CN110165701B

CN110165701B - Virtual synchronous machine grid-connection and off-grid control method in micro-grid system and micro-grid system

Info

Publication number: CN110165701B
Application number: CN201910370845.2A
Authority: CN
Inventors: 邵长伟; 符宇龙; 黄胜; 王丽芬; 钟斌; 覃日钊
Original assignee: China Electronics Greatwall Energy Shenzhen Co ltd
Current assignee: Great Wall Power Technology (Guangxi) Co.,Ltd.
Priority date: 2019-05-06
Filing date: 2019-05-06
Publication date: 2021-11-05
Anticipated expiration: 2039-05-06
Also published as: CN110165701A

Abstract

A method for controlling the connection and disconnection of virtual synchronizers in a microgrid system comprises the steps of judging whether the virtual synchronizers need to be switched in a parallel connection and disconnection manner in real time by acquiring voltage parameters of a mains supply power grid and output voltage parameters of the virtual synchronizers in the microgrid system, when the off-grid operation instruction is generated, the virtual synchronizer is quickly off-grid, when the grid-connected operation instruction is generated, the virtual synchronizer is controlled to adjust the parameters of the virtual synchronizer to be matched with the parameters of the power grid and then is connected to the power grid, the safe, seamless and smooth on-grid and off-grid switching process of the virtual synchronizer is realized, the problems that the virtual synchronizer in the traditional technical scheme cannot be suitable for the running mode of the microgrid and cannot realize seamless switching in the on-grid and off-grid switching process are solved, therefore, the problems that the charge output of the microgrid system where the virtual synchronous machine is located is not equal to the charge demand of the actual load, the continuous power supply of the important load cannot be maintained, and the microgrid cannot be timely disconnected after a fault occurs are caused.

Description

Virtual synchronous machine grid-connection and off-grid control method in micro-grid system and micro-grid system

Technical Field

The invention belongs to the technical field of micro-grids, and particularly relates to a method for controlling a virtual synchronous machine in a micro-grid system to be connected with and disconnected from the grid and the micro-grid system.

Background

With the rapid development of new energy, the occupation ratio of the new energy in a power grid is gradually improved, the new energy has the characteristics of intermittence, volatility and the like, the traditional grid-connected inverter control strategy is high in response speed and free of rotary inertia and cannot participate in power grid regulation, and the safe and stable operation of the power distribution grid and the microgrid is not facilitated The continuous power supply of important loads can not be maintained, and the problem that the system can not be off the network in time after a fault occurs is solved.

Therefore, in the conventional technical scheme, the virtual synchronous machine cannot be suitable for the operation mode of the microgrid and cannot be seamlessly switched in the grid-connected and off-grid switching process, so that the problems that the charge output of the microgrid system where the virtual synchronous machine is located is not equal to the charge demand of an actual load, continuous power supply of important loads cannot be maintained, and the microgrid cannot be timely off-grid after a fault occurs are caused.

Disclosure of Invention

In view of this, embodiments of the present invention provide a method for controlling a virtual synchronous machine in a microgrid system and a microgrid system, and aim to solve the problems that in a conventional technical scheme, a virtual synchronous machine cannot adapt to an operation mode of a microgrid and cannot perform seamless switching in a grid-connected and off-grid switching process, so that charge output in the microgrid system where the virtual synchronous machine is located is not equal to charge demand of an actual load, continuous power supply of an important load cannot be maintained, and timely off-grid operation cannot be performed after a fault occurs.

A first aspect of an embodiment of the present invention provides a method for controlling a virtual synchronous machine in a microgrid system from a grid connected state to a grid disconnected state, where the method includes:

acquiring a mains supply power grid voltage parameter and an output voltage parameter of a virtual synchronous machine in a microgrid system;

judging whether the virtual synchronous machine needs to perform grid-connection and grid-disconnection switching operation, generating a grid-disconnection operation instruction or a grid-connection operation instruction when the virtual synchronous machine needs to perform grid-connection operation, and generating a grid-connection operation instruction when the virtual synchronous machine needs to perform grid-connection operation;

when the virtual synchronous machine needs to be operated off the grid, disconnecting a switch of the virtual synchronous machine needing to be operated off the grid from a power grid according to the off-grid operation instruction;

when the virtual synchronous machine needs grid connection operation, the virtual synchronous machine is controlled to adjust the voltage parameter of the output end according to the generated grid connection operation instruction so as to match the voltage parameter of the power grid, and then the switch which needs grid connection and is connected with the power grid through the virtual synchronous machine with matched parameters is closed.

A second aspect of the embodiments of the present invention provides a microgrid system, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method as described above when executing the computer program.

A third aspect of the embodiments of the present invention provides a computer-readable storage medium, which stores a computer program, wherein the computer program is configured to implement the steps of the above method when executed by a processor.

The method for controlling the virtual synchronous machines in the microgrid system to be connected and disconnected judges whether the virtual synchronous machines need to be switched in a grid-connected mode or not in real time by acquiring the voltage parameters of a mains supply grid and the output voltage parameters of the virtual synchronous machines in the microgrid system, when the off-grid operation instruction is generated, the virtual synchronizer is quickly off-grid, when the grid-connected operation instruction is generated, the virtual synchronizer is controlled to adjust the parameters of the virtual synchronizer to be matched with the parameters of the power grid and then is connected to the power grid, the safe, seamless and smooth on-grid and off-grid switching process of the virtual synchronizer is realized, the problems that the virtual synchronizer in the traditional technical scheme cannot be suitable for the running mode of the microgrid and cannot realize seamless switching in the on-grid and off-grid switching process are solved, therefore, the problems that the charge output of the microgrid system where the virtual synchronous machine is located is not equal to the charge demand of the actual load, the continuous power supply of the important load cannot be maintained, and the microgrid cannot be timely disconnected after a fault occurs are caused.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

Fig. 1 is a schematic structural diagram of a virtual synchronous machine parallel operation system according to a first embodiment of the present invention;

fig. 2 is a flowchart illustrating an output control method of a virtual synchronous machine in a microgrid system according to a second embodiment of the present invention;

FIG. 3 is a detailed flowchart of step S100 shown in FIG. 2;

FIG. 4 is a detailed flowchart of step S300 shown in FIG. 2;

FIG. 5 is a detailed flowchart of step S400 shown in FIG. 2;

FIG. 6 is a detailed flowchart of step S400 shown in FIG. 2;

fig. 7 is a schematic diagram of a microgrid system according to an embodiment of the present invention;

fig. 8 is a specific flowchart of a parallel operation control method for virtual synchronous machines in a microgrid system according to a third embodiment of the present invention;

FIG. 9 is a detailed flowchart of step S300 shown in FIG. 8;

FIG. 10 is a detailed flowchart of step S400 shown in FIG. 8;

FIG. 11 is a detailed flowchart of step S500 shown in FIG. 8;

fig. 12 is a specific flowchart of a parallel operation control method for virtual synchronous machines in a microgrid system according to a third embodiment of the present invention;

fig. 13 is a schematic diagram of a microgrid system according to an embodiment of the present invention;

fig. 14 is a detailed flowchart of a method for controlling a virtual synchronous machine in a microgrid system to be connected to and disconnected from a grid according to a fourth embodiment of the present invention;

fig. 15 is a detailed flowchart of step S100 shown in fig. 14;

fig. 16 is a detailed flowchart of a step subsequent to step S310 shown in fig. 14;

fig. 17 is a detailed flowchart of step S400 shown in fig. 14;

fig. 18 is a schematic diagram of a microgrid system according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1, a schematic structural diagram of a microgrid system according to a first embodiment of the present invention only shows portions related to this embodiment for convenience of description, and the details are as follows:

the microgrid system provided by the first embodiment of the present invention includes a plurality of energy storage units, a plurality of virtual synchronous machines connected to the plurality of energy storage units in a one-to-one correspondence manner, an intelligent power distribution apparatus 300 respectively connected to the plurality of virtual synchronous machines and a power grid, and a centralized controller 400 connected to each energy storage unit, each virtual synchronous machine, and the intelligent power distribution apparatus 300.

In the present embodiment, the plurality of energy storage units includes a first energy storage unit 110, a second energy storage unit 120, a third energy storage unit 130, and a fourth energy storage unit 140. In other embodiments, the plurality of energy storage units may be any other number of energy storage units.

In this embodiment, the plurality of virtual synchronous machines include the first virtual synchronous machine 210, the second virtual synchronous machine 220, the third virtual synchronous machine 230, and the fourth virtual synchronous machine 240, and in other embodiments, the number of the plurality of virtual synchronous machines may be any number. Optionally, the microgrid system is further connected to a plurality of loads, in the present embodiment, a first load 510 and a second load 520 are illustrated, and in other embodiments, one or 3 or more loads may be included.

It should be understood that the centralized controller 400 is in communication connection with each energy storage unit, each virtual synchronous machine, and the intelligent power distribution device, the centralized controller 400 collects state information, data, and the like of each energy storage unit, each virtual synchronous machine, and the intelligent power distribution device 300 in real time and centrally controls each energy storage unit, each virtual synchronous machine, and the intelligent power distribution device, optionally, the centralized controller 400 may communicate with each energy storage unit, each virtual synchronous machine, and the intelligent power distribution device 300 through RS485, ECAN, or ethernet, and the like.

It should be noted that the intelligent power distribution apparatus 300 includes a plurality of switches, a switch C3 connected to the grid system at the utility grid end, switches connected to the grid system at each load, such as the switch CI and the switch C2 in this embodiment, and switches connected to the grid system at the utility grid end and the load at each virtual synchronous machine, such as the switch K1, the switch K2, the switch K3, the switch K4 in this embodiment.

Referring to fig. 2, a second embodiment of the present invention provides an output control method for a virtual synchronous machine in a microgrid system, including:

step S100: acquiring output end voltage parameters and output end current parameters, and performing active and reactive calculation;

the three-phase voltage and the three-phase current at the output end can be obtained by sampling and the like, and then other types of voltage and current parameters, such as voltage and current on a d-q axis, effective values of the voltage and the current, and the like, are obtained through DQ conversion (Park transformation), conversion and the like.

Step S200: according to the current parameter of the output end, and regulating the virtual resistor R_aAnd a virtual reactance L_sEnabling each virtual synchronous machine to achieve power equal division;

wherein, the dummy resistance R_aAnd a virtual reactance L_sFor adjustable parameters, a virtual resistance R_aAnd a virtual reactance L_sThe micro-grid system can be used for automatically adjusting the micro-grid system.

Step S300: obtaining output reference voltage E of virtual synchronous machine_VSGAnd an output reference power angle theta_VSG；

Step S400: according to the output end voltage parameter, the output end current parameter and the output reference voltage E_VSGAnd an output reference power angle theta_VSGAnd establishing a voltage ring and a current ring, and enabling the voltage output value of the virtual synchronous machine to be a target output value by adjusting internal parameters of the voltage ring and the current ring.

Wherein, the reference voltage E can be output according to the output_VSGAnd an output reference power angle theta_VSGAnd establishing a voltage ring according to the voltage parameter of the output end of the virtual synchronous machine, and establishing a current ring according to the output current value of the voltage ring and the current parameter of the output end of the virtual synchronous machine.

It should be noted that the virtual synchronous machine can be enabled to output the reference voltage E only according to the actual output end voltage parameter, the output end current parameter and the output end voltage parameter by the preset fixed internal parameter value_VSGAnd an output reference power angle theta_VSGTo obtain a target output value; the internal parameters of the voltage loop and the current loop can be adjusted in real time according to the required values by an internal preset rule, so that the output value of the virtual synchronous machine is the value required by the microgrid system, and the output control of the voltage loop and the current loop can be completed according to the parameters input by a user.

In the output control method of the virtual synchronous machine in the microgrid system in this embodiment, the virtual resistor R is adjusted according to the obtained output end current parameter of the virtual synchronous machine_aAnd a virtual reactance L_sEnabling each virtual synchronous machine to achieve power sharing, and outputting reference voltage E according to the obtained output end voltage parameter, output end current parameter and output end voltage parameter_VSGAnd an output reference power angle theta_VSGThe method comprises the steps of establishing a voltage ring and a current ring, and enabling the voltage output value of the virtual synchronous machine to be a target output value by adjusting internal parameters of the voltage ring and the current ring, so that the problems that the output of the virtual synchronous machine is not matched with power grid end data, the output is unstable and the adjustment is difficult in the traditional technical scheme are solved.

Referring to fig. 3, in a more detailed embodiment, step S100 includes:

step S110: obtaining three-phase voltage V of output end_ab、V_bc、V_caAnd three-phase current I of output end_a、I_b、I_cAnd extracting corresponding fundamental wave positive sequence component V'_ab、V′_bc、V′_ca、I′_a、I′_b、I′_c；

It should be noted that, the formula of step S110 may be:

where N is the number of discretized collection points, θ_k2 pi k/N, k is the frequency second-order system index, and z is the transformation complex variable. It should be understood that the number N of discretization collection points may be set according to the actual collection frequency requirement, and the actual collection frequency requirement may be a set fixed frequency, or may be a variable collection frequency.

Step S120: according to a fundamental wave positive sequence component V'_ab、V′_bc、V′_ca、I′_a、I′_b、I′_cAnd performing active and reactive calculation.

It should be noted that, step S120 may be the following formula:

P_m＝V′_ca×I′_c+V′_ab×I′_b；

Q_m＝V′_bc×I′_a+V′_ca×I′_b+V′_ab×I′_c；

in a more detailed embodiment, step S200 is performed by adjusting the virtual resistance R_aAnd a virtual reactance L_sThe step of making each virtual synchronous machine reach power average further comprises:

current fundamental wave I'_a、I′_b、I′_cThe positive sequence component is shifted to 90 degrees to obtain phase shift current fundamental wave I ″_a、I″_b、I″_c：

According to current fundamental wave I'_a、I′_b、I′_cPhase-shift current fundamental wave I_a、I″_b、I″_cVirtual resistance R_aAnd a virtual reactance L_sCalculating virtual impedance Z of virtual synchronous machine_va、Z_vb、Z_vcThe calculation formula can be:

it should be noted that the microgrid system is constantly in a state of judging whether the virtual synchronous machine is in a power sharing state, and when the power of the virtual synchronous machine is detected to be uneven, the microgrid system can automatically and continuously adjust the virtual resistor Ra and the virtual reactor Ls until the virtual synchronous machine is in the power sharing state. Or when the user feels that the virtual impedances Zva, Zvb and Zvc need to be adjusted again, the user can input an adjusting instruction, and the microgrid system can adjust the virtual impedances Zva, Zvb and Zvc according to the adjusting instruction input by the user.

In this embodiment, the virtual synchronous machine is in a state of adjusting the virtual resistance Ra and the virtual reactance Ls in real time, so that the virtual synchronous machine is in a state of power sharing in real time.

In a more detailed embodiment, step S300 specifically includes the following steps:

referring to fig. 4, a secondary voltage regulation reference value U is input to a stator excitation voltage equation and a rotor mechanical equation_AGCReference value omega of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGCCalculating the output voltage reference E of the virtual synchronous machine_VSGAnd power angle reference theta_VSG。

It should be noted that, if the virtual synchronous machine is in grid-connected operation, the reference value U of secondary voltage regulation_AGCReference value omega of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGCRelated to parameters between the virtual synchronous machine and a grid-connected end of a power grid connected with the virtual synchronous machine, the secondary voltage regulation reference value U can be obtained through specific target parameter requirements_AGCReference value omega of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGCIf the virtual synchronous machine does not run in a grid-connected mode, the secondary voltage regulation reference value U can be input into the virtual synchronous machine according to the preset parameter value_AGCReference value omega of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGC(ii) a In the output control method of the virtual synchronous machine in the microgrid system of the embodiment, the secondary voltage regulation reference value U_AGCReference value omega of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGCThe information can be obtained through external terminal communication or external direct input, such as: in a first embodiment of the invention, virtualizationThe synchronous machine can obtain a secondary voltage regulation reference value U through an integrated controller in communication connection with the synchronous machine_AGCReference value omega of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGCSecond regulation of voltage reference value U_AGCReference value omega of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGCAnd parameters between the virtual synchronous machine and a grid-connected end of a power grid connected with the virtual synchronous machine are related. For example: if the virtual synchronous machine does not run in a grid-connected mode, the secondary voltage regulation reference value U related to the input of the virtual synchronous machine can be automatically input according to the set data value_AGCReference value omega of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGC。

It should be understood that the virtual synchronous machine can obtain the secondary voltage regulation reference value U according to the obtained secondary voltage regulation reference value_AGCReference value omega of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGCAnd performing secondary voltage regulation operation, secondary frequency modulation operation and secondary phase modulation operation, thereby having secondary voltage regulation and frequency modulation capability.

Wherein the output voltage reference E of the virtual synchronous machine is obtained_VSGAnd power angle reference theta_VSGThe formula of (1) is:

E_VSG＝E₀+Z_V+K_Q(Q_n-Q_m)+U_AGC；

θ_VSG＝wt+θ_AGC。

the control method in the embodiment is implemented by obtaining the secondary voltage regulation reference value U_AGCReference value omega of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGCThe virtual synchronous machine is subjected to secondary voltage regulation operation, secondary frequency modulation operation and secondary phase modulation operation, so that the virtual synchronous machine has secondary voltage regulation and frequency modulation capability, a microgrid system comprising the virtual synchronous machine has a secondary voltage regulation and frequency modulation control strategy function, no-difference regulation is realized, and the power stability and the adjustability of the system are kept.

Referring to fig. 5 and 6, in a more detailed embodiment, in step S400, the output reference voltage E is outputted according to the output terminal voltage parameter, the output terminal current parameter and the output reference voltage E_VSGAnd an output reference power angle theta_VSGThe method for establishing the voltage loop and the current loop comprises the following steps:

step S410: for output voltage reference E_VSGSum power angle reference theta_AGCCarrying out DQ conversion to obtain d-q two-phase reference voltage V of voltage ring_d、V*_q。

It should be noted that step S410 may specifically be: for the output voltage reference E_VSGAnd the power angle reference theta_AGCDecoupling is carried out in a d-q coordinate system, so that a d-q two-phase reference voltage V is obtained_d、V*_qI.e. the real and reactive components of the voltage loop reference voltage.

Step S420: three-phase voltage V output to virtual synchronous machine_ab、V_bc、V_caObtaining d-q two-phase voltage V through DQ conversion_d、V_q。

It should be noted that, step S420 may specifically be: three-phase voltage V output to virtual synchronous machine_ab、V_bc、V_caDecoupling is carried out in a d-q coordinate system, so that d-q two-phase voltage V is obtained_d、V_qI.e. the real and reactive components of the voltage loop voltage.

Step S430: according to V_d、V*_qAnd V_d、V_qEstablishing a voltage ring based on PI + repeated control, wherein the voltage ring outputs d-q two-phase reference voltage current I_d、I*_q：

Step S440: reference I of output current according to voltage loop_d、I*_qTo virtual synchronous machineThree-phase current I at output end of output_a、I_b、I_cObtaining d-q two-phase current I of current loop through DQ conversion_d、I_q。

Step S450: reference I of output current according to voltage loop_d、I*_qAnd reference I of the current loop_d、I_qEstablishing a current loop based on PI control, and outputting voltage V of the current loop_md、V_mq。

Step S460: to the output voltage V of the current loop_md、V_mqDQ inverse transformation is carried out and a target output voltage V of the virtual synchronous machine is obtained by a third harmonic injection method_ma、V_mb、V_mc。

In this embodiment, the parameter k of the voltage loop and the current loop is adjusted_pAnd k_iThe target output voltage can be obtained, the method is suitable for output regulation of the virtual synchronous machine in any microgrid system, and the output of the virtual synchronous machine can be matched with parameters of a power grid end and parameters of an energy storage unit end.

Fig. 7 is a schematic diagram of a microgrid system according to an embodiment of the present invention. As shown in fig. 7, fig. 7 of the embodiment is a schematic diagram of a microgrid system according to an embodiment of the present invention. As shown in fig. 7, the microgrid system 10 of the embodiment includes: a processor 100, a memory 101, and a computer program 102 stored in the memory 101 and operable on the processor 100, such as an output control method program of a virtual synchronous machine in a microgrid system. The processor 100 executes the computer program 102 to implement the steps in the above-mentioned embodiment of the output control method for the virtual synchronous machine in each microgrid system, such as steps S100 to S400 shown in fig. 2.

Illustratively, the computer program 102 may be partitioned into one or more modules/units, which are stored in the memory 101 and executed by the processor 100 to implement the present invention. One or more of the modules/units may be a series of computer program instruction segments capable of performing certain functions, which are used to describe the execution of the computer program 102 in the microgrid system 10. For example, the computer program 102 may be divided into a synchronization module, a summarization module, an acquisition module, and a return module (a module in a virtual device), and each module specifically functions as follows:

the microgrid system 10 may be a computer or a central processing unit. The piconet system may include, but is not limited to, a processor 100, a memory 101. Those skilled in the art will appreciate that fig. 7 is merely an example of the microgrid system 10, and does not constitute a limitation on the microgrid system 10, and may include more or fewer components than those shown, or combine certain components, or different components, for example, the microgrid system may further include input-output devices, network access devices, buses, and the like.

The Processor 100 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.

The storage 101 may be an internal storage unit of the microgrid system 10, such as a hard disk or a memory of the microgrid system 10. The memory 101 may also be an external storage device of the piconet system 10, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), etc. provided on the piconet system 10. Further, the memory 101 may also include both an internal storage unit and an external storage device of the microgrid system 10. The memory 101 is used to store computer programs and other programs and data required by the piconet system. The memory 101 may also be used to temporarily store data that has been output or is to be output.

Referring to fig. 8, a third embodiment of the present invention provides a parallel operation control method for a virtual synchronous machine in a microgrid system, where the control method includes:

step S100: and acquiring the voltage of the power grid, and judging whether the voltage of the power grid meets a preset grid-connected standard.

It should be noted that the obtaining terminal may obtain the grid voltage through wireless or wired communication, for example, in the first embodiment of the present invention, the obtaining main body is the centralized controller, the centralized controller obtains the grid voltage through communication and compares the obtained grid voltage with a preset grid-connection standard, and the grid-connection standard is an acceptable grid-connection voltage range value in the actual microgrid system.

Step S200: and if the power grid voltage meets the preset grid-connected standard, acquiring the state information of each energy storage unit and the state information of each virtual synchronous machine.

It should be noted that the status information of each energy storage unit includes, but is not limited to, voltage, current, fault alarm status, capacity, and the like; the state information of each virtual synchronous machine includes, but is not limited to, voltage, current, frequency, fault alarm status, etc.

Step S300: and setting the working mode of each virtual synchronous machine according to the state information of each energy storage unit, and performing grid-connected startup.

It should be noted that whether each virtual synchronous machine is in the synchronous generator mode or the synchronous motor mode may be set according to whether each energy storage unit needs to be charged or discharged.

Step S400: if the power grid voltage does not accord with the preset grid-connected standard, one of the virtual synchronous machines is selected as a main virtual synchronous machine according to a preset rule, and the rest of the virtual synchronous machines are selected as auxiliary virtual synchronous machines.

Step S500: and controlling the master virtual synchronous machine to start off the network firstly and then controlling the slave virtual synchronous machine to start off the network.

In the parallel operation control method of the virtual synchronous machines in the microgrid system, the operating modes of the virtual synchronous machines are set according to the acquired state information of the energy storage units so that the virtual synchronous machines are matched with the operating states of the energy storage units in real time, when the grid voltage does not meet the preset grid-connected standard, one of the grid voltage is selected as a main virtual synchronous machine according to the preset rule, the other is the slave virtual synchronous machine, the master virtual synchronous machine is controlled to be started off the network firstly and then the slave virtual synchronous machine is controlled to be started off the network, so that each virtual synchronous machine can be normally connected with the power grid and the load, the problems that the working modes in the traditional technical scheme are single, the running state of the energy storage unit of the virtual synchronous machine cannot be matched in real time, and under the condition that a plurality of virtual synchronous machines exist, the power-on time sequence of each virtual synchronous machine is difficult to adjust so as to enable the virtual synchronous machine to be normally connected into a power grid and a load.

Referring to fig. 9, in a more detailed embodiment, step S300 specifically includes:

step S310: and determining the virtual synchronous machine in the current non-fault state according to the state information of each energy storage unit and the state information of each virtual synchronous machine, and determining whether each energy storage unit needs to be charged or discharged.

It should be understood that each virtual synchronous machine and each energy storage unit have a unique identifier, after the microgrid system determines a virtual synchronous machine in a non-fault state according to the acquired state information of each energy storage unit and each virtual synchronous machine, the virtual synchronous machines are correspondingly recorded one by one, fault information is fed back to the corresponding virtual synchronous machine in the fault, and the virtual synchronous machine in the fault gives a fault alarm after receiving the feedback information. The microgrid system can also feed back fault information to terminal equipment of maintenance personnel communicating with the microgrid system.

Step S320: and sending the power reference value to the virtual synchronous machine connected with each energy storage unit according to the charging and discharging requirements of each energy storage unit.

Wherein, step S320 specifically includes:

and when the energy storage unit is in a charging requirement, sending a negative power reference value to a virtual synchronous machine connected with the energy storage unit.

It should be noted that, after the virtual synchronous machine receives the negative power reference value, the virtual synchronous machine operates in the synchronous motor mode.

When the energy storage unit is in a discharge demand, a positive power reference value is sent to a virtual synchronous machine connected with the energy storage unit.

It should be noted that, after the virtual synchronous machine receives the positive power reference value, the virtual synchronous machine operates in the synchronous generator mode.

Step S330: and controlling the grid-connected startup of each virtual synchronous machine according to the power reference value.

It should be noted that grid-connected startup refers to startup after the virtual synchronous machine is connected to the power grid, for example, in the first embodiment of the present invention, if the first virtual synchronous machine is grid-connected startup, it refers to first controlling the switches K1 and C1 to be closed, and then starting the first virtual synchronous machine.

Referring to fig. 10, in a more detailed embodiment, step S400 specifically includes:

step S410: and acquiring the state information of each energy storage unit and the state information of each virtual synchronous machine.

It should be understood that the status information of the energy storage unit includes, but is not limited to, voltage parameters, current parameters, power parameters, fault alarm status, operational information, discharge or charge requirements, etc.; the state information of the virtual synchronous machine includes, but is not limited to, a voltage parameter, a current parameter, a power parameter, a fault alarm state, operation information, an operation mode, and the like.

Step S420: and determining the virtual synchronous machine in the current non-fault state according to the state information of each energy storage unit and the state information of each virtual synchronous machine, and determining whether each energy storage unit meets the discharge requirement.

Step S430: and determining the number N of the virtual synchronous machines which have no fault state and are connected with the energy storage units to meet the discharge requirement.

Step S440: and sequencing the communication IDs of the N virtual synchronous machines.

The order of the communication IDs may be set autonomously, and may be, for example, sorted by numbers, letters, or the like.

Step S450: and setting one virtual synchronous machine as a master virtual synchronous machine and setting the other virtual synchronous machines as slave virtual synchronous machines according to the communication ID.

The virtual synchronous machine with the smallest communication ID may be set as the master virtual synchronous machine, and the remaining virtual synchronous machines may be set as the slave virtual synchronous machines.

In other embodiments, the virtual synchronous machine with the largest communication ID or any designated communication ID may be set as the master virtual synchronous machine, and the remaining virtual synchronous machines may be set as the slave virtual synchronous machines.

Referring to fig. 11, in a more detailed embodiment, step S500 specifically includes:

step S510: and broadcasting and sending a starting-up instruction to the main virtual synchronous machine.

It should be noted that the master virtual synchronous machine is started up after receiving the start-up instruction, and feeds back a start-up completion signal to the centralized control end of the microgrid system, and if the centralized control end of the microgrid system does not receive the fed-back start-up completion signal within a preset time interval, the start-up signal is sent to the master virtual synchronous machine again until the start-up completion signal fed back by the virtual synchronous machine is received.

Step S520: and judging whether the master virtual synchronous machine provides parallel operation output voltage for the slave virtual synchronous machine after off-network startup, if so, broadcasting and sending a command to be started to the slave virtual synchronous machine.

It should be noted that, after determining whether the master virtual synchronous machine is off-network and started up first by whether a startup completion signal fed back by the master virtual synchronous machine is received or by detecting state information of the master virtual synchronous machine or by insisting on a closed state of a switch corresponding to the master virtual synchronous machine or by manual input of a user, determining whether the master virtual synchronous machine can provide voltage to the outside by obtaining output parameters of the master virtual synchronous machine to determine whether the master virtual synchronous machine can provide parallel operation output voltage for the slave virtual synchronous machines.

Step S530: and judging whether the voltage of the output side of the slave virtual synchronous machine meets the starting voltage, if so, sending a starting instruction to the slave virtual synchronous machine.

It should be noted that, whether the output side voltage of the slave virtual synchronous machine satisfies the boot voltage may be determined by obtaining information of the output parameter of the slave virtual synchronous machine, or by human judgment, or the like, wherein the output parameter may also be obtained by setting a sampling module at the output side of the slave virtual synchronous machine.

Referring to fig. 12, in a more detailed embodiment, the step S500 further includes:

step S600: and acquiring the number N of the virtual synchronous machines in the off-network running state at present.

It should be noted that each virtual synchronous machine and the switch corresponding to the virtual synchronous machine have a unique identifier, and it is possible to determine whether the virtual synchronous machine is in the off-network running state or not by obtaining the state information of the virtual synchronous machine and/or the state information of the switch or by the state information fed back by the virtual synchronous machine itself, thereby obtaining the number of virtual synchronous machines currently in the off-network running state.

Step S700: and acquiring the total rated capacity Sn of the N virtual synchronous machines, the first load access capacity SL1 and the second load access capacity SL2 of the current microgrid system.

It should be noted that, the obtaining of the total rated capacity Sn of the N virtual synchronous machines may be to obtain capacity values of each virtual synchronous machine in the N virtual synchronous machines, and then add the capacity values of each virtual synchronous machine to obtain the total rated capacity Sn of the N virtual synchronous machines.

It should be noted that each capacity value may be directly obtained, or the corresponding capacity value may be calculated after the obtained voltage parameter and current parameter are obtained.

Step S800: the total rated capacity Sn of each virtual synchronous machine, the first load access capacity SL1 of the current system, and the second load access capacity SL2 are compared in capacity.

It should be noted that, the total rated capacity Sn of each virtual synchronous machine may be compared with the sum of the first load access capacity SL1 and the second load access capacity SL2, and if the total rated capacity Sn of each virtual synchronous machine is smaller than the sum of the first load access capacity SL1 and the second load access capacity SL2, the total rated capacity Sn of each virtual synchronous machine may be compared with the first load access capacity SL 1.

Step S900: and closing the connection of the first load and/or the second load with the virtual synchronous machine according to the comparison result.

In a more detailed embodiment, step S900 includes:

when the total rated capacity Sn of the virtual synchronous machine is not less than the sum of the first load access capacity SL1 and the second load access capacity SL2, a control command or a signal is sent to the intelligent power distribution device to control the intelligent power distribution device to close the first switch of the first load access system and the second switch of the second load access system.

When the total rated capacity Sn of the virtual synchronous machine is not less than the access capacity SL1 of the first load and the total rated capacity Sn of the virtual synchronous machine is less than the sum of the access capacity SL1 of the first load and the access capacity SL2 of the second load, a control command or signal is sent to the intelligent power distribution device to control the intelligent power distribution device to close a first switch of the first load access system.

It should be understood that, in the present embodiment, the first load may be understood as the load having the highest importance level.

In the method in this embodiment, the total rated capacity Sn of the N virtual synchronous machines, the first load access capacity SL1 of the current microgrid system, and the second load access capacity SL2 are obtained and compared in real time to control the closing of the first switch of the first load access system and the second switch of the second load access system, so that the continuous power supply of the microgrid system to the load, particularly an important load, is realized.

Fig. 13 is a schematic diagram of a microgrid system according to an embodiment of the present invention. As shown in fig. 13, the microgrid system 20 of the present embodiment includes: a processor 200, a memory 201, and a computer program 202, such as a motor static initial angle positioning method program, stored in the memory 201 and executable on the processor 200. When the processor 200 executes the computer program 202, steps in the embodiment of the parallel machine control method for the virtual synchronous machine in the microgrid system are implemented, for example, steps S200 to S500 shown in fig. 8. Alternatively, the processor 200, when executing the computer program 202, implements the functions of each module/unit in the above-described device embodiments, for example, the functions of the modules/units shown in fig. 8.

Illustratively, the computer program 202 may be partitioned into one or more modules/units, which are stored in the memory 201 and executed by the processor 200 to implement the present invention. One or more of the modules/units may be a series of computer program instruction segments capable of performing certain functions, which are used to describe the execution of the computer program 202 in the microgrid system 20. For example, the computer program 202 may be divided into a synchronization module, a summarization module, an acquisition module, and a return module (a module in a virtual device), and each module specifically functions as follows:

the microgrid system 20 may be a centralized controller in the first embodiment of the present invention. The microgrid system may include, but is not limited to, a processor 200 and a memory 201. Those skilled in the art will appreciate that fig. 13 is merely an example of the microgrid system 20, and does not constitute a limitation on the microgrid system 20, and may include more or fewer components than those shown, or combine certain components, or different components, for example, the microgrid system may further include input and output devices, network access devices, buses, and the like.

The Processor 200 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.

The storage 201 may be an internal storage unit of the microgrid system 20, such as a hard disk or a memory of the microgrid system 20. The memory 201 may also be an external storage device of the piconet system 20, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), etc. provided on the piconet system 20. Further, the memory 201 may also include both an internal storage unit and an external storage device of the microgrid system 20. The memory 201 is used to store computer programs and other programs and data required by the microgrid system. The memory 201 may also be used to temporarily store data that has been output or is to be output.

Referring to fig. 14, a fourth embodiment of the present invention provides a method for controlling a virtual synchronous machine in a microgrid system, which only shows parts related to the present embodiment for convenience of description, and the specific steps are detailed as follows:

step S100: acquiring a mains supply power grid voltage parameter and an output voltage parameter of a virtual synchronous machine in a microgrid system;

the obtained voltage parameters of the utility power grid can be specifically voltage, current, frequency, phase and the like of the power grid; the obtained output voltage parameters of the virtual synchronous machine can be voltage, current, frequency, phase and the like output by the virtual synchronous machine; the microgrid system is a microgrid system with a virtual synchronous machine as a core, and the microgrid system can comprise the virtual synchronous machine, an energy storage unit connected with the virtual synchronous machine, a plurality of groups of switches connected with a power grid and a load by the virtual synchronous machine, and the like.

Step S200: judging whether the virtual synchronous machine needs to perform grid-connection and grid-disconnection switching operation, generating a grid-disconnection operation instruction when the virtual synchronous machine needs to perform grid-disconnection operation, and generating a grid-disconnection operation instruction when the virtual synchronous machine needs to perform grid-connection operation;

it should be noted that the off-grid operation instruction is used for controlling the virtual synchronous machine to switch from grid connection to off-grid. And the grid-connected operation direct current is used for controlling the virtual synchronous machine to be switched from off-grid to grid-connected.

Step S300: when the virtual synchronous machine needs to be operated off the grid, disconnecting the switch of the virtual synchronous machine needing to be operated off the grid from the grid according to the off-grid operation instruction;

for convenience of understanding, when it is assumed that the virtual synchronous machines are in the virtual synchronous machine parallel operation system in the first embodiment of the present invention, referring to fig. 1, if all the virtual synchronous machines need to be disconnected from the power grid, for example, when the power grid fails and the frequency and voltage thereof are abnormal, the switch C3 may be directly disconnected, and if a problem occurs in a certain virtual synchronous machine, only the failed virtual synchronous machine needs to be disconnected, the switch corresponding to the failed virtual synchronous machine may be disconnected, for example, the failed virtual synchronous machine is the first virtual synchronous machine, and only the switch K1 may be disconnected.

Step S400: when the virtual synchronous machine needs grid-connected operation, the virtual synchronous machine is controlled to adjust the voltage parameter of the output end according to the generated grid-connected operation instruction so as to match the voltage parameter of the power grid, and then the virtual synchronous machine which needs grid connection and is matched with the parameter is closed to be connected with a switch of the power grid.

For convenience of understanding, when it is assumed that the virtual synchronous machine is in the virtual synchronous machine parallel operation system in the first embodiment of the present invention, referring to fig. 1, generally, only the switch C3 needs to be closed, and the switches K1 to K4 keep the original state, but if a virtual synchronous machine is disconnected due to a fault and the fault is solved, if the virtual synchronous machine needs to be connected, the corresponding switch is closed, for example, if the virtual synchronous machine needs to be connected again after the fault occurs, and the first virtual synchronous machine needs to be connected again, the switch K1 may also need to be closed.

It should be noted that, the voltage parameter at the output end of the virtual synchronous machine can be matched with the voltage parameter of the power grid by performing primary voltage regulation and frequency regulation and/or secondary voltage regulation and frequency regulation equal operation on the virtual synchronous machine.

Optionally, after sending the close command signal to close the main connection switch, the method further includes:

step S500: acquiring the condition of accessing a load in a system where a virtual synchronous machine is currently located; when the important load of the system is connected to the grid and the secondary load is disconnected, a closing instruction is sent to control the secondary load to be connected into the system.

The generation of the off-network operation instruction in step S200 includes the following:

when the virtual synchronous machine is in a grid-connected state, judging whether the virtual synchronous machine is in an abnormal state or not according to the power grid voltage parameter and the output voltage parameter of the virtual synchronous machine, and if so, generating an active off-grid operation instruction;

it should be noted that the grid voltage parameters include, but are not limited to, three-phase voltage, effective voltage, and the like of the grid, and frequency and other parameters obtained by the grid; the virtual synchronous machine output voltage parameters include, but are not limited to, three-phase voltage, effective voltage and the like output by the virtual synchronous machine, and frequency and other parameters obtained by the power grid.

And when the virtual synchronous machine is in a grid-connected state and receives an externally input switching off-grid instruction, generating a passive off-grid operation instruction.

The generation of the grid-connection operation instruction in step S200 includes the following:

when the virtual synchronous machine is in a grid-connected state, judging that the grid connection of the virtual synchronous machine is recovered to a normal state from an abnormal state according to the power grid voltage parameter and the output voltage parameter of the virtual synchronous machine, and if so, generating an active grid-connected operation instruction;

and when the virtual synchronous machine is in an off-grid state and receives an externally input switching grid-connection instruction, generating a passive grid-connection operation instruction.

The virtual synchronous machine grid-connected and off-grid control method in the embodiment judges whether the virtual synchronous machine needs to be switched in a grid-connected and off-grid mode in real time by acquiring the voltage parameters of a mains supply power grid and the output voltage parameters of the virtual synchronous machine in a micro-grid system, when the off-grid operation instruction is generated, the virtual synchronizer is quickly off-grid, when the grid-connected operation instruction is generated, the virtual synchronizer is controlled to adjust the parameters of the virtual synchronizer to be matched with the parameters of the power grid and then is connected to the power grid, the safe, seamless and smooth on-grid and off-grid switching process of the virtual synchronizer is realized, the problems that the virtual synchronizer in the traditional technical scheme cannot be suitable for the running mode of the microgrid and cannot realize seamless switching in the on-grid and off-grid switching process are solved, therefore, the problems that the charge output of the microgrid system where the virtual synchronous machine is located is not equal to the charge demand of the actual load, the continuous power supply of the important load cannot be maintained, and the microgrid cannot be timely disconnected after a fault occurs are caused.

Referring to fig. 15, in a more detailed embodiment, the obtaining the grid voltage parameter and the output voltage parameter of the virtual synchronous machine in step S100 includes:

s110: collecting three-phase voltage V at electric network end_gab、V_gbc、V_gcaAnd the three-phase voltage V of the output end of the virtual synchronous machine_ab、V_bc、V_ca。

It should be noted that the information may be directly fed back to the grid and the virtual synchronous machine for collection, or collected by setting sampling modules at the grid side and the output side of the virtual synchronous machine, which is not limited herein.

S120: three-phase voltage V to the grid terminal_gab、V_gbc、V_gcaPhase-locked to obtain angular frequency w of power grid end_gAnd phase theta_g。

It should be understood that the phase locking in this embodiment may be implemented by establishing a phase-locked loop, specifically, using the three-phase voltage V at the grid end_gab、V_gbc、V_gcaControlling and deriving the frequency and phase of an oscillating signal within a phase-locked loop, i.e. the angular frequency w of the mains_gAnd phase theta_gThe phase-locked loop can be composed of a phase discriminator, a loop filter, a voltage-controlled oscillator and the like.

S130: three-phase voltage V to output end of virtual synchronous machine_ab、V_bc、V_caAnd performing phase locking to obtain the angular frequency w and the phase theta of the virtual synchronous machine.

It should be understood that the phase locking in this embodiment can be implemented by establishing a phase-locked loop, specifically, by using the three-phase voltage V at the output end of the virtual synchronous machine_ab、V_bc、V_caThe method comprises the steps of controlling and obtaining the frequency and the phase of an oscillation signal in a loop of a phase-locked loop, namely obtaining the angular frequency w and the phase theta of a virtual synchronous machine, wherein the phase-locked loop can be composed of a phase discriminator, a loop filter, a voltage-controlled oscillator and the like.

It should be noted that, in the above embodiment, each step S120 and each step S130 may be executed simultaneously, or may be executed in sequence or in reverse order, and the execution order of each process should be determined by its function and inherent logic, but should not be limited to the implementation process of the embodiment of the present invention.

Referring to fig. 16, in an embodiment, after step S300, the method further includes the following steps:

step S310: and acquiring the number N of the virtual synchronous machines in the current running state.

It should be noted that the obtaining terminal may obtain the state information of the virtual synchronous machine through a communication network such as RS485, ECAN, or ethernet, or wirelessly. For example, the communication modules are arranged in both the acquisition terminal and the virtual synchronous machine, and the acquisition terminal can acquire the information of the virtual synchronous machine in real time through the communication modules, so as to obtain the number N of the virtual synchronous machines in the current running state.

Step S320: and acquiring the total rated capacity Sn of the N virtual synchronous machines, the first load access capacity SL1 and the second load access capacity SL2 of the current microgrid system.

It should be noted that, for convenience of illustration, only the first load and the second load are listed in this embodiment, and the method is not limited to be only suitable for the microgrid system to have only two loads for access, for example, in other embodiments, the third load access capacity SL3 may also be obtained.

It is to be understood that the importance level of the first load is higher than that of the second load in the present embodiment.

Step S330: the total rated capacity Sn of each virtual synchronous machine, the first load access capacity SL1 of the current system, and the second load access capacity SL2 are compared in capacity.

It should be noted that, it may be first compared whether the total rated capacity Sn of each virtual synchronous machine is smaller than the first load access capacity SL1, and if not, then compared whether the total rated capacity Sn of each virtual synchronous machine is smaller than the sum of the first load access capacity SL1 and the second load access capacity SL 2.

Step S340: and disconnecting the first load and/or the second load from the virtual synchronous machine according to the comparison result.

In a more detailed embodiment, step S340 specifically includes:

step S341: and when the total rated capacity Sn of the N virtual synchronous machines is smaller than the first load access capacity SL1, sending a control command to disconnect the first load and the second load.

Step S342: and when the total rated capacity Sn of the N virtual synchronous machines is larger than the first load access capacity SL1 and the total rated capacity Sn of the N virtual synchronous machines is smaller than the sum of the first load access capacity SL1 and the second load access capacity SL2, sending a control command to disconnect the second load.

Note that, since the importance level of the first load is higher than that of the second load in this embodiment, power supply to the first load is prioritized.

According to the method in the embodiment, whether the first switch of the first load access system and the second switch of the second load access system are controlled by acquiring and comparing the total rated capacity Sn of the N virtual synchronous machines, the first load access capacity SL1 and the second load access capacity SL2 of the current microgrid system in real time, so that the stability of the microgrid system for supplying power to the load is realized, the stability of supplying power to important loads is kept as much as possible, and the serious consequence of load imbalance caused by insufficient power supply capacity is avoided.

Referring to fig. 17, in an embodiment, the step S400 of controlling the virtual synchronous machine to adjust the output terminal voltage parameter according to the generated grid connection operation instruction to match the grid voltage parameter specifically includes the steps of:

step S410: obtaining a secondary voltage regulation reference value U_AGCReference value w of secondary frequency modulation_AGCAnd a secondary phase modulation reference value θ AGC.

It should be noted that, the secondary voltage regulation reference value U of the corresponding state in the history can be directly obtained_AGCReference value w of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGCOr acquiring a preset secondary voltage regulation reference value U_AGCReference value w of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGCOr obtaining a secondary voltage regulation reference value U directly input by a user_AGCReference value w of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGCOr the output parameters of the power grid end and the virtual synchronous machine are obtained.

Step S420: sending a secondary voltage regulation reference value U_AGCAnd regulating the voltage operating instructions to the virtual synchronous machine.

It should be noted that the virtual synchronous machine may be sent through a wired network or a wireless network, and the virtual synchronous machine is detected to start the voltage regulation operation within a preset time interval, and if not, the virtual synchronous machine is detected to start the voltage regulation operation againSecondary transmission secondary voltage regulation reference value U_AGCAnd regulating the voltage operating instructions to the virtual synchronous machine.

Step S430: and when the error between the voltage of the power grid end and the voltage of the output end of the virtual synchronous machine is smaller than a preset first threshold value, sending a voltage regulation stopping operation instruction to the virtual synchronous machine.

It should be noted that the preset first threshold may be set arbitrarily, and is generally the maximum error value that can be received by the piconet system where the virtual synchronous machine is located.

Step S440: transmitting a secondary frequency modulated reference value w_AGCAnd frequency modulation operating instructions to the virtual synchronous machine.

Step S450: and when the error between the voltage of the power grid end and the frequency of the output end of the virtual synchronous machine is smaller than a preset second threshold value, sending a frequency modulation stopping operation instruction to the virtual synchronous machine.

It should be noted that the preset second threshold may be set arbitrarily, and is generally the maximum error value that can be received by the microgrid system where the virtual synchronous machine is located.

Step S460: transmitting a secondary phase modulation reference value theta_AGCAnd phasing the operating instructions to the virtual synchronous machine.

Step S470: and when the error between the voltage of the power grid end and the phase of the output end of the virtual synchronous machine is smaller than a preset third threshold value, sending a phase modulation stopping operation instruction to the virtual synchronous machine.

It should be noted that the preset third threshold may be set arbitrarily, and is generally the maximum error value that the system where the virtual synchronous machine is located can receive.

According to the method in the embodiment, the virtual synchronizer is controlled to sequentially perform the voltage regulation operation, the frequency modulation operation and the phase modulation operation, so that the virtual synchronizer can adapt to the real-time changes of the voltage, the frequency, the phase and the like of the microgrid system, and the power stability of the microgrid system is maintained.

In a more detailed embodiment, step S410 specifically includes the following steps:

step S411: for the three-phase voltage V of the collected power grid terminal_gab、V_gbc、V_gcaDQ conversion is carried out to obtain a two-phase rotating coordinate system of the power grid endVoltage value V_gd、V_gq。

Step S412: three-phase voltage V to output end of virtual synchronous machine_ab、V_bc、V_caDQ conversion is carried out to obtain a voltage value V of a two-phase rotating coordinate system of the virtual synchronous machine_d、V_q。

Can be as follows: three-phase voltage V at dq coordinate axis to output end of virtual synchronous machine_ab、V_bc、V_caDecoupling to obtain a two-phase rotating coordinate system voltage value V of the virtual synchronous machine_d、V_qNamely the active component and the reactive component of the output voltage of the virtual synchronous machine.

Step S413: according to V_gdAnd V_dCalculating secondary voltage regulation reference value U_AGCSpecifically, the following formula is used:

in addition, k is_pAnd k_iThe adjustable parameter can be changed according to different loads, power grids, energy storage units and the like.

Step S414: according to w_gAnd w calculating a quadratic frequency modulation reference value w_AGCSpecifically, the following formula is used:

wherein: k is a radical of_PIs a proportionality coefficient, k_iIs an integral coefficient.

Step S415: according to theta_gCalculating a secondary phase modulation reference value theta from the sum theta_AGCSpecifically, the following formula is used:

Fig. 18 is a schematic diagram of a microgrid system according to an embodiment of the present invention. As shown in fig. 18, fig. 18 of this embodiment is a schematic diagram of a microgrid system according to an embodiment of the present invention. As shown in fig. 18, the microgrid system 30 of this embodiment includes: a processor 300, a memory 301 and a computer program 302 stored in the memory 301 and operable on the processor 300, such as a program of an output control method of a virtual synchronous machine in a microgrid system. The processor 300 executes the computer program 302 to implement the steps in the embodiments of the virtual synchronous machine grid-connected and off-grid control method, such as the steps S300 to S400 shown in fig. 14.

Illustratively, the computer program 302 may be partitioned into one or more modules/units, which are stored in the memory 301 and executed by the processor 300 to implement the present invention. One or more of the modules/units may be a series of computer program instruction segments capable of performing certain functions, which are used to describe the execution of the computer program 302 in the microgrid system 30. For example, the computer program 302 may be divided into a synchronization module, a summarization module, an acquisition module, and a return module (a module in a virtual device), and each module specifically functions as follows:

the piconet system 30 may be a computer, a central processing unit or a centralized controller according to the first embodiment of the invention. The piconet system may include, but is not limited to, the processor 300 and the memory 301. Those skilled in the art will appreciate that fig. 18 is merely an example of the microgrid system 30, and does not constitute a limitation on the microgrid system 30, and may include more or fewer components than those shown, or combine certain components, or different components, for example, the microgrid system may further include input-output devices, network access devices, buses, and the like.

The Processor 300 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.

The storage 301 may be an internal storage unit of the microgrid system 30, such as a hard disk or a memory of the microgrid system 30. The memory 301 may also be an external storage device of the piconet system 30, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), or the like provided on the piconet system 30. Further, the memory 301 may also include both an internal storage unit and an external storage device of the microgrid system 30. The memory 301 is used to store computer programs and other programs and data required by the piconet system. The memory 301 may also be used to temporarily store data that has been output or is to be output.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated modules/units, if implemented in the form of software functional units and sold or used as separate products, may be stored in a computer readable storage medium. Based on such understanding, all or part of the flow in the method according to the embodiments of the present invention may also be implemented by a computer program to instruct related hardware, where the computer program may be stored in a computer readable storage medium, and when the computer program is executed by a processor, the computer program may implement the steps of the embodiments of the method. . Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer readable medium may include: any entity or device capable of carrying computer program code, recording medium, U.S. disk, removable hard disk, magnetic disk, optical disk, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, software distribution media, and the like. It should be noted that the computer readable medium may contain other components which may be suitably increased or decreased as required by legislation and patent practice in jurisdictions, for example, in some jurisdictions, in accordance with legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunications signals.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling virtual synchronizers to be connected with and disconnected from a network in a microgrid system is characterized in that the microgrid system comprises a plurality of energy storage units, a plurality of virtual synchronizers connected with the plurality of energy storage units in a one-to-one correspondence mode, an intelligent power distribution device respectively connected with the virtual synchronizers and a power grid, and a centralized controller connected with the energy storage units, the virtual synchronizers and the intelligent power distribution device, wherein the method for controlling the virtual synchronizers to be connected with and disconnected from the network in the microgrid system comprises the following steps:

judging whether the virtual synchronous machine needs to perform grid-connection and grid-disconnection switching operation or not, generating a grid-disconnection operation instruction when the virtual synchronous machine needs to perform grid-connection operation, and generating a grid-connection operation instruction when the virtual synchronous machine needs to perform grid-connection operation;

when the virtual synchronous machine needs grid-connected operation, controlling the virtual synchronous machine to adjust the voltage parameter of the output end according to the generated grid-connected operation instruction so as to match the voltage parameter of the power grid, and then closing a switch which needs grid connection and is connected with the power grid by the virtual synchronous machine with matched parameters;

the step of controlling the virtual synchronous machine to adjust the output end voltage parameter according to the generated grid-connected operation instruction so as to match the power grid voltage parameter comprises the following steps:

obtaining a secondary voltage regulation reference value U_AGCReference value w of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGC；

Sending a secondary voltage regulation reference value U_AGCAnd regulating the voltage operating instructions to the virtual synchronous machine;

when the error between the power grid voltage and the voltage of the output end of the virtual synchronous machine is smaller than a preset first threshold value, sending a voltage regulation stopping operation instruction to the virtual synchronous machine;

transmitting a secondary frequency modulated reference value w_AGCAnd frequency modulation operating instructions to the virtual synchronous machine;

when the error between the power grid voltage and the output end frequency of the virtual synchronous machine is smaller than a preset second threshold value, sending a frequency modulation stopping operation instruction to the virtual synchronous machine;

transmitting a secondary phase modulation reference value theta_AGCAnd phasing operating instructions to the virtual synchronous machine;

and when the error between the power grid voltage and the phase of the output end of the virtual synchronous machine is smaller than a preset third threshold value, sending a phase modulation stopping operation instruction to the virtual synchronous machine.

2. The method for controlling the virtual synchronous machine in the microgrid system connected to and disconnected from the grid according to claim 1, wherein the generating of the off-grid operation instruction comprises:

3. The method for controlling the virtual synchronous machine in the microgrid system in a grid-connected mode and a grid-disconnected mode according to claim 1, wherein the generating of the grid-connected operation instruction specifically comprises:

when the virtual synchronous machine is in a grid-connected state, judging that the grid connection of the virtual synchronous machine is recovered to a normal state from an abnormal state according to a power grid voltage parameter and a virtual synchronous machine output voltage parameter, and if so, generating an active grid-connected operation instruction;

4. The method for controlling the virtual synchronous machine in the microgrid system in a grid-connected mode and a grid-disconnected mode in the microgrid system of claim 1, wherein the step of obtaining the voltage parameters of the utility power grid and the output voltage parameters of the virtual synchronous machine comprises the following steps:

collecting three-phase voltage V at electric network end_gab、V_gbc、V_gcaAnd the three-phase voltage V of the output end of the virtual synchronous machine_ab、V_bc、V_ca；

To the three-phase voltage V of the grid end_gab、V_gbc、V_gcaPerforming phase locking to obtain angular frequency w of the power grid end_gAnd phase theta_g；

For the three-phase voltage V at the output end of the virtual synchronous machine_ab、V_bc、V_caAnd performing phase locking to obtain the angular frequency w and the phase theta of the virtual synchronous machine.

5. The method for controlling the virtual synchronous machines in the microgrid system to be connected and disconnected from the grid according to claim 1, further comprising, after the virtual synchronous machines needing to be disconnected from the grid are disconnected from a switch of the grid according to the off-grid operation instruction:

acquiring the number N of virtual synchronous machines in a current running state;

acquiring the total rated capacity Sn of the N virtual synchronous machines, the first load access capacity SL1 and the second load access capacity SL2 of the current microgrid system;

comparing the total rated capacity Sn of each virtual synchronous machine with the capacity of the first load access capacity SL1 and the second load access capacity SL2 of the current system;

and disconnecting the first load and/or the second load from the virtual synchronous machine according to the comparison result.

6. The method for controlling the virtual synchronous machines in the microgrid system in a grid-connected mode and a grid-disconnected mode according to the claim 5, wherein the step of disconnecting the first load and/or the second load from the virtual synchronous machines according to the comparison result specifically comprises the steps of:

when the total rated capacity Sn of the N virtual synchronous machines is smaller than the first load access capacity SL1, sending a control instruction to disconnect the first load and the second load;

and when the total rated capacity Sn of the N virtual synchronous machines is larger than the first load access capacity SL1 and the total rated capacity Sn of the N virtual synchronous machines is smaller than the sum of the first load access capacity SL1 and the second load access capacity SL2, sending a control command to disconnect the second load.

7. The method for controlling the grid-connected and off-grid of the virtual synchronous machine in the microgrid system according to claim 1, wherein the secondary voltage regulation reference value U is obtained_AGCReference value w of secondary frequency modulation_AGCAnd a secondary phase modulation reference value theta_AGCThe method comprises the following steps:

for the three-phase voltage V of the collected power grid terminal_gab、V_gbc、V_gcaDQ conversion is carried out to obtain a voltage value V of the two-phase rotating coordinate system of the power grid end_gd、V_gq；

Three-phase voltage V to output end of virtual synchronous machine_ab、V_bc、V_caDQ conversion is carried out to obtain a voltage value V of the two-phase rotating coordinate system of the virtual synchronous machine_d、V_q；

According to V_gdAnd V_dComputingReference value U for secondary voltage regulation_AGCSpecifically, the following formula is used:

according to w_gAnd w calculating a quadratic frequency modulation reference value w_AGCSpecifically, the following formula is used:

according to theta_gCalculating a secondary phase modulation reference value theta from the sum theta_AGCSpecifically, the following formula is used:

wherein: k is a radical of_PIs a proportionality coefficient, k_iIs an integral coefficient, w_gExpressed as the angular frequency of the grid side, w is expressed as the angular frequency of the virtual synchronous machine, theta_gDenoted as the phase of the grid side and theta as the phase of the virtual synchronous machine.

8. A microgrid system comprising a memory, a processor and a computer program stored in said memory and executable on said processor, characterized in that said processor implements the steps of the method according to any of claims 1 to 7 when executing said computer program.

9. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 7.