JP2023162979A - storage battery system - Google Patents

Abstract

To provide a storage battery system that can complete precharging without causing problems while supplying control power to an inverter.SOLUTION: A storage battery system A1 includes power storage equipment 2, an inverter circuit 11 that converts DC power output by the power storage equipment 2 into AC power, a smoothing capacitor 12 connected to the DC side of the inverter circuit 11, and a precharge circuit 3 that is connected between the power storage equipment 2 and the smoothing capacitor 12, and is used to precharge the smoothing capacitor 12. Power for controlling the inverter circuit 11 is supplied from a connection line that connects the power storage equipment 2 and the precharge circuit 3.SELECTED DRAWING: Figure 1

Description

The present invention relates to a storage battery system.

BACKGROUND ART A storage battery system is known that converts DC power of a storage battery into AC power using an inverter circuit and outputs the AC power. In the storage battery system, a smoothing capacitor is connected to the DC side of the inverter circuit. The smoothing capacitor stabilizes the operation of the inverter circuit by smoothing out fluctuations in DC voltage. If the storage battery directly charges the smoothing capacitor when the storage battery system starts up, an inrush current may flow and damage the circuit. The storage battery system includes a precharge circuit for precharging a smoothing capacitor to prevent inrush current. The precharge circuit is a circuit in which a resistor and a DC relay are connected in parallel. The precharge circuit first opens the DC relay and charges (precharges) the smoothing capacitor while limiting the current through the resistor. Thereafter, the precharge circuit closes the DC relay and charges the smoothing capacitor directly from the storage battery. Patent Document 1 discloses a storage battery system for an electric vehicle that includes a precharge circuit. Further, in a precharge circuit, various methods have been proposed as a method for determining the end of precharge in order to switch a DC relay. For example, there is a method of switching the DC relay to a closed state to complete precharging when the differential voltage, which is the difference between the terminal voltage of the storage battery and the voltage between the terminals of the smoothing capacitor, becomes less than a preset threshold. .

Patent No. 3736933

In the charging system disclosed in Patent Document 1, control power for the inverter is supplied from a connection line connecting a smoothing capacitor and a precharge circuit via a DC/DC converter. In this case, the current obtained by subtracting the load current of the control power source of the inverter from the current of the storage battery becomes the charging current of the smoothing capacitor. When the differential voltage decreases as the smoothing capacitor is charged, the current output by the storage battery decreases. When the current output by the storage battery becomes equal to the load current of the control power source, the smoothing capacitor is no longer charged. If the differential voltage at this time is larger than a preset threshold value, a problem arises in that the DC relay cannot be switched to a closed state and precharging cannot be completed. This problem can be avoided by setting a large value as the threshold, but the inrush current when switching the DC relay to the closed state increases, which may damage the circuit. Furthermore, by reducing the resistance value of the resistor in the precharge circuit, the differential voltage can be further reduced. However, as a countermeasure against a short circuit in the wiring between the inverter and the precharge circuit, it is necessary to increase the capacitance of the resistor in the precharge circuit, which is undesirable in terms of space and cost for arranging the precharge circuit.

The present invention was conceived under the above circumstances, and its purpose is to provide a storage battery system that can complete precharging without causing any problems while supplying control power to an inverter. .

In order to solve the above problems, the present invention takes the following technical measures.

A storage battery system provided by a first aspect of the present invention includes a storage battery, an inverter circuit that converts DC power outputted by the storage battery into AC power, a smoothing capacitor connected to the DC side of the inverter circuit, and a smoothing capacitor connected to the DC side of the inverter circuit. a precharge circuit connected between a storage battery and the smoothing capacitor to precharge the smoothing capacitor, and a power source for controlling the inverter circuit connects the storage battery and the precharge circuit. Supplied from the connecting line.

In a preferred embodiment of the present invention, the precharge circuit further includes a detection means for detecting a difference voltage between the terminal voltage of the storage battery and the voltage between the terminals of the smoothing capacitor, and the precharge circuit is configured to detect a voltage difference between an open circuit state and a closed circuit state. a resistor connected in parallel to the switching means; and a switching means for switching the switching means from the open state to the closed state when the differential voltage becomes a threshold value or less. We are prepared.

In a preferred embodiment of the present invention, the detection means detects a voltage between terminals of the resistor as the differential voltage.

In a preferred embodiment of the present invention, the opening/closing means is arranged on a connection line on the positive electrode side that connects the storage battery and the smoothing capacitor.

In a preferred embodiment of the present invention, the opening/closing means is arranged on a negative electrode side connection line that connects the storage battery and the smoothing capacitor.

According to the present invention, power for controlling the inverter circuit is supplied from the connection line that connects the storage battery and the precharge circuit. In this case, the combined resistance value between the precharge circuit and the inverter circuit is larger than that in the case where the power is supplied from the connection line connecting the smoothing capacitor and the precharge circuit. Therefore, the differential voltage when the smoothing capacitor is no longer charged becomes small. Thereby, the storage battery system according to the present invention can complete precharging without causing any problems.

Other features and advantages of the invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the overall configuration of a storage battery system according to a first embodiment. FIG. 1 is a block diagram showing the overall configuration of a conventional storage battery system. It is a figure showing a simulation result. FIG. 2 is a block diagram showing the overall configuration of a storage battery system according to a second embodiment.

Embodiments of the present invention will be specifically described below with reference to the drawings.

[First embodiment]
FIG. 1 is a block diagram showing the overall configuration of a storage battery system A1 according to the first embodiment.

Storage battery system A1 includes a power conditioner 1, power storage equipment 2, and a precharge circuit 3. In this embodiment, the power storage equipment 2 and the precharge circuit 3 are housed in a storage battery storage board 4. The storage battery system A1 converts DC power output from the power storage equipment 2 into AC power using the power conditioner 1, and supplies the AC power to, for example, an electric power system. Furthermore, the storage battery system A1 converts AC power input from the power grid into DC power using the power conditioner 1, and charges the power storage equipment 2.

The power storage facility 2 includes a plurality of storage batteries. Each storage battery is a secondary battery that can be repeatedly charged and discharged. Each storage battery is, for example, a lithium ion battery, a nickel-hydrogen battery, a nickel-cadmium battery, a lead-acid battery, or the like, although it is not particularly limited.
Note that each storage battery may be a capacitor such as an electric double layer capacitor instead of a secondary battery. FIG. 1 shows that power storage equipment 2 includes a plurality of storage batteries connected in series, and that power storage equipment 2 as a whole has an internal resistance. Note that the number and connection method of storage batteries included in the power storage equipment 2 are not limited. The power storage equipment 2 is charged by DC power input from the power conditioner 1, and also discharges the power stored therein.

Power conditioner 1 is electrically connected between power storage equipment 2 and a power system (not shown). The power conditioner 1 has a DC side connected to a power storage facility 2 and an AC side connected to an electric power system. The power conditioner 1 converts the DC power outputted by the power storage equipment 2 by discharging into AC power, and supplies the AC power to the power grid. The power conditioner 1 also charges the power storage equipment 2 by converting AC power input from the power grid into DC power and outputting the DC power to the power storage equipment 2 . That is, power conditioner 1 controls charging and discharging of power storage equipment 2 . The power conditioner 1 includes an inverter circuit 11, a smoothing capacitor 12, a DC breaker 13, and a DC/DC converter circuit 14.

The inverter circuit 11 is a three-phase inverter including, for example, three sets of six switching elements, and converts DC power to AC power by turning each switching element on and off. Note that the configuration of the inverter circuit 11 is not limited.

The smoothing capacitor 12 is a large capacitor connected between a pair of terminals on the DC side of the inverter circuit 11. Smoothing capacitor 12 stabilizes the operation of inverter circuit 11 by smoothing fluctuations in the DC voltage input from power storage equipment 2 .

The DC breaker 13 is a so-called circuit breaker, and interrupts the DC circuit when an abnormality such as overcurrent occurs. Resistors are connected in parallel to the inverter circuit 11 side and the power storage equipment 2 side of the DC breaker 13, respectively.

The DC/DC converter circuit 14 supplies power for controlling the power conditioner 1 (inverter circuit 11). The DC/DC converter circuit 14 has an input side connected to a connection line connecting the power storage equipment 2 and the precharge circuit 3, and an output side connected to a control device (not shown) of the power conditioner 1. The DC/DC converter circuit 14 steps down the voltage input from the power storage equipment 2 to a voltage (for example, 24 V) required by the control device and outputs the voltage. That is, power for controlling the power conditioner 1 (inverter circuit 11) is supplied from the connection line connecting the power storage equipment 2 and the precharge circuit 3 via the DC/DC converter circuit 14. Note that the configuration of the DC/DC converter circuit 14 is not limited.

Precharge circuit 3 is arranged on a connection line that connects power storage equipment 2 and power conditioner 1. The precharge circuit 3 prevents an inrush current flowing when the power storage equipment 2 directly charges the smoothing capacitor 12 when the storage battery system A1 is started up or when operation is resumed after maintenance. The precharge circuit 3 includes a resistor 31, a voltage sensor 32, a DC relay 33, and a switching circuit 34.

The DC relay 33 is arranged on the positive electrode side connection line that connects the power storage equipment 2 and the power conditioner 1. The DC relay 33 is a so-called electromagnetic contactor, and is opened and closed by a signal from the switching circuit 34 to switch between an open state and a closed state. Note that the DC relay 33 may be any opening/closing means that switches between an open state and a closed state, and its configuration is not limited. The resistor 31 is connected in parallel to the DC relay 33, and current flows when the DC relay 33 is in an open state. Resistor 31 limits the current flowing.

The voltage sensor 32 detects the voltage difference ΔV between the terminals of the power storage equipment 2 and the voltage between the terminals of the smoothing capacitor 12 by detecting the voltage between the terminals of the resistor 31 during precharging. Note that the voltage sensor 32 only needs to be able to detect the differential voltage ΔV, and its arrangement position and configuration are not limited. For example, the voltage sensor 32 includes a sensor that detects the terminal voltage of the power storage equipment 2, a sensor that detects the voltage between the terminals of the smoothing capacitor 12, and a calculation unit that calculates a differential voltage ΔV that is the difference between the detected values of both sensors. It may also include.

The switching circuit 34 switches the DC relay 33 between an open state and a closed state based on the differential voltage ΔV detected by the voltage sensor 32. The switching circuit 34 opens the DC relay 33 while the voltage difference ΔV is greater than the threshold value, and switches the DC relay 33 to the closed state when the voltage difference ΔV becomes equal to or less than the threshold value. The threshold value is set to an appropriate value based on simulations and experiments, as will be described later. When the DC relay 33 is in the closed state, the power storage equipment 2 and the power conditioner 1 are directly connected. On the other hand, when the DC relay 33 is in an open state, the power storage equipment 2 and the power conditioner 1 are connected via the resistor 31.

Since the smoothing capacitor 12 is not charged when the storage battery system A1 is started, the differential voltage ΔV is larger than the threshold value. Therefore, the switching circuit 34 opens the DC relay 33. Since power storage equipment 2 and power conditioner 1 are connected through resistor 31, smoothing capacitor 12 is charged while the current output from power storage equipment 2 is limited. As the smoothing capacitor 12 is charged, the differential voltage ΔV gradually decreases. When the differential voltage ΔV becomes equal to or less than the threshold value, the switching circuit 34 switches the DC relay 33 to a closed state. Although the power storage equipment 2 and the power conditioner 1 are directly connected, since the differential voltage ΔV is small, no large current flows.

FIG. 2 is a block diagram showing the overall configuration of a conventional storage battery system A100 for comparison with the storage battery system A1. Storage battery system A100 includes a power conditioner 100, power storage equipment 2, and precharge circuit 3. The storage battery system A100 differs from the storage battery system A1 in that power for controlling the power conditioner 100 is supplied inside the power conditioner 100.

As shown in FIG. 2, in the power conditioner 100, the input side of the DC/DC converter circuit 14 is connected to a connection line that connects the smoothing capacitor 12 and the DC breaker 13. That is, power conditioner 100 is supplied with power for control from a connection line connecting internal smoothing capacitor 12 and DC breaker 13 via DC/DC converter circuit 14 .

Simulations were performed for the storage battery system A1 shown in FIG. 1 and the storage battery system A100 shown in FIG. 2. In the simulation, the combined voltage of the plurality of storage batteries of the power storage equipment 2 is set to 600V, the resistance value of the internal resistance of the power storage equipment 2 is set to 250 mΩ, and the resistance value of the resistor 31 of the precharge circuit 3 is set to 600Ω. Further, the combined resistance of the resistors connected in parallel between the DC side input/output terminal pair of the power conditioner 1 (100) and the DC side terminal pair of the inverter circuit 11 is assumed to be 97.6 kΩ. Further, the capacitance of the smoothing capacitor 12 is assumed to be 13,200 μF. The control device of the power conditioner 1 (100) consumes about 50 W of power when used at maximum. The resistance conversion value obtained by converting the maximum power of 50 W consumed by the control device into a resistance value is 600 V x 600 V ÷ 50 W = 7.2 kΩ (note that this is an approximate estimate that ignores the voltage drop at each resistor), so in this simulation, , the DC/DC converter circuit 14 was a 7.2 kΩ resistor.

In the storage battery system A100 shown in FIG. 2, the 7.2 kΩ resistance connected in parallel is combined with the 97.6 kΩ combined resistance, so the total combined resistance value of the DC side circuit of the power conditioner 100 is 6705 Ω. . Therefore, the differential voltage ΔV (voltage between the terminals of the resistor 31 of the precharge circuit 3) when the smoothing capacitor 12 is no longer charged is the total sum of the resistor 31 (600Ω) and the DC side circuit of the power conditioner 100. The voltage is 49.3V from the resistance (6705Ω) and the internal resistance (250mΩ) of the power storage equipment 2. FIG. 3(a) shows a temporal change in the voltage between the terminals of the smoothing capacitor 12 in the simulation. As shown in FIG. 3A, the voltage between the terminals of the smoothing capacitor 12 has increased from "0" to a voltage (approximately 550 V) that is 49.3 V lower than the terminal voltage of the power storage equipment 2.

If you want to complete the precharging before the smoothing capacitor 12 is no longer charged, the threshold value of the differential voltage ΔV in the switching circuit 34 should be set at the time when the smoothing capacitor 12 is no longer charged, taking into consideration the error in the voltage measurement value. It is necessary to set a value approximately 5V larger than the differential voltage ΔV (49.3V). In the storage battery system A100, for example, 55V is set as the threshold value of the differential voltage ΔV. Therefore, when the differential voltage ΔV becomes equal to or less than the threshold value (55V), the switching circuit 34 completes the precharging and switches the DC relay 33 to the closed state. At this time, the maximum current flowing through the DC relay 33 and input to the power conditioner 1 is 55V÷250mΩ=220A. FIG. 3(b) shows a temporal change in the current flowing through the DC relay 33 in the simulation. As shown in FIG. 3(b), when the DC relay 33 is switched to the closed state, the current flowing through the DC relay 33 increases and immediately decreases. The maximum current is about 220A.

On the other hand, in the storage battery system A1 shown in FIG. remains at 97.6 kΩ. Therefore, the differential voltage ΔV when the smoothing capacitor 12 is no longer charged is determined by the resistor 31 (600Ω), the total combined resistance of the DC side circuit of the power conditioner 100 (97.6kΩ), and the internal resistance of the power storage equipment 2. (250mΩ) gives 3.7V. FIG. 3(c) shows a temporal change in the voltage between the terminals of the smoothing capacitor 12 in the simulation. As shown in FIG. 3(c), the voltage between the terminals of the smoothing capacitor 12 has increased from "0" to a voltage (approximately 596 V) that is 3.7 V lower than the terminal voltage of the power storage equipment 2.

If you want to complete the precharging before the smoothing capacitor 12 is no longer charged, the threshold value of the differential voltage ΔV in the switching circuit 34 should be set at the time when the smoothing capacitor 12 is no longer charged, taking into consideration the error in the voltage measurement value. It is necessary to set a value approximately 5V larger than the differential voltage ΔV (3.7V). In the storage battery system A1, the threshold value of the differential voltage ΔV is set to, for example, 10V. Therefore, when the differential voltage ΔV becomes equal to or less than the threshold value (10V), the switching circuit 34 completes the precharging and switches the DC relay 33 to the closed state. At this time, the maximum current flowing through the DC relay 33 and input to the power conditioner 1 is 10V÷250mΩ=40A. FIG. 3(d) shows a temporal change in the current flowing through the DC relay 33 in the simulation. As shown in FIG. 3(d), when the DC relay 33 is switched to the closed state, the current flowing through the DC relay 33 increases and immediately decreases. The maximum current is about 40A.

As described above, in the storage battery system A100 shown in FIG. 2, if the threshold value of the differential voltage ΔV is set so that precharging can be completed, the rush current when the DC relay 33 is switched to the closed state is a large current of about 220A. become. On the other hand, in the storage battery system A1 shown in FIG. 1, even if the threshold value of the differential voltage ΔV is set so that precharging can be completed, the rush current when switching the DC relay 33 to the closed state is suppressed to about 40 A.

Even if a short circuit occurs in the external wiring between the power conditioner 1 and the storage battery storage panel 4 and the current from the power storage equipment 2 continues to flow through the resistor 31 of the precharge circuit 3, the resistor The container 31 has a power capacity that will not cause burnout. Since the maximum current value when the external wiring is completely short-circuited is 1A (=600V÷600Ω), in the storage battery system A1 shown in FIG. 1, the power value at the resistor 31 (600Ω) is 600W. Therefore, with twice the margin, a resistor with a power capacity of 1200 W is adopted as the resistor 31. If, in the storage battery system A100 shown in FIG. 2, the threshold value set in the switching circuit 34 is set to the same value (3.7V) as in the storage battery system A1 shown in FIG. 1, the resistance value of the resistor 31 will be 41. It is necessary to set the voltage to 6Ω (=(6705Ω+0.25Ω)×3.7V/(600V−3.7V)). In this case, the maximum current value when the external wiring is completely short-circuited is 14.4A (=600V÷41.6Ω), so the power value at resistor 31 (41.6Ω) is 8626W (=41.6Ω×14.4A). ×14.4A). If the margin is doubled, a resistor with a power capacity of about 17.3 kW is required as the resistor 31. Therefore, a large space is required for arranging the precharge circuit 3, and the cost also increases.

Note that each value set in the simulation is an example for the simulation. In the actual storage battery system A1, the combined voltage of a plurality of storage batteries of the power storage equipment 2, the resistance value of the internal resistance, the resistance value of the resistor 31, the resistance value of each resistor inside the power conditioner 1, the capacity of the smoothing capacitor 12, Furthermore, the power consumption of the control device of the power conditioner 1 is not limited.

Next, the effects of the storage battery system A1 according to the present embodiment will be explained.

According to this embodiment, the storage battery system A1 includes a precharge circuit 3. The precharge circuit 3 opens the DC relay 33 and charges (precharges) the smoothing capacitor 12 while limiting the current through the resistor 31 while the differential voltage ΔV is greater than the threshold value. Therefore, the precharge circuit 3 can prevent the inrush current flowing when the power storage equipment 2 directly charges the smoothing capacitor 12 . Further, when the differential voltage ΔV becomes equal to or less than the threshold value, the precharge circuit 3 switches the DC relay 33 to a closed state and directly charges the smoothing capacitor 12 with the current output from the power storage equipment 2. However, since the differential voltage ΔV is small, no large current flows.

Further, according to the present embodiment, power for controlling the power conditioner 1 (inverter circuit 11) is supplied from the connection line that connects the power storage equipment 2 and the precharge circuit 3. In this case, the combined resistance value between the precharge circuit 3 and the inverter circuit 11 is larger than when the smoothing capacitor 12 and the precharge circuit 3 are supplied from the connection line. Since the differential voltage ΔV when the smoothing capacitor 12 is no longer charged becomes small, the threshold value of the differential voltage ΔV in the switching circuit 34 does not need to be set to a large value. Therefore, the storage battery system A1 can complete precharging without increasing the threshold value of the differential voltage ΔV in the switching circuit 34 or decreasing the resistance value of the resistor 31.

Further, according to this embodiment, the voltage sensor 32 detects the voltage between the terminals of the resistor 31. Therefore, voltage sensor 32 can easily detect differential voltage ΔV, which is the difference between the terminal voltage of power storage equipment 2 and the voltage between the terminals of smoothing capacitor 12, during precharging.

In addition, although this embodiment demonstrated the case where the storage battery system A1 is connected to an electric power system, it is not restricted to this. The storage battery system A1 may be connected to the motor, supply power from the power storage equipment 2 to the motor, and charge the power storage equipment 2 with power input from the motor through regeneration.

[Second embodiment]
FIG. 4 is a block diagram showing the overall configuration of a storage battery system A2 according to the second embodiment. In FIG. 4, the same or similar elements as in the first embodiment are given the same reference numerals as in the first embodiment. The storage battery system A2 according to the present embodiment is different from the storage battery system A1 according to the first embodiment in the arrangement position of the DC relay 33 of the precharge circuit 3.

In the precharge circuit 3 according to this embodiment, the DC relay 33 is arranged on the negative electrode side connection line that connects the power storage equipment 2 and the power conditioner 1.

Also in this embodiment, since the precharge circuit 3 opens the DC relay 33 and precharges the smoothing capacitor 12 while the differential voltage ΔV is greater than the threshold value, inrush current can be prevented. Further, the precharge circuit 3 switches the DC relay 33 to a closed state and charges the smoothing capacitor 12 when the differential voltage ΔV becomes equal to or less than the threshold value. However, since the differential voltage ΔV is small, no large current flows. Also, in this embodiment, the power for controlling the power conditioner 1 (inverter circuit 11) is supplied from the connection line connecting the power storage equipment 2 and the precharge circuit 3, so the storage battery system A2 can solve the problem. Precharge can be completed without any occurrence. Moreover, the storage battery system A2 has the same configuration as the storage battery system A1, and thus has the same effects as the storage battery system A1.

The storage battery system according to the present invention is not limited to the embodiments described above. The specific configuration of each part of the storage battery system according to the present invention can be modified in various ways.

A1 to A2: Storage battery system, 11: Inverter circuit, 12: Smoothing capacitor, 2: Power storage equipment, 3: Precharge circuit, 31: Resistor, 32: Voltage sensor, 33: DC relay, 34: Switching circuit

Claims (5)

storage battery and
an inverter circuit that converts the DC power output by the storage battery into AC power;
a smoothing capacitor connected to the DC side of the inverter circuit;
a precharge circuit connected between the storage battery and the smoothing capacitor for precharging the smoothing capacitor;
Equipped with
Power for controlling the inverter circuit is supplied from a connection line connecting the storage battery and the precharge circuit.
Storage battery system. further comprising detection means for detecting a differential voltage that is a difference between the terminal voltage of the storage battery and the voltage between the terminals of the smoothing capacitor,
The precharge circuit is
An opening/closing means for switching between an open circuit state and a closed circuit state;
a resistor connected in parallel to the switching means;
switching means for switching the opening/closing means from the open circuit state to the closed circuit state when the differential voltage becomes equal to or less than a threshold;
It is equipped with
The storage battery system according to claim 1. The detection means detects a voltage between terminals of the resistor as the differential voltage.
The storage battery system according to claim 2. The opening/closing means is arranged on a positive electrode side connection line connecting the storage battery and the smoothing capacitor,
The storage battery system according to claim 2 or 3. The opening/closing means is arranged on a negative electrode side connection line connecting the storage battery and the smoothing capacitor,
The storage battery system according to claim 2 or 3.

Images