JP4411436B2 - Soft switching circuit for bidirectional DC-DC converter - Google Patents

Description

  The present invention relates to a soft switching circuit of a bidirectional DC-DC converter connected to a current source inverter, and more particularly to a soft switching circuit of a bidirectional DC-DC converter that can be optimally used for a chargeable power storage device.

In recent years, various large-capacity power storage devices have been developed against the background of power electronics technology. There is a pumped storage power plant as a large-capacity power storage device in practical use at present, but future construction is difficult and has no potential for development. In addition, secondary batteries are worried about environmental impact.
In recent years, an electric double layer capacitor (EDLC) element with an amazing capacitance of several thousand μF order or more has appeared, and by using power electronics technology for this, energy density and output density comparable to a secondary battery can be obtained. Large capacity power storage devices have been developed.

In general, a voltage source inverter is used for an electric energy storage device (ECaSS) using an electric double layer capacitor bank. However, a characteristic characteristic of EDLC in which a withstand voltage of a single cell is 3 V or less and a decrease in terminal voltage due to energy discharge cannot be ignored. There are disadvantages such as a decrease in DC link voltage, a decrease in output, and difficulty in output control.
The inventors have conducted research to eliminate these drawbacks by applying a current source inverter to ECaSS. The current source inverter has advantages that the voltage source inverter does not have, such as easy overcurrent protection and no risk of isolated operation when used in a distributed power source. In the current source inverter, since the direction of the direct current does not change and the power is transferred by changing the polarity of the direct current link voltage, a bidirectional DC-DC converter is provided in the direct current section in order to charge and discharge.

Advantages of using a current source inverter are as follows: (1) A large amount of power can be output with a relatively small DC input voltage. (2) Even when the DC link voltage fluctuates due to a decrease in the terminal voltage of the EDLC associated with energy discharge. The output can be maintained, and (3) the internal resistance loss of the EDLC can be reduced by performing direct current control using a bidirectional DC-DC converter connected to the direct current section.
Thus, it is preferable to use a current source inverter for the power storage device, and improvement in versatility and conversion efficiency of the current source inverter are required. In particular, it is advantageous to use a current source inverter as a power conditioner for a distributed power source, and the demand for the current source inverter is expected to increase in the electric power industry.

However, current source inverters that perform hard switching using self-excited semiconductor elements have low energy conversion efficiency due to large power loss due to switching, and steep voltage and current waveforms, resulting in high device stress and high manufacturing costs. . Further, since electromagnetic interference (EMI) is generated, there is a problem in environmental characteristics.
In order to reduce switching loss and suppress electromagnetic interference, a soft switching technique is used in which resonance is used to turn a switching element on and off when the current or voltage is zero. However, the circuit configuration including the semiconductor element and the resonant element becomes complicated. Further, as a simple circuit, there is only a circuit limited to reactive power control without bidirectionality. Furthermore, since it is difficult to apply a bi-directional resonant circuit that enables charging and discharging of electric power to be applied to a power storage device, there is no example in which such a resonant circuit has been put to practical use in the field of handling high power. It was.

Patent Document 1 discloses a circuit capable of regenerating power to a DC power source using soft switching in a power converter having a DC link / LC series resonance type high frequency resonant link corresponding to a current source inverter. .
The disclosed circuit includes a switching element for controlling charging / discharging of a resonance capacitor in an LC series resonance circuit, and a series circuit of a feedback inductor and a diode magnetically tightly coupled to a DC current supply inductor as a DC power supply. When the DC current supplied from the power supply device becomes zero in parallel connection, a large feedback current flows through the feedback inductor according to Lenz's law, and surplus power is regenerated in the battery.

In the disclosed current source inverter, since the thyristor of the inverter performs soft switching, the switching loss is reduced, the inverter efficiency is improved, and EMI due to switching does not occur.
However, since the disclosed circuit cannot provide bidirectionality to the resonant circuit, surplus power generated on the system side simply by regenerating the current due to the electromotive force generated in the feedback inductor by the current supplied from the battery. It is not a mechanism to absorb.

  Patent Document 2 discloses a power generation facility that can be used on a remote island away from a distribution network of commercial power. This disclosed device is combined with an auxiliary power generator that is activated with fossil fuel that is activated each time the output of the main power generator using natural energy such as sunlight or wind power is insufficient and is operated until the output of the main power generator is recovered. In addition, a capacitor bank and a bidirectional converter for holding power compensation energy during the start-up transition period of the auxiliary power generator are provided.

When the output shortage of the main power generator using natural energy is detected, the direct current output of the capacitor bank can be controlled at a constant voltage by the inverter operation of the bidirectional converter, and the output can be supplemented by supplying it to the distribution line. Further, when there is a surplus in the output of the main power generator, the converter is operated to convert a part of the AC power of the distribution line into DC power for charging and charge the capacitor bank. Although a circuit inside the bidirectional converter is not disclosed, a circuit in which a charging path diode and a discharging path switch are assembled in parallel is used to switch between discharging and charging. This switching circuit is not a current resonance type, and the discharge path switch has only to be kept on during the discharge period, so there is little demand for soft switching.
In addition, since the start-up transition period of the auxiliary power generator is several seconds, the capacitor bank does not require a large amount of power storage.
JP-A-8-51781 Japanese Patent Laid-Open No. 2001-136681

  The problem to be solved by the present invention is to provide a simple resonant circuit that enables soft switching in a current source inverter applied to a power storage device, and in particular, a bidirectional DC-DC used for a DC link unit. It is an object of the present invention to provide a resonance circuit capable of soft switching using resonance for a converter.

  In order to solve the above problems, a soft switching circuit of a bidirectional DC-DC converter according to the present invention includes a first diode having an anode connected to an input-side negative terminal and a cathode connected to an output-side positive terminal, and an anode connected to an output-side negative terminal. And a second diode having a cathode connected to the input-side positive terminal, a first semiconductor switch provided between the input-side positive terminal and the output-side positive terminal, and provided between the output-side negative terminal and the input-side negative terminal In the bidirectional DC-DC converter configured by the second semiconductor switch, a first resonance inductor is provided in series with the first semiconductor switch, and a second resonance inductor is provided in series with the second semiconductor switch. A resonance capacitor is provided between the positive electrode terminal and the output negative electrode terminal, and the first semiconductor switch is turned on when the resonance current generated during charge / discharge is zero. Characterized in that when a so as to actuate the second semiconductor switch.

During the discharging period, the second semiconductor switch is maintained in an ON state, and the first semiconductor switch is opened and closed when the resonance current is zero according to a predetermined time schedule, thereby operating as a current resonance type step-down converter. Further, during the charging period, the first semiconductor switch is turned off, and the second semiconductor switch is operated when the resonance current is zero according to a predetermined time schedule to operate as a current resonance type boost converter.
The bidirectional DC-DC converter having the circuit of the present invention constitutes a simple bidirectional resonant circuit using the same resonant element in the charging direction and the discharging direction, and the semiconductor switch is turned on when the resonant current becomes zero. It can be operated to enable soft switching.

Therefore, it is possible to suppress power loss due to switching, improve energy conversion efficiency, and sufficiently suppress electromagnetic interference.
When the bidirectional DC-DC converter according to the present invention is used as a direct current link disposed between a power storage element and a current source inverter, a discharge process for supplying direct current power from the power storage element to the current source inverter, and an inverter from the system The surplus power can be distributed to the power storage element in both directions through the charging process.
In addition, since a steep voltage / current waveform does not occur, the circuit element is not required to have a high degree of tolerance, and the manufacturing cost is reduced in combination with a simple circuit configuration.

In the soft switching circuit of the bidirectional DC-DC converter of the present invention, the semiconductor switch is a GTO thyristor, and the first semiconductor switch has the anode directed toward the input-side positive terminal and the cathode directed toward the output-side positive terminal, The second semiconductor switch may be connected with the anode facing the output-side negative terminal and the cathode facing the input-side negative terminal.
In the circuit of the present invention, the direction of the direct current passing through the semiconductor switch does not change in any of the charging and discharging, so that the semiconductor switch is not limited to having bidirectionality, and even if current flows only in one direction. Good. As the semiconductor switch, a thyristor, a power transistor, an IGBT, or the like can be used. In particular, a GTO thyristor that can control a large-capacity current can be used and applied to a large-capacity power storage device.

The capacitance Cr of the resonance capacitor is an inequality when the input voltage is Vin, the DC output current connected to the output terminal is Idc, and the inductances of the first and second resonance inductors are Lr1 and Lr2, respectively.
Cr ≧ (Idc / Vin) ² (Lr1 + Lr2)
It is preferable to have a relationship represented by:
If this relationship is established, a resonance current can be obtained and a switching frequency lower than the resonance frequency can be set.
The inductance Lr1 of the first resonance inductor is preferably selected to be smaller than the inductance Lr2 of the second resonance inductor. The amplitude of the resonance current during discharge is proportional to (Cr / (Lr1 + Lr2)) ² Vin, and is proportional to (Cr / Lr2) ² Vin during charging. Therefore, Lr1 is reduced to resonate during charging and discharging. This is because the current stress of the switch is reduced if the current amplitude can be suppressed.

By arranging the soft switching circuit of the bidirectional DC-DC converter of the present invention between the power storage element and the current source inverter, the current source inverter for the power storage device can be configured.
When a capacitor bank formed by using a plurality of electric double layer capacitors is used as the power storage element, it is possible to store power with a small size and a large capacity, and it can be effectively used in various fields.

By using the current resonance type of the present invention, a power storage device that has a simple circuit configuration, performs soft switching of a semiconductor switch, reduces switching loss, improves energy conversion efficiency, and hardly causes electromagnetic interference. Can be provided.
Note that the bidirectional DC-DC converter of the present invention can be used as a power conditioner of a distributed power source, and can also be used as a converter for a DC device.

Hereinafter, the present invention will be described in detail using examples.
FIG. 1 is a main circuit configuration diagram of a current source power storage device incorporating a soft switching circuit of a bidirectional DC-DC converter according to the present embodiment.
The bidirectional DC-DC converter 2 provided with the soft switching circuit according to the present embodiment is arranged in a DC link unit between the DC power supply unit 1 and the inverter unit 3, and constitutes a power storage device as a whole, and has a three-phase configuration. AC power is supplied to a load such as the induction motor 4.
The DC power supply unit 1 is composed of a capacitor bank using an electric double layer capacitor (EDLC), and generates a DC terminal voltage Vin. Since the capacitor bank has an internal resistance, an equivalent resistance is shown in the circuit diagram.
The positive and negative output terminals of the DC power supply unit 1 are connected to the positive and negative input terminals of the DC link unit 2, respectively.

  The bidirectional DC-DC converter 2 provided in the DC link unit includes a first rectifier diode D1, a second rectifier diode D2, a first semiconductor switch SW1 configured with a GTO thyristor, and a second semiconductor switch configured with a GTO thyristor. With SW2. The bidirectional DC-DC converter 2 according to the present embodiment further includes a first resonance inductor Lr1, a second resonance inductor Lr2, and a resonance capacitor Cr. It is a quadrant DC-DC converter.

  The first rectifier diode D1 has an anode connected to the input-side negative terminal of the bidirectional DC-DC converter 2 and a cathode connected to the output-side positive terminal. The second rectifier diode D2 has an anode connected to the output-side negative terminal. Connect the cathode to the positive terminal on the input side. The GTO thyristor of the first semiconductor switch SW1 has an anode connected to the input-side positive terminal and a cathode connected to the output-side positive terminal. The second semiconductor switch SW2 has an anode connected to the output-side negative terminal and a cathode connected to the input-side negative terminal.

Further, the first resonance inductor Lr1 is connected in series with the first semiconductor switch SW1, the second resonance inductor Lr2 is connected in series with the second semiconductor switch SW2, and the resonance capacitor Cr is connected to the output positive terminal and the output side. It is provided between the negative terminals.
Charging and discharging are selected by operating the first semiconductor switch SW1 and the second semiconductor switch SW2, and switching loss is suppressed by turning on and off by soft switching during the charging / discharging process, thereby improving conversion efficiency. Let me.
The circuit configuration is simplified by using the same resonant elements (Lr1, Lr2, Cr) during charging and discharging.

  The output side positive terminal of the DC link unit 2 is connected to the positive input terminal of the current source inverter 3 via the DC inductor Ldc5, and the output side negative terminal of the DC link unit 2 is directly connected to the negative input terminal of the current source inverter 3. To do. The current source inverter 3 and the semiconductor switch are driven to perform DC-AC conversion and output, and three-phase AC power is supplied to a load 4 such as an electric motor through an AC filter 6 including an inductor Lac and a capacitor Cac.

FIG. 2 shows an equivalent circuit during charging in the fourth quadrant operation of the bidirectional DC-DC converter 2.
During charging, the first semiconductor switch SW1 is turned off (indicated by a dotted line in the figure), and the second semiconductor switch SW2 is turned on and off in accordance with a program (indicated by hatching in the figure), the second rectification is performed. Combined with the function of the diode D2, it operates as a current resonance type boost converter. The circuit on the left side of the arrow in the figure is equivalently converted to the circuit on the right side. The direct current Idc passing through the direct current inductor Ldc flows in the right direction in the figure as in the case of discharging, but the surplus current from the system side is charged to the resonance capacitor Cr and the capacitor voltage Vcr increases and exceeds the input voltage Vin. The second rectifier diode D2 is forward-biased, and the capacitor bank of the DC power supply unit 1 is charged as regenerative power.

On the other hand, FIG. 3 shows an equivalent circuit during the first quadrant operation of the bidirectional DC-DC converter 2 during discharging.
At the time of discharging, the second semiconductor switch SW2 is turned on during the period (shown with hatched hatching in the figure), and the first semiconductor switch SW1 is driven according to the program, so that the function of the first rectifier diode D1 is considered. Thus, it is operated as a current resonance type step-down converter.
Further, the direction of the current passing through the DC inductor Ldc does not change between charging and discharging.

Since the bidirectional DC-DC converter 2 is of a current resonance type, the soft switching technique at the time of charging and discharging is similar in operation waveform, so the operation analysis result at the time of charging will be described.
During charging, each switching period is divided into four modes: mode I during the inductor excitation period, mode II during the resonance period, mode III during the capacitor discharge period, and mode IV during the rectifier diode on period.

FIG. 4 shows an equivalent circuit for each mode during charging. (A) is a mode I, (b) is a mode II, (c) is a mode III, (d) is a mode IV equivalent circuit. At the time of charging, the first semiconductor switch SW1 is in an off state.
Here, an instantaneous voltage νak, an instantaneous current iak, and a switching loss (power loss) ωbo in the GTO thyristor used for the second semiconductor switch SW2 in each mode are derived.

  FIG. 5 is a waveform diagram of instantaneous voltage / current of each part in one switching period during charging, obtained by simulation. In the figure, the horizontal axis indicates time t, the state of the on / off command signal of the second semiconductor switch (GTO thyristor) SW2, the instantaneous value iak of the resonance current passing through the second semiconductor switch SW2, and the voltage applied to the second semiconductor switch SW2. Instantaneous value νak, power consumption PSbo when using soft switching obtained by multiplying instantaneous current iak and instantaneous voltage νak in second semiconductor switch SW2, energy loss amount WSbo obtained by time integration of power consumption PSbo, for resonance The time change of the charging current icr to the capacitor Cr, the terminal voltage νcr of the resonance capacitor Cr, and the input current iin from the power storage element is displayed. In the time axis direction, the positions of times T0, T1, T2, T3, and T4 at which the modes are separated by vertical dotted lines are shown.

  The simulation assumes that the DC current Idc does not change, and the GTO thyristor has an internal inductance Lon, an internal resistance Ron, and a forward voltage Vf in series with the switch as shown in the equivalent circuit diagram of FIG. Using the values in the parameter table of FIG. 8, the simulation was performed by the instantaneous simulation software MATLAB / SIMULINK and SimPowerSystems.

  For comparison, FIG. 6 shows the instantaneous voltage and current during charging by the hard switching method. In the figure, the horizontal axis indicates time t, the second semiconductor switch SW2 is turned on and off, the instantaneous current iak of the second semiconductor switch SW2, the instantaneous voltage νak, the power consumption PHbo during hard switching in the second semiconductor switch SW2, and hard switching The time change of the energy loss amount WHbo and the input current iin from the power storage element is displayed. The mode separation time is indicated by a vertical dotted line.

(1) Mode I: Inductor excitation period (T0 <t <T1)
In the period from time T0 to time T1 in FIG. 5, the second semiconductor switch SW2 is turned on at time T0 when the instantaneous current iak passing through the second semiconductor switch SW2 is zero, and the equivalent circuit shown in FIG. The DC current Idc is commutated to the second semiconductor switch SW2, the anode voltage of the second rectifier diode D2 reaches the terminal voltage νin of the power storage element, the second rectifier diode D2 is turned off, and the mode II It is a period until it switches to.

In mode I, the instantaneous current iak and the instantaneous voltage νak are expressed by equation (1).
iak = νin / Lr2 * (t−T0)
νak = Ron * iak + Vf (1)
Also, from equation (1), the energy loss in mode I is
Wbo1 ＝ ∫Pbo1 (t) dt ＝ ∫iak (t) νak (t) dt
= Ron / 3 (νin / Lr2) ² (T1−T0) ³ + νinVf / 2Lr2 (T1−T0) ² (2)
It is represented by
These changes are represented in FIG.

(2) Mode II: Resonance period (T1 <t <T2)
The period from time T1 to time T2 in FIG. 5 is a period in which the second rectifier diode D2 is turned off and the equivalent circuit state shown in FIG. 4B is obtained, and CL resonance is caused by Cr and Lr2. When the resonance current becomes zero, the mode is switched to the next mode III.
In mode II, the instantaneous current iak and the instantaneous voltage νak are expressed by equation (3).
iak = Idc + (Cr / Lr2) ^1/2 νinsinωrbo (t−T1)
νak = Ron * iak + Vf (3)
Here, ωrbo is a resonance angular frequency and is represented by 1 / (Lr2Cr) ^1/2 .

From equation (3), the energy loss Wbo2 in mode II is
Wbo2 ＝ ∫Pbo2 (t) dt ＝ ∫iak (t) νak (t) dt
= Ron [Idc ² (T2−T1) + 2νinIdcCr {1-cosωrbo (T2−T1)}
+ Νin ² Cr / Lr2 {(T2−T1) / 2−sin2ωr (T2−T1) / 4ωrbo2}]
+ Vf [Idc (T2−T1) + νinCr {1-cosωrbo (T2−T1)}] (4)
It is represented by These changes are represented in FIG.

(3) Mode III: Capacitor discharge period (T2 <t <T3)
In the period from time T2 to time T3 in FIG. 5, the second semiconductor switch SW2 is turned off by zero current switching (ZCS) at time T2 when the resonance current iak becomes zero, and the equivalent circuit state shown in FIG. become.
In mode III, the instantaneous current iak and the instantaneous voltage νak are expressed by equation (5).
iak = 0
νak = Ron * iak + Vf (5)

From equation (5), since the current is zero, the energy loss Wbo3 in mode III is zero.
Wbo3 ＝ ∫Pbo2 (t) dt ＝ ∫iak (t) νak (t) dt
= 0 (6)
In the mode III period, the resonant capacitor is charged with electric energy and the terminal voltage νcr of the resonant capacitor Cr starts to increase. When the terminal voltage νcr reaches the input voltage νin, the mode IV is entered.

(4) Mode IV: Rectifier diode on period (T3 <t <T4)
In the period from time T3 to time T4 in FIG. 5, when the terminal voltage νcr of the resonant capacitor Cr reaches the input voltage νin and the second rectifier diode D2 is forward biased and becomes conductive, the equivalent circuit state shown in FIG. become. In mode IV, the second rectifier diode D2 is turned on, the direct current Idc is commutated, and electric energy is charged in the capacitor bank. Note the current direction in FIG. 4 (d) and FIG. Since the instantaneous current iak is zero during mode IV, no energy loss occurs as in mode III. The mode is switched to mode I by turning on the second semiconductor switch SW2 at an arbitrary time.

Since the switching frequency fsbo is preferably smaller than the resonance frequency frbo, from the resonance current equation (3) during charging,
frbo = ωrbo / 2π = 1 / 2π (Lr2Cr) ^1/2 > fsbo (7)
It becomes.
Further, the resonance current iak at the time of discharge is expressed by the following equation (8).
iak = Idc + (Cr / (Lr1 + Lr2)) ^1/2 νinsin ωrbu (t−T1) (8)
Therefore, the switching frequency fsbu at the time of discharge is
frbu = ωrbu / 2π = 1 / 2π ((Lr1 + Lr2) Cr) ^1/2 > fsbu (9)
It becomes. Here, ωrbbu is represented by 1 / ((Lr1 + Lr2) Cr) ^1/2 .
As can be seen from the equations (7) and (9), the switching frequency must be set to a different value between discharging and charging. This difference is determined based on the resonance inductances Lr1 and Lr2.

Next, in order to achieve zero current switching (ZCS) from the resonance current equations of Equations (3) and (8),
Cr ≧ (Idc / νin) ² (Lr1 + Lr2) (10)
It is necessary to satisfy the following conditions.
The input voltage νin in the equation (10) corresponds to the terminal voltage of the electric double layer capacitor bank. Since the bank voltage decreases as the energy is discharged, the resonance state changes as the energy is charged and discharged.

Therefore, the ZCS condition is considered for a bank voltage of 60 V when the bank voltage at full charge is about 200 V and electric energy is discharged by about 95%.
The value of the resonant capacitor Cr when the input voltage νin is 60 V in the equation (10) is as shown in FIG. FIG. 9 shows that the first resonance inductor Lr1 is fixed to 1 μH (indicated by a solid line) or 0.5 μH (indicated by a dotted line in the figure), and the value (horizontal axis) of the second resonance inductor Lr2 is changed. The value of the resonance capacitor Cr to be set in order to achieve ZCS is plotted on the vertical axis.
An appropriate set value of the resonance capacitor Cr can be immediately found for the set of the first resonance inductor Lr1 and the second resonance inductor Lr2. The resonance capacitor Cr may be set to a value larger than the line in the figure.

Note that the current stress of the switch can be reduced by reducing the difference in amplitude of the resonance current between discharging and charging. Therefore, the relationship between the first resonance inductor Lr1 and the second resonance inductor Lr2 is
Lr2> Lr1 (11)
It is preferable to regulate so that.

Consider energy loss in a bidirectional DC-DC converter.
Comparing the theoretical value of the loss energy calculated by the previous calculation formula using the values in the parameter table of FIG. 8 and the loss energy obtained by the simulation, the theoretical value and the simulation result are obtained when soft switching is used during discharge. Although the theoretical value is 0.0357W, the simulation is 0.0430W, the hard switching is the theoretical value of 0.1755W, and the simulation is 0.208W, but the value during charging is soft switching. The theoretical value is 0,174 W for the simulation, 0.181 W in the simulation, and the hard switching, the theoretical value, 1.1019 W, the simulation is 1.210 W, which is relatively good agreement.
In either case, it can be seen that the energy loss is much smaller in soft switching than in hard switching.

  Soft switching efficiency is 96.95% compared to 84.51% during charging and 84.48% during discharging, and soft switching is 84.48% during discharging. Thus, 99.28%, it can be seen that the efficiency improvement is remarkable by soft switching.

The terminal voltage of the electric double layer capacitor bank (EDLC) 1 changes as the energy is charged and discharged. Further, the direct current Idc of the current source inverter 3 also changes with charge / discharge or depending on the amount of active / reactive power.
Accordingly, FIGS. 10 to 13 show the energy loss value and the conversion efficiency that change due to these factors. FIGS. 10 and 11 respectively show energy loss Wsbo and conversion efficiency ηsoft in soft switching of a bidirectional DC-DC converter, and FIGS. 12 and 13 show energy loss Whard and conversion efficiency ηhard in hard switching as DC current Idc and capacitor bank terminals. It is plotted against the tertiary axis with respect to the two-dimensional coordinate plane of the voltage νin.

It can be confirmed that the switching loss increases as the direct current increases, and the conversion efficiency decreases.
In addition, when comparing hard switching and soft switching, the scale on the third axis of soft switching is remarkably finely plotted. The energy loss in soft switching is extremely small in any region, and the conversion efficiency is low. It can be understood that it is extremely large.

In the above embodiment, an electric double layer capacitor is used as a power storage element, but a normal large-capacity capacitor or secondary battery may be used.
In addition, the bidirectional DC-DC converter of this embodiment is used for driving an AC device by configuring a power storage device in combination with a current source inverter, but it goes without saying that it can be applied to a DC device.
It should be noted that the above-described embodiment is merely a best mode for carrying out the invention of the present application, and that the person skilled in the art can conceive based on the technical idea described in the present specification and the description of the claims. It goes without saying that the apparatus and method belong to the technical scope of the present invention.

1 is a main circuit configuration diagram of a current source power storage device using a soft switching circuit of a bidirectional DC-DC converter according to an embodiment of the present invention. It is an equivalent circuit diagram at the time of charge of the bidirectional DC-DC converter of a present Example. It is an equivalent circuit diagram at the time of discharge of the bidirectional DC-DC converter of a present Example. It is the equivalent circuit diagram according to mode at the time of charge of the bidirectional | two-way DC-DC converter of a present Example. It is a waveform diagram of instantaneous voltage and current of each part in the present embodiment obtained by simulation. It is a waveform diagram of instantaneous voltage and current of each part by a hard switching technique obtained by simulation. It is an equivalent circuit diagram of a GTO thyristor. It is a table | surface of the parameter used for simulation. It is a graph showing the determination conditions of the capacitor parameter for resonance. It is a graph showing the energy loss in the soft switching of the bidirectional | two-way DC-DC converter of a present Example. It is a graph showing the conversion efficiency in the soft switching of the bidirectional | two-way DC-DC converter of a present Example. It is a graph showing the energy loss when hard-switching about the equivalent of the bidirectional | two-way DC-DC converter of a present Example. It is a graph showing the conversion efficiency when carrying out hard switching about the equivalent of the bidirectional | two-way DC-DC converter of a present Example.

Explanation of symbols

1 DC power supply 2 Bidirectional DC-DC converter 3 Current source inverter 3
4 Induction motor 5 DC inductor 6 AC filter

Claims (5)

A first diode having an input positive terminal and a negative terminal, an output positive terminal and a negative terminal, an anode connected to the input negative terminal and a cathode connected to the output positive terminal, and an anode connected to the output negative terminal A second diode having a cathode connected to the input-side positive terminal, a first semiconductor switch provided between the input-side positive terminal and the output-side positive terminal, and the output-side negative terminal and the input-side negative electrode In the bidirectional DC-DC converter constituted by the second semiconductor switch provided between the terminals,
A first resonance inductor is provided in series with the first semiconductor switch; a second resonance inductor is provided in series with the second semiconductor switch; a resonance capacitor is provided between the output-side positive terminal and the output-side negative terminal; A soft switching circuit for a current resonance type bidirectional DC-DC converter, comprising a controller for operating the first semiconductor switch and the second semiconductor switch when the resonance current is zero.   The first semiconductor switch is a GTO thyristor whose anode is directed toward the input-side positive terminal and the cathode is directed toward the output-side positive terminal, and the second semiconductor switch is a cathode whose anode is directed toward the output-side negative terminal. 2. A soft switching circuit for a bidirectional DC-DC converter according to claim 1, wherein the soft switching circuit is a GTO thyristor directed toward the input-side negative terminal. When the capacitance of the resonance capacitor is Cr, Cr is when the input voltage is Vin, the DC output current connected to the output terminal is Idc, and the inductances of the first and second resonance inductors are Lr1 and Lr2, respectively. Inequality
Cr ≧ (Idc / Vin) ² (Lr1 + Lr2)
The soft switching circuit of the bidirectional DC-DC converter according to claim 1, wherein the relationship is expressed by:   A power storage element is formed by connecting a power storage element to the input-side positive and negative terminals, the output anode terminal via an output inductor, and the output negative terminal directly to a current source inverter. The soft switching circuit of the bidirectional DC-DC converter according to any one of claims 1 to 3.   5. The soft switching circuit of the bidirectional DC-DC converter according to claim 4, wherein the power storage element includes a capacitor bank formed by using a plurality of electric double layer capacitors.

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