Electric Spring for Voltage and Power Stability and Power Factor Correction

ABSTRACT:

Electric Spring (ES), a new smart grid technology, has earlier been used for providing voltage and power stability in a weakly regulated/stand-alone renewable energy source powered grid. It has been proposed as a demand side management technique to provide voltage and power regulation. In this paper, a new control scheme is presented for the implementation of the electric spring, in conjunction with non-critical building loads like electric heaters, refrigerators and central air conditioning system. This control scheme would be able to provide power factor correction of the system, voltage support, and power balance for the critical loads, such as the building's security system, in addition to the existing characteristics of electric spring of voltage and power stability. The proposed control scheme is compared with original ES’s control scheme where only reactive-power is injected. The improvised control scheme opens new avenues for the utilization of the electric spring to a greater extent by providing voltage and power stability and enhancing the power quality in the renewable energy powered microgrids.

KEYWORDS:

1.      Demand Side Management

2.      Electric Spring

3.      Power Quality

4.       Single Phase Inverter

5.       Renewable Energy

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Electric Spring in a circuit

 EXPECTED SIMULATION RESULTS:

Fig. 2. Over-voltage, Conventional ES: RMS Line voltage, ES Voltage, and Non-Critical load voltage (ES turned on at t=0.5 sec)

Fig. 3. Over-voltage, Conventional ES: ower Factor of system (ES turned on at t = 0.5 sec)

Fig. 4. Over-voltage, Conventional ES: Active and Reactive power across critical load, non-critical load, and electric spring (ES turned on at t=0.5 sec)

Fig. 5. Under-voltage, Conventional ES: RMS Line voltage, ES Voltage, and

Non-Critical load voltage (ES turned on at t=0.5 sec)

Fig. 6. Under-voltage, Conventional ES: Power Factor of system (ES turned on at t = 0.5 sec)

Fig. 7. Under-voltage, Conventional ES: Active and Reactive power across critical load, non-critical load, and electric spring (ES turned on at t=0.5 sec)

Fig.8. Over-voltage, Improvised ES: RMS Line voltage, ES Voltage, and Non-Critical load voltage (ES turned on at t=0.5 sec)

Fig. 9. Over-voltage, Improvised ES: Power Factor of system (ES turned on at t = 0.5 sec)

Fig. 10. Over-voltage, Improvised ES: Active and Reactive power across critical load, non-critical load, and electric spring (ES turned on at t=0.5 sec)

Fig. 11. Under-voltage, Improvised ES: RMS Line voltage, ES Voltage, and Non-Critical load voltage (ES turned on at t=0.5 sec)

Fig. 12. Under-voltage, Improvised ES: Power Factor of system (ES turned on at t = 0.5 sec)

Fig. 13. Under-voltage, Improvised ES: Active and Reactive power across critical load, non-critical load, and electric spring (ES turned on at t=0.5 sec)

CONCLUSION:

In this paper as well as earlier literatures, the Electric Spring was demonstrated as an ingenious solution to the problem of voltage and power instability associated with renewable energy powered grids. Further in this paper, by the implementation of the proposed improvised control scheme it was demonstrated that the improvised Electric Spring (a) maintained line voltage to reference voltage of 230 Volt, (b) maintained constant power to the critical load, and (c) improved overall power factor of the system compared to the conventional ES. Also, the proposed ‘input-voltage-input-current’ control scheme is compared to the conventional ‘input-voltage’ control. It was shown, through simulation and hardware-in-loop emulation, that using a single device voltage and power regulation and power quality improvement can be achieved. It was also shown that the improvised control scheme has merit over the conventional ES with only reactive power injection. Also, it is proposed that electric spring could be embedded in future home appliances [1]. If many non-critical loads in the buildings are equipped with ES, they could provide a reliable and effective solution to voltage and power stability and insitu power factor correction in a renewable energy powered microgrids. It would be a unique demand side management (DSM) solution which could be implemented without any reliance on information and communication technologies.

REFERENCES:

[1] S. Y. Hui, C. K. Lee, and F. F. Wu, “Electric springs - a new smart grid technology,” IEEE Transactions on Smart Grid, vol. 3, no. 3, pp. 1552–1561, Sept 2012.

[2] S. Hui, C. Lee, and F. WU, “Power control circuit and method for stabilizing a power supply,” 2012. [Online]. Available: http://www.google.com/patents/US20120080420

[3] C. K. Lee, N. R. Chaudhuri, B. Chaudhuri, and S. Y. R. Hui, “Droop control of distributed electric springs for stabilizing future power grid,” IEEE Transactions on Smart Grid, vol. 4, no. 3, pp. 1558–1566, Sept 2013.

[4] C. K. Lee, B. Chaudhuri, and S. Y. Hui, “Hardware and control implementation of electric springs for stabilizing future smart grid with intermittent renewable energy sources,” IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 1, no. 1, pp. 18–27, March 2013.

[5] C. K. Lee, K. L. Cheng, and W. M. Ng, “Load characterisation of electric spring,” in 2013 IEEE Energy Conversion Congress and Exposition, Sept 2013, pp. 4665–4670.

DC Electric Springs – A Technology for Stabilizing DC Power Distribution Systems

ABSTRACT:

There is a growing interest in using DC power systems and microgrids for our electricity transmission and distribution, particularly with the increasing penetration of photovoltaic power systems. This paper presents an electric active suspension technology known as the DC electric springs for voltage stabilization and power quality improvement. The basic operating modes and characteristic of a DC electric spring with different types of serially-connected non-critical loads will first be introduced. Then, the various power delivery issues of the DC power systems, namely bus voltage variation, voltage droop, system fault, and harmonics, are briefly described. The operating limits of a DC electric spring in a DC power grid is studied. It is demonstrated that the aforementioned issues can be mitigated using the proposed DC electric spring technology. Experiment results are provided to verify the feasibility of the proposed technology.

KEYWORDS:

1.      Smart load

2.      Distributed power systems

3.      Power electronics

4.      Electric springs

5.      DC grids

6.      Smart grid

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. The basic configuration of DC electric springs.

 EXPECTED SIMULATION RESULTS:

Fig. 2. Enlarged experiment waveforms based on the raw data exported from the oscilloscope corresponding

Fig. 3. Enlarged experiment waveforms based on the raw data exported from the oscilloscope corresponding

CONCLUSION:

In this paper, the concept of DC electric springs (ES) is firstly introduced to cope with several issues of DC power grids. The DC-ES is proposed as an active suspension system. Similar to their AC counterparts, the DC-ES can provide dynamic voltage regulation for the DC bus. The DC-ES connected in series with different types of non-critical loads to form a smart load have been analyzed and their operating modes have been identified and explained. Furthermore, the operating limits of the DC-ES under a given set of system parameters is studied, which provides quantitative analytical procedures to estimate the theoretical limits of ES. The paper provides a fundamental study on the DC-ES including the characteristics, the modes of operation, and the operating limits. The theoretical analysis and the performance of the DCES have been practically verified.

REFERENCES:

[1] R. Lobenstein and C. Sulzberger, “Eyewitness to DC history,” Power and Energy Magazine, IEEE, vol. 6, no. 3, pp. 84–90, May 2008.

[2] G. Neidhofer, “Early three-phase power,” Power and Energy Magazine, IEEE, vol. 5, no. 5, pp. 88–100, Sep. 2007.

[3] B. C. Beaudreau, World Trade: A Network Approach. iUniverse, 2004.

[4] H. Kakigano, Y. Miura, and T. Ise, “Distribution voltage control for DC microgrids using fuzzy control and gain-scheduling technique,” IEEE Trans. Power Electron., vol. 28, no. 5, pp. 2246–2258, May 2013.

[5] P. Loh, D. Li, Y. K. Chai, and F. Blaabjerg, “Autonomous operation of hybrid microgrid with AC and DC subgrids,” IEEE Trans. Power Electron., vol. 28, no. 5, pp. 2214–2223, May 2013.

Adaptive Speed Control of Brushless DC (BLDC) Motor Based on Interval Type-2 Fuzzy Logic

ABSTRACT:

To precisely control the speed of BLDC motors at high speed and with very good performance, an accurate motor model is required. As a result, the controller design can play an important role in the effectiveness of the system. The classic controllers such as PID are widely used in the BLDC motor controllers, but they are not appropriate due to non-linear model of the BLDC motor. To enhance the performance and speed of response, many studies were taken to improve the adjusting methods of PID controller gains by using fuzzy logic. Use of fuzzy logic considering approximately interpretation of the observations and determination of the approximate commands, provides a good platform for designing intelligent robust controller. Nowadays type-2 fuzzy logic is used because of more ability to model and reduce uncertainty effects in rule-based fuzzy systems. In this paper, an interval type-2 fuzzy logic-based proportional-integral-derivative controller (IT2FLPIDC) is proposed for speed control of brushless DC (BLDC) motor. The proposed controller performance is compared with the conventional PID and type-1 fuzzy logic-based PID controllers, respectively in MATLAB/Simulink environment. Simulation results show the superior IT2FLPIDC performance than two other ones.

KEYWORDS:

1.      Brushless DC (BLDC) Motor

2.      Invertal Type-2 Fuzzy Logic

3.      Speed Control

4.      Self-tuning PID Controller

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1. Block Diagram of speed control of BLDC Motor

EXPECTED SIMULATION RESULTS:

Figure 2. Speed Deviation of BLDC Motor

Figure 3. Load Deviation of BLDC Motor

Figure 4. Torque Deviation of BLDC Motor

CONCLUSION:

In this paper, the speed control of the BLDC motor is studied and simulated in MATLAB/Simulink. In order to overcome uncertainties and variant working condition, the adjustment of PID gains through fuzzy logic is proposed. In this study, three controller types are considered and compared: conventional PID, type-1 and type-2 fuzzy-based self-tuning PID controllers. The simulation results show that type-2 fuzzy PID controller has superior performance and response than two other ones.

REFERENCES:

[1] A. Sathyan, N. Milivojevic, Y. J. Lee, M. Krishnamurthy, and A. Emadi, “An FPGA-based novel digital PWM control scheme for BLDC motor drives,” IEEE Trans. Ind. Electron., vol. 56, no. 8, pp. 3040–3049,Aug. 2009.

[2] F. Rodriguez and A. Emadi, “A novel digital control technique for brushless DC motor drives,” IEEE Trans. Ind. Electron., vol. 54, no. 5, pp. 2365–2373, Oct. 2007.

[3] Y. Liu, Z. Q. Zhu, and D. HoweDirect Torque Control of Brushless DC Drives With Reduced Torque Ripple” IEEE Trans. Ind. Appl., vol. 41, no. 2, pp. 599-608, March/April 2005.

[4] T. S. Kim, S. C. Ahn, and D. S. Hyun , “A New Current Control Algorithm for Torque Ripple Reduction of BLDC Motors,” in IECON'01, 27th Conf. IEEE Ind. Electron Society,2001

[5] W. A. Salah, D. Ishak, K. J. Hammadi, “PWM Switching Strategy for Torque Ripple Minimization in BLDC Motor” FEI STU, Journal of Electrical Engineering, vol. 62, no. 3, 2011, 141–146.

An Advanced Current Control Strategy for Three-Phase Shunt Active Power Fi

ABSTRACT:

This paper proposes an advanced control strategy to enhance performance of shunt active power filter (APF). The proposed control scheme requires only two current sensors at the supply side and does not need a harmonic detector. In order to make the supply currents sinusoidal, an effective harmonic compensation method is developed with the aid of a conventional proportional-integral (PI) and vector PI controllers. The absence of the harmonic detector not only simplifies the control scheme but also significantly improves the accuracy of the APF, since the control performance is no longer affected by the performance of the harmonic tracking process. Furthermore, the total cost to implement the proposed APF becomes lower, owing to the minimized current sensors and the use of a four-switch three-phase inverter. Despite the simplified hardware, the performance of the APF is improved significantly compared to the traditional control scheme, thanks to the effectiveness of the proposed compensation scheme. The proposed control scheme is theoretically analyzed, and a 1.5-kVA APF is built in the laboratory to validate the feasibility of the proposed control strategy.

KEYWORDS:

1.      Active power filters (APFs)

2.       Harmonic current compensation

3.       Power quality

4.       Resonant controller

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Typical control scheme of a shunt APF.

 Fig. 2. Structure of the proposed control scheme for three-phase shunt APF.

 EXPECTED SIMULATION RESULTS:

Fig. 3. Steady-state performance with PI current controller under RL load.

Fig. 4. Steady-state performance with proposed control scheme under RL load.

Fig. 5. Dynamic responses of proposed control scheme under RL load

variations: (a) load applied (b) load changed.

Fig. 6. Steady-state performance with proposed control scheme under RLC load.

Fig. 7. Dynamic responses of proposed control scheme under RLC load

variations: (a) load applied (b) load changed.

Fig. 8. Steady-state performance of the proposed control scheme under

distorted supply voltage condition with (a) RL load and (b) RLC load.

Fig. 9. Steady-state performances of the four-switch APF with (a) RL load

and (b) RLC load.

                                                                                                                                                                                                 CONCLUSION:

In this paper, an advanced control strategy for the three-phase shunt APF was proposed. The effectiveness of the proposed control strategy was verified through various experimental tests, where the proposed control strategy presented good steady-state performance with nonlinear RL and RLC loads as well as good dynamic response against load variations: the supply current is almost perfect sinusoidal and in-phase with the supply voltage even under the distorted voltage condition. The experimental results verified that the absence of a harmonic detector results in faster transient responses as well as assures notches free in steady-state performances of the supply current. Moreover, we also confirmed that the FSTPI can be used to implement the APF without any degradation in the APF performance. In all of the experiments, THD factor of the supply current was reduced to less than 2%, which completely comply with the IEEE-519 and IEC-61000-3-2 standards.

REFERENCES:

[1] Recommended Practice for Harmonic Control in Electric Power Systems, IEEE Std. 519-1992, 1992.

[2] Limits for Harmonic Current Emission, IEC 61000-3-2, 2001.

[3] H. Akagi, “New trends in active filters for power conditioning,” IEEE Trans. Ind. Appl., vol. 32, no. 2, pp. 1312–1332, Nov./Dec. 1996.

[4] F. Z. Peng, “Application issues of active power filters,” IEEE Ind. Appl. Mag., vol. 4, no. 5, pp. 21–30, Sep./Oct. 1998.

[5] H. Akagi, E. H. Watanabe, and M. Aredes, Instantaneous Power Theory and Applications to Power Conditioning, M. E. El-Hawari, Ed.New York: Wiley, 2007.