Multi-loop control of stand-alone inverters with minimum number of sensors

• Published in: IET power electronics Vol. 9; no. 12; pp. 2425 - 2433
• Main Authors: Razi, Reza, Monfared, Mohammad
• Format: Journal Article
• Language: English
• Published: The Institution of Engineering and Technology 05.10.2016
• Subjects: active damping; adaptive control; Algorithms; apparent power 600 VA; control system synthesis; Control systems; controllability; Controllers; digital control; digital control system; Electric potential; electric sensing devices; Electronics; feedback signals; frequency domain; frequency‐domain analysis; gradient descent adaptive control method; gradient methods; inner‐outer double‐loop controller; inverter current; Inverters; invertors; Kalman filters; linear Kalman filter algorithm; load current; load sensorless multiloop control system design; load voltage; minimum steady‐state error; observability; proportional inner‐controller; proportional‐resonant outer‐controller; protection purposes; Regular Papers; sensors; Stability; stability margin; stand‐alone inverter; transient performance; Voltage; protection purposes; active damping; minimum steady-state error; load current; frequency domain; invertors; controllability; inverter current; feedback signals; apparent power 600 VA; gradient descent adaptive control method; inner-outer double-loop controller; Kalman filters; gradient methods; observability; stability; proportional-resonant outer-controller; load voltage; linear Kalman filter algorithm; stability margin; digital control; control system synthesis; adaptive control; frequency-domain analysis; load sensorless multiloop control system design; transient performance; digital control system; sensors; stand-alone inverter; electric sensing devices; proportional inner-controller
• ISSN: 1755-4535; 1755-4543
• DOI: 10.1049/iet-pel.2016.0036

This study deals with the design of a load sensorless multi-loop control system for the stand-alone inverter. In the proposed strategy, only the inverter current is measured, which is practically required for both control and protection purposes, then the load voltage and current are both estimated using the linear Kalman filter algorithm, and the gradient descent adaptive control method, respectively. The estimated quantities are used as feedback signals of an inner-outer double-loop controller, which uses a proportional-resonant outer-controller to regulate the output voltage with minimum steady-state error and a simple proportional inner-controller to provide active damping and improve the transient performance. The controller parameters are designed in the frequency domain based on the required bandwidth and stability margin. Furthermore, the controllability and observability, as well as the stability of overall digital control system, including the dynamics of estimators, are analytically investigated. Simulation and experimental results, with a 600 VA prototype, confirm the theoretical achievements and illustrate the excellent performance of the proposed estimation and control scheme.