A magnetically coupled multi-port, multi-operation-mode micro-grid with a predictive dynamic programming-based energy management for residential applications

© 2018 Elsevier Ltd This paper presents the development of a residential micro-grid topology based on a combination of common magnetic and electrical buses. The magnetic bus interfaces two low voltage dc buses linking a PV and a fuel cell to a high voltage dc bus connected to a grid-tied single-phase bidirectional inverter. A battery is used to store the surplus energy of the system and stabilise the dc voltage of the fuel cell bus. A synchronised bus voltage balance (SBVB) technique is used to reduce the conduction losses and increase the soft switching operation range of the converters. To improve the maximum power point tracking (MPPT) performance and system efficiency, appropriate control techniques and compensation blocks are designed. The proposed micro-grid is able to operate in multiple grid-connected and off-grid operation modes according to a predictive 2D dynamic programming-based energy management. A mode selection and transition strategy is developed to select the appropriate operation mode and smooth the mode transition. A detailed study of the micro-grid including steady-state operation, small signal modelling, controller design, and energy management is presented. A prototype of the system is developed, and experimental tests are conducted for an energy management scenario

Design, analysis and control of a magnetically-coupled multi-port multi-operation-mode residential micro-grid

© 2017 IEEE. This paper proposes topology of a magnetically coupled residential micro-grid consisting of a multi-port DC-DC converter and a single phase grid-connected bi-directional inverter. It integrates photovoltaic (PV) and fuel cell energies to supply the residential load via a common high-voltage dc bus linked to a single phase bidirectional inverter. A battery is used to store the surplus energy of the system and stabilize the bus voltage of the fuel cell port. The multi-port converter includes a three port phase shift converter for integrating renewable sources, a bidirectional buck-boost converter for charging and discharging the battery and an interleaved boost converter for boosting the PV voltage and maximum power point tracking. Using interleaved topology has reduced the effects of both high frequency current ripple and low frequency voltage ripple propagated from inverter on the maximum power point tracking (MPPT) performance. The steady state operation and control strategy of the proposed micro-grid are discussed and simulation results are presented

Topology Derivation and Development of Non-Isolated Three-port Converters for DC Microgrids

Currently, three-port converters (TPCs) are gaining popularity in applications which integrate renewable energies, such as photovoltaics and wind, and energy storage elements, such as batteries and supercapacitors with load. This is due to the advantages of a single power conversion stage between any two ports for better conversion efficiency and a highly integrated structure for compactness. Most of the reported TPCs focus on the consuming load. However, there are applications such as hybrid-electric vehicle braking systems and DC microgrids which have power generating capability. A typical example is battery charging in a DC microgrid. When the photovoltaics has inadequate power to charge the battery, the TPCs that consider only consuming load need an extra DC/DC converter for the DC bus to charge the battery. Three-winding transformers associated with full-bridge configurations as the basis for TPCs can fulfill the purpose of bi-directional power flow between any two ports. However, bulkiness of transformers and the need for more switches and associated control mechanisms increases the converter complexity, volume and cost. Solutions for integrating a regenerative load in NITPCs are still limited. This research work focuses on the development of non-isolated three-port converters (NITPCs), as they are capable of driving a regenerative load while offering a compact solution. The study includes a systematic approach to deriving a family of NITPCs. They combine different commonly known power converters in an integrated manner while considering the voltage polarity, voltage levels among the ports and overall voltage conversion ratio. The derived converter topologies allow for all possible power flow combinations among the sources and load while preserving the single power processing feature of the TPC. A design example of a boost converter based TPC with a bi-directional buck converter is reported. In addition, a novel single-inductor NITPC is proposed. It is a further integrated topology according to the aforementioned design example where only one inductor is required instead of two, and the number of power transistors remains the same. The detailed topological derivation, operation principles, steady-state analysis, simulation results and experiment results are given to verify the proposed NITPCs

DC-DC power converter research for Orbiter/Station power exchange

This project was to produce innovative DC-DC power converter concepts which are appropriate for the power exchange between the Orbiter and the Space Station Freedom (SSF). The new converters must interface three regulated power buses on SSF, which are at different voltages, with three fuel cell power buses on the Orbiter which can be at different voltages and should be tracked independently. Power exchange is to be bi-directional between the SSF and the Orbiter. The new converters must satisfy the above operational requirements with better weight, volume, efficiency, and reliability than is available from the present conventional technology. Two families of zero current DC-DC converters were developed and successfully adapted to this application. Most of the converters developed are new and are presented

A plug-and-play ripple mitigation approach for DC-links in hybrid systems

© 2016 IEEE.In this paper, a plug-and-play ripple mitigation technique is proposed. It requires only the sensing of the DC-link voltage and can operate fully independently to remove the low-frequency voltage ripple. The proposed technique is nonintrusive to the existing hardware and enables hot-swap operation without disrupting the normal functionality of the existing power system. It is user-friendly, modular and suitable for plug-and-play operation. The experimental results demonstrate the effectiveness of the ripple-mitigation capability of the proposed device. The DC-link voltage ripple in a 110 W miniature hybrid system comprising an AC/DC converter and two resistive loads is shown to be significantly reduced from 61 V to only 3.3 V. Moreover, it is shown that with the proposed device, the system reliability has been improved by alleviating the components' thermal stresses