Design of a fixed-point digital filter for state estimation for UPS applications (original) (raw)
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The paper presents comparative studies of state estimation for a power system with and without the UPFC device. Weighted least squares state estimation is considered. Such parameters of state estimation are taken into account as: the condition number of the gain matrix, parameters characterizing accuracy of estimation results, and number of iterations in a computational process. During investigation, impact of existence UPFC in a power system on the mentioned parameters of the state estimation is analyzed for different coordinate systems, in which state vector is considered, for different levels of stress of a power system and data redundancy. In the paper, the considered parameters of state estimation are determined for the IEEE 14bus test system. The results of the analyses show, that in general, impact of existence UPFC in a power system on features of the state estimation is negative, and particularly essential in some cases.
IEEE Access, 2022
Uninterruptible Power Supplies (UPS) represent the key technology to continuously feed and protect a wide range of critical applications in electric power systems. Due to their continuous operation, UPS components degrade over time, including their filtering elements, leading to decreased filtering capabilities. With these deviations, UPS performance is typically reduced. Moreover, if filter parameter deviations are not considered in the control system, performance degradation can be further increased and the critical load can be seriously compromised. This is especially important with Model Predictive Control (MPC), which heavily relies on system parameters accuracy. Thus, control performance optimization using estimated filter parameters in UPS systems can be extremely important. Nevertheless, this has not yet been covered in the literature for UPS systems. In light of these facts, this paper proposes a new mechanism that, by using online estimated filter parameters, optimizes the performance of an MPC strategy, in a UPS system. In the scope of this optimization mechanism, an estimation method that enables parameter identification and control optimization not only in balanced but also in highly unbalanced filter conditions (rarely studied in the literature) is proposed. Experimental results demonstrate the accuracy of the proposed estimators and the effectiveness of the proposed control performance optimization mechanism. Under severe filter parameter variations, the proposed performance optimization scheme enabled to reduce the degradation (caused by filter variation) of the grid current and load voltage THD by 29.41 % and 91.60 %, respectively. Furthermore, the degradation of the RMS load voltage value was also significantly reduced by 97.89 %. INDEX TERMS Model predictive control, online inductance and capacitance estimation, power quality, real-time control performance optimization, uninterruptible power supply.
Phasor measurement unit reliability enhancement using real-time digital filter
International Journal of Circuits Systems and Signal Processing, 2011
Phasors and frequency of three-phase power system may be measured with high speed and accuracy using modern power instruments such as Phasor Measurement Unit (PMU). However, this accuracy may be affected by several power disturbances such as fast and slow dc offsets decaying due to sudden current changes, interharmonics, etc. To avoid these effects for improving the quality of measurements, this work proposes a new method of real-time filter for removing the unwanted DC offset and hence improving SDFT algorithm. To validate the present method, the performance of developed PMU is tested using the data generated by Simulink/MATLAB simulator. The obtained simulation results are very encouraging.
Digital measurement station for power quality analysis in distributed environments
IEEE Transactions on Instrumentation and Measurement, 2003
Abstract Today there is a wide application of different electronic apparatus that both produce electromagnetic disturbances on the supply power system and are sensitive to them. Power disturbances present on typical electric utility distribution systems degrade product quality, ...
Filter Implementation Using Output Transformer of UPS for Power Quality Improvement
International Journal of Power Electronics and Drive Systems, 2017
Power electronics play a significant role in different areas of technology, more usage of power electronic devices lead to more harmonic content and various power quality issues in the system. Therefore, power quality gains more significance in the current era of research. Power electronics equipment's with non-linear loads concludes with more harmonic disturbances and lower power factor. Harmonic impurities are the major problem ingredient due to the connection of non-linear load. To lessen the harmonics usually passive filters are used. The major objective of this work is to monitor and analyse the power quality of uninterrupted power supply by means of DAQ system that gathers real time data on the system and then the data is analysed using National Instruments LabVIEW. Once power quality analysis is done, a new technique of filter implementation using output transformer of the UPS was explored and passive filter was simulated using MATLAB/Simulink and then simulated filter was implemented in order to achieve power quality improvement.
Design and implementation of a digital control and monitoring system for an AC/DC UPS
2011 7th International Conference-Workshop Compatibility and Power Electronics (CPE), 2011
This paper presents the design and implementation of a digital control and monitoring module for an AC/DC uninterruptible power supply (UPS). A hardware and software of the system is developed. Moreover, a friendly graphical-user interface is provided. Management strategy of the UPS in different operation modes is described. The proposed digital control and monitoring system allows to realize the complex algorithms and this way increase the reliability and efficiency of the UPS. I.
IEEE Transactions on Industrial Electronics, 2000
A novel algorithm for fundamental frequency and harmonic components detection is presented in this paper. The technique is based on a real-time implementation of discrete Fourier transform, and it allows fast and accurate estimation of fundamental frequency and harmonics of a distorted signal with variable fundamental frequency. It is suitable for active shunt filter applications, when fast and accurate tracking of the reference signal is required to achieve a good control performance. The main application for the algorithm is aircraft ac power systems, where the fundamental frequency can be either fixed on 400 Hz and its actual value fluctuates around the nominal value, or variable in the range 360-900 Hz. Hence, a real-time estimation of fundamental frequency is essential for active filter control. The proposed algorithm has been at first implemented in Matlab/Simulink for computer simulation, and it has been compared with a Phase Locked Loop (PLL) algorithm for frequency detection and the synchronous dq reference method for harmonic detection. Experimental tests have been carried out in order to validate the simulation results. The distorted current absorbed by a nonlinear load is analyzed and processed by means of a digital implementation of the algorithm running on the active shunt power filter control DSP, in order to calculate the active filter compensating current.