Rectifier based on bridgeless ac-dc auxiliary converter and control method

Abstract

The application belongs to the technical field of electric power, and proposes a rectifier based on a bridgeless AC-DC auxiliary converter and a control method. In the application, the rectifier is composed of a main power converter and a bridgeless AC-DC auxiliary converter, and the two are connected in parallel and operate in parallel. The main power converter adopts a thyristor rectifier to provide main power support for an electrolysis stack. The bridgeless AC-DC auxiliary converter includes low-pass filters, IGBTs, high-frequency transformers, diode rectifiers and other elements. A control unit and a driving unit are responsible for controlling the operation of the rectifier. Through the control algorithm of the sampling circuit and the central processing unit, the output current and the input current of the rectifier can be accurately controlled and compensated, thereby reducing the content of ripples and harmonics in the rectifier. The rectifier and the control method proposed in the application can make the grid-side current distortion small.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a rectifier and control method based on a bridgeless AC-DC auxiliary converter. Background Technology

[0002] Hydrogen, as a potential future energy source, boasts advantages such as cleanliness, high energy density, and high conversion efficiency. Hydrogen electrolysis is a new energy technology that can efficiently absorb fluctuating renewable energy sources, achieve zero carbon emissions, and reduce grid interference. However, the AC bus structure used in hydrogen electrolysis systems requires AC / DC converters to transform energy into a form suitable for the hydrogen electrolysis load. Power supply quality is crucial to the hydrogen production efficiency of the electrolysis stack.

[0003] Recent studies have investigated the impact of converter output current quality on the efficiency of hydrogen electrolysis. The results show that the hydrogen production rate depends on the average supply current, but current ripple causes additional power losses in the electrolyzer, thus reducing efficiency. Currently, grid-connected AC / DC converters used for hydrogen electrolysis primarily employ two topologies: silicon controlled rectifiers (SCRs) and pulse width modulation (PWM) rectifiers. SCRs, using thyristor rectifiers, offer advantages such as simple structure, large capacity, and low cost, and are commonly used in high-power industrial applications. However, they generate significant harmonics and a low power factor. While harmonic content can be suppressed by installing filters on the AC side or adding auxiliary circuitry on the DC side, this increases the converter's size and cost. PWM rectifiers offer good control characteristics and a high power factor, and high-frequency modulation can effectively reduce harmonic content. However, fully controlled power devices are expensive and unsuitable for large-capacity hydrogen electrolysis applications.

[0004] A hybrid topology scheme combines the advantages of SCR and PWM rectifiers, overcoming their respective limitations. The hybrid topology not only improves output power levels but also effectively addresses input current distortion and large output current ripple. Various hybrid topologies, such as phase-controlled rectifiers and Vienna rectifiers, have been proposed for AC side harmonic suppression and unity power factor operation, but they have not yet been applied in the field of hydrogen electrolysis. Another type of parallel hybrid rectifier for hydrogen electrolysis based on an auxiliary converter is also proposed. The auxiliary converter is mainly used to improve grid current quality and suppress output current ripple. However, in high-capacity hydrogen production applications, the input side of the auxiliary converter is a low-voltage AC bus. Although it only transmits a portion of the power, it still needs to handle a considerable current, which increases manufacturing difficulty and cost.

[0005] Therefore, it is necessary to comprehensively consider the characteristics and limitations mentioned above, and to select the optimal topology and control method suitable for the electrolysis hydrogen production system. Summary of the Invention

[0006] The purpose of this invention is to provide a rectifier and control method based on a bridgeless AC-DC auxiliary converter, which can effectively overcome the shortcomings of the converter topologies mentioned above and meet the application scenarios of high-power, high-efficiency, and low-cost electrolytic hydrogen production.

[0007] The technical solution adopted by this invention to solve its technical problem is as follows:

[0008] On the one hand, the present invention proposes a rectifier based on a bridgeless AC-DC auxiliary converter, comprising: a main power converter and a bridgeless AC-DC auxiliary converter, wherein the main power converter and the bridgeless AC-DC auxiliary converter operate in parallel;

[0009] The main power converter is a thyristor rectifier, used to provide the main power support for the electrolytic stack;

[0010] The bridgeless AC-DC auxiliary converter includes a low-pass filter, three IGBTs, three high-frequency transformers, a diode rectifier, an output filter capacitor, a control unit, and a drive unit. The input terminal of the bridgeless AC-DC auxiliary converter is connected in parallel with the input terminal of the main power converter and then connected to the AC power grid. The output terminal of the bridgeless AC-DC auxiliary converter is connected in parallel with the output terminal of the main power converter and then connected to the electrolysis hydrogen production load.

[0011] The low-pass filter is a three-phase LC filter used to filter out the high-frequency components of the AC power input current while retaining the low-frequency components.

[0012] The three IGBTs correspond to the three-phase circuit. The IGBTs are located between the low-pass filter and the high-frequency transformer. The collector of the IGBT is connected to the output terminal of the low-pass filter, and the emitter of the IGBT is connected to the magnetizing inductor of the primary side of the high-frequency transformer to control the flow of current.

[0013] The primary and secondary excitation inductors of the three high-frequency transformers are all connected in a delta configuration. The primary and secondary excitation inductors are connected end to end in sequence. The primary excitation inductor is connected to the IGBT, and the secondary excitation inductor is connected to the diode rectifier.

[0014] The diode rectifier is used to rectify the output of the high-frequency transformer;

[0015] The output filter capacitor is used to filter out the AC component in the output current of the diode rectifier.

[0016] The control unit is used to generate drive signals through control methods, send them to the drive unit, and then control the main power converter and the bridgeless AC-DC auxiliary converter to work and operate.

[0017] The drive unit includes a pulse trigger circuit and a pulse width modulation drive circuit. The pulse trigger circuit is used to drive the main power converter, and the pulse width modulation drive circuit is used to drive the bridgeless AC-DC auxiliary converter. The drive unit is used to drive the power switching elements in the electrolytic hydrogen production rectifier.

[0018] As a further optimization, the control unit includes a current and voltage sampling circuit, a communication circuit, and a central processing unit. The voltage sampling circuit samples the three-phase AC grid voltage signal of the rectifier. The signal is sent to the central processing unit through the communication circuit, and the reference phase angle is calculated by the phase-locked algorithm in the central processing unit to quickly track changes in system frequency and realize the phase-locked function.

[0019] As a further optimization, the output current of the main power converter is controlled by a PI controller, and its control equation in the complex frequency domain is:

[0020]

[0021] In the formula, and These are the proportional and integral coefficients, respectively.

[0022] The DC output current of the main power converter is sampled by a current sampling circuit and compared with the DC output reference current of the main power converter to obtain the current error signal. Then, the signal is sent to the central processing unit to obtain the trigger angle of the main power converter through the PI control algorithm. After comparing it with the reference phase, the drive signal of the main power converter is generated. The drive signal is sent to the pulse trigger circuit in the drive unit through the communication circuit, thereby controlling the thyristor to turn on and off, and realizing the tracking control of the reference current.

[0023] As a further optimization, the output current of the bridgeless AC-DC auxiliary converter adopts proportional-integral-resonant control. The DC output current of the main power converter and the bridgeless AC-DC auxiliary converter are sampled by a current sampling circuit. The ripple component in the DC output current of the main power converter is calculated using a DFT sliding window mean filter algorithm in the central processing unit. This ripple component is then compared with the DC output current of the bridgeless AC-DC auxiliary converter to obtain the current error signal. The signal is sent to the central processing unit and the output current modulation signal is obtained through the proportional-integral-resonant control algorithm.

[0024] As a further optimization, the control equation for the proportional-integral-resonant control in the complex frequency domain is:

[0025]

[0026] In the formula, and These are the proportional and integral coefficients, respectively. This is the resonant gain coefficient. The system angular frequency, This is the cutoff angular frequency.

[0027] As a further optimization, the input current of the bridgeless AC-DC auxiliary converter adopts PI control + repetitive control. The AC input current of the main power converter and the bridgeless AC-DC auxiliary converter are sampled by a current sampling circuit. The central processing unit calculates the harmonic components of the AC input current of the main power converter using an instantaneous reactive power algorithm. The harmonic components of the AC input current of the main power converter and the AC input current of the bridgeless AC-DC auxiliary converter are compared to obtain the current error signal. The central processing unit will After being superimposed with the output current modulation signal, the modulation reference signal of the bridgeless AC-DC auxiliary converter is obtained through PI control + repetitive control algorithm. After being compared with the given carrier, the required drive signal of the bridgeless AC-DC auxiliary converter is generated. The drive signal is sent to the pulse width modulation drive circuit in the drive unit through the communication circuit, thereby driving the IGBT in the bridgeless AC-DC auxiliary converter to switch on and off, realizing the compensation of current ripple and harmonics of the main power converter.

[0028] As a further optimization, the control equation for the repetitive control in the discrete domain is:

[0029]

[0030] In the formula, It is a delayed process. For the fundamental period, It is usually a constant less than 1, used to improve system stability. This is a compensation stage set in the bridgeless AC-DC auxiliary converter to correct the amplitude and phase, denoted as... ,in To control the gain repeatedly, For phase lead, It is a filter.

[0031] On the other hand, the present invention also provides a control method based on a bridgeless AC-DC auxiliary converter, applied to the aforementioned electrolytic hydrogen production rectifier based on a bridgeless AC-DC auxiliary converter, comprising the following steps:

[0032] Connect the main power converter and the bridgeless AC-DC auxiliary converter in parallel;

[0033] The input terminals of the bridgeless AC-DC auxiliary converter and the main power converter are connected in parallel and then connected to the AC power grid. The output terminals of the bridgeless AC-DC auxiliary converter and the main power converter are connected in parallel and then connected to the electrolysis hydrogen production load.

[0034] The high-frequency components of the AC power input current are filtered out by a low-pass filter, while the low-frequency components are retained.

[0035] The three IGBTs are respectively assigned to the three-phase circuit, and the IGBTs are placed between the low-pass filter and the high-frequency transformer. The collector of the IGBT is connected to the output terminal of the low-pass filter, and the emitter of the IGBT is connected to the magnetizing inductor of the primary side of the high-frequency transformer to control the flow of current.

[0036] The primary and secondary magnetizing inductors of the three high-frequency transformers are all connected in a delta configuration. The primary and secondary magnetizing inductors are connected end to end in sequence. The primary magnetizing inductor is connected to the IGBT, and the secondary magnetizing inductor is connected to the diode rectifier. The control unit generates a drive signal through a control method and sends it to the drive unit to control the operation of the main power converter and the bridgeless AC-DC auxiliary converter.

[0037] The main power converter is driven by the pulse triggering circuit of the drive unit, and the bridgeless AC-DC auxiliary converter is driven by the pulse width modulation drive circuit of the drive unit. The drive unit is used to drive the power switching elements in the electrolytic hydrogen production rectifier.

[0038] The beneficial effects of this invention are:

[0039] (1) The electrolytic hydrogen production rectifier is suitable for large capacity and has high hydrogen production efficiency. The electrolytic hydrogen production rectifier adopts a parallel operation structure of main power converter and bridgeless AC-DC auxiliary converter, which can effectively improve the power level of electrolytic hydrogen production rectifier and the power density of electrolytic hydrogen production rectifier. Among them, the main power converter delivers most of the power required for electrolytic hydrogen production load, while the bridgeless AC-DC auxiliary converter delivers a small part of the power and compensates for the current ripple component of the main power converter, effectively improving the electro-hydrogen conversion efficiency in the electrolytic hydrogen production system.

[0040] (2) The electrolytic hydrogen production rectifier has a simple structure and low manufacturing cost. The main power converter in the electrolytic hydrogen production rectifier adopts a thyristor rectifier, and the bridgeless AC-DC auxiliary converter adopts a combination of low-pass filter, IGBT, high-frequency transformer and diode rectifier. Based on the bridgeless structure of the AC side of the AC-DC auxiliary converter, the number of devices in the electrolytic hydrogen production rectifier is small. Only 3 IGBTs are needed to achieve the megawatt power level. While improving the efficiency of electrolytic hydrogen production, the manufacturing cost of the rectifier is greatly reduced.

[0041] (3) The grid-side current distortion of the electrolytic hydrogen production rectifier is small. The bridgeless AC-DC auxiliary converter in the electrolytic hydrogen production rectifier can compensate for the harmonic components of the AC side current of the main power converter, thereby achieving optimized control of the grid-side current quality of the electrolytic hydrogen production rectifier.

[0042] Therefore, by using the rectifier and control method based on the bridgeless AC-DC auxiliary converter, the electrolytic hydrogen production rectifier can operate with low ripple and harmonic content in high-power electrolytic hydrogen production applications, and has the advantages of high efficiency, low cost and small grid-side current distortion. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the circuit structure of the rectifier based on the bridgeless AC-DC auxiliary converter in Embodiment 1 of the present invention;

[0044] Figure 2 This is a block diagram of the proportional-integral-resonant control of the output current of the bridgeless AC-DC auxiliary converter in Embodiment 1 of the present invention;

[0045] Figure 3 This is a block diagram of PI control + repetitive control for the input current of the bridgeless AC-DC auxiliary converter in Embodiment 1 of the present invention;

[0046] Figure 4 This is a flowchart of the control method for the bridgeless AC-DC auxiliary converter in Embodiment 2 of the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0048] Example 1

[0049] Referring to Figure 1, this embodiment provides a rectifier based on a bridgeless AC-DC auxiliary converter, including: a main power converter and a bridgeless AC-DC auxiliary converter, which operate in parallel;

[0050] The main power converter is a thyristor rectifier, specifically a 6-pulse thyristor rectifier. The main power converter provides the primary power support for the electrolysis stack and supplies the majority of the power required for the electrolysis hydrogen production load.

[0051] The bridgeless AC-DC auxiliary converter includes a low-pass filter and three IGBTs ( , , ), 3 high-frequency transformers ( , , The system includes a diode rectifier, a DC capacitor, a control unit, and a drive unit. The input terminal of the bridgeless AC-DC auxiliary converter is connected in parallel with the input terminal of the main power converter and then connected to the AC power grid. The output terminal of the bridgeless AC-DC auxiliary converter is connected in parallel with the output terminal of the main power converter and then connected to the electrolysis hydrogen production load.

[0052] The low-pass filter is a three-phase LC filter used to filter out the high-frequency components of the AC power input current while retaining the low-frequency components, effectively reducing interference and noise and improving the overall current quality of the rectifier.

[0053] The three IGBTs mentioned , , Each corresponds to a three-phase circuit. The IGBT is located between the low-pass filter and the high-frequency transformer. The IGBT collector is connected to the output of the low-pass filter, and the IGBT emitter is connected to the magnetizing inductor of the primary side of the high-frequency transformer. The IGBT drive signal is generated by the current control of the bridgeless AC-DC auxiliary converter, which flexibly controls the energy output in the bridgeless AC-DC auxiliary converter and meets the compensation requirements of the main power converter.

[0054] The three high-frequency transformers mentioned above ( , , The primary and secondary magnetizing inductors of the three phases are connected in a delta configuration. The primary and secondary magnetizing inductors are connected end to end in sequence. The primary magnetizing inductor is connected to the IGBT, and the secondary magnetizing inductor is connected to the diode rectifier. The high-frequency transformer provides input and output voltage isolation and improves the power density of the electrolytic hydrogen production rectifier. In addition, the delta connection structure allows the other two phases to still operate at reduced capacity when one phase circuit in the bridgeless AC-DC auxiliary converter fails, thereby improving the reliability of the bridgeless AC-DC auxiliary converter.

[0055] The diode rectifier is used to rectify the output of the high-frequency transformer;

[0056] The output filter capacitor is used to filter out the AC component in the output current of the diode rectifier.

[0057] The control unit includes a current and voltage sampling circuit, a communication circuit, and a central processing unit. The control unit generates a drive signal through a control method, sends it to the drive unit, and then controls the main power converter and the bridgeless AC-DC auxiliary converter to work and operate.

[0058] The drive unit includes a pulse trigger circuit and a pulse width modulation drive circuit. The pulse trigger circuit is used to drive the main power converter, and the pulse width modulation drive circuit is used to drive the bridgeless AC-DC auxiliary converter. The drive unit drives the power switching elements in the electrolytic hydrogen production rectifier.

[0059] In this embodiment, the control unit includes a current and voltage sampling circuit, a communication circuit, and a central processing unit. The voltage sampling circuit samples the three-phase AC grid voltage signal of the rectifier. The signal is sent to the central processing unit through the communication circuit, and the reference phase angle is calculated by the phase-locked algorithm in the central processing unit to quickly track changes in the system frequency and realize the phase-locked function.

[0060] Among them, the three-phase AC grid voltage signal of the rectifier can be sampled through the sampling circuit. , , The reference phase angle is calculated using a phase-locked algorithm in the central processing unit. θ It is used to quickly track changes in system frequency and realize phase-locked loop function.

[0061] Furthermore, the output current of the main power converter is controlled by a PI controller, and its control equation in the complex frequency domain is: In the formula, and These are the proportional and integral coefficients, respectively, and the DC output current of the main power converter is sampled by the sampling circuit. ,Compare With the DC output reference current of the main power converter Obtain the current error signal Then, the signal is sent to the central processing unit (CPU) to obtain the firing angle of the main power converter through a PI control algorithm. α Trigger angle α With reference phase θ The comparison generates a drive signal for the main power converter. The drive signal is sent to the pulse trigger circuit in the drive unit through the communication circuit, thereby controlling the thyristor to turn on and off, and realizing the tracking control of the reference current.

[0062] The output current of the bridgeless AC-DC auxiliary converter adopts proportional-integral-resonant (PIR) control, and its specific control block diagram is as follows: Figure 2 As shown, the DC output current of the main power converter is sampled through a sampling circuit. and the DC output current of the bridgeless AC-DC auxiliary converter The DC output current of the main power converter is calculated using the DFT sliding window mean filtering algorithm in the central processing unit. ripple component in ,Compare and the DC output current of the bridgeless AC-DC auxiliary converter Obtain the current error signal The signal is sent to the central processing unit and modulated by the PIR control algorithm to obtain the output current modulation signal. ;

[0063] The input current of the bridgeless AC-DC auxiliary converter adopts PI control + repetitive control, and its specific control block diagram is as follows. Figure 3 As shown, the AC input current of the main power converter is sampled through a sampling circuit. , , AC input current of bridgeless AC-DC auxiliary converter , , The components of the three-phase input current of the main power converter and the auxiliary converter in the dq coordinate system are as follows: , and , The central processing unit calculates the AC input current of the main power converter using an instantaneous reactive power algorithm. , , Harmonic components in the dq coordinate system 、 ,Compare 、 and , Obtain the current error signal , The central processing unit will , With output current modulation signal After superposition, the modulation reference signal of the bridgeless AC-DC auxiliary converter is obtained through a PI control + repetitive control algorithm. , , The modulation reference signal is compared with the given carrier to generate the drive signal required by the bridgeless AC-DC auxiliary converter. The drive signal is sent to the pulse width modulation drive circuit in the drive unit through the communication circuit, thereby driving the IGBT in the bridgeless AC-DC auxiliary converter to switch on and off, and realize the compensation of current ripple and harmonics of the main power converter.

[0064] In this embodiment, the control equation for the proportional-integral-resonant (PIR) control in the complex frequency domain is:

[0065]

[0066] In the formula, and These are the proportional and integral coefficients, respectively. This is the resonant gain coefficient. The system angular frequency, The cutoff angular frequency;

[0067] Specifically, the control equations for the above repetitive control in the discrete domain are as follows:

[0068]

[0069] In the formula It is a delayed process. For the fundamental period, It is usually a constant slightly less than 1 to improve system stability. This is a compensation stage set in the bridgeless AC-DC auxiliary converter to correct the amplitude and phase, denoted as... ,in To control the gain repeatedly, For phase lead, It is a filter.

[0070] Example 2

[0071] Based on Example 1, this example provides a control method based on a bridgeless AC-DC auxiliary converter, the flowchart of which is shown in Figure 4. The method includes the following steps:

[0072] S1. Connect the main power converter and the bridgeless AC-DC auxiliary converter in parallel;

[0073] S2. Connect the input terminal of the bridgeless AC-DC auxiliary converter in parallel with the input terminal of the main power converter and then connect it to the AC power grid. Connect the output terminal of the bridgeless AC-DC auxiliary converter in parallel with the output terminal of the main power converter and then connect it to the electrolysis hydrogen production load.

[0074] S3. Use a low-pass filter to remove the high-frequency components of the AC power input current while retaining the low-frequency components.

[0075] S4. Assign the three IGBTs to the three-phase circuit respectively, and place the IGBTs between the low-pass filter and the high-frequency transformer. Connect the collector of the IGBT to the output terminal of the low-pass filter, and connect the emitter of the IGBT to the magnetizing inductor of the primary side of the high-frequency transformer to control the flow of current.

[0076] S5. Connect the primary and secondary excitation inductors of the three phases of the three high-frequency transformers in a delta configuration. Connect the primary and secondary excitation inductors end to end in sequence. Connect the primary excitation inductor to the IGBT and the secondary excitation inductor to the diode rectifier.

[0077] S6. The control unit generates a drive signal through a control method and sends it to the drive unit, thereby controlling the main power converter and the bridgeless AC-DC auxiliary converter to work and operate.

[0078] S7. The main power converter is driven by the pulse triggering circuit of the drive unit, and the bridgeless AC-DC auxiliary converter is driven by the pulse width modulation drive circuit of the drive unit. The drive unit is used to drive the power switching elements in the electrolytic hydrogen production rectifier.

[0079] As can be seen from the description of this embodiment, the application principle of this embodiment is the same as that of embodiment 1, so it will not be repeated here.

[0080] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. Rectifier based on a bridgeless AC-DC auxiliary converter, characterized in that, include: The main power converter and the bridgeless AC-DC auxiliary converter operate in parallel. The main power converter is a thyristor rectifier, used to provide the main power support for the electrolytic stack; The bridgeless AC-DC auxiliary converter includes a low-pass filter, three IGBTs, three high-frequency transformers, a diode rectifier, an output filter capacitor, a control unit, and a drive unit. The input terminal of the bridgeless AC-DC auxiliary converter is connected in parallel with the input terminal of the main power converter and then connected to the AC power grid. The output terminal of the bridgeless AC-DC auxiliary converter is connected in parallel with the output terminal of the main power converter and then connected to the electrolysis hydrogen production load. The low-pass filter is a three-phase LC filter used to filter out the high-frequency components of the AC power input current while retaining the low-frequency components. The three IGBTs correspond to the three-phase circuit. The IGBTs are located between the low-pass filter and the high-frequency transformer. The collector of the IGBT is connected to the output terminal of the low-pass filter, and the emitter of the IGBT is connected to the magnetizing inductor of the primary side of the high-frequency transformer to control the flow of current. The primary and secondary excitation inductors of the three high-frequency transformers are all connected in a delta configuration. The primary and secondary excitation inductors are connected end to end in sequence. The primary excitation inductor is connected to the IGBT, and the secondary excitation inductor is connected to the diode rectifier. The diode rectifier is used to rectify the output of the high-frequency transformer; The output filter capacitor is used to filter out the AC component in the output current of the diode rectifier. The control unit is used to generate drive signals through control methods, send them to the drive unit, and then control the main power converter and the bridgeless AC-DC auxiliary converter to work and operate. The drive unit includes a pulse trigger circuit and a pulse width modulation drive circuit. The pulse trigger circuit is used to drive the main power converter, and the pulse width modulation drive circuit is used to drive the bridgeless AC-DC auxiliary converter. The drive unit is used to drive the power switching elements in the electrolytic hydrogen production rectifier.

2. The bridgeless AC-DC auxiliary converter based rectifier of claim 1, wherein, The control unit includes a current and voltage sampling circuit, a communication circuit, and a central processing unit. The voltage sampling circuit samples the three-phase AC grid voltage signal of the rectifier, sends the signal to the central processing unit through the communication circuit, and calculates the reference phase angle through the phase-locked algorithm in the central processing unit to quickly track changes in system frequency and realize the phase-locked function.

3. The bridgeless AC-DC auxiliary converter based rectifier of claim 2, wherein, The output current of the main power converter is controlled by a PI controller, and its control equation in the complex frequency domain is: wherein and are the proportional and integral coefficients, respectively. The DC output current of the main power converter is sampled by a current sampling circuit and compared with the DC output reference current of the main power converter to obtain the current error signal. Then, the signal is sent to the central processing unit to obtain the trigger angle of the main power converter through the PI control algorithm. After comparing it with the reference phase, the drive signal of the main power converter is generated. The drive signal is sent to the pulse trigger circuit in the drive unit through the communication circuit, thereby controlling the thyristor to turn on and off, and realizing the tracking control of the reference current.

4. The bridgeless AC-DC auxiliary converter based rectifier of claim 2, wherein, The output current of the bridgeless AC-DC auxiliary converter adopts proportional-integral-resonant control. The DC output current of the main power converter and the bridgeless AC-DC auxiliary converter are sampled by a current sampling circuit. The ripple component in the DC output current of the main power converter is calculated using a DFT sliding window mean filter algorithm in the central processing unit. This ripple component is then compared with the DC output current of the bridgeless AC-DC auxiliary converter to obtain the current error signal. The signal is sent to the central processing unit and the output current modulation signal is obtained through the proportional-integral-resonant control algorithm.

5. The bridgeless AC-DC auxiliary converter based rectifier of claim 4, wherein, The control equation for the proportional-integral-resonant control in the complex frequency domain is: wherein and are the proportional and integral coefficients, respectively, is the resonance gain coefficient, is the system angular frequency, is the cut-off angular frequency.

6. The bridgeless AC-DC auxiliary converter based rectifier of claim 2, wherein, The input current of the bridgeless AC-DC auxiliary converter adopts PI control + repetitive control. The AC input current of the main power converter and the bridgeless AC-DC auxiliary converter are sampled by a current sampling circuit. The central processing unit calculates the harmonic components of the main power converter's AC input current using an instantaneous reactive power algorithm. The harmonic components of the main power converter's AC input current and the bridgeless AC-DC auxiliary converter's AC input current are compared to obtain the current error signal. The central processing unit will After being superimposed with the output current modulation signal, the modulation reference signal of the bridgeless AC-DC auxiliary converter is obtained through PI control + repetitive control algorithm. After being compared with the given carrier, the required drive signal of the bridgeless AC-DC auxiliary converter is generated. The drive signal is sent to the pulse width modulation drive circuit in the drive unit through the communication circuit, thereby driving the IGBT in the bridgeless AC-DC auxiliary converter to switch on and off, realizing the compensation of current ripple and harmonics of the main power converter.

7. The bridgeless AC-DC auxiliary converter based rectifier of claim 6, wherein, The control equation for the repetitive control in the discrete domain is: wherein is a delay element, is a fundamental period, is a constant usually less than 1 to improve system stability, is a compensation element set for the bridgeless AC-DC auxiliary converter to correct the amplitude and phase correction, expressed as wherein is a repetitive control gain, is a phase lead element, is a filter.

8. The control method of the bridgeless AC-DC auxiliary converter, applied to the rectifier of the bridgeless AC-DC auxiliary converter of any one of claims 1-7, characterized in that, Includes the following steps: Connect the main power converter and the bridgeless AC-DC auxiliary converter in parallel; The input terminals of the bridgeless AC-DC auxiliary converter and the main power converter are connected in parallel and then connected to the AC power grid. The output terminals of the bridgeless AC-DC auxiliary converter and the main power converter are connected in parallel and then connected to the electrolysis hydrogen production load. The high-frequency components of the AC power input current are filtered out by a low-pass filter, while the low-frequency components are retained. The three IGBTs are respectively assigned to the three-phase circuit, and the IGBTs are placed between the low-pass filter and the high-frequency transformer. The collector of the IGBT is connected to the output terminal of the low-pass filter, and the emitter of the IGBT is connected to the magnetizing inductor of the primary side of the high-frequency transformer to control the flow of current. The primary and secondary excitation inductors of the three high-frequency transformers are all connected in a delta configuration. The primary and secondary excitation inductors are connected end to end in sequence. The primary excitation inductor is connected to the IGBT, and the secondary excitation inductor is connected to the diode rectifier. The control unit generates drive signals through control methods and sends them to the drive unit, thereby controlling the operation of the main power converter and the bridgeless AC-DC auxiliary converter. The main power converter is driven by the pulse triggering circuit of the drive unit, and the bridgeless AC-DC auxiliary converter is driven by the pulse width modulation drive circuit of the drive unit. The drive unit is used to drive the power switching elements in the electrolytic hydrogen production rectifier.

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