Power supply system

Abstract

To provide a power supply system which achieves miniaturization and low cost and avoids an early failure.SOLUTION: A power supply system includes: a DC power supply 1; a power converter 2 for converting power outputted from the DC power supply 1 into prescribed power and outputting the power to a load; a converter control unit 5 for controlling operation of the power converter 2; a first life evaluation unit 7 for calculating a life consumption amount of the power converter 2 in a prescribed period based on at least one of temperature information of the power converter 2 and a control command value of the power converter 1; and a load management control unit 8 for generating a command value to the converter control unit 5 for adjusting output of the power converter 2 by using an integration value obtained by integrating the life consumption amount and a life plan which is previously set.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a power supply system.

Background Art

[0002] For example, a DC power supply system, which is a power supply system for a DC electric railway, has characteristics of severe load fluctuations and large fluctuations in the voltage of the feeder wire. Also, in a DC power supply system, since it is common to generate a DC power supply using a diode rectifier, power regeneration to an AC power supply system cannot be implemented without installing a regeneration inverter. If there is no sufficient load around the regenerative vehicle to absorb the regenerative current of the regenerative vehicle, the regenerative vehicle will fall into regenerative failure.

[0003] In order to cope with voltage fluctuations and regenerative failures as described above, it has been practiced to install a storage battery in a DC electric railway vehicle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, in DC power supply systems that repeatedly charge and discharge batteries according to the overhead line voltage, fluctuations in the overhead line voltage occur due to the acceleration and deceleration of multiple trains, so the charging and discharging patterns of the batteries are not uniformly fixed. In addition, in power conversion devices for railway vehicle propulsion, the load pattern may not be standardized due to load conditions, train schedules, signaling systems, etc. Therefore, there was a risk that the lifespan of batteries and power converters would be shorter than the design expectations, leading to premature failure. In order to avoid the risk of premature failure, designing the devices with sufficient margin for lifespan tended to increase the size and cost of the devices.

[0006] The embodiments of the present invention have been made in view of the above circumstances, and aim to provide a power supply system that achieves miniaturization and cost reduction, as well as avoids premature failure. [Means for solving the problem]

[0007] The power supply system according to the embodiment includes a DC power supply, a power converter that converts the power output from the DC power supply into a predetermined power and outputs it to a load, a converter control unit that controls the operation of the power converter, a first life evaluation unit that calculates the life consumption of the power converter over a predetermined period based on at least one of the temperature information of the power converter and the control command value of the power converter, and a load management control unit that calculates a command value to the converter control unit for adjusting the output of the power converter so that the accumulated value obtained by accumulating the life consumption follows a preset life plan. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing one example configuration of a power supply system including a power converter according to the first embodiment. [Figure 2] Figure 2 is a schematic diagram showing one example of the configuration of power semiconductor elements in a power conversion device. [Figure 3] Figure 3 is a schematic diagram illustrating an example of a life plan for a storage battery and a power converter. [Figure 4]Figure 4 is a schematic diagram illustrating an example of the charge and discharge characteristics of the battery shown in Figure 1. [Figure 5] Figure 5 is a diagram illustrating an example of the control operation of a power converter using the life evaluation value of the power converter in the power supply system of this embodiment. [Figure 6] Figure 6 is a schematic diagram showing one example configuration of the converter control unit shown in Figure 5. [Figure 7] Figure 7 is a diagram illustrating an example of the control operation of a power converter using the battery life evaluation value in the power supply system of this embodiment. [Figure 8] Figure 8 is a schematic diagram showing one example configuration of the converter control unit shown in Figure 7. [Figure 9] Figure 9 illustrates another example of the control operation of the power converter using the battery life evaluation value in the power supply system of this embodiment. [Figure 10] Figure 10 is a schematic diagram showing one example configuration of a train organization control system including a power supply system of the second embodiment. [Figure 11] Figure 11 is a schematic diagram illustrating an example of a railway vehicle operation method controlled by the power supply system of the second embodiment. [Figure 12] Figure 12 schematically illustrates another example of how a railway vehicle is driven by the power supply system of the second embodiment. [Modes for carrying out the invention]

[0009] The power supply system of the embodiment will be described in detail below with reference to the drawings. Figure 1 is a schematic diagram showing one example configuration of the power supply system according to the first embodiment. The power supply system 10 of this embodiment is a system that supplies power to an electric vehicle (an electric motor for driving the electric vehicle and a power converter that drives it), which is a load 3, and charges a storage battery 1 with power regenerated from the load 3, and comprises a power storage device, a power converter, a monitoring and control device, and an interface unit 9.

[0010] The load 3 may include an electrified circuit composed of an overhead wire and a rail or a third rail and a rail, and a plurality of electric vehicles. In that case, the power supply system 10 supplies power to the plurality of electric vehicles via the electrified circuit.

[0011] The power storage device includes a storage battery 1 which is a DC power supply, and a storage battery monitoring unit 4. The storage battery 1 is configured by combining, for example, a plurality of battery cells. Note that the power storage device need not be limited to the storage battery 1 as long as it includes a DC power supply. Instead of the storage battery 1, a capacitor, an energy storage device such as a flywheel, or an electrified circuit composed of an overhead wire and a rail or a third rail and a rail may be used.

[0012] The storage battery monitoring unit 4 includes a measurement circuit that measures values of the voltage and temperature of the storage battery 1, and a management circuit (both not shown). The storage battery monitoring unit 4 may further include a measuring device that measures values of the charging current and discharging current of the storage battery 1. In this case, the measured current values are also monitored.

[0013] The management circuit is, for example, an arithmetic circuit including at least one processor and a memory in which a program executed by the processor is recorded. The management circuit calculates, for example, the state of charge (SOC) of the battery and the health (SOH) of the storage battery 1 based on the measured values. The health of the storage battery 1 is, for example, the capacity degradation rate of the storage battery 1, the internal resistance value of the battery cells constituting the storage battery 1, and the like. `

[0014] The power conversion device includes a power converter 2 and a switching control unit 5. The power converter 2 converts the DC power supplied from the storage battery into a predetermined power and outputs it to the load 3. The power converter 2 includes, for example, a plurality of power semiconductor devices such as an IGBT (Insulated Gate Bipolar Transistor) and a SiC-MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

[0015] FIG. 2 is a diagram schematically showing a configuration example of a power semiconductor device of the power conversion device shown in FIG. 1. The power converter 2 includes a module base MB on which a plurality of power semiconductor devices SW are formed. The module base MB is formed of, for example, copper or AlSiC.

[0016] Each of the power semiconductor devices SW includes an insulating substrate L2 disposed on the module base MB via a solder layer L1, a semiconductor chip L4 disposed on the insulating substrate L2 via a solder layer L3, and a bonding wire BW electrically connected to the semiconductor chip L4. The bonding wire BW is a wiring formed of aluminum or copper and is connected to the semiconductor chip L4 by, for example, ultrasonic bonding.

[0017] The switching control unit 5 includes an arithmetic circuit including at least one processor and a memory in which a program executed by the processor is recorded, and can realize various functions described below by software or a combination of software and hardware.

[0018] The switching control unit 5 controls the operations of a plurality of power semiconductors of the power converter 2. The switching control unit 5 generates a gate signal according to a command value supplied from a load management control unit 8 described later and outputs the gate signal to the power converter 2. Further, the switching control unit 5 outputs temperature information of the power converter 2, such as the estimated junction temperature (maximum junction temperature) of the power semiconductor device, the estimated case temperature (the temperature of the module base shown in FIG. 2), and the ambient temperature around the fins cooling the power converter 2, to the first life evaluation unit 7.

[0019] When the power converter 2 supplies DC power to the load 3, the switching control unit 5 may detect the voltage of the DC circuit between the power converter 2 and the load 3, and control the power converter 2 to charge the battery 1 when the detected value exceeds a predetermined threshold, and discharge to the load 3 when the detected value is below the predetermined threshold.

[0020] Figure 4 is a schematic diagram illustrating an example of the charge and discharge characteristics of the battery shown in Figure 1. In this example, the switching control unit 5 controls the power converter 2 so that, for example, when the voltage of the DC circuit exceeds V1, it charges the battery 1, and when the voltage of the DC circuit falls below V2, it discharges the battery 1. The monitoring and control device is an arithmetic unit comprising at least one processor and memory in which a program executed by the processor is stored, and can realize various functions described below by software or by a combination of software and hardware.

[0021] The monitoring and control device comprises a second life evaluation unit 6, a first life evaluation unit 7, and a load management control unit 8. The first life evaluation unit 7 is a means for evaluating the life of the power converter 2, and for example, evaluates the life of a module including a plurality of power semiconductor elements SW. Examples of failures of the power semiconductor elements SW include failures in which the bonding wire BW delaminates from the semiconductor chip L4 due to thermal cycle fatigue caused by temperature changes (ΔTj) of the semiconductor chip L4, and failures in which cracks form in the solder layer L1 due to thermal cycle fatigue caused by temperature changes (ΔTc) of the module base MB, increasing the thermal resistance between the semiconductor chip L4 and the module base MB, and ultimately destroying the semiconductor chip L4.

[0022] The first life evaluation unit 7 evaluates the lifespan of the power converter 2 due to failure by calculating the damage inflicted on the power semiconductor element SW and module by the aforementioned thermal cycle, using the temperature history of the power semiconductor element SW and module acquired from the switching control unit 5. The first life evaluation unit 7 can also calculate the damage (life consumption) accumulated in the power semiconductor based on the on-time of the power semiconductor element SW. In this embodiment, the first life evaluation unit 7 supplies to the load management control unit 8 a value obtained by adding, for example, the life evaluation value (life consumption) of the bonding wire BW due to the thermal cycle fatigue described above, the life evaluation value (life consumption) due to cracks in the solder layer L1, and the life consumption based on the on-time of the power semiconductor element SW, or at least one of these values.

[0023] The second life evaluation unit 6 is a battery life evaluation unit that calculates the life consumption of the battery 1 based on the information obtained from the battery monitoring unit 4. The specific definition of battery life varies depending on the application, but for example, at least one of the energy that the battery 1 can charge or discharge (energy capacity) or the internal resistance value of the battery 1 can be used as evaluation items. In this embodiment, the second life evaluation unit 6 obtains the temperature, voltage, charge rate, and charging current of the battery 1 (or battery cell) from the battery monitoring unit 4 and outputs an evaluation result (life consumption) based on at least one of the internal resistance value, chargeable capacity, and dischargeable capacity of the battery 1 (information related to the battery 1) to the load management control unit 8.

[0024] The load management control unit 8 obtains the life consumption of at least one of the storage battery 1 and the power converter 2 from the second life evaluation unit 6 and the first life evaluation unit 7, generates a command value to control the output of the power converter 2 so that the life consumption is in line with (or not below) a preset life plan, and outputs the command value to the switching control unit 5. The life plan may also be input by a user operating the interface unit 9.

[0025] Figure 3 is a schematic diagram illustrating an example of a life plan for a storage battery and a power converter. Figure 3 shows the expected remaining lifespan value (lifespan plan curve) 20 and the actual lifespan curve 21, depending on the operating time. For example, at point A, the actual lifespan curve is below the lifespan plan curve. If this situation continues, the initially planned lifespan (the time until the remaining lifespan value goes from 1 to 0) cannot be satisfied, and it is estimated that at least one of the battery 1 and the power converter 2 will fail prematurely. In that case, the load management control unit 8 outputs a command value to the switching control unit 5 to reduce the load on the battery 1 and the power converter 2.

[0026] Furthermore, the load management control unit 8 may output the life evaluation results (e.g., cumulative life consumption value) of the storage battery 1 and the power converter 2 to external devices such as the interface unit 9 or a power management system (e.g., including a power dispatch center).

[0027] The load management control unit 8 can command the switching control unit 5 to, for example, the maximum output current and maximum output power of the power converter 2, the switching frequency of the power semiconductor element SW, and so on. The load management control unit 8 may also output the charging start voltage value (V1 shown in Figure 4) and the discharging start voltage value (V2 shown in Figure 4) to the switching control unit 5. For example, to reduce the load on the power converter 2 and the battery 1, the load management control unit 8 can reduce the load by lowering the discharging start voltage value or raising the charging start voltage value. Conversely, to increase the load on the power converter 2 and the battery 1, the load management control unit 8 can increase the load on the power converter 2 and the battery 1 by raising the discharging start voltage value or lowering the charging start voltage value.

[0028] The interface unit 9 can display the life evaluation results obtained from the load management control unit 8 in a manner that is visible to the user. The interface unit 9 may also transmit the life evaluation results to an external party via a communication network.

[0029] Below, an example of the operation of the power supply system described above will be explained in detail with reference to the diagrams. Figure 5 is a diagram illustrating an example of the control operation of a power converter using the life evaluation value of the power converter in the power supply system of this embodiment.

[0030] The switching control unit 5 comprises a temperature calculation unit 51 and a converter control unit 52. The temperature calculation unit 51 calculates at least one of the following: the estimated junction temperature of the power semiconductor element SW, the maximum value of the junction temperature over a predetermined period, the estimated case temperature (temperature of the module base MB shown in Figure 2), and the ambient temperature of the fins cooling the power converter 2. The temperature calculation unit 51 may, for example, calculate the temperature of the power semiconductor SW, etc., from the operation of the power converter 2 based on the control command value of the power converter 2 calculated by the converter control unit 52, or it may calculate the above various temperature values ​​based on the temperature obtained from a temperature sensor attached to at least a part of the power converter 2. The temperature calculation unit 51 outputs the calculated values ​​to the first lifetime evaluation unit 7.

[0031] Furthermore, it is desirable that the period (sampling period) for calculating the temperature of the power semiconductor element SW in the temperature calculation unit 51 be 1 s or less, taking into account the thermal time constant of the semiconductor element SW.

[0032] The first life evaluation unit 7 comprises a history storage unit 7A, a thermal cycle analysis unit 7B, and a thermal fatigue analysis unit 7C. The history storage unit 7A stores the temperature values ​​supplied by the temperature calculation unit 51 in chronological order. The history storage unit 7A only needs to store temperature values ​​(time-series information) from the most recent value supplied by the temperature calculation unit 51 up to a predetermined period in the past, and may sequentially delete older data. Furthermore, the history storage unit 7A may transmit the temperature value history to the interface unit 9 as needed.

[0033] The thermal cycle analysis unit 7B performs thermal cycle analysis of the power semiconductor element SW using time-series information of temperature values ​​stored in the history storage unit 7A. At this time, it is desirable for the thermal cycle analysis unit 7B to perform thermal cycle analysis using temperature history data for one or more periodic load fluctuations (load cycles). For example, in the case of loads of social infrastructure equipment such as railways and elevators, it is desirable to perform thermal cycle analysis on the temperature history data for the previous day (24 hours) with a task cycle of 24 hours or more. The thermal cycle analysis unit 7B performs thermal cycle analysis using, for example, the rainflow method and supplies the analysis results, such as the magnitude of temperature changes, the number of times they occur, and their duration, to the thermal fatigue analysis unit 7C.

[0034] The thermal fatigue analysis unit 7C performs a thermal fatigue analysis using the results of the thermal cycle analysis (magnitude of temperature change, number of cycles, and duration) and calculates the daily life consumption for each failure mode of the power semiconductor element SW described above. The thermal fatigue analysis unit 7C outputs the calculated life consumption to the load management control unit 8.

[0035] The load management control unit 8 includes an adder 8A, a delay unit 8B, a subtractor 8C, a gain multiplier 8D, a limiter 8E, and a multiplier 8F. The adder 8A calculates and outputs a cumulative lifetime consumption value by adding the lifetime consumption output from the thermal fatigue analysis unit 7C and the previously calculated value output from the delay unit 8B. The value output from the adder 8A corresponds to the value of the lifetime actual curve in Figure 2.

[0036] The subtractor 8C outputs the difference obtained by subtracting the accumulated life consumption value from the pre-set remaining life plan value. The gain multiplier 8D outputs a value obtained by multiplying the difference output from the subtractor 8C by the adjustment gain Kp. The limiter 8E restricts the output from the gain multiplier 8D to an upper and lower limit so that the value output from the gain multiplier 8D is between 0 and 1.

[0037] The multiplier 8F outputs a value (limit command value) obtained by multiplying the output current limit value by the output value of the limiter 8E. In other words, the output value of the limiter 8E is the variable gain of the output current limit value. The limit command value output from the multiplier 8F is supplied to the converter control unit 52 of the switching control unit 5.

[0038] The converter control unit 52 acquires the voltage target value and the limit command value, and controls the duty cycle of the pulses that control the operation of the power semiconductor element SW of the power converter 2 according to the acquired values, thereby adjusting the load on the power converter 2 by limiting the maximum output current and maximum regenerative current of the power converter 2.

[0039] Figure 6 is a schematic diagram showing one example configuration of the converter control unit shown in Figure 5. The converter control unit 52 includes a voltage control unit 521, a current control unit 522, and a PWM modulation unit 523. The voltage control unit 521 includes subtractors 5A and 5C, and PI control units 5B and 5D. The subtractor 5A outputs the difference obtained by subtracting the voltage feedback value (charging voltage value) supplied from the power converter 2 from the target charging voltage value.

[0040] The PI control unit 5B calculates and outputs a current control command value using proportional-integral control so that the difference supplied from the subtractor 5A becomes zero, that is, so that the voltage feedback value (charging voltage value) follows the target charging voltage value. The subtractor 5C outputs the difference obtained by subtracting the voltage feedback value (discharge voltage value) supplied from the power converter 2 from the target discharge voltage value.

[0041] The PI control unit 5D calculates and outputs a current control command value using proportional-integral control so that the difference supplied from the subtractor 5C becomes zero, that is, so that the voltage feedback value (discharge voltage value) follows the target discharge voltage value.

[0042] The current control unit 522 includes a multiplier 5E, limiters 5F and 5G, an adder 5H, a subtractor 5I, and a PI control unit 5J. The multiplication unit 5E outputs the product of the limit command value supplied from the load management control unit 8 multiplied by -1. The limiter 5F limits the upper and lower limits of the current control command value supplied from the PI control unit 5B, using the value supplied from the multiplier unit 5E as the lower limit and 0 as the upper limit, and outputs the result.

[0043] Limiter 5G outputs the upper and lower limits of the current control command value supplied from PI control unit 5D, with 0 as the lower limit and the limit command value supplied from load management control unit 8 as the upper limit. Adder 5H outputs the sum of the current control command value output from limiter 5F and the current control command value output from limiter 5G.

[0044] The subtractor 5I outputs the difference obtained by subtracting the current feedback value supplied from the power converter 2 from the sum of the current control command values ​​output from the adder 5H. The PI control unit 5J calculates and outputs a voltage command value using proportional-integral control so that the difference output from the subtractor 5I becomes zero, that is, so that the current feedback value follows the sum of the current control command values. The PWM modulation unit 523 generates a gate command for the power semiconductor element SW by comparing the voltage command value supplied from the PI control unit 5J with the carrier wave, and outputs it to the power converter 2.

[0045] As described above, in the power supply system 10 of this embodiment, the current control unit 522 of the power converter 2 has a function to limit the current control command value for maintaining the target voltage, for example. At this time, by controlling the charging current limit (lower limit) and the discharge current limit (upper limit) based on the limit command value of the load management control unit 8, the maximum charging current and maximum discharge current of the storage battery 1 can be limited according to the remaining lifespan of the power converter 2, and as a result the load on the power converter 2 can be limited. As a result, the lifespan consumption of the power converter 2 can be achieved as planned without falling significantly below the expected lifespan plan curve.

[0046] Furthermore, the temperature calculation and history storage, thermal cycle analysis, and thermal fatigue analysis of the power semiconductor element SW described above do not need to be performed at the specific mounting location described in the above embodiment; they can be implemented and functioned at any functional location, and do not limit the configuration in which they are implemented.

[0047] Figure 7 illustrates another example of the control operation of the power converter using the power converter's lifetime evaluation value in the power supply system of this embodiment. Note that in Figure 7, components similar to those shown in Figure 5 are denoted by the same reference numerals and their explanations are omitted. Figure 7 shows an example of application to a DC1500V overhead line power conversion system that performs powering and regeneration. The power supply system 10 shown in Figure 7 differs from the configuration shown in Figure 5 in the load management control unit 8.

[0048] The load management control unit 8 comprises adders 8A and 8G, a delay unit 8B, subtractors 8C and 8I, a gain multiplier unit 8D, and limiters 8H and 8J. The adder 8A calculates and outputs a cumulative lifetime consumption value by adding the lifetime consumption output from the thermal fatigue analysis unit 7C and the previously calculated value output from the delay unit 8B.

[0049] The subtractor 8C outputs the difference obtained by subtracting the cumulative life consumption value from the pre-set life plan value. The gain multiplier 8D outputs a value obtained by multiplying the difference output from the subtractor 8C by the adjustment gain Kp. The adder 8G outputs the sum obtained by adding the output value of the gain multiplier 8D to the reference command value of the charging start voltage.

[0050] Limiter 8H outputs values ​​(charging start voltage command values) that limit the upper and lower limits of the sum output from adder 8G. In this embodiment, limiter 8H sets the upper limit of the charging start voltage command value to 1800V and the lower limit to 1000V. The subtractor 8I outputs the difference obtained by subtracting the output value of the gain multiplier 8D from the reference command value of the discharge start voltage.

[0051] The limiter 8J outputs a value (discharge start voltage command value) that limits the upper and lower limits of the difference output from the subtractor 8I. In this embodiment, the limiter 8J sets the upper limit of the discharge start voltage command value to 1800V and the lower limit to 900V. As described above, the load management control unit 8 adjusts the voltage range (dead zone width) between the charging start voltage and the discharging start voltage of the battery 1 according to the difference between the life plan value and the cumulative life consumption value.

[0052] Figure 8 is a schematic diagram showing one example configuration of the converter control unit shown in Figure 7. Note that the input values ​​for the converter control unit 52 shown in Figure 8 are different from those shown in Figure 6. The converter control unit 52 includes a voltage control unit 521, a current control unit 522, and a PWM modulation unit 523.

[0053] The voltage control unit 521 includes subtractors 5A and 5C, and PI control units 5B and 5D. The subtractor 5A outputs the difference obtained by subtracting the voltage feedback value (overhead line voltage value) from the charging start voltage command value. The PI control unit 5B calculates and outputs a current control command value using proportional-integral control so that the difference supplied from the subtractor 5A becomes zero, that is, so that the voltage feedback value (overhead line voltage value) follows the charging start voltage command value.

[0054] Subtractor 5C outputs the difference obtained by subtracting the voltage feedback value (overhead line voltage value) from the discharge start voltage command value. The PI control unit 5D calculates and outputs a current control command value using proportional-integral control so that the difference supplied from the subtractor 5C becomes zero, that is, so that the voltage feedback value (overhead line voltage value) follows the discharge start voltage command value.

[0055] The current control unit 522 includes a multiplier 5E, limiters 5F and 5G, an adder 5H, a subtractor 5I, and a PI control unit 5J. The multiplication unit 5E outputs the product of the limit command value supplied from the load management control unit 8 multiplied by -1. The limiter 5F limits the upper and lower limits of the current control command value supplied from the PI control unit 5B, using the value supplied from the multiplier unit 5E as the lower limit and 0 as the upper limit, and outputs the result.

[0056] Limiter 5G outputs the upper and lower limits of the current control command value supplied from PI control unit 5D, with 0 as the lower limit and the limit command value supplied from load management control unit 8 as the upper limit. Adder 5H outputs the sum of the current control command value output from limiter 5F and the current control command value output from limiter 5G.

[0057] The subtractor 5I outputs the difference obtained by subtracting the current feedback value supplied from the power converter 2 from the sum of the current control command values ​​output from the adder 5H. The PI control unit 5J calculates and outputs a voltage command value using proportional-integral control so that the difference output from the subtractor 5I becomes zero, that is, so that the current feedback value follows the sum of the current control command values.

[0058] The PWM modulation unit 523 generates a gate command for the power semiconductor element SW by comparing the voltage command value supplied from the PI control unit 5J with the carrier wave, and outputs it to the power converter 2.

[0059] In this example, as described above, the overhead line voltage is fed back to control the charging and discharging of the battery 1 based on the charge start voltage command value and the discharge start voltage command value. At this time, the gap that occurs between the charge start voltage value and the discharge start voltage value becomes a dead zone, which is a voltage region in which charging and discharging of the battery 1 does not occur. By adjusting the dead zone width of this voltage control system, for example, increasing the charge start voltage makes it difficult for the battery 1 to be charged, and decreasing the discharge start voltage makes it difficult for the battery 1 to be discharged. In this way, by varying the voltage difference between the charge start voltage and the discharge start voltage of the battery 1, it becomes possible to adjust the load on the power converter 2 and the charge / discharge load of the battery 1. That is, the wider the dead zone width, the less the load responsibility of the battery 1 for charging and discharging, and conversely, the narrower the dead zone width, the more the load responsibility of the battery 1 increases, making it possible to control the lifespan of the battery 1 and the power converter 2.

[0060] Figure 9 illustrates another example of the control operation of the power converter using the battery life evaluation value in the power supply system of this embodiment. The second life evaluation unit 6 includes a history storage unit 6A and a battery degradation table 6B.

[0061] The history storage unit 6A acquires the temperature of the battery 1, the charge state (SOC) of the battery 1 (or battery cells), the voltage of the battery 1 (or battery cells), and the charge / discharge current of the battery 1 from the battery monitoring unit 4, and stores the acquired values ​​in chronological order. The history storage unit 6A only needs to store values ​​from the most recent value supplied by the battery monitoring unit 4 up to a predetermined point in the past, and may sequentially delete older data. The history storage unit 6A may also transmit the history to the interface unit 9 as needed.

[0062] The battery degradation table 6B stores, for example, a numerical value (life consumption) indicating the degradation of battery 1, corresponding to the charge state (SOC) of battery 1, the temperature of battery 1 at that time, and the time spent in the system. The battery degradation table 6B uses the charge state (SOC) of battery 1 and the temperature of battery 1 supplied from the history storage unit 6A to output the life consumption corresponding to the time spent in the system.

[0063] The life consumption of the battery 1 may be calculated using the voltage and current of the battery 1. For example, the voltage fluctuation of the battery 1 when a certain current is flowing can be observed from the voltage and current of the battery 1 observed by the battery monitoring unit 4. For example, the second life evaluation unit 6 can calculate the internal resistance of the battery 1 from the relationship ΔV / ΔI, and the life consumption of the battery 1 may be calculated from the calculated internal resistance value. The internal resistance value of the battery 1 can serve as an indicator of the degradation of the battery 1, and if the internal resistance value relative to the usage period of the battery 1 is set as the remaining life value (life planning curve) 20, it is also possible to set the internal resistance value as the actual life value.

[0064] By performing a degradation calculation for battery 1 on a 24-hour cycle, the daily life consumption of battery 1 can be calculated. Once the daily life consumption is calculated, the output of the power converter 2 can be limited using the same method as the load limiting method used by the load management control unit 8 shown in Figure 5.

[0065] In other words, the load management control unit 8 comprises an adder 8A, a delay unit 8B, a subtractor 8C, a gain multiplier 8D, a limiter 8E, and a multiplier 8F. Note that in the load management control unit 8 shown in Figure 9 and the load management control unit 8 shown in Figure 5, the same components are denoted by the same reference numerals for explanatory purposes, but the input values ​​are different.

[0066] The adder 8A calculates and outputs a cumulative life consumption value by adding the life consumption of battery 1 output from the battery degradation table 6B and the previously calculated value output from the delay unit 8B. The value output from adder 8A corresponds to the value on the life consumption curve in Figure 2.

[0067] The subtractor 8C outputs the difference obtained by subtracting the accumulated life consumption value from the pre-set remaining life plan value. The gain multiplier 8D outputs a value obtained by multiplying the difference output from the subtractor 8C by the adjustment gain Kp. The limiter 8E restricts the output from the gain multiplier 8D to an upper and lower limit so that the value output from the gain multiplier 8D is between 0 and 1.

[0068] The multiplier 8F outputs a value (limit command value) obtained by multiplying the output current limit value by the output value of the limiter 8E. In other words, the output value of the limiter 8E is the variable gain of the output current limit value. The limit command value output from the multiplier 8F is supplied to the converter control unit 52 of the switching control unit 5.

[0069] The converter control unit 52 acquires the voltage target value and the limit command value, and controls the duty cycle of the pulses that control the operation of the power semiconductor element SW of the power converter 2 according to the acquired values, thereby adjusting the load on the battery 1 and the power converter 2 by limiting the maximum output current and maximum regenerative current of the power converter 2.

[0070] As described above, this embodiment provides a power supply system that achieves miniaturization and cost reduction while avoiding premature failure. Furthermore, the power supply system 10 of this embodiment does not need to include both the second life evaluation unit 6 and the first life evaluation unit 7; it only needs to include one of them. Even in that case, the above-described effects can be obtained.

[0071] Next, the power supply system of the second embodiment will be described in detail with reference to the drawings. In this embodiment, the power supply system 10 is applied to the train formation control system 73, which will be described later, and controls the lifespan of the storage battery 1 and the power converter 2 by adjusting the running method of the railway vehicles. In the power supply system 10 of this embodiment, the DC power supply of the energy storage device is a feeder circuit consisting of overhead lines and rails or a third rail and rails, and the load 3 is an electric motor for running an electric vehicle and a power converter that drives the electric motor.

[0072] Figure 10 is a schematic diagram showing one example configuration of a railway vehicle drive system including a power supply system of the second embodiment. The railway vehicle drive system shown in Figure 10 comprises an electric motor M, a power converter (second power converter) 72, a train formation control system 73, and a load detection device 74.

[0073] The electric motor M is rotationally driven by power supplied from the power converter 72, and drives the electric train. Multiple electric motor M units are installed within an electric train set. The power converter 72 converts the power supplied from the power converter 2, for example shown in Figure 1, into a predetermined power and supplies it to the motor M, and also converts the power regenerated from the motor M into a predetermined power and supplies it to the power converter 2. Multiple power converters 72 are installed in one train set to correspond to multiple motors M.

[0074] The load detection device 74 is a device that detects load information of railway vehicles within a train set, for example, from the pressure of the suspension. The train formation control system 73 changes the torque distribution of multiple electric motors M based on the value (load information) detected by the load detection device 74. Specifically, the train formation control system 73 outputs a torque command corresponding to the detected load value to the power converter 72 corresponding to the electric motor M that bears that load. As a result, the torque distribution is made such that the electric motor M that is responsible for a vehicle with a heavier load bears a larger torque.

[0075] When such control is implemented, the congestion rate and load capacity of each vehicle are not necessarily uniform, which can lead to an uneven load distribution on the motor M of a particular vehicle, potentially reducing the lifespan of the power converter 2 that supplies power to that motor M. Another method is to equalize the torque commands to each drive motor M within the train set, but this can induce wheel slip or skidding because the adhesion between the rails and wheels changes depending on the load conditions.

[0076] Therefore, in the power supply system 10 of this embodiment, the lifespan of the power converter 2 and the storage battery 1 is adjusted by changing the way the railway vehicle is driven. Figure 11 is a schematic diagram illustrating an example of a railway vehicle operation method controlled by the power supply system of the second embodiment. For example, if the actual life curve 21 falls below the life plan curve 20 in Figure 2, the load management control unit 8 calculates a command value for the converter control unit 5 to reduce the maximum speed of the target vehicle between stations. This shortens the time to reach the maximum speed, reduces the output current of the power converter, and extends the lifespan of the power converter 2 and the storage battery 1.

[0077] Figure 12 schematically illustrates another example of how a railway vehicle is driven by the power supply system of the second embodiment. For example, if the actual life curve 21 falls below the life plan curve 20 in Figure 2, the load management control unit 8 calculates command values ​​for the converter control unit 5 to reduce the acceleration and deceleration of the target vehicle when traveling between stations. This reduces the output current of the power converter during powered and regenerative driving, thereby extending the lifespan of the power converter 2 and the battery 1.

[0078] Electric trains may also be equipped with a travel plan creation unit (not shown), in which case they are controlled to travel between stations in a time that conforms to the travel plan. As described above, this embodiment provides a power supply system that achieves miniaturization and cost reduction while avoiding premature failure.

[0079] The program according to this embodiment may be transferred while stored on an electronic device, or it may be transferred without being stored on an electronic device. In the latter case, the program may be transferred via a network, or it may be transferred while stored on a storage medium. The storage medium is a non-temporary tangible medium. The storage medium is a computer-readable medium. The storage medium can be any medium that is capable of storing a program and is readable by a computer, such as a CD-ROM or memory card, and its form is not limited.

[0080] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0081] 1...Battery, 2...Power converter, 3...Load, 4...Battery monitoring unit, 5...Switching control unit, 6...Second life evaluation unit, 7...First life evaluation unit, 8...Load management control unit, 9...Interface unit, 10...Power supply system, 20...Life planning curve, 21...Actual life curve

Claims

1. DC power supply and A power converter that converts the power output from the DC power supply into a predetermined power and outputs it to the load, A converter control unit that controls the operation of the power converter, A first life evaluation unit calculates the life consumption of the power converter over a predetermined period based on at least one of the temperature information of the power converter and the control command value of the power converter. A power supply system comprising: a load management control unit that calculates a command value to the converter control unit for adjusting the output of the power converter so that the cumulative value obtained by accumulating the life consumption follows a preset life plan.

2. The power converter comprises a plurality of power semiconductor elements, The power supply system according to claim 1, wherein the temperature information of the power converter includes at least one of time-series information of the junction temperature of the power semiconductor element, time-series information of the case temperature of the module including the power semiconductor element, and the maximum value of the junction temperature of the power semiconductor element during the predetermined period.

3. The power supply system according to claim 2, wherein the sampling period of the time-series information is 1 s or less.

4. The predetermined period is a period of one or more load cycles of the power converter. The power supply system according to claim 3, wherein the lifetime consumption is calculated by performing a thermal fatigue analysis due to temperature changes of the power semiconductor element.

5. The power converter comprises a plurality of power semiconductor elements, The power supply system according to claim 1, wherein the first life evaluation unit calculates the life consumption of the power semiconductor element based on the on-time of the power semiconductor element according to the control command value.

6. The power converter comprises a plurality of power semiconductor elements, The power supply system according to claim 1, wherein the load management control unit calculates the command value for changing the switching frequency of the power semiconductor element.

7. The DC power supply is a power supply circuit including overhead lines and rails or a third rail and rails, The load comprises a plurality of electric motors for driving an electric vehicle and a plurality of second power converters for driving the electric motors. The system further comprises a train formation control system that changes the torque of a plurality of electric motors according to load information of the electric vehicle, The power supply system according to claim 1, wherein the load management control unit calculates the command value to adjust the maximum speed of the electric vehicle according to the accumulated value.

8. The DC power supply is a power supply circuit including overhead lines and rails or a third rail and rails, The load comprises a plurality of electric motors for driving an electric vehicle and a plurality of second power converters for driving the electric motors. The system further comprises a train formation control system that changes the torque of a plurality of electric motors according to load information of the electric vehicle, The power supply system according to claim 1, wherein the load management control unit calculates the command value to adjust the acceleration and deceleration of the electric vehicle according to the accumulated value.

9. Storage batteries and A power converter that converts the power output from the aforementioned battery into a predetermined power and outputs it to the load, A converter control unit that controls the operation of the power converter, A second life evaluation unit calculates the life consumption of the storage battery over a predetermined period based on information about the storage battery, A power supply system comprising: a load management control unit that calculates a command value to the converter control unit for adjusting the output of the power converter so that the cumulative value obtained by accumulating the life consumption follows a preset life plan.

10. The power supply system according to claim 9, wherein the information relating to the storage battery includes at least one of the energy capacity and internal resistance of the storage battery.

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