Abstract
A novel multi-stage time scale economic dispatch scheme is proposed for virtual power plants, taking into account the uncertainties arising from the connection of distribution network sources. This research introduces specific scheduling schemes tailored to various time scales within distribution networks, including a fuzzy optimized day ahead scheduling scheme, an intra-day scheduling scheme combined with Deep Q Network, and an adaptive optimized real-time scheduling scheme. This plan mainly considers the impact of photovoltaic output and conducts scheduling one day in advance through fuzzy optimization. In the intraday scheduling, different strategies were adopted in the study. By combining with Deep Q Network, research on scheduling for intraday demand within the power system. The analysis is conducted through rigorous modeling. Experimental tests were conducted to evaluate the performance of the proposed schemes. The day ahead dispatching primarily considers the impact of photovoltaic output and calculates the cost associated with each link in the grid under three different meteorological conditions. In the intra-day scheduling, the total costs for Scenario 1, Scenario 2, and Scenario 3 are found to be 34,724.5 yuan, 36,296.5 yuan, and 33,275.8 yuan, respectively. Notably, strategies 1 and 2 demonstrate lower costs compared to the pre-day scheduling, with the exception of Scenario 3. In real-time scheduling, considering the matching between sources and sources, the matching rate between sources and sources can be maintained at over 95%, and the stability and cost of the power grid have significantly decreased. In summary, by proposing a multi-stage time scale economic scheduling scheme, this study fully considers the uncertainty of the power supply of the distribution network access, as well as the different needs of day, day and real-time scheduling, providing an effective solution for the power dispatching of virtual power plants and providing important technical support for the reliability and economy of the power system.
Keywords
Introduction
The growing demand for electric energy in society has outpaced the capabilities of the existing distribution network, making it challenging to meet market needs [1]. To address this issue, enhancing the resource scheduling scheme within the distribution network is crucial and can be accomplished through the implementation of virtual power plant (VPP) technology. By considering various power grid trading market forms such as day-ahead, intra-day, and real-time, advanced VPP technology can effectively mitigate the adverse impacts of diverse distributed resources on the power grid system. Furthermore, it enables energy conservation within the distribution network system, thereby improving resource utilization efficiency. Therefore, this research focuses on the current distribution network system, specifically examining the influence of uncertain pressure loads from photovoltaic, wind power, hydrogen energy, and other sources on the distribution network. Taking into account the variability of distribution network sources, a multi-time scale power grid resource scheduling scheme encompassing day-ahead, intra-day, and real-time stages is proposed. This scheme integrates fuzzy technology, deep learning, and other advanced technologies to optimally manage power grid scheduling. Through this approach, the smart grid can achieve energy savings, cost control, intelligent control, and fulfill other necessary requirements for construction purposes. The research content is mainly divided into four parts. The first part is a brief introduction to the research topic of virtual power plant scheduling by other scholars. The second part is a review of the main methods used in this study, and the third part is the model results obtained through the use of methods and an analysis of the results. The fourth part is a summary of all the above studies and prospects for future research. The innovation of this study lies in integrating fuzzy logic, deep learning, and advanced communication technologies into the framework of virtual power plants. This integration makes power grid scheduling more complex and intelligent, achieving optimal resource utilization. By considering one day in advance, on the same day, and in real-time, the study recognized and addressed the diversity of distributed energy. This comprehensive approach makes the system more adaptable and responsive, minimizing the adverse effects of uncertain pressure loads from sources such as photovoltaics, wind energy, and hydrogen.
Related works
VPPs are an important direction for the development of the energy field. All countries are making arrangements in this direction to seek new ways to solve energy crises, environmental pollution, and economic development. Sun et al. aimed to achieve precise control over the dispersed and massive internal demand side resource clusters of virtual power plants, and to enable virtual power plants to quickly and effectively participate in demand response. The research team used pre learning methods to enrich historical data and clustered historical data based on spectral clustering. A distributed collaborative control strategy for MEST and an alternating direction multiplier method for online transmission of historical data were proposed. Divide the hierarchical relationship of control priorities based on the results of MEST power regulation tasks. The experimental results show that the proposed algorithm and control strategy have superiority in executing distributed optimization tasks [2]. Akbary et al. proposed a framework based on virtual power plants to extract appropriate location marginal prices for each type of reserve. The proposed reserve pricing scheme compensates for the opportunity loss of energy and reserves. By applying this framework, a fair price for capacity reserves can be obtained, which allocates the same price for the same services provided at the same location. Meanwhile, considering boundary constraints, the pricing problem is decomposed into different sub problems. Through experimental analysis, this technology has good performance and is of great significance for the development of intelligent power plants [3]. Bahloul et al. conducted research on existing VPP aggregation control strategies to evaluate the performance of distributed VPP for better commercialization. At the same time, pay attention to the relationship between the network and power distribution, and optimize power grid scheduling through self-consumption strategies. Through the application, the distributed VPP mode reduces power grid load and improves customer service effectiveness. However, due to a lack of consideration for multiple energy sources, it is unable to meet the requirements of complex multi-energy scheduling [4]. Li et al. conducted an investigation on multiple VPP active power grids and proposed a data-driven fully distributed electronic control Scenario to improve power grid scheduling effectiveness. This Scenario is based on a robust regression feedback optimization algorithm, achieving feedback and corrective control for multiple VPP systems, and has excellent application results in practical applications. However, this plan does not consider the needs of different user electricity scenarios and is only suitable for small-scale scheduling systems [5]. Yi et al. conducted research on the existing power system and found that power resource scheduling still faces a large room for improvement. Therefore, based on the consideration of a large number of delayed load aggregations, a multi-time-scale scheduling Scenario was proposed based on VPP technology, and the clustering method was used to construct an economic system scheduling model. The proposed scheme is verified experimentally, and the proposed scheduling scheme can effectively reduce system energy consumption [6].
Ammari et al. proposed a scheduling strategy based on an improved firefly algorithm for delay constrained applications in distributed green data centers and cost and energy efficient scheduling of multiple heterogeneous applications. The experimental results show that the proposed scheduling strategy model based on the improved firefly algorithm can meet the scheduling problem of distributed green data centers [7]. Freire et al. found that with the development of cloud and mobile applications, enterprises have an increasing demand for integration of applications and services in business processes. Many integration platforms use first in, first out heuristic algorithms to schedule tasks executed by computing resources. The research team has proposed a queue priority algorithm based on particle swarm optimization, which can handle large amounts of data in integrated process task scheduling. The experimental results show that the algorithm can execute the integration process and schedule data under high data volume [8]. Zhou et al. found that crowd perception can solve the problem of massive data collection faced by most data-driven applications. Therefore, the research team first proposed a workflow framework that captures the unique execution logic of perception tasks. Then, a phased approach was proposed to decouple the original scheduling problem. The experimental results show that the proposed algorithm model can perform well on scheduling problems [9].
Based on the aforementioned research, VPP technology emerges as a promising innovation in modern energy management, offering significant potential for power system management. While the mentioned research provides an analysis of the state-of-the-art features and applications of VPP, it falls short in considering multi-source storage and complex scenarios. Most studies have not fully considered the situation of multi-source energy storage, and actual power systems often face diverse scenarios and demands, such as emergencies and market changes. The current research mainly focuses on specific aspects and fails to fully cover the actual operational needs of complex multi energy and multi scenario scenarios. Some studies have not considered the electricity consumption scenarios of different users, which may lead to shortcomings in responding to actual needs. Some studies are only applicable to small-scale scheduling systems, and their feasibility and effectiveness in large-scale power grids have not been fully verified. Considering the uncertainties associated with sources, loads, and storage within the framework of VPP can greatly enhance power grid dispatching capabilities and facilitate energy conservation and emission reduction objectives. By addressing these aspects, VPP technology can provide essential support for grid dispatch operations while simultaneously promoting sustainability goals.
Construction of a multi-time scale economic regulation model considering multiple uncertainties of sources, loads and storages
Construction of fuzzy day-ahead scheduling model
VPP is a comprehensive intelligent power management technology that integrates computers and communication. Considering the impact of source data uncertainty on the entire power grid scheduling under virtual technology, the power grid scheduling is optimized according to different time scales of grid source response, and a multi-time scale scheduling model considering source load storage is constructed. The principle of multi-time scale scheduling is shown in Fig. 1 [10, 11].
Principle of structure of time scale scheduling.
From Fig. 1, it can be seen that the scheduling and planning process of the electricity market at different time scales. Firstly, scheduling one day in advance is based on hourly timescales, and the plan is updated every 24 hours. Next, the intraday scheduling adopts a rolling time scale of one hour, with the time scale further subdivided into 15 minutes. This scheduling plan needs to be updated every 15 minutes to cope with closer real-time changes. Finally, real-time scheduling is executed on a 5-minute time scale to achieve refined management and rapid response. The uncertainty of the source includes factors such as photovoltaic power generation, electricity prices, and vehicle loads [12, 13, 14]. The prediction error of photovoltaic power generation is represented by the normal distribution. In this context, the power generation error variable is defined as
In Eq. (1),
In Eq. (2),
In Eq. (3),
In Eq. (4),
The relationship between peak and valley electricity price difference and load transfer rate.
The flat-valley transfer rate
In Eq. (5),
Tram scheduling optimization principle.
From the information in Fig. 3, the tram load transfer situation can be obtained. Only the transfer amount is unknown in the signed contract, so the dispatch can be carried out according to the signed rules, and the expression of the car transfer amount can be referenced in Eq. (6).
In Eq. (6),
In Eq. (7),
In Eq. (8),
In Eq. (3.1),
The prediction of power grid sources belongs to nonlinear problems, and applying Deep Q Network (DQN) to power grid dispatch management has outstanding advantages [21, 22]. DDQN is an improvement on DQN, introducing the concept of Double Q-Learning. In standard Q-learning, using the same neural network to select and evaluate the value of actions may lead to overly optimistic estimates of certain actions. DDQN introduces additional networks and parameters compared to DQN, which may lead to a slight increase in the computational and storage costs of the algorithm. Therefore, on some simple problems, DQN may be easier to implement and train. Therefore, the Deep Deterministic Policy Gradient (DDPG) model proposed by the Deep Mind team on the basis of DQN for continuous action problems is adopted as a form of reinforcement learning, and its principle is shown in Fig. 4 [23].
Schematic diagram of DDPG principle.
In Fig. 4,
In Eq. (10),
In Eq. (11),
By the deterministic equation
According to Eq. (13), the network Scenario can be optimized through gradient updates. At the same time, it is also necessary to consider the power grid losses [24, 25]. In target scheduling, specific economic needs need to be considered, as referenced in Eq. (14).
In Eq. (14),
In Eq. (15),
In Eq. (3.2),
In Eq. (17),
Reinforcement learning intraday scheduling solution process.
In the real-time scheduling process, it is necessary to consider the impact of source and source matching and economy on power grid scheduling, to ensure the stability and economy of power grid scheduling [29, 30, 31]. The principle of real-time scheduling is shown in Fig. 6.
Schematic diagram of real-time adaptive scheduling.
Using the basic time scale scaling results for power grid optimization scheduling, when in a large fluctuation stage, a smaller scale is used, and the scheduling scaling value is set to 5 minutes, smaller scale results are used for power grid optimization scheduling. When in the stage of large fluctuations, it refers to the use of small-scale results to detect the power grid due to high load or high electricity consumption. The power matching degree of the source is referenced in Eq. (18).
In Eq. (18),
In Eq. (19),
In Eq. (20),
In Eq. (21),
The principle of real-time adaptive scheduling can be seen in Fig. 7.
Principle of real-time adaptive scheduling.
The scheduling basis is mainly obtained from optimization data such as day-ahead scheduling and intraday scheduling [37, 38, 39]. The minimum operating cost of the objective function at this stage is shown in Eq. (23).
In Eq. (23),
In Eq. (24),
In Eq. (25),
Introduction to experimental background
Taking a certain VPP project as the research object, the low voltage of the power grid is
Partial experimental parameter information
Partial experimental parameter information
The scheduling of three-time scales, namely pre-day, intra-day, and real-time, is a progressive relationship. Scenario 1: without considering the impact on the source and not guiding the tram; Scenario 2: without considering and guiding the tram; Scenario 3: without considering and guiding the tram; Scenario 4: without considering and guiding the tram. The results are shown in Table 2.
Grid dispatching cost of different photovoltaic output
In Table 2, Meteorological conditions 1, 2, and 3 respectively refer to conditions with strong light, weak light, and moderate light. Considering the influence of photovoltaic output, the total cost of weather conditions 1 and 3 is similar. The main reason is that the dispatch model optimizes the smoothness of the total power of the tie line to improve the stability of the power grid. The overall high cost of meteorological condition 2 is due to the increase in scheduling costs when the overall output is low. The corresponding tie line power change can be seen in Fig. 8.
In Fig. 8, at 10:00 in the morning, the total power consumption of the unoptimized weather state 2 is higher, 5.3 MW, and the optimized power consumption is 2.0 MW.
Results of time-of-use electricity price under different photovoltaic output
The results of the total power of the tie line under different photovoltaic outputs.s
Comparing the performance of various algorithm models, the results are shown in Fig. 9.
Comparison of recall rates and F1 values of four algorithms.
Figure 9(a) shows the accuracy of the four algorithms on different datasets, while Fig. 9(b) shows the F1 values of the four algorithms on different datasets. As shown in Fig. 9(a), as the training set increases, the accuracy of all four models increases. Among them, the proposed DQN algorithm model performs well among the four methods. When the dataset size is around 500, the recall rates of the four algorithm models are 0.96, 0.83, 0.79, and 0.63, respectively. As shown in Fig. 9(b), as the training set increases, the F1 values of the four algorithm models continue to increase. When the dataset size is 500, the F1 values of the four algorithm models are 0.97, 0.90, 0.76, and 0.65, respectively. The experimental results show that the proposed DQN algorithm model exhibits good performance in terms of recall and F1 value among the four models.
According to the electricity price measurement period of the Japanese Electricity Dispatcher in Table 3, the peak period is mainly concentrated after 16:00 p.m., and the valley period is mainly from 0 p.m. to 5 p.m. A deep reinforcement scheduling model is then used to train the results of three scheduling strategies for intraday scheduling. In Scenario 1, the meteorological condition is 1, and the signing rate of the tram contract is 0.5. Under Scenario 1, the daily scheduling results are shown in Fig. 10.
Optimization results of Scenario scheduling within 1 day.
In Fig. 10(a), network loss in Scenario 1 is to use day-ahead scheduling to obtain the final tie line power consumption through power flow calculation. The overall power consumption is 5% higher than day-ahead optimization and intra-day rolling optimization, and the absolute value difference between intra-day rolling scheduling and day-ahead scheduling is 0.8354 MW, which can be said that scheduling can improve the stability of the connecting line. Figure 10(b) shows the response results of the dispatching unit, the total output of the gas turbine is higher at 0–5 minutes, 35–45 minutes and 75–90 minutes, and the output of energy storage equipment is generally lower.
In Scenario 2, the weather condition is 1, and the tram contract signing rate is 0.2. The intraday scheduling results under Scenario 2 scheduling are shown in Fig. 11.
Optimization results of Scenario scheduling within 2 days.
In Fig. 11(a), considering that the tram contract is relatively low in this Scenario, the peak-shaving and valley-filling power of the tie line is not as good as Scenario 1. At the same time, the absolute value difference between the intraday rolling scheduling and the day-ahead scheduling is 0.8142 MW, still at a relatively good track result. Figure 11(b) corresponds to the response results of the dispatching unit. Compared with Scenario1, the overall output has effectively decreased, mainly due to the lower rate of tram contract signing.
In Scenario 3, the weather condition is 2, and the tram contract signing rate is 0.5. The intraday scheduling results under Scenario 3 scheduling are shown in Fig. 12.
Optimization results of Scenario scheduling within 3 days.
Figure 12(a) shows the Scenario 3 scheduling, due to the constraints of cost factors, the absolute value difference between intraday rolling scheduling and day-ahead scheduling is 2.1087 MW, which is better than Scenario 1 and Scenario 2. But in the rolling optimization, the power of the tie line can still approach the advance scheduling, so the optimization still meets the requirements. Figure 12(b) corresponds to the response result of the dispatching unit, and the output of the gas turbine decreases compared with Scenario 2. The results of the three intraday rolling scheduling optimizations are counted, as shown in Table 4.
In Table 4, compared with the day ahead dispatching, the cost of energy storage and fuel engines in Scenario 1 and Scenario 2 has increased, but the cost of power purchase and network loss has decreased, and the total cost has decreased significantly. Compared with the day ahead scheduling, the cost of energy storage and fuel engines in Scenario 3 has slightly decreased, but the cost of network loss has expanded, and the total cost has significantly increased compared with the day ahead scheduling, reaching 33275.8 yuan.
In real-time scheduling performance testing, the CIP protocol is used to monitor and record data on energy production, consumption, and demand energy consumption during each time period through a real-time energy monitoring system. On the basis of daily scheduling, energy storage units 1 and 2 will be used as optimization scheduling units. The matching rate of internal monitoring exceeds the set threshold of 95% within 15 minutes, and the real-time scheduling index value will be set to 5 minutes. The scheduling time will be set to 4–6 p.m., as shown in Fig. 13.
Results of intraday scheduling cost
Real-time scheduling optimization results.
In Fig. 13(a), it is observed that after optimizing the scheduling of the interconnection line, it shows a tendency towards the ideal fluctuation curve and demonstrates a commendable power performance. However, in Fig. 13(b), there is significant fluctuation from 4:5 to 4:30, yet the source-to-source matching rate remains above 95%. The experiment is conducted during the time intervals of 7:30–7:45 and 11:00–11:15. During these intervals, the matching rates between sources are measured at 93.15% and 94.25%, respectively. The reason for this situation is the use of advanced scheduling optimization algorithms, which enable the system to better adapt to the matching relationship between power demand and sources, reduce power fluctuations, and make the overall performance of the system more stable. By conducting real-time scheduling during critical periods, the system can more flexibly respond to changes in electricity demand. The adjustment of scheduling values takes into account the measurement results of the matching rate between sources, further improving the adaptability of the system. To ensure system stability and comprehensive considerations, a scheduling value of 2.5 is selected for the interval of 7:30–7:45, while a scheduling value of 1.25 is chosen for the interval of 11:00–11:15. By implementing the aforementioned real-time scheduling approach, the scheduling effect of the power grid is improved.
A daily real-time scheduling model is developed by leveraging virtual power plant technology and accounting for the uncertainty of distribution network sources. Due to the unpredictable nature of power supply and load in day-ahead dispatching, a fuzzy function is utilized to construct a dispatching model that accommodates uncertain sources and loads. The model takes into account power grid losses and incorporates deep reinforcement technology to optimize daily scheduling. Considering the fluctuation of sources and loads, a real-time scheduling model is constructed using a time scale switching Scenario. In the day-ahead dispatching test, three different meteorological conditions affecting photovoltaic output are analyzed, and the cost impact of each grid link is determined. Based on the day-ahead scheduling, further tests are conducted, optimizing three different scheduling strategies. As a result, Scenario 1 and Scenario 2 exhibit respective reductions in total cost by 34,724.5 yuan and 36,296.5 yuan compared to the initial day-ahead scheduling. Moving to real-time scheduling, appropriate scheduling values for each time period are selected based on changes in energy storage equipment data, achieving a source-to-source matching rate exceeding 95%. The model proposed in this study still has shortcomings. The small size of the trained dataset results in suboptimal performance of the model, and the proposed method may also have certain limitations when dealing with complex scheduling. In future research, it is possible to consider improving the algorithm to achieve better performance even in smaller datasets. For complex case designs, multiple assumptions can be added to make the model’s performance more superior. In future research, it is possible to consider improving the algorithm to achieve better performance even in smaller datasets. For complex case designs, multiple assumptions can be added to make the model’s performance more superior. In future work, the consideration of grid losses can be enhanced in later periods to improve the accuracy of grid dispatching, even though it is currently not factored into the day-ahead dispatching process.
Formulas
Abbreviations
Footnotes
Acknowledgments
The work was financially supported by Science and Technology Projects from State Grid Shanghai Municipal Electric Power Company (Research and Application of Key Technologies for Safe and Efficient Operation of Hydrogen-electricity Coupled Micro-energy Grid for Safety Visualization, 52091123000C).
