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Attia, Hussain A.,Freddy, Tan Kheng Suan,Che, Hang Seng,El Khateb, Ahmad H. The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1
Recently, the use of LLCL filters for grid inverters has been suggested to give better harmonic attenuation than the commonly used L and LCL filters, particularly around the switching frequency. Nevertheless, this filter is mainly designed for constant switching frequency pulse width modulation (CSF PWM) methods. In variable switching frequency PWM (VSF PWM), the harmonic components are distributed across a wide frequency band which complicates the use of a high order filter, including LCL and LLCL filters. Recently, a confined band variable switching frequency (CB-VSF) PWM method has been proposed and demonstrated to be superior to the conventional constant switching frequency (CSF) PWM in terms of switching losses. However, the applicability of LLCL filters for this type of CB-VSF PWM has not been discussed. In this paper, the authors study the suitability of an LLCL filter for CB-VSF PWM and propose design guidelines for the filter parameters. Using simulation and experimental results, it is demonstrated that the effectiveness of an LLCL filter with CB-VSF PWM depends on the parameters of the filters as well as the designed variable frequency band of the PWM. Simulation results confirm the performance of the suggested LLCL design, which is further validated using a lab scale prototype.
Munim, Wan Noraishah Wan Abdul,Tousizadeh, Mahdi,Che, Hang Seng The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4
Recently, there has been increased interest in the study of multiphase machines due to their higher fault-tolerant capability when compared to their conventional three-phase counterparts. For six-phase machines, stator windings configured with a single isolated neutral (1N) provide significantly more post-fault torque/power than two isolated neutrals (2N). Hence, this configuration is preferred in applications where post-fault performance is critical. It is well known that min-max injection has been commonly used for three-phase and multiphase machines in healthy condition to maximize the modulation limit. However, there is a lack of discussion on min-max injection for post-fault condition. Furthermore, the effects in terms of the common-mode voltage (CMV) in modulating signals has not been discussed. This paper investigates the effect of min-max injection in post fault-tolerant control on the voltage and speed limit of a symmetrical six-phase induction machine with single isolated neutral. It is shown that the min-max injection can minimize the amplitude of reference voltage, which maximizes the modulation index and post-fault speed of the machine. This in turn results in a higher post-fault power.
Wan Noraishah Wan Abdul Munim,Mahdi Tousizadeh,Hang Seng Che 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4
Recently, there has been increased interest in the study of multiphase machines due to their higher fault-tolerant capabilitywhen compared to their conventional three-phase counterparts. For six-phase machines, stator windings configured with a singleisolated neutral (1N) provide significantly more post-fault torque/power than two isolated neutrals (2N). Hence, this configuration ispreferred in applications where post-fault performance is critical. It is well known that min-max injection has been commonlyused for three-phase and multiphase machines in healthy condition to maximize the modulation limit. However, there is a lack ofdiscussion on min-max injection for post-fault condition. Furthermore, the effects in terms of the common-mode voltage (CMV)in modulating signals has not been discussed. This paper investigates the effect of min-max injection in post fault-tolerant controlon the voltage and speed limit of a symmetrical six-phase induction machine with single isolated neutral. It is shown that themin-max injection can minimize the amplitude of reference voltage, which maximizes the modulation index and post-fault speedof the machine. This in turn results in a higher post-fault power.
Hussain A. Attia,Tan Kheng Suan Freddy,Hang Seng Che,Ahmad H. El Khateb 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1
Recently, the use of LLCL filters for grid inverters has been suggested to give better harmonic attenuation than the commonlyused L and LCL filters, particularly around the switching frequency. Nevertheless, this filter is mainly designed for constantswitching frequency pulse width modulation (CSF PWM) methods. In variable switching frequency PWM (VSF PWM), theharmonic components are distributed across a wide frequency band which complicates the use of a high order filter, includingLCL and LLCL filters. Recently, a confined band variable switching frequency (CB-VSF) PWM method has been proposed anddemonstrated to be superior to the conventional constant switching frequency (CSF) PWM in terms of switching losses. However,the applicability of LLCL filters for this type of CB-VSF PWM has not been discussed. In this paper, the authors study thesuitability of an LLCL filter for CB-VSF PWM and propose design guidelines for the filter parameters. Using simulation andexperimental results, it is demonstrated that the effectiveness of an LLCL filter with CB-VSF PWM depends on the parametersof the filters as well as the designed variable frequency band of the PWM. Simulation results confirm the performance of thesuggested LLCL design, which is further validated using a lab scale prototype.