Switched reluctance starter/generator control system allowing operation with regenerative loads and electrical system employing same

An electric power generating system for convening mechanical energy from a prime mover to electrical energy, the electrical energy being distributed by a dc bus to utilization equipment for use thereby, comprising:

• a switched reluctance machine having a rotor drivably coupled to the prime mover by shaft means, and a stator having a first plurality of salient stator poles wound with phase windings, said rotor comprising a second plurality of salient rotor poles;
• an inverter having a dc input/output coupled to the dc bus, and at least a first and a second switching means responsive to switching control signals for coupling each of said phase windings to the dc bus, and at least a first and a second commutation means for cross-coupling each of said phase windings to the dc bus to allow current flow back when said switching means are disabled;
• controller means having a plurality of control inputs and outputs coupled to said inverter for monitoring and controlling system performance;
• and wherein
• said controller means continuously monitors current flowing in said phase windings and voltage level on the dc bus, said controller means calculating a variable maximum phase current control signal and a variable minimum phase current control signal therefrom;
• and wherein
• said controller means modulates said switching control signals to regulate said phase current within a range defined by said variable maximum phase current control signal and said variable minimum phase current control signal, said controller means maintaining said voltage level on the dc bus at a desired level thereby;
• and wherein
• said controller means, upon calculating a positive maximum phase current control signal, generates said switching control signals to enable at least said first and said second switching means for each of said phase windings at a first fixed angle prior to alignment of said rotor pole with said phase winding's associated stator pole, said controller further generating said switching control signals to disable at least said first and said second switching means at a second fixed angle after alignment of said rotor pole with said phase winding's associated stator pole, said switched reluctance machine generating sufficient electric power thereby to maintain said voltage level on the dc bus at said desired level;
• and wherein
• said controller means, upon calculating a negative maximum phase current control signal, generates said switching control signals to enable at least said first and said second switching means for each of said phase windings at a third fixed angle prior to alignment of said rotor pole with said phase winding's associated stator pole, said controller means further generating said switching control signals to disable at least said second switching means at a fourth fixed angle prior to alignment of said rotor pole with said phase winding's associated stator pole, said switched reluctance machine dissipating an amount of electric power thereby sufficient to maintain said voltage level on the dc bus at said desired level.

A method of controlling a switched reluctance machine to allow operation as a generator producing electric power in the presence of a net dissipative load, and dissipating electric power in the presence of a net regenerative load, the machine having a salient pole rotor drivably coupled to a prime mover by shaft means, and a multi-phase, multi-pole wound salient pole stator having its phase windings switchably coupled to a dc power bus by switching means having cross coupled commutation means, comprising the steps of:

• monitoring the voltage on the dc power bus at a point of regulation;
• comparing the voltage on the dc power bus with a predetermined voltage command threshold to determine a voltage error;
• calculating a maximum phase current control signal and a minimum phase current control signal based on the voltage error, said maximum phase current control signal and said minimum phase current control signal representing an amount of current required to minimize the voltage error;
• and
• when said maximum phase current control signal is a positive value, enabling the switching means for a selected phase winding to allow excitation current flow from the dc power bus to energize the selected phase winding at a first fixed angle prior to alignment of a rotor pole with the energized stator pole;
• and
• disabling the switching means to allow generation current flow through the commutation means to the dc power bus at a second fixed angle after alignment of the rotor pole with the energized stator pole;
• and
• when said maximum phase current control signal is a negative value, enabling the switching means for a selected phase winding to allow dissipation current flow from the dc power bus to the selected phase winding at a third fixed angle prior to alignment of a rotor pole with the selected stator pole;
• and
• disabling the switching means at a fourth fixed angle prior to alignment of the rotor pole with the selected stator pole;
• and
• regulating the voltage on the dc power bus by modulating the switching means to control the generation and dissipation current flow within the variable limits defined by said maximum phase current control signal and said minimum phase current control signal.

A method of controlling a switched reluctance machine to allow operation as a generator to produce electric power in the presence of a net dissipative load and to dissipate electric power in the presence of a net regenerative load, the machine having a salient pole rotor drivably coupled to an engine by shaft means, and a multi-phase, multi-pole wound salient pole stator having its phase windings switchably coupled to adc power bus by switching means and by commutation means to allow generation current flow and dissipation current flow, comprising the steps of:

• calculating a maximum phase current control signal and a minimum phase current control signal based on the dc power bus voltage deviation from a predetermined voltage command threshold said maximum phase current control signal and said minimum phase current control signal representing an amount of current required to minimize said dc power bus voltage deviation;
• enabling the switching means for a selected phase winding for a first period beginning at a first fixed angle prior to alignment of a rotor pole with the selected stator pole and ending at a second fixed angle after alignment of the rotor pole with the selected stator pole when said maximum phase current control signal is positive;
• enabling the switching means for a selected phase winding for a second period beginning at a third fixed angle prior to alignment of a rotor pole with the selected stator pole and ending at a fourth fixed angle after alignment of the rotor pole with the selected stator pole when said maximum phase current control signal is negative;
• and
• modulating the switching means during said first period and said second period to maintain the generation and dissipation current flow within the range defined by said maximum phase current control signal and said minimum current control signal.