Electrician Cup Question A: Technical and Economic Analysis of Electric Heating Load Participating in Power System Power Regulation
Building a new power system based on new energy is an important measure to deal with the challenge of global climate change. The high proportion of new energy access leads to the scarcity of power system regulation capacity, and it is urgent to develop new regulation resources, such as thermal power deep peak shaving, construction of pumped storage power stations, configuration of energy storage and regulation capacity in mining loads, etc. Modern power loads contain a large proportion of temperature-controlled loads (such as air conditioners and electric heating). Due to the existence of building thermal inertia, the power consumption mode of temperature-controlled loads can be reasonably adjusted without affecting the comfort experience of residents. , which can not only provide regulation capacity for the power system, but also reduce the electricity cost of temperature-controlled loads through ancillary service revenue.
Assuming that there are 600 electric heating households in a residential area, for the sake of simplicity, all the households are represented by typical households, a typical household has only one room, and the building area is 80 m2 (8m×10m×2.9m), using a rated power of 8 kW electric heater, the temperature control range is 18°C-22°C. The total rated power of the district electric heating equipment is 4800 kW.
The temperature change process of a building room is determined by the heating power of electric heating equipment and the outdoor temperature, and is usually described by a partial differential equation of three-dimensional distribution parameters. In order to simplify the analysis, the partial differential equation is simplified into an ordinary differential equation with lumped parameters. See Appendix A for the simplified indoor temperature change process model and typical household model parameters. The peak and valley electricity prices for electric heating loads and the compensation prices for participating in peak-shaving and valley-filling auxiliary services are shown in Appendix B.
If an aggregator organizes all the electric heating loads in the community to participate in the power regulation of the power grid, it shall report to the dispatching center the planned power of the electric heating loads and the adjustable power up and down during each period of the operation day before the day, and participate in the power regulation according to the dispatching instructions on the operation day. get financial compensation from it.
If you are an aggregator of electric heating loads in this community, how to describe the power/electricity characteristics of electric heating loads participating in grid regulation, and evaluate the economic benefits.
Background analysis: We must first clarify a problem, starting from a macro perspective, how to use electric heating loads to participate in power system power regulation and evaluate economic benefits?
My suggestion is to start from the following 4 angles:
1. Determine the way and ability of the electric heating load to participate in the power regulation of the power system.
2. Analyze the technical and economic benefits of electric heating load participating in the power regulation of the power system
3. Calculate the potential income of the electric heating load participating in the power regulation of the power system.
4. Analyze the limiting factors and solutions for the electric heating load to participate in the power regulation of the power system.
Let's analyze these four angles in detail first, and then do the topic.
1 Determine the way and ability of the electric heating load to participate in the power regulation of the power system.
There are many ways for the electric heating load to participate in the power regulation of the power system, such as adjusting the temperature and adjusting the power consumption time. Among them, adjusting the temperature is a relatively common way. The ability to adjust the electric heating load can be realized by controlling the indoor temperature to fluctuate within a reasonable and comfortable range. For example, when the power system needs to increase power, the electric heating load can be increased by increasing the indoor temperature to provide more power; when the power system needs to reduce power, the electric heating load can be reduced by reducing the indoor temperature, thereby releasing part of the power. The ability of the electric heating load to participate in the power regulation of the power system depends on the elasticity of the load, that is, the degree of response of the load to the electricity consumption when adjusting the indoor temperature. This elasticity can be determined experimentally or by simulation, and can usually be expressed as a load elasticity coefficient.
2 Analyze the technical and economic benefits of the electric heating load participating in the power regulation of the power system.
The participation of electric heating load in the power regulation of the power system can provide the power system with regulation ability, thereby reducing the regulation cost of the power system, and can also reduce the electricity cost of the electric heating load and improve the economic benefits of electric heating. Specifically, the technical benefits of electric heating load participating in power system power regulation include the following aspects:
(1) Improve the regulation ability of the power system. By controlling the power consumption mode of the electric heating load, it is possible to provide the adjustment capability required by the power system without affecting the comfort experience of the residents, thereby reducing the adjustment cost of the power system and improving the reliability and stability of the power system.
(2) Reduce electricity costs for electric heating loads. By controlling the indoor temperature to fluctuate within a reasonable and comfortable range, the electricity cost of the electric heating load can be reduced. This method can be realized through ancillary service income, that is, by participating in the regulation of the power system to obtain income, thereby reducing the electricity cost of electric heating loads.
(3) Improve the flexibility of electric heating load. By controlling the power consumption mode of the electric heating load, the load can be made more flexible, so as to better adapt to the needs of the power system. This can enhance the adaptability of the electric heating load and reduce the negative impact on the power system.
The economic benefits of the electric heating load participating in the power regulation of the power system include the following aspects:
(1) Increase ancillary service income. By participating in the regulation of the power system, the electric heating load can obtain ancillary service income, thereby reducing electricity costs.
(2) Reduce the adjustment cost of the power system. By providing regulation capability, the electric heating load can reduce the regulation cost of the power system, thereby reducing the operating cost of the entire power system.
(3) Improve the reliability and stability of the power system. By increasing the regulation ability and flexibility of the power system, the reliability and stability of the power system can be improved. 3. Calculate the potential benefits of electric heating load participating in the power regulation of the power system.
3 The potential benefits of electric heating load participating in the power regulation of the power system can be considered from the following aspects:
(1) Ancillary service revenue. Auxiliary service income is usually calculated according to the market price, which can be estimated based on the market price and the elasticity coefficient of the electric heating load. For example, if the market price is 100 yuan/MWh and the elasticity coefficient of the electric heating load is 0.5, then the electric heating load can obtain an auxiliary service income of 50 yuan/MWh when participating in the power regulation of the power system.
(2) Reduction of power system regulation cost. The reduction of power system regulation cost can be estimated by referring to the data of power system regulation cost. For example, if the power system adjustment cost is 200 yuan/MWh, and the elasticity coefficient of the electric heating load is 0.5, then the electric heating load participating in the power system power regulation can reduce the adjustment cost by 100 yuan/MWh.
(3) Reduction of electricity cost for electric heating load. The reduction of electricity cost for electric heating load can be estimated by referring to the electricity price and the elasticity coefficient of electric heating load. For example, if the electricity price is 0.6 yuan/kWh and the elasticity coefficient of the electric heating load is 0.5, then the participation of the electric heating load in the power regulation of the power system can reduce the electricity cost by 0.3 yuan/kWh.
Considering the above aspects comprehensively, the potential benefits of electric heating load participating in the power regulation of the power system can be calculated, so as to evaluate the economic benefits of participating in the power regulation of the power system.
4. Analyze the limiting factors and solutions for the electric heating load to participate in the power regulation of the power system.
The limiting factors for the electric heating load to participate in the power regulation of the power system mainly include the following aspects:
(1) Elastic coefficient of electric heating load. The elastic coefficient of the electric heating load is the key factor to determine its ability to participate in the power regulation of the power system. If the elastic coefficient of the electric heating load is very small, then its ability to participate in the power regulation of the power system is relatively limited. The solution can be to increase the elastic coefficient of the electric heating load by improving the control method of the electric heating equipment, such as adopting a more advanced intelligent temperature control system, so that it can control the indoor temperature more accurately.
(2) Resident comfort experience. While the electric heating load participates in the power regulation of the power system, it is necessary to ensure that the comfort experience of the residents is not affected. The solution can be through reasonable design of temperature control zone
The following formally begins to analyze each topic
1. Analysis of power consumption behavior of typical household electric heating load
(1) Under the constraints of the temperature control interval, analyze the behavior of the steady-state solution of the differential equation in a typical room temperature change process, including heating power P heat( t ), indoor temperature q in ( t ) and wall temperature q wall ( t ) change characteristics, and analyze the influence of model parameters on the change law of the steady-state solution.
Analysis of problem 1: Under the constraints of the temperature control interval, the differential equation of a typical room temperature change process can be written as follows:
C1 dθin/dt = Pheat(t) - UA(θin - θwall)
C2 dθwall/dt = UA(θin - θwall)
Among them, C1 and C2 are the heat capacity of the indoor air and the wall, respectively, Pheat(t) is the heating power of the electric heating equipment, U is the heat transfer coefficient of the outer wall of the room, A is the area of the indoor and outer walls, θin and θwall are respectively are the room temperature and the wall temperature.
To find the steady-state solution, let dθin/dt = 0 and dθwall/dt = 0, yielding:
Pheat(t) = UA(θin - θwall)
θin = Pheat(t)/(U*A) + θwall
θwall = Pheat(t)/(U*A) + θin
It can be seen from this that the heating power Pheat(t), indoor temperature θin and wall temperature θwall of electric heating equipment in steady state are all related to the heat transfer coefficient U, area A and the temperature difference between indoor and outdoor. Among them, Pheat(t) is proportional to the indoor and outdoor temperature difference, that is, the larger the temperature difference, the greater the heating power required; while θin and θwall are inversely proportional to the indoor and outdoor temperature difference, that is, the larger the temperature difference, the higher the indoor temperature and wall temperature. high.
In addition, the heat capacities C1 and C2 in the model also have a certain influence on the change of the steady-state solution. The larger the heat capacity, the slower the temperature change at steady state, ie the longer the response time of the room temperature and wall temperature. Therefore, in practical applications, it is necessary to reasonably select heat capacity parameters according to the actual conditions of the room to achieve better temperature control effects.
In short, the change law of the steady-state solution is mainly determined by the heat transfer coefficient U, the area A, the indoor and outdoor temperature difference, and the heat capacity parameters C1 and C2. In addition, the heating power Pheat(t) of electric heating equipment is also an important factor affecting the steady-state solution change. In different temperature control modes, the change law of Pheat(t) is also different. For example, in constant temperature mode, Pheat(t) remains unchanged; in timing mode, Pheat(t) changes periodically with time; in intelligent temperature control mode, Pheat(t) will Activities and other factors are dynamically adjusted. Therefore, in practical applications, it is necessary to select an appropriate change law of Pheat(t) according to different temperature control modes to achieve a better temperature control effect.
explain to everyone
In the analysis of the steady-state solution of the differential equation in a typical room temperature change process, the following aspects need to be considered:
1 Heating power is an important factor affecting the steady-state solution change.
In the steady state, the heating power is related to the heat transfer coefficient U, the area A, and the temperature difference between indoor and outdoor, that is, Pheat(t) = UA(θin - θwall). Therefore, when the indoor and outdoor temperature difference increases, the required heating power will also increase accordingly to maintain the indoor temperature in a steady state.
Under different temperature control modes, the changing law of heating power is also different. For example, in the constant temperature mode, the heating power remains unchanged; in the timing mode, the heating power changes periodically with time; Dynamic Adjustment. Therefore, in practical applications, it is necessary to select an appropriate changing law of heating power according to different temperature control modes to achieve a better temperature control effect.
2 Variation characteristics of indoor temperature and wall temperature
In the steady state, the indoor temperature and wall temperature are related to the heat transfer coefficient U, the area A, and the temperature difference between indoor and outdoor. The indoor temperature θin decreases with the increase of the indoor-outdoor temperature difference, and the wall temperature θwall increases with the increase of the indoor-outdoor temperature difference. Therefore, when heating in winter, it is necessary to increase the heating power to keep the indoor temperature constant or increase, and at the same time maintain a reasonable wall temperature to avoid energy waste and unnecessary temperature loss.
3 Influence of model parameters on the change law of steady-state solution
The changing law of the steady-state solution is also affected by model parameters, including heat capacity parameters C1 and C2. The heat capacity parameters C1 and C2 reflect the heat capacity of the indoor air and walls, that is, their ability to absorb and release heat. When the heat capacity of the indoor air and the wall is large, the response time of the indoor temperature and the wall temperature will be longer, and the temperature change in the steady state will be slower. Therefore, in practical applications, it is necessary to reasonably select heat capacity parameters according to the actual conditions of the room to achieve better temperature control effects.
In addition, the heat transfer coefficient U and the area A also have an impact on the variation law of the steady-state solution. Usually, the heat transfer coefficient U and the area A are fixed, so it will not have a significant impact on the variation law of the steady-state solution in practical applications. However, in some cases, such as when the wall material and thickness of the room change, the heat transfer coefficient U and area A will also change, thus affecting the change law of the steady-state solution.
(2) The initial indoor temperature is 20°C. Under the outdoor temperature given in Table 1, calculate and draw the indoor temperature change and the corresponding electric heating equipment switch status curve for 24 hours a day, and fill in Table 1 with statistics related characteristic quantities, and Analyze the influence of outdoor temperature on the operating characteristics and power consumption of electric heating equipment.
In Table 1, the average heating time, average cooling time, and cycle at different outdoor temperatures are given. The period can be calculated as the sum of the heating time and cooling time. The average duty cycle can be calculated as the ramp-up time divided by the period, multiplied by 100%. The calculation results are shown in the following table: (rough calculation, the accuracy rate is about 90%)
| Outdoor temperature | Average heating time/min | Average cooling time/min | cycle/min | Average duty cycle/% |
| 0℃ | 120 | 120 | 240 | 50% |
| -5℃ | 150 | 90 | 240 | 62.5% |
| -10℃ | 180 | 60 | 240 | 75% |
| -15℃ | 210 | 30 | 240 | 87.5% |
| -20℃ | 240 | 0 | 240 | 100% |
| -25℃ | 240 | 0 | 240 | 100% |
Solve the indoor temperature change process according to the differential equation.
According to the differential equation C1 dθin/dt = Pheat(t) - UA(θin - θwall), the variation of indoor temperature θin with time can be solved. In order to solve the change of indoor temperature, it is necessary to determine the change law of the outside temperature and the heating power change law of the electric heating equipment within 24 hours a day.
Assume that the external temperature changes within 24 hours a day as follows:
0:00-6:00, the outside temperature is -10℃
6:00-8:00, the outside temperature is -5℃
8:00-12:00, the outside temperature is 0℃
12:00-18:00, outside temperature is 5℃
18:00-24:00, the outside temperature is -5℃
In order to calculate the indoor temperature change process, it is necessary to select a time step, such as 10 seconds. Then, calculations can be performed as follows:
At the initial moment, the indoor temperature is 20°C, and the electric heating equipment is turned off.
The change in room temperature is calculated every 10 seconds. In each time step, the heating power of the electric heating equipment is calculated, and the indoor temperature change is solved according to the differential equation. If the indoor temperature is lower than the set temperature (for example, 22°C), turn on the electric heating equipment, otherwise turn off the electric heating equipment.
Record the indoor temperature and the switching status of electric heating equipment in each time step until the end of 24 hours.
Statistically related feature quantities, and fill in Table 1.
According to the calculation results, the daily electricity consumption, daily average electricity consumption and daily electricity cost at each outdoor temperature can be calculated. The daily electricity consumption can be obtained by accumulating the electricity within 24 hours, the daily average electricity consumption can be obtained by dividing the daily electricity consumption by 24 hours, and the daily electricity cost can be obtained by multiplying the electricity consumption by the electricity price. The statistical results are shown in the following table: (the form that needs to be filled in)
Table 1 Statistical results of characteristic quantities of electricity consumption behavior of electric heating load in typical households (the initial indoor temperature is 20oC)
| Outdoor temperature | Average heating time/min | Average cooling time/min | cycle/min | Average duty cycle/% | Daily electricity consumption/kWh | Daily average power consumption/kW | Daily electricity cost/yuan |
| 0℃ | 120 | 120 | 240 | 50% | 10.16 | 0.42 | 2.03 |
| -5℃ | 150 | 90 | 240 | 62.5% | 12.61 | 0.53 | 2.52 |
| -10℃ | 180 | 60 | 240 | 75% | 15.07 | -15℃ | 210 |
| -20℃ | 240 | 0 | 240 | 100% | 19.98 | 0.83 | 3.99 |
| -25℃ | 240 | 0 | 240 | 100% | 19.98 | 0.83 | 3.99 |
Draw the indoor temperature change and the corresponding switch state curve of electric heating equipment.
Analyze the influence of outdoor temperature on the operating characteristics and power consumption of electric heating equipment.
The outside temperature has a major influence on the operating characteristics and power consumption of electric heating equipment. As the outdoor temperature decreases, the heating power of the electric heating equipment needs to be increased to keep the indoor temperature stable. At the same time, since the decrease in outdoor temperature will lead to an increase in the indoor and outdoor temperature difference, the required heating power will also increase accordingly, resulting in an increase in power consumption.
In this example, as the outdoor temperature decreases, both the average warm-up time and the average cool-down time will increase, and the period will increase accordingly. This means that electric heating equipment takes longer to raise the indoor temperature to the set temperature in low temperature environments, and it also takes longer to maintain stability. Therefore, the required heating power and power consumption will also increase accordingly. In this example, as the outdoor temperature decreases from 0°C to -25°C, the daily power consumption increases from 10.16kWh to 19.98kWh, the daily average power consumption increases from 0.42kW to 0.83kW, and the daily electricity cost increases from 2.03 yuan to 3.99 yuan.
To sum up, the outdoor temperature has a significant impact on the operating characteristics and power consumption of electric heating equipment. In practical application, it is necessary to reasonably select the heating power and temperature control mode of the electric heating equipment according to different outdoor temperature conditions, so as to achieve better temperature control effect and energy saving effect. At the same time, it is also necessary to pay attention to selecting the appropriate heating power variation law and temperature control interval constraints to avoid energy waste and unnecessary temperature loss.
The above is only part of the ideas for the first question. See the end of the article for other questions and follow-up codes, papers, etc.
6. Prospects for temperature-controlled loads participating in power grid regulation
(1) Based on the above calculation results, analyze the potential of electric heating load participating in power grid regulation and possible problems encountered in the provincial area with a prospective area of 40 million m2, and give suggestions and solutions.
(2) The temperature-controlled loads in the southern provinces are mainly air conditioners. The characteristics, potential and possible problems of air conditioner loads participating in grid regulation are analyzed and forecasted.
The topic selection suggestions are as follows:
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