Adaptive backstepping approach for dc-side controllers of Z-source inverters in grid-tied PV system applications

• Published in: IET power electronics Vol. 11; no. 14; pp. 2346 - 2354
• Main Authors: Vu, Phuong, Nguyen, Quan, Tran, Minh, Todeschini, Grazia, Santoso, Surya
• Format: Journal Article
• Language: English
• Published: The Institution of Engineering and Technology 27.11.2018
• Subjects: ac‐side controllers; adaptive backstepping approach; adaptive backstepping controller; adaptive control; closed loop systems; control nonlinearities; control system synthesis; dc‐side controllers; electric current control; grid voltage fluctuations; grid‐tied photovoltaic systems; grid‐tied PV system applications; hardware‐in‐the‐loop real‐time simulations; inductor currents; inductor values; inner deadbeat current controller; invertors; maximum power point trackers; MPPT algorithm; multiloop control scheme; nonlinear control systems; nonminimum phase; novel nonlinear adaptive backstepping method; outer proportional–integral voltage controller; photovoltaic power systems; PI control; power factor; power generation control; power grids; PV arrays; PV irradiance; Research Article; robust control; shoot‐through duty ratio; shoot‐through states; single‐stage power converters; stable capacitor voltage; unique impedance network; unity power factor; voltage buck‐boost capabilities; voltage control; voltage‐current characteristics; ZSI impedance network; ZSI model; grid-tied PV system applications; PV arrays; power generation control; outer proportional–integral voltage controller; electric current control; nonminimum phase; shoot-through states; inner deadbeat current controller; adaptive backstepping approach; ZSI impedance network; unity power factor; invertors; control nonlinearities; robust control; novel nonlinear adaptive backstepping method; power grids; multiloop control scheme; PI control; MPPT algorithm; voltage-current characteristics; photovoltaic power systems; ac-side controllers; adaptive control; control system synthesis; stable capacitor voltage; grid voltage fluctuations; power factor; dc-side controllers; PV irradiance; hardware-in-the-loop real-time simulations; closed loop systems; grid-tied photovoltaic systems; maximum power point trackers; shoot-through duty ratio; single-stage power converters; nonlinear control systems; adaptive backstepping controller; inductor values; inductor currents; voltage buck-boost capabilities; voltage control; unique impedance network; ZSI model
• ISSN: 1755-4535; 1755-4543; 1755-4543
• DOI: 10.1049/iet-pel.2018.5763

Z-source inverters (ZSIs) are single-stage power converters with both voltage buck and boost capabilities provided by the unique impedance network and the ability to operate during shoot-through states. This study proposes a novel non-linear adaptive backstepping method for dc-side controllers in a multi-loop control scheme of the ZSI in grid-tied photovoltaic (PV) systems. Despite the variability of the capacitor and inductor values in the ZSI impedance network, the proposed controller guarantees robust and stable operation under varying levels of PV irradiance and temperature. The shoot-through duty ratio of the ZSI is obtained directly from the output of an MPPT algorithm and the measured PV and inductor currents. This strategy overcomes the disadvantages of the conventional approach such as the non-minimum phase at the dc side of the ZSI. It also eliminates the need to linearise the voltage/current characteristics of the PV arrays and ZSI model. The ac-side controllers consist of an outer proportional–integral voltage controller and an inner deadbeat current controller to achieve unity power factor and stable capacitor voltage in spite of grid voltage fluctuations. The efficacy of the proposed adaptive backstepping controller and the multi-loop control scheme is validated by offline and hardware-in-the-loop real-time simulations.