Boundary-free flexible DC power distribution network single-ended protection method and boundary-free flexible DC power distribution network single-ended protection system

The invention discloses a boundary-free flexible direct-current power distribution network single-ended protection method and system. The method comprises the steps that whether a direct-current line breaks down or not is judged according to direct-current voltage at a protection installation position in the direct-current line; after a fault occurs, positive and negative electrode voltage amplitude variation is detected, and a fault electrode is judged according to the polarity of the positive and negative electrode voltage amplitude variation; the current fault component of the fault pole is detected, the fault direction is judged according to the polarity of the current fault component of the fault pole and the fault pole judgment result, and the obtained fault direction is a forward fault or a reverse fault; and determining a line mode voltage first wave amplitude-time ratio according to the line mode voltage at the protection installation position, and determining a fault section according to the line mo