Countries worldwide are advocating for energy transition initiatives to promote the construction of low-carbon energy systems.The low voltage ride through(LVRT)characteristics of renewable energy units and commutation...Countries worldwide are advocating for energy transition initiatives to promote the construction of low-carbon energy systems.The low voltage ride through(LVRT)characteristics of renewable energy units and commutation failures in line commutated converter high voltage direct current(LCC-HVDC)systems at the receiving end leads to short-term power shortage(STPS),which differs from traditional frequency stability issues.STPS occurs during the generator’s power angle swing phase,before the governor responds,and is on a timescale that is not related to primary frequency regulation.This paper addresses these challenges by examining the impact of LVRT on voltage stability,developing a frequency response model to analyze the mechanism of frequency instability caused by STPS,deriving the impact of STPS on the maximum frequency deviation,and introducing an energy deficiency factor to assess its impact on regional frequency stability.The East China Power Grid is used as a case study,where the energy deficiency factor is calculated to validate the proposed mechanism.STPS is mainly compensated by the rotor kinetic energy of the generators in this region,with minimal impact on other regions.It is concluded that the energy deficiency factor provides an effective explanation for the spatial distribution of the impact of STPS on system frequency.展开更多
Power electronic-interfaced renewable energy sources(RES)exhibit lower inertia compared to traditional synchronous generators.The large-scale integration of RES has led to a significant reduction in system inertia,pos...Power electronic-interfaced renewable energy sources(RES)exhibit lower inertia compared to traditional synchronous generators.The large-scale integration of RES has led to a significant reduction in system inertia,posing significant challenges for maintaining frequency stability in future power systems.This issue has garnered considerable attention in recent years.However,the existing research has not yet achieved a comprehensive understanding of system inertia and frequency stability in the context of low-inertia systems.To this end,this paper provides a comprehensive review of the definition,modeling,analysis,evaluation,and control for frequency stability.It commences with an exploration of inertia and frequency characteristics in low-inertia systems,followed by a novel definition of frequency stability.A summary of frequency stability modeling,analysis,and evaluation methods is then provided,along with their respective applicability in various scenarios.Additionally,the two critical factors of frequency control—energy sources at the system level and control strategies at the device level—are examined.Finally,an outlook on future research in low-inertia power systems is discussed.展开更多
Grid-forming(GFM)control is a key technology for ensuring the safe and stable operation of renewable power systems dominated by converter-interfaced generation(CIG),including wind power,photovoltaic,and battery energy...Grid-forming(GFM)control is a key technology for ensuring the safe and stable operation of renewable power systems dominated by converter-interfaced generation(CIG),including wind power,photovoltaic,and battery energy storage.In this paper,we challenge the traditional approach of emulating a synchronous generator by proposing a frequency-fixed GFM control strategy.The CIG endeavors to regulate itself as a constant voltage source without control dynamics due to its capability limitation,denoted as the frequency-fixed zone.With the proposed strategy,the system frequency is almost always fixed at its rated value,achieving system active power balance independent of frequency,and intentional power flow adjustments are implemented through direct phase angle control.This approach significantly reduces the frequency dynamics and safety issues associated with frequency variations.Furthermore,synchronization dynamics are significantly diminished,and synchronization stability is enhanced.The proposed strategy has the potential to realize a renewable power system with a fixed frequency and robust stability.展开更多
The frequency regulation reserve setting of wind-PV-storage power stations is crucial.However,the existing grid codes set up the station reserve in a static manner,where the synchronous generator characteristics and f...The frequency regulation reserve setting of wind-PV-storage power stations is crucial.However,the existing grid codes set up the station reserve in a static manner,where the synchronous generator characteristics and frequency-step disturbance scenario are considered.Thus,the advantages of flexible regulation of renewable generations are wasted,resulting in excessive curtailment of wind and solar resources.In this study,a method for optimizing the frequency regulation reserve of wind PV storage power stations was developed.Moreover,a station frequency regulation model was constructed,considering the field dynamic response and the coupling between the station and system frequency dynamics.Furthermore,a method for the online evaluation of the station frequency regulation was proposed based on the benchmark governor fitting.This method helps in overcoming the capacity-based reserve static setting.Finally,an optimization model was developed,along with the proposal of the linearized solving algorithm.The field data from the JH4#station in China’s MX power grid was considered for validation.The proposed method achieves a 24.77%increase in the station income while ensuring the system frequency stability when compared with the grid code-based method.展开更多
In order to increase the stability of the Mongolia power system, a single-phase automatic reclosing device (SPAR) was introduced on double-circuit power lines built with a size of 330 kV, operating on a voltage of 220...In order to increase the stability of the Mongolia power system, a single-phase automatic reclosing device (SPAR) was introduced on double-circuit power lines built with a size of 330 kV, operating on a voltage of 220 kV and a length of 250 km. These overhead power lines (L-213, L-214) connect the 220/110/35 kV “Songino” substation with the “Mandal” substation and form system networks. This paper presents the challenges encountered when implementing single-phase automatic reclosing (SPAR) devices and compares the changes in power system parameters before and after SPAR deployment for a long 220 kV line. Simulations and analyses were carried out using DIgSILENT PowerFactory software, focusing on rotor angle stability, and the overall impact on the power system during short-circuit faults. The evaluation also utilized measurement data from the Wide Area Monitoring System (WAMS) to compare system behavior pre- and post-implementation of SPAR. The findings reveal that SPAR significantly enhances system reliability and stability, effectively mitigating the risk of oscillations and stability loss triggered by short circuits. This improvement contributes to a more resilient power system, reducing the potential for disturbances caused by faults.展开更多
A grid connected microgrid connects to the grid at a point of common coupling. Due to the great inertia of the grid which accelerates and decelerates the generator when its frequency tends to deviate, the grid connect...A grid connected microgrid connects to the grid at a point of common coupling. Due to the great inertia of the grid which accelerates and decelerates the generator when its frequency tends to deviate, the grid connected microgrid operates at a frequency of the infinity bus. Frequency instability is one of the major challenges facing the grid connected microgrid during islanding. The power demand variation causes the variation in rotor speed, resulting to frequency deviation. Frequency can be brought back to standard by varying the power generation to match with the varying load. The performance of the frequency stability control system at Mwenga hydroelectric microgrid has been studied. Through site visitation, the power demand and generation status data were collected and analysed for model preparation. The results of the study indicate that, during islanding, the Mwenga rural electrification project is observed to be subjected to power imbalance which leads to frequency instability. Although the frequency control system tries to keep the system at a nominal frequency by maintaining the continuous balance between generation and varying load demand, however the system still operates with large magnitude of overshoot, undershoot and longer settling time.展开更多
This paper presents a method of tuning governor control parameters of an isolated hydropower generator considering the primary frequency performance and small-signal stability. First, generators that can be operated i...This paper presents a method of tuning governor control parameters of an isolated hydropower generator considering the primary frequency performance and small-signal stability. First, generators that can be operated in isolated state are identified. Second, different schemes are proposed for generator mode switching from on-grid to off-grid state through comparison and mechanism analysis. Third, the time domain model and frequency domain model of the isolated generator governor are constructed to respectively estimate the primary frequency performance and small signal stability. Parameter sets that satisfy the primary frequency performance and small signal stability are acquired as optimal values of governor control parameters. Finally, the measurement-based parameters of the governor are identified and validated using simulations to demonstrate the feasibility and effectiveness of the method.展开更多
The dynamics of network power response play a crucial role in system stability.However,the integration of power electronic equipment leads to amplitude and angular frequency(abbreviated as"frequency")time-va...The dynamics of network power response play a crucial role in system stability.However,the integration of power electronic equipment leads to amplitude and angular frequency(abbreviated as"frequency")time-varying characteristics of the node voltage during dynamic processes.As a result,traditional calcu-lation methods for and characteristics of the power response of the network based on phasor and impe-dance lose their validity.Therefore,this paper undertakes mathematical calculations to reveal the power response of a network under excitation by voltage with time-varying amplitude and frequency(TVAF),relying on the original mathematical relationships and superimposed step response.Then,the multi-timescale characteristics of both the active and reactive power of the network are explored physically.Additionally,this paper reveals a new phenomenon of storing and releasing the active and reactive power of the network.To meet practical engineering requirements,a simplified power expression is presented.Finally,the theoretical analysis is validated through time-domain simulations.展开更多
In order to prepare the shielding fabrics with high efficiency of power frequency(PF)shielding and excellent electrical conductivity,different ratios of aramid/stainless steel fiber blended yarns were used to weave th...In order to prepare the shielding fabrics with high efficiency of power frequency(PF)shielding and excellent electrical conductivity,different ratios of aramid/stainless steel fiber blended yarns were used to weave the shielding fabrics with different specifications.The fabric structure,fabric areal density,number of fabric layers,embedding ratio of copper-clad wires wrapped aramid yarns(denoted as CCWWA)and embedding direction were designed,and a total of 34 different types of shielding fabrics were woven for testing.The experiments were mainly conducted to study the influence mechanism of various factors on the PF shielding effectiveness by testing the electrical conductivity and PF shielding effectiveness of the fabrics.The research results indicate that the PF shielding effectiveness improves with increasing fabric areal density and metal fiber content.The fabrics embedded with CCWWA,particularly those with bidirectional embedding,exhibit a significant enhancement in the PF shielding effectiveness,showing an increase of 8-20 dB compared to the fabrics without CCWWA.The PF shielding effectiveness varies across different fabric structures,with plain weave fabrics demonstrating the superior PF shielding effectiveness due to their compact structure.Non-conductive base fabric has minimal impact on the PF shielding effectiveness.As the number of fabric layers increases,the PF shielding effectiveness initially improves but then declines,peaking with double-layer fabrics.展开更多
Transient stability assessment(TSA)based on artificial intelligence typically has two distinct model management approaches:a unified management approach for all faulted lines and a separate management approach for eac...Transient stability assessment(TSA)based on artificial intelligence typically has two distinct model management approaches:a unified management approach for all faulted lines and a separate management approach for each faulted line.To address the shortcomings of the aforementioned approaches,namely accuracy,training time,and model management complexity,a multi-model management approach for power system TSA based on multi-moment feature clustering has been proposed.First,the steady-state and transient features present under fault conditions were obtained through a transient simulation of line faults.The input sample set was then constructed using the aforementioned multi-moment electrical features and the embedded faulty line numbers.Subsequently,K-means clustering was conducted on each line based on the similarity of their electrical features,employing t-SNE dimensionality reduction.The PSO-CNN model was trained separately for each cluster to generate several independent TSA models.Finally,a model effectiveness evaluation system consisting of five metrics was established,and the effect of the sample imbalance ratio on the model effectiveness was investigated.The model effectiveness was evaluated using the IEEE 39-bus system algorithm.The results showed that the multi-model management strategy based on multi-moment feature clustering can effectively combine the two advantages of superior evaluation performance and streamlined model management by fully extracting system features.Moreover,this approach allows for more flexible adjustments to line topology changes.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
A complete closed-loop third order s-domain model is analyzed for a frequency synthesizer. Based on the model and root-locus technique, the procedure for parameters design is described, and the relationship between th...A complete closed-loop third order s-domain model is analyzed for a frequency synthesizer. Based on the model and root-locus technique, the procedure for parameters design is described, and the relationship between the process,voltage,and temperature variation of parameters and the loop stability is quantitatively analyzed. A variation margin is proposed for stability compensation. Furthermore,a simple adjustable current cell in the charge pump is proposed for additional stability compensation and a novel VCO with linear gain is adopted to limit the total variation. A fully integrated frequency synthesizer from 1 to 1.05GHz with 250kHz channel resolution is implemented to verify the methods.展开更多
On the basis of high precision requirement for input signals in the power system protection and control system,this paper,only for the influence of power system frequency deviation on extracting fundamental harmonic,s...On the basis of high precision requirement for input signals in the power system protection and control system,this paper,only for the influence of power system frequency deviation on extracting fundamental harmonic,studies the amplitude error of Fourier algorithm,presents a method of correcting frequency deviation,and further derives the formulas of improved Fourier algorithm.The simulation results verified the effectiveness of the algorithm,it not only can greatly weaken the influence of frequency deviation,but also increase the precision of the power system protection and control.As a result the study in this paper has practical application value.展开更多
Primary frequency regulation is one of the important regulation means to maintain the stable operation of the power grid, and for a single unit, especially the nuclear power unit, the frequency regulation process is a...Primary frequency regulation is one of the important regulation means to maintain the stable operation of the power grid, and for a single unit, especially the nuclear power unit, the frequency regulation process is an unstable factor. With the increasing capacity of nuclear motor assembly machine, it is bound to shoulder the heavy responsibility of peak shaving and frequency modulation. However, its own particularity determines that it cannot be as flexible as thermal power plants and other power plants in terms of frequency modulation, and it is necessary to find a balance between maintaining the stability of the power grid and the safe and stable operation of units. Taking 650MW nuclear power steam turbine unit as an example, this paper introduces and analyzes in detail the control principle, control process, frequency modulation parameter setting of its primary frequency modulation, as well as the adverse effects of reactor protection actions such as reactor over power that may be caused by transient events and primary frequency modulation process. By taking technical measures such as adjusting the mode of primary frequency modulation operation, we can reduce the impact of external network faults on the unit, summarize the experience of transient disposal, and improve the plan, improve the ability of the main control operator to judge and deal with the transient, so as to ensure that the unit can meet the requirements of the primary frequency modulation response of the power grid on the basis of safe and stable operation.展开更多
The significant increase in the proportion of renewable energy sources(RESs)has elevated risks of extreme ramp events and frequency instability in power systems.In recent years,frequency stability events have occurred...The significant increase in the proportion of renewable energy sources(RESs)has elevated risks of extreme ramp events and frequency instability in power systems.In recent years,frequency stability events have occurred in several countries/regions worldwide due to flexibility deficiencies.Generation flexibility has emerged as a critical factor influencing the frequency stability of power systems.This paper proposes a domain of attraction(DOA)-based quantitative method to assess the frequency stability region of power systems with a high proportion of RESs,considering generation flexibility constraints.First,ramp rate is adopted as the core indicator to characterize generation flexibility within automatic generation control(AGC)timescale,through which a nonlinear AGC model with rate saturation constraints is established.Second,the concept of DOA is introduced to define the stability region of the nonlinear AGC.Third,a quadratic Lyapunov-based estimation method is employed to quantitatively analyze the DOA of the nonlinear AGC at different generation flexibility levels.Simulation results demonstrate that increased generation flexibility expands the estimated DOA of the nonlinear AGC,whereas generation flexibility deficiency induces AGC instability.Moreover,state trajectory and time-domain simulation verify that the proposed estimation method accurately represents the stability region of the nonlinear AGC.展开更多
The traditional voltage stability analysis method is mostly based on the deterministic mode1.and ignores the uncertainties of bus loads,power supplies,changes in network configuration and so on.However,the great expan...The traditional voltage stability analysis method is mostly based on the deterministic mode1.and ignores the uncertainties of bus loads,power supplies,changes in network configuration and so on.However,the great expansion of renewable power generations such as wind and solar energy in a power system has increased their uncertainty,and仃aditional techniques are limited in capturing their variable behavior.This leads to greater needs of new techniques and methodologies to properly quan tify the voltage stability of power systems.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
This paper addresses a terminal sliding mode control(T-SMC) method for load frequency control(LFC) in renewable power systems with generation rate constraints(GRC).A two-area interconnected power system with wind turb...This paper addresses a terminal sliding mode control(T-SMC) method for load frequency control(LFC) in renewable power systems with generation rate constraints(GRC).A two-area interconnected power system with wind turbines is taken into account for simulation studies. The terminal sliding mode controllers are assigned in each area to achieve the LFC goal. The increasing complexity of the nonlinear power system aggravates the effects of system uncertainties. Radial basis function neural networks(RBF NNs) are designed to approximate the entire uncertainties. The terminal sliding mode controllers and the RBF NNs work in parallel to solve the LFC problem for the renewable power system. Some simulation results illustrate the feasibility and validity of the presented scheme.展开更多
The increasing integration of wind power generation brings more uncertainty into the power system. Since the correlation may have a notable influence on the power system,the output powers of wind farms are generally c...The increasing integration of wind power generation brings more uncertainty into the power system. Since the correlation may have a notable influence on the power system,the output powers of wind farms are generally considered as correlated random variables in uncertainty analysis. In this paper, the C-vine pair copula theory is introduced to describe the complicated dependence of multidimensional wind power injection, and samples obeying this dependence structure are generated. Monte Carlo simulation is performed to analyze the small signal stability of a test system. The probabilistic stability under different correlation models and different operating conditions scenarios is investigated. The results indicate that the probabilistic small signal stability analysis adopting pair copula model is more accurate and stable than other dependence models under different conditions.展开更多
基金funded by the Technology Project of State Grid Corporation of China(Research on Safety and Stability Evaluation and Optimization Enhancement Technology of Flexible Ultra High Voltage Multiterminal DC System Adapting to the Background of“Sand and Gobi Deserts”),grant number J2024003。
文摘Countries worldwide are advocating for energy transition initiatives to promote the construction of low-carbon energy systems.The low voltage ride through(LVRT)characteristics of renewable energy units and commutation failures in line commutated converter high voltage direct current(LCC-HVDC)systems at the receiving end leads to short-term power shortage(STPS),which differs from traditional frequency stability issues.STPS occurs during the generator’s power angle swing phase,before the governor responds,and is on a timescale that is not related to primary frequency regulation.This paper addresses these challenges by examining the impact of LVRT on voltage stability,developing a frequency response model to analyze the mechanism of frequency instability caused by STPS,deriving the impact of STPS on the maximum frequency deviation,and introducing an energy deficiency factor to assess its impact on regional frequency stability.The East China Power Grid is used as a case study,where the energy deficiency factor is calculated to validate the proposed mechanism.STPS is mainly compensated by the rotor kinetic energy of the generators in this region,with minimal impact on other regions.It is concluded that the energy deficiency factor provides an effective explanation for the spatial distribution of the impact of STPS on system frequency.
基金supported by the National Natural Science Foundation of China(U2166601)。
文摘Power electronic-interfaced renewable energy sources(RES)exhibit lower inertia compared to traditional synchronous generators.The large-scale integration of RES has led to a significant reduction in system inertia,posing significant challenges for maintaining frequency stability in future power systems.This issue has garnered considerable attention in recent years.However,the existing research has not yet achieved a comprehensive understanding of system inertia and frequency stability in the context of low-inertia systems.To this end,this paper provides a comprehensive review of the definition,modeling,analysis,evaluation,and control for frequency stability.It commences with an exploration of inertia and frequency characteristics in low-inertia systems,followed by a novel definition of frequency stability.A summary of frequency stability modeling,analysis,and evaluation methods is then provided,along with their respective applicability in various scenarios.Additionally,the two critical factors of frequency control—energy sources at the system level and control strategies at the device level—are examined.Finally,an outlook on future research in low-inertia power systems is discussed.
基金supported by the National Key Research&Development Program of China under Grant 2024YFB2408900.
文摘Grid-forming(GFM)control is a key technology for ensuring the safe and stable operation of renewable power systems dominated by converter-interfaced generation(CIG),including wind power,photovoltaic,and battery energy storage.In this paper,we challenge the traditional approach of emulating a synchronous generator by proposing a frequency-fixed GFM control strategy.The CIG endeavors to regulate itself as a constant voltage source without control dynamics due to its capability limitation,denoted as the frequency-fixed zone.With the proposed strategy,the system frequency is almost always fixed at its rated value,achieving system active power balance independent of frequency,and intentional power flow adjustments are implemented through direct phase angle control.This approach significantly reduces the frequency dynamics and safety issues associated with frequency variations.Furthermore,synchronization dynamics are significantly diminished,and synchronization stability is enhanced.The proposed strategy has the potential to realize a renewable power system with a fixed frequency and robust stability.
基金supported by the Scientific Research Project of China Three Gorges Group Co.LTD(Contract Number:202103368).
文摘The frequency regulation reserve setting of wind-PV-storage power stations is crucial.However,the existing grid codes set up the station reserve in a static manner,where the synchronous generator characteristics and frequency-step disturbance scenario are considered.Thus,the advantages of flexible regulation of renewable generations are wasted,resulting in excessive curtailment of wind and solar resources.In this study,a method for optimizing the frequency regulation reserve of wind PV storage power stations was developed.Moreover,a station frequency regulation model was constructed,considering the field dynamic response and the coupling between the station and system frequency dynamics.Furthermore,a method for the online evaluation of the station frequency regulation was proposed based on the benchmark governor fitting.This method helps in overcoming the capacity-based reserve static setting.Finally,an optimization model was developed,along with the proposal of the linearized solving algorithm.The field data from the JH4#station in China’s MX power grid was considered for validation.The proposed method achieves a 24.77%increase in the station income while ensuring the system frequency stability when compared with the grid code-based method.
文摘In order to increase the stability of the Mongolia power system, a single-phase automatic reclosing device (SPAR) was introduced on double-circuit power lines built with a size of 330 kV, operating on a voltage of 220 kV and a length of 250 km. These overhead power lines (L-213, L-214) connect the 220/110/35 kV “Songino” substation with the “Mandal” substation and form system networks. This paper presents the challenges encountered when implementing single-phase automatic reclosing (SPAR) devices and compares the changes in power system parameters before and after SPAR deployment for a long 220 kV line. Simulations and analyses were carried out using DIgSILENT PowerFactory software, focusing on rotor angle stability, and the overall impact on the power system during short-circuit faults. The evaluation also utilized measurement data from the Wide Area Monitoring System (WAMS) to compare system behavior pre- and post-implementation of SPAR. The findings reveal that SPAR significantly enhances system reliability and stability, effectively mitigating the risk of oscillations and stability loss triggered by short circuits. This improvement contributes to a more resilient power system, reducing the potential for disturbances caused by faults.
文摘A grid connected microgrid connects to the grid at a point of common coupling. Due to the great inertia of the grid which accelerates and decelerates the generator when its frequency tends to deviate, the grid connected microgrid operates at a frequency of the infinity bus. Frequency instability is one of the major challenges facing the grid connected microgrid during islanding. The power demand variation causes the variation in rotor speed, resulting to frequency deviation. Frequency can be brought back to standard by varying the power generation to match with the varying load. The performance of the frequency stability control system at Mwenga hydroelectric microgrid has been studied. Through site visitation, the power demand and generation status data were collected and analysed for model preparation. The results of the study indicate that, during islanding, the Mwenga rural electrification project is observed to be subjected to power imbalance which leads to frequency instability. Although the frequency control system tries to keep the system at a nominal frequency by maintaining the continuous balance between generation and varying load demand, however the system still operates with large magnitude of overshoot, undershoot and longer settling time.
基金supported by the Fujian Provincial Government Project (Title: Research on whole process evaluation of dynamic stability and control strategy in condition of grid connection of ultra-high voltage and large scale penetration of nuclear power.No.2015H0023)the State Grid Science & Technology Project (Title: Research on the improvement on stability of primary frequency of generator in account of the tolerance of equipment.No.52130417002P)the Key project of State Grid Fujian Electric Power Company,Ltd (research on key technologies of primary frequency power oscillation mechanism analysis and inhibition measures in large-scale unit in Fujian power grid.No.52130417000J)
文摘This paper presents a method of tuning governor control parameters of an isolated hydropower generator considering the primary frequency performance and small-signal stability. First, generators that can be operated in isolated state are identified. Second, different schemes are proposed for generator mode switching from on-grid to off-grid state through comparison and mechanism analysis. Third, the time domain model and frequency domain model of the isolated generator governor are constructed to respectively estimate the primary frequency performance and small signal stability. Parameter sets that satisfy the primary frequency performance and small signal stability are acquired as optimal values of governor control parameters. Finally, the measurement-based parameters of the governor are identified and validated using simulations to demonstrate the feasibility and effectiveness of the method.
基金supported in part by the National Natural Science Fundation of China(52225704 and 52107096).
文摘The dynamics of network power response play a crucial role in system stability.However,the integration of power electronic equipment leads to amplitude and angular frequency(abbreviated as"frequency")time-varying characteristics of the node voltage during dynamic processes.As a result,traditional calcu-lation methods for and characteristics of the power response of the network based on phasor and impe-dance lose their validity.Therefore,this paper undertakes mathematical calculations to reveal the power response of a network under excitation by voltage with time-varying amplitude and frequency(TVAF),relying on the original mathematical relationships and superimposed step response.Then,the multi-timescale characteristics of both the active and reactive power of the network are explored physically.Additionally,this paper reveals a new phenomenon of storing and releasing the active and reactive power of the network.To meet practical engineering requirements,a simplified power expression is presented.Finally,the theoretical analysis is validated through time-domain simulations.
文摘In order to prepare the shielding fabrics with high efficiency of power frequency(PF)shielding and excellent electrical conductivity,different ratios of aramid/stainless steel fiber blended yarns were used to weave the shielding fabrics with different specifications.The fabric structure,fabric areal density,number of fabric layers,embedding ratio of copper-clad wires wrapped aramid yarns(denoted as CCWWA)and embedding direction were designed,and a total of 34 different types of shielding fabrics were woven for testing.The experiments were mainly conducted to study the influence mechanism of various factors on the PF shielding effectiveness by testing the electrical conductivity and PF shielding effectiveness of the fabrics.The research results indicate that the PF shielding effectiveness improves with increasing fabric areal density and metal fiber content.The fabrics embedded with CCWWA,particularly those with bidirectional embedding,exhibit a significant enhancement in the PF shielding effectiveness,showing an increase of 8-20 dB compared to the fabrics without CCWWA.The PF shielding effectiveness varies across different fabric structures,with plain weave fabrics demonstrating the superior PF shielding effectiveness due to their compact structure.Non-conductive base fabric has minimal impact on the PF shielding effectiveness.As the number of fabric layers increases,the PF shielding effectiveness initially improves but then declines,peaking with double-layer fabrics.
基金supported by the Science and Technology Project of SGCC(5100-202199558A-0-5-ZN).
文摘Transient stability assessment(TSA)based on artificial intelligence typically has two distinct model management approaches:a unified management approach for all faulted lines and a separate management approach for each faulted line.To address the shortcomings of the aforementioned approaches,namely accuracy,training time,and model management complexity,a multi-model management approach for power system TSA based on multi-moment feature clustering has been proposed.First,the steady-state and transient features present under fault conditions were obtained through a transient simulation of line faults.The input sample set was then constructed using the aforementioned multi-moment electrical features and the embedded faulty line numbers.Subsequently,K-means clustering was conducted on each line based on the similarity of their electrical features,employing t-SNE dimensionality reduction.The PSO-CNN model was trained separately for each cluster to generate several independent TSA models.Finally,a model effectiveness evaluation system consisting of five metrics was established,and the effect of the sample imbalance ratio on the model effectiveness was investigated.The model effectiveness was evaluated using the IEEE 39-bus system algorithm.The results showed that the multi-model management strategy based on multi-moment feature clustering can effectively combine the two advantages of superior evaluation performance and streamlined model management by fully extracting system features.Moreover,this approach allows for more flexible adjustments to line topology changes.
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A complete closed-loop third order s-domain model is analyzed for a frequency synthesizer. Based on the model and root-locus technique, the procedure for parameters design is described, and the relationship between the process,voltage,and temperature variation of parameters and the loop stability is quantitatively analyzed. A variation margin is proposed for stability compensation. Furthermore,a simple adjustable current cell in the charge pump is proposed for additional stability compensation and a novel VCO with linear gain is adopted to limit the total variation. A fully integrated frequency synthesizer from 1 to 1.05GHz with 250kHz channel resolution is implemented to verify the methods.
文摘On the basis of high precision requirement for input signals in the power system protection and control system,this paper,only for the influence of power system frequency deviation on extracting fundamental harmonic,studies the amplitude error of Fourier algorithm,presents a method of correcting frequency deviation,and further derives the formulas of improved Fourier algorithm.The simulation results verified the effectiveness of the algorithm,it not only can greatly weaken the influence of frequency deviation,but also increase the precision of the power system protection and control.As a result the study in this paper has practical application value.
文摘Primary frequency regulation is one of the important regulation means to maintain the stable operation of the power grid, and for a single unit, especially the nuclear power unit, the frequency regulation process is an unstable factor. With the increasing capacity of nuclear motor assembly machine, it is bound to shoulder the heavy responsibility of peak shaving and frequency modulation. However, its own particularity determines that it cannot be as flexible as thermal power plants and other power plants in terms of frequency modulation, and it is necessary to find a balance between maintaining the stability of the power grid and the safe and stable operation of units. Taking 650MW nuclear power steam turbine unit as an example, this paper introduces and analyzes in detail the control principle, control process, frequency modulation parameter setting of its primary frequency modulation, as well as the adverse effects of reactor protection actions such as reactor over power that may be caused by transient events and primary frequency modulation process. By taking technical measures such as adjusting the mode of primary frequency modulation operation, we can reduce the impact of external network faults on the unit, summarize the experience of transient disposal, and improve the plan, improve the ability of the main control operator to judge and deal with the transient, so as to ensure that the unit can meet the requirements of the primary frequency modulation response of the power grid on the basis of safe and stable operation.
基金supported in part by Science and Technology Project of State Grid Corporation of China(No.5100-202336015A-1-1-ZN)。
文摘The significant increase in the proportion of renewable energy sources(RESs)has elevated risks of extreme ramp events and frequency instability in power systems.In recent years,frequency stability events have occurred in several countries/regions worldwide due to flexibility deficiencies.Generation flexibility has emerged as a critical factor influencing the frequency stability of power systems.This paper proposes a domain of attraction(DOA)-based quantitative method to assess the frequency stability region of power systems with a high proportion of RESs,considering generation flexibility constraints.First,ramp rate is adopted as the core indicator to characterize generation flexibility within automatic generation control(AGC)timescale,through which a nonlinear AGC model with rate saturation constraints is established.Second,the concept of DOA is introduced to define the stability region of the nonlinear AGC.Third,a quadratic Lyapunov-based estimation method is employed to quantitatively analyze the DOA of the nonlinear AGC at different generation flexibility levels.Simulation results demonstrate that increased generation flexibility expands the estimated DOA of the nonlinear AGC,whereas generation flexibility deficiency induces AGC instability.Moreover,state trajectory and time-domain simulation verify that the proposed estimation method accurately represents the stability region of the nonlinear AGC.
文摘The traditional voltage stability analysis method is mostly based on the deterministic mode1.and ignores the uncertainties of bus loads,power supplies,changes in network configuration and so on.However,the great expansion of renewable power generations such as wind and solar energy in a power system has increased their uncertainty,and仃aditional techniques are limited in capturing their variable behavior.This leads to greater needs of new techniques and methodologies to properly quan tify the voltage stability of power systems.
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supported by National Natural Science Foundation of China(60904008,61273336)the Fundamental Research Funds for the Central Universities(2018MS025)the National Basic Research Program of China(973 Program)(B1320133020)
文摘This paper addresses a terminal sliding mode control(T-SMC) method for load frequency control(LFC) in renewable power systems with generation rate constraints(GRC).A two-area interconnected power system with wind turbines is taken into account for simulation studies. The terminal sliding mode controllers are assigned in each area to achieve the LFC goal. The increasing complexity of the nonlinear power system aggravates the effects of system uncertainties. Radial basis function neural networks(RBF NNs) are designed to approximate the entire uncertainties. The terminal sliding mode controllers and the RBF NNs work in parallel to solve the LFC problem for the renewable power system. Some simulation results illustrate the feasibility and validity of the presented scheme.
基金supported by National Natural Science Foundation of China(61533013,61273144)Scientific Technology Research and Development Plan Project of Tangshan(13130298B)Scientific Technology Research and Development Plan Project of Hebei(z2014070)
基金supported by the National Natural Science Foundation of China(51307107,51477098,51877133)SRFDP(20130073120034)State Grid Corporation of China Science and Technology Project(Hybrid AC/DC Power Grid Planning and Optimization Study Under the Framework of GEI)。
文摘The increasing integration of wind power generation brings more uncertainty into the power system. Since the correlation may have a notable influence on the power system,the output powers of wind farms are generally considered as correlated random variables in uncertainty analysis. In this paper, the C-vine pair copula theory is introduced to describe the complicated dependence of multidimensional wind power injection, and samples obeying this dependence structure are generated. Monte Carlo simulation is performed to analyze the small signal stability of a test system. The probabilistic stability under different correlation models and different operating conditions scenarios is investigated. The results indicate that the probabilistic small signal stability analysis adopting pair copula model is more accurate and stable than other dependence models under different conditions.
