Direct-current voltage adjusting device

Abstract

The invention discloses a direct current voltage adjusting device, and relates to the technical field of direct current voltage conversion, the device comprises a reconfigurable battery system and a digital energy processing calculation module, the reconfigurable battery system comprises a plurality of battery modules connected in series, each battery module comprises a battery unit, a first switch and a second switch, the battery unit is connected in series with the first switch, and the second switch is connected in parallel to two ends of a series branch of the battery unit and the first switch; the digital energy processing and calculating module is used for adjusting the voltage output by the reconfigurable battery system by controlling the working state of each battery module; when the first switch is switched on and the second switch is switched off, the battery module is in a non-working state, and when the first switch is switched off and the second switch is switched on, the battery module is in a working state. According to the invention, the DC voltage conversion cost and conversion complexity can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of direct current voltage conversion, and in particular to a direct current voltage regulating device. Background Art

[0002] At present, DC voltage converters, namely DC-DC converters, play a vital role in DC voltage conversion and energy transfer. At present, the commonly used DC-DC conversion schemes are mostly to invert DC power to AC power, and then rectify the inverted AC power into the required DC power. Commonly used DC voltage conversion equipment generally includes DC voltage conversion modules, monitoring modules, supporting user interfaces, and DC power distribution units. The DC voltage conversion modules are connected in parallel to share the load, converting -48V DC voltage into -24V (or +12V, +5V) DC voltage, and then outputting it to the load through the output shunt fuse; the monitoring module is responsible for monitoring the working status and performance of the converter module and the entire system, and is included in the upper-level monitoring system through the RS232 communication port. The converter module is responsible for converting -48V DC voltage into -24V DC voltage, and consists of two major parts: power circuit and control circuit. The power circuit realizes the conversion from DC input to DC output; the control circuit provides all control signals required for power conversion, including feedback loop, DC signal processing, analog and switch processing circuits, etc.

[0003] However, the commonly used DC-DC conversion solutions currently still have problems such as complex equipment components, cumbersome control mechanisms, and high overall equipment costs, making DC voltage regulation solutions difficult to promote and deploy on a large scale. Summary of the invention

[0004] The purpose of this application is to provide a DC voltage regulation device that can reduce the cost and complexity of DC voltage conversion.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] In a first aspect, the present application provides a DC voltage regulation device, comprising: a reconfigurable battery system and a digital energy processing and computing module, the reconfigurable battery system comprising a plurality of battery modules connected in series, each of the battery modules comprising a battery cell, a first switch and a second switch, the battery cell being connected in series with the first switch, and the second switch being connected in parallel to both ends of a series branch of the battery cell and the first switch; the digital energy processing and computing module being used to regulate the voltage output by the reconfigurable battery system by controlling the working state of each battery module; when the first switch is closed and the second switch is disconnected, the battery module is in a non-working state, and when the first switch is disconnected and the second switch is closed, the battery module is in a working state.

[0007] Optionally, the battery unit includes a plurality of battery cells connected in series.

[0008] Optionally, the digital energy processing calculation module includes a combination optimization unit, and the combination optimization unit is used to determine the working state of each battery module according to the combination optimization model;

[0009] The combined optimization model is expressed as:

[0010] Among them, V total is the total voltage output by each battery module, V L is the lower limit of the load side voltage, the load side is connected to the output of the reconfigurable battery system, N i is the number of battery cells in the i-th battery module, 1≤i≤E, E is the number of battery modules, V ij is the output voltage of the jth battery cell in the i-th battery module, S i is the switch variable of the ith battery module; when the first switch in the ith battery module is closed and the second switch is open, S i =0, when the first switch in the i-th battery module is disconnected and the second switch is closed, S i =1,Q ij is the capacity of the jth battery cell in the i-th battery module.

[0011] Optionally, the constraints of the combined optimization model include: L ≤V total ≤V H , S i ·V mL ≤S i ·V ij i∈E,j∈N i and S i Q mL ≤S i Q ij ;

[0012] Among them, V H is the upper limit of the load side voltage, V mL is the lower limit of the battery cell operating voltage, Q mL It is the lower limit of battery cell capacity.

[0013] Optionally, the total voltage output by each of the battery modules is expressed as:

[0014] Among them, V Mtotali is the output voltage of the i-th battery module.

[0015] Optionally, the output voltage of the i-th battery module is expressed as:

[0016] Optionally, in terms of determining the working state of each battery module according to the combined optimization model, the combined optimization unit is specifically configured to determine the working state of each battery module according to the combined optimization model once at a set time interval.

[0017] Optionally, the set time interval is 5 seconds.

[0018] Optionally, the output voltage of the battery cell is the open circuit voltage of the battery cell minus the product of the internal resistance of the battery cell and the load current.

[0019] Optionally, the capacity of the battery cell is expressed as:

[0020] Among them, Q0 is the initial capacitance, t0 is the accumulated time, i′ is the load current, and t is the time variable.

[0021] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0022] The present application provides a DC voltage regulation device, which regulates the voltage output by the reconfigurable battery system by controlling the working state of each battery module. The total output voltage can be controlled by only controlling the switch, which can reduce the cost and complexity of DC voltage conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of the structure of a DC voltage regulating device provided in one embodiment of the present application;

[0025] Figure 2 A schematic diagram of a battery cell internal resistance model provided in one embodiment of the present application;

[0026] Figure 3 A schematic diagram of the internal components of a battery module provided in one embodiment of the present application;

[0027] Figure 4 A schematic diagram of the working state of a battery module provided in one embodiment of the present application;

[0028] Figure 5 A schematic diagram of a total output voltage variation trend provided in an embodiment of the present application;

[0029] Figure 6 A schematic diagram of a control flow of a DC voltage regulation device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0032] The present application provides a DC voltage regulating device, such as Figure 1 As shown, the DC voltage regulating device includes: a reconfigurable battery system and a digital energy processing and computing module, the reconfigurable battery system includes a plurality of battery modules connected in series, each of the battery modules includes a battery cell, a first switch and a second switch, the battery cell is connected in series with the first switch, and the second switch is connected in parallel to both ends of the series branch of the battery cell and the first switch; the digital energy processing and computing module is used to adjust the voltage output by the reconfigurable battery system by controlling the working state of each battery module; when the first switch is closed and the second switch is disconnected, the battery module is in a non-working state, and when the first switch is disconnected and the second switch is closed, the battery module is in a working state.

[0033] The present application adjusts the voltage output by the reconfigurable battery system by controlling the working state of each battery module. The total output voltage can be controlled by only controlling the switch, which can reduce the cost and complexity of DC voltage conversion.

[0034] The battery unit includes a plurality of battery cells connected in series. This application focuses on the voltage characteristics of the battery under steady-state or quasi-steady-state conditions, so the internal resistance (RINT) model is used to equate the battery cell, that is, only the open circuit voltage OCV and internal resistance R of the battery cell are considered, and the dynamic components such as inductance and capacitance and the impact of the transient response caused by them are ignored. The internal resistance model is as follows: Figure 2 shown.

[0035] The output voltage of the battery cell is the open circuit voltage OCV of the battery cell minus the product of the internal resistance of the battery cell and the load current, which is expressed as: V=OCV-I·R(1).

[0036] Among them, V is the output voltage of the battery cell, and I is the load current.

[0037] The open circuit voltage can be considered as a function of the battery state of charge SOC: OCV = f(SOC) (2).

[0038] f(SOC) is a function of the battery state of charge and open circuit voltage.

[0039] The battery unit of each battery module is composed of battery cells of the same or different types connected in series. The sum of the voltages of the battery cells in the battery module serves as the total output voltage of the battery module to supply power to the load.

[0040] Depend on Figure 3 As shown, the i-th battery port (the output port of the i-th battery module) is composed of N i The voltage of the battery port is the sum of the voltages of the battery cells. Therefore, the construction length is N i The voltage sequence V i , used to indicate the voltage of each battery cell in the battery module.

[0041]

[0042] The output voltage of the i-th battery module is expressed as:

[0043] Where V ij Represents the output voltage of the jth battery cell in the ith battery module.

[0044] The reconfigurable battery system used in this application is composed of several battery modules and corresponding power electronic switches. The sum of the voltages of the battery modules is used as the total output voltage to supply power to the load. Figure 1 As shown, the total output voltage of the battery system is adjusted and controlled by controlling the working status of different battery modules.

[0045] The reconfigurable battery system, i.e., the dynamically reconfigurable battery system, is composed of E battery modules. Therefore, a switch sequence S with a length of E is constructed. i ,i∈E determines the working state of the module, S i If 1 is selected, the i-th battery module is connected to the working circuit. Otherwise, the battery module is in a non-working state and is not connected to the working circuit. Figure 4 As shown, Figure 4 Part (a) is the non-working state of the i-th battery module. Figure 4 Part (b) shows the working status of the i-th battery module.

[0046] The total voltage output by the reconfigurable battery system is expressed as:

[0047] The total voltage output by the reconfigurable battery system is the sum of the voltages output by each battery module.

[0048] Since the battery voltage changes gradually with the working time, the relationship between the total output voltage of the battery system and time is analyzed. From formula (5), it can be seen that the total output voltage of the battery system is the sum of the output voltages of all battery modules connected to the working circuit, so:

[0049]

[0050] Substituting formula (1) and formula (4) into formula (6) yields:

[0051]

[0052] The capacity of the battery cells is:

[0053] Among them, Q0 is the initial capacitance, t0 is the accumulated time, i′ is the load current, and t is the time variable.

[0054] Therefore, formula (8) can be expressed as:

[0055]

[0056] Converting the above formula into differential form, we can get:

[0057] Where ΔV total It indicates the voltage difference from the initial voltage when the battery system is put into operation to the voltage drop to the lower limit voltage of the load. The total output voltage change trend is roughly as follows Figure 5 shown.

[0058] From formula (11), we can see that in order to make the battery system work for as long as possible, formula (12) needs to be as large as possible:

[0059]

[0060] Therefore, according to the derivation of the above formula, the combinatorial optimization problem can be constructed to obtain the combinatorial optimization model.

[0061] The digital energy processing calculation module includes a combination optimization unit, and the combination optimization unit is used to determine the working state of each battery module according to the combination optimization model.

[0062] The combined optimization model is expressed as:

[0063] Among them, V total is the total voltage output by each battery module, V Lis the lower limit of the load side voltage, the load side is connected to the output of the reconfigurable battery system, N i is the number of battery cells in the i-th battery module, 1≤i≤E, E is the number of battery modules, V ij is the output voltage of the jth battery cell in the i-th battery module, S i is the switch variable of the ith battery module; when the first switch in the ith battery module is closed and the second switch is open, S i =0, when the first switch in the i-th battery module is disconnected and the second switch is closed, S i =1,Q ij is the capacity of the jth battery cell in the i-th battery module.

[0064] The constraints of the combined optimization model include: L ≤V total ≤V H , S i ·V mL ≤S i ·V ij i∈E,j∈N i and S i Q mL ≤S i Q ij .

[0065] Among them, V H is the upper limit of the load side voltage, V mL is the lower limit of the battery cell operating voltage, Q mL It is the lower limit of battery cell capacity.

[0066] Among them, V Mtotali is the output voltage of the i-th battery module.

[0067] In terms of determining the working state of each battery module according to the combined optimization model, the combined optimization unit is specifically used to determine the working state of each battery module according to the combined optimization model once every set time interval. The set time interval is 5 seconds, and the optimization problem is solved every 5 seconds, and the solution result is updated to the battery system topology.

[0068] The specific control process of a DC voltage regulating device in this application is as follows: Figure 6 As shown, firstly, the voltage of each battery module is obtained, and the current optimal battery module combination is determined among the feasible battery combinations that meet various constraints. The reconfigurable battery system supplies power to the load under this combination.

[0069] As the working time increases and the available battery capacity decreases, the total output voltage of the battery system will gradually decrease. When the current battery module combination cannot meet the corresponding constraints such as voltage and capacity, the current combination optimization is terminated. After the reconfigurable battery system is charged, the next combination optimization problem is solved and the working status of each battery module is updated and adjusted according to the solution results.

[0070] In an exemplary embodiment, the reconfigurable battery system includes 9 battery modules, and the solution of the combinatorial optimization problem is [011110100], that is, the switching variables of the 1st to 9th battery modules are 0, 1, 1, 1, 1, 0, 1, 0 and 0 respectively, and the corresponding total output voltage is 60.9267V. The load requirement voltage range is 57V-61V, which verifies the feasibility and effectiveness of the proposed DC voltage regulation device.

[0071] This application is based on a reconfigurable battery network topology and through the construction of a combinatorial optimization problem at the battery module level, determines the optimal battery module combination that meets various requirements and constraints, and uses this as a reconfigurable battery network topology to power the load, ensuring that the total output voltage meets the load requirements, while achieving precise control of the output DC voltage. The equipment required for this application includes heterogeneous battery cells, a battery management system (BMS) and corresponding power electronic switches, which have great advantages in equipment cost and cost compared to traditional DC-DC conversion solutions, and at the same time, reliability and practicality are improved.

[0072] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A DC voltage regulating device, characterized in that: The DC voltage regulating device includes: a reconfigurable battery system and a digital energy processing and computing module, the reconfigurable battery system includes a plurality of battery modules connected in series, each of the battery modules includes a battery cell, a first switch and a second switch, the battery cell is connected in series with the first switch, and the second switch is connected in parallel to both ends of the series branch of the battery cell and the first switch; the digital energy processing and computing module is used to regulate the voltage output by the reconfigurable battery system by controlling the working state of each battery module; when the first switch is closed and the second switch is disconnected, the battery module is in a non-working state, and when the first switch is disconnected and the second switch is closed, the battery module is in a working state.

2. The DC voltage regulating device according to claim 1, characterized in that: The battery unit includes a plurality of battery cells connected in series.

3. The DC voltage regulating device according to claim 2, characterized in that: The digital energy processing calculation module includes a combination optimization unit, which is used to determine the working state of each battery module according to the combination optimization model; The combined optimization model is expressed as: Among them, V total is the total voltage output by each battery module, V L is the lower limit of the load side voltage, the load side is connected to the output of the reconfigurable battery system, N i is the number of battery cells in the i-th battery module, 1≤i≤E, E is the number of battery modules, V ij is the output voltage of the jth battery cell in the i-th battery module, S i is the switch variable of the ith battery module; when the first switch in the ith battery module is closed and the second switch is open, S i =0, when the first switch in the i-th battery module is disconnected and the second switch is closed, S i =1,Q ij is the capacity of the jth battery cell in the i-th battery module.

4. The DC voltage regulating device according to claim 3, characterized in that: The constraints of the combined optimization model include: L ≤V total ≤V H , S i ·V mL ≤S i ·V ij i∈E,j∈N i and S i Q mL ≤S i Q ij ; Among them, V H is the upper limit of the load side voltage, V mL is the lower limit of the battery cell operating voltage, Q mL It is the lower limit of battery cell capacity.

5. The DC voltage regulating device according to claim 3, characterized in that: The total voltage output by each of the battery modules is expressed as: Among them, V Mtotali is the output voltage of the i-th battery module.

6. The DC voltage regulating device according to claim 5, characterized in that: The output voltage of the i-th battery module is expressed as:

7. The DC voltage regulating device according to claim 3, characterized in that: In terms of determining the working state of each battery module according to the combined optimization model, the combined optimization unit is specifically used to determine the working state of each battery module according to the combined optimization model once every set time interval.

8. The DC voltage regulating device according to claim 7, characterized in that: The set time interval is 5 seconds.

9. The DC voltage regulating device according to claim 2, characterized in that: The output voltage of the battery cell is the open circuit voltage of the battery cell minus the product of the internal resistance of the battery cell and the load current.

10. The DC voltage regulating device according to claim 2, characterized in that: The capacity of the battery cell is expressed as: Among them, Q0 is the initial capacitance, t0 is the accumulated time, i′ is the load current, and t is the time variable.

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