Capacity expansion control circuit of energy storage system and energy storage system

Abstract

The embodiment of the utility model relates to a capacity expansion control circuit of an energy storage system and the energy storage system, the capacity expansion control circuit is applied to the energy storage system, and a host battery and a capacity expansion battery in the energy storage system are both connected with a direct current bus; the capacity expansion battery is connected with the direct current bus through the capacity expansion protection circuit and the first bidirectional conversion circuit; the capacity expansion protection circuit comprises at least one normally open switch used for controlling the capacity expansion battery to be communicated with the direct current bus; the first bidirectional conversion circuit is connected with a bus through a first bus end and a second bus end; the first bidirectional conversion circuit is connected with the expansion battery through the first battery end and the second battery end; the first bidirectional conversion circuit comprises a plurality of control switches. According to the application, the voltage output to the direct current bus by the capacity expansion battery is adjusted to be consistent with the voltage output to the direct current bus by the host battery, so that discharging can be carried out at the same time, and co-working can be carried out.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of energy storage battery control, and in particular, to an expansion control circuit and an energy storage system for an energy storage system. Background Art

[0002] With the development of photovoltaic technology, direct current has attracted wide attention for its characteristics of low carbon, high efficiency, safety, and greenness. A series of new direct current appliances have emerged at home and abroad. At the same time, the development of photovoltaic technology and the decline in energy storage prices have also driven the household application of photovoltaic energy storage systems. In the future, photovoltaic energy storage systems and direct current appliances will appear in ordinary families more and more. Among them, the photovoltaic energy storage system equipped with an expansion battery pack allows users to select expansion battery packs with different capacities, and the configuration is more flexible; when the battery power of the host is insufficient, the expansion battery can be connected to meet the use in emergency situations.

[0003] For the expansion battery of the existing photovoltaic energy storage system, a fixed inverter is generally used. When charging the expansion battery, the inverter steps down the high-voltage voltage on the bus and inputs it into the expansion battery. When discharging the expansion battery, the inverter raises the voltage of the expansion battery and outputs it; however, since the output voltage of the expansion battery varies greatly with the remaining battery capacity, when the voltages of the expansion battery and the host battery are different, the currents of the two batteries are also inconsistent. Once both are connected to the bus, the current on the bus will cause a current impact on the expansion battery. In order to avoid the current impact, currently, only the control can be switched to use only one of the battery packs for power supply, resulting in some equipment being idle and the utilization rate being low. Summary of the Utility Model

[0004] In view of this, in order to solve the problem that the expansion battery of the energy storage system and the host battery cannot be used in cooperation, the embodiments of the present application provide an expansion control circuit and an energy storage system for an energy storage system.

[0005] In a first aspect, the embodiments of the present application provide an expansion control circuit for an energy storage system, which is characterized in that it is applied to an energy storage system, and the energy storage system includes: a host battery, an expansion battery, and a direct current bus. Among them, the host battery and the expansion battery are both connected to the direct current bus;

[0006] The expansion control circuit includes: an expansion protection circuit and a first bidirectional conversion circuit. Among them, the expansion battery is connected to the direct current bus through the expansion protection circuit and the first bidirectional conversion circuit;

[0007] The capacity expansion protection circuit includes at least one normally open switch for controlling the connection between the capacity expansion battery and the DC bus; the first bidirectional conversion circuit is connected to the bus through a first bus terminal and a second bus terminal; the first bidirectional conversion circuit is connected to the capacity expansion battery through a first battery terminal and a second battery terminal; the first bidirectional conversion circuit includes a plurality of control switches for controlling step-up / step-down switching in the direction from the DC bus to the capacity expansion battery and step-up / step-down switching in the direction from the capacity expansion battery to the DC bus.

[0008] Optionally, the first bidirectional conversion circuit includes: a first capacitor, a second capacitor, a first inductor, a third switching device, a fourth switching device, a fifth switching device, and a sixth switching device; wherein,

[0009] The first battery terminal is respectively connected to the first end of the first capacitor and the first connection end of the third switching device; the second battery terminal is respectively connected to the second end of the first capacitor and the first connection end of the fourth switching device;

[0010] The first bus terminal is respectively connected to the first end of the second capacitor and the first connection end of the fifth switching device; the second bus terminal is respectively connected to the second end of the second capacitor and the first connection end of the sixth switching device;

[0011] The first end of the first inductor is respectively connected to the second connection end of the fourth switching device and the second connection end of the fourth switching device; the second end of the first inductor is respectively connected to the second connection end of the fifth switching device and the second connection end of the sixth switching device.

[0012] Optionally, the normally open switch includes: a first switching device and a second switching device;

[0013] The first end of the capacity expansion battery is connected to the first connection end of the first switching device; the second connection end of the first switching device is connected to the first connection end of the second switching device;

[0014] The second connection end of the second switching device is connected to the first battery terminal, and the second end of the capacity expansion battery is connected to the second battery terminal.

[0015] Optionally, the capacity expansion protection circuit further includes: a capacity expansion controller, wherein,

[0016] The output end of the capacity expansion controller is respectively connected to the control ends of the first switching device, the second switching device, the third switching device, the fourth switching device, the fifth switching device, and the sixth switching device to control the conduction or cut-off of each switching device.

[0017] Optionally, the capacity expansion protection circuit further includes: a host battery controller and a bus information collector,

[0018] The host battery controller collects the operating state of the host battery and outputs a charging signal, a discharging signal, and a standby signal according to different operating states; the bus information collector is connected to the DC bus and collects the voltage signal of the DC bus;

[0019] The input end of the expansion controller is connected to the output end of the host battery controller and the output end of the bus information collector.

[0020] Optionally, the expansion protection circuit includes: a voltage sensor and a current sensor,

[0021] wherein, two acquisition ends of the current sensor are connected in series between the first end of the expansion battery and the first end of the first switching device, and the output end of the current sensor is connected to the input end of the expansion protection controller;

[0022] Two acquisition ends of the voltage sensor are respectively connected to the first end and the second end of the expansion battery; the output end of the voltage sensor is connected to the input end of the expansion controller.

[0023] In a second aspect, an embodiment of the present application provides an energy storage system, characterized in that the energy storage system includes: a host battery, an expansion battery, a DC bus, and an expansion control circuit according to any one of claims 1-6, wherein the host battery is connected to the DC bus, and the expansion battery is connected to the DC bus through the expansion control circuit;

[0024] The expansion control circuit includes: an expansion protection circuit and a first bidirectional conversion circuit, wherein the expansion battery is connected to the DC bus through the expansion protection circuit and the first bidirectional conversion circuit;

[0025] The expansion protection circuit includes at least one normally open switch for controlling the connection between the expansion battery and the DC bus; the first bidirectional conversion circuit is connected to the bus through a first bus end and a second bus end; the first bidirectional conversion circuit is connected to the expansion battery through a first battery end and a second battery end; the first bidirectional conversion circuit includes a plurality of control switches for controlling step-up / step-down switching in the direction from the DC bus to the expansion battery and step-up / step-down switching in the direction from the expansion battery to the DC bus.

[0026] Optionally, the energy storage system includes: a battery management module and a second bidirectional DC step-up / step-down circuit;

[0027] The host battery is connected to the DC bus through the battery management module and the second bidirectional DC step-up / step-down circuit.

[0028] Optionally, the energy storage system includes: a photovoltaic storage module and a photovoltaic inverter;

[0029] The photovoltaic module is connected to the DC bus through the photovoltaic inverter.

[0030] In the expansion control circuit of the energy storage system provided by the embodiment of the present application, the expansion protection circuit includes at least one normally open switch for controlling the connection between the expansion battery and the DC bus; the first bidirectional conversion circuit is connected to the bus through a first bus terminal and a second bus terminal; the first bidirectional conversion circuit is connected between the expansion battery and the DC bus, and the first bidirectional conversion circuit includes a plurality of control switches for controlling the step-up and step-down switching in the direction from the DC bus to the expansion battery, and for controlling the step-up and step-down switching in the direction from the expansion battery to the DC bus. Among them, the normally open switch in the expansion protection circuit can avoid the impact of the current on the DC bus on the expansion battery when the expansion battery is connected to the DC bus. In addition, through the combined operation of a plurality of control switches in the first bidirectional conversion circuit, the expansion battery and the DC bus are no longer unidirectional step-up and step-down, but can step up or step down in the direction from the DC bus to the expansion battery, and can also step up or step down in the direction from the expansion battery to the DC bus. Furthermore, the voltage output from the expansion battery to the DC bus can be adjusted to be consistent with the voltage output from the main battery to the DC bus, so that they can discharge simultaneously and work together. Description of the Drawings

[0031] The drawings here are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0032] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, unless otherwise stated, and the drawings in the figures do not constitute a proportional limitation.

[0034] Figure 1 It is a schematic structural diagram of an expanded energy storage system provided by an embodiment of the present application;

[0035] Figure 2Schematic diagram of another energy storage system with capacity expansion provided by an embodiment of the present application;

[0036] Figure 3 Schematic diagram of yet another energy storage system with capacity expansion provided by an embodiment of the present application;

[0037] Figure 4 Schematic diagram of still another energy storage system with capacity expansion provided by an embodiment of the present application;

[0038] Figure 5 Schematic diagram of a capacity expansion energy storage device provided by an embodiment of the present application. Detailed implementation manners

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some but not all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0040] The terms "including" and "having" in the embodiments of the present application are used to mean an open inclusion, and refer to the existence of additional elements / components / etc. in addition to the listed elements / components / etc.; the terms "first" and "second", etc. are only used as labels and do not limit the quantity of their objects. In addition, different elements and regions in the drawings are only schematically shown, so the present application is not limited to the sizes or distances shown in the drawings.

[0041] To facilitate the understanding of the embodiments of the present application, the following will further explain with specific embodiments in conjunction with the accompanying drawings. The embodiments do not constitute a limitation to the embodiments of the present application.

[0042] Figure 1 Schematic diagram of a capacity expansion energy storage system provided by an embodiment of the present application. Applied to the capacity expansion energy storage control process. According to Figure 1 the provided diagram, the structure of the energy storage system 100 specifically includes: a main battery, an expansion battery, and a DC bus. The main battery and the expansion battery are both connected to the DC bus. In Figure 1 , an electrical device 4 is also connected to the DC bus. Usually, the current on the DC bus is direct current, so the electrical device 4 can be a DC electrical device. When the electrical device is an AC electrical device, an AC-DC conversion module (not shown in the figure) is required between the electrical device 4 and the DC bus.

[0043] See Figure 1As shown in the figure, the expansion control circuit 10 includes: an expansion protection circuit 11 and a first bidirectional conversion circuit 12.

[0044] The expansion protection circuit 11 and the first bidirectional conversion circuit 12 are connected in series between the expansion battery and the DC bus. As an intermediate protection, it is used to control the voltage and current when the expansion battery is connected to the DC bus, avoiding problems such as inconsistent voltage and large current differences when the expansion battery is directly connected to the DC bus.

[0045] At least one normally open switch in the expansion protection circuit 11 for controlling the connection between the expansion battery and the DC bus. In the embodiments of the present application, the normally open switch can be a single-pole single-throw switch, solenoid valve, switch tube, transistor, or other devices with conduction or cut-off functions. The present application does not limit this. The role of the normally open switch is that when the first bidirectional conversion circuit is connected to the DC bus, since the normal state of the normally open switch is the off state, it will not directly connect the expansion battery to the DC bus, avoiding damage to the expansion battery caused by large current on the DC bus.

[0046] See Figure 1 As shown in the figure, there are a first bus terminal and a second bus terminal on the DC bus, serving as the connection points for the expansion battery to connect to the DC bus; on the expansion battery, there are a first battery terminal and a second battery terminal, serving as the connection points of the expansion battery.

[0047] The first bidirectional conversion circuit is connected to the bus through the first bus terminal and the second bus terminal; the first bidirectional conversion circuit is connected to the expansion battery through the first battery terminal and the second battery terminal; the first bidirectional conversion circuit includes multiple control switches, and the role of the control switches is to adjust the step-up and step-down relationship between the expansion battery and the DC bus.

[0048] In one scenario, adjusting the step-up and step-down relationship between the expansion battery and the DC bus is specifically: controlling to step up or step down in the direction from the DC bus to the expansion battery. For example, when the expansion battery discharges, the voltage of the expansion battery is lower than the voltage of the DC bus. At this time, the first bidirectional conversion circuit adjusts through the control switch for step-up control; similarly, when the expansion battery discharges, the voltage of the expansion battery is higher than the voltage of the DC bus. At this time, the first bidirectional conversion circuit adjusts through the control switch for step-down control.

[0049] In another scenario, adjusting the step-up and step-down relationship between the expansion battery and the DC bus is specifically: stepping up or stepping down in the direction from the expansion battery to the DC bus. For example, when the expansion battery charges, the voltage of the DC bus is higher than the charging voltage of the expansion battery. At this time, the first bidirectional conversion circuit adjusts through the control switch for step-down control; similarly, when the expansion battery charges, the voltage of the DC bus is lower than the charging voltage of the expansion battery. At this time, the first bidirectional conversion circuit adjusts through the control switch for step-down control.

[0050] Therefore, for the expansion control circuit of the energy storage system provided by the embodiments of the present application, on the one hand, through the normally open switch in the expansion protection circuit, when the expansion battery is connected to the DC bus, it is not directly connected to the DC bus, thus avoiding the impact of the current on the DC bus on the expansion battery. On the other hand, through the joint operation of multiple control switches in the first bidirectional conversion circuit, the expansion battery and the DC bus are no longer unidirectional step-up or step-down, but can achieve step-up or step-down in the direction from the DC bus to the expansion battery, and can also achieve step-up or step-down in the direction from the expansion battery to the DC bus. Furthermore, the voltage conversion requirements between the expansion battery and the DC bus can be flexibly adjusted to make it consistent with the voltage output from the host battery to the DC bus, and then they can discharge simultaneously and work together.

[0051] Figure 2 FIG. 6 is a schematic structural diagram of an expansion control circuit of another energy storage system provided by the embodiments of the present application. Figure 2 It is introduced on the basis of the previous embodiment. According to Figure 2 the provided diagram, the first bidirectional conversion circuit specifically includes: a second capacitor C2, a first inductor L1, a third switching device Q3, a fourth switching device Q4, a fifth switching device Q5, and a sixth switching device Q6.

[0052] The first battery terminal is respectively connected to the first end of the first capacitor and the first connection end of the third switching device; the second battery terminal is respectively connected to the second end of the first capacitor and the first connection end of the fourth switching device;

[0053] The first bus terminal is respectively connected to the first end of the second capacitor and the first connection end of the fifth switching device; the second bus terminal is respectively connected to the second end of the second capacitor and the first connection end of the sixth switching device;

[0054] The first end of the first inductor is respectively connected to the second connection ends of the fourth switching device and the fourth switching device; the second end of the first inductor is respectively connected to the second connection ends of the fifth switching device and the sixth switching device.

[0055] In the embodiments of the present application, the third switching device Q3, the fourth switching device Q4, the fifth switching device Q5, and the sixth switching device Q6 can be devices with on-off functions such as single-pole single-throw switches, solenoid valves, switching tubes, and transistors, and the present application does not limit this. In one embodiment, the switching device can be a MOS tube.

[0056] After the above settings, it can be seen that the first bidirectional conversion circuit has four switching devices. By controlling the conduction or cutoff of different switching devices, the first bidirectional conversion circuit can perform step-up or step-down conversions in two directions respectively.

[0057] In one scenario: when the fifth switching device Q5 is conducting and the sixth switching device Q6 is cutoff, at this time the third switching device Q3 and the fourth switching device Q4 are conducting respectively, and step-down conversion can be formed from the extended battery to the DC bus direction;

[0058] In another scenario: when the third switching device Q3 is conducting and the fourth switching device Q4 is cutoff, at this time the fifth switching device Q5 and the sixth switching device Q6 are conducting respectively, and step-up conversion can be formed from the extended battery to the DC bus direction.

[0059] See the following table:

[0060]

[0061] Figure 3 It is a schematic structural diagram of an extended capacity control circuit of another energy storage system provided by an embodiment of the present application. Figure 3 It is introduced based on the previous embodiment. According to Figure 3 The provided diagram, the normally open switches in the extended capacity protection circuit include: the first switching device Q1 and the second switching device Q2. In the embodiments of the present application, the switching device can be a single-pole single-throw switch, a solenoid valve, a switching tube, a transistor, or other devices with conduction or cutoff functions. In one embodiment, the switching device can be a MOS tube.

[0062] The first end of the extended battery is connected to the first connection end of the first switching device; the second connection end of the first switching device is connected to the first connection end of the second switching device;

[0063] The second connection end of the second switching device is connected to the first battery end, and the second end of the extended battery is connected to the second battery end.

[0064] In the embodiments of the present application, regardless of the type of the first switching device and the second switching device, in the default state, the first switching device and the second switching device are both in the normally open state, which can avoid the large current on the DC bus from impacting the extended battery and damaging the extended battery after the first bidirectional conversion circuit is connected to the DC bus.

[0065] For the control relationship between the switching devices Q1 and Q2, refer to the following embodiments.

[0066] In one embodiment, when there is power on the DC bus, first, the DC bus charges the energy storage capacitor C2. At this time, the switching devices Q3 - Q6 are turned off, and the first bidirectional conversion circuit does not work. After C2 reaches the threshold value V1, it can output voltage to both ends of C1 according to the charge and discharge state of the host system. For example, when the voltage at both ends of the extended battery 2 is 50V in the charging mode, the voltage at both ends of C1 is controlled to be slightly higher than the voltage of the extended battery, such as 52V, through the control of the switching devices. After the voltage at both ends of C1 is stable, the switching devices Q1 and Q2 are turned off to complete the charging or discharging of the battery.

[0067] In another embodiment, when the DC bus voltage is 0, the entire system is in the off - grid state. At this time, the switching devices Q1 and Q2 are controlled to conduct to charge the energy storage capacitor C1. At this time, the switching devices Q3 - Q6 are turned off, and the first bidirectional conversion circuit does not work. After the voltage of C1 reaches the threshold value, a stable bus voltage is output to the DC bus by operating the conduction or disconnection of the switching devices Q3 - Q6.

[0068] As Figure 3 shown, in the embodiment of the present application, the extended capacity control circuit may further include: an extended capacity controller 7. The extended capacity controller 7 can be a single - chip microcomputer or an integrated circuit. In addition, the extended capacity controller 7 can also be a circuit control system composed of a plurality of manual switching switches.

[0069] See Figure 3 shown, the output terminals of the extended capacity controller 7 are respectively connected to the control terminals of the first switching device Q1, the second switching device Q2, the third switching device Q3, the fourth switching device Q4, the fifth switching device Q5, and the sixth switching device Q6 to control the conduction or cut - off of each switching device.

[0070] When the extended capacity controller 7 controls the control devices, on the one hand, it can be manually controlled by the operator. On the other hand, a control relationship table can also be built in the controller. When specifically executed, the extended capacity controller 7 can also perform corresponding outputs according to each input electrical signal without performing operations.

[0071] When the first bidirectional conversion circuit is connected to the DC bus, the control relationship table is shown in the following table for illustration.

[0072]

[0073] Table 1

[0074] In Table 1, the preset voltage threshold V1 refers to the charging voltage of the extended battery 2. Generally, the voltage of the extended battery 2 is slightly higher. For example, when the voltage across the extended battery 2 is 50V in the charging mode, the voltage across C1 is controlled to be slightly higher than the voltage of the extended battery, such as 52V, through the control of the switching device. The change rate of the voltage of C1 being less than the preset threshold, which can be ±0.3V, means that the voltage fluctuation of C1 is small and tends to be stable, that is, the extended battery 2 is fully charged. The preset voltage threshold V2 refers to the working voltage of the normal DC bus; when the voltage of C1 is greater than the preset voltage threshold, at this time, the voltage of C1 needs to be higher than the voltage of the DC bus, and at this time, it is necessary to step down to the voltage of the DC bus. When the voltage of C1 is less than the preset voltage threshold, at this time, the voltage of C1 needs to be less than the voltage of the DC bus, and at this time, it is necessary to step up to the voltage of the DC bus.

[0075] As Figure 4 shown, the extended protection control circuit may further include: a host battery controller 111 and a bus information collector 112.

[0076] The host battery controller 111 collects the working state of the host battery 1 and outputs a charging signal, a discharging signal, and a standby signal according to different working states; the bus information collector 112 is connected to the DC bus and collects the voltage signal of the DC bus;

[0077] The input end of the extended controller 7 is connected to the output end of the host battery controller 111 and the output end of the bus information collector 112.

[0078] In addition, in order to make the working states of the extended battery 2 and the host battery 1 consistent, the extended controller 7 may also control that only when the host battery 1 is in the charging state, the control relationship of item 2 in Table 1 above is executed. In addition, only when the host battery 1 is in the discharging state, the states of items 5 and 6 in Table 1 above are executed.

[0079] In addition, in order to facilitate the detection of the state of the extended battery, as Figure 2 and Figure 3 shown, in the embodiment of the present application, the extended protection circuit may further include: a voltage sensor 5 and a current sensor 6,

[0080] wherein, the two acquisition ends of the current sensor 6 are connected in series between the first end of the extended battery 2 and the first end of the first switching device Q1, and the output end of the current sensor 6 is connected to the input end of the extended protection controller 7;

[0081] The two acquisition ends of the voltage sensor 5 are respectively connected to the first end and the second end of the extended battery 2; the output end of the voltage sensor 5 is connected to the input end of the extended controller 7.

[0082] The voltage sensor 5 and the current sensor 6 respectively collect the voltage and current of the battery and input them into the expansion controller 7.

[0083] As Figure 5 shown, in the embodiment of the present application, an energy storage system is also disclosed. As Figure 5 shown, the host battery 1, the expansion battery 2, the DC bus 3, and the expansion control circuit 10 as described in each of the foregoing embodiments, wherein the host battery 1 is connected to the DC bus 3, and the expansion battery 2 is connected to the DC bus 3 through the expansion control circuit 10.

[0084] As Figure 5 shown, the energy storage system includes: a battery management module 03 and a second bidirectional conversion circuit 04. The battery management module 03 and the second bidirectional conversion circuit 04 are connected between the host battery 1 and the DC bus 3 for controlling the charge and discharge of the host battery 1.

[0085] When specifically connected, the two ends of the host battery 1 are connected to the first battery connection end and the second battery connection end of the battery management module. The first output end of the battery management module is connected to the first input end of the second bidirectional conversion circuit, and the second output end of the battery management module is connected to the second input end of the second bidirectional conversion circuit. The two output ends of the first bidirectional change circuit are connected to the DC bus.

[0086] The second bidirectional change circuit 04 stabilizes the DC bus voltage when the host battery 1 discharges, and adjusts the DC voltage at both ends of the host battery 1 to maintain charging when charging. The battery management module 03 is responsible for monitoring the host battery 1 and cutting the host battery 1 out of the circuit in case of abnormality to protect the battery safety.

[0087] In other embodiments of the present application, as Figure 5 shown, the energy storage system includes: a photovoltaic module 01 and a photovoltaic inverter 02; wherein, the photovoltaic module is connected to the DC bus through the photovoltaic inverter.

[0088] In the embodiment of the present application, the photovoltaic inverter 02 is a maximum power point tracking (MPPT). The MPPT controller is a solar controller and an upgraded product of the traditional solar charge and discharge controller. The photovoltaic unit in the photovoltaic module 01 converts solar energy into electrical energy, and then the MPPT maximum power controller controls the photovoltaic unit to generate electricity in the maximum power state and outputs DC electrical energy.

[0089] The specific embodiments described above further elaborate on the purpose, technical solution, and beneficial effects of this application. It should be understood that the above description is only the specific embodiments of this application and is not used to limit the protection scope of this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims

1. An expansion control circuit for an energy storage system, characterized in that Applied to an energy storage system, the energy storage system includes: a main battery, an expansion battery, and a DC bus. Among them, the main battery and the expansion battery are both connected to the DC bus; The expansion control circuit includes: an expansion protection circuit and a first bidirectional conversion circuit. Among them, the expansion battery is connected to the DC bus through the expansion protection circuit and the first bidirectional conversion circuit; The expansion protection circuit includes at least one normally open switch for controlling the connection between the expansion battery and the DC bus; the first bidirectional conversion circuit is connected to the bus through a first bus terminal and a second bus terminal; the first bidirectional conversion circuit is connected to the expansion battery through a first battery terminal and a second battery terminal; the first bidirectional conversion circuit includes a plurality of control switches for controlling step-up / step-down switching in the direction from the DC bus to the expansion battery and step-up / step-down switching in the direction from the expansion battery to the DC bus.

2. The capacity expansion control circuit according to claim 1, wherein The first bidirectional conversion circuit includes: a first capacitor, a second capacitor, a first inductor, a third switching device, a fourth switching device, a fifth switching device, and a sixth switching device; among them, The first battery terminal is respectively connected to the first end of the first capacitor and the first connection end of the third switching device; the second battery terminal is respectively connected to the second end of the first capacitor and the first connection end of the fourth switching device; The first bus terminal is respectively connected to the first end of the second capacitor and the first connection end of the fifth switching device; the second bus terminal is respectively connected to the second end of the second capacitor and the first connection end of the sixth switching device; The first end of the first inductor is respectively connected to the second connection end of the fourth switching device and the second connection end of the fourth switching device; the second end of the first inductor is respectively connected to the second connection end of the fifth switching device and the second connection end of the sixth switching device.

3. The capacity expansion control circuit according to claim 2, characterized in that, The normally open switch includes: a first switching device and a second switching device; The first end of the expansion battery is connected to the first connection end of the first switching device; the second connection end of the first switching device is connected to the first connection end of the second switching device; The second connection end of the second switching device is connected to the first battery terminal, and the second end of the expansion battery is connected to the second battery terminal.

4. The capacity expansion control circuit according to claim 3, wherein The expansion protection circuit further includes: an expansion controller, among which, The output end of the expansion controller is respectively connected to the control ends of the first switching device, the second switching device, the third switching device, the fourth switching device, the fifth switching device, and the sixth switching device to control the conduction or cutoff of each switching device.

5. The expansion control circuit according to claim 4, wherein The expansion protection circuit further includes: a main battery controller and a bus information collector, The main battery controller collects the working state of the main battery and outputs a charging signal, a discharging signal, and a standby signal according to different working states; the bus information collector is connected to the DC bus to collect the voltage signal of the DC bus; The input end of the expansion controller is connected to the output end of the main battery controller and the output end of the bus information collector.

6. The capacity expansion control circuit according to claim 5, wherein The expansion protection circuit includes: a voltage sensor and a current sensor, Among them, two acquisition ends of the current sensor are connected in series between the first end of the extended-capacity battery and the first end of the first switching device, and an output end of the current sensor is connected to an input end of the extended-capacity protection controller; Two acquisition ends of the voltage sensor are respectively connected to the first end and the second end of the extended-capacity battery; an output end of the voltage sensor is connected to an input end of the extended-capacity controller.

7. An energy storage system, characterized in that, The energy storage system includes: a main battery, an extended-capacity battery, a DC bus, and an extended-capacity control circuit according to any one of claims 1-6, wherein the main battery is connected to the DC bus, and the extended-capacity battery is connected to the DC bus through the extended-capacity control circuit; The extended-capacity control circuit includes: an extended-capacity protection circuit and a first bidirectional conversion circuit, wherein the extended-capacity battery is connected to the DC bus through the extended-capacity protection circuit and the first bidirectional conversion circuit; The extended-capacity protection circuit includes at least one normally open switch for controlling the connection between the extended-capacity battery and the DC bus; the first bidirectional conversion circuit is connected to the bus through a first bus end and a second bus end; the first bidirectional conversion circuit is connected to the extended-capacity battery through a first battery end and a second battery end; the first bidirectional conversion circuit includes a plurality of control switches for controlling step-up / step-down switching in the direction from the DC bus to the extended-capacity battery, and step-up / step-down switching in the direction from the extended-capacity battery to the DC bus.

8. The energy storage system according to claim 7, characterized in that, The energy storage system includes: a battery management module and a second bidirectional conversion circuit; The main battery is connected to the DC bus through the battery management module and the second bidirectional conversion circuit.

9. The energy storage system according to claim 8, wherein The energy storage system includes: a photovoltaic module and a photovoltaic inverter; The photovoltaic module is connected to the DC bus through the photovoltaic inverter.

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