A frequency modulation method considering the flexible exit of thermal inertia of integrated energy system

Abstract

The present invention discloses a frequency modulation method that takes into account the flexible exit of thermal inertia of an integrated energy system. First, the slow-motion characteristics of the thermal system in the integrated energy system are deeply explored and modeled, and then the potential of thermal inertia to respond to power shortages in the power grid is used to provide support for power grid frequency failures. At the same time, the importance of heat demand to different heat loads is considered, allowing thermal inertia to be flexibly exited during the frequency modulation process according to the importance of heat demand. The present invention proposes a new idea for supporting power grid frequency failures, which ensures that the thermal inertia of the integrated energy system is fully utilized while also ensuring the heat demand of the load, thereby enhancing the safety and flexibility of system operation.

Description

Technical Field

[0001] The invention relates to a frequency modulation method for flexible exit of thermal inertia of an integrated energy system, belonging to the technical field of integrated energy. Background Art

[0002] In recent years, the extensive use of renewable energy in the power grid has greatly reduced the inertia of the system. At the same time, because renewable energy itself is volatile and uncertain, it is difficult to maintain the power balance between the supply and demand sides of the power grid, and the stability of the power grid frequency is severely challenged. Taking into account the electrical and thermal multi-energy coupling within the integrated energy system, unlike the fast dynamic characteristics of the power system, the thermal system is a slow dynamic system, which can provide a buffer space for energy fluctuations and increase the inertia of the system. Therefore, the slow dynamic characteristics of the thermal system are defined as thermal inertia, and the use of the slow dynamic characteristics of the thermal system to support the frequency drop of the power grid is considered to ensure the reliability and safety of the system operation. At the same time, considering the importance of heat demand to different heat loads, thermal inertia is allowed to be flexibly exited during the frequency modulation process according to the importance of heat demand, while ensuring the safe operation of the system and minimizing the impact on heat consumption on the load side. Summary of the invention

[0003] The present invention proposes a frequency modulation method that takes into account the flexible exit of the thermal inertia of the integrated energy system, fully utilizing the characteristic of the thermal inertia of the integrated energy system to provide a buffer space for energy fluctuations, and improving the economic efficiency of system operation while ensuring the reliability level of the system.

[0004] The present invention adopts the following technical solutions to solve the above technical problems:

[0005] A frequency modulation method taking into account the flexible exit of thermal inertia of an integrated energy system. The method comprises the following steps:

[0006] (1) Establish a thermal inertia power support model for the integrated energy system, including:

[0007] 1) Explore the inertial characteristics of the thermal system of the integrated energy system;

[0008] 2) Establish a thermal inertia power support model for the integrated energy system;

[0009] 3) Establish a thermal inertia power shortage response model for the integrated energy system;

[0010] (2) Establish a thermal inertia frequency modulation model for the integrated energy system, including:

[0011] 1) Provide a method for responding to thermal inertia after a frequency fault;

[0012] 2) Establish a thermal inertia frequency response model with the goal of minimizing the total frequency modulation cost;

[0013] (3) Considering the flexible exit of thermal inertia in the integrated energy system, a thermal inertia flexible exit model is established based on the actual heat demand on the load side;

[0014] Further, step (1) is specifically as follows:

[0015] 1) Exploring the inertial characteristics of the thermal system of the integrated energy system:

[0016] Thermal energy in the integrated energy system is a flexible demand energy, which divides the heat network into three parts: heat source, transmission pipeline, and heat load. The heat power transmitted from the heat source to the heat network is mainly transmitted by hot water. When hot water passes through the transmission pipeline, due to the temperature difference between the inside and outside of the pipeline, part of the heat in the hot water will be dissipated, resulting in heat loss. This part of the heat loss is expressed as:

[0017] H loss,p =μ p l p

[0018] In the formula, μ p is the heat loss rate of the transmission pipeline, l p is the transmission pipeline length, H loss,p is the heat loss of the transmission pipeline.

[0019] When the hot water reaches the load side, due to the temperature difference between the inside and outside of the load side building itself, some heat will be lost. This part of the heat loss is expressed as:

[0020] H loss,b =ε loss (T b,t -T out,t )

[0021] In the formula, H loss,b is the heat loss rate of the building, ε loss is the building heat dissipation coefficient, T b,t is the indoor temperature of the building at time t, T out,t is the outdoor temperature at time t.

[0022] If power fluctuations occur at the heat source, the impact on the load will be greatly reduced after reaching the load side due to heat loss in the transmission pipeline and the load-side building. At the same time, since the temperature on the load side does not need to be strictly maintained at a specific value, but can be kept within a comfort range, the power fluctuations entering the heat network from the heat source will not have too much impact on the load side. This characteristic is the thermal fuzziness of thermal inertia.

[0023] When the power fluctuation at the heat source is transmitted to the heat network, due to the long hot water transmission pipeline, the disturbance will reach the user side after a certain delay, thereby reducing the time for the load side temperature to bottom out or peak, which has a certain effect of reducing the impact of the disturbance. This characteristic is the thermal hysteresis characteristic of thermal inertia, and the expression is as follows:

[0024] τ p = l p / v p

[0025] In the formula, l p is the transmission pipeline length, v p is the hot water flow rate, τ p Thermal delay.

[0026] In summary, the thermal inertia of the integrated energy system is the thermal lag caused by the long transmission pipeline, as well as the thermal fuzziness caused by the heat loss during the transmission process and the comfort range on the load side. The integrated energy system maintains the system state or resists external changes through thermal inertia to provide power support for the system. The above-mentioned heat loss in the pipeline and thermal lag cause the heat input of the heat source to change. The total expression is as follows:

[0027]

[0028] In the formula, H in,t Input thermal power for the heat source, =t+l p / v p After a certain time, the heat network outputs heat.

[0029] Due to the thermal inertia of the load-side building shown above, the total expression of its temperature change is as follows:

[0030]

[0031] In the formula, Δt is the time variable, T b,t+Δt is the indoor temperature of the building at time t+Δt, T b,t is the indoor temperature of the building at time t, H b,t is the heat power transferred to the building at time t, C is the specific heat capacity of the indoor air, M s It’s the indoor air quality.

[0032] 2) Establish a thermal inertia power support model for the integrated energy system:

[0033] When power fluctuations occur at the heat source, the response of thermal inertia is mainly reflected in the indoor temperature of the thermal building. When the outdoor temperature remains unchanged, the above thermal inertia model is simplified to obtain the first-order response model of the indoor temperature of the thermal building, that is, the simplified thermal system model, which is expressed as follows:

[0034]

[0035] Where, T b (t) is the temperature of the load-side building at time t, H b (t) is the heating power of the heating network to the load-side building at time t. out is the outdoor temperature, which is a constant.

[0036] Performing Laplace transform on the above equation, we can get:

[0037]

[0038] Assume that the heating power provided by the heat network to the load-side building is 1 The moment decreases instantaneously from the normal value H b,1 Down to H b,2 , the process can be expressed as follows:

[0039] H b (tt 1 )=(H b,2 -H b,1 )ε(tt 1 )+H b,1

[0040] Perform an inverse Laplace transform on the simplified thermal system equation that has been Laplace transformed, and substitute the above formula into it, and the load-side building indoor temperature response model expression can be obtained as follows. For power fluctuations at the heat source, the power support of the thermal network is mainly reflected in the indoor temperature, so the following formula is the thermal inertia power support model:

[0041]

[0042] 3) Establish a thermal inertia power shortage response model for the integrated energy system:

[0043] The fitting formula of the thermal inertia support power and support time based on simulation is as follows. The power support provided by the thermal inertia of the integrated energy system changes in a negative exponential form over time:

[0044]

[0045] Where M 1 、N 1 、u 1 、v 1 All are constant coefficients. r,h is the response power of thermal inertia to power shortage, t r,h The thermal inertia of the integrated energy system has the potential to respond to power shortages, which can be used to provide emergency frequency support for the grid.

[0046] Further, step (2) is specifically as follows:

[0047] 1) Provide a method for thermal inertia response after frequency fault:

[0048] When a power grid fails, under the premise that the total power supply of the external power grid remains unchanged, part of the power can be rearranged to the transformer side instead of the electric boiler side to increase the power supply and make up for the power shortage. This method will cause the heat on the load side to shift, and the actual heat delivered will deviate from the specified heat. At this time, thermal fuzziness is used to sacrifice some user comfort to achieve the purpose of temporarily providing frequency response for the power grid. The expression of the heat shift on the load side caused by the redistribution of power is as follows:

[0049]

[0050] Where RH(t) is the amount of electricity transferred from the electric boiler side to the transformer side during period t, η EB is the efficiency of the electric boiler, P h (t) is the total thermal offset on the load side.

[0051] 2) Establish a thermal inertia frequency response model with the goal of minimizing the total frequency modulation cost:

[0052] The entire primary frequency regulation process is divided into two stages, using the thermal inertia of the integrated energy system to provide emergency support for grid frequency failures, with the goal of minimizing the total frequency regulation cost while ensuring the safety and reliability of system operation:

[0053]

[0054] Where Cost is the total cost of frequency regulation, CCOM 1 is the user comfort cost in stage 1, is the frequency offset penalty cost in stage 1, is the frequency offset penalty cost in phase 2, CCOM 2 is the user comfort cost in stage 2. Among them, for stage 1, the user comfort cost is In the formula, is the comfort cost price per user of the i-th order, is the heat offset of the i-th load side in period t, N is a time value in the frequency modulation process; for the frequency offset penalty cost of stage 1 In the formula, γ 1 is the frequency offset penalty coefficient of stage 1, f 0 is the specified frequency response value, f 1 The frequency response optimization value for stage one; the frequency offset penalty cost for stage two In the formula, γ 2is the frequency offset penalty coefficient of stage 2, f 2 For the phase II frequency response optimization value; for the phase II user comfort cost In the formula, is the comfort cost price per user of the i-th order, is the heat offset of the i-th load side in period t, M is the total frequency modulation time, M ≥ N. It is particularly noted that the user comfort cost adopts a ladder price, which is divided into Class A response levels. A is the total number of ladders in the user comfort cost ladder price.

[0055] For the thermal inertia frequency response optimization model, the electric power balance constraint expression is as follows:

[0056]

[0057] In the formula, k g is the unit adjustment coefficient, f 0 (t) is the frequency value of the specified curve in time period t, f 1 (t) is the value of the optimized frequency response curve in stage 1, f 2 (t) is the value of the optimized frequency response curve in stage 1, η T is the transformer efficiency, deltaP(t) is the power deficit that needs to be optimized.

[0058] For the thermal inertia frequency response optimization model, the output constraints and ramp constraints at each stage are expressed as follows:

[0059]

[0060] In the formula, α 1 is the maximum thermal inertia output in stage 1, α 2 is the maximum value of thermal inertia output in stage 2; β 1 , β 2 They are the maximum values ​​of thermal inertia output ramp in stage 1 and stage 2 respectively, N is a certain time value in the frequency modulation process, M is the total frequency modulation time, M≥N.

[0061] For the thermal inertia frequency response optimization model, the frequency offset constraint expressions for each stage are as follows:

[0062]

[0063] In the formula, f 0 (t) is the frequency response curve value specified in the t period, f 1 (t) is the frequency response curve value of the t period obtained by optimization in stage 1, f 2 (t) is the frequency response curve value of time period t obtained by optimization in stage 2.

[0064] Further, step (3) is specifically as follows:

[0065] In the above thermal inertia frequency response model, the overall frequency response process is divided into two stages, with the period before N defined as stage 1 and the period after N to M (the end of one frequency modulation) defined as stage 2. Considering the different importance of heat demand to different heat loads, the load-side thermal constraints should be determined according to the specific situation, so thermal inertia is allowed to partially exit during the frequency modulation process.

[0066] According to the different requirements for frequency modulation effect and the different importance of heat demand to different heat loads, two frequency offset penalty coefficients γ are used. 1 , γ 2 The setting is used to control the flexibility of thermal inertia in frequency modulation and determine the effect of the optimized frequency response curve. The expression is as follows:

[0067]

[0068] In the formula, λ 1 and λ 2 is a constant coefficient; F res (t) is the requirement for the frequency modulation effect in time period t, F res (t) is larger, the frequency offset penalty coefficient γ in period t is 1 The larger (t) is, the higher the penalty cost of frequency offset in stage 1 is. In the thermal inertia frequency response model with the goal of minimizing the total cost of frequency modulation, it can reduce the frequency offset to avoid increasing the total cost. imp (t) is the importance of heat demand to heat load during period t, L imp The larger (t) is, the more important the heat demand is to the heat load, because 2 is negative, then γ 1 The smaller (t), the lower the penalty cost of frequency deviation in stage 1. In the thermal inertia frequency response model with the goal of minimizing the total frequency regulation cost, the heat restriction on the load side can be reduced, but some frequency regulation effects are sacrificed. The above process is the same for stage 2. Therefore, γ 1 (t) and γ 2 The value of (t) determines the amount of thermal inertia output of the integrated energy system participating in the frequency response, giving the ability for thermal inertia to flexibly exit while taking into account the frequency regulation effect.

[0069] Beneficial effects:

[0070] The present invention fully considers the slow dynamic characteristics of the thermal system of the integrated energy system, explores the thermal inertia characteristics of the integrated energy system, and uses the established thermal inertia power support model and thermal inertia power shortage response model of the integrated energy system to provide support for power grid frequency failures. While ensuring the frequency regulation effect, the importance of heat demand to different heat loads is considered, and the operating thermal inertia is flexibly retreated in part during the frequency regulation process, thereby ensuring the safety of system operation and enhancing the flexibility of system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0072] Figure 1 is a general flow chart of the method of the present invention;

[0073] Figure 2 It is a schematic diagram of thermal inertia principle;

[0074] Figure 3 It is a schematic diagram of thermal inertia power support;

[0075] Figure 4 This is a schematic diagram of the power shortage response of the thermal inertia coping system;

[0076] Figure 5 This is the frequency modulation result diagram for flexible exit taking into account thermal inertia. DETAILED DESCRIPTION

[0077] The technical solution provided by the present invention will be described in detail below in conjunction with specific examples. It should be understood that the following specific implementation methods are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0078] A frequency modulation method taking into account the flexible exit of thermal inertia of integrated energy system, such as Figure 1 As shown, the following steps are included:

[0079] (1) Establishing a thermal inertia power support model for an integrated energy system

[0080] 1) Exploring the inertial characteristics of the thermal system of the integrated energy system:

[0081] Thermal energy in the integrated energy system is a flexible demand energy, such as Figure 2 As shown, the heat network can be divided into three parts: heat source, transmission pipeline, and heat load. The heat power transmitted from the heat source to the heat network is mainly transmitted through hot water. When hot water passes through the transmission pipeline, due to the temperature difference between the inside and outside of the pipeline, part of the heat in the hot water will be dissipated, resulting in heat loss. This part of the heat loss is expressed as:

[0082] H loss,p =μ p l p

[0083] In the formula, μ p is the heat loss rate of the transmission pipeline, l p is the transmission pipeline length, H loss,p is the heat loss of the transmission pipeline.

[0084] When the hot water reaches the load side, due to the temperature difference between the inside and outside of the load side building itself, some heat will be lost. This part of the heat loss is expressed as:

[0085] H loss,b =ε loss (T b,t -T out,t )

[0086] In the formula, H loss,b is the heat loss rate of the building, ε loss is the building heat dissipation coefficient, T b,t is the indoor temperature of the building at time t, T out,t is the outdoor temperature at time t.

[0087] Therefore, if power fluctuations occur at the heat source, the impact on the load will be greatly reduced after reaching the load side due to heat loss in the transmission pipeline and the load-side building. At the same time, since the temperature on the load side does not need to be strictly maintained at a specific value, but can be kept within a comfort range, the power fluctuations entering the heat network from the heat source will not have too much impact on the load side. This characteristic is the thermal fuzziness of thermal inertia.

[0088] When the power fluctuation at the heat source is transmitted to the heat network, due to the long hot water transmission pipeline, the disturbance will reach the user side after a certain delay, thereby reducing the time for the load side temperature to bottom out or peak, which has a certain effect of reducing the impact of the disturbance. This characteristic is the thermal lag of thermal inertia, and the expression is as follows:

[0089] τ p = l p / v p

[0090] In the formula, l p is the transmission pipeline length, v p is the hot water flow rate, τ p Thermal delay.

[0091] In summary, the thermal inertia of the integrated energy system is the thermal lag caused by the long transmission pipeline, as well as the thermal fuzziness caused by the heat loss during the transmission process and the comfort range on the load side. The integrated energy system maintains the system state or resists external changes through thermal inertia to provide power support for the system. The above-mentioned heat loss in the pipeline and thermal lag cause the heat input of the heat source to change. The total expression is as follows:

[0092]

[0093] In the formula, H in,t Input thermal power for the heat source, = t+l p / v pAfter a certain time, the heat network outputs heat.

[0094] Due to the thermal inertia of the load-side building shown above, the total expression of its temperature change is as follows:

[0095]

[0096] In the formula, Δt is the time variable, T b,t+Δt is the indoor temperature of the building at time t+Δt, T b,t is the indoor temperature of the building at time t, H b,t is the heat power transferred to the building at time t, C is the specific heat capacity of the indoor air, M s It’s the indoor air quality.

[0097] 2) Establish a thermal inertia power support model for the integrated energy system

[0098] When power fluctuations occur at the heat source, the response of thermal inertia is mainly reflected in the indoor temperature of the thermal building. When the outdoor temperature remains unchanged, the above thermal inertia definition model is simplified to obtain the first-order response model of the indoor temperature of the thermal building, that is, the simplified thermal system model, which is expressed as follows:

[0099]

[0100] Where, T b (t) is the temperature of the load-side building at time t, H b (t) is the heating power of the heating network to the load-side building at time t. out is the outdoor temperature, which is a constant.

[0101] Performing Laplace transform on the above equation, we can get:

[0102]

[0103] Assume that the heating power provided by the heat network to the load-side building is 1 The moment decreases instantaneously from the normal value H b,1 Down to H b,2 , the process can be expressed as follows:

[0104] H b (tt 1 )=(H b,2 -H b,1 )ε(tt 1 )+H b,1

[0105] Perform an inverse Laplace transform on the simplified thermal system equation that has been Laplace transformed, and substitute the above formula into the load-side building indoor temperature response model expression as follows. For power fluctuations at the heat source, the power support of the thermal network is mainly reflected in the indoor temperature, so the following formula is the thermal inertia power support model, and its schematic diagram is as follows Figure 3 As shown:

[0106]

[0107] 3) Establish a thermal inertia power shortage response model for the integrated energy system:

[0108] The fitting formula of the thermal inertia support power and support time based on simulation is as follows. The power support provided by the thermal inertia of the integrated energy system changes in a negative exponential form over time:

[0109]

[0110] Where M 1 、N 1 、u 1 、v 1 All are constant coefficients. r,h is the response power of thermal inertia to power shortage, t r,h The thermal inertia response time to power shortage. The thermal inertia of the integrated energy system has the potential to respond to power shortages in the power grid, which can be used to provide emergency frequency support for the power grid. The thermal inertia support power and support time curve is shown in the figure below: Figure 4 shown.

[0111] (2) Establishing a thermal inertia frequency modulation model for an integrated energy system

[0112] 1) Provide a method for responding to thermal inertia after a frequency fault:

[0113] Thermal inertia response process Figure 1 As shown. When a power grid fails, under the premise that the total power supply of the external power grid remains unchanged, part of the power can be rearranged to the transformer side instead of the electric boiler side to increase the power supply and make up for the power shortage. This method will cause the heat on the load side to shift, and the actual heat delivered will deviate from the specified heat. At this time, thermal fuzziness is used to sacrifice some user comfort to achieve the purpose of temporarily providing frequency response for the power grid. The expression of the heat shift on the load side caused by the redistribution of power is as follows:

[0114]

[0115] Where RH(t) is the amount of electricity transferred from the electric boiler side to the transformer side during period t, η EB is the efficiency of the electric boiler, P h(t) is the total thermal offset on the load side.

[0116] 2) Establish a thermal inertia frequency response model with the goal of minimizing the total frequency modulation cost:

[0117] The entire primary frequency regulation process is divided into two stages, using the thermal inertia of the integrated energy system to provide emergency support for grid frequency failures, with the goal of minimizing the total frequency regulation cost while ensuring the safety and reliability of system operation:

[0118]

[0119] Where Cost is the total cost of frequency regulation, CCOM 1 is the user comfort cost in stage 1, is the frequency offset penalty cost in stage 1, is the frequency offset penalty cost in phase 2, CCOM 2 is the user comfort cost in stage 2. Each discrete model is established as follows:

[0120] Stage 1 User Comfort Model:

[0121]

[0122] In the formula, is the comfort cost price per user of the i-th order, is the heat offset of the i-th load side in period t, and N is a time value in the frequency modulation process.

[0123] Phase 1 frequency offset penalty model:

[0124] P 1 f =γ 1 |f 0 -f 1 |

[0125] In the formula, γ 1 is the frequency offset penalty coefficient of stage 1, f 0 is the specified frequency response value, f 1 Frequency response optimization value for stage one.

[0126] Phase II frequency offset penalty model:

[0127]

[0128] In the formula, γ 2 is the frequency offset penalty coefficient of stage 2, f 2 Optimize the value for the stage 2 frequency response.

[0129] Phase 2 User Comfort Model:

[0130]

[0131] In the formula, is the comfort cost price per user of the i-th order, is the heat offset of the i-th load side in period t, M is the total frequency modulation time, M ≥ N. It is particularly noted that the user comfort cost adopts a ladder price, which is divided into Class A response levels. A is the total number of ladders in the user comfort cost ladder price.

[0132] Thermal inertia frequency response optimization model, the electric power balance constraint expression is as follows:

[0133]

[0134] In the formula, k g is the unit adjustment coefficient, f 0 (t) is the frequency value of the specified curve in time period t, f 1 (t) is the value of the optimized frequency response curve in stage 1, f 2 (t) is the value of the optimized frequency response curve in stage 1, η T is the transformer efficiency, deltaP(t) is the power deficit that needs to be optimized.

[0135] Thermal inertia frequency response optimization model, the output constraint and climbing constraint expressions at each stage are as follows:

[0136]

[0137] In the formula, α 1 is the maximum thermal inertia output in stage 1, α 2 is the maximum value of thermal inertia output in stage 2; β 1 , β 2 They are the maximum values ​​of thermal inertia output ramp in stage 1 and stage 2 respectively, N is a certain time value in the frequency modulation process, M is the total frequency modulation time, M≥N.

[0138] Thermal inertia frequency response optimization model, the frequency offset constraint expressions at each stage are as follows:

[0139]

[0140] In the formula, f 0 (t) is the frequency response curve value specified in the t period, f 1 (t) is the frequency response curve value of the t period obtained by optimization in stage 1, f 2 (t) is the frequency response curve value of time period t obtained by optimization in stage 2.

[0141] (3) Considering the flexible exit of thermal inertia in the integrated energy system, a thermal inertia flexible exit model is established based on the actual heat demand on the load side.

[0142] In the above thermal inertia frequency response model, the overall frequency response process has been divided into two stages, with the period before N defined as stage 1 and the period after N to M (the end of one frequency modulation) defined as stage 2. Considering the different importance of heat demand to different heat loads, the load-side thermal constraints should be determined according to the specific situation, so thermal inertia is allowed to partially exit during the frequency modulation process.

[0143] According to the different requirements for frequency modulation effect and the different importance of heat demand to different heat loads, two frequency offset penalty coefficients γ are used. 1 , γ 2 The setting is used to control the flexibility of thermal inertia in frequency modulation and determine the effect of the optimized frequency response curve. The expression is as follows:

[0144]

[0145] In the formula, λ 1 and λ 2 is a constant coefficient; F res (t) is the requirement for the frequency modulation effect in time period t, F res (t) is larger, the frequency offset penalty coefficient γ in period t is 1 The larger (t) is, the higher the penalty cost of frequency offset in stage 1 is. In the thermal inertia frequency response model with the goal of minimizing the total cost of frequency modulation, it can reduce the frequency offset to avoid increasing the total cost. imp (t) is the importance of heat demand to heat load during period t, L imp The larger (t) is, the more important the heat demand is to the heat load, because 2 is negative, then γ 1 The smaller (t), the lower the penalty cost of frequency deviation in stage 1. In the thermal inertia frequency response model with the goal of minimizing the total frequency regulation cost, the heat restriction on the load side can be reduced, but some frequency regulation effects are sacrificed. The above process is the same for stage 2. Therefore, γ 1 (t) and γ 2 The value of (t) determines the amount of thermal inertia output of the integrated energy system participating in the frequency response, giving the ability for thermal inertia to flexibly exit while taking into account the frequency regulation effect. Figure 5 The following figure shows different simplified frequency offset penalty coefficients γ for the same frequency fault and the same specified frequency response curve. 1 (t) and γ 2 (t) The different frequency adjustment effects obtained.

[0146] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above-mentioned technical features. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. A frequency modulation method taking into account the flexible exit of thermal inertia of an integrated energy system, characterized in that: The steps include: (1) Establish a thermal inertia power support model for the integrated energy system, including: 1) Explore the inertial characteristics of the thermal system of the integrated energy system; 2) Establish a thermal inertia power support model for the integrated energy system; 3) Establish a thermal inertia power shortage response model for the integrated energy system; (2) Establish a thermal inertia frequency modulation model for the integrated energy system, including: 1) Provide a method for responding to thermal inertia after a frequency fault; 2) Establish a thermal inertia frequency response model with the goal of minimizing the total frequency modulation cost; (3) Considering the flexible exit of thermal inertia in the integrated energy system, a thermal inertia flexible exit model is established based on the actual heat demand on the load side; Step (1) is specifically as follows: 1) Exploring the inertial characteristics of the thermal system of the integrated energy system: Thermal energy in the integrated energy system is a flexible demand energy. The heat network is divided into three parts: heat source, transmission pipeline, and heat load. The heat power transmitted from the heat source to the heat network is mainly transmitted through hot water. When hot water passes through the transmission pipeline, due to the temperature difference between the inside and outside of the pipeline, part of the heat in the hot water will be dissipated, resulting in heat loss. This part of the heat loss is expressed as: H loss,p =μ p l p In the formula, μ p is the heat loss rate of the transmission pipeline, l p is the transmission pipeline length, H loss,p It is the heat loss of the transmission pipeline; When the hot water reaches the load side, due to the temperature difference between the inside and outside of the load side building itself, some heat will be lost. This part of the heat loss is expressed as: H loss,b =ε loss (T b,t -T out,t ) In the formula, H loss,b is the heat loss rate of the building, ε loss is the building heat dissipation coefficient, T b,t is the indoor temperature of the building at time t, T out,t is the outdoor temperature at time t; If power fluctuations occur at the heat source, the impact on the load will be greatly reduced after reaching the load side due to heat loss in the transmission pipeline and the load-side building; at the same time, since the temperature on the load side does not need to be strictly maintained at a specific value, but can be maintained within a comfort range, the power fluctuations entering the heat network from the heat source will not have too much impact on the load side; this characteristic is the thermal fuzziness of thermal inertia; When the power fluctuation at the heat source is transmitted to the heat network, due to the long hot water transmission pipeline, the disturbance will reach the user side after a certain delay, thereby reducing the time for the load side temperature to bottom out or peak, which has a certain effect of reducing the impact of the disturbance; this characteristic is the thermal lag of thermal inertia, and the expression is as follows: t p =l p / v p In the formula, l p is the transmission pipeline length, v p is the hot water flow rate, τ p It is thermal delay; The heat loss in the pipeline and the thermal lag above change the heat input from the heat source to the heat network. The overall expression is as follows: In the formula, H in,t Input thermal power for the heat source, = t+l p / v p After a certain time, the heat network outputs heat; Due to the thermal inertia of the load-side building shown above, the total expression of its temperature change is as follows: Where Δt is the time variable, C is the specific heat capacity of the indoor air, M s is the indoor air quality, T b,t+Δt is the indoor temperature of the building at time t+Δt, T b,t is the indoor temperature of the building at time t, H b,t is the heat power transferred to the building at time t; 2) Establish a thermal inertia power support model for the integrated energy system: When power fluctuation occurs at the heat source, the response of thermal inertia is mainly reflected in the indoor temperature of the thermal building. When the outdoor temperature remains unchanged, the above thermal inertia model is simplified to obtain the first-order response model of the indoor temperature of the thermal building, that is, the simplified thermal system model, which is expressed as follows: Where, T b (t) is the temperature of the load-side building at time t, H b (t) is the heating work of the heating network to the load-side building at time t; T out is the outdoor temperature, which is a constant; Performing Laplace transform on the above equation, we can get: Assume that the heating power supplied by the heat network to the load-side building decreases instantaneously at time t1, from the normal value H b,1 Down to H b,2 , the process can be expressed as follows: H b (t-t1)=(H b,2 -H b,1 )ε(t-t1)+H b,1 Perform an inverse Laplace transform on the simplified thermal system equation that has been Laplace transformed, and substitute the above formula into it, and the expression of the load-side building indoor temperature response model can be obtained as follows; for power fluctuations at the heat source, the power support of the thermal network is mainly reflected in the indoor temperature, so the following formula is the thermal inertia power support model: 3) Establish a thermal inertia power shortage response model for the integrated energy system: The fitting formula of the thermal inertia support power and support time based on simulation is as follows. The power support provided by the thermal inertia of the integrated energy system changes in a negative exponential form over time: In the formula, M1, N1, u1, v1 are all constant coefficients, P r,h is the response power of thermal inertia to power shortage, t r,h The response time of thermal inertia to power shortage; the thermal inertia of the integrated energy system has the potential to respond to power shortage of the power grid, which can be used to provide emergency frequency support for the power grid.

2. A frequency modulation method taking into account the flexible exit of thermal inertia of an integrated energy system according to claim 1, characterized in that: Step (2) is specifically as follows: 1) Provide a method for responding to thermal inertia after a frequency fault; When a power grid fails, under the premise that the total power supply of the external power grid remains unchanged, part of the power can be rearranged to the transformer side instead of the electric boiler side to increase the power supply and make up for the power shortage; this method will cause the heat on the load side to shift, and the actual heat delivered will deviate from the specified heat. At this time, thermal fuzziness is used to sacrifice some user comfort to achieve the purpose of providing frequency response for the power grid for a short time; the expression of the heat shift on the load side caused by the redistribution of power is as follows: Where RH(t) is the amount of electricity transferred from the electric boiler side to the transformer side during period t, η EB is the efficiency of the electric boiler, P h (t) is the total thermal offset on the load side, M is the total time of thermal inertia frequency modulation; 2) Establish a thermal inertia frequency response model with the goal of minimizing the total frequency modulation cost: The entire primary frequency regulation process is divided into two stages, using the thermal inertia of the integrated energy system to provide emergency support for grid frequency failures, with the goal of minimizing the total frequency regulation cost while ensuring the safety and reliability of system operation: min Cost=CCOM1+P1 f +P2 f +CCOM2 In the formula, Cost is the total cost of frequency regulation, CCOM1 is the user comfort cost in stage 1, is the frequency offset penalty cost in stage 1, is the frequency offset penalty cost in stage 2, CCOM2 is the user comfort cost in stage 2; where, for stage 1 user comfort cost In the formula, is the comfort cost price per user of the i-th order, is the heat offset of the i-th load side in period t, N is a time value in the frequency modulation process; for the frequency offset penalty cost P1 in stage 1 f =γ1|f0-f1|, where γ1 is the frequency offset penalty coefficient of stage 1, f0 is the specified frequency response value, and f1 is the frequency response optimization value of stage 1; for stage 2 frequency offset penalty cost Where γ2 is the frequency offset penalty coefficient of the second stage, f2 is the frequency response optimization value of the second stage; for the user comfort cost of the second stage In the formula, is the comfort cost price per user of the i-th order, is the heat offset of the i-th load side in period t, M is the total frequency modulation time, M≥N; it should be noted that the user comfort cost adopts a ladder price, which is divided into Class A response level; A is the total number of ladder prices of user comfort cost; For the thermal inertia frequency response optimization model, the electric power balance constraint expression is as follows: In the formula, k g is the unit adjustment coefficient, f0(t) is the frequency value of the specified curve in period t, f1(t) is the value of the optimized frequency response curve in stage 1, f2(t) is the value of the optimized frequency response curve in stage 2, η T is the transformer efficiency, deltaP(t) is the power deficit to be optimized; For the thermal inertia frequency response optimization model, the output constraints and ramp constraints at each stage are expressed as follows: Wherein, α1 is the maximum value of thermal inertia output in stage 1, α2 is the maximum value of thermal inertia output in stage 2; β1 and β2 are the maximum values ​​of thermal inertia output ramp in stage 1 and stage 2 respectively, N is a certain time value in the frequency modulation process, M is the total frequency modulation time, M≥N; For the thermal inertia frequency response optimization model, the frequency offset constraint expressions for each stage are as follows: Where f0(t) is the frequency response curve value specified in period t, f1(t) is the frequency response curve value in period t obtained by optimization in stage one, and f2(t) is the frequency response curve value in period t obtained by optimization in stage two.

3. A frequency modulation method taking into account the flexible exit of thermal inertia of a comprehensive energy system according to claim 1, characterized in that: Step (3) is specifically as follows: In the above thermal inertia frequency response model, the total frequency response process is divided into two stages. The period before N is defined as stage one, and the period after N to M (the end of one frequency modulation) is defined as stage two. Considering that the importance of heat demand to different heat loads is different, the thermal constraints on the load side should be determined according to the specific situation, and thermal inertia is allowed to partially exit during the frequency modulation process. According to the different requirements for frequency modulation effect and the different importance of heat demand to different heat loads, two frequency offset penalty coefficients γ1 and γ2 should be set to control the flexibility of thermal inertia participating in frequency modulation and determine the effect of optimized frequency response curve. The expression is as follows: Where λ1 and λ2 are constant coefficients; F res (t) is the requirement for the frequency modulation effect in time period t, F res The larger the (t), the larger the penalty coefficient γ1(t) of the first stage frequency offset in the t period, and the higher the penalty cost of the first stage frequency offset. In the thermal inertia frequency response model with the minimum total frequency modulation cost as the goal, it can reduce the frequency offset in order to avoid the increase of the total cost; L imp (t) is the importance of heat demand to heat load during period t, L imp The larger (t) is, the more important the heat demand is to the heat load. Since λ2 is negative, the smaller γ1(t) is, the lower the frequency offset penalty cost in the first stage is. In the thermal inertia frequency response model with the goal of minimizing the total frequency regulation cost, the heat restriction on the load side can be reduced, but some frequency regulation effects are sacrificed. The above process is the same for the second stage. Therefore, the values ​​of γ1(t) and γ2(t) determine the amount of thermal inertia output of the integrated energy system participating in the frequency response, giving the ability of thermal inertia to flexibly exit while taking into account the frequency regulation effect.

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