CN107832959B - Voltage stability evaluation method considering load characteristics and power supply constraints - Google Patents
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Abstract
The invention discloses a voltage stability evaluation method considering load characteristics and power supply constraints, which is characterized by comprising the following steps of: the method comprises the following steps: simplified admittance matrix Y of simplified equivalent model of computing network+(ii) a Step two: calculating an equivalent network admittance matrix Y taking into account power constraintsS(ii) a Step three: forming a load characteristic matrix L related to the load characteristics; step four: calculating thevenin equivalent parameters of the system load, and performing voltage stability evaluation; the voltage stability evaluation method considering the load characteristics and the power supply constraints can correctly evaluate the voltage stability of the load in a complex system.
Description
Technical Field
The invention relates to the technical field of voltage stability evaluation, in particular to a voltage stability evaluation method considering load characteristics and power supply constraints.
Background
Since the 20 s of the last century, the stability of power systems was carefully studied as an important premise for safe operation, and until the end of the 70 s to the beginning of the 80 s of the last century, the voltage stability of power systems began to be regarded by people and became an important sub-topic for the study of the stability of power networks due to the successive grid disconnection accidents characterized by the breakdown of the voltage of the interconnected power networks.
With the advent of PMU, voltage stability evaluation of a system by using PMU data and thevenin equivalent method becomes an important direction in voltage stability research. Scholars at home and abroad do a lot of work on the aspect of the Thevenin equivalent parameter identification method. The original document states that within a data window, monitoring bus load changes are the main factors of grid disturbances, and other parts can be approximately regarded as being kept constant, so that the system side thevenin equivalent potential and equivalent impedance seen from the monitoring bus are kept constant. Therefore, the Thevenin equivalent potential and the equivalent impedance can be estimated by measuring phasor by using the voltage and the current of the monitoring bus in a data window with proper length. When monitoring the load change of the bus, the potential amplitude of the voltage source may not be changed, but the phase angle can be changed to a certain extent due to the power change, so that the assumption is not proper, and a thevenin equivalent model of the potential phase angle change is proposed in the literature. A better estimation result is obtained when only the bus load increase is monitored. If the multi-node load increases, then the Thevenin equivalent reactance will also change, and the above assumption cannot be satisfied. In addition, there is a document that the structure of thevenin equivalent potential and equivalent reactance is analyzed from the analytic angle by using a system node voltage equation, and the processing of other node load coupling terms is considered to be the key of an equivalent model, but a specific processing method is not proposed. At present, a traditional Thevenin equivalent model is still adopted in a large amount in voltage stability evaluation. The methods all use the assumption that the Thevenin equivalent parameters in the neighborhood data or the data window length are not changed, and documents indicate that the assumption is difficult to be established in actual parameter estimation, which is the fundamental reason that the methods cannot achieve good parameter estimation effect. Subsequently, full differential methods have been proposed to construct enough algebraic equations to solve for the equivalent parameters at each time instant. The method has the defects that the method depends on the initial value, and when the power grid disturbance is large, the estimation result has large errors.
It is therefore desirable to have a voltage stability evaluation method that takes into account load characteristics and power supply constraints to solve the problems in the prior art.
Disclosure of Invention
The invention aims to provide a voltage stability evaluation method considering load characteristics and power supply constraints, which can correctly evaluate the voltage stability of a load in a complex system.
The invention provides a voltage stability evaluation method considering load characteristics and power supply constraints, which comprises the following steps of:
the method comprises the following steps: simplified admittance matrix Y of simplified equivalent model of computing network+；
Step two: calculating an equivalent network admittance matrix Y taking into account power constraintsS；
Step three: forming a load characteristic matrix L related to the load characteristics;
step four: and calculating thevenin equivalent parameters of the system load, and performing voltage stability evaluation.
Preferably, the step one comprises the following steps:
(1) establishing an admittance matrix of the network according to the power grid topological structure parameters measured by the wide area measurement system, wherein a node voltage equation of the network is as follows:
(2) dividing nodes in the network into power supply nodes, load nodes and connecting nodes, wherein V in the step (1)L,VT,VGRespectively representing a load node voltage, a connection node voltage and a power supply node voltage with power injection, wherein the power supply node comprises a PV node and a balance node;
(3) eliminating the connecting nodes from the admittance matrix of the step (1) to obtain a simplified admittance matrix:
wherein, Y+ LL＝YLL-YLT(YTT)-1YTL、Y+ LG＝YLG-YLT(YLT)-1YTG、Y+ GL＝YGL-YGT(YTT)-1YTL、Y+ GG＝YGG-YGT(YTT)-1YTG；
(4) After the relevant rows and relevant columns of the balanced nodes of the simplified admittance matrix in the step (3) are removed, the simplified admittance matrix Y used in the subsequent calculation process is obtained+：
Preferably, the load nodes are of active power or reactive power injection quantity; the connection node refers to a node without any injection amount of active power and reactive power.
Preferably, said step two includes determining reactive power contributions of said PV nodes by a wide area metrology system, based on said simplified admittance matrix Y+Calculating an equivalent network admittance matrix YS：
Wherein,
diag(QG) Representing reactive power emitted by the power source; qGAs pairs of diagonal elementsAn angle matrix; (Y)+ LG)*Represents a pair Y+ LGEach element of the matrix is conjugated.
Preferably, the equivalent network admittance matrix YSThe method comprises the constraints of the power supply on the constancy of the voltage amplitude and the active power output, the voltage phase angle of the power supply can be changed, and the equivalent network admittance matrix YSThe constraints of the generator for maintaining constant active power output and constant voltage amplitude are considered, and the influence of the change of the reactive power output of the generator on the voltage stability of the system is considered.
Preferably, the load characteristics in step three include: a constant power model, a constant load model, a constant impedance model, and combinations thereof.
Preferably, in the third step, the derivative of each load node with respect to voltage and current forms a load characteristic matrix L, and the expression of the load characteristic matrix L is as follows:
the elements are diagonal matrices composed of the voltage or current of the load nodes.
Preferably, the step four is to use the load characteristic matrix L and the equivalent network admittance matrix YSAnd combining, and solving the sensitivity of the load voltage and the load current to disturbance parameters, namely solving the following equation:
wherein
Id represents an identity matrix, subscript d is added to distinguish from current I; then comparing the voltage sensitivity with the current sensitivity to obtain thevenin equivalent impedance of the load node based on the sensitivity:
voltage stability determination index VS based on Thevenin equivalence
Si＝|Zth,i|/|Vi/Ii|
When S isiThe closer to 1, the closer the system operating point is to the voltage collapse point.
Preferably, the equivalent system matrix Y of the second stepsThe load characteristic matrix L in the third step needs to be updated in each state; if the topological structure of the system changes, the simplified admittance matrix Y + needs to be updated in the first step; if the generator reactive power reaches the limit, then the load and power nodes in Y + need to be repartitioned at step one.
The invention discloses a voltage stability evaluation method considering load characteristics and power supply constraints. The load characteristics and the static constraint of the generator are considered, the information of a complete power flow equation is reserved, the unreasonable assumption that the system side Thevenin equivalent parameters are not changed is not needed, and the technical defects are fundamentally avoided. The Thevenin equivalent parameter error of the system obtained by the method is small, and the voltage stability of the load can be correctly evaluated in a complex system.
Drawings
Fig. 1 is a flowchart of a voltage stability evaluation method considering load characteristics and power supply constraints.
FIG. 2 is an example of the I EEE9 node standard.
Fig. 3 is a voltage stability evaluation index graph of the load node 5.
Fig. 4 is a graph of the calculated thevenin equivalent impedance of the load node 5.
Fig. 5 is a voltage stability evaluation index graph of the load node 7.
Fig. 6 is a graph of the calculated thevenin equivalent impedance of the load node 7.
Fig. 7 is a voltage stability evaluation index graph of the load node 9.
Fig. 8 is a graph of the calculated thevenin equivalent impedance of the load node 9.
Detailed Description
In order to make the implementation objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiments of the present invention. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, but not all embodiments of the invention. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
The voltage stability evaluation index calculation method considering the power supply constraint and the load characteristic comprises the following steps of:
step 1: simplified admittance matrix Y of simplified equivalent model of computing network+
And establishing an admittance matrix of the network according to the power grid topological structure parameters measured by the wide area measurement system. The nodes in the network are divided into power supply nodes, load nodes and connecting nodes, wherein the connecting nodes are nodes without any injection quantity of active power and reactive power. The node voltage equation of the original network is as follows:
wherein, VL,VT,VGRepresenting the load node voltage, the supply node voltage (the supply node includes the PV node and the balancing node, but the balancing node is not required for the calculations that follow, and is reserved here for convenience of representation), and the connection node voltage, respectively, with power injection. In addition, when there isWhen the reactive power of the power supply node reaches a limit value, the power supply node is converted into a PQ node from a PV node type, and then the power supply node is converted into a load node for processing, and the power supply node is not called as a power supply node any more.
The simplified equivalence model to the connected node is eliminated.
Wherein, Y+ LL＝YLL-YLT(YTT)-1YTL、Y+ LG＝YLG-YLT(YLT)-1YTG、Y+ GL＝YGL-YGT(YTT)-1YTL、Y+ GG＝YGG-YGT(YTT)-1YTG。
After the relevant rows and relevant columns of the balanced nodes of the simplified admittance matrix are removed, the simplified admittance matrix Y used in the subsequent calculation process is obtained+。
Step 2: calculating an equivalent network admittance matrix Y taking into account power constraintsS
And calculating an equivalent network admittance matrix according to the network simplified admittance matrix according to the reactive power output of the PV node obtained by the wide-area measurement system. This equivalent network admittance matrix implicitly contains the constraints of the power supply on the constancy of the voltage amplitude and the active power, the voltage phase angle of the power supply can vary. If it is assumed that neither the amplitude nor the phase angle of the power supply changes, the voltage stability evaluation results will have a large error, and this calculation method has no such assumption, and thus avoids such an error. This is rare for other evaluation methods.
YSThe expression of the matrix is as follows:
wherein,
diag (Q) in the formulaG) Representing reactive power Q delivered by a power supplyGIs a diagonal matrix of diagonal elements. (Y)+ LG)*Represents a pair Y+ LGEach element of the matrix is conjugated. This is also shown below.
And step 3: forming a load characteristic matrix L related to the load characteristics
It is generally believed that the load model has a large influence on the voltage stability of the system, so the typical load static characteristics are considered: a constant power model, a constant load model, a constant impedance model, and combinations thereof. Of course, other forms of representation of the load static characteristics may be used. The load signature matrix is formed from the voltage and current derivatives of each load node, as shown in table 1.
If a load node is a superposition of multiple load types, corresponding elements in table 1 are superposed.
TABLE 1 element to load type correspondence table in load characteristic matrix
| Type of load | f(V,V*,I,I*) | df/dV | df/dV* | df/dI | df/dI* | df/dλ |
| Constant impedance | f:Vi/Ii-λZ0i＝0 | 1/Ii | 0 | -Vi/Ii 2 | 0 | -Z0i |
| Constant current | f:Ii-λI0i＝0 | 0 | 0 | 1 | 0 | -I0i |
| Constant power | f:ViIi *-λS0i＝0 | Ii * | 0 | 0 | Vi | -S0i |
The expression of the load characteristic matrix L is as follows:
the elements are diagonal matrices composed of the voltage or current of the load nodes.
In step 3, the static characteristics of the load are taken into account. Even in the analysis of the voltage static stability, the static load characteristic has a large influence on the analysis of the voltage stability. Therefore, various load static characteristics can be conveniently added into the calculation method, and the calculation method is also an advantage.
And 4, step 4: and calculating thevenin equivalent parameters of the system load, and calculating a voltage stability evaluation index VS.
Combining the load characteristic matrix L and the system admittance matrix YSIn combination, the load voltage, and the sensitivity of the load current to the disturbance parameter can be solved, i.e. the following linear equation:
wherein
IdAnd (3) representing a unit matrix, adding subscript d to distinguish the unit matrix from current I, and then comparing the voltage sensitivity with the current sensitivity to obtain the Thevenin equivalent impedance of the load node based on the sensitivity:
voltage stability determination index VS based on Thevenin equivalence
Si＝|Zth,i|/|Vi/Ii|
When S isiThe closer to 1, the closer the system operating point is to the voltage collapse point.
The sensitivity of the electrical quantity to load changes in the system can be obtained by solving linear equation (1) based on the result of the power flow equation or on the result of the state estimation. Solving the linear equation can obtain the voltage stability sensitivity index V of all the loads in this state at one timeSiThe voltage sensitivity of only one of the loads may be determined. Depending on which loads are assigned df/d λ is not equal to 0.
As shown in fig. 2, the voltage stability evaluation method considering the load characteristics and the power supply constraints proposed by the present invention is an IEEE9 node standard system. The example comprises three generators, three power nodes ( nodes 2, 3 and a balancing node 1), three load nodes ( nodes 5, 7, 9), and three connecting nodes ( nodes 4, 6, 8). Since the constant power load is most prone to voltage instability problems and is more complex to analyze and compute than constant impedance and constant current, in this example, the three load nodes are taken as the constant power load. The load power of the three load nodes is increased in the same proportion, and the proportion coefficient is lambda. The method calculates a state index S for evaluating voltage stability, so that each lambda value corresponds to an S value. The following calculation process is a detailed process of finding the state index S. Load characteristic matrix L and equivalent system matrix YsIt needs to be updated each time the S-index is calculated.
Step 1: simplified admittance matrix Y of simplified equivalent model of computing network+
And establishing an admittance matrix of the network according to the power grid topological structure parameters measured by the wide area measurement system.
Wherein, VL,VG,VTRepresenting the load node voltage, the power supply node voltage (the power supply node includes the PV node and the balancing node), and the connection node voltage, respectively. In which the order of the load nodesNodes No. 5, 7 and 9; the power supply nodes are nodes No. 1, 2 and 3 in sequence; the order of connecting nodes is node numbers 4, 6 and 8. The simplified equivalence model to the connected node is eliminated.
Wherein, Y+ LL＝YLL-YLT(YTT)-1YTL、Y+ LG＝YLG-YLT(YLT)-1YTG、Y+ GL＝YGL-YGT(YTT)-1YTL、Y+ GG＝YGG-YGT(YTT)-1YTG。
Wherein the reduced admittance matrix removes Y after the associated row and associated column of the balancing node 1+I.e. the admittance matrix used in the subsequent calculation process. The system topology does not change and the matrix does not need to be updated. The calculation results are shown in Table 2.
TABLE 2 calculation results of elements of the reduced admittance matrix Y + (5 × 5)
| |
5 | 7 | 8 | 2 | 3 |
| 5 | 2.046-12.110i | -0.463+1.690i | -0.678+3.092i | 0 | -0.453+3.000i |
| 7 | -0.463+1.690i | 1.463-15.046i | -0.550+2.298i | -0.239+6.202i | -0.218+5.209i |
| 8 | -0.678+3.092i | -0.550+2.298i | 1.713-12.924i | -0.321+2.723i | 0 |
| 2 | 0 | -0.239+6.202i | -0.321+2.723i | 0.568-8.823i | 0 |
| 3 | -0.453+3.000i | -0.218+5.209i | 0 | 0 | 0.683-8.0598i |
Step 2: calculating an equivalent system admittance matrix Ys considering power supply constraints
Wherein,
this admittance matrix changes as the network operating conditions change, and therefore needs to be updated as the system parameters λ change. In this calculation example, Ys can be obtained as shown in table 3 when λ is 1, and Ys can be obtained as shown in table 4 when λ is 2.255.
When λ is 1 in table 3, the values of the elements in Ys matrix may be used
| 1.878-11.567i | -0.649+2.649i | -0.678+3.092i | 0.094-0.560i | 0.265-0.940i | 0 |
| -0.649+2.6485i | 1.152-11.159i | -0.7017+3.266i | 0.057-0.975i | 1.013-3.750i | 0.251-0.948i |
| -0.678+3.092i | -0.702+3.267i | 1.612-12.502i | 0 | 0.396-0.897i | 0.143-0.409i |
| 0.094+0.561i | 0.265+0.940i | 0 | 1.878+11.567i | -0.649-2.649i | -0.678-3.092i |
| 0.057+0.9753i | 1.013+3.749i | 0.25090+0.94769i | -0.649-2.649i | 1.152+11.160i | -0.7017-3.267i |
| 0 | 0.396+0.897i | 0.143376+0.40856i | -0.678-3.092i | -0.7017-3.266i | 1.612+12.502i |
Table 4 when λ is 2.255, the values of the elements of Ys matrix
And step 3: a load characteristic matrix L is formed from the load characteristics.
The three load nodes are all constant power loads. Therefore, it is not only easy to use
df/dIL＝0，
So as to obtain:
Table 5 λ 1, values of elements of L1 matrix
| 0.899+0.371i | 0 | 0 | 0 | 0 | 0 |
| 0 | 1.018+0.344i | 0 | 0 | 0 | 0 |
| 0 | 0 | 1.262+0.620i | 0 | 0 | 0 |
| 0 | 0 | 0 | 0.899-0.371i | 0 | 0 |
| 0 | 0 | 0 | 0 | 1.018-0.344i | |
| 0 | 0 | 0 | 0 | 1.262-0.620i |
Table 6 where λ is 1, the values of the elements of the L2 matrix
| 0 | 0 | 0 | 0.973-0.068i | 0 | 0 |
| 0 | 0 | 0 | 0 | 0.986+0.011i | 0 |
| 0 | 0 | 0 | 0 | 0 | 0.955-0.073i |
| 0.973+0.068i | 0 | 0 | 0 | 0 | 0 |
| 0 | 0.986-0.011i | 0 | 0 | 0 | |
| 0 | 0 | 0.955+0.073i | 0 | 0 | 0 |
Table 7 λ 2.255, values of elements of L1 matrix
| 1.397+2.668i | 0 | 0 | 0 | 0 | 0 |
| 0 | 0.745+2.740i | 0 | 0 | 0 | 0 |
| 0 | 0 | 1.592+4.437i | 0 | 0 | 0 |
| 0 | 0 | 0 | 1.397-2.668i | 0 | 0 |
| 0 | 0 | 0 | 0 | 0.745-2.740i | 0 |
| 0 | 0 | 0 | 0 | 0 | 1.592-4.437i |
Table 8 λ 2.255, values of elements of L2 matrix
| 0 | 0 | 0 | 0.512-0.493i | 0 | 0 |
| 0 | 0 | 0 | 0 | 0.477-0.693i | 0 |
| 0 | 0 | 0 | 0 | 0 | 0.427-0.482i |
| 0.512+0.493i | 0 | 0 | 0 | 0 | 0 |
| 0 | 0.477+0.693i | 0 | 0 | 0 | 0 |
| 0 | 0 | 0.427+0.482i | 0 | 0 | 0 |
And 4, step 4: and calculating thevenin equivalent parameters of the system load, and performing voltage stability evaluation.
Combining the load characteristic matrix L and the system admittance matrix YSIn combination, the sensitivity of the system electrical quantities to the parameter λ is solved, i.e. the following equation is solved:
then comparing the voltage sensitivity with the current sensitivity, the obtained Thevenin equivalent impedance based on the sensitivity of the load node is as follows:
voltage stability evaluation index VS based on Thevenin equivalence
Si＝|Zth,i|/|Vi/Ii|
When VSiThe closer to 1, the closer the system operating point is to the voltage collapse point.
The conditions at different load growth factors correspond to different voltage stability evaluations, see table 9.
TABLE 9 Voltage stability evaluation VS values for different load growth factors λ
It can be seen that when the load increase coefficient λ is 2.255, the system has voltage collapse, and the three load node voltage stability evaluation indicators VS are all equal to 1. The calculation method for evaluating the voltage stability is correct and accurate.
As shown in fig. 3, 5 and 7, the voltage and vs. target of load node 5, load node 7 and load node 9 are plotted as a function of λ.
As shown in FIGS. 4, 6 and 8, the static equivalent impedances, i.e., V, of the load nodes 5, 7 and 9Li/ILiThe impedance modulus of the AND system, i.e. ZThCurve with λ.
These curves show that the calculation of the VS index conforms to the real state of the system.
Finally, it should be pointed out that: the above examples are only for illustrating the technical solutions of the present invention, and are not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (3)
1. A voltage stability evaluation method considering load characteristics and power supply constraints, comprising the steps of:
the method comprises the following steps: simplified admittance matrix Y of simplified equivalent model of computing network+；
The method comprises the following steps: (1) will be provided withThe nodes in the network are divided into power supply nodes with active power injection, load nodes with power outflow and connection nodes without power injection and outflow, VL,VT,VGRespectively representing a load node voltage, a connection node voltage and a power supply node voltage, wherein the power supply node comprises a PV node and a balance node; current ILAnd IGRespectively representing the outflow current of a load node and the injection current of a power supply node; the linear relation between the voltage and the current is expressed by an admittance matrix, the admittance matrix of the network is established according to the power grid topological structure parameters measured by the wide area measurement system, and the node voltage equation of the network is as follows:
wherein the block matrix YLL、YLT、YLG、YTL、YTT、YTG、YGL、YGT、YGGIs a component of the system admittance matrix and respectively represents the load node current ILAnd load node voltage VLLoad node current ILAnd the voltage V of the connection nodeLLoad node current ILAnd a power supply node voltage VGConnecting node current and load node voltage VLThe current of the connection node and the voltage V of the connection nodeTConnecting node current to supply node voltage VGPower supply node current IGAnd load node voltage VLPower supply node current IGAnd the voltage V of the connection nodeTPower supply node current IGAnd a power supply node voltage VGThe proportional relationship of (a); the several block matrixes collectively represent the quantitative relationship between the current and voltage of the load node, the connection node and the power supply node;
(2) eliminating the connecting nodes from the admittance matrix of the step (1) to obtain a simplified admittance matrix:
wherein, Y+ LL＝YLL-YLT(YTT)-1YTL、Y+ LG＝YLG-YLT(YLT)-1YTG、Y+ GL＝YGL-YGT(YTT)-1YTL、Y+ GG＝YGG-YGT(YTT)-1YTG；
(3) After the relevant rows and relevant columns of the balanced nodes of the simplified admittance matrix in the step (2) are removed, the simplified admittance matrix Y used in the subsequent calculation process is obtained+：
The load nodes have active power or reactive power injection amount; the connection node refers to a node without any injection amount of active power and reactive power;
step two: calculating an equivalent network admittance matrix Y taking into account power constraintsS；
Confirming the reactive power output of the PV node through a wide area measurement system according to the simplified admittance matrix Y+Calculating an equivalent network admittance matrix YS：
Wherein,
diag(QG) Representing reactive power emitted by the power source; qGA diagonal matrix being diagonal elements; (Y)+ LG)*Represents a pair Y+ LGConjugate each element of the matrix;
step three: forming a load characteristic matrix L related to the load characteristics;
the load characteristics include: a constant power model, a constant load model, a constant impedance model, and combinations thereof;
the load characteristic matrix L is formed by the derivative of each load node to the voltage and the current, and voltage stability evaluation can be carried out on different types of loads in a unified mode through the matrix L; the expression of the load characteristic matrix L is as follows:
the elements are diagonal matrixes formed by the voltage or the current of the load nodes;
step four: calculating thevenin equivalent parameters of the system load, and performing voltage stability evaluation;
the load characteristic matrix L and the equivalent network admittance matrix Y are combinedSAnd combining, and solving the sensitivity of the load voltage and the load current to disturbance parameters, namely solving the following equation:
wherein
IdThe identity matrix is shown, subscript d is added to distinguish from current I; then comparing the voltage sensitivity with the current sensitivity to obtain the load nodePoint Thevenin equivalent impedance based on sensitivity:
voltage stability determination index VS based on Thevenin equivalence
Si＝|Zth,i|/|VLi/ILi|
When S isiThe closer to 1, the closer the system operating point is to the voltage collapse point.
2. The voltage stability evaluation method considering load characteristics and power supply constraints according to claim 1, wherein: the equivalent network admittance matrix YSThe method comprises the constraints of the power supply on the constancy of the voltage amplitude and the active power output, the voltage phase angle of the power supply can be changed, and the equivalent network admittance matrix YSThe constraints of the generator for maintaining constant active power output and constant voltage amplitude are considered, and the influence of the change of the reactive power output of the generator on the voltage stability of the system is considered.
3. The voltage stability evaluation method considering load characteristics and power supply constraints according to claim 2, wherein: the equivalent system matrix Y of the second stepsThe load characteristic matrix L in the third step needs to be updated in each state; if the topology of the system changes, the simplified admittance matrix Y needs to be updated in step one+(ii) a If the reactive power of the generator reaches the limit, Y needs to be set in step one+The medium load node and the power source node are divided again.
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