Due to the poor performance of traditional STATCOM in DC engineering, a compensation method using battery energy storage STATCOM (STATCOM/BESS) to suppress commutation failure of the weak receiving-end high voltage direct current transmission system is proposed, and its effect is better than traditional STATCOM. First, the mechanism and influencing factors of commutation failure are analyzed; the extinction angle of the converter valve is taken as the decision index of commutation failure; the relationship between various electrical parameters and extinction angle is studied under the condition of the single-phase grounding fault on the inverter side. Second, according to the differences between the positive and negative sequence reactive current output by STATCOM/BESS when a fault occurs in single-phase grounding, a compensation method is proposed to suppress commutation failure by STATCOM/BESS, which increases the proportion of positive sequence reactive current output by STATCOM/BESS under the condition of constant output so as to reduce the probability of commutation failure. At last, STATCOM/BESS is added into the standard model of LCC-HVDC for the simulation experiment and compared with conventional running characteristics of STATCOM in order to verify the effect of STATCOM/BESS in suppressing commutation failure.

When traditional STATCOM (Static Synchronous Compensator) performs large-capacity reactive power compensation, the control accuracy of the DC side voltage will be affected and the DC side voltage will fluctuate greatly. Therefore, this study proposes to use battery energy storage STATCOM (STATCOM/BESS) and gives the main circuit topology of STATCOM/BESS. By analyzing the working principle of STATCOM/BESS, the mathematical model and control method are derived and modeled, in which the Shepherd model is used as the energy storage battery in STATCOM/BESS. Aiming at the possible imbalance of the battery state of charge (SOC) in STATCOM/BESS, the phase-to-phase SOC balance control and phase control are proposed. At last, in PSCAD/EMTDC simulation software, STATCOM/BESS is tested for dynamic response and steady-state response performance of active power control, reactive power control, and transformation failure suppression test, which verifies the effectiveness and superiority of STATCOM/BESS commutation failure.

With the rapid development of cities and the increasing complexity of distribution network systems, the cableization of transmission lines and the diversification of power users have brought new challenges to the supply reliability of distribution networks. Short-time outages caused by power outages and maintenance are one of the factors that affect the reliability of the power supply in the distribution network. The non-stop load transfer through a phase-shifting transformer (PST) operation can effectively improve the reliability of power supply to complex distribution systems. Considering the operation mode and structure form and fault type of the urban distribution network in China, comparing and analyzing the applicable scenarios of different neutral grounding methods, and based on the structure and zero sequence path characteristics of PST, an improved PST-based phase shifting and grounding transformer loop closing device with low power consumption is proposed. The fault characteristics of the PST-based loop closing device under the small current grounding system are also analyzed by the sequence component method, and, finally, the effectiveness of the phase-shifting and grounding transformer device is verified by simulation under PSCAD/EMTDC for fault routing and protection configuration of the urban distribution network in China.