CN109525124B - Grid-connected inverter control cabinet - Google Patents

Grid-connected inverter control cabinet Download PDF

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Publication number
CN109525124B
CN109525124B CN201811419366.7A CN201811419366A CN109525124B CN 109525124 B CN109525124 B CN 109525124B CN 201811419366 A CN201811419366 A CN 201811419366A CN 109525124 B CN109525124 B CN 109525124B
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grid
control
inverter
current
sorc
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CN109525124A (en
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杨兴武
李豪
徐依明
黄玉辉
符杨
赵剑飞
向大为
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Shanghai University of Electric Power
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Shanghai University of Electric Power
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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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/003—Constructional details, e.g. physical layout, assembly, wiring or busbar connections
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal 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
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K7/00—Constructional details common to different types of electric apparatus
    • H05K7/20—Modifications to facilitate cooling, ventilating, or heating
    • H05K7/2089—Modifications to facilitate cooling, ventilating, or heating for power electronics, e.g. for inverters for controlling motor
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K7/00—Constructional details common to different types of electric apparatus
    • H05K7/20—Modifications to facilitate cooling, ventilating, or heating
    • H05K7/2089—Modifications to facilitate cooling, ventilating, or heating for power electronics, e.g. for inverters for controlling motor
    • H05K7/20909—Forced ventilation, e.g. on heat dissipaters coupled to components

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a grid-connected inverter control cabinet, which comprises a box body and an inverter, wherein the box body comprises a box cover and an accommodating space, the inverter is placed in the accommodating space, the inverter comprises a processing component and a control component, and the processing component sends an output command to the control component to control the running state of the inverter. The control cabinet has the advantages that the control cabinet has the function of controlling the internal inverter, and the heat dissipation part is arranged in the control cabinet and can dissipate internal heat.

Description

Grid-connected inverter control cabinet
Technical Field
The invention relates to the technical field of power electronics, in particular to a grid-connected inverter control cabinet.
Background
Distributed power generation is receiving more and more attention to deal with energy crisis and reduce environmental pollution. The grid-connected inverter is used as a main power interface unit for connecting a distributed power generation system and a power grid, has very important position, and has important significance for researching the stability and the grid-connected current quality.
In order to improve the quality of grid-connected current, an LCL type filter is often used in engineering to inhibit high-frequency switching frequency subharmonics generated by a grid-connected inverter, and the resonance problem caused by the subharmonics can be solved by an active damping strategy such as a capacitor branch series resistor, a capacitor current feedback, a capacitor voltage feedback or a state feedback and the like. The damping method of capacitance current feedback is more applied due to simplicity and excellent performance.
Due to the fact that various nonlinear devices and unbalanced loads are contained in the distributed power grid, various low-order harmonics are contained at the PCC voltage. The traditional hysteresis control, Proportional Integral (PI) control and Proportional Resonance (PR) control strategies have weak inhibition capacity on voltage harmonics, and the repetitive control based on the internal model principle utilizes the periodicity of interference signals, so that the interference of periodic harmonics in the PCC voltage can be effectively inhibited, and the design is simple and convenient. However, the internal model is easily affected by the frequency fluctuation of the power grid, so that the resonance frequency of the internal model deviates from the fundamental wave and the harmonic frequency of the power grid, and the control performance is reduced.
Disclosure of Invention
This section is for the purpose of summarizing some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. In this section, as well as in the abstract and the title of the invention of this application, simplifications or omissions may be made to avoid obscuring the purpose of the section, the abstract and the title, and such simplifications or omissions are not intended to limit the scope of the invention.
The present invention has been made keeping in mind the above and/or other problems occurring in the prior art.
Therefore, one of the purposes of the invention is to provide a grid-connected inverter control cabinet.
In order to solve the technical problems, the invention provides the following technical scheme: the utility model provides a grid-connected inverter switch board, includes the box, includes case lid and accommodation space, the inverter is placed to accommodation space's inside, the inverter, including processing component and control assembly, processing component gives with its output's command control assembly, control the running state of inverter.
As a preferable scheme of the grid-connected inverter control cabinet of the present invention, wherein: the box cover is provided with a control panel, the control panel is connected with the processing assembly, and the opening and closing of the inverter are regulated and controlled through buttons on the control panel.
As a preferable scheme of the grid-connected inverter control cabinet of the present invention, wherein: the control assembly comprises a first capacitor, an IGBT control circuit board and a flat cable, wherein the IGBT is connected with the first capacitor through the flat cable and is connected with the IGBT control circuit board.
As a preferable scheme of the grid-connected inverter control cabinet of the present invention, wherein: the control component further comprises a second capacitor, the second capacitor is connected with the first capacitor in parallel, the capacitance of the second capacitor is smaller than that of the first capacitor, and the operation processing speed of the second capacitor is greater than that of the first capacitor.
As a preferable scheme of the grid-connected inverter control cabinet of the present invention, wherein: the flat cable comprises a first bus bar, a second bus bar and a third bus bar, and the IGBT comprises a first main terminal, a second main terminal, a third main terminal, a first auxiliary terminal and a second auxiliary terminal; the first main terminal is connected with the first busbar, the second main terminal is connected with the second busbar, and the third busbar is connected with the third main terminal.
As a preferable scheme of the grid-connected inverter control cabinet of the present invention, wherein: the first main terminal and the second main terminal are connected to form direct current, and the third main terminal outputs alternating current.
As a preferable scheme of the grid-connected inverter control cabinet of the present invention, wherein: the box body is internally provided with a heat radiation piece.
As a preferable scheme of the grid-connected inverter control cabinet of the present invention, wherein: the heat dissipation piece comprises heat dissipation fins, the heat dissipation fins are arranged behind the containing space in an array mode, and heat in the containing space is dissipated.
As a preferable scheme of the grid-connected inverter control cabinet of the present invention, wherein: the heat dissipation piece further comprises a heat dissipation fan, and the heat dissipation fan is placed on the heat dissipation piece and dissipates heat in the box body.
The invention has the beneficial effects that: the control cabinet has the function of controlling the internal inverter, and the heat dissipation part is arranged in the control cabinet and can dissipate internal heat.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced 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 based on these drawings without inventive exercise. Wherein:
fig. 1 is a structural schematic diagram of a view angle of the overall structure of the grid-connected inverter control cabinet of the invention;
FIG. 2 is a schematic view of the overall structure of the grid-connected inverter control cabinet of the present invention with the outer casing removed;
fig. 3 is a schematic view of another view of the overall structure of the grid-connected inverter control cabinet according to the present invention;
fig. 4 is a schematic view of the internal overall structure of the inverter of the grid-connected inverter control cabinet according to the present invention;
fig. 5 is a schematic view of the overall structure of the IGBT of the grid-connected inverter control cabinet of the present invention.
Fig. 6 is a three-phase LCL type grid-connected inverter topology and control structure diagram provided by the second order repetitive control method of the LCL type grid-connected inverter of the present invention;
fig. 7 is an open-loop system root trace diagram provided by the second-order repetitive control method of the LCL type grid-connected inverter of the present invention;
FIG. 8 is a structural diagram of an SORC closed-loop system in the second-order repetitive control method of the LCL grid-connected inverter according to the present invention;
fig. 9 is a p (z) amplitude-frequency characteristic diagram in the second-order repetitive control method of the LCL grid-connected inverter according to the present invention;
fig. 10 is a diagram of an internal model of the SORC in the second-order repetitive control method of the LCL type grid-connected inverter according to the present invention;
FIG. 11 is a comparison of CRC and SORC internal model amplitude-frequency characteristics in the second-order repetitive control method of the LCL grid-connected inverter according to the present invention;
fig. 12 shows the error output response of the closed loop system when Q is 0.95 in the second order repetitive control method of the LCL type grid-connected inverter according to the present invention;
FIG. 13 shows the error output response of the closed loop system when Q is a low pass filter in the second order repetitive control method of the LCL grid-connected inverter according to the present invention;
FIG. 14 shows the error output response of the closed loop system using CRC and SORC in the second order repetitive control method of the LCL grid-connected inverter of the present invention;
FIG. 15 shows the gain of the internal models of CRC and SORC at the fundamental wave and the second harmonic with the delta T in the second-order repetitive control method of the LCL grid-connected inverter0(%) graph of variation;
fig. 16(a) is a steady-state simulation waveform of PCC voltage and grid-connected current and a frequency spectrum thereof under a rated grid frequency in the second-order repetitive control method of the LCL type grid-connected inverter according to the present invention;
fig. 16(b) is a steady-state simulation waveform of CRC voltage and grid-connected current and a frequency spectrum thereof under a rated grid frequency in the second-order repetitive control method of the LCL type grid-connected inverter according to the present invention;
fig. 16(c) is steady state simulation waveforms of the SORC voltage and the grid-connected current and a frequency spectrum thereof under the rated grid frequency in the second-order repetitive control method of the LCL type grid-connected inverter of the present invention;
fig. 17(a) is a dynamic simulation waveform of CRC voltage and grid-connected current under a rated grid frequency in the second-order repetitive control method of the LCL type grid-connected inverter according to the present invention;
fig. 17(b) is a dynamic simulation waveform of the SORC voltage and the grid-connected current under the rated grid frequency in the second-order repetitive control method of the LCL type grid-connected inverter of the present invention;
fig. 18(a) is a simulated waveform of PCC voltage and grid-connected current and a spectrogram thereof when the grid frequency is 49.75Hz in the second-order repetitive control method of the LCL type grid-connected inverter according to the present invention;
fig. 18(b) is a simulated waveform of CRC voltage and grid-connected current and a spectrogram thereof when the grid frequency is 49.75Hz in the second-order repetitive control method of the LCL-type grid-connected inverter according to the present invention;
fig. 18(c) is a simulated waveform of the SORC voltage and the grid-connected current and a frequency spectrum thereof when the grid frequency is 49.75Hz in the second-order repetitive control method of the LCL type grid-connected inverter 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 detail below.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.
Furthermore, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
Referring to fig. 1 to 5, the present invention provides a grid-connected inverter control cabinet, which includes a cabinet 100 and an inverter 200, and the inverter 200 is placed in the cabinet 100.
Specifically, the case 100 includes a case cover 101 and an accommodating space 102, and the inverter 200 is placed in the accommodating space 102.
Inverter 200, including processing component 201 and control component 202, processing component 201 gives the control component 202 its command of output, controls the running state of inverter 200.
The cover 101 is provided with a control panel 101a, the control panel 101a is connected with the processing component 201, and the opening and closing of the inverter 200 are controlled by buttons on the control panel 101 a.
It should be noted that the control panel 101a and the processing module 201 are electrically connected by a wire or by an electrical connection.
It should be noted that the control assembly 202 includes a first capacitor 202a, an IGBT202b, an IGBT control circuit board 202e, and a bus 202c, and the IGBT202b is connected to the first capacitor 202a and the IGBT control circuit board 202e through the bus 202 c.
The control component 202 further includes a second capacitor 202d, the second capacitor 202d is connected in parallel with the first capacitor 202a, the capacitance of the second capacitor 202d is smaller than that of the first capacitor 202a, and the processing speed of the second capacitor 202d is greater than that of the first capacitor 202 a.
The flat cable 202c comprises a first bus bar 202c-1, a second bus bar 202c-2 and a third bus bar 202c-3, and the IGBT202b comprises a first main terminal 202b-1, a second main terminal 202b-2, a third main terminal 202b-3, a first auxiliary terminal 202b-4 and a second auxiliary terminal 202 b-5;
the first main terminal 202b-1 is connected to the first bus bar 202c-1, the second main terminal 202b-2 is connected to the second bus bar 202c-2, and the third bus bar 202c-3 is connected to the third main terminal 202 b-3.
The first main terminal 202b-1 and the second main terminal 202b-2 are connected to form a direct current, and the third main terminal 202b-3 outputs an alternating current.
In the present application, a main control circuit board is provided in the processing module 201 of the inverter 200, and a second-order repetitive control method is adopted in the main control circuit board when controlling the inverter 200.
Preferably, the control assembly 202 further includes an inductor 203, and the inductor 203 is disposed at the front ends of the first busbar 202c-1 and the second busbar 202c-2 to filter input power.
Preferably, the inverter in the present application is an LCL grid-connected inverter.
The second-order repetitive control method comprises the following steps:
firstly, detecting a required voltage and current component by using a voltage and current transformer, and acquiring a grid-connected current reference component under dq coordinates after detecting the voltage, grid-connected current and capacitance current at a PCC;
secondly, converting the detected voltage and current components under the abc three-phase static coordinate system into an alpha beta two-phase static coordinate system, and obtaining the position angle theta of the PCC voltage by the detected PCC voltage through a phase-locked loopPLLThen, carrying out abc/alpha beta coordinate transformation on the detected grid-connected current and the detected capacitance current;
a third step of combining the position angle theta in the second stepPLLAnd grid-connected current reference components under abc/alpha beta coordinates, and acquiring a grid-connected current command signal synchronous with the PCC voltage through dq/alpha beta coordinate conversion;
fourthly, subtracting the grid-connected current command signal which is synchronous with the PCC voltage and is obtained in the third step from the grid-connected current in the second step to obtain an error;
the fifth step: and (4) after passing through a second-order repetitive controller, inputting the error obtained in the previous step into a PWM (pulse-width modulation) modulator for modulation calculation, thereby driving the switching tube to act.
In particularThe topology and control structure of the three-phase LCL grid-connected inverter is shown in FIG. 6, in which VdcIs a DC side input voltage, L1Is an inverter side inductor, L2For the grid-side filter inductance, R1、R2Respectively, its parasitic resistance; c is a capacitor; u shapegAnd ZgRespectively the grid voltage and the grid impedance. The control system obtains a grid-connected current command signal synchronous with the PCC voltage through a phase-locked loop
Figure GDA0003041181510000061
The inverter adopts the compound control of series connection of SORC and P, and the LCL filter adopts a capacitance current feedback active damping method.
The P controller parameter Kp is first designed. Neglecting the network impedance Zg and the parasitic resistance, the equivalent continuous domain transfer function of the LCL filter can be obtained:
Figure GDA0003041181510000062
and Kc is a capacitance current feedback active damping coefficient. The parameters of the LCL filter are:
l1 ═ 4mH, L2 ═ 1mH, and C ═ 10 μ F. The transfer function can be regarded as being formed by connecting an integral element and a second-order oscillation element in series. The natural frequency and damping of the second order element are as follows:
Figure GDA0003041181510000063
to obtain the best damping effect, let ε be 0.707, and Kc be 63. The sampling period T is taken as 100 μ s, and a zero-order keeper discretization method is adopted for GLCL _ ic(s). The root locus with KP as the open loop gain is plotted as shown in fig. 7. The figure shows that the setting range of KP is 0-0.23 when the system is stable.
The second is to design the SORC controller. Taking the α -axis current control as an example, the structure of the SORC closed-loop system is shown in fig. 8. In the figure, P (z) is the equivalent control object of the SORC, i.e. the closed-loop transfer function in the case of only P control; w (z) is the forward channel of the SORC inner die; q (z) is an internal model improvement link; kr is the gain of SORC; s (z) is a low-pass filtering link; zm is a phase lead element that compensates for the phase lag introduced by P (z) and S (z).
The principle of setting Kr is to maintain the unity gain of the amplitude-frequency characteristic of krp (z) in the mid-low frequency band, and as can be seen from fig. 9, p (z) is already the unity gain in the low frequency band, so Kr takes 1. The order m of the lead element zm is adapted to be 9 to better compensate for the phase lag of p (z) and s (z).
The core of the repetitive controller is an internal model link. The designed SORC internal mold structure is shown in FIG. 10. The SORC inner-die becomes the traditional repetitive control (CRC) inner-die when the coefficients on the inner-die forward path become 0 and 1.
Let q (z) be 1, and plot the amplitude-frequency characteristics of CRC and SORC internal models as shown in fig. 11. It can be known that the gain and bandwidth of the inner model of the SORC are large at the fundamental wave and each harmonic frequency, and when the grid frequency fluctuates, the inner model can still maintain high control gain, which indicates that the SORC can improve the robustness of the system to the grid frequency change. Whereas q (z) in practical applications typically takes a constant less than 1 (e.g. 0.95) or a low pass filter. Wherein, the expression of the low-pass filter is:
Figure GDA0003041181510000071
in order to ensure that the amplitude-frequency characteristic of the SORC internal model has a faster attenuation speed at a middle-high frequency so as to improve the stability of a system, a low-pass filter with a cut-off frequency of 1.06kHz is designed, and the expression is as follows:
Figure GDA0003041181510000072
FIG. 12 shows a graph of the error output response of the closed loop system when the command signal is sinusoidal, with Q (z) taken as 0.95 and the low pass filter, respectively. It can be seen that q (z) is 0.95 or a low pass filter, which can make the system steady state error converge to zero.
As can be seen from fig. 10, the delay link (z-N) on the forward channel of the SORC internal model is one more than the CRC, and qualitative analysis shows that: the dynamic performance of the SORC system is somewhat degraded compared to the CRC system. Fig. 13 shows the error output response of the system using CRC and SORC when the command signal is sin (2 tt 50). It can be seen that the error response at steady state is 0, which indicates that both strategies can make the system have excellent steady state performance. From the aspect of error convergence speed, the error can be converged to zero by adopting the method that SORC is 2 power frequency periods more than CRC.
Assuming that the grid fundamental frequency is changed from 1/T0 to 1/[ T0(1+ δ T0) ], the gain of the CRC and SORC internal models at the fundamental and second harmonics is plotted as a function of δ T0 (%), as shown in FIGS. 14 and 15. Analysis from the graph: the gains in the CRC and SORC modes at the fundamental and second harmonic frequencies both decrease with increasing δ T0 (%), but the gains in the SORC mode decrease more slowly. Taking δ T0 (%) as 0.5 as an example, when the grid frequency becomes 49.75Hz or 50.25Hz, the gain of the CRC internal model at the fundamental wave is only 30dB, while the gain of the SORC internal model can reach 65 dB. Therefore, the designed SORC has stronger robustness to the change of the power grid frequency, and the aim of realizing higher steady-state precision without adjusting the parameters of the controller when the power grid frequency is changed is fulfilled.
In order to verify the correctness of the above theoretical analysis and the effectiveness of the designed SORC strategy, a simulation model of the three-phase LCL type grid-connected inverter is built under the Matlab/Simulink simulation environment. In order to simulate nonlinear devices and local loads, harmonics with harmonic numbers of 5, 7, 11, 13, 17 and 19 are injected into the power grid, and the content of the harmonics is 2.85%, 2.52%, 2.36%, 2.05%, 1.89% and 1.57%, respectively.
Firstly, testing the steady-state performance of the grid-connected inverter under the rated grid frequency. Fig. 16(a) - (c) show steady state simulation waveforms and frequency spectrums of PCC voltage and grid-connected current by applying CRC and SORC. As can be seen from the figure, the harmonic waves can be effectively suppressed by the two strategies, and the grid-connected current quality is improved.
And secondly, testing the dynamic performance of the grid-connected inverter. FIGS. 17(a) and (b) show graphs of dynamic simulation waveforms of grid-connected current using CRC and SORC. It can be seen from fig. 17(a) and (b) that the error convergence time of the system is 2 power frequency cycles more than that of the system using CRC, which is consistent with the foregoing theoretical analysis.
Fig. 18(a) - (c) show simulated waveforms and frequency spectrums of CRC and SORC, PCC voltage and grid-connected current, respectively, when the grid frequency is 49.75 Hz. As can be seen from the figure: the grid frequency offset has a large influence on the CRC performance: firstly, the effective value (4.914A) of grid-connected current is more deviated from the specified value (5A) than the SORC (5.008A); and the second harmonic content of 11, 13, 17 and 19 in the current is higher. Therefore, the robustness of the SORC to the grid frequency is strong, i.e. the SORC can suppress the harmonics in the PCC voltage more effectively when the frequency changes. Simulation results under two working conditions of rated power grid frequency and power grid frequency change are integrated, and the designed SORC control strategy is proved to have remarkable superiority.
Preferably, referring to fig. 1 to 5, a heat sink 103 is disposed in the box 100, and the heat sink 103 includes heat dissipation fins 103a, which are arranged in an array behind the accommodating space 102 to dissipate heat in the accommodating space 102. The heat sink 103 further includes a heat sink fan 103b, and the heat sink fan 103b rests on the heat sink 103a to dissipate heat inside the case 100.
It should be noted that the above-mentioned embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.

Claims (4)

1. The utility model provides a grid-connected inverter switch board which characterized in that: comprises the steps of (a) preparing a mixture of a plurality of raw materials,
a case (100) including a case cover (101) and an accommodating space (102), an inverter (200) being placed in the accommodating space (102),
the inverter (200) comprises a processing component (201) and a control component (202), the processing component (201) sends an output command to the control component (202) to control the running state of the inverter (200), a control panel (101a) is arranged on the box cover (101), the control panel (101a) is connected with the processing component (201), the opening and closing of the inverter (200) are regulated and controlled through buttons on the control panel (101a), the control component (202) comprises a first capacitor (202a), an IGBT (202b), an IGBT control circuit board (202e) and a flat cable (202c),
the IGBT (202b) is connected with the first capacitor (202a) through the flat cable (202c) and is connected with the IGBT control circuit board (202e), the control assembly (202) further comprises a second capacitor (202d), the second capacitor (202d) is connected with the first capacitor (202a) in parallel, the capacitance of the second capacitor (202d) is smaller than that of the first capacitor (202a), the operational processing speed of the second capacitor (202d) is larger than that of the first capacitor (202a), the flat cable (202c) comprises a first bus bar (202c-1), a second bus bar (202c-2) and a third bus bar (202c-3),
the IGBT (202b) comprises a first main terminal (202b-1), a second main terminal (202b-2), a third main terminal (202b-3), a first auxiliary terminal (202b-4) and a second auxiliary terminal (202 b-5);
the first main terminal (202b-1) is connected with the first busbar (202c-1), the second main terminal (202b-2) is connected with the second busbar (202c-2), the third busbar (202c-3) is connected with the third main terminal (202b-3), the first main terminal (202b-1) and the second main terminal (202b-2) are connected with each other through direct current, alternating current is output by the third main terminal (202b-3), a main control circuit board is arranged in the processing assembly (201), and a second-order repetitive control method is adopted in the main control circuit board when the inverter (200) is controlled, and the second-order repetitive control method comprises the following steps:
firstly, detecting a required voltage and current component by using a voltage and current transformer, and acquiring a grid-connected current reference component under dq coordinates after detecting the voltage, grid-connected current and capacitance current at a PCC;
secondly, converting the detected voltage and current components under the abc three-phase static coordinate system into an alpha beta two-phase static coordinate system, and obtaining the position angle theta of the PCC voltage by the detected PCC voltage through a phase-locked loopPLLThen, the detected grid-connected current is detectedAnd carrying out abc/alpha beta coordinate conversion on the capacitance current;
a third step of combining the position angle theta in the second stepPLLAnd grid-connected current reference components under abc/alpha beta coordinates, and acquiring a grid-connected current command signal synchronous with the PCC voltage through dq/alpha beta coordinate conversion;
fourthly, subtracting the grid-connected current command signal which is synchronous with the PCC voltage and is obtained in the third step from the grid-connected current in the second step to obtain an error;
the fifth step: the error obtained in the previous step is input to a PWM modulator for modulation calculation after passing through a second-order repetitive controller, so as to drive a switching tube to act,
the second-order repetitive controller adopts compound control of series connection of SORC and P, the LCL filter adopts a capacitance current feedback active damping method, a parameter Kp of the P controller is designed, and an equivalent continuous domain transfer function of the LCL filter can be obtained by neglecting the impedance Zg and parasitic resistance of a power grid:
Figure FDA0003067248220000021
wherein, Kc is a capacitance current feedback active damping coefficient, the transfer function can be regarded as being formed by connecting an integral link and a second-order oscillation link in series, wherein the natural frequency and the damping of the second-order link are as follows:
Figure FDA0003067248220000022
to obtain the optimal damping effect, if epsilon is 0.707, Kc is 63;
and further comprising the following steps of designing the SORC controller:
in the SORC closed-loop system structure, P (z) is an equivalent control object of the SORC, namely a closed-loop transfer function only under the control of P;
w (z) is used as a forward channel of an SORC internal model, Q (z) is used as an internal model improvement link, Kr is used as a gain of the SORC, S (z) is used as a low-pass filtering link, zm is used as a phase advance link and is used for compensating phase lag brought by P (z) and S (z), Kr is 1, and the order m of the advance link zm is 9;
when the coefficients on the inner model forward channel become 0 and 1, the SORC inner model becomes the traditional repetitive control (CRC) inner model;
in order to ensure that the amplitude-frequency characteristic of the SORC internal model has a faster attenuation speed at a middle-high frequency so as to improve the stability of a system, a low-pass filter with a cut-off frequency of 1.06kHz is defined, and the expression is as follows:
Figure FDA0003067248220000023
when q (z) takes 0.95 or a low pass filter, the system is stable and the low pass filter converges the system steady state error to zero.
2. The grid-connected inverter control cabinet according to claim 1, characterized in that: a heat dissipation piece (103) is arranged in the box body (100).
3. The grid-connected inverter control cabinet according to claim 2, characterized in that: the heat dissipation member (103) comprises heat dissipation fins (103a) which are arranged behind the accommodating space (102) in an array mode and dissipate heat in the accommodating space (102).
4. The grid-connected inverter control cabinet according to claim 3, characterized in that: the heat sink (103) further comprises a heat sink fan (103b), and the heat sink fan (103b) rests on the heat sink (103a) and dissipates heat within the case (100).
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