Power conversion system and control method thereof

Abstract

The present disclosure provides a power conversion system and a control method thereof, the control method comprising: providing a power conversion module comprising a controller, and a damping circuit and a first capacitor connected in series, the damping circuit comprising a first inductor, a first switch tube, a second switch tube and a second capacitor, the first switch tube and the second switch tube are connected in series to form a first bridge arm, the first inductor is connected between an intermediate node of the first bridge arm and the first capacitor, and the second capacitor is connected in parallel with the first bridge arm; obtaining a first current reference value according to the input voltage of the power conversion module, the voltage of the second capacitor and the voltage reference value of the second capacitor; obtaining a second current reference value according to the input voltage of the power conversion module and a current signal related to the input current of the power conversion module; and according to the inductive current flowing through the first inductor and the inductive current reference value of the first inductor, outputting a driving signal to control the first switching tube and the second switching tube, wherein the current reference value of the first inductor is obtained according to the first current reference value and the second current reference value.

Description

Technical Field

[0001] The present disclosure relates to the field of power electronics technology, and in particular to a power conversion system and a control method thereof. Background Art

[0002] At present, the patent document with patent application number 202311063966.5 proposes a non-isolated DC / DC power converter, referring to Figure 1 The non-isolated DC / DC power converter 20 includes a power module 21 and an oscillation suppression module 22. The power module 21 includes a first power conversion circuit 211. The first power conversion circuit 211 is a non-isolated DC / DC conversion circuit. The first output terminal A of the first power conversion circuit 211 is connected to the first inductor Lf1, and the second output terminal B of the first power conversion circuit 211 is connected to the second inductor Lf2. The oscillation suppression module 22 has a first input terminal P and a second input terminal N. There is an input voltage Vin between the first input terminal P and the second input terminal N. It includes a second power conversion circuit 221 inside. The first port of the second power conversion circuit 221 is connected in parallel to the input end of the first power conversion circuit 211. The current of the first port of the second power conversion circuit 221 is in phase with at least part of the AC voltage component of the input voltage Vin of the oscillation suppression module 22.

[0003] The input end of the non-isolated DC / DC power converter 20 can be connected to the output end of any rectifier circuit, that is, the DC bus, and the rectifier circuit is connected to the AC power supply to form a power conversion system. Figure 2 As shown, the first power conversion circuit 211 can be considered as having an equivalent input impedance Z L (S) represents the constant power load (CPL), at its equivalent input impedance Z L (S) shows negative resistance characteristics. Figure 3 As shown, a damper is added to the source side formed by the AC power supply and the rectifier circuit, such as any second power conversion circuit in the above embodiment, and its source side equivalent impedance is Z S (S). Impedance-based analysis (e.g. Figure 4 The equivalent circuit model shown) and based on Figure 5 The frequency domain control model shown in the figure shows that, according to the Nyquist stability criterion, if the equivalent impedance on the source side is not sufficiently damped, a DC bus or AC power supply will be generated. Figure 6 Instability and oscillations shown.

[0004] How to provide a power conversion system and control method with high working efficiency and strong stability is a problem that needs to be solved urgently in the industry. Summary of the invention

[0005] The present disclosure aims to provide a power conversion system and a control method thereof, which can solve one or more defects of the prior art.

[0006] In order to achieve the above-mentioned purpose, the present disclosure provides a power conversion system, comprising a power conversion module, wherein the power conversion module comprises a controller and a damping circuit and a first capacitor connected in series, the damping circuit comprises a first inductor, a first switch tube, a second switch tube and a second capacitor, the first switch tube and the second switch tube are connected in series to form a first bridge arm, the first inductor is connected between the middle node of the first bridge arm and the first capacitor, and the second capacitor is connected in parallel to the first bridge arm, and the controller comprises: a capacitor voltage control unit, which obtains a first current reference value according to an input voltage of the power conversion module, a voltage of the second capacitor and a voltage reference value of the second capacitor; a damping current generating unit, which obtains a second current reference value according to the input voltage of the power conversion module and a current signal related to the input current of the power conversion module; and an inductor current control unit, which outputs a driving signal to control the first switch tube and the second switch tube according to the current flowing through the first inductor and the current reference value of the first inductor to stabilize the input voltage of the power conversion module, wherein the current reference value of the first inductor is obtained according to the first current reference value and the second current reference value.

[0007] In order to achieve the above-mentioned purpose, the present disclosure provides a control method for a power conversion system, comprising: providing a power conversion module, comprising a controller and a damping circuit and a first capacitor connected in series, the damping circuit comprising a first inductor, a first switch tube, a second switch tube and a second capacitor, the first switch tube and the second switch tube are connected in series to form a first bridge arm, the first inductor is connected between the middle node of the first bridge arm and the first capacitor, and the second capacitor is connected in parallel to the first bridge arm; obtaining a first current reference value according to an input voltage of the power conversion module, a voltage of the second capacitor and a voltage reference value of the second capacitor; obtaining a second current reference value according to the input voltage of the power conversion module and a current signal related to the input current of the power conversion module; and outputting a driving signal to control the first switch tube and the second switch tube according to the inductor current flowing through the first inductor and the inductor current reference value of the first inductor to stabilize the input voltage of the power conversion module, wherein the current reference value of the first inductor is obtained according to the first current reference value and the second current reference value.

[0008] The present disclosure provides a power conversion system and a control method thereof, which can improve the working efficiency and system stability of the power conversion system and reduce system loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solutions implemented in the present disclosure, the following briefly introduces the drawings required for use in the embodiments.

[0010] Figure 1A circuit topology diagram of a non-isolated DC / DC power converter in the prior art;

[0011] Figure 2 is an equivalent schematic diagram of a power conversion system including a first power conversion circuit;

[0012] Figure 3 is included Figure 1 An equivalent schematic diagram of a power conversion system of a non-isolated DC / DC power converter shown;

[0013] Figure 4 is based on Figure 3 Equivalent circuit model of the power conversion system;

[0014] Figure 5 is based on Figure 4 Frequency domain control model of

[0015] Figure 6 is based on Figure 5 Schematic diagram of voltage simulation on the DC bus;

[0016] Figure 7 is a schematic diagram of the structure of the power conversion system disclosed in the present invention;

[0017] Figure 8 is a circuit topology diagram of the power conversion module disclosed herein;

[0018] Fig. 9 is a schematic diagram of the control process of the controller disclosed herein;

[0019] Fig. 10A It is a schematic diagram of a three-phase rectifier circuit;

[0020] Fig. 10B Yes Fig. 10A Schematic diagram of output waveform of three-phase rectifier circuit shown;

[0021] Fig. 10C It is a schematic diagram of the main AC harmonic components of the output voltage of the three-phase rectifier circuit;

[0022] Fig.11A It is a schematic diagram of a single-phase diode rectifier circuit;

[0023] Fig. 11B yes Fig.11A Schematic diagram of the output waveform of the single-phase diode rectifier circuit shown;

[0024] Fig. 11C This is a schematic diagram of the main AC harmonic components of the single-phase diode rectifier output voltage;

[0025] Fig. 12A It is a simulation model for computer simulation of the control embodiment of the present disclosure;

[0026] Fig. 12B Based on Fig. 12A The simulation results of the simulation model shown;

[0027] Fig. 12C for Fig. 12B A magnified view of the simulation results shown;

[0028] Fig.13 is a simulation result of generating a damping current according to different first coefficients in a damping current generator;

[0029] Figures 14A-14B is a simulation schematic diagram of optimizing damping current;

[0030] Fig.15 is a graph of the relationship between the DC bus voltage and the resonant frequency of the rectifier output impedance;

[0031] Fig.16 The invention discloses a flow chart of a power conversion method.

[0032] Additional aspects and advantages of the present disclosure will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present disclosure. DETAILED DESCRIPTION

[0033] Example embodiments will now be described more fully with reference to the accompanying drawings, however, example embodiments can be implemented in many forms and should not be construed as limited to the embodiments described herein; on the contrary, these embodiments are provided so that this disclosure will be comprehensive and complete and will fully and completely convey the concept of the example embodiments to those skilled in the art.

[0034] When introducing the elements / components / etc. described and / or illustrated herein, the terms "one", "an", "the", "said" and "at least one" are used to indicate the presence of one or more elements / components / etc. The terms "comprise", "include" and "have" are used to indicate an open-ended inclusion and mean that additional elements / components / etc. may exist in addition to the listed elements / components / etc. In addition, the terms "first", "second", etc. in the claims are used only as labels and are not numerical limitations on their objects. The same numbers in the drawings represent the same or similar components. On the other hand, well-known components and steps are not described in the embodiments to avoid unnecessary limitations on the present disclosure. In addition, to simplify the drawings, some known conventional structures and elements will be illustrated in the drawings in a simple schematic manner.

[0035] Figure 7 FIG. 1 is a schematic diagram of the structure of the power conversion system 10 disclosed in the present invention. Figure 7As shown, the power conversion system 10 includes an AC power source 11 , a rectifier circuit 12 and a power conversion module 13 which are connected in sequence.

[0036] Figure 8 1 is a schematic diagram of the structure of the power conversion module 13 disclosed in the present invention. The power conversion module 13 includes a controller (not shown), a damping circuit 13a and a first capacitor 13b connected in series. The damping circuit 13a and the first capacitor 13b are connected in series to further reduce the rated voltage of the power semiconductor selected in the power conversion module 13. The damping circuit 13a includes a first inductor L d , the first switch tube S du , the second switch tube S db and the second capacitor C d_dc , the first switch tube S du and the second switch tube S db The first bridge arm is formed in series, and the first inductor L d connected between the middle node of the first bridge arm and the first capacitor 13b, the second capacitor C d_dc In parallel with the first bridge arm, the power conversion module 13 also has an input port, which includes a first input terminal P and a second input terminal N, wherein an input voltage V PN It is understandable that if Figure 8 As shown, the first input terminal P and the second input terminal N are also output terminals of the power module 13, that is, the input port and the output port of the power conversion module 13 are the same port. Fig. 9 As shown, the controller includes a capacitor voltage control unit 131, a damping current generating unit 132 and an inductor current control unit 133. The capacitor voltage control unit 131 generates a voltage according to the input voltage V PN , the voltage of the second capacitor V Cd_dc And the voltage reference value V of the second capacitor Cd_dc_ref The damping current generating unit 132 generates a first current reference value i1 according to the input voltage V PN and a current signal related to the input current of the power conversion module to obtain a second current reference value i2; the inductor current control unit 133 controls the current i flowing through the first inductor according to the current i Ld The current reference value i of the first inductor Ld_Ref The output drive signal is applied to the first switch tube S du and the second switch tube S db The control is performed, wherein the current reference value i of the first inductor is Ld_Ref The input voltage V of the power conversion module 13 can be stabilized by the above control.PN , further reducing the power loss and cost of the power conversion module 13.

[0037] Fig. 9 This is a schematic diagram of the control process of the controller disclosed in the present invention. The controller includes a capacitor voltage control unit 131, a damping current generating unit 132, and an inductor current control unit 133. Since the first capacitor 13b blocks the DC voltage between the first input terminal P and the second input terminal N, the damping circuit 13a in the power conversion module 13 is controlled to dynamically simulate a resistor at a frequency other than DC after being adjusted by the capacitor voltage control unit 131, the damping current generating unit 132, and the inductor current control unit 133. At this time, the damping current provided by the damping circuit 13a can be an AC current at the system interference frequency instead of a DC current, thereby further reducing the power loss and cost of the power conversion module 13. Fig. 9 In order to realize that the damping circuit 13a provides an AC current at the system interference frequency, the specific structure and control process of the controller are as follows:

[0038] Due to the existence of the first capacitor 13b, the second capacitor C d_dc The absorbed energy cannot be sent back to the input port of the power conversion module 13 through the first capacitor 13b as a direct current. Therefore, the capacitor voltage control unit 131 disclosed in the present invention includes a first filter 131-1 and a phase-locked loop 131-2. The first filter 131-1 and the phase-locked loop 131-2 can track the input voltage V of the power conversion module 13. PN at least part of the AC harmonic component, according to at least part of the AC harmonic component, the voltage V of the second capacitor Cd_dc and the voltage reference value V of the second capacitor Cd_dc_ref The first current reference value i1 is obtained. The input voltage V of the power conversion module 13 is tracked by using the phase-locked loop 131-2. PN At least part of the AC harmonic component is obtained by multiplying the unit waveform to obtain a current reference value, which can control the second capacitor voltage (V Cd_dc ) exchanges energy with the input port (i.e., the DC bus) of the power conversion module 13. Specifically, the capacitor voltage control unit 131 also includes a first subtractor 131-3, a first regulator 131-4, and a first multiplier 131-5. The first subtractor 131-3 performs a voltage multiplication on the second capacitor V Cd_dc and the voltage reference value V of the second capacitor Cd_dc_ref After subtraction, a first error signal V is output. error1 , the first error signal V error1 After being regulated by the first regulator 131-4, the per unit value V of at least part of the AC harmonic component PN_6f0The first current reference value i1 is obtained after multiplication by the first multiplier 131 - 5 .

[0039] In this embodiment, the AC power source 11 may be a three-phase AC power source, such as Fig. 10A As shown, the rectifier circuit 12 is a three-phase rectifier circuit, the input port of the power conversion module 13 is connected to the output port of the three-phase rectifier circuit 12 , and the input port of the three-phase rectifier circuit 12 is connected to the three-phase AC power supply 11 . Fig. 10B It is a schematic diagram of the output waveform of the three-phase rectifier circuit. Fig. 10C It is the main AC harmonic component of the output voltage of the three-phase rectifier circuit. When the power conversion module 13 is connected to the DC bus after the three-phase AC power source 11 passes through the six-pulse rectification (i.e., the three-phase rectifier circuit), the phase-locked loop 131-2 is used to track the main AC harmonic components on the DC bus voltage, including but not limited to the 6th harmonic component, the 12th harmonic component, the 18th harmonic component, etc., that is, at least part of the AC harmonic components tracked by the phase-locked loop 131-2 include the 6th harmonic component of the output voltage of the three-phase rectifier circuit, and / or the 12th harmonic component, and / or the 18th harmonic component, such as Figures 11A-11C The capacitor voltage control unit 131 can control the second capacitor C d_dc The absorbed damping energy is sent back to the input end (ie, the DC bus) of the power conversion module 13 through the corresponding harmonic frequency to ensure that the second capacitor C d_dc In other words, the second capacitor C can be realized by using the AC harmonics of the rectifier in the AC-DC energy conversion. d_dc In this embodiment, the phase-locked loop 131-2 tracks the sixth harmonic component of the output voltage of the three-phase rectifier circuit to obtain V PN_6f0 .

[0040] In other embodiments, the AC power source 11 may be a single-phase AC power source, such as Fig.11A As shown, the rectifier circuit 12 is a single-phase rectifier circuit, specifically, for example, a single-phase diode rectifier circuit. The input port of the power conversion module 13 is connected to the output port of the single-phase rectifier circuit 12, and the input port of the single-phase rectifier circuit 12 is connected to the single-phase AC power supply 11. Fig. 11B It is a schematic diagram of the output waveform of a single-phase rectifier circuit, which has two pulses in one line cycle. Fig. 11C It is the main AC harmonic component of the output voltage of the single-phase rectifier circuit. In this embodiment, at least part of the AC harmonic components tracked by the phase-locked loop 131-2 include the 2nd harmonic component, and / or the 4th harmonic component, and / or the 6th harmonic component of the output voltage of the single-phase rectifier circuit.

[0041] Please continue to refer to Fig. 9The damping current generating unit 132 is used to generate the damping current (i.e., the second current reference value i2) required by the power conversion system 10. The damping current generating unit 132 can generate the damping current (i.e., the second current reference value i2) required by the power conversion system 10 according to the equivalent impedance of the output port of the power conversion module 13 (e.g. Figure 2 The equivalent input impedance ZL of the constant power load shown in FIG. 1 and the input voltage V PN The damping current can be generated according to the current at the output port of the power conversion module 13 and the input voltage V PN A low-pass filter is performed, and the cut-off frequency may be, but is not limited to, 40 Hz to obtain a back-end circuit (eg, Figure 7 The parameters of the DC resistance (or DC conductance) of the load conversion circuit shown in the figure are then scaled by the first coefficient K to reflect the parameters of the DC resistance (or DC conductance) required by the power conversion system 10. To ensure that the power conversion module 13 generates sufficient damping, the first coefficient can be set but not limited to 0.5. The simulation results when the first coefficient is equal to 0.5 are as follows: Fig.13 Specifically, in this embodiment, the damping current generating unit 132 includes a second filter 132-1 and a second multiplier 132-2. The second filter 132-1 is used to filter the input voltage V PN Perform high-pass filtering to obtain the first voltage value V PN_ripple The second multiplier 132-2 performs a multiplication of the first voltage value V PN_ripple The damping current generating unit 132 further comprises a third filter 132-3, a fourth filter 132-4 and a second divider 132-5. The third filter 132-3 is used to filter the input voltage V of the power conversion module 13. PN Perform low-pass filtering to obtain a second voltage value V PN_dc The fourth filter 132-4 is used to filter the current signal i related to the input current of the power conversion module 13. Load Perform low-pass filtering to obtain the first current value i Load_dc , wherein the second divider 132-5 divides the first current value i Load_dc and the second voltage value V PN_dc After performing the division operation, a second admittance parameter is obtained, and the second admittance parameter is scaled according to a first coefficient K to obtain the first admittance parameter.

[0042] In other embodiments, the damping current generating unit 132 may include a second filter 132-1 and a first divider 132-2'. The second filter 132-1 is configured to generate a voltage V PN Perform high-pass filtering to obtain the first voltage value V PN_rippleThe first divider 132-2' divides the first voltage value VPN_ripple and a first resistance parameter to obtain a second current reference value i2. The damping current generating unit 132 includes a third filter 132-3, a fourth filter 132-4 and a second divider 132-5. The third filter 132-3 divides the input voltage V PN Perform low-pass filtering to obtain a second voltage value V PN_dc The fourth filter 132-4 is used to filter the current signal i related to the input current of the power conversion module 13. Load Perform low-pass filtering to obtain the first current value i Load_dc The second divider 132-5 calculates the second voltage value V PN_dc and the first current value i Load_dc After the division operation, a second resistance parameter is obtained, and the second resistance parameter is scaled according to the first coefficient K to obtain the first resistance parameter.

[0043] In the above embodiment, the cutoff frequency of the second filter 132-1 may be but not limited to 100 Hz, the cutoff frequencies of the third filter 132-3 and the fourth filter 132-4 may be but not limited to 40 Hz, and the first coefficient K is set to but not limited to 0.5.

[0044] The inductor current control unit 133 includes a second subtractor 133-1, a second regulator 133-2 and a first adder 133-3. The second subtractor 133-1 adjusts the current flowing through the first inductor L d The current i Ld and the current reference value i of the first inductor Ld_Ref After subtraction, a second error signal i is output. error2 , wherein the power conversion module further includes a second adder 134, wherein the first inductor L d The current reference value i Ld_Ref The second error signal V is obtained by adding the first current reference value i1 and the second current reference value i2 through the second adder 134. error2 After being adjusted by the second regulator 133-2 and a duty cycle feedforward value DFF, the first adder 133-3 performs an addition operation to obtain a driving signal d d , driving signal d d The output to the first switch tube S of the damping circuit 13b of the power conversion module 13 du and the second switch tube S db The driving end of the first switch tube S du and the second switch tube S db The on-off of the power conversion module can stabilize the input voltage of the power conversion module and further reduce the power loss and cost of the power conversion module.

[0045] Combination Figure 7 The power conversion system 10 also includes a load conversion circuit 14, the input port of the power conversion module 13 is connected in parallel to the output port of the rectifier circuit 12 and the input port of the load conversion circuit 14, wherein the input port and the output port of the power conversion module 13 are the same port, and the sum of the input current of the power conversion module 13 and the output current of the rectifier circuit 12 is the input current of the load conversion circuit 14 (that is, the output current of the power conversion module 13), wherein the load conversion circuit 14 is a DC-AC conversion circuit or a DC-DC conversion circuit.

[0046] The power conversion system 10 further includes an input inductor 15 and a bus capacitor 16, wherein the input inductor 15 is connected between the AC power source 11 and the input port of the rectifier circuit 12, and the bus capacitor 16 and the power conversion module 13 are sequentially connected in parallel to the output port of the rectifier circuit 12. The rectifier circuit 12 is, for example, Fig. 10A The three-phase rectifier circuit shown is Fig.11A The present disclosure is not limited to the single-phase rectifier circuit shown.

[0047] In some embodiments, the damping current can be optimized by adjusting the first coefficient K in the damping current generating unit 132. Based on the impedance stability analysis, the frequency of the damping current required by the power conversion module 13 depends on the source side equivalent impedance Z S (S) (i.e., power conversion module side) and load side equivalent Z L (S) impedance (i.e. load conversion circuit side) intersects the frequency range. Figure 7 and Fig.14A As shown, since the output impedance of the source side including the AC power supply 11 and the rectifier circuit 12 presents LC parallel resonance, when the inductance value of the input inductor 15 connected to the AC power supply increases, the resonant frequency becomes smaller, and at this time, the V required by the damping current generating unit 132 PN The ripple frequency is reduced, so the V PN The frequency range is wider. Fig. 14B It can be seen that the frequency range corresponding to the damping current should be within the source side impedance Z S (S) Resonance frequency amplitude ratio load impedance Z L (S) The frequency range with large frequency amplitude. Therefore, when a constant first coefficient K is used, such as K=0.5, the damping current generating unit 132 will be injected into all the currents higher than V PN Low pass filter cutoff frequency, e.g. Fig. 9In order to adaptively adjust the frequency of the AC component of the damping current injected by the power conversion module 13 with different input inductors 15, the first coefficient K can be adaptively changed according to the required frequency range to adjust the source side equivalent impedance Z S (S). Since the current signal related to the input current of the power conversion module 13 and the bus capacitor 16 can be preset, when the current signal related to the input current of the power conversion module 13 and the capacitance of the bus capacitor 16 are known, the input voltage V PN The average value of the DC bus voltage can be used to obtain the output impedance resonant frequency of the rectifier 12, such as Fig.15 As shown. When the inductance value L of the source side input inductor 15 ac When the output voltage of the rectifier circuit 12 increases, Fig.15 The LC parallel resonant frequency (e.g. Fig. 14B fr1 and fr2 in Fig.15 fr), so as to obtain the required frequency component of the damping current, that is, the V PN In this way, the damping current can be minimized, thereby improving the power of the power conversion module 13 and the efficiency of the entire power conversion system 10.

[0048] Therefore, in these embodiments, the damping current generating unit 132 generates a current according to the input voltage V PN The second current reference value i2 is obtained by using a current signal related to the input current of the power conversion module 13, including:

[0049] Get the input voltage V of the power conversion module 13 PN The ripple component, that is, the first voltage value V PN_ripple ;

[0050] According to the input voltage V of the power conversion module 13 PN Obtaining a resistance parameter from a current signal related to an input current of the power conversion module 13;

[0051] According to a first coefficient K, resistance parameters and the ripple component V of the input voltage PN_ripple A second current reference value i2 is obtained, wherein the first coefficient K is adaptively adjusted according to the input inductance 15 .

[0052] The current signal related to the input current of the power conversion module 13 is, for example, the input current of the load conversion circuit 14 (that is, the output current of the power conversion module 12) or the output current of the load conversion circuit 14. When the input inductance 15 increases, the resonant frequency of the LC parallel resonance of the output impedance of the rectifier circuit 12 and the bus capacitor 16 becomes smaller, and the frequency of the required second current reference value i2 is reduced. Therefore, the first coefficient K can be adaptively adjusted according to the input inductance 15 to minimize the damping current, thereby improving the power of the power conversion module 13 and the efficiency of the entire power conversion system 10.

[0053] Fig. 12A It is a simulation model simulated by computer when power is supplied to a constant power load (ie, load conversion circuit) through a three-phase rectifier. Fig. 12B Based on Fig. 12A The simulation model is used to simulate the results. Fig. 12C for Fig. 12B The enlarged diagram of the simulation results is based on Fig. 12B and Fig. 12C The simulation waveform shown shows that the second capacitor C d_dc The voltage V Cd_dc In a state of balance.

[0054] Fig.13 is the simulation result of the damping current generating unit 132 generating the damping current according to different first coefficients K. To ensure that the second power conversion circuit generates sufficient damping, the first coefficient can be set to, but not limited to, 0.5. The simulation result when the first coefficient is equal to 0.5 is as follows: Fig.13 shown.

[0055] Fig.16 The present disclosure is a flow chart of a control method applied to the aforementioned power conversion system 10, wherein the control method 100 of the power conversion system includes:

[0056] Step S101: providing a power conversion module, comprising a controller and a damping circuit and a first capacitor connected in series, wherein the damping circuit comprises a first inductor, a first switch tube, a second switch tube and a second capacitor, wherein the first switch tube and the second switch tube are connected in series to form a first bridge arm, the first inductor is connected between an intermediate node of the first bridge arm and the first capacitor, and the second capacitor is connected in parallel to the first bridge arm;

[0057] Step S102: obtaining a first current reference value according to the input voltage of the power conversion module, the voltage of the second capacitor and a voltage reference value of the second capacitor;

[0058] Step S103: obtaining a second current reference value according to the input voltage of the power conversion module and a current signal related to the input current of the power conversion module; and

[0059] Step S104: Outputting a driving signal to control the first switch tube and the second switch tube according to the inductor current flowing through the first inductor and the inductor current reference value of the first inductor to stabilize the input voltage of the power conversion module, wherein the current reference value of the first inductor is obtained according to the first current reference value and the second current reference value.

[0060] In some embodiments, the current reference value of the first inductor is obtained by adding the first current reference value and the second current reference value.

[0061] In some embodiments, step S102 specifically includes: obtaining at least part of the AC harmonic component of the input voltage of the power conversion module, and obtaining the first current reference value according to the at least part of the AC harmonic component, the voltage of the second capacitor, and the voltage reference value of the second capacitor. Specifically, a first error signal is output after subtracting the voltage of the second capacitor and the voltage reference value of the second capacitor, and the first error signal is adjusted and multiplied with the per-unit value of the at least part of the AC harmonic component to obtain the first current reference value.

[0062] In some embodiments, the power conversion system further includes a three-phase rectifier circuit, the input port of the power conversion module is connected to the output port of the three-phase rectifier circuit, the input port of the three-phase rectifier circuit is connected to a three-phase AC power supply, and at least part of the AC harmonic component includes the 6th harmonic component, and / or the 12th harmonic component, and / or the 18th harmonic component of the output voltage of the three-phase rectifier circuit.

[0063] In other embodiments, the power conversion system further includes a single-phase rectifier circuit, an input port of the single-phase rectifier circuit is connected to a single-phase AC power supply, an input port of the power conversion module is connected to an output port of the single-phase rectifier circuit, and at least part of the AC harmonic component includes a 2nd harmonic component, and / or a 4th harmonic component, and / or a 6th harmonic component of the output voltage of the single-phase rectifier circuit.

[0064] In some embodiments, step S103 specifically includes: high-pass filtering the input voltage of the power conversion module to obtain a first voltage value; multiplying the first voltage value and a first admittance parameter to obtain the second current reference value; or includes: high-pass filtering the input voltage of the power conversion module to obtain a first voltage value; dividing the first voltage value and a first resistance parameter to obtain the second current reference value.

[0065] Further, step S103 further includes: performing low-pass filtering on the input voltage of the power conversion module to obtain a second voltage value; performing low-pass filtering on the current signal related to the input current of the power conversion module to obtain a first current value. It also includes: performing a division operation on the second voltage value and the first current value to obtain a second resistance parameter; scaling the second resistance parameter according to a first coefficient to obtain the first resistance parameter; or it also includes: performing a division operation on the first current value and the second voltage value to obtain a second admittance parameter; scaling the second admittance parameter according to a first coefficient to obtain the first admittance parameter.

[0066] The cutoff frequency of the high-pass filter may be but not limited to 100 Hz, the cutoff frequency of the low-pass filter may be but not limited to 40 Hz, and the first coefficient may be set to but not limited to 0.5.

[0067] In some embodiments, step S104 specifically includes: outputting a second error signal after subtracting the current flowing through the first inductor and the current reference value of the first inductor; and obtaining the driving signal by adding the adjusted second error signal to a duty cycle feedforward value.

[0068] In some embodiments, the power conversion system further includes a rectifier circuit and a load conversion circuit, the input port of the power conversion module is connected in parallel to the output port of the rectifier circuit and the input port of the load conversion circuit, wherein the sum of the input current of the power conversion module and the output current of the rectifier circuit is the input current of the load conversion circuit, wherein the load conversion circuit is a DC-AC conversion circuit or a DC-DC conversion circuit. The damping circuit is equivalent to a resistor after being adjusted by the controller.

[0069] In some embodiments, the power conversion system further includes an AC power supply, an input inductor, a rectifier circuit, and a bus capacitor, wherein the input inductor is electrically connected between the AC power supply and an input end of the rectifier circuit, and the bus capacitor and the power conversion module are sequentially connected in parallel to an output end of the rectifier circuit, wherein step S103 further includes:

[0070] Acquiring a ripple component of an input voltage of the power conversion module;

[0071] Obtaining a resistance parameter according to the input voltage of the power conversion module and a current signal related to the input current of the power conversion module;

[0072] The second current reference value is obtained according to a first coefficient, the resistance parameter and the ripple component of the input voltage, wherein the first coefficient is adaptively adjusted according to the input inductance to minimize the damping current, thereby improving the power of the power conversion module and the efficiency of the entire power conversion system.

[0073] When the input inductance increases, the resonant frequency of the LC parallel resonance between the output impedance of the rectifier circuit and the bus capacitor becomes smaller, the required frequency of the second current reference value decreases, and the first coefficient is adaptively adjusted according to the input inductance.

[0074] The power conversion system also includes a load conversion circuit, the input port of the power conversion module is connected in parallel to the input port of the load conversion circuit, wherein the current signal related to the input current of the power conversion module includes the input current of the load conversion circuit or the output current of the load conversion circuit.

[0075] In summary, the embodiments of the present disclosure provide a power conversion system and a control method thereof. Compared with the prior art solutions, the power conversion system has higher working efficiency, stronger system stability and lower loss.

[0076] Although embodiments of the present disclosure have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present disclosure, and the scope of protection of the present disclosure shall be based on the scope defined by the appended claims.

Claims

1. A power conversion system, comprising a power conversion module, wherein the power conversion module comprises a controller and a damping circuit and a first capacitor connected in series, the damping circuit comprises a first inductor, a first switch tube, a second switch tube and a second capacitor, the first switch tube and the second switch tube are connected in series to form a first bridge arm, the first inductor is connected between the middle node of the first bridge arm and the first capacitor, and the second capacitor is connected in parallel to the first bridge arm, characterized in that: The controller comprises: a capacitor voltage control unit, which obtains a first current reference value according to an input voltage of the power conversion module, a voltage of the second capacitor, and a voltage reference value of the second capacitor; a damping current generating unit, which obtains a second current reference value according to an input voltage of the power conversion module and a current signal related to an input current of the power conversion module; as well as An inductor current control unit outputs a driving signal to control the first switch tube and the second switch tube according to the current flowing through the first inductor and the current reference value of the first inductor, so as to stabilize the input voltage of the power conversion module, wherein the current reference value of the first inductor is obtained according to the first current reference value and the second current reference value.

2. The power conversion system according to claim 1, characterized in that: The capacitor voltage control unit includes a first filter and a phase-locked loop, which are used to track at least part of the AC harmonic component of the input voltage of the power conversion module, and obtain the first current reference value according to the at least part of the AC harmonic component, the voltage of the second capacitor and the voltage reference value of the second capacitor.

3. The power conversion system according to claim 2, characterized in that: The capacitor voltage control unit also includes a first subtractor, a first regulator and a first multiplier. The first subtractor performs a subtraction operation on the voltage of the second capacitor and the voltage reference value of the second capacitor and outputs a first error signal. The first error signal is adjusted by the first regulator and multiplied by the per-unit value of at least part of the AC harmonic component through the first multiplier to obtain the first current reference value.

4. The power conversion system according to claim 2, characterized in that: The power conversion system also includes a three-phase rectifier circuit, the input port of the power conversion module is connected to the output port of the three-phase rectifier circuit, the input port of the three-phase rectifier circuit is connected to a three-phase AC power supply, and the at least part of the AC harmonic components tracked by the phase-locked loop include the 6th harmonic component, and / or the 12th harmonic component, and / or the 18th harmonic component of the output voltage of the three-phase rectifier circuit.

5. The power conversion system according to claim 2, characterized in that: The power conversion system also includes a single-phase rectifier circuit, an input port of the single-phase rectifier circuit is connected to a single-phase AC power supply, an input port of the power conversion module is connected to an output port of the single-phase rectifier circuit, and at least part of the AC harmonic components tracked by the phase-locked loop include the 2nd harmonic component, and / or the 4th harmonic component, and / or the 6th harmonic component of the output voltage of the single-phase rectifier circuit.

6. The power conversion system according to claim 1, characterized in that: The damping current generating unit comprises a second filter and a second multiplier, wherein the second filter performs high-pass filtering on the input voltage of the power conversion module to obtain a first voltage value, and the second multiplier performs multiplication operation on the first voltage value and a first admittance parameter to obtain the second current reference value; or The damping current generating unit includes a second filter and a first divider, the second filter performs high-pass filtering on the input voltage of the power conversion module to obtain a first voltage value, and the first divider performs a division operation on the first voltage value and a first resistance parameter to obtain the second current reference value.

7. The power conversion system according to claim 6, characterized in that: The damping current generating unit further comprises a third filter, a fourth filter and a second divider, wherein the third filter performs low-pass filtering on the input voltage of the power conversion module to obtain a second voltage value, and the fourth filter performs low-pass filtering on the current signal related to the input current of the power conversion module to obtain a first current value, wherein: The second divider performs a division operation on the first current value and the second voltage value to obtain a second admittance parameter, and scales the second admittance parameter according to a first coefficient to obtain the first admittance parameter; or The second divider divides the second voltage value and the first current value to obtain a second resistance parameter, and scales the second resistance parameter according to the first coefficient to obtain the first resistance parameter.

8. The power conversion system according to claim 7, characterized in that: The cutoff frequency of the second filter is 100 Hz, the cutoff frequencies of the third filter and the fourth filter are 40 Hz, and the first coefficient is 0.

5.

9. The power conversion system according to claim 1, characterized in that: The inductor current control unit includes a second subtractor, a second regulator and a first adder. The second subtractor performs a subtraction operation on the current flowing through the first inductor and the current reference value of the first inductor and outputs a second error signal. The second error signal is adjusted by the second regulator and added to a duty cycle feedforward value by the first adder to obtain the driving signal.

10. The power conversion system according to claim 1, characterized in that: The power conversion module also includes a second adder, wherein the current reference value of the first inductor is obtained by adding the first current reference value and the second current reference value through the second adder.

11. The power conversion system according to claim 1, characterized in that: The power conversion system also includes a rectifier circuit and a load conversion circuit, the input port of the power conversion module is connected in parallel to the output port of the rectifier circuit and the input port of the load conversion circuit, wherein the sum of the input current of the power conversion module and the output current of the rectifier circuit is the input current of the load conversion circuit, wherein the load conversion circuit is a DC-AC conversion circuit or a DC-DC conversion circuit.

12. The power conversion system according to claim 1, characterized in that: The damping circuit is equivalent to a resistor after being adjusted by the capacitor voltage control unit, the damping current generating unit and the inductor current control unit.

13. The power conversion system according to claim 1, characterized in that: The power conversion system further comprises an AC power supply, an input inductor, a rectifier circuit and a bus capacitor, wherein the input inductor is connected between the AC power supply and an input end of the rectifier circuit, the bus capacitor and the power conversion module are sequentially connected in parallel to an output end of the rectifier circuit, wherein the second current reference value is obtained according to an input voltage of the power conversion module and a current signal related to an input current of the power conversion module, comprising: Acquiring a ripple component of an input voltage of the power conversion module; Obtaining a resistance parameter according to an input voltage of the power conversion module and a current signal related to an input current of the power conversion module; The second current reference value is obtained according to a first coefficient, the resistance parameter and the ripple component of the input voltage, wherein the first coefficient is adaptively adjusted according to the input inductance.

14. The power conversion system according to any one of claims 1, 6 or 13, characterized in that: It also includes a load conversion circuit, the input port of the power conversion module is connected in parallel to the input port of the load conversion circuit, wherein the current signal related to the input current of the power conversion module is the input current of the load conversion circuit or the output current of the load conversion circuit.

15. The power conversion system according to claim 13, characterized in that: When the input inductance increases, the resonant frequency of the LC parallel resonance between the output impedance of the rectifier circuit and the bus capacitor becomes smaller, the required frequency of the second current reference value decreases, and the first coefficient is adaptively adjusted according to the input inductance.

16. A control method for a power conversion system, characterized in that: The control method comprises A power conversion module is provided, comprising a controller and a damping circuit and a first capacitor connected in series, wherein the damping circuit comprises a first inductor, a first switch tube, a second switch tube and a second capacitor, wherein the first switch tube and the second switch tube are connected in series to form a first bridge arm, the first inductor is connected between an intermediate node of the first bridge arm and the first capacitor, and the second capacitor is connected in parallel to the first bridge arm; Obtaining a first current reference value according to an input voltage of the power conversion module, a voltage of the second capacitor, and a voltage reference value of the second capacitor; Obtaining a second current reference value according to an input voltage of the power conversion module and a current signal related to an input current of the power conversion module; as well as The first switch tube and the second switch tube are controlled by outputting a driving signal according to the inductor current flowing through the first inductor and the inductor current reference value of the first inductor to stabilize the input voltage of the power conversion module, wherein the current reference value of the first inductor is obtained according to the first current reference value and the second current reference value.

17. The control method according to claim 16, characterized in that: The step of obtaining a first current reference value according to an input voltage of the power conversion module, a voltage of a second capacitor of the damping circuit, and a voltage reference value of the second capacitor comprises: At least part of the AC harmonic component of the input voltage of the power conversion module is obtained, and the first current reference value is obtained according to the at least part of the AC harmonic component, the voltage of the second capacitor, and the voltage reference value of the second capacitor.

18. The control method according to claim 17, characterized in that: The step of obtaining the first current reference value according to the at least part of the AC harmonic component, the voltage of the second capacitor, and the voltage reference value of the second capacitor comprises: A first error signal is outputted after subtracting the voltage of the second capacitor from the voltage reference value of the second capacitor, and the first error signal is adjusted and multiplied by the per-unit value of at least part of the AC harmonic component to obtain the first current reference value.

19. The control method according to claim 17, characterized in that: The power conversion system also includes a three-phase rectifier circuit, the input port of the power conversion module is connected to the output port of the three-phase rectifier circuit, the input port of the three-phase rectifier circuit is connected to a three-phase AC power supply, and the at least part of the AC harmonic component includes the 6th harmonic component, and / or the 12th harmonic component, and / or the 18th harmonic component of the output voltage of the three-phase rectifier circuit.

20. The control method according to claim 17, characterized in that: The power conversion system also includes a single-phase rectifier circuit, an input port of the single-phase rectifier circuit is connected to a single-phase AC power supply, an input port of the power conversion module is connected to an output port of the single-phase rectifier circuit, and at least part of the AC harmonic component includes a 2nd harmonic component, and / or a 4th harmonic component, and / or a 6th harmonic component of the output voltage of the single-phase rectifier circuit.

21. The control method according to claim 16, characterized in that: The step of obtaining a second current reference value according to the input voltage of the power conversion module and a current signal related to the input current of the power conversion module comprises: Performing high-pass filtering on the input voltage of the power conversion module to obtain a first voltage value; performing a multiplication operation on the first voltage value and a first admittance parameter to obtain the second current reference value; Or contain: Performing high-pass filtering on the input voltage of the power conversion module to obtain a first voltage value; The second current reference value is obtained by dividing the first voltage value and a first resistance parameter.

22. The control method according to claim 21, characterized in that: The method of obtaining a second current reference value according to the input voltage of the power conversion module and the current signal related to the input current of the power conversion module comprises: performing low-pass filtering on the input voltage of the power conversion module to obtain a second voltage value; performing low-pass filtering on the current signal related to the input current of the power conversion module to obtain a first current value; and further comprises: A second resistance parameter is obtained by dividing the second voltage value and the first current value; Scaling the second resistance parameter according to a first coefficient to obtain the first resistance parameter; or further comprising: Performing a division operation on the first current value and the second voltage value to obtain a second admittance parameter; The first admittance parameter is obtained by scaling the second admittance parameter according to a first coefficient.

23. The control method according to claim 22, characterized in that: The cutoff frequency of the high-pass filter is 100 Hz, the cutoff frequency of the low-pass filter is 40 Hz, and the first coefficient is 0.

5.

24. The control method according to claim 16, characterized in that: The step of outputting a driving signal to control the first switch tube and the second switch tube according to the inductor current flowing through the first inductor and the inductor current reference value of the first inductor comprises: Outputting a second error signal after performing a subtraction operation on the current flowing through the first inductor and a current reference value of the first inductor; The second error signal is adjusted and then added to a duty cycle feedforward value to obtain the driving signal.

25. The control method according to claim 16, characterized in that: The current reference value of the first inductor is obtained according to the first current reference value and the second current reference value, including: The current reference value of the first inductor is obtained by adding the first current reference value and the second current reference value.

26. The control method according to claim 16, characterized in that: The power conversion system also includes a rectifier circuit and a load conversion circuit, the input port of the power conversion module is connected in parallel to the output port of the rectifier circuit and the input port of the load conversion circuit, wherein the sum of the input current of the power conversion module and the output current of the rectifier circuit is the input current of the load conversion circuit, wherein the load conversion circuit is a DC-AC conversion circuit or a DC-DC conversion circuit.

27. The control method according to claim 16, characterized in that: The damping circuit is equivalent to a resistor after being adjusted by the controller.

28. The control method according to claim 16, characterized in that: The power conversion system further includes an AC power supply, an input inductor, a rectifier circuit, and a bus capacitor, wherein the input inductor is electrically connected between the AC power supply and an input end of the rectifier circuit, the bus capacitor and the power conversion module are sequentially connected in parallel to an output end of the rectifier circuit, wherein the second current reference value is obtained according to an input voltage of the power conversion module and a current signal related to an input current of the power conversion module, comprising: Acquiring a ripple component of an input voltage of the power conversion module; Obtaining a resistance parameter according to the input voltage of the power conversion module and a current signal related to the input current of the power conversion module; The second current reference value is obtained according to a first coefficient, the resistance parameter and the ripple component of the input voltage, wherein the first coefficient is adaptively adjusted according to the input inductance.

29. The control method according to any one of claims 16, 22 or 28, characterized in that: The power conversion system also includes a load conversion circuit, the input port of the power conversion module is connected in parallel to the input port of the load conversion circuit, wherein the current signal related to the input current of the power conversion module includes the input current of the load conversion circuit or the output current of the load conversion circuit.

30. The control method according to claim 28, characterized in that: When the input inductance increases, the resonant frequency of the LC parallel resonance between the output impedance of the rectifier circuit and the bus capacitor becomes smaller, the required frequency of the second current reference value decreases, and the first coefficient is adaptively adjusted according to the input inductance.

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