Comprehensive Mathematical Description and Harmonic Analysis of Hybrid Two-Dimensional–Three-Dimensional Space Vector Modulation

This paper presents deeply analysis and comparison of different modulation techniques for the modular multilevel converter without using arm inductor. In case of PWM, losses are more and Total Harmonic Distortion (THD) performance is very poor. With the introduction of delta modulation in MMC, the losses will reduce and THD will improve. It can be seen that the THD is 4.9% for delta modulation and 3.82% for adaptive delta modulation without using arm inductance but THD is 13.15% for delta modulation with arm inductance. It means THD has been improved without using arm inductance. It has been observed that the adaptive delta modulation has better THD response as compared to delta modulation due to its several advantages. The THD performance has been calculated and mentioned at different modulation indexes. It has been also observed that the THD performance is better with delta and adaptive delta modulation.

This paper provides a brief comparison between two different modulation methods for direct matrix converter (DMC). The power semiconductors are modelled as ideal bidirectional switches and the DMC is controlled using Venturini method, optimized Venturini and space vector modulation respectively. These methods are compared and analysed in some aspects such as total harmonic distortion and harmonic spectrum analysis of output voltage and input current. A simple model of DMC is proposed to represent the power circuit, including the input filter and a three-phase Y-connected RL load. Simulated input and output parameters of DMC are presented using PSIM software for both modulation strategies.

SUMMARYThis paper discusses pulse density modulation (PDM) control methods for a single‐phase to three‐phase matrix converter (MC) in high‐frequency applications. The proposed circuit is used as an interface converter for a wireless power transfer system. This converter can input a frequency of several hundred kilohertz and output a low frequency, that is, 50 Hz or 60 Hz, for a commercial power grid. The proposed circuit implements zero voltage switching (ZVS) operation by using PDM control methods and obtains high efficiency. In this paper, two PDM control strategies are compared: delta–sigma conversion and the PDM pattern generation method based on space vector modulation (SVM), which is proposed here. Also, the experimental results obtained with the proposed system will be presented and discussed. The total harmonic distortions (THDs) of the output voltage with delta–sigma conversion and the PDM pattern generation method based on SVM are found to be 5.96% and 2.15%, respectively. In addition, the maximum efficiencies with delta–sigma conversion and the PDM control based on SVM are 93.4% and 97.3%, respectively. From the results, the validity of the PDM control based on SVM has been confirmed for improvement of the output waveforms and reduction of the switching loss.

Employing space vector modulation in a multi-level H-bridge StatCom (H-StatCom) can provide an excellent trade-off between harmonic performance and switching frequency. However the nature of the techniques used to balance the capacitor voltages in this modulation strategy can increase capacitor voltage ripple. This paper compares the key performance indicators in differing space vector modulation techniques including capacitor voltage ripple, total harmonic distortion and switching losses. It is shown that while one of these techniques significantly improves the trade-off between harmonic performance and switching loss it can also significantly reduce the capacitor lifetime due to the form of the resultant ripple currents.

Проведено огляд топологій інверторів напруги, що знаходять широке використання у системах електроживлення з альтернативними джерелами енергії, визначено переваги та недоліки кожної з топологій. Більш детально розглянуто будову та принцип функціонування інверторів з імпедансним та квазі-імпедансним ланцюгом у вхідному колі. Проведено порівняння багаторівневої каскадної топології, топології з імпедансним ланцюгом у вхідному контурі (z-інверторів), топології з квазі-імпедансним ланцюгом у вхідному контурі (квазі-z-інверторів), а також багаторівневих каскадних топологій з використанням z- та квазі-z-інверторів у якості топології силової частини окремого модуля за коефіцієнтом нелінійних спотворень вихідної напруги. За результатами отриманими в результаті досліджень наведено рекомендації щодо застосування досліджених топологій виходячи з вимог навантаження до якості вихідної напруги та типу використовуваного джерела альтернативної енергії.

This research compared the performance of PWM (Pulse Width Modulation) inverter and multilevel inverter in terms of their output voltage and current total harmonic distortion (THD). The inverters were designed to have the output voltage of 220 V at 50 Hz. The input voltage for both inverters are 400 VDC. For PWM inverter, the PWM technique utilized was sinusoidal PWM (SPWM) and for multilevel converter, the number of voltage level is five with diode-clamped topology. The study included circuit implementation, analysis, and THD calculation, all of which were carried out through simulation using PSpice software. In controlling the SPWM inverter output, the adjusted parameters included amplitude modulation ratio, frequency modulation ratio, and filter components’ parameters. On the other hand, the firing angles of the switching components were designated as controlling parameters in multilevel inverter. From the study, it was found that the best THD values of the designed SPWM inverter are 4.2% (voltage) and 1.7% (current), while those of multilevel inverter are 27% and 11%, for voltage and current, respectively. Thus, it can be concluded that SPWM inverter is better than 5-level inverter for the application in solar panel due to its lower THD. In our study, 5-level inverter did not satisfy the THD requirement specified in IEEE 512-1992, i.e. 5%.

This paper analyzes the Total Harmonic Distortion (THD) performance of a single phase 5-level CHB MLI. The multi level inverter is simulated using the carrier overlapping APOD Pulse Width Modulation (PWM) switching control technique. The total harmonic distortion (THD) of the output voltage is observed for the PWM control technique at varying modulation index of 0.7-1.0. The performance of a 5-level CHB MLI is simulated using MATLAB/SIMULINK. It is observed that the carrier overlapping APODPWM provides output with relatively low THD.

Current source inverter (CSI) offers key merits of direct output current control, voltage gain operation, current limiting ability, and inherent short-circuit protection. The modulation and control for medium voltage high power application are implemented at low device switching frequency in order to attain high efficiency and to reduce cooling requirements. At low switching frequency operation, the conventional modulation techniques such as space vector modulation (SVM) and sinusoidal pulse width modulation (SPWM) cannot maintain low total harmonic distortion (THD). Synchronous optimal pulse width modulation (SOPWM) is a low frequency modulation technique that offers lower THD without compromising on device switching frequency. However, this technique requires a separate conversion technique for current source converters to incorporate additional switching constraints of CSI. Whereas, the SVM technique directly implements the switching constraints of CSI without any conversion technique and in addition SVM technique provides better dynamic performance compared to low frequency modulation techniques. Hence, the goal of this paper is to propose a hybrid modulation technique that combines the SVM technique and SOPWM technique. Three methods have been proposed for developing hybrid modulation scheme based on SVM and SOPWM. Performance of the proposed hybrid modulation is validated using experimental results.

In some applications of microgrids and distributed generation, it is necessary to feed islanded or stand-alone loads with high-quality voltage to provide low total harmonic distortion (THD). To fulfil these demands, an LC filter is usuallyconnected to the output terminals of power electronics converters. A cascaded voltage and current control loop with pulse-width modulation schemes are used to regulate the voltages and currents in these systems. However, these strategies have some drawbacks, particularly when multiple-input–multiple-output plants (MIMO) are controlled using single-input–single-output (SISO) design methods. This methodology usually produces a sluggish transient response and cross–coupling between different control loops and state variables. In this paper, a model predictive control (MPC) strategy based on the concept of optimal switching sequences (OSS) is designed to control voltage and current in an LC filter connected to a three-level neutral-point clamped converter. The strategy solves an optimisation problem to achieve control of the LC filter variables, i.e., currents and output voltages. Hardware-in-the-loop (HIL) results are obtained to validate the feasibility of the proposed strategy, using a PLECS–RT HIL platform and a dSPACE Microlab Box controller. In addition to the good dynamic performance of the proposed OSS–MPC, it is demonstrated using HIL results that the control algorithm is capable of obtaining low total harmonic distortion (THD) in the output voltage for different operating conditions.

This paper presents a selective harmonics reduction for a 3(n+1) shared switch inverter topology utilizing optimal arrangement of the n-modulated signal. Under different modulation indices and operating power frequencies the purpose of the proposed procedure is to select an optimal load connection and/or modulation offsetting based on the desired objective function. Three performance indices are studied in this paper, namely, the sum of the total harmonic distortion (THD), the sum of the weighted THD, and the sum THD of the first eleventh harmonics of all the loads. The proposed mathematical description will achieve extra degrees of freedom that improve the quality of the output signal without any additional burden. A general procedure for distributing the input dc voltage with correct sharing during linear modulation region and proper voltage utilization in overmodulation region is presented. Then, general and comprehensive presentation to the used pulse width modulation (PWM) technique is discussed showing the new degrees of freedom in the applied offsets as decision variables. Field-programmable gate array (FPGA) in-the-loop simulations are done to illustrate the effectiveness of the proposed procedure.

The demand for multi-level inverters has been increased over time. Less total harmonic distortion (THD) of output voltage, less voltage tension across switches, and low electromagnetic interference (EMI) are some of their favourable features. Among all the multi-level topologies, Cascade H-Bridge (CHB) inverters have more scalability, feasibility, and modularity; therefore, they are widely used. CHBs consist of full bridge converters required independent dc voltage sources that may be asymmetrical. In this paper, a SPWM cascade full-bridge single-phase 7-level inverter with optimized phase shift modulation is introduced. It uses capacitance voltage control and Genetic Algorithm for both symmetrical and asymmetrical conditions to alleviate harmonics and THD. MATLAB simulation is used to investigate the inverter performance under different operational conditions. In order to validate the simulation results, an experimental prototype of the inverter is implemented and practical results are presented.

This work presents the development and implementation of four control configurations for photovoltaic inverter. These configurations are: Proportional Integral plus Resonant controller, Proportional Integral plus Repetitive controller, Proportional Integral-Proportional plus Resonant Controller and Two Degrees of Freedom plus Repetitive control with the aim of reducing the Total Harmonic Distortion in Voltage. These techniques are useful in island mode operation of an inverter when it is working as a voltage source in microgrid. In this operation mode, these control techniques are successfully applied when the inverter feeds linear and nonlinear loads. The purpose is to keep the output voltage waveform, frequency and amplitude according to the standard IEEE 519. It is use is justified because currently most of the loads have nonlinear characteristics which increase considerably the Total Harmonic Distortion in voltage. A comparative analysis derived from inverter simulations with nonlinear loads has been performed in order to validate those control techniques, considering that its application to feed line loads proves to be effective.

This paper presents a Genetic Algorithm-based approach for optimal placement and sizing of passive power filters to mitigate harmonics in radial distribution systems with linear and nonlinear loads. The problem is formulated as a nonlinear multi-objective optimisation problem with equality and inequality constraints. For solving this problem, the Genetic Algorithm’s performances are analysed and evaluated using the standard IEEE 18- and 33-bus test systems. The optimal solutions are obtained based on the following four optimisation criteria: (1) minimisation of the maximum level of the total harmonic distortion in voltage, (2) minimisation of the initial investment costs of the filters, (3) minimisation of total active power losses in distribution lines and (4) a simultaneous minimisation of the maximum total harmonic distortion in voltage, initial investment costs of filters and total active power losses. The system harmonic levels are estimated using the Decoupled Harmonic Power Flow algorithm. Simulation results, obtained using the proposed Genetic Algorithm-based approach, are compared with those obtained using other optimisation algorithms and verified using the Harmonic Analysis module of the Electrical Transient Analysis Program. It is shown that the Genetic Algorithm-based approach provides effective, robust and high-quality solutions.

This paper proposes an offset voltage control scheme for the modular multilevel converter (MMC) operated in nearest level control (NLC) to improve the total harmonic distortion (THD) of AC phase voltages. The offset (neutral-to-zero-point) voltage is adjusted so that the magnitude of each AC pole voltage maintains constant value with N + 1 level in the range of whole modulation index (MI). The validity of the proposed scheme was confirmed by computer simulations for the MMC with 22.9 kV/25 MVA and experimental works for the scaled MMC with 380 V/10 kVA. It was confirmed that the proposed control scheme can generate linearly variable AC phase voltages with improved THD in the over-modulation region as well as the normal-modulation region.

Selective Harmonic Elimination of Cascaded Multilevel Inverter Using BAT Algorithm