Chad Abbey

Supercapacitor Energy Storage for Wind Energy Applications

As wind energy reaches higher penetration levels, there is a greater need to manage intermittency associated with the individual wind turbine generators. This paper considers the integration of a short-term energy storage device in a doubly fed induction generator design in order to smooth the fast wind-induced power variations. This storage device can also be used to reinforce the dc bus during transients, thereby enhancing its low-voltage ride through (LVRT) capability. The topology is evaluated in terms of its ability to improve the performance both during normal operation and during transients. Results show that when storage is sized based upon the LVRT requirement, it can effectively damp short-term power oscillations, and it provides superior transient performance when compared with conventional topologies

A Stochastic Optimization Approach to Rating of Energy Storage Systems in Wind-Diesel Isolated Grids

Wind-diesel systems represent a proactive step towards sustainable remote communities. However, for high ratios of wind energy, the necessity of a dump load and the diesel operating constraints need to be considered. Energy storage systems offer a means of optimizing energy use and further reducing consumption of diesel fuel. This paper proposes a methodology for storage sizing based on stochastic optimization. The problem is formulated and solved using representative data. The dependence of storage sizing and the cost of delivered energy on wind penetration levels, storage efficiency, and diesel operating strategies are considered. Results demonstrate that for high wind penetration, the availability of storage, together with an appropriate diesel operating approach, can result in significant cost savings in terms of fuel and operating costs.

A Knowledge-Based Approach for Control of Two-Level Energy Storage for Wind Energy Systems

The percentage of wind energy in a generation mix will ultimately be limited by its intermittency and uncertainty as a source of power. However, the pairing of wind with energy storage systems could be utilized in order to produce dispatchable power. This paper considers a two-level energy storage system for application to wind energy systems. A knowledge-based management algorithm is proposed in order to schedule the power from the two levels. The system is tested for two possible power systems applications and its performance is compared with that of an alternate scheduling approach. Results demonstrate that the proposed algorithm requires a lower storage rating due to its ability to better coordinate operation of the two devices.

Use of large capacity SMES to improve the power quality and stability of wind farms

High penetration of wind power can negatively affect the stability of the power system. This can be particularly evident during start-up of the wind generators, when the variation of the wind farms output power can cause oscillations of the system frequency and possible voltage collapse. This paper focuses on the application of a large capacity superconducting magnetic energy storage (SMES) unit. Simulations using the detailed wind turbine model and squirrel cage induction generators demonstrate that the SMES has the potential to significantly improve the wind farms performance. Through control of the charging and discharging of the SMES using a power electronic interface, it is shown that the wind farms output power can be controlled to a constant value. In addition, there is an overall improvement in the transient and dynamic response of the system

VRB Modelling for the Study of Output Terminal Voltages, Internal Losses and Performance

There is a growing interest in using large scale energy storage in wind systems for power smoothing and energy redistribution. Vanadium-redox batteries are well suited for this type of application because of their high efficiency, high scalability, fast response, long life and low maintenance requirements. This paper looks into determining an appropriate electrical vanadium-redox battery (VRB) model for this type of application. In particular, model details including stack voltage, series resistance, state of charge (SOC) and transients modeling are examined. The model is used to obtain results on the energy content, and terminal voltage profile of the battery. The battery performance is also assessed, including VI transfer characteristic, transient response and efficiency.

Wind Power Impact on System Frequency Deviation and an ESS based Power Filtering Algorithm Solution

Wind power is the fastest growing renewable energy. However due to its stochastic nature, fluctuating wind power results in adverse impacts on power systems, including system frequency deviations. Study on system frequency response in this paper shows power systems are more sensitive to the medium frequency power fluctuations (between 0.01 and 1 Hz), while the majority of wind power fluctuations are located in that regions and below. For small standalone power systems, even a modest wind penetration will lead to considerable system frequency deviation by the wind. To diminish the wind power impact on system frequency, an energy storage system (ESS) based wind power filtering algorithm is proposed in this paper, aimed at attenuation of those medium frequency fluctuations. Electromagnetic transient simulation results quantitatively demonstrate the effectiveness of this algorithm; the wind power is smoothed out and the system frequency deviations are limited to an acceptable level

Short-term energy storage for wind energy applications

The need to limit power fluctuations resulting from wind turbine generators (WTG) is becoming more important as wind energy reaches higher levels of penetration. This paper considers the integration of a short-term energy storage device in a doubly-fed induction generator (DFIG) design in order to smooth the fast, wind induced power variations. This storage feature can also enhance the low voltage ride through (LVRT) capability. The topology is evaluated in terms of its ability to improve both the steady state and transient performance. The system is modeled in EMTP and a number of cases and configurations are illustrated. Results show that when storage is sized based upon the LVRT requirement, it can provide improved performance both under steady state and during transients when compared with conventional technologies.

A review of active distribution networks enabling technologies

High levels of distributed generation have been installed in power systems and even a greater amount is expected to be deployed in the near future, with a large percentage likely to come from renewable energy sources. As such, Distribution System Operators (DNOs) will need to change their old “business as usual” passive approach, to one that adopts integration of control and communication technologies, together with emerging distribution network technologies, as a means of accommodating new generation in an optimal and economical manner. This paper presents a review of some of the impacts associated with the integration of distributed generation, together with some active distribution networks enabling technologies, intended to deal with the aforementioned problems. In particular, the present review focuses on technologies that are in advanced stages of Research and Development, or are even at the trial stage or are commercially available. However, further analyses are required in order to develop cheaper and more secure means to the increasing Distributed Generation connections.

An Online Control Algorithm for Application of a Hybrid ESS to a Wind–Diesel System

Energy storage systems (ESSs) can be applied to mitigate some of the negative impacts associated with a variable power generation source such as wind energy. The control of ESS power must be accomplished over numerous time frames to meet system objectives and respect ESS capacity constraints. This paper proposes a two-level ESS control structure for use with a wind-diesel system, which is suitable for online implementation. The control is developed to coordinate power delivered from the two ESS levels in order to minimize diesel fuel consumption and limit up/down rates of the diesel plant. Different control modes are evaluated by simulation, and a subset of the results are validated using a hardware-in-the-loop representation. The controller that combines all three functionalities-minimizing dump load, limiting intrahour diesel ramp rates, and maximizing ESS utilization-demonstrates superior performance as measured by defined metrics and is proven to work online.

Planned islanding on rural feeders — utility perspective

Planned islanding application, also known as intentional islanding, is an early utility adaptation of the Microgrid concept that is being promoted by major utilities around the world. The main objective of planned islanding projects in Canada is to enhance customer-based power supply reliability on rural feeders by utilizing an appropriately located independent power producer (IPP). This paper considers the process of planned islanding and the necessary steps that need to be taken in order to lead to successful projects. Some of the current experience from Canadian utilities in this area are investigated and the additional requirements, in terms of equipment and system studies, which are needed in order to plan for the operation of a planned island project are discussed. A case of planned islanding on rural feeders with multiple distributed generation units is also investigated, which represents the target of future projects in this area.