CN116365890A - Three-phase staggered T-shaped three-level LLC converter and wide voltage transformation control method thereof - Google Patents

Three-phase staggered T-shaped three-level LLC converter and wide voltage transformation control method thereof Download PDF

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CN116365890A
CN116365890A CN202310490003.7A CN202310490003A CN116365890A CN 116365890 A CN116365890 A CN 116365890A CN 202310490003 A CN202310490003 A CN 202310490003A CN 116365890 A CN116365890 A CN 116365890A
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switches
bridge
phase
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shaped
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CN116365890B (en
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姚志刚
罗港
陈维荣
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Southwest Jiaotong University
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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
    • H02M3/33573—Full-bridge at primary side of an isolation transformer
    • 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
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/4815—Resonant converters
    • 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
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • 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 discloses a three-phase staggered T-shaped three-level LLC converter and a wide voltage transformation control method thereof, comprising a capacitor: the three-phase three-level inverter bridge is formed by two capacitors Cdc1 and Cdc2 which equally divide input direct-current voltage and three T-shaped half-bridges; three T-shaped half-bridges are connected into three groups of resonance capacitors, resonance inductors and transformers which are connected in series, and the output end of each transformer is connected to a load after passing through a three-phase rectifier bridge and a direct-current capacitor Co; the converter can correspondingly perform flexible switching by a T-shaped three-phase topology, a T-shaped full bridge and a T-shaped half bridge according to the change of power and input voltage, and frequency conversion and duty ratio change control are combined, so that the gain range of the converter is widened; the resonant network input is clamped to zero by a T-half bridge or switch S, thereby creating a zero level and reducing the circulating current loss. The invention can widen the voltage regulating range of the high-power LLC converter, reduce zero level circulation loss, and realize high efficiency and wide voltage transformation of the LLC converter by utilizing the soft switching characteristic.

Description

Three-phase staggered T-shaped three-level LLC converter and wide voltage transformation control method thereof
Technical Field
The invention belongs to the technical field of power electronics and direct current converters, and particularly relates to a three-phase staggered T-shaped three-level LLC converter and a wide voltage transformation control method thereof.
Background
The LLC converter has high efficiency and lower electromagnetic noise because of the realization of zero-voltage on of the primary side switch and zero-current off of the secondary side switch, which makes the LLC converter widely applied. In a direct current converter, reducing the voltage and current stress of a power switching device is a key for improving the reliability of a system, reducing the size of an inductor is a key for improving the dynamic performance of the converter, and reducing the current ripple is beneficial to reducing the size of a filter capacitor and further reducing the size of the converter.
Three-level techniques, which can be used to reduce the voltage stress of the switching device and adjust the duty cycle by generating zero levels to adjust the voltage, and interleaved parallel techniques, which can be used to reduce the current stress of the switching device, reduce the inductor size, and ripple current, are two widely used techniques.
Some applications require the converter to have a wide input and wide output voltage regulation function, and the way in which the output voltage is regulated by the suspended resonant network input voltage in the conventional LLC converter scheme results in increased circulating current loss; the power level difference is larger when the full load and the light load work in some new energy systems, and the high efficiency requirement of the converter in the whole working range is difficult to be considered, while in the traditional topology-changing scheme, the topology switching has larger voltage and current pulses, so that larger loss and electromagnetic noise can be generated, and the control of the topologies is quite complex; that is, the single application of the three-level technology or the staggered parallel technology can not meet the requirement on the performance of the direct current converter in the new energy system.
Disclosure of Invention
In order to solve the problems, the invention provides a three-phase staggered T-shaped three-level LLC converter and a wide voltage transformation control method thereof, the converter can correspondingly carry out flexible switching by a T-shaped three-phase topology, a T-shaped full bridge and a T-shaped half bridge according to the change of power and input voltage, and the converter is controlled by combining frequency conversion and duty ratio variation, so that the gain range of the converter is widened; the resonant network input is clamped to zero by a T-half bridge or switch S, thereby creating a zero level and reducing the circulating current loss.
In order to achieve the above purpose, the invention adopts the following technical scheme: a three-phase interleaved T-type three-level LLC converter comprising:
the capacitor Cdc1 and the capacitor Cdc2 are connected in series to uniformly divide the input direct-current voltage;
three T-shaped half-bridges form a three-phase three-level inverter; first phase T-half bridge: switches Sa1 and Sa2 form a half-bridge, and switches Sa3 and Sa4 are connected in reverse series and connected to the midpoint of the input direct-current capacitor; second phase T-half bridge: the switches Sb1 and Sb2 form a half-bridge, and the switches Sb3 and Sb4 are connected in reverse series and connected to the midpoint of the input direct-current capacitor; third phase T-half bridge: the switches Sc1 and Sc2 form a half bridge, and the switches Sc3 and Sc4 are reversely connected in series and are connected to the midpoint of the input direct-current capacitor;
three groups of series resonant capacitors Cr, resonant inductors Lr and isolation transformers which are connected in by three T-shaped half bridges, wherein the midpoint of the primary Y-shaped connection of the isolation transformers is connected to the midpoint of the input direct current capacitor through a switch S;
and the diode rectifier bridge is arranged on the secondary side of the isolation transformer and is connected to a load after passing through the output direct current capacitor Co.
Further, the isolation transformer is of Y-Y type or Y-delta type.
Further, the diode rectifier bridge includes six diodes D1, D2, D3, D4, D5 and D6 connected in series two by two and then connected in parallel.
Further, three T-shaped half-bridges form a three-phase three-level inverter to convert direct current into alternating current with adjustable frequency and variable duty ratio, and energy is transferred to a load through a resonant network, a transformer and a diode rectifier bridge; the output voltage or current is regulated by changing the frequency and the effective value of fundamental wave components in the resonant network; the input voltage of the resonant network is clamped to zero through the midpoint of the T-shaped half bridge or the switch S, and the duty ratio of the input voltage of the resonant network is adjusted, so that the effective value of the equivalent input voltage is adjusted to adjust the transformation range, and the circulation loss of zero level is reduced.
On the other hand, the invention also provides a wide voltage transformation control method of the three-phase staggered T-shaped three-level LLC converter, the three-phase staggered T-shaped three-level LLC converter is based on the provided three-phase staggered T-shaped three-level LLC converter, the form of the required working topology is determined by the input voltage and the load power, the switching between the topological forms is realized through flexible topology change, and the topological forms comprise a three-level T-shaped three-phase staggered LLC conversion form, a three-level T-shaped full-bridge LLC conversion form and a three-level T-shaped half-bridge LLC conversion form;
the converter correspondingly carries out flexible switching by a T-shaped three-phase topology, a T-shaped full bridge and a T-shaped half bridge according to the change of power and input voltage, and combines frequency conversion and duty ratio control, so that the gain range of the converter is widened; the input end of the resonant network is clamped to zero voltage through a T-shaped half bridge or a switch S, so that the input voltage of the resonant network is equivalently regulated.
Further, the wide voltage transformation control method of the three-phase staggered T-shaped three-level LLC converter comprises the following steps:
s1, when the load power is more than 70% of the rated power: the converter works in a three-level T-shaped three-phase interleaved LLC conversion mode;
s2, when the load power is between 30% and 70% of the rated power: the converter works as a three-level T-type full-bridge LLC converter; when the input voltage is lower than 0.5 times of rated input voltage, the T-shaped full bridge works at three levels of Vdc/2,0, -Vdc/2; when the input voltage is higher than 0.5 times of rated input voltage, the T-shaped full bridge works at three levels of Vdc,0 and-Vdc;
s3, when the load power is less than 30% of the rated power: the converter operates in a three-level T-half bridge LLC conversion configuration.
Further, in step S1, when the converter operates in a three-level T-type three-phase interleaved LLC conversion mode:
the T-type three-phase topology operates at three levels Vdc/2,0 and-Vdc/2, with the switches Sa1 and Sa4 being complementarily turned on to produce a first phase level: vdc/2 and-Vdc/2; the switches Sa2, sa3, and S are turned on to generate a first phase level: 0; complementary conduction of switches Sb1 and Sb4 produces a second phase level: vdc/2, -Vdc/2; the conduction of switches Sb2, sb3 and S produces a second phase level: 0; the complementary conduction of the switches Sc1 and Sc4 produces a third phase level: vdc/2, -Vdc/2; the conduction of the switches Sc2, sc3 and S generates a third phase level: 0; the three phases are operated in 120 degree stagger.
Further, in the step S2, when the converter operates in a three-level T-type full-bridge LLC conversion mode:
the switch S is normally open; the switches Sc1, sc2, sc3 and Sc4 are normally open; the equivalent quality factor of the resonant network is 2 times that of the three-phase staggered working mode;
using a T-type full-bridge topology composed of Sa1 to Sa4 and Sb1 to Sb4, the switches S, sc1, sc2, sc3, and Sc4 remain open, and the switches Sa1 to Sa4 and Sb1 to Sb4 function as PWM high-frequency switches;
or using a T-type full-bridge topology formed by Sb1-Sb4 and Sc1-Sc4, wherein the switches S, the switches Sa1, sa2, sa3 and Sa4 are kept off, and the switches Sb1-Sb4 and Sc1-Sc4 are used as PWM high-frequency switches;
or using a T-type full-bridge topology formed by Sc1-Sc4 and Sa1-Sa4, and keeping the switches S, sb1, sb2, sb3 and Sb4 open; the switches Sc1 to Sc4 and Sa1 to Sa4 are PWM high-frequency switches;
the equivalent quality factor of the resonant network is 2 times that of the three-phase staggered working mode; when the input voltage is lower than 0.5 times rated input voltage, the T-type full bridge works with three levels of Vdc,0 and-Vdc: when the input voltage is higher than 0.5 times rated input voltage, the T-type full bridge works at three levels of Vdc/2,0, -Vdc/2.
Further, in said step S3, the converter operating as a three-level T-type half-bridge LLC converter comprises the steps of:
the half-bridge topology is formed by 6 switching tubes participating in work: using a T-type half-bridge topology formed by Sa1-Sa4 and Sb2-Sb3, keeping the switches S, sb1, sb4 and Sc1-Sc4 open, and using the switches Sa1-Sa4, sb2 and Sb3 as PWM high-frequency switches;
or a T-type half-bridge topology formed by Sb1-Sb4 and Sa2-Sa3 is used, the switches S, sa1, sa4 and Sc1-Sc4 are kept off, and the switches Sb1-Sb4 and Sa2-Sa3 are used as PWM high-frequency switches;
or a T-type half-bridge topology formed by Sc1-Sc4 and Sb2-Sb3 is used, the switches S, the switches Sb1, sb4 and Sa1-Sa4 are kept open, and the switches Sc1-Sc4 and Sb2-Sb3 are used as PWM high-frequency switches.
Further, in said step S3, the converter operating as a three-level T-type half-bridge LLC converter comprises the steps of:
the half-bridge topology is formed by 4 switching tubes and S switches participating in work: the T-type half-bridge topology is formed by Sa1-Sa4 and a switch S, the switches Sb1-Sb4 and Sc1-Sc4 are kept off, the switches Sa1-Sa4 serve as PWM high-frequency switches, and the switch S is kept on;
or a T-shaped half-bridge topology formed by Sb1-Sb4 and a switch S, wherein the switches Sa1-Sa4 and Sc1-Sc4 are kept off, the switches Sb1-Sb4 are used as PWM high-frequency switches, and the switch S is kept on;
or a T-type half-bridge topology formed by Sc1-Sc4 and a switch S, wherein the switches Sa1-Sa4 and Sb1-Sb4 are kept off, the switches Sc1-Sc4 are used as PWM high-frequency switches, and the switch S is kept on.
The beneficial effect of adopting this technical scheme is:
the converter can correspondingly and flexibly switch in a T-shaped three-phase topology, a T-shaped full bridge and a T-shaped half bridge according to the change of power and input voltage, and combines frequency conversion and duty ratio control, so that the gain range of the converter is widened, the load power range can be matched, and the efficiency of the converter is improved. The input end of the resonant network is clamped to zero voltage through a T-shaped half-bridge switch or a switch S, so that variable duty ratio control and variable frequency control of various three-level topologies are realized, the input voltage of the resonant network is equivalently regulated, the gain range of the converter is widened, the transformation range of the converter is widened, and the circulation loss is reduced.
According to the invention, flexible switching can be realized among various topologies according to the change of input voltage or load, so that the transformation range of the converter is further widened, and meanwhile, the efficiency of the converter in the whole working range is improved.
According to the invention, zero-voltage on or zero-current off of the switch can be realized without additional hardware and auxiliary circuits, and the switch carries out switching state transition in a multi-level mode, so that the switching loss is greatly reduced; meanwhile, the advantages of the input and output current ripple interleaving cancellation are maintained, the size of the converter is reduced, and the dynamic performance of the converter is improved.
The converter has certain self-current equalizing capability, and reduces the requirement on the tolerance of devices, so that the converter is more convenient to use.
Drawings
Fig. 1 is a schematic topology diagram of a three-phase interleaved T-type three-level LLC converter employing a Y-delta configuration for a transformer in accordance with the present invention.
Fig. 2 is a schematic topology diagram of a three-phase interleaved T-type three-level LLC converter with a Y-Y type structure for a transformer according to the present invention.
Fig. 3 is a schematic diagram of a three-phase interleaved T-type three-level LLC converter and its wide voltage transformation control according to the invention.
Fig. 4 is a schematic diagram of an operating waveform of a three-phase interleaved T-type three-level LLC converter based on variable frequency in combination with variable duty cycle control in accordance with the present invention.
Fig. 5 is a schematic topology diagram of the flexible switching to T-bridge three-level converter of the present invention.
Fig. 6 is a schematic diagram of a topology of the flexible switching to T-half bridge three-level converter of the present invention.
Fig. 7 is a schematic diagram of a topology of a T-half bridge three-level converter with an S-switch turned on in accordance with the present invention.
Fig. 8 is an equivalent simplified topology diagram of a T-half bridge three-level converter with an S-switch turned on in accordance with the present invention.
Detailed Description
The present invention will be further described with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent.
In this embodiment, referring to fig. 1 and 2, the present invention proposes a three-phase interleaved T-type three-level LLC converter comprising:
the capacitor Cdc1 and the capacitor Cdc2 are connected in series to uniformly divide the input direct-current voltage;
three T-shaped half-bridges form a three-phase three-level inverter; first phase T-half bridge: switches Sa1 and Sa2 form a half-bridge, and switches Sa3 and Sa4 are connected in reverse series and connected to the midpoint of the input direct-current capacitor; second phase T-half bridge: the switches Sb1 and Sb2 form a half-bridge, and the switches Sb3 and Sb4 are connected in reverse series and connected to the midpoint of the input direct-current capacitor; third phase T-half bridge: the switches Sc1 and Sc2 form a half bridge, and the switches Sc3 and Sc4 are reversely connected in series and are connected to the midpoint of the input direct-current capacitor;
three groups of series resonant capacitors Cr, resonant inductors Lr and isolation transformers which are connected in by three T-shaped half bridges, wherein the midpoint of the primary Y-shaped connection of the isolation transformers is connected to the midpoint of the input direct current capacitor through a switch S;
and the diode rectifier bridge is arranged on the secondary side of the isolation transformer and is connected to a load after passing through the output direct current capacitor Co.
Preferably, the isolation transformer is of the Y-delta type (as shown in FIG. 1) or of the Y-Y type (as shown in FIG. 2).
Preferably, the diode rectifier bridge comprises six diodes D1, D2, D3, D4, D5 and D6 which are connected in series and then connected in parallel.
Three T-shaped half-bridges form a three-phase three-level inverter to convert direct current into alternating current with adjustable frequency and variable duty ratio, and energy is transferred to a load through a resonant network, a transformer and a diode rectifier bridge; the output voltage or current is regulated by changing the frequency and the effective value of fundamental wave components in the resonant network; the input voltage of the resonant network is clamped to zero through the midpoint of the T-shaped half bridge or the switch S, and the duty ratio of the input voltage of the resonant network is adjusted, so that the effective value of the equivalent input voltage is adjusted to adjust the transformation range, and the circulation loss of zero level is reduced.
In order to match the realization of the device, the invention also provides a wide voltage transformation control method of the three-phase staggered T-shaped three-level LLC converter based on the same invention conception, the form of the required working topology is determined by the input voltage and the load power based on the proposed three-phase staggered T-shaped three-level LLC converter, the switching between the topological forms is realized by flexible topology transformation, and the topological forms comprise a three-level T-shaped three-phase staggered LLC conversion form, a three-level T-shaped full-bridge LLC conversion form and a three-level T-shaped half-bridge LLC conversion form;
the converter correspondingly carries out flexible switching by a T-shaped three-phase topology, a T-shaped full bridge and a T-shaped half bridge according to the change of power and input voltage, and combines frequency conversion and duty ratio control, so that the gain range of the converter is widened; the input end of the resonant network is clamped to zero voltage through a T-shaped half bridge or a switch S, so that the input voltage of the resonant network is equivalently regulated.
Specifically, the wide voltage transformation control method of the three-phase staggered T-shaped three-level LLC converter, as shown in FIG. 3, comprises the following steps:
s1, when the load power is more than 70% of the rated power: the converter operates in a three-level T-type three-phase interleaved LLC conversion scheme, such as the circuit topologies shown in fig. 1 or 2;
s2, when the load power is between 30% and 70% of the rated power: the converter operates as a three-level T-full bridge LLC converter, as shown in the circuit topology of fig. 5; when the input voltage is lower than 0.5 times of rated input voltage, the T-shaped full bridge works at three levels of Vdc/2,0, -Vdc/2; when the input voltage is higher than 0.5 times of rated input voltage, the T-shaped full bridge works at three levels of Vdc,0 and-Vdc;
s3, when the load power is less than 30% of the rated power: the converter operates in a three-level T-half bridge LLC conversion configuration, as shown in the circuit topologies of fig. 6-8, namely, vdc/2,0, -Vdc/2.
As an optimization scheme of the above embodiment, in step S1, when the converter operates in a three-level T-type three-phase interleaved LLC conversion mode:
the T-type three-phase topology operates at three levels Vdc/2,0 and-Vdc/2, with the switches Sa1 and Sa4 being complementarily turned on to produce a first phase level: vdc/2 and-Vdc/2; the switches Sa2, sa3, and S are turned on to generate a first phase level: 0; complementary conduction of switches Sb1 and Sb4 produces a second phase level: vdc/2, -Vdc/2; the conduction of switches Sb2, sb3 and S produces a second phase level: 0; the complementary conduction of the switches Sc1 and Sc4 produces a third phase level: vdc/2, -Vdc/2; the conduction of the switches Sc2, sc3 and S generates a third phase level: 0; the three phases are operated in 120 degree stagger, and the corresponding working waveforms are shown in figure 4.
As an optimization scheme of the above embodiment, in the step S2, when the converter operates in a three-level T-type full-bridge LLC conversion mode:
the switch S is normally open; the switches Sc1, sc2, sc3 and Sc4 are normally open; the equivalent quality factor of the resonant network is 2 times that of the three-phase staggered working mode;
using a T-type full-bridge topology of Sa1-Sa4 and Sb1-Sb4, switches S, sc1, sc2, sc3, and Sc4 remain open, switches Sa1-Sa4, and Sb1-Sb4 as PWM high-frequency switches, as shown in fig. 5;
or using a T-type full-bridge topology formed by Sb1-Sb4 and Sc1-Sc4, wherein the switches S, the switches Sa1, sa2, sa3 and Sa4 are kept off, and the switches Sb1-Sb4 and Sc1-Sc4 are used as PWM high-frequency switches;
or using a T-type full-bridge topology formed by Sc1-Sc4 and Sa1-Sa4, and keeping the switches S, sb1, sb2, sb3 and Sb4 open; the switches Sc1 to Sc4 and Sa1 to Sa4 are PWM high-frequency switches;
the equivalent quality factor of the resonant network is 2 times that of the three-phase staggered working mode; when the input voltage is lower than 0.5 times rated input voltage, the T-type full bridge works with three levels of Vdc,0 and-Vdc: when the input voltage is higher than 0.5 times rated input voltage, the T-type full bridge works at three levels of Vdc/2,0, -Vdc/2.
As an optimization of the above embodiment, in the step S3, the converter operates as a three-level T-type half-bridge LLC converter including the steps of:
the half-bridge topology is formed by 6 switching tubes participating in work: using a T-type half-bridge topology formed by Sa1-Sa4 and Sb2-Sb3, keeping the switches S, sb1, sb4 and Sc1-Sc4 open, and using the switches Sa1-Sa4, sb2 and Sb3 as PWM high-frequency switches; as shown in fig. 6;
or a T-type half-bridge topology formed by Sb1-Sb4 and Sa2-Sa3 is used, the switches S, sa1, sa4 and Sc1-Sc4 are kept off, and the switches Sb1-Sb4 and Sa2-Sa3 are used as PWM high-frequency switches;
or a T-type half-bridge topology formed by Sc1-Sc4 and Sb2-Sb3 is used, the switches S, the switches Sb1, sb4 and Sa1-Sa4 are kept open, and the switches Sc1-Sc4 and Sb2-Sb3 are used as PWM high-frequency switches.
As an optimization of the above embodiment, in the step S3, the converter operates as a three-level T-type half-bridge LLC converter including the steps of:
the half-bridge topology is formed by 4 switching tubes and S switches participating in work: the T-type half-bridge topology is formed by Sa1-Sa4 and a switch S, the switches Sb1-Sb4 and Sc1-Sc4 are kept off, the switches Sa1-Sa4 serve as PWM high-frequency switches, and the switch S is kept on; as shown in fig. 7;
or a T-shaped half-bridge topology formed by Sb1-Sb4 and a switch S, wherein the switches Sa1-Sa4 and Sc1-Sc4 are kept off, the switches Sb1-Sb4 are used as PWM high-frequency switches, and the switch S is kept on;
or a T-type half-bridge topology formed by Sc1-Sc4 and a switch S, wherein the switches Sa1-Sa4 and Sb1-Sb4 are kept off, the switches Sc1-Sc4 are used as PWM high-frequency switches, and the switch S is kept on.
That is, a T-type half-bridge LLC converter topology can be constructed by arbitrarily enabling one group from three groups of half-bridge switches Sa1-Sa4, sb1-Sb4 and Sc1-Sc4, as shown in FIG. 8.
The converter can correspondingly and flexibly switch in a T-shaped three-phase topology, a T-shaped full bridge and a T-shaped half bridge according to the change of power and input voltage, and frequency conversion and duty ratio change control are combined, so that the gain range of the converter is widened, the load power range can be matched, and the efficiency of the converter is improved. The input end of the resonant network is clamped to zero voltage through a T-shaped half-bridge switch or a switch S, so that the input voltage of the resonant network is equivalently regulated, and the gain range of the converter is widened.
The foregoing has shown and described the basic principles and main features of the present invention and the advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (10)

1. A three-phase interleaved T-type three-level LLC converter, comprising:
the capacitor Cdc1 and the capacitor Cdc2 are connected in series to uniformly divide the input direct-current voltage;
three T-shaped half-bridges form a three-phase three-level inverter; first phase T-half bridge: switches Sa1 and Sa2 form a half-bridge, and switches Sa3 and Sa4 are connected in reverse series and connected to the midpoint of the input direct-current capacitor; second phase T-half bridge: the switches Sb1 and Sb2 form a half-bridge, and the switches Sb3 and Sb4 are connected in reverse series and connected to the midpoint of the input direct-current capacitor; third phase T-half bridge: the switches Sc1 and Sc2 form a half bridge, and the switches Sc3 and Sc4 are reversely connected in series and are connected to the midpoint of the input direct-current capacitor;
three groups of series resonant capacitors Cr, resonant inductors Lr and isolation transformers which are connected in by three T-shaped half bridges, wherein the midpoint of the primary Y-shaped connection of the isolation transformers is connected to the midpoint of the input direct current capacitor through a switch S;
and the diode rectifier bridge is arranged on the secondary side of the isolation transformer and is connected to a load after passing through the output direct current capacitor Co.
2. A three-phase interleaved T-type three-level LLC converter in accordance with claim 1 wherein said isolation transformer is of the Y-Y type or the Y-delta type.
3. The three-phase interleaved T-type three-level LLC converter of claim 1 wherein said diode rectifier bridge comprises six diodes D1, D2, D3, D4, D5 and D6 connected in series in pairs and then connected in parallel.
4. A three-phase interleaved T-type three-level LLC converter in accordance with claim 1 wherein three T-half bridges form a three-phase three-level inverter to convert dc into ac of variable frequency and variable duty cycle, and energy is transferred to the load via the resonant network, the transformer and the diode rectifier bridge; the output voltage or current is regulated by changing the frequency and the effective value of fundamental wave components in the resonant network; the input voltage of the resonant network is clamped to zero through the midpoint of the T-shaped half bridge or the switch S, and the duty ratio of the input voltage of the resonant network is adjusted, so that the effective value of the equivalent input voltage is adjusted to adjust the transformation range, and the circulation loss of zero level is reduced.
5. A wide voltage transformation control method of a three-phase staggered T-shaped three-level LLC converter is characterized by comprising the following steps of: the capacitor Cdc1 and the capacitor Cdc2 are connected in series to uniformly divide the input direct-current voltage; three T-shaped half-bridges form a three-phase three-level inverter; first phase T-half bridge: switches Sa1 and Sa2 form a half-bridge, and switches Sa3 and Sa4 are connected in reverse series and connected to the midpoint of the input direct-current capacitor; second phase T-half bridge: the switches Sb1 and Sb2 form a half-bridge, and the switches Sb3 and Sb4 are connected in reverse series and connected to the midpoint of the input direct-current capacitor; third phase T-half bridge: the switches Sc1 and Sc2 form a half bridge, and the switches Sc3 and Sc4 are reversely connected in series and are connected to the midpoint of the input direct-current capacitor; three groups of series resonant capacitors Cr, resonant inductors Lr and isolation transformers which are connected in by three T-shaped half bridges, wherein the midpoint of the primary Y-shaped connection of the isolation transformers is connected to the midpoint of the input direct current capacitor through a switch S; the diode rectifier bridge is arranged on the secondary side of the isolation transformer and is connected to a load after passing through the output direct current capacitor Co;
determining a form of a required working topology by input voltage and load power, wherein the switching between the topological forms is realized by flexible topology change, and the topological forms comprise a three-level T-shaped three-phase staggered LLC conversion form, a three-level T-shaped full-bridge LLC conversion form and a three-level T-shaped half-bridge LLC conversion form;
the converter correspondingly carries out flexible switching by a T-shaped three-phase topology, a T-shaped full bridge and a T-shaped half bridge according to the change of power and input voltage, and combines frequency conversion and duty ratio control, so that the gain range of the converter is widened; the input end of the resonant network is clamped to zero voltage through a T-shaped half bridge or a switch S, so that the input voltage of the resonant network is equivalently regulated.
6. The wide voltage transformation control method of a three-phase interleaved T-type three-level LLC converter in accordance with claim 5, comprising the steps of:
s1, when the load power is more than 70% of the rated power: the converter works in a three-level T-shaped three-phase interleaved LLC conversion mode;
s2, when the load power is between 30% and 70% of the rated power: the converter works as a three-level T-type full-bridge LLC converter; when the input voltage is lower than 0.5 times of rated input voltage, the T-shaped full bridge works at three levels of Vdc/2,0, -Vdc/2; when the input voltage is higher than 0.5 times of rated input voltage, the T-shaped full bridge works at three levels of Vdc,0 and-Vdc;
s3, when the load power is less than 30% of the rated power: the converter operates in a three-level T-half bridge LLC conversion configuration.
7. The method according to claim 6, wherein in step S1, the converter is operated in a three-level T-type three-phase interleaved LLC conversion mode:
the T-type three-phase topology operates at three levels Vdc/2,0 and-Vdc/2, with the switches Sa1 and Sa4 being complementarily turned on to produce a first phase level: vdc/2 and-Vdc/2; the switches Sa2, sa3, and S are turned on to generate a first phase level: 0; complementary conduction of switches Sb1 and Sb4 produces a second phase level: vdc/2, -Vdc/2; the conduction of switches Sb2, sb3 and S produces a second phase level: 0; the complementary conduction of the switches Sc1 and Sc4 produces a third phase level: vdc/2, -Vdc/2; the conduction of the switches Sc2, sc3 and S generates a third phase level: 0; the three phases are operated in 120 degree stagger.
8. The method according to claim 6, wherein in the step S2, when the converter is operated in a three-level T-type full-bridge LLC conversion mode:
the switch S is normally open; the switches Sc1, sc2, sc3 and Sc4 are normally open; the equivalent quality factor of the resonant network is 2 times that of the three-phase staggered working mode;
using a T-type full-bridge topology composed of Sa1 to Sa4 and Sb1 to Sb4, the switches S, sc1, sc2, sc3, and Sc4 remain open, and the switches Sa1 to Sa4 and Sb1 to Sb4 function as PWM high-frequency switches;
or using a T-type full-bridge topology formed by Sb1-Sb4 and Sc1-Sc4, wherein the switches S, the switches Sa1, sa2, sa3 and Sa4 are kept off, and the switches Sb1-Sb4 and Sc1-Sc4 are used as PWM high-frequency switches;
or using a T-type full-bridge topology formed by Sc1-Sc4 and Sa1-Sa4, and keeping the switches S, sb1, sb2, sb3 and Sb4 open; the switches Sc1 to Sc4 and Sa1 to Sa4 are PWM high-frequency switches;
the equivalent quality factor of the resonant network is 2 times that of the three-phase staggered working mode; when the input voltage is lower than 0.5 times rated input voltage, the T-type full bridge works with three levels of Vdc,0 and-Vdc: when the input voltage is higher than 0.5 times rated input voltage, the T-type full bridge works at three levels of Vdc/2,0, -Vdc/2.
9. A wide voltage transformation control method of a three-phase interleaved T-type three-level LLC converter in accordance with claim 6, wherein in said step S3, the converter operates as a three-level T-type half-bridge LLC converter comprising the steps of:
the half-bridge topology is formed by 6 switching tubes participating in work: using a T-type half-bridge topology formed by Sa1-Sa4 and Sb2-Sb3, keeping the switches S, sb1, sb4 and Sc1-Sc4 open, and using the switches Sa1-Sa4, sb2 and Sb3 as PWM high-frequency switches;
or a T-type half-bridge topology formed by Sb1-Sb4 and Sa2-Sa3 is used, the switches S, sa1, sa4 and Sc1-Sc4 are kept off, and the switches Sb1-Sb4 and Sa2-Sa3 are used as PWM high-frequency switches;
or a T-type half-bridge topology formed by Sc1-Sc4 and Sb2-Sb3 is used, the switches S, the switches Sb1, sb4 and Sa1-Sa4 are kept open, and the switches Sc1-Sc4 and Sb2-Sb3 are used as PWM high-frequency switches.
10. A wide voltage transformation control method of a three-phase interleaved T-type three-level LLC converter in accordance with claim 6, wherein in said step S3, the converter operates as a three-level T-type half-bridge LLC converter comprising the steps of:
the half-bridge topology is formed by 4 switching tubes and S switches participating in work: the T-type half-bridge topology is formed by Sa1-Sa4 and a switch S, the switches Sb1-Sb4 and Sc1-Sc4 are kept off, the switches Sa1-Sa4 serve as PWM high-frequency switches, and the switch S is kept on;
or a T-shaped half-bridge topology formed by Sb1-Sb4 and a switch S, wherein the switches Sa1-Sa4 and Sc1-Sc4 are kept off, the switches Sb1-Sb4 are used as PWM high-frequency switches, and the switch S is kept on;
or a T-type half-bridge topology formed by Sc1-Sc4 and a switch S, wherein the switches Sa1-Sa4 and Sb1-Sb4 are kept off, the switches Sc1-Sc4 are used as PWM high-frequency switches, and the switch S is kept on.
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