Direct-current even harmonic load automatic matching device

Abstract

The utility model discloses a direct-current even harmonic load automatic matching device. A frequency and zero-crossing detection unit is used for measuring current frequency and zero-crossing signals and transmitting the signals to a main control calculation unit; the normal / even-order switching unit is used for converting normal current into output direct-current even-order harmonic current, the output direct-current even-order harmonic current comprises three parts, the output direct-current even-order harmonic current of the first part is transmitted to the frequency and zero-cross detection unit, and the output direct-current even-order harmonic current of the second part is transmitted to the half-wave generation unit; the output direct current even harmonic current of the third part is directly output as the output current; the half-wave generation unit is used for receiving and outputting direct-current even harmonic current and converting the direct-current even harmonic current into positive half-wave current and negative half-wave current; the MOS tube impedance matching unit is used for receiving the negative half-wave current and outputting the negative half-wave current as an output current. According to the utility model, the DC even-order harmonic device is used for solving the problems of low efficiency and large error influence of a DC even-order harmonic test based on a digital sampling MOS tube matching mode.

Description

Technical Field

[0001] The utility model relates to the field of automatic matching devices for DC even-order harmonic loads, in particular to an automatic matching device for DC even-order harmonic loads. Background Art

[0002] At present, there are two types of DC even harmonic test devices: the first type uses a diode plus a matching resistor or a matching meter (see Figure 1 ), after the current passes through the AC standard energy meter, it generates a half-wave current through the diode, and the matching energy meter load is as close as possible to the test energy meter; the second method uses a multi-level matching resistance method (see Figure 2 ), which can increase the number of tests on the energy meter. When multiple test meters are connected, the positive and negative half-wave balance can be ensured by adjusting the matching resistor. The above two methods have the following problems: 1) Since the diode is in the off state below the conduction voltage, the half-wave current generated by the diode will be distorted. 2) The matching resistor problem. The accuracy of the matching resistor affects the test error. The half-wave test current is usually a large current, which requires the matching resistor to have a good temperature drift. Usually, the matching resistor uses a manganese copper resistor (milliohm), which has a certain temperature drift. Long-term high-current testing can easily cause resistance changes, thereby affecting the test results. Summary of the Invention

[0003] In view of the above problems, the utility model proposes an automatic matching device for DC even harmonic loads, which solves the defects of the existing DC even harmonic test device, such as the distortion phenomenon caused by the half-wave current generated by the diode due to the diode being in the off state below the conduction voltage; and the matching resistor problem. The accuracy of the matching resistor affects the test error, and the half-wave test current is usually a large current, requiring the matching resistor to have a good temperature drift. Usually, the matching resistor adopts a manganese copper resistor (milliohm), which has a certain temperature drift. Long-term high-current testing is likely to cause resistance changes, thereby affecting the test results.

[0004] The technical solutions adopted by this utility model are as follows:

[0005] A DC even harmonic load automatic matching device, comprising:

[0006] a main control computing unit;

[0007] A frequency and zero-crossing detection unit; the frequency and zero-crossing detection unit is used to measure the current frequency and zero-crossing signal and transmit the signal to the main control calculation unit;

[0008] a normal / even switching unit; the normal / even switching unit is used to convert the normal current into an output DC even harmonic current, the output DC even harmonic current includes three parts, the first part of the output DC even harmonic current is delivered to the frequency and zero-crossing detection unit, the second part of the output DC even harmonic current is delivered to the half-wave generation unit; the third part of the output DC even harmonic current is directly output as the output current;

[0009] A half-wave generating unit; the half-wave generating unit is used to receive the output DC even harmonic current and convert it into a positive half-wave current and a negative half-wave current; and

[0010] A MOS tube impedance matching unit; the MOS tube impedance matching unit is used to receive the negative half-wave current and output it as the output current.

[0011] The utility model adopts a MOS tube matching method based on digital sampling of a DC even harmonic device to solve the problems of low efficiency and large error influence in DC even harmonic testing.

[0012] Optionally, the positive half-wave current is measured via a positive half-wave ammeter and a load measurement unit, and the positive half-wave ammeter and the load measurement unit are electrically connected to a main control metering unit.

[0013] Optionally, the negative half-wave current is measured via a positive half-wave ammeter and a load measurement unit, and the negative half-wave ammeter and the load measurement unit are electrically connected to a main control metering unit.

[0014] Optionally, the DC even harmonic load automatic matching device includes a chassis, which is equipped with an integrated circuit board, and the main control calculation unit, frequency and zero-crossing detection unit, normal / even switching unit, half-wave generation unit, and MOS tube impedance matching unit are all arranged on the front of the integrated circuit board.

[0015] Optionally, the integrated circuit board is further provided with current input and output terminals and communication terminals.

[0016] Optionally, the main control computing unit includes a measurement module, a half-wave generation module and a control module; the measurement module adopts a high-speed successive approximation type and collects 512 points per cycle.

[0017] Optionally, the control module adopts a 32-bit high-speed ARM single-chip microcomputer, which calculates the loop impedance and performs control in each cycle.

[0018] Optionally, the MOS tube impedance matching unit is used to control the measurement of the positive and negative half-wave currents and load voltages, calculate the impedances R+ and R- of the positive and negative half-wave circuits, perform PID control operations based on the positive half-wave impedance R+, and adjust the output signal G3 so that the negative half-wave impedance is equal to the positive half-wave impedance.

[0019] Optionally, the frequency and zero-crossing detection unit is used by the main control measurement board to measure the current frequency and zero-crossing signal. When the current is in the positive half-wave, the main control board outputs a high-level G1 signal and a low-level G2 signal, turning on the V1 IGBT tube and turning off the V2 IGBT tube, and the current flows from the test meter to the current low end. When the current is in the negative half-wave, the main control board outputs a low-level G1 signal and a high-level G2 signal, turning off the V1 IGBT tube and turning on the V2 IGBT tube, and the current flows from the MOS tube resistance matching unit to the current low end.

[0020] Optionally, the DC even harmonic load automatic matching device adopts a 4U standard chassis.

[0021] Beneficial effects

[0022] 1. The utility model proposes a MOS tube matching method based on digital sampling for a DC even harmonic device, which is used to solve the problems of low efficiency and large error influence in DC even harmonic testing.

[0023] 2. The present invention uses IGBTs instead of diodes to reduce current waveform distortion. The impedance matching unit utilizes the characteristics of MOS tubes to operate in an adjustable resistance range, accurately matching the loop impedance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a circuit diagram of a diode plus matching resistor or matching ammeter in the prior art of the present utility model;

[0025] Figure 2 This is a circuit diagram of a multi-stage matching resistance method in the prior art of the utility model;

[0026] Figure 3 This is a logic flow chart of the DC even harmonic load automatic matching device of Example 1 of the present utility model;

[0027] Figure 4 This is a circuit diagram of the frequency and zero-crossing detection unit and the half-wave generation unit of the DC even harmonic load automatic matching device of Example 1 of the present utility model;

[0028] Figure 5 This is a circuit diagram of a MOS tube impedance matching unit of a DC even harmonic load automatic matching device according to Example 1 of the present utility model;

[0029] Figure 6 1 is a circuit diagram of a main control calculation unit of a DC even harmonic load automatic matching device according to embodiment 1 of the present utility model;

[0030] Figure 7 This is a circuit diagram of a normal / even-order switching unit of a DC even-order harmonic load automatic matching device according to Example 1 of the present utility model.

[0031] Figure 8 It is a structural diagram of the DC even harmonic load automatic matching device of Example 1 of the present utility model.

[0032] The reference numerals in the figures are:

[0033] 1. Current input and output terminals, 2. Communication terminals, 3. Device heat dissipation vents. DETAILED DESCRIPTION

[0034] The following is a further detailed description of the specific implementation of the present invention in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0035] In the description of the present invention, unless otherwise specified, "plurality" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicating positions or location relationships, are based on the positions or location relationships shown in the accompanying drawings and are intended solely for the purpose of facilitating the description of the present invention and simplifying the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. In addition, the terms "first," "second," "third," etc., etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connected" should be understood broadly, for example, to mean a fixed connection, a detachable connection, or an integral connection; a mechanical connection, a direct connection, or an indirect connection through an intermediate medium. A person of ordinary skill in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0036] Example 1

[0037] The technical solutions adopted by this utility model are as follows:

[0038] like Figure 3 As shown, the utility model discloses a DC even harmonic load automatic matching device, comprising: a main control calculation unit, a frequency and zero-crossing detection unit, a normal / even-order switching unit, a half-wave generation unit and a MOS tube impedance matching unit; the frequency and zero-crossing detection unit is used to measure the current frequency and zero-crossing signal and transmit the signal to the main control calculation unit;

[0039] The normal / even switching unit is used to convert the normal current into an output DC even harmonic current. The output DC even harmonic current includes three parts. The output DC even harmonic current of the first part is delivered to the frequency and zero-crossing detection unit, the output DC even harmonic current of the second part is delivered to the half-wave generating unit; the output DC even harmonic current of the third part is directly output as the output current; the half-wave generating unit is used to receive the output DC even harmonic current and convert it into a positive half-wave current and a negative half-wave current; the MOS tube impedance matching unit is used to receive the negative half-wave current and output it as the output current.

[0040] The positive half-wave current is measured via a positive half-wave ammeter and a load measurement unit, which are electrically connected to a main control metering unit. The negative half-wave current is measured via a positive half-wave ammeter and a load measurement unit, which are electrically connected to the main control metering unit. The DC even-harmonic load automatic matching device includes a chassis housing an integrated circuit board. The main control calculation unit frequency, zero-crossing detection unit, normal / even-order switching unit, half-wave generation unit, and MOS tube impedance matching unit are all located on the front of the integrated circuit board. The integrated circuit board also includes current input and output terminals and communication terminals. The main control calculation unit includes a measurement module, a half-wave generation module, and a control module. The measurement module utilizes a high-speed successive approximation method, collecting 512 points per cycle. The control module utilizes a 32-bit high-speed ARM single-chip microcomputer, which calculates and controls the loop impedance for each cycle.

[0041] like Figure 4 As shown in the figure, the frequency and zero-crossing detection unit and half-wave generation unit work on the main control measurement board to measure the current frequency and zero-crossing signal. When the current is in the positive half-wave, the main control board outputs a high-level G1 signal and a low-level G2 signal, turning on the V1 IGBT and turning off the V2 IGBT. Current flows from the test meter to the low-current terminal. When the current is in the negative half-wave, the main control board outputs a low-level G1 signal and a high-level G2 signal, turning off the V1 IGBT and turning on the V2 IGBT. Current flows from the MOS tube resistor matching unit to the low-current terminal.

[0042] like Figure 5 The principle of the MOS tube impedance matching unit shown is that the main control measures the positive and negative half-wave currents and load voltages, calculates the impedances R+ and R- of the positive and negative half-wave circuits, performs PID control operation based on the positive half-wave impedance R+, and adjusts the output signal G3 to make the negative half-wave impedance equal to the positive half-wave impedance.

[0043] like Figure 6As shown, the main control computing unit is divided into three main parts: measurement, half-wave generation, and control. The measurement part uses a high-speed successive approximation method, collecting 512 points per cycle to ensure measurement accuracy. The MCU uses a 32-bit high-speed ARM microcontroller, which calculates the loop impedance and performs control on every cycle.

[0044] like Figure 7 As shown in the figure, the principle of the normal / even-order switching unit is: when normal current is output, relays K3 and K4 are closed, K1, K2, K5, and K6 are disconnected, and the current is output to the electric energy meter without passing through the even-order generating part; when even current is output, relays K1, K2, K5, and K6 are closed, K3 and K4 are disconnected, and the current passes through the even-order circuit and outputs DC even-order harmonic current to the electric energy meter.

[0045] like Figure 8 As shown, the DC even-harmonic load automatic matching device uses a standard 4U chassis. Current input and output terminals 1 are used to connect current input to the high and low terminals of a current source, and output to the measured energy meter. Communication terminal 2 supports RS232 and RS485 communication. The device's heat dissipation port 3, with a built-in fan, provides heat dissipation for the IGBT and MOS modules.

[0046] During implementation of this embodiment, when even harmonics are output, the switching unit switches to the even loop, the current source outputs current ACI, and the main control unit calculates the frequency and current zero-crossing point. Based on the zero point and the positive and negative half-waves, the V1 and V2 IGBT tubes are sequentially turned on. The positive half-wave current passes through V1 to the electric energy meter test stand, and the negative half-wave passes through V2 to the matching MOS tube V3. The main control unit measures the positive and negative half-wave currents I+ and I- and the load voltages U+ and U-, respectively, and calculates the impedances R+ and R- of the positive and negative half-wave loops. R+ is the load of the positive half-wave electric energy meter loop, and R- is the matching load. PID control calculations are performed based on the positive half-wave impedance R+, controlling the V3 matching MOS tube in real time and adjusting the R- impedance to the same value as the R+ load. At this point, matching is complete, and the error caused by the even harmonics meets the requirements.

[0047] The above description is only a preferred embodiment of the present invention and does not limit the scope of patent protection of the present invention. Any equivalent structural transformation made by using the contents of the description and drawings of the present invention, directly or indirectly applied in other related technical fields, is also included in the scope of protection of the present invention.

Claims

1. A DC even harmonic load automatic matching device, characterized in that: include: A main control computing unit; A frequency and zero-crossing detection unit; the frequency and zero-crossing detection unit is used to measure the current frequency and the zero-crossing signal and transmit the signal to the main control calculation unit; A normal / even switching unit; the normal / even switching unit is used to convert the normal current into an output DC even harmonic current, the output DC even harmonic current includes three parts, the first part of the output DC even harmonic current is delivered to the frequency and zero-crossing detection unit, the second part of the output DC even harmonic current is delivered to the half-wave generation unit; the third part of the output DC even harmonic current is directly output as the output current; A half-wave generating unit; the half-wave generating unit is used to receive the output DC even harmonic current and convert it into a positive half-wave current and a negative half-wave current; and A MOS tube impedance matching unit; the MOS tube impedance matching unit is used to receive a negative half-wave current and output it as an output current.

2. A DC even harmonic load automatic matching device as claimed in claim 1, characterized in that: The positive half-wave current is measured via a positive half-wave ammeter and a load measurement unit, and the positive half-wave ammeter and the load measurement unit are electrically connected to a main control metering unit.

3. A DC even harmonic load automatic matching device as claimed in claim 1 or 2, characterized in that: The negative half-wave current is measured via a positive half-wave ammeter and a load measurement unit, and the negative half-wave ammeter and the load measurement unit are electrically connected to a main control metering unit.

4. A DC even harmonic load automatic matching device as claimed in claim 3, characterized in that: It comprises a chassis, which is equipped with an integrated circuit board. The main control calculation unit frequency, zero-crossing detection unit, normal / even switching unit, half-wave generating unit and MOS tube impedance matching unit are all arranged on the front of the integrated circuit board.

5. A DC even harmonic load automatic matching device as claimed in claim 4, characterized in that: The integrated circuit board is also provided with current input and output terminals and communication terminals.

6. A DC even harmonic load automatic matching device as claimed in claim 5, characterized in that: The main control calculation unit includes a measurement module, a half-wave generation module and a control module; the measurement module adopts a high-speed successive approximation type and collects 512 points per cycle.

7. A DC even harmonic load automatic matching device as claimed in claim 6, characterized in that: The control module adopts a 32-bit high-speed ARM single-chip microcomputer, which calculates the loop impedance and performs control at each cycle.

8. A DC even harmonic load automatic matching device as claimed in claim 1 or 2, characterized in that: The MOS tube impedance matching unit is used to control the measurement of the positive and negative half-wave currents and load voltages, calculate the impedances R+ and R- of the positive and negative half-wave loops, perform PID control operations based on the positive half-wave impedance R+, and adjust the output signal G3 to make the negative half-wave impedance equal to the positive half-wave impedance.

9. A DC even harmonic load automatic matching device as claimed in claim 1 or 2, characterized in that: The DC even harmonic load automatic matching device adopts a 4U standard chassis.

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