In recent years,with increasing amounts of renewable energy sources connecting to power grids,sub-/super-synchronous oscillations(SSOs)occurred more frequently.Due to the time-variant nature of SsO magnitudes and freq...In recent years,with increasing amounts of renewable energy sources connecting to power grids,sub-/super-synchronous oscillations(SSOs)occurred more frequently.Due to the time-variant nature of SsO magnitudes and frequencies,as well as the mutual interferences among SsO modes with close frequencies,the accurate parameter estimation of SsO has become a particularly challenging topic.To solve this issue,this paper proposes an improved spectrum analysis method by improving the window function and a spectrum correction method to achieve higher precision.First,by aiming at the sidelobe characteristics of the window function as evaluation criteria,a combined cosine function is optimized using a genetic algorithm(GA).Furthermore,the obtained window function is self-convolved to extend its excellent characteristics,which have better performance in reducing mutual interference from other SSO modes.Subsequently,a new form of interpolated all-phase fast Fourier transform(IpApFFT)using the optimized window function is proposed to estimate the parameters of SsO.This method allows for phase-unbiased estimation while maintaining algorithmic simplicity and expedience.The performance of the pro-posed method is demonstrated under various conditions,com-pared with other estimation methods.Simulation results validate the effectiveness and superiority of the proposed method.展开更多
In recent years,sub/super-synchronous oscillations occur frequently in large-scale wind power bases throughout China.Since the oscillation frequencies are close to the fundamental frequency,the current components can ...In recent years,sub/super-synchronous oscillations occur frequently in large-scale wind power bases throughout China.Since the oscillation frequencies are close to the fundamental frequency,the current components can spread over a large area,and may destroy the shafting of rotating devices in the power grid.Improving the control strategy and parameters of wind turbines can prevent this problem to some extent,however,due to complex operational conditions and continuous development of wind power,the off-line improvement measures on wind turbines cannot eliminate the potential oscillation risks.This paper proposes an oscillation risk screening and stability assessment method,and develops a coordination control method for large-scale wind farm systems to prevent sub/supersynchronous oscillations.The Nyquist criterion and the modal analysis method are combined to generate quantitative factors for the stability assessment and the control strategy design.The coordination control method consists of minute-level power coordinated allocation and second-level fast power control to prevent and eliminate the oscillations.A detailed simulation model of a multiple wind farms system originated from an actual wind power base in China is presented to verify the effectiveness of the proposed method.展开更多
In recent years,the large-scale integration of re-newable energy sources represented by wind power and the widespread application of power electronic devices in power systems have led to the emergence of multi-frequen...In recent years,the large-scale integration of re-newable energy sources represented by wind power and the widespread application of power electronic devices in power systems have led to the emergence of multi-frequency oscillation problems covering multiple frequency segments,which seriously threaten system stability and restrict the accommodation of renewable energy.The oscillation problems related to renewable energy integration have become one of the most popular topics in the field of wind power integration and power system stability research.It has received extensive attention from both academia and industries with many promising research results achieved to date.This paper first analyzes several typical multi-frequency oscillation events caused by large-scale wind power integration in domestic and foreign projects,then studies the multi-frequency oscillation problems,including wind turbine’s shafting torsional oscillation,sub/super-synchronous oscillation and high frequency resonance.The state of the art is systematically summarized from the aspects of oscillation mechanism,analysis methods and mitigation measures,and the future research directions are explored.展开更多
—With the increase of converter-based renewable energy generation connected into the power grid, the interaction between renewable energy and grid impedance has introduced lots of new issues, among which the sub-and ...—With the increase of converter-based renewable energy generation connected into the power grid, the interaction between renewable energy and grid impedance has introduced lots of new issues, among which the sub-and super-synchronous oscillation phenomenon makes a big concern. The linear active disturbance rejection control(LADRC) is a potential way to improve the damping characteristics of the grid-connected system, but the key factors and influencing mechanism on system stability are unknown. This paper establishes the equivalent impedance and coupling admittance models of a typical three-phase grid-connected converter. Then, the influence of the key factors such as the bandwidth of the LADRC and grid impedance on the stability and frequency coupling effect is assessed in detail. Finally, the theoretical analysis results are verified by simulations and experiments.展开更多
基金supported in part by Science and Technology Project of State Grid Corporation of China(No.5108-202299269A-1-0-ZB).
文摘In recent years,with increasing amounts of renewable energy sources connecting to power grids,sub-/super-synchronous oscillations(SSOs)occurred more frequently.Due to the time-variant nature of SsO magnitudes and frequencies,as well as the mutual interferences among SsO modes with close frequencies,the accurate parameter estimation of SsO has become a particularly challenging topic.To solve this issue,this paper proposes an improved spectrum analysis method by improving the window function and a spectrum correction method to achieve higher precision.First,by aiming at the sidelobe characteristics of the window function as evaluation criteria,a combined cosine function is optimized using a genetic algorithm(GA).Furthermore,the obtained window function is self-convolved to extend its excellent characteristics,which have better performance in reducing mutual interference from other SSO modes.Subsequently,a new form of interpolated all-phase fast Fourier transform(IpApFFT)using the optimized window function is proposed to estimate the parameters of SsO.This method allows for phase-unbiased estimation while maintaining algorithmic simplicity and expedience.The performance of the pro-posed method is demonstrated under various conditions,com-pared with other estimation methods.Simulation results validate the effectiveness and superiority of the proposed method.
文摘In recent years,sub/super-synchronous oscillations occur frequently in large-scale wind power bases throughout China.Since the oscillation frequencies are close to the fundamental frequency,the current components can spread over a large area,and may destroy the shafting of rotating devices in the power grid.Improving the control strategy and parameters of wind turbines can prevent this problem to some extent,however,due to complex operational conditions and continuous development of wind power,the off-line improvement measures on wind turbines cannot eliminate the potential oscillation risks.This paper proposes an oscillation risk screening and stability assessment method,and develops a coordination control method for large-scale wind farm systems to prevent sub/supersynchronous oscillations.The Nyquist criterion and the modal analysis method are combined to generate quantitative factors for the stability assessment and the control strategy design.The coordination control method consists of minute-level power coordinated allocation and second-level fast power control to prevent and eliminate the oscillations.A detailed simulation model of a multiple wind farms system originated from an actual wind power base in China is presented to verify the effectiveness of the proposed method.
基金This work was supported by the National Natural Science Foundation of China(No.51577174).
文摘In recent years,the large-scale integration of re-newable energy sources represented by wind power and the widespread application of power electronic devices in power systems have led to the emergence of multi-frequency oscillation problems covering multiple frequency segments,which seriously threaten system stability and restrict the accommodation of renewable energy.The oscillation problems related to renewable energy integration have become one of the most popular topics in the field of wind power integration and power system stability research.It has received extensive attention from both academia and industries with many promising research results achieved to date.This paper first analyzes several typical multi-frequency oscillation events caused by large-scale wind power integration in domestic and foreign projects,then studies the multi-frequency oscillation problems,including wind turbine’s shafting torsional oscillation,sub/super-synchronous oscillation and high frequency resonance.The state of the art is systematically summarized from the aspects of oscillation mechanism,analysis methods and mitigation measures,and the future research directions are explored.
基金supported in part by the National Natural Science Foundation of China (No. 52077222)the Fundamental Research Funds for the Central Universities (No. 19CX02016A)。
文摘—With the increase of converter-based renewable energy generation connected into the power grid, the interaction between renewable energy and grid impedance has introduced lots of new issues, among which the sub-and super-synchronous oscillation phenomenon makes a big concern. The linear active disturbance rejection control(LADRC) is a potential way to improve the damping characteristics of the grid-connected system, but the key factors and influencing mechanism on system stability are unknown. This paper establishes the equivalent impedance and coupling admittance models of a typical three-phase grid-connected converter. Then, the influence of the key factors such as the bandwidth of the LADRC and grid impedance on the stability and frequency coupling effect is assessed in detail. Finally, the theoretical analysis results are verified by simulations and experiments.
