JP5862918B2 - Multiphase converter and design method of multiphase converter - Google Patents

Description

  The present invention relates to a multiphase converter, and more particularly, to a multiphase converter including a plurality of converters.

  In fuel cell systems mounted on automobiles, various hybrid fuel cell systems with fuel cells and batteries as power sources have been proposed in order to respond to sudden load changes exceeding the power generation capacity of fuel cells. Has been.

  In the hybrid fuel cell system, the output voltage of the fuel cell is controlled by a DC-DC converter. As a DC-DC converter that performs such control, a type that performs voltage conversion by causing a switching element such as a power transistor, IGBT, or FET to perform PWM operation is widely used. The DC-DC converter is desired to further increase the speed, increase the capacity, and reduce the ripple in accordance with power saving, miniaturization, and high performance of electronic devices. In order to meet such demand, a multi-phase DC-DC converter (multi-phase DC-DC converter) in which a plurality of DC-DC converters are connected in parallel has been conventionally used (see, for example, Patent Document 1).

JP 2006-340535 A

  However, since the ripple current generated in the multi-phase DC-DC converter increases with the number of drive phases, it is necessary to select a capacitor with a large allowable amount as a capacitor for smoothing the current when designing the system. Therefore, there is a problem that it is not possible to sufficiently meet the demand for further downsizing of the capacitor.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a multiphase converter capable of reducing ripple current.

In order to solve the above problems, a multiphase converter design method according to the present invention is a multiphase converter design method using a magnetically coupled reactor, in which self-inductance of each phase is L, mutual inductance is M, and an equation ( When the coupling ratio obtained by A) is a, the first ripple current generated when a multiphase converter using a magnetically coupled reactor is used is a multiphase converter having the same number of phases that does not use magnetic coupling. The coupling factor a is set so as to be lower than the second ripple current that is generated when used.
a = M / L (A)

  As described above, the first ripple current generated when the multiphase converter using the magnetic coupling reactor is used is the second ripple current generated when the multiphase converter having the same number of phases not using the magnetic coupling is used. By setting the coupling ratio a so as to be lower than the ripple current, it is possible to design a converter having a small physique while suppressing a current lip.

  Here, in the above method, it is preferable that the coupling rate a is set so that the first ripple current is always lower than the corresponding second ripple current.

  In the above method, the coupling factor a is set so that the first ripple current is lower than the corresponding second ripple current at the system voltage at which the first ripple current is maximum. The aspect which performs is also preferable.

The multiphase converter according to the present invention is a multiphase converter using a magnetically coupled reactor, wherein the self-inductance of each phase is L, the mutual inductance is M, and the coupling ratio obtained by the equation (A) is a.
In the case of the above, the coupling ratio a is obtained when the first ripple current generated when a multiphase converter using a magnetic coupling reactor is used uses a multiphase converter having the same number of phases that does not use magnetic coupling. It is characterized by being set to be lower than the second ripple current generated in the circuit.

  According to the present invention, the ripple current can be reduced in the multiphase converter as compared with the conventional one.

It is a system configuration figure of the FCHV system concerning a 1st embodiment. It is a figure which shows the main structures of the FC converter which concerns on the same embodiment. It is a figure for demonstrating the reactor voltage and reactor current which generate | occur | produce in each phase reactor which concerns on the same embodiment. It is the map which illustrated the relationship between SW pattern which concerns on the embodiment, and each phase reactor voltage. It is the figure which showed the relationship between SW pattern which concerns on the same embodiment, and an equivalent reactor. It is a figure which shows the fluctuation pattern of each phase reactor voltage which concerns on the same embodiment. It is a figure which shows the fluctuation pattern of each phase reactor voltage which concerns on the same embodiment. It is a figure which shows the current ripple calculation formula of the reactor in each step-up ratio which concerns on the same embodiment. It is the figure which illustrated the relation between the switching state and current ripple concerning the embodiment. It is the figure which illustrated the relation between the system voltage and current ripple concerning the embodiment. It is the figure which illustrated the relation between the system voltage and current ripple concerning the embodiment. It is a system configuration figure of the FCHV system concerning a 2nd embodiment. It is a figure which shows the main structures of the FC converter which concerns on the same embodiment. It is a figure for demonstrating the reactor voltage and reactor current which generate | occur | produce in each phase reactor which concerns on the same embodiment. It is the figure which showed the relationship between SW pattern which concerns on the same embodiment, and an equivalent reactor. It is a figure which shows the fluctuation pattern of each phase reactor voltage which concerns on the same embodiment. It is a figure which shows the fluctuation pattern of each phase reactor voltage which concerns on the same embodiment. It is a figure which shows the fluctuation pattern of each phase reactor voltage which concerns on the same embodiment. It is a figure which shows the current ripple calculation formula of the reactor in each step-up ratio which concerns on the same embodiment. It is the figure which illustrated the relation between the switching state and current ripple concerning the embodiment. It is the figure which illustrated the relation between the system voltage and current ripple concerning the embodiment. It is the figure which illustrated the relation between the system voltage and current ripple concerning the embodiment.

A. First Embodiment Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of an FCHV system mounted on a vehicle according to the first embodiment. In the following description, a fuel cell vehicle (FCHV) is assumed as an example of the vehicle, but the present invention can also be applied to an electric vehicle. Further, the present invention can be applied not only to vehicles but also to various moving bodies (for example, ships, airplanes, robots, etc.), stationary power sources, and portable fuel cell systems.

A-1. Overall Configuration of System The FCHV system 100 is provided with an FC converter 2500 between the fuel cell 110 and the inverter 140, and a DC / DC converter (hereinafter referred to as a battery converter) 180 between the battery 120 and the inverter 140. .

  The fuel cell 110 is a solid polymer electrolyte cell stack in which a plurality of unit cells are stacked in series. The fuel cell 110 is provided with a voltage sensor 2510 for detecting the DC voltage Vfcmes (= Vb) of the fuel cell 110 and a current sensor 2520 for detecting the output current Ifcmes. In the fuel cell 110, the oxidation reaction of the formula (1) occurs in the anode electrode, the reduction reaction of the formula (2) occurs in the cathode electrode, and the electromotive reaction of the formula (3) occurs in the fuel cell 110 as a whole.

H ₂ → 2H ⁺ + 2e ⁻ (1)
(1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + (1/2) O ₂ → H ₂ O (3)

  The unit cell has a structure in which a MEA in which a polymer electrolyte membrane or the like is sandwiched between two electrodes, a fuel electrode and an air electrode, is sandwiched between separators for supplying fuel gas and oxidizing gas. The anode electrode is provided with an anode electrode catalyst layer on the porous support layer, and the cathode electrode is provided with a cathode electrode catalyst layer on the porous support layer.

  The fuel cell 110 is provided with a system for supplying fuel gas to the anode electrode, a system for supplying oxidizing gas to the cathode electrode, and a system for supplying coolant (all not shown). By controlling the supply amount of the fuel gas and the supply amount of the oxidizing gas according to the signal, it is possible to generate desired power.

  The FC converter 2500 plays a role of controlling the DC voltage Vb of the fuel cell 110, and converts the voltage Vb input to the primary side (input side: fuel cell 110 side) into a voltage value different from that of the primary side (step-up). Alternatively, the voltage is stepped down and output to the secondary side (output side: inverter 140 side) as a voltage Vh. Conversely, the voltage input to the secondary side is converted to a voltage different from the secondary side and converted to the primary side. It is a bidirectional voltage converter that outputs. The FC converter 2500 controls the output voltage Vb of the fuel cell 110 to be a voltage corresponding to the target output.

  The battery 120 is connected in parallel to the fuel cell 110 with respect to the load 130, and stores a surplus power storage source, a regenerative energy storage source during regenerative braking, and an energy buffer when the load fluctuates due to acceleration or deceleration of the fuel cell vehicle. Function as. As the battery 120, for example, a secondary battery such as a nickel / cadmium storage battery, a nickel / hydrogen storage battery, or a lithium secondary battery is used.

  The battery converter 180 plays a role of controlling the input voltage of the inverter 140 and has a circuit configuration similar to that of the FC converter 2500, for example. Note that a step-up converter may be employed as the battery converter 180, but a step-up / step-down converter capable of step-up and step-down operations may be employed instead, and the input voltage of the inverter 140 can be controlled. Any configuration can be adopted.

  The inverter 140 is, for example, a PWM inverter driven by a pulse width modulation method, and converts DC power output from the fuel cell 110 or the battery 120 into three-phase AC power in accordance with a control command from the controller 160, thereby obtaining a traction motor. The rotational torque of 131 is controlled.

  The traction motor 131 is the main power of the vehicle, and generates regenerative power during deceleration. The differential 132 is a reduction device that reduces the high-speed rotation of the traction motor 131 to a predetermined number of rotations and rotates the shaft on which the tire 133 is provided. The shaft is provided with a wheel speed sensor (not shown) and the like, thereby detecting the vehicle speed of the vehicle. In the present embodiment, all devices (including the traction motor 131 and the differential 132) that can operate by receiving power supplied from the fuel cell 110 are collectively referred to as a load 130.

  The controller 160 is a computer system for controlling the FCHV system 100 and includes, for example, a CPU, a RAM, a ROM, and the like. The controller 160 inputs various signals (for example, a signal representing the accelerator opening, a signal representing the vehicle speed, a signal representing the output current and output terminal voltage of the fuel cell 110) supplied from the sensor group 170, and the load. The required power of 130 (that is, the required power of the entire system) is obtained.

  The required power of the load 130 is, for example, the total value of the vehicle running power and the auxiliary machine power. Auxiliary power is the power consumed by in-vehicle accessories (humidifiers, air compressors, hydrogen pumps, cooling water circulation pumps, etc.), and equipment required for vehicle travel (transmissions, wheel control devices, steering devices, and suspensions) Power consumed by devices, etc., and power consumed by devices (air conditioners, lighting fixtures, audio, etc.) disposed in the passenger space.

  Then, the controller 160 determines the distribution of the output power between the fuel cell 110 and the battery 120, and calculates the power generation command value. When the controller 160 obtains the required power for the fuel cell 110 and the battery 120, the controller 160 controls the operations of the FC converter 2500 and the battery converter 180 so that the required power is obtained.

A-2. Configuration of FC Converter As shown in FIG. 1, the FC converter 2500 has a circuit configuration as a two-phase converter (hereinafter referred to as a U-phase converter 2500a and a V-phase converter 2500b) configured by a U-phase and a V-phase. ing.

FIG. 2 is a diagram showing a main configuration of the FC converter 2500.
FC converter 2500 is a converter including power semiconductor switching elements (hereinafter also simply referred to as “switching elements”) Tr1 and Tr2 and diodes D1 and D2. It should be noted that either a unidirectional or bidirectional converter may be adopted as the converter configuration. In the present embodiment, an IGBT (Insulated Gate Bipolar Transistor) or a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is typically applied as the power semiconductor switching element.

  Switching element Tr1 constituting U-phase converter 2500a and switching element Tr2 constituting V-phase converter 2500b are connected in series between power supply line 301 and earth line 302. One end of the U-phase reactor 308 of the U-phase converter 2500a is connected to the magnetic coupling circuit 300, and the other end is connected to the connection point of the switching element Tr1. The anode of the U-phase diode D1 is connected to a connection point between the U-phase reactor 308 and the switching element Tr1, and the cathode of the U-phase diode D1 is connected to one end of the smoothing capacitor C1 on the power supply line 301 side.

  On the other hand, one end of V-phase reactor 309 of V-phase converter 2500b is connected to magnetic coupling circuit 300, and the other end is connected to a connection point of switching element Tr2. The anode of the V-phase diode D2 is connected to a connection point between the V-phase reactor 309 and the switching element Tr2, and the cathode of the V-phase diode D2 is connected to one end of the smoothing capacitor C1 on the power supply line 301 side. A smoothing capacitor C <b> 1 that smoothes the DC voltage of the power supply line 301 and supplies it to the load 130 is connected between the power supply line 301 and the earth line 302.

  The FC converter 2500 receives a DC voltage (hereinafter referred to as a battery voltage) supplied from the fuel cell 110, boosts the battery voltage by switching control of the switching elements Tr1 and Tr2, and outputs the boosted voltage to the power supply line 301. The current (hereinafter referred to as U-phase input current I1) input from fuel cell 110 to U-phase converter 2500a is detected by current sensor A1, while the current (hereinafter referred to as V-phase converter 2500b) input from fuel cell 110 to the V-phase converter 2500b. , V-phase input current I2) is detected by current sensor A2.

FIG. 3 is a diagram for explaining a reactor voltage and a reactor current generated in the U-phase reactor 308 and the V-phase reactor 309. In FIG. 3, the self-inductance of each phase of the U phase and the V phase is L, the mutual inductance is M, and the coupling rate is a.
First, the U-phase reactor voltage V1 and the V-phase reactor voltage V2 generated at both ends of the U-phase reactor 308 and the V-phase reactor 309 are obtained by the following formulas (1) and (2).

The U-phase reactor voltage V1, V-phase reactor voltage for each equivalent reactor _L 1 eq of _V2, when expressed by _{L 2 eq} is expressed as follows (Equation (3), (4) refer).

  The controller 160 determines the boost ratio so that the required system voltage Vh is obtained according to the required power of the load 130 and the like. Then, the controller 160 controls on / off of the switching elements Tr1 and Tr2 so that the determined step-up ratio is obtained. In this way, the FC converter 2500 boosts the battery voltage Vb supplied from the fuel cell 110 to the required system voltage Vh and outputs the boosted voltage to the load 130.

  Next, the magnetic coupling circuit 300 will be described with reference to FIG. The magnetic coupling circuit 300 includes a first transformer TW1. The first transformer TW1 includes a coil 310 having one end connected to the power supply line 301, a coil 320 having one end connected to the power supply line 301, and an annular core 315 around which the coil 310 and the coil 320 are wound. That is, the coil 310 and the coil 320 are wound around the same core 315, respectively. Note that the number of turns of the coil 310 and the coil 320 is set to be the same.

  The winding direction of the coil 310 and the coil 320 around the core 315 is determined as follows. That is, when the U-phase input current I1 flows from the fuel cell 110 through the resistor R1, the direction of the current flowing through the coil 320 by the electromotive force induced by the coil 310 is determined from the fuel cell 110 through the resistor R2. The coil 310 and the coil 320 are wound around the core 315 so as to be the same as the direction in which the phase input current I2 flows.

<Ripple reduction effect of FC converter 2500>
FIG. 4 is a map illustrating the relationship between the switching state of each switching element (hereinafter referred to as SW pattern) and the U-phase reactor voltage V1 and V-phase reactor voltage V2. FIG. 5 illustrates the relationship between the SW pattern and the equivalent reactor. FIG. In FIG. 5 and the following description, the duty ratio is represented by D.
6A and 6B are diagrams showing fluctuation patterns of the U-phase reactor voltage V1 and the V-phase reactor voltage V2 according to the SW pattern shown in FIG. 4, and FIG. 6A shows a case where the boost ratio α <2, and FIG. The case where the step-up ratio α ≧ 2 is shown. In FIGS. 6A and 6B, the first to fourth switching states are denoted as 1 to 4.

  The voltage pattern applied to each phase reactor is represented by a combination of switching states 2 to 4 (= 2 to 4) when the boost ratio α <2 (see FIG. 6A), while the boost ratio α ≧ 2. Is represented by a combination of switching states 1, 3, 4 (= 1, 3, 4) (see FIG. 6B).

FIG. 7 is a diagram showing a reactor current ripple calculation formula (two-phase magnetically coupled converter) in each of the boost ratio α <2 and the boost ratio α ≧ 2, and FIG. for alpha ≧ 2 in (see FIG. 6B) is a diagram illustrating a relationship between switching states and current ripple [Delta] I _L. FIG. 7 shows a reactor current ripple calculation formula of a conventional converter (conventional converter) that does not use magnetic coupling as a comparative example. Further, although a U-phase converter is assumed in FIG. 8, it is needless to say that a V-phase converter may be used.

9 and 10, in each case coupling factor a = 0.7, and a diagram showing the relationship between the system voltage Vh and a current ripple [Delta] I _L in the case of coupling factor a = 0.44, 2-phase magnetically coupled It shows the converter current ripple [Delta] I _L by a thick solid line shows the current ripple [Delta] I _L of the conventional converter with a broken line. 9 and 10 assume the case where the battery voltage Vb supplied from the fuel cell 110 is 200 V, the reactor L is 0.2 mH, and the switching cycle Tc is 0.1 ms.

As is well known, the larger the coupling rate, the smaller the physique. Therefore, it is desirable to set the coupling rate large from the viewpoint of demand for miniaturization. However, as shown in FIG. 9 (here, a = 0.7) coupling factor a if the large setting, towards the current ripple [Delta] I _L of 2-phase magnetically coupled converter, a conventional converter current ripple [Delta] I _L Larger region (hereinafter referred to as excessive ripple current region) RA occurs.

In order to prevent the occurrence of such an excessive ripple current region RA, in the present embodiment, the maximum boosted voltage of two-phase magnetically coupled converter current ripple [Delta] I _L is the maximum (assuming a 650V here), the following formula (5), (6) as shown in (here a = 0.44) equal to the current ripple [Delta] I _L of the conventional converter (or less in) so as to coupling factor a set of.

Thus, at the maximum boost voltage of two-phase magnetically coupled converter current ripple [Delta] I _L is the maximum, equal to the current ripple [Delta] I _L of the conventional converter (or less in) so as to set the coupling factor a By determining the self-inductance L and the mutual inductance M so that the set coupling ratio a can be obtained, it is possible to design a converter with a small physique while suppressing the current lip. Thereby, it becomes possible to improve the operation efficiency of a system compared with the past. In the above-described embodiment, current ripple [Delta] I _L is the boosted voltage of two-phase magnetically coupled converter becomes maximum, equal to the current ripple [Delta] I _L of the conventional converter (or less in) so as to coupling factor a was set to, for example, 2-phase magnetically coupled converter current ripple [Delta] I _L is a good setting the coupling factor a to be below the current ripple [Delta] I _L always conventional converter (this point, examples below The form is the same).

B. Second Embodiment In the first embodiment, the FC converter 2500 including the two-phase magnetic coupling circuit 300 has been described as an example. However, the present invention can also be applied to an FC converter including a three-phase or more magnetic coupling circuit. .
FIG. 11 is a diagram showing a configuration of the FCHV system 100 ′ according to the second embodiment, and FIG. 12 is a diagram showing a main configuration of the FC converter 2500 ′ according to the second embodiment, which will be described in the first embodiment. FIG. 3 is a diagram corresponding to FIGS. 1 and 2. In addition, since the other structure is the same, the same code | symbol is attached | subjected to a corresponding part and description is omitted.

As shown in FIG. 11, the FC converter 2500 ′ according to the present embodiment includes a three-phase converter (hereinafter referred to as a U-phase converter 2500a, a V-phase converter 2500b, and a W-phase converter 2500c) configured by a U-phase, a V-phase, and a W-phase. ) As a circuit configuration.
As shown in FIG. 12, switching element Tr3 constituting W-phase converter 2500c is connected in series between power supply line 301 and earth line 302, similarly to switching element Tr1 and switching element Tr2. One end of the W-phase reactor 307 of the W-phase converter 2500c is connected to the magnetic coupling circuit 300 ′, and the other end is connected to the connection point of the switching element Tr3.

  The W-phase diode D3 is connected to a connection point between the W-phase reactor 307 and the switching element Tr3, and the cathode of the W-phase diode D3 is connected to one end of the smoothing capacitor C1 on the power supply line 301 side.

  The FC converter 2500 ′ receives the battery voltage Vb supplied from the fuel cell 110, boosts the battery voltage Vb by switching control of the switching elements Tr <b> 1, Tr <b> 2, Tr <b> 3 and outputs the boosted voltage to the power supply line 301. A current (hereinafter referred to as w-phase input current I3) input from fuel cell 110 to W-phase converter 2500c is detected by a current sensor (not shown).

FIG. 13 is a diagram for explaining the reactor voltage and the reactor current generated in the U-phase reactor 308, the V-phase reactor 309, and the W-phase reactor 307. In FIG. 13, the self-inductance of each phase of the U phase and the V phase is L, the mutual inductance is M, and the coupling rate is a.
First, U-phase reactor voltage V1, V-phase reactor voltage V2, and W-phase reactor voltage V3 generated at both ends of U-phase reactor 308 and V-phase reactor 309 are obtained by the following formulas (7) to (9).

Respectively, for equivalent reactors _L 1 eq of the U-phase reactor voltage V1, V-phase reactor voltage V2, W-phase reactor voltage _V3, L 2 _eq, when expressed by _{L 3 eq} is expressed as follows (Equation (10) to (12) see ).

  The controller 160 determines the boost ratio so that the required system voltage Vh is obtained according to the required power of the load 130 and the like. Then, the controller 160 controls on / off of the switching elements Tr1 and Tr2 so that the determined step-up ratio is obtained. In this way, the FC converter 2500 boosts the battery voltage Vb supplied from the fuel cell 110 to the required system voltage Vh and outputs the boosted voltage to the load 130.

  Here, the magnetic coupling circuit 300 ′ shown in FIG. 12 includes a first transformer TW 1, a second transformer TW 2, and a third transformer TW 3. The first transformer TW1 includes a coil 310a having one end connected to the power supply line 301, a coil 320a having one end connected to the power supply line 301, and an annular core 315a around which the coil 310a and the coil 320a are wound. In other words, the coil 310a and the coil 320a are wound around the same core 315a. The number of turns of the coil 310a and the coil 320a is set to be the same.

  The second transformer TW2 has one end connected to the power supply line 301 and a coil 310b connected in series to the coil 320a, a coil 320b connected to the power supply line 301 at one end, and the coil 310b and the coil 320b. A rotated annular core 315b. In other words, the coil 310b and the coil 320b are wound around the same core 315b.

  Further, the third transformer TW3 has one end connected to the power supply line 301 and a coil 310c connected in series to the coil 310a, and one end connected to the power supply line 301 and a coil 320c connected to the coil 320b. The coil 310c and the coil 320c are wound around the annular coil 315c. In other words, the coil 310c and the coil 320c are wound around the same core 315c.

<Ripple reduction effect of FC converter 2500 '>
FIG. 14 is a diagram showing the relationship between the switching state (hereinafter referred to as SW pattern) of each switching element and the equivalent reactor. 15A to 15C are diagrams showing fluctuation patterns of the U-phase reactor voltage V1 and the V-phase reactor voltage V2 according to the SW pattern shown in FIG. 14, respectively. FIG. 15A shows a case where the boost ratio α <3/2. FIG. 15B shows a case where the boost ratio is 3/2 ≦ α <3, and FIG. 15C shows a case where the boost ratio is α ≧ 3. 15A to 15C, the first switching state to the eighth switching state are denoted as 1 to 8.

  The voltage pattern applied to each phase reactor is represented by a combination of switching states 2, 5, 6, 8 (= 2, 5, 6, 8) when the step-up ratio α <3/2 (see FIG. 15A). When the step-up ratio 3/2 ≦ α <3, it is represented by a combination of switching states 3 to 8 (= 3 to 8) (see FIG. 15B), and when the step-up ratio α ≧ 3, the switching states 1, 3, 4 , 7 (= 1, 3, 4, 7) (see FIG. 15C).

Here, FIG. 16 shows the reactor current ripple calculation formula (three-phase magnetically coupled converter) in each of the boost ratio 1 <α <3/2, the boost ratio 3/2 ≦ α <3, and the boost ratio α ≧ 3. ) is a diagram showing, FIG. 17 is a diagram illustrating a relationship between switching states and current ripple [Delta] I _L in the case of the step-up ratio 3/2 ≦ α <3 (see FIG. 15B). FIG. 16 shows a reactor current ripple calculation formula of a conventional converter (conventional converter) that does not use magnetic coupling as a comparative example. Moreover, although FIG. 17 assumes a U-phase converter, it is needless to say that a V-phase converter or a W-phase converter may be used.

18 and 19, in each case coupling factor alpha = 0.44, and a diagram showing the relationship between the system voltage Vh and a current ripple [Delta] I _L in the case of coupling factor α = 1/3, 3-phase magnetically coupled It shows the converter current ripple [Delta] I _L by a thick solid line shows the current ripple [Delta] I _L of the conventional converter with a broken line. 18 and 19 assume a case where the battery voltage Vb supplied from the fuel cell 110 is 200 V, the reactor L is 0.2 mH, and the switching cycle Tc is 0.1 ms.

In the example shown in FIG. 18, the maximum boosted voltage (assumed to 650V here) (here, a = 0.44) conventional converter current ripple [Delta] I _L becomes equal way coupling factor a set a there is (the formula (5), (6)), and in the case of a three-phase magnetic coupling converter, setting such coupling ratio a, the direction of current ripple [Delta] I _L of the three-phase magnetic coupling converter , conventional converter current ripple [Delta] I _L larger area than (hereinafter, an excessive ripple current region) RA occurs.
In this regard, in the case of 2-phase magnetic coupling converter, the maximum boosted voltage in (here assumed to 650V is), conventional converter current ripple [Delta] I _L becomes equal way coupling factor a (where a = 0.44) Is different in that the generation of the excessive ripple current region RA can be prevented (see FIG. 10).

In the present embodiment, in order to prevent the occurrence of an excessive ripple current region RA, the boosted voltage Vmax of 3-phase magnetically coupled converter current ripple [Delta] I _L is the maximum, equal to the current ripple [Delta] I _L of the conventional converter ( The coupling rate a (here, a = 1/3) is set so as to be (or less).

Thus, the boosting voltage of the three-phase magnetically coupled converter current ripple [Delta] I _L is the maximum, equal to the current ripple [Delta] I _L of the conventional converter (or less in) so as to set the coupling ratio a, By determining the self-inductance L and the mutual inductance M so as to obtain the set coupling rate a, it is possible to design a converter having a small physique while suppressing the current lip. Thereby, it becomes possible to improve the operation efficiency of a system compared with the past.
Further, by using a three-phase magnetic coupling type converter, it is possible to obtain a large ripple reduction effect as compared with the case of using a two-phase magnetic coupling type converter.

B. Modification <Modification 1>
In each of the embodiments described above, a case where a two-phase magnetic coupling type converter and a three-phase magnetic coupling type converter are used has been described, but it is needless to say that a magnetic coupling type converter having four or more phases may be used. Here, when an n-phase (n ≧ 2) magnetic coupling circuit is used, the controller (drive control means) 160 drives each phase switching element with a phase difference Pd shown in the following equation (13). It is sufficient to control.
Pd = 360 ° / n (13)
It should be noted that the present invention can be applied to both step-up / step-down converters.

<Modification 2>
In addition, about each transformer (magnetic coupling reactor) which comprises each magnetic coupling circuit 300,300 ', winding (coil) is wound from the ferrite of each phase by which winding (coil) was wound around the leg (core). The phase magnetic path lengths to the center legs that are not present may be set equal.

DESCRIPTION OF SYMBOLS 100 ... FCHV system, 110 ... Fuel cell, 120 ... Battery, 130 ... Load, 140 ... Inverter, 2500 ... FC converter, 2500a ... U phase converter, 2500b ... V phase converter, 2500c ... W phase converter, 160 ... Controller, 170 ... Sensor group, 180 ... Battery converter, 300, 300 '... Magnetic coupling circuit, Tr1, Tr2, Tr3 ... Switching element, C1 ... Smoothing capacitor, 307, 308, 309 ... Reactor, Tw1, Tw2, Tw3 ... Transformer, D1, D2 ... Diode, R1, R2 ... Resistance, A1, A2 ... Current sensor.

Claims (4)

A method of designing a multiphase converter using a magnetically coupled reactor,
When the self-inductance of each phase is L, the mutual inductance is M, and the coupling rate obtained by the equation (A) is a,
In a system voltage at which the first ripple current generated when using a multiphase converter using a magnetically coupled reactor is maximized, the first ripple current is a multiphase converter having the same number of phases without using magnetic coupling. A method for designing a multiphase converter, in which the coupling ratio a is set so as to coincide with the second ripple current generated when the power is used.
a = M / L (A) A multi-phase converter using a magnetically coupled reactor,
When the self-inductance of each phase is L, the mutual inductance is M, and the coupling rate obtained by the equation (A) is a,
The coupling ratio a is the same at a system voltage at which the first ripple current generated when using a multiphase converter using a magnetic coupling reactor is maximized, and the first ripple current does not use magnetic coupling. A multi-phase converter that is set to coincide with the second ripple current generated when a multi-phase converter having the number of phases is used.
a = M / L (A) The multiphase converter according to claim 2 , further comprising drive control means for driving the switching elements constituting each phase with a phase difference Pd represented by the formula (B) when the number of phases is n.
Pd = 360 ° / n (B) The magnetically coupled reactor is
The multiphase converter according to claim 2 , wherein each phase magnetic path length from the ferrite of each phase wound around the leg to the center leg not wound around the leg is set equal.