An introduction to the project

Yanfeng Automobile Ornament System Co., Ltd was established on September 21,1994. The business scope of the company includes development and production of the plastic products and ornamental products used on the automobiles, trucks and motorcycles, as well as the dies, stampings and standard fasteners; distribution of the products manufactured by the company itself. It is a group corporation and has more than 100 factories in China. The photovoltaic new energy has basically covered,almost all the factories. Among the photovoltaic power generation systems, most are connected to the grid on the 0.4kv side and on the 10kv side. The company has adopted the grid connecting mode in which the electricity which has been generated by the hotovoltaic power generation system is mainly for use by the company itself and surplus electricity will be transmitted to the grid.

 

The existing project of the company has adopted distributed photovoltaic power generation system and follows the rule that the electricity which has been generated by the photovoltaic power generation system is mainly for use by the company itself and surplus electricity will be transmitted to the grid. The distributed photovoltaic power generation system is connected to the grid on the low voltage side and has completed combined with the power grid system. According to the feedback of Yanfeng Automobile Ornament System Co., Ltd, the power factor of the company has maintained stable at 0.90-0.92 when the photovoltaic power generation system is not connected to the grid, and the system is stable; after the photovoltaic power generation system has been connected to the grid, the power factor of the system is changed and the rate of change is quick, and there is not any regular rule related to these changes. The reactive power compensation capacitor cabinet keeps performing frequent switching on and switching off. In addition, the photovoltaic power generation system which has been connected to the grid is easy to generate capacitive reactive power. As the result, overcompensation has been carried out for the power factor of the system and the power factor to become too advanced, leading to the failure of the power factor controller to work normally. There are mainly the following reasons:

 

The distributed photovoltaic generator set is connected to the grid on the low voltage side.

There are three main working states when the photovoltaic poer generation system has connected to the grid: ① The amount of electricity generated by the photovoltaic power generation system < the amount of electricity which has been consumed by the production equipment; ② The amount of electricity generated by the photovoltaic power generation system = the amount of electricity which has been consumed by the production equipment; ③ The amount of electricity generated by the photovoltaic power generation system > the amount of electricity which has been consumed by the production equipment. As to the above three states.

 

When the photovoltaic power is not connected to the grid or he amount of electricity generated by the photovoltaic power generation system < the amount of electricity which has been consumed by the production equipment, the whole system is under the inductive load and the electricity from the municipal grid is used, the power factor of the system will be normal, the traditional reactive power compensation capacitor cabinet controller can work normally, and the power factor in the system will be maintained in the range of 0.89 - 0.92.

 

After the the photovoltaic power power generation system is not connected to the grid or he amount of electricity generated by the photovoltaic power generation system = the amount of electricity which has been consumed by the production equipment, there is less active power in the system, the system is in a critical state, the system active power is less, the system power factor decreases sharply and the power factor is in the critical state. The traditional reactive power compensation capacitor cabinet controller will performing switching on and switching off frequently, resulting in the oscillated switching operations of the system.

 

After the the photovoltaic power generation system is not connected to the grid or he amount of electricity generated by the photovoltaic power generation system ＞ the amount of electricity which has been consumed by the production equipment, the system is in the state where the active power is returned into the system and the multiple function table of the incoming cabinet is in the state where “-" value are displayed. Therefore, the traditional reactive power compensation capacitor cabinet controller judges that the system is in the capacitive state, the power factor is too much advanced. This indicates that the system is in the stat of overcompensation, so the controller can not perform the normal switching on and switching off operations. 

 

In the above three working states of the photovoltaic power generation system, the reactive power required for normal use of the production equipment is necessary and fixed.