A novel non-isolated quasi-Z-source DC-DC converter with high voltage gain is proposed and analyzed in this paper. The suggested converter originating from the qZS converter replaces the common inductors and capacitors with active switched inductors and capacitors to enhance the voltage amplification. The suggested converter maintains the benefits of conventional qZS DC-DC converters, including common ground between input and output and continuous input current. Meanwhile, without adjusting the maximum duty cycle, there is a significant enhancement in voltage gain, while the voltage stress on switches is greatly diminished. Specifically, the circuit topology, working mode and steady-state characteristics of the converter are discussed in this paper. Finally, a 300V/300W prototype is designed and assembled. The experimental results validate the accuracy of the theoretical analysis and the practicality of the converter.

Boost mode single-stage multi-input current source inverter with high-frequency transformer and its three-mode one-cycle control strategy are raised and investigated. The inverter consists of multiple current source inverting units, a multi-input high-frequency transformer and a cycloconverter, it achieves single-stage power conversion and high-frequency galvanic isolation with a simple circuit structure. The bypass switch is added to the energy storage inductor to realize the three operation modes of energy storage, energy discharge and bypass, and the magnetic saturation problem in the current source inverter is effectively solved by calculating the duty cycle of energy release in real time, and the quality of output waveform is improved. The soft switch and main circuit parameters of the converter are designed. The practicability and advancement of the topologies and energy management strategy are verified by simulation and experiment.

The single-stage multi-input high-frequency-link grid-connected inverter are proposed and deeply investigated. The inverter is divided into three parts: a current source inverter unit, a transformer operating at high frequencies with multiple winding inputs and single winding outputs, and a cycle-converter. The current source inverter unit can contain multiple current source input links, and the boost inductor is connected in parallel with a bypass switch. The corresponding maximum power output energy management strategy of the inverter is proposed, and the magnetic saturation problem of the current source inverter is solved by calculating the energy-releasing duty cycle in real time. This article uses a simple circuit structure to achieve single-stage power conversion and high-frequency current isolation, and has good grid connected waveform quality. The soft switching process of the converter, duty cycle calculation formula and the design of the main circuit parameters are obtained. A 1.5kW experimental prototype of high-frequency-link inverter with two inputs is built and tested, verifying the feasibility of circuit topology and the effectiveness of the control strategy.

A current-source single-stage multi-input high-frequency-link grid-connected inverter and a three-mode one-cycle control strategy are proposed and deeply investigated in this paper. The inverter contains multiple current-source inverting units, a multi-input high-frequency transformer, and a cycloconverter. It achieves single-stage power conversion and high-frequency galvanic isolation with a simple circuit structure. The control strategy adds a by-pass switch to the energy storage inductor. It has energy-storing, energy-releasing, and three by-pass operation modes in a low frequency cycle. Through calculating the energy-releasing duty cycle in real time, the magnetic saturation problem of current-source inverters is solved and the output waveform quality is greatly improved. Soft-switching of the converter, a transfer function block diagram, and the design of the main circuit parameters are achieved. The simulation of a three-input inverter and experiment on a two-input inverter verify the feasibility and advancement of the proposed circuit topology and control strategy.

The Boost type multi-input independent generation system (IGS) with multi-winding simultaneous power supply is proposed and deeply investigated, the important conclusions are obtained. Its circuit structure is composed of a single-stage multi-winding Boost type multi-input inverter with high-frequency-link and a single-stage isolated battery charging/discharging converter connected together at the output end, its circuit topological family includes 4 types of circuit such as full-bridge etc, the maximum power energy management control strategy (EMCS) with output voltage single-loop and three-state one-cycle phase-shift modulation is adopted, and the magnetic saturation of the energy storage inductor and the distortion of output voltage of the IGS are effectively suppressed. By comparing the load power and the total input sources power, the proposed EMCS achieves smooth transition among different power supply modes. The designed and developed 2.5kVA experimental prototype has shown that the proposed IGS has advantages such as single-stage conversion, high frequency galvanic isolation among load, multi-input sources and battery, simultaneous power supply in a high-frequency switching cycle, wide regulating range of duty cycle, small size and light weight, and strong load adaptability, etc.

The single new energy power supply method has defects such as instability and discontinuousness. In order to improve the flexibility and stability of the power generation system and achieve the preferential utilization of new energy, this paper proposes a Boost type two-stage multi-input high frequency link's inverter with multi-winding simultaneous power supply, and the circuit topology, energy management control strategy (EMCS), high frequency switching process and active clamp circuit design of the inverter are studied and important conclusions are obtained. The circuit topology is composed of a two-level cascade of a multi-input Boost DC-DC converter and a Buck inverter. The front stage adopts the maximum power output phase-shifting pulse width modulation (PWM) control strategy with power limit. The rear stage adopts the single- polarity twice-frequency sinusoidal pulse width modulation (SPWM) control strategy. The maximum power output of multiple input sources is adjusted by controlling the DC bus voltage. The designed and developed 1kVA dual-input inverter prototype has excellent performance such as high frequency isolation between output and input and multiple input sources, small volume and weight, wide duty cycle adjustment range, high conversion efficiency, etc., which verifies the feasibility of circuit topology and EMCS.

The multi-winding Boost multi-input DC-DC converter type distributed generation system is proposed in the paper, the circuit topology, the maximum power and the master-slave power phase-shift PWM energy management control strategy are studied. Through the magnetic flux superposition of the high-frequency transformer, multiple input sources could supply power to the load simultaneously in a high-frequency switching period. Designed and developed 1kVA dual-input grid-connected and grid-off inverter prototypes have the advantages such as high-frequency isolation, wide regulating range of duty cycle, high conversion efficiency, smooth transition among different operating modes, etc.

针对传统两级多个单输入直流变换器型分布式发电系统结构复杂、整体效率低等问题,提出了隔离升压多输入直流变换器型分布式发电系统.该系统由前级Boost型多输入直流变换器和后级Buck型逆变器组成,并采用最大功率输出能量管理控制策略.文中分析研究了这种分布式发电系统的电路拓扑和控制策略,并对其进行建模和实验研究,1 kW隔离升压多输入直流变换器型分布式发电系统的实验证明了所提出设计方案的合理性.

A novel three-phase Boost mode photovoltaic (PV) grid-connected inverter was proposed. The topology, two-loop modified zone SPWM control strategy, low frequency mode, suppression of the energy storage switch turn-off voltage spike, high frequency switching process, maximum power point tracking (MPPT) of PV cells and design criteria of key circuit parameters were deeply investigated, and important conclusions were obtained. The circuit topology is a cascade of the input filter capacitance, the center-tapped energy storage inductance, three-phase inverting bridge and three-phase output filter, and there is an energy storage switch connected between the center tap of the energy storage inductance and the negative end of the input source; the control strategy is that three-phase grid voltage is divided by 60° to guarantee the operating mechanism of the current converter is satisfied in every switching period. The experimental results of the designed and developed 3kW 96VDC/380V50Hz3?ACinverter have shown that this kind of inverter has the excellent performances such as high voltage transmission ratio, high power density, high conversion efficiency, small the storage inductance and output filter, and high quality grid-connected current, which has important application prospect in single-stage three-phase low-voltage grid-connected inverting fields.

Aiming at the power loss caused by photovoltaic (PV) mismatch problem, a distributed maximum power point tracking (DMPPT) Flyback type PV grid-connected inverter and the sinusoidal pulse width modulation(SPWM) unified control strategy with DMPPT are proposed. Meanwhile, the circuit topology, operation modes and steady state relations are deeply investigated. The inverter is composed of n Buck choppers with their outputs connected in series and a Flyback type grid-connected inverter, it belongs to quasi-single-stage power conversion. The control strategy achieves the DMPPT of all PV cells and the control of grid-connected current simultaneously. Designed and implemented 500W 27-39VDC/220V50HzAC prototype has excellent performances such as high PV cell utilization efficiency, low cost, high conversion efficiency, high reliability, high quality of output waveforms, etc.

The power supply system with single kind of new energy is generally unstable,discontinuous and changed with the weather.In order to improve the continuity and stability of the system,the multi-energy joint-power-supply system is adopted.The two-stage multi-input DC/DC converter mode multi-energy joint-power-supply system is analysed,then an improved two-stage multi-winding power-simultaneously DC/DC converter mode and the quasi-singlestage multi-input DC/DC converter mode multi-energy joint-power-supply system are presented.Their circuit structures,circuit topology examples,energy management strategies and a design example are given,which will provide a guidance to the research and application of the multi-energy joint-power-supply system.

Based on the analysis of the inherent defects of the traditional single-phase current mode pulse width modulation(PWM) inverter, multiple solutions of the defects from aspects of the circuit topology and control strategy are systematically discussed, the design instance and are provided, and important conclusions are obtained.The solutions of circuit topology including such as differential bidirectional Boost DC-DC converter mode inverter, combined Boost/Buck/Buck-Boost inverter, and the single-phase current mode high frequency link inverter with additional flyback AC-DC energy feedback circuit has the characteristics of Boost converter control law, complex circuit, large loss, etc; the solutions of control strategy including such as nonlinear modulation control strategy with compensation link, passive control strategy has the characteristics of high quality of output waveform, large energy storage inductor, etc; the solutions of circuit topology and control strategy including such as the single-phase current inverter with the resonators in serial and parallel of input side, nonlinear PWM one-cycle controlled single-phase current mode inverter with limited energy storage inductor current has the characteristics of high quality of output waveforms, small energy storage inductor, and high conversion efficiency, etc.

Based on the analysis of the inherent defects of the traditional single-stage single-phase boost mode inverter,this paper proposed a novel single-stage single-phase boost mode of photovoltaic (PV) grid-connected power generating systems.The technologies such as circuit topologies with an additional energy storage inductance bypass switch,two kinds of switching modes with energy storage inductance current limited,the nonlinear PWM one-cycle control strategy,energy storage inductance current limits,the switch state equivalent circuit and operating modes within one low frequency output period,design of main circuit parameters,system modeling analysis were carried on the thorough theoretical analysis,and the research conclusions were obtained.The additional bypass switch and its two kinds of switching methods solve the problem of too much energy of the energy storage inductor and decrease effectively the value of the energy storage inductor and its current.Through sampling and feeding back the inverting bridge modulation currents in real-time,the nonlinear PWM one-cycle control strategy adjusts the regenerating energy duty ratio of the inverter,which makes the average value of the output current of the inverter bridge in each switching period to track the reference sinusoidal signal in order to obtain high quality grid-connected current waveforms.The experimental results of the designed and developed 1kVA 110V/DC-220W50Hz prototype have conformed the feasibility of the proposed topology and control strategy,which provides an effective method for single-stage boost medium and small capacity grid-connected power generating fields.

This paper presents the circuit configuration, topological family and the master-slave power energy management phase-shifting control strategy for multi-winding simultaneously-supplying DC-DC converter mode multi-input inverter. Meanwhile, this paper also investigates the control strategy, steady principle and design criteria of the main circuit parameters. This circuit configuration is composed of a Boost multi-winding DC-DC converter and a cascaded Buck type inverter, while the master-slave power energy management means the maximum powers of 1st, 2nd,…, (n-1)th input sources and the insufficient load power of nth source supplements. The simulation and experimental results of the 1 000V·A DC-AC full-bridge multi-input inverter have shown that the proposed converter has the advantages such as input/output isolation and input/input isolation, strong voltage matching ability, high power density, simultaneous power supply by multiple input sources in a high-frequency switching cycle, wide regulating range of duty cycle, and smooth transition among different operating modes, etc.

The circuit topology of full-bridge Boost multi-input DC-DC converter type grid-connected inverters,the maximum power output with the power-limiting loop energy management control strategy,and the clamp-capacitorbased magnetic saturation suppression of energy storage inductor startup scheme were proposed and deeply investigated.Meanwhile,the high frequency switching process analysis,voltage transfer ratio derivation and active-clamp circuit design were provided.The circuit topology is composed of a full-bridge Boost type multi-input DC-DC converter and a cascaded Buck inverter.The control strategy adds a power-limiting loop into the MPPT voltage loop,to prevent the DC bus voltage rising by reducing theduty cycle of the converter under abnormal conditions.The magnetic saturation suppression startup scheme takes 2m switching periods as a control period,in which the power switches of high-frequency inverter circuits and active-clamp switch work alternatively.Designed lkVA dual-input inverter prototype has the advantages such as high-frequency isolation,simultaneoussupplying of multiple input sources,wide regulating range of duty cycle,high conversion efficiency,full use of new energy and high reliability.

This paper proposes a circuit topology of a single-stage three-phase current-source photovoltaic (PV) grid-connected inverter with high voltage transmission ratio (VTR). Also, an improved zone sinusoidal pulsewidth modulation (SPWM) control strategy and an active-clamped subcircuit that can suppress the energy storage switch's turn-off voltage spike are introduced. The circuit topology, control strategy, steady principle characteristics, and high-frequency switching process are analyzed profoundly, as well as the VTR's expression and design criterion of the center-tapped energy storage inductor. The improved zone SPWM control strategy consists of two control loops, namely, the outer loop of input dc voltage of PV cells with the maximum power point tracking and the inner loop of the energy storage inductor current. The experimental results of a 3-kW 96VDC/380V50Hz3ϕAC prototype have shown that this kind of a three-phase inverter has the excellent performances such as single-stage power conversion, high VTR and power density, and high conversion efficiency. Nonetheless, it has small energy storage inductor and output CL filter, low output current total harmonic distortion, and flexible voltage configuration of the PV cells. This study provides an effective design method for single-stage three-phase inverting with high VTR.

论述了单相Boost型并网逆变器的电路拓扑、工作模态和两种正弦脉宽调制(SPWM)控制策略,深入研究了改进SPWM控制单相Boost型并网逆变器存在的储能占空比与电压传输比不平衡引发的现象,以及基于调制函数推导了逆变器储能电感电流的交、直流分量与电路参数之间的关系,揭示了该逆变器存在储能电感值大、储能电感电流大、输出并网电流波形畸变严重、变换效率低等固有缺陷的机理.提出一种新颖的单相Boost型SPWM并网逆变器,仿真和实验结果证实了理论分析的正确性.

A nonlinear pulse width modulation-controlled single-phase boostmode photovoltaic grid-connected inverter with limited storage inductance current is proposed in this paper. The circuit topology, control strategy, steady-state principle characteristic, and design criterion for the key circuit parameters of this kind of inverter are investigated in depth, and important conclusions are obtained. The inverter's regenerating energy duty ratio 1-D which decreases with the decline of the grid-connected voltage is real time adapted by sampling and feeding back the inverting bridge modulation current, and the average value of the modulation current in each switching cycle tracks the reference sinusoidal signal to get high-quality grid-connected current. The active control of the energy storage inductance current and the balance of the voltage step-up ratio are realized by adding a bypass switch connected in parallel with the energy storage inductance and using two kinds of switching pattern namely boost pattern and freewheeling pattern. The theoretical analysis and experimental results of the 1 kVA 110 VDC/220 V50 Hz photovoltaic grid-connected inverter prototype show that it has the advantages such as single-stage boost conversion, high conversion efficiency, high quality of grid-connected current waveform, low value of energy storage inductance, simple control, etc.

New energy such as photovoltaic, wind, fuel cells has many advantages, but the distributed power generation system (DPGS) supplied by single kind of new energy cannot provide sustained, stable and continuous power because of the instability and non-continuity of new energy. In order to improve the stability and flexibility of the power supply system and realize the prior or full use of new energy, the multi-energy DPGS is adopted. The two-stage single-input DC-DC converter mode, two-stage multi-input DC-DC converter mode, quasi-single-stage multi-input DC-DC converter mode multi-energy DPGS are systematically presented, their circuit structures, circuit topology examples, energy management control strategies(EMCSs), characteristics and design examples are given in this paper, which will provide a guidance to the research and application of the multi-energy DPGS.

To overcome the traditional single-phase current mode PWM inverter’s inherent defects such as large energy storage inductance, large energy storage inductance current and serious distortion of the output voltage waveform, the single-phase current mode PWM inverter of one-cycle control strategy with limited energy storage inductance current is proposed in this paper. The inverter is working at current freewheeling mode when the energy storage inductance current is above the limited value or at Boost mode when it is below the limited value separately. The steady principle characteristics of this kind of inverter such as eight operating modes in one low frequency output cycle, the state equations of the switches, and the high-frequency operating process are deeply investigated. And the main design criterias for the key circuit parameters such as the voltage transfer ratio, the limited value of the energy storage inductance current, the value of the the energy storage inductance, the input and output filters, and the voltage and current stress of the power switches are derived. Designed and developed 1kVA 110VDC/220V50Hz inverter prototype has the advantages such as single-stage boost conversion, high conversion efficiency, high quality output waveform, low energy storage inductance etc. The correctness and advancement of the proposed research scheme and theoretical analysis are fully confirmed, and effectively overcomes the inherent defects of the traditional single-phase current mode PWM inverter.