Power hardware in-the-loop laboratory test environment for small scale wind turbine prototype

This paper presents power hardware-in-the-loop (PHIL) laboratory test environment for wind turbine (WT) prototype. The environment utilizes dSPACE and RTDS real time simulators, converter controlled grid emulator (GE) and the prototype. The analysis is carried out using frequency response measurements. The main contribution is the detailed analysis of the grid emulator performance. The main performance limitations are revealed and it is shown that the performance of the GE is dependent on the hardware of the WT prototype in addition to the design of the emulator itself. The comparison of the operation of the GE with open loop and closed loop control modes is carried out. It is shown that the accuracy of the environment is clearly sufficient for symmetrical voltage dips when closed loop control system is used. However, the open loop controlled GE cannot execute correct point of common coupling voltages independent on the operation point of the WT which is relative to the wind conditions. If the GE is controlled at open loop or at closed loop, the network asymmetrical voltage dips are not generated accurately. The reason is that the system bandwidth is not wide enough to execute negative sequence 50 Hz component without gain and phase error. However, the accuracy of the PHIL environment is clearly enough for testing the operation of WT control functionalities under asymmetrical network voltages. These functionalities may include PCC voltage balancing or positive sequence reactive power injection.