Reactive power control for parallel wind parks comprising Q(U) characteristics

A common requirement for wind park reactive power control is the implementation of q(u) characteristics into the park controller. However, under some circumstances, the q(u) characteristic can cause voltage oscillations or even stability problems, e.g. in case of weak grid connections or if several wind parks are connected in parallel. This is why the q(u) characteristic has to be taken into account for controller design, in particular if the requirements for controller dynamics are high. This article focuses on the situation of connecting an additional wind park in parallel to an existing wind park, both comprising q(u) characteristics. An analysis of the overall control system is given, showing the negative effect of the second wind park on system stability. It is thus generally advisable to carry out a new stability analysis, when a new wind park is connected in parallel to an existing park. Two measures are proposed for stabilization: reduction of dynamics of one or both wind park controllers reduction of the required q(u) For the analytic approach, linear control theory is applied. Linear simulation results are included to illustrate the behaviour of the analysed systems. Nonlinear simulation results are shown in order to provide a justification of the linear approach.