CN117318138A - Photovoltaic flexible power point tracking method based on economic model predictive control - Google Patents

Photovoltaic flexible power point tracking method based on economic model predictive control Download PDF

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CN117318138A
CN117318138A CN202311048258.4A CN202311048258A CN117318138A CN 117318138 A CN117318138 A CN 117318138A CN 202311048258 A CN202311048258 A CN 202311048258A CN 117318138 A CN117318138 A CN 117318138A
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photovoltaic
formula
power
generation system
power generation
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朱政
刘向杰
孔小兵
马乐乐
王策
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North China Electric Power University
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North China Electric Power University
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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
    • 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
    • H02J3/004—Generation forecast, e.g. methods or systems for forecasting future energy generation
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/007—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources
    • H02J3/0075—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources for providing alternative feeding paths between load and source according to economic or energy efficiency considerations, e.g. economic dispatch
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • 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]
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • H02J2300/26—The renewable source being solar energy of photovoltaic origin involving maximum power point tracking control for photovoltaic sources
    • 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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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Electrical Variables (AREA)

Abstract

The invention relates to the field of photovoltaic power generation control, in particular to a photovoltaic flexible power point tracking method based on economic model predictive control, which is implemented by establishing a photovoltaic power generation system model based on a converter; constructing an EMPC optimization problem at the moment k; the method solves the problem that the traditional flexible power point tracking method based on hierarchical control is not feasible due to the change of the external environment, and solves the problem that the switching loss is ignored in the dynamic process. Compared with the traditional hierarchical control method, the economic model prediction control method ensures the power tracking performance of the system and improves the economic performance in the dynamic process.

Description

Photovoltaic flexible power point tracking method based on economic model predictive control
Technical Field
The invention relates to the field of photovoltaic power generation control, in particular to a photovoltaic flexible power point tracking method based on economic model predictive control.
Background
Among various new energy power generation technologies, photovoltaic power generation stands out for its abundant energy resources, clean power generation process and cost effectiveness. The control of the photovoltaic power generation system is mainly Maximum Point Power Tracking (MPPT) so as to improve the power conversion efficiency.
For example, chinese patent publication No.: CN112904930a discloses a method for tracking and controlling the maximum power point of a medium voltage photovoltaic power generation system, wherein the medium voltage photovoltaic power generation system comprises a photovoltaic array, a voltage regulating device and grid-connected interface circuits, the number of the grid-connected interface circuits is two, the photovoltaic array is connected with the voltage regulating device, the voltage regulating device is connected with the tail end of a first medium voltage feeder through a first grid-connected interface circuit, and is connected with the tail end of a second medium voltage feeder through a second grid-connected interface circuit; the first grid-connected interface circuit controls the active power output to the first medium-voltage feeder line, and the second grid-connected interface circuit controls the direct-current bus voltage of each photovoltaic grid-connected module to be rated voltage. The method can realize flexible distribution of the control output power on the two feeder lines according to the terminal voltage of the two feeder lines on the basis of capturing solar energy to the maximum extent of the system, and can effectively compensate three-phase current unbalance of the second grid-connected interface circuit when large unbalance occurs to each phase of output power of the medium-voltage photovoltaic power generation system.
However, the following problems are also present in the prior art:
1. as the capacity of the photovoltaic installation increases, the MPPT scheme cannot meet the requirement of the power grid on frequency stability;
2. in the prior art, the method has limitation in the aspect of economy, and the dynamic economical performance in the photovoltaic power generation process cannot be ensured.
Disclosure of Invention
In order to solve the problems that the MPPT scheme cannot meet the requirement of a power grid on frequency stability and has limitation in the aspect of economy and cannot ensure the dynamic economic performance in the photovoltaic power generation process along with the increase of the photovoltaic installed capacity in the prior art, the invention provides a photovoltaic flexible power point tracking method based on economic model predictive control, which comprises the following steps:
step S1, sampling a photovoltaic power generation system to obtain operation parameters of the photovoltaic power generation system;
step S2, a photovoltaic power generation system model based on a converter is established to describe the dynamic characteristics of the system, wherein the step S2 comprises the steps of describing output current by using a current-voltage characteristic function, constructing a dynamic equation for supplying power to a boost converter by a photovoltaic array based on the current-voltage characteristic function, and constructing the photovoltaic power generation system model based on the dynamic equation and the output power of the photovoltaic power generation system;
step S3, constructing an EMPC optimization problem at the moment k, wherein the EMPC optimization problem comprises setting an objective function according to economic index conditions, and the economic index conditions comprise the output power P pv And power reference P from load demand ref The power balance is realized, so that the switching loss is minimized;
and S4, solving the EMPC optimization problem at the k moment, acquiring a control signal of the switching element, and controlling the controlled switching element based on the control signal.
Further, in the step S1, the photovoltaic power generation system includes a photovoltaic array, a DC/DC boost converter, and a load, where the photovoltaic array includes a plurality of photovoltaic cells connected in series and a plurality of photovoltaic cells connected in parallel.
Further, in the step S2, the current-voltage characteristic function is represented by the formula (1),
in the formula (1), i pv Representing the output current, I sc Representing the short-circuit current of the photovoltaic cell, v pv Representing the output voltage, V oc Represents the open circuit voltage of the photovoltaic cell, n p Represents the number of parallel photovoltaic cells, n s Represents the number of photovoltaic cells connected in series, wherein A is represented by formula (2),
in the formula (2), V pm Representing the maximum power point of a photovoltaic cellVoltage, I pm Representing the maximum power point current of the photovoltaic cell, said I sc ，V oc ，V pm ，I pm Is measured under standard solar irradiance and temperature ambient conditions.
Further, in the step S2, a dynamic equation of the power supply of the photovoltaic array to the boost converter is represented by formula (3),
in the formula (3), I' sc Is parameter I sc Values under non-standard conditions, V' oc Is a parameter V oc Values under non-standard conditions, V' pm Is a parameter V pm Values under non-standard conditions, I' pm Is parameter I pm Values under non-standard conditions, Δt=t-T b T represents temperature, T b The temperature of the sample is indicated as a standard temperature,s represents solar irradiance, S b Representing standard solar irradiance, a=0.0025, b=0.5, c= 0.00288;
output power P of photovoltaic power generation system pv Represented by the formula (4),
P pv ＝i pv ·v pv (4)
available power P of maximum power point avail Represented by the formula (5),
P avail ＝n p n s V′ pm ·I′ pm (5)
the dynamic equation for the photovoltaic array to power the boost converter is represented by equation (6),
in the formula (6), C 1 Is input filter capacitance, L is converter inductance, i L For inductor current, C 2 Is the output filter capacitance, v o To output voltage, R o Is a load resistance, S w Is a control signal of the switching element, and is expressed by expression (7).
Further, in the step S2, a model of a photovoltaic power generation system based on a converter is established, which is represented by formula (8):
in formula (8), x represents a state variable including v pv 、i L ，v o ，u represents a control variable, u=s w Y represents the output variable, y=p pv Wherein, the method comprises the steps of, wherein,
in the formulas (9) and (10), f c (x, u) represents the dynamic equation of the power supplied by the photovoltaic array to the boost converter, g c (x, u) represents the output power of the photovoltaic power generation system.
Further, the step S3 sets an objective function according to an economic index condition, wherein the economic index condition is represented by formula (11),
in the formula (11), n c Represents the number of commutations required to switch from the current switch state to the switch state under evaluation, x (k) represents the state variable obtained by the kth sample, u (k) represents the control variable obtained by the kth sample, yRepresenting the output variable obtained for the kth sample;
the objective function is represented by equation (12),
l e (x(k)，u(k))＝w 1 l e1 +w 2 l e2 (12)
in formula (12), w 1 As the first weight coefficient, w 2 Is the second weight coefficient.
Further, in the step S3, an EMPC optimization problem at the k moment is constructed:
in the formula (13), N represents a prediction time domain,representing the predicted value.
Compared with the prior art, the photovoltaic power generation system model based on the converter is built; constructing an EMPC optimization problem at the moment k; an efficient algorithm is designed to solve the optimization problem. The problem that the traditional flexible power point tracking method based on hierarchical control is not feasible in set point due to external environment change is solved, and meanwhile, the problem that switching loss is ignored in a dynamic process is solved. Compared with the traditional hierarchical control method, the economic model prediction control method ensures the power tracking performance of the system and improves the economic performance in the dynamic process.
In particular, the hierarchical control structure of the traditional FPPT method is integrated into a layer through EMPC, and economic indexes of a photovoltaic power generation system are used as cost functions to realize economic optimization and power tracking.
In particular, since the photovoltaic power generation system has strong nonlinearity, the EMPC optimization problem is non-convex, and a local optimal solution exists; an algorithm utilizing the switch states of a limited number of converters is designed, so that the EMPC optimization problem can be effectively solved, and global optimum of the EMPC optimization problem can be obtained.
Drawings
FIG. 1 is a schematic diagram of steps of a photovoltaic flexible power point tracking method based on economic model predictive control according to an embodiment of the invention;
fig. 2 is a schematic structural diagram of a photovoltaic power generation system according to an embodiment of the invention.
Detailed Description
In order that the objects and advantages of the invention will become more apparent, the invention will be further described with reference to the following examples; it should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are merely for explaining the technical principles of the present invention, and are not intended to limit the scope of the present invention.
It should be noted that, in the description of the present invention, terms such as "upper," "lower," "left," "right," "inner," "outer," and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, which are merely for convenience of description, and do not indicate or imply that the apparatus or elements must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Furthermore, it should be noted that, in the description of the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those skilled in the art according to the specific circumstances.
Referring to fig. 1 and fig. 2, a schematic step diagram and a schematic structure diagram of a photovoltaic power generation system of a photovoltaic flexible power point tracking method based on economic model predictive control according to an embodiment of the present invention are shown, where the photovoltaic flexible power point tracking method based on economic model predictive control includes:
step S1, sampling a photovoltaic power generation system to obtain operation parameters of the photovoltaic power generation system;
step S2, a photovoltaic power generation system model based on a converter is established to describe the dynamic characteristics of the system, wherein the step S2 comprises the steps of describing output current by using a current-voltage characteristic function, constructing a dynamic equation for supplying power to a boost converter by a photovoltaic array based on the current-voltage characteristic function, and constructing the photovoltaic power generation system model based on the dynamic equation and the output power of the photovoltaic power generation system;
step S3, constructing an EMPC optimization problem at the moment k, wherein the EMPC optimization problem comprises setting an objective function according to economic index conditions, and the economic index conditions comprise the output power P pv And power reference P from load demand ref The power balance is realized, so that the switching loss is minimized;
and S4, solving the EMPC optimization problem at the k moment, acquiring a control signal of the switching element, and controlling the controlled switching element based on the control signal.
In particular, in said step S1, the operating parameters comprise several parameters required in the subsequent steps S1-S4.
Specifically, in step S1, the photovoltaic power generation system includes a photovoltaic array, a DC/DC boost converter, and a load, where the photovoltaic array includes a plurality of photovoltaic cells connected in series and a plurality of photovoltaic cells connected in parallel.
Specifically, in the step S2, the output current is described by a current-voltage characteristic function, which is represented by the formula (1):
in the formula (1), i pv Representing the output current, I sc Representing the short-circuit current of the photovoltaic cell, v pv Representing the output voltage, V oc Represents the open circuit voltage of the photovoltaic cell, n p Represents the number of parallel photovoltaic cells, n s Represents the number of photovoltaic cells connected in series, wherein A is represented by formula (2),
in the formula (2), V pm Representing the maximum power point voltage of the photovoltaic cell, I pm Representing the maximum power point current of the photovoltaic cell, said I sc ，V oc ，V pm ，I pm Is measured under standard solar irradiance and temperature ambient conditions.
Specifically, in the step S2, the dynamic equation of the power supply of the photovoltaic array to the boost converter is represented by the formula (3),
in the formula (3), I' sc Is parameter I sc Values under non-standard conditions, V' oc Is a parameter V oc Values under non-standard conditions, V' pm Is a parameter V pm Values under non-standard conditions, I' pm Is parameter I pm Values under non-standard conditions, Δt=t-T b T represents temperature, T b The temperature of the sample is indicated as a standard temperature,s represents solar irradiance, S b Representing standard solar irradiance, a=0.0025, b=0.5, c= 0.00288;
output power P of photovoltaic power generation system pv Represented by the formula (4),
P pv ＝i pv ·v pv (4)
available power P of maximum power point avail Represented by the formula (5),
P avail ＝n p n s V′ pm ·I′ pm (5)
the dynamic equation for the photovoltaic array to power the boost converter is represented by equation (6),
in the formula (6), C 1 Is input filter capacitance, L is converter inductance, i L For inductor current, C 2 Is the output filter capacitance, v o To output voltage, R o Is a load resistance, S w Is a control signal of the switching element, and is expressed by expression (7).
Specifically, in the step S2, a photovoltaic power generation system model based on a converter is established, and the model is represented by formula (8):
in formula (8), x represents a state variable including v pv 、i L ，v o ，u represents a control variable, u=s w Y represents the output variable, y=p pv Wherein, the method comprises the steps of, wherein,
in the formulas (9) and (10), f c (x, u) represents the dynamic equation of the power supplied by the photovoltaic array to the boost converter, g c (x, u) represents the output power of the photovoltaic power generation system,
discretizing a photovoltaic power generation system model based on a converter to obtain:
in photovoltaic power generation system model based on converter, x 1 ，x 3 ，y，S w Is constrained and limited by:
in the formulas (14) and (15), k represents the kth sample, g d (x(k)，u(k))＝g c (x(k)，u(k))，k 1 ＝f c (x(k)，u(k))，/> k 4 ＝f c (x(k)+T s k 4 ，u(k))，T s Representing the sampling time.
Specifically, the step S3 sets an objective function according to an economic index condition represented by formula (11),
in the formula (11), n c Representing the number of commutations required to switch from the current switch state to the switch state under evaluation, x (k) representing the state variable obtained by the kth sample, u (k) representing the control variable obtained by the kth sample, y representing the output variable obtained by the kth sample;
the objective function is represented by equation (12),
l e (x(k)，u(k))＝w 1 l e1 +w 2 l e2 (12)
in formula (12), w 1 As the first weight coefficient, w 2 Is the second weight coefficient.
Specifically, the hierarchical control structure of the traditional FPPT method is integrated into a layer through EMPC, and economic indexes of a photovoltaic power generation system are used as cost functions to realize economic optimization and power tracking.
Specifically, in the step S3, an EMPC optimization problem at time k is constructed:
in the formula (13), N represents a prediction time domain,representing the predicted value.
Specifically, in the step S4, the efficient algorithm is designed to solve the optimization problem, including constructing a cost function, represented by equation (16),
by employing the cost function J (k + J), the EMPC optimization problem is reconstructed, represented by equation (17),
in the formula (17), the amino acid sequence of the compound, the optimal solution of the optimization problem is expressed as +.> The reconstructed EMPC optimization problem is solved using an efficient algorithm to obtain an optimal solution, and then a first control quantity is applied to the controlled switching tube element.
Specifically, an optimal solution is obtainedThe specific steps include that,
step S41Input: x (k), u (k-1), output:
1. step S42, by using x (k), u (k-1), x (k+1) =f d (x (k), u (k)) and y (k) =g d (x (k), u (k)) to predict allStatus of->And output->
2. Step S43, according toAnd corresponding switching vector->Calculation of
Step S44, selecting an optimal switching vector:
step S45, returning to the optimal solution
Specifically, since the photovoltaic power generation system has strong nonlinearity, the EMPC optimization problem is non-convex, and a local optimal solution exists; an algorithm utilizing the switch states of a limited number of converters is designed, so that the EMPC optimization problem can be effectively solved, and global optimum of the EMPC optimization problem can be obtained.
Example 1
In the embodiment, MATLAB/Simulink is utilized for simulation, the discrete sampling time is set to 25 mu s, an EMPC program is operated under constant irradiance and temperature, and compared with a layered MPC, the power tracking performance is ensured, and meanwhile, the economic performance in a dynamic process is improved.
In order to evaluate the performance of the efficient algorithm, the efficient algorithm is compared with the calculation load of Bonmin widely used for solving the mixed integer nonlinear programming problem, and the calculation load is far smaller than Bonmin while guaranteeing the global optimal solution by verifying the efficient algorithm.
Thus far, the technical solution of the present invention has been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of protection of the present invention is not limited to these specific embodiments. Equivalent modifications and substitutions for related technical features may be made by those skilled in the art without departing from the principles of the present invention, and such modifications and substitutions will be within the scope of the present invention.

Claims (7)

1. The photovoltaic flexible power point tracking method based on economic model predictive control is characterized by comprising the following steps of:
step S1, sampling a photovoltaic power generation system to obtain operation parameters of the photovoltaic power generation system;
step S2, a photovoltaic power generation system model based on a converter is established to describe the dynamic characteristics of the system, wherein the step S2 comprises the steps of describing output current by using a current-voltage characteristic function, constructing a dynamic equation for supplying power to a boost converter by a photovoltaic array based on the current-voltage characteristic function, and constructing the photovoltaic power generation system model based on the dynamic equation and the output power of the photovoltaic power generation system;
step S3, constructing an EMPC optimization problem at the moment k, wherein the EMPC optimization problem comprises setting an objective function according to economic index conditions, and the economic index conditions comprise the output power P pv And power reference P from load demand ref The power balance is realized, so that the switching loss is minimized;
and S4, solving the EMPC optimization problem at the k moment, acquiring a control signal of the switching element, and controlling the controlled switching element based on the control signal.
2. The method for tracking the photovoltaic flexible power point based on the economic model predictive control according to claim 1, wherein in the step S1, the photovoltaic power generation system comprises a photovoltaic array, a DC/DC boost converter and a load, and the photovoltaic array comprises a plurality of photovoltaic cells connected in series and a plurality of photovoltaic cells connected in parallel.
3. The method for tracking a photovoltaic flexible power point based on economic model predictive control according to claim 1, wherein in the step S2, the current-voltage characteristic function is represented by formula (1),
in the formula (1), i pv Representing the output current, I sc Representing the short-circuit current of the photovoltaic cell, v pv Representing the output voltage, V oc Represents the open circuit voltage of the photovoltaic cell, n p Represents the number of parallel photovoltaic cells, n s Represents the number of photovoltaic cells connected in series, wherein A is represented by formula (2),
in the formula (2), V pm Representing the maximum power point voltage of the photovoltaic cell, I pm Representing the maximum power point current of the photovoltaic cell, said I sc ,V oc ,V pm ,I pm Is measured under standard solar irradiance and temperature ambient conditions.
4. The method for tracking the photovoltaic flexible power point based on the economic model predictive control according to claim 1, wherein in the step S2, a dynamic equation of the photovoltaic array supplying power to the boost converter is represented by formula (3),
in the formula (3), I' sc Is parameter I sc Values under non-standard conditions, V' oc Is a parameter V oc Values under non-standard conditions, V' pm Is a parameter V pm Values under non-standard conditions, I' pm Is parameter I pm Values under non-standard conditions, Δt=t-T b T represents temperature, T b The temperature of the sample is indicated as a standard temperature,s represents solar irradiance, S b Representing standard solar irradiance, a=0.0025, b=0.5, c= 0.00288;
output power P of photovoltaic power generation system pv Represented by the formula (4),
P pv ＝i pv ·v pv (4)
available power P of maximum power point avail Represented by the formula (5),
P avail ＝n p n s V' pm ·I' pm (5)
the dynamic equation for the photovoltaic array to power the boost converter is represented by equation (6),
in the formula (6), C 1 Is input filter capacitance, L is converter inductance, i L For inductor current, C 2 Is the output filter capacitance, v o To output voltage, R o Is a load resistance, S w Is a control signal of the switching element, and is expressed by expression (7).
5. The method for tracking the photovoltaic flexible power point based on the economic model predictive control according to claim 1, wherein in the step S2, a photovoltaic power generation system model based on a converter is established, and the model is represented by the formula (8):
in formula (8), x represents a state variable including v pv 、i L ，v o ，u represents a control variable, u=s w Y represents the output variable, y=p pv Wherein, the method comprises the steps of, wherein,
in the formulas (9) and (10), f c (x, u) represents the dynamic equation of the power supplied by the photovoltaic array to the boost converter, g c (x, u) represents the output power of the photovoltaic power generation system.
6. The method for tracking the photovoltaic flexible power point based on the predictive control of the economic model according to claim 1, wherein the step S3 sets an objective function according to an economic index condition represented by the formula (11),
in the formula (11), n c Representing the current switch stateThe number of commutations required to switch to the switch state under evaluation, x (k) represents the state variable obtained by the kth sample, u (k) represents the control variable obtained by the kth sample, y represents the output variable obtained by the kth sample;
the objective function is represented by equation (12),
l e (x(k),u(k))＝w 1 l e1 +w 2 l e2 (12)
in formula (12), w 1 As the first weight coefficient, w 2 Is the second weight coefficient.
7. The photovoltaic flexible power point tracking method based on economic model predictive control according to claim 1, wherein in the step S3, an EMPC optimization problem at k time is constructed:
in the formula (13), N represents a prediction time domain,representing the predicted value.
CN202311048258.4A 2023-08-21 2023-08-21 Photovoltaic flexible power point tracking method based on economic model predictive control Pending CN117318138A (en)

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