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The safety and reliability of inverters play a significant role in stable power electronic system operations. Considering a railway vehicle air-conditioning inverter as a case study, this paper presents a generic open-circuit fault diagnosis method that can be applied to various inverter and control schemes. First, a detailed model of three-phase output currents under both normal and fault status is derived, and then the concept of space trajectory is introduced based on the three-phase output currents. The open-circuit faults of the inverter lead to output phase current distortion. Therefore, different types of faults have different space trajectories, and the corresponding shape of the space trajectory is considered to be a fault feature. Then, the fault is located by the direction vector and center-of-mass coordinate. The effectiveness and reliability of the diagnosis method are verified and analyzed using a hardware-in-the-loop test platform. [ABSTRACT FROM AUTHOR]

This paper proposes a current-fed single-phase inverter without constant intermediate DC link. It eliminates electrolytic capacitor from the DC-link and introduces an intermediate pulsating DC bus. The proposed topology is modular with three full-bridges making it scalable for high-power applications. New pulsating-DC-modulation for back-end pulsating DC-link inverter and secondary modulation (SM) for front-end DC-to-pulsating DC converter is proposed. Soft-switching and device voltage clamping of both primary side and secondary side devices of front-end current-fed full-bridge converter is realized. A rotating partial hybrid pulsewidth modulation has been introduced. One leg of inverter is commutated at a low switching frequency, while the other leg is operated at a high switching frequency for partial period of a line frequency cycle. Thus, switching losses of the back-end inverter are considerably reduced. Rotating mechanism is used to equalize the switching losses of four switches of the inverter. This paper presents detailed operation and analysis of the topology with a proposed modulation scheme. Simulation and experimental results validate the effectiveness and accuracy of the proposed modulation scheme as well as soft-switching and performance of the converter. [ABSTRACT FROM PUBLISHER]

This paper deals with a control method that adapts the dc bus voltage of electric traction systems using permanent-magnet synchronous machine (PMSM) fed by bidirectional $Z$-source inverter (ZSI) or other improved topologies. This control allows reducing both the overestimation of the dc bus voltage and losses in the inverter. The sliding-mode control (SMC) method is used to control the $Z$-source converter, whereas flatness-based control is proposed to drive the actuator and generate the peak dc bus voltage reference. Flatness-based control is chosen because the actuator transients are well mastered. Extra shoot-through zero inverter states are inserted by means of implemented algorithm on a space-vector-modulation (SVM) scheme. Different short-circuit strategies are studied and compared according to constraint criteria. Both simulation and experimental results are presented and discussed to validate the proposed voltage adaptation strategy and the improvement on global efficiency. [ABSTRACT FROM AUTHOR]

Traction inverters are crucial components of modern electrified automotive powertrains. Advances in power electronics have enabled lower cost inverters with high reliability, efficiency, and power density, suitable for mass market consumer automotive applications. This paper presents an independent review of the state-of-the-art traction inverter designs from several production vehicles across multiple manufacturers. Future trends in inverter design are identified based on industry examples and academic research. Wide bandgap devices and trends in device packaging are discussed along with active gate driver implementations, current and future trends in system integration, and advanced manufacturing techniques. [ABSTRACT FROM AUTHOR]

This paper presents a six-phase current reconstruction scheme for dual traction inverters in hybrid electric vehicles (HEVs) with a single dc-link current sensor. During the phase current reconstruction, one of the inverters is proposed to operate using active vectors, whereas the other inverter operates using nonactive vectors. An advanced phase-shift scheme for all pulsewidth-modulated (PWM) signals based on the sequence of duty cycles is implemented. PWM signals are considered in three types: large, medium, and small duty cycles. Then, the minimum phase-shift scheme is applied to each type of PWM signal to ensure the minimum duration of the active vector for stable current reconstruction. With this proposed phase-shift scheme, the maximum allowable modulation index and dc-link voltage utilization are improved. In addition, the relationship between the minimum required time for stable phase current reconstruction and the maximum allowable modulation index is derived theoretically. The effectiveness of the proposed method is verified by both simulation and experimental results. With this scheme, cost and volume of dual inverters in HEVs are reduced, considering the lower number of current sensors. [ABSTRACT FROM PUBLISHER]

The article discusses various reports published within the issue, including one on hybrid electric vehicles based on a bidirectional Z-source nine-switch inverter, one on a simulation model for a military hybrid electric vehicle (HEV), and one on active common-mode (CM) voltage compensation in an induction motor drive.

This paper proposes a controller to minimize the overall drive system's losses and the key inverter and motor losses by mapping machine's speed and torque demands to an optimal state current and switching frequency. The objective function takes into account copper and core losses of the machine along with conduction and switching losses of the inverter. The effect of the inverter harmonics on the voltage and current waveforms is modeled and shows that while higher switching frequency increases inverter loss, it decreases the machine's loss. The inverter switching frequency varies with the speed and load torque. The voltage and current limitation are used as the constraint. The effects of the current, voltage, and switching frequency are shown on the losses of the machine and the inverter. The result of optimization for each pair of speed and load torque is the corresponding $dq$ axes current and switching frequency. A control system is implemented based on the optimization scheme to verify the optimization process. The effectiveness of the control system is verified experimentally. [ABSTRACT FROM AUTHOR]

This paper deals with the active common-mode (CM) voltage compensation in an induction motor drive where the inverter is supplied by a dc source, which is typical of vehicle applications. The CM voltage at motor terminals, creating a shaft voltage through the motor air gap with possible rise in bearing current, can endanger motor reliability and reduce its lifetime. Therefore, CM voltage filtering is desirable. On the other hand, the operation of an active filter has an impact on drive efficiency due to its specific losses and can affect the electromagnetic interference (EMI) emissions that are generated by the drive. Such effects are investigated in this paper. A detailed description of a CM active filter (CMAF) is presented. An analysis of the CM voltage and current on the motor ground connection before and after the introduction of the CMAF is performed. The power losses due to the CMAF operation are analyzed and experimentally evaluated. Furthermore, the EMI toward the vehicle dc power supply line is investigated. All phenomena are studied by simulation and experimentally. The simulated results "are obtained developing" a high-frequency circuit model of the drive system, including the CMAF, which is implemented using the PSpice software. To accurately perform the experimental tests, a new dedicated high voltage dual dc line impedance stabilization network (LISN) is designed and set up on purpose. The CMAF is found to be an effective solution for the increase in motor reliability and drive electromagnetic compatibility, and its operation does not significantly reduce drive efficiency. Moreover, the CMAF does not worsen the EMI toward the dc supply line. Therefore, its presence does not imply the need for additional filters with respect to the case where no CMAF is used. Simulated results are in good agreement with the experimental ones, confirming the validity of the proposed modeling of the drive system. [ABSTRACT FROM AUTHOR]

This paper introduces a new set of methods to directly integrate ultracapacitor banks into cascaded multilevel inverters that are used for large vehicle propulsion. The idea is to replace the regular dc-link capacitors with ultracapacitors in order to combine the energy storage unit and motor drive. This approach eliminates the need for an interfacing dc-dc converter and considerably improves the efficiency of regenerative braking energy restoration in large vehicles using multilevel converters. Utilizing the proposed modulation control set, the two cascaded inverters can have their dc voltage levels maintained at any ratio (even a noninteger ratio) or dynamically varied over a wide range without disrupting the normal operation of the electric motor. As an advantage, ultracapacitor voltage or state of charge can be freely controlled for braking and/or acceleration power management. A regenerative energy management scheme is also proposed based on the vehicle's speed range considerations. Detailed simulation and experimental results verified the proposed methods. [ABSTRACT FROM AUTHOR]

Cell voltage equalizers are necessary to ensure years of operation for series-connected supercapacitors (SCs) by eliminating cell voltage imbalance. Conventional equalizers require numerous switches and/or magnetic components; hence, the circuit complexity and size tend to increase. In this paper, a double-switch single-transformer equalizer, which is based on the combination of a half-bridge inverter and a voltage multiplier, is proposed. The operation of the proposed equalizer is analyzed in detail, and a dc equivalent circuit is mathematically derived. Experimental equalization tests were performed for eight SCs connected in series under a voltage-imbalanced condition. The energy of the series-connected SCs was preferentially redistributed to SCs with low voltages, and eventually, the voltage imbalance was eliminated, demonstrating the equalization performance. Simulation-based equalizations using the derived dc equivalent circuit were also performed under the same condition as the experiments. The experimental and simulation results were in good agreement, indicating that the derived dc equivalent circuit can adequately express real equalization profiles. [ABSTRACT FROM PUBLISHER]

Electrical energy storage has a significant role to play in improving the performance of future electric traction systems. This paper proposes a new power electronics topology that integrates the energy storage power electronics with those of the inverter drive system. This topology reduces weight and component count compared with previous topologies but still allows the use of standard machines. Practical results from a laboratory test system are shown, and indicative energy savings for a full-sized system are presented. A study on a City Class Tram on the public transportation system in Blackpool, U.K., shows that clear energy savings may be made by employing ultracapacitor energy storage with the proposed topology. [ABSTRACT FROM PUBLISHER]

Multiterminal converters are used in hybrid energy systems as a replacement for several conventional two-terminal converters to reduce volume and cost. This paper proposes a hybrid electric vehicle (HEV) based on a bidirectional z-source nine-switch inverter. A unidirectional z-source nine-switch inverter, which was proposed by the authors, has been improved to allow bidirectional power flow. The proposed converter has two ac and one dc bidirectional terminals that can be used in HEV. Performance of the proposed HEV has been verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

Modular parallel multi-inverters (MPMIs) with master-slave phase synchronization control is proposed for high-power wireless power transfer (WPT) where the MPMI output voltage phase is synchronized to suppress current circulation by compensating for the time delay of the slave inverters caused by signal propagation delay. Different power levels can be conveniently satisfied by flexibly adjusting the number of MPMIs. A modeling method based on the energy-amplitude and phase is developed and linearized to get the slowly changing phase variable and to analyze the system dynamic characteristics at its operating point. To achieve the required dynamic performance of the proposed model, the parameters of a PI controller are obtained by calculating the required settling time and overshoot of the closed-loop dominant poles. A 20.07 kW WPT prototype supplied by three MPMIs with an efficiency of 92.17% was designed and tested. Experimental results show that the proposed modeling method and controller design achieved both good performances of circulating current suppression and MPMIs output voltage phase synchronization. [ABSTRACT FROM AUTHOR]

A method that is suitable for ecovehicles, which controls the surge voltage appearing at motor terminals that are connected to a pulsewidth modulation inverter with short leads that are less than the critical cable length (i.e., the shortest length at which full reflection may occur), is described here. Also, a method to control electromagnetic interference (EMI) noise, which is induced by the surge voltage, is discussed. Ecovehicles have the problem where insulation degradation of motors occurs due to the surge voltage being repeatedly applied to motor terminals during long lifecycles. EMI noise such as the shaft current and the radiated noise, which are induced by the generated surge voltage, easily diffuse into other electric devices due to the high-density packaging structure. The diffused EMI noise may cause a malfunction of the vehicle controller. An EMI noise controller is studied, which can meet the high-density packaging requirements for ecovehicles like electric vehicles. The EMI noise controller is attached on the motor terminals and simultaneously suppresses the surge voltage and the noise. After clarifying surge voltage characteristics and a circuit model for expressing the surge phenomenon through experiments and simulations, an EMI noise controller is proposed, which uses a multilayer printed power circuit technique. It is verified through simulations and experiments that the proposed controller has the ability to simultaneously control the surge voltage and the EMI noise, such as the radiated noise and the shaft current (the bearing current), which are induced by the surge voltage. [ABSTRACT FROM AUTHOR]