CN116914757B - Method and device for determining maximum estimated attraction domain of flexible interconnection system of power distribution area - Google Patents
Method and device for determining maximum estimated attraction domain of flexible interconnection system of power distribution area Download PDFInfo
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Abstract
The invention relates to a method and a device for determining the maximum estimated attraction domain of a flexible interconnection system of a power distribution station, which belong to the field of analysis and control of power systems and comprise the steps of constructing an equivalent circuit model and a corresponding equivalent circuit mathematical model of the flexible interconnection system of the power distribution station; acquiring electrical parameter data and system state information of a flexible interconnection system of a power distribution area in real time; acquiring a small disturbance stable balance point of the system based on an equivalent circuit model, electric parameter data acquired in real time and system state information; and establishing a TS fuzzy model based on the equivalent circuit mathematical model and the small disturbance stable balance point to obtain a system maximum estimated attraction domain, and analyzing transient stability boundary of the flexible interconnection system of the power distribution station. And constructing an equivalent circuit model and an equivalent circuit mathematical model, acquiring the system state and data in real time to obtain a small disturbance stable balance point, constructing a TS fuzzy model to obtain a maximum estimated attraction domain, and obtaining a system transient stability boundary.
Description
Technical Field
The invention belongs to the technical field of power systems and power distribution, and particularly relates to a method and a device for determining a maximum estimated attraction domain of a flexible interconnection system of a power distribution area.
Background
With the development of power systems and the increase of power demand, flexible interconnection systems of distribution areas are attracting attention as a flexible power supply and management method. The power distribution area flexible interconnection system refers to enhancing flexibility and reliability of a power system by interconnecting a plurality of power distribution areas in a flexible interconnection manner. However, existing flexible interconnection systems for distribution areas often lack accurate stability analysis and capacity planning methods in the face of transient events and load fluctuations. In the current flexible interconnection system of distribution areas, there are some technical defects and challenges, which limit the determination of the maximum attraction domain of the system, and common technical defects are as follows:
1) Inadequate system modeling: in the prior art, modeling of a flexible interconnection system of a power distribution area is generally based on a simplified assumption or an empirical formula, and complex interaction and dynamic characteristics of each component in the system cannot be fully considered. This leads to limitations in accuracy and reliability of the model, limiting the accurate determination of the system's maximum estimated suction domain;
2) Lack of systematic dynamic analysis methods: in the prior art, the transient stability analysis method for the flexible interconnection system of the power distribution area is relatively few. The existing method mainly focuses on static analysis and equilibrium state analysis, and ignores dynamic response and stability of the system under transient working conditions. This makes it impossible to accurately evaluate the maximum estimated suction domain of the system under dynamic conditions, especially in the face of sudden load changes or fault conditions;
3) Failure to effectively cope with uncertainty: the flexible interconnection system of the power distribution station is affected by various uncertainty factors, such as weather conditions, photovoltaic energy supply and demand fluctuation, load change and the like. The prior art has certain limitation in the aspect of processing the uncertainties, and cannot effectively influence the uncertainties on the maximum estimated attraction domain of the system;
4) Lack of system optimization methods: the maximum estimated attraction domain of the flexible interconnection system of the power distribution area is determined, and a corresponding system optimization method is lacked in the prior art. The lack of an optimization strategy and algorithm for the maximum estimated attraction domain of the system can not realize the optimal configuration and control of the system, and limit the further improvement of the performance and stability of the system.
In summary, the prior art has some technical defects in determining the maximum estimated attraction of the flexible interconnection system of the distribution area, and the accurate estimation of the maximum estimated attraction of the system is crucial to ensure the stability and reliability of the power system.
Disclosure of Invention
In view of the above analysis, the embodiment of the invention aims to provide a method for determining the maximum estimated attraction of a flexible interconnection system of a power distribution station, and aims to provide a method for determining the maximum estimated attraction of the flexible interconnection system of the power distribution station with high efficiency and accuracy so as to improve the running stability and reliability of the flexible interconnection system of the power distribution station.
In order to solve the technical problems, the main technical scheme adopted by the invention comprises the following steps:
the specification provides a method for determining a maximum estimated attraction domain of a flexible interconnection system of a power distribution area, which comprises the following steps:
constructing an equivalent circuit model and a corresponding equivalent circuit mathematical model of the flexible interconnection system of the power distribution area;
Acquiring electrical parameter data and system state information of a flexible interconnection system of a power distribution area in real time;
Acquiring a small disturbance stable balance point of a system based on the equivalent circuit model, the electrical parameter data acquired in real time and the system state information;
and constructing a TS fuzzy model based on the equivalent circuit mathematical model and the small disturbance stable balance point to obtain a system maximum estimated attraction domain.
Optionally, the constructing an equivalent circuit model of the flexible interconnection system of the power distribution area is as follows:
Based on the equivalent single machine topological structure of the flexible interconnection system of the distribution area, combining with the sagging control link, the method for obtaining the equivalent circuit model comprises the following steps:
the droop controller is used for continuously comparing the voltage of the direct current bus with the voltage regulating value and regulating through the PID droop control to obtain the regulated direct current bus real-time tracking current;
The multiplier is used for obtaining the power of the direct current bus based on the real-time tracking current and the actual end voltage of the energy storage of the adjusted direct current bus;
the divider is used for obtaining direct current bus current based on the direct current bus power and the direct current bus voltage;
And an alternating-current side, wherein the alternating-current side current is obtained based on the direct-current bus current.
Optionally, based on the equivalent circuit model, constructing the corresponding equivalent circuit mathematical model is as follows:
Wherein, C is a direct current side capacitor, u dc is a direct current bus voltage, P is an energy storage power, V s is an energy storage actual end voltage, V ref is a voltage reference value of droop control, k d、kp and k i are gain parameters in PID droop control link, Δu= jv (V ref-kdP/udc-udc) dt.
Optionally, based on the equivalent circuit mathematical model, the electrical parameter data collected in real time, and the system state information, obtaining a system small disturbance stable balance point includes:
When (when) When the balance point is established, a first balance point and a second balance point are obtained;
Taking a first balance point with larger voltage and smaller current in the first balance point and the second balance point as a system balance point;
establishing a Jacobian matrix of the first balance point;
Calculating eigenvalues and determinant of the Jacobian matrix of the first balance point;
Based on Judging whether u dc≥Vref/2 is true or not; when the first balance point is established, the trace of the Jacobian matrix of the first balance point is smaller than or equal to 0, and the first balance point is determined to be a system small disturbance stable balance point.
Optionally, the obtaining the system maximum estimated attraction domain includes the steps of:
S41, constructing the TS fuzzy model based on the equivalent circuit mathematical model;
step S42, determining a maximum estimated attraction domain based on the TS fuzzy model;
And step S43, performing system stability boundary analysis based on the maximum estimated suction domain.
Optionally, the step S41 includes:
based on the equivalent circuit mathematical model, constructing the TS fuzzy model is as follows:
Wherein,
Optionally, the step S42 includes:
Based on the TS fuzzy model, two variables of u dc and ≡ (V ref-kdP/udc-udc) dt=deltau are taken as coordinate axes, an ellipsoidal region omega is selected around the first balance point, and the region boundary is
Solving the maximum value of each nonlinear term of A (x) in the ellipsoidal region, and replacing the nonlinear term in A (x) with the maximum value, wherein each nonlinear term corresponds to two linear matrixes A i;
The presence of the positive definite symmetric matrix M may be such that each matrix A i satisfies the linear matrix inequality Then at/>The internal system is asymptotically stable;
The ellipsoidal region Ω is increased while the boundary Ω c is updated until the positive definite matrix M that holds the linear matrix inequality is absent, at which point the boundary Ω c is the maximum estimated attractive domain of the first balance point.
Optionally, the step S43 includes:
The center point of the ellipsoidal region is the position of maximum stability in the estimated attraction domain, and is the transient stability convergence center, and the boundary Ω c of the ellipsoidal region is the system stability boundary.
Optionally, the collecting, in real time, electrical parameter data and system status information of the flexible interconnection system of the power distribution area includes:
The electrical parameter data includes voltage, current, frequency and power data based on monitoring equipment, and the system state information includes line switch state.
The specification provides a determining device of maximum estimated attraction domain of a flexible interconnection system of a power distribution station, which is characterized in that:
constructing an equivalent circuit model module, and constructing the equivalent circuit model and the corresponding equivalent circuit mathematical model of the flexible interconnection system of the distribution area;
the real-time acquisition module acquires the electrical parameter data and the system state information of the flexible interconnection system of the power distribution area in real time;
The small disturbance stable balance point acquisition module is used for acquiring the small disturbance stable balance point based on the equivalent circuit mathematical model, the electrical parameter data acquired in real time and the system state information;
The maximum attraction domain determining module establishes the TS fuzzy model based on the equivalent circuit mathematical model and the small disturbance stable balance point to obtain the maximum estimated attraction domain, wherein the central point of the ellipsoidal region is the position of the maximum stability in the estimated attraction domain and is a transient stability convergence center, and the boundary omega c of the ellipsoidal region is a system stability boundary;
and the system strategy design and optimization module is used for designing and optimizing a flexible interconnection system control strategy of the power distribution area based on the analysis result of the maximum estimated attraction domain.
Compared with the prior art, the invention has the beneficial effects that:
1. The method can accurately analyze the maximum estimated attraction domain of the small disturbance stable balance point of the system, simplifies the complexity of the flexible interconnection system of the power distribution station and reduces the computational complexity;
2. the method comprises the steps of collecting electrical parameter data and system state information in real time, and carrying out real-time transient stability assessment based on the data, so that transient stability problems in a system can be found timely, and monitoring and response capacity of the flexible interconnection system state of a power distribution area can be improved;
3. Constructing a TS fuzzy model, and applying a TS fuzzy model theory to power system analysis; determining the maximum attraction domain of a small disturbance stable balance point, providing boundary reference for system balance stability, and comprehensively evaluating the transient stability of the flexible interconnection system of the power distribution area; and the control strategy is optimized, and the transient stability and disturbance rejection capability of the system are improved.
In a word, the invention provides a method for determining the maximum estimated attraction domain of the integrated flexible interconnection system of the power distribution station, which can evaluate the stability of the system in real time, provide accurate evaluation results, and provide guidance for optimizing and improving the system, thereby improving the reliability and stability of the system.
In the invention, the technical schemes can be mutually combined to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.
FIG. 1 is a flow chart of a method for determining a maximum estimated suction domain of a flexible interconnection system of a power distribution area;
FIG. 2 is an equivalent single machine topological graph of a flexible interconnection system of distribution areas under the condition of grid connection of multiple converters;
FIG. 3 is an equivalent circuit model diagram of a flexible interconnection system of a power distribution area;
FIG. 4 is a diagram of the maximum estimated attractive domain of a flexible interconnect system for a power distribution area;
FIG. 5 is a graph of transient simulation results for condition A1);
FIG. 6 is a graph of transient simulation results for condition A2);
fig. 7 is a diagram of a maximum estimated attractive area determination device for a flexible interconnection system of a power distribution area.
Detailed Description
The following detailed description of preferred embodiments of the application is made in connection with the accompanying drawings, which form a part hereof, and together with the description of the embodiments of the application, are used to explain the principles of the application and are not intended to limit the scope of the application.
Example 1
The flexible interconnection system of the power distribution station is an alternating current/direct current interconnection system, and is mainly composed of a complex unity composed of power electronic equipment such as a bidirectional DC/AC converter, a DC/DC converter, a direct current transformer and the like. In order to evaluate the maximum estimated attraction domain of the flexible interconnection system of the power distribution area in real time, the embodiment of the invention provides a method for determining the maximum estimated attraction domain of the flexible interconnection system of the power distribution area.
The embodiment of the invention provides a method for determining the maximum estimated attraction domain of a flexible interconnection system of a power distribution station. As shown in fig. 2, the flexible interconnection system of the distribution transformer grid-connected distribution transformer area is in an equivalent single-machine topology, and the flexible interconnection system is connected with the distribution transformer area, the direct-current load, the photovoltaic power generation unit and the energy storage unit through the direct-current bus.
A flow chart of a method for determining the maximum estimated attraction of a flexible interconnection system of a power distribution area comprises steps S1-S5, as shown in figure 1.
S1, constructing an equivalent circuit model and a corresponding equivalent circuit mathematical model of the flexible interconnection system of the power distribution area.
Based on the equivalent single machine topological structure of the flexible interconnection system of the distribution area described in fig. 2, an equivalent circuit model of the corresponding flexible interconnection system of the distribution area and a corresponding equivalent circuit mathematical model are established. An equivalent circuit model is shown in fig. 3.
By establishing an equivalent circuit model of the flexible interconnection system of the power distribution area, the complexity of the system is simplified, and in view of the complexity of the flexible interconnection system of the power distribution area, a sagging control link is introduced into the equivalent circuit model. The droop control link represents a power control part of the flexible interconnection system of the power distribution area, and the droop control is used for controlling active power output of the flexible interconnection system and performing droop control adjustment on the voltage of the direct current bus so as to respond to the change of the frequency or the power demand of the power distribution area.
And S11, constructing an equivalent single-path model of the flexible interconnection system of the distribution transformer area based on the equivalent single-machine topology.
1. And the sagging controller is used for obtaining the adjusted real-time tracking current of the direct current bus through a PID sagging control link based on the direct current bus voltage.
The droop controller is used for comparing the direct-current bus voltage u dc with an adjusted droop control voltage reference value (V ref-kd i), and performing PID droop control adjustment on the comparison result through a regulator (k p+ki/s) to obtain a direct-current bus real-time tracking current i td, as shown in a formula (1):
itd＝{(Vref-kdi)-udc}(kp+ki/s)＝(Vref-kdP/udc-udc)(kp+ki/s)
(1)
Wherein i td is the real-time tracking current of the direct current bus, V ref is the sagging control reference voltage value, u dc is the direct current bus voltage, i is the alternating current side current which changes in real time, k d、kp and k i are gain parameters in the sagging control link and are used for adjusting the performance of sagging control, and the parameter values are adjusted in real time according to the system condition.
2. And the multiplier is used for obtaining the direct current bus power based on the direct current bus current and the energy storage actual terminal voltage.
Dc bus power, as shown in equation (2):
Pdc＝3/2Vs*itd (2)
Wherein P dc is the power of a direct current bus, V s is the actual end voltage of energy storage, and i td is the real-time tracking current of the direct current bus.
3. And the divider is used for obtaining direct current bus current based on the direct current bus power.
The dc bus current is shown in equation (3).
idc＝Pdc/udc＝(3/2Vs*itd)/udc (3)
I dc is direct current bus current, P dc is direct current bus power, u dc is direct current bus voltage, V s is energy storage actual end voltage, and i td is direct current bus real-time tracking current.
4. The dc bus current is the sum of the dc side current and the ac side current, i.e. the dc side current is equal to the difference between the dc bus current and the ac side current.
As shown in fig. 3, the dc bus current is equal to the sum of the dc side current and the ac side current, as shown in equation (4).
From equation (4), it is converted into equation (5).
And step S12, establishing a corresponding equivalent circuit mathematical model based on the system equivalent circuit model.
Based on a system equivalent circuit model, u dc and ≡ (V ref-kdP/udc-udc) dt are used as state variables, and ≡ (V ref-kdP/udc-udc) dt=deltau is defined to obtain an equivalent circuit mathematical model corresponding to the equivalent circuit model of the low-voltage area flexible interconnection system, as shown in a formula (6).
Wherein, C is a direct-current side capacitor, u dc is a parallel capacitor for photovoltaic and energy storage, P is energy storage power, V s is energy storage actual terminal voltage, V ref is a voltage reference value for droop control, k d、kp and k i are gain parameters in a droop control link, and n (V ref-kdP/udc-udc) dt=Δu.
And S2, acquiring electrical parameter data and system running state information of the flexible interconnection system of the power distribution area in real time.
The flexible interconnection system of the power distribution station is an alternating current/direct current interconnection system, and is mainly composed of a complex unity composed of power electronic equipment such as a bidirectional DC/AC converter, a DC/DC converter, a direct current transformer and the like. The system has the advantages of dynamic property, diversity and interconnectivity, and can realize the renewable, efficient utilization and flexible scheduling of the power.
And (3) using monitoring equipment to acquire electrical parameter data such as voltage, current, frequency, power and the like of components in the flexible interconnection system of the power distribution station and state information of the system in real time, and uploading the electrical parameter data to an automatic master station of the power distribution station.
The electrical parameter data and the system running state information acquired in real time are as follows:
1) Distribution area data: the power distribution system comprises a power distribution area number, an area current, a voltage, a power and a frequency, and is used for monitoring and controlling the power state of the area;
2) Converter data: converting current from one form to another, such as direct current to alternating current, collecting data including input and output current, voltage, power for monitoring converter operating conditions and performance;
3) Photovoltaic power generation unit data: the photovoltaic power generation unit converts solar energy into electric energy through light energy, and the collected data comprise illumination intensity, battery pack voltage and current output and are used for evaluating the efficiency and performance of photovoltaic power generation;
4) Energy storage unit data: the energy storage unit is used for storing electric energy so as to release the electric energy when the electric power system of the distribution transformer area is required, and the collected data comprise energy storage voltage, current, charging power, discharging power, energy storage rated voltage value (namely a voltage reference value for droop control), energy storage actual terminal voltage and real-time power (becoming energy storage power);
5) Direct current load data: the direct current load refers to direct current equipment or a load directly connected with the system, and the collected data comprises load current, voltage and power requirements;
6) Line data: dc bus voltage, real-time frequency (in Hz), line switching status.
Through the electrical parameter data and the system state information which are collected in real time, the transient stability of the power system can be monitored and evaluated in real time, and corresponding adjustment, correction and optimization are carried out, so that the safe and stable operation of the system is ensured, and accurate data support is provided for subsequent transient stability analysis and report output.
And step S3, obtaining a small disturbance stable balance point of the system based on the equivalent circuit model, the electrical parameter data acquired in real time and the system state information.
Based on an equivalent circuit model, determining the maximum estimated attraction domain of the small disturbance stable balance point, and dividing the method into two substeps:
Step S31, analyzing transient events based on an equivalent mathematical model, and analyzing whether a balance point exists in the system;
S32, analyzing whether the balance point of the system is a small disturbance stable balance point SEP (Small disturbance stable equilibriumpoint, small disturbance stable balance point);
Firstly, carrying out static stability analysis on a system, and then analyzing whether the balance point is a small disturbance stable balance point or not on the basis that the balance point exists in the system; and finally, constructing a maximum estimated attraction domain of the small disturbance stable balance point, and further analyzing the transient stability of the system.
And S31, analyzing transient events based on the equivalent circuit model, and analyzing whether a balance point exists in the system.
Based on an equivalent circuit model of the flexible interconnection system of the power distribution area, analyzing whether a balance point exists in the system according to the electrical parameter data and the system state information acquired in real time.
The static stable requirement of the flexible interconnection system of the distribution area is as shown in a formula (7):
Wherein P is energy storage power, V ref is voltage reference value of droop control, k d is proportional gain parameter of droop control link, and formula (6) is smaller than or equal to right side of sign Designated as P I.
When the energy storage power P in the system is smaller than or equal to P I, two balance points exist in the flexible interconnection system of the power distribution area, and the system is static and stable.
At this time, two balance points of the flexible interconnection system of the distribution area are shown in formula (8).
Wherein e 1 and e 2 are a first balance point and a second balance point of the system, V ref is a voltage reference value of droop control, k d is a proportional gain parameter of the droop control link, k p is an integral gain parameter of the droop control link, k i is a differential gain parameter of the droop control link, V s is an energy storage actual end voltage, and P is energy storage power.
Based on the above formula (8), the voltage at the first balance point is greater than the voltage at the second balance point, and the voltage at the second balance point e 2 is smaller and the current is larger, so that the system does not stably operate at the second balance point in actual engineering, and the stability of the second balance point e 2 is not studied in the present invention.
And taking the first balance point with larger voltage and smaller current in the first balance point and the second balance point as a system balance point. The equilibrium point is the point at which the system is in steady state and is important for small disturbance analysis.
Step S32, whether the balance point of the analysis system is a small disturbance stable balance point SEP is analyzed.
Based on the first method of the Lyapunov stability, if the real parts of the characteristic values of the Jacobian matrix of the system balance point are all smaller than zero, the balance point is a small disturbance stable balance point.
Based on the first equilibrium point e 1, it is determined whether the first equilibrium point e 1 is the small-disturbance stable equilibrium point SEP.
The linearization process of the jacobian matrix can make the nonlinear system approximate a linear system near the equilibrium point. The jacobian matrix describes the linear behavior of the nonlinear model at the equilibrium point.
The jacobian matrix of first equilibrium points e 1 is shown as equation (9):
Wherein k d、kp and k i are gain parameters in a droop control link, V s is energy storage actual terminal voltage, P is energy storage power, and u dc is direct current bus voltage.
The eigenvalue of J (e 1), lambda 1,λ2, has a real part less than zero, equivalent to lambda 1+λ2 < 0 and lambda 1λ2 > 0. Whereas lambda 1+λ2 is equal to trace tr of e 1 (determinant of J (e 1)),λ1λ2 is equal to J (e 1)), equation (10) can be obtained:
When u dc≥Vref/2 holds, the first equilibrium point e 1 is a small disturbance stabilization equilibrium point, otherwise e 1 is not a small disturbance equilibrium point.
Solving for the determinant of the jacobian matrix J (e 1) of the first equilibrium point e 1 as shown in equation (11):
Due to When u dc≥Vref/2:
From the Jacobian matrix characteristics, it is known that at this time, |J (e 1) | > 0 is constant.
Trace tr (J (e 1)) of jacobian matrix J (e 1), as shown in equation (13):
If the trace of the Jacobian matrix is positive (i.e. greater than 0), the system has a certain amplification, and disturbance is amplified under control, so that unstable conditions can be caused;
From the above analysis, it can be seen that tr (J (e 1)) is less than or equal to 0 when u dc≥Vref/2 is true, the system is statically stable, i.e. there is a small disturbance stability balance point, then the first balance point e 1 is a small disturbance stability balance point SEP of the system, otherwise e 1 is not a small disturbance stability balance point of the system.
And S4, constructing a maximum estimated attraction domain based on the equivalent circuit mathematical model and the small disturbance stable balance point.
Comprises four substeps as follows:
s41, establishing a fuzzy model based on the equivalent circuit mathematical model;
and step S42, determining the maximum estimated attraction domain based on the TS fuzzy model.
And step S43, determining a system stability boundary based on the maximum estimated suction domain.
S41, constructing a TS fuzzy model based on the equivalent circuit mathematical model;
Based on Takagi-Sugeno (TS) fuzzy model theory, constructing a maximum estimated attraction domain LEDA of a small disturbance stable equilibrium point e 1 of the flexible interconnection system of the power distribution area, and analyzing the transient stability of the flexible interconnection system of the power distribution area based on the LEDA.
An equivalent circuit mathematical model of the flexible interconnection system of the power distribution station is constructed into a TS fuzzy model, namelyIn the form of (2) as shown in equation (14):
Wherein the method comprises the steps of
For the followingWherein, x= [ u dc,Δu]T,
And step S42, determining the maximum estimated attraction domain based on the TS fuzzy model.
First, based on the fuzzy model, two variables of u dc and ≡ (V ref-kdP/udc-udc) dt=deltau are taken as right-angle coordinate axes, an ellipsoidal region omega is selected around a first balance point e 1 of the system, and the boundary is marked asSolving the maximum value of each nonlinear term of A (x) in the region, and respectively replacing the nonlinear terms in A (x) by the maximum values, so that each nonlinear term corresponds to two linear matrixes A i;
Second, if there is a positive definite symmetric matrix M such that each matrix A i in the first step satisfies the linear matrix inequality A i T·M+M·Ai < 0, then in The internal system is asymptotically stable, where V (x) =x T Mx.
And thirdly, increasing omega and updating an ellipsoidal boundary omega c until a positive symmetric matrix M which enables the linear matrix inequality in the second step to be established does not exist, wherein the boundary omega c at this time is the maximum estimated attraction domain LEDA of the first balance point e 1.
The maximum estimated attraction domain LEDA, describing the stability range of small disturbances around the equilibrium point, by analyzing the maximum estimated attraction domain, the stability and attraction of the equilibrium point can be estimated, with a larger attraction domain indicating that the equilibrium point is more stable to small disturbances and a smaller attraction domain indicating that the equilibrium point is more sensitive to small disturbances.
The maximum estimated attraction domain of the small disturbance stable balance point is estimated by constructing an ellipsoid by using an LEDA method, the center of the ellipsoid is the position of the balance point, the axial length and the direction of the ellipsoid represent the stability and attraction ranges of the system in different directions, the longer axis represents the greater stability and attraction of the system in the direction, and the shorter axis represents the greater sensitivity of the system to disturbance in the direction.
And step S43, determining a system stability boundary based on the maximum estimated suction domain.
Based on two variables of u dc and ≡ (V ref-kdP/udc-udc) dt=deltau, and the maximum estimated attraction domain of the small disturbance stable point obtained by construction is an ellipsoid, visual display can be performed, the center point of the ellipsoid is the position of maximum stability in the estimated attraction domain, namely the transient stability convergence center, and the ellipsoid boundary omega c of the ellipsoid is the system stability boundary. Knowing the location of the equilibrium point, and the characteristics of the equilibrium point in the estimated attraction domain, can help assess the stability of the system and take the necessary actions to maintain stable operation of the system at that equilibrium point when analyzing and designing the system control strategy.
For example, when p=300 KW can be constructed based on the above steps, the maximum estimated attraction domain of the system stability balance point is shown in fig. 4.
To further analyze and verify the effectiveness of the LEDA constructed in accordance with the present invention, the present invention simulates conditions A1) -A2) with the aid of PSCAD/EMTDC simulation software.
The power P is stepped from 200KW to 300KW under the working conditions of A1) and t=2s; when t=3s, the stored energy power P is stepped from 300KW to 350KW; when t=4s, the stored energy power P is stepped from 350KW to 400KW, and the simulation result is shown in fig. 5.
And when the working conditions A2) and t=2s, the energy storage power P is stepped from 200KW to 400KW, and the simulation result is shown in fig. 6.
Comparing the working condition A1) and the working condition A2) corresponding to the working conditions 5 and 6, it can be known that the transient stability of the system can be maintained in the transient process that P is stepped from 200KW to 300KW, then stepped from 300KW to 350KW and finally stepped from 350KW to 400 KW. And when P is 300KW, 350KW and 400KW, the balance points corresponding to the system are stable with small disturbance. However, when the power P is directly stepped from 200KW to 400KW, the transient instability of the system occurs, and the instability phenomenon cannot be explained through small disturbance stability analysis. However, by constructing the ellipsoid of the maximum estimated attraction domain LEDA of the small disturbance stable equilibrium point of the system, it is possible to achieve the following applications while ensuring that the system has good dynamics in the vicinity of the equilibrium point.
1) Stability assessment: the LEDA can help evaluate the stability of the equilibrium point of the system, the stability range of the equilibrium point can be determined by calculating the ellipsoid of the largest estimated attraction domain, a larger LEDA indicates that the equilibrium point has greater stability to small perturbations;
2) And (3) designing a control strategy: the LEDA can provide basis for the design of a control strategy, and by analyzing the maximum estimated attraction domain, the goal of a droop control link can be determined to guide the system state into the attraction domain so as to realize stability and robustness, and the design of a proper control strategy can be helped to maintain the stable operation of the system near the balance point;
3) Fault monitoring and fault tolerant control: the LEDA can be used for fault monitoring and fault-tolerant control, whether abnormality or fault exists can be monitored by monitoring the relation between the system state and the maximum estimated attraction domain, and corresponding fault-tolerant measures are adopted to ensure the safe and stable operation of the system;
4) Parameter estimation and optimization: the LEDA can be used for parameter estimation and optimization of the droop control loop, and parameters of the system model can be estimated by analyzing the LEDA so that the actual system behavior is matched with the expected attraction domain, and the parameters of the droop control loop are calibrated and optimized.
The analysis result of the maximum estimated attraction domain of the small disturbance balance of the flexible warfarin system of the power distribution area is real-timely determined based on the TS fuzzy model, the electrical parameter data and the state parameter data collected in real time, the maximum estimated attraction domain of the power distribution area is real-timely estimated, the transient stability analysis is carried out based on the determined maximum estimated attraction domain and the data collected in real time, the control strategy of the flexible interconnection system of the power distribution area can be further optimized, and a decision basis is provided for designing and optimizing the flexible interconnection system of the power distribution area.
1) Based on the electrical parameter data and system operation state information collected in real time, when u dc≥Vref/2, andWhen the system is established, a small disturbance stable balance point exists, a TS fuzzy model is established based on the small disturbance stable balance point, a maximum estimated attraction domain of the small disturbance stable balance point is established, the ellipsoid of the maximum estimated attraction domain is the stable range of the small disturbance stable balance point, at the moment, the direct current bus voltage u dc in the model is the direct current bus voltage corresponding to the flexible interconnection system of the distribution area, and accordingly, droop control link parameters and flexible interconnection system connection switches are adjusted. And (3) sorting the electrical parameter data, the system running state information, the sagging control link parameters and the flexible interconnection system connection switch state into a report form according to analysis results, and carrying out transient stability assessment results, potential risks and problems existing in the system under different conditions, typical log recording and log analysis. The report comprises characters, charts, images and visual results so as to intuitively present the evaluation results;
2) Advice and measures: providing corresponding suggestions and measures to improve transient stability of the system based on the determined maximum estimated attractive domain, comprising: the photovoltaic power generation unit and energy storage unit control strategy, direct current load adjustment and sagging control link parameter adjustment provide decision basis;
3) Updating in real time: the determination of the maximum estimated attraction domain is a dynamic continuous process, the state and the condition of the power system can change at any time, and the report has the function of updating in real time so as to ensure the accuracy and timeliness of the estimated result. The generation and updating of reports can be achieved through automated data processing and analysis tools, and integration with real-time monitoring systems is achieved;
4) Alarm and notification: in the implementation of transient stability assessment result report, alarm and notification functions are set, alarm information is generated when the system is in transient instability, and notification is sent to operation and maintenance personnel through proper communication channels (such as telephone and alarm sound) so as to take measures in time;
5) History and trend analysis: the report comprises analysis of historical records and trend prejudgement analysis, and through statistics and analysis of past transient stability evaluation results, the evolution trend and long-term stability performance of the system can be known, the change and potential problems of the system can be identified, corresponding measures can be taken for prevention, and the probability of instability is reduced.
Determining the maximum estimated attraction domain in real time, backtracking stored data such as voltage, current and power in the process, and carrying out further analysis and research on the evaluation process when needed by backtracking the evaluation result to the undetermined moment by using original basic data, parameters of an equivalent circuit model sagging control link and evaluation index information in the evaluation process;
The determination result of the maximum estimated attraction domain has the interface and integration capability with other systems and tools, for example, the interface and data sharing can be carried out with a power system monitoring and control system, an automatic analysis tool, a data analysis platform, an enterprise data lake and the like, so that real-time data transmission, collaborative work and decision support can be realized. Therefore, the transient stability evaluation result can be better closely combined with control and operation in actual operation, and the overall performance and reliability of the system are improved.
The invention relates to a method for determining the maximum estimated attraction domain of a flexible interconnection system of a power distribution station area based on an equivalent circuit mathematical model. The method has higher use value and application prospect, is suitable for transient stability analysis of the flexible interconnection system of the power distribution area, and can be widely applied to the aspects of design, operation, control optimization and the like of the flexible interconnection system of the power distribution area in the field of power systems.
Providing accurate evaluation results, and providing guidance for optimization and improvement of the system, thereby improving the reliability and stability of the system.
Based on the determination of the maximum estimated attraction domain of the flexible interconnection system of the power distribution station, the invention collects the electrical parameter data and the system state information of the flexible interconnection system of the power distribution station in real time on the basis of an equivalent circuit model and an equivalent circuit mathematical model, determines a small disturbance stable balance point of the system, creates a TS fuzzy model, determines the maximum attraction domain of the small disturbance stable balance point, and provides decision basis for the design and optimization of the flexible interconnection system of the power distribution station.
Example two
The device for determining the maximum estimated attraction domain of the flexible interconnection system of the power distribution area is shown in fig. 7, and the system comprises a module M71 for constructing an equivalent circuit model, a module M72 for acquiring real-time, a module M73 for acquiring a small disturbance stable balance point, a module M74 for determining the maximum attraction domain and a module M75 for designing and optimizing a system strategy.
Constructing an equivalent circuit model module M71, and constructing an equivalent circuit model and a corresponding equivalent circuit mathematical model of the flexible interconnection system of the power distribution area;
The real-time acquisition module M72 is used for acquiring the electrical parameter data and the system state information of the flexible interconnection system of the power distribution area in real time;
the small disturbance stable balance point acquisition module M73 is used for acquiring a small disturbance stable balance point of the flexible interconnection system of the power distribution station based on the equivalent circuit model, the equivalent circuit mathematical model, the electrical parameter data acquired in real time and the system state information;
The maximum attraction domain determining module M74 establishes the TS fuzzy model based on the equivalent circuit mathematical model and the small disturbance stable balance point to obtain the maximum estimated attraction domain, wherein the central point of the ellipsoidal region is the position of the maximum stability in the estimated attraction domain and is the transient stability convergence center, and the boundary omega c of the ellipsoidal region is the system stability boundary;
and a system strategy design and optimization module M75 for designing and optimizing the flexible interconnection system control strategy of the power distribution area based on the analysis result of the maximum estimated attraction domain.
Those skilled in the art will appreciate that all or part of the flow of the methods of the embodiments described above may be accomplished by way of a computer program to instruct associated hardware, where the program may be stored on a computer readable storage medium. Wherein the computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory, etc.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.
Claims (8)
1. A method for determining the maximum estimated attraction domain of a flexible interconnection system of a power distribution area comprises the following steps:
constructing an equivalent circuit model and a corresponding equivalent circuit mathematical model of the flexible interconnection system of the power distribution area;
Acquiring electrical parameter data and system state information of a flexible interconnection system of a power distribution area in real time;
Acquiring a small disturbance stable balance point of a system based on the equivalent circuit model, the electrical parameter data acquired in real time and the system state information;
constructing a TS fuzzy model based on the equivalent circuit mathematical model and the small disturbance stable balance point to obtain a system maximum estimated attraction domain;
based on the equivalent circuit model, constructing a corresponding equivalent circuit mathematical model as follows:
Wherein, C is a direct current side capacitor, u dc is a direct current bus voltage, P is an energy storage power, V s is an energy storage actual end voltage, V ref is a voltage reference value of droop control, k d、kp and k i are gain parameters in a PID droop control link, Δu= jv (V ref-kdPudc-udc) dt;
Based on the equivalent circuit mathematical model, the electrical parameter data acquired in real time and the system state information, the obtaining of the system small disturbance stable balance point comprises the following steps:
When (when) When the balance point is established, a first balance point and a second balance point are obtained;
Taking a first balance point with larger voltage and smaller current in the first balance point and the second balance point as a system balance point;
establishing a Jacobian matrix of the first balance point;
Calculating eigenvalues and determinant of the Jacobian matrix of the first balance point;
Based on Judging whether u dc≥Vref/2 is true or not; when the first balance point is established, the trace of the Jacobian matrix of the first balance point is smaller than or equal to 0, and the first balance point is determined to be a system small disturbance stable balance point.
2. The method for determining the maximum estimated attractive area according to claim 1, wherein the constructing an equivalent circuit model of the flexible interconnection system of the distribution transformer area is as follows:
Based on the equivalent single machine topological structure of the flexible interconnection system of the distribution area, combining with the sagging control link, the method for obtaining the equivalent circuit model comprises the following steps:
The droop controller is used for continuously comparing the voltage of the direct current bus with the voltage regulating value and regulating the voltage by PID droop control to obtain the regulated direct current bus real-time tracking current;
The multiplier is used for obtaining the power of the direct current bus based on the real-time tracking current and the actual end voltage of the energy storage of the adjusted direct current bus;
the divider is used for obtaining direct current bus current based on the direct current bus power and the direct current bus voltage;
And an alternating-current side, wherein the alternating-current side current is obtained based on the direct-current bus current.
3. The method for determining a maximum estimated attractive domain according to claim 1, said obtaining a system maximum estimated attractive domain comprising the steps of:
S41, constructing the TS fuzzy model based on the equivalent circuit mathematical model;
step S42, determining a maximum estimated attraction domain based on the TS fuzzy model;
And step S43, performing system stability boundary analysis based on the maximum estimated suction domain.
4. A method of determining a maximum estimated attractive area as claimed in claim 3, said step S41 comprising:
based on the equivalent circuit mathematical model, constructing the TS fuzzy model is as follows:
Wherein,
5. The method for determining the maximum estimated suction domain according to claim 4, wherein said step S42 comprises:
selecting an ellipsoidal region omega around the first balance point based on the TS fuzzy model and by taking two variables of u dc and ≡ (V ref-kdP/udc-udc) dt=deltau as coordinate axes, wherein the region boundary is omega c;
Solving the maximum value of each nonlinear term of A (x) in the ellipsoidal region, and replacing the nonlinear term in A (x) with the maximum value, wherein each nonlinear term corresponds to two linear matrixes A i;
The presence of the positive definite symmetric matrix M may be such that each matrix A i satisfies the linear matrix inequality Then at/>The internal system is asymptotically stable, wherein x= [ u dc,Δu]T,V(x)＝xT Mx;
The ellipsoidal region Ω is increased while the boundary Ω c is updated until the positive symmetric matrix M that holds the linear matrix inequality is absent, at which point the boundary Ω c is the maximum estimated attractive domain of the first balance point.
6. The method for determining the maximum estimated suction domain according to claim 5, wherein said step S43 comprises:
The center point of the ellipsoidal region is the position of maximum stability in the estimated attraction domain, and is the transient stability convergence center, and the boundary Ω c of the ellipsoidal region is the system stability boundary.
7. The method for determining a maximum estimated attractive area according to any one of claims 1 to 6, wherein the acquiring, in real time, electrical parameter data and system status information of the flexible interconnection system of the distribution transformer area includes:
The electrical parameter data includes voltage, current, frequency and power data based on monitoring equipment, and the system state information includes line switch state.
8. A device for determining a maximum estimated attraction domain of a flexible interconnection system of a power distribution area, which is characterized in that:
constructing an equivalent circuit model module, and constructing the equivalent circuit model and a corresponding equivalent circuit mathematical model of the flexible interconnection system of the distribution area;
the real-time acquisition module acquires the electrical parameter data and the system state information of the flexible interconnection system of the power distribution area in real time;
The small disturbance stable balance point acquisition module is used for acquiring the small disturbance stable balance point based on the equivalent circuit mathematical model, the electrical parameter data acquired in real time and the system state information;
The maximum attraction domain determining module is used for establishing a TS fuzzy model based on the equivalent circuit mathematical model and the small disturbance stable balance point to obtain the maximum estimated attraction domain, wherein the central point of an ellipsoidal region is the position of the maximum stability in the estimated attraction domain and is the transient stability convergence center, and the boundary omega c of the ellipsoidal region is the system stability boundary;
the system strategy design and optimization module is used for designing and optimizing a flexible interconnection system control strategy of the power distribution area based on the analysis result of the maximum estimated attraction domain;
based on the equivalent circuit model, constructing a corresponding equivalent circuit mathematical model as follows:
Wherein, C is a direct current side capacitor, u dc is a direct current bus voltage, P is an energy storage power, V s is an energy storage actual end voltage, V ref is a voltage reference value of droop control, k d、kp and k i are gain parameters in a PID droop control link, Δu= jv (V ref-kdP/udc-udc) dt;
Based on the equivalent circuit mathematical model, the electrical parameter data acquired in real time and the system state information, the obtaining of the system small disturbance stable balance point comprises the following steps:
When (when) When the balance point is established, a first balance point and a second balance point are obtained;
Taking a first balance point with larger voltage and smaller current in the first balance point and the second balance point as a system balance point;
establishing a Jacobian matrix of the first balance point;
Calculating eigenvalues and determinant of the Jacobian matrix of the first balance point;
Based on Judging whether u dc≥Vref/2 is true or not; when the first balance point is established, the trace of the Jacobian matrix of the first balance point is smaller than or equal to 0, and the first balance point is determined to be a system small disturbance stable balance point.
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