Inductor Saturation Compensation in Three-Phase Three-Wire Voltage-Source Converters via Inverse System Dynamics-II

Abstract

Current waveform quality and current control bandwidth are the figures of merit for current controllers in three-phase three-wire (3P3W) voltage-source converter (VSC) systems. When saturable inductors are employed as converter side inductors due to cost, size, and energy conversion efficiency benefits in 3P3W VSCs with conventional synchronous frame current control (CSCC); substantial drawbacks arise by means of these figures of merit. In the preceding part of this study, an inverse dynamic model based compensation (IDMBC) method has been proposed to deal with these drawbacks. Complementarily, this paper presents a thorough analytical investigation of the control system characteristics of CSCC and IDMBC methods that affect the current waveform quality and current control bandwidth. The analyses are verified via dynamic response and waveform quality simulations and experiments that employ saturable inductors reaching $1/9^{th}$ of the zero-current inductance at full current. The results obtained demonstrate the suitability of the IDMBC method for 3P3W VSCs employing saturable inductors.

Inductor Saturation Compensation in Three-Phase Three-Wire Voltage-Source Converters via Inverse System Dynamics-I

“…The nonlinear dynamics of 3P3W VSC current regulation systems with saturable inductors in Fig. 3 can be described by two-phase representation as in (16) which was formerly elaborated in [13]. Based on this representation, the CSCC becomes as shown in Fig.…”

“…In a subsequent paper [16], the command to output, disturbance to output, and cross-coupling decoupling characteristics of the proposed IDMBC method and CSCC method are elaborated analytically. Furthermore, simulation and experimental results are provided in comparison with the CSCC method to verify the analyses and to demonstrate the superiority of the IDMBC method.…”

Inductor Saturation Compensation in Three-Phase Three-Wire Voltage-Source Converters via Inverse System Dynamics-I

“…In (16), v σ represents the control column vector in a line-toline voltage manner to regulate the load current vector i σ . In the current regulation process, the load voltage, nonidealities such as semiconductor voltage drops, dead-time effects, and the load (grid) voltage appear as voltage disturbance sources and denoted as two-element line-to-line voltage vector v D .…”

“…Based on (16) and (17), two-phase column vector block diagram representation of 3P3W VSC conventional closedloop current control system is illustrated in Fig. 6.…”