Open-circuit fault diagnosis and fault tolerance for shunt active power filter

The open-circuit fault of the power switches in shunt active power filter(SAPF) would exacerbate the harmonic pollution of power grid, and degrade the reliability of the devices and system. A fault diagnosis method is proposed based on reference model and an over-modulation strategy under hardware fault tolerance for SAPF. First, a mathematic model is established for SAPF. Second, the residuals are generated by comparing the outputs of reference model and those of actual model, and open-switch fault is detected and diagnosed by residual evaluation. After that, hardware fault tolerance is performed with the three-phase four-switch(TPFS) topology to isolate the faulty phase. Finally, the over-modulation strategy is proposed to increase the voltage transfer ratio of the TPFS topology. Simulation and experimental results verified the feasibility and effectiveness of the proposed method.

Dynamic torque response analysis of IPMSM in flux weakening region for HEV applications

An over-modulation based vector control strategy for interior permanent magnet synchronous machine（ IPMSM） is proposed and investigated. The strategy increases the reference flux weakening voltage to improve efficiency in flux weakening region of IPMSMwith the same dynamic torque response performance in standard SV Mtechnique. The relationship between dynamic torque performance and the reference flux weakening voltage is also discussed. In order to achieve fast and smooth shift process,the torque response must be less than 20 ms in the parallel hybrid electric vehicle（ HEV）,according to this,modeling and experimental studies were carried out. The results show that the proposed strategy can achieve the same dynamic and steady state torque performance with higher reference flux weakening voltage,which means higher efficiency.

Control Scheme of Spread Frequency Band for High Power Impedance Measuring Converter with Chirp Signal Injection

Impedance measurement is an effective solution for evaluating stability of a power system with high penetration of renewable sources.In this paper,the impedance measurement is achieved by a typical high-power impedance measuring converter(HPIM-converter)with chirp signal injection.The modulation saturation phenomenon of the HPIM-converter is revealed,and the frequency sweep boundary is analyzed in detail.To expand the rated frequency range of the HPIM-converter,a spread frequency band control scheme based on an over-modulation technique is proposed in this paper.The proposed control method enlarges the rated frequency band and can inject a disturbance voltage into the system under test with consistent amplitude in the rated frequency band.Also,a smooth transition strategy between linear modulation mode and over-modulation mode is proposed for suppressing signal fluctuation.Finally,the effectiveness of the proposed method is verified by simulation tests.