Micro-grid refers to a self-contained, micro-grid system that can be self-controlled, protected and managed. It can be integrated into a large grid operation and can operate independently from the large grid. The emergence of micro-grid originates from the development of distributed new energy and the demand for efficient energy utilization. It has the characteristics of diverse and intermittent energy sources, scattered power grid structure, complex and varied operation modes, and weak stability. Control protection and energy management put forward higher requirements.
Micro-network control and protection technology is the key to micro-grid technology. It is necessary to overcome the difficulties of micro-grid system operation and frequent disturbances. The protection of the microgrid is different from the conventional grid protection device, especially the low-voltage distribution system. The conventional conventional low-voltage distribution system does not set complicated relay protection devices, and only configures current and voltage protection for specific loops, and the microgrid contains A large number of distributed power sources, their power flow and short-circuit current vary with different operating modes, so the traditional low-voltage power distribution protection method can not meet the needs of its protection.
The main function of the control of the microgrid is when the network structure changes or fails in the microgrid, the control system can coordinate the operation mode or output between the micro power sources in time, and control the operation state of the microgrid to ensure the safe and effective operation of the microgrid. To ensure that the load can be supplied with high quality under any circumstances.
Microgrid Energy Management System (MEMS) is an energy management system in a grid-specific application environment. It is part of the large grid energy management system, but some of its functions are relatively independent of the energy management system of the large grid. From the perspective of the microgrid The main functions of MEMS should meet the needs of efficient, economical, safe and reliable operation in the microgrid, coordinate and optimize the operation of distributed power, load and various regulating equipment in the microgrid; at the same time, it must meet the requirements of the superior grid and users. Network management and control protection requirements.
With the promotion and application of microgrid, microgrid control, protection and energy management technologies will be deeply researched and explored.
1 system compositionThis paper proposes a distributed energy microgrid control protection and energy management solution, which can be used to solve the control and protection of the microgrid in different operating modes, as well as the advanced energy management of the microgrid system, suitable for grid-connected or off-grid. Microgrid system.
Figure 1 MEMS architecture diagram
The microgrid technology solution proposed in this paper consists of a microgrid control protection device and an energy management system. The microgrid control protection device comprises a programmable logic controller CPU, a single chip relay protection module, a digital analog data acquisition device, a power parameter collection device, a bus communication device, a fiber optic communication device and a display screen.
The energy management system includes switches, pre-servers, historical data servers, user workstations, GPS satellite timing devices, liquid crystal displays, uninterruptible power supplies, database software, MEMS system software, and the like.
Figure 2 Control protection system topology diagram
Figure 3 Energy Management System Topology
2 system functionThe functions of the microgrid control protection cabinet and the microgrid energy management solution are as follows: control and protection integration function: switching control between off-network operation modes; voltage/frequency stability control in off-network mode; distributed power supply and energy storage system Cooperative control; grid-connected power exchange control; black start control; anti-island protection, three-stage time-limited current protection, overload protection, inverse time overcurrent protection, zero sequence protection, voltage protection, low frequency load shedding protection, reclosing, etc. ; cooperation between micro-grid and distribution network;
Energy management system function: operational efficiency and economical technical analysis of different types of energy storage systems; calculation and analysis of operational efficiency and economy of different types of distributed power sources; output prediction of renewable power sources in microgrids such as photovoltaic power generation prediction, wind power Power generation forecasting, energy storage power generation forecasting, etc.; a variety of distributed energy economic dispatching and control; cold, hot and electric triple-supply systems for cold and hot power optimization scheduling and control; microgrid adapting to electricity price mechanism, peaking and valley filling, etc. And control strategy.
3 System featuresThe control protection platform is powerful, scalable, adaptable, convenient for system integration and structural change; the control platform supports IEC61850 communication protocol; the adaptive technology of the micro-network protects the control system under the conditions of grid-connected and isolated mode switching; protection The grade meets the outdoor demand, the working temperature is -25~55°, self-heating at low temperature, can adapt to various harsh environmental conditions; the controller fully considers the influence of electromagnetic environment in the overall design, greatly improves the anti-interference performance; the energy management system has Good openness and scalability, easy to expand functions and upgrade functions; energy management system uses mobile client technology to support remote operation and maintenance; energy management system provides a complete human-machine interface, based on a common platform Collaborate through a unified interface to achieve flexible integration of devices “plug and play†in the micro network.
4 scope of useSuitable for wind, light, storage, diesel, gas turbine and other distributed energy components of the microgrid system; for different distributed energy components of the grid-connected or off-grid microgrid power supply system; suitable for cold and heat Triple-connected micro-grid system; suitable for regional micro-grid integrated systems.
5 actual application5.1 Shanghai Electric Transmission and Distribution Group Microgrid Demonstration System
The Shanghai Electric Transmission and Distribution Group Microgrid Demonstration System is a small microgrid experimental platform. Based on the company's office building distribution system, a microgrid system containing photovoltaic, energy storage, diesel generator, DVR and APF is constructed. The platform mainly studies the application of microgrid control protection integration and energy management system, and studies microgrid networking technology, island control technology and hybrid model and online simulation technology.
Figure 4 Shanghai Electric Transmission and Distribution Group microgrid demonstration system diagram
5.2 West Lake Technology Park Microgrid Demonstration System
The micro-grid demonstration system of Xihu Science and Technology Park is a multi-energy complementary distributed energy system integration and testing experimental platform. The experimental platform will realize the typical distributed energy operation mode of self-sufficiency of power, intelligent control, redundant Internet access, and surplus network supplementation; cold and heat supply and cascade utilization.
The platform establishes a pilot, R&D and demonstration integration platform for domestic leading and international high-level distributed energy and micro-grid integration technologies, and further researches and explores the key technologies in the application, promotion and operation of distributed energy and micro-grid. Core issues provide support.
Figure 5 Schematic diagram of the micro-grid demonstration system of Xihu Science and Technology Park
6 ConclusionThe microgrid control protection and energy management solution proposed in this paper is a three-layer system architecture model based on distributed energy microgrid system. It can be applied to a microgrid system composed of multiple distributed energy sources, which can solve microgrid islands and grids. Control and protection under the switchover of island integration mode, and advanced energy management of microgrid system, suitable for grid-connected or off-grid microgrid systems.
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