K. Rudion

Design of benchmark of medium voltage distribution network for investigation of DG integration

The widespread use of distributed generation (DG) relies on methods and techniques aimed at facilitating the network integration of DG. In this context a methodology for the evaluation of the quality and relative merits of these methods and techniques is missing. CIGRE Task Force C6.04.02, which is affiliated with CIGRE Study Committee C6, has addressed this problem by proposing a set of resource and network benchmarks. In the present paper, the benchmark for integrating DG in medium voltage distribution networks is described. The proposed benchmark is representative of a real network while it is also designed for ease of use. The application of the benchmark is described through several case studies that show the impact of DG on power flow and voltage profiles at the medium voltage level

Optimal operation of a virtual power plant

The increase in the amount of generators based on renewable energy sources (RES) in the power system is leading to many changes in its operation. Since the RES depends on weather conditions, coordinating the operation of the entire power system has become a more complex issue. New challenges need to be faced in order to supply the electric energy to the customers at the appropriate quality level. In this paper the concept and architecture of a complex Virtual Power Plant (VPP) will be introduced and discussed. The focus will be paid to the optimization of the structure of the VPP as well as to its optimal operation. The result of the optimization have been presented and discussed in the paper taking into account different operation scenarios.

Toward a Benchmark test system for the offshore grid in the North Sea

In an effort to protect the environment despite the projected development of the electrical power system, the European community is focusing on a significant increase in the installed wind power capacity up to the level of 300 GW by the year 2030 throughout Europe. Most of the planned installations - about 150 GW - are going to be realized in the offshore sector, a large part of which will be located in the North Sea. Such development will lead to new challenges regarding integration of the bulk offshore wind power into the power systems and will require a comprehensive analysis concerning various aspects such as optimal planning and operation taking into account new concepts, as multi-terminal VSC HVDC. In this paper the establishment of a test system for analysis of the offshore DC grid behavior is proposed taking into account the recent structural and technological concepts on this field as well as the national plans. Hence, in the first step the configuration of the analyzed offshore grid was defined, which includes a mix of AC and DC system. Further, the assumptions for the system parameters will be discussed and the implementation of this test system into a power system simulator as well as some exemplary calculations will be shown.

Grid connection of offshore wind farm based DFIG with low frequency AC transmission system

This paper uses a simulation to investigate the feasibility of applying low frequency AC (LFAC) transmission technology to connect large offshore wind farms to the onshore power system. Compared to the conventional AC transmission system with a power frequency of 50 or 60 Hz, the LFAC system can transfer more power through longer distance and with lower investment costs than the HVDC solution. Firstly, the characteristics of power cable operation at low frequency are discussed. Then a grid connection of an offshore wind farm based on a doubly fed induction generator (DFIG) through LFAC is studied. The simulation results show that there are no difficulties for the wind farm based DFIG when it operates at low frequency. Moreover, the reactive power control at the line side of DFIG can be applied to improve the operation of the cable.

MaWind - tool for the aggregation of wind farm models

The existing software for the simulation of power system operation was mainly developed and optimized for the analysis of conventional systems that are characterized by a low number of large, central synchronous generators. New forms of power generation, like wind turbines, that are characterized by a high number of small units can not be analyzed effectively with this software. In this paper a new software tool, MaWind, for the aggregation of wind farm models for dynamic system analysis is described. The MaWind tool uses a new mathematical approach to represent wind generation in system analysis. The background of this method, the method itself and some representative results of the calculation with MaWind are presented in the paper. MaWind allows for significant reduction of the model complexity while retaining a good approximation of dynamic farm behavior at the same time.

Non-linear load modeling — Requirements and preparation for measurement

The existing software for the simulation of power system operation uses mostly simple load models such as the constant power load model, the constant impedance load model or the static polynomial load model to represent the real system load characteristic. In some cases using such load models in power system dynamic simulation may produce inaccurate results and lead to inappropriate system operation. In this paper load modeling using field measurement data from a load bus in the power grid to improve the simulation accuracy in the study of power system stability is discussed. The goal is to investigate the influence of different perturbations in the power grid on load behaviors as preparation for field measurement. Furthermore, there is a focus on the definition of measurement requirements. In addition, the nonlinear least-squares algorithm used to identify load model is discussed. As preparation, a complex nonlinear load model with predetermined parameters will be simulated in some defined scenarios, the simulation results are compared with a constant power load model. By using the transformer tap changer to make perturbations in the power system, the load dynamic characteristics could be gathered, and the perturbations data could be used to identify the parameters of the non-linear load model.

Investigation of disposable reserve power in a large-scale wind farm

The increase of wind energy development is reflected in the specific requirements for the connection of large wind farms to the transmission system including requirements for the control and interaction between the wind farm and the power system. It is necessary to investigate the power system stability and control with regard to wind power generation. When modeling the behavior of a complex large-scale wind park the wind model with wake effect is very important. The wind distribution among the wind turbines determines the power produced by each single wind plant and, at the same time, the fluctuation of the whole power received from the wind farm. This paper presents, with an example, the determination of the range of expected power generation and the possibility of its inclusion into the network control.

Connecting the Dots: Regional Coordination for Offshore Wind and Grid Development

By 2020, it is expected that about 42 GW of offshore wind capacity will be built in European waters and 30 GW off the shore of China. According to the U.S. Department of Energys National Offshore Wind Strategy, estimates for the United States are for approximately 10 GW of offshore capacity by then. This article gives an overview of current developments in this area from a power system point of view, namely, the offshore grid deployment that needs to accompany the offshore wind generation development. General ideas are given concerning political plans and related studies about technology issues, regulatory and market arrangements, and experience with offshore grid demonstration projects.

Vision 2020 — Security of the network operation today and in the future. German experiences

Nowadays the supply of electrical energy from dispersed generation units has an increasing significance. Hence, security related power system operation strategies have to be adapted to face the new situation. In this paper the security of power system operation from the industry and research point of view will be discussed. After presenting an overview about the current situation, the problems will be pointed out. The promising ongoing research topics which have the ability to help the network operators to manage the turn towards a sustainable power system that will allow for exploiting as much regenerative energy as possible by reaching the high standards of security will be described.

Offshore Power System Operation Planning Considering Energy Market Schedules

This paper analyzes selected issues concerning operational strategies for multiterminal dc offshore power systems (OPSs). In the first section, the main challenges regarding the operation of such an OPS are discussed, and a proposal is given for a new observer-based management system (OBMS) used for operation coordination using references from the energy market. In the second section, different operational scenarios for the OPS are investigated in order to present the OBMS application. For this purpose, a test system that considers the expected European future wind power development is introduced. Then, using reference power flows from the hourly market, the influence of the OBMS optimization process on the power flows aiming at minimum deviations from the reference energy market signals will be presented. Some exemplary test simulations are performed and recommendations are given.