CN105762830A - Intelligent grid disconnection/connection switch with detection function, and implementation method therefor - Google Patents

Abstract

The invention relates to an intelligent off/grid switch with detection function and its realization method. The switch includes a DSP processor module connected with a power supply module, a clock module, a detection module, a relay control module, a communication module and a sensor module; the relay control module is connected with a circuit breaker The method includes the following steps: the DSP processor module judges the AC voltage phase difference between the microgrid side and the large grid side according to the voltage and current data detected by the AD sensor; if not connected, the relay control module maintains the three-phase Circuit breaker cut-off state; when the DSP processor obtains the grid-connected signal from the central controller of the micro-grid through the communication module, and when the voltage phase difference between the micro-grid side and the large grid side is less than the specified value, the control relay closes the circuit breaker; this The invention integrates the grid connection point detection function, automatic control function, and network communication function into one switch, which has the advantages of strong versatility, rich functions, and convenient use.

Description

Intelligent off-grid/grid-connected switch with detection function and its realization method

technical field

The invention relates to an intelligent off-grid/grid-connected switch with a detection function and an implementation method thereof, belonging to the technical field of intelligent micro-grids.

Background technique

As the pillar energy and economic lifeline of the country, electricity plays an irreplaceable supporting role in the sustainable development of the national economy. In order to cope with the energy crisis and environmental degradation, it is necessary to promote the application of distributed energy systems, and to promote the construction of smart grids while vigorously developing green energy. For this reason, many domestic research institutions have vigorously carried out theoretical and applied research on smart grid.

Microgrid research is one of the key contents of smart grid research. Microgrid is a small-scale distributed power system. Through modern power technology, distributed power generation equipment such as gas turbines, wind power, photovoltaic power generation, fuel cells, and energy storage equipment are directly connected to the user side and together with local power loads. form an independent system. Compared with the traditional distribution network, the microgrid has many advantages: increasing local reliability, reducing feeder loss, maintaining local voltage stability, improving energy utilization efficiency by utilizing waste heat, and providing uninterrupted power supply, etc. The microgrid can also perform two-way energy exchange with the large power grid, and the two sides serve as backups for each other, thereby improving the reliability of the overall power system. Microgrid can solve the problem of stable access and efficient utilization of distributed energy sources with unstable and intermittent power generation, and its potential for wide application is huge. However, the microgrid also has some problems that need to be solved urgently. During the process of connecting and disconnecting the microgrid to the large grid, the fluctuation of the grid due to the imbalance on both sides of the grid connection point will affect the power quality and even affect the security of the grid.

Contents of the invention

The present invention is designed for the characteristics of micro-grid disconnection and grid-connection. By detecting information such as voltage and phase angle on both sides of the grid-connection point, it analyzes the state of the micro-grid and automatically finds a suitable timing for disconnecting/grid-connecting to complete the operation of disconnecting/grid-connecting, which can effectively reduce micro-grid. The impact on both sides of the grid connection point during the grid separation and grid connection process.

The technical solution adopted by the present invention to achieve the above object is: a smart off/grid switch with detection function, including: DSP microprocessor module and its connected power supply module, clock module, relay control module, communication module, sensor modules, also including circuit breakers;

The DSP processor module is used to process the data from the sensor module to obtain the real-time voltage, current and phase angle data on both sides of the grid-connected point, and send the obtained data to the communication module, which receives the upper-level grid-connected command through the communication module and sends Control commands to the relay control module;

The power module is used to convert the external mains power to the voltage required by other modules;

A clock module is used to provide a system clock;

Relay control module: used to drive the on-off of the circuit breaker, and the control terminal receives the control command of the DSP processor module;

The communication module is used for the communication between the DSP processor module and the upper computer;

Sensor module: used to send the voltage, current and phase angle data on both sides of the grid connection point to the DSP processor module as the basis for controlling the grid connection;

The circuit breaker is connected with the relay control module, and is used to control the on-off of the grid-connected point driven by the relay control module.

The DSP processor module makes a real-time judgment on the power quality of the micro-grid according to the data on both sides of the grid-connected point.

A method for realizing an intelligent off-grid/grid-connected switch with a detection function, comprising the following steps:

The DSP processor module obtains the real-time information of the voltage and current on both sides of the circuit breaker at the grid-connected point through the sensor module, and calculates the phase angle between the micro-grid side and the large-grid side;

When the host computer sends a grid-connected signal, it sends the grid-connected signal to the DSP processor module through the communication module, and at the same time sends it to the V/F equipment in the microgrid;

After the V/F equipment obtains the grid-connected signal, it automatically adjusts the operating frequency of the micro-grid, so that the phase angle difference between the micro-grid and the large grid changes;

The sensor module detects both sides of the grid-connected point, that is, when the phase angle difference δ between the micro-grid and the large grid is less than 5°, the micro-grid is considered to be in an ideal grid-connected state, and the DSP processor module drives the circuit breaker to close through the relay control module to complete the grid connection process.

It also includes: when the host computer sends out a signal of disconnecting from the grid, the microgrid and the large grid are in the grid-connected state, and the DSP processor module detects the current value on both sides in real time through the sensor module. When the current value i is less than e, the DSP processor module controls The relay control module disconnects the circuit breaker to complete the off-grid process.

The e is set according to the capacity of the microgrid.

It also includes: during the grid-connected operation, the DSP processor module obtains the real-time information of the voltage and current of the sensor modules on both sides of the circuit breaker at the grid-connected point, calculates the three-phase electrical balance level of the micro-grid side, and can send this information to PC.

The present invention has the following beneficial effects and advantages:

1. The present invention has a power quality detection function. In this design, the AD sensor modules on both sides of the grid-connected point are used to detect the three-phase voltage and current of the micro-grid side and the large-grid side in real time. The DSP core processor uses these parameters to analyze and calculate the power quality parameters of the micro-grid (including frequency Deviation, voltage deviation, voltage fluctuation and flicker, three-phase unbalance, instantaneous or transient overvoltage, waveform distortion (harmonic), voltage sag, interruption, swell and power supply continuity, etc.).

2. With automatic safety protection function. This design integrates abundant sensors and relay controllers, and they cooperate with each other to realize overvoltage, overcurrent protection, and frequency mutation protection. When there is a power quality problem caused by equipment failure on the microgrid side, by cutting off the grid-connected circuit breaker switch, the fault can be prevented from being transmitted to the large grid side in time to cause a chain reaction, which greatly improves the security of the microgrid and the large grid.

3. Has anti-islanding effect. The so-called isolated island phenomenon means that when the grid power supply is tripped due to a fault accident or power outage maintenance, the distributed grid-connected power generation system (such as: photovoltaic power generation, wind power generation, fuel cell power generation, etc.) Cut itself off from the mains network, and form a self-sufficient power supply island composed of distributed power station grid-connected power generation systems and surrounding loads. This design has a real-time detection function on the large power grid side, and can judge the occurrence of islanding phenomenon according to abnormal voltage and frequency at the first time, and achieve island protection by controlling the grid-connected circuit breaker to cut off the connection between the micro-grid and the large power grid.

4. It has the function of communicating with the host computer. This design is equipped with a bus communication module, which can communicate with the host computer through a high-speed serial bus. The intelligent off/on-grid switch can transmit the detected data (voltage, current, frequency) to the host computer for analysis and storage through the serial bus; the intelligent off-grid/on-grid switch sends off/on-grid control commands through the serial bus host computer .

5. It has rich functions and convenient use. This design is an intelligent off-grid/grid-connected switch integrating real-time detection, automatic control, remote sensing and integration. With the help of the powerful computing power of the DSP micro-processing core, on-site analysis and calculation can be realized without the help of the host computer, which reduces the burden on the host computer. In terms of fault handling, due to the elimination of two-way communication time, the efficiency of fault handling of the entire microgrid system is greatly improved, and the domino effect of grid accidents can be effectively avoided.

Description of drawings

Figure 1 is the grid-connected phase diagram of the microgrid and the large grid;

Fig. 2 is a functional block diagram of the system of the present invention;

Fig. 3 is a block diagram of the system circuit of the present invention;

Fig. 4 is the flow chart of grid-connected operation of the present invention;

Fig. 5 is a flowchart of the off-grid operation of the present invention.

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Intelligent off-grid/grid-connected switch with detection function and its implementation method,

1) It includes a power collection module, which can collect the voltage and current on both sides of the grid connection point in real time;

2) Contains a relay drive control module, which can control the opening/closing of the off-grid/grid-connected circuit breaker, and then control the electrical on-off of the micro-grid and the large power grid;

3) Contains a DSP microprocessor module, which is responsible for analyzing and calculating the data of the power acquisition module. According to the real-time voltage and current data, the frequency power quality and other information are calculated. At the same time, as the core control module, it plays the role of coordinating the work of various functional modules;

4) Contains a communication module, which is used for communication between the intelligent off/on-grid switch and the computer, which can send the collected data to the host computer and receive control commands. A computer is used as a host computer to display microgrid status information and manage microgrid isolation/grid connection control;

5) Contains a real-time clock module, which provides a precise reference clock source for the entire system and ensures high time synchronization of real-time data collection;

6) Including the system reset and data storage module, the reset module provides the stable timing required for the system power-on reset and exception handling reset of the DSP microprocessor, and the storage module provides the emergency data protection function of the abnormal state of the system to improve the reliability of the system sex;

7) Contains a power module to provide a highly reliable power supply for the system to ensure the reliability and stability of the system;

As shown in Figure 1, based on the theoretical basis of this design, when the microgrid and the large power grid operate in isolation from each other, the microgrid has its own V/F control system to support the operation of the entire microgrid. Its voltage and frequency are roughly the same as those of the large grid, but there is a quantitative difference between the voltage phase angle θmg of the microgrid and the voltage phase angle θgrid of the large grid, which is calculated as δ. When the microgrid and the large grid need to be connected to the grid, the V/F controller of the microgrid loses its function, and the voltage, frequency, and phase angle of the microgrid are all provided by the large grid and change with the large grid. The closer the phase angle on both sides of the grid-connected point is, the smaller the impact and disturbance to the grid will be. This design is designed according to the above theory. When grid-connected operation is required, the smart off-grid/grid-connected switch can monitor the phase angle changes on both sides of the grid-connected point in real time. If the difference is less than a certain value, automatic grid-connected operation can be realized.

As shown in Figure 2, this design is composed of seven parts: power data acquisition module, relay control module, communication module, real-time clock module, reset and data storage module, microprocessor module and power supply module.

Fig. 3 has provided the concrete hardware composition of each module in the embodiment of the present invention:

The main controller of this design adopts the TMS320F28335DSP microcontroller of Texas Semiconductor Corporation of the United States. It needs an 8MHz crystal oscillator and reset circuit to form its minimum system. TMS320F28335 series microcontrollers have rich on-chip resources and peripheral interfaces can be convenient connected with other modules.

Voltage and current measurement adopts ADS8558IPM analog/digital conversion chip, and a single chip can realize real-time acquisition of voltage/current of 6 channels. In this design, two ADS8558IPMs are used to collect the 3-phase voltage and current of the micro grid side and the large grid side respectively.

The data communication module is composed of MAX3232CSE and its peripheral circuits. This design uses a serial communication interface. The serial port sends and receives bytes in bits. Although slower than byte-wise parallel communication, a serial port can send data on one wire while receiving data on the other. It is simple and enables long-distance communication. For the serial port, the length can reach 1200 meters. Typically, the serial port is used for the transmission of ASCII characters. The communication is completed using 3 wires, which are the ground wire, sending, and receiving. Since serial communication is asynchronous, the port can send data on one wire while receiving data on the other.

The relay control part adopts OMRON's G5LA-14-5VDC relay, powered by 5V power supply, and the microcontroller I/O port is directly controlled by optocoupler isolation and ULN2003D Darlington tube expansion.

The power module adopts two-stage power chips. Because this system needs to be able to generate 5V, 3.3V voltage, supply each module in the system. The 5V power supply is mainly supplied to the relay module, while other modules and chips need a 3.3V power supply. The 5V power supply part adopts LNK613AC/DC chip. LNK613 uses the principle of switching power supply to convert 95V-230V AC power into 5V DC power, and complete step-down, rectification, and voltage stabilization work at one time. The output power of this design circuit is ≥3.5W, and the accuracy of 5V power supply can reach ±5% to meet the system requirements. The 3.3V circuit uses the LDO power chip PAM3101-3.3. In order to ensure power stability and low power consumption, two sets of circuits are used, one set is dedicated to the analog-to-digital conversion module, and the other set is used for other modules. The advantage of doing this is that other modules interfere with the analog-to-digital acquisition circuit.

As shown in Figures 4 and 5, the method of the present invention includes the following steps: the DSP processor module obtains the voltage and current real-time information on both sides of the grid-connected point circuit breaker through the sensor module, and obtains the phase angle between the micro-grid side and the large-grid side through calculation; When the upper computer sends a grid-connected signal, it sends the grid-connected signal to the DSP processor module through the communication module, and at the same time sends it to the V/F device in the microgrid; after the V/F device obtains the grid-connected signal, it automatically adjusts the operating conditions of the microgrid. The frequency makes the phase angle difference between the microgrid and the large grid change; the sensor module detects both sides of the grid connection point, that is, when the phase angle difference δ between the microgrid and the large grid is less than 5°, the microgrid is considered to be in an ideal grid connection state, and the DSP The processor module drives the circuit breaker to close through the relay control module to complete the grid connection process. It also includes: when the host computer sends out a signal of disconnecting from the grid, the microgrid and the large grid are in the grid-connected state, and the DSP processor module detects the current value on both sides in real time through the sensor module. When the current value i is less than e, the DSP processor module controls The relay control module disconnects the circuit breaker to complete the off-grid process. The e is set according to the capacity of the microgrid. It also includes: during the grid-connected operation, the DSP processor module obtains the real-time information of the voltage and current of the sensor modules on both sides of the circuit breaker at the grid-connected point, calculates the three-phase electrical balance level of the micro-grid side, and can send this information to PC.

Claims (6)

1. An intelligent off/grid switch with detection function, is characterized in that, comprises: DSP microprocessor module and the power supply module that it connects, clock module, relay control module, communication module, sensor module, also comprise circuit breaker ; The DSP processor module is used to process the data from the sensor module to obtain the real-time voltage, current and phase angle data on both sides of the grid-connected point, and send the obtained data to the communication module, which receives the upper-level grid-connected command through the communication module and sends Control commands to the relay control module; The power module is used to convert the external mains power to the voltage required by other modules; A clock module is used to provide a system clock; Relay control module: used to drive the on-off of the circuit breaker, and the control terminal receives the control command of the DSP processor module; The communication module is used for the communication between the DSP processor module and the upper computer; Sensor module: used to send the voltage, current and phase angle data on both sides of the grid connection point to the DSP processor module as the basis for controlling the grid connection; The circuit breaker is connected with the relay control module, and is used to control the on-off of the grid-connected point driven by the relay control module. 2. The intelligent off-grid/grid-connected switch with detection function according to claim 1, characterized in that: the DSP processor module makes a real-time judgment on the power quality of the microgrid according to the data on both sides of the grid-connected point. 3. A method for realizing an intelligent off/grid-connected switch with a detection function, comprising the following steps: The DSP processor module obtains the real-time information of the voltage and current on both sides of the circuit breaker at the grid-connected point through the sensor module, and calculates the phase angle between the micro-grid side and the large-grid side; When the host computer sends a grid-connected signal, it sends the grid-connected signal to the DSP processor module through the communication module, and at the same time sends it to the V/F equipment in the microgrid; After the V/F equipment obtains the grid-connected signal, it automatically adjusts the operating frequency of the micro-grid, so that the phase angle difference between the micro-grid and the large grid changes; The sensor module detects both sides of the grid-connected point, that is, when the phase angle difference between the micro-grid and the large grid is less than 5°, the micro-grid is considered to be in an ideal grid-connected state, and the DSP processor module drives the circuit breaker to close through the relay control module to complete the grid-connected process . 4. The method for realizing the intelligent off-grid/grid-connected switch with detection function according to claim 3, further comprising: when the upper computer sends a signal to be connected to the grid, the microgrid and the large power grid are in a grid-connected state, The DSP processor module detects the current value on both sides in real time through the sensor module. When the current value is less than e, the DSP processor module controls the relay control module to disconnect the circuit breaker to complete the off-grid process. 5. The method for realizing the intelligent off-grid/grid-connected switch with detection function according to claim 4, characterized in that, said e is set according to the capacity of the microgrid. 6. The method for realizing the intelligent off-grid/grid-connected switch with detection function according to claim 3, further comprising: during the grid-connected operation, the DSP processor module obtains the sensors on both sides of the grid-connected point circuit breaker The voltage and current real-time information of the module can be calculated to obtain the three-phase electrical balance level on the microgrid side, and this information can be sent to the host computer.