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It is proposed to adopt two kinds of storage battery equipment in microgrid, energy storage zinc bromine flow battery and power storage lithium titanate battery. The hybrid energy storage system adopts micro-grid DC/DC converter and DC/AC converter two-stage control. The hybrid energy storage DC/DC converter control adopts a distribution method based on power fluctuations and constant current fast charge control, and the hybrid energy storage DC/AC converter adopts PQ control and an improved droop uniform frequency control method. The algorithm automatically switches in all kinds of operation modes of the microgrid to achieve the power quality indicators, such as voltage sag, frequency deviation, voltage deviation and voltage fluctuation, during the operation of the microgrid to meet the operating requirements. The simulation results prove that the control method is correct.

The influence on distribution network of the distributed generation (DG) is closely related to the location and capacity connected to the DG, therefore it is very important to study the problems of site selection and capacity determination. The reactive power optimization is considered to improve the voltage level of power grid and reduce line losses. According to the capacity of the DG, The problem about selecting site and determining capacity is decomposed into two kinds of pattern with Parallel operation and island operation, which means comprehensive target of grid losses. voltage deviation and static voltage stability margin is optimal while DG is full load. Optimal allocation model of DG is established, the constraints condition includes node voltage, the transmission current of line, the single DG capacity and the total capacity of all DG. The genetic — ant colony hybrid intelligent algorithm is put forward to calculate the location and capacity of the DG. Simulation results show that the method is effective in problem of location selecting and capacity determing of DG.

For direct drive synchronous wind power generation system, the converter of direct drive motor is connected to the stator side of permanent magnet synchronous generator side, through controlling the converter, the maximum wind energy can be captured. Main circuit design of the direct-drive grid-converter is studied. Firstly, power grid side filter is designed and calculated, LCL filter is used instead of traditional L type filter, in this way, the value of the inductance、 the volume and cost are reduced effectively, and its inhibitory effect on high frequency signal is more obvious. Not only meet the vector triangle, but also grid connection harmonic current is restrained. Secondly, the filter of motor side is also designed, about the problem of voltage reflection for long cable drive motor PWM converter on the motor side, the solution is to reduce the output value of the du/dt and increase the pulse rise time, at the same time the reflected voltage of the motor side is also reduced. Finally ,Brake unit is researched, at the instant of the power grid voltage dips is detected, chopper control is started to IGBT of brake unit, making the machine side power in addition to the net from the side of the part, the rest are consumed in the brake unit, to ensure that the equipment can grid-connected operated. The last but one, the pre-charging circuit is included.