Soft start control method and device for energy storage DC converter and energy storage system

Abstract

The present invention discloses a soft-start control method, device and energy storage system for an energy storage DC converter, belonging to the field of converter control technology. The energy storage DC converter includes a resonant conversion circuit and a buck-boost conversion circuit which are sequentially cascaded with an energy storage module. The method includes: controlling the duty cycle of a first drive signal for driving the resonant conversion circuit to gradually increase from a preset initial duty cycle; after the duty cycle of the first drive signal increases to a first target duty cycle, intermittently charging the DC bus capacitor of the buck-boost conversion circuit until the high-voltage side voltage of the buck-boost conversion circuit reaches the first target voltage. The present invention realizes soft-starting of an energy storage DC converter with a two-stage conversion circuit, thereby avoiding overcurrent or even damage to the converter during the process of establishing the DC bus voltage of the energy storage DC converter.

Description

Technical Field

[0001] The present invention belongs to the technical field of converter control, and in particular relates to a soft start control method and device for an energy storage DC converter and an energy storage system. Background Art

[0002] The energy storage DC converters (bidirectional DC-DC converters) currently used in energy storage systems include isolated LLC converters, non-isolated BUCK-BOOST converters, and two-stage energy storage DC converters composed of a front-stage LLC resonant conversion circuit and a rear-stage BUCK-BOOST conversion circuit. The so-called bidirectional DC-DC converter is a DC-DC converter that operates in two quadrants. The polarity of its input and output voltages remains unchanged, but the direction of the input and output currents can be changed, thus achieving bidirectional transmission of energy.

[0003] In order to improve the dynamic performance of the energy storage system, a larger DC bus capacitor is generally connected in parallel to the DC coupling bus, which can easily cause overcurrent or even damage to the converter during the process of establishing the DC bus voltage by the energy storage DC converter. Summary of the invention

[0004] The embodiments of the present invention provide a startup control method and device for an energy storage DC converter and an energy storage system, which realize soft starting of the energy storage DC converter in the energy storage system, so as to solve the technical problem of overcurrent or even damage of the energy storage DC converter during the process of establishing the DC bus voltage to a certain extent.

[0005] In a first aspect, an embodiment of the present invention provides a soft start control method for an energy storage DC converter, wherein the energy storage DC converter includes a resonant conversion circuit and a buck-boost conversion circuit which are sequentially cascaded with an energy storage module, and the method includes: controlling the duty cycle of a first drive signal to gradually increase from a preset initial duty cycle, wherein the first drive signal is used to drive the resonant conversion circuit; after the duty cycle of the first drive signal increases to a first target duty cycle, intermittently charging the DC bus capacitor of the buck-boost conversion circuit until the high-voltage side voltage of the buck-boost conversion circuit reaches the first target voltage.

[0006] In combination with the first aspect of the present invention, in some embodiments, after the duty cycle of the first drive signal increases to the first target duty cycle, it also includes: controlling the duty cycle of the first drive signal to continuously maintain the first target duty cycle; and performing fixed frequency control on the LLC resonant cavity of the resonant conversion circuit according to a first resonant frequency, wherein the first resonant frequency is the resonant frequency at which the resonant inductor and the resonant capacitor in the LLC resonant cavity resonate together.

[0007] In combination with the first aspect of the present invention, in some embodiments, the resonant conversion circuit includes multiple switching networks, and the first drive signal includes a first PWM signal and a second PWM signal corresponding to driving the upper and lower switch tubes of each bridge arm in each of the switching networks; in the process of gradually increasing the duty cycle of the first drive signal, the upper and lower switch tubes of each bridge arm in each of the switching networks are complementarily turned on and the dead time gradually decreases.

[0008] In combination with the first aspect of the present invention, in some embodiments, the duty cycle of the first drive signal is controlled to be continuously maintained at the first target duty cycle, including: generating a first PWM signal that meets the first target duty cycle based on a PWM signal generator, and driving a first pair of tubes of each of the switching networks; performing reverse processing on the first PWM signal based on an inverter to obtain a second PWM signal that meets the first target duty cycle; and driving a second pair of tubes of each of the switching networks based on the second PWM signal of the first target duty cycle.

[0009] In combination with the first aspect of the present invention, in some embodiments, before the intermittent charging of the DC bus capacitor of the buck-boost conversion circuit, it also includes: in response to a second start-up instruction to start the buck-boost conversion circuit, determining whether a soft start condition is met at the current moment; if the soft start condition is met at the current moment, executing the step of intermittently charging the DC bus capacitor of the buck-boost conversion circuit.

[0010] In combination with the first aspect of the present invention, in some embodiments, the determining whether the soft start condition is met at the current moment includes: determining whether the high voltage side voltage of the buck-boost conversion circuit is less than the first target voltage, and if so, determining that the soft start condition is met at the current moment; or determining whether the high voltage side voltage of the buck-boost conversion circuit is less than the first target voltage, and determining whether the medium voltage side voltage of the buck-boost conversion circuit is less than the second target voltage, and if both are satisfied, determining that the soft start condition is met at the current moment.

[0011] In combination with the first aspect of the present invention, in some embodiments, the intermittent charging of the DC bus capacitor of the buck-boost conversion circuit includes: monitoring the change of the inductor current of the buck-boost conversion circuit; when the inductor current rises to no less than a first current threshold, prohibiting the charging of the DC bus capacitor of the buck-boost conversion circuit by closing the voltage loop and the current loop of the buck-boost conversion circuit; when the inductor current drops to no more than a second current threshold, charging the DC bus capacitor of the buck-boost conversion circuit by opening the voltage loop and the current loop of the buck-boost conversion circuit, the second current threshold being less than the first current threshold.

[0012] In combination with the first aspect of the present invention, in some embodiments, the intermittent charging of the DC bus capacitor of the buck-boost conversion circuit includes: when the boost switch tube of the buck-boost conversion circuit is in a continuously closed state, driving the buck switch tube of the buck-boost conversion circuit to be turned on by a second drive signal satisfying a second duty cycle, so that the DC bus capacitor of the buck-boost conversion circuit is intermittently charged; wherein the duty cycle of the second drive signal is less than a second target duty cycle, and the second target duty cycle is the duty cycle of the second drive signal when the buck-boost conversion circuit is in a stable operation state.

[0013] In combination with the first aspect of the present invention, in some embodiments, after the high-voltage side voltage of the buck-boost conversion circuit reaches the first target voltage, it also includes: complementarily driving the boost switch tube and the buck switch tube of the buck-boost conversion circuit according to a second drive signal that satisfies the second target duty cycle.

[0014] In a second aspect, an embodiment of the present invention provides a soft start control device for an energy storage DC converter, wherein the energy storage DC converter includes a resonant conversion circuit and a buck-boost conversion circuit which are sequentially cascaded with an energy storage module, and the soft start control device includes: a duty cycle increasing unit, used to control the duty cycle of a first drive signal to gradually increase from a preset initial duty cycle, wherein the first drive signal is used to drive the resonant conversion circuit; an intermittent charging unit, used to intermittently charge the DC bus capacitor of the buck-boost conversion circuit after the duty cycle of the first drive signal increases to a first target duty cycle, until the high-voltage side voltage of the buck-boost conversion circuit reaches the first target voltage.

[0015] In a third aspect, an embodiment of the present invention provides an energy storage system, comprising an energy storage module, an energy storage DC converter and a control device, wherein the energy storage DC converter comprises a resonant conversion circuit and a buck-boost conversion circuit which are sequentially cascaded with the energy storage module, and the control device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor executes the program to implement the soft start control method of the energy storage DC converter described in any embodiment of the first aspect.

[0016] One or more technical solutions provided by the embodiments of the present invention achieve at least the following technical effects or advantages:

[0017] For an energy storage DC converter having a resonant conversion circuit and a buck-boost conversion circuit, the embodiment of the present invention first controls the duty cycle of the first driving signal for driving the resonant conversion circuit to gradually increase from a preset initial duty cycle to a first target duty cycle, and then intermittently charges the DC bus capacitor of the buck-boost conversion circuit until the high-voltage side voltage of the buck-boost conversion circuit reaches the first target voltage. Thus, the soft start of the two-stage DC conversion circuit is completed successively, avoiding the technical problem of overcurrent or even damage of the converter in the process of establishing the DC bus voltage in a two-stage energy storage DC converter with a large DC bus capacitor, thereby improving the reliability of the two-stage DC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 A schematic diagram of an application scenario of an energy storage DC converter in an embodiment of the present invention is shown;

[0020] Figure 2 The flowchart of the startup control method of the energy storage DC converter in the embodiment of the present invention is shown;

[0021] Figure 3 Show Figure 1 Topology of the DC converter with medium energy storage;

[0022] Figure 4 Shows Figure 1 The drive control block diagram of the resonant conversion circuit in the stable operation state;

[0023] Figure 5A Shows Figure 1 A soft start process for a resonant converter circuit;

[0024] Figure 5B Shows Figure 1 A soft start process for medium-voltage buck-boost converter circuit;

[0025] Figure 6 A functional module diagram of a startup control device for an energy storage DC converter in an embodiment of the present invention is shown;

[0026] Figure 7 A schematic structural diagram of an energy storage system in an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0027] 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.

[0028] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0029] A startup control method for an energy storage DC converter provided in an embodiment of the present invention can be used to soft-start an energy storage DC converter 20 having a two-stage DC conversion circuit to avoid overcurrent or even damage to the converter during the process of establishing a DC bus voltage.

[0030] like Figure 1 As shown, the energy storage DC converter 20 provided in the embodiment of the present invention includes a two-stage DC conversion circuit, specifically including a resonant conversion circuit 210 and a buck-boost conversion circuit 220 which are sequentially cascaded with the energy storage module 10 .

[0031] It should be understood that the resonant conversion circuit 210 is a bidirectional LLC topology, which can be: full-bridge LLC topology, half-bridge LLC topology, multiple LLC parallel connection, multiple transformers in series and / or parallel connection, and other commonly used bidirectional LLC topologies and their derivative topologies. The buck-boost conversion circuit 220 (also called BUCK-BOOST conversion circuit) can include BUCK-BOOST topologies and their derivative topologies such as multiple bidirectional BUCK-BOOST conversion and interleaved parallel BUCK-BOOST conversion.

[0032] refer to Figure 2 As shown, the soft start control method of the energy storage DC converter provided by the embodiment of the present invention includes the following steps S101-S102:

[0033] S101: Control the duty cycle of a first driving signal to gradually increase from a preset initial duty cycle, the first driving signal being used to drive the resonant conversion circuit 210.

[0034] Initiate a first start-up instruction for the resonant conversion circuit 210; in response to the first start-up instruction, detect whether the resonant conversion circuit 210 has a fault; if the resonant conversion circuit 210 does not have a fault, control the resonant conversion circuit 210 to perform a soft start. The process of controlling the resonant conversion circuit 210 to perform a soft start is step S101: control the duty cycle of the first driving signal used to drive the resonant conversion circuit 210 to gradually increase from a preset initial duty cycle.

[0035] It should be understood that the initial duty cycle is smaller than the first target duty cycle, and the duty cycle of the first drive signal is controlled to gradually increase from the initial duty cycle according to a preset increase strategy until the duty cycle of the first drive signal increases to the first target duty cycle, indicating that the soft start of the resonant conversion circuit 210 is completed, so that the resonant conversion circuit 210 enters a stable operation state.

[0036] The preset increase strategy may refer to: controlling the duty cycle of the first drive signal to gradually increase according to any one of the duty cycle increase methods such as increasing the duty cycle linearly, increasing the duty cycle logarithmically, and increasing the duty cycle exponentially.

[0037] Of course, any two or more of the above-mentioned duty cycle increasing methods can also be combined to control the duty cycle of the first drive signal to gradually increase in multiple control sections, wherein different control sections use different duty cycle increasing methods. For example, the duty cycle of the first drive signal can be controlled to gradually increase from the initial duty cycle to a certain duty cycle in a linear manner; and then the duty cycle of the first drive signal can be controlled to continue to gradually increase in a quadratic manner until it increases to the first target duty cycle.

[0038] It should be understood that the initial duty cycle is a certain value close to 0. In the specific implementation process, the initial duty cycle can be, but is not limited to, a certain value between 1% and 10% to prevent the medium-voltage side capacitor and the high-voltage side capacitor from being too large and causing overcurrent. The first target duty cycle is the duty cycle of the first drive signal when the resonant conversion circuit 210 is in a stable operating state. For example, if the resonant conversion circuit 210 needs to maintain the duty cycle of the first drive signal at 50% in a stable operating state, then after gradually increasing the duty cycle of the first drive signal to 50%, indicating that the soft start process of the resonant conversion circuit 210 is completed, the duty cycle of the first drive signal is maintained at 50% and no longer increases.

[0039] refer to Figure 3As shown, a relatively simple two-stage topology structure of the energy storage DC converter 20 is given, the resonant conversion circuit 210 is a bidirectional full-bridge LLC topology, and the buck-boost conversion circuit 220 adopts a simple BUCK-BOOST topology. When the energy storage module 10 discharges to the outside, the resonant conversion circuit 210 first converts the energy storage voltage U provided by the energy storage module 10 to bat Increase to medium voltage side voltage U mid The transformer T is used to realize the electrical isolation between the energy storage module 10 and the medium voltage side, and then the BUCK-BOOST conversion circuit 220 converts the medium voltage side voltage U output by the resonant conversion circuit 210 to mid Increase to high voltage side voltage U bus When charging the energy storage module 10, the BUCK-BOOST conversion circuit 220 first converts the high-voltage side voltage U bus Drop to medium voltage side voltage U mid , and then the resonant conversion circuit 210 converts the medium voltage side voltage U mid The energy storage voltage U drops to the energy storage module 10 side bat .

[0040] The resonant conversion circuit 210 includes a plurality of switch networks, each of which includes at least one bridge arm, and the first drive signal is used to drive each bridge arm of each switch network in the resonant conversion circuit 210. It can be understood that the first drive signal includes a first PWM (pulse width modulation) signal and a second PWM signal for correspondingly driving the upper and lower switch tubes of the same bridge arm of each switch network in the resonant conversion circuit 210.

[0041] The first PWM signal and the second PWM signal are a pair of complementary PWM signals, and the upper and lower switch tubes of each bridge arm in each switch network are complementary turned on based on the first PWM signal and the second PWM signal. In the specific implementation process, the duty cycle of the first PWM signal is the same as the duty cycle of the second PWM signal, and the duty cycle of the first PWM signal and the duty cycle of the second PWM signal are gradually increased from the initial duty cycle to the first target duty cycle. It should be understood that as the duty cycle of the first PWM signal and the duty cycle of the second PWM signal gradually increase, the dead time of the upper and lower switch tubes of each bridge arm in each switch network will gradually decrease.

[0042] refer to Figure 3The resonant conversion circuit 210 may include a first switch network 211, a transformer T, an LLC resonant cavity 212, and a second switch network 213 connected in cascade. The first switch network 211 may be a full-bridge topology composed of switch tubes S1, S2, S3, and S4; the second switch network 213 may be another full-bridge topology composed of switch tubes S5, S6, S7, and S8. The LLC resonant cavity 212 includes a resonant inductor Lr, a resonant capacitor Cr, and an excitation inductor Lm. The resonant conversion circuit 210 may also include a first capacitor CL connected in cascade before the first switch network 211, and a second capacitor CM connected in cascade after the second switch network 213. Based on this, the first drive signal is used to drive the switch tubes S1 to S8, wherein the first PWM signal is used to drive the switch tubes S1, S4, S5, and S8; the second PWM signal is used to drive the switch tubes S2, S3, S6, and S7. When the switch tubes S1, S4, S5, and S8 are in the on state, the switch tubes S2, S3, S6, and S7 are in the off state; when the switch tubes S1, S4, S5, and S8 are in the off state, the switch tubes S2, S3, S6, and S7 are in the on state.

[0043] After the duty cycle of the first drive signal increases to the first target duty cycle, the duty cycle of the first drive signal is controlled to remain at the first target duty cycle and no longer change, and the LLC resonant cavity of the resonant conversion circuit 210 is controlled at a fixed frequency according to the first resonant frequency, so that the resonant conversion circuit 210 remains in a stable operating state. Thus, the control resources are greatly reduced, the difficulty of the control algorithm is reduced, and the soft switching characteristics of the LLC converter are improved.

[0044] refer to Figure 4 As shown, in the stable operation state of the resonant conversion circuit 210, a first PWM signal satisfying the first target duty cycle is generated based on the PWM signal generator, and the first pair of transistors of each switch network in the resonant conversion circuit 210 is driven; the first PWM signal is reversely processed based on the inverter to obtain a second PWM signal satisfying the first target duty cycle, and the second pair of transistors of each switch network in each resonant conversion circuit 210 is driven based on the second PWM signal satisfying the first target duty cycle. Figure 3 In the second switch network 211 , the first pair of tubes are switch tubes S1 and S4 , and the second pair of tubes are switch tubes S2 and S3 ; in the first switch network 213 , the first pair of tubes are switch tubes S5 and S8 , and the second pair of tubes are switch tubes S6 and S7 .

[0045] It should be noted that the first resonant frequency is the resonant frequency of the resonant inductor Lr and the resonant capacitor Cr in the LLC resonant cavity 212.

[0046] S102: After the duty cycle of the first driving signal increases to the first target duty cycle, the DC bus capacitor C of the step-up / step-down conversion circuit 220 is H Intermittent charging is performed until the high-voltage side voltage of the buck-boost conversion circuit 220 reaches the first target voltage.

[0047] It can be understood that, in the process of gradually increasing the duty cycle of the first driving signal, the duty cycle of the first driving signal is monitored to see whether it reaches the first target duty cycle; when it is detected that the duty cycle of the first driving signal reaches the first target duty cycle, a second start instruction is sent to the buck-boost conversion circuit 220 to control the buck-boost conversion circuit 220 to perform a soft start. The process of controlling the buck-boost conversion circuit 220 to perform a soft start is as follows: the DC bus capacitor C of the buck-boost conversion circuit 220 is H Intermittent charging is performed until the high-voltage side voltage of the buck-boost conversion circuit 220 reaches the first target voltage.

[0048] It should be understood that after the soft start of the resonant conversion circuit 210 is completed, it is not necessary to control the buck-boost conversion circuit 220 to perform a soft start. Therefore, after the soft start of the resonant conversion circuit 210 is completed, in response to the second start instruction to start the buck-boost conversion circuit 220, it is determined whether the soft start condition is met at the current moment. If the soft start condition is met at the current moment, the DC bus capacitor C of the buck-boost conversion circuit 220 is increased. H Perform intermittent charging.

[0049] It can be understood that it is determined whether the high-voltage side voltage of the buck-boost conversion circuit 220 is less than the first target voltage. If the high-voltage side voltage of the buck-boost conversion circuit 220 is less than the first target voltage, it is determined that the soft start condition is met at the current moment; if the high-voltage side voltage of the buck-boost conversion circuit 220 is not less than the first target voltage, it indicates that the soft start condition is not met at the current moment, and there is no need to adjust the DC bus capacitor C of the buck-boost conversion circuit 220. H By performing intermittent charging, the buck-boost conversion circuit 220 can directly enter a stable operation state.

[0050] In order to avoid abnormality on the medium voltage side of the buck-boost conversion circuit 220, it is necessary to determine whether the high voltage side voltage of the buck-boost conversion circuit 220 is less than the first target voltage, and whether the medium voltage side voltage of the buck-boost conversion circuit 220 is less than the second target voltage; if both are satisfied, it is determined that the soft start condition is met at the current moment. If the medium voltage side voltage of the buck-boost conversion circuit 220 is not less than the second target voltage and the high voltage side voltage of the buck-boost conversion circuit 220 is not less than the first target voltage, it indicates that the soft start condition is not met at the current moment, and there is no need to adjust the DC bus capacitor C of the buck-boost conversion circuit 220. H By performing intermittent charging, the buck-boost conversion circuit 220 can directly enter a stable operation state.

[0051] It should be understood that the DC bus capacitor C of the step-up / step-down conversion circuit 220 may be adjusted according to the change of the inductor current. H The intermittent charging includes: monitoring the change of the inductor current of the buck-boost conversion circuit 220; when it is monitored that the inductor current of the buck-boost conversion circuit 220 rises to not less than the first current threshold, closing the voltage loop and the current loop of the buck-boost conversion circuit 220 to prohibit the DC bus capacitor C of the buck-boost conversion circuit 220 from charging. H When the inductor current of the buck-boost conversion circuit 220 drops to no more than the second current threshold, the DC bus capacitor C of the buck-boost conversion circuit is charged by opening the voltage loop and current loop of the buck-boost conversion circuit 220. H to charge.

[0052] It should be understood that the second current threshold is smaller than the first current threshold, and the specific value can be set according to actual conditions.

[0053] Due to the voltage loop and the current loop being executed to the DC bus capacitor C of the step-up / step-down conversion circuit 220 H During the charging process, the inductor current of the buck-boost conversion circuit 220 gradually increases; when the inductor current increases to not less than the first current threshold, the voltage loop and the current loop of the buck-boost conversion circuit 220 are closed. The closing of the voltage loop and the current loop will gradually reduce the inductor current. When the inductor current of the buck-boost conversion circuit 220 drops to not more than the second current threshold, the voltage loop and the current loop will be triggered to re-execute the DC bus capacitor C of the buck-boost conversion circuit 220. H Such a cycle can realize the DC bus capacitor C of the step-up / step-down conversion circuit 220. H Perform intermittent charging.

[0054] Different from the above embodiment, the DC bus capacitor C of the step-up / step-down conversion circuit 220 is H The intermittent charging may include: when the boost switch tube S9 of the boost-boost conversion circuit 220 is in a continuously closed state, driving the buck switch tube S10 of the boost-boost conversion circuit 220 by a second driving signal satisfying a second duty cycle, so that the DC bus capacitor C H The second duty cycle is less than the second target duty cycle, thereby realizing the intermittent small current to the DC bus voltage C H It should be noted that the second target duty cycle is the duty cycle that the second driving signal for driving the buck-boost conversion circuit 220 needs to satisfy when the buck-boost conversion circuit 220 is in a stable operating state.

[0055] By increasing the DC bus capacitor C of the step-up / step-down conversion circuit 220H Intermittent charging is performed until the high-voltage side voltage of the buck-boost conversion circuit 220 reaches the first target voltage, or until the high-voltage side voltage reaches the first target voltage and the medium-voltage side voltage reaches the second target voltage at the same time, indicating that the soft start of the buck-boost conversion circuit 220 is completed.

[0056] After the soft start of the buck-boost conversion circuit 220 is completed, the buck-boost conversion circuit 220 enters a stable operation state. Specifically, in the stable operation state of the buck-boost conversion circuit 220, the boost switch tube S9 and the buck switch tube S10 of the buck-boost conversion circuit 220 are complementarily driven according to the second driving signal that meets the second target duty cycle.

[0057] It should be understood that the second driving signal includes a third PWM signal for driving the boost switch tube S9 and a fourth PWM signal for driving the buck switch tube S10. In a stable operating state, the third PWM signal and the fourth PWM signal are a pair of complementary PWM signals, so that the boost switch tube S9 and the buck switch tube S10 are complementarily driven based on the third PWM signal and the fourth PWM signal, so that the boost switch tube S9 and the buck switch tube S10 are complementarily turned on in a stable operating state.

[0058] refer to Figure 3 The topology of the BUCK-BOOST conversion circuit 220 at least includes: a boost switch tube S9, a buck switch tube S10, a first inductor L and a DC bus capacitor C H One end of the first inductor L is connected to an output end of the second switch network 213, the other end of the first inductor L is connected to one end of the buck switch tube S10 and one end of the boost switch tube S9, and the other output end of the second switch network 213 and the other end of the boost switch tube S9 are both connected to the DC bus capacitor C H One end is connected to the DC bus capacitor C H Based on this, the inductor current refers to the current flowing through the first inductor L.

[0059] In order to facilitate understanding of the technical solution provided by the embodiments of the present invention, Figure 5A to Figure 5B Describe it. Figure 5A As shown:

[0060] S1: Initiate a first start-up instruction for the resonant conversion circuit 210 .

[0061] S2: In response to the first start instruction, detect whether the resonant conversion circuit 210 is faulty. If the resonant conversion circuit 210 is faulty, end this process; if the resonant conversion circuit 210 is not faulty, execute steps S3 to S5:

[0062] S3: Setting an initial duty cycle D_initial of the first driving signal.

[0063] S4: Control the current duty cycle D of the first driving signal for driving the resonant conversion circuit 210 to gradually increase according to the following rule: D=D_initial+ΔD, where ΔD is the current duty cycle increment.

[0064] S5: Determine whether the current duty cycle D of the first drive signal is less than the first target duty cycle D_ref. If so, continue to execute S4; otherwise, it indicates that the soft start of the resonant conversion circuit 210 is completed, and then execute S6: initiate a second start instruction for the buck-boost conversion circuit 220.

[0065] Execute S7: In response to the second start instruction, determine whether the medium voltage side voltage U mid ≥U mid_ref , and determine whether the high-voltage side voltage U bus ≥U bus_ref If both conditions are met, the resonant conversion circuit 210 and the buck-boost conversion circuit 220 enter a stable operation state; if both conditions are not met, the following step S7 is executed:

[0066] S7: The DC bus capacitor C of the step-up / step-down conversion circuit 220 H Perform intermittent charging until U mid ≥U mid_ref AndU bus ≥U bus_ref , it indicates that the soft start of the buck-boost conversion circuit 220 is completed. At this point, the resonant conversion circuit 210 and the buck-boost conversion circuit 220 both enter a stable operation state.

[0067] Among them, reference Figure 5B As shown, after executing S6, if U mid ≥U mid_ref AndU bus ≥U bus_ref , the executed S7 may include the following steps S71 to S74:

[0068] S71: Open the voltage loop and current loop of the buck-boost conversion circuit 220, and adjust the DC bus capacitor C of the buck-boost conversion circuit 220. H Charging;

[0069] S72: Based on the voltage loop and current loop of the step-up / step-down conversion circuit 220, the DC bus capacitor C H During the charging process, monitor whether the inductor current I of the first inductor L meets the requirement L ≥I L_h ; If satisfied, execute steps S73-S74:

[0070] S73: close the voltage loop and current loop of the buck-boost conversion circuit 220, and suspend the DC bus capacitor C of the buck-boost conversion circuit 220. H Charging;

[0071] S74: When the voltage loop and the current loop of the buck-boost conversion circuit 220 are in the closed state, monitor whether the inductor current I of the first inductor L meets the requirement. L ≤I L_low If yes, return to execute S71.

[0072] The above steps S71 to S74 are repeated until U is satisfied. mid ≥U mid_ref AndU bus ≥U bus_ref .

[0073] Based on the same inventive concept, an embodiment of the present invention provides a soft start control device for an energy storage DC converter, wherein the energy storage DC converter comprises a resonant conversion circuit and a buck-boost conversion circuit for sequentially cascading with an energy storage module, Figure 6 As shown, the soft start control device includes: a duty cycle increasing unit 601, used to control the duty cycle of the first drive signal to gradually increase from a preset initial duty cycle, wherein the first drive signal is used to drive the resonant conversion circuit; an intermittent charging unit 602, used to intermittently charge the DC bus capacitor of the buck-boost conversion circuit after the duty cycle of the first drive signal increases to a first target duty cycle, until the high-voltage side voltage of the buck-boost conversion circuit reaches the first target voltage.

[0074] It can be understood that the soft start control device also includes: a first stability control unit, which is used to control the duty cycle of the first drive signal to continuously maintain at the first target duty cycle after the duty cycle of the first drive signal increases to the first target duty cycle; a fixed frequency control unit, which is used to perform fixed frequency control on the LLC resonant cavity of the resonant conversion circuit according to a first resonant frequency, and the first resonant frequency is the resonant frequency of the resonant inductor and the resonant capacitor in the LLC resonant cavity.

[0075] It can be understood that the resonant conversion circuit includes multiple switching networks, and the first drive signal includes a first PWM signal and a second PWM signal corresponding to driving the upper and lower switch tubes of each bridge arm in each switching network; in the process of gradually increasing the duty cycle of the first drive signal, the upper and lower switch tubes of each bridge arm in each switching network are complementarily turned on and the dead time gradually decreases.

[0076] It can be understood that the first control unit is specifically used to: generate a first PWM signal that meets the first target duty cycle based on a PWM signal generator to drive the first pair of tubes of each of the switching networks; perform reverse processing on the first PWM signal based on an inverter to obtain a second PWM signal that meets the first target duty cycle; and drive the second pair of tubes of each of the switching networks based on the second PWM signal of the first target duty cycle.

[0077] It can be understood that the soft start control device also includes: a soft start judgment unit, which is used to respond to the second start instruction to start the buck-boost conversion circuit to determine whether the soft start condition is met at the current moment; if the soft start condition is met at the current moment, trigger the intermittent charging unit 602 to execute the step of intermittently charging the DC bus capacitor of the buck-boost conversion circuit.

[0078] It can be understood that the soft start judgment unit is specifically used to: judge whether the high-voltage side voltage of the buck-boost conversion circuit is less than the first target voltage, and if so, determine that the soft start condition is met at the current moment; or judge whether the high-voltage side voltage of the buck-boost conversion circuit is less than the first target voltage, and judge whether the medium-voltage side voltage of the buck-boost conversion circuit is less than the second target voltage, and if both are satisfied, determine that the soft start condition is met at the current moment.

[0079] It can be understood that the intermittent charging unit 602 is specifically used to: monitor the changes in the inductor current of the buck-boost conversion circuit; when the inductor current rises to no less than a first current threshold, the voltage loop and the current loop of the buck-boost conversion circuit are closed to prohibit charging of the DC bus capacitor of the buck-boost conversion circuit; when the inductor current drops to no more than a second current threshold, the DC bus capacitor of the buck-boost conversion circuit is charged by opening the voltage loop and the current loop of the buck-boost conversion circuit, and the second current threshold is less than the first current threshold.

[0080] It can be understood that the intermittent charging unit 602 is specifically used for: when the boost switch tube of the boost-buck conversion circuit is in a continuously closed state, the buck switch tube of the boost-buck conversion circuit is driven to be turned on by a second drive signal satisfying a second duty cycle, so that the DC bus capacitor of the boost-buck conversion circuit is intermittently charged; wherein the duty cycle of the second drive signal is less than the second target duty cycle, and the second target duty cycle is the duty cycle of the second drive signal when the boost-buck conversion circuit is in a stable operation state.

[0081] The soft start control device also includes: a second stability control unit, which is used to complementarily drive the boost switch tube and the buck switch tube of the boost-buck conversion circuit according to a second drive signal that satisfies the second target duty cycle after the high-side voltage of the boost-buck conversion circuit reaches the first target voltage.

[0082] The specific functions of each functional unit in the above device have been described in detail in the embodiment of the soft start control method of the energy storage DC converter provided in the embodiment of the present invention, and will not be elaborated here.

[0083] Based on the same inventive concept, the embodiment of the present invention further provides an energy storage system, referring to Figure 1 and Figure 7 As shown, it includes an energy storage module 10, an energy storage DC converter 20 connected to the energy storage module 10, and a control device for controlling the energy storage DC converter. The energy storage DC converter 20 includes a resonant conversion circuit 210 and a buck-boost conversion circuit 220 which are sequentially cascaded with the energy storage module 10. Figure 7 As shown, the control device includes a memory 704, a processor 702, and a computer program stored in the memory 704 and executable on the processor 702. The processor 702 executes the program to implement the soft start control method of the energy storage DC converter.

[0084] Among them, Figure 7 In the embodiment of the present invention, a bus architecture (represented by bus 700) is shown, which may include any number of interconnected buses and bridges, and bus 700 links various circuits including one or more processors represented by processor 702 and memory represented by memory 704. Bus 700 may also link various other circuits such as peripherals, voltage regulators, and power management circuits, which are well known in the art and are therefore not further described herein. Bus interface 706 provides an interface between bus 700 and receiver 701 and transmitter 703. Receiver 701 and transmitter 703 may be the same element, namely a transceiver, providing a unit for communicating with various other devices over a transmission medium. Processor 702 is responsible for managing bus 700 and general processing, while memory 704 may be used to store data used by processor 702 when performing operations.

[0085] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that has the functions specified in one or more boxes.

[0086] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0087] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0088] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0089] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0090] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A soft start control method for an energy storage DC converter, characterized in that: The energy storage DC converter comprises a resonant conversion circuit and a buck-boost conversion circuit which are sequentially cascaded with the energy storage module, and the method comprises: Controlling the duty cycle of a first drive signal to gradually increase from a preset initial duty cycle, wherein the first drive signal is used to drive the resonant conversion circuit; After the duty cycle of the first drive signal increases to the first target duty cycle, if the high voltage side voltage of the buck-boost conversion circuit is less than the first target voltage, or the high voltage side voltage of the buck-boost conversion circuit is less than the first target voltage and the medium voltage side voltage of the buck-boost conversion circuit is less than the second target voltage, the DC bus capacitor of the buck-boost conversion circuit is intermittently charged until the high voltage side voltage of the buck-boost conversion circuit reaches the first target voltage.

2. The method according to claim 1, characterized in that After the duty cycle of the first driving signal increases to a first target duty cycle, the method further includes: Controlling the duty cycle of the first driving signal to continuously maintain at the first target duty cycle; The LLC resonant cavity of the resonant conversion circuit is controlled at a fixed frequency according to a first resonant frequency, where the first resonant frequency is a resonant frequency at which a resonant inductor and a resonant capacitor in the LLC resonant cavity resonate together.

3. The method according to claim 2, characterized in that The resonant conversion circuit includes a plurality of switch networks, and the first drive signal includes a first PWM signal and a second PWM signal corresponding to driving the upper and lower switch tubes of each bridge arm in each of the switch networks; In the process of gradually increasing the duty cycle of the first driving signal, the upper and lower switch tubes of each bridge arm in each of the switch networks are complementarily turned on and the dead time is gradually reduced.

4. The method according to claim 3, characterized in that The step of controlling the duty cycle of the first driving signal to continuously maintain at the first target duty cycle includes: Generate a first PWM signal satisfying the first target duty cycle based on a PWM signal generator, and drive the first pair of tubes of each of the switch networks; Performing reverse processing on the first PWM signal based on an inverter to obtain a second PWM signal that meets the first target duty cycle; The second pair of transistors of each of the switch networks is driven by a second PWM signal based on the first target duty cycle.

5. The method according to claim 1, characterized in that The intermittent charging of the DC bus capacitor of the step-up / step-down conversion circuit comprises: Monitoring the change of the inductor current of the buck-boost conversion circuit; When the inductor current increases to a value not less than a first current threshold, the voltage loop and the current loop of the buck-boost conversion circuit are closed to prohibit charging of the DC bus capacitor of the buck-boost conversion circuit; When the inductor current drops to no more than a second current threshold, the DC bus capacitor of the buck-boost conversion circuit is charged by opening the voltage loop and the current loop of the buck-boost conversion circuit, and the second current threshold is less than the first current threshold.

6. The method according to claim 1, characterized in that The intermittent charging of the DC bus capacitor of the step-up / step-down conversion circuit comprises: When the boost switch tube of the boost-buck conversion circuit is in a continuously closed state, the buck switch tube of the boost-buck conversion circuit is driven to be turned on by a second driving signal satisfying a second duty ratio, so that the DC bus capacitor of the boost-buck conversion circuit is intermittently charged; The duty cycle of the second driving signal is smaller than the second target duty cycle, and the second target duty cycle is the duty cycle of the second driving signal when the buck-boost conversion circuit is in a stable operation state.

7. The method according to claim 6, characterized in that After the high-voltage side voltage of the step-up / down conversion circuit reaches the first target voltage, the method further includes: The boost switch tube and the buck switch tube of the buck-boost conversion circuit are complementarily driven according to the second drive signal that meets the second target duty cycle.

8. A soft start control device for an energy storage DC converter, characterized in that: The energy storage DC converter includes a resonant conversion circuit and a buck-boost conversion circuit which are sequentially cascaded with the energy storage module, and the soft start control device includes: a duty cycle increasing unit, configured to control the duty cycle of a first drive signal to gradually increase from a preset initial duty cycle, wherein the first drive signal is used to drive the resonant conversion circuit; An intermittent charging unit is used to intermittently charge the DC bus capacitor of the buck-boost conversion circuit after the duty cycle of the first drive signal increases to a first target duty cycle, if the high-voltage side voltage of the buck-boost conversion circuit is less than the first target voltage, or the high-voltage side voltage of the buck-boost conversion circuit is less than the first target voltage and the medium-voltage side voltage of the buck-boost conversion circuit is less than the second target voltage, until the high-voltage side voltage of the buck-boost conversion circuit reaches the first target voltage.

9. An energy storage system, comprising an energy storage module, an energy storage DC converter and a control device, wherein: The energy storage DC converter includes a resonant conversion circuit and a buck-boost conversion circuit which are sequentially cascaded with the energy storage module; the control device includes a memory, a processor, and a computer program stored in the memory and executable on the processor; the processor executes the program to implement the soft start control method of the energy storage DC converter as described in any one of claims 1 to 7.

Images