Abstract
Due to the rugged construction, high starting torque, wide speed range, inherent fault-tolerance and high operating efficiency, switched reluctance motors (SRMs) have been used in many fields such as household appliances, electric vehicles and industrial drives. At low and medium speeds, the current chopping control (CCC) are usually used for SRMs. The current sensors must be connected in series with each phase winding for detecting the phase current, and the number of sensors is usually equal to the number of motor phases. In order to reduce the number of current sensors and the cost of the drive system, this paper propose a general phase current reconstruction method for SRM drive system with two current sensors. Firstly, the excitation, freewheeling and demagnetization circuits of the asymmetric half-bridge power converter are separated into two different paths. The sensors placement method, winding connection method and calculation formula of each phase current are introduced in detail. Then the influence of the turn-off angles on the overlap interval of each phase current is analyzed, and the proposed reconstruction method is further extended to multi-phase SRM. This method can simplify the current decoupling process and is easy to implement without changing the asymmetric half-bridge topology and operating states. Finally, the feasibility of the proposed phase current reconstruction algorithm is verified by simulation and experiment.
Highlights
Switched Reluctance Motor (SRM) has the advantages of rugged construction, low cost high starting torque, wide speed range and inherent fault-tolerance [1,2,3], which have been used in many fields such as household appliances, electric vehicles and industrial drives [4,5,6,7,8]
The adjacent phase is staggered by 15°, and the specific calculation formula is as follows: Ce where Ce represents the rotor period, Nr represents the number of rotor poles, θmax is the maximum excitation angle, and θs is the lagging angle of each phase
For a four-phase SRM, such as the 8/6 structure, according to (1) to (3), it can be seen that the rotor period is 60°, and the maximum conduction angle is 30°, and each phase is staggered by 15°
Summary
Switched Reluctance Motor (SRM) has the advantages of rugged construction, low cost high starting torque, wide speed range and inherent fault-tolerance [1,2,3], which have been used in many fields such as household appliances, electric vehicles and industrial drives [4,5,6,7,8]. A universal two-sensor current detection scheme for multiphase SRM control with multiphase excitation, by selecting the currents flowing through each sensor is proposed in [19] This method is applicable for all three-phase, four-phase, five-phase, and six-phase drives, without external circuits and any changes in converter topologies. The methods with one current sensor require high-frequency pulse injection to the non-conducting phase and decouple the currents of each phase according to the rotor position information. This method requires the least number of sensors, it will increase the sampling complexity, and the injected pulses will affect the sampling accuracy. The effectiveness and reliability of the proposed method are verified through theoretical analysis, formula derivation, simulation, and experiment
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