Status: AWARD END DATE: 08/31/2024

Background:

Multi-port Energy Router using Intelligent Transformers (MERIT): Energy Management and Supervisory Control

The phase-I of the Multi-port Energy Routers using Intelligent Transformers (MERIT) project (March 2021 to February 2022) explored the interface of renewable resources and subsea O&G production systems with the High Voltage DC (HVDC) or Medium Voltage DC (MVDC) grid. Solid State Transformers (SSTs) enabled seamless interconnectivity and interoperability between the various energy sources, including wind, solar, battery energy storage systems (BESS), etc. The Phase-I research also investigated how to optimally design and integrate SSTs into the MERIT system in a ‘triple active bridge’ (TAB) configuration. However, several critical challenges related to the energy management and control of the interconnected system still remain. In this Phase-II of the MERIT project, the focus will be on the overall energy management strategy and its implementation considering interoperability of the interconnected energy sources to the MERIT system. As a part of this, efficient power conversion schemes for the renewable energy sources – wind, solar, fuel cells and BESS, will be developed, which will help interface these resources with the MERIT system. Interconnection with both MVDC and medium voltage AC (MVAC) grids will be explored in the investigation. The conversion, energy management and supervisory control schemes will then be devised in such a way that they satisfy the requirements of IEEE-1547 standards in terms of voltage sag/swell, low voltage ride through (LVRT) and reactive power. Due to the intermittency of renewable energy sources (RESs), the team will analyze the methods of maintaining secure operation of such offshore power systems for high power quality in the offshore grid even during transient conditions due to large motor loads. Also, due to the lengthy cables from the source to the subsea motor loads and due to the long distance from the motor controller to the motor, the rate of change of voltage (dv/dt) at the output of the power electronic converters and the noise in the sensor cables, it may lead to several problems such as EMI, cable insulation, thus affecting the overall operation. Hence, considering these effects of the transformer, cable, and motor, suitable filters will be designed and also sensor less operation techniques for the motors will be investigated as part of the overall energy management strategy. Real time hardware-in-the-loop (HiL) systems will be used to validate the developed methods and concepts.

Figure 1: Overall block diagram of the proposed MERIT system, with multiple energy sources and subsea load

Optimal Sizing of Onsite Generation Resources for Self-Sustainable Offshore Loads

Offshore oil and natural gas (O&G) rig platforms consume a significant amount of fossil fuels to power their operations. The Gulf of Mexico is an important region for offshore energy resource production. Most existing power systems for offshore O&G platforms heavily rely on local diesel generators or gas generators. Such power systems lead to substantial greenhouse gas emissions. This brings the opportunity for renewable energy. The advancement of offshore renewable generation technologies enables us to redesign the platforms’ power systems with clean energy for reliably supplying offshore loads, which will lead to a substantial reduction of CO2 emissions mitigating climate change.

Figure 2. Illustration of the proposed OHRES system for powering offshore loads with clean renewable energy.

Industry Impact

Multi-port Energy Router using Intelligent Transformers (MERIT): Energy Management and Supervisory Control

The investigators are actively working with the offshore industries in the area of power and energy systems to advance the research that can positively impact safe and reliable exploration and energy production, particularly in the Gulf of Mexico. The team recently started an industry consortium in the area of subsea power and energy systems to advance the subsea oil extraction that will lead to higher efficiency and lower emissions. The name of the consortium is “Power electronics - Energy storage - Microgrids and Subsea Electrical Consortium” (PEMSEC). The proposed research is one of the projects suggested by the existing consortium members as part of the future scope of PEMSEC. This project will advance the knowledge on advanced power conversion, energy management and control of offshore RESs with the MERIT system.

Optimal Sizing of Onsite Generation Resources for Self-Sustainable Offshore Loads

With various renewable generation and storage technologies being available, it becomes practically possible to replace traditional diesel/gas generators with a hybrid energy system supplying clean power. This project will design such a system and optimize the onsite energy resources considering cost and reliability. The proposed system will ensure continuous power supply to offshore platforms in an economic and reliable manner. The cost-benefit analysis will estimate the levelized cost of electricity; this information can be used to facilitate the decision-making for stake holders in the O&G industry. The success of this project will not only benefit the offshore loads in the Gulf of Mexico but also the offshore loads in other part of the world. In addition, this project is consistent with many initiatives on industry electrification and will lead to a substantial reduction of CO2 emissions and thus mitigate climate change.

Project Objectives

Multi-port Energy Router using Intelligent Transformers (MERIT): Energy Management and Supervisory Control.

In phase II of the MERIT project, SSI proposes to develop energy management and supervisory control strategies for interfacing the primary renewable energy sources using the Multi-port Energy Routers with Intelligent Transformers. SSI will:

1. Develop a detailed energy management scheme and supervisory control architecture for the seamless transfer of energy between the renewable energy resources and the MERIT system, and to the loads, by analyzing the source side and load side characteristics.
2. Study the state-of-the-art and develop power conversion schemes, along with control methods, to interface the primary renewable energy resources with the MERIT with both MVDC and MVAC grid interconnection.
3. Assess the controllability and efficiency of the power converters, and employ advanced techniques (like machine learning), and also modeling of different system components for drive including transformer, sine filter, long transmission line, transformer, and the PM motor to improve the performance with the energy management and supervisory controllers. Validation of the developed model in Typhoon HIL/ MATLAB simulation.
4. Development of algorithms for automatic parameter estimation of the equivalent circuit model for the complete system from drive perspective in subsea applications, and design and development of efficient control strategies for subsea drive systems.
5. Evaluate the overall power conversion scheme, energy management and supervisory control architecture on how well they satisfy the requirements of IEEE-1547 standards in terms of voltage sag/swell, low voltage ride through (LVRT) and reactive power.
6. Implement the system in a real time emulator and verify the overall operation using a simulator unit, such as Typhoon Hardware-in-the-loop (HiL) system.

Optimal Sizing of Onsite Generation Resources for Self-Sustainable Offshore Loads

The proposed research aims to design offshore renewables-dominated energy systems for supplying continuous power to offshore loads in a self-sustainable manner with onsite resources. The proposed system consists of clean and renewable generation and energy storage resources. The resources’ sizes will be optimized to meet the offshore demand while considering economics and reliability. This project focuses on the system architecture design.

1. Establish the models and conduct parameterization for offshore renewable resources and energy storage resources;
2. Develop a long-term planning model for energy asset investment decision-making considering battery degradation; time-domain simulations will be conducted to evaluate the designed hybrid energy system.
3. Develop an open-source tool that implements the proposed research and makes it publicly available. This tool will be able to handle customized resource specifications and projected electrical loads at an offshore platform that will allow academia and industry to use it.

Tasks:

Task 1: Multi-port Energy Router using Intelligent Transformers (MERIT): Energy Management and Supervisory Control

• Goal 1: Energy management and supervisory control strategies for seamless power transfer (100% complete)
  • Goal 1.1: Energy management and supervisory control architecture with the onshore grid (100% complete)
  • Goal 1.2: Energy management and supervisory control architecture without the onshore grid (100% complete)
• Goal 2: Power conversion and control methods for RESs’ interface with MVDC/MVAC grid (70% complete)
  • Goal 2.1: Converters and control methods to interface the WTGs with the MVDC grid (100% complete)
• Goal 3: Modeling of system components and control strategies with MCCL (35 % complete)
  • Goal 3.1: Modeling of different system components for PM drive using a transformer (100% complete)
  • Goal 3.2:  Modeling of sine filter, long transmission line, transformer, and the PM motor (70% complete)
  • Goal 3.3: Low-speed performance enhancement for sensorless control drive
  • Goal 3.4 - Control strategies for motor drives to mitigate the effect of sine-filter by MCCL
• Goal 4: Performance improvement of the power conversion/control stages (Not started)
  • Goal 4.1:  Assess the performance (including efficiency and response speed) of the RES converters, and use machine learning to improve the overall performance
  • Goal 4.2: Evaluate and compare the benefits/ drawbacks of MVDC vs. MVAC MERIT grid
• Goal 5: Providing grid services and satisfying standards such as IEEE-1547 (Not started)
  • Goal 5.1: Evaluation of the energy management and control scheme for LVRT (IEEE-1547)
  • Goal 5.2: Evaluation of the energy management and control for other grid services

Task 2: Optimal Sizing of Onsite Generation Resources for Self-Sustainable Offshore Loads

• Goal 6: Modelling and parametrization of three types of renewable generation resources and two types of energy storage resources
  • Goal 6.1: Renewable Generation Resources
    • Tidal Energy (100% complete)
    • Wave Energy (100% complete)
    • Offshore Wind Energy 
  • Goal 6.2: Energy Storage Resources
    • Battery Energy Storage System (100% complete)
    • Hydrogen Energy Storage System (100% completed)
• Goal 7: Modelling and quantifying Battery degradation using deep-learning methods (20% complete)
• Goal 8: Develop a long-term planning model to design the proposed OHRES system (20% complete)
• Goal 9: Time Domain Simulation and Stability Analysis for the designed OHRES system (Not started)
• Goal 10: Develop an opensource tool that implements the proposed research (Not started)

Gantt Chart: