Power System Voltage Stability Assessment Method Based On Response Of Nodal Injection Power

The power system has a complex structure and strong nonlinearity,which leads to the great difficulty of modeling.The state vigorously promotes the construction of "three types and two networks",and the rapid development of power grid technology puts forward requirements for the power system stability.In the actual operation of power system,there is always disturbance outside the system,and the system will respond under the influence of disturbance.By extracting the relevant information from the measured response,the system stability can be assessed online.The paper studies the analysis method of power system stability distributed assessment based on local measurement technology.Investigate the characteristics and connections of the multi-machine system power flow analysis method and the small disturbance method.To explore the influence of power flow analysis method on the static stability assessment,taking the static stability analysis of the twomachine system as an example,the stability conditions of the complex system are analyzed by the small disturbance method and the power flow method respectively and the paper points out the main error source of the power flow analysis method is that assumed that the inertia of the slack bus is infinite.This paper explains in detail the impact of the errors in the approximate assumptions of the slack bus,power node,load node and network loss in the power flow model on the static stability analysis results.It is pointed out that the possible causes of errors and the improving direction in the voltage stability assessment method based on the power flow and the improving direction.It shows that the online application of the power flow method based on random response can obtain the same accurate result of the small disturbance method,and overcomes the weakness that the small disturbance method must rely on an accurate mathematical model and has large the calculation workload.The criterion of voltage stability of nonlinear circuit is proposed.In order to assess the static stability of the system by local measurement,the power flow equation is analyzed to prove that the voltage stability criterion is equivalent to the singularity of Jacobian matrix.The load impedance modulus margin index that can quantitatively evaluate the static voltage stability of the load node is proposed.The difference between the static load impedance and the dynamic equivalent impedance of the load node is used to reflect the distance from the operating point to the SNB point.This paper analyzes the problems of assessing voltage stability by Thevenin equivalent method,that is,the uniqueness of identification of the power system Thevenin equivalent impedance must rely on wide-area phasor measurement technology,and the Thevenin equivalent parameter assessment method of voltage stability is not suitable for disturbance within the system.PV node static angle stability active-reactive power increment rate index based on random response is proposed.To obtain a more accurate,reliable and model-independent system stability assessment method,the dynamic response of reactive power control variable under the stimulation of active power disturbance variable is used to quantitatively assess the stability margin of the node.This paper explains the directive significance of active-reactive power increment rate index for power system planning and design and operation scheduling,and proposes the equal power increment rate principle.The IEEE39 system simulation results verify the correctness and effectiveness of the active-reactive power increment rate index.The promotion form of this index at load nodes will be an important index of online voltage stability distributed assessment.