CN-115765411-B - LLC resonant converter control system and method

CN115765411BCN 115765411 BCN115765411 BCN 115765411BCN-115765411-B

Abstract

The invention relates to the technical field of circuits, and particularly discloses an LLC resonant converter control system and method, wherein the control system comprises three high-frequency inverters and three-phase high-frequency transformers; three high-frequency inverters are connected in parallel, the phase difference is 120 degrees, the three-phase high-frequency transformers are connected by Dy, the primary side is connected in a triangular mode, and the secondary side is connected in a star mode. By adopting the technical scheme of the invention, the harmonic hazard can be solved, and the stability can be improved.

Inventors

CHEN XIANPING

Assignees

重庆平创半导体研究院有限责任公司

Dates

Publication Date: 20260512
Application Date: 20221209

Claims (4)

1. The LLC resonant converter control system is characterized by comprising three high-frequency inverters and a three-phase high-frequency transformer, wherein the three high-frequency inverters are connected in parallel and have 120-degree phase difference, the three high-frequency transformers are connected by Dy, and the primary side is in delta connection; The power supply, the switching network and three rectifying modules are also included; the three-phase high-frequency transformer comprises a first high-frequency transformer, a second high-frequency transformer and a third high-frequency transformer; of the three high-frequency inverters, the first ends of the first high-frequency inverter, the second high-frequency inverter and the third high-frequency inverter are all connected with the positive electrode of the power supply, and the second ends of the first high-frequency inverter, the second high-frequency inverter and the third high-frequency inverter are all connected with the negative electrode of the power supply; the third end of the first high-frequency inverter is connected with the first end of the primary side of the first high-frequency transformer respectively and is connected with the second end of the primary side of the third high-frequency transformer; The third end of the second high-frequency inverter is connected with the first end of the primary side of the second high-frequency transformer; The third end of the third high-frequency inverter is connected with the first end of the primary side of the third high-frequency transformer; the second end of the primary side of the first high-frequency transformer is connected with the first end of the primary side of the second high-frequency transformer; The second end of the primary side of the second high-frequency transformer is connected with the first end of the primary side of the third high-frequency transformer; Both ends of the secondary side of the first high-frequency transformer are connected with a first rectifying module; both ends of the secondary side of the second high-frequency transformer are connected with a second rectifying module; Both ends of the secondary side of the third high-frequency transformer are connected with a third rectifying module; The first rectifying module, the second rectifying module and the third rectifying module are also connected with a switch network; the system also comprises a sampling module, a control module and a cloud platform; The sampling module is used for respectively collecting current values of primary sides and secondary sides of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer; The control module is used for calculating current unbalance according to the acquired current value and adjusting the high-frequency inverter according to the current unbalance; the control module is also used for sending the current value to the cloud platform; The sampling module is used for respectively collecting current values TA1, TA2 and TA3 of primary sides of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer, and also used for respectively collecting current values TA4, TA5 and TA6 of secondary sides of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer; the control module is used for calculating three-phase current difference values of TA4, TA5 and TA 6; judging whether the following conditions are satisfied: condition one is that TA4> TA5> TA6, and TA4-TA6> TG1, wherein TG1 = TA 4; Condition II, TA2> TA1> TA3, and TA2-TA3> TG2; TA4-TA6> TG3; and TA4-TA6> TG3, tg3=ta4×s1; Condition four, TA2-TA3> TG4, and TA4-TA6> TG4, and Tg4=Ta2.S2; wherein S1 is a first threshold value, and S2 is a second threshold value; if the first or second condition is met, judging that the third high-frequency transformer has current unbalance, marking the third high-frequency transformer as a general fault, and reducing the PWM frequency of the third high-frequency inverter by the control module; Judging whether TA2 exceeds a design rated value, if so, the control module is also used for generating a shutdown instruction; the control module is further configured to send the current values TA1, TA2, TA3, TA4, TA5, and TA6, and the fault record to the cloud platform.
2. The LLC resonant converter control system according to claim 1, wherein the first high-frequency inverter comprises a MOS tube S1, a MOS tube S2 and a first LLC circuit, wherein a drain electrode of the MOS tube S1 is connected with an anode of a power supply, a source electrode of the MOS tube S1 is connected with a drain electrode of the MOS tube S2, a source electrode of the MOS tube S1 is also connected with one end of the first LLC circuit, a source electrode of the MOS tube S2 is connected with a cathode of the power supply, and the other end of the first LLC circuit is respectively connected with a first end of a primary side of the first high-frequency transformer and a second end of a primary side of the third high-frequency transformer; The second high-frequency inverter comprises an MOS tube S3, an MOS tube S4 and a second LLC circuit, wherein the drain electrode of the MOS tube S3 is connected with the positive electrode of the power supply, the source electrode of the MOS tube S3 is connected with the drain electrode of the MOS tube S4, the source electrode of the MOS tube S3 is also connected with one end of the second LLC circuit, the source electrode of the MOS tube S4 is connected with the negative electrode of the power supply, and the other end of the second LLC circuit is connected with the first end of the primary side of the second high-frequency transformer; The third high-frequency inverter comprises a MOS tube S5, a MOS tube S6 and a third LLC circuit, wherein the drain electrode of the MOS tube S5 is connected with the positive electrode of the power supply, the source electrode of the MOS tube S5 is connected with the drain electrode of the MOS tube S6, the source electrode of the MOS tube S5 is also connected with one end of the third LLC circuit, the source electrode of the MOS tube S6 is connected with the negative electrode of the power supply, and the other end of the third LLC circuit is connected with the first end of the primary side of the third high-frequency transformer.
3. A method of LLC resonant converter control using the system of claim 1, comprising the steps of: Collecting current values of primary sides and secondary sides of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer respectively; The analysis step is that the current unbalance degree is calculated according to the collected current value; An adjustment step of adjusting the high-frequency inverter according to the current unbalance; and uploading, namely sending the current value to the cloud platform.
4. The LLC resonant converter control method according to claim 3, wherein the step of collecting specifically comprises: Collecting current values TA1, TA2 and TA3 of primary sides of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer respectively, and collecting current values TA4, TA5 and TA6 of secondary sides of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer respectively; the analysis steps specifically include: Calculating three-phase current difference values of TA4, TA5 and TA 6; judging whether the following conditions are satisfied: condition one is that TA4> TA5> TA6, and TA4-TA6> TG1, wherein TG1 = TA 4; Condition II, TA2> TA1> TA3, and TA2-TA3> TG2; TA4-TA6> TG3; and TA4-TA6> TG3, tg3=ta4×s1; Condition four, TA2-TA3> TG4, and TA4-TA6> TG4, and Tg4=Ta2.S2; wherein S1 is a first threshold value, and S2 is a second threshold value; if the first condition or the second condition is met, judging that the third high-frequency transformer has current unbalance; if the third condition or the fourth condition is met, marking that the third high-frequency transformer has serious faults, judging whether TA2 exceeds the design rated value; the adjusting step specifically comprises the following steps: in the case of general faults, the PWM frequency of the third high-frequency inverter is reduced; Generating a shutdown command when TA2 exceeds a design rated value; The uploading step specifically comprises the following steps: And sending the current values TA1, TA2, TA3, TA4, TA5 and TA6 and the fault record to the cloud platform.

Description

LLC resonant converter control system and method Technical Field The invention relates to the technical field of circuits, in particular to an LLC resonant converter control system and method. Background The LLC resonant converter is improved by adding a parallel resonant inductance on the basis of the LC resonant converter, and compared with the series-connected and parallel-connected LC resonant converters, the LLC resonant converter has obvious improvement in gain characteristics and the like, and has excellent soft switching performance, can greatly reduce switching loss, is successfully applied to different power supply products, and is an important way for realizing high frequency of a power system. The resonant converter has the advantages of simple structure, high efficiency, convenience for magnetic integration and the like, and is increasingly widely applied to fields such as photovoltaics, new energy automobiles and the like. In certain circumstances, resonant converters are required to have a wide range of output voltages and a wide range of constant power capabilities, and so topology extension research into resonant converters has been a hotspot in the industry. Functionally, a typical resonant converter topology can be divided into several main parts, namely a high-frequency inverter mainly comprising a chopper and a resonant network, a high-frequency transformer, a rectifying module mainly comprising half-wave and full-wave rectifying modes, a switching network responsible for serial-parallel switching of the rectifying module, a filtering and loading module and an equivalent power supply. The current design modes of the high-frequency transformer mainly include the following modes: As shown in FIG. 1, the scheme I has the defects that 1, the high-frequency transformers have impedance difference and the circuits are connected in series and parallel to have parasitic parameter difference, so that the high-frequency inverter needs to control voltage equalizing and current equalizing simultaneously, and the control difficulty is high. 2, a plurality of transformers are connected in parallel, the loop current is increased due to inconsistent impedance, and the efficiency is reduced. And 3, the efficiency is lower under the light load condition due to the exciting current of the transformer. And 4, harmonic waves are brought by output rectification, so that a primary side switching tube is harmed, and a device is invalid. As shown in fig. 2, the scheme II is that the transformer is switched by multiple taps, and the scheme has the defects that 1, when the transformer low-voltage tap works, the high-voltage tap is idle, the utilization rate is low and the cost is high. And 2, when the tap of the transformer is switched, leakage inductance is changed, ZVS conditions are changed, loss is increased, and efficiency is reduced. And 3, when the tap of the transformer is switched, the resonance point is shifted, and the control difficulty is increased. And 4, harmonic waves are brought by output rectification, so that a primary side switching tube is harmed, and a device is invalid. As shown in fig. 3, the third scheme is that a three-phase transformer Yy is used, and the disadvantage of the third scheme is that 1, neutral point offset is easy to occur due to unbalanced load, local overheating is caused, efficiency is reduced, and the overall stability of the module is affected under serious conditions, so that shutdown is caused. 2, each phase can adopt a plurality of transformer windings to be connected in series, but the series connection has higher requirements on the impedance consistency of the transformer coil, so that the transformer is difficult to produce in large scale. And 3, harmonic waves are brought by output rectification, so that a primary side switching tube is harmed, and a device is invalid. As can be seen from the above typical design scheme, the mainstream design manner at present is not separated from the multi-channel serial-parallel design, wherein the multi-channel necessarily brings a plurality of semiconductor devices. The reliability of the semiconductor device will directly affect the module stability and if the topology is not well designed, some device failures will have catastrophic consequences. Therefore, there is a need for an LLC resonant converter control system and method that addresses the harmonic hazards and stability issues presented by prior art solutions. Disclosure of Invention One of the purposes of the invention is to provide an LLC resonant converter control system which can solve the harmonic hazard and improve the stability. In order to solve the technical problems, the application provides the following technical scheme: A control system of LLC resonant converter includes three high-frequency inverters and three-phase high-frequency transformers, the three high-frequency inverters are connected in parallel, the phase difference is 120 deg., the three-ph