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In this paper the control scheme of a three-level three-phase inverter for grid integration of distributed generation (DG) units is investigated. Furthermore, the inverter compensates the reactive power of the load. The presented control scheme is based on instantaneous power theory in order to generate the appropriate inverter reference currents. In the outer DC bus voltage control loop and in the inner current control loop, the fuzzy logic (FL) control and the Proportional-Resonant (PR) control is applied respectively. The switching pattern generation is achieved using Space Vector Pulse Width Modulation technique. The steady state and dynamic response of the proposed electric power system has been evaluated under various operating conditions. Simulation results verify the effectiveness of the proposed control system.

In this paper a grid connected photovoltaic (PV) system is presented. The grid integration of the PV system is carried out via a three phase three level neutral point clamped (NPC) inverter. To control the inverter a modified version of voltage oriented control (VOC) method and the space vector pulse width modulation (SVPWM) technique have been applied. With the proposed modification the PV system operates as a shunt active power filter (SAPF), a reactive power compensator, and a load’s current balancer simultaneously. In this way the PV system operates more efficiently compared to the conventional PV systems and offers ancillary services to electric power system. The effectiveness of the proposed control scheme is established through simulation results with Matlab/Simulink in steady state and transient response of the electric power distribution system.

In this paper, a photovoltaic (PV) system, with maximum power point tracking (MPPT), connected to a three phase grid is presented. The connection of photovoltaic system on the grid takes place in one stage using voltage source inverter (VSI). For a better utilization of the photovoltaic system, the control strategy applied is based on p–q theory. According to this strategy during sunlight the system sends active power to the grid and at the same time compensates the reactive power of the load. In case there is no sunlight (during the night for instance), the inverter only compensates the reactive power of the load. In this paper the use of p–q theory to supply the grid with active power and compensate the reactive power of the load is investigated. The advantage of this control strategy is that the photovoltaic system is operated the whole day. Furthermore, the p–q theory uses simple algebraic calculations without demanding the use of PLL to synchronize the inverter with the grid.

In this paper, a photovoltaic (P/V) system, with maximum power point tracking (MPPT), connected to a three phase grid is presented. The connection of photovoltaic system on the grid takes place in one stage using voltage source inverter (VSI). For a better utilization of the photovoltaic system, the control strategy applied is based on p-q theory. According to this strategy during sunlight the system sends active power to the grid and at the same time compensates the reactive power of the load. In case there is no sunlight (during the night for instance), the inverter only compensates the reactive power of the load. The advantage of this strategy is the operation of the photovoltaic system the whole day. In this paper the p-q theory is proposed, which does not demand the use of PLL and introduces simple algebraic calculations.

This paper investigates the control scheme of a multilevel cascade single phase converter -consisted of two cell cascaded full-bridge converters-, where the modified p-q theory with ramp comparison has been applied for the proper single-phase interconnection of a 5 kW photovoltaic park with the grid. With the proposed method the converter is able to generate a five level ac-voltage, to utilize maximum power point tracking operation and achieve both active power control of the grid connected photovoltaic park system along with reactive power control for the correction of the reactive power of the load. The switching pattern of the topology -where IGBTs can be used as switches- is realized with the use of the ramp comparison method and two PI controllers. In addition, this pattern has been implemented taking into consideration the two-cell cascaded full-bridge multilevel converter of the topology. On the other hand, the PI controllers have been selected based on the requirements of the system, while the control strategy was built taking into account the maximum power point tracking. Finally, for the dimensioning of the converter suitable waveforms are presented - based on the derivation of appropriate mathematical equations.

This paper discusses a new control scheme of a three-phase grid-connected wind energy conversion system (WECS). The control uses maximum power point tracker (MPPT) for optimal use of the wind energy. The wind turbine generator (WTG) consists of a variable speed wind turbine and the MPPT is implemented via a dc-dc boost converter. A three-level voltage source inverter (VSI) is used as interface with the ac power grid. The switching pattern generation for the VSI is achieved using SVM. Mamdani's FLC is applied in DC bus voltage control and current control. Validation of models and control schemes is performed by using the MATLAB/Simulink.

This paper presents a shunt active filter which eliminates current harmonics and compensates the reactive power of the load. The majority of shunt active power filter control methods which have been presented require a complex and sophisticated mathematical model, especially for the tuning of the PI controllers. To simplify and improve the shunt active filter control system, fuzzy logic theory is applied. In this paper, by the way of controlling the capacitor voltage of the dc bus a fuzzy logic algorithm is implemented. One such algorithm is also implemented to control the output current of the inverter. The performance of the capacitor voltage fuzzy logic control system was investigated, and the improvement of the dynamic response of the fuzzy controller compared to the conventional PI controller became evident. For the reduction of the grid current THDi index, a fuzzy logic hysteresis current controller is investigated. In order to improve the performance of shunt active filter under non ideal grid voltages, a modified version of the p-q theory is proposed. The simulation results are presented and discussed showing the advantages of fuzzy logic theory in the dc bus voltage control and current control.

In this paper the connection in single stage single phase of a photovoltaic system (PV) to the electric power system is presented. A modified version of p-q theory is proposed in order to implement this strategy in a single phase inverter. To extract maximum power from the PV array an algorithm Maximum Power Point Tracking (MPPT) is used. For the switching pattern generation the hysteresis controller is used. The behavior of both the permanent and the transient state, which includes changing the radiation and the load is analyzed using a computer.

This paper investigates the operation of a Distributed Generation (DG) unit which is connected via a three-phase voltage-source inverter to the distribution grid. The current control method with Space Vector pulse width modulation (SVPWM) is examined and compared to other current control methods. The strategy, which has been developed to control the reactive power and have a better utilization of DG unit, uses the p-q theory to achieve uninterrupted compensation of the reactive power of the system. A PI controller is used to control the active power and regulate the voltage of the capacitor. Finally, the proposed electrical power system is simulated on the computer and the steady-state and dynamic response of the system is evaluated.

In this paper the problems created by non linear load as well as the solutions having been applied so far are briefly reviewed. A new simple and effective reference current generation method of a shunt active power filter (SAPF) is proposed. This method aims at eliminating harmonics from the mains currents. It also compensates the reactive power which is created from the linear and non linear loads. The new method is applied both in the case that mains voltages are ideal and in the case that mains voltages are non ideal. The new method is compared to the conventional p-q theory and the results are analyzed and commented on. From the analysis and the commentary the advantages of the new technique are concluded.

This paper initially refers to the devices used to compensate upper harmonics. Subsequently, it examines the principal methods for controlling an active filter which is connected to the electricity grid in order to compensate reactive power and to eliminate the electricity harmonics. The mathematic model following the p-q theory is analyzed for the creation of a reference current, aiming at the elimination of the upper harmonics and at reactive power compensation. An improved control method is presented regarding current control through the use of a Hysteresis Band with an altering tolerance band. In this way, current control is adjusted onto the load current.