Frequency and voltage dynamics,as the focus of power systems,depend more and more on the frequency and amplitude response characteristics of renewable energy devices subjected to power imbalance.The doubly-fed inducti...Frequency and voltage dynamics,as the focus of power systems,depend more and more on the frequency and amplitude response characteristics of renewable energy devices subjected to power imbalance.The doubly-fed induction generator(DFIG)-based wind turbine(WT)is representative of renewable energy devices and shows different characteristics from those of conventional synchronous generators(SGs).Unfortunately,the individual characteristics of WTs during system frequency and voltage dynamics are not intuitively illustrated by the existing structure-oriented models.Therefore,this paper proposes a function-oriented modeling methodology by representing inertia-controlled DFIG-based WT as an internal voltage frequency and amplitude solely stimulated by active and reactive power imbalance.The individuality of the characteristics is demonstrated by the grid voltage detection-based controls that the internal voltage depends solely on the power imbalance of WTs,just like the case of SGs.Through the infinity gain equivalence of the fast-electromagnetic loops,a simplified analytical model illustrating the electromechanical characteristics of WTs is further proposed.Based on the model,the similarities and differences between the characteristics of WTs and SGs are recognized.Simulation results are also presented for verification.展开更多
Increasing penetration of power electronic(PE)grid-tied devices has caused more and more dynamic problems with unknown mechanisms.Since grid operation asks for a certain voltage amplitude and frequency level when ther...Increasing penetration of power electronic(PE)grid-tied devices has caused more and more dynamic problems with unknown mechanisms.Since grid operation asks for a certain voltage amplitude and frequency level when there is a power imbalance,roles of the PE grid-tied devices during dynamics must be characterized as internal voltage response under power excitation,in which the voltage vector evolves through its timevarying amplitude and frequency.Existing modeling works,unfortunately,fail to recognize amplitude and frequency modulation essence of grid voltage during dynamics,so corresponding linear models are inapplicable to small-perturbation grid dynamic analysis.Thus,taking current control timescale of grid-tied voltage source converter(VSC)for example,this paper establishes a model with active and reactive current excitation and internal voltage amplitude and frequency response.Especially,the role of the terminal voltage detection-based phase-locked loop(PLL)in the excitation-response relationship is revealed.Linearization is conducted by clarifying amplitude and frequency operating points and corresponding increments of AC signals.This model intuitively reflects the evolution of internal voltage amplitude and frequency excited by active and reactive currents,which represents characteristics of the device during dynamics.Then,simulations for verification of the linear model and time-varying nature of amplitude and frequency are presented.Features of the characteristics of VSC are preliminarily discussed.展开更多
基金supported by the Joint Fund of the National Natural Science Foundation of China(No.U1866601).
文摘Frequency and voltage dynamics,as the focus of power systems,depend more and more on the frequency and amplitude response characteristics of renewable energy devices subjected to power imbalance.The doubly-fed induction generator(DFIG)-based wind turbine(WT)is representative of renewable energy devices and shows different characteristics from those of conventional synchronous generators(SGs).Unfortunately,the individual characteristics of WTs during system frequency and voltage dynamics are not intuitively illustrated by the existing structure-oriented models.Therefore,this paper proposes a function-oriented modeling methodology by representing inertia-controlled DFIG-based WT as an internal voltage frequency and amplitude solely stimulated by active and reactive power imbalance.The individuality of the characteristics is demonstrated by the grid voltage detection-based controls that the internal voltage depends solely on the power imbalance of WTs,just like the case of SGs.Through the infinity gain equivalence of the fast-electromagnetic loops,a simplified analytical model illustrating the electromechanical characteristics of WTs is further proposed.Based on the model,the similarities and differences between the characteristics of WTs and SGs are recognized.Simulation results are also presented for verification.
基金supported by the National Key Research and Development Program of China(2017YFB0902901)and National Natural Science Foundation of China(51627811).
文摘Increasing penetration of power electronic(PE)grid-tied devices has caused more and more dynamic problems with unknown mechanisms.Since grid operation asks for a certain voltage amplitude and frequency level when there is a power imbalance,roles of the PE grid-tied devices during dynamics must be characterized as internal voltage response under power excitation,in which the voltage vector evolves through its timevarying amplitude and frequency.Existing modeling works,unfortunately,fail to recognize amplitude and frequency modulation essence of grid voltage during dynamics,so corresponding linear models are inapplicable to small-perturbation grid dynamic analysis.Thus,taking current control timescale of grid-tied voltage source converter(VSC)for example,this paper establishes a model with active and reactive current excitation and internal voltage amplitude and frequency response.Especially,the role of the terminal voltage detection-based phase-locked loop(PLL)in the excitation-response relationship is revealed.Linearization is conducted by clarifying amplitude and frequency operating points and corresponding increments of AC signals.This model intuitively reflects the evolution of internal voltage amplitude and frequency excited by active and reactive currents,which represents characteristics of the device during dynamics.Then,simulations for verification of the linear model and time-varying nature of amplitude and frequency are presented.Features of the characteristics of VSC are preliminarily discussed.
