11-02-2013, 04:51 PM
Renewable Energy Integration into Distribution Networks with Support of a new D-STATCOM System
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ABSTRACT
Today the integration of distributed renewable energy sources into existing networks is a challenging task. As the distribution networks have been designed without considering interconnection of distributed generation, it often results in poor power quality and underutilization of generating power in case of limited absorbing capability or instability of the network. The increasing amount of distributed generation is therefore seen as a negative development from network management point of view. With proper management of active resources the overall system performance may be improved from presently used practices.
A concept of an active distribution network can be characterized by words like flexible, intelligent, integration and co-operation. Because it should optimize the use of controllable resources throughout the network, new features and functions of such active network are based on the control and co operation of active devices. To achieve the required performance and flexibility, it will be cheaper to invest in D-STATCOM, protection relays, voltage controllers and information technology than in traditional High Voltage equipments.
The main goals of active distribution networks are to ensure safe operation and to increase reliability in networks integrating distributed generation, to maximize their utilization and to maintain the required level of power quality despite non predictable power production or consumption. In order to achieve these goals, individual technical solutions, like D-STATCOM, network protection relays and voltage controllers were developed by several partners in the joint project ADINE , funded by the European Commission. With the developed solutions, new active distribution network features were successfully demonstrated and validated in networks with a large amount of distributed generation.
The compact and powerful D-STATCOM control system is based on the latest DSP and FPGA technology. For the communication with other devices in the active distribution network the protocol IEC 61850 is supported. Due to the master-slave structure of the D-STATCOM controller, the necessary compensation power can be provided by paralleling power modules of 2 MVA each. This method guarantees a high level of reliability and availability and provides furthermore a good granularity concerning compensation power demand. Several power modules, consisting of Three-Level Voltage Source Converter, can be installed in a standardized sea container. The proposed D-STATCOM offers thus a flexible, “plug-and-play” solution, ideally suited for the simplification of renewable energy integration in critical distribution networks.
Within the ADINE project a ±6 MVAr D-STATCOM demonstrator was built and installed in a distribution network in the Republic of Ireland. With the help of the D-STATCOM, a new windfarm has been integrated into an existing distribution network, where another windfarm was already present. Network studies, performed beforehand, have proven that, without further actions, the new windfarm would not comply with the grid codes of the local utility company. After the D-STATCOM was installed together with a remote-SCADA system, the distribution network became fully compliant with the grid codes, by providing voltage control at both windfarm points of coupling which are 25 km away from each other.