BFA Optimal Control Of Harmonic Suppression In Mine Hoist Inverter

AC(Alternating Current) variable frequency speed control system with wide speedregulation range, high precision, convenient and flexible in control, low start current, hightorque at low speed, high operation efficiency characteristics, has been widely used in minehoist. However, due to the variable frequency control system using carrier-based PWM (PulseWidth Modulation) control, the inverter output voltage contains a large number of harmoniccontent in the process of converter driving mine hoist. These harmonic content not onlydirectly affects the stability of operation of the mine hoist, but also cause serious interferenceto the control system of mine hoist and cause pollution to the power grid. So the study ofmine hoist inverter harmonic suppression technology, to ensure efficient and stable operationof mine hoist, has a practical significance.Based on the analysis of three-phase three-level inverter under different modulation andharmonic generation mechanism, a minimizing THD(Total Harmonic Distortion) of PWMmethod has been proposed, with the target of minimizing THD of converter output voltage,using BFA(Bacterial Foraging Algorithm) to optimal solve the switching time of theminimum total harmonic distortion, and to verify the validity of the method by simulation andexperiment. The main contents are as follows:1. According to the high-voltage high-power of mine hoist on the inverter capacity andvoltage level requirements, taking the three-phase three-level inverter as the object to study,theoretical analysis harmonic generation mechanism of three types modulation (the triangularcarrier cascading PWM, the space vector PWM, the Selective Harmonic Elimination PWM),through the simulation to get results of various modulation mode. Combination of hoistconstant torque operating conditions, through the test experimental analysis the variation ofinverter output voltage harmonic of mine hoist under different torque, speed (frequency).2. Put forward a minimizing THD of PWM method, establish the output voltageharmonic mathematical model with the load, with the target of minimizing THD of converteroutput voltage, switching time of the inverter power devices as the optimization variables,considering condition of the single harmonic voltage amplitude, total harmonic distortion ratein a limited amount of range then establish a minimum output voltage THD harmonicoptimization mathematical model.3. On the basis of the establishment of the harmonic optimization model, using BFA tosolve the inverter power devices switching time in different frequency and different load, then compared with the single harmonic rate、harmonic distortion total rate obtained before andafter optimization under the same conditions, and contrast convergence in the process ofoptimization solution to verify the superiority of the bacterial foraging algorithm in harmonicoptimization solution.4. Establish the three level inverter simulation model with load, through the simulationget optimization switch time harmonic suppression effect of inverter output voltage underdifferent frequencies, different load. At the same time the optimized switch time is stored inthe DSP320F2812, and then the PWM pulse generated by extension, interrupt mode is appliedto the AC frequency comprehensive experimental platform. The experimental results verifythe validity of the minimize THD of PWM modulation method in the suppression of theinverter output voltage harmonics.