Power Quality Of Grid Research Articles

Multi Agent Interaction Mechanism of Intelligent Network Connection for Interaction Between EV and Power Grid

As a new type of flexible load, the charging behavior of electric vehicles is random and intermittent in space and time, which puts forward higher requirements for the safe, stable grid operation and power quality. When a large-scale electric vehicle charging load is connected to the power grid, its disordered charging behavior will also bring adverse effects to the power system. From the perspective of charging behavior, the gradual increase of devices such as electric vehicles and charging piles have formed the Internet of Electric Vehicles, power distribution network, and charging equipment Internet of Things. At the same time, more and more charging loads are connected to the grid, and the charging behavior also contains a lot of load information on the grid side. These data are fused through the server, which can provide an economical and reasonable charging strategy for the charging behavior of electric vehicles on the regional grid side.

Power Quality in the Hybrid Grid PV-Wind-Battery by the Multi-Input Transformer-Coupled Bidirectional DC-DC Converter

Abstract: A control strategy for power flow management of a grid-connected hybrid photovoltaic (PV)–wind-battery- based system with an efficient multi-input transformer-coupled bidirectional dc–dc converter is presented. The proposed system aims to satisfy the load demand, manage the power flow from different sources, inject the surplus power into the grid, and charge the battery from the grid as and when required. A transformer-coupled boost half-bridge converter is used to harness power from wind, while a bidirectional buck– boost converter is used to harness power from PV along with battery charging/discharging control. A single-phase full-bridge bidirectional converter is used for feeding ac loads and interaction with the grid. The proposed converter architecture has reduced number of power conversion stages with less component count and reduced losses compared with existing grid-connected hybrid systems. This improves the efficiency and the reliability of the system. Simulation results obtained using MATLAB/Simulink show the performance of the proposed control strategy for power flow management under various modes of operation. The effectiveness of the topology and the efficacy of the proposed control strategy are validated through detailed experimental studies to demonstrate the capability of the system operation in different modes.

Enhancing the Power Quality of Grid Connected Photovoltaic System during Fault Ride Through: A Comprehensive Overview

Enhancing the Power Quality of Grid Connected Photovoltaic System during Fault Ride Through: A Comprehensive Overview

A High-Frequency Digitiser System for Real-Time Analysis of DC Grids with DC and AC Power Quality Triggering

The presence of DC grids in distribution networks is being increased nowadays and is expected to be quite relevant in a near future, due to several advantages compared to traditional AC systems. Regardless of this, Power Quality in DC grids (DC PQ) (voltage variations, transients, spectral components, etc.) still remains not properly considered and there is a lack of reference normative documents such as standards, application guides or technical reports for their application. In this context, it is necessary to obtain more experience on real measurements, in order to define appropriate DC PQ parameters and limits that assess a reliable operation of the whole power network and eventually lead to establishing a reference frame acceptable for both generation sources and final users. In this work, a novel high frequency (up to 4 MS/s) digitiser system is presented for the study of DC PQ events. The system is designed to acquire waveforms with triggers fired by events in both DC and AC signals. The captured signals are pre-processed in real-time to be able to recover pre-trigger information stored in memory. The system was installed in a real DC micro-grid and configured to take data in an unattended way. Additionally, the results of the first months of data acquisition are presented.

Electrolytic capacitor‐less reduced power processing single‐phase LED driver with power decoupling using split capacitor

SummaryLight emitting diode (LED) driver systems are now moving toward reduced processing power to improve conversion efficiency in indoor and outdoor applications. LED drivers connected to a single‐phase supply must meet the requirements for power factor correction with lower input current harmonics to maintain the alternating current (AC) power grid's quality and maintain a constant current through the LED load to eliminate the flickering effect in the light output. An LED driver is required to fulfill these requirements. In this paper, a new reduced processing power LED driver is proposed. By splitting the output capacitor into two capacitors and with the help of hardware design, the processing power can be reduced by using fewer semiconductors than in earlier designs. The proposed driver employs a simple ripple cancellation control approach to eliminate the 100 Hz ripple in the LED load current. Using this principle, an LED driver was designed and tested. The experimental results demonstrated that the proposed LED driver achieved an input power factor close to unity with lower input current harmonics and 92.5% of peak efficiency when operating at full power.

A New Multilevel Inverter Based Grid Connected Reliable Solar Power Transfer Unit With Power Quality Enhancement

This article proposes a multilevel inverter (MLI) based grid-connected solar power transfer unit (PTU). This work is a technological enhancement for the interconnection of photovoltaic (PV) array and distribution grid for mitigating the present energy crisis and power quality issues. The proposed MLI generates nine-level output voltage with a minimum device count and reduced losses. Hence, it provides a low harmonic AC waveform with higher efficiency when compared to the reported topologies. The MLI configuration consists of two isolated DC sources, realized by PV array management in a ratio of 3:1. Eight switches are used in the circuit, out of them, two are bidirectional to achieve the four-quadrant operation and thereby realize the control of reactive power flow. The least number of ON-OFF transitions in high power switches are ensured to minimize the switching losses. The single-stage PTU is controlled to extract the maximum power from PV arrays at varying irradiance levels. The shunt-connected PTU is controlled with an adaptive least mean square algorithm to enhance the grid power quality by meeting the nonlinear local load demands. Three modes of PTU operation are presented in this work according to the available PV power and load power information, and the grid power quality compliance with the IEEE-519 standard is verified in each mode. Battery-supported DC bus voltage regulation is adopted to overcome the reliability issue of the solar PV array power. The proposed system is designed and simulated in MATLAB/Simulink and tested at various operating conditions. Further, the real-time system behavior is tested and validated on a hardware model.

A Unified Control of Grid-Interactive Off-Board EV Battery Charger With Improved Power Quality

This article presents a self-tuning filter (STF) and sliding mode control (SMC)-based control algorithm for a grid-interactive off-board electric vehicle (EV) battery charger to power the EV batteries and simultaneously improve the grid power quality. In grid-connected operation (GCO), the charger uses the STF-based control strategy to estimate the fundamental load current and synchronize voltage templates to generate a pure sinusoidal reference current. Compared to the phase-locked loop (PLL) and the second-order generalized integrator (SOGI), the STF-based technique precisely estimates the synchronizing voltage templates during nonideal grid voltage conditions. Therefore, in GCO, the charger reference current ensures the unit power factor in the grid-to-vehicle/vehicle-to-grid (G2V/V2G) operation mode and the harmonic free grid current in the charger-for-grid (C4G) operation mode. Furthermore, the charger operates in the vehicle-to-load (V2L) operation mode during grid outages to maintain an uninterrupted supply to the residential load. The control algorithm also includes a grid synchronization technique to achieve a smooth transition between GCO and V2L. Furthermore, an SMC-based dc-link voltage controller (SMC-DLVC) is proposed to reduce dc-link voltage overshoot with finite-time convergence during external disturbances in all operation modes. The performance of the proposed control algorithm is validated in a 12.6-kVA off-board charger laboratory prototype under ideal/nonideal grid voltage conditions.

Effect of LED Lighting on Selected Quality Parameters of Electricity.

Recently, various technological light sources have appeared on the market. As a result, it is extremely important to evaluate the characteristics of the available lamps and the impact they may have on the power grid. This article presents regulations and standards for power quality, including higher current and voltage harmonics, and analyzes three selected light-emitting diode lamps. The purpose of the study was to analyze the impact of LED lighting systems on the power quality (PQ) of the electric grid. The results of measurements of parameters determining the power quality of the electricity consumed by modern LED light sources used for room lighting are presented. Commercially available lamps and low-power power supplies (25 to 35 W) with an output current of 350 mA were used for the study. The current waveforms of selected lamps during their connection to the power grid, the results of harmonic emission tests, as well as the effect of increasing the load of selected DC power supplies (drivers) on THD, power factor (PF), and their efficiency are presented. The significant negative impact of power supply circuits in compact LED lamps on the power quality parameters of lighting circuits was demonstrated. The tested lamps significantly exceed the permissible limits of harmonics and THD. Test results have shown that LED lamps show significant savings in electricity consumption, but they behave as nonlinear loads. They generate high-frequency current harmonics, which can lead to degradation of power quality in the distribution network. Therefore, if the primary concern for the user is power quality rather than power savings, traditional incandescent lamps would be a much better choice. When using switched-mode power supplies, attention should be paid to their load rating. You should avoid using power supplies in the lower ranges of permissible load capacity. A more heavily loaded power supply has better performance due to power quality and efficiency.

Energy Management Optimization of Fuel Cell Hybrid Ship Based on Particle Swarm Optimization Algorithm

In order to optimize the energy management strategy and solve the problem of the power quality degradation of fuel cell hybrid electric ships, a particle swarm optimization algorithm based energy management strategy is proposed in this paper. Taking a fuel cell ship as the target ship, a system simulation model is built in Matlab/Simulink to verify the proposed energy management strategy. Through simulations and comparisons, the bus voltage curve of the optimized hybrid power system fluctuates more gently, and the voltage sag is smaller. The amplitude of the voltage fluctuation under maneuvering conditions is reduced by 55% compared with that of the original ship. The charging and discharging process of the composite energy storage system is optimized under maneuvering conditions, the power quality of the marine power grid is improved, and the use of the energy management strategy can extend the service life of the battery.

Design and Implementation of a SiC-Based Multifunctional Back-to-Back Three-Phase Inverter for Advanced Microgrid Operation.

Because of the worldwide trend of microgrid (MG) and renewable energy (RE)-based distributed power generation (DG), advanced power flow control schemes with wide bandgap (WBG) semiconductor technologies to ensure high-level performance of grid-connected MGs is one of the crucial research topics. In grid-connected MGs, a static switch (SS) is commonly used at the point of common coupling (PCC) of two systems. In this paper, the role of SS is replaced by a SiC-based three-phase back-to-back (BTB) inverter system for seamless switching between grid-connected and standalone modes through advanced power flow control schemes. According to scenarios of different grid/load conditions and available DG capacities in an MG, various advanced control functions can be developed for both MG operating modes: bidirectional control of active and reactive power flows, seamless switching between operating modes, improvement of grid power quality (PQ), and voltage stabilization. In this paper, mathematical models of the BTB inverter in a synchronous reference frame (SRF) is first derived, and the required controllers are then designed. For functional testing, two typical cases are simulated and analyzed in a MATLAB/Simulink environment and then verified through 1kVA small-scale hardware implementation with Texas Instruments (TI) digital signal processor (DSP) TMS320LF2812 as the control core. Results show satisfactory performances of power flow control and PQ improvement of MG.

Influence of photovoltaic microgeneration on the demand profile and its effects on the grid power quality

• Demand profile effects can cause a false impression of low power quality. • High PV inverter loading percentage conditions can improve the grid power quality. • PV inverter active current has a linear relationship with inverter loading. • PV inverter non-active current does not vary considerably with inverter loading. The connection of small-scale photovoltaic (PV) generation into the grid requires attention to the changes in load curve profile, the harmonic components in the current waveform, and the customer power factor (PF) variation measured by the grid operator. This paper evaluates aspects that can influence the power quality (PQ) at the point of common coupling (PCC) due to PV generation's insertion in the distribution grid, given the consumer demand profile. That evaluation considers different inverter loading percentage situations and the effects of the consumer's electric current considering its active and non-active components. This study used four grid-connected PV systems and a programmable electronic load to perform tests at different load demand situations. A data acquisition system collects the voltage waveforms at the PCC, and the grid's current waveforms, load, and PV inverter. Thus, it is possible to evaluate the effects of load profile (current intensity and waveform) on PQ at the PCC. At this point, there are different values of active and non-active currents, total harmonic distortion (THD), and PF when measured from the PV system, the grid, or the load sides. Depending on where the measure is, the PV system can cause a false impression of reducing the grid PQ.

Adaptive Polynomial Harmonic Distortion Compensation in Current and Voltage Transformers Through Iteratively Updated QR Factorization

Measuring current and voltage harmonics has paramount importance for improving the power quality of distribution grids. However, the achieved accuracy strongly depends on the adopted instrument transformer. The present paper proposes an adaptive technique that enables an effective compensation of both the filtering behavior and the harmonic distortion introduced by current and voltage transformers, namely the strongest nonlinear effect at low-order harmonics. The approach is based on a flexible, linear in the parameters polynomial modeling of harmonic distortion in the frequency domain. Model complexity can be different from one harmonic to the other, and it is selected through an automatic iterative process to suit the nonlinear behavior at each specific harmonic order, while avoiding overfitting. In particular, the number of parameters is increased by progressively updating the QR factorization of the regressor matrix trough Householder reflections, until a convergence condition is reached. Experimental tests performed on an inductive VT and CT highlight the effectiveness of the approach.

Simulation Model for Passive Harmonic Filters Using Matlab/Simulink: A Case Study

Electrical grid power quality is a global issue. The grid must supply electricity at sinusoidal voltages and currents without frequency or amplitude fluctuations. Harmonics from non-linear loads change the stable reference point voltage waveform and cause other problems. Harmonic reduction is essential for grid health. Electrical and electronic equipment users, manufacturers, and suppliers all contribute. This article presents a case analysis of the plastic processing industry, which has historically struggled with a difficulty related to the fifth harmonic. Unwanted harmonics are reduced by using a single-tuned passive filter, a double-tuned passive filter, and a second-order damped filter. The total harmonic distortion is almost identical, but the second-order damped filter provides the best harmonic mitigation, meeting the requirements of the IEE 519-1992 Standard.

Boost Packed E-Cell: A Compact Multilevel Converter for Power Quality Ancillary Services

This paper proposes Boost Packed E-Cell (BPEC) as an affordable Compact Multilevel Converter (CMLC) for the power quality ancillary services. The BPEC is a transformerless bidirectional CMLC topology and can generate symmetrical and asymmetrical multilevel voltage waveforms with 5-to-11-level resolution using only three low-voltage dc capacitors and eight power switches. Thanks to the serial expansion of the two dc capacitors, BPEC has two dc-links, which means two voltage sensors are enough to control three dc capacitors. Despite other CMLCs, BPEC does not need a fault detector and inherently generates a symmetrical 5-level or an asymmetrical 7-level voltage waveform in the event of a fault of the middle switches or their gate drivers. As a case study, a single-phase Compact Active Power Filter (CAPF) is designed in this paper based on the BPEC to compensate for harmonics and reactive power caused by unknown non/linear loads, simultaneously. Finite control set predictive control strategy is also adopted based on the switched model of the power system containing the grid, unknown non/linear loads, and the BPEC to address the grid power quality concerns. The experiments performed by a prototype including the BPEC power board, MicroLabBox, OPAL-RT OP8662, and Chroma 61086 verify the merits of the proposed CAPF in practice.

Deep learning based real time Demand Side Management controller for smart building integrated with renewable energy and Energy Storage System

Electric Power Consumption (EPC) and Renewable Energy Generation (REG) are inconsistent and this fickle nature affects the utility grid's power quality and system stability. The electric transmission and distribution infrastructure must be upgraded to meet the consumer's peak demand. Hence, proposing a Demand Side Management (DSM) program in smart grid to reduce utility grids Peak to Average Ratio (PAR) and end-users electricity tariff. Renewable energy with Energy Storage System (ESS) in the DSM controller is used to enhance the end user's economic and environmental features. This article proposes a Recurrent Neural Network (RNN) based Long Short Term Memory (LSTM) framework for Science Block (SCB) every minute and 5 min of EPC and REG forecasting to develop the DSM program. This proposed deep learning model performance, is evaluated using Mean Squared Error (MSE), Mean Absolute Error (MAE), Root Mean Square Error (RMSE) and R-squared. The results show that the proposed DSM program benefits end electricity users and smart grid operators.

Control of Dynamic Performance Through Feedback Converter SSC In Grid Integrated Wind Energy System

A feedback converter-based Static series compensator (FBC-SSC) is a device that can simultaneously compensate for currents and voltages in a distribution network to enhance the Power Quality (PQ) in Grid integrated Energy System (GIWES). PQ is a term that refers to the conjunction of voltage and current stability. Electronically operated and non-linear gadgets with significant applicability in distribution networks and enterprises have become significant aspects due to PQ constraints such as imbalance voltage and frequency, and transients. Improved hysteresis-based FBC-SSC is suggested in this study for optimizing PQ in GIWES. The novelty in this research is improved hysteresis or hybrid PI and PWM-based hysteresis controlled FBC-SSC. In a wind turbine generation system, improved hysteresis based is used to find the gate trigger pulse for SSC. The suggested controller, when combined with FBC-SSC, improves the WES dynamic performance. Simultaneously, the grid network can compensate for current and voltage irregularities in nearby terminals. All converters in the proposed topology share a standard dc-link capacitor. As a result, power can be transmitted from one distributor to another. The proposed topology is modelled in the MATLAB/SIMULINK environment. The effectiveness research is performed using the improved hysteresis controller. Finally, the obtained results are compared to two existing controllers: a Proportional Integral controller and a traditional Pulse Width Modulation (PWM) controller. As a consequence, the performance level can show that the advised technique is effective. When compared to another typical control approach, the suggested system obtains remarkably low THD values of 0.94 percent.

Extended Simplified Electro-Mechanical Model of a Variable-Speed Wind Turbine for Grid Integration Studies: Emulation and Validation on a Microgrid Lab

The energy transition towards renewable energies is crucial for the sustainable development of a society based on hydrocarbons. The current level of penetration and growth of wind energy in electric power systems is evident and many researchers have presented new methods for simulating and representing the electrical and mechanical characteristics of variable-speed wind turbines. However, complete mathematical models developed and implemented, for example, in MATLAB/Simulink® software, require significant computational efforts that could make grid studies impractical when its scale tends to increase. To contribute to facing this issue, this paper proposes an extended simplified model for a variable-speed wind turbine that considers the dynamic behavior of its mechanical system and includes an approximate representation of the power electronic converter. This approach broadens the scope of studies related to grid frequency control and power quality (fast-frequency response, primary frequency control, and voltage control, among others), considerably reducing the computational burden. Several validations of the proposed simplified model are presented, including comparisons with a doubly fed induction generator-based wind turbine model (phasor type) from the MATLAB/Simulink® library, and laboratory experiments under controlled conditions. The results show a good fit of the proposed simplified model to the MATLAB/Simulink® model, with minimal delays about 3% of the wind turbine inertia constant. Moreover, with the proposal, the computational time is reduced by up to 80% compared to a detailed model. This time reduction is achieved without penalizing the numerical accuracy and the estimation quality of the real behavior of the variable-speed wind turbine.

Integration of renewable energy sources in the dynamic voltage restorer for improving power quality using ANFIS controller

Nowadays, grid power loss and power quality deterioration are causing many problems, especially for sensitive uses such as data centers, airports, healthcare, banking, insurance, and telecom. These issues must be resolved through energy continuity coverage and optimization. Dynamic voltage restorers (DVR) are generally used to mitigate network voltage disturbances and maintain a constant voltage value between load terminals for a short and limited duration due to limited energy storage facilities. However, this paper's proposed (DVR) system controlled by the adaptive-network fuzzy inference system (ANFIS) controller can compensate for prolonged power quality disturbances by integrating a hybrid renewable energy system (HRES) managed using classical Proportional Integral (PI) controller power management. This paper proposes a new (DVR) topology coupled with a hybrid renewable energy system (HRES) to exploit free and clean energy, consisting of a solar panel, a PEM fuel cell, and a battery storage device connected through DC-DC converters to a DC transmission, the obtained results from the simulation process of the proposed DVR system in the environment of MATLAB / Simulink showed the ability to eliminate sag that exceeded 0.9 pu in a period of more than 3 min and swells that exceeded 1.2 pu in a period that exceeded one minute. In comparison, the load voltage's total harmonic distortion THDv was reduced from 29% to 5%, and the source current total harmonic distortion THDi from 30.25% to 2.79%.

Torque Control for PMSG-Based Wind-Power System Using Stationary abc-Reference Frame

The power system of wind farms is generally characterized by a weak grid, in which voltages may be heavily distorted and imbalanced, challenging the control scheme of wind-power converters that must be impervious to such disturbances. The control scheme in the stationary natural abc-frame has shown good performance under non-ideal voltage conditions, and then this paper proposes to analyze the operational performance of a wind-power system based on a permanent magnet synchronous generator subject to non-ideal conditions of the grid voltage, with its control scheme devised in the abc-reference frame. The proposed control scheme considers the torque control decoupling the flux and torque for the generator-side, showing the possibility to implement the machine torque control, without any coordinates transformation using a closed loop dot-product approach, between the field flux and stator currents. For the grid-side converter, the load current compensation is proposed, using the load current decomposition and conservative power theory (CPT), improving the grid power quality. The simulation results estimate the performance of the grid-side control under distorted and asymmetrical voltages, and the generator-side control against torque disturbances due to wind speed variation. Finally, experimental results in a small-scale test bench validate the proposed control scheme in injecting active and reactive power into the grid, and the torque control under wind speed variation.

Research on optimization strategy of harmonic suppression and reactive power compensation of photovoltaic multifunctional grid connected inverter

In this paper, a new harmonic suppression and reactive power compensation strategy based on photovoltaic multi-functional grid connected inverter (PVMFGCI) and a three-layer optimization model based on adaptive ant colony algorithm are proposed for optimal control of power quality of grid connected photovoltaic (PV) power generation system. Here, an improved CPT (Conservative Power Theory) current detection method is used to extract harmonic and reactive current components from the load current, and a new PVMFGCI hierarchical optimization model is developed to optimize the power quality at the common connection point (CCP). The proposed three-layer optimization model is an improved form of the two-layer optimization model, which successfully solves the contradiction between the active power grid connection of the PV grid connected inverter and the power quality control. The main objective of the proposed three-layer optimization model is to meet the requirements of active power output of PV power generation, and at the same time, to utilize the remaining capacity of the inverter to control harmonics and compensate reactive power. However, when the remaining capacity of PVMFGCI is sufficient, PVMFGCI can reasonably allocate the remaining capacity through the three-layer optimization model to meet the optimal power quality at the CCP. In this process, the power quality of the microgrid is improved. PVMFGCI provides reactive power compensation, harmonic control and other power quality problems. In addition, when the remaining capacity of PVMFGCI is insufficient, it only needs to maximize the active power and make the harmonic distortion rate and power factor meet the grid connection requirements, which improves the utilization rate of PVMFGCI. The proposed techniques are modeled and the IEEE 33 bus systems are analyzed and their performances are verified experimentally on a developed prototype, in PV output active power variation condition, imbalance loading condition for linear/nonlinear loads, where it has shown a very good performance. The effect of harmonic control and reactive power compensation at each node of the system is obvious.