Christian Ohler

Optimizing a Battery Energy Storage System for Primary Frequency Control

This paper presents a method for the dimensioning of a battery energy storage system (BESS) to provide a primary frequency reserve. Numerical simulations based on historic frequency measurements are used to determine the minimum possible capacity, i.e., the lowest possible cost, which fulfills the technical requirements of the grid code. We implement a novel control algorithm with adjustable state of charge limits and the application of emergency resistors. At current European market prices, an optimized lead-acid BESS can be a profitable utility solution for the primary frequency control.

Optimizing energy storage devices using Ragone plots

Abstract This paper describes how to optimize energy storage devices (ESDs) by maximizing their net present value (NPV). This requires both technical and economic information. The relevant technical information is specified in concise form by the energy–power relation (Ragone-plot) of the ESD and its lifetime. The economic information is given in terms of operation costs (energy costs), investment costs, and the economic benefit created by operating the ESD. The NPV is expressed as a function of variables such as the size of the ESD. An appropriate choice of these variables maximizes the NPV. If the benefit is given in terms of the energy supplied by the ESD and the lifetime is operation independent, the optimization reduces to a minimization of the total lifecycle costs. In this case a knowledge of the economic benefit, which is often the quantity that is most difficult to model, is not required. In more general cases, e.g. if the lifetime depends on optimization variables, a quantification of the benefit is necessary in order to maximize the NPV. We illustrate the approach with various stationary and mobile applications, and for batteries and capacitors.

Novel measurement methods for in-depth analysis of AC metallized film capacitors

Metallized film capacitors with self-healing properties become increasingly relevant for high voltage power applications due to their high capacitance density, high power density, and inherent safety. However, because of a lack of generic design rules, introduction of new capacitor designs requires time-consuming aging tests. We present a novel toolkit of measurement methods with the purpose of gaining a deeper knowledge on aging mechanisms and decreasing the development time for new capacitor designs.