Conference Papers
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Item DSC filter based unit vector estimator for reference generation and control of dynamic voltage restorer(Institute of Electrical and Electronics Engineers Inc., 2017) Kasyap, M.S.; Karthikeyan, A.; Venkatesa Perumal, B.V.; Nagamani, C.DVR control requires a robust algorithm for computing grid voltage magnitude and phase angle. Conventional SRF-PLL performs poorly as it cannot filter out negative sequence voltages and harmonics that could occur in the grid voltage. In this paper a Positive and Negative Sequence Extractor (PNSE) is formed by a Delayed Signal Cancellation (DSC) filter, which filters harmonics and extracts Instantaneous Symmetrical Components (ISC) of the source voltage in stationary reference frame. The phase angle information of the grid voltage is derived by computing the unit vectors of the ISC in stationary frame. This eliminates the need for a conventional PLL and thus simplifies the reference generation algorithm. A PI controller tracks the capacitor reference voltage in synchronous reference frame to restore the fundamental load voltage while resonant controllers are tuned to mitigate the lower order odd harmonics in the load voltage. Simulation studies carried out in PSCAD/EMTDC for a Medium Voltage DVR model shows that the presented control works effectively for all the test cases considered such as voltage sags and harmonics. © 2016 IEEE.Item Phase advance compensation of voltage sags using full bridge inverter based DVR(Institute of Electrical and Electronics Engineers Inc., 2018) Remya, V.K.; Parthiban, P.; Nandakumar, A.Voltage sag is considered as the most expensive power quality problem. With the advent of power electronics, custom power devices are introduced to mitigate the sag issues. Among the custom power devices, Dynamic Voltage Restorer (DVR) is the most cost-effective one. The voltage injected in series by the DVR compensates the load profile during sag events. The compensation techniques such as in-phase, energy minimized and phase advance methods determine the way in which the DVR voltage is injected into the grid. By providing a phase advance to the DVR voltage with respect to the supply voltage gives the merit of reduced active power injection and thereby reduces the rating of energy storage. The disadvantages such as increased DVR voltage magnitude, phase shift, load swings and discontinuity of wave shape are associated with this compensation technique. This method is suitable for magnitude sensitive loads. This paper presents simulation results showing the compensation of both sag and swell using phase advance compensation. © 2017 IEEE.Item Design and Analysis of Multi-Loop Feed Forward Control Schemes for DVR under Distorted Grid Conditions(Institute of Electrical and Electronics Engineers Inc., 2018) Karthikeyan, A.; Abhilash Krishna, D.G.A.; Kumar, S.; Nagamani, C.Voltage sags are considered as important power quality problems and the Dynamic Voltage Restorer(DVR) is an effective solution to mitigate the sags and other power quality problems related to voltage. The DVR involves two major aspects: (i) reference generation and (ii) control algorithm. Under unbalanced grid conditions the presence of negative sequence components in the grid voltage causes sustained oscillations in the estimated dq- voltages, which makes sag detection difficult with conventional SRF-PLL and there by chances of controller malfunctioning. In this paper, a Delayed Signal Cancellation (DSC) pre-filter based Positive and Negative Sequence Extractor (PNSE) is employed to extract the Instantaneous Symmetrical Components (ISC) of the grid voltage and filter out the harmonic voltages from the estimated dq-voltages. As the response of the DVR mainly depends on the controller action this paper presents an multiloop PI feed forward controller for enhancing the operation of DVR under distorted grid conditions. The efficacy of the proposed controller is illustrated by comparative study with multiloop feed forward P controller using time response and relative stability analysis. Simulation studies are performed in PSCAD/EMTDC for a 10kV medium voltage DVR under various voltage disturbances such as symmetric and asymmetric voltage sags. © 2017 IEEE.Item A comparative study of full-bridge inverter based DVR and SEMI-Z-source inverter based DVR(Institute of Electrical and Electronics Engineers Inc., 2018) Remya, V.K.; Parthiban, P.; Nandakumar, A.There is always a necessity to protect the voltage sensitive industrial systems from Power Quality (PQ) issues to prevent the loss of product quality and revenue. Generally, custom power devices take the responsibility to mitigate these PQ problems, restore the voltage and thus maintain the PQ standards. Dynamic Voltage Restorer (DVR) is one among the custom power devices which offers an economical compensation of load voltage under abnormal supply voltage conditions. The voltage injected in series by the DVR compensates the load profile during PQ events; appropriate voltage injected by the DVR in series with supply protects the load and restores the voltage to pre-defined values. The required injected voltage is generated by the inverter circuit in the DVR system. The most commonly used DVR inverter is the full-bridge inverter which consists of four switches. The Semi-Z-Source (SZS) inverter based DVR which offers same injection capability with only two-switches is compared with the full-bridge inverter. The in-phase compensation technique is employed in both the DVRs for injecting required voltage into the grid. The efficiency, quality of the injected voltage and load voltage are studied. This paper presents simulation results in MATLAB/Simulink environment to validate thecomparison. © 2018 IEEE.