Quasi-Z Source Inverter Control of PV Grid-Connected Based on Fuzzy PCI

The photovoltaic grid-connected inverter is an important interface between the photovoltaic power generation system and power grid.Its high-quality operation is directly related to the output power quality of the power grid.In order to further optimize the control effect of the quasi-Z source grid-connected photovoltaic inverter,a fuzzy proportional complex integral control(PCI)method is proposed for the current internal loop control.This method can eliminate the steady-state error,and has the characteristic of zero steady-state error adjustment for the AC disturbance signal of a specific frequency.The inductance-capacitance-inductance(LCL)filter is adopted in the grid-connected circuit,and the feedback capacitive current is taken as the control variable of the inner loop to form the active damping control method,which can not only effectively suppress the resonance of the LCL circuit,but also significantly inhibit the high-order harmonics in the grid-connected current.Finally,a system simulation model is built in MATLAB/Simulink to verify the superiority and effectiveness of the proposed method.

Practical Implementation of Embedded Controlled Reduced Switch Z-Source Inverter-Fed Induction Motor Drive

A cost-effective component minimized embedded controlled Z-source inverter for induction motor drive is presented. The proposed topology combines the advantages of a traditional four-switch three-phase inverter with the advantages of the z impedance network (two inductors in series and two X connected capacitors). This new topology, besides the self-boost property, has low switch count and it can operate as a buck-boost inverter. As a result, the new embedded controlled reduced switch Z-source inverter system provides ride through capability during voltage sags, reduces line harmonics, improves power factor, reliability and extends output voltage range. Analysis, simulation and experiment result will be presented to demonstrate these new features.

Soft switching arc welding power source using output inductor as resonant inductor

Full bridge Zero Voltage Switch PWM converter combines advantages of the PWM control technique and resonant technique. However, Full ZVS is achieved only under large load current because resonant tank of this circuit is made up of the parasitic capacitance of the power semiconductors and the leakage inductor of the transformer primary. In this paper two saturable inductors as magnetic switches are added to secondary, so output inductor is always reflected to primary and assists resonant transition. Full ZVS is achieved under lower load current. The above mentioned investigated results are validated by the computerized simulation and hardware circuit experiment.

Controlling the output power of soft switching arc welding inverter by two-stage continuous PWM method

The full bridge zero voltage zero current switching （ FB-ZVZCS ） , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circuit of soft switching arc welding inverter power source. However, when the duty ratio of leading leg was reduced to zero, the output power stayed the constant value instead of becoming zero. The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero. It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of paraUel capacitors, and the output power also could be reduced by reducing the duty ratio of lagging leg. A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper. This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.

Generalized Switched-Capacitor Step-up Multilevel Inverter Employing Single DC Source

In this paper,a new generalized step-up multilevel DC-AC converter is proposed,which is suitable for applications with low-voltage input sources,such as photovoltaic power generation and electric vehicles.This inverter can achieve a high voltage gain by controlling the series-parallel conversion of the DC power supply and capacitors.Only one DC voltage source and a few power devices are employed.The maximum output voltage and the number of output levels can be further increased through the switched-capacitor unit’s extension and the submodule cascaded extension.Moreover,the capacitor voltages are self-balanced without complicated voltage control circuits.The complementary operating mechanism between each pair of switches simplifies the modulation algorithm.The inductiveload ability is fully taken into account in the proposed inverter.Additionally,a remarkable characteristic of the inverter is that the charging and discharging states among different capacitors are synchronous,which reduces the voltage ripple of the frontend capacitors.The circuit structure,the working principle,the modulation strategy,the capacitors and losses analysis are presented in detail.Afterwards,the advantages of the proposed inverter are analyzed by comparing with other recently proposed inverters.Finally,the steady-state and dynamic performance of the proposed inverter is verified and validated by simulation and experiment.

Predictive Control Based on Ranking Multi-objective Optimization Approaches for a quasi-Z Source Inverter

In power converter control,predictive control has several merits,such as simple concept and fast response.However,the necessity to use the weighting factor inside the cost function makes the control design complex in the case of regulating multivariables where the value of the weighting factor is obtained by a nontrivial process.Also,it primarily depends on the system parameters and operating points of the control system.This paper aims to enhance the model predictive algorithm of the singlestage topology of a quasi-Z Source Inverter(qZSI).The concept of a multi-objective optimization approach is used in addition to the sub-cost function definition to remove the weighting factors.By using the sub-cost function definition,the inductor current is pushed away from the main loop of the predictive algorithm.Thus,no weighting factor is needed to manage the priority of the inductor current.The other two control targets,which are the capacitor voltage and load currents,will be controlled by the multi-objective optimization approach without using any weighting factors.A detailed theoretical analysis of the proposed technique will be given and validated based on simulation results.

开关电感型Quasi-Z源逆变器

提出了一种开关电感型Quasi-Z源逆变器的拓扑,该拓扑用开关电感代替传统Quasi-Z源的电感,在保留传统Quasi-Z源逆变器优点的同时,在相同直通占空比的情况下增大了其升压倍数,而且在较小的直通占空比情况下即可实现任意倍数的升压,给调制因子较大的取值空间,提高了输出电压的质量与系统的稳定性。采用改进的空间矢量实现了对改进Quasi-Z源逆变器的控制。仿真和实验证明了该拓扑在相同直通占空比的情况下具有更高的升压倍数的新特性。

开关电感型Quasi-Z源逆变器SVPWM调制策略仿真研究

针对开关电感型Quasi-Z源逆变器,采用Matlab/Simulink仿真平台对空间矢量脉宽调制(SVPWM)策略进行了仿真研究。仿真结果表明,与简单升压调制策略相比,SVPWM调制策略具有开关频率低、直流母线电压小、调制度较大等优点,可以提高直流母线电压的利用率。

开关电感Quasi-Z源逆变器SVPWM策略研究

开关电感Quasi-Z源逆变器具有无源器件个数少,电感、二极管电流低等特点。将SVPWM调制策略应用于开关电感Quasi-Z源逆变器,实现电源的逆变。在对调制过程分析的基础上,通过调整同一桥臂的开关管开通、关断时刻,实现直通的插入,分别采用4次、6次和8次直通插入方式,对开关电感Quasi-Z源逆变器进行控制。通过分析可得,在低频情况下,直通次数越多,电感电流脉动越小,电气应力比较低;而在高频情况下,直通次数的多少将不会引起效果的明显差异。

基于三相逆变器变开关频率和变直流母线电压的PMSM控制

针对三相电压源逆变器应用固定开关频率和额定直流母线电压的空间矢量脉宽调制(space vector pulse width modulation,SVPWM)驱动方式时存在直流电压利用率低、绝缘栅双极性晶体管(insulated gate bipolar tran⁃sistors,IGBT)损耗较高的缺点,建立永磁同步电机(permanent magnet synchronous motor,PMSM)和基于输出周期的IGBT损耗控制模型,在此基础上以输出电流质量为约束条件,以开关频率和直流母线电压为约束变量,应用猫鼬优化算法获得基于输出周期的IGBT损耗最优的开关频率和直流母线电压。对所提出的策略进行仿真和实验,通过比较输出电流总谐波畸变率(total harmonic distortion,THD)、电流波形、IGBT损耗和结温等验证所提策略在保证控制系统性能的条件下降低三相电压源逆变器损耗,增加三相电压源逆变器的可靠性。

多电平三相电压源逆变器结构优化设计

目前多电平三相电压源逆变器被广泛应用于高压、大功率电子设备中,为解决传统三相电压源逆变器运行中出现的直流侧电容电压失衡问题,基于空间矢量调制开关直流电源对逆变器结构进行优化设计。建立多电平三相电压源逆变器等效模型,利用60°坐标的空间矢量调制算法实现空间矢量调制,利用电容电压平衡算法充分考虑不同矢量间的切换顺序,实现电容电流平衡。实验结果表明,对比传统方法,该方法调制多电平三相电压源逆变器输出线电压波形畸变率为0.18%,电容点电压波动可控制在3 V以内,优于对比方法,具有更好的应用性能。

开关振荡事件驱动的VSI系统开路故障检测

此处提出了一种基于开关瞬态高频共模振荡事件驱动的电压源逆变器(VSI)系统功率器件开路故障检测方法,通过非接触方式捕获高频共模开关振荡电流信号,利用高频共模振荡信号的完整性来检测和定位VSI系统中的故障功率器件,具有高速和非侵入的优点。设计了基于高频共模开关振荡事件触发的开路故障高速检测系统,该系统由高频电流传感器、开关事件捕获电路和开路故障检测诊断单元组成。实验结果表明,该方法能够使用单一诊断变量,即高频共模开关振荡电流,对VSI系统中的6个功率器件进行开路故障检测。

具有高增益准开关阻抗源的分布式光伏逆变器

分布式发电应用的多电平逆变器存在升压能力受限于器件应力,且在高调制指数下性能不佳的问题。为此,提出一种具有高增益准开关阻抗源的多电平光伏逆变器,将新型混合准开关升压电路与降压开关单相多电平逆变器集成,在低器件应力和高调制指数下实现高增益转换。对拓扑不同工作模式进行建模,并在此基础上提出能无缝过渡孤岛模式的脉宽调制控制策略。对所提拓扑的高电压增益和低器件应力特性进行分析,同时建立小信号模型验证系统稳定性。最后搭建实验样机对所提方案进行验证,实验结果表明所提拓扑在高增益下工作时具有最低的器件应力,同时具备良好的击穿抗扰度。

基于开关函数模型的逆变器开路故障诊断方法

逆变器的安全性和可靠性直接关系到电机驱动系统的正常运行。在研究逆变器在正常和故障状态下开关函数模型的基础上,提出一种功率管开路故障快速简易诊断方法。该方法根据故障和正常态器件承受电压的不同,采用简单的硬件电路来诊断和定位器件的开路故障。为保障诊断的有效性和可靠性,提出采用开关信号上升沿延时的方法来避免因IGBT开通和关断延迟造成的误诊断,并给出延时时间的确定方法。在搭建的感应电机变频调速(variable voltage and variable frequency,VVVF)控制和永磁同步电动机矢量控制系统中进行实验验证,实验结果表明,所提故障诊断方法能有效诊断逆变器单管和桥臂的开路故障。

电机驱动用新型谐振直流环节电压源逆变器

为了实现电机控制系统的高功率密度和高性能运行,必须提高逆变器的工作频率以提高功率变换器的效率和增强性能。然而,较高的工作频率会引起严重的电磁干扰和开关损耗从而导致系统整体效率降低。软开关技术被认为是解决上述问题的有效方法,结合软开关技术的优点和脉宽调制(pulse width modulation,PWM)控制的特点,提出了一种新的用于电机驱动系统的谐振直流环节软开关电压源逆变器,通过在传统硬开关逆变器的直流环节添加辅助谐振单元,实现了逆变桥开关器件的PWM软开关动作,同时,辅助谐振单元的开关也为软开关操作。文中阐述了该软开关逆变器拓扑的动作时序和动作模式,并对软开关动作时序的瞬态过渡过程进行了数学分析。对提出的新型软开关逆变器驱动无刷直流电机进行了仿真和实验研究,结果验证了电路结构和理论分析的正确性与可行性。

软开关逆变式弧焊电源的设计

软开关技术是解决逆变弧焊电源可靠性的核心技术。本文提出了一种新的软开关逆变弧焊电源的设计方案 ,该方案基本上可实现空载、短路、燃弧全负载范围内的软开关状态。本文分析了超前臂的关断功耗与并联电容之间的关系 ,串联电容及回路电感对环流期的电流变化的影响。并指出了滞后桥臂零电流关断区域 ,以及超前臂和滞后臂的零开通条件。在此基础上提出了引入无功电流分量解决空载及轻载时软开关失败问题的方案 ,以及几个主要谐振参数的设计方法。在实践中采用本方案表明 ,降低了开关应力及损耗 ,提高了整机可靠性 。

双零软开关弧焊逆变电源

全桥零压零流脉宽调制变换器在全桥零电压脉宽调制变换器中增加一隔直电容 ,使原边电流在箝位续流时段很快的衰减到零并保持 ,固定臂的功率器件是零电流开关 ,移相臂的功率器件是零电压开关。这样 ,一方面使具有关断拖尾电流特性的IGBT可以很容易的用到全桥软开关变换器中 ,另一方面大大减少了变换器的附加环路能量 ,同时具有小的占空比损失 ,低的副边寄生振荡和宽的软开关切换的负载范围等优点。最后 ,采用上述研究成果研制了一台 10kW级采用FB -ZVZCS -PWM变换器的软开关弧焊逆变电源样机。温升试验表明 ,研制的软开关焊机的温升比同类型的硬开关焊机的温升低近 2 0℃ ,大大减少了焊机的开关损耗。同时 ,由于焊机的功率元件是零开关 ,大大减少了器件的电压、电流应力 。

适应负载大范围变动的高性能Z-源逆变器

提出的高性能Z-源逆变器,在保持原逆变器优点的基础上(输出电压可任意升/降;允许逆变桥上下管直通状态,提高了逆变器的安全性),克服了其固有的缺点和局限性。Z-源逆变器直流链电压受Z-源网络电感和负载的影响很大,在网络电感值较小或负载较轻时,直流链电压会出现明显的电压畸变,影响逆变器输出的交流电压。本文所述高性能Z-源逆变器消除了由于网络电感值小或负载很轻而引起的直流链电压畸变,电路对负载的适应能力很强,能够工作在重载和轻载的任何环境,Z-源网络电感可以设计得很小,减少了重量、体积和成本。同时电路部分可实现逆变桥开关管的零电压导通,减小了开关损耗,改善了开关环境。通过对电路工作模式的详细分析,得出了电路各部分的电压关系,并推导出逆变器开关管的电流应力。最后,通过仿真和实验验证了理论分析的正确性。

级联型多电平逆变器中的谐波控制

级联型多电平逆变器中,逆变器模块单元数越多,输出波形质量越好,但模块数的增加也同时意味着成本的增加。本文分析了最小模块单元数级联型多电平逆变器在高频应用中的谐波控制问题。通过求解器件开关角方程,给出了模块电源电压比值不同时开关角的选择范围及输出电压基波幅值的调节范围,并依据输出电压谐波畸变率与基波幅值关系,总结了模块电源电压比值的选择原则。仿真与实验结果证明了理论研究的正确性与可行性。

三相电压型并网逆变器预测直接功率控制

研究了一种用于三相电压型并网逆变器的新型直接功率控制策略——预测直接功率控制(Predictive Direct Power Control,P-DPC)。重点讨论了P-DPC不同的电压矢量选择原则和电压矢量作用时间的处理方法,以降低低次电流谐波成分,获得更好的动、静态性能。该P-DPC可实现恒定的开关频率,解决了传统开关表直接功率控制策略(LUT-DPC)开关频率不固定的弊病,继承了直接功率控制策略功率快速调节的固有特点,且无需旋转坐标变换和空间矢量脉宽调制。在一台2kVA并网逆变器实验样机上对传统LUT-DPC、矢量控制和P-DPC进行了仿真和实验研究。结果表明了本文提出方法的有效性和其在可再生能源开发利用中的工程实用前景。