电力系统无功优化模糊建模研究

传统无功优化算法的目标函数一般为满足电压限制下的有功网损最小,未考虑电压的“软约束”特性,这通常会使得优化后的系统部分母线电压非常接近其合格范围的边界,成为系统安全运行的隐患。针对无功优化问题的这些特点,引入模糊规划算法以解决这一问题。建立了带有模糊安全约束的无功优化模型,并采用非线性原-对偶内点法内嵌二次罚函数法求解。算例的结果表明,带有模糊安全约束的无功优化模型能够在降低系统网损的同时确保节点电压留有一定的安全裕度。     

电力系统无功优化模糊建模研究

传统无功优化算法的目标函数一般为满足电压限制下的有功网损最小,未考虑电压的"软约束"特性,这通常会使得优化后的系统部分母线电压非常接近其合格范围的边界,成为系统安全运行的隐患.针对无功优化问题的这些特点,引入模糊规划算法以解决这一问题.建立了带有模糊安全约束的无功优化模型,并采用非线性原-对偶内点法内嵌二次罚函数法求解.算例的结果表明,带有模糊安全约束的无功优化模型能够在降低系统网损的同时确保节点电压留有一定的安全裕度.     

考虑电压约束裕度的无功优化新模型

传统无功优化算法的目标函数一般为满足电压限制下的有功网损最小,未考虑电压的"软约束"特性,这通常会使得优化后的系统部分母线电压非常接近其合格范围的边界,成为系统安全运行的隐患。针对无功优化问题的这些特点,本文基于模糊集理论建立了带有模糊安全约束的无功优化模型,并采用非线性原-对偶内点法求解。算例的结果表明,该模型能够有效降低系统的网损并保证节点电压留有一定的安全裕度。     

基于模糊线性规划的无功电压优化

传统无功电压优化算法一般是单目标优化问题，并没有考虑有功网损的降低和限制控制量调节数最少，而且在处理电压约束时，未考虑“软约束”特性。针对电压无功问题的这些特点，引入模糊线性规划算法以解决这一问题。文中推导了将多目标模糊约束问题转化为单目标开明约束问题的数学模型。算例的计算结果表明，模糊线性规划算法可以很好地协调降低网损、限制调节量和确保节点电压裕度三者的关系，在有限控制量调节的前提下，可实现校正违界电压、降低系统网损和确保所有节点电压留有一定的裕度。     

考虑电压稳定约束的无功优化新模型

为了提高电力系统的安全水平,有必要在无功优化中考虑静态电压稳定约束.现有模型以发电机组恒定不变的无功上下限值来确定电压稳定极限,由此可能导致无功的优化运行不满足实际发电机组的运行极限约束.建立了一种含静态电压稳定约束的无功优化新模型.其中,目标函数为正常状态的有功网损最小,约束方程包括正常状态和临界状态的潮流及其他安全约束和电压稳定裕度约束.由于采用一组基于发电机运行极限图的分段函数来准确反映发电机组的无功限制,从而克服了现有模型可能违反发电机组运行极限约束的问题.采用预测-校正原对偶内点法来求解无功优化新模型,通过IEEE30节点系统的仿真计算,验证了本文所建模型的可行性.     

电力系统优化运行的电压安全成本研究

利用模糊建模方法处理可松弛约束的能力,提出一种估计电力系统电压安全成本的新方法。该方法可在一定程度上解决确定最小电压安全裕度指标的困难,通过最小电压安全裕度模糊参数,实现对该指标的松弛处理。在此基础上,建立了计及最小电压安全裕度指标的最优潮流模糊模型。采用预测-校正原对偶内点法求解该优化模型。通过对IEEE标准测试系统的仿真结果分析表明,该方法不仅可以实现系统总发电成本的最小化,同时还可以维持尽可能高的电压安全裕度,而且在系统运行低于规定的最小电压安全裕度时,通过电压安全成本的大小反应了维持系统电压安全所必须付出的经济代价。     

电力系统优化运行的电压安全成本研究

利用模糊建模方法处理可松弛约束的能力,提出一种估计电力系统电压安全成本的新方法.该方法可在一定程度上解决确定最小电压安全裕度指标的困难,通过最小电压安全裕度模糊参数,实现对该指标的松弛处理.在此基础上,建立了计及最小电压安全裕度指标的最优潮流模糊模型.采用预测-校正原对偶内点法求解该优化模型.通过对IEEE标准测试系统的仿真结果分析表明,该方法不仅可以实现系统总发电成本的最小化,同时还可以维持尽可能高的电压安全裕度,而且在系统运行低于规定的最小电压安全裕度时,通过电压安全成本的大小反应了维持系统电压安全所必须付出的经济代价.     

计及静态电压稳定约束的无功优化规划

选择无功补偿设备投资和系统有功网损的综合费用作为目标函数,同时考虑满足电压水平和电压稳定性两个约束条件来探讨无功规划问题。选取用电压稳定裕度不低于某一个允许的最小稳定裕度来表示电压稳定约束。分别对正常运行工作点和电压崩溃点引入2组变量和潮流方程,从而使得电压稳定裕度可以用临界运行状态下负荷的总视在功率与正常运行状态下负荷的总视在功率之差来显式表达。该模型相对于传统无功规划模型的优势表现在能够根据稳定裕度的目标值直接求得在合理电压水平下的最佳无功补偿配置方案,但其优化模型的等式和不等式约束及变量的数目却大幅增加,使得计算量远大于传统的无功规划问题。在IEEE 14节点和118节点2个试验系统的计算表明,采用非线性原对偶内点法求解该模型时,其计算精度及收敛性都比较好。     

基于改进Tabu搜索算法的区域电网无功优化

为了满足无功优化的实时控制要求,提出了考虑静态电压稳定的区域电网无功优化方案。该方案采用改进的Tabu搜索算法,以有功网损最小为目标进行无功优化,记录优化过程中搜索得到的前10位最优网损解;然后对这10个最优网损解进行静态电压稳定裕度计算,再运用模糊集理论,将网损最小和静态电压稳定裕度最大两个目标的优化问题转化为单目标优化问题。通过算例仿真,证明了改进Tabu算法适合于解决区域输电网无功优化问题,同时也验证了本文提出的考虑静态电压稳定性的区域输电网二级无功电压控制方案是可行的,有效的。     

结合无功二次精确矩法的混沌社会情感优化算法的多目标无功优化

针对配电网无功优化的特点,提出一种新的方法。首先,采用无功二次精确矩法确定无功补偿点;然后建立以有功网损最小、电压偏差最小及静态电压稳定裕度最大的多目标无功优化模型,用模糊方法将多目标优化问题转化为单目标问题,并以最大、一般和最小3种运行方式模拟配电网的实际运行;接着在社会情感优化算法上引入情感强度定律,模拟人类情感变化以提高寻优精度;同时引入混沌扰动机制,来增强种群多样性以提高全局搜索能力;最后对IEEE 33节点配电网系统进行仿真分析,结果表明该优化方法可以有效地降低网损与提高电压质量。     

Optimal shunt capacitor allocation by fuzzy dynamic programming

A new approach using fuzzy dynamic programming to decide the optimal location and size of compensation shunt capacitors for distribution systems with harmonic distortion is proposed. To decide the optimal capacitor placement, a fuzzy dynamic programming model in which the real power loss, voltage deviation, and harmonic distortion are all expressed in fuzzy set notation is developed. The problem is formulated as a fuzzy dynamic programming of the minimization of real power loss and capacitor cost under the constraints of voltage limits and total harmonic distortion. A simple algorithm that is based on the fuzzy set is proposed to determine an optimal solution. This algorithm greatly reduces the effort of finding the optimal location via an exhaustive search. A practical distribution system is selected for computer simulation to test the efficiency of the proposed fuzzy dynamic programming method. It is found that the system loss and harmonic distortion can be reduced very effectively by this proposed algorithm.     

Allocation of multi-type FACTS devices using multi-objective genetic algorithm approach for power system reinforcement

This paper presents a novel approach to find optimum locations and capacity of flexible alternating current transmission systems (FACTS) devices in a power system using a multi-objective optimization function. Thyristor controlled series compensator (TCSC) and static var compensator (SVC) are the utilized FACTS devices. Our objectives are: active power loss reduction, new introduced FACTS devices cost reduction, voltage deviation reduction, and increase on the robustness of the security margin against voltage collapse. The operational and controlling constraints, as well as load constraints, are considered in the optimum allocation. A multi-objective genetic algorithm (MOGA) is used to approach the Pareto-optimal front (non-dominated) solutions. In addition, the estimated annual load profile has been utilized in a sequential quadratic programming (SQP) optimization sub-problem to the optimum siting and sizing of FACTS devices. IEEE 14-bus Network is selected to validate the performance and effectiveness of the proposed method.     

Cost-based reactive power pricing with voltage security consideration in restructured power systems

In the restructuring power industry, voltage security has become a challenging problem since power systems tend to operate closer to security boundaries and as a consequence, the voltage instability, which is caused by insufficient reactive power supply, poses a serious threat to system security and reliability. Establishing an equitable and effective reactive power market with consideration of the voltage security problem is very important to provide a reliable restructured power system. Therefore, this paper proposes a cost-based reactive power pricing, which can integrate the reactive power cost minimization and the voltage security problem into the optimal power flow (OPF) problem, and the sequential quadratic programming (SQP) is employed to solve the optimization problem. The effectiveness of the proposed method is verified using a modified IEEE 14-bus system. A study on the effects of the voltage stability margin (VSM) requirement under normal condition and contingencies on the reactive power cost is also presented.     

基于轨迹灵敏度的紧急切负荷优化算法

超/特高压直流远距离、大容量输电使受端电网发生大功率缺额的概率增加。为防御失去大电源导致的电网安全稳定破坏,提出了一种兼顾暂态安全性和经济性的紧急切负荷优化模型,并设计了高效求解方法。优化模型以总切负荷代价最小为目标,计及暂态电压安全、暂态频率安全和切负荷量约束。暂态安全性均基于时域轨迹严格评估,是带时域参数约束的大规模非线性规划问题。分析了问题最优解的特征,针对带时域参量约束的非线性规划无法直接求解的问题,利用轨迹灵敏度将安全约束线性化,将问题转化为线性规划求解,并通过逐次迭代保证解的一致性。以实际省级电网为例进行仿真分析,验证了算法的有效性。     

基于全局序列二次规划算法的无功优化

为提高无功优化计算的收敛性和精确性,采用全局序列二次规划(SQP)算法来计算无功优化潮流.在优化的循环迭代过程中,电压相角和支路潮流并未当作常数看待,而是通过每次迭代后系统状态下的潮流计算重新获得的.对IEEE30节点系统进行无功优化仿真,结果表明全局SQP算法具有良好的收敛性和精确性.     

Network loss minimization with voltage security using differential evolution

This paper presents a differential evolution (DE) based optimal power flow (OPF) for reactive power dispatch in power system planning studies. DE is a simple population-based search algorithm for global optimization and has a minimum number of control parameters. The problem is formulated as a mixed integer non-linear optimization problem taking into account both continuous and discrete control variables. The proposed method determines control variable settings such as generator voltages (continuous), tap positions (discrete) and the number of shunt reactive compensation devices to be switched (discrete) for real power loss minimization in the transmission system using DE algorithm. Most of the evolutionary algorithm applications to optimization problems apply penalty function approach to handle the inequality constraints, involving penalty coefficients. The correct combination of these coefficients can be determined only by a trial and error basis. In the proposed approach, the inequality constraints are handled by penalty parameterless scheme. Voltage security margin was evaluated using continuation power flow (CPF), to ensure the feasibility of the optimal control variable setting. The suitability of the method was tested on IEEE 14 and IEEE RTS 24-bus systems and results compared with sequential quadratic programming (SQP) method. The DE provides near global solutions comparable to that obtained using SQP.     

直流船舶综合电力系统中混合储能的精确功率分配策略研究

直流船舶综合电力系统是未来船舶的重要发展趋势,可实现全船能源的集中控制和管理。确保船载直流微电网中各分布式电源间的精确功率分配以及母线电压稳定是维持系统安全、经济运行的先决条件。因此,提出一种基于二次规划算法的精确功率分配方法,该方法充分考虑混合储能系统中不同储能介质的额定容量、荷电状态、爬坡速率以及充放电效率的差异,旨在保证系统稳定性的前提下,实现调压成本最小化。具体而言,其通过直流母线电压波动值确定目标功率,采用二次规划算法将目标功率值在混合储能间进行合理分配,从而以最小成本维持母线电压在允许范围内。最后,通过两个实时仿真研究案例验证了所提控制方法的有效性。     

基于内点算法的电压校正控制

电力系统的实际运行中可能存在某些状态变量的越限，在线运动的无功／电压控制软件必须首先满足运行安全要求，保证电压在其合格范围内，并进一步在电压安全的基础上降低有功损耗。通过将越限约束转化为等式约束，推导了进行电压越限校正的原－对偶内点算法。求解目标函数为控制变量运作次数量少的优化问题得到电压校正控制。并针对控制变量的选取，违限约束校正方法问题进行了分析。实际计算表明，可以有效地降低问题规模，减少校正控制次数。