Interval Robust Controller to Minimize Oscillations Effects Caused by Constant Power Load in a DC Multi-Converter Buck-Buck System

Abstract

Multi-converter electronic systems are becoming widely used in many industrial applications; therefore, the stability of the whole system is a big concern to the real-world power supplies applications. A multi-converter system comprised of cascaded converters has a basic configuration that consists of two or more converters in series connection, where the first is a source converter that maintains a regulated dc voltage on the intermediate bus while remaining are load converters that convert the intermediate bus voltage to the tightly regulated outputs for the next system stage or load. Instability in cascaded systems may occur due to the constant power load (CPL), which is a behavior of the tightly regulated converters. CPLs exhibit incremental negative resistance behavior causing a high risk of instability in interconnected converters. In addition, there are other problems apart from the CPL, e.g., non-linearities due to the inductive element and uncertainties due to the imprecision of a mathematical model of dc-dc converters. Aiming to effectively mitigate oscillations effects in the output of source converter loaded with a CPL, in this paper, an interval robust controller, by linear programming based on Kharitonov rectangle, is proposed to regulate the output of source converter. Several tests were developed by using an experimental plant and simulation models when the multi-converter buck-buck system is subjected to a variation of power reference. Both simulation and experimental results show the effectiveness of the proposed controller. Furthermore, the performance indices computed from the experimental data show that the proposed controller outperforms a classical control technique. INDEX TERMS Constant power load (CPL), multi-converter buck-buck system, parametric uncertainties, robust control based on Kharitonov rectangle, mitigation oscillations in multi-converter buck-buck system.

Robust Control Design Procedure Based on Particle Swarm Optimization and Kharitonov’s Theorem with an Application for PMSMs

“…Assuming that the plant is described by a model whose coefficients are not precisely known, but belong to real intervals, the robust stability under uncertain parameters can be certified by the Kharitonov's Theorem [4], [14], [15]. In the context of power electronics, Kharitonov's Theorem was used to certify the robustness against uncertainties, for instance, in Buck converters [16], microgrids [17]- [19], and PMSMs [20]- [22]. Although Kharitonov's Theorem has been applied to define, a priori, regions of robust stability, employed for choosing the control gains, the use of this tool during the control tuning stage still demands further investigation.…”

Fixed Switching Frequency Digital Sliding-Mode Control of DC-DC Power Supplies Loaded by Constant Power Loads with Inrush Current Limitation Capability

“…In [18], a robust control approach has been considered for the elementary power electronics switching converters with a CPL. In [19] robust controller based on linear programming is proposed to regulate the output of buck converters loaded by another buck converter acting as a CPL. A comprehensive review of the compensation techniques for switching converters with CPL can be found in [20].…”

Comparative study of control strategies for oscillation damping in DC microgrids

“…The modeling and control of DC-DC converters allow the construction of DC microgrids. Microgrids are composed of feeders that must maintain a constant voltage of DC bus to which are connected DC loads as in (Marcillo et al, 2019;Singh et al, 2017). The behavior of the constant power loads (CPL) in the connection with the DC bus is studied in (Mosskull, 2018), where it is observed oscillations in the feeder due to the constant consumption of power of the CPL that causes a variation of current and voltage for the maintenance of the constant power.…”

“…The behavior of the constant power loads (CPL) in the connection with the DC bus is studied in (Mosskull, 2018), where it is observed oscillations in the feeder due to the constant consumption of power of the CPL that causes a variation of current and voltage for the maintenance of the constant power. These variations result in the occurrence of a negative resistance in which its effects are observed in the form of oscillations in the DC bus (Marcillo et al, 2019;Singh et al, 2017).…”

“…Ensuring the stability of the microgrid is fundamental to the proper functioning of the system and in (Riccobono and Santi, 2014) it is shown criteria that guarantee the stability of the system among which stands out the criterion of Middlebrook that ensure the DC microgrid stability if the output feeder impedance is less than the input impedance of CPL. The mitigation of CPL oscillations is already investigated in (Mosskull, 2018) that shows the relationship between good damping and small power variations, and in (Marcillo et al, 2019), that uses robust control strategies to reduce the oscillation effects. This paper proposes a DC microgrid model where the feeder is represented by a boost converter while the CPL is designed through a buck converter.…”