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The neutral-point voltage balancing problem is a key issue for three-level three-leg neutral-point clamped (NPC) inverter used in three-phase four-wire system. In this paper, a detailed discussion on this issue and a mathematical model for the neutral-point voltage fluctuation are given. Then a novel neutral-point voltage control strategy based on the disassembly of zero level is proposed. To balance...
In this paper, a new configuration of a multi-functional grid-connected inverter is proposed to improve both voltage-based and current-based power quality issue. By implementing bidirectional switches using semiconductor devices, a multi-functional grid-connected inverter can be connected in series or parallel to the grid and provides three modes of operation. This paper presents the control scheme...
Voltage dips or sag creates useless conflict at the customer side as well as utility side. In this paper, dynamic voltage restorer device based on voltage source converter (VSC) topology is used to compensate voltage sag. Dynamic Voltage Restorer (DVR) is a power electronic device that is utilized to improve voltage stability i.e. to reduce the power quality problems in electrical power system network...
Modernized grid needs ancillary service as a variety of distributed energy resources are connected. Vehicle-to-grid (V2G) application is one of promising distributed energy resources, which enables to transfer bidirectional power between batteries of plug-in electric vehicle and the grid as well as offer ancillary service to the grid. Benefits of V2G application are voltage and frequency regulation,...
This paper investigates the transient voltage sags/swells subsequent to islanding of a PV-Battery microgrid. For an unplanned islanding and micro-grid formation, during islanding detection time, the microgrid is disconnected from main grid while the control mode of the BESS stays the same as before. Consequently the microgrid will undergo transient voltage sag or swell caused by the mismatch of the...
Renewable power generation such as rooftop solar PV is resulting in high number of installation due to incentives as drop in prices and environmental awareness. The uncertainty of solar irradiance and cell temperature cause its output power to be varied. Considering high penetration of rooftop solar cell and also load profile in LV distribution system will lead to much more voltage fluctuations. Then,...
Solar Photovoltaic (PV) inverters are used to feed power to the grid. These PV inverters are equipped with anti islanding protection technique. As the PV penetration in the grid increases, this feature would affect the operation and reliability of grid during fault conditions. Thus, Low Voltage Ride Through (LVRT) capability is suggested for PV inverters connected to High Voltage (HV) and Medium Voltage...
Protection of Distributed Generation (DG) injected Distribution network (DN) is a challenging task in entire electrical ancestors. The connection of DG to the distribution network alters the nature of the network. Expose of DG can alter the fault current during the grid disturbance or external fault and perturb the existing distribution protection system, one of them in the event of a fault where...
Energy storage technologies are increasing their presence in the market and integration of these technologies into the power grid is slowly becoming a reality. An interline dynamic voltage restorer has used to provide sag and swell the compensation and improvement of displacement power factor during normal condition. The concept of integrating ultra-capacitor based energy storage into an interline...
Power Quality (PQ) is the most significant perspectives at transmission and distribution levels. The supply of high grade electrical services required to the customers illustrates this concept. The voltage sag and swell are the most frequent PQ problems that mainly occur in the distribution systems since it may cause equipment tripping, failure of drive systems, shutdown for domestic and industrial...
The Inrush Transient Current (ITC) in the output of the photovoltaic grid-connected inverters is usually generated when grid voltage sag occurs, which can trigger the protection of the grid-connected inverters, and even destroy the semiconductor switches. Then, the grid-connected inverters will thus fail to ride through the voltage sag and even further cause more serious grid faults. This paper analyzes...
This paper presents a new PAC-SRF based approach for UPQC to be used in single phase distribution systems. A necessary phase angle shift of load voltage is introduced with respect to the source voltage using the power angle control concept in order to integrate a reactive power sharing feature for series inverter part of UPQC. Synchronous reference frame (SRF) based controller is adapted for both...
Since the photovoltaic systems development is growing exponentially, the policies related to grid integration will also have to change so that more and more PV systems can be accommodated in the grid. This paper discusses existing Central Electricity Authority (CEA) technical interconnection regulations. As PV penetration increases the CEA can reevaluate the existing operating range for voltage and...
The work presented in this paper describes an improvement of a photovoltaic grid connected system based on P-V optimal slope MPPT technique. This system has a LVRT capability with reactive power injection. To achieve this improvement, no new component is added. Only the flexibility of the used MPPT technique is exploited to establish a control law which gives the system a suitable behavior when voltage...
On account of its stochastic generation, system voltage fluctuation is one of the impediments to further increase the penetration level of the grid-connected photovoltaic system. However, the reactive power capacity of the photovoltaic inverter can be controlled to regulate the grid voltage. In this paper, the outer current control loop, which is designed in the dq synchronous reference frame, is...
This article discussed a multilevel transistor clamped H-bridge topology for DVR application along with repetitive controller. This five level TCHB inverter topology can be used for low and medium voltage level application of DVR. The repetitive controller used in this paper for DVR application can compensate the three major voltage quality disturbances such as balanced voltage sag, voltage harmonics...
Fault ride through (FRT) capability is one of the challenges faced in the medium to high voltage large-scale grid-tied photovoltaic power plants (PVPPs). Besides that, due to the high penetration of installed distributed generation (DG) units, the grid voltage enhancement under unbalanced faults is a requirement of several standards and grid codes. The controller of the grid-connected inverter consists...
Flexible active and reactive power injection to the grid is one of the requirements of medium-scale PV power plants (PVPP). Due to the high penetration of installed distributed generation (DG) units to the power system, the flexible active/reactive power control capability is necessary for medium-scale PVPPs in order to maintain the power quality and reliability of the power system. A three-dimensional...
The interest for installation of solar Photovoltaic (PV) systems in the distribution network has been increasing due to their declining cost and high electricity price from the utilities. On the downside, the PV power generation is sensitive to the variation in solar irradiation, which can cause potential challenges in the low voltage network in terms of voltage quality and management. In this research,...
Electrical disturbance generators are basically controlled voltage sources that can be used to emulate various electrical disturbances; they are used mainly for the purpose of investigating the behavior of electrical equipment under power related faults. This paper presents a novel topology for an electrical disturbances generator that uses a back to back voltage source inverter controlled by a repetitive...
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