ABSTRACT:
Optimal currents with appropriate harmonic
components injected into the motor windings can effectively mitigate torque
ripple for interior permanent magnet (IPM) type brushless DC motors (BLDCMs).
However, existing approaches may fail to accurately inject the optimal currents
into motors due to the limited current loop bandwidth. This paper proposes a
simple enhanced generalized vector control strategy to mitigate the torque
ripple for IPM-type BLDCMs. With the proposed vector control strategy, the
control block diagram for IPM-type BLDCMs is as simple as that with traditional
vector control for sinusoidal permanent magnet synchronous motors. Firstly, an
electromechanical energy conversion voltage (EECV), considering the effects of
the non-sinusoidal back-EMF and the rotor salience property, is proposed in -axis. Then, a novel coordinate frame is
constructed with the proposed EECV, which is based on the arbitrary reference
frame theory. As a result, the currents of IPM-type BLDCMs can be decomposed
into two constant components, one being linked to the torque and the other one
to the flux linkage. Thus, the bandwidth of current loop with simple
proportional integral regulator can be equivalently expanded in the proposed
coordinate frame. Finally, comprehensive experiments are conducted in different
operation conditions to validate the effectiveness of the proposed vector
control strategy. 1
KEYWORDS:
1. Brushless DC motors (BLDCMs)
2. Vector control
3. Optimal currents
4. Torque ripple mitigation
SOFTWARE: MATLAB/SIMULINK
CONCLUSION:
An
enhanced generalized vector control strategy based on the arbitrary reference
frame theory is proposed. And a voltage component involving in
electromechanical energy conversion, namely EECV, is utilized to establish the novel
coordinate frame of the generalized vector control strategy. Therefore, the
current components of BLDCMs mapped in the proposed coordinate frame are
constant, surmounting the bandwidth limitations of PI current regulator
thoroughly. With the proposed strategy, the torque ripple minimization and MTPA
operation for BLDCMs can be achieved simultaneously, and the steady and dynamic
performance have been verified by experimental results. In addition, the
influence of permanent magnet flux and inductance term variations on the torque
ripple mitigation has been investigated with experimental tests.
In conclusion, the
proposed method has the following advantages:
1) Compared with
two phase feeding mode, the proposed method eliminates the switching of control
strategy between normal conducting period and commutation period, and between
low speed and high speedarea. Thus, the executability of torque ripple
mitigation is enhanced.
2) Compared with
the traditional vector control with Park transformation [4] and the vector
control with GSRF [11], the proposed method can simplify the mathematical model
of IPM-type BLDCMs, being similar with that of the surface sinusoidal PMSMs.
Then, with simple PI current regulator, the steady state and transient state
performance of torque ripple mitigation are improved.
3)
Compared with the vector control based on the conventional rotor orientation
with the additional resonant controllers[15]-[20]or repetitive controllers[21],
or the method based on multiple reference frames[22], all torque ripple
harmonic componentscan be mitigatedtheoretically, not only the selective torque
harmonic components.Thus, the torque ripple can be mitigated further with the
proposed method.
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