Sensorless Design Of Switched Reluctance Motor Based On Inductance Detection

Switched Reluctance Motor(SRM)has been widely used in electric vehicles,aerospace,coal mining,textiles and other fields because of its simple structure,low cost,and high efficiency.The traditional position signals of SRM are obtained through position sensors,but the position sensors are less adaptable to harsh environments,which limits the application of SRM in extreme environments and increases the cost and volume of the entire speed control system.This dissertation takes three-phase SRM as the research object to study the position detection technology at the start-up,low-speed and high-speed phases,and proposes the acquisition method of the inductance threshold,the smooth switching algorithm of the high-low-speed position detection method,and the filtering method of the response current slope.In the static start phase,high-frequency pulses are injected into the SRM three phases at the same time,and pulses are injected into the previous conduction phase in the low-speed phase.The response current is sampled multiple times and filtered by the linear regression equation to obtain the current slope.Because the current slope is inversely proportional to the inductance,the SRM is stationary,the initial starting phase can be determined by the inductance zone.SRM single-inductance threshold method at low speed.Knowing the current slope and bus voltage can obtain the real-time inductance.When the real-time inductance of the previous phase reaches the single inductance threshold,the current phase is turned off,the next phase is turned on,and the commutation is completed.In order to take advantage of the large starting torque of SRM,a dual inductance threshold algorithm with inductive turn-off threshold and turn-on threshold is used.When the real-time inductance of the previous conduction phase reaches the inductance turn-on threshold,the next phase is turned on.At this time,the SRM is in a two-phase conduction state.When the real-time inductance of the previous on-phase reaches the inductance turn-off threshold,the current phase is turned off.Realize the commutation judgment of SRM static and low-speed phases.The high-speed algorithm uses the midpoint of the inductance linear rise region as the inductance threshold,and estimates the SRM speed according to the time when the real-time inductance reaches the inductance threshold each time in the conduction phase,and derives the full cycle position information of the motor through the speed and special position points.When the conduction phase current is large,the magnetic circuit is saturated and the inductance curve will shift downward.The current chopping control method is used to read the rising and falling slopes of the conduction phase current in order to obtain the inductance thresholds of different current intervals,and the inductance threshold is selected to detect the location of special points according to the interval where the conduction phase current is located.In MATLAB/Simulink,the position detection algorithm and the high-low-speed switching algorithm of the three speed stages are simulated,and it is verified that the detection accuracy of the algorithm is high and the anti-load interference ability is strong.The controller of STM32F303 is designed as the main control chip,the program logic is designed according to the principle of position detection algorithm,and the SRM with a rated power of 1k W is used for experimental verification.The experiment testifies to the feasibility of the proposed algorithm,which turns out to be feasible.