Automatic calibration method for measuring power of electricity meter and inverter

Abstract

The invention provides an automatic calibration method for measurement power of an electric meter and an inverter, a communication end of the inverter is in communication connection with the electric meter, a voltage sampling port of the inverter is used for sampling three-phase voltage and neutral line voltage, and a current sampling port of the inverter is used for sampling three-phase current; a voltage sampling port of the ammeter is used for sampling three-phase voltage and neutral line voltage, and a current sampling port of the ammeter is used for sampling three-phase current through a current sensor; the method comprises the steps of controlling an inverter to work in a wiring detection state when neutral line voltage sampling wiring of an electric meter is correct; and adjusting the inversion power of at least one phase of the inverter, and determining the current variable quantity, the active variable quantity and the reactive variable quantity of each phase of the electric meter before and after the power change so as to identify the wiring phase sequence of the electric meter and the installation direction of the current sensor and obtain the actual feed network power of at least one phase of the inverter. According to the invention, re-wiring is not needed when wiring errors exist in the ammeter, the power fed back by the ammeter can be automatically corrected, and the working efficiency is greatly improved.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic storage technology, and in particular to an automatic calibration method for measuring power of an electric meter and an inverter. Background Art

[0002] In the photovoltaic storage system, in order to control the online power of the photovoltaic storage inverter, the electric meter needs to feedback the online power information. The electric meter needs to sample the voltage and current of the three-phase grid, but it is easy to have the wrong wiring phase sequence and the wrong installation direction of the current sensor. The wiring error will lead to the failure of online power control, and even the power flow that is completely opposite to the requirement. At present, the main way to confirm whether the wiring is correct is to manually observe the voltage, current, power, etc., which is inefficient. Summary of the invention

[0003] The present application provides an automatic calibration method for an electric meter to measure power and an inverter, so as to automatically perform calibration when there is an error in the connection of the electric meter, thereby improving work efficiency.

[0004] On one hand, the present application provides an automatic calibration method for measuring power by an electric meter, which is applied to an inverter, wherein the DC terminal of the inverter is connected to a photovoltaic array and / or an energy storage battery, the three-phase AC terminal and the neutral terminal of the inverter are connected to a power grid, the communication terminal of the inverter is communicatively connected to the electric meter, the voltage sampling port of the inverter is used to sample the three-phase voltage and the neutral voltage, and the current sampling port of the inverter samples the three-phase current; the voltage sampling port of the electric meter is used to sample the three-phase voltage and the neutral voltage, and the current sampling port of the electric meter samples the three-phase current through a current sensor;

[0005] The method comprises:

[0006] When the neutral line voltage sampling wiring of the electric meter is correct, controlling the inverter to work in a wiring detection state;

[0007] Adjust the inverter power of at least one phase of the inverter, determine the current change, active change and reactive change of each phase of the meter before and after the power change, so as to identify the wiring phase sequence of the meter and the installation direction of the current sensor, and obtain the actual grid feeding power of at least one phase of the inverter.

[0008] In one example, the method further includes:

[0009] The voltage value sampled by the electric meter and the voltage value sampled by the inverter are obtained to confirm whether the neutral line voltage sampling wiring of the electric meter is correct according to the voltage value sampled by the electric meter and the voltage value sampled by the inverter.

[0010] In one example, the method further includes:

[0011] If the absolute value of the difference between the effective value of the phase voltage sampled by the inverter and the effective value of the phase voltage sampled by the electric meter is greater than or equal to the preset voltage threshold, it is confirmed that the neutral line voltage sampling wiring of the electric meter is wrong.

[0012] In one example, the method further includes:

[0013] When it is confirmed that the neutral line voltage sampling wiring of the electric meter is wrong, wiring fault information is reported to prompt the user to replace the wiring.

[0014] In one example, adjusting the inverter power of at least one phase of the inverter includes:

[0015] The inverter power of at least one phase of the inverter is increased.

[0016] In one example, determining the current change amount, active change amount, and reactive change amount of each phase of the electric meter before and after the power change to identify the connection phase sequence of the electric meter and the installation direction of the current sensor, and obtaining the actual grid-fed power of at least one phase of the inverter includes:

[0017] Determine, according to the current change of at least one phase of the inverter and the current change of each phase of the electric meter, the corresponding phase of the electric meter for sampling the current of at least one phase of the inverter;

[0018] Determine the current sampling direction of the corresponding phase of the electric meter and the voltage sampling phase corresponding to the corresponding phase according to the power change of at least one phase of the inverter, the active change and the reactive change of the corresponding phase of the electric meter;

[0019] The actual grid-fed power of at least one phase of the inverter is determined according to the current sampling direction of the corresponding phase of the electric meter and the phase relationship between the voltage sampling phase and at least one phase of the inverter.

[0020] In one example, determining the corresponding phase of the electric meter for sampling the current of at least one phase of the inverter according to the current change of at least one phase of the inverter and the current change of each phase of the electric meter includes:

[0021] If the absolute value of the difference between the current change of at least one phase of the inverter and the current change of one phase of the electric meter is less than the preset current threshold, then one phase of the electric meter is the corresponding phase of the electric meter that samples the current of at least one phase of the inverter.

[0022] In one example, determining the current sampling direction of the corresponding phase of the electric meter and the voltage sampling phase corresponding to the corresponding phase according to the power change of at least one phase of the inverter, the active change and the reactive change of the corresponding phase of the electric meter includes:

[0023] Determine the correspondence between the active change and reactive change of the corresponding phase of the electric meter and the power change of at least one phase of the inverter, and match the corresponding relationship with the existing wiring conditions to determine the current sampling direction of the corresponding phase of the electric meter and the voltage sampling phase corresponding to the corresponding relationship.

[0024] In one example, determining the actual grid-fed power of at least one phase of the inverter according to the current sampling direction of the corresponding phase of the electric meter and the phase relationship between the voltage sampling phase and at least one phase of the inverter includes:

[0025] According to the current sampling direction of the corresponding phase of the electric meter and the phase relationship between the voltage sampling phase and at least one phase of the inverter, the measured power of the corresponding phase of the electric meter is automatically calibrated to determine the actual grid-fed power of at least one phase of the inverter.

[0026] On the other hand, the present application provides an inverter, wherein the DC end of the inverter is connected to a photovoltaic array and / or an energy storage battery, the three-phase AC end and the neutral line end of the inverter are connected to a power grid, the communication end of the inverter is communicatively connected to an electric meter, the voltage sampling port of the inverter is used to sample the three-phase voltage and the neutral line voltage, and the current sampling port of the inverter is used to sample the three-phase current; the voltage sampling port of the electric meter is used to sample the three-phase voltage and the neutral line voltage, and the current sampling port of the electric meter samples the three-phase current through a current sensor;

[0027] The inverter further comprises a control unit, and the control unit is configured to implement the automatic calibration method for measuring power with an electric meter.

[0028] The automatic calibration method for measuring power by an electric meter and the inverter provided in the present application first control the inverter to operate at the minimum power generation, then adjust the inverter power of at least one phase of the inverter, determine the current change of each phase, the active power change and the reactive power change of the electric meter before and after the power change, so as to identify the wiring phase sequence of the electric meter and the installation direction of the current sensor, and obtain the actual grid feed power of at least one phase; in this way, even if there is an error in the wiring of the electric meter, there is no need to rewire, and the power fed back by the electric meter can be automatically corrected, which greatly improves work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0030] Figure 1 is a schematic diagram of a photovoltaic storage system provided in an embodiment of the present application;

[0031] Figure 2 It is a schematic diagram of an automatic calibration method for measuring power by an electric meter provided in an embodiment of the present application;

[0032] Figure 3 This is a schematic diagram of a wiring phase sequence and current sensor installation direction provided in an embodiment of the present application;

[0033] Figure 4 This is another schematic diagram of wiring phase sequence and current sensor installation direction provided in an embodiment of the present application;

[0034] Figure 5 This is another schematic diagram of wiring phase sequence and current sensor installation direction provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to facilitate the understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art of the present application. The terms used in this specification in the specification of the present application are only for the purpose of describing specific embodiments and are not used to limit the present application. The term "and / or" used in this specification includes any and all combinations of one or more related listed items.

[0036] Figure 1 It is a schematic diagram of a photovoltaic storage system provided in an embodiment of the present application.

[0037] like Figure 1 As shown, the photovoltaic storage system includes a photovoltaic array, an energy storage battery, an inverter (i.e., the photovoltaic storage inverter in the figure), an electric meter (i.e., the three-phase electric meter in the figure), and a current sensor (shown as Z1, Z2, and Z3 in the figure).

[0038] The DC end of the inverter is connected to the photovoltaic array and / or the energy storage battery, the three-phase AC end (shown in A, B, and C in the figure) and the neutral line end (shown in N in the figure) of the inverter are connected to the power grid, and the communication end of the inverter is connected to the electric meter (refer to the communication connection line of the electric meter in the figure); the voltage sampling port of the electric meter is used to sample the three-phase voltage and the neutral line voltage (refer to the sampling voltage connection line in the figure), and the current sampling port of the electric meter samples the three-phase current through the current sensor (refer to the sampling current connection line in the figure). The direction of the arrow in the figure is the installation direction of the current sensor.

[0039] The inverter integrates a voltage sampling unit and a current sampling unit, and samples the three-phase voltage and the neutral line voltage through the voltage sampling port of the voltage sampling unit, and samples the three-phase current through the current sampling port of the current sampling unit. The inverter also integrates a control unit, which can be implemented as an array of multiple logic gates, or can be implemented as a combination of a general microcontroller and a memory, in which a program executable in the microcontroller is stored. It will be understood by those skilled in the art that the control unit can also be implemented in other forms of hardware.

[0040] Based on the above-mentioned solar energy storage system, the embodiment of the present application also provides an automatic calibration method for measuring power by an electric meter, such as Figure 2 As shown, the method comprises the steps of:

[0041] S11. When the neutral line voltage sampling wiring of the electric meter is correct, control the inverter to operate in a wiring detection state.

[0042] The wiring detection state refers to a state suitable for the inverter to perform wiring detection, which may be a minimum power generation state or a state in which the battery is charged from the power grid at maximum power.

[0043] In one example, the voltage value sampled by the electric meter and the voltage value sampled by the inverter may be obtained to confirm whether the neutral line voltage sampling wiring of the electric meter is correct based on the voltage value sampled by the electric meter and the voltage value sampled by the inverter.

[0044] Specifically, by comparing the voltage value sampled by the electric meter with the voltage value sampled by the inverter, it is confirmed whether the neutral line voltage sampling wiring of the electric meter, that is, the N-phase voltage sampling wiring is correct.

[0045] When the N-phase voltage sampling wiring is wrong, two of the three-phase voltages sampled by the meter must be line voltages, and the effective value of the line voltage is √3 times the phase voltage. Therefore, if the absolute value of the difference between the effective value of the phase voltage sampled by the inverter and the effective value of the phase voltage sampled by the meter is greater than the preset voltage threshold, it is considered that the N-phase voltage sampling wiring is wrong. Considering the sampling error, this preset voltage threshold can be between "10%*grid rated voltage" and "60%*grid rated voltage".

[0046] In further implementation, when it is confirmed that the N-phase voltage sampling wiring is wrong, the inverter directly reports the wiring fault information to remind the user or installer to replace the wiring.

[0047] The inverter is controlled to work in a wiring detection state. Specifically, the inverter can be set to discharge to the grid as the positive power direction, and the inverter can be controlled to work in a minimum power generation state, which should be suitable for wiring detection. This state can be that the inverter charges the battery from the grid at maximum power or the inverter generates power at zero power.

[0048] S12. Adjust the inverter power of at least one phase of the inverter, determine the current change, active power change and reactive power change of each phase of the electric meter before and after the power change, so as to identify the connection phase sequence of the electric meter and the installation direction of the current sensor, and obtain the actual grid feeding power of at least one phase of the inverter.

[0049] In one example, the inverter power of at least one phase of the inverter may be controlled to increase, and the increase value may be 10% of the maximum power of the single phase of the inverter.

[0050] In one example, determining the current change amount, active change amount, and reactive change amount of each phase of the electric meter before and after the power change to identify the connection phase sequence of the electric meter and the installation direction of the current sensor, and obtaining the actual grid-fed power of at least one phase of the inverter includes:

[0051] Determine, according to the current change of at least one phase of the inverter and the current change of each phase of the electric meter, the corresponding phase of the electric meter for sampling the current of at least one phase of the inverter;

[0052] Determine the current sampling direction of the corresponding phase of the electric meter and the voltage sampling phase corresponding to the corresponding phase according to the power change of at least one phase of the inverter, the active change and the reactive change of the corresponding phase of the electric meter;

[0053] The actual grid-fed power of at least one phase of the inverter is determined according to the current sampling direction of the corresponding phase of the electric meter and the phase relationship between the voltage sampling phase and at least one phase of the inverter.

[0054] Wherein, determining the corresponding phase of the electric meter for sampling the current of at least one phase of the inverter according to the current change of at least one phase of the inverter and the current change of each phase of the electric meter includes:

[0055] If the absolute value of the difference between the current change of at least one phase of the inverter and the current change of one phase of the electric meter is less than a preset current threshold, then one phase of the electric meter is the corresponding phase of the electric meter that samples the current of at least one phase of the inverter. The preset current threshold may be 1%*rated current.

[0056] Wherein, determining the current sampling direction of the corresponding phase of the electric meter and the voltage sampling phase corresponding to the corresponding phase according to the power change of at least one phase of the inverter, the active change and the reactive change of the corresponding phase of the electric meter, comprises:

[0057] Determine the correspondence between the active change and reactive change of the corresponding phase of the electric meter and the power change of at least one phase of the inverter, and match the corresponding relationship with the existing wiring conditions to determine the current sampling direction of the corresponding phase of the electric meter and the voltage sampling phase corresponding to the corresponding relationship.

[0058] Wherein, determining the actual grid-fed power of at least one phase of the inverter according to the current sampling direction of the corresponding phase of the electric meter and the phase relationship between the voltage sampling phase and at least one phase of the inverter includes:

[0059] According to the current sampling direction of the corresponding phase of the electric meter and the phase relationship between the voltage sampling phase and at least one phase of the inverter, the measured power of the corresponding phase of the electric meter is automatically calibrated to determine the actual grid-fed power of at least one phase of the inverter.

[0060] Take phase A as an example:

[0061] The inverter power of phase A is controlled to increase, and the increase value can be 10% of the maximum power of the inverter single phase. After a delay period, the change in the current of phase A of the inverter and the change in the current of each phase of the meter are detected. If the absolute value of the difference between the absolute value of the change in the current of phase A of the inverter and the absolute value of the change in the current of phase x (x can be A, B or C) of the meter is less than the preset current threshold, then the corresponding phase of the sampled current of phase A in the meter is phase x, that is, the current sensor of the meter corresponding to the actual feeder network A is phase x.

[0062] Assume that the power change of inverter phase A is ΔP, the active power change of meter phase x is ΔPx, and the reactive power change is ΔQx. Assume that the real active power of phase A feed network is Pma', the real reactive power of phase A feed network is Qma', the sampled active power of meter phase x is Pmx, and the sampled reactive power of meter phase x is Qmx.

[0063] For the x phase of the electric meter, since it has been confirmed that the sampling current of the x phase is the A phase, the connection status can be further judged according to the change of active power ΔPx and reactive power ΔQx of the electric meter. The error is taken into account in the actual judgment. The active power judgment threshold is 0.6*ΔP, -0.6*ΔP, 0, and the reactive power judgment threshold is 0. Specifically, there are only the following 6 connection situations:

[0064] 1) The current sampling direction is correct, and the voltage sampling phase is phase A. At this time, ΔPx = ΔP;

[0065] 2) The current sampling direction is correct, the voltage sampling phase is phase B, and the voltage of phase B lags behind the voltage of phase A by 120°. In this state, ΔPx = cos(-120°)*ΔP = -0.5*ΔP, ΔQx = sin(-120°)*ΔP = -0.866*ΔP;

[0066] 3) The current sampling direction is correct, the voltage sampling phase is phase C, and the voltage of phase C leads the voltage of phase A by 120°. In this state, ΔPx = ΔP*cos(120°) = -0.5*ΔP, ΔQx = ΔP*sin(120°) = 0.866*ΔP;

[0067] 4) The current sampling direction is wrong, the voltage sampling phase is phase A, ΔPx = -ΔP;

[0068] 5) The current sampling direction is wrong, the voltage sampling phase is phase B, and the voltage of phase B lags behind the voltage of phase A by 120°. In this state, ΔPx=-cos(-120°)*ΔP=0.5*ΔP, ΔQx=-sin(-120°)*ΔP=0.866*ΔP;

[0069] 6) The current sampling direction is wrong, the voltage sampling phase is phase C, and the voltage of phase C leads the voltage of phase A by 120°.

[0070] In this state, ΔPx=-ΔP*cos(120°)=0.5*ΔP, ΔQx=-ΔP*sin(120°)=-0.866*ΔP.

[0071] After determining the wiring status, the actual grid-feeding power can be inferred based on the current sampling direction, the voltage sampling phase and the voltage phase relationship between phase A, as follows:

[0072] 1) The current sampling direction is correct, the voltage sampling phase is phase A, Pma'=Pmx, Qma'=Qmx;

[0073] 2) The current sampling direction is correct, the voltage sampling phase is phase B, the phase lags behind phase A by 120°, Pma'=Pmx / cos(-120°)=_-Pmx*2, Qma'=Qmx / sin(-120°)=-Qmx / 0.866;

[0074] 3) The current sampling direction is correct, the voltage sampling phase is phase C, the phase leads phase A by 120°, Pma'=Pmx / cos(120°)=-Pmx*2, Qma'=Qmx / sin(120°)=Qmx / 0.866;

[0075] 4) The current sampling direction is wrong, the voltage sampling phase is phase A, Pma'=-Pmx, Qma'=-Qmx;

[0076] 5) The current sampling direction is wrong, the voltage sampling phase is phase B, which lags behind phase A by 120°, Pma'=-Pmx / cos(-120°)=Pmx*2, Qma'=-Qmx / sin(-120°)=Qmx / 0.866;

[0077] 6) The current sampling direction is wrong, the voltage sampling phase is phase C, which is 120° ahead of phase A, that is, phase C Pma'=-Pmx / cos(120°)=Pmx*2, Qma'=-Qmx / sin(120°)=-Qmx / 0.866.

[0078] The other two phases are identified in the same way.

[0079] In order to better illustrate the automatic calibration process of the meter to measure power, the following Figure 3-Figure 5 To explain:

[0080] like Figure 3 As shown in the figure, in a wiring phase sequence and current sensor installation direction schematic diagram, the voltage sampling wiring phase sequence of the meter is correct. That is, the A-phase voltage sampling port Ua of the meter is connected to the A-phase grid voltage sampling line, the B-phase voltage sampling port Ub of the meter is connected to the B-phase grid voltage sampling line, the C-phase voltage sampling port Uc of the meter is connected to the C-phase grid voltage sampling line, and the N-phase voltage sampling port Un of the meter is connected to the N-phase grid voltage sampling line.

[0081] The phase sequence of the current sampling wiring of the electric meter is wrong. Specifically, the output of the A-phase current sensor is connected to the B-phase current sampling port Ib of the electric meter, and the output of the B-phase current sensor is connected to the A-phase current sampling port Ia of the electric meter.

[0082] The installation direction of the A-phase current sensor, B-phase current sensor, and C-phase current sensor is correct (the arrows in the figure indicate the correct direction). Figure 1 same).

[0083] The automatic calibration process of the meter to measure power is as follows:

[0084] First, after the photovoltaic storage inverter is connected to the grid and operates normally, the photovoltaic storage inverter is controlled to operate in the minimum power generation state.

[0085] Then, control the inverter power of phase A to increase it by 10% of the inverter single-phase maximum power. The inverter collects the current and power fed back by the meter before and after the power change. If the difference between the change in phase B current fed back by the meter and the change in phase A current of the inverter is the smallest (i.e., less than the preset current threshold), it means that the current sampled by the phase B current of the meter is actually the current of phase A. The active change of phase B of the meter is "-0.5*inverter phase power change", and the reactive change of phase B of the meter is "-0.866*inverter phase power change", indicating that the current sampling direction of phase B of the meter is correct, and the voltage sampling phase corresponding to the current sampling of phase B of the meter is phase B. Then the actual active power fed to the grid of phase A is P ma '=P mb / cos(-120°)=-P mb *2, the actual reactive power of the feeder network is Q ma '=Q mb / sin(-120°)=-Q mb / 0.866.

[0086] Control the inverter power of phase B to increase the inverter single-phase maximum power by 10%. The inverter collects the current and power fed back by the meter before and after the power change. If the difference between the change in phase A current fed back by the meter and the change in phase B current of the inverter is the smallest, it means that the current sampling of phase A of the meter is actually sampling the current of phase B. The active change of phase A of the meter is "-0.5*change in inverter power", and the reactive change of phase A of the meter is "0.866*change in inverter power", which means that the current sampling direction of phase A of the meter is correct, and the voltage sampling phase corresponding to the current sampling of phase A of the meter is phase A. Then the actual active power of the phase B feed network is P mb '=P ma / cos(120°)=-P ma *2, the actual reactive power is Q mb '=Q ma / sin(120°)=Q ma / 0.866.

[0087] Control the C phase inverter power to increase the inverter single-phase maximum power by 10%. The inverter collects the meter current and power fed back by the meter before and after the power change. The difference between the C phase current change fed back by the meter and the inverter C phase current change is the smallest, which means that the meter C phase current sampling actually samples the C phase current; the active power change of the meter C phase>0.6*inverter phase power change, which means that the voltage sampling phase and current sensor installation direction corresponding to the meter C phase current sampling are correct. Then the actual active power of the meter C phase is P mc '=P mc , the actual reactive power is Q mc '=Q mc .

[0088] like Figure 4 As shown, in another schematic diagram of wiring phase sequence and current sensor installation direction, the meter voltage sampling wiring is correct, that is, the meter A phase voltage sampling port Ua is connected to the A phase grid voltage sampling line, the meter B phase voltage sampling port Ub is connected to the B phase grid voltage sampling line, the meter C phase voltage sampling port Uc is connected to the C phase grid voltage sampling line, and the meter N phase voltage sampling port Un is connected to the N phase grid voltage sampling line.

[0089] The phase sequence of the current sampling wiring of the meter is wrong. Specifically, the output of the A-phase current sensor is connected to the B-phase current sampling port of the meter, and the output of the B-phase current sensor is connected to the A-phase current sampling port of the meter.

[0090] The installation direction of the A-phase current sensor and the C-phase current sensor is wrong (refer to Figure 1 direction of the arrow shown).

[0091] The automatic calibration process of the meter to measure power is as follows:

[0092] First, after the photovoltaic storage inverter is connected to the grid and operates normally, the photovoltaic storage inverter is controlled to operate in the minimum power generation state.

[0093] Then, the inverter power of phase A is controlled to increase by 10% of the maximum single-phase power of the inverter. The inverter collects the current and power fed back by the meter before and after the power change. The difference between the change in the phase B current fed back by the meter and the change in the phase A current of the inverter is the smallest, indicating that the current sampled by the phase B current of the meter is actually the current of phase A; the active change of phase B of the meter is "0.5*the change in the inverter power", and the reactive change of phase B of the meter is "0.866*the change in the inverter power", indicating that the current sampling direction of phase B of the meter is reversed, and the voltage sampling phase corresponding to the current sampling of phase B of the meter is phase B. Then the actual active power of the phase A feed network is P ma '=-P mb / cos(-120°)=P mb *2, the actual reactive power is Q ma '=-Q mb / sin(-120°)=Q mb / 0.866.

[0094] Control the inverter power of phase B to increase it by 10% of the inverter's single-phase maximum power. The inverter collects the current and power fed back by the meter before and after the power change. If the difference between the A-phase current change fed back by the meter and the B-phase current change of the inverter is the smallest, it means that the A-phase current sampling of the meter is actually sampling the B-phase current; the active change of phase A of the meter is "-0.5*inverter phase power change", and the reactive change of phase A of the meter is "0.866*inverter phase power change", indicating that the current sampling direction of phase A of the meter is correct, and the voltage sampling phase corresponding to the current sampling of phase A of the meter is phase A. Then the actual active power of the B-phase feed network is P mb '=P ma / cos(120°)=-P ma *2, the actual reactive power is Q mb '=Q ma / sin(120°)=Q ma / 0.866.

[0095] Control the C phase inverter power to increase the inverter single-phase maximum power by 10%. The inverter collects the current and power fed back by the meter before and after the power change. The difference between the C phase current change fed back by the meter and the inverter C phase current is the smallest, which means that the C phase current sampling of the meter is actually the C phase current; the active change of the C phase of the meter is <-0.6*the inverter phase power change, which means that the voltage sampling phase corresponding to the C phase current sampling of the meter is the C phase, and the installation direction of the current sensor is reversed. The actual active power of the C phase of the meter is P mc '=-P mc , the actual reactive power is Q mc '=-Q mc .

[0096] like Figure 5 As shown, in another wiring phase sequence and current sensor installation direction schematic diagram, the meter voltage sampling wiring is wrong, the C-phase grid voltage sampling line is connected to the meter B-phase voltage sampling port, and the B-phase grid voltage sampling line is connected to the meter C-phase voltage sampling port.

[0097] The phase sequence of the current sampling wiring of the meter is wrong. Specifically, the output of the A-phase current sensor is connected to the B-phase current sampling port of the meter, and the output of the B-phase current sensor is connected to the A-phase current sampling port of the meter.

[0098] The installation direction of the A-phase current sensor and the C-phase current sensor is wrong (refer to Figure 1 direction of the arrow shown).

[0099] The automatic calibration process of the meter to measure power is as follows:

[0100] First, after the photovoltaic storage inverter is connected to the grid and operates normally, the photovoltaic storage inverter is controlled to operate in the minimum power generation state.

[0101] Then, the inverter power of phase A is controlled to increase by 10% of the maximum single-phase power of the inverter. The inverter collects the current and power fed back by the meter before and after the power change. The difference between the change in phase B current fed back by the meter and the current of phase A of the inverter is the smallest, indicating that the current sampling of phase B of the meter is actually sampling the current of phase A; the active change of phase B of the meter is "0.5*change in inverter power", and the reactive change of phase B of the meter is "-0.866*change in inverter power", indicating that the current sampling direction of phase B of the meter is reversed, and the voltage sampling phase corresponding to the current sampling of phase B of the meter is phase C. Then the actual active power of the A-phase feed network is P ma '=-P mb / cos(120°)=P mb *2, the actual reactive power is Q ma '=-Q mb / sin(120°)=-Q mb / 0.866.

[0102] Control the inverter power of phase B to increase it by 10% of the inverter's single-phase maximum power. The inverter collects the current and power fed back by the meter before and after the power change. If the difference between the change in phase A current fed back by the meter and the change in phase B current of the inverter is the smallest, it means that the current sampled by the meter for phase A is actually the current of phase B; the active change of phase A of the meter is "-0.5*inverter phase power change", and the reactive change of phase A of the meter is "0.866*inverter phase power change", indicating that the current sampling direction of phase A of the meter is correct, and the voltage sampling phase corresponding to the current sampling of phase A of the meter is phase A. Then the actual active power fed to the grid of phase B is P mb '=P ma / cos(120°)=-P ma *2, the actual reactive power is Q mb '=Q ma / sin(120°)=Q ma / 0.866.

[0103] The inverter power of phase C is controlled to increase the inverter single-phase maximum power by 10%. The inverter collects the current and power fed back by the meter before and after the power change. The difference between the change in phase C current fed back by the meter and the change in phase C current of the inverter is the smallest, indicating that the current sampling of phase C of the meter is actually sampling the current of phase C; the active change of phase C of the meter is "0.5*inverter phase power change", and the reactive change of phase C of the meter is "-0.866*inverter phase power change", indicating that the direction of the current sensor of phase C of the meter is reversed, and the voltage sampling phase corresponding to the current of phase C of the meter is phase B, then the actual active power of the C-phase feed network is P mc '=-P mc / cos(120°)=P mc *2, the actual reactive power is Q mc'=-Q mc / sin(120°)=-Q mc / 0.866.

[0104] It should be noted that the preferred embodiments of the present application are given in the specification and drawings of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described in the specification. These embodiments are not used as additional limitations on the content of the present application. The purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive. In addition, the above-mentioned technical features continue to be combined with each other to form various embodiments not listed above, which are all regarded as the scope of the description of the present application; further, for ordinary technicians in this field, they can be improved or transformed according to the above description, and all these improvements and transformations should belong to the scope of protection of the claims attached to the present application.

Claims

1. An automatic calibration method for measuring power by an electric meter, applied to an inverter, characterized in that: The DC end of the inverter is connected to a photovoltaic array and / or an energy storage battery, the three-phase AC end and the neutral line end of the inverter are connected to the power grid, the communication end of the inverter is communicatively connected to the electric meter, the voltage sampling port of the inverter is used to sample the three-phase voltage and the neutral line voltage, and the current sampling port of the inverter samples the three-phase current; the voltage sampling port of the electric meter is used to sample the three-phase voltage and the neutral line voltage, and the current sampling port of the electric meter samples the three-phase current through a current sensor; The method comprises: When the neutral line voltage sampling wiring of the electric meter is correct, controlling the inverter to work in a wiring detection state; Adjust the inverter power of at least one phase of the inverter, determine the current change, active change and reactive change of each phase of the meter before and after the power change, so as to identify the wiring phase sequence of the meter and the installation direction of the current sensor, and obtain the actual grid feeding power of at least one phase of the inverter.

2. The method according to claim 1, characterized in that The method further comprises: The voltage value sampled by the electric meter and the voltage value sampled by the inverter are obtained to confirm whether the neutral line voltage sampling wiring of the electric meter is correct according to the voltage value sampled by the electric meter and the voltage value sampled by the inverter.

3. The method as claimed in claim 2, characterized in that The method further comprises: If the absolute value of the difference between the effective value of the phase voltage sampled by the inverter and the effective value of the phase voltage sampled by the electric meter is greater than or equal to the preset voltage threshold, it is confirmed that the neutral line voltage sampling wiring of the electric meter is wrong.

4. The method as claimed in claim 2, characterized in that The method further comprises: When it is confirmed that the neutral line voltage sampling wiring of the electric meter is wrong, wiring fault information is reported to prompt the user to replace the wiring.

5. The method according to claim 1, characterized in that The step of adjusting the inverter power of at least one phase of the inverter comprises: The inverter power of at least one phase of the inverter is increased.

6. The method according to claim 1, characterized in that The determining of the current change amount, active change amount and reactive change amount of each phase of the electric meter before and after the power change, so as to identify the connection phase sequence of the electric meter and the installation direction of the current sensor, and obtain the actual grid-fed power of at least one phase of the inverter, includes: Determine, according to the current change of at least one phase of the inverter and the current change of each phase of the electric meter, the corresponding phase of the electric meter for sampling the current of at least one phase of the inverter; Determine the current sampling direction of the corresponding phase of the electric meter and the voltage sampling phase corresponding to the corresponding phase according to the power change of at least one phase of the inverter, the active power change and the reactive power change of the corresponding phase of the electric meter; The actual grid-fed power of at least one phase of the inverter is determined according to the current sampling direction of the corresponding phase of the electric meter and the phase relationship between the voltage sampling phase and at least one phase of the inverter.

7. The method as claimed in claim 6, characterized in that The determining, according to the current change of at least one phase of the inverter and the current change of each phase of the electric meter, the corresponding phase for sampling the current of at least one phase of the inverter in the electric meter comprises: If the absolute value of the difference between the current change of at least one phase of the inverter and the current change of one phase of the electric meter is less than the preset current threshold, then one phase of the electric meter is the corresponding phase of the electric meter that samples the current of at least one phase of the inverter.

8. The method as claimed in claim 6, characterized in that The step of determining the current sampling direction of the corresponding phase of the electric meter and the voltage sampling phase corresponding to the corresponding phase according to the power variation of at least one phase of the inverter, the active variation and the reactive variation of the corresponding phase of the electric meter comprises: Determine the correspondence between the active change and reactive change of the corresponding phase of the electric meter and the power change of at least one phase of the inverter, and match the corresponding relationship with the existing wiring conditions to determine the current sampling direction of the corresponding phase of the electric meter and the voltage sampling phase corresponding to the corresponding relationship.

9. The method as claimed in claim 6, characterized in that Determining the actual grid-fed power of at least one phase of the inverter according to the current sampling direction of the corresponding phase of the electric meter and the phase relationship between the voltage sampling phase and at least one phase of the inverter includes: According to the current sampling direction of the corresponding phase of the electric meter and the phase relationship between the voltage sampling phase and at least one phase of the inverter, the measured power of the corresponding phase of the electric meter is automatically calibrated to determine the actual grid-fed power of at least one phase of the inverter.

10. An inverter, characterized in that: The DC end of the inverter is connected to a photovoltaic array and / or an energy storage battery, the three-phase AC end and the neutral line end of the inverter are connected to the power grid, the communication end of the inverter is connected to the electric meter, the voltage sampling port of the inverter is used to sample the three-phase voltage and the neutral line voltage, and the current sampling port of the inverter samples the three-phase current; the voltage sampling port of the electric meter is used to sample the three-phase voltage and the neutral line voltage, and the current sampling port of the electric meter samples the three-phase current through a current sensor; The inverter further comprises a control unit, wherein the control unit is configured to execute the automatic calibration method for measuring power by an electric meter according to any one of claims 1 to 9.

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