【作者】 王建国；

【导师】 邹积岩；

【作者基本信息】 大连理工大学 ， 电机与电器， 2013， 硕士

【摘要】 分布式发电在全世界兴起,电力电子装置作为各种可再生能源发电系统与微电网连接的接口发挥着重要的作用,其中逆变器是不可缺少的组成部分,其控制策略直接决定系统运行稳定性。微电网工作在并网模式时逆变器一般采用电流控制,三相逆变器可以在3种不同的坐标系下控制,其中在dq同步旋转坐标系下交流信号被转换为直流信号,易于设计控制器,传统上采用PI控制器。本文将伪微分反馈(Pseudo-derivative-feedback, PDF)控制器应用于三相逆变器,用以控制入网电流。通过对电路和PWM进行小信号数字建模,得到了PDF控制器的控制参数。然后通过仿真和实验比较了dq坐标下的PDF和PI控制器,及αβ坐标下的PR和阻尼PR控制器对电流的控制过程,结果表明相比于其它3种控制器,PDF可以实现暂态响应无超调或振荡,能降低过流危险及减小电磁干扰。当电网发生故障时,电网电压存在正负序甚至零序电压,为了向电网输送稳定可控的功率,需要同时对正负序电流进行控制。双旋转dq坐标变换会引入2倍频交流振荡,本文采用一种振荡解耦PDF控制器,减小了控制误差并能增强系统稳定性。推导出3种正负序dq参考电流的计算公式,可以根据电网要求及故障类型,灵活选择对称对流控制、稳定瞬时有功功率控制或稳定瞬时无功功率控制,仿真结果证实了这些公式的正确性。更多还原

【Abstract】 Distributed power generation system is being developed all over the world. As the interface between renewable resources and Microgrids, electronics devices play a critical role in the DPGS, in which inverters are indispensable. And the performance of the generation system largely depends on the control topologies of inverters. The inverter generally acts as a current source when it works in grid-connected mode, and the control of three-phase inverter can be implemented in three different kinds of frames. In particular, in dq synchronous rotating frame, AC voltages and currents can be transformed into DC signals, which facilitates the design of current controller. Traditionally, a PI controller is employed in this frame.In this thesis, the Pseudo-derivative-feedback (PDF) controller is firstly applied in the control of the output current of three-phase inverters. The parameters of the controller are obtained by precise models of the circuit and PWM through small-signal digital analysis. The transient responses of system controlled by PDF and PI controller in dq frame, PR and damped PR controller in αβ frame are compared by simulations and experiments, showing that the transient response of PDF controller is with no overshoot or oscillation, which would reduce the risk of over-current and electromagnetic interference.When faults occur in the grid, the voltage would consist of positive and negative sequences components, even zero sequence voltage. In order to ride-through grid faults, grid code requires inverters to inject constant and controllable power into the grid. In this way, both positive sequence and negative sequence currents should be controlled. However, in dual dq synchronous frames, the signals would contain second-order oscillations. In this thesis, a decoupled PDF controller is proposed, by which the control is more accurate and the stability of the system is enhanced. Three kinds of formulas are derived for the reference current in dual dq frame. The simulation results verify that the inverter can produce balanced currents, constant instantaneous active power or constant instantaneous reactive according to the grid fault type and the utility network necessity.更多还原