List of contents Introduction Topology derivation with switch multiplexing Multi-objective model predictive control Case 1: Single-stage single-phase battery charger Case 2: LED drive without electrolytic capacitor Case 3: Advanced switched reluctance motor drive Conclusions

Case 3: Advanced switched reluctance motor drive Power fluctuation in SRM drive power ripple Conventional asymmetrical SRM drive Problems: Large electrolytic capacitor is necessary on the dc bus; There are 6 switches and 6 diodes in the SRM drive; DC source voltage must be high enough;

Case 3: Advanced switched reluctance motor drive How to reduce the capacitance requirement? In the current commutation period, ripple energy that C supplies is Methods to reduce the capacitance: Enlarge the capacitor voltage ripple; Increase the capacitor average voltage; Voltage limitation In order to minimize the capacitor, voltage ripple must be enlarged. Input voltage should be constant The capacitor cannot be connected directly on the DC bus

Case 3: Advanced switched reluctance motor drive Topology derivation for capacitance reduction Since the capacitor is not connected into the dc port any more, it can be treated as a source. Hence, there would be two dc sources in the power system which hints that the topology would be a multi-port converter, not a two-port DC-AC converter. A transient power unit is added in the previous converter. That unit is consists of one leg, an inductor as filter and the capacitor as buffer.

Case 3: Advanced switched reluctance motor drive Topology derivation for power decoupling of inverters Switch multiplexing technique Requirements: 1) The voltage of the capacitor should be always higher than the dc source. 2) S1 and S2 should keep modulation continually. While, the other switches S3, S4 and S5 would work alternatively. 3) The voltage stress of the switches is decided by the capacitor voltage directly. Derived topology

Case 3: Advanced switched reluctance motor drive Compared with the conventional topology, the presented IMPC has some advantages listed as following: 1) The required capacitance could be reduced . The voltage ripple and average voltage of the capacitor can be increased. The lifetime of the SRM drive is improved. The cost and size can be optimized. 2) The number of the switches and diodes are decreased as well. The cost and size of the SRM drive can be optimized. 3) The range of the dc source voltage is expanded since it doesn’t act as dc link. The dc source voltage can be low which is suitable for battery applications. 4) The dc link voltage is flexible. By increasing the dc link voltage, the time for discharging of each phase decreases so that conduction angle could be increased and larger average torque could be obtained. The power speed range is widened which is especially appealing for high speed application.

Case 3: Advanced switched reluctance motor drive Totally, there are two control loops: Input port control; Output port control; Input port control Explanation: inductor current reference is obtained by measuring the difference between the capacitor voltage and the detected value. The duty cycle of S1 and S2 is regulated according to the difference between the inductor current reference and the detected value. There are two control loops in input port control: capacitor voltage control(the outer one); inductor current control(the inner one);

Case 3: Advanced switched reluctance motor drive Output port control Explanation: the outer one (speed control) : it outputs the reference of the current injected into the motor. The inner one (current control) : the three switches S3, S4 and S5 are modulated here. Hysteresis control is used in consideration of that it is simple and easy to implement. There are two control loops in output port control: speed control (the outer one); current control (the inner one);

Case 3: Advanced switched reluctance motor drive Simulation Asymmetrical H-bridge Parameter Value DC Voltage Source(V1) 250V DC Capacitor Voltage(Vc) 250V DC, 20V AC Capacitor(C) 2000µF Integrated Multi-Port Converter 80µF 600V DC, 100V AC Inductor(L) 100µH, 10mΩ Switching frequency(fs) 20-kHz Switched Reluctance Machine Stator poles 6 Rotor poles 4 Te 40 Inertia 0.05kg.m.m Friction 0.02N.m.s Speed 1000RPM flux(V*s) three-phase current(A) Te(N*m)

Case 3: Advanced switched reluctance motor drive Simulation Input current(A) load torque change speed(RPM) Harmonic distribution Input current(A) The control method can restrain 91% 100-Hz ripple component of the inverter input current

Case 3: Advanced switched reluctance motor drive Experimental results prototype Current waveform DC port waveform Harmonic distribution Experimental results demonstrates that the proposed new topology can reduce 88% ripple current and the corresponding control method also works well.

Case 3: Advanced switched reluctance motor drive Experimental results 60V 20V Input waveform with 880µF on dc bus Input waveform with 220µF on dc bus Compared with the conventional topology, the presented topology with corresponding control methods can achieve power decoupling with only 30% capacitance requirement.

List of contents Introduction Topology derivation with switch multiplexing Multi-objective model predictive control Case 1: Single-stage single-phase battery charger Case 2: LED drive without electrolytic capacitor Case 3: Advanced switched reluctance motor drive Conclusions

Conclusion and future work Has achieved: Switch multiplexing technique based on basic units is proposed to derive multiport power electronic topologies. With switch multiplexing technique, multi-level units and resonant units are embedded into MPEI to achieve better performance including efficiency and power density improvement. Generalised predictive control method is proposed to improve the performance of power flow control in MPEI. The superior expansibility and low complexity make generalised predictive control suitable for achieving multi-objective control. A four-switch single-stage single-phase isolated rectifier based on LLC unit and T-type three- level unit is presented and analyzed.

Conclusion and future work A four-switch isolated single-phase AC-DC converter is derived and selected for high temperature LED drive application. Based on switch multiplexing technique, an integrated multiport power converter is proposed to drive switched reluctance motor. Future work: Even though the feasibility of switch multiplexing technique has been verified in this dissertation, its expansibility still needs development. This dissertation hasn’t included the voltage stress analysis for most derived topologies. Z-source topologies can change the port features flexibly and approach some interesting and specific functions. More applications can be analyzed in the future.

Publications Journal papers: Wen Cai and Fan Yi, "An Integrated Multi-Port Power Converter with Small Capacitance Requirement for Switched Reluctance Motor Drive," Accepted by IEEE Transactions on Power Electronics. Wen Cai, Bangyin Liu, Shanxu Duan and Ling Jiang, "An Active Low-Frequency Ripple Control Method Based on the Virtual Capacitor Concept for BIPV Systems," IEEE Transactions on Power Electronics, vol. 29, no. 4, pp. 1733-1745, 2014. Wen Cai, Bangyin Liu, Shanxu Duan and Changyue Zou, “An Islanding Detection Method based on Dual-Frequency Harmonic Current Injection under Grid Impedance Unbalanced Condition”, IEEE Transactions on Industrial Informatics, vol. 9, no. 2, pp. 1178-1187, 2012. Wen Cai, Ling Jiang, Bangyin Liu, Shanxu Duan and Changyue Zou, “A Power Decoupling Method based on Four-switch Three-Port DC/DC/AC Converter in DC Microgrid,” IEEE Transactions on Industry Applications, vol. 51, no. 1, pp. 336-343, 2015. Wen Cai, Fan Yi and Eva Cosoroaba, “Stability Optimization Method based on Virtual Resistor and Non-unity Voltage Feedback Loop for Cascaded DC-DC Converters,” Accepted by IEEE Transactions on Industry Applications. Fan Yi, and Wen Cai, “Modeling, Control and Seamless Transition of Bi-directional Battery-Driven Switched Reluctance Motor/Generator Drive based on IMPC,” In major revision for IEEE Transactions on Power Electronics.

Publications Wen Cai, and Fan Yi, “A Multiport Topology Derivation Method based on Switch Multiplexing Technique for Electric Vehicles,” In minor revision for IEEE Transactions on Transportation Electrification. Fan Yi, and Wen Cai, “A quasi-Z-Source Integrated Multiport Power Converter as switched reluctance motor drive for wide operation and capacitance reduction,” in minor revision for IEEE Transactions on Power Electronics. Conference papers: Wen Cai and Fan Yi, "Topology simplification method based on switch multiplexing technique to deliver DC-DC-AC converters for microgrid applications," Accepted by IEEE Energy Conversion Congress and Exposition (ECCE), 2015. Wen Cai, Lei Gu, Fan Yi, "An integrated multi-port power converter with small capacitance requirement for switched reluctance machine," IEEE Industrial Electronics Conference (IECON2014), pp. 3183-3189. Fan Yi and Wen Cai, "Repetitive control-based current ripple reduction method with a multi-port power converter for SRM drive", IEEE Transportation Electrification Conference and Expo (ITEC), 2015, pp. 1-6. Devendra Patil, Mark Ditsworth, Jose Pacheco and Wen Cai, "A magnetically enhanced wireless power transfer system for compensation of misalignment in mobile charging platforms", Accepted by IEEE Energy Conversion and Exposition (ECCE), 2015.

Publications Wen Cai, Babak Fahimi, Fan Yi and Eva Cosoroaba, "Stability analysis and voltage control method based on virtual resistor and proportional voltage feedback loop for cascaded DC-DC converters," in IEEE Energy Conversion Congress and Exposition (ECCE), 2014, pp. 3016-3022. Wen Cai, Fan Yi & Yikai Gao, “A single-stage single-phase isolated AC-DC converter based on LLC resonant unit and T-type three-level unit for battery charging applications," Accepted by Applied Power Electronics Conference (APEC), 2016. Wen Cai, Fan Yi & Dingyi He, “A power decoupling method with small capacitance requirement based on single-phase quasi-z-source inverter for DC microgrid," Accepted by Applied Power Electronics Conference (APEC), 2016. Wen Cai, Ling Jiang, Bangyin Liu, Shanxu Duan and Changyue Zou, "A power decoupling method based on four-switch three-port DC/DC/AC converter in DC microgrid," in IEEE Energy Conversion Congress and Exposition (ECCE), 2013, pp. 4678-4682. Wen Cai, Bangyin Liu, Shanxu Duan and Ling Jiang, "Power flow control and optimization of a three-port converter for photovoltaic-storage hybrid system," in IEEE Energy Conversion Congress and Exposition (ECCE), 2012, pp. 4121-4128. Xi Chen, Mengyin Ma, Shanxu Duan, Wen Cai and Changsong Chen, "Low frequency ripple propagation analysis in LLC resonant converter based on signal modulation-demodulation theory and reduction based on PIR control strategy," in IEEE Energy Conversion Congress and Exposition (ECCE), 2013, pp. 5390-5394.

Thank you for your attention and time ! Wen Cai PhD candidate and research assistant University of Texas at Dallas Phone: 4694120040 Email: wxc130530@utdallas.edu