A DSP Based Digital Control Strategy for ZVS Bidirectional Buck+Boost Converter

ABSTRACT:

The non-isolated bidirectional DC-DC converters are the most popular topology for low or medium power of the hybrid electric vehicle (HEV) or fuel cell vehicle (FCV) applications. These kinds of converters have the advantages of simple circuit topology, bidirectional flows, zero-voltageswitching (ZVS), high efficiency, and high power density. The turned-on ZVS for all MOSFETs is achieved by the negative offset of the inductor current at the beginning and the end of each switching period. To do this, the converter requires a complex switching strategy which is preferred to be implemented by the digital signal processing (DSP). This paper presents the digital implementation of the switching pattern to ensure the ZVS condition for such converter. A 5kW prototype is performed to verify the capability of such control scheme.

KEYWORDS:

1.      DC-DC converter

2.      Bidirectional converter

3.      Digital control

4.      Phase shift control

SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

Fig1. Bidirectional dc dc converter

 EXPECTED SIMULATION RESULTS:

Fig. 2. Inductor current waveforms of (a) boost mode and (b) buck mode

Fig. 3. ZVS turn on of switch S1

Fig. 4. Overall efficiency of both boost and buck operating modes

CONCLUSION:

A DSP based digital control strategy for the bidirectional DC-DC converter is proposed in this paper. The new control strategy provides a negative inductor current at the beginning of each pulse period that, in conjunction with just the parasitic MOSFET output capacitances but no additional components, allows ZVS with the full voltage and load range. The DSP chip TMS320F28035 from Texas Instruments is employed to perform this control algorithm. The experimental results not only show the ZVS for four switches but also provide an excellent overall efficiency at least 96% at the power range.

REFERENCES:

[1] S. S. Williamson, S. M. Lukic, and A. Emadi, “Comprehensive drive train efficiency analysis of hybrid electric and fuel cell vehicles based on motor controller efficiency modeling,” IEEE Trans. Power Electron., vol. 21, no. 3, pp. 730-740, May 2006.

[2] K. Wang, C. Y. Lin, L. Zhu, D. Qu, F. C. Lee, and J. Lai, “Bidirectional dc to dc converters for fuel cell systems,” in Conf. Rec. 1998 IEEE Workshop Power Electronics in Transportation, pp. 47-51.

[3] A. Emadi, S. S. Williamson, and A. Khaligh, “Power electronics intensive solutions for advanced electric, hybrid electric, and fuel cell vehicular power systems,” IEEE Trans. Power Electron., vol. 21, no. 3, pp. 567-577, May 2006.

[4] D. Patel Ankita, “Analysis of bidirectional Buck-Boost converter by using PWM control scheme,” ISSN: 2321-9939, Electronics and Communication, Marwadi Education Foundation Group of Institute, Rajkot, India.

[5] Texas Instruments, “Modeling of bidirectional Buck/Boost converter for digital control using C2000 microcontroller,” Application report SPRABX5, January 2015.

An Improved Control Algorithm of Shunt Active Filter for Voltage Regulation, Harmonic Elimination, Power-Factor Correction, and Balancing of Nonlinear Loads

 ABSTRACT:  

This paper deals with an implementation of a new control algorithm for a three-phase shunt active filter to regulate load terminal voltage, eliminate harmonics, correct supply power-factor, and balance the nonlinear unbalanced loads. A three-phase insulated gate bipolar transistor (IGBT) based current controlled voltage source inverter (CC-VSI) with a dc bus capacitor is used as an active filter (AF). The control algorithm of the AF uses two closed loop PI controllers. The dc bus voltage of the AF and three-phase supply voltages are used as feed back signals in the PI controllers. The control algorithm of the AF provides three-phase reference supply currents. A carrier wave pulse width modulation (PWM) current controller is employed over the reference and sensed supply currents to generate gating pulses of IGBT’s of the AF. Test results are presented and discussed to demonstrate the voltage regulation, harmonic elimination, power-factor correction and load balancing capabilities of the AF system.

KEYWORDS:

1.      Active filter

2.      Harmonic compensation

3.      Load balancing

4.      Power-factor correction

5.      Voltage regulation

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Fundamental building block of the active filter.

EXPECTED SIMULATION RESULTS:

Fig. 2. Performance of the AF system under switch IN and steady state conditions with a three-phase nonlinear load.

Fig. 3. Steady state response of the AF for voltage regulation and harmonic elimination with a three-phase nonlinear load.

Fig. 4. Steady state response of the AF for voltage regulation, harmonic elimination, and load balancing with a single-phase nonlinear load.

Fig. 5. Switch IN response of the AF for voltage regulation, harmonic elimination with a three-phase nonlinear load.

Fig. 6. Switch IN response of the AF for voltage regulation, harmonic elimination and load balancing with a single-phase nonlinear load.

Fig. 7. Dynamic response of the AF for voltage regulation, harmonic elimination, and load balancing under the load change from three-phase to single-phase.

Fig. 8. Dynamic response of the AF for voltage regulation, harmonic elimination, and load balancing under the load change from single-phase to three-phase.

Fig. 9. Steady state response of the AF for power-factor correction, harmonic elimination with a three-phase nonlinear load.

Fig. 10. Steady state response of the AF for power-factor correction, harmonic elimination, and load balancing with a single-phase nonlinear load.

Fig. 11. Switch IN response of the AF for power-factor correction and harmonic elimination with a three-phase nonlinear load.

Fig. 12. Switch IN response of the AF for power-factor correction, harmonic elimination, and load balancing with a single-phase nonlinear load.

CONCLUSION:

An improved control algorithm of the AF system has been implemented on a DSP system for voltage regulation/power-factor correction, harmonic elimination and load balancing of nonlinear loads. Dynamic and steady state performances of the AF system have been observed under different operating conditions of the load. The performance of the AF system has been found to be excellent. The AF system has been found capable of improving the power quality, voltage profile, power-factor correction, harmonic elimination and balancing the nonlinear loads. The proposed control algorithm of the AF has an inherent property to provide a self-supporting dc bus and requires less number of current sensors resulting in an over all cost reduction. It has been found that for voltage regulation and power-factor correction to unity are two different things and can not be achieved simultaneously. However, a proper weight-age to in-phase and quadrature components of the supply current can provide a reasonably good level of performance and voltage at PCC can be regulated with a leading power-factor near to unity. It has been found that the AF system reduces harmonics in the voltage at PCC and the supply currents well below the mark of 5% specified in IEEE-519 standard.

REFERENCES:

[1] L. Gyugyi and E. C. Strycula, “Active AC power filters,” in Proc.IEEE-IAS Annu. Meeting Record, 1976, pp. 529–535.

[2] T. J. E. Miller, Reactive Power Control in Electric Systems. Toronto,Ont., Canada: Wiley, 1982.

[3] J. F. Tremayne, “Impedance and phase balancing of main-frequency induction furnaces,” Proc. Inst. Elect. Eng. B, pt. B, vol. 130, no. 3, pp. 161–170, May 1983.

[4] H. Akagi, Y. Kanazawa, and A. Nabae, “Instantaneous reactive power compensators comprising switching devices without energy storage components,” IEEE Trans. Ind. Applicat., vol. IA-20, pp. 625–630, May/June 1984.

[5] T. A. Kneschki, “Control of utility system unbalance caused by single-phase electric traction,” IEEE Trans. Ind. Applicat., vol. IA-21, pp. 1559–1570, Nov./Dec. 1985.

Zero-Voltage-Switching Sinusoidal Pulse Width Modulation Method for Three-phase Four-wire Inverter

ABSTRACT:  

A Zero-Voltage-Switching (ZVS) sinusoidal pulse width modulation (SPWM) method for three-phase four-wire inverter is proposed in order to achieve higher efficiency and power density. With the proposed modulation scheme, the ZVS operation of all switches including the main switches and the auxiliary switch can be realized. Besides, all seven switches operate at a fixed frequency. The ZVS SPWM scheme is introduced by considering the various combinations of the polarities in three-phase filter inductors currents and analysis of operating stages is presented. ZVS condition of the ZVS SPWM scheme is derived and discussions of ZVS condition for typical three-phase loads are also provided. In addition, the resonant parameters design and loss analysis are briefly investigated. Finally the proposed ZVS SPWM scheme is verified on a 10 kW inverter prototype with SiC MOSFET devices.

KEYWORDS:

1.      Zero-Voltage-Switching (ZVS)

2.      Sinusoidal pulse width modulation (SPWM)

3.      Three-phase four-wire inverter

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. ZVS three-phase four-wire inverter.

EXPECTED SIMULATION RESULTS:

(a)                                                                                              (b)

(c)                                                                                                (d)

Fig. 2. Three-phase load voltages and filter inductors currents of the ZVS inverter under balanced resistive load: (a) Three-phase load voltage, (b) load voltage and filter inductor current of phase A, (c) load voltage and filter inductor current of phase B, and (d) load voltage and filter inductor current of phase C.

(a)                                                                                                (b)

(c)                                                                                                   (d)

Fig. 3. Three-phase load voltages and filter inductors currents of the ZVS inverter under unbalanced resistive load: (a) Three-phase load voltage, (b) load voltage and filter inductor current of phase A, (c) load voltage and filter inductor current of phase B, and (d) load voltage and filter inductor current of  phase C.

(a)                                                                                           (b)

(c)                                                           (d)

Fig. 4. Three-phase load voltages and filter inductors currents of the ZVS inverter under unbalanced inductive load: (a) Three-phase load voltage, (b)  load voltage and filter inductor current of phase A, (c) load voltage and filter inductor current of phase B, and (d) load voltage and filter inductor current of phase C.

CONCLUSION:

A ZVS SPWM method combining with aligned turn on gate signals and extra short circuit stage is proposed for three-phase four-wire inverter. The generalized ZVS condition of the ZVS SPWM scheme is derived and the discussions of ZVS condition for some typical three-phase loads are provided. For balanced resistive load, balanced inductive load and unbalanced resistive load, short circuit stage is required. The short circuit stage may not be needed during several intervals for some kinds of unbalanced inductive load. The estimated loss analysis show that significant efficiency advantages can be obtained by ZVS three-phase four-wire inverter at high switching frequency in comparison with the hard switching three-phase four-wire inverter.

The ZVS turn-on of all switches, including the main switches and auxiliary switch under both balanced and unbalanced resistive load are achieved in the complete fundamental period with experimental verification. Besides, the ZVS SPWM inverter shows significant efficiency advantage. The measured highest conversion efficiency of the ZVS SPWM inverter is 98.3 % and 1.7 % higher than that of the hard switching inverter. At full load, the ZVS SPWM inverter has 2.1 % higher efficiency than the hard switching inverter.

REFERENCES:

[1] M. E. Fraser, C. D. Manning and B. M. Wells, “Transformerless four-wire PWM rectifier and its application in AC-DC-AC converters, ” in IEE Proceedings - Electric Power Applications, vol. 142, no. 6, pp. 410-416, Nov 1995.

[2] M. Dai, M. N. Marwali, J. W. Jung and A. Keyhani, “A Three-Phase Four-Wire Inverter Control Technique for a Single Distributed Generation Unit in Island Mode,” in IEEE Transactions on Power Electronics, vol. 23, no. 1, pp. 322-331, Jan. 2008.

[3] E. L. L. Fabricio, S. C. S. Júnior, C. B. Jacobina and M. B. de Rossiter Corrêa, “Analysis of Main Topologies of Shunt Active Power Filters Applied to Four-Wire Systems,” in IEEE Transactions on Power Electronics, vol. 33, no. 3, pp. 2100-2112, March 2018.

[4] H. Zhang, C. da Sun, Z. x. Li, J. Liu, H. y. Cao and X. Zhang, “Voltage Vector Error Fault Diagnosis for Open-Circuit Faults of Three-Phase Four-Wire Active Power Filters,” in IEEE Transactions on Power Electronics, vol. 32, no. 3, pp. 2215-2226, March 2017.

[5] M. V. Manoj Kumar and M. K. Mishra, “Three-leg inverter-based distribution static compensator topology for compensating unbalanced and non-linear loads,” in IET Power Electronics, vol. 8, no. 11, pp. 2076-2084, 11 2015.