DETERMINATION AND USE OF POWER SYSTEM SENSITIVITIES

• US 20100094477A1
• Filed: 04/03/2009
• Published: 04/15/2010
• Est. Priority Date: 10/05/2006
• Status: Active Grant

• Current Assignee: Hitachi Energy Limited
• Original Assignee: ABB Research Ltd. (ABB Ltd.)
• Inventors: Larsson, Mats, Korba, Petr, Bengtsson, Tord, Oudalov, Alexandre, Berggren, Bertil
• Granted Patent: US 8,170,723 B2
• Time in Patent Office: Days
• US Class Current: 700/297
• CPC Class Codes: H02J 3/007 Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources for providing uninterruptable power supply H02J9/00
• CPC Class Codes: H02J 3/242 using phasor measuring units [PMU]
• CPC Class Codes: Y02E 40/70 Smart grids as climate change mitigation technology in the energy generation sector
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/00 Systems supporting electrical power generation, transmission or distribution
• CPC Class Codes: Y04S 10/22 Flexible AC transmission systems [FACTS] or power factor or reactive power compensating or correcting units

Abstract

The present disclosure relates to power system sensitivities as computed from power flow parameters and control parameters of a Power Flow Control Device (PFC). To this end, control parameter variations are applied to or generated by a PFC, and comprise variations in a control input u, a control effort e (injected series voltage, inserted series reactance), or a control effect q (power flow, active power transfer, phase-shift, current). A power flow response measuring unit measures a variation of a power flow response such as current, active or apparent power, in a way sufficiently synchronized with the control parameter variation to allow establishing an unambiguous causal relationship or correspondence in the form of a power system sensitivity. The latter may be on-line adapted to continuously reflect an updated aspect of the power system behaviour, and thus enable an improved, fast and reliable power flow control in power systems comprising a meshed power network with two parallel flow paths or corridors connecting two areas or sub-systems.

Claims

1. A method of determining a power flow control correction for a meshed power network with two parallel flow paths and a first Power Flow Control Device (PFC) arranged to control, based on at least one of a first control parameter u₁, e₁, and q₁, a power flow f₁ in a first one of the two parallel flow paths, comprising

determining a variation Δ

u₁, Δ

e₁, Δ

q₁ of the first control parameter in the first one of the two parallel flow paths,

determining, in a manner timely synchronized with the determination of the variation Δ

u₁, Δ

e₁, Δ

₁ of the first control parameter, a variation M of a power flow response f_i in a second one of the two parallel flow paths, and

calculating a power system sensitivity s_i,1 based on the variation Δ

u₁, Δ

e₁, Δ

q₁ of the first control parameter and the time-synchronized variation Δ

f_i of the power flow response and utilising the power system sensitivity to determine the power control correction.

2. The method according to claim 1, comprising:

determining a variation Δ

f_i of a power flow response f_i which is a derived quantity dependent on an actual power flow in the second one of the two parallel flow paths of the meshed power network.

3. The method according to claim 1, comprising:

determining a variation of the first control parameter as a variation Δ

e₁, Δ

q₁ of a control quantity of the PFC which is instantaneously correlated to the power flow response.

4. The method according to claim 3, comprising:

determining a variation of the control quantity of the PFC which is a variation Δ

q_j of the control effect, wherein the control effect q₁ a local feedback quality.

5. The method according to claim 3, comprising:

determining a variation Δ

e₁, Δ

q₁ of the control quantity which is generated by the first PFC in response to a control input variation Δ

u₁ fed to the PFC.

6. The method according to claim 2, comprising:

determining a variation Δ

e₁, Δ

q₁ of the control quantity which is generated by the first PFC in response to a variation of the power flow f₁ in the first one of the two parallel flow paths.

7. The method according to claim 1, comprising:

calculating the power system sensitivity s_i,1 by means of a parameter estimation or correlation analysis technique, wherein s_i,1 is initially calculated as at least one of Δ

f_i/Δ

e₁, Δ

f_i/Δ

u₁, Δ

f_i/Δ

q₁.

8. The method according to claim 1, comprising:

determining time synchronized power flow response variations Δ

f_i in a plurality of locations remote from the PFC.

9. The method according to claim 6, comprising:

determining the time synchronized power flow response variation Δ

f_i by means of Phasor Measurement Units (PMU).

10. A use of a power system sensitivity s_i,1 calculated according to claim 1 for controlling power flow in a meshed power system comprising two areas interconnected by a first transfer path controlled by a first PFC and a second transfer path in parallel to the first transfer path, comprising

calculating a correction Δ

r₁ to a nominal set-point r₁ of a local controller of the first PFC based on the power system sensitivity s_i,1 and an intended change Δ

f_i of a power flow response f_i in the second transfer path given an identified overload pattern, and

applying a corrected set-point ill as a control input to the local controller of the first PFC (20) as u₁=r₁+Δ

r₁.

11. The use according to claim 10, comprising:

specifying a limit value c₁ to the power flow response f_i in the second transfer path,

measuring a power flow response f₁ in the second path,

detecting an overload situation in the second path by comparing the limit value c_i to the measured power flow response f_i, and

calculating the correction Δ

r₁ in order to relief the overload situation in the second path.

12. The use according to claim 10, comprising:

applying a plurality of the corrected set-point u₁ as a control input to a plurality of the local controller of a plurality of PFCs in a serial manner.

13. The method according to claim 5, comprising:

determining time synchronized power flow response variations Δ

f_i in a plurality of locations remote from the PFC.

14. A use of a power system sensitivity s_i,1 calculated according to claim 9 for controlling power flow in a meshed power system comprising two areas interconnected by a first transfer path controlled by a first PFC and a second transfer path in parallel to the first transfer path, comprising

calculating a correction Δ

r₁ to a nominal set-point r₁ of a local controller of the first PFC based on the power system sensitivity s_i,1 and an intended change Δ

f_i of a power flow response f_i in the second transfer path given an identified overload pattern, and

applying a corrected set-point u₁ as a control input to the local controller of the first PFC as u₁=r₁+Δ

r₁.