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In the near future a significant amount of the consumed electrical energy will be generated by distributed generation (DG). Because of the small size these units are normally connected to the local distribution grid. Connection of DG changes the operation of the distribution grid. In order to minimize the effect of DG during grid disturbances some...
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... Fig. 1 the transmission grid of the province of Zuid Holland in the Netherlands is depicted. The transmission grid consists of a 150 kV grid and is connected to the national 380 kV transmission grid at three locations. Large power plants are connected to the transmission grid. From the 150 kV nodes the sub-transmission grids are connected via ...
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... area where CHP-plants are connected to. An overview of the distribution grid is depicted in Fig. 2. The considered distribution grid consists of a 10 kV MV-grid which is connected to a 25 kV sub-transmission grid. The sub-transmission grid is via 150/25 kV transformers connected to substation 'Sub 23' of the 150 kV transmission grid shown in Fig. 1. At the 25 kV side all transformers are grounded via a resistor of 10 Ω . The 10 kV distribution grid is operated with an isolated neutral point and radial feeders where the CHP-plants are connected to. The data of the load and generation connected to the 10 kV distribution grid is given in table 1. ...
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Nowadays the amount of distributed generation (DG) units is increasing rapidly. Most dominant are combined heat and power (CHP) plants and wind turbines. At this moment, in most systems, there are no requirements defined for short-circuit behavior of such generators connected to the medium voltage grid. However in the future this situation will not...
Citations
... New grid codes oblige distributed power-generation systems to remain connected to the power network during the fault to avoid massive chain disconnections. The goal of the FRT requirements is to prevent the disconnection of an undesirable portion of power generation during an abnormal condition [14], [15]. ...
Installation of small generators in distribution networks has been increased recently due to its various benefits. One of the important issues related to these distributed generators is the effect of system faults on their transient stability. Due to the low inertia constant of the small-scale generators and the slow operation of the distribution networks' protective relays, transient instability is quite probable for these generators. In this paper, the dynamic behavior of small-scale synchronous generators to the system faults and its sensitivity to the system parameters are investigated. Then, a practical protective method using the existing overcurrent and undervoltage relays is proposed, and its advantages and disadvantages are pointed out. Next, based on the obtained information from sensitivity analysis, a novel protective relay is proposed to protect the generators against instability. The proposed relay uses a generator active power to determine the appropriate time to disconnect the generator. Simulation results confirm the secure operation and robustness of the proposed relay against system transients. In addition, the proposed algorithm complies with the generator fault-ride-through requirements.
... The DGs connected to the feeder should have the fault ride through capability (i.e. the ability to remain connected for a specific time period during a fault) to obtain faulted section isolation. One of the main goals of fault ride through capability is to prevent unnecessary disconnections of DGs during abnormal conditions [16]. Different control strategies have been proposed to improve the fault ride through capability of DGs [17,18]. ...
The disconnection of distributed generators (DGs) from a distribution network for every abnormal condition drastically reduces the DG benefits and system reliability when DG penetration level is high. The DGs can be used to supply the load demand in the absence of grid supply if DGs are allowed to operate in islanded mode. In this paper, protection issues associated with disconnection of DGs are addressed in the context of a radial distribution feeder. Protection strategies are proposed to allow islanded operation and to restore the system performing auto-reclosing maintaining as many DG connections as possible. An overcurrent relay based protection scheme is proposed for a converter based DG connected radial feeder to operate either in grid-connected or islanded mode maximizing the DG benefits to customers. Moreover, an effective method is proposed to restore the system with DGs using auto-reclosers. The proposals are verified through PSCAD simulation and MATLAB calculations.
... The modeled distribution network contains a large amount of combined heat and power (CHP)plants. In [2], the effect of different fault types occurring in the transmission system on the FRT behavior of the CHP-plants is discussed. In this paper, in the same distribution grid CHPplants have been replaced by Doubly Fed Induction Generator (DFIG) wind turbines, in order to make a comparison of these two types of DGs on the way that they react on short-circuits (S/C) from the perspective of ability to stay connected, voltage support and fault current contribution. ...
... Considering this strategy as a starting point, in case of deep voltage dips <0.6 p.u. all the DG are disconnected. As it has been proven in [2], it is possible here to keep CHPs connected for a prolonged period of up to 200 ms, depending on the voltage dip, without endangering their stability By adopting these alternative settings, practically all DG units will survive any S/C occurring in the HV grid and stay connected, as protection will clear the fault in time. Based on this, results of DG support during and after S/C are presented bellow. ...
Notwithstanding the positive environmental impact, the increasing penetration of Distributed Generation (DG) units connected to the distribution network raises new topics concerning the expected response of these during outages. Grid disturbances especially at the transmission level can cause the unwanted disconnection of large amounts of DG, leading to undesired power imbalances causing line overloadings and/or voltage and frequency instability. This paper examines how transmission network faults can affect the operation of DG units connected on to the distribution network, how these units currently contribute to the voltage support and what are the consequences of actual and possible Fault Ride-Through (FRT) behaviors.
... In the Netherlands, no criteria are imposed on DG below a rating of 5 MW, In case of CHP, manufacturers and operators chose for a pick up voltage 0.8 p.u. with a delay of 100 ms themselves. In [5] it has been shown that a time setting of the undervoltage protection up to 200 ms is not endangering the stability of the generators. With this time setting DG can survive all the S/C occurring in the high voltage grid, providing them the potential to be able to participate actively in the voltage support during and after the S/C. ...
... In the case of the CHP (blue line) due to the high S/C contribution of the synchronous generator the voltage is kept at much higher levels than in case of the DFIG. The application of extended time tripping ensures that units will stay connected after the clearance where due to the reactive power absorption [5], however, the CHPs delay the voltage recovery. ...
This paper presents an algorithm for optimum utilization of the grid connected Voltage Source Converter (VSC) for power quality improvement and the integration of Distributed Generation (DG) sources. Conventionally, VSC is used as an interfacing device for DG with grid, and a separate VSC is used for intensification of power quality issues. This paper suggests the use of the same VSC for DG integration and for power quality enhancement also. The targets of the application is to: (1) inject available active power from DG to power grid, (2) harmonic mitigation of load side grid current, (3) keep grid current three phase balanced in case of fault at the load side, (4) operate system safely in condition of frequency deviation. The proposed algorithm shows very fast and robust response which is due to its less complex circuitry. Furthermore, the use of phase-locked loop (PLL) is eliminated with increase in the speed of operation of the system. Simulation of the proposed work considering most of the power system operating conditions is done to present the effectiveness of the work.KeywordsDistributed generationHarmonicsPower qualityVoltage source converter
Nowadays with an increase in the demand for electric vehicles, we need to increase the charging stations to provide continuous power to the public for transportation. At the same time to decrease the pressure on the local grid we have to use alternative energy sources like solar and wind. Recently the entire world has seen the importance of renewable energy in charging stations which received great applause. In this paper, we review the different types of renewable energy-based charging stations. This paper covers research on critical aspects in this field, architecture, location, optimal designing and sizing. The research also incorporates studying power management and control of charging station and also investigates various challenges faced by charging stations and suggested proper solutions for those challenges. The main objective of the paper is to give an overview of charging stations with renewable energy for electric vehicles.KeywordsElectric vehicleCharging stationRenewable energySolarWindVehicle to grid
https://research.tue.nl/en/studentTheses/adaptive-voltage-control-strategy-for-power-distribution-networks
The increasing penetration of Distributed Generation (DG) units connected to the distribution network, driven mainly by environmental reasons, gives the opportunity to explore a more flexible operation mode of electricity grids. Grid disturbances especially at the transmission level can lead to power interruptions in extended areas. This paper examines the possibility of an area with a significant penetration level of Combined Heat and Power plants (CHP) connected in Medium Voltage (MV) grid to survive after a loss of the connection with the High Voltage (HV) grid due preplanned or unplanned events by investigating how this affects the operation of DG units, how these units manage to contribute to the voltage and frequency control during the switch to autonomous operation and how this affects the operational parameters (voltage and frequency) of the network.
