Master-slave control maneuvering micro-grid host autonomous distribution method and system

Abstract

The invention discloses a master-slave control maneuvering micro-grid host autonomous allocation method and system, and the method comprises the steps: defining a power conversion unit control frame, an arbitration domain of the control frame comprises a device address of a power conversion unit, and the device address is located at a starting position of an identifier; a data field of the control frame comprises heartbeat data, and the heartbeat data changes according to a certain rule and is used for identifying normal operation of a program of the power conversion unit; when the maneuvering micro-grid supplies power in parallel, the host broadcasts a control frame to the bus according to a fixed period, the slave monitors data of the CAN bus, if the control frame of the host is not received within a certain timeout period or heartbeat data of the host received in multiple continuous periods are the same, it is judged that the host breaks down, and the control frame is sent to the CAN bus to compete for the host; if only one slave in the bus sends the control frame to the CAN bus, the slave sending the control frame is used as a new host; and if the plurality of slaves send the control frames to the bus at the same time, the CAN bus selects the slave with the small identifier as a new host. According to the invention, the power supply reliability of the maneuvering micro-grid is greatly improved.

Description

Technical Field

[0001] The invention relates to power electronics technology, and in particular to a method and system for autonomous distribution of hosts of a master-slave control mobile microgrid. Background Art

[0002] With the rapid development and cost reduction of new energy technologies such as photovoltaics, wind power generation, and energy storage batteries, microgrids constructed by combining wind power generation, photovoltaic power generation, traditional diesel generators, and traditional power grids have been widely used. Microgrids are generally fixed, including fixed distributed photovoltaic power generation systems, wind power generation systems, fixed installed energy storage systems, and provide high-reliability power supply for fixed power loads. Fixed microgrids are immobile. In order to meet economies of scale, they are usually large in scale, ranging from hundreds of kilowatts to tens of megawatts, such as industrial park microgrid systems, commercial area microgrid systems, and island-type microgrids. Mobile microgrids, which have been developed to meet special application needs such as field troops, armed police, firefighting, and emergency rescue, have mobile characteristics and can be transferred by personnel carrying, vehicle-mounted mobility, etc. to meet mobile power supply needs. The specific forms of mobile microgrids include modular mobile microgrids, cabin-type or container-type mobile microgrids. In order to meet the needs of carrying people or being on-board, mobile microgrids usually have a smaller capacity, ranging from portable photovoltaic storage power supply modules of several hundred watts, photovoltaic storage power supply cabinets of several kilowatts, to energy storage cabins or containers of tens of kilowatts.

[0003] In order to ensure mobility and minimize the size and weight, early mobile microgrids often only had one power source and did not have parallel function. However, with the development of power-consuming equipment, not only has the power consumption increased significantly, but the power supply reliability requirements have also become increasingly higher. Early mobile microgrids cannot meet the power demand of equipment, and mobile microgrids with parallel power supply functions and higher power supply reliability have emerged. At present, parallel function mobile microgrid systems generally adopt a master-slave control method, in which a host controls one or more slaves through communication. This control method is relatively mature and has the characteristics of simple control, fast response speed, good flow distribution, and high power quality, and has been widely used.

[0004] At present, mobile microgrids are usually powered independently, and as individual units, they supply power to loads to meet the power needs of personnel, regions or camps; some mobile microgrids have parallel power supply functions, which can realize independent power supply on the one hand, and meet the expansion function on the other hand, to supply power to higher-power electrical equipment. For the parallel power supply function of mobile microgrids, the master-slave control method is one of the most mature parallel control methods, that is, one power supply is the host, and the other one or more power supplies are slaves, which are controlled in real time by the host. The slaves receive the host's instructions through communication and execute according to the host's control instructions. At present, there are the following problems in the use of mobile microgrids: 1) A mobile microgrid with independent power supply cannot supply power to higher-power loads; if a mobile microgrid with a higher power level is required to meet the use of higher-power loads, and a high-power mobile microgrid is used to supply power to low-power loads, it will cause the "big horse pulling a small cart" phenomenon, resulting in a waste of resources. 2) For mobile microgrids with parallel function, the master and slave are configured before the equipment is operated. If the slave fails during operation, the parallel system can reduce the power supply and will not cause a great impact on the power supply system; but if the master fails, the entire parallel system collapses, which may have a serious impact on the power supply system, especially causing immeasurable losses to important loads. Summary of the invention

[0005] The purpose of the present invention is to provide a method for autonomous allocation of hosts in a master-slave control mobile microgrid.

[0006] The technical solution to achieve the purpose of the present invention is: a method for autonomous allocation of hosts in a master-slave control mobile microgrid, the steps of which are as follows:

[0007] A power conversion unit control frame is defined, wherein the arbitration field of the control frame includes the device address of the power conversion unit, and the device address is at the beginning of the identifier; the data field of the control frame includes heartbeat data, which changes according to a certain rule and is used to indicate that the power conversion unit program is running normally;

[0008] When the mobile microgrid is powered in parallel, the host broadcasts control frames to the CAN bus at a fixed period, and the slave monitors the CAN bus data. If the slave does not receive the host's control frame within a certain timeout period or receives the same heartbeat data from the host for multiple consecutive periods, the host is judged to be faulty and a control frame is sent to the CAN bus to compete with the host.

[0009] If only one slave sends a control frame to the CAN bus, the slave that sends the control frame will be used as the new master. If multiple slaves send control frames to the bus at the same time, the CAN bus selects the slave with the smaller identifier as the new master.

[0010] Furthermore, the control frame complies with the CAN2.0 specification, using a standard frame or an extended frame format, and the power conversion units in parallel of the mobile microgrid must use the same frame format.

[0011] Furthermore, in the arbitration field of the control frame, if the device address is not at the beginning of the identifier, all bits before the device address of the identifier should be the same.

[0012] Furthermore, after the original host eliminates the fault and enters the normal state, it will receive the control frame sent by the new host. The original host sets its own master-slave state to the slave and accepts the host control frame instruction.

[0013] A master-slave control mobile microgrid host autonomous allocation system implements the master-slave control mobile microgrid host autonomous allocation method to achieve master-slave control mobile microgrid host autonomous allocation.

[0014] Compared with the prior art, the present invention has the following significant advantages: 1) Realizing real-time control through the traditional master-slave control mode, meeting the parallel requirements of mobile microgrids, and improving power supply capacity and power quality; 2) Rapidly selecting the host through the CAN autonomous competition host mechanism, eliminating the drawbacks of the traditional master-slave control algorithm, realizing host redundancy, and greatly improving the power supply reliability of the mobile microgrid; 3) Utilizing the CAN bus's own bus competition mechanism, a unique address identification form is configured in the identifier of the CAN frame, which can quickly compete for the host on the one hand, and enable the slave to quickly know the host address on the other hand, reducing the possibility of continuous competition; 4) Using heartbeat data, the host pseudo-death phenomenon can be quickly discovered, thereby improving the host fault recognition rate, reducing the overall system fault rate, and improving system stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the master-slave parallel power supply of the photovoltaic power supply module. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0017] The present invention involves a microgrid, a mobile microgrid, a power conversion unit and a master-slave control, which are defined as follows:

[0018] Microgrid: A microgrid is a distributed small power grid constructed by combining wind power generation units, photovoltaic power generation units, internal combustion engine generator sets, energy storage batteries, fuel cells and other energy sources, including grid-connected microgrids and off-grid microgrids.

[0019] Mobile microgrid: A mobile microgrid refers to a microgrid equipment that has mobile characteristics and can be transferred by being carried by people, on vehicles, etc. to meet mobile power supply needs.

[0020] Power conversion unit: The power conversion unit is a key set of equipment for the microgrid to achieve power conversion, including the PCS connected to the AC bus (generally called energy storage converter, energy storage inverter, etc.) and the DC / DC converter inside the microgrid photovoltaic power supply module (also known as DC converter, bidirectional DC converter, etc.). A mobile microgrid is usually equipped with a set of power conversion units. A set of power conversion units can be composed of multiple PCS and DC / DC, which is determined by factors such as power. The PCS can be connected to the AC grid as a current source, or it can establish an industrial frequency voltage (AC220V / 230V or AC380V / 400V) to independently power the AC load; the DC / DC converter can be connected to other DC grids as a current source, or it can establish a DC voltage to power the DC load.

[0021] Master-slave control: Master-slave control means that one power conversion unit acts as the master and other power conversion units (one or more) act as slaves. The master sends control instructions or setting instructions and other control information to the slaves through high-speed communication methods (CAN, Ethernet, optical fiber, etc.). The slaves execute according to the control information and control algorithms to ensure the consistency of the control effects of each power unit.

[0022] The number of parallel mobile microgrids usually does not exceed 12. The power supply parallel mode is realized by the power conversion unit of each mobile microgrid (the definition of power conversion unit is shown in the "Abbreviations and Key Terms Definitions" in the previous text). Each power conversion unit adopts a master-slave control mode, that is, one power conversion unit is used as the master, and other power conversion units (one or more) are used as slaves. Control instructions are sent to the slaves through high-speed communication. The slaves execute according to the control instructions and control algorithms to ensure the consistency of the control parameters of each power unit, and then the power supply output characteristics are consistent, the power supply current is high, and the power supply quality is high.

[0023] Each mobile microgrid power output interface is connected through a power cable. The communication interface of the power conversion unit adopts CAN bus communication and is connected in bus form through shielded twisted pair cables. To ensure real-time control, the bus rate is usually 125kbps, 250kbps, 500kbps or 1Mbps; the CAN controller of the power conversion unit follows the CAN2.0 specification, and the CAN bus has terminal resistors at both ends; in order to reduce the impact of communication interference, the total length of the mobile microgrid communication cable should not exceed 30 meters. The frame format of the CAN communication of the power conversion unit follows the CAN2.0 specification and uses standard frames or extended frame formats for communication, but the same type of power conversion units must use the same frame format when connected in parallel, such as all using standard frames or extended frames. Regardless of whether standard frames or extended frames are used, they are referred to as control frames below.

[0024] CAN frame types include extended frames, standard frames, error frames, remote control frames, etc. Extended frames or standard frames include arbitration fields, control fields, data fields, and CRC. The identifier of the arbitration field (generally called frame ID, 29 bits for extended frames and 11 bits for standard frames) and the data field (64 bits) can be defined programmatically, and the rest are defined by the CAN2.0B specification and cannot be defined programmatically. This method defines the identifier and data field of the control frame to meet the needs of communication control.

[0025] Each power conversion unit is configured with a unique device address, such as 1 to n. If the control frame adopts the standard frame format, n is usually not greater than 2048; if the control frame adopts the extended frame format, n is usually not greater than 536870911.

[0026] When defining the control frame, the identifier should include the device address of the power conversion unit, which is used to identify the device address during communication. The device address should usually be at the beginning of the identifier; if it is not at the beginning, all bits before the device address should be the same. The data field can include heartbeat data, which usually consists of no less than 2 bits. Each time the heartbeat data is received, it will increase or change according to a certain rule to identify that the host program is running normally. The rest can be used to define control instructions or setting instructions and other information.

[0027] When the mobile microgrid is powered in parallel, normally only the host sends CAN frames to the CAN bus, and the slave saves the device address of the host and is in a listening state. Only when the host fails, the slave will send CAN frames to the CAN bus to compete with the host when it considers the host to be faulty according to certain rules.

[0028] When the mobile microgrid is connected in parallel for power supply, a mobile microgrid is first configured or defaulted as the host. When the mobile microgrid is running, the host broadcasts CAN extended frames or standard frames to the bus at a fixed period T (usually T ranges from 100 microseconds to 100 milliseconds); the slave monitors the CAN bus data and starts the timeout timer to calculate the host CAN frame timeout. Under normal circumstances, the slave periodically receives the CAN bus extended frame or standard frame, parses the CAN frame and executes the control instruction. The control process runs according to the traditional master-slave control method, and the heartbeat data also changes according to the rules, which can determine that the host is working normally.

[0029] During the parallel connection of the mobile microgrid, if the slave does not receive the CAN frame of the host within a certain timeout period (>T) or receives the same heartbeat data of the host CAN frame for n consecutive cycles (n>1), the host is judged to have failed. The slave begins to enter the competition host strategy. The slave immediately sends a control frame with its own device address to the CAN bus. At this time, if there is only one slave on the bus sending a control frame to the CAN bus, the slave will generally send data successfully; if multiple slaves send control frames to the bus at the same time, the CAN bus will select the priority according to the identifier of the control frame. The one with a smaller identifier has a higher priority and is usually sent successfully.

[0030] After receiving the control frame, the slave saves the device address of the control frame and recognizes the device address as the new host address. The slave stops sending control frames, accepts the control instructions of the control frame, and saves the master-slave state as a slave. The host that successfully sends the control frame considers itself as the master because it has not received control frames from other slaves. It saves the master-slave state as the master and continues to send control frames to the CAN bus at a fixed cycle. The host competition is completed.

[0031] If the original host computer is in normal state after the fault is eliminated, it will receive the control frame sent by the new host computer. The original host computer sets its own master-slave state to slave computer and accepts the control frame instruction of the host computer.

[0032] Host competition is usually completed in a very short time after the host failure is detected, so it will not have a significant impact on real-time control. This solution not only fully realizes the high power quality of the master-slave control mode and improves the capacity of the mobile microgrid, but also achieves host redundancy, reduces the catastrophic impact caused by system collapse due to host failure, and improves the reliability of parallel mobile microgrids.

[0033] In summary, the present invention adopts a master-slave control method for a mobile microgrid, and can utilize traditional master-slave control algorithms to meet parallel control requirements, reduce the difficulty of the control algorithm, and at the same time, improve the power supply capacity and power quality, and improve the response speed to load changes. The mature CAN bus communication form is adopted, and reliable parallel power supply can be achieved without increasing equipment costs; through the autonomous host competition mechanism, the host can be quickly selected, eliminating the drawbacks of the traditional master-slave control algorithm, achieving host redundancy, and greatly improving the power supply reliability of the mobile microgrid. The autonomous competition host mechanism of the present invention is not only suitable for AC parallel power supply of mobile microgrids, but also suitable for DC parallel power supply of mobile microgrids, and is suitable for places where the control cycle is between 100 microseconds and 100 milliseconds and high-speed real-time master-slave control.

[0034] Example

[0035] In order to verify the effectiveness of the scheme of the present invention, the following experimental design was carried out.

[0036] Figure 1 The figure shows the schematic diagram of the master-slave parallel power supply of the photovoltaic power supply module. The photovoltaic power supply module is a small mobile microgrid power supply module that can be carried by personnel and is equipped with energy storage batteries, photovoltaic power generation units, PCS and microgrid control units. The photovoltaic power supply module has the function of master-slave control parallel power supply, which can realize the parallel power supply of multiple photovoltaic power supply modules. When a single photovoltaic power supply module cannot meet the load power requirements, multiple photovoltaic power supply modules can meet the high-power load requirements in parallel. The figure shows 12 photovoltaic power supply modules connected in parallel. The power supply interface of each photovoltaic power supply module is connected to the power cable, the communication interface is connected to the CAN bus, the power load is connected to the power cable, and the photovoltaic power supply modules are connected in parallel to supply power to the power load. In actual product design, the type and number of mobile microgrids can be adjusted according to the needs of the power load.

[0037] Here, it is assumed that the photovoltaic power supply module is AC powered, the AC voltage level is AC230V, the rated power is 500W, and 12 units connected in parallel can meet the maximum power supply demand of 6kW. Internally, the parallel CAN bus of the PCS of the photovoltaic power supply module is connected to the communication interface, and the AC output of the PCS is connected to the power supply interface. The communication interface of the photovoltaic power supply module is connected to the CAN bus, and the power supply interface is connected to the power cable.

[0038] The CAN bus communication rate is 500kbps, and the CAN bus uses a shielded twisted pair. Matching resistors are configured at both ends of the bus to improve anti-interference capabilities. The device addresses of the photovoltaic power supply modules are 1 to 12, and the photovoltaic power supply module 1 is initially set as the host, and the other modules are slaves.

[0039] When the power switch of the optical storage power supply module is pressed, the internal PCS sends a control frame to the CAN bus as the host, and all PCSs supply power to the outside, and establish AC230V / 50Hz AC power to power the load under the control of the host PCS. The control frame sending cycle T is 500 microseconds, the control frame identifier is address 1, and the last byte of the data field is the heartbeat data. The heartbeat data starts from 0, and the heartbeat data increases by 1 each time a control frame is sent. When it increases to 255, it becomes 0 and increases again. All slaves save address 1 as the host and read the control frame sent by the host in real time.

[0040] When the host fails, one fault situation is that the host automatically stops sending control frames to make room for the host. Another fault situation is that the program is dead and may continue to send the same control frame to the bus. Both situations indicate that the host fails. All slaves cannot receive the host control frame for 4 cycles (the cycle cannot be too long or too short. If it is too long, it will cause a long competition for the host and a power failure; if it is too short, it may cause host competition due to bus interference) or the heartbeat of the host control frame received for 4 cycles has not changed. At this time, the slave thinks that the host has failed and starts to compete for the host.

[0041] All slaves send control frames to the CAN bus. Since the device address of the photovoltaic power supply module 2 is 2 with a high priority, its control frame is sent successfully. After receiving the control frame of the photovoltaic power supply module 2, other slaves set the host to address 2 and set their own master-slave status to slave. The photovoltaic power supply module 2 sets its own master-slave status to the host and periodically sends control frames to the CAN bus. The host competition is completed. When the photovoltaic power supply module 1 runs normally due to restart or other methods, it will receive the control frame sent by the photovoltaic power supply module 2, so it sets its own master-slave status to slave and receives the host control.

[0042] In summary, in the real-time control process of the host, the slave monitors the host status in real time. Once the host fails and goes offline, the slave selects a new host through an autonomous competition mechanism. The new host replaces the original host and continues the master-slave real-time control; other slaves continue to be slaves after the competition ends and accept the control of the host. This method can quickly select the host, has little impact on real-time control, and the system runs normally, thereby achieving host redundancy and greatly improving the reliability of power supply.

[0043] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0044] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A master-slave control mobile microgrid host autonomous allocation method, suitable for mobile microgrid AC parallel power supply and mobile microgrid DC parallel power supply, characterized in that: Here are the steps: A power conversion unit control frame is defined, wherein the arbitration field of the control frame includes the device address of the power conversion unit, and the device address is at the beginning of the identifier; the data field of the control frame includes heartbeat data, which changes according to a certain rule and is used to indicate that the power conversion unit program is running normally; When the mobile microgrid is powered in parallel, the host broadcasts control frames to the CAN bus at a fixed period, and the slave monitors the CAN bus data. If the slave does not receive the host's control frame within a certain timeout period or receives the same heartbeat data from the host for multiple consecutive periods, the host is judged to be faulty and a control frame is sent to the CAN bus to compete with the host. If only one slave sends a control frame to the CAN bus, the slave that sends the control frame will be used as the new master. If multiple slaves send control frames to the bus at the same time, the CAN bus selects the slave with the smaller identifier as the new master.

2. The method for autonomous allocation of hosts in a master-slave control mobile microgrid according to claim 1 is characterized in that: The control frame complies with the CAN2.0 specification and uses the standard frame or extended frame format. The power conversion units in parallel in the mobile microgrid must use the same frame format.

3. The method for autonomous allocation of hosts in a master-slave controlled mobile microgrid according to claim 1 is characterized in that: In the arbitration field of the control frame, if the device address is not at the beginning of the identifier, all bits before the identifier device address should be the same.

4. The method for autonomous allocation of hosts in a master-slave control mobile microgrid according to claim 1 is characterized in that: After the original host has eliminated its fault and entered the normal state, it will receive the control frame sent by the new host. The original host sets its own master-slave state to slave and accepts the host control frame command.

5. A master-slave control mobile microgrid host autonomous distribution system, characterized in that: The method for autonomous allocation of hosts in a master-slave controlled mobile microgrid as described in any one of claims 1 to 4 is implemented to realize autonomous allocation of hosts in a master-slave controlled mobile microgrid.

Images