Vehicle-to-grid aggregator to support power grid and reduce electric vehicle charging cost

This paper presents an optimised bidirectional Vehicle-to-Grid (V2G) operation, based on a fleet of Electric Vehicles (EVs) connected to a distributed power system, through a network of charging stations. The system is able to perform day-ahead scheduling of EV charging/discharging to reduce EV ownership charging cost through participating in frequency and voltage regulation services. The proposed system is able to respond to real-time EV usage data and identify the required changes that must be made to the day-ahead energy prediction, further optimising the use of EVs to support both voltage and frequency regulation. An optimisation strategy is established for V2G scheduling, addressing the initial battery State Of Charge (SOC), EV plug-in time, regulation prices, desired EV departure time, battery degradation cost and vehicle charging requirements. The effectiveness of the proposed system is demonstrated using a standardized IEEE 33-node distribution network integrating five EV charging stations. Two case studies have been undertaken to verify the contribution of this advanced energy supervision approach. Comprehensive simulation results clearly show an opportunity to provide frequency and voltage support while concurrently reducing EV charging costs, through the integration of V2G technology, especially during on-peak periods when the need for active and reactive power is high

Frequency-Locked Loop Based Estimation of Single-Phase Grid Voltage Parameters

Estimation of amplitude, instantaneous phase, and frequency of a single-phase grid voltage signal are studied in this letter. The proposed approach uses a novel circular limit cycle oscillator (CLO) coupled with a frequency-locked loop. Due to the nonlinear structure of the CLO, the proposed frequency adaptive CLO technique is robust against various perturbations faced in the practical settings, e.g., the discontinuous jump of phase, frequency, and amplitude. The global stability analysis of the CLO and local stability analysis of the frequency adaptive CLO are performed. Experimental results demonstrate the effectiveness of the proposed technique over a very recent technique proposed in the literature

Fast Estimation of Phase and Frequency for Single Phase Grid Signal

Accurate and fast estimation of single-phase grid voltage phase and frequency has the potential to improve the performances of various control and monitoring techniques used in electric power systems. This letter applies an adaptive sliding mode observer for frequency and phase estimation. The observer is simple, easy to tune, and suitable for real-time implementation. The proposed adaptive observer can be considered as an alternative to a phase-locked loop (PLL) with better performance. dSPACE-based experimental results are given to show the effectiveness and performance improvement of the proposed approach with respect to two other advanced PLL techniques, namely, pseudolinear enhanced PLL and second-order generalized integrator-frequency locked loop

Electric vehicle battery performance investigation based on real world current harmonics

Electric vehicle (EV) powertrains consist of power electronic components as well as electric machines to manage the energy flow between different powertrain subsystems and to deliver the necessary torque and power requirements at the wheels. These power subsystems can generate undesired electrical harmonics on the direct current (DC) bus of the powertrain. This may lead to the on-board battery being subjected to DC current superposed with undesirable high- and low- frequency current oscillations, known as ripples. From real-world measurements, significant current harmonics perturbations within the range of 50 Hz to 4 kHz have been observed on the high voltage DC bus of the EV. In the limited literature, investigations into the impact of these harmonics on the degradation of battery systems have been conducted. In these studies, the battery systems were supplied by superposed current signals i.e., DC superposed by a single frequency alternating current (AC). None of these studies considered applying the entire spectrum of the ripple current measured in the real-world scenario, which is focused on in this research. The preliminary results indicate that there is no difference concerning capacity fade or impedance rise between the cells subjected to just DC current and those subjected additionally to a superposed AC ripple current

Laboratory-based test bed of a three terminals DC networks using power hardware in the loop

In this paper a three stations MTDC grid is presented, providing a specific application of our work. The experimental platform is intended to combine electrical power components and communication/control equipment with real-time simulation tools. In this way the platform can test grid elements and evaluate different operation scenarios under various conditions

Laboratory Demonstration of a Multiterminal VSC-HVDC Power Grid

This paper presents the design, development, con- trol and supervision of a hardware-based laboratory Multi- Terminal-Direct-Current (MTDC) test-bed. This work is a part of the TWENTIES (Transmission system operation with large penetration of Wind and other renewable Electricity sources in Networks by means of innovative Tools and Integrated Energy Solutions) DEMO 3 European project which aims to demonstrate the feasibility of a DC grid through experimental tests. This is a hardware-in-the-loop DC system test-bed with simulated AC systems in real time simulation; the DC cables and some converters are actual, at laboratory scale. The laboratory scale test-bed is homothetic to a full scale high voltage direct current (HVDC) system: electrical elements are the same in per unit. The test-bed is supervised by a Supervisory Control And Data Acquisition (SCADA) system based on PcVue. Primary control based droop control method to provide DC grid power balance and coordinated control methods to dispatch power as scheduled by transmission system operator (TSO) are implemented. Since primary control acts as converter level by using local measure- ments, a coordinated control is proposed to manage the DC grid power flow. The implemented system is innovative and achievable for real-time, real-world MTDC-HVDC grid applications

ICT-Based Vehicle-to-Grid Operation Based on the Fast Discharge Power for Economic Value

Renewable energy sources require effective energy management systems to be efficient in smart grids. Although electric vehicles are all potential consumers, using electric vehicle batteries is an effective utilisation strategy for smart grids. Vehicle-to-grid (V2G) is a crucial future technology for the smart grid. V2G technology proposes employing electric vehicles to contribute the stored energy to the other intelligent grid users. Expansion of the V2G technology is possible by funding, installing, and optimal managing the charging stations. In this work, an economic value of V2G operation is proposed, and an advanced scheme of a V2G operations communication protocol that enables flexible control of the charging and discharging operations of the EV in an optimisation way has been developed, based on an energy arbitrage service, using two different discharge rates study. An economic study based on energy arbitrage using problem optimisation has been depicted. A use case based on the Nissan Leaf 40 kWh was simulated. The results show the economic benefit of using high discharge rate power (i.e., 3C) to the Li-ion battery over the regular discharge rate (1C)