Three-phase alternating-current voltage sampling and conditioning circuit and method for suppressing high-frequency interference

Abstract

The invention discloses a three-phase alternating-current voltage sampling and conditioning circuit for suppressing high-frequency interference in the technical field of power electronics and electrotechnics, the three-phase alternating-current voltage sampling and conditioning circuit is connected between a three-phase voltage source and a three-phase three-level AC / DC converter in a bypass mode, the three-phase voltage source supplies power to the three-phase three-level AC / DC converter, a direct-current bus is connected with a load and provides direct-current energy, and the direct-current bus is connected with the load. Comprising a three-phase alternating-current voltage resistance voltage dividing network, a direct-current biasing circuit and a digital signal processor AD port internal operational amplifier. The three-phase three-level AC / DC converter is composed of an internal operational amplifier and a small number of external resistors of an AD sampling port of a digital signal processor in a digital control system, an additional operational amplifier conditioning circuit is not needed, the structure is simple, high power density, high reliability and low cost of the three-phase three-level AC / DC converter are achieved, and the three-phase three-level AC / DC converter has high cost performance; the sampling circuits share the control ground, the formed alternating voltage sampling signal can effectively avoid the influence caused by the noise of a power switch in the three-phase three-level AC / DC converter, and the stability of the system can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics and electrical engineering, and in particular to a three-phase AC voltage sampling and conditioning circuit and method. Background Art

[0002] With the rapid development of modern power systems, especially in renewable energy applications such as wind power generation, photovoltaic energy storage inverters, and new energy vehicle charging and discharging modules, three-phase AC / DC converters are becoming increasingly popular. Three-phase AC voltage sampling technology, a key component in voltage monitoring and control for three-phase AC / DC converters, is becoming increasingly important. In traditional three-phase AC / DC circuits, particularly three-phase, three-level AC / DC circuits, isolated voltage Hall sensors are used for effective AC voltage sampling and control. However, the high cost of voltage Hall sensors hinders cost-effectiveness. Therefore, transformers are used to reduce costs. However, transformers are relatively large for power-frequency voltage sampling, making them unsuitable for the high power density required by today's modular power supplies. Therefore, resistor differential sampling is currently widely used. This involves constructing a differential circuit using an external op amp to achieve AC voltage sampling. This circuit offers the advantages of compact size and low cost, making it suitable for designs requiring high power density and low cost. However, currently, differential sampling is mostly performed on the bus voltage, which places high demands on the common-mode noise resistance of the op amp and the filtering design of the conditioning circuit. In particular, the high-voltage and high-frequency development trend of three-phase, three-level AC / DC circuits increases the difficulty of this voltage sampling design. In order to reduce the design cost and difficulty of the system, the bus midpoint ground sampling method is adopted. However, in higher power applications, due to the parasitic capacitance between the bus midpoint and the earth, the high-frequency changing electrical signal will generate large common-mode switching noise, which will inevitably interfere with the AC voltage sampling, thereby affecting the sampling accuracy and the stability of the control system. Summary of the Invention

[0003] In view of the deficiencies in the prior art, the present invention provides a three-phase AC voltage sampling and conditioning circuit and method for suppressing high-frequency interference, thereby solving the problems in the background art.

[0004] The objective of the present invention is achieved by: a three-phase AC voltage sampling and conditioning circuit for suppressing high-frequency interference, which is connected between a three-phase voltage source and a three-phase three-level AC / DC converter, wherein the three-phase voltage source supplies power to the three-phase three-level AC / DC converter, and a DC bus is connected to a load and provides DC energy. The circuit is characterized in that it includes: a three-phase AC voltage resistor divider network, a DC bias circuit, and an internal operational amplifier of an AD port of a digital signal processor;

[0005] The three-phase AC voltage resistor divider network is composed of voltage divider resistors of phase A, phase B and phase C, and the voltage divider resistors of phase A, phase B and phase C are all formed by high-voltage resistors and low-voltage resistors in series, and one end of the high-voltage resistor in each phase voltage divider resistor is connected to the corresponding AC power supply voltage, and one end of the low-voltage resistor in each phase voltage divider resistor is connected to the control ground, realizing a star connection of the three low-voltage resistors in the voltage divider resistors of phase A, phase B and phase C;

[0006] The DC bias circuit includes bias resistors for phases A, B, and C, and the bias resistors for phases A, B, and C are each formed by a high-end bias resistor and a low-end bias resistor connected in series, and one end of the high-end bias resistor in each phase bias resistor is connected to a DC reference voltage, and one end of the low-end bias resistor in each phase bias resistor is connected to a control ground, so that the three low-end bias resistors in the bias resistors of phases A, B, and C share a common control ground;

[0007] The three midpoints of the high-voltage resistor and the low-voltage resistor in series in the voltage divider resistors of phases A, B and C are correspondingly connected to the three midpoints of the high-end bias resistor and the low-end bias resistor in series in the bias resistors of phases A, B and C, and the three midpoint signals are respectively sent to the three AD port internal operational amplifiers of the digital signal processor to form AC voltage sampling signals of phases A, B and C.

[0008] Furthermore, the three midpoints of the high-voltage resistors and the low-voltage resistors in series in the voltage divider resistors of phases A, B and C are respectively used to obtain the AC voltage signals of phases A, B and C relative to the control ground, and the three midpoints of the high-end bias resistors and the low-end bias resistors in series in the bias resistors of phases A, B and C are respectively used to obtain the DC bias voltages of phases A, B and C relative to the control ground; the AC voltage signals of phases A, B and C and the DC bias voltages of phases A, B and C are linearly superimposed at the AD port of the digital signal processor to obtain the AC voltage sampling signals of phases A, B and C.

[0009] A three-phase AC voltage sampling and conditioning method for suppressing high-frequency interference includes: linearly superimposing the AC voltage signals of phases A, B, and C in a three-phase AC voltage resistor divider network and the DC bias voltages of phases A, B, and C through an operational amplifier inside an AD port of a digital signal processor, calculating the three-phase AC voltage sampling signal, and completing the conditioning.

[0010] Furthermore, the calculation of the three-phase AC voltage sampling signal is specifically as follows: the calculation description is based on the A-phase AC voltage sampling signal, specifically including:

[0011] Step 1) Calculate the resistance voltage component vAD1(1) of the A-phase AC voltage sampling signal.

[0012]

[0013] Where: va is the AC voltage of phase A, Rha is the high-voltage resistor of phase A in the three-phase AC voltage resistor divider network, and Rsa is the parallel resistance of the low-voltage resistor of phase A in the three-phase AC voltage resistor divider network and the low-end bias resistor of phase A in the DC bias circuit. , R7 is the high-end bias resistor of phase A in the DC bias circuit;

[0014] Step 2) Calculate the DC bias voltage component vAD1(2) of the A-phase AC voltage sampling signal.

[0015]

[0016] Where: VDD is the DC reference voltage of the DC bias circuit, Rha is the high-voltage resistor of phase A in the three-phase AC voltage resistor divider network, and Rsa is the parallel resistance of the low-voltage resistor of phase A in the three-phase AC voltage resistor divider network and the low-end bias resistor of phase A in the DC bias circuit. , R7 is the high-end bias resistor of phase A in the DC bias circuit;

[0017] Step 3) Calculate the A-phase AC voltage sampling signal:

[0018]

[0019] Where vAD1 is the A-phase AC voltage sampling signal, vAD1(1) is the resistance voltage division component of the A-phase AC voltage sampling signal, and vAD1(2) is the DC bias voltage component of the A-phase AC voltage sampling signal. The calculation methods of the B-phase AC voltage sampling signal and the C-phase AC voltage sampling signal are the same as those of the A-phase AC voltage sampling signal.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention utilizes the internal operational amplifier of the AD sampling port of the digital signal processor in the digital control system and a small amount of external resistors, and does not require an additional operational amplifier conditioning circuit, so the structure is simple. Compared with voltage Hall sampling or transformer sampling, the method is extremely low in cost and small in size, which helps to achieve high power density, high reliability and low cost of the three-phase three-level AC / DC converter, thereby having a high cost-effectiveness; in addition, because the three-phase AC voltage sampling and conditioning circuit of the invention has a common control ground, the AC voltage sampling signal formed can effectively avoid the influence of power switch noise in the three-phase three-level AC / DC converter, thereby helping to improve the stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0022] Figure 1 This is a three-phase AC voltage sampling and conditioning circuit diagram for suppressing high-frequency interference according to the present invention.

[0023] Figure 2 This is a schematic diagram of the A-phase AC voltage sampling and conditioning principle of the present invention.

[0024] Figure 3 This is an equivalent principle diagram for calculating the A-phase resistance voltage division component when the A-phase AC voltage va acts alone.

[0025] Figure 4 This is an equivalent principle diagram for calculating the A-phase DC bias voltage when the DC reference voltage VDD of the present invention acts alone.

[0026] Figure 5 Schematic diagram of the principle of a three-phase AC voltage sampling and conditioning circuit in an embodiment of the present invention.

[0027] Figure 6 This is a control system according to an embodiment of the present invention.

[0028] Figure 7 1 is the experimental waveform of the three-phase AC voltage sampling signal in the embodiment of the present invention.

[0029] Figure 8 1 and 2 are the experimental waveforms of the AC voltage and current of phase A and phase B in the embodiment of the present invention.

[0030] Figure 1 Symbolic names in:

[0031]

[0032] Figure 2 、 Figure 3 、 Figure 4 Symbol name reference in Figure 1 ;

[0033] Figure 5 Symbolic names in:

[0034]

[0035] Other Figure 1 Explanation of symbols in ;

[0036] Figure 6 Symbolic names in:

[0037]

[0038] Other Figure 1 Description of symbols in . DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] like Figure 1 As shown, the components of the present invention include: a three-phase AC voltage resistor divider network 1, a DC bias circuit 2 and an internal operational amplifier 3 of the AD port of a digital signal processor. The present invention implements three-phase AC voltage sampling of a three-phase three-level AC / DC converter 4.

[0041] like Figure 1 The three-phase AC voltage sampling and conditioning circuit shown here for suppressing high-frequency interference consists of a three-phase AC voltage resistor divider network 1, a DC bias circuit 2, and an internal operational amplifier 3 of the AD port of a digital signal processor. A three-phase voltage source (va, vb, vc) supplies power to a three-phase three-level AC / DC converter 4. The DC bus connects to the load and provides DC energy and a support voltage Vbus. The three-phase AC voltage resistor divider network 1 is composed of voltage divider resistors for phases A, B, and C. The voltage divider resistors for phases A, B, and C are each composed of a high-voltage resistor and a low-voltage resistor connected in series. Formed, wherein the A-phase voltage-dividing resistor is composed of a high-voltage resistor Rha and a low-voltage resistor R1 connected in series, the B-phase voltage-dividing resistor is composed of a high-voltage resistor Rhb and a low-voltage resistor R2 connected in series, and the C-phase voltage-dividing resistor is composed of a high-voltage resistor Rhc and a low-voltage resistor R3 connected in series; and one end of the high-voltage resistor in each phase voltage-dividing resistor is connected to the corresponding AC power supply voltage, that is, one end of the high-voltage resistor Rha in the A-phase voltage-dividing resistor, the high-voltage resistor Rhb in the B-phase voltage-dividing resistor, and the high-voltage resistor Rhc in the C-phase voltage-dividing resistor are respectively connected to the A-phase va, B-phase vb, and C-phase vc voltage sources. One end of the low-voltage resistor in each phase voltage-dividing resistor is connected to the control ground GND, that is, one end of the corresponding low-voltage resistors R4, R5, and R6 in the A-phase, B-phase, and C-phase voltage-dividing resistors are connected together to the control ground, thereby realizing a star connection of the three low-voltage resistors R4, R5, and R6 in the A-phase, B-phase, and C-phase voltage-dividing resistors;

[0042] like Figure 1The DC bias circuit 2 includes bias resistors for phase A, phase B, and phase C. The bias resistors for phase A, phase B, and phase C are all formed by connecting a high-end bias resistor and a low-end bias resistor in series, that is, the bias resistor for phase A is connected by connecting a high-end bias resistor R7 and a low-end bias resistor R4 in series, the bias resistor for phase B is connected by connecting a high-end bias resistor R8 and a low-end bias resistor R5 in series, and the bias resistor for phase C is connected by connecting a high-end bias resistor R9 and a low-end bias resistor R6 in series, and one end of the high-end bias resistor in each phase bias resistor is connected to the DC reference voltage VDD, that is, the bias resistors for phase A and B are connected by connecting a high-end bias resistor R7 and a low-end bias resistor R4 in series. One end of the high-end bias resistors R7, R8 and R9 of phase A and phase C are all connected to the DC reference voltage VDD, and one end of the low-end bias resistor in each phase bias resistor is connected to the control ground GND, that is, one end of the low-end bias resistors R4, R5 and R6 of phase A, phase B and phase C are all connected to the control ground, so that the three low-end bias resistors (R4, R5 and R6) in the bias resistors of phase A, phase B and phase C share the control ground; for the three-phase AC voltage resistor divider network 1, the high-voltage resistor Rha and the low-voltage resistor Rha in the phase A voltage divider resistor are connected to the control ground. R1 is connected in series to form a midpoint, the high-voltage resistor Rhb and the low-voltage resistor R2 in the B-phase voltage divider resistor are connected in series to form a midpoint, and the high-voltage resistor Rhc and the low-voltage resistor R3 in the C-phase voltage divider resistor are connected in series to form a midpoint; for the DC bias circuit 2, the high-end bias resistor R7 and the low-end bias resistor R4 in the A-phase bias resistor are connected in series to form a midpoint, the high-end bias resistor R8 and the low-end bias resistor R5 in the B-phase bias resistor are connected in series to form a midpoint, and the high-end bias resistor R9 and the low-end bias resistor R1 in the C-phase bias resistor are connected in series to form a midpoint. R6 is connected in series to form a midpoint; the three midpoints of the high-voltage resistor and the low-voltage resistor in the voltage divider resistors of phases A, B and C are connected in series with the three midpoints of the high-end bias resistor and the low-end bias resistor in the bias resistors of phases A, B and C to form the midpoints of phases A, B and C, and the signals of the three midpoints (midpoints of phases A, B and C) are respectively sent to the internal operational amplifiers of the three AD ports of the digital signal processor, thereby forming AC voltage sampling signals vAD1, vAD2 and vAD3 of phases A, B and C respectively;

[0043] The three midpoints formed by the corresponding series connection of the high-voltage resistors Rha, Rhb, Rhc and the low-voltage resistors R1, R2, R3 in the voltage divider resistors of phase A, phase B and phase C respectively obtain the AC voltage signals of phase A, phase B and phase C relative to the control ground (GND), and the three midpoints formed by the series connection of the high-end bias resistors R7, R8, R9 and the low-end bias resistors R4, R5, R6 in the bias resistors of phase A, phase B and phase C respectively obtain the DC bias voltages of phase A, phase B and phase C relative to the control ground (GND); the AC voltage signals of phase A, phase B and phase C and the DC bias voltages of phase A, phase B and phase C are linearly superimposed at the AD port of the digital signal processor to obtain the AC voltage sampling signals of phase A, phase B and phase C, which are vAD1, vAD2 and vAD3 respectively;

[0044] like Figure 1 and Figure 2 As shown, a three-phase AC voltage sampling and conditioning method for suppressing high-frequency interference includes a three-phase AC voltage resistor divider network 1, a DC bias circuit 2, and an internal operational amplifier 3 of a digital signal processor AD port. The AC voltage signals of phases A, B, and C in the three-phase AC voltage resistor divider network 1 and the DC bias voltages of phases A, B, and C are linearly superimposed through the internal operational amplifier 3 of the digital signal processor AD port to form a calculation method for the three-phase AC voltage sampling signal, thereby completing the conditioning. Figure 2 As shown in the figure, the A-phase AC voltage sampling and conditioning circuit based on the internal operational amplifier of the AD1 port of the digital signal processor is given. The calculation method of the A-phase AC voltage sampling signal vAD1 is explained by taking the calculation of the A-phase AC voltage sampling signal as an example:

[0045] According to the linear superposition theorem, the A-phase AC voltage signal generated by the A-phase AC voltage va acting alone on the AD1 port is based on Figure 2 The equivalent circuit is obtained as Figure 3 As shown, the resistance voltage component vAD1(1) of the A-phase AC voltage sampling signal can be calculated by the following formula, as shown in formula (1).

[0046] (1)

[0047] Where va is the AC voltage of phase A, Rha is the high-voltage resistor of phase A in the three-phase AC voltage resistor divider network 1, and Rsa is the parallel resistance of the low-voltage resistor of phase A in the three-phase AC voltage resistor divider network 1 and the low-end bias resistor of phase A in the DC bias circuit 2 ( ), R7 is the high-end bias resistor of phase A in the DC bias circuit 2.

[0048] According to the linear superposition principle, the A-phase DC bias voltage generated by the DC reference voltage VDD acting alone on the AD1 port is based on Figure 2 The equivalent circuit is obtained as Figure 4 As shown, the DC bias voltage component vAD1(2) of the A-phase AC voltage sampling signal can be calculated by the following formula, as shown in formula (2).

[0049] (2)

[0050] Where VDD is the DC reference voltage of the DC bias circuit 2, Rha is the high-voltage resistor of phase A in the three-phase AC voltage resistor divider network 1, and Rsa is the parallel resistance value of the low-voltage resistor of phase A in the three-phase AC voltage resistor divider network 1 and the low-end bias resistor of phase A in the DC bias circuit ( ), R7 is the high-end bias resistor of phase A in the DC bias circuit.

[0051] According to the linear superposition theorem, the A-phase AC voltage sampling signal vAD1 is calculated as follows:

[0052] (3)

[0053] Where vAD1 is the A-phase AC voltage sampling signal, vAD1(1) is the resistance voltage component of the A-phase AC voltage sampling signal, and vAD1(2) is the DC bias voltage component of the A-phase AC voltage sampling signal.

[0054] The B-phase AC voltage sampling signal vAD2 is obtained using the internal op amp at port AD2 of the digital signal processor, and the C-phase AC voltage sampling signal vAD3 is obtained using the internal op amp at port AD3 of the digital signal processor. The calculation methods for the B-phase AC voltage sampling signal vAD2 and the C-phase AC voltage sampling signal vAD3 are the same as those for the A-phase AC voltage sampling signal vAD1.

[0055] A specific embodiment of the present invention is as follows:

[0056] like Figure 5 The present invention is applied to three-phase three-level Vienna converter three-phase AC voltage sampling, Figure 6 This is the control system of the embodiment, which uses TI's TMS320F28021 as the digital control MCU. Figure 5 and Figure 6 In the example, the three-phase three-level Vienna converter has a three-phase AC voltage range of 220V to 260V. Therefore, the high-voltage resistors Rha, Rhb, and Rhc in the three-phase AC voltage resistor divider network 1 are all formed by five 1210 package chip resistors with a resistance of 200kΩ connected in series. The low-voltage resistor connected to the control ground is a 12.7kΩ 0805 package chip resistor. Figure 5 In the example, the low-end bias resistor of the DC bias circuit 2 is selected as a 12.7kΩ 0805 package chip resistor, the high-end bias resistor is selected as a 6.2kΩ 0603 package chip resistor, and the DC reference voltage VDD is 3V. The resistance divided voltage component vAD1(1) of the A-phase AC voltage sampling signal of the three-phase AC voltage resistor divider network and the DC bias voltage component vAD1(2) of the A-phase AC voltage sampling signal generated by the DC bias circuit 2 are linearly superimposed at the AD1 port of the operational amplifier 3 inside the AD port of the digital signal processor to obtain the A-phase AC voltage sampling signal vAD1. The same method can be used to realize the B-phase AC voltage sampling signal vAD2 and the C-phase AC voltage sampling signal vAD3.

[0057] Based on the three-phase AC voltage sampling circuit and method of the present invention, a Figure 6The control system of the three-phase three-level Vienna converter shown in the figure uses a control algorithm implemented in the TMS320F28021 chip. The TMS320F28021 has a total of 14 AD sampling ports. ADCINA1 can be configured as the sampling port AD1 for the A-phase AC voltage va, ADCINA3 as the sampling port AD2 for the B-phase AC voltage vb, and ADCINA6 as the sampling port AD3 for the C-phase AC voltage vc. The other AD ports are configured to sample the three-phase input currents ia / ib / ic and the DC bus voltage Vbus. The sampling signals are sent to the internal registers of the TMS320F28021 and converted into digital quantities. The real-time control cycle is formed by the AD sampling interrupt, and the control cycle is implemented Figure 6 The coordinate transformation, dual closed-loop control of the DC bus voltage outer loop and the AC side current inner loop, PLL phase-locked loop and PWM modulation algorithm shown in the figure can realize high power factor correction on the grid side of the three-phase three-level Vienna converter.

[0058] In the embodiment, the A-phase, B-phase and C-phase AC voltage signals in the three-phase AC voltage resistor divider network 1 and the A-phase, B-phase and C-phase DC bias voltages are linearly superimposed by the internal operational amplifier 3 of the AD port of the digital signal processor to form a calculation method for the three-phase AC voltage sampling signal; Figure 2 As shown in the figure, the A-phase AC voltage sampling and conditioning circuit based on the internal operational amplifier of the AD1 port of the digital signal processor is given. The calculation method of the A-phase AC voltage sampling signal vAD1 is explained by taking the calculation of the A-phase AC voltage sampling signal as an example:

[0059] According to the linear superposition theorem, the A-phase AC voltage signal generated by the A-phase AC voltage va acting alone on the AD1 port is based on Figure 2 The equivalent circuit is obtained as Figure 3 As shown, the 12.7kΩ low-voltage resistor R1 in the three-phase AC voltage resistor divider network 1, the 6.2kΩ high-end bias resistor R7 and the 12.7kΩ low-end bias resistor R4 in the DC bias circuit 2 are connected in parallel, and then connected in series with the 1000kΩ high-voltage resistor Rha in the three-phase AC voltage resistor divider network 1. The resistor divider component vAD1(1) of the A-phase AC voltage sampling signal can be calculated by the following formula, as shown in formula (1).

[0060] (4)

[0061] Where va is the AC voltage of phase A, and Rha is the high-voltage resistor of phase A in the three-phase AC voltage resistor divider network 1 ( ), Rsa is the parallel resistance value of the low-voltage resistor R1 of phase A in the three-phase AC voltage resistor divider network 1 and the low-end bias resistor R4 of phase A in the DC bias circuit 2 ( ), R7 is the high-end bias resistor of phase A in the DC bias circuit.

[0062] According to the linear superposition principle, the A-phase DC bias voltage generated by the DC reference voltage VDD acting alone on the AD1 port is based on Figure 2 The equivalent circuit is obtained as Figure 4 As shown, the 12.7kΩ low-end bias resistor R4 in the DC bias circuit 2 and the 1000kΩ high-voltage resistor Rha and 12.7kΩ low-voltage resistor R1 in the three-phase AC voltage resistor divider network 1 are connected in parallel, and then connected in series with the 6.2kΩ high-end bias resistor R7 in the DC bias circuit 2. The DC bias voltage component vAD1(2) of the A-phase AC voltage sampling signal can be calculated by the following formula, as shown in formula (5).

[0063] (5)

[0064] Where VDD is the 3.3V DC reference voltage of the DC bias circuit, and Rha is the high-voltage resistor of phase A in the three-phase AC voltage resistor divider network ( ), Rsa is the parallel resistance value of the low-voltage resistor R1 of phase A in the three-phase AC voltage resistor divider network 1 and the low-end bias resistor R4 of phase A in the DC bias circuit 2 ( ), R7 is the high-end bias resistor of phase A in the DC bias circuit.

[0065] According to the linear superposition theorem, the A-phase AC voltage sampling signal vAD1 is calculated by formula (6):

[0066] (6)

[0067] Where vAD1 is the A-phase AC voltage sampling signal, vAD1(1) is the resistance voltage component of the A-phase AC voltage sampling signal, and vAD1(2) is the DC bias voltage component of the A-phase AC voltage sampling signal.

[0068] The B-phase AC voltage sampling signal vAD2 is obtained based on the internal operational amplifier of the digital signal processor AD2 port, and the C-phase AC voltage sampling signal vAD3 is obtained based on the internal operational amplifier of the digital signal processor AD3 port. The calculation method of the B-phase AC voltage sampling signal vAD2 and the C-phase AC voltage sampling signal vAD3 is the same as that of the A-phase AC voltage sampling signal vAD1. In the embodiment of the present invention, the three-phase AC voltage is calculated based on the peak voltage, and the maximum peak voltage is generally 380V; the waveform of the three-phase AC voltage sampling signal is as follows: Figure 7 As shown in the figure, when the AC voltage signal value is 2.702 when the maximum peak voltage is 380V, and when the AC voltage signal value is -380V, it is 0.325. Substituting vAD1=3 into the formula, the maximum peak voltage that can be sampled is 475.4V.

[0069] In the embodiment of the present invention, the experimental waveforms of the AC voltage and current of phase A and phase B during the stable operation of the three-phase three-level Vienna converter are as follows: Figure 8 As shown in the figure, by suppressing high-frequency interference of the three-phase AC voltage sampling and conditioning circuit and method, the precise sampling signal is sent to the internal register of TMS320F28021 and converted into a digital quantity. The AD sampling interrupt constitutes a real-time control cycle, and the coordinate transformation, the dual closed-loop control of the DC bus voltage outer loop and the AC side current inner loop, the PLL phase-locked loop and the PWM modulation algorithm are implemented in the control cycle, so that the three-phase AC current phase tracks the three-phase AC voltage phase.

[0070] The present invention has the following advantages:

[0071] (1) The three-phase AC voltage sampling and conditioning circuit of the present invention has a simple topology and uses a small number of components, which helps to achieve high reliability, high power density and low cost, thereby achieving high cost performance.

[0072] (2) The three-phase AC voltage sampling and conditioning circuit and method of the present invention obtain a three-phase AC voltage sampling signal relative to the control ground, which can effectively suppress the common-mode interference caused by high-frequency switching noise, help improve the voltage sampling accuracy and ensure the reliable and stable operation of the system;

[0073] (3) The present invention is not limited to the application of AC voltage sampling of three-phase three-level AC / DC converters, but can be applied to other AC / DC converters powered by three-phase AC voltage, and can also be applied to AC output voltage sampling of three-phase inverters.

[0074] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A three-phase AC voltage sampling and conditioning circuit for suppressing high-frequency interference, connected between a three-phase voltage source and a three-phase three-level AC / DC converter, wherein the three-phase voltage source supplies power to the three-phase three-level AC / DC converter, and the DC bus is connected to a load and provides DC energy, characterized in that: include: Three-phase AC voltage resistor divider network, DC bias circuit and internal operational amplifier of the AD port of the digital signal processor; The three-phase AC voltage resistor divider network is composed of voltage divider resistors of phase A, phase B and phase C, and the voltage divider resistors of phase A, phase B and phase C are all formed by high-voltage resistors and low-voltage resistors in series, and one end of the high-voltage resistor in each phase voltage divider resistor is connected to the corresponding AC power supply voltage, and one end of the low-voltage resistor in each phase voltage divider resistor is connected to the control ground, realizing a star connection of the three low-voltage resistors in the voltage divider resistors of phase A, phase B and phase C; The DC bias circuit includes bias resistors for phases A, B, and C, and the bias resistors for phases A, B, and C are each formed by a high-end bias resistor and a low-end bias resistor connected in series, and one end of the high-end bias resistor in each phase bias resistor is connected to a DC reference voltage, and one end of the low-end bias resistor in each phase bias resistor is connected to a control ground, so that the three low-end bias resistors in the bias resistors of phases A, B, and C share a common control ground; The three midpoints of the high-voltage resistor and the low-voltage resistor in series in the voltage divider resistors of phases A, B and C are correspondingly connected to the three midpoints of the high-end bias resistor and the low-end bias resistor in series in the bias resistors of phases A, B and C, and the three midpoint signals are respectively sent to the three AD port internal operational amplifiers of the digital signal processor to form AC voltage sampling signals of phases A, B and C.

2. A three-phase AC voltage sampling and conditioning circuit for suppressing high-frequency interference according to claim 1, characterized in that: The three midpoints of the high-voltage resistor and the low-voltage resistor in series in the voltage divider resistors of phases A, B and C are respectively used to obtain the A-phase, B-phase and C-phase AC voltage signals relative to the control ground, and the three midpoints of the high-end bias resistor and the low-end bias resistor in series in the bias resistors of phases A, B and C are respectively used to obtain the A-phase, B-phase and C-phase DC bias voltages relative to the control ground; the A-phase, B-phase and C-phase AC voltage signals and the A-phase, B-phase and C-phase DC bias voltages are linearly superimposed at the AD port of the digital signal processor to obtain the A-phase, B-phase and C-phase AC voltage sampling signals.

3. A three-phase AC voltage sampling and conditioning method for suppressing high-frequency interference, using the three-phase AC voltage sampling and conditioning circuit for suppressing high-frequency interference as claimed in claim 1 or 2, characterized in that: include: The A-phase, B-phase and C-phase AC voltage signals in the three-phase AC voltage resistor divider network and the A-phase, B-phase and C-phase DC bias voltages are linearly superimposed through the operational amplifier inside the AD port of the digital signal processor to calculate the three-phase AC voltage sampling signal and complete the conditioning.

4. A three-phase AC voltage sampling and conditioning method for suppressing high-frequency interference according to claim 3, characterized in that: The calculation of the three-phase AC voltage sampling signal is as follows: The calculation instructions are based on the A-phase AC voltage sampling signal, which specifically include: Step 1) Calculate the resistance voltage component vAD1(1) of the A-phase AC voltage sampling signal. Where: va is the AC voltage of phase A, Rha is the high-voltage resistor of phase A in the three-phase AC voltage resistor divider network, and Rsa is the parallel resistance of the low-voltage resistor of phase A in the three-phase AC voltage resistor divider network and the low-end bias resistor of phase A in the DC bias circuit. , R7 is the high-end bias resistor of phase A in the DC bias circuit; Step 2) Calculate the DC bias voltage component vAD1(2) of the A-phase AC voltage sampling signal. Where: VDD is the DC reference voltage of the DC bias circuit, Rha is the high-voltage resistor of phase A in the three-phase AC voltage resistor divider network, and Rsa is the parallel resistance of the low-voltage resistor of phase A in the three-phase AC voltage resistor divider network and the low-end bias resistor of phase A in the DC bias circuit. , R7 is the high-end bias resistor of phase A in the DC bias circuit; Step 3) Calculate the A-phase AC voltage sampling signal: Where vAD1 is the A-phase AC voltage sampling signal, vAD1(1) is the resistance voltage division component of the A-phase AC voltage sampling signal, and vAD1(2) is the DC bias voltage component of the A-phase AC voltage sampling signal. The calculation methods of the B-phase AC voltage sampling signal and the C-phase AC voltage sampling signal are the same as those of the A-phase AC voltage sampling signal.

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