Grid Direct-current Flexible Loop Closing Control Device and Method

A grid direct-current flexible loop closing control method, comprising the following steps:

• step 1, establishing a grid direct-current flexible loop closing control device system model, monitoring for a long time power of two transmission lines requiring loop closing, and making preparation in real time for loop closing;
• step 2, before loop closing, setting a bus tie switch and an access switch to be in an off state and two loop closing control devices to be in a voltage control mode;
• step 3, after a loop closing instruction is received, determining whether direct-current bus voltages of the two loop closing control devices are identical;
• if not, regulating the direct-current bus voltages by a constant direct-current voltage control mode of parallel coupling units;
• after the direct-current bus voltages of the two loop closing control devices are determined as identical, turning on the direct-current access switch K to allow a system to enter a loop closing state;
• after loop closing, dynamically adjusting an amplitude and phase of an additional voltage of a series coupling transformer to realize flexible power mutual aid of two transformer regions subjected to loop closing;
• and
• step 4, before exiting loop closing, setting two flexible loop closing control devices to work in a PQ control mode, and turning off the access switch K after P and Q of the two flexible loop closing control devices are gradually decreased to zero, such that a direct-current flexible loop closing process is ended.