【作者】 周波；

【导师】 年珩；

【作者基本信息】 浙江大学 ， 电机与电器， 2014， 硕士

【摘要】 随着新能源发电技术研究的广泛开展,基于电流源输出的双馈(DFIG)风电机组并网运行控制已得到深入的研究和应用。但在分布式发电技术逐渐兴起的局面下,需要依托较为稳定的公共电网存在的DFIG风电机组电流源控制技术将极大的限制其在分布式发电系统中配置。为实现分布式发电系统中DFIG风电机组灵活有效的介入,首先,通过将间接定子磁链定向(ISFO)控制策略应用于DFIG机侧变流器,建立了其电压源输出特性,配合设计的风力机桨距角控制算法,满足了其孤岛单机运行需要。其次,考虑到分布式系统一般由多单元并联构成,引入下垂控制构建了DFIG与其他分布式发电单元协同时的功率分配机制,为其提供了参与分布式发电系统孤岛并联运行的渠道。同时,为检验ISFO与下垂控制算法的协调能力,建立了DFIG电气部分的小扰动数学模型,分析了关键控制参数对DFIG控制系统的影响,为风电机组运行的稳定性提供了必要的判据。再则,为满足分布式发电系统并网运行和工作模式无缝切换的需要,参照电力系统二次调节方式,分别基于公共节点电压频率、电压幅值反馈和发电单元输出功率反馈建立了分布式发电系统孤岛运行工作点和并网运行输出功率的调节机制,使得DFIG能在硬件拓扑结构和控制算法保持连贯的情况下参与分布式发电系统正常运行。以此为基础,提出了基于电压源控制的DFIG并网MPPT运行控制算法,以尽量提高系统风能利用效率。为应对不平衡的运行条件,提出了改进的ISFO控制,以满足DFIG孤岛单机运行带不平衡本地负荷的需要。而针对含DFIG风电机组分布式发电系统多机孤岛并联运行的不平衡工况,以实现负序电流的合理分配和系统公共节点电压不平衡度的降低为目的,通过负序下垂引入虚拟电导,改善了系统负序回路阻抗特性,最终达成控制目标的实现。针对分布式发电系统中DFIG风电机组运行控制技术的相关理论研究,基于MATLAB/Simulink仿真软件,搭建了DFIG由单机到系统的仿真模型,验明了所提系列控制算法在与之对应的运行工况或平衡、不平衡条件下的适应能力。最后通过建立DFIG风电机组硬件实验平台,协同中央控制器和储能硬件实验平台验证了部分工况下所提DFIG控制算法的实际可行性,为相关工作的继续开展奠定了较为良好的基础。更多还原

【Abstract】 Nowadays, with the extensive research on renewable energy generation technologies, control strategies of doubly fed induction generator (DFIG) wind system based on current output mode have been thoroughly studied. But the current output mode of DFIG relies on a relatively stable grid and that without doubt will limit the application of DFIG in distributed generation system, a power system form which has enjoyed worldwide popularity recently.Aiming at achieving DFIG’s flexible and effective penetration into distributed generation system, firstly, this paper applies indirect stator flux orientation (ISFO) strategies to the control of rotor side converter to establish its voltage source output characteristics. Along with the specially designed pitch angle control algorithms, ISFO can fit well for the autonomous working mode of DFIG. Secondly, taking into account that the distributed generation system generally consists of multiple parallel connected units, the droop characteristics is introduced into the control of DFIG, which lays the base of power assignment mechanism when DFIG need to cooperate with other units. And also, the droop control enables the distributed generation system with multiple parallel connected generation units to work under autonomous mode. While at the same time, to test the coordination of ISFO and droop, the small-signal mathematical analysis model of DFIG’s electrical part is constructed. Then the influence of critical control parameters on DFIG control system has been studied, which provides a necessary criterion for the stability analyze. After that, to realize the gird-connected working mode and seamless switch of distributed generation system, by reference to the secondary power system adjustment method, operating point regulation mechanism when islanded is achieved by feeding back the voltage frequency and amplitude of the point of common coupling (PCC), and also, output power adjustment mechanism when grid-connected is achieved by feeding back each generator’s output power. In all this process, the control algorithm of DFIG keeps a good consistence and there is no change on the hardware structure. Based on the secondary adjustment method, the maximum power point tracking (MPPT) of DFIG is provided to enhance the efficiency of wind system in distributed generation system when grid-connected, And of course, DFIG persists on voltage output mode.To dealing with imbalanced conditions, a revised ISFO is come up with to make DFIG suitable for an autonomous imbalanced local load. Also, considering that DFIG’s collaboration with other distributed generation units may be interrupted by imbalance when islanded, negative sequence droop is designed, which forms a virtual conductance and leads to the change of negative sequence resistance circuit. And eventually, negative sequence current is well assigned and the PCC voltage balance is well preserved under an extremely unbalanced load.The control strategies mentioned of above need to be verified, so with the help of MATLAB/Simulink, simulating models involve either a single DFIG or a whole distributed generation system is built. And the simulating results well testified those algorithms. At last, the hardware experimental platform of DFIG is established, and together with the energy storage platform and the distributed generation system central controller, a series of experiments are conducted, which validate the proposed control strategies of DFIG in a distributed generation system under various working mode.更多还原