CN104362675B - Inverter system and photovoltaic grid inverter control method and device - Google Patents

Abstract

The invention relates to the field of power electronic technology and nonlinear control application and discloses an inverter system and a photovoltaic grid inverter control method and device. Maximum power point voltage Udcm and maximum power point current idcm on the alternating-current side of the inverter are acquired by acquiring three-phase line voltage ueab, uebc and ueca and three-phase current ia, ib and ic on the alternating-current side of the inverter, and the inverter is controlled according to an inverter controller established on the basis of an EL equation model under the condition of unbalanced power grid. Alternating-current harmonic of the photovoltaic grid inverter power grid is reduced under the condition of the unbalanced power grid, dynamic decoupling of current is realized, and stable state and dynamic performance of the inverter are improved.

Description

Photovoltaic grid-connected inverter control method and device and inverter system

Technical Field

The invention relates to the field of power electronic technology and nonlinear control application, in particular to a photovoltaic grid-connected inverter control method and device and an inverter system.

Background

With the development of solar energy application technology, the mainstream development trend of the photovoltaic power generation system is undoubtedly the grid-connected photovoltaic power generation. The operation performance of the grid-connected inverter, which is one of the key devices of the photovoltaic grid-connected power generation system, directly affects the safe, reliable and high-efficiency operation of the photovoltaic grid-connected power generation system. Generally, for household medium and small power photovoltaic grid-connected power generation systems, a main circuit of a grid-connected inverter of the household medium and small power photovoltaic grid-connected power generation system usually adopts a single-phase topological structure to adapt to a single-phase power grid; for a centralized high-power photovoltaic grid-connected power generation system, a main circuit of a grid-connected inverter of the system usually adopts a three-phase topology structure so as to adapt to a three-phase power grid. For a three-phase operation environment, imbalance of a three-phase power grid is inevitable, and the conventional three-phase grid-connected inverter control system design generally ignores the imbalance of the three-phase power grid, namely, the three-phase power grid is unbalanced. However, once the three-phase grid-connected inverter designed according to the three-phase balanced grid condition is unbalanced, the grid-side current of the grid-connected inverter is distorted due to the generation of non-characteristic harmonics, which leads to the reduction of the operation performance and the increase of the loss of the grid-connected inverter, and the grid-connected inverter can be failed in severe cases, even the power modules therein are burned. Therefore, the research on the grid-connected inverter control strategy under the unbalanced condition of the three-phase power grid undoubtedly has important practical significance for safe, reliable and high-efficiency operation of the centralized high-power photovoltaic grid-connected power generation system under the three-phase operation environment.

Disclosure of Invention

The invention provides a photovoltaic grid-connected inverter control method, a photovoltaic grid-connected inverter control device and an inverter system, and solves the technical problem that a single charging device can only charge devices of the same type due to the fact that the existing wireless charging electromagnetic frequency is fixed.

The purpose of the invention is realized by the following technical scheme:

a control method for a photovoltaic grid-connected inverter is characterized by comprising the following steps:

obtaining three-phase line voltage u of inverter AC side_eab、u_ebc、u_ecaAnd three phase line current i_a、i_b、i_c；

Obtaining the maximum power point voltage U of the DC side of the inverter_dcmAnd maximum power point current i_dcm；

Controlling the inverter under the condition of unbalanced power grid according to an inversion controller established based on an EL equation model, wherein the model of the inverter is a mathematical model under a three-phase static coordinate system, the inversion controller is a passive controller based on the EL equation model, and the input of the inversion controller is u_eab、u_ebc、u_eca、i_a、i_b、i_c、U_dcmAnd i_dcmSaidThe output of the inversion controller is a switching function S under a three-phase static coordinate system_a、S_b、S_c；

According to the inverter controller based on EL equation model establishment, including:

for three-phase line current i at AC side of the inverter_a、i_b、i_cPerforming Park conversion to obtain alternating side current i under a two-phase synchronous rotating coordinate system_d、i_q；

Line switching function S for the inverter in a three-phase stationary coordinate system_ab、S_bc、S_caPerforming Park transformation to obtain a linear switching function S under a two-phase synchronous rotating coordinate system_ld、S_lq；

For the three-phase line voltage u at the AC side of the inverter_eab、u_ebc、u_ecaPerforming conversion to obtain AC side voltage u under two-phase synchronous rotating coordinate system_led、u_leq；

Will i_d、i_q、u_led、u_leq、S_ld、S_lqSubstituting the mathematical model of the inverter in a three-phase static coordinate system to obtain the mathematical model of the inverter in a two-phase synchronous rotating coordinate system;

establishing the inverter controller according to an EL equation model and a mathematical model of the inverter under a two-phase synchronous rotating coordinate system;

the mathematical model under the three-phase static coordinate system is expressed by formula (1):

wherein S is_a、S_b、S_cAs a function of the switching, S when the upper arm is switched on_k(k ═ a, b, c) ═ 1, and S is present when the lower arm is on_k(k＝a,b,c)＝0，S_ab、S_bc、S_caAs a function of the line switch, S_ab＝S_a-S_b、S_bc＝S_b-S_c、S_ca＝S_c-S_aWhen the upper bridge arm is on S_k(k ═ a, b, c) ═ 1, and S is present when the lower arm is on_k(k＝a,b,c)＝0；U_dcmThe maximum power point voltage of the photovoltaic array;

the establishing of the inverter controller according to the EL equation model and the mathematical model of the inverter under the two-phase synchronous rotating coordinate system comprises the following steps:

converting a mathematical model of the inverter under a two-phase synchronous rotating coordinate system into an EL equation model;

injecting damping into an EL equation model to obtain a control law of the inverter controller;

establishing an inversion controller according to the control law of the inversion controller, wherein the output of the inversion controller

S_a＝(1/3)*(S_ab-S_ca+△S)、

S_b＝(1/3)*(S_bc-S_ab+△S)、

S_c＝(1/3)*(S_ca-S_bc+△S)，△S＝S_a+S_b+S_c，

Wherein,

S_ab＝S_ldsin(ωt+30°)+S_lqcos(ωt+30°)，

S_bc＝S_ldsin(ωt-90°)+S_lqcos(ωt-90°)，

S_ca＝S_ldsin(ωt+150°)+S_lqcos(ωt+150°)，

R_a1、R_a2for damping of the injection i_dr、i_qrIs i_d、i_qThe expected value of (d); l is the inductance of the inductance filter at the network side or the alternating current side, and R is the resistance of the inductance filter at the network side or the alternating current side; u. of_ledIs d-axis component u of three-phase AC phase voltage in two-phase synchronous rotating coordinate system_leqThe q-axis component of the three-phase alternating-current phase voltage under the two-phase synchronous rotating coordinate system is shown.

A photovoltaic grid-connected inverter control device is characterized by comprising:

a first obtaining module for obtaining the three-phase line voltage u at the AC side of the inverter_eab、u_ebc、u_ecaAnd three phase line current i_a、i_b、i_c；

A second obtaining module for obtaining the maximum power point voltage U of the DC side of the inverter_dcmAnd maximum power point current i_dcm；

The control module is used for controlling the inverter under the condition of unbalanced power grid according to an inversion controller established based on an EL equation model, wherein the model of the inverter is a mathematical model under a three-phase static coordinate system, the inversion controller is a passive controller based on the EL equation model, and the input of the inversion controller is u_eab、u_ebc、u_eca、i_a、i_b、i_c、U_dcmAnd i_dcmThe output of the inverter controller is a switching function S under a three-phase static coordinate system_a、S_b、S_c(ii) a The control module includes:

a first conversion unit, configured to convert the three-phase line current i on the ac side of the inverter acquired by the first acquisition module_a、i_b、i_cConverted into alternating side current i under two-phase synchronous rotating coordinate system_d、i_q；

A second conversion unit, configured to convert the three-phase line voltage u on the ac side of the inverter obtained by the first obtaining module_eab、u_ebc、u_ecaConverted into AC side voltage u under two-phase synchronous rotating coordinate system_led、u_leq；

A damping input unit for inputting a damping R_a1、R_a2；

A current calculating unit for calculating a maximum power point voltage U_dcmAnd maximum power point current i_dcmCalculate i_d、i_qIs expected value i_dr、i_qr；

A process control unit for controlling the process according to i_d、i_q、u_led、u_leq、R_a1、R_a2、U_dcm、i_dr、i_qrCalculating the outgoing line switch function S_ab、S_bc、S_caAccording to said line switching function S_ab、S_bc、S_caCalculating a switching function S_a、S_b、S_cAnd by said switching function S_a、S_b、S_cControlling the inverter under the condition of unbalanced power grid; the mathematical model under the three-phase static coordinate system is expressed by formula (1):

wherein S is_a、S_b、S_cAs a function of the switching, S when the upper arm is switched on_k(k ═ a, b, c) ═ 1, and S is present when the lower arm is on_k(k＝a,b,c)＝0，S_ab、S_bc、S_caAs a function of the line switch, S_ab＝S_a-S_b、S_bc＝S_b-S_c、S_ca＝S_c-S_aWhen the upper bridge arm is on S_k(k ═ a, b, c) ═ 1, and S is present when the lower arm is on_k(k＝a,b,c)＝0；U_dcmThe maximum power point voltage of the photovoltaic array;

the process control unit includes:

a calculation subunit for calculating according to i_d、i_q、u_led、u_leq、R_a1、R_a2、U_dcm、i_dr、i_qrCalculating the linear switching function under the two-phase synchronous rotating coordinate system

Control output subunit for S pair_ldAnd S_lqCarrying out Park inverse transformation to obtain a line switch function S under a three-phase static coordinate system_ab、S_bc、S_ca；

A control execution subunit for executing a line switching function S_ab、S_bc、S_caCalculating a switching function S_a、S_b、S_cAnd by said switching function S_a、S_b、S_cControlling the inverter under the condition of unbalanced power grid; l is the inductance of the inductance filter at the network side or the alternating current side, and R is the resistance of the inductance filter at the network side or the alternating current side; u. of_ledIs d-axis component u of three-phase AC phase voltage in two-phase synchronous rotating coordinate system_leqThe q-axis component of the three-phase alternating-current phase voltage under the two-phase synchronous rotating coordinate system is shown.

According to the photovoltaic grid-connected inverter control method and device and the inverter system, the three-phase line voltage u at the AC side of the inverter is obtained_eab、u_ebc、u_ecaAnd three phase line current i_a、i_b、i_cObtaining the inverseMaximum power point voltage U of converter DC side_dcmAnd maximum power point current i_dcmAnd controlling the inverter under the condition of unbalanced power grid according to an inverter controller established based on an EL equation model. Alternating current harmonic waves of the photovoltaic grid-connected inverter merged into the power grid when the power grid is unbalanced are reduced, dynamic decoupling of current is achieved, and stable state and dynamic performance of the inverter are improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

Fig. 1 is an application scene diagram of a control method for a photovoltaic grid-connected inverter according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of an L-type filter three-phase photovoltaic grid-connected inverter according to an embodiment of the present invention;

fig. 3 is a flowchart of a control method of a photovoltaic grid-connected inverter according to an embodiment of the present invention;

fig. 4 is a flow chart illustrating the establishment of an inverter controller according to an embodiment of the present invention;

fig. 5 is a schematic diagram illustrating a principle of compensating for a voltage imbalance of a power grid according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of a control device of a photovoltaic grid-connected inverter according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of a photovoltaic grid-connected inverter according to an embodiment of the present invention;

fig. 8 is a schematic structural diagram of a photovoltaic grid-connected inverter system according to an embodiment of the present invention.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

An application scenario diagram of a control method of a photovoltaic grid-connected inverter is provided in the embodiment of the present invention, as shown in fig. 1, a photovoltaic array 110 is converted into alternating current by an inverter 120 and is incorporated into a power grid 130, and the inverter 120 is controlled by an inverter controller 130. For the structure of the inverter 120, an L-filter three-phase pv grid-connected inverter is exemplified, and as shown in fig. 2, the structure of the L-filter three-phase pv grid-connected inverter is schematically illustrated, and a mathematical model of the three-phase pv grid-connected inverter in a three-phase abc coordinate system can be represented by formula (1).

Wherein Sa, Sb and Sc are switching functions, and S is generated when the upper bridge arm is switched on_k(k ═ a, b, c) ═ 1, and S is present when the lower arm is on_k(k＝a,b,c)＝0，S_ab、S_bc、S_caAs a function of the line switch, S_ab＝S_a-S_b、S_bc＝S_b-S_c、S_ca＝S_c-S_aWhen the upper bridge arm is on S_k(k ═ a, b, c) ═ 1, and S is present when the lower arm is on_k(k＝a,b,c)＝0；U_dcmThe maximum power point voltage of the photovoltaic array.

Based on the application scenario shown in fig. 1, taking the inverter controller 130 as an example, the method for controlling a photovoltaic grid-connected inverter provided in the embodiment of the present invention is described, as shown in fig. 3, the method includes the following steps:

301, acquiring a three-phase line voltage and a three-phase line current at an alternating current side of the inverter;

wherein, can utilize voltage sensor to obtain the three-phase line voltage u of the AC side of the inverter_eab、u_ebc、u_ecaObtaining three-phase line current i by means of a current sensor_a、i_b、i_c；

Step 302, obtaining the maximum power point voltage and the maximum power point current of the direct current side of the inverter;

wherein, the maximum power point voltage U can be obtained by tracking the MPPT of the maximum power point of the photovoltaic system_dcmAnd maximum power point current i_dcm。

And 303, controlling the inverter under the condition of unbalanced power grid according to an inverter controller established based on an EL equation model.

The model of the inverter is a mathematical model under a three-phase static coordinate system, the inverter controller is a passive controller based on an EL equation model, and the input of the inverter controller is u_eab、u_ebc、u_eca、i_a、i_b、i_c、U_dcmAnd i_dcmThe output of the inverter controller is a switching function S under a three-phase static coordinate system_a、S_b、S_c。

The embodiment of the invention provides a control method of a photovoltaic grid-connected inverter, and the control method, device and inverter system of the photovoltaic grid-connected inverter provided by the invention are used for obtaining three-phase line voltage u at the AC side of the inverter_eab、u_ebc、u_ecaAnd three phase line current i_a、i_b、i_cObtaining the maximum power point voltage U of the DC side of the inverter_dcmAnd maximum power point current i_dcmAnd controlling the inverter under the condition of unbalanced power grid according to an inverter controller established based on an EL equation model. Is reduced inWhen the power grid is unbalanced, the photovoltaic grid-connected inverter is merged into the alternating current harmonic wave of the power grid, the dynamic decoupling of the current is realized, and the steady state and the dynamic performance of the inverter are improved.

Before step 301 of the embodiment of the present invention, an inverter controller needs to be established in advance, and the following describes in detail the establishment process of the inverter controller, and as shown in fig. 4, is an establishment flowchart of the inverter controller, including the following steps:

step 401, for the three-phase line current i at the AC side of the inverter_a、i_b、i_cPerforming Park conversion to obtain alternating side current i under a two-phase synchronous rotating coordinate system_d、i_q；

Wherein, according to the matrixTo i_a、i_b、i_cPerforming Park conversion to obtain alternating side current i under a two-phase synchronous rotating coordinate system_d、i_q，

Step 402, performing a line switching function S on the inverter in a three-phase static coordinate system_ab、S_bc、S_caPerforming Park transformation to obtain a switching function S under a two-phase synchronous rotating coordinate system_ld、S_lq；

Wherein, according to the matrixFormula (3) is to perform Park transformation on the switch functions Sab, Sbc and Sca to obtain the switches under the two-phase synchronous rotating coordinate systemCorrelation function S_ld、S_lq。

Step 403, applying the three-phase line voltage u to the AC side of the inverter_eab、u_ebc、u_ecaPerforming conversion to obtain AC side voltage u under two-phase synchronous rotating coordinate system_led、u_leq；

Wherein, according to the matrix formula (3), u is paired_eab、u_ebc、u_ecaPerforming Park conversion to obtain alternating-current side voltage u under a two-phase synchronous rotating coordinate system_led、u_leq。

Wherein, there is no sequence between steps 401 and 403.

Step 404, i_d、i_q、u_led、u_leq、S_ld、S_lqSubstituting the mathematical model of the inverter in a three-phase static coordinate system to obtain the mathematical model of the inverter in a two-phase synchronous rotating coordinate system;

wherein, i is_d、i_q、u_led、u_leq、S_ld、S_lqSubstituting the formula (1) into the formula (1) to obtain a mathematical model of the inverter under a two-phase synchronous rotating coordinate systemIn the formula (4), i_d、i_qThe components of the alternating current on d and q axes; s_ld、S_lqComponents of the line switching function on d and q axes; u. of_led、u_leqThe components of the grid voltage on the d and q axes are shown.

And 405, establishing the inverter controller according to an EL equation model and a mathematical model of the inverter under a two-phase synchronous rotating coordinate system.

In order to obtain an inverter passive control strategy based on an EL equation (Euler-Lagrange equation) in step 405, an inverter controller needs to be established according to an EL equation model and a mathematical model of the inverter in a two-phase synchronous rotating coordinate system, and the method specifically includes the following steps:

step 405-1, converting a mathematical model of the inverter under a two-phase synchronous rotating coordinate system into an EL equation model;

wherein the formula (4) is converted into an EL modelIn the formula (5)The derivative of x with respect to time is represented,

step 405-2, injecting damping into an EL equation model to obtain a control law of the inverter controller;

wherein, the expected current vector of the photovoltaic grid-connected inverter is set as x_rError current vector x_e＝x_r-x. The formula (5) is changed intoError energy function ofThe passive controller based on the EL equation has good steady-state performance, but the convergence speed is slow, in order to accelerate the system convergence speed, damping is injected into the controller, so that an error energy function is quickly changed into zero, and damping injection R is adopted_dx_e＝(R+R_a)x_e，R_aIn order to damp the injection matrix,R_a1、R_a2for injected damping, when a damping injection matrix is introduced, the commonFormula (6) is changed toDeriving an energy error function Let the control rate of the controller beThe derivative of the energy error function with respect to timeSo that H_e(x)→0，x→x_rUnder the action of the formula (7), the photovoltaic grid-connected inverter can realize the control target and adjust R_aCan adjust H_e(x) To a speed of 0. From equation (7), the line switching function to achieve the control objective can be obtained

R_a1、R_a2For damping of the injection i_dr、i_qrIs i_d、i_qIs calculated from the expected value of (c). When the power grid is unbalanced, the photovoltaic grid-connected inverter is required to output three-phase balanced sine alternating current synchronous with the power grid voltage, and i is required_drIs a non-zero constant value, i_qrIs zero. If the switching loss is neglected, the power balance can be obtained according to the power balance of the AC/DC side in consideration of the normal balance grid limit voltage

In the formula i_dcmThe maximum power point current of the photovoltaic array is shown, and Um is the direct-current side voltage.

To verify dynamic decoupling of the current, the line switch function is substituted into equation (4) to obtainIt can be seen that the inverter controller in the embodiment of the invention can not only realize the control target, but also realize the dynamic decoupling of the current, as long as R is used_a1、R_a2And when the voltage is adjusted to a proper value, the steady-state and dynamic performances of the photovoltaic grid-connected inverter can be improved.

And 405-3, establishing an inverter controller according to the control law of the inverter controller.

Wherein the output of the inverter controller is a switching function S_a、S_b、S_c，△S＝S_a+S_b+S_cWherein, first, S is passed_ldAnd S_lqCarrying out inverse transformation from dq0 to abc to obtain a line switching function S under a three-phase static coordinate system_ab、S_bc、S_ca，

S_ab＝S_ldsin(ωt+30°)+S_lqcos(ωt+30°)，S_bc＝S_ldsin(ωt-90°)+S_lqcos(ωt-90°)，

S_ca＝S_ldsin(ωt+150°)+S_lqcos(ωt+150°)，S_abFrom S_ldAnd S_lqBy inverse transformation of dq0 to abc, by substituting equation (10) into equation (1), wherein △ u is u_eab+u_ebc+u_eca。

To overcome the effect of △ u on the AC current, according to equation (10), one can choose to do soThen there is

The PWM signal obtained by the formula (12) can realize that when the power grid is unbalanced, the voltage at two ends of the filter at the side of the alternating current power grid is sinusoidal, namely the power grid voltage u_eab、u_ebc、u_ecaWhen the voltage is unbalanced, the output voltage u of the photovoltaic grid-connected inverter_a、u_b、u_cThe compensation principle for an unbalance, i.e. a compensation of the grid voltage unbalance with an unbalanced output voltage of the inverter, is shown in fig. 5.

An embodiment of the present invention provides a control device for a photovoltaic grid-connected inverter, as shown in fig. 6, including:

a first obtaining module 610, configured to obtain a three-phase line voltage u at an ac side of the inverter_eab、u_ebc、u_ecaAnd three phase line current i_a、i_b、i_c；

A second obtaining module 620, configured to obtain a maximum power point voltage U at the dc side of the inverter_dcmAnd maximum power point current i_dcm；

A control module 630, configured to control the inverter according to an inversion controller established based on an EL equation model under the condition of unbalanced power grid, where the model of the inverter is a mathematical model in a three-phase stationary coordinate system, the inversion controller is a passive controller based on the EL equation model, and an input of the inversion controller is u_eab、u_ebc、u_eca、i_a、i_b、i_c、U_dcmAnd i_dcmThe output of the inverter controller is a switching function S under a three-phase static coordinate system_a、S_b、S_c。

Wherein the control module 630 includes:

a first converting unit 631, configured to convert the three-phase line current i on the ac side of the inverter acquired by the first acquiring module_a、i_b、i_cConverted into alternating side current i under two-phase synchronous rotating coordinate system_d、i_q；

A second converting unit 632, configured to convert the three-phase line voltage u on the ac side of the inverter obtained by the first obtaining module_eab、u_ebc、u_ecaConverted into AC side voltage u under two-phase synchronous rotating coordinate system_led、u_leq；

A damping input unit 633 for inputting a damping R_a1、R_a2；

A current calculating unit 534 for calculating a maximum power point voltage U_dcmAnd maximum power point current i_dcmCalculate i_d、i_qIs expected value i_dr、i_qr；

A process control unit 635 for controlling the process according to i_d、i_q、u_led、u_leq、R_a1、R_a2、U_dcm、i_dr、i_qrAnd calculating out line switch functions Sab, Sbc and Sca, calculating out switch functions Sa, Sb and Sc according to the line switch functions Sab, Sbc and Sca, and controlling the inverter under the condition of unbalanced power grid through the switch functions Sa, Sb and Sc.

Further, the processing control unit 635 includes:

a computing subunit 6351 for computing according to i_d、i_q、u_led、u_leq、R_a1、R_a2、U_dcm、i_dr、i_qrCalculating the switching function under the two-phase synchronous rotating coordinate system

Control output subunit 6352 for pair S_ldAnd S_lqCarrying out Park inverse transformation to obtain a line switch function S under a three-phase static coordinate system_ab、S_bc、S_ca；

A control execution subunit 6353 for calculating the switching function S according to the line switching function_a、S_b、S_cAnd by said switching function S_a、S_b、S_cAnd controlling the inverter under the condition of unbalanced power grid.

An embodiment of the present invention provides a pv grid-connected inverter structure, which can obtain a pv grid-connected inverter structure when a grid is unbalanced according to equations (2), (3), (9), (8), and (10), as shown in fig. 7, wherein an input of a control part is a three-phase line voltage u on an ac side_eab、u_ebc、u_ecaThree phase line current i_a、i_b、i_cMaximum power point voltage U of DC side of inverter_dcmAnd maximum power point current i_dcm(ii) a The output being a switching function S_a、S_b、S_cThrough S_a、S_b、S_cSpace Vector Pulse Width Modulation (SVPWM) is realized.

The embodiment of the present invention further provides a photovoltaic grid-connected inverter system, as shown in fig. 8, including a photovoltaic array 810, an inverter 820 and an inverter controller 830, where the inverter controller 830 is configured to obtain a three-phase line voltage u at an ac side of the inverter_eab、u_ebc、u_ecaAnd three phase line current i_a、i_b、i_c(ii) a Obtaining the maximum power point voltage U of the DC side of the inverter_dcmAnd maximum power point current i_dcm(ii) a Controlling the inverter under the condition of unbalanced power grid according to an inversion controller established based on an EL equation model, wherein the model of the inverter is a mathematical model under a three-phase static coordinate system, the inversion controller is a passive controller based on the EL equation model, and the input of the inversion controller is u_eab、u_ebc、u_eca、i_a、i_b、i_c、U_dcmAnd i_dcmThe output of the inverter controller is a switching function S under a three-phase static coordinate system_a、S_b、S_c。

Through the above description of the embodiments, those skilled in the art will clearly understand that the present invention may be implemented by software plus a necessary hardware platform, and certainly may be implemented by hardware, but in many cases, the former is a better embodiment. With this understanding in mind, all or part of the technical solutions of the present invention that contribute to the background can be embodied in the form of a software product, which can be stored in a storage medium, such as a ROM/RAM, a magnetic disk, an optical disk, etc., and includes instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods according to the embodiments or some parts of the embodiments of the present invention.

The present invention has been described in detail, and the principle and embodiments of the present invention are explained herein by using specific examples, which are only used to help understand the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.

Claims (2)

1. A control method for a photovoltaic grid-connected inverter is characterized by comprising the following steps:

obtaining three-phase line voltage u of inverter AC side_eab、u_ebc、u_ecaAnd three phase line current i_a、i_b、i_c；

Obtaining the maximum power point voltage U of the DC side of the inverter_dcmAnd maximum power point current i_dcm；

According to an inverter controller established based on an EL equation model, under the condition of unbalanced power grid, the inverter is controlledAnd line control, wherein the model of the inverter is a mathematical model under a three-phase static coordinate system, the inversion controller is a passive controller based on an EL equation model, and the input of the inversion controller is u_eab、u_ebc、u_eca、i_a、i_b、i_c、U_dcmAnd i_dcmThe output of the inverter controller is a switching function S under a three-phase static coordinate system_a、S_b、S_c；

According to the inverter controller based on EL equation model establishment, including:

for three-phase line current i at AC side of the inverter_a、i_b、i_cPerforming Park conversion to obtain alternating side current i under a two-phase synchronous rotating coordinate system_d、i_q；

Line switching function S for the inverter in a three-phase stationary coordinate system_ab、S_bc、S_caPerforming Park transformation to obtain a linear switching function S under a two-phase synchronous rotating coordinate system_ld、S_lq；

For the three-phase line voltage u at the AC side of the inverter_eab、u_ebc、u_ecaPerforming conversion to obtain AC side voltage u under two-phase synchronous rotating coordinate system_led、u_leq；

Will i_d、i_q、u_led、u_leq、S_ld、S_lqSubstituting the mathematical model of the inverter in a three-phase static coordinate system to obtain the mathematical model of the inverter in a two-phase synchronous rotating coordinate system;

establishing the inverter controller according to an EL equation model and a mathematical model of the inverter under a two-phase synchronous rotating coordinate system;

the mathematical model under the three-phase static coordinate system is expressed by formula (1):

wherein S is_a、S_b、S_cAs a function of switching, as a bridgeWhen arm is on S_k(k ═ a, b, c) ═ 1, and S is present when the lower arm is on_k(k＝a,b,c)＝0，S_ab、S_bc、S_caAs a function of the line switch, S_ab＝S_a-S_b、S_bc＝S_b-S_c、S_ca＝S_c-S_aWhen the upper bridge arm is on S_k(k ═ a, b, c) ═ 1, and S is present when the lower arm is on_k(k＝a,b,c)＝0；U_dcmThe maximum power point voltage of the photovoltaic array;

the establishing of the inverter controller according to the EL equation model and the mathematical model of the inverter under the two-phase synchronous rotating coordinate system comprises the following steps:

converting a mathematical model of the inverter under a two-phase synchronous rotating coordinate system into an EL equation model;

injecting damping into an EL equation model to obtain a control law of the inverter controller;

establishing an inversion controller according to the control law of the inversion controller, wherein the output of the inversion controller

S_a＝(1/3)*(S_ab-S_ca+△S)、

S_b＝(1/3)*(S_bc-S_ab+△S)、

S_c＝(1/3)*(S_ca-S_bc+△S)，△S＝S_a+S_b+S_c，

Wherein,

S_ab＝S_ldsin(ωt+30°)+S_lqcos(ωt+30°)，

S_bc＝S_ldsin(ωt-90°)+S_lqcos(ωt-90°)，

S_ca＝S_ldsin(ωt+150°)+S_lqcos(ωt+150°)，

$S_{ld}=(3L{\stackrel{\·}{i}}_{dr}-3{\mathrm{\ωLi}}_q+3{\mathrm{Ri}}_{dr}+3R_{a1}(i_{dr}-i_d)+\sqrt{3}{u}_{led})/\sqrt{3}{U}_{dcm},$

R_a1、R_a2for damping of the injection i_dr、i_qrIs i_d、i_qThe expected value of (d); l is the inductance of the inductive filter at the network side or the alternating current side, and R is the resistance of the inductive filter at the network side or the alternating current side; u. of_ledIs d-axis component u of three-phase AC phase voltage in two-phase synchronous rotating coordinate system_leqThe q-axis component of the three-phase alternating-current phase voltage under the two-phase synchronous rotating coordinate system is shown.

2. A photovoltaic grid-connected inverter control device is characterized by comprising:

a first acquisition module forIn obtaining three-phase line voltage u of inverter AC side_eab、u_ebc、u_ecaAnd three phase line current i_a、i_b、i_c；

A second obtaining module for obtaining the maximum power point voltage U of the DC side of the inverter_dcmAnd maximum power point current i_dcm；

The control module is used for controlling the inverter under the condition of unbalanced power grid according to an inversion controller established based on an EL equation model, wherein the model of the inverter is a mathematical model under a three-phase static coordinate system, the inversion controller is a passive controller based on the EL equation model, and the input of the inversion controller is u_eab、u_ebc、u_eca、i_a、i_b、i_c、U_dcmAnd i_dcmThe output of the inverter controller is a switching function S under a three-phase static coordinate system_a、S_b、S_c(ii) a The control module includes:

a first conversion unit, configured to convert the three-phase line current i on the ac side of the inverter acquired by the first acquisition module_a、i_b、i_cConverted into alternating side current i under two-phase synchronous rotating coordinate system_d、i_q；

A second conversion unit, configured to convert the three-phase line voltage u on the ac side of the inverter obtained by the first obtaining module_eab、u_ebc、u_ecaConverted into AC side voltage u under two-phase synchronous rotating coordinate system_led、u_leq；

A damping input unit for inputting a damping R_a1、R_a2；

A current calculating unit for calculating a maximum power point voltage U_dcmAnd maximum power point current i_dcmCalculate i_d、i_qIs expected value i_dr、i_qr；

A process control unit for controlling the process according to i_d、i_q、u_led、u_leq、R_a1、R_a2、U_dcm、i_dr、i_qrCalculatingOutgoing line switch function S_ab、S_bc、S_caAccording to said line switching function S_ab、S_bc、S_caCalculating a switching function S_a、S_b、S_cAnd by said switching function S_a、S_b、S_cControlling the inverter under the condition of unbalanced power grid; the mathematical model under the three-phase static coordinate system is expressed by formula (1):

wherein S is_a、S_b、S_cAs a function of the switching, S when the upper arm is switched on_k(k ═ a, b, c) ═ 1, and S is present when the lower arm is on_k(k＝a,b,c)＝0，S_ab、S_bc、S_caAs a function of the line switch, S_ab＝S_a-S_b、S_bc＝S_b-S_c、S_ca＝S_c-S_aWhen the upper bridge arm is on S_k(k ═ a, b, c) ═ 1, and S is present when the lower arm is on_k(k＝a,b,c)＝0；U_dcmThe maximum power point voltage of the photovoltaic array;

the process control unit includes:

a calculation subunit for calculating according to i_d、i_q、u_led、u_leq、R_a1、R_a2、U_dcm、i_dr、i_qrCalculating the linear switching function under the two-phase synchronous rotating coordinate system

Control output subunit for S pair_ldAnd S_lqCarrying out Park inverse transformation to obtain a line switch function S under a three-phase static coordinate system_ab、S_bc、S_ca；

Control execution submenuAn element for switching function S according to line_ab、S_bc、S_caCalculating a switching function S_a、S_b、S_cAnd by said switching function S_a、S_b、S_cControlling the inverter under the condition of unbalanced power grid; l is the inductance of the inductive filter at the network side or the alternating current side, and R is the resistance of the inductive filter at the network side or the alternating current side; u. of_ledIs d-axis component u of three-phase AC phase voltage in two-phase synchronous rotating coordinate system_leqThe q-axis component of the three-phase alternating-current phase voltage under the two-phase synchronous rotating coordinate system is shown.