Search results for: Grzegorz Iwański
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Power Electronics and Drives > 2019 > Vol. 4 (39) > 63--77
The paper presents a control method for the three-phase power converter operating under unbalanced grid voltage conditions. The method uses a new transformation to the non-Cartesian frame, which makes the controlled current vector components balanced in this frame even if originally the three-phase current is referenced as unbalanced. Furthermore, Park’s transformation makes the controlled variables...
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Power Electronics and Drives > 2019 > Vol. 4 (39) > 47--61
One of the currently investigated problems in power electronics-based electrical energy conversion is proper operation of electronic converters during grid voltage imbalance and harmonics. In classic control methods, it introduces oscillations of variables, resulting in the necessity to improve control systems with signals filtration and usually by application of resonant terms as part of current...
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IEEE Transactions on Power Electronics > 2017 > 32 > 9 > 6836 - 6852
The paper deals with a new control method of three-phase rectifier operating under simultaneous grid voltage imbalance and harmonics. The proposed method uses virtual electromagnetic torque, which is calculated on the basis of converter current and virtual flux of the power grid. Direct calculation of reference alpha/beta components of current vector does not require any synchronization procedure...
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The paper deals with the current progressive balancing from the target of constant p or constant q component of instantaneous power to symmetrical current target. Referenced current imbalance depends on the operation mode and whether the current reaches the limit. The fixed p component of power is selected for the inverter operation mode. The fixed q component of power is selected for the rectifier...
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The paper presents Direct Torque Control method applied in Autonomous Doubly Fed Induction DC-Voltage Generator. The system consists of doubly fed induction generator which stator circuit is connected to dc-link by diode rectifier and rotor circuit converter is connected to the same dc-link. In such system the main problem are large torque oscillations caused by nonlinear stator connected diode rectifier...
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IEEE Transactions on Energy Conversion > 2016 > 31 > 4 > 1530 - 1538
Control methods of a stand-alone doubly fed induction generator mostly use either proportional-integral regulators in multiple synchronous reference frames or proportional-integral-resonant regulators in a stationary reference frame. These control schemes work well when the plant model is not complex and system decoupling is implemented into the control algorithm. However, when the control system...
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IEEE Transactions on Energy Conversion > 2016 > 31 > 3 > 1202 - 1211
The paper deals with the methods of either stator current or rotor current vector control of doubly fed induction machine connected to the unbalanced power network. Several alternative control targets, such as fixed electromagnetic torque, symmetrical stator current, or symmetrical rotor current, have been achieved. In spite of the selected target, the stator current is sinusoidal, however in some...
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This paper is focused on the unbalanced grid operation of a doubly fed induction generator. The main target taken into consideration for rotor converter control strategy is to reduce electromagnetic torque oscillations and simultaneously keep sinusoidal, but not necessarily symmetrical, stator current. The second, alternative target is to obtain symmetrical stator current, for which the generated...
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The paper presents properties and control methods of grid-connected doubly-fed induction generator (DFIG). The paper is focused on unbalanced grid operation, because presently it is the biggest challenge for this type of generator. There are discussed three most popular methods - direct power control, direct torque control, and vector control with proportional-resonant PR controllers of rotor current...
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More and more applications requires DC voltage for operation. With growing demand comes a need for high power DC generators. One of the most popular machines used for AC power generation are Double-Fed Induction Machines (DFIG), due to fractional power rotor side converter. But such machine is not fit for DC voltage generation. Nonlinear load produces torque pulsation causing mechanical stresses and...
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The paper presents a state controller for torque and reactive power tracking of a doubly fed induction generator operating in an unbalanced grid. The state feedback gain is tuned using linear-quadratic optimization. Reference stator currents are calculated using instantaneous power theory and precisely tracked by the current controller. In the paper there are presented simulation results of an electrical...
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The paper presents a new type of rotor position observer using cross and dot products of the estimated and measured rotor current vector. A novel synchronization error function contains modified function atan2 and the vector products. The modification of error function is aimed at making the function monotonic, what provides faster response of the observer. Two rotor speed and position observers with...
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Doubly-Fed Induction Machine (DFIM) still remains one of the most popular type of generation unit used in wind power conversion systems, due to variable-speed operation, price and reduced power of its bi-directional power converter. However, the machine connected to power grid is very sensitive to voltage unbalance. High DC-link voltage is required during unbalanced grid operation mode in order to...
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The paper presents the method of stator voltage control of the doubly fed induction machine based generation system feeding nonlinear load. The method uses load current signal as feedforward structure without the use of selective extraction of harmonics components. There are compared results with measured and estimated current of nonlinear and unbalanced load. The dynamic states of step loading and...
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Several methods can be used in the current control loop of a doubly-fed induction generator systems. The PI controllers in the rotating frame system oriented to the stator voltage (VOC) or flux (FOC) are the most popular control methods. In this case, controller response in each axis also gives an answer to the second axis. Therefore, a transient state of the system response is longer and may have...
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The paper describes a variable speed, doubly fed induction generator based, standalone power system supplying unbalanced and nonlinear load. A sensorless control method of the fundamental 50Hz harmonic uses a PLL for synchronization of the measured stator voltage vector with the reference one. Additional part of control includes feedbacks from the components of voltage asymmetry and harmonics, extracted...
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A paper describes cooperation of the standalone doubly fed induction generator with an energy storage or auxiliary power unit coupled with the DC bus of the main back-to-back power electronics converter. The control method and the energy management of the energy storage coupled through a bidirectional DC/DC converter with a DC-link of the main back-to-back converter is proposed. The control method...
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This paper presents a control strategy, which allows doubly-fed induction generator (DFIG) to generate a sinusoidal stator currents and minimize an electromagnetic torque oscillations under unbalanced grid conditions. The control does not require a positive and negative sequence decomposition of the control variables, so the independent control of positive and negative sequence is not used. Instead...
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The paper presents control method of rotor converter in variable speed DFIG based power generation system supplying nonlinear load. Control method allows to obtain high quality stator voltage without rotor speed or position. The method uses PLL structure for frequency control, PI controller for stator voltage amplitude regulation and separate controllers for reduction of harmonics in the frames connected...
