Performance evaluation of the slip power recovery system with a DC voltage intermediate circuit and a LC filter on the rotor

A new circuit configuration for the slip power recovery system is presented in this paper. The DC current intermediate circuit is replaced by a DC voltage link. A boost chopper is used to connect the diode rectifier to the DC link voltage inverter. The AC rotor harmonic currents, and consequently the torque harmonics, are filtered by a method similar to the one proposed by Prasad et. al. in 1989 to improve the power factor on the diode bridges working with fixed frequency connected to the mains. This method uses a 3 order filter and one boost converter. In this case the leakage inductance of the machine and a LC filter is used. The effects of variable frequency on the rotor side are eliminated by a different design of the filter. Low values of the L and C parameters are used. The use of a PWM voltage converter on the line side allows the possibility of controlling the reactive power in a wide range and with low current harmonics. The merits of the configuration presented are the cost, the simplicity and the allowable quasi optimum exploration of the electrical machine.