CN112821413A - Method, device, equipment and storage medium for controlling secondary voltage of micro-grid - Google Patents
Method, device, equipment and storage medium for controlling secondary voltage of micro-grid Download PDFInfo
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Abstract
The invention discloses a method, a device, equipment and a storage medium for controlling the secondary voltage of a microgrid, wherein the method comprises the steps of calculating a secondary reactive power sharing regulation target of a preset microgrid and a microgrid adjacent to the preset microgrid; distributing a first weighting coefficient to the first reactive power sharing adjustment target to obtain a weighted secondary reactive power sharing adjustment target; calculating a secondary voltage regulation target of a preset micro-grid; distributing a second weighting coefficient to the voltage-controlled rectifier circuit to obtain a weighted secondary voltage regulation target; the weighted secondary reactive power sharing regulation target and the weighted secondary voltage regulation target are added to obtain a sliding mode surface, the first weighting coefficient and the second weighting coefficient are adjusted until the voltage regulation and the reactive power sharing are compromised, so that the conflict between the voltage regulation and the reactive power sharing can be solved while the quick response is realized, the voltage deviation is eliminated, the accurate reactive power sharing is realized, the robustness is stronger, the flexibility of the system is increased, and the plug-and-play function is realized.
Description
Technical Field
The invention belongs to the technical field of distributed voltage control of a micro-grid, and particularly relates to a micro-grid secondary voltage control method, device, equipment and storage medium.
Background
In recent years, people pay more and more attention to energy problems, environmental problems and economic problems, Distributed Generation (DGs) have the advantages of less pollution, less loss, flexible operation and the like, so that people pay more attention to the Distributed Generation (DGs), a microgrid is needed for effectively managing the DGs, is a low-voltage power distribution system, can solve local energy problems, enhances the flexibility of power supply, can operate in an island mode, and can be connected to a main power grid.
In order to meet the uninterrupted demand of power consumption of users inside the microgrid, the microgrid needs to be freely and seamlessly switched between a networking state and an island state, and due to the intermittence of distributed power generation and random changes of loads, especially when the microgrid runs in an island, if a rapid and effective power balancing strategy is not available, the frequency and the voltage of the microgrid can fluctuate strongly and even cause instability. In order to solve the problem, a microgrid control strategy based on a hierarchical control scheme is widely adopted at present, an island microgrid is controlled in two stages, in order to realize power sharing, the first stage is usually droop control, which can quickly solve the problem of power balance, but the droop control can generate frequency and voltage deviations, so that the frequency and voltage deviations are eliminated through the second stage control, and accurate power sharing is realized. In the prior art, the prior work of a secondary control strategy based on centralized control, distributed control and distributed control is already completed, wherein the centralized control needs global information and centralized calculation, the flexibility and expandability are poor, the distributed control reduces the communication burden, but the high-efficiency coordination of DGs is sacrificed, the contradictions can be coordinated through the distributed control, namely, the information is shared with adjacent units through a local communication network, and the distributed control structure is widely applied to the secondary control so as to avoid using a microgrid central controller. However, despite the advantages of distributed control of frequency and voltage regulation and power sharing described above, it requires a dense communication architecture and is not scalable.
In the prior art, there is an islanding microgrid layered distributed control strategy based on a consistency theory, a first-level droop control strategy is proposed first to achieve fast response of distributed power supplies, then a distributed second-level frequency control and second-level voltage-reactive control strategy is proposed based on a finite time consistency algorithm, frequency and voltage offset caused by the first-level droop control is corrected, reactive power proportion distribution is achieved, and finally, an islanding microgrid distributed economic scheduling method is proposed further based on the finite time consistency algorithm to enable each distributed power supply to independently solve optimal output active power locally. However, in the above control strategy, some linear control strategies with asymptotic convergence rates may not be suitable for rapidly controlling microgrid operating conditions, such as intermittent and randomly varying loads of DGs; for these conditions, part of distributed nonlinear control strategies only focus on robustness and fast recovery to accelerate convergence speed, and few consider implementation of accurate active and reactive power sharing, that is, few adopt voltage and reactive power for cooperative control.
Disclosure of Invention
In order to solve the above problems, the present invention provides a method, an apparatus, a device and a storage medium for controlling a secondary voltage of a microgrid, which can solve a conflict between voltage regulation and reactive power sharing while achieving a quick response, eliminate voltage deviation and achieve accurate reactive power sharing, have a stronger robustness, increase flexibility of a system, and achieve a plug and play function.
The invention provides a method for controlling the secondary voltage of a microgrid, which comprises the following steps:
calculating a secondary reactive power sharing regulation target of a preset micro-grid and a micro-grid adjacent to the preset micro-grid;
distributing a first weighting coefficient to the secondary reactive power sharing regulation target to obtain a weighted secondary reactive power sharing regulation target;
calculating a secondary voltage regulation target of the preset micro-grid;
distributing a second weighting coefficient to the secondary voltage regulation target to obtain a weighted secondary voltage regulation target;
and adding the weighted secondary reactive power sharing regulation target and the weighted secondary voltage regulation target to obtain a sliding mode surface, and adjusting the first weighting coefficient and the second weighting coefficient until a compromise is reached between voltage regulation and reactive power sharing.
Preferably, in the method for controlling the secondary voltage of the microgrid, the calculating a secondary reactive power sharing regulation target of the preset microgrid and the microgrid adjacent to the preset microgrid comprises:
acquiring a first reactive power measured value of the preset micro-grid, and dividing the first reactive power measured value by a first reactive power reference value to obtain a first reactive power ratio;
acquiring a second reactive power measured value of a microgrid adjacent to the preset microgrid, and dividing the second reactive power measured value by a second reactive power reference value to obtain a second reactive power ratio;
subtracting the second reactive power ratio from the first reactive power ratio to obtain a reactive power ratio difference of adjacent micro-grids, and distributing a third weighting coefficient to the reactive power ratio difference, wherein the third weighting coefficient is an element in an adjacent matrix;
and adding all the reactive power ratio differences of the adjacent micro-grids to obtain the secondary reactive power sharing regulation target.
Preferably, in the method for controlling secondary voltage of a microgrid, the calculating a secondary voltage regulation target of the preset microgrid includes:
and acquiring an output voltage amplitude of the preset micro-grid, and subtracting a reference voltage amplitude from the output voltage amplitude to obtain an output voltage amplitude difference so as to obtain the secondary voltage regulation target.
Preferably, in the method for controlling secondary voltage of a microgrid, one of the microgrid is selected as a leader microgrid, the other microgrid is selected as a follower microgrid, the first weighting coefficient of the leader microgrid is set to be non-zero, the second weighting coefficient is set to be zero to achieve a secondary voltage regulation target, and the first weighting coefficient of the follower microgrid is set to be zero, and the second weighting coefficient is set to be non-zero to achieve a secondary reactive power sharing regulation target.
The invention provides a micro-grid secondary voltage control device, which comprises:
the first calculation component is used for calculating a secondary reactive power sharing regulation target of a preset micro-grid and a micro-grid adjacent to the preset micro-grid;
the first weighting component is used for distributing a first weighting coefficient to the secondary reactive power sharing regulation target to obtain a weighted secondary reactive power sharing regulation target;
the second calculation component is used for calculating a secondary voltage regulation target of the preset micro-grid;
the second weighting component is used for distributing a second weighting coefficient to the secondary voltage regulation target to obtain a weighted secondary voltage regulation target;
and the weighting coefficient adjusting component is used for adding the weighted secondary reactive power sharing regulation target and the weighted secondary voltage regulation target to obtain a sliding mode surface, and adjusting the first weighting coefficient and the second weighting coefficient until a compromise is reached between voltage regulation and reactive power sharing.
Preferably, in the microgrid secondary voltage control device, the first calculation means includes:
the first acquisition unit is used for acquiring a first reactive power measured value of the preset microgrid and dividing the first reactive power measured value by a first reactive power reference value to obtain a first reactive power ratio;
the second acquisition unit is used for acquiring a second reactive power measured value of the microgrid adjacent to the preset microgrid, and dividing the second reactive power measured value by a second reactive power reference value to obtain a second reactive power ratio;
the first weighting unit is used for subtracting the second reactive power ratio from the first reactive power ratio to obtain a reactive power ratio difference of adjacent micro-grids, and distributing a third weighting coefficient to the reactive power ratio difference, wherein the third weighting coefficient is an element in an adjacent matrix;
and the secondary reactive power sharing regulation target determining unit is used for adding all the reactive power ratio differences of the adjacent micro-grids to obtain the secondary reactive power sharing regulation target.
Preferably, in the microgrid secondary voltage control device, the second calculation means includes:
and the third acquisition unit is used for acquiring the output voltage amplitude of the preset micro-grid, and subtracting the reference voltage amplitude from the output voltage amplitude to obtain an output voltage amplitude difference and obtain the secondary voltage regulation target.
Preferably, in the microgrid secondary voltage control device, the microgrid secondary voltage control device further comprises a leader and follower determination unit, configured to select one of the microgrids as a leader microgrid and the other microgrids as follower microgrids, set a first weighting coefficient of the leader microgrid to be non-zero, set a second weighting coefficient to be zero to achieve a secondary voltage regulation target, and set a first weighting coefficient of the follower microgrid to be zero, set a second weighting coefficient to be non-zero to achieve a secondary reactive power sharing regulation target.
The invention provides a computer device comprising:
a memory for storing a computer program;
a processor for implementing the steps of the microgrid secondary voltage control method according to any of the above when said computer program is executed.
The invention provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the microgrid secondary voltage control method according to any of the above.
As can be seen from the above description, the method for controlling the secondary voltage of the microgrid provided by the present invention includes distributing a first weighting coefficient to the secondary reactive power sharing regulation target to obtain a weighted secondary reactive power sharing regulation target, distributing a second weighting coefficient to the secondary voltage regulation target to obtain a weighted secondary voltage regulation target, adding the weighted secondary reactive power sharing regulation target and the weighted secondary voltage regulation target to obtain a weighted secondary voltage regulation target, and adjusting the first weighting coefficient and the second weighting coefficient until a compromise is reached between the voltage regulation and the reactive power sharing, which can fully consider the two factors of the voltage regulation and the reactive power sharing without considering the loss of the two factors, thereby solving the conflict between the voltage regulation and the reactive power sharing while achieving a fast response, eliminating the voltage deviation and realizing an accurate reactive power sharing, the method has stronger robustness, increases the flexibility of the system and realizes the function of plug and play. The device, the equipment and the storage medium for controlling the secondary voltage of the microgrid have the same advantages as the method for controlling the secondary voltage of the microgrid.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic diagram of an embodiment of a method for controlling a secondary voltage of a microgrid according to the present invention;
FIG. 2 is a schematic diagram of the connection of parallel micro grids;
FIG. 3 is an E-Q diagram of droop control and SRPSRG alone in the prior art;
FIG. 4 is a graph illustrating the relationship between voltage and reactive power before and after SVRG is achieved using E-Q droop characteristics alone in the prior art;
FIG. 5 is a schematic view of a contiguous matrix configuration;
fig. 6 is a schematic diagram of an embodiment of a microgrid secondary voltage control apparatus according to the present invention;
FIG. 7 is a schematic diagram of one embodiment of a computer device;
FIG. 8 is a block diagram of a DCSM control architecture for a single DG;
FIG. 9 is a schematic diagram of the trajectory of the DCSM control system for DG1 in the phase plane;
FIG. 10 is a schematic diagram of a microgrid arrangement;
FIG. 11 is a schematic illustration of voltage magnitude and reactive power sharing during droop control;
FIG. 12 is a schematic diagram of forced secondary reactive power regulation;
FIG. 13 is a schematic diagram of forced secondary voltage regulation;
FIG. 14 is a schematic diagram of a trade-off of voltage regulation and reactive power sharing regulation;
FIG. 15 is a schematic diagram of the implementation of accurate reactive power sharing and good voltage regulation;
FIG. 16 is a diagram illustrating the performance of a DCSM controller in the event of a communication failure;
FIG. 17 is a schematic diagram of the performance of a DCSM controller removing any DGs in a microgrid during plug-and-play operation;
fig. 18 is a schematic diagram of the performance of a DCSM controller to add arbitrary DGs to a microgrid during plug-and-play operation.
Detailed Description
The core of the invention is to provide a method, a device, equipment and a storage medium for controlling the secondary voltage of the microgrid, which can solve the conflict between voltage regulation and reactive power sharing while realizing quick response, eliminate voltage deviation and realize accurate reactive power sharing, have stronger robustness, increase the flexibility of a system and realize the function of plug and play.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 shows an embodiment of a method for controlling a secondary voltage of a microgrid according to the present invention, where fig. 1 is a schematic diagram of an embodiment of a method for controlling a secondary voltage of a microgrid according to the present invention, and the method includes the following steps:
s1: calculating a secondary reactive power sharing regulation target of a preset micro-grid and a micro-grid adjacent to the preset micro-grid;
it should be noted that the microgrid is a small-sized power generation and distribution system comprising a distributed power supply, an energy storage device, a load, a monitoring device and a protection device, is a system capable of realizing self control, protection and management, can be operated in a grid-connected mode with a large power grid, and can also be operated independently with an isolated power grid, the voltage of each inverter is controlled by one-level droop, refer to fig. 2, fig. 2 is a connection schematic diagram of parallel microgrids, and X is a schematic diagram of a parallel microgrid0iRepresenting DGs connected to a common busiOf (2), therefore, DGiThe active power and reactive power injection of (a) is described as:
Eiand V represents DGiThe output voltage amplitude of and the common bus voltage,
is the line impedance angle, θiIs EiAnd V. DGiOutput impedance Z0iPredominantly inductive, and can be regarded as Z0i≈X0i，
E due to DGsiAnd V is smaller in formula (1) and formula (2), the output active power of DGs is proportional to the power angle, and the reactive power is proportional to the voltage magnitude difference.
ωi＝ω*-mi(Pi-Pi *)， (3)
Ei＝E*-ni(Qi-Qi *)， (4)
Wherein EiAnd ωiRepresents DGiOutput voltage amplitude and frequency, ω*And E*Respectively, reference frequency and voltage amplitude, miAnd niIs the sag factor, PiAnd QiActive and reactive power, P, of the ith DG respectivelyi *And Qi *Which are the reference values for the active and reactive power, respectively, of the ith DG. Under the influence of line reactance, it is difficult to achieve accurate reactive power distribution. The expression of the reactive power obtained by combining equations (2) and (4) is shown in equation (5):
to simplify the analysis, it is assumed that DGi has the same capacity and droop coefficient as DGj. Current phase angle thetaiIn hours, the relative difference in reactive power can be derived from equation (5):
by equation (6), the relative difference in reactive power can be reduced by reducing the line impedance difference between the DGs, increasing the gain of the reactive voltage drop coefficient and reducing the line impedance, but these adjustments may affect the magnitude of the output voltage and even cause the microgrid to crash. Therefore, in order to quickly eliminate the voltage deviation while achieving accurate reactive power distribution, robust nonlinear secondary control is required. The secondary voltage regulation has two targets, wherein the first target, namely the secondary reactive power sharing regulation target, namely the SRPSRG, is used for solving the problem of inaccurate power distribution, and various parameters of adjacent micro-grids can be acquired in a sparse communication mode.
S2: distributing a first weighting coefficient for the secondary reactive power sharing regulation target to obtain a weighted secondary reactive power sharing regulation target;
it should be noted that, in order to simplify the analysis, a parallel microgrid including two identical DGs is used as an example for explanation, and the conclusion can be relaxed to a case where a plurality of DGs are connected to a common busResistance difference, set as X01＞X02Fig. 3 is an E-Q diagram of droop control and SRPSRG alone in the prior art, as shown in fig. 3, where the reactive power of DG can be apportioned while still preserving the voltage deviation. Based on this, it is weighted in this embodiment to take this factor into account in the subsequent adjustment process.
S3: calculating a secondary voltage regulation target of a preset micro-grid;
it should be noted that the secondary voltage regulation target, SVRG, is used to regulate the voltage deviation, as shown in fig. 4, and fig. 4 is a schematic diagram of the relationship between the voltage before and after reaching SVRG and the reactive power by using the E-Q droop characteristic alone in the prior art, wherein the solid line and the dotted line are the voltage drop and SVRG, respectively. The dashed lines of two different colors indicate that the output voltages of the two DGs are different compared to the solid line, and the reactive power injection becomes Q 'although there is no deviation from the reference value'1＜Q1And Q'2＞Q2This indicates that the reactive power distribution becomes worse.
S4: distributing a second weighting coefficient to the secondary voltage regulation target to obtain a weighted secondary voltage regulation target;
based on the description in the above steps, in the present embodiment, the second weighting factor is assigned to the secondary voltage adjustment target to also take such a factor into account in the subsequent adjustment process.
S5: and adding the weighted secondary reactive power sharing regulation target and the weighted secondary voltage regulation target to obtain a sliding mode surface, and adjusting the first weighting coefficient and the second weighting coefficient until a compromise is reached between voltage regulation and reactive power sharing.
It should be noted that this makes it possible to achieve a compromise between conflicting objectives of voltage and reactive power, the size of the specific weighting factors being determined by the degree of compromise between these two objectives, in such a way that the voltage regulation and the reactive power distribution can be made more accurate.
As can be seen from the above description, in the embodiment of the method for controlling the secondary voltage of the microgrid provided by the present invention, since the method includes allocating a first weighting coefficient to the secondary reactive power sharing regulation target to obtain the weighted secondary reactive power sharing regulation target, and allocating a second weighting coefficient to the secondary voltage regulation target to obtain the weighted secondary voltage regulation target, then adding the weighted secondary reactive power sharing regulation target and the weighted secondary voltage regulation target to obtain a weighted surface, and adjusting the first weighting coefficient and the second weighting coefficient until a compromise is reached between the voltage regulation and the reactive power sharing, it can be seen that the two factors of the voltage regulation and the reactive power sharing are fully considered, and no consideration is given to the sliding mode, so that the method can solve the conflict between the voltage regulation and the reactive power sharing while achieving a fast response, eliminate the voltage deviation and achieve an accurate reactive power sharing, the method has stronger robustness, increases the flexibility of the system and realizes the function of plug and play.
In a specific embodiment of the method for controlling the secondary voltage of the microgrid, calculating the secondary reactive power sharing regulation target of the preset microgrid and the microgrid adjacent to the preset microgrid may include the following steps:
collecting a first reactive power measurement Q of a pre-set microgridiThe first reactive power measurement QiDivided by a first reactive power reference value Qi *Obtaining a first reactive power ratio;
collecting a second reactive power measurement Q of a microgrid adjacent to a predetermined microgridjSecond reactive power measurement QjDivided by a second reactive power reference value Qj *Obtaining a second reactive power ratio;
subtracting the second reactive power ratio from the first reactive power ratio to obtain a reactive power ratio difference of the adjacent micro-grids, and distributing a third weighting coefficient a to the reactive power ratio differenceijThird weighting factor aijIs an element in the adjacency matrix a;
adding all the reactive power ratio differences of the adjacent micro-grids to obtain a secondary reactive power sharing regulation target as follows:
wherein the expression of the adjacency matrix A is
The construction of such an adjacency matrix is shown in fig. 5, fig. 5 is a schematic diagram of the construction of the adjacency matrix, where a consistency algorithm is used, the communication layer between DGs will be described by a weighted graph G (v, e, a), the structure can be represented by a symmetric n × n order matrix a, the elements a of which are represented byijThe weight representing the edge is between vertices i and j. v ═ {1, …, n } represents a node,
is an edge. N is a radical ofiRepresenting a set of neighboring vertices for vertex i. x is the number ofiThe state variable representing node i, which may represent physical quantities of the islanded microgrid, such as voltage, frequency, etc., is consistent if and only if the state variables of all nodes are the same.
In a further embodiment of the above-mentioned secondary voltage control method of the microgrid, calculating a secondary voltage regulation target of the preset microgrid may include the steps of:
collecting output voltage amplitude E of preset micro-gridiWill output a voltage amplitude EiMinus the reference voltage amplitude E*And obtaining the amplitude difference of the output voltage to obtain a secondary voltage regulation target.
Specifically, the overall control method may be determined by a combination of the following equations:
wherein s isiRepresenting the sliding surfaces involved, the final control objective is to have the operating points of the DG units all operating at siOn the slip form face of 0 uiIs an auxiliary control variable, biAnd ciIs a first weighting coefficient and a second weighting coefficient, and aijIs the thirdThe weighting factors, by adjusting the first weighting factor and the second weighting factor, a compromise can be reached between conflicting goals of voltage regulation and reactive power sharing.
When b in the above formula (7)i≠0,ciWhen 0, the controller may implement SRPSRG if and only if all DGs are reached
The system can reach a steady state. When b in formula (7)i＝0,ciWhen the voltage is not equal to 0, SVRG can be realized, the voltage of each DG can be recovered to a reference value, however, SRPSRG can generate large voltage deviation, and SVRG can cause poor reactive power sharing, so that secondary voltage control of an island microgrid is realized. When b isi≠0,ciWhen the weight is not equal to 0, both SVRG and SRPSRG are included, and a first weighting coefficient b for embodying the weight of a secondary reactive power sharing regulation target (SRPSRG) is giveniAnd a second weighting coefficient c for weighting the two-stage voltage regulation target (SVRG)iThe relative size of the weighting coefficients is determined by the degree of compromise between the conflicting objectives of voltage and reactive power sharing, in such a way that voltage regulation and reactive power distribution can be made more accurate.
In order to improve the control performance, on the basis of the embodiment of the method for controlling the secondary voltage of the microgrid, one microgrid can be selected as a leader microgrid, the other microgrids can be used as follower microgrids, the first weighting coefficient of the leader microgrid is set to be non-zero, the second weighting coefficient is set to be zero to achieve a secondary voltage regulation target, and the first weighting coefficient of the follower microgrid is set to be zero, and the second weighting coefficient is set to be non-zero to achieve a secondary reactive power sharing regulation target.
In particular, the leader DG (e.g. DG)i) For the realization of bi＝0,ciSVRG not equal to 0, while others (j not equal to i) are used to implement bi≠0,ciSRPSRG of 0. In this way, DG can be convertediIs restored to the reference value, andall DGs can achieve accurate reactive power distribution. In addition, the follower DGj(j ≠ i) will follow DG with a voltageiVoltage E ofi＝E*。
Fig. 6 shows an embodiment of a microgrid secondary voltage control apparatus provided by the present invention, where fig. 6 is a schematic diagram of an embodiment of a microgrid secondary voltage control apparatus provided by the present invention, the apparatus includes:
the first calculation component 601 is used for calculating a secondary reactive power sharing regulation target of a preset microgrid and a microgrid adjacent to the preset microgrid, and the secondary voltage regulation has two targets, wherein the first target, namely the secondary reactive power sharing regulation target, namely the SRPSRG, is used for solving the problem of inaccurate power distribution;
a first weighting unit 602, configured to assign a first weighting coefficient to the secondary reactive power sharing adjustment target, obtain a weighted secondary reactive power sharing adjustment target, weight the secondary reactive power sharing adjustment target, and consider the factor in a subsequent adjustment process;
a second calculating unit 603, configured to calculate a secondary voltage regulation target of the preset microgrid, where the secondary voltage regulation target is an SVRG, and is used to regulate a voltage deviation;
a second weighting unit 604, configured to assign a second weighting coefficient to the secondary voltage regulation target to obtain a weighted secondary voltage regulation target, and assign a second weighting coefficient to the secondary voltage regulation target, where such a factor may also be considered in a subsequent adjustment process;
a weighting factor adjusting component 605, configured to add the weighted secondary reactive power sharing regulation target and the weighted secondary voltage regulation target to obtain a sliding mode surface, and adjust the first weighting factor and the second weighting factor until a compromise is reached between the voltage regulation and the reactive power sharing, it should be noted that, in this way, a compromise between conflicting targets of voltage and reactive power can be achieved, and the size of the specific weighting factor is determined by the degree of the compromise between the two targets, and in this way, the voltage regulation and the reactive power distribution can be more accurate.
In summary, the above device fully considers the two factors of voltage regulation and reactive power sharing, and does not consider them, so that the device can solve the conflict between voltage regulation and reactive power sharing while satisfying fast response, can eliminate voltage deviation and realize accurate reactive power sharing, has stronger robustness, increases flexibility of the system, and realizes the function of plug and play.
In a specific embodiment of the above-described microgrid secondary voltage control apparatus, the first calculation means may include:
a first acquisition unit for acquiring a first reactive power measurement value Q of a preset microgridiThe first reactive power measurement QiDivided by a first reactive power reference value Qi *Obtaining a first reactive power ratio;
a second acquisition unit for acquiring a second reactive power measurement value Q of the microgrid adjacent to the preset microgridjSecond reactive power measurement QjDivided by a second reactive power reference value Qj *Obtaining a second reactive power ratio;
the first weighting unit is used for subtracting the second reactive power ratio from the first reactive power ratio to obtain a reactive power ratio difference of adjacent micro-grids and distributing a third weighting coefficient a to the reactive power ratio differenceijThird weighting factor aijIs an element in the adjacency matrix a;
the secondary reactive power sharing regulation target determining unit is used for adding all the reactive power ratio differences of the adjacent micro-grids to obtain a secondary reactive power sharing regulation target as follows:
in a further embodiment of the above-mentioned microgrid secondary voltage control apparatus, the second calculation means may include:
a third acquisition unit for acquiring the output voltage amplitude E of the preset microgridiWill output a voltage amplitude EiMinus the reference voltage amplitude E*And obtaining the amplitude difference of the output voltage to obtain a secondary voltage regulation target.
Specifically, the control principle of the control device may be determined by using the following formula combination:
wherein s isiRepresenting the sliding surfaces involved, the final control objective is to have the operating points of the DG units all operating at siOn the slip form face of 0 uiIs an auxiliary control variable, biAnd ciIs a first weighting coefficient and a second weighting coefficient, and aijIs a third weighting factor, a compromise between conflicting goals of voltage regulation and reactive power sharing may be reached by adjusting the first weighting factor and the second weighting factor.
In order to improve the control performance, on the basis of the embodiment of the microgrid secondary voltage control device, a leader and follower determination unit may be further included, configured to select one of the microgrids as a leader microgrid and the other microgrids as follower microgrids, set the first weighting coefficient of the leader microgrid to be non-zero, set the second weighting coefficient to be zero to achieve a secondary voltage regulation target, and set the first weighting coefficient of the follower microgrid to be zero and set the second weighting coefficient to be non-zero to achieve a secondary reactive power sharing regulation target.
In particular, the leader DG (e.g. DG)i) For the realization of bi＝0,ciSVRG not equal to 0, while others (j not equal to i) are used to implement bi≠0,ciSRPSRG of 0. In this way, DG can be convertediThe output voltage of (c) is restored to the reference value and all DGs can achieve accurate reactive power distribution. In addition, the follower DGj(j ≠ i) will follow DG with a voltageiVoltage E ofi＝E*。
Fig. 7 illustrates an embodiment of a computer device provided by the present invention, and fig. 7 is a schematic diagram of an embodiment of a computer device provided by the present invention, where the computer device may include:
a memory 701 for storing a computer program;
a processor 702, configured to execute a computer program to implement the steps of any of the above methods for microgrid secondary voltage control.
In an embodiment of the present invention, a computer readable storage medium has a computer program stored thereon, where the computer program is executed by a processor to implement the steps of any of the above methods for controlling the secondary voltage of a microgrid.
The microgrid secondary voltage control device and the storage medium provided by the invention have the same advantages as the method and the device.
Based on the method, the apparatus, the computer device and the storage medium provided by the above embodiments, an islanding microgrid nonlinear distributed secondary voltage controller DCSM, that is, a DCSM controller, may be manufactured, referring to fig. 8, where fig. 8 is a structural block diagram of a single DG DCSM control architecture, and a phase trajectory method is used to analyze system stability. To simplify the analysis process, a delay is generated in the output voltage in equation (7) by a simple low pass filter, and then a dynamic system is generated as follows:
therefore, we use Δ Ei＝Ei-E*，
And the reactive power deviation Δ Q ═ Qi/Qi *-Qj/Qj *The phase trace was plotted to verify the stability of the DCSM controller.
Taking DG1 as an example, in an island microgrid, referring to fig. 9, fig. 9 is a schematic diagram of a trajectory of a DCSM control system of DG1 in a phase plane, a solid circle represents an origin, an open rectangle represents a starting point, and fig. 9 illustrates a state variable Δ E using a DCSM controlleri，
And Δ Q, the system state is far from the origin due to the occurrence of disturbance, and the sliding mode variable is not zero at the beginning, the sliding mode variable gradually converges to zero as the control proceeds, and the states are gradually driven to the vicinity of the origin, and finally, all the states are stable at the origin, and the sliding mode variable remains zero. According to the definition of system stability: in the phase trajectory, the system state changes within a certain range, the stable trajectory swings backward, the unstable trajectory diverges, and therefore, the entire system is stable.
Then, the performance of the above DCSM controller is verified by a series of simulations, considering a parallel multi-inverter island microgrid as shown in fig. 10, fig. 10 is a schematic diagram of a microgrid setup with three DGs and a variable load, the DCSM controller of each DG unit is implemented digitally in MATLAB/Simulink software (suitable for use in a DSP or microcontroller), and the adjacency matrix a under sparse communication is as follows:
the validity verification includes the following three parts. In section a, the performance of the DCSM secondary controller proposed in the foregoing is demonstrated by modifying the control gain; part B shows the robustness in case of communication failure; section C demonstrates flexibility under plug and play operation.
A. Controller performance
1) To verify the effectiveness of the DCSM controller in an islanded microgrid, the variable load is increased by 10kW/6kVar at 10s and the load is decreased at 20 s. As shown in fig. 11, fig. 11 is a schematic diagram of voltage amplitude and reactive power sharing in droop control, and fig. 11 shows the result of one-stage droop control, where the voltage deviates from the reference value and the reactive power of each DG cannot be distributed proportionally due to the difference in line reactance.
2) Based on the above analysis, SVRG and SRPSRG are conflicting, and to implement secondary reactive power control, DCSM is setB of the controlleri＝500,ciGiven a matrix a, fig. 12, which is a schematic diagram of forced two-stage reactive power regulation, it can be seen that the reactive power of DG is proportionally distributed, but it is clear that the voltage deviation becomes large, as shown in fig. 12. To achieve reverse testing of the secondary voltage control objective, the parameter is set to bi＝0,ciWith the result that, as shown in fig. 13, fig. 13 is a schematic diagram of forced two-stage voltage regulation, and although the voltage of DG can be restored to the reference voltage value, the reactive power cannot be proportionally distributed.
3) To verify the effectiveness of the DCSM controller's compromise between SVRG and SRPSRG, set bi＝100,c i1, e 0.004, as shown in fig. 14, fig. 14 is a schematic diagram of the trade-off between voltage regulation and reactive power sharing regulation, and this trade-off of fig. 14 reduces the voltage deviation by 12.5% to 71.698% by sacrificing a little power sharing accuracy, and it can be seen that more accurate power sharing can be achieved by sacrificing a little voltage deviation, and the error is reduced by 60.154% to 81.043%, and therefore, as shown in fig. 14, the trade-off makes the voltage regulation and reactive power distribution more accurate.
4) To achieve the best compromise for the DCSM controller, DG2 is set to b2＝0,c2Leader DG 100, ∈ 1, other DG b1＝b3＝250,c1＝c3As a result, fig. 15 shows the result, fig. 15 is a schematic diagram of the realization of accurate reactive power sharing and good voltage regulation, and as can be seen from fig. 15, the DCSM controller realizes reactive power sharing and the voltage regulation is more precise.
B. Communication failure
To test the robustness of the DCSM controller, the communication link between DG1 and DG3 was set to fail at t-7.5 s and to recover at t-15 s. The variable load is added at 10s and released at 20 s. When the controller is set to b2＝0,b1＝b3＝250,c2＝100,c1＝c3The results are shown in fig. 16 for 0 and 1, and fig. 16 is an illustration of the performance of the DCSM controller in the case of a communication failureIt is intended that it can be seen that in the event of a failure of the communication link between DG1 and DG3, the DCSM controller is still able to achieve precise control.
C. Plug and play
In order to verify the plug and play function of the DCSM controller, firstly, the connection of the DG3 is disconnected when t is 10s, and the connection is recovered when t is 20s, the parameters of the DCSM controller are the same as those of the above part, as a result, as shown in fig. 17, fig. 17 is a schematic diagram of the performance of the DCSM controller in removing any DGs in the microgrid under plug and play operation, and then, 20kVar DG4 is randomly switched, as shown in fig. 18, fig. 18 is a schematic diagram of the performance of the DCSM controller in adding any DGs in the microgrid under plug and play operation, and DG4 is connected to the microgrid at 10s and disconnected at 20 s. The results show that the controller can still achieve accurate reactive power sharing and smaller voltage deviation when DG is switched in or out during and after plug-and-play, and therefore, the DCSM controller has better flexibility.
In conclusion, the DCSM controller provided by the invention has strong robustness and quick response capability, can well adapt to randomness and uncertainty of DG and load, and in addition, based on a consistency algorithm under sparse communication, the improved DCSM controller also improves the flexibility of the system and achieves a compromise between conflicting goals of voltage regulation and reactive power sharing. A series of simulation studies are carried out in MATLAB/Simulink, the improved performance of the proposed DCSM controller is verified, and the simulation results show that: in the case of load changes, the DCSM controller can trade off conflicting goals faster and maintain high performance; in the face of communication failures, the controller shows strong robustness, and the bus voltage and bus frequency remain well regulated despite the disconnection of DG3, indicating the flexibility of the plug and play process. For future work, nonlinear control strategies may be applied to more complex power networks, such as AC/DC hybrid micro-grids.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A method for controlling the secondary voltage of a microgrid is characterized by comprising the following steps:
calculating a secondary reactive power sharing regulation target of a preset micro-grid and a micro-grid adjacent to the preset micro-grid;
distributing a first weighting coefficient to the secondary reactive power sharing regulation target to obtain a weighted secondary reactive power sharing regulation target;
calculating a secondary voltage regulation target of the preset micro-grid;
distributing a second weighting coefficient to the secondary voltage regulation target to obtain a weighted secondary voltage regulation target;
and adding the weighted secondary reactive power sharing regulation target and the weighted secondary voltage regulation target to obtain a sliding mode surface, and adjusting the first weighting coefficient and the second weighting coefficient until a compromise is reached between voltage regulation and reactive power sharing.
2. The microgrid secondary voltage control method according to claim 1, wherein the calculating of secondary reactive power sharing regulation targets of a preset microgrid and a microgrid adjacent thereto comprises:
acquiring a first reactive power measured value of the preset micro-grid, and dividing the first reactive power measured value by a first reactive power reference value to obtain a first reactive power ratio;
acquiring a second reactive power measured value of a microgrid adjacent to the preset microgrid, and dividing the second reactive power measured value by a second reactive power reference value to obtain a second reactive power ratio;
subtracting the second reactive power ratio from the first reactive power ratio to obtain a reactive power ratio difference of adjacent micro-grids, and distributing a third weighting coefficient to the reactive power ratio difference, wherein the third weighting coefficient is an element in an adjacent matrix;
and adding all the reactive power ratio differences of the adjacent micro-grids to obtain the secondary reactive power sharing regulation target.
3. The microgrid secondary voltage control method of claim 1, wherein the calculating of a secondary voltage regulation target of the preset microgrid comprises:
and acquiring an output voltage amplitude of the preset micro-grid, and subtracting a reference voltage amplitude from the output voltage amplitude to obtain an output voltage amplitude difference so as to obtain the secondary voltage regulation target.
4. The microgrid secondary voltage control method according to any one of claims 1-3, further comprising selecting one of the microgrids as a leader microgrid and the other microgrids as follower microgrids, setting a first weighting coefficient of the leader microgrid to be non-zero, setting a second weighting coefficient to be zero to achieve a secondary voltage regulation target, and setting a first weighting coefficient of the follower microgrid to be zero, setting a second weighting coefficient to be non-zero to achieve a secondary reactive power sharing regulation target.
5. A microgrid secondary voltage control apparatus, comprising:
the first calculation component is used for calculating a secondary reactive power sharing regulation target of a preset micro-grid and a micro-grid adjacent to the preset micro-grid;
the first weighting component is used for distributing a first weighting coefficient to the secondary reactive power sharing regulation target to obtain a weighted secondary reactive power sharing regulation target;
the second calculation component is used for calculating a secondary voltage regulation target of the preset micro-grid;
the second weighting component is used for distributing a second weighting coefficient to the secondary voltage regulation target to obtain a weighted secondary voltage regulation target;
and the weighting coefficient adjusting component is used for adding the weighted secondary reactive power sharing regulation target and the weighted secondary voltage regulation target to obtain a sliding mode surface, and adjusting the first weighting coefficient and the second weighting coefficient until a compromise is reached between voltage regulation and reactive power sharing.
6. The microgrid secondary voltage control apparatus of claim 5, wherein the first computing component comprises:
the first acquisition unit is used for acquiring a first reactive power measured value of the preset microgrid and dividing the first reactive power measured value by a first reactive power reference value to obtain a first reactive power ratio;
the second acquisition unit is used for acquiring a second reactive power measured value of the microgrid adjacent to the preset microgrid, and dividing the second reactive power measured value by a second reactive power reference value to obtain a second reactive power ratio;
the first weighting unit is used for subtracting the second reactive power ratio from the first reactive power ratio to obtain a reactive power ratio difference of adjacent micro-grids, and distributing a third weighting coefficient to the reactive power ratio difference, wherein the third weighting coefficient is an element in an adjacent matrix;
and the secondary reactive power sharing regulation target determining unit is used for adding all the reactive power ratio differences of the adjacent micro-grids to obtain the secondary reactive power sharing regulation target.
7. The microgrid secondary voltage control apparatus of claim 5, wherein the second computing component comprises:
and the third acquisition unit is used for acquiring the output voltage amplitude of the preset micro-grid, and subtracting the reference voltage amplitude from the output voltage amplitude to obtain an output voltage amplitude difference and obtain the secondary voltage regulation target.
8. The microgrid secondary voltage control device according to any one of claims 5 to 7, further comprising a leader and follower determination unit for selecting one of the microgrids as a leader microgrid and the other microgrids as follower microgrids, setting the first weighting coefficient of the leader microgrid to be non-zero, the second weighting coefficient to be zero to achieve a secondary voltage regulation target, and setting the first weighting coefficient of the follower microgrid to be zero and the second weighting coefficient to be non-zero to achieve a secondary reactive power sharing regulation target.
9. A computer device, comprising:
a memory for storing a computer program;
processor for implementing the steps of the microgrid secondary voltage control method according to any one of claims 1 to 4 when executing said computer program.
10. A computer-readable storage medium, characterized in that the computer-readable storage medium has stored thereon a computer program which, when being executed by a processor, carries out the steps of the microgrid secondary voltage control method according to any one of claims 1 to 4.
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