WP4: Grid Components


Innovation Challenges

The evolution of the electrical grid infrastructure imposes completely new constraints to the transmission and distribution network that can be only fulfilled by developing new efficient, cost-effective and environmental friendly grid components. A strong requirement for the new components is to have less environmental impact during production, operation and disposal (“green technology components”).
The main research challenges of the WP4 is the development of new concepts and technologies for future grid components capable to fulfil the needs and conflicting constraints of the future power systems. They are thus related to the improvement of switching components for Very Fast Transients (VFTs) in power systems applications with particular reference to materials used to achieve the electrical insulations.
Additionally, networking and communication among monitoring and control components of power systems (e.g. smart meters, intelligent electronic devices etc.) represent the main challenges in this field.


This WP will make further investigate the following items: improvement of the reliability of the testing methods for high voltage components; deeper understanding of novel material behaviour, lower operational costs for electricity suppliers and consequently for customers as well.
Still on the component side, the WP will study the optimal design of reversible pump-turbines since these components represent a major advancement for the energy storage systems within the Swiss context.
This WP comprises:
  • switching very fast transients (VFTs) modelling and experimental investigations;
  • improvement of performances of existing devices for high voltage and high power system;
  • improvement of the design of reversible pump-turbines.
The properties of specific (e.g. nano-structured or hybrid) materials used as well for insulation purpose cannot be analytically calculated but only approximated. Within the development of HVDC grid this approximation needs to be precise over the relevant parameter range. Since the need of accurate results, it is extremely difficult to establish multi-physical simulations of complex systems without significant computing power.
Methods for simplification of complex models without losing relevant physical and functional aspects thus have to be found. Reliability tests take long times since each test (even if accelerated) takes at least several days to weeks and a number of test specimen are needed for statistical reasons. It is yet unknown how much a “highly” accelerated test procedure would shorten the testing duration.

The objectives will be achieved through the implementation of specific activities. During Phase I (2014-2016), these activities were focus on the development of new innovative solutions which are validated during Phase II (2017-2020) in demonstration sites.

The activities for each Phase and the associated milestones are presented below.

Activities Phase II (2017-2020)

S 4.1 Multi-physics Simulations for Power Systems

Subtask leader: 10.1 HSLU, Prof. Casartelli

Description: Development of a tool for fully coupled electromagnetic-mechanic FEM simulations of an electric generation system consisting of hydro turbine, shaft, and generator. This will be used for the study of transient stability and turbine shaft fatigue; and the development of new methods for components’ stress mitigation.

M4.1.1 Coupling prototype for turbine/generator interaction (time discretization methods for the coupled system with constraints)  3.3. USI-ICS, Prof. Krause [Oct. 2017]
M4.1.2 Fluid structure interaction for turbine/water based on immersed boundary approach  3.3. USI-ICS, Prof. Krause [Oct. 2018]
M4.1.3 Reduced model for parts of the turbine/generator system  10.1 HSLU, Prof. Casartelli [Apr. 2019]
M4.1.4 Fully coupled Multiphysics FEM simulations with reduced/full model of turbine-shaft-generator system under transient loading  10.1 HSLU, Prof. Casartelli [Jun. 2020]
M4.1.5 Development of fatigue model prototype and its application as a post-processing tool  10.1 HSLU, Prof. Casartelli [Dec. 2020]

S 4.2 Reliability, Monitoring, and Failure Detection

Subtask leader: 9.1. HSR, Prof.Smajic

Description:  Increased reliability and performance of monitoring tools for grid components by (a) studying the reliability of the component insulation in detail in case of dry-band surface discharges on outdoor equipment and in Gas Insulated Substations (GIS) exposed to very fast transients; and (b) analysis of the application and sustainability of novel solid-date state transformer for the power distribution based on SiC-semiconductors and definition of the optimal dimensioning criteria

M4.2.1 Electrical characterization setup for SiC devices operational  7.1 FHNW, Prof.Schulz [Dec. 2017]
M4.2.2 Measurements, modeling, and simulations of discharges in barrier insulation systems 9.1 HSR, Prof.Smajic [June 2018]
M4.2.3 Experimental assessment of SiC reliability on package level  7.1 FHNW, Prof.Schulz [Dec. 2018]
M4.2.4 EMC analysis of large PV systems; comparison of measurements and simulations 9.1 HSR, Prof.Smajic [Sept. 2019]
M4.2.5 Analysis of insulation systems under Very Fast Transients stress due to converter switching 9.1 HSR, Prof.Smajic [Dec. 2012]

S4.3 Grid Integration of PV, and Storage

Subtask leader: 8.2 BFH – PV-Lab, Prof. Muntwyler

Description: Improved PV system components including inverter, battery, component test, and test norms by developing new fire prevention and anti-snow coverage strategies which will increase the reliability and safety of PV installations; test and develop norms for multi-tracker inverters combined with battery systems.

M4.3.1 Tests with Multi-tracker inverters and proposal for test norms with for “ multi – tracker ” – inverter and inverter – batteries  8.2 BFH – PV-Lab, Prof. Muntwyler [Mar. 2018]
M4.3.2 Development of strategies against snow coverage of PV plants  8.2 BFH – PV-Lab, Prof. Muntwyler [Sep. 2018]
M4.3.3 Cost calculations and cost forecast for PV Power based on long term historical data  8.2 BFH – PV-Lab, Prof. Muntwyler [Oct. 2019]
M4.3.4 Update of strategies against snow coverage of PV plants and development of recommendations for the use of mobiles storage  8.2 BFH – PV-Lab, Prof. Muntwyler [Oct. 2019]
M4.3.5 PV planning considering smart power users and batteries for cost optimised installation and high (10-20%) penetration of PV power into the grid  8.2 BFH – PV-Lab, Prof. Muntwyler [Oct. 2020]


PV inverter and battery inverter tests

PV inverter and battery test bench and test norms

Academic partner: BFH (PV-Lab) ( urs.muntwyler@bfh.ch )     
Non-FURIES partners:
HTW Berlin, TU München, Karlsruhe Institut of Technology, Austrian Institute of Technology, Swiss Renova AG, Genossenschaft Elektra Jegenstorf

Project duration
: 2014-2021 (7 years)

Funding: Studiengesellschaft Mont-Soleil, BFH, Genossenschaft Elektra Jegenstorf

For the smoothening of the PV power production and the enhancement of the own consumption of houses with PV installations, stationary batteries are increasingly installed. However, these PV-storage systems can serve multiple purposes and improve the economic performance of the PV installations.

This project aims to develop a “PV inverter and battery” test facility and a related EN test norm.

For the achievement of this goal, a PV inverter and battery test bench was developed based on existing infrastructure at the PV LAB at BFH in Burgdorf, i.e., PV inverter test benches.
First measurements of the dynamic battery-inverter units performances are currently being conducted, and the knowledge acquired is transferred and cross-checked with international partners. Data sheets are developed and a proposal for an EN Test norm is underway.
Real measurement of “battery-PV-inverter” units enabled a better understanding of the instance increasing their own self-consumption function and the parameters of such devices.
One of the results is that a poor dynamic response could result to system operation modes with low efficiency (<60%). Also, the EN-test norm enable the industry to be aware of the real performance of such systems and to improve them. For instance, PV planers can integrated in their work the real data of such devices.
The outcomes of this project will enable the owners of PV installations to improve the economic performance of their investments, by for on PV power. Also, utilities and others can learn to use the “PV-battery-inverter devices” to stabilize the grid and to optimize the economy of the electricity in their grid.
There are more than 15 possibilities for the different stakeholders to use the unit for improving different parameters (e.g., voltage control, power control, production of regulation power etc.).

Next step
As a next step, the test norm will be developed by the end of 2016, jointly with international partners, and a “round robin” test cycle will be undertaken with three other institutes for 2016/ 2017.
A software will be developed to semi-automatize some of the test procedures and an artificial load will be integrated to speed up the test procedures. The testing of small (<10 kWh) and big units (>>10 kWh) will continue during the 2017 – 2020 period. Tests of bidirectional EV-batteries are also planned in view of performing the same function as a stationary battery (2017-2021).

Fig. 39 – PV laboratory established test configuration and measures several batteries for a local utility company

Further reading:

Muntwyler , U., Gfeller , D., Borgna , L., Schuepbach , E., 2014, Ultra fast Multi-MPPT PV Inverter Test Bench ; Proceed . 30th EUPVSEC 2014, Amsterdam.
Muntwyler , U., Gfeller , D., 2015, Influence of a solar module fill factor on the static MPP tracking performance of single phase inverters ; Proceed . 31th EUPVSEC, Hamburg 2015 .
U. Muntwyler : “ Electric vehicles powered with PV as a new driver for the PV market ”, Proceed . 32nd EUPVSEC 2016, 20-24 June 2016, Munich , DE

Swiss Transformer: Application and sustainability of SiC SST in the Swiss electrical grid

Integration and application of solid-state transformers in the existing electric grid

Academic partner: FHNW (Prof. Schulz) ( nicola.schulz@fhnw.ch ); ETHZ  (LEM, HVL)
Industrial partners: ABB AG, BKW AG      Non-FURIES partners: PSI; EPFL (Prof. Thome)
Funding: SCCER-FURIES; NRP 70            Project duration: 2014-2018 (4 years)

Silicon carbide (SiC) -based power electronic transformers (SSTs) can play an important role on the stabilization of the power grid with strongly fluctuating electricity supply from PV and wind power plants. However, research is still needed on the development of technologies for the realization of SiC-based high-power semiconductor switching elements, and for the optimization of hardware concepts for SiC-based power electronic transformers (SSTs).

This project is part of the same program with the STT project mentioned under WP3. This project aims to assess the application of SiC SSTs in low- and medium voltage grids by grid simulations; to develop control algorithms; and assess the overall sustainability of grid-based SiC SSTs.
Target customers are DSOs operating both, MV and LV grids with strong decentralized feed-in by wind and PV.

As a result of the project, simulation models and control algorithms for SSTs were developed for voltage control of LV grids with a high penetration of decentralized PV generation. Also, the application of SST was assessed in MV grids in order to stabilize voltage, compensate reactive power and minimize grid losses.
Based on these outcomes, decision makers and end-users can decide whether and how SSTs will bring the required functionalities for grid operation and stabilization. Furthermore, they obtain information about how many SSTs should be used in a specific grid, at which locations and which control scheme to apply.

Next step
A sustainability model of SiC SSTs applied in the Swiss electric grid will be established; and reliability data of the underlying SiC power semiconductors will be acquired. The rolling out of this technology is foreseen for beyond 2025.

Fig. 41 – Overview of 2 LV grids in Rheinfelden AG, with calculated distributed PV potential (displayed columns), as enabled by SiC SSTs.

Further reading:

C. Hunziker, N. Schulz, “Potential of solid- state transformers for grid stabilization in existing low-voltage grid environments “, submitted to Electric Power Systems Research, 2016
N. Schulz, “Werden Trafos zukünftig zu Multifunktionstools?”, Spektrum Gebäudetechnik,  No . 5, 2015.
C. Hunziker, N. Schulz, “Solid-State Transformer Modeling for Analyzing its Application in Distribution Grids “, PCIM Europe 2016 ( Nuremberg ), VDE Verlag GmbH Berlin Offenbach, 2016, 2167-2174
C. Hunziker, N. Schulz, “Potential of Solid-State Transformers as Key Technology for Future Smart Grids “, poster presentation at the SCCER-FURIES 3rd Annual Conference 2015 (Lausanne)

SiC Solid-State Transformer

Report on state of art related to “holistic” optimization. (Deliverable 4.2.1)

Academic partner: FHNW ( nicola.schulz@fhnw.ch )                  Industrial Partner: ABB

In the context of the development of novel silicon-carbide (SiC) based power electronic modules and corresponding SiC high-frequency power electronic converters, the reliability and failure processes of SiC power electronic modules are assessed.
This includes the development, construction and implementation of a dedicated reliability test setup for SiC modules. Before testing, the state-of-the-art in SiC power-electronics reliability is assessed and the reliability tester and the testing procedure adapted accordingly.
Planned results will be (1) experimentally assessed lifetime data on novel 3.3kV SiC MOSFET modules; (2) a deep understanding of the physical processes leading to SiC device failure; (3) the ability to model the lifetime of SiC modules under a given performance profile.

A reliability testing procedure and test results of novel 3.3 kV SiC MOSFET modules; understanding of physical failure processes of SiC power electronic modules.

This achievement provides improved knowledge on SiC module lifetime and failure mechanisms; a method to assess the reliability of SiC power electronic devices; and dimensioning of SiC converters for optimal life-cycle sustainability.

What’s next
Installation and calibration of reliability testing setup.

Figure 16: SiC power-electronic module
(image source: CREE)
Figure 17: SEM scans of failed aluminium bond wires
(cracked and lifted-off) on power electronic chips, after active
load cycling (image source: Semikron)