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Current ripple reduction for finite control set model predictive control strategy of grid-tied inverter with reference current compensation

Jin Nan, Fan Wuchuang, Fang Jie, Wu Jie, Shen Yongpeng

Archives of Electrical Engineering

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2023

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Vol. 72, nr 1

5--22

EN

In the finite control set model predictive control (FCS-MPC) strategy of the grid-tied inverter, the current ripple (CR) affects the selection of optimal voltage vectors, which leads to the increase of output current ripples. In order to solve this problem, this paper proposes a CR reduction method based on reference current compensation (RCC) for the FCS-MPC strategy of grid-tied inverters. Firstly, the influence of the CR on optimal voltage vector selection is analyzed. The conventional CR prediction method is improved, which uses inverter output voltage and grid voltage to calculate current ripples based on the space state equation. It makes up for the shortcomings that the conventional CR prediction method cannot predict in some switching states. The improved CR method is more suitable for the FCS-MPC strategy. In addition, the differences between the two cost functions are compared through visual analysis. It is found that the sensitivity of the square cost function to small errors is better than that of the absolute value function. Finally, the predicted CR is used to compensate the reference current. The compensated reference current is substituted into the square cost function to reduce the CR. The experimental results show that the proposed method reduces the CR by 47.3%. The total harmonic distortion (THD) of output current is reduced from 3.86% to 2.96%.

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Finite control set MPC of LCL-filtered grid-connected power converter operating under grid distortions

Falkowski P., Godlewska A.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2020

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Vol. 68, nr 5

1069--1076

EN

Most of the basic control methods of the grid-connected converter (GCC) are defined to work with a sine wave grid voltage. In that case if the grid voltage is distorted by higher harmonics, the grid current may be distorted too, which, in consequence, may increase the value of the THD of the grid voltage. The paper deals with an improved finite control set model predictive control (FCS-MPC) method of an LCL-filtered GCC operating under distorted grid conditions. The proposed method utilizes supplementary grid current feedback to calculate the reference converter current. The introduced signal allows to effectively improve the operation when the grid is subject to harmonic distortion. The paper shows a simulation analysis of the proposed control scheme operating with and without additional feedback under grid distortions. To validate the practical feasibility of the proposed method an algorithm was implemented on a 32-bit microcontroller STM32F7 with a floating point unit to control a 10 kW GCC. The laboratory test setup provided experimental results showing properties of the introduced control scheme.

3

Predykcyjna regulacja momentu i strumienia silnika indukcyjnego - dobór współczynnika wagowego

Falkowski P.

Przegląd Elektrotechniczny

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2018

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R. 94, nr 3

30--37

PL

W artykule przedstawiono predykcyjną metodę regulacji momentu i strumienia (PTFC). Jej główną wadą jest konieczność doboru wartości współczynnika wagowego występującego w funkcji kosztu J. Wartość współczynnika wagowego decyduje o poziomie tętnień momentu i strumienia oraz średniej częstotliwości łączeń tranzystorów falownika i w obecnym stanie wiedzy jest ona najczęściej dobierana doświadczalnie. W artkule przedstawiono analityczny sposób doboru optymalnej wartości współczynnika wagowego zapewniającego porównywalne tętnienia składowych wektora prądu stojana na podstawie parametrów maszyny i falownika.

EN

These paper presents a predictive torque and flux control method (PTFC). Its main drawback is the need to choose the value of weighting factor in cost function J. The weight factor determines the level of torque and flux ripple and also the value of average switching frequency. In the present state of knowledge value of weighting factor is selected experimentally. The article presents an analytical way of selecting the optimal value of the weight factor providing comparable ripple level of components of the stator current vector based on the parameters of the machine and the inverter.