Eberhard Waffenschmidt

A new approach to transform an existing distribution network into a set of micro-grids for enhancing reliability and sustainability

Display Omitted This paper presents a new approach to cluster an existing distribution system into a set of MGs.Then DGs and reactive power resources are installed to meet the acceptable level of reliability in each MG area.Clustering procedure is based on weighted graph partitioning method.New indices are defined to assess the reliability of MG in terms of real and reactive power and loss, DGs installation and operation cost.A drastic multi-objective optimization algorithm based on interactive fuzzy method is used in this nonlinear complex problem. Optimal design of micro-grids (MGs) in distribution power systems is one of the major issues in planning stage for future distribution systems. In this way, clustering a conventional distribution system to construct MGs for special purposes may have numerous benefits for consumers and distribution system owners such as local control strategy to have less interaction between different MGs, local reactive power compensation to reduce power losses, preventing the fault propagation and finally improvement the reliability of system.This paper presents a new approach to cluster the existing distribution systems into a set of MGs. Also in this planning stage to meet the demands, installing DGs and reactive resources has been considered.Clustering procedure is based on weighted graph partitioning method and the weights are apparent power of the lines. New indices are defined to assess the reliability of micro-grids in terms of real and reactive power adequacy in addition to system losses, DGs installation and operation cost.Since this optimization problem has a nonlinear complex nature, classical mathematical methods cannot guarantee to achieve the global optimum solution. So, a multi-objective optimization algorithm based on interactive fuzzy method is proposed and used to solve the problem. The results on IEEE 34-bus distribution systems show the performance and effectiveness of the proposed method.

Proposal of a Figure of Merit for the Characterization of Soft-Magnetic Shielding Material Used in Inductive Wireless Power Transmission Systems

In inductive wireless power transmission systems, often soft-magnetic shielding is used to avoid lossy eddy currents being induced in electrically conducting components like batteries or ground layers of electronic circuits. Datasheet information on such shielding materials are often limited to magnetic permeability and sometimes exemplary loss information. For designing inductive wireless power systems, e.g., at variable frequency, detailed loss information are of interest. Therefore, it is proposed to measure the impact of these materials on the power transmission in a standardized setup, which is closely related to the real application. This consists of two coils, a transmitting and a receiving coil. Here, a configuration as described in the Qi standard for wireless charging of mobile devices published by the wireless power consortium is used as reference. A figure of merit, i.e., the product of the coupling factor k and the geometric average of the coils quality factors Q, is proposed to qualify materials concerning both: shielding against conducting components on the backside of the receiving coil; and establishing a high mutual inductance of the transformer coils, resulting in higher system efficiencies. Furthermore, considerations on the measurement setup as well as qualifications of shielding materials are presented.

Power Flow Analysis and Critical Design Issues of Retrofit Light-Emitting Diode (LED) Light Bulb

For retrofit applications, some high-brightness light-emitting diode (LED) products have the same form factor restrictions as existing incandescent light bulbs. Such form factor constraints may restrict the design and optimal performance of the LED technology. In this paper, some critical design issues for commercial LED bulbs designed for replacing E27 incandescent lamps are quantitatively analyzed. The analysis involves power audits on such densely packed LED systems so that the amounts of power consumption in: 1) the LED wafer; 2) the phosphor coating; and 3) the lamp translucent cover are quantified. The outcomes of such audits enable R&D engineers to identify the critical areas that need further improvements in a compact LED bulb design. The strong dependence of the luminous output of the compact LED bulb on ambient temperature is also highlighted.

Interactive Robust Model for Energy Service Providers Integrating Demand Response Programs in Wholesale Markets

Demand response (DR) has become a key player in energy efficiency programs of current electric power systems. This paper presents an effective decision-making model for energy service providers with a focus on day-ahead electricity market participation and demand allocation in the distribution network. A two-step iterative framework is proposed to consider the mutual effects of the DR and market prices, in which unit commitment and economic dispatch problems are solved in the first step to determine the locational marginal prices, and successively DR program is applied in the second step to minimize the total cost of providing energy for distribution network customers. This total cost includes the cost of power purchase from the market and distributed generation units, incentive cost paid to customers, and compensation cost of power interruptions. To consider the unexpected behaviors of other market participants, prices are modeled as uncertainty parameters using the robust optimization technique. Simulation results demonstrate the significant benefits of the proposed framework for the strategic performance of energy service providers.

Model predictive control of distributed generation micro-grids in island and grid connected operation under balanced and unbalanced conditions

Model Predictive Control (MPC) uses the model of system at current time to predict the system behavior at the future sampling interval in the prediction horizon and sets a number of variables to their references due to their controllability from input variables. This paper concentrates on the design and analysis of a controller for Distributed Generation (DG) microgrids in islanding and grid connected operation modes using a Receding Horizon MPC scheme. In this contribution, active and reactive powers are used in a cost function as an inner control loop to produce switching states. Two outer voltage and frequency droop loops share active and reactive powers between DGs in the microgrid. The design concept of the proposed control system is evaluated through simulation studies and experiment under different test scenarios. The impact of the simulation and the experimental results shows that the operations of the DG units within the microgrid can be coordinated effectively under the proposed control system t...

Primary control with batteries

In the near future renewable energy decentralized generators must provide grid control. Storages are attractive for grid control and especially for primary reserve power. However, providing primary control power with batteries is limited by the capacity of the battery. Losses and imprecise frequency measurements may soon lead to a depleted or full storage. It is possible to reduce this issue by making use of several parameters of freedom. Especially attractive is the compensation of a systematic frequency measurement error by applying a running average correction signal.

A tool for the simulation of large PV-diesel-systems with different dispatch strategies

Hybrid energy systems have the potential to bring modern energy services to the 17% of the global population with no access to electricity. The use of diesel generators to provide power for such applications has been the standard for several decades, but due to decreasing prices of photovoltaics, hybrid systems are becoming more common. As a special challenge expanding existing diesel generators with photovoltaics leads to increased dynamic specification and non-favored operation states for the diesel engine. While it is common to limit the photovoltaics or to add a battery storage to reduce non-favorite operation states, this paper presents load shifting and control as a solution for dispatch. 25 different households are simulated including in total 108 different devices and in total 1737 individual electrical consumers. The devices are operated based on ratings of the users to improve the overall subjective satisfaction with the control.

Cellular Power Grids for a 100 % Renewable Energy Supply

The decentralized generation and storage offers new opportunities for a reliable structure of the electrical power grid. It is proposed to subdivide the power grid into much smaller cells than in a traditional power grid. Since all of these cells contain distributed generators, they could be able to operate on their own, if necessary. In case of a global black-out, the individual cells could be able to survive. The paper discusses the size of such cells. In the next part, technical issues are discussed. In each cell the balance of power generation and demand must be maintained. Furthermore, a suitable grid control like virtual inertia must be applied to all related inverters. This requires an intelligent control not only of the generators but also of the selected loads, which need to be reduced or shut down in case of lack of energy. Solving these issues for an individual cell leads to a bottom-up approach to operate a complete global power grid with fluctuating, decentralized renewable energies.

Qualification of soft-magnetic shielding materials used in inductive wireless power transmission systems

In inductive wireless power transmission systems often soft-magnetic shielding is used to avoid lossy eddy currents being induced in electrically conducting components like batteries or ground layers of electronic circuits. Datasheet information on such shielding materials are often limited to magnetic permeability and sometimes exemplary loss information. For designing inductive wireless power systems e.g. at variable frequency or different flux excitation, detailed loss information are of interest. Therefore, it is proposed to measure the impact of these materials on the power transmission in a standardized setup, which is closely related to the real application. Here, a configuration as described in the Qi standard for wireless charging of mobile devices published by the Wireless Power Consortium is used as reference. A Figure of Merit (FoM) is presented to qualify materials concerning both a) shielding against conducting components on the backside of the receiving coil and b) establishing a high mutual inductance of the transformer coils, resulting in higher system efficiencies. Furthermore, this paper derives that material saturation is not given in properly designed 5W applications using single material sheets of 20μm thickness.