Showing papers by "Navid Reza Abjadi published in 2020"

Input–output current regulation of Zeta converter using an optimized dual-loop current controller

Abstract: In this paper, an optimized dual-loop current controller for current balancing of a Zeta converter is presented and analysed in continuous current mode. The proposed strategy has an inner loop which is defined based on the input inductor current control. The reference signal of the sliding manifold is changed through an outer loop which works to regulate the output current. The stability analysis of the two-loop controllers is established by means of Routh–Hurwitz criterion and the equivalent control method. Then, the gains of the outer loop compensator are optimized using the integral gain maximization method to guarantee the robustness and disturbance rejection of the closed loop system in the presence of model uncertainties. The controller performance is investigated in depth taking into account the parametric variations associated with the converter operation in various equilibrium points. Moreover, a laboratory set-up of the suggested controller has been implemented by using analogue component devices. The experimental results demonstrate the effective performance of the controller.

Decoupled Active and Reactive Power Control of a Grid-Connected Inverter-Based DG Using Adaptive Input–Output Feedback Linearization

Abstract: This paper presents a new direct active and reactive power control for DC–AC converters connected to three-phase network through a filter and lossless/lossy line. The control is based on adaptive input–output feedback linearization control (AIOFLC). The controller computes the reference voltages of the inverter to bring active and reactive power errors to zero without any inner current loop. With a suitable Lyapunov function, the control law and the estimation laws for inductance and resistance of filter and line are obtained in synchronous reference frame. The proposed controller has a simple structure which needs less computation and increases accuracy. Using space vector pulse width modulation (SVM), a fixed switching frequency is achieved which simplifies harmonic design of AC filter and more utilizes DC voltage source. The parameters of filter and line are uncertain or unknown; only their nominal values are available. Simulation results show the capability and effectiveness of the proposed AIOFLC in direct active and reactive power control in several case studies considering various unknown filter/line parameters.

Nonlinear Control for Positive Output Super Lift Luo Converter in Stand Alone Photovoltaic System

Abstract: This paper proposes a stand-alone photovoltaic (PV) system based on a DC-DC positive output super lift Luo (POSLL) converter. A conventional sliding mode control, a sliding mode controller using a simple sign function and a linear controller using proportional integrator (PI) are used for the control of the PV panel voltage and POSLL converter inductor current and these methods are compared together. The POSLL converter is a DC-DC converter with higher voltage gain compared to other conventional DC-DC converters, and has a good voltage regulation with a simple structure. The stability and accessibility of the proposed nonlinear controls are investigated widely. The internal dynamics of the proposed closed-loop control systems are also investiged. A practical implementation of the system on a hardware setup is performed using a low cost Discovery real time digital control platform. The experimental and simulation results demonstrate the validity of the proposed control schemes over a stand-alone real photovoltaic system.

Alleviating the right-half-plane zero effect on Z-source converter output voltage regulation using the cascaded sliding mode controller

Abstract: This study presents the cascaded variable structure control approach with respect to the non-minimum phase nature of the DC–DC Z-source converter (ZSC). The method is based on the sliding mode control technique for output voltage regulation. The control-to-output transfer function of the ZSC contains a right-half-plane (RHP) zero in continuous conduction mode. The RHP zero, obtained by a linearised small-signal model, results in frequency response limitation. In this case, the converter output voltage control should be studied regarding to the RHP zero effect. To alleviate this effect and enhance the dynamic performance, the cascaded sliding mode control method is proposed. The cascaded sliding mode controller guarantees asymptotically minimum phase stability as well as robustness against input voltage variation and load resistance uncertainty. The capability and effectiveness of the proposed control method are supported by experimental results.