Optimal Dynamic Voltage Restorer Using Water Cycle Optimization Algorithm

This paper proposes a low complexity control scheme for voltage control of a dynamic voltage restorer(DVR)in a three-phase system.The control scheme employs the fractional order,proportional-integral-derivative(FOPID)controller to improve on the DVR performance in order to enhance the power quality in terms of the response time,steady-state error and total harmonic distortion(THD).The result obtained was compared with fractional order,proportionalintegral(FOPI),proportional-integral-derivative(PID)and proportional-integral(PI)controllers in order to show the effectiveness of the proposed DVR control scheme.A water cycle optimization algorithm(WCA)was utilized to find the optimal set for all the controller gains.They were used to solve four power quality issues;balanced voltage sag,balanced voltage swell,unbalanced voltage sag,and unbalanced voltage swell.It showed that one set of controller gain obtained from the WCA could solve all the power quality issues while the others in the literature needed an individual set of optimal gain for each power quality problem.To prove the concept,the proposed DVR algorithm was simulated in the MATLAB/Simulink software and the results revealed that the four optimal controllers can compensate for all the power quality problems.A comparative analysis of the results in various aspects of their dynamic response and%THD was discussed and analyzed.It was found that PID controller yields the most rapid performance in terms of average response time while FOPID controller yields the best performance in term of average%steady-state error.FOPI controller was found to provide the lowest THD percentage in the average%THD.FOPID did not differ much in average response from the PID and average%THD from FOPI;however,FOPID provided the most outstanding average steady-state error.According to the CBMA curve,the dynamic responses of all controllers fall in the acceptable power quality area.The total harmonic distortion(THD)of the compensated load voltage from all the controllers were within the 8%limit in accordance to the IEEE std.519-2014.

Research Progress in Improving the Cycling Stability of High-Voltage LiNi0.5Mn1.5O4 Cathode in Lithium-Ion Battery

High-voltage lithium-ion batteries(HVLIBs) are considered as promising devices of energy storage for electric vehicle, hybrid electric vehicle, and other high-power equipment. HVLIBs require their own platform voltages to be higher than 4.5 V on charge. Lithium nickel manganese spinel LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathode is the most promising candidate among the 5 V cathode materials for HVLIBs due to its flat plateau at 4.7 V. However, the degradation of cyclic performance is very serious when LNMO cathode operates over 4.2 V. In this review, we summarize some methods for enhancing the cycling stability of LNMO cathodes in lithium-ion batteries, including doping, cathode surface coating,electrolyte modifying, and other methods. We also discuss the advantages and disadvantages of different methods.

Arm Voltage Balancing Control of Modular Multilevel Resonant Converter

Modular multilevel resonant converter is an promising candidate for high voltage applications since it has advantageous features,such as high efficiency,high voltage capability and easy fault-tolerant operation.However,the inequality of arm inductance in practice will lead to imbalance between the upper and lower arm voltages,which will induce large ripples in the circulating current and a dc bias on the voltage generated by modular circuits.To compensate for the voltage imbalance,effects of arm duty cycle changes on arm voltages are discussed.An arm voltage balancing control method is proposed:adjust arm duty cycle according to arm voltage deviation in every switching cycle.Simulation and experimental results are presented to validate the theoretical analysis and the proposed control method.

Investigation the improvement of high voltage spinel LiNi_(0.5)Mn_(1.5)O_(4) cathode material by anneal process for lithium ion batteries

The spinel LiNi_(0.5)Mn_(1.5)O_(4)(LNMO)has been attracted great attention as lithium ion cathode material due to its high voltage and large energy density.However,the practical application of LNMO is still limited by poor cycling stability.Herein,to improve the cycling stability of spinel LNMO,it was treated with anneal process at 900℃for 2 h after prepared by traditional solid-state method(LNMO-A).LNMO-A sample presented better electrochemical property especially under high rate,with capacity of 91.2 mAhg^(-1) after 1000 cycles under 10 C.Its superior electrochemical property was ascribed to the anneal process,resulting a stable crystal structure,indicated by XRD and Raman results of electrodes after 1000 cycles under 10 C and the longer solid-solution reaction,revealed by in-situ XRD.In addition,the optimized particle size,micro morphology and the larger BET area surface induced by the recrystallization in anneal process also contributes to its superior electrochemical property.What's more,the thin layer,which interacted LNMO-A particles with each other,induced by particles remelting in anneal process is also beneficial for its excellent electrochemical property.This study not only improved the electrochemical properties by anneal process,but also revealed the origins and mechanisms for its improvement.

A New Buck-Based Configuration AC Chopper Voltage Conditioner

This paper presents a new AC chopper voltage conditioner, which can generate high quality sinusoidal waveforms with adjustable amplitudes. The circuit structure, operation principle, and control mode are analyzed in detail, the system essentially consisting of an equal duty cycle modulation AC voltage buck chopper and a voltage polarity change H-bridge, a full-wave rectifier, to perform tightly closed-loop control of the AC chopper voltage condtioner, a digital controller on a new converter model has been developed. The controller has very well dynamic response. To evaluate the new circuit and proposed control scheme, a 5kW conditioner is developed and the experimental results demonstrate that the system has good performances.

Proposal of High Gain, Reduced Stress with Low-Duty-Cycle Two-Input Boost Converter for Renewable Energy Systems

A two-input boost converter with voltage multiplier cell is proposed in this paper. Then a family of two-input converters with and without voltage multiplier cell are derived and their results are compared to achieve high voltage gain, low duty cycle, and reduced voltage stress. From the analysis of different topologies, a modified two-input converter with two-stage voltage multiplier cell has good operating characteristics. The switch voltage stress and duty cycle of the modified converter is significantly very less than that of the other converter topologies. The modified DC-DC converter with 50% duty cycle achieves a voltage gain of 10 and the results are verified by using MATLAB/Simulink software.

Novel Control Method for Dynamic Voltage Regulator

Control strategy affects directly the working performances of dynamic voltage regulator （DVR）. One-cycle control is an effective nonlinear signal modulation control method. In this paper, a new one-cycle control scheme for DVR was proposed in single phase supply system. On the basis of principle analysis, the corresponding one-cycle control model for DVR was built up, which is characterized by simple control circuits, good control performance, and high control precision. As an example, a control model for single-phase DVR was simulated by using Matlab/Simulink and SimPowerSystem. The results show that the load voltage could be compensated quickly at the points of supply voltage stepping down and up, and the relative error was less than 4% in the whole voltage sag process. Both theory analysis and simulation results show that the new one-cycle control scheme for DVR is effective.

Effects of Al and Co doping on the structural stability and high temperature cycling performance of LiNi_(0.5)Mn_(1.5)O_(4) spinel cathode materials

The poor structural stability and capacity retention of the high-voltage spinel-type LiNi_(0.5)Mn_(1.5)O_(4)(LNMO)limits their further application.Herein,Al and Co were doped in LNMO materials for a more stable structure and capacity.The LNMO,LiNi_(0.45)Al_(0.05)Mn_(1.5)O_(4)(LNAMO)and LiNi_(0.45)Co_(0.05)Mn_(1.5)O_(4)(LNCMO)were synthesized by calcination at 900℃ for 8 h,which was called as solid-phase method and applied universally in industry.XRD,FT-IR and CV test results showed the synthesized samples have cation disordering Fd-3m space group structures.Moreover,the incorporation of Al and Co increased the cation disordering of LNMO,thereby increasing the transfer rate of Li+.The SEM results showed that the doped samples performed more regular and ortho-octahedral.The EDS elemental analysis confirmed the uniform distribution of each metal element in the samples.Moreover,the doped samples showed better electrochemical properties than undoped LNMO.The LNAMO and LNCMO samples were discharged with specific capacities of 116.3 mA·h·g^(-1)and 122.8 mA·h·g^(-1)at 1 C charge/discharge rate with good capacity retention of 95.8% and 94.8% after 200 cycles at room temperature,respectively.The capacity fading phenomenon of the doped samples at 50℃ and 1 C rate was significantly improved.Further,cations doping also enhanced the rate performance,especially for the LNCMO,the discharge specific capacity of 117.9 mA·h·g^(-1)can be obtained at a rate of 5 C.

电流体喷印脉冲电压参数配置对沉积液滴体积的影响

为了精准控制电流体喷印液滴的最小体积并提高电流体喷印加工的分辨率,研究了电流体喷印的脉冲电压参数配置规律。首先,基于流体力学和电动力学基本原理,分析了喷印过程中泰勒锥的受力情况,并基于此建立了锥射流的体积分数仿真模型,探究了初始脉冲电压参数窗口。然后,搭建了电流体喷印平台,通过实验分析发现沉积液滴体积随脉冲电压幅值增大而减小,随脉冲频率的变化不明显,随着脉冲占空比增大,液滴体积先增大后减小。对比了参数配置前后液滴阵列的沉积液滴体积,参数配置前沉积液滴体积为40.89~45.25 nL,参数配置后平均液滴沉积体积为39.54 nL,验证了脉冲电压参数配置规律的有效性,可为节约生产过程中的材料和人工成本,进一步提高微纳电子产品的使用寿命提供参考。

定频变占空比控制的倍压型宽增益LLC谐振变换器

传统LLC谐振变换器在宽电压范围应用时开关频率工作范围过宽,且电压调节性能较差。针对上述问题设计了一种定频变占空比的脉宽调制策略,该策略基于倍压结构的全桥LLC谐振变换器,通过改变原边侧开关网络工作在全桥和半桥的占空比,调节谐振槽输入电压;同时,控制副边侧双向开关,可改变整流网络工作在全桥和倍压两种整流模式的占比,最终实现4倍电压增益的调节范围。与变频控制相比,该策略下变换器负载和励磁电感对增益的影响较小,可选用较大的励磁电感来减小循环电流。变换器原边侧开关管实现ZVS导通,整流二极管实现ZCS关断。最后,仿真与实验验证了该调制策略下变换器的可行性。

基于磁通观测器的CVS异步电机矢量控制系统

文章介绍了一种基于磁通观测器的 CVS异步电机矢量控制系统 ,提出了磁通观测器的结构和电机解耦控制模型 ,用计算机仿真实验证实该控制系统动态特性良好 。

基于新型虚拟矢量调制方法的IPMSM模型预测电流控制方法

模型预测控制方法已经被广泛应用于内置式永磁同步电机(IPMSM)的控制之中,传统模型预测控制方法由于候选电压矢量数量有限,在电机运行过程中会产生较大的电流和转矩谐波。为了增加候选电压矢量数量,提出了构建虚拟电压矢量的方法。但是在应用虚拟矢量调制方法时,系统计算的负担会随虚拟矢量数量的增加而增加,因此控制效果会受到系统计算能力的限制。针对此问题,该文提出了一种新型的虚拟电压矢量调制方法,首先将电压扇区进行细分来增加虚拟电压矢量的数量,然后通过对指令电压矢量坐标进行标幺化处理的方法求得其角度,最后从基础和虚拟电压矢量之中由角度搜索选出最优电压矢量。在该方法中,系统的计算量大小与虚拟电压矢量的数量无关,因此可以在不增加系统计算负担的情况下提升系统的控制性能。实验结果表明,与虚拟矢量数量受到限制的虚拟矢量预测控制方法相比,该方法有效减少了三相电流谐波含量,并且减少了控制算法的执行时间。

Optimal Location and Sizing ofMulti-Resource Distributed Generator Based onMulti-Objective Artificial Bee Colony Algorithm

Distribution generation(DG)technology based on a variety of renewable energy technologies has developed rapidly.A large number of multi-type DG are connected to the distribution network(DN),resulting in a decline in the stability of DN operation.It is urgent to find a method that can effectively connect multi-energy DG to DN.photovoltaic(PV),wind power generation(WPG),fuel cell(FC),and micro gas turbine(MGT)are considered in this paper.A multi-objective optimization model was established based on the life cycle cost(LCC)of DG,voltage quality,voltage fluctuation,system network loss,power deviation of the tie-line,DG pollution emission index,and meteorological index weight of DN.Multi-objective artificial bee colony algorithm(MOABC)was used to determine the optimal location and capacity of the four kinds of DG access DN,and compared with the other three heuristic algorithms.Simulation tests based on IEEE 33 test node and IEEE 69 test node show that in IEEE 33 test node,the total voltage deviation,voltage fluctuation,and system network loss of DN decreased by 49.67%,7.47%and 48.12%,respectively,compared with that without DG configuration.In the IEEE 69 test node,the total voltage deviation,voltage fluctuation and system network loss of DN in the MOABC configuration scheme decreased by 54.98%,35.93%and 75.17%,respectively,compared with that without DG configuration,indicating that MOABC can reasonably plan the capacity and location of DG.Achieve the maximum trade-off between DG economy and DN operation stability.

基于周期组合序列调制的三电平双有源桥均压策略

应用在双极性直流微电网(BDC-MGs)的三电平双有源桥(TL-DAB)变换器,在匹配多类型不平衡负载运行时,输出侧正负母线电压的不平衡将影响系统稳定运行。该文首先分析不平衡负载工况时TL-DAB变换器输出侧上、下端口分电容电压的不均衡原因,并提出一种基于功率传输与电压均衡的周期组合序列调制策略。该均压策略无需附加额外电路和储能器件,仅通过改变功率传输的周期数及单周期内端口电平脉宽占比,便可实现输出侧上下端口传输功率的差额分配以达到分电容电压的均衡。仿真和实验结果表明,在上下分电容负载极不平衡工况下,相对于传统对称调制策略,该文所提均压策略可以将电压不均衡度从12%降低至1%以下。

集成型车载充电系统并网模式模型预测控制策略

相较于传统车载充电系统,集成型车载充电系统(integrated onboard charger system,IOCS)在成本、功率密度等方面具备显著优势。文中基于六相永磁电驱系统设计了一台IOCS,并研究了模型预测电流控制(model predictive current control,MPCC)算法在该系统并网模式下的应用。首先,分析所提IOCS的电路拓扑并建立数学模型,同时介绍传统MPCC的实施流程。然后,针对传统MPCC计算量大、稳态性能差等不足,提出一种基于占空比优化的MPCC(MPCC based on duty cycle optimization,DCO-MPCC)策略。一方面,减少备选电压矢量数量,降低电流预测环节带来的计算负担;另一方面,提出一种占空比优化技术,改善系统稳态性能。最后,通过实验验证了所提算法的有效性与优越性。实验结果表明,DCO-MPCC策略能够显著提升系统稳态性能并减少算法计算量。充电与车网互动(vehicle to grid,V2G)工况下,网侧电流总谐波畸变(total harmonic distortion,THD)分别降低6.18%与5.92%,算法运行时间减少17.54μs。

基于交交变换的动态电压恢复器及其控制策略

传统的动态电压恢复器(DVR)中直流储能环节体积重量大,不易集成,交交变换技术省去实现动态电压补偿,更加经济节约。虚拟整流逆变拓扑作为主电路拓扑,结构简洁,并且能够实现自然换流;单周期控制精度高,动态跟踪性能佳,控制鲁棒性好,应用于DVR可以更好地满足其特殊的快速性要求。在理论分析基础上,研制了实验样机进行实验验证,实验结果验证了变换器的可行性及单周期控制良好的动态特性。

并网光伏系统中3L-T-type QZSI参与电网电压不平衡控制

针对传统逆变器在不平衡网压情况下工作时较难抑制输入电网有功功率振荡分量的问题,提出一种基于三电平T型准阻抗源逆变器(three level T-type quasi-Z source inverter,3L-T-type QZSI)抑制有功功率振荡分量的控制策略。从功率理论推导得到其并网的参考电流,实现并网有功功率恒定且以单位功率因数为目标的控制策略。即:使用二阶广义积分器(second-order generalized integrator,SOGI)完成电压的正负序分离;再结合基于载波的电平位移脉宽调制(level-shift pulse width modulation,LS-PWM)技术,用以调节功率开关直通状态的占空比和叠加的平衡分量,实现直流侧电压控制和中点电压平衡。最后,在Simulink平台上模拟了电网电压不平衡情况,对间歇性能源不同出力情况进行了仿真,仿真结果表明,该策略可有效抑制间歇性能源的有功功率二倍频波动,有利于实现中点电位平衡和间歇性能源并网稳定运行。

Unrevealing the effects of low temperature on cycling life of 21700-type cylindrical Li-ion batteries

The low-temperature performance of Li-ion batteries(LIBs) has important impacts on their commercial applications. Besides the metallic lithium deposition, which is regarded as one of the main failure mechanisms of the LIBs at low temperatures, the synergistic effects originating from the cathode, anode, electrolyte, and separators to the batteries are still not clear. Here, the 21700-type cylindrical batteries were evaluated at a wide range of temperatures to investigate the failure mechanism of batteries. Voltage relaxation, and the post-mortem analysis combined with the electrochemical tests, unravel that the capacity degradation of batteries at low temperature is related to the lithium plating at graphite anodes,the formation of unsatisfied solid deposited/decomposed electrolyte mixture phase on the anode, the precipitation of solvent in the electrolytes and the block of separator pores, and the uneven dissolved transition metal-ions from the cathode. We hope this finding may open up a new avenue to alleviate the capacity degradation of advanced LIBs at low temperatures and shed light on the development of outstanding low-temperature LIBs via simultaneous optimization of all the components including electrodes, electrolytes and separators.

Grid Voltage Sensor-less Protection Scheme for One Cycle-Controlled Single-phase Photovoltaic Inverter Systems

One-cycle-controlled(OCC)inverters are suitable for small single-phase photovoltaic distributed-generator systems because of their simplicity,phase-locked-loop free structure,grid voltage sensor-less operation,and cost-effectiveness.Grid voltage sensor-less control helps reduce cost and increases reliability in operation.However various sensors are used for implementation of a protection mechanism.In this paper,a grid voltage sensorless protection scheme for OCC based single-phase inverter systems is proposed.The estimated value of voltage at point of common coupling(VPCC)is used for protecting the system during over/under voltage conditions of the grid,implementing of voltage ride through conditions,and for disconnecting the grid during islanded conditions.The VPCC is estimated from the measured inverter current,switching pulses,and the measured dc-link voltage using a second-order filter.Simulation and experimental studies are performed to verify the efficacy of the proposed voltage sensor-less protection mechanism triggered using estimated VPCC.