Power System

Abstract

To properly detect a failure in a power source system during an interconnection operation and an autonomous operation of the power source system.SOLUTION: A power source system P is formed of a plurality of battery units Bu that are connected in parallel. The battery units Bu each include a battery pack 1 and a DCDC converter 2. A control device 3 controls output power of the battery units Bu in accordance with a power command TP. In a failure determination routine, in a case where an interconnection operation is performed, it is determined that the power system P has a failure when a deviation ΔP between the power command TP and the output power OP of the battery units Bu is greater than a first threshold Th1, and, in a case where an autonomous operation is performed, it is determined that the power system P has a failure when the deviation ΔP is greater than a second threshold Th2 that is greater than the first threshold Th1.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a power supply system, and more particularly to a power supply system capable of switching between grid-connected operation in which power is exchanged with a power grid, and isolated operation in which the power supply system is disconnected from the power grid. [Background technology]

[0002] Japanese Patent Laying-Open No. 2009-213246 (Patent Document 1) discloses a method for detecting a fault in a DC / DC converter based on the deviation between the input power and the output power, or the difference between the input voltage / output voltage ratio and the duty ratio. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-213246 A [Patent Document 2] JP 2016-67132 A [Patent Document 3] JP 2015-154625 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, power supply systems (energy storage systems) equipped with chargeable and dischargeable energy storage devices have been utilized as one of the distributed energy resources to stabilize the power supply. By connecting a power supply system equipped with a power storage device in parallel with a power grid, when there is a request to increase the power demand of the power grid (upward DR (demand response)), the upward DR can be satisfied by charging the power storage device. Also, when there is a request to reduce the power demand of the power grid (downward DR), the downward DR can be satisfied by discharging the power stored in the power storage device and performing reverse power flow.

[0005] In such a power supply system, the input / output power of the power supply system is controlled based on the requested power from a PCS (Power Conditioning Subsystem: Power Conditioning System) that connects the power supply system to the power grid. The PCS converts the discharge power of the power supply system (power storage device) into AC power, and converts the AC power of the power grid into charging power for the power supply system (power storage device). During grid-connected operation (grid-connected) in which the power supply system is connected in parallel to the power grid and power is exchanged between the power supply system and the power grid, the input / output power of the power supply system is controlled to be a power command based on the requested power from the PCS. During grid-connected operation, power is supplied to an electric load (for example, a household load) connected to the PCS from the power grid, so that the requested power from the PCS is power that responds to DR, and the power command does not fluctuate greatly. Therefore, during grid-connected operation, the deviation between the power command and the output power of the power supply system (power storage device) falls within the range of the control error of the power control in the power supply system. Therefore, during grid-connected operation, if the deviation between the power command and the output power becomes large beyond the range of control error, a failure in the power supply system can be suspected, and a failure in the power supply system can be detected by comparing the deviation between the power command and the output power with a threshold value.

[0006] When it becomes difficult to supply power from the power grid due to a power outage or the like, the power grid and the power supply system are disconnected (cut off), and the power supply system operates autonomously. During autonomous operation, power is supplied to the electrical loads connected to the PCS from the power supply system (electrical storage device), so a power command is generated to output (discharge) all of the power consumed by the electrical loads from the power supply system. There are many and varied electrical loads connected to the PCS, and they repeatedly turn on and off at various times, so the power consumed by the electrical loads fluctuates greatly, and the power command also fluctuates greatly. For this reason, during autonomous operation, the deviation between the power command and the output power becomes large, and even if the deviation between the power command and the output power is compared with the threshold value during grid-connected operation, it is not possible to properly detect a failure in the power supply system.

[0007] An object of the present disclosure is to appropriately detect a fault in a power supply system during grid-connected operation and during isolated operation of the power supply system. [Means for solving the problem]

[0008] (1) The power supply system disclosed herein is a power supply system that can switch between grid-connected operation, which exchanges power with a power grid, and independent operation, which is disconnected from the power grid. The power supply system includes a battery unit including a power storage device and a DC-DC converter, and a control device that controls the output power of the battery unit based on a power command. In the independent operation, power from the battery unit is supplied to an electric load, and in the grid-connected operation, power supplied from the power grid is supplied to the electric load. When the power supply system is operating in a grid-connected manner, the control device determines that the power supply system has failed when the deviation between the power command and the output power of the battery unit is equal to or greater than a first threshold, and when the power supply system is operating in an independent manner, the control device determines that the power supply system has failed when the deviation between the power command and the output power of the battery unit is equal to or greater than a second threshold that is greater than the first threshold.

[0009] According to this configuration, the power supply system includes a battery unit including a power storage device and a DCDC converter, and is capable of switching between a grid-connected operation in which power is exchanged between the battery unit and the power grid, and an independent operation in which the battery unit is disconnected from the power grid. The control device of the power supply system controls the output power of the battery unit based on a power command. In the power supply system, in the independent operation, the power of the battery unit is supplied to an electric load, and in the grid-connected operation, the power supplied from the power grid is supplied to the electric load. When the power supply system is in the grid-connected operation, the control device determines that the power supply system has failed when the deviation between the power command and the output power of the battery unit is greater than a first threshold. When the power supply system is in the independent operation, the control device determines that the power supply system has failed when the deviation between the power command and the output power of the battery unit is greater than a second threshold that is greater than the first threshold. In this disclosure, "α or more" is synonymous with "greater than α".

[0010] The control device of the power supply system controls the output power of the battery unit based on the power command. During grid-connected operation, power is supplied to an electrical load (e.g., a household load) from the power grid, so the power command does not fluctuate significantly depending on the power consumption of the electrical load. Therefore, during grid-connected operation, the deviation between the power command and the output power of the battery unit falls within the range of the control error of the output power in the power supply system. Therefore, during grid-connected operation, if the deviation between the power command and the output power exceeds the range of the control error and becomes larger than a first threshold, the control device determines that the power supply system has failed.

[0011] During independent operation, the output power of the battery unit is supplied to the electrical load, so the power command and the output power fluctuate greatly depending on the power consumption of the electrical load. For this reason, even if the power supply system is normal, the deviation between the power command and the output power of the battery unit may become larger than the first threshold. During independent operation, the control device does not determine that the power supply system has failed even if the deviation between the power command and the output power exceeds the first threshold, but determines that the power supply system has failed when the deviation between the power command and the output power becomes larger than the second threshold. Therefore, with this configuration, it is possible to appropriately detect a failure in the power supply system during grid-connected operation and independent operation of the power supply system.

[0012] (2) Preferably, the first threshold is set based on a control error of the output power, and the second threshold is set based on power consumption of the electric load.

[0013] During grid-connected operation, when the power supply system is normal, the deviation between the power command and the output power of the battery unit (power supply system) falls within the range of the control error of the output power caused by the detection errors (individual differences) of various sensors and the characteristic differences of each element such as a switching element. Therefore, by setting the first threshold based on the control error of the output power, for example, to 1.5 to 2 times the control error, it is possible to quickly and appropriately determine a failure of the power supply system during grid-connected operation.

[0014] During independent operation, the output power of the battery unit (power supply system) is supplied to the electrical load, so the power command and the output power fluctuate greatly depending on the power consumption of the electrical load. The second threshold is set based on the power consumption of the electrical load, for example, to the maximum power consumption value of the electrical load that consumes the most power among the electrical loads to which power is supplied from the battery unit. This makes it possible to detect abnormal power output during independent operation and appropriately determine a failure in the power supply system.

[0015] (3) Preferably, in the above (1) or (2), the control device performs feedback control so that the output power of the battery unit becomes the power command, and limits the feedback amount calculated based on the deviation between the power command and the output power by upper and lower limit values, and when the power supply system is operating in a grid-connected manner, the upper and lower limit values ​​may be smaller than when the power supply system is operating in an independent manner.

[0016] According to this configuration, the output power of the battery unit is controlled by feedback control using a feedback amount calculated based on the deviation between the power command and the output power, and the feedback amount calculated based on the deviation between the power command and the output power is limited by an upper limit value and a lower limit value.

[0017] When the power supply system is operating in a grid-connected manner, the upper limit value and the lower limit value are made smaller than when the power supply system is operating in an independent manner. In the present disclosure, making the lower limit value smaller means making the negative value smaller when the lower limit value is negative. Note that when the upper limit value is negative, making the upper limit value smaller means making the negative value larger. During grid-connected operation, the feedback amount is limited by small upper and lower limit values, so that large fluctuations in output power due to disturbances, etc. are suppressed. During independent operation, the upper and lower limit values ​​that limit the feedback amount are large, so that the responsiveness of the output power to load fluctuations is improved.

[0018] (4) Preferably, in any of the above (1) to (3), the battery units are provided in plurality and are connected in parallel to each other.

[0019] According to this configuration, since a power supply system is configured by connecting a plurality of battery units in parallel, it is possible to increase the input / output power of the power supply system.

[0020] (5) In the above (1) to (4), the DC-DC converter may be a converted three-phase inverter, and a power storage device may be connected to each phase arm of the three-phase inverter.

[0021] In recent years, electric vehicles such as hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs) have become increasingly popular. It is desirable to recycle or reuse batteries (power storage devices) and PCUs (power control units) that are collected when these vehicles are replaced or dismantled. With this configuration, the reuse of PCUs can be promoted by converting the three-phase inverter of the collected PCU into a DC-DC converter of the power supply system. If the collected batteries (power storage devices) are also used as power storage devices of the power supply system, the reuse of batteries can also be promoted. Effect of the Invention

[0022] According to the present disclosure, it is possible to appropriately detect a fault in a power supply system during grid-connected operation and during independent operation of the power supply system. [Brief description of the drawings]

[0023] [Figure 1] 1 is a diagram showing an overall configuration of a power supply system according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a diagram illustrating an example of an electric vehicle. [Diagram 3] FIG. 2 is a diagram illustrating an example of the configuration of a control device of a power supply system. [Figure 4]1 is an example of a block diagram for controlling output power of a power supply system. [Diagram 5] 4 is a flowchart showing an example of a failure determination routine process executed by a control ECU. [Figure 6] FIG. 13 is a diagram illustrating a control device of a power supply system according to a first modified example. [Figure 7] FIG. 11 is a diagram showing an overall configuration of a power supply system in a second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0025] FIG. 1 is a diagram showing the overall configuration of a power supply system P according to the present embodiment. The power supply system P includes a battery unit Bu including a battery pack 1 and a DCDC converter 2, and a control device 3. The battery pack 1 corresponds to an example of an "electricity storage device" in the present disclosure. In the present embodiment, the battery unit Bu (battery pack 1 and DCDC converter 2) is a battery pack and a PCU (Power Control Unit) mounted on an electric vehicle that have been converted into the power supply system P. An example of the configuration of an electric vehicle equipped with a battery pack and a PCU will be described.

[0026] Fig. 2 is a diagram illustrating an example of an electric vehicle. In Fig. 2, the electric vehicle V is a hybrid vehicle that uses both a rotating electric machine and an engine to drive the vehicle. The electric vehicle V includes a battery pack 1, a PCU 20, an engine 30, motor generators MG1 and MG2 as rotating electric machines, a power split mechanism 40, and drive wheels 50.

[0027] The battery pack 1 includes a battery 10 and a system main relay (SMR) 11. The battery 10 is an assembled battery in which single cells (battery cells) made of secondary batteries such as nickel-metal hydride batteries and lithium-ion batteries are electrically connected in series. The output terminals (positive terminal, negative terminal) of the battery pack 1 are connected to a battery connection terminal 25 of the PCU 20. When the SMR 11 is closed, the battery 10 and the PCU 20 are connected, and when the SMR 11 is opened, the connection between the battery 10 and the PCU 20 is cut off. The battery pack 1 is provided with a monitoring unit 15, which detects the voltage VB of the battery 10, the input / output current IB of the battery 10, the temperature of the battery 10, etc.

[0028] The PCU 20 includes a boost converter 21, an inverter 22, and an inverter 23. The boost converter 21 boosts the battery voltage VB input from the battery pack 1 and outputs it to the inverter 22 and the inverter 23. The inverter 22 converts the DC power boosted by the boost converter 21 into three-phase AC power, and drives the motor generator MG1 to start the engine 30, for example. The inverter 22 also converts AC power generated by the motor generator MG1 using the power transmitted from the engine 30 into DC power and returns it to the boost converter 21. At this time, the boost converter 21 is controlled to operate as a step-down circuit. The inverter 23 converts the DC power output from the boost converter 21 into three-phase AC power and outputs it to the motor generator MG2.

[0029] The power split mechanism 40 is a mechanism that is connected to the engine 30 and the motor generators MG1, MG2 and distributes power therebetween. A planetary gear mechanism can be used as the power split mechanism 40, and for example, the engine 30 is connected to a planetary carrier, the motor generator MG1 is connected to a sun gear, and the motor generator MG2 is connected to a ring gear. The rotor of the motor generator MG2 (and the rotating shaft of the ring gear of the power split mechanism 40) is connected to the drive wheels 50 via a reduction gear, a differential gear, and a drive shaft (not shown).

[0030] The boost converter 21 of the PCU 20 includes a reactor and switching elements Q1a, Q1b, Q2a, and Q2b. The switching elements Q1a to Q2b are, for example, IGBT (Insulated Gate Bipolar Transistor) elements, and include a diode connected in anti-parallel to each IGBT element. The switching elements Q1a and Q1b are provided in parallel, and the switching elements Q2a and Q2b are provided in parallel, and the switching elements Q1a and Q1b are driven by the same drive signal, and the switching elements Q2a and Q2b are driven by the same drive signal. The collectors of the switching elements Q1a and Q1b are connected to the positive electrode line Pl, and the emitters of the switching elements Q2a and Q2b are connected to the negative electrode line Nl. The reactor is connected to the emitters of the switching elements Q1a and Q1b and the collectors of the switching elements Q2a and Q2b.

[0031] Inverter 22 is a three-phase inverter and includes a U-phase arm made up of switching elements Q3 and Q4 connected in series between positive electrode line Pl and negative electrode line Nl, a V-phase arm made up of switching elements Q5 and Q6 connected in series between positive electrode line Pl and negative electrode line Nl, and a W-phase arm made up of switching elements Q7 and Q8 connected in series between positive electrode line Pl and negative electrode line Nl. Similar to switching element Q1a, switching elements Q3 to Q8 are switching elements including diodes connected in anti-parallel to IGBT elements.

[0032] The midpoint of the arm of each phase is connected to the coil of each phase of motor generator MG1 via MG1 connection terminal 26. Motor generator MG1 is a three-phase permanent magnet synchronous motor, and may be, for example, an IPM (Interior Permanent Magnet) synchronous motor.

[0033] The inverter 23 is a three-phase inverter similar to the inverter 22, except that the switching elements of the arms of each phase are arranged in parallel. Switching elements Q9a and Q9b correspond to switching element Q3, and switching elements Q10a and Q10b correspond to switching element Q4, forming a U-phase arm. Switching elements Q11a and Q11b correspond to switching element Q5, and switching elements Q12a and Q12b correspond to switching element Q6, forming a V-phase arm. Switching elements Q13a and Q13b correspond to switching element Q7, and switching elements Q14a and Q14b correspond to switching element Q8, forming a W-phase arm.

[0034] The midpoint of the arm of each phase is connected to the coil of each phase of motor generator MG2 via MG2 connection terminal 27. Motor generator MG2 may also be an IPM synchronous motor.

[0035] The electric vehicle V includes, as control devices, a hybrid ECU (Electronic Control Unit) (HV-ECU) 200, a motor generator ECU (MG-ECU) 210, a battery ECU (BT-ECU) 220, and an engine ECU (EG-ECU) 230. Each ECU includes a CPU (Central Processing Unit), a memory, and a buffer (none of which are shown).

[0036] The BT-ECU 220 calculates a state of charge (SOC) of the battery 10 based on the voltage VB and the input / output power IB of the battery 10 detected by the monitoring unit 15, and transmits the SOC to the HV-ECU 200.

[0037] For travel control of electric vehicle V, HV-ECU 200 calculates required drive torque Tr based on, for example, accelerator opening, vehicle speed, etc., and multiplies required drive torque Tr by the rotation speed of drive wheels 50 to obtain required power Pd. Required power Pe required of engine 30 is set by subtracting charge / discharge power Pb (a positive value when discharging from battery 10) based on the SOC of battery 10 from required power Pd. Then, target engine rotation speed Ne, target engine torque Te, command torque Tm1 of motor generator MG1, and command torque Tm2 of motor generator MG2 are set so that required power Pe is output from engine 30 and required drive torque Tr is output to drive wheels 50.

[0038] The MG-ECU 210 performs PWM (Pulse Width Modulation) control on each switching element of the inverter 22 so that the command torque Tm1 is output from the motor generator MG1. The MG-ECU 210 also performs PWM (Pulse Width Modulation) control on each switching element of the inverter 23 so that the command torque Tm2 is output from the motor generator MG2.

[0039] The EG-ECU 230 controls the engine 30 so that the engine 30 is operated at a target engine speed Ne and a target engine torque Te.

[0040] Referring to FIG. 1, in the power supply system P, the battery pack 1 and the DCDC converter 2 are repurposed battery packs 1 and PCU 20 mounted on an electric vehicle V. The positive terminals of the output terminals of the three battery packs 1 (1-1-1, 1-1-2, 1-1-3) are connected to an MG2 connection terminal 27 to which the midpoints of the phase arms (U-phase arm, V-phase arm, W-phase arm) of an inverter 23 (three-phase inverter) of the PCU 20 are connected, via a coil (inductor) 5. The power line between the positive terminal of the battery pack 1 and the coil 5 is connected to the negative terminal of the output terminal of the battery pack 1, via a capacitor 6. The negative terminal of the battery pack 1 is connected to the negative line Nl of the PCU 20 by a power line Nl1. Note that the monitoring unit 15 is not shown in FIG. 1. The battery pack 1 corresponds to an example of the "electricity storage device" of the present disclosure.

[0041] In the DC-DC converter 2, the switching elements Q4, Q5, and Q7 of the inverter 22 of the PCU 20 are short-circuited. In the MG1 connection terminal 26 to which the midpoints of the phase arms of the inverter 22 are connected, a terminal to which the U-phase arm is connected is connected to the negative terminal of the battery connection terminal 25 by a power line Nl2. The negative terminal of the battery connection terminal 25 is connected to the negative terminal 28b of the battery unit Bu. In the MG1 connection terminal 26, a terminal to which the V-phase arm and the W-phase arm are connected is connected to the positive terminal 28a of the battery unit Bu by a power line Pl1.

[0042] In this way, by connecting each phase arm of the inverter 23 of the PCU 20 to the battery pack 1, shorting some of the switching elements of the inverter 22, and connecting the MG1 connection terminal 26 to the positive terminal 28a and negative terminal 28b of the battery unit Bu, the PCU 20 is converted into a DCDC converter 2 that boosts the voltage of the battery pack 1 (battery 10) connected to each phase arm of the inverter 23.

[0043] The power supply system P includes a plurality of battery units Bu including a DCDC converter 2 that is a repurposed PCU 20, and each battery unit Bu is connected in parallel to the PCS 100. In this embodiment, the battery unit Bu includes n battery units Bu (n is a positive integer), and may include, for example, 20 battery units Bu. In FIG. 1, n represents the n-th battery unit Bu, the DCDC converter 2 included in the battery unit Bu, and the battery pack 1. Three battery packs 1 are connected in parallel to the battery unit Bu, and in a power supply system P including 20 battery units Bu, 60 battery packs 1 are connected in parallel.

[0044] The positive terminal 28a of each battery unit Bu is connected via a positive line PL to an input / output terminal of the PCS 100. The negative terminal 28b of each battery unit Bu is connected via a negative line NL to an input / output terminal of the PCS 100.

[0045] The PCS100 is connected to a power system P, a power grid PG, a photovoltaic power generation device 650, and a load (electrical load) 300. The power grid PG is, for example, a commercial power source consisting of a power plant and a power transmission network. The PCS100 includes a power conversion device, and supplies power generated by the photovoltaic power generation device 650 to the load 300 and performs reverse power flow. When an upward DR is requested, the PCS100 converts AC power of the power grid PG to DC power and charges the power system P (battery unit Bu). When a downward DR is requested, the PCS100 converts the discharge power (output power) of the power system P (battery unit Bu) to AC power and performs reverse power flow. The load 300 may be a household load (home appliance) or an electrical load of an office or factory.

[0046] The power supply system P performs interconnected operation in which it receives and transmits power to and from the power grid PG, and independent operation in which it is disconnected (cut off) from the power grid PG. During interconnected operation, power is mainly supplied to the load 300 from the power grid PG. During interconnected operation, the power supply system P receives and transmits power to and from the power grid PG in response to a request for lowering DR or raising DR. During independent operation of the power supply system P, the output power (discharge power) of the power supply system P (battery unit Bu) is supplied to the load 300.

[0047] 3 is a diagram showing an example of the configuration of the control device 3 of the power supply system P. The control device 3 includes a control ECU 400 and a drive ECU 450. Each ECU includes a CPU, a memory, and a buffer (none of which are shown). The PCS-ECU 500 is a control device that controls the PCS 100, and outputs to the control ECU 400 a required value of power output from the power supply system P (battery unit Bu) or a required power RP that is a required value of power input to the power supply system P, and a voltage command VH that is a command value of the voltage output from the power supply system P.

[0048] The control ECU 400 generates a power command TP based on the required power RP and the voltage command VH when outputting electric power from the power supply system P (when discharging from the battery unit Bu). The drive ECU 450 PMW controls the battery unit Bu (DCDC converter 2) so that the output power of the power supply system P (battery unit Bu) becomes the power command TP.

[0049] FIG. 4 is an example of a block diagram for controlling the output power of the power supply system P. This block diagram may be configured in the control ECU 400. In FIG. 4, a voltage command VH and a required power RP are input from the PCS-ECU 500. The voltage command VH is a required value (target voltage) of the output voltage of the power supply system P, and may be, for example, 100V or 200V. The required power RP is a power value requested by the PCS-ECU 500 as power for performing reverse power flow when performing grid-connected operation in response to a request for down-driving. During the independent operation of the power supply system P, the power supply system P is disconnected from the power grid PG, and therefore the required power RP is 0 (zero). The required power RP may be an effective value.

[0050] 4, output voltage VP is the output voltage of power supply system P, and output power OP is the output power of power supply system P. The output power OP may be calculated from the output voltage VP and output current IP of power supply system P. A voltage command VH and the output voltage VP are input to a subtraction point 301, a voltage correction CP is generated so that the output voltage VP becomes the voltage command VH, and is input to a summing point 302. The voltage correction CP is a negative value when the output voltage VP is larger than the voltage command VH, and is a positive value when the output voltage VP is smaller than the voltage command VH.

[0051] The required power RP and the feedback amount FP are input to a summing point 302, and the value obtained by adding the required power RP, the feedback amount FP, and the voltage correction CP is output as a power command TP. The output power OP and the power command TP are input to a subtraction point 303, and the feedback amount FP generated by proportional-integral (PI) control based on the deviation ΔP between the power command TP and the output power OP is input to the summing point 302. The feedback amount FP is guarded by upper and lower limit values ​​(upper limit value and lower limit value) before being input to the summing point 302.

[0052] During the interconnected operation of the power supply system P, power is supplied to the load 300 from the power system PG. During the interconnected operation, the required power RP is a power value commanded (requested) by the PCS-ECU 500 as the power of the reverse flow, and does not fluctuate due to the load fluctuation (fluctuation of power consumption) of the load 300. During the interconnected operation, if there is no large fluctuation in the output voltage VP of the power supply system P, the difference between the output power OP and the required power RP falls within the range of the control error of the power supply system P. Therefore, during the interconnected operation, the deviation ΔP between the power command TP and the output power OP also falls within the range of the control error of the output power of the power supply system P. If some kind of failure / abnormality occurs in the power supply system P, the deviation ΔP becomes large beyond the range of the control error. A first threshold value Th1 (for example, a threshold value equivalent to 1.5 to 2 times the control error) considering the control error is set, and the deviation ΔP and the first threshold value Th1 are compared, and if the deviation ΔP becomes larger than the first threshold value Th1, it can be determined that a failure occurs in the power supply system P.

[0053] During the independent operation of the power supply system P, power is supplied to the load 300 from the power supply system P (battery unit Bu). Therefore, the output power OP of the power supply system P is equivalent to the power consumption of the load 300. Note that during the independent operation, the required power RP commanded from the PCS-ECU 500 is 0. When the power consumption of the load 300 fluctuates and increases, the output voltage VP of the power supply system P decreases, and when the power consumption decreases, the output voltage VP increases. When the output voltage VP fluctuates, in order to maintain the output voltage VP at the voltage command VH, the voltage correction CP fluctuates and the power command TP fluctuates. The fluctuation range of the power command TP corresponds to the fluctuation range of the power consumption of the load 300 and exceeds the range of the control error of the output power of the power supply system P. Therefore, during the independent operation, even if no failure / abnormality occurs in the power supply system P, the deviation ΔP between the power command TP and the output power OP becomes larger than the first threshold value Th1. Therefore, even during the independent operation, if the deviation ΔP is compared with the first threshold value Th1 to determine a failure of the power supply system P, an erroneous determination (erroneous detection) may be made. In this embodiment, during the independent operation of the power supply system P, a failure in the power supply system P is determined (detected) by comparing the deviation ΔP with a second threshold value Th2 that is larger than the first threshold value Th1. This makes it possible to appropriately determine a failure in the power supply system P even during the independent operation.

[0054] 5 is a flowchart showing an example of the processing of a failure determination routine executed by the control ECU 400. This flowchart is repeatedly processed at predetermined intervals while the power supply system P is in operation. First, in step (hereinafter, step is abbreviated as "S") 10, it is determined whether or not the power supply system P is in an independent operation. In this embodiment, information (signal) is transmitted from the PCS-ECU 500 indicating whether the power supply system P is in parallel with the power grid PG and in an interconnected operation, or whether the power supply system P is disconnected from the power grid PG and in an independent operation. If the information from the PCS-ECU 500 indicates the interconnected operation, a negative determination is made and the process proceeds to S11. If the information from the PCS-ECU 500 indicates the independent operation, a positive determination is made and the process proceeds to S12.

[0055] In S11, the threshold Th is set to a first threshold Th1. The first threshold Th1 may be a value equivalent to 1.5 to 5 times the control error of the output power of the power supply system P during grid-connected operation. For example, in this embodiment, the first threshold Th1 is 5 kW. Also, in S11, the upper limit Ul of the feedback amount FP is set to A, and the lower limit Ll is set to -A. Note that the value of ±A may be set in consideration of the control error of the output power of the power supply system P, similar to the first threshold Th1, and may be a value equivalent to 1.5 to 3 times the control error. For example, in this embodiment, the value of ±A is set to 5 kW.

[0056] In S12, the threshold Th is set to a second threshold Th2. The second threshold Th2 is a value larger than the first threshold Th1, and may be set based on the maximum power consumption of the load that consumes the most power in the load 300. For example, in this embodiment, the second threshold Th2 is 30 kW. Also, in S12, the upper limit Ul of the feedback amount FP is set to B, and the lower limit Ll is set to -B. The value of ±B is larger than the value of ±A, and is set based on the maximum power consumption of the load that consumes the most power, similar to the second threshold Th2. For example, in this embodiment, the value of ±B may be set to 30 kW.

[0057] In the next S13, it is determined whether the deviation ΔP between the power command TP and the output power OP is greater than a threshold value Th. Since the deviation ΔP has a positive or negative sign, the absolute value |ΔP| of the deviation ΔP is compared with the threshold value Th, and if |ΔP| is greater than the threshold value Th (|ΔP|>Th), it is determined that the deviation ΔP is greater than the threshold value Th (positive determination) and the process proceeds to S14. If |ΔP| is equal to or less than the threshold value Th (|ΔP|≦Th), it is determined that the deviation ΔP is equal to or less than the threshold value Th (negative determination), and the current routine is terminated.

[0058] In S14, it is determined that the power supply system P has failed, and the current routine is terminated. If it is determined in S14 that the power supply system P has failed, failure processing such as stopping the operation of the power supply system P is performed.

[0059] The upper limit value Ul and the lower limit value Ll calculated in S11 and S12 are used for guard processing of the feedback amount FP input to the summing point 302 in Fig. 4. When the feedback amount FP generated by proportional-integral (PI) control based on the deviation ΔP exceeds the upper limit value Ul, the feedback amount FP is set to the upper limit value Ul, and when the feedback amount FP falls below the lower limit value Ll, the feedback amount FP is set to the lower limit value Ll and input to the summing point 302.

[0060] According to this embodiment, the control device 3 (control ECU 400) of the power supply system P determines that the power supply system P has a fault when the deviation ΔP between the power command TP and the output power OP exceeds the range of the control error and becomes larger than the first threshold value Th1 during interconnected operation in which power is exchanged with the power grid PG. Furthermore, during independent operation in which the power supply system P is disconnected from the power grid PG, even if the deviation ΔP exceeds the first threshold value Th1, the control device 3 determines that the power supply system P has a fault when the deviation ΔP becomes larger than the second threshold value Th2 corresponding to the maximum power consumption of the load with the largest power consumption among the loads 300. Therefore, the power supply system P can be appropriately detected as having a fault during interconnected operation and independent operation of the power supply system P.

[0061] According to this embodiment, the control device (control ECU 400) of the power supply system P controls the output power of the power supply system P (battery unit Bu) by feedback control using a feedback amount FP calculated based on the deviation ΔP between the power command TP and the output power OP. The feedback amount FP is limited by an upper limit value Ul and a lower limit value Ll, but in the case of grid-connected operation, the upper limit value Ul and the lower limit value Ll are set smaller than in the case of independent operation. In the grid-connected operation, the feedback amount FP is limited by a small upper limit value (A) and lower limit value (-A), so that large fluctuations in the output power due to disturbances and the like are suppressed. In the independent operation, the upper limit value (B) and lower limit value (-B) are large, so that the responsiveness of the output power to load fluctuations is improved.

[0062] According to this embodiment, the power supply system P is composed of a plurality of battery units Bu connected in parallel, which makes it possible to increase the input / output power of the power supply system P.

[0063] According to this embodiment, the DC-DC converter 2 of the battery unit Bu is a repurposed inverter 23 (three-phase inverter) included in the PCU 20 of the electric vehicle V. In addition, the battery pack 1 of the electric vehicle V is used as the battery pack 1 of the battery unit Bu. This can promote the reuse of the battery and PCU that are collected when the electric vehicle V is replaced or dismantled.

[0064] In the above embodiment, in S13 (FIG. 5), it is determined whether or not the deviation ΔP between the power command TP and the output power OP is greater than the threshold value Th ("|ΔP|>Th?"). However, the configuration for comparing the deviation ΔP with the threshold value Th is not limited to this. For example, a moving average MAΔP of the deviation ΔP may be compared with the threshold value Th. The moving average MAΔP may be, for example, a simple moving average of the deviation ΔP over the past N times (for example, the past 10 times). This makes it possible to reduce the possibility that the deviation ΔP will momentarily exceed the threshold value Th due to a disturbance, a momentary drop in the power system PG, or the like. It is also desirable to calculate the deviation ΔP taking into account a response delay in power control and dead time.

[0065] In the above embodiment, in S13 (FIG. 5), it is determined whether or not the deviation ΔP between the power command TP and the output power OP is greater than a threshold value Th ("|ΔP|>Th?"). However, instead of or in addition to comparing the deviation ΔP with the threshold value Th, it may be determined that the power supply system P has failed when the feedback amount FP is limited by the upper limit value Ul or the lower limit value Ll for a predetermined period of time (e.g., 10 seconds). The feedback amount FP is a value generated by proportional-integral (PI) control based on the deviation ΔP. This configuration can also achieve substantially the same effect as the configuration in which the deviation ΔP is compared with a threshold value and it is determined that the power supply system P has failed if the deviation ΔP is greater than the threshold value.

[0066] (Variation 1) Fig. 6 is a diagram illustrating a control device 3a of a power supply system P according to the first modification. The control device 3a of the first modification utilizes an HV-ECU 200, an MG-ECU 210, and a BT-ECU 220 mounted on an electric vehicle V. In Fig. 6, an H / HV-ECU 220a, and HV-ECU(1) 220a-1 to HV-ECU(3) 220a-3 utilize the HV-ECU 200 mounted on the electric vehicle V. The MG-ECU 210a utilizes the MG-ECU 210. The BT-ECU 220a1 to BT-ECU 220a-3 utilize the BT-ECU 220.

[0067] 6, an interface ECU (I / F-ECU) 600 connects the PCS-ECU 500 and the control device 3a (H / HV-ECU 200a) and performs matching between the communication protocol of the PCS-ECU 500 and the communication protocol of the control device 3a. The H / HV-ECU 200a calculates a power command TP from the required power RP, the voltage command VH, and the like received from the PCS-ECU 500 via the I / F-ECU 600. The H / HV-ECU 200a also executes the failure determination routine shown in FIG.

[0068] The sub-control device 3a1, which is composed of the MG-ECU 210a, the HV-ECU(1) 220a-1 to the HV-ECU(3) 220a-3, and the BT-ECU 220a1 to the BT-ECU 220a-3, is a control device that controls the battery unit Bu. In Fig. 6, the sub-control device 3a1-1 is a control device that controls the battery unit Bu-1 in Fig. 1, and a sub-control device 3a1 is provided for each battery unit Bu. In other words, the control device 3a has n sub-control devices 3a1, namely, the sub-control device 3a1-1 to the sub-control device 3a1-n.

[0069] In Fig. 6, the BT-ECU(1) 220a-1 monitors the voltage VB, input / output current IB, temperature, etc. of the battery 10 of the battery pack 1-1-1 of the battery unit Bu-1, and calculates the SOC. The HV-ECU(1) 200a-1 receives a power command TP from the H / HV-ECU 200a, determines the input / output power of the battery pack 1-1-1, and controls the opening and closing of the SMR 11 of the battery pack 1-1-1. The HV-ECU 200a-1 also detects the degree of deterioration of the battery 10 of the battery pack 1-1-1. The BT-ECU(2) 220a-2 and the HV-ECU(2) 200a-2 perform the same processing as the BT-ECU(1) 220a-1 and the HV-ECU(1) 200a-1 for the battery pack 1-1-2. The BT-ECU(3) 220a-3 and the HV-ECU(3) 200a-3 perform the same processing as the BT-ECU(1) 220a-1 and the HV-ECU(1) 200a-1 for the battery pack 1-1-3. The MG-ECU 210a controls the DC-DC converter 2-1 (drives the switching elements of the phase arms of the inverter 23) so that the input / output power of each of the battery packs 1-1-1 to 1-1-3 is determined by the HV-ECU(1) 220a-1 to the HV-ECU(3) 220a-3.

[0070] Sub-control device 3a1-2 to sub-control device 3a1-n also perform the same process as sub-control device 3a1-1 for battery units Bu-2 to Bu-n. According to this modification 1, it is possible to promote the utilization of the hardware of HV-ECU 200, MG-ECU 210, and BT-ECU 220 mounted on electric vehicle V as control devices of power supply system P.

[0071] (Variation 2) 7 is a diagram showing the overall configuration of the power supply system Pa in the modified example 2. In the above embodiment, an example has been described in which the PCU 20 including the boost converter 21, the inverter 22, and the inverter 23 is diverted to the DCDC converter 2 of the power supply system P. In the above embodiment, in particular, in order to enable the passage of large power, the inverter 23 having switching elements provided in parallel is used as the switching element of the DCDC converter 2. However, among the PCUs mounted on electric vehicles, there are those provided with one inverter, and those without a boost converter.

[0072] The power supply system Pa in the second modification is a PCU having only one inverter, or a circuit in which the inverter portion is extracted from the PCU, and used as the DC-DC converter 2A of the power supply system Pa.

[0073] In FIG. 7, the DC-DC converter 2A is a repurposed inverter (three-phase inverter) of a PCU mounted on an electric vehicle. In FIG. 7, SR1 and SR2 of the battery pack 1 are system main relays (SMR). As in the above embodiment, the positive terminals of the output terminals of the three battery packs 1 (1-1-1, 1-1-2, 1-1-3) are connected to the midpoints of the phase arms (U-phase arm 2A1, V-phase arm 2A2, W-phase arm 2A3) of the three-phase inverter of the PCU via coils (inductors) 5. The power line between the positive terminal of the battery pack 1 and the coil 5 is connected to the negative terminal of the output terminal of the battery pack 1 via a capacitor 6. The upper arms of the phase arms (U-phase arm 2A1, V-phase arm 2A2, W-phase arm 2A3) of the three-phase inverter are connected to a positive line PL and are connected to the input / output terminals of the PCS 100. The lower arms of each phase arm (U-phase arm 2A1, V-phase arm 2A2, W-phase arm 2A3) of the three-phase inverter are connected to a negative line NL and connected to an input / output terminal of the PCS 100. The negative terminal of the battery pack 1 is connected to the negative line NL.

[0074] Thus, in the power supply system Pa in the second modification, each phase arm of the three-phase inverter of the PCU is connected to the battery pack 1, and the three-phase inverter is converted into a DCDC converter 2A. Similarly to the above embodiment, the power supply system Pa includes a DCDC converter 2A converted from a three-phase inverter, and a plurality of battery units Bua including three battery packs 1, and the battery units Bua are connected in parallel. Similarly to the above embodiment, in the second modification, the control device 3b executes the failure determination routine shown in FIG. 5, and the same effects as those of the above embodiment are achieved.

[0075] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0076] 1 battery pack, 2,2A DCDC converter, 3,3a,3b control device, 5 coil (inductor), 6 capacitor, 10 battery, 11 SMR, 15 monitoring unit, 20 PCU, 21 boost converter, 22,23 inverter, 25 battery connection terminal, 26 MG1 connection terminal, 27 MG2 connection terminal, 28a positive terminal, 28b negative terminal, 30 engine, 40 power split mechanism, 50 drive wheel, 100 PCS, 200 HV-ECU, 210 MEG-ECU, 220 BT-ECU 230 EG-ECU, 300 load, 400 control ECU, 450 drive ECU, 500 PCS-ECU, 600 I / F-ECU, 650 solar power generation device, Bu,Bua battery unit, MG1 motor generator, MG2 motor generator, P,Pa power supply system, PG Power system, V electric vehicle.

Claims

1. A power supply system capable of switching between a grid-connected operation in which power is exchanged between the power supply system and an independent operation in which the power supply system is disconnected from the power supply system, a battery unit including a power storage device and a DC-DC converter; a control device that controls the output power of the battery unit based on a power command, In the independent operation, the power of the battery unit is supplied to an electrical load, In the grid-connected operation, power is supplied from the power grid to the electrical load, The control device includes: When the power supply system is in the grid-connected operation, if a deviation between the power command and the output power of the battery unit is equal to or greater than a first threshold value, it is determined that the power supply system has a failure; When the power supply system is operating independently, if the deviation is equal to or greater than a second threshold value that is greater than the first threshold value, the power supply system is determined to have a failure.

2. The first threshold is set based on a control error of the output power; The power supply system according to claim 1 , wherein the second threshold value is set based on power consumption of the electric load.

3. The control device includes: executing a feedback control so that the output power of the battery unit becomes the power command, and limiting a feedback amount calculated based on the deviation by an upper limit value and a lower limit value; 3. The power supply system according to claim 1, wherein the upper limit value and the lower limit value are set smaller when the power supply system is operating in the grid-connected mode than when the power supply system is operating in the independent mode.

4. 3. The power supply system according to claim 1, wherein the battery units are a plurality of battery units connected in parallel with each other.

5. The DC-DC converter is a conversion of a three-phase inverter, The power supply system according to claim 4 , wherein the power storage device is connected to each phase arm of the three-phase inverter.

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