Operating Control Method, Device and Energy Storage System of Energy Storage DC Converter

Abstract

The present invention discloses an operation control method, device and energy storage system for an energy storage DC converter, belonging to the technical field of energy storage. The energy storage DC converter is used to connect an energy storage module to a DC bus, and the energy storage DC converter includes a resonant conversion circuit and a buck-boost conversion circuit cascaded with the energy storage module in sequence. The method includes: obtaining the current DC bus voltage in a state where the battery voltage of the energy storage module is linearly amplified based on the resonant conversion circuit; adjusting the duty cycle of a first driving signal and the duty cycle of a second driving signal based on the magnitude relationship between the current DC bus voltage and the target DC bus voltage; the first driving signal and the second driving signal are complementary, and the first driving signal and the second driving signal are used to drive the boost switch and the buck switch of the buck-boost conversion circuit correspondingly. Through the present invention, seamless switching between the charging and discharging functions of the energy storage DC converter is achieved.

Description

Technical Field

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

[0002] In the application environment of a household energy storage system, an energy storage DC converter (bidirectional DC-DC converter) needs to meet the requirements of a low-voltage battery and high gain. Generally, a two-stage structure is adopted, that is, after the front stage performs a boost conversion, the rear stage performs a boost control again. Among them, the two-stage structure can be composed of a front-stage LLC resonant conversion plus a rear-stage BUCK-BOOST conversion. Both two-stage structures of the energy storage DC converter need to have the ability of bidirectional energy flow to realize the charging and discharging functions of the energy storage module. The energy storage converter is controlled to switch between states such as charging, discharging, no-load and standby through command response.

[0003] However, by actively controlling the energy flow direction of the two-stage structure topology of the energy storage DC converter to realize charge and discharge switching, there are switching logic judgments and a certain switching time, which affect the charge and discharge switching efficiency. Summary of the Invention

[0004] Embodiments of the present invention provide an operation control method, device and energy storage system for an energy storage DC converter, realizing seamless switching between the charging and discharging functions of the energy storage DC converter to meet the requirements of rapid charge and discharge conversion of the energy storage DC converter in the energy storage system.

[0005] In a first aspect, an embodiment of the present invention provides an operation control method for an energy storage DC converter. The energy storage DC converter is used to incorporate an energy storage module into a DC bus. The energy storage DC converter includes a resonant conversion circuit and a buck-boost conversion circuit cascaded with the energy storage module in sequence. The method includes: obtaining a current DC bus voltage in a state where the battery voltage of the energy storage module is linearly amplified based on the resonant conversion circuit; adjusting the duty ratio of a first drive signal and the duty ratio of a second drive signal based on the magnitude relationship between the current DC bus voltage and a target DC bus voltage; wherein, the first drive signal and the second drive signal are complementary, and the first drive signal and the second drive signal are used to respectively drive a boost switch and a buck switch of the buck-boost conversion circuit.

[0006] In combination with the first aspect of the present invention, in some embodiments, adjusting the duty cycle of the first driving signal and the duty cycle of the second driving signal based on the magnitude relationship between the current DC bus voltage and the target DC bus voltage includes: performing a first PI adjustment based on the current DC bus voltage and the target DC bus voltage to obtain a reference current; obtaining the current inductor current of the buck-boost conversion circuit, and performing a second PI adjustment based on the current inductor current and the reference current to obtain a duty cycle parameter; adjusting the duty cycle of the first driving signal and the duty cycle of the second driving signal based on the duty cycle parameter.

[0007] In combination with the first aspect of the present invention, in some embodiments, adjusting the duty cycle of the first driving signal and the duty cycle of the second driving signal based on the duty cycle parameter includes: inputting the duty cycle parameter into a first PWM signal generator, and outputting a first driving signal for driving the boost switch through the first PWM signal generator; inputting the first driving signal into a first inverter, and outputting a second driving signal for driving the buck switch through the first inverter.

[0008] In combination with the first aspect of the present invention, in some embodiments, performing a first PI adjustment based on the current DC bus voltage and the target DC bus voltage to obtain a reference current includes: determining the voltage deviation between the current DC bus voltage and the target DC bus voltage; performing a first PI adjustment on the voltage deviation through a voltage PI regulator to obtain a current calculation result; comparing the preset current limit range with the current calculation result, and determining the reference current based on the comparison result.

[0009] In combination with the first aspect of the present invention, in some embodiments, performing a second PI adjustment based on the current inductor current and the reference current to obtain a duty cycle parameter includes: determining the current deviation between the current inductor current and the reference current; performing a second PI adjustment on the current deviation through a current PI regulator to obtain a duty cycle calculation result; comparing the preset duty cycle limit range with the duty cycle calculation result, and determining the duty cycle parameter based on the comparison result.

[0010] In combination with the first aspect of the present invention, in some embodiments, the resonant conversion circuit includes an LLC resonant cavity and at least one switching network, and each switching network includes at least one arm. Linearly amplifying the battery voltage of the energy storage module based on the resonant conversion circuit includes: correspondingly driving the upper and lower switching tubes of each arm in each switching network of the resonant conversion circuit based on a third driving signal and a fourth driving signal with a fixed duty cycle, wherein the third driving signal and the fourth driving signal are complementary; performing fixed-frequency control on the LLC resonant cavity based on a first resonant frequency.

[0011] In combination with the first aspect of the present invention, in some embodiments, it further includes: inputting a preset fixed duty cycle into a second PWM signal generator, and outputting a third driving signal for driving a first switching tube through the second PWM signal generator; inputting the third driving signal into a second inverter, and outputting a second driving signal for driving a second switching tube through the second inverter; wherein, the first switching tube and the second switching tube respectively correspond to the upper and lower switching tubes of the same bridge arm in each switching network of the resonant conversion circuit.

[0012] In combination with the first aspect of the present invention, in some embodiments, the fixed duty cycles of the third driving signal and the fourth driving signal are 50%.

[0013] In a second aspect, an embodiment of the present invention provides an operating control device for an energy storage DC converter. The energy storage DC converter is used to incorporate an energy storage module into a DC bus. The energy storage DC converter includes a resonant conversion circuit and a buck-boost conversion circuit cascaded with the energy storage module in sequence. The device includes: a voltage acquisition unit, configured to acquire the current DC bus voltage in a state where the battery voltage of the energy storage module is linearly amplified based on the resonant conversion circuit; a duty cycle adjustment unit, configured to adjust the duty cycles of a first driving signal and a second driving signal based on the magnitude relationship between the current DC bus voltage and a target DC bus voltage, wherein the first driving signal and the second driving signal are complementary, and the first driving signal and the second driving signal are used to respectively drive a boost switch and a buck switch of the buck-boost conversion circuit.

[0014] In a third aspect, an embodiment of the present invention provides an energy storage system, including an energy storage module, an energy storage DC converter, and a control device. The energy storage DC converter is used to incorporate the energy storage module into the DC bus. The energy storage DC converter includes a resonant conversion circuit and a buck-boost conversion circuit cascaded with the energy storage module in sequence. The control device includes a memory, a processor, and a computer program stored on the memory and executable on the processor. The processor executes the program to implement the operating control method of the energy storage DC converter according to any one of the embodiments of the first aspect.

[0015] One or more technical solutions provided by the embodiments of the present invention at least achieve the following technical effects or advantages:

[0016] While linearly amplifying the battery voltage of the energy storage module based on the resonant conversion circuit, a pair of complementary drive signals, namely the first drive signal and the second drive signal, are used to complementarily drive the boost switch and the buck switch of the buck-boost conversion circuit, so as to always maintain the DC bus voltage at the target DC bus voltage. This makes it such that whether the energy storage module is actually in the charging process, the discharging process, or the magnitude of the charge-discharge power, it completely depends on the power required by the externally connected load or the power that the charging power source can provide. There is no longer a need to turn on the boost switch during charging and turn on the buck switch during discharging to switch the charge-discharge function. Nor is there a need to first stop the machine from the current state and then switch to the discharging state, or first stop the machine and then switch to the charging state. Instead, the buck-boost conversion circuit's boost and buck switches are always driven by a pair of complementary drive signals, eliminating the need to execute the judgment logic for switching the charge-discharge function, thus avoiding the delay in switching between the charge-discharge functions, achieving seamless switching between the charging and discharging functions of the two-stage energy storage DC converter. Furthermore, it can meet the requirements of the energy storage DC converter for rapid charge-discharge transitions in the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 Shows a topology structure of the energy storage DC converter in an embodiment of the present invention;

[0019] Figure 2 Shows the flow of the operation control method of the energy storage DC converter in an embodiment of the present invention;

[0020] Figure 3 Shows the operation control logic of the buck-boost conversion circuit in an embodiment of the present invention;

[0021] Figure 4 Shows Figure 1 the topology structure of the energy storage DC converter in

[0022] Figure 5 Shows the operation control logic of the resonant conversion circuit in an embodiment of the present invention;

[0023] Figure 6 Shows the functional module diagram of the start control device of the energy storage DC converter in an embodiment of the present invention;

[0024] Figure 7 Shows the schematic structural diagram of the energy storage system in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0026] In addition, in the present invention, descriptions such as "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments may be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0027] The embodiment of the present invention provides an operation control method for an energy storage DC converter, which is used to control the operation of the energy storage DC converter with a two-stage DC conversion circuit during the entire operation process after soft start, so that the two-stage energy storage DC converter can seamlessly switch between charge and discharge functions without executing the switching judgment logic of the charge and discharge functions.

[0028] As Figure 1 shown, the energy storage DC converter 20 provided by the embodiment of the present invention is used to connect the energy storage module 10 to the DC bus. The energy storage DC converter 20 includes a two-stage DC conversion circuit, and the two-stage DC conversion circuit specifically includes a resonant conversion circuit 210 and a buck-boost conversion circuit 220 that are cascaded with the energy storage module 10 in sequence. It should be understood that the resonant conversion circuit 210 is a bidirectional LLC topology, and specifically may be: various common bidirectional LLC topologies such as full-bridge LLC topology, half-bridge LLC topology, multi-LLC parallel connection, multi-transformer series connection and / or parallel connection, and their derivative topologies. The buck-boost conversion circuit 220 (also called a BUCK-BOOST conversion circuit) may adopt a multi-phase bidirectional BUCK-BOOST conversion, interleaved parallel BUCK-BOOST conversion and other BUCK-BOOST topology structures and their derivative topologies. The energy storage module 10 may be a storage battery.

[0029] As Figure 2 shown, an operation control method for an energy storage DC converter provided by the embodiment of the present invention includes the following steps S101 to S102:

[0030] S101: Obtain the current DC bus voltage while linearly amplifying the battery voltage of the energy storage module 10 based on the resonant conversion circuit 210.

[0031] In the embodiment of the present invention, when the energy storage module 10 is incorporated into the DC bus through the energy storage DC converter 20. In step S101, the current DC bus voltage can be detected by a voltage sensor disposed at the DC bus terminal of the energy storage DC converter 20.

[0032] S102: Adjust the duty cycles of the first drive signal and the second drive signal based on the magnitude relationship between the current DC bus voltage and the target DC bus voltage, where the first drive signal and the second drive signal are complementary, and the first drive signal and the second drive signal are used to drive the boost switch and the buck switch of the buck-boost conversion circuit 220 correspondingly during the operation of the energy storage DC converter 20.

[0033] In a household scenario, there can also be a photovoltaic module incorporated into the DC bus through a unidirectional DC-DC converter, the power grid incorporated into the DC bus through a DC-AC converter, and various loads (various household electrical appliances: air conditioners, refrigerators, etc.) incorporated into the DC bus through unidirectional DC-DC converters respectively. Among them, the target DC bus voltage is a pre-given reference voltage value for the DC bus terminal and will not change with the external environment; while the current DC bus voltage is the voltage value measured at the DC bus terminal of the energy storage DC converter 20 and will change with the external environment. Among them, the change in the external environment refers to changes in the load, grid faults, changes in light affecting the power generation of the photovoltaic module, etc.

[0034] Since the change in the external environment will cause the charge and discharge power of the system to change, and the embodiment of the present invention obtains a pair of complementary drive pulses (the first drive signal and the second drive signal) through voltage and current closed-loop control to control the DC bus voltage, so as to have the ability to independently support the DC bus voltage, quickly make a power response within the maximum charging power and maximum discharge power ranges to suppress the DC bus voltage fluctuation, thereby improving the robustness and dynamic performance of the entire system.

[0035] It can be understood that by adjusting the duty cycles of the first drive signal and the second drive signal based on the magnitude relationship between the current DC bus voltage and the target DC bus voltage, during the switching between the charge and discharge functions of the energy storage DC converter 20 and the change of the charge and discharge power with the external environment (such as changing from 1000W to 2000W, changing from 1000W to -1000W), based on this pair of complementary drive pulses of the first drive signal and the second drive signal, the current DC bus voltage can always be stabilized near the target DC bus voltage, and there is no need to execute other switching judgment logics to achieve function switching.

[0036] It can be understood that the above step S102 may include multiple steps S1021 to S1023:

[0037] S1021: Perform a first PI regulation based on the current DC bus voltage and the target DC bus voltage to obtain a reference current.

[0038] Reference Figure 3 As shown, in order to improve the accuracy of the obtained reference current, determine the voltage deviation △U between the current DC bus voltage and the target DC bus voltage; perform a first PI regulation on the voltage deviation △U through a voltage PI regulator to obtain a current calculation result; obtain the reference current I according to the current calculation result L * .

[0039] It can be understood that a current limit range can be preset, compare the preset current limit range with the current calculation result, and determine the reference current I based on the comparison result L * . More simply, after obtaining the current calculation result, the current calculation result can also be directly used as the reference current I L * .

[0040] Specifically, the current limit range is based on the current upper threshold I L * max and the current lower threshold I L * min is constructed. If the current calculation result is within the current limit range constructed by the current upper threshold I L * max and the current lower threshold I L * min , use the current calculation result as the reference current I L * . In the case where the current calculation result is not within the current limit range, if the current calculation result is greater than the current upper threshold I L * max , then use the current upper threshold I L * max as the reference current I L * ; if the current calculation result is less than the current lower threshold I L * min , then use the current lower threshold I L * minAs the reference current I L * . Thus, the reference current I is limited by the current limiting range, L * avoiding damage to the components of the energy storage DC converter 20 caused by the reference current I being too large or too small. L *

[0041] Alternatively, if the DC bus voltage does not need to be stabilized by the energy storage DC converter 20 but by other converters (such as a PV inverter). Then, that is, when the DC bus voltage is already fixed, the charge and discharge power is controlled by directly controlling the inductor current of the buck-boost conversion circuit 220. At this time, Figure 3 the reference current I shown in L * is a preset fixed value and does not need to be calculated through step S1021. At this time, seamless switching between the charge and discharge functions is achieved by stabilizing the inductor current.

[0042] S1022: Obtain the current inductor current of the buck-boost conversion circuit 220, and perform a second PI regulation based on the current inductor current and the reference current to obtain the duty cycle parameter.

[0043] Refer to Figure 3 shown. The inductor current flowing through the first inductor L in the buck-boost conversion circuit 220 is detected by a current sensor to obtain the current inductor current I L ; determine the current deviation between the current inductor current I L and the reference current I L * ; perform a second PI regulation on the current deviation through a current PI regulator to obtain the duty cycle calculation result D_BUCK / BOOST; obtain the duty cycle parameter according to the duty cycle calculation result D_BUCK / BOOST.

[0044] It can be understood that a duty cycle limiting range can be preset, compare the preset duty cycle limiting range with the duty cycle calculation result D_BUCK / BOOST, and determine the duty cycle parameter based on the comparison result. More simply, after obtaining the duty cycle calculation result D_BUCK / BOOST, the duty cycle calculation result D_BUCK / BOOST can also be directly used as the duty cycle parameter.

[0045] Refer to Figure 3 shown. The duty cycle limiting range can be constructed based on the duty cycle upper threshold D max and the duty cycle lower threshold D min . If the duty cycle calculation result D_BUCK / BOOST is within the duty cycle upper threshold D​max and the lower limit threshold D of the duty cycle min If the calculated duty cycle result D_BUCK / BOOST is within the constructed duty cycle limit range, the calculated duty cycle result D_BUCK / BOOST is used as the duty cycle parameter. In the case where the calculated duty cycle result D_BUCK / BOOST is not within the duty cycle limit range: If the calculated duty cycle result D_BUCK / BOOST is greater than the upper limit threshold D of the duty cycle max , then the upper limit threshold D of the duty cycle max is used as the duty cycle parameter. If the calculated duty cycle result D_BUCK / BOOST is less than the lower limit threshold D of the duty cycle min , then the lower limit threshold D of the duty cycle min is used as the duty cycle parameter. Since the value range of the duty cycle parameter should be 0 to 1, the upper limit threshold Dmax of the duty cycle is 1, and the lower limit threshold Dmin of the duty cycle is 0, and the calculated duty cycle result may exceed the range of 0 to 1. The above technical solution can prevent incorrect duty cycle parameters from being input into the first PWM (pulse width modulation) signal generator, so that the first PWM signal generator always outputs the first drive signal and the second drive signal with correct duty cycles. Of course, if the calculated duty cycle result is not within the duty cycle limit range, a preset fixed duty cycle value within the duty cycle limit range can also be input into the first PWM signal generator. It can be understood that the first drive signal and the second drive signal are a pair of complementary PWM signals.

[0046] S1023: Adjust the duty cycle of the first drive signal and the duty cycle of the second drive signal based on the duty cycle parameter.

[0047] Refer to Figure 4 As 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. Among them, when the energy storage module 10 discharges outward, first the resonant conversion circuit 210 raises the battery voltage U provided by the energy storage module 10 bat to the medium voltage side voltage U mid , and realizes electrical isolation between the energy storage module 10 side and the medium voltage side through the transformer T. Then, the buck-boost conversion circuit 220 raises the medium voltage side voltage U output by the resonant conversion circuit 210 mid to the high voltage side voltage U bus (DC bus voltage). When charging the energy storage module 10, first the buck-boost conversion circuit 220 reduces the high voltage side voltage U bus to the medium voltage side voltage U mid , and then the resonant conversion circuit 210 reduces the medium voltage side voltage U midThe battery voltage U dropped to the energy storage module 10 bat .

[0048] Reference Figure 4 , the boost switch of the BUCK - BOOST conversion circuit 220 is specifically the boost switch tube S9, and the buck switch is specifically the buck switch tube S10. Based on this, the specific topology of the BUCK - BOOST conversion circuit 220 at least includes: the boost switch tube S9, the buck switch tube S10, the first inductor L (as the energy storage inductor), and the 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, 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 on one side, and the other end of the buck switch tube S10 is connected to the DC bus capacitor C H on the other side, and the current inductor current I L refers to the current of the first inductor L

[0049] Reference Figure 3 and Figure 4 As shown, the obtained duty cycle parameter is input into the first PWM signal generator, and the first drive signal for driving the boost switch S9 is output through the first PWM signal generator; the first drive signal is input into the first inverter, and the second drive signal for driving the buck switch S10 is output through the first inverter

[0050] It can be understood that before performing step S101, first control the buck - boost conversion circuit 220 to perform soft start. After the soft start of the buck - boost conversion circuit 220 is completed, then perform the above steps S101 - S102

[0051] In the embodiment of the present invention, the DC bus capacitor C of the buck - boost conversion circuit 220 H can be intermittently charged until the high - voltage side voltage of the buck - boost conversion circuit 220 reaches the target DC bus voltage, so as to realize the soft start of the buck - boost conversion circuit 220

[0052] It should be understood that the soft start of the buck - boost conversion circuit 220 can be performed after the soft start of the resonant conversion circuit 210 is completed. And after the soft start of the resonant conversion circuit 210 is completed, it is not necessarily required to control the buck - boost conversion circuit 220 to perform soft start. Therefore, after the soft start of the resonant conversion circuit 210 is completed, in response to the second start command for starting the buck - boost conversion circuit 220, determine whether the current moment meets the soft start condition. If the current moment meets the soft start condition, intermittently charge the DC bus capacitor C of the buck - boost conversion circuit 220 H ​

[0053] It can be understood that it is necessary to determine whether the high - voltage - side voltage of the buck - boost conversion circuit 220 is less than the target DC bus voltage. If the high - voltage - side voltage of the buck - boost conversion circuit 220 is less than the target DC bus voltage, it is determined that the soft - start condition is satisfied at the current moment; if the high - voltage - side voltage of the buck - boost conversion circuit 220 is not less than the target DC bus voltage, it indicates that the soft - start condition is not satisfied at the current moment, and there is no need to perform intermittent charging on the DC bus capacitor C of the buck - boost conversion circuit 220 H The buck - boost conversion circuit 220 can directly enter the stable operation state.

[0054] To avoid abnormalities 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 target DC bus voltage, and to determine whether the medium - voltage - side voltage of the buck - boost conversion circuit 220 is less than the medium - voltage - side target voltage; if both are satisfied, it is determined that the soft - start condition is satisfied at the current moment. If the medium - voltage - side voltage of the buck - boost conversion circuit 220 is not less than the medium - voltage - side target voltage and the high - voltage - side voltage of the buck - boost conversion circuit 220 is not less than the target DC bus voltage, it indicates that the soft - start condition is not satisfied at the current moment, and there is no need to perform intermittent charging on the DC bus capacitor C of the buck - boost conversion circuit 220 H The buck - boost conversion circuit 220 can directly enter the stable operation state and execute the above - mentioned steps S101 - S102.

[0055] It should be understood that intermittent charging of the DC bus capacitor C of the buck - boost conversion circuit 220 can be performed according to the change in the inductor current of the first inductor L, including: monitoring the change in the inductor current of the buck - boost conversion circuit 220; when it is monitored that the inductor current of the first inductor L in the buck - boost conversion circuit 220 rises to not less than the first current threshold, by closing the voltage loop and current loop of the buck - boost conversion circuit 220 to prohibit charging of the DC bus capacitor C of the buck - boost conversion circuit 220 H When the inductor current of the first inductor L in the buck - boost conversion circuit 220 drops to not greater than the second current threshold, by opening the voltage loop and current loop of the buck - boost conversion circuit 220, charge the DC bus capacitor C of the buck - boost conversion circuit H circuit. H

[0056] It should be understood that the second current threshold is less than the first current threshold, and the specific value can be set according to the actual situation. Since the voltage loop and current loop are executed to charge the DC bus capacitor C of the buck - boost conversion circuit 220 H ​During the charging process, the inductor current of the first inductor L in the buck-boost conversion circuit 220 gradually increases; when the inductor current of the first inductor L increases to no less than the first current threshold, the voltage loop and current loop of the buck-boost conversion circuit 220 are turned off. The turning off of the voltage loop and current loop causes the inductor current of the first inductor L to gradually decrease. When the inductor current of the first inductor L in the buck-boost conversion circuit 220 decreases to no greater than the second current threshold, it triggers the voltage loop and current loop to be re-executed for the DC bus capacitor C of the buck-boost conversion circuit 220 H to be charged; by cycling in this way, it is possible to achieve intermittent charging of the DC bus capacitor C of the buck-boost conversion circuit 220 H

[0057] Different from the above embodiment, intermittent charging of the DC bus capacitor C of the buck-boost conversion circuit 220 may include: when the boost switch tube S9 of the buck-boost conversion circuit 220 is in a continuously closed state, driving the buck switch tube S10 of the buck-boost conversion circuit 220 through a second driving signal that satisfies the second duty cycle, so that the DC bus capacitor C of the buck-boost conversion circuit 220 H is intermittently charged; wherein, the second duty cycle is less than the second target duty cycle, so as to achieve charging the DC bus voltage C with a discontinuous small current H It should be noted that the second target duty cycle is the duty cycle that the second driving signal required to drive the buck-boost conversion circuit 220 needs to satisfy when the buck-boost conversion circuit 220 is in a stable operating state. H

[0058] To reduce the control difficulty, the second duty cycle is a fixed value. For example, during the soft start process, the buck switch tube S10 is always driven by a second driving signal with a duty cycle of 5%, without the need for change.

[0059] By intermittently charging the DC bus capacitor C of the buck-boost conversion circuit 220 H until the high-side voltage of the buck-boost conversion circuit 220 reaches the target DC bus voltage, or until both the high-side voltage reaches the target DC bus voltage and the mid-side voltage reaches the mid-side target voltage, it indicates that the soft start of the buck-boost conversion circuit 220 is completed.

[0060] It can be understood that linearly amplifying the battery voltage of the energy storage module based on the resonant conversion circuit 210 includes: corresponding to driving the upper and lower switching tubes of each arm in each switching network of the resonant conversion circuit 210 based on a third driving signal and a fourth driving signal with a fixed duty cycle, wherein the third driving signal and the fourth driving signal are complementary; performing fixed-frequency control on the LLC resonant cavity 212 of the resonant conversion circuit 210 based on the first resonant frequency.

[0061] Reference​​Figure 4 As shown, the resonant conversion circuit 210 includes a plurality of switching networks, each switching network includes at least one leg, and the third driving signal and the fourth driving signal are jointly used to drive each leg of each switching network in the resonant conversion circuit 210. It can be understood that the third driving signal and the fourth driving signal are a pair of complementary PWM signals, and the upper and lower switching tubes of the same leg in each switching network of the resonant conversion circuit 210 are driven by a pair of complementary PWM signals to achieve complementary conduction of the upper and lower switching tubes of the same leg.

[0062] Reference Figure 4 , the resonant conversion circuit 210 may include a first switching network 211, a transformer T, an LLC resonant cavity 212, and a second switching network 213 connected in series in sequence. Among them, the first switching network 211 may be a full-bridge topology composed of switching tubes S1, S2, S3, and S4; the second switching network 213 may be another full-bridge topology composed of switching tubes S5, S6, S7, and S8. The LLC resonant cavity 212 includes a resonant inductor Lr, a resonant capacitor Cr, and an exciting inductor Lm. The resonant conversion circuit 210 may further include a first capacitor CL connected in series before the first switching network 211 and a second capacitor CM connected in series after the second switching network 213. Based on this, the third driving signal is used to drive the switching tubes S1, S4, S5, and S8; the fourth driving signal is used to drive the switching tubes S2, S3, S6, and S7, so that when the switching tubes S1, S4, S5, and S8 are in the conduction state, the switching tubes S2, S3, S6, and S7 are in the off state; when the switching tubes S1, S4, S5, and S8 are in the off state, the switching tubes S2, S3, S6, and S7 are in the conduction state.

[0063] It should be noted that the first resonant frequency is the resonant frequency at which the resonant inductor Lr and the resonant capacitor Cr in the LLC resonant cavity 212 resonate together

[0064] Since both the third driving signal and the fourth driving signal have a fixed duty cycle and perform fixed-frequency control on the LLC resonant cavity of the resonant conversion circuit 210 according to the first resonant frequency, the resonant conversion circuit 210 is maintained 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.

[0065] By simultaneously satisfying that the LLC resonant cavity operates at the first resonant frequency and the fixed duty cycles of the third driving signal and the fourth driving signal remain at 50%, the voltages Ubat and Umid on both sides of the resonant conversion circuit 210 are strongly correlated and strictly satisfy the linear amplification relationship of 1:N, realizing the linear amplification of the voltage Ubat of the energy storage module 10. This provides conditions for the seamless switching between the charge and discharge functions of the energy storage DC converter, where 1:N is the turn ratio of the transformer.

[0066] Reference Figure 5 As shown, a preset fixed duty cycle is input into the second PWM signal generator, and a third drive signal for driving the first switching tube is output through the second PWM signal generator; the third drive signal is input into the second inverter, and a fourth drive signal for driving the second switching tube is output through the second inverter; wherein, the first switching tube and the second switching tube correspond to the upper and lower switching tubes of the same arm in each switching network.

[0067] It should be understood that after the soft start of the resonant conversion circuit 210 is completed, the upper and lower switching tubes of each arm in each switching network of the resonant conversion circuit 210 can be correspondingly driven based on the third drive signal and the fourth drive signal with a fixed duty cycle.

[0068] During the soft start process of the resonant conversion circuit 210, it includes: controlling the duty cycles of the third drive signal and the fourth drive signal to gradually increase from a preset initial duty cycle until it increases to the fixed duty cycle. Initiate a first start command for the resonant conversion circuit 210; in response to the first start command, detect whether there is a fault in the resonant conversion circuit 210; if there is no fault in the resonant conversion circuit 210, control the resonant conversion circuit 210 to perform a soft start.

[0069] It should be understood that the initial duty cycle is less than the preset fixed duty cycle. According to the preset increasing strategy, control the duty cycles of the third drive signal and the fourth drive signal to gradually increase from the initial duty cycle until the duty cycles of the third drive signal and the fourth drive signal increase to the fixed duty cycle, which indicates that the soft start of the resonant conversion circuit 210 is completed.

[0070] Among them, the preset increasing strategy can refer to: controlling the duty cycles of the third drive signal and the fourth drive signal to gradually increase according to any one of the duty cycle increasing methods such as linearly increasing the duty cycle, logarithmically increasing the duty cycle, and exponentially increasing the duty cycle.

[0071] Of course, any two or more of the above duty cycle increasing methods can also be combined to control the duty cycles of the third drive signal and the fourth drive signal to gradually increase in multiple control segments, where different duty cycle increasing methods are used in different control segments. For example, the duty cycles of the third drive signal and the fourth drive signal can be first controlled to gradually increase from the initial duty cycle to a certain duty cycle in the way of linearly increasing the duty cycle; then the duty cycles of the third drive signal and the fourth drive signal can be controlled to continue to gradually increase in the way of increasing the duty cycle to the second power until it increases to the fixed duty cycle.

[0072] It should be understood that the initial duty cycle is a certain value close to 0. In a specific implementation process, the initial duty cycle can be, but is not limited to, a certain value between 1% and 10% to prevent overcurrent due to excessive capacitance on the medium-voltage side and the high-voltage side. The fixed duty cycle is the duty cycle of the third driving signal and the fourth driving 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 third driving signal and the fourth driving signal at 50% in a stable operating state, after gradually increasing the duty cycle of the third driving signal and the fourth driving signal to 50%, it indicates that the soft start process of the resonant conversion circuit 210 is completed, and the duty cycle of the third driving signal and the fourth driving signal is maintained at 50% and no longer increases.

[0073] Based on the same inventive concept, an embodiment of the present invention provides an operating control device for an energy storage DC converter. The energy storage DC converter 20 is used to incorporate the energy storage module 10 into the DC bus. The energy storage DC converter 20 includes a resonant conversion circuit 210 and a buck-boost conversion circuit 220 that are cascaded with the energy storage module 10 in sequence. Refer to Figure 6 As shown, the operating control device of the energy storage DC converter includes: a voltage acquisition unit 601, configured to acquire the current DC bus voltage in a state where the battery voltage of the energy storage module 10 is linearly amplified based on the resonant conversion circuit 210; a duty cycle adjustment unit 602, configured to adjust the duty cycle of the first driving signal and the duty cycle of the second driving signal based on the magnitude relationship between the current DC bus voltage and the target DC bus voltage, where the first driving signal and the second driving signal are complementary, and the first driving signal and the second driving signal are used to drive the boost switch and the buck switch of the buck-boost conversion circuit 220 correspondingly.

[0074] It can be understood that the duty cycle adjustment unit 602 includes: a first adjustment subunit, configured to perform a first PI adjustment based on the current DC bus voltage and the target DC bus voltage to obtain a reference current; a second adjustment subunit, configured to obtain the current inductor current of the buck-boost conversion circuit 220 and perform a second PI adjustment based on the current inductor current and the reference current to obtain a duty cycle parameter; a third adjustment subunit, configured to adjust the duty cycle of the first driving signal and the duty cycle of the second driving signal based on the duty cycle parameter.

[0075] It can be understood that the third adjustment subunit is specifically configured to: input the duty cycle parameter into a first PWM signal generator, and output a first driving signal for driving the boost switch through the first PWM signal generator; input the first driving signal into a first inverter, and output a second driving signal for driving the buck switch through the first inverter.

[0076] It can be understood that the first adjustment unit is specifically configured to: determine the voltage deviation between the current DC bus voltage and the target DC bus voltage; perform a first PI adjustment on the voltage deviation through a voltage PI regulator to obtain a current calculation result; compare the preset current limit range with the current calculation result, and determine the reference current based on the comparison result of the magnitudes.

[0077] It can be understood that the second adjustment subunit is specifically configured to: determine the current deviation between the current inductor current and the reference current; perform a second PI adjustment on the current deviation through a current PI regulator to obtain a duty cycle calculation result; compare the preset duty cycle limit range with the duty cycle calculation result, and determine the duty cycle parameter based on the comparison result of the magnitudes.

[0078] It can be understood that the resonant conversion circuit includes an LLC resonant cavity and at least one switching network. Each switching network includes at least one arm, and further includes a linear amplification unit configured to linearly amplify the battery voltage of the energy storage module 10 based on the resonant conversion circuit, including: corresponding to drive the upper and lower switching tubes of each arm in each switching network of the resonant conversion circuit based on a third drive signal and a fourth drive signal with a fixed duty cycle, where the third drive signal and the fourth drive signal are complementary; perform fixed-frequency control on the LLC resonant cavity based on a first resonant frequency.

[0079] It can be understood that the linear amplification unit is specifically configured to: input a preset fixed duty cycle into a second PWM signal generator, and output a third drive signal for driving a first switching tube through the second PWM signal generator; input the third drive signal into a second inverter, and output a second drive signal for driving a second switching tube through the second inverter; where the first switching tube and the second switching tube correspond to the upper and lower switching tubes of the same arm in each switching network of the resonant conversion circuit.

[0080] It can be understood that the fixed duty cycle of the third drive signal and the fourth drive signal is 50%.

[0081] The specific functions of each functional unit in the above device have been described in detail in the embodiment of the operation control method of the energy storage DC converter provided in the embodiment of the present invention, and will not be elaborated here.

[0082] Based on the same inventive concept, an embodiment of the present invention provides an energy storage system, including an energy storage module 10, an energy storage DC converter 20, and a control device. The energy storage DC converter 20 is configured to incorporate the energy storage module 10 into a DC bus. The energy storage DC converter 20 includes a resonant conversion circuit 210 and a buck-boost conversion circuit 220 cascaded with the energy storage module 10 in sequence, as Figure 7As shown, the control device includes a memory 704, a processor 702, and a computer program stored on the memory 704 and executable on the processor 702. The processor 702 executes the program to implement the steps described in any of the embodiments of the operating control method of the energy storage DC converter.

[0083] Among them, in Figure 7 , the bus architecture (represented by bus 700), bus 700 may include any number of interconnected buses and bridges. Bus 700 links together various circuits including one or more processors represented by processor 702 and a memory represented by memory 704. Bus 700 may also link together various other circuits such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and thus will not be 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, i.e., 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.

[0084] The present invention is described with reference to the 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 flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0085] These computer program instructions can 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, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the functions specified in Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0086] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operation steps are executed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions for implementing the functions specified in one process Figure 1 one process or a plurality of processes and / or blocks Figure 1 steps of the functions specified in one block or a plurality of blocks.

[0087] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made by those skilled in the art once they learn of the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0088] 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 equivalent technologies, the present invention also intends to include these modifications and variations.

[0089] The above are only the embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A method for operating and controlling an energy storage DC converter, characterized in that, the energy storage DC converter is used to incorporate an energy storage module into a DC bus. The energy storage DC converter includes a resonant conversion circuit and a buck-boost conversion circuit cascaded with the energy storage module in sequence. The method includes: acquiring a current DC bus voltage in a state where the battery voltage of the energy storage module is linearly amplified based on the resonant conversion circuit; in a state where the battery voltage of the energy storage module is linearly amplified based on the resonant conversion circuit, adjusting the duty cycle of a first drive signal and the duty cycle of a second drive signal based on the magnitude relationship between the current DC bus voltage and a target DC bus voltage, wherein the first drive signal and the second drive signal are complementary, and the first drive signal and the second drive signal are used to respectively drive a boost switch and a buck switch of the buck-boost conversion circuit; wherein, the resonant conversion circuit linearly amplifying the battery voltage of the energy storage module includes: based on a third drive signal and a fourth drive signal with a fixed duty cycle, respectively driving upper and lower switching tubes of each arm in each switching network of the resonant conversion circuit, wherein the third drive signal and the fourth drive signal are complementary; performing fixed-frequency control on the LLC resonant cavity of the resonant conversion circuit based on a first resonant frequency.

2. The method according to claim 1, characterized in that, the adjusting the duty cycle of the first drive signal and the duty cycle of the second drive signal based on the magnitude relationship between the current DC bus voltage and the target DC bus voltage includes: performing a first PI adjustment based on the current DC bus voltage and the target DC bus voltage to obtain a reference current; acquiring a current inductor current of the buck-boost conversion circuit, and performing a second PI adjustment based on the current inductor current and the reference current to obtain a duty cycle parameter; adjusting the duty cycle of the first drive signal and the duty cycle of the second drive signal based on the duty cycle parameter.

3. The method according to claim 2, characterized in that, the adjusting the duty cycle of the first drive signal and the duty cycle of the second drive signal based on the duty cycle parameter includes: inputting the duty cycle parameter into a first PWM signal generator, and outputting a first drive signal for driving the boost switch through the first PWM signal generator; inputting the first drive signal into a first inverter, and outputting a second drive signal for driving the buck switch through the first inverter.

4. The method according to claim 2, the performing a first PI adjustment based on the current DC bus voltage and the target DC bus voltage to obtain a reference current, includes: determining a voltage deviation between the current DC bus voltage and the target DC bus voltage; performing a first PI adjustment on the voltage deviation through a voltage PI regulator to obtain a current calculation result; comparing the size of a preset current limiting range with the current calculation result, and determining the reference current based on the size comparison result.

5. The method according to claim 2, characterized in that, Performing a second PI regulation based on the current inductor current and the reference current to obtain a duty cycle parameter, including: Determining the current deviation between the current inductor current and the reference current; Performing a second PI regulation on the current deviation through a current PI regulator to obtain a duty cycle calculation result; Comparing the size of a preset duty cycle limiting range with the duty cycle calculation result, and determining the duty cycle parameter based on the size comparison result.

6. The method according to claim 1, wherein, it further includes: Inputting a preset fixed duty cycle into a second PWM signal generator, and outputting a third driving signal for driving a first switching tube through the second PWM signal generator; Inputting the third driving signal into a second inverter, and outputting a second driving signal for driving a second switching tube through the second inverter; wherein, the first switching tube and the second switching tube respectively correspond to the upper and lower switching tubes of the same bridge arm in each switching network of the resonant conversion circuit.

7. The method according to claim 1, wherein, the fixed duty cycles of the third driving signal and the fourth driving signal are 50%.

8. An operating control device for an energy storage DC converter, wherein, the energy storage DC converter is used to incorporate an energy storage module into a DC bus, the energy storage DC converter includes a resonant conversion circuit and a buck-boost conversion circuit cascaded with the energy storage module in sequence, and the device includes: a voltage acquisition unit, configured to acquire the current DC bus voltage in a state where the battery voltage of the energy storage module is linearly amplified based on the resonant conversion circuit; a duty cycle adjustment unit, configured to adjust the duty cycle of a first driving signal and the duty cycle of a second driving signal based on the magnitude relationship between the current DC bus voltage and a target DC bus voltage in a state where the battery voltage of the energy storage module is linearly amplified based on the resonant conversion circuit, wherein the first driving signal and the second driving signal are complementary, and the first driving signal and the second driving signal are used to respectively drive a boost switch and a buck switch of the buck-boost conversion circuit; wherein, linearly amplifying the battery voltage of the energy storage module by the resonant conversion circuit includes: corresponding to driving the upper and lower switching tubes of each bridge arm in each switching network of the resonant conversion circuit based on a third driving signal and a fourth driving signal with a fixed duty cycle, wherein the third driving signal and the fourth driving signal are complementary; performing fixed-frequency control on the LLC resonant cavity of the resonant conversion circuit based on a first resonant frequency.

9. An energy storage system, including an energy storage module, an energy storage DC converter, and a control device, wherein, the energy storage DC converter is used to incorporate the energy storage module into the DC bus, the energy storage DC converter includes a resonant conversion circuit and a buck-boost conversion circuit cascaded with the energy storage module in sequence, and the control device includes a memory, a processor, and a computer program stored on the memory and executable on the processor, and the processor executes the program to implement the operating control method of the energy storage DC converter according to any one of claims 1-7.

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