This paper presents the design of an innovative scalable wind turbine emulator. The system’s hardware and software components are described in detail including test results, demonstrating the research potential of the proposed design. The uniqueness of the proposed solution lies in its scalability, achieved despite the use of physical devices with fixed parameters. This scalability allows for the flexible shaping of the system’s structure and parameters, allowing it to emulate both individual wind turbines with a capacity ranging from kilowatts to megawatts as well as aggregated models of entire wind farms. The emulator was developed using the hardware-in-the loop (HIL) concept and consists of a digital part including aerodynamic and mechanical models (wind, rotor, shaft models, disturbances, etc.) and control systems for mechanical and electrical devices within the wind turbine. The digital component has a modular structure, which allows for the replacement of any module of the native control system with the user’s custom designed one and testing its properties over a broad range of parameters. The test results presented in the article demonstrate a satisfactory level of accuracy of the developed emulator.

The paper proposes a new local method of controlling the on-load tap changer (OLTC) of a transformer to mitigate negative voltage phenomena in low-voltage (LV) networks with a high penetration of photovoltaic (PV) installations. The essence of the method is the use of the load compensation (LC) function with settings determined via artificial neural network (ANN) algorithms. The proposed method was compared with other selected local methods recommended in European regulations, in particular with those currently required by Polish distribution system operators (DSOs). Comparative studies were performed using the model of the 116-bus IEEE test network, taking into account the unbalance in the network and the voltage variation on the medium voltage (MV) side.

Deterioration of voltage conditions is one of the frequent consequences of connecting an increasing number of photovoltaic sources to the low-voltage (LV) power grid. Under adverse conditions, i.e. low energy consumption and high insolation, microgeneration can cause voltage surges that violate acceptable limits. Research shows that the increase in voltage is the main limitation for connecting new energy microsources to the LV network and forces the reconstruction of the network. An alternative to costly modernizations can be the implementation of appropriate strategies for controlling network operation to maintain the voltage at the required level. The article presents an overview of the methods and concepts of voltage control in a low-voltage network developed so far to mitigate the undesirable phenomenon of voltage boosting. The focus was mainly on local methods—not requiring communication infrastructure—as best suited to the conditions of Polish distribution networks. Gathering the results of many tests and simulations carried out in different conditions and on different models allowed for the formulation of general conclusions and can be a starting point for further research on a control method that can be widely used in the national power system.

The article presents the results of analyses of the impact of prosumer photovoltaic sources on selected electrical parameters monitored in the LV network. A model of distributed control of the LV network is presented, taking into account the possibility of voltage regulation in the MVILV substation and in selected network nodes. In this model, particular attention is paid to the correlation between the dynamics of changes in the network and the time constraints contained in the control algorithm and in the communication process. The time criteria for the operation of individual blocks of the distributed control algorithm are presented.

In low-voltage power networks with a large share of distributed energy sources, the phenomenon of overvoltage is increasingly observed. Although it may be desirable to raise the voltage value downstream of the network, in some cases the upper allowable voltage limit is exceeded. The method of eliminating voltage rises commonly used in the Polish power system is the installation of overvoltage protections, disconnecting the source from the grid. Such action reduces the profitability of prosumer installations, discouraging future potential investors. It turns out, however, that this is not the only disadvantage of such a solution. Sudden and uncoordinated disconnections and reconnections of more energy sources cause abrupt voltage changes that negatively affect the voltage conditions in the network. The aim of the paper is to present the operating algorithms of a standard overvoltage relay used in inverters of photovoltaic microinstallations. These algorithms – described in standards and national regulations – were tested in a typical inverter used in public low-voltage networks and implemented in the created simulation model of the relay. The described tests will be used for further work to demonstrate the need to coordinate the operation of overvoltage protections or replace them with other measures to improve voltage conditions in the grid with high share of photovoltaic sources.