The paper considers the possibility of steam production and supply process improvement by perfection of the steam boiler control system, applying invariance principle that makes possible preemptive compensation of the influence of steam expenditure as a disturbance on the control process quality and efficiency. For the development of invariant control system, the mathematical modeling and simulation in MATLAB - SIMULINK environment is made. The control unit is low pressure steam boiler with one input impact to control - the heat flow of burning gas mixture fuel, one measured output parameter of the process - the steam pressure, and the main disturbance as a load impact - the steam expenditure. The mathematical and virtual models and block-diagrams for transient process simulation is compiled, allowing to start practical design and investigation of steam boiler invariant control system with high operation stability under essentially fluctuating load. The simulation results prove that the optimal solution for the transient process improvement in steam boiler, taking in account fluctuating load, is invariant PID-DPC two loop control system with disturbance impact on steam pressure preemptive compensation. Under invariant control the steam pressure overshoots decreases substantially in comparison with the traditional PID-feedback control method.

Efficient vertical axis wind turbine (VAWT) technology is a key topic for the future wind energy market. At the moment, VAWTs are seldom used for electricity production. The development of new technologies for building a new generation of VAWTs, which will be more efficient, user-friendly, and with very low noise pollution levels is the target for many researchers. The goal of this research was to analyse an active pitch control system in an experimental setting through construction of an active pitch control system test bench using a Permanent Magnet Synchronous Motor (PMSM) and to develop new testing programmes for analytical system performance tests. The  current commercial turbines do not carry an active pitch system for a VAWT; however, the concept of an active turbine blade pitching opens new opportunities for boosting the efficiency, safety, and user-friendliness of VAWTs. The  research consists of the  mathematical model and control system operating in a simulation environment in a closed loop with the test bench setup consisting of an active pitch control system. By applying a specially developed VAWT simulation model implemented in MATLAB Simulink, an active pitch system was tested and analysed under various conditions, which were as close as possible to the real-world operating conditions. The results of the testing and analysis show that an active pitch system using the PMSM can be very efficient and fast-operating. An active pitch system is able to work on the needed conditions by using the PMSM. Analysis shows that while using the PMSM for a turbine active pitch system, certain conditions should be taken into account in order to achieve the best results and to reduce costs. Full and effective use of active pitch system components can improve VAWT performance.