CN117254705A - Three-phase six-switch PWM rectifier based on SiC device, main circuit and control method - Google Patents
Three-phase six-switch PWM rectifier based on SiC device, main circuit and control method Download PDFInfo
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- 229910010271 silicon carbide Inorganic materials 0.000 claims abstract description 67
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
- H02M7/2195—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration the switches being synchronously commutated at the same frequency of the AC input voltage
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
- H02M1/4208—Arrangements for improving power factor of AC input
- H02M1/4241—Arrangements for improving power factor of AC input using a resonant converter
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33592—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Abstract
The invention provides a three-phase six-switch PWM rectifier based on a SiC device, a main circuit and a control method, wherein a bridgeless active power factor correction circuit with a single-phase totem pole structure is used for realizing front-stage correction, and the front-stage circuit utilizes a silicon carbide (SiC) device as a high-frequency switch to provide higher closing speed and lower switching loss; the full-bridge LLC resonant converter is adopted in the two-stage conversion circuit, the primary side and the secondary side are both in full-bridge structures, the switching tube is a device based on wide forbidden band materials, the switching sequence of the switching tube is controlled to realize conversion and adjustment of alternating current energy, and switching loss and switching interference are effectively reduced. The rectifier of the invention can reduce the use of auxiliary circuits, improve the power factor of the rectifier, reduce the energy loss of a switching device, reduce the number of electronic elements, have better resonance characteristics and higher efficiency, and can reduce the volume of the rectifier and reduce the cost.
Description
Technical Field
The invention relates to the technical field of rectifiers, in particular to a three-phase six-switch PWM rectifier based on a SiC device, a main circuit and a control method.
Background
The development of wide band gap semiconductor materials and devices is the basis for the application of wide band gap power electronic devices. Modeling and characteristic analysis of the wide bandgap power electronic device are necessary means for developing new application concepts and providing effective device application technology, and have very important promotion effect on the wide-range application of the device.
At present, the three-phase six-switch PWM rectifier is a technology widely studied and applied in the field of power electronics, is mainly used for energy conversion from an alternating current power supply to a direct current load, and has the advantages of high efficiency, high power factor, accurate voltage control and the like. The three-phase six-switch PWM rectifier converts input three-phase alternating current into direct current power by controlling the switching states and the duty ratios of six power switching devices, can flexibly adjust output voltage and current, and is suitable for various power requirements and load types. There are many different rectifier topologies, such as bidirectional switch type rectifier, three-level rectifier, and multi-level rectifier, to meet the demands of different application scenarios. In addition, many improved algorithms and modulation techniques have been proposed by researchers for the control strategy of rectifiers to improve the performance and efficiency of rectifiers. Including improvements based on conventional PWM modulation techniques such as space vector modulation and multi-carrier modulation, and advanced control strategies based on predictive control, model predictive control, and neural network control.
To improve the reliability of rectifiers and reduce cost, it is a conventional option to use wide bandgap materials to provide higher switching frequencies and lower switching losses, with SiC devices having lower impedances, higher operating frequencies, and higher operating temperatures. The existing three-phase six-switch PWM rectifier mainly has the following problems:
(1) Power factor problem: the power factor is an index for measuring the ratio of the active power to the apparent power of the circuit, the existing three-phase six-switch PWM rectifier can generate lower power factor when in work, the low power factor means that more reactive power flows in the circuit, so that the energy is wasted, the load of a power grid can be unstable, and even the voltage fluctuation and harmonic pollution of the power grid are caused;
(2) Energy conversion efficiency: the traditional three-phase six-switch PWM rectifier adopts a traditional rectification topological structure, and a switching device has higher switching loss, so that the energy conversion efficiency is reduced, the working efficiency of the rectifier is lower, the switching loss can generate a large amount of heat, additional heat dissipation design and energy consumption are required, and the cost and complexity of a system are increased;
(3) Volume and cost: conventional three-phase six-switch PWM rectifiers typically require the use of a large number of capacitive, inductive, and diode components to perform their function, thereby increasing the size and cost of the rectifier, the introduction of these auxiliary components increasing the complexity of the system and requiring more space, limiting the feasibility and flexibility of the rectifier in some applications.
Therefore, it is necessary to develop a three-phase six-switch PWM rectifier based on SiC devices, a main circuit and a control method, reduce the use of auxiliary circuits, improve the power factor of the rectifier, reduce the energy loss of the switching devices, reduce the number of electronic components, reduce the volume and reduce the cost.
Disclosure of Invention
The invention aims to provide a three-phase six-switch PWM rectifier based on a SiC device, a main circuit and a control method, so as to solve the problems of low power factor, low energy conversion efficiency, large volume, high cost and the like of the existing three-phase six-switch PWM rectifier in the background art.
To achieve the above object, the present invention provides a three-phase six-switch PWM rectifier based on SiC devices, including:
correcting a front stage by using an active power factor of a single-phase totem pole bridgeless PFC structure, and using a silicon carbide device as a high-frequency switch;
a two-stage conversion circuit of a full-bridge LLC resonant converter is adopted, a primary side and a secondary side both adopt full-bridge structures, and a switching tube is a device based on a wide forbidden band material.
Based on the foregoing, a silicon carbide diode is connected in parallel with each of the high frequency switches.
Based on the scheme, the single-phase totem pole bridgeless PFC structure uses a silicon material as a low-frequency channel.
Based on the scheme, the transformer of the full-bridge LLC resonant converter adopts copper foil-clad solid sealing, and the integration of the resonant capacitor, the resonant inductor and the power transformer is realized by utilizing the capacitor produced by the copper foil and the solid sealing material.
Based on the scheme, the silicon carbide device is specifically a SiC MOSFET switch tube; the low-frequency channel is specifically a Si MOSFET switch tube; the primary side switching tube adopts a SiC MOSFET switching tube, and the secondary side switching tube adopts a GaN FET switching tube.
In addition, the invention also provides a main circuit of the three-phase six-switch PWM rectifier based on the SiC device, which comprises a bridgeless PFC part, an LCC resonant converter part, a bus capacitor and a battery.
Based on the above scheme, the bridgeless PFC part is specifically a totem pole bridgeless PFC circuit, and includes three single-phase totem pole bridgeless circuits, where the single-phase totem pole bridgeless circuits are connected with a three-phase power supply, and each single-phase totem pole bridgeless circuit is composed of two diodes and four SiC MOSFET switching tubes Q1 to Q4.
Based on the above scheme, the four SiC MOSFET switching tubes Q1 to Q4 are specifically, Q1 and Q2 form a left bridge arm, Q3 and Q4 form a right bridge arm, and the Q1 and Q2 are respectively connected in parallel with a silicon carbide diode.
Based on the scheme, the primary side and the secondary side of the LCC resonant converter part adopt full-bridge structures, and the switching tubes of the primary side and the secondary side adopt devices based on wide forbidden band materials.
Based on the scheme, the primary side comprises four SiC MOSFET switching tubes Q5-Q8, and the secondary side comprises four GaN FET switching tubes Q9-Q12.
In addition, the invention also provides a control method of the three-phase six-switch PWM rectifier based on the SiC device, which comprises the following steps:
correcting the front stage through a single-phase totem pole bridgeless active power factor, wherein in the positive half cycle, a switching tube Q2 is a high-frequency switch, Q4 is in a synchronous rectification state, and Q1 and Q3 are turned off; in the negative half cycle, the switching tube Q1 is a high-frequency switch, Q3 is in a synchronous rectification state, and Q2 and Q4 are turned off;
when the rectifier operates as an inverter, Q1 and Q2 serve as high-frequency switches, Q3 and Q4 serve as low-frequency switches, and a unipolar Sinusoidal Pulse Width Modulation (SPWM) technology is adopted for control;
a two-stage conversion circuit of a full-bridge LLC resonant converter is adopted, a controller is used for generating pulse width modulation signals, the on and off time of a switching tube is controlled, the on time of the switching tube is controlled by adjusting the duty ratio of the pulse width modulation signals, and the output voltage or current is adjusted;
on the primary side of the LLC resonant full-bridge, energy transmission and adjustment are performed by controlling the on-off time of a main switching tube, and on the secondary side of the LLC resonant full-bridge, energy transmission and adjustment are performed by controlling the on-off time of a secondary switching tube;
the composite laminated busbar technology is adopted to reduce stray inductance of a main loop as a main loop parasitic parameter control technology of the power module.
Based on the scheme, when Q2 is switched on during the positive half cycle, current flows through Q2 and Q4, and the inductance current rises; when Q1 is off, current flows through diode D1 and switching tube Q4, and the inductor current decreases.
Based on the above scheme, when Q1 is turned on during the negative half cycle, current flows through Q1 and Q3, and the inductor current rises; when Q1 is off, current will flow through diode D2 and switching tube Q3, and the inductor current will drop.
Compared with the prior art, the invention has at least the following advantages and positive effects:
(1) Improving the power factor: the two-stage conversion circuit of the single-phase totem pole type bridgeless active power factor correction front stage and the LLC resonance full-bridge soft switching converter is adopted, so that the power factor of the rectifier is effectively improved; the single-phase totem pole type bridgeless active power factor correction front stage can realize high power factor correction, reduce the use of auxiliary circuits, simplify the system structure and improve the power factor and the system performance.
(2) The energy conversion efficiency is improved: the LLC resonant full-bridge soft switching converter is adopted as a second-stage conversion circuit, the topological structure of the LLC full-bridge has lower switching loss and higher energy conversion efficiency, and compared with the traditional three-phase six-switch PWM rectifier, the LLC full-bridge can reduce the energy loss of switching devices, improve the energy conversion efficiency of the rectifier, and help to reduce energy waste and improve the heating problem of the system.
(3) Volume and cost are reduced: the two-stage conversion circuit of the single-phase totem pole type bridgeless active power factor correction front stage and the LLC resonance full-bridge soft switching converter is adopted, so that the number of electronic elements can be reduced, and the whole volume and cost are reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. Like elements or portions are generally identified by like reference numerals throughout the several figures. In the drawings, elements or portions thereof are not necessarily drawn to scale.
FIG. 1 shows an overall block diagram of a three-phase six-switch PWM rectifier based on a SiC device in accordance with an embodiment of the present invention;
FIG. 2 shows a main circuit diagram of a three-phase six-switch PWM rectifier based on a SiC device according to an embodiment of the invention;
fig. 3 shows a circuit topology of a single-phase totem pole bridgeless PFC structure according to an embodiment of the present invention;
FIG. 4 shows a circuit topology of a full-bridge LLC resonant converter according to an embodiment of the invention;
FIG. 5 shows a voltage gain curve for LLC converter operation in the forward direction of an embodiment of the present invention;
FIG. 6 shows a voltage gain curve for an LLC converter according to an embodiment of the present invention when operating in reverse;
FIG. 7 shows a control method flow chart of a three-phase six-switch PWM rectifier based on a SiC device according to an embodiment of the invention;
the silicon-based switching tubes are two types, and the thicker-line silicon-based switching tube represents the SiC MOSFET switching tube and the thinner-line silicon-based switching tube represents the Si MOSFET switching tube.
Detailed Description
For a clearer explanation of the objects, technical solutions and advantages of the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and that the exemplary embodiments can be implemented in various forms and should not be construed as being limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, devices, steps, etc. In other instances, well-known methods, devices, implementations, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
The block diagrams depicted in the figures are merely functional entities and do not necessarily correspond to physically separate entities. That is, the functional entities may be implemented in software, or in one or more hardware modules or integrated circuits, or in different networks and/or processor devices and/or microcontroller devices.
The flow diagrams depicted in the figures are exemplary only, and do not necessarily include all of the elements and operations/steps, nor must they be performed in the order described. For example, some operations/steps may be decomposed, and some operations/steps may be combined or partially combined, so that the order of actual execution may be changed according to actual situations.
The invention will be described in detail with reference to specific examples below:
example 1
The embodiment 1 of the invention provides a three-phase six-switch PWM rectifier based on a SiC device, and as shown in a figure 1, the integral structure diagram of the three-phase six-switch PWM rectifier based on the SiC device in the embodiment of the invention comprises the following steps:
correcting a front stage by using an active power factor of a single-phase totem pole bridgeless PFC structure, and using a silicon carbide device as a high-frequency switch;
a two-stage conversion circuit of a full-bridge LLC resonant converter is adopted, a primary side and a secondary side both adopt full-bridge structures, and a switching tube is a device based on a wide forbidden band material.
Specifically, in this embodiment, the silicon carbide device is used as the high-frequency switch, and in consideration of the advantages of the silicon carbide device such as high-temperature operation characteristics, high on-current, low switching loss, and the like, the silicon carbide device has a higher switching frequency and higher efficiency than the conventional silicon (Si) device, and the performance and efficiency of the rectifier can be improved by using the silicon carbide device as the high-frequency switch.
Specifically, in this embodiment, in the front-stage correction, three single-phase totem pole bridgeless power factor rectifiers (PFCs) are adopted, so that active power factor correction can be effectively implemented, and by combining the high-frequency switching characteristics of the silicon carbide device, the rectifier can implement high-efficiency and high-precision power factor correction, and the performance and efficiency of the rectifier are greatly improved.
Specifically, in the embodiment, the conversion circuit adopts a two-stage structure of the full-bridge LLC resonant converter, wherein the primary side and the secondary side adopt full-bridge structures, namely, the primary side and the secondary side both use four switching tubes, so that the transmission loss can be effectively reduced, the stability of output voltage can be improved, and the bidirectional operation of the converter can be realized; in addition, with LLC resonant converters, zero Voltage Switching (ZVS) and Zero Current Switching (ZCS) can be achieved at high frequency switching, reducing switching losses and electromagnetic interference.
Specifically, in this embodiment, a device based on a wide bandgap material is selected as the switching tube to improve the converter efficiency.
Preferably, in this embodiment, a silicon carbide diode is connected in parallel outside each of the high frequency switches.
Specifically, a silicon carbide diode is connected in parallel outside each high-frequency switch, zero reverse recovery current can be realized, switching loss is reduced, and the silicon carbide material has higher radiation and heat transduction performance, so that the working stability and reliability of the rectifier are ensured.
Preferably, in this embodiment, the single-phase totem pole bridgeless PFC structure uses a silicon-based material as the low frequency channel.
Preferably, in this embodiment, the transformer of the full-bridge LLC resonant converter is sealed with copper foil, and the integrated structure of the resonant capacitor, the resonant inductor and the power transformer is realized by using the capacitor generated by the copper foil and the sealing material, and the integrated structure not only can reduce the volume and weight of the rectifier, but also can improve the energy conversion efficiency and reliability of the rectifier.
Preferably, the silicon carbide device is specifically a SiC MOSFET switch tube; the low-frequency channel is specifically a Si MOSFET switch tube; the primary side switching tube adopts a SiC MOSFET switching tube, and the secondary side switching tube adopts a GaN FET switching tube.
Preferably, in the present embodiment, a three-phase six-switch PWM rectifier based on SiC devices is packaged using an embedded three-dimensional interconnection packaging technology, a plurality of dies are implanted on a ceramic carrier, a layer of electrolyte is silk-screened on the dies, and interconnection between the power device and an external circuit is realized by a metallization deposition method according to a designed format; the semiconductor device can be directly connected with an external circuit, welding can be realized without metallizing the non-weldable electrodes, the special interconnection structure has higher integration level, the signal path is short, parasitic parameters are very small, the heat dissipation capacity can be greatly improved due to the fact that the contact surface is very large, and the three-phase six-switch PWM rectifier based on the SiC device can work at higher switching frequency by adopting an active packaging technology, so that miniaturization and high power density are realized.
Preferably, a planar transformer and a magnetic integration technology are adopted to reduce the height of a magnetic device in the three-phase six-switch PWM rectifier, reduce the volume and weight of the magnetic device and improve the power density of the magnetic device and the performance of a switching power supply; and determining integration between the inductor and the transformer according to the topology of the circuit, establishing an equivalent model of the circuit before integration, selecting the shape and parameters of the magnetic core, and obtaining a magnetic integration technology through simulation software.
Preferably, because of the high power density and high temperature characteristics of SiC devices, heat dissipation is a key issue, in this embodiment, advanced heat dissipation materials and design heat sink structures are adopted on top of packaging technology to achieve better heat dissipation effects and temperature management, in this embodiment, thermal simulation software is used to perform thermal analysis and optimal design, the effects of heat dissipation schemes such as fin thickness, fin height and fin spacing of different heat sinks, fin shape of air-cooled heat sinks, and the like are evaluated, and a suitable scheme is selected according to actual requirements.
In this embodiment, the active power factor of the single-phase totem pole bridgeless PFC structure is used to correct the front stage, a two-stage conversion circuit of a full-bridge LLC resonant converter with a full-bridge structure is used in which both the primary side and the secondary side are connected in parallel with a silicon carbide diode, and a wide bandgap material is selected from the materials of each switching tube, so that the power factor of the rectifier is effectively improved, high-power factor correction is realized, the use of auxiliary circuits is reduced, the number of electronic components is reduced, the energy loss of the switching devices is reduced, the energy conversion efficiency of the rectifier is improved, the energy waste is reduced, the system heating problem is improved, the system structure is simplified, and the whole volume and cost are reduced.
Example 2
As shown in fig. 2, embodiment 2 of the present invention provides a main circuit of a three-phase six-switch PWM rectifier based on SiC devices, which includes a bridgeless PFC section, an LCC resonant converter section, a bus capacitor, and a battery.
Preferably, the bridgeless PFC part, that is, the preceding stage three-phase APFC circuit adopts a totem pole bridgeless PFC circuit topology shown in fig. 3, and includes three single-phase totem pole bridgeless circuits, each of which is connected with a three-phase power supply and is composed of two diodes and four SiC MOSFET switching tubes Q1 to Q4.
Preferably, the four SiC MOSFET switching tubes Q1 to Q4 are specifically a left bridge arm formed by the switching tubes Q1 and Q2, a right bridge arm formed by the switching tubes Q3 and Q4, and a silicon carbide diode is respectively connected in parallel outside the switching tubes Q1 and Q2.
Specifically, in this embodiment, in order to adapt to the working requirement of the bidirectional vehicle-mounted charger, the structure of the conventional totem pole PFC is adjusted, where the switching tubes Q1 and Q2 of the left bridge arm use silicon carbide devices as high-frequency switches, and the advantages of fast switching speed and small reverse recovery loss of the body diode are utilized to make up for the defect of the totem pole bridgeless PFC topology structure, and the parallel connection of the silicon carbide diode outside the switching tube improves the current guiding capability during freewheeling; meanwhile, the diode of the right bridge arm is replaced by the common silicon MOSFET Q3 and Q4 to be used as a low-frequency channel, so that the diode has the capability of inverting operation, and when the diode is used as a PFC circuit to operate, the Q3 and the Q4 operate in a synchronous rectification state, so that the working efficiency of the circuit can be further improved.
Specifically, in the embodiment, a totem pole bridgeless PFC structure is selected for correcting the front stage, so that the required power devices are few, the efficiency can reach 99%, and the value of PFC inductance can be greatly reduced due to the improvement of the switching frequency, thereby being beneficial to reducing the size and the cost of the inductive element.
Preferably, the LCC resonant converter part, i.e. the DC/DC converter, is shown in fig. 4 as a circuit topology diagram thereof, wherein the primary side and the secondary side of the LCC resonant converter are both in full-bridge structure to realize bidirectional operation of the converter, when the power grid charges the battery, energy is input from the DC bus side, output from the battery side, and the working state of the converter is similar to that of the conventional LLC resonant converter, and the difference is that the working frequency of the LLC DC transformer is fixed; fig. 5 shows a voltage gain curve when the LLC converter is operated in the forward direction, and fig. 6 shows a voltage gain curve when the LLC converter is operated in the reverse direction.
Specifically, the forward operation is a process of converting an input voltage into an output voltage through a converter, the reverse operation is a process of inverting a relationship between the input voltage and the output voltage, and when the forward operation is performed, the relationship between the output voltage and the input voltage can be determined according to a voltage gain curve through a boosting and a reducing process of the converter; the voltage gain curve of an LLC converter typically has a peak near the resonant frequency, q is the circuit quality factor, f in fig. 5 s /f r1 The ratio of the switching frequency to the resonant frequency, gain (Gain) refers to the voltage Gain of the LLC converter, and the voltage Gain curve follows f s /f r1 Is increased by first rising and then falling, at f s /f r1 <Zone 1 has oneThe maximum value point is positive in the curve slope at the left side of the maximum value, and is a ZCS region, the LLC resonant converter works in the region only to realize zero current switching, the circuit loss is large, the curve slope at the right side of the maximum value is a ZVS region, the LLC resonant converter works in the region to realize zero voltage switching, the LLC resonant converter generally hopefully works in the region, in actual use, the lowest working frequency of the LLC resonant converter is generally limited so as to avoid falling from the ZVS region to the ZCS region, and after the working frequency falls to the ZCS region, the negative feedback of a control loop is changed into positive feedback due to the change of the slope of a gain curve, so that the circuit cannot work normally; when the transformer works in the reverse energy feedback mode, the input voltage of the transformer is driven by the output voltage, the excitation inductor cannot participate in resonance, and the working state of the transformer is similar to that of a series resonance transformer. The gain curve at this time is shown in fig. 6, where the voltage gain is related to the switching frequency and the load condition, and when the switching frequency is operating near the resonant frequency, the voltage gain curve is independent of the load, so the grid charges the battery or discharges the battery to the grid, and the operating frequency of the LLC converter should be kept near the resonant frequency.
Preferably, in this embodiment, a single full-bridge LLC circuit is selected to be used as the LCC resonant converter, so that when the primary power tube is turned on at zero voltage and the secondary rectifying tube is turned off at zero current, the power device is soft-switched, and the circuit design is simplified, and the cost is reduced under the condition that the system requirement is met.
Specifically, in the rectifier with higher requirements, for the selection of the LCC resonant converter part, i.e. the DC/DC converter, parallel interleaved full-bridge LLC circuits can be used, and by connecting two full-bridge LLC circuits in parallel, the working times of the two full-bridge LLC circuits are staggered, so that each circuit is alternately responsible for processing half of the input voltage, the output voltage ripple can be effectively reduced, and the working frequency of each circuit can be halved, thereby reducing the switching loss, improving the power conversion efficiency, increasing the power density of the system, and being beneficial to reducing the cost; therefore, if lower output voltage ripple, higher power density, higher conversion efficiency and more compact design are required, and corresponding design and control are performed on the circuit, the selection of using the double interleaved full bridge LLC circuit as the DC/DC converter can be considered.
Specifically, IN this embodiment, the LCC resonant converter is of a 3-level structure, according to the input phase voltage/frequency 304-458 vac/50-60 hz, the output voltage is 200-1000 vdc, the output power is >40kW (single module, which can be connected IN parallel), the power density is >60W/IN3, the power factor is >0.99 (full load), the highest efficiency is >98%, the distortion rate is less than or equal to 3%, the standby power consumption is less than or equal to 5W and other technical index requirements, 600V components can be selected, the switching voltage stress of the power device is small, the efficiency is high, if a parallel staggered full-bridge LLC circuit is adopted, the output voltage ripple can be effectively reduced, the converter power is improved, the conversion efficiency is up to 97.6%, and the parameters of the output filter circuit are reduced, thereby being beneficial to reducing the cost.
Preferably, the switching tubes of the primary side and the secondary side are devices based on wide forbidden band materials to improve the efficiency of the converter, specifically, the primary side comprises four SiC MOSFET switching tubes Q5-Q8, and the secondary side comprises four GaN FET switching tubes Q9-Q12.
In particular, in the present embodiment, most of the switching transistors use a wide bandgap material, and devices of the wide bandgap material have higher voltage and current bearing capability, so that a higher power density design can be achieved. SiC MOSFETs and GaN FETs have less switching resistance and volume than conventional materials, so that the resonant converter can achieve smaller size and weight with the same power output requirements.
Example 3
As shown in fig. 7, embodiment 3 of the present invention provides a control method of a three-phase six-switch PWM rectifier based on SiC devices, including:
correcting a front stage through a single-phase totem pole type bridgeless active power factor, wherein the power grid voltage is in a positive half cycle, a switching tube Q2 is a high-frequency switch, a switching tube Q4 is in a synchronous rectification state, switching tubes Q1 and Q3 are turned off, the power grid voltage is in a negative half cycle, the switching tube Q1 is a high-frequency switch, the switching tube Q3 is in a synchronous rectification state, and the switching tubes Q2 and Q4 are turned off;
when the rectifier operates as an inverter, the switching tubes Q1 and Q2 serve as high-frequency switches, the switching tubes Q3 and Q4 serve as low-frequency switches, and a unipolar Sinusoidal Pulse Width Modulation (SPWM) technology is adopted for control;
a two-stage conversion circuit of a full-bridge LLC resonant converter is adopted, a controller is used for generating pulse width modulation signals, the on and off time of a switching tube is controlled, the on time of the switching tube is controlled by adjusting the duty ratio of the pulse width modulation signals, and the output voltage or current is adjusted;
on the primary side of the LLC resonance full-bridge, energy transmission and adjustment are performed by controlling the on-off time of a main switching tube, and on the secondary side of the LLC resonance full-bridge, energy transmission and adjustment are performed by controlling the on-off time of a secondary switching tube.
Preferably, when Q2 is on during the positive half cycle, current flows through Q2 and Q4, and inductor current rises; when Q1 is off, current flows through diode D1 and switching tube Q4, and the inductor current decreases.
Preferably, when Q1 is on during the negative half cycle, current flows through Q1 and Q3, and inductor current rises; when Q1 is off, current will flow through diode D2 and switching tube Q3, and the inductor current will drop.
Preferably, the duty ratio of the pulse width modulation signal is adjusted by monitoring the working state and the load characteristic of the rectifier in real time, and the duty ratio of the switch is dynamically adjusted, specifically by adopting a feedback control algorithm, the duty ratio of the Pulse Width Modulation (PWM) signal is adjusted according to the real-time feedback signal, so as to ensure that the circuit maintains high efficiency and stability under different load conditions.
Preferably, a composite laminated busbar technology is adopted to reduce stray inductance of a main loop as a main loop parasitic parameter control technology of the power module.
Preferably, a plurality of intelligent control algorithms based on context awareness are combined, circuit parameters are adjusted in real time, and the working states of the PFC structure and the LLC resonant converter are dynamically optimized, so that more efficient power conversion and transient response are realized; the intelligent control algorithm comprises, but is not limited to, model predictive control, reinforcement learning algorithm, neural network control and hybrid control algorithm.
Specifically, in this embodiment, the method for reducing the stray inductance of the main loop further includes, but is not limited to, adopting methods such as adaptive system, fuzzy control or neural network control according to the influence degree and change rule of the stray inductance on the circuit, so as to further reduce the influence of the parasitic parameter; more advanced analog simulation technology, such as finite element analysis and multi-physical field simulation, is adopted to deeply analyze the performance of the circuit and the influence of parasitic parameters so as to optimize the control method.
In this embodiment, the circuit is controlled by using a pulse width modulation technology, and the on time of the switching tube is controlled by adjusting the duty ratio of the pulse width modulation signal, so as to adjust the output voltage or current, thereby realizing efficient, stable and accurate output of the circuit and meeting different power requirements.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims. It is to be understood that the invention is not limited to the precise arrangements and instrumentalities shown in the drawings, which have been described above, and that various modifications and changes may be effected without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (10)
1. A three-phase six-switch PWM rectifier based on SiC devices, comprising:
correcting a front stage by using an active power factor of a single-phase totem pole bridgeless PFC structure, and using a silicon carbide device as a high-frequency switch;
the single-phase totem pole type bridgeless PFC structure uses silicon materials as a low-frequency channel, and a silicon carbide diode is connected in parallel outside each high-frequency switch;
the full-bridge LLC resonant converter is adopted as a two-stage conversion circuit, and the primary side and the secondary side are both in a full-bridge structure, namely, four switching tubes are arranged, and the switching tubes are devices based on wide forbidden band materials;
the transformer of the full-bridge LLC resonant converter adopts copper foil-clad solid sealing, and the integration of the resonant capacitor, the resonant inductor and the power transformer is realized by utilizing the capacitor produced by the copper foil and the solid sealing material.
2. A three-phase six-switch PWM rectifier based on SiC devices according to claim 1, characterized in that the silicon carbide devices are in particular SiC MOSFET switching tubes and the low frequency channels are in particular Si MOSFET switching tubes.
3. The three-phase six-switch PWM rectifier according to claim 1, wherein the primary side switching tube is a SiC MOSFET switching tube and the secondary side switching tube is a GaN FET switching tube.
4. The main circuit of the three-phase six-switch PWM rectifier based on the SiC device is characterized by comprising a bridgeless PFC part, an LCC resonant converter part, a bus capacitor and a battery.
5. The main circuit of the three-phase six-switch PWM rectifier based on the SiC device according to claim 4, wherein the bridgeless PFC part is specifically a totem pole bridgeless PFC circuit, and comprises three single-phase totem pole bridgeless circuits, wherein each single-phase totem pole bridgeless circuit is connected with a three-phase power supply, and each single-phase totem pole bridgeless circuit is composed of two diodes and four SiC MOSFET switching tubes Q1-Q4.
6. The main circuit of the three-phase six-switch PWM rectifier based on the SiC device according to claim 5, wherein the four SiC MOSFET switching tubes Q1-Q4 are specifically a left bridge arm formed by switching tubes Q1 and Q2, a right bridge arm formed by switching tubes Q3 and Q4, and the switching tubes Q1 and Q2 are respectively connected with a silicon carbide diode in parallel.
7. The main circuit of the three-phase six-switch PWM rectifier based on the SiC device according to claim 4, wherein the primary side and the secondary side of the LCC resonant converter part adopt full-bridge structures, and the switching tubes of the primary side and the secondary side adopt devices based on wide forbidden band materials.
8. The main circuit of a three-phase six-switch PWM rectifier based on SiC devices according to claim 7, wherein the primary side comprises four SiC MOSFET switching tubes Q5-Q8 and the secondary side comprises four GaN FET switching tubes Q9-Q12.
9. A control method of a three-phase six-switch PWM rectifier based on SiC devices, characterized by comprising:
correcting the front stage through a single-phase totem pole bridgeless active power factor, wherein in the positive half cycle, a switching tube Q2 is a high-frequency switch, a switching tube Q4 is in a synchronous rectification state, and switching tubes Q1 and Q3 are turned off; in the negative half cycle, the switching tube Q1 is a high-frequency switch, the switching tube Q3 is in a synchronous rectification state, and the switching tubes Q2 and Q4 are turned off;
when the rectifier operates as an inverter, the switching tubes Q1 and Q2 serve as high-frequency switches, the switching tubes Q3 and Q4 serve as low-frequency switches, and a unipolar sinusoidal pulse width modulation technology, namely SPWM, is adopted for control;
a two-stage conversion circuit of a full-bridge LLC resonant converter is adopted, a controller is used for generating pulse width modulation signals, the on and off time of a switching tube is controlled, the on time of the switching tube is controlled by adjusting the duty ratio of the pulse width modulation signals, and the output voltage or current is adjusted;
on the primary side of the LLC resonance full-bridge, energy transmission and adjustment are performed by controlling the on-off time of a main switching tube, and on the secondary side of the LLC resonance full-bridge, energy transmission and adjustment are performed by controlling the on-off time of a secondary switching tube.
10. The control method of a three-phase six-switch PWM rectifier based on a SiC device according to claim 9, wherein, when Q2 is on during the positive half cycle, current flows through Q2 and Q4, the inductor current rises, when Q1 is off, current flows through diode D1 and switching tube Q4, and the inductor current drops; when Q1 is on in the negative half cycle, current flows through Q1 and Q3, the inductance current rises, and when Q1 is off, the current can pass through a diode D2 and a switch tube Q3, and the inductance current drops.
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