EPE Association: EPE 2018 - LS4b: Control of Converters in Grids

EPE 2018 - LS4b: Control of Converters in Grids
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 03: Measurement and Control > EPE 2018 - LS4b: Control of Converters in Grids

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   Enhanced Grid-Forming Inverters in Future Power Grids
By Peter UNRUH [View]
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Abstract: New control approaches for grid integrated power inverters are under investigations while increasing the renewable power generation in electrical grids. This paper presents an extended grid-forming control and outlines a theoretical analysis. Unlike conventional current-controlled inverters, grid-forming inverters participate directly in forming the grid and therefore they provide inherently beneficial grid services. The merit is demonstrated experimentally with a Power-Hardware-in-the-Loop test bench.

   On the similarity and challenges of multiresonant and iterative learning current controllers for grid converters under frequency fluctuations and load transient
By Bartlomiej UFNALSKI [View]
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Abstract: There is an ongoing discussion among repetitive process control engineers whether to use multiresonant controllers or iterative learning ones. Power electronics engineers are often in favour of multiresonant controllers whereas motion control designers more often incorporate iterative learning controllers (ILC) into their systems. Both camps of researchers seem to be entrenched and rarely willing to admit that both techniques are capable of introducing exactly the same generating polynomial to the system. Moreover, both techniques in their basic forms suffer from a lack of robustness to a persevering non-zero control error, e.g. due to the physical limitations on the plant side. To render the techniques practical, several tweaks have to be made. Neither of them is also innately immune to the reference and/or disturbance signal frequency fluctuations. Even small frequency variations at the level of 1\% can render the basic ILC impractical in the case of the grid-tied converter discussed in this paper. The paper is supposed to serve as the second chapter of the conversational guide on the similarity and challenges of multiresonant and iterative learning controllers. Alongside sparking the discussion, our main contribution here is a novel conditional learning concept within the ILC, inspired by the variable damping proposed for multiresonant controllers. An improvement gained by augmenting the basic ILC with the conditional learning is illustrated based on numerical simulations. Further possibilities of introducing an adaptation algorithm into the modified controller are suggested.

   Particle swarm optimization of the state feedback current controller with oscillatory terms for a three-phase grid-tie converter
By Andrzej GALECKI [View]
[Download]

Abstract: The paper presents a feedback current controller with oscillatory terms which has been designed for a three-phase grid-tie voltage source converters (VSCs) operated under distorted grid voltage conditions. The linear quadratic regulator (LQR) or the pole placement technique are typically used for designing this type of multi-variable control systems. However, both of them usually require a lot of expert knowledge. The particle swarm optimization (PSO) is proposed for off-line tuning of the multi-oscillatory current controller. The entries of the state feedback gain matrix are determined in the optimization process. The PSO tuning process is carried out using a linear model of the system in order to reduce the optimization time. Finally, the numerical verification is performed based on a switching model of the converter including pulse width modulation.

   Smart Self-charging Method Implemented in a Triple-active-bridge Converter
By Kento KUROSAWA [View]
[Download]

Abstract: The DC microgird system is one of the potential candidates for future power systems. It could be easily connected with the renewable energies, and further, reduced the power consumptions without additional AC/DC conversion. In addition, the autonomous active distribution DC grid system by using triple-active-bridge (TAB) converter is considered as a high reliable and energy manageable network system. In high DC voltage applications, the pre-charging of DC capacitors in TAB converter is a preliminary mode which limits the inrush current during the power start-up procedure because the semiconductors in TAB are exposed to high surge current during the procedure. In conventional pre-charging method, a simple external circuit consisting of a resistor and a switch is used as a current limiter. However, it consumes additional power due to the resistor In this paper, a smart self-charging method without additional current limiter is proposed for TAB converter in high DC voltage application. The charging current of DC capacitor is programmable to control and shorten the capacitor charging time. Furthermore, the proposed method can smoothly switch the TAB converter from preliminary pre-charging mode to a constant voltage control mode. A 10 kW-TAB converter was made to demonstrate the feasibility. The validity of the method was verified by using the TAB converter under 400 V-input conditions.

EPE 2018 - LS4b: Control of Converters in Grids
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 03: Measurement and Control > EPE 2018 - LS4b: Control of Converters in Grids
	[return to parent folder]

	Enhanced Grid-Forming Inverters in Future Power Grids By Peter UNRUH	[View] [Download]
Abstract: New control approaches for grid integrated power inverters are under investigations while increasing the renewable power generation in electrical grids. This paper presents an extended grid-forming control and outlines a theoretical analysis. Unlike conventional current-controlled inverters, grid-forming inverters participate directly in forming the grid and therefore they provide inherently beneficial grid services. The merit is demonstrated experimentally with a Power-Hardware-in-the-Loop test bench.

	On the similarity and challenges of multiresonant and iterative learning current controllers for grid converters under frequency fluctuations and load transient By Bartlomiej UFNALSKI	[View] [Download]
Abstract: There is an ongoing discussion among repetitive process control engineers whether to use multiresonant controllers or iterative learning ones. Power electronics engineers are often in favour of multiresonant controllers whereas motion control designers more often incorporate iterative learning controllers (ILC) into their systems. Both camps of researchers seem to be entrenched and rarely willing to admit that both techniques are capable of introducing exactly the same generating polynomial to the system. Moreover, both techniques in their basic forms suffer from a lack of robustness to a persevering non-zero control error, e.g. due to the physical limitations on the plant side. To render the techniques practical, several tweaks have to be made. Neither of them is also innately immune to the reference and/or disturbance signal frequency fluctuations. Even small frequency variations at the level of 1\% can render the basic ILC impractical in the case of the grid-tied converter discussed in this paper. The paper is supposed to serve as the second chapter of the conversational guide on the similarity and challenges of multiresonant and iterative learning controllers. Alongside sparking the discussion, our main contribution here is a novel conditional learning concept within the ILC, inspired by the variable damping proposed for multiresonant controllers. An improvement gained by augmenting the basic ILC with the conditional learning is illustrated based on numerical simulations. Further possibilities of introducing an adaptation algorithm into the modified controller are suggested.

	Particle swarm optimization of the state feedback current controller with oscillatory terms for a three-phase grid-tie converter By Andrzej GALECKI	[View] [Download]
Abstract: The paper presents a feedback current controller with oscillatory terms which has been designed for a three-phase grid-tie voltage source converters (VSCs) operated under distorted grid voltage conditions. The linear quadratic regulator (LQR) or the pole placement technique are typically used for designing this type of multi-variable control systems. However, both of them usually require a lot of expert knowledge. The particle swarm optimization (PSO) is proposed for off-line tuning of the multi-oscillatory current controller. The entries of the state feedback gain matrix are determined in the optimization process. The PSO tuning process is carried out using a linear model of the system in order to reduce the optimization time. Finally, the numerical verification is performed based on a switching model of the converter including pulse width modulation.

	Smart Self-charging Method Implemented in a Triple-active-bridge Converter By Kento KUROSAWA	[View] [Download]
Abstract: The DC microgird system is one of the potential candidates for future power systems. It could be easily connected with the renewable energies, and further, reduced the power consumptions without additional AC/DC conversion. In addition, the autonomous active distribution DC grid system by using triple-active-bridge (TAB) converter is considered as a high reliable and energy manageable network system. In high DC voltage applications, the pre-charging of DC capacitors in TAB converter is a preliminary mode which limits the inrush current during the power start-up procedure because the semiconductors in TAB are exposed to high surge current during the procedure. In conventional pre-charging method, a simple external circuit consisting of a resistor and a switch is used as a current limiter. However, it consumes additional power due to the resistor In this paper, a smart self-charging method without additional current limiter is proposed for TAB converter in high DC voltage application. The charging current of DC capacitor is programmable to control and shorten the capacitor charging time. Furthermore, the proposed method can smoothly switch the TAB converter from preliminary pre-charging mode to a constant voltage control mode. A 10 kW-TAB converter was made to demonstrate the feasibility. The validity of the method was verified by using the TAB converter under 400 V-input conditions.