Determination and use of power system sensitivities
View Patent ↗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 behavior, 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.
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 u 1 , e 1 , and q 1 , a power flow f 1 in a first one of the two parallel flow paths, comprising:
determining a variation Δu 1 , Δe 1 , Δq 1 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 Δu 1 , Δe 1 , Δq 1 of the first control parameter, a variation Δf i of a power flow response f i in a second one of the two parallel flow paths;
calculating a power system sensitivity s i,1 based on the variation Δu 1 , Δe 1 , Δq 1 of the first control parameter and the time-synchronized variation Δf i of the power flow response in the second one of the two parallel flow paths, wherein the power system sensitivity s i,1 is calculated by means of a parameter estimation or correlation analysis technique, and wherein s i,1 is initially calculated as at least one of Δf i /Δe 1 , Δf i /Δu 1 , Δf i /Δq 1 ; and
utilising the power system sensitivity to determine the power control correction of the power flow in the first one of the two parallel flow paths.
2. The method according to claim 1 , comprising:
determining a variation Δf 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 Δe 1 , Δq 1 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 Δq j of the control effect, wherein the control effect q 1 a local feedback quality.
5. The method according to claim 3 , comprising:
determining a variation Δe 1 , Δq 1 of the control quantity which is generated by the first PFC in response to a control input variation Δu 1 fed to the PFC.
6. The method according to claim 2 , comprising:
determining a variation Δe 1 , Δq 1 of the control quantity which is generated by the first PFC in response to a variation of the power flow f 1 in the first one of the two parallel flow paths.
7. The method according to claim 1 , comprising:
determining time synchronized power flow response variations Δf i in a plurality of locations remote from the PFC.
8. The method according to claim 6 , comprising:
determining the time synchronized power flow response variation Δf i by means of Phasor Measurement Units (PMU).
9. 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 Δr 1 to a nominal set-point r 1 of a local controller of the first PFC based on the power system sensitivity s i,1 and an intended change Δf i based on the power system sensitivity s i,1 and a change Δf i of a power flow response f i in the second transfer path, the change Δfi configured to overcome an identified overload pattern; and
applying a corrected set-point u 1 as a control input to the local controller of the first PFC ( 20 ) as u 1 =r 1 +Δr 1 .
10. The use according to claim 9 , comprising:
specifying a limit value c i to the power flow response f i in the second transfer path,
measuring a power flow response f i 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 Δr 1 in order to relief the overload situation in the second path.
11. The use according to claim 9 , comprising:
applying a plurality of the corrected set-point u 1 as a control input to a plurality of the local controller of a plurality of PFCs in a serial manner.
12. The method according to claim 5 , comprising:
determining time synchronized power flow response variations Δf i in a plurality of locations remote from the PFC.
13. A use of a power system sensitivity s i,1 calculated according to claim 8 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 Δr 1 to a nominal set-point r 1 of a local controller of the first PFC based on the power system sensitivity s o and an intended change Δf i of a power flow response f i in the second transfer path given an identified overload pattern, and
applying a corrected set-point u 1 as a control input to the local controller of the first PFC as u 1 =r 1 +Δr 1 .