FUZZY BASED CASCADED MULTILEVEL SHUNT ACTIVE POWER FILTER FOR POWER LINE CONDITIONERS

In this paper shunt active power filter is used to improve the power quality at distribution system. Due to nonlinear loads, current harmonics, unbalanced voltages and current and reactive power problems will be created in the network. The Instantaneous real power theory (IRPT) provides the real power calculation with PI controller will not provide accurate result and good performance under both steady state and transient state. Compensating above problems by using fuzzy based on Cascaded multi-level voltage source inverter. The inverter switching signals are generated based on the triangular sampling current controller provides power line conditioning. The Paper deals with three phase, five level cascaded multi level voltage source inverter based shunt active filter with PI and Fuzzy controller by using MATLAB/Simulink

Performance investigation of an innovative H-bridge derived multilevel inverter topology for marine applications

441-449An innovative single-phase and three-phase H-bridge derived multilevel inverter topology is being proposed in this manuscript. The proposed topology makes use of relatively fewer switching devices compared to conventional Cascaded H-Bridge (CHB) multilevel inverter. In other words, the proposed inverter topology is capable of producing more number of levels in the voltage waveform with same number of switching devices. It is also established in this paper, that this proposed topology is superior in terms of requirement of lesser number of gate driving circuits and reduction in the harmonic content in the output voltage waveform. The proposed inverter topologies are driven by SPWM modulation technique. These converter topologies are not only beneficial for the power conditioning systems in the power system network but also for the other novel applications like in marine ships. In this manuscript, the performance comparisons of the proposed inverter topologies with that of conventional topology based on simulation results with MATLAB/SIMULINK have been presented

A Modulation Scheme for Floating Source Multilevel Inverter Topology with Increased Number of Output Levels

This paper presented and studied a new switching scheme for floating source multilevel inverters to produce more levels with the same number of switching devices. In the proposed scheme, the function of the dc sources, except the inner one, is to build up square wave or blocks that is close in the shape to the desired sinusoidal wave. The job of the inner switching devices is to increase the number of the levels to produce smother sinusoidal wave in the inverter output. This job can be done by adding or subtracting the value of the inner dc source to/from the blocks. The topology used in this paper is based on the conventional floating source multi-level inverter using two legs. This topology and modulation technique show substantial reduction in the total harmonics distortion when the modulation technique is the hybrid method. The performance of the proposed switching scheme in generating more levels has been evaluated by PSCAD/EMTDC simulation

Effect of duty cycle on THD for multilevel inverter based on selective harmonic elimination technique

Multilevel inverters controlled suffers from the issue of harmonic distortion in the output voltage. Selective Harmonic Elimination (SHE) technique plays an effective role to eliminate these harmonics. The undesirable odd harmonics can be eliminated by having optimized the switching angles in SHE signal. To optimized and obtained these switching angles, a number of nonlinear equations should be solved using a numerical method. In addition to the modulation index, by changing the value of the duty cycle the Total Harmonics Distortion (THD) will also change. In this paper, a novel Optimization Harmonic Elimination Technique (OHET) based on SHE scheme is proposed in order to minimize Total Harmonic Distortion (THD). To evaluate and investigate the performance of the proposed scheme, a seven-level cascaded inverter is simulated by MATLAB and PSIM software

A New Control Technique for Multilevel Cascaded H-Bridge Inverters

Multi cell converters are one of the alternative topologies for medium-voltage industrial drives. For an application modulation (PWM) rectifier as front end Multi level cascaded H-bridge (CHB) converters have been presented as a good solution for high-power applications. The choice of single-phase PWM rectifiers for the input of the cells results in a reduced number of power switches and a simpler input transformer than the three phase equivalent. However, its control is not as straightforward. In this paper, the steady-state power balance in the cells of a single-phase two-cell CHB is studied. The ability to receive active power network or to deliver active power to the grid in each cell is analyzed according to the DC-link voltage and the desired output AC voltage value. Simulation results are shown to validate the presented analysis

A Modified Three Phase Four-Wire UPQC Topology with Reduced DC-Link Voltage Rating

ABSTRACT: This circuit consists of capacitor in series with the interfacing inductor of the shunt active filter. The series capacitor enables reduction in dc-link voltage requirement of the shunt active filter and simultaneously compensating the reactive power required by the load, so as to maintain unity power factor, without compromising its performance. This allows us to match the dc-link voltage requirements of the series and shunt active filters with a common dc link capacitor. Further, in this topology, the system neutral is connected to the negative terminal of the dc bus.. This will avoid the requirement of the fourth leg in VSI of the shunt active filter and enables Independent control of each leg of the shunt VSI with single dc capacitor. The topology uses a capacitor in series with the interfacing inductor of the shunt active filter, and the system neutral is connected to the negative terminal of the dc-link voltage to avoid the requirement of the fourth leg in the voltage source inverter (VSI) of the shunt active filter. The average switching frequency of the switches in the VSI also reduces, consequently the switching losses in the inverters reduce. Detailed design aspects of the series capacitor and VSI parameters have been discussed in the paper. A simulation study of the proposed topology has been carried out using PSCAD simulator, and the results are presented. Experimental studies are carried out on three-phase UPQC prototype to verify the proposed topology. I. EXISTING SYSTEM In existing system the three phase three WIRE UPQC has used. Mainly Voltage rating of dc-link capacitor largely influences the compensation performance of an active filter. EXISTING SYSTEM METHODOLOGY The three phase three wires UPQC system used for compensation of power quality issues. DISADVANTAGES OF EXISTING SYSTEM: In this method the UPQC which requires more rating of series and shunt active filters. Additionally to maintain the Low harmonics level by adding passive filters

A novel center-tapped transformer based multilevel inverter with common DC source

In this paper, a novel multilevel inverter topology is proposed which uses lesser switches and anti-parallel diodes are eliminated in the circuit configuration of the multilevel inverter. Optimal switching strategy for the inverter using three different Space Vector Pulse Width Modulation (SVPWM) techniques is analyzed based on the power quality indices. The proposed model is simulated and tested using MATLAB/Simulink. Owing to the switching techniques used the harmonic content at the output of the inverter is mitigated which results in a lesser value of total harmonic distortion. Reduced number of power electronic switches results in lesser power loss. The performance of the proposed system is validated with simulation results of conventional multilevel inverters and pulse width modulation control methods. The results for various performance parameters such as efficiency, switching loss, voltage magnitude, and total harmonic distortion are analyzed

Real-Time Selective Harmonic Minimization for Multilevel Inverters Using Genetic Algorithm and Artificial Neural Network Angle Generation

This work approximates the selective harmonic elimination problem using Artificial Neural Networks (ANN) to generate the switching angles in an 11-level full bridge cascade inverter powered by five varying DC input sources. Each of the five full bridges of the cascade inverter was connected to a separate 195W solar panel. The angles were chosen such that the fundamental was kept constant and the low order harmonics were minimized or eliminated. A non-deterministic method is used to solve the system for the angles and to obtain the data set for the ANN training. The method also provides a set of acceptable solutions in the space where solutions do not exist by analytical methods. The trained ANN is a suitable tool that brings a small generalization effect on the angles\u27 precision and is able to perform in real time (50/60Hz time window)

Fault Tolerant Multilevel Inverter Topologies with Energy Balancing Capability: Photovoltaic Application

The continuous increase in energy demand and depletion of conventional resources motivates the research towards the environment friendly renewable energy sources like solar and wind energy. These sources are best suitable for rural, urban and offshore locations, because of easy installation, less running cost and ample resources (sun light and wind). The remote locations are mostly islanded in nature and far away from technical expertise in case of troubleshooting. This motivates the research on development of fault tolerant converters. These fault tolerant converters increases the reliability, which provides the continuous power supply to critical loads. From the last few decades, the integration of multilevel inverters with renewable energy systems is also increasing because of advantages like, improved power quality, total harmonic distortion (THD) and reduced output filter size requirement. Employing conventional multilevel inverters for increasing the number of voltage levels increases the device count and isolated DC sources. As a result probability of semiconductor switch failure is more and energy balancing issue between sources, which in-turn degrades the reliability and performance of the inverter. The majority of conventional multilevel inverter topologies cannot address energy balancing issues between multiple photovoltaic (PV) sources, which may need because of partial shading, hotspots, uneven charging and discharging of associated batteries etc. If energy sharing not addressed effectively, the batteries which are connected to the shaded or faulty PV system will discharge faster which may cause total system shutdown and leads to under-utilization of healthier part of the system. To address these issues, fault tolerant multilevel inverter topologies with energy balancing capability are presented in this thesis. The major contributions of the proposed work are Single phase and three phase fault tolerant multilevel inverter topologies. viii Energy balancing between sources and dc off set minimization (or batteries) due to uneven charging and discharging of batteries for five-level inverter. Extending the fault tolerance and energy balancing for higher number of voltage levels. The first work of this thesis is focused to develop fault tolerant single phase and three phase multilevel inverter topologies for grid independent photovoltaic systems. The topologies are formed by using three-level and two-level half bridge inverters. The topology fed with multiple voltage sources formed by separate PV strings with MPPT charge controllers and associated batteries. Here the topologies are analyzed for different switch open circuit and/or source failures. The switching redundancy of the proposed inverters is utilized during fault condition for supplying power with lower voltage level so that critical loads are not affected. In general, the power generation in the individual PV systems may not be same at all the times, because of partial shading, local hotspots, wrong maximum power point tracking, dirt accumulation, aging etc. To address this issue energy balancing between individual sources is taken care with the help of redundant switching combinations of proposed five-level inverter carried out in second work. Because of partial shading the associated batteries with these panels will charge and discharge unevenly, which results voltage difference between terminal voltages of sources because of SOC difference. The energy balance between batteries is achieved for all operating conditions by selecting appropriate switching combination. For example during partial shading the associated battery with low SOC is discharged at slower rate than the battery with more SOC until both SOC’s are equal. This also helps in minimization of DC offset into the ac side output voltage. The mathematical analysis is presented for possible percentage of energy shared to load by both the sources during each voltage level. The third work provides single phase multilevel inverter with improved fault tolerance in terms of switch open circuit failures and energy balancing between sources. Generally multilevel inverters for photovoltaic (PV) applications are fed ix with multiple voltage sources. For majority of the multilevel inverters the load shared to individual voltage sources is not equal due to inverter structure and switching combination. This leads to under-utilization of the voltage sources. To address this issue optimal PV module distribution for multilevel inverters is proposed. Mathematical analysis is carried out for optimal sharing of PV resources for each voltage source. The proposed source distribution strategy ensures better utilization of each voltage source, as well as minimizes the control complexity for energy balancing issues. This topology requires four isolated DC-sources with a voltage magnitude of Vdc/4 (where Vdc is the voltage requirement for the conventional NPC multilevel inverter). These isolated DC voltage sources are realized with multiple PV strings. The operation of proposed multilevel single phase inverter is analyzed for different switch open-circuit failures. All the presented topologies are simulated using MATLAB/Simulink and the results are verified with laboratory prototyp