Application of improved firefly algorithm for programmed PWM in multilevel inverter with adjustable DC sources

Programmed pulse width modulation is an optimized pulse width modulation which is particularly applicable for high-power applications where the power losses must be kept below firm limits. Based on the offline estimation, it is capable of pre programming the harmonic profile of the output waveform over a range of modulation indices by eliminating some lower order harmonics. In this paper, improved firefly algorithm (FA) is applied to determine the optimum switching angles for the 11- level cascaded H bridge multilevel inverter (MLI) with adjustable DC sources in order to eliminate pre specified lower order harmonics and to achieve the desired fundamental voltage. Though number of optimization algorithms is available for the estimation of switching angles, Firefly algorithm takes least computation time and surpasses all other 11 metaheuristic Algorithms. The algorithm and the model are developed using MATLAB and the validity of the simulation is confirmed by an experimental setup using FPGA Spartan 6A DSP. Results are compared with the results obtained using particle swarm optimization (PSO) and artificial bee colony algorithm (ABCA) and it is proved that the proposed method offers reduced total harmonic distortion (THD) with less computation period.     

串联H桥多电平逆变器特定谐波控制组合法

针对串联H桥多电平逆变器输出阶梯电压波形中存在低频谐波的问题,提出了一种特定谐波控制组合法。该方法以梯形波调制为基础,利用等面积法原理和谐波注入组合法,通过简单的三角公式递推计算获得实现特定谐波消除的开关导通角,并对开关导通角进行优化,从而实现谐波抑制。以三相九电平串联H桥逆变器为例,进行了仿真和实验,结果验证了该方法的可行性和有效性。     

Design of output filter for inverters using fuzzy logic

This paper proposes a design method to improve the harmonic of output voltage of a single phase inverter with an L-C output filter using fuzzy logic controller (FLC). In practice, the harmonic characteristics of circuits are complicated and entangled. There are two kinds of harmonic sources that cause inverter output voltage waveform distortion: One is the PWM switching of inverter and the other is the nonlinear characteristics of the load. In general, PI feedback control by coefficient diagram method (CDM) is used to design the output voltage filter. The relation between the L-C value and the system time constant are described with the closed form and the filter values must be calculated repeatedly to satisfy the prescribed voltage total harmonic distortion (THD) of the system. Therefore, the MATLAB Fuzzy Logic Toolbox for the fuzzy logic control algorithm is proposed. The L-C value of the filter can be set to a fixed range in the nonlinear characteristic of the practical condition, to improve the harmonic of output voltage more effectively and to avoid repeated calculation.     

An application of PSO technique for harmonic elimination in a PWM inverter

Harmonic elimination problem in PWM inverter is treated as an optimization problem and solved using particle swarm optimization (PSO) technique. The derived equation for computation of total harmonic distortion (THD) of the output voltage of PWM inverter is used as the objective function in the PSO algorithm. The objective function is minimized to contribute the minimum THD in the voltage waveform and the corresponding switching angles are computed. The method is applied to investigate the switching patterns of both unipolar and bipolar case. While minimizing the objective function, the individual selected harmonics like 5th, 7th, 11th and 13th can be controlled within the allowable limits by incorporating the constraints in the PSO algorithm. The results of the unipolar case using five switching angles are compared with that of a recently reported work and it is observed that the proposed method is effective in reducing the voltage THD in a wide range of modulation index. The simulated results are also validated through suitable experiments.     

Performance Enhancement of PV Based Boost Cascaded Fifteen Level Inverter for AC Loads

In this research work, single-stage fifteen levels cascaded DC-interface converter (CDDCLC) is proposed for sun arranged photovoltaic technology (PV) applications. The proposed geography is joined with help DC chopper and H-associate inverter to upgrade the power converter to accomplish the diminished harmonic profile. In assessment with the customary inverter structures, the proposed system is used with diminished voltage stress, decreased switch count and DC source tally. The proposed research work with cascaded DC link converter design requires three DC sources for combining fifteen-level AC output. This investigation structure switching technique is phase opposition and disposition pulse width modulation technique (POPD) which results in improved quality of obtained output AC power with 6.73% THD and also determinedly recommended for power converters used in UPS and drive applications since it is extremely affordable. A simulation and prototype model of fifteen-level CDDCLC system is deployed and its performance is analyzed for various operating conditions.     

基于AT波形重构方法的逆变技术研究

在中高压变频驱动系统中,通常采用多重化和多电平逆变技术,以降低逆变电压的谐波。本文提出了另外一种降低偕波的逆变技术,构成了一种基于波形童构的具有辅助变压器的逆变器拓扑。在介绍其基本工作原理的基础卜,分析了辅助变压器变比和逆变器导电制与输出电压总谐波畸变率之间的关系,并将该逆变器与几种常见的逆变器从直流电源利用率、总谐波畸变率等方面进行了比较分析。协真实验研究结果表明,对所提出的逆变器采用多重化技术,同样具有较女『的性能。     

Bacterial foraging optimization and adaptive version for economically optimum sitting,sizing and harmonic tuning orders setting of LC harmonic passive power filters in radial distribution systems with linear and nonlinear loads

This paper presents bacterial foraging optimization (BFO) algorithm and its adaptive version to optimize the planning of passive harmonic filters (PHFs).The important problem of using PHFs is determining location, size and harmonic tuning orders of them, which is reach standard levels of harmonic distortion with applying minimum cost of passive filters.In this study to optimize the PHFs location, size and setting the harmonic tuning orders in the distribution system, considered objective function includes the reduction of power loss and investment cost of PHFs. At the same time, constraints include voltage limits, number/size of installed PHFs, limit candidate buses for PHFs installation and the voltage total harmonic distortion (THDv) in all buses. The harmonic levels of system are obtained by current injections method and the load flow is solved by the iterative method of power sum, which is suitable for the accuracy requirements of this type of study. It is shown that through an economical placement and sizing of PHFs the total voltage harmonic distortion and active power loss could be minimized simultaneously.The considered objective function is of highly non-convex manner, and also has several constraints. On the other hand due to significant computational time reduction and faster convergence of BFO in comparison with other intelligent optimization approach such as genetic algorithm (GA), particle swarm optimization (PSO) and artificial bee colony (ABC) the simple version of BFO has been implemented. Of course other versions of BFO such as Adaptive BFO and combination of BFO with other method due to complexity of harmonic optimization problem have not considered in this research.The simulation results for small scale test system with 10 buses, showed the significant computational time reduction and faster convergence of BFO in comparison with GA, PSO and ABC. Therefore in large scale radial system with 34 buses, the proposed method is solved using BFO.The simulation results for a 10-bus system as a small scale and 34-bus radial system as a large scale show that the proposed method is efficient for solving the presented problem.     

矿用级联型高压变频器母线电容控制策略

针对H桥逆变器级联型高压变频器母线电容体积大的问题,提出了一种在基波调制信号中注入三次谐波以减小母线电容容量的控制策略。在总调制比不变的情况下,三次谐波注入等价于将母线电容电流的低次谐波部分转化为高次谐波,从而减小了母线电压纹波。推导了母线电容电流谐波含量与三次谐波注入量的关系,并给出了不同功率因数下三次谐波最大注入量的表达式。Matlab/Simulink仿真结果表明,在功率因数为0.85的典型负载下,采用本文控制策略可将母线电容容量降低24.2%,验证了该控制策略的可行性和有效性。     

级联变频器输出性能与载波移相量关系研究

载波移相PWM(CPS-SPWM)技术应用于级联型多电平变频器时,可在较低器件开关频率下实现较高等效开关频率的效果,从而改善其输出性能。目前载波移相量存在2π/N和π/N两种方式,且对不同级联数目的变频器输出有不同影响。为此,以载波移相技术的理论分析为切入点,研究了H桥级联型变频器输出性能与载波移相量的关系,2π/N移相方式对应的输出电压电平数在级联数是奇数情况下为2N+1,偶数情况下为N+1。而π/N移相方式不论级联数目奇、偶,对应的输出电压电平数均为2N+1。通过建立仿真模型及搭建实验平台加以验证,根据实验结果从谐波分析角度得出,π/N较之2π/N移相方式具有明显优越性及良好的谐波特性,目前π/N移相方式已成功应用于某水泥公司窑头风机变频系统并取得良好经济效益。     

改进型有源滤波器滞环电流控制方法

并联有源滤波器的变环宽滞环电流控制方法可根据电流幅值的变化实时调整滞环宽度,在保证参考电流跟踪精度的前提下,有效控制了逆变器的开关频率。对传统的变环宽滞环电流控制方法进行改进:增加环宽微调环节,当逆变器开关频率较低时,给已计算出的环宽值加入一个负的微调量,使环宽值减小。Matlab仿真结果表明,采用改进型变环宽滞环电流控制方法对并联有源滤波器谐波电流进行跟踪补偿时,系统总谐波畸变率为1.80%,小于采用传统变环宽滞环电流控制方法时的总谐波畸变率,且逆变器实际开关频率更加接近设定值。     

一种改进的混合级联多电平逆变器研究

文章以实际功率器件的耐压值为基础,采用增加低压单元的混合级联拓扑,辅以优化的PWM算法,设计出了适用中高压场合的多电平逆变器方案。改进的混合级联多电平逆变器不但输出波形质量好,而且有效地解决了倒灌电流的问题。     

级联多电平逆变器载波移相调制法的优化研究

针对传统级联高压变频器载波移相调制方法存在开关损耗大、直流电压利用率低等问题,及载波移相与矢量控制相结合的调制方法存在计算量大、计算繁琐、不易实现的问题,提出了级联多电平逆变器的优化控制方法——调制信号叠加零序分量法和两相控制法。该方法采用基于控制自由度组合的思想,通过向调制波中注入零序分量、直流分量等自由度来提高直流电压利用率、减小开关损耗。仿真结果验证了该方法的可行性。     

一种改进的谐波电流检测方法

针对传统的ip-iq谐波电流检测方法采用锁相环虽然能得到三相电流的基频和初相角,但当电网电压发生畸变时则存在检测精度较低、电路复杂的问题,提出了一种改进的无锁相环的谐波电流检测方法;详细分析了当电网电压发生畸变时,在三相电流对称和不对称的情况下该改进方法的检测原理,并给出了该改进方法应用于单相电路谐波电流检测的实现。实验结果表明,该改进方法能够准确、实时地检测谐波电流,且算法简单。     

Simulation modelling and analysis of modular cascaded multilevel converter based shunt hybrid active power filter for large scale photovoltaic system interconnection

Modular multilevel inverters are promising candidates for next generation of efficient, robust and reliable inverters in large scale photovoltaic system. A modular cascaded multilevel inverter based shunt hybrid active power filter (SHAPF) for three phase grid-connected large scale PV systems is represented in this paper. The main contribution of this paper is to model and control of grid interfaced large scale photovoltaic system with embedded hybrid active power filter functions. In proposed system, the features of hybrid active power filter have been amalgamated in the control circuit of the voltage controlled voltage source inverter interfacing the photovoltaic system to the grid. As a result, the same inverter part of SHAPF is utilized to inject power generated from photovoltaic source to the grid and also to act as hybrid active power filter to compensate harmonics and reactive power demand. With using compensation ability, the grid currents are sinusoidal and in phase with grid voltages. The whole system is modeled in PSCAD/EMTDC. The simulation results are demonstrated to verify the operation and the control system of the proposed system.     

Design and implementation of cascaded H-Bridge multilevel inverter using FPGA with multiple carrier phase disposition modulation scheme

The paper deals with design of Cascaded H-Bridge Multilevel Inverter (CHB-MLI) with separate DC source to each inverter using multiple carrier Phase Disposition PWM such as symmetric disposition, phase opposition disposition and alternative phase opposition disposition to reduce the Total Harmonic Distortion (THD) and to improve the power quality of the supply voltage and current. In early days, the multilevel inverters are controlled with high frequency PWM method. This is not suitable for high power applications due to the high switching losses. With the help of multiple carrier PWM switching losses in the inverter circuit are reduced, so it can be used for high switchi ng frequency applications. The simulation of proposed system is developed using MATLAB Simulink software. The Performance simulation results are validated through experimental test setup using SPARTAN - 6 FPGA. Simulation results and effectiveness of the proposed method is proved and validated by experimental data.     

Impact of wind farms on disturbance detection and classification in distributed generation using modified Adaline network and an adaptive neuro-fuzzy information system

A new disturbance detection and classification technique based on modified Adaline and adaptive neuro-fuzzy information system (ANFIS) is proposed for a distributed generation system comprising a wind power generating system (DFIG) and a photovoltaic array. The proposed technique is based on a fast Gauss–Newton parameter updating rule rather than the conventional Widrow–Hoff delta rule for the Adaline network. The voltage and current signals near the target distributed generation (DG), particularly the DFIG, whose speed varies from minimum to the maximum cut-off speed, are processed through the modified Adaline network to yield the features like the negative sequence power, harmonic amplification factor (HAF), total harmonic distortion (THD), etc. These features are then used as training sets for the ANFIS, which employs a gradient descent algorithm to update its parameters. The proposed technique distinguishes the islanding condition of the distributed generation system with some other disturbances, such as switching faults, capacitor bank switching, voltage swell, voltage sag, distorted grid voltage, unbalanced load switching, etc. which are referred to as non-islanding cases in this paper.     

一种新型的并联型单相有源电力滤波器

通过分析并联型有源电力滤波器的工作原理和系统结构,本文提出一种新型的电流闭环预测控制策略,相比于传统的PI控制、滞环控制和预测控制算法,该预测策略能减小计算量,并降低模型的复杂度。同时,谐波电流检测电路采用单相电流延迟60°构造三相电流d-q变换法,获取逆变主电路的参考电流。该滤波系统还引入PI外环以稳定直流侧的电容电压。最后,采用S imu link的电力系统分析模块进行仿真。结果表明,该滤波系统可有效检测高次谐波分量,迅速补偿谐波电流,同理论分析一致。     

Using passive filters to minimize torque pulsations and noises in surface PMSM derived field oriented control

This paper describes a new dissipative passive filter system to minimize torque pulsation and current harmonic noises in surface PMSM when derived with field oriented control algorithm. The passive filter system consists of complex dissipative filter cascaded by low pass filter. The complex filter has two setting frequency points, one at inverter switching frequency and the other at some average selected frequency point. The filter system is affecting the inverter switching frequency in such a way to decrease stress on the inverter switching elements and reducing the severe of dv/dt on the motor. The filter system uses series dissipative elements to assist in reshaping of the applied voltage waveform in order to provide almost semi-sinusoidal voltage to the motor windings. The simulation results show that the proposed filter system is effectively minimized torque pulsations and harmonic noises in surface PMSM.     

改进型单位功率因数谐波检测算法在三相并联型APF中的应用研究

为了降低电网电压不对称或畸变对UPF谐波检测算法的影响,通过引入锁相环电路的改进型UPF谐波检测算法产生基波正序电压,对有功功率进行修正,抑制了电压畸变的影响,同时提高了检测的实时性。在Matlab上对补偿前后电源侧电流波形进行对比研究,验证了改进型UPF谐波检测算法的可行性。实验结果表明,采用改进算法后,电源侧电流谐波成分中谐波含量最高的5次谐波含量由补偿前的22.8%降低为补偿后的8.1%,负载电流主要次谐波成分得到了有效抑制,实现了抑制谐波的目的。     

Particle swarm optimization technique for multilevel inverters in solar harvesting micro grid system

In on grid solar generation system the irradiance causes voltage mismatch as a result of this the nonlinearities increase in the output voltage of the multilevel inverter. The sunlight is not uniform at all places, variation in irradiance is inevitable when it comes to solar power. The Solar power is not similarly circulated there is a change in sun orientation with respect to geometrical positions. The un symmetrical voltage results in unbalancing and introduces more harmonics. The article proposed here analyses a topology where a DC-DC converter is utilized ahead of the multilevel inverter so as to overcome the voltage varieties, thereby reducing the harmonics in the system. Particle swarm optimization is carried out in minimizing the Harmonics. Different observation and studies working stages their simulations and results for both are studied and recorded. Since solar energy is an essential, a complete analysis of this is done. A variety of initial calculations in designing the converter are also carried out. Similar calculations are also carried out informing the solar panel and harvesting the energy. By facilitating MATLAB simulation of particle swarm optimization for firing angles employed in multilevel inverter along with the converter. The measure of total harmonic distortion THD obtained is taken as a measure of evaluation for the performance of this combined system.