Overvoltage protection for inverters that comprise an EMC filter at their input end

An overvoltage protection apparatus for an inverter configured to feed electric energy from a DC voltage source into an AC power grid, comprising:

• a DC voltage input stage comprising at least two current-carrying lines and an EMC filter that comprises interference suppressing capacitors and interference suppressing inductors;
• and
• surge arrestors configured to divert overvoltages with respect to ground, wherein the surge arrestors are connected to the current-carrying lines downstream of the EMC filter from a point of view of the DC voltage source,
• wherein at least one of the surge arrestors comprises:
• a series connection of a varistor and a lead fuse, wherein the lead fuse is thermally coupled to the varistor;
• and
• a monitoring device configured to monitor a voltage across the lead fuse.

An inverter, comprising:

• a DC-to-AC converter configured to receive a DC voltage and convert the DC voltage to an AC voltage for delivery to an AC power grid;
• and
• a DC input stage upstream of the DC-to-AC converter and configured to receive a DC input voltage from a DC voltage source, and provide a filtered DC input voltage to the DC-to-AC converter as the DC voltage,
• wherein the DC input stage comprises:
• an EMC filter coupled to input lines configured to receive the DC input voltage, and filter the DC input voltage to a filtered DC input voltage;
• and
• an overvoltage protection circuit connected between a line that receives the DC input voltage and ground, and arranged downstream of the EMC filter between the EMC filter and the DC-to-AC converter, wherein the overvoltage protection circuit is configured to suppress overvoltages thereat.

An inverter, comprising:

• a DC-to-AC converter configured to receive a DC voltage and convert the DC voltage to an AC voltage for delivery to an AC power grid;
• and
• a DC input stage upstream of the DC-to-AC converter and configured to receive a DC input voltage from a DC voltage source, and provide a filtered DC input voltage to the DC-to-AC converter as the DC voltage,
• wherein the DC input stage comprises:
• an EMC filter coupled to input lines configured to receive the DC input voltage, and filter the DC input voltage to a filtered DC input voltage;
• and
• an overvoltage protection circuit arranged downstream of the EMC filter between the EMC filter and the DC-to-AC converter, wherein the overvoltage protection circuit is configured to suppress overvoltages thereat,
• wherein the overvoltage protection circuit comprises:
• a lead fuse, and
• a varistor in series with and thermally coupled to the lead fuse,
• wherein the series combination of the lead fuse and the varistor is connected between one line configured to couple to one of the two terminals of the DC voltage source and ground, and
• a monitoring circuit configured to monitor a voltage across the lead fuse and determine whether an overvoltage condition exists, and further is configured to detect an electric arc condition from the monitored voltage.