The State of Charge Estimation of Lithium-Ion Batteries Based on a Proportional-Integral Observer

ABSTRACT:

With the development of electric drive vehicles (EDVs), the state-of-charge (SOC) estimation for lithium-ion (Li-ion) batteries has become increasingly more important. Based on the analysis of some of the most popular model-based SOC estimation methods, the proportional-integral (PI) observer is proposed to estimate the SOC of lithium-ion batteries in EDVs. The structure of the proposed PI observer is analyzed, and the convergence of the estimation method with model errors is verified. To demonstrate the superiority and compensation properties of the proposed PI observer, the simple-structure RC battery model is utilized to model the Li-ion battery. To validate the results of the proposed PI-based SOC estimation method, the experimental battery test bench is established. In the validation, the urban dynamometer driving schedule (UDDS) drive cycle is utilized, and the PI-based SOC estimation results are found to agree with the reference SOC, generally within the 2% error band for both the known and unknown initial SOC cases.

KEYWORDS:

1.      Battery

2.      Electric vehicle

3.      Lithium-ion (Li-ion) battery

4.      Proportional-integral (PI) observer

5.      Sliding-mode observer

6.      State of charge (SOC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Block diagram of different observer-based SOC estimation methods for Li-ion batteries. (a) Block diagram of the common structure. (b) Block diagram of a PI observer.

EXPECTED SIMULATION RESULTS:

Fig. 2. Identification results.

Fig. 3. UDDS current profile.

Fig. 4. SOC estimation results when the initial SOC is given.

Fig. 5. SOC estimation results when the initial SOC is unknown.

CONCLUSION:

A battery SOC estimation algorithm based on a PI observer has been proposed for Li-ion batteries. Acceptable accuracy has been verified by experiments on battery bench testing for both known and unknown initial SOC. The PI-based SOC estimation has a simple structure and is easy to implement. The compensation properties of the PI observer demonstrate that a simple RC model can be utilized to model the Li-ion battery. The estimated SOC with the PI observer converges to the reference SOC quickly, and the SOC estimation errors are maintained in a small band. Most of the errors of the PI-based SOC estimation method are confined to 2% when compared with the reference SOC that is based on Coulomb counting with known initial SOC.

REFERENCES:

[1] B. Pattipati, C. Sankavaram, and K. Pattipati, “System identification and estimation framework for pivotal automotive battery management system characteristics,” IEEE Trans. Syst., Man, Cybern. C, Appl. Rev., vol. 41, no. 6, pp. 869–884, Nov. 2011.

[2] K. Kutluay, Y. Cadirci, Y. S. Ozkazanc, and I. Cadirci, “A new online state-of-charge estimation and monitoring system for sealed lead-acid batteries in Telecommunication power supplies,” IEEE Trans. Ind. Electron., vol. 52, no. 5, pp. 1315–1327, Oct. 2005.

[3] M. Charkhgard and M. Farrokhi, “State-of-charge estimation for Lithiumion batteries using neural networks and EKF,” IEEE Trans. Ind. Electron., vol. 57, no. 12, pp. 4178–4187, Dec. 2010.

[4] L. Xu, J.Wang, and Q. Chen, “Kalman filtering state of charge estimation for battery management system based on a stochastic fuzzy neural network battery model,” Energy Convers. Manag., vol. 53, no. 1, pp. 33–39, Jan. 2012.

[5] X. Hu, F. Sun, and Y. Zou, “Estimation of state of charge of a Lithium-ion battery pack for electric vehicles using an adaptive Luenberger observer,” Energies, vol. 3, no. 9, pp. 1586–1603, 2010.

Direct Torque Control of Permanent-Magnet Synchronous Machine Drives With a Simple Duty Ratio Regulator

ABSTRACT:

The conventional switching-table-based direct torque- controlled (DTC) ac machine drive is usually afflicted by large torque ripple, as well as steady-state error of torque. The existing methods, which optimize the duty ratio of the active vector, are usually complicated and parameter dependent. Based on the analysis of instantaneous variation rates of stator flux and torque of each converter output voltage vector, a simple and effective method considering the effect of machine angular velocity is proposed to obtain the duty ratio. The experimental results carried on a dSPACE platform with a laboratory prototype of the permanent-magnet machine verify that the proposed duty-based DTC method can achieve excellent transient response, less torque ripple, and less steady-state error, without resorting to the complicated control method over a wide range of operating regions.

KEYWORDS:

1.      Direct torque control (DTC)

2.       Duty ratio

3.      Permanent-magnet synchronous machines (PMSMs)

4.       Steady-state error

5.       Torque ripple

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Control diagram of DTC of PMSM.

EXPECTED SIMULATION RESULTS:

Fig. 2. Comparison of steady-state performance of various DTC methods (rated condition: 400 r/min, 5 N · m). (a) Conventional DTC method. (b) M1. (c) M2. (d) Proposed DTC method.

Fig. 3. Dynamic performances of torque response with inner torque loop control only and without outer speed loop. Reference torque from 2 to −2 N · m. (a) Conventional DTC method. (b) M1. (c) M2. (d) Proposed DTC method.

.

Fig. 4. Dynamic and steady-state performances when reference speed changes from 200 to −200 r/min. (a) Conventional DTC. (b) Proposed DTC.

Fig. 5. Steady-state performance of the proposed DTC method with different control parameters: Ka = 0.7, Kb = 0.0005 (rated condition: 400 r/min,5 N · m).

CONCLUSION:

This paper has proposed, analyzed, and experimentally verified a simple and effective method for determining the appropriate duty ratio in DTC three-phase PMSM drives to reduce the torque ripple and the steady-state error of torque, accounting for the influence of machine angular velocity. A simple estimated method is proposed to obtain the range of the key control parameters. Compared to the existing duty-based DTC methods, the proposed method can achieve the decent performance of torque and flux at the lower price of increased average communication frequency.

The proposed duty ratio determination has the following features.

1) Simple structure: Compared to conventional DTC, just a very simple duty ratio regulator is added.

2) Parameter independent: Unlike the previous duty-based methods, where many parameters such as stator inductance and PM flux are required, in the proposed DTC method, only the torque error and speed are needed to compute the duty ratio, which makes it robust to parameter variation.

3) Outstanding steady-state performance over a wide range of operating regions, even when speed is reversed.

4) Similar excellent transient response to the conventional DTC.

Although the analysis and experiments in this paper are based on the DTC of three-phase PMSM drives, the proposed duty ratio determination can be also extended for general use and applied to the other machines of switching-table-based direct torque and power control methods, which may exhibit the same problem of ripple and/or steady-state error.

REFERENCES:

[1] I. Takahashi and T. Noguchi, “A new quick-response and high-efficiency control method of an induction-motor,” IEEE Trans. Ind. Appl., vol. IA-22, no. 5, pp. 820–827, Sep. 1986.

[2] M. Depenbrock, “Direct self-control (DSC) of inverter-fed induction machine,” IEEE Trans. Power Electron., vol. 3, no. 4, pp. 420–429, Oct. 1988.

[3] G.W. Chang, G. Espinosa-Perez, E. Mendes, and R. Ortega, “Tuning rules for the PI gains of field-oriented controllers of induction motors,” IEEE Trans. Ind. Electron., vol. 47, no. 3, pp. 592–602, Jun. 2000.

[4] A. K. Jain and V. T. Ranganathan, “Modeling and field oriented control of salient pole wound field synchronous machine in stator flux coordinates,” IEEE Trans. Ind. Electron., vol. 58, no. 3, pp. 960–970, Mar. 2011.

[5] S. Mathapati and J. Boecker, “Analytical and offline approach to select optimal hysteresis bands of DTC for PMSM,” IEEE Trans. Ind. Electron., vol. 60, no. 3, pp. 885–895, Mar. 2013.

Direct Torque Control of Permanent Magnet Synchronous Motor Based on Space Vector Modulation Control

ABSTRACT:

How to calculate the reference voltage vector is an important issue in space vector modulation direct torque control (SVM-DTC) of permanent magnet synchronous motor (PMSM). The effect of zero vector on electromagnetic torque during all speed range is analyzed on the basis of the relation between voltage vector and torque current component. And the analysis shows that in conventional DTC system of PMSM available voltage vector is only six which is the mainly cause of high ripple of torque. A robust SVM- DTC method of PMSM is designed in which the reference voltage vector is calculated with the flux position, error of torque and flux. The method is simple to implement and insensitive to motor parameters error. First order filter cascaded with high pass filter (HPF) is adopted to estimate stator flux accurately. The experimental results are carried out and show that the improved SVM-DTC has the advantage of simplicity, robustness and improved performance.

KEYWORDS:

1.      PMSM

2.      Direct torque control

3.      Space vector modulation

4.       Torque ripple

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1 Block diagram of improved SVM-DTC system

EXPECTED SIMULATION RESULTS:

a)       Experimental waveforms of conventional DTC

b)       Experimental waveforms of proposed SVM-DTC

CONCLUSION:

Available voltage vector has only six which mainly causes high ripple of torque in conventional DTC. To maintain robustness and simplicity of conventional DTC system, a simple method of calculating amplitude and angle of the voltage vector is adopted in SVM-DTC. It requires only the torque and flux errors. The simulation and experimental results show that the proposed SVM-DTC scheme has excellent steady-state performance while retaining the merits of the quick dynamic responses, simplicity and robustness as in conventional DTC.

REFERENCES:

[1] Bin Wang, Yue Wang, Zhaoan Wang. Direct torque control of permanent magnet synchronous motor drives using space vector modulation [J]. Electric machines and control, 2010, 14(6):45-50.

[2] Yong-chang Zhang, Jian-guo Zhu, Wei Xu , You-guang Guo. A Simple Method to Reduce Torque Ripple in Direct Torque-Controlled Permanent-Magnet Synchronous Motor by Using Vectors With Variable Amplitude and Angle[J]. IEEE Transactions on Industrial Electronics, 2011, 58(7): 2848-2859.

[3] Gilbert Foo, M. F. Rahman. A novel speed sensorless direct torque and flux controlled interior permanent magnet synchronous motor drive [C]. Power Electronics Specialists Conference, Rhodes, Greece, 2008: 50- 56.

[4] Huaqiang Zhang, Xinsheng Wang, Pengfei Wei, etal. Study on direct torque control algorithm based on space vector modulation [J]. Electric Machines and control, 2012, 16(6):13-17.

[5] Jing Yuan; Xigeng Ma; Jiannan Liu. Simulation research of induction motor based on SVM-DTC with three-level inverter [J]. Electronics Information and Emergency Communication, China, 5th.2015, 410- 413.

Direct Torque Control of Permanent Magnet Synchronous Motor (PMSM) – an approach by using Space Vector Modulation (SVM)

ABSTRACT:

This paper proposes a method of applying the Space Vector Modulation technique for Direct Torque Control (DTC) of a permanent magnet synchronous motor (PMSM) drive. By this method it is preserved the principle of the conventional DTC regarding the decoupled torque and flux control, while providing more flexibility for the inverter voltage utilization, in order to compensate the torque and flux errors in a smoother way than conventional DTC. For this purpose, a reference voltage space vector is calculated every sample time, using a simple algorithm, based on the torque error and the stator flux angle. Numerical simulations have been made to test the proposed method and results are presented.

KEYWORDS:

1.      Direct Torque Control

2.       permanent magnet synchronous motor

3.       Space Vector Modulation

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1 Block diagram of the conventional DTC

EXPECTED SIMULATION RESULTS:

Fig. 2 Classic DTC, at 100 rpm

Fig. 3 Classic DTC, at 1000 rpm

Fig. 4 DTC with voltage control using the proposed method, at 100 rpm

Fig. 5 DTC with voltage control using the proposed method, at 1000 rpm

CONCLUSION:

In this paper it was presented a method of utilisation of Space Vector Modulation for the Direct Torque Control of a PMSM. For this purpose, at every control sample time a reference voltage vector is calculated and applied to the inverter using SVM. To determine the reference voltage, a simple algorithm was proposed, based on the torque error and the flux phase angle.

The results show that a smooth steady state operation was obtained when using the proposed method. Moreover, a constant inverter switching frequency is ensured by using SVM.

REFERENCES:

[1] Takahashi I., Noguchi T., A New Quick-response and High Efficiency Control Strategy of an InductionMotor, IEEE Trans. Ind. Applicat., IA, 22, 1986, pp. 820–827.

[2] Tiitinen P., Surandra M., The next generation motor control method, DTC direct torque control, Proc. Int. Conf. on Power Electron., Drives and Energy System for Ind. Growth, N. Delhi, 1996, pp. 37–43.

[3] Lascu C., Boldea I., and Blaabjerg F., Variable-Structure Direct Torque Control—A Class of Fast and Robust Controllers for Induction Machine Drives IEEE Trans. On Ind. Electronics, 51, 4, 2004.

[4] Habetler T. G., Profumo F., Pastorelli M., and Tolbert L. M., Direct Torque Control of Induction Machines Using Space Vector Modulation, IEEE Trans. Ind. Applicat., 28, 1992, pp. 1045–1053.

[5] Vas P., Sensorless Vector and Direct Torque Control. New York: Oxford University Press, 1998, pp. 223–237.

Speed Control of Induction Motor Using New Sliding Mode Control Technique

ABSTRACT

Induction Motors have been used as the workhorse in the industry for a long time due to its easy build, high robustness, and generally satisfactory efficiency. However, they are significantly more difficult to control than DC motors. One of the problems which might cause unsuccessful attempts for designing a proper controller would be the time varying nature of parameters and variables which might be changed while working with the motion systems. One of the best suggested solutions to solve this problem would be the use of Sliding Mode Control (SMC). This paper presents the design of a new controller for a vector control induction motor drive that employs an outer loop speed controller using SMC. Several tests were performed to evaluate the performance of the new controller method, and two other sliding mode controller techniques. From the comparative simulation results, one can conclude that the new controller law provides high performance dynamic characteristics and is robust with regard to plant parameter variations.

KEYWORDS:

1.      Induction Motor

2.      Sliding Mode Control

3.      DC Motors

4.      PI Controller

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Induction motor drive system with sliding mode controller

EXPECTED SIMULATION RESULTS:

Fig.2 (a)Rotor speed tracking performance  (b)Rotor speed tracking error   (c)Control effort

  

Fig.3 (a)Rotor speed tracking performance  (b)Rotor speed tracking error   (c)Control effort

 Fig.4 (a)Rotor speed tracking performance  (b)Rotor speed tracking error   (c)Control effort

CONCLUSION

In this paper, new technique to reduced chattering for sliding mode control is submitted to design the rotor speed control of induction motor. To validate the performances of the new proposed control law, we provided a series of simulations and a comparative study between the performances of the new proposed sliding mode controller strategy and those of the Pseudo and Saturation sliding mode controller techniques. The sliding mode controller algorithms are capable of high precision rotor speed tracking. From the comparative simulation results, one can conclude that the three sliding mode controller techniques demonstrate nearly the same dynamic behavior under nominal condition. Also, from the simulation results, it can be seen obviously that the control performance of the new sliding mode controller strategy in the rotor speed tracking, robustness to parameter variations is superior to that of the other sliding mode controller techniques.

REFERENCES

[1]         S.Wade, M.W.Dunnigan, B.W.Williams, X.Yu, ‘Position control of a vector controlled induction machine using slotine’s sliding mode control’, IEE Proceeding Electronics Power Application, Vol. 145, No.3, pp.231-238, 1998.

[2]         V.I.Utkin, ‘Sliding mode control design principles and applications to electric drives’, IEEE Transactions on Industrial Electronics, Vol.40, No.1, pp. 23-36, February 1993.

[3]         P.K.Namdam, P.C.Sen, ‘Accessible states based sliding mode control of a variable speed drive system’, IEEE Transactions Industry Application, Vol.30, August 1995, pp.373-381.

[4]         R.Krishnan, ‘Electric motor drives: modelling, analysis, and control’, Prentice-Hall, New-Jersey, 2001.

[5]         R.J.Wai, K.H.Su, C.Y.Tu, ‘Implementation of adaptive enhanced fuzzy sliding mode control for indirect field oriented induction motor drive’, IEEE International Conference on Fuzzy Systems, pp.1440-1445, 2003.