A low-frequency ripple suppression device and system for a battery in series structure

Abstract

The application discloses a low-frequency ripple suppression device for a battery in a series structure, comprising: a first cascaded multi-level sub-module and a second cascaded multi-level sub-module which are connected in series and output, both comprising a battery pack and H-bridge switching tubes connected to both ends of the battery pack, which convert direct current output by the battery pack into alternating current output; a first capacitor is connected between both ends of the H-bridge switching tubes of the first cascaded multi-level sub-module, and a second capacitor is connected between both ends of the H-bridge switching tubes of the second cascaded multi-level sub-module; wherein the instantaneous power provided by the first capacitor and the second capacitor is equal to the pulsating power of the first cascaded multi-level sub-module and the second cascaded multi-level sub-module. The device can solve the problem that the existing battery energy storage system suppresses pulsating current by inserting a filter or increasing a conversion circuit, which greatly increases the cost, volume, circuit complexity and control difficulty of the system.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a battery low-frequency ripple suppression device and a battery low-frequency ripple suppression system with a series structure. Background Technology

[0002] The cascade multilevel converter (CMC) structure has advantages such as high modularity, good harmonic characteristics, and low single-unit power rating, making it very suitable as a power conversion device for large-capacity battery energy storage systems. However, the CMC submodule is a single-phase H-bridge converter. During power conversion, a pulsating current with twice the output frequency will appear on the DC side of the H-bridge. This low-frequency pulsating current far exceeds the battery's tolerance. If it flows directly into the battery, it will damage the battery's lifespan.

[0003] To suppress secondary ripple current flowing into the battery from the CMC submodule, a common method is to insert an LC filter at the H-bridge DC bus. However, the filter has a low cutoff frequency, and the large number of CMC submodules makes it difficult to optimize system size and weight. Another approach is to improve the submodule into a two-stage conversion circuit, adding a DC / DC converter between the original submodule's DC side and the battery, and connecting a bidirectional buck-boost circuit in parallel at the DC end of each submodule, which functions similarly to a DC APF. Both methods effectively reduce ripple flowing into the battery, but significantly increase control and circuit complexity, cost, and size. Summary of the Invention

[0004] In response to at least one defect or improvement requirement of the prior art, the present invention provides a series-structured battery low-frequency ripple suppression system, method and application, which aims to solve the problem that the existing battery energy storage system suppresses pulsating current by inserting filters or adding conversion circuits, resulting in a significant increase in system cost, size, circuit complexity and control difficulty.

[0005] To achieve the above objectives, according to a first aspect of the present invention, a battery low-frequency ripple suppression device with a series structure is provided, comprising: a first cascaded multilevel submodule and a second cascaded multilevel submodule connected in series; both the first cascaded multilevel submodule and the second cascaded multilevel submodule include a battery pack and an H-bridge switch connected to both ends of the battery pack, wherein the H-bridge switch converts the DC power output from the battery pack into AC power output; wherein the first end of the H-bridge switch of the first cascaded multilevel submodule is connected in series with the second end of the H-bridge switch of the second cascaded multilevel submodule, and the first... The second terminal of the H-bridge switch of the cascaded multilevel submodule and the first terminal of the H-bridge switch of the second cascaded multilevel submodule are connected to the transmission bus as AC output side; a first capacitor is connected between the first terminal of the H-bridge switch of the first cascaded multilevel submodule and the second terminal of the H-bridge switch of the first cascaded multilevel submodule, and a second capacitor is connected between the first terminal of the H-bridge switch of the second cascaded multilevel submodule and the second terminal of the H-bridge switch of the second cascaded multilevel submodule; wherein, the instantaneous power provided by the first capacitor and the second capacitor is equal to the pulsating power of the AC output side.

[0006] In one embodiment of the present invention, the series-connected battery low-frequency ripple suppression device further includes: a control module, used to acquire the output voltage through the first capacitor and the second capacitor, perform proportional-integral control according to a preset voltage value, and drive the H-bridge switch to switch after sinusoidal pulse width modulation.

[0007] In one embodiment of the present invention, the control module applies bias voltages of equal magnitude and opposite direction to the output voltage of the first capacitor and the output voltage of the second capacitor, respectively.

[0008] In one embodiment of the present invention, the control module controls the magnitude of the bias voltage so that the instantaneous power provided by the first capacitor and the second capacitor is equal to the pulsating power on the AC output side of the first cascaded multilevel submodule and the second cascaded multilevel submodule.

[0009] According to a second aspect of the present invention, a series-connected battery low-frequency ripple suppression system is also provided, comprising: a plurality of cascaded multilevel module groups, respectively connected in series to a power transmission bus, wherein each of the cascaded multilevel module groups includes a first cascaded multilevel submodule and a second cascaded multilevel submodule; the first cascaded multilevel submodule and the second cascaded multilevel submodule each include a battery pack and an H-bridge switch connected to both ends of the battery pack, wherein the H-bridge switch converts the DC power output from the battery pack into AC power output; wherein the first end of the H-bridge switch of the first cascaded multilevel submodule is connected to the second end of the H-bridge switch of the second cascaded multilevel submodule. The two terminals are connected in series, and the second terminal of the H-bridge switch of the first cascaded multilevel submodule and the first terminal of the H-bridge switch of the second cascaded multilevel submodule are connected to the power transmission bus as AC output side; a first capacitor is connected between the first terminal of the H-bridge switch of the first cascaded multilevel submodule and the second terminal of the H-bridge switch of the first cascaded multilevel submodule, and a second capacitor is connected between the first terminal of the H-bridge switch of the second cascaded multilevel submodule and the second terminal of the H-bridge switch of the second cascaded multilevel submodule; wherein, the instantaneous power provided by the first capacitor and the second capacitor is equal to the pulsating power of the AC output side.

[0010] In one embodiment of the present invention, the series-connected battery low-frequency ripple suppression system further includes: a control module, used to acquire the output voltage through the first capacitor and the second capacitor, perform proportional-integral control according to a preset voltage value, and drive the H-bridge switch to switch after sinusoidal pulse width modulation.

[0011] In one embodiment of the present invention, the control module applies bias voltages of equal magnitude and opposite direction to the output voltage of the first capacitor and the output voltage of the second capacitor, respectively.

[0012] In one embodiment of the present invention, the control module controls the magnitude of the bias voltage so that the instantaneous power provided by the first capacitor and the second capacitor is equal to the pulsating power on the AC output side of the first cascaded multilevel submodule and the second cascaded multilevel submodule.

[0013] In general, compared with the prior art, the above-described technical solutions conceived by this invention can achieve at least the following beneficial effects:

[0014] By grouping two cascaded multilevel submodules with series outputs together, and connecting a capacitor to the AC output side of each cascaded multilevel submodule, the instantaneous power provided by the two capacitors in the same group of cascaded multilevel submodules is controlled to be equal to the pulsating power of the two cascaded multilevel submodules. That is, the capacitor provides low-frequency AC pulsating power, which enables low-frequency ripple current to flow only through the H-bridge inverter in the cascaded multilevel submodule and no longer through the battery pack. This can effectively reduce the problem of battery life reduction caused by low-frequency ripple. Moreover, the system has a simple structure and does not require the insertion of filters or the addition of conversion circuits to suppress pulsating current, which can effectively reduce system cost, size, circuit complexity and control difficulty. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of a series-connected battery low-frequency ripple suppression device provided in an embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram of a battery energy storage system without the introduction of low-frequency ripple suppression.

[0018] Figure 3 This is a schematic diagram illustrating the control principle of the cascaded multilevel submodule provided in an embodiment of the present invention.

[0019] Figure 4 This is a schematic diagram of a series-connected battery low-frequency ripple suppression system provided in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0021] The terms "first," "second," "third," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0022] like Figure 1 As shown, the first embodiment of the present invention proposes a battery low-frequency ripple suppression device with a series structure, which includes, for example, a first cascaded multilevel submodule (CMC submodule 1) and a second cascaded multilevel submodule (CMC submodule 2) with outputs connected in series.

[0023] Both CMC submodule 1 and CMC submodule 2 include a battery pack and an H-bridge switch connected to both ends of the battery pack. The H-bridge switch converts the DC power output from the battery pack into AC power output. Specifically, the first end of the H-bridge switch in CMC submodule 1 is connected in series with the second end of the H-bridge switch in CMC submodule 2, and the second end of the H-bridge switch in CMC submodule 1 and the first end of the H-bridge switch in CMC submodule 2 are connected to the power transmission bus as AC output sides.

[0024] Furthermore, a first capacitor C1 is connected between the first terminal of the H-bridge switch of CMC submodule 1 and the second terminal of the H-bridge switch of CMC submodule 1, and a second capacitor C2 is connected between the first terminal of the H-bridge switch of CMC submodule 2 and the second terminal of the H-bridge switch of CMC submodule 2; wherein, the instantaneous power provided by the first capacitor C1 and the second capacitor C2 is equal to the pulsating power of CMC submodule 1 and CMC submodule 2.

[0025] Specifically, in combination Figure 2 The battery energy storage system without low-frequency ripple suppression shown in this embodiment provides a detailed explanation of its technical solution and beneficial effects:

[0026] exist Figure 2 In the absence of low-frequency ripple suppression, since the sub-modules in CMC module group 1 are connected in series, the current is equal to i. o =I max sin(ωt).

[0027] The output voltage of submodule 1 in the CMC module group is an AC sinusoidal voltage: V1 = Vmax sin(wt).

[0028] The output voltage of submodule 2 in the CMC module group is an AC sinusoidal voltage: V2 = Vmax sin(wt).

[0029] The CMC module output voltage is: v 组1 =V1+V2=2Vmax sin(wt).

[0030] The instantaneous AC power of the CMC module group is: p 组1 =v 组1 io = V max I max +V max I max cos(2ωt).

[0031] It can be seen that without low-frequency ripple suppression methods, the average power and instantaneous pulsating power in the CMC module group are transmitted to the battery pack, which will generate low-frequency ripple in the battery pack and reduce battery life.

[0032] exist Figure 1 When low-frequency ripple suppression is added, since the sub-modules in the CMC module group are connected in series, the voltage is equal to v. o =V max sin(ωt), first capacitor C1 = second capacitor C2 = C.

[0033] In the CMC module group, submodule 1 outputs an AC sinusoidal voltage with bias F(t) = Asin(wt+θ): V1 = Vc1 = Vmax sin(wt) + Asin(wt+θ); the output current is: The instantaneous power of C1 is: p C 1 = Vc1ic1.

[0034] In the CMC module group, submodule 2 outputs an AC sinusoidal voltage with a bias F(t): V2 = Vc2 = Vmaxsin(wt) - Asin(wt+θ); the output current is: The instantaneous power of C2 is: p C2 =Vc1ic1.

[0035] The output voltage of CMC module group 1 is: v 组1 =V1+V2=Vc1+Vc2=2Vmax sin(wt), low-frequency ripple suppression does not change the output voltage of the module group.

[0036] The instantaneous AC power provided by C1 and C2 in CMC module group 1 is: p C 1+p C2 =wCV 2 maxsin(2wt)+wCA 2 sin(2wt+2θ).

[0037] CMC module group 1 outputs instantaneous power p 组1 =v 组1 io = V max I max +V max I max cos(2ωt).

[0038] By controlling the voltage waveform function F(t) = Asin(wt + θ) of the energy storage circuit, the instantaneous power of the energy storage circuit capacitor can be made equal to the pulsating power on the AC side. Specifically, let wCV 2 maxsin(2wt)+wCA 2 sin(2wt+2θ)=V max I max cos(2ωt), then wCA 2 sin(2wt+2θ)=V max I max cos(2ωt)-wCV 2 maxsin(2wt).

[0039] The waveform function F(t) = Asin(wt + θ) can be obtained by calculating using trigonometric functions:

[0040]

[0041] Therefore, after adding low-frequency ripple suppression, the low-frequency AC pulsation power in the cascaded multilevel module group is provided by the capacitor, and the power provided by the battery is only the average power without low-frequency AC pulsation components. The low-frequency ripple current only flows through the H-bridge inverter in each CMC sub-module and no longer flows through the battery pack, thus eliminating the low-frequency ripple measured by the battery.

[0042] like Figure 3 The diagram shows the control principle of the cascaded multilevel submodule. In the CMC module group, the controller collects the output voltages of capacitors C1 and C2 in submodule 1 and submodule 2, respectively, and compares them with the given output voltage values ​​of inductors C1 and C2. After the comparison results are subjected to PI (proportional-integral) control, they are subjected to PWM control (sine pulse width calculation) and then fed to the H-bridge switches in submodule 1 and submodule 2 respectively to drive the H-bridge switches to switch.

[0043] In summary, the battery low-frequency ripple suppression device with a series structure proposed in the first embodiment of the present invention, by grouping two cascaded multilevel sub-modules with series outputs into a group, and connecting a capacitor to the AC output side of each cascaded multilevel sub-module, controls the instantaneous power provided by the two capacitors of the same group of cascaded multilevel sub-modules to be equal to the pulsating power of the two cascaded multilevel sub-modules. That is, the low-frequency AC pulsating power is provided by the capacitor, so that the low-frequency ripple current only flows through the H-bridge inverter in the cascaded multilevel sub-module and no longer flows through the battery pack, which can effectively reduce the problem of battery life reduction caused by low-frequency ripple. Moreover, the system has a simple structure and does not require the insertion of filters or the addition of conversion circuits to suppress pulsating current, which can effectively reduce system cost, size, circuit complexity and control difficulty.

[0044] like Figure 4 As shown, the second embodiment of the present invention also proposes a series-structured battery low-frequency ripple suppression system, for example including: a plurality of cascaded multilevel module groups, respectively connected in series to a power transmission bus, wherein each of the cascaded multilevel module groups includes a first cascaded multilevel submodule and a second cascaded multilevel submodule; the first cascaded multilevel submodule and the second cascaded multilevel submodule each include a battery pack and an H-bridge switch connected to both ends of the battery pack, wherein the H-bridge switch converts the DC power output from the battery pack into AC power output; wherein, the first end of the H-bridge switch of the first cascaded multilevel submodule is connected to the first end of the H-bridge switch of the second cascaded multilevel submodule. The two terminals are connected in series, and the second terminal of the H-bridge switch of the first cascaded multilevel submodule and the first terminal of the H-bridge switch of the second cascaded multilevel submodule are connected to the power transmission bus as AC output side; a first capacitor is connected between the first terminal of the H-bridge switch of the first cascaded multilevel submodule and the second terminal of the H-bridge switch of the first cascaded multilevel submodule, and a second capacitor is connected between the first terminal of the H-bridge switch of the second cascaded multilevel submodule and the second terminal of the H-bridge switch of the second cascaded multilevel submodule; wherein, the instantaneous power provided by the first capacitor and the second capacitor is equal to the pulsating power of the AC output side.

[0045] In one embodiment, the series-connected battery low-frequency ripple suppression system further includes: a control module, used to acquire the output voltage through the first capacitor and the second capacitor, perform proportional-integral control according to a preset voltage value, and drive the H-bridge switch to switch after sinusoidal pulse width modulation.

[0046] In one embodiment, the control module applies bias voltages of equal magnitude and opposite direction to the output voltages of the first capacitor and the second capacitor, respectively.

[0047] In one embodiment, the control module controls the magnitude of the bias voltage so that the instantaneous power provided by the first capacitor and the second capacitor is equal to the pulsating power on the AC output side of the first cascaded multilevel submodule and the second cascaded multilevel submodule.

[0048] It is worth mentioning that the series-structured battery low-frequency ripple suppression system disclosed in the second embodiment of the present invention includes the series-structured battery low-frequency ripple suppression device proposed in the first embodiment. The specific structure and function of the battery low-frequency ripple suppression device can be referred to the content described in the first embodiment. For the sake of brevity, it will not be described in detail here. Moreover, the series-structured battery low-frequency ripple suppression system provided in this embodiment has the same beneficial effects as the series-structured battery low-frequency ripple suppression device provided in the first embodiment.

[0049] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0050] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0051] In the several embodiments provided by this invention, it should be understood that the disclosed apparatus can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some service interface; the indirect coupling or communication connection between devices or units may be electrical or other forms.

[0052] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0053] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0054] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage device (CMD). Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a memory and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned memory includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0055] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, which may include: a flash drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, etc.

[0056] The foregoing description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of other embodiments of this disclosure upon considering the specification and practicing the disclosure herein. This invention is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

[0057] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0058] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A battery low-frequency ripple suppression device with a series structure, characterized in that, include: The first cascaded multilevel submodule and the second cascaded multilevel submodule are connected in series for output; Both the first cascaded multilevel submodule and the second cascaded multilevel submodule include a battery pack and an H-bridge switch connected to both ends of the battery pack. The H-bridge switch converts the DC power output from the battery pack into AC power output. The first end of the H-bridge switch in the first cascaded multilevel submodule is connected in series with the second end of the H-bridge switch in the second cascaded multilevel submodule, and the second end of the H-bridge switch in the first cascaded multilevel submodule and the first end of the H-bridge switch in the second cascaded multilevel submodule are connected to the power transmission bus as AC output sides. A first capacitor is connected between the first terminal of the H-bridge switch of the first cascaded multilevel submodule and the second terminal of the H-bridge switch of the first cascaded multilevel submodule, and a second capacitor is connected between the first terminal of the H-bridge switch of the second cascaded multilevel submodule and the second terminal of the H-bridge switch of the second cascaded multilevel submodule; wherein the instantaneous power provided by the first capacitor and the second capacitor is equal to the pulsating power of the AC output side.

2. The battery low-frequency ripple suppression device with a series structure according to claim 1, characterized in that, Also includes: The control module is used to acquire the output voltage through the first capacitor and the second capacitor, perform proportional-integral control according to the preset voltage value, and drive the H-bridge switching transistor to switch after sinusoidal pulse width modulation.

3. The battery low-frequency ripple suppression device with a series structure according to claim 2, characterized in that, The control module applies bias voltages of equal magnitude and opposite direction to the output voltages of the first capacitor and the second capacitor, respectively.

4. The battery low-frequency ripple suppression device with a series structure according to claim 3, characterized in that, The control module controls the magnitude of the bias voltage so that the instantaneous power provided by the first capacitor and the second capacitor is equal to the pulsating power on the AC output side of the first cascaded multilevel submodule and the second cascaded multilevel submodule.

5. A series-connected battery low-frequency ripple suppression system, characterized in that, include: Several cascaded multilevel module groups are connected in series to the power transmission bus, wherein each cascaded multilevel module group includes a first cascaded multilevel submodule and a second cascaded multilevel submodule; Both the first cascaded multilevel submodule and the second cascaded multilevel submodule include a battery pack and an H-bridge switch connected to both ends of the battery pack. The H-bridge switch converts the DC power output from the battery pack into AC power output. The first end of the H-bridge switch in the first cascaded multilevel submodule is connected in series with the second end of the H-bridge switch in the second cascaded multilevel submodule, and the second end of the H-bridge switch in the first cascaded multilevel submodule and the first end of the H-bridge switch in the second cascaded multilevel submodule are connected to the power transmission bus as AC output sides. A first capacitor is connected between the first terminal of the H-bridge switch of the first cascaded multilevel submodule and the second terminal of the H-bridge switch of the first cascaded multilevel submodule, and a second capacitor is connected between the first terminal of the H-bridge switch of the second cascaded multilevel submodule and the second terminal of the H-bridge switch of the second cascaded multilevel submodule; wherein the instantaneous power provided by the first capacitor and the second capacitor is equal to the pulsating power of the AC output side.

6. The battery low-frequency ripple suppression system with a series structure according to claim 5, characterized in that, Also includes: The control module is used to acquire the output voltage through the first capacitor and the second capacitor, perform proportional-integral control according to the preset voltage value, and drive the H-bridge switching transistor to switch after sinusoidal pulse width modulation.

7. The battery low-frequency ripple suppression system with a series structure according to claim 6, characterized in that, The control module applies bias voltages of equal magnitude and opposite direction to the output voltages of the first capacitor and the second capacitor, respectively.

8. The battery low-frequency ripple suppression system with a series structure according to claim 7, characterized in that, The control module controls the magnitude of the bias voltage so that the instantaneous power provided by the first capacitor and the second capacitor is equal to the pulsating power on the AC output side of the first cascaded multilevel submodule and the second cascaded multilevel submodule.

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