Modelling and suppression of bearing voltage of wind turbine permanent magnet synchronous generators

Abstract

The problem of bearing current is common in wind power generation system, which leads to the attenuation of generator life and great economic losses. Bearing voltage of a 5.5 MW wind-turbine permanent magnet synchronous generator is studied. The bearing voltage equivalent circuit is modelled by studying the internal system structure of the generator, and an extraction method of cable parameters, generator winding parameters and stray capacitance parameters based on experiments is proposed to simulate the system. A system test platform is built to test the common mode voltage, common mode current and bearing voltage, and the test results are compared with the simulation results in time domain and frequency domain. The result indicate that the common mode equivalent model can accurately simulate the actual bearing voltage. Finally, rotor flange insulation is adopted to suppress bearing voltage. The relationship between the design of rotor flange insulation with suppressing effect is discussed. Finally, an optimisation design method is presented for the proposed suppression scheme.