Due to the nonlinear nature of photovoltaic (PV) cells and the dependence of the maximum achievable power on environmental conditions, a robust nonlinear controller is essential to warrant maximum power point tracking (MPPT) by managing the nonlinearities of the system and making it robust against varying environmental conditions. Most methods used to obtain MPPT have some disadvantages; one of them is the oscillation around the operating point. In this paper, to minimize these problems, a robust nonlinear sliding mode controller based on the power curve of a PV (SMC-PCPV) was proposed to determine the maximum power point (MPP) of a PV panel, for a quasi Z-source inverter (qZSI) as a single-stage inverter. Single-stage inverters have lower components and prices, smaller sizes, more simplicity, and higher efficiency than two-stage inverters. One of the important features of this controller is its ease of implementation compared to other methods presented in the articles. To show the effectiveness and robustness of the proposed scheme, the SMC-PCPV was carried out on computer simulations and laboratory prototypes. The simulation and experimental results showed that the proposed controller was properly resistant to changes in input parameters, such as temperature and radiation, and controlled the converter at the best point to obtain the most power from the PV panel, and it had good speed in response to the changing environmental condition.

A tunable capacitor based on MEMS technology is presented in this paper. The proposed structure consists of two fixed-fixed parallel movable plates with 4 supports. Movability of two plates makes it possible to actuate the plates with a small voltage. When the actuation is applied, two plates move together and their distance is decreased, hence the capacitance is increased and tuning is achieved. The structure is simulated through the finite element method using COMSOL and ANSOFT HFSS software. Simulation results show that the actuation voltage required to access the 59% tuning, is 7 V. The effective area of the designed tunable capacitor is 200 x 200 µm2 with a thickness of 2 µm. The quality factor is 91 at 11 GHz which is sufficient for various RF communication applications such as filters, transceivers and so on. The low stress induced on the plates and low actuation voltage, are the main advantages of the design.

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