光伏逆变器企业如何应对光伏电站接入电网的技术要求

由于昼夜交替和天气的影响,光伏发电不可能像传统以燃料为核心能源的发电厂一样具有比较平稳的功率输出,光伏发电具有不可控性和间歇性。将太阳能转化为电网可以接受能源的核心设备是光伏并网逆变器,逆变器将直流电转换成交流电的功率电力电子器件在开通和关断过程会引起电网中谐波、三相电流不平衡、电压波动、闪变等     

光伏发电并网系统双向电能表的设计

太阳能光伏发电作为一种零排放、零污染的可再生能源,已经受到世界各国的关注和青睐.为了满足小型光伏发电系统并网测试记录双向电能的需求,本文基于Cirrus Logic公司的电能计量芯片CS 5463与宏晶科技公司的STC12C5A60S2芯片,完成了并网双向测试电表的设计和性能测量,并对并网过程中相关参数进行了理论分析和计算,达到了实时判别光伏发电和电网供电方向和分别记录各自所供电能的目标,实现了光伏发电并网的计量需要.     

光伏并网发电系统对电网的影响研究

光伏并网发电系统（太阳能并网发电系统）通过把光能转化为电能,不经过蓄电池储能,直接通过并网逆变光伏发电系统,把电能输送上电网。太阳能发电是一种可再生的能源,对石油、煤、天然气等有着替代的作用。现在我国对能源的需求量急速增长,不可再生能源消耗迅速,发展光伏发电技术可以有效地解决能源紧缺的问题,因此加强光伏发电具有重要意义。本文对并网光伏发电系统进行了简要介绍,对并网光伏发电的特性和光伏发电的优缺点及并网光伏发电对我国电网的影响进行分析,并制定了可靠的技术措施。     

光伏发电/电动汽车充电一体化停车棚的研制

描述了停车棚结构及电气控制设计方法,并提供了设计效果。停车棚长50 m,宽5.5 m,可停放18辆小轿车,在系统智能控制下,光伏电池发电自动优先给停车棚下停放的电动汽车充电,多余电能由蓄电池储存备用。蓄电池充满电后,光伏电池发出的电能将由光伏并网逆变器直接并入公共电网;当遇阴雨天而太阳能发电不足时,由公共电网自动接入为电动汽车充电。     

光伏发电系统低电压穿越技术综述

随着光伏并网容量的比重不断增加,给电力系统的安全稳定带来一系列问题。尤其是当电网电压跌落时光伏电站的低电压穿越能力的问题,已成为光伏并网技术中的研究热点。本文介绍了光伏发电原理及其光伏并网低电压要求,在对当前国内研究成果进行分析和归纳基础上,重点总结了基于光伏系统控制策略穿越低电压和基于增加辅助设备的穿越低电压的两种方案,为光伏发电系统低电压穿越技术的研究与应用提供参考。     

基于随机子空间方法的光伏变流器模态识别和分析

光伏大量并网给电网带来大量谐波谐振问题。针对光伏变流器产生的谐振问题,建立了包含光伏变流器和电网等值阻抗的联合模型。推导了含有光伏变流器阻抗和电网阻抗的s域模型,应用反拉普拉斯变换得到的光伏输出电流不仅含有电压频率分量,还含有光伏阻抗的谐振分量。应用随机子空间方法分析光伏并网点和电流含有的模态分量,对照两者模态的区别,提取出光伏变流器阻抗模态。最后,通过仿真和实测数据分析验证了该方法的有效性。     

准单级交错并联反激式微型逆变器研究与测试

分析有源钳位和反激式结构对电路的影响,针对在电流连续模式下的电网质量问题,提出了重复控制方式,改善并网输出电压和电流的波形质量,降低谐波含量.为了提高光伏能源利用效率,需要对光伏阵列实现最大功率点跟踪(MPPT).结合恒定电压法和扰动观察法,提出了一种改进的最大功率点跟踪算法,提高了MPP追踪速度.结合上海晴天的日照情况,利用光伏模拟器,进行了仿真测试.实验结果表明:重复控制方法可有效改善并网输出的电网质量,转换效率达到了94.2%,MPPT效率最高达到了99.7%,实验样机验证了产品实际应用的可行性.     

超低压光伏充电控制系统研究

当今,随着电子技术的发展,光伏发电不断向着大功率,高效率的方向发展,因此对伴随的光伏充电系统的要求也越来越高。本文主要介绍超低压光伏充电控制系统的设计。该设计由光伏电池、蓄电池、MSP430F169为核心的控制电路、电能调整电路几部分构成。其中MSP430F169单片机作为主控MCU电能调整部分采用DC／DC转换芯片MAX1775与MAX1709。MSP430F169单片机将采样返回的电压与电流差分信号进行A／D转换,得出实际电压、电流值。电流反馈信号经PID算法处理后再经D／A转换输出到调整管电路,以控制主回路充电电流。故障检测电路通过电压比较器LM393判断直流电源过压故障,过压时控制继电器使其断开连接。     

光伏并网对电网自动化控制系统的影响

随着光伏发电装机容量持续扩大,相应地增加光伏发电系统的占比,成为重要能源形式。光伏出力具有波动性和随机性,光伏并网将会对电网自动化控制系统产生严重冲击,所以必须深入分析影响作用,确保光伏并网系统运行安全。该次研究主要是讨论和分析光伏并网与电网自动化控制系统的影响关系,希望能够为相关人员提供参考。     

分布式光伏发电并网现状及案例研究

妥善解决分布式光伏发电并网是分布式光伏发电应用发展的关键所在,本文简要阐述了电网企业服务分布式光伏发电并网的现状,并介绍了分布式光伏发电并网成功案例。     

A grid-tie PV inverter with the ability to improve power quality under unbalanced and distorted source voltage conditions

ABSTRACT

This paper proposes a grid-tie PV inverter that is able to improve power quality under conditions of both distorted and unbalanced source voltage. The presented strategy is based on the instantaneous power theory and uses a second-order generalized integrator-quadrature signal generator (SOGI-QSG). The presented control strategy is aimed at compensating reactive power, eliminating current harmonics, load balancing, and enabling the PV to inject maximum power to the grid. The advantages of the control system are the use of SOGI-QSG adaptive filter and frequency-locked loop (FLL), and removing the low-pass filter and phase-locked loop (PLL). DC–DC and DC–AC converters are utilized for connecting the PV to the grid. The DC–DC and DC–AC converters are responsible for maximum PV power tracking and achieving the control aims, respectively. Using 4-leg converter structure for grid-tie inverter enables achieving the control objectives in 3-phase 4-wire distribution network without any transformer. The presented control strategy is applied to a 3-phase 4-wire distribution network and is simulated in MATLAB/SIMULINK environment. The results of this simulation are then compared with the conventional instantaneous power method in areas including load balancing, reactive power compensation and the elimination of current harmonics, under unbalanced and distorted source voltage conditions.     

A single phase photovoltaic inverter control for grid connected system

This paper presents a control scheme for single phase grid connected photovoltaic (PV) system operating under both grid connected and isolated grid mode. The control techniques include voltage and current control of grid-tie PV inverter. During grid connected mode, grid controls the amplitude and frequency of the PV inverter output voltage, and the inverter operates in a current controlled mode. The current controller for grid connected mode fulfills two requirements – namely, (i) during light load condition the excess energy generated from the PV inverter is fed to the grid and (ii) during an overload condition or in case of unfavorable atmospheric conditions the load demand is met by both PV inverter and the grid. In order to synchronize the PV inverter with the grid a dual transport delay based phase locked loop (PLL) is used. On the other hand, during isolated grid operation the PV inverter operates in voltage-controlled mode to maintain a constant amplitude and frequency of the voltage across the load. For the optimum use of the PV module, a modified P&O based maximum power point tracking (MPPT) controller is used which enables the maximum power extraction under varying irradiation and temperature conditions. The validity of the proposed system is verified through simulation as well as hardware implementation.     

Study on the new control scheme of class-E inverter for IH-jar application with clamped voltage characteristics using pulse frequency modulation

A new control scheme of Class-E inverter for induction heating jar applications with clamped voltage characteristics using pulse frequency modulation (PFM) is introduced. To reduce the voltage stress of a switch, the proposed PFM control scheme does not need any auxiliary circuit. It can decrease the voltage stress of a switch through the modulation of switching frequency. The Class-E inverter using the proposed control scheme has the advantages of not only the same output power when it is compared with an active clamped class-E (ACCE) inverter, but also zero-voltage-switching, which are characteristics of conventional Class-E and ACCE inverter. The control principles of the proposed method are explained in detail and its validity is verified through experimental results     

低调制度下二极管箝位型多电平 逆变器新型PWM控制方法

二极管箝位型多电平逆变器作为一种应用于高压大功率变换场合的变换器,其PWM控制技术是研究的核心内容之一。本文针对已有载波PWM方法中低调制度下电平退化的问题,提出了一种新颖的载波PWM方法,既便是在低调制度下,所有的电平都能够得到应用。仿真结果表明,这种方法可以提高二极管箝位型逆变器在低调制度下的器件利用率,使得逆变器在低调制度下工作于较高频率。     

Recurrent wavelet neural network controller with improved particle swarm optimisation for induction generator system

A recurrent wavelet neural network (RWNN) controller with improved particle swarm optimisation (IPSO) is proposed to control a three-phase induction generator (IG) system for stand-alone power application. First, the indirect field-oriented mechanism is implemented for the control of the IG. Then, an AC/DC power converter and a DC/AC power inverter are developed to convert the electric power generated by a three-phase IG from variable frequency and variable voltage to constant frequency and constant voltage. Moreover, two online trained RWNNs using backpropagation learning algorithm are introduced as the regulating controllers for both the DC-link voltage of the AC/DC power converter and the AC line voltage of the DC/AC power inverter. Furthermore, an IPSO is adopted to adjust the learning rates to further improve the online learning capability of the RWNN. Finally, some experimental results are provided to demonstrate the effectiveness of the proposed IG system.     

基于状态空间的PWM逆变器数字PI双环控制技术研究

主要研究了数字控制的实际应用情况以及脉宽调制(PWM)正弦波逆变器的特点,包括电流内环电压外环的双闭环控制。在建立逆变器控制系统状态空间模型的基础上,详细分析了外环为输出电压,内环为电感电流加负载电流前馈控制对应的控制策略的稳定性和动态响应。先对控制系统直接离散化,再利用极点配置的方法进行系统参数设计。从响应速度、外特性、稳定性方面进行了具体分析,结果说明在离散域里双环控制逆变器具有较好的动态响应速度和输出外特性。最后通过实验验证和仿真波形分析,证明这种双环控制技术能满足各项性能指标要求。     

A frequency‐dependent droop scheme for parallel control of ups inverters

Abstract

This paper presents a frequency‐dependent droop scheme for paralleling UPS inverters with no control interconnection, so the inverters can be tightly connected with the load. At the fundamental frequency, the reference voltage of the inverter is generated as a reactor connected between the inverter and the load. The intention is to control the real and reactive power sharing of inverters with the Q‐V and P‐ω droop scheme employed in the power system without needing a true transfer reactor. At the harmonic frequency, the reference voltage is generated as a resistor connected between the inverter and the load. The intention is that the load harmonic current can be shared equally and the voltage waveform distortion will be low. Two 1KVA single‐phase inverters are designed and implemented, some simulation and experimental results are provided for demonstrating the effectiveness of the proposed approach.     

Design and implementation of PV-based three-phase four-wire series hybrid active power filter for power quality improvement

This paper proposes a Photovoltaic (PV)-based three-phase four-wire Series Hybrid Active Power Filter (SHAPF), it comprises of a Series Active Power Filter (SAPF) and an LC shunt passive filter. The proposed system eliminates both the current and voltage harmonics and compensates reactive power, neutral current and voltage interruption. A SAPF demands a source of energy for compensating the voltage sag/swell. This system found a new topology for SHAPF which utilizes the PV with DC–DC boost converter as a source of DC power for the series active filter. The compensation current reference evaluation is based on the twin formulation of the vectorial theory of electrical power theorem with Fuzzy Logic Controller (FLC). The PV array/battery managed DC–DC boost converter is employed to step up the voltage to meet the DC bus voltage requirement of the three-leg Voltage Source Inverter (VSI). The foremost benefit of the proposed system is that, it will provide uninterrupted compensation for the whole day. This system utilizes the renewable energy; accordingly saves the energy and provides the uninterruptable power supply to critical/sensitive load, through the PV array/battery bank during both day time and night time. An experimental model was established and results were obtained, which indicated the capability of the proposed control scheme.     

Single-stage high-power-factor electronic ballast with complex frequency modulation for hid lamps

A single-stage, complex frequency-modulated (CFM), high-frequency-driven electronic ballast for high-intensity-discharging (HID) lamps is proposed. The presented ballast combines a power-factor-correction (PFC) converter with a half-bridge series-resonant parallel-loaded inverter as well as a CFM controller. The switching frequency of the integrated inverter is non-periodically modulated by the CFM signal that integrates DC-bus voltage ripples with an additional high-frequency sine-wave signal. Compared with constant-frequency and frequency-modulated (FM) control, the presented ballast offers a widely continuous power spectrum of lamp current with decreased amplitude in order to effectively expand the lamp power as well as reducing sideband frequencies and allowing for a much lower energy level of the eigen frequency that supplies the lamp. Because of its CFM operation, no acoustic resonance occurs; additionally, the obtained results include a 13 dBm reduction of power spectrum at the centre switching frequency compared with FM control, and a 22 dBm reduction compared with constant-frequency control. The ballast offers high power factor (0.99), high efficiency (90%), cost-effectiveness and a simple, easy-to-implement controller. A prototype ballast utilising the CFM control method with 110 V utility-line input voltage has been built, and experimental results were carried out on three different brands of 70 W metal-halide-type HID lamps     

A Modified-Simplified MPPT Technique for Three-Phase Single-State Grid-Connected PV Systems

Nowadays, the single state inverter for the grid-connected photovoltaic (PV) systems is becoming more and more popular as they can reduce circuit complexity resulting in less power losses of the inverter. This paper focuses on the use of model predictive control (MPC) to control a 3-phase and 2-level single-state grid-connected inverter in order to regulate the PV maximum power point (MPP). The algorithm of MPC scheme was done to measure the simultaneous current signal including predicting the next sampling current flow. The reference current (I_d*) was used to control the distribution of electrical power from the solar cell to the grid. To be able to control the maximum power point tracking (MPPT) when the sunlight suddenly changes, so that a developing MPPT based on estimation current perturbation and observation (ECP&O-MPPT) technique was used to control the reference current. This concept was experimented by using MATLAB/Simulink software package. The proposed technique was tested and compared with the old technique. The simulation results showed that the developed MPPT technique can track the MPP faster when the light changes rapidly under 1,000 W/m², 25°C standard climatic conditions. The MPPT time was 0.015 s. The total harmonic distortion (THD) was 2.17% and the power factor was 1.