A Transformation Technique for Decoupling Power Networks

Transcription

1 University of Alberta Department of Electrical and Computer Engineering A Transformation Technique for Decoupling Power Networks Iraj Rahimi Pordanjani, Yunfei Wang, and Wilsun Xu,

2 Overview 2 Introduction The proposed Transformation Decomposition of PV Curves Potential Applications Summary

3 Introduction 3 Phasor Measurement Units (PMU): The most accurate and advanced timesynchronized technology available to power engineers The network wide-area phasors (voltages and currents with synchronized phase angles) are available. How to use the data for power system analysis and monitoring is still not quite clear.

4 Introduction 4 Analogy with 3-phase data: V a V b V c I a I b I c 3-phase data PMUs data (network wide-area data) How to use the data Symmetrical Components Transform How to make effective use of the data A Support Theory Decompose the data into: Zero, positive, and negative sequences Various monitoring and protection schemes Power systems analysis and monitoring Special focus: Voltage stability analysis, and monitoring

5 The Proposed Transformation 5 A three-phase symmetrical line The symmetrical components transform is a method for decoupling the above system and is based on the eigen-decomposition of the [Z] matrix of the system

6 The Proposed Transformation 6 A general electric power network Phase coupling One generator One multi-phase line One load Multiple phase view of a power network

7 The Proposed Transformation 7 Conduct a modal transform to decouple the n-phase network into a n de-coupled networks called channel networks. Eigen-decomposition: Then: A complex network has been transformed into a set of decoupled simple circuits. By analyzing the decoupled networks, one may extract important information about the actual network.

8 Decomposition of PV Curves 8 PV curves Actual PV curves Channel PV curves Difficult to be obtained especially in online applications Can be easily obtained.

9 Decomposition of PV Curves 9 Conceptual case studies: Case study 1 responsible for power transfer

10 Decomposition of PV Curves 10 PV curves of the actual system Channel PV curve (Channel 1) The channel PV curve reaches its nose point when the physical PV curves reach their noise points.

11 Decomposition of PV Curves 11 Case study 2 The same network configuration but unequal impedances Channel 1 transfers the highest power and the maximum power transfer stops at the nose point of channel 1 PV curve. Channel 1 is the critical channel.

12 Decomposition of PV Curves 12 Results for IEEE 30-bus system:

13 Decomposition of PV Curves 13 Results for IEEE 57-bus system:

14 Potential Applications 14 Monitoring the stability level by monitoring the critical channel s margin. Identification of the critical load by determining the contributions of loads to the critical channel s load. Identification of the critical generator by determining the contributions of generators to the critical channel s voltage source....

15 Summary 15 A transformation has been proposed to convert a complex power system into simple decoupled modal networks. By analyzing and monitoring the characteristics of modal networks, one can extract important information about the actual system. This paper has presented the progress made on the voltage stability analysis and monitoring using the proposed transform. It has been shown that the PV curves of decoupled modal networks may be used instead of actual PV curves to monitor the voltage stability.

16 16 Thanks for your attention

17 Current Research Progress Critical Load Identification 17 Once the critical channel is known, it can be used to identify the critical bus. Low stability margin Large voltage drop The critical load bus is the most responsible for the voltage drop of the critical channel. Since the channel voltage drop is caused by the channel current, the contribution of bus currents I to the critical channel current J i can be used. The bus whose current has the highest contribution to the critical channel current is the critical bus. Verifications methods: Modal analysis method The sensitivity of loadability margin with respect to load shedding at different load buses

18 Current Research Progress Critical Load Identification 18 Bus ranking results in IEEE 30-bus system: Proposed index Modal analysis method Sensitivity-based method

19 Current Research Progress Critical Load Identification 19 Bus ranking results in IEEE 57-bus system: Proposed index Modal analysis method Sensitivity-based method

20 Current Research Progress Critical Load Identification 20 Summary of results: System Critical channel Critical load bus Proposed mthod Modal analysis Sensitivity-based 6-bus WSCC 9-bus bus IEEE 30-bus IEEE 57-bus AIES 2038-bus The proposed method can accurately identify the critical bus.