Current-mode PWM rectifier and its passive control method

Abstract

The application provides a current-mode PWM rectifier and a passive control method thereof, comprising a filter unit, a rectifier unit and a load unit connected in sequence; an input end of the filter unit is connected with a three-phase AC source, an output end of the filter unit is connected with an input end of the rectifier unit, a first output end of the rectifier unit is connected with an input end of the load unit, and a second output end of the rectifier unit is connected with an output end of the load unit; the filter unit is used for filtering high-order harmonics of the three-phase AC source received by the current-mode PWM rectifier on an AC side; the rectifier unit is used for rectifying a filtered voltage to obtain a rectified voltage; and the load unit is used for converting the received rectified voltage to realize energy output. The application can realize independent decoupling control of active power and reactive power and unit power factor control, can also be used for reactive power compensation function, and has the advantages of few control parameters, convenient debugging and strong anti-interference capability.

Description

Technical Field

[0001] This invention relates to the field of current-mode PWM rectifier technology, and in particular to a current-mode PWM rectifier and its passive control method. Background Technology

[0002] Current-mode PWM rectifiers offer advantages such as high AC current quality, controllable power factor, wide DC voltage range, and continuously adjustable current, making them widely used in applications such as superconducting magnetic energy storage, high-power power supplies, and DC de-icing. However, existing current-mode PWM rectifiers suffer from complex control processes and low interference immunity. Summary of the Invention

[0003] The purpose of this invention is to propose a current-type PWM rectifier and its passive control method, thereby solving the technical problems of complex control process and low anti-interference capability of existing current-type PWM rectifiers.

[0004] On the one hand, a current-mode PWM rectifier is provided, comprising:

[0005] The filter unit, rectifier unit, and load unit are connected in sequence.

[0006] The input terminal of the filter unit is connected to a three-phase AC source, the output terminal of the filter unit is connected to the input terminal of the rectifier unit, the first output terminal of the rectifier unit is connected to the input terminal of the load unit, and the second output terminal of the rectifier unit is connected to the output terminal of the load unit.

[0007] The filtering unit is used to filter out the high-order harmonics of the three-phase AC source received by the AC side of the current-type PWM rectifier.

[0008] The rectifier unit is used to rectify the filtered voltage to obtain a rectified voltage;

[0009] The load unit is used to convert the received rectified voltage to achieve energy output.

[0010] Preferably, the filtering unit includes a first inductor, a second inductor, and a third inductor, and the filtering capacitor unit includes a first capacitor, a second capacitor, and a third capacitor;

[0011] The first terminals of the first inductor, the second inductor, and the third inductor are respectively connected to a three-phase AC source; the second terminal of the first inductor and the first terminal of the first capacitor are connected to the first connection point, the second terminal of the second inductor and the first terminal of the second capacitor are connected to the second connection point, and the second terminal of the third inductor and the first terminal of the third capacitor are connected to the third connection point; the second terminals of the first capacitor, the second capacitor, and the third capacitor are interconnected.

[0012] Preferably, the rectifier unit includes a first switching unit, a second switching unit, a third switching unit, a fourth switching unit, a fifth switching unit, and a sixth switching unit;

[0013] The first switch unit and the fourth switch unit are connected to the first connection point, the third switch unit and the sixth switch unit are connected to the second connection point, and the fifth switch unit and the second switch unit are connected to the third connection point.

[0014] Preferably, the first switching unit includes a switch S1 and a diode D1 connected in series, the second switching unit includes a switch S2 and a diode D2 connected in series, the third switching unit includes a switch S3 and a diode D3 connected in series, the fourth switching unit includes a switch S4 and a diode D4 connected in series, the fifth switching unit includes a switch S5 and a diode D5 connected in series, and the sixth switching unit includes a switch S6 and a diode D6 connected in series.

[0015] The first terminal of switch S1 is connected to the anode of diode D1, the first terminal of switch S3 is connected to the anode of diode D3, the first terminal of switch S5 is connected to the anode of diode D5, and the cathodes of diodes D1, D3, and D5 are all connected to the input terminal of the load unit; the first terminal of switch S4 is connected to the anode of diode D4, the cathode of diode D4 is connected to the second terminal of switch S1, the first terminal of switch S6 is connected to the anode of diode D6, the cathode of diode D6 is connected to the second terminal of switch S3, the first terminal of switch S2 is connected to the anode of diode D2, the cathode of diode D2 is connected to the second terminal of switch S5, and the second terminals of switches S4, S6, and S2 are connected to the output terminal of the load unit.

[0016] Preferably, the load unit includes a load inductor L connected in series. dc and load resistance R L ;

[0017] The load inductor L dc One end is connected to the load resistor R L At one end, the load inductor L dc The other end serves as the input terminal of the load unit, and the load resistor R L The other end serves as the output of the load unit.

[0018] On the other hand, a passive control method for a current-source PWM rectifier is also provided, including:

[0019] Based on the actual current of the filter inductor, the actual output current of the rectifier unit, the reference output current of the rectifier unit, and the phase voltage of the three-phase AC source, calculate the dq reference voltage of the filter capacitor in the preset dq coordinate system.

[0020] The dq input reference current of the rectifier unit is calculated based on the actual current of the filter inductor, the dq reference voltage, and the actual voltage of the filter capacitor.

[0021] The PWM signal is obtained by performing back-dq transformation and PWM modulation based on the dq input reference current, so as to control the rectifier unit to perform rectification.

[0022] Preferably, the calculation of the dq reference voltage of the filter capacitor in the preset dq coordinate system specifically includes:

[0023] Calculate the current difference between the reference output current of the rectifier unit and the actual output current of the rectifier unit to obtain the current difference value; perform proportional-integral processing on the current difference value to determine the d-axis reference current of the filter inductor in the preset dq coordinate system;

[0024] The filter inductor's q-axis reference current in the dq coordinate system is determined based on the preset given value, and the dq reference current in the filter inductor in the preset dq coordinate system is determined based on the d-axis reference current and the q-axis reference current.

[0025] The actual current of the filter inductor and the phase voltage of the three-phase AC source are transformed into the dq coordinate system to obtain the actual dq current of the filter inductor and the dq phase voltage of the three-phase AC source in the preset dq coordinate system.

[0026] The dq reference voltage of the filter capacitor is calculated based on the dq reference current, the dq actual current, and the dq phase voltage.

[0027] Preferably, the dq reference voltage of the filter capacitor is calculated according to the following formula:

[0028]

[0029] Among them, v cd * and v cq * represents the dq reference voltage of the filter capacitor, i sd * and i sq * represents the dq reference current of the filter inductor, i sd and i sq dq is the actual current of the filter inductor, v sd and v sq R11 and R22 are the dq phase voltages of a three-phase AC source, and R11 and R22 are the damping coefficients.

[0030] Preferably, calculating the dq input reference current of the rectifier unit specifically includes:

[0031] The actual voltage of the filter capacitor is transformed by dq to obtain the actual dq voltage of the filter capacitor in the dq coordinate system;

[0032] The actual current of the filter inductor is transformed into the dq coordinate system to obtain the actual dq current of the filter inductor in the preset dq coordinate system.

[0033] The dq input reference current of the rectifier unit is calculated based on the dq reference voltage of the filter capacitor, the dq actual voltage of the filter capacitor, and the dq actual current of the filter inductor.

[0034] Preferably, the dq input reference current of the rectifier unit is calculated according to the following formula:

[0035]

[0036] Among them, i od * and i oq * is the input reference current for dq, v cd * and v cq * represents the dq reference voltage of the filter capacitor, v cd and v cq dq represents the actual voltage across the filter capacitor, and g11 and g22 are the damping coefficients.

[0037] In summary, implementing the embodiments of the present invention has the following beneficial effects:

[0038] The current-type PWM rectifier and its passive control method provided by this invention use a passive control method to control the current-type PWM rectifier. This not only enables independent decoupling control of active and reactive power and unity power factor control, but also allows for reactive power compensation. Furthermore, the passive control method has the advantages of fewer control parameters, convenient debugging, and strong anti-interference capability. Attached Figure Description

[0039] 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, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0040] Figure 1 This is a schematic diagram of a current-type PWM rectifier in an embodiment of the present invention.

[0041] Figure 2 This is a schematic diagram of the main flow of a current-type PWM rectifier and its passive control method in an embodiment of the present invention.

[0042] Figure 3 This is a logic diagram of a current-type PWM rectifier and its passive control method in an embodiment of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0044] like Figure 1 The diagram shown is a schematic representation of an embodiment of a current-mode PWM rectifier provided by the present invention. This embodiment includes:

[0045] A filter unit 110, a rectifier unit 120, and a load unit 130 are connected in sequence; the input terminal of the filter unit 110 is connected to a three-phase AC source, the output terminal of the filter unit 110 is connected to the input terminal of the rectifier unit 120, the first output terminal of the rectifier unit 120 is connected to the input terminal of the load unit 130, and the second output terminal of the rectifier unit 120 is connected to the output terminal of the load unit 130.

[0046] In this embodiment, the filtering unit 110 is used to filter out the high-order harmonics of the three-phase AC source received by the AC side of the current-type PWM rectifier; the filtering unit 110 includes a first inductor, a second inductor, and a third inductor, and the filtering capacitor unit includes a first capacitor, a second capacitor, and a third capacitor; the first ends of the first inductor, the second inductor, and the third inductor are respectively connected to the three-phase AC source; the second end of the first inductor and the first end of the first capacitor are connected to the first connection point, the second end of the second inductor and the first end of the second capacitor are connected to the second connection point, and the second end of the third inductor and the first end of the third capacitor are connected to the third connection point; the second ends of the first capacitor, the second capacitor, and the third capacitor are interconnected.

[0047] Understandably, the filter unit 110, including three filter inductors L and three filter capacitors C, is used to filter out high-order harmonics on the AC side of the current-type PWM rectifier 100. The first terminals of the filter inductors L are connected to the three-phase AC source, and the first terminals of the filter capacitors C are connected to the second terminals of the filter inductors L. The second terminals of the filter capacitors C are interconnected. The three-phase AC phase voltage v of the three-phase AC source... sa v sb v sc The output current of the three-phase AC source is filtered by the filter inductor L, and the actual current i in the filter inductor L is... sa i sbi sc and the actual voltage v of the filter capacitor C ca v cb v cc The filtered current i after passing through the filter capacitor C oa i ob i oc The filter current i oa i ob i oc The output is sent to rectifier unit 120.

[0048] In this embodiment, the rectifier unit 120 includes a first switch unit, a second switch unit, a third switch unit, a fourth switch unit, a fifth switch unit, and a sixth switch unit. The first switch unit and the fourth switch unit are connected to the first connection point, the third switch unit and the sixth switch unit are connected to the second connection point, and the fifth switch unit and the second switch unit are connected to the third connection point. The rectifier unit 120 is used to rectify the filtered voltage to obtain a rectified voltage.

[0049] Specifically, the first switching unit includes a switch S1 and a diode D1 connected in series, the second switching unit includes a switch S2 and a diode D2 connected in series, the third switching unit includes a switch S3 and a diode D3 connected in series, the fourth switching unit includes a switch S4 and a diode D4 connected in series, the fifth switching unit includes a switch S5 and a diode D5 connected in series, and the sixth switching unit includes a switch S6 and a diode D6 connected in series.

[0050] The first terminal of switch S1 is connected to the anode of diode D1, the first terminal of switch S3 is connected to the anode of diode D3, the first terminal of switch S5 is connected to the anode of diode D5, and the cathodes of diodes D1, D3, and D5 are all connected to the input terminal of the load unit; the first terminal of switch S4 is connected to the anode of diode D4, the cathode of diode D4 is connected to the second terminal of switch S1, the first terminal of switch S6 is connected to the anode of diode D6, the cathode of diode D6 is connected to the second terminal of switch S3, the first terminal of switch S2 is connected to the anode of diode D2, the cathode of diode D2 is connected to the second terminal of switch S5, and the second terminals of switches S4, S6, and S2 are connected to the output terminal of the load unit.

[0051] Understandably, the rectifier unit 120 includes a first to a sixth switching unit, each of which includes a switch and a diode connected in series. In the figure, the first switching unit includes switch S1 and diode D1, the second switching unit includes switch S2 and diode D2, the third switching unit includes switch S3 and diode D3, the fourth switching unit includes switch S4 and diode D4, the fifth switching unit includes switch S5 and diode D5, and the sixth switching unit includes switch S6 and diode D6. The first and fourth switching units are connected to a first connection point, the third and sixth switching units are connected to a second connection point, and the fifth and second switching units are connected to a third connection point.

[0052] In this configuration, the first terminal of switch S1 is connected to the anode of diode D1, the first terminal of switch S3 is connected to the anode of diode D3, and the first terminal of switch S5 is connected to the anode of diode D5. The cathodes of diodes D1, D3, and D5 are all connected to the input terminal of load unit 130. The first terminal of switch S4 is connected to the anode of diode D4, the first terminal of switch S6 is connected to the anode of diode D6, and the first terminal of switch S2 is connected to the anode of diode D2. The cathodes of diodes D4, D6, and D2 are respectively connected to the second terminals of switches S1, S3, and S5. The second terminals of switches S4, S6, and S2 are all connected to the output terminal of load unit 130. The second terminal of filter inductor L and the first terminal of filter capacitor C are respectively connected to the first connection point, the second connection point, and the third connection point.

[0053] In this embodiment, the load unit 130 includes a load inductor L connected in series. dc and load resistance R L The load inductance L dc One end is connected to the load resistor R L At one end, the load inductor L dc The other end serves as the input terminal of the load unit 130, and the load resistor R L The other end serves as the output terminal of the load unit 130. The load unit 130 is used to convert the received rectified voltage to achieve energy output.

[0054] In this embodiment, based on Figure 1 From the circuit structure shown, the voltage and current equations of the current-mode PWM rectifier can be obtained as follows:

[0055]

[0056] Where L is the value of the filter inductance, i sk V is the filter inductor current of phase k.sk V is the AC phase voltage of phase k of a three-phase AC source. ck Let i be the voltage of the filter capacitor in phase k. ok This is the k-phase input current of the rectifier unit.

[0057] The AC voltage and current described above are in the abc reference coordinate system. They can be transformed from the abc coordinate system to the dq coordinate system using the abc / dq coordinate transformation to obtain the dq-axis component v of the k-phase AC phase voltage. sd and v sq The dq-axis components of the filter capacitor voltage, v cd and v cq The dq-axis component i of the filter inductor current of phase k sd and i sq The dq-axis component i of the input current of the rectifier unit od and i oq The formulas can be expressed as follows:

[0058]

[0059]

[0060] Converted to EL format:

[0061]

[0062] in,

[0063]

[0064]

[0065] To achieve passive control, a passive controller can be designed as follows:

[0066]

[0067] Among them, X k * is X k The target value, X ek =X k -X k * represents the error phasor, R dk Let be the damping injection coefficient matrix. From the above equation, we can obtain:

[0068]

[0069]

[0070] Where r11, r22, g11 and g22 are all damping coefficients.

[0071] Based on the formula, the reference value v of the filter capacitor voltage can be obtained through passive control. cd * and v cq * Then, by performing passive control according to the formula, the input current reference value i of the rectifier unit 120 can be obtained. od * and i oq *. Input current reference value i od * and i oq Perform an inverse dq / abc transformation to obtain the reference value i of the input current. oa *、i ob * and i oc *. Based on the reference value i of the input current. oa *、i ob * and i oc *After PWM modulation, the signal is input to rectifier unit 120.

[0072] like Figure 2 and Figure 3 The diagram shown is a schematic representation of an embodiment of a passive control method for a current-source PWM rectifier provided by the present invention. In this embodiment, the method includes the following steps:

[0073] Based on the actual current of the filter inductor, the actual output current of the rectifier unit, the reference output current of the rectifier unit, and the phase voltage of the three-phase AC source, calculate the dq reference voltage of the filter capacitor in the preset dq coordinate system; that is, based on the actual current i of the filter inductor... sa i sb i sc The actual output current i of the rectifier unit dc The reference output current i of the rectifier unit dc * and the phase voltage v of the three-phase AC source sa v sb v sc The dq reference voltage v of the filter capacitor in the dq coordinate system is calculated. cd * and v cq *

[0074] In this embodiment, calculating the dq reference voltage of the filter capacitor in the preset dq coordinate system specifically includes: calculating the current difference between the reference output current of the rectifier unit and the actual output current of the rectifier unit to obtain the current difference value; performing proportional-integral processing on the current difference value to determine the d-axis reference current of the filter inductor in the preset dq coordinate system; using a preset given value as the q-axis reference current of the filter inductor in the dq coordinate system, and determining the dq reference current of the filter inductor in the preset dq coordinate system based on the d-axis reference current and the q-axis reference current; performing dq coordinate system transformation on the actual current of the filter inductor and the phase voltage of the three-phase AC source to obtain the dq actual current of the filter inductor and the dq phase voltage of the three-phase AC source in the preset dq coordinate system; and calculating the dq reference voltage of the filter capacitor based on the dq reference current, the actual dq current, and the dq phase voltage.

[0075] Understandably, based on the actual current i of the filter inductor sa i sb i sc The actual output current i of the rectifier unit dc and the reference output current i of the rectifier unit dc *Calculate the intermediate voltage v of dq in the dq coordinate system. 1d and v 1q Based on the aforementioned dq intermediate voltage (V 1d and v 1q ) and the phase voltage v of the three-phase AC source sa v sb v sc The dq reference voltage v of the filter capacitor in the dq coordinate system is calculated. cd * and v cq *

[0076] Specifically, the intermediate voltage dq in the dq coordinate system is calculated based on the actual current of the filter inductor, the actual output current of the rectifier unit, and the reference output current of the rectifier unit, including: based on the reference output current i of the rectifier unit... cd * and the actual output current i of the rectifier unit cd The dq reference current i of the filter inductor in the dq coordinate system is calculated. sd *、i sq *; The actual current i of the filter inductor sa i sb i sc By performing a dq coordinate system transformation, the actual dq current i of the filter inductor in the dq coordinate system is obtained. sd i sq The dq reference current i based on the filter inductorsd *、i sq * and the actual current i of dq sd i sq The intermediate voltage v of dq is obtained. 1d v 1q The intermediate voltage dq can include v. 1d =v sd -v cd and v 1q =v sq -v cq .

[0077] More specifically, regarding the phase voltage v of the three-phase AC source sa v sb v sc Performing a dq transformation yields the dq phase voltage v in the dq coordinate system. sd v sq ; Calculate the dq phase voltage v sd v sq and the intermediate voltage v of dq 1d v 1q The difference is used to obtain the dq reference voltage v of the filter capacitor in the dq coordinate system. cd *、v cq *

[0078] The dq reference current of the filter inductor in the dq coordinate system is calculated based on the reference output current and the actual output current of the rectifier unit. The actual current of the filter inductor and the phase voltage of the three-phase AC source are then transformed into the dq coordinate system to obtain the calculated dq actual current of the filter inductor and the dq phase voltage of the three-phase AC source in the dq coordinate system. The dq reference voltage of the filter capacitor is obtained based on the dq reference current, the actual dq current, and the dq phase voltage of the three-phase AC source. The reference output current i of the rectifier unit is calculated. cd * and the actual output current i of the rectifier unit cd The difference between them yields the current difference i. cd *-i cd Perform proportional-integral processing on the current difference to obtain the d-axis reference current i of the filter inductor in the dq coordinate system. sd *; The given value is used as the q-axis reference current i of the filter inductor in the dq coordinate system. sq *

[0079] The dq reference voltage of the filter capacitor is calculated using the following formula:

[0080]

[0081] Among them, v cd * and v cq * represents the dq reference voltage of the filter capacitor, i sd * and i sq * represents the dq reference current of the filter inductor, i sd and i sq dq is the actual current of the filter inductor, v sd and v sq R11 and R22 are the dq phase voltages of a three-phase AC source, and R11 and R22 are the damping coefficients.

[0082] Furthermore, the dq input reference current of the rectifier unit is calculated based on the actual current of the filter inductor, the dq reference voltage, and the actual voltage of the filter capacitor; that is, based on the actual current i of the filter inductor. sa i sb i sc The dq reference voltage v of the filter capacitor cd * and v cq * and the actual voltage v of the filter capacitor ca v cb v cc The dq input reference current i of the rectifier unit is calculated. od * and i oq *

[0083] In this embodiment, the actual voltage of the filter capacitor is transformed using the dq coordinate system to obtain the actual dq voltage of the filter capacitor in the dq coordinate system; the actual current of the filter inductor is transformed using the dq coordinate system to obtain the actual dq current of the filter inductor in the preset dq coordinate system; and the dq input reference current of the rectifier unit is calculated based on the dq reference voltage of the filter capacitor, the actual dq voltage of the filter capacitor, and the actual dq current of the filter inductor.

[0084] Specifically, the actual voltage v of the filter capacitor ca v cb v cc Perform a dq transformation to obtain the actual dq voltage v of the filter capacitor in the dq coordinate system. cd v cq The actual current i of the filter inductor sa i sb i sc By performing a dq coordinate system transformation, the actual dq current i of the filter inductor in the dq coordinate system is obtained. sd i sq ; based on the dq reference voltage v of the filter capacitor cd * and v cq * The actual voltage v of the filter capacitor (dq).cd and v cq The actual current i of the filter inductor is dq. sd and i sq The dq input reference current i of the rectifier unit is calculated. od *=i sd -i od i oq *=i sq -i oq .

[0085] More specifically, based on the dq reference voltage of the filter capacitor, the dq actual voltage of the filter capacitor, and the dq actual current of the filter inductor, the dq input reference current of the rectifier unit is calculated, including:

[0086]

[0087] Among them, i od * and i oq * is the input reference current for dq, v cd * and v cq * represents the dq reference voltage of the filter capacitor, v cd and v cq dq represents the actual voltage across the filter capacitor, and g11 and g22 are the damping coefficients.

[0088] Furthermore, a PWM signal is obtained by performing a reverse dq transformation and PWM modulation based on the dq input reference current, to control the rectifier unit 120 to perform rectification. That is, based on the dq input reference current i... od * and i oq Perform an inverse dq transform (e.g., to obtain i) oa *、i ob * and i oc The PWM signal is obtained by * and PWM modulation to control the rectifier unit 120 to perform rectification. Based on the dq input reference current i od * and i oq * Perform a reverse dq transformation to obtain the reference current i of rectifier unit 120 in the abc coordinate system. oa *、i ob * and i oc * and based on i oa *、i ob * and i oc * A PWM signal is obtained by performing PWM modulation to control the rectifier unit 120 to perform rectification.

[0089] It should be noted that the system described in the above embodiments corresponds to the method described in the above embodiments. Therefore, the parts of the method described in the above embodiments that are not described in detail can be obtained by referring to the content of the system described in the above embodiments, and will not be repeated here.

[0090] In summary, implementing the embodiments of the present invention has the following beneficial effects:

[0091] The current-type PWM rectifier and its passive control method provided by this invention use a passive control method to control the current-type PWM rectifier. This not only enables independent decoupling control of active and reactive power and unity power factor control, but also allows for reactive power compensation. Furthermore, the passive control method has the advantages of fewer control parameters, convenient debugging, and strong anti-interference capability.

[0092] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A passive control method of a current-fed PWM rectifier, characterized by, The current-source PWM rectifier includes a filter unit, a rectifier unit, and a load unit connected in sequence; the input terminal of the filter unit is connected to a three-phase AC source, the output terminal of the filter unit is connected to the input terminal of the rectifier unit, the first output terminal of the rectifier unit is connected to the input terminal of the load unit, and the second output terminal of the rectifier unit is connected to the output terminal of the load unit. The filtering unit is used to filter out the high-order harmonics of the three-phase AC source received by the AC side of the current-type PWM rectifier; the rectifier unit is used to rectify the filtered voltage to obtain the rectified voltage; the load unit is used to convert the received rectified voltage to realize energy output. The method includes the following steps: Based on the actual current of the filter inductor, the actual output current of the rectifier unit, the reference output current of the rectifier unit, and the phase voltage of the three-phase AC source, calculate the dq reference voltage of the filter capacitor in the preset dq coordinate system. The dq input reference current of the rectifier unit is calculated based on the actual current of the filter inductor, the dq reference voltage, and the actual voltage of the filter capacitor. A PWM signal is obtained by performing back-dq transformation and PWM modulation based on the dq input reference current, so as to control the rectifier unit to perform rectification; The calculation of the dq reference voltage of the filter capacitor in the preset dq coordinate system specifically includes: Calculate the current difference between the reference output current of the rectifier unit and the actual output current of the rectifier unit to obtain the current difference value; perform proportional integration processing on the current difference value to determine the d-axis reference current of the filter inductor in the preset dq coordinate system; The filter inductor's q-axis reference current in the dq coordinate system is determined based on the preset given value, and the filter inductor's dq reference current in the preset dq coordinate system is determined based on the d-axis reference current and the q-axis reference current. The actual current of the filter inductor and the phase voltage of the three-phase AC source are transformed into the dq coordinate system to obtain the actual dq current of the filter inductor and the dq phase voltage of the three-phase AC source in the preset dq coordinate system. The dq reference voltage of the filter capacitor is calculated based on the dq reference current, the dq actual current, and the dq phase voltage. The dq reference voltage of the filter capacitor is calculated using the following formula: wherein v cd *and v cq *are the dq reference voltages of the filter capacitor, i sd *and i sq *are the dq reference currents of the filter inductor, i sd and i sq are the dq actual currents of the filter inductor, v sd and v sq are the dq phase voltages of the three-phase AC source, and r11 and r22 are damping coefficients. The calculation of the dq input reference current of the rectifier unit specifically includes: The actual voltage of the filter capacitor is transformed by dq to obtain the actual dq voltage of the filter capacitor in the dq coordinate system; The actual current of the filter inductor is transformed into the dq coordinate system to obtain the actual dq current of the filter inductor in the preset dq coordinate system. The dq input reference current of the rectifier unit is calculated based on the dq reference voltage of the filter capacitor, the dq actual voltage of the filter capacitor, and the dq actual current of the filter inductor. The dq input reference current of the rectifier unit is calculated using the following formula: where i od *and i oq *is the dq input reference current, v cd *and v cq *is the dq reference voltage of the filter capacitor, v cd and v cq is the dq actual voltage of the filter capacitor, g11 and g22 are damping coefficients.

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