Low-cost, SCR-based premium power quality variable speed drive technology

Harmonic analysis currently plays an important role for the power quality analysis because the non-linear loads, as source of the harmonic distortion, have significantly increased. The harmonic distortion influences power quality in power systems such as overheating of electrical equipment and aging of electrical equipment. Therefore, non-linear loads should be monitored in real time. This research proposes the design and implementation of the prototype current harmonic analysis that can be applied in real time based on S-transform Method. The equipment of this prototype can be explained as follows: CT-235, TZ2L9 and CT for KWH meters as current sensor, microcontroller AT mega 8535 as data acquisition, and Visual Basic software as displaying current waveform, current spectrum, rms current value, and total harmonic distortion (THD) for current. S-transform method is used to obtain the THD for current. The experimental result is validated by FLUKE 43B and the THD for current is accurately measured.

To reduce the conducted common-mode (CM) electromagnetic interference (EMI) and current total harmonic distortion (THD) in permanent magnet synchronous motor drive systems, this article proposes a finite control set–model predictive control (FCS–MPC) method for an H8 inverter considering the dead-time (DT) effect. In a real system, the DT causes unexpected peak common-mode voltages (CMVs) and distortion of the inverter output voltage, which deteriorates both the CM EMI and current THD. The conventional double active voltage vector (VV) based MPC methods with an H6 inverter may not be a good solution because of the numerous CMV variations and the limit of the VV transitions. In contrast, the proposed FCS–MPC method allows all VV transitions possible without the peak CMVs by instantly operating the series-connected switch of the H8 inverter based on the previous VV, predicted current sector, and next optimal VV. Furthermore, the nonlinearity of the inverter output voltage due to the DT is compensated in a discrete-time model used for the current prediction, considering the calculation delay of the digital controller. Consequently, the current THD as well as the CM EMI can be improved. The simulation and experimental results are presented to verify the effectiveness of the proposed method.

The focus of this paper is a theoretical calculation of current Total Harmonic Distortion (THD) for a current source single-phase multilevel PWM inverter with CL-filter. Analytical approach to current ripple mean square / current THD calculation was introduced in the 1980s for a 2-level voltage source inverter with inductance dominated RL-load. This paper presents a generalization of this approach for a single-phase multilevel current source PWM inverter with an arbitrary number of current levels accounting for the CL-filter effect. The output of this research is a closed-form analytical current THD solution. Though one of the assumptions is large switching-to-fundamental frequencies ratio, the formulas are practically accurate for the said ratio larger than 20-25. The formulas become quite compact and simple without a loss of accuracy when using a Bessel function approximation. They demonstrate a single-phase PWM current source inverter current THD dependence on CL-filter parameters and current modulation index.

The Unified Power Quality Conditioner (UPQC) is a technology that has successfully addressed power quality issues. In this paper, a photovoltaic system with battery storage powered Unified Power Quality Conditioner is presented. Total harmonic distortion of the grid current during extreme voltage sag and swell conditions is more than 5% when UPQC is controlled with synchronous reference frame theory (SRF) and instantaneous reactive power theory (PQ) control. The shunt active filter of the UPQC is controlled by the artificial neural network to overcome the above problem. The proposed artificial neural network controller helps to simplify the control complexity and mitigate power quality issues effectively. This study aims to use a neural network to control a shunt active filter of the UPQC to maximise the supply of active power loads and grid and also used to mitigate the harmonic problem due to non-linear loads in the grid. The performance of the model is tested under various case scenarios, including non-linear load conditions, unbalanced load conditions, and voltage sag and voltage swell conditions. The simulations were performed in MATLAB/Simulink software. The results showed excellent performance of the proposed approach and were compared with PQ and SRF control. The percent total harmonic distortion (%THD) of the grid current was measured and discussed for all cases. The results show that the %THD is within the acceptable limits of IEEE-519 (less than 5%) in all test case scenarios by the proposed controller.

Multiphase machines are a promising alternative for high-reliability applications. In these applications, overmodulation (OVM) is important since it allows attaining higher modulation indices by injecting, besides zero-sequence voltage harmonics, current-producing ones. In general, the existing techniques are able to limit to some extent the current total harmonic distortion (THD). However, most do not ensure the minimum current THD, thereby not guaranteeing the minimum harmonic stator copper loss. Furthermore, most are intended just for particular phase numbers <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$n$</tex-math></inline-formula> , symmetrical/asymmetrical winding arrangements and neutral-point (NP) configurations. OVM with low THD remains unaddressed in most types of multiphase motors. This paper overcomes these limitations by proposing a generalized OVM strategy that attains the minimum current THD in induction motors with any <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$n$</tex-math></inline-formula> , winding arrangement and NP configurations. Two techniques are outlined. One of them injects only non-torque-related harmonics, while the other technique exploits torque-producing harmonics to further reduce the current THD and to attain modulation indices up to square waveform. The superiority of the proposal in terms of current THD is substantiated through studies for multiple kinds of multiphase machines. The experiments are performed by using two six-phase induction motors with symmetrical/asymmetrical windings when 1 and 2 NPs are set.

Exposing electric vehicles (EV) to extreme temperatures limits its performance and charging. For the foreseen adoption of EVs, it is not only important to study the technology behind it, but also the environment it will be inserted into. In Europe, temperatures ranging from −30 °C to +40 °C are frequently observed and the impacts on batteries are well-known. However, the impact on the grid due to the performance of fast-chargers, under such conditions, also requires analysis, as it impacts both on the infrastructure’s dimensioning and design. In this study, six different fast-chargers were analysed while charging a full battery EV, under four temperature levels (−25 °C, −15 °C, +20 °C, and +40 °C). The current total harmonic distortion, power factor, standby power, and unbalance were registered. Results show that the current total harmonic distortion (THDI) tended to increase at lower temperatures. The standby consumption showed no trend, with results ranging from 210 VA to 1650 VA. Three out of six chargers lost interoperability at −25 °C. Such non-linear loads, present high harmonic distortion, and, hence, low power factor. The temperature at which the vehicle’s battery charges is crucial to the current it withdraws, thereby, influencing the charger’s performance.

The new revision of IEEE Standard 519 became official in 1993. The new standard has been greatly expanded and includes additional stringent limits on individual and total current harmonic distortion in addition to the voltage distortion and line notching limits already included in IEEE Standard 519-1981. A modern industrial power system may include variable frequency drive (VFD) loads at several locations. The new standard requires a careful global harmonic analysis of the entire power system to specify the right type of VFD technology for the application and ensures compliance with the standard. This paper presents a general methodology for computing voltage and current distortion in accordance with IEEE 519-1992. The paper presents a case study that further emphasizes the importance of harmonic analysis. The impact of the new standard on the state-of-the-art of VFD technology is discussed. >

This paper presents a new topology of three-level transformer-less photovoltaic (PV) inverter. In this topology, a 240V AC system is developed from a full bridge inverter circuit using PIC microcontroller (PIC16F628A-I/P) connected to an array of PV panel through a power factor correction circuit. The output waveform of the inverter depends on the type of pulse driver. The inverter is connected to the utility supply, on the clear day, the ac load is served by the inverter but on the cloudy day or night where solar irradiance is low, the inverter through its PIC microcontroller automatically changes from the usage of inverter to the utility supply. Objective of this paper is to optimize the maximum voltage angle to obtain the lowest current total harmonic distortion (CTHD) of the uninterruptible power supply (UPS) on the three-level single phase transformer-less inverter. In this paper, the maximum voltage angle optimization of the AC three-level waveform transformer-less PV inverter is developed and created by a microcontroller PIC16F627A-I/P changing maximum voltage angle of the AC three-level waveform from 20° to 180°. Resistive load of 30 W lamp and inductive load of 20 W water pump are applied to the transformer-less PV single phase inverter. The result shows that the lowest CTHD of 15.448% is obtained when the maximum voltage angle is 134°.

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

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.

To reduce the conduction loss, a novel three-phase current source rectifier, named Delta-type Current Source Rectifier (DCSR), has been proposed in previous research. This rectifier has delta-type connection on its input side, and its dc-link current can be shared by multiple devices at a time to reduce up to 20% conduction loss. A high-efficiency modulation scheme for DCSR has been proposed, where the conduction states involve more switches to share the dc-link current. However, it causes current distortion when the input voltages have intersections. In this paper, the phenomenon is analyzed in detail. The clamped voltage on the diode bridge will fluctuate at the voltage intersections, resulting in false current pulse and distortion. An improved modulation scheme is then proposed for DCSR to reduce the input current distortion without sacrificing much efficiency. Through experiment in a 7.5 kW prototype, its effectiveness is verified and the total harmonic distortion (THD) of the input current is reduced dramatically.

Offline pulse width modulation (PWM) techniques are employed to reduce the line current distortion in induction motor (IM) drives where the switching frequency is highly constrained. An optimal PWM technique is proposed here for a neutral point clamped (NPC) inverter fed IM drive to minimize the motor current distortion, subject to constraints on number of switching instants per quarter cycle. Two types of pole voltage waveforms of the NPC inverter are considered, namely type-I and type-II. This paper reports optimal switching angles for both type-I and type-II waveforms to minimize the resulting total harmonic distortion (THD) in motor current. In general optimal type-II is found to result in lower THD than optimal type-I PWM. The optimal type-II PWM offers superior performance in terms of motor current distortion than synchronized sine-triangle PWM and selective harmonic elimination PWM, as shown by simulation and experimental results on an NPC inverter fed 3.7 kW induction motor drive.

In today's electrical system, the integration of Solar Photo Voltaic (PV) into the grid is actively promoted to address the rising demand for electrical power and mitigate environmental concerns associated with fossil fuel consumption. Power Quality (PQ) emerges as a crucial concern that impacts both utilities and consumers. The onset of PQ issues in the contemporary electric power system stems from the interconnection of PV, the adoption of grid technologies, the widespread utilization of power electronics equipment and the utilization of advanced optimization techniques to obtain maximum power from PV. This paper proposes a MOGWO controller-based PV DSTATCOM employing a PUC5 inverter to address the PQ problems, which are to obtain the maximum power from the three solar panels and minimum Total Harmonic Distortion. The voltage-source inverter's control signals are derived through the PQ control scheme. The effectiveness of the suggested system is validated through MATLAB outcomes. The results underscore the significance of the proposed MOGWO-based MPPT algorithm in enhancing performance and notable enhancements achieved in the performance of the PV-DSTATCOM, leading to simultaneous improvements in current Total Harmonic Distortion (THD), which is obtained around 3.29%.

This paper presents the modelling and simulating of a general wind power system with double-fed induction generator controlled by a back-to-back converter, in order to manage power delivery to or absorbed from the grid through reactive compensation and active filtering of electrical current. The system modelling and the controller design was developed in Matlab®/Simulink® software, where the rotor-side converter control regulates torque and controls active and reactive power. The grid-side converter control maintains the DC link voltage constant and compensates reactive power demanded from the load, besides this converter acts as an active power filter, which improves the total harmonic distortion of the grid current. The main difference of the proposed methodology with respect to others in the literature is the implementation of grid side converter control as an active power filter using proportional integral resonant to mitigate the 5ª, 7ª, 11ª and 13ª harmonics instead of simple Proportional-Integral (PI) controller, which reduces the accomplishment difficulties since the decoupled term is eliminated. The results obtained shows the correction of the power factor and the extraction of the maximum power from the wind. Finally, it is shown harmonic compensation for nonlinear loads and improvement of the total harmonic distortion of the grid current.

In this work, the direct torque control (DTC) is applied to the five-phase permanent magnet synchronous motor (FP-PMSM). The DTC method based on classical space vector pulse width modulation (SVPWM) is a common solution used to overcome traditional problems; such as stator flux ripple, electromagnetic torque ripple and gives more total harmonic distortion (THD) of the stator current. The actual paper is based on improving the performance of DTC-SVPWM by using the feedforward neural networks (FNNs) instead of the proportional-integral (PI) regulators and hysteresis comparators (HCs) of the conventional SVPWM strategy. This algorithm can solve the traditional PI regulators and HCs problems which are represented in responses dynamic and reduce the torque ripple, flux ripple, and the THD of stator current of FP-PMSM drives. The proposed strategy was tested in different tests with simulation using Matlab software.