Electric energy meter compatible with three-phase three-wire and three-phase four-wire

Abstract

The utility model discloses a three-phase three-wire and three-phase four-wire compatible electric energy meter, which comprises a power supply compatible circuit, the power supply compatible circuit comprises a primary side power supply circuit, a high-frequency transformer and a metering chip, the input end of the primary side power supply circuit is connected with a power grid, and the output end of the primary side power supply circuit is connected with the input end of the high-frequency transformer; the output end of the high-frequency transformer supplies power to the metering chip, and the output end of the metering chip outputs a metering result; an A-phase terminal, a B-phase terminal and a C-phase terminal of the primary side power supply circuit are connected with an A-phase wire, a B-phase wire and a C-phase wire of a power grid, an N-phase terminal in the three-phase three-wire mode is suspended, and an N-phase wire is connected in the three-phase four-wire mode. A current transformer is arranged in the primary side power supply circuit and comprises a primary coil, a secondary coil and a shielding winding, the shielding winding is arranged between the primary coil and the secondary coil, one end is grounded, the other end is suspended, and the shielding winding is used for shielding induced current between the primary coil and the secondary coil under the influence of stray capacitance. Compatibility is achieved, switching is not needed during switching, and long-term reliability and metering precision are improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of electric energy meter especially, it is a kind of electric energy meter compatible with three-phase three-wire and three-phase four-wire. BACKGROUND

[0002] With the continuous development of power system, higher requirements for flexibility and compatibility of electric energy metering equipment. Especially in some power transformation projects or multi-scene application occasions, a kind of electric energy meter compatible with three-phase three-wire and three-phase four-wire is needed to reduce installation errors, improve the accuracy and reliability of electric energy metering, and reduce the comprehensive cost.

[0003] The existing electric energy meter compatible with three-phase three-wire and three-phase four-wire, when realizing three-phase three-wire wiring, the B-phase line of the electric energy meter is connected to the N-phase terminal through the change-over switch, which is equivalent to connecting the B-phase to the N-phase. Through the change-over switch, the user can easily realize and debug during switching.

[0004] However, since the change-over switch is a mechanical contact, it will wear out with the increase of operation times, affecting long-term reliability. There are also transient errors and transient drifts in the switching process, which cause errors in the measurement of time, affect the measurement accuracy when the load is running, and also cause problems such as contact jitter and electromagnetic interference in high-current or high-voltage scenarios. SUMMARY

[0005] The utility model embodiment provides a kind of electric energy meter compatible with three-phase three-wire and three-phase four-wire to solve the problem of long-term reliability of the existing electric energy meter compatible with three-phase three-wire and three-phase four-wire, inaccurate measurement accuracy.

[0006] Based on the above purpose, in an embodiment, an electric energy meter compatible with three-phase three-wire and three-phase four-wire is provided, comprising: a power supply compatible circuit, the power supply compatible circuit comprising: a primary side power supply circuit, a high-frequency transformer, a metering power supply circuit and a metering chip, wherein the input end of the primary side power supply circuit is connected to the power grid, the first output end of the primary side power supply circuit is connected to the input end of the high-frequency transformer, the second output end of the primary side power supply circuit is connected to the second input end of the metering chip, the output end of the high-frequency transformer is connected to the input end of the metering power supply circuit, the output end of the metering power supply circuit is connected to the first input end of the metering chip, for powering the metering chip, and the output end of the metering chip is used for outputting metering result;

[0007] The A-phase terminal of the primary side power supply circuit is connected to the A-phase wire of the power grid, the B-phase terminal of the primary side power supply circuit is connected to the B-phase wire of the power grid, the C-phase terminal of the primary side power supply circuit is connected to the C-phase wire of the power grid, and the N-phase wire of the primary side power supply circuit is not connected to the power grid in a three-phase three-wire connection, and the N-phase wire of the primary side power supply circuit is connected to the N-phase wire of the power grid in a three-phase four-wire connection.

[0008] The primary side power supply circuit is provided with a current transformer, and the current transformer comprises a primary coil, a secondary coil and a shielding winding, wherein the shielding winding is arranged between the primary coil and the secondary coil, one end of the shielding winding is grounded, and the other end of the shielding winding is suspended, the primary coil is used to receive a current signal of the power grid, the secondary coil is used to connect a second input end of the metering chip, and the shielding winding is used to shield an induced current under the influence of a parasitic capacitance between the primary coil and the secondary coil.

[0009] In an embodiment, the primary side power supply circuit specifically comprises an A-phase current transformer, a B-phase current transformer and a C-phase current transformer, the input end of the A-phase current transformer is connected to the A-phase wire, the output end of the A-phase current transformer is connected to the input end of the metering chip, the input end of the B-phase current transformer is connected to the B-phase wire, the output end of the B-phase current transformer is connected to the input end of the metering chip, the input end of the C-phase current transformer is connected to the C-phase wire, and the output end of the C-phase current transformer is connected to the input end of the metering chip, wherein the A-phase current transformer is used to collect the current of the A-phase wire, the B-phase current transformer is used to collect the current of the B-phase wire, and the C-phase current transformer is used to collect the current of the C-phase wire.

[0010] In an embodiment, the shielding winding of the current transformer adopts an enameled wire covered with surface insulation paint.

[0011] In an embodiment, the calculation expression of the amplitude error is:

[0012] ,

[0013] wherein, is the amplitude error, is the current transformation ratio, is the number of turns of the primary coil, is the number of turns of the secondary coil, is the imaginary unit, is the angular frequency, is the value of the parasitic capacitance, is the resistance value of the secondary loop, is the imaginary part of the impedance of the secondary loop.

[0014] In an embodiment, the metering chip is model HT7136L.

[0015] In an embodiment, the primary side power supply circuit further comprises an alternating current signal conditioning circuit, a rectifier circuit, a protection circuit, a direct current signal conditioning circuit and a switching power supply integrated module, wherein the input end of the alternating current signal conditioning circuit is connected to the power grid, the output end of the alternating current signal conditioning circuit is connected to the input end of the rectifier circuit, the output end of the rectifier circuit is connected to the input end of the protection circuit, the output end of the protection circuit is connected to the input end of the direct current signal conditioning circuit, and the output end of the direct current signal conditioning circuit is connected to the input end of the high-frequency transformer.

[0016] A voltage divider is arranged in the direct current signal conditioning circuit, the input end of the voltage divider is connected to the input end of the high-frequency transformer, and the output end of the voltage divider is connected to the control end of the switching power supply integrated module.

[0017] In an embodiment, the voltage divider is a switching tube, and the direct current signal conditioning circuit further comprises a voltage dividing branch, a first voltage stabilizing branch, a second voltage stabilizing branch and a primary side absorption branch, one end of the voltage dividing branch is connected to a first power supply end, the other end of the voltage dividing branch is connected to the input end of the first voltage stabilizing branch, the output end of the second voltage stabilizing branch and the controlled end of the switching tube, the output end of the first voltage stabilizing branch is connected to a grounding end, the input end of the second voltage stabilizing branch is connected to the output end of the switching tube and the control end of the switching power supply integrated module, the input end of the primary side absorption branch is connected to the first power supply end, and the output end of the primary side absorption branch is connected to the input end of the high-frequency transformer.

[0018] In an embodiment, a feedback circuit is further included, and the feedback circuit comprises an optocoupler module, a first voltage stabilizing feedback module and a second voltage stabilizing feedback module, the input end of the first voltage stabilizing feedback module is connected to the first output end of the high-frequency transformer, the output end of the first voltage stabilizing feedback module is connected to the input end of the optocoupler module, the output end of the optocoupler module is connected to the input end of the second voltage stabilizing feedback module, and the input end of the second voltage stabilizing feedback module is connected to the power supply end of the switching power supply integrated module.

[0019] In an embodiment, the alternating current signal conditioning circuit comprises a pressure sensitive module and a filter module, the input end of the pressure sensitive module is connected to the power grid, the output end of the pressure sensitive module is connected to the input end of the filter module, and the output end of the filter module is connected to the input end of the rectifier circuit.

[0020] In an embodiment, the metering power supply circuit comprises a second absorption resistor, a second capacitor, a second rectifier diode and a second filter branch, wherein a second output end of the high-frequency transformer is connected to one end of the second absorption resistor and a cathode of the second rectifier diode, the second capacitor is connected in series with the second absorption resistor, the other end of the second absorption resistor is connected to an anode of the second rectifier diode, the anode of the second rectifier diode is further connected to an input end of the second filter branch, and the input end of the second filter branch is further connected to a third power supply end, and an output end of the second filter branch is connected to a ground end.

[0021] The above compatible three-phase three-wire and three-phase four-wire electric energy meter is provided with a power supply compatible circuit, so that the electric energy meter can be compatible with three-phase three-wire and three-phase four-wire modes; in the three-phase three-wire mode, the N-phase wire of the primary side power supply circuit is not connected to the power grid, and in the three-phase four-wire mode, the N wire of the primary side power supply circuit is connected to the N-phase wire of the power grid, without the need to set a conversion switch, so that the hardware structure of the electric energy meter is simpler, the long-term reliability of the electric energy meter is improved, and the cost is saved; the shielded winding is arranged in the current transformer, so that the induced current under the influence of the parasitic capacitance between the primary coil and the secondary coil of the current transformer is isolated, and the measurement accuracy of the electric energy meter is improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical scheme of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art.

[0023] Figure 1 is a schematic diagram of the connection of each part of the power supply compatible circuit of the electric energy meter in an embodiment of the present application;

[0024] Figure 2 is a schematic diagram of part of the primary side circuit and the metering chip in an embodiment of the present application;

[0025] Figure 3 is a specific schematic diagram of the primary side circuit, the high-frequency transformer and the metering power supply circuit in an embodiment of the present application;

[0026] Figure 4 is a schematic diagram of the current transformer in an embodiment of the present application.

[0027] Label: 1, primary side power supply circuit, 101, AC signal conditioning circuit, 1011, pressure sensitive module, 1012, filter module, 102, rectifier circuit, 103, protection circuit, 104, DC signal conditioning circuit, 1041, voltage division branch, 1042, first voltage stabilization branch, 1043, second voltage stabilization branch, 1044, primary side absorption branch, 2, high frequency transformer, 3, metering chip, 4, metering power supply circuit, 401, second filter branch, 5, feedback circuit, 501, optocoupler module, 502, first voltage stabilization feedback module, 503, second voltage stabilization feedback module. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0029] It should be understood that the present application can be implemented in different forms and should not be interpreted as being limited to the embodiments presented herein. On the contrary, these embodiments are provided to make the disclosure complete and full and to fully convey the scope of the present application to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity throughout the same reference numerals represent the same elements.

[0030] It should be understood that when an element or layer is referred to as "on", "adjacent", "connected to", or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or there can be intervening elements or layers. Conversely, when an element is referred to as "directly on", "directly adjacent to", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part without departing from the teachings of the present application.

[0031] Spatially relative terms, such as "beneath", "below", "lower", "under", "above", "upper" and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and / or operation in addition to the orientations depicted in the figures. For example, if a device in the figures is inverted, then a dependent element or feature that is described as "below" or "beneath" another element or feature is oriented "above" or "over" the other element or feature. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0032] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0033] For a thorough understanding of the present application, reference will be made to the following detailed description, in conjunction with the accompanying drawings, in which:

[0034] In one embodiment, as shown in Figure 1 and Figure 2 A power meter compatible with three-phase three-wire and three-phase four-wire is provided, comprising: a power supply compatible circuit, the power supply compatible circuit comprising: a primary power supply circuit 1, a high-frequency transformer 2, a metering power supply circuit 4 and a metering chip 3, wherein the input end of the primary power supply circuit 1 is connected to the power grid, the first output end of the primary power supply circuit 1 is connected to the input end of the high-frequency transformer 2, the second output end of the primary power supply circuit 1 is connected to the second input end of the metering chip 3, the output end of the high-frequency transformer 2 is connected to the input end of the metering power supply circuit 4, the output end of the metering power supply circuit 4 is connected to the first input end of the metering chip 3, for supplying power to the metering chip 3, and the output end of the metering chip 3 is used for outputting metering results;

[0035] The A-phase terminal of the primary power supply circuit is connected to the A-phase wire of the power grid, the B-phase terminal of the primary power supply circuit is connected to the B-phase wire of the power grid, and the C-phase terminal of the primary power supply circuit is connected to the C-phase wire of the power grid. In the case of three-phase three-wire connection, the N-phase wire of the primary power supply circuit is not connected to the power grid. In the case of three-phase four-wire connection, the N-phase wire of the primary power supply circuit is connected to the N-phase wire of the power grid.

[0036] The primary power supply circuit 1 is equipped with a current transformer, such as Figure 4 As shown, the current transformer includes a primary coil, a secondary coil, and a shielding winding. The shielding winding is disposed between the primary coil and the secondary coil. One end of the shielding winding is grounded, and the other end is left floating. The primary coil is used to receive the current signal from the power grid. The secondary coil is used to connect to the second input terminal of the metering chip 3. The shielding winding is used to shield the induced current caused by the parasitic capacitance between the primary coil and the secondary coil.

[0037] The primary power supply circuit collects both the current signal and the voltage signal from the power grid. The current signal is collected through the input terminal of the current transformer and transmitted to the metering chip through the output terminal of the current transformer. The voltage signal is transmitted to the transformer through the primary power supply circuit for processing. The processed voltage signal is then transmitted to the metering chip through the metering power supply circuit to power the metering chip.

[0038] Parasitic capacitance is mainly the parasitic capacitance formed by the coupling between the windings of a current transformer and other surrounding circuits;

[0039] When the electricity meter is in three-phase three-wire mode, if the current transformer does not have a shielding winding, when collecting the current signal from the power grid, since the N-phase terminal of the electricity meter is not connected to the power grid, the N-phase of the electricity meter is floating, and the reference ground of the metering chip is floating. This can easily cause fluctuations in the virtual reference ground potential, resulting in measurement errors. The parasitic capacitance between the primary and secondary coils of the current transformer will introduce additional induced current. The current transmitted to the secondary coil is the ideal secondary current plus the additional induced current. The current value transmitted to the metering chip will be too large, leading to inaccurate measurement results.

[0040] After the shield winding is arranged in the current transformer, a fixed low impedance path is formed between the shield winding and the ground, the shield winding introduces the additional induced current of the parasitic capacitance between the primary coil and the secondary coil of the current transformer into the ground terminal, the direct interference of the parasitic capacitance is isolated, the fluctuation amplitude of the virtual reference ground is reduced, and the high-frequency interference signals from the outside or between the primary and secondary coils can also be absorbed, compared with the current transformer without the shield winding, the current value transmitted to the metering chip is reduced, so that the current transmitted to the secondary coil is closer to the ideal secondary current, and therefore the metering result is more accurate.

[0041] The working process of the above electric energy meter is as follows:

[0042] In the three-phase three-wire mode, the A, B and C phase terminals of the primary side power supply circuit receive voltage signals and current signals from the A, B and C phase wires of the power grid respectively;

[0043] In the three-phase four-wire mode, the A, B, C and N phase terminals of the primary side power supply circuit receive voltage signals and current signals from the A, B, C and N phase wires of the power grid respectively;

[0044] The received voltage signals are processed by the primary side power supply circuit, transmitted to the high-frequency transformer, and output to the metering power supply circuit after energy conversion by the high-frequency transformer to supply power to the metering module;

[0045] Meanwhile, the received current signals are processed by the current transformer of the primary side power supply circuit and transmitted to the metering module for calculation.

[0046] In the embodiment, the power supply compatible circuit is arranged to enable the electric energy meter to be compatible with the three-phase three-wire and three-phase four-wire modes; in the three-phase three-wire mode, the N phase wire of the primary side power supply circuit is not connected to the power grid, and in the three-phase four-wire mode, the N phase wire of the primary side power supply circuit is connected to the N phase wire of the power grid, without the need to set a conversion switch to realize mode conversion, so that the hardware structure of the electric energy meter is simpler, the long-term reliability of the electric energy meter is improved, and the cost is saved; the shield winding is arranged in the current transformer to isolate the induced current under the influence of the parasitic capacitance between the primary coil and the secondary coil of the current transformer, and improve the metering accuracy of the electric energy meter.

[0047] In an embodiment, as Figure 2As shown, the primary side power supply circuit specifically comprises: an A-phase current transformer 105, a B-phase current transformer 106, and a C-phase current transformer 107, the input end of the A-phase current transformer 105 is connected with the A-phase electric wire, the output end of the A-phase current transformer 105 is connected with the input end of the metering chip 3, the input end of the B-phase current transformer 106 is connected with the B-phase electric wire, the output end of the B-phase current transformer 106 is connected with the input end of the metering chip 3, the input end of the C-phase current transformer 107 is connected with the C-phase electric wire, and the output end of the C-phase current transformer 107 is connected with the input end of the metering chip 3, wherein the A-phase current transformer 105 is used for collecting the current of the A-phase electric wire, the B-phase current transformer 106 is used for collecting the current of the B-phase electric wire, and the C-phase current transformer 107 is used for collecting the current of the C-phase electric wire.

[0048] As shown in the figure, Figure 2 Preferably, there are three current transformers, all of which are of one type, specifically comprising an A-phase current transformer 105, a B-phase current transformer 106, and a C-phase current transformer 107, which are used for collecting the currents of the A-phase, B-phase, and C-phase respectively and transmitting the processed signals to the metering chip.

[0049] In this embodiment, the three current transformers are all provided with shielded windings. The current transformer provided with the shielded winding reduces the interference of the parasitic capacitance and improves the stability of the virtual neutral point, so that the transmitted signal is more accurate. Since the algorithm of the virtual neutral point depends on the vector relationship of the three-phase voltage and current, if the induced current under the influence of the parasitic capacitance between the primary coil and the secondary coil of the current transformer causes signal distortion, it will directly affect the accuracy of the neutral point calculation. The setting of the shielded winding reduces signal distortion, so that the calculation result of the virtual neutral point is closer to the actual situation, thereby improving the metering accuracy of the electric energy meter.

[0050] In an embodiment, the shielded winding of the current transformer adopts an enameled wire covered with insulating paint on the surface.

[0051] In this embodiment, the shielded winding of the current transformer adopts an enameled wire covered with insulating paint on the surface, and adopts a tight winding method. The current transformer is set by a potting epoxy resin process. The potting epoxy resin process is a process of pouring liquid epoxy resin composite into a device containing electronic components and circuit, and curing into a thermosetting high polymer insulating material with excellent performance at room temperature or under heating conditions.

[0052] In the embodiment, the shielding winding adopts the enameled wire coated with insulating paint and is densely wound, so as to reduce the distributed capacitance of the shielding winding, improve the shielding performance, and adopt the epoxy resin pouring process to set the current transformer, so as to strengthen the integrity of the current transformer, improve the insulation of the current transformer, further isolate the induced current under the influence of the parasitic capacitance between the primary coil and the secondary coil of the current transformer, and improve the measurement accuracy of the electric energy meter.

[0053] In an embodiment, the calculation expression of the amplitude error is:

[0054] ,

[0055] wherein, is the amplitude error, is the turns ratio of the primary coil and the secondary coil, is the turns of the primary coil, is the turns of the secondary coil, is the imaginary unit, is the angular frequency, is the value of the parasitic capacitance, is the resistance value of the secondary loop, is the imaginary part of the impedance of the secondary loop.

[0056] wherein, the definition formula of the amplitude error is: , ①

[0057] wherein, is the amplitude error, is the actual secondary current, is the ideal secondary current, the greater the parasitic capacitance between the primary and secondary coils of the current transformer, the greater the induced current under the influence of the parasitic capacitance, and the greater the error influence on the secondary current;

[0058] The ideal current transformation ratio is , that is , ②

[0059] wherein, is the current of the primary coil, is the ideal current of the primary coil, is the turns ratio of the primary coil and the secondary coil;

[0060] The calculation expression of the total impedance of the secondary loop is: wherein, is the total impedance of the secondary loop, is the resistance value of the secondary loop, is the imaginary unit, is the capacitive reactance including the parasitic capacitance;

[0061] The capacitance of the parasitic capacitance is: , ③

[0062] wherein, is the capacitance of the parasitic capacitance, is the angular frequency, is the value of the parasitic capacitance;

[0063] The current relationship between the primary coil and the secondary coil is: , ④

[0064] wherein, is the induced current under the influence of the parasitic capacitance;

[0065] The expression of the actual induced current of the secondary coil is: , ⑤

[0066] Bringing ②, ③, ④, ⑤ into ①, and simplifying to obtain: .

[0067] In this embodiment, it can be obtained from the calculation expression of the amplitude error that the amplitude error is related to the parasitic capacitance, the angular frequency, the resistance value and the impedance of the secondary circuit. In this application, the influence of the parasitic capacitance between the primary coil and the secondary coil of the current transformer is eliminated, so that the value of the amplitude error is reduced, and the measurement accuracy of the electric energy meter is improved.

[0068] In an embodiment, the model of the metering chip is HT7136L.

[0069] Wherein, the active measurement of the metering chip of HT7136L meets the 0.2S, 0.5S level standard, the reactive measurement meets the 1st and 2nd level standard, the active power, the reactive power, the apparent power, the energy and the like of each phase and the combined phase can be measured, the current, the voltage effective value, the power factor, the phase angle, the frequency and the like parameters can be measured, the built-in voltage monitoring circuit ensures normal work when power on and power off.

[0070] In this embodiment, the metering chip with the model of HT7136L is used to participate in the calculation of the current signal transmitted by the current transformer, and the metering mode can be automatically switched according to the three-phase three-wire and the three-phase four-wire, so that the metering chip can accurately measure the electric energy, improve the accuracy of metering, and improve the reliability of the electric energy meter compatible with the three-phase three-wire and the three-phase four-wire.

[0071] In an embodiment, as Figure 2 and Figure 3As shown, the primary side power supply circuit 1 further comprises an AC signal conditioning circuit 101, a rectifier circuit 102, a protection circuit 103, a DC signal conditioning circuit 104 and a switching power supply integrated module U11, wherein the input end of the AC signal conditioning circuit 101 is connected to the power grid, the output end of the AC signal conditioning circuit 101 is connected to the input end of the rectifier circuit 102, the output end of the rectifier circuit 102 is connected to the input end of the protection circuit 103, the output end of the protection circuit 103 is connected to the input end of the DC signal conditioning circuit 104, and the output end of the DC signal conditioning circuit 104 is connected to the input end of the high-frequency transformer 2.

[0072] The DC signal conditioning circuit 102 is provided with a voltage divider M1, the input end of the voltage divider M1 is connected to the input end of the high-frequency transformer 2, and the output end of the voltage divider M1 is connected to the control end SW of the switching power supply integrated module U11.

[0073] The switching power supply integrated module U11 adopts 8234T series, realizes efficient conversion of electric energy through high-frequency switching action, and the rectifier circuit 102 includes 16 rectifier diodes D19-D34.

[0074] The working process of the primary side power supply circuit is as follows:

[0075] The input end of the AC signal conditioning circuit receives a power grid voltage signal, which is processed by the AC signal conditioning circuit and then output to the rectifier circuit, the rectifier circuit rectifies the three-phase AC voltage into a DC pulse voltage, which is then output to the protection circuit, the protection circuit processes the output and then outputs to the DC signal conditioning circuit, and the DC signal conditioning circuit processes the output and then outputs to the high-frequency transformer.

[0076] In this embodiment, the AC signal conditioning circuit processes the impact of the surge voltage of the power grid, processes the conducted radiation interference voltage generated by the switching power supply integrated module, and prevents external electromagnetic interference from affecting the normal operation of the circuit. Not only does it protect the power supply compatible circuit in the electric energy meter from the impact of voltage and current, but also improves the service life of the electric energy meter, makes the signal output by the power supply compatible circuit in the electric energy meter to the transformer more reliable, improves the long-term reliability of the electric energy meter, and saves costs.

[0077] In an embodiment, as Figure 3As shown, the voltage divider M1 is a MOS switch tube, and the direct current signal conditioning circuit 104 further comprises a voltage division branch 1041, a first voltage stabilization branch 1042, a second voltage stabilization branch 1043, and a primary side absorption branch 1044. One end of the voltage division branch 1041 is connected to a first power supply end HVIN, and the other end of the voltage division branch 1041 is connected to an input end of the first voltage stabilization branch 1042, an output end of the second voltage stabilization branch 1043, and a controlled end of the MOS switch tube M1. An output end of the first voltage stabilization branch 1042 is connected to a ground end GND1. An input end of the second voltage stabilization branch 1043 is connected to an output end of the MOS switch tube M1 and a control end SW of the switching power supply integrated module U11. An input end of the primary side absorption branch 1044 is connected to the first power supply end HVIN, and an output end of the primary side absorption branch 1044 is connected to an input end of the high-frequency transformer 2.

[0078] The MOS switch tube M1 is kept on during the operation of the circuit, is connected to the control end SW of the switching power supply integrated module U11, is connected in series with the MOS tube inside the switching power supply integrated module U11, shares the surge voltage and the VDS voltage, and improves the voltage and current of the power supply compatible circuit in the electric energy meter during the turn-on and turn-off, thereby reducing the fluctuation and impact.

[0079] The operation of the above direct current signal conditioning circuit is as follows:

[0080] The output signal of the protection circuit is processed by the voltage division branch and the primary side absorption branch, is output to the high-frequency transformer after being divided and filtered, is output to the switching tube after passing through the high-frequency transformer, and is output to the switching power supply integrated module after being divided by the switching tube.

[0081] In the embodiment, the switching tube is connected in series with the MOS tube inside the switching power supply integrated module, the withstand voltage of the MOS tube inside the switching power supply integrated module is improved, the withstand voltage range of the power supply compatible circuit in the entire electric energy meter is further improved, the wide voltage input in different modes of three-phase three-wire and three-phase four-wire is compatible, and the compatibility of the electric energy meter is improved.

[0082] In an embodiment, as shown in Figure 3 The feedback circuit 5 further comprises an optocoupler module 501, a first voltage stabilization feedback module 502, and a second voltage stabilization feedback module 503. An input end of the first voltage stabilization feedback module 502 is connected to a first output end of the high-frequency transformer 2. An output end of the first voltage stabilization feedback module 502 is connected to an input end of the optocoupler module 501. An output end of the optocoupler module 501 is connected to an input end of the second voltage stabilization feedback module 503. An input end of the second voltage stabilization feedback module 503 is connected to a power supply end of the switching power supply integrated module U11.

[0083] The feedback circuit 5 monitors the voltage of the power supply compatible circuit in the electric energy meter in real time, and when the voltage deviates from the set value, the voltage is adjusted to quickly restore the set voltage value, so that the electric energy meter can work normally in the case of external environment change.

[0084] In the embodiment, the voltage stabilizing feedback circuit can quickly restore the set voltage value, improve the efficiency of the power supply compatible circuit in the electric energy meter, and avoid circuit failure caused by abnormal voltage by monitoring the voltage in real time, thereby improving the long-term reliability of the electric energy meter and saving cost.

[0085] In an embodiment, as shown in Figure 2 The AC signal conditioning circuit 101 includes a voltage-sensitive module 1011 and a filter module 1012, the input end of the voltage-sensitive module 1011 is connected to the power grid, the output end of the voltage-sensitive module 1011 is connected to the input end of the filter module 1012, and the output end of the filter module 1012 is connected to the input end of the rectifier circuit 102.

[0086] The voltage-sensitive module 1011 includes three voltage-sensitive resistors V1, V2 and V3, the voltage terminal of the power grid passes through the three voltage-sensitive resistors in the voltage-sensitive module 1011 to suppress and discharge the impact of the surge voltage and current of the power grid, and then is output to the filter module 1012, the filter module 1012 includes three filter inductors L3, L4 and L5 and three filter capacitors C147, C129 and C130 to filter the conducted radiation disturbance voltage generated inside the switch power supply integrated module U11 in the power supply compatible circuit in the electric energy meter and external electromagnetic interference.

[0087] In the embodiment, the voltage-sensitive module and the filter module are arranged in the AC signal conditioning circuit to process the voltage signal of the power grid, thereby protecting the power supply compatible circuit in the electric energy meter and ensuring the working safety of the electric energy meter and the accuracy of metering.

[0088] In an embodiment, the metering power supply circuit 4 includes a second absorption resistor R172, a second capacitor C128, a second rectifier diode D33 and a second filter branch 401, wherein one end of the second absorption resistor R172 and the cathode of the second rectifier diode D33 are connected to the second output end of the high-frequency transformer 2, the second capacitor C128 is connected in series with the second absorption resistor R172, the other end of the second absorption resistor R172 is connected to the anode of the second rectifier diode D33, the anode of the second rectifier diode D33 is also connected to the input end of the second filter branch 401, the input end of the second filter branch 401 is also connected to a third power supply end VHH1, and the output end of the second filter branch 401 is connected to a ground end GND.

[0089] The metering power supply circuit 4 is used for supplying power to the metering module, the second absorption resistor R172 and the second capacitor C128 form an RC absorption circuit, the VDS peak pulse of the reverse voltage of the second rectifier diode D33 is reduced, and the four filtering capacitors C59, C52, C57 and C131 in the second filtering branch 401 are used for supplying power to the metering module after processing the signal.

[0090] In the embodiment, the metering power supply circuit is arranged to supply power to the metering module, the RC absorption circuit, the rectifier diode and the filtering capacitor are arranged to process the signal output to the metering module, and the metering precision of the electric energy meter is improved.

[0091] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A power meter compatible with three-phase three-wire and three-phase four-wire, characterized in that, The application relates to a power supply compatible circuit, which comprises a primary-side power supply circuit, a high-frequency transformer, a metering power supply circuit and a metering chip. The A-phase terminal of the primary-side power supply circuit is connected with the A-phase electric wire of the power grid, the B-phase terminal of the primary-side power supply circuit is connected with the B-phase electric wire of the power grid, the C-phase terminal of the primary-side power supply circuit is connected with the C-phase electric wire of the power grid, in three-phase three-wire connection, the N-phase electric wire of the primary-side power supply circuit is not connected with the power grid, and in three-phase four-wire connection, the N-phase electric wire of the primary-side power supply circuit is connected with the N-phase electric wire of the power grid. The primary-side power supply circuit is provided with a current transformer, which comprises a primary coil, a secondary coil and a shielding winding, one end of the shielding winding is grounded, the other end of the shielding winding is suspended, the primary coil is used for receiving the current signal of the power grid, the secondary coil is used for connecting the second input end of the metering chip, and the shielding winding is used for shielding the induced current under the influence of the parasitic capacitance between the primary coil and the secondary coil. The primary-side power supply circuit specifically comprises an A-phase current transformer, a B-phase current transformer and a C-phase current transformer, the input end of the A-phase current transformer is connected with the A-phase electric wire, the output end of the A-phase current transformer is connected with the input end of the metering chip, the input end of the B-phase current transformer is connected with the B-phase electric wire, the output end of the B-phase current transformer is connected with the input end of the metering chip, the input end of the C-phase current transformer is connected with the C-phase electric wire, and the output end of the C-phase current transformer is connected with the input end of the metering chip.

2. The electric energy meter of claim 1, characterized in that, The shielding winding of the current transformer adopts the enameled wire covered with surface insulating paint.

3. The electric energy meter of claim 1, wherein, The calculation expression of the amplitude error is as follows:

4. The electric energy meter according to claim 3, characterized in that, The model of the metering chip is HT7136L. ， wherein, is the amplitude error, is the current ratio, is the number of turns of the primary coil, is the number of turns of the secondary coil, is the imaginary unit, is the angular frequency, is the value of the parasitic capacitance, is the resistance value of the secondary circuit, is the imaginary part of the impedance of the secondary circuit.

5. The electric energy meter of claim 2, wherein, ​ 6. The electric energy meter of claim 5, wherein, The primary side power supply circuit further comprises an alternating current signal conditioning circuit, a rectifier circuit, a protection circuit, a direct current signal conditioning circuit and a switching power supply integrated module, wherein the input end of the alternating current signal conditioning circuit is connected to the power grid, the output end of the alternating current signal conditioning circuit is connected to the input end of the rectifier circuit, the output end of the rectifier circuit is connected to the input end of the protection circuit, the output end of the protection circuit is connected to the input end of the direct current signal conditioning circuit, and the output end of the direct current signal conditioning circuit is connected to the input end of the high-frequency transformer. The direct current signal conditioning circuit is provided with a voltage divider, the input end of the voltage divider is connected to the input end of the high-frequency transformer, and the output end of the voltage divider is connected to the control end of the switching power supply integrated module.

7. The electric energy meter of claim 6, wherein, The voltage divider is a switching tube, and the direct current signal conditioning circuit further comprises a voltage division branch, a first voltage stabilizing branch, a second voltage stabilizing branch and a primary side absorption branch, one end of the voltage division branch is connected to a first power supply end, the other end of the voltage division branch is connected to the input end of the first voltage stabilizing branch, the output end of the second voltage stabilizing branch and the controlled end of the switching tube, the output end of the first voltage stabilizing branch is connected to a grounding end, the input end of the second voltage stabilizing branch is connected to the output end of the switching tube and the control end of the switching power supply integrated module, the input end of the primary side absorption branch is connected to the first power supply end, and the output end of the primary side absorption branch is connected to the input end of the high-frequency transformer.

8. The electric energy meter of claim 7, wherein, Further comprising a feedback circuit, the feedback circuit comprises an optical coupling module, a first voltage stabilizing feedback module and a second voltage stabilizing feedback module, the input end of the first voltage stabilizing feedback module is connected to the first output end of the high-frequency transformer, the output end of the first voltage stabilizing feedback module is connected to the input end of the optical coupling module, the output end of the optical coupling module is connected to the input end of the second voltage stabilizing feedback module, and the input end of the second voltage stabilizing feedback module is connected to the power supply end of the switching power supply integrated module.

9. The electric energy meter of claim 8, wherein, The alternating current signal conditioning circuit comprises a pressure sensitive module and a filter module, the input end of the pressure sensitive module is connected to the power grid, the output end of the pressure sensitive module is connected to the input end of the filter module, and the output end of the filter module is connected to the input end of the rectifier circuit.

10. The electric energy meter of claim 9, wherein, The metering power supply circuit comprises a second absorption resistor, a second capacitor, a second rectifier diode and a second filter branch, wherein the second output end of the high-frequency transformer is connected to one end of the second absorption resistor and the cathode of the second rectifier diode, the second capacitor is connected in series with the second absorption resistor, the other end of the second absorption resistor is connected to the anode of the second rectifier diode, the anode of the second rectifier diode is also connected to the input end of the second filter branch, the input end of the second filter branch is also connected to a third power supply end, and the output end of the second filter branch is connected to a grounding end.

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