Urquidez, Omar Armando (2016-05). Technical and Economic Integration of Voltage Source Converter Based High Voltage Direct Current Transmission in Power Systems. Doctoral Dissertation. Thesis uri icon

abstract

  • New challenges face the electrical system every day. These new challenges may need to be addressed with more than just conventional AC solutions. Voltage Source Converter based High Voltage DC (VSC-HVDC) systems, although unconventional, may provide promising solutions to these challenges, but integration of these advanced devices into normal power system planning and operation continues to be slow. This research seeks to improve integration of VSC-HVDC into power system planning and operations by addressing both the technical and economic hurdles to integration. First, a ranking algorithm of prioritizing the incorporation of a VSC-based HVDC transmission line for improved economic dispatch is presented. This algorithm, termed as Smart Targeted Planning (STP), proposes a line shadow price-based weighting approach to ranking the potential economic impact of incorporating a new VSC-based HVDC link along existing transmission lines. This work allows for improved integration of VSC-HVDC in the planning stages. Second, a singular value sensitivity (SVS) based supplementary control algorithm is proposed for enhancing the quasi-steady-state voltage stability in AC power systems. The algorithm computes the optimal control policy for VSC power so that the system voltage stability margin is maintained. Also introduced is the singular value capability space of the embedded VSC-HVDC system which builds intuition for system operators to visualize how much the embedded VSC-HVDC system can migrate the system away from voltage instability. Third, a novel control algorithm is proposed for power system small signal dynamic performance improvement by use of an embedded voltage source converter (VSC) based high voltage direct current (HVDC) system. Embedded HVDC refers to a meshed AC grid with all HVDC terminals connected within the same AC grid. The concept of steady-state and dynamic impedance of the HVDC system is introduced as a novel time-scale separation of the impact of HVDC on the AC grid. In this system, the impedance of the connecting transmission lines is the same in the dynamic model as that in the steady-state model. The proposed control will have the VSC-HVDC mimic impedance in the dynamic model while not affecting the steady-state model. This allows the VSC-HVDC system to target improvement for dynamic problems while maintaining independence to use a different control to improve steady-state problems. To obtain optimal parameters for the enhanced small signal impedance mimicry (ESSIM) control, a sensitivity based optimal control loop is also proposed. The efficacy of the proposed algorithm is shown via case studies on a classic two area system and on the IEEE 10 generator 39 bus system. Finally, a multi-time scale techno-economic benefit mapping framework is proposed to aid in better economic integration of advanced transmission devices like VSC-HVDC. The proposed approach is to clearly map technical benefits to their corresponding economic causes and economic effects. The end result will be a scalar metric by which all devices can be compared. The proposed approach will address multi-time scale technical benefits and the resulting economic causes and effects providing clarity, transparency, and granularity to allow for a better one-to-one comparison of conventional and unconventional power system devices.
  • New challenges face the electrical system every day. These new challenges may need to be addressed with more than just conventional AC solutions. Voltage Source Converter based High Voltage DC (VSC-HVDC) systems, although unconventional, may provide promising solutions to these challenges, but integration of these advanced devices into normal power system planning and operation continues to be slow. This research seeks to improve integration of VSC-HVDC into power system planning and operations by addressing both the technical and economic hurdles to integration.

    First, a ranking algorithm of prioritizing the incorporation of a VSC-based HVDC transmission line for improved economic dispatch is presented. This algorithm, termed as Smart Targeted Planning (STP), proposes a line shadow price-based weighting approach to ranking the potential economic impact of incorporating a new VSC-based HVDC link along existing transmission lines. This work allows for improved integration of VSC-HVDC in the planning stages.

    Second, a singular value sensitivity (SVS) based supplementary control algorithm is proposed for enhancing the quasi-steady-state voltage stability in AC power systems. The algorithm computes the optimal control policy for VSC power so that the system voltage stability margin is maintained. Also introduced is the singular value capability space of the embedded VSC-HVDC system which builds intuition for system operators to visualize how much the embedded VSC-HVDC system can migrate the system away from voltage instability.

    Third, a novel control algorithm is proposed for power system small signal dynamic performance improvement by use of an embedded voltage source converter (VSC) based high voltage direct current (HVDC) system. Embedded HVDC refers to a meshed AC grid with all HVDC terminals connected within the same AC grid. The concept of steady-state and dynamic impedance of the HVDC system is introduced as a novel time-scale separation of the impact of HVDC on the AC grid. In this system, the impedance of the connecting transmission lines is the same in the dynamic model as that in the steady-state model. The proposed control will have the VSC-HVDC mimic impedance in the dynamic model while not affecting the steady-state model. This allows the VSC-HVDC system to target improvement for dynamic problems while maintaining independence to use a different control to improve steady-state problems. To obtain optimal parameters for the enhanced small signal impedance mimicry (ESSIM) control, a sensitivity based optimal control loop is also proposed. The efficacy of the proposed algorithm is shown via case studies on a classic two area system and on the IEEE 10 generator 39 bus system.

    Finally, a multi-time scale techno-economic benefit mapping framework is proposed to aid in better economic integration of advanced transmission devices like VSC-HVDC. The proposed approach is to clearly map technical benefits to their corresponding economic causes and economic effects. The end result will be a scalar metric by which all devices can be compared. The proposed approach will address multi-time scale technical benefits and the resulting economic causes and effects providing clarity, transparency, and granularity to allow for a better one-to-one comparison of conventional and unconventional power system devices.

publication date

  • May 2016