MMC system soft-start grid-connected method for flexible direct-current transmission

• Main Authors: LI LIN, ZHOU LIZHUAN, LAN JINGHAO
• Format: Patent
• Language: Chinese; English
• Published: 14.09.2016
• Subjects: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC,OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWERSUPPLY SYSTEMS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTINGELECTRIC POWER; CONTROL OR REGULATION THEREOF; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUTPOWER; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER; ELECTRICITY; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERATION; REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGYGENERATION, TRANSMISSION OR DISTRIBUTION; SYSTEMS FOR STORING ELECTRIC ENERGY; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS; TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINSTCLIMATE CHANGE

The invention discloses an MMC system soft-start grid-connected method for flexible direct-current transmission. The method comprises the following steps: setting an MMC converter valve control mode to be a direct-current voltage balance control mode; turning off an alternating-current side power supply switch, precharging a capacitor of an SM submodule, and enabling an MMC converter valve to be under a locking condition; issuing an unlocking command, and continuously charging the capacitor of the SM submodule; when the direct-current voltage of the SM submodule reaches a steady state, issuing a locking command, and then bypassing a charging resistor; issuing un unlocking command so that a soft-start control strategy starts, and slowly raising direct-current bus side voltage at a rated value, so that the whole start process of the single-ended MMC converter valve is completed; charging an MMC converter valve at the other end according to the above steps, wherein the steps can be performed at the same time. Th