This paper addresses a detailed design and tuning of a wind power plant slope voltage control with reactive power contribution of wind turbines and STATCOMs. First, smallsignal models of a single wind turbine and the whole wind power plant are developed, being appropriate for voltage control assessment. An exemplary wind power plant located in the United Kingdom and the corresponding grid code requirements are used as a base case. The final design and tuning process of the voltage controller results in a guidance, proposed for this particular control architecture. It provides qualitative outcomes regarding the impact of system delays, grid conditions and various operating conditions of the wind power plant, with and without incorporation of STATCOMs.