A Primary Full-Integrated Active Filter Auxiliary Power Module in Electrified Vehicles with Single-Phase On board Chargers

ABSTRACT

 In single-phase ac high-voltage (HV) battery chargers, as the input current is enforced to be varying sinusoidally in phase with the input voltage, the pulsating power at two times of the line frequency will be seen on the dc-link. Bulky capacitor bank or extra active filter circuits are needed to assimilate this harmonic current, which become a major barrier in terms of power density and cost. Sinusoidal charging method can be applied, while this might affect the charging efficiency and a deep study is still needed to further investigate on the impact to the Lithium-ion battery. An active filter auxiliary power module (AFAPM) based dual-mode dual-voltage charging system for vehicle application has been proposed. The AFAPM converter has two modes: 1) the HV active filtering mode, in which the vehicle is connected to the grid and the converter assimilates the significant second-order harmonic current; 2) the low-voltage (LV) battery charging mode, in which the vehicle is running and the converter charges the LV battery from HV battery. However, a relay and inductors are still required in that converter to achieve the dual-mode operation. This paper proposes a primary full-integrated AFAPM for electrified vehicle applications with single-phase onboard chargers. The proposed AFAPM converter is composed of a two-phase bidirectional buck converter to work as an active filter (AF) and a dual-active-bridge (DAB) to operate as a LV battery charger auxiliary power module (APM). With the proposed converter, only an extra active energy storage capacitor is needed to achieve the active filtering. All the switches and inductors on the primary stage are shared between the AF and APM. Therefore, the use of a bulky capacitor bank or an additional AF circuit is avoided and thus, the cost, size and weight of the dual-voltage charging system in the electrified vehicle applications can be reduced. To confirm the effectiveness of the proposed converter, a 720 W prototype.

KEYWORDS:

1.      Active filters, auxiliary power modules

2.      Dc/Dc converters

3.      Dual-voltage charging systems

4.      Plug-in hybrid electric vehicles

5.      Single-phase chargers.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1: The dual-voltage charging system with the proposed primary full-integrated AFAPM.

EXPECTED SIMULATION RESULTS:

Fig. 2: Simulation results of AF mode, (a) HV dc-link voltage v_dc, (b) capacitor C_r voltage v_cr, (c) transformer primary voltage v_pri, (d) inductor L_ra and L_rb current i_ra and i_rb, (e) capacitor C_r current i_cr.

Fig. 3: Simulation results of APM mode, (a) transformer primary voltage v_pri, (b) transformer secondary voltage v_sec, (c) inductor L_ra and L_rb current i_ra and i_rb, (d) LV output current i_Lo, (e) capacitor C_r voltage v_cr

CONCLUSION

In this paper, a new primary full-integrated AFAPM converter is proposed. The proposed converter is not only a LV battery charger APM, but also an AF for the HV battery charger. A full bridge and auxiliary inductors are shared between the DAB APM converter and the two phase buck AF converter. Only an active harmonic energy storage capacitor is needed to achieve active filtering. As a result, from the harmonic energy storage aspect for the 6.6 kW HV battery charger in the vehicle applications, with the proposed AFAPM method, the volume and cost can decrease to 45.8% and 44.7% of the volume and cost of the conventional extra active filter method, respectively.  A 720 W prototype has been built and experiments show promising results confirming the effectiveness of the proposed converter.

REFERENCES

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[1]   L. Xue, Z. Shen, D. Boroyevich, P. Matavelli, and D. Diaz, “Dual active bridge-based battery charger for plug-in hybrid electric vehicle with charging current containing low frequency ripple,” IEEE Transactions on Power Electronics, vol. 30, no. 12, pp. 7299-7307, Dec. 2015.

[2]   B. Bilgin, P. Magne, P. Malysz, Y. Yang, V. Pantelic, M. Preindl, A. Korobkine, W. Jiang, M. Lawford, and A. Emadi, “Making the case for electrified transportation,” IEEE Transactions on Transportation Electrification, vol. 1, no. 1, pp. 4-17, Jun. 2015.

[3]   S. Jahdi, O. Alatise, C. Fisher, R. Li, and P. Mawby, “An evaluation of silicon carbide unipolar technologies for electric vehicle drive-trains,” IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 2, no. 3, pp. 517–528, Sep. 2014.

[4]    H. A. Mantooth, M. D. Glover, and P. Shepherd, “Wide bandgap technologies and their implications on miniaturizing power electronic systems,” IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 2, no. 3, pp. 374-385, Sep. 2014.

A Sensorless Power Reserve Control Strategy for Two-Stage Grid-Connected PV Systems

ABSTRACT

Due to the still increasing penetration of grid connected Photovoltaic (PV) systems, advanced active power control functionalities have been introduced in grid regulations. A power reserve control, where namely the active power from the PV panels is reserved during operation, is required for grid support. In this paper, a cost-effective solution to realize the power reserve for two-stage grid-connected PV systems is proposed. The proposed solution routinely employs a Maximum Power Point Tracking (MPPT) control to estimate the available PV power and a Constant Power Generation (CPG) control to achieve the power reserve. In this method, the solar irradiance and temperature measurements that have been used in conventional power reserve control schemes to estimate the available PV power are not required, and thereby being a sensorless approach with reduced cost. Experimental tests have been performed on a 3-kW two-stage single-phase grid-connected PV system, where the power reserve control is achieved upon demands.

KEYWORDS:

1.      Active power control

2.      Power reserve control

3.      Maximum power point tracking

4.      Constant power generation control

5.      PV systems

6.      Grid-connected power converters.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1.System configuration and control structure of a two-stage grid connected

PV system with the Sensorless Power Reserve Control strategy.

EXPECTED EXPERIMENTAL RESULTS:

Fig. 2. Experimental results of the single-phase grid-connected PV system

with the proposed SPRC strategy during the steady-state operation (solar

irradiance level: 1000 W/m2; ambient temperature: 25⁰C; available power

estimation rate: f_APE = 0.2 Hz), where the reference power reserve ∆P are

700 W, 500 W, and 300 W: (a) PV voltage v_pv, (b) PV power P_pv and ac

power (P_ac), (c) dc-link voltage v_dc, and (d) reserved power ∆P.

Fig. 3. Experimental results of the single-phase grid-connected PV system

with the proposed SPRC strategy at the sampling rate of f_APE = 0.05 Hz

under a ramp-changing solar irradiance profile (ambient temperature: 25⁰C),

where the reference power reserve ∆P is 500 W: (a) PV voltage v_pv, (b)

PV power P^pv and ac power (Pac), (c) dc-link voltage v_dc, and (d) reserved

power ∆P.

Fig. 4. Experimental results of the single-phase grid-connected PV system

with the proposed SPRC strategy at the sampling rate of f_APE = 0.2 Hz under

a ramp-changing solar irradiance profile (ambient temperature: 25⁰C), where

the reference power reserve ∆P is 500 W: (a) PV voltage v_pv, (b) PV power

P_pv and ac power (Pac), (c) dc-link voltage v_dc, and (d) reserved power ∆P.

Fig. 5. Zoomed-in view of the results in Fig. 16: (a) PV voltage v_pv, (b) PV

power Ppv and ac power (P_ac), (c) dc-link voltage v_dc, (d) reserved power P.

Fig. 6. Experimental result of the PV voltage v_pv and the dc-link voltage

v_dc with different available power estimation sampling rates f_APE.

CONCLUSION

A cost-effective sensorless power reserve control strategy for two-stage grid-connected PV systems has been proposed in this paper. The cost-effectiveness of the proposal lies in the sensorless estimation of the available PV power, which is achieved by routinely employing a fast MPPT operation. Then, the estimated available power is used for calculating the set-point to limit the extracted PV power with the CPG operation. At the grid-side, the stored energy in the dc-link is adaptively controlled to minimize the power fluctuation during the available PV power estimation process, where the excessed energy is temporarily stored in the dc-link. With the above coordinated control strategy, the power reserve control can be achieved as it has been verified experimentally. Design considerations for a high control performance and the operational boundary have also been discussed to assist the practical implementations.

REFERENCES

[1]   REN21, “Renewables 2016: Global Status Report (GRS),” 2016. [Online]. Available: http://www.ren21.net/.

[2]    Fraunhofer ISE, “Recent Facts about Photovoltaics in Germany,” April 22, 2016. [Online]. Available: http://www.pv-fakten.de/.

[3]   Solar Power Europe, “Global Market Outlook For Solar Power 2015 - 2019,” 2015. [Online]. Available: http://www.solarpowereurope.org/.

[4]   E. Reiter, K. Ardani, R. Margolis, and R. Edge, “Industry perspectives on advanced inverters for us solar photovoltaic systems: Grid benefits, deployment challenges, and emerging solutions,” National Renewable Energy Laboratory (NREL), Tech. Rep. No. NREL/TP-7A40-65063., 2015.

[5]   Y. Yang, P. Enjeti, F. Blaabjerg, and H. Wang, “Wide-scale adoption of photovoltaic energy: Grid code modifications are explored in the distribution grid,” IEEE Ind. Appl. Mag., vol. 21, no. 5, pp. 21–31, Sep. 2015..

A 2 kW, Single-Phase,7-Level Flying Capacitor Multilevel Inverter with an Active Energy Buffer

ABSTRACT

High efficiency and compact single-phase inverters are desirable in many applications such as solar energy harvesting and electric vehicle chargers. This paper presents a 2 kW, 60 Hz, 450 VDC to 240 VAC power inverter, designed and tested subject to the specifications of the Google/IEEE Little Box Challenge. The inverter features a 7-level flying capacitor multilevel converter, with low-voltage GaN switches operating at 120 kHz. The inverter also includes an active buffer for twice-line-frequency power pulsation decoupling, which reduces the required capacitance by a factor of eight compared to conventional passive decoupling capacitors, while maintaining an efficiency above 99%. The inverter prototype is a self-contained box that achieves a high power density of 216 W/in3 and a peak overall efficiency of 97.6% while meeting the constraints including input current ripple, load transient, thermal and FCC Class B EMC specifications.

KEYWORDS:

1.      Single-phase

2.      Inverter

3.      Flying-capacitor multilevel

4.      GaN.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Full system overview of the single-phase inverter.

EXPECTED EXPERIMENTAL RESULTS:

Fig. 2. Waveforms showing active energy buffer operation at 2kW. Voltage

ripple on VC3 counters the ripple on VC1 so that the bus voltage is constant.

Fig. 3. Waveforms showing the output voltage, output current and the

switching node voltage (VSW) of the 7-level inverter at full load.

Fig. 4. Capacitor voltages of the 7-level inverter during full load operation,

obtained using National Instruments data acquisition system (PXIe-1073).

Fig. 5. Energy buffer operation during a load step-down from 100% to 75%.

The input current ripple becomes within specifications after 80 ms.

Fig. 6. Inverter operation during a load step-down from 100% to 75%.

Fig. 7. Conducted EMI measurement at full power (2kW) from 150 kHz to

30 MHz, obtained using Tektronix RSA5126A real-time signal analyzer.

CONCLUSION

This paper has presented a 2 kW, 450 VDC to 240 VRMS single-phase inverter. The dc to ac conversion is accomplished through a 7-level flying-capacitor multilevel converter, with GaN transistors switching at 120 kHz, which is the highest switching frequency achieved to date for a 7-level implementation. The commutation loop in the FCML converter is identified, and a switching cell design is used to minimize loop inductance and reduce the drain-source voltage ringing. In addition, the multilevel inverter is complemented by a series stacked buffer converter for twice-line-frequency ripple compensation. The active energy buffer achieves a high efficiency of 99% while reducing the required capacitor volume by a factor of eight. The combined inverter prototype successfully demonstrated a 216 W/in3 power density with a rectangular volume of 9.26 in3. A peak overall efficiency of 97.6% is achieved, including the power losses from control and cooling fan. The prototype meets all the specifications of the Google/IEEE Little Box Challenge, such as the current ripple, the load transient, the EMC and case temperature requirement, showcasing the capability of the multilevel converter design and the series stacked active energy buffer.

REFERENCES

[1]   J. W. Kolar, U. Drofenik, J. Biela, M. L. Heldwein, H. Ertl, T. Friedli, and S. D. Round, “Pwm converter power density barriers,” in Power Conversion Conference - Nagoya, 2007. PCC ’07, pp. P–9–P–29, April 2007.

[2]   T. Meynard and H. Foch, “Multi-level conversion: high voltage choppers and voltage-source inverters,” in Power Electronics Specialists Conference, 1992. PESC ’92 Record., 23rd Annual IEEE, pp. 397–403 vol.1, Jun 1992.

[3]    S. Allebrod, R. Hamerski, and R. Marquardt, “New transformerless, scalable modular multilevel converters for hvdc-transmission,” in Power Electronics Specialists Conference, 2008. PESC 2008. IEEE, pp. 174– 179, June 2008.

[4]   A. Antonopoulos, L. A¨ ngquist, S. Norrga, K. Ilves, L. Harnefors, and H. P. Nee, “Modular multilevel converter ac motor drives with constant torque from zero to nominal speed,” IEEE Transactions on Industry Applications, vol. 50, pp. 1982–1993, May 2014.

[5]   S. Debnath, J. Qin, B. Bahrani, M. Saeedifard, and P. Barbosa, “Operation, control, and applications of the modular multilevel converter: A review,” IEEE Transactions on Power Electronics, vol. 30, pp. 37–53, Jan 2015.

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A Frequency Adaptive Phase Shift Modulation Control Based LLC Series Resonant Converter for Wide Input Voltage Applications

 ABSTRACT

This paper presents an isolated LLC series resonant DC/DC converter with novel frequency adaptive phase shift modulation control, which suitable for wide input voltage (200-400V) applications. The proposed topology integrates two half-bridge in series on the primary side to reduce the switching stress to half of the input voltage. Unlike the conventional converter, this control strategy increases the voltage gain range with ZVS to all switches under all operating voltage and load variations. Adaptive frequency control is used to secure ZVS in the primary bridge with regards to load change. To do so, the voltage gain becomes independent of the loaded quality factor. In addition, the phase shift control is used to regulate the output voltage as constant under all possible inputs. The control of these two variables also significantly minimizes the circulating current, especially from the low voltage side, which increases the efficiency as compared to a conventional converter. Experimental results of a 1Kw prototype converter with 200-400V input and 48V output are presented to verify all theoretical analysis and characteristics.

KEYWORDS:

1.      LLC

2.      Resonant converter

3.      Frequency adaptive phase shift modulation control (FAPSM)

4.      Zero-Voltage-Switching (ZVS)

5.      Wide gain range.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Proposed LLC resonant converter.

EXPECTED SIMULATION RESULTS:

Fig. 2(a). Simulation waveforms of proposed converter under 400V input, 48V output and full load condition.

Fig. 2(b). Simulation waveforms of proposed converter under 200V input, 48V output and full load condition.

Fig. 2(c). Simulation waveforms of proposed converter under 400V input, 48V output and 20% load condition.

Fig. 2(d). Simulation waveforms of proposed converter under 200V input, 48V output and 20% load condition.

CONCLUSION

In this paper, a variable frequency phase shift modulation control for a DAB LLC resonant converter has been incorporated. This control strategy makes the converter operating at a wide gain range with ZVS over all load conditions. The combination of two half bridge connected in series on the inverter side reduces the voltage stress across each switch, which also makes the converter capable of operating at high-voltage applications. The voltage stresses remain half of the input voltage over all load variations. With the proposed control, the voltage gain becomes independent of Q and K values. Thus, the process of parameter design can be simplified. The magnetizing inductance has been calculated as high to reduce the conduction loss. It also reduced the circulating current (or, reactive power) from the secondary side even at light load condition, which increased the efficiency as compared to conventional DAB LLC resonant converter. The performance of the proposed LLC resonant converter is experimentally verified with 200-400V input and 48V output converter prototype. Therefore, the proposed converter becomes a good candidate for variable input and constant output voltage applications.

REFERENCES

[1]   D. Costinett, D. Maksimovic, and R. Zane, "Design and Control for High Efficiency in High Step-Down Dual Active Bridge Converters Operating at High Switching Frequency," IEEE Transactions on Power Electronics, vol. 28, pp. 3931-3940, 2013.

[2]   S. P. Engel, N. Soltau, H. Stagge, and R. W. D. Doncker, "Dynamic and Balanced Control of Three-Phase High-Power Dual-Active Bridge DC-DC Converters in DC-Grid Applications," IEEE Transactions on Power Electronics, vol. 28, pp. 1880-1889, 2013.

[3]   F. Krismer and J. W. Kolar, "Efficiency-Optimized High-Current Dual Active Bridge Converter for Automotive Applications," IEEE Transactions on Industrial Electronics, vol. 59, pp. 2745-2760, 2012.

[4]   F. Z. Peng, L. Hui, S. Gui-Jia, and J. S. Lawler, "A new ZVS bidirectional DC-DC converter for fuel cell and battery application," IEEE Transactions on Power Electronics, vol. 19, pp. 54-65, 2004.

[5]    S. Inoue and H. Akagi, "A Bidirectional DC-DC Converter for an Energy Storage System With Galvanic Isolation," IEEE Transactions on Power Electronics, vol. 22, pp. 2299-2306, 2007.

A High Efficiency Asymmetrical Half-Bridge Converter with Integrated Boost Converter in Secondary Rectifier

ABSTRACT

A conventional asymmetrical half-bridge (AHB) converter is one of the most promising topologies in low-to-medium power applications because of zero-voltage switching (ZVS) of all switches and small number of components. However, when the converter is designed taking a hold-up time into consideration, it has a large DC offset current in a transformer and a small transformer turns-ratio. To solve these problems, a new AHB converter with an integrated boost converter is proposed in this letter. Because the proposed converter compensates for the hold-up time using the integrated boost converter without additional loss in the nominal state, it can achieve the optimized efficiency regardless of the hold-up time. The effectiveness and feasibility are verified with a 250-400V input and 45V/3.3A output prototype.

KEYWORDS:

1.      Hold-up time

2.      DC/DC converter

3.      Asymmetrical half-bridge converter

4.      High efficiency.1

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. The conventional AHB converters. (a) DCS HB converter and (b)

boost-cascaded AHB converter.

Fig. 2. The proposed converter.

EXPECTED EXPERIMENTAL RESULTS:

Fig.3. Waveforms of the prototype converters with 400v input,3.3A/45v output

            (a)    The conventional AHB converter and (b) the proposed converter

Fig.4.Transient operation during the hold-up time

Fig.5. Measured Efficiency

CONCLUSION

In this letter, a boost-integrated AHB converter is proposed. The proposed converter integrates a boost converter in the rectifier in a new manner. Because the proposed converter can obtain an additional voltage gain during a hold-up time, it can be designed optimally in the nominal state regardless of the hold-up time requirement. Furthermore, since the proposed converter does not cause an additional loss in the nominal state, it can achieve the optimized efficiency.

REFERENCES

[1]   .J. K. Han, J. W. Kim, Y. Jang, B. Kang, J. Choi, and G. W. Moon, “Efficiency Optimized Asymmetric Half-Bridge Converter with Hold-Up Time Compensation,” in Proc. IEEE Power Electron. Conf., pp.2254-2261, May, 2016.

[2]   H. Wu, T. Mu, X. Gao, and Y. Xing, “A Secondary-Side Phase-Shift-Controlled LLC Resonant Converter With Reduced Conduction Loss at Normal Operation for Hold-Up Time Compensation Application," IEEE Trans. Power Electron., vol. 30, no. 10, pp. 5352-5357, Oct. 2015.

[3]   Y. S. Lai, Z. J. Su, and W. S. Chen, “New Hybrid Control Technique to Improve Light Load Efficiency While Meeting the Hold-Up Time Requirement for Two-Stage Server Power,” IEEE Trans. Power Electron., vol. 29, no. 9, pp. 4763-4775, Sep. 2014.

[4]   D. K. Kim, S. Moon, C. O. Yeon, G. W. Moon, “High-Efficiency LLC Resonant Converter With High Voltage Gain Using an Auxiliary LC Resonant Circuit,” IEEE Trans. Power Electron., vol. 31, no. 10, pp. 6901-6909, Oct. 2016

[5]   J. B. Lee, J. K. Kim, J. H. Kim, J. I. Baek, and G. W. Moon, “A High-Efficiency PFM Half-Bridge Converter Utilizing a Half-Bridge LLC Converter Under Light Load Conditions,” IEEE Trans. Power Electron., vol. 30, no. 9, pp. 4931-4942, Sep. 2015