A new quasi-resonant DC-link PWM inverter using single switch for soft switching

This paper presents a new quasi-resonant DC-link (QRDCL) inverter. Only one switching device is used to create zero voltage instants under all load conditions. The maximum voltage across the inverter devices is maintained at around (1.01-1.1) times the input source voltage. The circuit has the flexibility of selecting switching instants of the resonant link in synchronism with any PWM technique. Control technique does not require the help of inverter switches to create the zero voltage instants in the DC-link, and voltage and current sensors are eliminated from the control circuit. In this paper, the principle of operation and detailed analysis of the proposed QRDCL inverter are presented and design considerations for achieving soft switching are obtained. Detailed PSPICE simulation studies are carried out to study the feasibility of the proposed topology under various load conditions. The experimental results of the proposed QRDCL PWM inverter feeding a three phase induction motor are given.     

A novel single-stage full-bridge buck-boost inverter

A novel single-stage full-bridge series-resonant buck-boost inverter (FB-SRBBI) is proposed in this paper. The proposed inverter only includes a full-bridge topology and a LC resonant tank without auxiliary switches. The output voltage of the proposed inverter can be larger or lower than the dc input voltage, depending on the instantaneous duty-cycle. This property is not found in the classical voltage source inverter, which produces an ac output instantaneous voltage always lower than the dc input voltage. The proposed inverter circuit topology provides the main switch for turn-on at ZCS by a resonant tank. The nonlinear control strategy is designed against the input dc perturbation and achieves well dynamic regulation. An average approach is employed to analyze the system. A design example of 500 W dc/ac inverter is examined to assess the inverter performance and it provides high power efficiency above 90% under the rated power.     

A novel soft-switched PWM current source inverter with voltageclamped circuit

This paper develops a new series resonant (current resonant) DC link inverter with a voltage clamped circuit. The proposed circuit has a fixed pulse frequency operation. The fixed pulse frequency at 20-50 kHz enables the system to work without audible noise, and to involve the much smaller-sized DC inductance and output capacitors compared with hard-switched current source inverters. The proposed circuit has a voltage clamped circuit which could control the voltage stress of the switches. In this paper, explanations of the new circuit configuration, the simulation, design considerations, and some experimental results are included     

An induction motor drive using an improved high frequency resonantDC link invertor

An induction motor drive that uses an improved high-frequency resonant DC link inverter is presented. The resonant circuit was systematically analyzed first to establish the criteria for initial current selection, and a circuit to establish the bidirectional initial current was then proposed. The proposed current initialization scheme solves voltage overshoot and zero crossing failure problems in the ordinary resonant DC link inverters. A three-phase 3 kW insulated-gate-bipolar-transistor (IGBT) based 60 kHz resonant link inverter has been constructed and successfully tested with an induction motor drive. The speed control system is implemented using two microprocessors. Experimental results are presented to show superior operation of the proposed resonant DC link inverter drive     

Small-signal analysis of a low-cost power control for LCC series-parallel inverters with resonant current mode control for HID lamps

In this paper, a low-cost power control for LCC series-parallel inverters with resonant current mode control for high intensity discharge (HID) lamps is presented. These resonant inverters require controlling the power supplied to the lamp in order to avoid exceeding the maximum lamp power recommended by the lamp manufacturer. The classical control method measures the lamp voltage and current and they are multiplied analogically, obtaining the lamp power consumption measure. This control circuitry results very complex due to the lamp voltage and current wide variations range during ignition and discharge processes. Assuming a regulated input dc voltage (bus voltage) provided by the power factor correction (PFC) pre-regulator and an inverter constant efficiency along the lamp aging, the lamp power consumption may be estimated and regulated properly measuring the inverter average input current. Also, the small-signal analysis performed allows obtaining the small-signal resonant inverter input impedance and studying the connection stability between PFC pre-regulator and inverter. The inverter small-signal analysis has been performed and an electronic ballast prototype for 250-W HPS lamps has been implemented and tested verifying the low-cost lamp power control method proposed.     

Self-sustained oscillating resonant converters operating above theresonant frequency

This paper presents a new control technique for resonant converters. Unlike conventional variable frequency control which externally imposes the switching frequency, the proposed scheme is based on controlling the displacement angle between one of the resonant circuit variables, typically the current through the resonant inductor, and the voltage at the output of the inverter. As a result, zero-voltage switching (ZVS) can be ensured over a wide operating range. The proposed control technique cam be applied for series, parallel, and series-parallel resonant converters. As an example, the static characteristics and dynamic model of a series-parallel resonant converter with the proposed controller are derived and the system behaviour is investigated in detail. Experimental results are given to demonstrate the operation of resonant converters with the proposed controller and to validate the analysis     

A Frequency Multiplication Resonant Inverter With Constant Frequency Phase Control

The schematic and analysis of a voltage-fed resonant inverter are presented in this paper. The topology of the inverter allows operation of the resonant tank at higher harmonics and multiples of the switching frequency. The resulting loss in voltage gain is compensated through the use of multiple commutation poles employing low-cost modestly rated MOSFETs. The proposed topology can control power throughput at a fixed frequency through pole phase-shift modulation. Zero voltage switching is maintained down to no load and within the entire input voltage range. Measurements from a multimegahertz 100-W inverter confirm the theoretical predictions, as well as the suggested design and control approach.     

Performance evaluation of an FPGA controlled soft switched inverter

A field programmable gate array (FPGA) based controller is proposed for a dc link series resonant inverter. The basic operation of the zero current switching inverter is briefly described. A strategy of decoupling the control of the dc link current from the load current is identified and referred as decoupled current control (DCC). The use of gate-controlled devices like metal-oxide-semiconductor field-effect transistor/insulated gate bipolar transistor/MOS-controlled thyristor permits a higher resonance frequency at the link of the inverter. The increased frequency enables the application of pulse density modulation technique with a bang-bang controller to synthesise and control the wave-shapes of current and voltage of the inverter. The DCC strategy eliminates the conventional analogue controller. A digital sequence controller has been designed using the state machine technique for the reliable operation of the inverter. The digital design is implemented on a single chip FPGA. To verify the proposed control strategy and the FPGA controller, a prototype has been built and tested. The test results show that a sinusoidal inverter output voltage is maintained with total harmonic distortion less than 5% and a regulation of about 1% from no-load to full-load, including non-linear and transient loads. The performance of the inverter with the FPGA controller is promising and attractive for uninterrupted power supply applications.     

A novel current initialization scheme for parallel resonant dc link inverter

In this paper a novel current initialization scheme is proposed for a parallel resonant dc link inverter. The method of current initialization is based on the state transition analysis of the system as a boundary-value problem. It is shown that, for a given load current, it is possible to force the dc link voltage to go to zero at a prescribed time by properly choosing the initial dc link current. This technique makes it possible to operate the resonant dc link inverter without any zero-crossing failure, which is the most important issue for satisfactory operation of such an inverter. The proposed current initialization technique is validated through digital computer simulation studies and practical implementation results.     

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     

High power factor self-power-controlling electronic ballast usingcurrent source type push-pull resonant inverter

A new simple low cost high power factor correction circuit for electronic ballast employing a current source type push-pull resonant inverter is proposed. The proposed circuit provides high power factor, low current harmonic distortion, self-power-controlling operation for load variations and cost-effectiveness     

Self-oscillating resonant AC/DC converter topology for inputpower-factor correction

This paper presents the analysis and design of a single-phase single-stage high-power-factor AC/DC converter employing a series-parallel resonant topology operating in self-sustained oscillating mode. A control approach is proposed to achieve low total harmonic distortion of the input current. This approach does not require sensing of the input current. In addition, the inverter output current is limited during transients, and the converter operates with zero voltage switching for all operating conditions including open and short circuit. The performance of the proposed scheme is verified experimentally on a 500 W prototype     

A three-phase soft-transition inverter with a novel controlstrategy for zero-current and near zero-voltage switching

This paper proposes a new soft-transition control strategy for a three-phase zero-current-transition (ZCT) inverter circuit. Each phase leg of the inverter circuit consists of an LC resonant tank, two main switches, and two auxiliary switches. The proposed strategy is realized by planning the switching patterns and timings of these four switches based on the load current information. It enables all the main switches and auxiliary switches to be turned on and turned off under zero-current conditions, and achieves a near zero-voltage turn-on for the main switches. Compared with existing ZCT strategies, the diode reverse recovery current and switching turn-on loss are substantially reduced, the current and thermal stresses in the auxiliary devices are evenly distributed over every switching cycle, and the resonant capacitor voltage stress is reduced from twice the DC bus voltage to 1.3-1.4 times the DC bus voltage. The proposed strategy is also suitable for three-phase power-factor-correction (PFC) rectifier applications. The operation principles, including a detailed analyst based on the state-plane technique, and a design rule are described in this paper. The circuit operation is first verified by a computer simulation, and is then tested with a 50-kW three-phase inverter to the full power level together with a three-phase induction motor in a closed-loop speed/torque control. Significant reductions in switching losses and voltage/current stresses over existing techniques have been experimentally demonstrated     

A power-factor-corrected AC-AC inverter topology using a unified controller for high-frequency power distribution architecture

High-frequency power distribution architecture (HFPDA) has gained more and more attention from both academics and industry in recent years. It is not only applicable in space systems, but also found attractive in power system design for emerging telecommunication and computer systems. As the technology has matured, HFPDA even seems to be attractive for powering the desktop computers employing the latest generation fast microprocessors. This paper presents an ac-ac inverter for HFPDA. The inverter includes a high-frequency resonant inverter and a buck-boost converter for power-factor correction (PFC). A unified controller controls both the resonant inverter and the PFC stage. Unlike other single-stage power-factor-corrected inverter topologies, the proposed inverter system has reduced dc-bus voltage stress for the universal input line voltage. The proposed inverter is found attractive in low-power applications.     

New VVVF control-based high-frequency resonant inverters using static induction transistors

Voltage-fed high-frequency resonant inverters are proposed having a variable-voltage variable-frequency (VVVF) control function based on new circuit topologies called resonant voltage phasor controlled type and current phasor controlled type. The steady-state characteristics of the circuit topologies proposed are illustrated and the circuit design algorithm is described. A resonant voltage phasor controlled type high-frequency resonant inverter newly developed by using a static induction transistor (SIT) is applied as a 100-500 kHz induction-heating power supply. This paper thus refers to the results of an experiment including the optimum drive circuit of SITs.     

Minimum current magnitude control of surface PM synchronous machines during constant power operation

The dual-mode inverter control (DMIC) was initially developed to provide broad constant power speed range (CPSR) operation for a surface mounted permanent magnet machine (PMSM) having low inductance. The DMIC interfaces the output of a common voltage source inverter (VSI) to the PMSM through an ac voltage controller. The ac voltage controller consists of three pairs of anti-parallel silicon controlled rectifiers (SCRs), one anti-parallel SCR pair in series with each winding of the motor. In a recent paper a fundamental frequency model of DMIC type controllers was developed using an equivalent reactance interpretation of the in-line SCRs. In this work, the same fundamental frequency model is used to show that the DMIC may have considerable loss reduction benefits even if the motor winding inductance is large. Specifically, it is shown that the SCRs enable maximum watts per rms amp control during constant power operation. The rms motor current can be minimized for any given power level and sufficiently large speed with DMIC. A fixed winding inductance and a conventional inverter can only be optimized for a single speed and power level. The performance predicted by the fundamental frequency model of the DMIC is compared to that of a conventional PMSM drive where the motor has sufficiently large inductance to achieve an infinite CPSR. It is shown that the SCRs can reduce motor current by a factor of 0.7071 at high speed and rated power. This would reduce the motor copper losses by 50% and reduce the conduction losses in the VSI by 29.3%. At less than rated power the percentage of motor/VSI loss reduction enabled by the SCRs is seen to be even larger.     

A hysteresis current control for single-phase multilevel voltage source inverters: PLD implementation

In most high-performance applications of voltage source pulse-width modulation inverters, current control is an essential part of the overall control system. In this paper, a hysteresis current control technique for a single-phase five-level inverter with flying-capacitor topology is proposed. Logic controls and a programmable logic device are suitable for handling a large number of switches and implementation of state transitions. This method also considers how to improve unbalanced voltages of capacitors using voltage vectors in order to minimize switching losses. The simulation and experimental results describe and verify the current control technique for the inverter.     

直流环节逆变器的相平面分析及软开关条件研究

 新型谐振直流环节逆变器具有PWM和软开关双重优点,然而辅助谐振直流环节有4个换能元件,使逆变器具有复杂的动力学行为和高维时变特性,用解微分方程的方法研究系统的动态特性和求解软开关条件及设计规则是相当复杂和困难的.结合相平面法分析的特点,该文将4维电路分解在3个相平面研究了系统的动力学行为、软开关条件以及设计规则.文中详细阐述了相平面的构建和分析过程,利用相平面分析结果和解析几何方法求取了软开关条件及设计规则.利用设计规则,搭建了逆变器驱动无刷直流电机的实验,实验结果验证了相平面分析的正确性和设计规则的可行性.     

Control of Single-Phase-to-Three-Phase AC/DC/AC PWM Converters for Induction Motor Drives

This paper proposes a novel control scheme of single-phase-to-three-phase pulsewidth-modulation (PWM) converters for low-power three-phase induction motor drives, where a single-phase half-bridge PWM rectifier and a two-leg inverter are used. With this converter topology, the number of switching devices is reduced to six from ten in the case of full-bridge rectifier and three-leg inverter systems. In addition, the source voltage sensor is eliminated with a state observer, which controls the deviation between the model current and the system current to be zero. A simple scalar voltage modulation method is used for a two-leg inverter, and a new technique to eliminate the effect of the dc-link voltage ripple on the inverter output current is proposed. Although the converter topology itself is of lower cost than the conventional one, it retains the same functions such as sinusoidal input current, unity power factor, dc-link voltage control, bidirectional power flow, and variable-voltage and variable-frequency output voltage. The experimental results for the V/f control of 3-hp induction motor drives controlled by a digital signal processor TMS320C31 chip have verified the effectiveness of the proposed scheme     

A new quasi-parallel resonant DC link for soft-switching PWMinverters

A new quasi-parallel resonant DC-link inverter with the more flexible pulse-width-modulation (PWM) capability and easier control is proposed in this paper. With the addition of one coupling core and one diode, the circuit can be directly applied to the single/three-phase inverter to achieve the soft-switching action. For the proposed topology, it needs neither the help of the inverter switch devices nor the requirement of voltage/current sensors. Random duration of the zero DC-link voltage can be obtained, and the voltage stresses of the inverter switches can be maintained to the minimum. The relative analysis of the presented circuit has been performed and verified by the experiment