CN109038544B - Transient stability identification method based on voltage track characteristics - Google Patents

Transient stability identification method based on voltage track characteristics Download PDF

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CN109038544B
CN109038544B CN201810708424.1A CN201810708424A CN109038544B CN 109038544 B CN109038544 B CN 109038544B CN 201810708424 A CN201810708424 A CN 201810708424A CN 109038544 B CN109038544 B CN 109038544B
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孙应毕
刘志坚
宋琪
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Kunming University of Science and Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract

The invention relates to a transient stability identification method based on voltage track characteristics, and belongs to the technical field of power system stability. Collecting information of a bus node in a certain moment of the power system through a wide area measurement system; judging whether the power system fails, and if so, selecting a bus node with the fastest voltage drop as an observation point; selecting two sets with the largest power angle difference of the generator, and calculating the electrical distances from the observation points to the two sets respectively; predicting future voltage according to historical data of the voltage of the observation point; and judging whether the power angle instability of the system occurs according to the relation between the minimum value of the voltage of the observation point and the electrical distance. The method does not need to carry out quick grouping on the generators and calculate the inertia center of the system, and can judge the problem of the transient stability of any pendulum of the power system on line in real time.

Description

Transient stability identification method based on voltage track characteristics
Technical Field
The invention relates to a transient stability identification method based on voltage track characteristics, and belongs to the technical field of power system stability.
Background
Modern power systems are developed into large-scale regional interconnected power grids, and the development can bring great economy and make the transient stability problem more complicated. Transient instability remains one of the biggest threats faced by modern power systems. Effective real-time transient stability prediction and emergency control are of great importance. The traditional transient stability control strategy mainly adopts a control method of 'making a strategy table off line and matching in real time'. And the system model and the parameters have some deviation, thereby influencing the accuracy of the calculation result. At present, common transient stability analysis methods include time domain simulation, a direct method based on a lyapunov energy function, a mixed method combining a numerical simulation method and a direct method, a system equivalence method represented by an extended equivalence law, a transient stability analysis method guided by an artificial intelligence algorithm, and the like.
With the wide application of Wide Area Measurement Systems (WAMS), real-time power system transient instability identification based on PMU/WAMS has become one of the hot research topics. The transient stability identification method based on the voltage track characteristics only needs the voltage information of the bus node with the lowest voltage, and can judge whether the power angle instability occurs in the system or not by predicting the minimum value of the node voltage and comparing the minimum value with the electrical distance relationship between the observation point and the two generators with the maximum power angle difference.
Disclosure of Invention
The invention aims to provide a transient stability identification method based on voltage track characteristics, which is used for quickly identifying whether a power angle of a system is unstable or not.
The technical scheme of the invention is as follows: a transient stability identification method based on voltage track characteristics is characterized in that a wide area measurement system is used for collecting information of a bus node in a certain moment of an electric power system; judging whether the power system fails, and if so, selecting a bus node with the fastest voltage drop as an observation point; selecting two sets with the largest power angle difference of the generator, and calculating the electrical distances from the observation points to the two sets respectively; predicting future voltage according to historical data of the voltage of the observation point; and judging whether the power angle instability of the system occurs according to the relation between the minimum value of the voltage of the observation point and the electrical distance.
The method comprises the following specific steps:
step S1: at the moment t, the power angle delta of the ith generator of the power system is acquired in real time through a wide area measurement systemiAnd the voltage V of the q-th bus nodeqI is 1, 2 and 3 … … n, n is the number of all generators in the power system, q is 1, 2 and 3 … … m, and m is the number of all bus nodes in the power system;
step S2: judging whether the power system fails according to the generator information extracted in the step S1 by using the formula (1), and if the formula (1) is met, determining that the power system fails; if no fault occurs, returning to step S1, if a fault occurs, sorting all generators according to power angle and bus node voltage from large to small, and determining whether the power system has a fault according to the following formula:
Figure GDA0003097063320000021
wherein T is sampling time, T is sampling period, V (T) is bus node voltage at the time of T, V (T-T) is bus node voltage at the time of (T-T), V (T-2T) is bus node voltage at the time of (T-2T), and k is an empirical value; typically 10 is taken.
Step S3: firstly, selecting a bus node with the fastest voltage drop as an observation point, then selecting two sets with the largest and smallest power angles of the generator, and calculating the electrical distance from the observation point to the two sets, wherein the calculation method is the shortest line distance from the observation point to the two sets in the network topology structure of the power system;
step S4, predicting future voltage according to historical data of the maximum generator power angle difference and the lowest bus node voltage:
V＝a1*t^3+a2*t^2+a3*t+a4 (2)
wherein t is time, and a1, a2, a3 and a4 are obtained by least square method identification by using historical data;
step S5, determining whether power angle instability occurs in the system, and if the system satisfies equation (3), determining that a fault occurs:
Figure GDA0003097063320000022
wherein: vminObtaining a minimum voltage amplitude value for an observation point through prediction; z1、Z2The electrical distances from the observation point to the two sets with the maximum generator power angle difference are respectively.
The principle of the step S5 is:
(1) for a system with load and generator, a model can be built as shown in FIG. 2, where E1、Z1And E2、Z2Potential and impedance on the generator 1 side and generator 2 side, respectively, P, Q being the active power and reactive power of the load, respectively.
(2) According to thevenin equivalence theorem, a circuit outside a load point port can be equivalently replaced by a voltage source and a resistor, and the potential of the load point is equivalent to that of the load point through thevenin:
Figure GDA0003097063320000023
(3) the voltage amplitude of the load point determined for equation (4) is determined by the following equation:
Figure GDA0003097063320000031
(4) the minimum value of the voltage amplitude determined by equation (5) is:
Figure GDA0003097063320000032
the invention has the beneficial effects that:
the method does not need to carry out quick grouping on the generators and calculate the inertia center of the system, and can judge the problem of the transient stability of any pendulum of the power system on line in real time.
The method carries out voltage track real-time prediction based on the most disturbed measuring point, has simple calculation method and high prediction precision, can be used for system transient instability early warning, further improves the timeliness of instability judgment, and reduces the cost paid by subsequent control measures as much as possible.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a diagram of a dual-machine single-load model of the present invention;
FIG. 3 is a diagram of the 10 machine 39 node of the present invention;
fig. 4 is a diagram of the power angle time variation of the generator in embodiment 2 of the present invention;
FIG. 5 is a time chart of bus voltage in embodiment 2 of the present invention;
fig. 6 is a diagram of the power angle time variation of the generator in embodiment 3 of the present invention;
fig. 7 is a time chart of the bus voltage in embodiment 3 of the present invention.
Detailed Description
The invention is further described with reference to the following drawings and detailed description.
Example 1: as shown in fig. 1-3, a transient stability identification method based on voltage trace characteristics collects information of a bus node in a certain moment of an electric power system through a wide area measurement system; judging whether the power system fails, and if so, selecting a bus node with the fastest voltage drop as an observation point; selecting two sets with the largest power angle difference of the generator, and calculating the electrical distances from the observation points to the two sets respectively; predicting future voltage according to historical data of the voltage of the observation point; and judging whether the power angle instability of the system occurs according to the relation between the minimum value of the voltage of the observation point and the electrical distance.
The method comprises the following specific steps:
step S1: at the moment t, the power angle delta of the ith generator of the power system is acquired in real time through a wide area measurement systemiAnd the voltage V of the q-th bus nodeqI is 1, 2 and 3 … … n, n is the number of all generators in the power system, q is 1, 2 and 3 … … m, and m is the number of all bus nodes in the power system;
step S2: judging whether the power system fails according to the generator information extracted in the step S1 by using the formula (1), and if the formula (1) is met, determining that the power system fails; if no fault occurs, returning to step S1, if a fault occurs, sorting all generators according to power angle and bus node voltage from large to small, and determining whether the power system has a fault according to the following formula:
Figure GDA0003097063320000041
wherein T is sampling time, T is sampling period, V (T) is bus node voltage at the time of T, V (T-T) is bus node voltage at the time of (T-T), V (T-2T) is bus node voltage at the time of (T-2T), and k is an empirical value; typically 10 is taken.
Step S3: firstly, selecting a bus node with the fastest voltage drop as an observation point, then selecting two sets with the largest and smallest power angles of the generator, and calculating the electrical distance from the observation point to the two sets, wherein the calculation method is the shortest line distance from the observation point to the two sets in the network topology structure of the power system;
step S4, predicting future voltage according to historical data of the maximum generator power angle difference and the lowest bus node voltage:
V＝a1*t^3+a2*t^2+a3*t+a4 (2)
wherein t is time, and a1, a2, a3 and a4 are obtained by least square method identification by using historical data;
step S5, determining whether power angle instability occurs in the system, and if the system satisfies equation (3), determining that a fault occurs:
Figure GDA0003097063320000042
wherein: vminObtaining a minimum voltage amplitude value for an observation point through prediction; z1、Z2The electrical distances from the observation point to the two sets with the maximum generator power angle difference are respectively.
Example 2: in order to verify the stability identification method based on the phase trajectory and the transient energy, a BPA program is applied to simulate the conditions that the same fault occurs in different places and the same fault duration is different on an IEEE10 machine 39 node system, the calculation step length is 0.01s, and a generator is driven by an Eq' model. The operation mode is that the position of the bus 4 is 80% of constant impedance and 20% of constant current load, the position of the bus 7 is 70% of constant impedance and 30% of constant current load, the position of the bus 15 is 50% of constant impedance, 30% of constant current and 20% of constant power load, and the position of the bus 23 is 30% of constant impedance and 70% of constant power load. The set fault is a three-phase short circuit fault of a line 0s connecting the bus 26 to the bus 29, and the line is cut off by 0.28 s.
And step S1, acquiring the power angle of the first generator of the power system and the voltage of the q-th bus node in real time through the WAMS at the time t. And i is 1, 2 and 3 … … n, and n is the number of all generators in the power system. q is 1, 2 and 3 … … m, and m is the number of all bus nodes in the power system. The power angle of the generator is shown in fig. 4, and the bus voltage at each node is shown in fig. 5.
And step S2, judging whether the system has a fault or not, and knowing that the system has a fault at 0S according to the formula (1).
Step S3, according to fig. 4, the bus node with the minimum voltage amplitude is 38, and the generators with the maximum power angle difference are No. 38 and No. 30 sets, respectively. Therefore, the bus node 38 is selected as an observation point, and the electrical distance from the observation point to the two generator sets
Figure GDA0003097063320000051
Steps S4, 0.28S identify that voltage prediction can be entered, and therefore, future voltage is predicted according to the historical data of the maximum generator power angle difference and the minimum bus node voltage, and the predicted result is-0.01038 t ^3+2.18 t ^2-3.172 t + 1.546.
Step S5, judging whether the system has power angle instability:
the predicted minimum value of the voltage is 0.3881 at 0.73s and is less than 0.4, so that the system instability can be judged at 0.73 s.
Example 3: in order to verify the stability identification method based on the phase trajectory and the transient energy, a BPA program is applied to simulate the conditions that the same fault occurs in different places and the same fault duration is different on an IEEE10 machine 39 node system, the calculation step length is 0.01s, and a generator is driven by an Eq' model. The operation mode is that the position of the bus 4 is 80% of constant impedance and 20% of constant current load, the position of the bus 7 is 70% of constant impedance and 30% of constant current load, the position of the bus 15 is 50% of constant impedance, 30% of constant current and 20% of constant power load, and the position of the bus 23 is 30% of constant impedance and 70% of constant power load. The setting fault is that a three-phase short circuit fault occurs on a line 0s connecting the bus 26 to the bus 29, and the line is cut off by 0.20 s.
And step S1, acquiring the power angle of the first generator of the power system and the voltage of the q-th bus node in real time through the WAMS at the time t. And i is 1, 2 and 3 … … n, and n is the number of all generators in the power system. q is 1, 2 and 3 … … m, and m is the number of all bus nodes in the power system. The power angle of the generator is shown in fig. 6, and the bus voltage at each node is shown in fig. 7.
And step S2, judging whether the system has a fault or not, and knowing that the system has a fault at 0S according to the formula (1).
Step S3, according to fig. 4, the bus node with the minimum voltage amplitude is 38, and the generators with the maximum power angle difference are No. 38 and No. 30 sets, respectively. Therefore, the bus node 38 is selected as an observation point, and the electrical distance from the observation point to the two generator sets
Figure GDA0003097063320000052
The steps S4 and 0.20S identify that the voltage prediction can be entered, so that the future voltage is predicted according to the historical data of the maximum generator power angle difference and the minimum bus node voltage, and the predicted result is U5.336 t ^3-2.551 t ^2-0.689 t + 1.141.
Step S5, judging whether the system has power angle instability:
the predicted minimum value of the voltage is 0.81 and is more than 0.4, so that the system can be judged to be stable.
While the present invention has been described in detail with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, and various changes can be made without departing from the spirit and scope of the present invention.

Claims (2)

1. A transient stability identification method based on voltage track characteristics is characterized by comprising the following steps: collecting information of a bus node in a certain moment of the power system through a wide area measurement system; judging whether the power system fails, and if so, selecting a bus node with the fastest voltage drop as an observation point; selecting two sets with the largest power angle difference of the generator, and calculating the electrical distances from the observation points to the two sets respectively; predicting future voltage according to historical data of the voltage of the observation point; judging whether the system has power angle instability according to the relation between the minimum value of the voltage of the observation point and the electrical distance, and if so, judging that the power angle instability occurs
Figure FDA0003097063310000011
Then it is determined that a fault has occurred: wherein: vminObtaining a minimum voltage amplitude value for an observation point through prediction; z1、Z2The electrical distances from the observation point to the two sets with the maximum generator power angle difference are respectively.
2. The transient stability identification method based on the voltage trace characteristics as claimed in claim 1, wherein the specific steps are as follows:
step S1: at time t, by wide-area measuring systemReal-time acquisition of power angle delta of ith generator of power systemiAnd the voltage V of the q-th bus nodeqI is 1, 2 and 3 … … n, n is the number of all generators in the power system, q is 1, 2 and 3 … … m, and m is the number of all bus nodes in the power system;
step S2: judging whether the power system fails according to the generator information extracted in the step S1 by using the formula (1), and if the formula (1) is met, determining that the power system fails; if no fault occurs, returning to step S1, if a fault occurs, sorting all generators according to power angle and bus node voltage from large to small, and determining whether the power system has a fault according to the following formula:
Figure FDA0003097063310000012
wherein T is sampling time, T is sampling period, V (T) is bus node voltage at the time of T, V (T-T) is bus node voltage at the time of T-T, V (T-2T) is bus node voltage at the time of T-2T, and k is an empirical value;
step S3: firstly, selecting a bus node with the fastest voltage drop as an observation point, then selecting two sets with the largest and smallest power angles of the generator, and calculating the electrical distance from the observation point to the two sets, wherein the calculation method is the shortest line distance from the observation point to the two sets in the network topology structure of the power system;
step S4, predicting future voltage according to historical data of the maximum generator power angle difference and the lowest bus node voltage:
V＝a1*t^3+a2*t^2+a3*t+a4 (2)
wherein t is time, and a1, a2, a3 and a4 are obtained by least square method identification by using historical data;
step S5, determining whether power angle instability occurs in the system, and if the system satisfies equation (3), determining that a fault occurs:
Figure FDA0003097063310000021
wherein: vminObtaining a minimum voltage amplitude value for an observation point through prediction; z1、Z2The electrical distances from the observation point to the two sets with the maximum generator power angle difference are respectively.
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CN108092304A (en) * 2017-12-06 2018-05-29 昆明理工大学 Power system transient stability method of discrimination based on phase path Yu relative kinetic energy change rate

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