CN112838777B - Active power consumption cooperative control system and method for power switching devices of multi-grid-connected inverter - Google Patents

Active power consumption cooperative control system and method for power switching devices of multi-grid-connected inverter Download PDF

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CN112838777B
CN112838777B CN202110018369.5A CN202110018369A CN112838777B CN 112838777 B CN112838777 B CN 112838777B CN 202110018369 A CN202110018369 A CN 202110018369A CN 112838777 B CN112838777 B CN 112838777B
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CN112838777A (en
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许涛
高峰
刘梓柒
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Shandong University
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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
    • H02M7/42—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
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • 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
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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Abstract

The invention discloses a system and a method for cooperative control of active power consumption of a power switching device of a multi-grid-connected inverter, wherein the system comprises the following steps: the local active power consumption control parameter calculation module is configured to control the switching frequency to rise when the output of the grid-connected inverter falls so as to prevent the device from cooling, and control the switching frequency to fall when the output rises so as to prevent the temperature of the device from rising too high so as to smooth junction temperature fluctuation; the frequency optimization calculation module of the pulse width modulation wave of the multi-grid-connected inverter is configured to establish an active power consumption collaborative optimization model of a grid-connected inverter cluster and solve the model so as to obtain the optimal phase angle of the pulse width modulation frequency and the pulse width modulation wave and output the corresponding carrier phase; and the pulse width modulation wave frequency control local execution module is configured to output a local optimal phase shift angle according to the input phase locking result and the carrier phase. The invention can eliminate main high-frequency harmonic waves, reduce the requirement of output current harmonic wave constraint on PWM frequency, and further greatly improve the PWM frequency regulation range.

Description

Active power consumption cooperative control system and method for power switching devices of multi-grid-connected inverter
Technical Field
The invention relates to the technical field of electrical control, in particular to an active power consumption cooperative control system and method for a power switch device 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.
In recent years, the installed capacity of new energy mainly comprising wind power and photovoltaic is rapidly increased, and the important position of new energy power generation is highlighted. The grid-connected inverter is important flexible controllable equipment for connecting a new energy power generation system and a power grid, the operation reliability of the grid-connected inverter is a key index which is commonly concerned by inverter manufacturers and new energy users, and the grid-connected inverter is very important for reducing maintenance cost and improving power generation capacity.
According to international authority statistics, nearly 34% of grid-connected inverter faults are caused by the damage of a power switch device, and are mostly serious faults which are difficult to repair, and the cost is extremely high. Among the factors causing the damage of the power switching device, the thermal failure (the excessive average junction temperature and the junction temperature fluctuation amplitude cause the thermal fatigue damage of the material) occupies 55 percent, and is the main factor of the damage of the power switching device.
Therefore, active power consumption control theory is proposed successively at home and abroad: and the key control parameters of the inverter are dynamically adjusted according to the power change, so that the fluctuation range of power consumption is reduced, the fluctuation range of junction temperature is further reduced, and the thermal reliability is improved. In view of the large influence of the PWM frequency on the power consumption and the positive correlation between the PWM frequency and the power consumption, dynamically adjusting the PWM frequency (decreasing the PWM frequency when the power consumption increases, and increasing the PWM frequency when the power consumption decreases) becomes a main method of active power consumption control. The method is of great interest because it does not require a change in hardware architecture and is applicable to both existing inverters and newly designed inverters. However, the existing active power consumption control method does not break through the limitation of 'fighting each other' of the grid-connected inverter, and the regulation and control effect is not ideal: considering that reducing the PWM frequency reduces the harmonic frequency of the output current, the harmonic content of the output current of the inverter is inevitably increased, so that the PWM frequency is increased only and not decreased, and the increased PWM frequency causes the increase of the average junction temperature, which is not beneficial to the improvement of the thermal reliability.
The capacity of the grid-connected inverter is relatively small due to the restriction of natural resource distribution and dispersion, a power grid is connected into a new energy station in a large-scale and high-density mode, and the grid-connected inverter has natural cluster grid-connected characteristics, for example, about 100 to 200 groups of series-connected photovoltaic grid-connected inverters run in parallel in a typical 10MW photovoltaic power station. Researches show that by introducing the grid-connected inverter cluster PWM phase synchronization control, main high-frequency harmonic waves can be eliminated, the requirement of output current harmonic wave constraint on PWM frequency is reduced, and the PWM frequency adjusting range is further greatly enlarged.
The prior art discloses a global synchronous pulse width modulation system of a distributed grid-connected inverter system, which determines the basic structure of the global pulse width modulation system and comprises a main control unit (global synchronous unit) and a plurality of grid-connected inverters located at different geographical positions, wherein each grid-connected inverter is connected with a distributed power supply, each grid-connected inverter is connected with a power grid through a public grid-connected point, and the main control unit is communicated with all the grid-connected inverters. The main control unit receives information of each grid-connected inverter, after a global synchronization strategy is determined, global synchronization signals containing the global synchronization strategy are respectively sent to each grid-connected inverter, each grid-connected inverter utilizes the global synchronization signals to adjust the phase of pulse width modulation waves of the grid-connected inverter, so that phase difference of harmonic cancellation among the pulse width modulation waves of each grid-connected inverter can be met, and harmonic currents injected into a power grid by each grid-connected inverter are cancelled. The method can effectively reduce isumThe harmonic content of (a). However, the method only focuses on total grid-connected current harmonics, and does not focus on the reliability of the power switching device.
The prior art discloses a dynamic adjustment method for global synchronous pulse width phase and frequency of a distributed grid-connected inverter system, wherein in the normal operation process of inverters, the switching frequency of each inverter is reduced on the premise of meeting the requirement of grid-connected current harmonic wave, and the operation efficiency of the whole system can be improved. However, this method only considers reducing the switching frequency and does not involve dynamically adjusting the switching frequency.
Disclosure of Invention
In order to solve the problems, the invention provides a system and a method for cooperatively controlling the active power consumption of a power switch device of a multi-grid-connected inverter. And furthermore, from the perspective of optimal overall active power consumption control effect of the multi-grid-connected inverter, the average junction temperature and the junction temperature fluctuation range of the power switching device are synchronously reduced by cooperating with the frequency of the pulse width modulation wave of the multi-grid-connected inverter.
In some embodiments, the following technical scheme is adopted:
a multi-grid-connected inverter power switching device active power consumption cooperative control system comprises:
the local active power consumption control parameter calculation module is configured to control the switching frequency to rise when the output of the grid-connected inverter falls so as to prevent the device from cooling, and control the switching frequency to fall when the output rises so as to prevent the temperature of the device from rising too high so as to smooth junction temperature fluctuation;
the frequency optimization calculation module of the pulse width modulation wave of the multi-grid-connected inverter is configured to establish an active power consumption collaborative optimization model of a grid-connected inverter cluster and solve the model so as to obtain the optimal phase angle of the pulse width modulation frequency and the pulse width modulation wave and output the corresponding carrier phase;
and the pulse width modulation wave frequency control local execution module is configured to output a local optimal phase shift angle according to the input phase locking result and the carrier phase.
As a further improvement, the local active power consumption control parameter calculation module includes:
the power device loss calculation unit is configured to select a limited number of values from PWM frequencies lower than a rated value, and respectively calculate the switching loss at different PWM frequencies so as to obtain the power switching device loss at different PWM frequencies;
the active power consumption control unit is configured to control the switching frequency of the power device to increase to prevent the device from cooling when photovoltaic output is reduced, and control the switching frequency to decrease to prevent the temperature of the device from being excessively high when the photovoltaic output is increased so as to smooth junction temperature fluctuation;
and the service life prediction unit is configured to predict the service life of the device by using the junction temperature data of the power device after the active power consumption control smoothing junction temperature and a rain flow counting method so as to evaluate the active power consumption control effect.
As a further improvement, the multiple grid-connected inverter pulse width modulation wave frequency optimization calculation module comprises:
the active power consumption control evaluation function calculation unit is configured to construct a value function model by utilizing a functional relation between an active power consumption control effect and the selected PWM frequency and a service life prediction result;
the grid-connected inverter cluster high-frequency current harmonic general model calculation unit is configured to construct a general grid-connected inverter cluster high-frequency current harmonic model based on inverter and power grid parameters, an inverter closed-loop control circuit and a grid-connected inverter cluster high-frequency harmonic model by considering calculation delay, phase deviation and inverter start/stop factors;
the grid-connected inverter cluster active power consumption collaborative optimization model calculation unit is configured to utilize range transformation to quantize the importance degree of the inverter, utilize a linear transformation method to quantize historical power generation data, obtain a reliability weighting coefficient of the inverter based on the data and establish a total objective function; and (4) considering the constraint of the power grid on the total grid-connected current harmonic and the calculation loss of a power device, and obtaining an inequality constraint model with PWM frequency as a variable.
In other embodiments, the following technical solutions are adopted:
a cooperative control method for active power consumption of a multi-grid-connected inverter power switch device comprises the following steps:
calculating the loss of the power switching device under different PWM frequencies based on the operation parameters of the power switching device of the multi-grid-connected inverter;
calculating the service life reduction degree of the power switch device in the current short period to obtain the active power consumption control effect under a plurality of PWM frequencies;
constructing a grid-connected inverter cluster active power consumption collaborative optimization model;
solving the optimal PWM frequency of each inverter based on the active power consumption control evaluation function of each inverter, and splitting the overall optimization model into a plurality of intra-group constraint models by using decomposition and dimensionality reduction to form an inter-group inequality constraint model; simplifying the inter-group inequality constraint model;
solving the simplified grid-connected inverter cluster active power consumption collaborative optimization model to obtain a PWM frequency value and a PWM phase value in each inverter;
and respectively sending the calculated PWM frequency value and phase value commands to each inverter, and controlling an internal carrier generation unit of each inverter to generate triangular carriers with corresponding frequency and phase according to the received PWM frequency value and phase value commands so as to realize the control of the switching loss of the power switching device and further realize the active power consumption cooperative control of the power switching device.
As a further improvement, constructing a grid-connected inverter cluster active power consumption collaborative optimization model specifically comprises:
constructing a value function model by utilizing the function relation between the active power consumption control effect and the selected PWM frequency and the service life prediction result;
based on the inverter and power grid parameters, an inverter closed-loop control circuit and a grid-connected inverter cluster high-frequency harmonic model, considering calculation delay, phase deviation and inverter start/stop factors, and constructing a general grid-connected inverter cluster high-frequency current harmonic model;
quantizing the importance degree of the inverter by utilizing range transformation, quantizing historical generated energy data by utilizing a linear transformation method, obtaining a reliability weighting coefficient of the inverter based on the data, and establishing a total objective function; considering the constraint of the power grid on the total grid-connected current harmonic and the calculation loss of a power device, and obtaining an inequality constraint model with PWM frequency as a variable;
and the total objective function and the inequality constraint model form a grid-connected inverter cluster active power consumption collaborative optimization model.
As a further improvement, the general grid-connected inverter cluster high-frequency current harmonic model is specifically as follows:
Figure BDA0002887488320000061
wherein, Isum,hRepresenting the effective value of the harmonic of the total current, fcRepresents the PWM frequency row vector, ch (t) represents the inverter operating state row vector at time t,
Figure BDA0002887488320000062
representation is based on kTGSPWM optimal phase angle row vector calculated by inverter running state at moment, wherein k represents current period sequence value, TGSIt indicates the time interval of each calculation,
Figure BDA0002887488320000063
a row vector representing the ripple value of the PWM phase in operation,
Figure BDA0002887488320000064
represents the maximum range of PWM phase fluctuation; l represents inductance value of grid-connected inverter, eta represents harmonic amplification coefficient under different topologies and modulation modes, IM,hfA harmonic effective value representing the frequency f generated by the inverter M of the grid-connected inverter under rated operating parameters, M representing the serial number of the grid-connected inverter,
Figure BDA0002887488320000065
is a calculation function of the phase of the harmonic of frequency f in the grid-connected inverter M.
As a further improvement, the overall objective function is specifically:
Figure BDA0002887488320000066
wherein, L [ R (f)M,c(k))]Is a value function model, y represents the value of the active power consumption cooperative control evaluation function of the power switching device of the multi-grid-connected inverter, bMThe method comprises the steps of representing active power consumption cooperative control weight coefficients of power switching devices in a grid-connected inverter M, representing the total number of the grid-connected inverters by N, and representing the serial numbers of the grid-connected inverters by M.
As a further improvement, the method simplifies the inter-group inequality constraint model, and comprises the following specific processes:
aiming at each group of inverters, calculating an optimal phase angle by taking the minimum effective value of the high-frequency harmonic of the total current as a target;
changing the PWM phase angle from variable to optimal phase angle, and expressing the output harmonic effective value of each group of inverters as a function of the PWM frequency of the inverters;
and simplifying the total grid-connected high-frequency harmonic constraint into a plurality of equalities and an inequality.
As a further improvement, the total grid-connected high-frequency harmonic constraint is simplified into a plurality of equations and an inequality, specifically:
Figure BDA0002887488320000071
wherein, Isum,hRepresenting the effective value of the harmonic of the total current, fcRepresenting PWM frequency row vector, chM(t) represents the operating state of the inverter M at time t,
Figure BDA0002887488320000072
a calculation function for the phase of the harmonic with frequency f in the grid-connected inverter M; i isg,sum,h(G1, …, G) represents the output total current harmonic effective value of G groups of inverters, wherein G represents the total group number of grid-connected inverters; f. ofg(k) Representing the PWM frequency of the g groups of inverters; cgRepresenting g groups of inversionsHarmonic coefficients of the variator at nominal operating conditions.
As a further improvement, the simplified grid-connected inverter cluster active power consumption collaborative optimization model specifically includes:
Figure BDA0002887488320000073
Figure BDA0002887488320000074
wherein y represents the value of the evaluation function of the active power consumption cooperative control of the power switching devices of the multi-grid-connected inverter, and ygExpressing the value f of the evaluation function of the active power consumption cooperative control of the power switching devices of the g groups of grid-connected invertersg(k) (G-1, …, G) represents the PWM frequency of the G-group inverter; g represents the total group number of the grid-connected inverters; cgRepresenting harmonic coefficients of the g groups of inverters under rated working conditions; i islimitRepresenting the grid side harmonic limit.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the invention, the grid-connected inverter cluster PWM phase synchronization control is introduced, so that main high-frequency harmonic waves can be eliminated, the requirement of output current harmonic wave constraint on PWM frequency is reduced, and the PWM frequency regulation range is greatly enlarged.
(2) The active power consumption control of the invention can effectively smooth the junction temperature curve, reduce the junction temperature fluctuation and effectively prolong the service life of the power device.
(3) According to the active power consumption control method, the switching frequency is allowed to be reduced when the photovoltaic output is increased according to the effect (1), so that the average junction temperature can be reduced while the fluctuation range of the junction temperature is reduced, the service life of a power device is further prolonged, and the reliability of the power device can be greatly improved.
(4) The invention does not need to change the existing hardware structure of the inverter, only needs to add a small amount of programs in software, and improves the applicability of the global synchronous pulse width modulation method.
Additional features and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
Fig. 1 is a general schematic diagram of a power switching device active power consumption control system for a multi-grid-connected inverter according to an embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating active power consumption control in an embodiment of the present invention;
fig. 3 is a flowchart of an active power consumption cooperative control method for a multi-grid-connected inverter power switching device in the embodiment of the invention.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the 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 application 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 example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
Example one
In one or more embodiments, a multi-grid-connected inverter power switching device active power consumption cooperative control system is disclosed, referring to fig. 1, including:
a local active power consumption control parameter calculation module (L2) configured to control the switching frequency to increase to prevent the device from cooling when the grid-connected inverter output decreases, and to decrease to prevent the device temperature from increasing too high when the output increases, so as to smooth junction temperature fluctuation;
the frequency optimization calculation module (H1) of the pulse width modulation wave of the multi-grid-connected inverter is configured to establish a grid-connected inverter cluster active power consumption collaborative optimization model and solve the model so as to obtain the pulse width modulation frequency and the optimal phase angle of the pulse width modulation wave and output the corresponding carrier phase;
and the pulse width modulation wave frequency control local execution module (L1) is configured to output a local optimal phase shift angle according to the input phase locking result and the carrier phase.
The local active power consumption control parameter calculation module mainly comprises a power device loss calculation unit, an active power consumption control unit and a service life prediction unit;
the power device loss calculation unit selects a limited number of values from PWM frequencies lower than a rated value, and respectively calculates the switching loss at different PWM frequencies, so as to obtain the power switching device loss at different PWM frequencies;
the active power consumption control unit controls the switching frequency of the power device to be increased when the photovoltaic output is reduced so as to prevent the device from being cooled, and controls the switching frequency to be reduced when the photovoltaic output is increased so as to prevent the temperature of the device from being excessively increased so as to smooth junction temperature fluctuation;
the service life prediction unit predicts the service life of the device by using junction temperature data of the power device after the active power consumption control smoothing junction temperature and a rain flow counting method so as to evaluate the active power consumption control effect.
Specifically, the structure of the local active power consumption control parameter calculation module (L2) is shown in fig. 2. The control method mainly focuses on the junction temperature fluctuation range which has relatively larger influence on the service life, and controls the switching frequency to be increased when the output of the grid-connected inverter is reduced so as to prevent the device from being cooled, and controls the switching frequency to be reduced when the output is increased so as to prevent the temperature of the device from being excessively increased, so that the junction temperature fluctuation is smoothed. The control process comprises three parts of loss calculation, filtering and control frequency calculation. IGBT loss PlossTo make conduction loss PcondAnd switching loss PswAnd adding, and calculating according to formula (1).
Figure BDA0002887488320000101
Where cos (phi) is the power factor, m is the modulation ratio,
Figure BDA0002887488320000102
for peak load current, EonFor the on-loss of the device, EoffFor device turn-off loss, fswFor switching frequency, UdcIs a dc voltage. Then to PlossFiltering to obtain P'lossThe difference is then subtracted and the absolute value is taken to obtain the loss difference Δ P, which corresponds to the desired reduced temperature fluctuation.
Controlling the switching frequency f when the output decreases or increasesswΔ f is increased or decreased according to equation (2).
Figure BDA0002887488320000103
In the formula,. DELTA.fmaxΔ P determined by the range of switching frequencies that the device can toleratemaxThe maximum value of the output fluctuation of the grid-connected inverter can be generally selected through historical output.
The upper-layer multi-grid-connected inverter pulse width modulation wave frequency optimization calculation module comprises an active power consumption control evaluation function calculation unit, a grid-connected inverter cluster high-frequency current harmonic general model calculation unit and a grid-connected inverter cluster active power consumption collaborative optimization model calculation unit;
the active power consumption control evaluation function calculation unit utilizes the active power consumption control effect and the selected PWM frequency fM,c(k) Functional relationship between R [ f ]M,c(k)]And constructing a value function model L [ R (f) from the life prediction resultM,c(k))]；
The grid-connected inverter cluster high-frequency current harmonic model calculation unit establishes a general grid-connected inverter cluster high-frequency current harmonic model based on inverter and power grid parameters, an inverter closed-loop control circuit and a grid-connected inverter cluster high-frequency harmonic model researched by the applicant after considering influence factors such as calculation delay, phase deviation, inverter start/stop and the like after GSPWM application;
active power consumption collaborative optimization model calculation unit of grid-connected inverter cluster quantization inversion by utilizing range transformationThe importance degree is quantized by using a linear transformation method to obtain historical power generation data, and the reliability weighting coefficient of the inverter obtained by the two attributes is represented as bMAnd obtaining a total objective function, and obtaining an inequality constraint model taking PWM frequency as a variable by considering the constraint of the power grid on total grid-connected current harmonic and the calculation loss of the power device.
Example two
In one or more embodiments, a method for cooperative control of active power consumption of a multi-grid-connected inverter power switching device is disclosed, and with reference to fig. 3, the method includes the following steps:
(1) based on the loss calculation result of the existing power switching device, the voltage and current stress of the power switching device are calculated according to the operation parameters at the moment k, the conduction loss is obtained by using the parameters in a data manual of the power switching device, and the conduction loss is not influenced by PWM frequency and is expressed as PM,ON. Selecting a limited number of values from the PWM frequencies below the nominal value, calculating the switching losses at different PWM frequencies, respectively, and expressing PM,SW[fM,c(k)]. Thereby obtaining power switching device losses at different PWM frequencies.
PM,loss(k)＝PM,SW[fM,c(k)]+PM,ON fM,c(k)<fM,c,rated (3)
(2) Calculating short-period junction temperature by using short-period loss recorded data and current loss values based on a power switch device RC heat conduction model, calculating the service life reduction degree of the power switch device in the current short period by using a rain flow counting method and power switch device reliability test data, and expressing the service life reduction degree as bro [ f [ [ f ]M,c(k)]And the inverse number is used as the active power consumption control effect, and the process is repeated to obtain the active power consumption control effect under a plurality of PWM frequencies.
(3) Based on the obtained active power consumption control effect, obtaining the active power consumption control effect and f by using a data fitting methodM,c(k) Functional relationship between R [ f ]M,c(k)]And then a value function model L [ R (f) is constructed by combining the life prediction resultM,c(k))]。
(4) According to the inverter operating power, the scheduling instruction and the power grid parameters, a modulation wave expression of the grid-connected inverter is obtained based on a closed-loop control circuit of the grid-connected inverter, and a universal high-frequency harmonic model is obtained by utilizing a dual Fourier algorithm.
(5) On the basis, an accurate calculation model of the total grid-connected current harmonic is established based on a grid-connected inverter cluster high-frequency harmonic model researched by the applicant, as shown in a formula (4):
Figure BDA0002887488320000121
(6) and (3) considering influence factors such as calculation delay, phase deviation, inverter start/stop and the like after GSPWM application to obtain a more general grid-connected inverter cluster high-frequency current harmonic general model:
Figure BDA0002887488320000122
(6) quantizing the importance degree of the inverter by utilizing range transformation, quantizing historical generated energy data by utilizing a linear transformation method, and comprehensively considering the two attributes to obtain a reliability weighting coefficient of the inverter, wherein the reliability weighting coefficient is represented as bMThe overall objective function is expressed as:
Figure BDA0002887488320000123
(7) considering the constraint of the power grid on the total grid-connected current harmonic wave, and combining with the formula (5), obtaining an inequality constraint model expressed by taking the PWM frequency as a variable as follows:
Figure BDA0002887488320000131
(8) fusing an objective function and inequality constraints, and constructing a grid-connected inverter cluster active power consumption collaborative optimization model:
Figure BDA0002887488320000132
the model is to be evaluated by PWM phase and frequency.
(9) The optimal PWM frequency of each inverter is obtained based on the active power consumption control evaluation function of each inverter, and is expressed as fM,c,best(k) On the basis, f with approximate numerical values is divided into f by using methods such as a k-means clustering method and an intelligent grouping methodM,c,best(k) Are combined to the same value, indicating that the plurality of inverters will adopt the same PWM frequency, denoted as fg(k) Where G denotes the packet number and the total number of packets is denoted G. Then, decomposing and reducing dimensions are utilized to split the integral model into a plurality of intra-group constraint models:
Figure BDA0002887488320000133
(9) and forming an inter-group inequality constraint model on the basis:
Figure BDA0002887488320000134
(10) aiming at each group of inverters, the optimal phase angle is calculated based on the optimal phase angle calculation method in GSPWM (generalized minimum pulse width modulation) by taking the minimum effective value of the high-frequency harmonic of the total current as a target
Figure BDA0002887488320000135
Figure BDA0002887488320000136
(11) On the basis, the PWM phase angle is changed from a variable to a constant
Figure BDA0002887488320000137
Then, the effective value of the output harmonic wave of each group of inverters is expressed as frequency fg(k) As a function of (c). So far, the complex total grid-connected high-frequency harmonic constraint can be simplified into a plurality of equations and an inequality:
Figure BDA0002887488320000141
(12) according to the formula (8) and the formula (10), the grid-connected inverter cluster active power consumption collaborative optimization model can be simplified as follows:
Figure BDA0002887488320000142
(13) and converting an inequality constraint model in the model (13) into an unconstrained model by using an internal penalty function method, and realizing dynamic solution of the model (13) based on a particle swarm optimization algorithm and the like widely used in the existing achievements.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.

Claims (10)

1. The active power consumption cooperative control system for the power switching devices of the multi-grid-connected inverter is characterized by comprising the following steps of:
the local active power consumption control parameter calculation module is configured to control the switching frequency to rise when the output of the grid-connected inverter falls so as to prevent the device from cooling, and control the switching frequency to fall when the output rises so as to prevent the temperature of the device from rising too high so as to smooth junction temperature fluctuation;
the frequency optimization calculation module of the pulse width modulation wave of the multi-grid-connected inverter is configured to establish an active power consumption collaborative optimization model of a grid-connected inverter cluster and solve the model so as to obtain the optimal phase angle of the pulse width modulation frequency and the pulse width modulation wave and output the corresponding carrier phase;
and the pulse width modulation wave frequency control local execution module is configured to output a local optimal phase shift angle according to the input phase locking result and the carrier phase.
2. The system of claim 1, wherein the local active power consumption control parameter calculation module comprises:
the power device loss calculation unit is configured to select a limited number of values from PWM frequencies lower than a rated value, and respectively calculate the switching loss at different PWM frequencies so as to obtain the power switching device loss at different PWM frequencies;
the active power consumption control unit is configured to control the switching frequency of the power device to increase to prevent the device from cooling when photovoltaic output is reduced, and control the switching frequency to decrease to prevent the temperature of the device from being excessively high when the photovoltaic output is increased so as to smooth junction temperature fluctuation;
and the service life prediction unit is configured to predict the service life of the device by using the junction temperature data of the power device after the active power consumption control smoothing junction temperature and a rain flow counting method so as to evaluate the active power consumption control effect.
3. The active power consumption cooperative control system of the multi-grid-connected inverter power switching device according to claim 1, wherein the multi-grid-connected inverter pulse width modulation wave frequency optimization calculation module comprises:
the active power consumption control evaluation function calculation unit is configured to construct a value function model by utilizing a functional relation between an active power consumption control effect and the selected PWM frequency and a service life prediction result;
the grid-connected inverter cluster high-frequency current harmonic general model calculation unit is configured to construct a general grid-connected inverter cluster high-frequency current harmonic model based on inverter and power grid parameters, an inverter closed-loop control circuit and a grid-connected inverter cluster high-frequency harmonic model by considering calculation delay, phase deviation and inverter start/stop factors;
the grid-connected inverter cluster active power consumption collaborative optimization model calculation unit is configured to utilize range transformation to quantize the importance degree of the inverter, utilize a linear transformation method to quantize historical power generation data, obtain a reliability weighting coefficient of the inverter based on the data and establish a total objective function; and (4) considering the constraint of the power grid on the total grid-connected current harmonic and the calculation loss of a power device, and obtaining an inequality constraint model with PWM frequency as a variable.
4. A method for cooperatively controlling active power consumption of a multi-grid-connected inverter power switching device is characterized by comprising the following steps:
calculating the loss of the power switching device under different PWM frequencies based on the operation parameters of the power switching device of the multi-grid-connected inverter;
calculating the service life reduction degree of the power switch device in the current short period to obtain the active power consumption control effect under a plurality of PWM frequencies;
constructing a grid-connected inverter cluster active power consumption collaborative optimization model;
solving the optimal PWM frequency of each inverter based on the active power consumption control evaluation function of each inverter, and splitting the overall optimization model into a plurality of intra-group constraint models by using decomposition and dimensionality reduction to form an inter-group inequality constraint model; simplifying the inter-group inequality constraint model;
solving the simplified grid-connected inverter cluster active power consumption collaborative optimization model to obtain a PWM frequency value and a PWM phase value in each inverter;
and respectively sending the calculated PWM frequency value and phase value commands to each inverter, and controlling an internal carrier generation unit of each inverter to generate triangular carriers with corresponding frequency and phase according to the received PWM frequency value and phase value commands so as to realize the control of the switching loss of the power switching device and further realize the active power consumption cooperative control of the power switching device.
5. The active power consumption cooperative control method of the multi-grid-connected inverter power switching device according to claim 4, wherein the constructing of the grid-connected inverter cluster active power consumption cooperative optimization model specifically comprises:
constructing a value function model by utilizing the function relation between the active power consumption control effect and the selected PWM frequency and the service life prediction result;
based on the inverter and power grid parameters, an inverter closed-loop control circuit and a grid-connected inverter cluster high-frequency harmonic model, considering calculation delay, phase deviation and inverter start/stop factors, and constructing a general grid-connected inverter cluster high-frequency current harmonic model;
quantizing the importance degree of the inverter by utilizing range transformation, quantizing historical generated energy data by utilizing a linear transformation method, obtaining a reliability weighting coefficient of the inverter based on the data, and establishing a total objective function; considering the constraint of the power grid on the total grid-connected current harmonic and the calculation loss of a power device, and obtaining an inequality constraint model with PWM frequency as a variable;
and the total objective function and the inequality constraint model form a grid-connected inverter cluster active power consumption collaborative optimization model.
6. The active power consumption cooperative control method of the power switching device of the multi-grid-connected inverter according to claim 5, wherein the general grid-connected inverter cluster high-frequency current harmonic model specifically comprises:
Figure FDA0003487430360000031
chM(t)＝0 or 1；
chM(kTGS)＝0 or 1；
Figure FDA0003487430360000032
wherein, Isum,hRepresenting the effective value of the harmonic of the total current, fcRepresents the PWM frequency row vector, ch (t) represents the inverter operating state row vector at time t,
Figure FDA0003487430360000041
representation is based on kTGSPWM optimal phase angle row vector calculated by inverter running state at moment, wherein k represents current period sequence value, TGSThen it means each time of countingThe calculated time interval is calculated as the time interval,
Figure FDA0003487430360000042
a row vector representing the ripple value of the PWM phase in operation,
Figure FDA0003487430360000043
represents the maximum range of PWM phase fluctuation; l represents inductance value of grid-connected inverter, eta represents harmonic amplification coefficient under different topologies and modulation modes, IM,hfA harmonic effective value representing the frequency f generated by the inverter M of the grid-connected inverter under rated operating parameters, M representing the serial number of the grid-connected inverter,
Figure FDA0003487430360000044
is a calculation function of the phase of the harmonic of frequency f in the grid-connected inverter M.
7. The active power consumption cooperative control method of the multi-grid-connected inverter power switching device according to claim 5, wherein the total objective function is specifically:
Figure FDA0003487430360000045
wherein, L [ R (f)M,c(k))]Is a value function model, y represents the value of the active power consumption cooperative control evaluation function of the power switching device of the multi-grid-connected inverter, bMThe method comprises the steps of representing active power consumption cooperative control weight coefficients of power switching devices in a grid-connected inverter M, representing the total number of the grid-connected inverters by N, and representing the serial numbers of the grid-connected inverters by M.
8. The active power consumption cooperative control method of the multi-grid-connected inverter power switching device according to claim 4, wherein the inter-group inequality constraint model is simplified, and the specific process includes:
aiming at each group of inverters, calculating an optimal phase angle by taking the minimum effective value of the high-frequency harmonic of the total current as a target;
changing the PWM phase angle from variable to optimal phase angle, and expressing the output harmonic effective value of each group of inverters as a function of the PWM frequency of the inverters;
and simplifying the total grid-connected high-frequency harmonic constraint into a plurality of equalities and an inequality.
9. The active power consumption cooperative control method of the multi-grid-connected inverter power switching device according to claim 8, wherein the total grid-connected high frequency harmonic constraint is simplified into a plurality of equations and an inequality, and specifically:
Figure FDA0003487430360000051
wherein, Isum,hRepresenting the effective value of the harmonic of the total current, fcRepresenting PWM frequency row vector, chM(t) represents the operating state of the inverter M at time t,
Figure FDA0003487430360000052
a calculation function for the phase of the harmonic with frequency f in the grid-connected inverter M; i isg,sum,hThe harmonic effective value of the output total current of the group G of inverters is represented, wherein G is 1, …, G; g represents the total group number of the grid-connected inverters; f. ofg(k) Representing the PWM frequency of the g groups of inverters; cgRepresenting harmonic coefficients of the g groups of inverters under rated working conditions;
Figure FDA0003487430360000053
PWMbrepresenting a PWM optimal phase angle row vector of the grid-connected inverter M; m represents the serial number of the grid-connected inverter; i islimitRepresenting the grid side harmonic limit.
10. The method for the cooperative control of the active power consumption of the power switching devices of the multi-grid-connected inverter as claimed in claim 4, wherein the simplified cooperative optimization model of the active power consumption of the grid-connected inverter cluster is specifically as follows:
Figure FDA0003487430360000054
Figure FDA0003487430360000055
wherein y represents the value of the active power consumption cooperative control evaluation function of the power switching device of the multi-grid-connected inverter; y isgThe method comprises the steps of representing g groups of power switching devices of the grid-connected inverter to cooperatively control evaluation function values in active power consumption; f. ofg(k) Representing the PWM frequency of G groups of inverters, where G is 1, …, G; g represents the total group number of the grid-connected inverters; cgRepresenting harmonic coefficients of the g groups of inverters under rated working conditions; i islimitRepresenting the grid side harmonic limit.
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