Abstract
This thesis is mainly concerned with the development of a grid-connected three-phase battery energy storage systems (BESS) having plug-in energy harvesting from various AC and DC sources. All controls are digitally realized using digital signal processor (DSP). In the developed BESS, the DC-link voltage of grid-connected inverter is established from the battery bank via an interleaved bidirectional DC/DC converter with two modules. The DC-link single current sensing technique is applied for successfully conducting the current-mode controls of parallel converters. As to the inverter, the properly designed current control schemes in phase domain makes it possess good power conditioning control capability between BESS, local load and utility grid. In addition to the load reactive and harmonic power compensations, the proposed BESS is arranged to perform the following three modes: (i) Battery-to-grid (B2G) discharging mode: the BESS provides all load powers and sends the preset real power to the utility grid; (ii) Grid-to-battery (G2B) charging mode: the utility grid supplies all load real powers and charges the battery bank; (iii) Floating mode: all load real powers are supplied by utility grid. As the utility grid failure occurs, the BESS is isolated from utility grid and operated in battery-to-home (B2H) mode for supplying uninterruptible power to the load. To effectively utilize the possible renewable, distributed and backup energy, the plug-in energy harvesting system is developed to make the battery auxiliary charging. Two energy harvesting paths are provided: (i) Three-phase source followed by three-phase bridgeless discontinuous-current mode (DCM) switch-mode rectifier (SMR). Through proper arrangement, in addition to wind AC generators and three-phase back-up AC sources, the single-phase AC source or DC source can also be the harvesting inputs; (ii) DC source followed by interleaved buck-boost DC/DC converter. The harvested energies can perform the battery charging and the energy support to the BESS via two possible channels, namely: (i) Direct charging the battery via a buck DC/DC converter; and (ii) Through an isolated resonant DC/DC converter to the common DC-link of the BESS. The bidirectional interconnected operations between the developed BESS and the micro-grid (B2M/M2B) as well as the BESS and the electric vehicle (B2V/V2B) can also be applicable.