JP7301649B2 - power conversion system - Google Patents

Description

The present invention relates to a power conversion system that converts power of a power storage device.

2. Description of the Related Art Conventionally, in a system in which a plurality of power storage devices are operated in parallel, there is provided a master device that controls communication as a master of each power storage device. For example, in the battery control device 10 described in Patent Document 1, the control device 21 manages the SOC (State Of Charge) of a plurality of batteries 13 and 14 connected in parallel, and the plurality of batteries are in a balanced state. controlled to be

JP 2013-38831 A

However, in the conventional method of controlling the SOCs of a plurality of power storage devices using a master device, it is difficult to handle failure of the master device. In addition, when increasing or decreasing the number of power storage devices, it is necessary to adjust the control method by the master device, and furthermore, there is a problem that the provision of the master device increases the cost.

SUMMARY OF THE INVENTION An object of the present invention, which has been made in view of such circumstances, is to provide a power conversion system capable of balancing the SOCs of a plurality of power storage devices without having a master device.

In order to solve the above problems, a power conversion system according to the present invention is a power conversion system that includes a plurality of power storage devices and the same number of power conversion devices as the power storage devices that are connected to the power storage devices on a one-to-one basis. Each of the power conversion devices has an SOC detection unit that detects the remaining capacity of the corresponding power storage device, a command value determination unit that determines a command value according to the remaining capacity, and a command value determination unit that determines the command value based on the command value. and a power conversion unit that converts the voltage of the power storage device, and the command value determination unit, when the voltage of the DC bus connected to the power conversion unit is lower than a first threshold, converts the power storage device to If the voltage is greater than a second threshold, the power storage device is determined to be charged, and regardless of the remaining capacity of the power storage device, the first threshold and the second threshold are determined. When discharging from the power storage device with the respective threshold values constant, the command value is determined so that the upper limit value of the discharge current increases as the remaining capacity of the power storage device increases, and the power storage device is charged. (3), wherein the command value is determined such that the upper limit value of the charging current decreases as the remaining capacity of the power storage device increases .

Further , a power conversion system according to the present invention is a power conversion system that includes a plurality of power storage devices and power conversion devices that are connected to the power storage devices on a one-to-one basis and that are the same in number as the power storage devices. Each power conversion device includes an SOC detection unit that detects the remaining capacity of the corresponding power storage device, a command value determination unit that determines a command value according to the remaining capacity, and a voltage of the power storage device based on the command value. and the command value determination unit determines to discharge the power storage device when the voltage of the DC bus connected to the power conversion unit is lower than a first threshold. and if the voltage is greater than a second threshold, the power storage device is determined to be charged, and the first threshold and the second threshold are set constant regardless of the remaining capacity of the power storage device. Further, when the upper limit value of the discharge current and the upper limit value of the charge current are set to be constant and the power storage device is discharged, the higher the remaining capacity of the power storage device, the higher the voltage of the DC bus. When the command value is determined so that the current decreases from the upper limit value and the power storage device is charged, the higher the remaining capacity of the power storage device, the higher the charging current reaches the upper limit at the time when the voltage of the DC bus is high. The command value is determined so as to reach

Further , a power conversion system according to the present invention is a power conversion system that includes a plurality of power storage devices and power conversion devices that are connected to the power storage devices on a one-to-one basis and that are the same in number as the power storage devices. Each power conversion device includes an SOC detection unit that detects the remaining capacity of the corresponding power storage device, a command value determination unit that determines a command value according to the remaining capacity, and a voltage of the power storage device based on the command value. and the command value determination unit determines to discharge the power storage device when the voltage of the DC bus connected to the power conversion unit is lower than a first threshold. and if the voltage is greater than the second threshold, the power storage device is determined to be charged, and the upper limit of the discharge current and the upper limit of the charge current are set constant regardless of the remaining capacity of the power storage device. In the case of discharging from the power storage device, as the remaining capacity of the power storage device increases, the discharge current decreases from the upper limit value at the time when the voltage of the DC bus is high, and the first threshold value increases. In the case where the command value is determined to charge the power storage device, the second threshold increases as the remaining capacity of the power storage device increases, and the charging current increases at the time when the voltage of the DC bus is high. The command value is determined so as to reach the upper limit value.

Further , a power conversion system according to the present invention is a power conversion system that includes a plurality of power storage devices and power conversion devices that are connected to the power storage devices on a one-to-one basis and that are the same in number as the power storage devices. Each power conversion device includes an SOC detection unit that detects the remaining capacity of the corresponding power storage device, a command value determination unit that determines a command value according to the remaining capacity, and a voltage of the power storage device based on the command value. and the command value determination unit determines to discharge the power storage device when the voltage of the DC bus connected to the power conversion unit is lower than a first threshold. and if the voltage is greater than a second threshold, the power storage device is determined to be charged, and the first threshold and the second threshold are set constant regardless of the remaining capacity of the power storage device. When discharging from the power storage device, the upper limit of the discharge current increases as the remaining capacity of the power storage device increases, and the discharge current decreases from the upper limit when the voltage of the DC bus is high. In the case where the command value is determined and the power storage device is charged, the larger the remaining capacity of the power storage device, the higher the charging current reaches the upper limit value at the time when the voltage of the DC bus is high, and the charging current reaches the upper limit value. The command value is determined so that the upper limit value becomes small.

Further , a power conversion system according to the present invention is a power conversion system that includes a plurality of power storage devices and power conversion devices that are connected to the power storage devices on a one-to-one basis and that are the same in number as the power storage devices. Each power conversion device includes an SOC detection unit that detects the remaining capacity of the corresponding power storage device, a command value determination unit that determines a command value according to the remaining capacity, and a voltage of the power storage device based on the command value. and the command value determination unit determines to discharge the power storage device when the voltage of the DC bus connected to the power conversion unit is lower than a first threshold. If the voltage is greater than the second threshold, it is determined that the power storage device is to be charged. When the command value is determined so that the discharge current decreases from the upper limit value at the time when the value increases and the voltage of the DC bus is high, and the first threshold value increases, and the power storage device is charged, The second threshold increases as the remaining capacity of the power storage device increases, and the command value is set so that the charging current reaches the upper limit when the voltage of the DC bus is high, and the upper limit of the charging current decreases. It is characterized by determining.

According to the present invention, it is possible to balance the SOCs of a plurality of power storage devices without providing a master device.

It is a block diagram showing an example of composition of a power conversion system concerning one embodiment of the present invention. It is a block diagram which shows the structural example of the control part in the power conversion system which concerns on one Embodiment of this invention. It is a figure which shows the 1st example of the electric current command value in the power conversion system which concerns on one Embodiment of this invention. FIG. 5 is a diagram showing a second example of current command values in the power conversion system according to one embodiment of the present invention; FIG. 5 is a diagram showing a third example of current command values in the power conversion system according to one embodiment of the present invention; FIG. 9 is a diagram showing a fourth example of current command values in the power conversion system according to one embodiment of the present invention; FIG. 11 is a diagram showing a fifth example of current command values in the power conversion system according to one embodiment of the present invention;

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration example of a power conversion system 1 according to one embodiment of the present invention. The power conversion system 1 includes a plurality of power conversion devices 10 (first power conversion device 10-1 and second power conversion device 10-2), a plurality of power storage devices 20 (first power storage device 20-1 and second power storage device device 20-2). FIG. 1 shows an example in which the number of power converters 10 and power storage devices 20 is two. Since the configurations of the first power conversion device 10-1 and the second power conversion device 10-2 are the same, they will be described as the power conversion device 10 without distinguishing between them. Further, since the first power storage device 20-1 and the second power storage device 20-2 are also the same, they will be described as the power storage device 20 without distinguishing between them.

Since the power converters 10 are connected one-to-one with the power storage devices 20 such as batteries, the number of the power converters 10 is the same as that of the power storage devices 20 . Each of the plurality of power conversion devices 10 includes a control section 11 and a power conversion section 12 .

Control unit 11 controls power conversion unit 12 according to the remaining capacity of power storage device 20 . Details of the control unit 11 will be described later.

The power conversion unit 12 has a plurality of switching elements, and turns on and off the switching elements according to the gate signal input from the control unit 11 to convert the DC voltage input from the power storage device 20 into a different DC voltage. . The power converter 12 is connected to the DC bus 30 . For example, when applying the power conversion system 1 to a railroad vehicle, the DC bus 30 is a DC link, an overhead wire, or the like inside the vehicle.

FIG. 2 is a block diagram showing a configuration example of the control unit 11. As shown in FIG. In the example shown in FIG. 2 , the control section 11 includes a voltage detection section 111 , an SOC detection section 112 , a command value determination section 113 and a gate signal generation section 114 .

Voltage detection unit 111 detects the voltage of DC bus 30 and outputs the detected voltage to command value determination unit 113 .

SOC detection unit 112 detects the remaining capacity (SOC) of corresponding power storage device 20 and outputs the detected remaining capacity to command value determination unit 113 . Any conventional method can be adopted as the SOC detection method. For example, the SOC detection unit 112 detects the SOC using the specific gravity of the electrolyte of the power storage device 20, the integrated value of the charge/discharge current, and the like.

Command value determination unit 113 compares the DC bus voltage detected by voltage detection unit 111 with a predetermined threshold to determine charging/discharging of power storage device 20 . For example, when the DC bus voltage is lower than the first threshold V _th1 , the command value determination unit 113 determines that the power storage device 20 is to be discharged, and the DC bus voltage reaches the second threshold V _th2 (here, V _th2 >V _th1 ), it is determined that power storage device 20 is to be charged.

Further, command value determination section 113 determines a command value according to the remaining capacity detected by SOC detection section 112 and outputs the determined command value to gate signal generation section 114 . The command value may be a current command value or a power command value.

The gate signal generation unit 114 performs PWM control based on the command value generated by the command value determination unit 113 to generate a gate signal, and outputs the generated gate signal to the power conversion unit 12 . On/off of the switching element of the power converter 12 is controlled by the gate signal.

Next, the relationship between the command value determined by command value determination unit 113 and the voltage of DC bus 30 will be described.

FIG. 3 is a diagram showing a first example of a current command value determined by command value determining section 113. In FIG. In the following description, the command value determining unit 113 determines the current command value as the command value. In FIGS. 3 to 7, the horizontal axis indicates the voltage of the DC bus 30 and the vertical axis indicates the current command value. Since the direction of the current differs between discharging and charging, the discharge current and the charge current mean absolute values in the following description.

In the example illustrated in FIG. 3 , the command value determining unit 113 keeps the first threshold V _th1 and the second threshold V _th2 constant regardless of the remaining capacity of the power storage device 20 . In addition, command value determination unit 113 determines that the voltage of DC bus 30 becomes a constant voltage when the discharging current starts to decrease from the upper limit value and the charging current reaches the upper limit value, regardless of the remaining capacity of power storage device 20. The current command value is determined so that the voltage of the DC bus 30 at the time of switching is a constant voltage. When power storage device 20 is discharged, command value determination unit 113 determines the current command value such that the upper limit value of the discharge current increases as the remaining capacity of power storage device 20 increases. In addition, when power storage device 20 is charged, command value determination unit 113 determines the current command value such that the upper limit value of the charging current decreases as the remaining capacity of power storage device 20 increases.

FIG. 4 is a diagram showing a second example of the current command value determined by command value determining section 113. In FIG. In the example shown in FIG. 4, the command value determination unit 113 sets the first threshold value V _th1 and the second threshold value V _th2 constant regardless of the remaining capacity of the power storage device 20, and sets the upper limit value of the discharge current, and the upper limit of the charging current are set constant. In addition, when discharging from power storage device 20, command value determination unit 113 provides a current command such that the discharge current decreases from the upper limit value at the point in time when the voltage of DC bus 30 increases as the remaining capacity of power storage device 20 increases. determine the value. In addition, when charging power storage device 20, command value determination unit 113 issues a current command so that the charging current reaches the upper limit value at a point in time when the voltage of DC bus 30 increases as the remaining capacity of power storage device 20 increases. determine the value.

FIG. 5 is a diagram showing a third example of the current command value determined by command value determining section 113. In FIG. In the example shown in FIG. 5 , command value determination unit 113 sets the upper limit of discharge current and the upper limit of charge current to be constant regardless of the remaining capacity of power storage device 20 . In addition, when the power storage device 20 is discharged, the command value determination unit 113 determines that as the remaining capacity of the power storage device 20 increases, the discharge current decreases from the upper limit value at the time when the voltage of the DC bus 30 is high. The current command value is determined so that the threshold V _th1 of becomes large (that is, the discharge is stopped when the voltage of the DC bus 30 is high). In addition, when command value determination unit 113 causes power storage device 20 to be charged, second threshold V th2 increases as the remaining capacity of power storage device 20 increases (that is, when the voltage of DC bus 30 is high, the second threshold value V _th2 increases. charging is started) and the current command value is determined so that the charging current reaches the upper limit when the voltage of the DC bus 30 is high.

FIG. 6 is a diagram showing a fourth example of the current command value determined by command value determining section 113. In FIG. In the example illustrated in FIG. 6 , the command value determining unit 113 keeps the first threshold V _th1 and the second threshold V _th2 constant regardless of the remaining capacity of the power storage device 20 . In addition, when the power storage device 20 is discharged, the command value determination unit 113 increases the upper limit value of the discharge current as the remaining capacity of the power storage device 20 increases. Decide the current command value so that is lower than the upper limit. Further, when the power storage device 20 is to be charged, the command value determining unit 113 determines that the charging current reaches the upper limit value at the time when the voltage of the DC bus 30 is high and the charging current reaches the upper limit value as the remaining capacity of the power storage device 20 increases. The current command value is determined so that the upper limit of is small.

FIG. 7 is a diagram showing a fifth example of the current command value determined by command value determining section 113. In FIG. In the example shown in FIG. 7 , command value determination unit 113 determines that the larger the remaining capacity of power storage device 20 is, the higher the upper limit value of the discharge current is and the higher the voltage of DC bus 30 is. The current command value is determined so that the discharge current drops from the upper limit value at the point in time and the first threshold value V _th1 increases. Further, when charging power storage device 20, command value determining unit 113 increases second threshold V _th2 as the remaining capacity of power storage device 20 increases. reaches the upper limit and the upper limit of the charging current becomes smaller.

As described above, in the present invention, in the power conversion system 1 in which a plurality of power storage devices 20 are operated in parallel, there is no device that controls communication as a master of each power storage device 20, and communication between the power storage devices 20 is not performed. The SOC of the power storage device 20 can be balanced by lowering the burden rate of the power storage device 20 with a low SOC. Therefore, any number of power storage devices 20 can be connected in parallel, and the number of power storage devices 20 can be increased or decreased along the way.

Also, the method of determining the current command value according to the SOC of the present invention can be expected to have the effect of correcting the difference in the load rate due to the error of the voltage detector or the current detector. Moreover, even when there is a difference in battery capacity of power storage device 20, the burden ratio of the battery with the larger capacity increases, and the SOC is balanced. Further, when the DC bus 30 is an overhead wire, it can function as an overhead wire voltage compensating device for keeping the overhead wire voltage constant.

Although the above embodiments have been described as representative examples, it will be apparent to those skilled in the art that many modifications and substitutions may be made within the spirit and scope of the invention. Therefore, the present invention should not be construed as limited by the embodiments described above, and various modifications and changes are possible without departing from the scope of the appended claims. For example, it is possible to combine a plurality of configuration blocks described in the configuration diagrams of the embodiments into one, or divide one configuration block.

1 power conversion system 10 (10-1, 10-2) power conversion device 11 control unit 12 power conversion unit 20 (20-1, 20-2) power storage device 30 DC bus 111 voltage detection unit 112 SOC detection unit 113 command value Determination unit 114 Gate signal generation unit

Claims (5)

A power conversion system comprising: a plurality of power storage devices; and power conversion devices connected to the power storage devices in a one-to-one correspondence, the same number as the power storage devices,
Each of the power converters includes:
an SOC detection unit that detects the remaining capacity of the corresponding power storage device;
a command value determination unit that determines a command value according to the remaining capacity;
a power conversion unit that converts the voltage of the power storage device based on the command value;
with
The command value determination unit is
When the voltage of the DC bus connected to the power conversion unit is lower than a first threshold, it is determined to discharge the power storage device, and when the voltage is higher than a second threshold, the power storage device decide to let the device charge,
setting the first threshold and the second threshold constant regardless of the remaining capacity of the power storage device;
When discharging from the power storage device, the command value is determined so that the upper limit value of the discharge current increases as the remaining capacity of the power storage device increases,
A power conversion system , wherein when charging the power storage device, the command value is determined such that the upper limit of the charging current decreases as the remaining capacity of the power storage device increases. A power conversion system comprising: a plurality of power storage devices; and power conversion devices connected to the power storage devices in a one-to-one correspondence, the same number as the power storage devices,
Each of the power converters includes:
an SOC detection unit that detects the remaining capacity of the corresponding power storage device;
a command value determination unit that determines a command value according to the remaining capacity;
a power conversion unit that converts the voltage of the power storage device based on the command value;
with
The command value determination unit is
When the voltage of the DC bus connected to the power conversion unit is lower than a first threshold, it is determined to discharge the power storage device, and when the voltage is higher than a second threshold, the power storage device decide to let the device charge,
Regardless of the remaining capacity of the power storage device, the first threshold value and the second threshold value are set constant, and the upper limit value of the discharge current and the upper limit value of the charge current are set constant, respectively;
When discharging from the power storage device, the command value is determined so that the discharge current decreases from the upper limit value at the point in time when the voltage of the DC bus increases as the remaining capacity of the power storage device increases;
When the power storage device is charged, the command value is determined so that the charging current reaches an upper limit at a point in time when the voltage of the DC bus increases as the remaining capacity of the power storage device increases. power conversion system. A power conversion system comprising: a plurality of power storage devices; and power conversion devices connected to the power storage devices in a one-to-one correspondence, the same number as the power storage devices,
Each of the power converters includes:
an SOC detection unit that detects the remaining capacity of the corresponding power storage device;
a command value determination unit that determines a command value according to the remaining capacity;
a power conversion unit that converts the voltage of the power storage device based on the command value;
with
The command value determination unit is
When the voltage of the DC bus connected to the power conversion unit is lower than a first threshold, it is determined to discharge the power storage device, and when the voltage is higher than a second threshold, the power storage device decide to let the device charge,
Regardless of the remaining capacity of the power storage device, the upper limit of the discharge current and the upper limit of the charge current are set constant,
When discharging from the power storage device, the larger the remaining capacity of the power storage device, the higher the discharge current decreases from the upper limit when the voltage of the DC bus is high, and the first threshold is increased. determine the command value,
When the power storage device is charged, the second threshold increases as the remaining capacity of the power storage device increases, and the charging current reaches the upper limit when the voltage of the DC bus is high. A power conversion system characterized by determining a command value. A power conversion system comprising: a plurality of power storage devices; and power conversion devices connected to the power storage devices in a one-to-one correspondence, the same number as the power storage devices,
Each of the power converters includes:
an SOC detection unit that detects the remaining capacity of the corresponding power storage device;
a command value determination unit that determines a command value according to the remaining capacity;
a power conversion unit that converts the voltage of the power storage device based on the command value;
with
The command value determination unit is
When the voltage of the DC bus connected to the power conversion unit is lower than a first threshold, it is determined to discharge the power storage device, and when the voltage is higher than a second threshold, the power storage device decide to let the device charge,
setting the first threshold and the second threshold constant regardless of the remaining capacity of the power storage device;
When discharging from the power storage device, the upper limit of the discharge current increases as the remaining capacity of the power storage device increases, and the discharge current decreases from the upper limit when the voltage of the DC bus is high. determine the command value,
When the power storage device is charged, the higher the remaining capacity of the power storage device, the higher the charging current reaches the upper limit when the voltage of the DC bus is high, and the lower the upper limit of the charging current. A power conversion system characterized by determining a command value. A power conversion system comprising: a plurality of power storage devices; and power conversion devices connected to the power storage devices in a one-to-one correspondence, the same number as the power storage devices,
Each of the power converters includes:
an SOC detection unit that detects the remaining capacity of the corresponding power storage device;
a command value determination unit that determines a command value according to the remaining capacity;
a power conversion unit that converts the voltage of the power storage device based on the command value;
with
The command value determination unit is
When the voltage of the DC bus connected to the power conversion unit is lower than a first threshold, it is determined to discharge the power storage device, and when the voltage is higher than a second threshold, the power storage device decide to let the device charge,
When discharging from the power storage device, the higher the remaining capacity of the power storage device, the higher the upper limit of the discharge current. Determine the command value so that the threshold of
When the power storage device is charged, the larger the remaining capacity of the power storage device, the larger the second threshold value. A power conversion system, wherein the command value is determined so that the value becomes small.

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