A New Discrete Four Quadrant Control Technique for Grid-Connected Full-Bridge AC–DC Converters

ABSTRACT:

This paper presents a new control technique for grid-connected full-bridge AC–DC converters. The proposed control scheme is based on one-cycle control approach and enables the converter to process power in all four quadrants. In the proposed method, switching pulses are generated using a discrete control law with a superimposed fictitious reactive current term. This term enables seamless four-quadrant operation of the converter. Implementation of the discrete controller includes estimation of the current ripple based on measured values of the input current and voltages, sampled at the beginning of each switching cycle. The estimated current ripple is then used for a carrier-less implementation of the proposed control technique. A detailed controller stability analysis using Lyapunov theory is also presented. Theoretical analysis, simulation results, and experimental results show fast dynamic response for the grid current.

KEYWORDS:

1.      AC–DC Converters

2.      One-Cycle Control (OCC)

3.      Predictive-Digital Control

4.      Reactive Power Control

5.      Power Factor (PF)

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 

 

Fig. 1. The circuit diagram of the full-bridge AC–DC converter with the proposed four-quadrant OCC technique.

 EXPECTED SIMULATION RESULTS:

 

Fig. 2. Simulation Results for operation of converter using conventional OCC technique at (a) Heavy load operation - showing stable operation, (b) Light load - showing saturated variables.

 

 

Fig.3. Simulation results for stable operation of converter with proposed scheme of reactive power control using one-cycle control.

 

Fig. 4. Simulation results for stable operation of converter using fictitious resistance at (a) Rectifier Mode - Heavy load operation, (b) Rectifier Mode - Medium load operation(same operating point as the one in Fig. 8(b)), (c) Rectifier Mode - No Load operation, (d) Inverter Mode - stable heavy load operation, and (e) Inverter Mode - unstable heavy load operation

 

Fig. 5. Simulation results for transient performance of converter with active power control using conventional fictitious current based OCC ((a) & (b)), and reactive power control using proposed fictitious reactive current based OCC ( (c), (d), (e) & (f)).

 

Fig. 6. Simulation results for comparing the transient performance of the proposed digital OCC with the conventional digital OCC. The conventional controller (b) takes longer time as compared to the proposed controller (a) to reach steady state after a reactive current transient is applied to the converter.

 

Fig. 7. Simulation results for grid voltage transient applied to converter with four quadrant power control.

 CONCLUSION:

A novel discrete current control technique based on one cycle control scheme has been proposed in this paper. Four quadrant power flow has been achieved using the proposed control technique. By using this strategy, a fast transient response is achieved for EV battery charger applications. The proposed OCC includes a novel carrier-less implementation method using current ripple estimation, which simplifies its digital implementation. In addition, a generalized stability analysis of OCC scheme has been performed using discrete Lyapunov stability theory to ascertain the limits of stable converter operation. The simulation and experimental results presented in this paper verified that the proposed control technique is suitable for the operation of a single-phase ACDC converter in all four quadrants.

REFERENCES:

[1] B. K. Bose, “Global energy scenario and impact of power electronics in 21st century,” IEEE Transactions on Industrial Electronics, vol. 60, no. 7, pp. 2638–2651, Jul. 2013.

[2] R. Doolan and G. Muntean, “Reducing carbon emissions by introducing electric vehicle enhanced dedicated bus lanes,” in IEEE Intelligent Vehicles Symposium Proceedings, Dearborn, MI, USA,, 2014, pp. 1011– 1016.

[3] M. Yilmaz and P. T. Krein, “Review of the impact of vehicle-to grid technologies on distribution systems and utility interfaces,” IEEE Transactions on Power Electronics, vol. 28, no. 12, p. 5673–5689, Dec. 2013.

[4] C. A. Hill, M. C. Such, D. Chen, J. Gonzalez, and W. M. Grady, “Battery energy storage for enabling integration of distributed solar power generation,” IEEE Transactions on Smart Grid, vol. 3, no. 2, pp. 850–857, Jun. 2012.

[5] B. Koushki, A. Safaee, P. Jain, and A. Bakhshai, “Review and comparison of bi-directional AC-DC converters with V2G capability for onboard EV and HEV,” in IEEE Transportation Electrification Conference and Expo (ITEC), Dearborn, MI, USA, 2014, pp. 1–6.

A Multifunctional Non-Isolated Dual Input-Dual Output Converter for Electric Vehicle Applications

ABSTRACT:

High voltage conversion dc/dc converters have perceived in various power electronics applications in recent times. In particular, the multi-port converter structures are the key solution in DC microgrid and electric vehicle applications. This paper focuses on a modified structure of non-isolated four-port (two input and two output ports) power electronic interfaces that can be utilized in electric vehicle (EV) applications. The main feature of this converter is its ability to accommodate energy resources with different voltage and current characteristics. The suggested topology can provide a buck and boost output simultaneously during its course of operation. The proposed four-port converter (FPC) is realized with reduced component count and simplified control strategy which makes the converter more reliable and cost-effective. Besides, this converter exhibits bidirectional power flow functionality making it suitable for charging the battery during regenerative braking of an electric vehicle. The steady-state and dynamic behavior of the converter are analyzed and a control scheme is presented to regulate the power flow between the diversified energy supplies. A small-signal model is extracted to design the proposed converter. The validity of the converter design and its performance behavior is verified using MATLAB simulation and experimental results under various operating states.

KEYWORDS:

1.      Multi-port converter

2.      Electric vehicle

3.      Bidirectional dc/dc converter

4.       Battery storage

5.      Regenerative charging

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

  

Figure 1. Block Diagram Of (A) Conventional Converter (B) Proposed Integrated Four-Port Converter (Fpc) Interface In An Electric Vehicle System.

 EXPECTED SIMULATION RESULTS:

Figure 2. Experimental Results Of All The States: (I) State 1, (Ii) State 2, (Iii) State 3, (Iv) State 4, & (V) State 5.

 

 

Figure 2. (Continued.) Experimental Results Of All The States: (I) State 1, (Ii) State 2, (Iii) State 3, (Iv) State 4, & (V) State 5.

 

Figure 2. (Continued.) Experimental Results Of All The States: (I) State 1, (Ii) State 2, (Iii) State 3, (Iv) State 4, & (V) State 5.

 

Figure 3. Experimental Results With Change In Input Voltage Change In Duty Cycle And Load: (I) Change In Pv Voltage, Constant Battery Voltage, And Constant Duty Cycle, (Ii) Vo And Vo1, (Iii) Change Constant Duty Cycle, When Constant Pv Voltage And Battery Voltage, (Iv) Output Load Voltages.

Figure 3. (Continued.) Experimental Results With Change In Input Voltage Change In Duty Cycle And Load: (I) Change In Pv Voltage, Constant Battery Voltage, And Constant Duty Cycle, (Ii) Vo And Vo1, (Iii) Change Constant Duty Cycle, When Constant Pv Voltage And Battery Voltage, (Iv) Output Load Voltages.

 

CONCLUSION:

A single-stage four-port (FPC) buck-boost converter for hybridizing diversified energy resources for EV has been proposed in this paper. Compared to the existing buck-boost converter topologies in the literature, this converter has the advantages of a) producing buck, boost, buck-boost output even without the use of an additional transformer b) having bidirectional power flow capability with reduced component count c) handling multiple resources of different voltage and current capacity. Mathematical analysis has been carried out to illustrate the functionalities of the proposed converter. A simple control algorithm has been adopted to budget the power flow between the input sources. Finally, the operation of this converter has been verified through a low voltage prototype model. Experimental results validate the feasibility  of the proposed four-port buck-boost topology.

REFERENCES:

[1] H. Wu, Y. Xing, Y. Xia, and K. Sun, ``A family of non-isolated three-port converters for stand-alone renewable power system,'' IEEE Trans. Power Electron., vol. 1, no. 11, pp. 1030_1035, 2011.

[2] K. I. Hwu, K.W. Huang, and W. C. Tu, ``Step-up converter combining KY and buck-boost converters,'' Electron. Lett., vol. 47, no. 12, pp. 722_724, Jun. 2011.

[3] H. Xiao and S. Xie, ``Interleaving double-switch buck_boost converter,'' IET Power Electron., vol. 5, no. 6, pp. 899_908, Jul. 2012.

[4] H. Kang and H. Cha, ``A new nonisolated High-Voltage-Gain boost converter with inherent output voltage balancing,'' IEEE Trans. Ind. Electron., vol. 65, no. 3, pp. 2189_2198, Mar. 2018.

[5] T. Bang and J.-W. Park, ``Development of a ZVT-PWM buck cascaded buck_boost PFC converter of 2 kW with the widest range of input voltage,'' IEEE Trans. Ind. Electron., vol. 65, no. 3, pp. 2090_2099, Mar. 2018.

A Hysteresis Space Vector PWM for PV Tied Z-Source NPC-MLI With DC-Link Neutral Point Balancing

ABSTRACT:

The Photo-voltaic (PV) tied Z-source Neutral-point clamped multilevel inverter (Z-NPC-MLI) is used in solar grid connected applications due to its single stage conversion and better performance. Though the Z source inverters adaptation is accepted in grid connected technology, the need for suitable controller and PWM scheme are necessary to meet out the performance such as shoot through switching, neutral point balancing, and harmonic reduction. The space vector pulse width modulation (SVPWM) strategy is a prominent modulation technique for Z-source NPC-MLIs due to the flexibility to select the appropriate voltage vector. Previous publications have shown the control of a Z-source MLI using the SVPWM with and without modification of shoot through switching. However, the current controller (CC) based SVPWM is not matured, which is the most essential consideration for the grid connected inverter to provide neutral point balancing, shoot through control for low harmonic distortion and a high quality current. With all these aims, this paper presents a PV tied Z-NPC-MLI grid connected system with a unique hysteresis current control SVPWM (HSVM) strategy with neutral point (NP) balancing control and direct current control in the inverter input side. Also, the proposed HSVM is assuring the grid connection with high quality voltage and current waveforms. This CC based SVPWM for Z-NPC MLI has been validated through simulation and FPGA based experimental investigations. The results are confirmed the feasibility and reliability of the proposed HSVM for the PV tie grid connected Z- Source NPC-MLI.

KEYWORDS:

1.      Z source MLI

2.      Neutral-point clamped inverter

3.      Space vector PWM (SVPWM)

4.      Hysteresis current controller (HCC)

5.      Neutral point balancing

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

 

 

Figure 1. PV Tied Grid Connected Three-Phase Three-Level Z Source Npc-Mli.

 EXPECTED SIMULATION RESULTS:

Figure 2. Simulation Results Of Pv Output.

Figure 3. Simulation Results Of Three Phase Voltage And Current

Waveform Of Z-Npc-Mli

Figure 4. Simulation Results Of Harmonics Spectra For Z-Npc-Mli Atma D 0:9; (A) Voltage Harmonics Spectra,(B)Current Harmonics Spectra.

 

Figure 5. Simulation Results Of Actual Load Current And Reference Current When H Band Is Fixed At 5amps.

Figure 6. Simulation Results Of Z-Npc-Mli Voltage Across Dc-Link Capacitors; (A) Conventional Svm Method, (B) Hsvm.

Figure 7. Simulation Results -Transient Response Of Inverter Output Currents.

CONCLUSION:

In this paper the three-level Z source NPC-MLI has investigated for PV tied grid connected system. Further also developed the PV tied grid connected system with hysteresis current control combined Z source SVPWM is known as HSVM is developed. The proposed HSVM uses minimal ST compares to conventional Z source SVPWM. In addition the proposed HSVM eliminates the low frequency oscillations using suitable ST (Upper and Lower ST), with regular switching events, which ensures the neutral point DC-link capacitors balancing along with current control. The HSVM maintains the volt-second and inverter voltage boosting competence irrespective of the angular location of the reference vector throughout the inverter operation. A 2 kWp solar panels attached three-phase three-level IGBT based Z-NPC- MLI grid connected system is established with Xilinx family FPGA SPARTAN-6 controller. From the results, it shows that the performance of proposed method is superior than compare to conventional Z source SVPWM in terms of Neutral point fluctuation, current control capability and better harmonic performance. This proposed HSVM method well suited for wind tied inverters, industrial and Electrical vehicles motor applications.

REFERENCES:

[1] Z. Dobrotkova, K. Surana, and P. Audinet, ``The price of solar energy: Comparing competitive auctions for utility-scale solar PV in developing countries,'' Energy Policy, vol. 118, pp. 133_148, Jul. 2018.

[2] R. Teichmann and S. Bernet, ``A comparison of three-level converters versus two-level converters for low-voltage drives, traction, and utility applications,'' IEEE Trans. Ind. Appl., vol. 41, no. 3, pp. 855_865, May/Jun. 2005.

[3] F. Z. Peng, ``Z-source inverter,'' IEEE Trans. Ind. Appl., vol. 39, no. 2, pp. 504_510, Mar./Apr. 2003.

[4] N. Yadaiah, A. S. Kumar, and Y. M. Reddy, ``DSP based control of constant frequency and average current mode of boost converter for power factor correction (PFC),'' in Proc. Int. Conf. Adv. Power Convers. Energy Technol. (APCET), Aug. 2012, pp. 1_6.

[5] W. Liu, Y. Yang, T. Kerekes, and F. Blaabjerg, ``Generalized space vector modulation for ripple current reduction in quasi-Z-source inverters,'' IEEE Trans. Power Electron., vol. 36, no. 2, pp. 1730_1741, Feb. 2021.

Z-Source Converter Integrated Dc Electric Spring For Power Quality Improvement In DC Microgrid

 ABSTRACT:

Increasing penetration of renewable energy sources reveals the concept of dc microgrid which has the advantages of low cost and low losses because of the elimination of the AC/DC conversion processes.The most frequently encountered power quality problem in DC microgrid is voltage fluctuations due to the intermittent nature of renewable energy sources. Direct current (DC) electric spring (DCES), which is an emerging power quality device in DC microgrids, is employed in order to mitigate the effect of the related problem. In this paper, z source converter integrated DCES topology (zDCES) is proposed to provide a wide compensation voltage range with lower duty cycle range and a remarkable decrease in the battery nominal voltage in comparison with conventional systems. The proposed system composed of full-bridge converter, z source converter and battery pack. zDCES provides high voltage gain by using z source converter with passive components without any need for additional switches. The shoot through control, which is used to achieve high gain in z source converter, is implemented using existing full-bridge switches. The performance of the proposed system is compared with the traditional DCES system. The performance of the zDCES is validated with a case study with different voltage fluctuation states.

KEYWORDS:

1.      DC electric spring

2.      High gain

3.      Z source converter

4.      DC microgrid

5.      Power quality

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

 

Fig. 1. Equivalent circuit of zDCES.

EXPECTED SIMULATION RESULTS:

Fig. 2. Duty cycle variations during source voltage fluctuations.

 

Fig. 3. PCC voltages during source voltage fluctuations.

 

Fig. 4. Performance waveforms of the proposed zDCES..

 

CONCLUSION:

In this paper, a z source converter integrated full-bridge converter based DCES topology and control method have been proposed. The main superior aspects of the proposed Zdces topology are reduced battery voltage and lower duty cycle range as well as providing a wider compensation voltage range. Also, a wide range bipolar voltage at the output ports of the zDCES is achieved by z source converter without additional switches rather than relatively high voltage battery packs or HFT conversion rate methods used in traditional DCES topologies. Thus, a low cost solution has been developed to alleviate the voltage fluctuation problem. In order to verify the effectiveness of the proposed zDCES system, a case study that includes different dynamic operational changes has been conducted. Besides, to show the superiority of the zDCES system is compared with conventional DCES. Performance results show that the proposed system can keep the busbar voltage constant with a lower duty cycle range while the other system requires a higher duty cycle range. Hence, a wide voltage range can be provided in the input port of the fullbridge converter by z source converter in contrast to other systems. Besides, the zDCES can keep the voltage fluctuation in a lower range when compared with conventional DCES. As a result, zDCES shows better and more flexible mitigation performance for all operational conditions.

REFERENCES:

[1] Y. Yang, S. Tan, S.Y.R. Hui, Mitigating distribution power loss of DC microgrids with DC electric springs, IEEE Trans. Smart Grid 9 (2018) 5897–5906.

[2] M. Wang, S. Yan, S. Tan, S.Y. Hui, Hybrid-DC electric springs for DC voltage regulation and harmonic cancellation in DC microgrids, IEEE Trans. Power Electron. 33 (2018) 1167–1177.

[3] K. Mok, M. Wang, S. Tan, S.Y.R. Hui, DC electric springs—A technology for stabilizing DC power distribution systems, IEEE Trans. Power Electron. 32 (2017) 1088–1105

[4] H. Zhao, M. Hong, W. Lin, K.A. Loparo, Voltage and frequency regulation of microgrid with battery energy storage systems, IEEE Trans. Smart Grid 10 (1) (2019) 414–424.

[5] D. Kumar, F. Zare, A. Ghosh, DC microgrid technology: system architectures, AC grid interfaces, grounding schemes, power quality, communication networks, applications, and standardizations aspects, IEEE Access 5 (2017) 12230–12256.