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This paper presents new converter for torque ripple minimization of three phases Switched Reluctance Motor (SRM). The proposed converter has basic passive circuit which includes two diodes and one capacitor to the front end of an asymmetric converter with a specific end goal to get a high magnetization and demagnetization voltage. In view of this boost capacitor, the charge and demagnetization voltage are higher. Accordingly, it can reduce the negative torque generation from the tail current and enhance the output power. The proposed converter circuit is equipped for minimizing the SRM torque ripple furthermore enhancing the average torque when contrasted with traditional converter circuit. A three-phase SRM is modeled and the simulation output for no load and stacked condition depicts that the proposed converter has better performance when contrasted with traditional converter. It is appropriate for electric vehicle applications. The proposed framework is simulated by utilizing MATLAB/Simulink environment and their outcomes are examined extravagantly.

The switched reluctance motor incorporates straight forward and solid structure with low latency and direct drive capacity and is particularly suitable for top accuracy and fast creating mechanism. Inception of torque ripple can be found in [

Some researchers focused on machine outline approach by changing the primary dimension of motor. Torque sharing function was applied for reducing the torque ripple in SRM [

A well-known strategy to diminish torque ripple is to utilize suitable phase current profile. A strategy for torque ripple optimizing so as to lessen the phase current profile was contemplated in [

A single controllable switch four-quadrant SRM drive with the minimum component has effectively been exhibited in [

SRMs are unique in relation to other AC machines since they utilize reluctance torque in the variety locale of inductance, which requires a square-wave excitation current as opposed to the sinusoidal current that is utilized as a part of an AC machine. Keeping in mind the end goal to make a square-wave current controlled voltage is crucial at excitation and demagnetization modes. Nonetheless, the excitation and demagnetization voltages are restricted by the DC link voltage in traditional Switched Reluctance (SR) drives. Quick excitation and demagnetization are troublesome in rapid regions [

The numerical model of SRM is made out of an arrangement of electrical comparison for every phase and the mathematical statement of mechanical framework. The mathematical representation of voltage per phase is given by

R_{s}―Resistance per phase.

l―Flux linkage of winding per phase.

where L is the phase inductance relies on the rotor position and phase current.

The emf induced in the winding is written as

where Kb-emf constant

The torque produced in a phase is given by

The mechanical equation

where T_{l}―load torque, J_{m}―moment of inertia, B_{m}―friction coefficient. In view of the above mathematical statement [

The three phase traditional converter circuit outline is appeared in

The circuit diagram of proposed converter is appeared in _{cd}, D, and a boost capacitance C_{cd}. Notwithstanding, the higher voltages are connected to phase windings and it can acquire faster excitation current and demagnetization current. So it can enhance current following impact and productivity, lessen the torque ripple. It could likewise enhance the performance when the converter supplies an extra boosted voltage to SRM.

In the mode 1, two phases switch S_{1}, S_{2} and diode D all turn ON and the higher voltage is applied to phase winding because the capacitor voltage (V_{cd}) is added to the phase voltage. The winding is energized and the current flow path is shown in

In the mode 2, phase switches (S_{1}, S_{2}) turn ON and switch D turn OFF. The current flow path is shown in _{dc} is charging the switches (S_{1}, S_{2}) and diode D_{cd} turn ON, the circuit equation can be written as (9) As the switches turn OFF, capacitor is being discharged ,the capacitor voltage can be written as (10)

In the state 0, one of phase switches turn ON S_{2} and the other one S_{1} turn OFF and diode D_{2} turn OFF at the same time. The current flow path is shown in _{2} and one diode turn ON D_{1} can be written as (11)

In mode 4 all phase switches and diode D are turn OFF, the state is named as de-magnetization mode and higher negative voltage are applied to phase windings. The stored magnetic energy is returned to the supply when compared with asymmetric bridge converter, it can obtain faster demagnetization current when current is dropping and also obtain better performance. The current flow path is indicated in

From Equation (13) the value of boost capacitor is designed. The boost capacitor value must be less than the dc link capacitor. The value of boost capacitor is designed as 47 µF.

Since the saliency of the stator and rotor, the torque ripple is generated when the previous phase is being energized opposite voltage and the later phase has been energized. The purpose of crossing point between the two energized phases must be progressed to a higher quality for minimizing the torque ripple. Equation suggests (15), positive torque is created when the machine inductance is rising because the shaft angle is increasing dL/dQ is positive. Equally, a negative torque is generated by supplying the SRM winding with current while dL/dQ is negative. Henceforth by controlling the current and selecting the suitable turn ON and turn OFF angle will prompt minimize torque ripple in SRM drive.

The expression for the torque ripple is given in (15)

where T_{max}―Maximum estimation of torque (N∙m).

T_{min}―Minimum estimation of torque (N∙m).

T_{mean}―Mean estimation of torque (N∙m).

So as to minimize the torque ripple positive torque must be upgraded and negative torque generation must be entirely stayed away from.

To validate the performance of switched reluctance motor, the proposed converter was simulated by MATLAB/ simulink under load T_{L} = 2.5 N∙m is appeared in

the hysteresis band is chosen as ±10 A. The SRM is started by applying the step reference to the regulator input. The acceleration rate depends on the load characteristics. To shorten the starting time, a very light load was chosen. Since only the currents are controlled, the motor speed will increase according to the mechanical dynamics of the system. In current controlled mode, the average value of the developed torque is approximately proportional to the current reference. In addition to the torque ripple due to phase transitions, we note also the torque ripple created by the switching of the hysteresis regulator.

Comparative examination of the ordinary and proposed converter response are appeared in Figures 6-11 respectively.

45 degree and turn OFF angle 75 degree. It can be seen in _{L} = 2.5 N×m. From the torque waveform we observe that change in torque is 57 N∙m and the average torque is 23.89 N∙m and the torque ripple is ascertained from the above data and torque ripple rate got as 2.396. _{L} = 5 N∙m. From the torque waveform we observe that change in torque is 58 N∙m and the average torque is 26.79 N∙m and the torque ripple is ascertained from the above data and torque ripple rate acquired as 2.165. In proposed converter ,the presence of boost capacitor causes high demagnetisation voltage and also the fall time current get reduced to zero before the next phase is energised.

_{L} = 2.5 N∙m. From the torque waveform we observe that change in torque is 70 N∙m and the average torque is 35.19 N∙m and the torque ripple is computed from the above data and torque ripplerate acquired as 1.932. _{L} = 5 N∙m. From the torque waveform we observe that change in torque is 70 N∙m and the average torque is 38.22 N∙m and the torque ripple is computed from the above data and torque ripple rate got as 1.831.

A | B | C | D | |
---|---|---|---|---|

Traditional converter | 0 | 58 | 21.66 | 2.688 |

2.5 | 57 | 23.89 | 2.396 | |

5 | 58 | 26.79 | 2.165 | |

Proposed converter | 0 | 66 | 32.09 | 2.056 |

2.5 | 70 | 35.19 | 1.932 | |

5 | 70 | 38.22 | 1.831 |

A―load torque, B―change in torque, C―average torque, D―torque ripple.

converter at different switching angle. In proposed converter the current tracing effect is greater than ordinary converter. Henceforth dynamic performance is improved.

In this paper, a new front end capacitive switched reluctance motor drive has been introduced. This topology includes one boost capacitor and two diodes in addition to the traditional converter. The boost capacitor gives high magnetization and demagnetization voltage to the motor winding. The torque ripple is quite excessive and the current tracing effect is not very good for asymmetric converter. The proposed converter obtains faster excitation current during magnetization and quick demagnetization current for the duration of demagnetization period. So it will possibly also support current tracing effect, average torque, and reduce the torque ripple. It is well suited to electrical vehicle, electric traction and aerospace utility.

S. Muthulakshmi,R. Dhanasekaran, (2016) A New Front End Capacitive Converter Fed Switched Reluctance Motor for Torque Ripple Minimization. Circuits and Systems,07,585-595. doi: 10.4236/cs.2016.75050