Harmonic Analysis of a Static VAR Compensated Mixed Load System

Electric motor drives are the largest industrial loads. Due to the development of power electronics, Variable frequency drives (VFDs) and DC regulators are increasingly used to control induction and DC motors. Since they are non-linear elements, these loads cause a large distortion of the current they receive from the power grid, which then results in a distortion of the supply voltage. This paper presents the results of practical measurements of the current and voltage distortion of the 18.5 kW motor controlled with VFD. Modeling and simulation of this drive were performed, followed by a comparison of the measurement and simulation results. It was analyzed how the Total harmonic distortion (THD) of current and voltage depends on the R-L parameters of the power grid, the power of the transformer, and the motor speed. Methods for mitigation of high-order harmonics caused by these loads are listed at the end of this paper. Modeling and simulation were performed using the Matlab/Simulink/SPS library.

With the goals of a better power factor and reduction in energy use, variable frequency drives (VFDs) have been standardized in various industrial applications including Heating, Ventilation, and Air-conditioning (HVAC) systems. However, key issues related to the deterioration in the power quality associated parameters (voltage harmonic distortion and current harmonic distortion) due to the growing number of VFDs demand a wholesome analysis of the problems faced by the users. In this present work, an analysis has been performed to investigate the potential impact of using alternating current (AC) line reactor and direct current (DC) link choke combination on harmonic mitigation in a VFD driven water-cooled centrifugal chiller compressor. Using a combination of AC line reactor and DC link choke as one of the low cost solutions in harmonic mitigation of a VFD driven load in HVAC systems can be decided based on the investigation done in this research work.

Problem. Electrical distribution networks are plagued by power quality problems, which have a negative impact on sensitive electrical loads. These problems include reactive current, low power factor on the load side, and voltage harmonics, voltage sags and voltage swells on the grid voltage side. To address these issues, a unified power quality conditioner (UPQC) that combines shunt and series compensators is suggested. The goal of the work is to implement a UPQC integrated with a photovoltaic (PV) system to mitigate power quality problems in the power system, and boosting the grid supply through power injection from the PV system. Methodology. One of the less complex and effective ways to improve the grid’s voltage quality is by using the unit vector template generation (UVTG) strategy as the composition technique (UPQC-P) through the UPQC series compensator. The synchronous reference frame (SRF) strategy through the UPQC shunt compensator to improve the current quality on the load side is used. To further optimize the SRF strategy, it is used the snake optimization (SO) to find the optimal values for the PI controller’s parameters. Results. The UPQC-PV is used to mitigation the power quality issues in the grid and loads by UVTG and SRF techniques in series and shunt compensators, respectively. Scientific novelty. The composition technique (UPQC-P) through a series compensator and uses the SO for tuning the PI controller in the shunt compensator. Practical value. This study reduces the total harmonic distortion (THD) in the load voltage to 0.57 %, while the THD in the grid voltage remains at 10 %. It restores the load voltage to its reference value of 230 V during voltage sags (down to 161 V) and swells (up to 300 V) in the grid. Additionally, it mitigates the low power factor on the load side (0.707 lagging) to achieve a unity power factor in grid current, balances the unbalanced load current to a balanced grid current, and enhances grid stability by injecting power from the PV system into the grid. References 33, table 3, figures 7.

This paper presents the electric power system analysis and design of an expanding steel cogeneration plant. The power system configuration and the equipment parameters of the cogeneration plant are well designed according to the power flow, short circuit, voltage fluctuation, harmonic flow and transient stability analyses. According to the power flow analysis, the site and capacity of shunt capacitor banks as well as the tap position of transformers are determined to maintain all the buses voltage at acceptable range and to keep the power factor above 0.95. Also, to comply with the restriction of circuit breaker capacity, the high impedance transformers are designed even if they consumed more reactive power from the system. In addition, the voltage fluctuation resulted from the dramatic reactive power variation of hot strip rolling mill can be greatly reduced if proper static var compensator (SVC) is installed. The significant voltage sag due to the starting of induction motor can be effectively improved by applying wye-delta transformer starter. Furthermore, the total voltage harmonic distortion (THD <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</sub> ) and the total current demand distortion (TDD <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</sub> ) are both acceptable if the proper filters are installed. It is also found that the cogeneration system can keep stable operation in isochronous mode by applying the governor control action and the load shedding scheme after tie line tripping. It is concluded that the power system analyses is important for the steel plant with cogeneration unit to identify hidden problems and remedy strategy to ensure the system power quality and operation performance.

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.

The dynamic stability improvement of a longitudinal power system using a power system stabilizer (PSS) and a static VAr (reactive volt-ampere) compensator (SVC) is reported. An analytical approach is developed for the determination of PSS parameters. The effect of static VAr compensators installed at several different locations along 345 kV trunk lines on system responses is examined. Results from time-domain simulations indicate that the PSS and the SVC are very effective in damping system oscillations. >

Nowadays, the consumer of energy has the concern in operating with a value of power factor inside of a value stipulated by the energy concessionaries. It is know that the power factor is related with the displacement power factor and the total harmonic distortion. The present work has as main objective the development and implementation of a linear compensator of displacement power factor objectifying to attenuate the negative impact traditionally caused by the discrete control of the reactive power at the fundamental frequency. In this work, the implementation of a compensator is made using a static compensation structure of reactive power (static VAr compensator - SVC) called TCR-FC (thyristor controlled reactor-fixed capacitor). The prototype of this kind of SVC is composed by a fixed capacitor (FC) in parallel with a fixed reactor in series with a bidirectional ac thyristor valve (or switch) (TCR). The proposed structure can be a single-phase or three-phase compensator. In the three-phase configuration, the compensator can be connected in wye or delta. The development of a linear control of reactive power can solve problems generated by the frequent switching of capacitor banks and makes possible the dynamic compensation of the flow of reactive power in the electrical system.

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.

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.

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.

The use of capacitors for correcting power factor is a very well known approach in industry. However, the increase of harmonic sources in power systems is heightening the risk of resonance and, consequently, a drastic decrease in electric power quality. In order to keep the rating voltage, the power factor and the voltage and current harmonic distortions within acceptable limits, a fuzzy control approach was implemented. Based on this approach, a software program that is able to decide on the optimal distribution of the capacitor banks has also been developed. The program decision is based of the rating voltage, the power factor and the whole voltage and current harmonic distortions. When necessary, the computer program derides on the use of filters for harmonic compensation, indicating the best filter and the corresponding tuning frequency. Furthermore, the approach is able to deal with some aspects concerning the electric losses, both on the rating frequency and on the harmonic components.

Harmonic distortion caused by nonlinear loads is a significant challenge in power systems, often resulting in reduced efficiency, overheating, and equipment malfunction. Despite the availability of various mitigation techniques, many fail to offer a cost-effective and practical solution for distribution networks. This research addresses that gap by designing and analyzing a five-stage single-tuned passive filter (STPF) system to mitigate harmonics in a 400V, 50Hz distribution network. The main objective is to reduce Total Harmonic Distortion (THD) in voltage and current to meet IEEE 519-2022 standards. The proposed filter system targets the 5th, 7th, 9th, 11th, and 13th harmonic orders using a simulation model developed in MATLAB/Simulink. The system initially showed high THD levels of 16.06% in voltage and 17.57% in current. After applying the filters, the voltage THD was reduced to 3.89%, and the current THD dropped to 2.52%. These results confirm the effectiveness of STPFs in improving power quality under nonlinear loading conditions.

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

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