The effect of fault ride-through requirements on voltage dips and post-fault voltage recovery in a Dutch distribution network

In this paper the possibility to use Decentralized Generation (DG) units for voltage support in Distribution Networks during and after a Short Circuit (S/C) event is discussed. Two types of DG units will be examined, Combined Heat-Power (CHP) plants and Doubly-Fed Induction Generators (DFIG). Earlier approaches would oblige the disconnection of these units during grid disturbances, in order to avoid unwanted conditions such as interference with the protection system and islanding [1]. Newer grid codes for Transmission Networks like [2], taking into consideration the increased share of these units in energy production have set specific Fault Ride-Through (FRT) criteria which oblige them to stay connected during SC events when they are combined to large plants directly connected to the transmission grid, such as (off shore) wind farms.. If ever more DG is connected directly to distribution grids, the same reasoning leading to applying rault ride through criteria to DG connected in large groups to transmission grids, may be applied to DG connected to distribution grids, as a loss of a a large amount of DG connected to distribution grids has the same adverse effect as using DG connected directly to the transmission grid

Response of MV-connected Doubly-Fed Induction Generator wind turbines and CHP-plants to grid disturbances

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

Net (z)onder spanning

De betrouwbaarheid van de Nederlandse elektriciteitsnetten is zeer hoog. Kianten worden slechts zelden getroffen door een onderbreking van de voorziening. Naast onderbrekingen kunnen ook spannigsdips de energievoorziening verstoren. Hoewel ze minder ingrijpend zijn dan stroomuitval, kunnen deze dips wel degelijk schade aanrichten. Bedrijven met gevoelige apparatuur moeten daarom maatregelen nemen om dit te voorkomen

Possibilities for temporary autonomous operation of a MV grid with CHP-plants

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

Fault-ride through behavior of MV-connected wind turbines and CHP-plants during transmission grid disturbances

Apart from the positive technical consequences, the increasing penetration of Distributed Generation (DG) units connected to the distribution network brings new requirements in the protection strategy. Grid disturbances at the transmission level can cause the unwanted disconnection of large amount of DG, leading to undesired power imbalances. This paper examines how transmission network faults can affect the operation of DG units connected on to the distribution network, and how current under-voltage protection settings cope with these fault cases

The effect of advanced load shedding in the formation of islanded MV grids

The increasing penetration of Distributed Generation (DG) units connected to the distribution network, driven mainly by environmental reasons, gives the opportunity to consider islanded operation of electricity distribution grids. Grid disturbances at the transmission level can lead to power interruptions in extended areas. This paper examines the possibility to operate an area with a significant penetration level of Combined Heat and Power plants (CHP) connected to a Medium Voltage (MV) grid autonomously. In this way, a loss of the connection with the High Voltage (HV) grid due to planned or unplanned events could be survived instead of resulting in an outage. Previous work has shown that local power balance is an important factor affecting the successful formation of an MV island; therefore in this paper an overall approach, concerning also large imbalances is presented. For this purpose, the operation of DG units, how these units manage to contribute to the voltage and frequency control during the switch to autonomous operation, how advanced load techniques can help, and how this affects the operational parameters (voltage and frequency) of the network are investigated

Autonomous operation of a MV grid with high penetration of CHP

The increasing penetration of Distributed Generation (DG) units connected to the distribution network, driven mainly by environmental reasons, gives the opportunity to consider islanded operation of electricity distribution grids. Grid disturbances at the transmission level can lead to power interruptions in extended areas. This paper examines the possibility to operate an area with a significant penetration level of Combined Heat and Power plants (CHP) connected to a Medium Voltage (MV) grid autonomously. In this way, a loss of the connection with the High Voltage (HV) grid due preplanned or unplanned events could be survived instead of resulting in an outage. For this purpose 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 are investigated. Finally it investigates the possibility to reconnect to the HV grid when this has recovere

Overview of short-circuit contribution of various distributed generators on the distribution network

Apart from the positive technical consequences like reducing losses, the increasing penetration of distributed generation (DG) units connected to the distribution network, has lead to the increase of the short-circuit (sc) currents and the fault level. Therefore it is important to know the contribution of each unit. This paper presents the available analytical equations to calculate the short-circuit current, and makes a comparison between the IEC 60909 and the results obtained by the simulations in a test network that incorporates these unit

Stability support of autonomous networks with dispersed generation using rotary ride through systems

Dispersed generation (DG) could allow networks to operate autonomously. However, technical challenges need to be addressed to diminish transients in voltage and frequency. In this paper a commercial flywheel ride through system (FRT) is modeled using DigSILENT Power Factory and validated using experimental data. The model is tested with dispersed generation in a test network to simulate transients when disconnection of the grid occurs. The model is also simulated in two study cases: a remote autonomous network supplied by a wind farm and a section of the Dutch electricity grid called “Tiel Zuid” with high penetration of dispersed generation. The results indicate that a FRT can successfully be used to stabilize frequency within regulation limits and maintain stable conditions during disconnections. Additionally, the number of dispersed generation units and the voltage control deeply affect the performance of the RTs and the behavior of the grid

Response of MV-connected Doubly-Fed Induction Generator Wind Turbines and CHP plants to Grid Disturbances

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