Gauthier Delille

Dynamic Frequency Control Support by Energy Storage to Reduce the Impact of Wind and Solar Generation on Isolated Power System's Inertia

In electrical islands, frequency excursions are sizeable and automatic load shedding is often required in response to disturbances. Moreover, the displacement of conventional generation with wind and solar plants, which usually do not provide inertial response, further weakens these power systems. Fast-acting storage, by injecting power within instants after the loss of a generating unit, can back up conventional generation assets during the activation of their primary reserve. This paper relies on dynamic simulations to study the provision of such a dynamic frequency control support by energy storage systems in the French island of Guadeloupe with large shares of wind or solar generation. The results show that fast-acting storage, by acting as a synthetic inertia, can mitigate the impact of these sources on the dynamic performance of the studied island grid in the case of a major generation outage. The other concerns raised by renewables (e.g., variability, forecast accuracy, low voltage ride-through, etc.) have not been addressed within this project.

High Wind Power Penetration in Isolated Power Systems—Assessment of Wind Inertial and Primary Frequency Responses

Grid operational challenges are significant to increase securely the wind penetration level. New embedded control functions are therefore required in order to make participate wind generators in power system management. In this paper the implementation of inertial response and primary frequency control in a wind turbine controller are investigated. Main factors affecting the performances of the frequency regulation are identified and characterized. The influence of control parameters and the turbine operating point on the inertial response are analyzed through obtained performances in an islanded power system. The combined control scheme using both controllers is also developed and the potential of the obtained grid service at partial load is discussed.

Dynamic frequency control support: A virtual inertia provided by distributed energy storage to isolated power systems

In electrical islands, frequency excursions are sizeable and automatic load shedding is often required in response to disturbances. By injecting active power in the timeframe of hundreds of milliseconds up to a few seconds after the loss of a generating unit, fast-acting storage can support the conventional production assets during the activation of their primary reserve. Using dynamic and hardware-in-the-loop (realtime) simulations, the provision of such a dynamic frequency control support by distributed energy storage systems has been studied in the case of the French island of Guadeloupe. Dedicated control algorithms have been developed and tested on a small-scale ultracapacitor storage unit. By acting as a virtual inertia, it has been shown that fast storage systems can improve substantially the dynamic performances of electrical islands.

Real-time simulation: The missing link in the design process of advanced grid equipment

This paper describes a design process of advanced grid equipment including both dynamic simulations and power-hardware- in-the-loop. A case study concerning the insertion of an energy storage system in a large isolated grid is used as an illustrative example. First, the methodology developed to achieve a real-time simulation of the studied grid from its original dynamic model is presented. The real-time platform used within the framework of this project is based on the RT-LAB environment and is interfaced with real ultracapacitors through a power amplifier. Some experimental results are analyzed in the final part. The advantages of this methodology including power-hardware- in-the-loop are emphasized by illustrating its contribution to dynamic model validation and the obtained improvement in control system performances.

An energy supervision for distributed storage systems to optimize the provision of multiple services

This paper presents an innovative supervisory control for distributed energy storage systems that is able to 1) perform day-ahead scheduling of storage services to maximize profitability while satisfying material and grid constraints and 2) identify the intraday schedule changes that are required in order to take various contingencies into account. Several case studies have been carried out to test this advanced energy supervision. The considered storage system is connected to a rural medium-voltage distribution feeder with a high penetration of wind turbines. This work has made possible to identify several technical, economic and regulatory issues that seem critical to the emergence of distributed energy storage systems.

Taking advantage of load voltage sensitivity to stabilize power system frequency

This paper analyzes the provision of a new dynamic frequency support to isolated power systems using a fast control of the load through the grid voltage. This control has appealing advantages, among which: 1) no impact on customers provided that their voltage remains within admissible limits, 2) the only communication that is required is the grid voltage itself and 3) the response is almost instantaneous. The possible solutions for implementing such a concept in practice are reviewed, and a shortlist of selected options is characterized using dynamic simulations. The results show that it is possible to take advantage of load voltage sensitivity to improve the transient behavior of isolated power systems following major outages. The proposed control can be put in place by adding a new feature to the voltage regulators of conventional generation assets.

Assessing the impacts of distribution grid planning rules on the integration of renewable energy sources

This paper tackles the problem of designing planning rules for the integration of renewable energy sources into distribution networks. A novel method is proposed for the assessment and optimization of such planning rules over multi-year horizons. Especially, this method considers: 1) a random generator of multi-year scenarios, which allows taking uncertainties into account, and 2) a simulator of investment decisions, which applies the studied planning rules to the considered network over the multi-year scenarios. The challenge is to find the best planning strategies to reduce the average cost regarding the integration of various renewable generation levels. The proposed method is illustrated through a case study built from realistic data to assess current French planning rules over 10-year scenarios of RES integration on a test network.

Experimental validation of a novel approach to stabilize power system frequency by taking advantage of Load Voltage Sensitivity

This paper deals with a novel way to provide dynamic frequency support to isolated power systems by a fast control of the load through the grid voltage. Following the promising results of a preliminary analysis based on dynamic simulations, a field test was carried out in the archipelago of Guadeloupe at the beginning of 2014. It confirmed that the proposed control can significantly improve the transient performance of isolated power systems after generation outages. The experimental setup and the main results of this demonstration effort are presented.

Load modeling for power system simulation: A tradeoff between accuracy and usability

This paper deals with load modeling for power system simulation. It introduces a new, more complete quality criterion to identify load models, with interesting applications in an industrial framework. Until now, the identification of load models has often been carried out 1/ using a limited number of field measurements (without always making sure that it was sufficient) and 2/ considering accuracy as the main, or even as the only indicator to establish a merit order between the possible options. To be considered good in the present work, load models must not only well match field measurements (accuracy), but have the highest possible level of “usability” as well. This additional indicator evaluates notably the ability of the model to be used for the simulation of other events and network operating conditions than the ones used for its identification. This tradeoff between accuracy and “usability” is illustrated on a case study on a French isolated power system.