On Series Compensation of Open-Winding Permanent Magnet Machines

An open-winding machine drive with two voltage source inverters was originally conceived for high power applications in order to equally split the power into two single inverters to reduce the voltage rating of each converter. Some FACTS devices utilize voltage source inverter to generate reactive power for shunt or series compensation. In this work, the possibility of applying FACTS concepts to smaller single machine systems instead of utility sized power systems is investigated. Specifically, a three-phase voltage source inverter with a DC link capacitor is used to provide controllable reactive power compensation for open-winding PM machines. The concepts of impedance control, power flow control and voltage control by the means of series compensation are considered in different scenarios including both motoring and generating operations.;For motoring operation, it will be demonstrated by simulation and experiment results that the power supply DC voltage of a PM motor drive can be better utilized in both low and high speed regions. By supplying reactive power from the auxiliary inverter, the corner speed of the drive can be postponed to a higher speed. In addition, the CPSR of the PM motor drive can be improved. A control method for the open-winding PM motor drive is herein proposed and verified. The sizing of the auxiliary inverter based on machine parameters and required CPSR is studied.;For generating operation, a new diode rectifier based wind power topology employing an open-winding PMSG is proposed. Compared to conventional diode rectifier based wind power systems, the cost of the proposed system can be reduced by avoiding a full scale DC/DC converter without sacrificing the capability of controlling generated power. The proposed open-winding PMSG wind power system is applicable to both fixed and variable speed wind turbines. In addition, distribution side voltage regulation of an open-winding PM generator in a small CVVF power grid is also considered for generating operation.;The effectiveness of the proposed series compensation scheme has been verified by simulation and experimental studies. It has also been demonstrated that the proposed series compensation by open-winding configuration is a cost effective method compared to the existing compensation methods.