The invention relates to a method for realizing the insulation coordination of basic functional units of a
voltage source converter (VSC) based on a
half bridge circuit, which comprises the following steps of: 1) determining the insulation strength and properties of each component according to the steady-state over-
voltage level, transient-state over-
voltage level and transient over-voltage level of a sub-module under various operation conditions; 2) making equal the ground potential of a
metal shell and a secondary control protection board of primary equipment and the potential of the
cathode of the sub-module according to the potential distribution characteristics of the sub-module, and connecting the secondary control protection board and a primary circuit by using an
isolation transformer to isolate the influence of the
high voltage of the primary circuit on a
secondary circuit; 3) shielding the
electromagnetic interference of an insulated gate bipolar translator (IGBT) high speed switch in the secondary control protection board by using a
metal shielding box according to the
electromagnetic field distribution of the sub-module; 4) making
equipotential an operating mechanism of a bypass switch and the
cathode of the sub-module; and 5) selecting a
high voltage wire as a wire crossing a
high potential and a low potential to reduce the local
discharge capacity of the sub-module. By the insulation coordination method, the insulation requirements of a
system can be met, and
high security and high economy are achieved.