A three-phase rectifier circuit control method and a rectifier

Abstract

The application provides a three-phase rectifier circuit control method and a rectifier. The three-phase rectifier circuit control method comprises the following steps: determining a clamping phase and a non-clamping phase according to a current phase region; controlling the clamping phase to work in a clamping mode; controlling the non-clamping phase to work in a modulation switching mode, determining a continuous conduction time; determining a triangular conduction time; controlling the non-clamping phase to work in the continuous conduction mode or the triangular conduction mode according to the time comparison result of the continuous conduction time and the triangular conduction time; and cyclically executing the above steps until the end of a power frequency cycle. The application clamps the clamping phase, controls the working state of the non-clamping phase in the three-phase rectifier circuit according to the comparison result of the conduction time in the continuous conduction mode and the triangular conduction mode, and realizes hybrid modulation, thereby overcoming the problem of current sampling deviation of the modulation method based on DCM and simplifying the mode switching mode.

Description

Technical Field

[0001] This invention relates to the field of three-phase rectifier circuit control technology, and more particularly to a three-phase rectifier circuit control method and rectifier. Background Technology

[0002] Three-phase converters are one of the most widely used converter topologies. As the requirements for power converter efficiency and power density become increasingly stringent, soft-switching technology is widely adopted in three-phase converters.

[0003] Soft-switching modulation strategies typically employ auxiliary resonant networks or special pulse width modulation methods to enable power switching devices to switch on and off near the zero-crossing point of voltage or current, thereby significantly reducing switching losses. However, existing technologies generally achieve soft switching through mode mixing or modulation waveform adjustment based on discontinuous conduction mode (DCM). These methods involve complex control algorithms that rely on precise parameter presets or detection, resulting in low system stability. Furthermore, the discontinuous current waveforms used in mixing different modes contain significant harmonic components, leading to current sampling deviations and hindering the achievement of threshold-free, adaptive, and smooth switching.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a three-phase rectifier circuit control method and rectifier, thereby solving the problem that the current sampling of existing soft-switching modulation based on the discontinuous conduction mode strategy has deviations and cannot achieve threshold-free, adaptive smooth switching.

[0006] The technical solution of the present invention is as follows: This invention provides a three-phase rectifier circuit control method for controlling the operating states of the main tube and freewheeling tube in a three-phase rectifier circuit, the steps of which include: Obtain the current phase sector, and determine the clamped phase and non-clamped phase based on the current phase sector; The clamping phase is controlled to operate in clamping mode; The non-clamped phase is controlled to operate in modulation switching mode; the input voltage value, bus voltage and front sector switching cycle are acquired, and the continuous conduction time is determined using the bus voltage and the input voltage value; The triangular conduction time is determined based on the ratio of the reverse current conduction time, the main current conduction time, and the main pipe turn-on time. The continuous conduction time and the triangular conduction time are compared, and the non-clamping phase is controlled to switchably operate in either continuous conduction mode or triangular conduction mode based on the time comparison result; The above steps are repeated in the next phase sector until the power frequency cycle ends.

[0007] In a further embodiment of the present invention, the step of obtaining the current phase sector and determining the clamped phase and non-clamped phase based on the current phase sector includes: One power frequency cycle is divided into several phase sectors in terms of phase. Obtain the current phase angle, and obtain the current phase region sector based on the phase region sector entered by the current phase angle; In the current phase sector, one phase of the three-phase signal is determined to be the clamped phase based on the current phase angle, and the other two phases are the unclamped phases.

[0008] In a further embodiment of the present invention, the step of controlling the clamping phase to operate in clamping mode includes: Read the target clamping phase information in the three-phase rectifier circuit, and output a clamping control signal to the clamping phase according to the target clamping phase information; The clamping phase clamps the bus voltage according to the clamping control signal, and the bus voltage clamping adopts either a positive clamping mode or a negative clamping mode.

[0009] A further provision of the present invention includes the step of comparing the continuous conduction time and the triangular conduction time, and controlling the non-clamped phase to switchably operate in either the continuous conduction mode or the triangular conduction mode based on the time comparison result. Set a target supervisor's timeframe; The continuous conduction time and the triangular conduction time are compared; When the triangular transmission time is greater than the continuous transmission time, the target master time is the triangular transmission time, and the triangular mode signal is output as the comparison result signal; When the continuous conduction time is greater than the triangular conduction time, the target master time is the continuous conduction time, and a continuous mode signal is output as the comparison result signal; The target switching cycle is calculated based on the target main control time, and a calculation control signal is obtained by converting the target switching cycle and the comparison result signal. The calculation control signal is used to control the non-clamped phase of the three-phase rectifier circuit to switch between continuous conduction mode and delta conduction mode.

[0010] A further provision of the present invention, after the step of determining the target master time as the continuous conduction time when the continuous conduction time is greater than the triangular conduction time and outputting a continuous mode signal as a comparison result signal, further includes: Set the maximum switching cycle; The target switching period is compared with the maximum switching period. When the target switching period is greater than the maximum switching period, the target switching period is the maximum switching period, and a continuous mode signal is output as the comparison result signal.

[0011] A further provision of the present invention includes controlling the non-clamped phase to operate in modulation switching mode; the steps of acquiring the input voltage value, bus voltage, and front sector switching cycle, and determining the continuous conduction time using the bus voltage and the input voltage value include: The duty cycle of the freewheeling diode is determined using the input voltage and the bus voltage. The continuous conduction time is calculated using the front sector switching cycle and the duty cycle of the freewheeling tube.

[0012] In a further embodiment of the present invention, in the step where the clamping phase clamps the bus voltage according to the clamping control signal, and the bus voltage clamping adopts a positive clamping mode or a negative clamping mode, the clamping phase operates in a discontinuous pulse width modulation mode.

[0013] A further provision of the present invention includes the step of calculating the minimum inductor release current using the bus voltage and the front sector switching cycle, and using the minimum inductor release current to calculate the reverse freewheeling conduction time. For the dead zone after the freewheeling diode is turned off, the minimum inductor release current is calculated using the input voltage value and the bus voltage. Based on the minimum inductor release current, calculate the minimum reverse freewheeling conduction time when the inductor current is reverse freewheeling, and the reverse freewheeling conduction time is greater than or equal to the minimum reverse freewheeling conduction time.

[0014] A further provision of the present invention includes the step of calculating the main freewheeling conduction time ratio using the input voltage value and the bus voltage when the main conductor and the freewheeling tube are at the critical switching point: When the main pipe is turned on, the voltage across the inductor during the main pipe conduction period is calculated based on the input voltage value and the bus voltage. When the freewheeling diode is turned on, the voltage across the inductor during the freewheeling diode conduction period is calculated based on the input voltage value and the bus voltage. The main freewheeling conduction time ratio is calculated using the voltage across the inductor during the main conduction period and the voltage across the inductor during the freewheeling conduction period.

[0015] Based on the same inventive concept, this invention provides a rectifier that, when operating, implements the three-phase rectifier circuit control method described above. The rectifier includes a three-phase rectifier circuit and a computational drive module; wherein... The AC terminal of the three-phase rectifier circuit is connected to an AC source signal, and the DC terminal of the three-phase rectifier circuit is connected to a DC source or a DC load. The three-phase rectifier circuit includes three bridge arm circuits for DC rectification of the AC source signal. The detection terminal of the calculation drive module is connected to the three-phase rectifier circuit. It is used to collect the input voltage value and bus voltage of the three-phase rectifier circuit in each current phase sector, read the predetermined front sector switching cycle, and control one bridge arm circuit as a clamping phase and control the other bridge arm circuits as non-clamping phases according to the current phase sector. It also calculates the continuous conduction time and delta conduction time for the bridge arm circuits of the non-clamping phases, and controls the non-clamping phases to switch between delta conduction mode and continuous conduction mode according to the comparison result of the continuous conduction time and the delta conduction time.

[0016] This invention provides a three-phase rectifier circuit control method and rectifier. The three-phase rectifier circuit control method is used to control the operating state of the main tube and freewheeling tube in a three-phase rectifier circuit. The steps include: acquiring the current phase sector; determining the clamping phase and non-clamping phase based on the current phase sector; controlling the clamping phase to operate in clamping mode; controlling the non-clamping phase to operate in modulation switching mode; acquiring the input voltage value, bus voltage, and front sector switching cycle; determining the continuous conduction time using the bus voltage and the input voltage value; calculating the minimum inductor release current using the bus voltage and the front sector switching cycle, the minimum inductor release current being used to calculate the reverse freewheeling conduction time; and in... When the main current and freewheeling diode are critically switching, the main freewheeling conduction time ratio is calculated using the input voltage and bus voltage; the average inductor current and the change in inductor current are obtained, and when the average inductor current is equal to half of the change in inductor current, the main current turn-on time is calculated using the input voltage and bus voltage; the delta conduction time is determined based on the reverse freewheeling conduction time, the main freewheeling conduction time ratio, and the main current turn-on time; the continuous conduction time and the delta conduction time are compared, and the non-clamped phase is controlled to switchably operate in either continuous conduction mode or delta conduction mode based on the time comparison result; the above steps are repeated in the next phase sector until the power frequency cycle ends. This invention clamps a clamped phase within each phase sector, compares the conduction times in continuous conduction mode and triangular conduction mode, and controls the operating state of the non-clamped phases in the three-phase rectifier circuit based on the comparison result. This achieves hybrid modulation of DPWM (Discontinued Pulse Width Modulation) - CCM (Continuous Conduction Mode) - TCM (Triangular Conduction Mode), overcoming the current sampling deviation problem inherent in DCM modulation methods. Simultaneously, it achieves threshold-free, adaptive, and smooth switching, simplifying sampling and mode switching methods. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the steps of the three-phase rectifier circuit control method in this invention.

[0019] Figure 2This is the circuit diagram of the three-phase rectifier circuit in this invention.

[0020] Figure 3 This is the operating waveform of the bridge arm circuit in the continuous conduction mode in this invention.

[0021] Figure 4 This is the working waveform of the bridge arm circuit in the present invention when it operates in the delta conduction mode.

[0022] Figure 5 This is a schematic diagram of the circuit operation state at the first moment when the three-phase rectifier circuit in the present invention is operating in delta conduction mode.

[0023] Figure 6 This is a schematic diagram of the circuit operation state at the second moment when the three-phase rectifier circuit in this invention is operating in delta conduction mode.

[0024] Figure 7 This is a schematic diagram of the circuit operation state at the third moment when the three-phase rectifier circuit in this invention is operating in delta conduction mode.

[0025] Figure 8 This is a schematic diagram of the circuit operation state at the fourth moment when the three-phase rectifier circuit in this invention is operating in delta conduction mode.

[0026] Figure 9 This is a schematic diagram of the modulation modes of each phase sector in a preferred embodiment of the present invention.

[0027] Figure 10 This is a schematic diagram of the operating frequencies of different modulation modes in some preferred embodiments of the present invention.

[0028] The markings in the attached diagram are: 100, bridge arm circuit. Detailed Implementation

[0029] This invention provides a three-phase rectifier circuit control method and rectifier. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0030] In the implementation methods and claims, unless otherwise specified in the text, the terms "a," "an," "the," and "the" may also include plural forms. If the embodiments of the present invention involve descriptions of "first," "second," etc., such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0031] It should be further understood that the term "comprising" as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, "connected" or "coupled" as used herein can include wireless connections or wireless coupling. The term "and / or" as used herein includes all or any unit and all combinations of one or more associated listed items.

[0032] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0033] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0034] The inventors discovered that the three-phase converter is one of the most widely used converter topologies. Many related control and modulation schemes exist for this topology, such as commonly used continuous modulation strategies like SPWM and third harmonic injection SVPWM, discontinuous modulation strategies like DPWM, and frequency conversion modulation strategies aimed at achieving soft switching. Existing modulation strategies can be broadly classified into hard-switching modulation strategies and soft-switching modulation strategies. Due to limitations in switching losses, hard-switching modulation strategies struggle to simultaneously achieve high frequency, high power density, and high efficiency. Soft-switching modulation strategies, on the other hand, generally suffer from problems such as an excessively wide switching frequency range and difficulties in analysis and design caused by three-phase coupling.

[0035] For example, some prior art provides a three-phase inverter discontinuous modulation method and system. The method includes adding a common-mode voltage to the original three-phase reference voltage to ensure that two bridge arms perform PWM operation during any switching cycle; switching the carrier phase of the PWM according to the phase of the modulation wave; and switching the modulation wave phase during the PWM stopping phase to make the output current waveform more consistent with the requirements for zero-voltage turn-on. In the three-phase reference voltage signal, at any given time, one phase voltage is not switching, resulting in no switching losses. Therefore, it is not necessary to consider whether the phase current crosses zero to ensure soft switching. Furthermore, during the period when the PWM is not operating, switching the triangular wave phase does not cause current distortion. The modulation method achieves soft switching by making the current cross zero during switching. This method uses a DPWM modulation strategy, changing the carrier phase of the two non-clamped phases to reverse the inductor current in the non-clamped state, thereby achieving zero-voltage turn-on for the main bridge arm. This invention can only achieve zero-voltage turn-on under specific load rates, and its impact on the efficiency improvement of the three-phase converter is limited. Furthermore, it increases the complexity of the wave generation stage in practical DSP digital control, resulting in larger inductor current ripple, which is detrimental to engineering practice. It also requires changing the carrier phase based on the phase of the DPWM modulated wave, further increasing the complexity of the wave generation stage in practical DSP digital control.

[0036] In another part of the prior art, the provided three-phase converter includes an AC terminal, three filter circuits, three bridge arm circuits, a capacitor module, a DC terminal, and a controller connected in sequence. The midpoint of the filter capacitor in the three filter circuits is electrically coupled to the midpoint of the DC capacitor in the capacitor module. Within one line voltage cycle of the AC source, the controller controls each bridge arm circuit to operate at least in a first mode and a second mode. In the first mode, the bridge arm circuit operates in a clamped state. In the second mode, the bridge arm circuit can switch between DCM and TCM states, limiting the switching frequency to below a preset frequency. It can be seen that this prior art uses a DPWM modulation strategy, achieving zero-voltage turn-on under all operating conditions by changing the control method of the non-clamped two phases, i.e., a hybrid control method combining TCM and DCM. This technical solution suffers from current sampling deviation under DCM, and only the TCM mode has practical value. However, in TCM mode, a preset threshold for the reverse inductor current is required to turn on the main bridge arm, which lacks practical engineering operability and is difficult to implement in practice. Precise control of the switching timing is required. The freewheeling diode of the bridge arm needs to be turned off at a preset current value, and the main current diode of the bridge arm needs to be turned on at a preset voltage value. In actual DSP digital control, the timing of the switching transistors is controlled based on the parasitic parameters of resonant voltage and current. This is only theoretically feasible and not practical in actual engineering.

[0037] Meanwhile, some existing technologies employ a three-phase converter circuit control method. This involves designating one phase of the three-phase converter circuit corresponding to the phase with the largest absolute value of the amplitude among the three-phase input voltages (a, b, and c) as the delta current control phase, and designating the other two phases as discontinuous current control phases. The first energy storage time, first freewheeling time, and first switching cycle are obtained using the first energy storage inductor voltage and the first freewheeling inductor voltage of the delta current control phase, to generate a first control signal for controlling the delta current control phase. The second energy storage time and second freewheeling time are obtained using the first switching cycle and each second characteristic parameter, respectively, to generate a second control signal for controlling the discontinuous current control phase. This method facilitates zero-voltage turn-on and / or valley voltage turn-on, improving efficiency and reducing costs. However, this technology uses a TCM-DCM hybrid control method. Under DCM control, the simultaneous turn-off time of the upper and lower transistors in the bridge arm is relatively long, i.e., the dead zone is large, which affects the inductor current ripple and input current THDI under DCM control, placing higher demands on the EMI circuitry. Furthermore, it requires precise control of the switching timing and strict control of the parasitic capacitance resonance timing of the bridge arm switching devices. In actual DSP digital control, controlling the timing of the switching transistors based on the parasitic parameters of resonant voltage and current is only theoretically feasible and not practical in actual engineering.

[0038] To address the problems existing in the prior art, the present invention provides a three-phase rectifier circuit control method and rectifier for controlling the working state of the main tube and freewheeling tube in the three-phase rectifier circuit.

[0039] To facilitate understanding, this invention first introduces the three-phase rectifier and its internal three-phase rectifier circuit. For example... Figure 2As shown, the present invention provides a rectifier. When the rectifier is working, it is used to implement the three-phase rectifier circuit control method of the present invention. The rectifier includes a three-phase rectifier circuit and a computing drive module (not shown in the figure). The AC terminal of the three-phase rectifier circuit is connected to an AC source signal, and the DC terminal of the three-phase rectifier circuit is connected to a DC source or a DC load. The DC source or DC load can be equivalent to an output load circuit, which includes a slave output capacitor Cp, a main output capacitor Cn, and an output resistor R2. The three-phase rectifier circuit includes three bridge arm circuits 100 for DC rectification of the AC source signal. The detection terminal of the calculation drive module is connected to the three-phase rectifier circuit and is used to acquire the input voltage value and bus voltage of the three-phase rectifier circuit in each current phase sector, read the predetermined front sector switching cycle, and control the signal of one bridge arm circuit 100 as the clamping phase according to the current phase sector, and control the signals of other bridge arm circuits 100 to work in the non-clamping phase. The module also calculates the continuous conduction time and the delta conduction time for the non-clamping phase bridge arm circuit 100, and controls the non-clamping phase to switch between delta conduction mode (TCM) and continuous conduction mode (CCM) according to the comparison result of the continuous conduction time and the delta conduction time.

[0040] In the three-phase rectifier circuit, taking phase a bridge arm circuit 100 as an example, phase a bridge arm circuit 100 is connected to an AC source signal Va, and includes: main conductor San, main parasitic capacitor Can, main diode Dan, freewheeling diode Sap, slave parasitic capacitor Cap, and slave diode Dap; wherein, the driving terminal of the main conductor San is connected to the calculation driving module, the first connection terminal of the main conductor San is shared with the first connection terminals of the main conductors of other bridge arm circuits 100, the second connection terminal of the main conductor San is connected to the AC source signal and is connected to the first connection terminal of the freewheeling diode Sap; the main parasitic capacitor Can... The cathode of the main diode Dan is connected to the first connection terminal of the main diode San; the other end of the main parasitic capacitor Can and the anode of the main diode Dan are connected to the second connection terminal of the main diode San; the control terminal of the freewheeling diode Sap is connected to the first freewheeling diode Sap driving terminal of the computing driving module, and the second connection terminal of the freewheeling diode Sap is grounded; one end of the slave parasitic capacitor Cap and the cathode of the slave diode Dap are connected to the first connection terminal of the freewheeling diode Sap; the other end of the slave parasitic capacitor Cap and the anode of the slave diode Dap are connected to the second connection terminal of the freewheeling diode Sap. It should be noted that the bridge arm circuit 100 structures of phases a, b, and c are preferably consistent, and will not be described further here.

[0041] like Figure 1 As shown, the steps of the three-phase rectifier circuit control method include: S100: Obtain the current phase sector, and determine the clamped phase and non-clamped phase based on the current phase sector; Specifically, the three-phase rectifier circuit includes three bridge arm circuits 100, which together form a three-phase bridge arm circuit 100 structure for rectification and filtering. In this step, the three-phase signal of the current phase sector includes clamped phases and non-clamped phases; on each bridge arm circuit 100, the current phase sector is pre-determined based on the phase of the input voltage. If any two phases of the three-phase signal differ by 120°, then several sectors are divided for the entire power frequency cycle of the three-phase signal. For ease of explanation, each phase of the three-phase signal input is described independently in this step. Therefore, in each current phase sector, each phase of the three-phase signal can be divided into one of a clamped phase and a non-clamped phase. The clamped phase and the non-clamped phase are pre-determined based on the current phase sector at the current time.

[0042] S200: Control the clamping phase to operate in clamping mode; After determining the clamped phase and non-clamped phase in the current phase sector, the clamped phase is controlled to operate in clamping mode, and the non-clamped phase is controlled to operate in modulation switching mode. For the clamped phase, the main tube and freewheeling diodes and other switches on the bridge arm circuit 100 where it is located remain in a fixed state and do not operate. In some preferred embodiments, the duration for which the phase signal of each corresponding bridge arm circuit 100 operates in the clamping mode can be one-third or two-thirds of the power frequency cycle, and its value can be predetermined, which will not be elaborated here.

[0043] S300: Control the non-clamped phase to operate in modulation switching mode, acquire the input voltage value, bus voltage and front sector switching cycle; use the bus voltage and the input voltage value of the corresponding non-clamped phase to determine the continuous conduction time; The other two non-clamped phases in the current phase sector are operating in modulation switching mode. For each non-clamped phase, the input voltage value, bus voltage, and previous sector switching cycle are acquired. The previous sector switching cycle refers to the switching cycle of the corresponding bridge arm circuit 100 in the previous phase sector, which can be obtained by recording the cycle result of the previous phase sector. The continuous conduction time can be obtained using the bus voltage and the input voltage value of the corresponding non-clamped phase, or it can be obtained by reading the operating parameters from the previous phase sector. The continuous conduction time is used to characterize the turn-on time of the main pipe on the corresponding bridge arm circuit 100 when the non-clamped phase is operating in Continuous Conduction Mode (CCM).

[0044] S500. Determine the triangular conduction time based on the reverse current conduction time, the main current conduction time ratio, and the main pipe turn-on time. Correspondingly, the delta conduction time of the non-clamped phase is calculated. The delta conduction time can be calculated using the bus voltage and the input voltage value of the corresponding non-clamped phase, or it can be obtained by reading the operating parameters from the previous phase sector. The delta conduction time is used to characterize the turn-on time of the main pipe on the corresponding bridge arm circuit 100 when the non-clamped phase is working in delta conduction mode TCM.

[0045] S600. Compare the continuous conduction time and the triangular conduction time, and control the non-clamping phase to switchably operate in either the continuous conduction mode or the triangular conduction mode based on the time comparison result. In the modulation switching mode, the non-clamping phase can switchably operate in either Continuous Conducting Mode (CCM) or Triangular Conducting Mode (TCM). For example, under light or low load conditions, when the input current crosses zero, the non-clamping phase can be pre-set to operate in Continuous Conducting Mode (CCM), at which point the main conductor naturally operates in zero-voltage turn-on mode. To reduce input inductor current ripple, the frequency of the PFC switching device is limited to a maximum preset frequency fmax, such as... Figure 10 As shown. Simultaneously, when the load increases, it can automatically switch to delta conduction mode (TCM) by comparing the continuous conduction time and the delta conduction time. This facilitates zero-voltage turn-on of the switching transistors in the corresponding non-clamped bridge arm circuit 100, thereby allowing the switching frequency of the three-phase converter to naturally transition to the minimum preset frequency fmin under heavy loads. Figure 10 As shown.

[0046] S700, The above steps are repeated in the next phase sector until the power frequency cycle ends.

[0047] In the next phase sector, step S100 is executed to redetermine the clamping phase and the non-clamping phase, and the clamping phase is controlled until a complete power frequency cycle ends. It should be noted that the clamping phase and the non-clamping phase of each phase sector in each power frequency cycle are fixed according to the phase. Therefore, the above control method can be repeated in each power frequency cycle to achieve three-phase rectifier circuit control. This allows the bridge arm circuit 100 of the three-phase converter to switchably operate in clamping state, CCM (Continuous Conduction Modulation) state, and TCM (Triangular Current Modulation) state, enabling each bridge arm circuit 100 to achieve zero-voltage turn-on while limiting the frequency range of the frequency converter modulation, thereby restricting the change in switching frequency to a relatively small range.

[0048] In some preferred embodiments, the step of obtaining the current phase sector and determining the clamped phase and non-clamped phase based on the current phase sector includes: S110. Divide one power frequency cycle into several phase sectors in terms of phase. S120. Obtain the current phase angle, and obtain the current phase region sector based on the phase region sector entered by the current phase angle; S130. In the current phase sector, one phase of the three-phase signal is determined to be the clamped phase and the other two phases are the non-clamped phases based on the current phase angle.

[0049] Specifically, taking any one phase signal of the three-phase signal as an example, the current phase angle is the phase of the phase signal at the current moment. Based on the current phase angle, it can be determined which phase sector it is located in among all phase sectors. Preferably, the number of phase sectors is greater than or equal to six, and they can preferably be divided into as many phase sectors as possible with equal phase ranges. The pre-set clamping phase and non-clamping phase between adjacent sectors can be the same or different.

[0050] Furthermore, the step of controlling the clamping phase to operate in clamping mode includes: S210. Read the target clamping phase information in the three-phase rectifier circuit, and output a clamping control signal to the clamping phase according to the target clamping phase information; S220, The clamping phase clamps the bus voltage according to the clamping control signal, and the bus voltage clamping adopts a positive clamping mode or a negative clamping mode.

[0051] In traditional sinusoidal pulse width modulation (PWM), the three-phase modulation waves are sine waves with a 120° phase difference, and the three bridge arms switch at high frequency simultaneously. In this preferred embodiment, the clamping phase operates in clamping mode, optionally in discontinuous pulse width modulation (DPWM). To reduce switching losses, DPWM adds a predetermined zero-sequence component to the three-phase modulation waves, forcing the modulation wave of a certain phase to become +1 or -1, achieving positive and negative clamping modes. This ensures that the switch of that phase remains fixed within a power frequency sector, while only the other two phases switch frequencies. The target clamping phase information in this invention records the phase range contained in each sector and the target operating mode of each phase signal within that sector, thereby enabling control of the modulation mode of each phase of the three-phase signal based on the target clamping phase information. In a preferred embodiment, this scheme clamps one phase to the bus within every 60° sector according to a predetermined phase; this phase signal is the clamping phase. Therefore, for each sector: In the first sector,

[0052]

[0053] In the second sector,

[0054]

[0055] In the third sector,

[0056]

[0057] In the fourth sector,

[0058]

[0059] In the fifth sector,

[0060]

[0061] In the sixth sector,

[0062]

[0063] Among them, u a u b u c The original sinusoidal modulated wave of phases a, b, and c without clamping, u nbus For negative bus level, u pbus This is the positive bus level.

[0064] In the specific implementation, based on the current phase angle θ obtained by the phase-locked loop (PLL), which is the grid voltage phase angle, the 360° power frequency cycle is divided into six 60° phase sectors. In each sector, different zero-sequence components are superimposed, allowing each phase signal to be set to two states: clamped phase and non-clamped phase. The number of phase sector sectors can be equal to or an integer multiple of the number of sectors. Based on the current phase angle θ, the corresponding current phase sector sector can be determined. Simultaneously, macroscopically, the corresponding operating sector can be obtained, allowing identification of which phase acts as the clamped phase. For example, taking the first sector as an example, phase B's lower transistor is normally on, and its upper transistor is normally off, clamping it to the negative bus level. No switching action occurs in the first sector; therefore, phase B operates as the clamped phase. The final modulation waves of phases A and C can switch between continuous conduction mode (CCM) and triangular conduction mode (TCM) based on the time comparison between the continuous conduction time and the triangular conduction time. This demonstrates that it achieves DPWM-CCM-TCM hybrid modulation as a non-clamping phase. Furthermore, because the modulation wave is continuous at the sector boundaries, this invention does not cause current distortion in the three-phase rectifier circuit.

[0065] The steps of controlling the non-clamped phase to operate in modulation switching mode and acquiring the input voltage value, bus voltage, and front sector switching cycle, and determining the continuous conduction time using the bus voltage and the input voltage value include: S310. Determine the duty cycle of the freewheeling diode using the input voltage value and the bus voltage. S320. The continuous conduction time is calculated using the front sector switching cycle and the duty cycle of the freewheeling tube.

[0066] For ease of understanding, this invention uses the positive half-cycle of phase A as an example. In a portion of the phase sector during the positive half-cycle of phase A, phase A is a non-clamped phase. Specifically, for phase A, in continuous conduction mode (CCM), the inductor current is always greater than zero and will not be discontinuous or reversed. At this time, for each switching cycle, the energy stored in the inductor during the main conductor's conduction period is equal to the energy released by the inductor during the freewheeling diode's conduction period. Since the inductor current is continuous and the ripple is relatively small, the influence of the dead time on the average voltage can be ignored; therefore, the duty cycle is directly determined by the input voltage and the bus voltage. The input voltage and bus voltage can be obtained through real-time sampling by an analog-to-digital converter, or by reading pre-stored preset values, or other methods. For one non-clamped phase and its corresponding main conductor and freewheeling diode on the bridge arm circuit 100, in continuous conduction mode (CCM), the duty cycle of the main conductor is:

[0067] Among them, V in The input voltage value, V bus This refers to the bus voltage. It can be understood without question as, ignoring the dead zone, the main duty cycle D in one cycle. an and the duty cycle D of the freewheeling tube ap The sum is 1, therefore we have:

[0068] Based on the above two equations, the duty cycle of the freewheeling tube in the continuous conduction mode (CCM) can be obtained. Therefore, based on the calculated duty cycle D of the freewheeling tube ap By combining the current switching period Ts, the required on-time t of the freewheeling diode in CCM mode can be calculated. CCM :

[0069] It should be noted that the current switching period Ts is the switching period in the previous phase sector, that is, the current switching period Ts can be predetermined based on the current phase sector.

[0070] Furthermore, the steps for determining the triangular conduction time include: S410. The minimum inductor release current is calculated using the bus voltage and the front sector switching cycle. The minimum inductor release current is used to calculate the reverse freewheeling conduction time. The step of calculating the minimum inductor release current using the bus voltage and the front sector switching cycle, and using the minimum inductor release current to calculate the reverse freewheeling conduction time, includes: S411. For the dead zone after the freewheeling diode is turned off, the minimum inductor release current is calculated using the input voltage value and the bus voltage. S412. Based on the minimum inductor release current, calculate the minimum reverse freewheeling conduction time when the inductor current reverses, wherein the reverse freewheeling conduction time is greater than or equal to the minimum reverse freewheeling conduction time.

[0071] The three-phase rectifier circuit topology in this application is as follows: Figure 2 As shown, under actual operating conditions, during the positive half-cycle of phase A, Sap is the freewheeling diode, and San is the main switch. The freewheeling diode Sap is turned on at zero voltage, and the main switch San is a hard switch. Phases B and C are similar to phase A; therefore, the switching losses in the three-phase rectifier mainly exist in the main switch. If zero-voltage turn-on of the main switch is required, then during the dead time [t2, t3] after the freewheeling diode is turned off, the inductor current needs to discharge the parasitic capacitance of the main switch in reverse. For ease of explanation, phase C is used as an example. oss This refers to the parasitic capacitance value corresponding to any phase signal. It is assumed that the parasitic capacitance of all switching devices in the three-phase rectifier circuit is equal, i.e.: Cap = Can = Cbp = Cbn = Ccp = Ccn = C oss During the dead time, the inductor current completes the discharge of the parasitic capacitance voltage, then the minimum inductor release current I... L_min for:

[0072] Among them, t dead This represents the dead time. The inductor current needs the freewheeling diode to conduct for a certain period before reversing. Since the actual voltage across the inductor is equal to the induced electromotive force generated by the current change during the freewheeling diode's conduction period, we can obtain:

[0073] Where L is the inductance of the clamping circuit, t reverse_on Let be the reverse freewheeling conduction time. Combining the above formulas, we can obtain the minimum reverse freewheeling conduction time when the inductor current is reverse-flowing. This minimum reverse freewheeling conduction time is the minimum value that the reverse freewheeling conduction time can take, that is, for the reverse freewheeling conduction time:

[0074] S420. When the main tube is on and the freewheeling tube is on at the critical switching point, the ratio of the main freewheeling tube conduction time is calculated using the input voltage value and the bus voltage. A further provision of the present invention includes the step of calculating the main freewheeling conduction time ratio using the input voltage value and the bus voltage when the main conductor and the freewheeling tube are at the critical switching point: S421. When the main pipe is turned on, the voltage across the inductor during the main pipe conduction period is calculated based on the input voltage value and the bus voltage. S422. When the freewheeling diode is turned on, the voltage across the inductor during the freewheeling diode conduction period is calculated based on the input voltage value and the bus voltage. S423. Calculate the main freewheeling conduction time ratio using the voltage across the inductor during the main conduction period and the voltage across the inductor during the freewheeling conduction period.

[0075] S430. Obtain the average inductor current and the change in inductor current. When the average inductor current is equal to half of the change in inductor current, calculate the main pipe turn-on time using the input voltage value and the bus voltage. S440. The triangular conduction time is calculated based on the reverse current conduction time, the main current conduction time ratio, and the main pipe turn-on time.

[0076] Specifically, for the delta conduction mode (TCM), when the main conductor is turned on, the inductor current charges, preparing for the freewheeling phase. Therefore, the voltage across the inductor, VLAN, during the main conductor's conduction period is:

[0077] When the freewheeling diode is turned on, the inductor current discharges. Therefore, the voltage Vlap across the inductor during the freewheeling diode's conduction period is:

[0078] Combining the two formulas above, we can obtain the main freewheeling conduction time ratio:

[0079] Obtain the average inductor current I L and the change in inductor current ΔI L When the average inductor current equals the change in inductor current ΔI L At halfway point, the bridge arm circuit 100 of the non-clamped phase in the three-phase rectifier is in the critical current continuity stage, Δt an This represents the time variation during the period when the supervisor is on. This is due to the duration T when the supervisor is on. an If it remains unchanged, then the time change Δt during the conduction period of the main conductor is Δt. an With the predetermined supervisor activation time T anTo maintain consistency, the main pipe turn-on time is calculated using the input voltage value and the bus voltage. Therefore, at the critical continuity stage, we have:

[0080] The main control activation time under the critical continuous phase can then be calculated. It should be noted that the master switch-on time obtained here is the master switch-on time of the previous phase sector, that is, the master switch-on time of the previous moment. It can be calculated based on known parameters, or it can be predetermined or stored in any signal processing module or signal storage module. There are no restrictions here.

[0081] When the input voltage crosses zero, the duty cycle of the main tube and the freewheeling tube is 50%, and the conduction time of the freewheeling tube is greater than t. reverse_on During the critical continuity phase, because achieving zero-voltage turn-on in the triangular conduction mode (TCM) requires a certain amount of time for reverse current discharge to ensure complete discharge of parasitic capacitance within the dead zone, an additional conduction time is needed on top of the turn-on time. Therefore, the reverse freewheeling conduction time, the ratio of main freewheeling conduction time to the main conduction time, and the main conduction time t under critical continuity can be calculated. TCM The calculation formula between them is:

[0082] Further, the step of comparing the continuous conduction time and the triangular conduction time, and controlling the non-clamping phase to switchably operate in continuous conduction mode (CCM) or triangular conduction mode (TCM) based on the time comparison result includes: S510, Set a target supervisor's timeframe; S520. Compare the continuous conduction time and the triangular conduction time; S530. When the triangular transmission time is greater than the continuous transmission time, the target master time is the triangular transmission time, and the triangular mode signal is output as the comparison result signal. S540. When the continuous conduction time is greater than the triangular conduction time, the target master time is the continuous conduction time, and a continuous mode signal is output as a comparison result signal. S550. The target switching period is calculated based on the target main control time, and a calculation control signal is obtained by converting the target switching period and the comparison result signal. The calculation control signal is used to control the non-clamped phase of the three-phase rectifier circuit to switch between continuous conduction mode (CCM) and delta conduction mode (TCM).

[0083] Specifically, the continuous conduction time and the triangular conduction time are compared, and the larger of the two is taken as the target master time T. ap_on :

[0084] The target supervisor time T ap_on The target master time T is the conduction time length of the master master in the current phase sector. ap_on Used to calculate and adjust the target switching period t at the current moment. s .

[0085]

[0086] Among them, T an_on Let T be the conduction time of the freewheeling tube in the current phase region sector. Optionally, the conduction time of the freewheeling tube remains constant within a predetermined time period, therefore T an_on With T an If the values ​​are consistent, then the conduction time T of the freewheeling tube in the current phase region can be determined. an_on and dead zone time t dead It is predetermined, thus the target switching period t is visible. s Size and target supervisor time T ap_on The magnitudes are linearly related.

[0087] Optionally, when operating under low load, the clamping phase operates in continuous conduction mode (CCM) and switches modulation when it reaches the critical continuous current stage as the current value changes. When the triangular conduction time is greater than the continuous conduction time, the target master time is the triangular conduction time, and a triangular mode signal is output as a comparison result signal. The comparison result signal can be output to any computing device or driving device to achieve mode switching. The system enters triangular conduction mode (TCM) based on the comparison result signal and the target. Correspondingly, when the continuous conduction time is greater than the triangular conduction time, the target master time is the continuous conduction time, and a continuous mode signal is output as a comparison result signal. In this case, continuous conduction mode (CCM) is maintained in the current phase sector, and detection is performed again in the next phase sector. Thus, this invention controls the non-clamping phase to switch between triangular conduction mode (TCM) and continuous conduction mode (CCM) based on the comparison result of continuous conduction time and triangular conduction time, realizing DPWM-CCM-TCM hybrid modulation.

[0088] Furthermore, when the three-phase rectifier circuit is operating, as the output load increases, the target main control time T... ap_on The corresponding increase, while the conduction time of the freewheeling diode in the current phase region remains unchanged, leads to a change in the target switching period t. sIncreasing the switching frequency during the operation of the triangular conduction mode TCM results in a sharp decrease in the switching frequency, leading to an excessively wide switching frequency range. This causes significant inductor current ripple during circuit operation, increases the risk of magnetic component saturation, and increases audio noise during operation. Therefore, to address the problem of increased ripple due to an excessively wide switching frequency range in existing soft-switching modulation strategies, in a further embodiment of this invention, after the step of setting the target master time as the continuous conduction time when the continuous conduction time is greater than the triangular conduction time and outputting a continuous mode signal as the comparison result signal, the invention further includes: S560, Set the maximum switching cycle; S570. Compare the target switching period with the maximum switching period. When the target switching period is greater than the maximum switching period, the target switching period adopts the maximum switching period, and a continuous mode signal is output as the comparison result signal.

[0089] Specifically, the purpose of a three-phase rectifier circuit is to keep the input AC current and input voltage in phase. Taking phase A as an example, when the input current crosses zero, it operates in continuous conduction mode (CCM), and the main pipe naturally operates at zero-voltage turn-on. To reduce the input inductor current ripple, the frequency of the switching devices is limited to fmax at this time, such as... Figure 3 As shown.

[0090] Similarly, when the load increases, such as Figure 4 As shown, the inductor current will change from continuous conduction mode (CCM) to delta conduction mode (TCM). At this time, the main conductor's on-time remains constant, while the freewheeling transistor's on-time is increased. When the inductor current reverses direction, the freewheeling transistor is turned off for a predetermined time, and then the main conductor is turned on again at the next moment, thus achieving zero-voltage turn-on. Figures 5 to 8 As shown. This process leads to a longer switching cycle, indirectly causing a decrease in the switching frequency. When the switching frequency approaches the predetermined minimum preset frequency fmin, the same phase circuit may sequentially exhibit three operating conditions: Continuous Conductive Mode (CCM), Triangular Conductive Mode (TCM), and Clamping Mode (DPWM), as shown. Figure 9 and Figure 10 As shown, it is specifically as described in the previous section on DPWM-CCM-TCM hybrid modulation.

[0091] As the load continues to increase, the target switching period t s To further increase this, the target switching period t will be... s Compared with the predetermined maximum switching period, if the target switching period is greater than or equal to the maximum switching period, it proves that the switching frequency has reached the minimum preset frequency fmin under the existing load. In this case, the target switching period t is limited. sThe maximum value is set to a predetermined maximum switching cycle, which limits the switching frequency to the minimum value fmin. This maintains the maximum freewheeling diode conduction time, preventing the inductor current from building sufficient reverse current, thus switching back to Continuous Conductive Mode (CCM). In other words, on a non-clamped phase, as the load increases, it can switch back to Continuous Conductive Mode (CCM) when the target switching cycle after entering Triangular Conductive Mode (TCM) is greater than or equal to the maximum switching cycle, limiting the frequency range of the frequency converter modulation. This restricts the change in switching frequency to a small range until it is clamped into Clamped Mode (DPWM) at another moment when it transforms into a clamped phase, thereby locking the minimum frequency at a preset value and avoiding ripple and audio noise caused by excessively low frequencies under heavy loads.

[0092] This invention provides a three-phase rectifier circuit control method and rectifier. The three-phase rectifier circuit control method is used to control the operating state of the main tube and freewheeling tube in a three-phase rectifier circuit. The steps include: acquiring the current phase sector; determining the clamping phase and non-clamping phase based on the current phase sector; controlling the clamping phase to operate in clamping mode; controlling the non-clamping phase to operate in modulation switching mode; acquiring the input voltage value, bus voltage, and front sector switching cycle; determining the continuous conduction time using the bus voltage and the input voltage value; calculating the minimum inductor release current using the bus voltage and the front sector switching cycle, the minimum inductor release current being used to calculate the reverse freewheeling conduction time; and in... When the main current and freewheeling diode are critically switching, the main freewheeling conduction time ratio is calculated using the input voltage and bus voltage. The average inductor current and its change are obtained. When the average inductor current equals half the change in inductor current, the main current turn-on time is calculated using the input voltage and bus voltage. The delta conduction time is determined based on the reverse freewheeling conduction time, the main freewheeling conduction time ratio, and the main current turn-on time. The continuous conduction time and the delta conduction time are compared, and the non-clamped phase is controlled to switchably operate in either continuous conduction mode or delta conduction mode based on the comparison result. The above steps are repeated in the next phase sector until the power frequency cycle ends. This invention clamps a clamped phase in each phase sector, compares the conduction times in continuous conduction mode and delta conduction mode, and controls the operating state of the non-clamped phase in the three-phase rectifier circuit based on the comparison result to achieve DPWM-CCM-TCM hybrid modulation, overcoming the current sampling deviation problem in DCM-based modulation methods. It also achieves threshold-free, adaptive, and smooth switching, simplifying sampling and mode switching methods.

[0093] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A three-phase rectifier circuit control method for controlling the operating state of the main tube and freewheeling tube in a three-phase rectifier circuit, characterized in that the steps include... include: Obtain the current phase sector, and determine the clamped phase and non-clamped phase based on the current phase sector; The clamping phase is controlled to operate in clamping mode; The non-clamped phase is controlled to operate in modulation switching mode; the input voltage value, bus voltage and front sector switching cycle are acquired, and the continuous conduction time is determined using the bus voltage and the input voltage value; The minimum inductor release current is calculated using the bus voltage and the front sector switching cycle, and the minimum inductor release current is used to calculate the reverse freewheeling conduction time. When the main tube and freewheeling tube are at the critical switching point, the ratio of the main freewheeling tube conduction time is calculated using the input voltage value and the bus voltage. The average inductor current and the change in inductor current are obtained. When the average inductor current is equal to half of the change in inductor current, the main pipe turn-on time is calculated using the input voltage value and the bus voltage. The triangular conduction time is determined based on the ratio of the reverse current conduction time, the main current conduction time, and the main pipe turn-on time. The continuous conduction time and the triangular conduction time are compared, and the non-clamping phase is controlled to switchably operate in either continuous conduction mode or triangular conduction mode based on the time comparison result; The above steps are repeated in the next phase sector until the power frequency cycle ends.

2. The three-phase rectifier circuit control method according to claim 1, characterized in that, The step of obtaining the current phase sector and determining the clamped and non-clamped phases based on the current phase sector includes: One power frequency cycle is divided into several phase sectors in terms of phase. Obtain the current phase angle, and obtain the current phase region sector based on the phase region sector entered by the current phase angle; In the current phase sector, one phase of the three-phase signal is determined to be the clamped phase based on the current phase angle, and the other two phases are the unclamped phases.

3. The three-phase rectifier circuit control method according to claim 1, characterized in that, The step of controlling the clamping phase to operate in clamping mode includes: Read the target clamping phase information in the three-phase rectifier circuit, and output a clamping control signal to the clamping phase according to the target clamping phase information; The clamping phase clamps the bus voltage according to the clamping control signal, and the bus voltage clamping adopts either a positive clamping mode or a negative clamping mode.

4. The three-phase rectifier circuit control method according to claim 1, characterized in that, The step of comparing the continuous conduction time and the triangular conduction time, and controlling the non-clamped phase to switchably operate in either continuous conduction mode or triangular conduction mode based on the time comparison result, includes: Set a target supervisor's timeframe; The continuous conduction time and the triangular conduction time are compared; When the triangular transmission time is greater than the continuous transmission time, the target master time is the triangular transmission time, and the triangular mode signal is output as the comparison result signal; When the continuous conduction time is greater than the triangular conduction time, the target master time is the continuous conduction time, and a continuous mode signal is output as the comparison result signal; The target switching cycle is calculated based on the target main control time, and a calculation control signal is obtained by converting the target switching cycle and the comparison result signal. The calculation control signal is used to control the non-clamped phase of the three-phase rectifier circuit to switch between continuous conduction mode and delta conduction mode.

5. The three-phase rectifier circuit control method according to claim 4, characterized in that, After the step of determining the target master time as the continuous conduction time when the continuous conduction time is greater than the triangular conduction time, and outputting a continuous mode signal as the comparison result signal, the method further includes: Set the maximum switching cycle; The target switching period is compared with the maximum switching period. When the target switching period is greater than the maximum switching period, the target switching period is the maximum switching period, and a continuous mode signal is output as the comparison result signal.

6. The three-phase rectifier circuit control method according to claim 1, characterized in that, The steps of controlling the non-clamped phase to operate in modulation switching mode and acquiring the input voltage value, bus voltage, and front sector switching cycle, and determining the continuous conduction time using the bus voltage and the input voltage value include: The duty cycle of the freewheeling diode is determined using the input voltage and the bus voltage. The continuous conduction time is calculated using the front sector switching cycle and the duty cycle of the freewheeling tube.

7. The three-phase rectifier circuit control method according to claim 3, characterized in that, In the step of clamping the bus voltage according to the clamping control signal, and the bus voltage clamping adopts a positive clamping mode or a negative clamping mode, the clamping phase operates in a discontinuous pulse width modulation mode.

8. The three-phase rectifier circuit control method according to claim 1, characterized in that, The step of calculating the minimum inductor release current using the bus voltage and the front sector switching cycle, and using the minimum inductor release current to calculate the reverse freewheeling conduction time, includes: For the dead zone after the freewheeling diode is turned off, the minimum inductor release current is calculated using the input voltage value and the bus voltage. Based on the minimum inductor release current, calculate the minimum reverse freewheeling conduction time when the inductor current is reverse freewheeling, and the reverse freewheeling conduction time is greater than or equal to the minimum reverse freewheeling conduction time.

9. The three-phase rectifier circuit control method according to claim 1, characterized in that, The step of calculating the main freewheeling conduction time ratio using the input voltage value and bus voltage when the main conductor and freewheeling tube are critically switching includes: When the main pipe is turned on, the voltage across the inductor during the main pipe conduction period is calculated based on the input voltage value and the bus voltage. When the freewheeling diode is turned on, the voltage across the inductor during the freewheeling diode conduction period is calculated based on the input voltage value and the bus voltage. The main freewheeling conduction time ratio is calculated using the voltage across the inductor during the main conduction period and the voltage across the inductor during the freewheeling conduction period.

10. A rectifier, characterized in that, When the rectifier is in operation, it is used to implement the three-phase rectifier circuit control method as described in any one of claims 1 to 9, wherein the rectifier includes a three-phase rectifier circuit and a computing drive module; wherein... The AC terminal of the three-phase rectifier circuit is connected to an AC source signal, and the DC terminal of the three-phase rectifier circuit is connected to a DC source or a DC load. The three-phase rectifier circuit includes three bridge arm circuits for DC rectification of the AC source signal. The detection terminal of the calculation drive module is connected to the three-phase rectifier circuit. It is used to collect the input voltage value and bus voltage of the three-phase rectifier circuit in each current phase sector, read the predetermined front sector switching cycle, and control one bridge arm circuit as a clamping phase and control the other bridge arm circuits as non-clamping phases according to the current phase sector. It also calculates the continuous conduction time and delta conduction time for the bridge arm circuits of the non-clamping phases, and controls the non-clamping phases to switch between delta conduction mode and continuous conduction mode according to the comparison result of the continuous conduction time and the delta conduction time.

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