Abstract: The controllable line commutated converter（CLCC） is a new type of DC converter equipment to solve the commutation failure problem of conventional DC transmission converter valves. In June 2023, CLCC was put into operation in the ±500 kV/1 200 MW Gezhouba to Shanghai Nanqiao high voltage DC transmission system renovation project（referred to as “GezhoubaNanqiao renovation project”） in China. This paper describes the technical requirements and principles of CLCC and analyzes its technical economy. Combined with the implementation of the Gezhouba-Nanqiao renovation project, the development, testing,and application of CLCC are introduced. Then, the electrical parameters, structure design schemes and the type test schemes of CLCC are proposed. The key test items and test results of the low-voltage boosting test, the no-load boosting test, and the artificial short-circuit test during engineering commissioning are introduced in combination with the field recording waveforms. And the operation performance after the project was put into operation is also introduced. According to the field recording waveforms of AC fault events, the correctness of the operation sequence of the converter is analyzed in detail. Finally, the application prospects of CLCC in ultra-high voltage DC transmission projects, provincial AC tie-line renovation, and other scenarios are analyzed,providing a reference for further promotion and application of CLCC.