Abstract: The method for the implementation of a three-level pulse width modulation (PWM) scheme on the field programmable gate array (FPGA) is introduced. The PWM is with compensation for dead-band effect for flywheel magnetic bearing power amplifier with low current ripple and high output linearity. The proportional-derivative algorithm in the current loop is implemented by using floating-point IP core portfolio. In Simulink, the System Generator tool is used to build the three-level PWM model and to automatically generate the VHDL code. Two three-level modulation schemes, using or not using the diode in the power switch to conduct current, are analyzed. The effect of dead-band on the output linearity is researched on the basis of the test result of power amplifier current response and its Fourier analysis. Two compensating methods, one compensates the pulse duration ratio, the other adds offset to the input of the amplifier, are presented. The three-level modulation schemes together with the compensating methods are implemented on an FPGA power amplifier board to verify their feasibility and efficiency.

Key words: Active magnetic bearing, Field programmable gate array, Pulse-width modulation, Switching power amplifier