Rapid growth of wind power sector presents great challenge for power system operators in aspect of generation scheduling, grid management, balancing and ancillary services. Traditionally ancillary services are obtained from conventional power plants. However nowadays, through different set of control possibilities, wind power plants are able to partly participate in provision of ancillary services. This paper discusses the possibilities of providing ancillary system services by wind power plants, primarily regarding reactive power control and partially frequency control. In addition, real example is used to demonstrate the benefits from reactive power support by wind power plant to maintain regular voltage conditions in distribution network.