Network following and constructing control switching method, device, equipment, medium and product

Abstract

The invention discloses a network following and network construction control switching method, device, equipment, medium and product, and the method comprises the steps: when all buses of a transformer substation of a power grid system are detected not to operate, controlling the power grid system to operate in a network construction control mode; and when it is detected that at least one bus of the transformer substation of the power grid system operates, according to the effective short-circuit ratio corresponding to the bus, it is judged that the power grid system is controlled to operate in a network following / constructing control mode. The control mode can be automatically switched on the basis of a network following and network constructing dual-control framework, the operation requirements of the power grid in various scenes of a strong network, a weak network and an isolated network can be met, and safe and stable operation of a direct current project and a power grid system is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible DC power transmission control, and particularly to a switching method, device, equipment, medium and product for grid-following and grid-forming control. Background Art

[0002] In a regional power grid with flexible DC access, the short-circuit capacity of the regional power grid system is large under the grid-connected mode, and stable operation can be achieved by adopting grid-forming control for the flexible DC. However, when a bus maintenance occurs at a key hub substation in the regional power grid and another bus trips due to a fault, the regional power grid will form a scenario of operating as an islanded power grid with a 220 kV power grid relying on the flexible DC. After the regional power grid enters the islanded power grid passively, the short-circuit current of the regional power grid system decreases, and the strength of the regional power grid system will change from a strong grid system to a weak grid system. In extreme cases, the effective short-circuit ratio may reach 1.2. In this case, if the regional power grid relying on the flexible DC still adopts grid-following control, it will be difficult to operate stably and resist external fault disturbances. The regional power grid relying on the flexible DC must adopt grid-forming control to ensure the stable operation of the power grid system. Therefore, it is urgent to ensure the stable operation of the regional power grid in various scenarios of strong grid, weak grid and islanded power grid. Summary of the Invention

[0003] The present invention provides a switching method, device, equipment, medium and product for grid-following and grid-forming control, which automatically switches the control mode based on the dual control architectures of grid-following and grid-forming, can meet the operation requirements of the power grid in various scenarios of strong grid, weak grid and islanded power grid, and ensure the safe and stable operation of the DC project and the power grid system.

[0004] To achieve the above object, an embodiment of the present invention provides a switching method for grid-following and grid-forming control, which is applied to the dual control architectures of grid-following and grid-forming. The method includes:

[0005] When it is detected that all buses of the substation in the power grid system are not operating, the grid-forming control mode is adopted to control the operation of the power grid system;

[0006] When it is detected that at least one bus of the substation in the power grid system is operating, according to the effective short-circuit ratio corresponding to the bus, it is determined whether to adopt the grid-following / grid-forming control mode to control the operation of the power grid system.

[0007] As an improvement of the above solution, the step of when it is detected that at least one bus of the substation in the power grid system is operating, according to the effective short-circuit ratio corresponding to the bus, determining whether to adopt the grid-following / grid-forming control mode to control the operation of the power grid system includes:

[0008] When it is detected that at least one bus of the substation in the power grid system is operating, calculate the effective short-circuit ratio corresponding to the bus;

[0009] If the effective short-circuit ratio is less than the preset effective short-circuit ratio threshold, the grid-connected control mode is adopted to control the operation of the power grid system;

[0010] If the effective short-circuit ratio is greater than or equal to the preset effective short-circuit ratio threshold, the grid-following control mode is adopted to control the operation of the power grid system.

[0011] As an improvement to the above solution, when it is detected that at least one bus of the substation of the power grid system is operating, calculating the effective short-circuit ratio corresponding to the bus includes:

[0012] When it is detected that at least one bus of the substation of the power grid system is operating, obtaining the short-circuit capacity of the bus and the real-time active power of the converter;

[0013] According to the short-circuit capacity and the real-time active power, calculating the effective short-circuit ratio corresponding to the bus.

[0014] As an improvement to the above solution, when it is detected that all buses of the substation of the power grid system are not operating, adopting the grid-forming control mode to control the operation of the power grid system includes:

[0015] When it is detected that all buses of the substation of the power grid system are not operating, if the grid-forming control mode is adopted to control the operation of the power grid system at the current moment, then continue to adopt the grid-forming control mode to control the operation of the power grid system;

[0016] If the grid-following control mode is adopted to control the operation of the power grid system at the current moment, then switch from adopting the grid-following control mode to adopting the grid-forming control mode to control the operation of the power grid system.

[0017] As an improvement to the above solution, the grid-following and grid-forming dual control architecture includes a grid-following control mode and a grid-forming control mode, and the grid-following control mode and the grid-forming control mode share a current loop.

[0018] As an improvement to the above solution, before it is detected that all buses of the substation of the power grid system are not operating, the method further includes:

[0019] Obtaining the switch position signal in the substation of the power grid system, and detecting whether all buses of the substation are operating according to the switch position signal.

[0020] To achieve the above object, an embodiment of the present invention provides a switching device for grid-following and grid-forming control, which is characterized by including:

[0021] A first control module, configured to adopt the grid-forming control mode to control the operation of the power grid system when it is detected that all buses of the substation of the power grid system are not operating;

[0022] A second control module, configured to, when it detects that at least one bus of the substation of the power grid system is operating, determine to control the operation of the power grid system in a grid-following / grid-forming control mode according to the effective short-circuit ratio corresponding to the bus.

[0023] To achieve the above object, an embodiment of the present invention correspondingly provides a switching device for grid-following and grid-forming control, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, the above switching method for grid-following and grid-forming control is implemented.

[0024] To achieve the above object, an embodiment of the present invention further provides a computer-readable storage medium. The computer-readable storage medium includes a stored computer program. Wherein, when the computer program runs, it controls the device where the computer-readable storage medium is located to execute the above switching method for grid-following and grid-forming control.

[0025] To achieve the above object, an embodiment of the present invention further provides a computer program product. The computer program product is stored in a storage medium, and the program product is executed by at least one processor to implement the steps of the above switching method for grid-following and grid-forming control.

[0026] Compared with the prior art, a switching method, device, equipment, medium, and product for grid-following and grid-forming control disclosed in an embodiment of the present invention, when it detects that all buses of the substation of the power grid system are not operating, controls the operation of the power grid system in a grid-forming control mode; when it detects that at least one bus of the substation of the power grid system is operating, determines to control the operation of the power grid system in a grid-following / grid-forming control mode according to the effective short-circuit ratio corresponding to the bus. It can automatically switch the control mode based on the dual control architectures of grid-following and grid-forming, and can adapt to the operation requirements of the power grid in various scenarios such as strong grid, weak grid, and isolated grid, ensuring the safe and stable operation of the DC project and the power grid system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic flowchart of a switching method for grid-following and grid-forming control provided by an embodiment of the present invention;

[0028] Figure 2 is a schematic diagram of a dual control architecture for grid-following and grid-forming provided by an embodiment of the present invention;

[0029] Figure 3 is a schematic structural diagram of a switching device for grid-following and grid-forming control provided by an embodiment of the present invention;

[0030] Figure 4 is a block diagram of the structure of a switching device for grid-following and grid-forming control provided by an embodiment of the present invention. Detailed implementation manners

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] It should be noted that the terms "include" and "specific" in the present invention and any of their variations are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily limit to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0033] Please refer to Figure 1 , Figure 1 which is a schematic flowchart of a switching method for following network and constructing network control provided by an embodiment of the present invention. The switching method for following network and constructing network control is applied to a dual control architecture of following network and constructing network. The method includes:

[0034] S1. When it is detected that all busbars of the substation in the power grid system are not operating, the power grid system is controlled to operate in a constructing network control mode;

[0035] S2. When it is detected that at least one busbar of the substation in the power grid system is operating, it is determined to control the power grid system to operate in a following network / constructing network control mode according to the effective short-circuit ratio corresponding to the busbar.

[0036] Exemplarily, the switching method for following network and constructing network control described in the embodiment of the present invention is implemented by a control mode switching server. The control mode switching server can interact with the target user and interact with the power grid system. The control mode switching server obtains the switch position signal in the substation of the power grid system, detects whether the busbar corresponding to the substation is operating according to the switch position signal. When it is detected that all busbars of the substation in the power grid system are not operating, the power grid system is controlled to operate in a constructing network control mode; when it is detected that at least one busbar of the substation in the power grid system is operating, it is determined to control the power grid system to operate in a following network / constructing network control mode according to the effective short-circuit ratio corresponding to the busbar. The embodiment of the present invention can automatically switch the control mode based on the dual control architecture of following network and constructing network, can adapt to the operation requirements of the power grid in various scenarios of strong grid, weak grid and isolated grid, and ensure the safe and stable operation of the DC project and the power grid system.

[0037] Further, before detecting that all buses of the substation in the power grid system are not operating in step S1, it further includes:

[0038] S101, obtain the switch position signals in the substation of the power grid system, and detect whether all buses of the substation are operating according to the switch position signals.

[0039] Exemplarily, the switch position signals in the substation of the power grid system (such as the states of circuit breakers and disconnectors) can be obtained, and it can be determined whether the bus is operating with electricity according to the switch position signals in the substation.

[0040] Specifically, the step S2 includes:

[0041] S21, when it is detected that at least one bus of the substation in the power grid system is operating, calculate the effective short-circuit ratio corresponding to the bus;

[0042] S22, if the effective short-circuit ratio is less than the preset effective short-circuit ratio threshold, then adopt the grid-forming control mode to control the operation of the power grid system;

[0043] S23, if the effective short-circuit ratio is greater than or equal to the preset effective short-circuit ratio threshold, then adopt the grid-following control mode to control the operation of the power grid system.

[0044] Exemplarily, when it is detected that at least one bus of the substation is operating, the grid strength is determined by the effective short-circuit ratio (SCR), and then the grid-following / grid-forming control mode is dynamically switched. Taking the substation with two buses as an example, in the single-bus operation scenario, each bus is independently connected to the power grid, and its short-circuit capacity is determined by the power sources (such as the main grid and distributed power sources) and line impedances connected to the bus, reflecting the grid strength of this node. Assume that bus 1 is connected to the main grid, the short-circuit capacity S1 = 1000 MVA, and the converter power P = 400 MW, then SCR = 1000 / 400 = 2.5. If the preset effective short-circuit ratio threshold is 2.5 (that is, when bus 1 is connected to the main grid and operating, the grid strength is a strong grid), it can be understood that the preset effective short-circuit ratio threshold can be set as required. Bus 2 is connected to a small power source, the short-circuit capacity S2 = 360 MVA, then SCR = 360 / 400 = 0.9 (that is, when bus 2 is connected to the main grid and operating, the grid strength is a weak grid). In the double-bus parallel operation scenario, the two buses are connected in parallel through the bus-coupling breaker, and the short-circuit capacity is the sum of the two S = S1 + S2, usually a strong grid.

[0045] When the grid strength is strong (for example, when it is detected that at least one bus of the substation in the grid system is operating, and the effective short-circuit ratio corresponding to the bus is greater than or equal to the preset effective short-circuit ratio threshold), the short-circuit capacity of the bus is large enough, the support ability of the grid for the converter is strong, and the phase-locked loop instability is not likely to occur. The grid system is controlled to operate in a grid-following control mode: the phase of the bus voltage is tracked through a phase-locked loop (PLL) to synchronize the converter with the grid. The active power reference value and the reactive power reference value are quickly adjusted by the power loop to respond to the change of the grid load. The dynamic performance is excellent, the power fluctuation can be quickly suppressed, and the device overcurrent can be avoided.

[0046] When the grid strength is weak (when it is detected that at least one bus of the substation in the grid system is operating, and the effective short-circuit ratio corresponding to the bus is less than the preset effective short-circuit ratio threshold), the short-circuit capacity of the bus is small, and the grid-following control is prone to system oscillation due to the phase-locked loop instability. Therefore, the grid system is controlled to operate in a grid-forming control mode: the phase and frequency are autonomously generated according to a specific algorithm (such as the virtual synchronous machine algorithm) through a synchronization loop to simulate the characteristics of traditional power sources; the voltage loop droop control is used to maintain the stability of the bus voltage and frequency, actively support the grid, and improve the anti-disturbance ability under weak grids. It should be noted that the grid-following and grid-forming controls share the current loop, and during the switching, the current loop is quickly adjusted to suppress the transient impact, ensure smooth transition, and synchronize the controller parameters in advance (such as phase, power command) to avoid parameter jumps during strategy switching.

[0047] The embodiment of the present invention dynamically adapts to the grid strength, exerts the fast response ability of grid-following control under strong grids to improve the transmission efficiency; under weak grids, utilizes the autonomous support ability of grid-forming control to avoid system collapse; avoids the limitations of a single control mode under different working conditions, especially suitable for flexible DC projects with complex grid structures and variable operation scenarios, and can improve the system robustness; through an automatic discrimination and switching mechanism, it can respond to the change of the grid state in real time, reduce the operation and maintenance difficulty and operation risk, and reduce manual intervention. It realizes the adaptive stable operation of the converter under different grid strengths, and provides key technical support for the coordinated control of the flexible DC transmission system and the substation.

[0048] More specifically, the step S21 includes:

[0049] S211, when it is detected that at least one bus of the substation in the grid system is operating, obtain the short-circuit capacity of the bus and the real-time active power of the converter;

[0050] S212, calculate the effective short-circuit ratio corresponding to the bus according to the short-circuit capacity and the real-time active power.

[0051] It is understandable that at least one live bus means that among all the buses in the substation (double buses or multiple buses), any one bus is normally connected to the power grid (not in the state of maintenance or fault tripping). At this time, the power grid is in the grid-connected operation mode and is electrically connected to the main grid. Whether the bus is live can be judged by the switch position signals in the substation (such as the status of circuit breakers and disconnectors).

[0052] In this embodiment, when it is detected that at least one bus is operating, the short-circuit capacity of the bus and the real-time power of the converter are obtained in real time. The converter is connected to the bus, and the effective short-circuit ratio (SCR) corresponding to the bus is obtained by the ratio of the short-circuit capacity and the real-time power. The short-circuit capacity refers to the apparent power when a three-phase short circuit occurs at the bus, which reflects the support ability of the power grid for the short-circuit current and can be obtained in the following ways: based on the power grid topology structure and real-time operation data (such as line impedance, power source capacity), it is calculated in real time by using a short-circuit current calculation algorithm (such as the per-unit value method); or through the potential transformer (PT) and current transformer (CT) installed at the bus, the voltage U and the effective value I of the current during the short circuit are measured, and through the formula It is calculated. The real-time active power output of the converter can be directly read through the converter control system (such as the power measurement value on the DC side or the power calculation value on the AC side).

[0053] Among them, the calculation formula of the SCR is:

[0054] SCR = S / P,

[0055] In the formula, S is the short-circuit capacity at the bus where the flexible DC is included, which is calculated in real time by the flexible DC control system, representing the short-circuit capacity of the bus, and the unit is MVA; P is the real-time power of the flexible DC (the real-time active power of the converter), and the unit is MW.

[0056] It should be noted that if it is a single bus operation, the short-circuit capacity S of the operating bus is directly calculated (for example, when bus 1 or bus 2 operates alone, S = S1 or S = S2). If it is a double bus parallel operation, the sum of the short-circuit capacities of the two buses is calculated as S = S1 + S2, and at this time the power grid strength is higher (that is, the SCR is larger). In the embodiment of the present invention, when both double buses are operating but the data of a certain bus is abnormal, the SCR value of the other bus can be used as an alternative criterion, or the minimum value of the SCR of the double buses can be used for discrimination to improve the system reliability. If the SCR continuously drops below the preset effective short-circuit ratio threshold during single bus operation, it is necessary to combine the bus power loss signal to judge whether it enters the edge state of the islanded grid, and give an early warning and prepare for the switching of the grid-forming control mode.

[0057] Specifically, the step S1 includes:

[0058] S11. When it is detected that all the buses of the substation in the power grid system are not operating, if the power grid system is controlled to operate in the network-forming control mode at the current moment, then continue to control the power grid system to operate in the network-forming control mode.

[0059] S12. If the power grid system is controlled to operate in the grid-following control mode at the current moment, then switch from using the grid-following control mode to using the network-forming control mode to control the power grid system to operate.

[0060] Exemplarily, when it is detected that all the buses of the substation in the power grid system are not operating, it indicates that the power grid system has entered the islanding operation state. At this time, the short-circuit capacity of the power grid is extremely low (in extreme cases, the SCR may be only 1.2), and the traditional grid-following control cannot maintain stability. It is necessary to adopt the network-forming control mode to reconstruct the power grid voltage and frequency reference. Suppose the double-circuit buses of the substation (such as bus 1 and bus 2) are disconnected from the main grid due to maintenance, faults, etc.; or the substation is disconnected from the main grid to form an independent island system. The section power-off device configured in the substation monitors the bus voltage in real time. When there is no voltage signal on all the buses, it is determined as an islanded network and a switching signal is sent to the flexible DC control system; after receiving the switching signal, the flexible DC control system performs the following operations regardless of whether the current control mode is the network-forming control mode: If the original strategy is the network-forming control mode, maintain the current strategy and continue to maintain the stability of the islanded network (power grid system); if the original strategy is the grid-following control mode, forcefully switch to the network-forming control mode to avoid system collapse caused by the instability of the phase-locked loop.

[0061] It should be noted that the core implementation method of the grid-forming control mode is as follows: by autonomously generating a power grid reference (replacing the traditional synchronization mechanism), simulating the inertia and damping characteristics of a traditional synchronous generator through the virtual synchronous machine (VSM) algorithm, and autonomously generating stable phase and frequency without relying on external power grid signals; based on the droop characteristic, dynamically adjusting the amplitude and frequency of the converter output voltage according to the active power demand and reactive power demand within an islanded grid; for example, when the islanded grid load increases and causes the frequency to drop, the synchronization loop increases the virtual torque to boost the active power output and suppress the frequency deviation; the current loop, as a common execution unit for grid-following and grid-forming control modes, compares the current reference value calculated by the voltage loop with the actual current to generate the valve-side reference voltage and drive the converter switching devices to act; during the process of switching from grid-following to grid-forming, the current loop quickly adjusts and suppresses the transient current impact through smooth switching to ensure that the switching time ≤ 100 ms and the current fluctuation amplitude ≤ 20% (typical index); when a short-circuit fault occurs in the islanded grid, the current loop can quickly limit the fault current (such as controlling the overcurrent multiple within 1.5 times the rated current) to protect the converter and substation equipment. Active power control: By means of the droop characteristic, it matches the active power demand of the islanded grid load in real time to avoid large fluctuations in frequency. For example, when the load increases by 10%, the converter automatically increases the active output by 10% to maintain frequency stability. Reactive power control: Adjusts the reactive power output according to the voltage level of the islanded grid. For example, when the voltage is low, it increases the reactive power to boost the bus voltage to the rated value (such as restoring from 0.9 times the rated voltage to 1.0 times).

[0062] In the embodiment of the present invention, the grid-forming control mode can autonomously establish stable voltage and frequency references, solve the core problem of no power source support under an islanded grid, avoid system frequency collapse or voltage collapse, and maintain the stability of the power grid; support the islanded grid to operate with load, ensure the continuous power supply of critical loads (such as hospitals and transportation hubs); when an instantaneous fault (such as a line short circuit) occurs in the islanded grid, the grid-forming control mode quickly limits the fault current through the current loop. After cooperating with the substation protection device to cut off the fault point, it can automatically restore power supply and shorten the power outage time; improve the resilience and reliability of the power grid system.

[0063] Specifically, the grid-following and grid-forming dual control architecture includes a grid-following control mode and a grid-forming control mode, and the grid-following control mode and the grid-forming control mode share a current loop.

[0064] Exemplarily, see Figure 2 , Figure 2 which is a schematic diagram of a grid-following and grid-forming dual control architecture provided by an embodiment of the present invention, Figure 2The tracking network and network construction dual control architecture described in includes tracking network control and network construction control. The tracking network control includes a phase-locked loop, a power loop, and a common part (abc / dq coordinate transformation, common current loop, modulation link); the network construction control includes a synchronization loop, a voltage loop, and the common part. By adopting tracking network control, it relies on the phase-locked loop to track the phase of the grid voltage, exhibits excellent dynamic performance, and prevents device overcurrent; by adopting network construction control, it autonomously establishes voltage and frequency references through the synchronization loop, avoids the instability of the phase-locked loop under weak grid conditions, and improves the regulation performance of the grid frequency and voltage.

[0065] Phase-locked loop: The three-phase voltage signals U of the AC grid are collected through a potential transformer (PT) abc As the input of the phase-locked loop, the potential transformer converts the high voltage into a low voltage signal suitable for measurement and processing in proportion, generally the rated value of the secondary side; the phase-locked loop is based on the collected U abc , and uses a specific algorithm (such as the phase-locked loop algorithm based on the synchronous rotating coordinate system) to calculate the phase θ pll and frequency of the grid voltage. This algorithm will perform coordinate transformation on the voltage signal (such as abc / dq coordinate transformation), and calculate the phase and frequency information by analyzing the voltage components in the dq coordinate system.

[0066] Power loop: Receives the active power reference value P ref (The active power reference value is usually given by the superior dispatching system according to factors such as the power balance demand of the grid and the transmission plan. For example, when the grid needs to obtain a certain amount of active power from the flexible DC transmission system to meet the load demand, the dispatching system will issue the corresponding P ref value), reactive power reference value Q ref (The reactive power reference value is determined based on the voltage control target of the grid and the reactive power compensation demand, etc. If the voltage of a certain regional grid is low and the flexible DC transmission system is required to provide reactive power to support the voltage, a suitable reactive power reference value will be set at this time), AC voltage reference value V acref (The AC voltage reference value is set according to the rated voltage standard of the grid and the voltage quality requirements. For example, for a 110 kV AC grid, its V acref is generally set to 110 kV, but it will also be fine-tuned according to the actual voltage regulation demand); after the power loop receives the above reference values, it combines the phase information θ pll output by the phase-locked loop and the current I dq and voltage U dq information after coordinate transformation, and uses a control algorithm (such as the PI control algorithm) to calculate the current reference value I dqref1 in the dq coordinate system.

[0067] Synchronization loop: Receives the active power reference value P ref(Generally determined by factors such as the system's power distribution strategy, load demand, and new energy power generation prediction. For example, when operating in an isolated grid, P is set according to the active power demand of the local load and the charge and discharge strategy of the energy storage device.) ref ) The synchronization loop, based on an internal algorithm (such as the virtual synchronous machine algorithm), according to the input P ref and the operating state of the system (such as feedback information such as DC voltage, frequency, etc.), autonomously generates the phase θ gfm . The virtual synchronous machine algorithm simulates the operating characteristics of a traditional synchronous generator and generates a stable phase signal by adjusting internal links such as virtual torque and excitation.

[0068] Voltage loop: Receives the active power reference value P ref (The active power reference value is similar in source to the P input to the synchronization loop and is determined based on system power balance, load demand, new energy power generation, etc.), the reactive power reference value Q ref (The reactive power reference value is set according to the voltage control requirements of the power grid and the reactive power balance situation. For example, when the system voltage fluctuates greatly, the reactive power output is controlled by adjusting Q ref to stabilize the voltage), the AC voltage reference value V ref (The AC voltage reference value is set according to the rated voltage standard of the power grid, and the allowable voltage fluctuation range is also considered. For example, in a weak grid or isolated grid scenario, to ensure the normal operation of the load, an appropriate V acref is set and adjusted according to the actual voltage feedback); after receiving the above reference values, the voltage loop combines the phase information θ output by the synchronization loop acref and uses algorithms such as droop control to calculate the current reference value I in the dq coordinate system gfm . The droop control algorithm calculates the current reference value based on the P-f (active - frequency) and Q-U (reactive - voltage) droop characteristics according to the active power and reactive power deviations to achieve the regulation of the system frequency and voltage. dqref2

[0069] abc / dq coordinate transformation: Collects the three-phase AC voltage U through a potential transformer (PT) abc , and collects the three-phase AC current I through a current transformer (CT) abc . The current transformer converts the large current into a small current signal suitable for measurement and processing in proportion; the phase information θ output by the phase-locked loop (when following the grid control) or the synchronization loop (when forming the grid control) is also required pll or θ gfm as input. According to the coordinate transformation formula, using the collected U abc , I abc and the phase information, the voltage and current signals in the three-phase stationary coordinate system are converted into U in the dq rotating coordinate system dq and I​dq , which is convenient for subsequent control operations.

[0070] Shared current loop: When in grid-following control, the inputs are the current reference value I output by the power loop dqref1 and the actual current value I after coordinate transformation dq ; When in grid-forming control, the inputs are the current reference value I output by the voltage loop dqref2 and the actual current value I after coordinate transformation dq ; The current loop compares the current reference value with the actual current value to obtain a current deviation value, and then uses a control algorithm (such as a PI control algorithm) to adjust the current deviation to generate a valve-side reference voltage signal for controlling the switching actions of the converter, so that the output current tracks the reference value. It should be noted that the valve-side reference voltage is a reference value used in the converter control to determine the valve-side output voltage of the converter, and is a key parameter for controlling the on / off of the converter switching devices and realizing power regulation and voltage control.

[0071] In the embodiments of the present invention, the advantages of grid-following control and grid-forming control are integrated, automatically adapting to the operation requirements of strong grids and weak grids, and ensuring the safety and stability of DC projects and grid systems; The grid-following control and grid-forming control share a current loop. Regardless of how the mode is switched, the current loop always tracks the current reference value in real time, ensuring continuous current during the switching process and avoiding impacts; When switching modes (such as from grid-following to grid-forming), the current loop suppresses transient current fluctuations through rapid adjustment to achieve seamless connection of the control mode; During grid faults, the current loop can quickly limit the fault current to protect the converter devices.

[0072] A switching method for grid-following and grid-forming control disclosed in the embodiments of the present invention controls the operation of the grid system by adopting a grid-forming control mode when it is detected that all buses of the substation in the grid system are not operating; When it is detected that at least one bus of the substation in the grid system is operating, it is determined whether to adopt a grid-following / grid-forming control mode to control the operation of the grid system according to the effective short-circuit ratio corresponding to the bus. It can automatically switch the control mode based on the dual control architectures of grid-following and grid-forming, and can adapt to the operation requirements of the grid in various scenarios such as strong grids, weak grids, and isolated grids, ensuring the safe and stable operation of DC projects and grid systems.

[0073] See Figure 3 , Figure 3 is a schematic structural diagram of a switching device 10 for grid-following and grid-forming control provided by the embodiments of the present invention. The switching device 10 for grid-following and grid-forming control is applied to the dual control architectures of grid-following and grid-forming, and includes:

[0074] The first control module 11 is used to control the operation of the grid system by adopting a grid-forming control mode when it is detected that all buses of the substation in the grid system are not operating;

[0075] The second control module 12 is configured to, when it is detected that at least one bus of the substation of the power grid system is operating, determine to control the operation of the power grid system in a grid-following / grid-forming control mode according to the effective short-circuit ratio corresponding to the bus.

[0076] Further, the switching device 10 for grid-following and grid-forming control further includes:

[0077] A signal acquisition module, configured to acquire the switch position signals in the substation of the power grid system, and detect whether all the buses of the substation are operating according to the switch position signals.

[0078] The switching device 10 for grid-following and grid-forming control provided by the embodiment of the present invention can implement all the processes of the grid-following and grid-forming control switching method in the above embodiment. The functions of each module in the device and the achieved technical effects are respectively the same as the functions and the achieved technical effects of the grid-following and grid-forming control switching method in the above embodiment, and will not be elaborated here.

[0079] See Figure 4 , Figure 4 FIG. is a schematic structural diagram of a switching device 20 for grid-following and grid-forming control provided by an embodiment of the present invention. The switching device 20 for grid-following and grid-forming control in this embodiment includes: a processor 21, a memory 22, and a computer program stored in the memory 22 and executable on the processor 21. When the processor 21 executes the computer program, the steps in the embodiment of the grid-following and grid-forming control switching method are implemented. Alternatively, when the processor 21 executes the computer program, the functions of each module in the embodiment of the switching device for grid-following and grid-forming control are implemented.

[0080] Exemplarily, the computer program can be divided into one or more modules. The one or more modules are stored in the memory 22 and executed by the processor 21 to complete the present invention. The one or more modules can be a series of computer program instruction segments capable of performing specific functions, and these instruction segments are used to describe the execution process of the computer program in the switching device 20 for grid-following and grid-forming control.

[0081] The switching device 20 for following network and constructing network control can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The switching device 20 for following network and constructing network control may include, but is not limited to, a processor 21 and a memory 22. Those skilled in the art can understand that the schematic diagram is only an example of the switching device 20 for following network and constructing network control, and does not constitute a limitation on the switching device 20 for following network and constructing network control. It may include more or fewer components than those shown in the figure, or combine certain components, or different components. For example, the switching device 20 for following network and constructing network control may also include input / output devices, network access devices, buses, etc.

[0082] The so-called processor 21 may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc. The processor 21 is the control center of the switching device 20 for following network and constructing network control, and connects various parts of the entire switching device 20 for following network and constructing network control through various interfaces and lines.

[0083] The memory 22 can be used to store the computer programs and / or modules. The processor 21 realizes various functions of the switching device 20 for following network and constructing network control by running or executing the computer programs and / or modules stored in the memory 22, and by calling the data stored in the memory 22. The memory 22 may mainly include a program storage area and a data storage area. Among them, the program storage area can store an operating system, application programs required for at least one function (such as a sound playback function, an image playback function, etc.); the data storage area can store data created according to the use of the mobile phone (such as audio data, phone book, etc.). In addition, the memory 22 may include high-speed random access memory, and may also include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, at least one magnetic disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0084] Among them, if the module integrated with the network following and network constructing control switching device 20 is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, to implement all or part of the processes in the above-described embodiment methods of the present invention, it can also be completed by a computer program instructing relevant hardware. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor 21, the steps of the above various method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file, or some intermediate form, etc. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0085] It should be noted that the device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. In addition, in the attached drawings of the device embodiments provided by the present invention, the connection relationship between the modules indicates that they have a communication connection, which can be specifically implemented as one or more communication buses or signal lines. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0086] The embodiment of the present invention also provides a computer-readable storage medium. The computer-readable storage medium includes a stored computer program. Among them, when the computer program runs, it controls the device where the computer-readable storage medium is located to execute the network following and network constructing control switching method as described in the above embodiment.

[0087] In addition, the embodiment of the present invention also provides a computer program product. The computer program product is stored in a storage medium, and the program product is executed by at least one processor to implement the steps of the network following and network constructing control switching method as described in the above embodiment.

[0088] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A handover method for following network and constructing network control, characterized in that Applied to the dual control architecture of grid following and grid forming, the method includes: When it is detected that all buses of the substation in the power grid system are not operating, the grid forming control mode is adopted to control the operation of the power grid system; When it is detected that at least one bus of the substation in the power grid system is operating, according to the effective short-circuit ratio corresponding to the bus, it is determined whether to adopt the grid following / grid forming control mode to control the operation of the power grid system.

2. The method for switching between following network and constructing network control according to claim 1, wherein The step of, when it is detected that at least one bus of the substation in the power grid system is operating, according to the effective short-circuit ratio corresponding to the bus, determining whether to adopt the grid following / grid forming control mode to control the operation of the power grid system, includes: When it is detected that at least one bus of the substation in the power grid system is operating, calculate the effective short-circuit ratio corresponding to the bus; If the effective short-circuit ratio is less than the preset effective short-circuit ratio threshold, the grid forming control mode is adopted to control the operation of the power grid system; If the effective short-circuit ratio is greater than or equal to the preset effective short-circuit ratio threshold, the grid following control mode is adopted to control the operation of the power grid system.

3. The method for switching between following network and constructing network control according to claim 2, wherein, The step of, when it is detected that at least one bus of the substation in the power grid system is operating, calculating the effective short-circuit ratio corresponding to the bus, includes: When it is detected that at least one bus of the substation in the power grid system is operating, obtain the short-circuit capacity of the bus and the real-time active power of the converter; According to the short-circuit capacity and the real-time active power, calculate the effective short-circuit ratio corresponding to the bus.

4. The handover method for following network and constructing network control according to claim 1, wherein The step of, when it is detected that all buses of the substation in the power grid system are not operating, adopting the grid forming control mode to control the operation of the power grid system, includes: When it is detected that all buses of the substation in the power grid system are not operating, if the grid forming control mode is adopted to control the operation of the power grid system at the current moment, continue to adopt the grid forming control mode to control the operation of the power grid system; If the grid following control mode is adopted to control the operation of the power grid system at the current moment, switch from adopting the grid following control mode to adopting the grid forming control mode to control the operation of the power grid system.

5. The handover method for following network and constructing network control according to claim 1, wherein The dual control architecture of grid following and grid forming includes a grid following control mode and a grid forming control mode, and the grid following control mode and the grid forming control mode share a current loop.

6. The handover method for following network and constructing network control according to claim 1, characterized in that Before it is detected that all buses of the substation in the power grid system are not operating, the method further includes: Obtain the switch position signal in the substation of the power grid system, and detect whether all buses of the substation are operating according to the switch position signal.

7. A switching device for following network and network construction control, characterized in that, Includes: A first control module, configured to, when it is detected that all buses of the substation in the power grid system are not operating, adopt the grid forming control mode to control the operation of the power grid system; A second control module, configured to, when it is detected that at least one bus of the substation in the power grid system is operating, determine whether to adopt the grid following / grid forming control mode to control the operation of the power grid system according to the effective short-circuit ratio corresponding to the bus.

8. A switching device for follow-the-network and network-construction control, characterized in that Includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, the switching method of grid following and grid forming control as described in any one of claims 1-6 is implemented.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein when the computer program runs, it controls the device where the computer-readable storage medium is located to execute the handover method for network connection and network construction control according to any one of claims 1-6.

10. A computer program product, characterized in that, The computer program product is stored in a storage medium, and the program product is executed by at least one processor to implement the steps of the handover method for network connection and network construction control according to any one of claims 1-6.

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