基于分时电价和需求响应的家庭微电网系统协同控制策略及其实现

家庭微电网是智能配电网的重要组成部分和主要建设内容,随着智能电网的不断发展,家庭居民用电将参与电网的优化调度运行。为了适应社会的这种需要,首先以家庭可调度负荷、电动汽车和家用蓄电池工作状态作为约束条件,以用户用电成本最低和净负荷曲线平坦度为优化目标,建立了家庭微电网系统优化调度模型。其次,结合空调和热水器的工作负荷特性,提出了一种基于分时电价和需求响应的家庭微电网系统协同控制策略。对以北京市某居民小区的典型家庭微电网系统为实例的分析结果表明,采用基于所提出的优化调度模型的家庭微电网系统,可以实现对分布式光伏发电、家用蓄电池、电动汽车、家庭负荷设备的优化调度和控制。     

主动配电网多级无功电压协调控制研究

分布式光伏大量接入配电网后电压越限问题成为影响电网安全稳定运行的关键因素。为了适应高渗透率、大规模分布式光伏的接入,提高系统调压能力,本文依据主动配电网内调压资源特性的不同,对其进行了分类分级处理,提出了主动配电网多级无功电压控制策略,即分别利用小容量分布式光伏、光伏电站无功、传统VQC装置和光伏电站有功实现系统一、二、三、四级调压。其中,针对小容量分布式光伏所采用的分散式就地控制策略,提出了基于并网点电压和光伏实际有功出力的cosφ(U、P)控制模型。最后,基于改进的IEEE33节点算例进行了仿真,仿真结果表明本文所提出的四级调压策略,充分利用了主动配电网内分散的调压资源,有效减少了VQC装置动作次数,并改善了配电网电压水平。     

Optimal Energy Management for Smart Grid System Considering Battery Characteristics

This paper discusses optimal energy management considering battery characteristics for smart grid and microgrid systems. Energy storage systems are very important for energy peak shifting and peak load cutting in microgrid and smart grid systems, but optimal battery formulation and energy management in the use of expensive energy storage system and methods of taking account of battery characteristics are still in the developmental stage. First, the optimal battery placement for a smart grid system with lithium‐ion batteries is considered as a means of lifetime extension. The battery choice index for this optimal battery utilization problem of optimal energy management is discussed. Second, a smart grid system with a distributed battery system for grid frequency control with consideration of distributed control and battery characteristics is discussed. Optimal controllers for distributed battery systems to reduce the battery load and to expend the battery lifetime are designed. Simulations are used to demonstrate the effectiveness of the proposed method in comparison with conventional methods.     

含光伏电源的配电网故障定位策略研究

基于监测电压暂降的配电网故障定位逐渐成为研究热点,同时随着智能配电网的发展,光伏电源越来越多的接入配电网。光伏电源的接入使传统的辐射型配电网的网络结构发生变化,且光伏电源的故障电流特性与同步发电机不同,使得基于电压暂降的配电网故障定位方法运用于含光伏电源的配电网时会产生较大误差。为了解决含光伏电源配电网的故障定位问题,基于低电压穿越控制策略针对光伏电源的短路电流特性进行了分析,然后介绍了含光伏电源的配电网故障电流的求解算法。通过遍历搜索候选母线,确定使得电气故障后故障电压实测值与理论计算值最为吻合的母线和故障类型,从而确定故障最邻近的母线。基于对IEEE34节点配电系统改造后的算例进行计算仿真,验证了文章方法应用于含光伏电源配电网定位的正确性和有效性。     

含分布式光伏及储能变流器的微网故障特征与保护

在并网时,微网中所含的分布式电源可能包括恒功率控制的光伏变流器或电流下垂控制的储能变流器,其中传统电流下垂控制的储能变流器在电网电压跌落时所输出的较低的故障电流,以及可能会出现的功角失稳现象都为其故障保护带来了困难,而基于滞环控制的改进电流下垂控制可以使其在电网故障时保持功角稳定,同时具备低压穿越能力,给故障电流带来新的特征,有利于故障检测以及保护判据的配置。本文考虑变流器的低压穿越特性,分析了含分布式光伏及储能变流器的微网内部不同位置发生故障时的电流特征,利用正序电流故障分量与母线正序电压故障分量的相位差来判断故障方向,并提出基于EtherCAT工业以太网的集中式保护方案。最后,通过仿真与实验验证了所提方案的可行性。     

含风电的交直流互联电网AGC两级分层模型预测控制

随着大规模风电接入交直流互联电网,传统的自动发电控制(AGC)方法难以有效地抑制风功率波动带来的频率稳定问题。为此,提出基于两级分层模型预测的AGC策略。该两级分层控制方法在下层对多个区域电网采用分散式模型预测控制;在上层对下层分散的控制器采用动态协调控制方式。以含多电源的两区域交直流互联电网AGC模型为例,仿真结果表明:与集中式模型预测控制和分散式模型预测控制方法相比,文中所提控制策略不仅对频率和联络线功率等具有良好的控制效果,还兼具高可靠性。     

Packet-based feedback control of electrical drive and its application to trajectory tracking of manipulator

In systems disconnected from the external grid, such as mobile robots and vehicles, the effective use of renewables and energy harvesting techniques helps a longer operation with less weight and space for batteries. Power packet dispatching system is a promising measure to manage the complex power flow created by such distributed power sources of various profiles. In the system, power is transferred as a pulse, and information tag is attached to the pulse power in voltage waveforms. The physical integration of power and information realizes a smooth inclusion of sources and loads of different profiles and their decentralized operation. This paper discusses the application of the system to load control. We propose a decentralized packet-based feedback control scheme. The successful operation of the proposed scheme is confirmed by an application to an electrical drive. In addition, the application to trajectory control of 2-degree-of-freedom manipulator reveals the possibility of a peak-power reduction based on a demand response operation of the proposed scheme. The results contribute to a realization of decentralized flow control of power packets based on the convenience of both the sources and the loads.     

Nonlinear Decentralized Feedback Linearizing Controller Design for Islanded DC Microgrids

This paper aims to design decentralized controllers for different components in islanded DC microgrids. The major components in the DC microgrid as considered in this paper include a fuel cell, solar photovoltaic (PV) unit, and battery energy storage system (BESS) along with critical and non-critical loads. The main control objective is to maintain the power balance within the DC microgrid through the regulation of the common DC-bus voltage. The controllers are designed based on the dynamical models of the fuel cell, solar PV unit, and BESS. The feedback linearization technique is employed to obtain the control laws, which simplifies the original dynamical models and decouples different components in the form of several subsystems. In this way, the feedback linearization technique allows different components in DC microgrids to achieve the desired control objectives by using only the local information (i.e., in a decentralized manner). The performance of the proposed decentralized controllers for different components is evaluated on a test DC microgrid under different operating conditions. Simulation results demonstrate that the proposed control scheme performs in a much better way as compared to an existing proportional integral controller.     

单相并网LCL型逆变器的改进设计方案

随着越来越多的分布式能源接入电网,并网逆变器获得了更多的应用。并网逆变器能够成功实现并网运行的前提是其直流母线电压高于最小要求限值,这限制了并网逆变器的应用。为降低并网逆变器的应用门槛,提出一种单相并网LCL型逆变器的改进设计方案。该设计方案通过将LCL型滤波器设计成一个有一定升压增益的模块,降低了前端逆变桥的输出电压要求,进而能够降低并网逆变器的直流母线电压限制,扩大了单相并网逆变器在低功率场合下的应用。首先分析传统LCL型单相并网逆变器直流母线电压受限制的原因,然后基于一种改进LCL型滤波器设计思路,利用其电压增益功能,给出一种详细的单相并网LCL型逆变器的改进设计方案,最后通过仿真和实验验证了提出的设计方案的有效性。     

The impact of single-phase grid-connected distributed photovoltaic systems on the distribution network using P-Q and P-V models

The gradual emergence of photovoltaic (PV) systems as the most common distributed generation interconnected with the electric power system calls for a detailed power flow analysis with different models especially in the evolving unbalanced active distribution network. This paper is an extension of a previous study carried out on the performance evaluation of a 10 kWp grid-connected PV system deployed in a school, with the grid providing a virtual storage and access to upstream markets. For increased adoption of such systems in the unbalanced distribution network, it is pivotal to understand the mode of operation and the type of connection to the system. This article presents an impact analysis of such utility interactive single-phase PV systems distributed on all the single-phase load nodes of the traditional IEEE-13 bus distribution test feeder. The PV distributed generation (PV-DG) can be modelled as constant P-Q or P-V nodes with varied impacts in power flow studies for the unbalanced active distribution network. Results from these models are compared in terms of their impacts on voltage profiles at load buses, voltage unbalance, equipment loading, power losses and the total number of iterations for a converged power flow solution.     

一种基于HHT的光伏并网发电系统保护方法

当光伏发电系统所连电网发生短路故障时,光伏电源的故障电流会发生暂态突变,但由于逆变器控制电路的保护作用,短路电流的幅值较小,因而传统的保护方法对光伏并网发电系统不一定适用。为寻求适合光伏并网发电系统的保护方法,建立了基于PSCAD/EMTDC的光伏并网发电系统仿真模型,对其短路电流的特性进行了仿真分析,利用希尔伯特-黄变换(HHT)对故障电流的波形进行分解,提出一种基于HHT的光伏并网发电系统保护方法,并进行了算例分析。结果表明,在含有光伏发电的电网发生短路故障时,该保护方法具有一定的有效性和可行性。     

A network scheme for process bus in smart substations without using external synchronization

The development of smart substations plays a crucial role in the development of smart grid. The major difference between a smart substation and an existing conventional substation lies in the process bus. Based on a thorough study over the network schemes of sampled values for process bus in smart substations, this paper summarizes and analyses major characteristics of existing network schemes. In order to overcome shortcomings of existing network schemes in time synchronization, the paper proposes a novel network scheme for process bus in smart substations without using external synchronizing clock. Compared to conventional network schemes, the proposed scheme does not need an external global synchronizing clock, thus can significantly improve the reliability of the process bus network. As a major research output of the key technological project, this work has been successfully applied to the 110 kV Shenxiang Substation in Suzhou, China.     

10kV配网接入分布式电源后电压及网损的计算与分析

分布式发电是建设坚强智能电网的重要组成部分,大量分布式电源的接入会给配电网的运行、控制带来巨大挑战。针对分布式电源接入东北地区实际配电网后电压及网损的变化情况进行仿真计算,确定分布式电源的容量选择原则。通过分析不同出力、不同位置情况下电压及网损的变化情况,对实际配电网中分布式电源的选址、定容提供参考依据。     

计及模型误差的分布式光伏配电网优化调控方法

当前配电网存在信息采集不全、在线获取电网精确模型困难的问题,导致对分布式光伏的调控存在误差,难以满足配电网安全运行的要求,因此提出了一种计及模型误差的分布式光伏配电网调控方法。基于近似灵敏度建立了光伏调控量粗略计算模型;采用极限学习机(ELM)方法建立人工智能辅助决策模型,作为光伏调控量粗略计算模型的修正;进一步地,基于上述2个模型,设计了计及模型误差的分布式光伏优化调控策略;最后进行仿真分析,结果表明提出的调控方法弥补了仅依赖电网模型进行优化带来的误差,提高了优化调控的精度。     

基于一体化思维的主动配电网设计方法研究

主动配电网是智能电网的重要组成部分,对其进行设计需要贯穿一体化思维。对主动配电网的定义和特征进行介绍,分析主动配电网的设计要点与要求,提出基于"分步推进"和"一步一反馈"的渐进优化式总体设计思路。在前述工作基础上勾画出统筹分布式电源接入、实时数据采集、配电网自动化配置、一次接线优化等多个层面的主动配电网一体化设计流程。     

一种降低电网谐波影响的单相自适应锁频方案

随着分布式发电的发展,在单相光伏场景中性能可靠的电网同步技术是实现逆变器高效并网的重要前提。提出了一种有效的单相自适应锁频算法,该算法主要由1个级联的二阶广义积分正交信号发生器SOGIQSG(second-order generalized integrator-quadrature signal generator)和1个简单可靠的频率自适应控制器组成。理论分析表明,级联SOGI-QSG结构具有良好的滤波性能,可以改善谐波含量高的电压信号。在电网遭受频率波动时,所提出的频率自适应控制器可以快速跟踪电网频率的瞬时变化。仿真和实验验证了所提方案的可行性和有效性。     

光储直流微网能量协调控制方法

直流微网中分布式电源出力的随机波动性,不仅会引起直流母线电压大范围波动,还会影响系统的稳定运行。对此,提出了一种光储直流微网能量协调控制方法,实现了因系统功率供需不平衡引起的母线电压波动的快速平抑。该方法优先利用新能源为负荷供电,通过设定并网变换器和储能模块的工作阈值以协调管理各模块间的能量流动,避免直流母线电压小范围波动引起电力电子器件频繁动作,实现能量的最优利用。在并网状态下,直流微网通过并网变换器与大电网进行能量交换;在离网状态下,光伏模块与混合储能模块协调配合给本地负载供电。其中,考虑混合储能模块的充放电裕量,结合超级电容功率密度大和锂电池能量密度高的特点,混合储能模块让超级电容先工作来平衡系统瞬时功率,提高系统的动态响应特性,减少锂电池动作次数,延长使用寿命。锂电池工作后,可以配合超级电容调整直流母线电压,防止超级电容达到饱和的速度过快。仿真验证了所提方法的有效性。     

含储能分布式光伏系统并网点电压调整方案设计

随着配电网中光伏渗透率不断升高,分布式光伏对配电网电压质量和稳定性影响日益增大。分析了分布式光伏并网引起并网点电压变化的机理,在配备储能装置的分布式光伏发电系统典型结构基础上,提出了有功/无功-电压调节的系统控制方案。在有功电压调节回路中设置了具有施密特电路特性的死区控制环节,一方面死区控制可以保证无功调节优先性,另一方面由于有功电压调节的灵敏度较高,死区控制可能导致并网点电压在死区阈值电压附近频繁抖动,通过施密特电路设置不同的正/反向死区阈值电压可以有效消除抖动现象。仿真结果表明所提方案能有效处理光伏出力骤变、大容量负载投切、配电网自身扰动等引起的并网点电压质量问题。     

HERIC单相光伏并网逆变器无功调制及其直接功率控制

随着可再生能源在单相电网中渗透率的提高,电网对单相光伏并网逆变器提出了无功输出与功率因数灵活控制的要求。对HERIC(Highly Efficient and Reliable Inverter Concept)拓扑的无变压器隔离型单相光伏逆变器进行研究,提出了相应的无功调制策略。借助广义二阶积分构造两相静止坐标系,基于瞬时无功功率理论,建立了单相光伏逆变器的瞬时功率模型,实现了单相光伏逆变器的直接功率控制。搭建了5 k W的实验平台,通过实验对所提的调制策略与控制策略进行了有效性与实用性验证。     

智能配电网自愈控制系统技术研究与设计

对自愈、自愈能力、自愈控制、智能配电网自愈控制等智能配电网自愈控制系统相关的概念进行了介绍。围绕智能配电网自愈控制系统的目标和实现策略,介绍了智能配电网自愈控制系统相关的关键技术,分析了智能配电网自愈控制系统应具有的功能,对智能配电网自愈控制系统的架构、接口和相关指标进行了设计。所设计开发的智能配电网自愈控制系统已经成功应用于示范工程现场。示范工程现场实际应用表明,所设计开发的智能配电网自愈控制系统能够满足智能配电网自愈控制的实际需求。