Development and research of multizone rectifiers

In this work the new single-phase three-zone AC-DC voltage converter is compared with the existing scheme of the four-zone rectifier used in electric locomotives. It is shown, that in the new scheme of the three-zone (n-zone in general) rectifier essentially decrease reverse voltage on thyristors. Analytical expressions for total harmonic distortion of output voltage, input current, control and external characteristics, as well as power factor are presented. The diagrams illustrating results of computer modelling are given. Total comparison shows essential reduction of expenses by power semiconductor devices.

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.

Multi-level inverter used in applications that require high power. The important factor in multi-level inverter is Total Harmonic Distortion (THD). This study discuss nine level cascaded H-bridge multilevel inverter. Also, proposed the effects of using filter on waveform and Total Harmonic Distortion (THD) of output voltage and current. Discussed LC low pass filter and sinusoidal pulse width modulation as control technique of switches. Comparison THD of nine level cascaded H-bridge multilevel inverter with and without filter. The proposed level and filter are design and simulate by MATLAB 2010 Version 7.11.0. The simulation results show the effects of using filter on THD and waveform of output voltage and current. Different methods for choosing filter value are used to illustrate the filter effect.

This study presents a novel three‐level neutral‐point‐clamped quasi‐Z‐source inverter in the single‐stage buck‐boost multilevel inverter family. The topology was derived by combining the properties of the quasi‐Z‐source network with those of a three‐level neutral point clamped inverter. It features such advantages as low voltage stress of the switches, single‐stage buck‐boost power conversion, continuous input current, short‐circuit withstandability and low total harmonic distortion of the output voltage and current. The authors present a steady state analysis of the topology along with a special modulation technique to distribute shoot‐through states during the whole fundamental period. Component design guidelines for a single‐phase case study system are described. All the findings have been confirmed by simulations and experiments. The topology could be recommended for applications requiring continuous input current, high input voltage gain and enhanced quality of the output voltage.

The comparison of control methodologies for three phase inverter fed by photovoltaic (PV) module is presented in this paper. The approach adopted for controlling the switching of devices in inverters provides a deep insight to its working. Each control strategy offers different characteristics to the operation. This paper includes a fragment of the working results of the inverter when controlled by different modes. The various strategies used are: 180° conduction, 120° conduction and Sinusoidal Pulse Width Modulation (SPWM) with various values for modulation index. The static (series R-L) and dynamic (Asynchronous machine) load are fed through the inverter. The simulations have been performed using Simulink package of MATLAB (Matrix Laboratory). The software results are analyzed by plotting graphs of Total Harmonic Distortion (THD) of output voltage and output current of the three phase inverter with various loads at different power factors.

A ligation (CL) system with a very high frequency in an inverter was used, it is a novelty in this study. We also employed a three-phase dynamic load (positive sequence voltage) to correct the power factor and account for active and reactive power in the output system this work is a novelty. The technique through compound ligation (CL) can improve inverter output waveform by reducing losses caused by ingrained agents in voltage source inverters (VSI), such as dead time caused by overload or voltage drop in an inverter's output, or abnormal load current conditions such as a short circuit current occur in the output stage of the inverter, and so on. The invention relates to the conversion of D.C. to A.C. power inverters, it is preferable to use compound ligation to achieve high efficiency, the device is lightweight, and has low losses and good precision. In addition, the present invention relates to improving an inverter load request sensation circuit, smoothing operational current, inverter response, and inverter spontaneous power factor improvement, as well as correction of the reactive power of passive components. In addition, an inverter with high active power (P) equal to (2.6×106 Watt), reactive power (Q) (5.4×107 VAR), was designed, and used positive sequence voltage (1.6×108 Watt ), as well as the switching period (10µs), The system's total harmonic distortion (THD) in voltage and current was 0.11 percent, while the system's accuracy was 99 percent. This is developed by using FPGA and oscillator circuit and programmable peripheral interface 8255 A as well as, ultrasonic PWM with a high-frequency range of (20–500 kHz) as demonstrated evidenced by the results obtained

Harmonics are one of the key power quality issues on the front burner in the power system. Advancements in solid-state technology in recent times have resulted in the proliferation of non-linear loads which are the main sources of harmonics. Harmonics penetration in power system networks is detrimental to effective system operation and can result in frequent failures and damage to electrical equipment. This, therefore, creates the need for harmonic mitigation in power system networks for power quality enhancement. This work examined the impact of a shunt passive filter (SPF) in minimizing harmonic distortion on an electrical distribution network considering the power network layout of 7-Up Industry Plc as a case study. The indices for quantifying the level of harmonic distortion and shunt passive filter design for harmonic mitigation in power networks were respectively analysed and presented. The considered 7-Up Industry Plc power network was modelled and simulated with and without SPF in MATLAB/Simulink software environment R2020a. The voltage and current total harmonic distortion, VTHD and ITHD, from the two system states, were evaluated. The observed voltage and current waveforms from the simulation of the test network without any filter applied were distorted, signifying the harmonics’ presence. The estimated VTHD and ITHD values with no filter used were 6.084 and 19.79 % respectively. SPF application on the test network mitigated the VTHD and ITHD to 0.7802 and 2.448 %, giving an improvement of 5.304 and 17.342 % respectively in the minimization of voltage and current total harmonic distortion compared to the no filter case. This study established that a shunt passive filter is suitable for power quality enhancement in an electrical distribution network. Keywords: Electrical distribution network, harmonics, non-linear load, power quality, shunt passive filter, total harmonic distortion

Power quality analysis is one of the most important subjects of every power systems' interconnected parts. In fact, the nonsinusoidal regime represents the real operation mode of all the power systems, due mainly to distribution and consumers. Several parameters of power quality analysis are used by every national power system operator to impose specific standard limits and regulation which ensure optimal conditions of the electrical energy quality. Generally, all the limit values must be respected, even though they indirectly depend on one another. This paper proposes new relations between some parameters of power quality for the case of most common linear and inductive consumers, in order to unify the limits imposed on nonsinusoidal regime. Starting by the definition of relative values of voltage and current harmonics a new nonlinear dependence between the power factor and the total harmonic distortion of voltage and current is established. A quantitative approach of the nonlinear function has been assessed by using Matlab tools. The results are compared and discussed to the measured data for a large industrial consumer in two cases: with and without filters for power factor correction.

Assessment of non-sinusoidal reactive power of shunt capacitors in the presence of distorted substation voltage in radial distribution systems

The Class E2 dc-dc converter, composed by soft-switching based Class E power amplifier (PA) and rectifier, is popular for 6.78 MHz wireless power transfer (WPT) for its high efficiency and simple topology. Here, we take a comprehensive analysis on the harmonic voltages and currents on the transmitting and receiving coils in a Class E2 dc-dc converter. These harmonics can be radiated into the free space through the coils, causing low system efficiency and electromagnetic interference (EMI) issues. And thus, it is expected to eliminate these harmonics. Next, an improved Class E2 dc-dc converter with low harmonic distortion and high efficiency is proposed. The harmonic distortions on both receiving and transmitting coils are greatly reduced by the employment of the full-wave Class E rectifier and Pi impedance transformation network. The total harmonic distortion (THD) of voltages and currents are less than 57.5% of those of the classical system. In addition to the reduction of harmonic distortion, the proposed converter is able to maintain high efficiencies, over 70%, when the coil coupling changes, by carefully designing the Pi network.

In this paper, a novel integrated SHE - NLC control is proposed for the mitigation of unwanted lower-order harmonics in the cascaded H-bridge multilevel inverter. The proposed algorithm has been developed by hybridizing the NLC and SHE methods, in an attempt to keep the merits of both the individual control. The switching angles and nearest levels are calculated by applying the Genetic Algorithm (GA). The proposed technique reduces the calculation time and implementation complexity, thus can be a viable alternative to the real time implementation for SHE. Integrated NLC-SHE control is tested by varying the modulation index and load dynamics. This technique resulted in the reduction in Total Harmonic Distortion (THDs) in load voltage and current. Comparative analysis of NLC, SHE and Integrated NLC-SHE technique is also performed on the CHB nine-level inverter. There is significant reduction in voltage and current THD values and power losses. Efficiency of the inverter is increased. The efficacy of the proposed control CHB nine-level is tested on MATLAB Simulink environment and further validated by experimental results.

With an increase of non-linear load in today’s electrical power systems, the rate of power quality drops and the voltage source and frequency deteriorate if not properly compensated with an appropriate device. Filters are most common techniques that employed to overcome this problem and improving power quality. In this paper an improved optimization technique of filter applies to the power system is based on a particle swarm optimization with using artificial neural network technique applied to the unified power flow quality conditioner (PSO-ANN UPQC). Design particle swarm optimization and artificial neural network together result in a very high performance of flexible AC transmission lines (FACTs) controller and it implements to the system to compensate all types of power quality disturbances. This technique is very powerful for minimization of total harmonic distortion of source voltages and currents as a limit permitted by IEEE-519. The work creates a power system model in MATLAB/Simulink program to investigate our proposed optimization technique for improving control circuit of filters. The work also has measured all power quality disturbances of the electrical arc furnace of steel factory and suggests this technique of filter to improve the power quality.

The Doubly Fed Induction Motor (DFIM) is essential in Wind Energy Conversion Systems (WECS) for efficient wind energy harvesting. Conventional power converters in WECS often result in high Total Harmonic Distortion (THD) in output voltage and current, affecting wind energy economy. This research proposes replacing conventional converters with Modular Multi-level Converters (MMC) due to their scalable topology, low harmonic distortion, high efficiency, and the elimination of DC link capacitors. The MMC is connected in a back-to-back configuration between the rotor of the DFIM and the grid to enable four-quadrant operation. Circulating current in the MMC is minimized using a Modified Deer Hunting Optimization (MDHO) based Fractional Order PID (FOPID) controller and a Mexican Axolotl Optimization (MAO) based FOPID. Capacitor voltage balancing is achieved using Level-Shifting PWM (LSPWM) and Three-Dimensional Space Vector PWM (3D-SVPWM) techniques with voltage sorting algorithms. The impact of these control and modulation techniques on the DFIM is analyzed in terms of reduced THD, and steady state and transient performance. Simulations are conducted in MATLAB/R2022a, and experimental validation is performed using a 7-level 0.5 kW MMC in a Hardware-In-Loop (HIL) setup.

Multilevel converters in FACTS and distributed generation system are very promising area for academic researchers and industry interest. Here two different modulation schemes of 3-level Neutral point clamped inverter are proposed and presented. The inherent neutral point potential unbalance issues and balancing methods for LS-PWM and SVM techniques are analyzed in detail. Total Harmonic Distortion in output voltage and current is used as the performance indicator for the inverter. It can be concluded that LS-PWM has higher harmonic distortions and high losses when compared to SVM. SVM technique also is excellent in DC bus voltage balancing. The experimental results for a 1.5kW prototype validate the simulation and theoretical results.

This paper presents a grid-connected photovoltaic (PV) interface for delivering both active and reactive powers. The PV interface employs H-bridge topology DC-DC converter and inverter with analog control technology. The power flow is controlled solely by the adjustable DC output voltage of the DC to DC converter. In order to evaluate the PV interface system’s performances, it is tested by delivering power to the grid with low pawer factor. The experimental results show that at 300W active load, the inverter could deliver the reactive power of 400VAR. The PV interface could also produce very low harmonic voltage and current distorsions. The laboratory measurements show that the total harmonic distortions of inverter output voltage and current are 0.46% and 0.05%, respectively