New technical strategies for the connection of wind power plants into the distribution networks

Introduction

The mutualisation schemes for the connection of renewable power generation into the electricity network (in french “Schémas Régionaux de Raccordement au Réseau des Energies Renouvelables” S3REnR) have been implemented by the french government since 2012. However, after their implementation, the TSO (Transmission System Operator) and DSO (Distribution System Operators) face difficulties in terms of available power capacity and respecting deadlines when connecting new renewable energy projects. In fact, french regulatory framework is not compatible with energy goals. On the one hand, connecting a new renewable power plant could take more than 3 years because of the grid access lead time (for commissioning new power transformers, new overhead lines, etc). And on the other hand, the construction licenses granted by authority bodies have an expiration date. In most of the cases, these two periods do not match.

In addition, the costs of a project have increased substantially. The high shared costs imposed by the mutualisation schemes could jeopardize the viability of some projects. In parallel, locations of new projects are far from power substations also increasing costs for wind developers.

In this context, this work aims to propose new strategies for the connection of wind power plants into the distribution network to promote the feasibility of new projects in terms of costs and by capitalizing the available power capacity.

Approach

Our approach proposes to study new technical strategies for the connection of wind power plants to the electricity networks. The connection technical standards used by DSOs have become obsolete facing new technical challenges.
On the one hand, the classic approach of sizing electrical networks does not consider the intermittent behavior of the new power resources in planning study stage. In this work, we consider a dynamic method to calculate the availability of the network to accommodate wind power and to estimate the shortfall for the operator because of the power limitation.
On the other hand, our research aims to study new electrical configurations when connecting wind power plants into the distribution network by using new cable sizes and proposing new configurations at the medium voltage switchgear.
The reactive power compensation within wind power plants to minimize reactive power flow and needs from the power substation will be also considered.


Main body of abstract

Many strategies will be analyzed considering technical constraints as well as technical and economical optimization.

We will define different scenarios when connecting a new wind power plant depending on the operator's requirement:
- by optimizing the power availability at the electrical substation (matching between consumption and production)
- by using new cable sizes never used before by the french DSOs
- by proposing new configurations at the medium voltage switchgear
- by using reactive power compensation to minimize reactive power flow and remove voltage constraints

The costs from different scenarios will be compared to the classical strategies proposed by the DSO.

Conclusion

Currently the development of wind power requires high investment for electrical networks expansion while technical constraints are increasing. New connections strategies allow finding a technical and economic optimum for both wind project owners and network operators. Furthermore, the implementation of new electrical configurations when connecting wind power plants requires willingness from operators to change classical connections standards.

The use of the available power capacity in an optimal way requires PLCs and measuring devices in order to exchange information between producers, consumers and networks operators. This implementation of new devices is addressed in a smart grids context.



Learning objectives
- to optimize the of the electrical networks while integrating wind power into the grid
- to optimize the use of the available power capacity into the electricity networks
- comparing costs between different technical configurations (decision-making tool)