Solid-state micro-grid system and control method thereof

Abstract

The invention relates to a solid-state micro-grid system and a control method thereof, and the system comprises a DC bus which is connected with a DC bus port; the direct-current power unit adopts a modular design, the input side is connected with the direct-current port, and the output side is connected with the direct-current bus; the alternating-current power unit adopts a modular design, the direct-current side is connected with the direct-current bus, and the alternating-current side is connected with the alternating-current port; and the coordination control unit is respectively connected with the direct current power unit and the alternating current power unit and is used for realizing energy access, conversion, distribution, control and management. According to the invention, different types of energy and loads can be efficiently integrated.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and in particular to a solid-state microgrid system and a control method thereof. Background Art

[0002] As the global energy crisis intensifies, people are increasingly concerned about fuel depletion, power shortages and global warming. Clean and renewable solar and wind energy provide solutions to these problems through distributed generation. Microgrids, as an important interface for connecting the power generated by distributed power sources based on renewable energy to the power system, have become a hot topic of research.

[0003] With the increasing demand for intensive and miniaturized energy supply, as well as the rapid development of power electronics technology, especially new high-power semiconductor devices such as silicon carbide, the foundation has been laid for the further development of power electronics in microgrids. Under the traditional power transmission and distribution system structure, microgrids need to be equipped with corresponding power electronic converters for new energy power generation equipment, energy sources, energy storage systems and loads to achieve functions such as AC / DC conversion of voltage, local load power supply and grid connection. The traditional method of using multiple power converters for each distributed device brings challenges, including increased costs, reduced system power density and complex communication between power converters. In addition, the hierarchical control method of the traditional power transmission and distribution structure leads to complex dispatching management and cannot fully utilize the rapidity of power electronic converters to quickly respond to grid and load fluctuations.

[0004] Therefore, it is of great development prospect to replace the traditional power distribution system through more flexible and intelligent integration and multi-port design of microgrid converter equipment. The emergence of power conversion technologies such as dual-active bridge DC transformers, multi-port converters and solid-state transformers has laid the foundation for the integrated development of microgrid systems. However, the above microgrid technologies have only been studied from the perspective of the converter's individual topology or control method. The actual microgrid needs to provide an integrated platform for distributed power generation equipment, energy storage equipment, loads and user ends, and realize energy management and transmission control, voltage level conversion, electrical isolation, reactive power compensation and real-time control. System-level microgrid control is crucial to the stable operation of new energy equipment, so it is also an urgent problem to be solved in the integration of microgrids.

[0005] The existing open patent document CN109728581A discloses a composite energy router and control method, but the composite energy router is essentially a plurality of independent power distribution systems directly connected through conventional devices such as power frequency transformers and circuit breakers. It lacks modular and integrated ports, resulting in low power density, large equipment size and other problems. In terms of control, the scheme is limited to discussing the control of the DC bus voltage and harmonic distortion rate by the grid-side converter, and does not discuss the core of the energy router - the operation and control scheme of the power electronic solid-state transformer, nor does it discuss how the energy router can achieve internal energy management, distribution, monitoring and protection. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a solid-state microgrid system and a control method thereof, which can efficiently integrate different types of energy and loads.

[0007] The technical solution adopted by the present invention to solve the technical problem is: to provide a solid-state microgrid system, comprising:

[0008] A DC bus is connected to a DC bus port; the DC bus port is used to connect a DC load;

[0009] The DC power unit adopts a modular design, the input side is connected to the DC port, and the output side is connected to the DC bus; the DC port is used to connect the distributed energy storage device;

[0010] The AC power unit adopts a modular design, the DC side is connected to the DC bus, and the AC side is connected to the AC port; the AC port is used to connect to the AC network;

[0011] A coordination control unit is connected to the DC power unit and the AC power unit respectively, and is used to implement at least one of energy access, conversion, distribution, control and management.

[0012] The DC power unit comprises:

[0013] The sampling circuit part is used to sample the voltage and current of the DC port and the voltage and current of the DC bus;

[0014] The main circuit adopts a DC / DC structure that can realize bidirectional energy flow and has high-frequency isolation;

[0015] The control circuit part is used to identify the inserted device on the DC port side, transmit the identification result to the coordination control unit, and control the operation state of the main circuit part according to the control strategy of the DC power unit issued by the coordination control unit;

[0016] The coordination control unit is further used to determine the control strategy of the DC power unit according to the identification result of the inserted device on the DC port side.

[0017] The control strategy of the DC power unit includes a DC port voltage control mode, a DC bus voltage control mode and a power control mode; in the DC port voltage control mode, the DC bus voltage is not controlled, the DC port voltage is controlled, and the direction and magnitude of power flow are determined by the load; in the DC bus voltage control mode, the DC port voltage is not controlled, the DC bus voltage is controlled, and the direction and magnitude of power flow are determined by the load; in the power control mode, neither the DC bus voltage nor the DC port voltage is controlled, and only the magnitude and direction of power flow are controlled.

[0018] When the control strategy of the DC power unit received is the DC port voltage control mode, the control circuit part obtains a DC port current reference value through closed-loop control according to the expected voltage value of the DC port and the voltage of the DC port obtained by the sampling circuit part, and then obtains a preliminary DC port current control value through closed-loop control according to the DC port current reference value and the current of the DC port obtained by the sampling circuit part, and then performs current limiting on the preliminary DC port current control value to obtain a final DC port current control value; optimizes the control amount according to the current working condition of the main circuit part;

[0019] When the control strategy of the DC power unit received is the DC bus voltage control mode, the control circuit part obtains a DC bus current reference value through closed-loop control according to the DC bus voltage expected value and the DC bus voltage obtained by the sampling circuit part, and then obtains a bus voltage preliminary current control value through closed-loop control according to the DC bus current reference value and the DC bus current obtained by the sampling circuit part, and then performs current limiting on the preliminary bus voltage current control value to obtain a bus voltage final current control value; optimize the control amount according to the current working condition of the main circuit part;

[0020] When the control strategy of the DC power unit received is the power control mode, the control circuit part obtains the expected current value according to the expected value of the DC bus power, and dynamically tracks the expected current value with the actual current value through closed-loop control; and optimizes the control amount according to the current working condition of the main circuit part.

[0021] The AC power unit comprises:

[0022] The detection circuit part is used to detect the three-phase grid line voltage and phase current, DC bus voltage and current, output voltage and current;

[0023] The driving circuit part adopts a three-phase two-level converter structure or a CHB multi-level converter structure with a common DC bus;

[0024] The main control part is used to determine the control method of the driving circuit part according to the DC bus voltage control mode issued by the coordination control unit.

[0025] The main control part includes:

[0026] A first control subunit, used to control the driving circuit part by adopting a grid-connected or off-grid constant voltage or constant power when the DC bus is controlled by the energy storage unit;

[0027] The second control subunit is used to control the driving circuit part to operate in a networking mode when the DC bus is connected to the grid by controlling the inverter.

[0028] When the first control subunit uses a grid-connected or off-grid constant voltage or constant power to control the driving circuit part, the three-phase grid line voltage V detected by the detection circuit part is obtained. pabc , through coordinate transformation, the three-phase grid line voltage V pabc Transformed into the voltage V in the two-phase rotating coordinate system pd and V pq , the q-axis voltage signal V pq Input the PI controller to get the system real-time angular frequency deviation signal ω err , the system real-time angular frequency deviation signal ω err The real-time angular frequency signal ω is added to the rated angular frequency signal ω0, and the real-time angular frequency signal ω is integrated to obtain the phase angle signal reference θ of the whole system. pll ;

[0029] When the first control subunit adopts the constant voltage or constant power control of the driving circuit part in grid connection or off-grid connection, the three-phase grid line voltage V pabc and phase current i abc , use the system's phase angle signal reference to perform coordinate transformation to convert the three-phase grid line voltage V pabc The voltage amplitude signal is transformed into the two-phase rotating coordinate system; the phase current i in the three-phase stationary coordinate system is transformed into the voltage amplitude signal in the two-phase rotating coordinate system; abc The current signal I transformed into the two-phase rotating coordinate system d and I q ;

[0030] When the first control subunit adopts the constant voltage or constant power control of the driving circuit part in grid connection or off-grid connection, according to the rated value of the DC bus voltage U dcref The DC bus voltage U detected by the detection circuit dc The first deviation signal is input into the DC bus voltage controller to obtain the d-axis current reference signal i dref According to the reactive power demand of the power grid system, the reactive power control link is introduced to set the reactive power reference value Qref and the actual output value Q e The second deviation signal is input into the reactive power controller to obtain the q-axis current reference signal i qref .

[0031] When the second control subunit controls the drive circuit part to operate in the networking mode, according to the DC bus voltage rated value U dcref The DC bus voltage U detected by the detection circuit dc , the difference between the two is obtained to obtain a first deviation signal, and the first deviation signal is input into the DC bus voltage controller; the grid voltage frequency deviation is input into the synchronous generator speed regulator; based on the output of the DC bus voltage controller and the output of the synchronous generator speed regulator, the active power setting value P is obtained. ref , set the active power value P ref and the actual output value P e The deviation is input into the synchronous machine rotor swing equation to obtain the power synchronizer angular frequency deviation signal Δω. The power synchronizer angular frequency deviation signal Δω and the rated angular frequency signal ω0 are added to obtain the system real-time angular frequency signal ω. The phase angle signal reference θ is finally obtained through the integrator. vsg ; The real-time voltage amplitude U of the grid connection point measured by the grid connection point pf The grid voltage rating U N The deviation input droop controller generates a reactive power regulation deviation signal, and generates a power synchronous output voltage reference value through a reactive power loop; based on the power synchronous output voltage reference value, a phase angle signal reference is used to perform coordinate conversion to obtain an output voltage reference value V dref and V qref , and input the power synchronous output voltage closed loop to obtain the d-axis current reference value i dref and q-axis current reference value i qref ; According to the d-axis current reference value i dref , q-axis current reference value i qref and the actual d-axis current i d and q-axis current i q Comparison is performed to obtain a d-axis error signal and a q-axis error signal, and the d-axis error signal and the q-axis error signal are respectively closed-loop controlled by a PI controller to obtain an adjustment voltage on the output filter inductor, which is superimposed with a grid-connected point feedforward voltage to generate an output modulation voltage, and an inverse coordinate transformation is performed according to phase information to obtain a modulation voltage in a two-phase stationary coordinate system; the modulation voltage in the two-phase stationary coordinate system is input into a space vector pulse width modulation (SVPWM) module for processing to obtain a drive signal of the drive circuit part.

[0032] The technical solution adopted by the present invention to solve its technical problem is: to provide a control method for the above-mentioned solid-state microgrid system, including device-level control, wherein the device-level control refers to completing the control target of the AC power unit and the DC power unit of the physical layer of the solid-state microgrid based on control information.

[0033] The control method of the solid-state microgrid system also includes system-level control, the purpose of which is to provide an interface for the upper power grid.

[0034] Beneficial effects:

[0035] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: In order to adapt to the access of various energy sources, loads and energy storage devices, the present invention provides great flexibility and scalability through modularly designed AC and DC units and diversified interfaces, efficiently integrates different types of energy and loads, and enhances interface adaptability. In order to ensure the stable operation and flexible control of the solid-state microgrid system, the present invention adopts an overall control method of hybrid collaborative control, through the interaction of the main controller with the status information and operating conditions of each unit, intelligently identifies the port device and adjusts the operating mode output power of each sub-unit to adapt to different application scenarios, and at the same time embeds fault protection, grid-connected and off-grid control, power management and other intelligent microgrid control algorithms to achieve cross-level integration of the system, thereby having the advantages of high adaptability and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic structural diagram of a solid-state microgrid system according to an embodiment of the present invention;

[0037] Figure 2 is a schematic diagram of a DC power unit control strategy in an embodiment of the present invention;

[0038] Figure 3 is a control structure diagram of an AC power unit in an embodiment of the present invention;

[0039] Figure 4 It is an adaptive collaborative control integration diagram of the solid-state microgrid system control method in the implementation mode of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0041] The first embodiment of the present invention relates to a solid-state microgrid system, such as Figure 1 As shown, including:

[0042] A DC bus is connected to a DC bus port; the DC bus port is used to connect a DC load;

[0043] The DC power unit adopts a modular design, the input side is connected to the DC port, and the output side is connected to the DC bus; the DC port is used to connect the distributed energy storage device;

[0044] The AC power unit adopts a modular design, the DC side is connected to the DC bus, and the AC side is connected to the AC port; the AC port is used to connect to the AC network;

[0045] A coordination control unit is connected to the DC power unit and the AC power unit respectively, and is used to implement at least one of energy access, conversion, distribution, control and management.

[0046] The solid-state microgrid system adopts partial integrated design of AC power unit, DC power unit, DC bus, AC bus, coordinated control, etc. Magnetic integration is performed for filter inductors and transformers to optimize system performance and reduce overall cost. By sharing the topological structure of magnetic components, such as designing common-mode inductors or using multi-layer PCB technology, the magnetic components of different inductors and transformers are shared between vertical layers, thereby reducing the system volume. Consider selecting integrated magnetic materials, such as soft magnetic sheets or magnetic nanomaterials, to improve magnetic integration. In addition, compact physical layout, packaging technology and adaptive inductor design are adopted to enable multiple magnetic components to coexist efficiently. The solid-state microgrid integrates the output of DC power unit with the output of AC power unit. The AC / DC hybrid design reduces the redundant structure of AC and DC bus bars caused by the traditional transmission and distribution structure; by using new power devices for system integration and coordinated control between systems and modules, the integrated functions of energy access, conversion, distribution, control and management are realized.

[0047] The DC power unit in this embodiment includes: a sampling circuit part, which is used to sample the voltage and current of the DC port and the voltage and current of the DC bus; a main circuit part, which adopts a DC / DC structure that can realize bidirectional energy flow and has high-frequency isolation; a control circuit part, which is used to identify the inserted device on the DC port side, transmit the identification result to the coordination control unit, and control the operating state of the main circuit part according to the control strategy of the DC power unit issued by the coordination control unit.

[0048] The main circuit part adopts a DC / DC structure that can realize bidirectional energy flow and has high-frequency isolation. The input interface can be flexibly connected to photovoltaic, wind power generation, energy storage and other equipment, and the input voltage control strategy can be selected according to the intelligent interface recognition, which can realize the selection of maximum power tracking, power-limited operation and other modes of new energy power generation equipment, and can also realize the charging and discharging and energy management control of energy storage equipment. The output side of the DC power unit is connected to the DC bus of the solid-state microgrid system, and the DC bus interface can be directly connected to the DC distribution network to realize power transmission between the solid-state microgrid system and the DC system, thereby providing a household DC output interface and a high-voltage DC output interface. The number of DC power unit modules can be flexibly configured according to the capacity requirements of the solid-state microgrid system, without the need for complex wiring and communication.

[0049] In this implementation, the energy flow of the DC power unit into the solid-state microgrid is defined as forward operation, and the reverse is reverse operation. Without considering the specific instructions of the top-level control management unit, only the final action response of the DC power unit can be distinguished, and six scenarios can be obtained: 1. The DC power unit switches from stop to start operation; 2. The DC power unit is in forward boost operation; 3. The DC power is in forward buck operation; 4. The DC power unit is in reverse boost operation; 5. The DC power unit is in reverse buck operation; 6. The DC power unit switches from operation to stop. The working principles of the DC power unit in each scenario will be introduced below.

[0050] 1) The DC power unit switches from stop to start operation

[0051] Before the DC power unit is operated, the coordination control unit should set different control strategies according to different plug-in devices. Generally speaking, there are three typical control strategies: ① DC port voltage control mode. The DC bus voltage is not controlled, the DC port voltage is controlled, and the direction and size of power flow are determined by the load; ② DC bus voltage control mode. The DC port voltage is not controlled, the DC bus voltage is controlled, and the direction and size of power flow are determined by the load; ③ Power control mode. Neither the DC bus voltage nor the DC port voltage is controlled, and the converter controls the size and direction of power flow.

[0052] This implementation method selects appropriate control strategies according to different control modes, which can be divided into the following types:

[0053] DC port voltage control mode: DC port voltage outer loop and current inner loop control mode should be adopted. Figure 2As shown in (a), a DC port current reference value is obtained through PI control according to the expected voltage value of the DC port and the voltage of the DC port obtained by the sampling circuit part, and then a preliminary DC port current control value is obtained through PI control according to the DC port current reference value and the current of the DC port obtained by the sampling circuit part, and then the preliminary DC port current control value is current limited to obtain the final DC port current control value. At this time, the expected DC port voltage value is given by the system, and the DC power unit needs to dynamically track the given value according to the current DC port voltage output value, and realize current limiting at the same time.

[0054] DC bus voltage control mode: DC bus voltage outer loop and current inner loop control mode should be adopted. Figure 2 As shown in (b), a DC bus current reference value is obtained through PI control according to the DC bus voltage expected value and the DC bus voltage obtained by the sampling circuit part, and then a bus voltage preliminary current control value is obtained through PI control according to the DC bus current reference value and the DC bus current obtained by the sampling circuit part, and then the bus voltage preliminary current control value is current limited to obtain the bus voltage final current control value. At this time, the DC bus voltage expected value is given by the system, and the DC power unit needs to control the actual DC bus voltage value to dynamically track the given value, while realizing current limiting.

[0055] ③Power control mode: current loop control mode is required. Figure 2 As shown in (c), the expected current value is obtained according to the expected value of the DC bus power, and the actual current value is dynamically tracked by the PI control. At this time, the expected value of the power on the DC bus voltage side is given by the system, and the expected current value can be obtained according to the given value. The DC power unit controls the actual current value to dynamically track the given value.

[0056] 2) DC power unit forward and reverse, step-up and step-down operation

[0057] After determining the control strategy of the DC power unit, the operating conditions of the main circuit part can be divided into four types: forward and reverse, buck and boost. In order to optimize the working performance of the DC / DC structure of the main circuit part, it is necessary to optimize the control quantity for different working conditions to reduce the reflux power and improve the efficiency of the converter. Among them, the difference in buck and boost working conditions determines the duty cycle relationship of the inverter square wave of the primary and secondary bridge arms of the converter; the difference in forward and reverse working conditions determines the phase relationship of the inverter square wave of the primary and secondary bridge arms of the converter.

[0058] 3) The DC power unit changes from running to stopping

[0059] Assume that at a certain moment, the coordination control unit issues a command to stop operation to a DC power unit. The DC power unit needs to ensure smooth switching of the operating state at a faster response speed. To reduce the impact, the output power of the DC / DC structure of the main circuit part can be gradually reduced in the form of a ramp function, and the response speed can be adjusted by changing the slope. When the DC power unit stops completely, the switching device pulse should be blocked to ensure system safety. At this time, the DC power unit maintains communication with the control management unit, waiting for the next startup or the device to be removed from the solid-state power grid.

[0060] The AC power unit in this embodiment includes: a detection circuit part, which is used to detect the three-phase grid line voltage and phase current, the DC bus voltage and current, and the output voltage and current; a drive circuit part, which adopts a three-phase two-level converter structure or a CHB multi-level converter structure with a common DC bus; and a main control part, which is used to determine the control method of the drive circuit part according to the DC bus voltage control method issued by the coordination control unit.

[0061] Among them, the drive circuit part can choose the traditional three-phase two-level converter structure, or it can be designed as a CHB multi-level converter structure with a common DC bus, so as to realize the direct connection of the medium and high voltage distribution network without the need for an industrial frequency transformer. It can be flexibly configured and expanded according to the needs of the actual operation scenario. The output interface of the AC power unit can be connected to the power grid, or it can be used as an AC source to power the local AC load. The DC side of the AC power unit is connected to the DC bus, that is, the DC power unit and the AC power unit are connected through the DC bus. Under different DC bus voltage control modes, the control method of the AC power unit is also different. For example, when the DC bus is controlled by the energy storage unit, the AC power unit can operate in constant voltage or constant power control of grid-connected or off-grid. By controlling the inverter grid-connected mode, the flexible switching between grid-connected operation and off-grid operation of the solid-state microgrid can be realized. By controlling the inverter output voltage amplitude, harmonic components, and support for the grid and power quality regulation can also be achieved.

[0062] The AC power unit adopts vector control to realize the four-quadrant operation mode of the system, that is, the transmission direction and size of active and reactive power can be controlled separately according to the requirements of the solid-state microgrid system. At the same time, according to the power quality of the grid voltage, the reverse harmonic voltage can be injected through harmonic analysis of the grid voltage to improve the power quality. The main control part of the AC power unit includes: a first control subunit, which is used to control the drive circuit part by constant voltage or constant power connected to the grid or off the grid when the DC bus is controlled by the energy storage unit; and a second control subunit, which is used to control the drive circuit part to operate in a networking mode when the DC bus is connected to the grid by controlling the inverter. Among them, the control methods of the first control subunit and the second control subunit are as follows: Figure 3 shown.

[0063] Figure 3 In, V pabc Inverter drive signal; U dc Indicates the DC bus voltage; i abc Indicates the converter output three-phase current, f pcc represents the grid frequency, θ pll Indicates the grid voltage rotation angle.

[0064] When the first control subunit adopts the constant voltage or constant power control of the driving circuit part in grid connection or off-grid connection, such as Figure 3 As shown in the phase-locked loop 1 in FIG, the working process is as follows: the three-phase grid line voltage V detected by the detection circuit part is obtained pabc , through coordinate transformation, the three-phase grid line voltage V pabc Transformed into the port voltage V in the two-phase stationary coordinate system pαβ , and then transform the port voltage signal V in the two-phase stationary coordinate system through coordinate transformation pαβ Transformed into the voltage V in the two-phase rotating coordinate system pd and V pq , where the coordinate transformation angle signal is provided by the phase-locked loop output phase signal; the q-axis voltage signal V pq Input the PI controller to get the system real-time angular frequency deviation signal ω err , the system real-time angular frequency deviation signal ω err The real-time angular frequency signal ω is added to the rated angular frequency signal ω0, and the real-time angular frequency signal ω is integrated to obtain the phase angle signal reference θ of the whole system. pll .

[0065] When the first control subunit adopts the constant voltage or constant power control of the driving circuit part in grid connection or off-grid connection, such as Figure 3 As shown in the coordinate transformation 2, according to the collected three-phase grid line voltage V pabc and phase current i abc , use the system's phase angle signal reference to perform coordinate transformation to convert the three-phase grid line voltage V pabc The voltage amplitude signal is transformed into the two-phase rotating coordinate system; the phase current i in the three-phase stationary coordinate system is transformed into the voltage amplitude signal in the two-phase rotating coordinate system; abc The current signal I transformed into the two-phase rotating coordinate system d and I q .

[0066] When the first control subunit adopts the constant voltage or constant power control of the driving circuit part in grid connection or off-grid connection, Figure 3As shown in the output active and reactive current calculation link 3 in the figure, the system operates in the grid-following operation mode in this link, and the DC bus voltage management is realized by the AC converter. Therefore, through the DC bus voltage closed-loop control, the converter output active current is calculated, and the DC bus voltage is adjusted by adjusting the solid-state microgrid output active power. The details are as follows: According to the rated value of the DC bus voltage U dcref The DC bus voltage U detected by the detection circuit dc The first deviation signal is input into the DC bus voltage controller to obtain the d-axis current reference signal i dref According to the reactive power demand of the power grid system, the reactive power control link is introduced to set the reactive power reference value Q ref and the actual output value Q e The second deviation signal is input into the reactive power controller to obtain the q-axis current reference signal i qref .

[0067] The second control subunit is used to control the driving circuit part to operate in a networking mode when the DC bus is connected to the grid by controlling the inverter. In the networking mode, Figure 3 As shown, according to the DC bus voltage rated value U dcref The DC bus voltage U detected by the detection circuit dc , the difference between the two is obtained to obtain a first deviation signal, and the first deviation signal is input into the DC bus voltage controller 4; the grid voltage frequency deviation is input into the synchronous generator speed regulator 5; the output power is adjusted by the DC bus voltage controller 4 and the synchronous generator speed regulator 5, thereby realizing the primary frequency regulation capability of the solid-state microgrid. Afterwards, the active power setting value P is obtained based on the output of the DC bus voltage controller and the output of the synchronous generator speed regulator ref , set the active power value P ref and the actual output value P e The deviation is input into synchronous machine rotor swing equation 6 to obtain the power synchronizer angular frequency deviation signal Δω. The power synchronizer angular frequency deviation signal Δω and the rated angular frequency signal ω0 are added to obtain the system real-time angular frequency signal ω. The phase angle signal reference θ is finally obtained through the integrator. vsg ; The real-time voltage amplitude U of the grid connection point measured by the grid connection point pf The grid voltage rating U N The deviation input droop controller 7 generates a reactive power regulation deviation signal, and generates a power synchronous output voltage reference value through a reactive power loop 8; based on the power synchronous output voltage reference value, a coordinate conversion 9 is performed using a phase angle signal reference to obtain an output voltage reference value V dref and V qref , and input the power synchronous output voltage closed loop to obtain the d-axis current reference value idref and q-axis current reference value i qref ; According to the d-axis current reference value i dref , q-axis current reference value i qref and the actual d-axis current i d and q-axis current i q A comparison is performed to obtain a d-axis error signal and a q-axis error signal, and the d-axis error signal and the q-axis error signal are respectively closed-loop controlled by a PI controller 10 to obtain an adjustment voltage on the output filter inductor, which is superimposed with the grid-connected point feedforward voltage to generate an output modulation voltage, and an inverse coordinate transformation is performed according to the phase information to obtain a modulation voltage in a two-phase stationary coordinate system; the modulation voltage in the two-phase stationary coordinate system is input into the SVPWM module 11 for processing to obtain a drive signal of the drive circuit part.

[0068] It is not difficult to find that the present invention provides great flexibility and scalability through modularly designed AC and DC units and diversified interfaces to adapt to the access of various energy sources, loads and energy storage devices, efficiently integrate different types of energy and loads, and enhance interface adaptability. In order to ensure the stable operation and flexible control of the solid-state microgrid system, the present invention adopts an overall control method of hybrid collaborative control, through the interaction of the main controller with the status information and operating conditions of each unit, intelligently identifies the port device and adjusts the operating mode output power of each sub-unit to adapt to different application scenarios, while embedding fault protection, grid-connected and off-grid control, power management and other intelligent microgrid control algorithms to achieve cross-level integration of the system, thus having the advantages of high adaptability and high reliability.

[0069] The present embodiment also relates to a control method for the solid-state microgrid system. The solid-state microgrid in the present embodiment adopts a highly integrated system structure of hardware circuits and control systems to improve converter conversion, optimize the architecture, efficiency and economy of the microgrid system, minimize transmission and distribution links, thereby reducing the risk of failure, quickly responding to power supply and load fluctuations, and ensuring the purpose of system stability. Figure 4 This is an integrated diagram of the adaptive collaborative control of the solid-state microgrid system control method. Through integrated system-level control, flexible and unified control of each power unit in the solid-state microgrid can be achieved, thereby achieving the purpose of adaptive collaborative control of each power unit according to the actual operating conditions of the system.

[0070] Among them, device-level control refers to the completion of control objectives based on control information for the DC power units and AC power units (such as bidirectional DC / AC converters, AC / DC load interface converters, DC load interface converters, distributed power interface converters, and energy storage device interface converters) of the physical layer of the solid-state microgrid. The DC power unit is intelligently identified according to the interface. When the DC port of the DC power unit is not connected, the circuit remains locked. At this time, all switching devices of the DC / DC converter are blocked and there is no energy transmission. After the external device is connected to the bus interface, the control management unit identifies the connected device and performs corresponding identification, management, and control according to the port type. The main task of device-level control is to maintain the stability of the DC bus voltage, achieve power balance within the system, and ensure the safe and reliable operation of the solid-state microgrid. Figure 4 As shown in the figure, for different interface converters and different control objectives, the device-level control strategies are also different, mainly including: DC bus voltage control, AC / DC interconnection power control, AC / DC load voltage control, maximum power tracking, voltage-power droop control and constant power / current charging and discharging control.

[0071] like Figure 4 As shown in the figure, the main purpose of system-level control is to provide an interface for the upper power grid, realize the centralized management of micro-sources and loads connected to the solid-state microgrid, and improve the operation efficiency and reliability of the solid-state microgrid. Energy management and optimal operation are the main control targets of system-level control, and functional modules such as DC bus voltage regulation and smooth switching of multiple operation modes are important components to achieve this control target. According to the input power fluctuation of the DC power unit and the charging and discharging state of the energy storage, the variation characteristics of the DC voltage under different working conditions are analyzed, and the power transmission capacity between AC and DC power is coordinated based on the DC voltage information. Combined with the actual needs of various operation modes such as grid-connected, off-grid, energy storage battery charging / discharging, power scheduling, peak shaving and valley filling, the operation mode of the solid-state microgrid system is smoothly switched. Realizing the reasonable distribution of the output power of each power generation unit is one of the key goals in the system-level operation control of the solid-state microgrid. Under grid-connected operation, according to the system output power and the DC bus voltage state, the solid-state microgrid is controlled to adaptively adjust the interconnection transmission power with the upper power grid. When the solid-state microgrid operates independently, it automatically manages the distributed power sources, energy storage and loads according to the charge state and power demand of the system energy storage unit, and coordinates the power and energy distribution of the power generation unit to ensure that the main control unit in the microgrid (such as the energy storage device) can control the stability of the bus voltage.

[0072] The coordination strategy of this implementation method starts from the perspective of the system level, and according to the actual operating conditions of the system, it adaptively and collaboratively controls the operating mode of each functional unit of the solid-state microgrid, achieving the purpose of highly adaptable operation of the system. The system layer embeds intelligent microgrid control algorithms such as fault protection, grid-connection and off-grid control, and power management. By real-time monitoring of the voltage, current and other status signals of each port, it coordinates the operating status of each power unit to achieve flow control and energy management, effectively reducing the adverse effects of large-scale use of renewable energy on the safe and stable operation of the distribution network, and achieving high efficiency, high adaptability and high reliability of the entire solid-state microgrid system, and cross-level functional integration.

Claims

1. A solid-state microgrid system, characterized in that: include: A DC bus is connected to a DC bus port; the DC bus port is used to connect a DC load; The DC power unit adopts a modular design, the input side is connected to the DC port, and the output side is connected to the DC bus; the DC port is used to connect the distributed energy storage device; the DC power unit includes: The sampling circuit part is used to sample the voltage and current of the DC port and the voltage and current of the DC bus; The main circuit adopts a DC / DC structure that can realize bidirectional energy flow and has high-frequency isolation; The control circuit part is used to identify the inserted device on the DC port side, transmit the identification result to the coordination control unit, and control the operating state of the main circuit part according to the control strategy of the DC power unit issued by the coordination control unit; The AC power unit adopts a modular design, the DC side is connected to the DC bus, and the AC side is connected to the AC port; the AC port is used to connect to the AC network; A coordination control unit is respectively connected to the DC power unit and the AC power unit, and is used to realize at least one of energy access, conversion, distribution, control and management; the coordination control unit is also used to determine the control strategy of the DC power unit according to the identification result of the inserted device on the DC port side.

2. The solid-state microgrid system according to claim 1, characterized in that: The control strategy of the DC power unit includes a DC port voltage control mode, a DC bus voltage control mode and a power control mode; in the DC port voltage control mode, the DC bus voltage is not controlled, the DC port voltage is controlled, and the direction and magnitude of power flow are determined by the load; in the DC bus voltage control mode, the DC port voltage is not controlled, the DC bus voltage is controlled, and the direction and magnitude of power flow are determined by the load; in the power control mode, neither the DC bus voltage nor the DC port voltage is controlled, and only the magnitude and direction of power flow are controlled.

3. The solid-state microgrid system according to claim 2, characterized in that: When the control strategy of the DC power unit received is the DC port voltage control mode, the control circuit part obtains a DC port current reference value through closed-loop control according to the expected voltage value of the DC port and the voltage of the DC port obtained by the sampling circuit part, and then obtains a preliminary DC port current control value through closed-loop control according to the DC port current reference value and the current of the DC port obtained by the sampling circuit part, and then performs current limiting on the preliminary DC port current control value to obtain a final DC port current control value; optimizes the control amount according to the current working condition of the main circuit part; When the control strategy of the DC power unit received is the DC bus voltage control mode, the control circuit part obtains a DC bus current reference value through closed-loop control according to the DC bus voltage expected value and the DC bus voltage obtained by the sampling circuit part, and then obtains a bus voltage preliminary current control value through closed-loop control according to the DC bus current reference value and the DC bus current obtained by the sampling circuit part, and then performs current limiting on the preliminary bus voltage current control value to obtain a bus voltage final current control value; optimize the control amount according to the current working condition of the main circuit part; When the control strategy of the DC power unit received is the power control mode, the control circuit part obtains the expected current value according to the expected value of the DC bus power, and dynamically tracks the expected current value with the actual current value through closed-loop control; and optimizes the control amount according to the current working condition of the main circuit part.

4. The solid-state microgrid system according to claim 1, characterized in that: The AC power unit comprises: The detection circuit part is used to detect the three-phase grid line voltage and phase current, DC bus voltage and current, output voltage and current; The driving circuit part adopts a three-phase two-level converter structure or a CHB multi-level converter structure with a common DC bus; The main control part is used to determine the control method of the driving circuit part according to the DC bus voltage control mode issued by the coordination control unit.

5. The solid-state microgrid system according to claim 4, characterized in that: The main control part includes: A first control subunit, used to control the driving circuit part by adopting a grid-connected or off-grid constant voltage or constant power when the DC bus is controlled by the energy storage unit; The second control subunit is used to control the driving circuit part to operate in a networking mode when the DC bus is connected to the grid by controlling the inverter.

6. The solid-state microgrid system according to claim 5, characterized in that: When the first control subunit uses a grid-connected or off-grid constant voltage or constant power to control the driving circuit part, the three-phase grid line voltage V detected by the detection circuit part is obtained. pabc , through coordinate transformation, the three-phase grid line voltage V pabc Transformed into the voltage V in the two-phase rotating coordinate system pd and V pq , the q-axis voltage signal V pq Input the PI controller to get the system real-time angular frequency deviation signal ω err , the system real-time angular frequency deviation signal ω err The real-time angular frequency signal ω is added to the rated angular frequency signal ω0, and the real-time angular frequency signal ω is integrated to obtain the phase angle signal reference θ of the whole system. pll ; When the first control subunit adopts the constant voltage or constant power control of the driving circuit part in grid connection or off-grid connection, the three-phase grid line voltage V pabc and phase current i abc , use the system's phase angle signal reference to perform coordinate transformation to convert the three-phase grid line voltage V pabc The voltage amplitude signal is transformed into the two-phase rotating coordinate system; the phase current i in the three-phase stationary coordinate system is transformed into the voltage amplitude signal in the two-phase rotating coordinate system; abc The current signal I transformed into the two-phase rotating coordinate system d and I q ; When the first control subunit adopts the constant voltage or constant power control of the driving circuit part in grid connection or off-grid connection, according to the rated value of the DC bus voltage U dcref The DC bus voltage U detected by the detection circuit dc The first deviation signal is input into the DC bus voltage controller to obtain the d-axis current reference signal i dref According to the reactive power demand of the power grid system, the reactive power control link is introduced to set the reactive power reference value Q ref and the actual output value Q e The second deviation signal is input into the reactive power controller to obtain the q-axis current reference signal i qref .

7. The solid-state microgrid system according to claim 5, characterized in that: When the second control subunit controls the drive circuit part to operate in the networking mode, according to the DC bus voltage rated value U dcref The DC bus voltage U detected by the detection circuit dc , the difference between the two is obtained to obtain a first deviation signal, and the first deviation signal is input into the DC bus voltage controller; the grid voltage frequency deviation is input into the synchronous generator speed regulator; based on the output of the DC bus voltage controller and the output of the synchronous generator speed regulator, the active power setting value P is obtained. ref , set the active power value P ref and the actual output value P e The deviation is input into the synchronous machine rotor swing equation to obtain the power synchronizer angular frequency deviation signal Δω. The power synchronizer angular frequency deviation signal Δω and the rated angular frequency signal ω0 are added to obtain the system real-time angular frequency signal ω. The phase angle signal reference θ is finally obtained through the integrator. vsg ; The real-time voltage amplitude U of the grid connection point measured by the grid connection point pf The grid voltage rating U N The deviation input droop controller generates a reactive power regulation deviation signal, and generates a power synchronous output voltage reference value through a reactive power loop; based on the power synchronous output voltage reference value, a phase angle signal reference is used to perform coordinate conversion to obtain an output voltage reference value V dref and V qref , and input the power synchronous output voltage closed loop to obtain the d-axis current reference value i dref and q-axis current reference value i qref ; According to the d-axis current reference value i dref , q-axis current reference value i qref and the actual d-axis current i d and q-axis current i q Comparison is performed to obtain a d-axis error signal and a q-axis error signal, and the d-axis error signal and the q-axis error signal are respectively closed-loop controlled by a PI controller to obtain an adjustment voltage on the output filter inductor, which is superimposed with a grid-connected point feedforward voltage to generate an output modulation voltage, and an inverse coordinate transformation is performed according to phase information to obtain a modulation voltage in a two-phase stationary coordinate system; the modulation voltage in the two-phase stationary coordinate system is input into a space vector pulse width modulation module for processing to obtain a drive signal of the drive circuit part.

8. A control method for a solid-state microgrid system as claimed in any one of claims 1 to 7, characterized in that: It includes device-level control, and the device-level control refers to completing the control target of the AC power unit and the DC power unit of the physical layer of the solid-state microgrid based on control information.

9. The control method of the solid-state microgrid system according to claim 8, characterized in that: This includes system-level control, the purpose of which is to provide an interface for the upper power grid.

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