Research On Speed Control And Power Control Of Hydraulic Type Wind Turbine

In recent years, the world has been seeing a significant development in wind powerindustry, which plays an increasingly important role in solving energy and environmentcrisis. Compared with the DFIG (Doubly Fed Induction Generator) and Direct-DrivenGenerator, hydraulic wind generating unit, with a higher power-to-weight ratio, is capableof not using the doubly-fed gear box and avoids using the huge direct-driven permanentmagnet generator. Besides, the real-time adjustment to the speed ratio of hydraulic drivesystem makes it possible to use excitation synchronous generator, without therectifier-inverter device. For these reasons, studying on the hydraulic wind generator haspositively theoretical and realistic significances.The power transmission system of hydraulic wind generator, as the topic of this paper,has been studied by doing theoretical analysis and the experimental research. By startingfrom the characteristics of wind, wind turbine and excitation synchronous generator, westudied both the speed and power control technologies for hydraulic-drive system of thefixed-displacement pump/variable motor. The power control in this paper includes systemtransmission power control and the maximum power point tracking control.On the aspect of the speed control of the fixed-displacement pump/variable motor, acontrol method of variable motor speed based on indirect flow feedback plus direct speedclosed-loop is proposed, which has solved the controlling system concernedfixed-displacement pump/variable motor, variable speed input/constant speed output. Thismethod is capable of keeping the system work in constant flow status, with no overflowloss. Thus we realized the quasi-synchronization paralleling control of synchronousgenerator, obtained a control method of quasi-synchronization paralleling for hydraulicwind generating unit, and can effectively control the synchronization shock current andtorque.As for the power control of the system, we presented a method of real-time on-linepower regulating control parameters on the basis of system pressure and variable motor’sswing angle. This power control method gave solution to the inconsistent power responses and instability problems caused by multiplying nonlinear of the system, improved theprecision of power control. Besides, this power control method took the speed control asthe inner loop to control two variables of speed and power by a single variable of themotor’s swing angle, so as to coordinate the speed control and power control.Considering the maximum power point tracking, we put forward a new methodapplicable to the hydraulic wind generator unit, which has balanced fast response, stabilityand accuracy in power tracking control.In this paper, we established a simulation platform for the power transmission systemof the hydraulic wind generator unit and a simulation experiment platform for this30kVAunit itself, and also tested the effectiveness of the proposed controlling methods of thefixed-displacement pump/variable motor system speed, system transmission power andthe maximum power point tracking by simulation and doing experiments.