In the concept of distribution generators (DG) integration, distribution network becomes active and philosophy of network guidance and control changes. The presence of DG in the network often results in the active losses increase and thus the maintenance costs raise. This problem is offen noted in radial networks, as DG in this type of networks make network doubly fed. This paper gives an answer how to run one or more small hydropower plants (SHPP) in a radial network with minimal losses. In this paper, the analysis of power flows, combined with optimization methods and technical constraints (voltage constraints according to EN50160) are carried out. One example with detailed calculations, conclusions and diagrams comments is conducted. The conclusions in this paper directly indicate the possible measures to be implemented in order to achieve a higher SHPP and distribution network performance.

Power quality (PQ) is becoming important factor in proper functioning and operating of power systems (PS). Continuous PQ monitoring represents basics for efficient exploitation of power systems. Systems for continuous PQ monitoring and their networking with central system are major investments. This paper lists conditions for modeling of certain PS elements and describes concept of power network modeling in PQ analysis. First part of the paper gives mathematical formulation of the problem; second part describes high voltage transmission line in frequent domain using system of phase values, while the third part of the paper is an example in time domain modeled in EMTP-RV software package using system of phase values. Performance of power network in quasi-stationary state is analyzed and during the simulation five changes of voltage conditions occur as consequence of overloading. The PS is loaded with nonlinear loads generating high current and voltage harmonics. Voltage and current harmonic in the places of energy exchange are observed; furthermore estimation of voltage harmonics in the places with no PQ monitors is conducted. Conclusions of the paper indicate possible usage of presented algorithm for real time PQ analysis and for post PQ analysis.

This paper proposes a new closed-loop frequency based method for parametric identification of Hammerstein type plants with a transport delay. The method is a generalization of Ziegler Nichols' (ZN) experiment, with relay added in the control loop. It provides a simultaneous estimation of the parametric model of the plant dynamic, value of the time delay and a point by point relationship between input and output of the nonlinear part of the plant, which need not to be symmetrical. No extra equipment is needed, except the relay and a low pass filter.

This paper proposes a new closed loop frequency based method for a parametric identification of some types of Wiener-type nonlinear plants. It provides a parametric model of the linear part of the plant, and a point by point relationship between input and output of the nonlinear part of the plant. Two approaches are proposed for the identification of the nonlinear part. The first approach is slower, but it does not require any additional equipment expect the relay. The second approach is much faster, but it requires some additional equipment.

Application of new technology, the power electronics in the first place, has significantly improved the performance of individual consumers and increased their efficiency. The consequence of this is a presence of non-linear consumers in a network which are responsible for injection of higher harmonics and flickers into the network. A classification of consumers in the 0.4 kV network is presented in this paper. This classification is based on the measurements of the current waveform and the power of consumers. The measurements were realized using a measuring device for monitoring power quality. The measurements were made for a household that has appliances of new generation. It has been analyzed total and individual current of household appliances. In the first part of this work is presented relation between the new generation of household appliances and power quality (PQ). The second part of this paper is considering the problems of modeling a group of consumers with the purpose of analyzing the power quality. The measurements of a group of consumers, that were performed in laboratory conditions, provided us enough data for proposing a mathematical model.

This paper proposes a closed-loop frequency-based method for parametric identification of Wiener type plants with a transport delay in the linear part using a relay feedback. The method is a generalization of Ziegler Nichols' (ZN) experiment, with relay added in the control loop. It provides a simultaneous estimation of the linear plant dynamic, value of the time delay and approximate model of the input-output characteristic of the nonlinear part.