Nicholas Etherden

Increasing the hosting capacity of distribution networks by curtailment of renewable energy resources

This paper applies the hosting-capacity method to a realistic distribution system. Under given circumstances the hosting capacity for Distributed Energy Resources (DER) identifies the degree of DER in power grid that can be accepted without endangering the reliability or quality of power. In this case study two limits setting the hosting capacity were evaluated: overvoltage and overcurrent. Finally it is examined to what extent the hosting capacity can be increased with use of real-time information and calculation of dynamic performance indications that govern the hosting capacity. It is shown that there is significant potential for increasing the hosting capacity without having to build new lines.

Dimensioning of Energy Storage for Increased Integration of Wind Power

Energy storage can potentially allow for more production from renewable resources into existing grids. A methodology to quantify grid limitations and dimension battery energy storage systems is presented in this paper. By use of grid consumption and production data, the hosting capacity methodology is developed as a general framework for storage dimensioning that can be applied by grid operators. The method is successfully applied to an existing subtransmission grid; actual hourly production and consumption data during a two-year period is used. The role of a storage system compared to other means to handle overloading is studied. It is found that about one third of overloading instances are suitable to handle with a battery energy storage system. After this, diminishing returns per unit of storage capacity are shown to occur.

Virtual Power Plant for Grid Services Using IEC 61850

This paper assesses the communication, information, and functional requirements of virtual power plants (VPPs). A conceptual formulation of the interoperability requirements, as well as a comparative study of their fulfillment by state-of-the-art communication techniques, is presented. VPP requirements are then mapped against services and information models of IEC 61850 and common information model (CIM) power utility automation standards. Proposals are given for extensions of the IEC 61850 standard to enhance the interaction between the VPP controller and the distributed energy resources. Finally, the methodology and concepts are applied to a specific VPP consisting of hydro and wind plants, solar photovoltaic (PV) power, and storage facilities. Several applications to provide grid services from the proposed VPP in an existing 50-kV grid are covered. The implementation of the VPP communication and control architecture in the supervisory control and data acquisition (SCADA) of demonstration plant is also presented.

Application of the IEC 61850-7-420 data model on a Hybrid Renewable Energy System

IEC 61850 is the most promising standard for design of substation communication and automation systems. Recent revisions of the standard include support for modeling, and control of Distributed Energy Resources (DER). This paper presents an application of the IEC 61850-7-420 data model for DER in the implementation of a control and energy management system for a Hybrid Renewable Energy System (HRES). These systems are beginning to prove their usefulness in providing deployable electrical supply in locations where no such supply exists as well as for backup power or power quality related support functions. The motivation for applying the standard to the design process is twofold; to modularize the design according to an accepted international standard and to design for interoperability with other IEC 61850 enabled devices and SCADA systems.

Overload and overvoltage in low-voltage and medium-voltage networks due to renewable energy — Some illustrative case studies

This paper presents the use of curtailment to allow more wind or solar power to be connected to a distribution network when overcurrent or overvoltage set a limit. For four case studies, all based on measurements, the gain in produced energy is calculated. It is shown that the curtailment method has a large impact on this gain. The paper further discusses details of the curtailment algorithm and the communication needs as well as some further applications of curtailment.

Quantification of ancillary services from a virtual power plant in an existing subtransmision network

This paper presents the results of a feasibility study of a virtual power plant (VPP) in central Sweden designed to provide ancillary services to a 50-kV distribution network. The VPP consists of a wind park, hydro plant and reservoir as well as solar PVs and battery energy storage. The 50-kV subtransmission network was modeled in order to evaluate the ancillary services that could be provided by coordinating existing distributed energy resources in the network. Simulations were performed using measured hourly variations in production and consumption at all network nodes. The studied ancillary services include both reactive and active power control. Contribution from the VPP is evaluated for balancing, to enable a producer to meet spot markets bids and avoid purchases of balancing power minimize peak load in order to reduce subscribed power and tariff to the regional 130-kV network decrease network losses the contribution from reactive power control using the power converters to reduce the reactive power flow to the overlying network. Quantification of the economic gains from each operation case is provided.

Dimensioning of energy storage for increased integration of wind power

Energy storage can potentially allow for more production from renewable resources into existing grids. A methodology to quantify grid limitations and dimension battery energy storage systems is presented in this paper. By use of grid consumption and production data, the hosting capacity methodology is developed as a general framework for storage dimensioning that can be applied by grid operators. The method is successfully applied to an existing subtransmission grid; actual hourly production and consumption data during a two-year period is used. The role of a storage system compared to other means to handle overloading is studied. It is found that about one third of overloading instances are suitable to handle with a battery energy storage system. After this, diminishing returns per unit of storage capacity are shown to occur.

Physical-hybrid simulation for in-situ evaluation of energy storage system

This paper presents a method for testing of a grid-size battery energy storage system and its interaction with the grid. The method uses a real installation with relatively small storage capacity which is combined with a simulation model of the grid. The storage is cycled based on measurements from the potential grid location and desired application. A scaling factor is used to relate the physical installation capacity and power ratings with the grid-size storage in the simulation model. Such a hybrid method allows evaluating grid-size storage installations without disturbing the grid. The physical behavior of the battery and control algorithm can be evaluated under realistic conditions without the need to construct a full grid-size storage installation. An experiment is described in this paper were the method is applied to an actual grid and battery storage installation.