Large current AC constant current source and method for arbitrarily adjusting phases of multiple output voltages thereof

Abstract

The present invention relates to a large current AC constant current source and a method for arbitrarily adjusting the phases of multiple groups of output voltages thereof. The constant current source comprises an AC input terminal, an incoming line protection circuit, a diode semiconductor power unit, an energy storage capacitor, a thyristor semiconductor power unit, a filter circuit, a current boost transformer and an AC output terminal connected in sequence. The AC input terminal is also connected to a digital controller through a voltage sampling unit, and the AC output terminal is also connected to the digital controller through a current sampling unit. The driving signal of the digital controller is connected to a thyristor semiconductor control unit, and the output terminal of the thyristor semiconductor control unit is connected to the thyristor semiconductor power unit. The present invention uses a digital controller to control the thyristor semiconductor power unit in the constant current source, completely eliminates the current drift problem, overcomes the drawbacks of traditional electrical power supply devices, greatly improves the output current accuracy, reduces losses, and improves the stability of the constant current source.

Description

Technical Field

[0001] The invention belongs to the technical field of power supply equipment, in particular to a large-current AC constant-current source and a method for arbitrarily adjusting multiple output voltage phases thereof. Background Art

[0002] High-current AC constant-current power supplies are mainly used in places where electrical devices such as complete sets of switchgear, busbars, circuit breakers, fuses, thermal relays, magnetic starters and some non-standard products need to be strictly tested for the thermal effect of specific currents to meet the requirements of low-voltage electrical test power supplies.

[0003] At present, the test method of low-voltage electrical appliances is to connect one end of the test component to a low-voltage power supply with adjustable voltage, and short-circuit the other end, and through the automatic adjustment of the low-voltage power supply, close-loop control of the output current, thereby achieving constant current control. There are currently two main ways of low-voltage power supply: one is through a multi-stage transformer and compensator, and the other is to use a coarse-adjustment voltage regulator, a fine-adjustment voltage regulator and a corresponding transmission control unit. Both power supplies belong to electrical power supplies. The control accuracy is greatly affected by the manufacturing process accuracy of the voltage regulator and transformer, resulting in current drift and harmonic distortion. There is a large power loss that causes low efficiency, and long-term operation generates serious heat. In addition, there are the disadvantages of frequent starting of the voltage regulator motor, high carbon brush failure rate, slow current regulation response, and the need for an additional compensation source in the total circuit. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a high-precision, stable and easy-to-use large-current AC constant current source and a method for arbitrarily adjusting the phases of multiple output voltages thereof.

[0005] The present invention solves the technical problem by adopting the following technical solutions:

[0006] A large current AC constant current source comprises an AC input end, an incoming line protection circuit, a diode semiconductor power unit, an energy storage capacitor, a thyristor semiconductor power unit, a filter circuit, a current boost transformer and an AC output end which are connected in sequence. The AC input end is also connected to a voltage sampling unit, and the output end of the voltage sampling unit is connected to a digital controller. The AC output end is also connected to a current sampling unit, and the output end of the voltage sampling unit is connected to the digital controller. The driving signal of the digital controller is connected to a thyristor semiconductor control unit, and the output end of the thyristor semiconductor control unit is connected to the thyristor semiconductor power unit.

[0007] The digital controller is also connected to a human-machine interface for local operation and operation information display.

[0008] The human-machine interface adopts a touch liquid crystal display screen.

[0009] The digital controller is also connected to the computer in the workshop control room via RS232, RS485, DP or Ethernet to achieve remote control and intelligent networking functions.

[0010] The digitization is formed by connecting DSP and FPGA.

[0011] A method for arbitrarily adjusting the phases of multiple groups of output voltages of a large-current AC constant-current source comprises the following steps:

[0012] Step 1: Phase-lock the grid voltage to obtain the grid A phase angle value θ1;

[0013] Step 2, performing vector control on the output current to obtain a given value of the output voltage of the constant current source;

[0014] Step 3: Perform vector control according to the given output voltage, calculate and update the phase angle difference θ3 between the output voltage and the output current of the device, and realize the arbitrary adjustment of the output voltage phase of a single constant current source;

[0015] Step 4: When multiple groups of constant current sources form N-phase output, the angles of the outputs controlled by the constant current sources from the first phase to the Nth phase are 360*(N-1) / N respectively, so as to realize the function of arbitrarily adjustable phases of multiple groups of output voltages.

[0016] The specific implementation method of step 1 is: the three-phase grid voltage is subjected to 3 / 2 transformation and vector transformation to obtain the grid voltage value Uq under the stationary coordinate. The transformation angle used in the vector transformation is the grid A phase angle value θ1. In order to make Uq=0, PI adjustment is performed to obtain the rotation angular velocity ΔW, the rotation angular velocity ΔW is fed forward with the rated frequency, and then time integration is performed to obtain the grid A phase angle value θ1.

[0017] The specific implementation method of step 2 is: perform a virtual β-axis transformation on the sampled current to obtain the device output current values ​​Iα and Iβ under the two-phase rotating coordinates, and then use the phase angle difference θ3 between the output voltage and the output current to perform vector transformation to obtain the device output current values ​​Id and Iq under the two-phase stationary coordinates; after performing PI adjustment and vector inverse transformation on the D and Q axes respectively, the given value of the constant current source output voltage is obtained.

[0018] The specific implementation method of step 3 is: according to the given value of the output voltage, a vector transformation is performed through the grid A phase angle value θ1, so that the device output voltage value Uoq=0 under the stationary coordinates, and after PI adjustment, a time integration is performed to obtain the output current angle value θ2, and then the phase angle difference θ3=θ1-θ2 between the device output voltage and the output current is obtained. The phase angle difference plus the additional angle is used as a new angle to replace θ3, and finally the arbitrary adjustable function of the output voltage phase of a single constant current source is realized.

[0019] The additional angle has a value of 0-360°.

[0020] The advantages and positive effects of the present invention are:

[0021] 1. The present invention adopts a digital controller to control the thyristor semiconductor power unit in the constant current source, completely eliminating the current drift problem, overcoming the drawbacks of traditional electrical power supply devices, greatly improving the output current accuracy, reducing losses, and improving the stability of the AC constant current source.

[0022] 2. The digital controller of the present invention is connected to a human-machine interface or a computer in a remote control room, and controls the thyristor semiconductor control unit according to data instructions from the human-machine interface or a remote host computer, thereby realizing a constant current control function, and the control is flexible and easy to use.

[0023] 3. The present invention adopts digital control function and performs vector analysis on voltage data to realize phase-locking function, thereby utilizing phase-locking angle to control the angle of output current relative to grid voltage. When multiple groups are connected to the network, the angle difference between the output voltages of each group can be adjusted arbitrarily to realize multi-phase output, which has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a circuit principle block diagram of a large current AC constant current source of the present invention;

[0025] Figure 2 This is a schematic diagram of the constant current source of the present invention in which the output voltage angle can be arbitrarily adjusted;

[0026] Figure 3 This is a schematic diagram of a constant current source network multi-phase output of the present invention;

[0027] Figure 2 In the above, Uα and Uβ are the grid voltage values ​​in two-phase rotating coordinates, Ud and Uq are the grid voltage values ​​in two-phase stationary coordinates, ΔW is the grid rotation angular frequency, Wn is the grid rated frequency, θ1 is the grid A phase angle value, Iα and Iβ are the device output current values ​​in two-phase rotating coordinates, Id and Iq are the device output current values ​​in two-phase stationary coordinates, Uod and Uoq are the device output voltage values ​​in two-phase stationary coordinates, θ2 is the angle value of the device output current, and θ3 is the phase angle difference between the device output voltage and output current. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings.

[0029] The present invention proposes an electronic high-precision large current AC constant current source, such as Figure 1As shown, it includes a power input terminal 1, an incoming line protection circuit 2, a diode semiconductor power unit 3, an energy storage capacitor 4, a thyristor semiconductor power unit 5, a filter circuit 6, a current boost transformer 7, an AC output terminal 8, a current sampling unit 9, a voltage sampling unit 10, a digital controller 11, a thyristor semiconductor control unit 12 and a human-machine interface 13. The power input terminal 1 is connected to the outside by an aviation plug to provide power input to the device. The incoming line protection circuit 2 is used to improve the quality of the grid-side current and prevent current shock. The diode semiconductor power unit 3 converts AC power into DC power. The energy storage capacitor 4 is used to keep the DC voltage stable. The thyristor semiconductor power unit 5 converts DC power into AC power. The filter circuit 6 is used to improve the output current quality. The current boost transformer 7 realizes the large current output of the device. The voltage output terminal 8 is fixed at the output position of the device using a wide copper plate for connecting the tested device. The current sampling unit 9 uses a high-precision sampling circuit to perform current sampling. The voltage sampling unit 10 uses a vector control method to perform voltage processing. The digital controller (DSP+FPGA) 11 is used as a data processing center to realize constant current algorithm control, realize the control signal of the power unit, and provide communication for fault protection, human-machine interface and remote control, and realize the digitization of the control system. The controller contains multiple remote communication interfaces that can respectively realize RS232, RS485, DP and Ethernet host computer control methods. The thyristor semiconductor control unit 12 realizes the processing of the power unit control signal. The human-machine interface 13 uses a touch-screen LCD screen for local operation, such as setting the output current, setting the operating mode of the device, and setting the control mode of the device. At the same time, it can display the operating information and fault information of the device to realize the local control function.

[0030] The specific connection relationship of each unit of the electronic high-precision large-current AC constant current source is as follows: the AC input terminal 1 is connected to the incoming line protection circuit 2, the output of the incoming line protection circuit 2 is connected to the input terminal of the diode semiconductor power unit 3, the output terminal of the diode semiconductor power unit 3 is connected to the energy storage capacitor 4, and at the same time, the energy storage capacitor 4 is connected to the input terminal of the thyristor semiconductor power unit 5, the output terminal of the thyristor semiconductor power unit 5 is connected to the input terminal of the boost transformer 7 after passing through the filter circuit 6, and the output of the boost transformer 7 is connected to the AC output terminal 8, the AC output terminal 8 is connected to the current sampling unit 9, the current sampling unit 9 is connected to the digital controller 11, the input terminal of the voltage sampling unit 10 is connected to the AC output terminal 1, the output terminal of the voltage sampling unit 10 is connected to the digital controller 11, the driving signal of the digital controller 11 is connected to the thyristor semiconductor control unit 12, the thyristor semiconductor control unit 12 is connected to the thyristor semiconductor power unit 5, and a communication interface of the digital controller 11 is connected to the human-machine interface 13, the human-machine interface 13 is used for local control to realize the device operation monitoring, parameter setting and fault protection functions. The digital controller 11 also has four communication interfaces that support different communication protocols, namely RS232, RS485, DP and Ethernet, which can connect the computer in the workshop control room to the digital controller, realize the digital control of the device and the intelligent networking function of multiple devices.

[0031] In this embodiment, the digital controller 11 is composed of a DSP and an FPGA connected to perform digital processing on data, has the function of driving the thyristor power unit and the fault protection function, is provided with a multi-channel switch output port and a switch input port, realizes the control of each electrical node in the power circuit and the collection of feedback signals, has a phase-locking function for the grid voltage, and the initial angle of the current output waveform can be adjusted arbitrarily. When networking, the phase difference between multiple groups of current outputs can be adjusted arbitrarily. The digital controller 11 greatly improves the response speed of the output current, completely eliminates the current drift problem of the traditional power supply, improves the current accuracy, and improves the conversion efficiency.

[0032] In the present invention, the incoming line protection circuit 2 can not only improve the current quality on the grid side but also prevent current shock. The alternating current is converted into direct current after passing through the diode semiconductor power unit 3. Part of the direct current is stored in the energy storage capacitor 4, and part of it is output through the thyristor semiconductor power unit 5. The thyristor semiconductor power unit 5 outputs a voltage pulse modulated waveform, which is converted into alternating current after passing through the filter circuit 6, and then passes through the current boosting transformer 7 to achieve high current output, and is output to the AC output terminal 8 for connecting the load device.

[0033] In the present invention, the voltage sampling unit 10 transmits the sampling data to the digital controller (DSP+FPGA) 11, and the digital controller (DSP+FPGA) 11 performs vector analysis on the voltage data to realize the phase-locking function, thereby using the phase-locking angle to control the angle of the output current relative to the grid voltage. When multiple groups are connected to the network, the angle difference between the output voltages of each group can be arbitrarily adjusted to achieve multi-phase output.

[0034] The present invention also proposes a method for arbitrarily adjusting the phases of multiple output voltages based on the above-mentioned large current AC constant current source, such as Figure 2 As shown, the following steps are included:

[0035] Step 1: Complete phase-locking processing on the grid voltage to obtain the grid A phase angle value θ1.

[0036] The specific implementation method of this step is: the three-phase grid voltage is transformed by 3 / 2 and vector transformation to obtain Uq, the transformation angle used in the vector transformation is θ1, and PI adjustment is performed to obtain the rotation angular velocity ΔW to make Uq=0. The rotation angular velocity is fed forward at the rated frequency, and then time integrated to obtain the grid phase-locking angle θ1, which is the angle of the A phase voltage in the three-phase voltage of the grid.

[0037] Step 2: Perform vector control on the output current to obtain a given value of the output voltage of the constant current source.

[0038] The specific implementation method of this step is: perform a virtual β-axis transformation on the sampled current to obtain the device output current values ​​Iα and Iβ under the two-phase rotating coordinates, and then perform a vector transformation. During the vector transformation, the phase angle difference θ3 between the output voltage and the output current is used to obtain the device output current values ​​Id and Iq under the two-phase stationary coordinates; after performing PI adjustment on the D and Q axes respectively, perform a vector inverse transformation to obtain the given value of the constant current source output voltage.

[0039] Step 3: Perform vector control based on the given output voltage, calculate and update the phase angle difference θ3 between the output voltage and output current of the device, and realize the arbitrary adjustment of the output voltage phase of a single constant current source.

[0040] In this step, vector transformation is performed again according to the given output voltage. The angle used for the vector transformation is the grid A phase angle value θ1. In order to make the phase of the output voltage controllable, the phase of the output voltage is first made consistent with the grid voltage, that is, Uoq=0. After PI adjustment, time integration is performed. At this time, the output current angle value θ2 is obtained, and then the phase angle difference between the device output voltage and the output current θ3=θ1-θ2, so that the phase of the output voltage is consistent with the grid A phase voltage phase, and θ3+X is used as the new angle to replace θ3, that is, the arbitrary adjustable output voltage phase of a single constant current source is realized. Where X represents the additional angle, and the value range is 0-360°

[0041] Step 4: When multiple groups of constant current sources form multi-phase output, for example, N-phase output (where N represents any number of phases, and the value range is N≥1), the angle X of the output controlled by the constant current source from the first phase to the Nth phase is 360*(N-1) / N respectively, so as to realize the function of arbitrarily adjustable phase of multiple groups of output voltages.

[0042] like Figure 3 As shown, multiple constant current sources can be used for intelligent networking of multiple devices. According to the input requirements of the specific load 14, the power grid 15 and the output current of each phase are processed using the principle of arbitrary adjustable voltage phase. The first to fifth paths assign X in θ3+X to 0°, 72°, 144°, 216° and 288° respectively. Taking the initial angle of the power grid A phase voltage as ∠0°, the initial angle of the first phase output voltage is ∠0°, the initial angle of the second phase output voltage is ∠72°, the initial angle of the third phase output voltage is ∠144°, the initial angle of the fourth phase output voltage is ∠216°, and the initial angle of the fifth phase output voltage is ∠288°.

[0043] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive, and therefore the present invention is not limited to the embodiments described in the specific implementation manners. Any other implementation manners derived by those skilled in the art based on the technical solutions of the present invention also fall within the scope of protection of the present invention.

Claims

1. A method for arbitrarily adjusting the phases of multiple groups of output voltages of a large current AC constant current source, the large current AC constant current source comprising an AC input end, an incoming line protection circuit, a diode semiconductor power unit, an energy storage capacitor, a thyristor semiconductor power unit, a filter circuit, a current boost transformer and an AC output end connected in sequence, the AC input end is also connected to a voltage sampling unit, the output end of the voltage sampling unit is connected to a digital controller, the AC output end is also connected to a current sampling unit, the output end of the voltage sampling unit is connected to a digital controller, the driving signal of the digital controller is connected to a thyristor semiconductor control unit, the output end of the thyristor semiconductor control unit is connected to the thyristor semiconductor power unit, characterized in that: The method for arbitrarily adjusting the phases of multiple output voltage groups comprises the following steps: Step 1: Phase-lock the grid voltage to obtain the grid A phase angle value θ1; Step 2, performing vector control on the output current to obtain a given value of the output voltage of the constant current source; Step 3: Perform vector control according to the given output voltage, calculate and update the phase angle difference θ3 between the output voltage and the output current of the device, and realize the arbitrary adjustment of the output voltage phase of a single constant current source; Step 4, when multiple groups of constant current sources form N-phase output, the angles of the outputs controlled by the constant current sources from the first phase to the Nth phase are 360*(N-1) / N respectively, so as to realize the function of arbitrarily adjustable phases of multiple groups of output voltages; The specific implementation method of step 3 is: according to the given value of the output voltage, a vector transformation is performed through the grid A phase angle value θ1, so that the device output voltage value Uoq=0 under the stationary coordinates, and after PI adjustment, a time integration is performed to obtain the output current angle value θ2, and then the phase angle difference θ3=θ1-θ2 between the device output voltage and the output current is obtained. The phase angle difference plus the additional angle is used as a new angle to replace θ3, and finally the arbitrary adjustable function of the output voltage phase of a single constant current source is realized.

2. The method for arbitrarily adjusting the phases of multiple groups of output voltages of a large current AC constant current source according to claim 1, characterized in that: The specific implementation method of step 1 is: the three-phase grid voltage is subjected to 3 / 2 transformation and vector transformation to obtain the grid voltage value Uq under the stationary coordinate. The transformation angle used in the vector transformation is the grid A phase angle value θ1. In order to make Uq=0, PI adjustment is performed to obtain the rotation angular velocity ΔW, the rotation angular velocity ΔW is fed forward with the rated frequency, and then time integration is performed to obtain the grid A phase angle value θ1.

3. The method for arbitrarily adjusting the phases of multiple groups of output voltages of a large current AC constant current source according to claim 1, characterized in that: The specific implementation method of step 2 is: perform a virtual β-axis transformation on the sampled current to obtain the device output current values ​​Iα and Iβ under the two-phase rotating coordinates, and then use the phase angle difference θ3 between the output voltage and the output current to perform vector transformation to obtain the device output current values ​​Id and Iq under the two-phase stationary coordinates; after performing PI adjustment and vector inverse transformation on the D and Q axes respectively, the given value of the constant current source output voltage is obtained.

4. The method for arbitrarily adjusting the phases of multiple groups of output voltages of a large current AC constant current source according to claim 1, characterized in that: The additional angle has a value of 0-360°.

5. The method for arbitrarily adjusting phases of multiple groups of output voltages of a large current AC constant current source according to claim 1, characterized in that: The digital controller is also connected to a human-machine interface for local operation and operation information display.

6. The method for arbitrarily adjusting phases of multiple groups of output voltages of a large current AC constant current source according to claim 5, characterized in that: The human-machine interface adopts a touch liquid crystal display screen.

7. The method for arbitrarily adjusting phases of multiple groups of output voltages of a large current AC constant current source according to claim 1, characterized in that: The digital controller is also connected to the computer in the workshop control room via RS232, RS485, DP or Ethernet to achieve remote control and intelligent networking functions.

8. The method for arbitrarily adjusting the phases of multiple output voltages of a large current AC constant current source according to claim 1, 5, 6 or 7, characterized in that: The digital controller is composed of a DSP and an FPGA connected together.

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