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A novel smooth switching control strategy for multiple photovoltaic converters in DC microgrids
Qinjin Zhang,Wangbao Hu,Yancheng Liu,Hanwen Zhang,Honglai Wang 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.2
With the photovoltaic (PV) penetration rate increasing in PV-storage-based DC microgrids, the conventional PV controller with only the maximum power point tracking (MPPT) control function can hardly meet the needs of the coordinated operation. The PV converter should operate at the MPPT or the constant voltage droop (CVD) mode according to the load demand. Two sets of relatively independent control loops are used to control the two modes. Inevitably, bus voltage and PV output power fluctuations are caused in the process of mode switching. This paper proposes a novel smooth switching control strategy for the smooth transition of multiple PV converters between MPPT and CVD modes. When combined with the PV array output characteristic curve, the value of dp/di is selected as the control variable. By tracking different dp/di command values, the PV converter can realize the control of the MPPT mode, the CVD mode, and smooth switching between the two modes. The MPPT and CVD modes are unified in the sense of using the same control loop, which avoids control loop switching during the PV mode switching. Finally, the effectiveness of the novel smooth switching control strategy is verified by the simulation and hardware in loop (HIL) experimental tests.
Liu, Yancheng,Wang, Honglai,Zhang, Qinjin,Wen, Yuanquan,Hu, Wangbao,Zhang, Hanwen The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.8
During the navigation of all-electric ships, a hybrid energy storage system (HESS) is required to compensate power imbalance and maintain bus voltage stability. For a HESS composed of multiple energy storage (ES) devices, an unreasonable power distribution causes the ES devices with a low state of charge (SoC) to draw from power supply early, which deepens the operating pressure of the other ES devices. This in turn, affects the stable operation of the entire system. To achieve power distribution based on the SoC of different ES devices, a novel power distribution strategy for use in all-electric ships was proposed. In the proposed strategy, the virtual impedance of an ES device is connected with the SoC through exponential functions. As a result, the output power can be dynamically changed according to changes of the SoC. On the premise of obtaining a proper dynamic power distribution among ES devices with complementary characteristics, the SoC balance among ES devices with the same characteristics can be realized. Meanwhile, the bus voltage deviation induced by the virtual resistor is eliminated via an added compensation voltage. The effectiveness of proposed method is verified by both simulations and a StarSim hardware in loop (HIL) experimental platform.
Zhang Qinjin,Qu Tengda,Liu Yancheng,Zeng Yuji,Hu Wangbao,Zhang Hanwen 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3
A dynamic state of charge (SoC) balancing strategy for parallel battery energy storage units (BESUs) based on dynamic adjustment factor is proposed under the hierarchical control framework of all-electric propulsion ships, which can achieve accurate power distribution, bus voltage recovery, and SoC balance accuracy. In the primary control layer, the arccot function is introduced into the improved balancing strategy, and the bus voltage drop is effectively limited while the SoC balancing speed is quickly achieved by adjusting the SoC convergence factors. In the secondary control layer, power and voltage compensation controllers are designed individually to improve the SoC balance accuracy and compensate the bus voltage. Furthermore, neighbor-to-neighbor communication network is constructed by using dynamic consensus algorithm to reduce the communication burden as well as its error rate. Finally, the simulation and StarSim HIL experimental results show that the proposed control strategy can achieve accurate power distribution, bus voltage recovery, and has a faster SoC convergence speed than advanced methods.
The detection efficiency study of NaI(Tl) scintillation detector with the different numbers of SiPMs
Wang Bao,Zhang Xiongjie,Wang Qingshan,Wang Dongyang,Li Dong,Xiahou Mingdong,Zhou Pengfei,Ye Hao,Hu Bin,Zhang Lijiao 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.7
SiPMs are generally coupled into whole columns in gamma energy spectrum measurement, but the relationship between the distribution of whole SiPM columns and the energy resolution of the measured energy spectra is rarely reported. In this work, ∅ 3 3 inch NaI scintillator is placed on an 8 8 SiPM array, and the energy resolution of the 137Cs peak at 662 keV corresponding to the g-ray is selected as a reference. Each SiPM is switched to explore the influence of the number of SiPM arrays, distribution position, and reflective layer on the energy resolution of SiPMs. Results show that without coupling, the energy resolution is greatly improved when the number of SiPMs ranges from 4 to 32. However, after 32 slices (the area covered by SiPMs relative to the scintillator reaches 25.9%), the improvement in energy resolution and total pulse count is not obvious. In addition, the position of SiPMs relative to the scintillator does not exert much impact on the energy resolution. Results also indicate that by adding a reflective film (ESR), the energy resolution of the tested group increases by 10.38% on average. This work can provide a reference for the design and application of miniaturized SiPM gamma spectrometers