Controller, control device and switching power supply

Abstract

The invention discloses a control method, a control device and a switching power supply, the control method is applied to an N-phase converter, and the control method comprises the following steps: calculating an electrical parameter output by the N-phase converter and a modulation wave required by each phase bridge arm switching tube when a common-mode voltage reaches an expected value through voltage loop and current loop double closed-loop control; adjusting the current modulation wave of each phase of bridge arm switch tube so as to obtain N first modulation waves; calculating a second frequency required by a modulation wave of each phase of bridge arm switch tube when each phase of bridge arm switch tube realizes ZVS by predicting the magnitude of bridge arm side inductive current pulsation in each phase of LCL filter, taking the second frequency as the frequency of a carrier wave, and generating N carrier waves; and comparing the first modulation wave of each phase of bridge arm switch tube with the corresponding carrier wave to obtain a driving signal for controlling the on and off of each phase of bridge arm switch tube. According to the invention, good harmonic performance can be obtained while low common-mode voltage is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power conversion, and in particular to a controller, a control device and a switching power supply. Background Art

[0002] The three-phase converter is the core equipment for clean power conversion and new energy generation, and is widely used in different power generation and terminal energy occasions such as automobile charging, new energy, and motor drive. Traditional PWM modulation produces serious common-mode voltage hazards in three-phase converters. For example, the excessive shaft current caused by the common-mode voltage will burn the motor bearings in a short time. Therefore, the suppression of common-mode voltage is of great significance to improving the safety and stability of three-phase inverters.

[0003] One of the traditional common-mode voltage suppression strategies is to add passive devices and change the circuit topology, which will lead to an increase in hardware cost and control complexity; the second strategy is to optimize the modulation wave. For example, AZSPWM, which is well known to technicians in this field, suppresses the common-mode voltage by optimizing the modulation wave. The English abbreviation AZSPWM is the full name of Active Zero State PWM, which is translated into Chinese as zero-vector pulse width modulation. For typical control algorithms, refer to Giovanna Briti's paper "A New Space Vector Modulation Strategy for Common Mode Voltage Reduction 1997". The solution of this paper is to synthesize non-zero vector PWM of zero vector through complementary vectors. For example, RSPWM and NSPWM, which are well known to technicians in this field, also suppress the common-mode voltage by optimizing the modulation wave. Although these strategies can greatly reduce the common-mode voltage, they also bring about harmonic deterioration.

[0004] On the other hand, soft switching operation can increase the operating frequency to reduce the deterioration of harmonics and improve efficiency and power density, but it will bring great switching losses. Although the resonant DC bus inverter and the auxiliary resonant commutated pole inverter can realize soft switching of the main switch and the auxiliary switch, the complexity of the power supply circuit and the control strategy increases dramatically, resulting in increased costs and reduced reliability. The paper published by Li Zeyuan's team, "Critical-Conduction-Mode-Based Soft-Switching Modulation for Three-Phase PV Inverters With Reactive Power Transfer Capability", achieves soft switching while reducing the frequency range by operating one phase in critical conduction mode and one phase in discontinuous mode. Although this soft switching solution can improve working efficiency, it cannot solve the problem of common-mode voltage at the same time.

[0005] The application of wide bandgap semiconductor device SiC can enable the converter to operate at a higher operating frequency (about 75kHz), but at the same time it will cause insulation degradation, leakage current and electromagnetic interference to the system, and will cause greater common-mode interference, posing a threat to the reliability of the system. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a control method, a control device and a switching power supply, which can at least to a certain extent solve the problems of severe common mode interference and deterioration of harmonics in the above-mentioned prior art.

[0007] As a first aspect of the present invention, the technical solution of the control method provided is as follows:

[0008] A control method is applied to an N-phase converter, where N is an integer greater than or equal to 1, and the N-phase converter includes an LCL filter and an N-phase bridge circuit, each phase bridge arm includes an upper switch tube and a lower switch tube, and the upper switch tube and the lower switch tube are driven by complementary signals with a dead time, and the N-phase converter works in a rectification and inversion state, wherein the control method includes the following steps:

[0009] A first modulation wave acquisition step, calculating the modulation wave required by the bridge arm switch tube of each phase when the electrical parameters and common mode voltage output by the N-phase converter reach the expected value through dual closed-loop control of the voltage loop and the current loop, and adjusting the current modulation wave of the bridge arm switch tube of each phase, thereby obtaining N first modulation waves;

[0010] Carrier acquisition step, by predicting the magnitude of the inductor current pulsation on the bridge arm side of each phase LCL filter, calculating the second frequency required for the modulation wave of each phase bridge arm switch tube when each phase bridge arm switch tube realizes ZVS, and using them as the frequency of the carrier respectively, to generate N carriers;

[0011] The driving signal acquisition step compares the first modulation wave of the bridge arm switch tube of each phase with the corresponding carrier to obtain a driving signal for controlling the on and off of the bridge arm switch tube of each phase.

[0012] Preferably, the modulation wave in the first modulation wave acquisition step is an AZSPWM modulation wave.

[0013] Furthermore, the acquisition of the first modulated wave comprises the following steps:

[0014] Step 1: sampling a first voltage signal representing the output voltage of the N-phase converter by the voltage loop;

[0015] Step 2: The current loop circuit samples a second voltage signal representing the magnitude of the inductor current on the bridge arm side of the LCL filter of each phase of the N-phase converter, and a third voltage signal representing the magnitude of the input voltage of each phase of the N-phase converter;

[0016] Step three, adjusting the current modulation wave of the switch tube of each phase bridge arm according to the first voltage signal, each of the second voltage signals and each of the third voltage signals, so as to obtain N first modulation waves;

[0017] The first voltage signal is used to achieve an expected value of an electrical parameter output by the N-phase converter, and each of the second voltage signals and each of the third voltage signals are used to achieve an expected value of a common-mode voltage of the N-phase converter.

[0018] Furthermore, the condition for each phase bridge arm switch tube to achieve ZVS is that there is a negative current before each switch tube is turned on, ensuring that the parasitic capacitance of the switch tube that needs to be turned on is completely discharged.

[0019] Furthermore, the second frequency required for the modulation wave of the bridge arm switch tube of each phase when the bridge arm switch tube of each phase realizes ZVS is calculated according to the sector selection formula.

[0020] Preferably, when N is 3, the calculation formula of the second frequency in different sectors is as follows:

[0021]

[0022] Among them, f s represents the second frequency of the switch tube of a certain phase bridge arm of the N-phase converter, i represents the current of the inductor on the bridge arm side in the LCL filter of a certain phase of the N-phase converter, V represents the input voltage of a certain phase of the N-phase converter, V o represents the output voltage of the N-phase converter, L represents the inductance value of the bridge arm side inductor in a certain phase LCL filter of the N-phase converter, I bias In order to achieve the bias current of soft switching, m represents the first modulation wave of a phase of the N-phase converter, and the corresponding relationship between the additional subscripts xyz of each parameter and the three phases abc in different sectors is as follows:

[0023] Sector 1 2 3 4 5 6 x a b b c c a y b a c b a c z c c a a b b

[0024] Further, when N is 3, the N carriers are unified into a carrier generated by the smallest of the second frequencies, and the smallest of the second frequencies in different sectors is selected as follows, where f sa Indicates the second frequency of phase a, f sb represents the second frequency of phase b, f sc Represents the second frequency of phase c:

[0025]

[0026] Furthermore, the N carriers are unified into a carrier generated by the second frequency corresponding to the one with the largest absolute value of the input voltage.

[0027] As a second aspect of the present invention, the technical solution of the embodiment of the control device provided is as follows:

[0028] A control device is applied to an N-phase converter, where N is an integer greater than or equal to 1, and the N-phase converter includes an LCL filter and an N-phase bridge circuit, each phase bridge arm includes an upper switch tube and a lower switch tube, and the upper switch tube and the lower switch tube are driven by complementary signals with a dead time, and the N-phase converter works in a rectification and inversion state, wherein the control device includes the following units:

[0029] A first modulation wave acquisition unit is used to calculate the modulation wave required by the bridge arm switch tube of each phase when the electrical parameters and common mode voltage output by the N-phase converter reach the expected value through a voltage loop and a current loop double closed-loop control, and adjust the current modulation wave of the bridge arm switch tube of each phase, so as to obtain N first modulation waves;

[0030] The carrier acquisition unit is used to calculate the second frequency required for the modulation wave of each phase bridge arm switch tube when each phase bridge arm switch tube realizes ZVS by predicting the magnitude of the inductor current pulsation on the bridge arm side of each phase LCL filter, and use the second frequency as the carrier frequency to generate N carriers;

[0031] The driving signal acquisition unit is used to compare the first modulation wave of the bridge arm switch tube of each phase with the corresponding carrier to obtain a driving signal for controlling the conduction and shutdown of the bridge arm switch tube of each phase.

[0032] As a third aspect of the present invention, the technical solution of the embodiment of the switching power supply provided is as follows:

[0033] A switching power supply, comprising an N-phase converter, N being an integer greater than or equal to 1, the N-phase converter comprising an LCL filter and an N-phase bridge circuit, each phase bridge arm comprising an upper switch tube and a lower switch tube, and the upper switch tube and the lower switch tube are driven by complementary signals with a dead time, the N-phase converter operates in rectification and inversion states, wherein: the switching power supply also includes the control device of the second aspect above.

[0034] Furthermore, the N is 3.

[0035] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0036] The first modulation wave obtained in the embodiment of the present invention can suppress the common-mode voltage, and on this basis, it is compared with the frequency-converted carrier obtained by ripple prediction, and finally a driving signal is obtained, so that all switching tubes realize soft switching, and the operating frequency of the N-phase converter is increased, thereby improving the problem of harmonic degradation caused by common-mode voltage suppression. In addition, the realization of soft opening of the switching tube is conducive to reducing switching losses and improving efficiency, and the increase in operating frequency can reduce the volume of the switching power supply and improve power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of a three-phase converter according to the present invention;

[0038] Figure 2 is a flow chart of a control method according to a first embodiment of the present invention;

[0039] Figure 3 is a timing diagram of input voltage when the control method of the first embodiment of the present invention is applied to a three-phase converter;

[0040] Figure 4 AZSPWM and inductor current waveform in sector 1 of the first embodiment of the present invention;

[0041] Figure 5 It is a schematic diagram of the second frequency change of the first embodiment of the present invention;

[0042] Figure 6 is a principle block diagram of a control device according to a second embodiment of the present invention;

[0043] Figure 7 This is a specific principle block diagram of the control device of the second embodiment of the present invention when it is applied to a three-phase converter. DETAILED DESCRIPTION

[0044] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0045] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0046] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application are described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, the process, method, system, product or equipment comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0047] It should be understood that, in the specification, claims and drawings, when a step is described as being connected to another step, the step may be directly connected to the other step, or be connected to the other step through a third step; when an element / unit is described as being "connected" to another element / unit, the element / unit may be "directly connected" to the other element / unit, or be "connected" to the other element / unit through a third element / unit.

[0048] In addition, the drawings of the present disclosure are only schematic diagrams of the present disclosure and are not necessarily drawn to scale. The same symbols in the drawings represent the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented using software, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontrollers.

[0049] First embodiment

[0050] The present embodiment provides a control method, which is applied to an N-phase converter, where N is an integer greater than or equal to 1. The N-phase converter includes an LCL filter and an N-phase bridge circuit, each phase bridge arm includes an upper switch tube and a lower switch tube, and the upper switch tube and the lower switch tube are driven by complementary signals with a dead time, and the N-phase converter works in a rectification and inversion state. Figure 1 This is a schematic diagram of a three-phase converter involved in the present invention, that is, the value of N is 3, wherein the a-phase voltage is Va, the b-phase voltage is Vb, the c-phase voltage is Vc, the inductor L2, the capacitor C1 and the inductor L1 in each phase constitute an LCL filter, the switch tube Q1 and the switch tube Q2 constitute the a-phase bridge arm, the switch tube Q3 and the switch tube Q4 constitute the b-phase bridge arm, the switch tube Q5 and the switch tube Q6 constitute the c-phase bridge arm, and the capacitor C is the output filter capacitor of the three-phase converter.

[0051] It should be noted that the bridge arm side inductance in the LCL filter of the present invention refers to the inductance directly connected to the midpoint of the corresponding bridge arm in each phase LCL filter, for example Figure 1 The inductor L1 in each phase LCL filter is the inductor on the bridge arm side of the LCL filter of the present invention.

[0052] Figure 2 The control method of the first embodiment of the present invention is shown in the flowchart, which includes the following steps:

[0053] The first modulation wave acquisition step S100 is to calculate the modulation wave required by the bridge arm switch tube of each phase when the electrical parameters and common mode voltage output by the N-phase converter reach the expected value through the voltage loop and the current loop double closed-loop control, and adjust the current modulation wave of the bridge arm switch tube of each phase, so as to obtain N first modulation waves;

[0054] Carrier acquisition step S200, by predicting the magnitude of the inductor current pulsation on the bridge arm side of each phase LCL filter, calculates the second frequency required for the modulation wave of each phase bridge arm switch tube when each phase bridge arm switch tube realizes ZVS, and uses them as the frequency of the carrier respectively, to generate N carriers;

[0055] In the drive signal acquisition step S300, the first modulation wave of the bridge arm switch tube of each phase is compared with the corresponding carrier wave to obtain a drive signal for controlling the on and off of the bridge arm switch tube of each phase.

[0056] The first modulation wave obtained in the control method of this embodiment can suppress the common mode voltage. On this basis, it is compared with the frequency-converted carrier obtained by ripple prediction, and finally a driving signal is obtained, so that all switch tubes can achieve soft switching, and the operating frequency of the N-phase converter is increased, thereby improving the problem of harmonic degradation caused by common mode voltage suppression. In addition, the realization of soft opening of the switch tube is conducive to reducing switching losses and improving efficiency, and the increase in operating frequency can reduce the size of the switching power supply and improve power density.

[0057] Furthermore, the modulation wave in the first modulation wave acquisition step is an AZSPWM modulation wave. The reason why AZSPWM is preferably used is that AZSPWM has the advantages of a wide modulation range, fewer switching times in one cycle, and low loss compared to RSPWM and NSPWM.

[0058] As a specific embodiment, the acquisition of the first modulation wave includes the following steps:

[0059] Step 1: sampling a first voltage signal representing the output voltage of the N-phase converter by a voltage loop;

[0060] Step 2: sampling a second voltage signal representing the magnitude of the inductor current on the bridge arm side of the LCL filter of each phase of the N-phase converter and a third voltage signal representing the magnitude of the input voltage of each phase of the N-phase converter by a current loop circuit;

[0061] Step three, adjusting the current modulation wave of the switch tube of each phase bridge arm according to the first voltage signal, each second voltage signal and each third voltage signal, so as to obtain N first modulation waves;

[0062] The first voltage signal is used to achieve an expected value of an electrical parameter output by the N-phase converter, and each of the second voltage signals and each of the third voltage signals is used to achieve an expected value of a common-mode voltage of the N-phase converter.

[0063] As a specific embodiment, the condition for each phase bridge arm switch tube to achieve ZVS is that there is a negative current before each switch tube is turned on, ensuring that the parasitic capacitance of the switch tube that needs to be turned on is discharged.

[0064] It is known to those skilled in the art that the three-phase voltage is divided into six sectors according to the size and position relationship. If the first phase voltage is 0-60°, the first phase voltage is greater than 0, the second phase voltage is less than 0, the third phase voltage is less than 0, and the absolute values ​​of the three-phase voltages are arranged in order of size: the first phase is greater than the third phase, which is greater than the second phase. This is recorded as sector 1, and the other sectors are similarly divided. Figure 4 For a timing diagram of input voltage when the control method of the first embodiment of the invention is applied to a three-phase converter, see Figure 3 , where 0-60° is the 1st sector, 60°-120° is the 2nd sector, 120°-180° is the 3rd sector, 180°-240° is the 4th sector, 240°-300° is the 5th sector, and 300°-360° is the 6th sector.

[0065] Figure 4 For the AZSPWM and inductor current waveforms in the first sector of the first embodiment of the present invention, please refer to Figure 4 , where ma represents the a-phase modulation wave, mb represents the b-phase modulation wave, mc represents the c-phase modulation wave, Q1 represents Figure 1 The drive of the upper tube of the bridge arm of the middle phase a (the abbreviation of the upper switch tube, correspondingly, the lower tube is the abbreviation of the lower switch tube, the same below) and Q3 represent Figure 1 The drive of the upper tube of the bridge arm of phase b, Q5 represents Figure 1 In the figure, the driving of the upper tube of the bridge arm of phase c, ia represents the current ripple of the inductor located in phase a of the inductor L1, ib represents the current ripple of the inductor located in phase b of the inductor L1, ic represents the current ripple of the inductor located in phase c of the inductor L1, and the vectors 111 (all the upper tubes of the bridge arm are turned on) and 000 (all the lower tubes of the bridge arm are turned on) are zero vectors. Figure 4In the example, the upper tube of phase a remains on at t5 in sector 1, so a positive current must be present in the upper tube of phase a to achieve ZVS; it is turned off at t3, at which time the upper tube of phase a is turned off and the lower tube is turned on, and at this time the lower tube must have a negative current to achieve ZVS. The same goes for phase b and phase c. Therefore, when all six high-frequency switching devices are required to achieve ZVS, the specific requirements can be expressed as follows:

[0066]

[0067] Among them I bias The bias current is used to realize soft switching. Its size is determined by the equivalent capacitance. Specifically, Ibias>2Ceq*Vds / Td, where Ceq is the equivalent capacitance, Vds is the voltage on the equivalent capacitance before the switch is turned on, Td is the set dead time, and I bias The value can also be determined based on actual experience. The value of Ibias is generally 1.5-2A.

[0068] The other sectors are similar to the first sector and will not be described in detail.

[0069] It can be seen from the above analysis that, as a specific embodiment, the second frequency required for the modulation wave of each phase bridge arm switch tube when each phase bridge arm switch tube realizes ZVS can be calculated according to the sector selection formula.

[0070] As a specific embodiment, when N is 3, the calculation formulas for the second frequency of different sectors are derived based on the required current size of the inductance on the bridge arm side of each phase LCL filter at each moment as the boundary condition:

[0071]

[0072] Among them, f s represents the second frequency of the switch tube of a certain phase bridge arm of the N-phase converter, i represents the current of the inductor on the bridge arm side of the LCL filter of a certain phase of the N-phase converter, V represents the input voltage of a certain phase of the N-phase converter, V o represents the output voltage of the N-phase converter, L represents the inductance value of the bridge arm side inductor in a certain phase LCL filter of the N-phase converter, I bias In order to achieve the bias current of soft switching, m represents the first modulation wave of a phase of the N-phase converter, and the corresponding relationship between the additional subscripts xyz of each parameter and the three phases abc in different sectors is as follows:

[0073] Sector 1 2 3 4 5 6 x a b b c c a y b a c b a c z c c a a b b

[0074] As a specific embodiment, when N is 3, the N carriers are unified into a carrier generated by the smallest of the second frequencies, in order to keep the three-phase frequencies consistent and to achieve ZVS of all switch tubes. Figure 5 FIG. 1 is a schematic diagram of the second frequency change of the first embodiment of the present invention, wherein the horizontal axis t is time, and the vertical axis fx_min (Hz) is the selected minimum switching frequency, see Figure 5 , the smallest of the second frequencies of different sectors is selected as follows, where f sa Indicates the second frequency of phase a, f sb represents the second frequency of phase b, f sc Represents the second frequency of phase c:

[0075]

[0076] As a specific embodiment, the N carriers are unified into a carrier generated by the second frequency corresponding to the one with the largest absolute value of the input voltage, in order to make the judgment simpler and reduce the amount of calculation.

[0077] Second embodiment

[0078] The present embodiment provides a control device, which is applied to an N-phase converter, where N is an integer greater than or equal to 1. The N-phase converter includes an LCL filter and an N-phase bridge circuit, each phase bridge arm includes an upper switch tube and a lower switch tube, and the upper switch tube and the lower switch tube are driven by complementary signals with a dead time, and the N-phase converter works in a rectification and inversion state. Figure 6 This is a principle block diagram of a control device according to a second embodiment of the present invention, which includes the following units:

[0079] The first modulation wave acquisition unit 100 is used to calculate the modulation wave required by the bridge arm switch tube of each phase when the electrical parameters and common mode voltage output by the N-phase converter reach the expected value through the voltage loop and the current loop double closed-loop control, and adjust the current modulation wave of the bridge arm switch tube of each phase, so as to obtain N first modulation waves;

[0080] The carrier acquisition unit 200 is used to calculate the second frequency required for the modulation wave of each phase bridge arm switch tube when each phase bridge arm switch tube realizes ZVS by predicting the magnitude of the inductor current pulsation on the bridge arm side of each phase LCL filter, and use the second frequency as the carrier frequency to generate N carriers;

[0081] The driving signal acquisition unit 300 is used to compare the first modulation wave of the bridge arm switch tube of each phase with the corresponding carrier to obtain a driving signal for controlling the conduction and shutdown of the bridge arm switch tube of each phase.

[0082] The technical means adopted by the control device of this embodiment are consistent with the control method of the first embodiment, and the beneficial effects are the same, so they are not repeated; in addition, the preferred technical means or further improved means of each step in the control method of the first embodiment can be extended to the corresponding units of this embodiment, and this embodiment will not describe them one by one.

[0083] Figure 7 This is a specific principle block diagram of the control device of the second embodiment of the present invention when it is applied to a three-phase converter. Figure 7 :

[0084] The output voltage detection module samples the output voltage of the three-phase converter and sends it to the voltage loop, and adjusts the current modulation wave of the switch tube of each phase bridge arm so that the electrical parameters output by the three-phase converter reach the expected value. Since the first voltage signal is used to achieve the output voltage of the three-phase converter to reach the expected value, that is, to achieve the output voltage stability of the three-phase converter, the voltage loop is also called a voltage stabilization loop at this time.

[0085] Among them, the three-phase voltage detection module and the three-phase current detection module respectively detect the input voltage Va / Vb / Vc of each phase of the three-phase converter and the current Ia / Ib / Ic of the bridge arm side inductance in each phase LCL filter, and then perform coordinate transformation and sector identification, transform each three-phase detection signal into a corresponding two-phase signal, and determine which sector the current input of the three-phase converter is in. The current loop adjusts the current modulation wave of the bridge arm switch tube of each phase according to the current two-phase signal and sector so that the common mode voltage reaches the expected value;

[0086] Among them, the common-mode voltage optimization modulation wave mode is three first modulation waves ma / mb / mc, and these three first modulation waves can make the electrical parameters and common-mode voltage output by the three-phase converter reach the expected values;

[0087] Among them, the signals output by the three-phase voltage detection module, the three-phase current detection module and the coordinate transformation and sector identification module and the three first modulation waves are also sent to the frequency calculation module. The frequency calculation module calculates the second frequency required for the modulation wave of each phase bridge arm switch tube when each phase bridge arm switch tube realizes ZVS by predicting the size of the inductor current pulsation on the bridge arm side of each phase LCL filter, selects the smallest fx_min of the second frequencies as the frequency of the carrier, generates three carriers, and then compares the three first modulation waves with the corresponding carriers to generate three-phase drive signals Sa1, Sb1 and Sc1. These three signals are respectively Figure 7 The upper tube driving signal of the a-phase bridge arm, the upper tube driving signal of the b-phase bridge arm and the upper tube driving signal of the c-phase bridge arm. Since the upper tube driving signal and the lower tube driving signal of each bridge arm are complementary, the lower tube driving signal Sa2 of the a-phase bridge arm, the lower tube driving signal Sb2 of the b-phase bridge arm and the lower tube driving signal Sc2 of the c-phase bridge arm can be obtained.

[0088] It should be noted that, since there are three first modulation waves in the above-derived calculation formula for the second frequency of different sectors, Figure 7 The above formula is used in the specific implementation, so the three first modulation waves need to be sent to the frequency calculation module.

[0089] Figure 7 The optimized modulation wave of the common mode voltage is the zero vector space vector (AZSPWM) modulation wave. The AZSPWM modulation process will cause harmonic deterioration. By optimizing the current ripple by frequency, the soft switching of all switches can be realized, and the operating frequency can be further increased to reduce the deterioration of harmonics and obtain better harmonic performance. Due to the coupling characteristics of the three phases, it is difficult to realize the soft switching of all switches at the same time without adding auxiliary circuits. Therefore, the operating frequency of the phase with the smallest frequency required to realize soft switching among the three phases is selected as the carrier frequency, and it is calculated and updated in real time.

[0090] In one switching cycle of the AZSPWM modulation process, the current has multiple sections of excitation and demagnetization. The current ripple requirement that needs to be met to achieve soft switching is that there is a positive and negative current conversion within one switching cycle. Specifically, for example, when the lower tube of the a-phase bridge arm is turned on, the negative current flowing out of the a-phase can extract the charge of the equivalent output capacitor of the switching tube; when the upper tube of the a-phase bridge arm is turned on, the positive current flows into the a-phase, causing the upper tube body diode to turn on first. At the same time, the average current of the a-phase must meet the voltage loop and current loop requirements.

[0091] Third embodiment

[0092] The present embodiment provides a switching power supply, which includes an N-phase converter, where N is an integer greater than or equal to 1, and the N-phase converter includes an LCL filter and an N-phase bridge circuit, each phase bridge arm includes an upper switch tube and a lower switch tube, and the upper switch tube and the lower switch tube are driven by complementary signals with a dead time, and the N-phase converter works in a rectification and inversion state, wherein: the switching power supply also includes any one of the control devices in the second embodiment above. Since the present embodiment includes any one of the control devices in the second embodiment above, low common mode voltage can be achieved while obtaining good harmonic performance

[0093] As a specific embodiment, N is 3.

[0094] The above are only preferred embodiments of the present invention, and it should be noted that the above preferred embodiments should not be regarded as limiting the present invention. For those skilled in the art, several equivalent substitutions, improvements and modifications can be made without departing from the spirit and scope of the present invention, and these equivalent substitutions, improvements and modifications should also be regarded as the protection scope of the present invention. The embodiments will not be repeated here, and the protection scope of the present invention shall be based on the scope defined by the claims.

Claims

1. A control method, applied to an N-phase converter, N is an integer greater than or equal to 1, the N-phase converter comprises an LCL filter and an N-phase bridge circuit, each phase bridge arm comprises an upper switch tube and a lower switch tube, and the upper switch tube and the lower switch tube are driven by complementary signals with a dead time, the N-phase converter works in a rectification and inversion state, characterized in that: The control method comprises the following steps: A first modulation wave acquisition step, calculating the modulation wave required by the bridge arm switch tube of each phase when the electrical parameters and common mode voltage output by the N-phase converter reach the expected value through dual closed-loop control of the voltage loop and the current loop, and adjusting the current modulation wave of the bridge arm switch tube of each phase, thereby obtaining N first modulation waves; Carrier acquisition step, by predicting the magnitude of the inductor current pulsation on the bridge arm side of each phase LCL filter, calculating the second frequency required for the modulation wave of each phase bridge arm switch tube when each phase bridge arm switch tube realizes ZVS, and using them as the frequency of the carrier respectively, to generate N carriers; The driving signal acquisition step compares the first modulation wave of the bridge arm switch tube of each phase with the corresponding carrier to obtain a driving signal for controlling the on and off of the bridge arm switch tube of each phase.

2. The control method according to claim 1, characterized in that: The modulation wave in the first modulation wave acquisition step is an AZSPWM modulation wave.

3. The control method according to claim 1, characterized in that: The acquisition of the first modulation wave comprises the following steps: Step 1: sampling a first voltage signal representing the output voltage of the N-phase converter by the voltage loop; Step 2: The current loop circuit samples a second voltage signal representing the magnitude of the inductor current on the bridge arm side of the LCL filter of each phase of the N-phase converter, and a third voltage signal representing the magnitude of the input voltage of each phase of the N-phase converter; Step three, adjusting the current modulation wave of the switch tube of each phase bridge arm according to the first voltage signal, each of the second voltage signals and each of the third voltage signals, so as to obtain N first modulation waves; The first voltage signal is used to achieve an expected value of an electrical parameter output by the N-phase converter, and each of the second voltage signals and each of the third voltage signals are used to achieve an expected value of a common-mode voltage of the N-phase converter.

4. The control method according to claim 1, characterized in that: The condition for each phase bridge arm switch tube to achieve ZVS is that there is a negative current before each switch tube is turned on, ensuring that the parasitic capacitance of the switch tube that needs to be turned on is completely discharged.

5. The control method according to claim 1, characterized in that: The second frequency required for the modulation wave of each phase bridge arm switch tube when each phase bridge arm switch tube realizes ZVS is calculated according to the sector selection formula.

6. The control method according to claim 5, characterized in that: When N is 3, the calculation formula of the second frequency in different sectors is as follows: Among them, f s represents the second frequency of the switch tube of a certain phase bridge arm of the N-phase converter, i represents the current of the inductor on the bridge arm side of the LCL filter of a certain phase of the N-phase converter, V represents the input voltage of a certain phase of the N-phase converter, V o represents the output voltage of the N-phase converter, L represents the inductance value of the bridge arm side inductor in a certain phase LCL filter of the N-phase converter, I bias In order to achieve the bias current of soft switching, m represents the first modulation wave of a phase of the N-phase converter, and the corresponding relationship between the additional subscripts xyz of each parameter and the three phases abc in different sectors is as follows:

7. The control method according to claim 1, characterized in that: When N is 3, the N carriers are unified into a carrier generated by the smallest of the second frequencies, and the smallest of the second frequencies in different sectors is selected as follows, where f sa Indicates the second frequency of phase a, f sb represents the second frequency of phase b, f sc Represents the second frequency of phase c:

8. The control method according to claim 1, characterized in that: The N carriers are unified into a carrier generated by the second frequency corresponding to the one with the largest absolute value of the input voltage.

9. A control device, applied to an N-phase converter, N is an integer greater than or equal to 1, the N-phase converter comprises an LCL filter and an N-phase bridge circuit, each phase bridge arm comprises an upper switch tube and a lower switch tube, and the upper switch tube and the lower switch tube are driven by complementary signals with a dead time, the N-phase converter works in a rectification and inversion state, characterized in that: The control device comprises the following units: A first modulation wave acquisition unit is used to calculate the modulation wave required by the bridge arm switch tube of each phase when the electrical parameters and common mode voltage output by the N-phase converter reach the expected value through a voltage loop and a current loop double closed-loop control, and adjust the current modulation wave of the bridge arm switch tube of each phase, so as to obtain N first modulation waves; The carrier acquisition unit is used to calculate the second frequency required for the modulation wave of each phase bridge arm switch tube when each phase bridge arm switch tube realizes ZVS by predicting the magnitude of the inductor current pulsation on the bridge arm side of each phase LCL filter, and use the second frequency as the carrier frequency to generate N carriers; The driving signal acquisition unit is used to compare the first modulation wave of the bridge arm switch tube of each phase with the corresponding carrier to obtain a driving signal for controlling the conduction and shutdown of the bridge arm switch tube of each phase.

10. A switching power supply, comprising an N-phase converter, N being an integer greater than or equal to 1, the N-phase converter comprising an LCL filter and an N-phase bridge circuit, each phase bridge arm comprising an upper switch tube and a lower switch tube, and the upper switch tube and the lower switch tube are driven by complementary signals with a dead time, the N-phase converter operates in a rectification and inversion state, characterized in that: The switching power supply further comprises the control device as claimed in claim 9.

11. The switching power supply according to claim 10, characterized in that: The N is 3.

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