A New Simplified Multilevel Inverter Topology for DC–AC Conversion

Multilevel converters offer high power capability, associated with lower output harmonics and lower commutation losses. Their main disadvantage is their complexity, requiring a great number of power devices and passive components, and a rather complex control circuitry. This work reports a new multilevel inverter topology using an H-bridge output stage with a bidirectional auxiliary switch. The new topology produces a significant reduction in the number of power devices and capacitors required to implement a multilevel output. The new topology is used in the design of a five-level inverter; only five controlled switches, eight diodes, and two capacitors are required to implement the five-level inverter using the proposed topology. The new topology achieves a 37.5% reduction in the number of main power switches required (five in the new against eight in any of the other three configurations) and uses no more diodes or capacitors that the second best topology in the literature, the Asymmetric Cascade configuration. Additionally, the dedicated modulator circuit required for multilevel inverter operation is implemented using a FPGA circuit, reducing overall system cost and complexity. Theoretical predictions are validated using simulation in SPICE, and satisfactory circuit operation is proved with experimental tests performed on a laboratory prototype.     

Maximum Power Point Tracking in a One-Cycle-Controlled Single-Stage Photovoltaic Inverter

In this paper, the design of the one-cycle controller of a single-stage inverter for photovoltaic applications is carried out by means of a multiobjective strategy to optimize inverter performance at both high and low insolation levels. Design constraints that account for different weather conditions are adopted. The optimization algorithm also provides useful information concerning the system sensitivity with respect to each of the controller parameters. This allows the design of a maximum power point tracking perturb and observe controller that significantly improves inverter performance. Experimental measurements confirm the predictions of theoretical and simulation results.     

Redundancy optimization of static series-parallel reliabilitymodels under uncertainty

This paper extends the classical model of Ushakov on redundancy optimization of series-parallel static coherent reliability systems with uncertainty in system parameters. Their objective function represents the total capacity of a series-parallel static system, while the decision parameters are the nominal capacity and the availability of the elements. They obtain explicit expressions (both analytic and via efficient simulation) for the constraint of the program, viz, for the Cdf of the system total capacity and then show that the extended program is convex mixed-integer. Depending on whether the objective function and the associated constraints are analytically available or not, they suggest using deterministic and stochastic (simulation) optimization approaches, respectively. The last case is associated with likelihood ratios (change of probability measure). A genetic algorithm for finding the optimal redundancy is developed and supporting numerical results are presented     

Numerically efficient optimal design of cosine-modulated filter banks with peak-constrained least-squares behavior

Several current applications related to signal compression and representation and high-speed transmission require very selective filter banks/transmultiplexers. A possible solution is to employ the cosine-modulated filter banks/transmultiplexers (CMFBTs) where the prototype filters satisfy demanding constraints with respect to both the total stopband energy and maximum stopband ripple. This work proposes an efficient procedure to design nearly-perfect reconstruction CMFBT prototype filters with peak-constrained least-squares characteristics using a modified weighted least-squares algorithm. Substantial flexibility is added in the design of the magnitude response of the prototype filter, ranging from minimum stopband energy to minimum stopband ripple, which may be required in many applications. Some constraints are imposed to the CMFBTs in order to control the direct transfer and aliasing distortion functions, related to the intercarrier and intersymbol interferences. Algebraic simplifications are also provided on the overall objective function and associated constraints, leading to substantial reduction on the computational burden of the optimization process. The procedure is proven to be very powerful in designing CMFBT systems satisfying multiple constraints as indicated by numerical examples.     

RF integrated inductor modeling and its application to optimization-based design

In this paper an optimization-based approach for the design of RF integrated inductors is addressed. For the characterisation of the inductor behaviour the double ??-model is used. The use of this model is twofold. On one hand it enables the generation of the inductor characterisation in a few seconds. On the other hand its integration into the optimization procedure is straightforward. For the evaluation of the model element values analytical expressions based on technology parameters as well as on the device geometric characteristics are used. The use of a technology-based methodology for the evaluation of the model parameters grants the adaptability of the model to any technology. The inductor analytical characterization is integrated into an optimization-based tool for the automatic design of RF integrated inductors. This tool uses a modified genetic algorithm (MGA) optimization procedure, which has proved its validation in previous work. Due to the design parameter constraints nature as well as the topology constraints, discrete variables optimization techniques are used. The accuracy of the results is checked against a non-commercial software.     

The coupled inductor filter: analysis and design for AC systems

Coupled inductors have been used in specific DC-to-DC converters to provide ripple-current steering. Switching ripple currents may be preferentially directed away from a source or a load. This paper shows that general purpose filters can be produced using coupled inductors and capacitors. These are equally applicable to AC and DC applications. A transfer function is developed for a filter based on a coupled inductor and capacitor. The resulting filter is third order and is significantly more effective than an inductor. The sensitivity of the filter to errors in the turns ratio is examined. Finally, results from an experimental power factor correction circuit are presented     

Analysis and Design Optimization of Diode Front-End Rectifier Passive Components for Voltage Source Inverters

This paper presents a systematic design optimization approach for inductors and capacitors in diode front-end rectifiers for voltage source inverters. Analytical relationships between various design variables, operating conditions, and performance and physical constraints are established under nominal, overload, and inrush conditions. A new method to analytically calculate the inrush current is developed considering the nonlinear characteristics of the inductor core materials. A design optimization program based on the established analytical relationships and a genetic algorithm is developed. Examples show that the optimization process can lead to a smaller/lower cost inductor and capacitor design. Experiments are conducted to verify key analytical relationships and the optimized design.      

Integrated RF components in a SiGe bipolar technology

Several components for the design of monolithic RF transceivers on silicon substrates are presented and discussed. They are integrated in a manufacturable analog SiGe bipolar technology without any significant process alterations. Spiral inductors have inductance values in the range of ~0.15-80 nH with typical maximum quality-factors (Q_max ) of 3-20. The Q_max's are highest if the doping concentration under the inductors is kept minimum. It is shown that the inductor area is an important parameter toward optimization of Q_max at a given frequency. The inductors can be represented in circuit design by a simple lumped-element model. MOS capacitors have Q's of ~20/f (GHz)/C(pF), metal-insulator-metal (MIM) capacitors reach Q's of ~80/f (GHz)/C(pF), and varactors with a 40% tuning range have Q's of ~70/f (GHz)/C(pF). Those devices can he modeled by using lumped elements as well. The accuracy of the modeling is verified by comparing the simulated and the measured high-frequency characteristics of a fully integrated, passive-element bandpass filter     

Switching Characterization of Cascaded Multilevel-Inverter-Controlled Systems

In this paper, the method of triangular carrier switching control of two-level inverters is extended to cascaded multilevel inverters using phase-shifted multicarrier unipolar pulsewidth modulation (PWM). The condition for smooth modulation is obtained using the Bessel's function representation of the PWM output and the switching condition of the multilevel-inverter-controlled system. A method is proposed for the determination of the minimum amplitude of the triangular carrier for smooth modulation at fixed switching frequency. It is shown that the multilevel modulation based on the phase-shifted carriers significantly reduces the ripple magnitude in the switching function and allows the use of a smaller carrier amplitude under closed loop. This increases the forward gain and, hence, improves the tracking characteristics. The proposed cascaded multilevel inverter control is implemented for the operation of a distribution static compensator (DSTATCOM) in the voltage control mode. The experimental verification of the theoretical and simulation results is provided through a field-programmable gate array (FPGA) based control of a laboratory model of a single-phase DSTATCOM.     

A fuzzy logic based approach for parametric optimization of MOS operational amplifiers

In this work, we have used the concept of fuzzy logic to build a CAD tool for the parametric optimization of MOS operational amplifiers (op-amps). In order to capture human intentions to express the requirements for a particular application, e.g. minimize power, maximize gain, etc., each of the performance specifications of a given topology is assigned a membership function to measure the degree of fulfillment of the objectives and the constraints. A number of objectives are optimized simultaneously by assigning weights to each of them representing their relative importance, and then by clustering them to form the objective function, which is solved by Powell's direct search algorithm. After optimization, the program creates a SPICE netlist of the circuit topology for the verification of the design. Initially, this approach was used for parametric optimization of simple bipolar and MOS circuits, e.g. current mirrors, gain stages, differential amplifiers, etc. Encouraged by these results, it was applied to much more complex blocks, such as op-amps. The design results obtained from our optimization program showed an excellent agreement with those obtained from SPICE simulation for the op-amp topologies considered in this work.     

连铸坯视觉定重线结构光平面调整方法研究

鉴于传统三电平逆变电路存在谐波含量高的缺点, 在分析模块化多电平换流器(MMC)工作原理的基础上, 提出使用模块化多电平电路实现光伏并网逆变功能, 采用微分-跟踪器法实现光伏阵列最大功率点跟踪(MPPT)及逆变器PQ解耦控制, 实现了光伏系统以单位功率因数并网。在PSCAD中建立光伏并网系统动态仿真模型, 仿真结果表明, 所建模型具有开关损耗低、谐波量小的优点, 验证了所提方法的正确性和可行性。     

A novel heuristic simulation‐optimization method for critical infrastructure in smart transportation systems

A simulation‐based optimization is a decision‐making tool that helps in identifying an optimal solution or a design for a system. An optimal solution and design are more meaningful if they enhance a smart system with sensing, computing, and monitoring capabilities with improved efficiency. In situations where testing the physical prototype is difficult, a computer‐based simulation and its optimization processes are helpful in providing low‐cost, speedy and lesser time‐ and resource‐consuming solutions. In this work, a comparative analysis of the proposed heuristic simulation‐optimization method for improving quality‐of‐service (QoS) is performed with generalized integrated optimization (a simulation approach based on genetic algorithms with evolutionary simulated annealing strategies having simplex search). In the proposed approach, feature‐based local (group) and global (network) formation processes are integrated with Internet of Things (IoT) based solutions for finding the optimum performance. Further, the simulated annealing method is applied for finding local and global optimum values supporting minimum traffic conditions. A small‐scale network of 50 to 100 nodes shows that genetic simulation optimization with multicriteria and multidimensional features performs better as compared to other simulation‐optimization approaches. Further, a minimum of 3.4% and a maximum of 16.2% improvement is observed in faster route identification for small‐scale IoT networks with simulation‐optimization constraints integrated model as compared to the traditional method. The proposed approach improves the critical infrastructure monitoring performance as compared to the generalized simulation‐optimization process in complex transportation scenarios with heavy traffic conditions. The communicational and computational‐cost complexities are least for the proposed approach.     

Diode-clamped multilevel converters: a practicable way to balance DC-link voltages

The converter topologies identified as diode-clamped multilevel (DCM) or, equivalently, as multipoint clamped (MPC), are rarely used in industrial applications, owing to some serious drawbacks involving mainly the stacked bank of capacitors that constitutes their multilevel DC link. The balance of the capacitor voltages is not possible in all operating conditions when the MPC converter possesses a passive front end. On the other hand, in AC/DC/AC power conversion, the back-to-back connection of a multilevel rectifier with a multilevel inverter allows the balance of the DC-link capacitor voltages and, at the same time, it offers the power-factor-correction capability at the mains AC input. An effective balancing strategy suitable for MPC conversion systems with any number of DC-link capacitors is presented here. The strategy has been carefully studied to optimize the converter efficiency. The simulation results related to a high-power conversion system (up to 10 MW) characterized by four intermediate DC-link capacitors are shown.     

Generation of surrogate models of Pareto-optimal performance trade-offs of planar inductors

Systematic design methodologies for wireless transceivers require an efficient design of integrated inductors. Early availability of feasible trade-offs between inductance, quality factor, self-resonance frequency and area, is a key enabler towards the improvement of such design methodologies. This paper introduces such an approach in two steps. First, a Pareto-optimal performance front of integrated inductors is generated by embedding a performance evaluator into a multi-objective optimization tool. Then, starting from the optimal front samples, a surrogate model of the performance front is obtained. Experimental results in a 0.35-μm CMOS technology are provided.     

IPOSIM-IGBT仿真工具在变频器设计中的应用

IPOSIM是一个功能强大的IGBT仿真工具，能够计算IGBT和续流二极管的开关损耗和导通损耗，仿真其温度分布和结温纹波。本文简单介绍了计算IGBT损耗的基本理论和相关热分析模型以及应用该工具的相关原则。同时，又介绍了了一些最新的功能，如能够比较不同IGBT模块在不同开关频率条件下输出电流能力的大小；自定义负荷能够完成在给定的变频器负荷条件下IGBT的仿真分析。最后给出了一些应用该工具的仿真技巧和实例。     

Filter design method for a PWM feedback inverter system

A novel approach to filter design for a closed-loop, pulse-width-modulated (PWM) DC-AC inverter system driving an RL load is investigated. The system has a rectangular hysteresis in the forward path and it is closed by current feedback. When it is excited by a sinusoidal input reference, it provides square pulses that produce a nearly sinusoidal current in the load. Using a describing function technique, design equations for the filter are derived. The data needed for the filter evaluation are the amplitude of current ripple and the frequency of square pulses delivered by the power bridge. System simulation and experimental results show that the design of the filter can be based on the method proposed and that the filter can provide a significant reduction of current ripple, or otherwise a significant reduction of switching frequency     

Switching frequency imposition and ripple reduction in DTC drivesby using a multilevel converter

A new strategy for direct torque control with imposed switching frequency (DiCoIF) is proposed. This strategy was specially designed to operate with a multicell (flying capacitors) inverter with any number of levels, which means it can also be used for standard two-level inverters. This approach combines the well known advantages of the multicell. inverter with those of a direct torque controlled (DTC) based strategy. It is shown that the multicell topology presents enough degrees of freedom to control both torque and flux with very low ripple and high dynamics on one hand, and to impose the switching frequency and the capacitors voltage balance on the other hand. Experimental and simulation results, obtained with a standard two-level inverter and with a four-level multicell inverter, are presented and discussed. Finally, a comparative analysis either with the classical DTC and field oriented techniques is carried out     

Control of Three-Phase, Four-Wire PWM Rectifier

This paper presents the analysis, design, and control of a four-wire rectifier system using split-capacitor topology. The proposed controller does not require any complex transformation or input voltage sensing. A detailed analysis of the distortions in the line and the neutral currents is presented. It is shown that the single-carrier-based, conventional sine-triangle PWM (CSPWM) scheme results in a peak-to-peak neutral current ripple, which is greater than the peak-to-peak ripple of any of the line currents. Also, for the same operating condition, the distortions in the line and the neutral currents increase considerably, when a three-limb boost inductor is used instead of three single-phase inductors. A three-carrier-based SPWM scheme is proposed in this paper. Compared to CSPWM, the proposed scheme significantly reduces the neutral current ripple when three single-phase inductors are used, and reduces both line and neutral current ripples when a three-limb inductor is used. The control scheme is verified through Matlab simulation. It is implemented on an field-programmable gate-array (FPGA)-based digital controller and tested on a prototype. Simulation and experimental results are presented.     

基于优化设计线性矩阵不等式的三相DC-AC变换器鲁棒性跟踪控制

本文介绍了一种优化设计的鲁棒性控制技术,针对逆变系统中可能存在的不确定性,如滤波电感值,滤波电容值,通过状态反馈和整合跟踪错误,优化设计线性矩阵不等式（LMI）,获得状态估计器最佳增益,使收敛速度最大化,在同步dq坐标系中加以描述,采用空间矢量调制技术实施。仿真结果和实验测试证明该优化控制方法具有良好的跟踪性能。     

Analog circuit design optimization based on symbolic simulation andsimulated annealing

A methodology for the automatic design optimization of analog integrated circuits is presented. A non-fixed-topology approach is realized by combining the optimization program OPTIMAN with the symbolic simulator ISAAC. After selecting a circuit topology, the user invokes ISAAC to model the circuit. ISAAC generates both exact and simplified analytic expressions, describing the circuit's behavior. The model is then passed to the design optimization program OPTIMAN. This program is based on a generalized formulation of the analog design problem. For the selected topology, the independent design variables are automatically extracted and OPTIMAN sizes all elements to satisfy the performance constraints, thereby optimizing a user-defined design objective. The global optimization method used on the analytic circuit models is simulated annealing. Practical examples show that OPTIMAN quickly designs analog circuits, closely meeting the specifications, and that it is a flexible and reliable design and exploration tool