Sun Hongbin: Comprehensive energy management of multi-energy complementarity for regional energy internet

China Energy Storage Network News: "IEMS can be considered as the fourth generation of energy management system (EMS), which can solve the optimal control problem of multi-energy flow networks, that is, to achieve maximum benefits under the premise of safe energy supply through multi-energy complementarity and source-grid-load coordination."

Figure: Professor Sun Hongbin, Director of the Energy Management and Regulation Research Center of the Energy Internet Innovation Institute of Tsinghua University, gave a special report

1. Energy Internet moves from the “conceptual year” to the “implementation year”

I think last year and the year before last were the "conceptual years" of the energy internet. At that time, everyone was still discussing "what is the energy internet", "why do we need to do the energy internet", and "what the energy internet might look like". However, this year has entered the "implementation year" of the energy internet, and everyone is discussing in depth how to do it. The National Energy Administration and the Ministry of Science and Technology have many supporting projects with a large amount of capital investment, such as the first batch of "Internet +" smart energy (energy internet) demonstration projects announced by the National Energy Administration this year.

2. Optimal control problem for maximizing benefits

How to maximize the benefits under the premise of safe energy supply through "multi-energy complementation and source-grid-load coordination" is a focus issue that experts are very concerned about in the implementation of energy Internet demonstration projects. This is not easy to achieve. From a technical perspective, this focus issue can be attributed to the optimal control problem of a complex multi-energy flow network. This optimal control problem is to pursue the maximization of benefits, benefit = income-cost, and the constraint premise is safe energy supply. The income here includes energy sales and service sales, and the costs include energy purchases and service purchases. The means of optimization are distributed in various links such as cold, heat, gas, electricity, water, transportation, source, network, load, and storage. Constraints include supply and demand balance, physical range of operation, and energy supply safety. This focus issue is ultimately achieved through a system called the multi-energy complementary integrated energy management system (Integrated Energy Management System), referred to as IEMS.

3. The development history of EMS

IEMS can be considered as the fourth generation of Energy Management System (EMS). EMS is a computer decision-making system for online analysis, optimization and control used in the power grid dispatching and control center. It is the nerve center and dispatching command headquarters of the power grid operation and the core of the wisdom of the large power grid. Our research group has been studying EMS for more than 30 years. First, let's review the history of EMS.

The first generation of EMS appeared before 1969, which is called early EMS. This type of EMS only includes SCADA power supply and just collects data. There is no real-time network analysis, optimization, and collaborative control. Network analysis and optimization mainly rely on offline calculations, which belongs to experience-based scheduling. Today's park management must not stay at the level of experience-based scheduling, but requires lean management to improve core competitiveness.

The second generation of EMS appeared from the early 1970s to the early 21st century, and was called traditional EMS. The founder of this generation of EMS was Dr. Dy-Liacco, who proposed the basic model of power system safety control and developed real-time network analysis, optimization, and collaborative control. Therefore, in the 1970s, EMS developed rapidly. In 1988, my country completed the introduction of the four major power grid dispatching automation systems, and then completed digestion, absorption, and re-innovation to develop EMS with independent intellectual property rights. At that time, Tsinghua University was responsible for the introduction, digestion, and absorption of the Northeast Power Grid EMS, because the Northeast was a heavy industrial base at the time, and the Northeast Power Grid had the largest network dispatching, and the largest load in the country was in the Northeast. At present, domestic EMS has been basically localized, and the dispatching during this period has already belonged to analytical dispatching, which has risen to a new level.

The third generation of EMS is a smart grid EMS that coordinates sources, networks and loads. It appeared after the development of large-scale renewable energy. At that time, there was no multi-energy horizontal coordination, only source-grid-load coordination. In view of the uncontrollable and volatile characteristics of large-scale renewable energy, a large amount of flexible resources are needed, shifting from source-transmission to load-distribution. At this time, EMS can integrate and utilize various distributed resources, develop a distributed self-discipline-centralized coordination architecture, and have corresponding EMS from source to network to load. The source includes EMS for wind farms and photovoltaic stations, the load includes EMS for electric vehicles, buildings and households, and the network includes EMS for transmission, distribution and microgrids. These EMS are first self-disciplined, and then connected together through the communication network to form coordination. At this time, it can be called the EMS family. The EMS family has many members, and different members have different characteristics, and together they realize the coordination of sources, networks and loads in smart grids.

The fourth or next generation EMS is called the multi-energy complementary integrated energy management system, or IEMS. The integration here refers to the integration and integration of various energy sources. Due to the fragmentation of various energy sources and low comprehensive energy efficiency, it is necessary to integrate and utilize them in a cascade manner; at the same time, due to the serious shortage of flexible resources, a large amount of wind, water, and light are abandoned, so it is necessary to expand to multiple energy interconnection and find new flexible resources from multiple energy sources to support the consumption of large-scale renewable energy; through comprehensive optimization and scheduling with maximum benefits, on the premise of ensuring energy supply safety and quality, reduce energy costs and improve the economic benefits of integrated energy services.

The figure below shows a schematic diagram of IEMS.

It is like a brain, with an integrated energy system underneath, including cold, heat, gas, electricity, water, and transportation, all kinds of energy flows, called multi-energy flows. A few days ago, I introduced this system at the International Conference on Applied Energy (ICAE) held in the UK. It is generally recognized that there is no precedent in the world. The latest achievement released at Tsinghua this morning, "Park Multi-Energy Complementary Integrated Energy Management System", is the world's first IEMS product. It is very difficult for our research group to expand the power grid EMS that has been developed for 30 years into IEMS. People who study electricity do not understand heat, gas, and transportation. At this time, they need to learn knowledge of other disciplines such as heat energy, gas, and automobiles. Our team has been learning rapidly in the past five years and finally successfully developed IEMS. Of course, if there is no previous 30 years of experience in the development of power grid EMS, it will not be possible to do it in another 10 years.

4 Main functions of IEMS

(1) Multi-energy flow SCADA

It is used to realize complete, high-performance quasi-steady-state real-time data acquisition and monitoring functions, and is the basis for subsequent early warning, optimization and control functions, and uses the services provided by the system software support platform. Multi-energy flow SCADA is the "sensory system" of IEMS. Based on the energy Internet of Things, it collects multi-energy flow data (sampling frequency: electricity is at the second level, heat/cold/gas is at the second or minute level), completes the corresponding monitoring functions, and provides data to state estimation and subsequent advanced application function modules, receives system operation control instructions, and sends them to system equipment for execution through remote control/remote adjustment signals. The functional interface of multi-energy flow SCADA includes energy flow distribution, station wiring, system functions, comprehensive monitoring, operation information, analysis and evaluation, intelligent alarm, etc.

(2) Multi-energy flow state estimation

Due to the wide distribution of measurement points in the multi-energy flow sensing network, the variety of measurements, low data quality, high maintenance difficulty, and high cost sensitivity, it is inevitable that the collected data will be incomplete and erroneous. Therefore, the multi-energy flow network requires state estimation technology to provide real-time, reliable, consistent, and complete network status to provide a basis for the evaluation and decision-making of IEMS. Multi-energy flow state estimation can make bad data estimable, detectable, and identifiable by completing the measurement data and eliminating bad data, ultimately achieving the effect of reducing the number of sensors installed, reducing the complexity of the communication network, and reducing the investment and maintenance costs of the sensor network. By improving the reliability of basic data, the reliability of evaluation and decision-making can be improved, and the risk of energy network operation accidents can be reduced.