Sensorless Model Predictive Control of Single-Phase Inverter for UPS Applications via Accurate Load Current Estimation

Distorted voltage supplied as unbalanced and/or non-constant frequency can be found in weak grids, such as microgrids, or systems working in islanding mode. These kinds of systems are more sensitive under load changes. Particularly, an unbalanced voltage supply may be produced for large, single-phase loads. On the other hand, the connection/disconnection of high current loads may lead to important frequency variation, especially in weak grids where the short circuit current capacity is reduced. These conditions make the control of the power converter a more difficult task, because of the variations in the frequency and unbalancing. To address these issues, this paper proposes a resonant control algorithm to deal with variations in the voltage amplitude as well as grid frequency when a distorted power supply is considered. The frequency variation is an important drawback for resonant control because the resonance must be tuned at the grid frequency. This issue is overcome by using a variable sampling frequency in order to avoid re-tuning the controller parameters. On the other hand, under unbalanced conditions, the proposed method relaxes the phase with lower voltage amplitude by taking more power from the other phases in order to help the stability of the grid supply. To corroborate the mathematical analysis and the proposed control, a stability study is performed, including experimental and simulated results.

Section: Power Converter Modelmentioning

confidence: 99%

“…The abc current references are imposed by the active and reactive power references ( 13) and ( 16), which means a current in phase with a supply voltage (active power) and π/2 radians (reactive power) phase-shifted with respect to the supply voltage. Assuming the voltage in (17), the current references have the following form:…”

Section: Current Referencesmentioning

confidence: 99%

Power Converter Resonant Control for an Unbalanced and Non-Constant Frequency Supply

Rohten

Villarroel

Silva

et al. 2023

“…The FBQ modulation scheme is discrete and has characteristics similar to the Finite Control Set Model Predictive Control (FCS-MPC); it requires low system sampling times for high performance, generating a sparse harmonic spectrum and variable switching frequency [ 23 , 24 , 25 , 26 ].…”

Section: Introductionmentioning

confidence: 99%

Improved Feedback Quantizer with Discrete Space Vector

Veillon,

Espinosa,

Melin

et al. 2024

The use of advanced modulation and control schemes for power converters, such as a Feedback Quantizer and Predictive Control, is widely studied in the literature. This work focuses on improving the closed-loop modulation scheme called Feedback Quantizer, which is applied to a three-phase voltage source inverter. This scheme has the natural behavior of mitigating harmonics at low frequencies, which are detrimental to electrical equipment such as transformers. This modulation scheme also provides good tracking for the voltage reference at the fundamental frequency. On the other hand, the disadvantage of this scheme is that it has a variable switching frequency, creating a harmonic spectrum in frequency dispersion, and it also needs a small sampling time to obtain good results. The proposed scheme to improve the modulation scheme is based on a Discrete Space Vector with virtual vectors to obtain a better approximation of the optimal vectors for use in the algorithm. The proposal improves the conventional scheme at a high sampling time (200 μs), obtaining a THD less than 2% in the load current, decreases the noise created by the conventional scheme, and provides a fixed switching frequency. Experimental tests demonstrate the correct operation of the proposed scheme.

“…By estimating the values in such a way, a better control quality is achievable. A state observer scheme is proposed in [14] for uninterruptible power supply applications and it is compared to classical approaches like with Kalman filters. The study presented in [15] shows an approach to deal with ocean environment disturbances by designing a nonlinear disturbance observer for unmanned surface vehicles to obtain safe and effective motion control performance.…”

Section: Introductionmentioning

confidence: 99%

Fast Nonlinear Predictive Control Using Classical and Parallel Wiener Models: A Comparison for a Neutralization Reactor Process

Nebeluk,

Ławryńczuk

2023

The Wiener model, composed of a linear dynamical block and a nonlinear static one connected in series, is frequently used for prediction in Model Predictive Control (MPC) algorithms. The parallel structure is an extension of the classical Wiener model; it is expected to offer better modeling accuracy and increase the MPC control quality. This work discusses the benefits of using the parallel Wiener model in MPC. It has three objectives. Firstly, it describes a fast MPC algorithm in which parallel Wiener models are used for online prediction. In the presented approach, sophisticated trajectory linearization is performed online, which leads to computationally fast quadratic optimization. The second objective of this work is to study the influence of the model structure on modeling accuracy. The well-known neutralization benchmark process is considered. It is shown that the parallel Wiener models in the open-loop mode generate significantly fewer errors than the classical structure. This work’s third objective is to validate the efficiency of parallel Wiener models in closed-loop MPC. For the neutralization process, it is demonstrated that parallel models demonstrate better control quality using various indicators, but the difference between the classical and parallel models is not significant.