JP2013169074A - Method and device for controlling converter, and fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent variations in current value passing through a converter while a drive phase number is changed, in the converter of a fuel cell.SOLUTION: A method for controlling a converter, includes the steps of: when changing the number of drive phases, equally dividing a total current command value At of the whole of the converter by the changed number of drive phases to calculate a target current value Af of the drive phase; calculating a current deviation ΔAfb as a difference between the target current value Af and a current command value before the phase change, for each phase; setting the phase of which the calculated current deviation ΔAfb becomes maximum, to a maximum deviation phase Dm; setting a current command value Am of the maximum deviation phase Dm so that it comes close to the target current value Af at a predetermined change speed; and setting current command values An of the other phases Dn other than the maximum deviation phase Dm to a value obtained by subtracting the current command value Am of the maximum deviation phase Dm from the total current command value At and equally dividing the resulting value by the number of the other phases Dn.

Description

  The present invention relates to a control method for a multi-phase converter for adjusting an output voltage of a fuel cell, a converter control device, and a fuel cell system.

  A so-called fuel cell vehicle is equipped with a fuel cell system including a fuel cell that generates electricity by electrochemically reacting a fuel gas and an oxidizing gas. In the fuel cell system, a DC / DC converter that adjusts an output voltage of a large amount of power generated by the fuel cell is provided between the fuel cell and the load.

  The DC / DC converter has a plurality of phases, and appropriately changes the number of drive phases according to the electric power passing therethrough. The number of drive phases is changed by newly driving or stopping the phases with a predetermined priority (see Patent Document 1).

JP 2009-158204 A

  However, in the control of the DC / DC converter at the time of changing the number of driving phases described above, for example, the current command value of the phase in which driving is started or stopped (switching phase) is changed, and the current command values of the other driving phases are changed. Maintained constant. As a result, while changing the number of drive phases, the total current command value of the entire DC / DC converter varies, and the current value passing through the DC / DC converter varies. The fluctuation of the current value passing through the DC / DC converter is not intended by, for example, a control device that controls the output of the entire fuel cell system, and is not preferable in controlling the output power of the fuel cell supplied to the load.

  The present invention has been made in view of such a point, and an object thereof is to prevent the current value passing through the converter from fluctuating during the change of the number of drive phases.

  In order to achieve the above object, the present invention provides a control method for controlling a multi-phase converter for adjusting the output voltage of a fuel cell, and the total current command value of the entire converter when the number of drive phases is changed. The target current value and the number of phases are calculated for the process of calculating the target current value of the drive phase by equally dividing the drive phase number after the change and the phase that is driven either before or after the change of the drive phase number. A step of calculating a current deviation that is a difference from the current command value, a step of setting a phase having the maximum calculated current deviation as a maximum deviation phase, and a current change of the current command value of the maximum deviation phase with a predetermined change Subtracting the current command value of the maximum deviation phase from the total current command value by subtracting the current command value of the phase other than the maximum deviation phase from the step of setting the speed so as to approach the target current value. A step of setting the value equally divided by the number of phases of the converter It is a control method.

  According to the present invention, the current command value of the maximum deviation phase during the change of the number of drive phases is set, the current command value of the other phase is subtracted from the total current command value, Since the values are equally divided by the number of phases, it is possible to prevent the total current command value of the converter from fluctuating during the change of the number of drive phases. Therefore, it is possible to prevent the current value passing through the converter from fluctuating.

  The maximum deviation phase may be fixed while changing the number of drive phases in which the current command value of the maximum deviation phase is close to the target current value.

  In the converter control method, when the total current command value of the whole converter is changed during the change of the number of drive phases, the new total current command value of the whole converter is equally divided by the number of drive phases after the change. A step of calculating a new target current value of the driving phase, a step of setting the current command value of the maximum deviation phase so as to be close to the target current value at a predetermined change rate, and the steps other than the maximum deviation phase And subtracting the current command value of the maximum deviation phase from the new total current command value and setting the current command value of the other phase equally by the number of phases of the other phase. May be.

  Another aspect of the present invention is a control device that controls a multi-phase converter for adjusting the output voltage of a fuel cell, and when the number of drive phases is changed, the total current command value of the entire converter is changed. Means to calculate the target current value of the drive phase by equally dividing by the number of drive phases and the current command before the target current value and the phase number change for the phase driven either before or after the change of the drive phase number A means for calculating a current deviation which is a difference from the value, a means for setting a phase where the calculated current deviation is maximum as a maximum deviation phase, and a current command value of the maximum deviation phase at a predetermined change rate. A means for setting the current value to be close to the current value, and a current command value of a phase other than the maximum deviation phase by subtracting the current command value of the maximum deviation phase from the total current command value Means for setting the value equally divided by A.

  The maximum deviation phase may be fixed while changing the number of drive phases in which the current command value of the maximum deviation phase is close to the target current value.

  When the total current command value of the entire converter is changed during the change of the number of drive phases, the control device of the converter equally divides the total current command value of the new whole converter by the number of drive phases after the change. Means for calculating a new target current value of the drive phase, means for setting the current command value of the maximum deviation phase so as to be close to the target current value at a predetermined change rate, and the other than the maximum deviation phase Means for subtracting the current command value of the maximum deviation phase from the new total current command value and equally dividing the current command value of the other phase by the number of phases of the other phase. May be.

  Another aspect of the present invention is a fuel cell system including the control device for the converter.

  According to the present invention, it is possible to prevent the current value passing through the converter from fluctuating while changing the number of drive phases.

It is a block diagram which shows the structure of the electric power system of the fuel cell vehicle carrying a fuel cell system. It is a flowchart of the control method of a 1st converter. It is explanatory drawing which shows an example of the fluctuation | variation of the electric current command value of each phase of the 1st converter at the time of a drive phase number increase. It is explanatory drawing which shows an example of the fluctuation | variation of the electric current command value of each phase of the 1st converter at the time of a drive phase number reduction. It is a flowchart of the control method of the 1st converter when total current command value fluctuates during the number of drive phases change. It is explanatory drawing which shows an example of the fluctuation | variation of the electric current command value of each phase of a 1st converter when the total electric current command value fluctuates during the drive phase number change.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows functional blocks of a power system of a fuel cell vehicle 1 equipped with a fuel cell system 10 according to this embodiment.

  The fuel cell vehicle 1 equipped with the fuel cell system 10 includes, for example, a fuel cell (FC) 20 that generates power by an electrochemical reaction between an oxidizing gas and a fuel gas, and an output voltage of the power generated by the fuel cell 20 DC / DC converter (FDC) 30 (hereinafter referred to as first converter 30), a battery (BATT) 40 serving as a chargeable / dischargeable auxiliary power source, and a DC / DC converter (step-up / step-down of the output voltage of battery 40) BDC) 50 (hereinafter referred to as second converter 50) and a traction inverter (INV) that converts DC power into AC power (for example, three-phase AC) and supplies power to a traction motor (M) 60 that is a load. 70 and a main control unit (ECU) 80.

  The fuel cell 20 is, for example, a polymer electrolyte fuel cell, and has a stack structure in which a large number of single cells are stacked. The single cell includes an air electrode formed on one surface of an electrolyte membrane made of an ion exchange membrane, a fuel electrode formed on the other surface of the electrolyte membrane, and a pair of separators that sandwich the air electrode and the fuel electrode from both sides. Have

  The first converter 30 is a direct-current voltage converter for a fuel cell, and can raise and lower the output voltage of the fuel cell 20 to a predetermined direct-current voltage and supply it to the traction inverter 70. The first converter 30 has a plurality of phases, for example, a U phase, a V phase, a W phase, and an X phase, and operates with a predetermined number of phases according to the passing power. Note that the U phase, V phase, W phase, and X phase are preferentially driven in this order. The first converter 30 includes a general converter circuit including, for example, a transistor as a switching element, a reactor, a smoothing capacitor, and a diode as a rectifying element.

  The first converter 30 includes a control unit 31, for example. The control unit 31 is a control device including a CPU, a ROM, a RAM, and an input / output interface. Based on the output command value of the fuel cell 20 from the main control unit 80, the number of driving phases and the phase of each phase of the first converter 30 are controlled. The current command value can be controlled. In the present embodiment, the control unit 31 corresponds to a converter control device.

  The battery 40 is a power storage device that functions as a surplus power storage source, a regenerative energy storage source during regenerative braking, and an energy buffer during load fluctuations associated with acceleration or deceleration of the fuel cell vehicle 1. A cadmium storage battery, a nickel / hydrogen storage battery, a lithium secondary battery, or the like is preferable.

  The second converter 50 can charge the battery 40 by lowering the surplus power of the fuel cell 20 or the regenerative power collected by the traction motor 60.

  The traction inverter 70 can control the rotational torque of the traction motor 60 by converting DC power supplied from either or both of the fuel cell 20 and the battery 40 into AC power (for example, three-phase AC). The traction motor 60 is, for example, a three-phase AC motor, and generates a driving propulsion force when the vehicle is traveling, and functions as a motor generator when the vehicle is braked, and can convert kinetic energy into electric energy and recover regenerative power.

  The main control unit 80 is a control device including a CPU, a ROM, a RAM, and an input / output interface, and controls the operation of the fuel cell 20 and an on-vehicle power converter (for example, the first converter 30, the second converter 50, and the traction inverter). 70) and the like.

  Next, a method for controlling the first converter 30 will be described. The control of the first converter 30 is executed by the control unit 31. FIG. 2 shows a flowchart of such a control method.

  First, during operation of the fuel cell system 10, the output command value of the fuel cell 20, that is, the voltage command value and the current command value are output from the main control unit 80 to the control unit 31 of the first converter 30. In the control unit 31, the drive phase number N of the first converter 30 is determined accordingly (step S1 in FIG. 2). When the drive phase number N is changed, the total current command value At of the first converter 30 (current command value output from the main control unit 80) is equally divided by the changed drive phase number N. Then, the target current value Af of the drive phase is calculated (step S2 in FIG. 2). Next, a current deviation ΔAfb that is a difference (absolute value) between the target current value Af and the current command value Ab before the phase change is calculated for the phase driven either before or after the change of the number of drive phases ( Step S3 in FIG. The current deviation ΔAfb of each phase is compared, and the phase having the maximum current deviation ΔAfb is set as the maximum deviation phase Dm (step S4 in FIG. 2). In addition, when there are a plurality of maximal phases, priority is set in the order of the U phase, the V phase, the W phase, and the X phase, which are driving orders. Next, the current command value Am of the maximum deviation phase Dm is set so as to approach the target current value Af at a predetermined change speed R (step S5 in FIG. 2). Then, the current command value An of the phase Dn other than the maximum deviation phase Dm is obtained by subtracting the current command value Am of the maximum deviation phase Dm from the total current command value At and equally dividing it by the number of phases of the other phase Dn. (Step S6 in FIG. 2).

  FIG. 3 shows a variation example of the current command value of each phase when the number of phases increases. For example, when the total current command value At of the entire first converter 30 is 150 A and the drive phase number N is changed from two phases to three phases (when W-phase drive is started), first the total 50A (= 150A / 3 (phase)), which is the target current value Af for the U phase, V phase, and W phase, is calculated by equally dividing 150 A of the current command value At by the number of drive phases after the change. . Then, the current deviation ΔAfb of each phase is calculated, the U phase is 25A (= | 50A-75A |), the V phase is 25A (= | 50A-75A |), and the W phase is 50A (= | 0A−). 50A |). As a result, the maximum deviation phase Dm is set to the W phase. Next, a change rate R of the W-phase current command value Am, which is the maximum deviation phase Dm, is set. After that, when the W-phase current command value Am fluctuates at a predetermined change rate R, the current command value An of the other phase Dn (U-phase, V-phase) is changed from the total current command value At to the W-phase current command. The value Am is subtracted and set to a value ((150A−current command value Am) / 2) equally divided by the number of phases 2 of the other phases Dn. As a result, the total current command value At obtained by adding the current command values of the U-phase, V-phase, and W-phase during the change of the number of drive phases is always 150A.

  When the drive phase number change is started and the current command values Am and An of the W phase, the U phase, and the V phase become 50 A, which is the target current command value Af, the drive phase number change is completed.

  As another specific example, FIG. 4 shows a variation example of the current command value of each phase when the number of phases decreases. For example, when the total current command value At of the entire first converter 30 is 150 A and the number of drive phases N is changed from three phases to two phases (when driving of the W phase is stopped), first, the total 75A (= 150 A / 2 (phase)), which is the target current value Af for the U phase and V phase, is calculated by equally dividing 150 A of the current command value At by the number of drive phases 2 after the change. The target current value Af for the W phase to be stopped is necessarily 0 A. Next, the current deviation ΔAfb of each phase is calculated, the U phase is 25A (= | 50A-75A |), the V phase is 25A (= | 50A-75A |), and the W phase is 50A (= | 50A−). 0A |). As a result, the maximum deviation phase Dm is set to the W phase. Next, a change rate R of the W-phase current command value Am, which is the maximum deviation phase Dm, is set. After that, when the W-phase current command value Am fluctuates at a predetermined change rate R, the current command value An of the other phase Dn (U-phase, V-phase) is changed from the total current command value At to the W-phase current command. The value Am is subtracted and set to a value ((150A−current command value Am) / 2) equally divided by the number of phases 2 of the other phases Dn. As a result, the total current command value At obtained by adding the current command values of the U-phase, V-phase, and W-phase whose number of phases is being changed is always 150A.

  When the drive phase number change is started and the current command values Am and An of the W phase, the U phase, and the V phase become 75A and 0A, which are the target current command values Af, the drive phase number change is completed.

  According to the present embodiment, the current command value Am of the maximum deviation phase Dm during the change of the number of drive phases is set, and the current command value An of the other phase Dn is changed from the total current command value At to the current of the maximum deviation phase Dm. Since the command value Am is subtracted to obtain a value equally divided by the number of phases of the other phase Dn, it is possible to prevent the total current command value At of the first converter 30 from changing during the change of the number of drive phases. Therefore, it is possible to prevent the current value passing through the first converter 30 from fluctuating.

  Incidentally, the total current command value At of the entire first converter 30 may be intentionally changed during the above-described change in the number of drive phases. In such a case, if the process of setting the maximum deviation phase Dm is performed, the maximum deviation phase Dm may change. If the maximum deviation phase Dm is changed and the current command values Am and An of each phase are reset based on the maximum deviation phase Dm, the current command values Am and An may fluctuate rapidly and discontinuously. In order to avoid this, the maximum deviation phase Dm may be fixed while the number of drive phases is being changed. FIG. 5 shows a flowchart of the control method of the first converter 30 in such a case.

  When the total current command value At of the entire first converter 30 is changed during the change of the drive phase number, the new total current command value At of the entire first converter 30 is changed to the drive phase number N after the change, etc. Thus, a new target current value Af is calculated (step S7 in FIG. 2). Next, the current command value Am of the maximum deviation phase Dm is set to be close to the target current value Af at a predetermined change speed R ′ (step S8 in FIG. 2). Next, the current command value An of the phase Dn other than the maximum deviation phase Dm is equally divided by the number of phases of the other phase Dn by subtracting the current command value An of the maximum deviation phase Dm from the new total current command value At. The value is set (step S9 in FIG. 2).

  FIG. 6 shows an example of fluctuation of the current command value of each phase when the total current command value At is changed during the change of the number of drive phases. In this example, the driving phase number N is changed from three phases to two phases. For example, when the total current command value At of the entire first converter 30 is changed from 150A to 120A during the change in the number of drive phases, the total current command value At of the first converter 30 is changed to 120A. 60A (= 120A / 2) of the new target current value Af of the U phase and V phase of the drive phase is calculated by equally dividing the number of drive phases by 2. The target current value Af for the W phase to be stopped is zero. At this time, the maximum deviation phase Dm is maintained in the W phase without being changed. Next, the W-phase current command value Am that is the maximum deviation phase Dm is set so as to approach 0 A that is the target current value Af at a predetermined change speed R ′. Next, the current command value An of the other phase Dn (U phase and V phase) other than the maximum deviation phase Dm is obtained by subtracting the W phase current command value An from 120A of the total current command value At. It is set to a value ((120A−current command value Am) / 2) equally divided by equation (2). As a result, the total current command value At obtained by adding the current command values for the U phase, the V phase, and the W phase after the total current command value At is intentionally changed is always 120 A.

  In this case, since the maximum deviation phase Dm is not changed while the number of drive phases is changed, even if the total current command value At of the entire first converter 30 is intentionally changed, the current value of each phase is It is possible to prevent discontinuous and sudden fluctuations. The intentional change of the total current command value At may be performed any number of times during the change of the number of drive phases.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

  For example, the fuel cell system 10 described in the above embodiment can be mounted on various moving bodies such as ships, airplanes, and robots in addition to vehicles such as automobiles. It can also be applied to a stationary power source or the like.

  INDUSTRIAL APPLICABILITY The present invention is useful in a fuel cell converter for preventing the current value passing through the converter from fluctuating while changing the number of drive phases.

1 Fuel Cell Vehicle 10 Fuel Cell System 20 Fuel Cell 30 First Converter 31 Control Unit At Total Current Command Value Af Target Current Value ΔAfb Current Deviation Am, An Current Command Value Dm Maximum Deviation Phase Dn Other Phase

Claims (7)

A control method for controlling a multi-phase converter for adjusting an output voltage of a fuel cell,
When changing the number of drive phases,
A step of equally dividing the total current command value of the entire converter by the number of drive phases after the change, and calculating a target current value of the drive phase;
A step of calculating a current deviation that is a difference between a target current value and a current command value before the phase number change for a phase driven either before or after the change of the drive phase number;
Setting the phase with the largest calculated current deviation as the maximum deviation phase;
Setting the current command value of the maximum deviation phase so as to approach the target current value at a predetermined rate of change;
Setting a current command value of a phase other than the maximum deviation phase to a value obtained by subtracting the current command value of the maximum deviation phase from the total current command value and equally dividing by the number of phases of the other phase; A method for controlling a converter.   The method for controlling a converter according to claim 1, wherein the maximum deviation phase is fixed during a change in the number of drive phases in which the current command value of the maximum deviation phase is close to a target current value. When the total current command value of the whole converter is changed during the drive phase number change,
A step of equally dividing the total current command value of the whole new converter by the number of drive phases after the change, and calculating a new target current value of the drive phase;
Setting the current command value of the maximum deviation phase to be close to the target current value at a predetermined change rate;
The current command value of the other phase other than the maximum deviation phase is set to a value obtained by subtracting the current command value of the maximum deviation phase from the new total current command value and equally dividing by the number of phases of the other phase. The method for controlling a converter according to claim 2, further comprising: A control device for controlling a multiphase converter for adjusting an output voltage of a fuel cell,
Means for calculating the target current value of the drive phase by equally dividing the total current command value of the entire converter by the number of drive phases after the change when changing the number of drive phases;
Means for calculating a current deviation which is a difference between the target current value and the current command value before the phase number change for the phase driven either before or after the drive phase number change;
Means for setting the phase with the maximum calculated current deviation as the maximum deviation phase;
Means for setting the current command value of the maximum deviation phase to be close to the target current value at a predetermined change rate;
Means for setting the current command value of the other phase other than the maximum deviation phase to a value obtained by subtracting the current command value of the maximum deviation phase from the total current command value and equally dividing by the number of phases of the other phase; A converter control device.   5. The converter control device according to claim 4, wherein the maximum deviation phase is fixed during a change in the number of drive phases in which the current command value of the maximum deviation phase is close to a target current value. 6. When the total current command value of the whole converter is changed during the change of the number of drive phases, the new total target current value of the whole converter is equally divided by the number of drive phases after the change, and a new target of the drive phase Means for calculating a current value;
Means for setting the current command value of the maximum deviation phase to be close to the target current value at a predetermined change rate;
The current command value of the other phase other than the maximum deviation phase is set to a value obtained by subtracting the current command value of the maximum deviation phase from the new total current command value and equally dividing by the number of phases of the other phase. The converter control device according to claim 5, further comprising:   A fuel cell system comprising the converter control device according to claim 4.

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