# Online Estimation Method of DC-Link Capacitors for Reduced DC-Link Capacitance IPMSM EEE Academic

ABSTRACT:

DC-Link Capacitance In order to extend the lifetime and save the system cost, the film capacitor is applied in the DC-link of IPMSM drives. Many active damping control methods have been carried out to improve the drive system stability, which need the accurate value of the DC-link film capacitor.

DC-link

DC-Link Capacitance In this letter, an online DC-link capacitance estimation method is investigated for reduced capacitance IPMSM drives, which does not need any additional signal injection or sensor. The power coupling characteristics are analyzed to obtain the instantaneous power of the DC-link capacitor from the inverter and the grid sides.

Voltage

DC-Link Capacitance The band-pass filter is applied to extract the DC-link voltage and capacitor power with twice the frequency of the grid voltage. The DC-link capacitance could be estimated by the fundamental component of the DC-link voltage. The proposed method can be used for different kinds of load types and motor types of the drive system. Experimental results are performed to verify the estimation method, and the estimation error is within 1%.

KEYWORDS:

1. Online capacitance estimation
2. Motor drive
3. Online capacitance estimation
4. Reduced DC-link capacitance

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Block diagram of DC-link capacitance estimation.

EXPECTED SIMULATION RESULTS:

Fig. 2. Experimental results when the motor operates at 1800rpm. (a) Waveforms of grid power, inverter power, capacitor power and its fundamental component. (b) Waveforms of the DC-link voltage, the product of DC-link voltage and its derivative, and the fundamental component of the product M. (c) Detailed waveform of the fundamental component of capacitor power, M, and the estimated DC-link capacitance.

Fig. 3. Experimental results when the motor operates at 4800rpm. (a) Waveforms of grid power, inverter power, capacitor power, and its fundamental component. (b) Waveforms of the DC-link voltage, the product of DC-link voltage and its derivative, and the fundamental component of the product M. (c) Detailed waveform of the fundamental component of capacitor power, M, and the estimated DC-link capacitance.

Fig. 4. Experimental results when the motor operates at 3000rpm and the DC-link capacitance is 59.5μF. (a) Waveforms of grid power, inverter power, capacitor power and its fundamental component. (b) Waveforms of the DC-link voltage, the product of DC-link voltage and its derivative, and the fundamental component of the product M. (c) Detailed waveform of the fundamental component of capacitor power, M, and the estimated DC-link capacitance.

CONCLUSION:

DC-Link Capacitance As for the reduced DC-link capacitance IPMSM drive system, a real-online DC-link capacitance estimation method is investigated in this letter, which does not need an additional signal injection. The power coupling characteristics are analyzed, and the instantaneous DC-link capacitor power is obtained.

Capacitance

DC-Link Capacitance The DC-link capacitance could be estimated by the ratio of the fundamental component of DC-link capacitor power and that of the product between DC-link voltage and its derivative term. Moreover, the proposed method only depends on the DC-link voltage and the instantaneous DC-link capacitor power,

Motor

DC-Link Capacitance which benefits its application in other motor type and load type reduced DC-link capacitance motor drive system. Experimental results verify the effectiveness of the proposed DC-link capacitance estimation method, which could realize the estimation precision within an error of 1% for the several tens microfarad of DC-link capacitance.

REFERENCES:

[1] Y. Zhang, Z. Yin, J. Liu, R. Zhang and X. Sun, “IPMSM Sensorless Control Using High-Frequency Voltage Injection Method With Random Switching Frequency for Audible Noise Improvement,” IEEE Trans. Ind. Electron., vol. 67, no. 7, pp. 6019-6030, Jul. 2020.

[2] K. Liu and Z. Zhu, “Fast Determination of Moment of Inertia of Permanent Magnet Synchronous Machine Drives for Design of Speed Loop Regulator,” IEEE Trans. Control Syst. Technol., vol. 25, no. 5, pp. 1816-1824, Sept. 2017.

[3] J. Hang, H. Wu, S. Ding, Y. Huang and W. Hua, “Improved Loss Minimization Control for IPMSM Using Equivalent Conversion Method,” IEEE Trans. Power Electron., vol. 36, no. 2, pp. 1931-1940, Feb. 2021

[4] K. Abe, H. Haga, K. Ohishi and Y. Yokokura, “Current ripple suppression control based on prediction of resonance cancellation voltage for electrolytic-capacitor-less inverter,” IEEJ J. Ind. Appl., vol. 6, no. 1, pp. 1-11, 2017.

[5] Y. Zhou, W. Huang, and F. Hong, “Single-phase input variable-speed AC motor system based on electrolytic capacitor-less single-stage boost three-phase inverter,” IEEE Trans. Power Electron., vol. 31, no. 10, pp. 7043-7052, Oct. 2016.