• Journal of Power Electronics
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• v.17 no.2
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• pp.389-397
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• 2017

A control scheme for stand-alone inverters that utilizes an inductor current observer (ICO) is proposed. The proposed method measures disturbance load currents using a current sensor and it estimates the inductor current using the ICO. The filter parameter mismatch effect is analyzed to confirm the ICO's controllability. The ICO and controllers are designed in a continuous-time domain and transferred to a discrete-time domain with a digital delay. Experimental results demonstrate the effectiveness of the ICO using a 5-kVA single-phase stand-alone inverter prototype. The experimental results demonstrate that the observed current matches the actual current and that the proposed method can archive a less than 2.4% total harmonic distortion (THD) sinusoidal output waveform under nonlinear load conditions.

• Journal of Power Electronics
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• v.17 no.3
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• pp.610-620
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• 2017

The Finite Control Set-Model Predictive Controller (FCS-MPC) for quasi Z-Source Inverters (qZSIs) is designed to reduce the number of sensors by proposing a current observer for the inductor current. Unlike the traditional FCS-MPC algorithm, the proposed model removes the inductor current sensor and observes the inductor current value based on the deposited prior optimized state as well as the capacitor voltage during this state. The proposed observer has been validated versus a typical MPC. Then, a comparative study between the proposed Modified Finite Control Set-Model Predictive Controller (MFCS-MPC) and a linear PID controller is provided under the same operating conditions. This study demonstrates that the dynamic response of the control objectives by MFCS-MPC is faster than that of the PID. On the other hand, the PID controller has a lower Total Harmonic Distortion (THD) when compared to the MFCS-MPC at the same average switching. Experimental results validate both methods using a DSP F28335.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.1
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• pp.22-28
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• 2016

Multi-loop control of a boost converter needs a current-sensing circuit to detect the inductor current. Current sensorless multi-loop control reduces the cost, size and weight of the converter. The Luenberger observer (LO) is widely used to estimate the inductor current for current sensorless control of a switching converter. However, the design of the LO-based sensorless multi-loop control has not been well presented, so far. In this paper, a closed-loop characteristics evaluation method is proposed to design an LO-based current sensorless multi-loop control for boost converters. Simulations show evaluations of the closed-loop characteristics. Practical experiments on a digital processor confirm the simulations.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.2038-2040
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• 2009

This paper studies the state estimation problem for the current of DC/DC boost converters with parasitic inductor resistance. The parasitic resistance increases the system uncertainty when the output load variation occurs. In order to enhance the observation performance of the Luenberger observer this paper includes the integral of the estimation error signal to the estimation algorithm. By using the proposed PI observer the converter current signal is successfully reconstructed with the voltage measurement regardless of the load uncertainty. Computer simulation has been carried out by using Simulink/Sim Power System. Simulation results show the proposed method maintains robust estimation performance against the model uncertainty.

• Journal of Power Electronics
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• v.13 no.3
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• pp.469-478
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• 2013

This paper proposes a novel scheme for the current controller for the grid-side converter (GSC) of permanent-magnet synchronous generator (PMSG) wind turbines to eliminate the high-order harmonics in the grid currents under grid voltage disturbances. The voltage unbalance and harmonics in three-phase systems cause grid current distortions. In order to mitigate the input current distortions, multi-loop current controllers are applied, where the positive-sequence component is regulated by proportional-integral (PI) controllers, and the negative-sequence and high-order harmonic components are regulated by proportional-resonance (PR) controllers. For extracting the positive/negative-sequence and harmonic components of the grid voltages and currents without a phase delay or magnitude reduction, composite observers are applied, which give faster and more precise estimation results. In addition, an active damping method using PR controllers to damp the grid current component of the resonant frequency is employed to improve the operating stability of VSCs with inductor-capacitor-inductor (LCL) filters. The validity of the proposed method is verified by simulation and experimental results.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.369-371
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• 2007

Due to the measurement noise or system noise, the performance of photovoltaic power generation system can be degraded. If this noise is contained in the solar array voltage measurement signal, the correct operation of the maximum power point tracker can not be guaranteed. The application of the extended Kalman filter to the photovoltaic system can obtain enhanced states estimation result. The Kalman filter provides a recursive solution to optimally estimate from random noise signals. Additionally, as a consequence of Kalman filter, the unmeasurable state such as inductor current can be estimated without current sensor. The methods for system modeling and extended Kalman filter design are presented and the experimental results verify the validity of the proposed system.

• Journal of Power Electronics
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• v.18 no.1
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• pp.147-159
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• 2018

In this paper, the voltage tracking control of a conventional DC-DC boost converter affected by unknown, time-varying circuit parameter perturbations is investigated. Based on the fundamental property of incremental passivity, a passivity based control law is designed. Then, to obtain a better disturbance rejection property, two generalized proportional integral (GPI) observers are employed to estimate the time-varying uncertainties in the output voltage and inductor current channels, and the estimated values are applied as feedforward compensation. Moreover, the global trajectory tracking performance of a system with disturbances is ensured under the composite controller. Finally, simulation and experiment studies are provided to demonstrate the feasibility and effectiveness of the proposed method. The results show that the proposed controller delivers a promising disturbance rejection capability as well as a good nominal tracking performance.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.2
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• pp.149-155
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• 2012

This paper provides an efficient model predictive control for the output voltage control of three-phase inverter system which includes output LC filters. Use of SVPWM (Space Vector Pulse-Width-Modulation) and the rotating d-q frame is made to obtain an input constrained dynamic model of the inverter system. From the measured/estimated output current and reference output voltage, corresponding equilibrium values of the inductor current and the control input are computed. Derivation of a feasible and invariant set around the equilibrium state is made and then a receding horizon strategy which steers the current state deep into the invariant set is proposed. In order to remove offset error, use of disturbance observer is made in the form of state estimator. The efficacy of the proposed method is verified through simulations.