Control method, device, equipment, medium and product of direct-current micro-grid

Abstract

The invention discloses a direct-current micro-grid control method, device and equipment, a medium and a product. The method comprises the following steps: according to a scheduling management layer, a bus voltage control layer and a converter control layer, constructing a hierarchical control architecture corresponding to the DC micro-grid; through a bus voltage control layer in the hierarchical control architecture, according to a required threshold range of the bus voltage, a corresponding control strategy is adopted to carry out coordination control on the bus voltage in the DC micro-grid; through a converter control layer in the hierarchical control architecture, interface converters corresponding to a photovoltaic unit, an energy storage unit and a grid-connected unit in the DC microgrid are respectively determined, and the corresponding interface converters are adopted to realize coordinated control of the photovoltaic unit, the energy storage unit and the grid-connected unit. According to the technical scheme, coordination control can be carried out on different functional units in the micro-grid, and the operation efficiency of the micro-grid is improved under the condition that stable operation of the micro-grid is guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of microgrids, and in particular to a control method, device, equipment, medium and product of a direct current microgrid. Background Art

[0002] With the global climate change and energy crisis, promoting green and low-carbon transformation and improving the development and efficient management of new energy have become the focus of global attention. Since new energy is easily affected by weather, resulting in randomness of power generation and non-centralized distribution, it is often difficult to connect to the power grid in the traditional way.

[0003] The relevant technology selection combines distributed energy, energy storage components and control devices into a small controllable power generation system to ensure its independent operation capability and stable grid-connected working capability, thus the concept of "microgrid" came into being. Microgrid is a new network structure composed of multiple distributed power sources and their related loads. It can effectively give play to the advantages of distributed power generation, rationally plan and use decentralized renewable energy, and its small size and independence can better and more efficiently coordinate and manage local loads, thereby ensuring high-quality power quality and realizing power supply reliability.

[0004] How to coordinate and control different functional units in a microgrid to ensure stable operation of the microgrid and improve its operating efficiency is an urgent problem to be solved. Summary of the invention

[0005] The present invention provides a control method, device, equipment, medium and product for a direct current microgrid, so as to coordinate and control different functional units in the microgrid, thereby improving the operation efficiency of the microgrid while ensuring the stable operation of the microgrid.

[0006] According to one aspect of the present invention, a control method for a DC microgrid is provided, comprising:

[0007] According to the dispatch management layer, bus voltage control layer and converter control layer, a hierarchical control architecture corresponding to the DC microgrid is constructed;

[0008] Through the bus voltage control layer in the hierarchical control architecture, the bus voltage in the DC microgrid is coordinated and controlled by adopting the corresponding control strategy according to the required threshold range of the bus voltage;

[0009] Through the converter control layer in the hierarchical control architecture, the interface converters corresponding to the photovoltaic unit, energy storage unit and grid-connected unit in the DC microgrid are determined respectively, and the corresponding interface converters are used to realize the coordinated control of the photovoltaic unit, energy storage unit and grid-connected unit.

[0010] According to another aspect of the present invention, a control device for a DC microgrid is provided, comprising:

[0011] A construction module is used to construct a hierarchical control architecture corresponding to a DC microgrid according to a dispatch management layer, a bus voltage control layer, and a converter control layer;

[0012] The first control module is used to coordinate and control the bus voltage in the DC microgrid by adopting a corresponding control strategy according to a required threshold range of the bus voltage through a bus voltage control layer in a hierarchical control architecture;

[0013] The second control module is used to determine the interface converters corresponding to the photovoltaic unit, energy storage unit and grid-connected unit in the DC microgrid through the converter control layer in the hierarchical control architecture, and use the corresponding interface converters to achieve coordinated control of the photovoltaic unit, energy storage unit and grid-connected unit.

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

[0015] at least one processor; and

[0016] a memory communicatively connected to the at least one processor; 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 so that the at least one processor can execute the control method of the DC microgrid described in any embodiment of the present invention.

[0018] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to implement the control method of a DC microgrid according to any embodiment of the present invention when executed.

[0019] According to another aspect of the present invention, a computer program product is further provided. The computer program product includes a computer program. When the computer program is executed by a processor, the control method of the DC microgrid according to any embodiment of the present invention is implemented.

[0020] The technical solution of the embodiment of the present invention constructs a hierarchical control architecture corresponding to the DC microgrid according to the dispatch management layer, the bus voltage control layer and the converter control layer; 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 coordinate the bus voltage in the DC microgrid; through the converter control layer in the hierarchical control architecture, the interface converters corresponding to the photovoltaic unit, energy storage unit and grid-connected unit in the DC microgrid are respectively determined, and the corresponding interface converters are adopted to realize the coordinated control of the photovoltaic unit, energy storage unit and grid-connected unit. By coordinating and controlling different functional units in the microgrid, the operating efficiency of the microgrid can be improved while ensuring the stable operation of the microgrid.

[0021] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1A is a flow chart of a control method of a DC microgrid provided in Embodiment 1 of the present invention;

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

[0025] Figure 1C is a schematic diagram of a parallel control structure provided by Embodiment 1 of the present invention;

[0026] Figure 2A This is a control flow diagram of a DC microgrid provided by Embodiment 2 of the present invention;

[0027] Figure 2B is a schematic diagram of a hierarchical control structure provided by Embodiment 2 of the present invention;

[0028] Figure 3 This is a structural block diagram of a control device for a DC microgrid provided in Embodiment 3 of the present invention;

[0029] Figure 4 It is a schematic diagram of the structure of an electronic device provided in Embodiment 4 of the present invention. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first", "second", "target", "candidate", "alternative", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. The acquisition, storage, use, processing, etc. of data in the technical solution of this application comply with the relevant provisions of national laws and regulations.

[0032] Embodiment 1

[0033] Figure 1A is a flow chart of a control method of a DC microgrid provided in Embodiment 1 of the present invention; Figure 1B is a schematic diagram of a target duty cycle determination process provided in the first embodiment of the present invention; Figure 1C Schematic diagram of parallel control structure provided by Embodiment 1 of the present invention; This embodiment is applicable to the case of coordinated control of bus voltage, photovoltaic unit, energy storage unit and grid-connected unit in a microgrid. The method can be executed by a control device of a DC microgrid. The control device of the DC microgrid can be implemented in the form of hardware and / or software. The control device of the DC microgrid can be configured in an electronic device, such as a master control device of a power grid, and executed by a microgrid system, such as Figure 1A As shown, the control method of the DC microgrid includes:

[0034] S101. Construct a hierarchical control architecture corresponding to the DC microgrid according to the dispatch management layer, the bus voltage control layer and the converter control layer.

[0035] Among them, the dispatch management layer is used to predict and dispatch data such as bus voltage in the DC microgrid, and generate dispatch instructions to instruct the bus voltage control layer to coordinate the bus voltage. This level involves long-term dispatch and planning to meet energy demand and market operation, usually at the hour to day level. The bus voltage control layer is mainly used to coordinate the DC bus voltage (DC Bus voltage Signaling, DBS) to maintain bus voltage stability and system power balance. This layer is usually in the short or medium time scale (minute to hour level) to ensure the voltage stability of the node. The converter control layer is used to determine and adjust the converters of the photovoltaic unit, energy storage unit and grid-connected unit, respectively, to achieve coordinated control of the photovoltaic unit, energy storage unit and grid-connected unit. The hierarchical control architecture corresponding to the DC microgrid refers to the hierarchical control architecture based on the physical characteristics of the DC microgrid, which can specifically include the dispatch management layer, bus voltage control layer and converter control layer. The DC microgrid includes photovoltaic units, energy storage units and grid-connected units, and the grid-connected unit includes a grid-connected inverter.

[0036] Optionally, corresponding functions can be configured for the dispatching management layer, the bus voltage control layer and the converter control layer, and a hierarchical control architecture corresponding to the DC microgrid can be constructed based on the structural relationship between the dispatching management layer, the bus voltage control layer and the converter control layer, so as to realize coordinated control of different functional modules in the DC microgrid based on the hierarchical control architecture.

[0037] S102. The bus voltage in the DC microgrid is coordinated and controlled by adopting 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.

[0038] The threshold range may be a first range, a second range, a third range or a fourth range. The first range may be 720V to 740V, the second range may be 700V to 720V, the third range may be 680V to 700V, and the fourth range may be 660V to 680V. The control strategy refers to a strategy for coordinated control of the operation modes of the grid-connected inverter, the energy storage unit and the photovoltaic unit. Specifically, it may be a strategy for coordinated control of the bus voltage by using at least one of the dominant bus voltages of the photovoltaic unit, the grid-connected inverter and the energy storage unit when connected to the grid and off the grid.

[0039] Optionally, the microgrid system may perform coordinated control operations on the bus voltage in the DC microgrid by calling the bus voltage control layer in the hierarchical control architecture.

[0040] Optionally, according to the required threshold range of the bus voltage, a corresponding control strategy is adopted to coordinate the control of the bus voltage in the DC microgrid, including: according to the required threshold range of the bus voltage, the control strategy for the DC microgrid when connected to the grid and off the grid is determined respectively, so as to coordinate the use of at least one of the photovoltaic unit, the grid-connected inverter and the energy storage unit to dominate the bus voltage and realize the coordinated control of the bus voltage in the DC microgrid.

[0041] Optionally, according to the required threshold range of the bus voltage, the control strategies of the DC microgrid when connected to the grid and when off the grid are determined respectively, so as to coordinate the use of at least one of the photovoltaic unit, the grid-connected inverter and the energy storage unit to dominate the bus voltage and realize the coordinated control of the bus voltage in the DC microgrid, including:

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

[0043] Exemplarily, when connected to the grid, if it is detected that the grid-connected inverter has reached its upper limit and the energy storage unit has reached its charging power upper limit, the photovoltaic unit is controlled to reduce power to enter a droop control mode to dominate the bus voltage; when off the grid, if it is detected that the energy storage unit has reached its charging upper limit, the photovoltaic unit is controlled to droop to dominate the bus voltage by limiting power operation.

[0044] (2) If the required threshold range of the bus voltage is the second range, the energy storage unit and the photovoltaic unit are monitored when connected to the grid, so as to control the dominant bus voltage of the grid-connected inverter when the corresponding conditions are met;

[0045] Exemplarily, when connected to the grid, if it is detected that the energy storage unit has reached the upper limit of the charging power and the photovoltaic unit is operating in the maximum power generation power mode (Maximum Power Point Tracking, MPPT), the grid-connected inverter is controlled to operate in the droop control mode, dominating the bus voltage; when off the grid, there is no functional unit that dominates the bus, and the bus voltage drops until it is in the third range.

[0046] (3) If the required threshold range of the bus voltage is the third range, when connected to the grid, the working modes of the photovoltaic unit, the grid-connected inverter and the energy storage unit are controlled to achieve a common dominant bus voltage, and when off-grid, the working modes of the photovoltaic unit and the energy storage unit are controlled to achieve a common dominant bus voltage;

[0047] For example, when connected to the grid, if it is detected that the photovoltaic unit is operating in the maximum power generation mode, the grid-connected inverter and the energy storage unit can be controlled to operate in the droop control mode to jointly dominate the bus voltage; when off the grid, if it is detected that the photovoltaic unit is operating in the MPPT mode, the energy storage unit can be controlled to operate in the droop control mode for charging to dominate the bus voltage.

[0048] (4) If the required threshold range of the bus voltage is the fourth range, then when connected to the grid, the grid-connected inverter is monitored to control the photovoltaic unit and the energy storage unit to dominate the bus voltage when the corresponding conditions are met, and when off-grid, the working mode of the photovoltaic unit and the energy storage unit is controlled to achieve a common dominant bus voltage.

[0049] Exemplarily, when connected to the grid, if it is detected that the grid-connected inverter has reached the upper limit of rectification, the photovoltaic unit is controlled to operate in the MPPT maximum power generation mode, and the energy storage unit is controlled to operate in the droop control discharge mode to achieve dominant bus power generation; when off the grid, the photovoltaic unit is controlled to operate in the MPPT discharge mode, and the energy storage unit is controlled to operate in the droop control discharge mode, so as to jointly dominate the bus voltage.

[0050] It should be noted that, by setting different voltage requirement threshold ranges, the present invention can enable each converter to take on the responsibility of controlling the dominant bus voltage in turn as the DC bus voltage in the microgrid system drops, thereby maximizing photovoltaic power generation and realizing distributed energy voltage regulation and energy-saving operation mode.

[0051] S103, through the converter control layer in the hierarchical control architecture, respectively determine the interface converters corresponding to the photovoltaic unit, energy storage unit and grid-connected unit in the DC microgrid, and use the corresponding interface converters to achieve coordinated control of the photovoltaic unit, energy storage unit and grid-connected unit.

[0052] Among them, the interface converters corresponding to the photovoltaic unit, energy storage unit and grid-connected unit in the DC microgrid can be a boost chopper converter (Boost Chopper), a DC-DC (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; the grid-connected inverter needs to have a current limiting inversion / rectification 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 microgrid are respectively determined, and the corresponding interface converters are used to realize the coordinated control of the photovoltaic unit, the energy storage unit and the grid-connected unit, including:

[0055] (1) The interface converter of the photovoltaic unit in the DC microgrid is determined to be a boost chopper BOOST converter, and based on the maximum power point tracking MPPT controller and BOOST converter, the operating point of the photovoltaic array is adjusted to achieve coordinated control of the photovoltaic unit.

[0056] Optionally, based on the maximum power point tracking MPPT controller and the BOOST converter, the operating point of the photovoltaic array is adjusted to achieve coordinated control of the photovoltaic units, including: determining the output voltage and output current of the photovoltaic array by sampling, and determining whether the duty cycle adjustment conditions are met through the MPPT controller based on the output voltage and output current; if so, adjusting the current duty cycle to obtain a target duty cycle, and inputting the target duty cycle into the BOOST converter to adjust the operating point of the photovoltaic array to achieve coordinated control of the photovoltaic units.

[0057] The target duty cycle may be the difference between the current duty cycle Dk and the duty cycle adjustment step Dstp, or may be 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 DC bus voltage, so it needs to be boosted by a Boost converter to reach or exceed the reference value of the DC bus voltage. This selection is based on the boost characteristics of the Boost converter.

[0059] Exemplarily, the IU relationship at the output end of the photovoltaic array can be expressed as:

[0060]

[0061] Among them, 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; D represents the duty cycle in the Boost converter.

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

[0063] Optional, see Figure 1B The output voltage and output current of the photovoltaic array at the current moment can be determined by system sampling, that is, U k and I kRespectively refers to the output voltage U PV and output current I PV At the current moment, further, according to the output voltage and output current U of the photovoltaic array at the current moment k and I k The product of is used to determine the output power of the photovoltaic array at the current moment, and finally the difference between the output power at the current moment and the output power at the previous moment, that is, the power change ΔP. In addition, according to the output voltage of the photovoltaic array at the current moment and the previous moment, the voltage change ΔU is determined.

[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 Dstp is determined as the duty cycle D at the next moment. k+1 If not, the sum of the current duty cycle Dk and the duty cycle adjustment step Dstp is determined as the duty cycle D at the next moment. k+1 .

[0065] It should be noted that after the target duty cycle is input into the BOOST converter, if the target duty cycle is obtained by summing, 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, so that the operating point of the photovoltaic array will move 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, so that the operating point of the photovoltaic array will move to the right, thereby realizing coordinated control of the photovoltaic units.

[0066] (2) Determine that the interface converter of the energy storage unit in the DC microgrid is a DC-DC converter, and based on the DC / DC converter, adopt a droop control mode and a voltage-current dual closed-loop structure to achieve coordinated control of the energy storage unit;

[0067] Among them, the DC / DC converter has two working states: Boost and Buck, which can meet the bidirectional charging and discharging requirements of the energy storage unit.

[0068] For example, based on the control strategy of the droop control mode, the input reference voltage and the photovoltaic output current can be subjected to IV droop control, and then the reference current of the battery charge and discharge current inner loop is output through the PI (Proportion Integration) controller and the limiter. Secondly, the on-off duty ratio of the switch tubes S1 and S2, i.e. D1 and D2, is obtained through the output of the PI controller. At the same time, the battery is introduced to consider its load state (State of Charge, SOC) to prevent the battery from being overcharged or over-discharged.

[0069] Among them, D1 and D2 respectively represent the charging process and discharging process of the battery. By adjusting D1 and D2 to control the on and off time of the switch tube, the efficient operation of the battery in different working conditions can be controlled.

[0070] (3) The interface converter of the grid-connected unit in the DC microgrid is determined to be a voltage-type three-phase bridge inverter circuit. Based on the voltage-type three-phase bridge inverter circuit, a droop control outer loop and a voltage-current dual-loop controller are combined to achieve coordinated control of the grid-connected unit.

[0071] Among them, the grid-connected unit interface design in the present invention includes a voltage-type three-phase bridge inverter circuit and a DC microgrid DC / AC (direct current-alternating current) inverter; specifically, the interface converter of the grid-connected unit is determined to be a voltage-type three-phase bridge inverter circuit, because this inverter can efficiently convert direct current into alternating current, and its output voltage and frequency can be accurately adjusted through a control strategy to achieve 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 DC power into AC power, and output voltage and frequency to achieve synchronization with the large power grid. At the same time, the use of the droop control outer loop and the dq (voltage and current dual-loop controller) current inner loop control can ensure the power quality and load balancing, thereby optimizing the connection and operation of the DC microgrid and the large power grid.

[0073] Optionally, the present invention can also improve the grid-connected efficiency of the grid-connected unit through a parallel control strategy of multiple virtual synchronous generator inverters. Specifically, it includes: constructing a parallel control structure based on at least two virtual synchronous generators VSG; based on the parallel control structure, according to the relationship between the moment of inertia, damping coefficient, active power parameters and reactive power parameters, reasonably distributing the output power of multiple virtual synchronous generators to achieve grid-connected operation of the grid-connected unit.

[0074] The virtual synchronous generator (VSG) refers to a VSG inverter used for grid-connected operation, which is used to improve the dynamic response capability and stability of the microgrid system. The parallel control structure can specifically be a topology structure in which multiple VSG inverters are connected in parallel to the load.

[0075] For example, see Figure 1C , E 1 、E 2 ,…,E n Respectively represent access to VSG 1 、VSG 2 、…、VSG n The input voltage of the port passes through the line resistance reactance R on the VSG side 1 +jX 1 , R 2 +jX 2 , …, R n +jX n After that, it is connected in parallel to the external circuit load, I 1 ,I 2 ,…,I n Respectively represent VSG 1 、VSG 2 、…、VSG n The output port current.

[0076] It should be noted that the connection method of the line of the present invention is not directly connected to the large power grid, but to a variable load, and the microgrid system operates in off-grid mode. In this way, the microgrid system can operate independently of the main power grid, and can rely on the internal distributed power supply (ie, VSG inverter) and the connected load to achieve independent power supply and management.

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

[0078]

[0079] Among them, J 1 and D 1 They refer to the moment of inertia and damping coefficient of the No. 1 virtual synchronous machine respectively; J 2 and D 2 They refer to the moment of inertia and damping coefficient of the No. 2 virtual synchronous machine respectively; K w1 and K w2 K is the active power parameter of virtual synchronous machine No. 1 and virtual synchronous machine No. 2, that is, the active power-frequency (Pf) link coefficient. v1 and K v2is the reactive power parameter of the No. 1 virtual synchronous machine and the No. 2 virtual synchronous machine, that is, the reactive power-voltage regulation (QE) link coefficient Kv. n is the acceleration factor of the control link. The active power parameter can be the active power-frequency (Pf) link coefficient, and the reactive power parameter can be the reactive power-voltage regulation (QE) 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 proportional to the moment of inertia J, the damping coefficient D and the system set capacity; the reactive-voltage regulation (QE) link coefficient Kv can be set inversely proportional to the moment of inertia J and the damping coefficient D and the system set capacity.

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

[0082]

[0083] Among them, n is the acceleration factor of the control link; C is the power distribution balance control constant; K w K is the active power-frequency Pf control link coefficient; w * is the set value of the active power-frequency control loop.

[0084] Optional, adjustment constant C, active power K w Specifically, when the constant C decreases, the active frequency control coefficient K w The active power K of the virtual synchronous machine also decreases. w1 and K w2 As the damping coefficient D and the moment of inertia J between the two virtual synchronous machines change, the ratio of the damping coefficient D and the moment of inertia J between the two virtual synchronous machines also changes. At the same time, if the damping coefficient is large, it will adjust the output power and suppress power oscillation faster when the load changes; otherwise, it will cause slow response to load changes and less power adjustment. Therefore, the design of the damping coefficient can change the load response and power oscillation capabilities, thereby achieving the expected balance state of the power distribution load between the VSGs.

[0085] The technical solution of the embodiment of the present invention constructs a hierarchical control architecture corresponding to the DC microgrid according to the dispatch management layer, the bus voltage control layer and the converter control layer; 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 coordinate the bus voltage in the DC microgrid; through the converter control layer in the hierarchical control architecture, the interface converters corresponding to the photovoltaic unit, energy storage unit and grid-connected unit in the DC microgrid are respectively determined, and the corresponding interface converters are adopted to realize the coordinated control of the photovoltaic unit, energy storage unit and grid-connected unit. By coordinating and controlling different functional units in the microgrid, the operating efficiency of the microgrid can be improved while ensuring the stable operation of the microgrid.

[0086] Embodiment 2

[0087] Figure 2A This is a control flow diagram of a DC microgrid provided by Embodiment 2 of the present invention; Figure 2B It is a schematic diagram of the hierarchical control structure provided in the second embodiment of the present invention; based on the above embodiment, this embodiment provides a preferred solution for coordinating and controlling the microgrid through the scheduling management layer, the bus voltage control layer and the converter control layer.

[0088] like Figure 2A As shown, the method may include the following process:

[0089] Step A: Hierarchical architecture design, specifically constructing the hierarchical control architecture corresponding to the DC microgrid, which includes the dispatch management layer, bus voltage control layer and converter control layer. The dispatch management layer is used to send the results of the forecast dispatch to the bus voltage control layer, and the bus voltage control layer is used to adjust the distribution voltage and output it to the converter control layer. The converter control layer is used to design the parallel control structure of the grid-connected unit.

[0090] Step B: Through the bus voltage control layer, set the voltage threshold and determine the operation mode of each functional unit to perform bus voltage control.

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

[0092] Optionally, step C may include the following processes: S11, determine that the interface converter of the photovoltaic unit is a BOOST circuit; S12, control the voltage and current output by the photovoltaic array in the photovoltaic unit through MPPT and BOOST circuits. Specifically, the MPPT control process can be used to control the photovoltaic array output voltage UPV, and the droop control method can be used to determine the output voltage. S21, determine that the interface converter of the energy storage unit is a DC / DC converter, and use IV droop control and voltage-current dual closed loops to achieve control of the energy storage unit. S31, determine the interface converter of the grid-connected unit, and use the droop control outer loop and the dq current inner loop to achieve control.

[0093] Step D: Improve the operation performance of the grid-connected unit based on VSG technical support.

[0094] For example, the control process between the dispatch management layer, the bus voltage control layer and the converter control layer can be as follows: Figure 2B As shown, the dispatch management layer communicates based on the communication bus, the bus voltage control layer communicates based on the DC bus, and each interface converter of the converter control layer is connected to the corresponding micro source. Among them, the micro source is a small distributed power generation energy device, including renewable energy power generation sources, distributed energy storage systems and other power generation equipment. Due to its flexibility and reliability, it provides power support for the microgrid, realizes local energy consumption and reduces loss output.

[0095] Embodiment 3

[0096] Figure 3 : is a structural block diagram of a control device for a DC microgrid provided in Embodiment 3 of the present invention; this embodiment can be applied to the situation where the bus voltage, photovoltaic unit, energy storage unit and grid-connected unit in the microgrid are coordinated and controlled. The control device for the DC microgrid provided in the embodiment of the present invention can execute the control method for the DC microgrid provided in any embodiment of the present invention, and has the functional modules and beneficial effects corresponding to the execution method; the control device for the DC microgrid can be implemented in the form of hardware and / or software, and configured in an electronic device having the control function of the DC microgrid, such as the master control device of the power grid, such as Figure 3 As shown, the control device of the DC microgrid specifically includes:

[0097] A construction module 301 is used to construct a hierarchical control architecture corresponding to a DC microgrid according to a dispatch management layer, a bus voltage control layer, and a converter control layer;

[0098] The first control module 302 is used to coordinate and control the bus voltage in the DC microgrid by adopting a corresponding control strategy according to a required threshold range of the bus voltage through a bus voltage control layer in a hierarchical control architecture;

[0099] The second control module 303 is used to determine the interface converters corresponding to the photovoltaic unit, energy storage unit and grid-connected unit in the DC microgrid through the converter control layer in the hierarchical control architecture, and use the corresponding interface converters to achieve coordinated control of the photovoltaic unit, energy storage unit and grid-connected unit.

[0100] The technical solution of the embodiment of the present invention constructs a hierarchical control architecture corresponding to the DC microgrid according to the dispatch management layer, the bus voltage control layer and the converter control layer; 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 coordinate the bus voltage in the DC microgrid; through the converter control layer in the hierarchical control architecture, the interface converters corresponding to the photovoltaic unit, energy storage unit and grid-connected unit in the DC microgrid are respectively determined, and the corresponding interface converters are adopted to realize the coordinated control of the photovoltaic unit, energy storage unit and grid-connected unit. By coordinating and controlling different functional units in the microgrid, the operating efficiency of the microgrid can be improved while ensuring the stable operation of the microgrid.

[0101] Furthermore, the first control module 302 may include:

[0102] The voltage control unit is used to determine the control strategy of the DC microgrid when it is connected to the grid and when it is off the grid according to the required threshold range of the bus voltage, so as to coordinate the use of at least one of the photovoltaic unit, the grid-connected inverter and the energy storage unit to dominate the bus voltage and realize the coordinated control of the bus voltage in the DC microgrid.

[0103] Furthermore, the voltage control unit is specifically used for:

[0104] If the required threshold range of the bus voltage is the first range, the grid-connected inverter and the energy storage unit are monitored respectively when connected to the grid and when off the grid, 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 the second range, then when connected to the grid, the energy storage unit and the photovoltaic unit are monitored to control the dominant bus voltage of the grid-connected inverter when the corresponding conditions are met;

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

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

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

[0109] The first control unit is used to determine that the interface converter of the photovoltaic unit in the DC microgrid is a boost chopper BOOST converter, and adjust the working point of the photovoltaic array based on the maximum power point tracking MPPT controller and the BOOST converter to achieve coordinated control of the photovoltaic unit;

[0110] The second determination unit is used to determine that the interface converter of the energy storage unit in the DC microgrid is a DC-DC DC / DC converter, and based on the DC / DC converter, adopts a droop control mode and a voltage-current dual closed-loop structure to achieve coordinated control of the energy storage unit;

[0111] The third determination unit is used to determine that the interface converter of the grid-connected unit in the DC microgrid is a voltage-type three-phase bridge inverter circuit, and based on the voltage-type three-phase bridge inverter circuit, a droop control outer loop and a voltage-current dual-loop controller are combined to achieve coordinated control of the grid-connected unit.

[0112] Further, the first determining unit is specifically used for:

[0113] Determine the output voltage and output current of the photovoltaic array by sampling, and determine whether the duty cycle adjustment conditions are met through the MPPT controller based on the output voltage and output current;

[0114] If so, the current duty cycle is adjusted to obtain the 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 units.

[0115] Furthermore, the above device is also used for:

[0116] A parallel control structure is constructed based on at least two virtual synchronous generators VSG;

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

[0118] Embodiment 4

[0119] Figure 4 It is a schematic diagram of the structure of an electronic device provided in Embodiment 4 of the present invention. Figure 4A schematic diagram of the structure of an electronic device 10 that can be used to implement an embodiment of the present invention is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices (such as helmets, glasses, watches, etc.) and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present invention described and / or required herein.

[0120] like Figure 4 As shown, the electronic device 10 includes at least one processor 11, and a memory connected to the at least one processor 11, such as a read-only memory (ROM) 12, a random access memory (RAM) 13, etc., wherein the memory stores a computer program that can be executed by at least one processor, and the processor 11 can perform various appropriate actions and processes according to the computer program stored in the read-only memory (ROM) 12 or the computer program loaded from the storage unit 18 to the random access memory (RAM) 13. 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] A number of 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, speakers, etc.; a storage unit 18, such as a 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 may be a variety of general and / or special 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 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 executes the various methods and processes described above, such as a control method for a DC microgrid.

[0123] In some embodiments, the control method of the DC microgrid may be implemented as a computer program, which is tangibly contained in a computer-readable storage medium, such as a storage unit 18. In some embodiments, part or all of the computer program may be loaded and / or installed on the electronic device 10 via the ROM 12 and / or the communication unit 19. When the computer program is loaded into the RAM 13 and executed by the processor 11, one or more steps of the control method of the DC microgrid described above may be performed. Alternatively, in other embodiments, the processor 11 may be configured to execute the control method of the DC microgrid in any other appropriate manner (e.g., by means of firmware).

[0124] Various implementations of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), system-on-chips (SOCs), complex programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include: being implemented in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0125] Computer programs for implementing the methods of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when the computer program is executed by the processor, the functions / operations specified in the flow chart and / or block diagram are implemented. The computer program may be executed entirely on the machine, partially on the machine, partially on the machine and partially on a remote machine as a stand-alone software package, or entirely on a remote machine or server.

[0126] In the context of the present invention, a computer readable storage medium may be a tangible medium that may contain or store a computer program for use by or in conjunction with an instruction execution system, device, or equipment. A computer readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, semiconductor systems, devices, or equipment, or any suitable combination of the foregoing. Alternatively, a computer readable storage medium may be a machine readable signal medium. A more specific example of a machine readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, 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 disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0127] To provide interaction with a user, the systems and techniques described herein may 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 trackball) through which the user can provide input to the electronic device. Other types of devices may also be used to provide interaction with the user; for example, the feedback provided to the user may be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user may be received in any form (including acoustic input, voice input, or tactile input).

[0128] The systems and techniques described herein may be implemented in a computing system that includes backend components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes frontend components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such backend components, middleware components, or frontend components. The components of the system may 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] A computing system may include a client and a server. The client and the server are generally remote from each other and usually interact through a communication network. The client and server relationship is generated by computer programs running on the corresponding computers and having a client-server relationship with each other. The server may be a cloud server, also known as a cloud computing server or cloud host, which is a host product in the cloud computing service system to solve the defects of difficult management and weak business scalability in traditional physical hosts and VPS services.

[0130] In one embodiment, the embodiment of the present invention further includes a computer program product, the computer program product includes a computer program, and the computer program implements the control method of the DC microgrid of any embodiment of the present invention when executed by a processor.

[0131] In the process of implementation, the computer program product can be written in one or more programming languages ​​or a combination thereof to perform the computer program code of the present invention, including object-oriented programming languages, such as Java, Smalltalk, C++, and conventional procedural programming languages, such as "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, 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 can be connected to an external computer (for example, using an Internet service provider to connect through the Internet).

[0132] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0133] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for a DC microgrid, characterized in that: include: According to the dispatch management layer, bus voltage control layer and converter control layer, a hierarchical control architecture corresponding to the DC microgrid is constructed; Through the bus voltage control layer in the hierarchical control architecture, the bus voltage in the DC microgrid is coordinated and controlled by adopting the corresponding control strategy according to the required threshold range of the bus voltage; Through the converter control layer in the hierarchical control architecture, the interface converters corresponding to the photovoltaic unit, energy storage unit and grid-connected unit in the DC microgrid are determined respectively, and the corresponding interface converters are used to realize the coordinated control of the photovoltaic unit, energy storage unit and grid-connected unit.

2. The method according to claim 1, characterized in that The method of using a corresponding control strategy to coordinately control the bus voltage in the DC microgrid according to the required threshold range of the bus voltage includes: According to the required threshold range of the bus voltage, the control strategies of the DC microgrid when connected to the grid and off the grid are determined respectively, so as to coordinate the use of at least one of the photovoltaic unit, the grid-connected inverter and the energy storage unit to dominate the bus voltage and realize the coordinated control of the bus voltage in the DC microgrid.

3. The method according to claim 2, characterized in that According to the required threshold range of bus voltage, the control strategies of the DC microgrid when connected to the grid and off the grid are determined respectively, so as to coordinate the use of at least one of the photovoltaic unit, the grid-connected inverter and the energy storage unit to dominate the bus voltage and realize the coordinated control of the bus voltage in the DC microgrid, including: If the required threshold range of the bus voltage is the first range, the grid-connected inverter and the energy storage unit are monitored respectively when connected to the grid and when off the grid, so as to control the photovoltaic unit to dominate the bus voltage when the corresponding conditions are met; If the required threshold range of the bus voltage is the second range, then when connected to the grid, the energy storage unit and the photovoltaic unit are monitored to control the dominant bus voltage of the grid-connected inverter when the corresponding conditions are met; If the required threshold range of the bus voltage is the third range, then when connected to the grid, the working modes of the photovoltaic unit, the grid-connected inverter and the energy storage unit are controlled to achieve a common dominant bus voltage, and when off-grid, the working modes of the photovoltaic unit and the energy storage unit are controlled to achieve a common dominant bus voltage; If the required threshold range of the bus voltage is the fourth range, the grid-connected inverter is monitored when connected to the grid to control the photovoltaic unit and the energy storage unit to dominate the bus voltage when the corresponding conditions are met, and when off-grid, the working modes of the photovoltaic unit and the energy storage unit are controlled to achieve a common dominant bus voltage.

4. The method according to claim 1, characterized in that: Determine the interface converters corresponding to the photovoltaic unit, energy storage unit and grid-connected unit in the DC microgrid respectively, and use the corresponding interface converters to achieve coordinated control of the photovoltaic unit, energy storage unit and grid-connected unit, including: The interface converter of the photovoltaic unit in the DC microgrid is determined to be a boost chopper BOOST converter, and based on the maximum power point tracking MPPT controller and BOOST converter, the working point of the photovoltaic array is adjusted to achieve coordinated control of the photovoltaic unit; The interface converter of the energy storage unit in the DC microgrid is determined to be a DC-DC DC / DC converter, and based on the DC / DC converter, a droop control mode and a voltage-current dual closed-loop structure are adopted to achieve coordinated control of the energy storage unit; The interface converter of the grid-connected unit in the DC microgrid is determined to be a voltage-type three-phase bridge inverter circuit. Based on the voltage-type three-phase bridge inverter circuit, a droop control outer loop and a voltage-current dual-loop controller are combined to achieve coordinated control of the grid-connected unit.

5. The method according to claim 4, characterized in that Based on the maximum power point tracking MPPT controller and BOOST converter, the working point of the photovoltaic array is adjusted to achieve coordinated control of the photovoltaic units, including: Determine the output voltage and output current of the photovoltaic array by sampling, and determine whether the duty cycle adjustment conditions are met through the MPPT controller based on the output voltage and output current; If so, the current duty cycle is adjusted to obtain the 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 units.

6. The method according to claim 1, characterized in that Also includes: A parallel control structure is constructed based on at least two virtual synchronous generators VSG; Based on the parallel control structure, the output power of multiple virtual synchronous generators is reasonably distributed according to the relationship between the moment of inertia, the damping coefficient, the active power parameter and the reactive power parameter to realize the grid-connected operation of the grid-connected unit.

7. A control device for a DC microgrid, characterized in that: include: A construction module is used to construct a hierarchical control architecture corresponding to a DC microgrid according to a dispatch management layer, a bus voltage control layer, and a converter control layer; The first control module is used to coordinate and control the bus voltage in the DC microgrid by adopting a corresponding control strategy according to a required threshold range of the bus voltage through a bus voltage control layer in a hierarchical control architecture; The second control module is used to determine the interface converters corresponding to the photovoltaic unit, energy storage unit and grid-connected unit in the DC microgrid through the converter control layer in the hierarchical control architecture, and use the corresponding interface converters to achieve coordinated control of the photovoltaic unit, energy storage unit and grid-connected unit.

8. An electronic device, characterized in that: The electronic device comprises: at least one processor; and a memory communicatively connected to the at least one processor; 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 so that the at least one processor can execute the control method of the DC microgrid according to any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to implement the control method of the DC microgrid according to any one of claims 1 to 6 when executed.

10. A computer program product, characterized in that The computer program product comprises a computer program, and when the computer program is executed by a processor, the computer program implements the control method of the DC microgrid according to any one of claims 1 to 6.

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