The paper presents the study of a three-phase system coupling a DC power source to a power grid. This study, based on an FPGA, implements a real-time control system and digital models of the power circuit. The proposed proportional–resonant (P+R) controller with a modified structure was part of the system, which can be used as an alternative controller to traditional ones, e.g., in photovoltaic systems. Due to difficulties in implementing resonant controllers, a P+R with a new structure using a PI controller was elaborated. With an appropriate approach to the generation of phase current patterns, it is possible to set the reactive current and, thus, compensate for the reactive power. The operation of the system for typical operating conditions (e.g., system startup, change in preset load) was characterized and compared with a classical solution using a PI controller.

This paper presents a novel maximum power point tracking method for photovoltaic inverters with a single phase connection to the onboard 400Hz vehicle or aircraft grid, supplying drives operating in a critical mode. By taking into account that the power fluctuations cause voltage ripples at the termini of photovoltaic panels connected to the DC-link capacitor, this paper proposes a conductance base maximum power point tracking method. The impact of varying voltage has been reduced to ensure the constant reference current for the grid current calculation problem, which has been reported in previous studies. Accordingly, a conductance base tracking method, grid current control, is proposed and implemented to ensure the expected output current with respect to varying power. As described in this paper, the exemplified solar converter prototype can implement constant reference photovoltaic current control with a maximum power point achievement under continuous voltage rippling. Experimental results are given to verify the feasibility of the proposed MPPT method, which significantly improves the power efficiency for solar powered vehicles or aircraft.

Grid synchronization and power monitoring are the important problems when the power converters operate with the grid. The signals generated by the grid synchronization algorithm are used in the control system of a grid-connected converter. The signal proportional to the voltage amplitude and the information about phase-angle of the grid voltage allow control of the energy delivered to the grid. The paper describes the fuzzy logic grid synchronization technique used for single-phase systems and compares results with the other known techniques. The hardware setup using three types of synchronization techniques was elaborated and examined. Based on the Signal Tap II tool the pulling process of synchronizations, transient response when the input signal frequency changes and response time for different values of the initial phase angle were measured and analyzed.

The size reduction in on-board apparatuses in flying platforms, ships, and aerospace vehicles can be achieved by increasing the frequency of the on-board grid voltage. In the case of renewable powered platforms, a grid converter is used that has the primary task of feeding the generated energy into the on-board grid. The paper describes the developed control system of the grid converter, which, in addition to transferring the generated power to the single-phase grid, effectively compensates the reactive power occurring in it. The proposed structure of the proportional resonant regulator with finite gain that cooperates with the single-phase grid was discussed. The use of quadrature estimators of voltage and current enabled independent control of the active and reactive components of the current, thus compensating for the reactive power. The proposed control system structure was implemented on the FPGA platform and experimentally tested in steady state and dynamic condition considering grid disturbances and solar irradiance variations.

Solar power plant system represents the clean energy generation systems which convert and deliver the large amounts of solar radiation energy to the grid. The main purpose of the study is to maximize the amount of energy delivered to the grid from the solar photovoltaic cells. The solar irradiance and the grid voltage are the complex and dynamic system and need the universal solution which can provide more power at high dynamics of changes in external, various conditions. This work focuses on investigations provided in detail for the fuzzy logic-based synchronization technique which significantly increases the energy efficiency of the photovoltaic system. The multi-photovoltaic system’s controller concept was elaborated and evaluated using the programmable logic device, particularly useful for power critical drives. The dynamic responses of photovoltaic system were measured, which refers to the start procedure, solar irradiance, grid frequency and phase angle change. The results of the photovoltaic system investigation are made to appoint the efficiency in relation to the standard solution. The proposed fuzzy logic-based synchronization method delivers more energy to the grid in dynamic states in relation to the standard phase-locked loop method. The normal operation of the photovoltaic system is the dynamic operation. Therefore, the solution described in work allows to increase the efficiency of solar farms.