High-speed Brushless DC Motors(BLDCMs)usually adopt a sensorless control strategy and operate in three-phase six-state drive mode.However,the sampling errors of the rotor position and the driving method increase the I...High-speed Brushless DC Motors(BLDCMs)usually adopt a sensorless control strategy and operate in three-phase six-state drive mode.However,the sampling errors of the rotor position and the driving method increase the Internal Power Angle(IPA),resulting in a decrease in the efficiency of the system.Conventional IPA reduction strategies are either sensitive to motor parameters,or ignore diode freewheeling during the commutation process,or require additional current sensors.In this paper,a new strategy to reduce the IPA is proposed.Firstly,a Zero-Crossing Point(ZCP)detection method for the back-EMF without filter is proposed to reduce the sampling errors of the rotor position.Secondly,the relationship between the non-energized terminal voltage and the ZCP of the corresponding back-EMF is analyzed.The non-energized terminal voltage that has completed the diode freewheeling is divided into two triangles by half of the bus voltage.When the IPA is suppressed,the areas of the two triangles are equal.Thirdly,an advanced angle for reducing the IPA is obtained through a PI regulator which can eliminate the deviation between the two areas.Finally,both a simulation model and an experimental circuit are built to verify the proposed control strategy.展开更多
Virtual synchronous generators(VSGs)can provide voltage and frequency support to power systems due to their inertial and damping features.Unfortunately,power angle stability and fault current limitations are still cha...Virtual synchronous generators(VSGs)can provide voltage and frequency support to power systems due to their inertial and damping features.Unfortunately,power angle stability and fault current limitations are still challenging aspects of VSGs under large disturbances.Power angle stability and fault current limitations are indispensable for the safe operation of a VSG.However,in existing studies,these aspects are mostly solved as two independent problems.In this paper,the comprehensive transient stability enhancement(CTSE)control strategy for a VSG,considering power angle stability and fault current limitations is proposed.With a CTSE control,VSG's transient power angle stability is guaranteed.In addition,the steady-state and impulse components of the fault current are fully limited.Furthermore,CTSE control parameters adapted to different fault degrees are presented.Finally,simulation and experimental tests are performed to validate the performance of the proposed method.展开更多
The transient stability of a single machine to infinite-busbar power system with resistortype superconducting fault current limiters （SFCL） is analyzed under asymmetrical short-circuit fault conditions. The SFCL is ...The transient stability of a single machine to infinite-busbar power system with resistortype superconducting fault current limiters （SFCL） is analyzed under asymmetrical short-circuit fault conditions. The SFCL is considered to introduce a resistance into the three-phase circuits when faults occur. Based on the power-angle curves for different short-circuit conditions of the single-line to ground, double-line to ground and line to line short-circuit faults, the influences of the SFCLs on transient stability are analyzed in detail. The time-domain simulation of transient stability is carried out to verify the analytical results.展开更多
To increase the transmission efficiency of a wireless power transmission system while ensuring high stability and low cost,a two-degree-of-freedom two-sided control strategy to control the phase-shift duty ratio of th...To increase the transmission efficiency of a wireless power transmission system while ensuring high stability and low cost,a two-degree-of-freedom two-sided control strategy to control the phase-shift duty ratio of the triggered pulse of the primary inverter and the angle between the resonant current and the AC voltage of the secondary side is proposed.The control strategy does not require additional DC-DC converters and components,and only some parameters of the basic circuit can be adjusted.The zero-voltage switching(ZVS)of all the MOSFETs in the system can be achieved by adjusting the shift duty ratio and power angle,and the current and voltage on the load side can be adjusted in real time.First,the basic principle of the two-sided control and the relationship of the phase angle are analyzed,and the operating range is determined by analyzing the operating modes on both sides.Second,the power loss of each link is analyzed,and the best operating point is determined.Subsequently,the system structure and the control strategy of the proposed method are presented.The two-sided control strategy is verified experimentally,which shows that the system can achieve the ZVS of all the MOSFETs while maintaining a constant current output.展开更多
Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct...Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.展开更多
Traditional transient angle stability analysis methods do not fully consider the spatial characteristics of the network topology and the temporal characteristics of the time-series disturbance.Hence,a data-driven meth...Traditional transient angle stability analysis methods do not fully consider the spatial characteristics of the network topology and the temporal characteristics of the time-series disturbance.Hence,a data-driven method is proposed in this study,combining graph convolution network and long short-term memory network(GCN-LSTM)to analyze the transient power angle sta-bility by exploring the spatiotemporal disturbance char-acteristics of future power systems with high penetration of renewable energy sources(wind and solar energy)and power electronics.The key time-series electrical state quantities are considered as the initial input feature quantities and normalized using the Z-score,whereas the network adjacency matrix is constructed according to the system network topology.The normalized feature quan-tities and network adjacency matrix were used as the inputs of the GCN to obtain the spatial features,reflecting changes in the network topology.Subsequently,the spa-tial features are inputted into the LSTM network to ob-tain the temporal features,reflecting dynamic changes in the transient power angle of the generators.Finally,the spatiotemporal features are fused through a fully con-nected network to analyze the transient power angle stability of future power systems,and the softmax activa-tion cross-entropy loss functions are used to predict the stability of the samples.The proposed transient power angle stability assessment method is tested on a 500 kV AC-DC practical power system,and the simulation results show that the proposed method could effectively mine the spatiotemporal disturbance characteristics of power sys-tems. Moreover, the proposed model has higher accuracy, higher recall rate, and shorter training and testing times than traditional transient power angle stability algo-rithms.展开更多
This study presents a comprehensive impact analysis of the rotor angle stability of a proposed international connection between the Philippines and Sabah,Malaysia,as part of the Association of Southeast Asian Nations(...This study presents a comprehensive impact analysis of the rotor angle stability of a proposed international connection between the Philippines and Sabah,Malaysia,as part of the Association of Southeast Asian Nations(ASEAN)Power Grid.This study focuses on modeling and evaluating the dynamic performance of the interconnected system,considering the high penetration of renewable sources.Power flow,small signal stability,and transient stability analyses were conducted to assess the ability of the proposed linked power system models to withstand small and large disturbances,utilizing the Power Systems Analysis Toolbox(PSAT)software in MATLAB.All components used in the model are documented in the PSAT library.Currently,there is a lack of publicly available studies regarding the implementation of this specific system.Additionally,the study investigates the behavior of a system with a high penetration of renewable energy sources.Based on the findings,this study concludes that a system is generally stable when interconnection is realized,given its appropriate location and dynamic component parameters.Furthermore,the critical eigenvalues of the system also exhibited improvement as the renewable energy sources were augmented.展开更多
The d-axis inductance(Ld)of the negative-salient permanent magnet synchronous motor(NSPMSM)is larger than the q-axis inductance(Lq).Compared with the traditional motor,the NSPMSM has the characteristics of a high over...The d-axis inductance(Ld)of the negative-salient permanent magnet synchronous motor(NSPMSM)is larger than the q-axis inductance(Lq).Compared with the traditional motor,the NSPMSM has the characteristics of a high overload capacity,wide speed range,and preventing permanent magnet demagnetization.Positive d-axis current(id)is applied to control positive reluctance torque when running at base speed.When the motor is running at high speed,a relatively small id can achieve speed expansion and effectively expand the motor flux-weakening range.The use of a magnetic bridge to increase the Ld and a W-type permanent magnet to reduce the Lq is proposed in this article as a novel NSPMSM rotor structure.Firstly,the working principle of the NSPMSM was determined according to the equivalent magnetic circuit.Secondly,using the finite element method,the influence of motor structure on torque and speed performance of NSPMSM was analyzed,and the motor structure was optimized.Thirdly,the effect of the internal power factor angle on the performance of the two motors is analyzed.Finally,the short circuit simulation and analysis verified that the NSPMSM has a stronger short circuit current suppression ability without sacrificing overload ability.展开更多
Remote monitoring of transmission lines of a power system is significant for improved reliability and stability during fault conditions and protection system breakdowns.This paper proposes a smart backup monitoring sy...Remote monitoring of transmission lines of a power system is significant for improved reliability and stability during fault conditions and protection system breakdowns.This paper proposes a smart backup monitoring system for detecting and classifying the type of transmission line fault occurred in a power grid.In contradiction to conventional methods,transmission line fault occurred at any locality within power grid can be identified and classified using measurements from phasor measurement unit(PMU)at one of the generator buses.This minimal requirement makes the proposed methodology ideal for providing backup protection.Spectral analysis of equivalent power factor angle(EPFA)variation has been adopted for detecting the occurrence of fault that occurred anywhere in the grid.Classification of the type of fault occurred is achieved from the spectral coefficients with the aid of artificial intelligence.The proposed system can considerably assist system protection center(SPC)in fault localization and to restore the line at the earliest.Effectiveness of proposed system has been validated using case studies conducted on standard power system networks.展开更多
基金supported by the National Natural Science Foundation of China(No.51877006)the Key R&D Program of Shaanxi Province,China(No.2021GY-340 and 2020GY-140)the Aeronautical Science Foundation of China(No.20181953020)。
文摘High-speed Brushless DC Motors(BLDCMs)usually adopt a sensorless control strategy and operate in three-phase six-state drive mode.However,the sampling errors of the rotor position and the driving method increase the Internal Power Angle(IPA),resulting in a decrease in the efficiency of the system.Conventional IPA reduction strategies are either sensitive to motor parameters,or ignore diode freewheeling during the commutation process,or require additional current sensors.In this paper,a new strategy to reduce the IPA is proposed.Firstly,a Zero-Crossing Point(ZCP)detection method for the back-EMF without filter is proposed to reduce the sampling errors of the rotor position.Secondly,the relationship between the non-energized terminal voltage and the ZCP of the corresponding back-EMF is analyzed.The non-energized terminal voltage that has completed the diode freewheeling is divided into two triangles by half of the bus voltage.When the IPA is suppressed,the areas of the two triangles are equal.Thirdly,an advanced angle for reducing the IPA is obtained through a PI regulator which can eliminate the deviation between the two areas.Finally,both a simulation model and an experimental circuit are built to verify the proposed control strategy.
基金supported by the National Natural Science Foundation of China(51907057,52077072).
文摘Virtual synchronous generators(VSGs)can provide voltage and frequency support to power systems due to their inertial and damping features.Unfortunately,power angle stability and fault current limitations are still challenging aspects of VSGs under large disturbances.Power angle stability and fault current limitations are indispensable for the safe operation of a VSG.However,in existing studies,these aspects are mostly solved as two independent problems.In this paper,the comprehensive transient stability enhancement(CTSE)control strategy for a VSG,considering power angle stability and fault current limitations is proposed.With a CTSE control,VSG's transient power angle stability is guaranteed.In addition,the steady-state and impulse components of the fault current are fully limited.Furthermore,CTSE control parameters adapted to different fault degrees are presented.Finally,simulation and experimental tests are performed to validate the performance of the proposed method.
文摘The transient stability of a single machine to infinite-busbar power system with resistortype superconducting fault current limiters （SFCL） is analyzed under asymmetrical short-circuit fault conditions. The SFCL is considered to introduce a resistance into the three-phase circuits when faults occur. Based on the power-angle curves for different short-circuit conditions of the single-line to ground, double-line to ground and line to line short-circuit faults, the influences of the SFCLs on transient stability are analyzed in detail. The time-domain simulation of transient stability is carried out to verify the analytical results.
基金Supported by the National Natural Science Foundation of China(51877070,U20A20198,51577048)the Natural Science Foundation of Hebei Province of China(E2024208079).
文摘To increase the transmission efficiency of a wireless power transmission system while ensuring high stability and low cost,a two-degree-of-freedom two-sided control strategy to control the phase-shift duty ratio of the triggered pulse of the primary inverter and the angle between the resonant current and the AC voltage of the secondary side is proposed.The control strategy does not require additional DC-DC converters and components,and only some parameters of the basic circuit can be adjusted.The zero-voltage switching(ZVS)of all the MOSFETs in the system can be achieved by adjusting the shift duty ratio and power angle,and the current and voltage on the load side can be adjusted in real time.First,the basic principle of the two-sided control and the relationship of the phase angle are analyzed,and the operating range is determined by analyzing the operating modes on both sides.Second,the power loss of each link is analyzed,and the best operating point is determined.Subsequently,the system structure and the control strategy of the proposed method are presented.The two-sided control strategy is verified experimentally,which shows that the system can achieve the ZVS of all the MOSFETs while maintaining a constant current output.
基金Project(HEUCF110707)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(E201216)supported by Heilongjiang Natural Science Fund,China
文摘Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.
基金supported by the National Key R&D Program of China“Response-driven Intelligent Enhanced Analysis and Control for Bulk Power System Stability”(No.2021YFB2400800 and No.SGSDDKOOWJJS 2200092).
文摘Traditional transient angle stability analysis methods do not fully consider the spatial characteristics of the network topology and the temporal characteristics of the time-series disturbance.Hence,a data-driven method is proposed in this study,combining graph convolution network and long short-term memory network(GCN-LSTM)to analyze the transient power angle sta-bility by exploring the spatiotemporal disturbance char-acteristics of future power systems with high penetration of renewable energy sources(wind and solar energy)and power electronics.The key time-series electrical state quantities are considered as the initial input feature quantities and normalized using the Z-score,whereas the network adjacency matrix is constructed according to the system network topology.The normalized feature quan-tities and network adjacency matrix were used as the inputs of the GCN to obtain the spatial features,reflecting changes in the network topology.Subsequently,the spa-tial features are inputted into the LSTM network to ob-tain the temporal features,reflecting dynamic changes in the transient power angle of the generators.Finally,the spatiotemporal features are fused through a fully con-nected network to analyze the transient power angle stability of future power systems,and the softmax activa-tion cross-entropy loss functions are used to predict the stability of the samples.The proposed transient power angle stability assessment method is tested on a 500 kV AC-DC practical power system,and the simulation results show that the proposed method could effectively mine the spatiotemporal disturbance characteristics of power sys-tems. Moreover, the proposed model has higher accuracy, higher recall rate, and shorter training and testing times than traditional transient power angle stability algo-rithms.
文摘This study presents a comprehensive impact analysis of the rotor angle stability of a proposed international connection between the Philippines and Sabah,Malaysia,as part of the Association of Southeast Asian Nations(ASEAN)Power Grid.This study focuses on modeling and evaluating the dynamic performance of the interconnected system,considering the high penetration of renewable sources.Power flow,small signal stability,and transient stability analyses were conducted to assess the ability of the proposed linked power system models to withstand small and large disturbances,utilizing the Power Systems Analysis Toolbox(PSAT)software in MATLAB.All components used in the model are documented in the PSAT library.Currently,there is a lack of publicly available studies regarding the implementation of this specific system.Additionally,the study investigates the behavior of a system with a high penetration of renewable energy sources.Based on the findings,this study concludes that a system is generally stable when interconnection is realized,given its appropriate location and dynamic component parameters.Furthermore,the critical eigenvalues of the system also exhibited improvement as the renewable energy sources were augmented.
基金supported in part by the National Natural Science Foundation of China under Grant 51307045in part by the Natural Science Foundation of Heilongjiang Province of China under Grant LH2019E075in part by the Fundamental Research Funds for the Heilongjiang Province Universities under Grant KJCX201915。
文摘The d-axis inductance(Ld)of the negative-salient permanent magnet synchronous motor(NSPMSM)is larger than the q-axis inductance(Lq).Compared with the traditional motor,the NSPMSM has the characteristics of a high overload capacity,wide speed range,and preventing permanent magnet demagnetization.Positive d-axis current(id)is applied to control positive reluctance torque when running at base speed.When the motor is running at high speed,a relatively small id can achieve speed expansion and effectively expand the motor flux-weakening range.The use of a magnetic bridge to increase the Ld and a W-type permanent magnet to reduce the Lq is proposed in this article as a novel NSPMSM rotor structure.Firstly,the working principle of the NSPMSM was determined according to the equivalent magnetic circuit.Secondly,using the finite element method,the influence of motor structure on torque and speed performance of NSPMSM was analyzed,and the motor structure was optimized.Thirdly,the effect of the internal power factor angle on the performance of the two motors is analyzed.Finally,the short circuit simulation and analysis verified that the NSPMSM has a stronger short circuit current suppression ability without sacrificing overload ability.
文摘Remote monitoring of transmission lines of a power system is significant for improved reliability and stability during fault conditions and protection system breakdowns.This paper proposes a smart backup monitoring system for detecting and classifying the type of transmission line fault occurred in a power grid.In contradiction to conventional methods,transmission line fault occurred at any locality within power grid can be identified and classified using measurements from phasor measurement unit(PMU)at one of the generator buses.This minimal requirement makes the proposed methodology ideal for providing backup protection.Spectral analysis of equivalent power factor angle(EPFA)variation has been adopted for detecting the occurrence of fault that occurred anywhere in the grid.Classification of the type of fault occurred is achieved from the spectral coefficients with the aid of artificial intelligence.The proposed system can considerably assist system protection center(SPC)in fault localization and to restore the line at the earliest.Effectiveness of proposed system has been validated using case studies conducted on standard power system networks.
