Bidirectional Power Flow Control Integrated With Pulse and Sinusoidal-Ripple-Current Charging Strategies for Three-Phase Grid-Tied Converters

ABSTRACT:

The objective of this paper is to propose bidirectional charging/discharging strategies for three-phase grid-tied converters. The bidirectional power flow control feature of the converter is able to realize both charging and discharging capability. Besides, in order to achieve high charging efficiency as well as extend the life of the battery, five charging strategies are adopted and developed: 1) the constant current (CC) charging, 2) the pulse-ripple-current (PRC) charging, 3) the sinusoidal-ripple-current (SRC) charging, 4) the bidirectional pulse-ripple-current (BPRC) charging and 5) the bidirectional sinusoidal ripple- current (BSRC) charging. The direct quadrature (d-q) transformation is utilized for the converter to realize different charging methods. These methods can be achieved by the digital signal processor (DSP) without adding extra circuit components. In addition, the charging power differences between each strategy are considered and analyzed in this paper. Finally, both simulation and experimental results obtained from a 5-kW prototype circuit verify the performance and feasibility of the proposed bidirectional charger.

KEYWORDS:

1.      Three-phase grid-tied converter

2.      Bidirectional chargers

3.      Energy storage system

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 

Figure 1. The Circuit Diagram And Control Blocks.

 EXPECTED SIMULATION RESULTS:

Figure 2. Simulation Waveforms Of The V_bat , I^bat , I_d;C_md , I_ac And V_ac With Different Charging Strategies (A) The CC Charging (B) The PRC Charging (C) The SRC Charging (D) The BPRC Charging (E) The BSRC Charging.

CONCLUSION:

This paper proposes a bidirectional three-phase grid-tied converter with charging/discharging strategies. The converter is able to be operated in the AC-DC (PFC) mode and the DC-AC (inverter) mode to realize the bidirectional power flow control feature. In order to increase the charging efficiency as well as extend the battery life, five charging strategies are considered and developed. Main contributions of this paper can be concluded as: 1) a three-phase AC-DC converter with bidirectional power flow control is developed, 2) five charging/ discharging strategies are integrated with the proposed charger, 3) detailed control concepts and operational principles are revealed with mathematical derivations and 4) the charging power analysis of different charging strategies is presented. These charging methods can be achieved by the proposed bidirectional converter with the d-q transformation concept. Moreover, comprehensive analysis and mathematical derivations of the charging power differences between each strategy are presented. Finally, both simulation and experimental results obtained from a 5-kW prototype demonstrate the performance and feasibility of the proposed bidirectional charger.

REFERENCES:

[1] K. Thirugnanam, S. K. Kerk, C. Yuen, N. Liu, and M. Zhang, ``Energy management for renewable microgrid in reducing diesel generators usage with multiple types of battery,'' IEEE Trans. Ind. Electron., vol. 65, no. 8, pp. 6772_6786, Aug. 2018.

[2] P. B. L. Neto, O. R. Saavedra, and L. A. de Souza Ribeiro, ``A dual-battery storage bank con_guration for isolated microgrids based on renewable sources,'' IEEE Trans. Sustain. Energy, vol. 9, no. 4, pp. 1618_1626, Oct. 2018.

[3] U. Manandhar, N. R. Tummuru, S. K. Kollimalla, A. Ukil, G. H. Beng, and K. Chaudhari, ``Validation of faster joint control strategy for battery- and supercapacitor-based energy storage system,'' IEEE Trans. Ind. Electron., vol. 65, no. 4, pp. 3286_3295, Apr. 2018.

[4] F. Wu, X. Li, F. Feng, and H. B. Gooi, ``Multi-topology-mode gridconnected inverter to improve comprehensive performance of renewable energy source generation system,'' IEEE Trans. Power Electron., vol. 32, no. 5, pp. 3623_3633, May 2017.

[5] Z. Zhang, Y.-Y. Cai, Y. Zhang, D.-J. Gu, and Y.-F. Liu, ``A distributed architecture based on microbank modules with self-recon_guration control to improve the energy ef_ciency in the battery energy storage system,'' IEEE Trans. Power Electron., vol. 31, no. 1, pp. 304_317, Jan. 2016.

An Improved Technique for Energy-Efficient Starting and Operating Control of Single Phase Induction Motors

ABSTRACT:

 The recent increase in electricity prices and the usage of single-phase induction motors (SPIMs)provide a stimulus for a focused research on energy-efficient optimization of SPIM load such as air-conditioners and refrigerators. Variable speed control of SPIM provides a promising way forward to reduce its power consumption. However, during variable speed operation under the popular constant V=f method, SPIM is required to operate at non-rated conditions. The operation of SPIM at non-rated conditions disturbs its symmetrical and balanced operation, thus degrading its efficiency. Moreover, soft-starting of SPIM at non-rated conditions is also challenging due to the resulting reduction in starting-torque. In this article, after a detailed analysis of SPIM energy-efficiency, an improved sensor-less optimal speed control strategy is developed to enable the symmetrical and balanced operation of SPIM at all the operating points over the entire speed-range to improve its performance. A novel algorithm, termed as the phase-shift algorithm, is also devised for efficient implementation of the proposed optimal speed control strategy. In addition, a unique framework for efficient soft-starting of SPIM at very low frequencies is also developed. The simulation-based results of the motor operated through the proposed phase-shift algorithm validate the energy-saving potential of the proposed control strategy.

KEYWORDS:

1.      Energy-efficient control

2.      Variable speed drives

3.      Speed-sensorless induction motor control

4.      Magnetic field control

5.      Inrush current reduction

6.      Starting torque

7.      Pulsating torque

8.      Energy savings in HVAC

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

 

Figure 1. Switching Pattern Generation Using The Phase-Shift Algorithm For Efficient Variable Speed Operation Of Spim.

EXPECTED SIMULATION RESULTS:

Figure 2. Simulation-Based Results Of Spim Operation Under The Proposed Optimal Control At F D 30 Hz.

Figure 3. Simulation-Based Results Of Spim Operation Under The Constant V =F Control Method At F D 30 Hz.

 

 

Figure 4. Simulation-Based Results Of Spim Operation Under The Proposed Optimal Control Strategy At F D 60 Hz.

 

Figure 5. Simulation-Based Results Of Spim Operation Under The Constant V =F Control Method At F D 60 Hz.

 

Figure 6. Simulation-Based Results Of Spim Operation Under The Proposed Optimal Control Strategy At F D 10 Hz.

 

 

Figure 7. Simulation-Based Results Of Spim Operation Under The Constant V =F Control Method At F D 10 Hz.

 

Figure 8. Simulation-Based Results Of Spim Soft-Starting At F D 10 Hz Under The Proposed Soft-Starting Strategy.

 

 

Figure 9. Simulation-Based Results Of Spim Soft-Starting At F D 10 Hz Under The Constant V =F Control Method.

 

CONCLUSION:

In this article, it is demonstrated that conventional techniques for speed control of SPIMs are inefficient because they cause the formation of elliptical magnetic fields inside them at non-rated starting and operating conditions. After a detailed analysis of SPIM energy-efficiency, a novel sensor-less con- trol strategy was devised to improve the performance at non-rated conditions by enabling the symmetrical and balanced operation of SPIM. Formation of circular magnetic field inside SPIMs over the entire speed range is achieved by dynamically and optimally controlling the auxiliary volt- age and phase-difference between the windings voltages simultaneously with constant V=f control using the developed phase-shift algorithm. Simulation-based evaluation of the optimal control strategy demonstrates an improvement of more than 400% in energy-efficiency as compared to maximum 18% reported in case of conventional SPIM energy-efficiency optimization techniques. The developed control algorithm also enables the soft-starting of SPIM with substantial starting torque at low-frequencies, resulting in a significant reduction in inrush current. Simulation-based results of the proposed sensor-less optimal control strategy confirm an inrush current reduction of more than 84%. This efficient soft-starting results in further energy-savings.

REFERENCES:

[1] J. C. Gomez, C. Reineri, G. Campetelli, and M. M. Morcos, ``A study of voltage sags generated by induction motor starting,'' Electr. Power Compon. Syst., vol. 32, no. 6, pp. 645_653, Jun. 2004.

[2] X. Wang, J. Yong, W. Xu, and W. Freitas, ``Practical power quality charts for motor starting assessment,'' IEEE Trans. Power Del., vol. 26, no. 2, pp. 799_808, Apr. 2011.

[3] Z. B. Duranay and H. Guldemir, ``Selective harmonic eliminated V/f speed control of single-phase induction motor,'' IET Power Electron., vol. 11,no. 3, pp. 477_483, Mar. 2018.

[4] A. Sampathkumar, ``Speed control of single phase induction motor using V/f technique,'' Middle-East J. Sci. Res., vol. 16, no. 12, pp. 1807_1812, 2013.

[5] E. R. Collins, ``Torque and slip behavior of single-phase induction motors driven from variable-frequency supplies,'' IEEE Trans. Ind. Appl., vol. 28, no. 3, pp. 710_715, May/Jun. 1992.

Voltage Oriented Controller Based Vienna Rectifier for Electric Vehicle Charging Stations

ABSTRACT:

Vienna rectifiers have gained popularity in recent years for AC to DC power conversion for many industrial applications such as welding power supplies, data centers, telecommunication power sources, aircraft systems, and electric vehicle charging stations. The advantages of this converter are low total harmonic distortion (THD), high power density, and high efficiency. Due to the inherent current control loop in the voltage-oriented control strategy proposed in this paper, good steady-state performance and fast transient response can be ensured. The proposed voltage-oriented control of the Vienna rectifier with a PI controller (VOC-VR) has been simulated using MATLAB/Simulink. The simulations indicate that the input current THD of the proposed VOC-VR system was below 3.27% for 650V and 90A output, which is less than 5% to satisfy the IEEE-519 standard. Experimental results from a scaled-down prototype showed that the THD remains below 5% for a wide range of input voltage, output voltage, and loading conditions (up to 2 kW). The results prove that the proposed rectifier system can be applied for high power applications such as DC fast-charging stations and welding power sources.

KEYWORDS:

1.      Front-end converters

2.      High power applications

3.      Power factor

4.      Total harmonic distortion

5.      Vienna rectifier

6.      Voltage oriented controller

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

Figure 1. The Proposed Electric Vehicle Charger Is Based On Vienna Rectifier With A Voc Controller (Voc-Vr) System.

EXPECTED SIMULATION RESULTS:

Figure 2. Input Current Waveform Of The Proposed Voc-Vr System With 440 V Rms In And 650 V Dc Out.

 

Figure 3. Total Harmonic Distortion Of The Proposed Voc-Vr System With 440 V Rms In And 650 V Dc Out.

 

Figure 4. Dc Output Voltage And Output Current Of The Vienna Rectifier With Voc Controller With 350 V Ac Rms Input And 650 V Dc Output Voltage.

Figure 5. Dc Output Voltage And Output Current Of The Vienna Rectifier

With Voc Controller With 350 V Ac Rms Input And 220 V Dc Output Voltage For Slow Charging Stations.

 

 

CONCLUSION:

In this research work, a three-level Vienna rectifier based on a voltage-oriented controller (VOC-VR) has been designed and experimentally tested. The proposed system has been simulated using MATLAB Simulink software targeting high power applications such as DC-fast chargers for electric vehicles. The proposed controller for Vienna rectifier focused on combining voltage-oriented controllers with the PWM method. In proposed design, the reactive and unstable active currents are counteracted by the input and output filters and Voltage Oriented Controller (VOC) with Vienna rectifier. The proposed design also guarantees a sinusoidal current at the input side with minimum ripples and distortions. The system's power factor is maintained at unity, and total harmonic distortion of the input current is kept less than 5 %, which meets the IEEE-519 standard. The benefit of the proposed controller over conventional PFC controller has been demonstrated by simulations and experimental results. Low THD, good power factor, and smaller filtering requirements make the voltage-oriented controller-based Vienna rectifier an ideal candidate in electric vehicle charging stations.

REFERENCES:

[1] F. Nejabatkhah, Y. W. Li, and H. Tian, ``Power quality control of smart hybrid AC/DC microgrids: An overview,'' IEEE Access, vol. 7, pp. 52295_52318, 2019.

[2] P. Arboleya, G. Diaz, and M. Coto, ``Unified AC/DC power flow for traction systems:Anewconcept,'' IEEE Trans. Veh. Technol., vol. 61, no. 6, pp. 2421_2430, Jul. 2012.

[3] W. Su, H. Eichi,W. Zeng, and M.-Y. Chow, ``A survey on the electrification of transportation in a smart grid environment,'' IEEE Trans. Ind. Informat., vol. 8, no. 1, pp. 1_10, Feb. 2012.

[4] I. Pavi¢, T. Capuder, and I. Kuzle, ``Value of flexible electric vehicles in providing spinning reserve services,'' Appl. Energy, vol. 157, pp. 60_74, Nov. 2015.

[5] L. Hang, H. Zhang, S. Liu, X. Xie, C. Zhao, and S. Liu, ``A novel control strategy based on natural frame for Vienna-type rectifier under light unbalanced-grid conditions,'' IEEE Trans. Ind. Electron., vol. 62, no. 3, pp. 1353_1362, Mar. 2015.

Scalar and Vector Controlled Infinite Level Inverter (ILI) Topology Fed Open-Ended Three-Phase Induction Motor

ABSTRACT:

The design and performance analysis of an open-ended three-phase induction motor, driven by an Infinite Level Inverter (ILI) with its speed control using scalar and direct vector control techniques are presented in this paper. The ILI belongs to an Active-Front-End (AFE) Reduced-Device-Count (RDC) Multi-level Inverter (MLI) topology. The fundamental structure of this inverter topology is a dc-to-dc buck converter followed by an H-bridge. This topology performs a high-quality power conversion without any shoot-through issues and reverse recovery problems. The performance of the proposed topology is validated using a resistive load. The THD of output voltage waveform obtained is 1.2%. Moreover, this topology has exhibited a high degree of dc-source voltage utilization. ILI considerably reduces the switching and conduction losses, since only one switch per phase is operated at high frequency, and other switches are operated at power frequency. The overall efficiency of the inverter is 98%. The speed control performance of the ILI topology using three-phase open-ended induction motor has been further validated through scalar and direct vector control techniques. Results obtained from simulation studies are verified experimentally.

KEYWORDS:

1.      Active-front-end

2.      Multi-level inverters

3.       Reduced-device-count

4.      Scalar and direct vector control

5.       Three-phase infinite level inverter

SOFTWARE: MATLAB/SIMULINK

SCHEMATIC DIAGRAM:

 

Figure 1. Three Phase Infinite Level Inverter Topology. Basic Structure Of The Proposed Topology Is A Buck Converter (Afe Converter) Followed By An H-Bridge. This Topology Consists Of One High-Frequency Operated Switch For Every Buck Circuit And Four Low-Frequency Operated Switches For Every H-Bridge; Hence, One Inductor And One Capacitor Per Phase.

EXPECTED SIMULATION RESULTS:

Figure 2. Simulated Waveforms Of Ili. (A) High Frequency, (B,C) Low Frequency Switching Pulses.

Figure 3. Simulated Waveforms Of Ili Using Resistive Load. Voltage And Current Wave Forms Across The Afe Converter Components. (A,B) High Frequency Switch, (C,D) Diode,(E,F) Inductor, (G,H) Capacitor,(I,J) Voltage Across Low Frequency Operating Switches.

 

Figure 4. Simulated Waveforms Of Ili Using Resistive Load. (A) Voltage Waveforms Across

The Buck Capacitor, (B) Voltage ,(C) current Wave Form Across The Load Resistance.

 

Figure5. Simulated Waveforms Of Ili Using Resistive Load. (A) Three-Phase Output Voltage Waveforms Across

The Buck Capacitor, (B) Three-Phase Output Voltage Wave Form Across The Load Resistance.

 

Figure 6. Simulated Waveforms Of (A) Third Harmonic Injection Pwm Control Implementation Logic, (B) Phase Voltage Waveform Of The Ili Using Resistive Load.

 

 

Figure 7. The Dynamic Responses Of The Simulated Output Voltage Waveforms Using V/F Control. (A) Voltage Waveform Across The Buck Capacitor, (B) Line-To-Line Voltage Across The Load.

Figure 8. The Dynamic Responses Of The Simulated Output Voltage Waveforms Using Direct Vector Control. (A,C) Voltage Waveform Across The Buck Capacitor, (B,D) Line-To-Line Voltage Across The Load.

 

Figure 9. The Simulated Output Voltage Waveforms Using Resistive Load (A) Conventional 2-Level H-Bridge Inverter, (B) 3-Level H-Bridge Inverter, (C) 5-Level Cascaded H-Bridge Mli, (D) Proposed Topology.

 CONCLUSION:

Design and analysis of the performance of an infinite level inverter driven induction motor have been discussed in this paper. ILI has been found to impart better performance to an induction motor drive. The ILI which belongs to an AFERDC- MLI topology has been tested with a resistive load and found to possess very good quality voltage and current waveforms in terms of THD. While conventional inverter topologies contain tens of percentage of THD, the topology mentioned in this paper contains a THD as low as 1.2%. Moreover, the dc- voltage requirement for generating a fixed ac-voltage output has been found to be much less than that required by other similar topologies, making the dc-source utilization better with this topology. While it is required to have a dc-voltage requirement of 677V in a conventional inverter working in sine PWM mode, the requirement of dc-voltage in the new inverter is only 338V. Use of third harmonic injection modulation scheme has also been performed using this inverter and found that the dc-source utilization can be improved further. Efficiency of inverter has also been found to be better, since only one switch per phase is operated at high frequency. All the switches in conventional inverters are operated at high frequency. Scalar and vector control of induction motor have also been performed using this topology. It has been found that the dynamic performance is better with this topology. This has been validated by accelerating and decelerating the machine with different reference speeds. Since the harmonic content in current has been very less, torque pulsations experienced by the motor would be negligible. Requirement of de-rating associated with induction motors fed by conventional inverters is not present in this case. Since there is no shoot-through menace, the chances of the inverter getting damaged is less, which results in better life and reliability of the drive system.

REFERENCES:

[1] P. Omer, J. Kumar, and B. S. Surjan, ``A review on reduced switch count multilevel inverter topologies,'' IEEE Access, vol. 8, pp. 22281_22302,Jan. 2020.

[2] J. Rodríguez, J.-S. Lai, and F. Z. Peng, ``Multilevel inverters: A survey of topologies, controls, and applications,'' IEEE Trans. Ind. Electron., vol. 49, no. 4, pp. 724_738, Aug. 2002.

[3] L. M. Tolbert, F. Z. Peng, and T. G. Habetler, ``Multilevel converters for large electric drives,'' IEEE Trans. Ind. Appl., vol. 35, no. 1, pp. 36_44, Jan./Feb. 1999.

[4] J.-S. Lai and F. Z. Peng, ``Multilevel converters_A new breed of power converters,'' IEEE Trans. Ind. Appl., vol. 32, no. 3, pp. 509_517, May 1996.

[5] S. Kouro, M. Malinowski, K. Gopakumar, J. Pou, L. G. Franquelo, B.Wu, J. Rodríguez, M. A. Pérez, and J. I. Leon, ``Recent advances and industrial applications of multilevel converters,'' IEEE Trans. Ind. Electron., vol. 57,

no. 8, pp. 2553_2580, Aug. 2010.