An Improved Non-isolated LED Converter with Power Factor Correction and Average Current Mode Control

A new type of high power LED drivers is proposed by adopting an improved two-stages non-isolated configuration. In order to improve power factor and achieve accurate average current control under universal input voltages ranging from 100 Vrms to 240 Vrms, the power factor correction and average current mode control methods operating in continuous current conduction mode are designed and implemented. With the LUMILEDS emitter type LEDs, a laboratory prototype is built and measured. And from the measured results, it could be concluded that the proposed driver has many better performances such as high power factor, low current harmonic, accurate average current control and switch protection.

Economical Optimization of Grid Power Factor Using Predictive Data

We present an electrical grid optimization method for economical benefit. After simplifying an IEEE feeder diagram, we build a compact smart grid system including a photovoltaic-inverter system, a shunt capacitor, an on-load tapchanger(OLTC) and transmission lines. The system power factor(PF) regulation and reactive power dispatching are indispensable to improve power quality. Our control method uses predictive weather and load data to decide engaging or tripping the shunt capacitor, or reactive power injection by the photovoltaic-inverter system, ultimately to keep the system PF in a good range. From the perspective of economics, the economical model is considered as a decision maker in our predictive data control method.Capacitor-only control strategy is a common photovoltaic(PV)regulation method, which is treated as a baseline case. Simulations with GridLAB-D on profiled loads and residential loads have been carried out. The comparison results with baseline control strategy and our predictive data control method show the appreciable economical benefit of our method.

Model Predictive Current Control for Low-Cost Shunt Active Power Filter

Performance of a three-phase shunt active power filter(SAPF)relies on the capability of the controller to track the reference current.Therefore,designing an accurate current controller is crucial to guarantee satisfactory SAPF operation.This paper presents a model predictive current controller(MPCC)for a low-cost,four-switch,shunt active power filter for power quality improvement.A four-switch,B4,converter topology is adopted as an SAPF,hence offering a simple,robust,and low-cost solution.In addition,to further reduce overall cost,only two interfacing filter inductors,instead of three,are used to eliminate switching current ripple.The proposed SAPF model MPCC is detailed for implementation,where simulation and experimental results validate effectiveness of the proposed control algorithm showing a 20%improvement in total harmonic distortion compared with a conventional hysteresis band current controller.

A RESEARCH TO HIGH-PERFORMANCE MULTI-LEVEL SINGLE-PHASE AC/DC POWER FACTOR CORRECT SWITCHING CONVERTER

This letter studies and analyzes the working features of main circuit of tri-level boost Power Factor Correct(PFC) converter and the advantages of tri-level switch converter in aspects of bearing high-voltage of power components,overall system loss and magnetic component selection based upon the single-level boost PFC switch converter.Besides,relying on the application of mi-croprocessor in power converter technology and DSP(Digital Signal Processing) chip's strong cal-culating capacity,the letter presents the adoption of modified scheme of tri-level boost PFC converter under the control of predictive control algorithm.Moreover,the operating principle and control method are specified,the results of circuit test and analysis are provided and the advantages of pre-dictive control technology-based multi-level boost PFC converter is verified.

Distributed Model Predictive Load Frequency Control of Multi-area Power System with DFIGs

Reliable load frequency control LFC is crucial to the operation and design of modern electric power systems. Considering the LFC problem of a four-Area interconnected power system with wind turbines, this paper presents a distributed model predictive control DMPC based on coordination scheme. The proposed algorithm solves a series of local optimization problems to minimize a performance objective for each control area. The generation rate constraints GRCs, load disturbance changes, and the wind speed constraints are considered. Furthermore, the DMPC algorithm may reduce the impact of the randomness and intermittence of wind turbine effectively. A performance comparison between the proposed controller with and without the participation of the wind turbines is carried out. Analysis and simulation results show possible improvements on closed-loop performance, and computational burden with the physical constraints. © 2014 Chinese Association of Automation.

Model-predictive control of power supply for particle accelerators

In this paper, model-predictive control(MPC) is proposed for controlling power source of accelerators. The system state equation is employed as the predictive model. With MPC, the difference between possible output and the ideal output is forecasted and decreased, so that the system can trace the ideal trail as closely and quickly as possible. The results of simulations and experiments show that this method can reduce influence of low frequency noise.

Efficient Supply Current Control Strategies for Bridgeless Interleaved AC-DC Converter

This paper presents an efficient supply current wave shaping technique for bridgeless interleaved Single Ended Primary Inductor Converter(SEPIC).The SEPIC converter converts an Alternating Current(AC)to Direct Current(DC)with the boost converter.Power Factor Correction(PFC)is progressively significant to achieve high energy efficiency.The overall system efficiency can be increased as the bridgeless topology has less conduction losses from rectifying bridges.Also,the bridgeless and interleaved techniques are incorporated in this study to achieve better performance.The performance of the system is analyzed on both current control and sensor-less techniques.Different controllers such as Proportional Integral(PI)control,peak current control,Non-Linear Carrier(NLC)control,and sensor-less current control are integrated.All the above controllers are implemented using MATrix LABoratory(MATLAB)/SIMULINK.The performance parameter,namely Power Factor(PF),Total Harmonic Distortion(THD),is computed for both open loop and closed loop condition.The sensor-less current control method is implemented using the DsPIC30F2010 controller.The circuit performance is also verified from the simulation and hardware results.The proposed controller has inbuilt Analog-to-Digital Converter(ADC),Digital-to-Analog Converter(DAC),Pulse Width Modulation(PWM)generator,and provides fast responses.

Investigation of Current Control Techniques of AC-DC Interleaved Boost PFC Converter

This paper presents the comparison of various current control strategies employed for an interleaved power factor correction (PFC) boost converter for improving the power quality. The major control strategies discussed in this paper are: peak current control, average current control, hysteresis control, borderline current control and non-linear control. These strategies are implemented in MATLAB/SIMULINK and the performance of the proposed converter is compared under open loop and closed loop operation. From the results, the input current waveform was close to input voltage waveform implying improved power factor and reduced total harmonic distortion for nonlinear current control technique. Experimental results validate the proposed method.

Low-complexity model predictive control of a four-level active neutral point clamped inverter without weighting factors

The four-level active neutral point clamped(ANPC)inverter has become increasingly widely used in the renewable energy indus-try since it offers one more voltage level without increasing the total number of active switches compared to the three-level ANPC inverter.The model predictive current control(MPCC)is a promising control method for multi-level inverters.However,the conven-tional MPCC suffers from high computational complexity and tedious weighting factor tuning in multi-level inverter applications.A low-complexity MPCC without weighting factors for a four-level ANPC inverter is proposed in this paper.The computational burden and voltage vector candidate set are reduced according to the relationship between voltage vector and neutral point voltage balance.The proposed MPCC shows excellent steady-state and dynamics performances while ensuring the neutral point voltage balancing.The efficacy of the proposed MPCC is verified by simulation and experimental results.

Nonlinear Model Predictive Controller for Compensations of Single Line-to-ground Fault in Resonant Grounded Power Distribution Networks

An nonlinear model predictive controller(NMPC)is proposed in this paper for compensations of single line-to-ground(SLG)faults in resonant grounded power distribution networks(RGPDNs),which reduces the likelihood of power line bushfire due to electric faults.Residual current compensation(RCC)inverters with arc suppression coils(ASCs)in RGPDNs are controlled using the proposed NMPC to provide appropriate compensations during SLG faults.The proposed NMPC is incorporated with the estimation of ASC inductance,where the estimation is carried out based on voltage and current measurements from the neutral point of the power distribution network.The compensation scheme is developed in the discrete time using the equivalent circuit of RGPDNs.The proposed NMPC for RCC inverters ensures that the desired current is injected into the neutral point during SLG faults,which is verified through both simulations and control hardware-in-the-loop(CHIL)validations.Comparative results are also presented against an integral sliding mode controller(ISMC)by demon-strating the capability of power line bushfire mitigation.

Adaptive perturb and observe maximum power point tracking with current predictive and decoupled power control for gridconnected photovoltaic inverters

In order to improve maximum power point tracking(MPPT) performance, a variable and adaptive perturb and observe(P&O)method with current predictive control is proposed. This is applied in three-phase threelevel neutral-point clamped(NPC) photovoltaic(PV)generation systems. To control the active power and the reactive power independently,the decoupled power control combined with a space vector modulation block is adopted for three-phase NPC inverters in PV generation systems.To balance the neutral-point voltage of the three-phase NPC grid-connected inverter, a proportional and integral control is used by adj usting the dwell time of small voltage vectors. A three-phase NPC inverter rated at 12 kVA was established. The performance of the proposed method was tested and compared with the fixed perturbation MPPT algorithm under different conditions. Experimental results confirm the feasibility and advantages of the proposed method.

Control strategy optimization for energy efficiency and harmonic mitigation in multi-series converters

To provide electrical power for the Research System of Superconducting Magnets(RSSMs)including the background field superconducting magnet and the tested superconducting objects,the high power phase-controlled converter will be used to develop the power supply system.However, because of its inner nonlinear feature, the current harmonics and the reactive power are injected into the AC power supply system. To improve the quality of the power supply system for RSSMs, an improved synchronous control strategy is suggested for the superconducting magnet power supply system, which comprises four series-connected six-pulse converters fed by a phase-shifting transformer, respectively. According to the proposed control strategy, the basic unit is two 12-pulse converters and the control method will be changed in terms of loadfluctuations which are represented by the per unit value of converter output voltage. As a result,harmonic is greatly reduced but the power factor is also high.

三电平辅助变流器寿命优化控制

辅助变流系统是动车组车辆上关键的电气组成部分,主要为空调机组、风机、照明等交流负载提供稳定的三相电源。结温是影响动车组三电平辅助变流器IGBT(Insulated-gate Bipolar Transistor)模块寿命的主要因素。为了提高动车组三电平中点钳位(Neutral-Point Clamped,NPC)型辅助变流器寿命,提出一种降低结温的模型预测电流控制(Model Predictive Current Control,MPCC)策略。首先,考虑传统MPCC在每个采样周期需要代入27个电压矢量循环计算,计算量较大,因此将三电平基本电压矢量划分在间隔60°的6个扇区中,通过计算电压矢量在两相静止坐标下的相角,进而判断参考电压矢量所处扇区,将备选矢量数目从27缩减至10,减少了计算量;其次,传统MPCC直接应用于动车组辅助变流器会使IGBT模块的结温较高,老化速度加快,对变流器安全稳定运行产生不可预测的损害,本文对IGBT模块的开关损耗和导通损耗进行近似等效,得到了和集射极电压、集电极电流相关的功率损耗因子。通过预测每相电流的方向,进而预测IGBT模块的开关和导通情况,动态加入功率损耗因子,并在代价函数中约束每相IGBT及其续流二极管(Free Wheeling Diode,FWD)的功率损耗,使得最优电压矢量在降低功率损耗的同时保证一定的控制性能。通过仿真与实验验证,本文所提方法相比传统MPCC策略降低了功率器件的结温,提高了变流器寿命。

基于无差拍预测算法的双向隔离型AC-DC矩阵变换器高动态电流控制策略

针对双向隔离型AC-DC矩阵变换器采用传统双闭环控制策略存在的控制参数多、整定困难等问题,提出了一种基于无差拍预测算法的高动态电流控制策略,通过引入无差拍预测算法对网侧电流进行控制,以减少控制器参数,消除数字控制时延。考虑到算法中电压电流检测量众多,故采用输入电压观测器以降低检测成本,减小采样误差的影响。变换器采用后级单重移相的调制方法来协调配合无差拍预测算法,其中参考输入电流指令与移相角为双射函数关系,简单易实现。仿真和实验结果表明:采用所提控制策略可以实现网侧电流正弦,功率因数接近于1;直流侧电压稳定,电流纹波率小于1%;直流电流在参考值突变时,跟踪快速且无超调、无振荡;同时,在变换器功率正向传输、反向传输以及正反向切换过程中,采用所提控制策略相比于传统的双闭环控制策略,电流动态调节时间分别缩短了69%、85%、67%。由此证明所提控制策略可以保证变换器良好的输入输出性能,并且相比于传统的双闭环控制策略在切换过程中动态性能得到显著提升。

面向电流源型PWM整流器的双矢量模型预测直接功率控制

电流源型脉宽调制(Pulse width modulation,PWM)整流器因其网侧存在LC滤波器,系统的控制难度增加。传统直接功率控制策略下的整流器功率波形存在脉动,因模型预测控制具有卓越的动态特性以及直观的控制规律,采用模型预测直接功率控制(Model predictive direct power control,MPDPC)对传统控制策略进行改进。首先建立了三相PWM整流器的数学模型,给出了每个采样周期内的功率变化率,并推导出相邻采样周期之间的功率关系,然后给出基于单矢量的模型预测直接功率控制策略,提出了基于双矢量的模型预测直接功率控制策略,并优选出两个电流矢量,计算在一个采样周期内的作用时间,并对其进行修正。最后,在Matlab/Simulink仿真软件验证了所提控制策略的可行性和有效性。

无电流传感复合前馈控制无桥功率因数校正变换器

有源功率因数校正(APFC)是AC-DC变换器的重要组成部分,其目的是改善输入侧电能质量,提高系统功率因数。传统的有源电流控制功率因数校正(PFC)变换器需要准确地提取升压电感电流,而双二极管式无桥PFC变换器升压电感位于整流部分之前,电感电流不再是单一方向流动,这使得其电流采样电路相比更复杂。为此该文提出一种基于观测器的无电流传感方案。方案中针对占空比误差的不确定影响修正了无桥PFC电流观测器算法,实现了占空比误差自适应的电流观测器,进一步基于所提观测器实现对负载信息的观测,设计出无电流传感的复合前馈控制方案,运用负载观测信息改进电流内环参考形式,同时利用输出电压纹波观测值进行2次谐波前馈补偿,最终实现无电流传感控制条件下变换器高动态响应设计。该文搭建了225 W单相双二极管式无桥PFC的实验样机,实验结果表明,在开关频率100 kHz时电流观测精度达到96.75%,所提控制方案输入电流的总谐波畸变率(THD)含量约为5%,功率因数(PF)约为99.85%,半载动态响应时间10 ms,相比于传统PI控制无桥PFC变换器提高了约90%。

深海洋流发电系统的PWM整流策略设计

洋流能是一种环保的清洁可再生能源,要实现洋流能的开发利用,离不开发电设备的研究。同时也能解决深海各种传感器水下长期供电的问题,优化当前采用的锂电池供电方式,减少锂电池的更换,节省人力物力,所以,设计一种利用深海洋流能发电的系统具有十分重要的意义。在深海洋流发电系统中,这里针对洋流发电机脉宽调制(PWM)整流器提出使用模型预测直接功率控制策略替代传统电压电流双闭环的控制策略,实现发电机的单位功率因数运行,不仅提高了深海发电系统的稳定性,而且提高了发电机的运行效率,从而提高了洋流能的转换效率。

混合式潮流控制器关键参数设计与控制策略研究

随着分布式光伏等新能源接入电网的规模快速增长,给新能源电力汇聚、疏散、消纳和电网潮流优化控制带来严峻挑战。基于电力电子技术的柔性交流输电系统装置可有效提升输电网络的传输容量,由大容量Sen变压器(sen transformer,ST)和小容量统一潮流控制器(unified power flow controller,UPFC)组成的混合式潮流控制器(hybrid unified power flow controller,HPFC)在实现潮流连续调节的基础上,能够有效提升装置的经济性,具有很好的应用前景。为了确保HPFC调节潮流的准确性和可靠性,给出了HPFC容量分配的一般性方法及其主电路参数确定方法;为解决ST机械有载分接开关和UPFC电力电子开关二者响应速度的协调问题,提出了一种基于预测电流控制的潮流控制策略,并在Simulink中搭建220 kV双回线路及三机九节点系统进行仿真。仿真结果验证了HPFC容量分配方法正确有效,且预测电流控制策略能够合理计算抽头位置,减缓过渡电流对HPFC控制系统的冲击,使系统功率快速调节至目标值。

变母线电压的LLC高压电容充电电源设计

提出了一种两级式可变母线电压的高压电容充电电源技术方案,该拓扑在半桥LLC谐振电路的基础上增加了一级图腾柱无桥功率因数校正(PFC)电路,通过改变母线电压来解决传统LLC谐振电源在输出更高电压时,工作频率变化范围过大带来的充电效率下滑的问题。由于图腾柱电路本身具备功率因数校正的功能,该电源设计还拥有能够直接从电网取电而不影响电网电能质量的优势。首先介绍了本电源设计中两部分的电路拓扑和工作原理,采用等效电阻法分析了电容负载下的电源输出特性。针对前级图腾柱电路设计了双环控制器以实现对母线电压和功率因数的控制,针对后级LLC电路提出了比例积分(PI)加低通滤波的恒流控制器以降低高频噪声带来的不利影响。最后通过模型构建与仿真分析,研究了高压电容充电电源3000 V/1 A时的充电特性,验证了本电源技术方案、设计和控制策略的可行性。

图腾柱功率因数校正器的二自由度控制分析

TPFC一般采用一自由度输出电压控制,在负载变化时输出电压动态特性较差,且启动过程存在明显超调。本文在推导TPFC双闭环控制结构基础上,引用了负载电流前馈控制和输出电压反馈补偿控制,构成两种二自由度(2DOF)控制结构。仿真分析表明,负载电流前馈型2DOF控制可以有效抑制负载变化引起的输出电压波动,但启动过程超调明显;输出电压反馈补偿型2DOF控制可以实现输出电压无超调启动,但是抑制负载变化的能力较差;综合负载电流前馈型和输出电压反馈补偿型的2DOF控制获得满意的输出电压控制效果,表现为启动过程无超调和变载过程无波动。