TWI631792B - Power system and method for limiting current thereof - Google Patents

Abstract

An electric power system and its current limiting method. The power system includes a plurality of battery units, an inverter, and a power management circuit. The battery unit has a first terminal, a second terminal, and a data terminal, respectively. The inverter has a first power supply terminal coupled to the first end of the battery unit and a second power supply terminal coupled to the second end of the battery unit, and receives a current limit value to limit a total of the battery cells according to the current limit value. Charge current or a total discharge current. The power management circuit is coupled to the data terminal of the battery unit to read a specific current limit value and a current value of each battery unit, and calculate the current limit value based on the individual current limit value and the current value of the battery unit.

Description

Power system and current limiting method

The present invention relates to a power management technology, and more particularly, to a power system and a current limiting method thereof.

Generally speaking, the charging and discharging current of the battery needs to be determined according to the specifications. Improper charging and discharging current may cause the battery to operate in a higher temperature environment, which will affect the battery life and even cause dangers such as thermal runaway. Therefore, in the energy storage system, the battery pack is designed to report the appropriate charge / discharge current limit to the inverter, so that the inverter will limit the battery output current within the rated range to ensure the battery Life and safety.

In an actual energy storage system, the battery management system (BMS) can report the charging current limit (CCL) and discharging current limit (DCL) of the inverter according to the current battery status. This limits the charging and discharging current.

For the inverter, the setting of the charge current limit and discharge current limit can only control the charge and discharge current of the entire parallel battery bank, and it cannot ensure that the charge current and discharge current to each battery bank are operated safely. Within range. However, when the old and new batteries are mixed in parallel, the output current of each battery pack in the battery pack appears uneven due to the different internal resistance values of the old and new batteries.

The invention provides a power system and a current limiting method thereof. The charging / discharging current limit is determined in consideration of the charging / discharging current of each battery unit, so as to ensure that the charging current and the discharging current of each battery unit are operated within a safe range.

The power system of the present invention includes a plurality of battery cells, an inverter, and a power management circuit. The battery unit has a first terminal, a second terminal, and a data terminal, respectively. The inverter has a first power source terminal coupled to the first end of the battery cell and a second power source terminal coupled to the second end of the battery cell at the same time, and receives a current limit value to limit the battery cell's voltage according to the current limit value. A total charge current or a total discharge current. The power management circuit is coupled to the data terminal of the battery unit to read a specific current limit value and a current value of each battery unit, and calculate the current limit value based on the individual current limit value and the current value of the battery unit.

In the current limiting method of the power system of the present invention, the power system includes a plurality of battery cells connected in parallel, and the current limiting method includes the following steps. Read a specific current limit value and a current value of each battery unit through a power management circuit. A current limit value is calculated through the power management circuit and according to the individual current limit value and current value of the battery unit. A total charging current or a total discharging current of the battery unit is limited by an inverter and according to a current limit value.

Based on the above, the power system and the current limiting method of the embodiments of the present invention determine the current limit in consideration of the current value of each battery cell and the individual current limit value, so as to ensure that the charging current and the discharge current of each battery unit are operated within a safe range .

In order to make the above features and advantages of the present invention more comprehensible, embodiments are hereinafter described in detail with reference to the accompanying drawings.

FIG. 1 is a system schematic diagram of a power system according to an embodiment of the present invention. Please refer to FIG. 1. In this embodiment, the power system 100 includes an inverter 110, a power management circuit 120, and a plurality of battery units 130_1 ~ 130_n, where n is a positive integer greater than zero, and the battery units 130_1 ~ 130_n can be regarded as one The battery pack, and the power management circuit 120 and the plurality of battery cells 130_1 to 130_n are in parallel.

Further, the first power terminal P + of the inverter 110 is simultaneously coupled to the first terminal B + of the battery units 130_1 ~ 130_n, and the second power terminal P- of the inverter 110 is simultaneously coupled to the second of the battery units 130_1 ~ 130_n.端 B-. In addition, the inverter 110 is coupled to the power management circuit 120 to receive the current limit value CL from the power management circuit 120 and limit the total charging current Itc or the total discharge current of the battery cells 130_1 to 130_n according to the current limit value CL, wherein the total charging current The main difference between Itc and total discharge current is that the current direction is opposite.

The power management circuit 120 is coupled to the data terminal D of the battery units 130_1 ~ 130_n to read individual current limit values (such as CL1 ~ CLn) and current values (such as I1 ~ In) of each battery unit 130_1 ~ 130_n, and according to the battery unit Individual current limit values (eg CL1 ~ CLn) and current values (eg I1 ~ In) of 130_1 ~ 130_n are used to calculate the current limit value CL.

FIG. 2 is a system schematic diagram of a power management circuit according to an embodiment of the present invention. Please refer to FIG. 1 and FIG. 2. In this embodiment, the power management circuit 120 includes at least one subtractor 121, a calculation unit 123, and a comparison unit 125. Among them, the number of subtractors 121 depends on the orientation of the circuit design. In other words, if the circuit design orientation is speed orientation, more subtractors 121 can be used; if the circuit design orientation is cost orientation, fewer subtractors 121 can be used, or even only one.

First, the power management circuit 120 calculates individual current limit values (such as CL1 ~ CLn) and current error values (such as Cerror_1 ~ Cerror_n) of the battery cells 130_1 ~ 130_n. In this embodiment, the current error values Cerror_1 ~ Cerror_n can be calculated according to the equation Cerror = CLi-Ii, where Cerror is the current error value Cerror_1 ~ Cerror_n, and CLi is the individual current limit value CL1 ~ CLn of each battery cell 130_1 ~ 130_n, Ii is the current value I1 ~ In of each battery cell.

Then, the calculation unit 123 and the comparison unit 125 calculate the current limit value CL according to the current error values Cerror_1 to Cerror_n of the battery units 130_1 to 130_n. Further, the calculation unit 123 calculates a new current limit value CL. In this embodiment, the new current limit value CL can be calculated according to the equation CL, new = CL, pre + K × N × Eref, where CL, new is the new current limit value CL, and CL, pre is the previous current. Limit value, K is the response speed parameter and is between 0 and 1, N is the number of battery cells 130_1 ~ 130_n, and Eref is the minimum value of the current error values Cerror_1 ~ Cerror_n.

In addition, the calculation unit 123 calculates a current saturation value CL, sat according to the individual current limit values CL1 to CLn and current values I1 to In of the battery cells 130_1 to 130_n. In this embodiment, the current saturation value CL, sat can be calculated according to the equation = [ΣIi + Eref] / Iratio + Ioffset, where ΣIi is the sum of the current values I1 ~ In of the battery cells 130_1 ~ 130_n, and Eref is defined as above. , Iratio is the error proportion of the measured current of the inverter 110, and Ioffset is the error offset of the measured current of the inverter 110.

Then, the comparison unit 125 compares the new current limit value CL, new with the current saturation value CL, sat. When the new current limit value CL, new is less than or equal to the current saturation value CL, sat, the current limit value CL will be equal to the new current limit value CL, new; when the new current limit value CL, new is greater than the current saturation value CL, sat At this time, the current limit value CL will be equal to the current saturation value CL, sat. In other words, the current limit value CL will be less than or equal to the current saturation value CL, sat.

In some embodiments, the calculation unit 123 may not calculate the current saturation value CL, sat, and the comparison unit 125 may be ignored.

FIG. 3 is a flowchart of a current limiting method for a power system according to an embodiment of the present invention. Referring to FIG. 3, in this embodiment, the current limiting method of the power system includes the following steps. In step S310, the individual current limit value and current value of each battery unit are read through the power management circuit. Next, in step S320, the current limit value is calculated through the power management circuit and according to the current limit value and the current value of the battery cells. Finally, in step S330, the total charging current or the total discharging current of these battery cells is limited through the inverter and according to the current limit value. The sequence of steps S310, S320, and S330 is for illustration, and the embodiment of the present invention is not limited thereto. In addition, for details of steps S310, S320, and S330, reference may be made to the embodiments shown in FIG. 1 and FIG. 2, and details are not described herein again.

In summary, the power system and the current limiting method of the embodiment of the present invention determine the current limit in consideration of the current value of each battery cell and the individual current limit value, so as to ensure that the charging current and the discharging current of each battery unit are operated safely. Within range.

Although the present invention has been disclosed as above with the examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some modifications and retouching without departing from the spirit and scope of the present invention. The protection scope of the present invention shall be determined by the scope of the attached patent application.

100‧‧‧ Power System
110‧‧‧ Inverter
120‧‧‧Power Management Circuit
121‧‧‧ Subtractor
123‧‧‧ Computing Unit
125‧‧‧ Comparison Unit
130_1 ~ 130_n‧‧‧Battery unit
B-‧‧‧ the second end
B + ‧‧‧ first end
Cerror_1 ~ Cerror_n‧‧‧Current error value
CL, new‧‧‧New current limit value
CL, sat‧‧‧Current saturation value
CL‧‧‧Current Limit
CL1 ~ CLn‧‧‧ Individual current limit value
D‧‧‧data terminal
I1 ~ In‧‧‧Current value
Itc‧‧‧Total charging current
P-‧‧‧Second power terminal
P + ‧‧‧First power terminal
S310, S320, S330‧‧‧ steps

FIG. 1 is a system schematic diagram of a power system according to an embodiment of the present invention. FIG. 2 is a system schematic diagram of a power management circuit according to an embodiment of the present invention. FIG. 3 is a flowchart of a current limiting method for a power system according to an embodiment of the present invention.

Claims (12)

An electric power system includes: a plurality of battery units, each having a first terminal, a second terminal, and a data terminal; an inverter having a first terminal coupled to the first terminals of the battery cells; A power supply terminal and a second power supply terminal coupled to the second terminals of the battery cells at the same time, and receiving a current limit value to limit a total charging current or a total discharge current of the battery cells according to the current limit value And a power management circuit coupled to the data terminals of the battery cells to read a specific current limit value and a current value of each of the battery cells, and according to the individual current limits of the battery cells Value and the current values to calculate the current limit value. The power system according to item 1 of the patent application scope, wherein the power management circuit calculates a current error value between the individual current limit value and the current value of each of the battery cells, and is based on the currents of the battery cells. The error value calculates the current limit value. The power system according to item 2 of the scope of patent application, wherein the current limit value is calculated according to the following equation: CL, new = CL, pre + K × N × Eref, where CL, new is the current limit value, CL, pre is the previous current limit value, K is a response speed parameter and is between 0 and 1, N is the number of the battery cells, and Eref is a minimum value of the current error values. According to the power system described in the second item of the patent application, the current error values are calculated according to the following equation: Cerror = CLi-Ii where Cerror is the current error value and CLi is the The individual current limit value, Ii is the current value of each of the battery cells. The power system according to item 2 of the patent application scope, wherein the power management circuit calculates a current saturation value according to the individual current limit values of the battery cells and the current values, and the current limit value is less than or equal to the current Saturation value. The power system according to item 5 of the scope of patent application, wherein the current saturation value is calculated according to the following equation: CL, sat = [ΣIi + Eref] / Iratio + Ioffset where CL, sat is the current saturation value and ΣIi is The sum of the current values of the battery cells, Eref is a minimum value of the current error values, Iratio is the error proportion of the measured current of the inverter, and Ioffset is the error deviation of the measured current of the inverter . A current limiting method for a power system. The power system includes a plurality of battery cells connected in parallel. The current limiting method includes: reading a specific current limit value and a current value of each of the battery cells through an electric energy management circuit; A power management circuit that calculates a current limit value based on the individual current limit values of the battery cells and the current values; and an inverter that limits a total charge current of the battery cells or A total discharge current. The current limit method of the power system according to item 7 of the scope of patent application, wherein calculating the current limit value according to the individual current limit values of the battery cells and the current values includes: calculating each of the current limit values through the power management circuit. A current error value of the individual current limit value of the battery cells and the current value; and calculating the current limit value through the power management circuit and according to the current error values of the battery cells. The current limit method of the power system according to item 8 of the scope of patent application, wherein the current limit value is calculated according to the following equation: CL, new = CL, pre + K × N × Eref, where CL, new is the current limit Value, CL, pre is the previous current limit value, K is a reaction speed parameter and is between 0 and 1, N is the number of the battery cells, and Eref is a minimum value of the current error values. The current limit method of the power system according to item 8 of the scope of patent application, wherein the current error values are calculated according to the following equation: Cerror = CLi-Ii where Cerror is the current error value and CLi is the each The individual current limit values of the battery cells, Ii is the current value of each of the battery cells. The current limit method of the power system according to item 8 of the scope of patent application, further comprising: calculating a current saturation value through the power management circuit and according to the individual current limit values of the battery cells and the current values, wherein The current limit value is less than or equal to the current saturation value. The current limit method of the power system according to item 11 of the scope of patent application, wherein the current saturation value is calculated according to the following equation: CL, sat = [ΣIi + Eref] / Iratio + Ioffset where CL, sat is the current saturation Value, ΣIi is the sum of the current values of the battery cells, Eref is a minimum value of the current error values, Iratio is the error proportion of the measured current of the inverter, and Ioffset is the measured current of the inverter Error offset.