Design and implementation bidirectional SEPIC/ZETA converter using Fuzzy Logic Controller in DC microgrid application

Abstract

The electrical energy has been dependent on fossil fuels, but the availability of fossil energy is running low with increasing electricity demand in society. Therefore a lot of research is done on renewable energy sources, one of which is solar energy. Solar energy can be applied to home scale DC microgrid systems. In the DC microgrid system the independent source of energy for the supply of loads comes from two sources, namely DC bus and 120 volt battery. To combine these two energy sources, a bidirectional converter is needed which will regulate power flow and electricity storage. In this system the battery can become a burden and can be a source of energy in the same series. Bidirectional converters can work in two directions, namely charging mode and discharging mode. The type of converter used in this bidirectional converter is SEPIC/ZETA Converter. The use of this type of converter is expected to reduce the ripple at the output voltage and minimize voltage disturbances during switching. The control method used is a fuzzy logic controller for voltage control which is expected to produce stable output.

Sliding-mode controller for a step up-down battery charger with a single current sensor

“…Replacing the value of the switching function derivative, reported in (13), into the first reachability condition (16) leads to (18). Under steady-state conditions iL2=idc as it was demonstrated in (6), and the controller action ensures that the averaged value of vdc must be equal to vR. Therefore, ( 18) is positive since Z<0, vd>0 and L1>0, which fulfills the first reachability condition (16).…”

“…Moreover, DC microgrids have a common bus in which both sources and loads are connected, hence the stability of such a bus is required to guarantee the safe operation of both sources and loads [1], [2]. Therefore, the batteries in DC microgrids can be interfaced using DC/DC converters, which are controlled to regulate the DC bus: When the sources produce higher power with respect to the load request, the bus voltage increases, hence the DC/DC converter must to charge the battery to ensure a regulated DC bus; similarly, when the requested load power is higher than the power produced by the sources, the bus voltage decreases and the DC/DC converter must to discharge the battery to ensure a regulated DC bus [5], [6]. In this way, the DC/DC converter ensures both the voltage stability and the power balance of the DC bus.…”

“…Therefore, Fakham et al [17] was proposed a voltage control oriented (VOC) where the decomposition of direct and quadrature components allows to correct the power factor and avoid the total harmonic distortion, also controlling the DC voltage bus. Other non-linear controllers were proposed in the literature to provide a voltage regulation in battery chargers, such as fuzzy controllers [6], [19], [20] model predictive controllers (MPC) [21] and sliding mode controllers (SMC) [5], [15], [22]. In particular, the surface of the SMC used for battery chargers, based on high-order converters, frequently requires the measurement of two voltages and two currents to ensure bus stability in both charging and discharging modes, which is the case of the charger controller presented in [23].…”

“…boost and buck based solutions [2], [7]- [11], [28]. Moreover, the Zeta converter has an inductor at the output port connected to the DC bus [6], [28]- [31], which makes possible to control the bus voltage with high precision and, at the same time, this enables the converter to provide a continuous current to the DC bus, reduces the harmonic components present in the microgrid; this is an advantage over battery chargers based on converters with discontinuous output current, e.g. buck and buck-boost based solutions [15], [32]- [34].…”

ZETA Converter as a Voltage Stabilizer with Fuzzy Logic Controller Method in The Pico Hydro Power Plant

“…A zeta converter is a type of fourth-order DC-DC converter that can increase or decrease the output voltage without having to change the polarity of the output converter as well as the SEPIC converter [7][8][9][10][11]. The zeta converter has the same capability as the buck-boost converter which can increase or decrease the value of the output voltage but has the advantage that the output polarity is not reversed.…”