A Neutral-Point Voltage Balance Controller for the Equivalent SVPWM Strategy of NPC Three-Level Inverters

Lyu, Jianguo,Hu, Wenbin,Wu, Fuyun,Yao, Kai,Wu, Junji The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

Based on the space vector pulse width modulation (SVPWM) theory, this paper realizes an easier SVPWM strategy, which is equivalently implemented by CBSPWM with zero-sequence voltage injection. The traditional SVPWM strategy has no effect on controlling the neutral-point voltage balance. In order to solve the neutral-point voltage unbalance problem for neutral-point-clamped (NPC) three-level inverters, this paper proposes a neutral-point voltage balance controller. The proposed controller realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the three-phase modulation waves of an equivalent SVPWM strategy. Compared with the traditional SVPWM strategy, the proposed neutral-point voltage balance controller has a strong ability to balance the neutral-point voltage, has good steady-state performance, improves the output waveforms quality and is easy for digital implementation. An experiment has been carried out on a NPC three-level inverter prototype based on a digital signal processor-complex programmable logic device (DSP-CPLD). The obtained experimental results verify the effectiveness of the proposed neutral-point voltage balance controller.

New DPWM Method to Suppress the Low Frequency Oscillation of the Neutral-Point Voltage for NPC Three-Level Inverters

Jianguo Lyu,Wenbin Hu,Fuyun Wu,Kai Yao,Junji Wu 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.5

In order to suppress the low frequency oscillation of the neutral-point voltage for three-level inverters, this paper proposes a new discontinuous pulse width modulation (DPWM) control method. The conventional sinusoidal pulse width modulation (SPWM) control has no effect on balancing the neutral-point voltage. Based on the basic control principle of DPWM, the relationship between the reference space voltage vector and the neutral-point current is analyzed. The proposed method suppresses the low frequency oscillation of the neutral-point voltage by keeping the switches of a certain phase no switching in one carrier cycle. So the operating time of the positive and negative small vectors is equal. Comparing with the conventional SPWM control method, the proposed DPWM control method suppresses the low frequency oscillation of the neutral-point voltage, decreases the output waveform harmonics, and increases both the output waveform quality and the system efficiency. An experiment has been realized by a neutral-point clamped (NPC) three-level inverter prototype based on STM32F407-CPLD. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed DPWM method.

A Neutral-Point Voltage Balance Controller for the Equivalent SVPWM Strategy of NPC Three-Level Inverters

Jianguo Lyu,Wenbin Hu,Fuyun Wu,Kai Yao,Junji Wu 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

Based on the space vector pulse width modulation (SVPWM) theory, this paper realizes an easier SVPWM strategy, which is equivalently implemented by CBSPWM with zero-sequence voltage injection. The traditional SVPWM strategy has no effect on controlling the neutral-point voltage balance. In order to solve the neutral-point voltage unbalance problem for neutral-point-clamped (NPC) three-level inverters, this paper proposes a neutral-point voltage balance controller. The proposed controller realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the three-phase modulation waves of an equivalent SVPWM strategy. Compared with the traditional SVPWM strategy, the proposed neutral-point voltage balance controller has a strong ability to balance the neutral-point voltage, has good steady-state performance, improves the output waveforms quality and is easy for digital implementation. An experiment has been carried out on a NPC three-level inverter prototype based on a digital signal processor-complex programmable logic device (DSP-CPLD). The obtained experimental results verify the effectiveness of the proposed neutral-point voltage balance controller.

A New DPWM Method to Suppress the Low Frequency Oscillation of the Neutral-Point Voltage for NPC Three-Level Inverters

Lyu, Jianguo,Hu, Wenbin,Wu, Fuyun,Yao, Kai,Wu, Junji The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.5

In order to suppress the low frequency oscillation of the neutral-point voltage for three-level inverters, this paper proposes a new discontinuous pulse width modulation (DPWM) control method. The conventional sinusoidal pulse width modulation (SPWM) control has no effect on balancing the neutral-point voltage. Based on the basic control principle of DPWM, the relationship between the reference space voltage vector and the neutral-point current is analyzed. The proposed method suppresses the low frequency oscillation of the neutral-point voltage by keeping the switches of a certain phase no switching in one carrier cycle. So the operating time of the positive and negative small vectors is equal. Comparing with the conventional SPWM control method, the proposed DPWM control method suppresses the low frequency oscillation of the neutral-point voltage, decreases the output waveform harmonics, and increases both the output waveform quality and the system efficiency. An experiment has been realized by a neutral-point clamped (NPC) three-level inverter prototype based on STM32F407-CPLD. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed DPWM method.

In uence of In dopant on PL Spectra of CdZnTe Crystals

Jianyong Teng,Wenbin Sang,Gang Li,Zhubin Shi,Jiahua Min,Dongni Hu,Yongbiao Qian 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1

Photoluminescence (PL) spectra are used to characterize the high resistivity of an In-doped CdZnTe (CZT) crystal. The features of the PL spectra vary with changing In-dopant concentration, indicating that the In-dopant concentration has a great impact on the defect type and density and on the extent of compensation in the In-doped CZT crystal. With the addition of In donors, a new sharp neutral donor bound exciton [D0, X] peak at 1.65 eV, corresponding to In substituting defect (In+ Cd) and a new defect complex band centered at 1.505 eV, related to the singly negative complex (VCd-InCd)- are observed. Meanwhile, the intensity and position of the feature peaks in PL spectra vary with the change of the In dopant concentration, representing the changes of the defect type and density and the extent of compensation in the crystal. It conrms that the Cd vacancy or residual impurity acceptors are dominantly compensated by In donors. The measured conduction type and carrier densities are the results of compensation between Cd vacancies and In donors and Te antisites, which are related to the In-dopant concentration and the stoichiometry for the CZT crystal. Photoluminescence (PL) spectra are used to characterize the high resistivity of an In-doped CdZnTe (CZT) crystal. The features of the PL spectra vary with changing In-dopant concentration, indicating that the In-dopant concentration has a great impact on the defect type and density and on the extent of compensation in the In-doped CZT crystal. With the addition of In donors, a new sharp neutral donor bound exciton [D0, X] peak at 1.65 eV, corresponding to In substituting defect (In+ Cd) and a new defect complex band centered at 1.505 eV, related to the singly negative complex (VCd-InCd)- are observed. Meanwhile, the intensity and position of the feature peaks in PL spectra vary with the change of the In dopant concentration, representing the changes of the defect type and density and the extent of compensation in the crystal. It conrms that the Cd vacancy or residual impurity acceptors are dominantly compensated by In donors. The measured conduction type and carrier densities are the results of compensation between Cd vacancies and In donors and Te antisites, which are related to the In-dopant concentration and the stoichiometry for the CZT crystal.

High-temperature steam oxidation behaviors of a ZrO₂/CrAlSi composite coating on Zr-2 alloy deposited by PEO duplex FCVA treatments

Qian Zhou,Yizhao Liao,Hui Li,Hu Chen,Chi Xu,Xiaoyue Jin,Wenbin Xue 한국표면공학회 2023 한국표면공학회 학술발표회 초록집 Vol.2023 No.11-1

Effect of Cu-Coated Short Carbon Fibers on the Mechanical and Electrical Properties of the Epoxy Composites

Weiwei Li,Lei Liu,Bin Shen,Yating Wu,Wenbin Hu 한국고분자학회 2012 Macromolecular Research Vol.20 No.4

In this study, short carbon fiber (SCF)-reinforced epoxy composites were prepared through changing of the fiber content (0.1-0.7 wt%). An electrodeposition process was used to produce Cu-coated SCFs. To investigate the effect of Cu-coated SCFs on the composite mechanical and electrical properties, we prepared two kinds of reinforcements:SCFs treated by 400 oC (400 oC-treated SCFs) and Cu-coated SCFs (Cu-SCFs). Fracture characteristics of the composites revealed that the Cu coating and the epoxy matrix had a better interface, meaning that the tensile and bending strength results were better in epoxy/Cu-SCFs composites than those in epoxy/400 oC-treated SCFs composites. The 400 oC-treated SCFs decreased the electrical resistivity of the epoxy composites compared to the pure epoxy. However the epoxy/Cu-SCFs composites had lower electrical resistivity than epoxy/400 oC-treated SCFs with the same fiber content.

Life-Cycle Economic Evaluation of Batteries for Electeochemical Energy Storage Systems

Zhang Donghao,Cai Xiangyu,Song Chunyan,Liu Jie,Ding Jia,Zhong Cheng,Hu Wenbin 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.5

Batteries are considered as an attractive candidate for grid-scale energy storage systems (ESSs) application due to their scalability and versatility of frequency integration, and peak/capacity adjustment. Since adding ESSs in power grid will increase the cost, the issue of economy, that whether the benefi ts from peak cutting and valley fi lling can compensate for the cost input of adding energy storage system or not, is particularly concerned. Here we show how the cost of battery deployment can potentially be minimized by carrying out an economic assessment for the cases of diff erent batteries applied in ESSs. To make this analysis, we develop a techno-economic model and apply it to the cases of ESSs with batteries in applications. Our results show that batteries could be attractive for investors even now if appropriate batteries are selected for ESSs applications. Valve regulated lead acid batteries has a lower cost of initial investment, which is suitable for the situations that are sensitive to the initial investment cost. Lithium iron phosphate (LiFePO 4 , LFP) battery can be applied in the situations with a high requirement for service life. While zinc-air batteries still have great application prospects to cope with resource depletion due to excellent performance, low cost and low pollution. The current policy debate should therefore be refocused so as to promote technological development and to encompass the removal of such barriers.