基于直流母线电压信号的小型独立直流微电网自主平滑模式切换控制策略

在独立直流微电网中,储能系统(ESSs)和光伏(PV)是主要能源。在极端条件下,储能和光伏变换器需要进行工作模式切换以协调功率,为了优化切换性能,该文提出一种基于直流总线信号(DBS)的自主平滑模式切换控制策略,用于多个光伏电源和ESS的无通信协同工作,提高了系统的可靠性。针对多模式切换过程中的抖振和死锁问题,所提出的控制策略利用具有反馈抑制机制的PI控制器实现了在饱和与激活之间无缝切换。同时,为了进一步提升光伏能量的利用率,所提出的控制策略充分考虑了ESS的荷电状态(SOC),并使光伏电源能够直接参与直流母线电压的调节。此外,还对模式切换时间与控制器参数的设计进行了详细的分析建模,以优化模式切换性能。最后,建立了一个小型独立直流微电网实验系统,以验证所提出的直流微电网控制方法的可行性。

自适应下垂控制的多光伏源直流微网功率分配

现有直流微网下垂控制普遍采用固定下垂值,因此存在电压恢复能力差且无法应对瞬时电压的问题,为此提出一种自适应比例下垂指数控制的多光伏源直流微网功率分配策略。基于归一化电流分配差值和变流器输出侧电压偏差值的函数,引入比例下垂指数(PDI)算法实现对微网负荷的功率比例分配。在此基础上引入下垂电阻自适应更新策略,借助两个下垂校正因子实时更新下垂电阻值,以解决电压恢复能力差和瞬时电压跌落的问题,同时消除传统下垂控制在电流分配和电压调节之间的矛盾。最后搭建实验样机对所提方案进行验证,实验结果表明所提方案实现了微网负荷的比例分配和负荷电压的快速恢复,从而提高系统的整体性能。

An Adaptive Control Strategy for Energy Storage Interface Converter Based on Analogous Virtual Synchronous Generator

In the DC microgrid,the lack of inertia and damping in power electronic converters results in poor stability of DC bus voltage and low inertia of the DC microgrid during fluctuations in load and photovoltaic power.To address this issue,the application of a virtual synchronous generator(VSG)in grid-connected inverters control is referenced and proposes a control strategy called the analogous virtual synchronous generator(AVSG)control strategy for the interface DC/DC converter of the battery in the microgrid.Besides,a flexible parameter adaptive control method is introduced to further enhance the inertial behavior of the AVSG control.Firstly,a theoretical analysis is conducted on the various components of the DC microgrid,the structure of analogous virtual synchronous generator,and the control structure’s main parameters related to the DC microgrid’s inertial behavior.Secondly,the voltage change rate tracking coefficient is introduced to adjust the change of the virtual capacitance and damping coefficient flexibility,which further strengthens the inertia trend of the DC microgrid.Additionally,a small-signal modeling approach is used to analyze the approximate range of the AVSG’s main parameters ensuring system stability.Finally,conduct a simulation analysis by building the model of the DC microgrid system with photovoltaic(PV)and battery energy storage(BES)in MATLAB/Simulink.Simulation results from different scenarios have verified that the AVSG control introduces fixed inertia and damping into the droop control of the battery,resulting in a certain level of inertia enhancement.Furthermore,the additional adaptive control strategy built upon the AVSG control provides better and flexible inertial support for the DC microgrid,further enhances the stability of the DC bus voltage,and has a more positive impact on the battery performance.

基于事件触发的直流微电网无差拍预测控制

针对光伏(Photovoltaic, PV)-电池-超级电容直流微电网系统中光伏发电间歇性造成的功率失配问题,提出一种基于事件触发的无差拍预测控制(Event-triggered deadbeat predictive control, ETDPC)方法,以实现有效的能量管理. ETDPC方法结合事件触发控制策略和无差拍预测控制策略(Deadbeat predictive control, DPC)的优点,根据微电网的拓扑结构构建状态空间模型,用于设计适用于微电网能量管理的触发条件:当ETDPC的触发条件满足时, ETDPC中无差拍预测控制模块被激活,可以在一个控制周期内产生最优控制信号,实现对于扰动的快速响应,减小母线电压纹波;当系统状态不满足ETDPC中的触发条件时,无差拍预测控制模块被挂起,从而消除非必要运算,以减轻实现能量管理的运算负担.因此,对于电池-超级电容器混合储能系统(Hybrid energy storage system, HESS), ETDPC能够缓解间歇性光伏发电与负荷需求之间的功率失衡,以稳定母线电压.最后,数字仿真和硬件在环(Hardware-in-loop, HIL)实验结果表明,相较于传统无差拍控制方法,运算负担减小了50.63%,母线电压纹波小于0.73%,验证了ETDPC方法的有效性与性能优势,为直流微电网的能量管理提供了一种参考.

某机修工程光储直柔系统方案探讨

在分析光储直柔系统原理基础上,以某新建机修工程智慧低碳建筑为例,构建光储直柔微网系统和光储充微网系统,并对两种方案进行设计对比分析探讨,以实现新能源的更好利用。

工业园区微电网项目中风电与光伏发电的容量配置及推广策略研究

以工业园区微电网项目中的风电和光伏发电为研究对象,在考虑场址条件、资源情况和设备选型的情况下,分析了工业园区微电网项目中风电和光伏发电的容量配置方法,并根据经济性评价得到最优的风电和光伏发电容量配置方案;通过对包含中国4类风能资源区、4类太阳能资源区在内,处于不同地域且采用不同电价的15个典型城市的工业园区开发微电网项目进行经济性测算,以投资收益测算结果作为依据来评判此类项目中风电和光伏发电的投资价值,从而得到可执行的风电和光伏发电的推广策略。研究结果表明:1)小型风电机组的投资价值较差,只有在风能资源优且平段电价高的城市才适合应用;大型风电机组的投资价值较高,在园区不限高且安全距离足够的情况下,只有在风能资源差且平段电价低的城市才不适合应用;由于风能资源分布的不连续性,考虑工业园区微电网项目的风电投资时,仍需根据园区实际位置对其风能资源情况进行测算,以确定是否具备风电投资价值。2)光伏发电的盈利能力较好,投资价值较高,可以大力推广;但在太阳能资源较差或平段电价较低的城市,光伏发电不具备开发价值。研究结果可为未来工业园区的风电和光伏发电开发提供参考,并为新能源在工业园区的应用推广提供指导。

风光储直流微电网的双输入MPPT控制策略分析

针对以输出功率为判断标准的传统的单输入扰动观察法(下文简称为“传统扰动观察法”)存在的弊端,提出一种可用于风光储直流微电网的双输入变步长扰动观察法(下文简称为“双输入MPPT控制策略”),并对风电机组和光伏发电系统分别采用两种控制策略时的占空比、发电效率等进行了对比分析。分析结果显示:相较于传统扰动观察法,风电机组采用双输入MPPT控制策略追踪最大功率点后,扰动步长减小90%的同时追踪时间减少了72.3%;光伏发电系统采用双输入MPPT控制策略追踪最大功率点后,扰动步长减小90%的同时追踪时间减少了39%。仿真结果验证了双输入MPPT控制策略的有效性,该策略适用于电感参与调压的多种场景。

基于改进高斯滤波器的含锁相环PV-BES微电网的孤岛检测和无缝切换控制

该文提出了一种基于锁相环(PLL)的电网监测和无缝传输控制的改进高斯滤波器,用于改善含光伏电池储能(PVBES)微电网的电能质量。在并网模式下,该文提出了一种基于正交信号发生器的二阶广义积分器(QSG-SOGI)前置滤波的改进高斯滤波器,已实现MG向非线性负载和主网提供电能,同时在公共耦合点(PCC)给电网提供无功功率补偿和电能质量改善。此外,光伏前馈项可实现光伏功率注入调节,也可改善系统的动态特性;在电网故障时,控制器将PV-BES微电网转换为孤岛运行模式,可确保不间断地向负荷供电。最后,在各种场景下该文对所提控制器的有效性和优越性进行了测试,并通过实验进行了验证。

PV-Hybrid Off-Grid and Mini-Grid Systems for Rural Electrification in Sub-Saharan Africa

Rural electrification remains a great challenge for Sub-Saharan Africa (SSA) as access to electricity is a prerequisite to accelerate its development. The present paper reviews the measures adopted to promote access to electricity in rural and remote areas of SSA. The main barriers to rural electrification in these developing countries are presented before showing technologies used for the aforementioned purpose. Then, adopted methods for enhancing the use of renewable energy in SSA are shown. Moreover, the policy adopted by decision makers and project planners are also highlighted. In addition, the optimal solutions proposed by researchers are given such as the cost-effective off-grid system type that might be a viable alternative to diesel power generation.

Research and practice of designing hydro/ photovoltaic hybrid power system in microgrid

Small-hydro power station is often used in remote areas beside a river,but it doesn't match electricity demand so well,especially in dry seasons. A photovoltaic (PV) system with battery is a suitable option to complement the electricity gap. In this paper,a new structure of megawatt-class PV system integrating battery at DC-bus (DC: direct current) is proposed to be used in hydro/PV hybrid power system,and 4 main designing considerations and several key equipments are discussed. In 2011,a 2 MWp PV station with the proposed structure was built up in Yushu,China. From stability analysis,the station shows a strong stability under load cut-in/off and solar irradiance's fluctuation.

Short-term Distributed Energy Resource Scheduling for a DC Microgrid

A microgrid is associated with a low voltage distribution power network and inherits small modular generation systems and loads that have certain coordinated functions to provide the solution to supply premium power to remote or specific areas. Similar to conventional power systems, the energy management of distributed generation resources (DERs) is carried out to minimize the operation cost and maximize benefit of installation of DERS in a microgrid. This paper presents the process of implementing the short-term DER scheduling function for a dc microgrid. The optimal scheduling results for two operation modes are then reported.

基于光伏热PV/T冷热电联产的研究

分析冷热电联供优化设计研究现状,研究光伏半导体硅电池。通过MATLAB仿真显示了温度对光伏电池光电转化效率的重大影响。在此基础上,引出了PV/T光伏光热一体化组件,提出了一种改进型的光伏冷热电联供微电网模型。构建了一个5 MW的光伏微电网社区。由于天然气不可再生,该系统内只使用太阳能发电,实现节能减排。建立多目标下的优化函数,并结合具体算例,分析了夏季冬季典型日优化运行方案。

Feasibility Analysis of an Islanded Microgrid in Tohatchi, New Mexico Using HOMER Pro

Microgrids are becoming more popular in areas where there is still no connectivity to the main grid largely due to their remote geographical location. This paper focuses on the feasibility analysis, using the HOMER Pro simulation program, of an islanded micro-grid for the Navajo community in Tohatchi, New Mexico using different energy mixes of a Photovoltaics (PV) system, a Wind Energy system, a Battery Energy Storage System (BESS) and a Diesel Generator. The Net Present Cost (NPC), and the Levelized Cost of Electricity (LCOE), were the two crucial economic factors considered. Through the analysis, the system with the PV, wind turbines, battery, and a diesel generator was found to have the lowest LCOE and NPC. There was a reduction of 75% in the costs of the combined system as compared to the diesel-only base case. Also, this combined system provided the minimum emission levels. The analysis suggests that the integration of renewable energy using microgrids to help the access of energy for rural areas was possible. The analysis could very well be extended to any other community by considering the wind and solar resources present at that location.

Optimal Scheduling of PEV Charging/Discharging in Microgrids with Combined Objectives

While renewable power generation and vehicle electrification are promising solutions to reduce greenhouse gas emissions, it faces great challenges to effectively integrate them in a power grid. The weather-dependent power generation of renewable energy sources, such as Photovoltaic (PV) arrays, could introduce significant intermittency to a power grid. Meanwhile, uncontrolled PEV charging may cause load surge in a power grid. This paper studies the optimization of PEV charging/discharging scheduling to reduce customer cost and improve grid performance. Optimization algorithms are developed for three cases: 1) minimize cost, 2) minimize power deviation from a pre-defined power profile, and 3) combine objective functions in 1) and 2). A Microgrid with PV arrays, bi-directional PEV charging stations, and a commercial building is used in this study. The bi-directional power from/to PEVs provides the opportunity of using PEVs to reduce the intermittency of PV power generation and the peak load of the Microgrid. Simulation has been performed for all three cases and the simulation results show that the presented optimization algorithms can meet defined objectives.

Optimal Sizing of Solar/Wind Hybrid Off-Grid Microgrids Using an Enhanced Genetic Algorithm

This paper presents a method for optimal sizing of an off-grid hybrid microgrid (MG) system in order to achieve a certain load demand. The hybrid MG is made of a solar photovoltaic (PV) system, wind turbine (TW) and energy storage system (ESS). The reliability of the MG system is modeled based on the loss of power supply probability (SPSP). For optimization, an enhanced Genetic Algorithm (GA) is used to minimize the total cost of the system over a 20-year period, while satisfying some reliability and operation constraints. A case study addressing optimal sizing of an off-grid hybrid microgrid in Nigeria is discussed. The result is compared with results obtained from the Brute Force and standard GA methods.

光储微电网两阶段日前能量管理策略

针对并网运行的光伏储能微电网,提出含集中控制、分布式控制的两阶段日前能量管理策略。第1阶段将微电网内所有分布式光储单元等效为1个集群,以微电网与大电网交互成本最小为目标建立经济优化调度模型,采用天牛群算法求解,得到储能单元总充放电功率和微电网购售电计划;第2阶段以储能单元充电损耗最小为优化目标建立分布式控制模型,采用“Leader-Follower”模式的增量成本一致性算法,将第1阶段计算得到的储能总功率进行实时优化分配,最终实现光储微电网的日前经济优化调度。算例分析结果验证了所提策略的有效性。

基于粒子群算法的光储微电网谐波电流抑制参数组寻优策略

单相逆变器负荷的瞬时功率含有二倍频脉动功率分量,导致输入源中存在二次谐波电流。以光储微电网为例,提出基于陷波器和准比例谐振控制器的谐波电流抑制方法。在陷波器和准比例谐振控制器的作用下,电感支路表现出在二倍频处呈现高阻抗、非二倍频处呈现低阻抗的差异化特性,既实现了二次谐波电流的抑制,又满足了动态性的需求。针对该控制器参数选取不当导致动态性变差和谐波抑制能力下降等问题,提出基于粒子群算法的抑制参数组寻优策略,利用其精度高和收敛速度快的优点,获得兼顾动态品质、稳定性及谐波抑制能力的最优抑制参数组。实验结果验证了所提方法和寻优策略的有效性。

直流微网下的光伏可调度下垂控制方法

为了提升光伏调度的灵活性,并解决传统基于U-I下垂的光伏控制方法中的过载问题,提出了以U-dp/du下垂控制为第1层,以调度指令跟踪为第2层的分层可调度下垂控制方法。在不同的时间尺度上,实现了不同的控制目标。在短时间尺度上,U-dp/du下垂控制可以在光伏电源之间分担瞬态功率波动;在长时间尺度上,跟踪调度指令以实现电压控制或功率调节。而且,以dp/du作为控制变量实现了光伏运行模式的无缝切换,不仅避免了过载问题,还能作为调度中的功率裕量指标。最后,在硬件在环实验中验证了所提算法的有效性。

微电网联网/孤岛模式下光伏发电系统控制仿真

针对传统光伏发电系统接入电网的不可控及其输出扰动对电网的动态影响,利用PSCAD平台建立基于微电网的光伏发电系统模型。在联网/孤岛模式下,分别研究了基于功率外环-电流内环的双闭环数字PQ控制方法。研究结果表明,采用该控制方法能够保证光伏逆变器的输出稳定在中央控制器发出的功率指令值,且直流侧电压输出稳定,实现了光伏发电系统在微电网联网/孤岛模式运行的可控性及良好的动态调节性。

不确定裕度分段量化和弃风弃光分段惩罚的孤岛型微电网经济调度算法

针对孤岛微电网在运行过程中受新能源出力及负荷功率不确定性的影响,提出基于不确定裕度分段量化和弃风弃光分段惩罚的孤岛型微电网经济调度算法。日前计划阶段,利用基于不确定裕度分段量化的不确定集,并采用列约束生成算法,将原问题分为主问题和子问题进行交互迭代求解,得到在“最恶劣场景”下的最优经济调度方案。日内调度阶段,保持日前计划得到的储能系统出力,对传统能源出力、需求响应负荷、新能源弃风弃光量进行调整优化。最终,通过算例仿真验证了该算法在不同的场景下的经济性和鲁棒性。