Impact of non-idealities on the Performance of an Ultracapacitor based Bidirectional DC/DC Converter

Abstract

This paper analyses the impact of non-idealities on the performance of an ultracapacitor based bidirectional DC/DC converter. In particular, this work analyses the impact of ON state resistance of the MOSFET switches on the performance of bidirectional DC/DC converter. It is shown that, under particular operating conditions, the ON state resistance of the MOSFET can have a significant impact on the performance of th DC/DC converter and can cause an unstable response. An analytical expression is derived to identify the operating conditions under which the non-idealities can have a significant impact on the performance of the DC/DC converter. Simulation results are presented to aid the analysis reported in this paper.

Coordinated Control of PV-Ultracapacitor System for Enhanced Operation Under Variable Solar Irradiance and Short-Term Voltage Dips

“…The sizing of the ultracapacitor stack depends on (a) the desired power level (i.e., the power level required as a back up for the PV system), (b) the typical duration of discharge and (c) the minimum allowable discharge voltage of the ultracapacitor stack. Given the discharge power (P 0 ), duration of discharge (∆t) and rated voltage across the UC stack (V uc,n ), the minimum capacitance of the UC stack is given by [35], [36].…”

“…3. The filter inductor (L) of the bidirectional DC/DC converter is designed [36] based on the maximum allowable current ripple (δ i ; expressed as a fraction of average current). For a given δ i , the minimum value of inductance that will ensure that the current ripple criterion is satisfied (during charging and discharging modes) is given by…”

“…If the power is positive P uc > 0, then the converter will be operating in DM, during which the bidirectional DC/DC converter acts as a boost converter. The corresponding G uc (s) can be computed using state space averaging as [36]…”

“…During the CM ( i.e. P uc < 0), the bidirectional DC/DC converter acts as a buck converter, and the corresponding transfer function of the system can be computed as [36]…”