Comprehensive dynamic analysis of photovoltaic generator interfacing DC–DC boost power stage

Abstract

In transformer-less grid-connected renewable energy systems, interfacing of photovoltaic (PV) generators is typically implemented by means of DC-DC boost-power-stage converter, mainly because of its voltage-boosting capability. In order to track the maximum power point of a PV generator, input voltage of the converter is usually feedback controlled, forcing the converter to operate as a current-sourced rather than voltage-sourced converter. Nevertheless, PV generator interfacing power stage is commonly assumed to possess the same dynamic properties as corresponding voltage-sourced power stage. Investigations presented in this study reveal explicitly that the dynamics of PV generator interfacing DC-DC boost power stage resembles conventional buck power stage behaviour with duty-cycle independent resonance and additional right-halfplane zeros. In addition, the duty cycle has to be decreased for increasing the corresponding output variables (i.e. input voltage and output current). Extended experimental results are given to support the theoretical findings.

Review of PV Generator as an Input Source for Power Electronic Converters

“…Equation (5) indicates that the converter with input filter contains two RHP zeros approximately at Figure 12 for the variable and component definitions). The RHP zeros are the same as in the output control dynamics of the current-fed boost-power-stage converter reported in [50].…”

“…The RHP zeros are the same as in the output control dynamics of the current-fed boost-power-stage converter reported in [50]. …”

“…It changes the steady-state and dynamic properties of the current-fed converter to resemble the properties of the dual of the corresponding voltage-fed converter (i.e., a buck converter is the dual of boost converter and vice versa) (cf. [48,50]). If the original switch-control scheme is maintained the same as in the voltage-fed converter, then the duty ratio has to be decremented for increasing the output variables of the current-fed converter [64] or the gate-drive signals have to be inverted for increasing the output variables along the increase in duty ratio as well [87].…”

“…Figure 2b), and, therefore, Y pv ≈ 1/r pv + sc pv . As Figure 8 indicates, the resistance dominates in Z pv (Y −1 pv ) up to some kHz, and therefore, it may be obvious that the dynamic resistance (r pv ) will be responsible for the observed changes in the interfacing-converter dynamics [9,10,28,50]. The input capacitor or LC input filter is, in practice, an essential part in the PV-interfacing converter either for satisfying the theoretical terminal constrains stipulated by the current source (i.e., input capacitor) [90] or for preventing the output capacitance of the PV generator to damage the associated switches (i.e., LC input filter, cf.…”

“…The open-loop input-control dynamics does not usually contain RHP zeros (cf. [48,50,52,53]). If the converter operates in open loop or the feedback loops are taken from the input voltage then the RHP zero does not have effect on the interfacing-converter behavior.…”