Power storage device, power storage control method

Abstract

To effectively utilize surplus regenerative power in a direct current feeding system.SOLUTION: In a power storage device 1, when a voltage of a feeder line 70 is higher than a predetermined charging start voltage and a charging rate of a storage battery board 3 is within a predetermined operating range, a controller 100 causes a power converter 2 to perform a charging operation so as to charge the storage battery board 3 to cause the voltage of the feeder line 70 to approach the charging start voltage. Meanwhile, when the voltage of the feeder line 70 is lower than the charging start voltage, and a current flowing through the feeder line 70 is higher than a predetermined current threshold, and the charging rate of the storage battery board 3 is within a second range, the controller causes the power converter 2 to perform a discharging operation so as to cause the storage battery board 3 to discharge to output the direct current to the feeder line 70 together with a rectifier system 50.SELECTED DRAWING: Figure 1

Description

Technical Field

[0005]

[0001] The present invention relates to a power storage device and a power storage control method for a DC power system.

Background Art

[0002] In recent years, in more than 150 regions and countries around the world, the shift towards a carbon-neutral social system has been progressing. In addition, with the changes in the global situation, phenomena such as the soaring price of liquefied natural gas have occurred. Due to these circumstances, in the electric railway business, which is a consumer of electricity, further energy conservation has become an important issue.

[0003] From the above background, in recent electric railway systems, railway vehicles equipped with a regenerative operation function that converts the mechanical energy during deceleration into electrical energy (regenerated power) and transmits it to the overhead line have come to be used as standard. That is, by utilizing the regenerated power obtained when the vehicle during deceleration performs regenerative operation as the acceleration energy of another vehicle, energy conservation of the entire electric railway system can be achieved. In this case, when the regenerative operation of the vehicle is performed, there must be another vehicle nearby that can utilize the regenerated power obtained by that vehicle as acceleration energy.

[0004] However, even when using a railway vehicle equipped with a regenerative operation function, another vehicle does not always exist near the vehicle performing regenerative operation, and even when it exists, that vehicle is not always accelerating. Therefore, for the purpose of further effective utilization of regenerated power, a power storage device that charges a storage battery with the power (excess regenerated power) that could not be completely consumed by the accelerating power (traction power) of other vehicles and discharges when traction power is generated has been devised and put into practical use.

[0005] As a prior art related to the above power storage device, for example, Patent Document 1 is known. In Patent Document 1, a technique for detecting the output current of a substation and controlling a power converter based on the detection result to perform charge / discharge control of a storage element is disclosed.

Prior Art Documents

[0006] [Patent Document 1] Patent No. 5044340 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Patent Document 1 detects the sum of the rectifier's output current and the charging / discharging current of the energy storage element as the substation's output current. By comparing this output current with a predetermined reference value, the energy consumption state on the power supply side, i.e., the vehicle's regenerative braking state and powering state, is determined, and the power converter is controlled accordingly. However, with such a charging / discharging control method, the energy storage element may be charged even when no surplus regenerative power is generated in the power supply circuit. Therefore, when surplus regenerative power is generated, the charge level of the energy storage element may be high, and there is a risk that the surplus regenerative power cannot be sufficiently charged.

[0008] This invention has been made in view of the above, and its main purpose is to make effective use of surplus regenerative power in a DC power supply system. [Means for solving the problem]

[0009] The power storage device according to the present invention comprises a rechargeable energy storage element, a power converter that converts the power input and output between the energy storage element and a power line in both directions to charge and discharge the energy storage element, and a control circuit that controls the operation of the power converter and causes the power converter to perform a charging operation to charge the energy storage element or a discharging operation to discharge the energy storage element, wherein a rectifier system capable of outputting a DC current to the power line is connected to the power line, and the control circuit causes the power converter to perform the charging operation to charge the energy storage element and bring the voltage of the power line closer to the charging start voltage when the voltage of the power line is greater than a predetermined charging start voltage and the charge rate of the energy storage element is within a predetermined operating range, and when the voltage of the power line is less than or equal to the charging start voltage and the current flowing through the power line is greater than a predetermined current threshold and the charge rate of the energy storage element A predetermined range is set for a portion of the aforementioned operating range. If within the second range, the power converter is instructed to perform the discharge operation so as to discharge the energy storage element and output a DC current to the feeder line together with the rectifier system. The power storage control method according to the present invention is a method for controlling the power stored in a rechargeable energy storage element by controlling the operation of a power converter that converts power input and output between a rechargeable energy storage element and a power line in both directions to charge and discharge the energy storage element, wherein a rectifier system capable of outputting DC current to the power line is connected to the power line, and when the voltage of the power line is greater than a predetermined charging start voltage and the charge level of the energy storage element is within a predetermined operating range, the operation of the power converter is controlled to charge the energy storage element and bring the voltage of the power line closer to the charging start voltage, and when the voltage of the power line is less than or equal to the charging start voltage and the current flowing through the power line is greater than a predetermined current threshold and the charge level of the energy storage element is A predetermined range is set for a portion of the aforementioned operating range. If the range is within the second range, the operation of the power converter is controlled to discharge the energy storage element and output a DC current to the feeder line together with the rectifier system. [Effects of the Invention]

[0010] According to the present invention, it is possible to effectively utilize surplus regenerative power in a DC power supply system. [Brief explanation of the drawing]

[0011] [Figure 1] It is a configuration diagram of a power generation system including a power storage device according to the first embodiment of the present invention. [Figure 2] It is a diagram showing the arithmetic unit configuration of a controller according to the first embodiment of the present invention. [Figure 3] It is an explanatory diagram of the main circuit configuration of a power converter. [Figure 4] It is an explanatory diagram of a rectifier support arithmetic unit. [Figure 5] It is an explanatory diagram of a battery tray. [Figure 6] It is a diagram showing an operation example of a power storage device according to the first embodiment of the present invention. [Figure 7] It is an arithmetic flow diagram of a control mode determination method according to the first embodiment of the present invention. [Figure 8] It is an operation map of a power storage device according to the first embodiment of the present invention. [Figure 9] It is a configuration diagram of a power generation system including a power storage device according to a modified example of the present invention. [Figure 10] It is a diagram showing the arithmetic unit configuration of a controller according to a modified example of the present invention. [Figure 11] It is a configuration diagram of a power generation system including a power storage device according to the second embodiment of the present invention. [Figure 12] It is a diagram showing the arithmetic unit configuration of a controller according to the second embodiment of the present invention. [Figure 13] It is an arithmetic flow diagram of a control mode determination method according to the second embodiment of the present invention. [Figure 14] It is an operation map at the time of stopping the operation of the rectification system of a power storage device according to the second embodiment of the present invention. [Figure 15] It is an explanatory diagram of an arm.

Embodiments for Carrying Out the Invention

[0012] (First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

[0013] FIG. 1 is a configuration diagram of an electric power storage system including a power storage device according to a first embodiment of the present invention. As shown in FIG. 1, the electric power storage system 30 of the present embodiment includes a power storage device 1, a circuit breaker 40, and a rectification system 50. These components in the electric power storage system 30 are provided, for example, in the same substation.

[0014] The power storage device 1 is electrically connected in parallel with the rectification system 50 between the positive electrode line 41 and the negative electrode line 42. The positive electrode line 41 and the negative electrode line 42 are respectively connected to the trolley wire 70 and the rail 71 via the circuit breaker 40. Thereby, the power storage device 1 and the rectification system 50 are electrically connected to the trolley wire 70 and the rail 71, respectively.

[0015] The railway vehicle 80 traveling on the rail 71 can obtain acceleration energy from the DC power supplied from the power storage device 1 and the rectification system 50 via the trolley wire 70 and the rail 71. Further, during deceleration, it has a function of transmitting the regenerative power obtained by performing regenerative operation to the trolley wire 70 side. Although only one railway vehicle 80 is shown in FIG. 1, actually, a plurality of railway vehicles 80 are respectively connected to the trolley wire 70 and the rail 71. Hereinafter, even when the plurality of railway vehicles 80 are collectively described, they will be simply referred to as "railway vehicle 80".

[0016] In the power storage device 1, a current detector 60 is provided on the negative electrode line 42 connected to the rail 71 via the circuit breaker 40. The current detector 60 detects the current flowing through the negative electrode line 42 and outputs the detection result to the controller 100 as the total negative electrode current I_SS. The total negative electrode current I_SS detected by the current detector 60 corresponds to the sum of the currents output by the power storage device 1 and the rectification system 50 to the trolley wire 70, respectively.

[0017] The rectifier system 50 obtains AC power from an AC power system (not shown) via a transformer 51, and converts this AC power into DC power using a thyristor rectifier 52. Specifically, the output voltage of the power supply system 30 is stabilized by controlling the firing angle of the thyristor rectifier 52 so that the voltage sent from the rectifier system 50 to the power supply line 70 side is a constant value.

[0018] As described above, the thyristor rectifier 52 can convert AC power to DC power, but it cannot convert DC power back to AC power. Therefore, if the railway vehicle 80 generates regenerative power that it cannot consume (excess regenerative power), the excess regenerative power has nowhere to go, and the voltage between the feeder line 70 and the rail 71 (feeder line voltage) rises. As a result, when the feeder line voltage exceeds a predetermined value, the railway vehicle 80 gradually switches its deceleration means from regenerative driving to mechanical braking to avoid overvoltage in the feeder line. However, in this case, instead of converting kinetic energy into electrical energy through regenerative driving, the kinetic energy is converted into thermal energy by mechanical braking, and the resulting thermal energy is wasted without being recovered. Therefore, frequent use of mechanical braking hinders the effective utilization of excess regenerative power.

[0019] Therefore, in this embodiment, when surplus regenerative power is generated, the power storage device 1 stores that electrical energy by charging it into the battery pack in the battery storage panel 3, and when the railway vehicle 80 is accelerating, it discharges power from the battery pack and supplies it to the railway vehicle 80. This realizes the effective utilization of surplus regenerative power.

[0020] Here, the configuration of the power storage device 1 will be explained. As shown in Figure 1, the power storage device 1 comprises a battery panel 3 having a battery pack and functioning as a rechargeable and dischargeable energy storage element, a power converter 2 that converts the power input and output between the battery panel 3 and the power line 70 in both directions to charge and discharge the battery panel 3, thereby realizing bidirectional power exchange with the power supply line 70, and a control circuit (controller) 100 that controls the operation of the power converter 2 and causes the power converter 2 to perform either a charging operation to charge the battery panel 3 or a discharging operation to discharge the battery panel 3.

[0021] One end of the power converter 2 is electrically connected in parallel with the DC output of the rectifier system 50 to the feeder line 70. The other end of the power converter 2 is connected to the battery storage panel 3. The controller 100 generates a gate signal, which is a control signal for the power converter 2, based on the detected values ​​of the voltage of the feeder line 70 (feeder line voltage) and the current of the battery storage panel 3 (battery current) obtained from the power converter 2, the charge level of the battery pack obtained from the battery storage panel 3, and the detected value of the combined current of the rectifier system 50 and the power storage device 1, and outputs it to the power converter 2.

[0022] The main circuit configuration of the power converter 2 will be explained using Figure 3. As shown in Figure 3, the power converter 2 has an arm 23 made up of switching elements such as IGBTs (Insulated Gate Bipolar Transistors). On the terminal side of this arm 23 that is connected to the feeder line 70 in parallel with the rectifier system 50 (left side of Figure 3), a reactor 21 and a capacitor 22 are provided, and on the terminal side that is connected to the battery storage panel 3 (right side of Figure 3), a reactor 24 is provided. The reactor 21 and capacitor 22 are provided to suppress PWM noise caused by the switching operation of the arm 23 from flowing out to the feeder line 70, and the reactor 24 is provided to smooth the voltage output to the battery storage panel 3.

[0023] Arm 23 is a two-level output arm configured by connecting two sets of IGBTs and diodes connected in antiparallel to the IGBTs in series, as shown in Figure 15, for example. The positive terminal P1 on the feeder line 70 side is connected to the positive terminal of capacitor 22 and reactor 21, and the positive terminal AC on the battery panel 3 side is connected to reactor 24. The potential of the negative terminal N1 on the feeder line 70 side and the potential of the negative terminal N2 on the battery panel 3 side are common, and negative terminal N1 is connected to the negative terminal of capacitor 22, and negative terminal N2 is connected to the negative terminal of battery panel 3. By controlling the duty cycle of the two series-connected IGBTs (IGBT1, IGBT2) using complementary PWM, arm 23 can output any voltage less than or equal to the terminal voltage of capacitor 22 to the battery panel 3 side.

[0024] Returning to the explanation of Figure 3, the arm 23 and reactor 24 constitute a bidirectional step-down DC-DC converter. The operation of this DC-DC converter enables the desired charging and discharging of the battery panel 3. In this embodiment, as shown in Figure 15, the power converter 2 is a two-level DC-DC converter, but it may also be a three-level or multi-level DC-DC converter.

[0025] In the power storage device 1, the DC current output from the power converter 2 to the feeder line 70 is detected by a current detector 25 connected in series with the reactor 21, and the detection result is output to the controller 100 as the output current I_BESS of the power storage device 1. In addition, the voltage across the capacitor 22, i.e., the voltage of the feeder line 70, is detected by a voltage detector 26, and the detection result is output to the controller 100 as the feeder line voltage V_LINE. Furthermore, the current flowing through the battery panel 3 is detected by a current detector 27 connected in series with the reactor 24, and the detection result is output to the controller 100 as the battery current I_BATT. Based on these values, the controller 100 generates a gate signal GateSig to control the power converter 2.

[0026] The gate signal GateSig generated by the controller 100 is input to the arm 23 in the power storage device 1. In response to this gate signal GateSig, the two IGBTs (IGBT1, IGBT2) in the arm 23 are complementaryly controlled to be ON or OFF. This controls the charge / discharge current (battery current I_BATT) of the battery panel 3 to a desired value. The specific method for controlling the battery current I_BATT will be described later.

[0027] The configuration of the battery storage panel 3 will be explained using Figure 5. As shown in Figure 5, the battery storage panel 3 has a battery pack 31 configured by connecting multiple battery modules in multiple series and multiple parallel connections, and a battery management unit 32 that detects the voltage and current of the battery pack 31 and calculates the state of charge (SOC) of the battery pack 31.

[0028] The main circuit of the battery pack 31 is connected to the power converter 2, and the charge and discharge current of the battery pack 31 is controlled according to the voltage output by the arm 23 of the power converter 2, shown in Figure 3, to the battery storage panel 3. The state of charge (SOC) calculated by the battery management unit 32 is input to the controller 100 and used by the controller 100 to select the operating mode of the power converter 2 and calculate the charge and discharge command values.

[0029] Next, the arithmetic unit configuration of the controller 100 of the power converter 2 will be explained using Figures 2 and 4.

[0030] Figure 2 shows the arithmetic unit configuration of the controller 100 according to the first embodiment of the present invention. As shown in Figure 2, the controller 100 of this embodiment has the following arithmetic units: a control mode determination unit 101, a charge start voltage calculation unit 102, a charge-side voltage controller 103, a charge rate controller 104, a rectifier support calculation unit 105, an adder 106, and a current controller 107. These arithmetic units in the controller 100 are realized, for example, by the CPU (Central Processing Unit) of the controller 100 executing a predetermined program. Note that some or all of the arithmetic units shown in Figure 2 may be realized using devices other than the CPU, such as a GPU (Graphics Processing Unit), FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), etc.

[0031] The controller 100 receives the detected value of the total negative electrode current I_SS from the current detector 60. In addition, the controller 100 receives the detected values ​​of the output current I_BESS, feeder line voltage V_LINE, and battery current I_BATT from the current detector 25, voltage detector 26, and current detector 27 in the power converter 2 shown in Figure 3. Furthermore, the charge level (SOC) of the battery pack 31 is also received from the battery management unit 32 in the battery storage panel 3 shown in Figure 5.

[0032] The charging start voltage calculator 102 calculates the charging start voltage V_ABS according to the charge rate (SOC). For example, if the charge rate (SOC) is below a predetermined reference value, the charging start voltage calculator 102 outputs a preset fixed value as the charging start voltage V_ABS. On the other hand, if the charge rate (SOC) is greater than the reference value, the charging start voltage V_ABS is corrected to a higher value by adding a value proportional to the difference between the charge rate (SOC) and the reference value to the above fixed value. This prevents overcharging of the battery panel 3 by ensuring that the charging start voltage V_ABS increases as the charge rate (SOC) increases. The above fixed value used to calculate the charging start voltage V_ABS needs to be set to a value that is sufficiently higher than the output command of the thyristor rectifier 52 and lower than the feeder line voltage of 1800V, which is the voltage at which the railway vehicle 80 starts to reduce regenerative operation, in the case of a power supply system 30 with a rated voltage of 1500V. Taking into account the overshoot of the feeder line voltage at the start of regenerative operation, it is preferable to set the fixed value of the charging start voltage V_ABS between, for example, 1550V and 1700V.

[0033] The control mode determination unit 101 determines the control mode of the power storage device 1 based on the total negative electrode current I_SS, feeder line voltage V_LINE, and charge level SOC input to the controller 100, and the charge start voltage V_ABS determined by the charge start voltage calculator 102. Depending on the control mode determined by the control mode determination unit 101, the current command value calculation by the charge-side voltage controller 103, charge level controller 104, and rectifier support calculator 105 is enabled or reset to zero, respectively. Details of the control mode determination method by the control mode determination unit 101 will be described later.

[0034] The charging-side voltage controller 103 calculates a current command value for the power converter 2 to charge the battery panel 3 and bring the feeder line voltage V_LINE closer to the charging start voltage V_ABS when the feeder line voltage V_LINE becomes greater than the charging start voltage V_ABS. Specifically, for example, when the current command value calculation is enabled by the control mode determination unit 101, the charging-side voltage controller 103 calculates the difference between the feeder line voltage V_LINE and the charging start voltage V_ABS, and performs a PI control calculation using that difference as input to calculate a current command value that suppresses the rise in the feeder line voltage V_LINE. When the current command value calculation of the charging-side voltage controller 103 is reset by the control mode determination unit 101, the values ​​of the internal variables of the PI calculator in the charging-side voltage controller 103 are cleared, and at the same time, the output of the charging-side voltage controller 103 becomes zero.

[0035] The charge rate controller 104 calculates a current command value for the power converter 2 so that the charge rate (SOC) approaches a predetermined target value by charging and discharging the battery panel 3. Specifically, for example, when the current command value calculation is enabled by the control mode determination device 101, the charge rate controller 104 calculates the deviation between the charge rate (SOC) and a predetermined target charge rate value, and calculates a current command value that brings the charge rate (SOC) closer to the target value by performing a proportional calculation on that deviation. Note that when the current command value calculation of the charge rate controller 104 is reset by the control mode determination device 101, the output of the charge rate controller 104 becomes zero.

[0036] Here, in the event that there is insufficient power on the feeder line 70 to power the railway vehicle 80, it is desirable to limit the current command value output from the charge rate controller 104 to a low value in order to prevent the feeder line voltage V_LINE from rising excessively even when the charge rate controller 104 performs the above charge rate control. For example, it is conceivable to apply a limiter to the current command value calculated by the charge rate controller 104 so that the input and output power of the power storage device 1 when performing charge rate control is limited to less than a few percent of the rated capacity of the power storage device 1. Furthermore, in order to ensure that there is sufficient charging capacity remaining in the battery panel 3 when surplus regenerative power is generated, while also preventing the value of the charge rate SOC from dropping excessively and degrading the batteries in the battery panel 3, it is desirable to set the charge rate target value to an appropriate value within the range of 0% to 100%, for example, between 10% and 40%.

[0037] The rectifier support calculator 105 calculates the current command value based on the combined negative electrode current I_SS, which is the sum of the output currents of the rectifier system 50 and the power storage device 1, and the state of charge (SOC). Details of the current command value calculation method by the rectifier support calculator 105 will be described later.

[0038] The adder 106 sums the current command values ​​calculated by the charging voltage controller 103, the charge rate controller 104, and the rectifier support calculator 105, and calculates the current command value when the power converter 2 charges and discharges the battery panel 3.

[0039] The current controller 107 calculates the duty cycle of the gate signal GateSig for the power converter 2 so that the battery current I_BATT matches the current command value output from the adder 106, and generates a gate signal GateSig corresponding to this duty cycle. Then, by outputting the generated gate signal GateSig to each IGBT on the arm 23 of the power converter 2, the controller controls the operation of the power converter 2 and causes the power converter 2 to perform charging or discharging operations.

[0040] Next, we will describe in detail the rectifier support calculator 105 and the control mode determination unit 101, which are features of the present invention.

[0041] The rectifier support calculator 105 receives the total negative electrode current I_SS, the state of charge (SOC), and the control mode determination result from the control mode determination unit 101 as inputs. When the current command value calculation is enabled by the control mode determination unit 101, the rectifier support calculator 105 calculates a current command value based on the total negative electrode current I_SS and the state of charge (SOC) so that the power storage device 1 outputs DC power to the feeder line 70 together with the rectifier system 50, thereby supplying a portion of the current necessary for the traction operation of the railway vehicle 80 from the power storage device 1. The calculated current command value is then output to the adder 106. When the current command value calculation of the rectifier support calculator 105 is reset by the control mode determination unit 101, the output of the rectifier support calculator 105 becomes zero.

[0042] The specific calculation blocks of the rectifier support arithmetic unit 105 will be explained using Figure 4. As shown in Figure 4, the rectifier support arithmetic unit 105 includes a multiplier 1051, a maximum value calculator 1052, a variable limiter 1053, a minimum value calculator 1054, and a toggle switch 1055.

[0043] The multiplier 1051 calculates the product of the total negative electrode current I_SS multiplied by the fixed gain K1. The maximum value calculator 1052 compares the product of the total negative electrode current I_SS and the fixed gain K1 calculated by the multiplier 1051 with zero and outputs the larger of the two values ​​to the minimum value calculator 1054.

[0044] The variable limiter 1053 calculates a limit value for the discharge current based on the state of charge (SOC) and outputs it to the minimum value calculator 1054. Specifically, when the SOC is less than or equal to a predetermined reference SOC2, it outputs zero as the limit value for the discharge current. When the SOC is SOC2+Δ (Δ>0), it outputs a predetermined maximum discharge current value as the limit value for the discharge current. Furthermore, when the SOC is between the reference SOC2 and SOC2+Δ, it outputs a value obtained by linearly interpolating the SOC value between zero and the maximum discharge current value as the limit value for the discharge current.

[0045] The minimum value calculator 1054 outputs the smaller of the outputs of the variable limiter 1053 and the maximum value calculator 1052 as the current command value I_ref3 to the changeover switch 1055. Depending on the control mode determination result by the control mode determination unit 101, the changeover switch 1055 selects and outputs the current command value I_ref3 when the rectifier support calculator 105 is activated, and outputs zero when it is reset.

[0046] In the controller 100 of this embodiment, the rectifier support calculator 105 has the above configuration, so that when the railway vehicle 80 is powered, the battery panel 3 is discharged and a DC current is output to the feeder line 70 together with the rectifier system 50, and a portion of the output current from the feeder system 30 to the railway vehicle 80 is output from the power storage device 1. Furthermore, when the charge level (SOC) of the battery panel 3 falls to near a predetermined reference charge level (SOC2), it is possible to gradually limit the discharge current from the battery panel 3 and stop discharging below the reference charge level (SOC2). This makes it possible to avoid over-discharge of the battery panel 3 while suppressing disturbances on the feeder line 70 side.

[0047] Furthermore, it is desirable to set the above reference charge level (SOC2) to an appropriate value within the range of 0% to 100%, for example, between 10% and 40%, similar to setting the target charge level value during charge level control in the charge level controller 104 described above.

[0048] The control mode determination method of the control mode determination device 101 according to the first embodiment of the present invention will be described below using the calculation flow shown in Figure 7.

[0049] The control mode determination device 101 takes the total negative electrode current I_SS, feeder line voltage V_LINE, charge level SOC, and charging start voltage V_ABS as inputs and performs the calculation process shown in the calculation flow of Figure 7 based on these inputs to select one of the following four control modes as the control mode of the power storage device 1. (1) First control mode (MODE=1): A charging-side voltage control mode that stabilizes the feeder line voltage V_LINE by charging the battery panel 3. (2) Second control mode (MODE=2): Rectifier support mode that handles a portion of the load current supplied from the power supply system 30 to the railway vehicle 80 by the discharge of the battery panel 3. (3) Third control mode (MODE=3): A charge rate control mode that charges or discharges the battery panel 3 to bring the charge rate (SOC) closer to a predetermined target value. (4) Fourth control mode (MODE=4): Standby mode in which the operation of the power converter 2 is stopped and the operating conditions are met.

[0050] When one of the four control modes is selected, the control mode determination unit 101 outputs an output signal MODE indicating the selection result to the charging voltage controller 103, the charge rate controller 104, the rectifier support calculator 105, and the current controller 107. The charging voltage controller 103 is activated when MODE=1 and reset otherwise. The rectifier support calculator 105 is activated when MODE=2 and reset otherwise. The charge rate controller 104 is activated when MODE=3 and reset otherwise. The current controller 107 is reset when MODE=4 to suppress the output of the gate signal GateSig, and otherwise generates the gate signal GateSig for the power converter 2 so that the battery current I_BATT matches the current command value output from the adder 106.

[0051] In the calculation process shown in the calculation flow of Figure 7, the control mode determination unit 101 first compares the feeder line voltage V_LINE and the charging start voltage V_ABS in step S101 and determines the condition V_LINE > V_ABS. If the result of the condition determination in step S101 is true, the process proceeds to step S102; otherwise, the process proceeds to step S103.

[0052] In step S102, the control mode determiner 101 determines whether the state of charge (SOC) is within the operating range of the battery pack 3. Here, the operating range of the battery pack 3 is set as the range of the state of charge defined by a predetermined upper operating limit value SOC_H and a lower operating limit value SOC_L, and for this operating range, a condition determination of SOC_L < SOC < SOC_H is performed. If the condition determination result in step S102 is true (True), the process proceeds to step S108; if it is false (False), the process proceeds to step S109.

[0053] In step S103, the control mode determiner 101 compares the total negative electrode current I_SS with a predetermined current threshold I_TH and performs a condition determination of I_SS > I_TH. If the condition determination result in step S103 is true (True), the process proceeds to step S104; if it is false (False), the process proceeds to step S105. The current threshold I_TH corresponds to a margin for avoiding instability in the operation mode switching of the power storage device 1 due to detection errors of the total negative electrode current I_SS or the operation of accessories of the railway vehicle 80. This current threshold I_TH is set to a value lower than the rated current of the rectification system 50, for example, a value on the order of a few percent of the rated current, so that when the railway vehicle 80 is under power running, the power storage device 1 can promptly implement the rectifier support mode and take part of the load current supplied from the power generation system 30 to the railway vehicle 80 by the discharge of the battery pack 3.

[0054] In step S104, the control mode determiner 101 determines whether the state of charge (SOC) is within a predetermined range within the operating range of the battery pack 3. Here, for the range of the state of charge (hereinafter referred to as the "second range") defined by the aforementioned reference state of charge SOC2, which is greater than the lower operating limit value SOC_L, and the upper operating limit value SOC_H, a condition determination of SOC2 < SOC < SOC_H is performed. If the condition determination result in step S104 is true (True), the process proceeds to step S110; if it is false (False), the process proceeds to step S106.

[0055] In step S105, the control mode determiner 101 performs the same condition determination as in step S104. If the condition determination result in step S105 is true (True), it proceeds to step S111; if it is false (False), it proceeds to step S107.

[0056] In step S106, the control mode determiner 101 determines whether the state of charge (SOC) is within a predetermined range different from the aforementioned second range within the operating range of the battery pack 3. Here, for the range of the state of charge defined by a predetermined state of charge SOC3 smaller than the aforementioned reference state of charge SOC2 and the operating lower limit value SOC_L (hereinafter referred to as the "third range"), a condition determination of SOC_L < SOC < SOC3 is performed. If the condition determination result in step S106 is true (True), it proceeds to step S112; if it is false (False), it proceeds to step S113.

[0057] In step S107, the control mode determiner 101 performs the same condition determination as in step S106. If the condition determination result in step S107 is true (True), it proceeds to step S111; if it is false (False), it proceeds to step S109.

[0058] When the condition determination result in step S102 is true, in step S108, the control mode determiner 101 sets the control mode determination result to MODE = 1 and switches the control mode of the power storage device 1 to the charging-side voltage control mode.

[0059] When the condition determination result in step S102 or step S107 is false, in step S109, the control mode determiner 101 sets the control mode determination result to MODE = 4 and switches the control mode of the power storage device 1 to the standby mode.

[0060] When the condition determination result in step S104 is true, in step S110, the control mode determiner 101 sets the control mode determination result to MODE = 2 and switches the control mode of the power storage device 1 to the rectifier support mode.

[0061] If the result of the condition determination in step S105 or step S107 is true, in step S111, the control mode determination unit 101 sets the control mode determination result to MODE=3 and switches the control mode of the power storage device 1 to the charge rate control mode.

[0062] If the condition determination result in step S106 is true, in step S112, the control mode determination unit 101 sets the control mode determination result to MODE=3 and switches the control mode of the power storage device 1 to the charge rate control mode.

[0063] If the condition determination result in step S106 is false, in step S113, the control mode determination device 101 sets the control mode determination result to MODE=4 and switches the control mode of the power storage device 1 to standby mode.

[0064] If the control mode determination result is set to one of MODE=1 to 4 in any of steps S108 to S113, in step S114, the control mode determination unit 101 waits until the next calculation trigger. Upon receiving the next calculation trigger, it returns to step S101 and resumes the calculation flow shown in Figure 7. This executes the calculation process according to the calculation flow shown in Figure 7 at predetermined calculation cycles to determine the control mode.

[0065] By performing the above control mode determination in the control mode determination device 101, the operation map of the power storage device 1 shown in Figure 8 is realized. Here, the horizontal axis of Figure 8 represents the charge level (SOC), the vertical axis represents the feeder line voltage V_LINE, and the thick line represents the charging start voltage V_ABS. In addition, the positions where the charge level (SOC) is the aforementioned operating lower limit value SOC_L, predetermined value SOC3, predetermined value SOC2, and operating upper limit value SOC_H are indicated by dashed lines, respectively. Each control mode of the power storage device 1 is defined by the regions demarcated by these dashed lines and the charging start voltage V_ABS. In Figure 8, the control modes corresponding to each region are shown by the value of the variable MODE.

[0066] An example of the operation of the power storage device 1 according to this embodiment will be explained using the graphs shown in Figure 6. In Figure 6, the following six types of graphs are shown from top to bottom. (1) Example of the time change of vehicle current received by railway vehicle 80 from power line 70 (2) Example of time change of feeder line voltage V_LINE (3) Example of the time variation of the current I_REC output from the rectifier system 50 to the feeder line 70 (4) Example of time variation of the output current I_BESS of the power storage device 1 (5) Example of the time change of the charge level (SOC) (6) Example of the time change of the output signal MODE representing the control mode determination result by the control mode determination unit 101

[0067] Furthermore, in each graph of Figure 6, examples of the time changes of each of the above variables are shown, assuming a situation where only one railway vehicle 80 exists on the power supply circuit, as in Figure 1, and there are no powered vehicles consuming the regenerative power of the railway vehicle 80.

[0068] When the railway vehicle 80 begins to accelerate at time t1, the vehicle current becomes a positive current, which is the power side. At this time, the output signal of the control mode determination device 101 is MODE=2, so the power storage device 1 operates in rectifier support mode, and vehicle current is supplied from the rectification system 50 and the power storage device 1 to the railway vehicle 80. In addition, the state of charge (SOC) of the power storage device 1 decreases as the battery panel 3 discharges.

[0069] At time t2, when the charge level SOC drops to SOC2+Δ, the variable limiter 1053 in the rectifier support calculator 105 of the controller 100 limits the discharge current of the battery panel 3 to a predetermined maximum discharge current. As a result, the output current I_BESS from the power storage device 1 begins to decrease. At this time, since the vehicle current flowing to the railway vehicle 80 remains unchanged, the output current I_REC from the rectifier system 50 increases to compensate for the decrease in output current I_BESS.

[0070] At time t3, when the charge level (SOC) drops to the reference charge level (SOC2), the output signal of the control mode determination unit 101 changes from MODE=2 to MODE=4. This switches the control mode of the power storage device 1 from rectifier support mode to standby mode, and the power storage device 1 stops the operation of the power converter 2 and goes into standby mode. At this time, because the discharge current of the battery panel 3 was limited according to the charge level (SOC) between time t2 and time t3, even if the operation of the power converter 2 stops at time t3, no sharp power fluctuations occur on the feeder line 70 side. Therefore, disturbances to the feeder circuit can be avoided.

[0071] When the railway vehicle 80 finishes accelerating at time t4, the vehicle current becomes zero, and consequently, the output current I_REC of the rectifier system 50 also becomes zero.

[0072] When the railway vehicle 80 starts regenerative operation at time t5, the regenerative power charges the filter capacitor inside the railway vehicle 80, causing the voltage across the filter capacitor to rise, and consequently the feeder line voltage V_LINE to rise. When the feeder line voltage V_LINE exceeds the charging start voltage V_ABS, the output signal of the control mode determination unit 101 in the power storage device 1 changes from MODE=4 to MODE=1. As a result, the control mode of the power storage device 1 is switched from standby mode to charging-side voltage control mode, and the power storage device 1 starts voltage control of the feeder line voltage V_LINE by charging the battery panel 3. This stabilizes the feeder line voltage V_LINE and enables charging of surplus regenerative power.

[0073] At time t6, when the railway vehicle 80 ends regenerative operation, the output signal of the control mode determination device 101 in the power storage device 1 changes from MODE=1 to MODE=3. As a result, the control mode of the power storage device 1 is switched from the charging voltage control mode to the charge rate control mode, and the power storage device 1 controls the charge rate of the battery panel 3. At this time, as described above, by limiting the input and output power of the power storage device 1 in charge rate control to a low value (for example, a few percent of the rated capacity of the power storage device 1), it becomes possible to supply a portion of the power consumed by the auxiliary equipment of the railway vehicle 80 from the power storage device 1 to the railway vehicle 80 as power for charge rate control.

[0074] When the railway vehicle 80 starts accelerating again at time t7, the output signal of the control mode determination device 101 changes from MODE=3 to MODE=2 in the power storage device 1. As a result, the power storage device 1 operates in rectifier support mode, similar to the period between time t1 and time t2, and can supply the surplus regenerative power charged in the battery panel 3 between time t5 and t6 to the railway vehicle 80 as part of the power for acceleration.

[0075] When the railway vehicle 80 finishes accelerating at time t8, the vehicle current becomes zero, and consequently, the output current I_REC of the rectifier system 50 also becomes zero. At this time, since the charge level SOC is greater than the reference charge level SOC2, the output signal of the control mode determination unit 101 changes from MODE=2 to MODE=3. As a result, the control mode of the power storage device 1 is switched back to the charge level control mode, and the power storage device 1 controls the charge level of the battery panel 3, just as it did between time t6 and time t7.

[0076] As described above, according to this embodiment, in the DC power supply system 30 powered by the thyristor rectifier 52, the battery panel 3, which is the energy storage element of the power storage device 1, can be discharged in advance in preparation for charging surplus regenerative power. Furthermore, when surplus regenerative power is generated, the regenerative power absorbed from the power supply line 70 is charged into the battery panel 3, and the power stored in the battery panel 3 is discharged when the railway vehicle 80 is powered, thereby enabling effective utilization of surplus regenerative power. In addition, when the battery panel 3 is discharged, the variable limiter 1053 of the rectifier support calculator 105 can limit the discharge current according to the charge rate (SOC). This prevents over-discharge of the battery panel 3 and also prevents abrupt disturbances to the power supply circuit.

[0077] According to the first embodiment of the present invention described above, the following effects are achieved.

[0078] (1) The power storage device 1 comprises a battery panel 3 which is a rechargeable and dischargeable energy storage element, a power converter 2 which converts the power input and output between the battery panel 3 and the power line 70 in both directions to charge and discharge the battery panel 3, and a control circuit (controller) 100 which controls the operation of the power converter 2 and causes the power converter 2 to perform a charging operation to charge the battery panel 3 or a discharging operation to discharge the battery panel 3. A rectifier system 50 capable of outputting DC current to the feeder line 70 is connected to the feeder line 70. When the voltage V_LINE of the feeder line 70 is greater than a predetermined charging start voltage V_ABS (Step S101: True) and the charge level SOC of the battery storage unit 3 is within a predetermined operating range (Step S102: True), the controller 100 sets the control mode of the power storage device 1 to the charging-side voltage control mode (Step S108: MODE=1), causing the power converter 2 to perform a charging operation to charge the battery storage unit 3 and bring the voltage V_LINE of the feeder line 70 closer to the charging start voltage V_ABS. On the other hand, if the voltage V_LINE of the feeder line 70 is less than or equal to the charging start voltage V_ABS (step S101: False), the current I_SS flowing through the feeder line 70 is greater than a predetermined current threshold I_TH (step S103: True), and the charge level SOC of the battery panel 3 is within the second range (step S104: True), the control mode of the power storage device 1 is set to the rectifier support mode (step S110: MODE=2), causing the power converter 2 to perform a discharge operation so as to discharge the battery panel 3 and output a DC current to the feeder line 70 together with the rectification system 50. In this way, surplus regenerative power in the DC power supply system 30 can be effectively utilized.

[0079] (2) The controller 100 obtains the total negative electrode current I_SS, which is the detected total current obtained by combining the DC currents output from the power converter 2 and the rectification system 50 to the feeder line 70, and determines the current flowing through the feeder line 70 based on the obtained total negative electrode current I_SS. In this way, the current flowing through the feeder line 70 can be accurately determined.

[0080] (3) When the controller 100 causes the power converter 2 to perform a discharge operation in rectifier support mode, the rectifier support calculator 105 calculates a current command value I_ref3 based on the charge level SOC of the battery panel 3 and the current I_SS flowing through the feeder line 70. Using this current command value I_ref3, the controller controls the magnitude of the output current I_BESS, which is the DC current output from the power converter 2 to the feeder line 70. In this way, when the operation of the power converter 2 is stopped afterward, it is possible to prevent abrupt power fluctuations from occurring on the feeder line 70 side and avoid disturbances in the feeder circuit.

[0081] (4) The controller 100 checks if the voltage V_LINE of the feeder line 70 is less than or equal to the charging start voltage V_ABS (Step S101: False), the current I_SS flowing through the feeder line 70 is less than or equal to the current threshold I_TH (Step S103: False), and the charge level SOC of the battery panel 3 is within the second range (Step S105: True), or within the third range which is lower than the second range (Step S107: True), or if the voltage V_LINE of the feeder line 70 is less than or equal to the charging start voltage V_ABS If (Step S101: False), the current I_SS flowing through the power line 70 is greater than the current threshold I_TH (Step S103: True), and the charge level SOC of the battery panel 3 is within the third range (Step S106: True), the control mode of the power storage device 1 is set to the charge level control mode (Steps S111, S112: MODE=3), causing the power converter 2 to perform charging or discharging operations to charge and discharge the battery panel 3 and bring the charge level SOC of the battery panel 3 closer to a predetermined target value. In this way, the charge level SOC of the battery panel 3 can be maintained within a certain range even when the railway vehicle 80 is not performing either powered operation or regenerative operation, or when the charge level SOC of the battery panel 3 is low.

[0082] (5) The controller 100 has a first control mode (MODE=1: charging-side voltage control mode) in which it controls the power converter 2 to charge the battery panel 3 and bring the voltage V_LINE of the feeder line 70 closer to the charging start voltage V_ABS; a second control mode (MODE=2: rectifier support mode) in which it calculates a current command value I_ref3 as a discharge current command based on the charge rate SOC of the battery panel 3 and the current I_SS flowing through the feeder line 70 and controls the power converter 2 to discharge the battery panel 3 based on the calculated current command value I_ref3; a third control mode (MODE=3: charge rate control mode) in which it charges and discharges the battery panel 3 and controls the power converter 2 to bring the charge rate SOC of the battery panel 3 closer to a predetermined target value; and a fourth control mode (MODE=4: standby mode) in which it stops the operation of the power converter 2. Then, based on at least one of the following: the voltage V_LINE of the feeder line, the charge level SOC of the battery panel 3, and the current I_SS flowing through the feeder line 70, one of the first, second, third, or fourth control modes is selected according to the calculation flow shown in Figure 7. In this way, the appropriate control mode can be selected according to the state of the feeder circuit, and the operation of the power converter 2 can be controlled.

[0083] (6) The reference charge rate SOC2, which is the lower limit of the second range described above, is the charge rate SOC of the battery panel 3, and may be set to, for example, between 10% and 40%. In this way, the switch from the rectifier support mode to other control modes can be made at an appropriate timing, and as a result, the charge rate SOC of the battery panel 3 can be maintained at an appropriate value in preparation for charging surplus regenerative power.

[0084] In the first embodiment of the present invention described above, as shown in Figure 1, a current detector 60 is provided on the negative electrode wire 42 connected to the rail 71 via a circuit breaker 40, and the current detector 60 is used to detect the total negative electrode current I_SS flowing through the negative electrode wire 42. However, the current detector 60 may be provided on the positive electrode wire 41 side instead of the negative electrode wire 42 side. Also, in the first embodiment of the present invention, the current detector 60 is shown in a position where it can detect the total negative electrode current I_SS, which is the combined output current of the rectifier system 50 and the power storage device 1. However, the current detector 60 may be provided in a different position. Modified examples of when the current detector 60 is provided in a different position will be described below with reference to Figures 9 and 10.

[0085] For example, as shown in the modified example in Figure 9, if the current detector 60 is installed in a position to detect only the output current of the rectifier system 50, the power storage device 1 has a controller 100a instead of the controller 100 described in the first embodiment. The controller 100a acquires the detected value of the DC current output from the power converter 2 to the feeder line 70, i.e., the output current I_BESS of the power storage device 1 described in the first embodiment, and the detected DC current I_REC output from the rectifier system 50 to the feeder line 70, and determines the current value flowing through the feeder line 70 based on the acquired detected values ​​of each DC current. This current value is used in place of the overall negative electrode current I_SS to control the operation of the power converter 2.

[0086] Figure 10 shows the arithmetic unit configuration of a modified controller 100a according to the present invention. For example, as shown in Figure 10, the controller 100a has an adder 108 in addition to the control mode determination unit 101, charge start voltage calculation unit 102, charge-side voltage controller 103, charge rate controller 104, rectifier support calculation unit 105, adder 106, and current controller 107 described in the first embodiment. The adder 108 adds the output current I_BESS of the power storage device 1 detected by the current detector 25 in the power converter 2 and the output current I_REC of the rectifier system 50 detected by the current detector 60, and outputs the calculation result to the control mode determination unit 101 and the rectifier support calculation unit 105. The control mode determination unit 101 and the rectifier support calculation unit 105 use the output of the adder 108 in place of the total negative electrode current I_SS and execute the calculation processing described in the first embodiment, respectively. As a result, the modified form shown in Figure 9 can achieve the same effects as the first embodiment.

[0087] Furthermore, in the first embodiment and its modifications described above, the rectification system 50 and the power storage device 1 are installed in the same substation as the power supply system 30. However, if the power storage device 1 is located in the same power supply section as the rectification system 50, and the controllers 100 and 100a can acquire the detected values ​​of the current flowing through the feeder line 70 or the current output from the rectification system 50 to the feeder line 70, the rectification system 50 and the power storage device 1 may be installed in separate locations. In this case as well, the same effects as in the first embodiment can be achieved. The detected values ​​of the current flowing through the feeder line 70 or the current output from the rectification system 50 to the feeder line 70 may be transmitted to the controllers 100 and 100a by electrical wiring, or by light or wireless communication.

[0088] Furthermore, in the first embodiment and its modifications described above, the rectifier 52 in the rectifier system 50 is a thyristor rectifier, but it may also be a diode rectifier. In this case, it is desirable to set the charging start voltage V_ABS to a value higher than the no-load output voltage of the rectifier system 50 having the diode rectifier, taking into consideration the voltage fluctuations of the AC system. Even in this case, the same effects as in the first embodiment can be achieved.

[0089] (Second embodiment) A second embodiment of the present invention will be described below with reference to the drawings. In the following description, elements that have the same configuration or calculation functions as in the first embodiment are assigned the same reference numerals, and these elements will not be described unless specifically necessary.

[0090] Figure 11 is a configuration diagram of a power supply system including a power storage device according to a second embodiment of the present invention. As shown in Figure 11, the power supply system 30 of this embodiment comprises a power storage device 1b, a circuit breaker 40, and a rectifier system 50b. The difference between this embodiment and the first embodiment is that the rectifier system 50b includes a circuit breaker 53, and the thyristor rectifier 52 is connected to the positive electrode line 41 and the negative electrode line 42 via the circuit breaker 53, and an operating status signal SR_STATE representing the operating status of the rectifier system 50b is output from the rectifier system 50b to the power storage device 1b and input to the controller 100b of the power storage device 1b. The operating status signal SR_STATE is, for example, contact information of the circuit breaker 53 and is input to the controller 100b via a signal interface (not shown) of the power storage device 1b.

[0091] In this embodiment, the controller 100b of the power storage device 1b acquires the operating status of the rectifier system 50b based on the operating status signal SR_STATE input from the rectifier system 50b. Then, it switches the control of the power converter 2 depending on whether the rectifier system 50b is operating or stopped. Specifically, when the rectifier system 50b is operating normally, the power storage device 1b performs the surplus regenerative power charging and rectifier support operation described in the first embodiment above. On the other hand, when the rectifier system 50b stops operating, the battery panel 3 is discharged to prevent the voltage of the feeder line 70 from dropping excessively. This contributes to stabilizing the feeder voltage.

[0092] In this embodiment, for example, the operating status signal SR_STATE is represented as 1 or 0. When the rectifier system 50b is operating normally and the circuit breaker 53 is closed, the operating status signal SR_STATE is 1. When the rectifier system 50b has stopped operating and the circuit breaker 53 is open, the operating status signal SR_STATE is 0. With this configuration, when the rectifier system 50b stops operating due to maintenance or a malfunction, and the circuit breaker 53 is released accordingly, the operating status signal SR_STATE becomes 0, allowing the power storage device 1 to detect that the rectifier system 50b has stopped.

[0093] Figure 12 shows the arithmetic unit configuration of the controller 100b according to the second embodiment of the present invention. As shown in Figure 12, the controller 100b of this embodiment differs from the controller 100 of Figure 2 described in the first embodiment in that it includes a control mode determination unit 101b, a charge / discharge start voltage calculation unit 102b, and an adder 106b instead of the control mode determination unit 101, charge start voltage calculation unit 102, and adder 106, and further includes a discharge-side voltage controller 109.

[0094] The charge / discharge start voltage calculator 102b calculates the charge start voltage V_ABS and the discharge start voltage V_DISC according to the charge level (SOC). The charge start voltage V_ABS can be calculated in the same way as described in the first embodiment and output to the charge-side voltage controller 103 and the control mode determination unit 101b. As for the discharge start voltage V_DISC, for example, if the charge level (SOC) is equal to or greater than the aforementioned reference charge level (SOC2), the charge / discharge start voltage calculator 102b outputs a preset fixed value as the discharge start voltage V_DISC. On the other hand, if the charge level (SOC) is less than the reference charge level (SOC2), the discharge start voltage V_DISC is corrected to a lower value by subtracting a value proportional to the difference between the charge level (SOC) and the reference value from the above fixed value. This prevents over-discharge of the battery panel 3 by ensuring that the discharge start voltage V_DISC decreases as the charge level (SOC) decreases. The charge / discharge start voltage calculator 102b outputs the calculated discharge start voltage V_DISC to the discharge-side voltage controller 109 and the control mode determination unit 101b.

[0095] The control mode determination unit 101b determines the control mode of the power storage device 1b based on the total negative electrode current I_SS, feeder line voltage V_LINE, charge level SOC, and charge start voltage V_ABS, as well as the operating status signal SR_STATE. As a result, the current command value calculation by the charge-side voltage controller 103, charge level controller 104, rectifier support calculator 105, and the discharge-side voltage controller 109 is activated or reset to zero.

[0096] The discharge-side voltage controller 109 calculates a current command value for the power converter 2 so as to discharge the battery panel 3 and bring the feeder line voltage V_LINE closer to the discharge start voltage V_DISC when the feeder line voltage V_LINE becomes lower than the discharge start voltage V_DISC. Specifically, for example, when the current command value calculation is enabled by the control mode determination unit 101b, the discharge-side voltage controller 109 calculates the difference between the feeder line voltage V_LINE and the discharge start voltage V_DISC, and performs a PI control calculation using this difference as input to calculate a current command value that suppresses the decrease in the feeder line voltage V_LINE. When the current command value calculation of the discharge-side voltage controller 109 is reset by the control mode determination unit 101b, the values ​​of the internal variables of the PI controller in the discharge-side voltage controller 109 are cleared, and at the same time, the output of the discharge-side voltage controller 109 becomes zero.

[0097] The adder 106b sums the current command values ​​calculated by the charging voltage controller 103, the discharging voltage controller 109, the charge rate controller 104, and the rectifier support calculator 105, and calculates the current command value when the power converter 2 charges and discharges the battery panel 3.

[0098] The control mode determination method of the control mode determination device 101b according to the second embodiment of the present invention will be described below using the calculation flow shown in Figure 13.

[0099] In the calculation process shown in the calculation flow of Figure 13, the control mode determination unit 101b first checks the operating status signal SR_STATE in step S201 and makes a condition determination that SR_STATE=1. If the condition determination result in step S201 is true, that is, if the rectification system 50b is operating normally, the same process as steps S101 to S113 in Figure 7 described in the first embodiment is performed, and then the process proceeds to step S214. On the other hand, if the condition determination result in step S201 is false, that is, if the rectification system 50b is stopped, the process proceeds to step S202.

[0100] In step S202, the control mode determiner 101b compares the traction line voltage V_LINE with the charging start voltage V_ABS and determines the condition of V_LINE > V_ABS. If the condition determination result of step S202 is true (True), it proceeds to step S203; if it is false (False), it proceeds to step S204.

[0101] In step S203, the control mode determiner 101b determines whether the state of charge SOC is within the operating range of the battery pack 3. Here, similar to step S102 in FIG. 7, the range of the state of charge defined by the upper operating limit value SOC_H and the lower operating limit value SOC_L is set as the operating range of the battery pack 3, and for this operating range, the condition determination of SOC_L < SOC < SOC_H is performed. If the condition determination result of step S203 is true (True), it proceeds to step S208; if it is false (False), it proceeds to step S209.

[0102] In step S204, the control mode determiner 101b compares the traction line voltage V_LINE with the discharging start voltage V_DISC and determines the condition of V_LINE < V_DISC. If the condition determination result of step S204 is true (True), it proceeds to step S205; if it is false (False), it proceeds to step S206.

[0103] In step S205, the control mode determiner 101b performs the same condition determination as in step S203. If the condition determination result of step S205 is true (True), it proceeds to step S210; if it is false (False), it proceeds to step S211.

[0104] In step S206, the control mode determiner 101b performs the condition determination of SOC_L < SOC < SOC3 for the aforementioned third range, similar to step S106 in FIG. 7. If the condition determination result of step S206 is true (True), it proceeds to step S212; if it is false (False), it proceeds to step S207.

[0105] In step S207, the control mode determiner 101b performs a condition determination of SOC2 < SOC < SOC_H for the aforementioned second range, similar to step S104 in FIG. 7. If the condition determination result in step S207 is true (True), the process proceeds to step S212; if it is false (False), the process proceeds to step S213.

[0106] When the condition determination result in step S203 is true, in step S208, the control mode determiner 101b sets the control mode determination result to MODE = 1 and switches the control mode of the power storage device 1b to the charging side voltage control mode.

[0107] When the condition determination result in step S203 is false, in step S209, the control mode determiner 101b sets the control mode determination result to MODE = 4 and switches the control mode of the power storage device 1b to the standby mode.

[0108] When the condition determination result in step S205 is true, in step S210, the control mode determiner 101b sets the control mode determination result to MODE = 并べ替える5 and switches the control mode of the power storage device 1b to the discharging side voltage control mode. In this discharging side voltage control mode, the discharging side voltage controller 109 is activated, and the charging side voltage controller 103, the charging rate controller 104, and the rectifier support arithmetic unit 105 are reset. Thereby, in the controller 100b, the operation of the power converter 2 is controlled according to the voltage command value from the discharging side voltage controller 109, and the storage battery panel 3 is discharged to stabilize the traction line voltage V_LINE.

[0109] When the condition determination result in step S205 is false, in step S211, the control mode determiner 101b sets the control mode determination result to MODE = 4 and switches the control mode of the power storage device 1b to the standby mode.

[0110] If the result of the condition determination in step S206 or step S207 is true, in step S212, the control mode determination device 101b sets the control mode determination result to MODE=3 and switches the control mode of the power storage device 1b to the charge rate control mode.

[0111] If the condition determination result in step S207 is false, in step S213, the control mode determination device 101b sets the control mode determination result to MODE=4 and switches the control mode of the power storage device 1b to standby mode.

[0112] If the control mode determination result is set to one of MODE=1 to 5 in either steps S108 to S113 or S208 to S213, in step S214, the control mode determination unit 101b waits until the next calculation trigger. Upon receiving the next calculation trigger, it returns to step S201 and resumes the calculation flow shown in Figure 13. This executes the calculation process according to the calculation flow shown in Figure 13 at predetermined calculation cycles to determine the control mode.

[0113] By performing the above control mode determination in the control mode determination device 101b, if the rectification system 50b is operating normally, the operation map of Figure 8 described in the first embodiment is realized in the power storage device 1b. On the other hand, if the rectification system 50b is stopped, the operation map of Figure 14 is realized in the power storage device 1b. Here, the horizontal axis of Figure 14 represents the charge level (SOC), and the vertical axis represents the feeder line voltage V_LINE, with the thick lines indicating the charging start voltage V_ABS and the discharge start voltage V_DISC. In addition, the positions where the charge level (SOC) is at the operating lower limit value SOC_L, a predetermined value SOC3, a predetermined value SOC2, and an operating upper limit value SOC_H are indicated by dashed lines, respectively. Each control mode of the power storage device 1b is defined by the regions demarcated by these dashed lines and the charging start voltage V_ABS and the discharge start voltage V_DISC. In Figure 14, the control modes corresponding to each region are shown by the value of the variable MODE.

[0114] As described above, according to this embodiment, in the DC power supply system 30 powered by the thyristor rectifier 52, the battery panel 3, which is the energy storage element of the power storage device 1b, can be discharged in advance in preparation for charging surplus regenerative power. Furthermore, when surplus regenerative power is generated, the regenerative power absorbed from the power supply line 70 is charged into the battery panel 3, and the power stored in the battery panel 3 is discharged when the railway vehicle 80 is powered, thereby enabling effective utilization of surplus regenerative power. In addition, when the battery panel 3 is discharged, the variable limiter 1053 of the rectifier support calculator 105 can limit the discharge current according to the charge rate (SOC). This prevents over-discharge of the battery panel 3 and also prevents abrupt disturbances to the power supply circuit. In addition to the same effects as those of the first embodiment, by switching the control mode of the power storage device 1b depending on whether the rectification system 50 is operating or stopped, it is possible to suppress an excessive drop in the feeder line voltage due to the discharge of the battery panel 3 even when the rectification system 50b is stopped. This further contributes to stabilizing the feeder line voltage.

[0115] Furthermore, according to the second embodiment of the present invention, when the rectification system 50b is operating (step S201: True), the controller 100b controls the power converter 2 in the same manner as in the first embodiment. Also, when the rectification system 50b is stopped (step S201: False), if the voltage V_LINE of the feeder line 70 is greater than the charging start voltage V_ABS (step S202: True) and the charge level SOC of the battery storage panel 3 is within the operating range (step S203: True), the controller 100b sets the control mode of the power storage device 1b to the charging-side voltage control mode (step S208: MODE=1), causing the power converter 2b to perform a charging operation to charge the battery storage panel 3 and bring the voltage V_LINE of the feeder line 70 closer to the charging start voltage V_ABS. On the other hand, if the voltage V_LINE of the feeder line 70 is less than a predetermined discharge start voltage V_DISC which is lower than the charge start voltage V_ABS (Step S204: True), and the charge level SOC of the battery panel 3 is within the operating range (Step S205: True), the control mode of the power storage device 1b is set to the discharge-side voltage control mode (Step S210: MODE=5), causing the power converter 2b to perform a charging operation to discharge the battery panel 3 and bring the voltage V_LINE of the feeder line 70 closer to the discharge start voltage V_DISC. In this way, the surplus regenerated power in the DC power supply system 30 can be effectively utilized, while the feeder line voltage can be stabilized when the rectification system 50b is stopped.

[0116] It should be noted that the present invention is not limited to the embodiments or modifications described above, and can be implemented using any components without departing from the spirit of the invention. Furthermore, each embodiment and modification can be implemented in any combination.

[0117] The embodiments and modifications described above are merely examples, and the present invention is not limited to these, as long as the features of the invention are not impaired. Furthermore, although various embodiments and modifications have been described above, the present invention is not limited to these. Other embodiments conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention. [Explanation of Symbols]

[0118] 1,1b: Power storage device 2: Power converter 3: Battery panel 21,24: Reactor 22: Capacitor 23: Arm 25,27: Current detector 26: Voltage detector 30: Power supply system 31: Battery pack 32: Battery Management Unit 40: Circuit breaker 41: Positive electrode wire 42: Negative electrode wire 50, 50b: Rectification system 51: Transformer 52: Thyristor Rectifier 60: Current detector 70: Power line 71: Rail 80: Railway vehicles 100, 100a, 100b: Control circuit (controller) 101,101b: Control mode determination device 102: Charging start voltage calculator 102b: Charge / Discharge Start Voltage Calculator 103: Charging side voltage controller 104: Charge level controller 105: Rectifier support calculator 106,106b: Adder 107: Current controller 109: Discharge-side voltage controller 1051: Multiplier 1052: Maximum Value Calculator 1053: Variable limiter 1054: Minimum Value Calculator 1055: Changeover switch

Claims

1. A rechargeable and dischargeable energy storage element, A power converter that converts the power input and output between the energy storage element and the power line in both directions to charge and discharge the energy storage element, The power converter includes a control circuit that controls the operation of the power converter and causes the power converter to perform a charging operation to charge the energy storage element or a discharging operation to discharge the energy storage element, A rectifier system capable of outputting a DC current to the feeder line is connected to the feeder line. The aforementioned control circuit is If the voltage of the feeder line is greater than a predetermined charging start voltage and the charge level of the energy storage element is within a predetermined operating range, the power converter is instructed to perform the charging operation to charge the energy storage element and bring the voltage of the feeder line closer to the charging start voltage. A power storage device that, when the voltage of the feeder line is less than or equal to the charging start voltage, the current flowing through the feeder line is greater than a predetermined current threshold, and the charge rate of the energy storage element is within a predetermined second range set for a portion of the operating range, causes the power converter to perform the discharge operation so as to discharge the energy storage element and output a DC current to the feeder line together with the rectifier system.

2. A power storage device according to claim 1, The control circuit acquires a detected value of the total current, which is the sum of the DC currents output to the feeder line from the power converter and the rectification system, respectively, and determines the current flowing through the feeder line based on the acquired detected value of the total current.

3. A power storage device according to claim 1, The control circuit is a power storage device that acquires a detected value of the DC current output from the power converter to the feeder line and a detected value of the DC current output from the rectifier system to the feeder line, and determines the current flowing through the feeder line based on the acquired detected values ​​of each DC current.

4. A power storage device according to any one of claims 1 to 3, The control circuit controls the magnitude of the DC current output from the power converter to the feeder line based on the charge level of the energy storage element and the current flowing through the feeder line when the power converter performs the discharge operation, in this power storage device.

5. A power storage device according to any one of claims 1 to 3, The aforementioned control circuit is If the voltage of the feeder line is less than or equal to the charging start voltage, and the current flowing through the feeder line is less than or equal to the current threshold, and the charge level of the energy storage element is within the second range, or within a predetermined third range set for a part of the operating range that is lower than the second range, or When the voltage of the feeder line is less than or equal to the charging start voltage, the current flowing through the feeder line is greater than the current threshold, and the charge level of the energy storage element is within the third range, A power storage device that causes the power converter to perform the charging operation or the discharging operation so that the charge level of the energy storage element approaches a predetermined target value by charging and discharging the energy storage element.

6. A power storage device according to any one of claims 1 to 3, The aforementioned control circuit is A first control mode controls the power converter to charge the energy storage element and bring the voltage of the feeder line closer to the charging start voltage, A second control mode that calculates a discharge current command based on the charge level of the energy storage element and the current flowing through the feeder line, and controls the power converter to discharge the energy storage element based on the calculated discharge current command, A third control mode controls the power converter to charge and discharge the energy storage element so that the charge level of the energy storage element approaches a predetermined target value, A fourth control mode for stopping the operation of the power converter is included, A power storage device that selects one of the first control mode, the second control mode, the third control mode, or the fourth control mode based on at least one of the voltage of the feeder line, the charge level of the energy storage element, and the current flowing through the feeder line.

7. A power storage device according to any one of claims 1 to 3, The control circuit acquires the operating status of the rectifier system and switches the control of the power converter depending on whether the rectifier system is operating or stopped, and is a power storage device.

8. A power storage device according to claim 7, When the rectification system is operating, the control circuit will If the voltage of the feeder line is greater than the charging start voltage and the charge level of the energy storage element is within the operating range, the power converter is instructed to perform the charging operation to charge the energy storage element and bring the voltage of the feeder line closer to the charging start voltage. When the voltage of the feeder line is less than or equal to the charging start voltage, the current flowing through the feeder line is greater than the current threshold, and the charge level of the energy storage element is within the second range, the power converter is made to perform the discharge operation so as to discharge the energy storage element and output a DC current to the feeder line together with the rectifier system. When the rectification system is stopped, the control circuit will: If the voltage of the feeder line is greater than the charging start voltage and the charge level of the energy storage element is within the operating range, the power converter is instructed to perform the charging operation to charge the energy storage element and bring the voltage of the feeder line closer to the charging start voltage. A power storage device that, when the voltage of the feeder line is lower than a predetermined discharge start voltage which is lower than the charging start voltage, and the charge level of the energy storage element is within the operating range, causes the power converter to perform the discharge operation so as to discharge the energy storage element and bring the voltage of the feeder line closer to the discharge start voltage.

9. A power storage device according to any one of claims 1 to 3, A power storage device in which the lower limit of the second range is set between 10% and 40% in terms of the charge rate of the energy storage element.

10. A power storage device according to any one of claims 1 to 3, A power storage device in which the charging start voltage is set to a value higher than the no-load output voltage of the rectifier system.

11. A method for controlling the power stored in a rechargeable energy storage element by controlling the operation of a power converter that charges and discharges the energy storage element by converting the power input and output between the rechargeable energy storage element and a power line in both directions, A rectifier system capable of outputting a DC current to the feeder line is connected to the feeder line. If the voltage of the feeder line is greater than a predetermined charging start voltage and the charge level of the energy storage element is within a predetermined operating range, the operation of the power converter is controlled to charge the energy storage element and bring the voltage of the feeder line closer to the charging start voltage. A power storage control method that controls the operation of the power converter to discharge the energy storage element and output a DC current to the feeder line together with the rectifier system when the voltage of the feeder line is less than or equal to the charging start voltage, the current flowing through the feeder line is greater than a predetermined current threshold, and the charge rate of the energy storage element is within a predetermined second range set for a part of the operating range.

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