Multi-phase parallel LLC resonant converter current sharing system based on virtual control main ring

Abstract

The invention discloses a multi-phase parallel LLC resonant converter current sharing system based on a virtual control main ring, and belongs to the technical field of power control. The system comprises a charge control unit and an output current balancing unit which are arranged on the input side of an inverter. The output current balancing unit calculates the difference of the output power among the phases according to the current unbalance degree among the phases, and the power transmitted among the phases is changed by changing the switching frequency; the charge control unit adopts a hysteresis charge control strategy, and controls the quantity of charges flowing to a resonant cavity in each switching period by controlling the resonant capacitor voltage at the moment when an upper bridge arm and a lower bridge arm of an inverter are switched on; switching signals output by the unit are input to four bridge arms of the inverter; and synchronizing each phase of the output current balancing unit by using the virtual control main ring, accumulating the resonant capacitor voltage of each phase at the switching moment so as to feed back to the virtual control main ring, and taking the output current of the virtual control main ring as the output current reference signal of each synchronized phase.

Description

Technical Field

[0001] The invention belongs to the technical field of power control, and in particular relates to a multi-phase parallel LLC resonant converter current sharing system based on a virtual control main loop. Background Art

[0002] Due to the limitations of power semiconductor devices in terms of withstand voltage, current carrying capacity and switching speed, when a single-phase LLC resonant converter is used in high-power applications, large current stress will reduce the efficiency and reliability of the power device. In addition, too much power will cause the output current ripple to be too large, and the loss of the output filter capacitor will increase. A capacitor with a larger capacitance is required to meet the output voltage ripple requirement, which greatly limits the operating scenario of the LLC converter. For this reason, LLC parallel technology came into being. By evenly distributing power to each phase of LLC running in parallel, it can be applied to higher power occasions. However, considering the differences in device parameters in actual application scenarios, the voltage gain of each phase of LLC will be different, which will cause serious imbalance in the output current and lose the meaning of parallel operation. For this reason, LLC parallel operation must use current equalization technology.

[0003] The current sharing methods for multi-phase LLC parallel connection can be mainly divided into two categories: passive current sharing and active current sharing. Passive current sharing is to achieve circuit current sharing through the design of circuit topology. This method is only applicable to a specific number of phases and overly dependent on the current sharing ability of the topology and components themselves, and the current sharing effect is not good. Active current sharing is to add detection links and control links to the original circuit and achieve current sharing through additional control. The current sharing method based on gain control aims to balance the voltage gain between LLCs of each phase. Common methods include using controllable capacitors to compensate for component parameter errors and using phase shift control to adjust the gain. The small signal models based on this type of method are all derived from frequency control, and the design of its operating stability and controller is often very complicated. Another current sharing method based on power balance aims to balance the output power between each phase. Commonly used methods are power control methods based on charge control, such as hysteresis charge control. The first-order model obtained by the small signal modeling of hysteresis charge control is very beneficial to the design of the system, and the characteristics of hysteresis charge control from power control are consistent with the characteristics of multi-phase parallel system that each phase shares power equally when equalizing current. The use of hysteresis charge control for equalizing current is superior to traditional frequency control in terms of design simplicity and effect. In terms of multi-phase synchronization, commonly used synchronization strategies include master-slave control, master command control, cross-coupling control, etc. Among them, cross-coupling control is difficult to extend to any phase and is not suitable for any phase LLC parallel system; master command control is the most direct synchronization control method, and the response speed depends entirely on each phase itself, and the synchronization effect is poor; master-slave control requires a master phase with a faster response speed, and the fast response speed of LLC can largely meet the requirements. However, the loss of the main phase may cause the parallel system to be completely paralyzed.

[0004] In summary, for a multi-phase LLC parallel system having component parameter differences in actual operation, the present invention proposes a multi-phase parallel LLC resonant converter current sharing system based on a virtual control main loop. Summary of the invention

[0005] In view of the deficiencies in the prior art, an object of the present invention is to provide a multi-phase parallel LLC resonant converter current sharing system based on a virtual control main loop, which solves the problems in the prior art.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A multi-phase parallel LLC resonant converter current balancing system based on a virtual control main loop includes a charge control unit and an output current balancing unit arranged at the input side of the inverter;

[0008] The output current balancing unit calculates the difference in output power between phases according to the current imbalance between phases, and changes the power transmitted between phases by changing the switching frequency to achieve a balanced power distribution;

[0009] The charge control unit adopts a hysteresis charge control strategy, and controls the amount of charge flowing to the resonant cavity in each switching cycle by controlling the resonant capacitor voltage at the moment when the upper and lower bridge arms of the inverter are turned on, thereby adjusting the input power; the switching signal output by the unit is input to the four bridge arms of the inverter;

[0010] The virtual control main loop is used to synchronize the phases of the output current balancing unit, and the resonant capacitor voltage of each phase at the switch switching moment is accumulated and fed back to the virtual control main loop. The output current of the virtual control main loop is used as the reference signal of the synchronized output current of each phase. The charge control unit is the control logic used by the output current balancing unit for each phase LLC.

[0011] Furthermore, in the charge control unit, LLC modeling based on the hysteresis charge control strategy is analyzed from the perspective of system input and output power conservation. Under the premise of ignoring losses, the LLC input power is equal to the output power; the input power is obtained by the change of the resonant capacitor voltage within a switching cycle:

[0012]

[0013] Among them, P in Represents input power, V in is the DC input voltage, C r is the resonant capacitor value, t AHoff represents the moment when Q1 bridge arm is turned off, t ALoff represents the moment when the Q2 bridge arm is turned off, f s represents the switching frequency, Cj represents the junction capacitance, v Cr (t AHoff ) and v Cr (t ALoff ) are the resonant capacitor voltage values ​​at the switching moment of the two bridge arms respectively;

[0014] Furthermore, the transfer function from the control variable to the output voltage in the LLC small signal model under the hysteresis charge control strategy is expressed as a first-order function:

[0015]

[0016] In the formula, is the small signal quantity of the instantaneous value of the output voltage, is the small signal value of the resonant capacitor voltage setting value, F s is the instantaneous value of the switching frequency, R L is the load resistance, V o is the average output voltage, C o is the filter capacitor value, K d is the voltage gain of the LLC.

[0017] Furthermore, in the output current balancing unit, the LLC parallel current sharing mechanism is analyzed based on the state plane method, and the state equations corresponding to the PON mode are:

[0018]

[0019] In the formula, the subscript N represents the normalized value, v Cr is the resonant capacitor voltage, i Lr is the resonant inductor current, v Cr0 with i Lr0 is a set of resonant capacitor voltage and resonant inductor current values ​​corresponding to the steady state, L n It is the ratio of magnetizing inductance to resonant inductance.

[0020] Furthermore, each phase of the output current balancing unit is synchronized by a reference signal given by the virtual control main loop; the resonant capacitor voltage of each phase at the switch switching moment is accumulated and fed back to the virtual control main loop, and the output current of the virtual control main loop is used as the output current reference signal of each synchronized phase; the frequency domain expression of the output current phase and the reference current between each phase under the synchronous control is:

[0021]

[0022] In the formula, LLC VCL (s) is the transfer function of the virtual LLC, G VCL (s) is the controller of the virtual phase, the summation term is the feedback of each phase to the virtual phase, LLC i(s) is the first-order transfer function number of the LLC of the i-th phase under the control of hysteresis charge control; I ref is the reference current signal input to the virtual LLC, The current reference value given by the virtual phase, I seci is the actual output current of each phase.

[0023] The multi-phase parallel LLC resonant converter current sharing method based on virtual control main loop uses the multi-phase parallel LLC resonant converter current sharing system based on virtual control main loop, including the following steps:

[0024] S1, collects the output voltage, compares it with the set voltage value, and obtains the current reference value through the controller;

[0025] S2, collect the output current of each phase, compare it with the current reference value, and obtain the control signal of the hysteresis charge control of each phase through the controller. The hysteresis control outputs the switch signal to the switch tube of each phase inverter;

[0026] S3, accumulating the control signals of the hysteresis charge control of each phase and inputting them into the virtual control main loop, and the output current of the virtual control main loop is used as the new reference value of the input current of each phase;

[0027] S4, repeat S2 to S3 until the output currents of all phases are evenly distributed.

[0028] A computer storage medium stores a readable program, which can execute the above-mentioned multi-phase parallel LLC resonant converter current sharing method based on virtual control main loop when the program is running.

[0029] An electronic device, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus;

[0030] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform operations corresponding to the above-mentioned multi-phase parallel LLC resonant converter current sharing method based on virtual control main loop.

[0031] A computer program product includes computer instructions, wherein the computer instructions instruct a computing device to execute operations corresponding to the above-mentioned multi-phase parallel LLC resonant converter current sharing method based on a virtual control main loop.

[0032] Beneficial effects of the present invention:

[0033] The present invention can realize the current sharing of multi-phase LLC resonant converters in parallel, and is particularly suitable for the current sharing control of any phase system with more than two phases. When the parallel system causes uneven current due to the change in the resonant cavity gain caused by the component parameter error, the hysteresis charge control will adjust the switching frequency of each phase according to the difference in output power to adjust each phase to the same output power. At the same time, the first-order response characteristics of the hysteresis charge control enable each parallel phase to have a faster response speed. When a new phase is connected in parallel to the system or the original phase is dropped, the characteristics of the power control will prevent the output current from fluctuating significantly, and the current changes during the transition process will be more stable. Under the virtual LLC synchronous control strategy, the relative error of the output current between the phases decreases rapidly, and the virtual LLC will not be affected by the fault, which improves the reliability of the system when running in parallel. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a structural diagram of a current sharing control system of a multi-phase full-bridge parallel LLC resonant converter of the present invention;

[0036] Figure 2 A block diagram of hysteresis charge control used in the present invention;

[0037] Figure 3 Schematic diagram of three mode decompositions of LLC according to the present invention;

[0038] Figure 4 This is a functional relationship diagram of the control amount and different output amounts under different loads using hysteresis charge control in the present invention;

[0039] Figure 5 Comparison of theoretical and actual Bode diagrams of LLC under hysteresis charge control modeling used in the present invention;

[0040] Figure 6 It is a state plane trajectory diagram of the output voltage change under the frequency control of the parallel system according to the present invention;

[0041] Figure 7 It is a state plane trajectory diagram of the output voltage change under the hysteresis charge control of the parallel system according to the present invention;

[0042] Figure 8 This is the output current result of the three-phase LLC parallel connection without current sharing control in the simulation;

[0043] Fig. 9The output current results of the LLC parallel shedding and phase addition using phase shift control in the simulation;

[0044] Fig.10 The output current results of the LLC parallel shedding and adding phases using frequency control in the simulation;

[0045] Fig.11 The output current result of the control method of the present invention when the LLC is disconnected and added in parallel in the simulation;

[0046] Fig.12 It is the result of the average output current when the LLC is disconnected and added in parallel using the control method of the present invention in the simulation. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] Example 1

[0049] like Figure 1 As shown, a multi-phase parallel LLC resonant converter current balancing system based on a virtual control main loop includes a charge control unit and an output current balancing unit arranged at the input side of the inverter;

[0050] The DC voltage input port of the converter and the output port of the rectifier circuit are both in parallel form. The diode bridge on the secondary side prevents the reverse flow of current, so there is no need to consider the circulation problem.

[0051] The output current balancing unit calculates the difference in output power between phases according to the current imbalance between phases, and changes the power transmitted between phases by changing the switching frequency to achieve a balanced power distribution;

[0052] The charge control unit uses a hysteresis charge control strategy to control LLC, and controls the amount of charge flowing to the resonant cavity in each switching cycle by controlling the resonant capacitor voltage at the moment when the upper and lower bridge arms of the inverter are turned on, so as to adjust the input power; the switching signal output by the unit is input to the four bridge arms of the inverter, which is essentially to adjust the energy transfer in a switching cycle through frequency control;

[0053] The virtual LLC (virtual control main loop, i.e., virtual phase) is used to synchronize the phases of the output current balancing unit, and the resonant capacitor voltage of each phase at the switching moment is accumulated and fed back to the virtual LLC. The output current of the virtual LLC is used as the reference signal of the synchronized output current of each phase. The charge control unit is the control logic used by the output current balancing unit for each phase LLC.

[0054] In the charge control unit, the modeling of LLC based on hysteresis charge control is analyzed from the perspective of system input and output power conservation. Considering that the resonant capacitor voltage is the integral of the resonant inductor current, the input power can be obtained by analyzing the voltage change within a switching cycle:

[0055]

[0056] Among them, P in Represents input power, V in Represents the DC input voltage, C r is the resonant capacitor value, t AHoff represents the moment when Q1 bridge arm is turned off, t ALoff represents the moment when the Q2 bridge arm is turned off, f s represents the switching frequency, C j represents the junction capacitance, v Cr (t AHoff ) and v Cr (t ALoff ) are the resonant capacitor voltage values ​​at the switching moment of the two bridge arms, and the influence of the junction capacitance can be ignored to simplify the analysis. According to the symmetry of the resonant converter, the full-bridge LLC at t AHoff Time and t ALoff At this moment, the resonant capacitor voltage is symmetrical about zero voltage, and the input power is simplified to:

[0057] P in =4V in C r f s v Cr (t AHoff )

[0058] The average current flowing to the secondary side is i sec , the output voltage is v o , ignoring the loss, the input power is equal to the output power, i sec This translates to:

[0059] i sec v o =4V in C r f s v Cr (t AHoff )

[0060] like Figure 2 As shown, the hysteresis charge control is to set the resonant capacitor voltage v thH As the control quantity, by comparing v Cr (t AHoff ) and v thH 、v Cr (t BHoff ) with -v thH The size of the switch is used to give the conduction signal of each switch tube. In essence, the energy transfer within a switching cycle is adjusted by frequency control. The LLC large signal model under hysteresis charge control modeling is solved based on LLC modal analysis. The equivalent circuits corresponding to the three modes are as follows: Figure 3 As shown in (a), (b) and (c) in FIG. 1 , the initial value of the inductor current in the P phase is K, and the initial value in the O phase is i Lr0 ; The initial value of the capacitor voltage in the P phase is J, and the initial value in the O phase is v Cr0 , the duration of the P phase is β, then we can get six unknowns K, β, T s 、V o 、i Lr0 、v Cr0 The corresponding six equations are:

[0061]

[0062] eq3:KZ0sin(ω0β)+(JV in +nV o )cos(ω0β)+V in -nV o =V Cr0

[0063] eq4:I Lr0 Z1cos[ω1(0.5T s -β)]-(V Cr0 -V in )sin[ω1(0.5T s -β)]=-KZ1

[0064] eq5:I Lr0 Z1sin[ω1(0.5T s -β)]+[V Cr0 -V in ]cos[ω1(0.5T s -β)]=-JV in

[0065]

[0066] In the formula, is the resonant angular frequency, is the series-parallel resonant angular frequency, L m is the magnetizing inductance value.

[0067] Equations 1 and 2 are derived from the fact that the inductor current at the end of the P phase is equal to the initial value of the O phase, Equation 3 is derived from the fact that the capacitor voltage at the end of the P phase is equal to the initial value of the O phase, Equations 4 and 5 are derived from the symmetry of the inductor current and capacitor voltage respectively, and Equation 6 is derived from the relationship between the current and voltage flowing to the secondary side. When the control quantity J = -V thH When it keeps changing, the corresponding variables can be solved. Figure 4 (a) and (b) are V thH With output voltage V o Functional relationship, V thH With the switching frequency f s This verifies that V thH With V o The linear relationship between V thH With f s As the load increases, V thH With f s The nonlinearity intensifies, but is always related to V o Maintain a good linear relationship, that is, the hysteresis charge control avoids the complex characteristics of the resonant cavity and directly adjusts the output voltage. It also verifies that V thH With V o The monotonic relationship between the voltage and the control signal can be obtained by the analysis result, and the analysis result can also be used as a reference signal for feedforward control. The feedforward amount of the control signal can be directly given according to the demand for voltage regulation, thereby greatly improving the response speed.

[0068] The transfer function from the control variable to the output voltage in the LLC small signal model under hysteresis charge control modeling can be analytically expressed as a first-order function:

[0069]

[0070] In the formula, is the small signal quantity of the instantaneous value of the output voltage, is the small signal value of the resonant capacitor voltage setting value, F s is the instantaneous value of the switching frequency, R L is the load resistance, V o is the average output voltage, C o is the filter capacitor value, K d is the voltage gain of the LLC. Figure 5 The Bode diagram obtained under the small signal model is compared with the actual Bode diagram, which is consistent with the analysis of the large signal model when the frequency is less than the resonant frequency.

[0071] In the output current balancing unit, the LLC parallel current sharing mechanism is analyzed based on the state plane method. The state equations corresponding to the PON mode are:

[0072]

[0073] In the formula, the subscript N represents the normalized value, v Cr is the resonant capacitor voltage, i Lr is the resonant inductor current, v Cr0 with i Lr0 is a set of resonant capacitor voltage and resonant inductor current values ​​corresponding to the steady state, L n It is the ratio of magnetizing inductance to resonant inductance.

[0074] Figure 6 (a) and (b) are the state plane trajectories of the output voltage changes when connected in parallel under frequency control. oN When <1, the state trajectory will appear in N mode, and there may be a transitional PON mode before that. oN Further decrease leads to the disappearance of O mode, and the PN mode appears. This is because L m The voltage on the o , which will cause the secondary side to conduct. In the process of the system transitioning to steady state, as the state quantity continues to increase, the radius of the circle corresponding to the P stage continues to grow, the time of the N mode connecting the two P modes will gradually decrease, and the state quantity will continue to increase so that the system can be transformed back to the P mode. Therefore, if the secondary side is connected to an ideal voltage source, theoretically the state quantity will approach infinity; for the actual parallel system, the greater the phase gain is than the parallel system, the greater the state quantity corresponding to its steady state, and in this case the output current will be very large. In nV oN When the state trajectory is transitioning to a steady state, the O mode will appear. This is because the secondary voltage rises, causing the clamped L m The rising speed is accelerated, while the rising speed of the resonant inductor current is slowed down, which makes the O mode come earlier. The appearance of the O mode reduces the output current duty cycle, which results in a significant reduction in the average output current.

[0075] Figure 7 (a) and (b) are the state plane trajectories after the output voltage changes when connected in parallel under hysteresis charge control. oN1 From 1 to nV oN2 =1.5, the clamped L m The voltage on the Lm The rising speed suddenly accelerates, and the increase of the secondary voltage will cause L rEnter a special mode, the response result of this mode is similar to the response result of P mode in the other half switching cycle, but the center of its trajectory will be changed from (1-nV oN1 ,0) becomes (1-nV oN2 ,0), such as the process from t0 to t1. During t1 to t2, i Lm Continuously increasing, at this time L m With L r Common resonance, in O mode; from t2 to t3, the resonant current continues to increase, but at this time L m The voltage on the upper side is still lower than the secondary side voltage and is still in the L m With L r O mode of common resonance; after t3~t4 Lm has increased to a sufficient value, once L m When the voltage on the MOSFET is equal to the voltage on the secondary side, the MOSFET is clamped and enters the P mode. From then on, the system will stabilize in the PO mode. oN1 From 1 to nV oN2 = 0.5, this will change the original P mode center from the original (-1 + nV oN1 ,0) becomes (-1+nV oN2 ,0), as shown in the trajectory from t0 to t1. When a new switching cycle arrives, due to the short switching time, before the end of P mode, the i Lr =i Lm The switch is switched, and now it is i Lr >i Lm Then according to symmetry, at the beginning of N mode, it must be i Lr <i Lm The system enters the NP mode. This usually occurs when the switching frequency is greater than the resonant frequency. At this time, the center of the N mode will be (1-nV oN1 ,0) becomes (-1-nV oN2 ,0), corresponding to the time period t1 to t2 in the above figure. Lr Rise to equal i Lm , the system does not enter O mode because the secondary voltage suddenly decreases, which causes L m It is still clamped, so the system will enter the P mode, corresponding to the time period t2 to t3. It can be seen that this process only goes through the conversion process from P mode to NP mode in one switching cycle, so the response speed is extremely fast. Compared with the previous nV oN2 = 0.5, it does not need to go through L m The voltage on the circuit gradually increases because nV oN2 =0.5, the secondary voltage suddenly decreases, so L mTherefore, when using hysteresis charge control, even if the secondary voltage source voltage changes, the output current will not change as drastically as under fixed frequency control, and only a small uneven current will occur.

[0076] When using virtual LLC for synchronous control, each phase of the current balancing unit is synchronized by the reference signal given by the virtual LLC. The resonant capacitor voltage of each phase at the switching moment is accumulated and fed back to the virtual LLC, and the output current of the virtual LLC is used as the output current reference signal of each synchronized phase. The transfer function of the output current of the i-th phase to the reference current under master synchronization is MR i (s):

[0077]

[0078] In the formula, G ci (s) is the controller transfer function from the error between the i-th phase reference current and the actual output current to the LLC hysteresis charge control input signal, LLC i (s) is the first-order transfer function of the LLC of the i-th phase under hysteresis charge control, I ref is the reference current signal input to the virtual LLC, I seci is the actual output current of each phase. The synchronization of each phase in this synchronization mode is determined by its own response speed. The algorithm is suitable for reducing the error between each phase and the reference signal, rather than eliminating the relative error between phases. Master-slave control requires selecting one phase as the master phase, and all other phases are slave phases. Taking the first phase as the master phase as an example, its current transfer function is MR1(s). Then the transfer function from the reference signal to the remaining slave phases will pass through one more master phase and become MR1(s)*MR i (s). The relative error between the slave phase and the master phase can be expressed by MR i (s) for adjustment, but this requires the main phase to have a faster response speed, and the failure of the main phase will affect the operation of the entire system.

[0079] Under the synchronous control of the virtual LLC of the present invention as the main phase, the frequency domain expression of the output current phase between each phase and the reference current is:

[0080]

[0081] In the formula, LLC VCL (s) is the transfer function of the virtual LLC, G VCL (s) is the controller of the virtual phase, the summation term is the feedback of each phase to the virtual phase, LLC i (s) is the first-order transfer function of the LLC of the i-th phase under hysteresis charge control, The current reference value given for the virtual phase. This synchronization mode inherits the characteristics of master-slave synchronization to reduce the relative error between phases. The designed virtual main phase has a fast response speed and will not be affected by faults.

[0082] Example 2

[0083] In this embodiment, a simulation experiment is performed on the system in Embodiment 1;

[0084] Figure 8 This is the simulation result after current sharing control using three-phase LLC parallel connection as an example. It can be seen from the figure that when no control is used, two phases have no output current and the output current is seriously uneven. Fig. 9 (a) and (b) in Fig.10 (a) and (b) in the figure are the responses of the instantaneous output current of each phase after removing and adding a phase when phase shift control and frequency control are used, respectively. Under both control modes, the addition of a new phase causes a short-term severe current imbalance in the system. This is because the newly added phase has a higher gain than the original phase. Based on the modeling based on frequency control, this will cause severe current imbalance. At the same time, the slow frequency makes the gain adjustment slow, and a long transition time is required to achieve current balance.

[0085] When one phase is removed and one phase is added to the current sharing system designed by the present invention, the instantaneous value response result of the output current of each phase corresponds to Fig.11 In (a) and (b), the average response results correspond to Fig.12 It can be seen that no matter whether a phase is removed or added, the system can quickly achieve current sharing. And this current sharing method does not require the actual main phase to be specified, and the removal and addition of any phase will not affect the operation of the system.

[0086] Example 3

[0087] In this embodiment, based on the current sharing system proposed in Embodiment 1, a current sharing method of a multi-phase parallel LLC resonant converter based on a virtual control main loop is proposed, including the following steps:

[0088] S1, collects the output voltage, compares it with the set voltage value, and obtains the current reference value through the controller;

[0089] S2, collects the output current of each phase, compares it with the current reference value, and obtains the control signal of the hysteresis charge control of each phase through the controller. The hysteresis control outputs the switching signal to the switch tube of each phase inverter.

[0090] S3, accumulating the control signals of the hysteresis charge control of each phase and inputting them into the virtual control main loop, and the output current of the virtual control main loop is used as a new reference value of the input current of each phase.

[0091] S4, repeat S2 to S3 until the output currents of all phases are evenly distributed.

[0092] Based on similar inventive concepts, an embodiment of the present invention further provides a computer storage medium storing a readable program, which can execute the above-mentioned multi-phase parallel LLC resonant converter current sharing method based on virtual control main loop when the program is running.

[0093] Based on similar inventive concepts, an embodiment of the present invention provides an electronic device, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus;

[0094] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform operations corresponding to the above-mentioned multi-phase parallel LLC resonant converter current sharing method based on virtual control main loop.

[0095] Based on similar inventive concepts, an embodiment of the present invention further provides a computer program product, including computer instructions, which instruct a computing device to execute operations corresponding to the above-mentioned multi-phase parallel LLC resonant converter current sharing method based on virtual control main loop.

[0096] The method of the present invention may be implemented in hardware, firmware, or as software or computer code that may be stored in a recording medium (such as a CDROM, RAM, floppy disk, hard disk, or magneto-optical disk), or as computer code that is originally stored in a remote recording medium or a non-temporary machine-readable medium downloaded over a network and will be stored in a local recording medium, so that the method described herein may be stored in such software processing on a recording medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware (such as an ASIC or FPGA). It is understood that a computer, processor, microprocessor controller, or programmable hardware includes a storage component (e.g., RAM, ROM, flash memory, etc.) that can store or receive software or computer code, and when the software or computer code is accessed and executed by a computer, processor, or hardware, the method described herein is implemented. In addition, when a general-purpose computer accesses the code for implementing the method shown herein, the execution of the code converts the general-purpose computer into a dedicated computer for executing the method shown herein.

[0097] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A multi-phase parallel LLC resonant converter current sharing system based on a virtual control main loop, characterized in that: It includes a charge control unit and an output current balancing unit arranged at the input side of the inverter; The output current balancing unit calculates the difference in output power between phases according to the current imbalance between phases, and changes the power transmitted between phases by changing the switching frequency to achieve a balanced power distribution; The charge control unit adopts a hysteresis charge control strategy, and controls the amount of charge flowing to the resonant cavity in each switching cycle by controlling the resonant capacitor voltage at the moment when the upper and lower bridge arms of the inverter are turned on, thereby adjusting the input power; the switching signal output by the unit is input to the four bridge arms of the inverter; The virtual control main loop is used to synchronize the phases of the output current balancing unit, and the resonant capacitor voltage of each phase at the switch switching moment is accumulated and fed back to the virtual control main loop. The output current of the virtual control main loop is used as the reference signal of the synchronized output current of each phase. The charge control unit is the control logic used by the output current balancing unit for each phase LLC.

2. The multi-phase parallel LLC resonant converter current sharing system based on virtual control main loop according to claim 1 is characterized in that: In the charge control unit, LLC modeling based on the hysteresis charge control strategy is analyzed from the perspective of system input and output power conservation. Under the premise of ignoring losses, the LLC input power is equal to the output power; the input power is obtained by the change of the resonant capacitor voltage within a switching cycle: Among them, P in Represents input power, V in is the DC input voltage, C r is the resonant capacitor value, t AHoff represents the moment when Q1 bridge arm is turned off, t ALoff represents the moment when Q2 bridge arm is turned off, f s represents the switching frequency, C j represents the junction capacitance, v Cr (t AHoff ) and v Cr (t ALoff ) are the resonant capacitor voltage values ​​at the switching moment of the two bridge arms.

3. The multi-phase parallel LLC resonant converter current sharing system based on virtual control main loop according to claim 2 is characterized in that: The transfer function from the control variable to the output voltage in the LLC small signal model under the hysteresis charge control strategy is expressed as a first-order function: In the formula, is the small signal quantity of the instantaneous value of the output voltage, is the small signal value of the resonant capacitor voltage setting value, F s is the instantaneous value of the switching frequency, R L is the load resistance, V o is the average output voltage, C o is the filter capacitor value, K d is the voltage gain of the LLC.

4. The multi-phase parallel LLC resonant converter current sharing system based on virtual control main loop according to claim 1 is characterized in that: In the output current balancing unit, the LLC parallel current sharing mechanism is analyzed based on the state plane method, and the state equations corresponding to the PON mode are: In the formula, the subscript N represents the normalized value, v Cr is the resonant capacitor voltage, i Lr is the resonant inductor current, v Cr0 with i Lr0 is a set of resonant capacitor voltage and resonant inductor current values ​​corresponding to the steady state, L n It is the ratio of magnetizing inductance to resonant inductance.

5. The multi-phase parallel LLC resonant converter current sharing system based on virtual control main loop according to claim 4 is characterized in that: Each phase of the output current balancing unit is synchronized by a reference signal given by the virtual control main loop; the resonant capacitor voltage of each phase at the switching moment is accumulated and fed back to the virtual control main loop, and the output current of the virtual control main loop is used as the output current reference signal of each synchronized phase; the frequency domain expression of the output current phase and the reference current between each phase under the synchronous control is: In the formula, LLC VCL (s) is the transfer function of the virtual LLC, G VCL (s) is the controller of the virtual phase, the summation term is the feedback of each phase to the virtual phase, LLC i (s) is the first-order transfer function number of the LLC of the i-th phase under the control of hysteresis charge control; I ref is the reference current signal input to the virtual LLC, The current reference value given by the virtual phase, I seci is the actual output current of each phase.

6. A multi-phase parallel LLC resonant converter current balancing method based on a virtual control main loop, using the multi-phase parallel LLC resonant converter current balancing system based on a virtual control main loop according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, collects the output voltage, compares it with the set voltage value, and obtains the current reference value through the controller; S2, collect the output current of each phase, compare it with the current reference value, and obtain the control signal of the hysteresis charge control of each phase through the controller. The hysteresis control outputs the switch signal to the switch tube of each phase inverter; S3, accumulating the control signals of the hysteresis charge control of each phase and inputting them into the virtual control main loop, and the output current of the virtual control main loop is used as the new reference value of the input current of each phase; S4, repeat S2 to S3 until the output currents of all phases are evenly distributed.

7. A computer storage medium storing a readable program, characterized in that: When the program is running, the current sharing method of a multi-phase parallel LLC resonant converter based on a virtual control main loop as described in claim 6 can be executed.

8. An electronic device, characterized in that: include: A processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus; The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform operations corresponding to the current sharing method of a multi-phase parallel LLC resonant converter based on a virtual control main loop as described in claim 6.

9. A computer program product comprising computer instructions, characterized in that The computer instructions instruct the computing device to execute operations corresponding to the current sharing method of a multi-phase parallel LLC resonant converter based on a virtual control main loop as claimed in claim 6.

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