K. Srinivas Bhaskar

Bio: K. Srinivas Bhaskar is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Inverter & Inductor. The author has an hindex of 2, co-authored 3 publications receiving 21 citations.

Power quality survey in a technological institute

Abstract: This paper discusses the power quality survey conducted in the distribution system of Indian Institute of Technology Madras, Chennai, India. Individual power quality parameters measured from the survey are analyzed and presented in detail. To assess the power quality, measured data are compared with various power quality standards including IEEE 519-1992 standard for the measured voltage and current harmonics. The information obtained from this survey will be useful in improving the quality of power in the Institute.

Capacitor voltage balancing in neutral clamped inverters for DSTATCOM application

Abstract: Multilevel neutral point clamped inverter systems are increasingly used in load compensation applications. But, the most significant problem associated with these compensators is the capacitor voltage imbalances and drift due to dc components in the zero sequence current, resulting in degradation of tracking performance of the voltage source inverter. This paper proposes a carrier based PWM control for an inverter-chopper circuit in order to regulate the capacitor voltages to their reference values. To demonstrate the simplicity and effectiveness of the above control scheme, a three-phase four-wire, three-level neutral point clamped compensator system is taken as an example. Detailed simulation has been carried out in PSCAD 4.2.1. Experiments are conducted to validate the proposed control scheme.

PSO-based feedback controller design of DSTATCOM for load compensation with non-stiff sources

Abstract: Shunt compensating devices like distribution static compensator (DSTATCOM) are extensively used for compensating harmonics/unbalance/voltage sag-swell in a power distribution system. The design and performance of DSTATCOM for load compensation with stiff and non-stiff sources have been well reported in literature. Using linear control strategies like linear quadratic regulator (LQR), feedback controllers have been designed for DSTATCOM to track the reference currents for effective compensation under non-stiff source. There are many uncertain parameters like the feeder impedance, load impedance and harmonic content in load currents etc. Due to the parametric uncertainties, feedback controller designed using LQR may not be robust to these uncertainties. In this paper, a particle swarm optimisation(PSO)-based feedback controller is designed for DSTATCOM for load compensation. This feedback controller has optimal performance in various operating conditions and is robust to parametric uncertainties. The performance of the proposed feedback controller is compared with that of the conventional feedback controller designed with LQR.

DC Capacitor Balancing

Abstract: Methods and devices for balancing voltages of capacitors in an electronic circuit are provided. The device includes a chopper circuit having a chopper inductor. Further, the chopper circuit may detect voltages across capacitors as well as an output current of the electronic circuit. In addition, the device may include a chopper control unit receiving the output current then generating a signal representing charging of the chopper inductor based on the output current. Also, the chopper control unit may receive the voltages across the capacitors and detect an imbalance between the voltages based on a polarity of the output current. Additionally, the chopper control unit may transfer of charge between the two capacitors, using the chopper inductor. Further, the chopper inductor is substantially discharged, during the transfer of charge between the capacitors.

Power quality surveys of photovoltaic power plants: characterisation and analysis of grid-code requirements

Abstract: In the past few years, grid-code requirements for grid-connected photovoltaic power plants have experienced a continuous evolution in different countries to ensure a reliable power system operation as the level of renewable energy penetration increases to high levels. According to several European grid-codes, PV power plants must be able to ride through specific and severe disturbances without disconnections. Under this new framework, the present study analyses intensive power quality surveys carried out from 2008 to 2011 in three different Spanish PV power plants: a fixed array installation with 4 MW PV power capacity, a PV power plant including dual axis-trackers with 1 MW PV power capacity, and one more fixed array PV power plant with 5 MW PV power capacity. Voltage dips and supply interruptions have been collected, discussing several methods to characterise the monitored disturbances and to compare these events to current Grid-Code requirements. Furthermore, the time interval around the residual voltage is proposed and defined by the authors as an additional parameter to provide a complete characterisation of the severity of the disturbances. Results from both characterisations of collected data and comparison with current requirements are also included in the study.

Methods for Harmonic Analysis and Reporting in Future Grid Applications

Abstract: The rollout of advanced metering infrastructure, advanced distribution automation schemes, and integration of generation into distribution networks, along with a raising of awareness of power quality (PQ), means that there is an increase in the availability of power system monitoring data. In particular, the data for harmonics, whether it is voltage or current harmonics, is now available from a large number of sites and from a diverse range of PQ instruments. The traditional analysis and reporting of power quality examines harmonic orders to the 50th. This means that the harmonic data available for analysis are significantly larger than, for example, steady-state voltage variations where only a few parameters are examined (e.g., the voltage on each phase). Higher frequency components, sometimes called high-frequency harmonics, in the 10–250 kHz range arising primarily due to power-electronic interfaced generation are also becoming significant. Given the vast amount of harmonic data that will be captured through grid instrumentation, a significant challenge lies in developing methods of analysis and reporting that reduces the data to a form that is easily understood and clearly identifies issues but does not omit important details. This paper introduces a number of novel methods of analysis and reporting which can be used to reduce vast amounts of harmonic data for individual harmonic orders down to a small number of indices or graphical representations which can be used to describe harmonic behavior at an individual site as well as at many sites across an electricity network. The methods presented can be used to rank site performance in order for mitigation strategies. The application of each method described is investigated using real-world data.

Simplified Four-Level Inverter-Based Single-Phase DSTATCOM Using Model Predictive Control

Abstract: The conventional two-level inverter-based distribution static compensator (DSTATCOM) requires high switching frequency and fast digital signal processors (DSPs) to obtain smaller voltage/current ripples and low total harmonic distortion (THD). This increases the switching loss and computational burden. To solve such problems, this article proposes a simplified four-level (S4L) inverter-based DSTATCOM. The proposed inverter has a two-stage structure. The first stage produces three different voltage levels of full, two-thirds, and one-third of dc link voltage. These voltage levels are supplied to the second stage two-level inverter. Together with the zero voltage produced by the two-level inverter, the output of the proposed inverter can be four levels. With the same switching frequency and computational time, the S4L inverter-based DSTATCOM achieves much better performance than the conventional ones. Moreover, compared with the existing multilevel inverter-based DSTATCOMs, it is more cost-effective. To further enhance its performance, model predictive control (MPC) is employed. Experimental results are presented to verify the validity of the proposed system.

Power Quality Assessment for Industrial Plants: A Comparative Study

Abstract: Power quality (PQ) assessment has become a major area of interest in recent years because of increased use of sensitive equipments. It is necessary to know the level of disturbances in order to have necessary remedial or preventive measures to avoid equipment malfunction. Power quality surveys play a major role in achieving that. For the study carried out in this paper, power quality monitoring equipments were installed at three industrial sites to record the data. The observed PQ parameters are analyzed, compared and presented in detail. Observed PQ parameters are also compared with relevant standards to understand their severity levels.