Study On Power Smoothing Control Strategy Of Direct-driven Wind-power Generation System With Flywheel Energy Storage Unit

Wind power was an important way to solve the environmental pollution and thecrisis of energy. The power output of wind power system is fluctuated by wind’srandomness, intermittent characteristics and the inherent features of wind turbine whichreducing the output power quality of wind turbines. As the scale of wind powerconnection to grid, the wave power brings adverse effects on the safe and stableoperation of the network, so it was quite necessary to take reasonable control strategyand excellent equipments to improve the quality of wind turbines. On the analysis ofdirect-driven permanent magnet synchronous generator (DD-PMSG) and flywheelenergy storage system, a flywheel energy storage unit (FESU) was introduced to smooththe output active power of the PMSG system.The use of new energy storage system and flywheel energy storage unit in theapplication of wind power and PMSG is introduced. Then the working principle andrequirements of flywheel generator is proposed. On the analysis of the mathematicalmodel and control strategy of PMSG, the mode of wind machine, generator and gridside are established respectively. The entirety control strategy of PMSG is presentedaccording to various parts of the mathematical model. Maximum wind energy trackingis achieved using the generator side converter and the grid side converter is used tostable DC voltage and implement active/reactive power decoupling control. Themathematical model of FESU is established based on the analysis of DD-PMSG withflywheel energy storage system, then the control strategy of normal state and theflywheel motor speed out of limit is proposed. The simulation results show that thecontrol strategy is effective.In order to solve the drawbacks of the traditional control strategy, the controlstrategy based on the average power and the grid side active power filter is proposed tosmooth output active power fluctuations. By the simulation on a PMSG system with aFESU which compared with PMSG without storage system, the results showed thatwhile the goal of maximal wind energy capture was achieved, the proposed controlstrategy could effectively reduce the output active power fluctuations. The small signalmodel of the whole system was built up for the stability analysis of the control systembased on grid side active power filter, which showed that the whole system could keepstable under the small disturbance conditions. Some theoretical references for the design of active power smoothing controlstrategy of direct-driven permanent magnet synchronous wind-power generation systemwith energy storage unit is provided and the foundation for industry applications laid bythe research work of this paper.