Tutorial 1

Empower A Billion Lives - Understanding Principles of Energy Access

Deepak Divan, Professor, Georgia Institute of Technology
Szilard Liptak, Engineer, Georgia Institute of Technology

IEEE Empower a Billion Lives (EBL) is a biennial global competition that is sponsored by the IEEE Power Electronics Society and is focused on harnessing global innovation and creativity along common metrics to create a pipeline of solutions for energy access for the billions of people living in extreme energy poverty. EBL seeks to create solutions that are regionally relevant, scalable and technically as well as economically viable. This tutorial will familiarize attendees with the basic issues around energy access, as well as a review of technologies, solutions and challenges faced in this area. The tutorial will also cover specifics related to the EBL competition, including competition process and timeline, judging process, field test requirements, and specific metrics that will be used in judging the competition. Attendees will also be able to participate in a ‘mash-up', meeting other like-minded individuals, and to form stronger teams with the breadth and skill sets required for the EBL competition.

Tutorial 2a

Control for Grid-Friendly Power Converter Systems

Yongheng Yang, Associate Professor, Aalborg University
Yi Tang, Assistant Professor, Nanyang Technological University

With an increasing installation of renewable energy systems into the power grid, more and more fluctuating power is being processed through power electronic converters and, more importantly, injected into the grid. Challenges like overvoltage and frequency variation are witnessed in practical cases, e.g., in German photovoltaic (PV) power systems. Hence, grid-connection requirements for power electronics-based power systems have also been revolutionizing, where the power converter systems are not just an energy generation unit, but becoming more active in the grid regulations. This is referred to as "Grid-Friendly Power Converter Systems." For instance, to alleviate potential frequency variations, grid-connected PV systems should be able to control its power ramp-rate and reserve certain amount of active power during operation (Delta Power Control) to contribute to the frequency regulation. Moreover, by reducing the active power production, overvoltage can be avoided during peak power production periods in sunny days. In addition, with the development of smart- and micro-grids, PV systems have been integrated more and more with energy storages, where maximizing the energy production and also coordinating the energy flow are in focus. Also, in recent years, grid-connected power electronics-based systems are controlled to mimic the behavior of conventional synchronous generators to provide inertial control (i.e., virtual inertial control). Hence, this tutorial is intended to address the emerging challenges in the control for grid-friendly power converter systems in terms of flexible active power regulation and virtual inertial control. 

Tutorial 2b

Discrete Controller Design and Validation for Grid Connected Smart Inverters

Humberto Pinheiro, Professor, Federal University of Santa Maria

In this practically oriented workshop we will walk through the design, testing, and validation of discrete time current controllers and different synchronization methods for grid-tied smart inverters. As an example, a complete controller for 700kVA grid connected three-level neutral point clamped (3L-NPC) inverter with an LCL filter will be designed and implemented.

We will demonstrate design, testing, and performance validation of a complete digital controller. First, we will detail the overall controller architecture and develop discrete time average model of the inverter. Subsequently we will discuss different current controller architectures, yet focus on the resonant controller design and how to design optimal parameters. In addition, we will review main PLL grid synchronization algorithms and detail design and tuning of one. We will focus on practical issues for digital implementation and complete controller will be demonstrated in Texas Instruments DSP-TMS320F28335 directly interfaced with ultra-high fidelity real-time simulation. The impact of the different controllers and synchronization parameters, on the overall performance of the systems, is demonstrated with the controller Hardware in the Loop (HIL). We will introduce the HIL based methodology to test and validate the performance and robustness of the inverter controller in realistic grid tie settings (i.e. weak and strong grid conditions) and we will introduce some of the key grid support requirements for the UL1741 SA and Rule 21.

Tutorial 3a

Real-Time Power Electronic Models for Grid-connected Solar PV and Microgrids in PLECS RT Box

Vitalik Ablaev, Engineer, Plexim, Inc.

In this tutorial, we will first explore an example design life cycle for a grid-connected solar system application, and then show a microgrid model with fault scenarios. The workflow consists of using PLECS for model development in conjunction with the RT Box for verification of a real controller. We will demonstrate the generation of discretized code for the PV inverter model and show how the fidelity of the model can first be verified by means of running the generated code within PLECS. Once the discretization step size is tuned to satisfaction, the real-time code will be deployed onto the PLECS RT Box. Waveforms demonstrating the proper operation of the control algorithms executing on a TI LaunchPad will be shown both on a real oscilloscope as well as on the new PLECS soft-scope. 

Tutorial 3b

Non-Communication Coordinative Control of Distributed Energy Source Converters

Jinjun Liu, Distinguished Professor of Power Electronics, Xi'an Jiatong University

The primary objective of the coordinative control for distributed energy source converters in a power system under standalone operation is to ensure the system voltage to be within a nominal magnitude/frequency range while at the same time with adequate output power sharing among all these energy sources. Although this can be realized with the help of wire or wireless communications among source converters, it is still very often required to implement the coordinative control without any communication means so that higher reliability and easy-to-implement plug-and-play could be achieved. There are two types of non-communication coordinative control, i.e. master-slave control and droop control. The focus of this tutorial will be the droop control, which is more widely used. The basic operation principles of droop control will be introduced with DC bus power systems, with detailed illustration based on the simplest system structure of 2 paralleled source converters and one common load. These principles will then be extended to AC bus power systems, where droop control has to be implemented in two channels: the active power channel and the reactive power channel. Several major technical issues that need to be dealt with in droop control will then be identified and some of them will be discussed extensively, including the coupling between the two channels for AC bus system, the compromise between output power sharing and bus voltage regulation, and the output power sharing for nonlinear or 3-phase unbalanced load. The most recent researches carried out at Xi'an Jiaotong University to handle these issues will be introduced in detail with the major existing methods and techniques to be summarized for comparison. Finally a thorough comparison between Virtual Synchronous Generator control, which is also a quite hot topic nowadays, and droop control will be supplied. 

Tutorial 4a

Time Domain Evaluation of Power Quality for Grid-Tied Inverters

Alexander Ruderman, Associate Professor, Nazarbayev University

The Tutorial addresses voltage and current Total Harmonic Distortion (THD) calculation for grid-tied inverters with both high frequency PWM and low frequency synchronous switching. On theoretical side, THD is historically being analysed in frequency domain probably due to its frequency domain definition. The author systematically develops voltage and current THD time domain evaluation approach. Such analysis is based on Parseval theorem (Rayleigh energy equality) and requires calculation of voltage and current waveform mean squares. For PWM, it originates from the 1988 paper by Prof. H.W. van der Broeck; for synchronous optimal low frequency modulation, it was first independently suggested in 1977 papers by Profs. S. Halasz and G. Buja. For PWM inverters, the analysis uses a realistic asymptotic assumption - large apparent switching-to-fundamental frequencies ratio. For voltage THD, simple closed-form formulas are obtained for single- and three-phase multilevel inverters; for current THD - for single-phase multilevel voltage source inverters with inductance dominated RL-load and in the presence of LCL-filter and for current source inverters with CL-filters. For low frequency synchronous modulation, minimal THD problems are formulated in time domain as constrained optimization ones. The natural generalisations include: combined minimal THD and Selected Harmonic Elimination (SHE) problem formulation that some degrees of freedom are spent on SHE while the rest - on THD minimization; Selected Harmonic Mitigation to meet international standards (TDD) with a minimum coupling inductor. 

Tutorial 4b

Optimization Techniques for Solar Power Plants

Martin Ordonex, Associate Professor, University of British Columbia
Francisco Paz, PhD Candidate, University of British Columbia

Solar power installations are extremely sensitive to the cost of the installation, the expected payback ime, and the availability of energy generation over time. Many factors must be weighed in the design of a PV system (e.g., panels, arrays, inverters), but traditional design rules are too simplistic and do not make use of critical information. Often, oversized components are used that do not produce any advantages for the PV system. An alternative to the traditional approach is to optimize the different components of the system to obtain an overall system that minimizes installation cost, payback time, or other user defined targets. In this tutorial, models, methods, and techniques will be presented to optimize the performance of the PV systems. Three aspects of the design process will be addressed: 1) PV plant size optimization, based on detailed models; 2) PV inverter stage optimization, based on power envelope and mini-boost stages; and 3) maximum power point tracking strategies. The discussion of each of these topics will focus on design considerations and on the trade-offs between different factors that lead to optimal solutions. The topics are discussed in relation to industry standard practices, and this is followed by the introduction of advanced techniques that yield better performance.