WO2021208154A1

WO2021208154A1 - Ac voltage detection circuit and power electronic device

Info

Publication number: WO2021208154A1
Application number: PCT/CN2020/089045
Authority: WO
Inventors: 吴桢生
Original assignee: 深圳市汇川技术股份有限公司
Priority date: 2020-04-15
Filing date: 2020-05-07
Publication date: 2021-10-21
Also published as: CN111351981A

Abstract

An AC voltage detection circuit and a power electronic device. The AC voltage detection circuit is used to implement voltage detection on N AC input signal lines, wherein N is an integer greater than or equal to 2. The AC voltage detection circuit comprises a rectifier unit (21, 31) and N voltage dividing units (22, 32). An input terminal of the rectifier unit (21, 31) is connected to the AC input signal lines, and the rectifier unit (21, 31) comprises a positive DC output terminal and a negative DC output terminal. Each voltage dividing unit (22, 32) is connected in series between one AC input signal line and the negative DC output terminal of the rectifier unit (21, 31), and the AC voltage detection circuit outputs a detection signal by means of an output terminal of the voltage dividing unit (22, 32). The AC voltage detection circuit obtains a voltage signal no greater than the lowest potential of an AC input signal by means of the rectifier unit (21, 31), so that the detection of the AC input signal may be completed without providing a separate negative voltage power supply, which greatly simplifies the AC voltage detection circuit and is advantageous in reducing the area of a printed circuit board, and reduces costs.

Description

AC voltage detection circuit and power electronic equipment

Technical field

This application relates to the field of voltage detection of electrical equipment, and more specifically, to an AC voltage detection circuit and power electronic equipment.

Background technique

In power electronic equipment such as inverters/drives/UPS (Uninterruptible Power System)/power supplies, the input voltage is usually detected to obtain real-time input voltage information, so as to achieve system control, power calculation, and grid status Monitoring and abnormal judgment, etc.

As shown in Figure 1, it is a schematic diagram of a commonly used three-phase input voltage detection circuit. Among them, R, S, T are three-phase AC power input signals. In the three-phase input voltage detection circuit, the voltage divider resistors R101-R106 (the resistance of each resistor has the following relationship: R101=R102=R103, R104=R105=R106) converts the three-phase alternating current R, S, T into For low-voltage AC signals, in order to meet safety regulations and temperature rise and fall requirements, resistors R101, R102, and R103 can usually be made up of multiple resistors with larger resistance in series. Since an analog-to-digital converter (ADC) usually can only sample a positive voltage signal, it is necessary to convert a low-voltage AC signal into a positive voltage signal. The power supply VCC of the control system converts the AC signal into a positive voltage signal of AC+DC through resistors R109-R112 (the resistance of each resistor has the following relationship: R9=R10=R11=R12). Capacitors C11, C12, C13, C14, C15 are filter capacitors. The three-phase input voltage detection circuit outputs the line voltage detection signal U _RS between R phase and S phase and the line voltage detection signal U _{RT between R phase and T phase.} .

If the actual voltage between R phase and S phase is V _RS , and the actual voltage between R phase and T phase is V _RT , then

The input voltage signals required to realize system control, electric energy calculation, grid status monitoring and other functions are usually V _RS , V _ST , V _TR , according to equations (1) and (2), the microcontroller is sampled by the analog-to-digital converter After U _RS and U _{RT are} _{reached, V RS} and V _TR can be calculated according to the following formulas (3) and (4) _{, and V ST can be} calculated by formula (5) according to the basic circuit principle:

V _ST ＝-V _RS -V _TR (5)

However, the above-mentioned three-phase input voltage detection circuit needs to first convert the high-voltage AC signal into a low-voltage AC signal, and then bias the low-voltage AC signal. Therefore, the op amps U11 and U12 in the circuit need to output negative voltage signals, resulting in the op amp U11 , U12 must have positive and negative power supply. In some control systems, there may only be a positive power supply, and an additional negative power supply needs to be added at this time, resulting in a complicated power supply circuit. In addition, the above-mentioned three-phase input voltage detection circuit also has the problem of more electronic components, which leads to higher costs.

Summary of the invention

The embodiments of the present application provide an AC voltage detection circuit and power electronic equipment to solve the problems that the above-mentioned three-phase input voltage detection circuit needs to be configured with a negative voltage, and there are many electronic components and high cost.

The technical solution of the embodiments of the present application to solve the above technical problems is to provide an AC voltage detection circuit for realizing voltage detection of N AC input signal lines, where N is an integer greater than or equal to 2, and the AC voltage detection circuit The circuit includes a rectifying unit and N voltage dividing units. The input end of the rectifying unit is connected to the AC input signal line, and the rectifying unit includes a positive DC output terminal and a negative DC output terminal; each of the voltage dividing units is connected in series It is connected between an AC input signal line and the negative DC output terminal of the rectifier unit, and the AC voltage detection circuit outputs a detection signal through the output terminal of the voltage dividing unit.

Preferably, the AC voltage detection circuit includes an analog-to-digital conversion unit, the input end of the analog-to-digital conversion unit is connected to the output end of the voltage dividing unit, and the detection signal output by the voltage dividing unit is converted into a digital detection unit. Signal.

Preferably, the AC voltage detection circuit further includes a micro-control unit, the input terminal of the micro-control unit is connected to the output terminal of the analog-to-digital conversion unit, and the digital detection signal output by the analog-to-digital conversion unit is converted into The detection voltage of the AC input signal line.

Preferably, each of the voltage dividing units includes a first resistor group and a second resistor group, and the first resistor group and the second resistor group are connected in series between the AC input signal line and the negative DC output terminal of the rectifier unit The connection point of the first resistance group and the second resistance group constitutes the output terminal of the voltage dividing unit.

Preferably, each of the voltage dividing units further includes a filter capacitor, and the filter capacitor is connected in parallel with the second resistor group.

Preferably, the N is 2, and the rectifier unit includes a single-phase rectifier bridge.

Preferably, the N is 3, and the rectifier unit includes a three-phase rectifier bridge.

The implementation of this application also provides a power electronic device, which includes a rectifier module and a DC power device, and the input end of the rectifier module is connected to N AC input signal lines, and the DC power device passes through a positive DC bus and a negative DC bus. Connected to the rectifier module, the power electronic device further comprises the AC voltage detection circuit according to any one of claims 1-7.

Preferably, the rectification unit of the AC voltage detection circuit is constituted by the rectification module, and each of the voltage dividing units is connected in series between an AC input signal line and the negative DC bus.

The AC voltage detection circuit and power electronic equipment of the embodiments of the present application obtain a voltage signal that is not greater than the lowest potential of the AC input signal through the rectifier unit, so that the AC input signal detection can be completed without providing a separate negative voltage power supply, which greatly simplifies the AC voltage The detection circuit is beneficial to reduce the area of the printed circuit board and save costs.

Description of the drawings

Figure 1 is a schematic diagram of an existing AC voltage detection circuit;

2 is a schematic diagram of the AC voltage detection circuit provided by the first embodiment of the present application;

Fig. 3 is a schematic diagram of an AC voltage detection circuit provided by a second embodiment of the present application.

Detailed ways

In order to make the purpose, technical solutions, and advantages of this application clearer and clearer, the following further describes the application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application, and are not used to limit the present application.

As shown in Figure 2, it is a schematic diagram of the AC voltage detection circuit provided by the first embodiment of the present application. The AC power detection circuit can be applied to inverters, drives, UPS, converters and other devices that need to detect AC input voltage. , And realize the voltage detection of N AC input signal lines, the above N is an integer greater than or equal to 2. The AC voltage detection circuit of this embodiment includes a rectifier unit 21 and three voltage dividing units 22. The input end of the rectifier unit 21 is connected to three AC input signal lines R, S, T (the AC voltage detection circuit of this embodiment is used to detect The voltage of the three-phase AC input signal line, that is, N=3), and the rectifier unit 21 includes a positive DC output terminal and a negative DC output terminal; each voltage divider unit 22 is connected in series to an AC input signal line and the rectifier unit 21 Between the negative DC output terminals, and the AC voltage detection circuit of this embodiment outputs three detection signals U _RN1 , U _SN1 , U _TN1 through the output terminals of the three voltage dividing units 22 (the above detection signals may specifically be fluctuating DC Signal).

The above-mentioned rectifier unit 21 can adopt a three-phase full-bridge uncontrolled rectifier or a three-phase full-bridge controllable rectifier circuit. The potentials of the lowest potential phases of the lines R, S, T are equal, because as long as the potential of any one of the three AC input signal lines R, S, T is lower than the potential of the negative DC output terminal N1, the lower bridge of this phase will be turned on immediately . If the voltage drop of the electronic components in the rectifier unit is ignored, the potential of the three AC input signal lines R, S, T must be greater than or equal to the potential of the negative DC output terminal of the rectifier unit 21. Assuming that the voltage between the AC input signal line R and the negative DC output terminal N1 is V _RN1 , the voltage between the AC input signal line S and the negative DC output terminal N1 is V _SN1 , the AC input signal line T and the negative DC output terminal N1 The voltage between is V _TN1 , then:

V _RN1 , V _SN1 , V _TN1 ≥0 (6)

The voltage dividing unit 22 can convert the high-voltage V _RN1 , V _SN1 , and V _TN1 signals into low-voltage U _RN1 , U _SN1 , U _TN1 signals and output them, thereby facilitating further processing by the low-voltage processing circuit to obtain corresponding voltage detection values.

In the above-mentioned AC voltage detection circuit, since a voltage signal not greater than the lowest potential of the AC input signal is obtained by the rectifier unit 21, the AC input signal detection can be completed without providing a separate negative voltage power supply, and electronic components such as operational amplifiers are omitted. The ground simplifies the AC voltage detection circuit, which is beneficial to reduce the area of the printed circuit board and save costs.

In an embodiment of the present application, the above-mentioned AC voltage detection circuit may further include an analog-to-digital conversion unit. It is converted into a digital detection signal to facilitate the acquisition of the detection value.

In addition, the above-mentioned AC voltage detection circuit may also include a micro-control unit, and the micro-control unit may specifically adopt MCU (Micro Controller Unit, micro-control chip), DSP (Digital Signal Processor, digital signal processor), etc., and the micro-control unit The input terminal of is connected to the output terminal of the analog-to-digital conversion unit, and converts the digital detection signal output by the analog-to-digital conversion unit into the detection voltage of the AC input signal line.

In another embodiment of the present application, the above three voltage dividing units 22 respectively include a first resistor group and a second resistor group, and the first resistor group and the second resistor group are connected in series between the AC input signal line and the rectifying unit 21. Between the negative DC output terminals. For example, the voltage divider unit 22 connected to the AC input signal line R includes a first resistor group R21 and a second resistor group R24. The first resistor group R21 and the second resistor group R24 are connected in series to the AC input signal line R and the rectifier unit 21. The connection point of the first resistor group R21 and the second resistor group R24 constitutes the output terminal of the voltage dividing unit 22; the voltage dividing unit 22 connected to the AC input signal line S includes the first resistor group R22 and the second resistor group R25. The first resistor group R22 and the second resistor group R25 are connected in series between the AC input signal line S and the negative DC output terminal N1 of the rectifier unit 21, and the first resistor group R22 and the second resistor group R25 are connected in series. The connection point of the resistor group R25 constitutes the output terminal of the voltage dividing unit 22; the voltage dividing unit 22 connected to the AC input signal line T includes a first resistor group R23 and a second resistor group R26, the first resistor group R23 and the second resistor The group R26 is connected in series between the AC input signal line T and the negative DC output terminal N1 of the rectifier unit 21, and the connection point of the first resistor group R23 and the second resistor group R26 constitutes the output terminal of the voltage dividing unit 22.

In order to meet the requirements of safety regulations and temperature rise and fall, the above-mentioned first resistor group R21, R22, and R23 can be formed by connecting multiple resistors with larger resistance in series. According to the circuit characteristics, the relationship between the high-voltage AC input signal line voltages V _RN1 , V _SN1 , V _TN1 _{and the output voltages U RN1} , U _SN1 , U _{TN1 of the} low-voltage divider unit 22 is as follows: 8) and (9) show:

Combining formula (6), we can see:

U _RN1 , U _SN1 , U _TN1 ≥0 (10)

To facilitate subsequent processing, the reference ground of the control system can be connected to the negative DC bus N1 of the rectifier unit 21, so that the output voltages U _RN1 , U _SN1 , U _{TN1 of the} low voltage divider unit 22 can be directly input to the analog-to-digital conversion unit _{, The micro-control unit can sample the output voltages U RN1} , U _SN1 , U _{TN1 of the} low-voltage divider unit 22 through the analog-to-digital conversion unit, and then calculate the high-voltage voltage according to the formulas (7), (8), and (9). AC input signal line voltage V _RN1 , V _SN1 , V _TN1 .

According to the basic circuit principle, there are

V _RS ＝V _RN1 -V _SN1 (11)

V _ST ＝V _SN1 -V _TN1 (12)

V _TR ＝V _TN1 -V _RN1 (13)

By calculating formulas (11), (12), (13), the input voltage signals V _RS , V _ST , V _{TR of} the three AC input signal lines R, S, T, and the input voltage signals V _RS , V _ST , V _TR can be directly applied to system control, power calculation, grid status monitoring, etc.

In addition, in order to improve the anti-interference performance, each voltage divider unit 22 described above further includes a filter capacitor, and the filter capacitor is connected in parallel with the second resistor group. For example, the second resistor group R24 is connected in parallel with the filter capacitor C21, and the second resistor group R25 is connected in parallel with the filter capacitor C21. It is connected in parallel with the filter capacitor C22, and the second resistor group R26 is connected in parallel with the filter capacitor C23.

Compared with the traditional input voltage detection solution, the AC voltage detection circuit of this embodiment requires one rectifier unit. However, in power electronic equipment such as frequency converters, drives, UPS, converters, the main power topology or auxiliary power supplies usually have rectifier bridges. The AC voltage detection circuit of this embodiment can directly borrow the existing rectifier bridges in the system. Will not increase the cost; and because the negative power supply is reduced, the circuit is greatly simplified and the cost is reduced.

In some electrical equipment, it may not be allowed or inconvenient to connect the reference ground of the control system directly to the negative DC bus N1 of the rectifier unit, and the output voltage U _RN1 , U _SN1 , U _TN1 signals of the low voltage divider unit 22 can be passed through The isolated operational amplifier or linear optocoupler performs isolation and signal transmission, and then sends it to the analog-to-digital conversion unit. In this way, the advantage of not needing a negative power supply can still be retained, but the cost will rise due to the relatively expensive price of the isolated operational amplifier/linear optocoupler.

In addition, as shown in FIG. 3, in the second embodiment of the present application, the AC voltage detection circuit can also realize the voltage detection of the single-phase AC input signal line, that is, N=2. Correspondingly, the rectifier unit 31 adopts a single-phase full-bridge uncontrolled rectifier circuit or a single-phase full-bridge controllable rectifier circuit, and the AC voltage detection circuit of this embodiment includes two voltage dividing units 32.

Specifically, in the AC voltage detection circuit of this embodiment, two AC input signal lines L, N (ie live wire and neutral wire) are respectively connected to the input end of the rectifier unit 31, and the two voltage dividing units 32 are respectively connected to one Between an AC input signal line and the negative DC output terminal N1 of the rectifier unit, and meet:

V _LN = V _LN1 -V _NN2 (16)

By sampling the output signals U _LN2 and U _{NN2 of the} voltage dividing unit 32, the input voltage V _LN can be calculated.

The embodiment of the present application also provides a power electronic device, the power electronic device may be a frequency converter, a drive, a UPS, a converter, etc., the power electronic device includes a rectifier module, a DC power device (such as an inverter module, etc.), and The AC voltage detection circuit as described above, and the input end of the rectifier module is connected to N AC input signal lines, and the DC electric equipment is connected to the rectifier module through a positive DC bus and a negative DC bus.

In particular, the rectifier unit of the AC voltage detection circuit is composed of a rectifier module, and each voltage divider unit is connected in series between an AC input signal line and the negative DC bus.

The above are only preferred specific implementations of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily think of changes or changes within the technical scope disclosed in this application. Replacement shall be covered within the scope of protection of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

An AC voltage detection circuit for realizing voltage detection of N AC input signal lines, where N is an integer greater than or equal to 2, characterized in that the AC voltage detection circuit includes a rectifier unit and N voltage dividing units , The input end of the rectification unit is connected to the AC input signal line, and the rectification unit includes a positive DC output end and a negative DC output end; each of the voltage dividing units is connected in series to an AC input signal line and the rectifier Between the negative DC output terminals of the unit, and the AC voltage detection circuit outputs a detection signal through the output terminal of the voltage dividing unit.
The AC voltage detection circuit according to claim 1, wherein the AC voltage detection circuit comprises an analog-to-digital conversion unit, and the input terminal of the analog-to-digital conversion unit is connected to the output terminal of the voltage dividing unit, and The detection signal output by the voltage dividing unit is converted into a digital detection signal.
The AC voltage detection circuit according to claim 2, wherein the AC voltage detection circuit further comprises a micro control unit, the input end of the micro control unit is connected to the output end of the analog-to-digital conversion unit, and The digital detection signal output by the analog-to-digital conversion unit is converted into a detection voltage of the AC input signal line.
The AC voltage detection circuit according to any one of claims 1-3, wherein each of the voltage dividing units includes a first resistor group and a second resistor group, and the first resistor group and the second resistor group The resistance group is connected in series between the AC input signal line and the negative DC output end of the rectifier unit, and the connection point of the first resistance group and the second resistance group constitutes the output end of the voltage dividing unit.
4. The AC voltage detection circuit according to claim 4, wherein each of the voltage dividing units further comprises a filter capacitor, and the filter capacitor is connected in parallel with the second resistor group.
The AC voltage detection circuit according to any one of claims 1 to 3, wherein the N is 2, and the rectifier unit includes a single-phase rectifier bridge.
The AC voltage detection circuit according to any one of claims 1 to 3, wherein the N is 3, and the rectifier unit includes a three-phase rectifier bridge.
A power electronic device includes a rectifier module and a DC power device, and the input end of the rectifier module is connected to N AC input signal lines. The DC power device is connected to the rectifier module through a positive DC bus and a negative DC bus. The connection is characterized in that the power electronic equipment further comprises the AC voltage detection circuit according to any one of claims 1-7.
The power electronic equipment according to claim 8, wherein the rectification unit of the AC voltage detection circuit is constituted by the rectification module, and each of the voltage dividing units is connected in series with an AC input signal line and the Between negative DC buses.