Control of Generator- and Grid-side Converter for the Interior Permanent Magnet Synchronous Generator

Permanent magnet synchronous generators have wide application in wind energy conversion systems. If interior permanent magnet synchronous generator (IPMSG) is connected to the grid by a full scale AC-DC-AC converter, the wind turbine can be operated to extract maximum wind power at different wind speeds by optimally adjusting shaft speed. In this paper the model of the AC-DC-AC converter and related control structures for the control of IPMSG were developed in MATLAB/Simulink. Control of generator-side converter was achieved using field oriented control (FOC) which separately controls the electromagnetic torque and the magnetic flux. Optimal stator current references were calculated using maximum torque per ampere algorithm (MTPA) which ensures minimum stator current magnitude for electromagnetic torque reference. Control of grid-side converter was achieved using voltage oriented control (VOC) which separately controls active and reactive power injected to the grid. Outer control loop, with slower dynamics, ensures that DC circuit voltage is kept at reference value which ensures transfer of the active power from the DC circuit to the grid. Inner control loops, with faster dynamics, control the d- and the q-axis grid currents. Using developed control structures, the stator and the grid current PI controllers were designed using technical optimum while DC voltage PI controller was designed using symmetrical optimum. Proposed control methods were verified by simulation using laboratory model parameters.