Bidirectional constant power control structure and method of full-bridge interleaved parallel bidirectional LLC converter

Abstract

The present invention discloses a bidirectional constant power control structure and method for a full-bridge interleaved parallel bidirectional LLC converter, including a first bidirectional full-bridge LLC converter, a second bidirectional full-bridge LLC converter, a load R at the power supply output end load , an interleaving angle adjustment module STM, a PFM1 module, a PFM2 module, a commutation control module SPM, a primary-secondary asynchronous compensation angle adjustment module PIM, a constant voltage control loop of the LLC resonant converter, a constant current control loop of the LLC resonant converter, a first current sampling module, a second current sampling module, and a voltage sampling module. The control method of the present invention is simple and does not increase any hardware cost, and can achieve bidirectional constant power control of the interleaved parallel bidirectional LLC resonant converter.

Description

Technical Field

[0001] The invention belongs to the field of electronic technology, and in particular relates to a bidirectional constant power control structure and method of a full-bridge staggered parallel bidirectional LLC converter. Background Art

[0002] With the widespread application of energy storage, the requirements for high-power DC power supplies are constantly increasing. The urgency of improving the safety, efficiency and power density of power supplies is particularly prominent today under the dual carbon goals. Interleaved parallel connection can not only reduce the input and output current ripple, but also increase the output power of the converter. It not only effectively reduces the use of input and output capacitors, but also increases the power density and reduces the hardware cost of the converter. Due to the consistency of the manufacturing process, the resonant component has a tolerance of ±5%, which makes the normalized frequency of the converter inconsistent. This not only leads to the uneven power distribution between phases and severe heating of one phase, but also causes the output current ripple to increase, reducing the service life of the converter. The traditional LLC resonant converter uses PFM control to adjust the gain. In order to ensure the minimum input and output ripple, the current interleaving angle of the interleaved parallel connection must be maintained at one tenth of a cycle, so the gain compensation of the phase with lower power cannot be performed through PFM, and another gain compensation control strategy needs to be proposed. The current power sharing control, although it can achieve power sharing, will cause the converter to lose zero voltage switching (ZVS). Some power sharing control is achieved through additional hardware circuits, and they are all concentrated in unidirectional LLC converters. Summary of the invention

[0003] In view of the shortcomings of the prior art, the present application provides a bidirectional constant power control structure and method for a full-bridge interleaved parallel bidirectional LLC converter, in which the output current and voltage of the two LLC resonant converter modules are used as the input of the interleaving angle adjustment module STM, and the parallel LLC interleaving is achieved through STM for a quarter of a cycle. The output current of the two LLC resonant converter modules is used as the input of the main and secondary side asynchronous compensation angle adjustment module PIM and the phase change control module SPM, and constant power control is achieved through SPM and PIM.

[0004] A bidirectional constant power control structure of a full-bridge staggered parallel bidirectional LLC converter, comprising a first bidirectional full-bridge LLC converter, a second bidirectional full-bridge LLC converter, a load R at the output end of the power supply load , staggered angle adjustment module STM, PFM1 module, PFM2 module, commutation control module SPM, primary and secondary side asynchronous compensation angle adjustment module PIM, LLC resonant converter constant voltage control loop, LLC resonant converter constant current control loop, first current sampling module, second current sampling module and voltage sampling module;

[0005] The first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter input and output terminals are connected in parallel;

[0006] The first current sampling module collects a first output current sample of the first bidirectional full-bridge LLC converter;

[0007] The second current sampling module collects the second output current sampling of the second bidirectional full-bridge LLC converter;

[0008] The voltage sampling module collects output voltage samples of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter;

[0009] The staggered angle adjustment module STM takes the first output current sampling of the first bidirectional full-bridge LLC converter, the second output current sampling of the second bidirectional full-bridge LLC converter and the output voltage sampling of both as inputs, and outputs a signal to the PFM2 module;

[0010] The commutation control module SPM takes the first output current sample and the second output current sample as input;

[0011] The primary and secondary side asynchronous compensation angle adjustment module PIM takes the first output current sampling and the second output current sampling as input, and the output is judged by the phase change control module SPM to select the PFM1 module or the PFM2 module;

[0012] The LLC resonant converter constant voltage control loop takes the output voltage sampling as input, and the output frequency signal F is determined by the control mode and given to the PFM1 module and the PFM2 module;

[0013] The LLC resonant converter constant current control loop takes the first output current sample and the second output current sample as input, and the output frequency signal F is determined by the control mode and given to the PFM1 module and the PFM2 module.

[0014] Furthermore, the commutation control module SPM is used to detect the first output current sampling and the second output current sampling respectively, and determine which bidirectional full-bridge LLC converter needs to compensate the gain through the current sampling signal.

[0015] Furthermore, the main-secondary side asynchronous compensation angle adjustment module PIM is used to detect the first output current sampling and the second output current sampling respectively, determine the gain deviation and obtain the required main-secondary side asynchronous compensation angle β, and provide the main-secondary side asynchronous compensation angle β to the PFM module corresponding to the bidirectional full-bridge LLC converter to be compensated, so as to realize the forward operation gain compensation M z and reverse operation gain compensation M f .

[0016] Furthermore, the main and secondary side asynchronous compensation angle β and the forward operation gain compensation M z and reverse operation gain compensation M f The relationship is as follows:

[0017]

[0018]

[0019] Where F is the normalized frequency and Q is the quality factor Q = π 2 Z r I o / 8n 2 V o , Z r is the characteristic impedance I o is the converter output current, V o is the converter output voltage, n is the transformer turns ratio, C r is the resonant capacitance value, K = L r / L m is the ratio of resonant inductance to magnetizing inductance, L r is the resonant inductance value, L m is the magnetizing inductance value.

[0020] Furthermore, the staggered angle adjustment module STM is used to detect the first output current sampling, the second output current sampling and the output voltage sampling respectively, and determine the staggered angle of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter. The current staggered angle of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter is kept at a quarter of a cycle at all times to achieve minimum ripple output.

[0021] Furthermore, the staggered angle is determined as follows:

[0022]

[0023] Where k = L r / L m is the ratio of resonant inductance to magnetizing inductance, β is the primary-secondary asynchronous compensation angle, F is the normalized frequency, and M is the voltage gain.

[0024] The present invention also provides a bidirectional constant power control method for a full-bridge staggered parallel bidirectional LLC converter, comprising:

[0025] Step 1: collect the output current I of the first bidirectional full-bridge LLC converter through the first current sampling module o1 , the output current I of the second bidirectional full-bridge LLC converter is collected by the second current sampling module o2 The output voltage V of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter is collected by the voltage sampling module. o ;

[0026] Step 2: The converter operates in constant current mode. The LLC resonant converter constant current control loop (8) converts the current signal I o1 and I o2 The sum is used as the feedback signal and the given current signal I o_ref The difference is given to the PID controller output signal to the PFM1 module and the PFM2 module to obtain the operating frequency F of the converter; the converter works in the constant voltage mode, and the LLC resonant converter constant voltage control loop (9) converts the voltage signal V o As the feedback signal and the given voltage signal V o_ref The difference is given to the output signal of its own PID controller to the PFM1 module and the PFM2 module to obtain the operating frequency F of the converter;

[0027] Step 3: The staggered angle adjustment module STM uses the current signal I o1 , current signal I o2 , voltage signal V o The interleaving angle of the second bidirectional full-bridge LLC converter is determined by the operating frequency F And the staggered angle Input PFM2 module, always keep the current phase of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter at one quarter cycle to achieve minimum ripple output;

[0028] Step 4, the commutation control module SPM uses the current sampling data of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter to determine the power of the two bidirectional full-bridge LLC converters, and then determines which bidirectional full-bridge LLC converter needs to compensate the gain;

[0029] Step 5, the primary-secondary side asynchronous compensation angle adjustment module PIM determines the primary-secondary side asynchronous compensation angle β of the phase with smaller compensation power by using the current sampling data of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter and the operating frequency F;

[0030] Step 6, when F>1 is running in the forward direction or when running in the reverse direction, the main and secondary side asynchronous compensation angle β is given to the PFM module of the phase with smaller power; when F<1 is running in the forward direction, the main and secondary side asynchronous compensation angle β is given to the PFM module of the phase with larger power, and finally the bidirectional constant power control of the full-bridge staggered parallel LLC is realized.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The control method of the present invention is simple and does not increase any hardware cost. It can realize bidirectional constant power control of staggered parallel bidirectional LLC resonant converters and realize ZVS of all switch tubes. Under constant power control, the output current ripple cancellation effect of the two LLC converters is optimized, with more superior output ripple performance, effectively increasing the power density of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of a bidirectional constant power control structure;

[0034] Figure 2 It is the topology diagram of the interleaved parallel bidirectional LLC resonant converter;

[0035] Figure 3 It is a bidirectional constant power control flow chart;

[0036] Figure 4 Output waveform for PFM module;

[0037] Figure 5 Resonant waveform without constant power control

[0038] Figure 6 It is a resonant waveform diagram with constant power control;

[0039] Figure 7 This is a schematic diagram of the thermal imaging comparison of the switch tube before and after constant power control. DETAILED DESCRIPTION

[0040] In the description of the present invention, it is necessary to understand that the terms "one end", "the other end", "outside", "upper", "inside", "horizontal", "coaxial", "center", "end", "length", "outer end" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0041] The present invention will be further described below in conjunction with the accompanying drawings.

[0042] See also Figure 1 and Figure 2 A bidirectional constant power control structure of a full-bridge interleaved parallel bidirectional LLC converter, comprising a first bidirectional full-bridge LLC converter 1, a second bidirectional full-bridge LLC converter 2, a load R at the power output end load, staggered angle adjustment module STM5, PFM1 module, PFM2 module, commutation control module SPM7, main and secondary side asynchronous compensation angle adjustment module PIM6, LLC resonant converter constant voltage control loop 9, LLC resonant converter constant current control loop 8, first current sampling module 3, second current sampling module 10 and voltage sampling module 4.

[0043] The input and output ends of two bidirectional full-bridge LLC converters are connected in parallel.

[0044] The first current sampling module 3 collects the first output current sampling of the first bidirectional full-bridge LLC converter 1 .

[0045] The second current sampling module 10 collects the second output current samples of the second bidirectional full-bridge LLC converter 2 .

[0046] The voltage sampling module 4 collects output voltage samples of the first bidirectional full-bridge LLC converter 1 and the second bidirectional full-bridge LLC converter 2 .

[0047] The interleaving angle adjustment module STM5 takes the first output current sampling of the first bidirectional full-bridge LLC converter 1, the second output current sampling of the second bidirectional full-bridge LLC converter 2, and the output voltage sampling of both as inputs, and outputs a signal to the PFM2 module. Specifically, the interleaving angle adjustment module STM5 is used to detect the first output current sampling, the second output current sampling, and the output voltage sampling, respectively, to determine the interleaving angle of the first bidirectional full-bridge LLC converter 1 and the second bidirectional full-bridge LLC converter 2. The current staggered angle of the first bidirectional full-bridge LLC converter 1 and the second bidirectional full-bridge LLC converter 2 is kept at a quarter cycle at all times to achieve minimum ripple output.

[0048] The commutation control module SPM7 takes the first output current sampling and the second output current sampling of the two bidirectional full-bridge LLC converters as inputs. The commutation control module SPM7 is used to detect the first output current sampling and the second output current sampling respectively, and determine which bidirectional full-bridge LLC converter needs to compensate the gain through the current sampling signal.

[0049] The main-side asynchronous compensation angle adjustment module PIM6 takes the first output current sampling and the second output current sampling of the two bidirectional full-bridge LLC converters as input, and the output is judged by the above-mentioned commutation control module SPM7 to select the PFM1 module or the PFM2 module. Specifically: the main-side asynchronous compensation angle adjustment module PIM6 is used to detect the first output current sampling and the second output current sampling respectively, determine the gain deviation and obtain the required main-side asynchronous compensation angle β, and give the main-side asynchronous compensation angle β to the PFM module corresponding to the bidirectional full-bridge LLC converter to be compensated, so as to achieve gain compensation.

[0050] The LLC resonant converter constant voltage control loop 9 takes the output voltage samples of the two bidirectional full-bridge LLC converters as input, and outputs a frequency signal F determined by the control mode and given to the PFM1 module and the PFM2 module.

[0051] The LLC resonant converter constant current control loop 8 takes the first output current sampling and the second output current sampling of the two bidirectional full-bridge LLC converters as inputs, and outputs a frequency signal F determined by the control mode and given to the PFM1 module and the PFM2 module.

[0052] The control method of the above bidirectional constant power control structure is as follows:

[0053] Furthermore, the main and secondary side asynchronous compensation angle β and the forward operation gain compensation M z and reverse operation gain compensation M f The relationship is as follows:

[0054]

[0055]

[0056] Where F is the normalized frequency and Q is the quality factor Q = π 2 Z r I o / 8n 2 V o , Z r is the characteristic impedance I o is the converter output current, V o is the converter output voltage, n is the transformer turns ratio, C r is the resonant capacitance value, K = L r / L m is the ratio of resonant inductance to magnetizing inductance, L r is the resonant inductance value, L m is the magnetizing inductance value.

[0057] Interleaving angle of two bidirectional full-bridge LLC converters is determined as follows:

[0058]

[0059] in, is the interleaving angle of two bidirectional full-bridge LLC converters, K = L r / L m is the ratio of resonant inductance to magnetizing inductance, β is the asynchronous angle of primary and secondary control signals, F is the normalized frequency, and M is the voltage gain.

[0060] like Figure 2 As shown, the resonant component L of the A-phase LLC converterr1 =57.4mH, L m1 =203mH、C r1 =45nF, resonant component L of B-phase LLC converter r1 =53.2mH, L m1 =201mH、C r1 =47.5nF, transformer ratio 2:1, input 100V output 43V constant voltage mode, operating frequency 110Khz, the converter runs in the forward direction, as an example, Figure 3 As shown, the control method of the above bidirectional constant power control structure includes the following steps:

[0061] Step 1: collect the output current I of the first bidirectional full-bridge LLC converter 1 through the first current sampling module 3 o1 The output current I of the second bidirectional full-bridge LLC converter 2 is collected by the second current sampling module 10. o2 The output voltage V of the first bidirectional full-bridge LLC converter 1 and the second bidirectional full-bridge LLC converter 2 is collected by the voltage sampling module 4. o ;

[0062] Step 2: The converter operates in constant current mode. The LLC resonant converter constant current control loop 8 converts the current signal I o1 and I o2 Sum I o As feedback signal and given current signal I o_ref The error is output to the PFM1 module and the PFM2 module before being given to its own PID to obtain the converter operating frequency F;

[0063] This embodiment adopts the constant voltage mode. The LLC resonant converter constant voltage control loop 9 converts the voltage signal V o As the feedback signal and the given voltage signal V o_ref The error is output to its own PID controller to the PFM1 module and the PFM2 module to obtain the converter operating frequency F of 110Khz;

[0064] Step 3: The CSTM module uses the current sampling signal, voltage sampling signal and operating frequency F of the bidirectional full-bridge LLC resonant converter to determine the interleaving angle of the LLC resonant converter. Will Input PFM2 module, such as Figure 4 As shown in the figure, the waveform output by the PFM2 module is as follows: Figure 6 As shown, the interleaving time of the LLC current of phase A and the LLC current of phase B is 2.727 microseconds, the cycle is 9.09 microseconds, and the current phase of the two bidirectional full-bridge LLC resonant converters is maintained for a quarter of a cycle to achieve minimum ripple output;

[0065] Step 4, the DSPM module uses the current sampling data of the bidirectional full-bridge LLC resonant converter to determine the power of the two bidirectional full-bridge LLC resonant converters, and the power flowing through the A-phase LLC converter is greater than the power flowing through the B-phase LLC converter;

[0066] Step 5: In this embodiment, the converter operates in the forward mode, and the primary and secondary asynchronous compensation angle adjustment module PIM6 uses the bidirectional full-bridge LLC resonant converter current sampling data I o1 ,I o2 The operating frequency F = 110Khz determines the main and secondary side asynchronous compensation angle β = 30.2° for the phase with smaller compensation power;

[0067] Step 6, when the forward operation F>1 or reverse operation, the main and secondary side asynchronous compensation angle β is given to the PFM module of the phase with smaller power, and when the forward operation F<1, the main and secondary side asynchronous compensation angle β is given to the PFM module of the phase with larger power. In this embodiment, the converter operates in the forward mode, such as Figure 4 As shown, the main and secondary side asynchronous compensation angle β = 30.2° is given to the PFM2 module of the LLC converter of the B phase with smaller power, as shown in Figure 6 As shown, the resonant current amplitude of the full-bridge staggered parallel LLC is finally realized to achieve constant power control, such as Figure 7 As shown, on the left side of the figure, the temperature difference between the switch tubes of the A-phase and B-phase LLC converters is obvious without constant power control, while on the right side of the figure, the temperature of the switch tubes of the A-phase and B-phase LLC converters remains the same after constant power control.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bidirectional constant power control structure of a full-bridge interleaved parallel bidirectional LLC converter, characterized in that: The invention comprises a first bidirectional full-bridge LLC converter, a second bidirectional full-bridge LLC converter, and a load R at the output end of the power supply. load , staggered angle adjustment module STM, PFM1 module, PFM2 module, commutation control module SPM, primary and secondary side asynchronous compensation angle adjustment module PIM, LLC resonant converter constant voltage control loop, LLC resonant converter constant current control loop, first current sampling module, second current sampling module and voltage sampling module; The first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter input and output terminals are connected in parallel; The first current sampling module collects a first output current sample of the first bidirectional full-bridge LLC converter; The second current sampling module collects the second output current sampling of the second bidirectional full-bridge LLC converter; The voltage sampling module collects output voltage samples of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter; The staggered angle adjustment module STM takes the first output current sampling of the first bidirectional full-bridge LLC converter, the second output current sampling of the second bidirectional full-bridge LLC converter and the output voltage sampling of both as inputs, and outputs a signal to the PFM2 module; The commutation control module SPM takes the first output current sample and the second output current sample as input; The primary and secondary side asynchronous compensation angle adjustment module PIM takes the first output current sampling and the second output current sampling as input, and the output is judged by the phase change control module SPM to select the PFM1 module or the PFM2 module; The LLC resonant converter constant voltage control loop takes the output voltage sampling as input, and the output frequency signal F is determined by the control mode and given to the PFM1 module and the PFM2 module; The LLC resonant converter constant current control loop takes the first output current sample and the second output current sample as input, and the output frequency signal F is determined by the control mode and given to the PFM1 module and the PFM2 module.

2. The bidirectional constant power control structure of a full-bridge interleaved parallel bidirectional LLC converter according to claim 1, characterized in that: The switching control module SPM is used to detect the first output current sampling and the second output current sampling respectively, and determine which bidirectional full-bridge LLC converter needs to compensate the gain through the current sampling signal.

3. The bidirectional constant power control structure of a full-bridge interleaved parallel bidirectional LLC converter according to claim 2, characterized in that: The main-side asynchronous compensation angle adjustment module PIM is used to detect the first output current sampling and the second output current sampling respectively, determine the gain deviation and obtain the required main-side asynchronous compensation angle β, and provide the main-side asynchronous compensation angle β to the PFM module corresponding to the bidirectional full-bridge LLC converter to be compensated, so as to realize the forward operation gain compensation M. z and reverse operation gain compensation M f .

4. The bidirectional constant power control structure of a full-bridge interleaved parallel bidirectional LLC converter according to claim 3, characterized in that: The main and secondary side asynchronous compensation angle β and the forward operation gain compensation M z and reverse operation gain compensation M f The relationship is as follows: Where F is the normalized frequency and Q is the quality factor Q = π 2 Z r I o / 8n 2 V o , Z r is the characteristic impedance I o is the converter output current, V o is the converter output voltage, n is the transformer turns ratio, C r is the resonant capacitance value, K = L r / L m is the ratio of resonant inductance to magnetizing inductance, L r is the resonant inductance value, L m is the magnetizing inductance value.

5. The bidirectional constant power control structure of a full-bridge interleaved parallel bidirectional LLC converter according to claim 1, characterized in that: The staggered angle adjustment module STM is used to detect the first output current sampling, the second output current sampling and the output voltage sampling respectively, and determine the staggered angle of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter. The current staggered angle of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter is kept at a quarter of a cycle at all times to achieve minimum ripple output.

6. The bidirectional constant power control structure of a full-bridge interleaved parallel bidirectional LLC converter according to claim 5, characterized in that: The stagger angle is determined as follows: Where k = L r / L m is the ratio of resonant inductance to magnetizing inductance, β is the primary-secondary asynchronous compensation angle, F is the normalized frequency, and M is the voltage gain.

7. A bidirectional constant power control method for a full-bridge interleaved parallel bidirectional LLC converter, characterized in that: include: Step 1: collect the output current I of the first bidirectional full-bridge LLC converter through the first current sampling module o1 , the output current I of the second bidirectional full-bridge LLC converter is collected by the second current sampling module o2 The output voltage V of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter is collected by the voltage sampling module. o ; Step 2: The converter operates in constant current mode. The LLC resonant converter constant current control loop converts the current signal I o1 and I o2 The sum is used as the feedback signal and the given current signal I o_ref The difference is given to the output signal of its own PID controller to the PFM1 module and the PFM2 module to obtain the operating frequency F of the converter; the converter works in the constant voltage mode, and the LLC resonant converter constant voltage control loop converts the voltage signal V o As the feedback signal and the given voltage signal V o_ref The difference is given to the output signal of its own PID controller to the PFM1 module and the PFM2 module to obtain the operating frequency F of the converter; Step 3: The staggered angle adjustment module STM uses the current signal I o1 , current signal I o2 , voltage signal V o The interleaving angle of the second bidirectional full-bridge LLC converter is determined by the operating frequency F And the staggered angle Input PFM2 module, keep the current phase of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter at one quarter cycle at all times to achieve minimum ripple output; Step 4, the commutation control module SPM uses the current sampling data of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter to determine the power of the two bidirectional full-bridge LLC converters, and then determines which bidirectional full-bridge LLC converter needs to compensate the gain; Step 5, the primary-secondary side asynchronous compensation angle adjustment module PIM determines the primary-secondary side asynchronous compensation angle β of the phase with smaller compensation power by using the current sampling data of the first bidirectional full-bridge LLC converter and the second bidirectional full-bridge LLC converter and the operating frequency F; Step 6, when F>1 during forward operation or reverse operation, the main and secondary side asynchronous compensation angle β is given to the PFM module of the phase with smaller power; when F<1 during forward operation, the main and secondary side asynchronous compensation angle β is given to the PFM module of the phase with larger power, and finally the bidirectional constant power control of the full-bridge staggered parallel LLC is realized.

Images