The integration of renewable energy sources(RESs)with inverter interfaces has fundamentally reshaped power system dynamics,challenging traditional stability analysis frameworks designed for synchronous generator-domin...The integration of renewable energy sources(RESs)with inverter interfaces has fundamentally reshaped power system dynamics,challenging traditional stability analysis frameworks designed for synchronous generator-dominated grids.Conventional classifica-tions,which decouple voltage,frequency,and rotor angle stability,fail to address the emerging strong voltage‒angle coupling effects caused by RES dynamics.This coupling introduces complex oscillation modes and undermines system robustness,neces-sitating novel stability assessment tools.Recent studies focus on eigenvalue distributions and damping redistribution but lack quantitative criteria and interpretative clarity for coupled stability.This work proposes a transient energy-based framework to resolve these gaps.By decomposing transient energy into subsystem-dissipated components and coupling-induced energy exchange,the method establishes stability criteria compatible with a broad variety of inverter-interfaced devices while offering an intuitive energy-based interpretation for engineers.The coupling strength is also quantified by defining the relative coupling strength index,which is directly related to the transient energy interpretation of the coupled stability.Angle‒voltage coupling may induce instability by injecting transient energy into the system,even if the individual phase angle and voltage dynamics themselves are stable.The main contributions include a systematic stability evaluation framework and an energy decomposition approach that bridges theoretical analysis with practical applicability,addressing the urgent need for tools for managing modern power system evolving stability challenges.展开更多
On the basis of the theoretical analysis of a single-machine infinite-bus （SMIB）, using the modified linearized Phil- lips-Heffron model installed with unified power flow controller （UPFC）, the potential of the UP...On the basis of the theoretical analysis of a single-machine infinite-bus （SMIB）, using the modified linearized Phil- lips-Heffron model installed with unified power flow controller （UPFC）, the potential of the UPFC supplementary controller to enhance the dynamic stability of a power system is evaluated by measuring the electromechanical controllability through singular value decomposition （SVD） analysis. This controller is tuned to simultaneously shift the undamped electromeehanical modes to a prescribed zone in the s-plane. The problem of robust UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multi-objective function comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using gravitational search algorithm （GSA） that has a strong ability to find the most optimistic results. The different loading conditions are simulated on a SMIB system and the rotor speed deviation, internal voltage deviation, DC voltage deviation and electrical power deviation responses are studied with the effect of this flexible AC transmission systems （FACTS） controller. The results reveal that the tuned GSA based UPFC controller using the proposed multi-objective function has an excellent capability in damping power system with low frequency oscillations and greatly enhances the dynamic stability of the power systems.展开更多
In order to analyze power system stability in environment of WAMS(wide area measurement system),a new steady state stability model with time-varying delay was proposed for power system.The factors of exciter and power...In order to analyze power system stability in environment of WAMS(wide area measurement system),a new steady state stability model with time-varying delay was proposed for power system.The factors of exciter and power system stabilizer with delay were introduced into analytical model.To decrease conservativeness of stability analysis,an improved Lyapunov-Krasovskii functional was constructed,and then a new delay-dependent steady state stability criterion for power system,which overcomes the disadvantages of eigenvalue computation method,was derived.The proposed model and criterion were tested on synchronous-machine infinite-bus power system.The test results demonstrate that Lyapunov-Krasovskii functional based power system stability analysis method is applicable and effective in the analysis of time delay power system stability.展开更多
Quickly getting back the synchronism of a disturbed interconnected multi-area power system due to variations in loading condition is recognized as prominent issue related to automatic generation control(AGC).In this r...Quickly getting back the synchronism of a disturbed interconnected multi-area power system due to variations in loading condition is recognized as prominent issue related to automatic generation control(AGC).In this regard,AGC system based on fuzzy logic,i.e.,so-called FLAGC can introduce an effectual performance to suppress the dynamic oscillations of tie-line power exchanges and frequency in multi-area interconnected power system.Apart from that,simultaneous coordination scheme based on particle swarm optimization(PSO)along with real coded genetic algorithm(RCGA)is suggested to coordinate FLAGCs of the all areas.To clarify the high efficiency of aforementioned strategy,two different interconnected multi-area power systems,i.e.,three-area hydro-thermal power system and five-area thermal power system have been taken into account for relevant studies.The potency of this strategy has been thoroughly dealt with by considering the step load perturbation(SLP)in both the under study power systems.To sum up,the simulation results have plainly revealed dynamic performance of FLAGC as compared with conventional AGC(CAGC)in each power system in order to damp out the power system oscillations.展开更多
For solving the dynamic instability problem of Yunnan Provincial Power System (YNPS) and the South China Interconnected Power System (SCIPS), Lubuge Hydropower Station was chosen to install Power System Stabilizer (PS...For solving the dynamic instability problem of Yunnan Provincial Power System (YNPS) and the South China Interconnected Power System (SCIPS), Lubuge Hydropower Station was chosen to install Power System Stabilizer (PSS). This paper introduces the principles and methods of parameter selection for PSS, in addition to field test. The test results show that the PSS installed can significantly improve the system damping.展开更多
Automatic line reclosing schemes used in an extra-high-voltage power system is an economical and effective means to maintain transient stability. A novel method is proposed in the paper to adaptively optimize the auto...Automatic line reclosing schemes used in an extra-high-voltage power system is an economical and effective means to maintain transient stability. A novel method is proposed in the paper to adaptively optimize the automatic line reclosing time after a transient fault for enhancement of interconnected power system transient stability. Both the study on the transient energy over network and the structure-preserving multi-machines power system model illustrate that the excessive convergence of potential energy on the lines with a certain cutset deteriorate power system stability, and therefore, an optimum line reclosing strategy can be established by minimizing the change in transient potential energy distribution across a cutset lines in the vicinity of the faulty line as an optimization target, and the optimal reclosure time is set to the time of minimum line phase angle difference. Without any pre-determined knowledge, the method is adaptive to various power system operation modes and fault conditions, and easy to implement because only a limited number of data measured at one location on a tie-line linking sub-networks are required. Simulations have been performed with the OMIB(One Machine and Infinite Bus System) and a real inter-connected power system to verify the applicability of the method proposed.展开更多
Power system security and stability is very important to national economy and people's life,so it has been paid great attention by governments and power utilities.In order to avoid huge economic losses caused by l...Power system security and stability is very important to national economy and people's life,so it has been paid great attention by governments and power utilities.In order to avoid huge economic losses caused by large-scale blackouts,State Grid Corporation of China(SGCC)have invested sufficient human and financial resources to carry out related researches,and remarkable achievements have been achieved.However,large grid stability problem is very complex,it is still difficult to completely avoid the blackouts.展开更多
Hybrid power sources have attracted much attention in the electric vehicle area. Particularly, electric-electric hybrid powertrain system consisting of supercapacitor modules and lithium-ion batteries has been widely ...Hybrid power sources have attracted much attention in the electric vehicle area. Particularly, electric-electric hybrid powertrain system consisting of supercapacitor modules and lithium-ion batteries has been widely applied because of the high power density of supercapacitors. In this study, we design a hybrid powertrain system containing two porous carbon electrode-based supercapacitor modules in parallel and one lithium ion battery pack. With the construction of the testing station, the performance and stability of the used supercapacitor modules are investigated in correlation with the structure of the supercapacitor and the nature of the electrode materials applied. It has been shown that the responding time for voltage vibration from 20 V to 48.5 V during charging or discharging process decreases from about 490 s to 94 s with the increase in applied current from 20 A to 100 A. The capacitance of the capacitor modules is nearly independent on the applied current. With the designed setup, the energy efficiency can reach as high as 0.99. The results described here provide a guidance for material selection of supercapacitors and optimized controlling strategy for hybrid power system applied in electric vehicles.展开更多
This paper focuses on the small signal stability analysis of Doubly-Fed Induction Generator (DFIG) fed wind power system under three modes of operation. The system stability is affected by the influence of electromech...This paper focuses on the small signal stability analysis of Doubly-Fed Induction Generator (DFIG) fed wind power system under three modes of operation. The system stability is affected by the influence of electromechanical oscillations, which can be damped using Power System Stabilizer (PSS). A detailed modeling of DFIG fed wind system including controller has been carried out. The damping controller is designed using fuzzy logic to damp the oscillatory modes for stability. The robust performance of the system with controllers has been evaluated using eigen value analysis and time domain simulations under various disturbances and wind speeds. The effectiveness of the proposed fuzzy based PSS is compared with the performance of conventional PSS implemented in the wind system.展开更多
A method of enhancing power system stability for a single machine to infinite bus power system is presented. The technique used compromises the effectiveness of Proportional-Integral-Derivative controller （PID）. In ...A method of enhancing power system stability for a single machine to infinite bus power system is presented. The technique used compromises the effectiveness of Proportional-Integral-Derivative controller （PID）. In order to satisfy the damping characteristics for the proposed power system over a wide range of operating interval, rotational speed, torque angle and terminal voltage signals of the synchronous machine are utilized as control signals of the system. It is well known that these variables have significant effects on damping the generators shaft mechanical oscillations, it＇ll be so easy to validate the most suitable controller as seen from the simulation results.展开更多
In the stability study of the regional structures in the area of the Longyang Gorge Hydroelectrical Power Station, a model of the current stress-deformation field of the area was constructed based on analyses of avail...In the stability study of the regional structures in the area of the Longyang Gorge Hydroelectrical Power Station, a model of the current stress-deformation field of the area was constructed based on analyses of available data of regional surveys and historical earthquakes and field investigations of active faults and ancient earthquakes. This model was examined and verified by physical and mathematical simulation experiments, and quantitative relations and data were obtained.展开更多
In this paper,a strength-constrained unit commitment(UC)model incorporating system strength constraints based on the weighted short-circuit ratio(WSCR)is proposed.This model facilitates the comprehensive assessment of...In this paper,a strength-constrained unit commitment(UC)model incorporating system strength constraints based on the weighted short-circuit ratio(WSCR)is proposed.This model facilitates the comprehensive assessment of area-wide system strength in power systems with high inverter-based resource(IBR)penetration,thereby contributing to the mitigation of weak grid issues.Unlike traditional models,this approach considers the interactions among multiple IBRs.The UC problem is initially formulated as a mixed-integer nonlinear programming(MINLP)model,reflecting WSCR and bus impedance matrix modification constraints.To enhance computational tractability,the model is transformed into a mixed-integer linear programming(MILP)form.The effectiveness of the proposed approach is validated through simulations on the IEEE 5-bus,IEEE 39-bus,and a modified Korean power system,demonstrating the ability of the proposed UC model enhancing system strength compared to the conventional methodologies.展开更多
A miniaturized atomic spin-exchange relaxation-free(SERF)co-magnetometer measures angular velocity using a balanced polarimetry technique which is easily affected by the laser power.A laser power closed-loop control s...A miniaturized atomic spin-exchange relaxation-free(SERF)co-magnetometer measures angular velocity using a balanced polarimetry technique which is easily affected by the laser power.A laser power closed-loop control system is usually used to suppress the fluctuation of the laser power.Although this method can greatly eliminate the fluctuation of the in-loop laser power(the feedback laser),it cannot fully eliminate the fluctuation of the out-of-loop laser power(the signal measurement laser).This leads to SERF gyroscope laser power error,which reduces the inertial measurement accuracy.In this paper,the influence mechanism of the split ratio(the ratio of the in-loop laser power to the out-of-loop laser power)on the out-of-loop laser power control accuracy is analyzed by establishing a laser power transmission model inside and outside the loop.Moreover,a method is developed to improve the out-of-loop laser power stability by optimizing the split ratio.Comparative experiments showed that the relative Allan standard deviation of the out-of-loop laser power decreased from 5.48×10^(-6)to 2.62×10^(-6)at 100 s,and decreased by an order of magnitude from 1.76×10^(-5)to 3.30×10^(-6)at1000 s.Correspondingly,the rate ramp coefficient in the Allan standard deviation curve of the SERF gyroscope test data decreased from 1.312[(°/h)/h]to 0.246[(°/h)/h].And the bias stability increased from 0.032°/h to 0.019°/h.Therefore,the proposed method can improve the long-term stability of the probe laser power and effectively suppress the laser power error of the SERF gyroscope.展开更多
A novel technique for the optimal tuning of power system stabilizer (PSS) was proposed,by integrating the modified particle swarm optimization (MPSO) with the chaos (MPSOC).Firstly,a modification in the particle swarm...A novel technique for the optimal tuning of power system stabilizer (PSS) was proposed,by integrating the modified particle swarm optimization (MPSO) with the chaos (MPSOC).Firstly,a modification in the particle swarm optimization (PSO) was made by introducing passive congregation (PC).It helps each swarm member in receiving a multitude of information from other members and thus decreases the possibility of a failed attempt at detection or a meaningless search.Secondly,the MPSO and chaos were hybridized (MPSOC) to improve the global searching capability and prevent the premature convergence due to local minima.The robustness of the proposed PSS tuning technique was verified on a multi-machine power system under different operating conditions.The performance of the proposed MPSOC was compared to the MPSO,PSO and GA through eigenvalue analysis,nonlinear time-domain simulation and statistical tests.Eigenvalue analysis shows acceptable damping of the low-frequency modes and time domain simulations also show that the oscillations of synchronous machines can be rapidly damped for power systems with the proposed PSSs.The results show that the presented algorithm has a faster convergence rate with higher degree of accuracy than the GA,PSO and MPSO.展开更多
Small signal instability may cause severe accidents for power system if it can not be dear correctly and timely. How to maintain power system stable under small signal disturbance is a big challenge for power system o...Small signal instability may cause severe accidents for power system if it can not be dear correctly and timely. How to maintain power system stable under small signal disturbance is a big challenge for power system operators and dispatchers. Time delay existing in signal transmission process makes the problem more complex. Conventional eigenvalue analysis method neglects time delay influence and can not precisely describe power system dynamic behaviors. In this work, a modified small signal stability model considering time varying delay influence was constructed and a new time delay controller was proposed to stabilize power system under disturbance. By Lyapunov-Krasovskii function, the control law in the form of nonlinear matrix inequality （NLMI） was derived. Considering synthesis method limitation for time delay controller at present, both parameter adjustment method by using linear matrix inequality （LMI） solver and iteration searching method by solving nonlinear minimization problem were suggested to design the controller. Simulation tests were carried out on synchronous-machine infinite-bus power system. Satisfactory test results verify the correctness of the proposed model and the feasibility of the stabilization approach.展开更多
Power system stability is enhanced through a novel stabilizer developed around an adaptive fuzzy sliding mode approach which applies the Nussbaum gain to a nonlinear model of a single-machine infinite-bus （SMIB） and...Power system stability is enhanced through a novel stabilizer developed around an adaptive fuzzy sliding mode approach which applies the Nussbaum gain to a nonlinear model of a single-machine infinite-bus （SMIB） and multi-machine power system stabilizer subjected to a three phase fault. The Nussbaum gain is used to avoid the positive sign constraint and the problem of controllability of the system. A comparative simulation study is presented to evaluate the achieved performance.展开更多
A frequency servo system-on-chip(FS-SoC)featuring output power stabilization technology is introduced in this study for high-precision and miniaturized cesium(Cs)atomic clocks.The proposed power stabilization loop(PSL...A frequency servo system-on-chip(FS-SoC)featuring output power stabilization technology is introduced in this study for high-precision and miniaturized cesium(Cs)atomic clocks.The proposed power stabilization loop(PSL)technique,incorporating an off-chip power detector(PD),ensures that the output power of the FS-SoC remains stable,mitigating the impact of power fluctuations on the atomic clock's stability.Additionally,a one-pulse-per-second(1PPS)is employed to syn-chronize the clock with GPS.Fabricated using 65 nm CMOS technology,the measured phase noise of the FS-SoC stands at-69.5 dBc/Hz@100 Hz offset and-83.9 dBc/Hz@1 kHz offset,accompanied by a power dissipation of 19.7 mW.The Cs atomic clock employing the proposed FS-SoC and PSL obtains an Allan deviation of 1.7×10^(-11) with 1-s averaging time.展开更多
The variable polarity power source which incorporates a constant current power and a secondary inverter does not need special apparatus for stabilizing arc. The pulse for stabilizing arc is created by the circuit stru...The variable polarity power source which incorporates a constant current power and a secondary inverter does not need special apparatus for stabilizing arc. The pulse for stabilizing arc is created by the circuit structure itself. The paper analyzes the principle of acquiring the pulse, provides the better method to improve the arc stabilization under smaller welding current. Test shows the arc is highly stable , and the process has no high frequency electromagnetic interference, which is suitable for automatic welding case.展开更多
Torus bifurcation is a relatively complicated bifurcation caused by a pair of complex conjugate Floquet multipliers coming out of unit circle on the Poincare section. A three-bus system is employed to reveal the relat...Torus bifurcation is a relatively complicated bifurcation caused by a pair of complex conjugate Floquet multipliers coming out of unit circle on the Poincare section. A three-bus system is employed to reveal the relationship between torus bifurcation and some complex dynamics. Based on theoretical analysis and simulation studies, it is found that torus bifurcation is a typical route to chaos in power system. Some complex dynamics usually occur after a torus bifurcation, such as self-organization, deep bifurcations, exquisite structure, coexistence of chaos and divergence. It is also found that chaos has close relationship with various instability scenarios of power systems. Studies of this paper are helpful to understand the mechanism of torus bifurcation in power system and relationship of chaos and power system instabilities.展开更多
The parameters of power system slowly change with time due to environmental effects or may change rapidly due to faults. It is preferable that the control technique in this system possesses robustness for various faul...The parameters of power system slowly change with time due to environmental effects or may change rapidly due to faults. It is preferable that the control technique in this system possesses robustness for various fault conditions and disturbances. The used flexible alternating current transmission system （FACTS） in this paper is an advanced super-conducting magnetic energy storage （ASMES）. Many control techniques that use ASMES to improve power system stability have been proposed. While fuzzy controller has proven its value in some applications, the researches applying fuzzy controller with ASMES have been actively reported. However, it is sometimes very difficult to specify the rule base for some plants, when the parameters change. To solve this problem, a fuzzy model reference learning controller （FMRLC） is proposed in this paper, which investigates multi-input multi-output FMRLC for time-variant nonlinear system. This control method provides the motivation for adaptive fuzzy control, where the focus is on the automatic online synthesis and tuning of fuzzy controller parameters （i.e., using online data to continually learn the fuzzy controller that will ensure that the performance objectives are met）. Simulation results show that the proposed robust controller is able to work with nonlinear and nonstationary power system （i.e., single machine-infinite bus （SMIB） system）, under various fault conditions and disturbances.展开更多
基金supported by the Science and Technology Project of China Southern Power Grid Co.,Ltd under Grant 036000KC23090004(GDKJXM20231026).
文摘The integration of renewable energy sources(RESs)with inverter interfaces has fundamentally reshaped power system dynamics,challenging traditional stability analysis frameworks designed for synchronous generator-dominated grids.Conventional classifica-tions,which decouple voltage,frequency,and rotor angle stability,fail to address the emerging strong voltage‒angle coupling effects caused by RES dynamics.This coupling introduces complex oscillation modes and undermines system robustness,neces-sitating novel stability assessment tools.Recent studies focus on eigenvalue distributions and damping redistribution but lack quantitative criteria and interpretative clarity for coupled stability.This work proposes a transient energy-based framework to resolve these gaps.By decomposing transient energy into subsystem-dissipated components and coupling-induced energy exchange,the method establishes stability criteria compatible with a broad variety of inverter-interfaced devices while offering an intuitive energy-based interpretation for engineers.The coupling strength is also quantified by defining the relative coupling strength index,which is directly related to the transient energy interpretation of the coupled stability.Angle‒voltage coupling may induce instability by injecting transient energy into the system,even if the individual phase angle and voltage dynamics themselves are stable.The main contributions include a systematic stability evaluation framework and an energy decomposition approach that bridges theoretical analysis with practical applicability,addressing the urgent need for tools for managing modern power system evolving stability challenges.
文摘On the basis of the theoretical analysis of a single-machine infinite-bus （SMIB）, using the modified linearized Phil- lips-Heffron model installed with unified power flow controller （UPFC）, the potential of the UPFC supplementary controller to enhance the dynamic stability of a power system is evaluated by measuring the electromechanical controllability through singular value decomposition （SVD） analysis. This controller is tuned to simultaneously shift the undamped electromeehanical modes to a prescribed zone in the s-plane. The problem of robust UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multi-objective function comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using gravitational search algorithm （GSA） that has a strong ability to find the most optimistic results. The different loading conditions are simulated on a SMIB system and the rotor speed deviation, internal voltage deviation, DC voltage deviation and electrical power deviation responses are studied with the effect of this flexible AC transmission systems （FACTS） controller. The results reveal that the tuned GSA based UPFC controller using the proposed multi-objective function has an excellent capability in damping power system with low frequency oscillations and greatly enhances the dynamic stability of the power systems.
基金Projects(60425310,60974026) supported by the National Natural Science Foundation of ChinaProject(200805330004) supported by the Doctor Subject Foundation of China+1 种基金Projects(NCET-06-0679) supported by Program for New Century Excellent Talents in UniversityProject(08JJ1010) supported by the Natural Science Foundation of Hunan Province,China
文摘In order to analyze power system stability in environment of WAMS(wide area measurement system),a new steady state stability model with time-varying delay was proposed for power system.The factors of exciter and power system stabilizer with delay were introduced into analytical model.To decrease conservativeness of stability analysis,an improved Lyapunov-Krasovskii functional was constructed,and then a new delay-dependent steady state stability criterion for power system,which overcomes the disadvantages of eigenvalue computation method,was derived.The proposed model and criterion were tested on synchronous-machine infinite-bus power system.The test results demonstrate that Lyapunov-Krasovskii functional based power system stability analysis method is applicable and effective in the analysis of time delay power system stability.
文摘Quickly getting back the synchronism of a disturbed interconnected multi-area power system due to variations in loading condition is recognized as prominent issue related to automatic generation control(AGC).In this regard,AGC system based on fuzzy logic,i.e.,so-called FLAGC can introduce an effectual performance to suppress the dynamic oscillations of tie-line power exchanges and frequency in multi-area interconnected power system.Apart from that,simultaneous coordination scheme based on particle swarm optimization(PSO)along with real coded genetic algorithm(RCGA)is suggested to coordinate FLAGCs of the all areas.To clarify the high efficiency of aforementioned strategy,two different interconnected multi-area power systems,i.e.,three-area hydro-thermal power system and five-area thermal power system have been taken into account for relevant studies.The potency of this strategy has been thoroughly dealt with by considering the step load perturbation(SLP)in both the under study power systems.To sum up,the simulation results have plainly revealed dynamic performance of FLAGC as compared with conventional AGC(CAGC)in each power system in order to damp out the power system oscillations.
文摘For solving the dynamic instability problem of Yunnan Provincial Power System (YNPS) and the South China Interconnected Power System (SCIPS), Lubuge Hydropower Station was chosen to install Power System Stabilizer (PSS). This paper introduces the principles and methods of parameter selection for PSS, in addition to field test. The test results show that the PSS installed can significantly improve the system damping.
文摘Automatic line reclosing schemes used in an extra-high-voltage power system is an economical and effective means to maintain transient stability. A novel method is proposed in the paper to adaptively optimize the automatic line reclosing time after a transient fault for enhancement of interconnected power system transient stability. Both the study on the transient energy over network and the structure-preserving multi-machines power system model illustrate that the excessive convergence of potential energy on the lines with a certain cutset deteriorate power system stability, and therefore, an optimum line reclosing strategy can be established by minimizing the change in transient potential energy distribution across a cutset lines in the vicinity of the faulty line as an optimization target, and the optimal reclosure time is set to the time of minimum line phase angle difference. Without any pre-determined knowledge, the method is adaptive to various power system operation modes and fault conditions, and easy to implement because only a limited number of data measured at one location on a tie-line linking sub-networks are required. Simulations have been performed with the OMIB(One Machine and Infinite Bus System) and a real inter-connected power system to verify the applicability of the method proposed.
文摘Power system security and stability is very important to national economy and people's life,so it has been paid great attention by governments and power utilities.In order to avoid huge economic losses caused by large-scale blackouts,State Grid Corporation of China(SGCC)have invested sufficient human and financial resources to carry out related researches,and remarkable achievements have been achieved.However,large grid stability problem is very complex,it is still difficult to completely avoid the blackouts.
基金Funded by the National Key Basic Research Development Program of China(973 Plan)(No.2013CB632505)the National Natural Science Foundation of China(51477125)the Scientific Research Foundation for the Returned Overseas Chinese Scholars
文摘Hybrid power sources have attracted much attention in the electric vehicle area. Particularly, electric-electric hybrid powertrain system consisting of supercapacitor modules and lithium-ion batteries has been widely applied because of the high power density of supercapacitors. In this study, we design a hybrid powertrain system containing two porous carbon electrode-based supercapacitor modules in parallel and one lithium ion battery pack. With the construction of the testing station, the performance and stability of the used supercapacitor modules are investigated in correlation with the structure of the supercapacitor and the nature of the electrode materials applied. It has been shown that the responding time for voltage vibration from 20 V to 48.5 V during charging or discharging process decreases from about 490 s to 94 s with the increase in applied current from 20 A to 100 A. The capacitance of the capacitor modules is nearly independent on the applied current. With the designed setup, the energy efficiency can reach as high as 0.99. The results described here provide a guidance for material selection of supercapacitors and optimized controlling strategy for hybrid power system applied in electric vehicles.
文摘This paper focuses on the small signal stability analysis of Doubly-Fed Induction Generator (DFIG) fed wind power system under three modes of operation. The system stability is affected by the influence of electromechanical oscillations, which can be damped using Power System Stabilizer (PSS). A detailed modeling of DFIG fed wind system including controller has been carried out. The damping controller is designed using fuzzy logic to damp the oscillatory modes for stability. The robust performance of the system with controllers has been evaluated using eigen value analysis and time domain simulations under various disturbances and wind speeds. The effectiveness of the proposed fuzzy based PSS is compared with the performance of conventional PSS implemented in the wind system.
文摘A method of enhancing power system stability for a single machine to infinite bus power system is presented. The technique used compromises the effectiveness of Proportional-Integral-Derivative controller （PID）. In order to satisfy the damping characteristics for the proposed power system over a wide range of operating interval, rotational speed, torque angle and terminal voltage signals of the synchronous machine are utilized as control signals of the system. It is well known that these variables have significant effects on damping the generators shaft mechanical oscillations, it＇ll be so easy to validate the most suitable controller as seen from the simulation results.
文摘In the stability study of the regional structures in the area of the Longyang Gorge Hydroelectrical Power Station, a model of the current stress-deformation field of the area was constructed based on analyses of available data of regional surveys and historical earthquakes and field investigations of active faults and ancient earthquakes. This model was examined and verified by physical and mathematical simulation experiments, and quantitative relations and data were obtained.
基金partially supported by Korea Electrotechnology Research Institute(KERI)Primary research program through the National Research Council of Science&Technology(NST)funded by the Ministry of Science and ICT(MSIT)(No.25A01038)partially supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.RS-2024-00218377).
文摘In this paper,a strength-constrained unit commitment(UC)model incorporating system strength constraints based on the weighted short-circuit ratio(WSCR)is proposed.This model facilitates the comprehensive assessment of area-wide system strength in power systems with high inverter-based resource(IBR)penetration,thereby contributing to the mitigation of weak grid issues.Unlike traditional models,this approach considers the interactions among multiple IBRs.The UC problem is initially formulated as a mixed-integer nonlinear programming(MINLP)model,reflecting WSCR and bus impedance matrix modification constraints.To enhance computational tractability,the model is transformed into a mixed-integer linear programming(MILP)form.The effectiveness of the proposed approach is validated through simulations on the IEEE 5-bus,IEEE 39-bus,and a modified Korean power system,demonstrating the ability of the proposed UC model enhancing system strength compared to the conventional methodologies.
基金the National Natural Science Foundation of China(Grant Nos.61925301 and 62103026).
文摘A miniaturized atomic spin-exchange relaxation-free(SERF)co-magnetometer measures angular velocity using a balanced polarimetry technique which is easily affected by the laser power.A laser power closed-loop control system is usually used to suppress the fluctuation of the laser power.Although this method can greatly eliminate the fluctuation of the in-loop laser power(the feedback laser),it cannot fully eliminate the fluctuation of the out-of-loop laser power(the signal measurement laser).This leads to SERF gyroscope laser power error,which reduces the inertial measurement accuracy.In this paper,the influence mechanism of the split ratio(the ratio of the in-loop laser power to the out-of-loop laser power)on the out-of-loop laser power control accuracy is analyzed by establishing a laser power transmission model inside and outside the loop.Moreover,a method is developed to improve the out-of-loop laser power stability by optimizing the split ratio.Comparative experiments showed that the relative Allan standard deviation of the out-of-loop laser power decreased from 5.48×10^(-6)to 2.62×10^(-6)at 100 s,and decreased by an order of magnitude from 1.76×10^(-5)to 3.30×10^(-6)at1000 s.Correspondingly,the rate ramp coefficient in the Allan standard deviation curve of the SERF gyroscope test data decreased from 1.312[(°/h)/h]to 0.246[(°/h)/h].And the bias stability increased from 0.032°/h to 0.019°/h.Therefore,the proposed method can improve the long-term stability of the probe laser power and effectively suppress the laser power error of the SERF gyroscope.
文摘A novel technique for the optimal tuning of power system stabilizer (PSS) was proposed,by integrating the modified particle swarm optimization (MPSO) with the chaos (MPSOC).Firstly,a modification in the particle swarm optimization (PSO) was made by introducing passive congregation (PC).It helps each swarm member in receiving a multitude of information from other members and thus decreases the possibility of a failed attempt at detection or a meaningless search.Secondly,the MPSO and chaos were hybridized (MPSOC) to improve the global searching capability and prevent the premature convergence due to local minima.The robustness of the proposed PSS tuning technique was verified on a multi-machine power system under different operating conditions.The performance of the proposed MPSOC was compared to the MPSO,PSO and GA through eigenvalue analysis,nonlinear time-domain simulation and statistical tests.Eigenvalue analysis shows acceptable damping of the low-frequency modes and time domain simulations also show that the oscillations of synchronous machines can be rapidly damped for power systems with the proposed PSSs.The results show that the presented algorithm has a faster convergence rate with higher degree of accuracy than the GA,PSO and MPSO.
基金Project(51007042)supported by the National Natural Science Foundation of China
文摘Small signal instability may cause severe accidents for power system if it can not be dear correctly and timely. How to maintain power system stable under small signal disturbance is a big challenge for power system operators and dispatchers. Time delay existing in signal transmission process makes the problem more complex. Conventional eigenvalue analysis method neglects time delay influence and can not precisely describe power system dynamic behaviors. In this work, a modified small signal stability model considering time varying delay influence was constructed and a new time delay controller was proposed to stabilize power system under disturbance. By Lyapunov-Krasovskii function, the control law in the form of nonlinear matrix inequality （NLMI） was derived. Considering synthesis method limitation for time delay controller at present, both parameter adjustment method by using linear matrix inequality （LMI） solver and iteration searching method by solving nonlinear minimization problem were suggested to design the controller. Simulation tests were carried out on synchronous-machine infinite-bus power system. Satisfactory test results verify the correctness of the proposed model and the feasibility of the stabilization approach.
文摘Power system stability is enhanced through a novel stabilizer developed around an adaptive fuzzy sliding mode approach which applies the Nussbaum gain to a nonlinear model of a single-machine infinite-bus （SMIB） and multi-machine power system stabilizer subjected to a three phase fault. The Nussbaum gain is used to avoid the positive sign constraint and the problem of controllability of the system. A comparative simulation study is presented to evaluate the achieved performance.
基金supported by the National Natural Science Foundation of China under Grant 62034002 and 62374026.
文摘A frequency servo system-on-chip(FS-SoC)featuring output power stabilization technology is introduced in this study for high-precision and miniaturized cesium(Cs)atomic clocks.The proposed power stabilization loop(PSL)technique,incorporating an off-chip power detector(PD),ensures that the output power of the FS-SoC remains stable,mitigating the impact of power fluctuations on the atomic clock's stability.Additionally,a one-pulse-per-second(1PPS)is employed to syn-chronize the clock with GPS.Fabricated using 65 nm CMOS technology,the measured phase noise of the FS-SoC stands at-69.5 dBc/Hz@100 Hz offset and-83.9 dBc/Hz@1 kHz offset,accompanied by a power dissipation of 19.7 mW.The Cs atomic clock employing the proposed FS-SoC and PSL obtains an Allan deviation of 1.7×10^(-11) with 1-s averaging time.
基金This research was supported inpart by the Found ation !(No .990 951 1 1 2 )for Research admini stered by HarbinInstituteof Te
文摘The variable polarity power source which incorporates a constant current power and a secondary inverter does not need special apparatus for stabilizing arc. The pulse for stabilizing arc is created by the circuit structure itself. The paper analyzes the principle of acquiring the pulse, provides the better method to improve the arc stabilization under smaller welding current. Test shows the arc is highly stable , and the process has no high frequency electromagnetic interference, which is suitable for automatic welding case.
基金Supported by the Special Fund of the National Fundamental Research (No. 2004CB217904)National Natural Science Foundation of China (No. 50595413)Program for New Century Excellent Talents in Universities, Fok Ying Tung Education Foundation (No.104019 )Foundation for the Authors of National Excellent Doctoral Dissertation (No. 200439) ,Key Project of Chinese Ministry of Education (No. 10047).
文摘Torus bifurcation is a relatively complicated bifurcation caused by a pair of complex conjugate Floquet multipliers coming out of unit circle on the Poincare section. A three-bus system is employed to reveal the relationship between torus bifurcation and some complex dynamics. Based on theoretical analysis and simulation studies, it is found that torus bifurcation is a typical route to chaos in power system. Some complex dynamics usually occur after a torus bifurcation, such as self-organization, deep bifurcations, exquisite structure, coexistence of chaos and divergence. It is also found that chaos has close relationship with various instability scenarios of power systems. Studies of this paper are helpful to understand the mechanism of torus bifurcation in power system and relationship of chaos and power system instabilities.
文摘The parameters of power system slowly change with time due to environmental effects or may change rapidly due to faults. It is preferable that the control technique in this system possesses robustness for various fault conditions and disturbances. The used flexible alternating current transmission system （FACTS） in this paper is an advanced super-conducting magnetic energy storage （ASMES）. Many control techniques that use ASMES to improve power system stability have been proposed. While fuzzy controller has proven its value in some applications, the researches applying fuzzy controller with ASMES have been actively reported. However, it is sometimes very difficult to specify the rule base for some plants, when the parameters change. To solve this problem, a fuzzy model reference learning controller （FMRLC） is proposed in this paper, which investigates multi-input multi-output FMRLC for time-variant nonlinear system. This control method provides the motivation for adaptive fuzzy control, where the focus is on the automatic online synthesis and tuning of fuzzy controller parameters （i.e., using online data to continually learn the fuzzy controller that will ensure that the performance objectives are met）. Simulation results show that the proposed robust controller is able to work with nonlinear and nonstationary power system （i.e., single machine-infinite bus （SMIB） system）, under various fault conditions and disturbances.
