Centralized megawatt autonomous grid-connected device, system and control method

Abstract

The invention provides a centralized megawatt-level autonomous grid-connected device, system and control method, and relates to the technical field of energy routers wherein the centralized megawatt-level autonomous grid-connected device comprises an energy router and a photovoltaic controller; an alternating current port of the energy router is used for accessing a power grid; a plurality of direct current ports of the energy router are used for being connected with a distributed power generation device; a plurality of power modules in the energy router adopt an H-bridge cascade structure, and direct current buses of the plurality of power modules are connected together to form a common direct current bus; the common DC bus is connected with an external photovoltaic array through a photovoltaic controller. According to the invention, the CHB topological structure is adopted to directly hang the power grid, the conversion from the AC port to the DC port is realized, the photovoltaic controller is matched, the centralized photovoltaic access of the power grid side is realized, the difference of the access grid-connected modes of the high-proportion distributed power generation device is simplified, the data information interaction real-time performance is higher, and the regional autonomous coordination difficulty is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of energy routers, and in particular to a centralized megawatt-level autonomous grid-connected device, system and control method. Background Art

[0002] With the rapid development and high-proportion access of new energy and distributed power sources, the large-scale application of energy storage, the accelerated electrification of terminal loads, and the widespread access of new power electronic loads represented by electric vehicles, the operating characteristics of the power system have changed significantly, especially on the distribution side. It has rapidly transformed from a supplier-dominated, one-way power supply, and manual management model to a diversified, intelligent, and digital one. The physical characteristics, operating mode, and functional form of the power grid are also changing. The difficulty of maintaining safe and stable operation by relying solely on traditional means of regulation will be greatly increased.

[0003] Distributed power generation has the advantages of being clean and pollution-free, flexible in installation location, and high in energy efficiency, and can effectively ensure the safe operation of the power grid. At present, distributed power generation mainly uses a high proportion of distributed power generation devices, but the requirements for the support functions of the power grid operation are diverse, resulting in large differences in the access and grid connection methods of high-proportion distributed power generation devices, and regional regulation has high requirements for real-time data information interaction, which makes regional autonomy and coordination difficult. Summary of the invention

[0004] In order to overcome the defects of the above-mentioned large differences in the access and grid-connection methods of high-proportion distributed power generation devices and the difficulty of regional autonomous coordination, the present invention provides a centralized megawatt-level autonomous grid-connected device, including: an energy router and a photovoltaic controller;

[0005] The AC port of the energy router is used to access the power grid;

[0006] The multiple DC ports of the energy router are used to connect to the distributed power generation device;

[0007] The multiple power modules in the energy router adopt an H-bridge cascade structure, and the DC buses of the multiple power modules are connected together to form a common DC bus;

[0008] The common DC bus is connected to an external photovoltaic array through the photovoltaic controller.

[0009] Preferably, the DC buses of the multiple power modules are connected together via a three-phase common DC bus isolation type CHB architecture.

[0010] Preferably, the power module includes a high-frequency isolation transformer.

[0011] Preferably, the photovoltaic controller is further used to regulate the voltage output by the photovoltaic array to a bus voltage corresponding to the common DC bus, and to track the maximum power point of the photovoltaic array.

[0012] Preferably, the plurality of DC ports are connected to the common DC bus through a combiner box;

[0013] The combiner box is used to divide the common DC bus into multiple paths and control the on / off of each path, wherein the multiple paths correspond one-to-one to the multiple DC ports.

[0014] Preferably, the plurality of DC ports are configured as one or more of the following port types:

[0015] A charging station port, used for a charging pile to access the common DC bus through the charging station port;

[0016] A photovoltaic port, used for accessing the common DC bus through the photovoltaic controller;

[0017] An energy storage port, used for an energy storage device to access the common DC bus through the energy storage port;

[0018] A DC load port, used for DC load and DC panel backup power supply to access the common DC bus through the DC load port;

[0019] The AC 380V port is used for the AC load backup power supply to be connected to the common DC bus through the AC 380V port.

[0020] Preferably, it also includes a communication controller;

[0021] The communication controller is connected to the energy router and is used for receiving and / or sending power quality control instructions.

[0022] On the other hand, the present invention also provides a control method based on a centralized megawatt-level autonomous grid-connected device, characterized by comprising:

[0023] Acquire attribute information of a device connected to the AC port and / or the DC port of the energy router in the centralized megawatt-level autonomous grid-connected device;

[0024] Determine whether the attribute information meets the corresponding regulation condition; if so, adopt the control strategy corresponding to the attribute information to regulate the attribute information.

[0025] Preferably, the attribute information includes branch load rate;

[0026] The determining whether the attribute information meets the corresponding control condition includes:

[0027] Determining whether the branch load rate reaches a first threshold;

[0028] The adopting the control strategy corresponding to the attribute information to regulate the attribute information includes:

[0029] The branch load rate is regulated according to the branch energy storage power adjustment strategy and / or the branch photovoltaic power generation power adjustment strategy.

[0030] Preferably, it also includes:

[0031] If the branch load rate does not reach the first threshold value, determining the distribution transformer load rate;

[0032] Determining whether the load rate of the distribution transformer reaches a second threshold value;

[0033] If so, the load rate of the distribution transformer is regulated according to the distribution transformer control strategy corresponding to the load rate of the distribution transformer, wherein the distribution transformer control strategy includes one or more of the following: a gear adjustment strategy of the distribution transformer, a power adjustment strategy of a flexible interconnection device, an energy storage power adjustment strategy, or a photovoltaic power generation power adjustment strategy;

[0034] If not, then the restrictions on photovoltaic power output will be lifted.

[0035] Preferably, the attribute information includes photovoltaic reverse current risk level;

[0036] The determining whether the attribute information meets the corresponding control condition includes:

[0037] Determining whether the photovoltaic reverse current risk level reaches a set risk level;

[0038] The adopting the control strategy corresponding to the attribute information to regulate the attribute information includes:

[0039] Calculate the substation control value under the current AC / DC scenario;

[0040] The photovoltaic reverse current risk level is regulated according to the substation control value.

[0041] Preferably, the calculating of the substation control value in the current AC / DC scenario includes:

[0042] Determine whether the station area is an AC station area;

[0043] If yes, calculating the control value of the AC substation in phases;

[0044] If not, calculate the zone control value of the DC zone.

[0045] Preferably, the attribute information includes the average load rate of each substation;

[0046] The determining whether the attribute information meets the corresponding control condition includes:

[0047] Determining whether the average load rate of each area reaches a third threshold value;

[0048] The adopting the control strategy corresponding to the attribute information to regulate the attribute information includes:

[0049] Determine the operating power of the mutual aid equipment;

[0050] The power action is sent to the mutual aid device.

[0051] Preferably, the method is implemented based on the above-mentioned centralized megawatt-level autonomous grid-connected device.

[0052] On the other hand, the present invention further provides a centralized megawatt-level autonomous grid-connected system, the system comprising a centralized megawatt-level autonomous grid-connected device and a switch cabinet as described in any one of the above items;

[0053] The centralized megawatt-level autonomous grid-connected device is connected to the power grid through the switch cabinet.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] 1. The present invention provides a centralized megawatt-level autonomous grid-connected device, including: an energy router and a photovoltaic controller; the AC port of the energy router is used to access the power grid; the multiple DC ports of the energy router are used to connect to distributed power generation devices; the multiple power modules in the energy router adopt an H-bridge cascade structure, and the DC buses of the multiple power modules are connected together to form a common DC bus; the photovoltaic array is connected to the common DC bus through a photovoltaic controller. The centralized megawatt-level autonomous grid-connected device adopts a CHB topology structure to directly connect to the power grid, realizes the transformation from the AC port to multiple DC ports, and is equipped with a photovoltaic controller to realize centralized photovoltaic access on the grid side, simplifying the differences in the access and grid-connected methods of high-proportion distributed power generation devices. In addition, regional regulation can be completed through the centralized megawatt-level autonomous grid-connected device, and the data information interaction is more real-time, reducing the difficulty of regional autonomous coordination.

[0056] 2. The H-bridge cascade structure in the device topology of the present invention solves the problem of insufficient withstand voltage of a single power electronic device, and provides an independent and flexible DC interface, which is convenient for the access of DC power generation devices such as photovoltaics and energy storage and DC loads, reduces energy conversion links, improves overall conversion efficiency, and realizes bidirectional energy flow; no distribution transformer is required, which overcomes the shortcomings of traditional transformers operating at power frequency, large size, high no-load loss, uncontrollable voltage, inability to isolate faults, and the need for external power quality management measures. In addition, the device can not only realize functions such as voltage level conversion, electrical isolation and energy transfer, but also realize additional functions such as flow control and power quality control. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 A schematic diagram of the principle of a centralized megawatt-level autonomous grid-connected device provided by the present invention;

[0058] Figure 2 A block diagram of an application system of a centralized megawatt-level autonomous grid-connected device provided by the present invention;

[0059] Figure 3 A system block diagram of a centralized megawatt-level autonomous grid-connected device provided by the present invention;

[0060] Figure 4 A flow chart of a control method based on a centralized megawatt-level autonomous grid-connected device provided by the present invention;

[0061] Figure 5 A control flow chart of a heavy overload management technology provided by the present invention;

[0062] Figure 6 A photovoltaic backflow prevention technology control flow chart provided by the present invention;

[0063] Figure 7 A mutual assistance management technology control flow chart provided by the present invention;

[0064] Figure 8 A schematic diagram of the structure of a centralized megawatt-level autonomous grid-connected system provided by the present invention;

[0065] Fig. 9 A schematic diagram of the architecture of a centralized megawatt-level autonomous grid-connected system provided by the present invention;

[0066] Fig.10 A schematic diagram of the architecture of a centralized megawatt-level autonomous grid-connected system provided by the present invention. DETAILED DESCRIPTION

[0067] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0068] Embodiment 1:

[0069] The present invention provides a centralized megawatt-level autonomous grid-connected device, including an energy router and a photovoltaic controller;

[0070] The AC port of the energy router is used to access the power grid;

[0071] A plurality of DC ports of the energy router for connecting with distributed generation devices;

[0072] The multiple power modules in the energy router adopt an H-bridge cascade structure, and the DC buses of the multiple power modules are connected together to form a common DC bus;

[0073] The common DC bus is connected to the external photovoltaic array through a photovoltaic controller.

[0074] Since distributed power generation has the advantages of being clean and pollution-free, flexible in installation location, and high in energy utilization efficiency, and can effectively ensure the safe operation of the power grid, the present invention proposes a centralized megawatt-level autonomous grid-connected device, which can not only weaken the adverse effects of distributed power sources accessing the power grid, but also integrate the many advantages brought by distributed power generation, and at the same time better improve the economy, reliability, and stability of the power system operation. In addition, the centralized megawatt-level autonomous grid-connected device proposed in the present invention has the ability to safely access a high proportion of distributed power generation, which can meet the grid-connected requirements of high efficiency, high reliability, and high power density of large-scale distributed power generation systems in the future, as well as the requirements for safe grid-connected access of a high proportion of distributed power generation to the county distribution network, and realize the observable, measurable, controllable, and adjustable coordinated operation of the grid-connected point source, grid-load, and storage, power quality control, and distributed photovoltaic access. For example, the centralized megawatt-level autonomous grid-connected device can also be used for the county distribution network with a high proportion of photovoltaic access to ensure the safe, stable, and efficient operation of the county distribution network.

[0075] The centralized megawatt-level autonomous grid-connected device (hereinafter referred to as the device) includes an energy router, so there is no need for a distribution transformer. It can overcome the shortcomings of traditional distribution transformers operating at industrial frequency, large size, high no-load loss, uncontrollable voltage, inability to isolate faults, and the need for external power quality control measures. Based on the energy router, the device can not only realize functions such as voltage level conversion, electrical isolation, reactive power compensation, harmonic control and energy transfer, but also realize additional functions such as flow control and power quality control.

[0076] For example, the power grid connected to the energy router through the AC port may include a 10kV power grid, and the DC port of the energy router may include a 750V port. The device adopts a PET (Power Electronic Transformer) topology to directly connect to the 10kV power grid, where the PET is a part of the energy router, and can realize the conversion from the AC (Alternating Current) 10kV port to the DC (Direct Current) 750V port, that is, realize the voltage level conversion.

[0077] The energy router is a multi-port energy router. In the present invention, the energy router provides an independent and flexibly accessible DC interface to facilitate the access of DC power generation devices such as photovoltaics and energy storage and DC loads, reduce energy conversion links, improve overall conversion efficiency, and realize two-way energy flow.

[0078] The energy router includes multiple power modules, which adopt a CHB (Cascaded H-Bridge) structure, which can solve the problem of insufficient withstand voltage of a single power electronic device, such as an IGBT (Insulate-Gate Bipolar Transistor). In one implementation, the power module includes a high-frequency isolation transformer, and the energy router intermediate stage adopts a high-frequency isolation transformer, which can achieve electrical isolation and improve power density.

[0079] The common DC bus includes a three-phase common DC bus. In one implementation, the DC buses of multiple power modules are connected together through a three-phase common DC bus isolated CHB architecture. The optional common DC bus isolated CHB architecture includes a DC / DC converter that plays an isolation role, that is, a DC / DC high-frequency isolation converter part, which is an example of the above-mentioned high-frequency isolation transformer. The DC / DC converter consists of two single-phase full-bridge converters, which are coupled and connected through a high-frequency transformer. This topology is a DAB (Dual Active Bridge) topology. The DAB topology can realize bidirectional power flow, has inversion and rectification functions, and provides high flexibility and energy conversion efficiency. The coupling of high-frequency transformers makes power transmission more efficient and reduces physical size and weight.

[0080] The photovoltaic controller can adjust the voltage output by the photovoltaic array (or photovoltaic module) to the bus voltage corresponding to the common DC bus, and track the maximum power point of the photovoltaic array, so that the photovoltaic array can continue to output at maximum power. For example, the photovoltaic controller can include a DC / DC photovoltaic controller, which can boost the voltage output by the photovoltaic array.

[0081] In one implementation, multiple DC ports of the energy router are connected to the common DC bus through a combiner box. The combiner box is used to divide the common DC bus into multiple paths and control the on / off of each path, where the multiple paths correspond to multiple DC ports one by one, that is, each path of the combiner box controls one DC port. For example, different DC ports are connected to the DC750V DC bus through a combiner box, which divides the DC750V DC bus into several paths, and one path can be disconnected at any time without affecting the normal use of the other paths.

[0082] Multiple DC ports can optionally be configured as one or more of the following port types:

[0083] (1) Charging station port, used for charging piles to access the public DC bus through the charging station interface. For example, if the total charging power reaches 2000kW, the charging piles are directly connected to the DC750V DC bus, which can achieve a wide range of 200-750V output and 400-750V constant power output, which can charge most electric vehicles. Through the flexible charging and orderly charging algorithms, the system economy and reliability are improved. Each charging pile can be connected to the DC bus with a ZC-YJV-0.6 / 1kV-2*95 specification cable.

[0084] (2) Photovoltaic port, used to access the public DC bus through the photovoltaic controller. For example, the photovoltaic controller is connected to the DC750V DC bus. Each photovoltaic controller has a fault isolation function. Each photovoltaic controller can be composed of 3 MPPT (Maximum Power Point Tracking) units, which can automatically track the maximum power point of the photovoltaic string to enable the photovoltaic array to achieve maximum power generation. The photovoltaic controller / photovoltaic port can be connected to the DC bus using a ZC-YJV-0.6 / 1kV-2*16 cable.

[0085] (3) Energy storage port, used for energy storage devices to access the public DC bus through the energy storage port. For example, it is equipped with 600kW / 600kWh energy storage, which is used to serve as a backup power supply and realize the peak-shaving and valley-filling function, thereby improving the reliability and economy of the energy station. The energy storage device / energy storage port can be connected to the DC bus using a cable (double-spliced) with the specification of ZC-YJV-0.6 / 1kV-2*185.

[0086] (4) DC load port, used for DC load and DC panel backup power supply to connect to the common DC bus through the DC load port. For example, the DC load and DC panel backup power can be connected through a DC / DC module.

[0087] (5) AC 380V port, used for AC load backup power supply to connect to the public DC bus through the AC 380V port. For example, the AC 380V port can be used as a backup power supply for AC loads to supply power to AC loads when a system failure occurs and power is cut off unexpectedly.

[0088] The device can realize the access of renewable energy such as photovoltaics, and has the DC access capability of fast charging stations. It can build a multi-voltage AC / DC seamless hybrid distribution network, realize the organic integration of new energy vehicle charging, AC / DC loads, distributed power sources, energy storage, and information flow, improve the acceptance of new energy electric vehicles by the power grid, and promote the development and construction of new energy electric vehicles and fast charging stations. Based on the data collection of autonomous grid-connected devices, through big data analysis technology, the whole process of source-grid-load-storage can be perceived, and the photovoltaic power generation and charging pile energy consumption plan can be accurately predicted through historical data. Then, through the charge and discharge control of the energy storage system, the purpose of intelligent optimization and scheduling of energy consumption can be finally achieved, providing highly reliable and low-cost power supply services.

[0089] For example, Figure 1 The schematic diagram of the principle of a centralized megawatt-level autonomous grid-connected device provided by the present invention is a centralized 10kV megawatt-level autonomous grid-connected device on the grid side, which adopts a three-phase common DC bus isolation CHB photovoltaic grid-connected inverter. The DC buses of all modules are connected together to form a common DC bus. The photovoltaic array is connected through a DC / DC photovoltaic controller (such as Figure 1 The boost circuit in the PV module is connected to the common DC bus. The DC / DC PV controller changes the voltage output by the PV module to the bus voltage and tracks its maximum power point, so that the PV module can continue to output at maximum power. The above DAB topology can be found in Figure 1 It can be understood that the energy router includes PET and also has functions such as energy management, and PET includes CHB+DAB topology.

[0090] Another example, Figure 2 This is a block diagram of the application system of a centralized megawatt-level autonomous grid-connected device provided by the present invention. The 10kV port of the device is connected to the power grid, and the DC750V port is connected to the charging pile, DC / DC controller, and then connected to photovoltaic, energy storage, etc. Figure 2 The photovoltaic panels are connected to the public DC bus through the DC / DC photovoltaic controller. The multi-port energy router in the device adopts an H-bridge cascade structure, and the intermediate stage adopts a high-frequency isolation transformer, without the need for a distribution transformer. The above DAB topology can be found in Figure 2 DC / AC+transformer+AC / DC in it.

[0091] Above Figure 1 and Figure 2The centralized megawatt-level autonomous grid-connected device shown in the figure adopts a CHB+DAB topology structure directly connected to the 10kV power grid.

[0092] In one implementation, the device may further include a communication controller connected to the energy router for receiving and / or sending power quality control instructions. In addition, each DC / DC control unit has the function of communicating with the PET and the master station and accepting the dispatch of the master station.

[0093] Another example, Figure 3 The present invention provides a system block diagram of a centralized megawatt-level autonomous grid-connected device, which includes a photovoltaic control system, an energy router system and a communication system. The photovoltaic control system is mainly composed of an input EMI (Electromagnetic Interference) filter circuit, an arc detection circuit, a maximum power tracking circuit, an input voltage sampling circuit, an input current sampling circuit, a drive circuit, an insulation impedance detection circuit and an MPPT controller, which mainly realizes the maximum power tracking of photovoltaic strings, converts the photovoltaic output into a constant direct current, and completes the insulation impedance detection function. The energy router system is mainly composed of a DC bus, an inverter circuit, an output filter circuit, a grid-connected switch circuit, a residual current sampling circuit, an output EMI filter circuit, a bus voltage sampling circuit, an output current sampling circuit, an output voltage sampling circuit, a grid voltage sampling circuit, a drive circuit and a multi-port energy router, and its main function is to convert the DC voltage output by the maximum power tracking system into AC mains power and complete the relevant control functions of power quality management. The communication system is mainly composed of display circuit, carrier communication circuit, RS-485 communication circuit, Bluetooth communication circuit, remote communication circuit and communication controller. Its main function is to realize the external communication and display functions of the system, and accept the superior control instructions to complete the sending and receiving of the four functions and power quality control instructions. In addition, regional control can be completed through this centralized megawatt-level autonomous grid-connected device, and the data information interaction is more real-time, which reduces the difficulty of regional autonomous coordination.

[0094] Embodiment 2:

[0095] The present invention also provides a control method based on the above centralized megawatt-level autonomous grid-connected device, the flow chart is as follows: Figure 4 As shown, including:

[0096] Step 401: Acquire attribute information of a device connected to an AC port and / or a DC port of an energy router.

[0097] Step 402: Determine whether the attribute information meets the corresponding control condition; if so, execute step 403.

[0098] Step 403: adopting the control strategy corresponding to the attribute information to regulate the attribute information.

[0099] The control method can be implemented based on the centralized megawatt-level autonomous grid-connected device in the above embodiment. Specifically, the centralized megawatt-level autonomous grid-connected device in the above embodiment can execute the control process shown in this embodiment.

[0100] In the device, the AC port of the energy router is connected to the power grid, and the devices connected to the AC port include each substation and each distribution transformer. The device can obtain the relevant action information of each substation and each distribution transformer, and based on the relevant action information, one or more attribute information corresponding to the AC port can be determined. The DC port of the energy router is connected to the distributed power generation device, and the devices connected to the DC port include each branch, photovoltaic array, and each distributed power generation device. The device can obtain the relevant action information of each branch, photovoltaic array, and each distributed power generation device, and based on the relevant action information, one or more attribute information corresponding to the DC port can be determined.

[0101] For the AC port, the attribute information corresponding to the AC port includes but is not limited to: one or more of the load rate of the distribution transformer, the gear of the distribution transformer, the energy storage power corresponding to the distribution transformer, the power generation power, the active power, the reactive power, the reverse current risk level, the capacity of the distribution transformer, the load of the substation, etc.; for the DC port, the attribute information corresponding to the DC port includes but is not limited to: one or more of the branch load rate, the branch energy storage power, the branch photovoltaic power generation power, etc.

[0102] The following describes the control process in several possible scenarios.

[0103] Scenario 1: Heavy overload control scenario. Heavy overload refers to the phenomenon that the equipment in the power system operates beyond the rated load. Heavy overload will threaten the safe and stable operation of power equipment, so it needs to be controlled.

[0104] In this scenario 1, the attribute information includes at least a branch load factor and / or a distribution transformer load factor.

[0105] For example, the attribute information includes the branch load rate. The device can calculate the branch load rate by obtaining the relevant action information of the branch. The calculation process is not limited here. In the above step 402, it is determined whether the branch load rate reaches the first threshold value. The device can be pre-configured and saved with a first threshold value, which is used to determine whether the branch load rate exceeds the limit, or to determine whether the branch load rate exceeds the set safety range. If so, it is considered that the branch load rate is too high, and the device can start heavy overload management and execute step 403; if not, it is considered that the branch does not have a heavy overload, and the limit on the photovoltaic power output power can be released.

[0106] In the above step 403, the device can adjust the branch load rate according to the branch energy storage power adjustment strategy and / or the branch photovoltaic power generation power adjustment strategy. Optionally, the device can first adjust the branch energy storage power adjustment strategy and then adjust the branch photovoltaic power generation power adjustment strategy.

[0107] As another example, the attribute information includes the load rate of the distribution transformer. The device can calculate the load rate of the distribution transformer by obtaining the relevant action information of the distribution transformer. The calculation process is not limited here. In the above step 402, it is determined whether the load rate of the distribution transformer reaches the second threshold value. The device can be pre-configured and saved with a second threshold value, which is used to determine whether the load rate of the distribution transformer exceeds the limit, or to determine whether the load rate of the distribution transformer exceeds the set safety range. If so, it is considered that the load rate of the distribution transformer is too high, and the device can start heavy overload management and execute step 403; if not, it is considered that the distribution transformer is not heavily overloaded, and the limit on the output power of photovoltaic power generation can be released.

[0108] In the above step 403, the device can regulate the load rate of the distribution transformer according to the distribution transformer control strategy corresponding to the load rate of the distribution transformer, and the distribution transformer control strategy includes one or more of the following: the gear adjustment strategy of the distribution transformer, the power adjustment strategy of the flexible interconnection device, the energy storage power adjustment strategy, or the photovoltaic power generation power adjustment strategy. Optionally, the device can give priority to the gear adjustment strategy of the distribution transformer for regulation (for example, increase the gear, increase the capacity of the on-load capacity and voltage regulating transformer), and then give priority to the flexible interconnection device power adjustment strategy for regulation, followed by the energy storage power adjustment strategy, and then the photovoltaic power generation power adjustment strategy.

[0109] In another example, the attribute information includes a branch load rate and a distribution transformer load rate. The device can simultaneously determine the branch load rate and the distribution transformer load rate and adjust them, or the device can first determine and adjust the branch load rate and then determine and adjust the distribution transformer load rate, or the device can first determine and adjust the distribution transformer load rate and then determine and adjust the branch load rate. In other words, in this embodiment, there is no restriction on the order of determining and adjusting the attribute information. Take the example of first determining and adjusting the branch load rate and then determining and adjusting the distribution transformer load rate. Figure 5As shown, the device calculates the branch load rate and determines whether the branch load rate exceeds the limit. If so, the branch load rate is too high, and the branch energy storage setting / branch photovoltaic setting is performed according to the branch energy storage power adjustment strategy / branch photovoltaic power generation power adjustment strategy. If the branch load rate does not exceed the limit, the distribution transformer load rate is calculated to determine whether the distribution transformer load rate exceeds the limit. If so, the distribution transformer load rate is too high, and the distribution transformer gear adjustment / flexible interconnection setting / energy storage setting / photovoltaic setting is performed according to the distribution transformer gear adjustment strategy / flexible interconnection device power adjustment strategy / energy storage power adjustment strategy / photovoltaic power generation power adjustment strategy. If the distribution transformer load rate does not exceed the limit and is lower than the heavy overload recovery threshold, the photovoltaic output limit can be released.

[0110] It can be seen that in this scenario, the heavy overload management technology monitors the load rate of the transformer and each branch. When the load rate exceeds the set safety range, the heavy overload management is started, and the load rate is controlled to enter the safe range by changing the injected active power, reactive power regulation, flexible interconnection of substations and other means.

[0111] Scenario 2: Photovoltaic backflow prevention control scenario.

[0112] In this scenario 2, the attribute information at least includes the photovoltaic reverse current risk level. The device can determine the reverse current risk level in the AC / DC scenario according to the acquired active power on the low-voltage outlet side of the distribution transformer. For example, in the DC scenario, the device can directly obtain the active power on the low-voltage outlet side of the distribution transformer. In the AC scenario, the device can first obtain the system topology and then obtain the active power on the low-voltage outlet side of the distribution transformer. In the above step 402, it is determined whether the photovoltaic reverse current risk level reaches the set risk level. The set risk level is used to determine whether regulation is required. If so, the photovoltaic grid-connected power can be consumed or limited by the corresponding control strategy, thereby realizing the anti-reverse current function of the photovoltaic grid-connected system. If not, the next round of judgment and regulation can be carried out.

[0113] In the above step 403, the device can calculate the substation control value under the current AC / DC scenario, and regulate the photovoltaic reverse current risk level according to the substation control value. Optionally, when calculating the substation control value under the current AC / DC scenario, it can be determined whether the substation is an AC substation. If so, the substation control value of the AC substation is calculated in phases. If not, the substation control value of the DC substation is calculated. When regulating according to the substation control value, the photovoltaic reverse current risk level can be regulated by an energy storage power adjustment strategy, an adjustable load adjustment strategy, or a photovoltaic output power limitation adjustment strategy.

[0114] A possible photovoltaic backflow prevention control process is as follows: Figure 6As shown, the device confirms the AC and DC scenarios. If it is a DC scenario, the active power on the low-voltage outlet side of the distribution transformer is directly obtained. If it is an AC scenario, the system topology is first obtained, and then the active power on the low-voltage outlet side of the distribution transformer is obtained. Then, based on the obtained active power on the low-voltage outlet side of the distribution transformer, it is determined whether the reverse flow risk level needs to be regulated. If regulation is required, it is determined whether it is an AC substation. If it is an AC substation, the substation regulation value is calculated by phase. If it is not an AC substation, the substation regulation value is calculated. Then, according to the substation regulation value, the device uses the energy storage power adjustment strategy / adjustable load adjustment strategy / photovoltaic output power restriction adjustment strategy to perform energy storage setting / adjustable load / photovoltaic output restriction and other adjustments to consume or limit the photovoltaic grid-connected power, thereby achieving reverse flow prevention. If the reverse flow phase risk does not need to be regulated, the device can continue with the next round of judgment and regulation. The control logic includes: 1) In the grid-connected power generation system, since the external environment is constantly changing, monitoring and regulation are required to prevent photovoltaic reverse flow. The reverse flow risk level is determined by real-time monitoring of the active power (including direction) on the low-voltage outlet side of the distribution transformer and combining the results of source-load prediction. 2) Further, according to the system topology, energy storage, adjustable load, and photovoltaic output power limitation are used to consume or limit the photovoltaic grid-connected power, thereby realizing the anti-reverse flow function of the photovoltaic grid-connected system.

[0115] It can be seen that in this scenario, the photovoltaic backflow prevention technology controls the electricity generated by the photovoltaic grid-connected system to be consumed by local loads, and the excess electricity is not allowed to be reversely transmitted through the low-voltage distribution transformer grid.

[0116] Scenario 3: Mutual assistance management and control scenario.

[0117] In this scenario 3, the attribute information includes the average load factor of each station area.

[0118] For example, the device can calculate the average load rate of each substation by obtaining the load of each substation and the capacity of the distribution transformer. The calculation process is not limited here. In the above step 402, it is determined whether the average load rate of each substation reaches the third threshold value. The device can be pre-configured to save the third threshold value, and the third threshold value is used to determine whether the average load rate of each substation exceeds the limit. If so, it is considered that the average load rate of each substation is too high. The device can start mutual assistance management and execute step 403; if not, the next round of judgment and regulation can be carried out.

[0119] In the above step 403, the device can determine the action power of the mutual aid device and send the action power to the mutual aid device. Optionally, the device can determine the execution algorithm, if it is overloaded, select the heavy overload management algorithm to calculate the action power of the mutual aid device, if it is reverse flow, select the reverse flow control algorithm to calculate the action power of the mutual aid device, and the calculated action power of the mutual aid device is used as the control value for control.

[0120] A possible mutual aid management control process is as follows Figure 7 As shown, the device obtains the load and transformer capacity of each substation, and then calculates the average load rate based on the obtained data to determine whether it exceeds the limit. If so, the judgment execution algorithm selects the heavy overload management algorithm to calculate the action power of the mutual aid device if it is overloaded, and selects the reverse flow control algorithm to calculate the action power of the mutual aid device if it is reverse flow. The calculated action power of the mutual aid device is used as the control value, and the action power is sent to the mutual aid device through the mutual aid instruction. If it does not exceed the limit, the device can continue the next round of judgment and regulation. The control logic includes: 1) The autonomous terminal collects the voltage, current, power and other electrical quantity data of the transformer, mutual aid equipment, energy router, photovoltaic equipment, and non-electrical quantity data such as status and operation mode. 2) The autonomous terminal determines the average load rate calculation method according to the type of voltage stabilizing port equipment and calculates the average load rate of the substation. 3) The autonomous terminal determines the execution of the reverse flow control algorithm and the heavy overload management algorithm according to the status of the transformer equipment, obtains the power that the mutual aid equipment should act, and then sends the action power data to the mutual aid equipment.

[0121] It can be seen that in this scenario, the mutual aid management technology collects the voltage and current on the grid side and the equipment side to calculate the power on the grid side and the equipment side, and transmits the above data and the equipment operation status to the terminal, calculates the power that the mutual aid equipment should operate, and then sends the action power data to the mutual aid equipment.

[0122] In this embodiment, the control strategy of the centralized megawatt-level autonomous grid-connected device is based on the basic energy router grid-connected control strategy. The key control technologies of autonomous grid-connected are studied, and a control strategy for autonomous grid-connected devices integrating heavy overload management technology, photovoltaic backflow prevention technology, and mutual assistance management technology is proposed to achieve high-proportion photovoltaic safe access and efficient consumption, and flexible interconnection and mutual assistance among substations.

[0123] The centralized megawatt-level autonomous grid-connected energy router contains various types of distributed power generation and load units, energy storage and grid-connected interface converters, and integrates heavy overload control technology, photovoltaic backflow prevention technology, and mutual assistance management technology to achieve high-proportion photovoltaic safe access and efficient absorption. Through regional intelligent autonomous control, it realizes regional autonomy and cross-regional mutual assistance in the county distribution network, balances the load rate of the station area, realizes dynamic capacity expansion of the transformer, alleviates heavy overload of the transformer, and alleviates the problem of transformer backflow.

[0124] Embodiment 3:

[0125] The present invention also provides a centralized megawatt-level autonomous grid-connected system, the system comprising the centralized megawatt-level autonomous grid-connected device and switch cabinet described in the above embodiment;

[0126] The centralized megawatt-level autonomous grid-connected device is connected to the grid through a switch cabinet.

[0127] Optionally, the system may also include a starter cabinet, a power cabinet and a control cabinet. Figure 8 As shown, the centralized megawatt-level autonomous grid-connected device is connected to the 10kV system through a switch cabinet. The control cabinet is controlled by sampling the voltage and current signals during operation by CT (Current Transformer) and PT (Potential Transformer). Control instructions are sent between the switch cabinet, starter cabinet, and power cabinet through optical fiber, and terminal scheduling can also be accepted through remote control communication.

[0128] A specific implementation example Fig. 9 As shown in the figure, charging stations, photovoltaics, energy storage, AC and DC loads are aggregated through the AC and DC busbars (i.e., the above-mentioned public DC busbars) of the autonomous grid-connected device based on the energy router, and connected to the 10kV AC distribution network, which forms an AC and DC hybrid microgrid on the substation side of the distribution network. The autonomous grid-connected device monitors the data information of each port, accepts the upper-level dispatch of distribution automation, and can effectively manage heavy overloads and prevent photovoltaic backflow through autonomous control technology.

[0129] Another specific implementation example Fig.10 As shown in the figure, the three low-voltage areas derived from the 10kV AC distribution network line are connected through an autonomous grid-connected device based on an energy router, and the DC port is also connected to photovoltaic and energy storage. When the load rates of these three areas are uneven, there are heavily overloaded areas, and areas with high photovoltaic penetration rates, the energy interaction between the heavily loaded areas and the lightly loaded areas can be carried out through the mutual assistance management and control strategy of the autonomous grid-connected device. The load rate is calculated by collecting the electrical quantity data of each device through the terminal, the load rate of the area is balanced, the dynamic capacity increase of the transformer is realized, the heavy overload of the transformer is alleviated, the reverse current problem of the transformer is alleviated, and the dispatch of the distribution master station can be accepted in real time.

[0130] Embodiment 4:

[0131] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory, the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in a computer storage medium. The processor may be a CPU (Central Processing Unit), or other general-purpose processors, DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in a computer storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of the control method based on the centralized megawatt-level autonomous grid-connected device in the above embodiment.

[0132] Embodiment 5:

[0133] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It can be understood that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of a control method based on a centralized megawatt-level autonomous grid-connected device in the above embodiment.

[0134] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0135] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0136] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0137] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit its protection scope. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that after reading the present invention, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the application, but these changes, modifications or equivalent substitutions are all within the protection scope of the claims to be approved.

Claims

1. A centralized megawatt-level autonomous grid-connected device, characterized in that: include: Energy routers and photovoltaic controllers; The AC port of the energy router is used to access the power grid; The multiple DC ports of the energy router are used to connect to the distributed power generation device; The multiple power modules in the energy router adopt an H-bridge cascade structure, and the DC buses of the multiple power modules are connected together to form a common DC bus; The common DC bus is connected to an external photovoltaic array through the photovoltaic controller.

2. The device according to claim 1, characterized in that The DC buses of the multiple power modules are connected together through a three-phase common DC bus isolation type CHB architecture.

3. The device according to claim 2, characterized in that The power module includes a high-frequency isolation transformer.

4. The device according to any one of claims 1 to 3, characterized in that: The photovoltaic controller is also used to adjust the voltage output by the photovoltaic array to the bus voltage corresponding to the common DC bus, and to track the maximum power point of the photovoltaic array.

5. The device according to any one of claims 1 to 3, characterized in that: The multiple DC ports are connected to the common DC bus through a combiner box; The combiner box is used to divide the common DC bus into multiple paths and control the on / off of each path, wherein the multiple paths correspond one-to-one to the multiple DC ports.

6. The device according to claim 5, characterized in that The plurality of DC ports are configured as one or more of the following port types: A charging station port, used for a charging pile to access the common DC bus through the charging station port; A photovoltaic port, used for accessing the common DC bus through the photovoltaic controller; An energy storage port, used for an energy storage device to access the common DC bus through the energy storage port; A DC load port, used for DC load and DC panel backup power supply to access the common DC bus through the DC load port; The AC 380V port is used for the AC load backup power supply to be connected to the common DC bus through the AC 380V port.

7. The device according to any one of claims 1 to 3, characterized in that: Also included is a communications controller; The communication controller is connected to the energy router and is used for receiving and / or sending power quality control instructions.

8. A control method based on a centralized megawatt-level autonomous grid-connected device, characterized in that: include: Acquire attribute information of a device connected to an AC port and / or a DC port of an energy router in the centralized megawatt-level autonomous grid-connected device; Determining whether the attribute information meets the corresponding control condition; If so, the control strategy corresponding to the attribute information is adopted to regulate the attribute information.

9. The method according to claim 8, characterized in that The attribute information includes a branch load rate, and the determining whether the attribute information meets a corresponding regulation condition includes: Determining whether the branch load rate reaches a first threshold; The adopting the control strategy corresponding to the attribute information to regulate the attribute information includes: The branch load rate is regulated according to the branch energy storage power adjustment strategy and / or the branch photovoltaic power generation power adjustment strategy.

10. The method according to claim 9, characterized in that Also includes: If the branch load rate does not reach the first threshold value, determining the distribution transformer load rate; Determining whether the load rate of the distribution transformer reaches a second threshold value; If so, the load rate of the distribution transformer is regulated according to the distribution transformer control strategy corresponding to the load rate of the distribution transformer, wherein the distribution transformer control strategy includes one or more of the following: a gear adjustment strategy of the distribution transformer, a power adjustment strategy of a flexible interconnection device, an energy storage power adjustment strategy, or a photovoltaic power generation power adjustment strategy; If not, then the restrictions on photovoltaic power output will be lifted.

11. The method according to claim 8, characterized in that The attribute information includes a photovoltaic reverse current risk level, and the determining whether the attribute information meets a corresponding control condition includes: Determining whether the photovoltaic reverse current risk level reaches a set risk level; The adopting the control strategy corresponding to the attribute information to regulate the attribute information includes: Calculate the substation control value under the current AC / DC scenario; The photovoltaic reverse current risk level is regulated according to the substation control value.

12. The method according to claim 11, characterized in that The calculation of the substation control value in the current AC / DC scenario includes: Determine whether the station area is an AC station area; If so, calculating the area control value of the AC area in phases; If not, calculate the DC substation control value.

13. The method according to claim 8, characterized in that The attribute information includes the average load rate of each area, and the determination of whether the attribute information meets the corresponding control condition includes: Determining whether the average load rate of each area reaches a third threshold value; The adopting the control strategy corresponding to the attribute information to regulate the attribute information includes: Determine the operating power of the mutual aid equipment; The action power is sent to the mutual aid device.

14. The method according to any one of claims 8 to 13, characterized in that: The method is implemented based on the centralized megawatt-level autonomous grid-connected device described in any one of claims 1-7.

15. A centralized megawatt-level autonomous grid-connected system, characterized in that: The system comprises a centralized megawatt-level autonomous grid-connected device and a switch cabinet as described in any one of claims 1 to 7; The centralized megawatt-level autonomous grid-connected device is connected to the power grid through the switch cabinet.

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