阅读说明：本技术 一种电动汽车能源站 (Electric automobile energy station ) 是由 周俭节 方日 曹伟 于 2021-09-15 设计创作，主要内容包括：本发明提供一种电动汽车能源站,其内部各电池单元与第一直流汇流母线直接或间接相连,以通过该第一直流汇流母线实现其与外界之间的电能交换；另外,该第一直流汇流母线还通过第一级变换单元与第二汇流母线相连,并且,各电池单元也分别通过第二级变换单元与第二汇流母线相连,进而使得挂接于该第二汇流母线上的充电枪,可以通过第一级变换单元接收第一直流汇流母线上的电能,也可以通过第二级变换单元接收相应电池单元的电能；也即,本实施例为充电枪提供了两种充电路径。而且,充电枪接收电池单元的电能时,仅需要经过该第二级变换单元这一级变换即可,减少了能量损耗,避免了系统收益的降低。(The invention provides an electric automobile energy station, wherein each battery unit in the electric automobile energy station is directly or indirectly connected with a first direct current bus bar so as to realize electric energy exchange between the electric automobile energy station and the outside through the first direct current bus bar; in addition, the first direct current bus bar is also connected with the second bus bar through the first-stage conversion unit, and each battery unit is also connected with the second bus bar through the second-stage conversion unit, so that a charging gun hung on the second bus bar can receive electric energy on the first direct current bus bar through the first-stage conversion unit and can also receive electric energy of the corresponding battery unit through the second-stage conversion unit; that is, the present embodiment provides two charging paths for the charging gun. Moreover, when the charging gun receives the electric energy of the battery unit, only the secondary conversion unit is needed, so that the energy loss is reduced, and the reduction of the system benefit is avoided.)

1. An electric vehicle energy station, comprising: the charging device comprises at least two battery units, a first-stage conversion unit, a second-stage conversion unit and at least one charging gun; wherein:

each battery unit is directly or indirectly connected with the first direct current bus bar;

the first side of the first-stage conversion unit is connected with the first direct current bus bar;

the second side of the first-stage transformation unit is connected with the first side of the second-stage transformation unit through a second bus bar;

the second sides of the second-stage transformation units are respectively connected with the corresponding battery units;

and the charging gun receives the output electric energy of the first-stage conversion unit and/or the output electric energy of the second-stage conversion unit through the second bus bar.

2. The electric vehicle energy station of claim 1, wherein the second sides of the second-stage transformation units are respectively connected in series to the power transmission loops corresponding to the battery units to form a series branch with the corresponding battery units;

two ends of each series branch are connected in parallel to the first direct current bus bar.

3. The electric vehicle energy station of claim 1, wherein each of the battery cells are connected in series in sequence, and both ends of the series connection are connected to the first dc bus bar;

and the second sides of the second-stage transformation units are respectively connected with the corresponding battery units in parallel.

4. The electric vehicle energy station of claim 1, wherein the second stage transformation unit is further configured to balance the operating parameters of the battery units.

5. The electric vehicle energy station of any of claims 1-4, wherein the first stage transformation unit comprises: at least one first converter;

when the number of the first converters is more than 1, the first side and the second side of each first converter are respectively connected in parallel;

the second-stage transformation unit includes: at least one second converter;

a first side of each of the second inverters is connected to the second bus bar in parallel, and a second side of each of the second inverters is connected to the corresponding battery cell;

the first converter and the second converter are both isolated converters.

6. The electric vehicle energy station of claim 5, wherein the first inverter and the second inverter are both unidirectional inverters such that:

and when the second-stage conversion unit realizes the balance function of each battery unit, the second-stage conversion unit supplies power to the charging gun through the second bus bar.

7. The electric vehicle energy station of claim 5, wherein the second inverter is a unidirectional inverter and the first inverter is a bidirectional inverter, such that:

when the second-stage conversion unit achieves the balance function of each battery unit, the second bus bar supplies power to the charging gun, or the second bus bar and the first-stage conversion unit supply power to the first direct current bus bar.

8. The electric vehicle energy station of claim 5, wherein the second inverter is a bidirectional inverter and the first inverter is a unidirectional inverter, such that:

when the second-stage conversion unit achieves the balance function of each battery unit, the electric energy generated on the second bus bar is zero, or the charging gun is supplied with power through the second bus bar.

9. The electric vehicle energy station of claim 5, wherein the first inverter and the second inverter are both bidirectional inverters such that:

when the second-stage conversion unit achieves the balance function of each battery unit, the electric energy generated on the second bus bar is zero, or the charging gun is supplied with power through the second bus bar, or the first-stage conversion unit supplies power to the first direct current bus bar through the second bus bar.

10. The electric vehicle energy station of claim 5, wherein the second inverter is connected to the battery cells in a one-to-one correspondence.

11. The electric vehicle energy station of claim 5, wherein the second bus bar is a direct current bus bar, the first converter is a DCDC converter, and the second converter is a DCDC converter;

alternatively, the first and second electrodes may be,

the second bus bar is an alternating current bus bar, the first converter is a DCAC converter, and the second converter is a DCAC converter.

12. The electric vehicle energy station of claim 5, wherein when the second sides of the second-stage converters are respectively connected in series to the power transmission loops corresponding to the battery units, an electrically controlled switch is further connected between the positive and negative poles of the second side of the second converter.

13. The electric vehicle energy station of any of claims 1-4, further comprising: an energy storage converter, and/or a photovoltaic power generation system; wherein:

the alternating current side of the energy storage converter is used for connecting a power grid;

and the battery side of the energy storage converter and the output end of the photovoltaic power generation system are connected with the first direct current bus bar.

14. The electric vehicle energy station of any of claims 1-4, wherein the photovoltaic power generation system comprises: at least one photovoltaic unit and a DCDC conversion module thereof;

and each photovoltaic unit is connected with the first direct current bus bar through the DCDC conversion module.

Technical Field

The invention relates to the technical field of power electronics, in particular to an electric automobile energy station.

Background

The current electric vehicle energy station mainly comprises a charging station and a battery replacement station; generally, due to the consideration of peak-to-valley price difference of a power grid or the retention and charging requirements of a power battery in a battery replacement station, a plurality of battery units need to be hung in a system; the common hanging scheme is that each battery unit and an energy storage system formed by the energy storage converter of each battery unit and a charging pile are hung on an alternating current bus respectively in a relatively independent mode.

Because the energy storage converter is needed to pass between the battery units in the energy storage system and the alternating current bus, the energy storage converter is internally provided with at least a DCAC conversion circuit, and a plurality of DCDC conversion circuits may be arranged between the DCAC conversion circuit and each battery unit; moreover, a corresponding power converter is needed between the alternating current bus and the charging guns of the charging pile, at least a corresponding ACDC conversion circuit is arranged in the power converter, and a plurality of DCDC conversion circuits may be arranged between the ACDC conversion circuit and each charging gun; therefore, the energy from the battery unit to the charging gun needs to be converted in multiple stages (as shown in fig. 1), which results in large energy loss and reduces the system yield.

Disclosure of Invention

In view of this, the present invention provides an electric vehicle energy station to reduce energy loss when a battery unit supplies power to a charging gun.

In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:

the invention provides an electric automobile energy station in a first aspect, which comprises: the charging device comprises at least two battery units, a first-stage conversion unit, a second-stage conversion unit and at least one charging gun; wherein:

each battery unit is directly or indirectly connected with the first direct current bus bar;

the first side of the first-stage conversion unit is connected with the first direct current bus bar;

the second side of the first-stage transformation unit is connected with the first side of the second-stage transformation unit through a second bus bar;

the second sides of the second-stage transformation units are respectively connected with the corresponding battery units;

and the charging gun receives the output electric energy of the first-stage conversion unit and/or the output electric energy of the second-stage conversion unit through the second bus bar.

Optionally, the second sides of the second-stage transformation units are respectively connected in series to the power transmission loops corresponding to the battery units, so as to form a series branch with the corresponding battery units;

two ends of each series branch are connected in parallel to the first direct current bus bar.

Optionally, the battery units are sequentially connected in series, and two ends of the battery units after being connected in series are connected with the first direct current bus bar;

and the second sides of the second-stage transformation units are respectively connected with the corresponding battery units in parallel.

Optionally, the second-stage transformation unit is further configured to achieve equalization between operating parameters of the battery units.

Optionally, the first-stage transformation unit includes: at least one first converter;

when the number of the first converters is more than 1, the first side and the second side of each first converter are respectively connected in parallel;

the second-stage transformation unit includes: at least one second converter;

a first side of each of the second inverters is connected to the second bus bar in parallel, and a second side of each of the second inverters is connected to the corresponding battery cell;

the first converter and the second converter are both isolated converters.

Optionally, the first converter and the second converter are both unidirectional converters, and then:

and when the second-stage conversion unit realizes the balance function of each battery unit, the second-stage conversion unit supplies power to the charging gun through the second bus bar.

Optionally, if the second converter is a unidirectional converter and the first converter is a bidirectional converter, then:

when the second-stage conversion unit achieves the balance function of each battery unit, the second bus bar supplies power to the charging gun, or the second bus bar and the first-stage conversion unit supply power to the first direct current bus bar.

Optionally, if the second converter is a bidirectional converter and the first converter is a unidirectional converter, then:

when the second-stage conversion unit achieves the balance function of each battery unit, the electric energy generated on the second bus bar is zero, or the charging gun is supplied with power through the second bus bar.

Optionally, the first converter and the second converter are both bidirectional converters, and then:

when the second-stage conversion unit achieves the balance function of each battery unit, the electric energy generated on the second bus bar is zero, or the charging gun is supplied with power through the second bus bar, or the first-stage conversion unit supplies power to the first direct current bus bar through the second bus bar.

Optionally, the second converters are connected to the battery units in a one-to-one correspondence.

Optionally, the second bus bar is a dc bus bar, the first converter is a DCDC converter, and the second converter is a DCDC converter;

alternatively, the first and second electrodes may be,

the second bus bar is an alternating current bus bar, the first converter is a DCAC converter, and the second converter is a DCAC converter.

Optionally, when the second side of the second-stage conversion unit is respectively connected in series to the power transmission circuit corresponding to the battery unit, an electric control switch is further connected between the positive electrode and the negative electrode of the second side of the second converter.

Optionally, the method further includes: an energy storage converter, and/or a photovoltaic power generation system; wherein:

the alternating current side of the energy storage converter is used for connecting a power grid;

and the battery side of the energy storage converter and the output end of the photovoltaic power generation system are connected with the first direct current bus bar.

Optionally, the photovoltaic power generation system includes: at least one photovoltaic unit and a DCDC conversion module thereof;

and each photovoltaic unit is connected with the first direct current bus bar through the DCDC conversion module.

According to the electric automobile energy station provided by the invention, each battery unit in the electric automobile energy station is directly or indirectly connected with the first direct current bus bar so as to realize electric energy exchange between the electric automobile energy station and the outside through the first direct current bus bar; in addition, the first direct current bus bar is also connected with the second bus bar through the first-stage conversion unit, and each battery unit is also connected with the second bus bar through the second-stage conversion unit, so that a charging gun hung on the second bus bar can receive electric energy on the first direct current bus bar through the first-stage conversion unit and can also receive electric energy of the corresponding battery unit through the second-stage conversion unit; that is, the present embodiment provides two charging paths for the charging gun. Moreover, when the charging gun receives the electric energy of the battery unit, only the secondary conversion unit is needed, so that the energy loss is reduced, and the reduction of the system benefit is avoided.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings to be used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a schematic structural diagram of an electric vehicle energy station provided in the prior art;

FIG. 2 is a schematic structural diagram of an electric vehicle energy station according to an embodiment of the present invention;

fig. 3 is another schematic structural diagram of an electric vehicle energy station according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

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

The invention provides an electric automobile energy station, which is used for reducing energy loss when a battery unit supplies power to a charging gun.

The electric vehicle energy station can be a charging station, a battery replacement station or a combination of the charging station and the battery replacement station; without limitation, are intended to be within the scope of the present application. As shown in fig. 2 or fig. 3, it specifically includes: the charging system comprises at least two battery units, a first-stage conversion unit 101, a second-stage conversion unit 102 and at least one charging gun; wherein:

in practical applications, the battery unit may be a battery cluster (such as the 1# battery module, the 2# battery module, …, and the n # battery module shown in fig. 2), a battery pack (such as the 1# battery module, the 2# battery module, …, and the n # battery module shown in fig. 3), or a power battery retained in the power conversion station, which is determined by the specific application environment and is not limited herein.

Each battery unit is directly or indirectly connected with a first direct current bus bar (a direct current bus bar 1 shown in the figure); the connection mode with the first dc bus bar is not limited, and it is within the scope of the present application as long as the charging and discharging of each battery cell can be achieved by the first dc bus bar.

In addition, the first dc bus bar may be connected to the grid directly or indirectly through an energy storage converter (such as PCS shown in the figure), and may further be combined with a photovoltaic system, that is, the photovoltaic units are connected through corresponding DCDC conversion modules, for example, the photovoltaic modules are connected through an optimizer, or the photovoltaic strings are connected through a DCDC converter; depending on the specific application environment, are all within the scope of the present application.

A first side of the first-stage conversion unit 101 is connected with a first direct current bus bar; the second side of the first-stage transformation unit 101 is connected to the first side of the second-stage transformation unit 102 through a second bus bar (a dc bus bar 2 as shown in the figure); the second sides of the second-stage transformation units 102 are respectively connected with the corresponding battery units; and the charging gun is also hung on the second bus bar so as to charge the connected electric automobile after taking electricity from the second bus bar.

In the process of charging the electric vehicle connected with the charging gun, the charging gun may specifically receive the output electric energy of the first-stage conversion unit 101 through the second bus bar, or may also receive the output electric energy of the second-stage conversion unit 102 through the second bus bar, or may also receive the output electric energy of the first-stage conversion unit 101 and the output electric energy of the second-stage conversion unit 102 through the second bus bar; depending on the specific application environment, are all within the scope of the present application.

For example, during a peak period of power consumption, a power grid has a high price, or the output power of the photovoltaic system is insufficient, if the SOC (State of Charge, battery State of Charge, also called remaining capacity) of most of the battery units is greater than a preset value, the battery units may be used to discharge to the second bus bar through the second-stage conversion unit 102, so as to provide electric energy for the charging gun.

When the output power of the photovoltaic system is high, the first-stage conversion unit 101 can receive the power supply of the photovoltaic system on the first direct current bus bar, and then the power is discharged through the second bus bar to provide the charging electric energy for the charging gun to pass through the electric automobile; alternatively, when both the output power of the photovoltaic system and the SOC of the battery unit are insufficient, the first-stage conversion unit 101 may receive the power supplied by the PCS on the first dc bus, and then discharge the power through the second dc bus, so as to provide the charging gun with the charging power required by the electric vehicle. Meanwhile, in the process of discharging to the second bus bar through the first-stage conversion unit 101, whether each battery unit needs to be charged or not can be selected according to the specific situation.

In practical applications, in order to avoid mutual influence between the two power sources under the two charging paths implemented by the second-stage conversion unit 102 and the first-stage conversion unit 101, it is preferable that both the first-stage conversion unit 101 and the second-stage conversion unit 102 are configured as isolated conversion units.

In the electric vehicle energy station provided by the embodiment, each battery unit in the electric vehicle energy station is directly or indirectly connected with the first direct current bus bar so as to realize electric energy exchange between the electric vehicle energy station and the outside through the first direct current bus bar; in addition, the first dc bus bar is further connected to the second bus bar through the first stage converter unit 101, and each battery unit is also connected to the second bus bar through the second stage converter unit 102, so that the charging gun hung on the second bus bar can receive the electric energy on the first dc bus bar through the first stage converter unit 101, and can also receive the electric energy of the corresponding battery unit through the second stage converter unit 102; that is, the present embodiment provides two charging paths for the charging gun. Moreover, when the charging gun receives the electric energy of the battery unit, only one-stage conversion of the second-stage conversion unit 102 is needed, so that the energy loss is reduced, and the reduction of the system benefit is avoided.

It is worth to be noted that, in a system in which photovoltaic, energy storage and charging pile are integrated, there is also a scheme of sharing a dc bus in the prior art, specifically, a dc bus is built through an energy storage converter, each battery unit is respectively connected to the dc bus through a corresponding bidirectional DCDC converter, and other dc devices such as a photovoltaic inverter and a dc charging pile can also be directly connected to the dc bus. Although the direct current bus is established, the battery unit and the charging pile are both required to be provided with corresponding power electronic converters to be connected with the direct current bus.

In the embodiment, the two bus bars are constructed, so that each battery unit is connected with the first direct current bus bar without an additional power electronic converter, and the structural cost and the energy loss are saved; while providing two charging paths for the charging gun through the second bus bar. In addition, the number of bus bars in practical use is not limited to two, and may be expanded according to the number of devices in the system, the capacity of the battery unit, and the like, as long as the above functions are achieved, and all of them are within the scope of the present application.

In addition, another scheme of sharing a direct current bus exists in the prior art, the system cost is reduced by multiplexing the charging pile and the battery unit with the DCDC converter, but the DCDC converters in the scheme can only be multiplexed in a time-sharing mode and cannot be operated simultaneously.

And this electric automobile energy station that this embodiment provided, its each battery unit can realize through first direct current busbar to self charge-discharge, and its rifle that charges can realize through second busbar to the electric automobile that connects charging, and work of both can go on simultaneously, each other does not influence.

On the basis of the above embodiment, it should be noted that, the connection manner between each battery unit and the first dc bus bar may specifically be parallel connection (as shown in fig. 2), for example, when the battery unit is a battery cluster, each battery cluster may be parallel connected to the first dc bus bar to form a battery system; in addition, each battery unit may be sequentially connected in series between the positive and negative electrodes of the first dc bus bar (as shown in fig. 3), for example, when the battery unit is a battery pack, each battery pack may be connected in series between the positive and negative electrodes of the first dc bus bar to form one battery cluster. Of course, a plurality of battery clusters may also be applied in series, and a plurality of battery packs may also be applied in parallel, which are only examples, and are determined according to the specific application environment, and all are within the protection scope of the present application.

For the case shown in fig. 2, specifically, the second sides of the second-stage transformation units 102 are respectively connected in series to the power transmission loops of the corresponding battery units, so as to form a series branch with the corresponding battery units; both ends of each series branch are then connected in parallel to the first dc bus bar.

In the case shown in fig. 3, specifically, the battery cells are connected in series in sequence, and both ends of the series connection are connected to the first dc bus bar; the second sides of the second-stage conversion units 102 are connected in parallel to the corresponding battery cells, respectively.

In any case, in the electric vehicle energy station, the first stage transformation unit 101 may include: at least one first converter (one shown for example); when the number of the first converters is greater than 1, the first side and the second side of each first converter are connected in parallel respectively. The second-stage transformation unit 102 may include: at least one second converter; the first side of each second inverter is connected in parallel to the second bus bar, and the second side of each second inverter is connected to the corresponding battery cell. The first converter and the second converter are both isolated converters.

In practical application, the number of the second converters and the number of the battery units can be the same or different, and preferably, the second converters are connected with the battery units in a one-to-one correspondence manner; or, a plurality of battery units may share one second converter, for example, battery units with similar operating conditions may share the same second converter, and some special battery units, such as newly added battery clusters or battery packs, or old power batteries of a battery replacement station, may be configured with a corresponding second converter independently; it is not limited herein, and is within the scope of the present application, depending on the specific application environment.

For the case shown in fig. 2, the second side of each second converter may be connected to the positive bus, the negative bus of the corresponding battery unit, or between any two series structures of the battery units, such as between any two adjacent battery packs in the battery cluster, or between any two battery cores in the battery pack; fig. 2 illustrates an example in which the second sides of the second inverters are respectively connected to the negative electrode buses of the corresponding battery cells, but the present invention is not limited thereto.

In addition, in practical applications, the connection relationship between each battery unit and its corresponding second inverter may be different, and is not limited to the case shown in fig. 2.

In addition, in the case shown in fig. 2, a corresponding electrically controlled switch (e.g., K1, K2, …, Kn shown in fig. 2) may be connected between the positive and negative poles on the second side of each second converter, and if one or more battery cells need to be equalized or supply power to the charging gun, the corresponding electrically controlled switch is controlled to be switched to the off state; and other battery units which do not need to be balanced and do not need to supply power to the charging gun keep a closed state corresponding to the electric control switch so as to avoid the loss caused by the operation of the second converter. Specifically, when the electrically controlled switch is closed, the corresponding second converter is bypassed, and the voltage of the series branch is the voltage of the battery unit. When the electric control switch is turned off, the voltage of the series branch circuit is the sum of the voltage of the corresponding battery unit and the voltage output by the second side of the second converter.

In the case shown in fig. 3, the second side of each second inverter may be connected in parallel with each battery cell.

In practical applications, the second bus bar may be a dc bus bar (such as the dc bus bar 2 shown in fig. 2 and 3) or an ac bus bar (not shown).

When the second bus bar is a DC bus bar, the first converter is a DCDC converter (m # DC/DC shown in fig. 2 and 3), and the second converter is a DCDC converter (1 # DC/DC, 2# DC/DC, …, n # DC/DC shown in fig. 2 and 3).

When the second bus bar is an alternating current bus bar, the first inverter is a DCAC inverter, and the second inverter is a DCAC inverter.

On the basis of the foregoing embodiments, preferably, the second-stage transformation unit 102 of the electric vehicle energy station provided in this embodiment may also be used to implement balancing between operation parameters of each battery unit, such as balancing between SOC, voltage, SOH (state of health) or average temperature.

The equalizing process may be specifically implemented in the process of providing charging power for the charging gun by the second-stage conversion unit 102, may be implemented in the process of providing charging power for the charging gun by the first-stage conversion unit 101, and may be implemented in the process of providing charging power for the charging gun by the second-stage conversion unit 102 and the first-stage conversion unit 101 at the same time; are all within the scope of the present application.

That is, the electric vehicle energy station provided by this embodiment constructs a second bus bar for balance control of a battery system on the basis of light storage fusion, and leads out a charging pile interface on the basis of not adding additional hardware cost, that is, for charging an electric vehicle; and further, the balance of the operation parameters among the multiple branch battery units can be realized while the charging gun charges the electric automobile.

In the prior art, no matter the scheme of sharing the alternating current bus or the scheme of sharing the direct current bus, the balance of the battery units of the multiple branches cannot be synchronously controlled by means of the work of the charging gun, and the potential exertion of a battery system is not facilitated.

In addition, in practical application, the equalization process is not limited to be synchronously realized when the charging gun works, but can also be realized when the charging gun does not work, and even can be realized when the system is in standby; for example, the method is executed during the standing period of the system, namely, the equalization among the battery units is realized in advance before the system operates, and the state synchronization of the battery units is ensured before the battery units are connected into the PCS to integrally operate. Depending on the specific application environment, are all within the scope of the present application.

The equalization scheme is suitable for the battery changing station and the charging station, and all the battery modules can be fully charged synchronously through the equalization scheme in the process that the new battery module and the old battery module are connected into the charging process; the intelligent household energy flow switching device is suitable for a household light, storage and charging combined scene, and can flexibly switch energy flows, so that the charging, power generation and power storage can reach the best economic model.

Based on the above embodiments, in the electric vehicle energy station, whether the topology shown in fig. 2 or the topology shown in fig. 3 is adopted, the main operation of the first converter and the second converter is to supply power to the charging gun, and the first converter and the second converter preferably have the function of balancing each battery unit.

Therefore, in practical application, the arrangement of the first converter and the second converter can be selected in various ways, specifically:

(1) the first converter and the second converter are both unidirectional converters, then:

when the second-stage conversion unit 102 realizes the equalization function for each battery unit, only the battery units with higher SOC can transmit some more electric energy to the second bus bar, and the first-stage conversion unit 101 can only supply power to the second bus bar, so that the electric energy on the second bus bar can only supply power to the charging gun. That is, the second-stage transforming unit 102 can only realize the balancing function for each battery unit by the timing of supplying power to the charging gun.

(2) The second converter is a unidirectional converter and the first converter is a bidirectional converter, then:

when the second-stage conversion unit 102 realizes the balance function of each battery unit, only a certain amount of electric energy can be transmitted to the second bus bar by the battery unit with higher SOC, but the electric energy transmitted to the second bus bar can be supplied to a charging gun or supplied to the first dc bus bar through the first-stage conversion unit 101; the second-stage transforming unit 102 can implement the balancing function for each battery unit at any time, such as when the charging gun is working or not working or the system is in standby.

(3) The second converter is a bidirectional converter and the first converter is a unidirectional converter, then:

when the second-stage transformation unit 102 realizes the balancing function for each battery unit, the battery unit with higher SOC may transmit some more electric energy to the second bus bar, or the battery unit with lower SOC may be charged after taking electricity from the second bus bar.

Through reasonable arrangement, the total electric energy generated by the second-stage conversion unit 102 to the second bus bar can be zero; furthermore, the second-stage conversion unit 102 can realize the equalization function for each battery unit when the charging gun does not work or the system is in standby state, or when the charging gun receives the power supply of the first-stage conversion unit 101.

Or, through another reasonable arrangement, the second-stage conversion unit 102 may supply power to the charging gun through the second bus bar; furthermore, the second-stage conversion unit 102 can realize the balance function of each battery unit when the charging gun receives the power supply of the second-stage conversion unit 102 and works.

That is, in this case, the second-stage transforming unit 102 may implement the equalizing function for each battery cell at any time.

(4) The first converter and the second converter are both bidirectional converters, then:

when the second-stage transformation unit 102 realizes the balancing function for each battery unit, the battery unit with higher SOC may transmit some more electric energy to the second bus bar, or the battery unit with lower SOC may be charged after taking electricity from the second bus bar.

Through reasonable setting, can make its electric energy to producing on the second busbar be zero, or, have the surplus electric energy in order to converge the busbar and supply power to the rifle that charges through the second, or, have the surplus electric energy in order to converge busbar and first order transform unit 101 to supply power to first direct current busbar through the second.

That is, in this case, the second-stage conversion unit 102 can also realize the equalizing function for each battery cell at any time.

It should be noted that, since the SOC of the battery unit is in direct proportion to the voltage, the practical application is not limited to performing the balancing control based on the SOC, and the voltage may be used to replace the SOC to implement the balancing process; alternatively, SOH or average temperature may also be used, and the detailed description is omitted here, and the SOH or average temperature is within the protection scope of the present application as long as the SOH or average temperature meets the requirement of balance between the respective indexes of the battery cells.

In practical applications, the first converter and the second converter may be set according to specific needs of the system, and are not limited herein and are within the scope of the present application.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, the system or system embodiments are substantially similar to the method embodiments and therefore are described in a relatively simple manner, and reference may be made to some of the descriptions of the method embodiments for related points. The above-described system and system embodiments are only illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

In the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other to enable 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 generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended 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.