Robust decentralized voltage control of DC-DC converters with applications to power sharing and ripple sharing

Abstract

Abstract-This paper addresses the problem of output voltage regulation for multiple DC-DC converters connected to a grid, and prescribes a robust scheme for sharing power among different sources. Also it develops a method for sharing 120 Hz ripple among DC power sources in a prescribed proportion, which accommodates the different capabilities of DC power sources to sustain the ripple. We present a decentralized control architecture, where a nested (inner-outer) control design is used at every converter. An interesting aspect of the proposed design is that the analysis and design of the entire multi-converter system can be done using an equivalent single converter system, where the multi-converter system inherits the performance and robustness achieved by a design for the single-converter system. Another key aspect of this work is that the voltage regulation problem is addressed as a disturbance-rejection problem, where unknown load current is viewed as an external signal, and thus, no prior information is required on the nominal loading conditions. The control design is obtained using robust optimalcontrol framework. Case studies presented show the enhanced performance of prescribed optimal controllers.

Distributed apportioning in a power network for providing demand response services

“…The inner-loop controller consists of a voltage controller loop that generates a current reference signal i refj and a fast current controller loop for voltage regulation of the j th DC-DC Converter. An extensive design of such inner-loop controller is proposed in [14] that implements a decentralized control architecture for load sharing among multiple parallel converters similar to the topology proposed here. The converter devices are assumed to be lossless in this article.…”

A robust scheme for distributed control of power converters in DC microgrids with time-varying power sharing

“…The design for the inner-loop controller K c is inherited from our previous work [1]. The main objective for designing the inner-loop controller K c is to decide the trade-off between the 120Hz ripple on the capacitor current i C (equivalently on the output voltage V) and the inductor current i L of the converter.…”

“…The readers are encouraged to refer to Sec. III in [1] for further details on the inner-loop control design.…”

“…The control architecture proposed in this paper addresses the following primary objectives -a) voltage regulation at the DC-link with guaranteed robustness margins, b) prescribed time-varying power sharing in a network of parallel converters, c) controlling the tradeoff between 120Hz ripple on the total current provided by the power sources and the ripple on the DC-link voltage. While these objectives are partially addressed in our prior work [1] on the robust control of DC-DC converters, a main drawback of the design proposed in [1] is that the control framework does not allow for time-varying power sharing requirements. In this work, we propose a new architecture wherein the power requirements on each converter are imposed through external reference signals; this allows for time-varying power sharing/priority prescriptions.…”

“…In this work, we propose a new architecture wherein the power requirements on each converter are imposed through external reference signals; this allows for time-varying power sharing/priority prescriptions. This is achieved without sacrificing any advantages of the design in [1].…”