Microgrid EMS

A microgrid is a medium to low voltage AC/DC power system that includes distributed energy and loads. According to the connection relationship between microgrids and large grids, microgrids can be divided into two types: independent and grid connected. Among them, there is no electrical connection between the independent microgrid and the large grid, and it only operates in islanding mode; Grid connected microgrids, as controllable units, are connected to the power grid and can operate in both grid connected and islanded modes.

Overview

A microgrid is a medium to low voltage AC/DC power system that includes distributed energy and loads. According to the connection relationship between microgrids and large grids, microgrids can be divided into two types: independent and grid connected. Among them, there is no electrical connection between the independent microgrid and the large grid, and it only operates in islanding mode; Grid connected microgrids, as controllable units, are connected to the power grid and can operate in both grid connected and islanded modes.

ST895Microgrid EMSA system module capable of comprehensive monitoring, analysis, and control of photovoltaic, energy storage, distribution systems, and diesel power generation. Its main functions include data acquisition and processing, alarm processing, control and operation recording (including manual operation, controller automatic control, grid energy management system automatic control, grid stability control, interactive services, optimization scheduling, safety verification, source grid load storage collaborative optimization, load management, etc.), management functions, control and operation (with seamless switching control functions of various modes such as photovoltaic storage, photovoltaic storage, diesel storage, wind solar storage, etc., with switching time not exceeding 20ms, etc.), online statistical calculation, screen display function, human-machine interface function, communication interface, system self diagnosis and self recovery, maintenance function, permission management, etc.

General principle

(1) The concepts, technologies, methods, and equipment adopted by the system are both reliable and mature, reflecting the current international level, and have development potential. The overall technical performance of the system should reach the current level in ChinaMicrogrid EMSThe level of system construction and maintaining its nature for a certain period of time.

(2) The selection of system software and hardware should follow open system specifications and support multiple international standard protocols, including the use of open operating systems, databases, applications, development tools, interface protocols, etc.

(3) The system should have expandability in terms of system capacity, communication capability, processing capability, etc., which can facilitate product upgrades, replacements, and functional expansion. The technology, methods, and equipment used by the system provide open standard interfaces for third-party applications. In future upgrades, it can effectively protect existing investments and has a high comprehensive performance price ratio.

(4) The system can operate normally 24 hours a day, 365 days a year, and all equipment has high reliability and excellent performance.

(5) The system has high security and confidentiality, and various forms of illegal intrusion into the system are prevented through graded protection, control of data storage permissions, and network security isolation.

(6) The system administrator is able to maintain and manage the system, and during maintenance and repair, it does not affect the overall business operation of the system. At the same time, all documents of the recording system must be complete, accurate, and consistent, and the accuracy of physical connections must be accurately recorded in the corresponding documents. In addition to accurately recording themselves, various documents must also ensure logical consistency between each other. Facilitating user maintenance after handover.

System Network Structure

Microgrid EMSThe main components of the system include EMS workstation main and backup, Beidou timing device, coordination controller, communication networking equipment, etc. The system adopts a three-layer structure of station control layer, interval layer, and local layer. The schematic diagram of the system structure is shown in the following figure:

The EMS workstation (or server) is the core of the entire system, mainly responsible for running energy management software, receiving scheduling instructions, and issuing control instructions to the local level. The EMS server adopts a dual machine hot standby redundancy form, and the operating system adopts a domestic Unix or Linux secure operating system to ensure the security of network related system data. The equipment adopts rack mounted installation, and the supporting server cabinet is installed in the equipment container.

feature

Main Features

(1) The EMS system has two control algorithms: grid connected and islanding, and can smoothly switch between the two operating modes;

(2) The system can make long-term and short-term predictions on load electricity consumption, and achieve advanced energy management of the microgrid system through predictive analysis, enabling the microgrid to operate safely and economically;

(3) The system supports timing function and IEEE1588 subtle level precise clock synchronization;

(4) Support C/S structure, support real-time processing of multitasking and multi-user front-end and back-end;

(5) The system has cross platform running characteristics and can run on Windows, Linux, and domestic operating system platforms;

System performance requirements

system reliability

(1) The annual reliability rate of the system is greater than 99.9%;

(2) The average N failure time of unit (module) components is greater than 50000 hours;

(3) The average N failure time of important (critical) components is>100000 hours.

Operating lifespan

(1) The lifespan of all equipment shall not be less than 15 years under normal use (with certain spare parts) conditions;

(2) All devices operate within the given performance indicators and do not require manual adjustment or maintenance for 4000 consecutive hours.

Real time performance indicators of the system

(1) Remote measurement over dead zone transmission time less than 3 seconds

(2) Remote signal displacement transmission time is less than 2 seconds

(3) Remote control and remote adjustment command transmission time is less than 1 second

(4) Real time data scanning time of the system is 1-10 seconds (adjustable)

(5) Real time data transmission time in computer remote network communication is less than 3 seconds

(6) Screen call response time less than 2 seconds

(7) The real-time data refresh cycle of the screen is 1-10 seconds (adjustable)

(8) Simulated screen data refresh cycle of 2-5 seconds

(9) The minimum time interval for archiving is 10 minutes, and the maximum storage period is 6 months

accuracy

(1) The telemetry accuracy is greater than 99.5%

(2) Remote signaling accuracy rate of 100%

(3) Remote control accuracy rate of 100%

(4) Remote adjustment accuracy rate of 100%

(5) The on-site resolution is less than or equal to 2ms

(6) System Accident Recall (PDR) Time

(7) 15 minutes of pre accident review time for the system

(8) 15 minutes post accident review time

System load rate indicator

Under normal conditions of the power grid:

(1) Within any 5-minute period, the average load rate of the server CPU is ≤ 20%

(2) Within any 5-minute period, the average load rate of MMI workstation CPU is ≤ 30%

(3) Within any 5-minute period, the average load rate of the main station LAN is ≤ 10%

In the event of a power grid accident:

(1) Within any minute, the average load rate of the server CPU is ≤ 30%

(2) Within any minute, the average load rate of MMI workstation CPU is ≤ 40%

(3) Within any minute, the average load rate of the main station LAN is ≤ 20%

function

Microgrid EMSIt mainly includes functions such as data collection, data processing, alarm processing, human-computer interaction, real-time statistics, energy management, etc;

data collection

(1) Information on various wind and photovoltaic inverters (power generation status, power, AC/DC circuit breaker status, DC side voltage and current, AC three-phase voltage, frequency, current, temperature, various alarm information, etc.);

(2) Energy storage inverter information (charging and discharging status, power, AC/DC circuit breaker status, DC side voltage and current, AC three-phase voltage, frequency, current, temperature, various alarm information, etc.);

(3) Battery management system information (charging and discharging status, power, contactor status, SOC, SOH, DC side voltage and current, individual battery voltage and temperature, various alarm/protection information, etc.);

(4) Information of various multifunctional electricity meters in the grid connected distribution cabinet (phase voltage, line voltage, three-phase current, active/reactive power, apparent power, power factor, frequency, active/reactive energy, etc.);

(5) User distribution cabinet multifunctional electricity meter information (phase voltage, line voltage, three-phase current, active/reactive power, apparent power, power factor, frequency, active/reactive energy, etc.);

(6) Energy storage outdoor cabinet information (air conditioning information, fire protection system information);

(7) Diesel engine system (operating mode, power, AC circuit breaker status, AC phase voltage, line voltage, three-phase current, active/reactive power, apparent power, power factor, frequency, active/reactive energy, etc.);

(8) Hydrogen fuel cell system (operating mode, power, AC circuit breaker status, AC phase voltage, line voltage, three-phase current, active/reactive power, apparent power, power factor, frequency, active/reactive energy, etc.);

data processing

The data processing module of the energy management system provides functions such as analog quantity processing, state quantity processing, non measured data processing, calculation, and statistics.

(1) Analog processing: Analog describes the real-time quantitative values of each system's operation; The processing of analog quantities should enable automatic list display of all manually set analog quantities, and the corresponding wiring diagram should be retrieved based on the station to which the analog quantity belongs.

(2) State quantity processing: State quantities include switch quantities and digital quantities of multiple states, specifically including equipment status, switch position, isolation knife switch, grounding knife switch position, protection hard contact status, and other various signal quantities. State variables can be manually set, and when the manually set state is consistent with the collected state, prompt information can be provided.

(3) Non measured data processing: Non directly collected data is called non measured data, which may be manually input or calculated.

(4) Calculation: It has custom formula calculation and commonly used standard calculation functions. Users can customize standard calculation functions.

(5) Statistics: Conduct statistical analysis on important data such as diesel engine power generation, photovoltaic power generation, energy storage charging and discharging capacity, charging and discharging time, number of faulty batteries, etc. The statistics of measurement values include maximum, minimum, average, and corresponding time statistics.

Alarm Handling

The EMS system has accident alarm and warning alarm functions. Accident alarm includes circuit breaker tripping and protection device action signals caused by abnormal operation; Pre warning alarms include general equipment displacement, abnormal status information, analog or temperature exceeding limits, abnormal software and hardware status of computer monitoring systems, etc.

human-computer interaction

real-time statistics

The EMS system has the following real-time monitoring and statistical functions:

(1) Distributed power generation statistics: comprehensively monitor the real-time operation information and alarm information of distributed photovoltaic power sources, and conduct multi-faceted statistics and analysis of photovoltaic power generation to achieve comprehensive control over distributed power sources.

(2) Energy storage monitoring: comprehensively monitor the real-time operation information and alarm information of energy storage batteries, and conduct multi-faceted statistics and analysis of energy storage to achieve comprehensive control over energy storage.

(3) Load monitoring: Monitor, control, and count conditional loads, and provide a basis for low cycle load shedding, power grid balance control analysis, etc.

(4) Integrated monitoring and statistics of distribution network: Unify the comprehensive information of the operation of the distribution system, including online frequency, bus voltage, distribution power, and real-time statistics of total power generation output, remaining energy storage capacity, total active load, total reactive load, sensitive load total active, controllable load total active, and removable load total active. It can also monitor the real-time information of each circuit breaker switch status, reactive power of each branch, and alarms of each equipment, formulate response strategies, and achieve stable control of the entire distribution network. Reserved communication interface for external power grid to meet power requirements, without providing additional equipment.

energy management

The EMS system can perform normal and necessary operations such as circuit breakers and toggle switches based on commands input by the operator. It can also perform balance calculations and strategic responses based on power and load monitoring data and statistical results. The execution results of the operation control can be fed back to the relevant equipment diagram, and its execution status can generate normal (or abnormal) execution reports that can be displayed.

Switch control function

EMS can remotely turn off all circuit breakers in the distribution cabinet (except for manual circuit breakers configured in the system). The main interface of the system can accurately display the status and position of each circuit breaker, and the operator can perform circuit breaker opening/closing operations after entering the corresponding instructions. In automatic mode, EMS can automatically open/close the corresponding circuit breaker according to demand. When cutting off some loads or switching between multiple power sources, switch on/off some power switches.

Photovoltaic inverter control

EMS can monitor the real-time operation status of photovoltaic inverters and has the functions of continuous active and reactive power regulation of photovoltaic inverters. Real time adjustment of active power output of photovoltaic inverters based on system operating status.

Energy storage system control

EMS can monitor the real-time operation status of BMS and PCS, and dynamically adjust the charging mode, charging power, charging current, discharging power and other operating parameters of PCS according to BMS instructions and status. EMS has battery protection function, which controls PCS to perform shutdown, standby, discharge only, charge only and other functions based on BMS uploaded instructions and real-time status. It can also issue continuous active and reactive power adjustment instructions to PCS based on BMS status.

Diesel engine system control

EMS can monitor the operation status of diesel generators in real time and monitor their status through communication. The diesel generator power supply circuit is equipped with circuit breakers and intelligent instruments, and the system can monitor the current, voltage, power, and power generation of the power supply circuit. The system has the function of controlling the diesel generator's control circuit.

Off grid and grid connected logic control

Off grid logic control

The off grid control logic mainly deals with islanding operation mode without the participation of mains power. Realize stable spontaneous, self storage, and self sales regulation; The specific operating logic is shown in the following figure:

For the logical process, efficient C logic algorithm is mainly used to implement:

Grid connected logic control

The grid connected control logic mainly deals with the grid connected operation mode under the participation of mains power. The specific operating logic is shown in the following figure:

For the logical process, efficient C logic algorithm is mainly used to implement:

summary

ST890Microgrid EMSThe system is at the core of the entire microgrid system, serving as a monitoring system for measuring, monitoring, controlling, protecting, and implementing advanced rough operations on the microgrid. It plays a crucial role in achieving real-time energy scheduling, management, tracking, detection, and other aspects of microgrids.

case

The project is located in a high-altitude area, with an altitude of about 5400 meters. The system mainly consists of EMS workstations BMS、PCS、 Photovoltaic power generation, diesel generators and loads, etc.

On site data collection, grid connected operation control strategy, and off grid control strategy debugging for multifunctional instruments, DC screens, photovoltaic inverters, BMS, PCS, and other equipment. EMS can monitor the real-time operation status of BMS and PCS, and dynamically adjust the charging mode, charging power, charging current, discharging power and other operating parameters of PCS according to BMS instructions and status. EMS has battery protection function, which controls PCS to perform shutdown, standby, discharge only, charge only and other functions based on BMS uploaded instructions and real-time status. It can also issue continuous active and reactive power adjustment instructions to PCS based on BMS status.