A fast disconnection method for microgrid based on adaptive control

Abstract

The invention discloses a microgrid fast decoupling method based on adaptive control, comprising the following steps: S01, at the start time of decoupling of the microgrid system, adjusting the converter in the microgrid to a voltage control mode, sampling the instantaneous value of the current grid voltage at the same time, and calculating the current grid voltage phase information according to the instantaneous value; S02, setting a converter output voltage reference instruction adjustment increment with positive and negative polarity in advance, and assuming that the initial polarity of the adjustment increment is positive; S03, superimposing the positive polarity voltage increment on the instantaneous value of the grid voltage, and using the obtained value as the AC output target value of the converter circuit in the voltage control mode during the decoupling transition process; S04, according to the current grid current change trend, adaptively adjusting the polarity and size of the converter voltage reference instruction adjustment increment. The invention avoids the judgment process of the grid current polarity before decoupling, which can not only shorten the time interval of the microgrid decoupling process, but also smooth the AC bus voltage fluctuation of the microgrid system, and improve the reliability and stability of the microgrid operation state switching, especially the switching transition process from the grid-connected operation state to the island operation state.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent microgrid control, and in particular to a microgrid fast decoupling method based on adaptive control. Background Art

[0002] Among the four basic operating states of the microgrid system, the decoupling transition operating state is not only related to the current state of the public grid and the power supply and consumption planning of the microgrid itself, but more importantly, it is related to the basic characteristics of the grid-connected switch used in the microgrid system, which can be regarded as the process of disconnecting the microgrid from the main grid. More importantly, the stability of the AC bus voltage of the microgrid in this process fundamentally determines the reliable operation of the load in the microgrid, especially the sensitive load. Considering factors such as large capacity, high reliability, low cost and design difficulty, most microgrid systems will choose reverse parallel thyristors as basic units to form grid-connected switches, namely STS (Static Transfer Switch) switches, and by directly connecting the above basic units in series and directly in parallel, the voltage level and current level are respectively improved to meet different application scenarios. Due to the semi-controlled characteristics of thyristors, certain forced shutdown measures must be taken to shorten the time interval of the decoupling process, while also ensuring the smooth transition of the AC bus voltage. The existing technical solutions usually need to first determine the side of the anti-parallel thyristor that is in the on state based on the positive and negative polarities of the current in the thyristor, and based on the current polarity judgment result, form a fixed reverse voltage bias at both ends of the on thyristor, thereby accelerating the shutdown process of the STS switch and ensuring that the microgrid system can quickly switch the operating state.

[0003] There are certain limitations in the reverse voltage forced shutdown technical solutions including the above-mentioned prior art records. Since the microgrid decoupling process has a certain randomness and is affected by factors such as the linear working range of the sensor, the accuracy of the sampling chip and the zero drift of the operational amplifier, the conventional hardware circuit sampling link has a certain linear effective area, especially when the instantaneous value of the current at the start of the reverse voltage forced shutdown is close to zero, the accuracy of the judgment of the current polarity in the thyristor cannot be guaranteed. Once the polarity of the above current is judged incorrectly, it will not be possible to form a reverse voltage at both ends of the thyristor in the on state, causing the forced shutdown process to fail. More seriously, since the microgrid converter has been switched to a voltage control mode at this time, the microgrid converter is equivalent to a controlled voltage source with a small output impedance. The continuous conduction of the thyristor in the STS switch will make the conversion circuit showing the voltage source characteristics directly connected in parallel with the power grid. When there is an amplitude or phase deviation between the voltages of the two, power oscillation will be formed, which will cause the microgrid converter to overload, and the amplitude or frequency fluctuation of the AC bus, affecting the stable operation of the load. Summary of the invention

[0004] The purpose of the present invention is to provide a microgrid fast decoupling method based on adaptive control for use in a microgrid mode switching process, so as to reduce the impact of the transient process of microgrid decoupling transition on the load in the microgrid, especially the sensitive load.

[0005] In order to achieve the above object, the present invention provides the following technical solution: a microgrid fast decoupling method based on adaptive control, comprising the following steps:

[0006] S01. At the start of the microgrid system disconnection, the converter in the microgrid is adjusted to a voltage control mode, and the instantaneous value of the current grid voltage is sampled at the same time, and the current grid voltage phase information is calculated according to the instantaneous value;

[0007] S02, setting in advance a converter output voltage reference instruction adjustment increment with positive and negative polarity, and assuming that the initial polarity of the adjustment increment is positive;

[0008] S03, superimposing the voltage increment of the positive polarity onto the instantaneous value of the grid voltage, and using the obtained value as the AC output target value of the converter circuit in the voltage control mode during the decoupling transition process;

[0009] S04, detect the instantaneous value of the grid current at several consecutive sampling moments adjacent to the current control cycle, and judge whether the thyristor in the on state has started the shutdown process by comparing the instantaneous value of the grid current. Specifically, according to the decay speed of the instantaneous value of the grid current in this control cycle, the output voltage target value of the microgrid conversion circuit is adaptively adjusted through the voltage reference instruction increment, and acts on the next control cycle;

[0010] S05. According to the size of the tracking error between the actual output voltage and the target voltage of the microgrid converter in controlling the output voltage, dynamically adjust the proportional coefficient of the voltage closed-loop controller based on the traditional forced shutdown strategy.

[0011] Preferably, the microgrid system includes a public power grid, a grid-connected switch, a three-phase voltage-type two-stage converter circuit, a DC power supply unit, an AC load, a storage battery with a microgrid DC bus, a converter main circuit, a filter output circuit, a microgrid controller, a first converter control circuit, and a second converter control circuit. Specifically:

[0012] The grid connection switch is used to establish a network connection between the public power grid and the AC load;

[0013] The DC power supply unit is used to output a stable current to the energy storage battery;

[0014] The first current conversion control circuit and the second current conversion control circuit are connected in parallel with a PWM controller;

[0015] The first output terminal of the microgrid controller is data-connected to the PWM controller;

[0016] The second output terminal of the microgrid controller is connected in parallel data with the first current conversion control circuit and the second current conversion control circuit;

[0017] The third output terminal of the microgrid controller is data-connected to the main circuit of the converter;

[0018] The converter main circuit and the filter output circuit are connected in series;

[0019] Wherein, the grid-connected switch is an STS switch having one or more groups of thyristors connected in reverse parallel;

[0020] The first current conversion control circuit adopts PQ direct current control;

[0021] The second current conversion control circuit adopts V / f voltage and current dual closed-loop control;

[0022] As a preferred embodiment, the instantaneous value of the current grid voltage sampled in step S01 is a set of input current selection i s The current sample value and n The deviation of the absolute value of the value before the sampling cycle is used to generate the adjustment value Δ of the reference command amplitude of the output voltage of the conversion circuit U ;

[0023] Another set of inputs of the adaptive controller selects the current inverter circuit output voltage u p With voltage reference command u ref The deviation between the absolute values ​​is used to generate the proportional coefficient of the voltage closed-loop control of the converter circuit K pu The adjustment amount Δ K pu .

[0024] Preferably, judging in step S04 whether the thyristor in the on state starts the shut-off process includes:

[0025] If it is detected that the instantaneous value of the grid current decays toward zero, the thyristor in the on state has formed a reverse voltage bias;

[0026] If it is detected that the instantaneous value of the grid current increases in the reverse direction, the two ends of the thyristor in the on state are still forward voltage biased, and the output voltage target initial value polarity needs to be changed immediately to quickly form a reverse voltage bias in the thyristor in the on state.

[0027] Preferably, the thyristors are located between different control targets of the microgrid converter and are assembled flexibly in the following situations:

[0028] When the grid-connected thyristors are fully turned on, the microgrid is in grid-connected operation;

[0029] When the grid-connected thyristor switches from the on state to the off state, the microgrid is in the decoupling transition state;

[0030] When the grid-connected thyristors are completely turned off, the microgrid is in island operation;

[0031] When the grid-connected thyristors are switched from the off state to the on state, the microgrid is in a synchronous transition state.

[0032] Preferably, the step S05 dynamically adjusts the target value of the output voltage of the microgrid converter circuit according to the speed of the grid current instantaneous value attenuation instruction, including the following steps:

[0033] S41. When the grid current decays faster, the output voltage target value is reduced according to a predetermined plan to reduce the transient oscillation of the AC side output voltage during the microgrid decoupling process;

[0034] S42. When the grid current decays slowly, the output voltage target value is increased according to a predetermined plan to stabilize the reliability of the thyristor forced shutdown process in the microgrid system.

[0035] Preferably, in the method for dynamically adjusting the proportional coefficient of the voltage closed-loop controller in step S05, when the absolute value of the AC output voltage of the converter and the absolute value of its target instruction are:

[0036] When there is a large positive deviation, the converter AC output voltage has over-regulated;

[0037] If the deviation remains basically unchanged or shows an increasing trend, reduce the proportional coefficient of the voltage closed-loop controller;

[0038] If the deviation is decreasing, reduce the proportional coefficient of the voltage closed-loop controller or keep it at its original size.

[0039] In the above technical scheme, the present invention provides a microgrid rapid disconnection method based on adaptive control, which has the following beneficial effects: there is no need to judge the polarity of the current in the grid-connected switch, that is, the grid-side current in advance, by giving an initial value of the AC output voltage of the microgrid converter at the beginning of the disconnection transition process, and adaptively adjusting the target value of the AC side output voltage of the microgrid converter and the voltage closed-loop control parameters according to the change trend of the current in the grid-connected switch and the AC side output voltage of the converter circuit itself, thereby realizing rapid disconnection of the microgrid system from the public power grid.

[0040] Secondly, this embodiment not only reduces the impact of the grid-connected switch's own action delay on the microgrid system's disconnection process, but also avoids the reliance on current polarity judgment in the traditional reverse voltage forced shutdown technical solution, alleviates the bus voltage and power fluctuations caused by the AC bus voltage amplitude or phase jump during the microgrid disconnection process, improves the reliability of the microgrid system mode switching as a whole, and eliminates the impact of the microgrid system's disconnection transient process on its internal loads, especially sensitive loads.

[0041] In addition, the design principle is reliable and the structure is simple. There is no need to add additional circuits or equipment in the microgrid system. The output of the power conversion circuit in the system is directly used to achieve rapid disconnection of the microgrid system. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0043] Figure 1 A schematic diagram of a single-phase equivalent circuit and a control structure of the smart microgrid system according to an embodiment of the present invention;

[0044] Figure 2 This is a control structure diagram for realizing rapid disconnection of a microgrid system based on adaptive regulation of converter port voltage adopted in an embodiment of the present invention;

[0045] Figure 3 A strategy flow chart of the adaptive control method adopted in the embodiment of the present invention;

[0046] Figure 4 The embodiment of the present invention is the grid voltage u s is positive and the grid current i s When is also positive, the waveform diagram of the simulation experiment results using the adaptive split control strategy;

[0047] Figure 5 The embodiment of the present invention is the grid voltage u s The grid current is negative i s When is positive, the waveform diagram of the simulation experiment results using the adaptive split control strategy;

[0048] Figure 6 The embodiment of the present invention is the grid voltage u s The grid current is positive i sWhen the value is negative, the waveform of the simulation experiment results using the adaptive split control strategy;

[0049] Figure 7 The embodiment of the present invention is the grid voltage u s is negative and the grid current i s When it is also negative, the waveform of the simulation experiment results using the adaptive split control strategy;

[0050] Figure 8 This is a waveform diagram of the MPQR system mode switching experiment when the embodiment of the present invention adopts the traditional reverse voltage forced shutdown method and the current polarity judgment is wrong;

[0051] Fig. 9 This is a waveform diagram of an adaptive reverse voltage forced shutdown experiment when both the grid voltage and the grid current are in the positive half cycle according to an embodiment of the present invention;

[0052] Fig.10 This is a waveform diagram of an adaptive reverse voltage forced shutdown experiment when the grid voltage is in the negative half cycle and the grid current is in the positive half cycle according to an embodiment of the present invention.

[0053] Description Figure Numbers:

[0054] 1.1, public power grid; 1.2, grid connection switch; 1.3, DC power supply unit; 1.4, AC load; 1.5, microgrid DC bus; 1.6, converter main circuit; 1.7, filter output circuit; 1.8, microgrid controller; 1.9, first current conversion control circuit; 1.10, second current conversion control circuit. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0056] like Figure 3 As shown, a microgrid fast decoupling method based on adaptive control includes the following steps:

[0057] S01. At the start of the microgrid system disconnection, the converter in the microgrid is adjusted to a voltage control mode, and the instantaneous value of the current grid voltage is sampled at the same time, and the current grid voltage phase information is calculated according to the instantaneous value;

[0058] S02, setting in advance a converter output voltage reference instruction adjustment increment with positive and negative polarity, and assuming that the initial polarity of the adjustment increment is positive;

[0059] S03, superimposing the voltage increment of the positive polarity onto the instantaneous value of the grid voltage, and using the obtained value as the AC output target value of the converter circuit in the voltage control mode during the decoupling transition process;

[0060] S04, detecting the instantaneous value of the grid current at several consecutive sampling moments adjacent to the current control cycle, and judging whether the thyristor in the on state has started the shut-down process by comparing the instantaneous value of the grid current, and if so, dynamically adjusting the output voltage target value of the microgrid conversion circuit according to the speed of the grid current instantaneous value attenuation instruction;

[0061] S05. According to the size of the tracking error between the actual output voltage and the target voltage of the microgrid converter in controlling the output voltage, dynamically adjust the proportional coefficient of the voltage closed-loop controller based on the traditional forced shutdown strategy.

[0062] Specifically, if it is detected that the instantaneous value of the grid current decays toward zero, it means that the thyristor in the on state has formed a reverse voltage bias.

[0063] On the contrary, if it is detected that the instantaneous value of the grid current increases in the reverse direction, it means that the two ends of the thyristor in the on state are still forward voltage biased. At this time, the output voltage target initial value polarity needs to be changed immediately to quickly form a reverse voltage bias in the thyristor in the on state.

[0064] The above embodiment adopts the traditional forced shutdown strategy, but when the current polarity is wrongly judged, after the conduction pulse is removed, the two ends of the thyristor in the on state in the grid-connected switch fail to form a reverse voltage bias. At the same time, since the current conversion circuit is directly connected in parallel with the power grid, a certain degree of oscillation occurs between the two, affecting the power supply stability of the load end.

[0065] See attached Fig. 9 , when the grid connection switch starts to shut down, the grid voltage u s With grid current is In the same positive half cycle, the current at the turn-off time is i s Rapidly decays to zero, PCC point voltage u p and load current iz There is basically no obvious change at the moment of mode switching.

[0066] See attached Fig.10 , when the grid connection switch starts to shut down, the grid voltage u s In the negative half cycle, the grid currenti s When in the positive half cycle, i g The output current of the conversion circuit. Although the reverse voltage forced shutdown undergoes a short period of dynamic adjustment, it still affects the system PCC point voltage. u p There is basically no impact on the continuity and reliability of the load current iz.

[0067] In a large-capacity microgrid system with on-grid / off-grid operation function, the above technology adaptively adjusts the configured output target value and control parameters through the current converter output state, thereby realizing rapid disconnection of the microgrid system from the public power grid, so as to eliminate the impact of the transient process of microgrid system working mode switching on its internal loads, especially sensitive loads. Example

[0068] Combination Figure 1-2 Regarding the circuit relationship of the microgrid system provided, the microgrid system recorded in the above embodiment 1 includes a public power grid 1.1, a grid connection switch 1.2, a three-phase voltage type two-stage converter circuit, a DC power supply unit 1.3, an AC load 1.4, an energy storage battery with a microgrid DC bus 1.5, a converter main circuit 1.6, a filter output circuit 1.7, a microgrid controller 1.8, a first converter control circuit 1.9 and a second converter control circuit 1.10, specifically:

[0069] The grid connection switch 1.2 is used to establish a network connection between the public power grid 1.1 and the AC load 1.4;

[0070] The DC power supply unit 1.3 is used to output a stable current to the energy storage battery;

[0071] The first current conversion control circuit 1.9 and the second current conversion control circuit 1.10 are connected in parallel with a PWM controller;

[0072] The first output terminal of the microgrid controller 1.8 is connected to the PWM controller data;

[0073] The second output terminal of the microgrid controller 1.8 is connected in parallel with the first current conversion control circuit 1.9 and the second current conversion control circuit 1.10;

[0074] The third output terminal of the microgrid controller 1.8 is data-connected to the converter main circuit 1.6;

[0075] The converter main circuit 1.6 and the filter output circuit 1.7 are connected in series;

[0076] The grid connection switch 1.2 is an STS switch having one or more groups of thyristors connected in reverse parallel;

[0077] The first current conversion control circuit 1.9 adopts PQ direct current control;

[0078] The second current conversion control circuit 1.10 adopts V / f voltage and current dual closed-loop control.

[0079] Specifically, the grid-connected switch 1.2 uses an STS switch composed of bidirectional anti-parallel thyristors, and the distributed power generation part uses photovoltaic power generation, and the energy storage battery is connected to the microgrid DC bus 1.5 to provide corresponding energy support for different working modes of the system. The converter main circuit 1.6 uses a voltage source bridge converter circuit, and the filter output circuit 1.7 uses an LC filter circuit. The microgrid controller 1.8 monitors the public power grid in real time and outputs a drive signal to control the on and off of the thyristor, thereby changing the connection state between the user load and the public power grid to ensure reliable power supply to the user load.

[0080] According to the on-off state of the AC bus thyristor, there are two different working modes in the microgrid system, namely, public grid power supply and independent power supply of distributed generation system. When the bidirectional thyristor in the grid-connected switch is in the on state, the microgrid system is in the grid-connected operation state, and the conversion circuit adopts PQ direct current control 1.9, which can provide a certain amount of active and reactive power support for the microgrid system. When the bidirectional thyristors in the grid-connected switch are all in the off state, the microgrid system is in the island operation state, and the conversion circuit adopts V / f voltage and current dual closed-loop control 1.10. The active and reactive power required by the user load is completely provided independently by the distributed generation system and the DC energy storage device through the converter.

[0081] The adaptive controller has a set of inputs that select the current i s The absolute deviation between the current sampling value and the value n sampling cycles ago is used to generate the adjustment value Δ of the reference command amplitude of the output voltage of the conversion circuit U The other input selects the current inverter circuit output voltage u p With voltage reference command u ref The deviation between the absolute values ​​is used to generate the proportional coefficient of the voltage closed-loop control of the converter circuit K pu The adjustment amount Δ K pu .

[0082] It should be noted that in practical applications, it is necessary to comprehensively consider the tolerance of the connected sensitive load to the duration of the reverse voltage forced shutdown process, as well as the inherent non-ideal factors of the system such as hardware circuit sampling error and control delay, and select the specific value of n by compromise. The value of n in this embodiment is 5. Example

[0083] Since there are multiple variables coupled simultaneously in the forced shutdown process of the thyristor and it has strong nonlinear characteristics, it is impossible to fully control the shutdown process current. The adaptive strategy can better control the process indirectly by adjusting limited parameters. In step S04, judging whether the thyristor in the on state starts the shutdown process includes:

[0084] If it is detected that the instantaneous value of the grid current decays toward zero, the thyristor in the on state has formed a reverse voltage bias;

[0085] If it is detected that the instantaneous value of the grid current increases in the reverse direction, the two ends of the thyristor in the on state are still forward voltage biased, and the output voltage target initial value polarity needs to be changed immediately to quickly form a reverse voltage bias in the thyristor in the on state.

[0086] Step S05 dynamically adjusts the output voltage target value of the microgrid conversion circuit according to the speed of the grid current instantaneous value attenuation instruction, including the following steps:

[0087] S41. When the grid current decays faster, the output voltage target value is reduced according to a predetermined plan to reduce the transient oscillation of the AC side output voltage during the microgrid decoupling process;

[0088] S42. When the grid current decays slowly, the output voltage target value is increased according to a predetermined plan to stabilize the reliability of the thyristor forced shutdown process in the microgrid system.

[0089] In the method for dynamically adjusting the proportional coefficient of the voltage closed-loop controller in step S05, when the absolute value of the AC output voltage of the converter and the absolute value of its target instruction are:

[0090] When there is a large positive deviation, the converter AC output voltage has over-regulated;

[0091] If the deviation remains basically unchanged or shows an increasing trend, reduce the proportional coefficient of the voltage closed-loop controller;

[0092] If the deviation is decreasing, reduce the proportional coefficient of the voltage closed-loop controller or keep it at its original size. Example

[0093] The coordination of thyristors between different control targets of microgrid converters includes the following situations:

[0094] When the grid-connected thyristor is fully turned on, the microgrid is in grid-connected operation state. Figure 4 (a), (b), when u s is positive and i s It is also positive, assuming that the grid connection switch conduction control command is removed at time t2. us With grid current i s are all within the positive half cycle, the initial value of the adaptive controller output ΔU can meet the shutdown condition, and the current i s It immediately starts to decay towards the zero axis and is completely shut down at t3. At the same time, after a control system calculation cycle, the output voltage of the converter circuit is adjusted. u p The load side resumes supplying rated voltage according to the reference instruction.

[0095] When the grid-connected thyristor switches from the on state to the off state, the microgrid is in the disconnection transition state. Figure 5 (a), (b), when u s Negative i s When is positive, it is assumed that the grid-connected switch conduction control command is removed at time t2. Since the initial value of the voltage command adjustment amount ΔU will make the two ends of the thyristor that conducts negative current unable to meet the reverse voltage bias condition, the grid current i s In the next control cycle of the system, the controller changes the output ΔU polarity and reduces the voltage control loop proportional coefficient to reduce the overshoot of the output voltage when following the changing command. u p Less than the grid voltage u s At t3, the grid current is begins to decay toward the zero axis and is completely shut down.

[0096] When the grid-connected thyristor is completely turned off, the microgrid is in island operation. Figure 6 (a), (b), when u s For the sake of justice i s When the grid voltage is in the positive half cycle and the grid current is negative, it is assumed that the grid connection switch conduction control command is removed at time t2. i s In the negative half cycle, the voltage command adjustment amount Δ U The initial value of will make the two ends of the thyristor that conducts negative current unable to meet the reverse bias condition, and the grid current i s In the next control cycle of the system, the controller changes the output Δ U polarity, and at the same time reduce the voltage control loop proportional coefficient to reduce the overshoot when the output voltage follows the changing command. u p Less than the grid voltage us When the grid current i s It starts to decay toward the zero axis and is completely shut down at time t3.

[0097] When the grid-connected thyristor switches from the off state to the on state, the microgrid is in a synchronous transition state. Figure 7 (a), (b), when u s is negative and i s When the grid voltage is negative, it is assumed that the grid connection switch conduction control command is removed at time t2. u s With grid current i s are all in the negative half cycle, the output of the adaptive controller Δ U The initial value of can meet the turn-off condition of the thyristor in the current grid-connected switch, and the current i s Immediately begins to decay towards the zero axis. Figure 4 The difference between the working conditions of (a) and (b) is that the current decay speed is slow and the voltage at the PCC point is over-regulated. In the next control cycle, the voltage reference command amplitude is increased and the voltage control loop proportional coefficient is reduced to speed up the current. i s The decay speed can be reduced and the output voltage overshoot can be suppressed.

[0098] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0099] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0100] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0101] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0102] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0103] The embodiments of the present application also provide a specific implementation of an electronic device capable of implementing all steps of the method in the above embodiments, and the electronic device specifically includes the following contents:

[0104] Processor, memory, communications interface and bus;

[0105] Wherein, the processor, memory, and communication interface communicate with each other via the bus;

[0106] The processor is used to call the computer program in the memory, and when the processor executes the computer program, all the steps in the method in the above embodiment are implemented.

[0107] The embodiments of the present application also provide a computer-readable storage medium capable of implementing all the steps of the method in the above embodiments, wherein a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, all the steps of the method in the above embodiments are implemented.

[0108] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the hardware + program embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. Although the embodiment of this specification provides the method operation steps as described in the embodiment or flowchart, more or fewer operation steps may be included based on conventional or non-creative means. The order of steps listed in the embodiment is only one way of executing the order of many steps, and does not represent the only execution order. When the device or terminal product in practice is executed, it can be executed in sequence or in parallel according to the method shown in the embodiment or the accompanying drawings (for example, a parallel processor or a multi-threaded processing environment, or even a distributed data processing environment). The term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, product or device including a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements inherent to such process, method, product or device. In the absence of more restrictions, it is not excluded that there are other identical or equivalent elements in the process, method, product or device including the elements. For the convenience of description, the above device is described by dividing it into various modules according to its functions. Of course, when implementing the embodiments of this specification, the functions of each module can be implemented in the same or more software and / or hardware, or the module implementing the same function can be implemented by a combination of multiple sub-modules or sub-units. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms. The present invention is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the process Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0109] Those skilled in the art should understand that the embodiments of this specification can be provided as methods, systems or computer program products. Therefore, the embodiments of this specification can be in the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware. Moreover, the embodiments of this specification can be in the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. Each embodiment in this specification is described in a progressive manner, and the same and similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. In the description of this specification, the description of the reference term "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of this specification.

[0110] In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradicting each other. The above is only an embodiment of the embodiment of this specification and is not intended to limit the embodiment of this specification. For those skilled in the art, the embodiment of this specification may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiment of this specification shall be included in the scope of the claims of the embodiment of this specification.

Claims

1. A microgrid fast disconnection method based on adaptive control, characterized in that: The following steps are involved: S01. At the start of the microgrid system disconnection, the converter in the microgrid is adjusted to a voltage control mode, and the instantaneous value of the current grid voltage is sampled at the same time, and the current grid voltage phase information is calculated according to the instantaneous value; S02, setting in advance a converter output voltage reference instruction adjustment increment with positive and negative polarity, and assuming that the initial polarity of the adjustment increment is positive; S03, superimposing the voltage increment of the positive polarity onto the instantaneous value of the grid voltage, and using the obtained value as the AC output target value of the converter circuit in the voltage control mode during the decoupling transition process; S04, detecting the instantaneous value of the grid current at several consecutive sampling moments adjacent to the current control cycle, and judging whether the thyristor in the on state has started the shut-down process by comparing the instantaneous value of the grid current, and if so, dynamically adjusting the output voltage target value of the microgrid conversion circuit according to the speed of the grid current instantaneous value attenuation instruction; S05, dynamically adjusting the proportional coefficient of the voltage closed-loop controller based on the traditional forced shutdown strategy according to the magnitude of the tracking error between the actual output voltage and the target voltage in the output voltage control of the microgrid converter; The microgrid system comprises a public power grid (1.1), a grid connection switch (1.2), a three-phase voltage type two-stage current conversion circuit, a DC power supply unit (1.3), an AC load (1.4), an energy storage battery with a microgrid DC bus (1.5), a converter main circuit (1.6), a filter output circuit (1.7), a microgrid controller (1.8), a first current conversion control circuit (1.9) and a second current conversion control circuit (1.10), specifically: The grid-connecting switch (1.2) is used to establish a network connection between the public power grid (1.1) and the AC load (1.4); The DC power supply unit (1.3) is used to output a stable current to the energy storage battery; The first current conversion control circuit (1.9) and the second current conversion control circuit (1.10) are connected in parallel with a PWM controller; The first output terminal of the microgrid controller (1.8) is data-connected to the PWM controller; The second output end of the microgrid controller (1.8) is data-connected in parallel with the first current conversion control circuit (1.9) and the second current conversion control circuit (1.10); The third output terminal of the microgrid controller (1.8) is data-connected to the converter main circuit (1.6); The converter main circuit (1.6) and the filter output circuit (1.7) are connected in series; Wherein, the grid connection switch (1.2) is an STS switch having one or more groups of thyristors connected in reverse parallel; The first current conversion control circuit (1.9) adopts PQ direct current control; The second current conversion control circuit (1.10) adopts V / f voltage and current dual closed-loop control.

2. A microgrid fast disconnection method based on adaptive control according to claim 1, characterized in that: The instantaneous value of the current grid voltage sampled in step S01 is a set of input current selection i s The current sample value and n The deviation of the absolute value of the value before the sampling period is used to generate the adjustment value Δ of the reference command amplitude of the output voltage of the conversion circuit U ; Another set of inputs of the adaptive controller selects the current inverter circuit output voltage u p With voltage reference command u ref The deviation between the absolute values ​​is used to generate the proportional coefficient of the voltage closed-loop control of the converter circuit K pu The adjustment amount Δ K pu .

3. A microgrid fast disconnection method based on adaptive control according to claim 1, characterized in that: The process of judging whether the thyristor in the on state starts to turn off in step S04 includes: If it is detected that the instantaneous value of the grid current decays toward zero, the thyristor in the on state has formed a reverse voltage bias; If it is detected that the instantaneous value of the grid current increases in the reverse direction, the two ends of the thyristor in the on state are still forward voltage biased, and the output voltage target initial value polarity needs to be changed immediately to quickly form a reverse voltage bias in the thyristor in the on state.

4. A microgrid fast disconnection method based on adaptive control according to claim 3, characterized in that: The coordination of the thyristors between different control targets of the microgrid converter includes the following situations: When the grid-connected thyristors are fully turned on, the microgrid is in grid-connected operation; When the grid-connected thyristor switches from the on state to the off state, the microgrid is in the decoupling transition state; When the grid-connected thyristors are completely turned off, the microgrid is in island operation; When the grid-connected thyristors are switched from the off state to the on state, the microgrid is in a synchronous transition state.

5. The microgrid fast disconnection method based on adaptive control according to claim 1, characterized in that: The step S05 dynamically adjusts the output voltage target value of the microgrid conversion circuit according to the speed of the grid current instantaneous value attenuation instruction, and includes the following steps: S41. When the grid current decays faster, the output voltage target value is reduced according to a predetermined plan to reduce the transient oscillation of the AC side output voltage during the microgrid decoupling process; S42. When the grid current decays slowly, the output voltage target value is increased according to a predetermined plan to stabilize the reliability of the thyristor forced shutdown process in the microgrid system.

6. A microgrid fast disconnection method based on adaptive control according to claim 1, characterized in that: In the method for dynamically adjusting the proportional coefficient of the voltage closed-loop controller in step S05, when the absolute value of the AC output voltage of the converter and the absolute value of its target instruction are: When there is a large positive deviation, the converter AC output voltage has over-regulated; If the deviation remains basically unchanged or shows an increasing trend, reduce the proportional coefficient of the voltage closed-loop controller; If the deviation is decreasing, reduce the proportional coefficient of the voltage closed-loop controller or keep it at its original size.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of a microgrid fast decoupling method based on adaptive control as described in any one of claims 1 to 6 are implemented.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of a microgrid fast disconnection method based on adaptive control as described in any one of claims 1 to 6 are implemented.

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