Transformer‐less single‐phase unified power quality conditioner of no circulating current

Abstract

This study presents a unified current-source power quality conditioner of inherent no circulating current. It is formed of a three-leg current-source ac/ac converter and a specially designed small size dc-link. Owing to the transformers-less feature and small size dc-link, the proposed topology has the benefit of high power density. In addition, without the need to address the circulating current issue, it is easier to design the controllers and filters for the circulating current compared to other existing transformer-less unified power quality conditioners. To handle the harmonic currents compensation, voltage sags/swells elimination, power factor correction simultaneously and achieve excellent dynamic and steady-state performance, a direct control method based on an extended repetitive disturbance observer is proposed. Detailed analysis of topology and operation principles is given, followed by the modulation scheme and the developed control method. Simulations and experimental results are presented to verify the effectiveness of the conditioner.

A new configuration of grid‐connected photovoltaic‐based multifunctional power converter for single‐phase system

“…The fundamental active component of load current is obtained using the single-phase dq theory. Here, the sensed load current i l is first converted into αβ and then to dq frame using Equations ( 9), (10), and (11).…”

“…The work in previous studies 4 − 8 presents the conventional topology of UPQC with a back‐to‐back (B2B) converter and transformer. Some transformerless topologies are also developed to decrease system cost and bulkiness and discussed in previous studies 9–11 …”

Power quality improvement using three‐phase transformerless grid interfaced SECS enabling leakage current suppression

“…In conventional strategies [25][26][27], these controllers fails to accomplish the revised harmonics control standard for an electric power system as the total harmonic distortions of the grid currents violate the standard with the presence of nonlinear loads. Owing to this issue, the repetitive controller is analysed in the voltage control strategy [29][30][31][32] to provide harmonics compensation. The repetitive controller is tuned at a specific frequency to estimate the harmonics component from the input signal.…”

A new six‐switch converter based unified power quality conditioner for improving power quality in single‐phase system

“…Work in Reference 13 suggests a way to minimize the total VA rating of single‐phase UPQC. Recent work proposes transformerless UPQC in References 14, 15, and 16, which reduces system cost and bulkiness. Control of transformerless three‐leg UPQC with a novel space vector modulation method is explained in Reference 15.…”

“…Recent work proposes transformerless UPQC in References 14, 15, and 16, which reduces system cost and bulkiness. Control of transformerless three‐leg UPQC with a novel space vector modulation method is explained in Reference 15. A new trend in UPQC has emerged where active power from distributed generation is also additionally fed to a connected network 17‐23 …”