Phasor Monitoring Units (PMUs) are being more widely installed across the UK electricity network; as protection and control technology develops. The PMUs can detail the shape of the AC electrical wave at the monitoring point; which can be used to provide several key electrical system parameters and significantly aids knowledge of how the network operates under both normal and abnormal conditions.
Objectives
There are two key objects with this project;
· Explore if electrical system phasor measurements can be used as a means of HVDC control; and if successful;
Exploring if there are benefits to phasor measurement HVDC Control systems against present methods.
Learnings
Outcomes
The project has successfully provided GE with remote access to their servers in the National HVDC Centre via a wireless VPN connection.
In the safe environment which mimics the transmission system it was possible for GE to develop and positively prove the operation and functionality of their wide-area phasor-based monitoring solution for HVDC control. The results highlight this means of HVDC control in certain system situations such as an electrically weak network, as beneficial. Also it is recognised that there are research limitations and more testing on different network configurations is required to progress solution development.
The following project reports were prepared as a part of the project:
1. “PMU Performance Testing” - WP1: Validation of PMU models in RTDS against physical PMUs
2. “Phasor-Based Monitoring with HVDC Control” – WP2: Application of Phasor-Based Functionality to HVDC Control in Reduced System Strength (This report mainly covers the scheme design and logics)
3. “Simulations to test PBM-HVDC Control Scheme” – WP2A&B (This report covers the scheme testing using RTDS; 2A: open loop – 2B: closed loop)
4. “Simulations for the Analysis of Effective Inertia” - WP2C: Effective Inertia offline analysis
Lessons Learnt
Given the office access restriction a solution had to be found to permit GE access to their server within the National HVDC Centre. The option of a wireless VPN was selected on the assumption that it could be installed in less time than a secondary fibre optical cable. In progressing this option, it was discovered that the mobile SIM card needed a fixed address. A SIM card with the necessary fixed address is not something that can be purchased off-the-shelf, nor was it something that the SIM card suppliers could support. After much perseverance a company called Mobiuos was identified who could provide a solution to
the SIM card challenge which then enabled the wireless VPN to be established.
GE have been able to build an HVDC ‘smarter controller’ which provides a response-based approach that follows the system changes to an event rather than the prescribed event-based approach of using circuit breakers state. The disadvantages of event-based approach using circuit breakers which is the only options available today, include:
• Direct detection of pre-selected outages
• Design is model-based and may not work if the model change
• Design is deterministic and therefore doesn’t cater for all possibilities
• For larger grids more measurements may be required to monitor all the breakers
• Doesn’t always adapt to system conditions
• Over-conservative triggering
The data processing time in PhC was tested and provides fast control mode decisions in few milliseconds. In addition, PhC can send control commands via IEC 61850 GOOSE protocol, which provide a fast and secure communication.
