Research on Virtual DC Generator-Based Control Strategy of DCMicrogrid with Photovoltaic and Energy Storage

With the penetration of a large number of photovoltaic power generation units and power electronic converters,the DC microgrid shows low inertia characteristics,which might affect the stable operation of the microgrid in extreme cases.In order to enhance the“flexible features”of the interface converter connected to the DC bus,a control strategy of DCmicrogrid with photovoltaic and energy storage based on the virtual DC generator(VDCG)is proposed in this paper.The interface converters of the photovoltaic power generation system and the energy storage system simulates the inertia and damping characteristics of the DC generator to improve the stability of the DC bus voltage.The impedance ratio of DC microgrid was obtained by establishing the small-signal model of photovoltaic power generation system and energy storage system,and the Nyquist curves was applied to analyze the small-signal stability of the system.Finally,the simulation results were verified with MATLAB/Simulink.The results show that the proposed control strategy can slow down the fluctuation of bus voltage under the conditions of photovoltaic power fluctuation and load mutation,thus enhancing the system stability.

Distributed Virtual Inertia Based Control of Multiple Photovoltaic Systems in Autonomous Microgrid

The large inertia of a traditional power system slows down system's frequency response but also allows decent time for controlling the system.Since an autonomous renewable microgrid usually has much smaller inertia,the control system must be very fast and accurate to fight against the small inertia and uncertainties.To reduce the demanding requirements on control,this paper proposes to increase the inertia of photovoltaic(PV) system through inertia emulation.The inertia emulation is realized by controlling the charging/discharging of the direct current(DC)-link capacitor over a certain range and adjusting the PV generation when it is feasible and/or necessary.By well designing the inertia,the DC-link capacitor parameters and the control range,the negative impact of inertia emulation on energy efficiency can be reduced.The proposed algorithm can be integrated with distributed generation setting algorithms to improve dynamic performance and lower implementation requirements.Simulation studies demonstrate the effectiveness of the proposed solution.

Optimal configuration for photovoltaic storage system capacity in 5G base station microgrids

Base station operators deploy a large number of distributed photovoltaics to solve the problems of high energy consumption and high electricity costs of 5G base stations.In this study,the idle space of the base station’s energy storage is used to stabilize the photovoltaic output,and a photovoltaic storage system microgrid of a 5G base station is constructed.Aiming at the capacity planning problem of photovoltaic storage systems,a two-layer optimal configuration method is proposed.The inner layer optimization considers the energy sharing among the base station microgrids,combines the communication characteristics of the 5G base station and the backup power demand of the energy storage battery,and determines an economic scheduling strategy for each photovoltaic storage system with the goal of minimizing the daily operation cost of the base station microgrid.The outer model aims to minimize the annual average comprehensive revenue of the 5G base station microgrid,while considering peak clipping and valley filling,to optimize the photovoltaic storage system capacity.The CPLEX solver and a genetic algorithm were used to solve the two-layer models.Considering the construction of the 5G base station in a certain area as an example,the results showed that the proposed model can not only reduce the cost of the 5G base station operators,but also reduce the peak load of the power grid and promote the local digestion of photovoltaic power.

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.

A digital twin model-based approach to cost optimization of residential community microgrids

This paper presents a peer-to-peer community cost optimization approach based on a single-prosumer energy management system.Its objective is to optimize energy costs for prosumers in the community by enhancing the consumption efficiency.This study was conducted along two main axes.The first axis focuses on designing a digital twin for a residential community microgrid platform.This phase involves data collection,cleaning,exploration,and interpretation.Moreover,it includes replicating the functionality of the real platform and validating the results.The second axis involves the development of a novel approach that incorporates two distinct prosumer behaviors within the same community microgrid,while maintaining the concept of peer-to-peer energy trading.Prosumers without storage utilize their individual PV systems to fulfill their energy requirements and inject excess energy into a local microgrid.Meanwhile,a single prosumer with a storage system actively engages in energy exchange to maximize the community’s profit.This is achieved by optimizing battery usage using a cost optimization solution.The proposed solution is validated using the developed digital twin.

A novel coordinated control strategy considering power smoothing for a hybrid photovoltaic/battery energy storage system

This work presents a novel coordinated control strategy of a hybrid photovoltaic/battery energy storage(PV/BES) system. Different controller operation modes are simulated considering normal, high fluctuation and emergency conditions. When the system is grid-connected, BES regulates the fluctuated power output which ensures smooth net injected power from the PV/BES system. In islanded operation, BES system is transferred to single master operation during which the frequency and voltage of the islanded microgrid are regulated at the desired level. PSCAD/EMTDC simulation validates the proposed method and obtained favorable results on power set-point tracking strategies with very small deviations of net output power compared to the power set-point. The state-of-charge regulation scheme also very effective with SOC has been regulated between 32% and 79% range.

Impact of Photovoltaics

Photovoltaics(PV)can convert sunlight into electricity by making use of the photovoltaic effect.Solar panels consist of photovoltaic cells made of semiconductor materials(such as silicon)to utilise the photovoltaic effect and convert sunlight into direct current(DC)electricity.Nowadays,PV has become the cheapest electrical power source with low price bids and low panel prices.The competitiveness makes it a potential path to mitigate the global warming.In this paper,we investigate the relationship of PC array output with irradiance and temperature,the performance of PV array over 24 hours period,and the simulation of PV micro grid by MATLAB simulation.

Optimal Design of Grid-Connected Microgrid System for Cold Chain Logistics Centre in China

The growing interest in energy conservation has inspired companies to seek alternatives to highly polluting fuel electricity generation. This study designed an optimised solar wind power generation system to fulfil the energy requirement of a cold chain logistics centre. This study first conducted a thorough analysis of the clarity indicators and daily temperature positions of the cold chain logistics centre, determined the average daily electricity demand, and proposed an effective design scheme. The energy simulation software, RETScreen 8.0, was used to determine the scale of solar photovoltaic and wind power projects that meet the expected energy needs of the cold chain logistics centre. The results indicated that the estimated annual total energy demand was 833689.2 kWh. The annual power generation of 6 kW from solar photovoltaic projects and 150 kW from wind power projects was found to be enough to meet the expected electricity demand. Solar photovoltaic power generation and wind power generation account for 2.44% and 97.56%, respectively. The hybrid energy system achieved a 96.6% reduction in carbon emissions and provides a reasonable payback period of 6.1 years and an electricity generation of 904368.674 kWh per year. The feasibility of the project and the calculated period of investment return are very reasonable. Therefore, this hybrid renewable energy system provides reliable power by combining energy sources.

考虑保供电需求的光储微电网优化配置及电能质量评估

针对用户日益迫切的保供电需求以及光伏出力与负荷用电的随机性、波动性引发的电能质量的问题,建立了考虑保供电需求的光储微电网双层优化模型,并对规划配置的微电网电能质量进行评估。该模型以等效净负荷标准差和弃光率最小为上层优化目标,以微电网有功功率损耗最小为下层优化目标,以储能满足保供电负荷的保供电需求作为附加约束条件,采用遗传算法求解。然后设计源、网、荷三类指标,采用组合赋权法确定各指标权重,实现对微电网电能质量的综合评估。最后以改进的IEEE-33系统验证了所提模型的有效性。结果表明考虑保供电需求后能够提高微电网电能质量,并在一定范围内保供电负荷越大时越能提高微电网电能质量和用户满意度。

离网型风光储微电网控制策略研究

为了解决偏远地区电力供应不足的问题,笔者提出一种含风力发电、光伏发电及蓄电池储能的离网型风光储微电网系统。风力发电最大功率点跟踪(maximum power point tracking,MPPT)采用叶尖速比法的控制策略,光伏发电MPPT采用变步长扰动观察法的控制策略,蓄电池储能系统采用基于双闭环控制的充放电控制策略。结合广西地区实际风速及光照强度变化情况,利用MATLAB/Simulink平台对所提出的风光储微电网系统进行了建模及仿真,验证了所提系统的可靠性和控制策略的有效性。

含电动船充电站的海岛光储微网系统容量优化配置

海岛光储微电网作为电动船充电站的主要电能来源,其容量配置受到电动船需求不确定性的影响。提出了含电动船充电站的海岛光储微网系统容量优化配置方法。首先,结合电动船的用能特点对其充电站的电能需求进行分析;然后,以综合经济成本最小化为目标函数构建了考虑电动船能耗不确定性的海岛光储微网容量配置鲁棒优化模型;最后,通过仿真实验验证了本文构建模型的有效性和合理性。仿真结果表明,所提模型得到的微网容量配置方案可以有效保证电动船的电能供应,方案的选择与决策者对供能可靠性和经济成本的偏好程度有关。

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。

基于分层控制的光伏与储能联合智能微电网协调优化策略研究

针对智能微电网电压不稳定、功率输出不均问题,提出基于分层控制的光伏与储能联合智能微电网协调优化策略。分析不同运行模式下含光伏与储能设备的智能微电网系统负载功率边界,并提出基于分层控制的放电下垂控制策略和充电模糊控制策略,确定光伏与储能联合智能微电网的新负载功率边界。随后,设计基于分层控制的光伏与储能联合智能微电网协调优化策略,在实现储能模块间充电或放电功率自动调节分配,增强智能微电网负载功率承载能力的同时,可克服电压波动问题。最后,仿真模型和实验平台获得的仿真实验结果证实,所提协调优化策略具有可行性,有利于提高光伏与储能联合智能微电网电压稳定性、安全性及经济性。

船舶光伏发电最大功率点跟踪无模型自适应控制

针对船舶光伏发电系统输出功率优化控制问题,并充分考虑复杂海况天气、船舶横摇和海盐结晶导致的船舶光伏发电系统模型参数时变,提出一种船舶光伏发电最大功率点跟踪无模型自适应控制方法。首先,根据光伏发电系统的输出和输入数据建立了离散非线性系统;其次,采用基于紧格式动态线性化的数据模型设计最大功率点跟踪无模型自适应控制器;最后,给出了伪偏导数估计算法。通过对比仿真实验,所提控制方法提高了船舶光伏发电系统的输出功率的稳定性。在恒定25℃环境温度及辐照度900 W·m^(-2)下,采用无模型自适应控制和基于扰动观察法的最大功率点跟踪时间分别为0.1、0.3 s,功率振荡幅度分别为5、18 W;在2 s时刻辐照度变化为500 W·m^(-2)时,采用无模型自适应控制和基于扰动观察法的最大功率点跟踪时间分别为0.02、0.06 s,功率振荡幅度分别为100、250 W。可以看出,采用无模型自适应控制的最大功率点跟踪方法可改善船舶光伏系统最大功率跟踪性能,验证了所提控制方法的有效性和优越性。

光储逆变器的虚拟同步机自适应控制策略研究

针对具有固定转动惯量的常规光伏储能虚拟同步发电机并网发电系统容易出现功率振荡以及频率超调等问题,提出光储并网系统的虚拟同步发电机(virtual synchronous generator,VSG)自适应控制策略。首先,搭建虚拟同步发电机控制的光伏储能并网发电系统模型,系统前级采用光伏最大功率点跟踪(maximum power point tracking,MTTP)控制以及储能控制策略;然后,根据功角特性和转子角频率特性曲线分析转动惯量对VSG动态特性的影响,将RBF神经网络应用到VSG中,对转动惯量进行自适应调整,同时,在固定阻尼比的基础上,随着转动惯量的变化自适应调整阻尼系数;在MATLAB/SIMULINK上建立光储并网系统的VSG自适应控制仿真模型,验证此控制策略的可行性;最后,将自适应转动惯量阻尼控制策略与其他控制策略进行对比,仿真结果表明:采用此控制策略能够使光储并网系统的有功功率振荡得到抑制,改善转子角频率超调。

电力物联网光伏微网多目标容量配置优化研究

光伏微网内部容量配置较小,导致光伏并网自我消纳能力不足,造成经济损失。为了解决这个问题,提出了电力物联网光伏微网多目标容量配置优化研究。建立运行成本、投资成本、年收益目标函数,以经济最优为目标,构建多目标容量配置目标函数。在改进乌鸦搜索算法中引入最优粒子群算法,求解目标函数,以乌鸦评判感知率为依据,输出配置结果最优解。实验结果表明,该方法光伏负荷曲线与理想光伏负荷曲线一致,总收益比理想收益高1 410万元,说明使用该方法经济效益较高。

轨道交通车辆基地交直流混合微电网的应用模式研究

轨道交通车辆基地作为轨道交通的重要组成部分,占地面积大、光照条件充足,其光伏资源开发利用潜力大。总结了目前车辆基地建筑能源使用情况,同时分析了现有光伏发电在轨道交通系统中的交流接入模式;针对车辆基地建筑用能特点,结合“直流微电网”新型建筑供配电的理念,提出了轨道交通车辆基地交直流混合供配电系统的架构,并给出直流微电网在车辆基地实际工程中的并网接线图,与现有光伏发电交流接入模式比较,提出的交直流混合供配电系统具有能效高与低碳效益,可为轨道交通绿色低碳发展提供技术支撑。

基于力控组态软件的光伏微电网远程监控系统的设计

为提高光伏微电网的自动化程度和能源利用效率,保证光伏微电网安全稳定运行,以智慧新能源实训系统V2.0为研究基础,基于力控组态软件设计开发了光伏微电网远程监控系统。该系统由上位监控机和前端数据采集单元组成。数据采集模块以西门子S7-1200plc控制器为核心,通过RS485通信总线,将环境模拟平台的太阳光照度、温度、湿度、太阳倾角等数据采集传输给PLC控制器。PLC控制器通过PROFENET通信,将采集数据传输给力控组态软件,以达到实时数据采集、监测显示、管理控制等远程控制的目的。

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。

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.