CN117559540B - Control method of modularized high-gain boost photovoltaic system - Google Patents
Control method of modularized high-gain boost photovoltaic system 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
- H02J3/381—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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
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- 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
- H02M1/00—Details of apparatus for conversion
- H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
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- 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
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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
- 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
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- 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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Abstract
The invention belongs to the technical field related to photovoltaic control systems, and provides a control method of a modularized high-gain boost photovoltaic system, which comprises the following steps: obtaining a state average equation of a boost circuit in the on and off periods of a switch device of a modularized high-gain photovoltaic boost circuit structure, and then processing by using a space state average method to obtain a typical affine nonlinear state equation; defining a new virtual output function so that the affine nonlinear system can realize accurate feedback linearization; according to the newly defined virtual output function, completely linearizing the affine nonlinear system into a Brunovsky standard system, and giving a coordinate transformation equation and a state feedback control rate thereof; and taking a new state variable tracking error as an input of the controller, and applying a feedback control law of a robust sliding mode variable structure design system. Compared with the prior art, the invention has the advantages of large voltage gain, high response speed, strong anti-interference capability and the like.
Description
Technical Field
The invention belongs to the technical field of photovoltaic control systems, and particularly relates to a control method of a modularized high-gain boost photovoltaic system.
Background
The boost circuit is gradually developed in the photovoltaic grid-connected micro-inverter under the influence of energy shortage. At present, the problem of boosting capability of the existing boost converter is solved, but the problem that a circuit cannot meet the boosting requirement of a micro-inverter, particularly when ultra-low voltage is input, a boosting circuit is needed to be added to improve the power utilization rate, so that the problems of high voltage stress of a power switch, overlarge loss of a switching tube and a diode, reduced service life of a device, limited shape selection and the like are solved. Therefore, it is important to design a topology combination circuit with high boosting capability and low switching stress for the micro-inverter.
The existing high-gain Boost circuit has voltage gain effects of different degrees, but even the high-gain Boost circuit has the phenomenon of circuit instability, and as a strong coupling and nonlinear system, the high-gain Boost circuit brings difficulty to the design of a controller, and the common control method is difficult to meet the requirements of stability, rapidity, anti-interference capability, stability of the voltage of a direct current bus and the like.
The accurate feedback linearization method converts a nonlinear system into a linear system by utilizing nonlinear state feedback and local differential synblast, the original nonlinear term is reserved in the conversion process, the conversion is integral and accurate, the introduced feedback can ensure the stability of the system and good dynamic quality in the conversion, in the traditional boost circuit, the stability, the rapidity and the voltage stabilization of the traditional boost circuit have more excellent effects than PI control, but the high-gain boost circuit system is more complex, and the accurate feedback linearization is not widely applied to the high-gain boost circuit.
Disclosure of Invention
In order to solve the defects of the prior art, the invention provides a control method of a modularized high-gain boost photovoltaic system based on practical application, and the control method has the advantages of large voltage gain, high response speed, strong anti-interference capability and the like.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
The invention provides a circuit structure of a modularized high-gain boost photovoltaic system, which comprises Group switch inductance,/>Diode, a switching tube/>And a capacitor/>Composition, when switching tube/>On, voltage input terminal/>Pair/>The group switch inductors are charged in parallel, all the inductors are in an energy storage state, and the filter capacitor/>Discharging the load at the voltage output end when the switch tube/>When turned off, the voltage input terminal/>And/>Group switch inductance vs. filter capacitance/>And a load series discharge at the voltage output, the circuit voltage gain being/>（/>For switching tube/>Duty cycle of (v-a) is the/>, of the voltage gain of a conventional boost circuitMultiple times.
The invention provides a control method of a modularized high-gain boost photovoltaic system, which comprises the following steps:
Step one, two switch inductors in the modularized high-gain photovoltaic boost circuit structure have the same size, and the initial states of the two switch inductors can be assumed to be identical, so that the inductor current and the output voltage of any one switch inductor can be taken as state variables of the system, and according to the voltage-current relationship of the inductor and the capacitor and kirchhoff current and voltage law, a state average equation of the boost circuit of the switch device in the on and off periods is obtained, and then the state average equation is processed by using a space state average method, so that a typical affine nonlinear state equation is obtained. In the step, obtaining a state average equation of a Boost circuit in the on and off periods of a modularized high-gain photovoltaic Boost circuit structure switching device, and then processing to obtain an affine nonlinear state equation;
step two, calculating the relative order of the output function according to the obtained typical affine nonlinear state equation And with its system dimension/>By comparison, the relative order/>, of the system output function can be knownLess than its system dimension/>It follows that the output function of the affine nonlinear system cannot be precisely feedback linearized, thereby defining a new virtual output function that enables the affine nonlinear system to be precisely feedback linearized by comparing the relative order/>, of its output functionsAnd with its system dimension/>In contrast, defining a new virtual output function so that the affine nonlinear system can realize accurate feedback linearization;
step three, according to a newly defined virtual output function, completely linearizing the affine nonlinear system into a Brunovsky standard system by utilizing nonlinear state feedback and local differential synembryo, and giving a coordinate transformation equation and a state feedback control rate thereof;
Step four, according to the mapping relation of the differential synembryo, the Brunovsky standard system obtained in the step three is controlled to control the original nonlinear system, so that the control target, namely the output voltage, of the original modularized high-gain photovoltaic boost circuit can be controlled Tracking output voltage reference value/>The method is converted into the origin stabilization problem of a bias variable system, a new state variable tracking error is used as the input of a controller, and a feedback control law of a robust sliding mode variable structure design system is applied; in the step, the control target of the original modularized high-gain photovoltaic Boost circuit can be converted into the origin stabilization problem of the bias variable system, a new state variable tracking error is used as the input of the controller, and the feedback control law of the robust sliding mode variable structure design system is applied.
And fifthly, carrying out inverse transformation on the feedback control law designed by the robust sliding mode variable structure principle in the step four according to the state feedback control rate obtained in the step three to obtain the control rate of the original system, namely the modularized high-gain photovoltaic Boost circuit, inputting the output control quantity and the sawtooth wave into the pulse width modulation module at the same time, and generating PWM signals to drive and control the power devices in the modularized high-gain photovoltaic Boost circuit so as to realize accurate control. In the step, inverse transformation is performed according to a feedback control law and a state feedback control rate, so that the control rate of an original system, namely the modularized high-gain photovoltaic Boost circuit, is obtained, and a power device in the modularized high-gain photovoltaic Boost circuit is driven and controlled.
Further, in the step one, the switch device is turned on and turned off, and the voltage input end charges all the switch inductors in parallel when the switch device is turned on, and the filter capacitor discharges the load of the voltage output end, and when the switch device is turned off, the voltage input end and all the switch inductors discharge the filter capacitor and the load of the voltage output end in series, so that the state equation of the modularized high-gain boost photovoltaic system during the turn-on and turn-off of the switch device can be obtained as follows:
；
In the method, in the process of the invention, Is the group number of the switch inductance,/>For system input voltage,/>For the current of any one switch inductance,/>Is the inductance value capacitance of a switch inductance,/>、/>For output terminal voltage and output current,/>The capacitance value of the filter capacitor, R is equivalent constant impedance load, and there is/>。
Respectively selecting current of switch inductanceOutput terminal voltage/>For two state variables/>、/>The duty cycle of the switching device is/>Output voltage reference value is/>. Obtaining typical affine nonlinear state equations such as (3) and output/>, according to a space state averaging methodEquation (4):
；
Further, in the second step, the relative order of the system output function is calculated Can be provided with，/>，/>. The verification is as follows:
；
The relative order of the system output function can be known from (5) Less than its system dimension/>. It is therefore necessary to define a new virtual output function/>Make/>So that the affine nonlinear system can realize accurate feedback linearization. Let/>A new virtual output function/>, can be obtainedThe following are provided:
；
Further, in the third step, according to the newly defined virtual output function, the affine nonlinear system is completely linearized into a Brunovsky standard system, as follows:
；
、/> and/> The state variable and the control variable of the Brunovsky standard system are based on nonlinear state feedback and local differential stratosphere principle, and the coordinate transformation formula is as follows:
；
Order the The state feedback control rate is as follows:
；
further, in step four, the output voltage of the original circuit is outputted Tracking output voltage reference value/>Is converted into the origin stabilization problem of a bias variable system, and an error function/>, is defined、/>The following are provided:
；
for/> Numerical value at steady state, constant/>. Constructing Lyapunov function/>, according to a robust sliding mode variable structure control principleThe following are provided:
；
The derivatives are as follows:
；
Defining a switching function In which the constant/>：
；
As can be seen from formula (13), whenWhen you can solve/>，/>The formula is as follows:
；
as can be seen from formulas (14) and (15), at this time, it is preferable that And/>Make/>Exponentially converging to 0 for a finite time, and at this point/>。
Therefore, a second Lyapunov function needs to be further constructedThe following are provided:
；
For a pair of Deriving and bringing the formulae (7), (10), (12) and (13) into the following formulae can be obtained:
According to the robust sliding mode control principle, a sliding mode surface can be arranged for ensuring the stability of the system And the sliding mode approach rate is as follows:
Wherein the parameter is ，/>，/>，/>. Design control Rate according to equations (17), (18), (19)/>The following are provided:
To verify Can be obtained by substituting formula (20) into formula (17):
is easily deduced from the formula (21) if a matrix can be ensured Is positive matrix, i.e. can prove/>The system has stability. Thus, if appropriate/>、/>And/>The value of (2) is established so that the positive quality of Q and the stability of the system can be ensured,。
The invention has the beneficial effects that:
1. The invention relates to a modularized high-gain boost photovoltaic system based on accurate feedback linearization robust synovial membrane control and a control method thereof, wherein in the circuit structure of the boost photovoltaic system, the circuit voltage gain is as follows For switching tube/>Duty cycle of (v-a) is the/>, of the voltage gain of a conventional boost circuitMultiple times.
2. The control method provided by the invention can enable the output voltage to reach the given value in a very short time, has more excellent starting speed, has excellent anti-interference capability under the condition of abrupt load change, and can well cope with the power generation requirement of an output end power grid; under the condition of abrupt change of an input power supply, the system can quickly return to a steady state and has smaller fluctuation range, and when the output of the photovoltaic power generation assembly fluctuates, the stability of the system voltage can be well maintained, and compared with the traditional sliding mode control method, the system has the advantages that the variation range of the output voltage is smaller and can quickly converge to an expected value, so that the system has better dynamic performance.
Drawings
Fig. 1 is a schematic diagram of a modular high-gain boost photovoltaic system and a method for controlling a precise feedback linearization robust sliding film.
Fig. 2 is a schematic diagram of a modular high-gain boost photovoltaic system structure with n=2 and a precise feedback linearization robust sliding film control method in the embodiment.
Fig. 3 is a modular high-gain boost photovoltaic system based on n=2 and its simulation model designed according to the control method herein in the example.
Fig. 4 is a waveform diagram of comparing output voltage waveforms of 0s to 0.45s of the n=2 modularized high gain boost photovoltaic system under the control method and the dual closed loop PI control method according to the embodiment of the present invention.
Fig. 5 is a graph showing waveforms of output voltages of 0.45s to 1.1s of a modularized high-gain boost photovoltaic system with n=2 in the control method and the dual closed-loop PI control method according to the embodiment of the present invention.
Fig. 6 is a graph showing waveforms of output voltages of 1.1s to 1.6s of the modularized high-gain boost photovoltaic system with n=2 in the control method and the dual closed-loop PI control method according to the embodiment of the present invention. Concrete embodiments
Detailed Description
The application will be further described with reference to the accompanying drawings and specific embodiments. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application. Further, it will be understood that various changes and modifications may be made by those skilled in the art after reading the teachings of the application, and equivalents thereof fall within the scope of the application as defined by the claims.
The embodiment provides a control method of a modularized high-gain boost photovoltaic system.
Fig. 1 is a schematic diagram related to a modularized high-gain boost photovoltaic system and a control method according to the present embodiment. As can be seen from the figure, the circuit is composed of two groups of switch inductorsAnd/>4 Diode inductance/>、/>、/>、/>(I.e., n=2), a switching tube/>And a capacitor/>Composition, when switching tube/>On, voltage input terminal/>Charging two groups of switch inductors in parallel, and leading the inductors to be/>、/>Energy storage, and filter capacitance/>Discharging the load at the voltage output end when the switch tube/>When turned off, the voltage input terminal/>And two sets of switching inductances/>、/>To filter capacitance/>And a load series discharge at the voltage output, the circuit voltage gain being/>（/>For switching tube/>Duty cycle of (v-a) is the/>, of the voltage gain of a conventional boost circuitMultiple times. The design method of the accurate feedback linearization robust sliding film control of the circuit comprises the following steps:
Step one, two switch inductors in the modularized high-gain photovoltaic boost circuit structure have the same size, and the initial states of the two switch inductors can be assumed to be consistent, so that the inductance current of any one switch inductor can be taken And output voltage/>Together as a state variable for the system.
When the switching device is turned on, the voltage input end charges all the switch inductors in parallel, the filter capacitor discharges the load of the voltage output end, and when the switching device is turned off, the voltage input end and all the switch inductors discharge the load of the filter capacitor and the load of the voltage output end in series, and according to the voltage-current relationship of the inductance capacitors and kirchhoff current and voltage law, the state equation of the modularized high-gain boost photovoltaic system in the on and off periods of the switching device can be obtained as follows:
In the method, in the process of the invention, For system input voltage,/>For the current of any one switch inductance,/>Is the inductance value capacitance of a switch inductance,/>、/>For output terminal voltage and output current,/>The capacitance value of the filter capacitor, R is equivalent constant impedance load, and there is/>。
Respectively selecting current of switch inductanceOutput terminal voltage/>For two state variables/>、/>The duty cycle of the switching device is/>Output voltage reference value is/>. Obtaining typical affine nonlinear state equations such as (3) and output/>, according to a space state averaging methodEquation (4):
step two, according to the obtained typical affine nonlinear state equation, solving the relative order of the system output function Can be provided with/>. Relative order/>, of its system output functionThe following are provided:
calculating the relative order of its output function And with its system dimension/>In contrast, the relative order/>, of the system output function can be known from equation (5)Less than its system dimension/>Relative order of system output function/>Less than its system dimension/>. It follows that the output function of the affine nonlinear system cannot be precisely feedback linearized. It is therefore necessary to define a new virtual output function/>Make/>So that the affine nonlinear system can realize accurate feedback linearization. Let/>A new virtual output function/>, can be obtainedThe following are provided:
And thirdly, completely linearizing the affine nonlinear system into a Brunovsky standard system by utilizing nonlinear state feedback and local differential stratosphere according to a newly defined virtual output function, wherein the method comprises the following steps of:
、/> and/> The state variable and the control variable of the Brunovsky standard system are based on nonlinear state feedback and local differential stratosphere principle, and the coordinate transformation formula is as follows:
Order the The state feedback control rate is as follows:
And step four, controlling the Brunovsky standard system obtained in the step three to control the original nonlinear system according to the mapping relation of the differential synblast. Thus, the control target of the original modularized high-gain photovoltaic boost circuit, namely the output voltage Tracking output voltage reference value/>Converting into an origin stabilization problem of a bias variable system, converting into an origin stabilization problem of the bias variable system, and defining an error function/>、/>The following are provided:
for/> Numerical value at steady state, constant/>. Taking a new state variable tracking error as an input of a controller, and designing a feedback control law of the system by using a robust sliding mode variable structure; constructing Lyapunov function/>, according to a robust sliding mode variable structure control principleThe following are provided:
The derivatives are as follows:
Defining a switching function In which the constant/>：
As can be seen from formula (13), whenWhen you can solve/>，/>The formula is as follows:
as can be seen from formulas (14) and (15), at this time, it is preferable that And/>Make/>Exponentially converging to 0 for a finite time, and at this point/>。
Therefore, a second Lyapunov function needs to be further constructedThe following are provided:
For a pair of Deriving and bringing the formulae (7), (10), (12) and (13) into the following formulae can be obtained:
According to the robust sliding mode control principle, a sliding mode surface can be arranged for ensuring the stability of the system And the sliding mode approach rate is as follows:
Wherein the parameter is Design control Rate according to equations (17), (18), (19)/>The following are provided:
To verify Can be obtained by substituting formula (20) into formula (17):
is easily deduced from the formula (21) if a matrix can be ensured Is positive matrix, i.e. can prove/>The system has stability. Thus, if appropriate/>、/>And/>The value of (2) is established so that the positive quality of Q and the stability of the system can be ensured,
。
And fifthly, carrying out inverse transformation on the feedback control law designed by the robust sliding mode variable structure principle in the fourth step according to the state feedback control rate obtained in the third step to obtain the control rate of the original system, namely the modularized high-gain photovoltaic boost circuit, inputting the output control quantity and the sawtooth wave of the control rate into the pulse width modulation module at the same time, and generating PWM signals to drive and control the power devices in the modularized high-gain photovoltaic boost circuit so as to realize accurate control.
The design process of the modularized high-gain boost photovoltaic system control method of the embodiment is verified through a Matlab/Simulink simulation platform in a simulation manner, and the simulation verification is shown in FIG. 3. The system parameters are respectively input terminal voltage 100V, output DC bus voltage given value is 500V, rated load 100 Ω, two switch inductances L=1mH, filter capacitance C=3000 μF, and switch frequency fs=50kHz. At 0s, the photovoltaic system is started with rated load and enters into a working state, at 0.5s, the load is suddenly reduced from rated load 100 omega to 10 omega, then at 1s, rated load 100 omega is restored, at 1.5s, the input end voltage is suddenly reduced from 100V to 60V, and at 2s, the input end voltage is changed from 60V to 100V. The simulation experiment applies double-closed-loop PI control and accurate feedback linearization robust sliding film control (EFL+RSMC) to the modularized high-gain boost photovoltaic system respectively, and compares waveforms of the double-closed-loop PI control and the accurate feedback linearization robust sliding film control to determine control effects of the modularized high-gain boost photovoltaic system under different working conditions.
Through simulation, output voltage waveforms of the modularized high-gain boost photovoltaic system under the condition that the input voltage and the load have disturbance can be obtained, wherein the output voltage waveforms are respectively applied to the double-closed-loop PI control method and the control method adopted by the embodiment, and the output voltage waveforms are shown in fig. 4, 5 and 6.
As can be seen from fig. 4, when the photovoltaic power generation is started, under the double closed loop PI control, the photovoltaic system uses 0.38s to make the output voltage reach the given value of 500V, while the control method only needs 0.05s to make the output voltage reach the given value, so that the starting speed is more excellent.
As can be seen from fig. 5, in the case of abrupt load change, the voltage of the double closed-loop PI control method needs 0.1s to be recovered to a given value, and the fluctuation range during the period is ±8v. The voltage under the control method can be recovered to the given value voltage only by 0.005s, the fluctuation range in the period is +/-0.7V, the method has excellent anti-interference capability and good stability, and the method can well cope with the power generation requirement of an output end power grid.
As can be seen from fig. 6, in the case of abrupt change of the input power, the voltage of the double closed loop PI control method needs 0.1s to be recovered to a given value, and the fluctuation range during the period is ±13V. The voltage under the control method can be recovered to the given value voltage only by 0.005s, the fluctuation range in the period is +/-0.7V, the anti-interference capability is excellent, and the stability of the system can be well maintained and the stability is better when the output of the photovoltaic power generation assembly changes.
Compared with the traditional sliding mode control method, the control method adopted by the embodiment has smaller variation amplitude of output voltage and can quickly converge to an expected value, so that the system has better dynamic performance.
In summary, the control method provided by the embodiment enables the novel boost converter to have higher boosting capability, and compared with other types of boosting circuits, the novel boost converter has the advantages of simple structure and modularization expansion. Experiments prove that the novel boost converter ensures a large boost conversion ratio and a high output voltage, and simultaneously can enable the output voltage to reach a given value in a very short time, so that the starting speed is more excellent, the novel boost converter has excellent anti-interference capability under the condition of abrupt load change, and the power generation requirement of an output end power grid can be well met; under the condition of abrupt change of an input power supply, the system can quickly return to a steady state, the fluctuation range is smaller, and when the output of the photovoltaic power generation assembly fluctuates, the stability of the system voltage can be well maintained, and the stability is better. Compared with the traditional sliding mode control method, the control method has the advantages that the variation amplitude of the output voltage is small and can be converged to an expected value quickly, so that the system has better dynamic performance.
Claims (3)
1. A control method of modularized high-gain boost photovoltaic system, the photovoltaic system circuit includes N (N is more than or equal to 2) groups of switch inductances, (3N-2) diodes, a switch tube S and a filter capacitor, when the switch tube S is conducted, the voltage input end charges N groups of switch inductances in parallel, the filter capacitor discharges the load of the voltage output end, when the switch tube S is turned off, the voltage input end and N groups of switch inductances discharge the load of the filter capacitor and the voltage output end in series, the voltage gain of the circuit isThe control method is 1+ (N-1) d times of the voltage gain of the traditional boost circuit, d is the duty ratio of a switching tube S, and is characterized by comprising the following steps:
Taking the inductance current and the output voltage of any switch inductor in a modularized high-gain boost photovoltaic circuit structure as state variables of the system, obtaining a state average equation of a boost circuit of a switching tube S in on and off periods according to the voltage-current relation of a capacitor and kirchhoff current and voltage law, and then processing by using a space state average method to obtain a typical affine nonlinear state equation;
Step two, according to the obtained typical affine nonlinear state equation, the relative order r of the system output function is smaller than the system dimension n, and a new virtual output function is defined so that the affine nonlinear system can realize accurate feedback linearization;
step three, according to a newly defined virtual output function, completely linearizing the affine nonlinear system into a Brunovsky standard system by utilizing nonlinear state feedback and local differential synembryo, and giving a coordinate transformation equation and a state feedback control rate thereof;
Step four, according to the mapping relation of the differential stratosky, the Brunovsky standard system obtained in the step three is controlled, the control target of the original modularized high-gain boost photovoltaic circuit is converted into the origin stabilization problem of a bias variable system, a new state variable tracking error is used as the input of a controller, and the feedback control law of the robust sliding mode variable structure design system is applied;
Step five, the feedback control law designed by the robust sliding mode variable structure principle in the step four is inversely transformed according to the state feedback control rate obtained in the step three, the control rate of the modularized high-gain boost photovoltaic circuit is obtained, the output control quantity and the sawtooth wave are simultaneously input into the pulse width modulation module, and PWM signals are generated to drive and control the power devices in the modularized high-gain boost photovoltaic circuit so as to realize accurate control;
In the first step, the state average equation of the boost circuit during the on and off periods of the switching tube S is as follows:
Wherein N is the group number of the switch inductors, E is the voltage of the input end of the system, i L is the current of any one switch inductor, L is the inductance value capacitance of one switch inductor, u 0、i0 is the voltage of the output end and the output current, C is the capacitance value of the filter capacitor, R is the equivalent constant impedance load, and u 0＝Ri0 exists;
The current i L of the switch inductor and the output end voltage u 0 are respectively selected as two state variables x 1、x2, the duty ratio of the switch device is d, the output voltage reference value is u oref, and a typical affine nonlinear state equation such as (3) and an equation such as (4) of the output y are obtained according to a space state averaging method:
y＝x2-uoref (4)；
In the second step, the relative order r of the system output function can be calculated by H (x) =x 2-uoref, validated as follows:
from equation (5), it can be known that the relative order of the system output function r=1, which is smaller than the system dimension n=2, so that a new virtual output function ω (x) needs to be defined so that r=n, so that the affine nonlinear system can achieve accurate feedback linearization, so that The new virtual output function ω (x) can be obtained as follows:
2. The method for controlling a modular high-gain boost photovoltaic system according to claim 1, wherein in step three, the affine nonlinear system is completely linearized into a Brunovsky standard system according to a newly defined virtual output function, as follows:
z 1、z2 and v are state variables and control variables of the Brunovsky standard system, and the coordinate transformation formula is shown as follows according to nonlinear state feedback and local differential stratosphere principle:
Let v=a+bd, the state feedback control rate thereof is as follows:
3. The method for controlling a modular high-gain boost photovoltaic system according to claim 2, wherein in the fourth step, the control target of the original modular high-gain boost photovoltaic circuit is converted into an origin stabilization problem of the bias variable system, and an error function e 1、e2 is defined as follows:
z 1ref is the value of z 1 at steady state, the constant c 1 >0, and according to the robust sliding mode variable structure control principle, the Lyapunov function V 1 is constructed as follows:
The derivatives are as follows:
the switching function e 3 is defined as follows, where the constant c 2 >0:
As can be seen from the formula (13), when e 3 =0, e 1,V1 can be solved as follows:
As can be seen from formulas (14), (15), at this point, appropriate c 1 and c 2 are desirable such that e 1 converges exponentially to 0 for a finite period of time, at this point
It is therefore necessary to construct a second Lyapunov function V 2 as follows:
Deriving V 2 and bringing formulae (7), (10), (12) and (13) into the following formulae can be obtained:
According to the robust sliding mode control principle, in order to ensure the stability of the system, a sliding mode surface s and a sliding mode approach rate can be set as follows:
s＝e3(18)
wherein the parameters k 1>0,k2 >0, ε >0,0< α <1, design the control rate v according to equations (17), (18), (19) as follows:
To verify the stability of V 2, substitution of formula (20) into formula (17) yields:
is easily deduced from the formula (21) if a matrix can be ensured Is positive matrix, i.e. can prove/>The system has stability, so that if appropriate values of c 1、c2 and k 1 are selected so that the following formula (22) is established, the positive quality of Q and the stability of the system can be ensured,
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