Strategies and Operating Point Optimization of STATCOM Control for Voltage Unbalance Mitigation in Three-Phase Three-Wire Systems

Abstract

Reactive power control through the static compensator (STATCOM) has gained wide attentions due to its outstanding performance. But for a STATCOM with traditional control strategies, unbalanced utility voltages will greatly affect the performance of the STATCOM and, in severe cases, may even cause the shutdown of the STATCOM for overcurrent protection. This paper proposes novel control strategies to ensure normal operation of STATCOM in three-phase three-wire systems when severe system voltage unbalance occurs and, furthermore, to mitigate voltage unbalance at the point of common coupling (PCC) whether it is caused by the utility or load. The control laws, operation principles, compensation characteristics, and operating point optimization of the proposed control strategies are analyzed and compared in detail. The power flow in the STATCOM and corresponding dc-side voltage-control schemes for these control strategies are also introduced. It is shown that the proposed voltage-controlled current source (VCCS) strategy and modified voltage-controlled voltage source strategy are valid for voltage unbalance compensation, especially the VCCS strategy for low rating under the same performance. Finally, the simulation and experimental investigations were carried out with these three parameter-optimized control strategies, respectively, for light and heavy load conditions. The results verified that the current passing through the STATCOM is under control and the voltage at the PCC is more balanced than before compensation. The compensation performance of the STATCOM is thus proven satisfactory.Index Terms-Control strategy, point of common coupling (PCC), static compensator (STATCOM), voltage-controlled current source (VCCS), voltage-controlled voltage source (VCVS), voltage unbalance.

Stability Enhancement in HVDC System with STATCOM

“…The terminal voltage and current of the STATCOM, at the point of connection, can be modeled by a vector representation [8][9][10]. This vector representation is extended by a d-q model which leads to the definitions of instantaneous reactive current and active current.…”

“…Also, the voltage equations in the rotating d-q frame and the input voltages in the rotating d-q frame are shown on Equation (8).…”

Optimal Control of VSC for STATCOM Applications

“…Some authors (El-Moursi et al, 2010) have analyzed the benefits of using STATCOM to mitigate voltage fluctuations and Sub-Synchronous Resonance (SSR). Wind farm integration in power system by using STAT-COM has been studied by (Saad-Saoud et al, 1998;Han et al, 2008), and the mitigation of unbalanced voltages is considered by (Li et al, 2007). The impact and stability analysis of the presence of STATCOM devices in the power system have been performed by (Cañizares et al, 2003;Khederzadeh and Ghorbani, 2011).…”

Control of grid-interfacing inverters with integrated voltage unbalance correction

“…There are power electronic converters designed for mitigation of voltage unbalance of the utility grid that work by regulating reactive power [2] [3], but this approach is not suitable for underground cables where the resistance of a cable dominates its inductance. To maintain a balanced voltage at the load terminals, an often used idea is to inject a series voltage [4] [5].…”