Impulse Commutation Research Articles

Impulse Commutated High-Frequency Soft-Switching Modular Current-Fed Three-Phase DC/DC Converter for Fuel Cell Applications

Current-fed converters offer enormous potential as power conditioning units for fuel cell applications, owing to precise fuel cell stack current control, short-circuit protection, voltage gain, and stiff fuel cell dc current. Aspects such as low current ripple and smaller input current slope ensure energy efficient operation and better fuel utilization, and enhance the lifetime of the fuel cell stack. However, the demerits of turn-off voltage spike across semiconductor devices limits the operating frequency. This paper proposes, analyzes, and implements a simple and cost-effective impulse commutated modular three-phase circuit to eliminate and solve the associated turn-off spike problem. Impulse commutation permits soft turn-off of devices and clamps the device voltage. The converter efficiently handles the variations in the fuel cell stack voltage and current with variable frequency modulation. Detailed steady-state operation, analysis, and performance of the proposed modular converter with impulse commutation are reported. The proposed impulse commutated three-phase circuit is a potential candidate for high-current applications. The validation of the converter operation on a 1-kW proof-of-concept hardware prototype is performed to substantiate the claims.

Analysis and Design of Impulse-Commutated Zero-Current-Switching Single-Inductor Current-Fed Three-Phase Push–Pull Converter

Impulse commutation obtains zero current commutation of devices in a circuit with a short resonance impulse using a simple resonant tank. This concept has been studied, extended, and implemented for a three-phase push–pull current-fed single-inductor topology to achieve soft commutation and device voltage clamping solving the traditional issue of device turn-off voltage overshoot. The push–pull topology is attractive owing to single inductor, all common source devices connected to common supply ground, and reduced gate driving requirements. Detailed operation, analysis, and design of this topology have been reported with impulse commutation. With a small resonant tank and partial resonance, impulse commutation procures merits of voltage clamping, low circulating current, and load adaptive zero-current switching of the devices. Variable-frequency modulation regulates load voltage and maintains the impulse commutation with source voltage variation. Experimental results on a 1-kW proof-of-concept hardware prototype are demonstrated to observe the operation, performance, and verify the proposed concept and claims.

Soft-Switching Non-Isolated Current-Fed Inverter for PV/Fuel Cell Applications

A non-isolated impulse commutated current-fed voltage doubler based non-isolated inverter for a solar photovoltaic, battery or fuel cell application is proposed in this paper. Impulse commutation enables device voltage clamping with zero current commutation of the semiconductor devices. It eliminates the traditional problem of turn-off voltage spike across the devices in current-fed converters. Unlike resonant converters, resonance pulse appears for a very short interval leading to zero current turn-off of devices. It therefore, limits peak and circulating currents through the components. Voltage doubler is selected to achieve 2 $\times$ gain. Variable frequency modulation ensures output voltage regulation with input and load variations. Steady-state operation and analysis of front-end converter is explained. A 500 W prototype has been designed and developed to demonstrate the performance and verify the proposed operation, analysis, and claims.

Impulse Commutated Zero-Current Switching Current-Fed Push–Pull Converter: Analysis, Design, and Experimental Results

Impulse commutated current-fed push-pull (ICCPP) converter has been analyzed and designed. The topology maintains zero-current switching (ZCS) of the semiconductor devices. Variable frequency modulation has been adopted to regulate load voltage and achieve ZCS over variable input voltage. At fixed input voltage, ZCS and load voltage are load independent. Natural clamping of devices is achieved via impulse commutation. Push-pull converters have only two devices with common ground with source requiring simple gate drive circuitry. A comprehensive study of the proposed converter, including steady-state analysis and design, has been reported. A 500-W prototype was developed in the laboratory to evaluate and demonstrate the performance of the converter.

Impulse Commutated Zero Current Switching Current-fed Three-phase DC/DC Converter

An impulse-commutated current-fed three-phase dc/dc converter is proposed. It is a three-inductor current divider topology that reduces the current stress of the components. The proposed converter attains zero current switching (ZCS) of the semiconductor devices via impulse commutation utilizing the circuit paracitics. The devices' voltage is clamped at Vo/n. Voltage clamping and zero-current commutation of devices are load independent. Load voltage is regulated by employing variablefrequency modulation. The current-fed topology with inherent boost ability simplifies the transformer design by reducing the required turns ratio. Rectifier diodes also commutate with ZCS without ringing and eliminate the need for a secondary snubber. A comprehensive study of the proposed converter together with the experimental results obtained from a laboratory prototype of 1 kW have been presented to validate the claims and to evaluate the converter's performance. The proposed converter is suitable for low-voltage high-current applications requiring high voltage gain. It inherently offers short-circuit protection.

Automation of construction of characteristic curves in impulse control problems for the power amplifier-servomotor system. I. Speed-torque characteristics

An automated approach to deriving analytical expressions for the speed-torque characteristics for an arbitrary impulse control method for the power amplifier-servomotor electric drive system is developed. Mathematical expressions for the speed-torque characteristics for impulse modes and commutation methods are obtained based on the suggested approach, and an interactive application is developed. This application makes it possible to represent the family of speed-torque characteristics for the corresponding control method and impulse mode and study voltage and current wave-form diagrams at an arbitrary point of the speed-torque characteristics for the given motor parameters and pulse-width modulation period. Automation of the procedure of deriving analytical expressions and the development of the interactive application were carried out using the Mathematica system.

Design of an Impulse Commutation Bridge for the Solid-State Transfer Switch

Voltage sags have become a very critical power quality issue in recent years. In particular, in the high-tech industry parks of Taiwan, manufacturers can lose up to one million U.S. dollars for each voltage sag event. Some utility companies provide dual power feeders to these high-tech manufacturers to enhance power quality and reliability. The solid-state transfer switch (STS) based on thyristors can thus utilize the dual power feeders to protect sensitive loads against voltage sags. Conventional STS often requires more than a quarter cycle to complete the transfer process because its commutation is load dependent. An improved STS with impulse commutated circuit can greatly reduce the transfer time and provide better ride-through capability against voltage sags. In this paper, an impulse commutation bridge STS (ICBSTS) system is proposed to further simplify the forced-commutation circuitry. This paper also discusses the in-rush phenomenon of the transformer due to the line transfer. A flux estimator is developed with the ICBSTS system to reduce the in-rush current.

An In-Rush Current Suppression Technique for the Solid-State Transfer Switch System

More and more utility companies provide dual power feeders as a premier service of high power quality and reliability. To take advantage of this, the solid-state transfer switch (STS) is adopted to protect the sensitive load against the voltage sag. However, the fast transfer process may cause in-rush current on the load-side transformer due to the resulting DC-offset in its magnetic flux as the load-transfer is completed. The in-rush current can reach 2∼6 p.u. and it may trigger the over-current protections on the power feeder. This paper develops a flux estimation scheme and a thyristor gating scheme based on the impulse commutation bridge STS (ICBSTS) to minimize the DC-offset on the magnetic flux. By sensing the line voltages of both feeders, the flux estimator can predict the peak transient flux linkage at the moment of load-transfer and evaluate a suitable moment for the transfer to minimize the in-rush current. Laboratory test results are presented to validate the performance of the proposed system.

Design and Implementation of an Impulse Commutated Solid-State Transfer Switch

Design and Implementation of an Impulse Commutated Solid-State Transfer Switch

A Novel Current Impulse Commutation Circuit for Thyristor Inverters

A novel current impulse commutation circuit for single- and three-phase thyristor inverters is presented and fully analyzed. Relevant design expressions are also derived. Moreover, it is shown that the proposed circuit has a number of significant advantages over commutation circuits currently employed.

A novel three-phase stepped-wave inverter using eight thyristors

The three-phase stepped-wave inverter is based on a new method of synthesizing waveforms. The proposed system comprises a 120° conduction type three-phase bridge inverter and a single-phase triple-frequency square-wave inverter. The triple-frequency inverter need for wave-shaping is of low power and is used in the neutral circuit of the three-phase inverter. A special complementary impulse commutation circuit realizes the above system with only eight thyristors. The output voltage waveform has three steps per quarter cycle and has a total harmonic distortion of 15.1%. The kVA ratings of the wound components are derived. The experimental results are presented and discussed.

Design Methods for Current Source Inverter/Induction Motor Drive Systems

A current source inverter combined with a controlled slip induction motor is a reliable and rugged ac drive system. The majority of the inverters in use today are the voltage source type using auxiliary impulse commutation. However, recent advances in SCR blocking voltage capability are making the complementary impulse commutated current source inverter a viable competitor

Impulse commutation in an AC-to-AC frequency converter

Impulse commutation in an AC-to-AC frequency converter