CN116436276B - DPWM zero sequence control method - Google Patents
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- CN116436276B CN116436276B CN202310693289.9A CN202310693289A CN116436276B CN 116436276 B CN116436276 B CN 116436276B CN 202310693289 A CN202310693289 A CN 202310693289A CN 116436276 B CN116436276 B CN 116436276B
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- 238000000034 method Methods 0.000 title claims abstract description 34
- 230000000670 limiting effect Effects 0.000 claims abstract description 51
- 230000008859 change Effects 0.000 claims abstract description 27
- 230000035772 mutation Effects 0.000 claims abstract description 27
- 230000001629 suppression Effects 0.000 claims description 12
- 238000005457 optimization Methods 0.000 claims description 7
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 5
- 230000010355 oscillation Effects 0.000 abstract description 12
- 230000002829 reductive effect Effects 0.000 abstract description 11
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 238000010586 diagram Methods 0.000 description 6
- 238000004364 calculation method Methods 0.000 description 4
- 230000001960 triggered effect Effects 0.000 description 4
- 230000007704 transition Effects 0.000 description 3
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 239000000969 carrier Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
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- 238000010248 power generation Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
Classifications
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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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
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0048—Circuits or arrangements for reducing losses
- H02M1/0054—Transistor switching losses
- H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K7/00—Modulating pulses with a continuously-variable modulating signal
- H03K7/08—Duration or width modulation ; Duty cycle modulation
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- 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
Abstract
The application discloses a DPWM zero sequence control method, comprising the following steps: at zero sequence voltage v zero The output side of the power supply is added with a slope limiting unit, the slope of the zero sequence mutation is limited by the slope limiting unit, and then a new zero sequence voltage v is obtained zero * . The application has the beneficial effects that: the abrupt change slope of the zero sequence voltage is restrained by adding a slope limiting unit on the output side of the traditional zero sequence voltage, so that the oscillation amplitude of current in a circuit can be reduced, and further overcurrent protection of a trigger system is avoided. Meanwhile, the method is simple in implementation mode, and various alternatives exist.
Description
Technical Field
The application relates to the technical field of photovoltaic power generation, in particular to a DPWM zero sequence control method.
Background
The photovoltaic grid-connected system generally adopts a three-phase three-wire system; the three-phase grid-connected current of the device is symmetrical current, and the control method is generally conventional dq control.
To effectively reduce losses and improve system efficiency, modulation schemes typically employ discontinuous PWM modulation (DPWM). In fact, the DPWM strategy can be implemented in a carrier-based manner, i.e. adding the third harmonic on the basis of a three-phase symmetric reference. As shown in fig. 1, the three phases without zero sequence are referenced v x Zero sequence v zero Adding three-phase reference of zero sequence as v x +v zero Then modulation can be performed according to the conventional PWM.
However, as can be seen from fig. 1, the zero sequence is suddenly changed, and the sudden change of the zero sequence easily causes the current to suddenly change, and even triggers the system protection. Fig. 2 shows simulation results of a photovoltaic system, which can cause oscillation (dashed circle position) of output inductor current when zero sequence is suddenly changed, and when the oscillation is large, the overcurrent protection of the system can be triggered. Thus, improvements to existing zero sequence based PWM modulation methods are now urgently needed.
Disclosure of Invention
One of the purposes of the application is to provide a control method capable of inhibiting zero sequence mutation.
In order to achieve the purpose, the application adopts the following technical scheme: the DPWM zero sequence control method includes the following steps: at zero sequence voltage v zero The output side of the power supply is added with a slope limiting unit, the slope of the zero sequence mutation is limited by the slope limiting unit, and then a new zero sequence voltage v is obtained zero * 。
Preferably, the slope limiting unit is adapted to optimize the global domain of the zero sequence voltage, thereby realizing suppression of the slope of the zero sequence mutation.
Preferably, the limiting of the slope of the zero sequence mutation by the slope limiting unit comprises the following processes:
s100: the zero sequence voltage output at the last moment is used as the historical data v of the current zero sequence voltage zero_history ；
S200: zero sequence voltage v at current moment zero And historical zero sequence voltage v zero_history Carrying out conversion in a set limiting formula;
s300: according to the conversion result, obtaining new zero sequence voltage v zero * And outputting historical data serving as zero sequence voltage at the next moment.
Preferably, the constraint formula in step S200 is:
；
in the formula DeltaV limit Representing the set zero sequence limit increment.
Preferably, the zero sequence limits delta V limit The value of (a) is related to the variation delta I of the inductance current; the larger the value of the variation delta I of the inductance current is, the zero sequence limit increment delta V limit The smaller the value of (c), the larger the other way around.
Preferably, the zero sequence limits delta V limit Is added to the value of the inductance current I and the efficiency of the photovoltaic grid-connected systemRelated to; when the slope of zero sequence mutation is suppressed, the inductance current I and the efficiency of the photovoltaic grid-connected system are reduced>Is carried into the optimization function f to obtain the required zero sequence limit increment delta V limit 。
Preferably, the slope limiting unit is adapted to optimize the abrupt change region of the zero sequence voltage, thereby realizing suppression of the slope of the zero sequence abrupt change.
Preferably, the frequency of the zero sequence voltage is the frequency multiplication of the reference wave; limiting the slope of the zero sequence mutation by a slope limiting unit comprises the following processes: zero sequence increment amplitude limiting is added near pi/3, 2 pi/3, pi, 4 pi/3, 5 pi/3 and 2 pi of each wave period of the reference wave, and the rest areas are kept unchanged.
Preferably, an enable is set by which the start-up of the slope limiting unit is conditionally limited; the starting conditions of the slope limiting unit are: when the output current I is greater than the set current threshold I A At this time, the slope limiting unit starts up.
Preferably, the current threshold I A The rated current I with the value of 70% -90% rate 。
Compared with the prior art, the application has the beneficial effects that:
the abrupt change slope of the zero sequence voltage is restrained by adding a slope limiting unit on the output side of the traditional zero sequence voltage, so that the oscillation amplitude of current in a circuit can be reduced, and further overcurrent protection of a trigger system is avoided. Meanwhile, the method is simple in implementation mode, and various alternatives exist.
Drawings
Fig. 1 is a schematic diagram of a waveform structure of a three-phase harmonic wave in the prior art.
Fig. 2 is a schematic diagram of waveform simulation of three-phase harmonic waves in the prior art.
Fig. 3 is a schematic flow chart of zero sequence calculation in the prior art.
Fig. 4 is a schematic flow chart of zero sequence calculation in the present application.
FIG. 5 is a flow chart illustrating an embodiment of the slope limiting unit according to the present application.
Fig. 6 is a schematic diagram of the relationship between zero sequence limit increment and inductance current variation in the present application.
FIG. 7 is a schematic diagram of zero sequence limiting delta versus inductor current and efficiency of a photovoltaic grid-tie system in accordance with the present application.
FIG. 8 is a schematic diagram of a partial waveform structure for slope suppression of zero sequence mutations in the present application.
FIG. 9 is a flowchart illustrating the enabling control of the slope limiting unit according to the present application.
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.
Those skilled in the art will appreciate that the zero sequence injection method of the conventional three-phase three-wire system photovoltaic grid-connected system is as follows:
let us assume a three-phase primary modulated wave v x The expression of (x=a, b, c) is:
（1）。
definition v hx And v xl Respectively three-phase primary modulation wave v x The distances to the upper and lower boundaries of the corresponding carriers are expressed as follows:
（2）。
（3）。
as shown in FIG. 3, three-phase primary modulation wave v a 、v b And v c Respectively brought into the above formula (2) and formula (3), the distances from the three-phase original modulation wave to the corresponding carrier upper boundary are respectively v ha 、v hb And v hc The distances from the three-phase original modulation wave to the lower boundary of the corresponding carrier wave are v respectively al ，v bl And v cl 。
According to the distance values from the three-phase original modulated wave to the upper and lower boundaries of the corresponding carrier wave, the calculation formula (4) about the three-phase minimum value can be obtained as follows:
（4）。
when v min_hk Less than v min_kl Zero sequence voltage v zero V is min_hk The method comprises the steps of carrying out a first treatment on the surface of the Otherwise, zero sequence voltage v zero Is-v min_kl . It can also be understood by the following formula (5).
（5）。
After passing through the zero sequence calculation flow as shown in figure 3,the obtained zero sequence voltage v zero Is injected into a three-phase three-wire system photovoltaic grid-connected system to obtain the added zero sequence three-phase reference v as shown in fig. 1 and 2 zero +v x Is a waveform diagram of (a). As can be seen from fig. 1 and 2, there is a zero sequence jump in the waveforms of the zero sequence voltages, which results in the addition of a zero sequence three-phase reference v zero +v x The transition of the waveform is not smooth. As can be seen from fig. 2, the abrupt change of the zero sequence voltage can cause the output inductance current to oscillate with a larger amplitude, so that the overcurrent protection of the photovoltaic grid-connected system is easily triggered.
Therefore, in order to inhibit zero sequence mutation when the traditional three-phase three-wire system photovoltaic grid-connected system carries out zero sequence injection. One preferred embodiment of the present application, as shown in fig. 4 to 9, provides a DPWM zero sequence control method, comprising the steps of: at zero sequence voltage v zero The output side of the power supply is added with a slope limiting unit, the slope of the zero sequence mutation is limited by the slope limiting unit, and then a new zero sequence voltage v can be obtained zero * . By applying a new zero sequence voltage v zero * The method is used for outputting and injecting the zero sequence mutation oscillation amplitude of the inductance current into a three-phase three-wire system photovoltaic grid-connected system, so that the oscillation amplitude of the inductance current caused by the zero sequence mutation can be reduced preferably, and further, the over-current protection can be prevented from being triggered by the photovoltaic grid-connected system by mistake.
In this embodiment, when the slope limiting unit performs suppression optimization on the abrupt change of the zero sequence voltage, two manners may be generally adopted.
The first mode is that the slope limiting unit can inhibit and optimize the whole domain of the zero sequence voltage, namely, the whole waveform transition of the zero sequence voltage is smooth by controlling the whole domain waveform of the zero sequence voltage, so that the slope of the zero sequence mutation can be inhibited, and the zero sequence mutation can be reduced or avoided.
The second mode is that the abrupt change region of the zero sequence voltage can be restrained and optimized through the slope limiting unit, namely, the waveform of the abrupt change region of the zero sequence voltage is controlled, so that the waveform transition of the zero sequence voltage in the abrupt change region is smooth, the slope of the zero sequence abrupt change can be restrained, and the zero sequence abrupt change can be reduced or avoided.
It will be appreciated that from the waveforms shown in fig. 1 and 2, the zero sequence abrupt change can be seen as a slope with a large slope connecting the amplitude between adjacent chords. Therefore, the essence of suppressing the zero sequence mutation is to reduce the slope of the oblique line. Therefore, the first way to suppress the abrupt change of the zero sequence voltage is to adjust the overall waveform of the sine wave, so that the adjacent sine waves are smoothly transited, and the slope of the abrupt change of the zero sequence can be reduced. The second way of suppressing the abrupt change of the zero sequence voltage is to adjust the amplitude of the sine wave close to the zero sequence abrupt change position so as to ensure that the amplitude difference between adjacent sine waves is reduced to realize the reduction of the slope of the zero sequence abrupt change.
In one embodiment of the present application, as shown in fig. 5, the first way to perform slope suppression on zero sequence mutation for the zero sequence limiting unit includes the following procedures:
s100: the zero sequence voltage output at the last moment is used as the historical data v of the current zero sequence voltage zero_history 。
S200: zero sequence voltage v at current moment zero And historical zero sequence voltage v zero_history And carrying out conversion in a set limiting formula.
S300: according to the conversion result, obtaining new zero sequence voltage v zero * And outputting historical data serving as zero sequence voltage at the next moment.
In this embodiment, the constraint formula in step S200 is:
（6）。
it will be appreciated that DeltaV in the formula limit Representing the set zero sequence limit increment; the specific expression of the above formula (6) is: when the zero sequence voltage v zero And historical zero sequence voltage v zero_history Is greater than zero sequence limitDelta DeltaV of system limit When a new zero sequence voltage v zero * Can be output as v zero_history +ΔV limit The method comprises the steps of carrying out a first treatment on the surface of the When the zero sequence voltage v zero And historical zero sequence voltage v zero_history The difference is less than negative zero sequence limit delta V limit When a new zero sequence voltage v zero * Can be output as v zero_history -ΔV limit The method comprises the steps of carrying out a first treatment on the surface of the Other cases, new zero sequence voltage v zero * Can be output as v zero 。
For ease of understanding the above equation (6), slope suppression of zero sequence mutations may be described below in conjunction with fig. 8. Since the waveform of the zero sequence voltage is a periodic waveform, the waveform can be expressed by a half-period waveform.
As shown in a point a of fig. 8, the waveform of the zero sequence voltage is located at the peak position; since the absolute value of the slope of the waveform from point a to point c increases gradually. Suppose there is exactly v at point b of the waveform from point a to point c zero -v zero_history =ΔV limit The method comprises the steps of carrying out a first treatment on the surface of the The points a to b of the waveform segment meet other conditions in the formula (6), namely the waveform of the output new zero sequence voltage is the same as the original waveform; v in the above formula (6) is satisfied from point b to point c of the waveform segment zero -v zero_history ＜-ΔV limit In the case of v zero ＜v zero_history -ΔV limit The method comprises the steps of carrying out a first treatment on the surface of the Then the new zero sequence voltage v is output zero * =v zero_history -ΔV limit Is located above the original waveform, i.e., the imaginary line segment above the b-point to c-point waveform segment in fig. 8. As can be derived from the above procedure, the amplitude of the waveform segment from point b to point c is increased compared to the original waveform.
Then, in the abrupt phase of the zero sequence voltage, i.e. the waveform segment from the point c to the point d in fig. 8; as is apparent from the waveform in FIG. 8, the waveform segment from point c to point d corresponds to v in the above formula (6) zero -v zero_history ＞ΔV limit A situation; so that the waveform section v of the new zero sequence voltage corresponding to the point c to the point d zero * =v zero_history +ΔV limit Below the original waveform segment.
And then, the structure from the point d to the point f of the waveform segment is centrosymmetric with the structure from the point a to the point c of the waveform segment, namely, the waveform of the new zero sequence voltage corresponding to the point d to the point e of the waveform segment is positioned above the original waveform, and the waveform of the new zero sequence voltage corresponding to the point e to the point f of the waveform is the same as the original waveform.
Finally, the slope of the new waveform of the zero sequence voltage in the zero sequence mutation area is obviously reduced in view of the whole waveform, so that the oscillation amplitude of the inductance current after adding the zero sequence can be effectively reduced, and further, the false triggering of the overcurrent protection of the photovoltaic grid-connected system can be effectively avoided.
In this embodiment, the zero sequence limits delta V limit The value may be a constant value or a variable value. Because the output of the photovoltaic grid-connected system is a dynamic process, the zero sequence of the fixed value limits the increment delta V limit Has certain limitations. Therefore, in the zero sequence limiting increment DeltaV limit Preferably, a dynamic variable value is used for setting. For zero sequence limit delta DeltaV limit Various ways of selecting the dynamic variable values of (a) include, but are not limited to, the following two ways.
Selecting a first mode: zero sequence limit delta V limit The value of (2) is related to the variation deltai of the inductor current. Generally, the larger the value of the variation Δi of the inductor current I, the larger the oscillation amplitude of the inductor current I, and the stronger the requirement for suppressing the abrupt change of the zero-sequence voltage; thus, the zero sequence limit delta V at this time can be increased limit The smaller the value limit of (c) so that the degree of suppression of the zero sequence mutation slope becomes higher. If the value of the variation delta I of the inductance current I is smaller, the smaller the oscillation amplitude of the inductance current I is, and the requirement on the sudden change suppression of the zero sequence voltage is relatively flat; thus, the zero sequence limit delta V at this time can be increased limit The larger the value limit is, the lower the suppression degree of the zero sequence mutation slope is, and the normal operation of the photovoltaic grid-connected system can be better protected.
Specifically, as shown in FIG. 6, a zero sequence limit delta DeltaV may be set limit kX, k=i/Δi; wherein the method comprises the steps ofX is a set constant, and k is a variable coefficient; thus, when the variation delta I of the inductance current I is larger, the value of k is smaller, and the zero sequence limit increment delta V is further realized limit The smaller the value of (2); similarly, when the variation delta I of the inductance current I is smaller, the value of k is larger, and the zero sequence limit increment delta V is further realized limit The greater the value of (c).
Selecting a second mode: zero sequence limit delta V limit Is added to the value of the inductance current I and the efficiency of the photovoltaic grid-connected systemRelated to the following. As shown in FIG. 7, a photovoltaic inductor current I and the efficiency of the photovoltaic grid-connected system can be set>The output of the optimization function f is the zero sequence limit increment delta V limit . Therefore, when the slope of zero sequence mutation is suppressed, the inductance current I and the efficiency of the photovoltaic grid-connected system can be increased>Is carried into the optimization function f to obtain the required zero sequence limit increment delta V limit 。
It is understood that the specific content and working principle of the optimization function f are well known to those skilled in the art, and the common optimization function f may be an iterative function or a fitting function.
In one embodiment of the present application, the second way to perform slope suppression on zero sequence mutation for the zero sequence limiting unit includes the following procedures:
as can be seen from fig. 1 and 2, the frequency of the zero sequence voltage is a frequency multiplication of the reference wave; i.e. the waveform period of the zero sequence voltage is one third of the reference wave. Zero sequence delta clipping is added near pi/3, 2 pi/3, pi, 4 pi/3, 5 pi/3, 2 pi of each wave period of the reference wave, and the rest area is kept unchanged.
It will be appreciated that from fig. 1 and 2, the zero sequence abrupt positions of the zero sequence voltages correspond to the pi/3, 2 pi/3, pi, 4 pi/3, 5 pi/3, 2 pi positions of the reference wave period, respectively. Therefore, zero sequence increment amplitude limiting is added near pi/3, 2 pi/3, pi, 4 pi/3, 5 pi/3 and 2 pi of each wave period of the reference wave, and zero sequence abrupt change slope is compensated or inhibited through zero sequence increment amplitude limiting, so that zero sequence abrupt change slope can be inhibited, and the oscillation amplitude of the inductance current at the corresponding position of the zero sequence abrupt change is reduced.
Considering that the slope limit of the zero sequence mutation affects the efficiency of the photovoltaic grid-connected system to a certain extent, so as to reduce the influence on the system efficiency as much as possible; as shown in fig. 9, the slope limiting unit may be set to be enabled, and only when the output current is large, the slope limiting unit may be triggered by the enabling. That is, it is possible to make a conditional restriction on the start-up of the slope limiting unit by setting; the start condition of the slope limiting unit may be set as: when the output current I is greater than the set current threshold I A The slope limiting unit is then enabled.
In the present embodiment, the current threshold I for enabling adjustment A The value of (2) can be determined by the current threshold I A The rated current I can be 70% -90% rate . For example, as shown in FIG. 9, the current threshold I A Is 80% rated current I rate . Therefore, when the output inductance current is smaller, the circuit of the photovoltaic grid-connected system is unaffected; when the output current is larger, the enabling can trigger the slope limiting unit to carry out zero sequence abrupt change slope limiting, so that current oscillation can be effectively prevented, and further system overcurrent caused by the current oscillation is prevented.
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 (7)
1. The DPWM zero sequence control method is characterized by comprising the following steps: at zero sequence voltage v zero The output side of the power supply is added with a slope limiting unit, the slope of the zero sequence mutation is limited by the slope limiting unit, and then a new zero sequence voltage v is obtained zero * ；
The slope limiting unit is suitable for optimizing the whole domain of the zero sequence voltage, so as to inhibit the slope of the zero sequence mutation;
limiting the slope of the zero sequence mutation by a slope limiting unit comprises the following processes:
s100: the zero sequence voltage output at the last moment is used as the historical data v of the current zero sequence voltage zero_history ；
S200: zero sequence voltage v at current moment zero And historical zero sequence voltage v zero_history Carrying out conversion in a set limiting formula;
s300: according to the conversion result, obtaining new zero sequence voltage v zero * Outputting and serving as historical data of zero sequence voltage at the next moment;
the constraint formula in step S200 is:
；
in the formula DeltaV limit Representing the set zero sequence limit increment.
2. The DPWM zero sequence control method of claim 1, further comprising: zero sequence limit delta V limit The value of (1) is related to the current variation delta I; the larger the value of the current variation delta I, the zero sequence limit increment delta V limit The smaller the value of (c), the larger the other way around.
3. The DPWM zero sequence control method of claim 1, further comprising: zero sequence limit delta V limit The value of (2) is related to the inductance current I and the efficiency ƞ of the photovoltaic grid-connected system; in the slope of zero sequence mutationDuring suppression, the inductance current I and the efficiency ƞ of the photovoltaic grid-connected system are brought into an optimization function f to obtain the required zero sequence limit increment delta V limit 。
4. The DPWM zero sequence control method of claim 1, further comprising: the slope limiting unit is suitable for optimizing the abrupt change region of the zero sequence voltage, and further realizing the suppression of the slope of the zero sequence abrupt change.
5. The DPWM zero sequence control method of claim 4, further comprising: the frequency of the zero sequence voltage is the triple frequency of the reference wave; limiting the slope of the zero sequence mutation by a slope limiting unit comprises the following processes: zero sequence increment amplitude limiting is added near pi/3, 2 pi/3, pi, 4 pi/3, 5 pi/3 and 2 pi of each reference wave period of the reference wave, and the rest areas are kept unchanged.
6. The DPWM zero sequence control method of any one of claims 1-5, characterized by: setting an enable, and performing conditional restriction on the starting of the slope restriction unit by the enable; the starting conditions of the slope limiting unit are: when the output current I is greater than the set current threshold I A At this time, the slope limiting unit starts up.
7. The DPWM zero sequence control method of claim 6, further comprising: current threshold I A The rated current I with the value of 70% -90% rate 。
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| Title |
|---|
| 基于 DPWM 算法的三电平光伏逆变器效率提升研究;王青龙等;《自动化技术与应用》;第37卷(第12期);第92-97页 * |
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| CN116436276A (en) | 2023-07-14 |
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