【作者】 姚骏；

【导师】 廖勇；

【作者基本信息】 重庆大学 ， 电气工程， 2007， 博士

【摘要】 交流励磁发电机可实现变速恒频运行,具有优越的稳态和暂态运行性能,特别适用于变水头水力发电、抽水蓄能以及风力发电等可再生能源发电系统。采用合适的励磁控制策略和性能优良的变频励磁电源是交流励磁发电机能够发挥其良好的调节性能、运行的灵活性及可靠性的关键,本论文主要针对电网正常运行和电网短路故障时交流励磁发电机及其励磁电源的控制策略进行了深入地研究。论文首先提出了一种基于全模糊控制器的解耦励磁控制策略,建立并详细分析了基于全模糊控制器的交流励磁发电机解耦励磁控制系统。仿真和实验结果验证了采用全模糊控制器的交流励磁发电机系统可实现有功、无功和转速的稳态解耦控制以及变速恒频发电运行,系统具有较强的鲁棒性以及良好的动静态控制性能。详细分析了采用传统矢量控制策略的双PWM变换器直流链电压波动机理,提出了一种基于转子侧变换器瞬时功率直接反馈的双PWM变换器改进控制策略。仿真和实验结果验证了双PWM变换器改进直流链电压控制策略的正确性和有效性,改进方案显著提高了发电机运行状态突变时直流链电压的稳定控制能力,有效提高了交流励磁发电系统的动态响应能力和稳定性。详细分析了电网短路故障时交流励磁发电机的暂态物理过程以及发电机转子出现过电流或过电压的原因。根据故障时转子过电流的原因提出了一种电网短路故障时保持交流励磁发电机不脱网运行的改进励磁控制策略。改进方案从限制电网故障时定子工频过电流的角度出发,有效限制了由定子电流工频分量引起的转子电流交流分量,同时利用发电机定子电阻实现定子磁场暂态直流分量的衰减,实现了故障时避免转子出现过电流的目的。仿真结果验证了改进控制方案的有效性,实现了电网短路故障期间发电机转子励磁变频器的安全运行,提高了交流励磁发电系统在电网故障下的不间断运行能力。电网发生短路故障时准确控制双PWM变换器中的电网侧变换器和转子侧变换器是实现交流励磁发电机不脱网运行的关键,论文详细分析并提出了一种电网短路故障时双PWM控制交流励磁电源电网侧变换器的改进控制策略。仿真结果验证了改进控制方案在电网故障发生和切除时稳定控制励磁电源直流链电压的有效性,为故障过程发电机不脱网励磁控制奠定了基础,同时该方案也能有效地保护直流侧电容及提高系统的稳定性。建立了双PWM变换器励磁的交流励磁发电机励磁控制实验系统,利用实验系统对交流励磁发电机的励磁控制以及双PWM变换器在交流励磁发电机变速恒频运行中的运行行为进行了全面深入的实验研究,取得了有实用价值的结论。更多还原

【Abstract】 The Alternating Current Excited Generator (ACEG), which has features of variable speed constant frequency operation, superior steady-state and transient-state operation characteristics, is especially suitable for the renewable energy generation system such as hydropower generation with variable water head, pumping storage generation and wind-power generation. The appropriate excitation control strategy and excellent excitation power supply should be used to realize the good regulation performance, agility and reliability of operation for ACEG system. The control strategies of the ACEG and its excitation power supply under the grid normal operation condition and grid short-circuit fault condition have been deeply studied in this dissertation.Firstly, the decoupling excitation control strategy based on the full fuzzy controller is proposed, and the decoupling excitation control system of ACEG based on the full fuzzy controller is established and analyzed in detail. Both the simulation and experiment results are used to validate the respectively control ability of active power, reactive power and rotor speed for ACEG system used full fuzzy controller, and the variable speed constant frequency generation can also be realized. The system has strong robustness and good dynamic and static performance.The reason of the DC-link voltage fluctuation within a back-to-back PWM converter controlled by the traditional vector control strategy has been analyzed in detail, and an improved back-to-back PWM converter control strategy based on the rotor-side converter instantaneous power feedback control has been proposed. Both the simulation and experiment results are used to validate the proposed method. The stable control ability of the DC-link voltage can be effectively improved when regulating the generator and it improves the dynamical response ability and stability of the ACEG system.The transient physical process of the ACEG and the reason for the rotor over current or over voltage at that time of a grid fault process are deeply analyzed. An improved excitation control strategy is proposed for the rotor side converter in ACEG to allow the system to ride through the grid short-circuit fault. In order to avoid the over current in the rotor during the fault, the rotor current AC components produced by the stator currents at 50Hz have been successfully restrained and the stator resistance is also used to realize the decay of DC component of the stator current during the grid fault process. The proposed control strategy is validated by the simulation results under the grid symmetrical and unsymmetrical fault conditions. The rotor excitation converter has been successfully protected during the grid fault and it improves the fault ride-through ability of the ACEG generation system.It is the key point that the grid-side converter and rotor-side converter in a back-to-back PWM converter should be accurately controlled to realize the fault ride-through control of ACEG during the grid short-circuit fault. An improved control strategy of the grid-side converter for grid fault is analyzed and proposed in detail and the proposed control strategy is validated by the simulation results. The DC-link voltage of excitation power supply can be stably controlled during the fault, and the effect of ride-through control for the generator can be improved. Furthermore, the DC-link capacitor can also be protected and the system stability can be improved during the fault.An experimental ACEG excitation control system excited by back-to-back PWM converter is established. The excitation control of ACEG and the operation performance of the back-to-back PWM converter in the ACEG variable speed constant frequency generation have been deeply studied by experiment, and some valuable conclusions have been achieved.更多还原