Katarina Knezovic

Analysis of voltage support by electric vehicles and photovoltaic in a real Danish low voltage network

With conventional generating units being replaced by renewable sources which are not required to provide same high level of ancillary services, there is an increasing need for additional resources to achieve certain standards regarding frequency and voltage. This paper investigates the potential of incorporating electric vehicles (EVs) in a low voltage distribution network with high penetration of photovoltaic installations (PVs), and focuses on analysing potential voltage support functions from EVs and PVs. In addition, the paper evaluates the benefits that reactive power control may provide with addressing the issues regarding voltage control at the expense of increased loading. Analysed real Danish low voltage network has been modelled in Matlab SimPowerSystems and is based on consumption and PV production data measured individually for number of households.

Enhancing the Role of Electric Vehicles in the Power Grid: Field Validation of Multiple Ancillary Services

With increased penetration of distributed energy resources and electric vehicles (EVs), different EV integration strategies can be used for mitigating various adverse effects, and supporting the grid. However, the research regarding EV smart charging has mostly remained on simulations, whereas the experimental validation has rarely been touched upon. This paper focuses mainly on evaluating the technical feasibility of a series-produced EV to provide flexibility in real distribution grids. The implemented controller uses contemporary and widely supported standards for limiting the EV charging rate, which essentially means that it is applicable to any EV complying with IEC 61851 and SAE J1772 standards. The field test validation is conducted in a real Danish distribution grid with a Nissan Leaf providing three ancillary services through unidirectional ac charging, namely, congestion management, local voltage support, and primary frequency regulation. Several performance parameters, such as EV response time and accuracy, are assessed and benchmarked with current requirements. Ultimately, this paper aims to strengthen the applied research within the EV integration domain through validating smart grid concepts on original standard-compliant equipment.

Distribution grid services and flexibility provision by electric vehicles: A review of options

Due to the increasing penetration of distributed generation and new high-power consumption loads - such as electric vehicles (EVs) - distribution system operators (DSO) are facing new grid security challenges. DSOs have historically dealt with such issues by making investments in grid reinforcement. However, an alternative solution, enabled by the expected roll-out of smart meters and high penetration of flexible loads, would be the increased use of flexibility services. Flexible loads, with EVs at their forefront, can modulate their consumption or even inject power back to the grid depending on current grid conditions. In return, flexibility provision should be remunerated accordingly. In this paper, the authors are interested in making an accurate description of the flexibility services at the distribution level which could be provided by EVs as well as their requirements, e.g. location, activation time and duration. Market design recommendations for enhancing the provision of DSO grid services by EVs are derived from the conducted analysis.

Concurrent provision of frequency regulation and overvoltage support by electric vehicles in a real Danish low voltage network

Expected deployment of electric vehicles (EVs) introduces big technical challenges for power system operation, but also offers advantages provided that EVs are not considered merely as passive loads. With the development of Vehicle-to-Grid technology, EVs will be able to provide a number of ancillary services for grid support, e.g. implemented electronic equipment will allow them to exchange reactive power with the grid for voltage regulation while using active power for other services. This paper investigates the concurrent provision of local and system wide services from EVs in a real Danish low voltage network with high penetration of photovoltaic installations (PVs). The main focus is potential reactive power support when EV provision of frequency regulation coincides with PV production. Furthermore, the paper evaluates benefits of overvoltage support and addresses the issue of increased loading. The analysed network has been modelled in Matlab SimPowerSystems and is based on real hourly metered data from a Danish MV/LV substation with numerous households.

Management of Power Quality Issues in Low Voltage Networks Using Electric Vehicles: Experimental Validation

As electric vehicles (EVs) are becoming more widespread, their high power consumption presents challenges for the residential low voltage networks, especially when connected to long feeders with unevenly distributed loads. However, if intelligently integrated, EVs can also partially solve the existing and future power quality problems. One of the main aspects of the power quality relates to voltage quality. The aim of this work is to experimentally analyze whether series-produced EVs, adhering to contemporary standard and without relying on any vehicle-to-grid capability, can mitigate line voltage drops and voltage unbalances by a local smart charging algorithm based on a droop controller. In order to validate this capability, a low-voltage grid with a share of renewable resources is recreated in SYSLAB PowerLabDK. The experimental results demonstrate the advantages of the intelligent EV charging in improving the power quality of a highly unbalanced grid.

A dynamic behaviour analysis on the frequency control capability of electric vehicles

The paper presents results of a study on the dynamic response of Electric Vehicles (EV) when participating in frequency control of an islanded system. The following cases were considered: when there is no EV performing frequency control, when the EV participates in primary frequency control and when the EV participates in both primary and secondary frequency control. Different parameters are tested in various combinations, and their influence on frequency deviation as well as power and energy provided by the EV with vehicle-to-grid (V2G) capability is shown.

Comparative analysis of possible designs for flexible distribution system operation

A massive amount of distributed energy resources will be connected to the distribution system in the near future. This emerging phenomenon will pose significant challenges to the traditional operation of distribution systems. This clearly calls for a growing need to develop novel grid designs for achieving the most efficient utilization of these resources while meeting the forecasted load. In this paper, we present possible system design frameworks proposed for flexible distribution system operation. Critical evaluations and comparison of these models are made based on a number of key attributes which are foundational to the success of these proposed designs.