Ritwik Chattopadhyay

Comparison of PR controller and damped PR controller for grid current control of LCL filter based grid-tied inverter under frequency variation and grid distortion

Voltage Source Inverters (VSIs) are essential component for integration of renewable energy sources into utility grid or microgrid. Most of the utility grid regulation standards demand high quality sinusoidal current regulation by these inverters with renewable sources, which necessitates the use of LCL filters at the output of VSIs. Different load conditions and other factors influence grid conditions, such as voltage profile, harmonic distortion and frequency variation. The scope of this paper include comparison of effects on grid current of LCL filter based inverter while using PR controller and damped PR controller under distorted grid voltage and frequency variation conditions. The effects are analyzed through simulation studies in MATLAB/PLECS and real time simulation studies are carried out in Typhoon HIL environment.

Modular isolated DC-DC converter with multi-limb transformer for interfacing of renewable energy sources

This paper presents a modular isolated scalable three phase dual active bridge(DAB) DC-DC converter configuration using three multi limb high frequency transformers. The proposed converter has the advantage of having multiple low and high voltage dc links, which can be used at different power levels. The converter has three high voltage dc links which can be used for cascaded inverters or can be connected in series to provide a high dc link voltage for medium voltage grid-tie inverter. Multiple number of renewable energy sources(RES) can be connected to the low voltage side dc links to feed power to the grid. The paper work contains converter configuration, equivalent circuit of multi limb transformer, control of converter for a single renewable energy source and multiple renewable energy sources.

ZVS analysis and power flow control for three limb transformer enabled SiC Mosfet based three port DAB integrating PV and Energy Storage(ES)

Multi-port dc-dc converters are the modular power electronic building blocks for integration of PV and Energy Storages(ES). The work in this paper focuses on ZVS characteristics for independent power flow control of three port DAB converter integrating PV and Energy Storage(ES), using three limb high frequency transformer. The independent power flow control discussed here, focuses on ES charging scenario for the converter using two different modulation techniques. ZVS scenario variations for two different modulation control technique for two different designs of three limb transformers, are discussed in the paper. A laboratory scale prototype using 1200V and 1700V SiC Mosfets has been made and preliminary results have been obtained for experimental validation of the ZVS scenarios.

Power flow control and ZVS analysis of three limb high frequency transformer based three-port DAB

The work presented in this paper focuses on the power flow control and study of three-limb high frequency transformer enabled three port Dual Active Bridge(DAB) converter, using 1200V and 1700V SiC devices. The advantage of using three-limb transformer is given by the low inter-winding parasitic capacitances due to placement of windings on different limbs and elimination of inter-winding insulations unlike concentric windings. The focus of the paper is based on power characterization for independent power flow of three port DAB using modulation control, and ZVS scenario study under the modulation control. Detailed analysis for power flow control and turn-on/turn-off ZVS conditions have been realized. A laboratory scale prototype using SiC Mosfets has been made and experimental results have been obtained for 500V dc input voltages and 1000V dc output voltage at 8.2kW of power.

Control of modular dual active bridge DC/DC converter for photovoltaic integration

The DC transmission system provides a cost effective solution for long distance power transmission compared to the AC transmission system. Hence, this has increased the emphasis on the development of the DC transmission system. Development of power converter with modular structure has now made it possible to achieve higher voltage and power level. This opens the possibility for further development of a multi-terminal DC grid. Now once the DC grid system has been formed, it is also important to include more renewable energy sources directly to the DC grid. Therefore, a power conversion stage is required to condition the available power from a source to the grid. This paper shows the operation and control of such a kind of converter system which integrates the solar cell to the DC grid directly. The paper mainly focuses on control of the series connected DAB that have been integrated to HVDC power network. In order to deliver power in HVDC system, the total number of DABs must be high enough to achieve the DC link voltage. The control in that case must be a combination of current and voltage control. In order to validate the proposed control, complete system has been implemented on Opal-RT™ and hardware in the loop (HIL) using external controller has also been implemented to show the system operation.

Low voltage PV power integration into medium voltage grid using high voltage SiC devices

High voltage high power semiconductor devices are being used for grid integration of renewable energy sources. 1200V, 100A SiC Mosfets, 10 kV SiC Mosfets and 10kV SiC JBS Diodes have proven to be beneficial for high voltage application. High Voltage SiC devices enable high switching frequency operation thus reducing size of passive elements. Scope of this paper focuses on an alternative approach for 0.9 MW PV power plant, which is currently being constructed in Brazil. Use of high power SiC devices for PV power plant for integration into 13.8 kV grid provides higher efficiency, reduction in size and volume.

Flux vector modulation for single-phase inverter with LC output filter

The inverter often connects to load or grid through inductor-capacitor (LC) filter for feeding the filtered voltage and current. The carrier based modulation techniques, such as sinusoidal pulse width modulation (SPWM) and space vector modulation (SVM), require some kind of current control in LC filter connected inverter to damp out the LC resonance. The major advantage of flux vector modulation for the inverter with output LC filter is that the voltage control loop alone can damp out the resonance of LC filter. Hence, there is no need to use extra passive components or active damping controller. In this paper, the flux vector modulation for single-phase voltage source inverter (VSI) is proposed. The theoretical development and the digital implementation steps of flux vector modulation are described. The synchronously rotating reference frame (SRRF) proportional-integral (PI) controller is used for output voltage control for stand-alone operation of inverter. The single-phase inverter with output LC filter in stand-alone mode controlled by only voltage control loop with the flux vector modulation is validated through laboratory experiments.

Vehicle-to-grid scheme based on inductive power transfer for advanced distribution automation

The latest technological advances in battery and converter technology, along with government mandates on energy independence and resilience, are expected to pave the way for higher deployment of plug-in electric vehicles (PEV) in the transportation fleet. These vehicles, when equipped with bidirectional energy transfer capabilities, can function as mobile energy resources and can be utilized in a Vehicle-to-Grid (V2G) scheme in order to temporarily inject energy back into the power grid, thereby functioning as energy storage systems. The forecasted increase in the number of these dispersed vehicles can potentially turn them into a significant energy resource that can be used by the utilities for ancillary services or even for long-term integration with the power system. The notion of energy injection through V2G schemes has been conceptually investigated in the literature for charging stations or single residential charging devices. In all these case studies, the vehicle needs to be parked, and a connection be established by the driver, for the duration of the battery charge or discharge. This paper looks into V2G through the employment of contactless means for energy transfer, namely inductive power transfer (IPT). IPT adds flexibility to V2G schemes by allowing energy exchange with vehicles in motion or when the driver is not physically present to establish a connection. The performance of IPT for bidirectional power flow has been shown through simulation as well as experimental results. Also, statistical analysis are provided that demonstrate the large scale integration of these vehicles into the grid.

Decoupled power flow using phase shift control and ZVS cases for a three limb high frequency transformer based three-port DAB integrating PV and energy storage

The work presented in this paper focuses on the decoupled power flow control using phase shift control technique and resulting ZVS scenarios for three-limb high frequency transformer enabled three port Dual Active Bridge(DAB) converter, integrating PV and Energy Storage(ES). The advantage of using three-limb transformer is the low inter-winding parasitic capacitances due to positioning of windings on different limbs and elimination of high insulation requirements unlike concentric windings. The focus of the paper is based on decoupled power flow control of three port DAB using phase shift control, and ZVS scenario study under the phase shift control. Detailed analysis for power flow control and turn-on/turn-off ZVS conditions have been realized. Detailed Simulation Studies have been done and comprehensive results have been obtained for 700V dc PV//ES voltage and 1200V dc output voltage.

Split-winding type three limb core structured HF transformer for integrating PV and energy storage(ES)

The work presented in this paper focuses on the drawbacks of three limb three winding transformer for use in three port dc-dc converter and proposes a split-winding type transformer approach using three limb core for use in three port dc-dc converter. The three limb three winding type transformer has drawback due to limitation of power flow when one port is idle and also has a very limited ZVS operating region for phase shift control. The proposed split-winding type transformer has the equivalent circuit of single core based transformer, has no limitation of power flow when one of the three port is idle and has wide ZVS range. Detailed analysis for idle condition operation, equivalent circuit derivation and ZVS operating range analysis is carried out in this paper.