A control method, control device and switching power supply

Abstract

This invention discloses a control method, control device, and switching power supply. The control method employs a variable frequency SVPWM modulation strategy, comprising the following steps: calculating the SVPWM modulation wave for controlling the on / off state of each phase bridge arm switch when the electrical parameters output by the N-phase converter reach the desired value through a dual closed-loop control of the voltage outer loop and current inner loop; calculating the frequency required for each phase bridge arm switch to achieve ZVS by predicting the magnitude of the current ripple of the second filter inductor in each phase, comparing the frequencies of each phase, and selecting the minimum frequency among the N phases as the frequency of the triangular carrier wave; using the calculated frequency to generate a shared triangular carrier wave; and comparing the SVPWM modulation wave of each phase bridge arm switch with the shared triangular carrier wave to obtain a PWM drive signal for controlling the on / off state of each phase bridge arm switch. This invention enables soft switching of each sector through variable frequency, eliminating the need for clamping each phase.

Description

Technical Field

[0001] This invention relates to the field of three-phase converters, and particularly to a control method, control device, and switching power supply. Background Technology

[0002] With the rapid development of switching power supply technology, three-phase converters have been widely used, especially in energy storage systems, electric vehicle chargers, and motor drivers. However, most existing traditional solutions use continuous conduction mode (CCM) hard switching for modulation, which increases the losses of switching devices. With the rapid development of switching devices such as silicon carbide (SiC) and gallium nitride (GaN), three-phase converters are showing a trend towards lighter, smaller, and higher-frequency designs. Traditional hard switching no longer meets these development trends, leading to the development of soft-switching modulation methods to achieve high efficiency and high power density in three-phase converters. However, traditional soft switching has the following drawbacks:

[0003] (1) Passive or active devices need to be added to assist in the implementation of soft switching, such as adding a zero current detection (ZCD) circuit, which will increase the complexity of the corresponding control and the cost of the devices;

[0004] (2) Since the current and voltage of the three-phase converter are coupled to each other, traditional soft switching requires decoupling and clamping of the current, which will further increase the complexity of soft switching implementation. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to provide a control method, control device and switching power supply that does not require additional passive or active components, and uses variable frequency to achieve zero-voltage turn-on of the switching transistors of each phase bridge arm of the N-phase converter, thereby improving product efficiency and reducing product size and inductor cost.

[0006] As a first aspect of the present invention, the technical solution of the provided control method is as follows:

[0007] A control method is applied to an N-phase converter, the N-phase converter including an N-phase LCL filter and an N-phase bridge circuit. Each phase filter in the N-phase LCL filter includes a first filter inductor, a second filter inductor, and a filter capacitor. Each phase arm of the N-phase bridge circuit includes an upper switch and a lower switch. One end of the first filter inductor of each phase is connected to the input terminal of the corresponding phase of the N-phase converter, and the other end is connected to one end of the second filter inductor of the corresponding phase. The other end of the second filter inductor of each phase is connected to the midpoint of the corresponding phase arm. The filter capacitor of each phase is connected between the midpoint of the corresponding phase filter inductor and the midpoint of the next phase filter inductor. Each bridge arm is connected in parallel to form the output terminal of the N-phase bridge circuit. The driving signals for the upper and lower switches of each bridge arm are complementary PWM signals with dead time. The N-phase converter operates in rectification and inversion states. The control method employs a frequency conversion SVPWM modulation strategy and includes the following steps:

[0008] The modulation wave acquisition step involves calculating the SVPWM modulation wave by controlling the switching of each phase bridge arm switch when the electrical parameters output by the N-phase converter reach the desired value through dual closed-loop control of the voltage outer loop and current inner loop.

[0009] The triangular carrier acquisition step involves calculating the frequency required for ZVS in each phase bridge arm switch by predicting the magnitude of the current ripple in the second filter inductor of each phase, comparing the frequencies of each phase, selecting the minimum frequency among the N phases as the frequency of the triangular carrier, and then using the calculated frequency to generate a shared triangular carrier.

[0010] The PWM drive signal acquisition step involves comparing the SVPWM modulation wave of each phase bridge arm switch with the shared triangular carrier wave to obtain the PWM drive signal, which is used to control the turn-on and turn-off of each phase bridge arm switch.

[0011] Preferably, the SVPWM is a seven-segment SVPWM.

[0012] Furthermore, when N equals 3, the modulation wave acquisition step specifically includes the following steps:

[0013] Step 1: The first voltage signal, which represents the output voltage of the N-phase converter, is sampled by the outer voltage loop and compared with the reference signal of the outer voltage loop. The result is then sent to the outer voltage loop PI controller to obtain the reference signal of the inner current loop.

[0014] Step 2: Phase information is obtained by sampling the input voltage of each phase of the N-phase converter. The phase information is then sent to the DSP for rotating coordinate transformation of the N-phase current and voltage.

[0015] Step 3: The input current of each phase of the N-phase converter is sampled by the inner current loop. After N-phase rotating coordinate transformation, two-phase current information is obtained. The two-phase current information is compared with their respective reference information and then sent to the inner current loop PI controller to obtain the first change.

[0016] Step 4: After transforming the input voltage of each phase of the N-phase converter into N-phase rotating coordinates, obtain the two-phase voltage information;

[0017] Step 5: Add the values ​​of the d-axis and q-axis in the first change quantity to the values ​​of the d-axis and q-axis in the two-phase voltage information respectively, and then transform the two-phase rotating coordinates to the two-phase stationary coordinate system to obtain the voltage information uα in the two-phase stationary coordinate system. and uβ It serves as the input terminal of the variable frequency SVPWM module, utilizing uα and uβ Calculate the SVPWM modulation waveform of each phase bridge arm switch.

[0018] Furthermore, the phase information is obtained by using a digital controller to lock the grid voltage into phase.

[0019] Furthermore, when comparing the two-phase current information with their respective reference information, the reference value of the q-axis is set to 0.

[0020] Furthermore, the condition for each phase bridge arm switch to achieve ZVS is that there is a negative current before each switch is turned on, ensuring that the parasitic capacitance of the switch to be turned on is completely discharged.

[0021] As a second aspect of the present invention, the technical solution of the provided control device embodiment is as follows:

[0022] A control device is applied to an N-phase converter. The N-phase converter includes an N-phase LCL filter and an N-phase bridge circuit. Each phase filter in the N-phase LCL filter includes a first filter inductor, a second filter inductor, and a filter capacitor. Each phase arm of the N-phase bridge circuit includes an upper switch and a lower switch. One end of the first filter inductor of each phase is connected to the input terminal of the corresponding phase of the N-phase converter, and the other end is connected to one end of the second filter inductor of the corresponding phase. The other end of the second filter inductor of each phase is connected to the midpoint of the corresponding phase arm. The filter capacitor of each phase is connected between the midpoint of the corresponding phase filter inductor and the midpoint of the next phase filter inductor. Each arm is connected in parallel to form the output terminal of the N-phase bridge circuit. The driving signals for the upper and lower switches of each arm are complementary PWM signals with dead time. The N-phase converter operates in rectification and inversion states. The control device adopts a frequency conversion SVPWM modulation strategy. The control device includes the following units:

[0023] The modulation wave acquisition unit calculates the SVPWM modulation wave of the N-phase converter output electrical parameters when the desired values ​​are reached through dual closed-loop control of voltage outer loop and current inner loop;

[0024] The triangular carrier acquisition unit calculates the frequency required for each phase bridge arm switch to achieve ZVS by predicting the magnitude of the current ripple of the second filter inductor in each phase, compares the frequencies of each phase, selects the minimum frequency among the N phases as the frequency of the triangular carrier, and uses the calculated frequency to generate a common triangular carrier.

[0025] The PWM drive signal acquisition unit compares the SVPWM modulation wave of each phase bridge arm switch with the common triangular carrier to obtain the PWM drive signal, which is used to control the turn-on and turn-off of each phase bridge arm switch.

[0026] As a third aspect of the present invention, the technical solution of the provided switching power supply embodiment is as follows:

[0027] A switching power supply includes an N-phase converter, the N-phase converter including an N-phase LCL filter and an N-phase bridge circuit, each phase filter of the N-phase LCL filter including a first filter inductor, a second filter inductor and a filter capacitor, each phase bridge arm of the N-phase bridge circuit including an upper switch and a lower switch, one end of each phase first filter inductor being connected to the input terminal of the corresponding phase of the N-phase converter, and the other end being connected to one end of the corresponding phase second filter inductor, the other end of each phase second filter inductor being connected to the midpoint of the corresponding phase bridge arm, each phase filter capacitor being connected to the midpoint of the corresponding phase filter inductor and the midpoint of the next phase filter inductor, each bridge arm being connected in parallel as the output terminal of the N-phase bridge circuit, the driving signals of the upper and lower switches of each bridge arm being complementary PWM signals with dead time, the N-phase converter operating in rectification and inversion states, wherein: the switching power supply further includes the control device described in any of the second aspects above.

[0028] Furthermore, the N-phase converter operates at unity power factor.

[0029] Furthermore, N is 3.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The embodiments of the present invention predict the ripple current on the bridge arm side and then use the frequency-variable SVPWM modulation strategy, so that the zero voltage conduction of the switch tubes of each phase bridge arm of the N-phase converter can be achieved without the need to add passive or active devices. Furthermore, ZVS can be achieved for the N-phase bridge arm at any time, keeping each phase working in TCM mode, thereby enabling each bridge arm to naturally achieve soft switching, greatly reducing switching losses and improving product efficiency.

[0032] (2) The embodiments of the present invention can improve the switching frequency by using a frequency-variable SVPWM modulation strategy by predicting the ripple current on the bridge arm side. Furthermore, since the inductance value of the filter is very small, it is beneficial to reduce the volume and cost of the inductor, facilitates the planar design of the inductor, and helps to reduce the overall volume of the three-phase converter and improve the power density.

[0033] (3) In the embodiments of the present invention, since the smallest frequency in the N phases is selected as the frequency of the triangular carrier, a common triangular carrier is generated by using the calculated frequency. That is, the control device of the provided three-phase converter greatly limits the range of the converter switching frequency by operating the first phase bridge arm, the second phase bridge arm and the third phase bridge arm with the same switching frequency, so that magnetic devices and EMI circuits can be conveniently designed and the cost of the product is reduced. Attached Figure Description

[0034] Figure 1 A diagram showing the division of three-phase voltage into six sectors;

[0035] Figure 2 A three-phase converter topology diagram for the control method of the first embodiment of the present invention:

[0036] Figure 3 This is a flowchart of the control method according to the first embodiment of the present invention;

[0037] Figure 4 This is a flowchart of the control device according to the second embodiment of the present invention;

[0038] Figure 5 This is a specific control principle diagram of a switching power supply according to the third embodiment of the present invention;

[0039] Figure 6 This is a diagram showing the ripple current of the first sector of the switching power supply and the driving diagram of the switching transistor in the third embodiment of the present invention. Detailed Implementation

[0040] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention and its beneficial effects will be further described in detail below with reference to specific embodiments and accompanying drawings. However, the specific embodiments of the present invention are not limited thereto. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0041] It should be noted that the terms "comprising" and "having," and any variations thereof, described in the specification and claims of this application, are intended to cover a non-exclusive inclusion. For example, including a series of components, unit circuits, or control timings is not necessarily limited to those explicitly listed, but may include components, unit circuits, or control timings not explicitly listed or inherent to these circuits. Without conflict, the embodiments and features described in this application can be combined with each other.

[0042] Furthermore, the accompanying drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions thereof will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0043] First Embodiment

[0044] This embodiment improves a control method applied to an N-phase converter. The N-phase converter includes an N-phase LCL filter and an N-phase bridge circuit. Each phase filter in the N-phase LCL filter includes a first filter inductor, a second filter inductor, and a filter capacitor. Each phase bridge arm in the N-phase bridge circuit includes an upper switch and a lower switch. One end of the first filter inductor of each phase is connected to the input terminal of the corresponding phase of the N-phase converter, and the other end is connected to one end of the second filter inductor of the corresponding phase. The other end of the second filter inductor of each phase is connected to the midpoint of the corresponding phase bridge arm. The filter capacitor of each phase is connected at the midpoint of the corresponding phase filter inductor and the midpoint of the next phase filter inductor. Each bridge arm is connected in parallel to form the output terminal of the N-phase bridge circuit. The driving signals of the upper and lower switches of each bridge arm are complementary PWM signals with dead time. The N-phase converter operates in rectification and inversion states.

[0045] Figure 2The diagram shows the topology of a three-phase converter used in the control method of the first embodiment of the present invention, where N is 3. The three-phase converter includes a three-phase LCL filter and a three-phase bridge circuit. The a-phase LCL filter includes a first filter inductor La1, a second filter inductor La2, and a filter capacitor Ca1. The b-phase LCL filter includes a first filter inductor Lb1, a second filter inductor Lb2, and a filter capacitor Cb1. The c-phase LCL filter includes a first filter inductor Lc1, a second filter inductor Lc2, and a filter capacitor Cc1. The a-phase bridge arm includes an upper switch Q1 and a lower switch Q2. The b-phase bridge arm includes an upper switch Q3 and a lower switch Q4. The c-phase bridge arm includes an upper switch Q5 and a lower switch Q6. The bus capacitor C connected in parallel with each phase bridge arm is the output voltage filter capacitor of the three-phase converter.

[0046] Figure 3 For a flowchart of the control method of the first embodiment of the present invention, please refer to [link / reference]. Figure 3 The control method employs a frequency conversion SVPWM modulation strategy, including the following steps:

[0047] In the modulation wave acquisition step S100, the SVPWM modulation wave is calculated by using the voltage outer loop and current inner loop dual closed-loop control to control the switching of each phase bridge arm switch to turn on and off when the electrical parameters output by the N-phase converter reach the desired value.

[0048] In the triangular carrier acquisition step S200, the frequency required for ZVS to be achieved by the bridge arm switch of each phase is calculated by predicting the magnitude of the current ripple of the second filter inductor of each phase, and the frequency of each phase is compared. The minimum frequency among the N phases is selected as the frequency of the triangular carrier, and a common triangular carrier is generated using the calculated frequency.

[0049] In step S300, the PWM drive signal acquisition step compares the SVPWM modulation wave of each phase bridge arm switch with the common triangular carrier to obtain the PWM drive signal, which is used to control the turn-on and turn-off of each phase bridge arm switch.

[0050] The control method of this embodiment predicts the ripple current on the bridge arm side and then uses a frequency-variable SVPWM modulation strategy, so that zero-voltage conduction of the bridge arm switches of each phase of the N-phase converter can be achieved without the need to add passive or active devices. Furthermore, ZVS can be achieved for the N-phase bridge arm at any time, keeping each phase working in TCM mode, thereby enabling each bridge arm to achieve soft switching naturally, greatly reducing switching losses and improving product efficiency.

[0051] The control method in this embodiment improves the switching frequency by predicting the ripple current on the bridge arm side and then using a frequency-variable SVPWM modulation strategy. Furthermore, since the inductance value of the filter is very small, it is beneficial to reduce the size and cost of the inductor, facilitates the planar design of the inductor, reduces the overall size of the three-phase converter, and improves the power density.

[0052] The control method in this embodiment selects the smallest frequency among the N phases as the frequency of the triangular carrier and uses the calculated frequency to generate a common triangular carrier. That is, the control device of the provided three-phase converter greatly limits the range of the converter's switching frequency by operating the first phase bridge arm, the second phase bridge arm and the third phase bridge arm with the same switching frequency. This makes it easier to design magnetic devices and EMI circuits and reduces the cost of the product.

[0053] SVPWM, or Space Vector Pulse Width Modulation, includes five-segment and seven-segment modulation schemes. This invention preferably uses seven-segment SVPWM, thus eliminating the need for structural decoupling of the N-phase converter and phase-to-phase decoupling using control methods. ZVS of the bridge arm switches of the N-phase converter can be achieved using the traditional SVPWM modulation method.

[0054] When N equals 3, a specific implementation of the modulation wave acquisition step includes the following steps:

[0055] Step 1: The first voltage signal, which is sampled by the voltage outer loop to represent the magnitude of the output voltage of the N-phase converter, is compared with the reference signal of the voltage outer loop and then sent to the voltage outer loop PI controller to obtain the reference signal of the current inner loop.

[0056] Step 2: Phase information is obtained by sampling the input voltage of each phase of the N-phase converter. The phase information is then sent to the DSP for rotating coordinate transformation of the N-phase current and voltage.

[0057] Step 3: The input current of each phase of the N-phase converter is sampled by the current inner loop. After the N-phase rotating coordinate transformation, the two-phase current information is obtained. The two-phase current information is compared with their respective reference information and then sent to the current inner loop PI controller to obtain the first change.

[0058] Step 4: After transforming the input voltage of each phase of the N-phase converter into N-phase rotating coordinates, obtain the two-phase voltage information;

[0059] Step 5: Add the values ​​of the d-axis and q-axis in the first change quantity to the values ​​of the d-axis and q-axis in the two-phase voltage information respectively, and then transform them into a two-phase stationary coordinate system to obtain the voltage information uα in the two-phase stationary coordinate system. and uβ It serves as the input terminal of the variable frequency SVPWM module, utilizing uα and uβ Calculate the SVPWM modulation waveform of each phase bridge arm switch.

[0060] In order to ensure that the specific implementation of the above-mentioned modulation wave acquisition step can be carried out smoothly and in real time, the third embodiment provides a more detailed description of the specific control principle, in which the modulation wave acquisition step is consistent with the specific implementation of the above-mentioned modulation wave acquisition step.

[0061] Furthermore, phase information is obtained by using a digital controller to lock the grid voltage into phase.

[0062] Furthermore, when comparing the two-phase current information with their respective reference information, the reference value of the q-axis is set to 0.

[0063] Furthermore, the condition for each phase arm switch to achieve ZVS is that there is a negative current before each switch is turned on, ensuring that the parasitic capacitance of the switch to be turned on is completely discharged.

[0064] Second Embodiment

[0065] This embodiment provides a control device applied to an N-phase converter. The N-phase converter includes an N-phase LCL filter and an N-phase bridge circuit. Each phase filter in the N-phase LCL filter includes a first filter inductor, a second filter inductor, and a filter capacitor. Each phase arm of the N-phase bridge circuit includes an upper switch and a lower switch. One end of the first filter inductor of each phase is connected to the input terminal of the corresponding phase of the N-phase converter, and the other end is connected to one end of the second filter inductor of the corresponding phase. The other end of the second filter inductor of each phase is connected to the midpoint of the corresponding phase arm. The filter capacitor of each phase is connected between the midpoint of the corresponding phase filter inductor and the midpoint of the next phase filter inductor. The bridge arms are connected in parallel to form the output terminal of the N-phase bridge circuit. The drive signals for the upper and lower switches of each bridge arm are complementary PWM signals with dead time. The N-phase converter operates in rectification and inversion states. The control device adopts a frequency conversion SVPWM modulation strategy. Figure 4 For a flowchart of the control device according to the second embodiment of the present invention, please refer to [link / reference]. Figure 4 The control device includes the following units:

[0066] The modulation wave acquisition unit 100 calculates the SVPWM modulation wave of the output electrical parameters of the N-phase converter through dual closed-loop control of voltage outer loop and current inner loop, and controls the switching of each phase bridge arm switch to turn on and off when the desired value is reached.

[0067] The triangular carrier acquisition unit 200 calculates the frequency required for each phase bridge arm switch to achieve ZVS by predicting the magnitude of the current ripple of the second filter inductor in each phase, compares the frequencies of each phase, selects the minimum frequency among the N phases as the frequency of the triangular carrier, and uses the calculated frequency to generate a common triangular carrier.

[0068] The PWM drive signal acquisition unit 300 compares the SVPWM modulation wave of each phase bridge arm switch with a common triangular carrier to obtain the PWM drive signal, which is used to control the turn-on and turn-off of each phase bridge arm switch.

[0069] The technical means adopted by the control device in this embodiment are consistent with the control method in the first embodiment, and the beneficial effects are the same, so they will not be described in detail. 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 unit in this embodiment, and will not be described in detail in this embodiment.

[0070] Third Embodiment

[0071] This embodiment provides a switching power supply, which includes an N-phase converter, an N-phase LCL filter, and an N-phase bridge circuit. Each phase filter in the N-phase LCL filter includes a first filter inductor, a second filter inductor, and a filter capacitor. Each phase arm in the N-phase bridge circuit includes an upper switch and a lower switch. One end of the first filter inductor of each phase is connected to the input terminal of the corresponding phase of the N-phase converter, and the other end is connected to one end of the second filter inductor of the corresponding phase. The other end of the second filter inductor of each phase is connected to the midpoint of the corresponding phase arm. The filter capacitor of each phase is connected at the midpoint of the corresponding phase filter inductor and the midpoint of the next phase filter inductor. Each bridge arm is connected in parallel to form the output terminal of the N-phase bridge circuit. The driving signals for the upper and lower switches of each bridge arm are complementary PWM signals with dead time. The N-phase converter operates in rectification and inversion states. The switching power supply also includes any of the control devices described in the second embodiment above.

[0072] Furthermore, the N-phase converter operates at unity power factor.

[0073] Furthermore, N is 3.

[0074] Figure 5 This is a specific control principle diagram of a switching power supply according to the third embodiment of the present invention, wherein the N-phase converter is... Figure 2 The control device for the voice transducer is given a specific principle block diagram, and the working principle of the control device is as follows:

[0075] Step 1: Sample the output voltage Vdc and use it as the inverting input of the voltage comparator. Set the DC voltage reference value Vdc at the output port. As the non-inverting input of the voltage comparator, it is fed into the outer voltage loop PI controller for comparison to obtain the reference value id for the inner current loop. .

[0076] Step 2: To make the reactive power zero, set the reference value of the q-axis to 0, i.e., iq. When the voltage is equal to 0, the three-phase grid voltages Va, Vb, and Vc are sampled to obtain phase information. At this time, the currents ia, ib, and ic of the second filter inductors of each phase are sampled through current sensors. The collected phase information and three-phase current information are sent to the DSP for rotational coordinate transformation to obtain two-phase current information id and iq.

[0077] Step 3: Use id and iq as the inverting inputs of the voltage comparator, id iq As the non-inverting input of the voltage comparator, the comparison result is sent to the current inner-loop PI controller. The output of the PI controller is Δud and Δuq. The collected three-phase voltages Va, Vb, and Vc are sent to the DSP controller for two-phase rotating coordinate transformation to obtain the voltage information in the two-phase stationary coordinate system, resulting in the two-phase voltage information ud and uq. Δud and ud are added together, and Δuq and uq are added together. After the two-phase rotating coordinate transformation, the voltage information uα in the two-phase stationary coordinate system is obtained. and uβ ,uα and uβ As the input port of the variable frequency SVPWM, it is used to calculate the modulation wave of each phase;

[0078] Step 4: Calculate the minimum switching frequency for each phase in each sector. Taking the first sector as an example, illustrate the conduction conditions for each switch to achieve ZVS, including its specific drive waveform and current ripple. Figure 6 .

[0079] See Figure 6 Q1 is the driving waveform of the upper switch of phase a, Q3 is the driving waveform of the upper switch of phase b, and Q5 is the driving waveform of the upper switch of phase c. When the driving signal is 1, the upper switch is turned on and the lower switch is turned off; when the driving signal is 0, the upper switch is turned off and the lower switch is turned on. ia, ib, and ic are the ripple currents of the second filter inductors of phases a, b, and c, respectively. The current flowing through the upper switch of phase a must be greater than 0 at time t1 and less than 0 at time t7. The goal is to achieve zero-voltage turn-on for the upper and lower switches of phase a. For phase b, the current flowing through the upper switch of phase b must be greater than 0 at time t2 and less than 0 at time t6. Similarly, for phase c, the current flowing through the upper switch of phase c must be greater than 0 at time t3 and less than 0 at time t5. The conditions for achieving zero-voltage turn-on for each phase at different times are:

[0080] , ,

[0081] Combining the three equations, we get:

[0082]

[0083] Based on the above formula, the frequency required for each phase arm switch in the first sector to achieve ZVS is:

[0084]

[0085] In the above formula: f represents the frequency required for a certain phase arm switch to achieve ZVS; i represents the input current of a certain phase; V represents the input voltage of a certain phase; V o Indicates the output voltage of the three-phase converter; L represents the inductance value of the second filter inductor of a certain phase; I bias This means that the bias current required to achieve soft switching is determined by the equivalent capacitance; specifically, Ibias > 2Ceq. Vds / Td, where Ceq is the equivalent capacitance, Vds is the voltage across 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 practical experience. To meet the requirements of dynamic load switching and still achieve soft switching, the value of Ibias is generally 1.5-2A; m represents the SVPWM modulation wave of a certain phase, calculated using a digital controller; the additional subscripts abc for each parameter are the parameters corresponding to abc, for example, f a This indicates the frequency required for the phase a bridge arm switch to achieve ZVS.

[0086] The method for calculating the frequency in other sectors is the same as in the first sector, and will not be described again here. The frequency required for each phase arm switch in each sector to achieve ZVS is:

[0087]

[0088] The additional subscripts x, y, and z for each parameter correspond to the three phases a, b, and c in different sectors as follows:

[0089]

[0090] Step 5: Specifically, compare the switching frequencies required for each phase arm switch in each sector to achieve ZVS, and select the smaller value as the common switching frequency for all three phases. A shared triangular carrier wave is then generated using this common switching frequency. The purpose is to unify the switching frequency, thereby increasing the overall frequency and reducing the size of the inductor and output capacitor.

[0091] The table below shows the sector containing the minimum frequency required for each phase arm switch to achieve ZVS in each sector:

[0092]

[0093] Step Six: Specifically, the minimum frequency calculated above is sent to the frequency converter carrier generator. The reciprocal of the frequency is used as the period of the frequency converter carrier generator. The output of the frequency converter carrier generator is a triangular wave, and the calculated frequency is the frequency that changes in real time.

[0094] Step 7: Specifically, the triangular carrier wave serves as the inverting input of the voltage comparator, while the non-inverting input is the modulation wave mx calculated by the DSP. The purpose is to compare the modulation wave with the carrier module to obtain the drive signals for the three-phase transistors (a, b, and c). These transistors can be either MOSFETs or IGBTs. Using SVPWM modulation eliminates the need for decoupling the three phases and alters the topology of the three-phase converter. Furthermore, SVPWM generates fewer harmonics compared to other modulation strategies.

[0095] In this embodiment, the N-phase converter in the switching power supply is controlled by any of the control devices described in the second embodiment, enabling it to operate in TCM mode without phase-to-phase decoupling. Each sector can achieve soft switching via variable frequency, eliminating the need for clamping each phase. The N-phase switching transistors can achieve zero-voltage turn-on, thereby improving the efficiency of the N-phase converter. Frequency calculation using current ripple prediction increases the switching frequency and reduces the size of the N-phase converter, thus increasing power density. This embodiment of the switching power supply achieves zero-voltage turn-on while reducing inductor costs and optimizing EMI.

[0096] It should be understood that although specific embodiments of the invention have been described to aid in a better understanding of the invention, other equivalent embodiments exist. Unless otherwise specified, the embodiments and features described in this application can be combined with each other. The above embodiments are given by way of illustration rather than limitation; therefore, any modifications or substitutions to all or part of the technical features of the technical solutions described in the embodiments without departing from the spirit or essence of the invention should be considered as covered within the scope of the claims.

Claims

1. A control method applied to an N-phase converter, the N-phase converter comprising an N-phase LCL filter and an N-phase bridge circuit, each phase filter of the N-phase LCL filter comprising a first filter inductor, a second filter inductor, and a filter capacitor, each phase bridge arm of the N-phase bridge circuit comprising an upper switch and a lower switch, one end of each phase's first filter inductor being connected to the input terminal of the corresponding phase of the N-phase converter, and the other end being connected to one end of the corresponding phase's second filter inductor, the other end of each phase's second filter inductor being connected to the midpoint of the corresponding phase bridge arm, each phase's filter capacitor being connected at the midpoint of the corresponding phase's filter inductor and the midpoint of the next phase's filter inductor, each bridge arm being connected in parallel as the output terminal of the N-phase bridge circuit, the driving signals for the upper and lower switches of each bridge arm being complementary PWM signals with dead time, the N-phase converter operating in rectification and inversion states, characterized in that... The control method employs a variable frequency SVPWM modulation strategy and includes the following steps: The modulation wave acquisition step involves calculating the SVPWM modulation wave by controlling the switching of each phase bridge arm switch when the electrical parameters output by the N-phase converter reach the desired value through dual closed-loop control of the voltage outer loop and current inner loop. The triangular carrier acquisition step involves calculating the frequency required for ZVS in each phase bridge arm switch by predicting the magnitude of the current ripple in the second filter inductor of each phase, comparing the frequencies of each phase, selecting the minimum frequency among the N phases as the frequency of the triangular carrier, and then using the calculated frequency to generate a shared triangular carrier. The PWM drive signal acquisition step involves comparing the SVPWM modulation wave of each phase bridge arm switch with the common triangular carrier wave to obtain the PWM drive signal, which is used to control the turn-on and turn-off of each phase bridge arm switch. The frequency required for each phase arm switch to achieve ZVS satisfies the following relationship: ； In the above formula: f represents the frequency required for ZVS of the switching tube of the phase bridge arm; i represents the input current of the phase; V represents the input voltage of the phase; V o represents the output voltage of the three-phase converter; L represents the inductance value of the second filter inductance of the phase; I bias represents the bias current for realizing soft switching; m represents the SVPWM modulation wave of the phase; the additional subscript xyz of each parameter has a corresponding relationship with the abc three-phase in different sectors as follows: 。 2. The control method according to claim 1, characterized in that: The SVPWM is a seven-segment SVPWM.

3. The control method according to claim 1, characterized in that: When N equals 3, the modulation wave acquisition step specifically includes the following steps: Step 1: The first voltage signal, which represents the output voltage of the N-phase converter, is sampled by the outer voltage loop and compared with the reference signal of the outer voltage loop. The result is then sent to the outer voltage loop PI controller to obtain the reference signal of the inner current loop. Step 2: Phase information is obtained by sampling the input voltage of each phase of the N-phase converter. The phase information is then sent to the DSP for rotating coordinate transformation of the N-phase current and voltage. Step 3: The input current of each phase of the N-phase converter is sampled by the current inner loop. After N-phase rotating coordinate transformation, two-phase current information is obtained. The two-phase current information is compared with their respective reference information and then sent to the current inner loop PI controller to obtain the first change. Step 4: After transforming the input voltage of each phase of the N-phase converter into N-phase rotating coordinates, obtain the two-phase voltage information; Step 5: Add the values ​​of the d-axis and q-axis in the first change quantity to the values ​​of the d-axis and q-axis in the two-phase voltage information respectively, and then transform the two-phase rotating coordinates to the two-phase stationary coordinate system to obtain the voltage information uα in the two-phase stationary coordinate system. and uβ It serves as the input terminal of the variable frequency SVPWM module, utilizing uα and uβ Calculate the SVPWM modulation waveform of each phase bridge arm switch.

4. The control method according to claim 3, characterized in that: The phase information is obtained by using a digital controller to lock the grid voltage into phase.

5. The control method according to claim 3, characterized in that: When comparing the two-phase current information with their respective reference information, the reference value of the q-axis is set to 0.

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

7. A control device applied to an N-phase converter, the N-phase converter comprising an N-phase LCL filter and an N-phase bridge circuit, each phase filter of the N-phase LCL filter comprising a first filter inductor, a second filter inductor, and a filter capacitor, each phase bridge arm of the N-phase bridge circuit comprising an upper switch and a lower switch, one end of each phase's first filter inductor being connected to the input terminal of the corresponding phase of the N-phase converter, and the other end being connected to one end of the corresponding phase's second filter inductor, the other end of each phase's second filter inductor being connected to the midpoint of the corresponding phase bridge arm, each phase's filter capacitor being connected at the midpoint of the corresponding phase's filter inductor and the midpoint of the next phase's filter inductor, each bridge arm being connected in parallel as the output terminal of the N-phase bridge circuit, the drive signals for the upper and lower switches of each bridge arm being complementary PWM signals with dead time, the N-phase converter operating in rectification and inversion states, characterized in that... The control device is used to implement the frequency conversion SVPWM modulation strategy in the control method according to any one of claims 1-6, and the control device includes the following units: The modulation wave acquisition unit calculates the SVPWM modulation wave of the N-phase converter output electrical parameters when the desired value is reached through dual closed-loop control of voltage outer loop and current inner loop; The triangular carrier acquisition unit calculates the frequency required for each phase bridge arm switch to achieve ZVS by predicting the magnitude of the current ripple of the second filter inductor in each phase, compares the frequencies of each phase, selects the minimum frequency among the N phases as the frequency of the triangular carrier, and uses the calculated frequency to generate a common triangular carrier. The PWM drive signal acquisition unit compares the SVPWM modulation wave of each phase bridge arm switch with the common triangular carrier to obtain the PWM drive signal, which is used to control the turn-on and turn-off of each phase bridge arm switch.

8. A switching power supply, the switching power supply comprising an N-phase converter, the N-phase converter comprising an N-phase LCL filter and an N-phase bridge circuit, each phase filter of the N-phase LCL filter comprising a first filter inductor, a second filter inductor and a filter capacitor, each phase bridge arm of the N-phase bridge circuit comprising an upper switch and a lower switch, one end of each phase first filter inductor being connected to the input terminal of the corresponding phase of the N-phase converter, and the other end being connected to one end of the corresponding phase second filter inductor, the other end of each phase second filter inductor being connected to the midpoint of the corresponding phase bridge arm, each phase filter capacitor being connected to the midpoint of the corresponding phase filter inductor and the midpoint of the next phase filter inductor, each bridge arm being connected in parallel as the output terminal of the N-phase bridge circuit, the driving signals of the upper and lower switches of each bridge arm being complementary PWM signals with dead time, the N-phase converter operating in rectification and inversion states, characterized in that: The switching power supply also includes the control device as described in claim 7.

9. The switching power supply according to claim 8, characterized in that: The N-phase converter operates at unity power factor.

10. The switching power supply according to claim 8 or 9, characterized in that: The value of N is 3.

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