并网逆变器二自由度控制策略研究

为应对新能源分布式发电系统接入所致的电网阻抗变化对并网逆变器稳定运行的影响,提高其应对电网变化的能力,提出含电网阻抗估测的并网逆变器二自由度控制策略。首先构建含电网阻抗的并网逆变器模型,研究电网阻抗变化所致的阻抗失配对并网系统稳定性的影响;其次提出一种可独立调整跟随控制和抗扰控制的二自由度控制策略,设计出跟随控制器及抗扰控制器,采用非特征次谐波注入法实时估测电网阻抗,给出含电网阻抗检测的完整二自由度控制方案;最后进行仿真研究和实验验证。结果表明:所提二自由度控制策略具有同时兼顾电流快速跟随和抗电网阻抗扰动能力,可有效提高并网逆变器的稳定性。     

带LCL滤波的单相逆变器滑模控制

针对带LCL滤波器的并网逆变器的不稳定性,提出一种基于逆变器侧电流反馈滑模控制策略,间接控制并网电流,以避免系统谐振。将并网电流参考值看成和电网电压成比例,推导出逆变器侧参考电流,解决间接控制并网电流相位滞后问题。理论推导滑模变结构控制律在并网逆变器应用的存在性和系统稳定性,所提控制策略无需增加额外的传感器。应用电压基波信号估计,以减轻电网高次谐波对系统控制的影响。仿真实验证明提出的控制策略可实现逆变器并网电流与电网电压同频同相,提高了系统的鲁棒性。     

基于输出阻抗的三相LCL型光伏逆变器稳定性分析

针对三相LCL型光伏逆变器接入弱电网发生功率失稳的问题,基于阻抗稳定性判据,建立dq坐标系下计及锁相环和控制环路的逆变器动态等效输出阻抗模型,分析逆变器和弱电网之间的交互影响。构建基于阻抗稳定性判据的光伏逆变系统稳定性分析方法,揭示逆变器输出阻抗和电网阻抗间的交互作用所引起的系统失稳机理,搭建光伏逆变单元接入弱电网仿真、实验系统,通过仿真算例与实验结果验证理论分析的正确性。     

基于丰田混合动力汽车的电网发电系统研究

为保证汽车的正常行驶，混合动力汽车配有大容量电机和逆变器。文中研究了在发生地震及类似紧急情况时利用汽车的混合动力系统提供紧急电源，利用混合动力汽车现有的驱动电机和逆变器，通过电机中性点向电网输出大容量电力，并在丰田Prius轿车上进行实验。     

基于电网电压前馈的光伏并网逆变器的仿真与实现

介绍了光伏并网逆变器的基本原理和拓扑结构;提出了一种基于电网电压前馈和电流跟踪控制技术的并网控制方法;建立了仿真模型;给出了系统控制的软件和硬件设计.在一台10kHz,3kW的实验样机上对该方案进行了实验,实验结果验证了该方法的有效性.     

一种基于前馈控制的双模式逆变器无缝切换控制方法

对一个微电网系统的组成进行详细介绍,说明双模式逆变器在微电网系统中所发挥的作用。分别对双模式逆变器在并网和脱网模式下的控制方法进行了解。创新地提出一种基于前馈控制的无缝切换控制方法,并通过仿真结果证明该方法的可行性。同时对电网状态检测方法进行说明。最后介绍实验平台,并对实验波形进行介绍和分析,说明以上理论的正确性和可行性。     

弱电网条件下并网逆变器的稳定性

位于偏远地区分布式发电系统长距离传输线给电网引入不可忽略的阻抗,使电网呈弱电网特点。当弱电网阻抗与逆变器输出阻抗不匹配时,并网电流在某些特定频率发生谐振,从而破坏逆变器的稳定性。基于阻抗分析法研究弱电网阻抗对LCL型并网逆变器稳定性的影响,并给出一种新型电容并联虚拟电阻有源阻尼算法来提高弱电网下并网逆变器的稳定性。最终,在一台500 W实验平台中对算法进行验证。     

微电网三相逆变器网络控制并联运行策略及信号时延分析

在分析现有逆变器并联方法优缺点的基础上,提出一种基于网络控制功率下垂三相逆变器并联方法,给出自主式和主从式两种网络控制策略。分析建模三相逆变器后,利用MATI方法分析系统所能允许的时延。通过Matlab仿真表明时延允许的范围内并联逆变器在稳定性及在有网络时延情况等方面具备良好的综合性能。建立两台1 k W三相逆变器组成的网络控制实验平台,实验结果验证了所提出控制方法以及时延分析的可行性和有效性。     

微电网储能双模式逆变器控制方法的研究

文章设计了应用于微电网的储能双模式逆变器系统,该系统利用三相逆变器SVPWM算法实现了对双模式逆变器并网运行的有效控制,利用与并网模式有相同电流内环的独立运行控制方法,对逆变器独立运行时电压幅值和频率控制,基于前馈控制的无缝切换控制方法,对电网状态检测方法以及防冲击的切换方法进行试验,试验结果验证了文章所提出理论的正确性和可行性。     

光伏系统中控制器与逆变器的二合一

提出将光伏系统中的控制器和逆变器的控制融为一体,可以做到资源共享,结构紧凑,进下不提高系统的效率和可靠性,描述了设计方案、软件编帛,给出了实验结果。     

高新能源占比系统的低频减载优化方法

电网系统中大规模新能源的并网对电网的安全稳定提出新的挑战,在高新能源占比电网中,系统的第三道防线的适应能力对于系统的安全稳定尤为重要,低频减载是第三道防线中频率紧急控制的主要手段。该文介绍适用于低频减载整定计算的频率响应模型,在此模型的基础上分析得出传统低频减载方案对高新能源占比系统的适应性较差的结论,提出基于df/dt的低频减载闭锁优化策略。通过仿真对比验证所提方案的可行性与适应性。此种方案也可为低惯性的受端网络系统的频率稳定第三道防线的协调配置提供借鉴。     

Enhancement of transient stability of an industrial cogeneration system with superconducting magnetic energy storage unit

This paper has developed the coordination of load shedding scheme and superconducting magnetic energy storage (SMES) unit to enhance the transient stability of a large industry cogeneration facility. The load-shedding scheme and the tie line tripping strategy by using the frequency relays have been designed to prevent the power system from collapse when an external fault of utility power system occurs. An actual external fault case and a simulated internal fault case have been selected to verify the accuracy of the load shedding scheme by executing the transient stability analysis. To improve the frequency and voltage responses, an SMES unit with various control modes has been installed in the cogeneration system. The sensitivity analysis of the SMES unit with different parameters is applied to achieve better system responses. Besides, an SMES unit with active power deviation as feedback signal is also considered to improve the electric power fluctuation of the study plant with rolling mills. It is found that the SMES system will enhance the electric power quality and minimize the economic losses of the cogeneration facility due to unnecessary load shedding.     

基于热泵群灵活控制的电热微网联络线功率分层协同平抑策略

为有效平抑电热微网的联络线功率波动,提出一种基于热泵群灵活控制的电热微网联络线功率分层协同平抑策略,即根据热泵启停控制与功率调节控制的特点,灵活运用两种控制方式使热泵群有效参与微网联络线中低频波动功率的平抑。建立含蓄热水箱的热泵群模型,并将波动功率协调分配层分频后的波动功率平抑目标在热泵与超级电容间分配;由热泵群优化控制层分析热泵群优先度序列,通过模拟退火算法优化启停方案,同时调节热泵动态运行功率;最后调节超级电容出力平抑剩余波动。算例结果表明,该策略能有效优化微网电热能流,平抑联络线波动功率,提升微网运行可靠性。     

A novel line drop secondary voltage control algorithm for variable speed wind turbines

This paper addresses the design and implementation of the line drop secondary voltage control (LDSVC) for the doubly fed induction generator‐wind turbine (DFIG‐WT) complemented with reactive power allocation algorithm to achieve more efficient voltage regulation, reactive power compensation and to enhance the transient stability margin of the electric power system. The LDSVC is used to generate the local voltage reference, providing an improvement for overall voltage profile. The paper presents the influence of the integration of variable speed wind turbines‐based doubly fed induction generator (DFIG) while employing LDSVC for increasing the transient stability margin. This paper proposes an improved voltage control scheme, based on a secondary voltage controller complemented with an automatic gain controller (AGC). The scheme is applied to a wind energy system incorporating DFIG‐based wind turbines. The controller structure is developed and the performance of the self‐tuning AGC scheme is developed and analysed. The proposed controller is tested in response to system contingencies for different short circuit ratios. The performance of the secondary voltage control without and with AGC is verified. The influence of the AGC in improving the transient response and damping of voltage oscillations is verified. Copyright © 2010 John Wiley & Sons, Ltd.     

限制过电压条件下的光伏发电并网设计

大规模发展分布式光伏发电有助于缓解能源危机,但随着分布式光伏发电的大规模接入,将对配电系统产生较大影响.阐述了光伏发电并网系统结构,结合分布式光伏发电特点和电网工程实际,设计出限制过电压条件下的光伏发电并网方案,提出光伏发电系统并网后直流与谐波分量的治理措施.实际运行表明,所设计的分布式光伏发电并网方案既能够保证接入点电压不越限,又能够有效减少占用线路走廊资源和电网调度、运行维护工作量.     

A novel approach for fault location on transmission lines

A new approach for power transmission line fault location is investigated. The fault locator estimation is based on the noise generated by the fault in the sending-end current signal. The proposed scheme consists of a wavelet-based filter module, a Prony-based signal processor and an ANN-based estimator. Input data has been generated using the Alternative Transient Program (ATP). A three-phase, frequency-dependent (FD) transmission line model was used. The scheme is tested using data employed in the ANN training as well as new data sets. The proposed locator has a good level of accuracy     

地区电力负荷无线双向管理系统功能扩展研究

以南阳地区电力负荷无线双向管理系统为例，并根据地区供电管理的实际需要，为了啬线损分析、语音警告等功能扩展的需求，提出了功能扩展技术方案。     

Optimal placement and sizing of PV systems and electric parking lots considering reactive power capability and load variation

Power systems should operate in reliable, stable, and efficient conditions. Addition of new generation units or loads to the power systems may change their performance. Therefore, appropriate decisions should be made to manage these elements to improve the power system performance. In this study, optimal placement and sizing of photovoltaic systems and electric parking lots (EPLs) are studied considering the reactive power capability of the inverters and load variation in a 24-h period. For the EPL, a proper charge/discharge scheme (CDS) is initially proposed to flatten the daily load profile; then the EPL with the associated CDS is considered to find its optimal location. Voltage profile, energy losses, bus, and line voltage stability are considered as the objectives of the problem. Genetic algorithm and backward–forward power flow method are utilised to solve the problem considering the IEEE 33-bus system. The results show that all objectives are improved utilising the proposed method.     

Experimental Evaluation of Active Filtering in a Single-Phase High-Frequency AC Microgrid

Population growth in the world along with rapid technological expansion of the society demand efficient, economically viable, and environment-friendly energy conversion systems. The previous theoretical and simulation works have demonstrated that a 500-Hz single-phase high-frequency ac (HFAC) microgrid is a novel step toward integrating renewable energy sources in a distributed generation system. This paper goes one step further in describing the practical implementation of HFAC microgrid with active filters for a small 1-kW system. The protection issues for both the source and series converters are also addressed in this paper by developing a new but simple protection scheme. In the experimental microgrid system, a universal active power line conditioner (UPLC) and a unified power quality conditioner (UPQC) are incorporated to control the power flow and power quality, respectively. Controllers for both the UPQC and UPLC are developed based on the instantaneous single-phase p-q theory, and controlled pulsewidth modulated inverters are then implemented to synthesize the desired compensating waveforms. The experimental results obtained confirm that the HFAC microgrid is a practical and useful step toward successfully integrating distributed renewable energy sources ensuring the improved system utilization.      

Control design and dynamic performance analysis of a windturbine-induction generator unit

This paper presents the modeling and control design for a wind energy conversion scheme using induction generators. The scheme consists of a three-phase induction generator driven by a horizontal axis wind turbine and interfaced to the utility through a double overhead transmission line. A static VAr compensator was connected at the induction generator terminals to regulate its voltage. The mechanical power input was controlled using the blade pitch-angle. Both state and output feedback controllers are designed using MATLAB software to regulate the generator output. From the simulation results, the response of closed loop system exhibited a good damping and fast recovery under different type of large disturbances