Economic dispatch of flexibility options for Grid services on distribution level

Due to the ascending capacity of Renewable Energy Sources, new challenges arise in the operation of distribution grids. Existing Smart Grid solutions have shown, that direct control interventions into distributed generation and demand facilities may contribute to ensure a reliable and economic grid operation. In extension of these direct control methods, this paper presents a new approach for an economic dispatch of flexibility options for grid services on distribution level. The developed modelling framework for a local flexibility market offers the possibility to simulate the market behavior. The modular set up of a grid operator model and several unit operator models allows research on the interaction between both domains in order to find the economically optimal operation mode for avoidance of critical grid states. The results of a one year simulation of a distribution grid are showing the advantageousness of the system.

I. Introduction

The increasing installed capacity of distributed generation (DG) is accompanied with several new challenges in the planning and operation of power systems. In Germany, the expansion of Renewable Energy Sources (RES) is mainly driven by highly volatile wind and photovoltaic (PV) power plants. The weather dependent electricity generation will increase the overall need for operational flexibility in order to balance supply and demand at all times [1]. Furthermore the majority of RES in Germany is connected at distribution level, which was not designed for high amounts of DG [2]. The grid capacity is exceeded in a growing number of grid districts, resulting in violations of the tolerable voltage range and in the overload of electrical equipment. Due to the fluctuating infeed of RES, these limit value violations may only occur in a few hours per year but still cause the need for grid enhancement. Besides the conventional enhancement, these temporary problems can be solved by distribution grid services (DGS). In this paper, distribution grid services are defined as the supply of operational flexibility by technical units, meaning the modification of infeed or consumption patterns, as a reaction to the local grid operation state coordinated by a Smart Grid system. The consideration of grid services in the operation of distribution grids has a high potential to reduce or postpone the necessary conventional enhancement of the grid [3].