Modeling Approach Based On Internal Voltage Motion Equation For Power System Dynamic Voltage Stability Analysis And Study Of Apparatus Dynamic Characteristics

Today,china is faced with energy security,environment problem and climate change problem.In order to solve these thorny problems,many electronic devices are adding to the power systems.The power systems of china inevitably become power electronics dominated power systems.Since the electronic devices behaves differently in multiple time-scales,the dynamic voltage problems can be divided to rotor speed control,DC-voltage control and AC-current control time-scales.Dynamic voltage stability issues,which happened in real conditions around the world,becomes severe due to the poor grid conditions,complex control and structures of electronic devices.Therefore,it is significant for modeling with power equipment to analyze dynamic voltage problems.This paper reviews the study results of the modeling of system dynamic voltage issues,and summarizes the deficiencies of these model.These models are specialized,mathematization and structuring,which are not suitable for the complicated systems in the future studies of dynamic voltage stability.Thus,by using the internal voltage to presents the devices status,this paper proposes the amplitude-phase motion equation.The characteristics of devices are regarded as the relationship between the unbalance power of input and output active/reactive power and internal voltage amplitude/phase.This modeling method placed great emphasis on concrete analysis of physical characteristics of devices.The physical explanations and mechanism of phase/amplitude motion of are also given based on the phase-amplitude motion equation.Meanwhile,the characteristics of transmitting reactive power are studied.During the AC-current control time-scale,this paper choose static rectangular coordinate system to model the devices.The influence factors for the system dynamic voltage stability prombles are also given.The whole content can be divided into the following aspects:(1)The series-control characteristics of power electronic devices and the multiple time-scales in electronic systems are introduced.Based on the bandwidth of typical control loops,the dynamic voltage stability issues are divided into rotor speed control,DC-votlage control and AC-current control time-scales.As a result,the research framework is established from the time-scale,disturbance characteristics and study conditions.(2)This paper choose the internal voltage to present the devices conditions in power systems.Meanwhile,the amplitude-phase motion equation is proposed to describe the dynamic characteristics of devices,which means the characteristics of devices are regarded as the relationship between the unbalance power of input and output active/reactive power and internal voltage amplitude/phase.Moreover,this paper takes synchronous generator and doubly fed induction generator wind turbine(DFIG WT)as examples in rotor speed control time-scale.And permanent magnet synchronous generator wind turbine(PMSG WT)in DC-voltage control time-scale as example.The specific modeling methods are given under two time-scales.In the single-machine system,time-domain simulations are made to compare among these specific models.The eigenvalues in the small-signal analysis are also compared in the same way.The accuracy and rationality of the proposed model have been proved according to the analysis.Eventually,the modeling method based on phase-amplitude motion equation has been summarized.(3)The physical understanding of DFIG WT's internal voltage phase and amplitude are deepen by analogizing to the real dynamical system,such as the rotor's rotating and the voltage on the capacitor.This paper introduces the equal capacitor and analysis its impact on the reactive power allocation.The mechanism of voltage phase and amplitude motion has been revealed in the single DFIG WT integrated system.The control parameter's impact on the characteristics of voltage phase and amplitude motion has also been analyzed.Moreover,the influence of the characteristics of transmission line transmitting reactive power on voltage dynamics is preliminarily studied and explored.(4)During the AC-current control time-scale,this paper choose static rectangular coordinate system to model the devices.The small signal model to analyze dynamic voltage stability is given according to the understanding of converter's dynamic voltage motion.The influence of current control,voltage feed forward and grid strength on terminal voltage stability are studied.This paper also analyze the key parameters of dynamic voltage stability,which can provide guidance to the design of converter current controller under different grid strength.