Damir Sumina

Load angle estimation of a synchronous generator

The article is focused on a load angle estimation method in excitation regulation systems of synchronous generators. The estimation method is based on synchronous generator parameters given by the corresponding voltage-current vector diagram. The estimation results were compared with the measured ones. The estimation method gives satisfactory accuracy for load angles less than 120/spl deg/ el. Load angle regulation in excitation systems improves the stability of a synchronous generator in capacitive operating mode.

Determination of Load Angle for Salient-pole Synchronous Machine

Determination of Load Angle for Salient-pole Synchronous Machine This paper presents two methods for load angle determination for salient-pole synchronous generator. The first method uses optical encoder to detect the rotor position. In some cases the end of the rotor shaft is not free to be used and mounting of an encoder is impossible. Therefore, the second method proposes estimation of the load angle based on the measured electrical values that have been already used in excitation control system of the synchronous generator. Estimation method uses corresponding voltage-current vector diagram and parameters of the synchronous generator, transformer and transmission lines. Both methods were experimentally verified on the digital control system and synchronous generator connected to power system. The estimation and measured results were compared. The accuracy of load angle estimation method depends on voltage and current measurement accuracy as well as generator, transformer and transmission line parameter accuracy. The estimation method gives satisfactory accuracy for load angles less than 120° el. Thus, it can be applied in excitation control system to provide stable work of synchronous generator in under-excitation operating area.

Excitation control of a synchronous generator using fuzzy logic stabilizing controller

This article is focused on the implementation of simple fuzzy logic excitation control of a synchronous generator. A simple fuzzy logic control scheme for voltage control and generator stabilization is tested on the real laboratory model that includes digital system for excitation control (based on four DSPs) and synchronous generator connected to an AC system through transformer and two parallel transmission lines. The behaviour of the excitation system with fuzzy logic stabilizing controller is compared with excitation system based on the PI voltage controller and conventional power system stabilizer

Simulation model of Neural Network based synchronous generator excitation control

Usage of neural network (NN) based excitation control on single machine infinite bus and its simulation studies are reported in this paper. The proposed feed forward neural network integrates a voltage regulator and a power system stabilizer. It is trained on-line from input and output signals of a synchronous generator. A modified error function used for training the neural network by the back propagation algorithm uses the reference and terminal voltage as controlling voltage and active power deviation to provide stabilization. The complete algorithm is simulated in Matlab Simulink. Synchronous generator (83 kVA, 50 Hz, 400V) is connected over transmission lines to AC power system. The proposed algorithm shows advantages of this method and satisfactory results.

Comparison of maximum torque per ampere and loss minimization control for the interior permanent magnet synchronous generator

In this paper maximum torque per ampere and loss minimization control methods for an interior permanent magnet synchronous generator are compared. Permanent magnet synchronous generators have wide application in wind energy conversion systems due to high efficiency, high power density, high power factor and wide speed operating range. Maximum torque per ampere control method finds optimal d-and q-axis stator currents that produce desired electromagnetic torque while minimizing stator current magnitude. Loss minimization control method takes into account both copper and iron losses and finds optimal d- and q-axis stator currents that produce desired electromagnetic torque while minimizing total power loss. Characteristic curves for both control methods considering magnetic saturation are presented. Feed-forward torque control model developed in MATLAB/Simulink was used to verify described control methods.

Synchronous generator load angle estimation

In the paper is proposed a load angle estimation method for synchronous generators. The estimation method is based on synchronous generator corresponding voltage-current vector diagram and parameters of generator, transformer and transmission lines. In addition measurement of the load angle is presented. The estimation results were compared with the measured ones. The estimation method gives satisfactory accuracy for load angles less then 120° el. Although the load angle is a key variable for generator stability, it is rarely used as a variable in excitation control system, because the measurement problems. Hence, this estimation method has a wide area of application in excitation systems for control algorithm and to provide stabile work of synchronous generator in capacitive operating area.

The appliance of the estimated load angle in the fuzzy power system stabilizer

This paper investigates the application of the fuzzy logic power system stabilizer. Proposed stabilizer use estimated load angle of synchronous generator as the input. The load angle estimation is based on the real parameters of a synchronous generator, which are given by the corresponding voltage-current vector diagram. A fuzzy logic control scheme for synchronous generator stabilization is tested on the real laboratory model that includes digital system for excitation control (based on four DSPs) and synchronous generator connected to an AC system through transformer and two parallel transmission lines. The experiments were performed for step change of voltage reference. The behavior of the excitation system with fuzzy logic stabilizer is compared with excitation system based on the PI voltage controller and conventional power system stabilizer

Practical approach for parameter determinations of interior permanent magnet generator

Recently, there has been a lot of researches on various methods for a sensorless control of permanent magnet generators (PMG) in wind turbines. The sensorless control of the PMG considers estimations of a rotor angle and speed which are based on the PMG parameters estimation. The parameters that have been estimated are stator resistance, rotor flux, d-axis and q-axis inductance. For more precise rotor angle and speed estimation, it is essential to determinate values of the PMG parameters in every operating point as accurately as possible. A change of the operating point (different rotor speed, shaft torque etc.) causes the change of the PMG parameters due to stator currents and temperature variation. Accordingly, the PMG parameters could be measured during a PMG commissioning. In this work, the stator resistance is measured while taking into considering a dead time compensation and voltage drop on a power switching devices. A determination of the d-axis and q-axis inductances is based on PMG voltage equations in a dq synchronous reference frame. Thus, the measurements of the rotor speed, stator currents and voltages are required. The experimental measurements are carried out on a 375 kW interior permanent magnet generator. Finally, the measured values could be saved on a digital signal processor (DSP) as look-up tables and used for the sensorless control of the PMG.

Control of generator- and grid-side converter for the interior permanent magnet synchronous generator

Permanent magnet synchronous generators have wide application in wind energy conversion systems. If interior permanent magnet synchronous generator (IPMSG) is connected to the grid by a full scale AC-DC-AC converter, the wind turbine can be operated to extract maximum wind power at different wind speeds by optimally adjusting shaft speed. In this paper the model of the AC-DC-AC converter and related control structures for the control of IPMSG were developed in MATLAB/Simulink. Control of generator-side converter was achieved using field oriented control (FOC) which separately controls the electromagnetic torque and the magnetic flux. Optimal stator current references were calculated using maximum torque per ampere algorithm (MTPA) which ensures minimum stator current magnitude for electromagnetic torque reference. Control of grid-side converter was achieved using voltage oriented control (VOC) which separately controls active and reactive power injected to the grid. Outer control loop, with slower dynamics, ensures that DC circuit voltage is kept at reference value which ensures transfer of the active power from the DC circuit to the grid. Inner control loops, with faster dynamics, control the d- and the q-axis grid currents. Using developed control structures, the stator and the grid current PI controllers were designed using technical optimum while DC voltage PI controller was designed using symmetrical optimum. Proposed control methods were verified by simulation using laboratory model parameters.

Fuzzy Logic Control of Synchronous Generator Under the Condition of Transient Three Phase Short Circuit

This article is focused on the implementation of fuzzy logic excitation control of a synchronous generator. A simple fuzzy logic control scheme for voltage control and generator stabilization is tested on the real laboratory model that includes digital system for excitation control (based on four DSPs) and synchronous generator connected to an AC system through transformer and two parallel transmission lines. The experiments were performed for transient three phase short circuit on the one transmission line. The behaviour of the excitation system with fuzzy logic stabilizing controller is compared with excitation system based on the PI voltage controller and conventional power system stabilizer