High-impedance voltage division circuit, device and system

Abstract

The invention belongs to the technical field of electrical measurement, and particularly discloses a high-impedance voltage division circuit, device and system. The high-impedance voltage division circuit comprises a high-voltage arm resistor, a low-voltage arm resistor, a high-voltage arm capacitor, a low-voltage arm capacitor and an adjustable capacitor, two ends of the high-voltage arm resistor and the high-voltage arm capacitor are respectively connected with the input end and the output end; the low-voltage arm resistor and the low-voltage arm capacitor are connected in parallel with the adjustable capacitor, and two ends are respectively connected with the output end and the grounding end. The technical problem that the partial pressure ratio of the whole measurement system changes along with the secondary loop is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical measurement, and in particular relates to a high-impedance voltage divider device. Background Art

[0002] With the vigorous construction of distributed photovoltaic systems, the access of photovoltaic new energy to the power grid is becoming more and more common. Photovoltaic new energy is different from traditional fossil energy power generation. The main feature is that it is significantly affected by environmental and climate characteristics and has obvious randomness, volatility and intermittent characteristics. In addition, distributed photovoltaic systems use a large number of power electronic equipment such as inverters to generate high-frequency oscillation waveforms in the power grid with frequencies close to integer multiples of the switching frequency. In order to accurately monitor the increasingly frequent high-frequency voltage signals, traditional electromagnetic voltage transformers are no longer applicable and voltage dividers need to be used for measurement. Since the resistor voltage divider is limited by the withstand voltage characteristics of the resistor, it is not suitable for long-term operation under the power frequency voltage. The broadband capacitor voltage divider will play an important role in the monitoring of the voltage signal of the new energy grid due to its good shielding effect and small impact on the power grid.

[0003] Although the wideband voltage divider has the measurement capability of tens of kHz bandwidth, the capacitance of the voltage divider will be affected by the secondary load. When the impedance parameter of the low-voltage arm is very small, the internal impedance of the circuit at the back end of the low-voltage arm, including the measuring cable, voltage divider device, digital recorder, etc., will participate in the voltage division in parallel with the low-voltage arm impedance, resulting in a scale factor offset.

[0004] The voltage divider is usually placed at the back end of the voltage divider to divide the voltage of the voltage divider twice to meet the input voltage range requirements of the back-end digital recorder. Its measurement bandwidth is often close to or larger than the measurement bandwidth of the front-end wide-band voltage divider. The internal structure of the voltage divider is connected in parallel with the capacitive voltage divider, and the impedance parameters after parallel connection are the impedance parameters actually involved in the voltage division.

[0005] Usually, secondary voltage dividers are mostly developed based on concentrated resistors ranging from tens of kΩ to 1MΩ. The input impedance of such voltage dividers is too small, and the impact of the secondary loop impedance on the scale factor of the overall measurement system when used as a secondary interface of a capacitive voltage divider is not considered, and its own calibration problem is not considered. Summary of the invention

[0006] The object of the present invention is to provide a high impedance voltage divider device to solve the technical problem that the voltage divider ratio of the overall measurement system changes with the secondary circuit.

[0007] To achieve the above object, the present invention adopts the following technical solution: A high-impedance voltage divider circuit comprises: a high-voltage arm resistor, a low-voltage arm resistor, a high-voltage arm capacitor, a low-voltage arm capacitor and an adjustable capacitor; the high-voltage arm resistor is connected in parallel with the high-voltage arm capacitor and the two ends are respectively connected to an input end and an output end; the low-voltage arm resistor, the low-voltage arm capacitor and the adjustable capacitor are connected in parallel with the two ends being respectively connected to an output end and a ground end.

[0008] A high impedance voltage divider device comprises the above-mentioned high impedance voltage divider circuit and also comprises: a shielding shell, wherein the size of the shielding shell is not greater than 60 mm×30 mm.

[0009] A high-impedance voltage divider system includes the above-mentioned high-impedance voltage divider device, and also includes: a capacitive voltage divider and a digital recorder, the above-mentioned capacitive voltage divider is used to measure a primary voltage, the above-mentioned digital recorder is used to ensure that the voltage division ratio of the above-mentioned high-impedance voltage divider device is fixed during the verification process, the above-mentioned high-impedance voltage divider device is connected in parallel with the low-voltage arm of the above-mentioned capacitive voltage divider, and the output end of the above-mentioned high-impedance voltage divider device is connected to the above-mentioned digital recorder.

[0010] In the present invention, the high-voltage arm resistor is connected in parallel with the high-voltage arm capacitor, and the two ends are connected to the input end and the output end respectively; the low-voltage arm resistor, the low-voltage arm capacitor and the adjustable capacitor are connected in parallel, and the two ends are connected to the output end and the ground respectively, so that the scale factor of the overall voltage measurement system is kept constant and will not change with the change of the secondary circuit, thereby realizing accurate and stable measurement of the high-frequency voltage signal of the new energy grid. The voltage divider circuit and the voltage divider device can be widely used in the monitoring of the voltage signal of the new energy grid, and provide accurate sensing technology for building a new power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a structural schematic diagram of a high impedance voltage divider circuit in an embodiment of the present invention; in, R 1 is the high voltage arm resistance; R 2 is the low voltage arm resistance; C 1 is the high voltage arm capacitor; C 2 is the low voltage arm capacitor; C p It is an adjustable capacitor.

[0012] Figure 2 is a schematic diagram of a three-dimensional structure of a high-impedance voltage divider device in an embodiment of the present invention; Among them, ①, chip resistor; ②, mica capacitor; ③, adjustable capacitor; ④, grounding copper sheet; ⑤, shielding shell; ⑥, input interface; ⑦, output interface.

[0013] Figure 3 is a structural schematic diagram of a high impedance voltage divider system in an embodiment of the present invention; Among them, (1) a capacitive voltage divider; (2) a high impedance voltage divider device; and (3) a digital recorder. DETAILED DESCRIPTION

[0014] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are all in very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0015] It should be noted that, in order to clearly explain the content of the present invention, the present invention specifically cites multiple embodiments to further illustrate different implementations of the present invention, wherein the multiple embodiments are enumerated rather than exhaustive. In addition, for the sake of brevity of explanation, the contents mentioned in the previous embodiments are often omitted in the subsequent embodiments. Therefore, the contents not mentioned in the subsequent embodiments can refer to the previous embodiments accordingly.

[0016] Example 1 A high impedance voltage divider circuit, not limited to Figure 1 As shown, including: high voltage arm resistor R 1. Low voltage arm resistance R 2. High voltage arm capacitor C 1. Low voltage arm capacitor C 2 and adjustable capacitor C p ; High voltage arm resistor R 1 and high voltage arm capacitor C 1 are connected in parallel and the two ends are connected to the input end and the output end respectively; Low voltage arm resistor R 2. Low voltage arm capacitor C 2 with adjustable capacitor C p Connect in parallel with both ends connected to the output end and ground respectively.

[0017] Specifically, the input impedance is at least 10MΩ to have sufficient load capacity, and the voltage divider ratio is k Not limited to: (1) As an optional implementation, the high-voltage arm resistor and the low-voltage arm resistor are chip resistors, and the chip resistors are MΩ-level precision resistors.

[0018] The MΩ-level precision resistor ensures that after the voltage divider device is connected in parallel with the low-voltage arm of the capacitive voltage divider, the impedance of the low-voltage arm of the capacitive voltage divider changes less, and the scale factor of the capacitive voltage divider changes less.

[0019] As an optional implementation, the high-voltage arm capacitor and the low-voltage arm capacitor are mica capacitors, and the mica capacitors are pF-level capacitors.

[0020] The use of pF-level mica capacitors avoids the impact of the capacitor access of the voltage divider on the entire circuit.

[0021] As an optional implementation, the capacitance of the adjustable capacitor is 5-65 pF.

[0022] The adjustable capacitor is used to adjust the capacitance of the low voltage arm.

[0023] Example 2 A high-impedance voltage divider device includes the high-impedance voltage divider circuit in the above embodiment, and further includes: a shielding shell, the size of the shielding shell is not greater than 60mm×30mm.

[0024] As an optional implementation, the high-voltage arm resistor and the low-voltage arm resistor are chip resistors, and the high-voltage arm capacitor and the low-voltage arm capacitor are mica capacitors.

[0025] As an optional implementation, the high-voltage arm resistor, the high-voltage arm capacitor and the low-voltage arm resistor, the low-voltage arm capacitor, and the adjustable capacitor are arranged in double layers.

[0026] As an optional implementation, grounding uses a grounding copper sheet.

[0027] As an optional implementation manner, the distance between the grounding copper sheet and the low-voltage arm resistor and the low-voltage arm capacitor is smaller than the distance between the grounding copper sheet and the high-voltage arm resistor and the high-voltage arm capacitor.

[0028] Specifically, the hardware implementation of the high impedance voltage divider is not limited to the following: Figure 2 As shown, the high-voltage arm resistor and the low-voltage arm resistor are both chip resistors①, the high-voltage arm capacitor and the low-voltage arm capacitor are both mica capacitors②, the adjustable capacitor is an adjustable capacitor③, and also includes a grounding copper sheet④, a shielding shell⑤, an input interface⑥ and an output interface⑦.

[0029] Chip resistor for high voltage arm R 1. Mica capacitor C 1. Chip resistor with low voltage arm R 2. Mica capacitor C 2. Adjustable capacitor C p There is a double-layer arrangement between them to avoid short circuit failures caused by staggered installation of components.

[0030] The adjustable end of the adjustable capacitor ③ is always facing upwards, ensuring that there is space for adjusting the capacitance with a flat-blade screwdriver.

[0031] The grounding copper sheet ④ is used to ground the voltage divider device and to compensate for the capacitance of the voltage divider device. R 2. Capacitor C 2 is always smaller than the distance between it and the high voltage arm resistor R 1. Capacitor C 1 to avoid excessive capacitance between the high voltage arm and the ground, which would cause deviation in the voltage divider ratio.

[0032] The plane size of the shielding shell ⑤ is not greater than 60 mm × 30 mm, and the internal inductance of the voltage divider device is reduced as much as possible to avoid affecting the high-frequency response characteristics of the voltage divider.

[0033] The input interface ⑥ and the output interface ⑦ are respectively the input end and the output end of the voltage divider device, and are not limited to using BNC interfaces, and have good shielding characteristics.

[0034] Furthermore, the high voltage arm resistor R The resistance value of 1 is greater than 10MΩ to ensure that the impedance of the voltage divider device is much greater than the low-voltage arm impedance of the front-end capacitor divider, and the impedance value after parallel connection is close to the low-voltage arm impedance of the capacitor divider.

[0035] High voltage arm capacitor C The capacitance value of 1 is between 10pF and 20pF. The capacitance value is small enough to ensure that after the capacitance of the voltage divider device is connected in parallel with the low-voltage arm capacitance of the front-end capacitance divider, the capacitance value is infinitely close to the low-voltage arm capacitance of the capacitance divider.

[0036] Example 3 A high-impedance voltage divider system includes the high-impedance voltage divider device in the above embodiment, and also includes: a capacitive voltage divider and a digital recorder, the capacitive voltage divider is used to measure a primary voltage, and the digital recorder is used to ensure that the voltage divider ratio of the high-impedance voltage divider device is fixed during the verification process, the high-impedance voltage divider device is connected in parallel with the low-voltage arm of the capacitive voltage divider, and the output end of the high-impedance voltage divider device is connected to the digital recorder.

[0037] Specifically, the high-impedance voltage divider is connected in parallel with the low-voltage arm of the capacitive voltage divider for measuring the primary voltage, and the output end of the high-impedance voltage divider is connected to a digital recorder, which is used to ensure that the voltage divider ratio of the high-impedance voltage divider is fixed during the calibration process. The high-impedance voltage divider is calibrated based on the inductance value obtained by the calibrator to obtain the voltage divider ratio under different voltages.

[0038] Optionally, the high impedance voltage divider system is not limited to Figure 3As shown. The input of the high-impedance voltage divider device (2) is connected to the capacitor voltage divider (1), and the output is connected to the digital recorder (3). The high-impedance voltage divider device as a whole is connected in parallel with the low-voltage arm of the capacitor voltage divider (1) for measuring the primary voltage. By making the overall impedance of the voltage divider device much greater than the impedance of the low-voltage arm of the capacitor voltage divider (1), the voltage divider ratio of the voltage divider device will not change significantly regardless of how the secondary voltage of the capacitor voltage divider (1) changes. The low-voltage arm of the voltage divider device is connected in parallel with the internal impedance of the digital recorder (3), and together they constitute the low-voltage arm of the voltage divider device, that is, R 2 / / R L .

[0039] It is not limited to fixing a digital recorder during the calibration process of the voltage divider ratio of the voltage divider device to ensure that the voltage divider ratio of the voltage divider device will not change due to changes in the back-end digital recorder. Before the voltage divider device is calibrated, it is not limited to connecting a calibrator with the same impedance as the voltage divider device to the back end of the capacitive voltage divider, and obtaining the inductance value by calibration and comparison with the standard mutual inductor. When the voltage divider device is calibrated, the voltage divider device is calibrated based on the obtained inductance value to obtain its voltage divider ratio under different voltages.

[0040] Resistance of digital recorder (3) R L and C L When the resistances are 1MΩ and 20pF~30pF respectively, after the digital recorder (3) is incorporated into the circuit, the formula (1) is not limited to being corrected to: (2) Specifically, the above voltage divider device was connected to the rear end of the capacitive voltage divider for testing. Compared with the traditional secondary voltage follower and attenuator, the measurement error is shown in Table 1. It can be clearly seen that the measurement accuracy under broadband voltage is greatly improved. When measuring standard lightning waves, the error of wavefront time and wavetail time is reduced from more than 5% to about 0.5%; when measuring standard operating voltage, the wavefront time and wavetail time are reduced from about 3% to about 0.2%.

[0041]

[0042] In an embodiment of the present application, the high-impedance voltage divider device effectively solves the problem of weak load capacity of the capacitor voltage divider when measuring the access of new energy to the grid, so that the scale factor of the capacitor voltage divider will not change due to changes in the secondary circuit, thereby achieving stable measurement of broadband voltage signals under new energy access.

[0043] In the embodiments of the present application, the overall function of maintaining a constant voltage divider ratio of the overall measurement system is realized based on a high-impedance voltage divider device; the measurement accuracy problem of the high-impedance voltage divider device is solved by adopting high-precision shielding technology and cooperating with a digital recorder; finally, an equal input impedance calibrator is used for collaborative calibration to solve the calibration problem of the high-impedance voltage divider device, providing a good solution and method for the stable measurement of broadband voltage signals under new energy access.

Claims

1. A high impedance voltage divider circuit, characterized in that: include: High voltage arm resistor, low voltage arm resistor, high voltage arm capacitor, low voltage arm capacitor and adjustable capacitor; The high-voltage arm resistor is connected in parallel with the high-voltage arm capacitor and both ends are connected to the input end and the output end respectively; The low-voltage arm resistor, the low-voltage arm capacitor and the adjustable capacitor are connected in parallel, and both ends are connected to the output end and the ground end respectively.

2. The high impedance voltage divider circuit according to claim 1, wherein: The high-voltage arm resistor and the low-voltage arm resistor are MΩ-level precision resistors.

3. The high impedance voltage divider circuit according to claim 1, wherein: The high-voltage arm capacitor and the low-voltage arm capacitor are pF level capacitors.

4. The high impedance voltage divider circuit according to claim 1, wherein: The capacitance of the adjustable capacitor is 5-65pF.

5. A high impedance voltage divider device, comprising the high impedance voltage divider circuit according to any one of claims 1 to 4, characterized in that: Also includes: The shielding shell has a size not greater than 60 mm×30 mm.

6. The high impedance voltage divider device according to claim 5, characterized in that: The high-voltage arm resistor and the low-voltage arm resistor are chip resistors, and the high-voltage arm capacitor and the low-voltage arm capacitor are mica capacitors.

7. The high impedance voltage divider device according to claim 5, characterized in that: The high-voltage arm resistor, the high-voltage arm capacitor, the low-voltage arm resistor, the low-voltage arm capacitor, and the adjustable capacitor are arranged in double layers.

8. The high impedance voltage divider device according to claim 5, characterized in that: The grounding terminal adopts a grounding copper sheet.

9. The high impedance voltage divider device according to claim 8, characterized in that: The distance between the grounding copper sheet and the low-voltage arm resistor and the low-voltage arm capacitor is smaller than the distance between the grounding copper sheet and the high-voltage arm resistor and the high-voltage arm capacitor.

10. A high impedance voltage divider system, comprising the high impedance voltage divider device according to any one of claims 5 to 8, characterized in that: Also includes: A capacitive voltage divider and a digital recorder, wherein the capacitive voltage divider is used to measure a primary voltage and the digital recorder is used to ensure that the voltage dividing ratio of the high-impedance voltage divider device is fixed during the verification process; the high-impedance voltage divider device is connected in parallel with the low-voltage arm of the capacitive voltage divider, and the output end of the high-impedance voltage divider device is connected to the digital recorder.

Images