Control of a 6/4 switched reluctance motor by means of a DC voltage supply with DC high voltage intermediary circuit

This paper presents the control scheme of a three phase switched reluctance motor (6/4), powered by a specialized DC voltage source, provided with a high voltage intermediary circuit. Rated voltage of the DC intermediary circuit is about 1000 V. Output rated voltage of the DC power supply is 230 V, allowing a maximum variation of 1 V to the reference value. SRM control scheme also includes: a control loop of the rotor angular velocity within certain prescribed limits and a stator phase current control loop to a certain reference value respectively. Each of them use for adjustment a relay block circuit. It is permitted a maximum variation of 2 A of the stator phase current from the reference value, and at most 2 rad/s of the rotor angular velocity to the prescribed value respectively. At the end of the energizing cycle of each stator phase, the energy stored in the magnetic field of that phase is returned to the power supply. This is achieved by reconnecting the considered stator phase with reverse polarity, to the DC intermediary circuit of 1000 V. Thus, the stator phase current decreases from its maximum to zero with a greater slope, which value is about 4 times higher compared to the classical situation. The turn-off angle of each stator phase is chosen so that the current through that winding is zero for the interval corresponding to the decreasing slope of the considered stator phase inductance. Thus, the electromagnetic torque developed by each SRM phase is always maintained positive. Another advantage of using this type of voltage source for energizing the SRM phases, is the possibility of changing the turn-off angle corresponding to each stator phase, closer to the aligned position of that phase. At the end of this paper are presented the simulation results obtained using the Matlab - Simulink software package.