Filtering circuit for improving harmonic influence of single-phase electric energy meter

Abstract

The utility model relates to harmonic circuit technical field, and disclose a kind of filter circuit of single-phase electric energy meter improvement harmonic influence, including input live wire L, input zero line N, winding resistance RX1, rectifier bridge, safety capacitor CX1 and I-shaped inductance LF1;By one winding resistance RX1 before rectifier bridge, safety capacitor CX1 and I-shaped inductance LF1 are all moved to rectification, when input high frequency harmonic comes in, only in input voltage peak valley can make rectifier bridge conduction, time is very short, harmonic current effective value is very small, winding resistance RX1 does not heat, improvement is obvious, effectively improve the security of field application.

Description

Technical Field

[0001] This utility model relates to the field of harmonic circuit technology, and more specifically to a filter circuit for improving the harmonic effects of a single-phase energy meter. Background Technology

[0002] With the rapid development of the modern power industry, nonlinear devices such as high-power rectifier frequency converters, switching power supplies, and semiconductor high-frequency switching devices have been widely used in daily life and production. While these devices improve power efficiency, they also bring increasingly serious harmonic pollution problems to AC power grid lines.

[0003] The root cause of harmonic pollution lies in the fact that the high-frequency operating current of nonlinear devices does not follow the sinusoidal wave of the input power grid voltage; instead, the operating current contains high-frequency harmonic components of various frequencies. If these products are directly connected to the power grid without proper filtering, it will distort the sinusoidal voltage waveform of the power grid and generate high-frequency harmonic voltage noise.

[0004] Although national and international standards clearly stipulate the harmonic current standards injected into the power grid when various electrical appliances are working, the domestic product quality supervision system is still imperfect, and some countries and regions have not paid enough attention to this issue. As a result, some unscrupulous manufacturers omit the input filter of the product or cut corners in the production process in order to reduce costs, causing the harmonic index of the product to far exceed the relevant limit standards.

[0005] With the rise of new energy sources, various high-frequency synthesized AC power sources (such as photovoltaic, wind power, and energy storage) are being connected to the power grid, making the power supply composition of the grid increasingly complex. Simultaneously, the rapid growth of new energy vehicles has led to a large number of charging devices being connected to the grid. These devices are becoming increasingly concentrated, resulting in more serious potential pollution to the power grid. When the high-frequency harmonic voltage in a local power grid reaches a certain amplitude, it can threaten electrical equipment connected to the same network, potentially causing malfunctions or even damage. Older filtering structures are easily affected by harmonics in application, leading to damage to electricity meters. New structures effectively improve the impact of harmonics on electricity meters. Utility Model Content

[0006] In order to overcome the above-mentioned defects of the prior art, the present invention provides a filter circuit for improving the harmonic effects of a single-phase energy meter, so as to solve the problems existing in the background art.

[0007] This utility model provides the following technical solution: a filter circuit for improving the harmonic effects of a single-phase energy meter, comprising:

[0008] Input live wire L, input neutral wire N, wire-wound resistor RX1, rectifier bridge, safety capacitor CX1, and I-shaped inductor LF1;

[0009] A winding resistor is retained on the input side. After the live wire L and neutral wire N are input, a winding resistor RX1 is connected in series to limit the surge current.

[0010] The rectifier bridge is equipped with a post-filter element, which moves the safety capacitor CX1 and the I-beam capacitor LF1 to the output of the rectifier bridge to form an LC filter network.

[0011] Preferably, the resistance value of the wire-wound resistor RX1 is in the range of 1-10Ω and the power is ≥5W; the rectifier bridge is a full-wave rectifier circuit composed of four diodes; the capacitance value of the safety capacitor CX1 is in the range of 0.1-1μF and the withstand voltage is ≥630V; the inductance of the I-shaped inductor is in the range of 1-10mH and the current is ≥2A.

[0012] Preferably, the formula for calculating the resistance value of the wire-wound resistor RX1 is as follows:

[0013] ;

[0014] in, Indicates the peak input voltage. This indicates the voltage after rectification. The allowable surge current.

[0015] Preferably, the capacitance value of the safety capacitor CX1 is calculated as follows:

[0016] ;

[0017] in, Represented as the cutoff frequency, this embodiment selects... It is used to suppress high-frequency harmonics.

[0018] Preferably, the inductance of the I-shaped inductor LF1 needs to satisfy:

[0019] ;in, Indicates the allowable ripple voltage. Indicates the switching frequency. It represents radio wave ripples.

[0020] Preferably, high-frequency harmonics only pass through the rectifier bridge at the peak / trough of the input voltage, resulting in an extremely short conduction time and a low effective value for the harmonic current. Significantly reduced, as expressed by the formula:

[0021] ;

[0022] in, Indicates the effective value of harmonic current. Indicates period, It represents the instantaneous value of harmonic waves.

[0023] Preferably, the formula for the heat loss P of the winding resistor RX1 is as follows:

[0024] ;in, Represents the effective value of harmonic current The square of.

[0025] The technical effects and advantages of this utility model are as follows:

[0026] This invention, by incorporating a wire-wound resistor RX1, facilitates the relocation of the safety capacitor CX1 and the I-shaped inductor LF1 after rectification. When high-frequency harmonics are input, the rectifier bridge only conducts during the peak and trough of the input voltage, resulting in a very short conduction time and a very small effective value of the harmonic current. The wire-wound resistor RX1 does not heat up, significantly improving safety in field applications, enhancing long-term operational reliability, and significantly improving harmonic current suppression efficiency. It also reduces resistor heating, enhances system safety, and provides better protection against field harmonic interference. Attached Figure Description

[0027] Figure 1 This is a circuit diagram of a filter circuit for improving the harmonic effects of a single-phase energy meter according to this utility model.

[0028] Figure 2 This is the circuit diagram of the power supply filtering structure of the original single-phase energy meter. Detailed Implementation

[0029] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. In addition, the forms of the various structures described in the following embodiments are merely illustrative. The filter circuit for improving the harmonic effects of a single-phase energy meter involved in this utility model is not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0030] like Figure 1 As shown, this utility model provides a filter circuit for improving the harmonic effects of a single-phase energy meter, comprising:

[0031] Input live wire L, input neutral wire N, wire-wound resistor RX1, rectifier bridge, safety capacitor CX1, and I-shaped inductor LF1;

[0032] A winding resistor is retained on the input side. After the live wire L and neutral wire N are input, a winding resistor RX1 is connected in series to limit the surge current.

[0033] The rectifier bridge is equipped with a post-filter element, which moves the safety capacitor CX1 and the I-beam capacitor LF1 to the output of the rectifier bridge to form an LC filter network.

[0034] In this embodiment, it should be specifically noted that the resistance value of the wire-wound resistor RX1 is in the range of 1-10Ω and the power is ≥5W; the rectifier bridge is a full-wave rectifier circuit composed of four diodes; the capacitance value of the safety capacitor CX1 is in the range of 0.1-1μF and the withstand voltage is ≥630V; the inductance of the I-shaped inductor is in the range of 1-10mH and the current is ≥2A.

[0035] In this embodiment, it should be specifically noted that the formula for calculating the resistance value of the winding resistor RX1 is as follows:

[0036] ;

[0037] in, Indicates the peak input voltage. This indicates the voltage after rectification. For permissible surge current;

[0038] The capacitance value of the safety capacitor CX1 is calculated as follows:

[0039] ;in, Represented as the cutoff frequency, this embodiment selects... This is used to suppress high-frequency harmonics;

[0040] The inductance of the I-shaped inductor LF1 must meet the following requirements:

[0041] ;in, Indicates the allowable ripple voltage. Indicates the switching frequency. It represents radio wave ripples.

[0042] In this embodiment, it should be specifically explained that a wire-wound resistor is a resistive element that is implemented by winding a resistance wire on an insulating material. It limits the flow of current in the circuit to prevent excessive current from damaging circuit components; it divides the voltage in the circuit to provide the required voltage for other circuit components; it acts as a damper in an oscillating circuit to reduce circuit oscillation; and it consumes electrical energy in the circuit and converts it into heat energy to help the circuit dissipate heat.

[0043] Safety capacitors are mainly used in filtering, coupling, bypassing and other applications in power circuits; in power circuits, they are used to smooth the pulsating DC voltage after rectification and provide a more stable DC output; in signal transmission circuits, they are used to couple AC signals and isolate DC components; in circuits, they provide a bypass channel for AC signals to reduce interference during signal transmission; they comply with safety standards and can prevent overvoltage generated during circuit failures from damaging the circuit and equipment to a certain extent.

[0044] The toroidal inductor is a common inductor component, whose shape is similar to the Chinese character "工". It is mainly used for storing and releasing electrical energy and suppressing high-frequency noise in circuits; it stores energy in the circuit to maintain the continuity of the current in the circuit; in the power circuit, it is used in conjunction with a capacitor to play a filtering role and reduce the interference of high-frequency noise; in low-frequency circuits, it is used to block the flow of alternating current and play a current-limiting role; in high-frequency circuits, it is used in conjunction with a capacitor to form a resonant circuit for frequency selection or filtering.

[0045] As Figure 2 shown, it is the circuit diagram of the power supply filtering structure of the original single-phase watt-hour meter. L and N are the input live wire and neutral wire respectively. When there is high-frequency harmonic interference on-site, it will form a loop through RX1, LF1, and CX1. Harmonic current will be generated on RX1. As the amplitude of the harmonic increases, the harmonic current will also increase. If the frequency of the on-site harmonic is close to the resonance point of LF1 and CX1, the loop impedance will be very low, and the harmonic current will be even larger, resulting in RX1 heating and burning out, and the watt-hour meter cannot measure. In severe cases, there will be potential safety hazards.

[0046] This embodiment is the circuit diagram of the improved power supply filtering structure of the single-phase watt-hour meter. L and N are the input live wire and neutral wire respectively. Compared with Figure 2 before the rectifier bridge, there is only a wire-wound resistor RX1. The safety capacitor CX1 and the toroidal inductor LF1 are both moved to after the rectifier. When high-frequency harmonics enter the input, the rectifier bridge will only conduct when the input voltage is at the peak and trough. The time is very short, and the effective value of the harmonic current is very small. The wire-wound resistor RX1 will not heat up, and the improvement is obvious, making it safer for on-site applications.

[0047] In this embodiment, it should be specifically noted that high-frequency harmonics only pass through the rectifier bridge when the input voltage is at the peak / trough, and the conduction time is extremely short. The effective value of the harmonic current is significantly reduced, which is expressed by the formula:

[0048] ;

[0049] where represents the effective value of the harmonic current, represents the period, represents the instantaneous value of the harmonic electric wave;

[0050] The heat loss P of the wire-wound resistor RX1 is significantly reduced. The formula for heat loss P is as follows:

[0051] .

[0052] In this embodiment, it should be specifically noted that the advantage of this embodiment is that it effectively reduces the temperature rise of the resistor, improves the long-term operational reliability, significantly improves the harmonic current suppression efficiency, reduces resistor heating, improves system safety, and is safer in dealing with on-site harmonic interference, and can effectively deal with on-site harmonic interference.

[0053] Finally: The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

[0054] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A filter circuit for improving harmonic effects in a single-phase energy meter, characterized in that: include: Input live wire L, input neutral wire N, wire-wound resistor RX1, rectifier bridge, safety capacitor CX1, and I-shaped inductor LF1; A winding resistor is retained on the input side. After the live wire L and neutral wire N are input, a winding resistor RX1 is connected in series to limit the surge current. The rectifier bridge is equipped with a post-filter element, which moves the safety capacitor CX1 and the I-beam capacitor LF1 to the output of the rectifier bridge to form an LC filter network.

2. The filter circuit for improving harmonic effects in a single-phase energy meter according to claim 1, characterized in that: The resistance value of the winding resistor RX1 is 1-10Ω and the power is ≥5W. The rectifier bridge is a full-wave rectifier circuit composed of four diodes. The capacitance value of the safety capacitor CX1 is 0.1-1μF and the withstand voltage is ≥630V. The inductance of the I-shaped inductor is 1-10mH and the current is ≥2A.

3. The filter circuit for improving harmonic effects in a single-phase energy meter according to claim 2, characterized in that: The formula for calculating the resistance value of the winding resistor RX1 is as follows: ； in, Indicates the peak input voltage. This indicates the voltage after rectification. The allowable surge current.

4. The filter circuit for improving harmonic effects in a single-phase energy meter according to claim 3, characterized in that: The capacitance value of the safety capacitor CX1 is calculated as follows: ； in, Represented as the cutoff frequency, selected It is used to suppress high-frequency harmonics.

5. The filter circuit for improving harmonic effects in a single-phase energy meter according to claim 4, characterized in that: The inductance of the I-shaped inductor LF1 must meet the following requirements: ;in, Indicates the allowable ripple voltage. Indicates the switching frequency. It represents radio wave ripples.

6. The filter circuit for improving harmonic effects in a single-phase energy meter according to claim 5, characterized in that: High-frequency harmonics only pass through the rectifier bridge at the peak / trough of the input voltage, resulting in extremely short conduction times and low effective values ​​of harmonic currents. Significantly reduced, as expressed by the formula: ； in, Indicates the effective value of harmonic current. Indicates period, It represents the instantaneous value of harmonic waves.

7. The filter circuit for improving harmonic effects in a single-phase energy meter according to claim 6, characterized in that: The formula for the heat loss P of the winding resistor RX1 is as follows: ;in, Represents the effective value of harmonic current The square of.

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