Mahesh Kumar Mishra

This paper proposes a boost inverter topology to realize the reference currents generated by Instantaneous Symmetrical Component theory. The circuit topology and the switching pattern of the boost inverter boosts up a low voltage DC (e.g. photovoltaic panel or fuel cell) of a sustainable energy source to inject the required filter currents. The proposed boost inverter can perform load balancing, harmonic compensation and reactive power control while supplying real power to the grid. In a PV based boost inverter, PV panels of low output voltage can be connected in parallel, and eventually, a panel's defect or malfunction will not affect the operation of the whole system significantly. The boost inverter's switching are controlled by the Power Balance concept. This inverter topology is connected to the Point of Common Coupling (PCC) of the distribution system. The reference waveform generated from instantaneous symmetrical component theory are used further to generate instantaneous boost reference parameters. These boost reference parameters are then tracked by the boost converters to inject the desired filter currents into the corresponding phase. ©2012 IEEE.

In this paper, a unified energy management scheme is proposed for renewable grid integrated systems with battery-supercapacitor hybrid storage. The intermittent nature of renewable-energy resources (RES), coupled with the unpredictable changes in the load, demands high-power and high-energy-density storage systems to coexist in today's microgrid environment. The proposed scheme dynamically changes the modes of renewable integrated systems based on the availability of RES power and changes in load as well. The participation of battery-supercapacitor storage to handle sudden/average changes in power surges results in fast dc link voltage regulation, effective energy management, and reduced current stress on battery. In addition, the proposed energy management scheme enables the real power transfer along with ancillary services such as current harmonic mitigation, reactive power support, and power factor improvement at the point of common coupling. The proposed scheme is validated through both simulation and experimental studies.

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. ©2009 IEEE.

Dynamic Voltage Restorer (DVR) restores the distribution system load voltage to a nominal balanced sinusoidal voltage, when the source voltage has distortions, sag/swell and unbalances. DVR has to inject required amount of Volt-Amperes (VA) into the system in order to maintain a nominal balanced sinusoidal voltage at the load. A new control technique is applied to compensate the sag and harmonics with phase jumps in the source voltages. Keeping the cost effectiveness of DVR, it is desirable to have a minimum VA rating of the DVR, for a given system without compromising compensation capability. Hence, a methodology has been proposed in this work to minimize VA rating of DVR. The optimal angle at which DVR voltage has to be injected in series to the line impedance so as to have minimum VA rating of DVR as well as the removal of phase jumps in the three-phases is computed by Particle Swarm Optimization (PSO) technique. The present method was able to compensate voltage harmonics and sags with phase jumps by keeping the DVR voltage and power ratings minimum, effectively. The proposed method has been validated through detailed simulation studies. ©2009 IEEE.

This paper presents the development of a prototype module for DSP based Distribution Static Var Compensator (DSTATCOM) to compensate unbalanced and non-linear load in power system. A digital signal processor starter kit TMS 320F2812PGFA is chosen due to its analog/digital input-output compatibility, fast processing speed and cost effectiveness to implement the shunt algorithm based on instantaneous symmetrical component theory. The design details of logic circuits and power circuits are presented. The experimental studies are carried out and the results are discussed.

This paper investigates the challenges in mitigating several power quality (PQ) problems by a single distribution static compensator (DSTATCOM), and proposes a reduced rating voltage controlled hybrid DSTATCOM with multi-functional features. This scheme connects a suitably designed external inductor, as a part of the load, between the source and load points. This inductor improves the voltage regulation bandwidth of DSTATCOM and reduces the current requirement for voltage sag mitigation. Along with this, a multi-functional algorithm is proposed to generate dynamic reference load voltage. This algorithm indirectly controls the source currents during normal operation to mitigate current related PQ problems, whereas maintains a constant voltage at the load terminal during voltage disturbances. Simulation results are presented to validate the capability of single DSTATCOM to mitigate several PQ problems. © 2013 IEEE.

This paper derives a generalized mathematical model of a three-phase, four-wire, four-leg voltage source inverter topology for a DSTATCOM application. The four-leg inverter is operated in a current controlled mode by a suitable control strategy, to inject compensator currents in order to achieve harmonic compensation, load balancing and power factor correction. The four-leg compensator topology is also capable of compensating the dc component of the zero sequence current in the neutral conductor. The reference currents extracted through the instantaneous symmetrical component theory are tracked through hysteresis current control technique. The conditions required for a stable switching control are obtained using the Lyapunov stability criterion. The derived model has been verified by carrying out simulation studies through MATLAB and PSCAD, along with relevant results and discussions. Compensation is found to be effective with the supply relieved of harmonics, reactive power and unbalanced currents, confirming the correctness of the model developed. ©2010 IEEE.

Deadbeat controllers are commonly employed in grid connected inverter systems for their fast transient response. In this article, a loss modulated deadbeat current control (DCC) is proposed for a grid connected inverter system. This control calculates the required modulation signal by considering the losses in the system at every switching cycle. The proposed method tracks the reference current with negligible error. The loss component used in the control method eliminates the effect of sensing and computational time delay and adapts to variation in system parameter. The proposed DCC is extended for deadbeat-based direct power control (DDPC) without employing inner current control loop. Furthermore, a modified DDPC is presented to eliminate the delay of one switching cycle, which is inherently present for the grid current in DCC. The proposed control concepts are realized on a multisource fed switched capacitor-based multilevel inverter. The topology considered features more number of voltage levels with less component count, high gain, self capacitor charge balancing, and increased source utilization. The steady-state and transient behavior of the control methods are verified in simulation and experimental studies for a power rating of 500 W under various system conditions. The proposed algorithms are able to track the reference signals with fast transient response and negligible steady-state error.

This paper proposes a modified four-leg distribution static compensator (DSTATCOM) topology for compensation of unbalanced and nonlinear loads in three-phase four-wire distribution system. DSTATCOM, connected in parallel to the load, supplies reactive and harmonic powers demanded by unbalanced nonlinear loads. In this proposed topology, the voltage source inverter (VSI) of DSTATCOM is connected to point of common coupling (point of interconnection of source, load, DSTATCOM) through interface inductor and series capacitance, unlike the conventional topology which consists of interface inductor alone. Load compensation with a lower value of input DC link voltage of VSI is possible in this modified topology compared to conventional topology. A comparative study on modified and conventional topologies in terms of voltage rating of inverter power switches, switching losses in VSI and power rating of input DC capacitor of VSI is presented. The detailed design aspects of DC link capacitor and interface series capacitor are also presented. The reference filter currents are generated using instantaneous symmetrical component theory and are tracked using hysteresis current control technique. A detailed simulation study is carried out, to compare the compensation performances of conventional, modified topologies using PSCAD simulator and experimental studies are done to validate the simulation results.

The transient response of the distribution static compensator (DSTATCOM) is very important while compensating rapidly varying unbalanced and nonlinear loads. Any change in the load affects the dc-link voltage directly. The sudden removal of load would result in an increase in the dc-link voltage above the reference value, whereas a sudden increase in load would reduce the dc-link voltage below its reference value. The proper operation of DSTATCOM requires variation of the dc-link voltage within the prescribed limits. Conventionally, a proportional-integral (PI) controller is used to maintain the dc-link voltage to the reference value. It uses deviation of the capacitor voltage from its reference value as its input. However, the transient response of the conventional PI dc-link voltage controller is slow. In this paper, a fast-acting dc-link voltage controller based on the energy of a dc-link capacitor is proposed. Mathematical equations are given to compute the gains of the conventional controller based on fast-acting dc-link voltage controllers to achieve similar fast transient response. The detailed simulation and experimental studies are carried out to validate the proposed controller. © 2009 IEEE.