Soft Switching PWM Inverter Research Articles

A novel topology and control strategy for a soft-switched single-phase grid connected inverter

This paper represents a novel soft switched PWM inverter topology and a control strategy using switching flow graph theory. The switching flow graph is a unique graphical model for analysis of PWM switching converters. All power switches operate at zero-voltage-switching (ZVS) turn-ON and turn-OFF conditions as a result, commutations of power switches have lower losses furthermore higher efficiency is reached. The proposed approach is analyzed theoretically and demonstrated experimentally by making a testing prototype.

Study on Soft Switching Technology to Reduce Electromagnetic Interference of PWM Inverter

To reduce the electromagnetic interference(EMI) of traditional PWM inverter, the paper puts forward a novel soft switching PWM inverter, expounds the inverter's configuration and working principle, analyses it's realization method, and validates it through simulation and experiment. The EMI conductive noise of AC inverter system was measured, analyzed and compared under hard switching and soft switching respectively. It testifies the validity of soft switching inverter on reducing EMI.

Optimal Design of a DC-DC Converter for Photovoltaic Generation

This paper presents novel circuit topology of half-bridge soft-switching PWM inverter type DC-DC high power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed, half-bridge high frequency PWM inverter with a high frequency planar transformer link PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode-equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC bus lines can achieve ZCS turn-on and ZVS turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, high switching frequency IGBTs can actually be selected in the frequency range of 40[㎑] under the principle of soft-switching. The performance evaluations of the experimental setup are illustrated practically.

A Novel Prototype of Duty Cycle Controlled Soft-Switching Half-Bridge DC-DC Converter with Input DC Rail Active Quasi Resonant Snubbers Assisted by High Frequency Planar Transformer

This paper presents a new circuit topology of active edge resonant snubbers assisted half-bridge soft switching PWM inverter type DC-DC high power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed half-bridge high frequency PWM inverter with a high frequency planar transformer link in addition to input DC busline side power semiconductor switching devices for PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC buslines can achieve ZCS turn-on and ZVS turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, a high switching frequency IGBTs can be actually selected in the frequency range of 60 kHz under the principle of soft switching. The performance evaluations of the experimental setup are illustrated practically. The effectiveness of this new converter topology is proved for such low voltage and large current DC-DC power supplies as DC bus feeding from a practical point of view.

Three-phase soft-switched PWM inverter for motor drive application

A novel soft-switched inverter topology in which three mutually coupled inductors at a time are involved in the resonance process is proposed. By the introduction of magnetic coupling between three resonant inductors, the zero-voltage instants for the inverter can be generated by one auxiliary switch. Also, the resonant energy can be recycled, and the maximum voltage stress on the auxiliary circuit diode components is confined to the DC-link clamp voltage level. The DC link can be clamped to 1.1-1.3 times the DC-source value. This is unlike the soft-switched inverter in which two mutually coupled inductors are at a time are involved in a resonance process, wherein the clamping diode experiences voltage stress of the order of 11 per unit when clamping the DC-link voltage at 1.1 per unit. The proposed inverter also provides pulse-width modulated operation. An analysis of this novel quasi-resonant DC-link inverter topology is presented to reveal its soft-switching characteristics. Simulation and laboratory experiments are performed to validate the analysis.

A Novel type of High-Frequency Transformer Linked Soft-Switching PWM DC-DC Power Converter for Large Current Applications

This paper presents a new circuit topology of DC busline switch and snubbing capacitor-assisted full-bridge soft-switching PWM inverter type DC-DC power converter with a high frequency link for low voltage large current applications as DC feeding systems, telecommunication power plants, automotive DC bus converters, plasma generator, electro plating plants, fuel cell interfaced power conditioner and arc welding power supplies. The proposed power converter circuit is based upon a voltage source-fed H type full-bridge high frequency PWM inverter with a high frequency transformer link. The conventional type high frequency inverter circuit is modified by adding a single power semiconductor switching device in series with DC rail and snubbing lossless capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge inverter arms and DC busline can achieve ZVS/ZVT turn-off and ZCS turn-on commutation operation. Therefore, the total switching losses at turn-off and turn-on switching transitions of these power semiconductor devices can be reduced even in the high switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules is selected to be 60 kHz. It is proved experimentally by the power loss analysis that the more the switching frequency increases, the more the proposed DC-DC converter can achieve high performance, lighter in weight, lower power losses and miniaturization in size as compared to the conventional hard switching one. The principle of operation, operation modes, practical and inherent effectiveness of this novel DC-DC power converter topology is proved for a low voltage and large current DC-DC power supplies of arc welder applications in industry.

A Novel Prototype of Auxiliary Edge Resonant Bridge Leg-Link Snubber-Assisted Soft-Switching Sinewave PWM Inverter

This paper proposes a new circuit topology of the three-phase soft switching PWM inverter and PFC converter using IGBT power modules, which has the improved active auxiliary switch and edge resonant bridge leg-commutation-link soft-switching snubber circuit with pulse current regenerative feedback loop as compared with the typical auxiliary resonant pole snubber discussed previously. This three-phase soft switching PWM double converter is more suitable and acceptable for a large capacity uninterruptible power supply, PFC converter, utility-interactive bi-directional converter and so forth. In this paper, the soft switching operation and optimum circuit design of the novel type active auxiliary edge resonant bridge leg commutation link snubber treated here are described for high power applications. Both the main active power switches and the auxiliary active power switches achieve soft switching under the principles of ZVS or ZCS in this three-phase inverter switching. This three-phase soft switching commutation scheme can effectively minimize the switching surge related electromagnetic noise and the switching power losses of the power semiconductor devices; IGBTs and modules used here. This three-phase inverter and rectifier coupled double converter system does not need any sensing circuit and its peripheral logic control circuits to detect the voltage or the current and does not require any unwanted chemical electrolytic capacitor to make the neutral point of the DC power supply voltage source. The performances of this power conditioner are proved on the basis of the experimental and simulation results. Because the power semiconductor switches (IGBT module packages) have the relation of the trade-off in the switching fall time and tail current interval characteristics as well as the conductive saturation voltage characteristics, this three-phase soft-switching PWM double converter can perform to improve actual efficiency in the output power ranges with a trench gate controlled MOS power semiconductor devices which is much more improved to the low saturation voltage. The effectiveness of this is verified from a practical point of view.

Selection of carrier waveforms for PWM inverter

In this paper the influence of different carrier waveforms upon the output characteristics of PWM inverter is described in detail. When a triangular carrier waveform is used in hard-switching PWM inverters, harmonics exist in the neighborhood of the output frequency of the inverter output voltage and current due to the dead time. The triangular carrier waveform used in soft-switching PWM inverter will cause difficulties in controlling resonance-trigger time, higher loss in the resonant circuit, and less utilization of the DC bus voltage. If a sawtooth carrier is used in hard-switching PWM inverter, there will be severe distortion in the current waveform. When sawtooth carriers with alternate positive and negative slopes are used in soft-switching PWM inverters, the resonance-trigger time is easy to control, and distortion in the output voltage and current caused by the dead time will not appear.

Effective Improvement of DC Busline Voltage Utilization Factor in Two Switch-Auxiliary Quasi-Resonant DC Link Snubber Assisted Three Phase Voltage Source Type Soft-Switching PWM Inverter

In recent years, a resonant snubber to minimize switching power losses and EMI noises have attracted special interest for the voltage-fed soft switching sinewave PWM inverters and active rectifiers. The authors have discussed the performance evaluations on lower noise and high efficiency for two switch auxiliary resonant DC link snubber assisted three-phase voltage-fed soft switching PWM inverter. It was proved that cost effective three phase soft switching inverter treated here is able to improve both efficiency and EMI noise. However, some practical problems to be improved have recognized for the soft-switching three phase PWM inverter treated here from a practical point of view. This three phase soft-switching inverter with two switch type auxiliary resonant DC link snubber has significant disadvantages of DC busline link voltage reduction for the existence of the zero voltage mode transition period as well as the larger size and physical volume of electrolytic capacitor incorporated into the resonant DC link snubber. The additional technology to minimize the busline DC link zero voltage period in order to overcome the practical problems mentioned above is newly proposed in this paper. From experimental and simulation viewpoints, the modified version of this soft-switching inverter is discussed and evaluated for the DC busline voltage utilization factor as compared with the previously developed one.

系統連系高周波2石フライバックトランス絶縁方式ソフトスイッチングPWM正弦波インバータ

This paper presents two novel prototypes of the utility AC power source connected sinewave inverter using the high-frequency two-switch flyback transformer which is more suitable and acceptable for the small-scale solar photovoltaic and fuel cell generator interfaced power conditioners. The proposed sinewave soft-switching PWM power conditioner with a high-frequency AC link has a function of electrical isolation including sinewave hard-switching PWM power conditioner with a high frequency link, which is considered for solar photovoltaic power conditioner and fuel cell generator related power conditioner from the viewpoints of safety and reliability in total system. The discontinuous conduction mode (DCM) operation of the flyback transformer in this circuit system is also introduced to feature a simple, low-cost and high-efficiency topology of the sinewave inverter circuit and digital control implementation. The operating principle of the proposed sinewave soft-switching PWM inverter circuit as compared with sinewave hard-switching PWM inverter are described for the designing of circuit parameters. Moreover, the digitally controlled sinewave PWM control processing scheme is presented herein. Finally, the sinewave soft-switching PWM inverter prototype is actually built and tested to verify the validity of the proposed power conditioner for new energy generation systems.

Effects on commutation elements in inductor commutation soft-switched PWM inverter and its design equations

The inductor commutation soft-switched PWM inverter (ICSI) and ICSI driven by frequency modulated PWM signal (FM-ICSI) are analyzed, considering the effects on the commutation elements for the soft switching. From the analysis, the design equations for the commutation elements is clarified and these are verified experimentally.

Auxiliary resonant snubber bridge-leg associated soft-switching PWM inverter type DC-DC converter family with bidirectional active switches and voltage clamping diodes

A prototype of voltage-source soft-switching PWM inverter-type auxiliary resonant bridge-leg link snubbers is proposed with bidirectional active power switches and voltage clamping diodes for a new high-power high-voltage application. The voltage clamping diodes in the active resonant snubber are more effective in protecting the bidirectional active switches in the bridge-leg linked auxiliary resonant snubber from surge voltage spikes caused by energy stored in the auxiliary quasiresonant inductors and inductive parasitic wiring components. A variety of resonant snubber circuit topologies with voltage clamping diodes are presented and demonstrated. As an example of the variations of the proposed auxiliary active resonant-commutation snubber topologies, operation of a single-IGBT bidirectional switch with two voltage clamping diodes is analysed and discussed in detail for the auxiliary resonant bridge-leg link snubbers. The operating performance of the new active auxiliary resonant snubber-associated inverter-fed DC to DC power converter with voltage clamping diodes is practically demonstrated and evaluated to verify its effectiveness for a high-power high-voltage X-ray generator.

A New Soft-Switched PWM Inverter with Simple Control

This paper describes a new soft-switched PWM inverter with simple control. The control of the proposed inverter uses only PWM pattern for the output control The special control for ensuring the soft-switching operation is unnecessary. When the main switches are turned on, the zero-current-switching operation can be realized by the reactors in series. When the main switches are turned off, the zero-voltage-switching operation can be automatically realized by the cap acitors in parallel. The output currents of the proposed inverter have no distortion caused the blanking time for the prevention of the arm shorted fault at low output frequency because the load current can flow during the blanking time.In this paper, the operation principle, the experimental results and the output characteristics of the proposed inverter will be described.

Design of Commutation Elements in Inductor Commutation Soft Switched PWM Inverter

We have proposed an inductor commutation soft-switched PWM inverter (ICSI) and the carrier frequency modulated ICSI (FM-ICSI) without sensors for the current and voltage. It is realized by connecting a series circuit with an inductor LZC and a capacitor CZC between the output terminals of the conventional hard switched inverter (CHIS), and by connecting a capacitor CR in parallel with each main switch. The commutation elements LZC, CZC and CR control the magnitude of the circulating current, short current and efficiency of ICSI and FM-ICSI. The circulating current always flows through the main switches and LZC and CZC from the dc source to realize soft switching. Therefore, in this paper, the relations of the commutation elements and these currents are analyzed and verified experimentally for design of ICSI and FM-ICSI.

Efficiency improvement by frequency modulation of carrier signal for an inductor commutation soft‐switched PWM inverter

AbstractThe inductor communication soft switched PWM inverter (ICSI) gives good output waveforms and allows high carrier frequencies. However, to realize soft switching, a circulating current must always flow, so that the efficiency is not as good as in the conventional hard‐switched PWM inverter (CHSI).In this paper, to alleviate the efficiency deterioration due to the circulating current, we propose a technique which uses frequency modulation (FM) of the carrier signal. The frequency is designed to be higher at zero of the input signal and lower at its peak. By this technique, the circulating current is suppressed efficiently without sensing of the voltage and current of the main circuit, and efficiency is greatly improved. We quantitatively investigate this FM method and analyze the loss and efficiency of ICSI based on the FM method (FM‐ICSI). We also compare it with ICSI without the FM method and discuss the effectiveness of the FM method.