Power supply system

Abstract

This suppresses the flow of unintended current during parallel charging and power supply. [Solution] When charging the first and second batteries in parallel using the power of the charging equipment, the minimum values ​​of the first allowable input power of the first battery and the second allowable input power of the second battery are set as the common required power of the first and second batteries, twice the common required power is set as the total required power, and the total required power or total required current based on the total required power is requested from the charging equipment, and the first and second inverters are controlled using the common required power or the current command of the second battery based on the common required power, and when the upper arm of the first inverter is fixed on and the upper and lower arms of the second inverter are under duty cycle control, the upper arms of the first and second inverters are fixed on after the duty cycle ratio in the duty cycle control of the second inverter becomes equal to or greater than a predetermined ratio.

Description

Technical Field

[0001] The present disclosure relates to a power supply system.

Background Art

[0002] Conventionally, there has been proposed a power supply system including a power storage device having a first battery and a second battery, a switching relay capable of switching between a first state of connecting these batteries in series and a second state of connecting them in parallel, and an inlet connected to a positive electrode wire and a negative electrode wire connecting the power storage device and a PCU that drives a motor (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, as a power supply system, there has been devised one including a first battery and a second battery and a charging connector, and capable of parallel charging in which the first battery is charged via a first charging path and the second battery is charged via a second charging path using power from a charging facility connected to the charging connector. In such a power supply system, due to the difference in the open-circuit voltage between the first battery and the second battery, an unintended current may flow during parallel charging and discharging. The main object of the power supply system of the present disclosure is to suppress the flow of an unintended current during parallel charging and discharging.

Means for Solving the Problems

[0005] The power supply system of the present disclosure employs the following means to achieve the above-mentioned main objective. The power supply system of the present disclosure is a power supply system comprising first and second batteries, comprising: a motor having a three-phase coil; a first inverter connected to the first battery via a first positive electrode line and a negative electrode line and connected to one end of the three-phase coil; a second inverter connected to the second battery via a second positive electrode line and the negative electrode line and connected to the other end of the three-phase coil; a charging connector connected to the first positive electrode line and the negative electrode line and electrically connectable to a charging device; and, in parallel charging of the first and second batteries using the power of the charging device, the minimum values ​​of the first allowable input power of the first battery and the second allowable input power of the second battery are set to the first battery The gist of the invention is a control device that sets a common power requirement for the pond and the second battery, sets twice the common power requirement as the total power requirement, requests the charging equipment for the total power requirement or the total current requirement based on the total power requirement, controls the first inverter and the second inverter using the common power requirement or the current command for the second battery based on the common power requirement, and when the upper arm of the first inverter is fixed on and the upper and lower arms of the second inverter are under duty cycle control, fixes the upper arms of the first and second inverters on after the duty cycle ratio in the duty cycle control of the second inverter becomes equal to or greater than a predetermined ratio. [Brief explanation of the drawing]

[0006] [Figure 1] A schematic diagram showing the power system and charging station configuration. [Figure 2] An explanatory diagram showing the flow of current during parallel charging. [Figure 3] A flowchart illustrating an example of a processing routine. [Modes for carrying out the invention]

[0007] Embodiments for implementing this disclosure will be described with reference to the drawings. Figure 1 is a schematic diagram of a power supply system 10 and a charging station 80 according to an embodiment of this disclosure. The power supply system 10 is installed in an electric vehicle or a hybrid vehicle and comprises a battery 12, a motor 20, a first inverter 22, a second inverter 24, a switching circuit 30, a charging circuit 40, and a system electronic control unit (hereinafter referred to as "system ECU") 50 as a control device. The power supply system 10 is capable of charging the battery 12 using power from a charging station (charging equipment) 80 installed at home or a charging station.

[0008] Battery 12 comprises a first battery 13 and a second battery 14, which are the first and second batteries, respectively. The first battery 13 and the second battery 14 are each configured as secondary batteries with the same specifications, for example, having a rated voltage slightly lower than the first voltage Vs1 (e.g., 400V). The positive terminal of the first battery 13 is connected to the first positive line 31, and the negative terminal of the second battery 14 is connected to the negative line 33. The negative terminal of the first battery 13 is connected to the positive terminal of the second battery 14 via a series line 35 to which a series relay Rs is attached. Therefore, by turning on the series relay Rs, the first battery 13 and the second battery 14 are connected in series with each other.

[0009] The motor 20 comprises, for example, a rotor in which permanent magnets are embedded in the rotor core, and a stator in which three-phase (U-phase, V-phase, W-phase) coils are wound around the stator core. The first and second inverters 22 and 24 each comprise six transistors T11-T16 and T21-T26 as switching elements, and six diodes D11-D16 and D11-D16 connected in parallel to each of the six transistors T11-T16 and T21-T26. The transistors T11-T16 and T21-T26 are arranged in pairs, with two on each side, acting as the source and sink sides with respect to the first and second positive lines 31 and 32 and the negative line 33. Each connection point of a pair of transistors T11-T16 and T21-T26 is connected to one end and the other end of the three-phase coils of the motor 20, respectively. The first and second positive electrode lines 31 and 32 and the negative electrode line 33 are connected to the first and second capacitors 26 and 28, respectively. Transistors T11-13 and T21-T23 are sometimes called the "upper arm," and transistors T14-T16 and T24-T26 are sometimes called the "lower arm." In addition to the first positive electrode line 31, the second positive electrode line 32, the negative electrode line 33, the series line 35, and the series relay Rs mentioned above, the switching circuit 30 includes a parallel line 36 connecting the negative terminal of the first battery 13 to the negative electrode line 33, a first parallel relay Rp1 attached to the parallel line 36, and a second parallel relay Rp2 attached to the second positive electrode line 32. The charging and power supply circuit 40 includes a charging and power supply line 42 connected to the first positive electrode line 31 and the negative electrode line 33, and a charging and power supply connector (charging connector) 44 connected to the charging and power supply line 42 and configured to be connectable to a stand connector 82 of a charging and power supply stand 80 provided at home or a charging station.

[0010] The system ECU 50 is equipped with a microcomputer having a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, as well as various drive circuits and various logic ICs. Signals from various sensors are input to the system ECU 50. Examples of these sensors include voltage sensors 13v and 14v and temperature sensors 13t and 14t that detect the voltages Vb1 and Vb2 and temperatures Tb1 and Tb2 of the first and second batteries 13 and 14, current sensors 20u, 20v, and 20w that detect the currents Iu, Iv, and Iw flowing through each phase of the motor 20, voltage sensors 26v and 28v that detect the voltages VH and VL of the first and second capacitors 26 and 28, and current sensors 31i and 32i that detect the currents Ip1 and Ip2 flowing through the first and second positive electrode lines 31 and 32. The system ECU 50 calculates the charge storage ratios SOC1 and SOC2 of the first and second batteries 13 and 14, the allowable input power (first and second allowable input power) Win1 and Win2, and the allowable output power Wout1 and Wout2. The charge storage ratios SOC1 and SOC2 are calculated, for example, based on the integrated values ​​of the currents Ip1 and Ip2 (currents flowing to the first and second batteries 13 and 14) flowing through the first and second positive electrode lines 31 and 32 when the series relay Rs is off and the first and second parallel relays Rp1 and Rp2 are on, and the integrated value of the current Ip1 (currents flowing to the first and second batteries 13 and 14) flowing through the first positive electrode line 31 when the series relay Rs is on and the first and second parallel relays Rp1 and Rp2 are off. The allowable input powers Win1 and Win2 are calculated based on the energy storage ratios SOC1 and SOC2 and the temperatures Tb1 and Tb2. The allowable output powers Wout1 and Wout2 are calculated based on the energy storage ratios SOC1 and SOC2 and the temperatures Tb1 and Tb2. The system ECU 50 outputs control signals to the series relay Rs, the first and second parallel relays Rp1 and Rp2, and the first and second inverters 22 and 24. The system ECU 50 is able to communicate with the electronic control unit (stand ECU) 86 of the charging and power supply stand 80.

[0011] The charging and supplying stand 80 includes a stand connector 82 configured to connect to the charging and supplying connector 44 of the power supply system 10, a charging and supplying device 84 that converts AC power from an AC power source such as a household power supply or a commercial power supply into DC power and supplies it to the stand connector 82, and converts DC power from the stand connector 82 into AC power and supplies power to the device to be charged, and a stand ECU 86. Signals from various sensors are input to the stand ECU 86. Control signals are output from the stand ECU 86 to the charging and supplying device 84. As described above, the stand ECU 86 is capable of communicating with the system ECU 50. Examples of charging and power supply stands 80 include a first voltage stand where the voltage of the charging power or power supply is a first voltage Vs1 (e.g., 400V), a second voltage stand where the voltage of the charging power or power supply is a second voltage Vs2 (e.g., 800V) which is higher than the first voltage Vs1, and a third voltage stand in which either the first voltage Vs1 or the second voltage Vs2 can be selectively set as the voltage of the charging power or power supply.

[0012] In the power supply system 10, the system ECU 50 selects parallel charging and supply, or series charging and supply, when the charging and supplying power voltages of the charging and supplying stand 80 are first and second voltages Vs1 and Vs2, respectively, when the charging and supplying connector 44 and the stand connector 82 are connected. In parallel charging and supply, the series relay Rs is turned off and the first and second parallel relays Rp1 and Rp2 are turned on, thereby connecting the first and second batteries 13 and 14 in parallel as seen from the charging and supplying connector 44. This allows the first and second batteries 13 and 14 to be charged using power from the charging and supplying stand 80, and power to be supplied to the charging and supplying stand 80 using power from the first and second batteries 13 and 14. Figure 2 is an explanatory diagram showing the current flow during parallel charging. In the figure, the thick solid lines and thick dashed lines with arrows indicate the charging currents of the first and second batteries 13 and 14, respectively. In parallel charging, the first battery 13 is charged by current flowing in the following order from the charging connector 44 to the positive terminal line of the charging line 42, the first positive terminal line 31, the first battery 13, the parallel line 36 (first parallel relay Rp1), the negative terminal line 33, the negative terminal line of the charging line 42, and the charging connector 44, as shown by the thick solid line with arrows in Figure 2. The second battery 14 is charged by current flowing in the following order from the charging connector 44 to the positive terminal line of the charging line 42, the first positive terminal line 31, the first inverter 22, the motor 20, the second inverter 24, the second positive terminal line 32 (second parallel relay Rp2), the second battery 14, the negative terminal line 33, the negative terminal line of the charging line 42, and the charging connector 44, as shown by the thick dashed line with arrows in Figure 2. The current flow during parallel power supply is the reverse of the current flow during parallel charging. At this time, by fixing the upper arm of the second inverter 24 to ON (fixing the lower arm to OFF) and simultaneously performing duty cycle control on the upper and lower arms of the first inverter 22, the motor 20 and the first inverter 22 function as a three-phase step-down converter, and the input power of the first inverter 22 is stepped down and output from the motor 20 (step-down control).Furthermore, by fixing the upper arm of the first inverter 22 to the ON position and performing duty cycle control on the upper and lower arms of the second inverter 24, the motor 20 and the second inverter 24 function as a three-phase boost converter, and the input power of the motor 20 is boosted and output from the second inverter 24 (boost control). Since series charging and power supply is not central to this embodiment, its description is omitted.

[0013] Next, the operation of the power supply system 10 in the embodiment, particularly the operation during parallel charging, will be described. Figure 3 is a flowchart of an example of a processing routine executed by the system ECU 50. This routine is executed repeatedly during parallel charging. Before the start of repeated execution of this routine, the series relay Rs is turned off, and the first parallel relay Rp1 and the second parallel relay Rp2 are turned on.

[0014] When the processing routine shown in Figure 3 is executed, the system ECU 50 first sets the minimum values ​​of the allowable input powers Win1 and Win2 of the first battery 13 and the second battery 14 as the common required power Pb*, which is the common required power for the first battery 13 and the second battery 14 (S100). Subsequently, it sets twice the common required power Pb* as the total required power Pt* (S110), sets the total required current It* based on the set total required power Pt*, and transmits it to the stand ECU 86 of the charging and power supply stand 80 (S120). The total required current It* is calculated, for example, by dividing the total required power Pt* by the output voltage Vs of the charging and power supply device 84, or by dividing the total required power Pt* by the maximum values ​​of the voltages Vb1 and Vb2 of the first battery 13 and the second battery 14. When the stand ECU 86 receives the total requested current It*, it controls the charging and discharging device 84 so that the charging and discharging stand 80 supplies a current equivalent to the total requested current It* to the power supply system 10.

[0015] Then, a current command Ib2* for the second battery 14 is set based on the common required power Pb* (S130), and the first inverter 22 and the second inverter 24 are controlled based on the set current command Ib2* for the second battery 14 (S140). The current command Ib2* is calculated, for example, by dividing the common required power Pb* by the voltage Vb2 of the second battery 14. Through this control of the first inverter 22 and the second inverter 24, the second battery 14 is charged with a current corresponding to the current command Ib2* (power corresponding to the common required power Pb*) out of the total required current It* from the charging and power supply stand 80 (power corresponding to the total required power Pt*, i.e., power corresponding to twice the common required power Pb*), and the first battery 13 is charged with a similar current.

[0016] Next, in the control of S140, it is determined whether the duty cycle D2 of the second inverter 24 exceeds a predetermined ratio D2ref (S150). The predetermined ratio D2ref is set to a value close to 100%, for example, 97%, 98%, 99%, etc. If the duty cycle D2 does not exceed the predetermined ratio D2ref, it is determined that the charge level SOC1 of the first battery 13 is smaller than the charge level SOC2 of the second battery 14, and that boost control is being performed in which the upper and lower arms of the second inverter 24 are duty-cycle controlled. Then, it is determined whether the power to charge the first battery 13 (=(Ip1+ΔIb)·Vb1) when the current command Ib2* of the second battery 14 is lowered by a change amount ΔIb from the current current command Ib2* exceeds the allowable input power Win1 of the first battery 13 (S160). When the power used to charge the first battery 13 does not exceed the allowable input power Win1, the current command Ib2* for the second battery 14 is changed to one that is lower than the current current command Ib2* by a change of ΔIb (S170). Currently, the charge level SOC1 of the first battery 13 is smaller than the charge level SOC2 of the second battery 14, so in S170, the charging current of the SOC of the first battery 13 increases, and the current command Ib2* is changed in a direction that brings the charge level SOC1 of the first battery 13 closer to the charge level SOC2 of the second battery 14. When the power used to charge the first battery 13 exceeds the allowable input power Win1 in S160, the current command Ib2* for the second battery 14 is maintained at the current current command Ib2* (S180). Since the current command Ib2* for the second battery 14 is kept at the current current command Ib2*, it is possible to suppress the power used to charge the first battery 13 from significantly exceeding the allowable input power Win1. Once the current command Ib2* is changed or maintained, the process returns to S140, where the upper and lower arms of the second inverter 24 are duty-controlled using the changed or maintained current command Ib2*. The process from S140 to S180 is repeated until the duty cycle D2 exceeds the predetermined ratio D2ref in S150, gradually bringing the duty cycle D2 closer to the predetermined ratio D2ref. When the duty cycle D2 exceeds the predetermined ratio D2ref in S150, the upper arms of the first and second inverters 22 and 24 are turned ON and fixed (S190), ending the routine.In this way, by changing the current command Ib2* in a direction that brings the charge level SOC1 of the first battery 13 closer to the charge level SOC2 of the second battery 14, and gradually bringing the duty cycle D2 of the second inverter 24 closer to a predetermined ratio D2ref, the upper arms of the first and second inverters 22 and 24 are turned on and fixed, thereby suppressing the discrepancy between the charge level SOC1 of the first battery 13 and the charge level SOC2 of the second battery 14, and preventing unintended current from flowing.

[0017] Although the embodiments for implementing this disclosure have been described above, this disclosure is not limited in any way to these embodiments, and it is of course possible to implement it in various forms without departing from the gist of this disclosure. [Explanation of symbols]

[0018] 13 First battery, 14 Second battery, 22 First inverter, 24 Second inverter.

Claims

[Claim 1] A power supply system comprising a first and a second battery, A motor having three-phase coils, A first inverter is connected to the first battery via a first positive electrode line and a first negative electrode line, and is also connected to one end of the three-phase coil, A second inverter is connected to the second battery via a second positive electrode line and a second negative electrode line, and is also connected to the other end of the three-phase coil, A charging connector connected to the first positive electrode line and the negative electrode line, and electrically connectable to the charging equipment, When charging the first and second batteries in parallel using the power of the charging equipment, the control device sets the minimum values ​​of the first allowable input power of the first battery and the second allowable input power of the second battery as the common required power of the first and second batteries, sets twice the common required power as the total required power, requests the charging equipment for the total required power or the total required current based on the total required power, and controls the first and second inverters using the common required power or the current command for the second battery based on the common required power, and when the upper arm of the first inverter is fixed on and the upper and lower arms of the second inverter are under duty cycle control, the control device fixes the upper arms of the first and second inverters on after the duty cycle ratio in the duty cycle control of the second inverter becomes equal to or greater than a predetermined ratio, A power supply system equipped with the following features.

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