具有无功馈送绕组的多相直驱永磁同步发电机HVDC风电系统研究

在10MW超大功率近海风电机组的现有技术方案中，采用直驱多相永磁同步发电机（MPPMSG）和串联单向变流器组构成的高压直流（HVDC）变换方案具有高效率和显著的可靠性。本项目在已有的研究基础上提出了具有独立无功馈送绕组的MPPMSG及对应HVDC风电变换方案，这种新方案保留了单向变流器拓扑简单和可靠性高的优点，同时解决了其只能采用单位功率因数变速控制的缺点，可以实现对发电机励磁的控制，从而进一步提高发电机的效率和变速控制性能；同时新的技术方案还能在HVDC母线短路时，对短路电流峰值进行抑制，从而实现对变流器的保护。另外，本项目还提出了一种应用于岸上HVDC变电站的新型混合式多电平逆变器方案，其原理是把二极管中点钳位五电平逆变器与低压H桥变流器级联，利用H桥的高频工作能力来提高整个逆变器的开关频率，从而改善逆变器的谐波和动态性能。这种新型逆变器可借助多相变压器串联实现对HVDC的高压逆变。

CAmong the various wind power conversion solutions for 10MW large offshore wind turbine, the multiphase permanent magnet synchronous generator (MPPMSG) with series-connected undirectional conveters offers high efficiency and good reliability. This project proposes an improved HVDC wind power conversion system based on a kind of new MPPMSG with isolated reactive power fed windings. The new system not only keeps the merits of the undirectional converter with simple and robust topology, but also overcomes the shortcoming that is only unity power factor variable-speed control strategy can be applied for it. The new system can control the magnetic field of MPPMSG, as a result, the efficiency and speed-control capability of MPPMSG are impoved. Simultaneously, when HVDC transmission is shorted to ground, the new system can protect the converters from damage by supressing the short-circuit peak current. In addtion, this project also proposes a new hybrid multilevel inverter based on the diode neutral-point-clamped five-level inverter series-connected with low voltage H bridge converter for onshore power station. The switching frequency of the hybrid multilevel inverter will be increased by high frequency operational capability of H bridge converter. As a result, hamonics and control capability of the hybrid multilevel converter are improved greatly. High voltage DC-AC conversion can be implemented by series-connection of hybrid multilevel converters by means of multiphase transformer.