This workshop, moderated by Volker Wachenfeld, SMA Solar Technology AG, aimed at clarifying grid connection requirements and responsibilities in an increasingly liberalized electricity market.

Three presentations were given during this workshop followed by an active discussion. (See presentations). The panel speakers were:

1. Volker Wachenfeld, SMA Solar
2. Eckard Quitmann, Enercon
3. Martin Braun, ISET

Volker Wachenfeld, SMA Solar, presented the high variety of technical requirements for Inverter manufacturers that exist along the different European countries regarding the connection to the electricity grid.

The idea of having well defined grid codes is based in the necessity to assure minimum technical requirements in order to assure a stable and safe electricity grid along Europe. However, each country – and even worse in some of the countries: each Distribution System Operator - defines its own technical requirement, and this fact represents a big barrier for the deployment of PV in Europe. 

The aim is to create, if possible, a set of minimum technical requirements for the connection to the grid which could be applicable to all European countries. 

Eckard Quitmann, Enercon, who comes from the wind power sector, gave an overview on the situation regarding grid connection for Wind Power plants. 

Wind farms usually connect to the MV or HV grid, so the situation can be compared only with big centralized PV. Nevertheless some aspects can also be learned for LV connected PV. So far, there is only one internationally known and accepted certificate which deals with wind power connection: IEC61400-21. The certificate aims to assure power quality; it doesn’t establish the limits but defines what& how the parameter must be measured. However, other aspects as the reference point (physical point where the measurements have to be done) need to be further defined.

The additional cost to fulfill the existing grid codes in wind power plants represents less than 1% of the turbine cost. However that depends very much on how far go the technical requirements of the grid code. This is the similar case for Photovoltaics.

What is considered by a specific power system operator a “minimum technical requirement” and what is an “ancillary service” varies a lot, depending on the technical needs of the power system, the legal and organizational structure of the system operators and also the historically established way of grid management in the different countries.

Aspects as injection of reactive power, fault-ride-through, frequency variation, voltage control and over-voltage should be redefined by the system operators together with the inverter manufacturers (of PV and Wind) in order to optimize the value of renewable in the electricity grid.

The problem is that, in many cases, the system operator deals with these technical issues in a very confidential way. Whereas this is the case for central European countries, other countries like UK are completely transparent and provide all the information via internet.

Martin Braun, ISET presented the added value of PV to the electricity grid. In one hand, PV can contribute by providing ancillary services to the system; it is technical and economically feasible.

In the other hand, the generation of PV electricity correlated very well with the electricity demand and therefore, reduces the load of the transmission network which has a positive impact on the cost for operating the grid.

Photovoltaic (Inverters) can provide high security in the system frequency, as well as voltage control and reactive power. Of course, this potential has also a cost. Therefore the technical requirements need to be defined in order to evaluate if it is also economically feasible.

There is a European project called DERlab which aims at defining the inverter requirements in all Europe, however, the PV sector is not participating so far.

Conclusions:

If requirements are clear Photovoltaics can provide and added value to the electricity network

Compensation of voltage &frequency should be discussed among inverter manufacturers, governments and system operators.

We are experience a transition from an old and outdate European electricity network to a modern network which will be completely based on inverters. This transition must be fast and efficient and for that reason the cooperation of all the players is needed. As an example, the wind sector has needed more than 3 years to define the necessary details for certification of just one requirement (Fault-Ride-Through) This certification is valid solely in Spain.

Have a look at the picture gallery.