Inverter with monitoring unit for intermediate circuit protection

Patent metadata

Field	Value
Publication number	US-11626792-B2
Application number	US-201917258526-A
Country	US
Kind code	B2
Filing date	Jul 30, 2019
Priority date	Jul 30, 2018
Publication date	Apr 11, 2023
Grant date	Apr 11, 2023

Abstract

An inverter includes a DC/DC converter which converts a direct current received from a DC voltage source into an intermediate circuit voltage of an intermediate circuit, a DC/AC converter which converts the intermediate circuit voltage into an AC voltage, and a monitoring unit which monitors capacitors of the intermediate circuit for protection against overvoltages. If an overvoltage occurs at one of the capacitors of the intermediate circuit the overvoltage unit decouples the DC voltage source from the intermediate circuit by actuating the DC/DC converter.

First claim

The invention claimed is:

1. An inverter comprising:
a DC/DC converter configured to convert a direct current received from a DC voltage source into an intermediate circuit voltage of an intermediate circuit,
a DC/AC converter configured to convert the intermediate circuit voltage into an AC voltage, and
a monitoring unit configured to monitor a plurality of capacitors of the intermediate circuit for protection against overvoltages, the monitoring unit further configured to reduce energy transmitted from the DC voltage source to the intermediate circuit by actuating the DC/DC converter when an overvoltage occurs at one of the plurality of capacitors of the intermediate circuit or when an asymmetrical voltage distribution of voltage drops at the plurality of capacitors of the intermediate circuit occurs,
wherein the plurality of capacitors of the intermediate circuit are connected in series, and
wherein the DC/DC converter includes a clocked switch that is clocked periodically in such a way that the energy transmitted from the DC voltage source to the intermediate circuit is reduced to reduce energy transmitted from the DC voltage source to the intermediate circuit when the overvoltage occurs at one of the plurality of capacitors of the intermediate circuit or when the asymmetrical voltage distribution of voltage drops at the plurality of capacitors of the intermediate circuit occurs,
wherein the clocking of the clocked switch of the DC/DC converter is maintained even when the overvoltage or the asymmetrical voltage distribution is detected,
wherein the DC/DC converter includes a step-up converter circuit that is configured to raise a DC voltage generated by the DC voltage source to a predetermined intermediate circuit voltage of the intermediate circuit, in which the step-up converter circuit includes the clocked switch,
wherein the monitoring unit is configured to actuate the clocked switch of the step-up converter circuit via an actuation logic when the overvoltage at one of the plurality of capacitors of the intermediate circuit or the asymmetrical voltage distribution of the voltage drops at the plurality of capacitors of the intermediate circuit is detected by the monitoring unit, and
wherein the DC/AC converter is connected at an output thereof, via at least one choke and at least one AC relay, to a power supply network.

2. The inverter according to claim 1 , wherein the DC voltage source connected to the DC/DC converter includes at least one photovoltaic module.

3. The inverter according to claim 1 , wherein the monitoring unit is configured to store an occurrence of the overvoltage at one of the plurality of capacitors of the intermediate circuit and to store an occurrence of the asymmetrical voltage distribution of the voltage drops at the plurality of capacitors of the intermediate circuit in a store of the monitoring unit or to activate a protective mode of operation of the inverter to protect the plurality of capacitors of the intermediate circuit against overvoltages.

4. The inverter according to claim 1 , wherein the monitoring unit is configured to output an error signal via an interface when the overvoltage at one of the plurality of capacitors of the intermediate circuit or the asymmetrical voltage distribution of the voltage drops at the plurality of capacitors of the intermediate circuit is detected by the monitoring unit.

5. The inverter according to claim 1 , wherein the monitoring unit includes voltage sensors configured to measure the voltage drops across each of the plurality of capacitors.

6. The inverter according to claim 1 , wherein the plurality of capacitors of the intermediate circuit includes at least two electrolyte capacitors connected in series.

7. The inverter according to claim 1 , wherein the monitoring unit and the actuation logic are supplied by the DC voltage source or include a dedicated power unit which is connected to the power supply network.

8. The inverter according to claim 1 , wherein the monitoring unit is further configured to determine a voltage difference between the voltage drops across the plurality of capacitors of the intermediate circuit.

9. A method for protecting an intermediate circuit of an inverter, the intermediate circuit is provided for buffering a voltage outputted by a DC/DC converter and which has a plurality of capacitors, and the inverter includes a monitoring unit and a DC/AC converter configured to convert an intermediate circuit voltage into an AC voltage, the method comprising the following steps:
(a) detecting voltage drops across the plurality of capacitors of the intermediate circuit;
(b) monitoring, by the monitoring unit, whether an overvoltage at one of the plurality of capacitors of the intermediate circuit or an asymmetrical voltage distribution of the voltage drops at the plurality of capacitors of the intermediate circuit is occurring; and
(c) reducing energy transmitted from a DC voltage source to the intermediate circuit by actuating the DC/DC converter when the overvoltage or the asymmetrical voltage distribution is detected,
wherein the DC/DC converter includes a clocked switch that is clocked periodically in such a way that the energy transmitted from the DC voltage source to the intermediate circuit is reduced when reducing energy transmitted from the DC voltage source to the intermediate circuit and when the overvoltage or the asymmetrical voltage distribution is detected,
wherein the clocking of the clocked switch of the DC/DC converter is maintained even when the overvoltage or the asymmetrical voltage distribution is detected,
wherein the DC/DC converter includes a step-up converter circuit that is configured to raise a DC voltage generated by the DC voltage source to a predetermined intermediate circuit voltage of the intermediate circuit, in which the step-up converter circuit includes the clocked switch,
wherein the monitoring unit is configured to actuate the clocked switch of the step-up converter circuit via an actuation logic when the overvoltage at one of the plurality of capacitors of the intermediate circuit or the asymmetrical voltage distribution of the voltage drops at the plurality of capacitors of the intermediate circuit is detected by the monitoring unit, and
wherein the DC/AC converter is connected at an output thereof, via at least one choke and at least one AC relay, to a power supply network.

10. The method according to claim 9 , wherein the asymmetrical voltage distribution is detected when a determined voltage difference between the voltage drops across the plurality of capacitors of the intermediate circuit exceeds a voltage threshold.

11. The method according to claim 9 , wherein the plurality of capacitors of the intermediate circuit are connected in series and the monitoring step includes determining a voltage difference between the voltage drops across the plurality of capacitors of the intermediate circuit.

Assignees

• Fronius Int Gmbh

Inventors

• Oberzaucher Friedrich
• Wallisch Gerhard
• Danmayr Joachim
• Luger Andreas

Classifications

• Y02E10/56

  Power conversion systems, e.g. maximum power point trackers · CPC title

• H02M1/32 Primary

  Means for protecting converters other than automatic disconnection · CPC title

• H02M3/155

  using semiconductor devices only · CPC title

• H02M3/156

  with automatic control of output voltage or current, e.g. switching regulators · CPC title

• H02M7/4835

  comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage · CPC title