EPE Association: EPE 2014 - LS3d: Renewable Energy Systems

EPE 2014 - LS3d: Renewable Energy Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2014 ECCE Europe - Conference > EPE 2014 - Topic 05: Renewable Energy Power Systems > EPE 2014 - LS3d: Renewable Energy Systems

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   Dynamic Performance of Grid Converters using Adaptive DC Voltage Control
By Ionut TRINTIS, Bo SUN, Josep GUERRERO, Stig MUNK-NIELSEN, Flemming ABRAHAMSEN, Paul THØGERSEN [View]
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Abstract: This paper investigates a controller that ensures minimum operating dc-link voltage of a back-to-backconverter system. The dc-link voltage adapts its reference based on the system state, reference givenby an outer loop to the dc-link voltage controller. The operating dc-link voltage should be kept as lowas possible to increase the power conversion efficiency and increase the reliability of converters. Thedynamic performance of the proposed controller is investigated by simulations and experiments.

   Fixed-Reference-Frame-Control: A novel robust control concept for grid side inverters in HVDC connected weak offshore grids
By Hans-Joachim KNAAK, Magdalena GIERSCHNER, Hans-Günter ECKEL [View]
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Abstract: Offshore wind energy plants built at a long distance from public ac-grid are connected by HVDC-transmission. Hence an offshore ac-island-grid results, in which the HVDC station generates the grid while the inverters of the wind power plants synchronize themselves on that gird. As the power of the HVDC-station is not significant higher than that of the sum of all wind power plants, the grid is relative weak. This could lead to stability problems of wind power plants grid side converters. In this paper, this stability problem is analyzed and a theoretic stability limit of the PLL is given. The critical parameter for stability is the internal impedance of the grid. Also a novel control concept to solve the stability problems is presented in this paper. The basic idea is, that all converters in the grid are synchronized on an external signal the fixed reference frame and that the HVDC converter acts as a voltage source and the wind power plant inverters as current sources.

   Maximum Power Point Tracking and Sensorless control for permanent magnet generators tested on a wind turbine emulator
By Danilo LLANO, Richard MCMAHON [View]
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Abstract: This paper presents a maximum power point tracking algorithm (MPPT) and sensorless control for permanent magnet generators associated with small scale wind turbines. The basis for the wind energy conversion is presented to model the wind turbine emulator test-rig and support the proposed MPPT algorithm. The maximum power point tracking algorithm is based on estimations of the load torque and shaft speed. The shaft speed and position are estimated with an extended Kalman filter. The load torque is estimated with a discrete time observer. A sliding mode controller in the rotor reference frame drives the generator in speed control mode. A minimum number of sensors is required for this implementation: one voltage sensor for the DC link and two current sensors for the phase currents. Experimental implementation on the wind emulator test-rig is given. The proposed estimators, sensorless controller and MPPT algorithm were shown to be well integrated and work properly. The sensorless controller was able to track a speed reference calculated by the MPPT algorithm and based on the speed and load torque estimations.

   Phase Shift-Based Equivalent Virtual Impedance Loop for Droop-Controlled Inverters
By Abderrahmane EL BOUBAKRI, Luiz LOPES [View]
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Abstract: Virtual impedance (VI) loops are frequently employed in droop based controllers for grid-connected inverters so as to improve the dynamic response which can be very oscillatory when large droop factors are used. They neither yield active power losses nor reactive power demand but they tend to create a drop in the bus voltage. This paper discusses an approach based on phase shifting the reference voltage, which is shown to be equivalent to a virtual impedance loop but does not reduce the bus voltage. Simulation results with MATLAB Simulink are presented.

EPE 2014 - LS3d: Renewable Energy Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2014 ECCE Europe - Conference > EPE 2014 - Topic 05: Renewable Energy Power Systems > EPE 2014 - LS3d: Renewable Energy Systems
	[return to parent folder]

	Dynamic Performance of Grid Converters using Adaptive DC Voltage Control By Ionut TRINTIS, Bo SUN, Josep GUERRERO, Stig MUNK-NIELSEN, Flemming ABRAHAMSEN, Paul THØGERSEN	[View] [Download]
Abstract: This paper investigates a controller that ensures minimum operating dc-link voltage of a back-to-backconverter system. The dc-link voltage adapts its reference based on the system state, reference givenby an outer loop to the dc-link voltage controller. The operating dc-link voltage should be kept as lowas possible to increase the power conversion efficiency and increase the reliability of converters. Thedynamic performance of the proposed controller is investigated by simulations and experiments.

	Fixed-Reference-Frame-Control: A novel robust control concept for grid side inverters in HVDC connected weak offshore grids By Hans-Joachim KNAAK, Magdalena GIERSCHNER, Hans-Günter ECKEL	[View] [Download]
Abstract: Offshore wind energy plants built at a long distance from public ac-grid are connected by HVDC-transmission. Hence an offshore ac-island-grid results, in which the HVDC station generates the grid while the inverters of the wind power plants synchronize themselves on that gird. As the power of the HVDC-station is not significant higher than that of the sum of all wind power plants, the grid is relative weak. This could lead to stability problems of wind power plants grid side converters. In this paper, this stability problem is analyzed and a theoretic stability limit of the PLL is given. The critical parameter for stability is the internal impedance of the grid. Also a novel control concept to solve the stability problems is presented in this paper. The basic idea is, that all converters in the grid are synchronized on an external signal the fixed reference frame and that the HVDC converter acts as a voltage source and the wind power plant inverters as current sources.

	Maximum Power Point Tracking and Sensorless control for permanent magnet generators tested on a wind turbine emulator By Danilo LLANO, Richard MCMAHON	[View] [Download]
Abstract: This paper presents a maximum power point tracking algorithm (MPPT) and sensorless control for permanent magnet generators associated with small scale wind turbines. The basis for the wind energy conversion is presented to model the wind turbine emulator test-rig and support the proposed MPPT algorithm. The maximum power point tracking algorithm is based on estimations of the load torque and shaft speed. The shaft speed and position are estimated with an extended Kalman filter. The load torque is estimated with a discrete time observer. A sliding mode controller in the rotor reference frame drives the generator in speed control mode. A minimum number of sensors is required for this implementation: one voltage sensor for the DC link and two current sensors for the phase currents. Experimental implementation on the wind emulator test-rig is given. The proposed estimators, sensorless controller and MPPT algorithm were shown to be well integrated and work properly. The sensorless controller was able to track a speed reference calculated by the MPPT algorithm and based on the speed and load torque estimations.

	Phase Shift-Based Equivalent Virtual Impedance Loop for Droop-Controlled Inverters By Abderrahmane EL BOUBAKRI, Luiz LOPES	[View] [Download]
Abstract: Virtual impedance (VI) loops are frequently employed in droop based controllers for grid-connected inverters so as to improve the dynamic response which can be very oscillatory when large droop factors are used. They neither yield active power losses nor reactive power demand but they tend to create a drop in the bus voltage. This paper discusses an approach based on phase shifting the reference voltage, which is shown to be equivalent to a virtual impedance loop but does not reduce the bus voltage. Simulation results with MATLAB Simulink are presented.