Modelling and control of cascaded multilevel converters for dynamic compensation

Abstract

Purpose -This paper aims to integrate cascaded multilevel converters in the static compensator (STATCOM) systems in order to assure dynamic compensation of the reactive power absorbed by fixed speed wind turbines. Design/methodology/approach -The cascaded multilevel converter topology is incorporated as a variable source of reactive power required by the wind farm. The evaluation of reference reactive currents is assured by the technique of instantaneous power theory. Thus, the STATCOM, with its appropriate control strategy, continuously compensates the reactive currents. Findings -A developed non-linear state representation makes possible the analysis of static and dynamic behaviour of the proposed system. The STATCOM-based cascaded multilevel converter is able to provide continuous compensation and proves highly dynamic under steady state and transient operating conditions. Practical implications -The paper formulates a mathematical model which includes all parameters describing the system composed by a medium voltage network, a wind farm and a STATCOM-based cascaded multilevel converter. The study may help to develop new control methods of such power systems containing non-linearities and an extended number of parameters. Originality/value -Since there are few studies on comprehensive and complete models of power systems, the paper contributes to make both a study and a simulation based on a developed non-linear state model which perfectly describes the state and transient behaviour of the proposed system.

STATCOM – A Preface to Power Quality in Power Systems Performance

“…Instantaneous power theory for reference current extraction has been executed for multi-level inverter used in wind mill. The approach of the author is to analyze dynamic response of STATCOM for constant speed wind turbine [79]. Modular structure of cascaded multilevel inverter with two full-bridge units in parallel with two halfbridge units with single control loop to control both DC link voltage [80] and to improve power factor [81] has been obtained.…”

Current balancing of cascaded H-bridge converters for PV systems with partial shading

“…According to the statement of DG in distribution network, this paper analyses a three-phase PV power system connected to a LV distribution grid as described in Rivera et al (2011); Xiao et al (2013). The PV system is based on a three-phase Y-connected cascaded H-bridge topology (Fathi et al, 2009;Jaafar et al, 2008). The analytical model of the PV system and a control strategy for unbalanced operations of the PV system is proposed in this paper.…”

Asymmetrical cascaded multilevel converter applied in photovoltaîc systems

“…[10] [11] [12]. The peak to peak amplitude Am is equal to the sum of the voltages E of the DC continues bus of the CMC inverter.…”