1 Introduction
2 Storage System Overview
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Energy storage: \(E_{\mathrm{Storage}}=1{\ldots}2\,\mathrm{kWh}\)
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On-grid power: \(P_{\mathrm{Grid}}=800\,\mathrm{W}\)
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Off-grid power: \(P_{\mathrm{Island}}=1000\,\mathrm{W}\)
3 LiBIF Structure
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Small size
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Low weight
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Low cost
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High efficiency
3.1 Topology Selection
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Bidirectional rectification and sinusoidal line-side currents
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Isolated DC-DC conversion
3.2 Modeling
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The Dual Active Bridge input voltage \(v_{\mathrm{in}}(t)\) is constant over one switching period$$v_{\mathrm{in}}(t)\approx V_{\mathrm{in}}$$(1)
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The battery voltage \(v_{\mathrm{batt}}(t)\) is constant over one switching period$$v_{\mathrm{batt}}(t)\approx V_{\mathrm{batt}}$$(2)
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The total transformer leakage inductance is the sum of the leakage inductance of the primary winding (grid-side winding) and the transferred leakage inductance of the secondary winding (battery-side winding) and they are approximately equal in magnitude$$L_{\mathrm{\sigma}}=L_{\mathrm{\sigma 1}}+L_{\mathrm{\sigma 2}}^{{}^{\prime}}\approx 2\cdot L_{\mathrm{\sigma 1}}$$(3)
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The total transformer leakage inductance \(L_{\mathrm{\sigma}}\) is much lower than the transformer magnetizing inductance \(L_{\mathrm{mag}}\)$$L_{\mathrm{\sigma}}\ll L_{\mathrm{mag}}$$(4)
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Conduction power losses \(P_{\mathrm{cond}}\)
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Switching power losses \(P_{\mathrm{sw}}\)
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Transformer core power losses \(P_{\mathrm{core}}\)
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Gate driving losses \(P_{\mathrm{dr}}\)
4 Dual Active Bridge Optimization
Parameter | Value | Unit |
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\(L_{\mathrm{\sigma}}\) | 30 | µH |
\(L_{\mathrm{mag}}\) | 200 | µH |
\(N\) | 10 | – |
Parameter | Lower bound | Upper bound | Unit |
---|---|---|---|
\(T_{\mathrm{sw}}\) | 4.00 | 15.38 | µs |
\(\phi\) | -0.25 | 0.25 | – |
\(d_{\mathrm{1}}\) | 0.00 | 0.50 | – |
\(d_{\mathrm{1}}\) | 0.00 | 0.50 | – |