A Novel DC Voltage Control Method for STATCOM Based on Hybrid Multilevel H-Bridge Converter

Abstract

This paper presents a transformerless static synchronous compensator (STATCOM) system based on hybrid multilevel H-bridge converter with delta configuration. This hybrid multilevel STATCOM is characterized by per-phase series connection of a high-voltage H-bridge converter operating at fundamental frequency and a low-voltage H-bridge converter operating at 5 kHz without any other circuit for dc voltage control. A new control strategy is proposed in this paper with focus on dc voltage regulation. Clustered balancing control is realized by injecting a zero-sequence current to the delta-loop, while individual voltage control is achieved by adjusting the fundamental content of ac quasi-square-waveform voltage of high-voltage converter. A downscaled experimental prototype rated at 100 V and 3 kVA is constructed in author's laboratory. Experimental results show that the hybrid multilevel STATCOM performs satisfactory not only improving efficiency and waveform quality, but also compensating reactive power and negative-sequence current while maintaining dc voltage at the given value. Index Terms-Cascade H-bridge, dc voltage control, hybrid multilevel, static synchronous compensator (STATCOM).

Reactive Power Strategy of Cascaded Delta-Connected STATCOM Under Asymmetrical Voltage Conditions

“…With the current references solved in (24), the voltage and current control of delta-connected STATCOM is presented in Fig. 3.…”

“…to adjust the active component of each phase current. After adding the active power components with the phase current references solved in (24), the final phase current references are obtained. In order to enhance the re- performance, the deadbeat controller is adopted for the current inner-loop; v rab , v rbc and v rca are the modulation signals for the three clusters.…”

“…Since the maximum reactive power decreased under asymmetrical voltage conditions, the three methods APOE, RPOE and BPSC are analyzed and compared taking peak current limitation into account to investigate the reactive power support capability of STATCOM. In the analysis, the maximum current value shown in Fig.4 is calculated according to (20) and (22), and phase current references are calculated from (24) to limit the maximum current value.…”

“…In [21]- [23], reactive power and unbalanced load compensation were illustrated in detail. Voltage balancing control and performance optimization were discussed in [24]- [27]. Two compensation modes of delta-connected STATCOM were discussed in [28], and an individual phase instantaneous current control method was proposed to simplify the compensation method.…”

A Novel Controller for Electric Springs Based on Bode Diagram Optimization

“…However, for future smart grids with low inertia, the aforementioned issue could be problematic. Although static var compensators (SVCs) and static var generators (SVGs) can act as reactive power compensators to stabilize ac mains voltages [4]- [9], neither can realize the function in which the load demand matches the power generation dynamically. Moreover, SVCs and SVGs can only provide pure reactive power compensation.…”