Wide-range integrated OBC-LDC three-port converter system and control method thereof

Abstract

The invention discloses a wide-range integrated OBC-LDC three-port converter system and a control method thereof. The wide-range integrated OBC-LDC three-port converter system comprises a step-down conversion module and a three-active-bridge conversion module, the three-active-bridge conversion module is composed of a first full-bridge network, a second full-bridge network, a third full-bridge network and a transformer. The step-down conversion module is connected with the first full-bridge network, and the first full-bridge network is respectively connected with the second full-bridge network and the third full-bridge network through the transformer. Charging modes controlled by the control method comprise a charger mode, a low-voltage direct-current converter mode and a combined working mode. Compared with an existing three-port converter, the novel integrated OBC-LDC three-port converter has the advantages that under the condition that low-voltage output is stable, high-voltage output has a wider voltage range.

Description

Technical Field

[0001] This invention belongs to the field of electric vehicle charging technology, specifically relating to a wide-range integrated OBC-LDC three-port converter system and its control method. Background Technology

[0002] The electrical system of an electric vehicle comprises three parts: power supply, drive, and auxiliary subsystems. The power supply subsystem includes an on-board charger, a high-voltage battery, and a battery management system; the drive subsystem includes an electric motor and a motor controller; and the auxiliary subsystem includes a low-voltage auxiliary battery, a low-voltage DC-DC converter, and on-board electronic equipment. The on-board charger converts AC power from the grid into DC power to charge the high-voltage battery. It typically consists of a power factor correction module and a DC-DC converter. The low-voltage DC-DC converter converts the high voltage of the high-voltage battery into a low voltage to power low-voltage electrical equipment and charge the low-voltage battery. In traditional power supply methods, the circuits of the on-board charger and the low-voltage DC-DC converter operate separately, resulting in drawbacks such as large space requirements, high cost, and low efficiency. With the development of battery technology and the electric vehicle industry, higher requirements are placed on on-board charging equipment for electric vehicles: high efficiency, miniaturization, lightweight design, and wide operating range. Therefore, researching integrated electric vehicle charging technology is of great significance for promoting the development of the electric vehicle industry.

[0003] In existing research, the DC-DC converters in integrated three-port converters are mainly derived from full-bridge converters. These previous research results have successfully achieved the design goals of high efficiency, miniaturization, and lightweight vehicle chargers. However, the gain range of converters in existing research is generally narrow. With the increasing diversification of electric vehicle applications, vehicle chargers need to adapt to different operating conditions and cover a wider range of output voltages, which existing converters cannot meet. Summary of the Invention

[0004] This invention aims to address the shortcomings of existing technologies and provides the following solutions:

[0005] A wide-range integrated OBC-LDC three-port converter system includes: a buck converter module and a three-active-bridge converter module;

[0006] The three-active-bridge converter module consists of a first full-bridge network, a second full-bridge network, a third full-bridge network, and a transformer;

[0007] The step-down converter module is connected to the first full-bridge network, and the first full-bridge network is connected to the second full-bridge network and the third full-bridge network respectively through the transformer.

[0008] Preferably, the buck converter module is composed of capacitor C1, MOSFET S1, MOSFET S2 and inductor L, and the buck converter module also includes an input port;

[0009] The first full-bridge network consists of MOSFETs S3, S4, S5, and S6, and a leakage inductance L. k1 constitute;

[0010] The second full-bridge network consists of MOSFETs S7, S8, S9, and S1. 10 Leakage inductance L k2 The second full-bridge network, consisting of capacitor C2, also includes a high-voltage port;

[0011] The third full-bridge network is composed of MOSFETs. 11 MOSFET 12 MOSFET 13 MOSFET 14 Leakage inductance L k3 The third full-bridge network, consisting of capacitor C3, also includes a low-voltage port.

[0012] The present invention also provides a control method for a wide-range integrated OBC-LDC three-port converter system. The control method is used to control the above-mentioned converter system, including: charger mode, low-voltage DC converter mode and combined operation mode.

[0013] Preferably, in the charger mode:

[0014] The input port serves as a DC input terminal, and the high-voltage port outputs DC power with a wide voltage range to charge the high-voltage battery of the electric vehicle. At this time, the low-voltage port is in a non-operating state.

[0015] During the control process, the output voltage is precisely controlled by adjusting the duty cycle of the buck converter module and the duty cycle of the two pairs of MOSFETs in the full-bridge section of the input port. The full-bridge section of the high-voltage port is used as a rectifier bridge.

[0016] Preferably, in the low-voltage DC-DC converter mode:

[0017] The high-voltage port provides DC input to the high-voltage battery, and the low-voltage port outputs low-voltage DC power to power the low-voltage battery and low-voltage electrical equipment.

[0018] At this time, voltage control is achieved by adjusting the duty cycle of the two pairs of MOS transistors in the full-bridge section of the high-voltage port, while the full-bridge section of the low-voltage port is used as a rectifier bridge.

[0019] Preferably, in the joint working mode:

[0020] The input port receives DC power, the high-voltage port outputs high-voltage DC power, and the low-voltage port outputs low-voltage DC power.

[0021] At this time, the duty cycle of the buck converter module and the duty cycle of the two pairs of MOSFETs in the full-bridge section of the input port are adjusted to control the output voltage of the high-voltage port; the duty cycle of the two pairs of MOSFETs in the full-bridge section of the low-voltage port is adjusted to control the output voltage of the low-voltage port.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] Compared with existing three-port converters, the novel integrated OBC-LDC three-port converter of this invention has a wider voltage range for high-voltage output while ensuring stable low-voltage output. Attached Figure Description

[0024] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a system circuit diagram according to an embodiment of the present invention;

[0026] Figure 2 The following are structural diagrams of three mode controllers in an embodiment of the present invention: a is a structural diagram of the closed-loop controller in charger mode, b is a structural diagram of the closed-loop controller in low-voltage DC-DC converter mode, and c is a structural diagram of the closed-loop controller in combined working mode.

[0027] Figure 3 This is a control timing diagram of the embodiment of the present invention in the joint working mode, where a is the timing diagram in Buck mode and b is the timing diagram in Boost mode;

[0028] Figure 4 This is a modal diagram of Buck mode in the joint working mode according to an embodiment of the present invention, wherein a is the mode in Buck mode during time t0 to t1, b is the mode in Buck mode during time t1 to t2, c is the mode in Buck mode during time t2 to t3, d is the mode in Buck mode during time t3 to t4, e is the mode in Buck mode during time t4 to t5, and f is the mode in Buck mode during time t5 to t6.

[0029] Figure 5This is a modal diagram of the Boost mode in the joint working mode of an embodiment of the present invention, wherein a is the mode in the Boost mode during time t0 to t1, b is the mode in the Boost mode during time t1 to t2, c is the mode in the Boost mode during time t2 to t3, d is the mode in the Boost mode during time t3 to t4, and e is the mode in the Boost mode during time t4 to t5.

[0030] Figure 6 The following are simulation waveform diagrams of the present invention in the charger working mode, wherein a is the simulation waveform diagram in Buck mode and b is the simulation waveform diagram in Boost mode.

[0031] Figure 7 This is a simulation waveform diagram of an embodiment of the present invention in low-voltage DC-DC converter mode;

[0032] Figure 8 The following are simulation waveforms of the present invention in the combined working mode, wherein a is the simulation waveform in Boost mode and b is the simulation waveform in Buck mode.

[0033] Figure 9 The following are simulation waveforms of voltage surges at the high-voltage port under the full output range of the embodiments of the present invention and the three active bridge converter. Among them, a is the simulation waveform of voltage surges at the high-voltage port in the combined working mode of the embodiment of the present invention, and b is the simulation waveform of voltage surges at the high-voltage port of the three active bridge converter in the combined working mode. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1

[0037] In this embodiment, a wide-range integrated OBC-LDC three-port converter system includes: a buck converter module and a three-active-bridge converter module.

[0038] The three-phase active bridge converter module consists of a first full-bridge network, a second full-bridge network, a third full-bridge network, and a transformer; the step-down converter module is connected to the first full-bridge network, and the first full-bridge network is connected to the second and third full-bridge networks respectively through the transformer.

[0039] Circuit structure as follows Figure 1 As shown, the buck converter module consists of capacitor C1, MOSFETs S1 and S2, and inductor L. The buck converter module also includes an input port. The first full-bridge network consists of MOSFETs S3, S4, S5, and S6, and leakage inductor L. k1 Composition; the second full-bridge network consists of MOSFETs S7, S8, S9, and S1. 10 Leakage inductance L k2 The second full-bridge network consists of capacitor C2 and a high-voltage port; the third full-bridge network consists of MOSFET S. 11 MOSFET 12 MOSFET 13 MOSFET 14 Leakage inductance L k3 The third full-bridge network, consisting of capacitor C3, also includes a low-voltage port. In this embodiment, within each full-bridge network, diagonally opposite MOSFETs form a pair. The same pair of MOSFETs receives the same control signal, while the control signals between the two pairs of MOSFETs have the same duty cycle and frequency, and are 180 degrees out of phase.

[0040] A control method for a wide-range integrated OBC-LDC three-port converter system, wherein the control method controls charging modes including: charger mode, low-voltage DC-DC converter mode, and combined operating mode.

[0041] In charger mode: the input port is used as a DC input terminal, and the high-voltage port outputs DC power with a wide voltage range to charge the high-voltage battery of the electric vehicle. At this time, the low-voltage port is in a non-working state. During the control process, the output voltage is precisely controlled by adjusting the duty cycle of the buck converter module and the duty cycle of the two pairs of MOSFETs in the full-bridge section of the input port. The full-bridge section of the high-voltage port is used as a rectifier bridge.

[0042] In this embodiment, in charger mode, the input-output relationship is V out / V in= D1 / (2n(1-D2)), where D1 is the duty cycle of MOSFET S1, MOSFET S2 and MOSFET S1 are complementary conductions, D2 is the duty cycle of MOSFETs S3, S4, S5, and S6, and n is the turns ratio of the transformer at the input port to that at the high-voltage port. The output V2 of the high-voltage port is stabilized by adjusting the duty cycles D1 and D2. To prevent a sudden change in inductor current L caused by all four MOSFETs being turned off, the duty cycle D2 should be greater than 0.5. In this case, the controller has two operating modes: Buck mode and Boost mode. In Buck mode, the duty cycle D2 is set to its minimum value D. 2min =0.52, adjust the duty cycle D1; in Boost mode, set the duty cycle of S1 to the maximum value D. 1max =1, adjust duty cycle D2. The two modes use independent controllers, such as... Figure 2 As shown in (a), the two controllers employ voltage PI control, where V ref2 The target value is output to the high-voltage port via V. ref2 Determine whether the converter is operating in Buck mode or Boost mode.

[0043] In low-voltage DC-DC converter mode: the high-voltage battery at the high-voltage port provides DC input, and the low-voltage port outputs low-voltage DC power to power the low-voltage battery and low-voltage electrical equipment; at this time, voltage control is achieved by adjusting the duty cycle of the two pairs of MOSFETs in the full-bridge section of the high-voltage port, and the full-bridge section of the low-voltage port is used as a rectifier bridge.

[0044] In this embodiment, in low-voltage DC-DC converter mode, the high-voltage port supplies power to the low-voltage port, and D3 represents MOSFETs S7, S8, S9, and S1. 10 The duty cycle is used to control the output voltage; D3 is less than 0.5, n 23 This refers to the turns ratio of the high-voltage and low-voltage ports. At this point, the output V3 of the low-voltage port is stabilized by adjusting the duty cycle D3, as follows: Figure 2 As shown in (b), the closed-loop controller uses a voltage PI controller for control, where V ref3 The target value is output for the low-voltage port.

[0045] In combined operation mode: DC power is input at the input port, high voltage DC power is output at the high voltage port, and low voltage DC power is output at the low voltage port. At this time, the duty cycle of the buck converter module and the duty cycle of the two pairs of MOSFETs in the full bridge section of the input port are adjusted to control the output voltage of the high voltage port; the duty cycle of the two pairs of MOSFETs in the full bridge section of the low voltage port is adjusted to control the output voltage of the low voltage port.

[0046] In this embodiment, in the combined operating mode, the input port is controlled in the same way as in the charger mode, that is, the output V2 is stabilized by adjusting the duty cycles D1 and D2. The controller also has Buck mode and Boost mode. In addition, it is also necessary to adjust the MOSFET S. 11 MOSFET 12 MOSFET 13 MOSFET 14 The duty cycle D4 is used to control the stability of the output V3 at the low-voltage port, where D4 is less than 0.5. Figure 2 As shown in (c), the closed-loop controller uses a voltage PI controller for control.

[0047] Figure 3 The timing diagram for the integrated OBC-LDC three-port converter in joint operating mode is shown below. Figure 3 (a) is a timing diagram under the Buck pattern. Figure 3 (b) is the timing diagram in Boost mode; Figure 4 Control mode diagram of the integrated OBC-LDC three-port converter in joint operating mode.

[0048] In Buck mode, including Figure 4 The six modes are (a), (b), (c), (d), (e), and (f). During the time interval t0 to t1... Figure 4 In (a)), MOSFETs S1, S3, S4, S5, S6, and S7 are listed. 11 MOSFET 14 When L is turned on, the current through the bridge arm MOSFETs S3, S4, S5, and S6 increases at a charging slope of V1 / L. k3 The current flows through C3 at a charging slope of -V3 / L k3 The rise. During the time interval t1 to t2 ( Figure 4 In (b)), MOSFETs S1, S3, S6, and S7 are... 11 MOSFET 14 When the circuit is turned on, the current of L flows through the output high-voltage port and low-voltage port at a charging slope (V1-V2 / n). 12 ) / L rises, L k3 The current flows through the high-voltage port load at a discharge slope (V2 / n) 23 -V3) / L K3 Decrease. During the time interval t2 to t3 ( Figure 4 In step (c), MOSFETs S1, S3, and S6 are turned on, and the current slope of L is the same as in the previous stage. k3 The current flows through the high-voltage port load at a discharge slope (V2 / n)23 +V3) / L K3 It decreases until it reaches 0. During the time interval t3 to t4 ( Figure 4 In the middle (d) stage, MOSFETs S1, S3, and S6 are turned on, and the current slope of L is the same as in the previous stage. k3 The current flows through the high-voltage port at a charging slope (V2 / n) 23 -V3) / L K3 The rise occurs during the time interval t4 to t5. Figure 4 In the middle (e), MOSFETs S2, S3, and S6 are turned on, and the current in L flows through the high-voltage port and the low-voltage port at a discharge slope of -V2 / n. 12 L decreases, L k3 The current slope is the same as in the previous stage. During the time interval t5 to t6 ( Figure 4 In the middle (f), MOSFETs S2, S3, and S6 are turned on, and the current of L flows through the low-voltage port at a discharge slope of -V3 / (L / n). 13 +n 13 L k3 ) decrease, L k3 The current flows at a discharge slope of -V3 / (L / n) 13 2 +L k3 The decline occurs in the latter half of the cycle, from t6 to t7. 12 Within a certain time interval, the current change of L is the same as that of the first half of the cycle. k3 The current is symmetrical in the opposite direction to that of the first half of the cycle.

[0049] In Boost mode, it includes Figure 5 The five modes (a), (b), (c), (d), and (e) are the same as in the Buck mode during the time intervals t0~t1, t1~t2, t2~t3, and t3~t4. During the time interval t4~t5... Figure 5 In the middle (e)), MOSFETs S1, S2, S3, and S6 are turned on, and the current of L flows through the low-voltage port at a charging slope of V1 / L-(n 13 2 V1L k3 +n 13 V3L) / (L 2 +n 13 2 LL k3 ) rise, L k3 The current flows through the low-voltage port at a charging slope (n 13 V1L k3 +V3L) / (LL k3 +n 13 2 L k3)-V3 / L k3 Rising. In the latter half of the cycle, t5~t 10 Within a certain time interval, the current change of L is the same as that of the first half of the cycle. k3 The current is symmetrical in the opposite direction to that of the first half of the cycle.

[0050] Example 2

[0051] The method of this invention was simulated and analyzed in the time domain using PSIM simulation software, and the results are as follows.

[0052] The simulation circuit parameters are: inductance L = 600uH, leakage inductance L... K1 =5uH, L K2 =5uH, L K3 =5uH, capacitors C1=220uF, C2=220uF, C3=2000uF, transformer ratio n1:n2:n3=7:6:1, input voltage reference value of the input port is 400V, output voltage reference value of the high voltage port is 410V, output voltage range is 250V~600V, output voltage reference value of the low voltage port is 14V, rated output power of the high voltage port is 3.3kW, rated output power of the low voltage port is 300W, when working together, the rated output power of the input port is 3kW, and the rated output power of the high voltage port is 300W. The frequency of the control signal is 80kHz for MOSFETs S1 and S2, and for MOSFETs S3~S2. 15 It is 40kHz.

[0053] Figure 6 The simulation waveforms in charger mode are shown, among which, Figure 6 (a): Input V1 = 400V, output V2 = 600V, the controller works in Boost mode. When the load at the high-voltage port changes from full load to half load, the output voltage remains constant at 600V. There will be a brief fluctuation when the load changes and then it will recover quickly. The output current decreases in a step manner with the load. Figure 6 (b) Input V1 = 400V, output V2 = 250V, the controller works in Buck mode. When the load on the high-voltage port changes from full load to half load, the output voltage stabilizes at 250V. When the load changes, there is a small fluctuation and the recovery is fast. The output current also decreases accordingly. Figure 7 The simulation waveform is shown in the low-voltage DC-DC converter mode. The input V2 is at the reference value of 410V and the output V3 = 14V. When the load at the low-voltage port changes from full load to half load, the output voltage remains constant at 14V in steady state. After a small transient fluctuation during load switching, it recovers quickly, and the output current decreases smoothly. Figure 8 The simulation waveforms are for the combined working mode. Figure 8 (a) and Figure 8 The input voltage V1 in (b) is 400V; Figure 8In (a), the outputs are V2 = 600V and V3 = 14V. When the load on the high-voltage port changes from full load to half load, V2 remains stable at 600V and the controller operates in Boost mode. On the low-voltage side, V3 remains unchanged at 14V. Figure 8 The output of (b) is V2 = 250V and V3 = 14V. When the load on the high-voltage port changes from full load to half load, V2 stabilizes at 250V and the controller operates in Buck mode. The low-voltage side V3 is not significantly affected. Figure 9 This is a simulation waveform diagram of voltage surges at the high-voltage port of an embodiment of the present invention and a three-active-bridge converter under the full output range. Figure 9 The input V1 = 400V, the low-voltage port output V3 = 14V, and when the high-voltage port output V2 changes from 250V to 600V... Figure 9 The outputs V2 and V3 in (a) can be restored to stability. Figure 9 In (b), the output V2 can recover to stability, but the output V3 does not reach the expected value of 14V. From the overall simulation results, the output voltage exhibits good stability under load fluctuations in all operating modes: in the charger's Boost and Buck modes, the voltage fluctuation at the high-voltage port is small and recovers quickly during load switching, while the current changes stepwise with the load; in the low-voltage DC-DC conversion mode, the 14V output exhibits only minor transient fluctuations during load switching, with smooth current adjustment. In the combined operating mode, the high-voltage port can stably output a wide range of high voltage from 250V to 600V, while the low-voltage port maintains a constant 14V low-voltage output. Even if the high-voltage port dynamically switches between 250V and 600V, the voltages at both the high-voltage and low-voltage ports can return to a stable state with extremely fast response. Compared with a three-phase active bridge converter, this invention significantly expands the high-voltage output range while ensuring continuous stability of the low-voltage output, fully demonstrating its good adaptability and reliability in multi-voltage power supply scenarios.

[0054] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A wide-range integrated OBC-LDC three-port converter system, characterized in that, include: Buck converter module and three active bridge converter module; The three-active-bridge converter module consists of a first full-bridge network, a second full-bridge network, a third full-bridge network, and a transformer; The step-down converter module is connected to the first full-bridge network, and the first full-bridge network is connected to the second full-bridge network and the third full-bridge network respectively through the transformer.

2. The wide-range integrated OBC-LDC three-port converter system according to claim 1, characterized in that, The buck converter module consists of capacitor C1, MOSFET S1, MOSFET S2 and inductor L, and also includes an input port. The first full-bridge network consists of MOSFETs S3, S4, S5, and S6, and a leakage inductance L. k1 constitute; The second full-bridge network consists of MOSFETs S7, S8, S9, and S1. 10 Leakage inductance L k2 The second full-bridge network, consisting of capacitor C2, also includes a high-voltage port; The third full-bridge network is composed of MOSFETs. 11 MOSFET 12 MOSFET 13 MOSFET 14 Leakage inductance L k3 The third full-bridge network, consisting of capacitor C3, also includes a low-voltage port.

3. A control method for a wide-range integrated OBC-LDC three-port converter system, the control method being used to control the converter system according to any one of claims 1-2, characterized in that, include: Charger mode, low-voltage DC-DC converter mode, and combined operation mode.

4. The control method for a wide-range integrated OBC-LDC three-port converter system according to claim 3, characterized in that, In the charger mode: The input port serves as a DC input terminal, and the high-voltage port outputs DC power with a wide voltage range to charge the high-voltage battery of the electric vehicle. At this time, the low-voltage port is in a non-operating state. During the control process, the output voltage is precisely controlled by adjusting the duty cycle of the buck converter module and the duty cycle of the two pairs of MOSFETs in the full-bridge section of the input port. The full-bridge section of the high-voltage port is used as a rectifier bridge.

5. The control method for a wide-range integrated OBC-LDC three-port converter system according to claim 3, characterized in that, In the low-voltage DC-DC converter mode: The high-voltage port provides DC input to the high-voltage battery, and the low-voltage port outputs low-voltage DC power to power the low-voltage battery and low-voltage electrical equipment. At this time, voltage control is achieved by adjusting the duty cycle of the two pairs of MOS transistors in the full-bridge section of the high-voltage port, while the full-bridge section of the low-voltage port is used as a rectifier bridge.

6. The control method for a wide-range integrated OBC-LDC three-port converter system according to claim 3, characterized in that, The joint working mode: The input port receives DC power, the high-voltage port outputs high-voltage DC power, and the low-voltage port outputs low-voltage DC power. At this time, the duty cycle of the buck converter module and the duty cycle of the two pairs of MOS transistors in the full-bridge section of the input port are adjusted to control the output voltage of the high-voltage port; Adjusting the duty cycle of the two pairs of MOSFETs in the full-bridge section of the low-voltage port is used to control the output voltage of the low-voltage port.

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