CN107947192B - Reactive power optimization configuration method for droop control type island microgrid - Google Patents
Reactive power optimization configuration method for droop control type island microgrid Download PDFInfo
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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
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
- H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
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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
- H02J3/04—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
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
-
- 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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/76—Power conversion electric or electronic aspects
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
Abstract
The invention discloses a reactive power optimization configuration method of a droop control type island microgrid, which comprises the steps of sampling a droop control type island microgrid by adopting a Monte Carlo method according to the probability distribution of wind speed or illumination intensity to obtain a sample set of output of Ns wind turbine generators or photovoltaic power generation units, and performing scene reduction on the sampled sample based on a backward reduction technology to obtain Ns scene samples; then, an IMG power flow model of the droop control type DG networking is established and solved, singular value decomposition is carried out on a Jacobian matrix when an IMG power flow equation converges to obtain a minimum singular value and a left singular vector and a right singular vector corresponding to the minimum singular value, then a system reactive compensation node is obtained, a compensation capacity optimization configuration model is established, an IPOPT optimization tool package is called to carry out optimization solution to obtain an optimization configuration scheme, and the problem that optimization planning of a reactive compensation device for an island micro-grid containing a droop control type distributed power supply in the prior art is difficult to implement is solved.
Description
Technical Field
The invention belongs to the technical field of optimization planning of power systems, and particularly relates to a reactive power optimization configuration method of a droop control type island micro-grid.
Background
The installation of reactive power compensation devices is advantageous for improving the quality of the distribution voltage and reducing the network loss, so that the problem of optimal planning of reactive power compensation devices has long been the subject of much attention. With the large access of intermittent Distributed Generation (DG) such as wind power Generation, photovoltaic and the like, the installation of the reactive compensation device can reduce the adverse effect of the random fluctuation of the DG output on the voltage on one hand, and can also improve the utilization rate of clean energy by matching and adjusting the reactive compensation device and the DG power factor on the other hand.
The micro-grid is used as a form for flexibly and efficiently utilizing distributed energy, and has two forms of grid connection and isolated island operation. The Islanded Microgrid (IMG) is small in scale, the impact of intermittent power supply output and load fluctuation on the Islanded Microgrid is relatively large, and reactive compensation on the Islanded Microgrid can improve the voltage quality and the voltage stability. The IMG has two structures of master-slave control and peer-to-peer control. A main power supply in a microgrid of a master-slave control structure provides voltage frequency support, the operation mechanism of the microgrid is similar to that of a traditional power grid, in a peer-to-peer control structure, a plurality of controllable distributed power supplies jointly participate in voltage and frequency regulation and control, the DGs usually adopt a droop control method, and the operation mechanism of a system is obviously different from that of the traditional power grid. Therefore, there is a need to study the reactive optimization planning problem of such IMG in combination with the characteristics of droop control.
Regarding the reactive power optimization planning problem, scholars at home and abroad respectively make researches on the optimization planning of parallel capacitors on a distribution line, the reactive power compensation optimization planning of a low-voltage side of a distribution network, the reactive power compensation optimization configuration of a medium-voltage distribution line and the low-voltage side of the distribution network, the reactive power compensation optimization configuration of a rural distribution network, the reactive power optimization of an alternating current and direct current system, the reactive power optimization configuration of the distribution network containing DGs such as photovoltaic or wind generating sets and the like, and establish an optimization planning model; and solving methods such as a nonlinear programming method, an intelligent optimization algorithm, robust optimization and the like are provided. However, no research on reactive power optimization planning of an island micro-grid of a droop control type micro-source networking exists at present.
Disclosure of Invention
The invention aims to provide a reactive power optimization configuration method for a droop control type island microgrid, and solves the problem that optimization planning of a reactive power compensation device for the island microgrid with a droop control type distributed power supply is difficult to implement in the prior art.
The invention adopts the technical scheme that a reactive power optimization configuration method of a droop control type island microgrid is implemented according to the following steps:
and 6, calling an IPOPT optimization tool package to carry out optimization solution to obtain an optimized configuration scheme.
The present invention is also characterized in that,
in step 1, an initial scene set of the sample is set as omega, a target scene set after reduction is set as omega, and a scene reduction algorithm is as follows:
step 1.1, calculating scene distance KD of any two scenes in the initial scene set, establishing a scene distance matrix, and marking as KDM;
step 1.2, aiming at any scene xiiFinding the scene xi closest to itjAnd is denoted by min { KD (ξ)i,ξj) And marking the scene in a KDM matrix;
step 1.3, for each pair of scenes in step 1.2, P is calculatedKDi=min{KD(ξi,ξj)}×P(ξi) Wherein P (ξ)i) For the probability of the evaluated scene, P of all scene pairs in KDM is then foundKDMinimum value of (1), denoted as PKDsTo PKDsCorresponding scene pair, will xiiAnd xijOne of the two is closer to other scenes and has smaller probability, such as subtracting xii;
Step 1.4, cut down xiiThen, a new KDM is constructed, and the scene probability P (xi) is updatedj)=P(ξi)+P(ξj);
And 1.5, repeating the steps 1.2-1.4 until the target scene number is reduced.
wherein, PGi、QGiThe power active power and the reactive power of the power supply are respectively; pLi、QLiRespectively the active power and the reactive power of the load; u shapeiAnd UkThe voltages of node i and node k, respectively; y isikAnd thetaikThe amplitude and the phase angle of the element of the node admittance matrix are respectively; deltaiAnd deltakVoltage phase angles of the node i and the node k respectively; b is a set of all nodes;
active power P of loadLiAnd reactive power QLiThe calculation is shown below:
in the formula, PLi0And QLi0Respectively the active power and the reactive power of the initial load of the node i; u shapei0Is the initial value of the voltage at node i; omega is the angular frequency of the system, omega0Is the initial value of angular frequency; a. thepi、BpiAnd CpiRespectively, the static voltage characteristic coefficient of the active power of the load, Aqi、BqiAnd CqiRespectively, the load reactive power static voltage characteristic coefficient, kPfiAnd kQfiStatic frequency characteristic coefficients of load active power and reactive power respectively;
active and reactive power P for the power supplyGi、QGiIn other words, it is calculated by the following equation:
in the formula, PDroopiAnd QDroopiActive power and reactive power P of droop control type micro-source accessed by node iWTGiAnd QWTGiActive power and reactive power P of the wind generating set respectively connected to the node iPViAnd QPViRespectively the active power and the reactive power of the photovoltaic unit accessed by the node i;
if wind turbine generator or photovoltaic unit is connected, PWTGiOr PPViSubstituting according to the actual active power, otherwise, taking the value as zero;
if constant power factor control, then QWTGiOr QPViSubstituting according to actual reactive power;
if the control is constant voltage control, i is a PV node, the reactive power of the PV node is an unknown quantity, and a corresponding balance equation is not temporarily listed in a power flow equation set;
if there is no droop control type micro source access, PDroopiAnd QDroopiValues are all zero; for nodes with Droop-controlled micro-sources, commonly referred to as Droop nodes, then PDroopiAnd QDroopiCalculated as follows:
wherein m ispi、nqiDroop coefficients of active power and reactive power of the droop control micro source of the node i are respectively; omega0Is an initial value of angular frequency, U0Is the initial value of the voltage; b isDroopIs a collection of drop nodes.
The step 3 is as follows:
solving the IMG power flow model by adopting a Newton-Raphson method, wherein the modified equation form is as follows:
wherein, the delta P and the delta Q are the unbalance amount of the active power and the reactive power of the node respectively; delta theta and delta U are respectively voltage phase angle and amplitude correction; Δ ω is a correction amount of the frequency; j is a Jacobian matrix.
The step 4 is as follows:
the Jacobian matrix J when the IMG tide equation converges is subjected to singular value decomposition as shown in the following formula to obtain a minimum singular value delta2n-mAnd its corresponding left and right singular vectors M2n-mAnd N2n-m:
Wherein M isiAnd NiRespectively are left and right singular vectors of a system singular value; sigma is a diagonal matrix taking positive real singular values arranged from large to small as diagonal elements; m is the number of PV nodes, and n is the total number of nodes of the microgrid;
the maximum element of the right singular vector of the minimum singular value indicates the most sensitive node voltage, so that a few large index values in the right singular vector are selected as the reactive compensation nodes of the system:
wherein, Δ θ and Δ U are correction values of voltage phase angle and amplitude respectively; Δ ω is the correction amount of the frequency.
The step 5 is as follows:
for the reduced scene set, with the expectation of economic targets in all scenes as an objective function and the trend equation and the safety inequality in each scene as constraints, establishing a compensation capacity optimization configuration model, which is specifically as follows:
step 5.1, setting a target function:
the method is characterized in that a capacitor is used as reactive compensation equipment of the micro-grid, the randomness of the output of a wind turbine generator in the micro-grid is considered, the economic benefit brought by the capacitor is maximized into a target function of reactive planning, the economic benefit brought by the compensation capacitor installed on the micro-grid is evaluated by adopting a net present value criterion, and the target function is expressed as
In the formula, d is the discount rate; l is the engineering period; cIInvestment cost for adding compensation capacitors; cOAnd C'ORespectively representing the annual average cost of active loss of the micro-grid before and after the compensation capacitor is added, wherein,
in the formula, σEIs the price of electricity;andrespectively obtaining the expected values of the network loss of the s th scene of the microgrid before and after reactive power optimization; rhosProbability of the s-th scene of the microgrid;
the investment cost of the compensation capacitor is
In the formula, nCCompensating the point number for the capacitor; qCjMounting capacity for the capacitor at the jth compensation point; p is a radical ofCjA unit price of a capacitor installed for the jth compensation point;
and 5.2, setting constraint conditions:
step 5.2.1, power flow equation constraint:
according to the formulas (1) to (4), the power flow equation constraint of the IMG having the droop control type DG networking is expressed as follows, corresponding to any scene s, s is 1,2 … ns:
in the formula (I), the compound is shown in the specification,andvoltage amplitudes and phase angle differences of the node i and the node j in the s-th scene are respectively; omegasThe angular frequency of the system under the s-th scene;andthe active power and the load active power of the wind turbine generator and the photovoltaic connected with the node i in the s-th scene are respectively;andthe reactive power of the wind turbine generator and the photovoltaic of the node i in the s-th scene, the reactive power of the reactive compensation capacitor bank and the load reactive power are respectively;
step 5.2.2, setting droop control type micro-source capacity inequality constraint:
the power of the DG for droop control of access node i needs to meet the capacity limit inequality constraint:
wherein the content of the first and second substances,andcontrolling the active power and the reactive power of a DG (distributed generation) for the droop connected with the node i in the s-th scene respectively;andthe upper and lower limit values of the capacity of the droop control type DG are respectively;
for a reactive compensation capacitor bank:
0≤QCi≤QCimax (14)
wherein Q isCiFor capacitor mounting capacity at i-th compensation point, QCimaxMaximum allowable mounting capacity for the access capacitor at the ith compensation point;
and 5.2.3, setting system safe operation inequality constraints:
in order to ensure the normal operation of the system, the safety limit constraint of the node voltage and the safety constraint of the branch power need to be met, in addition, the system frequency is also one of the variables, and the safety constraint of the system also needs to be considered in the optimization process:
in the formula (I), the compound is shown in the specification,andrespectively an upper voltage amplitude limit and a lower voltage amplitude limit of the node i;an upper limit value of the amplitude of the current allowed to flow for the branch ij; omegamaxAnd ωminAre respectively provided withThe upper and lower limits of the angular frequency of the system;the current amplitude of branch ij under the s-th scenario is shown.
The optimization solving method in the step 6 can be replaced by an interior point method, a genetic algorithm and a particle swarm optimization algorithm.
The reactive power optimization configuration method has the advantages that the reactive power optimization configuration method for the droop control type island micro-grid is suitable for optimizing and planning the reactive power compensation device for the island micro-grid of the droop control type distributed power supply networking; the mounting position of the reactive power compensation device is determined through a singular value decomposition method, so that the solution efficiency of the optimization problem is improved on one hand, and the stability of the static voltage of the system is improved on the other hand.
Drawings
Fig. 1 is a flow chart of a reactive power optimization configuration method of a droop control type island micro-grid according to the invention;
fig. 2 is a node average voltage curve before and after compensation in schemes 1-3 in the reactive power optimization configuration method for a droop control type island microgrid of the present invention;
fig. 3 is a right singular vector element diagram of corresponding node voltages in different scenes in the reactive power optimization configuration method of the droop control island microgrid of the present invention;
fig. 4 is a node voltage diagram before and after compensation in the reactive power optimization configuration method of the droop control island microgrid of the invention;
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The invention discloses a reactive power optimization configuration method of a droop control type island microgrid, which is implemented according to the following steps as shown in a flow chart shown in figure 1:
step 1.1, calculating scene distance KD of any two scenes in the initial scene set, establishing a scene distance matrix, and marking as KDM;
step 1.2, aiming at any scene xiiFinding the scene xi closest to itjAnd is denoted by min { KD (ξ)i,ξj) And marking the scene in a KDM matrix;
step 1.3, for each pair of scenes in step 1.2, P is calculatedKDi=min{KD(ξi,ξj)}×P(ξi) Wherein P (ξ)i) For the probability of the evaluated scene, P of all scene pairs in KDM is then foundKDMinimum value of (1), denoted as PKDsTo PKDsCorresponding scene pair, will xiiAnd xijOne of the two is closer to other scenes and has smaller probability, such as subtracting xii;
Step 1.4, cut down xiiThen, a new KDM is constructed, and the scene probability P (xi) is updatedj)=P(ξi)+P(ξj);
Step 1.5, repeating the step 1.2 to the step 1.4 until the target scene number is reduced;
wherein, PGi、QGiThe power active power and the reactive power of the power supply are respectively; pLi、QLiRespectively the active power and the reactive power of the load; u shapeiAnd UkThe voltages of node i and node k, respectively; y isikAnd thetaikThe amplitude and the phase angle of the element of the node admittance matrix are respectively; deltaiAnd deltakVoltage phase angles of the node i and the node k respectively; b is a set of all nodes;
active power P of loadLiAnd reactive power QLiThe calculation is shown below:
in the formula, PLi0And QLi0Respectively the active power and the reactive power of the initial load of the node i; u shapei0Is the initial value of the voltage at node i; omega is the angular frequency of the system, omega0Is the initial value of angular frequency; a. thepi、BpiAnd CpiRespectively, the static voltage characteristic coefficient of the active power of the load, Aqi、BqiAnd CqiRespectively, the load reactive power static voltage characteristic coefficient, kPfiAnd kQfiStatic frequency characteristic coefficients of load active power and reactive power respectively;
active and reactive power P for the power supplyGi、QGiIn other words, it is calculated by the following equation:
in the formula, PDroopiAnd QDroopiActive power and reactive power P of droop control type micro-source accessed by node iWTGiAnd QWTGiActive power and reactive power P of the wind generating set respectively connected to the node iPViAnd QPViRespectively the active power and the reactive power of the photovoltaic unit accessed by the node i;
if wind turbine generator or photovoltaic unit is connected, PWTGiOr PPViSubstituting according to the actual active power, otherwise, taking the value as zero;
if constant power factor control, then QWTGiOr QPViSubstituting according to actual reactive power;
if the control is constant voltage control, i is a PV node, the reactive power of the PV node is an unknown quantity, and a corresponding balance equation is not temporarily listed in a power flow equation set;
if there is no droop control type micro source access, PDroopiAnd QDroopiValues are all zero; for nodes with Droop-controlled micro-sources, commonly referred to as Droop nodes, then PDroopiAnd QDroopiCalculated as follows:
wherein m ispi、nqiDroop coefficients of active power and reactive power of the droop control micro source of the node i are respectively; omega0Is an initial value of angular frequency, U0Is the initial value of the voltage; b isDroopA set of Droop nodes;
solving the IMG power flow model by adopting a Newton-Raphson method, wherein the modified equation form is as follows:
wherein, the delta P and the delta Q are the unbalance amount of the active power and the reactive power of the node respectively; delta theta and delta U are respectively voltage phase angle and amplitude correction; Δ ω is a correction amount of the frequency; j is a Jacobian matrix;
the Jacobian matrix J when the IMG tide equation converges is subjected to singular value decomposition as shown in the following formula to obtain a minimum singular value delta2n-mAnd its corresponding left and right singular vectors M2n-mAnd N2n-m:
Wherein M isiAnd NiRespectively are left and right singular vectors of a system singular value; Σ is so as to press from large toThe small-arranged positive real singular values are diagonal matrixes of diagonal elements; m is the number of PV nodes, and n is the total number of nodes of the microgrid;
the maximum element of the right singular vector of the minimum singular value indicates the most sensitive node voltage, so that a few large index values in the right singular vector are selected as the reactive compensation nodes of the system:
wherein, Δ θ and Δ U are correction values of voltage phase angle and amplitude respectively; Δ ω is a correction amount of the frequency;
for the reduced scene set, with the expectation of economic targets in all scenes as an objective function and the trend equation and the safety inequality in each scene as constraints, establishing a compensation capacity optimization configuration model, which is specifically as follows:
step 5.1, setting a target function:
the method is characterized in that a capacitor is used as reactive compensation equipment of the micro-grid, the randomness of the output of a wind turbine generator in the micro-grid is considered, the economic benefit brought by the capacitor is maximized into a target function of reactive planning, the economic benefit brought by the compensation capacitor installed on the micro-grid is evaluated by adopting a net present value criterion, and the target function is expressed as
In the formula, d is the discount rate; l is the engineering period; cIInvestment cost for adding compensation capacitors; cOAnd C'ORespectively representing the annual average cost of active loss of the micro-grid before and after the compensation capacitor is added, wherein,
in the formula, σEIs the price of electricity;andrespectively obtaining the expected values of the network loss of the s th scene of the microgrid before and after reactive power optimization; rhosProbability of the s-th scene of the microgrid;
the investment cost of the compensation capacitor is
In the formula, nCCompensating the point number for the capacitor; qCjMounting capacity for the capacitor at the jth compensation point; p is a radical ofCjA unit price of a capacitor installed for the jth compensation point;
and 5.2, setting constraint conditions:
step 5.2.1, power flow equation constraint:
according to the formulas (1) to (4), the power flow equation constraint of the IMG having the droop control type DG networking is expressed as follows, corresponding to any scene s, s is 1,2 … ns:
in the formula (I), the compound is shown in the specification,andvoltage amplitudes and phase angle differences of the node i and the node j in the s-th scene are respectively; omegasThe angular frequency of the system under the s-th scene;andthe active power and the load active power of the wind turbine generator and the photovoltaic connected with the node i in the s-th scene are respectively;andthe reactive power of the wind turbine generator and the photovoltaic of the node i in the s-th scene, the reactive power of the reactive compensation capacitor bank and the load reactive power are respectively;
step 5.2.2, setting droop control type micro-source capacity inequality constraint:
the power of the DG for droop control of access node i needs to meet the capacity limit inequality constraint:
wherein the content of the first and second substances,andcontrolling the active power and the reactive power of a DG (distributed generation) for the droop connected with the node i in the s-th scene respectively;andthe upper and lower limit values of the capacity of the droop control type DG are respectively;
for a reactive compensation capacitor bank:
0≤QCi≤QCimax (14)
wherein Q isCiFor electricity at the i-th compensation pointContainer mounting capacity, QCimaxMaximum allowable mounting capacity for the access capacitor at the ith compensation point;
and 5.2.3, setting system safe operation inequality constraints:
in order to ensure the normal operation of the system, the safety limit constraint of the node voltage and the safety constraint of the branch power need to be met, in addition, the system frequency is also one of the variables, and the safety constraint of the system also needs to be considered in the optimization process:
in the formula (I), the compound is shown in the specification,andrespectively an upper voltage amplitude limit and a lower voltage amplitude limit of the node i;an upper limit value of the amplitude of the current allowed to flow for the branch ij; omegamaxAnd ωminRespectively the upper and lower limits of the angular frequency of the system;the current amplitude of the branch ij under the s-th scene;
and 6, calling an IPOPT optimization tool kit to carry out optimization solution to obtain an optimization configuration scheme, wherein the optimization solution method can be replaced by an interior point method, a genetic algorithm and a particle swarm optimization algorithm.
Examples
Referring to fig. 2, the micro-source is configured by an IEEE33 node system and operates in an island.
TABLE 1 controllable micro-Source Access locations and parameters
DG# | Node point | Rated capacity | U0 | ω0 | mpi | nqi |
1 | 4 | 3.0 | 1.05 | 1.004 | 0.0033 | 0.0667 |
2 | 22 | 1.5 | 1.05 | 1.004 | 0.0067 | 0.1333 |
3 | 25 | 1.0 | 1.05 | 1.004 | 0.0100 | 0.2000 |
TABLE 2 typical scenes after cut
Scene s | PWTG3 | PWTG16 | ρs |
1 | 0.0000 | 0.0000 | 0.297 |
2 | 0.0657 | 0.0117 | 0.065 |
3 | 0.1229 | 0.0780 | 0.074 |
4 | 0.1889 | 0.1444 | 0.150 |
5 | 0.2469 | 0.2295 | 0.055 |
6 | 0.2933 | 0.2658 | 0.080 |
7 | 0.3810 | 0.3708 | 0.105 |
8 | 0.4546 | 0.4628 | 0.076 |
9 | 0.6352 | 0.7046 | 0.054 |
10 | 0.7427 | 0.8000 | 0.044 |
and determining a compensation point according to the right singular vector, and selecting a node set {12, 17, 30 and 32} with larger right singular vector elements as the compensation point in consideration of the fact that the number of parallel capacitors installed on the same line is not too large. For comparison, the effectiveness of selecting compensation points according to the size of the right singular vector is illustrated, secondary sets {9, 14, 26 and 29} and smaller nodes {1, 18, 21 and 24} are simultaneously selected as compensation points to be selected, and are respectively marked as a scheme 1, a scheme 2 and a scheme 3, and optimization planning is respectively carried out;
TABLE 3 Compensation results under the respective scenarios
TABLE 4 analysis of economic benefits of different reactive compensation schemes
Claims (1)
1. A reactive power optimization configuration method for a droop control type island microgrid is characterized by being implemented according to the following steps:
step 1, sampling the wind speed or illumination intensity probability distribution by adopting a Monte Carlo method to obtain a sample set of the output of Ns wind turbine generators or photovoltaic power generation units, and performing scene reduction on the sampled samples based on a backward reduction technology to obtain Ns scene samples;
step 2, establishing an IMG power flow model of a droop control type DG networking, wherein the IMG is an island micro-grid;
step 3, solving the IMG power flow model by adopting a Newton-Raphson method;
step 4, performing singular value decomposition on the Jacobian matrix during IMG tidal current equation convergence to obtain a minimum singular value and left and right singular vectors corresponding to the minimum singular value, and further obtain a system reactive power compensation node;
step 5, establishing a compensation capacity optimization configuration model;
step 6, calling an IPOPT optimization toolkit to carry out optimization solution to obtain an optimization configuration scheme;
in the step 1, the initial scene set of the sample is set to be ω, the reduced target scene set is set to be ω, and the scene reduction algorithm is as follows:
step 1.1, calculating scene distance KD of any two scenes in the initial scene set, establishing a scene distance matrix, and marking as KDM;
step 1.2, aiming at any scene xiiFinding the scene xi closest to itjAnd is denoted by min { KD (ξ)i,ξj) And marking the scene in a KDM matrix;
step 1.3, for each pair of scenes in step 1.2, P is calculatedKDi=min{KD(ξi,ξj)}×P(ξi) Wherein P (ξ)i) For the probability of the evaluated scene, P of all scene pairs in KDM is then foundKDMinimum value of (1), denoted as PKDsTo PKDsCorresponding scene pair, will xiiAnd xijOne of the two is closer to other scenes and has smaller probability, such as subtracting xii;
Step 1.4, cut down xiiThen, a new KDM is constructed, and scene probability is updated
P(ξj)=P(ξi)+P(ξj);
Step 1.5, repeating the step 1.2 to the step 1.4 until the target scene number is reduced;
step 2, establishing an IMG power flow model of the droop control type DG networking, as shown in the following formula:
wherein, PGi、QGiRespectively the active power and the reactive power of the power supply; pLi、QLiRespectively the active power and the reactive power of the load; u shapeiAnd UkThe voltages of node i and node k, respectively; y isikAnd thetaikThe amplitude and the phase angle of the element of the node admittance matrix are respectively; deltaiAnd deltakVoltage phase angles of the node i and the node k respectively; b is a set of all nodes;
active power P of loadLiAnd reactive power QLiThe calculation is shown below:
in the formula, PLi0And QLi0Respectively the active power and the reactive power of the initial load of the node i; u shapei0Is the initial value of the voltage at node i; omega is the angular frequency of the system, omega0Is the initial value of angular frequency; a. thepi、BpiAnd CpiRespectively, the static voltage characteristic coefficient of the active power of the load, Aqi、BqiAnd CqiRespectively, the load reactive power static voltage characteristic coefficient, kPfiAnd kQfiStatic frequency characteristic coefficients of load active power and reactive power respectively;
active and reactive power P for the power supplyGi、QGiIn other words, it is calculated by the following equation:
in the formula, PDroopiAnd QDroopiActive power and reactive power P of droop control type micro-source accessed by node iWTGiAnd QWTGiActive power and reactive power P of the wind generating set respectively connected to the node iPViAnd QPViRespectively the active power and the reactive power of the photovoltaic unit accessed by the node i;
if wind turbine generator or photovoltaic unit is connected, PWTGiOr PPViSubstituting according to the actual active power, otherwise, taking the value as zero;
if constant power factor control, then QWTGiOr QPViSubstituting according to actual reactive power;
if the control is constant voltage control, i is a PV node, the reactive power of the PV node is an unknown quantity, and a corresponding balance equation is not temporarily listed in a power flow equation set;
if there is no droop control type micro source access, PDroopiAnd QDroopiValues are all zero; for the node connected with the Droop control type micro source, called Droop node, P isDroopiAnd QDroopiCalculated as follows:
wherein m ispi、nqiDroop coefficients of active power and reactive power of the droop control micro source of the node i are respectively; omega0Is an initial value of angular frequency, U0Is the initial value of the voltage; b isDroopA set of Droop nodes;
the step 3 is specifically as follows:
solving the IMG power flow model by adopting a Newton-Raphson method, wherein the modified equation form is as follows:
wherein, the delta P and the delta Q are the unbalance amount of the active power and the reactive power of the node respectively; delta theta and delta U are respectively voltage phase angle and amplitude correction; Δ ω is a correction amount of the frequency; j is a Jacobian matrix;
the step 4 is specifically as follows:
the Jacobian matrix J when the IMG tide equation converges is subjected to singular value decomposition as shown in the following formula to obtain a minimum singular value delta2n-mAnd its corresponding left and right singular vectors M2n-mAnd N2n-m:
Wherein M isiAnd NiRespectively are left and right singular vectors of a system singular value; sigma is a diagonal matrix taking positive real singular values arranged from large to small as diagonal elements; m is the number of PV nodes, and n is the total number of nodes of the microgrid;
the maximum element of the right singular vector of the minimum singular value indicates the most sensitive node voltage, so that a few large index values in the right singular vector are selected as the reactive compensation nodes of the system:
wherein, Δ θ and Δ U are correction values of voltage phase angle and amplitude respectively; Δ ω is a correction amount of the frequency;
the step 5 is specifically as follows:
for the reduced scene set, with the expectation of economic targets in all scenes as an objective function and the trend equation and the safety inequality in each scene as constraints, establishing a compensation capacity optimization configuration model, which is specifically as follows:
step 5.1, setting a target function:
the method is characterized in that a capacitor is used as reactive compensation equipment of the micro-grid, the randomness of the output of a wind turbine generator in the micro-grid is considered, the economic benefit brought by the capacitor is maximized into a target function of reactive planning, the economic benefit brought by the compensation capacitor installed on the micro-grid is evaluated by adopting a net present value criterion, and the target function is expressed as
In the formula, d is the discount rate; l is the engineering period; cIInvestment cost for adding compensation capacitors; cOAnd C'ORespectively representing the annual average cost of active loss of the micro-grid before and after the compensation capacitor is added, wherein,
in the formula, σEIs the price of electricity;andrespectively obtaining the expected values of the network loss of the s th scene of the microgrid before and after reactive power optimization; rhosProbability of the s-th scene of the microgrid;
the investment cost of the compensation capacitor is
In the formula, nCCompensating the point number for the capacitor; qCjMounting capacity for the capacitor at the jth compensation point; p is a radical ofCjA unit price of a capacitor installed for the jth compensation point;
and 5.2, setting constraint conditions:
step 5.2.1, power flow equation constraint:
according to the formulas (1) to (4), the power flow equation constraint of the IMG having the droop control type DG networking is expressed as follows, corresponding to any scene s, s is 1,2 … ns:
in the formula (I), the compound is shown in the specification,andvoltage amplitudes and phase angle differences of the node i and the node j in the s-th scene are respectively; omegasThe angular frequency of the system under the s-th scene;andthe active power and the load active power of the wind turbine generator and the photovoltaic connected with the node i in the s-th scene are respectively;andthe reactive power of the wind turbine generator and the photovoltaic of the node i in the s-th scene, the reactive power of the reactive compensation capacitor bank and the load reactive power are respectively;
step 5.2.2, setting droop control type micro-source capacity inequality constraint:
the power of the DG for droop control of access node i needs to meet the capacity limit inequality constraint:
wherein the content of the first and second substances,andcontrolling the active power and the reactive power of a DG (distributed generation) for the droop connected with the node i in the s-th scene respectively;andthe upper and lower limit values of the capacity of the droop control type DG are respectively;
for a reactive compensation capacitor bank:
0≤QCi≤QCimax (14)
wherein Q isCiFor capacitor mounting capacity at i-th compensation point, QCimaxMaximum allowable mounting capacity for the access capacitor at the ith compensation point;
and 5.2.3, setting system safe operation inequality constraints:
in order to ensure the normal operation of the system, the safety limit constraint of the node voltage and the safety constraint of the branch power need to be met, in addition, the system frequency is also one of the variables, and the safety constraint of the system also needs to be considered in the optimization process:
in the formula (I), the compound is shown in the specification,andrespectively an upper voltage amplitude limit and a lower voltage amplitude limit of the node i;an upper limit value of the amplitude of the current allowed to flow for the branch ij; omegamaxAnd ωminRespectively the upper and lower limits of the angular frequency of the system;the current amplitude of branch ij under the s-th scenario is shown.
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