Research On Common Mode Voltage And Harmonic Suppression Of Explosion-proof Integrative Motor

In this paper， EMC and harmonic suppression of an1140V/75kW EPIM(explosion-proof integrative motor) was researched according to the problems of narrowmine working space and EMC, harmonic, volume and cost caused by the highly integrationbetween the variable-frequency speed control system and motor based on the background ofMinistry of Education innovation team project, education department of Liaoning provinceinnovation team project and project of Fushun Coal Mine Motor Manufacturing Ltd. Themain contents of this paper include the following aspects:（1）EPIM is a integrated system consisted by the controller and the variable-frequencymotor, so its design is restricted by the room size and EMC. In order to make sure that powerelectronic devices operate safely and steadily in the limited space, the EMC of EPIM mustbe considered carefully. Firstly，improved unified voltage modulation technique (UVMT)was used to cancel the effects of zero vector and reduce the common-mode voltage of EPIMspeed control system. This modulation algorithm also needn t to judge sectors and easy toimplemented, saving system resources. At the same time, electromagnetic coupling pathbetween IGBT and radiator was adopted to reduce common mode interference of speedcontrol system, and tradition bus was instead by the adopted multilayer bus to reduce strayinductance of line. The capacitance value of IGBT was calculated through maximum energyabsorption method based on power electronics system modeling. In order to suppress thepeak voltage in the breaking process of IGBT; A kind of four-stage capacitance topologywas proposed which can provide a low impedance circuit for the high frequency harmonics,which make these harmonics return the device directly through the capacitor withoutcontamination grid.（2）The problem that a lot of space harmonics and time harmonics caused byvariable-frequency speed control system will be not conducive to the operation of the gridand the variable frequency motor. In this paper, reactors were used in the input terminal tofilter harmonic current and reduce harmonic disturbances to power grid which come fromthe speed control system. A model of calculating the limit of reactor was proposed based onpower electronic systems, the program compared with traditional computing solutions cansignificantly reduce the volume of the line reactors. At the same time, the EPIM loadchanged frequently which leaded to harmonic changes. Harmonic suppression technique consisting of controllable reactor was used at the output terminal. The inductance of reactorcould be regulated by this scheme according to change of load and the harmonic could besuppressed in this way.（3）In order to suppress the harmonic caused by rectifier, reduce the electromagneticinterference to the electronic components, improve stability of the system and narrow thevolume of EPIM, the PWM rectification control strategy was applied in this paper. Thevirtual voltage reconstruction technology was applied to estimate the grid side voltagewithout using the voltage sensor which enhanced the reliability of system; On the otherhand，in order to avoid the waste time caused by the optimization of PI parameters and thesecurity risks caused by incorrect regulation of PI parameters, the strategy of PI regulationbased on ant colony algorithm was studied and the PI regulation of controllable rectifierwere studied.（4）The design of variable-frequency motor is different from the traditional motor,both the efficiency and the power factor should be considered. What s more, the maximumtorque parameter in the speed regulation range must be taken the dynamic performance intoaccount. From the perspective of frequency control system, the motor was designedoptimally based on harmonic analysis model. The space harmonic and the time harmonicwere considered comprehensively which strengthened the anti-harmonic ability of theintegrative motor. An1140V/75kW EPIM was developed and experiment platform was built.Feasibility of the proposed scheme and the design of EPIM were verified in this paper.