Carrier Based Synchronous control and performance analysis of an S-PSI using PV for Microgrid Applications

Two and three level VSC inverters are the building blocks of most of inverter applications necessitating the employment of appropriate switching techniques that result in harmonic free sinusoidal output. The paper presents the generalized method for harmonic elimination in two and three level voltage sourced converter. The technique used for suppression of selective low-ordered harmonics form the inverter's output voltage waveform is Selective harmonic elimination (SHE). The inverter's output voltage waveform is mathematically modeled using Fourier series that results in the system of nonlinear equations. The non-linear equations are solved for eliminating the specific low order harmonics. The main objective in calculating appropriate switching angle is to minimize the value of Total Harmonic Distortion (THD). To solve the system of non-linear equations numerical method Newton Raphson is applied and appropriate switching angles are calculated. The remaining uneliminated higher order harmonics are eliminated by connecting appropriate value of filter at the output stage of VSC inverter. The model of two level VSC is simulated in SimPowerSystem Matlab tool bar together with the algorithm of Newton Raphson technique. The time domain plot and frequency spectrum of inverter's output waveform is presented in the results section. The results of two and three level VSC inverters are analyzed and debated together with the comparative analysis on the basis of THD. Moreover, a comparison is presented on the basis of IEEE standard Std. 519 and EN 50160.

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.

In the present scenario to meet out the goal, multilevel inverter technology has introduced recently which helps to provide too much useful alternative in the field of huge power moderate range of voltage application. In this work an attempt has been made to study the complicated nature such as nonlinearities and chaos in cascaded multilevel dc to ac converter system. Cascaded multilevel H-bridge inverter has been taken and nonlinear behavior phenomena are observed using matlab/Simulink software package. It is reported that the dc to ac converter shifted their position from a stable operating condition to unstable operating condition as the bifurcation parameter like load varied for the power inverter system. Simulation results obtained through by software Matlab/Simulink demonstrate output voltage and current waveform of inverter along with its fftspectrum. This study for getting information about nonlinear behavior of power multilevel inverter system is playing very vital role for designing and fabrication of practical circuits in power electronics field.

The objective of this paper is to develop a new voltage source inverter (VSI) that acts as a boost inverter. The proposed inverter topology will acts as inverter and also boosts the output voltage with respect to the applied input. In general, the output voltage (AC) of a conventional full-bridge inverter is lower than the input DC voltage. Boost inverters are used in systems, where the output AC voltage is required to be larger than the input DC voltage. In order to obtain output AC voltage higher than the input DC voltage, an additional step up chopper is usually required at the front end, bestowing a two-stage power conversion which yields increased circuit complexity. Hence, in this paper a Dual boost inverter (DBI) has been developed, as a single-stage converter with advantages of a small structure, reduced power devices, and good buck-boost ability. The conventional modulation strategy (full cycle modulation) of the proposed circuit makes all the switches to operate in high frequency and leads to high voltage/current stress, which in turn results in heavy conduction losses and switching losses. The proposed system uses Half Cycle modulation scheme which use the power switches in half cycle, and can greatly reduce the conduction and switching losses of the power devices. In addition, an improved DBI with two clamping switches is also proposed in this paper, to reduce the current circulation losses in DBI with low switching stress. Thus our proposed topology will achieve higher efficiency with reduced losses and switching stress. The simulation results are presented for DBI model and improved DBI model. An experimental prototype is also developed to realize the Dual boost inverter output (without clamping switches) to validate the simulation results.

The objective of the present work is to improve the output waveform of three level inverters used in high-power applications, where the switching frequency is very low. This is achieved by maintaining the synchronization, half-wave symmetry, quarter-wave symmetry, and three-phase symmetry in the pulsewidth modulation (PWM) waveforms. The principles of achieving synchronization and symmetries in terms of space vectors for three level inverters are presented. A novel synchronized space vector pulsewidth modulation (SVPWM) algorithms is proposed and verified experimentally. The experimental waveforms of the inverter output voltage and motor no load current for different operating conditions of the drive are presented. The performance measure in terms of the weighted total harmonic distortion (THD) of the line voltage is computed for the linear modulation region of the drive for the proposed algorithm and compared with that of synchronized SVPWM and synchronized sine-triangle pulsewidth modulation (SPWM) technique. The comparative results show that consideration of synchronization and symmetry results in improved THD. Another significant feature of the proposed algorithm is that the symmetry and synchronization leads to self-balancing of the direct current (dc) bus capacitor voltages over every one third cycle of the fundamental

The objective of this paper is to present an approach for isolating the harmonic contents in both voltage and current waveforms of the montage feeder of Gharb Talkha substation (60/11 KV). A novel technique using Discrete Wavelet transform (DWT) for the analysis of the waveforms harmonics content At the beginning the substation is simulated using Simulink toolbox in Matlab program with and without the presence of capacitor bunk. The obtained voltage and current waveforms are compared to the actual data. The proposed model is used to study the effect of replacing the capacitor bank with single tuned parallel passive filter. The resulting current and voltage waveforms are analyzed using the proposed DWT technique. The analysis showed that the Total Harmonic Distortion (THD) of both voltage and current waveforms is improved as well as the power factor.

Impedance networks inverters (INI) have emerged as an alternative to improve traditional inverters, allowing their operation as a buck-boost type converter, through the utilization of the "shoot-through" conduction state, where switches of one or more inverter legs are gated on simultaneously. Recently introduced, the Quasi-Y-Source inverter (QYSI) is a magnetic coupled INI that has particular performance advantages, specially for renewable sources and distributed generation. To control the QYSI there is several techniques based on Sinusoidal Pulse Width Modulation (SPWM), that are modified to allow the shootthrough state. This work aims to present, through computational simulations, a comparative analysis of three SPWM techniques applied in three-phase QYSI, considering a fixed boost factor and a three-phase/three-wire RL load connected to the inverter output. The following modulation techniques were compared: Simple Boost Control (SBC), Maximum Boost Control with third harmonic injection (MBC3h) and Maximum Constant Boost Control with third harmonic injection (MCBC3h). Simulation results show operation characteristics of the QYSI for the different modulation techniques. A Fourier analysis was performed in order to evaluate harmonic distortion and harmonic spectrum for both inverter output voltage and current, and a comparative analysis was performed showing several relationships among voltage gain, switch voltage stress, shoot-through duty ratio and modulation index for the different SPWM techniques. Simulation results shows the advantages and disadvantages of each SPWM technique applied to QYSI and the impact of the coupled inductor on inverter performance, helping to establish proper criteria for choosing among SPWM techniques for different power systems applications.

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.

Active ripple decoupling technique of single-phase inverter is a popular topic to minimize the dc-link capacitance. However, the existing control methods are based on tracking sinusoidal or predetermined voltage waveform of compensation capacitor, where they assume the inverter outputs are pure sinusoidal voltage and current. Therefore, the performance of existing methods degrades when the inverter output voltage and current are not purely sinusoidal. Furthermore, the limited dynamic performance threatens the safety of dc-link capacitor when the load changes, because the inrush ripple power is injected into dc link with small capacitance and the dc-link voltage will suddenly rise up when the ripple power is not buffered during transients. In this paper, a direct instantaneous power predictive control is proposed to buffer ripple power of single-phase inverter, which combines instantaneous ripple power control with model predictive control to overcome the issues above. The proposed method tracks instantaneous ripple power rather than voltage or current waveform. In this way, it can fully buffer all ripple powers in the system even for distorted output voltage and current of the inverter; the voltage waveform of the capacitor has the different shape in different operation cases, which enables the full utilization of storage capacitor. Model predictive control makes the proposed method have fast dynamic and perfectly compensate ripple power during transients and steady states. The buck-type active ripple decoupling circuit is chosen by comparing with another typical topology to implement the proposed method. Simulation and experimental results on a 3-kW prototype verify the theoretical analysis and the proposed control method.

A likely candidate for a series controller is the inverter based static synchronous series controller (SSSC). A possible application of a SSSC is to achieve an increase in power transfer in a meshed transmission system. It is shown that the SSSC control strategy affects power quality related issues such as voltage fluctuation and harmonic voltage distortion. The work presented gives an overview of the power quality issues to be considered when applying a SSSC and selecting a suitable control algorithm.

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

Asymmetric Cascaded H-bridge (ACHB) level inverters can output more voltage waveforms with fewer cascaded units while ensuring the quality of output voltage waveforms, so they have attracted more and more attention. Taking the topology of Type-III asymmetric CHB multilevel inverters as the research object, a Modified Hybrid Frequency Pulse Width Modulation (MHF-PWM) strategy is proposed in this paper. This modulation strategy overcomes the local overshoot of low-voltage unit in the presence of traditional Hybrid Frequency Pulse Width Modulation (HF-PWM), thus completely eliminating the low frequency harmonics in the output voltage waveform of Type-III ACHB nine-level inverters, and the Total Harmonic Distortion (THD) of output line voltage of the modulation strategy is lower than that of PS-PWM strategy in the whole modulation degree, which effectively improves the quality waveform of the output line voltage. At the same time, the strategy can also improve the problems of current backflow and energy feedback caused by the high-voltage unit pouring current to the low-voltage unit, thereby reducing the imbalance of the output power of the high-voltage and low-voltage units. Finally, the Matlab/Simulink simulation model and experimental platform are established to verify the validity and practicality of the modulation strategy.

For grid-tied inverters, islanding occurs when the grid is disconnected but the inverters are still energizing the local loads. When the inverter output active and reactive power match the local loads, the inverter output voltage and frequency will keep the same values as before. Islanding poses a hazard to maintenance workers and equipment. To detect islanding, a disturbance signal is usually added to the reference of the inverter output real power or reactive power with positive feedback manner. If the inverter output voltage or inverter output frequency is driven outside of the normal range, islanding is detected and the inverter will be de-energized. A parallel RLC load is widely used to verify effectiveness of anti-islanding detection. In this paper, transfer functions of anti-islanding loop gain are derived. These transfer functions are used to design anti-islanding control loop. Time domain simulation results are also included.

This paper demonstrates a novel method to integrate and control PV source and Battery storage in to a microgrid system to attain reduction in total harmonic distortion at the output. The closed-loop control of inverter has been achieved through using proportional integral controller (PI) and fuzzy logic controller. The results of output harmonics contents are compared for simple open-loop control and proposed closed-loop controls, and it clearly indicates that the closed-loop results far superior in terms of harmonic contents at the inverter output voltage. The control of battery energy storage system (BESS) has been presented, with the aid of a DC–DC bidirectional buck–boost converter for the different modes of operation, such as hold state, charging state and discharging state. With the intention of tracking the maximum power point from PV array, P&O MPPT technique has been used by which duty cycle of converter is controlled. Various operating conditions, such as photovoltaic source alone supplying to the entire load requirement and supplying to battery for its charging, PV source supplying to load requirement only, battery storage unit supplying to load requirement and lastly PV source and battery storage unit jointly supplying to the load requirement, have been analyzed extensively. Detailed analysis has been carried out on the output voltage, output current and output power waveforms for different operating conditions as discussed above, and the output results are analyzed for achieving more beneficial performance of the system. The suggested microgrid energy management system has been modeled and analyzed using MATLAB/Simulink tool.

The overall performance of the electricity distribution network is determined from various parameters. Power quality indices such as drop in voltage, rise in voltage, and harmonics play an essential role in this context. The article introduces a new index called the power quality distortion (DI). This index gives information about the contribution of non-linear load to the harmonic distortion in power. This effect has been observed due to the presence of non-linear component of current drawn by the load. Changes in the supply voltage in the form of dips, over voltages, harmonics, transients, etc., are considered major power quality issues. This has led to deterioration in the quality of the energy delivered to end customers and generates disruptions on the utility side. Load presents at the consumer end also explains the degradation in the quality of the power supply. Initially, penalties were charged for low p.f. consumers, and then, corrective measures were initiated by the consumer. In the same way to control the power quality, penalty is proposed to the consumers who are hampering the quality of power by application of non-linear load without using any mitigation technique. One of the mitigation techniques is custom power devices (CPDs). It is more effective as compared to traditional methods. This article provides various power quality indices such as distortion index as a power quality calculation parameter and the results obtained by application of dynamic voltage restorer (DVR) and hybrid-STATCOM for reducing the effect of the voltage sag and other indices of the quality of power in the electrical network. The proposed concept allows operation in non-linear conditions on the consumer side. The design of the system parameters is proposed based on the compensation parameter as an index of distortion of the distribution network. The simulation is carried out by the MATLAB model, and the results are compared with the analyzed performance of the power distribution system with regards to the index of distortion with injection of DVR and hybrid-STATCOM.KeywordsPower quality (PQ)Custom power devices (CPDs)Dynamic voltage restorer (DVR)Hybrid-STATCOMDistortion index (DI)Total harmonic distortion in voltage (VTHD)Total harmonic distortion in current (ITHD)Active power filters (APFs)Battery energy storage systems (BESSs)