PSI Blog

Easy and Reliable Implementation of Redispatch 2.0

07 Apr 2021 - Energy, Artificial Intelligence, Technology, Sustainability

iStock/peterschreiber.media
iStock/peterschreiber.media

The new legal regulations for the extended redispatch process requires not only the transmission system operators (TSO) but also the distribution system operators (DSO) to participate in the elimination of congestions and to ensure system stability. PSI has developed a reliable tool for this purpose: PSIsaso/DSO enables distribution network operators to aggregate extensive forecasts and planning data as well as to forecast future network states easily and reliably.

The so-called dispatch allows a power plant operator to run his plants on the most profitable schedule. All operators are obliged to report this schedule to the respective TSO. While the original power plant schedule by the operator is referred to as dispatch, the corrections made by the TSO are called redispatch.

Redispatch means interventions in the power generation of power plant operators in order to prevent powerline overloads.

In case of possible congestions at specific points in the network, the TSO instructs the operators  associated with the congestion to reduce their infeed while other power plants must increase their infeed. This generates a power flow which counteracts the congestion.

Redispatch 2.0: What Will Change After October 1, 2021?

The Network Expansion Acceleration Act (NABEG 2.0) includes a number of new regulations and presents network operators with new challenges. Until now, only the transmission system operators were responsible for the lookahead redispatch based on scheduled values.

Now the distribution network operators are becoming main pillars of the redispatching process.

Just like the TSO, they will have to model and forecast the expected loads of their networks and include all systems  greater than 100 kW. This also includes renewable energy systems, CHP systems and systems that can be remotely controlled by the network operator at any time such as by smart meter gateway technology and storage.

Implement Redispatch 2.0 Processes Easily

With the right software, companies can easily implement the expanded redispatch process requirements. The focus is on the task of summarizing extensive forecasts and planning data and reliably predicting future network states.

In this regulatory environment, the modular software solution PSIsaso/DSO, which is independent of the control system, provides distribution network operators with the ability to react flexibly to legal requirements. It also enables quick and easy participation in the planning and forecasting processes.

The main modules GLDPM, network state forecast and the redispatch module are based on the PCOM+ and a PSIsaso basic module. Source: PSI
The main modules GLDPM, network state forecast and the redispatch module are based on the PCOM+ and a PSIsaso basic module. Source: PSI

The software solution consists of the PSIsaso basic module as shown in the figure above. It works hand in hand with the PCOM+ module. Building on this, module extensions can be added flexibly such as GLDPM, network state forecast or the redispatch module.

Each module provides specific functions and the relevant information based on the requirements.

We explain step by step how you can meet the requirements of Redispatch 2.0 with PSIsaso/DSO.

1. Secure Processing of Input Data

The independent module PCOM + is used to exchange and archive time series.
The independent module PCOM + is used to exchange and archive time series.

First of all, secure processing of the input data must be guaranteed. The independent module PCOM+ is used to exchange and archive time series. The expandable communication center works as a bidirectional communication interface to other systems. In combination with the PSIsaso basic module, it ensures the processing of the input data. This includes:

  • The snapshot network model from the control system
  • The infeed data
  • The forecast load data
  • The planned switching operations

It also includes the topological distribution of infeed and load data to subordinate areas, the cyclical processing of the time series and the calculations based on them.

For example, PCOM+ exports network models in CGMES format, forecasted infeed management (Eins-Man) measures, reactive power potentials and network loss forecasts. PSI's export and import functionality in CGMES format has been certified by the Association of European Transmission System Operators.

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The following profiles are generated in CGMES format:

  • Equipment profiles to describe static data
  • Steady state hypothesis profiles to describe dynamic data
  • Topology profiles to describe the current topological relationships
  • State variable profiles to describe the results of a load flow calculation

2. Data Exchange Between DSO and TSO

With the help of the GLDPM module, the predictive data from the DSO is made available to the TSO.
With the help of the GLDPM module, the predictive data from the DSO is made available to the TSO.

To provide the highest possible transparency when determining the transmission capacities, the GLDPM module is used to provide the lookahead data from the distribution network operators to the transmission network operators.

The GLDPM implementation guide summarizes the relevant data. These mainly represent network data models of the distribution network for future periods (intraday, day-ahead and 2-day-ahead) as well as the load forecasts of the consumers and the infeed forecasts of conventional power plants and renewable energies.

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GLDPM

In order to guarantee secure cross-border network operation, the European transmission system operators have to create and exchange models of their networks. The "Generation and Load Data Provision Methodology" (GLDPM) describes how the necessary network data are collected and transferred.

3. Calculation of the Future Network State

The network condition forecast module calculates the future network condition.
The network condition forecast module calculates the future network condition.

A proven network state forecast with an optimal selection and dimensioning of measures enables the effects in the network to be designed transparently and efficiently. An assessment of the requirements of the upstream network operator can be made on the basis of the network model from the control system and the network state forecasts. Any necessary measures to avoid congestions in the own or downstream network can be initiated.

The network state forecast module calculates the future network state for a period of typically three days into the future based on 15 or 60 minutes intervals. The calculation is based on:

  • The imported network model 
  • The infeed and load forecasts
  • Power plant schedules
  • Schedules of controllable loads
  • Renewable energy schedules
  • Planned switching operations

This is done in three steps:

  1. Checking the alarm limits: The contingency analysis checks whether the voltages and the flows in the base case and in the (n-1) case comply with the alarm limits.
  2. Adjust with infeed management: Topological measures are used to resolve faults in the own network. If the current violations persists after the interventions, the infeed management (EinsMan) controller is used to counteract these. Finally, the OPF (Optimal Power Flow) calculation adjusts the reactive power sources and the tap positions of the tap changers.
  3. Check by contingency analysis and short circuit calculation: After the adjustment, the improvements are verified by a subsequent contingency analysis. The check also includes the permitted short circuit power using a short circuit calculation (either Takahashi or IEC).

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As a result of the network condition forecast, the following data can be exported:

  • Network model in CGMES format including load flow results in own and external network
  • Forecast measures
  • Export of time series to a control system: reactive power potential, network loss forecast

4. Clustering for Controlling Resources

Data from several systems are used for the redispatch network status forecast.
Data from several systems are used for the redispatch network status forecast.

For Redispatch 2.0, PSIsaso establishes numerous connections with adjacent systems. For the redispatch network state forecast, data from upstream or downstream network operators, forecasting systems, and the control system are used.

After the calculation of the network state, the determination of the findings as well as the measures, demands, and cluster formation, the data and reports are exported to the neighboring network operators, the network control system, and to trading and billing systems.

The task of cluster formation is to group controllable resources by cost and effectiveness. The desired clustering must be coordinated with the upstream network operator. The measure dimensioning is designed to determine the most economical measures to eliminate the congestions.

PSI provides two alternative methods for this purpose:

  • In the first procedure, a linear optimization problem is solved based on the input data (cost of flex resources, flex potentials and constraints, congestion sensitivity, etc.).
  • In the merit order method, the congestions are resolved in the order in which they are most exceeded.

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Modular Design for Different Requirements

Distribution system operators are affected by Redispatch 2.0 in different ways. The extremes range from DSO with their own congestions and requirements caused by the upstream network operator to a minimal variant without congestions and requirements.

In order to be able to respond to the different circumstances, the Redispatch module has a modular structure.

Modules that are not required, such as measure dimensioning, demand control and balancing, can be deactivated and accounted for accordingly in the license model. The network state forecasts in a possibly simplified variant as well as the transfer of master and transaction data then play an essential role.

The entire process is to be understood as an iterative sequence within the framework of a coordination process for mutual coordination of measures between network operators. With the obligation of a DSO to maintain a redispatch balancing group, the balancing group management also becomes part of the coordination process.

Redispatch 2.0 - The process at a glance:

  1. Each calculation cycle of the redispatch module starts with input data processing.
  2. A specific network state calculation is performed for the configured time slices.
  3. The redispatch module persists the sensitivities for further processing in the measure dimensioning.
  4. The coordination process is based on continuous exchange of information between the network operators. The distribution system operator therefore sends the information for flex data objects such as flex potentials, base line and flex constraints to the upstream system operator.
  5. This means that the upstream network operator is aware of the DSO options and can include them in planning calculations. All changing data are periodically exchanged.
  6. The resulting binding demands on the upstream network operator are received by the DSO and included in its planning process.

Mastering Future Requirements Successfully

PSIsaso/DSO enables you to respond individually and flexibly to the different circumstances related to Redispatch 2.0. You are now optimally equipped for the new regulations. We have developed a future-proof solution to meet these requirements and to benefit you as a distribution network operator to meet the data exchange requirements.

Find more information here

Dr. Guido Remmers

Manager Division DSO

+49 6021 366-337
gremmers@psi.de