Output‐voltage feedback control topology for inverters dedicated to renewable energy systems

We present a new control topology for inverters, mainly dedicated to renewable energy applications. The originality is due to the integration in the inverter of an adaptive regulation of its output voltage controlled by a closed feedback loop allowing compensating the voltage drops induced by load variations. The feedback control is based on an adaptive pulse wave modulation (APWM) technique, that controls the power switches of the inverter to obtain the purest possible sine‐wave voltage. The APWM technique straightforwardly compares the inverter output voltage with a reference signal at the grid frequency. In this contribution, this technique is applied to a single‐phase push‐pull inverter but could have been integrated for the control of all kinds of inverter topologies in renewable energy systems. We have shown that the APWM technique allows generating pure sine‐wave voltage, with low total harmonic distortion compared with the generally obtained by classical systems and that load variations do not affect the quality of the output. An experimental prototype of a single‐phase inverter with an adaptive regulation based on APWM technique was developed. The experimental characterizations of the prototype confirm the simulations. Copyright © 2017 John Wiley & Sons, Ltd.     

Asymmetrical modulation and overmodulation of parallel-connected NPC-PWM inverters

The neutral point clamped (NPC)-PWM inverter has significant advantages, such as its ability to operate motors with nearly sinusoidal current waveforms. For this reason, in larger-capacity inverter systems, NPC-PWM inverters using GTOs and the like have been put into practical use, because of great advantages to large-capacity ac motor drives, such as lower ripple currents and higher output voltages. With the spread of applications, inverters of still larger capacity are expected. However, since the capacities of such switching devices are insufficient, a certain technique and controlling method are proposed for the parallel connection of NPC inverters. In this paper, conventional modulation techniques are extended to improve the inverter characteristics; asymmetrical modulation and overmodulation techniques are introduced for the parallel-connected NPC inverter. In the proposed modulation strategies, the waveforms become more complicated, so that it is difficult to analyze the output waveforms. For those waveforms, an analytical waveform analysis method using the switching function is proposed. With such a method, the physical meaning of harmonic generation can be realized to some extent. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 49–58, 1997     

Optimized coordinated control of LFC andSMES to enhance frequency stability of areal multi-source power system consideringhigh renewable energy penetration

With rapidly growing of Renewable Energy Sources (RESs) in renewable power systems, several disturbances influence on the power systems such as; lack of system inertia that results from replacing the synchronous generators with RESs and frequency/voltage fluctuations that resulting from the intermittent nature of the RESs. Hence, the modern power systems become more susceptible to the system instability than conventional power systems. Therefore, in this study, a new application of Superconducting Magnetic Energy Storage (SMES) (i.e., auxiliary Load Frequency Control (LFC)) has been integrated with the secondary frequency control (i.e., LFC) for frequency stability enhancement of the Egyptian Power System (EPS) due to high RESs penetration. Where, the coordinated control strategy is based on the PI controller that is optimally designed by the Particle Swarm Optimization (PSO) algorithm to minimize the frequency deviations of the EPS. The EPS includes both conventional generation units (i.e., non-reheat, reheat and hydraulic power plants) with inherent nonlinearities, and RESs (i.e., wind and solar energy). System modelling and simulation results are carried out using Matlab/ Simulink® software. The simulation results reveal the robustness of the proposed coordinated control strategy to preserve the system stability of the EPS with high penetration of RESs for different contingencies.     

新能源汇集系统短路故障清除后的暂态过电压机理

新能源汇集系统交流短路故障后产生的非工频暂态过电压可能导致新能源机组大规模脱网甚至损毁,这已成为制约新能源汇集系统送电极限的决定性因素。基于华北地区典型新能源汇集系统构建算例系统,分析短路故障下的暂态过电压形态特征,阐明易产生暂态过电压的系统参数条件,建立数学模型进行定量研究,利用RLC电路的全响应理论解释产生暂态过电压的本质原因。分析结果表明,短路故障清除后新能源汇集系统的电路固有谐振过程是导致暂态过电压的主要原因之一。     

A novel modulation technique with interleaved‐and‐shifted shoot‐through state placement for quasi‐Z‐source inverters

In this paper, a single‐phase quasi‐Z‐source (qZS) inverter (qZSI), integrating the pulse width modulation (PWM) control with interleaved‐and‐shifted shoot‐through state (STS) placement modulation technique, is proposed to simultaneously achieve both dc voltage boost and dc‐ac inversion. Instead of placing the STS in both inverter legs simultaneously, the addressed method inserts the STS only in left/right inverter leg separately during the positive/negative half cycle of the output voltage to reduce switching losses and thermal stresses of the power devices. The STS shift is also studied to decrease the switching numbers of power devices and thus can improve the efficiency further. Theoretical analysis and design guidelines of the studied inverter are included. Improvement in effectiveness and performance of the devised scheme and modulation strategy are proved experimentally and compared with the previous studies on a built laboratory prototype.     

新能源分布式发电系统储能电池综述

风、光等新能源分布式发电受天气和气候的影响出现间隙性和随机性等使得发电的不稳定缺点正成为阻碍其深度发展的重要障碍。储能技术的发展和应用,打破了风电、光伏发电等的接入和消纳瓶颈问题。介绍了应用于储能系统的主要化学储能电池:铅酸电池、液流电池、钠硫电池和锂电池的技术发展、组成结构和储能原理,详细对比了各种电池的性能及特点,特别对能量密度、功率密度和功率等级进行介绍,这是储能系统电池元件选择的关键,最后对储能电池的应用和发展作了展望。     

Microgrid dynamic security consideringhigh penetration of renewable energy

This paper presents a coordination strategy of Load Frequency Control (LFC) and digital frequency protection for an islanded microgrid (MG) considering high penetration of Renewable Energy Sources (RESs). In such MGs, the reduction in system inertia due to integration of large amount of RESs causes undesirable influence on MG frequency stability, leading to weakening of the MG. Furthermore, sudden load events, and short circuits caused large frequency fluctuations, which threaten the system security and could lead to complete blackouts as well as damages to the system equipment. Therefore, maintaining the dynamic security in MGs is one of the important challenges, which considered in this paper using a specific design and various data conversion stages of a digital over/under frequency relay (OUFR). The proposed relay will cover both under and over frequency conditions in coordination with LFC operation to protect the MG against high frequency variations. To prove the response of the proposed coordination strategy, a small MG was investigated for the simulation. The proposed coordination method has been tested considering load change, high integration of RESs. Moreover, the sensitivity analysis of the presented technique was examined by varying the penetration level of RESs and reducing the system inertia. The results reveal the effectiveness of the proposed coordination to maintain the power system frequency stability and security. In addition, the superiority of the OUFR has been approved in terms of accuracy and speed response during high disturbances.     

A suitable single-phase pulse width modulation current source inverter for utility interactive photovoltaic generation system

A suitable single-phase inverter for the utility interactive photovoltaic generation system is proposed. The single-phase Pulse Width Modulation (PWM) current source inverter has a novel circuit configuration in which an auxiliary branch is added to the normal single-phase bridge circuit. To reduce the size and weight of the dc reactor, a double frequency parallel resonance circuit (LC tank circuit) is inserted in the dc side of the inverter. As a result, the double frequency voltage appearing in the dc side of the inverter due to the pulsation of the single-phase instantaneous power is perfectly suppressed by the tank circuit. The constant dc current without pulsation is supplied from PV array to the inverter. The inverter provides a sinusoidal ac current for domestic loads and the utility line with unity power factor. The virtual maximum power of the PV array can be obtained without any feedback control. In the system, the PV array can play an important role as a current-limiter due to its V-I characteristics. Computed waveforms by simulation are shown. Excellent inverter equipment will be realized that is smaller in size and lighter in weight than is usual for a conventional inverter.     

应用升压电路的蓄电池放电设备

对蓄电池进行放电是维护其性能的重要手段,鉴于目前国内市场上放电设备的各种问题,有必要研制一种性能更好的放电设备。介绍了一种新型的蓄电池放电设备,该放电设备主电路采用升压电路,应用开关电源技术,采用PI调节器进行控制。和目前国内现有蓄电池放电设备相比,该设备具有放电电流连续,控制精度高,可靠性好的特点。讨论了系统的结构、组成和工作原理,重点阐述了脉冲放电电流对蓄电池的影响,给出了实验数据,经过在某机场的实际应用,效果良好,具有良好的应用前景。     

斩波串级调速系统逆变侧电子保护电路的研究与设计

根据常规斩波串级调速系统的拓扑结构,分析了调速设备故障时接触器保护在动作保护过程中主回路的暂态过程。由于接触器动作时间较长,在其动作期间调速设备易受到高电压、大电流的冲击,导致电力电子器件损坏。针对接触器保护的弊端,设计了带电子保护电路的主回路拓扑结构。并分析了高压失电工况下常规的和带电子保护电路的斩波串级调速系统的暂态过程,同时进行详细的理论推导,得出高压失电工况下理论分析的依据。最后在模拟带载试验平台上分别对常规斩波串级调速系统和增加电子保护电路的调速系统在高压失电的工况下进行测试。测试结果表明理论计算与实际测量值基本一致,同时验证了电子保护电路有效解决了有源逆变结构下的高压失电或者逆变颠覆的问题。     

Strategic approach for reinforcement of intermittent renewable energy sources and capacitor bank for sustainable electric power distribution system

To meet ever increasing load demand in a sustainable way, reinforcement of photovoltaic (PV) array, wind turbine (WT) and capacitor bank in distribution network is proposed in this paper. A comprehensive planning model is presented to determine location and required installation capacity of multiple PV array, WT and capacitor units in an electric power distribution network under heavy load growth situation. Intermittent power generation of renewable energy sources (RESs) are quantified with suitable probability distribution functions and incorporated in the planning model. The planning approach considers several welfare areas in the distribution systems, viz., increment of profit margin, reduction of carbon-di-oxide emission, minimization of distribution power losses, enhancement of voltage stability level and improvement of the network security considering power flow, voltage limit, line capacity, RES penetration, capacitor penetration and utility economy constraint. Non-dominated sorting based multi-objective particle swarm optimization algorithm along with fuzzy decision making criteria is used to find the best allocation alternative for mix RES and capacitor planning problem. The effectiveness of the proposed model has been tested on a typical 28-bus Indian rural distribution network. The results show that more efficient techno-eco-environmental optimization can be obtained from combined RES and capacitor planning model.     

Exploring the cost implications of increased renewable energy for the U.S. power system

Over the last decade, the fraction of annual U.S. electricity generation for renewable energy has doubled from 10 % to 20 %. This growth has been driven by several factors, including technology cost reductions and policy support. The share of renewable generation is projected to increase over time. Reference case scenarios from four different organizations show least-cost U.S. electricity buildouts with renewable energy generation fractions of 31–36 % by 2030 and 40–65 % by 2050. Using a capacity expansion modeling tool, we investigate how changing the amount of renewable energy from the least-cost solution impacts the cost of building and operating the electricity system. The relationship between system cost and renewable energy generation fraction is non-linear. Small deviations near the least-cost solution have minimal cost impacts (changing the renewable energy penetration by +/- 5% results in system cost changes of less than 1%), while similar deviations that are farther from the least-cost solution can result in large cost changes. Increased levels of RE lead to lower absolute emissions, and we evaluate the trade-offs between emissions savings and system costs for higher and lower levels of RE penetration.     

机房无人值班报警系统硬件电路的设计

论述了机房无人值班报警系统数据采集系统硬件电路的设计思想,重点介绍了8051单片机、8155可编程RAM I/O芯片、静态8kRAM6264芯片、A/D转换器等硬件电路的设计选型及工作原理。     

逆变器中IGBT模块的损耗计算及其散热系统设计

介绍了一种在工程上比较适用的IGBT模块损耗的理论计算方法,并将其计算结果与厂家给出的仿真结果相比较,精度满足设计要求.在计算出IGBT模块损耗后,利用散热系统热阻等效电路,求出散热器热阻,进而设计出符合逆变器的强迫风冷散热系统.最后,通过ICEPAK软件对散热器进行仿真,由仿真结果表明散热器达到要求.     

Contours of the energy transition: Investment by international oil and gas companies in renewable energy

International oil and gas companies are deploying a range of strategies to invest in renewable energy technologies and projects. By now, the IOCs have become substantive players in the renewables market, lending their scale and business expertise to deploying clean energy. But they have seen mixed success in their efforts thus far, and the models IOCs choose to follow as they become interested in deploying renewables are still emerging.     

A novel active auxiliary circuit for efficiency enhancement integrated with synchronous buck converter

In this paper, a novel auxiliary circuit is introduced for the synchronous buck converter. This auxiliary circuit provides zero‐current, zero‐voltage switching conditions for the main and synchronous switches while providing zero‐current condition for the auxiliary switch and diodes. The proposed active auxiliary circuit integrated with synchronous buck converter that emanates to zero‐voltage transition (ZVT)–zero‐current transition (ZCT) pulse width‐modulated (PWM) synchronous buck converter is analyzed, and its operating modes are presented. The additional voltage and current stresses on main, synchronous and auxiliary switches get decimated because of the resonance of the auxiliary circuit that acts for a small segment of time in the proposed converter. The important design feature of soft‐switching converters is the placement of resonant components that mollifies the switching and conduction losses. With the advent of ZVT–ZCT switching, there is an increase in the switching frequency that declines the resonant component values in the converters and also constricts the switching losses. The characteristics of the proposed converter are verified with the simulation in the Power Sim (PSIM) software co‐simulated with MATLAB/SIMULINK environment and implemented experimentally. Copyright © 2016 John Wiley & Sons, Ltd.     

新能源系统物理模拟实验平台设计及应用

从物理模拟实验的角度对新能源电力系统进行研究。首先,总结了国内外新能源电力系统的发展现状。然后阐述了通过物理模拟实验探究新能源电力系统的必要性,以及新能源物理模拟实验的研究现状。随后设计、介绍了新能源物理模拟实验平台的主要构成。最后,应用实验平台,重点针对并网运行的暂稳态特性,设计了实验方案,分析了实验结果,表明物理实验平台对研究新能源电力系统具有重要意义。     

适用于含新能源逆变电源网络的全时域短路电流计算方法

含新能源逆变电源在故障后无恒定电动势,因而传统交流网络短路电流计算所用的内电动势-阻抗方法不再适用。为解决该问题,提出了一种包含新能源逆变电源故障稳态和暂态2种时间尺度下的全时域短路电流计算方法。故障稳态计算中结合逆变电源的控制策略,将逆变电源视为非线性电流源,充分反映了逆变电源短路后的故障特性。故障暂态计算中基于稳态短路电流结果,利用由控制系统推演出的暂态微分方程,求解出暂态过程中的电流表达式。最后将计算值和仿真结果、录波结果进行对比,验证了该方法的可行性。     

Target and demand for renewable energy across 10 ASEAN countries by 2040

The member countries of Southeast Asia have renewable energy sources that never run out like solar energy, wind, geothermal, hydropower, biomass, etc. Geographically, Southeast Asian countries are between two continents that have tropical and humid climate conditions in general, while only Myanmar has a subtropical climate because it is astronomically. This provides easier access to many renewable energy sources. The governments of ASEAN member countries have made several policies and promoted renewable energy to encourage individuals and industries to use renewable energy in the future. This study provides information on the status of renewable energy as a comprehensive substitute for fossils in Southeast Asian countries, which includes the potential for renewable energy in the region and the capacity of renewable energy currently available. The study also provides brief information on the potential of renewable energy, renewable energy targets, and challenges to energy demand in Southeast Asia. In addition, this paper provides several recommendations for renewable energy in Southeast Asian countries.     

PWM变频器的能耗制动与再生制动

本文介绍了用于ＰＷＭ变频器的两种制动电路。此电路在实际应用中效果很好。