CN114050597B - Cooperative active heat control system and method for multiple grid-connected inverters - Google Patents

Cooperative active heat control system and method for multiple grid-connected inverters Download PDF

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CN114050597B
CN114050597B CN202111376296.3A CN202111376296A CN114050597B CN 114050597 B CN114050597 B CN 114050597B CN 202111376296 A CN202111376296 A CN 202111376296A CN 114050597 B CN114050597 B CN 114050597B
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grid
connected inverter
unit
switching frequency
loss
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CN114050597A (en
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许涛
谭鹏飞
高峰
方旌扬
孟祥剑
周康佳
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Shandong University
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Shandong University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The present disclosure provides a collaborative active thermal control system and method for a multi-grid-connected inverter, comprising the steps of: acquiring power loss and a correlation matrix of each grid-connected inverter unit; performing correlation grouping of grid-connected inverter units according to the correlation matrix; obtaining the switching frequency of the same group of grid-connected inverter units based on the grouping information of the relevance grouping, the switching frequency adjusting limit value of the weighted switching frequency adjusting unit and the switching frequency adjusting limit value of the global synchronous pulse width modulating unit; and obtaining the optimal PWM phase of the grid-connected inverter units in the same group according to the obtained switching frequency and the global synchronous pulse width modulation unit. The method and the device synchronously adjust PWM frequency of the inverter cluster, compensate heat loss and reduce junction temperature fluctuation of the inverter cluster.

Description

Cooperative active heat control system and method for multiple grid-connected inverters
Technical Field
The disclosure belongs to the technical field of electrical control, and particularly relates to a cooperative active heat control system and method of a multi-grid-connected inverter.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
With the continuous development of renewable energy power generation technology, the installed capacity of renewable energy is rapidly increasing. The grid-connected inverter is key equipment for connecting renewable energy sources such as a photovoltaic panel, a wind driven generator and the like into a power grid. A large number of grid-connected inverters are required to be equipped in a large renewable energy power generation system typified by a centralized photovoltaic power station and a wind farm.
The renewable energy source power generation has the characteristics of randomness and fluctuation, and the power generated to the power grid through the grid-connected inverter also fluctuates, so that the heat loss generated by the power switching device in the inverter also fluctuates, and the temperature fluctuation along the heat path causes repeated expansion and contraction of each layer of the power switching device. Because of the large difference in thermal expansion coefficients of the materials of the adjacent layers of the power switch device package, shear stress is generated on the interfaces between the layers of different materials, so that mechanical-thermal fatigue of the packaging material layers is caused, and finally, thermal failure of the power switch device is caused.
In order to reduce thermal stress on the power device and improve the service life of the device, various nationists sequentially propose an active thermal control method to compensate the loss of the power device in real time by controlling a variable related to the loss, such as increasing the switching frequency, so as to reduce the amplitude of junction temperature fluctuation.
The inventor knows that the prior art can only protect the inverter from overheat damage under some extreme working conditions by limiting the highest junction temperature, and the effect of smoothing the junction temperature is limited; the method for adjusting the voltage of the driving circuit needs to add an additional circuit, increases the cost, has extremely high control precision and is difficult to apply; by increasing the switching frequency, the switching frequency is increased when the input power is reduced, and the heat loss is increased, so that the fluctuation of the junction temperature can be reduced, but the average junction temperature is increased at the same time, and the service life of the inverter is not prolonged.
Disclosure of Invention
In order to solve the above problems, the present disclosure provides a coordinated active thermal control system and method for a multi-grid-connected inverter, while reducing junction temperature fluctuations and average junction temperature.
According to some embodiments, a first aspect of the present disclosure provides a collaborative active thermal control system for a multi-grid-connected inverter, which adopts the following technical scheme:
A collaborative active thermal control system of a plurality of grid-connected inverters comprises a plurality of grid-connected inverter modules which are consistent in structure and are mutually connected in a communication mode; each grid-connected inverter module comprises a grid-connected inverter unit, a correlation grouping unit, a weighted switching frequency adjusting unit and a global synchronous pulse width modulating unit which are sequentially connected, wherein communication connection among the grid-connected inverter modules is established by a communication line among the grid-connected inverter units;
based on the correlation grouping, the weighted switching frequency adjusting unit and the global synchronous pulse width modulating unit, the switching frequency of the grid-connected inverter units in the same group is obtained; and obtaining the optimal PWM phase of the same group of grid-connected inverter units under the action of the global synchronous pulse width modulation unit according to the obtained switching frequency.
As a further technical limitation, each grid-connected inverter module further comprises a power generation unit connected with the input end of the grid-connected inverter unit, and the output ends of the grid-connected inverter units are connected with a power grid through a public grid-connected point.
As a further technical limitation, the data information of each grid-connected inverter unit is shared to other grid-connected inverter units through a communication line, and the other grid-connected inverter units utilize the received data information to perform PWM phase and frequency control, so that cooperative active thermal control of the multiple grid-connected inverters is realized.
According to some embodiments, a second aspect of the present disclosure provides a collaborative active thermal control method for a multi-grid-connected inverter, which adopts the following technical scheme:
a cooperative active heat control method of a multi-grid-connected inverter comprises the following steps:
acquiring a correlation matrix of the grid-connected inverter cluster according to the output power of each grid-connected inverter unit;
Performing correlation grouping of grid-connected inverter units according to the correlation matrix;
acquiring the power loss of each grid-connected inverter unit;
obtaining an estimated junction temperature of each grid-connected inverter unit through power loss and a thermal network model;
acquiring life loss according to the estimated junction temperature in the group, and acquiring the weight of each inverter in the weighted switching frequency adjusting unit;
Obtaining the switching frequency of the same group of grid-connected inverter units based on the grouping information of the relevance grouping, the switching frequency adjusting limit value of the weighted switching frequency adjusting unit and the switching frequency adjusting limit value of the global synchronous pulse width modulating unit;
And obtaining the optimal PWM phase of the grid-connected inverter units in the same group according to the obtained switching frequency and the global synchronous pulse width modulation unit.
As a further technical definition, the process of obtaining the correlation matrix of each grid-connected inverter unit is as follows:
acquiring correlation coefficients of any two grid-connected inverters;
And calculating correlation coefficients between every two inverters in all the inverters, and arranging according to the number of the inverters to obtain a correlation matrix of the grid-connected inverter cluster.
Further, when correlation grouping of the grid-connected inverter units is carried out, selecting the grid-connected inverter unit with the largest correlation coefficient in the correlation matrix for correlation grouping, and then selecting the grid-connected inverter unit with the largest correlation coefficient with the selected grid-connected inverter unit in the group to be added into the group as the next grid-connected inverter unit; repeatedly selecting the inverter with the largest correlation coefficient with the grid-connected inverter units selected in the group until the number of the grid-connected inverter units in the group reaches a set value, thereby completing a grouping; the next group is then grouped until all grid-connected inverter units are grouped.
As a further technical definition, the process of obtaining the power loss of each grid-connected inverter unit is as follows:
obtaining the switching frequency, the output current, the direct current voltage, the modulation ratio, the junction temperature and the power factor angle of each grid-connected inverter unit, and calculating and estimating the junction temperature;
and obtaining the power loss according to the estimated junction and the thermal network model.
Further, the process of obtaining the estimated junction temperature of each grid-connected inverter unit includes:
The heat network model of the grid-connected inverter is formed by connecting a plurality of heat resistance and heat capacity units in series, each heat resistance and heat capacity unit is formed by connecting a heat resistance and a heat capacity in parallel, the tail end of the heat network model is an equivalent voltage source of ambient temperature, the head end of the heat network model is input into an equivalent current source of power loss, and the voltage generated at the head end of the heat network model is the calculated estimated junction temperature.
Further, the process of obtaining the life loss of each grid-connected inverter unit is as follows:
And obtaining all thermal cycles in the estimated junction temperature by a rain flow counting method, and calculating life loss generated by the thermal cycles according to a life model.
Further, in the weighted switching frequency adjusting unit, a weighted loss value and a loss reference value are obtained according to the power loss of all grid-connected inverter units in the group, an increased value of PWM switching frequency of the same group of grid-connected inverter units is obtained based on the difference value between the weighted loss value and the loss reference value, and the switching frequency of the same group of grid-connected inverter units is obtained by combining the switching frequency of each grid-connected inverter unit.
According to some embodiments, a third aspect of the present disclosure provides a computer-readable storage medium, which adopts the following technical solutions:
a computer readable storage medium having stored thereon a program which when executed by a processor implements steps in a method of collaborative active thermal control of a multiple grid-tie inverter according to the first aspect of the present disclosure.
According to some embodiments, a fourth aspect of the present disclosure provides an electronic device, which adopts the following technical solutions:
An electronic device comprising a memory, a processor and a program stored on the memory and executable on the processor, the processor implementing steps in a method of collaborative active thermal control of a multiple grid-tie inverter according to the first aspect of the disclosure when the program is executed.
Compared with the prior art, the beneficial effects of the present disclosure are:
On the basis of the traditional single-machine active heat control method, the method of Global Synchronous Pulse Width Modulation (GSPWM) is introduced during parallel operation of a plurality of inverters, so that the switching frequency is reduced on the premise of meeting the requirement of grid-connected harmonic waves, and the average junction temperature is reduced. Meanwhile, real-time correlation grouping is carried out on grid-connected inverter units, loss weighted cooperative active heat control is introduced into each grouping, PWM frequency of the inverter cluster is synchronously regulated, heat loss is compensated, and junction temperature fluctuation of the inverter cluster is reduced.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate and explain the exemplary embodiments of the disclosure and together with the description serve to explain the disclosure, and do not constitute an undue limitation on the disclosure.
FIG. 1 is a schematic diagram of a coordinated active thermal control system for a multiple grid-tie inverter in accordance with an embodiment of the present disclosure;
FIG. 2 is a flow chart of a method of coordinated active thermal control of a multiple grid-tie inverter in a second embodiment of the disclosure;
fig. 3 is a flow chart of a correlation packet in a second embodiment of the present disclosure.
The specific embodiment is as follows:
The disclosure is further described below with reference to the drawings and examples.
It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments in accordance with the present disclosure. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
Embodiments of the present disclosure and features of embodiments may be combined with each other without conflict.
Example 1
The first embodiment of the disclosure introduces a cooperative active thermal control system of a multi-grid-connected inverter.
The cooperative active heat control system of the multiple grid-connected inverters shown in fig. 1 comprises a plurality of grid-connected inverter modules which are consistent in structure and are connected with each other in a communication manner; each grid-connected inverter module comprises a grid-connected inverter unit, a correlation grouping unit, a weighted switching frequency adjusting unit and a global synchronous pulse width modulating unit which are sequentially connected, wherein communication connection among the grid-connected inverter modules is established by a communication line among the grid-connected inverter units; each grid-connected inverter module further comprises a power generation unit connected with the input end of the grid-connected inverter unit, and the output ends of the grid-connected inverter units are connected with a power grid through a public grid-connected point; the data information of each grid-connected inverter unit is shared to other grid-connected inverter units through a communication line, and the other grid-connected inverter units utilize the received data information to carry out PWM phase and frequency control, so that the cooperative active thermal control of the multiple grid-connected inverters is realized.
On the basis of the traditional single-machine active heat control method, global Synchronous Pulse Width Modulation (GSPWM) is introduced when a plurality of inverters are in parallel operation, so that the switching frequency is reduced on the premise of meeting the requirement of grid-connected harmonic waves, and the average junction temperature is reduced; meanwhile, real-time correlation grouping is carried out on grid-connected inverter units, loss weighted cooperative active heat control is introduced into each grouping, PWM frequency of the inverter cluster is synchronously regulated, heat loss is compensated, and junction temperature fluctuation of the inverter cluster is reduced.
Example two
The second embodiment of the disclosure introduces a cooperative active thermal control method of a plurality of grid-connected inverters based on the cooperative active thermal control system of the plurality of grid-connected inverters described in the first embodiment.
The cooperative active heat control method of the multi-grid-connected inverter shown in fig. 2 comprises the following steps:
Step S01: acquiring a correlation matrix of the grid-connected inverter cluster according to the output power of each grid-connected inverter unit;
step S02: performing correlation grouping of grid-connected inverter units according to the correlation matrix;
step S03: acquiring the power loss of each grid-connected inverter unit;
step S04: obtaining an estimated junction temperature of each grid-connected inverter unit through power loss and a thermal network model;
Step S05: acquiring life loss according to the estimated junction temperature in the group, and further acquiring the weight of each inverter in the weighted switching frequency adjusting unit;
step S06: obtaining the switching frequency of the same group of grid-connected inverter units based on the grouping information of the relevance grouping, the switching frequency adjusting limit value of the weighted switching frequency adjusting unit and the switching frequency adjusting limit value of the global synchronous pulse width modulating unit;
step S07: and obtaining the optimal PWM phase of the grid-connected inverter units in the same group according to the obtained switching frequency and the global synchronous pulse width modulation unit.
As one or more embodiments, in step S01, when the correlation matrix is calculated, the correlation coefficients of any two grid-connected inverters are:
Wherein, P i,load and P j,load respectively represent the output power of the ith and jth inverters, M is the number of the inverters;
Calculating correlation coefficients of all inverters pairwise, and arranging according to inverter numbers to obtain a correlation matrix of the grid-connected inverter cluster:
In step S02, when performing correlation grouping, selecting two grid-connected inverter units with the largest correlation coefficient in the correlation matrix for performing correlation grouping, and then selecting a grid-connected inverter unit with the largest correlation coefficient with the selected grid-connected inverter units in the group, and adding the selected grid-connected inverter unit into the group as the next grid-connected inverter unit; repeatedly selecting the inverter with the largest correlation coefficient with the grid-connected inverter units selected in the group until the number of the grid-connected inverter units in the group reaches a set value, thereby completing a grouping; the next group is then grouped until all grid-connected inverter units are grouped.
As one or more embodiments, in step S03, for all grid-connected inverter units, the switching frequency f m,SW, the output current I m, the direct-current voltage V DC, and the modulation ratio m are collected, and the turn-on loss P cond(T) and the switching loss P SW(T) of the IGBTs, and the turn-on loss P cond(D) and the switching loss P SW(D) of the antiparallel diodes in the grid-connected inverter are calculated:
Wherein ,VCE0、rCE、Eon+off、TCESW、VF0、rF、Err、TCErr、Iref、Vref、KV、Ki is available from the data manual of the selected power switching device.
The power loss P T of the IGBT and the power loss P D of the antiparallel diode can be obtained by the following formulas:
PT＝Pcond(T)+PSW(T) (7)
PD＝Pcond(D)+PSW(D) (8)
As one or more embodiments, in step S04, calculation by the thermal network model is required when performing power loss calculation. The heat network model of the grid-connected inverter is formed by connecting a plurality of heat resistance and heat capacity units in series, each heat resistance and heat capacity unit is formed by connecting a heat resistance and a heat capacity in parallel, the tail end of the heat network model is an equivalent voltage source of ambient temperature, the head end of the heat network model is input into an equivalent current source of power loss, and the voltage generated at the head end of the heat network model is the calculated estimated junction temperature.
And inputting the power loss P T of the IGBT and the power loss P D of the anti-parallel diode into a thermal network model to obtain the estimated junction temperature T j of the grid-connected inverter unit.
As one or more embodiments, in step S05, when obtaining the weight of each inverter in the weighted switching frequency adjustment unit, all thermal cycles in the estimated junction temperature are extracted by a rain flow counting method to obtain junction temperature fluctuation Δt j and average junction temperature T m of each thermal cycle, and the estimated cycle number N f of each thermal cycle is calculated according to the Coffin-Manson life model:
wherein a, n, E a, k are constants.
Obtaining service life damage of the grid-connected inverter unit according to a linear accumulated damage theory:
Where N i is the actual number of cycles per estimated number of cycles N i.
The weight w m of each inverter in the weighted switching frequency adjustment unit can be calculated as:
As one or more embodiments, in step S06, the weighted switching frequency adjustment unit first calculates a weighted loss value P weighted from the power losses P m,loss of all the inverters in the group:
The weighted loss value P weighted is input to a low pass filter to obtain a loss reference value P ref, and then Δp is obtained by the difference between P ref and P weighted. The delta P is used to obtain the increment delta f of the PWM frequency:
The PWM frequency increment Δf is added to the minimum PWM frequency to obtain PWM frequency f SW.
According to the embodiment, on the basis of a traditional single-machine active heat control method, a Global Synchronous Pulse Width Modulation (GSPWM) method is introduced during parallel operation of a plurality of inverters, so that on the premise of meeting grid-connected harmonic requirements, the switching frequency is reduced, and the average junction temperature is reduced. Meanwhile, real-time correlation grouping is carried out on grid-connected inverter units, loss weighted cooperative active heat control is introduced into each grouping, PWM frequency of the inverter cluster is synchronously regulated, heat loss is compensated, and junction temperature fluctuation of the inverter cluster is reduced.
Example III
A third embodiment of the present disclosure provides a computer-readable storage medium.
A computer-readable storage medium having stored thereon a program which, when executed by a processor, implements steps in a coordinated active thermal control method of a multiple grid-tie inverter as described in embodiment two of the present disclosure.
The detailed steps are the same as those of the cooperative active heat control method of the multi-grid-connected inverter provided in the second embodiment, and are not described herein again.
Example IV
The fourth embodiment of the disclosure provides an electronic device.
An electronic device comprising a memory, a processor and a program stored on the memory and executable on the processor, wherein the processor, when executing the program, implements the steps in a coordinated active thermal control method of a multiple grid-tie inverter according to embodiment two of the present disclosure.
The detailed steps are the same as those of the cooperative active heat control method of the multi-grid-connected inverter provided in the second embodiment, and are not described herein again.
The foregoing description of the preferred embodiments of the present disclosure is provided only and not intended to limit the disclosure so that various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.

Claims (4)

1. The cooperative active heat control method of the multi-grid-connected inverter is characterized by comprising the following steps of:
acquiring a correlation matrix of the grid-connected inverter cluster according to the output power of each grid-connected inverter unit;
Performing correlation grouping of grid-connected inverter units according to the correlation matrix;
acquiring the power loss of each grid-connected inverter unit;
obtaining an estimated junction temperature of each grid-connected inverter unit through power loss and a thermal network model;
acquiring life loss according to the estimated junction temperature in the group, and acquiring the weight of each inverter in the weighted switching frequency adjusting unit;
Obtaining the switching frequency of the same group of grid-connected inverter units based on the grouping information of the relevance grouping, the switching frequency adjusting limit value of the weighted switching frequency adjusting unit and the switching frequency adjusting limit value of the global synchronous pulse width modulating unit;
obtaining the optimal PWM phase of the same group of grid-connected inverter units according to the obtained switching frequency and the global synchronous pulse width modulation unit;
When the correlation matrix is calculated, the correlation coefficient r ij of any two grid-connected inverters is as follows:
Wherein, P i,load and P j,load respectively represent the output power of the ith and jth inverters, M is the number of the inverters;
calculating correlation coefficients of all inverters pairwise, and arranging according to inverter numbers to obtain a correlation matrix R of the grid-connected inverter cluster:
When correlation grouping is carried out, selecting two grid-connected inverter units with the largest correlation coefficient in the correlation matrix for correlation grouping, and then selecting the grid-connected inverter unit with the largest correlation coefficient with the selected grid-connected inverter units in the group to be added into the group as the next grid-connected inverter unit; repeatedly selecting the inverter with the largest correlation coefficient with the grid-connected inverter units selected in the group until the number of the grid-connected inverter units in the group reaches a set value, thereby completing a grouping; then grouping the next group until all grid-connected inverter units are grouped;
The method comprises the steps that for all grid-connected inverter units, the switching frequency f m,SW, the output current I m, the direct-current voltage V DC and the modulation ratio m are collected, and the conduction loss P cond(T) and the switching loss P SW(T) of IGBT, the conduction loss P cond(D) of anti-parallel diodes and the switching loss P SW(D) of the grid-connected inverter are calculated:
Wherein ,VCE0、rCE、Eon+off、TCESW、VF0、rF、Err、TCErr、Iref、Vref、KV、Ki is available through a data manual of the selected power switching device;
The power loss P T of the IGBT and the power loss P D of the antiparallel diode are:
PT＝Pcond(T)+PSW(T)；
PD＝Pcond(D)+PSW(D)；
When power loss calculation is carried out, the calculation is needed through a thermal network model, the thermal network model of the grid-connected inverter is formed by connecting a plurality of thermal resistance-heat capacity units in series, each thermal resistance-heat capacity unit is formed by connecting a thermal resistance and a thermal capacity in parallel, the tail end of the thermal network model is an equivalent voltage source of ambient temperature, the head end of the thermal network model is input into an equivalent current source of power loss, and the voltage generated at the head end of the thermal network model is the calculated estimated junction temperature;
Inputting the power loss P T of the IGBT and the power loss P D of the anti-parallel diode into a thermal network model to obtain the estimated junction temperature T j of the grid-connected inverter unit;
When the weight of each inverter in the weighted switching frequency adjusting unit is obtained, all thermal cycles in the estimated junction temperature are extracted by a rain flow counting method to obtain junction temperature fluctuation DeltaT j and average junction temperature T m of each thermal cycle, and the estimated cycle number N f of each thermal cycle is calculated according to a Coffin-Manson life model, namely Wherein a, n, E a, k are constants;
Obtaining service life damage D m of the grid-connected inverter unit according to the linear accumulated damage theory, namely Wherein N i is the actual number of cycles per estimated number of cycles N i;
The weight w m of each inverter in the weighted switching frequency adjusting unit is:
The weighted switching frequency adjusting unit first calculates a weighted loss value P weighted by the power loss P m,loss of all the inverters in the group, namely
The weighted loss value P weighted is input into a low-pass filter to obtain a loss reference value P ref, then delta P is obtained through the difference value between P ref and P weighted, and the delta P is used for obtaining the increment value delta f of PWM frequency, namelyThe PWM frequency increment Δf is added to the minimum PWM frequency to obtain PWM frequency f SW.
2. A coordinated active thermal control system for a multiple grid-tie inverter for implementing the method of claim 1, comprising a plurality of structurally identical, interconnected grid-tie inverter modules; each grid-connected inverter module comprises a grid-connected inverter unit, a correlation grouping unit, a weighted switching frequency adjusting unit and a global synchronous pulse width modulating unit which are sequentially connected, wherein communication connection among the grid-connected inverter modules is established by a communication line among the grid-connected inverter units;
based on the correlation grouping, the weighted switching frequency adjusting unit and the global synchronous pulse width modulating unit, the switching frequency of the grid-connected inverter units in the same group is obtained; according to the obtained switching frequency, under the action of a global synchronous pulse width modulation unit, obtaining the optimal PWM phase of the same group of grid-connected inverter units;
Each grid-connected inverter module further comprises a power generation unit connected with the input end of the grid-connected inverter unit, and the output ends of the grid-connected inverter units are connected with a power grid through public grid-connected points;
The data information of each grid-connected inverter unit is shared to other grid-connected inverter units through a communication line, and the other grid-connected inverter units utilize the received data information to carry out PWM phase and frequency control, so that the cooperative active thermal control of the multiple grid-connected inverters is realized.
3. A computer readable storage medium having a program stored thereon, which when executed by a processor, implements the steps in the coordinated active thermal control method of a multiple grid-tie inverter of claim 1.
4. An electronic device comprising a memory, a processor, and a program stored on the memory and executable on the processor, wherein the processor, when executing the program, performs the steps in the coordinated active thermal control method of a multiple grid-tie inverter of claim 1.
CN202111376296.3A 2021-11-19 2021-11-19 Cooperative active heat control system and method for multiple grid-connected inverters Active CN114050597B (en)

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