The three-phase resonant DC link inverter with soft-switching function

ABSTRACT

In order to realise the energy-saving operation of the three-phase inverter, a three-phase resonant DC link inverter with soft-switching function is proposed. The auxiliary resonant circuit on the DC side participates in the commutation process, so that the DC link voltage can change to zero before the main switch on the bridge arm is switched. Therefore, the main switch can complete the zero-voltage soft-switching and realise the energy-saving operation of the inverter by reducing the switching power loss. The circuit workflow and parameter design rules in each switching period are analysed. As indicated from the experimental results, the switching device is in the soft-switching state when it is switched, and when the output power reaches the rated value of 2.5 kW, the efficiency of the prototype is 98.4%, which is higher than that of the same type of soft-switching inverters. Thus, the auxiliary resonant circuit structure has reference value for the research and development of energy-saving three-phase inverters.     

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.     

The novel resonant DC link three-level soft-switching inverter

ABSTRACT

In the paper, the novel topology of the resonant DC link three-level soft-switching inverter is proposed to reduce switching losses and improve the efficiency of three-level inverter at high switching frequency. Symmetrical auxiliary resonant circuits are set in the DC link of three-level hard-switching inverter. Moreover, the terminal voltage of the resonant capacitors between the DC buses periodically drops to zero via the resonance of auxiliary circuits. Furthermore, under such condition, the main switches of the three-level inverter would be operated, in order to achieve zero-voltage switching. Based on the equivalent circuits in different operating modes, the paper analyses the working process of the soft-switching inverter in detail. In addition, a 3 kW laboratory prototype of resonant DC link three-phase three-level soft-switching inverter is built. The experimental results show that the main switches and auxiliary switches of the inverter are operated under soft-switching conditions, and the efficiency is significantly improved compared with the three-level hard-switching inverter. Therefore, the proposed topology can effectively reduce switching losses and prove to be more practical in engineering.     

A low frequency AC to high frequency AC inverter with build-in power factor correction and soft-switching

This paper presents a full bridge AC-AC inverter for high frequency power distribution system with power factor correction stage controlled by a unified controller. The proposed inverter has the following features: 1) load independent output voltage with constant frequency and very low total harmonic distortion (THD); 2) soft switching of the full bridge switches for a wide range of input voltage and load conditions; 3) low DC bus voltage; 4) simple control and cost effectiveness for the power factor correction stage. Operating principles and performance characteristics are presented, and guidance to design the converter is given. Experimental results of a 90-265V/sub ac/ input, 30 V/sub ac/ output at 100 kHz, 250 W laboratory prototype are given to verify the theoretical and simulation results. The proposed ac-ac inverter is attractive for low power (up to 250 W) high frequency applications.     

Random space vector modulation technique for high switchingfrequency inverter control

A new random space vector modulation (RSVM) technique is presented, which dramatically reduces both the number of calculations required for high switching frequency inverter control in real time and the annoying noise by randomising the harmonic spectrum     

Current source inverter modulation

Pulse width modulation strategies are applicable to current source inverters (CSIs). In particular, space vector modulation analysis developed for voltage source inverters (VSIs) is shown to apply to CSI. Using these tools, an equivalence between modulation patterns being used for VSI and those possible for CSI is established. A new modulation pattern is developed and analyzed for an eight-switch CSI, implementing neutral modulation. The analysis tools used to show the CSI/VSI equivalence in the standard case enable analysis of this eight-switch CSI structure. An improved modulation strategy arises from this analysis tool. An experimental eight-switch CSI circuit was constructed and a microcontroller was used to implement modulation based on space vector analysis. The resulting load voltage spectra shows on advantage over standard eight-switch CSIs     

一种新颖的逆变器的造型,分析和设计

本文借助于CAD技术对一种新颖的逆变器——具有磁耦合的晶体管阶梯波逆变器进行了分析。将功率晶体管用理想开关代替,对磁耦合器件作相应的等效处理、建立起电路的通用等效模型。文中还给出了仿真曲线和实验波形。结果表明,仿真过程是可行的,设计思想是合理的。     

Novel soft-switching inverter for brushless DC motor variable speed drive system

Brushless DC motor has been widely used in industrial applications because of its low inertia, fast response, high power density, high reliability and maintenance-free. It is usually supplied by a hard-switching PWM inverter, which normally has low efficiency since the power losses across the switching devices are high. In order to reduce the losses, many soft switching inverters have been designed. Unfortunately, there are many drawbacks, such as high device voltage stress, large DC link voltage ripple, complex control scheme and so on. This paper introduces a novel soft-switching inverter which generates notches of the DC bus voltage becomes to zero during chopping switches commutation to guarantee all switches working in zero voltage state. The result of this investigation will be very useful for industrial applications.     

Voltage modulation factor of the magnetic flux control PWM methodfor inverter

The voltage modulation factor of the magnetic flux control pulse-width modulation (PWM) method is discussed. The modulation factor is derived from a theoretical study on the flux locus produced from the inverter output voltage. The derivation is based on the fact that the fundamental component of the inverter output voltage is proportional to the radius of the flux locus. It is shown theoretically that the voltage modulation factor is expressed by the content of a zero vector in one cycle of the selected PWM pattern of the space vector expression. The modulation factor of the magnetic flux control PWM method is calculated. The modulation factor can be varied from zero to 12/π². The output voltage of the magnetic flux control PWM method can be controlled by the modulation factor linearly from zero up to overmodulation. The simulation and experimental results are also shown     

Three-phase series VAr compensation based on a voltage-controlledcurrent source inverter with supplemental modulation index control

Shunt-type static VAr compensators have been shown to be an effective means of increasing the transmission capability of power systems and of increasing the power factor of industrial loads. This paper presents an alternative to the shunt connection consisting of a series-connected transformer-coupled pulsewidth modulation (PWM) inverter. The scheme consists of a current source inverter (CSI) fed from a self-controlled DC current bus and presents the following features: (1) instantaneous series injected voltage control through online PWM of the DC link current; and (2) steady-state modulation index of the PWM pattern near unity through DC link current minimization. The first feature results in fast dynamic response, while the second feature ensures low and fixed injected voltage harmonic distortion and reduced steady-state compensator losses. Operation of the compensator and of the two-loop control scheme are presented. Simulation and experimental results on a 2 kVA laboratory prototype unit confirm the feasibility of the proposed VAr compensator structure     

软切换链路下的混合编码与副载波调制方案

为了提高自由空间光/射频（FSO/RF）混合通信链路的性能，采用混合低密度奇偶校验（LDPC）编码与副载波相移键控/正交振幅调制（PSK/QAM）联合调制的方法，对不同传输比例下混合系统的误比特率性能进行了仿真分析，取得了不同信道条件下单链路和混合链路传输方案的误比特率数据。结果表明，在弱中强湍流条件下采用副载波二进制相移键控（BPSK）调制，相比开关键控（OOK）调制可获得大约4.4dB~5.2dB的增益。采用软切换的混合LDPC编码与副载波BPSK/16QAM调制方案，依据链路状态调整比例为1:1和3:1时，不同湍流强度下可获得大约0.3dB~7.4dB的性能增益。这一研究结果对于提高FSO/RF混合通信系统的全天候高效可靠传输性能具有重要的参考价值。     

A novel switch-mode DC-to-AC inverter with nonlinear robust control

A switch-mode DC-to-AC inverter based on a DC-to-DC converter topology using a novel nonlinear robust control to generate a sinusoidal output waveform is presented. The control scheme is based on simultaneous feedback of the output voltage and feedforward of the input voltage and inductor voltage. As a result, the output voltage remains dynamically unchanged when there are large disturbances in input voltage or load current. The nature of the control law is explained. Computer simulation results show the robustness and fast dynamical response of the control system. The experimental results are presented to verify the analysis and demonstrate the feasibility of the control strategy     

Design of phase-controlled class E inverter with asymmetric circuit configuration

A design of phase-controlled class E inverter with asymmetric circuit configuration is presented. By using the presented design method, it is possible to derive the design values, which let the inverters achieve zero-voltage switching continuously in the control range, are derived. By carrying out circuit experiments, it is verified that the experimental results agree with numerical predictions quantitatively, and the validity of the presented design procedure is denoted.     

PWM型逆变器多重化的仿真研究

针对飞机变频电源系统的工程实际,基于Saber仿真器构建多重化逆变器,运用仿真手段对正弦脉宽调制(SPWM)和准最优脉宽调制(SUBPWM)两种控制算法进行了验证性研究,提出一种在变频电源系统中获得恒频电的解决方案。     

PWM型逆变器多重化的仿真研究

针对飞机变频电源系统的工程实际,基于Saber仿真器构建多重化逆变器,运用仿真手段对正弦脉宽调制（SPWM）和准最优脉宽调制（SUBPWM）两种控制算法进行了验证性研究,提出一种在变频电源系统中获得恒频电的解决方案。     

A new optimized space-vector modulation strategy for acomponent-minimized voltage source inverter

This paper presents a new space-vector modulation strategy suitable for a low-cost pulse-width-modulation (PWM) voltage-source (VS) inverter employing only four switches, four diodes, and a split-capacitor bank in the DC link. The work is motivated by the need for an efficient and flexible modulation method, which is optimized with respect to minimum machine-torque ripple. The modulation strategy is named space-vector modulation for four-switch inverter (SVMFSI), and it is realized by planning the switching patterns between four active voltage vectors on the basis of a desired flux trajectory for the stator-flux vector in the AC machine. The strategy is implemented in a single 8-bit microcontroller as a double-sided modulation strategy. Simulations of the machine-torque ripple are performed at a switching frequency of 4 kHz and indicate a torque ripple of 14% at nominal load. Finally, selected results are verified experimentally on a 1.5-kVA prototype B4 inverter. The test results indicate high-quality output-voltage spectra with no low-order voltage harmonics and a harmonic-loss factor (HLF) of 1.12% at unity modulation index     

Versatile composite amplifier configuration

This paper describes a versatile composite amplifier in which a current feedback amplifier (CFA) drives an operational amplifier (OPA). In the conventional OPA–CFA composite amplifier, an OPA drives a CFA resulting in a composite structure that combines the DC input stability of the OPA and the high speed capability of the CFA. The proposed composite configuration combines different features of the CFA and OPA, specifically the constant bandwidth property of the CFA and the high power and high current output capacity of the OPA. The new circuit is easily implemented in the standard inverting and non-inverting configurations using commercially available devices, and the accuracy and constant bandwidth features were experimentally verified. Local feedback around the associated CFA ensures that the proposed composite amplifier possesses a higher level of bandwidth constancy than a single CFA.     

特殊逆变器调制技术研究

特殊逆变器工作频率为数kHz,通常采用脉冲法控制策略,输出波形特性差。针对传统特殊逆变器缺点,提出阶梯波调制方法。介绍特殊逆变器的拓扑结构,分析了基于阶梯波调制的特殊逆变器的基本原理,研究了阶梯调制算法。该特殊逆变器拓扑结构简单、开关器件开断损耗小、整机效率高,具有良好的谐波抑制能力。建立仿真模型,并进行分析,得出仿真结果。从仿真结果可以看出,采用阶梯波调制算法的特殊逆变器输出波形特性好,谐波含量低。     

Voltage-readable nonvolatile memory cell with programmable ferroelectric multistates in organic inverter configuration

We demonstrate a voltage-readable nonvolatile memory cell with programmable ferroelectric multistates in an organic inverter configuration. The intermediate memory states of a ferroelectric gate insulator, varying with the magnitude of the programming voltage, allow the multilevels of the drain current at zero gate-source voltage in a ferroelectric organic field-effect transistor (OFET). The current output from the ferroelectric memory is directly converted into the voltage-readable output in a zero-gate load inverter configuration where both a driving paraelectric OFET having a paraelectric buffer layer and a load ferroelectric OFET are monolithically integrated in a single substrate. The multilevel voltage-readable output characteristics are obtained from the ferroelectric multistates as a function of the programming voltage.     

Three-level inverter configuration with common mode voltage elimination for induction motor drive

A scheme for a three-level voltage space phasor generation with common-mode voltage elimination is proposed. An open-end-winding induction motor, fed from both ends by two three-level inverters, which are realized by a cascading two two-level inverter, is used in this configuration. The voltage space vectors of individual three- level inverters, which generate the same common mode voltage in the inverter pole voltage, are variously grouped When these voltage space vectors are used to switch individual three-level inverters, it results in zero commonmode voltage across the motor windings. In the proposed scheme, voltage space phasors from individual inverters with zero common mode voltage in the inverter pole voltage are used for PWM control. For the proposed drive configuration, the DC link voltage requirement is only half when compared to the DC link voltage of a conventional neutral-point-clamped （NPC） three-level inverter. The proposed inverter configuration offers reduced circuit and control complexity when compared to similar schemes with NPC or H-bridge inverter configurations.