@article{won_jalali_liang_zhang_srdic_lukic_2019, title={Auxiliary Power Supply for Medium-Voltage Power Converters: Topology and Control}, volume={55}, ISSN={["1939-9367"]}, DOI={10.1109/TIA.2019.2915511}, abstractNote={This paper presents an isolated auxiliary power supply for medium-voltage power electronics systems. The proposed converter comprises two stages: a non-isolated ac/dc stage that connects directly to the medium-voltage line, and an isolated dc/dc stage that provides 100-W output power at 24 V, with 10 kV isolation. The proposed modular ac/dc stage uses just one active semiconductor device per module, features an internal capacitor voltage balancing, and achieves power factor correction by employing predictive current control. High switching frequency operation of both converter stages enable a reduction in system size and weight when compared to traditional low-frequency transformer-based approach. The proposed converter is simulated and its operation is validated experimentally on a 100-W prototype.}, number={4}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Won, Jehyuk and Jalali, Gholamreza and Liang, Xinyu and Zhang, Chi and Srdic, Srdjan and Lukic, Srdjan M.}, year={2019}, pages={4145–4156} }
 @article{liang_zhang_srdic_lukic_2018, title={Predictive Control of a Series-Interleaved Multicell Three-Level Boost Power-Factor-Correction Converter}, volume={33}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2017.2780244}, abstractNote={This paper presents a new predictive power-factor-correction (PFC) controller for series-interleaved three-level boost (TLB) converters. Compared to the state-of-the-art TLB PFC controllers, where a two-cycle prediction and a detection of an operating region are necessary, the proposed controller achieves a low total harmonic distortion of the input current by using a single equation to predict the input current in all operating regions of the converter, in just one operating cycle. The average current control is achieved by sampling at the peak of the triangular carrier. The proposed PFC controller significantly reduces the distortion of the input ac current near the zero-crossing points, resulting in a low total harmonic distortion of the input current. The operation of the proposed controller was evaluated, and its stability and robustness to parameter changes was confirmed analytically. The controller operating principles were verified in simulations and validated by experiments on a medium-voltage 50-kW converter prototype.}, number={10}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Liang, Xinyu and Zhang, Chi and Srdic, Srdjan and Lukic, Srdjan M.}, year={2018}, month={Oct}, pages={8948–8960} }
 @article{goetz_li_liang_zhang_lukic_peterchev_2017, title={Control of Modular Multilevel Converter With Parallel Connectivity-Application to Battery Systems}, volume={32}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2016.2645884}, abstractNote={This paper presents a multiobjective real-time controller for a modular multilevel converter capable of parallel module connectivity, the so-called modular multilevel series parallel converter (MMSPC). The MMSPC topology allows the batteries to be dynamically rewired in various series–parallel configurations, generating a wide range of output voltage levels. The novel control method parallelizes the modules to balance their voltages without the need for individual module voltage monitoring. Additionally, the controller optimizes across the large number of feasible system configurations to minimize switching and conduction losses. Finally, the controller efficiently encodes the system configuration with module interconnection states rather than the module switch states, which substantially simplifies control. Furthermore, this work experimentally validates the MMSPC topology and concept. In the prototype, the parallel mode reduced the system losses at 5 kW output power by 18% and 24% for load power factors of 1.0 and 0.8, respectively. Sensorless balancing via parallelization maintained well-matched module voltages (standard deviation = 0.045 V) over a 5-h battery discharge with highly variable load current. The reduced conduction losses and simple balancing capability of the MMSPC can enable new applications at medium and low voltages that benefit from its high-quality output, elimination of filtering magnetics, fast response, and modularity.}, number={11}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Goetz, Stefan M. and Li, Zhongxi and Liang, Xinyu and Zhang, Chengduo and Lukic, Srdjan M. and Peterchev, Angel V.}, year={2017}, month={Nov}, pages={8381–8392} }
 @inproceedings{srdic_liang_zhang_yu_lukic_2016, title={A SiC-based high-performance medium-voltage fast charger for plug-in electric vehicles}, DOI={10.1109/ecce.2016.7854777}, abstractNote={This paper presents an isolated medium-voltage, high-power-quality and high efficiency (over 96%), fast charger for plug-in electric vehicles. The proposed fully modular fast charger uses off-the-shelf Silicon Carbide (SiC) power devices to convert the rectified single-phase 2.4 kV medium-voltage input to variable dc output. The adopted input-series-output-parallel unidirectional topology enables converter scalability in both the input voltage and the output power. Using wide bandgap (WBG) power devices enables 9 times reduction in volume and 6 times reduction in weight, compared to the state-of-the-art fast chargers, while exceeding the efficiency of the state-of-the-art fast chargers by more than 1.5% Based on the system requirements, the appropriate converter topology was selected, its operation was simulated and validated by experiments on the developed fast charger prototype.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Srdic, S. and Liang, X. Y. and Zhang, C. and Yu, Wensong and Lukic, Srdjan}, year={2016} }
 @inproceedings{srdic_zhang_liang_yu_lukic_2016, title={A SiC-based power converter module for medium-voltage fast charger for plug-in electric vehicles}, DOI={10.1109/apec.2016.7468247}, abstractNote={This paper presents an isolated power converter module for medium-voltage (2.4 kV), high-power-quality (PF ≥ 0.98, current THD ≤ 2%), 50 kW fast charger for plug-in electric vehicles. The proposed high-efficiency (above 96%), and reduced-footprint converter module utilizes off-the-shelf Silicon Carbide (SiC) devices to step down the rectified single-phase medium-voltage input. The developed module can also serve as a building block for other medium voltage rectifier applications, including power supplies for data centers and other dc power distribution systems. Based on the system requirements, the appropriate unidirectional converter topology was selected, its operation was simulated and validated by experiments on the developed converter prototype.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Srdic, S. and Zhang, C. and Liang, X. Y. and Yu, Wensong and Lukic, Srdjan}, year={2016}, pages={2714–2719} }
 @inproceedings{goetz_li_peterchev_liang_zhang_lukic_2016, title={Sensorless scheduling of the modular multilevel series-parallel converter: Enabling a flexible, efficient, modular battery}, DOI={10.1109/apec.2016.7468193}, abstractNote={We present a control approach for the modular multilevel converter (MMC) with series and parallel module connectivity (MMSPC) that provides natural module balancing, reduced conduction losses, and enhanced robustness afforded by the parallel mode. In conventional MMC control, the voltage of each module's storage element has to be measured or estimated to enable the controller to equalize the voltages across all modules. This requirement has been one of the key barriers for MMCs in low and medium power applications. In contrast, we use the parallel connectivity of the MMSPC for module voltage balancing. It also enables robust operation in the presence of battery failure by supporting the module voltage with frequent parallelizations of the residual module capacitance. The parallel connectivity further reduces conduction losses at voltage levels below the system maximum by decreasing the effective source impedance. This approach renders attractive for the first time low and medium power MMC applications as well as MMC-based battery storage. These are illustrated with an experimental MMSPC system comprising eight battery modules that generates high-quality ac output without filtering magnetics.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Goetz, S. M. and Li, Z. X. and Peterchev, A. V. and Liang, X. Y. and Zhang, C. D. and Lukic, S. M.}, year={2016}, pages={2349–2354} }