A control method, device, equipment, medium and product of a direct-current microgrid

Abstract

The application discloses a kind of control method, device, equipment, medium and product of direct current microgrid. The method comprises: according to dispatch management layer, bus voltage control layer and converter control layer, the hierarchical control architecture corresponding to direct current microgrid is constructed;Through bus voltage control layer in hierarchical control architecture, according to the requirement threshold range of bus voltage, corresponding control strategy is used to carry out coordinated control to bus voltage in direct current microgrid;Through converter control layer in hierarchical control architecture, respectively determine the interface converter corresponding to photovoltaic unit, energy storage unit and grid-connected unit in direct current microgrid, and adopt corresponding interface converter to realize the coordinated control to photovoltaic unit, energy storage unit and grid-connected unit.The technical scheme of the application can carry out coordinated control to different functional units in microgrid, improve the operation efficiency of microgrid under the condition of ensuring the stable operation of microgrid.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of micro-grid, and particularly relates to a control method, device, equipment, medium and product of a direct-current micro-grid. BACKGROUND

[0002] With the problems of global climate change and energy crisis, promoting green low-carbon transformation, improving the development and efficient management of new energy, has become the focus of global attention. Due to the randomness of power generation and the problem of uneven distribution caused by the influence of weather on new energy, it is often difficult to access the power grid in the traditional way.

[0003] The related technology selects a distributed energy, an energy storage element and a control device to jointly form a small controllable power generation system, so as to ensure independent operation ability and stable grid connection working ability, and thus the concept of "micro-grid" emerges as the times require. The micro-grid is a new network structure composed of multiple distributed power sources and related loads, which can effectively exert the advantages of distributed power generation, reasonably plan and use dispersed renewable energy, and at the same time, the small and independent characteristics can better and more efficiently coordinate and manage local loads, so as to ensure high-quality power quality and realize power supply reliability.

[0004] However, how to coordinate and control different functional units in the micro-grid to improve the operation efficiency of the micro-grid under the condition of ensuring stable operation of the micro-grid is a problem to be solved at present. SUMMARY

[0005] The present application provides a control method, device, equipment, medium and product of a direct-current micro-grid, to coordinate and control different functional units in the micro-grid, to improve the operation efficiency of the micro-grid under the condition of ensuring stable operation of the micro-grid.

[0006] According to an aspect of the present application, a control method of a direct-current micro-grid is provided, comprising:

[0007] According to the dispatching management layer, the bus voltage control layer and the converter control layer, a hierarchical control architecture corresponding to the direct-current micro-grid is constructed;

[0008] According to the requirement threshold range of the bus voltage, the corresponding control strategy is adopted to coordinate and control the bus voltage in the direct-current micro-grid through the bus voltage control layer in the hierarchical control architecture;

[0009] The interface converters corresponding to the photovoltaic unit, the energy storage unit and the grid-connected unit in the direct-current micro-grid are determined respectively through the converter control layer in the hierarchical control architecture, and the corresponding interface converters are adopted to realize the coordinated control of the photovoltaic unit, the energy storage unit and the grid-connected unit.

[0010] According to another aspect of the present application, there is provided a control device of a direct-current micro-grid, comprising:

[0011] a construction module, configured to construct a hierarchical control architecture corresponding to the direct-current micro-grid according to a scheduling management layer, a bus voltage control layer and a converter control layer;

[0012] a first control module, configured to adopt a corresponding control strategy to perform coordinated control on bus voltage in the direct-current micro-grid according to a required threshold range of the bus voltage through the bus voltage control layer in the hierarchical control architecture;

[0013] a second control module, configured to determine corresponding interface converters of a photovoltaic unit, an energy storage unit and a grid-connected unit in the direct-current micro-grid through the converter control layer in the hierarchical control architecture, and to realize coordinated control on the photovoltaic unit, the energy storage unit and the grid-connected unit by using the corresponding interface converters.

[0014] According to another aspect of the present application, there is provided an electronic device, comprising:

[0015] at least one processor; and

[0016] a memory connected with the at least one processor in communication; wherein,

[0017] the memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor to enable the at least one processor to perform the control method of the direct-current micro-grid according to any one of the embodiments of the present application.

[0018] According to another aspect of the present application, there is provided a computer readable storage medium storing computer instructions for enabling a processor to perform the control method of the direct-current micro-grid according to any one of the embodiments of the present application when executed by the processor.

[0019] According to another aspect of the present application, there is also provided a computer program product comprising a computer program, and the computer program performs the control method of the direct-current micro-grid according to any one of the embodiments of the present application when executed by a processor.

[0020] The technical scheme of the embodiment of the present application constructs the hierarchical control architecture corresponding to the direct-current micro-grid according to the scheduling management layer, the bus voltage control layer and the converter control layer; the bus voltage control layer in the hierarchical control architecture is used to adopt the corresponding control strategy to coordinately control the bus voltage in the direct-current micro-grid according to the required threshold range of the bus voltage; the converter control layer in the hierarchical control architecture is used to determine the corresponding interface converter of the photovoltaic unit, the energy storage unit and the grid-connected unit in the direct-current micro-grid respectively, and the corresponding interface converter is used to realize the coordinative control of the photovoltaic unit, the energy storage unit and the grid-connected unit. The different functional units in the micro-grid are coordinately controlled, so that the operation efficiency of the micro-grid can be improved under the condition of ensuring the stable operation of the micro-grid.

[0021] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0023] Figure 1A is a flowchart of a control method of a direct-current micro-grid provided by the first embodiment of the present application;

[0024] Figure 1B is a schematic diagram of a target duty cycle determination process provided by the first embodiment of the present application;

[0025] Figure 1C is a schematic diagram of a parallel control structure provided by the first embodiment of the present application;

[0026] Figure 2A is a control flowchart of a direct-current micro-grid provided by the second embodiment of the present application;

[0027] Figure 2B is a schematic diagram of a hierarchical control structure provided by the second embodiment of the present application;

[0028] Figure 3 is a structural block diagram of a control device of a direct-current micro-grid provided by the third embodiment of the present application;

[0029] Figure 4 is a structural schematic diagram of an electronic device provided by the fourth embodiment of the present application. DETAILED DESCRIPTION

[0030] In the following, the technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work should fall within the protection scope of the present application.

[0031] It should be noted that the terms "first", "second", "target", "candidate", "alternative" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. The acquisition, storage, use, processing and the like of data in the technical solutions of the present application comply with the relevant provisions of national laws and regulations.

[0032] Embodiment one

[0033] Figure 1A is a flowchart of a control method of a direct-current micro-grid provided by the embodiment one of the present application; Figure 1B is a schematic diagram of a target duty cycle determination process provided by the embodiment one of the present application; Figure 1C is a schematic diagram of a parallel control structure provided by the embodiment one of the present application. The embodiment can be applicable to the case of coordinated control of bus voltage, photovoltaic unit, energy storage unit and grid-connected unit in a micro-grid. The method can be executed by a control device of the direct-current micro-grid, which can be realized in the form of hardware and / or software. The control device of the direct-current micro-grid can be configured in an electronic device, such as a total control device of the grid, and executed by a micro-grid system, as shown in Figure 1A The control method of the direct-current micro-grid includes:

[0034] S101, constructing a hierarchical control architecture corresponding to the direct-current micro-grid according to a scheduling management layer, a bus voltage control layer and a converter control layer.

[0035] The scheduling management layer is configured to predict and schedule data such as bus voltage in the DC micro-grid, and generate scheduling instructions to instruct the bus voltage control layer to perform coordinated control of the bus voltage. The scheduling management layer is related to long-term scheduling and planning to meet energy demand and market operation, and is usually at the level of hours to days. The bus voltage control layer is mainly configured to perform coordinated control of the DC bus voltage (DBS) to maintain bus voltage stability and system power balance. The bus voltage control layer is usually at a short or medium time scale (minutes to hours) to ensure voltage stability of the node. The converter control layer is configured to determine and adjust the converters of the photovoltaic unit, energy storage unit and grid-connected unit, and to perform coordinated control of the photovoltaic unit, energy storage unit and grid-connected unit, respectively. The hierarchical control architecture corresponding to the DC micro-grid refers to a hierarchical control architecture based on the physical characteristics of the DC micro-grid, and can specifically include the scheduling management layer, the bus voltage control layer and the converter control layer. The DC micro-grid includes a photovoltaic unit, an energy storage unit and a grid-connected unit, and the grid-connected unit includes a grid-connected inverter.

[0036] Optionally, the scheduling management layer, the bus voltage control layer and the converter control layer can be configured with corresponding functions, and the hierarchical control architecture corresponding to the DC micro-grid can be constructed according to the structural relationship between the scheduling management layer, the bus voltage control layer and the converter control layer, so as to perform coordinated control of different functional modules in the DC micro-grid based on the hierarchical control architecture.

[0037] S102, through the bus voltage control layer in the hierarchical control architecture, according to the required threshold range of the bus voltage, a corresponding control strategy is adopted to perform coordinated control of the bus voltage in the DC micro-grid.

[0038] The required threshold range can be a first range, a second range, a third range or a fourth range. The first range can be 720V-740V, the second range can be 700V-720V, the third range can be 680V-700V, and the fourth range can be 660V-680V. The control strategy refers to a strategy for coordinating the operation mode of the grid-connected inverter, the energy storage unit and the photovoltaic unit. Specifically, at least one of the photovoltaic unit, the grid-connected inverter and the energy storage unit can be used to dominate the bus voltage for coordinated control of the bus voltage in grid-connected and off-grid modes.

[0039] Optionally, the micro-grid system can perform the operation of coordinated control of the bus voltage in the DC micro-grid by calling the bus voltage control layer in the hierarchical control architecture.

[0040] Optionally, according to the requirement threshold range of the bus voltage, a corresponding control strategy is adopted to coordinately control the bus voltage in the DC micro-grid, including: according to the requirement threshold range of the bus voltage, control strategies for the DC micro-grid in grid-connected and off-grid modes are determined respectively to coordinate at least one of the photovoltaic unit, the grid-connected inverter and the energy storage unit to dominate the bus voltage, thereby realizing the coordinative control of the bus voltage in the DC micro-grid.

[0041] Optionally, according to the requirement threshold range of the bus voltage, control strategies for the DC micro-grid in grid-connected and off-grid modes are determined respectively to coordinate at least one of the photovoltaic unit, the grid-connected inverter and the energy storage unit to dominate the bus voltage, thereby realizing the coordinative control of the bus voltage in the DC micro-grid, including:

[0042] (1) If the requirement threshold range of the bus voltage is a first range, the grid-connected inverter and the energy storage unit are monitored respectively in the grid-connected and off-grid modes to control the photovoltaic unit to dominate the bus voltage when the corresponding conditions are met;

[0043] For example, in the grid-connected mode, if it is detected that the grid-connected inverter reaches the upper limit and the energy storage unit reaches the upper limit of the charging power, the photovoltaic unit is controlled to operate at a reduced power to enter a droop control mode and dominate the bus voltage; in the off-grid mode, if it is detected that the energy storage unit reaches the upper limit of the charging power, the photovoltaic unit is controlled by the droop control mode to dominate the bus voltage through the limited power operation.

[0044] (2) If the requirement threshold range of the bus voltage is a second range, the energy storage unit and the photovoltaic unit are monitored in the grid-connected mode to control the grid-connected inverter to dominate the bus voltage when the corresponding conditions are met;

[0045] For example, in the grid-connected mode, if it is detected that the energy storage unit reaches the upper limit of the charging power and the photovoltaic unit operates in the maximum power generation power mode (MPPT), the grid-connected inverter is controlled to work in the droop control mode to dominate the bus voltage; in the off-grid mode, there is no functional unit dominating the bus voltage, and the bus voltage decreases until it is in a third range.

[0046] (3) If the requirement threshold range of the bus voltage is the third range, the working modes of the photovoltaic unit, the grid-connected inverter and the energy storage unit are controlled in the grid-connected mode to realize the common domination of the bus voltage, and the working modes of the photovoltaic unit and the energy storage unit are controlled in the off-grid mode to realize the common domination of the bus voltage;

[0047] Exemplarily, when the grid is connected, if it is detected that the photovoltaic unit operates in a maximum power generation power mode, the grid-connected inverter and the energy storage unit can be controlled to operate in a droop control mode to jointly dominate the bus voltage; when the grid is disconnected, if it is detected that the photovoltaic unit operates in an MPPT mode, the energy storage unit can be controlled to operate in a droop control mode to charge and dominate the bus voltage.

[0048] (4) If the required threshold range of the bus voltage is the fourth range, the grid-connected inverter is monitored to control the photovoltaic unit and the energy storage unit to dominate the bus voltage when the corresponding condition is met when the grid is connected, and the working modes of the photovoltaic unit and the energy storage unit are controlled to jointly dominate the bus voltage when the grid is disconnected.

[0049] Exemplarily, when the grid is connected, if it is detected that the grid-connected inverter reaches a rectification upper limit, the photovoltaic unit is controlled to operate in an MPPT maximum power generation mode, and the energy storage unit is controlled to operate in a droop control discharging mode to realize bus generation domination; when the grid is disconnected, the photovoltaic unit is controlled to operate in an MPPT discharging mode, and the energy storage unit is controlled to operate in a droop control discharging mode to jointly dominate the bus voltage.

[0050] It should be noted that, by setting different voltage required threshold ranges, the present application can make each converter take on the responsibility of dominating the bus voltage control in turn as the DC bus voltage in the micro-grid system drops, maximize photovoltaic power generation, and realize distributed energy voltage regulation and energy-saving operation mode.

[0051] S103, determine the interface converters corresponding to the photovoltaic unit, the energy storage unit and the grid-connected unit in the DC micro-grid through the converter control layer in the hierarchical control architecture, and realize coordinated control of the photovoltaic unit, the energy storage unit and the grid-connected unit by using the corresponding interface converters.

[0052] The interface converters corresponding to the photovoltaic unit, the energy storage unit and the grid-connected unit in the DC micro-grid can be a Boost Chopper, a DC / DC converter and a voltage-type three-phase bridge inverter circuit, respectively.

[0053] Optionally, the DC / DC converter corresponding to the photovoltaic unit needs to have an MPPT mode and a droop control mode; the bidirectional DC / DC converter corresponding to the energy storage unit needs to have a current-limiting charging and discharging mode and a droop control mode; and the grid-connected inverter needs to have a current-limiting inverter / rectifier mode and a droop control mode.

[0054] Optionally, the interface converters corresponding to the photovoltaic unit, the energy storage unit and the grid-connected unit in the DC micro-grid are determined respectively, and coordinated control of the photovoltaic unit, the energy storage unit and the grid-connected unit is realized by using the corresponding interface converters, including:

[0055] (1) Determine the interface converter of the photovoltaic unit in the direct current micro-grid as a boost chopper BOOST converter, and based on a maximum power point tracking MPPT controller and the BOOST converter, adjust the working point of the photovoltaic array to realize coordinated control of the photovoltaic unit.

[0056] Optionally, based on the maximum power point tracking MPPT controller and the BOOST converter, the working point of the photovoltaic array is adjusted to realize coordinated control of the photovoltaic unit, including: determining the output voltage and output current of the photovoltaic array through sampling, determining whether the duty cycle adjustment condition is met through the MPPT controller according to the output voltage and output current; if yes, the current duty cycle is adjusted to obtain a target duty cycle, and the target duty cycle is input into the BOOST converter to adjust the working point of the photovoltaic array and realize coordinated control of the photovoltaic unit.

[0057] Optionally, the target duty cycle can be the difference between the current duty cycle Dk and the duty cycle adjustment step Dstp, or the sum of the current duty cycle Dk and the duty cycle adjustment step Dstp.

[0058] It should be noted that the output voltage of the photovoltaic array is usually less than the reference value of the direct current bus voltage, so it needs to be boosted by the Boost converter to reach or exceed the reference value of the direct current bus voltage. This selection is based on the boost characteristic of the Boost converter.

[0059] Illustratively, the I-U relationship of the output end of the photovoltaic array can be represented as:

[0060]

[0061] wherein U PV is the input voltage of the Boost converter, i.e. the output voltage of the photovoltaic array; I PV is the input current of the Boost converter, i.e. the output current of the photovoltaic array; I out represents the output current of the Boost converter; U out represents the output voltage of the Boost converter; and D represents the duty cycle in the Boost converter.

[0062] Optionally, the U PV and I PV output by the photovoltaic array can be determined through system sampling, and then the duty cycle D input into the Boost converter is calculated through the MPPT controller to change the working point of the photovoltaic array.

[0063] Optionally, referring to Figure 1B the output voltage and output current of the photovoltaic array at the current time, i.e. U k and I kThese refer to the output voltage U of the photovoltaic array. PV and output current I PV The value at the current moment, further, based on the current output voltage and output current U of the photovoltaic array. k and I k The product of the two values ​​determines the output power of the photovoltaic array at the current moment. Finally, the difference between the output power at the current moment and the output power at the previous moment is determined, i.e., the change in power ΔP. In addition, the change in voltage ΔU is determined based on the output voltage of the photovoltaic array at the current moment and the previous moment.

[0064] Optionally, after determining the power change ΔP and the voltage change ΔU, it can be determined whether the power change ΔP is equal to 0. If so, the process ends without further processing; if not, it is further determined whether the product of the power change ΔP and the voltage change ΔU is greater than zero. If so, the difference between the current duty cycle Dk and the duty cycle adjustment step size Dstp is determined as the duty cycle Dk for the next time step. k+1 If not, then the sum of the current duty cycle Dk and the duty cycle adjustment step size Dstp is used to determine the duty cycle D at the next time step. k+1 .

[0065] It should be noted that after inputting the target duty cycle into the Boost converter, if the target duty cycle is obtained by summation, that is, when the duty cycle increases, the output voltage of the Boost converter will increase, the output voltage of the photovoltaic array will decrease, and the output current of the photovoltaic array will increase, thus shifting the operating point of the photovoltaic array to the left. If the target duty cycle is obtained by difference, that is, when the duty cycle decreases, the output voltage of the Boost converter will decrease, the output voltage of the photovoltaic array will increase, and the output current of the photovoltaic array will decrease, thus shifting the operating point of the photovoltaic array to the right, achieving coordinated control of the photovoltaic units.

[0066] (2) The interface converter of the energy storage unit in the DC microgrid is determined to be a DC-DC / DC converter. Based on the DC / DC converter, a droop control mode and a voltage and current dual closed-loop structure are adopted to realize the coordinated control of the energy storage unit.

[0067] The DC / DC converter has two operating modes, Boost and Buck, which can meet the bidirectional charging and discharging needs of the energy storage unit.

[0068] Exemplarily, the input reference voltage and the output current of the photovoltaic can be subjected to I-V droop control based on a control strategy of a droop control mode, and then output the reference current of the battery charging and discharging current inner loop through a PI (Proportion Integration) controller and a limiter, and then output the on-off duty cycle of the switch tubes S1 and S2, i.e., D1 and D2, through a PI controller, so as to obtain the on-off duty cycle of the switch tubes S1 and S2. Meanwhile, the state of charge (SOC) of the battery is introduced to prevent the battery from overcharging or overdischarging.

[0069] wherein D1 and D2 represent the adjustment of the charging process and the discharging process of the battery, respectively. The on-off time of the switch tubes is controlled by adjusting D1 and D2, so as to control the efficient operation of the battery under different working conditions.

[0070] (3) The interface converter of the grid-connected unit in the direct-current micro-grid is determined as a voltage-type three-phase bridge inverter circuit, and based on the voltage-type three-phase bridge inverter circuit, a combination of a droop control outer loop and a voltage-current double-loop controller is adopted to realize the coordinated control of the grid-connected unit.

[0071] In the present application, the interface design of the grid-connected unit includes a voltage-type three-phase bridge inverter circuit and a direct-current micro-grid DC / AC (direct-current alternating-current) inverter. Specifically, the interface converter of the grid-connected unit is determined as a voltage-type three-phase bridge inverter circuit, because this kind of inverter can efficiently convert direct current into alternating current, and the output voltage and frequency thereof can be accurately adjusted through a control strategy to realize synchronous grid connection with the large power grid.

[0072] It should be noted that the voltage-type three-phase bridge inverter circuit as the interface converter of the grid-connected unit can efficiently convert direct current into alternating current and output voltage and frequency to realize synchronization with the large power grid. Meanwhile, the combination of the droop control outer loop and the dq (voltage-current double-loop controller) current inner loop control can ensure power quality and load sharing, thereby optimizing the connection and operation of the direct-current micro-grid and the large power grid.

[0073] Optionally, the present application can also improve the grid connection efficiency of the grid-connected unit through a parallel control strategy of multiple virtual synchronous generator inverters. Specifically, the parallel control structure is constructed according to at least two virtual synchronous generators VSGs, and the reasonable distribution of the output power of the multiple virtual synchronous generators is performed based on the relationship between the moment of inertia, the damping coefficient, the active power parameter and the reactive power parameter, so as to realize the grid connection operation of the grid-connected unit.

[0074] The virtual synchronous generator (VSG) refers to a VSG inverter used for grid operation, and is used to improve the dynamic response capability and stability of the micro-grid system.

[0075] For example, referring to Figure 1C , E1, E2, …, E n respectively represent the input voltage of the access VSG1, VSG2, …, VSG n port, through the VSG side line resistance reactance R1+jX1, R2+jX2, …, R n +jX n , and are connected in parallel to the external circuit load, I1, I2, …, I n respectively represent the output port current of VSG1, VSG2, …, VSG n .

[0076] It should be noted that the connection mode of the line is not directly connected to the large power grid, but is connected to a variable load, and the micro-grid system operates in an off-grid mode. Through such a mode, the micro-grid system can operate independently of the main power grid, and can rely on the internal distributed power supply (i.e. VSG inverter) and connected load to achieve independent power supply and management.

[0077] For example, the relationship between the moment of inertia, the damping coefficient, the active power parameter and the reactive power parameter can be represented by the following formula:

[0078]

[0079] Wherein, J1 and D1 respectively refer to the moment of inertia and the damping coefficient of the first virtual synchronous machine; J2 and D2 respectively refer to the moment of inertia and the damping coefficient of the second virtual synchronous machine; K w1 and K w2 are the active power parameters of the first virtual synchronous machine and the second virtual synchronous machine, i.e. the active-frequency (P-f) link coefficient. K v1 and K v2 are the reactive power parameters of the first virtual synchronous machine and the second virtual synchronous machine, i.e. the reactive-voltage (Q-E) link coefficient Kv. n is the acceleration factor of the control link. The active power parameter can be the active-frequency (P-f) link coefficient, and the reactive power parameter can be the reactive-voltage (Q-E) link coefficient.

[0080] Optionally, based on the parallel control structure, according to the relationship between the moment of inertia, damping coefficient, active power parameters, and reactive power parameters, that is, in the off-grid operation of multiple VSG inverters connected in parallel to the load, the active-frequency (Pf) link coefficient Kw can be set to be directly proportional to the moment of inertia J, damping coefficient D, and the system set capacity; the reactive-voltage regulation (QE) link coefficient Kv can be set to be inversely proportional to the moment of inertia J, damping coefficient D, and the system set capacity.

[0081] For example, the active power-frequency Pf control element coefficient K w It can be determined using the following formula:

[0082]

[0083] Where n is the acceleration factor of the control loop; C is the power distribution equalization control constant; K w K represents the coefficient of the active-frequency control link Pf; w * represents the setting value of the active-frequency control loop.

[0084] Optional, adjustment constant C, active power K w Consequently, the active power frequency regulation control coefficient K changes; specifically, when the constant C decreases, the active power frequency regulation control coefficient K... w The active power K of the virtual synchronizer also decreases accordingly. w1 and K w2 Consequently, the ratio of the damping coefficient D to the moment of inertia J between the two virtual synchronizers also changes. Furthermore, a larger damping coefficient results in faster output power adjustment and suppression of power oscillations during load changes; conversely, a smaller damping coefficient leads to slower load response and less power adjustment. Therefore, the design of the damping coefficient can alter the load's response and power oscillation capability, thereby affecting the expected balance of power distribution between the VSGs.

[0085] The technical solution of this invention constructs a hierarchical control architecture for a DC microgrid based on a scheduling management layer, a bus voltage control layer, and a converter control layer. Through the bus voltage control layer, corresponding control strategies are adopted based on the required threshold range of the bus voltage to coordinately control the bus voltage in the DC microgrid. Through the converter control layer, the interface converters corresponding to the photovoltaic units, energy storage units, and grid-connected units in the DC microgrid are determined, and the corresponding interface converters are used to achieve coordinated control of these units. By coordinating the control of different functional units in the microgrid, the operating efficiency of the microgrid can be improved while ensuring stable operation.

[0086] Example 2

[0087] Figure 2A is a control flow diagram of a direct current micro-grid provided by the second embodiment of the present application; Figure 2B is a schematic diagram of a hierarchical control structure provided by the second embodiment of the present application; the present embodiment provides an optimal solution for coordinating and controlling the micro-grid by means of a scheduling management layer, a bus voltage control layer and a converter control layer, based on the above-mentioned embodiment.

[0088] As shown in Figure 2A , the method can include the following processes:

[0089] Step A: hierarchical architecture design, specifically constructing the hierarchical control architecture corresponding to the direct current micro-grid, which includes a scheduling management layer, a bus voltage control layer and a converter control layer, wherein the scheduling management layer is configured to send the results of the predicted scheduling to the bus voltage control layer, the bus voltage control layer is configured to adjust the distribution voltage and output to the converter control layer, and the converter control layer is configured to design the parallel control structure of the grid-connected unit.

[0090] Step B: through the bus voltage control layer, setting the voltage threshold value, determining the operation mode of each functional unit, to perform bus voltage control.

[0091] Step C: converter control, by determining the interface converter corresponding to the photovoltaic unit, energy storage unit and grid-connected unit, to realize converter control, wherein the photovoltaic unit can include a BOOST circuit, MPPT and droop control.

[0092] Optionally, step C can include the following processes: S11, determining the interface converter of the photovoltaic unit as a BOOST circuit; S12, controlling the voltage and current output by the photovoltaic array in the photovoltaic unit through MPPT and BOOST circuit, specifically, MPPT control flow can be used to control the photovoltaic array output voltage UPV, and droop control method can be used to determine the output voltage. S21, determining the interface converter of the energy storage unit as a DC / DC converter, and using I-V droop control and voltage-current double closed loop to realize control of the energy storage unit. S31, determining the interface converter of the grid-connected unit, and using droop control outer ring and dq current inner ring to realize control.

[0093] Step D: based on VSG technology support, improving the operation performance of the grid-connected unit.

[0094] Exemplarily, the control flow among the scheduling management layer, the bus voltage control layer and the converter control layer can be as shown in Figure 2BAs shown, the scheduling management layer communicates based on a communication bus, the bus voltage control layer communicates based on a DC bus, and each interface converter of the converter control layer is connected to a corresponding micro source. The micro source is a small distributed power generation energy device, including a renewable energy power generation source, a distributed energy storage system, and other power generation devices. Due to its flexibility and reliability, the micro grid provides power support, realizes local consumption of energy, and reduces loss output.

[0095] Embodiment three

[0096] Figure 3 is a structural block diagram of a control device of a DC micro grid provided by an embodiment of the present application; the present embodiment can be applicable to the case of coordinated control of bus voltage, photovoltaic unit, energy storage unit and grid-connected unit in the micro grid, the control device of the DC micro grid provided by the embodiment of the present application can execute the control method of the DC micro grid provided by any embodiment of the present application, has the corresponding function modules and beneficial effects of the execution method; the control device of the DC micro grid can be realized in the form of hardware and / or software, and be configured in an electronic device with the control function of the DC micro grid, such as the total control device of the power grid, such as Figure 3 As shown, the control device of the DC micro grid specifically comprises:

[0097] The construction module 301 is configured to construct the corresponding hierarchical control architecture of the DC micro grid according to the scheduling management layer, the bus voltage control layer and the converter control layer;

[0098] The first control module 302 is configured to adopt a corresponding control strategy to perform coordinated control on the bus voltage in the DC micro grid according to the requirement threshold range of the bus voltage through the bus voltage control layer in the hierarchical control architecture.

[0099] The second control module 303 is configured to determine the corresponding interface converter of the photovoltaic unit, the energy storage unit and the grid-connected unit in the DC micro grid through the converter control layer in the hierarchical control architecture, and adopt the corresponding interface converter to perform coordinated control on the photovoltaic unit, the energy storage unit and the grid-connected unit.

[0100] The technical scheme of the embodiment of the application constructs a hierarchical control architecture corresponding to the DC micro-grid according to the scheduling management layer, the bus voltage control layer and the converter control layer; the bus voltage control layer in the hierarchical control architecture is used to adopt a corresponding control strategy to coordinately control the bus voltage in the DC micro-grid according to a required threshold range of the bus voltage; the converter control layer in the hierarchical control architecture is used to determine the interface converters corresponding to the photovoltaic unit, the energy storage unit and the grid-connected unit in the DC micro-grid respectively, and the interface converters are used to coordinately control the photovoltaic unit, the energy storage unit and the grid-connected unit. By coordinately controlling different functional units in the micro-grid, the operation efficiency of the micro-grid can be improved while ensuring stable operation of the micro-grid.

[0101] Further, the first control module 302 can include:

[0102] The voltage control unit is configured to determine control strategies for the grid-connected and off-grid states of the DC micro-grid respectively according to a required threshold range of the bus voltage, so as to coordinate at least one of the photovoltaic unit, the grid-connected inverter and the energy storage unit to dominate the bus voltage and achieve coordinated control of the bus voltage in the DC micro-grid.

[0103] Further, the voltage control unit is specifically configured to:

[0104] If the required threshold range of the bus voltage is a first range, the grid-connected inverter and the energy storage unit are monitored respectively in the grid-connected and off-grid states, so as to control the photovoltaic unit to dominate the bus voltage when the corresponding conditions are met;

[0105] If the required threshold range of the bus voltage is a second range, the energy storage unit and the photovoltaic unit are monitored in the grid-connected state, so as to control the grid-connected inverter to dominate the bus voltage when the corresponding conditions are met;

[0106] If the required threshold range of the bus voltage is a third range, the working modes of the photovoltaic unit, the grid-connected inverter and the energy storage unit are controlled in the grid-connected state to achieve common domination of the bus voltage, and the working modes of the photovoltaic unit and the energy storage unit are controlled in the off-grid state to achieve common domination of the bus voltage;

[0107] If the required threshold range of the bus voltage is a fourth range, the grid-connected inverter is monitored in the grid-connected state, so as to control the photovoltaic unit and the energy storage unit to dominate the bus voltage when the corresponding conditions are met, and the working modes of the photovoltaic unit and the energy storage unit are controlled in the off-grid state to achieve common domination of the bus voltage.

[0108] Further, the second control module 303 can include:

[0109] The first control unit is configured to determine that the interface converter of the photovoltaic unit in the DC micro-grid is a boost converter, and to adjust the working point of the photovoltaic array based on a maximum power point tracking (MPPT) controller and the boost converter, so as to realize coordinated control of the photovoltaic unit.

[0110] The second determination unit is configured to determine that the interface converter of the energy storage unit in the DC micro-grid is a DC / DC converter, and to realize coordinated control of the energy storage unit by adopting a droop control mode and a voltage-current double closed-loop structure based on the DC / DC converter.

[0111] The third determination unit is configured to determine that the interface converter of the grid-connected unit in the DC micro-grid is a voltage-type three-phase bridge inverter circuit, and to realize coordinated control of the grid-connected unit by adopting a combination of a droop control outer ring and a voltage-current double-loop controller based on the voltage-type three-phase bridge inverter circuit.

[0112] Further, the first determination unit is specifically configured to:

[0113] The output voltage and the output current of the photovoltaic array are determined by sampling, and whether the duty cycle adjustment condition is met is determined by the MPPT controller according to the output voltage and the output current.

[0114] If yes, the current duty cycle is adjusted to obtain a target duty cycle, and the target duty cycle is input into the boost converter to adjust the working point of the photovoltaic array, so as to realize coordinated control of the photovoltaic unit.

[0115] Further, the above device is also configured to:

[0116] A parallel control structure is constructed according to at least two virtual synchronous generators (VSGs).

[0117] Based on the parallel control structure, reasonable distribution of output power of the multiple virtual synchronous generators is performed according to the relationship among the moment of inertia, the damping coefficient, the active power parameter and the reactive power parameter, so as to realize grid-connected operation of the grid-connected unit.

[0118] Embodiment four

[0119] Figure 4 is a structural schematic diagram of an electronic device provided in the embodiment four of the present application. Figure 4A structural diagram of an electronic device 10 that can be used to implement embodiments of the present application is shown. The electronic device is intended to represent various forms of digital computers, such as laptops, desktops, tablets, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. The electronic device can also represent various forms of mobile devices, such as personal digital assistants, cellular telephones, smartphones, wearable devices (e.g., headsets, glasses, watches, etc.), and other similar computing devices. The components shown here, their connections and relationships, and their functions, are meant to be examples only, and are not intended to limit the implementations of the present application described and / or claimed in this document.

[0120] As shown in Figure 4 The electronic device 10 includes at least one processor 11, and a memory, such as a read-only memory (ROM) 12, a random access memory (RAM) 13, etc., connected in communication with the at least one processor 11, where the memory stores computer programs executable by the at least one processor. The processor 11 can perform various appropriate actions and processes according to the computer programs stored in the read-only memory (ROM) 12 or loaded into the random access memory (RAM) 13 from the storage unit 18. In the RAM 13, various programs and data required for the operation of the electronic device 10 can also be stored. The processor 11, the ROM 12, and the RAM 13 are connected to each other through a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0121] Various components in the electronic device 10 are connected to the I / O interface 15, including an input unit 16, such as a keyboard, a mouse, etc., an output unit 17, such as various types of displays, a speaker, etc., a storage unit 18, such as a magnetic disk, an optical disk, etc., and a communication unit 19, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 19 allows the electronic device 10 to exchange information / data with other devices through a computer network, such as the Internet, and / or various telecommunication networks.

[0122] The processor 11 can be various general and / or special purpose processing components with processing and computing capabilities. Some examples of the processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any appropriate processor, controller, microcontroller, etc. The processor 11 performs various methods and processes described above, such as the control method of the direct current microgrid.

[0123] In some embodiments, the control method of the direct current microgrid can be implemented as a computer program tangibly embodied in a computer readable storage medium, e.g., storage unit 18. In some embodiments, parts or all of the computer program can be loaded and / or installed onto electronic device 10 via, e.g., ROM 12 and / or communication unit 19. When the computer program is loaded onto RAM 13 and executed by processor 11, one or more steps of the control method of the direct current microgrid as described above can be performed. Alternatively, in other embodiments, processor 11 can be configured to perform the control method of the direct current microgrid by other any suitable means, e.g., by means of firmware.

[0124] Various implementations of the systems and techniques described above can be realized in digital electronic circuitry, integrated circuitry, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a system on a chip (SOC), a complex programmable logic device (CPLD), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and / or interpretable on a programmable system including at least one programmable processor, which can be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device.

[0125] Computer programs used to implement the processes of the present application can be written in any combination of one or more programming languages. These computer programs can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the computer program, when executed, implements the functions / acts specified in the flowcharts and / or block diagrams. The computer program can be executed entirely on a machine, partially on a machine, partially on a machine as part of a standalone software package, partially on a machine and partially on a remote machine or entirely on a remote machine or server.

[0126] In the context of the present application, a computer-readable storage medium can be a tangible medium that can contain or store a computer program for use by or in connection with an instruction execution system, apparatus, or device. A computer-readable storage medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, semiconductor system, apparatus, or device, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium can be a machine-readable signal medium. More specific examples of a machine-readable storage medium will include one or more lines of a program of instructions in a transitory signal, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0127] To provide for interaction with a user, the systems and techniques described here can be implemented on an electronic device having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user and a keyboard and a pointing device (e.g., a mouse or a trackball) by which the user can provide input to the electronic device. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form, including acoustic, speech, or tactile input.

[0128] The systems and techniques described here can be implemented in a computing system that includes a back end component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a front end component (e.g., a user computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such back end, middleware, or front end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include a local area network (LAN), a wide area network (WAN), a blockchain network, and the Internet.

[0129] The computing system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. Servers can be cloud servers, also known as cloud computing servers or cloud hosts, which are a host product in the cloud computing service system to solve the defects of large management difficulty and weak business scalability in traditional physical hosts and VPS services.

[0130] In an embodiment, the present embodiment further includes a computer program product comprising a computer program which, when executed by a processor, implements the control method of the direct current micro-grid of any of the embodiments of the present application.

[0131] The computer program product can be written in any of one or more programming languages, including object-oriented programming languages, such as Java, Smalltalk, C++, and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0132] It should be understood that the various forms of flow shown above can be re-ordered, added to, or deleted from without departing from the spirit and scope of the present application. For example, the steps recited in the present application can be performed in parallel, in series, or in a different order, and the present application is not limited in this regard.

[0133] The specific embodiments described above are not intended to limit the scope of the present application. Those skilled in the art will understand that various modifications, combinations, sub-combinations, and alternatives can be made to the specific embodiments without departing from the spirit and principles of the present application. Any further modifications, equivalents, and / or alternatives come within the scope of the present application as recited by the claims.

Claims

1. A control method of a direct current microgrid, characterized by, The application relates to a hierarchical control architecture of a DC micro-grid. The hierarchical control architecture comprises a scheduling management layer, a bus voltage control layer and a converter control layer. The bus voltage control layer is used for controlling the bus voltage of the DC micro-grid according to a required threshold range of the bus voltage. The converter control layer is used for determining interface converters of a photovoltaic unit, an energy storage unit and a grid-connected unit in the DC micro-grid, and realizing the coordinated control of the photovoltaic unit, the energy storage unit and the grid-connected unit by using the interface converters. The required threshold range of the bus voltage is used for determining control strategies of the DC micro-grid in grid-connected and off-grid modes, and at least one of the photovoltaic unit, the grid-connected inverter and the energy storage unit is used to dominate the bus voltage, so that the coordinated control of the bus voltage in the DC micro-grid is realized. If the required threshold range of the bus voltage is a first range, the grid-connected inverter and the energy storage unit are monitored in the grid-connected and off-grid modes, so that the photovoltaic unit dominates the bus voltage when the corresponding conditions are met. If the required threshold range of the bus voltage is a second range, the energy storage unit and the photovoltaic unit are monitored in the grid-connected mode, so that the grid-connected inverter dominates the bus voltage when the corresponding conditions are met. If the required threshold range of the bus voltage is a third range, the working modes of the photovoltaic unit, the grid-connected inverter and the energy storage unit are controlled in the grid-connected mode, so that the bus voltage is dominated by the three units, and the working modes of the photovoltaic unit and the energy storage unit are controlled in the off-grid mode, so that the bus voltage is dominated by the two units. If the required threshold range of the bus voltage is a fourth range, the grid-connected inverter is monitored in the grid-connected mode, so that the photovoltaic unit and the energy storage unit dominate the bus voltage when the corresponding conditions are met, and the working modes of the photovoltaic unit and the energy storage unit are controlled in the off-grid mode, so that the bus voltage is dominated by the two units. The interface converter of the photovoltaic unit in the DC micro-grid is determined as a BOOST converter, and the working point of a photovoltaic array is adjusted based on a maximum power point tracking (MPPT) controller and the BOOST converter, so that the coordinated control of the photovoltaic unit is realized.

2. The method of claim 1, wherein, The interface converter of the energy storage unit in the DC micro-grid is determined as a DC / DC converter, and a droop control mode and a voltage-current double closed loop structure are used based on the DC / DC converter, so that the coordinated control of the energy storage unit is realized. ​ ​ The interface converter of the grid-connected unit in the direct-current micro-grid is determined as a voltage-type three-phase bridge inverter circuit, and based on the voltage-type three-phase bridge inverter circuit, a combination of a droop control outer ring and a voltage-current double-loop controller is adopted to realize coordinated control of the grid-connected unit.

3. The method of claim 2, wherein, Based on a maximum power point tracking (MPPT) controller and a BOOST converter, the operating point of the photovoltaic array is adjusted to realize coordinated control of the photovoltaic unit, including: The output voltage and output current of the photovoltaic array are determined through sampling, and whether the duty cycle adjustment condition is met is determined through the MPPT controller according to the output voltage and output current; If yes, the current duty cycle is adjusted to obtain a target duty cycle, and the target duty cycle is input into the BOOST converter to adjust the operating point of the photovoltaic array, thereby realizing coordinated control of the photovoltaic unit.

4. The method of claim 1, wherein, Further comprising: A parallel control structure is constructed according to at least two virtual synchronous generators (VSGs); Based on the parallel control structure, reasonable distribution of output powers of the multiple virtual synchronous generators is performed according to the relationship among the moment of inertia, the damping coefficient, the active power parameter and the reactive power parameter, so as to realize grid-connected operation of the grid-connected unit.

5. A control device of a direct current microgrid, characterized by, Comprise: A construction module is configured to construct a hierarchical control architecture corresponding to the direct-current micro-grid according to a scheduling management layer, a bus voltage control layer and a converter control layer; A first control module is configured to adopt a corresponding control strategy according to a required threshold range of the bus voltage through the bus voltage control layer in the hierarchical control architecture, to perform coordinated control on the bus voltage in the direct-current micro-grid; A second control module is configured to determine corresponding interface converters of the photovoltaic unit, the energy storage unit and the grid-connected unit in the direct-current micro-grid through the converter control layer in the hierarchical control architecture, and to perform coordinated control on the photovoltaic unit, the energy storage unit and the grid-connected unit by using the corresponding interface converters; The first control module comprises a voltage control unit configured to determine control strategies for grid-connected and off-grid operations of the direct-current micro-grid respectively according to the required threshold range of the bus voltage, to coordinate at least one of the photovoltaic unit, the grid-connected inverter and the energy storage unit to dominate the bus voltage, and to realize coordinated control on the bus voltage in the direct-current micro-grid; The voltage control unit is specifically configured to: If the required threshold range of the bus voltage is a first range, the grid-connected inverter and the energy storage unit are monitored during grid-connected and off-grid operations respectively, to control the photovoltaic unit to dominate the bus voltage when the corresponding condition is met; If the required threshold range of the bus voltage is a second range, the energy storage unit and the photovoltaic unit are monitored during grid-connected operation, to control the grid-connected inverter to dominate the bus voltage when the corresponding condition is met; If the required threshold range of the bus voltage is a third range, the working modes of the photovoltaic unit, the grid-connected inverter and the energy storage unit are controlled during grid-connected operation to jointly dominate the bus voltage, and the working modes of the photovoltaic unit and the energy storage unit are controlled during off-grid operation to jointly dominate the bus voltage. If the required threshold range of the bus voltage is the fourth range, the grid-connected inverter is monitored when grid-connected to control the photovoltaic unit and the energy storage unit to dominate the bus voltage when the corresponding condition is met, and the working mode of the photovoltaic unit and the energy storage unit is controlled when off-grid to realize common domination of the bus voltage.

6. An electronic device, comprising: The electronic device comprises: at least one processor; and a memory connected to the at least one processor in communication; wherein The memory stores a computer program executed by the at least one processor, and the computer program is executed by the at least one processor to enable the at least one processor to execute the control method of the direct-current micro-grid in any one of claims 1-4.

7. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer instructions for enabling the processor to execute the control method of the direct-current micro-grid in any one of claims 1-4 when executed.

8. A computer program product, characterised in that, The computer program product comprises a computer program which, when executed by a processor, implements the control method of the direct-current micro-grid according to any one of claims 1-4.

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