Active Filter Modelling To Mitigate Harmonics Generated By Electric Vehicle Chargers

The Automotive industry is going through a rapid transformation to adopt electrified technology. A major share of the electrified vehicles is going to be in the Battery electric vehicles (BEVs) and plug in hybrids segments that need to connect to the grid to recharge the batteries. For customer convenience, the time required for fully charging the battery need to be brought down significantly. EV charging stations are getting installed that could bring down the charging time to less than 30 minutes. However this pose a unique issue to the power quality of the utility grid. During charging, the EV charging unit injects harmonics to the grid. When a large number of EVs are getting charge simultaneously, which is a likely scenario in the future, the degradation in the power quality of the grid would be significant. This thesis discuss the modelling of an active filter to reduce the Total harmonic distortion (THD) generated by electric vehicle (EV) chargers. The main objective of this thesis is to determine the percentage of harmonic current injected by the EV chargers to the power grid and to model an active filter to mitigate the harmonic distortion generated by these chargers. The active filter is modelled as bidirectional three-phase pulse width modulation (PWM) rectifier. The EV in this proposed model is represented as an injected current harmonic source. Positive sequence synchronous reference frame controller (SRFC) is used to generate the reference current. The hysteresis controller is used to compare the load current and injected current, and its output is used to generate the switching pulses for Metal oxide semiconductor field effect transistor (MOSFET). The DC link voltage control is achieved by using conventional Proportional and integral controller (PI) and fuzzy logic control PI. MATLAB/Simulink simulation result shows that the proposed filter can be used to mitigate the THD of EV chargers without violating the limit set by IEEE Std. 519 - 1992

Power quality and electromagnetic compatibility: special report, session 2

The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems. Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages). The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks: Block 1: Electric and Magnetic Fields, EMC, Earthing systems Block 2: Harmonics Block 3: Voltage Variation Block 4: Power Quality Monitoring Two Round Tables will be organised: - Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13) - Reliability Benchmarking - why we should do it? What should be done in future? (RT 15

Investigation of domestic level EV chargers in the Distribution Network: An Assessment and mitigation solution

This research focuses on the electrification of the transport sector. Such electrification could potentially pose challenges to the distribution system operator (DSO) in terms of reliability, power quality and cost-effective implementation. This thesis contributes to both, an Electrical Vehicle (EV) load demand profiling and advanced use of reactive power compensation (D-STATCOM) to facilitate flexible and secure network operation. The main aim of this research is to investigate the planning and operation of low voltage distribution networks (LVDN) with increasing electrical vehicles (EVs) proliferation and the effects of higher demand charging systems. This work is based on two different independent strands of research. Firstly, the thesis illustrates how the flexibility and composition of aggregated EVs demand can be obtained with very limited information available. Once the composition of demand is available, future energy scenarios are analysed in respect to the impact of higher EVs charging rates on single phase connections at LV distribution network level. A novel planning model based on energy scenario simulations suitable for the utilization of existing assets is developed. The proposed framework can provide probabilistic risk assessment of power quality (PQ) variations that may arise due to the proliferation of significant numbers of EVs chargers. Monte Carlo (MC) based simulation is applied in this regard. This probabilistic approach is used to estimate the likely impact of EVs chargers against the extreme-case scenarios. Secondly, in relation to increased EVs penetration, dynamic reactive power reserve management through network voltage control is considered. In this regard, a generic distribution static synchronous compensator (D-STATCOM) model is adapted to achieve network voltage stability. The main emphasis is on a generic D-STATCOM modelling technique, where each individual EV charging is considered through a probability density function that is inclusive of dynamic D-STATCOM support. It demonstrates how optimal techniques can consider the demand flexibility at each bus to meet the requirement of network operator while maintaining the relevant steady state and/or dynamic performance indicators (voltage level) of the network. The results show that reactive power compensation through D-STATCOM, in the context of EVs integration, can provide continuous voltage support and thereby facilitate 90% penetration of network customers with EV connections at a normal EV charging rate (3.68 kW). The results are improved by using optimal power flow. The results suggest, if fast charging (up to 11 kW) is employed, up to 50% of network EV customers can be accommodated by utilising the optimal planning approach. During the case study, it is observed that the transformer loading is increased significantly in the presence of D-STATCOM. The transformer loading reaches approximately up to 300%, in one of the contingencies at 11 kW EV charging, so transformer upgrading is still required. Three-phase connected DSTATCOM is normally used by the DSO to control power quality issues in the network. Although, to maintain voltage level at each individual phase with three-phase connected device is not possible. So, single-phase connected D-STATCOM is used to control the voltage at each individual phase. Single-phase connected D-STATCOM is able maintain the voltage level at each individual phase at 1 p.u. This research will be of interest to the DSO, as it will provide an insight to the issues associated with higher penetration of EV chargers, present in the realization of a sustainable transport electrification agenda

A Practical Approach for Coordination of Plugged- In Electric Vehicles To Improve Performance and Power Quality of Smart Grid

This PhD research is undertaken by supplications including 14 peer-reviewed published articles over seven years research at Curtin University. This study focuses on a real-time Plugged-in Electric Vehicle charging coordination with the inclusion of Electric Vehicle battery charger harmonics in Smart Grid and future Microgrids with incorporation of Renewable Energy Resources. This strategy addresses utilities concerns of grid power quality and performance with the application of SSCs dispatching, active power filters or wavelet energy

Harmonic and Supraharmonic Emissions of Plug-In Electric Vehicle Chargers

open1noElectric vehicle (EV) charging represents a relevant electric load with a rapid evolution in terms of number, power rating and distortion, in particular, considering the connection to the low-voltage public grid: available short-circuit power may be limited and particularly susceptible loads may co-exist in the same grid portion. Standards can partially address the problem cover-ing only the harmonic interval, but they necessitate significant extension and improvement in the supraharmonic range. In addition, EV chargers have been observed to violate in some scenarios the applicable harmonic limits, so that the mechanisms of emission and distortion should be better understood and evaluated, including phenomena of mutual influence between EV chargers and with pre-existing grid distortion. Although models can help simulate large-scale scenarios in terms of fundamental frequency phenomena, such as power flow, voltage fluctuation and imbalance, sub-stantial and reliable information can come from experimental results, providing measured harmonic and supraharmonic emissions, accompanied by details on loads mix, grid characteristics and EV charger operating conditions. This work thus defines the applicable constraints in terms of limits and compatibility levels for public and light industrial low-voltage grids, discusses the available experimental results and datasets, analyzing the typical distortion behavior and providing indication of sources of information for further studies.openMariscotti, AndreaMariscotti, Andre

Analysis and Modelling of Power-Dependent Harmonic Characteristics of Modern PE Devices in LV Networks

This paper presents results of experimental and analytical evaluation of power-dependent harmonic emission of three common types of modern low-voltage (LV) power-electronic (PE) devices. After a detailed analysis of comprehensive test results, based on both existing and new waveform distortion indices, the development of component-based models of PE devices is discussed. This paper demonstrates the importance of including PE devices' controls for accurate modelling of their characteristics over the entire range of operating powers. Most of the analyzed PE devices exhibit strong power-dependent changes of characteristics, additionally influenced by supply-voltage conditions, which are important for the analysis of both existing networks and future 'smart grids'

Fast charging diversity impact on total harmonic distortion due to phase cancellation effect: Fast Charger's testing experimental results

Full charging cycles were performed in the studied chargers and THDV and THDI were observed. From the measurements it can be observed that the phase angles vary within a preferential range, i.e. remain within a range which is actually <90˚of amplitude. Two of the Chargers, working individually, failed to comply with the standards. Charger A barely makes it in terms of TDD and Charger C is out of the limit. In terms of individual harmonics also Charger A and Charger C are out of the limit of 4.5% for the 11th and 13th harmonics. The next step of the research will be to obtain the statistical distribution of each of the phase angles for all Chargers and perform simulations with different scenarios. Results so far suggest that stand alone Chargers with low short circuit values are recommended to have filters <13% THD.JRC.C.3-Energy Security, Distribution and Market

An experimental approach for assessing the harmonic impact of fast charging electric vehicles on the distribution systems

Fast charging is seen by users as a preferential way for electric vehicles (EV) to extend average daily mobility. Fast chargers rated power, their expected operation mostly during peak hours and clustering in designated stations, raise significant concerns. On one hand it raises concerns about power quality standard requirements, especially harmonic distortion due to the use of power electronics connecting to high loads typically ranging from 18-24 kWh, and on the other hand infrastructure dimensioning and design for those investing on such facilities. We performed four sets of measurements during an EV complete fast charging cycles and analysed individual harmonic’s amplitude and phase angles behaviour and calculated the voltage and current total harmonic distortion (THD) and Total Demand Distortion (TDD) comparing it with IEEE519, IEC 61000/EN50160 standards. Additionally, we simulated, two vehicles being fast charged while connected to the same feeder, and analysed how the harmonic phase angles would relate. We concluded that the use of TDD was a better indicator than THD since the first one uses the maximum current (IL) and the latter uses the fundamental current, sometimes misleading conclusions, hence suggested to be included in IEC/EN standard updates. Voltage THD and TDD for the analysed charger, were within the standards limitations 1.2% and 12% respectively, however individual harmonics (11th and 13th ) failed to comply with the 5.5% limit in IEEE 519 (5% and 3% respectively in IEC61000). Phase angles tended to have preferential range differences from the fundamental. We found that the average difference between the same harmonic order phase angles, are lower than 90°, meaning that when more than one vehicle is connected to the same feeder the amplitudes will tend to add. Since the limits are dependable on the upstream short circuit current (ISC), if the number of vehicles increase (i.e. IL), the standard limits will decrease and eventually are broken. The harmonic limitation is hence a first binding condition, well before the power limitation is. The number of chargers will be limited first not by the power capacity of the upstream power circuit but by the harmonic limits for electric pollution.JRC.F.3-Energy Security, Systems and Marke