CN116260163B - Three-phase inverter and output power control method and device - Google Patents
Three-phase inverter and output power control method and device Download PDFInfo
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- CN116260163B CN116260163B CN202310127894.XA CN202310127894A CN116260163B CN 116260163 B CN116260163 B CN 116260163B CN 202310127894 A CN202310127894 A CN 202310127894A CN 116260163 B CN116260163 B CN 116260163B
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Classifications
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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
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
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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
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
- H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
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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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Inverter Devices (AREA)
Abstract
The invention relates to the technical field of grid connection of three-phase inverters, and discloses a three-phase inverter and an output power control method and device.
Description
Technical Field
The invention relates to the technical field of grid connection of three-phase inverters, in particular to a three-phase inverter and an output power control method and device.
Background
With the development of new energy technology, more and more families introduce household energy conversion devices, and other energy is converted into electric energy through the energy conversion devices, so that electric energy consumption on an electric network is reduced, wherein the other energy is mainly solar energy, and therefore, most of energy conversion devices are photovoltaic inverters.
For a common three-phase photovoltaic inverter, the output power supply not only can provide power for loads of a user side, but also can upload redundant power to a power grid, so that efficient utilization of the power is realized. For the three-phase power input to the electric power, the power balance of each phase of power is required, otherwise, the three-phase power with unbalanced three-phase power can impact a power grid, so that the power quality of the power grid is affected, and the power grid is unstable. However, since the consumer side load has a mixed single-phase load and three-phase load, and the output power of the inverter is equal to the sum of the power used for the end load and the power of the grid side, the power imbalance of the consumer side load may cause the power imbalance of the three-phase power uploaded to the grid side by the inverter.
At present, most of control modes of the three-phase inverter control current or voltage input to a power grid, and the control modes are not aimed at controlling power input to the power grid, for example, a grid-connected current balancing control system of the three-phase cascade photovoltaic inverter disclosed in patent document with a publication number of CN109802434B balances all currents which are connected in a grid.
Disclosure of Invention
In view of the shortcomings of the background art, the invention provides a three-phase inverter and an output power control method and device, and aims to solve the technical problem that the existing three-phase inverter can cause unbalanced three-phase power input to a power grid due to unbalanced power at a user load end.
In order to solve the technical problems, in a first aspect, the present invention provides the following technical solutions: the output power control method of a three-phase inverter, the said three-phase inverter is three-phase four-wire system structure, including A phase, B phase, C phase and N line; the method comprises the following steps:
s1: acquiring an instantaneous output power value of each phase of the three-phase inverter and an instantaneous power value of each phase of a power grid end;
s2: calculating the instantaneous power value of each phase of the user load based on the instantaneous output power value of each phase of the three-phase inverter and the instantaneous power value of each phase of the power grid end;
s3: calculating the total expected power of the power grid end based on a preset uplink power duty ratio allowed by the power grid end, and equally dividing the total expected power of the power grid end to each phase of electricity of the power grid end so as to obtain each phase of expected power value of the power grid end; the uplink power duty ratio is the ratio of the total expected power of the power grid end to the rated power of the three-phase inverter;
s4: and adjusting the output power of each phase of the three-phase inverter based on the instantaneous power value of each phase of the user load and the expected power value of each phase of the power grid end, so that the output power of each phase of the three-phase inverter is the sum of the instantaneous power value of each phase of the user load and the expected power value of each phase of the power grid end.
In a certain implementation manner of the first aspect, the method of obtaining the output instantaneous power value of each phase of the three-phase inverter in step S1 is as follows:
firstly, respectively obtaining each phase output voltage and each phase output current of the three-phase inverter through a sampling circuit, and respectively marking the output voltage and each phase output current as U A 、U B 、U C 、I A 、I B And I C ；
Then calculating the instantaneous output power value of each phase of the three-phase inverter, respectively denoted as P A1 、P B1 、P C1 The calculation formula is as follows:
P A1 ＝U A I A cos(θ A )，P B1 ＝U B I B cos(θ B )，P C1 ＝U C I C cos(θ C ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein θ is A 、θ B 、θ C
The phase angles of the A-phase voltage, the B-phase voltage and the C-phase voltage of the three-phase inverter are respectively.
In the step S1, each phase of instantaneous power value of the power grid end is acquired in real time through a three-phase ammeter and is respectively recorded as P gA1 、P gB1 And P gC1 。
In a certain implementation manner of the first aspect, step S2 is specifically as follows: recording the instantaneous power value of each phase of the user load as P LA 、P LB And P LC P is then LA 、P LB And P LC The calculation formula of (2) is as follows:
P LA ＝P A1 -P gA1 ，P LB ＝P B1 -P gB1 ，P LC ＝P C1 -P gC1 。
in step S3, the allowable uplink power duty ratio of the power grid end is recorded as K g The expected power value of each phase of the power grid end is respectively marked as P gA2 、P gB2 And P gC2 The method comprises the steps of carrying out a first treatment on the surface of the Then P gA2 、P gB2 、P gC2 The calculation formula of (2) is as follows:
P gA2 ＝P gB2 ＝P gC2 ＝(K g ×P N )/3；P N is the rated power value of the three-phase inverter.
In an embodiment of the first aspect, in step S4, the expected value of the power per phase of the three-phase inverter is denoted as P A2 、P B2 And P C2 P is then A2 、P B2 And P C2 The calculation formula is as follows:
P A2 ＝P LA +P gA2 ，P B2 ＝P LB +P gB2 ，P C2 ＝P LC +P gC2 。
in a certain implementation manner of the first aspect, the present invention further includes step S5, where step S5 is as follows:
s5: and (5) acquiring the instantaneous power value of each phase of the power grid terminal again, judging whether the three-phase power of the power grid terminal is balanced, ending the step (S5) if the three-phase power of the power grid terminal is balanced, and returning to the step (S1) if the three-phase power of the power grid terminal is unbalanced.
In a certain implementation manner of the first aspect, the determining in step S5 whether the three-phase power at the grid end is balanced is as follows:
in step S5, the mode of determining whether the three-phase power at the power grid end is balanced is as follows:
the obtained instantaneous power values of each phase of the power grid end are respectively marked as P gA3 、P gB3 And P gC3 ；
Firstly, calculating an average value P of three-phase power of a current power grid end average ，P average ＝(P gA3 +P gB3 +P gC3 )/3；
Then calculating the absolute value of the difference between the instantaneous value of each phase of the power grid end and the average value, and recording as delta P gA 、ΔP gB 、ΔP gC Then: ΔP gA ＝|P gA3 -P average |，ΔP gB ＝|P gB3 -P average |，ΔP gC ＝|P gC3 -P average |；
Then find the maximum absolute value of the difference, record as DeltaP g ＝max{ΔP gA ,ΔP gB ,ΔP gC }；
Then calculate the unbalance level unbalance, wherein unbalance=Δp g /P average ；
And finally judging whether the unbalance degree is smaller than a judging threshold value, if so, considering the three-phase power balance of the power grid end, otherwise, considering the three-phase power unbalance of the power grid end.
In a second aspect, the invention also provides a three-phase inverter, which comprises a T-shaped three-level inverter circuit, a control unit and a sampling unit;
the sampling unit is configured to collect each phase output voltage and each phase output current of the T-shaped three-level inverter circuit and send the each phase output voltage and each phase output current to the control unit;
the control unit is electrically connected with the T-shaped three-level inverter circuit and is configured to adjust the output power of each phase of the T-shaped three-level inverter circuit;
the control unit calculates the total expected power of the power grid end based on the preset uplink power duty ratio allowed by the power grid end, and equally divides the total expected power of the power grid end to each phase of electricity of the power grid end so as to obtain each phase of expected power value of the power grid end; the uplink power duty ratio is the ratio of the total expected power of the power grid end to the rated power of the three-phase inverter;
the control unit calculates each phase instant output power of the T-shaped three-level inverter circuit based on the each phase output voltage and each phase output current;
the control unit calculates the instantaneous power of each phase of the user load through the instantaneous power of each phase of the T-shaped three-level inverter circuit and the obtained instantaneous power of each phase of the power grid end;
and after obtaining the instantaneous power of each phase of the user load and the expected power of each phase of the power grid end, the control unit adjusts the output power of each phase of the T-shaped three-level inverter circuit to ensure that the output power of each phase of the T-shaped three-level inverter circuit is the sum of the instantaneous power of each phase of the user load and the expected power of each phase of the power grid end.
In a certain implementation manner of the second aspect, the control unit includes an ARM control unit and a DSP control unit, where the DSP control unit is electrically connected to the sampling unit, and obtains, through the sampling unit, an output voltage and an output current of each phase of the T-type three-level inverter circuit; the ARM control unit is configured to be in communication connection with a three-phase ammeter, acquires the power grid end each phase instant power provided for a power grid by the T-shaped three-level inverter circuit from the three-phase ammeter, and sends the power grid end instant power to the DSP control unit, and the DSP control unit is used for calculating each phase output instant power of the T-shaped three-level inverter circuit, each phase instant power of a user load, the total expected power of the power grid end, each phase expected power of the power grid end and adjusting each phase output power of the T-shaped three-level inverter circuit.
In a third aspect, the present invention also provides an output power control device of a three-phase inverter, including the three-phase inverter, and further including a three-phase ammeter;
the three-phase ammeter is electrically connected with the T-shaped three-level inverter circuit and is configured to collect each phase of instantaneous power provided by the T-shaped three-level inverter circuit to a power grid end of the power grid;
the control unit is in communication connection with the three-phase ammeter and is configured to acquire the instantaneous power of each phase of the power grid end from the three-phase ammeter.
In a certain implementation manner of the third aspect, the three-level inverter circuit further comprises a photovoltaic array, a DC/DC conversion unit and a DC bus capacitor, wherein the DC/DC conversion unit is electrically connected with the photovoltaic array and is used for performing DC/DC conversion on output voltage of the photovoltaic array, and a signal output end of the DC/DC conversion unit is electrically connected with an inverter voltage input end of the three-level inverter circuit through the DC bus capacitor.
Compared with the prior art, the invention has the following beneficial effects: according to the invention, the expected power value of each phase of the power grid end is set in advance, the instantaneous power value of each phase of the user load can be obtained based on the instantaneous power value of each phase of the three-phase inverter and the instantaneous power value of each phase of the power grid end, and then the output power of each phase of the three-phase inverter is adjusted according to the instantaneous power value of each phase of the user load and the expected power value of each phase of the power grid end, so that the output power of each phase of the three-phase inverter is the sum of the instantaneous power value of each phase of the user load and the expected power value of each phase of the power grid end, and the power balance of each phase of the three-phase inverter input to the power grid can be ensured.
Drawings
Fig. 1 is a schematic diagram of a first configuration of a three-phase inverter according to the present invention;
fig. 2 is a schematic diagram of a second structure of the three-phase inverter according to the present invention;
FIG. 3 is a schematic diagram of a structure for adjusting output power of each phase of a three-phase inverter according to the present invention;
fig. 4 is a schematic diagram of a first configuration of an output power control apparatus of a three-phase inverter according to the present invention;
fig. 5 is a schematic diagram of a second configuration of an output power control apparatus of a three-phase inverter according to the present invention;
fig. 6 is a schematic diagram of an output power control method of a three-phase inverter according to the present invention.
Detailed Description
The invention will now be described in further detail with reference to the accompanying drawings. The drawings are simplified schematic representations which merely illustrate the basic structure of the invention and therefore show only the structures which are relevant to the invention.
Because the existing load connected with the three-phase inverter has the condition that the single-phase load and the three-phase load are mixed, the power input to the power grid by the three-phase inverter is unbalanced, and the power grid is impacted, based on the condition, as shown in fig. 1, the invention provides the three-phase inverter which comprises a T-shaped three-level inverter circuit 1, a control unit 2 and a sampling unit 3;
the sampling unit 3 is configured to collect each phase output voltage and each phase output current of the T-type three-level inverter circuit 1, and send each phase output voltage and each phase output current to the control unit 2;
the control unit 2 is electrically connected with the T-shaped three-level inverter circuit 1 and is configured to adjust the output power of each phase of the T-shaped three-level inverter circuit 1;
the control unit 2 calculates the total expected power of the power grid end based on the preset uplink power duty ratio allowed by the power grid end, and equally divides the total expected power of the power grid end to each phase of electricity of the power grid end so as to obtain each phase of expected power value of the power grid end; the uplink power duty ratio is the ratio of the total expected power of the power grid end to the rated power of the three-phase inverter;
for example, if the rated power of the three-phase inverter is 6000W and the uplink power duty ratio is 2%, the total expected power of the grid end is 6000 x 2% =120w, and the expected power value of each phase of the grid end is 120/3=40w;
the control unit 2 calculates the instantaneous output power of each phase of the T-type three-level inverter circuit 1 based on the output voltage of each phase and the output current of each phase;
the control unit 2 calculates the instantaneous power of each phase of the user load through the instantaneous power of each phase of the T-shaped three-level inverter circuit 1 and the obtained instantaneous power of each phase of the power grid end; subtracting the instantaneous power of each phase of the power grid end from the instantaneous power of each phase of the T-shaped three-level inverter circuit 1 to obtain the instantaneous power of each phase of the user load;
after obtaining the instantaneous power of each phase of the user load and the expected power of each phase of the power grid end, the control unit 2 adjusts the output power of each phase of the T-shaped three-level inverter circuit 1 to ensure that the output power of each phase of the T-shaped three-level inverter circuit is the sum of the instantaneous power of each phase of the user load and the expected power of each phase of the power grid end.
When the three-phase inverter is actually used, the output power of each phase of the three-phase inverter can be adjusted according to the load power of a user and the expected power of each phase of a power grid end which is set in advance, so that the power input to the power grid by the three-phase inverter is balanced, and no impact is generated on the power grid.
The process of adjusting the output power of each phase of the T-type three-level inverter circuit 1 by the control unit 2 of the present invention is as shown in fig. 3:
first, three-phase output voltage U of T-type three-level inverter circuit 1 is obtained A 、U B And U C After that, the control end unit 2 calculates the output voltage U through the phase-locked loop A 、U B And U C Is the phase angle theta of (2) A 、θ B And theta C The method comprises the steps of carrying out a first treatment on the surface of the To obtain three-phase output current i of T-type three-level inverter circuit 1 A 、i B And i C After that, the control unit 2 outputs the current i to three phases through the park converting unit A 、i B And i C Performing park conversion, wherein the park conversion formula is as follows:
wherein i is dA D-axis component i representing A-phase output current of three-phase inverter qA Q-axis component, i representing a phase A output current of a three-phase inverter dB D-axis component i representing B-phase output current of three-phase inverter qB Q-axis component, i representing B-phase output current of three-phase inverter dC D-axis component i representing C-phase output current of three-phase inverter qC A q-axis component representing a C-phase output current of the three-phase inverter;
the control unit 2 obtains the three-phase output voltage U of the T-type three-level inverter circuit 1 A 、U B And U C Three-phase output current i of T-type three-level inverter circuit 1 A 、i B And i C Then the three-phase active power and the three-phase reactive power of the T-shaped three-level inverter circuit 1 are calculated by an active power and reactive power calculation unit and respectively marked as P A 、P B 、P C 、Q A 、Q B And Q C ；
It should be noted that, the adjustment mode of each phase output power of the three-phase inverter is the same, and two control branches are shared, taking the mode of adjusting the phase output power as an example, one control branch is as follows:
target power P of phase A * A (sum of instantaneous power of A phase of user load and expected power of each phase of power grid end) and active power P of A phase of T-shaped three-level inverter circuit 1 A Performing subtraction to obtain a first operation result, performing PI operation (proportional integral operation) on the first operation result to obtain a second operation result, and adding the second operation result and current i dA Performing subtraction operation to obtain a third operation result, performing PI operation on the third operation result to obtain a fourth operation result, and outputting a first control signal based on the fourth operation result;
the other control branch is as follows:
target reactive power Q of A phase * A (self-settable) AND T-type IIIA-phase reactive power Q of level inverter circuit 1 A Performing subtraction to obtain a fifth operation result, performing PI operation (proportional integral operation) on the fifth operation result to obtain a sixth operation result, and combining the sixth operation result with current i qA Performing subtraction operation to obtain a seventh operation result, performing PI operation on the seventh operation result to obtain an eighth operation result, and outputting a second control signal based on the eighth operation result;
the first control signal and the second control signal output by the control unit 2 are input into the A-phase modulation unit, and the A-phase modulation unit adjusts the on-off of a switching tube of an A-phase inverter circuit of the T-type three-level inverter circuit 1 based on the first control signal and the second control signal, so that the A-phase output power of the T-type three-level inverter circuit 1 is adjusted, and the A-phase output power of the T-type three-level inverter circuit 1 is the sum of the A-phase instantaneous power of a user load and each phase expected power of a power grid end.
As shown in fig. 2, in this embodiment, the control unit 2 includes an ARM control unit 20 and a DSP control unit 21, the DSP control unit 21 is electrically connected with the sampling unit 3, and each phase of output voltage and each phase of output current of the T-type three-level inverter circuit 1 are obtained by the sampling unit 3; the ARM control unit 20 is configured to be in communication connection with the three-phase ammeter 4, obtain the power grid end each phase instant power provided to the power grid by the T-shaped three-level inverter circuit 1 from the three-phase ammeter 4, and send the power grid end instant power to the DSP control unit 21, and the DSP control unit 20 is used for calculating the power per phase instant output of the T-shaped three-level inverter circuit 1, the power grid end total expected power, the power grid end expected power per phase and adjusting the power per phase output of the T-shaped three-level inverter circuit 1.
In practical use, the ARM control unit 20 and the DSP control unit 21 are microprocessors, wherein the DSP control unit can convert received analog signals into digital signals, so that the DSP control unit can be used for carrying out signal interaction with external devices, namely receiving analog sampling signals sent by the sampling unit 3 and sending control signals for switching on and off of a switching tube of the T-type three-level inverter circuit 1; the ARM control unit 20 is mainly used for communicating with the three-phase electric meter 4 (485 communication is possible), and obtains the electric network instantaneous power from the three-phase electric meter 4 through a communication mode, while the DSP control unit 21 is not suitable for communicating with the three-phase electric meter 4, so the control unit 2 of the present invention comprises the ARM control unit 20 and the DSP control unit 21.
As shown in fig. 4, the present invention further provides an output power control device of a three-phase inverter, including the three-phase inverter, and further including a three-phase ammeter 4;
the three-phase ammeter 4 is electrically connected with the T-shaped three-level inverter circuit 1 and is configured to collect each phase of instantaneous power provided by the T-shaped three-level inverter circuit 1 to a power grid end of the power grid;
the control unit 2 is in communication connection with the three-phase electric meter 4 and is configured to obtain the instantaneous power per phase at the grid end from the three-phase electric meter 4.
As shown in fig. 5, on the basis of the structure shown in fig. 4, the invention also provides an output power control device of a three-phase inverter with another structure, which further comprises a photovoltaic array 5, a DC/DC conversion unit 6 and a direct current bus capacitor C bus The DC/DC conversion unit 6 is electrically connected with the photovoltaic array 5, performs DC/DC conversion on the output voltage of the photovoltaic array 5, and the signal output end of the DC/DC conversion unit 6 passes through the DC bus capacitor C bus Is electrically connected with an inversion voltage input end of the T-shaped three-level inversion circuit 1, and provides direct current voltage for the T-shaped three-level inversion circuit 1.
Example two
As shown in fig. 6, the present invention also provides a method for controlling output power of a three-phase inverter, in which each phase of output power of the three-phase inverter needs to be adjusted separately, the three-phase inverter is in a three-phase four-wire system structure, and includes a phase a, a phase B, a phase C and a line N; the method comprises the following steps:
s1: and acquiring the instantaneous output power value of each phase of the three-phase inverter and the instantaneous power value of each phase of the power grid end.
In actual use, the method for obtaining the output instantaneous power value of each phase of the three-phase inverter in step S1 is as follows:
firstly, respectively obtaining each phase output voltage and each phase output current of a three-phase inverter through a sampling circuit, and respectively marking as U A 、U B 、U C 、I A 、I B And I C ；
Then calculating the instantaneous output power value of each phase of the three-phase inverter, respectively denoted as P A1 、P B1 、P C1 The calculation formula is as follows:
P A1 ＝U A I A cos(θ A )，P B1 ＝U B I B cos(θ B )，P C1 ＝U C I C cos(θ C ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein θ is A 、θ B And theta C Phase angles of A phase voltage, B phase voltage and C phase voltage of the three-phase inverter respectively, theta A 、θ B And theta C Can be calculated by a phase locked loop.
In the step S1, each phase of instantaneous power value of the power grid end is acquired in real time through a three-phase ammeter and is respectively recorded as P gA1 、P gB1 And P gC1 . When in actual use, the model of the three-phase ammeter can be selected according to actual demands.
S2: and calculating the instantaneous power value of each phase of the user load based on the instantaneous output power value of each phase of the three-phase inverter and the instantaneous power value of each phase of the power grid terminal.
The step S2 is specifically as follows: : recording the instantaneous power value of each phase of the user load as P LA 、P LB And P LC P is then LA 、P LB And P LC The calculation formula of (2) is as follows:
P LA ＝P A1 -P gA1 ，P LB ＝P B1 -P gB1 ，P LC ＝P C1 -P gC1 。
s3: calculating the total expected power of the power grid end based on a preset uplink power duty ratio allowed by the power grid end, and equally dividing the total expected power of the power grid end to each phase of electricity of the power grid end so as to obtain each phase expected power value of the power grid end; the uplink power duty ratio is the ratio of the total expected power of the power grid end to the rated power of the three-phase inverter.
Specifically, the allowable uplink power duty ratio at the grid end in step S3 is denoted as K g The expected power value of each phase of the power grid end is respectively marked as P gA2 、P gB2 And P gC2 The method comprises the steps of carrying out a first treatment on the surface of the Then P gA2 、P gB2 、P gC2 The calculation formula of (2) is as follows:
P gA2 ＝P gB2 ＝P gC2 ＝(K g ×P N )/3；P N is the rated power value of the three-phase inverter.
S4: and adjusting the output power of each phase of the three-phase inverter based on the instantaneous power value of each phase of the user load and the expected power value of each phase of the power grid end, so that the output power of each phase of the three-phase inverter is the sum of the instantaneous power value of each phase of the user load and the expected power value of each phase of the power grid end.
In step S4, the expected value of the power per phase of the three-phase inverter is denoted as P A2 、P B2 And P C2 P is then A2 、P B2 And P C2 The calculation formula is as follows:
P A2 ＝P LA +P gA2 ，P B2 ＝P LB +P gB2 ，P C2 ＝P LC +P gC2 。
for the invention, because the instantaneous output power of each phase of the three-phase inverter is known, the instantaneous power value of each phase of the user load can be obtained after the instantaneous power value of each phase of the power grid end can be obtained, and then the expected power value of each phase of the power grid end is set, so that the output power of each phase of the three-phase inverter can be regulated through the expected power value of each phase of the power grid end and the instantaneous power value of each phase of the user load, thereby stabilizing the balance of the three-phase power input into the power grid.
In a certain implementation manner of the first aspect, the present invention further includes step S5, where step S5 is as follows:
s5: and (5) acquiring the instantaneous power value of each phase of the power grid terminal again, judging whether the three-phase power of the power grid terminal is balanced, ending the step (S5) if the three-phase power of the power grid terminal is balanced, and returning to the step (S1) if the three-phase power of the power grid terminal is unbalanced.
For step S5, the manner of determining whether the three-phase power at the grid end is balanced in step S5 is as follows:
in step S5, the mode of determining whether the three-phase power at the power grid end is balanced is as follows:
the obtained instantaneous power values of each phase of the power grid end are respectively marked as P gA3 、P gB3 And P gC3 ；
Firstly, calculating an average value P of three-phase power of a current power grid end average ，P average ＝(P gA3 +P gB3 +P gC3 )/3；
Then calculating the absolute value of the difference between the instantaneous value and the average value of each phase at the power grid end, and recording as delta P gA 、ΔP gB 、ΔP gC Then: ΔP gA ＝|P gA3 -P average |，ΔP gB ＝|P gB3 -P average |，ΔP gC ＝|P gC3 -P average |；
Then find the maximum absolute value of the difference, record as DeltaP g ＝max{ΔP gA ,ΔP gB ,ΔP gC }；
Then calculate the unbalance level unbalance, wherein unbalance=Δp g /P average ；
And finally judging whether the unbalance degree is smaller than a judging threshold value, if so, considering the three-phase power balance of the power grid end, otherwise, considering the three-phase power unbalance of the power grid end.
The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide a portable electronic device capable of performing various changes and modifications without departing from the scope of the technical spirit of the present invention. The technical scope of the present invention is not limited to the description, but must be determined according to the scope of claims.
Claims (7)
1. The output power control method of the three-phase inverter is characterized in that the three-phase inverter is of a three-phase four-wire system structure and comprises an A phase, a B phase, a C phase and an N wire; the method comprises the following steps:
s1: acquiring an instantaneous output power value of each phase of the three-phase inverter and an instantaneous power value of each phase of a power grid end;
s2: calculating the instantaneous power value of each phase of the user load based on the instantaneous output power value of each phase of the three-phase inverter and the instantaneous power value of each phase of the power grid end;
s3: calculating the total expected power of the power grid end based on a preset uplink power duty ratio allowed by the power grid end, and equally dividing the total expected power of the power grid end to each phase of electricity of the power grid end so as to obtain each phase of expected power value of the power grid end; the uplink power duty ratio is the ratio of the total expected power of the power grid end to the rated power of the three-phase inverter;
s4: adjusting each phase output power of the three-phase inverter based on the user load each phase instantaneous power value and the power grid end each phase expected power value, so that each phase output power of the three-phase inverter is the sum of the user load each phase instantaneous power value and the power grid end each phase expected power value;
the method for obtaining the output instantaneous power value of each phase of the three-phase inverter in the step S1 is as follows:
firstly, respectively obtaining each phase output voltage and each phase output current of the three-phase inverter through a sampling circuit, and respectively marking the output voltage and each phase output current as U A 、U B 、U C 、I A 、I B And I C ；
Then calculating the instantaneous output power value of each phase of the three-phase inverter, respectively denoted as P A1 、P B1 、P C1 The calculation formula is as follows:
P A1 ＝U A I A cos(θ A )，P B1 ＝U B I B cos(θ B )，P C1 ＝U C I C cos(θ C ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein θ is A 、θ B 、θ C
The phase angles of the A phase voltage, the B phase voltage and the C phase voltage of the three-phase inverter are respectively;
in the step S1, each phase of instantaneous power value of the power grid end is acquired in real time through a three-phase ammeter and is respectively recorded as P gA1 、P gB1 And P gC1 ；
The step S2 is specifically as follows: recording the instantaneous power value of each phase of the user load as P LA 、P LB And P LC P is then LA 、P LB And P LC The calculation formula of (2) is as follows:
P LA ＝P A1 -P gA1 ，P LB ＝P B1 -P gB1 ，P LC ＝P C1 -P gC1 ；
in step S3, the allowable uplink power duty ratio of the power grid end is recorded as K g The expected power value of each phase of the power grid end is respectively marked as P gA2 、P gB2 And P gC2 The method comprises the steps of carrying out a first treatment on the surface of the Then P gA2 、P gB2 、P gC2 The calculation formula of (2) is as follows:
P gA2 ＝P gB2 ＝P gC2 ＝(K g ×P N )/3；P N is the rated power of the three-phase inverter;
in step S4, each phase output power value of the three-phase inverter is denoted as P A2 、P B2 And P C2 P is then A2 、P B2 And P C2 The calculation formula of (2) is as follows:
P A2 ＝P LA +P gA2 ，P B2 ＝P LB +P gB2 ，P C2 ＝P LC +P gC2 。
2. the method of claim 1, further comprising step S5, step S5 being as follows:
s5: and (5) acquiring the instantaneous power value of each phase of the power grid terminal again, judging whether the three-phase power of the power grid terminal is balanced, ending the step (S5) if the three-phase power of the power grid terminal is balanced, and returning to the step (S1) if the three-phase power of the power grid terminal is unbalanced.
3. The method for controlling output power of a three-phase inverter according to claim 2, wherein the determining in step S5 whether the three-phase power at the grid end is balanced is as follows:
the obtained instantaneous power values of each phase of the power grid end are respectively marked as P gA3 、P gB3 And P gC3 ；
Firstly, calculating an average value P of three-phase power of a current power grid end average ，P average ＝(P gA3 +P gB3 +P gC3 )/3；
Then calculating the absolute value of the difference between the instantaneous value of each phase of the power grid end and the average value, and recording as delta P gA 、ΔP gB 、ΔP gC Then: ΔP gA ＝|P gA3 -P average |，ΔP gB ＝|P gB3 -P average |，ΔP gC ＝|P gC3 -P average |；
Then find the maximum absolute value of the difference, record as DeltaP g ＝max{ΔP gA ,ΔP gB ,ΔP gC }；
Then calculate the unbalance level unbalance, wherein unbalance=Δp g /P average ；
And finally judging whether the unbalance degree is smaller than a judging threshold value, if so, considering the three-phase power balance of the power grid end, otherwise, considering the three-phase power unbalance of the power grid end.
4. The three-phase inverter is characterized by comprising a T-shaped three-level inverter circuit, a control unit and a sampling unit;
the sampling unit is configured to collect each phase output voltage and each phase output current of the T-shaped three-level inverter circuit and send the each phase output voltage and each phase output current to the control unit;
the control unit is electrically connected with the T-shaped three-level inverter circuit and is configured to adjust the output power of each phase of the T-shaped three-level inverter circuit;
the control unit calculates the total expected power of the power grid end based on the preset uplink power duty ratio allowed by the power grid end, and equally divides the total expected power of the power grid end to each phase of electricity of the power grid end so as to obtain each phase of expected power value of the power grid end; the uplink power duty ratio is the ratio of the total expected power of the power grid end to the rated power of the three-phase inverter;
the control unit calculates each phase instant output power of the T-shaped three-level inverter circuit based on the each phase output voltage and each phase output current;
the control unit calculates the instantaneous power of each phase of the user load through the instantaneous power of each phase of the T-shaped three-level inverter circuit and the obtained instantaneous power of each phase of the power grid end;
and after obtaining the instantaneous power of each phase of the user load and the expected power of each phase of the power grid end, the control unit adjusts the output power of each phase of the T-shaped three-level inverter circuit to ensure that the output power of each phase of the T-shaped three-level inverter circuit is the sum of the instantaneous power of each phase of the user load and the expected power of each phase of the power grid end.
5. The three-phase inverter according to claim 4, wherein the control unit comprises an ARM control unit and a DSP control unit, the DSP control unit is electrically connected with the sampling unit, and each phase of output voltage and each phase of output current of the T-shaped three-level inverter circuit are obtained through the sampling unit; the ARM control unit is configured to be in communication connection with a three-phase ammeter, acquires the power grid end each phase instant power provided for a power grid by the T-shaped three-level inverter circuit from the three-phase ammeter, and sends the power grid end instant power to the DSP control unit, and the DSP control unit is used for calculating each phase output instant power of the T-shaped three-level inverter circuit, each phase instant power of a user load, the total expected power of the power grid end, each phase expected power of the power grid end and adjusting each phase output power of the T-shaped three-level inverter circuit.
6. An output power control device of a three-phase inverter, characterized by comprising the three-phase inverter of claim 4 or 5, and further comprising a three-phase ammeter;
the three-phase ammeter is electrically connected with the T-shaped three-level inverter circuit and is configured to collect each phase of instantaneous power provided by the T-shaped three-level inverter circuit to a power grid end of the power grid;
the control unit is in communication connection with the three-phase ammeter and is configured to acquire the instantaneous power of each phase of the power grid end from the three-phase ammeter.
7. The output power control device of a three-phase inverter according to claim 6, further comprising a photovoltaic array, a DC/DC conversion unit and a DC bus capacitor, wherein the DC/DC conversion unit is electrically connected to the photovoltaic array, performs DC/DC conversion on an output voltage of the photovoltaic array, and a signal output terminal of the DC/DC conversion unit is electrically connected to an inverter voltage input terminal of the T-type three-level inverter circuit through the DC bus capacitor.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR20060068537A (en) * | 2004-12-16 | 2006-06-21 | 엘지전자 주식회사 | A method for calculating instantaneous power for parallel operation of single-phase inverters and apparatus thereof, and an apparatus for driving electrical load incorporating the same method |
| CN114844065A (en) * | 2022-05-17 | 2022-08-02 | 浙江艾罗网络能源技术股份有限公司 | Three-phase unbalanced output control method and system thereof |
| CN115189374A (en) * | 2022-08-04 | 2022-10-14 | 沈阳农业大学 | Three-phase unbalance management system and method for light storage power supply and dynamic power regulation |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20060068537A (en) * | 2004-12-16 | 2006-06-21 | 엘지전자 주식회사 | A method for calculating instantaneous power for parallel operation of single-phase inverters and apparatus thereof, and an apparatus for driving electrical load incorporating the same method |
| CN114844065A (en) * | 2022-05-17 | 2022-08-02 | 浙江艾罗网络能源技术股份有限公司 | Three-phase unbalanced output control method and system thereof |
| CN115189374A (en) * | 2022-08-04 | 2022-10-14 | 沈阳农业大学 | Three-phase unbalance management system and method for light storage power supply and dynamic power regulation |
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