A modularized multi-level flexible direct current topology circuit applicable to fault ride-through, comprising a modular cascade circuit, a voltage conversion circuit and a compensation circuit, wherein the modular cascade circuit is connected in parallel with the voltage conversion circuit and then connected in series with the compensation circuit; wherein the voltage conversion circuit is connected in parallel with a direct current outlet end of the modular cascade circuit, and the compensation circuit is positioned at an anode or a cathode of the direct current outlet of a combined structure of the voltage conversion circuit and the modular cascade circuit; wherein the modular cascade circuit is formed by serially connecting at least two half-bridge submodules; and the modular cascade circuit is configured to generate direct current voltage by controlling the on-off state of each half-bridge submodule; wherein each half-bridge submodule is composed of two full-controlled switch devices and a capacitor, and the two full-controlled switch devices are connected in series with each other and then connected in parallel with the capacitor; wherein the full-controlled devices are configured to output zero-sum capacitor voltage by controlling on-off thereof so as to form voltage steps; and the full-controlled switch devices are IGBTs or GTOs; wherein the voltage conversion circuit is formed by a power electronic H bridge structure comprising four bridge arms, each bridge arm being respectively connected with an alternating current end and a direct current end, each bridge arm being composed of a plurality of cascaded IGBTs with inversely parallel-connected diodes; wherein the voltage conversion circuit is configured to turn on paired IGBTs in the voltage conversion circuit to form alternating current positive half waves, and when the voltage reaches a zero crossing point, to turn off the paired IGBTs and turn on other paired IGBTs in the voltage conversion circuit, to form alternating current negative half waves, thereby accomplishing conversion of direct current into alternating current; wherein the compensation circuit is formed by serially connecting full-bridge submodules, each full-bridge submodule being composed of four full-controlled switch devices and a capacitor, and the full-controlled switch devices are IGBTs or GTOs; characterised in that the compensation circuit is configured to compensate harmonics under a normal condition, to compensate a dropped direct current voltage when an alternating current system has a fault to ensure constant direct current voltage, and to generate negative total direct current voltage when a direct current system has a fault to isolate the fault. wherein the voltage conversion circuit is connected in parallel with a direct current outlet end of the modular cascade circuit, and the compensation circuit is positioned at an anode or a cathode of the direct current outlet of a combined structure of the voltage conversion circuit and the modular cascade circuit; wherein the modular cascade circuit is formed by serially connecting at least two half-bridge submodules; and the modular cascade circuit is configured to generate direct current voltage by controlling the on-off state of each half-bridge submodule; wherein each half-bridge submodule is composed of two full-controlled switch devices and a capacitor, and the two full-controlled switch devices are connected in series with each other and then connected in parallel with the capacitor; wherein the full-controlled devices are configured to output zero-sum capacitor voltage by controlling on-off thereof so as to form voltage steps; and the full-controlled switch devices are IGBTs or GTOs; wherein the voltage conversion circuit is formed by a power electronic H bridge structure comprising four bridge arms, each bridge arm being respectively connected with an alternating current end and a direct current end, each bridge arm being composed of a plurality of cascaded IGBTs with inversely parallel-connected diodes; wherein the voltage conversion circuit is configured to turn on paired IGBTs in the voltage conversion circuit to form alternating current positive half waves, and when the voltage reaches a zero crossing point, to turn off the paired IGBTs and turn on other paired IGBTs in the voltage conversion circuit, to form alternating current negative half waves, thereby accomplishing conversion of direct current into alternating current; wherein the compensation circuit is formed by serially connecting full-bridge submodules, each full-bridge submodule being composed of four full-controlled switch devices and a capacitor, and the full-controlled switch devices are IGBTs or GTOs; characterised in that the compensation circuit is configured to compensate harmonics under a normal condition, to compensate a dropped direct current voltage when an alternating current system has a fault to ensure constant direct current voltage, and to generate negative total direct current voltage when a direct current system has a fault to isolate the fault.