A power converting apparatus disposed between an AC power system, which generates an AC power, and a DC circuit, the power converting apparatus comprising: a voltage source converter (121, 122, 123) comprising an Alternating Current connection terminal (124, 125, 126) to connect to the AC power system and a Direct Current connection terminal (191, 192) to connect to the DC circuit, and comprising a converter arm unit (121p, 121n) being disposed between the DC connection terminal and the AC connection terminal and including a first voltage source converter and a second voltage source converter connecting the AC connection terminal with the DC connection terminal in series; and a semiconductor protection circuit connected to the converter arm unit in parallel, and diverting a fault current flowing through the converter arm unit, when a failure is generated in a DC circuit connected to the DC connection terminal, wherein the converter arm unit includes a plurality of unit modules connected with each other in series, the unit modules converting the DC power into the AC power or the AC power into the DC power, wherein the semiconductor protection circuit comprises a thyristor and is connected in parallel to the connection in series of all of the unit modules, wherein the power converting apparatus is connected to the AC power system using the AC connection terminal and connected to the DC circuit using the DC connection terminal, wherein the power converting apparatus converts the DC power provided from the DC circuit into the AC power to provide the AC power to the AC power system through the AC connection terminal and converts the AC power provided from the AC power system through the AC connection terminal into the DC power to provide the DC power to the DC circuit through the DC connection terminal. a voltage source converter (121, 122, 123) comprising an Alternating Current connection terminal (124, 125, 126) to connect to the AC power system and a Direct Current connection terminal (191, 192) to connect to the DC circuit, and comprising a converter arm unit (121p, 121n) being disposed between the DC connection terminal and the AC connection terminal and including a first voltage source converter and a second voltage source converter connecting the AC connection terminal with the DC connection terminal in series; and a semiconductor protection circuit connected to the converter arm unit in parallel, and diverting a fault current flowing through the converter arm unit, when a failure is generated in a DC circuit connected to the DC connection terminal, wherein the converter arm unit includes a plurality of unit modules connected with each other in series, the unit modules converting the DC power into the AC power or the AC power into the DC power, wherein the semiconductor protection circuit comprises a thyristor and is connected in parallel to the connection in series of all of the unit modules, wherein the power converting apparatus is connected to the AC power system using the AC connection terminal and connected to the DC circuit using the DC connection terminal, wherein the power converting apparatus converts the DC power provided from the DC circuit into the AC power to provide the AC power to the AC power system through the AC connection terminal and converts the AC power provided from the AC power system through the AC connection terminal into the DC power to provide the DC power to the DC circuit through the DC connection terminal.