Variants of Secondary Control with Power Recovery for Loading Hydraulic Driving Device

Current high power load simulators are generally incapable of obtaining both high loading performance and high energy efficiency. Simulators with high energy efficiency are used to simulate static-state load, and those with high dynamic performance typically have low energy efficiency. In this paper, the variants of secondary control（VSC） with power recovery are developed to solve this problem for loading hydraulic driving devices that operate under variable pressure, unlike classical secondary control（CSC） that operates in constant pressure network. Hydrostatic secondary control units are used as the loading components, by which the absorbed mechanical power from the tested device is converted into hydraulic power and then fed back into the tested system through 4 types of feedback passages（FPs）. The loading subsystem can operate in constant pressure network, controlled variable pressure network, or the same variable pressure network as that of the tested device by using different FPs. The 4 types of systems are defined, and their key techniques are analyzed, including work principle, simulating the work state of original tested device, static operation points, loading performance, energy efficiency, and control strategy, etc. The important technical merits of the 4 schemes are compared, and 3 of the schemes are selected, designed, simulated using AMESim and evaluated. The researching results show that the investigated systems can simulate the given loads effectively, realize the work conditions of the tested device, and furthermore attain a high power recovery efficiency that ranges from 0.54 to 0.85, even though the 3 schemes have different loading performances and energy efficiencies. This paper proposes several loading schemes that can achieve both high dynamic performance and high power recovery efficiency.

Enhancement of Distributed Generation by Using Custom Power Device

Wind energy （WE） has become immensely popular for distributed generation （DG）. This case presents the monitoring, modeling, control, and analysis of the two-level three-phase WE based DG system where the electric grid interfacing custom power device （CPD） is controlled to perform the smart exchanging of electric power as per the Indian grid code. WE is connected to DC link of CPD for the grid integration purpose. The CPD based distributed static compensator, i.e. the distributed static synchronous compensator （DSTATCOM）, is utilized for injecting the wind power to the point of common coupling （PCC） and also acts against the reactive power demand. The novel indirect current control scheme of DSTATCOM regulates the power import and export between the WE and the electric grid system. It also acts as a compensator and performs both the key features simultaneously. Hence, the penetration of additional generated WE power to the grid is increased by 20% to 25%. The burden of reactive power compensation from grid is reduced by DSTATCOM. The modeling and simulation are done in MATLAB. The results are validated and verified.

Fuzzy Decision Method Applied in Action of Reactive Power Compensation Devices in Wind System

Frequent occurrence of large-scale cascading trip-off of wind turbine raises the concern about the decision process of ordered control of reactive power compensation devices. The theory of fuzzy multi-attribute decision making is adopted to ascertain the action sequence of reactive power compensation devices. First, a set of evaluation indexes including control sensitivity, regulation margin, response time, response level and cost is set up, and fuzziness of the proposed qualitative indexes is introduced to make them comparable to the proposed quantitative indexes. Then a method to calculate fuzzy weight of each index is put forward for evaluating relative importance of the proposed indexes. Finally, the action sequence of reactive power compensation devices is determined through the theory of fuzzy compromise decision making. The case study shows that the proposed method is effective to obtain the action sequence of reactive power compensation device which correspond to experience.

Analysis of the Load Flow Problem in Power System Planning Studies

Load flow is an important tool used by power engineers for planning, to determine the best operation for a power system and exchange of power between utility companies. In order to have an efficient operating power system, it is necessary to determine which method is suitable and efficient for the system’s load flow analysis. A power flow analysis method may take a long time and therefore prevent achieving an accurate result to a power flow solution because of continuous changes in power demand and generations. This paper presents analysis of the load flow problem in power system planning studies. The numerical methods: Gauss-Seidel, Newton-Raphson and Fast Decoupled methods were compared for a power flow analysis solution. Simulation is carried out using Matlab for test cases of IEEE 9-Bus, IEEE 30-Bus and IEEE 57-Bus system. The simulation results were compared for number of iteration, computational time, tolerance value and convergence. The compared results show that Newton-Raphson is the most reliable method because it has the least number of iteration and converges faster.

The Development of Network based Composite Power quality Regulation Device

First, the paper analyzes the advantages and disadvantages of all kinds of reactive power compensation technology, and then proposes a principle and integrated control strategy of the composite operation of TSC and SVG, also the paper designs and develops the main controller of Network based composite power quality regulation device, based on RTDS, the real-time digital simulation model of The Device is established, and finally the prototype of the device is developed with the function of filter and split-phase compensation. The main controller determines the cooperative operation of both TSC and SVG, and the switching strategy of TSC. The simulation result in RTDS can verify the precision of the measure system and the validity of the control logic, the prototype has finished the type test according to the national standard.

A New Model for Transmission Network Expansion and Reactive Power Planning in a Deregulated Environment

Transmission network expansion planning (TNEP) is a challenging issue especially in new restructured electricity mar-kets environment. TNEP can be incorporated with reactive power planning in which the operating conditions will be satisfied. In this paper a combinatorial mathematical model has been presented to solve transmission expansion and reactive power planning problem (TEPRPP) simultaneously. The proposed model is a non-convex problem having a mixed integer nonlinear nature where the number of candidate solutions to be evaluated increases exponentially according to the system size. The objective function of TEPRPP comprises the new circuits’ investment and production costs as well as load curtailment penalty payments. A real genetic algorithm (RGA) aimed to obtaining a significant quality solution to handle such a complicated problem has been employed. An interior point method (IPM) is applied to solve the proposed concurrent optimization problem in the solution steps of TEPRPP model. This paper proposes a new methodology for the best location as well as the capacity of VAr sources;it is tested on two well-known systems;the Garver and IEEE 24-bus systems. The obtained results show the capability and the viability of the proposed TEPRPP model incorporating operating conditions.

考虑风电谐波影响与出力随机性的电力系统无功优化方法

电容器组等无功补偿装置的优化调整不仅可以减小电力系统网损,还会对电力系统的谐波潮流与谐波网损产生影响.风电不仅存在出力不确定性,而且会产生谐波污染,影响谐波潮流与谐波网损.然而,传统无功优化方法没有同时考虑风电的谐波特性与出力不确定性对谐波潮流和谐波网损的影响,可能导致谐波超标问题,不利于电力系统降低网损.因此,本文首先构建计及风电谐波影响的电力系统无功随机优化模型.该模型通过场景法对风电出力随机性进行建模,目标函数同时考虑基波和谐波网损,约束条件包括基波和谐波潮流约束、电压谐波总畸变率约束等.然后,针对该谐波约束的无功随机优化模型,本文提出了融合驱动力可调粒子群算法和全连接型深度神经网络的高效求解方法 .最后,通过三个修改后的IEEE测试系统对所提模型与方法的有效性进行了验证.

含电动汽车和光伏的配电网演化动态博弈调度策略

针对大规模电动汽车的无序充电行为可能导致电网出现的三相不平衡问题,基于演化动态博弈模型,提出一种考虑三相负荷平衡和光伏消纳的电动汽车充电调度策略。首先,基于电动汽车接入时段的主观性以及光伏出力和负荷的不确定性,引入游牧集群和定居集群之间的演化动态博弈方程;然后,考虑用户侧和电网侧双方利益关系,设计以最小化电动汽车充电费用、三相负荷不平衡度和无功需求为目标的调度优化模型;最后,通过对某商业区配电网算例进行仿真求解,对比分析三相有功曲线、三相无功曲线以及荷电状态曲线的变化趋势。算例结果表明,该调度策略可有效降低三相不平衡度,满足无功补偿的需求以及改善用户充电成本。

基于分布式协同控制技术的分散式无功补偿技术方案研究

结合实际工程的应用实例从分散式无功补偿方案的提出、分布式协同吸收方案的理论、具体工程方案的设计进行简单的论述。结合线路开通后的实际运行工况,利用设置于正线的能量回馈吸收装置实现了分散式无功补偿,该方案可减少或完全取消设置于主变电所侧的SVG容量,充分开发和利用了能馈吸收装置的能力,节约了工程投资,实现了既定设计目标。

基于“先无功–后有功”功率补偿的配电网电压协同控制策略

整县分布式光伏电源的大量开发与利用及分布式电源规模化并网对实现“碳达峰、碳中和”与“乡村振兴”两大国家战略具有重要的现实意义。由于分布式电源发电尖峰和低谷阶段与负荷峰谷时常不同步,进而导致配电系统过/欠电压问题,严重影响了电能质量,甚至威胁系统安全。针对上述问题,本文提出一种基于“先无功–后有功”功率补偿的配电网层级式电压协同控制策略。首先,建立基于“先无功–后有功”功率补偿的配电网层级式电压协同控制框架。其次,结合多微电网节点注入电流与电压的方程与功率–电压灵敏度分析,根据多节点电压越限程度,提出一种基于“先无功–后有功”功率补偿的多智能体协同调节策略,该策略先通过无功补偿器进行无功调节,当电压尚未得到有效治理时,再采用多微电网进行有功调节。再次,为了进一步满足各节点微电网有功功率调节需求,并考虑电网内部源–荷–储运行成本与污染排放,提出一种基于多目标优化的微电网内部分布式源–荷–储优化协调功率控制策略。最后,在MATLAB平台中设计了3种仿真场景以及IEEE测试系统模型对所提控制策略进行了验证。结果表明,所提出的电压协同控制方法在最经济的情况下可以实现各节点电压的综合高效治理,同时,所提出的微电网优化协调功率控制策略能使源–荷–储在绿色经济的供电模式下实时精准地满足电压治理目标下微电网有功调节的需求。仿真实验结果验证了本文所提控制策略的有效性。

发电机组低负荷下的SVG无功补偿技术应用分析

低负荷运行容易导致发电机组无功功率不足、电压不稳定等问题,影响电力系统的稳定性和可靠性。探讨了在发电机组低负荷条件下应用静止无功发生器(SVG)技术进行无功补偿的途径。分析了SVG在维持电压稳定、改善功率因数以及减轻低负荷运行对发电机组的不良影响等方面的表现和有效性,并通过实验和仿真开展评估验证。

核电站棒电源机组发电机励磁调差特性研究

将分析核电站棒电源机组发电机励磁调差装置的接线形式。基于正调差接线方式,针对发电机组不同负荷工况,通过电压相量图研究励磁调差装置的输出电压与电流和接入电阻之间的关系。通过发电机组、测量比较单元、放大单元、触发单元和晶阐管单元形成的闭环回路分析,计算发电机组的自然调差系数和附加调差系数。在满足发电机组静态性能和动态性能的前提下,通过调整附加调差系数可以使两套发电机组的总调差系数一致,实现无功均分。

适应多元源荷接入的配电网两阶段灵活性提升优化方法

配电网灵活性提升优化过程中易受不均匀电压、强磁场、电流效应等问题的干扰,灵活性提升效果不明显。为了解决上述问题,提出适应多元源荷接入的配电网两阶段灵活性提升优化方法。该方法首先采用瞬时功率平衡算法保证配电网达到三相平衡状态,其次通过无功出力与有功损耗的输出特点实现配电网的无功规划,有效地提高配电网运行质量,降低网损。最后采用多元源荷接入的两阶段提升优化法提升配电网的灵活性,第一阶段基于灵活性三指标与多源源荷供给特性构建灵活性提升优化模型,第二阶段考虑配电网灵活性指标的概率平衡性,并采用线性转换算法对模型求解,完成配电网灵活性提升优化。试验结果表明,所提方法的网损率小,净负荷波动曲线小,计算时间短,配电网分布式电源接入的灵活适应性强。可见通过灵活性优化调度,可以有效提升含分布式电源配电网的灵活性,提高配电网接纳分布式电源的能力。

基于GTO的静止无功补偿装置研究

本文介绍了基于大功率全控型电力电子器件GTO的静止无功补偿装置，控制电路以DSP技术为核心，快速准确地检测系统的无功参数，自动发出GTO投切控制脉冲，快速投切电容器，来实现无功调节。该装置具有响应速度快，可分级吸收无功功率，控制简单，噪音和损耗小，结构简单造价低廉等特点。

考虑不确定性的配电网损耗分析方法研究

针对配电网损耗分析时分布式电源(DG)功率输出存在的不确定性问题,提出了一种基于拉丁超立方体采样(LHS)的考虑不确定性的配电网损耗分析方法。首先,建立了配电网损耗模型,分析了负荷配电损耗和DG损耗计算方法。其次,针对DG功率输出的不确定性问题,应用LHS评估配电网随机损耗。在试验阶段,以IEEE 36馈线系统为例验证所提方法。与随机采样方法相比,所提方法电压平均值误差更低,且误差曲线更加光滑。该方法可以更精确地计算配电节点的损耗。

考虑源网荷储协调互动的配电网无功优化

高比例新能源发电是新型电力系统的主要特征,挖掘新能源发电、储能以及柔性负荷等柔性可控资源的无功电压潜力能有效提高新型电力系统运行的稳定性和安全性。文中提出了一种考虑源网荷储互动的配电网无功电压控制方法。该方法从负荷需求侧响应出发,基于市场实时电价信息,以负荷转移成本和用户购电成本为基础,提出基于价格驱动需求响应的负荷平移策略;利用储能系统协调新能源发电出力和负荷平移规则,构建综合考虑源网荷储互动的配电网无功优化模型。通过调节无功补偿设备、储能充放电策略协调新能源出力,在满足负荷需求侧响应需求的基础上达到系统无功电压的最优控制。通过改进的IEEE33节点系统仿真分析,实验结果表明通过源网荷储的充分互动能够有效提高系统无功电压调节能力,实现配电网安全、经济运行。

分布式光伏接入炼化企业对功率因数的影响及对策研究

针对某炼化企业光伏接入后存在功率因数不达标的问题,考虑企业实际情况,提出电容器调档以及光伏逆变器和电容器协调控制两种解决方案。结果表明:当采用电容器补偿无功,输出为阶跃型无功,存在无功倒送可能性,仍存在有功、无功潮流方向不同的问题,当光伏波动较大时,电容器需逐级投切,响应速度慢;采用光伏逆变器和电容器协调控制时,光伏逆变器功率因数设定为0.98,电容器无需频繁切换,无功补偿响应速度快,无潮流问题,区域功率因数满足0.92的控制要求。通过对比两种方案分析结果,采用光伏逆变器和电容器协调控制,功率因数调节更加简便,可靠性更高。