High performance current control of single‐phase grid‐connected converter with harmonic mitigation, power extraction and frequency adaptation capabilities

Abstract

Grid-connected converters in distributed generation systems are required to operate under highly distorted voltage with a wide frequency range, and to provide active/reactive power information for ancillary services and power control. This paper presents multiple unbalanced synchronous reference frame control for regulating and mitigating the grid current distortion of a voltage source converter caused by grid voltage distortion and converter deadtime. The proposed control technique has intrinsic power extraction and frequency adaptation capabilities. The multiple unbalanced synchronous reference frame control is compared with the proportional multi-resonant control. A new controller which combines the unbalanced synchronous reference frame control for regulation of the fundamental component current and the multi-resonant control for harmonic compensation is presented. The proposed control techniques were verified with a 1.5-kVA LCL-filtered grid connected inverter. The multiple unbalanced synchronous reference frame control with odd harmonic orders 3rd to 13th exhibited excellent harmonic rejection with a total harmonic distortion (THD) less than 0.60% under a highly distorted voltage. The proposed combined control technique provided slightly inferior performance with the grid current THD less than 0.65%. The combined control scheme retains functionalities as the multiple unbalanced synchronous reference frame control with a significant reduction of computational effort. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Fast Bus Voltage Control of Single-Phase Grid-Connected Converter With Unified Harmonic Mitigation

“…The harmonic voltages also cause grid current distortion at the PCC and the VSC terminals due to a dead time T DT in each VSC leg [21], [22]. Feedforward of the PCC voltage partly mitigates the grid current distortion [22].…”

“…The harmonic voltages also cause grid current distortion at the PCC and the VSC terminals due to a dead time T DT in each VSC leg [21], [22]. Feedforward of the PCC voltage partly mitigates the grid current distortion [22]. However, a DC offset in the voltage measurement induces an undesirable DC component injecting to the grid [23].…”

“…The PCC and dead-time harmonic voltages are the grid current control loop's disturbances, which can be mitigated by using a grid current controller with selective harmonic mitigation. Multi-frequency synchronous reference frame controllers [22], multi-frequency proportional-resonant controllers [22], [26], [27], and repetitive controllers (RC) were proven to be effective solutions [21].…”

“…The bus voltage control schemes in [12], [13], [14], [16], [17], [18], [19], and [20] were carried out under a sinusoidal voltage with negligible dead time. Meanwhile, a sinusoidal reference was applied to the current control loop under the grid voltage harmonics [21], [22] and the dead-time voltage compensation schemes [21], [22], [24], [25], which do not guarantee a sinusoidal grid current with the bus voltage control loop. Therefore, we present a comprehensive analysis of the current harmonic sources of the single-phase grid-connected VSC, which results in an alternative approach to the VSC bus voltage control under a distorted PCC voltage and a significant VSC dead time.…”

An improved capacitor voltage full feedforward control strategy for LCL‐type grid‐connected inverter based on control delay compensation

“…In recent years, renewable energy power generation schemes based on wind energy and photovoltaics have been extensively researched and used. As the connector between distributed power generation and the public grid, grid-connected inverters have been widely dispersed in distributed generation (DG) systems such as photovoltaic panels, wind turbines, and energy storage [1,2].…”