Introduction:This paper uses a dynamic voltage restorer(DVR)to improve the voltage quality from voltage sags.It is difficult to satisfy various of compensation quality and time of the voltage sag by using single compe...Introduction:This paper uses a dynamic voltage restorer(DVR)to improve the voltage quality from voltage sags.It is difficult to satisfy various of compensation quality and time of the voltage sag by using single compensation method.Furthermore,high-power consumption of the phase jump compensation increases the size and cost of a dynamic voltage restorer(DVR).Methods&Results:In order to improve the compensating efficiency of DVR,an optimized compensation strategy is proposed for voltage sag of micro-grid caused by interconnection and sensitive loads.The proposed compensation strategy increases the supporting time for long voltage sags.Discussion:Firstly,the power flow and the maximum compensation time of DVR are analyzed using three basic compensation strategies.Then,the phase jump is corrected by pre-sag compensation.And a quadratic transition curve,which involves the injected voltage phases of pre-sag strategy and minimum energy strategy,is used to transform pre-sag compensation to minimum energy compensation of DVR.Conclusions:The transition utilizes the storage system to reduce the rate of discharge.As a result,the proposed strategy increases the supporting time for long voltage sags.The analytical study shows that the presented method significantly increases compensation time of DVR.The simulation results performed by MATLAB/SIMULINK also confirm the effectiveness of the proposed method.展开更多
The giant magnetostrictive rotary ultrasonic processing system(GMUPS)with a loosely-coupled contactless power transfer(LCCPT)has emerged as a high-performance technique for the processing of hard and brittle materials...The giant magnetostrictive rotary ultrasonic processing system(GMUPS)with a loosely-coupled contactless power transfer(LCCPT)has emerged as a high-performance technique for the processing of hard and brittle materials,owing to its high power density.A capacitive compensation is required to achieve the highest energy efficiency of GMUPS to provide sufficient vibration amplitude when it works in the resonance state.In this study,an accurate model of the optimal compensation capacitance is derived from a new electromechanical equivalent circuit model of the GMUPS with LCCPT,which consists of an equivalent mechanical circuit and an electrical circuit.The phase lag angle between the mechanical and electrical circuits is established,taking into account the non-negligible loss in energy conversion of giant magnetostrictive material at ultrasonic frequency.The change of system impedance characteristics and the effectiveness of the system compensation method under load are analyzed.Both idle vibration experiments and machining tests are conducted to verify the developed model.The results show that the GMUPS with optimal compensation capacitance can achieve the maximum idle vibration amplitude and smallest cutting force.In addition,the effects of magnetic conductive material and driving voltages on the phase lag angle are also evaluated.展开更多
Selecting a cost optimum subset of discrete-value dispersion compensation modules (DV-DCMs) subject to maximum module count from an available set of DV-DCMs is a NP-hard problem. We derive a novel dynamic programming ...Selecting a cost optimum subset of discrete-value dispersion compensation modules (DV-DCMs) subject to maximum module count from an available set of DV-DCMs is a NP-hard problem. We derive a novel dynamic programming algorithm with pseudo-polynomial time bound and show that DV-DCM cost re-scaling can improve the running time.展开更多
基金supported by National Nature Science Foundation under Grant 51477070,and the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘Introduction:This paper uses a dynamic voltage restorer(DVR)to improve the voltage quality from voltage sags.It is difficult to satisfy various of compensation quality and time of the voltage sag by using single compensation method.Furthermore,high-power consumption of the phase jump compensation increases the size and cost of a dynamic voltage restorer(DVR).Methods&Results:In order to improve the compensating efficiency of DVR,an optimized compensation strategy is proposed for voltage sag of micro-grid caused by interconnection and sensitive loads.The proposed compensation strategy increases the supporting time for long voltage sags.Discussion:Firstly,the power flow and the maximum compensation time of DVR are analyzed using three basic compensation strategies.Then,the phase jump is corrected by pre-sag compensation.And a quadratic transition curve,which involves the injected voltage phases of pre-sag strategy and minimum energy strategy,is used to transform pre-sag compensation to minimum energy compensation of DVR.Conclusions:The transition utilizes the storage system to reduce the rate of discharge.As a result,the proposed strategy increases the supporting time for long voltage sags.The analytical study shows that the presented method significantly increases compensation time of DVR.The simulation results performed by MATLAB/SIMULINK also confirm the effectiveness of the proposed method.
基金supported by the National Natural Science Foundation of China(Nos.51875311 and 52105458)the Tsinghua-Foshan Innovation Special Fund(No.2021THFS0204)the Huaneng Group Science and Technology Research Project(No.HNKJ22-U22YYJC08),China。
文摘The giant magnetostrictive rotary ultrasonic processing system(GMUPS)with a loosely-coupled contactless power transfer(LCCPT)has emerged as a high-performance technique for the processing of hard and brittle materials,owing to its high power density.A capacitive compensation is required to achieve the highest energy efficiency of GMUPS to provide sufficient vibration amplitude when it works in the resonance state.In this study,an accurate model of the optimal compensation capacitance is derived from a new electromechanical equivalent circuit model of the GMUPS with LCCPT,which consists of an equivalent mechanical circuit and an electrical circuit.The phase lag angle between the mechanical and electrical circuits is established,taking into account the non-negligible loss in energy conversion of giant magnetostrictive material at ultrasonic frequency.The change of system impedance characteristics and the effectiveness of the system compensation method under load are analyzed.Both idle vibration experiments and machining tests are conducted to verify the developed model.The results show that the GMUPS with optimal compensation capacitance can achieve the maximum idle vibration amplitude and smallest cutting force.In addition,the effects of magnetic conductive material and driving voltages on the phase lag angle are also evaluated.
文摘Selecting a cost optimum subset of discrete-value dispersion compensation modules (DV-DCMs) subject to maximum module count from an available set of DV-DCMs is a NP-hard problem. We derive a novel dynamic programming algorithm with pseudo-polynomial time bound and show that DV-DCM cost re-scaling can improve the running time.
