OPTIMAL INTERIOR PARTIAL REGULARITY FOR NONLINEAR ELLIPTIC SYSTEMS UNDER THE NATURAL GROWTH CONDITION:THE METHOD OF A-HARMONIC APPROXIMATION

In this article, the authors consider the nonlinear elliptic systems under the natural growth condition. They use a new method introduced by Duzaar and Grotowski, for proving partial regularity for weak solutions, based on a generalization of the technique of harmonic approximation. And directly establish the optimal Holder exponent for the derivative of a weak solution.

A Uniaxial Optimal Perfectly Matched Layer Method for Time-harmonic Scattering Problems

We develop a uniaxial optimal perfectly matched layer （opt PML） method for solving the time-harmonic scattering problems by choosing a particular absorbing function with unbounded integral in a rectangular domain. With this choice, the solution of the optimal PML problem not only converges exponentially to the solution of the original scatting problem, but also is insensitive to the thickness of the PML layer for sufficiently small parameter ε0. Numerical experiments are included to illustrate the competitive behavior of the proposed optimal method.

Particle swarm optimization algorithm for simultaneous optimal placement and sizing of shunt active power conditioner(APC)and shunt capacitor in harmonic distorted distribution system

Due to development of distribution systems and increase in electricity demand,the use of capacitor banks increases.From the other point of view,nonlinear loads generate and inject considerable harmonic currents into power system.Under this condition if capacitor banks are not properly selected and placed in the power system,they could amplify and propagate these harmonics and deteriorate power quality to unacceptable levels.With attention of disadvantages of passive filters,such as occurring resonance,nowadays the usage of this type of harmonic compensator is restricted.On the other side,one of parallel multi-function compensating devices which are recently used in distribution system to mitigate voltage sag and harmonic distortion,performs power factor correction,and improves the overall power quality as active power conditioner(APC).Therefore,the utilization of APC in harmonic distorted system can affect and change the optimal location and size of shunt capacitor bank under harmonic distortion condition.This paper presents an optimization algorithm for improvement of power quality using simultaneous optimal placement and sizing of APC and shunt capacitor banks in radial distribution networks in the presence of voltage and current harmonics.The algorithm is based on particle swarm optimization(PSO).The objective function includes the cost of power losses,energy losses and those of the capacitor banks and APCs.

Optimization and experimental research on a new-type short cylindrical cup-shaped harmonic reducer

In order to obtain a new-type short cylindrical cup-shaped flexspline that can be applied to space mechanisms,the APDL language of ANSYS software was employed to develop a parameterized equivalent contact model between a flexspline and a wave generator. The validity of the parameterized equivalent contact model was verified by comparing the results of the analytic value of the contact model and the value calculated by the theoretical formula. The curvilinear trend of stress was obtained by changing the structural parameter of the flexspline. Based on the curvilinear trend of stress,multi-objective optimizations of key structural parameters were achieved. Flexspline,wave generator,and circular spline of a new 32-type short cylindrical cup-shaped harmonic reducer were designed and manufactured. A performance test bench to carry out tests on the harmonic reducer was designed. Contrast experiments were implemented to determine the efficiency of the new 32-type short cylindrical cup-shaped harmonic reducer and the conventional 32-type harmonic reducer under different conditions. The experimental results reveal that there is approximately equality in terms of efficiency between the new 32-type short cylindrical cup-shaped harmonic reducer and the conventional 32-type harmonic reducer. The volume of the flexspline of the new 32-type short cylindrical cup-shaped harmonic reducer is reduced by approximately 30% through multi-objective optimization. When the new 32-type short cylindrical cup-shaped harmonic reducer is used on the wheel of a rover prototype,the mass of the wheel hub is decreased by 0.42 kg. Test analysis of wheel motion verifies that the new 32-type short cylindrical cup-shaped harmonic reducer can meet the requirements regarding bearing capacity and efficiency.

A global harmony search algorithm for finding optimal capacitor location and size in distribution networks

Shunt capacitors are broadly applied in distribution systems to scale down power losses, improve voltage profile and boost system capacity. The amount of capacitors added and location of deployment in the system highly determine the advantage of compensation. A novel global harmony search(GHS) algorithm in parallel with the backward/ forward sweep power flow technique and radial harmonic power flow was used to investigate the optimal placement and sizing of capacitors in radial distribution networks for minimizing power loss and total cost by taking account load unbalancing, mutual coupling and harmonics. The optimal capacitor placement outcomes show that the GHS algorithm can reduce total power losses up to 60 k W and leads to more than 18% of cost saving. The results also demonstrate that the GHS algorithm is more effective in minimization of power loss and total costs compared with genetic algorithm(GA), particle swarm optimization(PSO) and harmony search(HS) algorithm. Moreover, the proposed algorithm converges within 800 iterations and is faster in terms of computational time and gives better performance in finding optimal capacitor location and size compared with other optimization techniques.

Spherical parametrization of genus-zero meshes by minimizing discrete harmonic energy

The problem of spherical parametrization is that of mapping a genus-zero mesh onto a spherical surface. For a given mesh, different parametrizations can be obtained by different methods. And for a certain application, some parametrization results might behave better than others. In this paper, we will propose a method to parametrize a genus-zero mesh so that a surface fitting algorithm with PHT-splines can generate good result. Here the parametrization results are obtained by minimizing discrete har- monic energy subject to spherical constraints. Then some applications are given to illustrate the advantages of our results. Based on PHT-splines, parametric surfaces can be constructed efficiently and adaptively to fit genus-zero meshes after their spherical parametrization has been obtained.

Harmonic Suppression Method Based on Immune Particle Swarm Optimization Algorithm in Micro-Grid

Distributed generation has attracted great attention in recent years, thanks to the progress in new-generation technologies and advanced power electronics. And micro-grid can make full use of distributed generation, so it has been widespread concern. On the other hand due to the extensive use of power electronic devices and many of the loads within micro-grid are nonlinear in nature, Micro-grid generate a large number of harmonics, so harmonics pollution needs to be addressed. Usually we use passive filter to filter out harmonic, in this paper, we propose a new method to optimize the filter parameters, so passive filter can filter out harmonic better. This method utilizes immune particle swarm optimization algorithm to optimize filter parameters. It can be shown from the simulation results that the proposed method is effective for micro-grid voltage harmonics compensation.

Optimization of multi-color laser waveform for high-order harmonic generation

With the development of laser technologies,multi-color light-field synthesis with complete amplitude and phase control would make it possible to generate arbitrary optical waveforms.A practical optimization algorithm is needed to generate such a waveform in order to control strong-field processes.We review some recent theoretical works of the optimization of amplitudes and phases of multi-color lasers to modify the single-atom high-order harmonic generation based on genetic algorithm.By choosing different fitness criteria,we demonstrate that：（i） harmonic yields can be enhanced by 10 to 100 times,（ii） harmonic cutoff energy can be substantially extended,（iii） specific harmonic orders can be selectively enhanced,and（iv） single attosecond pulses can be efficiently generated.The possibility of optimizing macroscopic conditions for the improved phase matching and low divergence of high harmonics is also discussed.The waveform control and optimization are expected to be new drivers for the next wave of breakthrough in the strong-field physics in the coming years.

Coordinated Control Strategy for Harmonic Compensation of Multiple Active Power Filters

In order to minimize the harmonic distortion rate of the current at the common coupling point,this paper proposes a coordinated allocation strategy of harmonic compensation capacity considering the performance of active power filters(APF).On the premise of proportional distribution of harmonic compensation capacity,the harmonic compensation rate of each APF is considered,and the harmonic current value of each APF to be compensated is obtained.At the same time,the communication topology is introduced.Each APF takes into account the compensation ability of other APFs.Finally,three APFs with different capacity and performance are configured at the harmonic source to suppress the same harmonic source,and the harmonic distortion rate is reduced to 1.73%.The simulation results show that the strategy can effectively improve the compensation capability of the multiple APF cascaded system to the power grid without increasing the installed capacity.

OPTIMAL INTERIOR PARTIAL REGULARITY FOR NONLINEAR ELLIPTIC SYSTEMS WITH DINI CONTINUOUS COEFFICIENTS

In this article, we consider nonlinear elliptic systems of divergence type with Dini continuous coefficients. The authors use a new method introduced by Duzaar and Grotowski, to prove partial regularity for weak solutions, based on a generalization of the technique of harmonic approximation and directly establish the optimal HSlder exponent for the derivative of a weak solution on its regular set.

Topology Optimization for Harmonic Excitation Structures with Minimum Length Scale Control Using the Discrete Variable Method

Continuumtopology optimization considering the vibration response is of great value in the engineering structure design.The aimof this studyis toaddress the topological designoptimizationof harmonic excitationstructureswith minimumlength scale control to facilitate structuralmanufacturing.Astructural topology design based on discrete variables is proposed to avoid localized vibration modes,gray regions and fuzzy boundaries in harmonic excitation topology optimization.The topological design model and sensitivity formulation are derived.The requirement of minimum size control is transformed into a geometric constraint using the discrete variables.Consequently,thin bars,small holes,and sharp corners,which are not conducive to the manufacturing process,can be eliminated from the design results.The present optimization design can efficiently achieve a 0–1 topology configuration with a significantly improved resonance frequency in a wide range of excitation frequencies.Additionally,the optimal solution for harmonic excitation topology optimization is not necessarily symmetric when the load and support are symmetric,which is a distinct difference fromthe static optimization design.Hence,one-half of the design domain cannot be selected according to the load and support symmetry.Numerical examples are presented to demonstrate the effectiveness of the discrete variable design for excitation frequency topology optimization,and to improve the design manufacturability.

Reactive Compensator Synthesis in Time-Domain as an Alternative to Harmonic Method

The source reactive-current compensation is crucial in energy transmission efficiency. The compensator design in frequency-domain was already widely discussed and examined. This paper presents results of a study on how to design reactive compensators in time-domain. It’s the first time the reactive compensator have been designed in time domain. The example of compensator design was presented.

An Insight into the Second-Harmonic Current Reduction Control Strategies in Two-Stage Converters

Due to the components at twice the fundamental frequency of output voltage in the instantaneous output power of a two-stage single-phase inverter(TSI),the second harmonic current(SHC)is generated in the frontend dc-dc converter(FDC).To reduce the SHC,optimizing the control strategy of the FDC is an effective and costless approach.Fromthe view of visual impedance,this paper conducts an intensive study on the SHC reduction strategies.Origin of the SHC is illustrated first.Then,the equivalent circuit models of the FDC under different control strategies are proposed to analyse the SHC propagation characteristic.The derived model can offer a better insight into how the inductor SHC is affected by the control parameters.According to the derived models,a synthesis of different control strategies is presented and the relevant parameters are listed for control design to achieve better suppression effect.The benefits and limitations of these control strategies are also discussed.Based on the proposed equivalent circuit models,several optimization methods are proposed to enhance the effect.A 1500 VA TSI prototype is built and simulated on MATLAB/Simulink,verifying the effectiveness of the proposed optimization methods.This paper is aimed to provide a guideline for the control design and control optimization of the TSIs.

Costless-Function Model Predictive Current Control of Seven-Phase PMSM to Improve Dynamic Performance and Suppress Harmonics of Marine Electric Propulsion System

In order to improve the dynamic performance and suppress current harmonic for seven-phase PMSM(permanent magnet synchronous motor),this paper proposed an MPCC(mode predict current control)scheme based on SVPWM(space vector pulse width modulation)technique.By this scheme,the 14 virtual voltage vectors are first calculated based on the principle:the voltage vector synthesized in the 3rd harmonic subspace and the 5th harmonic subspace should be zero,in each sampling period,the optimal voltage vector is directly selected from the 14 virtual voltage vectors to achieve the best output current performance of seven-phase PMSM.In addition,no cost function related calculations are required in the MPCC scheme,reducing the calculation time and improving the dynamic response of the system.The simulation model of the seven-phase PMSM vector control system is established by using the Simulink tool of MATLAB,and the effectiveness of the scheme will be presented.

Harmonic Minimization in Seven-Level Cascaded Multilevel Inverter Using Evolutionary Algorithm

Inverters are power electronic devices that change over DC to sinusoidal AC quantity. Be that as it may, in down to earth, these devices produce non-sinusoidal yield which contains harmonics, so as to blend a close sinusoidal component and to lessen the harmonic distortion multilevel inverters developed. Mathematical methods, which were developed, are derivative based and need initial considerations. To overcome this, evolutionary algorithms, which are derivative free and accurate, were developed for obtaining multi levels of output voltage. The proposed work uses two evolutionary algorithms, namely, Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) algorithm. These algorithms are used to generate the switching angles by satisfying the non linear transcendental equations that govern the low order harmonic components. A seven level cascaded full bridge inverter is designed using MATLAB/Simulink and the results validate the results for switching angles. The Total Harmonic Distortion (THD) value obtained for GA and PSO is 11.81% and 10.84% respectively. The solution obtained from GA algorithm was implemented in hardware using dsPIC controller to validate the simulation results. The THD value obtained for cascaded seven-level multilevel inverter in the hardware prototype is 25.9%.

光伏多功能并网逆变器不同出力状态下无功和谐波优化方法

利用光伏多功能并网逆变器所具有的电能质量治理、谐波谐振抑制的主动优势,结合逆变器在不同出力状态下光伏发电系统的输出特性,构建光伏多功能并网逆变器不同出力状态下的无功和谐波优化方法。在所提3层优化策略中,上层优化策略以光伏并网有功功率最大化为目标函数,中层优化策略以电压谐波总畸变率和电压偏差达到相应电能质量规定指标为目标函数,下层优化策略以电压谐波总畸变率和电压偏差最小为目标函数,并采用自适应蚁群算法进行求解。基于IEEE 33节点系统进行算例分析,结果表明:基于逆变器不同出力状态的优化方法可以有效改善电网的电能质量,较好地提升电网运行的经济性;在系统稳定运行的基础上,光伏多功能并网逆变器在不同出力状态下分阶段、分主次地治理谐波和调整电压偏差,治理效果更佳。

新能源汽车电池回收网点竞争选址模型及算法

针对考虑排队论的新能源汽车电池回收网点竞争设施选址问题,提出一种改进的人类学习优化(IHLO)算法。首先,构建包含排队时间约束、容量约束和门槛约束等条件的新能源汽车电池回收网点竞争设施选址模型;然后,考虑到该问题属于NP-hard问题,针对人类学习优化(HLO)算法前期收敛速度较慢、寻优精度不够高、求解稳定性不够高的不足,通过引入精英种群反向学习策略、团队互助学习算子和调和参数自适应策略提出IHLO算法;最后,以上海市和长江三角洲为例进行数值实验,并将IHLO算法和改进二进制灰狼(IBGWO)算法、改进二进制粒子群(IBPSO)算法、HLO算法和融合学习心理学的人类学习优化(LPHLO)算法进行比较。大、中、小三种不同规模的实验结果表明,IHLO算法在15个指标中的14个指标上表现最优,IHLO算法比IBGWO算法求解精度至少提高了0.13%,求解稳定性至少提高了10.05%,求解速度至少提高了17.48%。所提算法具有较高的计算精度和优化速度,可有效解决竞争设施选址问题。

考虑光伏不确定性的配电网谐波监测优化配置方法

大规模分布式光伏接入的配电网在运行过程中易产生大量谐波,严重影响电能质量,亟需实现谐波全局可观,为其治理提供数据基础。因此,提出了一种考虑光伏不确定性的谐波监测点优化配置方法。该方法提出了节点综合谐波敏感因子评估配电网节点受谐波影响的程度,从而对节点进行权重划分;进一步地,考虑光照强度和负荷随时间变化的特点,为保证系统在不同时间段内产生的谐波均能被观测到,在谐波潮流计算的基础上,提出了谐波可观测矩阵;基于上述2个评价指标,建立了考虑节点谐波敏感因子的谐波监测优化配置模型,并采用非支配排序遗传算法求解得到了谐波监测点配置方案。在IEEE 33节点配电系统上仿真验证所提方法的有效性,并将所提方法与已有方法进行了对比分析,验证了所提方法的优越性。

基于多源数据的馈线谐波频谱估计方法

随着分布式电源和非线性负荷的投运规模不断增加,电网谐波污染愈加严重和复杂,有必要对各馈线谐波电流进行监测。但基于经济性考虑,对变电站所有馈线均进行谐波电流监测并不可行。针对上述问题,提出了基于多源数据的馈线谐波频谱估计方法。该方法基于电网现有电能质量监测系统、调度系统、营销业务应用系统等多源数据,只需对母线谐波电压和进线谐波电流开展监测,即可估计出变电站所有馈线的谐波电流情况。首先,根据馈线谐波电流的相量运算关系和功率关系构建馈线谐波频谱估计的目标函数。其次,基于多源数据利用改进粒子群算法求解目标函数,进而得到各馈线的各次谐波电流含有率及馈线谐波电流间的相角差,实现了各馈线谐波电流频谱的估计。最后,通过仿真算例和实测算例验证了方法的可行性。算例表明该方法仅需在变电站母线处安装一台电能质量监测终端,结合现有业务系统的基本电气数据等信息,可实现馈线谐波频谱的估计,有助于节约变电站监测装置的配置成本。

改进蛇算法的七电平逆变器SHEPWM研究

多电平逆变器控制策略中的特定谐波消除脉宽调制(SHEPWM)能够以较低的开关频率得到较好的电压输出波形,重点在于开关角的求取。在多电平逆变器SHEPWM调制的开关角求解算法上提出改进蛇优化算法,对传统蛇优化算法采用Tend混沌映射初始种群,使初始种群分布更加均匀;引入Levy飞行策略增强算法的全局搜素能力,能够更加精准快速得到全局开关角的最优解。仿真结果表明,改进蛇优化算法所求的开关角相较于传统算法更好地消除低次谐波,并降低了输出线电压的畸变率,充分验证了该方法的可行性。