A Novel T-Connected Autotransformer-Based 18-Pulse AC–DC Converter for Harmonic Mitigation in Adjustable-Speed Induction-Motor Drives

This paper presents the design, analysis, and development of a novel autotransformer-based 18-pulse AC-DC converter with reduced kilovoltampere rating, feeding vector-controlled induction-motor drives (VCIMDs) for power-quality improvement at the point of common coupling (PCC). The proposed autotransformer consists of only two single-phase transformers for its realization against three single-phase transformers required in other configurations. The proposed 18-pulse AC-DC converter is suitable for retrofit applications, where, presently, a six-pulse diode bridge rectifier is being used. A set of power-quality parameters, such as total harmonic distortion (THD) and crest factor of AC mains current, power factor, displacement factor, and distortion factor at AC mains, THD of supply voltage at PCC, and DC-bus-voltage ripple factor for a VCIMD fed from an 18-pulse AC-DC converter, are computed to observe its performance. The presented design technique provides flexibility to give an average DC output from the proposed converter, which is the same as that of a conventional three-phase diode bridge rectifier. However, it is also possible to step-up or step-down the output voltage as required. The effect of load variation on VCIMD is also studied to observe the effectiveness of the proposed harmonic mitigator. A laboratory prototype of the proposed autotransformer-based 18-pulse AC-DC converter is developed to validate the design and simulation model.     

A Novel Polygon Based 18-Pulse AC–DC Converter for Vector Controlled Induction Motor Drives

This paper presents a novel configuration of an autotransformer based 18-pulse ac-dc converter for improving the power quality at the point of common coupling (PCC) in variable frequency induction motor drives (VFIMDs). The polygon based connection of autotransformer for achieving 18-pulse rectification is utilized to result in reduction in rating of the magnetics. The design of the autotransformer is carried out for an 18-pulse ac-dc converter feeding a vector controlled induction motor drive (VCIMD). Moreover, the autotransformer design is modified for making it suitable for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. The effect of load variation on VCIMD is also studied and the performance of the proposed 18-pulse ac-dc converter is compared in terms of different power quality indices on both ac as well as dc side with other ac-dc converters. A laboratory prototype of the proposed autotransformer based 18-pulse ac-dc converter feeding a 10-hp induction motor drive is developed to verify the design and simulated results     

A single-switch AC-DC converter with power factor correction

A new single-stage, single-switch power factor correction converter with output electrical isolation is proposed in this paper. The topology of this converter is derived by combining a boost circuit and a forward circuit in one power stage. To improve the performance of the AC-DC converter (i.e., good power factor correction, low total harmonic distortion (THD) and low DC bus voltage), two bulk storage capacitors are adopted. Its excellent line regulation capability makes the converter suitable for universal input application. Due to its simplified power stage and control circuit, this converter presents a better efficiency, lower cost and higher reliability. Detailed steady state analysis and design procedure are presented. To verify the performance of the proposed converter, a design example along with P-simulation program with integrated circuit emphasis (PSPICE) simulation and experimental implementation are given. The measured power factor and efficiency are 99% and 87% at low line (i.e. 110 VAC) operation, and 95% and 81% at high line (i.e. 220 VAC) operation, respectively     

DC harmonic distortion minimization of thyristor converters underunbalanced voltage supply using asymmetrical firing angle

Noncharacteristic harmonics of significant magnitude are produced at the output and input terminals of phase-controlled power converters under unbalanced voltage supply conditions. The concept of switching functions has been proposed before to evaluate the harmonics produced by a phase-controlled six-pulse power converter under both balanced and unbalanced power supply conditions. This paper extends the switching-functions approach to establish analytical equations for the DC output voltage harmonics produced by 12-, 18-, and 24-pulse power converters. The problem is approached from the standpoint of symmetrical voltage components. The increase in distortion under unbalance is caused by the appearance of a second harmonic component. A method, based on an asymmetrical firing angle, to cancel the second harmonic at the power converter output under unbalanced voltage supply is also presented. Cancellation of the second harmonic improves power converter DC output voltage quality     

A new passive 28-step current shaper for three-phase rectification

A new passive 28-step current shaper for three-phase rectification is proposed in this paper. With a phase-shifting transformer on the AC side and six interphase transformers on the DC side, per-phase input current can be shaped into a 28-step sinusoidal waveform. The total harmonic distortion of AC input currents obtained is 6.53%, lower than one-half of that in a conventional 12-pulse converter. The transformer voltampere rating is also lowered down to one-fifth of that in a 12-pulse converter. A 2 kW experiment is performed to verify the proposed circuit.     

DC side harmonic reduction in rectifiers by direct ripplereinjection

A new technique for eliminating DC side harmonics in rectifiers is proposed, based on the direct reinjection of the voltage ripple in series with the DC line. The operation of the proposed scheme is analysed and provides experimental verification in a 12-pulse scaled down model of a converter     

A novel single-stage half-bridge AC-DC converter with high powerfactor

A new single-stage AC-DC power converter based on a half-bridge converter suitable for low-power applications is proposed. The proposed converter offers high power factor and direct conversion from the line voltage to an isolated DC output voltage. High power factor is achieved by adding a resonant circuit between the rectifying diodes and half-bridge leg. For soft switching, a half-bridge series-loaded resonant converter is adopted as a DC-DC converter part. A prototype is built and tested to show the validity of the proposed converter     

Unified constant-frequency integration control of active powerfilters-steady-state and dynamics

An active power filter (APF) is a device that is connected in parallel to and cancels the reactive and harmonic currents from a group of nonlinear loads so that the resulting total current drawn from the AC mains is sinusoidal. This paper presents a unified constant-frequency integration (UCI) APF control method based on one-cycle control. This method employs an integrator with reset as its core component to control the pulse width of an AC-DC converter so that its current draw is precisely opposite to the reactive and harmonic current draw of the nonlinear loads. In contrast to previously proposed methods, there is no need to generate a current reference for the control of the converter current, thus no need for a multiplier and no need to sense the AC line voltage, the APF current, or the nonlinear load current. Only one AC current sensor is used to sense the AC main current and one DC voltage sensor is used to sense the DC capacitor voltage. The control method features constant switching frequency operation, minimum reactive and harmonic current generation, and simple analog circuitry. It provides a low cost and high performance solution for power quality control. Steady-state and dynamic study is presented in this paper. Design example is given using a two-level AC-DC boost topology. A prototype was developed to demonstrate the performance of the proposed APF. This control method is generalized to control a family of converters that are suitable for APF applications. All findings are supported by experiments and simulation     

Quasi-multi-pulse voltage source converter design with two control degrees of freedom

In this article, the design details of a quasi-multi-pulse voltage source converter (VSC) switched at line frequency of 50 Hz are given in a step-by-step process. The proposed converter is comprised of four 12-pulse converter units, which is suitable for the simulation of single-/multi-converter flexible alternating current transmission system devices as well as high voltage direct current systems operating at the transmission level. The magnetic interface of the converter is originally designed with given all parameters for 100 MVA operation. The so-called two-angle control method is adopted to control the voltage magnitude and the phase angle of the converter independently. PSCAD simulation results verify both four-quadrant converter operation and closed-loop control of the converter operated as static synchronous compensator (STATCOM).     

A New Topology Pattern for AC-DC Mixed Microgrid

In order to realize the modular design of the microgrid, this paper proposed a new modular topology for the AC-DC mixed microgrid. In that topology, the AC microgrid unit and the DC microgrid unit were packaged together by the back-to-back converter. The battery-supercapacitor hybrid energy storage system was connected to the DC bus of back-to-back converter. By the reasonable design on the battery-supercapacitor hybrid system, the energy storage system could supply the rapid power and energy support for the microgrid spontaneously. The mathematical model and the control algorithm of that microgrid topology were studied. By the simulation analysis, it can be concluded that AC-DC mixed modular microgrid topology could operate steadily on both the grid-connected mode and the isolated mode. Furthermore, we can conclude by the simulation that the designed modular microgrid could operate uninterrupted when the microgrid topology switched from the grid-connected mode to the isolated mode. The seamless switching became the natural property for the modular microgrid. As a result, the modular microgrid topology can be considered as a usual power/load module to realize the friendly power interaction with the power grid.     

ITER极向场电源系统的设计与仿真

ITER极向场电源由两台三相桥式整流器通过平衡电抗器并联输出12脉波,额定电流45kA,额定电压2kV。文章提出电源运行方案为无环流与有环流运行相结合,可以实现四象限运行模式。通过Ansoft Simplorer仿真软件,建立了详细ITER主整流器模型,并设计其电压电流控制器,通过仿真验证了设计方案。     

矩阵整流器输入与输出滤波器特性的研究

矩阵整流器是一种真正的降压型四象限AC-DC变换器,可以用在各种三相电压供电的直流电源领域。鉴于矩阵整流器采用波形高频合成原理实现输入电压-输出电压的变换和输出电流-输入电流的变换,并非纯硅变换器,输入LC滤波器与输出LC滤波器的设计至关重要,并决定着整流器系统的功能、性能和可靠性。在理论分析矩阵整流器与电流源PWM整流器具有共同变换本质的基础上,采用电路DQ转换方法,建立输入LC滤波器-矩阵整流器-输出LC滤波器系统的DC等效电路,重点分析了DC特性高低对滤波器参数设计要求,进而给出设计原则和参数选择公式,并进行实验验证。     

矩阵变换器的间接空间矢量控制

矩阵变换器是一种新型的电力电子技术,具有能量可双向流通,可产生正弦输入电流和输出电压以及输入功率角可调等优点。文章基于矩阵变换器空间矢量调制法,分析虚拟整流器和逆变器的空间矢量调制,综合两个过程,得到一种直接的交-交变换器,利用MATLAB的仿真模块组建成矩阵变换器的仿真模型。仿真结果验证了空间矢量调制策略的有效性,矩阵变换器的优越性。     

Efficiency Comparison of Voltage-Source and Current-Source Drive Systems for Medium-Voltage Applications

This paper calculates and compares the efficiency and loss distribution in the three most popular state-of-the-art types of large motor drive systems: 1) current-source drive with active front-end rectifier; 2) current-source drive with 18-pulse thyristor rectifier; and 3) three-level voltage-source drive with 12-pulse/24-pulse diode rectifier. For converter systems with efficiencies better than 90%, it is suggested to calculate or measure the losses of all the components separately and add them up to calculate the total efficiency. A simple and accurate method of calculating switching losses for a current-source and voltage-source converter is proposed. Through the calculation and simulation of each loss factor such as switching losses, conduction losses, and snubber and filter losses, the three-level voltage-source drive system has been found to have the highest efficiency of 98.77% under the rated load of 1.6 MW.     

Single-stage three-phase buck-boost type AC-DC converter with highpower factor

A new control process for single-stage three-phase buck-boost type AC-DC power converters with high power factor, sinusoidal input currents and adjustable output voltage is proposed. This converter allows variable power factor operation, but this work focus on achieving unity power factor. The proposed control method includes a fast and robust input current controller based on a vectorial sliding mode approach. The active nonlinear control strategy applied to this power converter, allows high quality input currents. Given the comparatively slow dynamics of the DC output voltage, a proportional integral (PI) controller is adopted to regulate the converter output voltage. The voltage controller modulates the amplitudes of the current references, which are sinusoidal and synchronous with the input source voltages. Experimental results from a laboratory prototype show the high power factor and the low harmonic distortion characteristics of the circuit     

An improved automotive power distribution system using nonlinearresonant switch converters

An improved automotive electrical system is proposed in which the generator is a high-efficiency AC machine connected to the battery by an AC-DC converter. The electrical loads are isolated from the battery by a DC-DC converter. This will allow gradual conversion to higher battery voltage, regulation of DC distribution voltage, and multiple distribution voltage levels. In the low-voltage, high-current, high-temperature environment of the automobile, in addition to packaging and thermal management, a major problem is the switching loss caused by leakage, package, and other parasitic inductances. The nonlinear resonant switch can remove this source of loss, achieving zero current switching without sacrificing conduction loss or MOSFET switch utilization. For the nonlinear resonant switch in a 1.5 kW load converter application, the upper limit is approximately 20 nH. Hence, device interconnections have low inductance, and MOSFET package inductances are taken into account. A low-voltage, high-current nonlinear resonant switch converter operating at 700 kHz an producing 600 W is described     

Single-inductor dual-output (SIDO) DC–DC converters for minimized cross regulation and high efficiency in soc supplying systems

A compact size and high efficiency single-inductor dual-output (SIDO) DC–DC converter is proposed. The proposed SIDO DC–DC converter not only provides dual output sources (one buck and one boost outputs) but also has minimized cross regulation without using any external compensation components. Generally speaking, it is important to minimize the number of components and footprint area in the design of SIDO converters. However, usually large external compensation resistors and capacitors are required to stabilize DC–DC converters. Importantly, our proposed hysteresis mode operation can effectively avoid the oscillation problems that may exist in many SIMO designs. Furthermore, the dynamic dc current level like that in the continuous conduction mode (CCM) operation can make the proposed SIDO DC–DC converter achieve high conversion efficiency at light loads owing to small conduction loss. Experimental results show a high efficiency from 85% at light loads to 94% at heavy loads.     

Design of Novel Dual Input DC–DC Converter for Energy Harvesting System in IoT Sensor Nodes

A new DC–DC converter capable of working with more than one source for harvesting energy from clean energy sources is proposed. Key features of this proposed converter are single inductor and reduced total number of components. In addition the converter has reduced stresses and power losses. Dual input and output modes, with its operation and steady-state analysis are discussed. Comparative study of the topologies given in literature with a proposed topology for parameters considered like the number of components and voltage gain is presented. Compatibility of the proposed converter is proved with reduced losses using loss distribution analysis of the converter and it is more reliable for energy system in telecom applications, which is validated using reliability analysis, is also highlighted. Finally, to substantiate the working of the non isolated DC–DC converter considered the test results are presented.

     

Analysis of high voltage step-up nonisolated DC–DC boost converters

A high voltage step-up nonisolated DC–DC converter based on coupled inductors suitable to photovoltaic (PV) systems applications is proposed in this paper. Considering that numerous approaches exist to extend the voltage conversion ratio of DC–DC converters that do not use transformers, a detailed comparison is also presented among the proposed converter and other popular topologies such as the conventional boost converter and the quadratic boost converter. The qualitative analysis of the coupled-inductor-based topology is developed so that a design procedure can be obtained, from which an experimental prototype is implemented to validate the theoretical assumptions.     

A novel single-phase soft-switched rectifier with unity power factor and minimal component count

A novel, single-phase soft-switched boost AC-DC rectifier that operates with power-factor correction is proposed in this paper. The rectifier is a modified boost voltage-doubler converter well suited for low-line-input applications. It operates with fewer conduction losses and half the switch voltage stresses found in a standard boost converter. Soft switching in the converter is achieved using a zero-current-switching quasi-resonant technique. In the paper, the converter and its modes of operation are discussed and analyzed. The method of control is explained, and a design procedure is derived and then demonstrated with an example. The feasibility of the converter is shown with experimental results obtained from a prototype.