Direct-hanging energy storage current converter and control method thereof

Abstract

The invention provides a direct-hanging energy storage current converter and a control method thereof, each energy storage branch in the direct-hanging energy storage current converter is connected between a direct current bus and a grounding end, each energy storage branch comprises a balance bridge arm, a bridge arm reactor and a first energy storage bridge arm, the balance bridge arm is used for maintaining energy balance between the balance bridge arm and the first energy storage bridge arm, and the bridge arm reactor is connected with the first energy storage bridge arm. The bridge arm reactor is used for filtering the current of the balance bridge arm or the current of the first energy storage bridge arm, and the first energy storage bridge arm is used for storing energy from the direct current bus. According to the invention, energy balance can be realized through the balance bridge arm, and the voltage stress of the first energy storage bridge arm is greatly reduced, so that the direct-hanging energy storage converter can be applied to a high-voltage scene. According to the invention, the voltage level and the series level of the energy storage array can be effectively reduced, the fireproof isolation design of the energy storage battery is facilitated, the current sharing control of the first energy storage bridge arm and the second energy storage bridge arm can be realized, and the controllable throughput of the power of the direct-hanging energy storage converter can be realized.

Description

Technical Field

[0001] The present application relates to the technical field of flexible direct current transmission, and in particular to a direct-mounted energy storage converter and a control method thereof. Background Art

[0002] With the increasing proportion of new energy sources such as photovoltaics and wind power, the power system is gradually transitioning to a stage characterized by a high proportion of new energy and power electronic equipment. Since new energy has the characteristics of randomness, volatility and intermittency, and energy storage devices can perform grid peak and frequency regulation, improve power quality and enhance the stability of the power system, they can effectively achieve a dynamic balance between new energy generation and grid power.

[0003] In recent years, with the rapid development of flexible DC transmission technology and DC power grid, energy storage devices such as direct-mounted energy storage converters have received widespread attention. Direct-mounted energy storage converters can be directly connected in parallel to the DC power grid, greatly improving their ability to actively support long-term inertia, shaving peaks and filling valleys, and fault crossing. They have significant advantages such as simple operation control, fast response speed, strong system stability, and real-time online investment and withdrawal. They are suitable for DC transmission scenarios such as offshore wind power. However, the direct-mounted energy storage converters provided by the relevant technology cannot maintain energy balance, resulting in large voltage stress on the energy storage bridge arm, and cannot be applied to high-voltage scenarios. In other words, the direct-mounted energy storage converters provided by the relevant technology have poor applicability. Summary of the invention

[0004] In order to solve the problem of poor applicability in the prior art, the present application provides a direct-mounted energy storage converter, which may include multiple energy storage branches. The multiple energy storage branches are all connected between a DC bus and a ground terminal. That is, the first end of each of the multiple energy storage branches is connected to the DC bus, and the second end of each energy storage branch is connected to the ground terminal.

[0005] Each of the multiple energy storage branches includes a balancing bridge arm, a bridge arm reactance and a first energy storage bridge arm. The balancing bridge arm is connected to the first energy storage bridge arm through a common point. The bridge arm reactance is located between the balancing bridge arm and the common point, or the bridge arm reactance is located between the common point and the first energy storage bridge arm.

[0006] The balancing bridge arm is used to maintain energy balance between the balancing bridge arm and the first energy storage bridge arm.

[0007] The bridge arm reactance is used to filter the current of the balancing bridge arm or the current of the first energy storage bridge arm.

[0008] The first energy storage bridge arm is used to store energy from the DC bus.

[0009] In some possible implementations, the balanced bridge arm includes a plurality of first submodules connected in series. The first submodules adopt a half-bridge topology structure or a full-bridge topology structure.

[0010] In some other possible implementations, the first energy storage bridge arm includes a plurality of second submodules connected in series.

[0011] The second submodule adopts a half-bridge topology structure, a full-bridge topology structure, a half-bridge-dual active topology structure, or a full-bridge-dual active topology structure.

[0012] Exemplarily, the first submodule includes a voltage stabilizing capacitor. Of course, the first submodule also includes a power tube and the like.

[0013] The second submodule includes one or more energy storage batteries connected in series. Of course, the second submodule also includes a power tube and the like.

[0014] Furthermore, each energy storage branch also includes a second energy storage bridge arm. The second energy storage bridge arm is connected in parallel with the first energy storage bridge arm to form an energy storage array.

[0015] On the other hand, the present application also provides a control method for a direct-mounted energy storage converter, comprising:

[0016] The DC voltage at the common point, the AC voltage at the common point, the actual AC current of the energy storage branch in the direct-mounted energy storage converter, and the voltage of the DC bus are collected.

[0017] The AC / DC decoupling control of the balancing bridge arm in the direct-mounted energy storage converter is performed according to the DC voltage at the common point, the AC voltage at the common point and the actual AC current of the energy storage branch.

[0018] According to the actual AC current of the energy storage branch and the voltage of the DC bus, the first energy storage bridge arm in the direct-mounted energy storage converter is subjected to constant voltage control, constant power control or electric energy maintenance control.

[0019] In a possible implementation, the AC / DC decoupling control of the balancing bridge arm in the direct-mounted energy storage converter is performed according to the DC voltage at the common point, the AC voltage at the common point, and the actual AC current of the energy storage branch, including:

[0020] The DC voltage at the common point is subtracted from a preset DC reference voltage to obtain a DC voltage difference, and the DC voltage difference is proportionally and integrally controlled to obtain the input quantity of the first submodule in the balanced bridge arm corresponding to the DC component of the bridge arm.

[0021] The AC voltage at the common point is subtracted from a preset AC reference voltage to obtain an AC voltage difference, and the AC voltage difference is subjected to proportional-integral control to obtain a reference AC current of the energy storage branch.

[0022] The actual AC current of the energy storage branch is subtracted from the reference AC current of the energy storage branch to obtain a first current difference, and the first current difference is subjected to proportional integral control to obtain the input quantity of the first submodule corresponding to the AC component of the bridge arm.

[0023] The number of first submodules in the balanced bridge arm corresponding to the DC component of the bridge arm is added to the number of first submodules in the balanced bridge arm corresponding to the AC component of the bridge arm to obtain the number of first submodules in the balanced bridge arm.

[0024] The input quantity of the first submodule in the balance bridge arm is modulated to obtain a first driving signal and drive the first submodule.

[0025] In another possible implementation, the first energy storage bridge arm in the direct-mounted energy storage converter is subjected to constant voltage control, constant power control or power maintenance control according to the actual AC current of the energy storage branch and the voltage of the DC bus, including:

[0026] The direct-mounted energy storage converter is controlled at a constant voltage according to the voltage of the DC bus and the actual AC current of the energy storage branch.

[0027] Constant power control is performed according to the actual AC current of the energy storage branch and the output power of the direct-mounted energy storage converter.

[0028] When the charging voltage of each energy storage battery in the first energy storage bridge arm reaches a preset first voltage threshold or the discharging voltage of each energy storage battery reaches a preset second voltage threshold, the first energy storage bridge arm is controlled to maintain power; wherein the first voltage threshold is greater than the second voltage threshold.

[0029] Furthermore, the direct-mounted energy storage converter is controlled at a constant voltage according to the voltage of the DC bus and the actual AC current of the energy storage branch, including:

[0030] The voltage of the DC bus is controlled by an outer loop, and the actual AC current of the energy storage branch is controlled by an inner loop. Or,

[0031] Collect the DC component of the balancing bridge arm or the first energy storage bridge arm, and the AC component of the balancing bridge arm or the first energy storage bridge arm; use the DC component of the balancing bridge arm or the first energy storage bridge arm to perform voltage outer loop control on the voltage of the DC bus, and use the AC component of the balancing bridge arm or the first energy storage bridge arm to perform current inner loop control on the actual AC current of the energy storage branch.

[0032] Exemplarily, the constant power control is performed according to the actual AC current of the energy storage branch and the output power of the direct-mounted energy storage converter, including:

[0033] Collect the output power of the direct-mounted energy storage inverter.

[0034] The output power of the direct-mounted energy storage converter is controlled by an outer power loop, and the actual AC current of the energy storage branch is controlled by an inner current loop; or, the DC component of the balancing bridge arm or the first energy storage bridge arm, and the AC component of the balancing bridge arm or the first energy storage bridge arm are collected, and the DC component of the balancing bridge arm or the first energy storage bridge arm is used to control the output power of the direct-mounted energy storage converter by an outer power loop, and the AC component of the balancing bridge arm or the first energy storage bridge arm is used to control the actual AC current of the energy storage branch by an inner current loop.

[0035] In some other possible implementations, the control method provided by the present application further includes:

[0036] The first bridge arm current of the first energy storage bridge arm and the second bridge arm current of the second energy storage bridge arm in the direct-mounted energy storage converter are collected.

[0037] Calculate the average current of the first bridge arm current and the second bridge arm current.

[0038] The first bridge arm current is subtracted from the average current to obtain a second current difference, and proportional-integral control is performed on the second current difference.

[0039] The second bridge arm current is subtracted from the average current to obtain a third current difference, and proportional-integral control is performed on the third current difference.

[0040] Compared with the prior art, the beneficial effects of this application are:

[0041] In the direct-mounted energy storage converter provided by the present application, each energy storage branch is connected between the DC bus and the ground terminal, and each energy storage branch includes a balancing bridge arm, a bridge arm reactance, and a first energy storage bridge arm. The balancing bridge arm is used to maintain the energy balance between the balancing bridge arm and the first energy storage bridge arm, and the bridge arm reactance is used to filter the current of the balancing bridge arm or the current of the first energy storage bridge arm. The first energy storage bridge arm is used to store energy from the DC bus. It can be seen that the present application can achieve energy storage through the first energy storage bridge arm, and energy balance through the balancing bridge arm, which greatly reduces the voltage stress of the first energy storage bridge arm, so that the direct-mounted energy storage converter can be applied to high-voltage scenarios.

[0042] In the direct-mounted energy storage inverter provided in the present application, each bridge arm is independently controlled and has low coupling, and has the advantages of energy replenishment, grid support, and battery protection.

[0043] The direct-mounted energy storage converter provided in this application has good power quality, high equivalent switching frequency, fast limit response speed, controllable safety risks, and high working efficiency.

[0044] The present application can effectively reduce the voltage level and the number of series connections of the energy storage array, and is beneficial to the fire isolation design of the energy storage battery.

[0045] The present application can realize current sharing control of the first energy storage bridge arm and the second energy storage bridge arm, and further realize controllable power throughput of the direct-mounted energy storage converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the present application or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0047] Figure 1 This is a schematic structural diagram of a direct-mounted energy storage converter in an embodiment of the present application;

[0048] Figure 2 This is another schematic structural diagram of the direct-mounted energy storage converter in the embodiment of the present application;

[0049] Figure 3a This is a schematic diagram of a half-bridge topology structure adopted by the first submodule in an embodiment of the present application;

[0050] Figure 3b This is a schematic diagram of a full-bridge topology structure adopted by the first submodule in an embodiment of the present application;

[0051] Figure 4a This is a schematic diagram of a half-bridge topology structure adopted by the second submodule in an embodiment of the present application;

[0052] Figure 4b This is a schematic diagram of a full-bridge topology structure adopted by the second submodule in an embodiment of the present application;

[0053] Figure 4c This is a schematic diagram of a half-bridge-dual active topology structure adopted by the second submodule in an embodiment of the present application;

[0054] Figure 4d This is a schematic diagram of a full-bridge-dual active topology structure adopted by the second submodule in an embodiment of the present application;

[0055] Figure 5 This is a schematic structural diagram of a direct-mounted energy storage converter in an embodiment of the present application;

[0056] Figure 6 This is another schematic structural diagram of the direct-mounted energy storage converter in the embodiment of the present application;

[0057] Figure 7 A schematic flowchart of a control method for a direct-mounted energy storage inverter in an embodiment of the present application. DETAILED DESCRIPTION

[0058] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0059] The terms "first", "second", etc. in the specification embodiments, claims, and drawings of the present application are only used for the purpose of distinguishing descriptions, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, including a series of steps or units. The method, system, product, or device is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or devices.

[0060] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0061] The present application embodiment provides a direct-mounted energy storage converter, such as Figure 1 and Figure 2 As shown. The direct-mounted energy storage converter 100 may include a plurality of energy storage branches. The plurality of energy storage branches are all connected between the DC bus BUS and the ground terminal. That is, the first end of each of the plurality of energy storage branches is connected to the DC bus BUS, and the second end of each energy storage branch is connected to the ground terminal.

[0062] The embodiment of the present application is described by taking the direct-mounted energy storage converter 100 including two energy storage branches as an example. The two energy storage branches include energy storage branch 11 and energy storage branch 12. Each energy storage branch (i.e., energy storage branch 11 and energy storage branch 12) includes a balancing bridge arm 1A, a bridge arm reactance L1, and a first energy storage bridge arm 1B. The balancing bridge arm 1A is connected to the first energy storage bridge arm 1B via a common point S. The bridge arm reactance L1 is located between the balancing bridge arm 1A and the common point S, as shown in FIG. Figure 1 Alternatively, the bridge arm reactance L1 is located between the common point S and the first energy storage bridge arm 1B, as shown in Figure 2 shown.

[0063] The balancing bridge arm 1A is used to maintain energy balance between the balancing bridge arm 1A and the first energy storage bridge arm 1B.

[0064] The bridge arm reactance L1 is used to filter the current of the balancing bridge arm 1A or the current of the first energy storage bridge arm 1B.

[0065] The first energy storage bridge arm 1B is used to store energy from the DC bus BUS.

[0066] In some embodiments, Figure 1 and Figure 2 As shown, the balanced bridge arm 1A includes a plurality of first submodules SM1 connected in series. The first submodule SM1 adopts Figure 3a The half-bridge topology shown or Figure 3b The full-bridge topology shown in the figure, etc.

[0067] refer to Figure 3a and Figure 3b The first submodule SM1 includes a voltage stabilizing capacitor C1. Of course, the first submodule SM1 also includes a power tube and the like. Figure 3a The half-bridge topology structure shown further includes a power tube S1 and a power tube S2. Figure 3b The full-bridge topology structure shown further includes a power tube S1 , a power tube S2 , a power tube S3 and a power tube S4 .

[0068] It is conceivable that the first submodule SM1 can be switched on or off by controlling the power tube inside the first submodule SM1 to be switched on or off.

[0069] In other embodiments, Figure 1 and Figure 2 As shown, the first energy storage bridge arm 1B includes a plurality of second submodules SM2 connected in series.

[0070] The second submodule SM2 adopts Figure 4a The half-bridge topology shown in the figure Figure 4b The full-bridge topology shown in Figure 4c The half-bridge dual active topology shown or Figure 4d The full-bridge-dual active topology shown in the figure can realize the electrical isolation between the energy storage battery and the DC bus.

[0071] refer to Figures 4a to 4d The second submodule SM2 includes one or more energy storage batteries connected in series. The multiple energy storage batteries connected in series may include energy storage batteries B1 to BN.

[0072] Of course, the second submodule SM2 also includes a power tube and the like. Figure 4aThe half-bridge topology structure shown further includes a power tube S1 and a power tube S2. Figure 4b The full-bridge topology structure shown further includes a power tube S1 , a power tube S2 , a power tube S3 and a power tube S4 . Figure 4c The half-bridge dual active topology structure shown also includes power tube S1, power tube S2, power tube S3, power tube S4, power tube S5, power tube S6, power tube S7, power tube S8, power tube S9, power tube S10, capacitor C2, inductor L2 and transformer T. Figure 4d The full-bridge-dual active topology structure shown also includes power tube S1, power tube S2, power tube S3, power tube S4, power tube S5, power tube S6, power tube S7, power tube S8, power tube S9, power tube S10, power tube S11, power tube S12, capacitor C2, inductor L2 and transformer T.

[0073] It is conceivable that the second submodule SM2 can be switched on or off by controlling the power tube inside the second submodule SM2 to be switched on or off.

[0074] Optionally, the power tube may be a power tube with a diode connected in anti-parallel.

[0075] For example, Figure 5 and Figure 6 As shown, each energy storage branch (such as energy storage branch 11 and energy storage branch 12) further includes a second energy storage bridge arm 1C. The second energy storage bridge arm 1C is connected in parallel with the first energy storage bridge arm 1B to form an energy storage array.

[0076] The second energy storage bridge arm 1C may include a plurality of third submodules SM3 connected in series. The specific structure of the third submodule SM3 may refer to the second submodule SM2, and will not be described in detail in the present embodiment.

[0077] The present application also provides a control method for a direct-mounted energy storage converter. Figure 7 The control method may include the following steps:

[0078] Step S1: collecting the DC voltage of the common point S, the AC voltage of the common point S, the actual AC current of the energy storage branches (such as the energy storage branch 11 and the energy storage branch 12) in the direct-mounted energy storage converter 100, and the voltage of the DC bus.

[0079] Step S2: performing AC / DC decoupling control on the balancing bridge arm 1A in the direct-mounted energy storage converter 100 according to the DC voltage at the common point S, the AC voltage at the common point S and the actual AC current of the energy storage branches (such as the energy storage branches 11 and 12).

[0080] Step S3: performing constant voltage control, constant power control or power maintenance control on the first energy storage bridge arm 1B in the direct-mounted energy storage converter 100 according to the actual AC current of the energy storage branch (such as energy storage branch 11 and energy storage branch 12) and the voltage of the DC bus.

[0081] In a possible implementation, in the above step S2, the AC / DC decoupling control of the balancing bridge arm 1A in the direct-mounted energy storage converter 100 is performed according to the DC voltage of the common point S, the AC voltage of the common point S and the actual AC current of the energy storage branch (such as the energy storage branch 11 and the energy storage branch 12), including:

[0082] The DC voltage at the common point S is subtracted from the preset DC reference voltage to obtain a DC voltage difference, which is then proportionally and integrally controlled to obtain the number of first submodules SM1 in the balanced bridge arm 1A corresponding to the DC component of the bridge arm (which can be represented by N1).

[0083] The AC voltage at the common point S is subtracted from a preset AC reference voltage to obtain an AC voltage difference, and the AC voltage difference is proportionally and integrally controlled to obtain a reference AC current of the energy storage branch (such as energy storage branch 11 and energy storage branch 12).

[0084] The actual AC current of the energy storage branch (such as energy storage branch 11 and energy storage branch 12) is subtracted from the reference AC current of the energy storage branch (such as energy storage branch 11 and energy storage branch 12) to obtain a first current difference, and the first current difference is subjected to proportional integral control to obtain the number of first submodules SM1 put into operation corresponding to the AC component of the bridge arm (which can be represented by N2).

[0085] The number of first submodules SM1 in the balanced bridge arm 1A corresponding to the DC component of the bridge arm is added together with the number of first submodules SM1 in the balanced bridge arm 1A corresponding to the AC component of the bridge arm, N2, to obtain the number of first submodules SM1 in the balanced bridge arm 1A (which can be represented by N3). That is, N3 = N1 + N2.

[0086] The input quantity N3 of the first submodule SM1 in the balancing bridge arm 1A is modulated to obtain a first driving signal and drive the first submodule SM1.

[0087] In another possible implementation, in the above step S3, the first energy storage bridge arm 1B in the direct-mounted energy storage converter 100 is subjected to constant voltage control, constant power control or power maintenance control according to the actual AC current of the energy storage branch (such as the energy storage branch 11 and the energy storage branch 12) and the voltage of the DC bus BUS, including:

[0088] Step S31: performing constant voltage control on the direct-mounted energy storage converter 100 according to the voltage of the DC bus BUS and the actual AC current of the energy storage branch (such as the energy storage branch 11 and the energy storage branch 12).

[0089] Step S32: performing constant power control according to the actual AC current of the energy storage branch (such as the energy storage branch 11 and the energy storage branch 12) and the output power of the direct-mounted energy storage inverter 100.

[0090] Step S33: When the charging voltage of each energy storage battery in the first energy storage bridge arm 1B reaches a preset first voltage threshold or the discharging voltage of each energy storage battery reaches a preset second voltage threshold, the first energy storage bridge arm 1B is controlled to maintain power; wherein the first voltage threshold is greater than the second voltage threshold.

[0091] Furthermore, in step S31, the direct-mounted energy storage converter 100 is controlled at a constant voltage according to the voltage of the DC bus BUS and the actual AC current of the energy storage branch (such as the energy storage branch 11 and the energy storage branch 12), which can be achieved in the following two ways:

[0092] Method 1: Performing voltage outer loop control on the voltage of the DC bus BUS, and performing current inner loop control on the actual AC current of the energy storage branch (such as the energy storage branch 11 and the energy storage branch 12).

[0093] Method 2: Collect the DC component of the balancing bridge arm 1A or the first energy storage bridge arm 1B, and the AC component of the balancing bridge arm 1A or the first energy storage bridge arm 1B; use the DC component of the balancing bridge arm 1A or the first energy storage bridge arm 1B to perform voltage outer loop control on the voltage of the DC bus BUS, and use the AC component of the balancing bridge arm 1A or the first energy storage bridge arm 1B to perform current inner loop control on the actual AC current of the energy storage branch (such as energy storage branch 11 and energy storage branch 12).

[0094] Exemplarily, in step S32, constant power control is performed according to the actual AC current of the energy storage branch (such as the energy storage branch 11 and the energy storage branch 12) and the output power of the direct-mounted energy storage converter 100, including:

[0095] The output power of the direct-mounted energy storage inverter 100 is collected.

[0096] The output power of the direct-mounted energy storage converter 100 is controlled by an outer power loop, and the actual AC current of the energy storage branch (such as the energy storage branch 11 and the energy storage branch 12) is controlled by an inner current loop. Alternatively, the DC component of the balancing bridge arm 1A or the first energy storage bridge arm 1B and the AC component of the balancing bridge arm 1A or the first energy storage bridge arm 1B can be collected, and the DC component of the balancing bridge arm 1A or the first energy storage bridge arm 1B is used to control the output power of the direct-mounted energy storage converter 100 by an outer power loop, and the AC component of the balancing bridge arm 1A or the first energy storage bridge arm 1B is used to control the actual AC current of the energy storage branch (such as the energy storage branch 11 and the energy storage branch 12) by an inner current loop.

[0097] In some other possible implementations, the control method provided in the embodiment of the present application further includes:

[0098] The first bridge arm current of the first energy storage bridge arm 1B and the second bridge arm current of the second energy storage bridge arm 1C in the direct-mounted energy storage converter 100 are collected.

[0099] Calculate the average current of the first bridge arm current and the second bridge arm current.

[0100] The first bridge arm current is subtracted from the average current to obtain a second current difference, and proportional-integral control is performed on the second current difference.

[0101] The second bridge arm current is subtracted from the average current to obtain a third current difference, and proportional-integral control is performed on the third current difference.

[0102] It can be seen that the above process can make the current of the first bridge arm and the current of the second bridge arm as consistent as possible with the average current, that is, the current sharing of the first energy storage bridge arm 1B and the second energy storage bridge arm 1C can be achieved. The multi-bridge arm automatic current sharing control can improve the transient steady-state performance of the direct-mounted energy storage converter by introducing a deviation current feedback link, with higher control accuracy, and the current sharing adjustment of a single bridge arm will not affect the operating status of other bridge arms.

[0103] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A direct-mounted energy storage inverter, characterized in that: It includes multiple energy storage branches; the multiple energy storage branches are all connected between the DC bus and the ground terminal; Each of the multiple energy storage branches includes a balancing bridge arm, a bridge arm reactance and a first energy storage bridge arm; the balancing bridge arm is connected to the first energy storage bridge arm through a common point, and the bridge arm reactance is located between the balancing bridge arm and the common point, or the bridge arm reactance is located between the common point and the first energy storage bridge arm; The balancing bridge arm is used to: maintain energy balance between the balancing bridge arm and the first energy storage bridge arm; The bridge arm reactance is used to: filter the current of the balancing bridge arm or the current of the first energy storage bridge arm; The first energy storage bridge arm is used to store energy from the DC bus.

2. The direct-mounted energy storage inverter according to claim 1, characterized in that: The balancing bridge arm comprises a plurality of first submodules connected in series; The first submodule adopts a half-bridge topology structure or a full-bridge topology structure.

3. The direct-mounted energy storage inverter according to claim 2, characterized in that: The first energy storage bridge arm includes a plurality of second submodules connected in series; The second submodule adopts a half-bridge topology structure, a full-bridge topology structure, a half-bridge-dual active topology structure or a full-bridge-dual active topology structure.

4. The direct-mounted energy storage inverter according to claim 3 is characterized in that: The first submodule includes a voltage stabilizing capacitor; The second submodule includes one or more energy storage batteries connected in series.

5. The direct-mounted energy storage inverter according to claim 1, characterized in that: Each of the energy storage branches also includes a second energy storage bridge arm; The second energy storage bridge arm is connected in parallel with the first energy storage bridge arm to form an energy storage array.

6. A control method for a direct-mounted energy storage converter, characterized in that: include: Collecting the DC voltage of the common point, the AC voltage of the common point, the actual AC current of the energy storage branch in the direct-mounted energy storage converter, and the voltage of the DC bus; Performing AC / DC decoupling control on the balancing bridge arm in the direct-hung energy storage converter according to the DC voltage of the common point, the AC voltage of the common point and the actual AC current of the energy storage branch; The first energy storage bridge arm in the direct-hung energy storage converter is subjected to constant voltage control, constant power control or electric energy maintenance control according to the actual alternating current of the energy storage branch and the voltage of the DC bus.

7. The control method according to claim 6, characterized in that: The method of performing AC / DC decoupling control on the balancing bridge arm in the direct-hung energy storage converter according to the DC voltage of the common point, the AC voltage of the common point and the actual AC current of the energy storage branch includes: Subtracting the DC voltage of the common point from a preset DC reference voltage to obtain a DC voltage difference, and performing proportional-integral control on the DC voltage difference to obtain the number of first submodules in the balancing bridge arm corresponding to the DC component of the bridge arm; Subtracting the AC voltage at the common point from a preset AC reference voltage to obtain an AC voltage difference, and performing proportional-integral control on the AC voltage difference to obtain a reference AC current of the energy storage branch; Subtracting the actual AC current of the energy storage branch from the reference AC current of the energy storage branch to obtain a first current difference, and performing proportional integral control on the first current difference to obtain the number of the first submodules that are put into operation corresponding to the AC component of the bridge arm; Adding the number of first submodules in the balanced bridge arm corresponding to the DC component of the bridge arm and the number of first submodules in the balanced bridge arm corresponding to the AC component of the bridge arm to obtain the number of first submodules in the balanced bridge arm; The input quantity of the first submodule in the balancing bridge arm is modulated to obtain a first driving signal and drive the first submodule.

8. The control method according to claim 6, characterized in that: The method of performing constant voltage control, constant power control or electric energy maintenance control on the first energy storage bridge arm in the direct-hung energy storage converter according to the actual alternating current of the energy storage branch and the voltage of the DC bus includes: Performing constant voltage control on the direct-mounted energy storage converter according to the voltage of the DC bus and the actual AC current of the energy storage branch; Performing constant power control according to the actual AC current of the energy storage branch and the output power of the direct-mounted energy storage converter; When the charging voltage of each energy storage battery in the first energy storage bridge arm reaches a preset first voltage threshold or the discharging voltage of each energy storage battery reaches a preset second voltage threshold, the first energy storage bridge arm is controlled to maintain power; wherein the first voltage threshold is greater than the second voltage threshold.

9. The control method according to claim 8, characterized in that: The method of controlling the direct-mounted energy storage converter to a constant voltage according to the voltage of the DC bus and the actual AC current of the energy storage branch includes: Performing voltage outer loop control on the voltage of the DC bus, and performing current inner loop control on the actual AC current of the energy storage branch; or, Collect the DC component of the balancing bridge arm or the first energy storage bridge arm, and the AC component of the balancing bridge arm or the first energy storage bridge arm; use the DC component of the balancing bridge arm or the first energy storage bridge arm to perform voltage outer-loop control on the voltage of the DC bus, and use the AC component of the balancing bridge arm or the first energy storage bridge arm to perform current inner-loop control on the actual AC current of the energy storage branch.

10. The control method according to claim 8, characterized in that: The constant power control is performed according to the actual AC current of the energy storage branch and the output power of the direct-mounted energy storage converter, including: Collecting the output power of the direct-mounted energy storage inverter; The output power of the direct-mounted energy storage converter is controlled by an outer power loop, and the actual AC current of the energy storage branch is controlled by an inner current loop; or, the DC component of the balancing bridge arm or the first energy storage bridge arm, and the AC component of the balancing bridge arm or the first energy storage bridge arm are collected, and the DC component of the balancing bridge arm or the first energy storage bridge arm is used to control the output power of the direct-mounted energy storage converter by an outer power loop, and the AC component of the balancing bridge arm or the first energy storage bridge arm is used to control the actual AC current of the energy storage branch by an inner current loop.

11. The control method according to claim 6, characterized in that: The control method further comprises: Collecting a first bridge arm current of the first energy storage bridge arm and a second bridge arm current of the second energy storage bridge arm in the direct-mounted energy storage converter; Calculating an average current of the first bridge arm current and the second bridge arm current; Subtracting the first bridge arm current from the average current to obtain a second current difference, and performing proportional-integral control on the second current difference; The second bridge arm current is subtracted from the average current to obtain a third current difference, and proportional-integral control is performed on the third current difference.

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