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Delta compensated UPS can compensate ± 15% fluctuation of the grid voltage. In this condition, UPS supplies a stable sinusoidal voltage and maintains the input and out power balance by regulating the input current. The power balance is completed by cooperative work of the two converters, one converter operates in the rectifier state, and the other one operates in the inverter state, so that ensure...
This paper presents the power-quality measurement results of a photovoltaic (PV) system connected to the distribution system of Peng-Hu Power System, Taiwan. The studied PV system with capacity of 70.38 kW is connected to the distribution system of 380 V through thirteen DC/AC inverters that are located at the top floor of one of the buildings of National Peng-Hu University of Science and Technology,...
The behavior of wind farms with doubly fed induction generators (DFIGs) in fault ride through (FRT) conditions is investigated in the first part of this article. The requirements mandated by grid-codes to contribute to the voltage stability are introduced. Afterwards, the problems associated with applying the crowbar system in FRT conditions are discussed. In the next part, modeling of this problem...
This paper proposes a fast single-phase voltage sag detection for voltage sag compensation system. The operation of proposed method is based on synchronously rotating reference frame which provides fast and accurate voltage sag detection. a proposed fast single-phase voltage sag detection uses the differentiator as a (−90)-degree phase shifter to produce an orthogonal AC voltage (Vβ) from existing...
The presence of unbalanced voltage sag in grid actual operation gives rise to the output power fluctuation of PV inverter, the increasing of output current harmonics and unbalanced current. The calculation of the output current reference is a key technology in the control of PV inverter and has important influence on the output of the PV inverter under unbalanced grid voltage. Base on the instantaneous...
The low voltage ride-through (LVRT) grid-connected performance test of the controller of two-level photovoltaic grid-connected inverter is studied by RT-LAB hardware-in-the-loop (HIL) simulation technology, and a HIL modeling and testing scheme is presented for photovoltaic grid-connected inverter LVRT performance. First, a HIL LVRT test platform, which contains PV array model, voltage sag generator...
This paper investigates the impacts of distributed generator such as solar PV and energy storage on the utility grid. Initially experiment was conducted by increasing PV penetration into the grid and analysed the voltage fluctuation at PCC and harmonic emission on the network. Later, a software model was developed and same impacts were investigated with increased penetration of solar PV. The model...
A bidirectional interface converter is attractive for the flexible operation and control of a system consisting of a DC sub-grid and an AC sub-grid. Cascaded connection of a dual-active-bridge (DAB) with an inverter is an ideal topology for the bidirectional interface. However, due to the bidirectional power flow, and the potential different control bandwidth of the DAB and the inverter, the DC-link...
Faults in medium and high voltage grids lead to voltage sags in the low voltage level. Due to the voltage dip, distributed generators disconnect from the low voltage grid. Depending on the amount of disconnected generation, system stability could be compromised. With a dynamic grid support, distributed generators remain connected to the grid during faults, also called fault ride-through. Moreover,...
The fast developments in power electronic technology have made it possible to mitigate voltage disturbances in power system. Among the voltage disturbances challenging the industry, the voltage sags are considered the most important problem to the sensitive loads. Dynamic voltage restorer (DVR) is a series connected power electronic based device that can quickly mitigate the voltage sags in the system...
A Distribution Static Synchronous Compensator (DSTATCOM) is introducing here to compensate the voltage sag problem by injecting proper reactive current at the point of common coupling. In this paper, the performances and effectiveness of DSTATCOM to nullify the voltage sag are analyzed and a control algorithm based on PI and Hysteresis PWM current controller is developed to verify the results. A 6...
This paper presents a Z-Source inverter system and Double carrier control technique applied for Induction motor drive system. Z-Source Inverter system consists of a unique impedance structure of two capacitors and inductors connected in cross fashion, which cannot be observed in traditional inverter system. This special Z-Source network effectively utilizes shoot through state to boost the DC link...
Power quality is acquiring increased attention in the present power system environment. Increased use of sensitive and nonlinear loads in electrical power systems and the rapid growth of renewable energy sources are the major causes of poor power quality. The most regular power quality situations are voltage dip, voltage swell, harmonic contents and so on. Among these, voltage sag is considered as...
Series active power filter (SAPF) improves power quality as a key technology, which has been highly valued and widely used at present. NPC (neutral point clamped) three-level SAPF enables to compensate harmonic voltage in the field of high voltage, but traditional NPC three-level SAPF has a problem of neutral-point voltage excessive fluctuation which will cause switch devices damage. In order to solve...
Power quality in distribution grids is already a concern in many European Countries where there is a strong presence of renewable energy generation. There is therefore a growing interest in new technologies able to improve the power quality level, among them the Open Uninterruptible Power Quality Conditioner (Open UPQC). Despite several proposals have been analyzed in literature, there are still few...
Rapid changes in the output of photovoltaic (PV) generations may lead to serious voltage fluctuation in distribution systems. This paper proposes a controlling method of only PV plants those have had active power changes to suppress the fluctuation. Without a requirement of high speed data exchange between the PV plant and the utility control center for voltage regulation, the proposed method helps...
Due to massive increase in prices of fossil fuels as well as alarming rate of environmental pollution, researchers and scientists are paying good number of attentions towards sustainable energy and technology. Among various sources of renewable energy, fuel cell technology is becoming quite popular now a days. A comprehensive analysis of fuel cell generation and stability enhancement has been presented...
The impact of power quality disturbances on customer equipment has been a topic of interest to equipment manufacturers, electricity utilities, customers and to those involved in the development of electromagnetic compatibility standards. Recently, a new interest has developed in the possible impact of voltage fluctuations on customer equipment because of suggestions to relax voltage fluctuation limits...
With the growing number and capacity of photovoltaic installations connected to distribution networks, power quality issues related to voltage regulation, are becoming relevant problems for power distribution companies and for PV owners. In this context, the paper investigates on unintentional disconnection of photovoltaic plants connected to weak low voltage distribution network. Measurement results...
Adaptive linear neuron (ADALINE) is a powerful estimation technique that has been used in power system applications, such as fault detection and classification, and shunt active power filter (APF). In this paper, an ADALINE based approach for control of three-phase three-wire unified power quality conditioner (UPQC) is presented. Two ADALINEs are used in the UPQC control strategy, one for load current...
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