Madis Lehtla

Residential electricity consumption and loads pattern analysis

This article analyses household electricity consumption in Estonia. Energy consumption of workday and holiday by loads is discussed. The final part describes the evaluation of feasibility of common investments

Analysis of Household Electricity Consumption Patterns and Economy of Water Heating Shifting and Saving Bulbs

Analysis of Household Electricity Consumption Patterns and Economy of Water Heating Shifting and Saving Bulbs This article analyses household electricity consumption based on an object in Estonia. Energy consumption of workday and holiday by loads (including high and low tariff energy consumption) is discussed. The final part describes the evaluation of profitability of common investments of consumption shifting and replacing inefficient devices with more efficient ones. Additionally it describes shifting problems and shifting equipment profitability in real-time tariff system.

Survey of loss minimization methods in tram systems

This paper analyzes energy flows, conversions and losses in tram systems. Proposals for improvement of the efficiency of tram systems by the help of energy storage modules are described. In addition, such advanced methods of energy efficiency improvement as load sharing, real-time traffic management and Ecodriving are discussed.

Computer Models for Simulation and Control of a Traction Supply System

The paper discusses modelling and simulation of power circuits. Models were used to study energy exchange and develop a control system, in particular for vehicles with regenerative braking capability. SIMULINK models were used in control system design, including the selection of circuit components for feedbacks of switched mode converters. Models of the supply circuit were designed as independent blocks. These blocks can be used both, for AC induction motor drives and DC chopper drives. This structure can be used for the behavioural modelling of supply for switched-mode voltage-source traction converters.

Comparison of renewable electricity generation options with household electrical load patterns

This paper analyzes output time-series of different small scale power generation systems such as wind and photovoltaic (PV) systems and their combinations, according to the wind and global irradiance data measured in the Tallinn-Harku Aerological Station (Estonia) and household load patterns. Renewable energy resources and energy production are reviewed and household loads and their need for stored energy reserves to cover periods without power generation are analyzed.

Design of devices for advanced protection, voltage-quality and load priority control in residential microgrids

This paper describes design of protection and load-priority control devices for distributed generation. Possibilities of recent energy-metering integrated circuits are utilized in system diagnostics and protection. The experimental prototype is based on sensor modules and metering IC. Modules could be integrated with converters and distribution centres for voltage quality monitoring and equipment protection.

Design of renewable micro generation monitoring and control application

A multitude of flexible low-cost communication hardware with sufficient performance is available for control of microgeneration and loads in households, but proprietary software is often limited. Robust and simply maintainable solutions are often required in practical applications besides highly-multifunctional programmable logic controllers developed for large industries. Software should be flexible for adoption to control processes and environment. Open-source software is under development and requires more effort. Perspective practical approach to high-quality automation and telemetry, based on open-source software and ultralow component cost is described in this paper. Developed add-ons can be further used for control of micro generation units with power range from 0.5 to 20 kW, such as small-windmills, hydropower stations or different loads in households.

Slip control upgrades for light-rail electric traction drives

Many obsolete drives such as a rheostat, contactor or camshaft-contact controlled DC motor drives have often poor dynamic properties in insufficient adhesion conditions. Light-rail vehicles running in many cities already have switched-mode traction drives with thyristor-based or IGBT-based converters that often lack high quality slip, antilock or creep control. Switched-mode converter based multi-motor drives could be partially upgraded to microcontroller-based control. This paper presents and analyses some approaches to be used for performance, efficiency and safety improvement.

Modeling of demand side management scenarios in apartment buildings

Large apartment buildings dated from 1960 to 1992 compose 79% of Estonian residences. Since design and construction, load profile of these buildings has changed significantly: 30-50 years ago, peak loads were much lower than today and simultaneity factor values used for in-house electrical system design were different. Implementation of demand side management (DSM) and load aggregation results in additional changes in residential load profiles. Most loads are not stochastic any more, their simultaneity increases. At the same time, studies of possibilities and impacts of DSM implementation in a block of apartments where individual households are under direct mutual influence are limited. This paper describes a study in an Estonian 60-apartment building where total electricity consumption was measured, a bottom-up simulation model for the entire apartment block was developed and three different load aggregation scenarios were analyzed. Based on results, major technical barriers to DSM implementation are identified and measures to overcome them are proposed.