State‐space modelling of LLC resonant half‐bridge DC–DC converter

Abstract

Recently, LLC resonant converters have attracted significant research from industry and academia for AC-DC and DC-DC power conversion with high efficiency and remarkable power density. They are appealing candidates for numerous vehicular and renewable energy applications including battery chargers for electric vehicles and drivers of LED lights. This study introduces a mathematical model of LLC resonant half-bridge DC-DC converter, which captures its steady-state behaviours for both continuous conduction mode and discontinuous conduction mode operations. One major advantage of the proposed model lies in accurate estimation of the switching frequency of power switches under a wide range of parametric variations. This benefit is, however, not offered by the prevailing method based on the first harmonic approximation (FHA). The analytical derivations of the system's state-space model, as well as equations for calculating the switching frequency by FHA, are discussed in details. For illustration, a 340 W digitally controlled LLC resonant converter is targeted in this study. The simulation analyses of current and voltage waveforms for light and heavy load conditions are presented. Moreover, the experimental results, along with the comparison of switching frequency estimation for both methods, are demonstrated and discussed, which confirms the validity and effectiveness of the proposed model.

Application-Oriented Review of the LLC-Based Resonant Converters

“…fvco is Voltage Controlled Oscillator (VCO) center frequency, Vcr, Cr voltage, VD diode voltage drop,  feedback variable, x is state vector x=[vcr ir im vc ] T and u is input vector u=[Vin Vref] T . Therefore, the following equations are obtained [234,237,238]: There are four operational states, which are shown in Fig. 27.…”

Part II: State-of-the-Art Technologies of Solar-Powered DC Microgrid with Hybrid Energy Storage Systems: Converter Topologies

“…Du all the converters possess a high circulating current, resulting in low shows the LLC resonant converter, introduced to solve the above-m This converter has a lower minimum circulating energy than the form therefore, the MG system efficiency can be eventually improved. How uration, the input-side DC-HF AC inverter is of the half-bridge type, w siderable stress on the semiconductors compared to both sides' full-br (l) SPCD converter topology [62] Below, Figure 26 depicts the series-parallel current-driven (SPC DC converter [62], which comprises a series branch containing Ls and taining Lp and Cp. As per Figure 26, the voltage pulses are converted using this series branch inductor Ls, and the reactive current for ZVS shunt branches Lp and Cp, and hence, implementation follows the curr design.…”

“…As per Figure 26, the voltage pulses are converted using this series branch inductor Ls, and the reactive current for ZVS shunt branches Lp and Cp, and hence, implementation follows the curr design. (l) SPCD converter topology [62] Below, Figure 26 depicts the series-parallel current-driven (SPCD) full-bridge DC-DC converter [62], which comprises a series branch containing L s and shunt branches containing L p and C p . As per Figure 26, the voltage pulses are converted to current pulses by using this series branch inductor L s , and the reactive current for ZVS is generated by the shunt branches L p and C p , and hence, implementation follows the current-driven converter design.…”

Transient response improvement of half‐bridge LLC resonant converter with full‐bridge rectifier for DC microgrid

“…DC-DC converters are widely implemented as the interface in electric vehicles (EV) [1], microgrids [2], and hybrid energy storage systems [3,4]. Resonant converter, especially LLC converter, has been extensively studied in the field of DC-DC converter due to its efficient power transfer characteristics [5]. The LLC converter features soft switching, high efficiency, low noise, and low electromagnetic interference (EMI) [6].…”