A main circuit topology and soft-start control method for a three-phase VIENNA rectifier

Abstract

This invention discloses a main circuit topology and soft-start control method for a three-phase VIENNA rectifier. The main circuit topology includes an EMI circuit, two current-limiting resistors, two relays or switches, three filter inductors, six power diodes, six power switching transistors, and a filter capacitor. The soft-start control method consists of three stages: the first stage involves uncontrolled rectification with series current-limiting resistors to pre-charge the bus voltage; the second stage involves PWM rectification at a fixed slope to continue charging the bus voltage and smoothly disconnecting the current-limiting resistors; the third stage involves PWM rectification at a fixed slope to charge the bus voltage to its default value. By employing measures such as smooth disconnection of the current-limiting resistors and stable transition of the control process, dynamic stability can be achieved throughout the soft-start process, avoiding the inrush current caused by the disconnection of the current-limiting resistors and the inrush current caused by excessive control deviation during the control process, thus effectively suppressing the starting inrush current.

Description

Technical Field

[0001] This invention relates to a three-phase three-level VIENNA rectifier, and more particularly to a main circuit topology and soft-start control method for a three-phase VIENNA rectifier. Background Technology

[0002] The three-phase three-level VIENNA rectifier can actively mitigate harmonic pollution in the power grid, improve power quality, and achieve power factor correction. It boasts advantages such as high power factor, low input current harmonic content, low switching stress, no need for dead-time settings, and fewer switching devices, making it suitable for high-power applications. Therefore, the three-phase three-level VIENNA rectifier has attracted widespread attention from scholars both domestically and internationally and has been applied in fields such as aviation power supplies, electric vehicle chargers, wind power generation, and uninterruptible power supplies (UPS).

[0003] However, rectifiers suffer from excessive inrush current during startup. A traditional solution is to insert a current-limiting resistor in series with the rectifier's main topology to pre-charge the DC bus capacitor using uncontrolled diode rectification. However, after pre-charging, the presence of the current-limiting resistor voltage causes an inrush current during resistor removal. Simultaneously, a significant deviation exists between the bus voltage setpoint and the feedback value after uncontrolled rectification, resulting in inrush current during the transition from uncontrolled rectification to PWM rectification.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a main circuit topology and soft-start control method for a three-phase VIENNA rectifier to solve the aforementioned technical problems in the prior art.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] The main circuit topology of the three-phase VIENNA rectifier of the present invention includes an EMI circuit. The input terminal of the EMI circuit is connected to a three-phase AC power supply, and the output terminal is connected to a three-phase filter inductor. A current-limiting resistor is connected in series in front of two phase filter inductors, and a relay or switch is connected in parallel with the current-limiting resistor.

[0008] The rear end of the three-phase filter inductor is connected to the midpoint of one arm of a bridge consisting of six power diodes.

[0009] The two power switching transistors are connected in anti-series common source, with one end connected to the midpoint of a bridge arm and the other end connected to the midpoint O of the two DC-side capacitors C0.

[0010] The DC output terminal is connected to an equivalent resistance R. O .

[0011] The soft-start control method for the main circuit topology of the three-phase VIENNA rectifier described above consists of three stages:

[0012] The first stage involves pre-charging the bus voltage using an uncontrolled rectifier connected in series with a current-limiting resistor.

[0013] The second stage of PWM rectification continues to charge the bus voltage at a fixed slope and smoothly removes the current-limiting resistor;

[0014] The third stage of PWM rectification charges the bus voltage to the default value at a fixed slope.

[0015] Compared with the prior art, the main circuit topology and soft-start control method of the three-phase VIENNA rectifier provided by the present invention adopts measures such as smooth removal of current-limiting resistors and smooth transition of control process, which can achieve dynamic stability throughout the soft-start process, avoid the inrush current caused by the removal of current-limiting resistors and the inrush current caused by excessive control deviation during the control process, effectively suppress the starting inrush current, and solve the inrush current problem in the process of removing current-limiting resistors and control transition. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the main circuit principle of an embodiment of the present invention;

[0017] Figure 2 The voltage given in this embodiment of the invention corresponds to the ramp signal;

[0018] Figure 3 This is a flowchart of a soft-start control method according to an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them, and do not constitute a limitation on the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0020] First, the following explanations are provided for the terms that may be used in this article:

[0021] The term "and / or" means that either or both can be achieved simultaneously. For example, X and / or Y means that it includes both "X" or "Y" as well as the three cases of "X and Y".

[0022] The terms “including,” “comprising,” “containing,” “having,” or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, “including a technical feature element (such as raw material, component, ingredient, carrier, dosage form, material, size, part, component, mechanism, device, step, process, method, reaction conditions, processing conditions, parameter, algorithm, signal, data, product or article of manufacture, etc.)” should be interpreted as including not only the expressly listed technical feature element, but also other technical feature elements that are not expressly listed and are well-known in the art.

[0023] The term "composed of" excludes any technical features not expressly listed. When used in a claim, it closes the claim to exclude all technical features other than those expressly listed, except for associated conventional impurities. If the term appears only in a clause of a claim, it limits the claim to the elements expressly listed in that clause; elements recited in other clauses are not excluded from the overall claim.

[0024] Unless otherwise explicitly specified or limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this document according to the specific circumstances.

[0025] The terms “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” and “counterclockwise” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience and simplification of description and do not imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this document.

[0026] The contents not described in detail in the embodiments of this invention are prior art known to those skilled in the art. Where specific conditions are not specified in the embodiments of this invention, they shall be performed according to conventional conditions in the art or conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments used in the embodiments of this invention are not specified, they are all conventional products that can be purchased commercially.

[0027] The main circuit topology of the three-phase VIENNA rectifier of the present invention includes an EMI circuit. The input terminal of the EMI circuit is connected to a three-phase AC power supply, and the output terminal is connected to a three-phase filter inductor. A current-limiting resistor is connected in series in front of two phase filter inductors, and a relay or switch is connected in parallel with the current-limiting resistor.

[0028] The rear end of the three-phase filter inductor is connected to the midpoint of one arm of a bridge consisting of six power diodes.

[0029] The two power switching transistors are connected in anti-series common source, with one end connected to the midpoint of a bridge arm and the other end connected to the midpoint O of the two DC-side capacitors C0.

[0030] The DC output terminal is connected to an equivalent resistance R. O .

[0031] The power diode is a power fast recovery diode or a power SiC diode, and the power switch is a MOSFET or an IGBT.

[0032] The soft-start control method for the main circuit topology of the three-phase VIENNA rectifier described above consists of three stages:

[0033] The first stage involves pre-charging the bus voltage using an uncontrolled rectifier connected in series with a current-limiting resistor.

[0034] The second stage of PWM rectification continues to charge the bus voltage at a fixed slope and smoothly removes the current-limiting resistor;

[0035] The third stage of PWM rectification charges the bus voltage to the default value at a fixed slope.

[0036] The charging control of the bus capacitor is based on the charging command signal of the three-section bus capacitor. The control method includes:

[0037] In the first stage, the DC bus capacitor is pre-charged using a current-limiting resistor. The AC input switch is closed, and the AC input power supply charges the DC bus capacitor using a full-bridge uncontrolled rectifier. The current-limiting resistor limits the inrush current at startup. Based on the circuit consisting of the grid voltage, current-limiting resistor, filter inductor, and bus capacitor, the pre-charge voltage or charging time is considered. This process continues until the DC bus voltage feedback value is U. fb1 The corresponding DC bus voltage setpoint is U ref1 The voltage across the current-limiting resistor is U. R ;

[0038] In the second stage, the DC bus capacitor continues to be charged using PWM rectification. When the DC bus voltage reaches the set value and the input current is relatively small, the current-limiting resistor is smoothly disconnected, and the system transitions from full-bridge uncontrolled rectification to PWM rectification. Simultaneously, the current-limiting resistor remains unchanged and is connected in series with the main circuit. This process continues until the final set value of the DC bus voltage is U. ref2 U ref2 ≈U ref1 +U R The DC bus voltage setpoint is set as a ramp signal that increases at a certain slope to the desired value. The DC bus capacitor continues to charge until the DC bus voltage reaches the desired value, i.e., the final DC bus voltage setpoint U. ref2 The corresponding DC bus voltage feedback value is U fb2 At this time, the control signal controls the closing of the relay or switch connected in parallel with the current-limiting resistor;

[0039] In the third stage, the DC bus capacitor continues to be linearly charged using PWM rectification until the DC bus voltage reaches the final given voltage value, i.e., the default value. During the PWM rectification process, the bus voltage increases smoothly and linearly until the final given value of the DC bus voltage is U. ref3 The DC bus voltage setpoint is set as a ramp signal that increases at a certain slope to the desired value. The DC bus capacitor continues to charge until the DC bus voltage reaches the desired value, i.e., the final DC bus voltage setpoint U. ref3 The corresponding DC bus voltage feedback value is U fb3 .

[0040] In summary, the main circuit topology and soft-start control method of the three-phase VIENNA rectifier in this embodiment of the invention, by adopting measures such as smooth removal of the current-limiting resistor and smooth transition of the control process, can achieve dynamic stability throughout the soft-start process, avoid the inrush current caused by the removal of the current-limiting resistor and the inrush current caused by excessive control deviation during the control process, effectively suppress the starting inrush current, and solve the inrush current problem in the process of removing the current-limiting resistor and the control transition process.

[0041] To more clearly demonstrate the technical solution and its effects provided by the present invention, the embodiments of the present invention will be described in detail below with reference to specific examples.

[0042] Example 1

[0043] A schematic diagram of the main circuit principle of a three-phase VIENNA rectifier is shown below. Figure 1 As shown, U, V, and W represent three-phase input AC power supplies, and R... rREL1 and REL2 represent current-limiting resistors connected in series, and are relays or switches; L represents a three-phase filter inductor used to suppress high-order harmonics; Co represents a DC bus filter capacitor used to effectively reduce DC voltage ripple; D Z1 ~D Z6 Indicates a power diode (power fast recovery diode or power SiC diode); S A1 and S A2 S B1 and S B2 S C1 and S C2 These are power switching transistors (MOSFETs or IGBTs), connected in anti-series common-source configurations in pairs. One end is connected to the midpoint of each bridge arm, and the other end is connected to the midpoint O of the DC-side capacitor. O The equivalent resistance on the DC side is used; an EMI filter circuit is added between the AC input and the filter inductor. The current-limiting resistor only needs to be connected in series in two phases of the AC input; it does not need to be connected in series in all three phases.

[0044] A soft-start control method for a three-phase VIENNA rectifier, such as Figure 2 As shown, the charging control of the bus capacitor is based on the charging command signal of the three-section bus capacitor. The flowchart of the control method is as follows. Figure 3 As shown.

[0045] In the first stage, the DC bus capacitor is pre-charged using a current-limiting resistor. The AC input switch is closed, and the AC input power supply charges the DC bus capacitor using a full-bridge uncontrolled rectifier. The current-limiting resistor limits the inrush current at startup. The pre-charge voltage or charging time is considered based on the circuit consisting of the grid voltage, current-limiting resistor, filter inductor, and bus capacitor. This process continues until the DC bus voltage feedback value is U. fb1 The corresponding DC bus voltage setpoint is U ref1 The voltage across the current-limiting resistor is U. R Meanwhile, the charging time for this process is t1. Due to the series current limiting, this process limits the inrush current at the moment of startup. With a fixed bus capacitance value, the charging time is directly proportional to the current limiting resistor. The larger the current limiting resistor, the smaller the inrush current but the slower the startup process; the smaller the current limiting resistor, the larger the inrush current but the faster the startup process.

[0046] In the second stage, the DC bus capacitor continues to be charged using PWM rectification. The current-limiting resistor is smoothly removed when the DC bus voltage reaches the set value and the input current is relatively small. The system then transitions from full-bridge uncontrolled rectification to PWM rectification, while maintaining the current-limiting resistor unchanged and connected in series with the main circuit. This process continues until the final set value of the DC bus voltage is U. ref2 U ref2≈U ref1 +U R The DC bus voltage setpoint is set as a ramp signal that increases at a certain slope to the desired value. The DC bus capacitor continues to charge until the DC bus voltage reaches the desired value, i.e., the final DC bus voltage setpoint U. ref2 The corresponding DC bus voltage feedback value is U fb2 At this time, the control signal closes the relay or switch connected in parallel with the current-limiting resistor. Since PWM control compensates for the DC bus voltage difference, the rate of current change during the removal of the current-limiting resistor is sufficiently small to avoid generating new inrush current, thus preventing a large voltage difference during the switching process and achieving smooth removal of the current-limiting resistor. Simultaneously, the charging time for this process is t2. Since the given voltage is from U... ref1 The voltage is gradually increased at a certain slope until the final given voltage value U is reached. ref2 This avoids the generation of new inrush currents.

[0047] In the third stage, the DC bus capacitor continues to be linearly charged using PWM rectification until the DC bus voltage reaches the final given voltage value, i.e., the default value. During the PWM rectification process, the bus voltage increases smoothly and linearly until the final given value of the DC bus voltage is U. ref3 The DC bus voltage setpoint is set as a ramp signal that increases at a certain slope to the desired value. The DC bus capacitor continues to charge until the DC bus voltage reaches the desired value, i.e., the final DC bus voltage setpoint U. ref3 The corresponding DC bus voltage feedback value is U fb3 Meanwhile, the charging time for this process is t3. Since the given voltage is from U... ref2 The voltage is gradually increased at a certain slope until the final given voltage value U is reached. ref3 This avoids the generation of new inrush currents.

[0048] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of the present invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. A soft-start control method for the main circuit topology of a three-phase VIENNA rectifier, characterized in that: The main circuit topology includes an EMI circuit. The input terminal of the EMI circuit is connected to a three-phase AC power supply, and the output terminal is connected to a three-phase filter inductor. A current-limiting resistor is connected in series in front of two phase filter inductors, and a relay or switch is connected in parallel with the current-limiting resistor. The rear end of the three-phase filter inductor is connected to the midpoint of one arm of a bridge consisting of six power diodes. The two power switching transistors are connected in anti-series common-source configuration, with one end connected to the midpoint of one bridge arm and the other end connected to the midpoint of the two DC-side capacitors C0. ; The DC output terminal is connected to an equivalent resistance. ; The power diode is a power fast recovery diode or a power SiC diode, and the power switch is a MOSFET or an IGBT. The soft-start control method described herein consists of three stages: The first stage involves pre-charging the bus voltage using an uncontrolled rectifier connected in series with a current-limiting resistor. The second stage of PWM rectification continues to charge the bus voltage at a fixed slope and smoothly removes the current-limiting resistor; The third stage of PWM rectification charges the bus voltage to the default value at a fixed slope. The charging control of the bus capacitor is based on the charging command signal of the three-section bus capacitor. The control method includes: In the first stage, the DC bus capacitor is pre-charged using a current-limiting resistor. The AC input switch is closed, and the AC input power supply charges the DC bus capacitor using a full-bridge uncontrolled rectifier. The current-limiting resistor limits the inrush current at startup. Based on the circuit consisting of the grid voltage, current-limiting resistor, filter inductor, and bus capacitor, the pre-charge voltage or charging time is considered. This process continues until the DC bus voltage feedback value is reached. The corresponding DC bus voltage setpoint is The voltage across the current-limiting resistor is ; In the second stage, the DC bus capacitor continues to be charged using PWM rectification. When the DC bus voltage reaches the set value and the input current is relatively small, the current-limiting resistor is smoothly disconnected, and the system transitions from full-bridge uncontrolled rectification to PWM rectification. Simultaneously, the current-limiting resistor remains unchanged and is connected in series with the main circuit. This process continues until the final set value of the DC bus voltage is reached. ,in The DC bus voltage setpoint is set as a ramp signal that increases at a certain slope to the desired value. The DC bus capacitor continues to charge until the DC bus voltage reaches the desired value, which is the final setpoint value. The corresponding DC bus voltage feedback value is At this time, the control signal controls the closing of the relay or switch connected in parallel with the current-limiting resistor; In the third stage, the DC bus capacitor continues to be linearly charged using PWM rectification until the DC bus voltage reaches the final given voltage value, i.e., the default value. During the PWM rectification process, the bus voltage increases steadily and linearly until the final given DC bus voltage value is reached. The DC bus voltage setpoint is set as a ramp signal that increases at a certain slope to the desired value. The DC bus capacitor continues to charge until the DC bus voltage reaches the desired value, which is the final setpoint value. The corresponding DC bus voltage feedback value is .

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