A battery energy storage system

Abstract

This disclosure provides a battery energy storage system, including multiple battery modules, a controller, and DC-DC converters corresponding to each battery module. The battery modules are adapted to be connected to the DC bus of the battery energy storage system through the corresponding DC-DC converters. The controller is configured to control a first DC-DC converter to start in response to a start command, based on a target output current, such that the first DC-DC converter outputs current to the DC bus, so that the inrush current between the DC bus and the first DC-DC converter is less than or equal to a first threshold. The first DC-DC converter is any DC-DC converter in the battery energy storage system other than the first DC-DC converter to start.

Description

Technical Field

[0001] This disclosure relates to the field of energy storage technology, and more specifically, to a battery energy storage system. Background Technology

[0002] In recent years, the new energy industry has developed comprehensively and continued to grow. Among them, battery energy storage systems, as an indispensable part of the new energy industry, have seen the most rapid technological development, and more and more battery energy storage systems have emerged.

[0003] In existing battery energy storage systems, there are usually multiple battery modules, a DC-DC converter and a contactor corresponding to each battery module. Each battery module is connected to the input terminal of the corresponding DC-DC converter, and the output terminal of each DC-DC converter is connected to the DC bus through the corresponding contactor.

[0004] When the DC bus is connected to a load, the DC-DC converter's output current changes abruptly at the moment the corresponding contactor engages during startup. This short-term surge is significant, causing the DC-DC converter's control loop to malfunction and leading to startup failure. It may also cause other DC-DC converters on the bus to fail and shut down, significantly impacting the performance of the entire battery energy storage system. Summary of the Invention

[0005] One object of this disclosure is to provide a technical solution that can reduce the current surge generated when a DC-DC converter is connected in parallel to a DC bus.

[0006] According to one aspect of this disclosure, a battery energy storage system is provided, including a plurality of battery modules, a controller, and DC-DC converters corresponding to each of the battery modules, wherein the battery modules are adapted to be connected to the DC bus of the battery energy storage system through the corresponding DC-DC converters;

[0007] The controller is configured to respond to a start command and control the first DC-DC converter to start according to the target output current, such that the first DC-DC converter outputs current to the DC bus, so that the inrush current between the DC bus and the first DC-DC converter is less than or equal to a first threshold, wherein the first DC-DC converter is a DC-DC converter in the battery energy storage system other than the first DC-DC converter to start.

[0008] Optionally, the controller is further configured to: acquire a first actual inductor current through the inductor in the first DC-DC converter and a first actual output current actually output by the first DC-DC converter to the DC bus; determine a first target inductor current through the inductor in the first DC-DC converter based on the target output current and the first actual output current; obtain a modulation reference current based on the first target inductor current and the first actual inductor current; and generate a first modulation signal for driving the power transistor of the first DC-DC converter based on the modulation reference current, so that the first actual output current output by the first DC-DC converter reaches the target output current.

[0009] Optionally, when the controller generates a first modulation signal for driving the power transistor of the first DC-DC converter based on the modulation reference current, it is configured to: acquire a first actual input voltage and a first actual output voltage of the first DC-DC converter; determine the ratio of the first actual input voltage to the first actual output voltage; sum the ratio and the reference modulation current, and generate the first modulation signal based on the summation result.

[0010] Optionally, when the controller obtains the modulation reference current based on the first target inductor current and the first actual inductor current, it is configured to: perform proportional-integral control on the difference between the target output current and the first actual output current to obtain the first target inductor current; and perform proportional-integral control on the difference between the first target inductor current and the actual inductor current to obtain the modulation reference current.

[0011] Optionally, the controller is further configured to: when the output of the first DC-DC converter is detected to be stable, control the first DC-DC converter to output voltage to the DC bus according to the target output voltage.

[0012] Optionally, the controller is further configured to: detect the first actual output voltage and the first actual output current actually output by the first DC-DC converter to the DC bus, and determine that the output of the first DC-DC converter is stable when the fluctuation range of the first actual output voltage is less than or equal to a second threshold and the fluctuation range of the first actual output current is less than or equal to a third threshold.

[0013] Optionally, the controller is further configured to: control the first DC-DC converter to start according to the target output current, such that the inrush current between the DC bus and the first DC-DC converter is 0.

[0014] Optionally, when the controller controls the first DC-DC converter to output voltage to the DC bus according to the target output voltage, it is configured to:

[0015] The following steps are taken: 1. Obtain the average output current, the second actual output voltage and the second actual output current of the first DC-DC converter actually output to the DC bus, and the second actual inductor current through the inductor of the first DC-DC converter; wherein, the average output current is the average value of the actual output current of the DC-DC converters already activated in the battery energy storage system; 2. Determine the second target inductor current through the inductor of the first DC-DC converter based on the target output voltage, the average output current, the second actual output voltage, and the second actual output current; 3. Obtain a modulation reference voltage based on the second actual inductor current and the second target inductor current; 4. Generate a second modulation signal based on the modulation reference voltage to drive the power transistor of the first DC-DC converter, thereby driving the second actual output voltage output by the first DC-DC converter to reach the target output voltage.

[0016] Optionally, when the controller determines the second target inductor current through the inductor of the first DC-DC converter based on the target output voltage, the average output current, the second actual output voltage, and the second actual output current, it is configured to: determine the difference between the target output voltage and the second actual output voltage as a first difference; determine the difference between the second actual output current and the average output current as a second difference; and perform proportional-integral control on the sum of the first difference and the second difference to obtain the second target inductor current.

[0017] Optionally, when the controller obtains the modulation reference voltage based on the second actual inductor current and the second target inductor current, it is configured to: perform proportional-integral control on the difference between the second target inductor current and the second actual inductor current to obtain the modulation reference voltage.

[0018] Optionally, the controller is further configured to respond to a start command and, upon detecting that the voltage of the DC bus is zero, control the second DC-DC converter to start according to the target output voltage and output voltage to the DC bus, such that the voltage of the DC bus is equal to the third actual output voltage of the second DC-DC converter; wherein the second DC-DC converter is the first DC-DC converter to start in the energy storage system.

[0019] Through the embodiments of this disclosure, the controller controls the first DC-DC converter to start up according to the target output current, so that the first DC-DC converter outputs current to the DC bus to offset the inrush current between the DC bus and the first DC-DC converter, so that the inrush current is less than or equal to a first threshold. This can reduce the current inrush generated when the first DC-DC converter is connected in parallel to the DC bus, avoid the failure of the first DC-DC converter to start up, and also avoid the failure of other DC-DC converters to exit, thereby ensuring the power supply performance of the battery energy storage system.

[0020] Other features and advantages of this disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0021] The accompanying drawings, which form part of this specification, illustrate embodiments of this disclosure and, together with the specification, serve to explain the principles of this disclosure.

[0022] Figure 1 This is a circuit diagram of a battery energy storage system according to an embodiment of the present disclosure;

[0023] Figure 2 This is a circuit diagram of a battery energy storage system according to another embodiment of the present disclosure;

[0024] Figure 3 This is a schematic diagram of a constant voltage mode according to an embodiment of the present disclosure;

[0025] Figure 4 This is a schematic diagram of a constant current mode according to an embodiment of the present disclosure. Detailed Implementation

[0026] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present disclosure.

[0027] The following description of several exemplary embodiments is merely illustrative and is in no way intended to limit this disclosure or its application or use.

[0028] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0029] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0030] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0031] <Battery Energy Storage System>

[0032] Figure 1 This is a schematic block diagram of a battery energy storage system according to an embodiment of the present disclosure.

[0033] according to Figure 1 As shown, the battery energy storage system 1000 may include multiple battery modules 1100, a controller 1200, and DC-DC converters 1300 corresponding to each battery module 1100.

[0034] Battery module 1100 can be connected to the DC bus of battery energy storage system 1000 via a corresponding DC-DC converter 1300. Specifically, each battery module 1100 can be connected to the input terminal of the corresponding DC-DC converter 1300, and the output terminal of the DC-DC converter 1300 can be connected to the DC bus.

[0035] In this embodiment, the DC-DC converter 1300 can boost or buck the DC voltage provided by the battery module 1100 and output the processed DC voltage to the DC bus.

[0036] The controller 1200 is configured to respond to a start command and control the first DC-DC converter to start based on a target output current, causing the first DC-DC converter to output current to the DC bus, such that the inrush current between the DC bus and the first DC-DC converter is less than or equal to a first threshold. The first DC-DC converter is any DC-DC converter in the battery energy storage system 1000 other than the first one started. The first threshold is a current value preset according to the application scenario or specific requirements.

[0037] The target output current can be preset according to the application scenario or specific requirements, or it can be preset according to the load of the DC bus. The controller 1200 controls the first DC-DC converter to output current to the DC bus according to the target output current, so that the first actual output current of the first DC-DC converter to the DC bus gradually approximates the target output current.

[0038] In this embodiment, when all DC-DC converters are not activated, all battery modules are not connected to the DC bus through their respective DC-DC converters, and the voltage of the DC bus is zero. When at least one DC-DC converter is activated, the corresponding battery module is connected to the DC bus through the activated DC-DC converter, thus ensuring that the voltage of the DC bus is not zero.

[0039] When the first DC-DC converter starts up, the actual output voltage of the first DC-DC converter to the DC bus is different from the voltage of the DC bus, that is, there is a voltage difference between the DC bus and the first DC-DC converter, which causes an inrush current to be generated between the DC bus and the first DC-DC converter.

[0040] If the generated inrush current exceeds the first threshold, it may cause the control loop of the first DC-DC converter to malfunction, resulting in the failure of the first DC-DC converter to start up. It may also cause other DC-DC converters connected to the DC bus to fail and exit, which will have a significant impact on the performance of the entire battery energy storage system.

[0041] Specifically, after the first DC-DC converter starts up, it can output the voltage after boosting or bucking the DC voltage provided by the corresponding battery module to the DC bus, so that the voltage of the DC bus is not zero, that is, the voltage of the DC bus is approximately equal to the voltage of the battery module electrically connected to it.

[0042] When the controller 1200 controls the first DC-DC converter to start according to the target output current, the first DC-DC converter will start in constant current mode, that is, output current to the DC bus DC according to the target output current. The target output current is the expected value of the first actual output current of the first DC-DC converter to the DC bus DC.

[0043] Through the embodiments of this disclosure, the controller controls the first DC-DC converter to start up according to the target output current, so that the first DC-DC converter outputs current to the DC bus to offset the inrush current between the DC bus and the first DC-DC converter, so that the inrush current is less than or equal to a first threshold. This can reduce the current inrush generated when the first DC-DC converter is connected in parallel to the DC bus, avoid the failure of the first DC-DC converter to start up, and also avoid the failure of other DC-DC converters to exit, thereby ensuring the power supply performance of the battery energy storage system.

[0044] In one embodiment, such as Figure 1As shown, all DC-DC converters 1300 in the battery energy storage system 1000 can be connected to the controller 1200, meaning the DC-DC converters 1300 and the controller 1200 are provided by different devices. Specifically, the DC-DC converters 1300 and the controller 1200 can be connected via a CAN line.

[0045] In another embodiment, such as Figure 2 As shown, the battery energy storage system 1000 may include a controller 1200 corresponding to each DC-DC converter 1300. The corresponding DC-DC converter 1300 and controller 1200 may be provided by the same device or by different devices. Each controller may control the start-up of the corresponding DC-DC converter and control the corresponding DC-DC converter to output voltage or current to the DC bus.

[0046] In one embodiment of this disclosure, such as Figure 2 As shown, the battery energy storage system 1000 may also include a contactor 1400 corresponding to the DC-DC converter 1300. The contactor 1400 may be connected between the output terminal of the corresponding DC-DC converter 1300 and the DC bus.

[0047] The controller 1200 can also be configured to close the contactor 1300 in response to a start command, so that the corresponding DC-DC converter 1300 is connected in parallel to the DC bus.

[0048] In one embodiment of this disclosure, the controller 1200 is further configured to: control the first DC-DC converter to start according to the target output current, such that the first actual output current of the first DC-DC converter to the DC bus is 0.

[0049] Specifically, if a voltage difference exists between the DC bus and the first DC-DC converter, the first DC-DC converter can output current to the DC bus to offset the inrush current by providing a first actual output current to the DC bus based on the first target output current. Ultimately, the target output current must be zero, and under this condition, the inrush current must be less than or equal to a first threshold. The inrush current is caused by the voltage difference between the DC bus and the first DC-DC converter.

[0050] The first actual output current output by the first DC-DC converter based on the first target output current cancels out the inrush current, ultimately making the first actual output current zero. This minimizes the current surge generated when the first DC-DC converter is connected in parallel to the DC bus. Furthermore, making the first actual output current zero ensures that the actual output voltage of the first DC-DC converter equals the voltage of the DC bus, facilitating the controller 1200's control of the first DC-DC converter.

[0051] In one embodiment of this disclosure, the controller 1200 may further be configured to: acquire a first actual inductor current through an inductor in the first DC-DC converter and a first actual output current actually output by the first DC-DC converter to the DC bus; determine a first target inductor current through an inductor in the first DC-DC converter based on a target output current and the first actual output current; obtain a modulation reference current based on the first target inductor current and the first actual inductor current; and generate a first modulation signal for driving the power transistor of the first DC-DC converter based on the modulation reference current, so that the first actual output current output by the first DC-DC converter reaches the target output current.

[0052] Wherein, the first actual output current is the current actually output by the first DC-DC converter when the controller 1200 controls the first DC-DC converter to output current to the DC bus according to the target output current. The first actual inductor current is the actual current through the inductor in the first DC-DC converter when the controller 1200 controls the first DC-DC converter to output current to the DC bus according to the target output current. The first target inductor current is the target current through the inductor in the first DC-DC converter when the controller 1200 controls the first DC-DC converter to output current to the DC bus according to the target output current.

[0053] In this embodiment, the DC-DC converter can boost or buck the input voltage; therefore, the DC-DC converter can include at least a power transistor and an inductor. Thus, the first actual inductor current can be the current flowing through the inductor in the first DC-DC converter.

[0054] The controller 1200 generates a first modulation signal in this embodiment to drive the power transistor of the first DC-DC converter, thereby controlling the output current of the first DC-DC converter and enabling the first actual output current of the first DC-DC converter to reach the target output current.

[0055] In one embodiment of this disclosure, such as Figure 3 As shown, when the controller 1200 determines the first target inductor current of the DC-DC converter based on the target output current and the actual output current, it is also configured to: perform proportional-integral control on the difference between the target output current Iobj and the first actual output current I1out to obtain the first target inductor current IL1obj; and perform proportional-integral control on the difference between the first target inductor current IL1obj and the first actual inductor current IL1 to obtain the modulation reference current Iref.

[0056] The controller 1200 obtains the modulation reference current through this embodiment, which enables the first modulation signal generated based on the modulation reference current to more accurately control the output current of the first DC-DC converter.

[0057] In one embodiment of this disclosure, such as Figure 3 As shown, when the controller 1200 generates a first modulation signal for driving the power transistor of the first DC-DC converter based on the modulation reference current, it is also configured to: acquire the first actual input voltage Uin and the first actual output voltage U1out of the first DC-DC converter; determine the ratio T of the first actual input voltage Uin and the first actual output voltage U1out; sum the ratio T with the reference modulation current Iref, and generate the first modulation signal based on the summation result.

[0058] The first actual output voltage is the voltage actually output by the first DC-DC converter when the controller 1200 controls the first DC-DC converter to output current to the DC bus according to the target output current.

[0059] Specifically, the comparison value T and the reference modulation current Iref are summed, and a first modulation signal is generated based on the summation result. Alternatively, the summation result can be amplified by a first set factor, and the ratio between the amplified summation result and the first set value can be determined as the first ratio. A first modulation signal with a duty cycle of the first ratio is then generated.

[0060] The first set multiple and the first set value can be set in advance according to the application scenario or specific needs.

[0061] In this embodiment, the duty cycle of the first modulation signal can be adjusted gradually from the initial value corresponding to the ratio T of the actual input voltage and the first actual output voltage, based on the sum of the ratio T of the first actual input voltage Uin and the first actual output voltage U1out and the reference modulation current Iref.

[0062] The controller 1200 generates a first modulation signal in this embodiment to drive the power transistor of the first DC-DC converter, which can make the control of the output current of the first DC-DC converter more precise.

[0063] In another embodiment of this disclosure, when the controller 1200 generates a first modulation signal for driving the power transistor of the first DC-DC converter based on the modulation reference current, it is further configured to: amplify the modulation reference current by a second set factor, determine the ratio between the amplified modulation reference current and the second set value as the second ratio, and generate a first modulation signal with a duty cycle of the second ratio.

[0064] The second set multiple and the second set value can be set in advance according to the application scenario or specific needs.

[0065] In this embodiment, the duty cycle of the first modulation signal can be started from zero and gradually adjusted according to the reference modulation current Iref.

[0066] In one embodiment of this disclosure, the controller 1200 is further configured to: control the first DC-DC converter to output voltage to the DC bus according to the target output voltage when the output of the first DC-DC converter is detected to be stable.

[0067] When the output of the first DC-DC converter is stable, the controller 1200 switches from a constant current mode, which controls the output current of the first DC-DC converter to the DC bus based on the target output current, to a constant voltage mode, which controls the output voltage of the first DC-DC converter to the DC bus based on the target output voltage. This can improve the power supply efficiency of the battery energy storage system.

[0068] In one embodiment of this disclosure, the controller 1200 is further configured to: detect the first actual output voltage and the first actual output current of the first DC-DC converter actually output to the DC bus, and determine that the output of the first DC-DC converter is stable when the fluctuation range of the first actual output voltage is less than or equal to a second threshold and the fluctuation range of the first actual output current is less than or equal to a third threshold.

[0069] The second threshold is a voltage value preset according to the application scenario or specific requirements, and the third threshold is a current value preset according to the application scenario or specific requirements. The fluctuation range of the first actual output voltage is less than or equal to the second threshold, meaning the difference between the maximum and minimum values ​​of the first actual output voltage within the set time period is less than or equal to the second threshold. The fluctuation range of the first actual output current is less than or equal to the third threshold, meaning the difference between the maximum and minimum values ​​of the first actual output current within the set time period is less than or equal to the third threshold.

[0070] If the fluctuation range of the first actual output voltage is less than or equal to the second threshold and the fluctuation range of the first actual output current is less than or equal to the third threshold, the output of the first DC-DC converter is determined to be stable. The first DC-DC converter can be switched from constant current mode to constant voltage mode in a timely manner to improve the power supply efficiency of the battery energy storage system.

[0071] In one embodiment of this disclosure, when the controller 1200 controls the first DC-DC converter to output voltage to the DC bus according to the target output voltage, it is configured to: acquire the average output current, the second actual output voltage and the second actual output current actually output by the first DC-DC converter to the DC bus, and the second actual inductor current through the inductor of the first DC-DC converter; wherein, the average output current is the average value of the actual output current of the DC-DC converters that have been started in the battery energy storage system; determine the second target inductor current through the inductor of the first DC-DC converter according to the target output voltage, the average output current, the second actual output voltage, and the second actual output current; obtain a modulation reference voltage according to the second actual inductor current and the second target inductor current; and generate a second modulation signal for driving the power transistor of the first DC-DC converter according to the modulation reference voltage, so as to drive the second actual output voltage output by the first DC-DC converter to reach the target output voltage.

[0072] Wherein, the second actual output voltage is the voltage actually output by the first DC-DC converter when the controller 1200 controls the first DC-DC converter to output voltage to the DC bus according to the target output current. The second actual inductor current is the actual current through the inductor of the first DC-DC converter when the controller 1200 controls the first DC-DC converter to output voltage to the DC bus according to the target output current. The second actual output current is the actual current output by the first DC-DC converter when the controller 1200 controls the first DC-DC converter to output voltage to the DC bus according to the target output current. The second target inductor current is the target current through the inductor of the first DC-DC converter when the controller 1200 controls the first DC-DC converter to output voltage to the DC bus according to the target output current.

[0073] Specifically, when the DC-DC converter is started, it can collect its own actual output current at the corresponding first sampling frequency and upload the collected actual output current to the controller 1200. The controller 1200 can determine the average value of the latest uploaded actual output current of each started DC-DC converter as the average output current.

[0074] The controller 1200 generates a second modulation signal in this embodiment to drive the power transistor of the first DC-DC converter, thereby controlling the output voltage of the first DC-DC converter and enabling the second actual output voltage of the first DC-DC converter to reach the target output voltage.

[0075] In one embodiment of this disclosure, such as Figure 4As shown, when the controller 1200 determines the second target inductor current through the inductor of the first DC-DC converter based on the target output voltage, average output current, second actual output voltage, and second actual output current, it is configured to: determine the difference between the target output voltage Uobj and the second actual output voltage U2out as the first difference U1; determine the difference between the second actual output current I2out and the average output current Iavg as the second difference I1; and perform proportional-integral control on the sum of the first difference U1 and the second difference I1 to obtain the second target inductor current IL2obj.

[0076] The controller 1200 obtains the second target inductor current through this embodiment, which enables the second modulation signal generated based on the second target inductor current to more accurately control the output voltage of the first DC-DC converter.

[0077] In one embodiment of this disclosure, such as Figure 4 As shown, when the controller 1200 obtains the modulation reference voltage based on the second actual inductor current and the second target inductor current, it is configured to perform proportional-integral control on the difference between the second target inductor current IL2obj and the second actual inductor current IL2 to obtain the modulation reference voltage Uref.

[0078] The controller 1200 obtains the modulation reference voltage through this embodiment, which enables the second modulation signal generated based on the modulation reference voltage to more accurately control the output voltage of the first DC-DC converter.

[0079] In one embodiment of this disclosure, a second modulation signal is generated based on a modulation reference voltage to drive the power transistor of the first DC-DC converter to output a target output voltage. This can be achieved by amplifying the modulation reference voltage by a third set factor, determining the ratio between the amplified modulation reference voltage and the third set value, and using this ratio as the third ratio; and then generating a second modulation signal with a duty cycle of the third ratio.

[0080] The third setting multiple and the third setting value can be set in advance according to the application scenario or specific needs.

[0081] In one embodiment of this disclosure, the controller 1200 is further configured to, in response to a start command, control the second DC-DC converter to start according to a target output voltage and output voltage to the DC bus when the voltage of the DC bus is detected to be zero, such that the voltage of the DC bus is equal to the third actual output voltage of the second DC-DC converter; wherein the second DC-DC converter is the first DC-DC converter to start in the energy storage system.

[0082] In this embodiment, the controller 1200 controls the second DC-DC converter to start according to the target output voltage and output voltage to the DC bus, so that the voltage of the DC bus is equal to the third actual output voltage of the second DC-DC converter. This method can be referred to as the method by which the controller 1200 controls the first DC-DC converter to output voltage to the DC bus according to the target output voltage.

[0083] Specifically, when the controller 1200 controls the second DC-DC converter to output voltage to the DC bus according to the target output voltage, it is configured to: acquire the average output current, the third actual output voltage of the second DC-DC converter, and the third actual inductor current through the inductor of the second DC-DC converter; wherein, the average output current is the average value of the actual output current of the DC-DC converters that have been started in the battery energy storage system; determine the third target inductor current through the inductor of the second DC-DC converter according to the target output voltage, the average output current, the third actual output voltage, and the third actual output current; obtain another modulation reference voltage according to the third actual inductor current and the third target inductor current; and generate a third modulation signal for driving the power transistor of the second DC-DC converter according to the other modulation reference voltage, so as to drive the third actual output voltage output by the second DC-DC converter to reach the target output voltage.

[0084] In one embodiment of this disclosure, when the controller 1200 determines the third target inductor current through the inductor of the second DC-DC converter based on the target output voltage, average output current, third actual output voltage, and third actual output current, it is configured to: determine the difference between the target output voltage and the third actual output voltage as a third difference; determine the difference between the third actual output current and the average output current as a fourth difference; and perform proportional-integral control on the sum of the third difference and the fourth difference to obtain the third target inductor current.

[0085] In one embodiment of this disclosure, when the controller 1200 obtains the other modulation reference voltage based on the third actual inductor current and the third target inductor current, it is configured to: perform proportional-integral control on the difference between the third target inductor current and the third actual inductor current to obtain the other modulation reference voltage.

[0086] In one embodiment of this disclosure, a third modulation signal is generated based on another modulation reference voltage to drive the power transistor of the second DC-DC converter to output a target output voltage. This can be achieved by amplifying the other modulation reference voltage by a fourth set factor, determining the ratio between the amplified other modulation reference voltage and the fourth set value as the fourth ratio, and generating a third modulation signal with a duty cycle of the fourth ratio.

[0087] The fourth setting multiple and the fourth setting value can be set in advance according to the application scenario or specific needs.

[0088] In this embodiment, the controller controls the second DC-DC converter to start up according to the target output voltage and output voltage to the DC bus, so that the second DC-DC converter starts up in constant voltage mode. This can establish voltage support for the DC bus, allowing the controller to control the first DC-DC converter to start up in constant current mode. This reduces the current surge generated when the first DC-DC converter is connected in parallel to the DC bus, avoids startup failure of the first DC-DC converter, and also avoids failure shutdown of other DC-DC converters, thereby ensuring the power supply performance of the battery energy storage system.

[0089] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein. The scope of the invention is defined by the appended claims.

Claims

1. A battery energy storage system, characterized in that, It includes multiple battery modules, a controller, and a DC-DC converter corresponding to each battery module. The battery modules are adapted to be connected to the DC bus of the battery energy storage system through the corresponding DC-DC converter. The controller is configured to respond to a start command and control the first DC-DC converter to start in constant current mode according to the target output current, so that the first DC-DC converter outputs current to the DC bus, so that the inrush current between the DC bus and the first DC-DC converter is less than or equal to a first threshold, wherein the first DC-DC converter is a DC-DC converter in the battery energy storage system other than the first DC-DC converter to start. The controller is also configured to: when the output of the first DC-DC converter is detected to be stable, control the first DC-DC converter to switch to constant voltage mode to output voltage to the DC bus according to the target output voltage.

2. The battery energy storage system according to claim 1, characterized in that, The controller is further configured to: acquire a first actual inductor current through the inductor in the first DC-DC converter, and a first actual output current actually output by the first DC-DC converter to the DC bus; determine a first target inductor current through the inductor in the first DC-DC converter based on the target output current and the first actual output current; and obtain a modulation reference current based on the first target inductor current and the first actual inductor current. A first modulation signal is generated based on the modulation reference current to drive the power transistor of the first DC-DC converter, so that the first actual output current output by the first DC-DC converter reaches the target output current.

3. The battery energy storage system according to claim 2, characterized in that, When the controller generates a first modulation signal for driving the power transistor of the first DC-DC converter based on the modulation reference current, it is configured to: acquire the first actual input voltage and the first actual output voltage of the first DC-DC converter; and determine the ratio of the first actual input voltage to the first actual output voltage. The ratio and the reference modulation current are summed, and the first modulation signal is generated based on the summation result.

4. The battery energy storage system according to claim 2, characterized in that, When the controller obtains the modulation reference current based on the first target inductor current and the first actual inductor current, it is configured to: perform proportional-integral control on the difference between the target output current and the first actual output current to obtain the first target inductor current. The difference between the first target inductor current and the actual inductor current is subjected to proportional-integral control to obtain the modulation reference current.

5. The battery energy storage system according to claim 1, characterized in that, The controller is further configured to: detect the first actual output voltage and the first actual output current actually output by the first DC-DC converter to the DC bus, and determine that the output of the first DC-DC converter is stable when the fluctuation range of the first actual output voltage is less than or equal to a second threshold and the fluctuation range of the first actual output current is less than or equal to a third threshold.

6. The battery energy storage system according to claim 1, characterized in that, The controller is also configured to: control the first DC-DC converter to start according to the target output current, so that the first actual output current actually output by the first DC-DC converter to the DC bus is 0.

7. The battery energy storage system according to claim 1, characterized in that, When the controller controls the first DC-DC converter to output voltage to the DC bus according to the target output voltage, it is configured as follows: The following steps are taken:

1. Obtain the average output current, the second actual output voltage and the second actual output current of the first DC-DC converter actually output to the DC bus, and the second actual inductor current through the inductor of the first DC-DC converter; wherein, the average output current is the average value of the actual output current of the DC-DC converters already activated in the battery energy storage system; 2. Determine the second target inductor current through the inductor of the first DC-DC converter based on the target output voltage, the average output current, the second actual output voltage, and the second actual output current; 3. Obtain a modulation reference voltage based on the second actual inductor current and the second target inductor current; 4. Generate a second modulation signal based on the modulation reference voltage to drive the power transistor of the first DC-DC converter, thereby driving the second actual output voltage output by the first DC-DC converter to reach the target output voltage.

8. The battery energy storage system according to claim 7, characterized in that, When the controller determines the second target inductor current through the inductor of the first DC-DC converter based on the target output voltage, the average output current, the second actual output voltage, and the second actual output current, it is configured to: determine the difference between the target output voltage and the second actual output voltage as the first difference; The difference between the second actual output current and the average output current is determined as the second difference; The sum of the first difference and the second difference is subjected to proportional-integral control to obtain the second target inductor current.

9. The battery energy storage system according to claim 7, characterized in that, When the controller obtains the modulation reference voltage based on the second actual inductor current and the second target inductor current, it is configured to perform proportional-integral control on the difference between the second target inductor current and the second actual inductor current to obtain the modulation reference voltage.

10. The battery energy storage system according to claim 1, characterized in that, The controller is also configured to respond to a start command and, upon detecting that the voltage of the DC bus is zero, control the second DC-DC converter to start according to the target output voltage and output voltage to the DC bus, such that the voltage of the DC bus is equal to the third actual output voltage of the second DC-DC converter; wherein the second DC-DC converter is the first DC-DC converter to start in the energy storage system.

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