An energy storage device and its cyclic charging method

Abstract

The present invention discloses an energy storage device and its cyclic charging method. The control module controls the voltage commands of the inverters of the first energy storage module and the second energy storage module, so as to control the cyclic charging between the first energy storage module and the second energy storage module. And during the cyclic charging process, the rectification module supplies power to the first energy storage module and the second energy storage module. The present invention can realize the self-power supply of the energy storage device only by adding a small-power uncontrolled rectifier device. This device has simple control and low cost, and is very suitable for product performance verification.

Description

Technical Field

[0001] The present invention relates to the technical field of supercapacitor energy storage devices, and particularly relates to an energy storage device and a cyclic charging method thereof. Background Art

[0002] With the realization of the localization of supercapacitors, supercapacitor energy storage devices are more and more widely used, especially in rail transit, wind power and other applications. Supercapacitor energy storage has the advantages of high power density, fast charge and discharge speed, and relatively low price.

[0003] Before the supercapacitor energy storage device is officially put into operation, generally, cyclic charge and discharge tests are carried out with reference to the actual working conditions. On the one hand, to verify the stability and safety of the device under long-term operating conditions; on the other hand, to test the temperature rise of each key device in the device.

[0004] The current cyclic charge and discharge usually uses a large-scale bidirectional power supply device to perform cyclic charge and discharge tests on the supercapacitor energy storage unit. However, due to the large power of the supercapacitor device, such a method requires huge cost investment. In addition, there are problems such as power quality with the electric energy fed back by the bidirectional power supply, and it does not save electricity costs, greatly increasing the electricity consumption. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect of high cost for cyclic charge and discharge of supercapacitor devices in the prior art, so as to provide an energy storage device and a cyclic charging method thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] In a first aspect, an embodiment of the present invention provides an energy storage device, including: a first energy storage module, a second energy storage module, a rectification module, a braking module, and a control module; the first energy storage module, whose output end is connected to the high-voltage DC bus; the second energy storage module, whose output end is connected to the high-voltage DC bus; the rectification module, whose input end is connected to the AC bus and whose output end is connected to the high-voltage DC bus, and which is used to charge the first energy storage module and the second energy storage module; the braking module, whose output end is connected to the high-voltage DC bus; the control module, which is used to control cyclic mutual charging between the first energy storage module and the second energy storage module.

[0008] In an embodiment, both the first energy storage module and the second energy storage module include: a supercapacitor and a bidirectional DC-DC circuit; the bidirectional DC-DC circuit, whose first end is connected to the high-voltage DC bus and whose second end is connected to the supercapacitor.

[0009] In one embodiment, the bidirectional DC-DC circuit includes: a positive bus contactor, a high-voltage side pre-charge contactor, a negative bus contactor, a first pre-charge resistor, a first inductor, a support capacitor, a converter, a fuse, a second inductor, and a supercapacitor bank contactor; the positive bus contactor, whose first end is connected to the positive high-voltage DC bus, and whose second end is connected to the positive pole of the DC side of the converter through the first inductor; the high-voltage side pre-charge contactor, which is connected in series with the first pre-charge resistor and then connected in parallel with the positive bus contactor; the negative bus contactor, whose first end is connected to the negative high-voltage DC bus, and whose second end is connected to the negative pole of the DC side of the converter; the support capacitor, which is connected in parallel with the DC side of the converter; the converter, whose three-phase AC sides are all connected to a point in sequence through the fuse and the second inductor, and then connected to the first end of the supercapacitor bank contactor; the supercapacitor bank contactor, whose second end is connected to the first end of the supercapacitor; the supercapacitor, whose second end is connected to the negative pole of the DC side of the converter.

[0010] In one embodiment, the bidirectional DC-DC circuit further includes: a low-voltage side main contactor, a low-voltage side pre-charge contactor, and a second pre-charge resistor; the three-phase AC sides of the converter are all connected to a point in sequence through the fuse and the second inductor, and then connected to the first end of the supercapacitor bank contactor through the low-voltage side main contactor; the low-voltage side pre-charge contactor is connected in series with the second pre-charge resistor and then connected in parallel with the low-voltage side main contactor.

[0011] In a second aspect, the present invention provides a method for cyclic charging of an energy storage device. Based on the energy storage device of the first aspect, the method includes: the control module turns on the rectification module; the control module controls the operating states of the bidirectional DC-DC circuits of the first energy storage module and the second energy storage module, so that the support capacitors of the first energy storage module and the second energy storage module are pre-charged; the control module controls the voltage commands of the converters of the first energy storage module and the second energy storage module to control cyclic mutual charging between the first energy storage module and the second energy storage module, and during the cyclic charging process, the rectification module replenishes power for the first energy storage module and the second energy storage module.

[0012] In one embodiment, the process of pre-charging the support capacitor includes: the control module closes the negative bus contactor, the high-voltage side pre-charge contactor, the low-voltage side pre-charge contactor, and the supercapacitor bank contactor, and opens the positive bus contactor and the low-voltage side main contactor.

[0013] In one embodiment, the process of cyclic charging includes: the control module starts the converters of the first energy storage module and the second energy storage module, and charges the supercapacitors of the first energy storage module and the second energy storage module to a first voltage threshold and a second voltage threshold respectively, where the first voltage threshold is greater than the second voltage threshold; the control module alternately sets the voltage commands of the double closed-loop control links of the converters of the first energy storage module and the second energy storage module to a first voltage command and a second voltage command, where the first voltage command is greater than the second voltage command; when the temperatures of the first energy storage module and the second energy storage module reach a preset temperature, the control module blocks the trigger pulses of the converters of the first energy storage module and the second energy storage module, and disconnects the connections between the first energy storage module, the second energy storage module and the high-voltage DC bus.

[0014] In one embodiment, the process of the control module alternately setting the voltage commands of the double closed-loop control links of the converters of the first energy storage module and the second energy storage module to a first voltage command and a second voltage command includes: the control module respectively sets the voltage commands of the double closed-loop control links of the converters of the first energy storage module and the second energy storage module to the first voltage command and the second voltage command; when the second energy storage module is charged to the upper limit voltage, the control module turns off the pulses of the converters of the first energy storage module and the second energy storage module, and after a preset time, the control module respectively sets the voltage commands of the double closed-loop control links of the converters of the first energy storage module and the second energy storage module to the second voltage command and the first voltage command, and repeats the above process until the temperatures of the first energy storage module and the second energy storage module reach equilibrium.

[0015] In one embodiment, the process of disconnecting the connections between the first energy storage module, the second energy storage module and the high-voltage DC bus includes: the control module disconnects the negative bus contactors and the supercapacitor cabinet contactors of the first energy storage module and the second energy storage module; when the voltage of the high-voltage DC bus drops to the undervoltage point, the control module disconnects the positive bus contactors and the low-voltage side main contactors of the first energy storage module and the second energy storage module.

[0016] In one embodiment, the cyclic charging method of the energy storage device further includes: the control module detects whether the temperatures of the bidirectional DC-DC circuits and the supercapacitors of the first energy storage module and the second energy storage module exceed a preset temperature threshold; when the temperatures of the bidirectional DC-DC circuits and the supercapacitors of the first energy storage module and the second energy storage module exceed the preset temperature threshold, the control module blocks the trigger pulses of the converters of the first energy storage module and the second energy storage module, and the control module disconnects the negative bus contactors and the supercapacitor cabinet contactors of the first energy storage module and the second energy storage module; when the voltage of the high-voltage DC bus drops to the undervoltage point, the control module disconnects the positive bus contactors and the low-voltage side main contactors of the first energy storage module and the second energy storage module.

[0017] The technical solution of the present invention has the following advantages:

[0018] The energy storage device provided by the present invention and its cyclic charging method. The control module controls the voltage commands of the inverters of the first energy storage module and the second energy storage module, controls the cyclic mutual charging between the first energy storage module and the second energy storage module, and during the cyclic charging process, the rectification module supplies power to the first energy storage module and the second energy storage module. The present invention can achieve self-power supply of the energy storage device only by adding a small-power uncontrolled rectifier device. This method is simple to control and low in cost, and is very suitable for product performance verification. Description of the Drawings

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. 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.

[0020] Figure 1 Composition diagram of a specific example of the energy storage device provided by an embodiment of the present invention;

[0021] Figure 2 Circuit topology diagram of a specific example of the first energy storage module and the second energy storage module provided by an embodiment of the present invention;

[0022] Figure 3 Circuit topology diagram of another specific example of the first energy storage module and the second energy storage module provided by an embodiment of the present invention;

[0023] Figure 4 Flowchart of a specific example of the cyclic charging method provided by an embodiment of the present invention;

[0024] Figure 5 Dual closed-loop control block diagram provided by an embodiment of the present invention. Detailed Embodiments

[0025] The following will clearly and completely describe the technical solutions of the present invention with reference to the drawings. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0027] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can also be the communication inside two elements. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Embodiment 1

[0030] The embodiment of the present invention provides an energy storage device, as Figure 1 shown, including: a first energy storage module 1, a second energy storage module 2, a rectification module 3, a braking module 4 and a control module 5.

[0031] As Figure 1 shown, for the first energy storage module 1, its output terminal is connected to the high-voltage DC bus; for the second energy storage module 2, its output terminal is connected to the high-voltage DC bus.

[0032] Specifically, the first energy storage module 1 and the second energy storage module 2 can be composed of a super capacitor and a current conversion device. The current conversion device can charge the super capacitor and, after the super capacitor discharges, the discharge voltage is converted by the current conversion device and then transmitted to the high-voltage DC bus.

[0033] As Figure 1 shown, for the rectification module 3, its input terminal is connected to the AC bus, its output terminal is connected to the high-voltage DC bus, and it is used to replenish electricity for the first energy storage module 1 and the second energy storage module 2.

[0034] Specifically, the rectification module 3 is a single-phase power supply device. The rectification module 3 can be composed of an uncontrolled rectifier, a transformer, and a three-phase circuit breaker. The AC side of the uncontrolled rectifier is sequentially connected to the AC bus through the transformer and the three-phase circuit breaker. The uncontrolled rectifier converts alternating current into direct current, and this direct current is transmitted to the high-voltage DC bus.

[0035] As Figure 1 shown, the braking module 4, whose output terminal is connected to the high-voltage DC bus; when the high-voltage DC bus supplies power to the load, the braking module 4 can absorb the redundant electric energy on the line.

[0036] Specifically, the braking module 4 can be composed of a braking resistor and a braking chopper. Among them, the braking resistor is connected to the high-voltage DC bus through the braking chopper.

[0037] As Figure 1 shown, the control module 5 is respectively connected to the first energy storage module 1 and the second energy storage module 2, and is used to control the cyclic mutual charging between the first energy storage module 1 and the second energy storage module 2.

[0038] Specifically, the control module 5 controls the operating states of the bidirectional DC-DC circuits of the first energy storage module 1 and the second energy storage module 2, so that the support capacitors of the first energy storage module 1 and the second energy storage module 2 are pre-charged; the control module 5 controls the voltage commands of the converters of the first energy storage module 1 and the second energy storage module 2 to control the cyclic mutual charging between the first energy storage module 1 and the second energy storage module 2, and during the cyclic charging process, the rectification module 3 replenishes power for the first energy storage module 1 and the second energy storage module 2.

[0039] Specifically, the first energy storage module 1 and the second energy storage module 2 respectively send the temperature information of their internal components to the control module 5 in real time through CAN communication. The control module 5 determines whether the first energy storage module 1 and the second energy storage module 2 are abnormal based on the received temperature information. When abnormal, the control module 5 timely cuts off their connections with the high-voltage DC bus.

[0040] In a specific embodiment, both the first energy storage module 1 and the second energy storage module 2 include: a super capacitor and a bidirectional DC-DC circuit; the bidirectional DC-DC circuit, its first end is connected to the high-voltage DC bus, and its second end is connected to the super capacitor.

[0041] In a specific embodiment, as Figure 2 shown, the bidirectional DC-DC circuit includes: a positive bus contactor KM1, a high-voltage side pre-charging contactor KM2, a negative bus contactor KM3, a first pre-charging resistor R1, a first inductor L1, a support capacitor C, a converter 11, a fuse FU, a second inductor L2, and a super capacitor bank contactor KM6.

[0042] AsFigure 2 As shown in the figure, there is a positive bus contactor KM1, whose first end is connected to the positive high-voltage DC bus, and whose second end is connected to the positive pole of the DC side of the converter 11 through a first inductor L1; a high-voltage side pre-charge contactor KM2, which is connected in series with a first pre-charge resistor R1 and then connected in parallel with the positive bus contactor KM1; a negative bus contactor KM3, whose first end is connected to the negative high-voltage DC bus, and whose second end is connected to the negative pole of the DC side of the converter 11; a support capacitor C, which is connected in parallel with the DC side of the converter 11; a converter 11, whose three-phase AC sides all pass through fuses FU and a second inductor L2 in sequence and meet at a point, and then are connected to the first end of a supercapacitor bank contactor KM6; a supercapacitor bank contactor KM6, whose second end is connected to the first end of a supercapacitor; a supercapacitor SC, whose second end is connected to the negative pole of the DC side of the converter 11.

[0043] Specifically, as Figure 2 shown in the figure, the positive bus contactor KM1 and the high-voltage side pre-charge contactor KM2 cooperate to pre-charge the support capacitor C to prevent excessive current impact on the support capacitor C when the device is started; the function of the negative bus contactor KM3 is to disconnect the negative pole; the fuse FU serves to forcibly disconnect the circuit after a line short circuit; the supercapacitor bank contactor KM6 is a contactor in the supercapacitor bank, mainly serving to disconnect the circuit during maintenance.

[0044] In a specific embodiment, as Figure 3 shown in the figure, the bidirectional DC-DC circuit further includes: a low-voltage side main contactor KM4, a low-voltage side pre-charge contactor KM5, and a second pre-charge resistor R2; the three-phase AC sides of the converter 11 all pass through fuses FU and a second inductor L2 in sequence and meet at a point, and then are connected to the first end of the supercapacitor bank contactor KM6 through the low-voltage side main contactor KM4; the low-voltage side pre-charge contactor KM5 is connected in series with the second pre-charge resistor and then connected in parallel with the low-voltage side main contactor KM4.

[0045] Specifically, the functions of the low-voltage side main contactor KM4 and the low-voltage side pre-charge contactor KM5 are also to pre-charge the support capacitor C. Different from KM1 and KM2, they pre-charge the support capacitor C through the supercapacitor on the low-voltage side.

[0046] Specifically, Figure 3 As shown in the topology, the converter 11 and each contactor are controlled by a control module 5 through IO terminals. For example: when the control module 5 is a PLC, the relay switch is controlled through the IO terminals of the PLC, thereby controlling whether the contactor coil is energized, and thus controlling the on / off of the contactor switch.

[0047] Embodiment 2

[0048] An embodiment of the present invention provides a cyclic charging method for an energy storage device. Based on the energy storage device of Embodiment 1, the specific circuit topologies of the first energy storage module 1 and the second energy storage module 2 are taken Figure 3 as the topologies shown, as Figure 4 shown, the cyclic charging method includes:

[0049] Step S11: The control module 5 turns on the rectification module 3.

[0050] Specifically, before turning on the rectification module 3 and during the entire cycle, the control module 5 detects whether the temperatures of the bidirectional DC-DC circuits of the first energy storage module 1 and the second energy storage module 2 and the supercapacitor exceed a preset temperature threshold; when the temperatures of the bidirectional DC-DC circuits of the first energy storage module 1 and the second energy storage module 2 and the supercapacitor exceed the preset temperature threshold, the control module 5 blocks the trigger pulses of the converters 11 of the first energy storage module 1 and the second energy storage module 2, and the control module 5 disconnects the negative bus contactor KM3 of the first energy storage module 1 and the second energy storage module 2 and the supercapacitor cabinet contactor KM6; when the DC bus voltage drops to the undervoltage point, the control module 5 disconnects the positive bus contactor KM1 and the low-voltage side main contactor KM4 of the first energy storage module 1 and the second energy storage module 2.

[0051] Specifically, when the temperatures of the bidirectional DC-DC circuits of the first energy storage module 1 and the second energy storage module 2 and the supercapacitor do not exceed the preset temperature threshold, the control module 5 turns on the rectification module 3, and the rectification module 3 outputs a voltage U1.

[0052] It should be noted that the temperatures of the bidirectional DC-DC circuits of the first energy storage module 1 and the second energy storage module 2 actually may include the temperatures of the power electronic switches and inductors of the converter 11, but this is only an example and is not limited thereto.

[0053] Step S12: The control module 5 controls the operating states of the bidirectional DC-DC circuits of the first energy storage module 1 and the second energy storage module 2 to pre-charge the support capacitors C of the first energy storage module 1 and the second energy storage module 2.

[0054] Specifically, in order to prevent excessive current impact on the support capacitor C when the device is turned on, it is necessary to pre-charge the support capacitor C. The specific pre-charging process is as follows: The control module 5 closes the negative bus contactor KM3, the high-voltage side pre-charging contactor KM2, the low-voltage side pre-charging contactor KM5, and the supercapacitor cabinet contactor KM6, and disconnects the positive bus contactor KM1 and the low-voltage side main contactor KM4.

[0055] Specifically, after the high-voltage side pre-charge contactor KM2 is closed, the high-voltage DC bus pre-charges the support capacitor C, and when the low-voltage side pre-charge contactor KM5 is closed, the super capacitor pre-charges the support capacitor C. When the voltage difference between the voltage of the support capacitor C and the output voltage of the rectification module 3 is less than the preset voltage difference threshold, the positive bus contactor KM1 and the low-voltage side main contactor KM4 are closed, and the pre-charging of the support capacitor C is completed.

[0056] Step S13: The control module 5 controls the voltage commands of the converters 11 of the first energy storage module 1 and the second energy storage module 2, controls the first energy storage module 1 and the second energy storage module 2 to charge each other in a cycle, and during the cycle charging process, the rectification module 3 replenishes power for the first energy storage module 1 and the second energy storage module 2.

[0057] Specifically, the process of cycle charging in the embodiment of the present invention includes:

[0058] (1) The control module 5 starts the converters 11 of the first energy storage module 1 and the second energy storage module 2, and charges the super capacitors of the first energy storage module 1 and the second energy storage module 2 to a first voltage threshold and a second voltage threshold respectively, and the first voltage threshold is greater than the second voltage threshold.

[0059] Specifically, in the embodiment of the present invention, it is first necessary to start the first energy storage module 1 and the second energy storage module 2. The control module 5 sends a charging threshold U2 (U2 = U1 - 20, where the value 20 can be set as required) and a start command to the converters 11 of the first energy storage module 1 and the second energy storage module 2 to start charging. When the first energy storage module 1 is charged to 100% SOC, the terminal voltage of the super capacitor of the first energy storage module 1 is denoted as U scmax , and the second energy storage module 2 is charged to 20% SOC, and the terminal voltage of the super capacitor of the second energy storage module 2 is denoted as U scmin , where the value 20% can be set as required.

[0060] (2) The control module 5 alternately sets the voltage commands of the double closed-loop control links of the converters 11 of the first energy storage module 1 and the second energy storage module 2 to a first voltage command and a second voltage command, and the first voltage command is greater than the second voltage command.

[0061] Specifically, the block diagram of the double closed-loop control link of the first energy storage module 1 and the second energy storage module 2 in the embodiment of the present invention is as Figure 5 shown, Figure 5 where U bus_fdb is the real-time value of the high-voltage DC bus voltage, U bus_ref is the voltage command, i L_ref is the current command, and i L_fdb is the real-time value of the current of the second inductor L2. Figure 5Among them, the outer loop is the high-voltage side voltage loop, and the inner loop is the supercapacitor current loop. When the output of the voltage loop saturates, the device automatically switches to single current loop control.

[0062] Specifically, in the embodiment of the present invention, the voltage commands of the double closed-loop control links of the converters 11 of the first energy storage module 1 and the second energy storage module 2 are alternately set to the first voltage command and the second voltage command, so that the first energy storage module 1 and the second energy storage module 2 charge each other.

[0063] Specifically, the process in which the control module 5 alternately sets the voltage commands of the double closed-loop control links of the converters 11 of the first energy storage module 1 and the second energy storage module 2 to the first voltage command and the second voltage command includes: the control module 5 respectively sets the voltage commands of the double closed-loop control links of the converters 11 of the first energy storage module 1 and the second energy storage module 2 to the first voltage command and the second voltage command; when the second energy storage module 2 is charged to the upper limit voltage, the control module 5 turns off the pulses of the converters 11 of the first energy storage module 1 and the second energy storage module 2, and after a preset time, the control module 5 respectively sets the voltage commands of the double closed-loop control links of the converters 11 of the first energy storage module 1 and the second energy storage module 2 to the second voltage command and the first voltage command, and the above process is repeated until the temperatures of the first energy storage module 1 and the second energy storage module 2 reach equilibrium.

[0064] Exemplarily, taking Figure 3 the topology shown as an example, the specific process of a single-cycle charging process is as follows:

[0065] ① Set the voltage command value of the first energy storage module 1 to U1 + 20, the voltage command value of the second energy storage module 2 to U1 - 20, and the current limiting values of the first energy storage module 1 and the second energy storage module 2 are both set to the maximum current value Imax required for cyclic charge and discharge.

[0066] ② The first energy storage module 1 charges the second energy storage module 2. At this time, the high-voltage side bus voltage remains at U1 + 20. The supercapacitor voltage of the first energy storage module 1 is Usc1, and the supercapacitor voltage of the second energy storage module 2 is Usc2. At this time, Usc1 > Usc2.

[0067] ③ When the supercapacitor voltages of the first energy storage module 1 and the second energy storage module 2 are equal, the high-voltage side bus voltage starts to drop and stabilizes near U1. At this time, the uncontrolled rectifier of the rectification module 3 automatically turns on to replenish the supercapacitor of the second energy storage module 2.

[0068] Assume that the efficiency of single charging and single discharging is equal, which is e, and the equal voltage U of the first energy storage module 1 and the second energy storage module 2 sc0 The calculation formula is as follows:

[0069]

[0070] The charging current I of the second energy storage module 2 is as follows:

[0071]

[0072] ④ When the second energy storage module 2 is charged to the upper limit voltage, the supercapacitor voltage U of the first energy storage module 1 sc1min is as follows:

[0073] Usc1min = 2Usc0 - Uscmax (3)

[0074] The output current of the uncontrolled rectifier reaches the maximum value, and its relationship with the rated current Imax is as follows:

[0075]

[0076] At this time, the control module 5 turns off the pulses of the converters 11 of the first energy storage module 1 and the second energy storage module 2, and stands still for a preset time, such as 1 min.

[0077] ⑤ Adjust the voltage command value of the second energy storage module 2 to U1 + 20, and adjust the voltage command value of the first energy storage module 1 to U1 - 20. Note that the second energy storage module 2 needs to be adjusted first, otherwise it will cause overcurrent in the rectifier output; afterwards, the high-voltage DC bus voltage will rise and stabilize at U1 + 20.

[0078] ⑥ When the supercapacitor voltages of the first energy storage module 1 and the second energy storage module 2 are equal, the high-voltage DC bus voltage drops to near U1. At this time, the uncontrolled rectifier is automatically turned on to charge the supercapacitor of the first energy storage module 1.

[0079] The charging current of the supercapacitor of the first energy storage module 1 is as follows:

[0080]

[0081] ⑦ When the voltage of the first energy storage module 1 reaches the voltage upper limit, turn off the pulses of the converters 11 of the first energy storage module 1 and the second energy storage module 2 again, and stand still for a preset time, such as 1 min.

[0082] Thus, a complete charge-discharge cycle is completed, and then the above steps are repeated.

[0083] (3) When the temperatures of the first energy storage module 1 and the second energy storage module 2 reach the preset temperature, the control module 5 blocks the trigger pulses of the converters 11 of the first energy storage module 1 and the second energy storage module 2, and disconnects the connections between the first energy storage module 1, the second energy storage module 2 and the high-voltage DC bus.

[0084] Specifically, when the control module 5 detects that the temperatures of the power electronic switches, inductors, and supercapacitors of the converters 11 of the first energy storage module 1 and the second energy storage module 2 tend to be stable, it is considered that the temperature balance is reached. The current temperature and historical temperature data are automatically recorded and stored, and the control module 5 blocks the trigger pulses of the converters 11 of the first energy storage module 1 and the second energy storage module 2, and disconnects the connections between the first energy storage module 1, the second energy storage module 2 and the high-voltage DC bus.

[0085] Specifically, the process of disconnecting the connections between the first energy storage module 1, the second energy storage module 2 and the high-voltage DC bus includes: the control module 5 disconnects the negative bus contactor KM3 and the supercapacitor cabinet contactor KM6 of the first energy storage module 1 and the second energy storage module 2; when the voltage of the high DC bus drops to the undervoltage point, the control module 5 disconnects the positive bus contactor KM1 and the low-voltage side main contactor KM4 of the first energy storage module 1 and the second energy storage module 2.

[0086] Obviously, the above embodiments are only examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. An energy storage device, characterized in that, it includes: a first energy storage module, a second energy storage module, a rectification module, a braking module and a control module; The first energy storage module, whose output terminal is connected to the high-voltage DC bus; The second energy storage module, whose output terminal is connected to the high-voltage DC bus; The rectification module, whose input terminal is connected to the AC bus and whose output terminal is connected to the high-voltage DC bus, and is used to charge the first energy storage module and the second energy storage module; The braking module, whose output terminal is connected to the high-voltage DC bus; The control module is used to control the cyclic mutual charging between the first energy storage module and the second energy storage module; Both the first energy storage module and the second energy storage module include: a super capacitor and a bidirectional DC-DC circuit; the bidirectional DC-DC circuit, its first end is connected to the high-voltage DC bus, and its second end is connected to the super capacitor; The bidirectional DC-DC circuit includes: a positive bus contactor, a high-voltage side pre-charge contactor, a negative bus contactor, a first pre-charge resistor, a first inductor, a support capacitor, an inverter, a fuse, a second inductor, a super capacitor cabinet contactor; the positive bus contactor, its first end is connected to the positive pole of the high-voltage DC bus, and its second end is connected to the positive pole of the DC side of the inverter through the first inductor; the high-voltage side pre-charge contactor is connected in series with the first pre-charge resistor and then connected in parallel with the positive bus contactor; the negative bus contactor, its first end is connected to the negative pole of the high-voltage DC bus, and its second end is connected to the negative pole of the DC side of the inverter; the support capacitor is connected in parallel with the DC side of the inverter; the inverter, its three-phase AC sides are all connected to a point in turn through a fuse and a second inductor, and then connected to the first end of the super capacitor cabinet contactor; the super capacitor cabinet contactor, its second end is connected to the first end of the super capacitor; the super capacitor, its second end is connected to the negative pole of the DC side of the inverter; The bidirectional DC-DC circuit further includes: a low-voltage side main contactor, a low-voltage side pre-charge contactor and a second pre-charge resistor; the three-phase AC sides of the inverter are all connected to a point in turn through a fuse and a second inductor, and then connected to the first end of the super capacitor cabinet contactor through the low-voltage side main contactor; the low-voltage side pre-charge contactor is connected in series with the second pre-charge resistor and then connected in parallel with the low-voltage side main contactor.

2. A cyclic charging method for an energy storage device, characterized in that, based on the energy storage device described in claim 1, the method includes: The control module turns on the rectification module; The control module controls the operating states of the bidirectional DC-DC circuits of the first energy storage module and the second energy storage module, so that the support capacitors of the first energy storage module and the second energy storage module are pre-charged; The control module controls the voltage commands of the inverters of the first energy storage module and the second energy storage module to control the cyclic mutual charging between the first energy storage module and the second energy storage module, and during the cyclic charging process, the rectification module charges the first energy storage module and the second energy storage module. The process of supporting capacitor pre-charging includes: the control module closes the negative bus contactor, the high-voltage side pre-charging contactor, the low-voltage side pre-charging contactor and the super capacitor bank contactor, and disconnects the positive bus contactor and the low-voltage side main contactor; The process of cyclic charging includes: the control module starts the converters of the first energy storage module and the second energy storage module, and charges the super capacitors of the first energy storage module and the second energy storage module to a first voltage threshold and a second voltage threshold respectively, where the first voltage threshold is greater than the second voltage threshold; the control module alternately sets the voltage commands of the double closed-loop control links of the converters of the first energy storage module and the second energy storage module to a first voltage command and a second voltage command, where the first voltage command is greater than the second voltage command; when the temperatures of the first energy storage module and the second energy storage module reach a preset temperature, the control module blocks the trigger pulses of the converters of the first energy storage module and the second energy storage module, and disconnects the connections between the first energy storage module and the second energy storage module and the high-voltage DC bus; The process that the control module alternately sets the voltage commands of the double closed-loop control links of the converters of the first energy storage module and the second energy storage module to a first voltage command and a second voltage command includes: the control module respectively sets the voltage commands of the double closed-loop control links of the converters of the first energy storage module and the second energy storage module to a first voltage command and a second voltage command; when the second energy storage module is charged to the upper limit voltage, the control module turns off the pulses of the converters of the first energy storage module and the second energy storage module, and after a preset time, the control module respectively sets the voltage commands of the double closed-loop control links of the converters of the first energy storage module and the second energy storage module to a second voltage command and a first voltage command, and repeats the above process until the temperatures of the first energy storage module and the second energy storage module reach equilibrium.

3. The cyclic charging method of the energy storage device according to claim 2, characterized in that the process of disconnecting the connections between the first energy storage module and the second energy storage module and the high-voltage DC bus includes: the control module disconnects the negative bus contactors and the super capacitor bank contactors of the first energy storage module and the second energy storage module; when the voltage of the higher DC bus drops to the under-voltage point, the control module disconnects the positive bus contactors and the low-voltage side main contactors of the first energy storage module and the second energy storage module.

4. The cyclic charging method of the energy storage device according to claim 2, characterized in that it further includes: the control module detects whether the temperatures of the bidirectional DC-DC circuits and the super capacitors of the first energy storage module and the second energy storage module exceed a preset temperature threshold; when the temperatures of the bidirectional DC-DC circuits and the super capacitors of the first energy storage module and the second energy storage module exceed the preset temperature threshold, the control module blocks the trigger pulses of the converters of the first energy storage module and the second energy storage module, and the control module disconnects the negative bus contactors and the super capacitor bank contactors of the first energy storage module and the second energy storage module; when the voltage of the higher DC bus drops to the under-voltage point, the control module disconnects the positive bus contactors and the low-voltage side main contactors of the first energy storage module and the second energy storage module.

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