High boost‐ratio bidirectional converter for interfacing low‐voltage battery energy storage system to a DC bus

Abstract

Supply and demand mismatches in renewable energy systems are addressed by integrating battery banks. Selecting battery bank terminal voltage to match DC-bus voltage (350-450 V for single-phase AC loads), necessitates employing battery banks with long-string connections along with their attendant shortcomings. To employ short-string battery banks, high-boostratio bidirectional interfaces are required between the DC-bus and battery bank. Current literature lacks a single source where high-boost-ratio converters' are categorised and their strengths and weaknesses identified. Comprehensive literature review is hence carried out to determine attributes of various high-boost-ratio DC-DC converters and also categorise them. The key attributes of a topology to interface battery storage to a DC-bus are determined. Based on these a bidirectional tapped-inductor boost converter emerges as the best candidate. Moreover, in order to regulate output voltage, voltage-gain versus duty-ratio characteristics should not be very steep. Since battery terminal voltage varies with state-of-charge, closed-loop control is necessary. Converter's small-signal transfer-functions are derived and a two-loop controller to regulate output voltage and inductor current while allowing bidirectional power flow designed. A novel bidirectional passive lossless snubber circuit is employed to clamp the voltage spikes across the active switches, without altering the normal operation of the converter.

Modular Circuit Synthesis Oriented Modelling Approach for Non-Isolated DC-DC Converters in DCM

“…The available literature does capture the relevant merits and demerits of two-port parameters and network connection [28,38]. Figure 3 provides a graphical representation of the modelling procedure, i.e., (1) the input and output BBBs are modelled independently, (2) the connection of the input and output BBB dictates the type of parameters used for the two-port network and, (3) the generalised transfer functions are derived. The modelling process is the same for both steady-state and dynamic small-signal models.…”

“…In this section, the presented modelling scheme based on BBBs is shown to be directly applicable to non-conventional converters with well-defined BBBs. For non-conventional converters, the modelling burden is the same as that for conventional converters, i.e., (1) identify the constituent BBBs and, (2) identify the accompanying connection. Thus, once the constituent BBBs have been identified, each BBB will be modelled as a two-port network.…”

“…The need to replace fossil fuel-based energy generation with environmentally friendly generation schemes warrants the large-scale integration of renewable energy-sources (RES) [1]. The compatibility of most RES like solar PV with DC networks warrants an equivalent overhaul of the grid from AC to DC in order to increase operating efficiency [2,3].…”

Improved bidirectional DC/DC converter configuration with ZVS for energy storage system: analysis and implementation

“…A bidirectional tapped inductor boost converter [10] has been realised to interface a battery bank and DC bus effectively. These converter switching devices are operated with hard‐switching at high switching frequency and by utilising tapped inductors, high voltage conversion ratio is achieved.…”