Preparation and Characterization of Hyperbranched Poly(ether ether ketone)s Suitable as Rheology Control Agents for Linear Poly(ether ether ketone)s

Zhenhua Jiang,Xiujie Li,Shuling Zhang,Fugui Zhou,Jinhui Pang,Chunfeng Zhang,Dong Sun,Jianxin Mu,Guibin Wang 한국고분자학회 2011 Macromolecular Research Vol.19 No.5

Hyperbranched poly(ether ether ketone)s (HPEEKs) that were suitable as rheology control agents for linear poly(ether ether ketone)s (LPEEKs) were first prepared via commercially available hydroquinone (A2 monomer,HQ) and synthesized 3,4',5-trifluoro-benzophenone (BB'2 monomer, TF) effortlessly. The polymerization mode of A2 + BB'2 was demonstrated by MS. Moreover, FTIR, 1H NMR, 13C NMR, and 19F NMR spectroscopy revealed the structure and degree of branching (DB) of the resulting polymers. In comparison with A2 + B3 approach, HPEEK prepared using an A2 + BB'2 strategy possessed a higher molecular weight, and improved the melt processability of LPEEK. Remarkably, with the addition of HPEEK, the mechanical properties of LPEEK increased with a HPEEK content of 5%. The improved mechanical properties were attributed to the good miscibility. Moreover, the addition of HPEEK did not decrease the thermal stability of LPEEK.

New Strategy for Eliminating Zero-sequence Circulating Current between Parallel Operating Three-level NPC Voltage Source Inverters

Li, Kai,Dong, Zhenhua,Wang, Xiaodong,Peng, Chao,Deng, Fujin,Guerrero, Josep,Vasquez, Juan The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

A novel strategy based on a zero common mode voltage pulse-width modulation (ZCMV-PWM) technique and zero-sequence circulating current (ZSCC) feedback control is proposed in this study to eliminate ZSCCs between three-level neutral point clamped (NPC) voltage source inverters, with common AC and DC buses, that are operating in parallel. First, an equivalent model of ZSCC in a three-phase three-level NPC inverter paralleled system is developed. Second, on the basis of the analysis of the excitation source of ZSCCs, i.e., the difference in common mode voltages (CMVs) between paralleled inverters, the ZCMV-PWM method is presented to reduce CMVs, and a simple electric circuit is adopted to control ZSCCs and neutral point potential. Finally, simulation and experiment are conducted to illustrate effectiveness of the proposed strategy. Results show that ZSCCs between paralleled inverters can be eliminated effectively under steady and dynamic states. Moreover, the proposed strategy exhibits the advantage of not requiring carrier synchronization. It can be utilized in inverters with different types of filter.

New Strategy for Eliminating Zero-sequence Circulating Current between Parallel Operating Three-level NPC Voltage Source Inverters

Kai Li,Zhenhua Dong,Xiaodong Wang,Chao Peng,Fujin Deng,Josep M. Guerrero,Juan Vasquez 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

A novel strategy based on a zero common mode voltage pulse-width modulation (ZCMV-PWM) technique and zero-sequence circulating current (ZSCC) feedback control is proposed in this study to eliminate ZSCCs between three-level neutral point clamped (NPC) voltage source inverters, with common AC and DC buses, that are operating in parallel. First, an equivalent model of ZSCC in a three-phase three-level NPC inverter paralleled system is developed. Second, on the basis of the analysis of the excitation source of ZSCCs, i.e., the difference in common mode voltages (CMVs) between paralleled inverters, the ZCMV-PWM method is presented to reduce CMVs, and a simple electric circuit is adopted to control ZSCCs and neutral point potential. Finally, simulation and experiment are conducted to illustrate effectiveness of the proposed strategy. Results show that ZSCCs between paralleled inverters can be eliminated effectively under steady and dynamic states. Moreover, the proposed strategy exhibits the advantage of not requiring carrier synchronization. It can be utilized in inverters with different types of filter.

A Dynamic Adjustment Method of Service Function Chain Resource Configuration

( Xiaoyang Han ),( Xiangru Meng ),( Zhenhua Yu ),( Dong Zhai ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.8

In the network function virtualization environment, dynamic changes in network traffic will lead to the dynamic changes of service function chain resource demand, which entails timely dynamic adjustment of service function chain resource configuration. At present, most researches solve this problem through virtual network function migration and link rerouting, and there exist some problems such as long service interruption time, excessive network operation cost and high penalty. This paper proposes a dynamic adjustment method of service function chain resource configuration for the dynamic changes of network traffic. First, a dynamic adjustment request of service function chain is generated according to the prediction of network traffic. Second, a dynamic adjustment strategy of service function chain resource configuration is determined according to substrate network resources. Finally, the resource configuration of a service function chain is pre-adjusted according to the dynamic adjustment strategy. Virtual network functions combination and virtual machine reusing are fully considered in this process. The experimental results show that this method can reduce the influence of service function chain resource configuration dynamic adjustment on quality of service, reduce network operation cost and improve the revenue of service providers.

Novel Model Predictive Control Method to Eliminate Common-mode Voltage for Three-level T-type Inverters Considering Dead-time Effects

Xiaodong Wang,Jianxiao Zou,Zhenhua Dong,Chuan Xie,Kai Li,Josep M. Guerrero 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5

This paper proposes a novel common-mode voltage (CMV) elimination (CMV-EL) method based on model predictive control (MPC) to eliminate CMV for three-level T-type inverters (3LT²Is). In the proposed MPC method, only six medium and one zero voltage vectors (VVs) (6MV1Z) that generate zero CMV are considered as candidates to perform the MPC. Moreover, the influence of dead-time effects on the CMV of the MPC-based 6MV1Z method is investigated, and the candidate VVs are redesigned by pre-excluding the VVs that will cause CMV fluctuations during the dead time from 6MV1Z. Only three or five VVs are included to perform optimization in every control period, which can significantly reduce the computational complexity. Thus, a small control period can be implemented in the practical applications to achieve improved grid current performance. With the proposed CMV-EL method, the CMV of the 3LT²Is can be effectively eliminated. In addition, the proposed CMV-EL method can balance the neutral point potentials (NPPs) and yield satisfactory performance for grid current tracking in steady and dynamic states. Simulation and experimental results are presented to verify the effectiveness of the proposed method.

Novel Model Predictive Control Method to Eliminate Common-mode Voltage for Three-level T-type Inverters Considering Dead-time Effects

Wang, Xiaodong,Zou, Jianxiao,Dong, Zhenhua,Xie, Chuan,Li, Kai,Guerrero, Josep M. The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5

This paper proposes a novel common-mode voltage (CMV) elimination (CMV-EL) method based on model predictive control (MPC) to eliminate CMV for three-level T-type inverters (3LT2Is). In the proposed MPC method, only six medium and one zero voltage vectors (VVs) (6MV1Z) that generate zero CMV are considered as candidates to perform the MPC. Moreover, the influence of dead-time effects on the CMV of the MPC-based 6MV1Z method is investigated, and the candidate VVs are redesigned by pre-excluding the VVs that will cause CMV fluctuations during the dead time from 6MV1Z. Only three or five VVs are included to perform optimization in every control period, which can significantly reduce the computational complexity. Thus, a small control period can be implemented in the practical applications to achieve improved grid current performance. With the proposed CMV-EL method, the CMV of the $3LT^2Is$ can be effectively eliminated. In addition, the proposed CMV-EL method can balance the neutral point potentials (NPPs) and yield satisfactory performance for grid current tracking in steady and dynamic states. Simulation and experimental results are presented to verify the effectiveness of the proposed method.