# US 2021/0344281 A1 · Power conversion device

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- Number: US 2021/0344281 A1
- Document ID: US20210344281A1
- Status: Published application
- Kind: A1
- Application number: 17/378,979
- Filed: 2021-07-19
- Published: 2021-11-04
- Earliest claimed: 2019-01-30
- Assignees: Daikin Industries, Ltd.
- Applicants: Daikin Industries, Ltd.
- Inventors: Ryou MATSUYAMA; Masaki KONO; Tomoisa TANIGUCHI
- Web page: https://patentgrep.com/patent/US20210344281A1

## CPC

- H02M 7/53871: {with automatic control of output voltage or current}
- H02M 1/0006: {Arrangements for supplying an adequate voltage to the control circuit of converters}
- H02M 1/32: Means for protecting converters other than automatic disconnection
- H02M 1/322: {Means for rapidly discharging a capacitor of the converter for protecting electrical components or for preventing electrical shock}
- H02M 5/44: using discharge tubes or semiconductor devices to convert the intermediate DC into AC
- H02M 7/05: {Capacitor coupled rectifiers}
- H02M 7/2173: {in a biphase or polyphase circuit arrangement (H02M7/2176 takes precedence; voltage multipliers H02M7/25)}
- H03K 17/08104: {in field-effect transistor switches (H03K17/0812, H03K17/0814 take precedence)}
- G05F 1/571: with overvoltage detector
- H02M 5/453: using devices of a triode or transistor type requiring continuous application of a control signal
- H02M 5/458: using semiconductor devices only
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)
- G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES

## Abstract

A converter circuit converts AC electric power into DC power. An inverter circuit converts the DC power into AC power. A capacitor is connected in parallel to each of the converter circuit and the inverter circuit between these circuits. The capacitor allows variation of an output voltage from the converter circuit, and absorbs variation of an output voltage from the inverter circuit due to a switching operation. An overvoltage protection circuit includes a resistor and a semiconductor element connected in series to each other. The overvoltage protection circuit is connected in parallel to the capacitor to protect the inverter circuit from an overvoltage. First and second control units respectively control the inverter circuit and the overvoltage protection circuit.

## Claims

### Claim 1

A power conversion device comprising:
a converter circuit configured to convert AC electric power output from an AC power source into DC power;
an inverter circuit including a plurality of switching elements, and configured to convert the DC power into AC power to supply the AC power to a load;
a capacitor connected in parallel to each of the converter circuit and the inverter circuit between the converter circuit and the inverter circuit, the capacitor allowing variation of an output voltage from the converter circuit, the capacitor absorbing variation of an output voltage from the inverter circuit due to a switching operation;
an overvoltage protection circuit including a resistor and a semiconductor element connected in series to each other, the overvoltage protection circuit being connected in parallel to the capacitor, the overvoltage protection circuit being configured to protect the inverter circuit from an overvoltage applied to the inverter circuit; and
a control circuit configured to control the inverter circuit and the overvoltage protection circuit.

### Claim 2 (depends on 1)

The power conversion device of claim 1, wherein
a capacitance of the capacitor is set such that voltage variation of the capacitor during a switching period for the switching elements is 1/10 or less of an average voltage of the capacitor.

### Claim 3 (depends on 1)

The power conversion device of claim 1, wherein
the following formula is satisfied:
C(Vc12−Vc22)/2<E
where C represents a capacitance of the capacitor, Vc1 represents a withstand voltage of the capacitor, Vc2 represents a peak voltage of the capacitor during the switching operation, and E represents a maximum magnetic energy that is capable of being stored in the load.

### Claim 4 (depends on 1)

The power conversion device of claim 1, wherein
the converter circuit, the inverter circuit, the overvoltage protection circuit, and the control circuit are mounted on an identical substrate.

### Claim 5 (depends on 1)

The power conversion device of claim 1, wherein
at least the inverter circuit and the overvoltage protection circuit are housed in an identical package.

### Claim 6 (depends on 1)

The power conversion device of claim 1, wherein
a capacitance C of the capacitor is determined to satisfy the following formula based on a power supply voltage Vac of the electric power and a maximum power Pmax of the AC power:
C
≤
350
×
10
-
6
×
Pmax
Vac
2
[
Formula
⁢
⁢
3
]

### Claim 7 (depends on 1)

The power conversion device of claim 1, wherein
the control circuit activates the overvoltage protection circuit when supply of power from the inverter circuit to the load is stopped.

### Claim 8 (depends on 1)

The power conversion device of claim 1, wherein
the control circuit activates the overvoltage protection circuit in a portion of a period during which the capacitor is charged immediately after a sudden rise in a voltage of the AC power source.

### Claim 9 (depends on 1)

The power conversion device of claim 1, wherein
the control circuit activates the overvoltage protection circuit in a portion of a period during which resonance occurs in a circuit including the capacitor.

### Claim 10 (depends on 1)

The power conversion device of claim 1, wherein
the control circuit
turns the semiconductor element on to activate the overvoltage protection circuit, if an input voltage applied through the capacitor to the inverter circuit is higher than or equal to a first predetermined value,
turns the semiconductor element off to deactivate the overvoltage protection circuit, if the input voltage applied to the inverter circuit is lower than or equal to a second predetermined value after activating the overvoltage protection circuit, and
sets the second predetermined value to be lower than the first predetermined value.

### Claim 11 (depends on 1)

The power conversion device of claim 1, wherein
the control circuit
turns the semiconductor element on to activate the overvoltage protection circuit, if an input voltage applied through the capacitor to the inverter circuit is higher than or equal to a third predetermined value, and
turns the semiconductor element off to deactivate the overvoltage protection circuit, if a predetermined time has elapsed since the activation of the overvoltage protection circuit.

### Claim 12 (depends on 1)

The power conversion device of claim 1, wherein
the control circuit
turns the semiconductor element on to activate the overvoltage protection circuit, if an input voltage applied through the capacitor to the inverter circuit that is stopping the switching operation is higher than or equal to a fourth predetermined value, and
switches at least one of the switching elements of the inverter circuit that is stopping the switching operation from off to on after activating the overvoltage protection circuit.

### Claim 13 (depends on 12)

The power conversion device of claim 12, wherein
after turning at least one of the switching elements on, the control circuit turns the semiconductor element of the overvoltage protection circuit off to deactivate the overvoltage protection circuit.

### Claim 14 (depends on 1)

The power conversion device of claim 1, wherein
during activation of the overvoltage protection circuit, the control circuit performs turn-on control to turn at least one of the switching elements on so that an absolute value of an average output power from the inverter circuit is less than if all of the switching elements are turned off.

### Claim 15 (depends on 14)

The power conversion device of claim 14, wherein
the turn-on control is performed so that the average output power from the inverter circuit is substantially zero.

### Claim 16 (depends on 14)

The power conversion device of claim 14, wherein
the turn-on control allows the inverter circuit to be in a zero-vector state.

### Claim 17 (depends on 14)

The power conversion device of claim 14, wherein
the turn-on control is performed to switch the output power from the inverter circuit between positive and negative values during a switching period for the switching elements so that the average output power from the inverter circuit during the switching period is substantially zero.

### Claim 18 (depends on 14)

The power conversion device of claim 14, wherein
the turn-on control is performed to switch the output power from the inverter circuit between positive and negative values during a plurality of successive ones of switching periods for the switching elements so that the average output power from the inverter circuit during the successive ones of the switching periods is substantially zero.

### Claim 19 (depends on 14)

The power conversion device of claim 14, wherein
the turn-on control is performed to control switching signals for controlling the switching elements, based on at least one of a current flowing from the inverter circuit to the capacitor or a voltage of the capacitor.

### Claim 20 (depends on 14)

The power conversion device of claim 14, wherein
the switching period for the switching elements during the turn-on control is set to be shorter than the switching period during supply of power to the load,

### Claim 21 (depends on 14)

The power conversion device of claim 14, wherein
the load is a magnet motor, and
the turn-on control is performed to satisfy the following formula:
(Id+Φm/Ld)2+Iq2<Im2
where Id is a d-axis current of the load during the turn-on control, Iq is a q-axis current of the load, Im is a minimum magnitude of the d-axis current causing irreversible demagnetization of a magnet of the load, Φm is a magnetic flux of the magnet, and Ld is a d-axis inductance of the load.

### Claim 22 (depends on 14)

The power conversion device of claim 14, wherein
the turn-on control is performed to satisfy the following formula:
Idq<Im−Φm/Ld
where Idq is a dq-axis current vector of the load during the turn-on control, Im is a minimum magnitude of a d-axis current causing irreversible demagnetization of a magnet of the load, Φm is a magnetic flux of the magnet, and Ld is a d-axis inductance of the load.

### Claim 23 (depends on 1)

The power conversion device of claim 1, wherein
the switching elements are mainly made of a wide-bandgap semiconductor containing silicon carbide, gallium nitride, or diamond.

### Claim 24 (depends on 1)

The power conversion device of claim 1, wherein
the semiconductor element is mainly made of a wide-bandgap semiconductor containing silicon carbide, gallium nitride, or diamond.

### Claim 25

A power conversion device comprising:
an inverter circuit including a plurality of switching elements, and configured to convert DC power into AC power to supply the AC power to a load; and
an overvoltage protection circuit including a resistor and a semiconductor element connected in series to each other, the overvoltage protection circuit being connected in parallel to a DC portion of the inverter circuit, the overvoltage protection circuit being configured to protect the inverter circuit from an overvoltage applied to the inverter circuit,
the inverter circuit and the overvoltage protection circuit being housed in an identical package.

### Claim 26 (depends on 25)

The power conversion device of claim 25, wherein
the switching elements are mainly made of a wide-bandgap semiconductor containing silicon carbide, gallium nitride, or diamond.

### Claim 27 (depends on 25)

The power conversion device of claim 25, wherein
the semiconductor element is mainly made of a wide-bandgap semiconductor containing silicon carbide, gallium nitride, or diamond.