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SUKIČ, P., DREVENŠEK, D., BELIČ, E., ŠTUMBERGER, G.
EFFICIENCY OF INVERTERS IN SOLAR POWER PLANTS WITH REACTIVE POWER GENERATION
KOMUNALNA ENERGETIKA / POWER ENGINERING, 14
The paper discusses possibilities for reactive power generation using inverters for solar power plants. Measurements performed on an inverter for solar systems were performed for different values of generated active and reactive power in order to determine the efficiency characteristic. The obtained characteristic is approximated with a surface. It is applied to evaluate increase of inverter losses due to reactive power generation as well as to evaluate the potential of inverters in solar power plants for reactive power generation.
HERMAN, L., PAPIČ, I.
OPTIMAL REACTIVE POWER CONTROL IN INDUSTRIAL NETWORKS WITH DISTORTED VOLTAGES AND CURRENTS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 15
In modern industrial processes, the number of nonlinear loads, which are known to be a major source of current harmonics, is constantly growing. At the same time, the number of reactive power compensators operating in these networks is also growing. Although compensators are not sources of harmonic distortions, they may cause high amplifications of harmonics by creating resonance conditions. This can cause malfunctions or even loss of equipment. Due to the growing number of reactive power compensators in a typical industrial network, the control of these networks is also becoming increasingly demanding. An industrial network operator has a difficult task of finding an optimal configuration of compensators, which covers reactive power demands and at the same time does not cause resonance amplifications of harmonics. Thus, in this paper, a concept of a virtual compensator is proposed. It combines all reactive power devices of a certain network within a single control scheme. This gives the operator the ability to control each compensator independently in real time and to achieve optimal configuration of compensators, for every operation point of the network. The effectiveness of the proposed algorithm is demonstrated on the realistic industrial network model by means of simulation.
SUKIČ, P., ŠTUMBERGER, G.
GENERATION OF REACTIVE POWER WITH SOLAR POWER PLANTS AND EXAMPLES OF IMPROPER OPERATION OF SOLAR POWER
KOMUNALNA ENERGETIKA / POWER ENGINERING, 30
The article discusses the generation of reactive power with solar power plants. Discussed is the impact of reactive power generation on the efficiency of solar inverter. Throughout the year solar power plants operate with maximum power only in short time intervals. Therefore it is possible to generate large amounts of reactive power with solar power inverters, if needed. Due to improper operation of solar power plants, anomalies in the distribution network occur. This paper presents some of these anomalies.
BELIČ, E., DEŽAN, K., LUKAČ, N., ŠTUMBERGER, G.
EVALUATION OF ENERGY SAVINGS ACHIEVED WITH OPTIMUM PHOTOVOLTAIC SYSTEMS REACTIVE POWER GENERATION IN LOW VOLTAGE DISTRIBUTION NETWORK
KOMUNALNA ENERGETIKA / POWER ENGINERING, 32
This paper deals with the evaluation of energy savings that can be achieved in low voltage distribution network by photovoltaic systems (PVS) reactive power generation according to the network needs. Whole analysis is done on the model of real low voltage distribution network, where two 50 kWp PVS are installed. For evaluation of energy savings, time frame of one year is considered. Active powers of PVS are determined on the basis of average measured solar irradiance in half hour intervals and loads active powers on the basis of load profile. Since installed photovoltaic systems are relatively large, the analysis is also performed for smaller PVS with rated power of 5 kWp. The presented results shows, that energy savings can be achieved with existing PVS when they generate optimal reactive power. However, savings can be even improved if instead of big, smaller PVS are installed at sites where consumption is present.
BELIČ, E., VOH, J., SUKIČ, P., ŠTUMBERGER, G.
IMPACT OF PHOTOVOLTAIC SYSTEMS’ REACTIVE POWER GENERATION ON ACTIVE POWER GENERATION AND TRANSMISSION LOSSES IN
THE LOW VOLTAGE DISTRIBUTION NETWORK
KOMUNALNA ENERGETIKA / POWER ENGINERING, 33
This paper evaluates the impact of photovoltaic systems’ reactive power generation on active power generation and transmission losses in the low voltage distribution network. The introduced experimental system consists of two major parts. The photovoltaic system represents the first part, in which every photovoltaic module is connected to the low voltage network by the individual microinverter. Two way communication is established to each microinverter by the communication gateway. The second part consists of a control system with data acquisition system. The flexible experimental system offers a possibility to add and establish different network connections of the single-phase or three-phase smart grids. Within the scope of this work, additional cable was installed to establish one phase low voltage network with the photovoltaic system on one side and network on the other. The results of the analysis and measurements performed for operation of experimental low voltage network show that the reactive power generation in photovoltaic systems increases the amount of active power that can be generated in photovoltaic systems without to violate voltage profile. However, with both of these actions transmission losses in the low voltage network increase.
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