Auxiliary resonant commutated pole inverter using two internalvoltage-points of DC source

This paper presents a new auxiliary resonant commutated pole inverter that has series-connected batteries as the DC source. This inverter has two main switches and two auxiliary switches, and of all these devices achieve soft switching. The resonant operations are employed only during the commutating intervals; therefore, pulsewidth modulation (PWM) can be applied to the circuit. This circuit has the feature of using two internal voltage points of the DC source. Consequently, the circuit has the advantages of stability, simplicity in control, and high efficiency. The principle of the circuit operation and the experimental results are described in this paper     

A current source PWM inverter with actively commutated SCRs

Conventional SCR based current source inverters suffer from poor waveform quality due to six step switching. Pulse width modulated current source inverters typically require gate turn off devices with reverse voltage blocking capability which have limited their application. In this paper, a new pulse width modulated current source inverter topology using one gate turn off switch and six SCRs is presented. The converter uses active commutation to realize pulse width modulation in a conventional SCR based current source inverter. Modulation techniques for the proposed inverter, simulation and experimental results are described in the paper. This topology is suitable for high performance, high power applications     

A rugged soft commutated PWM inverter for AC drives

A novel DC-DC power converter for variable-speed AC power drives using the zero-voltage switching technique is described. This converter combines the advantages of soft commutated inverters and those of conventional pulsewidth modulated (PWM) inverters. In the proposed scheme, the soft commutation reduces the constraints on the switches, and the PWM enables simple and efficient regulation of the power flow. Furthermore, the zero-voltage switching technique makes operation safe, and the switching of bipolar transistors at 20 kHz is easily achieved without compromising the efficiency of the system     

A high-power-factor DC-linked resonant inverter

A new approach of power-factor correction for the DC-linked high-frequency resonant inverters is proposed. The high-power-factor operation is achieved by altering the energy delivery process of the conventionally used topology. The load resonant circuit of the proposed topology draws a high-frequency pulse current directly from the AC source. This approach can be accomplished merely with an additional small capacitor as the energy buffer and a diode as the energy transfer switch. The design and experimental results for an implementation example are given to verify the theoretical analyses     

A comparison of load commutated inverter systems for inductionheating and melting applications

A comparative analysis of a current source inverter and a voltage source inverter suitable for induction heating and melting applications is presented. Both power supplies considered operate on the principle of load commutation. The comparison is based on criteria such as input power factor, component ratings, maximum and minimum operating frequencies, operation under varying load conditions, inverter starting capability, and system and control simplicity. The voltage source series resonant inverter is found to offer the best overall performance with respect to converter utilization     

A simplified three-phase zero-current-transition inverter with three auxiliary switches

Most existing three-phase soft-switching inverters with fewer than six auxiliary switches have fundamental drawbacks in performance. There exist a few soft-switching inverters with six auxiliary switches that can potentially achieve desirable performance, but are penalized with the high cost and large size associated with the auxiliary switches. This paper proposes a zero-current-transition (ZCT) inverter topology that requires only three auxiliary switches. Each phase of the proposed circuit employs one auxiliary switch and one LC resonant tank to assist switching transitions. With considerable reduction in device count, cost, and size, the proposed topology realizes zero-current turn-off for all main switches and auxiliary switches, and provides soft commutation for all diodes. Meanwhile, it requires no modification to normal pulsewidth modulated (PWM) algorithms. The operation principles, design and control guidelines, and an analysis using the state-plane technique are presented. Based on the proposed topology, a 50-kW three-phase prototype inverter has been developed for electric vehicle propulsions, and tested to the full power level with a closed-loop induction motor drive system. Experimental results on the 50-kW prototype are provided to verify the proposed concept in high-power AC adjustable speed drive applications.     

A high voltage resonant inverter for dielectric discharge barrier cell plasma applications

Among the applications of dielectric barrier discharge cells (DBDCs), the generation of cold plasmas for the degradation of toxic organic compounds has received a great deal of attention in recent years. Normally, a DBDC can be energized by means of a high voltage power supply operating at line frequency. In this paper, the analysis, design and construction of a power resonant seriesinverter is presented; this inverter is aimed to operate at high-voltages/high-frequencies, and its suitability to excite a DBDC is investigated. The topological analysis of the inverter is carried out using the fundamental approximation technique, where the DBDC has been modelled as a capacitor whose terminals' voltage is provided by a pulse transformer. Both, the DBDC and the pulse transformer are represented in an RLC equivalent circuit. The resonant inverter is designed to operate in a region where the transfer function is load dependent. The series resonant inverter performance has been experimentally tested in a DBDC application, showing its effectiveness in the generation of the electron discharge by means of a charge/voltage figure of merit.     

A higher levels multilevel inverter with reduced number of switches

This paper presents a high-levels multilevel inverter (MLI) with a reduced number of the required switches. Forty-nine levels can be obtained in the output voltage from this circuit by using only 12 semiconductor switches, while in conventional topologies of MLI, a higher number of switches is required producing a lower number of levels in the output voltage. Reduction in the number of semiconductor switches, gate drivers, DC voltage sources and increasing the number of voltage levels are advantages of the proposed MLI compared with other topologies. These advantages result in smaller size, lower loss and low installation cost. Total harmonic distortion (THD) in the output waveform of the inverter is very low, thus, using a filter to improve the output waveform is not needed. A switching pulse system has been presented to produce nearly sinusoidal waveforms. Mathematical relations and switching states of the proposed topology have been discussed. Simulation results have been obtained and studied. The prototype of the modified MLI has been built and tested in the laboratory using a dSPACE (DS1104) evaluation board in order to verify the simulation results. Several of the experimental results of the proposed topology have been included and discussed.     

A resonant inverter for electronic ballast applications

Electronic ballasts must provide enough open circuit voltage to start the fluorescent lamp and current limiting while the lamp is running. Resonant inverters may be utilized in electronic ballasts because of their load-dependent characteristics. The three basic types of resonant inverters, the series-loaded, parallel-loaded, and the series-parallel-loaded, are compared using fundamental approximation techniques for their applicability in electronic ballasts operating from a low voltage source. A parallel-loaded resonant inverter operating slightly above its resonant frequency is selected because of the high voltage gains possible. Operation above the resonant frequency allows zero-voltage turn on of the semiconductor devices. Zero-voltage turn off can be achieved with the addition of lossless snubber capacitors. Experimental results from a lab prototype are used to verify the design procedure     

A forced commutated inverter as a small series tap on a DC line

A forced commutated inverter used for tapping energy to a remote load from a DC line running through a rural area is described, and the results of a study conducted on Manitoba Hydro's Electromagnetic Transients Program are presented. It is shown that a passive load requiring real and reactive power can easily be supplied. The tap itself is capable of responding quickly to changes of load without a communication link to the main converter terminals. The tap is able to recover easily from all anticipated faults and disturbances taking place in its own system as well as at the main converter terminals. It is noted that the series inverter tap with forced communication is not as sensitive to AC side disturbances as was the multiterminal system with a small parallel tap     

A multilevel inverter system for an induction motor with open-end windings

In this paper, a multilevel inverter system for an open-end winding induction motor drive is described. Multilevel inversion is achieved by feeding an open-end winding induction motor with two two-level inverters in cascade (equivalent to a three-level inverter) from one end and a single two-level inverter from the other end of the motor. The combined inverter system with open-end winding induction motor produces voltage space-vector locations identical to a six-level inverter. A total of 512 space-vector combinations are available in the proposed scheme, distributed over 91 space-vector locations. The proposed inverter drive scheme is capable of producing a multilevel pulsewidth-modulation (PWM) waveform for the phase voltage ranging from a two-level waveform to a six-level waveform depending on the modulation range. A space-vector PWM scheme for the proposed drive is implemented using a 1.5-kW induction motor with open-end winding structure.     

A near-zero current-switching series resonant inverter using GTOs

A novel implementation of fast gate-turn-off thyristors (GTOs) for a series resonant power converter operating above 10 kHz and an output power rating of 10 kW or greater is presented. A zero current switching gating strategy that eliminates the need for large negative gate drive circuits is presented. This permits the operation of the converter at a near-unity load power factor independent of the operating frequency. Consequently, for a given output power, the installed kVA capacity of the converter is minimized, and the system simplicity is maintained. A simplified analysis and component ratings for the GTO-based converter are presented. All the results are verified experimentally     

Quasi-parallel resonant DC link inverter with improved PWMcapability

A quasi-parallel resonant DC-link (QPRDCL) circuit with improved PWM capability is proposed for the zero voltage switching (ZVS) three phase PWM inverter. The circuit has minimum voltage stresses and improved PWM capability due to the flexible selectability of the on/off instants of the resonant link     

Efficiency optimization in ZVS series resonant inverters with asymmetrical voltage-cancellation control

This paper presents a time-domain analysis and a computerized search algorithm for optimizing the efficiency in zero-voltage switching (ZVS) full-bridge series resonant inverters with asymmetrical voltage-cancellation (AVC) control for different load quality factors. The optimum AVC control found allows all the switches to be turned on with zero voltage with the minimum switching frequency. In order to minimize losses, the switching frequency is kept as close as possible to resonance. The optimum AVC control is compared with previous fixed or narrow frequency range control strategies to show that it improves performance over all the output power range for different loads. The detailed steady-state analysis carried out here increases the precision of the first-harmonic analysis of a previous work, which is especially important with distorted output currents due to low load quality factors or highly asymmetrical modulation strategies. The theoretical results are verified experimentally.     

A unique fault-tolerant design for flying capacitor multilevel inverter

This paper presents a unique design for flying capacitor type multilevel inverters with fault-tolerant features. When a single-switch fault per phase occurs, the new design can still provide the same number of converting levels by shorting the fault power semiconductors and reconfiguring the gate controls. The most attractive point of the proposed design is that it can undertake the single-switch fault per phase without sacrificing power converting quality. Future more, if multiple faults occur in different phases and each phase have only one fault switch, the proposed design can still conditionally provide consistent voltage converting levels. This paper will also discuss the capacitor balancing approach under fault-conditions, which is an essential part of controlling flying capacitor type multilevel inverters. Suggested fault diagnosing methods are also discussed in this paper. Computer simulation and lab results validate the proposed controls.     

A six-phase multilevel inverter for MEMS electrostatic induction micromotors

The construction of miniaturized rotating electric machines through microfabrication techniques is becoming a reality. Applications of such micromotors include miniaturized pumps, compressors, fans, coolers, and turbogenerators. However, the characteristics of these devices make the design of power electronics for them challenging. These characteristics include high-voltage and high frequency operation, tightly constrained operating waveforms and timing, and capacitive input impedances. This paper explores the design of power electronics for microfabricated electrostatic induction machines. We describe the structure and operation of these machines, and establish the operating requirements of power converters for them. We provide a comparison of inverter topologies for this application, and propose an appropriate architecture. The design and experimental evaluation of a prototype six-phase, five-level inverter for this application is presented. The inverter operates at frequencies up to 2 MHz and at voltages up to 300 V, and meets the stringent waveform and timing constraints posed by this application.     

A single-stage high-power-factor electronic ballast withduty-ratio-controlled series resonant inverter

A single-stage high-power-factor electronic ballast is developed by making an integration of an active filter and a series resonant inverter. The function of power-factor correction is performed by adjusting the duty ratio of the inverter power switches with a simple control circuit. A prototype unit designed for a 36-W compact fluorescent lamp is built and tested to verify the predicted results     

Transformerless series sag compensation with a cascaded multilevel inverter

The use of a cascaded multilevel inverter for transformerless sag/dip compensation is investigated. This topology is investigated as a cost-effective means for series sag compensation by eliminating the large injection transformer and output filter components that are used in conventional series injection devices. This prototype inverter is designed for sag compensation of a 250-kVA load. In this design, cost effectiveness plays a major role in the selection of the energy storage and the switching components. Control schemes are discussed for series sag compensation with this multilevel inverter. New control methods for sag compensation and injection are also introduced. A prototype is developed and the control schemes of this sag compensator are successfully verified in the practical results and show successful compensation for sags for different types of loads. The performance of this compensator makes it promising for future power rating upgrade and industrialization.     

A ZVS PWM inverter with active voltage clamping using the reverse recovery energy of the diodes

This paper presents a zero-voltage-switching (ZVS) pulsewidth modulated inverter with active voltage clamping using only a single auxiliary switch. The structure is particularly simple and robust. It is very attractive for single-phase high-power applications. Switching losses are reduced due to implementation of the simple active snubber circuit that provides ZVS conditions for all switches, including the auxiliary one. Its main features are: simple modulation strategy, robustness, low weight and volume, low harmonic distortion of the output current and high efficiency. The principle of operation for steady-state conditions, mathematical analysis and experimental results from a laboratory prototype are presented.     

Resonant DC link soft-switching inverter with low-loss auxiliary circuit

An auxiliary switching device is usually set on the DC bus of the resonant DC link inverter, which restricts the efficiency of the inverter and is also one of the reasons for its not extensive application and promotion in the high-power field. To solve the problem, auxiliary circuits and DC bus of the resonant DC link soft-switching inverter designed in this paper are connected in parallel, and auxiliary switching devices and resonant elements are not connected in series on the DC bus, which help to improve the efficiency and reduce the power losses of the auxiliary resonant circuits. Based on the equivalent circuits in different operating modes, the paper analyzes the working process of the soft-switching inverter, soft-switching realization conditions and design rules. A 10 kW laboratory prototype is built, and through the comparison of the experimental results from it and the hard-switching inverter, it is shown that the efficiency improvement value of the designed inverter at full load is higher than that at light load. Therefore, the soft-switching inverter designed in this paper is conductive to reducing the power losses of the auxiliary resonant circuits and ensuring the efficient use of the electric energy.