Current sharing system based on multiphase parallel LLC resonant converter with virtual control main loop

Abstract

This invention discloses a current sharing system for a multiphase parallel LLC resonant converter based on a virtual control master loop, belonging to the field of power control technology. The system includes a charge control unit and an output current balancing unit located on the inverter input side. The output current balancing unit calculates the difference in output power between each phase based on the current imbalance between each phase and changes the power transferred between each phase by changing the switching frequency. The charge control unit adopts a hysteresis charge control strategy, controlling the amount of charge flowing to the resonant cavity in each switching cycle by controlling the resonant capacitor voltage at the turn-on time of the upper and lower bridge arms of the inverter. The switching signal output by this unit is input to the four bridge arms of the inverter. Using the virtual control master loop, the phases of the output current balancing unit are synchronized, and the resonant capacitor voltage of each phase at the switching time is accumulated and fed back to the virtual control master loop. The output current of the virtual control master loop serves as the reference signal for the output current of each synchronized phase.

Description

Technical Field

[0001] This invention belongs to the field of power control technology, specifically relating to a current sharing system for a multiphase parallel LLC resonant converter based on a virtual control main loop. Background Technology

[0002] Due to limitations in voltage withstand capability, current carrying capacity, and switching speed of power semiconductor devices, the high current stress in single-phase LLC resonant converters applied to high-power applications reduces the efficiency and reliability of the power devices. Furthermore, excessive power leads to excessive output current ripple, increasing the losses of the output filter capacitor and requiring a larger capacitor to meet the output voltage ripple requirements, which significantly limits the operating scenarios of LLC converters. To address this, LLC parallel operation technology was developed. By evenly distributing power to each LLC phase operating in parallel, it can be applied to even higher power applications. However, considering the differences in device parameters in practical applications, the voltage gain of each LLC phase will differ, leading to a severe imbalance in output current and negating the purpose of parallel operation. Therefore, current sharing technology must be used when LLCs are operated in parallel.

[0003] Current sharing methods for multi-phase LLC parallel circuits can be mainly divided into two categories: passive current sharing and active current sharing. Passive current sharing achieves current sharing through circuit topology design. This type of method is only applicable to a specific number of phases, overly reliant on the topology and the current sharing capabilities of the components themselves, and thus has poor current sharing effect. Active current sharing adds detection and control circuits to the original circuit, achieving current sharing through additional control. Gain-based current sharing methods aim to balance the voltage gain between each phase LLC. 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 underlying these methods are derived from frequency control, and their operational stability and controller design are often very complex. Another type of current sharing method is based on power balance, aiming to balance the output power between each phase. Commonly used methods are charge-based power control methods, such as hysteresis charge control. The first-order model obtained by small-signal modeling of hysteresis charge control is highly advantageous for system design. Furthermore, the power-based control characteristic of hysteresis charge control aligns well with the characteristic of power sharing among phases in multiphase parallel systems during current sharing. Using hysteresis charge control for current sharing offers superior ease of design and effectiveness compared to traditional frequency control. Regarding multiphase synchronization, common synchronization strategies include master-slave control, master control, and cross-coupling control. Cross-coupling control is difficult to extend to arbitrary phases and is not suitable for arbitrary-phase LLC parallel systems. Master control, as the most direct synchronization method, has a response speed entirely dependent on each phase, resulting in poor synchronization. Master-slave control requires a fast-responding master phase, and the fast response speed of LLC largely meets this requirement. However, the loss of the master phase can lead to complete paralysis of the parallel system.

[0004] In summary, for multiphase LLC parallel systems with component parameter differences in actual operation, this invention proposes a multiphase parallel LLC resonant converter current sharing system based on a virtual control master loop. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a current sharing system for a multiphase parallel LLC resonant converter based on a virtual control main loop, thereby solving the problems in the prior art.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A current sharing system for a multiphase parallel LLC resonant converter based on a virtual control main loop includes a charge control unit and an output current balancing unit located on the input side of the inverter.

[0008] The output current balancing unit calculates the difference in output power between each phase based on the current imbalance between each phase, and changes the power transmitted between each phase by changing the switching frequency to achieve a balance in power distribution.

[0009] The charge control unit adopts a hysteresis charge control strategy, which 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 regulating the input power; the switching signal output by this unit is input to the four bridge arms of the inverter.

[0010] Using a virtual control master loop, each phase of the output current balancing unit is synchronized. The resonant capacitor voltage of each phase at the switching moment is accumulated and fed back to the virtual control master loop. The output current of the virtual control master loop is used as the reference signal for the output current of each synchronized 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, the LLC modeling based on the hysteresis charge control strategy is analyzed from the perspective of system input-output power conservation. Ignoring losses, the LLC's input power equals its output power; the input power is obtained from the change in the resonant capacitor voltage over one switching cycle.

[0012]

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

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

[0015]

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

[0017] Furthermore, in the output current equalization 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 as follows:

[0018]

[0019] In the formula, the subscript N represents the per-unit value, v Cr It is the resonant capacitor voltage, i Lr It is the resonant inductor current, v Cr0 with i Lr0 These are the values ​​of the resonant capacitor voltage and resonant inductor current under steady-state conditions, L n It is the ratio of magnetizing inductance to resonant inductance.

[0020] Furthermore, each phase of the output current equalization unit is synchronized by a reference signal provided by the virtual control master loop; the resonant capacitor voltage of each phase at the switching moment is accumulated and fed back to the virtual control master loop, and the output current of the virtual control master loop serves as the output current reference signal for each synchronized phase; the frequency domain expression of the output current phase and the reference current between each phase under this synchronization control is:

[0021]

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

[0023] The current sharing method for a multiphase parallel LLC resonant converter based on a virtual control master loop, using the aforementioned multiphase parallel LLC resonant converter current sharing system based on a virtual control master loop, includes 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 collects the output current of each phase, compares it with the current reference value, and obtains the control signal for the hysteresis charge control of each phase through the controller. The hysteresis control outputs the switching signal to the switching transistor of each phase inverter.

[0026] S3, the control signals of each phase hysteresis charge control are accumulated and input to 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 current of each phase is equalized.

[0028] A computer storage medium storing a readable program that, when the program is run, can execute the aforementioned current sharing method for a multiphase parallel LLC resonant converter based on a virtual control main loop.

[0029] An electronic device includes: 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, which causes the processor to perform the operation corresponding to the current sharing method of the multiphase parallel LLC resonant converter based on the virtual control main loop described above.

[0031] A computer program product includes computer instructions that instruct a computing device to perform the operations corresponding to the above-described current sharing method for a multiphase parallel LLC resonant converter based on a virtual control master loop.

[0032] The beneficial effects of this invention are:

[0033] This invention enables current sharing in parallel multi-phase LLC resonant converters, and is particularly suitable for current sharing control in systems with more than two phases. When current imbalance occurs in the parallel system due to changes in resonant cavity gain caused by component parameter errors, hysteresis charge control adjusts the switching frequency of each phase according to the difference in output power to bring all phases to the same output power. Simultaneously, the first-order response characteristic of hysteresis charge control provides a fast response speed for each parallel phase. When a new phase is added to the system or an existing phase is removed, the power control characteristics prevent significant fluctuations in output current, resulting in smoother current changes during the transition. Under the virtual LLC synchronous control strategy, the relative error of output current between phases decreases rapidly, and the virtual LLC is unaffected by faults, improving the reliability of the system during parallel operation. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0036] Figure 2 This is a block diagram of the hysteresis charge control used in this invention;

[0037] Figure 3 This is a schematic diagram illustrating the three modal decompositions of LLC according to the present invention;

[0038] Figure 4 This is a graph showing the functional relationship between the control quantity and the output quantity under different loads using hysteresis charge control in this invention.

[0039] Figure 5 This invention provides a comparison of the theoretical and practical Bode plots of LLC modeled using hysteresis charge control.

[0040] Figure 6 This invention relates to a state plane trajectory diagram of the output voltage after frequency control of a parallel system.

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

[0042] Figure 8 The output current results of a three-phase LLC parallel circuit without current sharing control in the simulation;

[0043] Figure 9The output current results using phase-shift control during the simulation of LLC parallel disconnection and phase addition;

[0044] Figure 10 The output current results using frequency control are shown in the simulation when LLC parallel disconnection and phase addition occur.

[0045] Figure 11 The output current results of the control method of this invention are shown in the simulation when LLC parallel disconnection and phase addition occur.

[0046] Figure 12 The result is the average output current of the control method of this invention when LLC parallel disconnection and phase addition occur in the simulation. Detailed Implementation

[0047] 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.

[0048] Example 1

[0049] like Figure 1 As shown, the current sharing system of a multiphase parallel LLC resonant converter based on a virtual control main loop includes a charge control unit and an output current equalization unit located on the input side of the inverter.

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

[0051] The output current balancing unit calculates the difference in output power between each phase based on the current imbalance between each phase, and changes the power transmitted between each phase by changing the switching frequency to achieve a balance in power distribution.

[0052] The charge control unit uses a hysteresis charge control strategy to control the LLC. It controls the amount of charge flowing to the resonant cavity in each switching cycle by controlling the resonant capacitor voltage at the turn-on time of the upper and lower bridge arms of the inverter, thereby regulating the input power. The switching signal output by this unit is input to the four bridge arms of the inverter. Essentially, it regulates the energy transfer in one switching cycle through frequency control.

[0053] The virtual LLC (virtual control main loop, i.e. virtual phase) is used to synchronize each phase of the output current balancing unit. 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 for the output current of each synchronized 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 one switching cycle.

[0055]

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

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

[0058] Let the average current flowing to the secondary side be i. sec The output voltage is v o Ignoring losses, the input power equals the output power, i sec This is therefore converted to:

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

[0060] like Figure 2 As shown, hysteresis charge control involves setting the resonant capacitor voltage v. thH As a control variable, by comparing v Cr (t AHoff ) and v thH v Cr (t BHoff ) and -v thH The magnitude of the signal determines the conduction signal for each switch, essentially regulating energy transfer within a switching cycle through frequency control. The LLC large-signal model under hysteresis charge control is solved based on LLC modal analysis, where the equivalent circuits corresponding to the three modes are as follows: Figure 3 As shown in (a), (b), and (c) in the diagram. Let the initial value of the inductor current in phase P be K, and the initial value in phase O be i. Lr0 The initial value of the capacitor voltage in phase P is J, and the initial value in phase O is v. Cr0 If the duration of phase P is β, then we have six unknowns: K, β, T, and T. s V o i Lr0 v Cr0 The corresponding six equations:

[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] Where, It is the resonant angular frequency. The series-parallel resonant angular frequency, L m This is the value of the magnetizing inductance.

[0067] Equations 1 and 2 are derived from the fact that the final value of the inductor current P in stage 1 equals the initial value in stage 0; Equation 3 is derived from the fact that the final value of the capacitor voltage P in stage 1 equals the initial value in stage 0; 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 flowing to the secondary side and the voltage. When the control quantity J = -V thH When things are constantly changing, the corresponding variables can be solved. Figure 4 In the text, (a) and (b) represent V respectively. thH With output voltage V o Functional relationship, V thH With switching frequency f s The functional relationship of V. This verifies V. thH With V o linear relationship, V thH with f s The inverse proportional relationship. As the load increases, V thH with f s The nonlinearity is amplified, but it always remains related to V. o Maintaining a good linear relationship, the hysteresis charge control bypasses the complex characteristics of the resonant cavity and directly regulates the output voltage. This also verifies V... thH With V o The monotonicity relationship of the signal can be analyzed, and the results 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 needs of voltage regulation, thereby greatly improving the response speed.

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

[0069]

[0070] In the formula, It is a small signal quantity representing the instantaneous value of the output voltage. It is a small signal quantity, F, representing the resonant capacitor voltage setting value. s It is the instantaneous value of the switching frequency, R L It is the load resistance, V o It is the average value of the output voltage, C o It is the capacitance value of the filter capacitor, K. d It is the voltage gain of LLC. Figure 5 The Bode plot obtained under the small-signal model is compared with the actual Bode plot, and it is consistent with the analysis of the large-signal model when the frequency is below the resonant frequency.

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

[0072]

[0073] In the formula, the subscript N represents the per-unit value, v Cr It is the resonant capacitor voltage, i Lr It is the resonant inductor current, v Cr0 with i Lr0 These are the values ​​of the resonant capacitor voltage and resonant inductor current under steady-state conditions, L n It is the ratio of magnetizing inductance to resonant inductance.

[0074] Figure 6 In the diagram, (a) and (b) represent the state plane trajectories of the output voltage after changes when connected in parallel under frequency control, at nV. oN When nV < 1, the state trajectory will exhibit an N-mode, preceded by a transitional PON-mode. oN As the value decreases further, the O mode disappears, resulting in the PN mode. This is because L... m The voltage on it dropped to nV o This will cause the secondary side to conduct. During the system's transition to steady state, as the state variables increase, the radius of the circle corresponding to the P phase continuously grows, and the time of the N mode, which connects the two P modes, gradually decreases. The state variables will continuously increase so that the system can transition back to the P mode. Therefore, if the secondary side is connected to an ideal voltage source, theoretically the state variables will approach infinity; for actual parallel systems, the greater the phase gain is compared to the parallel system, the larger the state variables corresponding to its steady state will be, and in this case, the output current will be very large. At nV oN When the value is greater than 1, the state trajectory will exhibit a zero-mode during the transition to steady state. This is because the increase in secondary voltage causes the clamped L... m The faster rise rate, coupled with the slower rise rate of the resonant inductor current, causes the zero-mode to arrive earlier. The emergence of the zero-mode reduces the output current duty cycle, resulting in a significant decrease in the average output current.

[0075] Figure 7 In the diagram, (a) and (b) represent the state-plane trajectories of the output voltage after changes when connected in parallel under hysteresis charge control. When nV oN1 From 1 to nV oN2 When = 1.5, the clamped L m The voltage on it suddenly increased, causing i Lm The sudden increase in the rate of rise, along with the increase in the secondary voltage, will cause L... rEntering a special mode, the response of this mode is similar to that of the P mode during the other half of the switching cycle, except that the center of its trajectory will be (1-nV). oN1 ,0) becomes (1-nV oN2 ,0), such as the process from t0 to t1. From t1 to t2, i Lm It keeps increasing, at this point L m With L r The two systems resonate together, operating in the 0 mode. From t2 to t3, the resonant current continuously increases, but at this point, L... m The voltage on the upper side is still lower than the voltage on the lower side, and it remains in the L range. m With L r Common resonance O-mode; i after t3~t4 Lm It has been increased to a sufficient value, at which point once L m When the voltage on the primary side equals the voltage on the secondary side, it is clamped and enters the P mode; from this point on, the system will stabilize in the PO mode. When nV oN1 From 1 to nV oN2 After setting it to 0.5, this will change the center of the original P mode, from the original (-1+nV) oN1 ,0) becomes (-1+nV oN2 The trajectory from t0 to t1 is shown. After a new switching cycle arrives, due to the short switching time, i is not reached before the end of the P mode. Lr =i Lm The switch was changed, and now it's i. Lr >i Lm Therefore, based on symmetry, at the beginning of mode N, it must be i. Lr <i Lm The system enters the NP mode. This phenomenon generally occurs when the switching frequency is higher than the resonant frequency. At this time, the center of the N mode will be shifted from (1-nV) oN1 ,0) becomes (-1-nV oN2 ,0), corresponding to the time period t1~t2 in the above figure. When i Lr Rise to equal i Lm At this time, the system will not enter the 0 mode because the secondary voltage suddenly drops, which will cause L m Still clamped, the system will enter the P mode, corresponding to the time interval t2 to t3. It can be seen that this process only involves a one-switch-cycle transition from P mode to NP mode, resulting in extremely fast response. Compared to the previous nV... oN2 The process of 0.5 does not require going through L. m The voltage gradually increases because nV oN2 When L = 0.5, the secondary voltage drops suddenly, so L mIt can be directly clamped. Therefore, when using hysteresis charge control, even if the secondary voltage source voltage changes, the output current will not show extreme changes as it does under fixed frequency control; only a small current imbalance will occur.

[0076] When using a virtual LLC for synchronization control, each phase of the current equalization unit is synchronized by a reference signal provided 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 serves as the reference signal for the output current of each synchronized phase. Let MR be the transfer function of the output current of the i-th phase with respect to the reference current under master synchronization. i (s):

[0077]

[0078] In the formula, G ci (s) is the transfer function of the controller from the error between the i-th phase reference current and the actual output current to the LLC hysteresis charge control input signal. i (s) is the first-order transfer function of the i-th phase LLC under hysteresis charge control, I ref I is the reference current signal input to the virtual LLC. seci This represents the actual output current of each phase. In this synchronization method, the synchronicity of each phase 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 as 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 other slave phases will pass through an additional master phase, becoming MR1(s)*MR. i (s). The relative error between the phase and the main phase can be obtained from MR. i (s) can be adjusted, but this requires the main phase to have a fast response speed, and a failure of the main phase will affect the operation of the entire system.

[0079] Under the synchronous control of the virtual LLC as the main phase in this invention, the frequency domain expressions of the output current phase and the reference current between each phase are as follows:

[0080]

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

[0082] Example 2

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

[0084] Figure 8 The simulation results are based on the current sharing control of three-phase LLC in parallel as an example. As can be seen from the figure, when no control is used, two phases have no output current, and the output current is severely uneven. Figure 9 (a) and (b) in Figure 10 (a) and (b) in the figure show the instantaneous output current values ​​of each phase after removing and adding a phase, respectively, when using phase-shift control and frequency control. Under both control methods, the addition of a new phase causes a brief but severe current imbalance in the system. This is because the newly added phase has a higher gain than the original phase, which will generate a severe current imbalance based on the frequency control model. At the same time, the slow frequency makes the gain adjustment slow, requiring a long transition time to achieve current equalization.

[0085] The instantaneous response of the output current of each phase in the current sharing system designed in this invention when removing and adding a phase corresponds to... Figure 11 In (a) and (b), the average response results correspond to Figure 12 As can be seen, the system can quickly achieve current sharing regardless of whether a phase is removed or added. Furthermore, this current sharing method does not require specifying an actual dominant phase, and the removal or 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 for a multiphase 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 for the hysteresis charge control of each phase through the controller. The hysteresis control outputs the switching signal to the switching transistor of each phase inverter.

[0090] S3, the control signals of each phase hysteresis charge control are accumulated and input to 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.

[0091] S4, repeat S2 to S3 until the output current of each phase is equalized.

[0092] Based on a similar inventive concept, embodiments of the present invention also provide a computer storage medium storing a readable program that, when the program is run, can execute the above-described current sharing method for a multiphase parallel LLC resonant converter based on a virtual control main loop.

[0093] Based on a similar inventive concept, this invention provides an electronic device, including: 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, which causes the processor to perform the operation corresponding to the current sharing method of the multiphase parallel LLC resonant converter based on the virtual control main loop described above.

[0095] Based on a similar inventive concept, embodiments of the present invention also provide a computer program product, including computer instructions, which instruct a computing device to perform the operation corresponding to the above-described current sharing method for a multiphase parallel LLC resonant converter based on a virtual control main loop.

[0096] The methods of the present invention can be implemented in hardware, firmware, or as software or computer code that can be stored in a recording medium (such as a CD-ROM, RAM, floppy disk, hard disk, or magneto-optical disk), or as computer code originally stored on a remote recording medium or a non-transitory machine-readable medium and subsequently stored on a local recording medium, downloaded via a network. Thus, the methods described herein can be processed by software stored 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 the computer, processor, microprocessor controller, or programmable hardware includes storage components (e.g., RAM, ROM, flash memory, etc.) capable of storing or receiving software or computer code that, when accessed and executed by the computer, processor, or hardware, implements the methods described herein. Furthermore, when a general-purpose computer accesses the code used to implement the methods shown herein, the execution of the code transforms the general-purpose computer into a dedicated computer for performing the methods shown herein.

[0097] The foregoing has shown and described 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. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A current sharing system for a multiphase parallel LLC resonant converter based on a virtual control master loop, characterized in that, This includes a charge control unit and an output current balancing unit located on the input side of the inverter; The output current balancing unit calculates the difference in output power between each phase based on the current imbalance between each phase, and changes the power transmitted between each phase by changing the switching frequency to achieve a balance in power distribution. The charge control unit adopts a hysteresis charge control strategy, which 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 regulating the input power; the switching signal output by this unit is input to the four bridge arms of the inverter. The virtual control master loop is used to synchronize each phase of the output current balancing unit. The resonant capacitor voltage of each phase at the switching moment is accumulated and fed back to the virtual control master loop. The output current of the virtual control master loop is used as the reference signal for the output current of each phase that is synchronized. The charge control unit is the control logic used by the LLC of each phase in the output current balancing unit.

2. The current sharing system of a multiphase parallel LLC resonant converter based on a virtual control master loop according to claim 1, characterized in that, In the charge control unit, the LLC modeling based on the hysteresis charge control strategy is analyzed from the perspective of system input-output power conservation. Ignoring losses, the LLC's input power equals its output power; the input power is obtained from the change in resonant capacitor voltage over one switching cycle. Among them, P in Represents input power, V in It is the DC input voltage, C r It is the capacitance value of the resonant capacitor, t AHoff t represents the moment when the Q1 bridge arm is turned off. ALoff f represents the moment when the Q2 bridge arm is turned off. s Represents the switching frequency, C j Represents junction capacitance, v Cr (t AHoff ) and v Cr (t ALoff ) are the resonant capacitor voltage values ​​at the switching moments of the two bridge arms.

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

4. The current sharing system of a multiphase parallel LLC resonant converter based on a virtual control master loop according to claim 1, characterized in that, In the output current equalization 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 as follows: In the formula, the subscript N represents the per-unit value, v Cr It is the resonant capacitor voltage, i Lr It is the resonant inductor current, V o It is the average output voltage, where n is the transformer turns ratio, and V Cr0 with I Lr0 These are the values ​​of the resonant capacitor voltage and resonant inductor current under steady-state conditions, L n It is the ratio of magnetizing inductance to resonant inductance.

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

6. A current sharing method for a multiphase parallel LLC resonant converter based on a virtual control main loop, using the multiphase parallel LLC resonant converter current sharing system based on a virtual control main loop as described in any one of claims 1-5, characterized in that, Includes the following steps: S1: Collects the output voltage, compares it with the set voltage value, and obtains the current reference value through the controller; S2 collects the output current of each phase, compares it with the current reference value, and obtains the control signal for the hysteresis charge control of each phase through the controller. The hysteresis control outputs the switching signal to the switching transistor of each phase inverter. S3, the control signals of each phase hysteresis charge control are accumulated and input to 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 current of each phase is equalized.

7. A computer storage medium storing a readable program, characterized in that, When the program runs, it can execute the current sharing method of the multiphase parallel LLC resonant converter based on the virtual control main loop as described in claim 6.

8. An electronic device, characterized in that, include: The processor, memory, communication interface, and communication bus are provided, wherein the processor, memory, and communication interface communicate with each other via the communication bus. The memory is used to store at least one executable instruction, which causes the processor to perform the operation corresponding to the current sharing method of the multiphase parallel LLC resonant converter based on the 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 perform the operation corresponding to the current sharing method for the multiphase parallel LLC resonant converter based on the virtual control main loop as described in claim 6.

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