Enhanced Gain Two-Quadrant DC–DC Converters—Mixed Sensitivity Based Controller Design

In this article, three bipolar two-quadrant dc–dc converters are formulated. The Z-source dc–dc converters and LCL-cell are the basis for these evolutions. These topologies are effective in generation of bipolar voltages but constitute higher order systems. Also, the component count is higher (six L/C components and four switching devices) in these topologies. In an attempt to minimize the component count and yet to exhibit better voltage gain in bipolar mode like in quadratic boost topologies, a bipolar voltage cell based four different bipolar topologies are evolved. The bipolar voltage generation cell (BPVC) is simple in structure [contains four-switches and four-LC elements (2-L, 2-C)] and yet is effective in buck–boost voltage magnitude realization in bipolar mode. All these four topologies [bipolar boost dc–dc converter (BPBDC) Type-1 to Type-4] exhibit low ripple content in the source current. Additionally, BPBDC Type-4 exhibits better buck–boost voltage profile both in positive and negative load voltage polarity mode. Detailed steady-state analysis is formulated and performance aspects are investigated for BPBDC Type-4, while brief formulations are listed for other bipolar topologies. Bipolar mode of operation of these topologies necessitates robust controller for automatic power control and polarity reversal. In view of this, operating point sweeps over wide ranges, and hence a mixed sensitivity based H_∞ optimization is adopted for robust controller design. Sensitivity and complementary sensitivities are simultaneously optimized so that the resulting controller preserves better noise and disturbance rejection features. A 24 to ±42 V, 50 kHz BPBDC Type-4 prototype is built to demonstrate the effectiveness of the BPVC in bipolar mode of operation. Experimental results are in close agreement with the analytical results.