带有光伏发电的UPS双向逆变器控制策略的研究

本文提出了一种带有光伏发电的UPS系统,阐述了该系统的结构图。在分析双向变换器的拓扑结构、工作原理的基础上,采用基于前馈解耦控制的双环控制策略,实现整流逆变不同模式的自动切换以达到能量双向流动的目的。该方法具有输入电流无静差跟踪,对电网谐波污染少、功率因数高等优点。     

高可靠型非隔离三电平光伏并网逆变器

为解决二极管箝位三电平光伏并网逆变器存在直通危险而导致可靠性降低的问题,提出一种改进型三电平并网逆变器电路拓扑,将双降压式半桥逆变器的防直通结构引入传统二极管箝位三电平电路中,并结合光伏并网逆变器要求单位功率因数运行的特点省略了双降压式半桥逆变器的桥臂续流二极管,使得新拓扑十分简洁.详细分析了新型三电平逆变器的工作模态、运行方式、共模特性和控制策略,并通过仿真和实验验证了新型逆变器的防直通、定频滞环控制和低漏电流特性.     

Z源光伏逆变器中感性负载的改进控制方法

简单z源逆变器的控制方法通过在普通SPWM零状态中插入固定直通占空比来获得.该方法虽然实现简单,但是在感性负载情况下,由于换向过程中无法提供续流通道,给输出电压和电流造成严重的崎变.基于产生崎变的机理,提出了一种改进的SPWM控制方法.该方法在换向时提供续流通道,不仅消除由于感性负载引起的输出交流波形的崎变,而且减少了...     

A new simple analytical method for calculating the optimum inverter size in grid-connected PV plants

A new simple analytical method for the calculation of the optimum inverter size in grid-connected PV plants in any location is presented. The derived analytical expressions contain only four unknown parameters, three of which are related to the inverter and one is related to the location and to the nominal power of the PV plant. All four parameters can be easily estimated from data provided by the inverter manufacturer and from freely available climate data. Additionally, analytical expressions for the calculation of the annual energy injected into the ac grid for a given PV plant with given inverter, are also provided. Moreover, an expression for the effective annual efficiency of an inverter is given. The analytical method presented here can be a valuable tool to design engineers for comparing different inverters without having to perform multiple simulations, as is the present situation. The validity of the proposed analytical model was tested through comparison with results obtained by detailed simulations and with measured data.     

一种新型太阳能逆变器辅助电源设计

详细分析了反激控制器边界工作模式原理,设计了一种具有5路独立输出的3 kW太阳能逆变器辅助电源,无需复杂的光耦反馈稳压控制回路,具有结构简单、成本低、效率高和工作可靠等特点.论文给出了多输出太阳能逆变器辅助电源的原理图和反激式高频变压器的具体设计,并对太阳能逆变器辅助电源设计中的EMI抑制措施进行了详细介绍.所设计的电源已经应用于太阳能逆变器中,实验结果表明,电源工作稳定,输出纹波小,变压器无发热现象,满足太阳能逆变器的设计要求.     

Applying control scheme function of PV inverter for minimizing voltage fluctuation and imbalance with consideration of maximum PV generation

At present, connections of photovoltaic (PV) systems to low‐voltage (LV) distribution systems are growing rapidly because of the compliance with government policies, drop in the prices of PV technologies, and environmental awareness. Unfortunately, the high penetration of solar PV systems, which suffers from the intermittence of sunlight, leads to voltage fluctuation and voltage imbalance, thereby deteriorating the power quality. To cope with this problem, this paper proposes a control strategy of the PV inverter to improve the limiting and balancing of voltage profiles in an unbalanced, three‐phase, four‐wire LV distribution system. The control strategy is based on the real power limitation and the reactive power adjustment through a control scheme function that is embedded in all PV inverters for supporting high penetration of PV systems. However, real power limitation leads to less utilization of solar energy. Then, the concern on PV generation (real power) regarding voltage fluctuation and imbalance is optimally analyzed by multi‐objective particle swarm optimization. The optimal solution of the control scheme function is numerically demonstrated in a modified 29‐node LV distribution system. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

面向欧洲效率增强的在线拓扑可变型光伏发电并网逆变系统

为了在满足并网约束条件的前提下拓展光伏电池的并网发电范围以及提高系统的欧洲效率,以提高光伏并网逆变系统的利用率,提出新的在线拓扑可变型并网逆变技术。通过在级联型多电平逆变器中增加双向切换开关,使其在光伏电池输出电压/功率较低时工作于级联模式,而在输出电压/功率较高时切换为H桥逆变器模式,从而实现只采用单级逆变结构即可获得较宽的并网发电范围和提高逆变器欧洲效率。给出了基于5电平级联型逆变器的在线拓扑可变型并网逆变器的具体结构及详细的实验结果,以验证所提出方案的正确性。     

LCL滤波的光伏并网逆变器有源阻尼与无源阻尼混合控制

通过建立LCL滤波的光伏并网电流控制内环模型,就电网电感对谐振频率、无源阻尼效果和电容电流反馈的有源阻尼效果三者的影响进行了分析.结果表明,电网电感能降低谐振频率,增强有源阻尼效果,削弱无源阻尼效果.结合有源阻尼受延迟等控制非理想因素影响较大、而无源阻尼不受此影响的特点提出了一种采用有源阻尼与无源阻尼相结合的混合阻尼策略,它对于电网电感和控制延迟都具有良好的适应性.混合阻尼设计中以阻尼系数为对象,以阻尼系统对电网电感的适应能力为设计目标,计算和校验电流反馈系数和阻尼电阻取值,给出了具体设计方法.设计实例的仿真和实验结果证明,该方法设计的阻尼可以稳定运行,并对弱电网具有良好的适应性.     

A single-phase inverter system for PV power injection and active power filtering with nonlinear inductor consideration

This paper proposes a single-phase two-wire inverter system for photovoltaic (PV) power injection and active power filtering (APF) with nonlinear inductor consideration. The proposed system can fully or partially perform APF, process PV power, eliminate harmonic currents, improve power factor, and take into account the nonlinear effect of its output filter inductor. In the system, even though only the utility current is sensed, both APF and maximum power point tracking features can be still achieved, reducing the number of current sensors and cost significantly. To prevent output current from exceeding switch ratings, inverter current is properly controlled through a current estimator and a defined limit circle. A self-learning algorithm is also proposed to determine nonlinear inductance, which can increase the accuracy of the estimated current. Simulations and experimental results have verified the feasibility of the proposed PV inverter system and the algorithm.     

光伏并网逆变器空间电压矢量双滞环电流控制新策略

提出了一种适用于三相光伏并网逆变器的双滞环电流控制改进算法。根据逆变器线电流与功率器件开关状态的关系,对线电流实行解耦控制,利用双滞环来判断参考空间电压矢量的位置,结合锁相环电路对输出的开关状态进行检测,构成频率闭环控制。最后利用Matlab/Simulink工具箱和3 kW实验平台对双滞环控制算法进行验证。结果表明,该算法保留了传统滞环控制电流跟踪响应快、有限流能力的优点,同时也有效地克服了开关频率变化不固定、开关损耗较大等问题。     

利用光伏电池给蓄电池充电

磷酸锂铁（LiFePO4）电池对比钻基德Li离子/聚合物电池,具有安全性性高、浮充电压小、自放电率低、使用寿命长等一系列优点。本文所述LT36521C为可实现太阳能跟踪、单块式补偿蓄电池充电的集成电路。当LT3652由单块太阳能电池板供电时,其输入调节回路能确保在最大输出功率下工作,充分体现出这一新型太阳能充电器的优越特性。     

A pumping technique using electrohydrodynamic flow inside a gel

We demonstrated a new type of electrohydrodynamic (EHD) pump that had a pair of electrodes placed inside a gel (poly(vinyl alcohol) swollen by dimethyl sulfoxide). The fluid (decahydronaphthalene) was in contact with the gel surface. During a voltage application to the electrodes, the EHD flow of dimethyl sulfoxide inside the gel caused the flow of the fluid outside the gel. An advantage of this pumping technique is that one can dissolve some chemicals in the fluid without the fear of their electrochemical decomposition because the electrodes inside the gel are not in contact with the fluid.     

A regenerative centrifuge drive using a current-fed inverter withvector control

The authors describe the development of a centrifuge drive based on a current-fed inverter. The power circuit circuit is briefly described and a block diagram of the vector control is presented. Experience in tuning the speed regulator and modifying the torque pulsations in order to prevent coupling chatter is discussed. A specially shaped enclosure was designed to accommodate the end user's space requirement and also to provide space for the electronics that control the sequence of operation. A number of these drives have been in operation for more than two years, and operating experience concerning cycle time, power consumption, and reliability is presented     

Distribution system compensation using a new binary multilevelvoltage source inverter

A new binary multilevel voltage source inverter with separate DC sources is proposed. This n-level voltage source inverter produces a (2 ⁿ⁺¹-1)-steps AC voltage output with n full bridge inverters connected in series. The use of selective harmonic elimination modulation technique to either completely eliminate or minimize harmonics is studied. A closed-loop controller to control the capacitor voltages and adjust the inverter reactive power output is developed. Application of such a compensator for dynamic compensation of 13.8 kV distribution system is examined through transient studies using a PSCAD/EMTDC program. The proposed inverter configuration not only reduces the system complexity and its size, but also improves the harmonic profile significantly     

A vector control system using a neutral-point-clamped voltage-source pwm inverter

This paper describes a vector control system of an induction machine using a neutral-point-clamped voltage-source inverter (NPC-VSI) that is one of the double series-connected inverters. The NPC-VSI is able to output five-level step-shaped line-to-line voltage without output transformers or reactors, and it may reduce harmonic currents corresponding to torque ripples. However, the NPC-VSI has a problem in that excessive high voltage is applied to switching devices when a neutral point of two dc capacitors of the NPC-VSI varies from the center of the dc link voltage, because the neutral point is floating. This paper proposes also a current controller to which the space vector theory is applied. This can reduce harmonic currents to one-fourth those of a conventional voltage-source inverter using six switching devices, and regulate the neutral point potential within a preset range. To simplify the current controller, information about voltage space vectors is given from the vector controller to the current controller. The validity of the current controller is confirmed by a prototype using an induction machine of 2.2 kW.     

Multilevel inverter using cascaded 3-phase transformers with common-arm configuration

In multilevel inverter development for 3-phase applications, total number of transformer in the circuit can be reduced by using of cascaded 3-phase transformer circuit instead of single-phase transformer circuit. In the scheme, total number of switching components in the circuit is still a drawback to achieve lower cost and smaller size of the inverter compared with conventional multilevel inverter. This paper includes a challenging method to reduce total switching components in the multilevel inverter by adopting common-arm structure.The proposed inverter has been operated by two control schemes, Newton-Raphson and Equal-area method. After theoretical and experimental comparison of the methods, we found that Newton-Raphson method is useful to eliminate a specific harmonic order. However, the method has a shortcoming in real time operation which is performed by iterative calculation of the nonlinear equations. With Equal-area method, we can easily find the switching angles by calculating a trigonometric function. It can sufficiently minimize Total Harmonic Distortion (THD) of output voltage in real time operation of Digital Signal Processor (DSP).     

Research tokamak system with multimode discharges using inverter power supply

In the Current Sustaining Tokamak of the Nagoya University (CSTN)‐IV research tokamak system, using a compact 40‐kHz pulse width modulation (PWM) inverter power supply, which is controlled through the LabVIEW program, we construct a new tokamak discharge system with multimode including a stable alternating current discharge and a high‐repetition high‐duty one. These discharge modes can be operated continuously for as long as 60 seconds. The continuous discharge of long duration is able to simulate the important physical and chemical processes of long discharges in fusion devices, in which the heat load to the wall and the particle balance in the plasma‐wall system are crucial topics in order to realize a long pulse fusion reactor, like ITER. An ergodic divertor is one of the tools used to control the particle balance and the heat load to the wall. In addition, we installed another inverter power supply to generate a rotating magnetic perturbation for a dynamic ergodic divertor (DED) with the appropriate measurement system so that we could carry out experiments on heat and particle control with DED in prolonged operation. © 2000 Scripta Technica, Electr Eng Jpn, 133(4): 8–18, 2000     

Compensation for magnetizing inrush currents in transformers using a PWM inverter

When a transformer is connected to a circuit, under certain conditions, magnetizing inrush currents may be about ten times the full load current of the transformer. The currents contain a large amount of harmonic components and cause some relays to trip out. In this paper, the magnetizing inrush currents are compensated using a PWM inverter. The magnetizing inrush currents are detected and the PWM inverter generates compensating currents for the inrush currents. Hysteresis current controllers are used for fast response. The validity of this compensation is investigated by the simulation results. In addition, hardware implementation for the compensator is accomplished to verify the simulation results. Moreover, for the compensator, the relation between the compensating characteristics, the maximum switching frequency, and the coupling reactor is discussed based on the simulation results. Finally, characteristics of two current controllers (hysteresis band current controller and ramp‐comparison controller) are compared and it is shown that the hysteresis band current controller is more suitable for the compensator. The PSCAD/EMTDC electromagnetic transient simulator is used for the simulations. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(2): 53–64, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10023     

基于等价输入干扰的三电平AC－DC逆变器中点电压控制(英文)

One problem with a single source three-level inverter is the drafting of its neutral-point voltage. This may occur during transition or when unbalanced loads are connected to the inverter system. Variation of neutral-point voltage may greatly deteriorate the power quality. In this paper, we employ an equivalent-input-disturbance approach to deal with this problem. By adding an extra neutral leg, the control problem of neutral-point voltage is converted to a disturbance rejection problem. This method suppresses the variation of the neutral-point voltage to a low level and reduces the capacity of DC-link capacitors. Simulation results show the effectiveness of the method.     

Variable frequency inverter with sinusoidal voltage outputs using rotating coordinate transformation

An ideal inverter should have sinusoidal voltage and current outputs. Generally, output voltages of a voltage-source PWM inverter contain high-level switching frequency harmonies due to the PWM operation, while output currents are kept nearly sinusoidal. High-level harmonics contained in output voltages of a voltage-source inverter cause acoustic noises, iron losses and electromagnetic interferences. An LC filter was used to suppress the switching frequency harmonics; however, there is a danger of resonance in the LC filter. Accordingly, to remove harmonics of the LC filter resonance frequency, the authors add a voltage feedback loop. A conventional system can operate without difficulty within 50 Hz. However, with accompanying increases in the output frequency, output voltages are largely delayed and reduced by a high-pass filter inserted in the feedback loop. These problems are caused by a high-pass filter inserted in the feedback loop. Accompanied by the inverter output frequency, a high-pass filter cannot remove the fundamental component perfectly. As a result, a small fundamental component is fed back, which causes a delay and decrease in output voltage. This paper proposes the application of coordinate transformation to a high-pass filter inserted in the feedback loop. As a result, the proposed system realizes an ideal filter which can suppress fundamental frequency components perfectly, and improves the characteristics of the inverter with sinusoidal voltage outputs greatly. Theoretical analyses, simulations and experiments showed satisfactory results. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (4): 94–102, 1997