Reliable Power Systems Using Maximum Use of System Flexibility

With the increased interconnection between different countries and the integration of large amounts of renewable energy sources, the manner in which future transmission systems are planned and operated will change. Different changes are foreseen.

First of all, the variability of power injections will increase drastically, and this due to the variability of renewable energy sources on the one hand, but also due to the variations in power exchanges between regions and countries, in normal operation and emergency. This variability could lead to temporary congestions in the grid, leading to inefficient energy exchanges. At the same time, smart grids have enabled the system operator to have enhanced controls in the system, and this at much shorter time frames.

The second trend is related to the re-examine the manner in which the security of the power system should be managed. This is an indirect consequence of the first topic, as the uncertainty due to the variability makes it more difficult to maintain the same security level (typically in the form of maintaining N-1 security). At the same time, the flexibility in operations allow to address the problem in a more dynamic manner, and more targeted manner. However, by doing so, conceptual choices regarding reliability, cost-efficiency and fairness are inevitable.

The workshop will address the different the evolutions mentioned above, and the consequences for the computational tools needed to address them.

Active Distribution Grids

Renewables will play a major role in the transition to a clean energy system. A policy to increase renewables as well as to reduce CO2 emissions has, next to the many potential benefits, a number of effects related to the electricity system: (1) an increasingly decentralized injection of renewable generation showing a high simultaneity of generated electricity, (2) an increase of the electrical load caused by a shift from fossil-fueled systems towards high efficient electrical equipment for transport and heating, and (3) an increased need for flexibility in the electricity system due to the high intermittency of renewable generation.

These effects may introduce severe issues in the local distribution grid, including deteriorated voltage quality and grid congestions and consequently the security of supply, if not adequately managed. If the network management principles are not altered, the problems can be solved by reinforcing the network. This can, however, lead to high distribution network total costs and, consequently, larger electricity bills to the customers.

On the other hand, the installation of new controllable technologies and resources in the distribution grid, such as tap changing transformers, capacitor banks, electrical storage (batteries), etc. give new opportunities to the Distribution System Operators (DSOs) to optimize and secure the operation of their grids.  The adaption of production or consumption of locally connected resources by demand response is not only deployed to meet the increased demand for flexibility on system level but also to avoid issues on the local distribution grid. Also reactive power control capability of distributed generators or by the inverter front-end of battery instalations can be utilized in network control. These new opportunities for increased control in the local distribution grid offer the means to deal with the expected grid issues. Utilizing active network management methods instead of the current passive approach decreases the distribution network total costs in many cases substantially.

In this workshop an overview will be given of the main issues a distribution system operator is facing, given the current trends towards a low carbon energy system. VITO/Energyville develops technology and tools for distribution system operators to cope and manage these issues to secure power supply. Case studies of applying active grid management tools to systems in Belgium will be presented.

Real-time Electric Circuit Diagnostics Using Waveform Analytics—Predicting Failures and Preventing Outages, Making the System More Reliable and Safe

The operation of today’s power system can be describe as run to failure, then repair. All protection, restoration, and data systems currently available to utilities are reactive by nature. Operators wait until a fault or outage occurs, then react to restore service as rapidly as possible.

New developments in waveform analytics are transforming the reactive mode of operation into anticipatory and predictive diagnostics. Researchers at Texas A&M University have developed diagnostic algorithms capable of detecting the earliest stages of incipient fault behavior as well as abnormal events on the power system that ultimately cause outages. Called Distribution Fault Anticipation or DFA, this new technology will allow proper Raiders practiced for the first time true condition based magnets. A failing device can be detected, identified, and located allowing operators to dispatch repair crews before an outage occurs. Reliability and safety are hereby enhanced.

In 15 years of monitoring circuits and developing detection algorithms, A&M researchers have accumulated hundreds of case studies of failing devices which most often are not detected by current utility protection. The workshop will present selected case studies and describe the ways power systems fail to cause outages. DFA technology will be presented as a new operating alternative, allowing operators to avoid many outages and failures that cause dangerous downed power lines.

All case studies will be selected from failures occurring on operational circuits from up to a dozen different utilities. The application of the new technology by local industry and stakeholders and how it can significantly improve safety will be explored.

Harmonic and Reactive Power Compensation – Improving the Efficiency and Resiliency of the Distribution Network to Cope with Increased Penetration of Distributed Energy Resources including Energy Efficient Appliances, Photovoltaic Systems, Electric Vehicles

The addition of distributed energy resources, particularly photovoltaic power and electric vehicles, in the distribution networks, has the potential to complicate the voltage regulation problem. For example, in San Diego Gas and Electric distribution territory, PV installations accounted for 617 MW of peak load from 93000 installations at the end of June 2016. In August of 2013, these numbers were 175 MW from 24000 PV installations. This represents a substantial increase in the PV penetration over the course of roughly three years. The high penetration of PV was initiated by government policies and recently fueled by declining PV system costs which makes the technology economically sustainable. With this trend, it is clear that network operators will have to contend with an increasing surge in the range of problems concerned with the regulation of voltage and power on distribution feeders.

The fundamental concern about the photovoltaic generation is the intermittency involved which when combined with other factors such as a fluctuating load profile can induce irregularities not only in the voltage on the distribution feeder but also in the operational activity of several electro-mechanical devices which are designed and placed on the feeder for the purpose of voltage regulation. This places stress on the distribution systems and operators which are obligated under the ANSI standards to provide voltage within a dead band of ± 5V from the nominal distribution voltage. It is shown that with increased variability of the PV output, the number of tap changing operations also increases. In one example, a distribution system with a 20 MVA, 69 kV/12,47 kV, Δ-Y connected transformer serving two residential feeders experienced a 4x increase in the frequency of tap changes as PV penetration went from 0% to 20%.

Results from an ongoing NPRP project to develop a point-of-use power quality compensator will be presented. This new technology is designed for the environment of Qatar, and intended to be deployed and dispatched within the distribution system to compensate for reactive and harmonic power before they flow upstream to the substation. Case studies of the impact will be examined. The application of the new technology by local industry and stakeholders and how it can significantly improve safety will be explored.

Power Electronics as the Enabling Technology for Sustainable Energy

Power electronics is a crucial technology behind the transition happening in the energy system, linking electrification, decentralization and digitalization. In this energy transition three trends go hand in hand:

• Further electrification due to environmental and economic reasons, e.g. in building HVAC through heat pumps and electric vehicles in public and private transportation.
• Decentralization: with the further shift to distributed electricity generation, storage and load control, the focus of the electricity grid operations shift to smaller decentralized sections of the distribution system.
• Digitalization: due to ubiquitous IT technology, a better management of the energy system components is achieved.

Power electronics was originally the enabling technology for renewables-based electricity generation and improved energy efficiency, mainly in industry, but once more it proves to deliver the required building blocks for the energy transition at city, district and building level. Examples are (building integrated) photovoltaics, distributed storage and local low-voltage DC grids.

This workshop will discuss the main technology trends in power electronics, starting from the semiconductor technologies, where classic silicon-based switches are being replaced by novel wide band gap semiconductors.

In a next step, some important circuits are introduced at high level, thereby linking them to the specific applications in smart grids, photovoltaics, and drives for robotics, electric vehicles and wind turbines. This also includes a discussion of the associated control and reliability challenge.

Finally, a look into the future is made, indicating where the main challenges for this technology lie, allowing further upscaling of its use.

Arc Fault and Flash Detection in Photovoltaic and Building Wiring Systems – Detecting Electrical Safety Problems, Making the Electrical System Safer for the Customer

Arc faults have always been a concern for electrical systems as they can cause fires, personnel shock hazard, and system failure. Even more important is to detect arc flash, the pre-fault (before a sustained arc forms) events of sparking and dielectric breakdown. Arc flash may only last for a short duration (less than a second), but serves as an early indicator of incipient arc faults. Detecting arc flash is a difficult problem because unlike a bolted “hard short” fault in which high current flows through a metal-to-metal connection, arc flash involves short-term current flowing through ionized air or along an ion path and may not draw sufficiently high RMS current, or have a high enough I²t energy to trip a thermal circuit breaker. This is particularly true in energy-constrained systems, such as many of the proposed DC microgrids and systems energized by renewable energy sources which have finite short-circuit current ratings yet still can pose a significant risk.

The process of detecting an arc fault involves selecting and monitoring system voltage and current signals, signal analysis and then feature identification. Existing commercialized arc detector techniques that rely on pattern recognition in the time domain, or frequency domain analysis using a Fourier Transform do not work well because the signal to noise ratio is low and the arc signal is not periodic. Commercial arc flash detectors have been limited to substation switch gear where there is the possibility of a high-energy discharge. Instead, a new approach uses wavelet transform which can uses a time and frequency approach to analyze signals with multiple resolutions. Machine learning techniques then classify the sensed signals to determine if an arc or arc flash is occurring. The technique is well-suited to scale-down to low-voltage wiring systems to provide protection at customer interface, much like ground-fault detection circuit breakers which are not ubiquitous and required for certain application.

The presentation will walk through a comparison of existing and new techniques, examining the scientific basis for each, discuss the challenges of sending arc faults in solar photovoltaic systems, and show how the new methods can be utilized to improve the arc detection process. The application of the new technology by local industry and stakeholders and how it can significantly improve safety will be explored.