小功率水电站变速恒频控制系统研究

Research on Variable Speed Constant Frequency Control System of Small Hydropower Station

针对传统小水电站并网系统控制复杂、低流量下效率低等问题,提出一种基于电压空间矢量脉宽调制的永磁直驱水电并网控制系统。该系统采用背靠背的双PWM变流器将水轮发电机组和电网分离,通过电压空间矢量脉宽调制法实现能量的双向流动。机侧变流器采用单位功率因素控制,以发电机转速为控制对象,将水流冲击产生的有功电能输送到直流母线上,同时实时跟踪水轮机最佳转速点,实现水轮机组最大功率输出。网侧变流器采用基于电网电压矢量定向的有功、无功分解控制,以直流母线电压为控制对象,往电网传输有功电能,同时进行无功补偿。最后仿真及实验验证了该控制系统的有效性。

This paper aims at the problems of complex control and low efficiency in the grid-connected system of traditional small hydropower station to propose a grid-connected control system for permanent magnet direct-drive hydropower based on voltage space vector pulse width modulation.The proposed system adopts back-to-back dual PWM converter to separate the hydraulic generator set from the power grid and realize the bidirectional flow of energy through the voltage space vector pulse width modulation method.The generator-side converter adopts the unit power factor control to control the speed of generator,and with the generator speed taken as the control object,transmits the active electric energy generated by the water rushing impact to the DC bus.At the same time,the optimal speed point of the turbine is tracked in real time to achieve the maximum power output of the turbine set.The grid-side converter adopts active and reactive power decomposition control based on power grid voltage vector orientation,takes the DC bus voltage as the control object,and transmits active power to the grid,and also makes reactive power compensation at the same time.Finally,the effectiveness of the control system is verified by simulation and experiment.