Publications

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The report summarizes the work and accomplishments of DOE SETO funded project 36533 “Adaptive Protection and Control for High Penetration PV and Grid Resilience”. In order to increase the amount of distributed solar power that can be integrated into the distribution system, new methods for optimal adaptive protection, artificial intelligence or machine learning based protection, and time domain traveling wave protection are developed and demonstrated in hardware-in-the-loop and a field demonstration.

This new research provides transformative marine energy technology to effectively power the blue economy. Harmonizing the energy capture and power from Wave Energy Converter (WEC) arrays require innovative designs for the buoy, electric machines, energy storage systems (ESS), and coordinated onshore electric power grid (EPG) integration. This paper introduces two innovative elements that are co-designed to extract the maximum power from; i) individual WEC buoys with a multi-resonance controller design and ii) synchronized with power packet network phase control through the physical placement of the WEC arrays reducing ESS requirements. MATLAB/Simulink models were created for the WEC array dynamics and control systems with Bretschneider irregular wave spectrum as inputs. The numerical simulation results show that for ideal physical WEC buoy array phasing of 60 degrees the ESS peak power and energy capacity requirements are minimized while the multi-resonant controllers optimize EPG power output for each WEC buoy.

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Communication-assisted adaptive protection can improve the speed and selectivity of the protection system. However, in the event, that communication is disrupted to the relays from the centralized adaptive protection system, predicting the local relay protection settings is a viable alternative. This work evaluates the potential for machine learning to overcome these challenges by using the Prophet algorithm programmed into each relay to individually predict the time-dial (TDS) and pickup current (IPICKUP) settings. A modified IEEE 123 feeder was used to generate the data needed to train and test the Prophet algorithm to individually predict the TDS and IPICKUP settings. The models were evaluated using the mean average percentage error (MAPE) and the root mean squared error (RMSE) as metrics. The results show that the algorithms could accurately predict IPICKUP setting with an average MAPE accuracy of 99.961%, and the TDS setting with a average MAPE accuracy of 94.32% which is sufficient for protection parameter prediction.

For the protection engineer, it is often the case, that full coverage and thus perfect selectivity of the system is not an option for protection devices. This is because perfect selectivity requires protection devices on every line section of the network. Due to cost limitation, relays may not be placed on each branch of a network. Therefore, a method is needed to allow for optimal coordination of relays with sparse relay placement. In this paper, methods for optimal coordination of networks with sparse relay placement introduced in prior work are applied to a system where both overcurrent and distance relays are present. Additionally, a method for defining primary (Zone 1) and secondary (Zone 2) protection zones for the distance relays in such a sparse system is proposed. The proposed method is applied to the IEEE 123-bus test case. The proposed method is found to successfully coordinate the system while also limiting the maximum relay operating time to 1.78s which approaches the theoretical lower bound of 1.75s.

Penetration of the power grid by renewable energy sources, distributed storage, and distributed generators is becoming more widespread. Increased utilization of these distributed energy resources (DERs) has given rise to additional protection concerns. With radial feeders terminating in DERs or in microgrids containing DERs, standard non-directional radial protection may be rendered useless. Moreover, coordination will first require the protection engineer to determine what combination of directional and nondirectional elements is required to properly protect the system at a reasonable cost. In this paper, a method is proposed to determine the type of protection that should be placed on each line. Further, an extreme cost constraint is assumed so that an attempt is made to protect a meshed network using only overcurrent protection devices. A method is proposed where instantaneous reclosers are placed in locations that cause the system to temporarily become radial when a fault occurs. Directional and nondirectional overcurrent (OC) relays are placed in locations that allow for standard radial coordination techniques to be utilized while the reclosers are open to clear any sustained faults. The proposed algorithm is found to effectively determine the placement of protection devices while utilizing a minimal number of directional devices. Additionally, it was shown for the IEEE 14-bus case that the proposed relay placement algorithm results in a system where relay coordination remains feasible.

An array of Wave Energy Converters (WEC) is required to supply a significant power level to the grid. However, the control and optimization of such an array is still an open research question. This paper analyzes two aspects that have a significant impact on the power production. First the spacing of the buoys in a WEC array will be analyzed to determine the optimal shift between the buoys in an array. Then the wave force interacting with the buoys will be angled to create additional sequencing between the electrical signals. A cost function is proposed to minimize the power variation and energy storage while maximizing the delivered energy to the onshore point of common coupling to the electrical grid.

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Power systems with highly flexible architectures (i.e. permitting many configurations) may allow for more economic operation as well as improved reliability and resiliency. The greater number of configurations enable optimization for attaining the former benefit and redundancy for achieving the latter. Flexibility is of great importance in electric ship power systems wherein the system must ensure delivery of power to vital loads. The United States (US) Navy is currently investigating new architectures that enable a greater number of interconnection permutations. Among the new features considered are generators that may supply two buses; this may be done using conventional (single winding set) generators and two rectifiers or a dual wound machine with two rectifiers. In systems supplied by dual-wound machines, buses may not be tied directly but are linked dynamically through the shared generator dynamics. In systems with conventional generation supplying two rectifiers, the two buses are tied through a common AC bus supplying both rectifiers. This paper presents a comparison of these two approaches of supplying two buses from one generator; the evaluation considers issues associated with dynamic coupling through these two candidate architectures, including the coupled response due to faults and systems with pulsed loads. Results are based on analysis, simulation results, and hardware experiment.

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