- 1Shenzhen Power Supply Co., Ltd., Shenzhen, China
- 2School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, China
- 3Shenzhen Institute of Artificial Intelligence and Robotics for Society, Shenzhen, China
Accurate load forecasting is crucial to improve the stability and cost-efficiency of smart grid operations. However, how to integrate multiple significant factors for enhancing load forecasting performance is insufficiently investigated in previous studies. To fill the gap, this study proposes a novel hybrid deep learning model for short-term load forecasting. First, the long short-term memory network is utilized to capture patterns from historical load data. Second, a time pattern attention (TPA) mechanism is incorporated to improve feature extraction and learning capabilities. By discerning valuable features and eliminating irrelevant ones, the TPA mechanism enhances the learning process. Third, fully-connected layers are employed to integrate external factors such as climatic conditions, economic indicators, and temporal aspects. This comprehensive approach facilitates a deeper understanding of the impact of these factors on load profiles, leading to the development of a highly accurate load forecasting model. Rigorous experimental evaluations demonstrate the superior performance of the proposed approach in comparison to existing state-of-the-art load forecasting methodologies.
1 Introduction
With the increasing complexity of electrical infrastructure, the power industry has embraced the emergence of smart grids (Wang et al., 2018), which integrate conventional power system equipment with advanced intelligent digital communication devices, aiming to enhance system’s performance, safety, and reliability (Yu et al., 2014). The integration of intelligent electronic devices into smart grids enables inter-device communication and real-time data sharing with control centers, resulting in the accumulation of significant amounts of data. Although initially unproductive, this data can be utilized for system assessments, ultimately improving the operational performance of smart grids.
As the energy internet emerges (Wang et al., 2019a) and energy demands escalate, there is a growing emphasis on energy conservation, leading to an amplified need for load forecasting, particularly in the commercial and industrial sectors. Load forecasting offers several advantages, including the mitigation of supply-demand imbalances and optimization of energy utilization benefits. With the increasing availability of big data, artificial intelligence techniques play a crucial role in load forecasting (Ruan et al., 2023b).
Short-term load forecasting, which commonly predicts loads within a range from hours to weeks, enables utilities and power plants to adjust generation in response to market demands. Research has shown that a mere 1% reduction in load forecasting errors can lead to an annual operating cost reduction of £10 million for a British power company (Gilanifar et al., 2019). Additionally, accurate load forecasts facilitate the implementation of dynamic pricing structures in the electricity market (Ruan et al., 2023b). However, due to the intricacies and uncertainties associated with power demands (Ruan et al., 2022a), load forecasting remains some significant challenges. To address it, recent advancements in data analysis techniques and data collection systems, such as smart meters (Li et al., 2021), have the potential to greatly enhance load forecasting accuracy. Specifically, machine learning-based load forecasting methods, including autoregressive integrated moving average (ARIMA), multiple linear regression (Yu et al., 2014), Gaussian process regression (Akorede et al., 2010), support vector regression (SVR) (Hossain et al., 2019), artificial neural networks (ANN) (Virote and Neves-Silva, 2012; Candanedo et al., 2017), and deep neural networks (DNN) (Menezes et al., 2014), have gained substantial attention.
Deep learning techniques have proven to be effective in developing highly accurate load forecasting models. For example, the literature (Wang et al., 2019a) proposed a deep belief network (DBN)-based model for short-term load forecasting, which is able to learn probability distribution so as to determine future load profiles. Other studies recommended the use of self-recurrent wavelet neural networks (SRWNN) for load forecasting in microgrids by introducing a Levenberg-Marquardt learning algorithm to improve the forecast accuracy for highly volatile and non-smooth time series of microgrid electricity load (Chitsaz et al., 2015), the employment of multi-layer perceptron (MLP) for non-residential building electric load forecasting with analyses of most relevant features (Massana et al., 2015), and the application of recurrent neural networks (RNN) for short-term load forecasting that can effectively handle time-series data (Wen et al., 2022). These models utilize historical data in digital formats to predict future electric load variations.
However, the extensive integration of renewable energy sources (Yang et al., 2021), the widespread adoption of electric vehicles (Hartvigsson et al., 2021; Yang et al., 2022), the large-scale deployment of energy storage systems (Zhang et al., 2021), and emerging cyber threats (Ruan et al., 2023a) have introduced greater uncertainty and disturbances in short-term load forecasting (Wang et al., 2019b). To address the limitations of existing models in capturing these dynamic changes, this paper proposes a deep learning-based approach that incorporates a time pattern attention (TPA) mechanism to construct a highly accurate load forecasting model. The contributions of this article can be summarized as follows.
• To our knowledge, it is the first study to propose an adaptive short-term load forecasting framework that can accommodate various critical features, thereby facilitating accurate forecasting results.
• A specific deep learning-based hybrid model is proposed. It incorporates the long short-term memory (LSTM) network and the TPA mechanism as well as various deep learning techniques that can effectively utilize historical load data and external factors (e.g., climate, economy, and date) to discern dynamic load trends for load forecasting.
• Comprehensive experiments are conducted by using Panama data to analyze of the proposed model and compare it with alternative state-of-the-art load forecasting models. The results demonstrate the superior performance of the proposed method.
The remainder of the paper is organized as follows. Section 2 introduces preliminaries of load forecasting, including its importance, features, and challenges. Section 3 elaborates on deep learning-based TPA mechanism and the proposed short-term load forecasting model as well as the overall framework. Section 4 demonstrates and discusses the case studies on the proposed load forecasting model. At last, section 5 summarizes the article.
2 Preliminaries of load forecasting
2.1 Importance of load forecasting
Load forecasting has consistently been a vital concern for the power industry (Li et al., 2023b), as forecasting data enables power generation and load management departments to bolster their performance and reliability. In addition to economic and environmental considerations, load forecasting serves the following essential functions.
1) Comprehending load profiles allows power companies to devise rational electricity demand plans for customers, make economically prudent decisions, and mitigate risks for the organization.
2) Load forecasting aids power generation enterprises in anticipating potential resource requirements, facilitating the storage of necessary resources, such as fuel, to guarantee an uninterrupted power supply.
3) It assists in projecting the evolution of electricity generation within society and determining the need for future power plants, thus guiding power companies in preparations for constructing additional generating units to accommodate escalating electricity demands.
4) It contributes to the analysis and planning of power system maintenance;
5) By reducing energy production shortages and surpluses, load forecasting helps power companies minimize economic and energy losses.
2.2 Load forecasting features
The outcomes of load forecasting techniques are influenced by various factors. To obtain accurate predictions, it is crucial to consider the relevant factors of the dataset and use them appropriately. Numerous variables may affect the load forecasting performance. Here are some factors related to load forecasting.
2.2.1 Time factors
Due to the deductive nature of electric load over time (Ruan et al., 2022b), the most critical aspect in forecasting is time. As the available data generated by various devices (such as smart meters, sensors, data servers, and other equipment) is time-series data, the importance of time in forecasting is paramount. Time has different attributes that can be used for prediction, such as “day of the week,” “week of the month,” “month of the season,” and so on (Ruzic et al., 2003). The selection of time horizon in forecasting is also a key factor (Lusis et al., 2017). Employing a more extended time range allows for the utilization of additional historical data.
2.2.2 Climate factors
Climate stands as a paramount factor in load forecasting, as it substantially influences both the agricultural sector and household consumption behaviours. Specifically, the usage patterns of various electrical devices, contingent upon weather-related warmth or coldness, can give rise to distinct load profiles. Consequently, load forecasting models may incorporate weather data sourced from the nearest accessible meteorological station, encompassing variables such as temperature, precipitation, humidity, dew point temperature, solar radiation intensity, wind speed, wind chill index (WCI), temperature-humidity index (THI), and other meteorological parameters.
2.2.3 Other factors
Economic determinants, including market stability, electricity price fluctuations, load control, and industrial growth rates, profoundly influence system average load and peak demand (Li et al., 2023a). Moreover, the physical attributes of structural, housing, or surrounding areas exhibit distinct load characteristics. Load forecasting for edifices and other structures can generally be executed utilizing building attribute parameters, such as the number of rooms and floors, window-to-wall ratio, orientation, window-wall thermal efficiency, fresh air volume, and occupant density.
2.3 Challenges in load forecasting
For a long time, researchers have been dedicated to improving load forecasting techniques. However, when it comes to the specific modeling of load forecasting, there are still some obstacles.
First, weather is a key factor when performing load forecasting. Since the weather cannot be accurately estimated, it is impossible to accurately determine its impact on the load. Sudden weather changes can have significant effects on the expected load characteristics.
Second, the variety of meters utilized by consumers considerably influences load forecasting performance. Consumers employ an array of meters, encompassing smart and conventional meters, each with distinct measurement frequencies. As meter measurement frequencies and customer consumption behavior diverge, employing combined data for load forecasting may result in significant prediction errors.
Third, to further refine load forecasting, a series of other complex factors can be considered, but this adds to the difficulty of accommodating multiple variables, rendering the selection of an appropriate load forecasting model extremely challenging.
Fourth, since power systems may experience faults, power outages, and other intermittent events during dynamic operation, load forecasting models cannot account for such sudden occurrences, which also affect the load forecasting performance.
Fifth, consumer electricity demand is influenced by changes in economic market conditions or tariff changes. Although these economic factors significantly impact load forecasting outcomes, they are often overlooked by existing load forecasting methodologies.
3 Proposed short-term load forecasting model based on the time pattern attention mechanism
3.1 Long short-term memory network
In constructing a load forecasting model, the time dimension emerges as a critical factor influencing forecasting performance. Dynamic patterns can be discerned from historical load time series data. Consequently, employing neural networks adept at handling time series data can effectively extract inherent feature information and augment model accuracy. Long short-term memory (LSTM) networks, a unique variant of recurrent neural networks (RNNs), exhibit a natural advantage in processing sequential data (Hochreiter and Schmidhuber, 1997), as shown in Figure 1. The LSTM network manipulates the cell state through internal input gates, output gates, and forget gates, ultimately yielding their hidden state, as demonstrated in the ensuing equations:
where
3.2 Time pattern attention mechanism
While the LSTM network has exhibited remarkable proficiency in managing time series data, the advent of the attention mechanism facilitates the extraction of pertinent information among features (Ruan et al., 2023c), thereby augmenting the model’s learning capacity and accuracy. Consequently, this article incorporates a TPA mechanism, grounded in the LSTM network, to bolster the load forecasting model’s ability to learn from historical load time series data.
First, a one-dimensional convolutional neural network (1-D CNN) layer is used to extract the feature learning capability of the LSTM network’s hidden state. Let
where the convolution operation
Subsequently, a scoring mechanism is employed to evaluate the relevance between the hidden state
where
By applying the Sigmoid activation function to the scoring mechanism, the attention coefficient
Based on the obtained attention coefficients, performing attention-weighted summation and addition operations yields the output under the TPA mechanism:
where both
3.3 Time pattern attention mechanism-based short-term load forecasting
An overall model for the TPA-LSTM-based short-term load forecasting considering multi-regional factors is described in Figure 2, encompassing three modules. Module 1 employs TPA-LSTM to learn from historical load data, initially establishing a load baseline. Module 2 assimilates various factors from distinct regions, such as climate and economy, utilizing fully connected layers (FCLs) to learn diverse climate conditions, including temperature, humidity, wind speed, precipitation, and economic factors like market stability, electricity price adjustments, load control, and industrial growth. Module 3 constitutes the date information learning module, which examines the influence of varying seasons and typical days on electric load and integrates the output of Module 2 through a concatenation operation to learn the impact of date information on the electric load across various regions. Ultimately, the three modules enter the fusion layer and yield the final load profile in the form of a fully connected layer.
The determination of hyperparameters can be accomplished through a combined implementation of random search and
The employment of the proposed load forecasting model is illustrated in Figure 3. The process begins with the careful preparation of the dataset, followed by the construction of the load forecasting model as demonstrated in Figure 2. Subsequently, the hyperparameters of the load forecasting model are selected by employing a combination of random search and
4 Results and discussions
4.1 Set up
To evaluate the performance of the proposed load forecasting model, a historical load dataset encompassing all regions in Panama from 2015 to 2020 is employed for simulation. The data has a time granularity of 1 h and includes total load (MWh), temperature (°C), relative humidity (%), liquid precipitation (L/m2), wind speed (m/s), school day indicator (0/1), holiday indicator (0/1), and holiday index (integer) for three cities in Panama. The dataset is divided into training, validation, and test sets with a non-overlapping partition ratio of 8:1:1. The whole dataset starts from 3 January 2015, and ends by 27 June 2020. Accordingly, the sample sizes of the training, validation, and test sets are 1596, 199, 200, respectively.
In addition, three prevalent deep learning models serve as comparative models, as shown in Table 1. The MLP model learns climate information, economic factors, and date information to predict the load profile for the next 24 h. Based on the learning of external factors such as climate information and date information, the LSTM and GRU models learn from the historical load profile for the past week to predict the load profile for the next 24 h. Their model structure is similar to that shown in Figure 2, with the only difference being that they use LSTM and GRU instead of TPA-LSTM to process time-series data. The TPA-LSTM model predicts the load profile for the next 24 h by learning the impact of external factors on future loads while simultaneously extracting the features of historical load curves based on the temporal pattern attention mechanism.
4.2 Numerical results and discussions
During the model training process, standard deviation normalization transformation is applied to all data features to mitigate the influence of feature units on prediction outcomes. The mathematical expression for this transformation is as follows,
where
After all data is transformed, the models can be trained, with the mean squared error (MSE) as the training loss function, as follows,
where
The training process of the four models is shown in Figure 4. It is clear that all models converge at the end of the training.
For visualization, the last week of data in the test set is selected to compare the predictive performance over the four models. These predicted results are denormalized to the normal scale, as shown in Figure 5. It is evident that the MLP model, which only focuses on climate information, economic factors, and date information, cannot accurately predict the load profile. The LSTM and GRU, two special types of RNNs, can fit the load profile to a certain extent based on the extraction of external factors, but still have significant errors. However, the TPA-LSTM model can not only capture the changes in the load itself but also pay attention to the impact of external factors on the load. The attention mechanism can focus on high-value features, thereby accurately predicting the electric load.
To comprehensively evaluate the performance of the four models, the mean absolute percentage error (MAPE), mean absolute error (MAE), and root mean squared error (RMSE) are used as indicators to statistically analyze the predictions of the four models on the test set, as follows,
The statistical results are shown in Table 2. It can be seen that the proposed TPA-LSTM model demonstrates superior predictive performance in all indicators. The reason is that this model not only takes into account the external factors for load variations, but also considers the influence from the historical load profile. More importantly, it employs the TPA mechanism that can identify valuable features and eliminate irrelevant ones to improve the model performance.
In summary, the model proposed in this article processes historical load data based on the TPA mechanism to establish a baseline for load forecasting. It also uses fully-connected layers to extract the impact of external factors (such as regional climate information, economic factors, and date information on the load), thereby accurately predicting the load curve. According to the MAPE statistics, the model has an error of only 4.41%, making it suitable for use in actual load forecasting models.
5 Conclusion
Accurate load forecasting is crucial for ensuring the stable operation of smart grids. This study introduces a short-term load forecasting approach utilizing the TPA mechanism to fulfill the goal. First, the LSTM network is applied to process historical load time-series data, while the TPA mechanism is incorporated to extract temporal feature correlations, thereby enhancing the model’s learning capability. Second, FCLs are employed to analyze external factors such as climate, economy, and dates, investigating their influence on future load patterns and establishing a high-precision forecasting model. Last, the proposed method is simulated and compared through a realistic dataset from Panama. The simulation results demonstrate that the proposed load forecasting approach achieves the lowest errors in terms of MAPE, MAE, and RMSE indicators, displaying the closest alignment with the actual load values. Thus, this method holds significant potential for practical load forecasting applications.
It is worth noting that the proposed load forecasting method still has two unresolved challenges. As a result, future work will focus on the integration of various sampling frequency meters into load forecasting methods, as well as the development of highly robust load forecasting techniques that are able to handle unconventional emergencies.
Data availability statement
The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author.
Author contributions
WL and JR proposed the research methods, wrote the code for experiments, and wrote the manuscript. YX and QW conceived the overall structure and framework of the article. JL, RW, and JZ provided constructive discussions and technical support for the manuscript. All authors contributed to the article and approved the submitted version.
Funding
This work was supported in part by the National Natural Science Foundation of China under Grant 72171206, 71931003, and 72061147004; in part by the Shenzhen Institute of Artificial Intelligence and Robotics for Society; in part by the Shenzhen Key Lab of Crowd Intelligence Empowered Low-Carbon Energy Network under Grant ZDSYS20220606100601002.
Conflict of interest
Authors WL, YX, QW, JL, and RW were employed by the Shenzhen Power Supply Co., Ltd.
The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Publisher’s note
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Keywords: load forecasting, deep learning, time pattern attention, smart grid, data driven
Citation: Liao W, Ruan J, Xie Y, Wang Q, Li J, Wang R and Zhao J (2023) Deep learning time pattern attention mechanism-based short-term load forecasting method. Front. Energy Res. 11:1227979. doi: 10.3389/fenrg.2023.1227979
Received: 24 May 2023; Accepted: 14 July 2023;
Published: 31 July 2023.
Edited by:
Zhengmao Li, Nanyang Technological University, SingaporeReviewed by:
Guibin Wang, Shenzhen University, ChinaJing Qiu, The University of Sydney, Australia
Bing Luo, Duke Kunshan University, China
Copyright © 2023 Liao, Ruan, Xie, Wang, Li, Wang and Zhao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Jiaqi Ruan, amlhcWlydWFuQGxpbmsuY3Voay5lZHUuY24=