Ammeter phase sequence correction method

Abstract

The invention discloses an ammeter phase sequence deviation rectifying method, and relates to an ammeter phase sequence deviation rectifying device, the device comprises an ammeter, a current transformer and an upper computer, the ammeter is provided with an MCU, the current transformer is connected with the MCU of the ammeter and is used for being installed on an electric wire in a sleeving mode to sense the current of the electric wire, and the ammeter is in communication connection with the upper computer through the MCU; the method comprises the following three conditions: the first condition is connection detection of the current transformer; the second condition is reverse connection correction of the current transformer; and the third condition is line sequence deviation correction of the current transformer. According to the invention, the connection state of the current transformer can be detected, and the detection accuracy and stability are improved; when the current transformer is reversely connected, the power utilization data can be corrected, so that the detection accuracy is ensured, the current transformer does not need to be reconnected, and the operation is convenient; when the current transformer is wrongly connected, the current sampling channel corresponding to the current transformer can be adjusted, the current transformer does not need to be reconnected, and the operation is flexible.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power measurement, and in particular to a method for correcting phase sequence deviation of an electric meter. Background Art

[0002] With the rapid development of photovoltaic power generation technology, distributed grid-connected photovoltaic systems are becoming increasingly popular. Current transformers (CTs) are key measurement components in photovoltaic power generation systems, and their wiring accuracy directly impacts the accuracy of energy metering. However, CT wiring errors frequently occur during installation and maintenance, posing a significant challenge to the stable operation and accurate metering of photovoltaic systems.

[0003] Photovoltaic power generation systems have significant differences compared to traditional power grids: First, they feature bidirectional power flow, allowing them to both draw power from and feed power back into the grid. Second, the photovoltaic output current is significantly affected by sunlight intensity, exhibiting wide fluctuations and rapid changes. Furthermore, the inverter output current contains a high number of harmonics and may contain a DC component. These characteristics further complicate the issue of incorrectly connected CTs in photovoltaic meters. Summary of the Invention

[0004] The object of the present invention is to provide a method for correcting phase sequence deviation of an electric meter, which can improve the flexibility and convenience of electric meter detection when a wiring error occurs in a current transformer.

[0005] To achieve the above-mentioned objectives, the present invention provides a solution: a phase sequence correction device for an electric meter, comprising an electric meter, a current transformer, and a host computer. The electric meter is provided with an MCU, the current transformer is connected to the MCU of the electric meter, and is used to be sleeved and installed on the electric wire to sense the current of the electric wire. The electric meter is in communication with the host computer via the MCU.

[0006] The phase sequence correction method of the electric meter includes the following three situations:

[0007] The first case is the connection detection of the current transformer:

[0008] The MCU of the electric meter is equipped with a sampling module, which is connected to the current transformer. The electric meter collects the current signal of the current transformer through the sampling module, compares the current signal of the current transformer with the set threshold, and then obtains the connection status of the current transformer;

[0009] The second case is the current transformer reverse connection correction:

[0010] Define the default reference current direction of the wire. The host computer uses the meter to detect the socket installation direction of the current transformer. If the socket installation direction of the current transformer is opposite to the default reference current direction of the wire, the host computer corrects the power consumption data collected by the meter.

[0011] The third case is the line sequence correction of the current transformer:

[0012] The MCU of the meter is equipped with a sampling module, which is connected to the current transformer. The host computer switches the current sampling channel of the sampling module by controlling the register level state of the MCU of the meter, thereby adjusting the wiring sequence of the current transformer installed on the wire.

[0013] In a preferred embodiment, the current signal of the current transformer is a sampled voltage. If the sampled voltage is greater than a set threshold, it is determined that the current transformer connection is abnormal.

[0014] Preferably, the electricity consumption data includes phase current, active power, reactive power, power factor, bidirectional active power measurement and four-quadrant reactive power measurement.

[0015] In a preferred embodiment, if the socket installation direction of the current transformer is opposite to the default reference current direction of the wire, the correction processing formulas for the phase current, active power, reactive power and power factor are as follows:

[0016]

[0017] Where I is the phase current, P is the active power, Q is the reactive power, and PF is the power factor.

[0018] In a preferred embodiment, if the socket installation direction of the current transformer is consistent with the default reference current direction of the wire, the original metering formula for the bidirectional active power metering and four-quadrant reactive power metering is:

[0019]

[0020] If the socket installation direction of the current transformer is opposite to the default reference current direction of the wire, the correction processing formula for the bidirectional active power measurement and four-quadrant reactive power measurement is:

[0021]

[0022] Among them, AEE is the reverse active energy, AEI is the forward active energy, RE_Q1 is the reactive energy in the first quadrant, RE_Q2 is the reactive energy in the second quadrant, RE_Q3 is the reactive energy in the third quadrant, RE_Q4 is the reactive energy in the fourth quadrant, tol is the cumulative amount, and measured is the measured increment.

[0023] In a preferred embodiment, the current sampling channel includes channel A and channel B, the wires include phase L1 and phase L2, and when the register of the switching module is at a low level, the phase L1 is sampled through channel A and the phase L2 is sampled through channel B; when the register of the switching module is at a high level, the phase L1 is sampled through channel B and the phase L2 is sampled through channel A.

[0024] Preferably, the sampling module is an ADC sampling module.

[0025] Preferably, a communication connection is established between the electric meter and the host computer via the Modbus protocol.

[0026] After adopting the above solution, the beneficial effects of the present invention are:

[0027] 1. The electric meter of the present invention collects the current signal of the current transformer through the sampling module, so that the operator can detect the connection status of the current transformer, ensure that the current transformer is always in normal working condition, and improve the accuracy and stability of detection.

[0028] 2. The present invention defines a default reference current direction for the electric wire, and the upper computer detects the socket installation direction of the current transformer through the electric meter. When the socket installation direction of the current transformer on the electric wire is opposite to the default reference current direction of the electric wire, the operator can use the upper computer to correct the electricity consumption data collected by the electric meter to ensure the accuracy of the detection. There is no need to rewire the current transformer, which is more convenient to operate.

[0029] 3. The host computer of the present invention switches the current sampling channel of the sampling module by controlling the register level state of the MCU of the electric meter, so that when the current transformer is connected to the wrong phase line, the operator can adjust the current sampling channel corresponding to the current transformer to ensure the accuracy of the detection without rewiring the current transformer, which is more flexible in operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the connection relationship between the host computer, the electric meter and the current transformer in an embodiment of the present invention;

[0031] Figure 2 is a partial circuit schematic diagram of a detection circuit in an embodiment of the present invention;

[0032] Figure 3 This is a flowchart of determining whether a current transformer is installed in a sleeve on the L1 phase line and the L2 phase line in an embodiment of the present invention;

[0033] Figure 4 This is a schematic diagram of using a host computer in conjunction with an electric meter to perform reverse connection correction on a current transformer in an embodiment of the present invention;

[0034] Figure 5 This is a schematic diagram of using a host computer in conjunction with an electric meter to perform line sequence deviation correction on a current transformer in an embodiment of the present invention.

[0035] Description of labels:

[0036] 1. Current transformer; 11. First current transformer; 12. Second current transformer; 2. Electric meter; 3. Host computer; 4. L1 phase line; 5. L2 phase line. DETAILED DESCRIPTION

[0037] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0038] This embodiment provides a method for correcting phase sequence deviation of an electric meter, and relates to a device for correcting phase sequence deviation of an electric meter, such as Figure 1 As shown, the device includes an electric meter 2, a current transformer 1 and a host computer 3. The electric meter 2 is provided with an MCU. The current transformer 1 is connected to the MCU of the electric meter 2 and is used to be installed on the wire to sense the current of the wire. The electric meter 2 is connected to the host computer 3 through the MCU.

[0039] The phase sequence correction method of the electric meter includes the following three situations:

[0040] The first case is the connection detection of the current transformer:

[0041] The MCU of the electric meter 2 is provided with a sampling module (not shown in the figure). The sampling module is connected to the current transformer 1. The electric meter 2 collects the current signal of the current transformer 1 through the sampling module, compares the current signal of the current transformer 1 with the set threshold value, and then obtains the connection status of the current transformer 1;

[0042] This embodiment can collect the current signal of the current transformer 1 in real time through the sampling module, and then detect the connection status of the current transformer 1, that is, whether the current transformer 1 is installed on the wire, or whether the current transformer 1 is installed on the wire but a detection error is caused by a fault in the current transformer 1 itself. In specific operations, an alarm mechanism can also be set. That is, if a fault in the current transformer 1 is detected, the electric meter 2 can send the fault information to the host computer 3 for alarm. The electric meter 2 and the host computer 3 can use remote communication to allow the operator to remotely obtain the fault information.

[0043] Furthermore, the current signal of the current transformer 1 is a sampled voltage. If the sampled voltage is greater than a set threshold, it is determined that the connection of the current transformer 1 is abnormal.

[0044] In this embodiment, two current transformers 1 are provided to detect the current of the two phase lines L1 and L2, but the present invention is not limited thereto. Figure 2As shown, this embodiment uses this detection circuit to detect whether the current transformer 1 is installed on the two phase lines L1 and L2. Specifically, when both current transformers 1 are installed on the two phase lines L1 and L2, the voltage measured at the CT_DET_AO node is 1.985V. When the current transformer 1 can only identify the induced current of one phase line, L1 or L2, due to a fault or other reasons, the voltages measured at the CT_DET_AO node are 1.650V and 1.115V, respectively.

[0045] Based on this, the thresholds of the sampling voltage are set to 1.786V, 1.485V and 1.0035V in this embodiment. Figure 3 As shown, when the sampled voltage is greater than 1.7865V, it is determined that neither phase line L1 nor L2 is socketed with current transformer 1. When the sampled voltage is greater than 1.485V and less than 1.7865V, it is determined that phase line L1 4 is not socketed with current transformer 1. When the sampled voltage is greater than 1.0035V and less than 1.485V, it is determined that phase line L2 5 is not socketed with current transformer 1. When the sampled voltage is less than 1.0035V, it is determined that both phase lines L1 and L2 are socketed with current transformer 1. This configuration provides a certain margin for the determination of the sampled voltage, avoiding detection errors caused by hardware differences and improving detection accuracy.

[0046] It should be noted that the voltage measured at the above-mentioned CT_DET_AO node is obtained according to the specific setting of the detection circuit. In other embodiments, the hardware such as the resistance of the detection circuit can be adjusted according to actual conditions or other detection circuits can be used to adjust the threshold of the sampling voltage.

[0047] The second case is the current transformer reverse connection correction:

[0048] The default reference current direction of the wire is defined, and the upper computer 3 detects the socket installation direction of the current transformer 1 through the electric meter 2. If the socket installation direction of the current transformer 1 is opposite to the default reference current direction of the wire, the upper computer 3 corrects the electricity consumption data collected by the electric meter 2 without powering off or restarting the electric meter 2, nor does it need to adjust the socket installation direction of the current transformer 1, thereby improving the convenience of operation.

[0049] like Figure 4As shown, this embodiment uses two current transformers 1 corresponding to two phase lines L1 and L2 as an example. The current direction of the two phase lines L1 and L2 is from left to right, which is the default reference current direction. The host computer 3 detects the socket installation direction of the current transformer 1 through the electric meter 2. At this time, the detection direction of the second current transformer 12 is consistent with the current direction of the L2 phase line 5, while the detection direction of the first current transformer 11 is opposite to the current direction of the L1 phase line 4. Therefore, the host computer 3 needs to correct the power consumption data collected by the first current transformer 11.

[0050] Since the current transformer 1 is marked with a default detection direction, if it is found that the detection direction of the current transformer 1 is opposite to the default reference current direction, the operator can adjust the detection direction of the current transformer 1 by configuring the high and low levels of the register on the electric meter 2. For example, when the register is at a low level, the detection direction of the current transformer 1 is positive, and when the register is at a high level, the detection direction of the current transformer 1 is negative, but not limited to this, to ensure the smooth progress of the subsequent correction processing of the electricity consumption data.

[0051] Specifically, the electricity consumption data that need to be corrected include phase current, active power, reactive power, power factor, bidirectional active power metering and four-quadrant reactive power metering to ensure the accuracy of subsequent electricity metering.

[0052] If the socket installation direction of the current transformer 1 is opposite to the default reference current direction of the wire, the correction processing formulas for the phase current, active power, reactive power and power factor are as follows:

[0053]

[0054] Where I is the phase current, P is the active power, Q is the reactive power, and PF is the power factor.

[0055] When the polarity of current transformer 1 is reversed, the measured current will be opposite to the actual current, but the absolute value of the current will remain unchanged. By negating the current, the true direction of the current can be restored, making the measured value consistent with the actual physical quantity. Similarly, the direction of active and reactive power is determined by the phase relationship between voltage and current. An incorrect current direction will cause the power sign to reverse. After negation, the corrected value can accurately reflect the direction of power flow, such as the load consumption or power output. The power factor reflects the compensation status of reactive power, i.e., inductive or capacitive. If the PF sign is incorrect after reverse connection, negation can accurately assess reactive power demand and avoid reactive power compensation errors.

[0056] Furthermore, if the socket installation direction of the current transformer 1 is consistent with the default reference current direction of the wire, the original metering formula for the bidirectional active power metering and four-quadrant reactive power metering is:

[0057]

[0058] If the socket installation direction of the current transformer 1 is opposite to the default reference current direction of the wire, the correction processing formula for the bidirectional active power measurement and four-quadrant reactive power measurement is:

[0059]

[0060] Among them, AEE is the reverse active energy, AEI is the forward active energy, RE_Q1 is the reactive energy in the first quadrant, RE_Q2 is the reactive energy in the second quadrant, RE_Q3 is the reactive energy in the third quadrant, RE_Q4 is the reactive energy in the fourth quadrant, tol is the cumulative amount, and measured is the measured increment.

[0061] During actual operation, due to site conditions, equipment layout, and other factors, the socket installation direction of current transformer 1 may not align with the default reference current direction. Using a different metering formula avoids measurement errors caused by differences in the socket installation direction of current transformer 1, improving measurement accuracy. Furthermore, operators do not need to power off or restart meter 2, nor do they need to readjust the socket installation direction of current transformer 1. This improves operational convenience, reduces time and labor costs, effectively increases detection efficiency, and ensures detection safety.

[0062] The third case is the line sequence correction of the current transformer:

[0063] The MCU of the electricity meter 2 is provided with a sampling module, which is connected to the current transformer 1. The host computer 3 switches the current sampling channel of the sampling module by controlling the register level state of the MCU of the electricity meter 2, thereby adjusting the wiring sequence of the current transformer 1 installed on the wire. The operator does not need to rewire the current transformer 1, which makes the operation more flexible.

[0064] Furthermore, the current sampling channel includes channel A and channel B, and the wires include L1 phase line 4 and L2 phase line 5. When the register of the switching module is at a low level, L1 phase line 4 is sampled through channel A and L2 phase line 5 is sampled through channel B. When the register of the switching module is at a high level, L1 phase line 4 is sampled through channel B and L2 phase line 5 is sampled through channel A.

[0065] This embodiment takes two current transformers 1 corresponding to two phase lines L1 and L2 and two current sampling channels as an example. The first current transformer 11 is connected to channel A, and the second current transformer 12 is connected to channel B. The first current transformer 11 is used to be installed on the L1 phase line 4, and the second current transformer 12 is used to be installed on the L2 phase line 5. However, in actual operation, due to the operator or other external factors, the first current transformer 11 is installed on the L2 phase line 5, and the second current transformer 12 is installed on the L1 phase line 4. Figure 5 shown.

[0066] After the operator finds that the line sequence is wrong, he can use the host computer 3 to control the register level state of the MCU of the meter 2 through the communication protocol to switch the current sampling channel of the sampling module, that is, to exchange the power consumption data collected by channel A and channel B. Figure 5 In the case shown, the power consumption data of L2 phase line 5 collected by channel A will be regarded as collected by channel B, and the power consumption data of L1 phase line 4 collected by channel B will be regarded as collected by channel A, ensuring the accuracy of electricity metering.

[0067] Furthermore, the sampling module of this embodiment is an ADC sampling module, which can perform high-resolution sampling, has strong anti-interference ability, can perform multi-channel sampling, is flexible to use, and is easy to control. Of course, other sampling modules can also be used according to actual needs in other embodiments.

[0068] Furthermore, in this embodiment, the communication connection between the electric meter 2 and the host computer 3 is established via the Modbus protocol, which has high reliability and stability, a standardized communication interface, and is relatively easy to deploy, allowing the host computer 3 to remotely monitor and collect data from the electric meter 2. Of course, other embodiments may also use different communication protocols based on actual needs.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the design of this case. Any equivalent changes made based on the key design of this case shall fall within the scope of protection of this case.

Claims

1. A method for correcting phase sequence of an electric meter, characterized by: A phase sequence correction device for an electric meter is provided. The device includes an electric meter, a current transformer, and a host computer. The electric meter is provided with an MCU. The current transformer is connected to the MCU of the electric meter and is used to be installed on an electric wire to sense the current of the electric wire. The electric meter is connected to the host computer through the MCU. The phase sequence correction method of the electric meter includes the following three situations: The first case is the connection detection of the current transformer: The MCU of the electric meter is equipped with a sampling module, which is connected to the current transformer. The electric meter collects the current signal of the current transformer through the sampling module, compares the current signal of the current transformer with the set threshold, and then obtains the connection status of the current transformer; The second case is the current transformer reverse connection correction: Define the default reference current direction of the wire. The host computer uses the meter to detect the socket installation direction of the current transformer. If the socket installation direction of the current transformer is opposite to the default reference current direction of the wire, the host computer corrects the power consumption data collected by the meter. The third case is the line sequence correction of the current transformer: The MCU of the meter is equipped with a sampling module, which is connected to the current transformer. The host computer switches the current sampling channel of the sampling module by controlling the register level state of the MCU of the meter, thereby adjusting the wiring sequence of the current transformer installed on the wire.

2. The method for correcting phase sequence deviation of an electric meter according to claim 1, wherein: The current signal of the current transformer is a sampling voltage. If the sampling voltage is greater than a set threshold, it is determined that the current transformer connection is abnormal.

3. The method for correcting phase sequence deviation of an electric meter according to claim 1, wherein: The electricity consumption data includes phase current, active power, reactive power, power factor, bidirectional active power measurement and four-quadrant reactive power measurement.

4. A method for correcting phase sequence deviation of an electric meter as claimed in claim 3, characterized in that: If the socket installation direction of the current transformer is opposite to the default reference current direction of the wire, the correction processing formulas for the phase current, active power, reactive power and power factor are as follows: Where I is the phase current, P is the active power, Q is the reactive power, and PF is the power factor.

5. The method for correcting phase sequence deviation of an electric meter according to claim 2, wherein: If the socket installation direction of the current transformer is consistent with the default reference current direction of the wire, the original metering formula for the bidirectional active power measurement and four-quadrant reactive power measurement is: If the socket installation direction of the current transformer is opposite to the default reference current direction of the wire, the correction processing formula for the bidirectional active power measurement and four-quadrant reactive power measurement is: Among them, AEE is the reverse active energy, AEI is the forward active energy, RE_Q1 is the reactive energy in the first quadrant, RE_Q2 is the reactive energy in the second quadrant, RE_Q3 is the reactive energy in the third quadrant, RE_Q4 is the reactive energy in the fourth quadrant, tol is the cumulative amount, and measured is the measured increment.

6. The method for correcting phase sequence deviation of an electric meter according to claim 1, wherein: The current sampling channel includes channel A and channel B, and the wires include phase L1 and phase L2. When the register of the switching module is at a low level, the phase L1 is sampled through channel A and the phase L2 is sampled through channel B. When the register of the switching module is at a high level, the phase L1 is sampled through channel B and the phase L2 is sampled through channel A.

7. The method for correcting phase sequence deviation of an electric meter according to claim 1, wherein: The sampling module is an ADC sampling module.

8. The method for correcting phase sequence deviation of an electric meter according to claim 1, wherein: A communication connection is established between the electric meter and the host computer via the Modbus protocol.

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