Recently, the selection results of "The 7th China Association for Science and Technology Excellent Scientific and Technological Papers" were announced. The academic paper "Decomposition-Coordination Based Optimization for PV-BESS-CHP Integrated Energy Systems", written by Zhang Yuman, Liu Xuezhi, Yan Zheng and Zhang Peichao from the School of Electronic Information and Electrical Engineering (SEIEE) of Shanghai Jiao Tong University (SJTU), published in the Journal “Transactions of China Electrotechnical Society”, Volume 35, Issue 11, 2020, was successfully selected as the outstanding scientific and technological paper of the China Association for Science and Technology. The selection was publicized after multiple rounds, including recommendation by experts in various disciplines, preliminary evaluation and final evaluation.

The selected paper from the SEIEE explored the decomposition-coordination mechanism to achieve the global optimum of the integrated electricity and heat systems under privacy protection. The mathematical language form of this mechanism was represented by Benders optimization principle. The mathematical language of Benders cut was refined, and then a set of mechanism criteria was summarized for transferring variables and interactive iterative information between electricity and heat coupling subsystems. It is also indicative for Multi-Party Computing MPC (such as data privacy protection between e-commerce platforms).

1.      Research Overview

The paper studied the coordinated optimal operation of the photovoltaic-battery- cogeneration (CHP) integrated energy system. On the premise of ensuring the effective protection and isolation of the respective information of the electricity and heating systems as much as possible, the electric heating coupling system model was decomposed into the main problem of the thermal system and the sub problem of the electrical system using the Benders decomposition method, and the optimal output of each system device was obtained. At the same time, the interaction mode between systems based on Benders decomposition method and the effective information protection of the system were studied, and the feasibility of using decomposition-coordination optimization method to solve the problem under the premise of privacy protection was discussed. The proposed method realized the global optimium of the integrated electricity and heating networks under the respective information privacy protection.

2.      Research Background

The development of energy system interconnection makes it impossible to upload detailed data of the thermal system to the power system control center due to the user privacy, quantity and scale, etc. Therefore, in the district energy system, the electric power system and the thermal power system are related to each other to some extent, but maintain their independence. In this case, the information between the two cannot be fully differentiated and transparent, and the privacy protection of system information is necessary. Therefore, how to optimize the independent electricity and heating systems to maximize the overall benefit is a challenging problem. Based on Benders decomposition method, the modeling can protect the information privacy between different energy networks or different conversion devices in the integrated energy system, reduce information sharing and protect information security while realizing the optimal operation of each system under the condition of information encryption in the dispatching center.

3.      Research Methods

In order to solve the optimal operation problem of the integrated energy system under the protection of electricity and heat privacy, the Benders decomposition method was commonly used. The Benders decomposition-coordination method only required some privacy encrypted information, which can decompose the optimization problem, independently solve it, and achieve the optimal overall benefit through repeated iterations.

Schematic diagram of decomposition-coordination for optimal operation of integrated energy networks

Firstly, the decomposition optimal operation model of the electricity and thermal coupling system was established. Secondly, the Benders decomposition method was used to solve the model. The model was decomposed into the main problem of the thermal system and the sub problem of the power system. Through the iterative calculation between the two systems, the optimal output distribution of each system conversion device was obtained. Thirdly, the interaction mode between systems based on the Benders decomposition method was studied. On the premise of ensuring the effective protection and isolation of the respective information of the main and sub problems as much as possible, the two systems only needed to exchange the parameters and Benders constraints with privacy, which protects the information privacy of the electric/thermal system to the greatest extent.

Division of variables of master problem and sub-problem in Benders decomposition

In the iterative interaction mode of information privacy, the objective function and constraint conditions were analyzed comprehensively, and the effective information protection and sharing of power grid and heat network were summarized. The interaction mode of main and sub problem with information privacy encryption was summarized, including the information transfer and return process:

1.      For heating system, the information sent to power system during each iteration of Benders decomposition process is: H parameters , , , local optimal solution of thermal system calculated after optimization of the equipment

2.      For power system, the information returned to the thermal system during each iteration of the Benders decomposition process, is: the dual variable  of the power grid output, the local optimal solution of the power system, and Benders cut in the newly formed sub problem.

4.      Concluding Remarks

The study showed that independent optimization of the integrated electricity and heat system under the condition of information privacy protection, and following certain mechanism criteria of the interactive iterative information between the two systems, can maximize the overall benefit, which is guaranteed by the Benders decomposition optimization principle. Based on Benders decomposition method, under the condition of information encryption in the dispatching center, it can protect the information privacy between different energy networks or conversion devices in the integrated energy system, reduce information sharing and protect information security while realizing the optimal operation of each system.

Since 2016, the China Association for Science and Technology has organized the "Selection of Excellent Scientific and Technological Papers of the China Association for Science and Technology" every year, aiming to select excellent papers that have influence in the international academic community, make breakthroughs and achievements in the forefront of science and technology, play a leading role in original innovation, and make significant contributions to the national economic and social construction, promote the improvement of the quality of Chinese journals from the root, maintain the right of the premium release of achievements of Chinese scientific and technological journals, and master the leading role of academic evaluation. In this way, China's voice in the international scientific and technological community will be enhanced, and the scientific and technological innovation ability will be better improved to serve the majority of scientific and technological communities.