Advanced Control Embedded Modular Multi-Port Converter for Smooth Integration of Renewables to Microgrid

MOTIVATION:

Distributed Generators (DG - including Photo – Voltaic (PV) systems, fuel cell etc) are a major steppingstone to achieve green and reliable microgrid. Solar PV sources are dominant DG sources in the local microgrids. However, DG suffer from variability (due to environmental factors) and intermittency. This concern is usually addressed by integrating Battery Energy Storage System (BESS) with DG. However, this integrated system requires optimum design and integrated control. To address this concern, this project aims at designing a modular multi–port converter to achieve expandable integration of DG. In addition to DG ports, two ports are provided to accommodate battery storage and conventional utility grid in the system. The presence of multiple elements (sources and loads) poses a control and optimization challenge for conventional PI based control algorithms. This concern can be addressed by using Artificial Neural Network (ANN) based advanced control scheme to achieve optimum green power generation, economic cost of generation and minimal chances of power black out.

INDUSTRY BENEFIT:

  • Designed and developed modular system would facilitate scalable grid integration process of DG sources to the utility grid (with improved efficiency and component minimization)

  • Deployment of ANN based advanced control algorithm would help in achieving economic operation with accurate and robust performance

TASKS:

  1. Design and development of Modular Multi – Port Converter (minimum component design) in SIMULINK environment
  2. Development of ANN based Advanced Control Algorithm for closed loop operation of connected sources
  3. Formulation of objective function (consisting of DG sources with different constraints) to achieve economic load dispatch in microgrid
  4. Hardware implementation of scaled – down prototype to verify the developed closed loop control algorithm

SITE/TEAM:

TAMUG Site: CARES Lab led by Dr. Irfan A. Khan

TAKEAWAY:

Embedded BESS to address concerns related to variability and intermittency of DG sources Scalable integration of sources to the grid without significant modification in the existing structure ANN based economic load dispatch to minimize cost of energy generation and carbon emissions

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Multi-winding SST Structure for Addressing Storage & Power Quality Problems in PV dominated Utility Grid

MOTIVATION:

When concentration of PV system becomes more prominent in utility grid, voltage sag/swells happens very frequently. There are two options available in the literature to address this concern – Shunt and Series compensation. Both these methods require an independent voltage source. However, shunt compensation method such as& Front-End& Converter (FEC) is a voltage intensive scheme with current rating equal be desired compensation (± 2-5% only), whereas, series compensation method such as& Dynamic& Voltage& Restorer (DVR) is a current intensive scheme with voltage rating equal to desired compensation. Therefore, DVR suffers from high switching losses due to high current requirement. To address these issues in DVR, this project aims at developing a multi–winding& Solid-State& Transformer (SST) solution for addressing voltage sag/swell and power quality problems in high PV penetrated utility grid. Multi- winding SST would be used here to replace conventional& Low& Frequency& Transformer (LFT), which leads to compact and modular design, and superior performance including low THD and control dynamics. Three-winding SST would serve as a central power flow controller for bidirectional power flow among solar PV grid,& Battery& Energy& Storage& System (BESS) and DVR. Here, isolated BESS would act as primary power source for DVR, however, in case of low& State of& Charge (SoC) of BESS, solar PV grid may act as secondary power source for DVR, thus improving the system reliability. Furthermore, bidirectionality of power flow from all the connected windings would address all power quality concerns in utility grid. To achieve minimal switching losses, wide-band gap devices with low forward resistance would be employed.

INDUSTRY BENEFIT:

  • Replacing LFT with SST for implementation of DVR would help in achieving compact design including lower footprint and lower cooling requirement.

  • Novel design of multi-winding SST would help in minimizing transformer parasitics to achieve minimum losses and high-power transfer capability in SST.

  • Optimized and reliable design (with both grid and BESS acting as sources for DVR) of DVR would help in alleviating voltage sag/swell and other power quality issues

TASKS:

  1. Design and development of multi-winding SST based converter for interconnection of PV grid, BESS and DVR in SIMULINK

  2. Design and development of robust control algorithm to demonstrate bidirectional power flow capability through each winding

  3. Optimization of multi – winding SST with ANSYS software for minimizing parasitics

  4. Hardware implementation of scaled – down prototype using wide – band gap devices (SiC) to verify the proposed concept

SITE/TEAM:

TAMUG Site: CARES Lab led by Dr. Irfan A. Khan

TAKEAWAY:

  • Proposed architecture would help in realizing goal of carbon free, green and reliable utility grid
  • SST based DVR would address power quality issues thereby minimizing downtime
  • SST based design (instead of LFT) would help in reducing space and cooling requirements

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High Gain Quasi Switched Boost Converter Based DC Homes with Embedded Energy Storage System

MOTIVATION:

Solar PV grid infrastructure for grid integration has relentlessly attracted the researchers. Conventionally individual PV panels are rated for 200-350 Watts with voltage rating between 30 – 36V at MPPT for dc home applications. For grid integration, these PV panels requires high gain converters. However, conventional dc-dc converters (such as boost, buck – boost and other derived circuits) are unable to achieve this gain requirement. This hindrance is due to their inability to operate under extreme duty cycles conditions and detrimental effects of parasitics (internal resistance of inductors and capacitors). To address this concern, this project focusses on developing and deployment of novel high-gain quasi Switched Boost Converter (qSBC), which employs quasi switched boost structure (two dc-dc converter switches only as shown) with gain capability up to 8 times the conventional Z source converter. This will help in achieving the following objectives: MPPT operation, Battery Energy Storage System (BESS) charging/discharging and grid integration while using minimal passive and active components. To achieve these objectives with limited switching devices, Model Predictive Control (MPC) based control algorithm will be developed. Furthermore, since multiple objectives with different priorities are required to be optimized, different weights will be allocated to these objective functions based on their preferences.

INDUSTRY BENEFIT:

  • High-gain converter solution for integrating battery embedded PV generation to domestic dc grid (typical 2 -3 kW). This will eliminate need for additional converters used in conventional design.

  • Proposed converter design helps in direct battery discharge (without any additional power converter with battery) to the load thereby improving efficiency and reliability of operation.

  • An Accurate and robust MPC will be developed, which would serve as a design guideline for developing MPC for other similar power converters being used in industry.

TASKS:

  1. Investigation and comparison of proposed converter system with other high gain converters available in the existing literature

  2. Theoretical analysis of gain limiting factors in the proposed converter and potential solution to address these hindrances

  3. Development and implementation of MPC based modulation technique to achieve reliable and continuous operation of dc homes

  4. Hardware implementation of scaled – down prototype using wide – band gap devices (SiC) to verify the proposed concept

SITE/TEAM:

TAMUG Site: CARES Lab led by Dr. Irfan A. Khan

TAKEAWAY:

  • Battery embedded PV system to control power flow in dc grid with minimum hardware
  • Reliable and robust high – gain converter for filtering intermittency of PV sources
  • Potential solution for realization of charge controller in dc homes which would promote the concept of dc grids in residential and commercial buildings

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Development of a High Gain Converter Based on Fast Converging MPPT Technique for EV Application

MOTIVATION:

A lot of research activity is already going on in the area of solar PV Maximum Power Point Tracking (MPPT). However, MPPT algorithm for high-gain converters may not always converge to its global MPPT point. In this project, investigators are proposing a high gain dc-dc converter with fast converging MPPT algorithm. The high gain DC to DC cubic converter, employs a non-isolated high voltage gain boost converter structure. Advantages obtained are simple construction and operation with high voltage gain and high efficiency. Fast converging MPPT algorithm employs Electromagnetic Field Optimization (EFO) approach. EFO is a metaheuristic search-based nature-inspired method. Unlike, Particle Swarm Optimization (PSO) and other algorithms which depend heavily on the coefficients as parameters, EFO has no dominant effect of the coefficients in the search process. Only a random constant is given as input to the iterative equations to maintain the stochastic behavior of the algorithm. Moreover, the presence of random constant doesn’t affect the performance and thus careful tuning is not required in EFO. The proposed high-gain converter with MPPT algorithm will be tested for achieving optimum Battery Energy Storage System (BESS) and Electric Vehicle (EV) charging performance.

INDUSTRY BENEFIT:

  • Development of high-gain converter solution for battery embedded PV generation for EV application. This will eliminate need for additional converters used in conventional design.
  • Fast converging MPPT technique would result in higher PV power generation thereby decreasing payback period.
  • Due to fast converging MPPT, duration of circuit transients would be minimized thereby reducing the stress on active and passive components (including BESS and EV batteries). This would result in longer batteries’ life and lower maintenance cost.

TASKS:

  1. Mathematical modelling of proposed high-gain dc-dc cubic converter would be developed in SIMULINK environment.

  2. Fast convergence MPPT algorithm for the proposed converter would be developed and tested.

  3. Fast converging MPPT algorithm based high-gain converter will be tested for EV application.

  4. Scaled-down experimental prototype would be developed using wide-band gap devices (SiC) to verify the proposed concept.

SITE/TEAM:

TAMUG Site: CARES Lab led by Dr. Irfan A. Khan

TAKEAWAY:

  • Promotion and development of green charging solutions for Electric Vehicles
  • Novel MPPT technique to address dynamic energy storage and EV charging transients
  • Reliable and robust high – gain converter for filtering intermittency of BESS embedded PV sources for EV applications

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Modular Multilevel UPC For Power Quality Improvement in PV Dominant Microgrids

MOTIVATION:

Increasing penetration of PV sources and nonlinear loads brings forth a chain of Power Quality (PQ) problems at all levels of usage in the grid for which Unified Power Controller (UPC) has been accepted as a universal solution. Traditionally, the application of two-level Voltage Source Inverter (VSI-UPC) or Current Source Inverter (CSI-UPC) faces limitations of low voltage and power ratings, and additional cost due to higher number of switches. To resolve these issues, multilevel configurations including Neutral Point Clamped (NPC), Cascaded H- Bridge (CHB) and multi-cell converters are proposed. The NPC converter suffers from DC capacitor’s voltage-sharing problem, the CHB requires more elements, while the multi-cell converter presents poor reliability against short circuit. This project will focus on developing a novel Modular Multilevel Converter (MMC) for UPC. MMC has numerous advantages including lower harmonic content, modular design with distributed capacitance, desirable dynamic characteristics, filterless grid integration and lower losses. The proposed Modular Multi Level UPC (MM-UPC) is novel in a sense that it will require only nine switches of which three switches are common for shunt VSI and series VSI operation. In addition it offers modular design such that new modules can be added for additional voltage and power requirements.

INDUSTRY BENEFIT:

  • PV generation with less number of switching devices, minimum filtering requirement, improved power quality, improved efficiency and hence overall cost saving.

TASKS:

  1. To identify the critical PQ problems in PV generation and investigate the potential application of MM-UPC to mitigate these issues

  2. To model and design the proposed novel MM-UPC for PV dominant microgrid

  3. To develop control strategies for MM-UPC in order to address the power quality issues including voltage sag/swell, harmonics and reactive power compensation

  4. To develop and test scaled down prototype for the proposed MM-UPC converter under emulated grid conditions

SITE/TEAM:

TAMUG Site: CARES Lab led by Dr. Irfan A. Khan

TAKEAWAY:

The proposed MM-UPC will result in minimum hardware requirement thereby making system compact with improved efficiency and lower cost. Furthermore, the converter is modular in nature which adds reliability and scalability to meet additional power requirements.

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