CN116937671A - Constant frequency distributed control method for island alternating-current micro-grid - Google Patents
Constant frequency distributed control method for island alternating-current micro-grid 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
- H02J3/38—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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- 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
- H02J3/381—Dispersed generators
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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
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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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
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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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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Abstract
The invention discloses a constant frequency distributed control method of an island alternating-current micro-grid, relates to the field of control of new energy alternating-current micro-grids, and aims to solve the problems that the operation control of the existing micro-grid affects the quality of electric energy, the frequency stability is low and the power distribution precision is low; according to the invention, the consistency algorithm and the GPS synchronization module are combined, so that accurate power distribution is realized when each distributed power supply of the micro-grid is in a constant frequency running state, and frequency correction is not required by a secondary control loop; the accurate distribution of active power according to the capacity of each power supply is realized, the synchronization among the power supplies of the micro-grid is realized, and the problem of deviation of the frequency of the micro-grid under the traditional droop control is avoided; and finally, establishing a small signal model based on the control method, and analyzing the stability of the small signal model to establish each parameter so as to realize the stable operation of the system under constant frequency.
Description
Technical Field
The invention relates to the technical field of control of new energy alternating-current micro-grids, in particular to a constant-frequency distributed control method of an island alternating-current micro-grid.
Background
In recent years, with an increasing energy crisis, a large amount of distributed new energy is continuously connected into an electric power system in the form of a micro-grid. The photovoltaic and wind power distributed new energy sources are easily affected by the environment, the output of the photovoltaic and wind power distributed new energy sources has the characteristics of randomness and instability, and great challenges are brought to the safe and stable operation of the traditional power grid. Different from a thermal generator in a traditional power grid, distributed new energy in a micro-grid is mostly connected into the power grid through power electronics and other inversion devices to transmit electric energy. Due to the fact that a large number of power electronic devices exist, the micro-grid often has the characteristic of low inertia, large frequency offset is easy to occur along with load fluctuation, and the mutual matching among a plurality of distributed power supplies connected through the inverter is more difficult. Therefore, how to maintain the voltage and the frequency of the island micro-grid stable and simultaneously realize the accurate distribution of active and reactive loads among all distributed power supplies in proportion becomes a key problem of the popularization and the use of new energy.
Currently, a lot of droop control is applied in the operation control of the micro-grid, and the main idea is derived from droop characteristics between active output and frequency, reactive output and voltage in the traditional grid synchronous generator. However, in principle, a power supply employing droop control inevitably generates frequency and voltage offsets, which affect the power quality. To meet the requirements of stable operation of the micro-grid, the frequency offset is often offset or corrected by two-layer control. However, the implementation of secondary control of the micro-grid requires the deployment of a communication network in each node of the micro-grid, or centralized control by a central controller. The former increases the investment and operating costs of the grid, while the latter increases the risk of single point faults of the micro grid affecting global stability. The constant frequency control is implemented on the micro-grid, so that the system frequency can be fixed, the frequency fluctuation generated by power distribution is completely eliminated, and the electric energy quality and the frequency stability of the system are improved to a great extent.
Disclosure of Invention
The invention aims to solve the problems that the existing micro-grid operation control has the influence on the electric energy quality, the frequency stability is low, the power distribution precision is low and the global stability risk is influenced, and provides a constant frequency distributed control method of an island alternating-current micro-grid.
The aim of the invention can be achieved by the following technical scheme: a constant frequency distributed control method of an island alternating current micro-grid comprises the following steps:
step one: constructing each distributed power supply communication structure in the micro-grid, and establishing each power supply information exchange vector;
step two: constructing an active power regulator, taking each power supply information exchange vector as input to obtain a phase angle expected reference value;
step three: a phase synchronization module based on GPS signals is constructed, and a phase angle expected reference value is overlapped with a synchronous rotation reference phase angle to obtain a voltage synchronous rotation reference phase angle;
step four: the voltage synchronous rotation reference phase angle is used as an inverter modulation reference signal, the reference frequency is kept unchanged at 50Hz, and constant frequency control is carried out on the inverter;
step five: based on each control link in the first to fourth steps, the controller accesses the micro-grid at the time t=0, establishes a complete micro-grid small signal model, analyzes the influence of key parameters in the micro-grid small signal model on the system stability, and completes parameter design and establishment and simulation analysis of the micro-grid complete control model; the micro-grid small signal model comprises a micro-grid inverter small signal model, a micro-grid transmission line small signal model and a micro-grid control loop small signal model.
As a preferred embodiment of the present invention, the specific process of constructing each distributed power communication structure in the micro-grid is as follows:
s11: regarding each distributed power supply in the micro-grid as an independent intelligent agent, wherein specific communication connection exists among the independent intelligent agents; for a micro-grid consisting of N distributed power sources, the adjacency matrix a of its communication network is:
A＝[a ij ]∈R N×N wherein a is ij If the node i receives information from the node j, the node j is adjacent to the node i, and a is indicated as the communication weight between the nodes i and j ij >0, otherwise, a ij ＝0；
S12: the micro-grid is provided with an input degree matrix D:
wherein d i Representing the total communication weight of node i, N i Representing a set of all neighboring nodes of node i;
s13: obtaining a Laplacian matrix L of the communication network topological structure according to the adjacency matrix A and the degree matrix D, wherein the Laplacian matrix L is specifically:
as a preferred embodiment of the present invention, the process of establishing each power information exchange vector is as follows: carrying out power calculation on the outlet voltage and the current of each distributed power supply, carrying out normalization processing on the measured power according to the installed capacity of each distributed power supply, and forming each power supply information exchange vector by the active power subjected to normalization processing, wherein the power supply information exchange vector comprises the following specific steps: u (u) i ＝{P i norm }, wherein P i norm For the per unit value of the active power of the node i, P i norm ＝P i /P i rated ，P i rated Rated active power for node i; p (P) i Is the measured value of the power supply outlet.
As a preferred embodiment of the present invention, the process of constructing the active power regulator is as follows:
the active power of the inverter generates an active power mismatch term through a consistency algorithm, and is directly overlapped to the phase of the outlet voltage of the inverter as a phase correction term after integration, specifically:
s21: measuring local output active power and reactive power, and receiving adjacent node information vectors based on a communication topological structure:wherein N is i Representing a set of all neighboring nodes of node i;
s22: the active power mismatch term generated by the active power per unit value at the node i through the consistency algorithm is as follows:wherein, mP i Representing an active power mismatch term of the node i; b is a coefficient to be determined; a, a ij The communication weight between the nodes i and j;
s23: integrating the active power mismatch term to obtain a phase correction term:then there is a corresponding phase reference value for the inverter outlet voltage at time t The initial phase is node i.
As a preferred embodiment of the present invention, the process of obtaining the voltage synchronous rotation reference phase angle is:
s31: calculating local time errors of each distributed power supply: the GPS receiver in each distributed power source captures the rising edge of the 1HzGPS pulse signal and records as t sig Acquiring a local clock and a GPS receiver signal t sig Time offset t between offset ：t offset ＝mod{t sig ,1}；
S32: correcting each distributed power supply to synchronous time;t ilocal is the local time of the inverter;
s33: generating a synchronous rotation reference phase angle: multiplying the synchronous time by the rated frequency, and obtaining the synchronous rotation reference phase angle delta by taking the modulus with 2 pi offset ：δ offset ＝mod[ω n t sync ,2π]。
As a preferred embodiment of the present invention, the inverter in the fourth step is at time tReference voltageThe method comprises the following steps: />Wherein omega n Is rated at 50Hz; />Is the inverter outlet voltage amplitude.
As a preferred embodiment of the present invention, the micro-grid inverter small signal model isWherein (1)>And->Respectively a matrix containing an actual phase angle and a reference phase angle of the outlet voltage of the inverter; g Δ Is the phase transfer function of the inverter;
the micro-grid transmission line small signal model is that The transfer coefficients are P-delta and P-e;
the construction process of the micro-grid control loop small signal model comprises the following steps:
the controller accesses at t=0s, then there are:
the simultaneous inverter model, the transmission line model and the controller model can obtain a micro-grid control loop small signal modelWherein T is MG Is an active balance matrix, and the expression is as follows: /> L is a rated power matrix, a transmission line coefficient matrix and a Laplacian matrix respectively; b is a parameter.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention provides a constant frequency control method for an island alternating current micro-grid, which combines a consistency algorithm and a GPS synchronization module, so that each distributed power supply of the micro-grid is in a constant frequency running state to realize accurate power distribution without secondary control loop for frequency correction.
2. Firstly, constructing a communication structure among distributed power supplies in a micro-grid, and obtaining a normalized information matrix transmitted and exchanged by each node by using a power measurement device as communication content of each node; then, constructing an active power regulator based on a consistency algorithm, obtaining a phase angle reference value, and realizing accurate distribution of active power according to the capacity of each power supply; then constructing a phase angle synchronization module based on GPS to obtain an actual reference value of a synchronization phase angle, so that synchronization among all power supplies of the micro-grid is realized, and the problem of deviation of the frequency of the micro-grid under the traditional droop control is avoided; and finally, establishing a small signal model based on the control method, and analyzing the stability of the small signal model to establish each parameter so as to realize the stable operation of the system under constant frequency.
Drawings
The present invention is further described below with reference to the accompanying drawings for the convenience of understanding by those skilled in the art.
FIG. 1 is a schematic diagram of a constant frequency distributed control method of an AC micro grid according to the present invention;
fig. 2 is a schematic diagram of a ring communication topology of the ac microgrid of the present invention;
FIG. 3 is a schematic diagram of a micro-grid simulation structure according to the present invention;
FIG. 4 is a schematic diagram showing the variation of the system characteristic root with the parameter b;
FIG. 5 is a schematic diagram of the active power variation of each distributed power source according to the present invention;
fig. 6 is a graph showing the change of active power per unit value of each distributed power supply according to the present invention.
Detailed Description
The technical solutions of the present invention will be clearly and completely described in connection with the embodiments, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1-6, a constant frequency distributed control method for an island ac micro-grid includes the following steps:
step 1: constructing each distributed power supply communication structure in the micro-grid, and obtaining a normalized information matrix transmitted and exchanged by each node by using a power measurement device as communication content of each node; and establish each power information exchange vector;
step 2: constructing an active power regulator based on a consistency algorithm, and taking the power supply information exchange vectors in the step 1 as input to obtain a phase angle expected reference value;
step 3: each distributed power supply in the micro-grid is provided with a GPS receiver, a phase synchronization module based on GPS signals is constructed, and the phase angle reference value in the step 2 is overlapped with the synchronous rotation reference phase angle to obtain the synchronous rotation reference phase angle;
step 4: taking the voltage synchronous rotation reference phase angle generated in the step 3 as an inverter modulation reference signal, and keeping the reference frequency unchanged at 50Hz to realize constant frequency control of the inverter;
step 5: and (3) combining the control links in the steps 1-4, establishing a complete micro-grid small signal model, analyzing the influence of key parameters in the control model on the system stability, and completing the parameter design.
Specifically, in step 1, each distributed power source in the micro-grid is regarded as an independent agent, and sparse communication connection exists between each agent. The communication topology between the nodes is represented by a directed graph G, which can be defined by the following steps:
s11: and regarding each distributed power supply in the micro-grid as an independent intelligent agent, wherein specific communication connection exists among the intelligent agents, and the communication topology among the nodes can be represented by a directed graph G. For a micro-grid consisting of N distributed power sources, its communication network has an adjacency matrix a as follows:
A＝[a ij ]∈R N×N (1)
wherein a is ij Is the communication weight between nodes i, j. If node i receives information from node j, it means that node j is adjacent to node i, a ij >0, otherwise, a ij ＝0。
S12: for the micro-grid described above, there is an occupancy matrix D:
wherein d i Representing the total communication weight of node i, N i Representing the set of all neighboring nodes of node i.
S13: according to the formula (1) and the formula (2), the laplace matrix L of the communication network topology structure can be obtained as follows:
in order to enable the control link in the method to converge in a stable state, the topological structure of the micro-grid communication network needs to be a connected graph, namely, the number of directed spanning trees in the graph G is not less than one, the number of zero characteristic roots of the corresponding Laplacian matrix L is 1, and the real parts of the other N-1 characteristic values are larger than zero. Thus, the microgrid adopts a ring communication topology as shown in fig. 2.
Specifically, in step 1, power calculation is performed on the output voltage and current of each distributed power supply, and the measured power is normalized according to the installed capacity of each distributed power supply. The normalized active power forms each power supply information exchange vector as follows:
u i ＝{P i norm } (4)
wherein P is i norm The active power per unit value of the node i is:
P i norm ＝P i /P i rated (5)
wherein P is i rated Rated active power for node i; p (P) i Is the measured value of the power supply outlet.
Specifically, in step 2, an active power regulator is constructed, the active power of the inverter generates an active power mismatch term through a consistency algorithm, and the active power mismatch term is directly superimposed on the phase of the output voltage of the inverter as a phase correction term after integration, so that the problem of frequency deviation in the traditional droop control is avoided. The active distribution of the micro-grid is completed by the following steps:
s21: the node i measures the local output active power and the local output reactive power according to the method shown in the step 2, and simultaneously receives the adjacent node information vector based on the communication topological structure established in the step 1:
wherein N is i Representing the set of all neighboring nodes of node i.
S22: the active power mismatch term generated by the active power per unit value at the node i through the consistency algorithm is as follows:
wherein, mP i Representing an active power mismatch term of the node i; b is a coefficient to be determined; a, a ij The communication weight between the nodes i and j is determined by the step 1.
S23: integrating the active power mismatch term to obtain a phase correction term:
then there is a corresponding phase reference value for the inverter outlet voltage at time t
Wherein, the liquid crystal display device comprises a liquid crystal display device,the initial phase is node i.
Specifically, in step 3, global synchronization of the micro-grid is achieved by constructing a GPS phase angle synchronization module. The phase angle reference value generated by the active power regulator in the step 2 is not directly used as an inverter control reference, but is overlapped with the synchronous rotation reference phase angle in the GPS phase angle synchronous module in the step 3 to obtain a synchronous actual reference phase angle. The method comprises the following steps:
s31: calculating local time errors of each distributed power supply:
the GPS receiver in each distributed power source captures the rising edge of the 1Hz GPS pulse signal and records as t sig . Acquiring local clock and GPS receiver signal t sig Time offset t between offset ：
t offset ＝mod{t sig ,1} (10)
Since the GPS pulse signal takes 1 second as a time period, t is offset In fact, t is represented by sig Is a fraction of the fraction of (c).
S32: correcting each distributed power supply to synchronous time;
wherein t is ilocal Is the local time of the inverter.
S33: generating a synchronous rotation reference phase angle;
multiplying the synchronous time by the rated frequency, and obtaining the synchronous rotation reference phase angle delta by taking the modulus with 2 pi offset ：
δ offset ＝mod[ω n t sync ,2π] (12)
Specifically, in step 4, the reference frequency is maintained to be constant by using the synchronous rotation reference phase angle of the voltage generated in step 3 as the modulation reference signal of the inverter, so as to realize constant frequency control of the inverter.
Reference voltage of inverter at time tThe method comprises the following steps:
wherein omega n Is rated at 50Hz, and is kept unchanged;is the inverter outlet voltage amplitude. Since the inverter reference frequency is maintained constant at 50Hz, each distributed power supply in the microgrid operates at a constant frequency of 50Hz and achieves accurate distribution of active power by varying the mains outlet voltage phase angle. And each distributed power supply of the micro-grid is in a constant-frequency running state, and a secondary control loop is not needed for frequency correction.
Specifically, in step 5, the micro grid may be regarded as being composed of an inverter, a transmission line, and the control system connected to the communication connection portion. And analyzing the partial transfer characteristics, respectively establishing corresponding small signal models, and synthesizing the models into a complete micro-grid small signal model. And finally, carrying out stability analysis on the system small signal model to finish the selection of the controller parameters.
S61: assuming that the controller accesses the microgrid at time t=0, any variable x in the time domain is represented as follows:
wherein x is q The static part of the variable x represents the steady state value of the variable x at the time t < 0;the small signal portion of the variable x represents its response to the controller accessing at time t=0.
S62: establishing a micro-grid inverter small signal model:
wherein, the liquid crystal display device comprises a liquid crystal display device,and->Respectively a matrix containing an actual phase angle and a reference phase angle of the outlet voltage of the inverter; g Δ Is the phase transfer function of the inverter. Since the dynamic response of the inverter phase modulation is much faster than the controller, it can be approximately considered +.>
S63: further, a micro-grid transmission line small signal model is established:
wherein, the liquid crystal display device comprises a liquid crystal display device,the transfer coefficients are P-delta and P-e. Since the micro-grid transmission line parameters are mainly inductive, the micro-grid transmission line parameters are
S64: establishing a micro-grid control loop small signal model;
assuming that the controller is accessing at t=0s, there are:
substituting formula (2) into the above formula can give:
substituting equation (3) into (18) can transform it into the following matrix form:
equation (19) represents a dynamic model of the controller containing the communication connection. The simultaneous inverter model, the transmission line model and the controller model can obtain a micro-grid small signal model
Wherein TMG is an active balance matrix, and the expression is as follows:
for a special purposeFixed micro-grid, rated power matrixTransmission line coefficient matrix->And the laplace matrix L are known, so that equation (20) is a normal differential equation, the stability of which is evaluated by setting different parameters b, a suitable gain can be found for b under normal operating conditions.
The characteristic equation of the entire micro grid described in (20) can be expressed as
det(-λI N +T MG )＝0 (22)
By verifying the stability of the micro-grid with different values of parameter b, suitable design criteria can be established for parameter b.
The technical scheme of the invention is described in more detail below in combination with an actual simulation model:
(1) Simulation model: and constructing a 220/380V micro-grid simulation model on a MATLAB/SIMULINK simulation platform as shown in figure 3. The power grid consists of 4 parallel distributed power supplies (DER), wherein each DER is connected with a load through an inverter, LCL filtering and line impedance, and the parameter setting is shown in a table 1.
Table 1 microgrid simulation model parameter settings
In order to ensure the stable operation and the plug and play performance of the micro-grid, annular communication is adopted among all distributed power supplies, and bidirectional information transmission is carried out among adjacent distributed power supplies. The micro-grid corresponding to the communication connection has a communication network adjacency matrix A as follows:
input degree matrix D in The method comprises the following steps:
the corresponding laplace matrix L is:
(2) Parameter setting: for the micro grid shown in fig. 3, the stability of the system was studied by analyzing the eigenvalues of the matrix TMG. Fig. 4 shows a trace of eigenvalues for parameter b varying between 0.2-3. When the parameter b is small, all eigenvalues are far from the imaginary axis, which means that the system has a good stability margin, but the dynamic response speed of the system is also slow. As the parameter b increases, both pairs of eigenvalues move in the direction of the imaginary axis. When b >3, a pair of eigenvalues pass through the imaginary axis from the left half plane, and the system loses stability.
To ensure a good stability margin and a faster response characteristic of the system, the parameter b is determined to be 2.
(3) Simulation result analysis: the micro-grid is operated as shown in fig. 3, the control is accessed at t=1s, meanwhile, in order to embody the effectiveness of the method on the power distribution of the micro-grid, the active load is increased at t=6s, and the simulation results are shown in fig. 5 to 6. The analysis simulation results show that the active power of each distributed power supply is distributed according to rated capacity in fig. 5, and the values of the active power per unit of each power supply finally tend to be consistent in a steady state in fig. 6, which shows that the method can realize accurate distribution of the active power. Meanwhile, the method adjusts the power by changing the phase of the output voltage without passing through the frequency, so that the frequency of the output voltage of each power supply is kept unchanged at 50 Hz.
The invention provides a constant frequency control method for an island alternating current micro-grid, which combines a consistency algorithm and a GPS synchronization module, so that each distributed power supply of the micro-grid is in a constant frequency running state to realize accurate power distribution without secondary control loop for frequency correction. Firstly, constructing each distributed power supply communication structure in a micro-grid, and obtaining a normalized information matrix transmitted and exchanged by each node by using a power measurement device as communication content of each node; then, constructing an active power regulator based on a consistency algorithm, obtaining a phase angle reference value, and realizing accurate distribution of active power according to the capacity of each power supply; then constructing a phase angle synchronization module based on GPS to obtain a synchronous rotation reference phase angle, so that synchronization among all power supplies of the micro-grid is realized, and the problem of deviation of the frequency of the micro-grid under the traditional droop control is avoided; and finally, establishing a small signal model based on the control method, and analyzing the stability of the small signal model to establish each parameter so as to realize the stable operation of the system under constant frequency.
The preferred embodiments of the invention disclosed above are intended only to assist in the explanation of the invention. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise form disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best understand and utilize the invention. The invention is limited only by the claims and the full scope and equivalents thereof.
Claims (7)
1. The constant frequency distributed control method for the island alternating current micro-grid is characterized by comprising the following steps of:
step one: constructing each distributed power supply communication structure in the micro-grid, and establishing each power supply information exchange vector;
step two: constructing an active power regulator, taking each power supply information exchange vector as input to obtain a phase angle expected reference value;
step three: a phase synchronization module based on GPS signals is constructed, and a phase angle expected reference value is overlapped with a synchronous rotation reference phase angle to obtain a voltage synchronous rotation reference phase angle;
step four: the voltage synchronous rotation reference phase angle is used as an inverter modulation reference signal, the reference frequency is kept unchanged at 50Hz, and constant frequency control is carried out on the inverter;
step five: based on each control link in the first to fourth steps, the controller accesses the micro-grid at the time t=0, establishes a complete micro-grid small signal model, analyzes the influence of key parameters in the micro-grid small signal model on the system stability, and completes parameter design and establishment and simulation analysis of the micro-grid complete control model; the micro-grid small signal model comprises a micro-grid inverter small signal model, a micro-grid transmission line small signal model and a micro-grid control loop small signal model.
2. The constant frequency distributed control method of the island ac micro-grid according to claim 1, wherein the specific process of constructing each distributed power supply communication structure in the micro-grid is as follows:
s11: regarding each distributed power supply in the micro-grid as an independent intelligent agent, wherein specific communication connection exists among the independent intelligent agents; for a micro-grid consisting of N distributed power sources, the adjacency matrix a of its communication network is:
A＝[a ij ]∈R N×N wherein a is ij If the node i receives information from the node j, the node j is adjacent to the node i, and a is indicated as the communication weight between the nodes i and j ij >0, otherwise, a ij ＝0；
S12: the micro-grid is provided with an input degree matrix D in ：
Wherein d i Representing the total communication weight of node i, N i Representing a set of all neighboring nodes of node i;
s13: according to the adjacency matrix A and the receptivity matrix D in The laplace matrix L of the communication network topological structure is obtained, and specifically comprises the following steps:
3. the method according to claim 1The constant frequency distributed control method for the island alternating-current micro-grid is characterized in that the process of establishing each power supply information exchange vector is as follows: carrying out power calculation on the outlet voltage and the current of each distributed power supply, carrying out normalization processing on the measured power according to the installed capacity of each distributed power supply, and forming each power supply information exchange vector by the active power subjected to normalization processing, wherein the power supply information exchange vector comprises the following specific steps: u (u) i ＝{P i norm }, wherein P i norm For the per unit value of the active power of the node i, P i norm ＝P i /P i rated ，P i rated Rated active power for node i; p (P) i Is the measured value of the power supply outlet.
4. The constant frequency distributed control method of an island ac micro-grid according to claim 1, wherein the process of constructing the active power regulator is:
the active power of the inverter generates an active power mismatch term through a consistency algorithm, and is directly overlapped to the phase of the outlet voltage of the inverter as a phase correction term after integration, specifically:
s21: measuring local output active power and reactive power, and receiving adjacent node information vectors based on a communication topological structure:wherein N is i Representing a set of all neighboring nodes of node i;
s22: the active power mismatch term generated by the active power per unit value at the node i through the consistency algorithm is as follows:wherein, mP i Representing an active power mismatch term of the node i; b is a parameter; a, a ij The communication weight between the nodes i and j;
s23: integrating the active power mismatch term to obtain a phase correction term:then there is a corresponding phase reference value +.> The initial phase is node i.
5. The constant frequency distributed control method of an island ac micro-grid according to claim 1, wherein the process of obtaining the voltage synchronous rotation reference phase angle is:
s31: calculating local time errors of each distributed power supply: the GPS receiver in each distributed power source captures the rising edge of the 1HzGPS pulse signal and records as t sig Acquiring a local clock and a GPS receiver signal t sig Time offset t between offset ：t offset ＝mod{t sig ,1}；
S32: correcting each distributed power supply to synchronous time;t ilocal is the local time of the inverter;
s33: generating a synchronous rotation reference phase angle: multiplying the synchronous time by the rated frequency, and obtaining the synchronous rotation reference phase angle delta by taking the modulus with 2 pi offset ：δ offset ＝mod[ω n t sync ,2π]。
6. The constant frequency distributed control method of an island ac micro-grid according to claim 5, wherein the reference voltage of the inverter at time t in the fourth stepThe method comprises the following steps:wherein omega n Is rated at 50Hz;is the inverter outlet voltage amplitude.
7. The constant frequency distributed control method of an island ac micro-grid according to claim 1, wherein the micro-grid inverter small signal model isWherein (1)>And->Respectively a matrix containing an actual phase angle and a reference phase angle of the outlet voltage of the inverter; g Δ Is the phase transfer function of the inverter;
the micro-grid transmission line small signal model is that The transfer coefficients are P-delta and P-e;
the construction process of the micro-grid control loop small signal model comprises the following steps:
the controller accesses at t=0s, then there are:
the simultaneous inverter model, the transmission line model and the controller model can obtain a micro-grid control loop small signal modelWherein T is MG Is an active balance matrix, and the expression is as follows: /> L is a rated power matrix, a transmission line coefficient matrix and a Laplacian matrix respectively; b is a parameter.
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