Bidirectional DC-DC power converters are increasingly employed in diverse applications whereby power flow in both forward and reverse directions are required. These include but not limited to energy storage systems, uninterruptable power supplies, electric vehicles, and renewable energy systems, to name a few. This paper aims to review these converters from the point of view of topology as well as control schemes. From the point of view of topology, these converters are divided into two main categories, namely non-isolated and isolated configurations. Each category is divided into eight groups along with their respective schematics and a table of summary. Furthermore, the common control schemes and switching strategies for these converters are also reviewed. Some of the control schemes are typically applied to all DC-DC power converters such as PID, sliding mode, fuzzy, model predictive, digital control, etc. In this context, it should be noted that some switching strategies were designed specifically for isolated bidirectional DC-DC converters in order to improve their performance such as single phase shift, dual phase shift, triple phase shift, etc. The features of each topology and control scheme along with their typical applications are discussed, in order to provide a ground of comparison for realizing new configurations or finding the appropriate converter for the specific application.INDEX TERMS Batteries, bidirectional power flow, control systems, dc-dc power converters. 5) CASCADED BIDIRECTIONAL DC-DC CONVERTER [19], [20] 4) FORWARD BIDIRECTIONAL DC-DC CONVERTER [35]-[39]
A new transformer-less buck-boost converter is proposed, which owns a quadratic voltage gain ratio. The proposed converter (a) has only one active switch, which makes the implementation of the gate driver and control system simpler; (b) has a quadratic voltage gain without using a transformer, which equips the designers to obtain a high-voltage gain ratio and avoid the complexity of magnetic utilisations; (c) works both in step-up or step-down mode, while most of the existing quadratic topologies are able to work either in step-up or step-down mode; and (d) shares a common ground between the input and output terminals. The operating states of the proposed converter along with its steady-state performance are analysed. Then, the small-signal modelling and the power loss analysis are performed. A comparison shows the unique features of the converter, specifically in terms of voltage gain ratio and the count of power switches. Finally, the experimental results of a laboratory prototype, as well as the simulation results from PSIM software, are used for validation. The converter was tested in different conditions to inspect its transient response and to record its efficiency. The maximum recorded efficiencies in boost and buck modes, respectively were 94.7 and 93%.
Maximum power point tracking (MPPT) techniques have been vastly researched and developed in order to obtain the maximum terminal power of photovoltaic (PV) arrays in the solar renewable energy system. The aim of this paper is to present a new principal scheme-based review of the categorised MPPT methods (conventional, novel, and hybrid) with respect to the deployment of their input variables (solar irradiance, PV arrays' temperature, and PV arrays' terminal voltage and current), where MPPT methods are categorised to six different schemes. For each scheme, previous MPPT studies are extracted from literature and analysed. Then the critical benefits and limitations of the six presented MPPT schemes are compared and discussed. It is concluded that those MPPT schemes deploying the measured external variables would be able to track the global maximum power point with high reliability; however, their implementation cost and applicability remains as a challenge due to increasing the sensor deployment cost and complexity. The conclusion of this paper will help new researchers to deliberately select an appropriate MPPT scheme based on their projects' objectives and limitations, prior to selecting an optimisation algorithm for MPPT.
A high voltage ratio DC-DC converter is proposed which is comprised of four stages. First, an impedance network along with a switching network have been used to boost the input voltage. The boosted voltage waveform is then followed by an isolation transformer to provide another degree of freedom and obtain higher boost ability. Finally, a voltage multiplier rectifier is utilised to rectify the secondary voltage of the transformer. No switching dead-time is required, which increases the reliability of the converter. The proposed converter benefits from the continuous input current. Besides, a comparison with the existing step-up topologies indicates that the number of passive elements and hence the weight and size have been reduced. The operating principles were analysed and the experimental tests on a 260 W prototype reveal that a high efficiency above 91% can be achieved.
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