Abstract:

In the off-grid power distribution system which is powered by wind power generator and uses energy storage device as power source of seawater desalination device, in order to maximize the use of wind energy and reduce the dependence of distribution system on the capacity of energy storage device, the seawater desalination device adopts the power regulation mode combined with stair-like and smooth tactics, and the energy storage device adopts V/f control. Further, the stair-like power regulation mode is implemented by dividing the load operation into conditions. The smooth power regulation mode adopts frequency converter to change the speed of motor, and uses its characteristics of soft start and reactive power output to effectively maintain the voltage stability of distribution system. Based on the control strategy above, the calculation was processed through a dynamic load model which was established in PSCAD simulation software, and analyzed combined with the load test data. The results of both simulation and experiment show that, the control strategy can achieve effective tracking of wind energy output power for seawater desalination system; finely adapt to the dynamic of wind waves; make full use of the wind generator output power; reduce the dependence on the capacity of energy storage device; and improve the stability and economy of the operation of whole system.

Key words: seawater desalination, off-grid power distribution system, energy storage device, frequency converter, constant voltage frequency ratio control