Design and Analysis of the Main AC/DC Converter System for ITER

A design of the main AC/DC converter system for ITER is described and the configuration of the main AC/DC converters is presented. To reduce the reactive power absorbed from the converter units, the main AC/DC converters are designed to be series-connected and work in a sequential mode. The structure of the regulator of the converter system is described. A simulation model was built up for the PSCAD/EMTDC code, and the design was validated accordingly. Harmonic analysis and reactive power calculation of the converters units are presented. The results reveal the advantage of sequential control in reducing reactive power and harmonics.

Single-stage active clamp power factor correction AC/DC converter

A simple single-stage AC/DC converter circuit with active clamp is presented. The operation theory and state are analyzed. The experimental results show that the voltage across main switch can be clamped to a certain value,and zero voltage switching (ZVS) can be achieved. The voltage stress and switching loss are both decreased. In range of the whole load,power factors can be always more than 97%,and the highest efficiency can reach 88%.

An Adaptive Control Strategy for Energy Storage Interface Converter Based on Analogous Virtual Synchronous Generator

In the DC microgrid,the lack of inertia and damping in power electronic converters results in poor stability of DC bus voltage and low inertia of the DC microgrid during fluctuations in load and photovoltaic power.To address this issue,the application of a virtual synchronous generator(VSG)in grid-connected inverters control is referenced and proposes a control strategy called the analogous virtual synchronous generator(AVSG)control strategy for the interface DC/DC converter of the battery in the microgrid.Besides,a flexible parameter adaptive control method is introduced to further enhance the inertial behavior of the AVSG control.Firstly,a theoretical analysis is conducted on the various components of the DC microgrid,the structure of analogous virtual synchronous generator,and the control structure’s main parameters related to the DC microgrid’s inertial behavior.Secondly,the voltage change rate tracking coefficient is introduced to adjust the change of the virtual capacitance and damping coefficient flexibility,which further strengthens the inertia trend of the DC microgrid.Additionally,a small-signal modeling approach is used to analyze the approximate range of the AVSG’s main parameters ensuring system stability.Finally,conduct a simulation analysis by building the model of the DC microgrid system with photovoltaic(PV)and battery energy storage(BES)in MATLAB/Simulink.Simulation results from different scenarios have verified that the AVSG control introduces fixed inertia and damping into the droop control of the battery,resulting in a certain level of inertia enhancement.Furthermore,the additional adaptive control strategy built upon the AVSG control provides better and flexible inertial support for the DC microgrid,further enhances the stability of the DC bus voltage,and has a more positive impact on the battery performance.

DC-Link Capacitor Optimization in AC–DC Converter by Load Current Prediction

Alternating Current–Direct Current(AC–DC)converters require a high value bulk capacitor or afilter capacitor between the DC–DC conversion stages,which in turn causes many problems in the design of a AC–DC converter.The component package size for this capacitor is large due to its high voltage rating and capacitance value.In addition,the high charging current creates more pro-blems during the product compliance testing phase.The shelf life of these specific high value capacitors is less than that of Multilayer Ceramic Capacitors(MLCC),which limits its use for the highly reliable applications.This paper presents a fea-sibility study to overcome these two problems by adding a few sensing mechan-isms to the typical AC–DC converter topology.In majority of the AC–DC converter,Al-Elko capacitor takes approximately 3%to 5%of the converter size.The proposed method reduces this to approximately 50%size and so it effectively approximates 2%to 3%size reduction in converter size.The proposed method basically works based on the load current prediction method and hence it is highly suitable for the constant load application.Moreover,the converter response time increases in this method,which limit its application in high-speed systems.The high temperature application of Al-Elko capacitor is limited because of its poor performance,which is significantly rectified by replacing the Al-Elko with MLCC as it delivers good performance in high temperature.

单级三相谐波电流注入可升降压AC/DC变换器

为适应电动车充电电压宽范围变化需求,本文针对传统充电桩前级整流器拓扑开展研究,提出一种新式单级三相AC/DC变换器。该变换器集成了三相桥式不控整流电路与Cuk模块,为降低输入侧电流谐波分量,选用双向开关管构建谐波电流回馈通路,整体构造成单级式拓扑结构。文章阐述了变换器的电路结构及工作模态,通过建立变换器的等效模型推导出电压增益。变换器通过简单的控制逻辑即可实现正弦输入电流并拥有高功率因数。最后通过搭建变换器数字控制实验平台验证了所提变换器的可行性。

高频链AC-DC矩阵变换器的变控制频率软开关调制策略

针对高频链AC-DC矩阵变换器的高效率要求,提出了一种变控制频率软开关调制策略。该调制策略在基于零矢量嵌入的分段同步控制策略基础上,以单控制周期平均功率不变为原则,通过改变控制周期长度,并调整一个控制周期内的电压矢量排布,优化脉冲宽度,使变换器在换流时全部开关器件的零电压开通成为可能。通过仿真分析和实验证明,采用本文提出的变控制频率调制策略,变换器在整流和逆变模式下,均可实现网侧电流三相平衡正弦,功率因数达到0.981,输出电压纹波小,最高效率达到96.9%,实现了高性能、高效率运行。

隔离型双向AC-DC矩阵变换器闭环控制方法研究

根据隔离型双向AC-DC矩阵变换器(Isolated AC-DC Matrix Converter,IAMC)没有中间电容缓冲环节,输入和输出变换器控制之间存在耦合,研究提出了IAMC两级功率变换器的控制方法。通过对全桥变换器进行闭环控制进而实现对直流侧输出电流和功率的直接控制;三相-单相矩阵变换器实现对有功和无功功率的独立控制,以满足网侧功率因数的高精度控制。所提控制策略有效降低了两级变换器的耦合强度,保证了系统的良好性能。在MATLAB中进行仿真,结果表明,所提出的控制方法在使系统电能质量得到提高的同时,可以实现单位功率因数可调,验证了所提控制策略的正确性和有效性。

V2G车网互联的双向AC/DC变换器直流阻抗模型及特性分析

双向AC/DC变换器的控制及直流输出阻抗是电动汽车充电桩并网运行及稳定性分析的关键。首先,提出含直流下垂环节的虚拟同步电机(VSM)控制策略,并利用上层功率指令实现双向AC/DC变换器直流电压的无差调节。然后,建立VSM功率控制环小信号模型,分析有功功率传输、有功功率指令与直流电压间的交互作用及影响。接着,建立双向AC/DC变换器在直流下垂VSM控制策略下的直流输出阻抗模型,详细分析阻尼系数、惯性系数、直流侧电容、传输功率、直流下垂系数等关键参数对直流输出阻抗的影响。最后,通过仿真及阻抗测量验证了所提直流下垂VSM控制策略的有效性和阻抗模型的正确性。

AC/DC Matrix Converters for V2G Applications

由于当前V2G系统中普遍采用的电压型脉宽调制（pulse width modulation,PWM）整流方案中所存在的蓄电池电压匹配、功率体积比及系统效率问题,提出一种采用AC/DC矩阵变换器的解决方案。针对经典电流空间矢量调制策略中充电电流纹波较大的缺点,提出一种在全输出范围内减小充电电流纹波的分段优化调制策略,并深入对比分析这两种调制策略下充电电流纹波的大小。仿真和实验结果表明,所提分段优化调制策略的正确性和可行性。

DC-Modulated PFC Buck-Type AC/AC Converter for Light Dimming

Dimmers are very widely applied in theatres,cinemas,dancing-parties, auditoriums and signal systems.They are usually supplied by single-stage AC/AC converters in the past with voltage regulation technique with the disadvantages of high total harmonic distortion,low power factor and poor power transfer efficiency.This paper introduces a novel method-DC-modulation that implements DC/DC conversion technology into AC/AC converters.The DC-modulated single-stage PFC AC/AC converters effectively improved the power factor up to 0.999 and the power transfer efficiency up to 97.8 %.The experimental results verified our design and calculation.This technique will be widely used in light dimming and other industrial applications.

A new high-performance AC/DC power factor correction switching converter based on one-cycle control technology and active floating-charge technology

A new family of converters,high-performance AC/DC power factor correction(PFC) switching converters with one-cycle control technology and active floating-charge technology,was derived and experimentally verified.The topology of a single-phase CCM and DCM Boost-PFC switching converter was also analyzed.Its operating prniciples and control methods were expounded.Based on these,a new type of AC/DC switching converter circuits for PFC combined with one-cycle control technology was presented herein.The proposed AC/DC switching converter significantly helps improve the converter efficiency and its power factor value.

Design of Second Order Sliding Mode and Sliding Mode Algorithms:A Practical Insight to DC-DC Buck Converter

This paper presents a simple and systematic approach to design second order sliding mode controller for buck converters.The second order sliding mode control(SOSMC)based on twisting algorithm has been implemented to control buck switch mode converter.The idea behind this strategy is to suppress chattering and maintain robustness and finite time convergence properties of the output voltage error to the equilibrium point under the load variations and parametric uncertainties.In addition,the influence of the twisting algorithm on the performance of closed-loop system is investigated and compared with other algorithms of first order sliding mode control such as adaptive sliding mode control(ASMC),nonsingular terminal sliding mode control(NTSMC).In comparative evaluation,the transient response of the output voltage with the step change in the load and the start-up response of the output voltage with the step change in the input voltage of buck converter were compared.Experimental results were obtained from a hardware setup constructed in laboratory.Finally,for all of the surveyed control methods,the theoretical considerations,numerical simulations,and experimental measurements from a laboratory prototype are compared for different operating points.It is shown that the proposed twisting method presents an improvement in steady state error and settling time of output voltage during load changes.

A Novel Topology of Single-Phase AC-DC Integrated Boost-SEPIC (IBS) Converter Using Common Part Sharing Method (CPSM) for High Step-Up Applications

A novel topology of Integrated Boost-SEPIC (IBS) AC-DC converter using common part sharing method (CPSM) has been proposed in this paper. Conventional boost converters with bridge rectifier configuration are inefficient due to limited voltage step-up ratio which may not be applicable for high step-up applications as in the case of micro generators. The proposed IBS topology is based on the common part sharing method capable of operating both for positive and negative half cycle of the input signal. Result and simulation were conducted using PSIM environment. The proposed AC-DC IBS topology eliminates the requirement of bridge rectifier achieving high efficiency (about 99%), improved power factor (0.75, leading) and lower THD (about 38.8%) which is within IEEE standard.

Investigation on some key problems of large power AC-DC-AC converter

China is an important country in iron and steel industry.Power electronics converters are widely used.For the cold rolling mills of high speed,AC-DC-AC converters should be used.In the paper,the design and the control system of the large power three-level AC - DC - AC converter with IGCTs is investigated,and a back-to-back large power three-level AC - DC - AC converter with IGCTs has been got. With a series experiments,the performance of the converter is examined.The experiment result indicates the converter reaches the design requirement and it shows excellent performance.The converter system has been put into use safely.It is estimated that the AC - DC - AC converter system will be used in the drive systems for rolling mills in the near future.

LIMITATION OF SOFT-SWITCHING TECHNIQUE IN AC/DC POWER CONVERTER'S EFFICIENCY IMPROVEMENT

Soft-switching techniques are attractive to unity-power-factor AC/DC converter in the view of the size reduction and EMI suppression. A soft-switched boost PFC converter has been studied based on its topology analysis, PSIM simulation and circuit experiment. A special limitation of soft-switching techniques has been found in their AC/DC applications.

Simulations of the Performance of Maximum Power Point Tracking Algorithms Based on Experimental Data According to the Topologies of DC-DC Converters

Maximum Power Point Tracking (MPPT) algorithms are now widely used in PV systems independently of the weather conditions. In function of the application, a DC-DC converter topology is chosen without any previous performance test under normal weather conditions. This paper proposes an experimental evaluation of MPPT algorithms according to DC-DC converters topologies, under normal operation conditions. Four widely used MPPT algorithms i.e. Perturb and Observe (P & O), Hill Climbing (HC), Fixed step Increment of Conductance (INCF) and Variable step Increment of Conductance (INCV) are implemented using two topologies of DC-DC converters i.e. buck and boost converters. As input variables to the PV systems, recorded irradiance and temperature, and extracted photovoltaic parameters (ideality factor, series resistance and reverse saturation current) were used. The obtained results show that buck converter has a lot of power losses when controlled by each of the four MPPT algorithms. Meanwhile, boost converter presents a stable output power during the whole day. Once more, the results show that INCV algorithm has the best performance.

Efficient Single-Stage Bridgeless AC to DC Converter Using Grey Wolf Optimization

Bridgeless single-stage converters are used for efficient(alternative current)AC-(direct current)DC conversion.These converters control generators,likeelectromagnetic meso-and micro-scale generators with low voltage.Power factorcorrection helps increase the factor of the power supply.The main advantage ofthe power factor is it shapes the input current for increasing the real power of theAC supply.In this paper,a two-switch bridgeless rectifier topology is designedwith a power factor correction capability.For the proposed converter topologyto have good power quality parameters,the closed loop scheme,which uses thegrey wolf optimization(GWO)algorithm,is implemented.The successes ofGWO encourage this research to implement GWO in the topology.The performanceof the proposed topology is analyzed under different load conditions.Simulation is carried out using the MATLAB/Simulink environment,and theresults are compared with those of conventional(proportional integral derivative)PID and(particle swarm optimization)PSO controllers.To validate the simulation results,a 350-W hardware prototype is implemented,and the voltage ripple,efficiency,and power factor under different load conditions are analyzed and tabulated.The comparative study clearly indicates that the proposed convertertopology with a closed loop control scheme using the GWO algorithm improves the power factor to 0.9732 and reduces the voltage ripple to 0.12%with a conversion efficiency of 98.25%.

Power Factor Improvement of AC-DC Converter Based on Separately Excited DC Motor Using Passive Filter

In industries DC motor drives are very essential due to their high performance applications such as its reliability, ease of control, low cost and simplicity. And speed control of these motors is very easy due to power electronic AC-DC converters. These power electronic converters are with prominent low power factor and higher Total Harmonic Distortion (THD). These converters operate only for short time resulting non-sinusoidal waveform. This problem of harmonic distortion can be mitigated by reshaping the non-sinusoidal waveform to pure sine wave. Different wave shaping techniques have been developed by using different filters among which one is tuned passive filter. This paper proposed power factor improvement and harmonic mitigation of AC-DC converters based on separately excited DC motor using tuned passive filter. In this context experimental model is designed and results are analyzed by power quality analyzer.

一种面向储能系统的双向隔离型AC-DC矩阵变换器控制策略

为了满足网侧高电能质量以及储能元件安全可靠和长使用寿命的需求,本文针对双向隔离型AC-DC矩阵变换器提出了一套系统的控制策略,包括对系统的双闭环控制和变换器的后级单重移相调制方法。其中双闭环控制包含网侧电流内环控制和直流侧电流外环控制,调制方法中保持前后级电路间协调同步,前级电路采用双线电压调制方式,后级电路采用等比例移相调制方式。仿真和实验结果显示,变换器的网侧功率因数可达0.99,直流侧电压纹波在0.15%以内。直流侧电流指令突变时,电流跟踪速度快且无超调。因此,采用所提出的控制策略可以保证网侧电能质量高、直流侧具有良好的动静态特性。