A Anton Ishchenko

Overview of short-circuit contribution of various Distributed Generators on the distribution network

Apart from the positive technical consequences like reducing losses, the increasing penetration of distributed generation (DG) units connected to the distribution network, has lead to the increase of the short-circuit (sc) currents and the fault level. Therefore it is important to know the contribution of each unit. This paper presents the available analytical equations to calculate the short-circuit current, and makes a comparison between the IEC 60909 and the results obtained by the simulations in a test network that incorporates these units.

Transient Stability Analysis of Distribution Network with Dispersed Generation

In this paper transient stability of an existing 10 kV distribution network with combined heat and power plants, microturbinesand wind turbines is analyzed. In order to do this, dynamic models of the network and generators have been created and simulations for faults at different network locations have been done. From the analysis it appears that the most critical parameter, which influences transient stability in the test network, is the inertia of a microturbine. Simulations have shown that there is linear relationship between inertia constant of microturbine and critical clearing time. After that it has been checked that the protection of DG satisfies transient stability requirements. In the end, the possibility for providing DG support to the network during and after disturbances using fault ride-through concept has been considered and simulations illustrate that DG protection can guarantee transient stability in this case as well.

Protection, transient stability and fault ride-through issues in distribution networks with dispersed generation

This paper describes the transient stability analysis of a 10 kV distribution network with wind generators, microturbines and CHP plants. The network being modeled in Matlab/Simulink takes into account detailed dynamic models of the generators. Fault simulations at various locations are investigated. For the studied cases, the critical clearing times are calculated. Some network parameters which influence transient stability are also observed. The compliance of DG protection to stability criteria requirements is further studied. The ride-through capability of the DG units is also investigated through transient stability analysis and the equivalent CCT-voltage dip curves are derived. It is concluded that during fault DG unit availability can be increased through modification of undervoltage protection requirements.

Control aspects and the design of a small-scale test virtual power plant

Nowadays the amount of distributed generation (DG) is growing rapidly. This is valid both for units connected to MV grids as well as LV networks. Although now the share of LV-connected units is quite limited, this situation might change with the increase of number of installed micro CHP units in residential areas, further stimulus of solar power production and introduction of electric and fuel cell based cars. Management and control of such small and medium-scale inverter-interfaced generation can be optimised using the virtual power plant (VPP) principle. Various control aspects of VPP as an attribute of the interconnected power system are analyzed, and the design of a small-scale experimental setup is proposed.

Dynamic Equivalencing of Distribution Networks with Dispersed Generation Using Krylov Methods

Nowadays the number of dispersed generators (DG) is growing rapidly. This change will greatly influence the power system dynamics. A distribution network, where DG are connected to the grid, cannot be considered as passive anymore. So in future it will not be possible to use simple equivalents of distribution networks for power system dynamic modeling as it was done before. In dynamic studies the whole power system cannot be represented in a detailed manner because of huge system dimension. Therefore special techniques have to be applied for aggregation and order-reduction of distribution networks with DG. In this paper brief review of existing techniques has been given, and after that dynamic reduction using Krylov methods is performed for a distribution network consisting of DG of different types.

Control aspects of distribution networks with dispersed generation

The increase of dispersed generation (DG) has a strong impact on power system operation. A distribution network, where most of dispersed generators are connected, cannot be considered as passive anymore. Active character of the distribution networks brings problems and uncertainties, but at the same time offers more possibilities for control. Control of distribution networks with DG can be performed by means of primary controllers of dispersed generators, compensating devices and tap changers of transformers. Most of the control normally is using only local measurements. At the same time, it is obvious that the problems, which will arise with the increase of the DG in the future, must be solved by partially decentralized control (control, centralized inside defined area). In this paper, possible structure for such control is presented.

Modeling, Simulating and Validating Wind Turbine Behavior During Grid Disturbances

Due to the liberalized energy market distributed generation, DG, is increasing. At this moment, most of the power produced by DG, is generated by CHP-plants and variable speed wind turbines. Integration of wind turbines have impact on several aspects of power systems such as power system stability, protection and power quality. This paper focusses on the effect of wind farms on power quality phenomena during and after a grid disturbance. A dynamic model of a modern wind turbine will be presented in order to simulate grid disturbances. The results of the simulations are validated by measurements.