23:T48c,

PEBB (power electronics building block) systems are typical nonlinear systems. Under the conventional but still popular linear control design, the system stability margin varies from one operating point to another. This paper introduces a novel approach to monitoring the DC bus stability margin of a PEBB system online. At the steady state of the system, a small-signal perturbation current î _p is injected into the DC bus, and the load-side response current î _L is measured. By checking the validation |î _L (jw)| < |î _p (jw)|, the system stability margin can be examined. Experiments on a 48 V DC DPS demonstrate the proposed measurement approach. An implementation approach is also proposed for an 800 V DC PEBB-based testbed system.

24:T48f,

In a distributed power system based on power electronics building blocks (PEBBs), it is desirable to use a parallel structure with standardized PEBB modules in order to increase power level, provide redundancy and improve system performance. Nonlinear couplings and interactions, however, may occur among the parallel modules. Compared with their counterpart DC/DC converters, three-phase AC/DC or DC/AC converters exhibit stronger dynamics when they operate in parallel. The objective of this paper is to comprehensively analyze the nonlinear dynamics among two parallel three-phase converters. The paper firstly develops a nonlinear average model in rotating coordinates. Based on the model, the nonlinear dynamics, such as small-signal interaction, zero-sequence circulating current and high frequency noise, are analyzed. To improve the system performance and minimize the interactions, some feedback control strategies are proposed. To deal with high-frequency noise, a feedforward control scheme is proposed. The scheme can significantly reduce both common-mode and differential-mode noise. Simulations and preliminary experimental results are presented.

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PEBB System Stability Margin Monitoring

Dynamics Analysis of Parallel Three-Phase Converters