CN111835038B - Pre-synchronization method, system and terminal equipment - Google Patents
Pre-synchronization method, system and terminal equipment Download PDFInfo
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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
- H02J3/40—Synchronising a generator for connection to a network or to another generator
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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
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
- H02J3/241—The oscillation concerning frequency
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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
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
Abstract
The invention is suitable for the technical field of electrical control, and discloses a pre-synchronization method, a pre-synchronization system and terminal equipment, wherein the method comprises the following steps: acquiring the real-time angular frequency of the power grid based on an ECAP (equal cost adaptive processing) capturing unit; acquiring the angular frequency automatically constructed by an inverter system; based on a linear approximation method, the angular frequency automatically constructed by the inverter system gradually approaches the real-time angular frequency of the power grid. The invention does not influence the output of the inverter system when the phase angle and the frequency of the power grid are suddenly changed or the harmonic content of the power grid is larger, and the inverter system can stably run and has higher robustness.
Description
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a pre-synchronization method, a pre-synchronization system and terminal equipment.
Background
With the increasing exhaustion of traditional fossil energy, the war of new energy power generation systems such as photovoltaic power generation and wind power generation, an inverter system which can operate independently and in a grid-connected mode becomes a hotspot of research in recent years, grid-connected and island operation are two normal operation modes of a micro-grid system, and whether grid-connected and island are in stable transition is a key for judging whether the micro-grid system is stable, so that the reasonable design of a control scheme of the inverter system has important significance.
In the traditional island grid-connected switching method, a PLL (phase locked loop) is adopted to realize the same frequency and phase with a power grid, namely, pre-synchronization is realized. However, the method for realizing pre-synchronization may cause phase angle fluctuation after phase locking when the phase angle and frequency of the power grid suddenly change or the harmonic content of the power grid is large, so that the output of the inverter system fluctuates, and the stability of the inverter system is affected.
Disclosure of Invention
In view of this, embodiments of the present invention provide a pre-synchronization method, system and terminal device, so as to solve the problem in the prior art that a phase angle after phase locking fluctuates when a phase angle and a frequency of a power grid suddenly change or a harmonic content of the power grid is large, so that an output of an inverter system fluctuates and stability of the inverter system is affected.
A first aspect of an embodiment of the present invention provides a pre-synchronization method, including:
acquiring the real-time angular frequency of the power grid based on an ECAP (equal cost adaptive processing) capturing unit;
acquiring the angular frequency automatically constructed by an inverter system;
based on a linear approximation method, the angular frequency automatically constructed by the inverter system gradually approaches the real-time angular frequency of the power grid.
A second aspect of an embodiment of the present invention provides a pre-synchronization system, including:
the power grid angular frequency acquisition module is used for acquiring the real-time angular frequency of the power grid based on the ECAP acquisition unit;
the inverter angular frequency acquisition module is used for acquiring the angular frequency constructed by the inverter system;
and the linear approximation module is used for gradually approximating the angular frequency automatically constructed by the inverter system to the real-time angular frequency of the power grid based on a linear approximation method.
A third aspect of embodiments of the present invention provides a terminal device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the pre-synchronization method according to the first aspect when executing the computer program.
A fourth aspect of embodiments of the present invention provides a computer-readable storage medium, in which a computer program is stored, and the computer program, when executed by one or more processors, implements the steps of the pre-synchronization method according to the first aspect.
Compared with the prior art, the embodiment of the invention has the following beneficial effects: the embodiment of the invention firstly obtains the real-time angular frequency of the power grid based on the ECAP capturing unit, obtains the angular frequency automatically constructed by the inverter system, and then gradually approximates the angular frequency automatically constructed by the inverter system to the real-time angular frequency of the power grid based on the linear approximation method, so that the inverter system and the power grid realize same frequency and phase, and pre-synchronization is realized.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a schematic flow chart illustrating an implementation of a pre-synchronization method according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a model of an inverter system provided by an embodiment of the present invention;
FIG. 3 is a schematic diagram of an inverter small signal model provided by an embodiment of the invention;
fig. 4 is a schematic diagram of a nyquist plot for an inverter system provided by an embodiment of the present invention;
FIG. 5 is a schematic diagram of the output simulation waveform when PLL phase locking is used when the power grid adds harmonics;
FIG. 6 is a schematic diagram of an output simulation waveform when an Ecap capture unit is used when a harmonic is added to a power grid according to an embodiment of the present invention;
FIG. 7 is a schematic block diagram of a linear approximation method for pre-synchronization according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of an output simulation waveform using PLL phase locking when harmonics are added to the grid when the inverter system is in an islanded state;
fig. 9 is a schematic diagram of an output simulation waveform using an Ecap capture unit when an inverter system is in an islanded state and a grid is normal according to an embodiment of the present invention;
fig. 10 is a schematic diagram of an output simulation waveform using an Ecap capture unit when a harmonic wave is added to a grid when an inverter system is in an islanded state according to an embodiment of the present invention;
FIG. 11 is a schematic diagram of an output simulation waveform when the grid frequency abruptly changes from 45Hz to 50Hz in the conventional pre-synchronization process;
FIG. 12 is a schematic diagram of an output simulation waveform when the grid frequency abruptly changes from 50Hz to 45Hz in the conventional pre-synchronization process;
FIG. 13 is a schematic diagram of an output simulation waveform when the grid frequency abruptly changes from 50Hz to 55Hz in the conventional pre-synchronization process;
FIG. 14 is a schematic diagram of an output simulation waveform when the grid frequency abruptly changes from 55Hz to 50Hz in the conventional pre-synchronization process;
FIG. 15 is a schematic diagram of an output simulation waveform when a harmonic wave is added to a power grid and the frequency of the power grid suddenly changes in a conventional pre-synchronization process;
fig. 16 is a schematic diagram illustrating a pre-synchronization process between an inverter system and a power grid in the pre-synchronization method according to an embodiment of the present invention;
fig. 17 is a schematic diagram of an output simulation waveform when a harmonic is added to a power grid and a frequency of the power grid suddenly changes in the pre-synchronization method according to an embodiment of the present invention;
fig. 18 is a schematic diagram of an output simulation waveform when an islanding grid-connected switching is realized by using the pre-synchronization method provided in an embodiment of the present invention;
fig. 19 is a schematic diagram of an output simulation waveform when a pre-synchronization method provided by an embodiment of the present invention is used to implement grid-connected island switching;
FIG. 20 is a schematic block diagram of a pre-synchronization system provided by an embodiment of the present invention;
fig. 21 is a schematic block diagram of a terminal device according to an embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.
In order to explain the technical means of the present invention, the following description will be given by way of specific examples.
Fig. 1 is a schematic flow chart of an implementation of a pre-synchronization method according to an embodiment of the present invention, and for convenience of description, only a part related to the embodiment of the present invention is shown. The execution main body of the embodiment of the invention can be terminal equipment. As shown in fig. 1, the method may include the steps of:
s101: and acquiring the real-time angular frequency of the power grid based on the ECAP capturing unit.
In one embodiment of the invention, the frequency of the grid is in the range of 45Hz-55 Hz.
In the embodiment of the invention, an inverter system is taken as a research object, the wide power grid frequency (45Hz-55Hz) is considered, and a pre-synchronization method used in a grid-connected island smooth switching method is provided.
In an embodiment of the present invention, an inverter system is modeled. The output voltage and the inductive current of the inverter system are respectively sampled, the voltage reference and the output voltage are compared to form a closed loop, the output value is used as the inductive current closed loop reference after PI regulation, the inductive current closed loop reference is output after PI regulation, the duty ratio is formed by comparison with a PWM wave, a switching tube is driven, and the double closed loop mode of an output voltage outer loop and an inductive current inner loop is realized.
Referring specifically to fig. 2, the output voltage v of the inverter system is sampled0And the inductor current iinvtTo v is to v0DQ coordinate transformation is carried out to obtain a component v of the output voltage on a D axis0dAnd the component v of the output voltage on the Q-axis0qTo i, pairinvtDQ coordinate transformation is carried out to obtain a component i of the inductive current on a D axisinvtdAnd the component i of the inductor current on the Q axisinvtq. Component v of reference voltage value on D axis0d *And v0dMaking a difference to obtain a first difference value, after the first difference value is subjected to PI regulation,obtaining a first adjustment value, the first adjustment value and iinvtdAnd performing difference to obtain a second difference value, and performing PI regulation on the second difference value to obtain a second regulation value. The components 0 and v of the voltage reference value on the Q axis0qObtaining a third difference value by performing difference, and obtaining a third regulating value after the third difference value is subjected to PI regulation; the third adjustment value is compared with iinvtqAnd performing difference to obtain a fourth difference value, and performing PI regulation on the fourth difference value to obtain a fourth regulation value. And carrying out alpha and beta coordinate transformation on the second regulating value and the fourth regulating value to obtain a control value after alpha and beta transformation. And carrying out space vector pulse width modulation on the control value after alpha and beta conversion to obtain a driving signal, namely comparing the control value after alpha and beta conversion with a PWM (pulse-width modulation) wave to form a duty ratio, wherein the driving signal is used for driving a switching tube.
An inverter small signal model is constructed according to the double-closed-loop mode, and as shown in fig. 3, a double-closed-loop transfer function can be derived:
wherein v is0To output voltage, v0 *To output a voltage reference, i0For output current, L is filter inductor, r is parasitic resistance of inductor, C is filter capacitor, GvAs a voltage loop PI regulator, GcIs a current loop PI regulator, and is characterized in that,
delay introduced for digital control systems,. tau.apprxeq.1.5Ts，TsFor the switching cycle, the switching frequency in the embodiment of the present invention is 25KHz, and thus
And small, negligible, S is an S-domain complex variable formed after laplace transform, and z (S) ═ ts +1 (Ls + r).
And (4) according to the transfer function, carrying out Nyquist diagram plotting on the stability of the inverter system, wherein the Nyquist diagram of the inverter system does not cross the (-1, j0) point and the system is stable as shown in FIG. 4.
From the above description, it can be seen that the system is ideally stable, but if a conventional PLL phase-locked loop is used for phase locking, in the non-ideal case, if harmonics exist in the grid, i is0Harmonic waves are introduced due to the influence of the power grid harmonic waves, so that the inverter system is more dependent on the stability of power grid voltage sampling, the instability of the power grid voltage directly influences the output, the harmonic waves are introduced into a phase-locked loop, and therefore the problems of output oscillation and system instability are caused due to new harmonic wave disturbance. Therefore, the embodiment of the invention provides a new pre-synchronization method, and a method for capturing phase lock is used, so that harmonic waves are not introduced under the non-ideal condition, and the system is relatively stable.
In an embodiment of the present invention, the above S101 may include the following steps:
based on a zero-crossing detection circuit, acquiring a zero-crossing point of the power grid in real time, and capturing the zero-crossing point of the power grid through an ECAP capturing unit;
and calculating the real-time angular frequency of the power grid according to the zero crossing point of the power grid.
In an embodiment of the present invention, the calculating the real-time angular frequency of the power grid according to the zero-crossing point of the power grid may include the following steps:
detecting the frequency of the power grid in real time based on a frequency detection circuit;
and calculating the real-time angular frequency of the power grid according to the frequency of the power grid and the zero crossing point of the power grid.
In the embodiment of the invention, the frequency of the power grid can be detected in real time through a frequency detection circuit built by hardware; the zero-crossing point of the power grid can be detected in real time through a zero-crossing detection circuit built by hardware, and the zero-crossing point of the power grid is captured through an Ecap capturing unit. Based on the captured zero crossing point of the power grid, the detected frequency of the power grid and the time delay of a hardware circuit (a frequency detection circuit and a zero crossing detection circuit), the real-time angular frequency of the power grid can be calculated by adopting the existing method.
For the simulation waveforms of the output using the PLL phase lock and the Ecap capture unit when the harmonic wave is added to the power grid, as shown in fig. 5 and fig. 6, respectively, it can be clearly seen that the harmonic wave of the output waveform using the PLL phase lock is significantly large.
S102: and acquiring the angular frequency self-constructed by the inverter system.
In the embodiment of the present invention, the angular frequency of the inverter system that is constructed by itself, that is, the initial angular frequency of the inverter system in the linear approximation method, may be obtained by using an existing method.
S103: based on a linear approximation method, the angular frequency automatically constructed by the inverter system gradually approaches the real-time angular frequency of the power grid.
In an embodiment of the present invention, the S103 may include:
according to
Angular frequency omega for self-construction of inverter systemiSuccessive approximation to real-time angular frequency omega of power grid0；
Wherein, the delta omega is a preset threshold value,
b is a predetermined coefficient, b<1，fgIs the grid frequency; omegaiThe angular frequency of the inverter system when the inverter system approaches the power grid for the ith time; omegai+1The angular frequency of the inverter system when the inverter system approaches the power grid for the (i +1) th time; i is a positive integer; kt is a linear function of the time series. And t is the time which is gradually increased after the angular frequency of the power grid is obtained when the inverter system approaches the power grid for the first time and the timing is started.
Specifically, the above formula can be derived from the following formula:
Wherein, ω isiThe current angular frequency of the inverter system when the inverter system approaches the power grid for the ith time; omegai+1The angular frequency of the inverter system after the inverter system approaches the grid for the ith time is also the current angular frequency of the inverter system when the inverter system approaches the grid for the (i +1) th time.
The synchronization of the angular frequency of the inverter system and the angular frequency of the power grid is a gradual approximation process, and is realized by multiple approximations, each time the angular frequency approaches a small value.
Specifically, a linear approximation method is adopted, the static-error-free tracking of the power grid phase of the module is realized, the numerical value of each approximation is different according to the difference of the power grid frequency, pre-synchronization is realized in advance before switching from island to grid connection, and the pre-synchronization process refers to the formula. Wherein b can be determined according to actual conditions.
Referring to fig. 7, due to the fluctuation of the grid frequency between 45Hz and 55Hz, kt Δ ω is limited, the size of the limitation is related to the value of k, k is a preset coefficient, and t is a value which gradually increases with time. In the above formula, if ωi-ω0When the value is more than or equal to delta omega, the addition and subtraction selection module is subtraction, namely omegai+1＝ωi-kt Δ ω; if omega0-ωiWhen the value is more than or equal to delta omega, the addition and subtraction selection module is addition, namely omegai+1＝ωi+ kt Δ ω. By the formula, the angular frequency automatically constructed by the inverter system slowly approaches to the angular frequency of the power grid.
In the linear approximation method, the adaptive threshold frequency is realized by using an addition and subtraction selection module. I.e. omegaiAnd omega0Is compared to Δ ω, in particular according to the formula
The larger the grid frequency is, the smaller the grid period is, and the smaller the corresponding delta omega is, so that the addition and subtraction selection module has a frequency self-adaption function.
The linear approximation process realizes the step value frequency self-adaption. Specifically, the approximation process uses a very small step value kt Δ ω, which is different according to the change of the frequency, and the larger the frequency is, the smaller the step value is, and the frequency detected by the hardware frequency detection circuit does not change abruptly. For the traditional presynchronization process, if the power grid suddenly changes or the harmonic interference of the power grid is large, the real-time phase angle suddenly changes, the power grid phase angle directly influences the presynchronization step value, and the oversynchronization phenomenon exceeding the synchronous value can occur when the step value is too large. By adopting the presynchronization method provided by the embodiment of the invention, even if the power grid suddenly changes and the synchronization phenomenon is misinformed, the presynchronization method can only change in a minimum step value within the misinformation time, cannot generate sudden change and cannot generate the oversynchronization phenomenon, has strong anti-interference capability and higher reliability and universality, and has the advantages of reducing harmonic waves, reducing energy consumption and preventing output distortion.
According to the presynchronization method provided by the embodiment of the invention, when the micro-grid system, namely an inverter system, runs and the grid frequency is suddenly changed in a wider frequency range, the micro-grid system can realize no-difference following under the switching of an island, a grid connection or a grid connection island, can realize the stable running of the system, and has higher robustness.
The embodiment of the invention uses a software control strategy, even if the frequency, the phase angle mutation or the harmonic wave of the power grid is larger in the range of wide power grid frequency (45Hz-55Hz), the invention does not depend on a PLL (phase locked loop), has low requirements on factors such as filtering of a hardware sampling circuit, and the like, uses an Ecap capture unit to monitor the zero crossing point of the power grid in real time, realizes the presynchronization process, and enables the grid connection, the isolated island and the switching between the grid connection and the isolated island to stably operate.
The embodiment of the invention verifies the stability of the pre-synchronization method through experiments. In the experiment, the system adopts the mode that the rated voltage amplitude is 220V, the frequency is 45Hz-55Hz, and harmonic waves are introduced into a power grid, under the condition that the power grid frequency is 50Hz, a traditional PLL is used for obtaining a real-time phase angle, the output waveform in an island is shown in figure 8, and as is obvious from figure 8, under the condition that the power grid has harmonic waves, the PLL is used for obtaining the phase angle, and the output voltage and current waveform have obvious harmonic waves.
Under the condition of 50Hz, the PLL phase locking mode is changed into a mode of acquiring a phase angle by Ecap capture, when a power grid is normal, an output waveform is shown in figure 9, when the phase angle is acquired by Ecap capture, an output waveform when the power grid suddenly adds harmonics is shown in figure 10. As is apparent from fig. 9 and 10, when the power grid is normal, a perfect output waveform can be output, and when the power grid suddenly adds a harmonic wave, the perfect waveform can still be output without being affected by the harmonic wave of the power grid by using the Ecap capture method to obtain the phase angle.
By using the traditional presynchronization process, in the presynchronization process, when the frequency of the power grid suddenly changes, the step value in the approaching process can be greatly changed, the specific experimental waveform is shown in fig. 11, 12, 13 and 14, the phase angle suddenly changes, and the oversynchronization phenomenon occurs. In the conventional pre-synchronization process, when the frequency of the power grid suddenly changes, harmonic waves are added at the same time, and the specific experimental waveform is shown in fig. 15, so that the output oscillation occurs in the pre-synchronization process.
The presynchronization process in the embodiment of the invention can realize a fixed stepping value, the specific synchronization process is shown in fig. 16, the inversion output follows the phase angle of the power grid within a period of time to realize the same frequency and phase, meanwhile, when the frequency of the power grid changes suddenly, the harmonic wave of the power grid is added, the slight output voltage amplitude change is found in the sudden change process, but finally, a perfect waveform can be output within a shorter time, as shown in fig. 17, compared with the traditional presynchronization process, the presynchronization process in the embodiment of the invention can not generate the phase angle sudden change, and can not generate output oscillation.
The presynchronization process of the embodiment of the invention is used for switching from the isolated island to the grid-connected mode, as shown in fig. 18, and the switching process from the grid-connected mode to the isolated island, as shown in fig. 19, it can be seen that the switching process is smoothly carried out.
In summary, in the embodiment of the present invention, even if there is a sudden change in the power grid, no matter the harmonic wave, the frequency, etc., in a wider power grid frequency range (45Hz-55Hz), by using the Ecap capture method and the pre-synchronization process of the embodiment of the present invention, the output can be unaffected, and a perfect waveform can be formed no matter whether isolated island, grid connection, or switching between the isolated island and the grid connection.
It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.
Corresponding to the pre-synchronization method, an embodiment of the present invention provides a pre-synchronization system, which has the same beneficial effects as the pre-synchronization method. Fig. 20 is a schematic block diagram of a pre-synchronization system according to an embodiment of the present invention, and only the relevant parts of the pre-synchronization system according to the embodiment of the present invention are shown for convenience of illustration.
In an embodiment of the present invention, the pre-synchronization system 30 may include a grid angular frequency acquisition module 301, an inverter angular frequency acquisition module 302, and a linear approximation module 303.
The power grid angular frequency acquisition module 301 is configured to acquire a real-time angular frequency of a power grid based on an ECAP capture unit;
an inverter angular frequency obtaining module 302, configured to obtain an angular frequency that an inverter system constructs by itself;
and the linear approximation module 303 is configured to gradually approximate the angular frequency, which is automatically constructed by the inverter system, to the real-time angular frequency of the power grid based on a linear approximation method.
Optionally, the linear approximation module 303 is further configured to:
according to
Angular frequency omega for self-construction of inverter systemiSuccessive approximation to real-time angular frequency omega of power grid0；
Wherein, the delta omega is a preset threshold value,
b is a predetermined coefficient, b<1，fgIs the grid frequency; omegaiThe angular frequency of the inverter system when the inverter system approaches the power grid for the ith time; omegai+1The angular frequency of the inverter system when the inverter system approaches the power grid for the (i +1) th time; i is a positive integer; kt is a linear function of the time series.
Optionally, the grid angular frequency obtaining module 301 is further configured to:
based on a zero-crossing detection circuit, acquiring a zero-crossing point of the power grid in real time, and capturing the zero-crossing point of the power grid through an ECAP capturing unit;
and calculating the real-time angular frequency of the power grid according to the zero crossing point of the power grid.
Optionally, the grid angular frequency obtaining module 301 is further configured to:
detecting the frequency of the power grid in real time based on a frequency detection circuit;
and calculating the real-time angular frequency of the power grid according to the frequency of the power grid and the zero crossing point of the power grid.
Optionally, the frequency of the grid is in the range of 45Hz-55 Hz.
It is obvious to those skilled in the art that, for convenience and simplicity of description, the foregoing division of the functional units and modules is merely used as an example, and in practical applications, the foregoing function distribution may be performed by different functional units and modules as needed, that is, the internal structure of the pre-synchronization system is divided into different functional units or modules to perform all or part of the above-described functions. Each functional unit and module in the embodiments may be integrated in one processing unit, or each unit may exist alone physically, or two or more units are integrated in one unit, and the integrated unit may be implemented in a form of hardware, or in a form of software functional unit. In addition, specific names of the functional units and modules are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present application. The specific working processes of the units and modules in the above-mentioned apparatus may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
Fig. 21 is a schematic block diagram of a terminal device according to an embodiment of the present invention. As shown in fig. 21, the terminal device 40 of this embodiment includes: one or more processors 401, a memory 402, and a computer program 403 stored in the memory 402 and executable on the processors 401. The processor 401, when executing the computer program 403, implements the steps in the various embodiments of the pre-synchronization method described above, such as the steps S101 to S103 shown in fig. 1. Alternatively, the processor 401, when executing the computer program 403, implements the functions of the modules/units in the pre-synchronization system embodiment, for example, the functions of the modules 301 to 303 shown in fig. 20.
Illustratively, the computer program 403 may be partitioned into one or more modules/units that are stored in the memory 402 and executed by the processor 401 to accomplish the present application. The one or more modules/units may be a series of computer program instruction segments capable of performing specific functions, which are used for describing the execution process of the computer program 403 in the terminal device 40. For example, the computer program 403 may be divided into a grid angular frequency acquisition module, an inverter angular frequency acquisition module, and a linear approximation module, and each module has the following specific functions:
the power grid angular frequency acquisition module is used for acquiring the real-time angular frequency of the power grid based on the ECAP acquisition unit;
the inverter angular frequency acquisition module is used for acquiring the angular frequency constructed by the inverter system;
and the linear approximation module is used for gradually approximating the angular frequency automatically constructed by the inverter system to the real-time angular frequency of the power grid based on a linear approximation method.
Other modules or units can be referred to the description of the embodiment shown in fig. 20, and are not described again here.
The terminal device 40 may be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The terminal device 40 includes, but is not limited to, a processor 401 and a memory 402. Those skilled in the art will appreciate that fig. 21 is only one example of a terminal device 40, and does not constitute a limitation to the terminal device 40, and may include more or less components than those shown, or combine some components, or different components, for example, the terminal device 40 may further include an input device, an output device, a network access device, a bus, etc.
The Processor 401 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic device, discrete hardware component, or the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The storage 402 may be an internal storage unit of the terminal device 40, such as a hard disk or a memory of the terminal device 40. The memory 402 may also be an external storage device of the terminal device 40, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), and the like, which are provided on the terminal device 40. Further, the memory 402 may also include both an internal storage unit of the terminal device 40 and an external storage device. The memory 402 is used for storing the computer program 403 and other programs and data required by the terminal device 40. The memory 402 may also be used to temporarily store data that has been output or is to be output.
In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and reference may be made to the related descriptions of other embodiments for parts that are not described or illustrated in a certain embodiment.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
In the embodiments provided in the present application, it should be understood that the disclosed pre-synchronization system and method may be implemented in other ways. For example, the pre-synchronization system embodiments described above are merely illustrative, and for example, the division of the modules or units is only one logical division, and there may be other divisions when actually implemented, for example, multiple units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated modules/units, if implemented in the form of software functional units and sold or used as separate products, may be stored in a computer readable storage medium. Based on such understanding, all or part of the flow in the method of the embodiments described above can be realized by a computer program, which can be stored in a computer-readable storage medium and can realize the steps of the embodiments of the methods described above when the computer program is executed by a processor. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, usb disk, removable hard disk, magnetic disk, optical disk, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, software distribution medium, and the like. It should be noted that the computer readable medium may contain other components which may be suitably increased or decreased as required by legislation and patent practice in jurisdictions, for example, in some jurisdictions, computer readable media which may not include electrical carrier signals and telecommunications signals in accordance with legislation and patent practice.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.
Claims (8)
1. A method of presynchronization, comprising:
acquiring the real-time angular frequency of the power grid based on an ECAP (equal cost adaptive processing) capturing unit;
acquiring the angular frequency automatically constructed by an inverter system;
based on a linear approximation method, gradually approximating the angular frequency automatically constructed by the inverter system to the real-time angular frequency of the power grid;
the step-by-step approximation of the angular frequency, which is automatically constructed by the inverter system, to the real-time angular frequency of the power grid based on the linear approximation method comprises the following steps:
according to
Angular frequency ω of the inverter system self-builtiSuccessive approximation of a real-time angular frequency ω of the grid0；
Wherein, the delta omega is a preset threshold value,
b is a predetermined coefficient, b<1，fgIs the grid frequency; omegaiThe angular frequency of the inverter system when the inverter system approaches the power grid for the ith time; omegai+1The angular frequency of the inverter system when the inverter system approaches the power grid for the (i +1) th time; i is a positive integer; kt is a linear function of the time series.
2. The presynchronization method according to claim 1, wherein the acquiring a real-time angular frequency of the grid based on the ECAP capture unit comprises:
based on a zero-crossing detection circuit, acquiring a zero-crossing point of the power grid in real time, and capturing the zero-crossing point of the power grid through an ECAP capturing unit;
and calculating the real-time angular frequency of the power grid according to the zero crossing point of the power grid.
3. The presynchronization method according to claim 2, wherein the calculating of the real-time angular frequency of the grid from zero crossings of the grid comprises:
detecting the frequency of the power grid in real time based on a frequency detection circuit;
and calculating the real-time angular frequency of the power grid according to the frequency of the power grid and the zero crossing point of the power grid.
4. A method of presynchronization according to any of claims 1 to 3, characterized in that the frequency of the power grid is in the range of 45-55 Hz.
5. A pre-synchronization system, comprising:
the power grid angular frequency acquisition module is used for acquiring the real-time angular frequency of the power grid based on the ECAP acquisition unit;
the inverter angular frequency acquisition module is used for acquiring the angular frequency constructed by the inverter system;
the linear approximation module is used for gradually approximating the angular frequency automatically constructed by the inverter system to the real-time angular frequency of the power grid based on a linear approximation method;
the linear approximation module is further configured to:
according to
Angular frequency ω of the inverter system self-builtiSuccessive approximation of a real-time angular frequency ω of the grid0；
Wherein, the delta omega is a preset threshold value,
b is a predetermined coefficient, b<1，fgIs the grid frequency; omegaiThe angular frequency of the inverter system when the inverter system approaches the power grid for the ith time; omegai+1The angular frequency of the inverter system when the inverter system approaches the power grid for the (i +1) th time; i is a positive integer; kt is a linear function of the time series.
6. The pre-synchronization system of claim 5, wherein the grid angular frequency acquisition module is further configured to:
based on a zero-crossing detection circuit, acquiring a zero-crossing point of the power grid in real time, and capturing the zero-crossing point of the power grid through an ECAP capturing unit;
and calculating the real-time angular frequency of the power grid according to the zero crossing point of the power grid.
7. Terminal device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that the processor realizes the steps of the pre-synchronization method according to any of claims 1 to 4 when executing the computer program.
8. A computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program which, when executed by one or more processors, implements the steps of the pre-synchronization method according to any one of claims 1 to 4.
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