Power conversion device

Patent metadata

Field	Value
Publication number	US-9787170-B2
Application number	US-201214366042-A
Country	US
Kind code	B2
Filing date	Sep 26, 2012
Priority date	Feb 13, 2012
Publication date	Oct 10, 2017
Grant date	Oct 10, 2017

Abstract

Provided are a solar panel ( 1 ), a first DC/DC conversion circuit ( 13 ), a DC/AC conversion circuit ( 21 ) connected via a DC bus ( 25 ), a second DC/DC conversion circuit ( 17 ) for controlling bus voltage in the case of power outage, a first control section ( 14 ) having two kinds of control modes and controlling the first DC/DC conversion circuit ( 13 ), a second control section ( 18 ) for controlling the second DC/DC conversion circuit ( 17 ), and a third control section ( 22 ) for controlling the DC/AC conversion circuit ( 21 ). The second control section ( 18 ) controls bus voltage in the case of power outage, and the first control section ( 14 ) switches the control mode based on information of the second control section ( 18 ).

First claim

The invention claimed is:

1. A power conversion device for converting DC power from a distributed power supply and supplying the converted power to a power system and a load, the power conversion device comprising:
a first DC/DC conversion circuit that converts a first DC voltage outputted from the distributed power supply to a second DC voltage;
a DC/AC conversion circuit connected to the first DC/DC conversion circuit via positive and negative DC buses and that converts DC voltage to a desired AC voltage and outputs the desired AC voltage to the power system and the load;
a second DC/DC conversion circuit that controls a bus voltage between the DC buses at least in a self-sustained operation when power from the power system is not available, the second DC/DC conversion circuit being connected to a power accumulator that is charged and discharged by the second DC/DC conversion circuit based on an operation of the power conversion device;
a bus voltage meter that measures the bus voltage;
a first controller that drive-controls the first DC/DC conversion circuit, the first controller having two control modes including a power control mode for deriving the maximum power of the distributed power supply and a voltage control mode for controlling bus voltage between the DC buses;
a second controller that drive-controls the second DC/DC conversion circuit; and
a third controller that drive-controls the DC/AC conversion circuit, wherein
the second controller drive-controls the second DC/DC conversion circuit, based on a measured value of the bus voltage measured by the bus voltage meter, to control the bus voltage, in the self-sustained operation,
the first controller switches the two control modes, based on a measured value of the bus voltage measured by the bus voltage meter, in the self-sustained operation, and
the third controller measures voltage and current output by the power system to determine whether to enter self-sustained operation.

2. The power conversion device according to claim 1 , wherein
the second controller, based on a measured value of the bus voltage measured by the bus voltage meter, controls output voltage from the second DC/DC conversion circuit, to control the bus voltage, in the self-sustained operation, and
the control information of the second controller for switching the two control modes is a measured value of the bus voltage measured by the bus voltage meter.

3. The power conversion device according to claim 2 , wherein
a control target voltage of the bus voltage for the first DC/DC conversion circuit is set in the voltage control mode for the distributed power supply in the self-sustained operation, and
if the measured value of the bus voltage is equal to or smaller than a first, threshold value which is smaller than the control target voltage, the first controller selects the power control mode, and if the measured value of the bus voltage is equal to or greater than a second threshold value which is greater than the control target voltage, the first controller selects the voltage control mode.

4. The power conversion device according to claim 3 , wherein
if the measured value of the bus voltage is equal to or smaller than a predetermined threshold value, the second controller starts discharge control for the power accumulator by the second DC/DC conversion circuit, and
the first threshold value is set to be smaller than the predetermined threshold value.

5. The power conversion device according to claim 2 , wherein
the control information of the second controller circuit for switching the two control modes is charge/discharge control information of the power accumulator.

6. The power conversion device according to claim 5 , wherein
switching of charge/discharge control for the power accumulator is performed based on an estimated value of surplus power that can be generated by the distributed power supply.

7. The power conversion device according to claim 1 , wherein
the second DC/DC conversion circuit includes a power meter that measures a charge/discharge power of the power accumulator, and
the first controller performs control to, if the power accumulator is in a charged state, or if the power accumulator is in a discharging state and a discharge power outputted from the power meter is equal to or greater than a first predetermined value, switch control for the first DC/DC conversion circuit to the power control mode, and if the power accumulator is in a discharging state and the discharge power outputted from the power meter is smaller than the first predetermined value, switch control for the first DC/DC conversion circuit to the voltage control mode.

8. The power conversion device according to claim 7 , wherein
in the case of switching the control from the power control mode to the voltage control mode by the first controller, the switching is controlled to be inhibited during a predetermined period.

9. The power conversion device according to claim 7 , wherein
the first predetermined value for switching a control method by the first controller when control is performed in the voltage control mode is greater than when control is performed in the power control mode.

10. The power conversion device according to claim 7 , wherein
in the case of switching the power accumulator from charging to discharging or from discharging to charging, the first controller forcibly switches the control to the voltage control mode.

11. The power conversion device according to claim 1 , wherein the power accumulator is a storage battery.

12. The power conversion device according to claim 1 , wherein the voltage control mode further includes setting a voltage control range at a higher voltage than a voltage corresponding to a maximum power point of a power-voltage characteristic of the distributed power supply.

Assignees

• Inoue Sadayuki
• Kawano Hideki
• Mitsubishi Electric Corp

Inventors

• Inoue Sadayuki
• Kawano Hideki

Classifications

• H02M7/42

  Conversion of DC power input into AC power output without possibility of reversal · CPC title

• H02M7/48

  using discharge tubes with control electrode or semiconductor devices with control electrode · CPC title

• Y02E70/30

  Systems combining energy storage with energy generation of non-fossil origin · CPC title

• H02J7/35

  with light sensitive cells · CPC title

• H02J7/00

  Circuit arrangements for charging or discharging batteries or for supplying loads from batteries · CPC title