A device for direct connection of energy storage to DC bus and its control method

Abstract

This invention provides an energy storage direct-connection DC bus interface device and its control method, comprising: an energy storage battery unit, a voltage compensator, and a controller; the voltage compensator and the energy storage battery unit are connected in series between the positive and negative terminals of the DC bus; the voltage compensator includes: multiple sub-modules connected in series; the rated voltage of each sub-module is equal; the controller is used to determine the sub-modules to be positively and negatively connected based on the current of the energy storage battery unit; that is, the controller can determine the number of sub-modules to be switched on and off based on the current, and control the switching state of the corresponding sub-modules; in addition, the capacity efficiency of the voltage compensator is adjustable, realizing efficient operation of the whole machine, and the capacity that can be connected can be larger; at the same time, a reference current is set to reduce the switching frequency of each sub-module and improve the conversion efficiency of the entire system.

Description

Technical Field

[0001] This invention belongs to the field of DC bus technology, and more specifically, relates to an energy storage direct-connected DC bus interface device and its control method. Background Technology

[0002] To promote the optimization and upgrading of the energy industry, wind power and photovoltaic power have achieved rapid development in recent years, and the proportion of installed capacity of new energy sources has been increasing. However, while clean energy is developing rapidly, the grid connection of fluctuating and intermittent new energy sources has brought adverse effects to the power grid in many aspects, such as regulation and operation and safety control, greatly limiting the effective utilization of clean energy. Battery energy storage power stations can be used in conjunction with distributed / centralized new energy power generation and are one of the effective ways to solve the grid connection problem of new energy power generation. This technology will continue to grow with the increasing scale of new energy power generation and the continuous development of battery energy storage technology.

[0003] There are currently two ways to connect energy storage systems: AC connection and DC connection. Most power plants currently use AC connection, where the energy storage system is connected to the AC grid via an energy storage inverter and a boost converter. The other connection method is DC connection, which is still in the research stage and has not yet been widely applied. In the future, with the development of DC networks, direct connection of energy storage systems to the DC grid will have more application potential.

[0004] Existing methods for connecting energy storage batteries to medium-voltage DC networks typically employ DC / DC converters with high-frequency transformers for isolation. However, this approach is limited by the capacity and efficiency of the high-frequency transformer, resulting in low overall efficiency and limited connection capacity. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an energy storage direct-connected DC bus interface device and its control method, which is used to reduce the switching frequency of each sub-module and improve the conversion efficiency of the entire system by setting an adjustment voltage threshold.

[0006] The first aspect of the present invention discloses an energy storage direct-connected DC bus interface device, comprising: an energy storage battery unit, a voltage compensator, and a controller;

[0007] The voltage compensator and the energy storage battery unit are connected in series between the positive and negative terminals of the DC bus;

[0008] The voltage compensator includes: multiple sub-modules connected in series;

[0009] The controller is used to determine the sub-modules that are positively or negatively engaged based on the current of the energy storage battery unit.

[0010] Optionally, the voltage compensator further includes: an inductor, a resistor, and two controllable switches;

[0011] The first ends of the two controllable switches are connected; the connection point is connected to one end of the series branch of each of the sub-modules;

[0012] The second terminal of one of the controllable switches is connected to the energy storage battery unit via the inductor;

[0013] The second terminal of another controllable switch is connected to the corresponding pole of the DC bus via the resistor.

[0014] Optionally, the submodule is a full-bridge circuit.

[0015] Optionally, the submodule includes: a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, and a capacitor;

[0016] The first terminal of the first switching transistor is connected to the first terminal of the second switching transistor, and the connection point is connected to one end of the capacitor.

[0017] The second end of the first switching transistor is connected to the first end of the third switching transistor, and the connection point serves as the positive terminal of the submodule.

[0018] The second terminal of the second switch is connected to the first terminal of the fourth switch, and the connection point serves as the negative terminal of the submodule.

[0019] The second end of the third switch is connected to the second end of the fourth switch, and the connection point is connected to the other end of the capacitor.

[0020] The second aspect of this invention discloses a control method for an energy storage direct-connected DC bus interface device, applied to a controller of the energy storage direct-connected DC bus interface device as described in any one of the first aspects of this invention, the control method comprising:

[0021] Obtain the current from the energy storage battery cell;

[0022] Based on the current of the energy storage battery cell and the reference current, determine the modulation voltage that the voltage compensator needs to adjust;

[0023] Based on the modulation voltage, the positive input submodule and the negative input submodule in the voltage compensator are determined and activated.

[0024] Optionally, based on the current of the energy storage battery cell and the reference current, the modulation voltage that the voltage compensator needs to adjust is determined, including:

[0025] The positive reference current is superimposed with the reverse current of the energy storage battery cell, and then modulated by a regulator to obtain the modulated voltage.

[0026] Optionally, based on the modulation voltage, the positive input submodule and the negative input submodule in the voltage compensator are determined and activated, including:

[0027] Determine the initial pre-projection module corresponding to the modulation voltage;

[0028] Based on the direction of the modulation voltage, the initial pre-donation module, and the charging and discharging conditions of the energy storage battery unit, the positive pre-donation sub-module and the negative pre-donation sub-module are determined.

[0029] Calculate the number of sub-modules in the positive pre-donation sub-module and the negative pre-donation sub-module that are respectively within the dead zone voltage range, and take the minimum value as the number of adjustment modules;

[0030] Based on the number of the positive pre-investment submodule, the negative pre-investment submodule, the initial pre-investment module, and the adjustment module, the positive investment submodule and the negative investment submodule are determined respectively, and the positive investment submodule is used for positive investment and the negative investment submodule is used for negative investment.

[0031] Optionally, the formula used to calculate the positive input submodule is: N + =N 初始 +N ﹢初始 -N 调整 The formula used in the negative input submodule is: N - =N -初始 -N 调整 ;

[0032] Where, N + This is the submodule that is being deployed; N 初始 For the initial pre-projection module; N ﹢初始 For the positive pre-throw submodule; N 调整 N represents the number of adjustment modules; - For the negative input submodule; N -初始 This refers to the negative pre-investment submodule.

[0033] Optionally, based on the direction of the modulation voltage, the initial pre-donation module, and the charging and discharging conditions of the energy storage battery unit, a positive pre-donation submodule and a negative pre-donation submodule are determined, including:

[0034] The sub-modules are sorted according to their voltage magnitude;

[0035] If the modulation voltage is positive and the current is in the charging direction, or if the modulation voltage is negative and the current is in the discharging direction, then the N with the lowest voltage is selected first. 初始 The remaining submodules are then selected, with the highest voltage N among them. -初始 The aforementioned submodules serve as the negative pre-throw submodules, and the N with the lowest voltage... +初始Each of the sub-modules mentioned above serves as the positive pre-projection sub-module;

[0036] If the modulation voltage is positive and the current is in the discharge direction, or if the modulation voltage is negative and the current is in the charging direction, then the N with the highest voltage is selected first. 初始 The remaining submodules are then selected, with the lowest voltage N among them. -初始 The aforementioned submodule serves as the negative pre-throw submodule, and the N with the highest voltage... +初始 Each submodule serves as the positive pre-projection submodule;

[0037] The formula used to calculate the number of positive and negative pre-investments is: N +初始 =N -初始 =(NN) 初始 ) / 2, where N is the total number of sub-modules.

[0038] Optionally, the formula used to calculate the initial pre-projection module is:

[0039] N 初始 =Δu / Uc;

[0040] Wherein, Δu is the modulation voltage; and Uc is the rated voltage of the submodule.

[0041] As can be seen from the above technical solution, the present invention provides an energy storage direct-connected DC bus interface device, comprising: an energy storage battery unit, a voltage compensator, and a controller; the voltage compensator and the energy storage battery unit are connected in series between the positive and negative poles of the DC bus; the voltage compensator includes: multiple sub-modules connected in series; the rated voltage of each sub-module is equal; the controller is used to determine the sub-modules to be positively and negatively connected based on the current of the energy storage battery unit; that is, the controller can determine the number of sub-modules to be switched on and off based on the current, and control the switching state of the corresponding sub-modules; in addition, the capacity efficiency of the voltage compensator is adjustable, realizing efficient operation of the whole machine, and the capacity that can be connected can be larger; at the same time, a reference current is set to reduce the switching frequency of each sub-module and improve the conversion efficiency of the entire system. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of an energy storage direct-connected DC bus interface device provided in an embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of another energy storage direct-connected DC bus interface device provided in an embodiment of the present invention;

[0045] Figure 3 This is a flowchart of a control method for an energy storage direct-connected DC bus interface device provided in an embodiment of the present invention;

[0046] Figure 4 This is a modulation diagram of a control method for an energy storage direct-connected DC bus interface device provided in an embodiment of the present invention;

[0047] Figure 5 This is a flowchart of a control method for another energy storage direct-connected DC bus interface device provided in an embodiment of the present invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0050] This invention provides an energy storage direct-connection DC bus interface device to solve the problems of low capacity and efficiency of high-frequency transformers in the prior art, as well as low overall efficiency and limited access capacity.

[0051] See Figure 1 The energy storage direct-connected DC bus interface device includes: an energy storage battery unit, a voltage compensator, and a controller.

[0052] The voltage compensator and the energy storage battery unit are connected in series between the positive and negative terminals of the DC bus. Specifically, one end of the voltage compensator is connected to the positive terminal of the DC bus, and the other end of the voltage compensator is connected to one end of the energy storage battery unit; the other end of the energy storage battery unit is connected to the negative terminal of the DC bus. Alternatively, one end of the voltage compensator is connected to the negative terminal of the DC bus, and the other end of the voltage compensator is connected to one end of the energy storage battery unit; the other end of the energy storage battery unit is connected to the positive terminal of the DC bus.

[0053] Because the voltage of the DC bus is higher than the voltage of the energy storage battery unit, the function of this voltage compensator is to compensate for the voltage difference between the two.

[0054] The energy storage battery unit includes at least one energy storage battery. When there is only one energy storage battery, its two ends serve as the two ends of the energy storage battery unit. When there are multiple energy storage batteries, the two ends of each energy storage battery connected in series and / or parallel serve as the two ends of the energy storage battery unit. The specific structure of the energy storage battery unit is not specifically limited here, but can be determined according to the actual situation, and all are within the protection scope of this application.

[0055] The voltage compensator comprises multiple sub-modules connected in series. In practical applications, the rated voltage of each sub-module is equal, meaning that each sub-module is of the same model; however, it is not impossible for the models of the sub-modules to be different, which will not be elaborated here, and all are within the scope of protection of this application.

[0056] The controller is used to determine the positive and negative input sub-modules based on the current of the energy storage battery cell and the reference current.

[0057] Specifically, based on the current of the energy storage battery unit and the reference current, the positive input sub-module and the negative input sub-module are determined, and the positive input sub-module is controlled to be positively input, and the negative input sub-module is controlled to be negatively input, while other sub-modules are switched off.

[0058] It should be noted that the sub-modules for positive and negative input can be determined when the current of the energy storage battery unit is greater than the reference current, or when the current of the energy storage battery unit and the reference current meet a preset relationship. There is no specific limitation here, and it can be determined according to the actual situation. All of these are within the protection scope of this application.

[0059] In this embodiment, the controller can determine the number of sub-modules to be switched based on the current and control the switching status of the corresponding sub-modules. In addition, the capacity efficiency of the voltage compensator is adjustable, enabling the whole machine to operate efficiently and allowing for a larger connected capacity. At the same time, a reference current is set to reduce the switching frequency of each sub-module and improve the conversion efficiency of the entire system.

[0060] In practical applications, such as Figure 2As shown, the voltage compensator also includes an inductor, a resistor, and two controllable switches.

[0061] The first terminals of two controllable switches are connected; the connection point is connected to one end of the series branch of each submodule. The second terminal of one controllable switch is connected to the energy storage battery unit through an inductor; that is, the second terminal of the controllable switch is connected to one end of the inductor, and the other end of the inductor is connected to the energy storage battery unit. The second terminal of the other controllable switch is connected to the corresponding terminal of the DC bus through a resistor; that is, the second terminal of the controllable switch is connected to one end of the resistor, and the other end of the resistor is connected to the corresponding terminal of the DC bus. The other end of the series branch of each submodule is connected to the other terminal of the DC bus.

[0062] It should be noted that the inductor's function is filtering. The resistor's function is a soft-start resistor. That is, when the voltage compensator is in soft-start mode, the control resistor is engaged to achieve soft start. When the voltage compensator is in normal operating mode, the control inductor is engaged to achieve filtering.

[0063] In practical applications, such as Figure 2 As shown, this submodule is a full-bridge circuit.

[0064] Specifically, the submodule includes: a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, and a capacitor.

[0065] The first terminal of the first switch is connected to the first terminal of the second switch, and the connection point is connected to one end of the capacitor; the second terminal of the first switch is connected to the first terminal of the third switch, and the connection point serves as the positive terminal of the submodule; the second terminal of the second switch is connected to the first terminal of the fourth switch, and the connection point serves as the negative terminal of the submodule; the second terminals of the third switch and the fourth switch are connected, and the connection point is connected to the other end of the capacitor.

[0066] It should be noted that when a submodule is in a positive state of operation, the voltage between its positive and negative terminals is positive; when a submodule is in a negative state of operation, the voltage between its positive and negative terminals is negative. After a submodule is disconnected, the voltage across its terminals is 0.

[0067] like Figure 2 As shown, the following relationship exists: Udc=Ub+Δu+Ldi / dt.

[0068] Where Udc is the DC bus voltage, Ub is the voltage of the energy storage battery cell, Δu is the voltage of the voltage compensator, and Ldi / dt is the current electrochemical conductivity of the inductor, which is also the voltage of the inductor.

[0069] Additionally, Δu=(N) + -N - )Uc; where N +N represents the number of submodules currently being deployed. - Let N be the number of submodules with negative input, and Uc be the submodule voltage. And let N = N0. + +N - +N 0 Where N is the total number of submodules, N 0 This represents the number of tissues removed.

[0070] Another embodiment of the present invention provides a control method for an energy storage direct-connected DC bus interface device, which is applied to the controller of the energy storage direct-connected DC bus interface device as provided in any of the above embodiments.

[0071] For details on the specific structure and principle of the energy storage direct-connected DC bus interface device, please refer to the above embodiments. They will not be repeated here, and all are within the protection scope of this application.

[0072] like Figure 3 As shown, the control method for the energy storage direct-connected DC bus interface device includes:

[0073] S101, Obtain the current of the energy storage battery cell.

[0074] It should be noted that when the voltage difference between the energy storage battery cell and the DC bus changes, the current of the energy storage battery cell will change. In other words, the current of the energy storage battery cell can characterize the voltage relationship between the two.

[0075] S102. Based on the current of the energy storage battery cell and the reference current, determine the modulation voltage that the voltage compensator needs to adjust.

[0076] It should be noted that the modulation voltage to be adjusted by the voltage compensator can be determined when the current of the energy storage battery cell is greater than the reference current, or it can be determined when the current of the energy storage battery cell and the reference current meet a preset relationship. There is no specific limitation here, and it can be determined according to the actual situation. Both are within the protection scope of this application.

[0077] In practical applications, such as Figure 4 As shown, the specific process of step S102 can be as follows: the positive reference current Iref is superimposed with the reverse current Idc of the energy storage battery cell, and then the result is processed by a regulator (such as...). Figure 4 The modulated voltage Δu is obtained by modulating the PID controller shown. That is, the controller can be a PID controller, but it is not limited to this. All of them are within the scope of protection of this application.

[0078] Specifically, when the reference current is equal to the current of the energy storage battery cell, the summed value is 0, and modulation by the regulator is not required; modulation is possible, but the modulation result, i.e., the modulation voltage, is 0; that is, the voltage compensator does not need to adjust the compensation voltage. When the reference current is greater than the current of the energy storage battery cell, the summed value is positive, and the modulation result, i.e., the modulation voltage, is positive; in this case, the voltage compensator needs to adjust the compensation voltage. When the reference current is less than the current of the energy storage battery cell, the summed value is negative, and the modulation result, i.e., the modulation voltage, is negative; in this case, the voltage compensator needs to adjust the compensation voltage. Of course, this is not the only possible scenario, and will not be elaborated further here, all of which are within the scope of protection of this application.

[0079] S103. Based on the modulation voltage, determine and activate the positive input submodule and the negative input submodule in the voltage compensator.

[0080] Both the magnitude and direction of the modulation voltage can be used to determine the positive and negative input submodules. For example, the larger the value of the modulation voltage, the larger the absolute value of the difference between the positive and negative input submodules; the smaller the value of the modulation voltage, the smaller the absolute value of the difference between the positive and negative input submodules.

[0081] In this embodiment, the number of sub-modules to be switched can be determined based on the current, and the switching status of the corresponding sub-modules can be controlled. In addition, the capacity efficiency of the voltage compensator is adjustable, so as to achieve high-efficiency operation of the whole machine and the capacity that can be connected can be larger. At the same time, a reference current is set to reduce the switching frequency of each sub-module and improve the conversion efficiency of the entire system.

[0082] In practical applications, see Figure 5 The working process of step S103 above is as follows:

[0083] S201. Determine the initial pre-throw module corresponding to the modulation voltage.

[0084] It should be noted that the number of initial pre-projection modules is related to the value of the modulation voltage. The relationship between the number of initial pre-projection modules and the modulation voltage can be directly proportional; for example, the larger the modulation voltage, the more initial pre-projection modules there are, and the smaller the modulation voltage, the fewer initial pre-projection modules there are.

[0085] In practical applications, the formula used to calculate the initial pre-projection module is:

[0086] N 初始 =Δu / Uc;

[0087] Where Δu is the modulation voltage; Uc is the rated voltage of the submodule; N 初始 This is the initial pre-projection module.

[0088] In other words, under rated conditions, N初始 Each submodule can achieve the voltage across the voltage compensator as the modulation voltage; however, in practical applications, the voltage of each submodule is inconsistent with its rated voltage and there is a certain deviation. Therefore, positive pre-throw submodules and negative pre-throw submodules are required in subsequent steps.

[0089] S202. Based on the direction of the modulation voltage, the initial pre-donation module, and the charging and discharging conditions of the energy storage battery unit, determine the positive pre-donation sub-module and the negative pre-donation sub-module.

[0090] It should be noted that the positive pre-throw submodule and the negative pre-throw submodule are mainly for adjusting the voltage across the voltage compensator within a small range, so as to make the voltage across the voltage compensator equal to the modulation voltage as much as possible.

[0091] In practical applications, the specific working process of step S202 can be as follows:

[0092] (1) Sort each submodule according to its voltage.

[0093] Specifically, the capacitor voltages in each submodule are first collected, and then the capacitor voltages in each submodule are sorted.

[0094] Specifically, the sub-modules can be sorted from largest to smallest voltage, or eliminated from smallest to largest; other sorting methods are also possible, as long as the size relationship between the sub-modules can be determined.

[0095] (2) If the modulation voltage is positive and the current is in the charging direction, or if the modulation voltage is negative and the current is in the discharging direction, then first select the N with the lowest voltage. 初始 First, select one submodule; then, select N with the highest voltage from the remaining submodules. -初始 Each submodule serves as a negative pre-throw submodule, and the N module has the lowest voltage. +初始 Each of the complaint sub-modules serves as the pre-investment sub-module.

[0096] In other words, the specific process for determining the positive pre-donation submodule and the negative pre-donation submodule is the same in both cases: when the modulation voltage is positive and the current is in the charging direction, and when the modulation voltage is negative and the current is in the discharging direction.

[0097] Take the N with the lowest voltage 初始 Each submodule is used as the initial pre-projection module. That is, all modules are sorted by capacitor voltage from largest to smallest, and the module with the lowest voltage, N, is selected. 初始 These are several sub-modules that need to be deployed. At the highest voltage N... -初始 When a submodule is engaged, specifically the negative pre-energized submodule, the capacitors within that submodule will discharge, lowering their voltage and preventing excessive voltage buildup. This occurs at the lowest voltage level, N. +初始Once a submodule is put into operation, that is, after the pre-operational submodule is put into operation, the capacitor in the submodule will be charged, and the capacitor voltage will increase, which can prevent the capacitor voltage from being too low.

[0098] (3) If the modulation voltage is positive and the current is in the discharge direction, or if the modulation voltage is negative and the current is in the charging direction, then first select N with the highest voltage. 初始 First, select one submodule; then, select the N module with the lowest voltage from the remaining submodules. -初始 Each submodule serves as a negative pre-throw submodule, and the N module has the highest voltage. +初始 Each submodule serves as a pre-investment submodule.

[0099] In other words, the specific process for determining the positive pre-donation submodule and the negative pre-donation submodule is the same in both cases: when the modulation voltage is positive and the current is in the direction of discharge, and when the modulation voltage is negative and the current is in the direction of charging.

[0100] (3) is similar in principle to (2), and will not be elaborated here, but both are within the scope of protection of this application.

[0101] It should be noted that charging and discharging can be determined by detecting the direction of the current. The specific working process will not be described in detail here, but is within the scope of protection of this application.

[0102] The formula used to calculate the number of positive and negative pre-throws is: N +初始 =N -初始 =(NN) 初始 ) / 2, the formula uses the floor rule; N is the total number of sub-modules.

[0103] The rounding principle can be either rounding down or rounding to the nearest whole number. No specific limitation is made here; it can be determined according to the actual situation, and both are within the scope of protection of this application.

[0104] It should be noted that since step S202 involves adjusting the voltage of the voltage compensator within a small range, the positive pre-throw submodule and the negative pre-throw submodule need to be equal in order to achieve the small-range adjustment.

[0105] S203. Calculate the number of sub-modules within the dead zone voltage range in the positive pre-load sub-module and the negative pre-load sub-module, and take the minimum value as the number of adjustment modules.

[0106] The dead zone voltage range is preset and can be determined based on the upper and lower limits of the submodule capacitor voltage operation. No specific limitation is made here; it can be determined according to the actual situation, and all of them are within the protection scope of this application.

[0107] Specifically, calculate the number of dead zone submodules to be adjusted: count the number of modules within the dead zone voltage range in step S202 above, and denot them as N. -死区 and N+死区 The smaller of the two values ​​is taken as the adjustment number, i.e., N. 调整 =min(N) -死区 N +死区 N -死区 For N -初始 These submodules are those located within the dead-zone voltage range; N +死区 For N +初始 These are the submodules that fall within the dead-zone voltage range.

[0108] S204. Based on the number of positive pre-investment sub-modules, negative pre-investment sub-modules, initial pre-investment modules, and adjustment modules, determine the positive investment sub-modules and negative investment sub-modules respectively, and put the positive investment sub-modules into positive investment and the negative investment sub-modules into negative investment.

[0109] Specifically, the formula used to calculate the positive input submodule is: N + =N 初始 +N ﹢初始 -N 调整 The formula used in the negative input submodule is: N - =N -初始 -N 调整 .

[0110] Where, N + This is the submodule that is being deployed; N 初始 For the initial pre-projection module; N ﹢初始 For positive pre-investment submodule; N 调整 To adjust the number of modules; N - For negative input submodules; N -初始 This is a negative pre-investment submodule.

[0111] It should be noted that the DC bus voltage is greater than the voltage of the energy storage battery unit, so under normal circumstances, the voltage across the voltage compensator is greater than 0. Therefore, N... 初始 It is incorporated into the active sub-module.

[0112] The features described in the various embodiments of this specification can be substituted for or combined with each other. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. 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 modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0113] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0114] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A device for direct connection of energy storage to a DC bus, characterized in that, include: Energy storage battery cells, voltage compensators, and controllers; The voltage compensator and the energy storage battery unit are connected in series between the positive and negative terminals of the DC bus; The voltage compensator includes: multiple sub-modules connected in series; The controller is used to determine the sub-modules for positive and negative input based on the current of the energy storage battery unit. The voltage compensator also includes: an inductor, a resistor, and two controllable switches; The first ends of the two controllable switches are connected; the connection point is connected to one end of the series branch of each of the sub-modules; The second terminal of one of the controllable switches is connected to the energy storage battery unit via the inductor; The second terminal of another controllable switch is connected to the corresponding terminal of the DC bus via the resistor; The controller is used for: Obtain the current from the energy storage battery cell; Based on the current of the energy storage battery cell and the reference current, determine the modulation voltage that the voltage compensator needs to adjust; Based on the modulation voltage, determine and engage the positive engagement submodule and the negative engagement submodule in the voltage compensator; The controller is specifically used for: Determine the initial pre-projection module corresponding to the modulation voltage; Based on the direction of the modulation voltage, the initial pre-donation module, and the charging and discharging conditions of the energy storage battery unit, the positive pre-donation sub-module and the negative pre-donation sub-module are determined. Calculate the number of sub-modules in the positive pre-donation sub-module and the negative pre-donation sub-module that are respectively within the dead zone voltage range, and take the minimum value as the number of adjustment modules; Based on the number of the positive pre-investment submodule, the negative pre-investment submodule, the initial pre-investment module, and the adjustment module, the positive investment submodule and the negative investment submodule are determined respectively, and the positive investment submodule is used for positive investment and the negative investment submodule is used for negative investment.

2. The energy storage direct-connected DC bus interface device according to claim 1, characterized in that, The submodule is a full-bridge circuit.

3. The energy storage direct-connected DC bus interface device according to claim 2, characterized in that, The submodule includes: a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, and a capacitor; The first terminal of the first switching transistor is connected to the first terminal of the second switching transistor, and the connection point is connected to one end of the capacitor. The second end of the first switching transistor is connected to the first end of the third switching transistor, and the connection point serves as the positive terminal of the submodule. The second terminal of the second switch is connected to the first terminal of the fourth switch, and the connection point serves as the negative terminal of the submodule. The second end of the third switch is connected to the second end of the fourth switch, and the connection point is connected to the other end of the capacitor.

4. A control method for an energy storage direct-connected DC bus interface device, characterized in that, A controller applied to the energy storage direct-connected DC bus interface device as described in any one of claims 1-3, wherein determining the modulation voltage to be adjusted by the voltage compensator based on the current of the energy storage battery cell and the reference current includes: The positive reference current is superimposed with the reverse current of the energy storage battery cell, and then modulated by a regulator to obtain the modulated voltage.

5. The control method for the energy storage direct-connected DC bus interface device according to claim 4, characterized in that, The formula used to calculate the positive input submodule is: N + =N 初始 +N ﹢初始 -N 调整 ; The formula used in the negative input submodule is: N - =N -初始 -N 调整 ; Where, N + This is the submodule that is being deployed; N 初始 For the initial pre-projection module; N ﹢初始 For the positive pre-throw submodule; N 调整 N represents the number of adjustment modules; - For the negative input submodule; N -初始 This refers to the negative pre-investment submodule.

6. The control method for the energy storage direct-connected DC bus interface device according to claim 5, characterized in that, Based on the direction of the modulation voltage, the initial pre-donation module, and the charging and discharging conditions of the energy storage battery unit, a positive pre-donation submodule and a negative pre-donation submodule are determined, including: The sub-modules are sorted according to their voltage magnitude; If the modulation voltage is positive and the current is in the charging direction, or if the modulation voltage is negative and the current is in the discharging direction, then the N with the lowest voltage is selected first. 初始 The remaining submodules are then selected, with the highest voltage N among them. -初始 The aforementioned submodules serve as the negative pre-throw submodules, and the N with the lowest voltage... +初始 Each of the sub-modules mentioned above serves as the positive pre-projection sub-module; If the modulation voltage is positive and the current is in the discharge direction, or if the modulation voltage is negative and the current is in the charging direction, then the N with the highest voltage is selected first. 初始 The remaining submodules are then selected, with the lowest voltage N among them. -初始 The aforementioned submodule serves as the negative pre-throw submodule, and the N with the highest voltage... +初始 Each submodule serves as the positive pre-projection submodule; The formula used to calculate the number of positive and negative pre-investments is: N +初始 =N -初始 =(NN) 初始 ) / 2, where N is the total number of sub-modules.

7. The control method for the energy storage direct-connected DC bus interface device according to claim 5, characterized in that, The formula used to calculate the initial pre-projection module is as follows: N 初始 =Δu / Uc; Wherein, Δu is the modulation voltage; and Uc is the rated voltage of the submodule.

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