CN118100295A - Carrier synchronization method and system of multiple inverters and readable storage medium - Google Patents
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Abstract
The application discloses a carrier synchronization method, a carrier synchronization system and a readable storage medium of multiple inverters; the method comprises the following steps: sampling the power grid voltage, and modulating the frequency of the triangular carrier wave based on the frequency of the power grid voltage so that one power frequency period of the power grid voltage corresponds to the triangular carrier wave with integer times; the triangular carrier wave is subjected to phase modulation based on zero crossing points of the power grid voltage, so that the phase of the triangular carrier wave after phase modulation is consistent with the absolute value of the phase of the power grid voltage; the steps are executed for each inverter, so that carrier synchronization of multiple inverters is realized. The readable storage medium is for implementing the foregoing method, and the system includes the readable storage medium. The application has the beneficial effects that: compared with the traditional carrier synchronization scheme, the external communication equipment which relies on high-speed information interaction carries out information interaction among the inverters; the scheme of the application does not need external communication equipment, and has the effects of saving cost and being convenient to realize.
Description
Technical Field
The application relates to the technical field of new energy power generation, in particular to a carrier synchronization method and system of multiple inverters and a readable storage medium.
Background
Along with the high-speed development of current new energy, the current photovoltaic grid-connected inverter is increasingly applied to a ground power station, and the ground power station has the characteristics of large capacity and more single box-type inverters. The inverters are connected in parallel, and a loop current of a switching frequency is easily generated. Therefore, the carrier synchronization scheme can effectively avoid the problem, and the current carrier synchronization scheme is mostly dependent on hardware to provide external high-speed communication equipment, so that a plurality of slave inverters acquire carrier synchronization signals of a main inverter and then perform carrier synchronization. The scheme of realizing carrier synchronization by adopting external communication has the advantages of complex wiring and high realization cost, and communication interfaces and the like must be preset at the beginning of design, and the realization is difficult if the communication interfaces are not preset at first. Based on this, a software multi-inverter carrier synchronization method is urgently needed.
Disclosure of Invention
One of the objects of the present application is to provide a carrier synchronization method for multiple inverters, which can solve at least one of the above-mentioned drawbacks of the related art.
Another object of the present application is to provide a carrier synchronization system of multiple inverters that can solve at least one of the above-mentioned drawbacks of the related art.
It is still another object of the present application to provide a readable storage medium capable of implementing a carrier synchronization method of multiple inverters.
In order to achieve at least one of the above objects, the present application adopts the following technical scheme: a carrier synchronization method of multiple inverters comprises the following specific steps:
Sampling the power grid voltage;
Modulating the frequency of the triangular carrier based on the frequency of the power grid voltage, so that one power frequency period of the power grid voltage corresponds to the triangular carrier with integral multiple;
the triangular carrier wave is subjected to phase modulation based on zero crossing points of the power grid voltage, so that the phase of the triangular carrier wave after phase modulation is consistent with the absolute value of the phase of the power grid voltage;
The steps are executed for each inverter, so that carrier synchronization of multiple inverters is realized.
Preferably, the frequency modulation of the triangular carrier based on the frequency of the grid voltage comprises the following processes:
according to the frequency of the power grid voltage, calculating the switching frequency of the triangular carrier wave corresponding to integer times in one power frequency period;
calculating a period value T 0 of the triangular carrier through the calculated switching frequency f;
And adjusting the period value T 'of the current triangular carrier to T' (T 0).
Preferably, the phase modulation of the triangular carrier based on the zero crossing point of the grid voltage comprises the following processes:
Reading two power grid voltage sampling values U1 and U2 before and after the power grid voltage zero crossing point;
judging whether the middle points of the two power grid voltage sampling values are zero crossing points of the power grid voltage;
If the midpoint of the sampling values of the two power grid voltages is the zero crossing point of the non-power grid voltage, calculating the phase synchronization value DeltaT of the triangular carrier according to the sampling values of the two power grid voltages, and carrying out synchronization adjustment.
Preferably, the absolute average value of the two power grid voltage sampling values and the offset value DeltaV of one of the power grid voltage sampling values are calculated, and whether the midpoint of the two power grid voltage sampling values is the zero crossing point of the power grid voltage is judged based on the value of the offset value DeltaV
Preferably, the calculation formula of the offset value DeltaV is: deltav= |u1|- (|u1|+|u2|)/2; if the DeltaV value is zero, judging that the midpoint of the sampling values of the two power grid voltages coincides with the zero crossing point of the power grid voltages; if the DeltaV value is negative, judging that the midpoints of two power grid voltage sampling values are positioned on the right side of a zero crossing point of the power grid voltage, and enabling the triangular carrier wave to need to move left for synchronization; if the DeltaV value is positive, judging that the midpoints of the two power grid voltage sampling values are positioned at the left side of the zero crossing point of the power grid voltage, and the triangular carrier wave needs to move right to be synchronized.
Preferably, the calculation formula of the offset value DeltaV is: deltav= |u2|- (|u1|+|u2|)/2; if the DeltaV value is zero, judging that the midpoint of the sampling values of the two power grid voltages coincides with the zero crossing point of the power grid voltages; if the DeltaV value is negative, judging that the midpoints of two power grid voltage sampling values are positioned at the left side of a zero crossing point of the power grid voltage, and enabling the triangular carrier waves to need to move right for synchronization; if the DeltaV value is positive, judging that the midpoints of the two power grid voltage sampling values are positioned on the right side of the zero crossing point of the power grid voltage, and the triangular carrier wave needs to be shifted left to carry out synchronization.
Preferably, the phase synchronization value DeltaT of the triangular carrier is calculated as follows:
; or,/> ；
Wherein TBPRD is the period value of the current triangular carrier.
A computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the above-described carrier synchronization method for multiple inverters.
A carrier synchronization system of multiple inverters, comprising the computer readable storage medium and EPWM modules; at the moment of the zero crossing point of the power grid voltage, the phase value of TBPHS in the EPWM module is adjusted based on the phase adjustment signal of the triangular carrier wave output by the computer readable storage medium, and then the software is triggered SWFSYNC in one power frequency period.
Preferably, in the carrier synchronization process, the timing of phase shift adjustment needs to be judged, and the specific judgment process is as follows: in the synchronous adjustment process, comparing the value of the software phase modulation with the value of the CMPA in the EPWM module, and waiting if the current value of the CMPA is between the period values of the triangular carrier before and after phase shifting; and if the current value of the CMPA is equal to the period value of the triangular carrier after phase shifting, executing a phase shifting program.
Compared with the prior art, the application has the beneficial effects that:
(1) Compared with the traditional carrier synchronization scheme, the external communication equipment which relies on high-speed information interaction carries out information interaction among the inverters; the scheme of the application does not need external communication equipment, and has the effects of saving cost and being convenient to realize.
(2) Compared with the traditional carrier synchronization scheme, a master-slave inverter needs to be set, and a slave inverter depends on master inverter information to realize carrier synchronization; according to the scheme, synchronization can be realized only by depending on the power grid voltage information, a master-slave inverter is not required to be distinguished, and a carrier synchronization function can be realized when power grid voltage sampling exists.
(3) According to the scheme of the application, the phase can be adjusted timely according to the relative position of the triangular carrier and the power grid voltage, and the situation that the phase cannot be recovered after the phase deviation is caused by the error of each control chip crystal oscillator can be effectively avoided.
Drawings
Fig. 1 is a schematic diagram of a topology circuit structure of two single-phase machines connected in parallel in the prior art.
Fig. 2 is an equivalent circuit schematic diagram of the topology shown in fig. 1.
FIG. 3 is a schematic diagram of carrier modeling in the present invention.
Fig. 4 is a schematic of the overall workflow of the present invention.
Fig. 5 is a schematic diagram of sampling grid voltage twice before and after a grid voltage zero crossing in the present invention.
Fig. 6 is a schematic diagram of experimental results of grid current and inductor current when carrier synchronization is not performed.
Fig. 7 is a schematic diagram of an experimental structure of a grid current and an inductor current after carrier synchronization according to the present invention.
Detailed Description
The present application will be further described with reference to the following specific embodiments, and it should be noted that, on the premise of no conflict, new embodiments may be formed by any combination of the embodiments or technical features described below.
In the description of the present application, it should be noted that, for the azimuth words such as terms "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., the azimuth and positional relationships are based on the azimuth or positional relationships shown in the drawings, it is merely for convenience of describing the present application and simplifying the description, and it is not to be construed as limiting the specific scope of protection of the present application that the device or element referred to must have a specific azimuth configuration and operation.
It should be noted that the terms "first," "second," and the like in the description and in the claims are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.
The terms "comprises" and "comprising," along with any variations thereof, in the description and claims, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
In order to facilitate understanding of the technical scheme of the application, the situation that the carriers are not synchronized can be analyzed first. As shown in fig. 1, taking two single-phase parallel systems as an example, two inverters are respectively labeled as #1 and #2; wherein the output voltage of the inverter #1 is u n1, and the output voltage of the inverter #2 is u n2; the output impedance of the two inverters is assumed to be the same and Z L, and the impedance of the power grid side is Z s. The equivalent circuit shown in fig. 2 can be obtained according to the topology circuit shown in fig. 1; the two inverter circuits in the equivalent circuit can be seen as two modules connected in parallel to the grid. The analysis method based on the parallel system of the two single-phase machines can be expanded to any parallel system of a plurality of inverters.
Assuming that the grid V g is ignored first, only the high-frequency current components I 1 and I 2 due to carrier dyssynchrony of the equivalent output voltages U n1 and U n2 of the two inverters are considered, the following expression (1) can be obtained.
。
Wherein I s represents grid-side current, I s=I1+I2.
To facilitate clear expression of the high-frequency current components I 1 and I 2, I 1 and I 2 can be simplified, and the following hypothetical expression (2) can be obtained
。
According to expression (2), the high-frequency current components I 1 and I 2 in expression (1) can be deformed, and the following expression (3) can be obtained.
。
As is clear from the above expression (3), the high-frequency current components I 1 and I 2 are each composed of two parts. The first part is related only to the equivalent output voltages U n1 and U n2 of the two modules, i.e., I 11 and I 22, respectively; this portion of the current flows to the grid. The second part is related to the difference in voltage Δu=u n1–Un2, i.e. I 12 and I 21; the current is a circulating current. The component size of the circulating current will be analyzed below under carrier dyssynchrony.
As shown in fig. 3, the carrier wave is modeled first, and the expression of the reference wave u s may be employed as the following expression (4).
。
Where U m denotes the peak voltage of the triangular carrier, ω c is the frequency of the high frequency carrier,Representing the phase.
According to the intersection of the reference wave and the triangular carrier wave in fig. 3, bipolar modulation may be employed, resulting in expression (5) of the modulated wave signal u as follows.
。
Wherein U dc/2 represents the peak value of the modulated wave.
Performing fourier series expansion on the expression (5) to obtain u=a+b; wherein the specific expressions of the A part and the B part are shown as follows.
。
。
As can be seen from the above expression, the a part is a modulated wave part, which is a low frequency signal; the B part is a high-frequency component, and is related to not only the modulated wave but also the frequency ω c of the high-frequency carrier wave.
Suppose that the corresponding SPWM carrier of inverter #2 lags behind inverter #1 by a phase ofFrom the above expression of the fourier series expansion of the modulated wave signal u, an expression of the fourier series expansion corresponding to the equivalent high-frequency component voltage difference Δu n=un1-un2;Δun can be obtained as shown in the following expression.
。
The high frequency component voltage difference Deltau n can cause high frequency loop current, the size of the loop current is:。
as is clear from the above analysis results, when the carriers are not synchronized, a high-frequency loop current occurs. In order to suppress the high frequency circulating current, an aspect of the present application provides a carrier synchronization method of a multi-inverter for achieving carrier synchronization and suppressing the high frequency circulating current. As shown in fig. 1, one preferred embodiment includes the following specific steps:
the grid voltage is sampled.
And modulating the frequency of the triangular carrier based on the frequency of the power grid voltage, so that one power frequency period of the power grid voltage corresponds to the triangular carrier with integral multiple.
And carrying out phase modulation on the triangular carrier based on the zero crossing point of the power grid voltage, so that the phase of the triangular carrier after phase modulation is consistent with the absolute value of the phase of the power grid voltage.
The steps are executed for each inverter, so that carrier synchronization of multiple inverters is realized.
It will be appreciated that for carrier synchronization of multiple inverters, it can be seen as a set of carrier synchronization for each individual inverter. That is, the method of carrier synchronization for each individual inverter is the same, and after all the inverters individually complete carrier synchronization for each individual inverter, since the grid voltages corresponding to the plurality of inverters are the same, the waveform structures of the triangular carriers corresponding to the plurality of inverters are also the same.
For carrier synchronization of the inverters, the basic working principle is to use a zero crossing point of the power grid voltage as a reference of a plurality of inverters, and then realize carrier synchronization of the inverters; the method can be divided into frequency modulation and phase modulation. The purpose of frequency modulation is to realize a triangular carrier with a power frequency period corresponding to integer times, namely, the length of the power frequency period is the period length of the triangular carrier with integer times, so that the triangular carrier can be aligned with the waveform of the power grid voltage in a relatively neat structure after synchronization. The phase modulation is carried out on the basis of frequency modulation, namely, the position of the triangular carrier of different inverters relative to the zero crossing point of the power grid voltage is unified, namely, the phase of the first triangular carrier is kept consistent with the absolute position of the power grid voltage phase after the phase modulation, so that the function of carrier synchronization is realized.
It should be appreciated that reference selections for inverter carrier synchronization, including but not limited to zero crossings of the grid voltage; for example, peak points of the grid voltage may also be selected, including positive peak points and negative peak points. Generally, the power grid voltage is in a zero level state at the zero crossing point, so that the influence on the system is minimal, and the zero crossing point of the power grid voltage is preferably used as a reference for carrier synchronization in the embodiment.
As is apparent from the above, information exchange is performed between the inverters in comparison with the conventional carrier synchronization scheme which relies on an external communication device for high-speed information exchange. The scheme of the application does not need external communication equipment, and has the effects of saving cost and being convenient to realize.
Meanwhile, compared with the traditional carrier synchronization scheme, a master-slave inverter needs to be set, and a slave inverter depends on master inverter information to realize carrier synchronization. According to the scheme, synchronization can be realized only by depending on the power grid voltage information, a master-slave inverter is not required to be distinguished, and a carrier synchronization function can be realized when power grid voltage sampling exists.
The scheme of the application can also timely adjust the phase according to the relative position of the triangular carrier and the power grid voltage, and can effectively avoid the situation that the phase cannot be recovered after the phase deviation is caused by the error of each control chip crystal oscillator.
In this embodiment, there are various manners of performing frequency modulation of the triangular carrier, one of which includes the following steps:
and calculating the switching frequency of the triangular carrier wave corresponding to integer times in one power frequency period according to the frequency of the power grid voltage.
The period value T 0 of the triangular carrier is calculated by the calculated switching frequency f.
And adjusting the period value T 'of the current triangular carrier to T' (T 0).
It should be noted that, since the carrier synchronization process is performed separately in each inverter, in order to ensure that the carrier synchronization of multiple inverters is accurate, it is necessary to ensure that the same phase grid voltage is sampled within a certain error accuracy. After the sampling of the grid voltage is completed, the frequency of the grid voltage can be obtained through calculation of a certain algorithm. The specific number of the triangular carriers corresponding to one power frequency period can be determined according to the actual needs of the person skilled in the art.
For ease of understanding, it may be represented by parameters; the frequency of the power grid voltage is f, and the number N of triangular carriers corresponding to one power frequency period can be obtained by calculating the switching frequency of the triangular carriers corresponding to the integer multiple in the one power frequency period; the period value T 0 =1/(fN) of the triangular carrier calculated by theory. After the theoretical calculation result of the period value of the triangular carrier is obtained, the period value T 'of the triangular carrier can be compared with the current period value T'; if T' =t 0, judging that the current triangular carrier meets the carrier synchronization requirement; if T 'is not equal to T 0, it is determined that the current triangular carrier does not meet the carrier synchronization requirement, and frequency modulation is required to be performed on the current triangular carrier until T' =t 0. The frequency modulation is realized by fine adjustment on the period value of the current triangular carrier, and the length of each power frequency period after the frequency modulation is finished is an integer multiple of the period length of the triangular carrier. Therefore, when the initial triangular carrier phase of the zero crossing point in one power frequency period is fixed with the absolute position of the power grid voltage, the phase of the triangular carrier in each power frequency period relative to the power grid voltage is unified.
In this embodiment, the zero crossing points of the different inverters subjected to the triangular carrier frequency modulation and the initial triangular carrier phase are not necessarily unified, and thus carrier synchronization of a plurality of inverters cannot be achieved. Namely, after finishing the frequency modulation of the triangular carrier, the triangular carrier is required to be subjected to phase modulation; as shown in fig. 5, the delta carrier phase modulation includes the following specific procedures:
and reading two power grid voltage sampling values U1 and U2 before and after the power grid voltage zero crossing point.
And judging whether the middle point of the two power grid voltage sampling values is a zero crossing point of the power grid voltage.
If the midpoint of the sampling values of the two power grid voltages is the zero crossing point of the non-power grid voltage, calculating the phase synchronization value DeltaT of the triangular carrier according to the sampling values of the two power grid voltages, and carrying out synchronization adjustment.
It can be understood that the zero crossing point of the grid voltage can be directly identified by an algorithm or software, and can also be identified by the positive and negative conditions of two continuous grid voltage sampling values; namely, when the sampling value of the continuous two power grid voltages is negative, the zero crossing point of the power grid voltages can be judged to be positioned between the sampling values of the continuous two power grid voltages; the sampling values of the two power grid voltages are sampling values U1 and U2 of the two power grid voltages before and after the zero crossing point of the power grid voltage.
It should be noted that, since the grid voltage is sinusoidal, if the grid voltage is in a carrier synchronous state, the absolute values of the sampled values U1 and U2 of the two grid voltages before and after the zero crossing point of the grid voltage are equal in theory. I.e. the midpoint of the sampled values U1 and U2 of the grid voltage corresponds to the zero crossing position of the grid voltage. In the subsequent process, whether the power grid voltage is in a carrier synchronization state can be judged by judging whether the midpoint of sampling values U1 and U2 of the power grid voltage is coincident with the zero crossing point position of the power grid voltage; if the power grid voltage is not in the carrier synchronization state, the phase difference value between the triangular carrier and the power grid voltage can be calculated through the values of sampling values U1 and U2 of the power grid voltage, and finally, the phase modulation of the triangular carrier is carried out according to the calculated phase difference value so as to finally realize carrier synchronization.
In this embodiment, there are various judging modes for whether the midpoints of the sampling values U1 and U2 of the grid voltage coincide with the zero crossing point of the grid voltage; including but not limited to the two examples described below.
Example one: as shown in fig. 5, the absolute values of the sampled values U1 and U2 of the two grid voltages may be calculated to determine whether the midpoint of the sampled values U1 and U2 of the two grid voltages coincides with the zero crossing point of the grid voltages.
Specifically, if the absolute value of the sampling value U1 is equal to the absolute value of the sampling value U2, it may be determined that the midpoint of the sampling values of the two grid voltages coincides with the zero crossing point of the grid voltage. If the absolute value of the sampling value U1 is smaller than the absolute value of the sampling value U2, it can be judged that the sampling value midpoints of the two grid voltages are not coincident with the zero crossing point position of the grid voltages, and the midpoints are positioned on the right side of the zero crossing point of the grid voltages, then the triangular carrier wave needs to be shifted left to realize synchronization. If the absolute value of the sampling value U1 is larger than the absolute value of the sampling value U2, it can be judged that the sampling value midpoints of the two grid voltages are not coincident with the zero crossing point position of the grid voltages, and the midpoints are positioned on the left side of the zero crossing point of the grid voltages, then the triangular carrier wave needs to move right to realize synchronization.
Example two: as shown in fig. 5, an offset DeltaV between the absolute average value of the two grid voltage sampling values and one of the grid voltage sampling values may be calculated, and based on the value of the offset DeltaV, it may be determined whether the midpoint of the two grid voltage sampling values is a zero crossing of the grid voltage.
Specifically, if the average value obtained by adding the absolute values of the sampling values U1 and U2 is equal to the absolute value of one of the sampling values of the grid voltages, it may be determined that the midpoint of the sampling values of the two grid voltages coincides with the zero crossing point of the grid voltages. If the average value obtained by adding the absolute values of the sampling values U1 and U2 is not equal to the absolute value of one of the sampling values of the grid voltage, the fact that the points of the sampling values of the two grid voltages are not coincident with the zero crossing point of the grid voltage can be judged. Specific analyses can be performed below with respect to specific offset directions in relation to selected grid voltage sampling values.
If the absolute value of the power grid voltage sampling value U1 is compared with the average value obtained by adding the absolute values of the sampling values U1 and U2, the calculation formula of the offset value DeltaV is as follows: deltav= |u1|- (|u1|+|u2|)/2. And if the DeltaV value is zero, judging that the midpoint of the sampling values of the two power grid voltages coincides with the zero crossing point of the power grid voltages. If the DeltaV value is negative, judging that the midpoints of the two power grid voltage sampling values are positioned on the right side of the zero crossing point of the power grid voltage, and then the triangular carrier wave needs to be shifted left to realize synchronization. If the DeltaV value is positive, judging that the midpoints of the two power grid voltage sampling values are positioned at the left side of the zero crossing point of the power grid voltage, and then right shifting the triangular carrier wave to realize synchronization.
If the absolute value of the power grid voltage sampling value U2 is compared with the average value obtained by adding the absolute values of the sampling values U1 and U2, the calculation formula of the offset value DeltaV is as follows: deltav= |u2|- (|u1|+|u2|)/2. And if the DeltaV value is zero, judging that the midpoint of the sampling values of the two power grid voltages coincides with the zero crossing point of the power grid voltages. If the DeltaV value is negative, judging that the midpoints of the two power grid voltage sampling values are positioned at the left side of the zero crossing point of the power grid voltage, and then right shifting the triangular carrier wave to realize synchronization. If the DeltaV value is positive, judging that the midpoints of the two power grid voltage sampling values are positioned on the right side of the zero crossing point of the power grid voltage, and then the triangular carrier wave needs to be shifted left to realize synchronization.
It should be appreciated that both of the above examples may satisfy the needs of the present application; meanwhile, in order to facilitate the calculation of the phase adjustment amount required for the subsequent triangular carrier synchronization, in this embodiment, the second example is adopted for the determination of whether the midpoint of the sampling values U1 and U2 of the grid voltage coincides with the zero crossing point of the grid voltage.
In this embodiment, the calculation formula of the phase synchronization value DeltaT of the triangular carrier is as follows:
DeltaT = TBPRD×2×DeltaV/(|U1|+|U2|)。
wherein TBPRD is the period value of the current triangular carrier; according to the difference of specific value formulas of the offset value DeltaV, the calculation formulas of the phase synchronization value DeltaT of the triangular carrier can be developed as follows:
; or,/> 。
It can be understood that the above two formulas can meet the requirements of the present application, and the calculation results of the two formulas based on the same power grid voltage sampling values U1 and U2 only have positive and negative relationships, that is, the absolute values of the delta carrier phase synchronization values DeltaT calculated by the two formulas are the same.
For the convenience of understanding, the carrier synchronization method provided by the application can be used for carrying out experiments, and carrier synchronization among a plurality of inverters can be effectively realized based on the experimental results. Taking two inverters as an example, specific experimental results are shown in fig. 6 and fig. 7, and comparison of the two diagrams can show that when the carrier synchronization scheme of the application is not adopted, as shown in fig. 6, the grid current (red waveform) has larger switching circulation; meanwhile, inductance current (green waveform and blue waveform) ripples of the two inverters are in a non-overlapping state. After the carrier synchronization scheme of the present application is adopted, as shown in fig. 7, the switching circulation of the grid current (red waveform) is significantly improved, and the inductance current (green waveform and blue waveform) ripples of the two inverters are substantially coincident.
Another aspect of the present application provides a computer readable storage medium having a computer program stored thereon, wherein a preferred embodiment is: the carrier synchronization method of multiple inverters described above may be implemented when the computer program is executed by a processor.
In yet another aspect, the present application provides a carrier synchronization system of multiple inverters, wherein a preferred embodiment includes the above-described computer-readable storage medium and EPWM modules. At the moment of the zero crossing point of the grid voltage, the phase value of TBPHS (phase register) in the EPWM module is adjusted based on the phase adjustment signal of the triangular carrier wave output by the computer readable storage medium, so that the software triggers SWFSYNC (software forced synchronization pulse) in one power frequency period.
In this embodiment, in the process of carrier synchronization, the timing of phase shift adjustment needs to be determined, and the specific determining process is as follows: in the synchronous adjustment process, comparing the value of the software phase modulation with the value of the CMPA (comparison register A) in the EPWM module, and waiting if the current value of the CMPA is between the period values of the triangular carrier before and after phase shifting; and executing a phase shifting program to perform carrier synchronization until the current value of the CMPA is equal to the period value of the phase-shifted triangular carrier. So as to ensure that the CMPA values before and after phase shifting can not lose efficacy due to phase shifting, and ensure that the CMPA values can still normally work as EPWM modules, thereby avoiding the change of wave generation in the phase shifting switch period.
The foregoing has outlined the basic principles, features, and advantages of the present application. It will be understood by those skilled in the art that the present application is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present application, and various changes and modifications may be made therein without departing from the spirit and scope of the application, which is defined by the appended claims. The scope of the application is defined by the appended claims and equivalents thereof.
Claims (10)
1. The multi-inverter carrier synchronization method based on zero crossing point power grid voltage sampling is characterized by comprising the following steps of:
Sampling the power grid voltage;
Modulating the frequency of the triangular carrier based on the frequency of the power grid voltage, so that one power frequency period of the power grid voltage corresponds to the triangular carrier with integral multiple;
the triangular carrier wave is subjected to phase modulation based on zero crossing points of the power grid voltage, so that the phase of the triangular carrier wave after phase modulation is consistent with the absolute value of the phase of the power grid voltage;
The steps are executed for each inverter, so that carrier synchronization of multiple inverters is realized.
2. The multi-inverter carrier synchronization method based on zero crossing grid voltage sampling of claim 1, wherein frequency modulating the triangular carrier based on the frequency of the grid voltage comprises the following processes:
according to the frequency of the power grid voltage, calculating the switching frequency of the triangular carrier wave corresponding to integer times in one power frequency period;
Calculating a period value T 0 of the triangular carrier based on the calculated switching frequency f;
And adjusting the period value T 'of the current triangular carrier to T' (T 0).
3. The multi-inverter carrier synchronization method based on zero crossing grid voltage sampling as set forth in claim 1, wherein phase modulating the delta carrier based on zero crossing of the grid voltage comprises the steps of:
Reading two power grid voltage sampling values U1 and U2 before and after the power grid voltage zero crossing point;
judging whether the middle points of the two power grid voltage sampling values are zero crossing points of the power grid voltage;
If the midpoint of the sampling values of the two power grid voltages is the zero crossing point of the non-power grid voltage, calculating the phase synchronization value DeltaT of the triangular carrier according to the sampling values of the two power grid voltages, and carrying out synchronization adjustment.
4. The multi-inverter carrier synchronization method based on zero-crossing grid voltage sampling as set forth in claim 3, wherein an absolute average value of two grid voltage sampling values and an offset value DeltaV of one of the grid voltage sampling values are calculated, and whether a midpoint of the two grid voltage sampling values is a zero-crossing of the grid voltage is determined based on the value of the offset value DeltaV.
5. The multi-inverter carrier synchronization method based on zero-crossing grid voltage sampling as set forth in claim 4, wherein the calculation formula of the offset value DeltaV is: deltav= |u1|- (|u1|+|u2|)/2;
If the DeltaV value is zero, judging that the midpoint of the sampling values of the two power grid voltages coincides with the zero crossing point of the power grid voltages;
If the DeltaV value is negative, judging that the midpoints of two power grid voltage sampling values are positioned on the right side of a zero crossing point of the power grid voltage, and enabling the triangular carrier wave to need to move left for synchronization;
If the DeltaV value is positive, judging that the midpoints of the two power grid voltage sampling values are positioned at the left side of the zero crossing point of the power grid voltage, and the triangular carrier wave needs to move right to be synchronized.
6. The multi-inverter carrier synchronization method based on zero-crossing grid voltage sampling as set forth in claim 4, wherein the calculation formula of the offset value DeltaV is: deltav= |u2|- (|u1|+|u2|)/2;
If the DeltaV value is zero, judging that the midpoint of the sampling values of the two power grid voltages coincides with the zero crossing point of the power grid voltages;
If the DeltaV value is negative, judging that the midpoints of two power grid voltage sampling values are positioned at the left side of a zero crossing point of the power grid voltage, and enabling the triangular carrier waves to need to move right for synchronization;
If the DeltaV value is positive, judging that the midpoints of the two power grid voltage sampling values are positioned on the right side of the zero crossing point of the power grid voltage, and the triangular carrier wave needs to be shifted left to carry out synchronization.
7. The multi-inverter carrier synchronization method based on zero crossing grid voltage sampling according to any one of claims 3-6, wherein the calculation formula of the phase synchronization value DeltaT of the triangular carrier is as follows:
; or,/> ；
Wherein TBPRD is the period value of the current triangular carrier.
8. A computer readable storage medium, on which a computer program is stored, characterized in that the carrier synchronization method of a multiple inverter according to any one of claims 1-7 is implemented when the computer program is executed by a processor.
9. A multi-inverter carrier synchronization system comprising the computer readable storage medium of claim 8 and EPWM modules; at the moment of the zero crossing point of the power grid voltage, the phase value of TBPHS in the EPWM module is adjusted based on the phase adjustment signal of the triangular carrier wave output by the computer readable storage medium, and then the software is triggered SWFSYNC in one power frequency period.
10. The multi-inverter carrier synchronization system of claim 9, wherein the timing of the phase shift adjustment is determined during carrier synchronization, and the specific determining process is as follows:
in the process of synchronous adjustment, comparing the value of the software phase modulation with the value of the CMPA in the EPWM module;
if the current value of the CMPA is between the period values of the triangular carrier before and after phase shifting, waiting;
And if the current value of the CMPA is equal to the period value of the triangular carrier after phase shifting, executing a phase shifting program.
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