necessary to take protective measures such as current limiting for the inverter power supply. At present, in addition to the method of connecting the fault current limiter in series on the AC side of the di...

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Problems solved by technology

The controller has a good limiting effect on the steady-state current value after a fault. Its shortcoming is that, because the controller needs to go through the steps of measurement, conversion, and control in the process of implementing the control, it needs a certain start-up time, so it makes it It cannot act quickly when a fault occurs, and cannot play a good role in limiting the inrush current value at the moment of a short-circuit fault.

[0004] Second, PWM blocking current limiting is adopted, which takes the output current of the inverter power supply as the criterion. When the amplitude of a certain phase current exceeds the preset value, the inverter device IGBT of the upper and lower bridge arm commutation devices corresponding to the phase current Send out a blocking signal to turn off the corresponding switching device, and the output is zero. Although the PWM blocking current limiting method is simple and fast, it can solve the problem that the controller cannot respond to the impact current value at the moment of a short circuit fault. However, the current limiting method using PWM blocking current limiting is relatively extensive, which is not conducive to the steady-state operation of the inverter power supply.

Moreover, the line protection of the distribution network needs to collect relevant electrical information after the fault to take corresponding positioning and isolation protection measures for the fault point. In order to meet the needs of line relay protection, the inverter power supply cannot be completely blocked

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