光伏发电参与配电网电压调节的控制策略研究

分析了光伏发电并入点电压特性和含光伏发电的放射状配电网内电压分布特性,从光伏电源并入点和配电网电压分布两方面提出光伏发电参与电压控制的支撑作用.将电压问题分为由光伏电源输出的缓慢波动和外部负荷等情况大扰动两类问题,分别提出光伏电源参与电压调节策略,控制策略利用全局静态信息和局部动态信息,在每个周波的采样计算时间内对光伏发电无功输出和配网无功分布进行实时管理,并给出具体控制框图.通过仿真,论证了所提出的电压管理策略在改善含大量光伏发电的配电网电压质量和稳定性方面的作用.     

适应电网侧AGC不同控制模式的光伏发电参与电网频率调节

大规模光伏发电并网致使电力系统面临惯量减小与调频能力不足。文章在备用一定有功功率的基础上,提出有功功率-频率下垂控制策略,通过修正逆变器的原有控制结构,实现光伏发电主动参与电网频率一次调节。考虑一次频率调节偏移与越界等问题,提出自适应电网侧AGC不同控制模式(定频率控制模式、定联络线功率控制模式以及联络线功率频率偏差控制模式)的二次频率调节控制策略,进而实现频率的无差调节。最后,基于PSCAD/EMTDC仿真平台验证了控制策略的有效性与可行性。     

光伏发电主动参与电网频率调节的机理分析

针对大规模光伏发电并网致使电力系统转动惯量减小、一次调频能力不足的问题,其主动参与电网频率调节是解决这一问题的重要手段。在分析传统电力系统的频率响应特性的基础上,建立了含光伏发电的电力系统频率动态响应模型。以电网频率变化率初始值、频率最低跌落点、超调量和稳定时间作为评估频率调节动态过程的特征量,定性分析了新型的光伏调频控制策略及调频参数对系统频率动态特性的影响及变化规律。最后,在PSCAD/EMTDC电力仿真软件中搭建两区四机仿真模型,通过时域仿真验证机理分析其有效性和新型调频控制策略的可行性。     

双级式光伏并网变换器的控制策略研究

文章针对双级式光伏并网前级Boost变换器,提出了一种具有功率、电压双闭环结构和基于梯度信息的变步长MPPT控制策略,它直接从光伏阵列的功率-电压特性出发,依据梯度信息直接给出最大功率点电压,进而通过电压闭环实现自动寻优,快速实现最大功率跟踪控制。针对后级含有LCL滤波器的逆变器,基于常规矢量控制技术,引入了有源阻尼控制中的电容电流反馈技术,给出了一种含有LCL滤波器的逆变器有源阻尼功率解耦控制策略,能够实现直流侧电压恒定和单位功率因数的并网控制,且在不增加系统损耗的情况下有效抑制系统谐振。建立了10 kW双级式光伏并网系统仿真模型,仿真结果表明,系统能够快速跟踪光强变化,实现MPPT控制及单位功率因数并网控制,具有良好的动态调节性能和静态特性。     

一种具有频率支撑功能的MPPT控制策略

随着光伏发电的渗透率增大,光伏并网逆变器输出的有功功率会影响到电网频率的稳定。该文根据同步发电机输出的有功功率与频率之间的下垂特性关系,在已有的扰动观察法的基础上,提出一种具有倒下垂特性的MPPT控制策略。该MPPT策略可在电网频率增大时增加光伏并网逆变器输出的有功功率以降低电网频率,在电网频率减小时减小光伏并网逆变器输出的有功功率以增大电网频率,起到对电网频率的支撑作用。最后,通过RTLAB仿真对所提出的MPPT策略进行了验证。     

一种新型家用光伏供电系统

提出了一种新的家用光伏供电系统.系统采用了无变压器式的能量变换器、216 V供电体制和小电流放电方式.实验分析表明,该系统可降低光伏系统成本,效率高,具有应用的可靠性,为低成本光伏发电的推广 .应用提供一条新途径.     

光伏发电参与电力系统调频的研究综述

受化石能源的枯竭及环境毁坏的影响,光伏发电并网容量快速增长,而大规模光伏发电并网严重减弱了电力系统的调频能力,加大了电力系统的运行风险。首先阐述了光伏发电大规模并网后,电力系统的动态变化趋势;然后从光伏电站单一调频、综合自动发电控制(AGC)调频2方面进行了调研总结,并对光储联合调频和光伏虚拟同步发电机提高光伏发电调频能力等进行了综述分析。结论表明,储能技术及光伏虚拟同步发电机技术是提高光伏发电调频能力的有效方法,随着储能成本的降低及光伏虚拟同步发电机技术的日益成熟,针对光伏发电参与电力系统调频进行研究将具有更高的实际应用价值。     

局部阴影下光伏电站参与一次调频的控制策略

针对采用光伏虚拟同步发电机（PV-VSG）控制策略的光伏电站参与电网一次调频的问题，考虑光伏阵列受局部阴影遮挡的情况，提出一种基于自适应虚拟惯量的有功备用式PV-VSG控制策略，采用粒子群优化算法实现局部阴影条件下光伏阵列的最大功率点跟踪和减载备用运行，并根据电网频率变化过程中不同阶段的特性，自适应调节虚拟惯量参数以减小频率超调量并加快频率的恢复速度。此外，为了使调频模式下光伏电站内各PV-VSG的有功功率合理分配，采用一种基于等可调容量比的有功分配策略，使站内各光伏机组具有相同的调频功率裕度，避免部分光伏机组的过度调节。最后，以10 MW光伏电站参与电网一次调频为例进行仿真分析，验证了所提控制策略的有效性。     

光伏逆变器参与电网无功电压控制策略

分布式电源规模化大批量接入配电网,极大地改变了传统配电网的结构,其对供电安全、经济与可靠性的影响不容忽视。首先分析了分布式光伏接入电网对电能质量的影响,尤其是光伏反送电量导致的配电网末端电压高、谐波干扰大等问题,随后提出了光伏逆变器参与电网无功电压控制的方案,极大消除了分布式光伏大量接入系统对电能质量带来的不利影响。     

A multi-objective control strategy for grid connection of DG (distributed generation) resources

This paper presents a flexible control technique for connection of DG (distributed generation) resources to distribution networks, especially during ride-through on faulty grid. This strategy is derived from the abc/αβ and αβ/dq transformations of the ac system variables. The active and reactive currents injected by the DG source are controlled in the synchronously rotating orthogonal dq reference frame. The transformed variables are used to control the VSI (voltage source inverter) which connects the DG to the distribution network. Using a P.L.L. (phase locked loop) in circuit of proposed control technique, the angle of positive sequence has been detected, in order to synchronize the currents to the distribution network. The proposed control technique has the capability of providing active and reactive powers and harmonic currents to nonlinear loads with a fast dynamic response. Simulation results and mathematical analysis have been completed in order to achieve a reduced THD (total harmonic distortion), increased power factor and compensated load’s active and reactive powers. The analyses show the high performance of this control strategy in DG applications in comparison with other existing strategies.     

A novel islanding detection technique for grid connected photovoltaic system

Islanding detection is the major issue in Grid Connected Photovoltaic (PV) System and still it remains a challenge for researchers to interconnect the PV system with the Grid. The algorithms which are listed in the literature are failed to identify the Islanding phenomena for the several source configuration. In this paper a novel islanding detection technique is presented to reduce the non-detection zone (NDZ) at the point of common coupling (PCC) and it can be widely used for various renewable energy system configurations. The simulations have been carried out in Matlab/Simulink for several test conditions. The simulations results are presented to confirm the effectiveness of the proposed method.     

基于MPPT的两级单相光伏并网发电系统控制策略研究

文章对两级单相光伏并网发电系统进行研究,系统前级使用新型变步长电导增量法,来实现最大功率点跟踪;后级逆变器采用P-Q控制方式,实现快速电网电压跟踪;使用电压外环,电流内环的双环控制,使逆变器输出稳定的无功和有功功率。在Simulink中搭建仿真模型,结果验证系统不仅能够有效提高跟踪速度和精度,而且可以较好的抑制系统在最大功率处的波动,满足光伏发电对并网逆变器的要求。     

响应电网调度需求的光伏发电系统建模及运行控制研究

针对现有光伏仿真模型无法执行电网调度指令的问题,提出响应电网调度需求的光伏发电系统建模及运行控制方法。根据不同容量光伏系统组成结构搭建了基于DIg SILENT的适用于不同容量的并网光伏发电系统模型,以光伏发电系统响应电网有功需求时间最小化为期望目标,考虑光伏发电系统出力的随机性,通过调整直流电压控制信号响应电网调度需求,利用控制模块中的有功出力限制满足并网点频率约束条件,采用电导增量法优化了MPPT控制策略。仿真结果表明,在有电网调度需求时构建的模型能够快速地响应电网调度指令,在无调度需求时能够很好地实现最大功率跟踪或限制有功出力以满足并网点频率约束。     

The Spanish regulation of the photovoltaic demand-side generation

It is usually expected that demand-side generation gains momentum in places where retail grid parity is being reached. This is, for example, the case of photovoltaic generation in Spain. However, many different support schemes can be implemented. In Spain, the PV promotion policy gave priority to the ground-mounted installations. For years, the coupling of customer-side generation with excess energy exports was never specifically considered. Nonetheless, some months ago this option was suggested as a way to recover Spain's PV sector from the current moratorium on the RES-E policy. A first decree draft on on-site generation was issued, its central point being the consideration of electricity exports as delayed consumption rights. But several barriers hindered its entry into force. Finally, a second decree draft was issued in July 2013, which is expected to enter into force soon. This second draft impedes the economic viability of demand-side generation, thus complicating the recovery of the Spanish PV sector.     

A novel real-time simulation technique of photovoltaic generation systems using RTDS

For the performance test of photovoltaic (PV) generation systems, actual system apparatuses: a solar panel, converter system, and load facilities should be installed. It is also hardly possible to compare a maximum power point tracking (MPPT) control scheme with others under the same weather and load conditions in an actual PV generation system. One of the possible alternatives is to realize a transient simulation scheme for PV generation systems under real weather conditions of insolation and surface temperature of solar cell. The authors propose a novel real-time simulation method for PV generation systems under real weather conditions using a real-time digital simulator (RTDS). V--I curves of a real PV panel are tested using electric load device, and a hypothetical network of the tested PV panel is created on the RTDS by arranging electrical components from the customized component model libraries. The real weather conditions, insolation, and temperature of the PV panel, are interfaced through the analog input ports of the RTDS for real-time simulation. The outcomes of the simulation demonstrate the effectiveness of the proposed simulation technique, and also show that cost-effective verification of availability and stability of PV generation systems is possible using the built-in simulator.     

一种基于光/水互补孤立发电系统的新型频率控制策略

针对由光伏电压源型逆变器并联组成的微电网与小型水轮发电机构成的孤立互补发电系统,其频率响应受到水轮机调速器特性的影响,存在调节过程时间长、超调大,存在稳态误差的问题。在现有微电网分层控制策略的基础上,提出了一种新型光伏微电网功率控制策略,通过调节光伏微电网的有功出力,实现了对互补孤立发电系统频率的控制,改善了原发电系统频率调节的动态响应,消除了稳态误差,最后通过仿真验证了所提控制策略的有效性。     

Providing power reserve for secondary grid frequency regulation of offshore wind farms through yaw control

The ability to significantly contribute to the frequency regulation and provide valuable ancillary services to the transmission system operator (TSO) is one of the present wind farm (WF) challenges, due to the limitations of wind speed forecasting and insufficient power reserve in certain operating conditions notably. In this work, the feasibility of WFs to participate in frequency restoration reserve (FRR) through yaw control is assessed. To this end, a distributed yaw optimization method is developed to evaluate the power gain achieved by yaw redirection based on wind turbine cooperation and compared with a greedy approach. The method relies on a static wake model whose parameters are estimated in a systematic way from simulation data generated with FAST.Farm. Through a case study based on a scaled version of the Belgian Mermaid offshore WF, it is demonstrated that the requirements of the TSO are fulfilled both in terms of response time and level of power reserve for most wind directions. The assessment is limited to wind speeds below the rated speed of the considered wind turbines.     

一种直驱永磁风电机组的减载调频控制策略

文章针对风电并网容量增加导致系统调频能力不足的问题,提出了一种超速和变桨距协调的减载调频控制策略。首先给出了低、中、高3种风速模式的判定方法,然后通过设置初始功率跟踪曲线系数和调节桨距角实现直驱永磁风电机组的减载运行。在频率控制中,优先采用超速控制,当转速达到额定转速时,再启用变桨距控制,并且变桨距控制可分为低、中、高3种风速控制模式。仿真分析表明,基于所提减载调频控制策略,直驱永磁风电机组能在全风速范围预留一定比例的备用容量,实现双向频率控制,并能改善系统频率的暂态和稳态响应。