METHOD FOR REGULATING PRIMARY FREQUENCY OF POWER GRID BASED ON AIR CONDITIONING LOAD CLUSTER IN LARGE BUILDING

20170351228

15/609510

May 31, 2017

The present disclosure relates to a method for primary frequency regulation of an electric network based on large building air conditioning loads cluster. The method includes the use of a two layer control structure with a central coordinating layer and a local control layer. Each local controller performs a thermal model parameter identification and a local air conditioning autonomous control, and uploads local information to the central controller at the end of each communication interval tgap, the central controller broadcasts coordinating information to each local controller. Based on the coordinating information sent from the central controller, each local controller determines whether a power deviation is beyond an action dead zone at the beginning of each action period tact, if beyond, then perform a frequency regulation control action, else, perform no action and estimate operation states of all the air conditionings at the beginning of the next action period.

1. A method for regulating primary frequency of a power grid based on an air conditioning load cluster in a large building, wherein, a two-layer control structure comprising a central coordinating layer and a local control layer is used in the air conditioning load cluster, the central coordinating layer comprises a central controller, the local control layer comprises N local controllers, N air conditionings, and temperature sensors and frequency sensors provided in rooms the air conditionings located in; and the method comprises: 1) performing, by each local controller, a thermal model parameter identification and an air conditioning autonomous control to obtain local information corresponding to each of the air conditionings, and uploading the local information to the central controller at an end of each communication interval tgap, and broadcasting, by the central controller, coordinating information to each local controller; 2) when a communication between the central controller and each of the local controllers in step 1) is finished, based on the coordinating information sent from the central controller, determining, by each local controller, whether a power deviation in the air conditionings is beyond an action dead zone at a beginning of each action period tact, if yes, a frequency regulation control action is performed, else, no action is performed and operation states of all the air conditionings at a beginning of a next action period are estimated; if a current time reaches to a beginning of a next communication interval, step 1) is executed, else, step 2) is repeated.

2. The method according to claim 1, wherein, step 1) comprises: 1-1) performing, by each local controller i, i=1.2 . . . N, the room thermal model parameter identification according to air temperature data recorded at each temperature acquisition period to obtain thermal model parameters corresponding to each room; 1-2) identifying, by the local controller i, parameters of the thermal model corresponding to room i according to air temperature data recorded at each temperature acquisition period ttemp in a communication interval tgap to obtain identified thermal model parameters of each room; 1-3) performing, by each local controller, the air conditioning autonomous control according to following equations: [mathematical expression included] where, i=1.2 . . . N, Tai is an air temperature in the i th room, Δi is a temperature control dead zone corresponding to an ith air conditioning, Ti corresponds to an upper bound of the temperature control dead zone Δi, Ti corresponds to a lower bound of the temperature control dead zone Δi, Tsi is the required temperature corresponding to the i th air conditioning set by the user, statei is the on-off state of the i th conditioning, wherein statei=1 corresponds to state ON, statei=0 corresponds to state OFF; 1-4) at an end moment of the communication interval tgap between the local controller and the central controller, uploading, by each local controller, the local information to the central controller, wherein the local information comprises the indoor air temperature acquired most recently Tai of room i, the on-off state statei, the operation power Pi, the required temperature Tsi, the temperature control dead zone Δi, and the thermal model parameters αiON,γiON, αiOFF,γiOFF, Taitog, and titog; 1-5) collecting, by the central controller, all the local information from the local controllers and broadcasting all collected information to each local controller as the coordinating information, obtaining, by the central controller, a reference power P0i of each air conditioning after the thermal model parameters corresponding to each local controller are collected, obtaining a reference power P0 of all the air conditionings by summing reference powers of all the air conditionings, and broadcasting the reference power of all the air conditionings to each of the local controllers, wherein the coordinating information comprises the indoor air temperature Tai, the on-off state statei, the operation power Pi, the required temperature Tsi, the temperature control dead zone Δi, and the thermal model parameters αiON,γiON, αiOFF,γiOFF, Taitog, and titog wherein the coordination information comprises indoor air temperatures, on-off states, operation powers, required temperatures, temperature control dead zones, and thermal model parameters uploaded by all the local controller.

3. The method according to claim 2, wherein a precision degree of the thermal model parameters is determined according to a hardware storage capability of the local controller and an error requirement between a thermal model identification curve and an actual temperature curve.

4. The method according to claim 3, wherein the thermal model corresponding to ith room comprises a zero-order thermal model, a first-order thermal model, or a second-order thermal model, represented by equations (1)-(3) respectively: ΔTi=αiΔti  (1) ΔTi=αieγiΔti−αi  (2) ΔTi=αi1eγi1Δti+αi2eγi2Δti−αi1−αi2  (3) where, numbers of parameters to be identified in the three thermal models are 1, 2, and 4 respectively, αi in equation (1) is a thermal model parameter to be identified in the zero-order thermal model, αi,γi in equation (2) are thermal model parameters to be identified in the first-order thermal model, αi1,γi1,αi2,γi2 in equation (3) are thermal model parameters to be identified in the second-order thermal model, ΔTi is a difference between a current temperature Tai and an indoor temperature Taitog when an on-off state of the air conditioning is last switched, and Δti is a difference between a current time and a time titog when an on-off state of the air conditioning is last switched, where, ΔTi=Tai−Taitog  (4) Δti=ti−titog  (5) wherein, Taitog and titog are thermal model parameters.

5. The method according to claim 4, if the thermal model corresponding to ith room is the first-order thermal model, the thermal model parameters comprises αiON,γiON and αiOFF,γiOFF.

6. The method according to claim 2, wherein, the reference power P0i corresponds to an average power of the i th air conditioning during an on-off period Ti in a communication interval tgap, and step 1-5) comprises: obtaining, by the central controller, a first time ti(1), a second time ti(1), a third time ti(1), and a forth time ti(1) by solving the following equations respectively according to the upper Ti, the lower temperature bound Ti, the thermal model parameters αiON,γiON, αiOFF,γiOFF, Taitog, and titog, the required temperature Tsi, and the temperature control dead zone Δi: Ti−Taitog=αiONeγiON(ti(1)-titog)−αiON Ti−Taitog=αiONeγiON(ti(2)-titog)−αiON Ti−Taitog=αiOFFeγiOFF(ti(3)-titog)−αiOFF Ti−Taitog=αiOFFeγiOFF(ti(4)-titog)−αiOFF wherein, ti(1) is a moment when the indoor temperature is equal to the upper bound temperature Ti and the air conditioning is in an “ON” state; ti(2) is a moment when the indoor temperature is equal to the lower bound temperature Ti and the air conditioning is in an “ON” state; ti(3) is a moment when the indoor temperature is equal to the upper bound temperature Ti and the air conditioning is in an “OFF” state; ti(4) is a moment when the indoor temperature is equal to the lower bound temperature Ti and the air conditioning is in an “OFF” state; obtaining a total time period Toni when the ith air conditioning is in an “ON” state in an on-off period Ti, and a total time period Toffi when the ith air conditioning is in an “OFF” state in an on-off period Ti according to following equations: Toni=ti(1)−ti(2)  (8) Toffi=ti(4)−ti(3)  (9) obtaining the reference power P0i of each air conditioning as: [mathematical expression included] wherein, P0i is an reference power of the ith air conditioning, Toni is the total time period when the ith air conditioning is in an “ON” state in an on-off period Ti, Toffi is the total time period when the ith air conditioning is in an “OFF” state in an on-off period Ti, Pi is an operation power of the ith air conditioning; obtaining the reference power of all the air conditionings P0 by summing all the reference powers P0i of the air conditionings according to following equation: [mathematical expression included] broadcasting, by the central controller, the reference power P0 of all the air conditionings to each local controller.

7. The method according to claim 1, wherein, step 2) comprises: 2-1) acquiring, by a frequency sensor, a frequency of the power grid every action period tact, and calculating, by each local controller, a power deviation δ of all the air conditionings according to the acquired frequency of the power grid at the beginning of each action period tact; 2-2) determining, by each local controller, whether the power deviation δ is in the action dead zone ξ, when the power deviation δ is in the action dead zone ξ, the air conditioning does not participate in the frequency regulation control; when the power deviation δ is not in the action dead zone ξ, the air conditioning participates in the frequency regulation control action in the present action period; 2-3) estimating, by each local controller, on-off states of all the air conditionings at a beginning of a next action period; 2-4) estimating, by each local controller, air temperatures in other rooms at the beginning of the next action period, and modifying the on-off state statei of the i th air conditioning at the beginning of the next action period tact according to the coordinating parameters transmitted from the central controller and estimated on-off states of all the air conditionings via the air conditioning autonomous control in step 1-2), and executing step 2-1) when the next action period comes or executing step 1) when a next communication interval begins.

8. The method according to claim 7, wherein, step 2-1) comprises: calculating, by each local controller, a real-time total power P(t) of all the air conditionings according to the received coordinating information broadcasted by the central controller via following equation: [mathematical expression included] where. i=1.2 . . . N, Pi is an operation power of the ith air conditioning, statei is an on-off state of the ith air conditioning; calculating the power deviation δ of all the air conditionings according to following equation: δ=P(t)−P0−KΔf, where, P(t) is the real-time total power of all the air conditionings, P0 is the reference power of all the air conditionings, K is a power-frequency response coefficient set for all the local controllers, Δf is a real-time frequency deviation;

9. The method according to claim 7, wherein, step 2-2) comprises: 2-2-1) obtaining a temperature priority Tprii of each local controller according to following equation: [mathematical expression included] where, Tprii is a temperature priority of ith local controller, Tai is the indoor air temperature, Tsi is the required temperature corresponding to the ith air conditioning set by the user, Δi is the temperature control dead zone, statei is the on-off state of the i th air conditioning; 2-2-2) when δ>ξ, selecting temperature priorities of air conditionings whose statei=1, and generating an array quON accordingly with its rows arranged according to values of the temperature priorities in a descending order, wherein, a first column of the array is the temperature priorities, a second column is operation powers corresponding to the temperature priorities, a third column is mark numbers of air conditionings corresponding to the temperature priorities, and a number of rows in the array quON is denoted as r; selecting a minimum regulation control set which can regulate the power deviation into the dead zone according to r*=min{r|Σd=1rquON(d,2)≧δ−ξ}, extracting a set of mark numbers of air conditionings to be regulated in a present operation from the minimum regulation control set according to ION=quON(j,3), j=1, 2, . . . , r*, and calculating ION′={iεION|TaiTgoffi}, if a number of an air conditioning controller ilocalεIOFF′, controlling the air conditioning corresponding to the an air conditioning controller ilocal to participate in the present frequency regulation control, i.e. switching a state of the air conditioning corresponding to the an air conditioning controller ilocal, else, performing no action.

10. The method according to claim 1, wherein the central controller and the local controllers communicate in both-way at every communication interval, the local controllers acquire data from the temperature sensors at each temperature sampling period.

11. The method according to claim 1, wherein the local controllers regulate and control the air conditionings once during each action period according to local information and coordination information transmitted from the central controller.

12. The method according to claim 1, wherein each of the air conditionings is constant power air conditioning with an operation power and having two states; ON and OFF.

13. The method according to claim 1, wherein each temperature sensor acquires an indoor air temperature of a corresponding room in real-time, and the local controller acquires temperature data from the temperature sensors every the temperature acquisition period.

05; 05; 24; 05; 05

edspap.20170351228