CN117895813A - Control method of photovoltaic VSG inverter based on improved approach law integral sliding mode - Google Patents

Control method of photovoltaic VSG inverter based on improved approach law integral sliding mode Download PDF

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CN117895813A
CN117895813A CN202410098169.9A CN202410098169A CN117895813A CN 117895813 A CN117895813 A CN 117895813A CN 202410098169 A CN202410098169 A CN 202410098169A CN 117895813 A CN117895813 A CN 117895813A
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voltage
inverter
current
law
photovoltaic
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周铭浩
徐姣姣
穆朝絮
徐伟
刘毅
蔡蔚
成佳敏
李佳霖
王胤帆
费雪然
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Harbin University of Science and Technology
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Harbin University of Science and Technology
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

Abstract

A control method of a photovoltaic VSG inverter based on an improved approach law integral sliding mode relates to the technical field of photovoltaic power generation. The invention aims to enhance the robustness and steady-state precision of the photovoltaic grid-connected VSG system. According to the control method of the photovoltaic VSG inverter based on the improved approach law integral sliding mode, disclosed by the invention, independent control of dq-axis voltage and current is realized by performing feedforward decoupling control on a three-phase inverter mathematical model under a dq coordinate system, non-matching uncertainty disturbance in a system is compensated by a backstepping method, integral sliding mode controllers are designed for a voltage outer ring subsystem and a current inner ring subsystem, and quick response of d-axis current, active power and reactive power of the inverter under the condition of external disturbance and internal parameter perturbation and accurate tracking of d-axis current actual values and reference values are realized.

Description

Control method of photovoltaic VSG inverter based on improved approach law integral sliding mode
Technical Field
The invention belongs to the technical field of photovoltaic power generation.
Background
With increasingly depleted reserves of fossil resources and increasing energy demands, new energy power generation has become a trend. In 2022, the new installation of national wind power and photovoltaic power generation breaks through 1.2 hundred million kilowatts, and the history is new and high. The wind power and photovoltaic power generation amount reaches 1.19 kilowatts, and the same proportion increases by 21 percent. The new energy power generation can relieve the traditional energy supply pressure, reduce the emission of greenhouse gases and promote the development of low-carbon economy, and the photovoltaic power generation is taken as a typical representative of new energy power generation, so that the development of the photovoltaic industry has important significance for low carbon and environmental protection. In recent years, the economical driving photovoltaic industry is rapidly expanded, the accumulated export amount of the inverter in China reaches 31.18 hundred million in the first quarter of 2023, the accumulated export amount is increased by 137.4% in the same proportion, and the accumulated export amount is increased by 3.6% in the fourth quarter of 2022, so that the high-speed growth situation is maintained.
A photovoltaic grid-connected VSG (virtual synchro) system is a micro-grid consisting of a photovoltaic power source and power electronics, similar to a conventional synchro generator, as a typical non-matching uncertainty system. The system can operate in an island mode and a grid-connected power generation mode, and can realize the controllability of micro-grid power generation by adopting a reasonable control method. However, the system stable operation is seriously affected by non-linear load in the actual operation process, uncertainty caused by fluctuation of the photovoltaic module and parameter perturbation caused by multiple power electronic devices. The outer loop voltage system, the source output and the DC voltage regulation loop bring about uncertainty, and such mismatch uncertainty cannot be compensated by the system itself, thereby causing output voltage fluctuation and steady state error. Therefore, it is particularly important to provide a control method for enhancing robustness and steady-state accuracy for a non-matching nonlinear system such as an inverter in a photovoltaic grid-connected VSG system.
Disclosure of Invention
The invention aims to enhance the robustness and steady-state precision of a photovoltaic grid-connected VSG system, and provides a control method of a photovoltaic VSG inverter based on an improved approach law integral sliding mode.
The control method of the photovoltaic VSG inverter based on the improved approach law integral sliding mode comprises the following steps:
step one: constructing a mathematical model of the inverter based on an LC filter under a two-phase rotation coordinate system;
step two: performing feedforward decoupling control on voltage and current in a mathematical model based on an LC filter under the two-phase rotation coordinate system;
step three: respectively constructing a voltage outer loop state equation and a current inner loop state equation which consider parameter perturbation;
step four: respectively designing an integral sliding mode surface of the voltage outer ring according to a state equation of the voltage outer ring and a state equation of the current inner ringAnd the integral slip plane of the current inner loop +.>
Step five: respectively designing novel composite approach law of voltage outer ringNovel compound approach law of sum current inner loop->
Step six: respectively to the sliding mode surface of the outer ring of the voltageAnd slip form face of inner loop of current +.>Solving a first derivative, and then respectively carrying out new compound approach law with the voltage outer loop +.>Novel compound approach law of sum current inner loop->Connecting, thereby constructing a virtual control law of a voltage outer loop>And current inner loop virtual control law u i Virtual control law using a voltage outer loop>And current inner loop virtual control law u i Obtaining a voltage outer loop control signal and a current inner loop control signal, realizing control on the photovoltaic virtual synchronous machine inverter,
the virtual control law of the voltage outer ringThe expression is as follows:
the current inner loop virtual control law u i The expression is as follows:
u i ＝u ieq +u in ，
in the above-mentioned formula(s),and->The voltage outer loop equivalent control law and the actual control law are respectively, u ieq And u in The equivalent control law and the actual control law of the inner loop of the current are respectively, and the intermediate variable f 1 ＝-i 0 /C f Intermediate variable f 2 ＝-R f i g -u g Intermediate variable g 1 ＝-1/C f ，/>Is u ref U ref For the output voltage setpoint of the inverter, < >>For voltage outer loop tracking error, < >>I is the current inner loop tracking error g And u g Respectively the actual values of the current and the voltage at the power grid side, i 0 C is the actual value of the output current of the inverter f And R is f The capacitance and resistance of the LC filter, p is Laplacian, C' 1 、C' 2 、C 1 And C 2 Are both positive and real numbers, and the two are all positive and real numbers,η, k, a and q are constants, sat () is a saturation function, and the expression +.>Delta is boundary layer, intermediate variable->Gamma is the saturation function variable.
Further, in the first step, a mathematical model of the inverter under the three-phase stationary coordinate system is first established according to kirchhoff's voltage law and current law:
wherein u is abc And i abc Three-phase output voltage and three-phase output current of inverter, u gabc And i gabc Three-phase output voltage and three-phase output current at the power grid side respectively, L f The inductance of the LC filter under a three-phase static coordinate system;
and then carrying out coordinate transformation on the mathematical model of the inverter under the three-phase static coordinate system to obtain the mathematical model of the inverter based on the LC filter under the two-phase rotating coordinate system.
Further, the mathematical model expression of the inverter based on the LC filter under the two-phase rotation coordinate system is as follows:
wherein u is gd And u gq Respectively the actual values of the d-axis voltage and the q-axis voltage on the power grid side, i gd And i gq Actual value currents of d axis and q axis on the power grid side, u d And u q Respectively, invertersActual d-axis and q-axis voltages of i d And i q The actual values of d-axis current and q-axis current of the inverter are respectively, and ω is the inverter synchronous rotation angular velocity.
Further, the turning frequency of the LC filterSatisfies the following formula:
wherein F is the fundamental frequency of the output waveform of the LC filter, F s The switching frequency is PWM modulated.
Further, in the second step, feedforward decoupling control is performed on the voltages and currents in the mathematical model based on the LC filter in the two-phase rotation coordinate system, so that the mathematical model of the inverter is transformed into:
wherein,is->U gref For a grid-side voltage setpoint, ">Is i g Is the first derivative of (1), intermediate variable>L f The inductance of the LC filter under the three-phase static coordinate system is shown, and u is the actual value of the output voltage of the inverter.
Further, in the third step, a voltage outer loop state equation and a current inner loop state equation considering parameter perturbation are respectively constructed, and the method comprises the following steps:
defining current inner loop tracking errorThe expression is:
based on the current inner loop tracking errorConstructing the voltage outer loop state equation:
based on the current inner loop tracking errorConstructing the current inner loop state equation:
wherein i is gref For the given value of the current on the power grid side, d u For lumped uncertainty parameters of the voltage outer loop, ΔL f And DeltaR f Inductance and resistance of LC filter, R f0 And L f0 The initial values of the LC filter resistance and inductance, respectively.
Further, the above parametric perturbation is described as:
wherein DeltaR f 、ΔL f And DeltaC f Perturbation quantities of LC filter resistor, inductor and capacitor, C f0 An initial value of the LC filter capacitance.
Further, the lumped uncertainty parameter d of the voltage outer loop u The expression is:
further, in the fourth step, the integral sliding surface of the outer ring of the voltageAnd the integral slip plane of the current inner loop +.>The expressions are as follows:
further, in the fifth step, the voltage outer loop is novel and compound to approach the lawNovel compound approach law of sum current inner loop->The expressions of (2) are as follows:
the invention provides a control method of a photovoltaic VSG inverter based on an improved approach law integral sliding mode, which realizes independent control of dq axis voltage and current by performing feedforward decoupling control on a three-phase inverter mathematical model under a dq coordinate system, and utilizes a backstepping method to compensate non-matching uncertainty disturbance in a system, and designs an integral sliding mode controller aiming at a voltage outer ring and a current inner ring subsystem so as to realize parameter perturbation, quick response of d-axis current, active power and reactive power of the inverter under the non-matching uncertainty disturbance and accurate tracking of d-axis current actual values and reference values.
Drawings
FIG. 1 is a flow chart of a control method of a photovoltaic VSG inverter based on an improved approach law integral sliding mode according to the present invention;
fig. 2 is a structural model diagram of an inverter;
fig. 3 is a schematic block diagram of feedforward decoupling control of an inverter
Fig. 4 is a functional block diagram of a control method of a photovoltaic VSG inverter based on an improved approach law integral sliding mode.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but 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. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
External interference such as parameter perturbation, external temperature and humidity change and the like exists in the operation process of the photovoltaic VSG inverter system, so that the inverter output d-axis current response is slower, the current tracking error is larger and the power tracking error is larger. The traditional PI algorithm cannot compensate non-matching uncertainty disturbance existing in the system, current amplitude is large, and waveform distortion is serious. The sliding mode control has stronger robustness and anti-interference capability, and can cope with system parameter changes and external interference, so that the sliding mode control is widely applied to the fields of permanent magnet synchronous motors, robots, aerospace and the like. However, the traditional sliding mode control algorithm can compensate a part of non-matching uncertainty, but has larger buffeting, and has higher requirements on the controller.
Aiming at the problems, the embodiment provides an inverter control method of the photovoltaic virtual synchronous machine based on an approach law integral sliding mode, which replaces the original high-frequency switching item with an integral control law compared with the traditional sliding mode, and eliminates system buffeting while keeping the robustness of the sliding mode. Referring to fig. 1 to 4, a method for controlling an inverter of a photovoltaic virtual synchronous machine according to the present embodiment based on an approach law integral sliding mode, the method comprising:
step S1), constructing a mathematical model of an inverter in a photovoltaic VSG (virtual synchronous machine) system based on an LC filter under a two-phase rotation coordinate system, and simplifying and determining parameters of the mathematical model on the premise of guaranteeing the filtering performance of the model.
Specifically, a mathematical model of the inverter under the three-phase stationary coordinate system is established according to kirchhoff's voltage law and current law:
wherein L is f 、R f 、C f Inductance, resistance and capacitance of LC filter, respectively, u abc And i abc Three-phase output voltage and three-phase output current of inverter, u gabc And i gabc The three-phase output voltage and the three-phase output current are respectively at the power grid side.
The mathematical model expression of the inverter based on the LC filter under the two-phase rotation coordinate system can be obtained through coordinate transformation, and the mathematical model expression is as follows:
wherein L is f 、R f 、C f Inductance, resistance and capacitance of LC filter respectively，u gd And u gq Respectively the actual values of the d-axis voltage and the q-axis voltage on the power grid side, i gd And i gq Actual value currents of d axis and q axis on the power grid side, u d And u q The actual values of the d-axis voltage and the q-axis voltage of the inverter, i d And i q The actual values of d-axis current and q-axis current of the inverter are respectively, and ω is the inverter synchronous rotation angular velocity.
On the premise of ensuring the basic function of the LC filter, the parameters of the control system are simplified and designed, the basic function of the LC filter is limited to voltage fluctuation, harmonic waves are eliminated, and the sine degree of PWM modulation waves is improved. The LC filter is a typical second-order system, and analyzes the amplitude-frequency characteristic, the phase-frequency characteristic and the transfer function, and the known frequency is higher than the inherent frequency omega n The amplitude of attenuation of the high frequency harmonic is 40dB/sec. Designed LC filter turning frequencyIs far greater than the fundamental frequency F (50 Hz) of the output waveform and is far less than the PWM modulation switching frequency F s The present embodiment is set to 10kHz, that is, satisfies the following formula:
comprehensively considering, in order to filter the high-frequency signal output by PWM, the stable output of the low-frequency signal, the filtering effect and the stability of the filter are ensured, and finally, the inductance of the LC filter is 3.5mH, the capacitance is 8 mu F, and the turning frequency is 952Hz.
Step S2) coupling exists in an inverter mathematical model under a two-phase rotation coordinate system (dq coordinate system), and feedforward decoupling control is needed to be carried out on the dq axis current to realize independent control, so that inter-axis coupling is eliminated. After dq feedforward decoupling, the mathematical model of the inverter under the dq coordinate system is transformed into:
wherein the intermediate variable f 1 ＝-i 0 /C f ，f 2 ＝-R f i g -u g ，i g And u g Respectively the actual values of the current and the voltage at the power grid side, i 0 The actual value of the current is output for the inverter.
g 1 And g 2 The nonlinear gain matrixes of the state variable and the control quantity are respectively continuously conductive, and the nonlinear gain matrixes comprise: g 1 ＝-1/C f ，g 2 ＝1/L f 。
Is->First derivative of>Is a voltage outer loop tracking error and has +.>u ref The given value of the output voltage of the inverter.
And->I respectively g And u ref Is a first derivative of (a).
u is the actual value of the inverter output voltage.
The active power P and the reactive power Q output by the inverter after the dq coordinate system feedforward decoupling are respectively as follows:
u gd and u gq Respectively the actual values of the d-axis voltage and the q-axis voltage on the power grid side, i d And i q Respectively are inversions ofActual d-axis and q-axis currents of the device.
In order to meet the requirements of static stability and dynamic quick response of the inverter, the same-voltage vector control can be adopted, so that the q-axis voltage at the power grid side is 0, and the above-mentioned steps can be converted into:
considering that an inverter is a typical second-order system, respectively designing double closed-loop control of a voltage outer loop and a current inner loop, and adding a model of a controller after closed-loop control is as follows:
wherein k is p Is a proportionality coefficient, k i For the integral coefficients, s is the differential operator,and->The reference values of the d-axis output current and the q-axis output current of the inverter are respectively, and L is the line inductance of the inverter.
And (3) converging the voltage tracking error to 0 through a voltage outer loop controller, and outputting an inner loop current given value. After current decoupling and current inner loop controller, output voltage u of dq axis of inverter d And u q The coordinates are transformed to obtain alpha and beta axes, which are used as output signals to output pulse signals after SVPWM modulation.
Transfer function G of inner loop of current i The (lambda) equivalent is:
wherein T is a Sampling time constant for IGBT switch, H i (lambda) is the current inner loop feedback function, lambda is the complex function variable, delta is the complex frequencyThe rate.
The voltage outer loop changes slowly compared with the current inner loop, the voltage outer loop transfer function G u (lambda) is:
in the formula e d For the error of the output voltage of the inverter and the given voltage value, T c ＝T b +3T a ，T b For voltage sampling time constant, U dc For dc side voltage of inverter τ b Is constant and satisfies τ b ＝K bp /K bI C is the inverter capacitance.
Step S3) when the inverter is running, there are conditions such as component aging, temperature and humidity change, and the like, which can cause fluctuation of resistance, capacitance and inductance parameters, and component parameter perturbation can be described as:
wherein DeltaR f 、ΔL f And DeltaC f The perturbation quantities of the LC filter resistance, inductance and capacitance, respectively, and respectively exist at the upper limit M R 、M L And M C 。R f0 、L f0 And C f0 The initial values of the LC filter resistance, inductance and capacitance are respectively.
An inverter in a photovoltaic grid-connected VSG system is a typical non-matching nonlinear second-order system, and a traditional PI algorithm cannot control the condition that parameter perturbation occurs in a non-control signal channel. Resulting in reduced controllability and control accuracy. However, the sliding mode control has strong robustness, can effectively cope with the conditions of internal parameter perturbation and external disturbance, and is widely applied to the fields of motor control, mechanical control, automatic driving and the like. Meanwhile, the sliding mode control based on the back-stepping method can solve the parameter perturbation problem of the non-control signal channel and eliminate the influence of the non-control signal channel on the controller.
For non-matching uncertainty caused by outer loop parameter perturbation, defining current inner loop tracking error
Wherein i is gref For a grid-side current setpoint.
Then a given error is tracked according to the current inner loopThe state equation for constructing the voltage outer loop is:
in the method, in the process of the invention,is a virtual control law of a voltage outer loop and is provided with +.>
d u The lumped uncertainty parameter for the voltage outer loop is expressed as:
in the state equation of the voltage outer loop, the PWM switching signal is used as the actual control input, and the control input and the input gain are equivalent to the current inner loop control law u i The state equation of the current inner loop at this time is:
step S4) designing an integral sliding mode surface of the voltage outer ring according to a state equation of the voltage outer ringThe method comprises the following steps:
wherein C is 1 And C 2 Are all positive real numbers, and a polynomial p needs to be ensured 2 +C 1 p+C 2 The eigenvalue real part of =0 is negative, where p is the Laplace operator, C in this embodiment 1 ＝C 2 ＝600。
To ensure that the current inner loop tracks a given error e ig And its derivative all converged to 0 in limited time, and the current inner loop integral sliding mode surface was designedThe method comprises the following steps:
and is present:
step S5) designing novel composite approach law of voltage outer ring
Novel composite approach law for designing current inner loop
Step S6) integrating the slip plane of the voltage outer ringNovel compound approach law with voltage outer loop after first derivative is calculatedConnecting to obtain the voltage outer loop control law +.>The method comprises the following steps:
is the equivalent control law of the outer ring of the voltage, +.>For the voltage outer loop actual control law, the expressions are as follows:
slip form surface for current inner loop integrationNovel compound approach law with current inner loop after first derivative is calculated->Connecting and waiting to obtain the current inner loop control law u i The method comprises the following steps:
u i ＝u ieq +u in ，
wherein u is ieq U is the equivalent control law of the inner loop of the current in For the current inner loop actual control law, the expression is as follows:
in the above formula, the intermediate variable f 1 ＝-i 0 /C f Intermediate variable f 2 ＝-R f i g -u g Intermediate variable g 1 ＝-1/C f ，Is u ref U ref For the output voltage setpoint of the inverter, < >>For voltage outer loop tracking error, < >>I is the current inner loop tracking error g And u g Respectively the actual values of the current and the voltage at the power grid side, i 0 C is the actual value of the output current of the inverter f And R is f The capacitance and resistance of the LC filter, p is Laplacian, C' 1 ＝C' 2 ＝600、C 1 And C 2 Are all positive real numbers, ">Eta is more than 0, a is more than 0 and less than 1, q is more than 0, k are constants, and the disturbance of the system is within a rangeThe regulation is performed so that the output voltage and the output current of the inverter system stably track a given value, and the overshoot is not large. In this embodiment, k=150, η=20, q=100, and a=3/5.
sat () is a saturated function, expressed asDelta is boundary layer, switching control is adopted outside boundary layer, linearization control is adopted inside boundary layer, intermediate variable +.>Gamma is the saturation function variable.
By means of the Liapunov stability criterionIt can prove that the voltage outer loop tracking error +.>Will reach the slide face in a limited time +.>And converges to 0.
Finally, the voltage outer loop control law is utilizedAnd current inner loop control law u i The voltage outer loop and the current inner loop of the inverter are respectively controlled as control signals.
Through the Liapunov stability criterion, it can be shown that the inner loop current will reach the designed integral sliding mode surface in a limited time, the tracking virtual control law and the tracking error of the voltage outer loop will converge to 0, the designed integral terminal sliding mode controller based on the back-stepping method can counteract non-matching uncertainty, and the accuracy and the robustness of voltage tracking and current tracking are improved.
In summary, the embodiment discloses a control method of a photovoltaic VSG inverter based on an improved approach law integral sliding mode, which improves the tracking speed of output power when power is suddenly changed compared with the traditional PI and the traditional sliding mode, reduces the ripple of output current and output power, and improves the control precision and robustness of the system.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein may be combined in ways other than as described in the original claims. It is also to be understood that features described in connection with separate embodiments may be used in other described embodiments.

Claims (10)

1. The control method of the photovoltaic VSG inverter based on the improved approach law integral sliding mode is characterized by comprising the following steps of:
step one: constructing a mathematical model of the inverter based on an LC filter under a two-phase rotation coordinate system;
step two: performing feedforward decoupling control on voltage and current in a mathematical model based on an LC filter under the two-phase rotation coordinate system;
step three: respectively constructing a voltage outer loop state equation and a current inner loop state equation which consider parameter perturbation;
step four: respectively designing an integral sliding mode surface of the voltage outer ring according to a state equation of the voltage outer ring and a state equation of the current inner ringAnd the integral slip plane of the current inner loop +.>
Step five: respectively designing novel composite approach law of voltage outer ringNovel compound approach law of sum current inner loop->
Step six: respectively to the sliding mode surface of the outer ring of the voltageAnd slip form face of inner loop of current +.>Solving a first derivative, and then respectively carrying out new compound approach law with the voltage outer loop +.>Novel compound approach law of sum current inner loop->Connecting, thereby constructing a virtual control law of a voltage outer loop>And current inner loop virtual control law u i Virtual control law using a voltage outer loop>And current inner loop virtual control law u i Obtaining a voltage outer loop control signal and a current inner loop control signal to realize control of the photovoltaic virtual synchronous machine inverter;
the virtual control law of the voltage outer ringThe expression is as follows:
the current inner loop virtual control law u i The expression is as follows:
u i ＝u ieq +u in ，
in the above-mentioned formula(s),and->The voltage outer loop equivalent control law and the actual control law are respectively, u ieq And u in The equivalent control law and the actual control law of the inner loop of the current are respectively, and the intermediate variable f 1 ＝-i 0 /C f Intermediate variable f 2 ＝-R f i g -u g Intermediate variable g 1 ＝-1/C f ，/>Is u ref U ref For the output voltage setpoint of the inverter, < >>For voltage outer loop tracking error, < >>I is the current inner loop tracking error g And u g Respectively the actual values of the current and the voltage at the power grid side, i 0 C is the actual value of the output current of the inverter f And R is f The capacitance and resistance of the LC filter, p is Laplacian, C' 1 、C′ 2 、C 1 And C 2 Are all positive real numbers, ">η, k, a and q are constants, sat () is a saturation function, and the expression +.>Delta is boundary layer, intermediate variableGamma is the saturation function variable.
2. The method for controlling a photovoltaic VSG inverter based on an improved approach law integral sliding mode according to claim 1, wherein in the first step, a mathematical model of the inverter under a three-phase stationary coordinate system is first established according to kirchhoff's voltage law and current law:
wherein u is abc And i abc Three-phase output voltage and three-phase output current of inverter, u gabc And i gabc Three-phase output voltage and three-phase output current at the power grid side respectively, L f The inductance of the LC filter under a three-phase static coordinate system;
and then carrying out coordinate transformation on the mathematical model of the inverter under the three-phase static coordinate system to obtain the mathematical model of the inverter based on the LC filter under the two-phase rotating coordinate system.
3. The control method of a photovoltaic VSG inverter based on an improved approach law integral sliding mode according to claim 1 or 2, characterized in that the inverter is based on the mathematical model expression of LC filter in two-phase rotation coordinate system:
wherein u is gd And u gq Respectively the actual values of the d-axis voltage and the q-axis voltage on the power grid side, i gd And i gq Actual value currents of d axis and q axis on the power grid side, u d And u q The actual values of the d-axis voltage and the q-axis voltage of the inverter, i d And i q The actual values of d-axis current and q-axis current of the inverter are respectively, and ω is the inverter synchronous rotation angular velocity.
4. The method for controlling a photovoltaic VSG inverter based on an improved approach law integral slip mode of claim 3, wherein the turning frequency of the LC filterSatisfies the following formula:
wherein F is the fundamental frequency of the output waveform of the LC filter, F s The switching frequency is PWM modulated.
5. The method for controlling a photovoltaic VSG inverter based on an improved approach law integral sliding mode according to claim 1, wherein in the second step, the voltage and the current in the mathematical model based on LC filter in the two-phase rotation coordinate system are feedforward decoupled controlled such that the mathematical model of the inverter is transformed into:
wherein,is->U gref For a grid-side voltage setpoint, ">Is i g First derivative of (a), intermediate variableL f The inductance of the LC filter under the three-phase static coordinate system is shown, and u is the actual value of the output voltage of the inverter.
6. The method for controlling a photovoltaic VSG inverter based on an improved approach law integral sliding mode according to claim 1, wherein in the third step, a voltage outer loop state equation and a current inner loop state equation considering the perturbation of the parameters are respectively constructed, comprising:
defining current inner loop tracking errorThe expression is:
based on the current inner loop tracking errorConstructing the voltage outer loop state equation:
based on the current inner loop tracking errorConstructing the current inner loop state equation:
wherein i is gref For the given value of the current on the power grid side, d u For lumped uncertainty parameters of the voltage outer loop, ΔL f And DeltaR f Inductance and resistance of LC filter, R f0 And L f0 The initial values of the LC filter resistance and inductance, respectively.
7. The method for controlling a photovoltaic VSG inverter based on an improved approach law integral slip mode of claim 6, wherein the parametric perturbation is described as:
wherein DeltaR f 、ΔL f And DeltaC f Perturbation quantities of LC filter resistor, inductor and capacitor, C f0 An initial value of the LC filter capacitance.
8. The method for controlling a photovoltaic VSG inverter based on an improved approach law integral slip mode of claim 7, wherein the lumped uncertainty parameter d of the voltage outer loop u The expression is:
9. the method for controlling a photovoltaic VSG inverter based on an improved approach law integral slip mode of claim 1, wherein in step four, the integral slip mode surface of the voltage outer ringAnd the integral slip plane of the current inner loop +.>The expressions are as follows:
10. the method for controlling a photovoltaic VSG inverter based on an improved approach law integral slip mode of claim 1, wherein in step five, the voltage outer loop is a novel composite approach lawNovel compound approach law of sum current inner loop->The expressions of (2) are as follows:
CN202410098169.9A 2024-01-23 2024-01-23 Control method of photovoltaic VSG inverter based on improved approach law integral sliding mode Pending CN117895813A (en)

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