CN116581740B - Distribution network self-healing hybrid control method based on emergency switching of distributed energy operation mode - Google Patents

Distribution network self-healing hybrid control method based on emergency switching of distributed energy operation mode Download PDF

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CN116581740B
CN116581740B CN202310447133.2A CN202310447133A CN116581740B CN 116581740 B CN116581740 B CN 116581740B CN 202310447133 A CN202310447133 A CN 202310447133A CN 116581740 B CN116581740 B CN 116581740B
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control
der
distribution network
switching
power
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CN116581740A (en
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陈鼎
岳东
窦春霞
郁家麟
李春
汤东升
钟伟东
严婷
程杰
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Nanjing University of Posts and Telecommunications
Jiaxing Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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Nanjing University of Posts and Telecommunications
Jiaxing Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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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
    • H02J3/007—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources
    • H02J3/0075—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources for providing alternative feeding paths between load and source according to economic or energy efficiency considerations, e.g. economic dispatch
    • 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
    • H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
    • H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
    • 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
    • H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
    • H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The invention discloses a distribution network self-healing hybrid control method based on emergency switching of a distributed energy operation mode, which comprises the following steps: performing upper discrete control based on characteristic indexes of distributed energy sources; performing lower-layer continuous control based on dynamic characteristics and multiple modes of distributed energy sources; performing mixed control on the power distribution network according to upper discrete control and lower continuous control; according to the invention, a two-stage layered hybrid control architecture is designed, a hybrid control strategy is formulated according to a layered control structure, and aiming at the complex and changeable power distribution network operation time situation, a hybrid control, discrete control strategy and continuous controller are adopted, and the distributed energy operation mode is switched based on a colored Petri network, so that the layered hybrid intelligent control of the high-permeability power distribution network is realized, and the intelligence, the high flexibility, the stability, the safety and the self-healing capacity of the power distribution network are improved.

Description

Distribution network self-healing hybrid control method based on emergency switching of distributed energy operation mode
Technical Field
The invention relates to the technical field of smart power grids, in particular to a self-healing hybrid control method for a power distribution network based on emergency switching of a distributed energy operation mode.
Background
With the increasing prominence of energy shortage and environmental problems, distributed power generation technology based on renewable energy sources is receiving more attention and application, and research and practice show that a power distribution network containing multiple distributed energy sources (DERs, distributed energy resources) can effectively improve the power supply reliability and the power quality of the system and reduce the cost, so that the method is an effective way for solving and improving the distributed power demands in remote areas, and is an effective way for improving the power supply reliability of the power distribution network. However, in the distribution network, the control and operating strategy should be significantly different, even conceptually different, from the conventional control and operating strategy, depending on the penetration depth of the DER units. The technical integration of new energy sources and various power electronic control devices has led to a need for new operating strategies to improve the safety and reliability of the distribution network.
The intelligent control of the distribution network not only requires highly automated continuous control to adjust the dynamic behavior of the components, but also requires an online discrete control strategy to achieve the reconfiguration of the operational modes.
In the prior art, flexible regulation and control on a power distribution network are lacked, so that the power supply reliability and the power quality of the power distribution network are reduced.
Disclosure of Invention
The invention mainly solves the problem that the prior art lacks flexible regulation and control of the power distribution network; the self-healing hybrid control method for the power distribution network based on the emergency switching of the distributed energy operation mode is provided, a two-stage layered hybrid control architecture based on operation mode switching is provided, and under a high-permeability power distribution network, intelligent control with high flexibility is realized according to a hybrid control strategy formulated by the layered architecture.
The technical problems of the invention are mainly solved by the following technical proposal: a power distribution network self-healing hybrid control method based on emergency switching of a distributed energy operation mode comprises the following steps: performing upper discrete control based on characteristic indexes of distributed energy sources; performing lower-layer continuous control based on dynamic characteristics and multiple modes of distributed energy sources; and performing mixed control on the power distribution network according to the upper discrete control and the lower continuous control.
Preferably, during the upper discrete control process, unbalanced power compensation after disturbance is performed based on different operation modes of the DER unit.
Preferably, the upper discrete control performs a control action according to the distributed area of the DER unit, and the lower continuous control performs a dynamic adjustment according to the operation mode of the DER unit.
Preferably, the characteristic index of the distributed energy source includes: the frequency stability risk index and the voltage stability risk index are established by the following steps:
ΔP i ＝(2H i /f n )×(df i /dt)
wherein H is i And f i The inertia constant and the frequency, f, of the ith DER unit, respectively n For nominal frequency, deltaP i For mismatch power of the ith cell, N C For the number of DER units, f C The frequency of the center of inertia, Δp, is the disturbance power, expressed as:
by comparing measured disturbance power with mismatch power P TH To determine FSRI, which can be expressed as:
FSRI＝P TH +ΔP
FSRI represents a frequency stability risk indicator,P TH is the maximum overload of all DER units.
Preferably, the construction method of the voltage stability risk index comprises the following steps:
wherein,represents a voltage stability risk indicator at the j-th time, U th Selecting positive value less than 1, < >>The voltage moving average at the j-th time is shown.
Preferably, the specific method for unbalanced power compensation is as follows:
judging whether the operation mode of the DER unit needs to be switched;
determining a switching priority of an ith DER unit for effectively recovering the disturbed voltage;
and resetting the set point recovery frequency through the output power after the DER unit is switched, and realizing power compensation.
Preferably, the multiple modes of the DER unit are stabilized based on multiple Lyapunov functions, specifically:
constructing a mathematical model of the DER unit;
designing a local controller of each control unit into state feedback control based on a mathematical model of the DER unit and a plurality of Lyapunov functions to obtain constraint inequality and minimize problems;
the local multi-modal continuous controller parameters for each DER unit are obtained based on solving a minimization problem of constraint inequality.
Preferably, a colored Petri network is used to represent the switching process of the operating mode and the setting process of the setpoint.
Preferably, the lower layer continuous control is performed using a P-Q control method based on non-schedulability of the DER units.
Preferably, the lower layer continuous control is performed using an f-V control method based on schedulability of the DER units.
The beneficial effects of the invention are as follows: the method comprises the steps that a layered mixed control structure consisting of an upper discrete control strategy, a lower local continuous controller and interaction between the upper discrete control strategy and the lower local continuous controller is constructed, in the upper discrete control strategy, the self-healing capacity of the power distribution network when the power distribution network encounters serious interference is enhanced by switching a distributed energy operation mode, and the power output of each controlled unit is dynamically regulated by the lower continuous control, so that the safety performance of the power distribution network is ensured; the two-stage layered hybrid control architecture is designed, a hybrid control strategy is formulated according to a layered control structure, hybrid control, discrete control strategy and continuous controller are adopted according to the complex and changeable power distribution network operation, the distributed energy operation mode is switched based on the colored Petri network, layered hybrid intelligent control of the high-permeability power distribution network is realized, and the intelligence, the high flexibility, the stability, the safety and the self-healing capacity of the power distribution network are improved.
Drawings
FIG. 1 is a block diagram of the architecture of a hybrid control of an embodiment of the present invention.
Fig. 2 is a diagram illustrating a CPN-based operation mode switching process according to an embodiment of the present invention.
FIG. 3 is a schematic diagram of an f-V control scheme according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of a P-Q control scheme according to an embodiment of the present invention.
FIG. 5 is a schematic diagram of the DER unit structure according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, further detailed description of the technical solutions in the embodiments of the present invention will be given by the following examples with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
In order to improve stability, safety and self-healing capacity of the power distribution network, intelligent control adopts a hybrid control mode. Hybrid control theory is the development of multi-modal control, which has certain specific characteristics, providing new capabilities for controlling complex hybrid systems. The development of hybrid control theory provides a new opportunity for power system control design. As an effective means, this technique has been proposed for power system control. In the power system, the novel hybrid distributed control can relieve the network thermal overload problem of power flow management by limiting the actual output power of the region DG and DR units. Therefore, in real-time power flow analysis, only the line thermal limit of a certain power distribution network is considered, and under the autonomous area control environment, the distributed power supply and the demand response unit perform joint control on the relief power flow management. Implementation of such demand side management, integrated active network management and distributed control techniques contributes to network enhanced latency, supply economy and efficient capital expenditure.
Examples:
a self-healing hybrid control method of a power distribution network based on emergency switching of a distributed energy operation mode is shown in fig. 1, wherein an upper layer and a lower layer respectively relate to a discrete control strategy and a multi-mode local control strategy; the upper layer determines to switch the distributed energy operation mode based on the colored Petri network by researching the characteristic index related to the continuous dynamic behavior, the operation mode switching process based on CPN is shown in figure 2, and the single color set, the library and the transition description are listed in tables 1,2 and 3 respectively; the lower layer carries out systematic controller design on various DER units according to the required functions and the dynamic characteristics of the DER units, and provides a designed control scheme, as shown in fig. 3 and 4, and designs a corresponding control method. Through the layered mixed control structure of the power distribution network, the mixed control of the high-permeability power distribution network based on operation mode switching is realized by combining with a corresponding control strategy. The method specifically comprises the following steps:
s1: performing upper discrete control based on characteristic indexes of distributed energy sources; for the coordination control target of the high-permeability power distribution network, a two-stage hybrid control structure is established, the power distribution network control structure is divided into an upper layer and a lower layer, the upper layer performs discrete control, the control action is executed according to the distributed area of the DER units, the control action is executed preferentially, and the control action is designed in a regional coordination mode, namely, the regional discrete control strategy only coordinates and controls the running mode of the DER units in the region.
Considering the characteristic indexes related to continuous dynamic behaviors in the upper discrete control process, determining an upper discrete control strategy, and researching the characteristic indexes reflecting the stability risk indexes:
(1) Construction of Frequency Stability Risk Indicator (FSRI):
the DER unit frequency control is similar to the frequency control of a synchronous motor (i.e. the terminal voltage of the converter is similar to the internal voltage of the synchronous motor). Thus, as with conventional large turbo-generator units, the FSRI is approximately fitted based on the disturbance power and calculated from the initial frequency rate of change as follows:
ΔP i ＝(2H i /f n )×(df i /dt) (1)
wherein H is i And f i The inertia constant and the frequency, f, of the ith DER unit, respectively n For nominal frequency, deltaP i For mismatch power of the ith cell, N C For the number of DER units, f C The frequency of the center of inertia, Δp, is the disturbance power, expressed as:
by comparing measured disturbance power with mismatch power P TH To determine FSRI, which can be expressed as:
FSRI＝P TH +ΔP (4)
wherein P is TH Is the maximum overload of all DER units. The following characteristics of FSRI are used to formulate frequency stability criteria:
(1) the risk of system occurrence frequency drop with the smallest negative index is highest.
(2) If fsri=p TH And if +DeltaP is more than or equal to 0, the frequency after disturbance is stable.
(3) If fsri=p TH The system frequency is considered to be unstable, +ΔP < 0.
(2) Construction of a Voltage Stability Risk Indicator (VSRI):
voltage instability is typically manifested as a slow decay of voltage after a sharp drop in the breakdown point. Since the voltage amplitude itself is not a reliable indicator of voltage instability, the use of a voltage threshold to detect instability may lead to erroneous conclusions. A dynamic voltage stability criterion based on VSRI is adopted to evaluate whether the system can realize a stable state after voltage disturbance.
Let the i-th specific bus voltage PMU measurement be V i ＝[V i 1 ,V i 2 ,...,V i m ] T At a rate of 30 frames/second in a 60Hz system or 25 frames/second in a 50Hz system, the VSRI formula is as follows:
(a) Moving average of the voltage of the bus at the j-th moment measured by N PMUs
(b) Measured voltage V i j Moving average V from time j i (j) Percent difference between
(c) Dividing the area under the difference percentage curve by N yields the value at the j-th time instant
(d) VSRI at the j-th time
Wherein U is TH A positive value slightly less than 1 is chosen, depending on system characteristics such as reactive compensation properties, load characteristics, etc. The following characteristics of VSRI are used to establish a voltage stability criterion:
(1) the bus voltage with the smallest negative index at any given time has the highest risk of voltage sag.
(2) If the voltage stabilizes after the disturbance, the VSRI on the bus converges to U th 。
(3) If it isThe ith bus voltage is considered to be unstable.
S2: in the upper discrete control process, unbalanced power compensation after disturbance is performed based on different operation modes of the DER unit; the unbalanced power after disturbance is effectively compensated by the modal switching of the DER unit:
(1) Judging whether the operating mode of DER needs to be switched or not:
if fsri=p TH +ΔP < 0 orThe upper level discrete control strategy requires switching the DER unit to the appropriate mode of operation to bring the system frequency or voltage back to the set point. Wherein N is b For the number of bus bars, N is the number of PMU measurements available.
(2) Determining a switching priority of an ith DER unit that is effective to recover the post-disturbance voltage:
definition:
wherein N is i To be the number of voltage-unstable bus bars with shortest distance to the ith DER unit as compared with other DER units, N D For all voltagesThe number of unstable bus bars, K, is the moment of pre-switching.
Maximum r i Indicating that the voltage drop risk of the i-th DER cell in the vicinity is highest. If r i Maximum, and the ith DER unit has the ability to power compensate by switching modes of operation, it should have the highest mode switching priority. Of course, with a minimum r i Has the lowest mode switching priority. Furthermore, according to r i The magnitude of the value, in combination with the current mode of operation of the DER unit, may locate a subsequent mode of operation.
(3) The power compensation is achieved by resetting the set point with the switched output power of the DER unit to restore the frequency:
definition:
wherein N is C For all numbers of DER units switching the operation mode, the simplifying assumptions in equations (1) and (2) are compensated with a factor of 1.05,pre-switching output power for the ith DER cell,/->Is the set value of the output power after switching.
Selection of the output power constraint of the DER unit according to equation (12) and after switching modesAccording to the selected->Frequency set point
Wherein f i,set For the frequency set point of the ith DER unit, f op Lambda for the desired post-switch operating frequency i Is the droop gain of the ith DER cell.
S3: a colored Petri network is adopted to represent a switching process of an operation mode and a setting process of a set point; CPN is defined as a 7-tuple set Σ= (P; T; F; D; I-; I+; M using normal symbols 0 ) Where P is a finite collection of libraries (represented by circles in the graphical representation). T is a finite set of transitions (represented by squares). F is a finite set of arcs where the arcs from the library to the transitions represent input arcs and the arcs from the transitions to the library represent output arcs. D is a non-empty finite set representing a separate set of all colored tokens. I-and I+ are positive and negative functions on the input and output arcs, respectively. M is M 0 Is a set of initial markers.
Tables 1-3, corresponding to the CPN shown in fig. 2, give descriptions of the individual color sets, bins, and transitions, respectively, and the input/output arcs are labeled in the figure. Initial mark M 0 (p OM ) =m+g+set, the initial flags of the other banks are empty.
TABLE 1 description of individual color sets
Table 2 library describes
TABLE 3 transition description
S4: performing lower-layer continuous control based on dynamic characteristics and multiple modes of distributed energy sources; lower layer continuous control, which is to dynamically adjust according to the operation mode of the DER unit, and is responsible for dynamic adjustment under the corresponding operation mode, and is designed according to unit dispersion. In addition, the lower level controller is designed as a set of local multi-mode stability controllers for each unit, corresponding to a plurality of operation modes and stability control targets.
From a generation power perspective, DER units are generally divided into two major categories, schedulable power sources and non-schedulable power sources. A dispatchable power supply is a fast responding energy source with sufficient backup capacity to meet the active and reactive transient power balances. Such power sources typically include an interface through a power converter and an energy storage device on the DG side, e.g., a variable speed wind turbine based power generation unit or a fuel cell driven converter. An unscheduled power supply is defined as a slow responding power supply, also called an uncontrollable power supply. The output power of such a power supply is highly dependent on a pre-specified reference value or the power supplied by its main power supply. The non-schedulable power supply helps to meet steady state power balance. Such as a photovoltaic source or a generator based on a fixed speed wind turbine. From a control point of view, a follow-up control is typically chosen as the control scheme for the non-schedulable DER unit. The following control mainly comprises Maximum Power Point Tracking (MPPT) control of a renewable energy unit, V-Q control of a direct current source unit and P-Q control. The mesh-type control is generally proposed as a control scheme for the schedulable DER unit. The net-type control mainly includes f-V control and load distribution based on sagging characteristics.
The f-V control scheme for schedulable DER units is shown in fig. 3 and the P-Q control scheme for non-schedulable DER units is shown in fig. 4.
In order to reduce the switching times of DERs operation modes as much as possible and improve the intelligence and the high flexibility of the system, the robust stability problem in a multi-mode switching scene is considered to be processed, and a robust stability method based on a multi-Lyapunov function is provided for multiple modes of a DER unit:
(1) A mathematical model of the DER unit is constructed as shown in fig. 5:
under balanced conditions, if U is selected dq As a reference vector, U q ＝0，Transferring (14) from the abc coordinate system to a rotating reference coordinate system (dq coordinate system).
The dynamic model of the ith DER unit (15) is scalable to the following form, corresponding to the operation multi-mode, taking into account the uncertainty of the load and line parameters
Wherein,is the state vector of the i-th DER cell. i.epsilon.1, 2, …, N c ,N c Is the number of controlled DER units. u (u) is ＝U is,td Is the control input of the ith cell in the s-th mode of operation. z i ＝U id Is output, omega i ＝U itq Is assumed to be an interfering signal and is preferably set to zero. A is that is 、B is 、C is 、D is Sum lambda is Is a matrix of coefficients having suitable dimensions. ΔA is ,ΔB is And DeltaD is Is an uncertainty matrix of appropriate dimensions. t is t s Representing when t is e t s ,t s+1 ]The s-th mode of operation of the i-th controlled unit is activated at time t s The ith controlled unit switches from the (s-1) th control mode to the s-th control mode. Δx i (t) is the state vector pulse change of the ith cell at the switching time point.
First, assume that the parameter uncertainty in (16) is norm-bounded in the form
[ΔA is ΔB is ΔD is ]＝H is F is (t)[E 1is E 2is E 3is ] (17)
Wherein H is is 、E 1is 、E 2is And E is 3is Is a real constant matrix with proper dimension, F is (t) is an unknown matrix function with Lebesgue measurable elements and satisfies F is T (t)F is (t)≤I i Wherein I i Is an identity matrix.
(2) The local controller of each control unit is designed to be state feedback control based on a mathematical model of the DER unit and a plurality of Lyapunov functions, so that constraint inequality and minimization problem are obtained:
u is (t)＝k is x i (t) (18)
wherein k is is Is the controller parameter of the ith controlled unit in the ith operating mode, i.epsilon.1, 2, …, N C 。
By (16) - (18), the dynamic model of the ith closed loop control unit in the ith mode of operation may be rearranged as follows
Wherein,defining multiple Lyapunov functions of a controlled system as
Wherein P is is Is a symmetric positive weighting matrix for the ith closed loop control unit in the ith mode of operation.
The H-infinity performance associated with the controlled output is shown in the following equation taking into account the initial conditions
Wherein ρ is is Is a prescribed level of attenuation.
The controlled unit (19) may be a robust stabilization of the H-infinity local controller (18), only whenIs the common solution of the following symmetric matrix inequalities.
Wherein,Φ 12 ＝P is (D is +H is F is (t)E 3is )
and (3) proving: v (V) is (t) the derivative along the trajectory of the system (19) satisfies:
it is readily available:
according to the above results, if the matrix inequality (23) is satisfied, the system of (19) is H-infinity robust stable by the local controller (18), except possibly at the switching point.
In inequality (22) there is an unknown matrix function F is (t) processing the problem about parameter uncertainty based on the following arguments.
And (5) lemma: for matrices (or vectors) Y, D and E with the appropriate dimensions, there are
Y+DFE+E T F T D T ＜0
Wherein Y is a symmetric array. If and only if there is a set of scalar ε > 0, all F satisfy F T F is less than or equal to I
Y+ε -1 DD T +εE T E＜0
Again using the lemma and Schur complement lemma, and the left-hand and right-hand matrixThe above inequality (23) is equivalent to inequality (24).
Wherein ε is is1 And epsilon is2 Is a positive scalar, and
definition of the definitionThen
Thus, inequality (24) is a Linear Matrix Inequality (LMI).
To obtain better robust performance, H-infinity robust stability control can be considered as the following minimization problem, thereby minimizing the H-infinity performance in (21)
minρ is (25)
Constraint conditions: inequality (22) and (24).
The minimization problem in formula (25) can be translated into an LMI optimization problem.
(3) By using the convex optimization technology of the LMI, the H-infinity robust performance can be minimized, the minimization problem is solved based on constraint inequality to obtain the local multi-mode continuous controller parameters of each DER unit, and the performance stability is realized.
S5: and carrying out mixed control on the power distribution network according to upper discrete control and lower continuous control, wherein the interaction between the upper control and the lower control is as follows: including direct and indirect interactions. From the upper layer to the lower layer, the discrete control strategy switches the operating mode of the DER units, thereby achieving a direct interaction. Conversely, the interaction from the lower layer to the upper layer is an indirect interaction. The lower layer continuous control modifies the state data of the operating environment, triggering a change in the upper layer discrete control strategy.
The above-described embodiment is only a preferred embodiment of the present invention, and is not limited in any way, and other variations and modifications may be made without departing from the technical aspects set forth in the claims.

Claims (6)

1. A power distribution network self-healing hybrid control method based on emergency switching of a distributed energy operation mode is characterized by comprising the following steps:
performing upper discrete control based on characteristic indexes of distributed energy sources;
performing lower-layer continuous control based on dynamic characteristics and multiple modes of distributed energy sources;
performing mixed control on the power distribution network according to upper discrete control and lower continuous control;
the characteristic indexes of the distributed energy source comprise: the frequency stability risk index FSRI and the voltage stability risk index VSRI are constructed by the following steps:
△P i ＝(2H i /f n )×(df i /dt)
in the method, in the process of the invention,H i and f i The inertia constant and the frequency, f, of the ith DER unit, respectively n For nominal frequency, deltaP i For mismatch power of the ith cell, N C For the number of DER units, f C Is the frequency of the inertia center, delta P is the disturbance power, f C Expressed as:
by perturbing the power ΔP with a threshold value P of mismatch power TH To determine FSRI, expressed as:
FSRI＝P TH +△P
FSRI represents a frequency stability risk indicator, a threshold P of mismatch power TH Maximum overload for all DER units;
the construction method of the voltage stability risk index VSRI comprises the following steps:
let the n-th specific bus voltage PMU measurement be
(a) The moving average of the voltage of the bus at the j-th moment measured by N PMUs is:
(b) Measurement valueMoving average value +.about.bus voltage at j-th moment>Differences betweenThe percentages are as follows:
(c) The VSRI at the j-th time is:
wherein,represents a voltage stability risk indicator at the j-th time, U th Selecting a positive value less than 1;
in the upper discrete control process, unbalanced power compensation after disturbance is performed based on different operation modes of the DER unit;
the specific method for unbalanced power compensation is as follows:
judging whether the operation mode of the DER unit needs to be switched; if fsri=p TH A + [ delta ] P < 0 or The upper discrete control strategy requires switching the DER unit to a proper operation mode, so that the system frequency or voltage is restored to a set value; wherein N is b N is the number of available PMU measurements;
determining a switching priority of an ith DER unit for effectively recovering the disturbed voltage; definition:
wherein N is i To be the number of voltage-unstable bus bars with shortest distance to the ith DER unit as compared with other DER units, N D K is the time of pre-switching for the number of all buses with unstable voltage; if r i Maximum, the ith DER unit has the highest mode switching priority with the smallest r i Has the lowest mode switching priority;
resetting the set point through the output power after the DER unit is switched to restore the frequency, and realizing power compensation;
definition:
wherein N is C1 For the number of DER units for all switching modes of operation,pre-switching output power for the ith DER cell,/->Setting value of output power after switching;
according to the set value of the output power after switchingThe frequency set point is:
wherein f i,set For the frequency set point of the ith DER unit, f op Lambda for the desired post-switch operating frequency i Is the droop gain of the ith DER cell.
2. The self-healing hybrid control method of the power distribution network based on the emergency switching of the distributed energy operation mode according to claim 1, wherein,
the upper layer discrete control performs control actions according to the distributed areas of the DER units, and the lower layer continuous control performs dynamic adjustment according to the operation modes of the DER units.
3. The self-healing hybrid control method of the power distribution network based on the emergency switching of the distributed energy operation mode according to claim 1 or 2, wherein,
the multimode of the DER unit is stabilized based on a plurality of Lyapunov functions, specifically:
constructing a mathematical model of the DER unit;
designing a local controller of each control unit into state feedback control based on a mathematical model of the DER unit and a plurality of Lyapunov functions to obtain constraint inequality and minimize problems;
the minimization problem is solved based on constraint inequality, and local multi-mode continuous controller parameters of each DER unit are obtained.
4. The self-healing hybrid control method of the power distribution network based on the emergency switching of the distributed energy operation mode according to claim 1, wherein,
a colored Petri net is used to represent the switching process of the operation mode and the setting process of the set point.
5. The self-healing hybrid control method of the power distribution network based on the emergency switching of the distributed energy operation mode according to claim 1 or 2, wherein,
the underlying continuous control is performed using a P-Q control method based on the non-schedulability of the DER units.
6. The self-healing hybrid control method of the power distribution network based on the emergency switching of the distributed energy operation mode according to claim 1 or 2, wherein,
the lower layer continuous control is performed using an f-V control method based on schedulability of the DER units.
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