光伏发电在实际应用中用户端的负载是不断变化的,当一台变压器下有多个用户且只有单个用户使用光伏时,如果光伏输出电流大于负载消耗时,会发生逆流现象,这种现象不利于同一变压器下各个用户之间电费的结算.为了解决这一问题,通过S7-200PLC设计一套自动切换系统,采集负载端的电流信号,根据电流变化情况通过PLC控制并网逆变器的输出负载对象,最终达到了光伏并网逆变器和负载之间的最佳匹配,消除逆流现象,便于用户之间电费的结算.此系统正式投入使用以来一直处于正常运行状态,并且达到了预期的效果.%In practical application of photovoltaic power generation,the load in the client side changes constantly. When a transformer controls multiple users and only one user is using the photovoltaic power,reversal current phenomenon may occur if the photovoltaic output current is greater than the load consumption. This phenomenon is not conductive to electricity settlement among the individual users controlled by the same transformer. To resolve this problem,an automatic switching system based on S7-200PLC is designed to collect current signals in the load side. The output load object of the grid-connected inverter is con-trolled by PLC according to current change. Finally the best match between the photovoltaic grid-connected inverter and the load is reached and the reversal current phenomenon is eliminated,which facilitates the settlement of users′ electric charge. The sys-tem has been in normal operation and has achieved the expected effect since it was put into use.
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