Control device for multi-phase converter, multi-phase converter system and power supply system

Abstract

Control device (4) for a multi-phase converter (20) having converter circuits (20a to 20c) of m (where m is an integer of at least 3) phases, each of which comprises a switching element (36a to 36c) and which are connected in parallel to one another, the control device (4) comprising: a controlled-phase number control unit configured to increase the number of controlled phases of the converter circuits (20a to 20c) by increasing the number of switching elements (36a to 36c) on which on / off control is performed as a current value input to the multi-phase converter (20) increases, and to control the multi-phase converter (20) in n-phase drive where the number of controlled phases is n (where n is an integer less than m and at least 2 and is an integer that is not a divisor of m), or in m-phase drive where the number of controlled phases is m; a storage unit configured to store first and second patterns which are phase patterns in which on-times of the switching elements of m phases are defined; a selection unit configured to select the first or second pattern while the multiphase converter (20) has been stopped; an on / off control unit configured to perform on / off control on the switching elements of the plurality of driven phases based on the phases set in the selected first or second pattern under a condition that a period and a duty ratio are substantially equal; and a prediction unit configured to predict a correlation value that correlates with a time ratio that is, in a predetermined time, a ratio of a time for which the execution of a control in the m-phase drive is predicted to a time for which the execution of a control in the n-phase drive is predicted, wherein an absolute value of a difference between a maximum value of a phase difference between two switching elements set to be sequentially turned on in the n-phase drive based on the second pattern and 360° / n is smaller than an absolute value of a difference between a maximum value of a phase difference between two switching elements set to be sequentially turned on in the n-phase drive based on the first pattern and 360° / n, wherein the selection unit is configured to select the first pattern if the predicted correlation value indicates that the time ratio is at least as large as a first threshold, and to select the second pattern if the predicted correlation value indicates that the time ratio is smaller than a second threshold which is at most as large as the first threshold, wherein the on / off control unit is arranged to stop the on / off control on the switching elements of (mn) phases in the n-phase drive based on the second pattern, wherein the switching elements are classified into a plurality of combinations such that each of the combinations is composed of three switching elements which are determined to be sequentially turned on in the m-phase drive based on the second pattern, wherein, when (mn)=1, the switching element of the (mn) phase at which the on / off control was stopped in the n-phase drive based on the second pattern is the switching element that is switched on between the switching element that is switched on first and the switching element that is switched on last, out of the three switching elements in a combination having a phase difference that is the smallest among the plurality of combinations, the phase difference being a phase difference between the switching element that is switched on first and the switching element that is switched on last, and wherein, when (mn)≥2, the switching elements of (mn) phases at which the on / off control was stopped in the n-phase drive based on the second pattern are switching elements other than a combination of two switching elements set to be sequentially turned on in the m-phase drive based on the second pattern, and each turned on between the switching element that is turned on first and the switching element that is turned on last among the three switching elements in a corresponding one of (mn) combinations among the plurality of combinations, the (mn) combinations being selected in ascending order of the phase difference between the switching element that is turned on first and the switching element that is turned on last.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to a control device for a multiphase converter, a multiphase converter system and a power supply system. 2. Description of the state of the art

[0002] A multiphase converter comprising converter circuits in multiple phases is known. Japanese Patent Application Laid-Open No. 2017-60303 A discloses that, when the number of controlled phases of the converter circuits changes, it is possible to attenuate a ripple current in the multiphase converter and reduce loss by controlling the phases so that phase differences in the switching of the converter circuits are substantially constant. Japanese Patent Application Laid-Open No. 2014-30285 A sets the switching phases of converter circuits in advance, and the switching of some converter circuits is stopped according to a current command value. Finally, DE 10 2013 001 564 A1 discloses an electrical circuit arrangement for controlling an electric drive motor to which electrical energy is supplied via an inverter and a plurality of upstream parallel voltage converters.The electric drive motor is subjected to time-varying loads, and a controller detects or calculates the expected load. Depending on the calculated or detected load, the appropriate number of parallel voltage converters is predicted and switched. SUMMARY OF THE INVENTION

[0003] In JP 2017-60303 A, controlling the phases of switching elements is complicated because it is necessary to change the phases of switching elements to match the number of controlled phases while changing the number of controlled phases of the converter circuits. In JP 2014-30285 A, since the switching of some converter circuits has been stopped, a ripple current in the multiphase converter increases, and loss may increase.

[0004] The invention provides a control device for a multi-phase converter, a multi-phase converter system, and a power supply system that can dampen an increase in losses due to a ripple current with simple control.

[0005] According to one aspect of the invention, a control device for a multi-phase converter is provided, which includes converter circuits having m (where m is an integer of at least 3) phases, each of which includes a switching element and which are connected in parallel with each other. The control device comprises: a number of driven phases control unit configured to increase the number of driven phases of the converter circuits by increasing the number of switching elements to which on / off control is performed as a current value input to the multi-phase converter increases, and to control the multi-phase converter in an n-phase drive in which the number of driven phases is n (where n is an integer less than m and at least 2 and is an integer that is not a divisor of m), or in an m-phase drive in which the number of driven phases is m; a storage unit,which is configured to store first and second patterns, which are phase patterns in which on-times of the switching elements of m phases are defined; a selection unit configured to select the first or second pattern while the multi-phase converter is stopped; an on / off control unit configured to perform on / off control on the switching elements of the plurality of driven phases based on the phases specified in the selected first or second pattern under the condition that a period and a duty ratio are substantially equal; and a prediction unit configured to predict a correlation value correlated with a time ratio that is—in a predetermined time—a ratio of a time for which execution of control in the m-phase drive is predicted to a timefor which the execution of a control in the n-phase drive is predicted. An absolute value of a difference between a maximum value of a phase difference between two switching elements that have been determined to be sequentially turned on in the n-phase drive based on the second pattern and 360° / n is smaller than an absolute value of a difference between a maximum value of a phase difference between two switching elements that have been determined to be sequentially turned on in the n-phase drive based on the first pattern and 360° / n. The selection unit is configured to select the first pattern when the predicted correlation value indicates that the time ratio is at least as large as a first threshold, and to select the second pattern when the predicted correlation value indicates that the time ratio is smaller than a second threshold.which is at most as large as the first threshold value. The on / off control unit is configured to stop the on / off control at the switching elements of (mn) phases in the n-phase drive based on the second pattern. The switching elements are classified into multiple combinations such that each of the combinations is composed of three switching elements that are determined to be sequentially turned on in the m-phase drive based on the second pattern. If (mn)=1, the switching element of (mn) phase at which the on / off control is stopped in the n-phase drive based on the second pattern is the switching element that is turned on between the switching element that is turned on first and the switching element that is turned on last, among the three switching elements in a combination having a phase difference that is the smallest among the multiple combinations.wherein the phase difference is a phase difference between the switching element that is turned on first and the switching element that is turned on last. If (mn)≥2, the switching elements of (mn) phases at which the on / off control was stopped in the n-phase drive based on the second pattern are switching elements other than a combination of two switching elements that are set to be sequentially turned on in the m-phase drive based on the second pattern, and which are each turned on between the switching element that is turned on first and the switching element that is turned on last, out of the three switching elements in a corresponding one of (mn) combinations among the plurality of combinations, wherein the (mn) combinations are in ascending order of the phase difference between the switching element that is turned on first and the switching element,which is switched on last. It should be noted that in this specification, a switching element of a single phase in the case where (mn)=1, and switching elements of two or more phases in the case where (mn)≥2, are collectively referred to as "switching elements of (mn) phases" when appropriate.

[0006] In the aspect, the second threshold may be equal to the first threshold.

[0007] In the aspect, the second threshold may be smaller than the first threshold, the storage unit may be configured to store a third pattern that is a phase pattern in which on-times of the m switching elements are specified and that is not the first and second patterns, the selection unit may be configured to select the first pattern while the multiphase converter has been stopped if the predicted correlation value indicates that the time ratio is at least as large as the first threshold, to select the second pattern while the multiphase converter has been stopped if the predicted correlation value indicates that the time ratio is smaller than the second threshold, and to select the third pattern while the multiphase converter has been stopped if the predicted correlation value indicates that the time ratio is smaller than the first threshold and at least as large as the second threshold,an absolute value of a difference between a maximum value of a phase difference between two switching elements set to be sequentially turned on in the n-phase drive based on the third pattern and 360° / n may be greater than an absolute value of a difference between a maximum value of a phase difference between two switching elements set to be sequentially turned on in the n-phase drive based on the second pattern and 360° / n, and may be smaller than the absolute value of the difference between the maximum value of the phase difference between two switching elements set to be sequentially turned on in the n-phase drive based on the first pattern and 360° / n, and the on / off control unit may be configured toto stop the on / off control at the switching elements of (mn) phases in the n-phase drive based on the third pattern. The switching elements may be classified into multiple combinations such that each of the combinations is composed of three switching elements that are determined to be sequentially turned on in the m-phase drive based on the third pattern. If (mn)=1, the switching element of (mn) phase at which the on / off control is stopped in the n-phase drive based on the third pattern may be the switching element that is turned on between the switching element that is turned on first and the switching element that is turned on last, among the three switching elements in a combination having a phase difference that is the smallest among the multiple combinations, wherein the phase difference is a phase difference between the switching element,that is turned on first and the switching element that is turned on last. If (mn)≥2, the switching elements of (mn) phases at which the on / off control was stopped in the n-phase drive based on the third pattern may be switching elements other than a combination of two switching elements that are set to be sequentially turned on in the m-phase drive based on the third pattern, and which are each turned on between the switching element that is turned on first and the switching element that is turned on last, among the three switching elements in a corresponding one of (mn) combinations from the plurality of combinations, where the (mn) combinations are selected in ascending order of the phase difference between the switching element that is turned on first and the switching element that is turned on last.

[0008] In the aspect, among the first, second, and third switching elements that are sequentially turned on in the m-phase drive based on at least one of the first and second patterns, a phase difference between the first switching element and the second switching element may be greater than 360° / m and less than 360° / n, and a phase difference between the first switching element and the third switching element may be less than (360° / m)×3.

[0009] In the aspect, the control device for a multi-phase converter may further include a route acquisition unit configured to acquire travel route planning information about a planned travel route of a vehicle traveling using a battery that inputs an input current to the multi-phase converter as a power source, and the prediction unit may be configured to predict a predicted current value that the battery predictively inputs to the multi-phase converter based on the travel route planning information as the correlation value.

[0010] In the aspect, the control device for a multi-phase converter may further include a history acquisition unit configured to acquire history information about a time when the control is executed in the n-phase drive and a time when the control is executed in the m-phase drive, and the prediction unit may be configured to predict the correlation value based on the history information.

[0011] In the aspect, the control device for a multi-phase converter may further include a traveling mode acquisition unit configured to acquire traveling mode information about a traveling mode of a vehicle traveling using a battery that supplies an input current to the multi-phase converter as a power source, and the prediction unit may be configured to predict the predicted correlation value based on the traveling mode information.

[0012] According to another aspect of the invention, a multiphase converter system is provided, comprising: the control device; and the multiphase converter.

[0013] According to another aspect of the invention, a power supply system is provided, comprising: the multiphase converter system; and a power supply configured to supply an input current to the multiphase converter.

[0014] In this aspect, the power supply can be a fuel cell.

[0015] According to the invention, it is possible to provide a control device for a multi-phase converter, a multi-phase converter system, and a power supply system, which can dampen an increase in losses due to a ripple current with simple control. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, in which like reference numerals designate like elements, and in which: Fig. 1 is a diagram schematically illustrating an embodiment of a fuel cell system mounted in a vehicle; Fig. 2 is a diagram illustrating a circuit configuration of a boost converter; Fig. 3A is a diagram illustrating operations of switching elements in a three-phase drive based on pattern A; Fig. 3B is a diagram illustrating reactor currents and an output current of the boost converter in a three-phase drive based on Pattern A; Fig. 4A is a diagram illustrating operations of switching elements in a two-phase drive based on pattern A; Fig. 4B is a diagram illustrating inductor currents and an output current of the boost converter in a two-phase drive based on Pattern A; Fig. 5A is a diagram illustrating operations of switching elements in a single-phase drive based on pattern A; Fig. Figure 5B is a diagram illustrating reactor currents in a single-phase drive based on pattern A; Fig. 6A is a diagram illustrating operations of switching elements in a three-phase drive based on Pattern B; Fig. 6B is a diagram illustrating reactor currents and an output current of the boost converter in a three-phase drive based on Pattern B; Fig. 7A is a diagram illustrating operations of switching elements in a two-phase drive based on Pattern B; Fig. 7B is a diagram illustrating inductor currents and an output current of the boost converter in a two-phase drive based on Pattern B; Fig. 8A is a table for comparing a magnitude of a ripple current between samples A and B; Fig. Figure 8B is a graph illustrating phases and phase differences in patterns A and B; Fig. 9 is a flowchart illustrating an example of pattern selection control; Fig. 10A is an example of a graph illustrating the change of a calculated predicted current value; Fig. 10B is another example of a graph illustrating the change in a calculated predicted current value; Fig. 11 is a diagram showing a relationship between the Fig. 10A and Fig. 10B and a time at which control is executed based on the predicted current values. Fig. 12 is a flowchart illustrating an example of pattern selection control according to a first modified example; Fig. 13 is a diagram illustrating a configuration of a fuel cell system according to a second modified example; Fig. 14 is a flowchart illustrating an example of pattern selection control according to the second modified example; Fig. 15A is a diagram illustrating operations of switching elements in a three-phase drive based on Pattern C; Fig. 15B is a diagram illustrating reactor currents and an output current of the boost converter in a three-phase drive based on Pattern C; Fig. 16A is a diagram illustrating operations of switching elements in a two-phase drive based on Pattern C; Fig. 16B is a diagram illustrating reactor currents and an output current of the boost converter in a two-phase drive based on Pattern C; Fig. 17A is a table for comparing a magnitude of a ripple current between samples A and C; Fig. Figure 17B is a graph illustrating phases and phase differences in pattern C; Fig. 18 is a flowchart illustrating an example of pattern selection control according to a third modified example; Fig. 19A is a diagram illustrating operations of switching elements in a three-phase drive based on Pattern D; Fig. 19B is a diagram illustrating reactor currents and an output current of the boost converter in a three-phase drive based on Pattern D; Fig. 20A is a diagram illustrating operations of switching elements in a two-phase drive based on Pattern D; Fig. 20B is a diagram illustrating reactor currents and an output current of the boost converter in a two-phase drive based on Pattern D; Fig. 21A is a table for comparing a magnitude of a ripple current between the samples A to D; Fig. Figure 21B is a graph illustrating phases and phase differences in pattern D; Fig. 22 is a flowchart illustrating an example of pattern selection control according to a fourth modified example; Fig. 23 is a flowchart illustrating an example of pattern selection control according to a fifth modified example; Fig. 24 is a diagram illustrating a circuit configuration of a boost converter according to a sixth modified example; Fig. Figure 25 is a diagram illustrating phases and phase differences in patterns E to G; Fig. 26 is a diagram illustrating a circuit configuration of a boost converter according to a seventh modified example; and Fig. Figure 27 is a diagram illustrating phases and phase differences in patterns H to J. DETAILED DESCRIPTION OF EMBODIMENTS Rough representation of an embodiment of a fuel cell system

[0017] Fig. 1 is a diagram schematically illustrating a configuration of a fuel cell system 1 mounted in a vehicle. The fuel cell system 1 includes an electronic control unit (ECU) 4, a secondary battery (hereinafter referred to as "BAT") 7, a battery converter (hereinafter referred to as BDC) 8, an inverter (hereinafter referred to as INV) 9, a fuel cell stack (hereinafter referred to as FC) 10, a boost converter (hereinafter referred to as FDC) 20, and a navigation device 50. Although in Fig. 1, the fuel cell system 1 includes an oxidant gas supply system and a fuel gas supply system that supply an oxidant gas and a fuel gas to the FC 10. The vehicle includes a motor M for traveling, vehicle wheels W, an accelerator pedal operation amount sensor 5, and an ignition switch 6.

[0018] The FC 10 is supplied with fuel gas and oxidant gas and generates electric power. Multiple solid polymer electrolyte-type unit cells are stacked in the FC 10. Each unit cell includes a membrane-electrode assembly, a power generation element in which electrodes are arranged on both surfaces of an electrolyte membrane, and a pair of separators between which the membrane-electrode assembly is sandwiched. The electrolyte membrane is a solid polymer membrane formed from a fluorine-based resin or a hydrocarbon-based resin containing a sulfonate group, and exhibits excellent proton conductivity in a wet state. The electrodes include carbon supports and ionomers, which are solid polymers containing a sulfonate group, and exhibit excellent proton conductivity in a wet state.The carbon supports support a catalyst (e.g., a platinum or platinum-cobalt alloy) to support a power-generating reaction. Each unit cell contains a manifold for the flow of reactant gases or a coolant. The reactant gases flowing in the manifold are delivered to a power-generating region of each unit cell via gas flow channels located within each unit cell.

[0019] The FDC 20 is a DC / DC converter that steps up a DC voltage output from the FC 10 at a predetermined step-up ratio and feeds the electric power output from the FC 10 to the INV 9. It is an example of a power converter. The INV 9 converts the input DC power into three-phase AC power and feeds the three-phase AC power to the motor M. The motor M drives the vehicle wheels W to make the vehicle run. The BDC 8 is a bidirectional DC / DC converter. That is, the BDC 8 steps down a DC voltage set by the FDC 20 or steps up a DC voltage from the BAT 7 and feeds an electrical output from the BAT 7 to the INV 9. The BDC 8 is not required. In this case, the INV 9 serves as a power converter. The BAT 7 can store electrical power from the FC 10.

[0020] The ECU 4 includes a central processing unit (CPU), a read-only memory (ROM), and a random access memory (RAM). The ECU 4 is electrically connected to the accelerator pedal operation amount sensor 5, the ignition switch 6, a current sensor 10A, a voltage sensor 10V, the FDC 20, the BDC 8, and the navigation device 50. Map data, a past driving history of the vehicle 1, and the like are stored in a storage device of the navigation device 50. A Global Positioning System (GPS) receiver that acquires position information of the vehicle is built into the navigation device 50. The ECU 4 controls the electric output of the FC 10 based on a detected value of the accelerator pedal operation amount sensor 5 or the like. The ECU 4 detects an output current value of the FC 10 measured by the current sensor 10A and an output voltage value of the FC 10 measured by the voltage sensor 10V.The ECU 4 is an example of a control device that controls the FDC 20 and includes a driven phase number control unit, a storage unit, a selection unit, an on / off control unit, and a prediction unit, the details of which will be described later and which are functionally realized by the CPU, ROM, and RAM of the ECU 4. The ECU 4 and the FDC 20 constitute an example of a multi-phase converter system, and the ECU 4, the FDC 20, and the FC 10 constitute an example of a power supply system. Circuit design of the FDC

[0021] Fig. 2 is a diagram illustrating a circuit configuration of the FDC 20. In Fig. 2, the FC 10 and the INV 9 are also illustrated. The FDC 20 is a multi-phase converter with m phases, where m is 3 in this embodiment. Accordingly, the FDC 20 comprises three converter circuits 20a to 20c and a capacitor 24. Here, m is an integer of at least 3. The converter circuit 20a comprises a reactor 21a, a current sensor 22a, and an intelligent power module (IPM) 23a. The converter circuit 20b comprises a reactor 21b, a current sensor 22b, and an IPM 23b. The converter circuit 20c comprises a reactor 21c, a current sensor 22c, and an IPM 23c. The IPM 23a comprises a switching element 36a and a diode 37a. The IPM 23b comprises a switching element 36b and a diode 37b. The IPM 23c includes a switching element 36c and a diode 37c. The switching elements 36a to 36c are referred to as SWs 36a to 36c in this specification.

[0022] The reactor 21a, the current sensor 22a, and the diode 37a are connected in series. Similarly, the reactor 21b, the current sensor 22b, and the diode 37b are connected in series. The reactor 21c, the current sensor 22c, and the diode 37c are also connected in series. These series-connected components are connected in parallel between a positive electrode side of the FC 10 and a positive electrode side of the INV 9. Accordingly, it is possible to reduce heat dissipation by reducing the current values ​​flowing in the reactors 21a to 21c and the IPMs 23a to 23c. The SW 36a is connected between a portion between the reactor 21a and the diode 37a and a negative electrode side of the FC 10. Similarly, the SW 36b is connected between a portion between the choke 21b and the diode 37b and a negative electrode side of the FC 10.The SW 36c is connected between a portion between the reactor 21c and the diode 37c and a negative electrode side of the FC 10. The reactors 21a to 21c are, for example, but not limited to, identical components with the same configuration and capacitance. The current sensors 22a to 22c are connected to the reactors 21a to 21c downstream of them, but are not limited to, and may also be connected upstream of them. The FC 10 and the reactors 21a to 21c are electrically connected to each other via a conductive member such as a busbar or a cable.

[0023] The control device 4 switches the SWs 36a to 36c on and off, for example, at the same constant period. By switching the SWs 36a to 36c between on and off, currents flowing in the SWs 36a to 36c are controlled. The on and off of the SWs 36a to 36c are controlled based on duty ratios of pulse signals input to the SWs 36a to 36c. A duty ratio is the ratio of an on-state duration to an on / off period. The ECU 4 determines the duty ratio based on current values ​​detected by the current sensors 22a to 22c or a target boost ratio.

[0024] When the SW 36a is turned on, a current begins to flow from the FC 10 to the SW 36a via the reactor 21a, and magnetic energy based on DC excitation is accumulated in the reactor 21a. When the SW 36a is turned off, the magnetic energy accumulated in the reactor 21a during the on-period is output as a current to the INV 9 via the diode 37a. Accordingly, by controlling the duty cycles of the SWs 36a to 36c, it is possible to control the energy accumulated in the reactors 21a to 21c (a time average) and control the currents flowing in the reactors 21a to 21c on average (effective currents).

[0025] An induced voltage generated by the magnetic energy accumulated in the reactor 21a when the SW 36a is turned off is applied across an output voltage of the FC 10, and a voltage higher than the output voltage of the FC 10 is applied to the INV 9. The same applies to the SWs 36b and 36c and the reactors 21b and 21c. The ECU 4 sends a control signal such that the SWs 36a to 36c are sequentially turned on, and the induced voltages are sequentially applied across the output voltage of the FC 10. Accordingly, the voltage input to the INV 9 is kept higher than the output voltage of the FC 10. The capacitor 24 is connected between a portion between the diodes 37a to 37c and the positive electrode side of the INV 9 and the negative electrode side of the INV 9, and serves to reduce voltage fluctuations.

[0026] The ECU 4 selects Pattern A or Pattern B as a phase pattern in which the phases of the SWs 36a to 36c of the converter circuits 20a to 20c are specified. The phases of the SWs 36a to 36c in Pattern A are 0°, 120°, and 240°, respectively. The phases of the SWs 36a to 36c in Pattern B are 0°, 180°, and 270°, respectively. These phases define on-times of the switching elements. Patterns A and B are stored in advance in the ROM of the ECU 4. The ROM of the ECU 4 is an example of a storage unit. Details of Patterns A and B will be described later.

[0027] Here, the ECU 4 controls the on and off of the SWs 36a to 36c in substantially the same period and with substantially the same duty ratio. In this text, "substantially the same period" does not only mean the case where the periods of the SWs 36a to 36c completely coincide with each other; rather, the periods may differ from each other to such an extent that the phase differences between the SWs 36a to 36c in which on and off are repeated hardly change in a given period. This is because, for example, in the case of uneven transmission speeds of the drive signals to the SWs 36a to 36c, the periods may not completely coincide with each other. Furthermore, "substantially the same duty ratio" does not only mean the case where the duty ratios of the SWs 36a to 36c completely coincide with each other.For example, if the average values ​​of reactor currents flowing in reactors 21a to 21c in a single period can be considered substantially equal, the duty cycles may not completely agree with each other. This is because, for example, in the case of unevenness in a resistance value of the busbars connecting reactors 21a to 21c to FC 10 or the like, and if the duty cycles are brought into full agreement with each other, there is a possibility that the average values ​​of the reactor currents will differ to such an extent that they cannot be considered substantially equal.

[0028] The ECU 4 performs a process of detecting an input current value of the FDC 20 measured by the current sensor 10A and increasing the number of driven phases of the converter circuits 20a to 20c as the input current value of the FDC 20 increases. Specifically, single-phase drive in which the on-off of only one of the SWs 36a to 36c is controlled, two-phase drive in which the on-off of two of the SWs 36a to 36c is controlled, and three-phase drive in which the on-off of all the SWs 36a to 36c is controlled are switched. This process is an example of processes executed by a number of driven phases control unit and an on / off control unit.

[0029] The ECU 4 may increase the number of driven phases of the converter circuits 20a to 20c when an input power value of the FDC 20 increases or when an input voltage value of the FDC 20 decreases. The ECU 4 may increase the number of driven phases of the converter circuits 20a to 20c when a target output current value of the FDC 20 increases, when a target output power value of the FDC 20 increases, or when a target output voltage value of the FDC 20 increases. This is because each case corresponds to the case where electric power generated by the FC 10 increases and the input current value of the FDC 20 increases. Patterns A and B (m=3, n=2)

[0030] The case where three (m=3) converter circuits 20a to 20c are driven (hereinafter referred to as three-phase drive), the case where two (n=2) converter circuits 20a and 20b are driven (hereinafter referred to as two-phase drive), and the case where a single converter circuit 20a is driven (hereinafter referred to as single-phase drive) are described in patterns A and B below. As described above, m is an integer of at least 3, and n is an integer less than m and of at least 2, and is an integer that is not a divisor of m. Pattern A (m=3, n=2)

[0031] Pattern A is described first below. Fig. 3A is a diagram illustrating operations of SWs 36a to 36c in a three-phase drive based on Pattern A. Fig. Figure 3B is a diagram illustrating inductor currents Ia to Ic and an output current IT of the FDC 20 in a three-phase drive based on pattern A. In the Fig. 3A and Fig. 3B, the horizontal axis represents a phase. The vertical axis in Fig. 3A shows on / off states of the switching elements. The vertical axis in Fig. 3B represents a current. In this embodiment, the duty cycles of the SWs 36a to 36c are assumed to be 0.5. The inductor currents Ia to Ic are currents flowing in the inductors 21a to 21c. The output current IT of the FDC 20 is a combined current of the inductor currents Ia to Ic.

[0032] Fig. 4A is a diagram illustrating operations of the SWs 36a to 36c in a two-phase drive based on Pattern A. Fig. Figure 4B is a diagram illustrating reactor currents Ia and Ib and an output current IT of the FDC 20 under two-phase driving based on Pattern A. Under two-phase driving, the on-and-off control of the SWs 36a and 36b is controlled, and the on / off control of the SW 36c is stopped. Accordingly, no reactor current Ic flows.

[0033] Fig. 5A is a diagram illustrating operations of the SWs 36a to 36c in a single-phase drive based on Pattern A. Fig. Figure 5B is a diagram illustrating reactor current Ia under single-phase control based on Pattern A. Under single-phase control, only the SW 36a is controlled on and off, and the on / off control of SWs 36b and 36c is stopped. Accordingly, reactor currents Ib and Ic do not flow. Under single-phase control, reactor current Ia serves as the output current IT of FDC 20.

[0034] In Pattern A, the ripple current of the output current IT in the case of a duty cycle of 0.5 in single-phase driving is larger than that in two-phase driving and three-phase driving, and is smaller than that in single-phase driving and two-phase driving in three-phase driving, assuming that the currents flowing in the phases are equal. If the magnitude of the ripple current of the output current IT in single-phase driving, where the magnitude of the ripple current of the output current IT is a maximum, is defined as 1, here the magnitude of the ripple current of the output current IT in two-phase driving based on Pattern A is 2 / 3, and the magnitude of the ripple current in three-phase driving based on Pattern A is 1 / 3.The ripple current of the output current IT indicates the difference between the maximum and minimum values ​​of the output current IT. When reference is made simply to "ripple current" in the following description, this refers to the ripple current of the output current IT and not to the ripple current of the inductor currents Ia to Ic. Pattern B (m=3, n=2)

[0035] Pattern B is described below. Fig. 6A is a diagram illustrating operations of the SWs 36a to 36c in a three-phase drive based on Pattern B. Fig. 6B is a diagram illustrating reactor currents Ia to Ic and an output current IT of the FDC 20 in a three-phase drive based on pattern B. The reactor currents Ia to Ic are currents flowing in the reactors 21a to 21c. Fig. 7A is a diagram illustrating operations of the SWs 36a to 36c in a two-phase drive based on Pattern B. Fig. 7B is a diagram illustrating reactor currents Ia and Ib and an output current IT of the FDC 20 in a two-phase drive based on Pattern B. The operations of the SWs 36a to 36c and the reactor currents Ia to Ic in a single-phase drive based on Pattern B are the same as those in a single-phase drive based on Pattern A.

[0036] If it is assumed that the currents flowing in the phases are equal and the magnitude of the ripple current in a single-phase drive is defined as 1 as described above, the magnitude of the ripple current in a two-phase drive based on pattern B is 0, and the magnitude of the ripple current in a three-phase drive based on pattern B is 1. Comparison between patterns A and B

[0037] Fig. Figure 8A is a table comparing the magnitude of the ripple current between Patterns A and B. The ripple current under three-phase driving is smaller in Pattern A than in Pattern B. Conversely, the ripple current under two-phase driving is smaller in Pattern B than in Pattern A. When the ripple current is smaller, the loss can be further reduced. Accordingly, Pattern A is suitable for three-phase driving, and Pattern B is suitable for two-phase driving.

[0038] Fig. Figure 8B is a diagram illustrating phases and phase differences in patterns A and B. The phase differences in pattern A are defined as follows. A phase difference D A(a-b) between the SW 36a and the SW 36b, a phase difference D A(b-c) between the SW 36b and the SW 36c, and a phase difference D A(c-a) between the SW 36c and the SW 36a are 120°. In pattern B, a phase difference DB(a-b) between the SW 36a and the SW 36b 180°, a phase difference D B(b-c) between the SW 36b and the SW 36c is 90°, and a phase difference D B(c-a) between SW 36c and SW 36a is 90°.

[0039] Which of the patterns A and B is suitable for two-phase control can be determined as follows. The maximum value of the phase differences D A(a-b) , D A(b-c) and D A(c-a) in pattern A is 120°. The maximum value of the phase differences D B(a-b) , D B(b-c) and D B(c-a) in pattern B is D B(a-b)=180°. The absolute value of a difference between the maximum value in pattern A and 180° is 60°. The absolute value of the difference between the maximum value in pattern B and 180° is 0°. Here, 180° is a value calculated from 360° / n=360° / 2 and is a phase difference at which the ripple current of the output current IT is the smallest in a two-phase drive. The absolute value is smaller in pattern B than in pattern A. The pattern with the thus smaller absolute value is suitable for a two-phase drive. Accordingly, pattern B is more suitable for a two-phase drive than pattern A. In other words, pattern A is more suitable for a three-phase drive than pattern B.

[0040] A switching element whose on / off control should be stopped at the time of two-phase control based on pattern B can be determined as follows. As shown in Fig. 8B, a phase difference between a phase of a switching element to be turned on first and a phase of a switching element to be turned on last of any three switching elements that are set to be turned on sequentially at the time of three-phase driving based on Pattern B is defined as follows. The phase difference D B(a-c) between SW 36a and SW 36c is 270°. The phase difference D B(b-a) between SW 36b and SW 36a is 180°. The phase difference D B(c-b) between the SW 36c and the SW 36b is 270°. The phase difference D B(b-a)of the three phase differences has a minimum value. A switching element whose on / off control is to be stopped is SW 36c, which is switched on between the on time of SW 36b and the on time of SW 36a, which define the minimum phase difference at the time of three-phase control. The phase difference when the on / off control of SW 36c is stopped at the time of two-phase control is D B(a-b) =D B(b-a) =180°, which corresponds to 360° / 2=180°.

[0041] For example, when the on / off control of SW 36a is stopped at the time of two-phase control, the phase differences are D B(b-c) =90° and D B(c-b) =270°, and a difference between the phase differences and 180° is larger than that when the SW 36c is stopped. Similarly, the phase differences when the on / off control of the SW 36b is stopped at the time of two-phase control are D B(a-c)=270° and D B(c-a) =90°, and a difference between the phase differences and 180° is larger than that when SW 36c is stopped. Accordingly, by stopping the on / off control of SW 36c among SWs 36a to 36c, it is possible to attenuate the ripple current in the two-phase drive based on Pattern B.

[0042] Since the on / off control of SW 36c is stopped at the time of two-phase control based on pattern A and D A(a-b) =D A(b-c) =D A(c-a) =120°, only the on / off control of one of the SWs 36a to 36c needs to be stopped, but not limited to this. The on / off control of two of the SWs 36a to 36c only needs to be stopped in one of the patterns A and B at the time of single-phase control. Pattern selection control

[0043] Fig. 9 is a flowchart illustrating an example of pattern selection control. The pattern selection control is repeatedly executed at intervals of a predetermined time. The ECU 4 calculates the change in a predicted current value, which is a current value whose output from the FC 10 is predicted (step S1). The process of step S1 is an example of a process executed by a prediction unit.

[0044] The change in the predicted current value is calculated as follows. The ECU 4 performs a process of acquiring route planning information about a planned route from a current location of the vehicle to a destination. The planned route is a route for which guidance is performed by the navigation device 50 from the current location of the vehicle to a destination set in the navigation device 50 by a user, or a route predicted from the past travel history stored in the navigation device 50 when no destination is set. The ECU 4 acquires road information (such as an expressway, an uphill road, a downhill road, a traffic jam, and signals) of a planned route, which can be acquired from the navigation device 50 as the route planning information.This process is an example of a process executed by a route acquisition unit that acquires travel route planning information and is functionally realized by the CPU, ROM, and RAM of the ECU 4. The ECU 4 predicts a traveling speed of the vehicle at each point along the planned travel route based on such information. The ECU 4 calculates a predicted power of the engine M at each time point taking into account the predicted traveling speed and a road gradient. The ECU 4 calculates, together with this, a predicted power of an auxiliary machine of the fuel cell system 1. The ECU 4 calculates a predicted power of an air conditioner based on information of an outside air temperature or a set air conditioner temperature. The ECU 4 calculates a predicted required output of all external loads at each time point by summing the predicted outputs.Then, the ECU 4 calculates a predicted required power for the FC 10 considering a state of charge of the BAT 7 and calculates a predicted current value of the FC 10 at each time point by referring to current-power characteristics of the FC 10 stored in the ECU 4. Here, since the FC 10 is connected to the FDC 20, the output current of the FC 10 matches the input current of the FDC 20.

[0045] Then, the ECU 4 determines whether the FDC 20 is stopped (step S3). For example, if the vehicle temporarily stops and enters an intermittent operation state in which the FC 10 is continuously supplied with fuel gas but the generation of electric power is stopped, the on / off control of all the SWs 36a to 36c is stopped, and the FDC 20 stops. If the determination result of step S3 is NO, that is, if the on / off control of at least one of the SWs 36a to 36c is being executed, this control routine ends.

[0046] If the determination result of step S3 is YES, the ECU 4 determines whether an average value of the predicted current values ​​is at least as large as a threshold value α (step S5). The average value of the predicted current values ​​can be calculated, for example, by integrating the predicted current value at each time point from the current location to a destination and dividing the resulting value by the time from a current time point to a time point when the vehicle arrives at the destination. The threshold value α is set, for example, to an input current value of the FDC 20 when switching from two-phase drive to three-phase drive, that is, an output current value of the FC 10 when switching from two-phase drive to three-phase drive.If the determination result of step S5 is YES, it can be predicted that, in a predetermined period of time in which the vehicle moves from the current location to the destination, the time in which the FDC 20 is controlled in the three-phase drive is longer than the time in which it is controlled in the two-phase drive. Accordingly, in this case, the ECU 4 selects pattern A suitable for the three-phase drive as the phase pattern (step S7). If the determination result of step S5 is NO, it can be predicted that the time in which the FDC 20 is controlled in the two-phase drive is longer than the time in which it is controlled in the three-phase drive, and the ECU 4 selects pattern B as the phase pattern (step S9). The processes of steps S7 and S9 are an example of a process executed by a selection unit.

[0047] Fig. 10A and Fig. 10B is an example of a graph illustrating the change in the calculated predicted current value. Fig. 10A illustrates the case where the average value PaA of the calculated predicted current values ​​Pa is relatively large, and Fig. Figure 10B illustrates the case where the average value PbA of the calculated predicted power values ​​Pb is relatively small. The predicted power values ​​Pa and Pb are calculated based on the same time and different planned routes from a current location to a destination. If the average value PaA is at least as large as a threshold value α, as in Fig. 10A, the pattern A is selected. If the average value PbA is smaller than the threshold value α, as in Fig. 10B, pattern B is selected.

[0048] Fig. 11 is a diagram showing a relationship between the Fig. 10A and Fig. 10B and the times at which control is executed based on the predicted current values. The horizontal axis represents the predicted current value, and the vertical axis represents time. Fig. Figure 11 illustrates the ranges of predicted current values ​​in which control is executed in single-phase control, two-phase control, and three-phase control. The predicted current value Pa is larger in the time ratio in which control is executed in three-phase control than in the time ratio in which control is executed in two-phase control or in the time ratio in which control is executed in single-phase control.The predicted current value Pb is larger in the time ratio in which control is executed in single-phase drive than in the time ratio in which control is executed in two-phase drive, or in the time ratio in which control is executed in three-phase drive, and is larger in the time ratio in which control is executed in two-phase drive than in the time ratio in which control is executed in three-phase drive. At a ratio of a drive time of three-phase drive to a drive time of two-phase drive, the predicted current value Pa is larger than the predicted current value Pb. When the average value of the predicted current values ​​is larger, the time ratio in which control is executed in three-phase drive is generally larger than when the average value is smaller.Accordingly, the average value PaA of the predicted current values ​​Pa or the average value PbA of the predicted current values ​​Pb shown in the . Fig. 10A and Fig. 10B can be regarded as an example of a predicted correlation value correlated with the time ratio, which is a ratio of the time for which control is predicted to be executed in the three-phase drive to the time for which control is predicted to be executed in the two-phase drive, in a predetermined period of time.

[0049] In this way, when the average value of the predicted current values ​​is at least as large as the threshold value α, the time for which control is executed in the three-phase drive is predicted to be relatively long, and pattern A suitable for the three-phase drive is selected as the phase pattern while the FDC 20 is stopped. When the average value of the predicted current values ​​is less than the threshold value α, the time for which control is executed in the single-phase drive or in the two-phase drive is predicted to be relatively long, and pattern B suitable for the two-phase drive is selected as the phase pattern while the FDC 20 is stopped. Since the phase pattern is selected while the FDC 20 is stopped, control can be executed more easily in this way than when the phase pattern is switched while the FDC 20 is driven.Since an optimal pattern is selected depending on the average value of the predicted current values, it is possible to reduce the ripple current and dampen an increase in losses due to the ripple current.

[0050] In step S1, the ECU 4 acquires road information of a planned route from the navigation device 50, but is not limited to this and may also acquire the road information of the planned route from, for example, an external server in which the road information of the planned route is stored via a radio communication network.

[0051] In step S1, the ECU 4 calculates the change in the predicted current value from a current position to a destination set in the navigation device 50, but is not limited to this and may also calculate the change in the predicted current value from the current position of the vehicle to a point where the vehicle will temporarily stop in the near future and the FDC 20 is predicted to stop. In this case, when the FDC 20 stops, the ECU 4 can calculate the change in the predicted current value from this position to a destination or a point where the FDC 20 is predicted to stop again. Accordingly, since the change in the predicted current value is calculated for each short route, the FDC 20 can be driven in a phase pattern suitable for that route, and it is possible to attenuate a loss due to an increase in the ripple current in the FDC 20.

[0052] Within a predetermined period of time, a total time in which the predicted current value is less than a predetermined value and a total time in which the predicted current value is at least as large as the predetermined value can be predicted. In this case, pattern A can be selected if the time ratio of the latter total time to the former total time is at least as large as a threshold, and pattern B can be selected if the time ratio is less than the threshold. In this case, the time ratio itself is an example of the predicted correlation value.

[0053] Pattern A is an example of a first pattern selected when the time ratio at which control is executed in the m-phase drive is relatively large, and Pattern B is an example of a second pattern selected when the time ratio at which control is executed in the m-phase drive is relatively small. First modified example

[0054] Several modified examples will be described below. In the several modified examples, the same elements or the same processes as in the above embodiment are denoted by the same reference numerals, and their descriptions will not be repeated. Fig. 12 is a flowchart illustrating an example of pattern selection control according to a first modified example. The ECU 4 acquires history information about a drive state of the FDC 20 (step S1a). Specifically, the history information about the drive state of the FDC 20 is a cumulative drive time in which the FDC 20 was controlled in the past in two-phase drive and a cumulative drive time in which the FDC 20 was controlled in the past in three-phase drive, and is stored in the RAM of the ECU 4. The process of step S1a is an example of a process executed by a history acquisition unit functionally realized by the CPU, ROM, and RAM of the ECU 4.

[0055] If the determination result of step S3 is YES, it is determined whether a time ratio of the cumulative drive time in which control is executed in three-phase drive to the cumulative drive time in which control is executed in two-phase drive is at least as large as a threshold value β (step S5a). The threshold value β is, for example, 1, but is not limited thereto. The time ratio is an example of the aforementioned predicted correlation value. The threshold value β is an example of a first threshold value. The ECU 4 selects pattern A (step S7) if the determination result of step S5a is YES, and the ECU 4 selects pattern B if the determination result of step S5a is NO (step S9).

[0056] In this way, it is possible to improve prediction accuracy and reduce the burden of a control routine for prediction because the decision as to whether the time for executing control in two-phase drive or the time for executing control in three-phase drive is longer is predicted based on the cumulative drive time for actually executing control in two-phase drive and the cumulative drive time for actually executing control in three-phase drive. As historical information, for example, information within the past few months can be acquired. Accordingly, it is possible to cope with the case of a driver change or a driver's driving style changing.The history information can be updated at intervals of a predefined period, for example, at intervals of one month. Second modified example

[0057] Fig. 13 is a diagram illustrating a configuration of a fuel cell system 1a according to a second modified example. The fuel cell system 1a includes a drive mode switch 52 used for selecting a drive mode. A driver can select one of a normal mode, a sports mode, and an eco mode as the drive mode by operating the drive mode switch 52. In the sports mode, the output response of the FC 10 in the case of accelerator pedal operation is set to be high. In the eco mode, the output response of the FC 10 in the case of accelerator pedal operation is set to be low. In the normal mode, the output response of the FC 10 in the case of accelerator pedal operation is set to be midway between that in the sports mode and that in the eco mode. An output signal of the drive mode selected by the drive mode switch 52 is input to the ECU 4.

[0058] Fig. 14 is a flowchart illustrating an example of pattern selection control according to the second modified example. The ECU 4 acquires travel mode information about the currently selected travel mode based on the output signal of the travel mode selected by the travel mode switch 52 (step S1b). The process of step S1b is an example of a process executed by a travel mode acquisition unit functionally realized by the CPU, ROM, and RAM of the ECU 4.

[0059] If the determination result of step S3 is YES, it is then determined whether the driving mode is the sport mode (step S5b). If the determination result of step S5b is YES, it can be predicted that the time for which the vehicle is driven at a high speed is relatively long, and it can be predicted that the driving time of the three-phase drive is longer than the driving time of the two-phase drive. More specifically, it can be predicted that, in a predetermined period of time, the time ratio, which is a ratio of the time in which control is predicted to be executed in the three-phase drive and the time in which control is predicted to be executed in the two-phase drive, is at least as large as a threshold value. Accordingly, pattern A is selected (step S7).If the determination result of step S5b is NO, that is, if the driving mode is the normal mode or the eco mode, it can be predicted that the time for which the vehicle is driven at a low speed is relatively long, and it can be predicted that the driving time of the two-phase drive is longer than the driving time of the three-phase drive. More specifically, it can be predicted that the time ratio is smaller than the threshold. Accordingly, pattern B is selected (step S9).

[0060] In this way, in the predetermined period, the time ratio, which is a ratio of the time in which control is predicted to be executed in three-phase control to the time in which control is predicted to be executed in two-phase control, can be predicted depending on the selected driving mode. Accordingly, the driving mode is an example of the predicted correlation value correlated with the time ratio. In this modified example, if the driving mode is the sports mode, it means that the time ratio is at least as large as the first threshold. If the driving mode is the normal mode or the eco mode, it means that the time ratio is smaller than the first threshold.The invention is not limited thereto, and when the driving mode is the sport mode or the normal mode, for example, it may be determined that the time ratio is at least as large as the first threshold, and pattern A may be selected. When the driving mode is the eco mode, it may be determined that the time ratio is smaller than the first threshold, and pattern B may be selected.

[0061] At least two of the predicted current value described in the above embodiment, the history information described in the first modified example, and the driving mode described in the second modified example can be fully considered to select the phase pattern. Third modified examplePatterns A to C, m=3, n=2

[0062] In a third modified example, one of patterns A to C is selected as the phase pattern. Pattern C is stored in advance in the memory of the ECU 4. The phases of the SWs 36a to 36c in pattern C are 0°, 140°, and 250°, respectively. Fig. 15A is a diagram illustrating operations of the SWs 36a to 36c in a three-phase drive based on Pattern C. Fig. Figure 15B is a diagram illustrating the inductor currents Ia to Ic and the output current IT of the FDC 20 under three-phase driving based on pattern C. Fig. 16A is a diagram illustrating operations of the SWs 36a to 36c in a two-phase drive based on Pattern C. Fig. Figure 16B is a diagram illustrating the inductor currents Ia to Ic and the output current IT of the FDC 20 under two-phase driving based on Pattern C.

[0063] Fig. Figure 17A is a table comparing the magnitude of ripple current between Patterns A to C. When the same current value is caused to flow in the phases and the magnitude of the ripple current of the output current IT in single-phase drive is set to 1, the magnitude of the ripple current of the output current IT in two-phase drive based on Pattern C is 4 / 9, and the magnitude of the ripple current in three-phase drive based on Pattern C is 5 / 9. In comparison between Patterns A to C, the ripple current in two-phase drive is smaller in Pattern C than in Pattern A and larger than in Pattern B. The ripple current in three-phase drive is smaller in Pattern C than in Pattern B and larger than in Pattern A.

[0064] Fig. Figure 17B is a diagram illustrating phases and phase differences in pattern C. The phase differences in pattern C are defined as follows. The phase difference D C(a-b) between SW 36a and SW 36b is 140°. The phase difference D C(b-c) between the SW 36b and the SW 36c and the phase difference D C(c-a) between SW 36c and SW 36a are 110°.

[0065] Which of the patterns A and C is suitable for two-phase control can be determined as follows. The maximum value of the phase differences D C(a-b) , D C(b-c) and D C(c-a) in pattern C is D C(a-b)=140°. The absolute value of a difference between the maximum value in Pattern C and 180° is 40°. On the other hand, since all phase differences between two switching elements sequentially turned on in three-phase control based on Pattern A are 120° as described above, their maximum value is 120°, and the absolute value of the difference between 120° and 180° is 60°. The absolute value is smaller in Pattern C than in Pattern A. Accordingly, Pattern C is more suitable for two-phase control than Pattern A. In other words, Pattern A is more suitable for three-phase control than Pattern C.

[0066] Similarly, it can be determined as follows which of patterns B and C is a suitable pattern for two-phase driving. As described above, the absolute value in pattern B is 0°, and the absolute value in pattern C is 40°. Since the absolute value in pattern B is smaller than that in pattern C, pattern B is more suitable for two-phase driving than pattern A. In other words, pattern C is more suitable for three-phase driving than pattern B. It follows that pattern C is not more suitable for three-phase driving than pattern A, but is more suitable for three-phase driving than pattern B, and is not more suitable for two-phase driving than pattern B, but is more suitable for two-phase driving than pattern A. Accordingly, pattern C can attenuate a large increase in ripple current in both two-phase driving and three-phase driving.

[0067] In pattern C, the maximum value D satisfies C(a-b) the phase differences the following conditions. 120°(=360° / m=360° / 3) <DC(a−b)<180°(=360° / n=360° / 2) DC(a−b) <DC(a−c)<360°(=(360° / m)×3=(360°⁄3)×3)

[0068] Da D C(a-b) =140° and D C(a-c) =250°, the above conditions are met. On the other hand, in pattern A, 120° <D A(a-b) not fulfilled because D A(a-b) =120°. In pattern B, D B(a-b) <180° not fulfilled, because D B(a-b) =180°. Since pattern C meets these conditions, pattern C is no better suited for three-phase control than pattern A, but is better suited for three-phase control than pattern B, and is no better suited for two-phase control than pattern B, but is better suited for two-phase control than pattern A.

[0069] The switching element whose on / off control should be stopped at the time of two-phase control based on pattern C can be determined as follows. As shown in Fig. 17B, ​​in pattern C the phase difference D C(a-c) between the SW 36a and the SW 36c 250°, the phase difference D C(b-a) between the SW 36b and the SW 36a is 220°, and the phase difference D C(c-b) between the SW 36c and the SW 36b is 250°. Of these three phase differences, the phase difference D C(b-a) a minimum value. The switching element whose on / off control is to be stopped is SW 36c, which is switched on between the on-time of SW 36b and the on-time of SW 36a, which define the minimum phase difference. The phase differences when the on / off control of SW 36c is stopped at the time of two-phase control are D C(a-b) =140° and D C(b-a) =220°.

[0070] For example, when the on / off control of SW 36a is stopped at the time of two-phase control based on pattern C, the phase differences are D C(b-c) =110° and D C(c-b) =250°. The absolute value of the difference between D C(b-c) and 180° and the absolute value of the difference between D C(c-b) and 180° are 70°. The phase differences when the on / off control of SW 36b is stopped at the time of two-phase control are D C(a-c) =250° and D C(c-a) =110°. Here the absolute value of the difference between D C(a-c) and 180° and the absolute value of the difference between D C(c-a) and 180° 70°. On the other hand, if the on / off control of SW 36c is stopped at the time of two-phase control, the absolute value of the difference between D C(a-b) and 180° and the absolute value of the difference between D C(b-a)and 180° 40°. As described above, if the on / off control of SW 36c is stopped at the time of two-phase control, the absolute value decreases and is suitable for two-phase control.

[0071] During the single-phase control period, similar to patterns A and B, only in pattern C the on / off control of two of the SWs 36a to 36c must be stopped.

[0072] Fig. 18 is a flowchart illustrating an example of pattern selection control according to the third modified example. If the determination result of step S3 is YES, it is determined whether the average value of the predicted current values ​​is at least as large as a threshold value α1 (step S5c). Pattern A is selected if the determination result of step S5c is YES (step S7), and it is determined whether the average value of the predicted current values ​​is at least as large as a threshold value α2 if the determination result of step S5c is NO (step S5d). Here, the threshold value α2 is smaller than the threshold value α1. The threshold value α1 is an example of a first threshold value, and the threshold value α2 is an example of a second threshold value smaller than the first threshold value α1. If the determination result of step S5d is NO, pattern B is selected (step S9).If the determination result of step S5d is YES, pattern C is selected (step S8).

[0073] In this way, when the average value of the predicted current values ​​is less than the threshold α1 and at least as large as the threshold α2, it can be predicted that a time ratio (in a predetermined period, a ratio of the time in which control is predicted to be executed in the three-phase drive to the time in which control is predicted to be executed in the two-phase drive) is not as high as when the predicted current values ​​are at least as large as the threshold α1, and the time ratio is not as low as when the predicted current values ​​are less than the threshold α2. Accordingly, by selecting pattern C in this case, it is possible to achieve a reduction in the ripple current of the output current IT at the time of both the two-phase drive and the three-phase drive.

[0074] In the third modified example, similarly to the first modified example, the history information of the FDC 20 may be acquired, in step S5c, it may be determined whether the time ratio of the cumulative drive time of a three-phase drive to the cumulative drive time of a two-phase drive is at least as large as the first threshold, and it may be determined in step S5d whether the time ratio is at least as large as the second threshold. In the third modified example, in a vehicle in which the drive mode can be selected as described above in the second modified example, it may be determined in step S5c whether the drive mode is the sport mode, and in step S5d whether the drive mode is the normal mode.At least two of the predicted current value, the history information described in the first modified example, and the driving mode described in the second modified example may be fully considered to select the phase pattern. Fourth modified examplePatterns A to D, m=3, n=2

[0075] In a fourth modified example, one of patterns A to D is selected as the phase pattern. Pattern D is stored in advance in the memory of the ECU 4. The phases of the SWs 36a to 36c in pattern D are 0°, 160°, and 260°, respectively. Fig. 19A is a diagram illustrating operations of the SWs 36a to 36c in a three-phase drive based on Pattern D. Fig. Figure 19B is a diagram illustrating the inductor currents Ia to Ic and the output current IT of the FDC 20 under three-phase driving based on Pattern D. Fig. 20A is a diagram illustrating operations of the SWs 36a to 36c in a two-phase drive based on Pattern D. Fig. Figure 20B is a diagram illustrating the inductor currents Ia to Ic and the output current IT of the FDC 20 under two-phase driving based on Pattern D.

[0076] Fig. Figure 21A is a table comparing the magnitude of ripple current between Patterns A to D. When the same current value is caused to flow in the phases and the magnitude of the ripple current of the output current IT in single-phase drive is set to 1, the magnitude of the ripple current of the output current IT in two-phase drive based on Pattern D is 2 / 9, and the magnitude of the ripple current in three-phase drive based on Pattern D is 7 / 9. In comparison between Patterns A to D, the ripple current in two-phase drive is smaller in Pattern D than in Pattern C and larger than in Pattern B. The ripple current in three-phase drive is smaller in Pattern D than in Pattern B and larger than in Pattern C.

[0077] Fig. Figure 21B is a diagram illustrating phases and phase differences in pattern D. In pattern D, the phase difference D D(a-b) between the SW 36a and the SW 36b 160°, and the phase difference D D(b-c) between SW 36b and SW 36c and the phase difference D D(c-a) between SW 36c and SW 36a are 100°.

[0078] Which of the patterns C and D is suitable for two-phase control can be determined as follows. The maximum value of the phase differences D D(a-b) , D D(b-c) and D D(c-a) in pattern D is D D(a-b)=160°. The absolute value of a difference between the maximum value in pattern D and 180° is 20°. On the other hand, the absolute value in pattern C is 40°, as described above. The absolute value is smaller in pattern D than in pattern C. Accordingly, pattern D is more suitable for two-phase control than pattern C. In other words, pattern C is more suitable for three-phase control than pattern D.

[0079] Similarly, it can be determined as follows which of patterns B and D is a suitable pattern for two-phase control. As described above, the absolute value in pattern B is 0°, and the absolute value in pattern D is 20°. In this way, pattern B is more suitable for two-phase control than pattern D because the absolute value in pattern B is smaller than that in pattern D. In other words, pattern D is more suitable for three-phase control than pattern B. It follows that pattern D is not more suitable for three-phase control than patterns A and C, but is more suitable for three-phase control than pattern B, and is not more suitable for two-phase control than pattern B, but is more suitable for two-phase control than patterns A and C.Accordingly, with pattern D, similar to pattern C, it is possible to dampen a large increase in the ripple current in both the two-phase drive and the three-phase drive compared to patterns A and B.

[0080] In pattern D, the maximum value D D(a-b) the phase differences the following conditions. 120°(=360° / m=360° / 3) <DD(a−b)<180°(=360° / n=360° / 2) DD(a−b) <DD(a−c)<360°(=(360° / m)×3=(360°⁄3)×3)

[0081] Da D D(a-b) =160° and D D(a-c) =260°, the above conditions are met.

[0082] The switching element whose on / off control should be stopped at the time of two-phase control based on pattern D can be determined as follows. As shown in Fig. 21B, in pattern D the phase difference D D(a-c) between the SW 36a and the SW 36c 260°, the phase difference D D(b-a)between the SW 36b and the SW 36a is 200°, and the phase difference D D(c-b) between the SW 36c and the SW 36b is 260°. Of these three phase differences, the phase difference D D(b-a) a minimum value. The switching element whose on / off control is to be stopped is SW 36c, which is switched on between the on-time of SW 36b and the on-time of SW 36a, which define the minimum phase difference. The phase differences when the on / off control of SW 36c is stopped at the time of two-phase control are D D(a-b) =160° and D D(b-a) =200°.

[0083] For example, when the on / off control of SW 36a is stopped at the time of two-phase control, the phase differences are D D(b-c) =100°and D D(c-b) =260°. The absolute value of the difference between D D(b-c) and 180° and the absolute value of the difference between D D(c-b)and 180° are 80°. The phase differences when the on / off control of SW 36b is stopped at the time of two-phase control are D D(a-c) =260° and D D(c-a) 100°. Here the absolute value of the difference between D D(a-c) and 180° and the absolute value of the difference between D D(c-a) and 180° 80°. On the other hand, if the on / off control of SW 36c is stopped at the time of two-phase control, the absolute value of the difference between D D(a-b) and 180° and the absolute value of the difference between D D(b-a) and 180° 20°. As described above, if the on / off control of SW 36c is stopped at the time of two-phase control, the absolute value decreases and is suitable for two-phase control.

[0084] For a single-phase control based on pattern D, only two of the SWs 36a to 36c need to be stopped.

[0085] Fig. 22 is a flowchart illustrating an example of pattern selection control according to the fourth modified example. Pattern A is selected when the determination result of step S5c is YES (step S7), and it is determined whether the average value of the predicted current values ​​is at least as large as a threshold α3 when the determination result of step S5c is NO (step S5e). Here, the threshold α3 is a value between the threshold α1 and the threshold α2. Pattern C is selected when the determination result of step S5e is YES (step S8). If the determination result of step S5e is NO, the determination of step S5d is executed. If the determination result of step S5d is YES, Pattern D is selected (step S8a). If the determination result of step S5d is NO, Pattern B is selected (step S9).In this way, it is possible to effectively reduce the ripple current of the output current IT by selecting a more suitable phase pattern depending on the average value of the predicted current values.

[0086] In the fourth modified example, when the vehicle's driving mode can be selected from, for example, an eco mode, a comfort mode, a normal mode, and a sport mode, it may be determined in step S5c whether the driving mode is the sport mode, it may be determined in step S5e whether the driving mode is the normal mode, and it may be determined in step S5d whether the driving mode is the comfort mode. In the comfort mode, the power output response of the FC 10 in the case of an accelerator pedal operation is set to be midway between the normal mode and the eco mode. Fifth modified examplePatterns C and D, m=3, n=2

[0087] In a fifth modified example, pattern C or D is selected. Patterns C and D are stored in advance in the memory of the ECU 4, but patterns A and B are not stored. Fig. 23 is a flowchart illustrating an example of pattern selection control in the fifth modified example. The ECU 4 selects pattern C when the determination result of step S5 is YES (step S8), and the ECU 4 selects pattern D when the determination result of step S5 is NO (step S8a). As described above, pattern D is more suitable for two-phase drive than pattern C, that is, pattern C is more suitable for three-phase drive than pattern D.

[0088] Pattern A is more suitable for three-phase driving than pattern C, but pattern A is not more suitable for two-phase driving than pattern C. Accordingly, even if the average value of the predicted current values ​​is at least as large as the threshold α, it is possible to achieve a reduction in the ripple current in both two-phase driving and three-phase driving by selecting pattern C instead of pattern A. Pattern B is more suitable for two-phase driving than pattern D, but pattern B is not more suitable for three-phase driving than pattern D. Accordingly, it is possible to achieve a reduction in the ripple current in both two-phase driving and three-phase driving by selecting pattern D instead of pattern B, even if the average value of the predicted current values ​​is smaller than the threshold α.

[0089] A combination of phase patterns that can be selected is not limited to those described above in the embodiment and the modified examples. For example, the combination of phase patterns that can be selected may be any one of a combination of patterns A and C, a combination of patterns A and D, a combination of patterns B and C, a combination of patterns A, B, and D, a combination of patterns A, C, and D, and a combination of patterns B, C, and D. Sixth modified examplePatterns E to G, m=4, n=3

[0090] Fig. 24 is a diagram illustrating a circuit configuration of an FDC 20A according to a sixth modified example. The FDC 20A includes four-phase converter circuits 20a to 20d. The converter circuit 20d includes a reactor 21d, a current sensor 22d, and an IPM 23d. The IPM 23d includes an SW 36d and a diode 37d. In the sixth modified example, the single-phase drive is sequentially switched to four-phase drive with an increase in the input current of the FDC 20A, but the invention is not limited thereto, and for example, the drive may be switched in the order of single-phase drive, three-phase drive, and four-phase drive, may be switched in the order of two-phase drive, three-phase drive, and four-phase drive, or may be switched in the order of three-phase drive and four-phase drive.

[0091] Fig. Figure 25 is a diagram illustrating phases and phase differences of patterns E to G. The phases of SWs 36a to 36d in pattern E are 0°, 90°, 180°, and 270°, respectively. The phases of SWs 36a to 36d in pattern F are 0°, 120°, 240°, and 300°, respectively. The phases of SWs 36a to 36d in pattern G are 0°, 100°, 180°, and 260°, respectively. The phase differences in pattern E are D E(a-b) =D E(b-c) =D E(c-d) =D E(d-a) =90°. The phase differences in pattern F are D F(a-b) =D F(b-c) =120° and D F(c-d) =D F(d-a) =60°. The phase differences in pattern G are D G(a-b) =D G(d-a) =100° and D G(b-c) =D G(c-d) =80° .

[0092] Which of the patterns E to G is suitable for three-phase driving can be determined as follows. All phase differences in pattern E are 90°, and their maximum value is 90°. The maximum value of the phase differences in pattern F is 120°. The maximum value of the phase differences in pattern G is 100°. The absolute value of a difference between the maximum value and 120° in pattern E is 30°. The absolute value of a difference between the maximum value and 120° in pattern F is 0°. The absolute value of a difference between the maximum value and 120° in pattern G is 20°. Here, 120° is a value calculated by 360° / n=360° / 3 and is a phase difference at which the ripple current of the output current IT is minimized at the time of three-phase driving. The absolute value is smallest in pattern F and largest in pattern E.Accordingly, pattern E is best suited for four-phase control, pattern F is best suited for three-phase control, and pattern G is not better suited for four-phase control but is better suited for three-phase control than pattern E and is not better suited for three-phase control but is better suited for four-phase control than pattern F.

[0093] In pattern G, the maximum value D satisfies G(a-b) the phase differences the following conditions. 90°(=360° / m=360° / 4) <DG(a−b)<120°(=360° / n=360° / 3) DG(a−b) <DG(a−c)<270°(=(360° / m)×3=(360°⁄4)×3)

[0094] Da D G(a-b) =100° and D G(a-c) =180°, the above conditions are met. On the other hand, in patterns E and FD E(a-b) =90°, 90° <D E(a-b) is not fulfilled, D F(a-b) =120°, and D F(a-b)<120° is not met. Since these conditions are met, pattern G is not better suited for four-phase control, but is better suited for three-phase control than pattern E, and is not better suited for three-phase control, but is better suited for four-phase control than pattern F.

[0095] The switching element whose on / off control should be stopped at the time of three-phase control based on pattern F can be determined as follows. As shown in Fig. 25, in pattern F the phase difference D F(a-c) between the SW 36a and the SW 36c 240°, the phase difference D F(b-d) between the SW 36b and the SW 36d is 180°, the phase difference D F(c-a) between the SW 36c and the SW 36a is 120°, and the phase difference D F(d-b) between the SW 36d and the SW 36b is 180°. Of these four phase differences, the phase difference D F(c-a)a minimum value. The switching element whose on / off control is to be stopped is SW 36d, which is switched on between SW 36c and SW 36a, which define the minimum phase difference. The phase differences when the on / off control of SW 36d is stopped at the time of three-phase control are D F(a-b) =D F(b-c) =D F(c-a) =120°, and it is possible to reduce the ripple current of the output current IT in a three-phase drive based on pattern F.

[0096] The switching element whose on / off control should be stopped at the time of three-phase control based on pattern G can be determined as follows. The phase difference D G(a-c) between the SW 36a and the SW 36c is 180°, the phase difference D G(b-d) between the SW 36b and the SW 36d is 160°, the phase difference D G(c-a)between the SW 36c and the SW 36a is 180°, and the phase difference D G(d-b) between the SW 36d and the SW 36b is 200°. Of these phase differences, the phase difference D G(b-d) a minimum value. The switching element whose on / off control is to be stopped is SW 36c, which is switched on between SW 36b and SW 36d, which define the minimum phase difference. The phase differences when the on / off control of SW 36c is stopped at the time of three-phase control are D G(a-b) =D G(d-a) =100°and D G(b-d )=160°.

[0097] For example, if the on / off control of SW 36a is stopped at the time of three-phase control based on pattern G, the maximum value of the phase differences between two switching elements that are sequentially turned on is D G(d-b)=200°. When the on / off control of SW 36b is stopped at the time of three-phase control based on pattern G, the maximum value of the phase differences between two switching elements that are sequentially turned on is D G(a-c) =180°. If the on / off control of the SW 36d is stopped at the time of three-phase control based on pattern G, the maximum value of the phase differences between two switching elements that are sequentially switched on is D G(c-a) =180°. The absolute value of the difference between D G(d-b) and 120° is 80°. The absolute value of the difference between D G(a-c) and 120° is 60°. The absolute value of the difference between D G(c-a) and 120° is 60°. On the other hand, if the on / off control of SW 36c is stopped at the time of three-phase control, the maximum value of the phase differences D G(b-d) =160°, and the absolute value of the difference between D G(b-d)and 120° is 40°. As described above, if the on / off control of SW 36c is stopped at the time of three-phase control, the absolute value decreases and is suitable for three-phase control.

[0098] For example, in the sixth modified example, as in Fig. 18, pattern E may be selected as the phase pattern when the determination result of step S5c is YES, the phase pattern may be switched to pattern G when the determination result of step S5d is YES, and pattern F may be selected when the determination result of step S5d is NO. Seventh modified example Pattern H to J, m=6, n=4

[0099] Fig. 26 is a diagram illustrating a circuit configuration of an FDC 20B according to a seventh modified example. The FDC 20B includes six-phase converter circuits 20a to 20f. The converter circuit 20e includes a reactor 21e, a current sensor 22e, and an IPM 23e. The IPM 23e includes an SW 36e and a diode 37e. The converter circuit 20f includes a reactor 21f, a current sensor 22f, and an IPM 23f. The IPM 23f includes an SW 36f and a diode 37f. In the seventh modified example, the single-phase drive is sequentially switched to the six-phase drive with an increase in the input current of the FDC 20B, but the invention is not limited to this, and for example, the drive may be switched in the order of two-phase drive, four-phase drive, and six-phase drive, or may be switched in the order of at least four-phase drive and six-phase drive.

[0100] Fig. Figure 27 is a diagram illustrating phases and phase differences of patterns H to J. The phases of SWs 36a to 36f in pattern H are 0°, 60°, 120°, 180°, 240°, and 300°, respectively. The phases of SWs 36a to 36f in pattern I are 0°, 45°, 90°, 180°, 270°, and 315°, respectively. The phases of SWs 36a to 36f in pattern J are 0°, 80°, 130°, 180°, 260°, and 310°, respectively. The phase differences in pattern H are D H(a-b) =D H(b-c) =D H(c-d) =D H(d-e) =D H(e-f) =D H(f-a) =60°. The phase differences in pattern I are D I(a-b) =D I(b-c) =D I(e-f) =D I(f-a) =45° and D I(c-d) =D I(d-e) =90°. The phase differences in pattern J are D J(a-b) =D J(d-e) =80° and D J(b-c) =D J(c-d) =D J(e-f) =D J(f-a) =50°.

[0101] Which of the patterns H to J is suitable for four-phase driving can be determined as follows. All phase differences in pattern H are 60°, and their maximum value is 60°. The maximum value of the phase differences in pattern I is 90°. The maximum value of the phase differences in pattern J is 80°. The absolute value of a difference between the maximum value and 90° in pattern H is 30°. The absolute value of a difference between the maximum value and 90° in pattern I is 0°. The absolute value of a difference between the maximum value and 90° in pattern J is 10°. Here, 90° is a value calculated from 360° / n=360° / 4 and is a phase difference at which the ripple current is minimized at the time of four-phase driving. The absolute value is smallest in pattern I and largest in pattern H.Accordingly, pattern H is best suited for six-phase control, pattern I is best suited for four-phase control, and pattern J is not better suited for six-phase control but is better suited for four-phase control than pattern H, and is not better suited for four-phase control but is better suited for six-phase control than pattern I.

[0102] In pattern J, the maximum value D satisfies J(a-b) the phase differences the following conditions. 60°(=360° / m=360° / 6) <DJ(a−b)<90°(=360° / n=360° / 4) DJ(a−b) <DJ(a−c)<180°(=(360° / m)×3=(360°⁄6)×3)

[0103] Da D J(a-b) =80° and D J(a-c) =130°, the above conditions are met. On the other hand, in the patterns H and ID H(a-b) =60°, 60° <D H(a-b) is not fulfilled, D I(c-d) =90°, and D I(c-d)<90° is not met. Since these conditions are met, Pattern J is not better suited for six-phase control, but is better suited for four-phase control than Pattern H, and is not better suited for four-phase control, but is better suited for six-phase control than Pattern I.

[0104] The switching elements whose on / off control should be stopped at the time of four-phase control based on Pattern I can be determined as follows. As in Fig. 27, in pattern I the phase difference D I(a-c) between the SW 36a and the SW 36c 90°, the phase difference D I(b-d) between the SW 36b and the SW 36d is 135°, the phase difference D I(c-e) between the SW 36c and the SW 36e is 180°, the phase difference D I(d-f) between the SW 36d and the SW 36f is 135°, the phase difference D I(e-a)between the SW 36e and the SW 36a is 90°, and the phase difference D I(f-b) between the SW 36f and the SW 36b is 90°. Of these phase differences, three phase differences D I(a-c) , D I(e-a) and D I(f-b) the same minimum value.

[0105] According to the above method, in the six-phase drive, the switching elements whose on / off control is to be stopped at the time of four-phase drive based on Pattern I are three switching elements, including SW 36b turned on between SW 36a and SW 36c, SW 36f turned on between SW 36e and SW 36a, and SW 36a turned on between SW 36f and SW 36b. Here, SWs 36a and 36b, or SWs 36f and 36a, are a combination in which they are sequentially turned on at the time of six-phase drive. Accordingly, when the on / off control of SWs 36a and 36b is stopped at the time of four-phase drive, the phase difference between SW 36f and SW 36c, which is subsequently turned on, increases.Similarly, when the on / off control of SWs 36f and 36a is stopped, the phase difference between SW 36e and SW 36b, which is subsequently turned on, increases. Accordingly, since the switching elements whose on / off control is to be stopped at the time of four-phase driving are the switching elements, the on / off control of SWs 36b and 36f, which are not the combination of two switching elements sequentially turned on at the time of six-phase driving, is stopped. By stopping the on / off control of SWs 36b and 36f at the time of four-phase driving, the phase differences are all 90° in four-phase driving based on pattern I, and it is possible to attenuate the ripple current of the output current IT.

[0106] The switching elements whose on / off control should be stopped at the time of four-phase control based on pattern J can be determined as follows. As shown in Fig. 27, in pattern J the phase difference D J(a-c) between the SW 36a and the SW 36c 130°, the phase difference D J(b-d) between the SW 36b and the SW 36d is 100°, the phase difference D J(c-e) between the SW 36c and the SW 36e is 130°, the phase difference D J(d-f) between the SW 36d and the SW 36f is 130°, the phase difference D J(e-a) between the SW 36e and the SW 36a is 100°, and the phase difference D J(f-b) between the SW 36f and the SW 36b is 130°. Of these phase differences, two phase differences D J(b-d) and D J(e-a)the same minimum value. Accordingly, the switching elements whose on / off control should be stopped are SW 36c, which is turned on between SW 36b and SW 36d, which define the minimum phase difference, and SW 36f, which is turned on between SW 36e and SW 36a. Here, in Pattern J, unlike Pattern I, SW 36c and SW 36f are not two switching elements that are sequentially turned on at the time of six-phase driving. Accordingly, by stopping the on / off control of SW 36c and SW 36f at the time of four-phase driving based on Pattern J, it is possible to attenuate the ripple current in four-phase driving. Accordingly, the phase differences at the time of four-phase driving based on Pattern JD are J(a-b) =D J(d-e) =80° and D J(b-d) =D J(e-a)=100°. In this case, it is possible to further reduce the ripple current compared to the case where a combination of two switching elements other than the combination of SWs 36c and 36f is stopped.

[0107] At the time of four-phase driving based on Pattern H, only any two switching elements other than two switching elements that are sequentially turned on at the time of six-phase driving need to be stopped from SWs 36a to 36f. This is because all phase differences in Pattern H are equal.

[0108] For example, in the seventh modified example, as in Fig. 18, pattern H may be selected when the determination result of step S5c is YES, pattern J may be selected when the determination result of step S5d is YES, and pattern I may be selected when the determination result of step S5d is NO.

[0109] In the seventh modified example, switching elements other than the combination of two switching elements sequentially turned on at the time of six-phase driving are identified as the switching elements whose on / off control should be stopped at the time of four-phase driving based on Pattern 1. However, since the on / off control of only a single switching element can be stopped at the time of two-phase driving in the FDC 20, which is of a three-phase type as in the above embodiment, the above consideration is unnecessary. Since the on / off control of only a single switching element can be stopped at the time of three-phase driving in the FDC 20A, which is of a four-phase type as in the sixth modified example, the above consideration is unnecessary. That is, when (mn)=1, the above consideration is unnecessary.

[0110] In pattern I of the seventh modified example, three phase differences D I(a-c) , D I(e-a) and D I(f-b) from D I(a-c) , D I(b-d) , D I(c-c) , D I(d-f) , D I(e-a) and D I(f-b) have the same minimum value, but are not limited to the same value. For example, if the phase difference D I(a-c) of these phase differences is the minimum, the phase difference D I(f-b) is the second minimum and the phase difference D I(e-a) the third minimum, it is assumed that the on / off control of SWs 36a and 36b is stopped, since D I(a-c) is the minimum and D I(f-b) is the second minimum. However, since these two switching elements correspond to two switching elements that are sequentially turned on at the time of six-phase control, the on / off control of SWs 36b and 36f is based on the smaller phase difference D I(e-a) which does not contain any of the minimum phase differences DI(a-c) and D I(f-b) is stopped.

[0111] In pattern J, two phase differences D J(b-d) and D J(e-a) have the same minimum value, but are not limited to the same value.

[0112] In the embodiment and the modified examples, the case where the converter circuits 20a to 20c are provided with three phases, the case where the converter circuits 20a to 20d are provided with four phases, and the case where the converter circuits 20a to 20f are provided with six phases have been described, but the number of phases of the converter circuits is not limited thereto.

[0113] In the embodiment and modified examples, a boost converter was described as an example; however, a buck converter, a boost / buck converter, or a bidirectional converter may also be used. In the embodiment and modified examples, an example in which one switching element is provided for each single-phase converter circuit was described, but the invention is not limited to this, and multiple switching elements may also be provided for each single-phase converter circuit.For example, as in a bidirectional converter in which two switching elements are provided for each phase, a configuration may be adopted in which on / off control of one switching element is performed and the other switching element is maintained normally on or normally off in a boost mode, and one switching element is maintained normally off or normally on and on / off control of the other switching element is performed in a buck mode. When the operation of a converter circuit in which multiple switching elements are provided in this manner is stopped, the on / off control of all its switching elements is stopped and kept off. When the converter circuit is driven, the on / off control of at least one switching element is performed.

[0114] In the embodiment and modified examples, the ECU 4, which comprehensively controls the vehicle-mounted fuel cell system 1 as a whole, was described as an example of a control device that controls the FDC 20; but the invention is not limited to this, and, for example, a computer provided separately from the ECU 4, which controls the FDC 20, and which includes a CPU, a ROM, and a RAM may be used.

[0115] In the embodiment and modified examples, the vehicle-mounted fuel cell system 1 was described as an example of a power supply system, but the invention is not limited to this, and a stationary fuel cell system may also be used. For example, in a stationary fuel cell system, a predicted power value may be predicted depending on seasons in which an amount of generated power or a power generation time of a fuel cell varies.For example, in fuel cell systems for commercial facilities, it is considered that the amount of power generated in the fuel cell increases during the day due to refrigeration or the like, and the predicted power value of the FDC increases in summer, and the amount of power generated in the fuel cell increases at night due to a heating mechanism or the like, and the predicted power value of the FDC increases in winter. In a fuel cell system for residential facilities, a pattern may be selected based on historical information about a time when control is executed in n-phase drive and a time when control is executed in m-phase drive.In such a residential fuel cell system, the drive mode can be switched to a normal drive mode or a quiet mode, in which the amount of generated electric power is reduced compared to the normal drive mode, to reduce noise at night, either manually by a user or automatically. For example, in this case, as shown in . Fig. 14, pattern A can be selected while the FDC is stopped when the normal mode is selected, and pattern B can be selected while the FDC is stopped when the quiet mode is selected.

[0116] In the above embodiment, the FC 10, which is a solid polymer fuel cell, is used as the power supply, however, a fuel cell other than a solid polymer fuel cell may be used, or a secondary battery such as a lithium-ion battery or a nickel-hydride battery may be used.

[0117] Although an embodiment of the invention has been described in detail above, the invention is not limited to such a specific embodiment and may be modified in various forms without departing from the spirit of the invention as described in the appended claims.

Claims

[1] Control device (4) for a multi-phase converter (20) having converter circuits (20a to 20c) of m (where m is an integer of at least 3) phases, each of which comprises a switching element (36a to 36c) and which are connected in parallel to one another, the control device (4) comprising: a controlled-phase number control unit configured to increase the number of controlled phases of the converter circuits (20a to 20c) by increasing the number of switching elements (36a to 36c) on which on / off control is performed as a current value input to the multi-phase converter (20) increases, and to control the multi-phase converter (20) in n-phase drive where the number of controlled phases is n (where n is an integer less than m and at least 2 and is an integer that is not a divisor of m), or in m-phase drive where the number of controlled phases is m; a storage unit configured to store first and second patterns which are phase patterns in which on-times of the switching elements of m phases are defined; a selection unit configured to select the first or second pattern while the multiphase converter (20) has been stopped; an on / off control unit configured to perform on / off control on the switching elements of the plurality of driven phases based on the phases set in the selected first or second pattern under a condition that a period and a duty ratio are substantially equal; and a prediction unit configured to predict a correlation value that correlates with a time ratio that is, in a predetermined time, a ratio of a time for which the execution of a control in the m-phase drive is predicted to a time for which the execution of a control in the n-phase drive is predicted, wherein an absolute value of a difference between a maximum value of a phase difference between two switching elements set to be sequentially turned on in the n-phase drive based on the second pattern and 360° / n is smaller than an absolute value of a difference between a maximum value of a phase difference between two switching elements set to be sequentially turned on in the n-phase drive based on the first pattern and 360° / n, wherein the selection unit is configured to select the first pattern if the predicted correlation value indicates that the time ratio is at least as large as a first threshold, and to select the second pattern if the predicted correlation value indicates that the time ratio is smaller than a second threshold which is at most as large as the first threshold, wherein the on / off control unit is arranged to stop the on / off control on the switching elements of (mn) phases in the n-phase drive based on the second pattern, wherein the switching elements are classified into a plurality of combinations such that each of the combinations is composed of three switching elements which are determined to be sequentially turned on in the m-phase drive based on the second pattern, wherein, when (mn)=1, the switching element of the (mn) phase at which the on / off control was stopped in the n-phase drive based on the second pattern is the switching element that is switched on between the switching element that is switched on first and the switching element that is switched on last, out of the three switching elements in a combination having a phase difference that is the smallest among the plurality of combinations, the phase difference being a phase difference between the switching element that is switched on first and the switching element that is switched on last, and wherein, when (mn)≥2, the switching elements of (mn) phases at which the on / off control was stopped in the n-phase drive based on the second pattern are switching elements other than a combination of two switching elements set to be sequentially turned on in the m-phase drive based on the second pattern, and each turned on between the switching element that is turned on first and the switching element that is turned on last among the three switching elements in a corresponding one of (mn) combinations among the plurality of combinations, the (mn) combinations being selected in ascending order of the phase difference between the switching element that is turned on first and the switching element that is turned on last. [2] Control device (4) according to claim 1, wherein the second threshold value is equal to the first threshold value. [3] Control device (4) according to claim 1, wherein the second threshold value is smaller than the first threshold value, wherein the storage unit is arranged to store a third pattern which is a phase pattern in which on-times of the m switching elements are set and which is not the first and second patterns, wherein the selection unit is configured to select the first pattern while the multiphase converter (20) has been stopped if the predicted correlation value indicates that the time ratio is at least as large as the first threshold, to select the second pattern while the multiphase converter (20) has been stopped if the predicted correlation value indicates that the time ratio is less than the second threshold, and to select the third pattern while the multiphase converter (20) has been stopped if the predicted correlation value indicates that the time ratio is less than the first threshold and at least as large as the second threshold, wherein an absolute value of a difference between a maximum value of a phase difference between two switching elements set to be sequentially turned on in the n-phase drive based on the third pattern and 360° / n is greater than an absolute value of a difference between a maximum value of a phase difference between two switching elements set to be sequentially turned on in the n-phase drive based on the second pattern and 360° / n, and is smaller than the absolute value of the difference between the maximum value of the phase difference between two switching elements set to be sequentially turned on in the n-phase drive based on the first pattern and 360° / n, wherein the on / off control unit is arranged to stop the on / off control on the switching elements of (mn) phases in the n-phase drive based on the third pattern, wherein the switching elements are classified into a plurality of combinations such that each of the combinations is composed of three switching elements which are determined to be sequentially turned on in the m-phase drive based on the third pattern, wherein, when (mn)=1, the switching element of the (mn) phase at which the on / off control was stopped in the n-phase drive based on the third pattern is the switching element that is switched on between the switching element that is switched on first and the switching element that is switched on last, out of the three switching elements in a combination having a phase difference that is the smallest among the plurality of combinations, the phase difference being a phase difference between the switching element that is switched on first and the switching element that is switched on last, and wherein, when (mn)≥2, the switching elements of (mn) phases at which the on / off control was stopped in the n-phase drive based on the third pattern are switching elements other than a combination of two switching elements set to be sequentially turned on in the m-phase drive based on the third pattern, and each turned on between the switching element that is turned on first and the switching element that is turned on last among the three switching elements in a corresponding one of (mn) combinations among the plurality of combinations, the (mn) combinations being selected in ascending order of the phase difference between the switching element that is turned on first and the switching element that is turned on last. [4] The control device (4) according to any one of claims 1 to 3, wherein, among the first, second, and third switching elements which are sequentially turned on in the m-phase drive based on at least one of the first and second patterns, a phase difference between the first switching element and the second switching element is greater than 360° / m and less than 360° / n, and a phase difference between the first switching element and the third switching element is less than (360° / m)×3. [5] The control device (4) according to any one of claims 1 to 4, further comprising a route acquisition unit configured to acquire travel route planning information about a planned travel route of a vehicle traveling using a battery that supplies an input current to the multi-phase converter (20) as a power source, wherein the prediction unit is configured to predict a predicted current value that the battery predictively supplies to the multi-phase converter (20) as the predicted correlation value based on the travel route planning information. [6] The control device (4) according to any one of claims 1 to 5, further comprising a history acquisition unit configured to acquire history information about a time when control is executed in the n-phase drive and a time when control is executed in the m-phase drive, wherein the prediction unit is configured to predict the correlation value based on the history information. [7] The control device (4) according to any one of claims 1 to 6, further comprising a traveling mode detecting unit configured to detect traveling mode information about a traveling mode of a vehicle traveling using a battery that supplies an input current to the multi-phase converter (20) as a power source, wherein the predicting unit is configured to predict the predicted correlation value based on the traveling mode information. [8] Multiphase converter system comprising: the control device (4) according to one of claims 1 to 7; and the multiphase converter (20). [9] Power supply system comprising: the multiphase converter system according to claim 8; and a power supply adapted to supply an input current to the multiphase converter (20). [10] A power supply system according to claim 9, wherein the power supply is a fuel cell (10).

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