Battery energy storage system (BESS) is promising to be implemented in residential applications for supporting PV integration, load shifting, and backup power purposes. For this application, 48V second-life battery draws more and more attentions for their cost-effectiveness, safe voltage level, reliability, and potential large market. This thesis proposes the comprehensive control and design of an isolated battery-driven grid interface (IBDGI) with the dual-active-bridge (DAB) converter for residential applications with 48V battery pack.
The three-phase DAB converter is a promising candidate as the front-end DC/DC converter in the two-stage IBDGI due to its high efficiency, high power density, and low capacitance requirement. An effective design strategy for the three-phase DAB converter is proposed based on the zero-voltage-switching (ZVS) zone and back-ow power to achieve high efficiency for a wide operating voltage range and different load conditions. Based on the power loss model, an easily-implemented variable switching frequency operating method is proposed to further increase the efficiency at light load conditions.
The dead-time effect is observed in the three-phase DAB converter. To avoid the dead-time effect and better understand the phenomena, a comprehensive analysis is proposed. All the cases of the dead-time effect in the three-phase DAB converter are analyzed in terms of the buck, boost, and matching states. The expressions of the transmission power, constraint conditions, and key time of the dead-time effect are derived for each state. The operation waveforms of the dead-time effect are also presented.
The hybrid capacitor bank composed by the LC resonant lter with electrolytic
capacitor and lm capacitor is utilized for the DC bus of the IBGDI. The electrolytic
capacitors work as passive decoupling purpose while the lm capacitor is responsible
for high switching harmonic ltering. Moreover, a current sharing method between
the hybrid capacitor bank is proposed to extend the electrolytic capacitor's life.
The LCL single-phase inverter is applied for the downstream of the IBDGI. A
step-by-step design procedure of the LCL lter with passive damping is proposed for
the 120V/240V dual grid-tied and standalone modes. The PR controllers are also
designed for the LCL inverter for standalone and grid-tied modes.
At the system level, a novel second harmonic current (SHC) reduction strategy is
proposed for the IBDGI with the three-phase DAB converter by adding a load current
feedforward (LCFF) path to the DAB voltage closed-loop controller. This method will
suppress the SHC without modi cations of the original controller's bandwidth, which
make it easy to be implemented. The small-signal model of the three-phase DAB
converter is provided and veri ed by the step response. The parameter sensitivity
analysis for the LCFF method is proposed to show that the SHC is well suppressed
within ±20% parameter error.
The proposed converter and control methods are veri ed by simulation and experimental
results. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/23389 |
| Date | 22 June 2018 |
| Creators | Deqiang, Wang |
| Contributors | Emadi, Ali, Electrical and Computer Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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