Control methods for flexible multi-state switches and multi-energy fusion systems

Abstract

This invention provides a control method for a flexible multi-state switch and a multi-energy fusion system. The operating modes of the flexible multi-state switch ports include U... dc -Q mode, PQ mode, and VF mode. U dc The -Q and PQ modes share the first current inner loop and each has its own outer loop controller. The VF mode has a corresponding third outer loop controller and a second current inner loop. When a fault is detected in any port feeder, the dq-axis input voltage of the third outer loop controller is obtained based on a preset droop adjustment model. Based on the third outer loop controller, the dq-axis reference value of the control model of the second current inner loop is obtained. Under the control of a preset inertial control model, the dq-axis reference value of the control model of the second current inner loop is input into the second current inner loop to obtain the dq-axis output voltage of the VF mode. This reduces the impact of mode switching transitions and improves the stability and reliability of the system operation.

Description

Technical Field

[0001] This invention relates to the field of flexible power distribution equipment control technology, specifically providing a control method for flexible multi-state switches and a multi-energy fusion system. Background Technology

[0002] Currently, power distribution networks suffer from problems such as lagging construction, unreasonable structure, and limited control methods. Flexible multi-state switches (FMSS) can achieve flexible control of the power distribution network. An FMSS is a power electronic converter connected between multiple feeders in the distribution network. It adopts new power electronics technologies and not only has both on and off states, but also adds a continuously controllable power state. It also features flexible switching of operating modes and diverse control methods.

[0003] For multi-port FMSS, to leverage its advantages of precise power flow control and rapid power restoration, coordinated control of each port converter is required. During normal operation, one port of the FMSS typically operates in constant DC voltage and reactive power mode, referred to here as constant DC side voltage control mode, or U for short. dc -Q mode, other ports operate in constant power mode, referred to here as current source mode, or PQ mode for short; when the PQ port feeder fails, it needs to switch to voltage source mode, or VF mode for short, to supply power to important loads in the fault-affected area, and then switch back to the initial operating mode after the feeder returns to normal; when U dc When the Q port feeder fails, one of the other ports needs to be switched to U. dc -Q mode, and will transmit the U signal of a feeder fault. dc -Q port switches to VF mode.

[0004] However, the switching between different operating modes of the port inevitably involves a transient adjustment process. The traditional dual closed-loop control strategy applied to FMSS cannot effectively suppress the current surge and the fluctuation of DC and AC voltages during the mode switching process, and cannot guarantee the stability and reliability of the system operation. Summary of the Invention

[0005] To overcome the above-mentioned defects, the present invention is proposed to provide a control method, apparatus, system, and storage medium for smart home devices that solves, or at least partially solves, the technical problem that when the sleep music played by a smart home device is not suitable for a user's needs, it not only fails to achieve the sleep aid effect but also affects the user's sleep quality.

[0006] In a first aspect, the present invention provides a control method for a flexible multi-state switch, wherein the flexible multi-state switch has at least two ports; the operating modes of each port include a constant DC side voltage control mode under grid-connected operation, a current source mode under grid-connected operation, and a voltage source mode under off-grid operation; wherein the constant DC side voltage control mode and the current source mode share a first current inner loop, and the constant DC side voltage control mode has a corresponding first outer loop controller, the current source mode has a corresponding second outer loop controller; the voltage source mode has a corresponding third outer loop controller and a second current inner loop; when the flexible multi-state switch is operating normally, one port operates in the constant DC side voltage control mode, and all other ports operate in the current source mode; the method includes:

[0007] When a feeder fault is detected at any port, the port with the feeder fault is switched from the current operating mode to the voltage source mode based on a preset smooth switching control method, so as to supply power to the important loads in the fault-free area.

[0008] The preset smooth switching control method includes a state tracking control method based on adding an inertial element;

[0009] The state tracking control method based on adding an inertial element includes:

[0010] Based on the preset droop adjustment model, the dq axis input voltage of the third outer loop controller is obtained;

[0011] Based on the third outer loop controller, the dq axis reference value of the control model of the second current inner loop is obtained, and under the control of the preset inertial control model, the dq axis reference value of the control model of the second current inner loop is input into the second current inner loop.

[0012] Based on the control model of the second current inner loop, the dq axis output voltage of the voltage source mode is obtained; wherein, the dq axis output voltage of the voltage source mode is the same as the dq axis output voltage of the current operating mode.

[0013] In a second aspect, the present invention provides a multi-energy integrated system, including a flexible multi-state switch, a power generation station, an energy storage station, and a load;

[0014] The power plant, the energy storage station, and the load are each electrically connected to the flexible multi-state switch.

[0015] The flexible multi-state switch operates under the control method of the flexible multi-state switch as described in any of the above claims.

[0016] The above-described technical solutions of the present invention have at least one or more of the following beneficial effects:

[0017] In implementing the technical solution of this invention, by using a state tracking control method based on adding an inertial element, the difference between the dq axis output voltages of the two modes is tracked and controlled by a PI controller before the working mode switch, and the output of this PI controller is used as the reference value of the VF mode current inner loop. This can achieve the same output voltage between the two modes at the moment of switching. At the same time, an inertial element is added after the switching switch to avoid the impact caused by the jump in the dq axis output voltage during switching, thereby improving the stability and reliability of the system operation. Attached Figure Description

[0018] The disclosure of this invention will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Furthermore, similar numbers in the drawings are used to denote similar components, wherein:

[0019] Figure 1 This is a control block diagram of a flexible multi-state switch according to an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the FMSS operating mode of the three-port FMSS system of the present invention when the feeder is normal;

[0021] Figure 3 This is a schematic diagram of the FMSS operating mode when the feeder connected to the PQ port fails and needs to be disconnected from the network;

[0022] Figure 4 yes Figure 3 A schematic diagram of the voltage waveform at the corresponding fault point;

[0023] Figure 5a This is a waveform diagram of the DC-side voltage when a state follower controller is used in a three-port FMSS.

[0024] Figure 5b This is a waveform diagram of the three-phase load voltage on the power failure side when a state follower controller is used in a three-port FMSS.

[0025] Figure 5c This is a waveform diagram of the output active power when a three-port FMSS uses a state follower controller;

[0026] Figure 6a This is a waveform diagram of the DC side voltage after the three-port FMSS adopts a state follower controller and adds an inertial element and phase pre-synchronization control;

[0027] Figure 6b This is a waveform diagram of the three-phase load voltage on the power failure side after the three-port FMSS adopts a state follower controller and adds an inertial element and phase pre-synchronization control;

[0028] Figure 6c This is the waveform of the active power output after the three-port FMSS adopts a state follower controller and adds an inertial element and phase pre-synchronization control;

[0029] Figure 7 It's U dc - A diagram illustrating the FMSS operating mode when the feeder connected to the Q port fails and the network needs to be disconnected;

[0030] Figure 8 yes Figure 7 A schematic diagram of the voltage waveform at the corresponding fault point;

[0031] Figure 9a This is a DC-side voltage waveform diagram of FMSS after mode switching based on the control method of the flexible multi-state switch of the present invention.

[0032] Figure 9b The active power waveform of FMSS after mode switching is based on the flexible multi-state switch control method of the present invention.

[0033] Figure 10 This is a schematic diagram of the structure of an embodiment of the multi-energy fusion system of the present invention. Detailed Implementation

[0034] Some embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0035] In the description of this invention, "module" and "processor" can include hardware, software, or a combination of both. A module can include hardware circuitry, various suitable sensors, communication ports, memory, and may also include software components, such as program code, or a combination of software and hardware. A processor can be a central processing unit, microprocessor, image processor, digital signal processor, or any other suitable processor. The processor has data and / or signal processing capabilities. The processor can be implemented in software, in hardware, or a combination of both. Non-transitory computer-readable storage media includes any suitable medium capable of storing program code, such as magnetic disks, hard disks, optical disks, flash memory, read-only memory, random access memory, etc. The term "A and / or B" means all possible combinations of A and B, such as only A, only B, or A and B. The terms "at least one A or B" or "at least one of A and B" have a similar meaning to "A and / or B" and can include only A, only B, or A and B. The singular terms "a" or "this" can also include plural forms.

[0036] See appendix Figure 1 , Figure 1This is a control block diagram of a flexible multi-state switch according to an embodiment of the present invention. In a specific implementation, the number of ports of the flexible multi-state switch is not less than 2; the operating mode of each port includes U under grid-connected operation. dc -Q mode, PQ mode under grid-connected operation, and VF mode under off-grid operation. For example... Figure 1 As shown, the U dc -Q mode and PQ mode share the first current inner loop, and the U dc The -Q mode has a corresponding first outer loop controller, and the PQ mode has a corresponding second outer loop controller; the U dc -Q mode has a separate DC voltage control section, and PQ mode has a separate active power control section, wherein U dc The -Q mode shares the reactive power control section with the PQ mode. The VF mode has a corresponding third outer loop controller and a second current inner loop.

[0037] like Figure 1 As shown, all logic switches are integrated and can be switched simultaneously. When the switch is in position 1, the flexible multi-state switch is in grid-connected steady-state operation mode; when the switch is in position 0, the flexible multi-state switch is in off-grid operation mode.

[0038] When the flexible multi-state switch is operating normally, one port operates in a constant DC side voltage control mode, while the other ports operate in current source mode; the control method of the flexible multi-state switch includes:

[0039] When a feeder fault is detected at any port, the port with the feeder fault is switched from the current operating mode to the voltage source mode based on a preset smooth switching control method, so as to supply power to the important loads in the fault-free area.

[0040] The preset smooth switching control method includes a state tracking control method based on adding an inertial element;

[0041] The state tracking control method based on adding an inertial element includes:

[0042] (1) Based on the preset droop adjustment model, the dq axis input voltage of the third outer loop controller is obtained;

[0043] In a specific implementation, the droop adjustment calculation formula corresponding to the droop adjustment model is:

[0044]

[0045] Where f represents the voltage frequency obtained from the droop adjustment formula, f0 represents the reference frequency, U represents the voltage amplitude obtained from the droop adjustment formula, U0 represents the reference voltage amplitude, P represents the active power of the input port converter, P0 represents the active power required by the critical load of the faulty feeder, Q represents the reactive power of the input port converter, and Q0 represents the reactive power required by the critical load of the faulty feeder; m and n are the droop adjustment coefficients, both constants. P and Q are obtained based on the voltage and current measurements of the faulty feeder.

[0046] (2) Based on the third outer loop controller, the dq axis reference value of the control model of the second current inner loop is obtained, and under the control of the preset inertial control model, the dq axis reference value of the control model of the second current inner loop is input into the second current inner loop;

[0047] The calculation formula corresponding to the voltage loop of the third outer loop controller is:

[0048]

[0049] Among them, I cd,ref I represents the d-axis reference value of the control model for the second current inner loop. cq,ref This represents the q-axis reference value of the control model for the second current inner loop. This represents the d-axis input voltage of the third outer loop controller. I represents the q-axis input voltage of the third outer loop controller. d I represents the d-axis transformation value of the three-phase current measurement of the faulty feeder. q U represents the q-axis transformation value of the three-phase current measurement of the faulty feeder. d U represents the d-axis transformation value of the three-phase voltage measurement of the faulty feeder. q This represents the q-axis transformation value of the three-phase voltage measurements of the faulty feeder; k vp and k vI These are the proportional and integral coefficients of the outer loop PI regulator in voltage source mode, respectively.

[0050] After obtaining the dq axis reference value of the control model of the second current inner loop, it is possible to use the preset inertial control model ( Figure 1 In Under the control of ), the dq axis reference value of the control model of the second current inner loop is input into the second current inner loop to prevent I cd,ref and I cq,ref The role of mutation.

[0051] (3) Based on the control model of the second current inner loop, the dq axis output voltage of the voltage source mode is obtained;

[0052] The dq axis output voltage of the voltage source mode is the same as the dq axis output voltage of the current operating mode, so as to ensure that the two operating modes have the same output voltage.

[0053] The calculation formula corresponding to the control model of the second current inner loop is as follows:

[0054]

[0055] in, This represents the d-axis component of the output voltage under constant active power control in VF mode. This represents the q-axis component of the output voltage under constant reactive power control in VF mode. Indicates constant active power. k represents constant reactive power. ip and k iI These are the proportional and integral coefficients of the second current inner loop PI regulator, respectively; I cd I represents the d-axis component of the AC side output current. cq ω represents the q-axis component of the AC side output current, ω represents the AC side voltage angular frequency, and L represents the AC side output filter inductance.

[0056] The control method of the flexible multi-state switch in this embodiment, through a state tracking control method based on adding an inertial element, tracks and controls the difference between the dq axis output voltages of the two modes before switching the working mode, and uses the output of this PI controller as the reference value of the VF mode current inner loop. This can ensure that the output voltages of the two modes are consistent at the moment of switching. At the same time, an inertial element is added after the switching, avoiding the impact caused by the jump in dq axis output voltage during switching, thereby improving the stability and reliability of the system operation.

[0057] In a specific implementation process, when a power failure occurs in the feeder, the power failure area needs FMSS to provide voltage and frequency support. Although the state tracking controller with added inertial link can achieve a smooth transition between the two control modes, it cannot achieve the same voltage phase when connected to and disconnected from the grid. Therefore, in order to reduce the impact caused by the phase difference at the moment of connection and disconnection, a phase pre-synchronization control method is set up.

[0058] Specifically, the preset smooth switching control method further includes a phase pre-synchronization control method;

[0059] The phase pre-synchronization control method includes the following steps:

[0060] (11) Obtain the grid-side voltage phase angle on the normal feeder side obtained by the phase-locked loop and the reference phase angle obtained based on the droop adjustment model;

[0061] In a specific implementation process, the voltage frequency obtained by the droop adjustment calculation formula corresponding to the above droop adjustment model can be obtained, and then the required reference phase angle can be obtained according to the voltage frequency obtained by the droop adjustment calculation formula.

[0062] (12) Determine the pre-synchronization phase angle based on the grid-side voltage phase angle of the normal feeder side and the reference phase angle.

[0063] Specifically, the grid-side voltage phase angle on the normal feeder side and the reference phase angle can be input into a preset phase angle calculation formula to calculate the pre-synchronization phase angle;

[0064] The preset phase angle calculation formula is as follows:

[0065]

[0066] Where, θ 1,ref θ represents the pre-synchronization phase angle. 1,droop The reference phase angle is represented by θ0, which represents the grid-side voltage phase angle on the normal feeder side. K P,θ and K I,θ These are the proportional and integral coefficients of the pre-synchronous regulator, respectively. θ1 represents the voltage phase angle of each port under grid-connected conditions, and θ1 is obtained from the phase-locked loop.

[0067] The flexible multi-state switch control method of this implementation can perform real-time tracking control of the voltage phase at any time when connected to or disconnected from the grid. This structure of real-time tracking control of the voltage phase reduces the process of the converter output phase approaching the grid phase before the control mode switch. It can switch the control mode at the same time as receiving the grid connection signal, making the control structure simpler and more reliable. It can also ensure that the voltage phase is basically equal to the grid-side voltage phase before and after the control mode switch, reducing the switching impact.

[0068] In a specific implementation process, if the current operating mode is U dc In the -Q mode, the control method for the flexible multi-state switch further includes:

[0069] By using a weighted adjustment method, any port that has not experienced a feeder fault is switched from current source mode to constant DC side voltage control mode.

[0070] In a specific implementation, the formula for calculating the first current inner loop d-axis reference value corresponding to the weight adjustment method is as follows:

[0071]

[0072] Among them, I d,ref This represents the d-axis reference value of the first current inner loop. I represents the d-axis reference value of the constant DC voltage control section in the first outer loop controller. d,P represents the d-axis reference value of the constant active power control section in the second outer loop controller, and i represents the weight of the d-axis reference value of the constant active power control section in the second outer loop controller. i varies from 1 to 0 at a preset rate.

[0073] It should be noted that if grid connection is required, i changes from 0 to 1 at a preset rate.

[0074] The flexible multi-state switch control method implemented in this paper avoids jumps in the current inner loop reference value by introducing weighting coefficients from the constant DC voltage control section in the first outer loop controller and the constant active power control section in the second outer loop controller, thus ensuring that the PQ mode is consistent with U. dc -Q mode control ensures a smooth transition during switching, reducing the impact on the DC bus voltage during mode switching and enabling more smooth and stable voltage switching on sensitive loads.

[0075] Figure 1 The meanings of the other characters involved are as follows:

[0076] This represents the d-axis component of the output voltage under constant active power control in PQ mode. U represents the q-axis component of the output voltage under constant active power control in PQ mode. dc,ref U dc -Q port DC voltage reference value; U dc U dc -Q port output voltage; P ref Q represents the active power reference value output by the port in PQ mode. ref This indicates the reactive power reference value output by the port in PQ mode.

[0077] In a specific implementation process, the control method of the flexible multi-state switch of the present invention can be simulated, verified, and analyzed based on the following examples:

[0078] To verify the effectiveness of the proposed flexible multi-state switch control method, this embodiment builds a system model of a three-port FMSS system in the MATLAB / Simulink environment, and tests and analyzes its dynamic operating characteristics. In this simulation model, the AC side line voltage is 380V and the frequency is 50Hz. When the feeder is working normally, the port converter VSC1 operates at U... dc -Q mode is used to stabilize DC voltage. Converters VSC2 and VSC3 operate in PQ control mode for precise regulation of active and reactive power in the feeder. When the feeder is normal, the FMSS operating mode is as follows: Figure 2 As shown in Table 1, the basic parameters of the simulation model are as follows. Figure 2This is a schematic diagram of the FMSS operating mode of the three-port FMSS system of the present invention when the feeder is normal.

[0079] Table 1

[0080]

[0081] In a specific implementation, the conventional smooth switching strategy when the feeder connected to the PQ port fails is as follows:

[0082] During the 0–0.3s interval, all three feeders are operating normally. At this time, port converter VSC1 operates in Udc-Q mode, while converters VSC2 and VSC3 operate in PQ mode. Assuming the power flowing into the FMSS is positive, then P... 1ref =20kW, P 2ref =20kW, P 3ref = -40kW. Between 0.3 and 0.45 seconds, a power outage fault occurred on the third feeder, and VSC3 switched from PQ mode to VF mode. 1ref Adjusted to 30kW, P 2ref Adjusted to 30kW, P 3ref Adjusted to -60kW, VSC3 now supplies power to critical loads on the third feeder. When a feeder connected to the PQ port fails and needs to be disconnected from the grid, the FMSS operating mode is as follows: Figure 3 As shown. The fault in the third feeder was repaired between 0.45 and 0.6 seconds, and the FMSS port converter control strategy and power reference value also returned to normal. The voltage waveform at the fault point is as follows. Figure 4 As shown. Figure 3 This is a schematic diagram of the FMSS operating mode when the feeder connected to the PQ port fails and the network needs to be disconnected. Figure 4 yes Figure 3 A schematic diagram of the voltage waveform at the corresponding fault point.

[0083] Figure 5a This is a waveform diagram of the DC-side voltage when a state follower controller is used in a three-port FMSS. Figure 5b This is a waveform diagram of the three-phase load voltage on the power failure side when a state-following controller is used in a three-port FMSS. Figure 5c This is a waveform diagram of the output active power when a three-port FMSS uses a state follower controller.

[0084] Depend on Figures 5a-5c It can be seen that during the 0.3s grid-connected to off-grid switching, the DC side voltage will fluctuate by about ±30V, and the three-phase load voltage and FMSS inflow power will fluctuate significantly and require a 0.05s adjustment time to reach a steady state value. At the 0.45s grid-connected instant, due to the phase difference between the grid-connected and off-grid conditions, a drastic change in the three-phase current and active power will occur, which will cause irreversible damage to the FMSS and other devices on the feeder.

[0085] Figure 6a This is a waveform diagram of the DC-side voltage after a three-port FMSS is implemented using a state-following controller with added inertial elements and phase pre-synchronization control. Figure 6b This is a waveform diagram of the three-phase load voltage on the power failure side after a state-following controller is used in a three-port FMSS with the addition of an inertial element and phase pre-synchronization control. Figure 6c This is a waveform diagram of the active power output after the three-port FMSS adopts a state follower controller and adds an inertial element and phase pre-synchronization control.

[0086] Depend on Figures 6a-6c It can be seen that at the moment of grid connection to off-grid in 0.3s, the fluctuation of DC side voltage value is reduced to ±5V, the fluctuation of three-phase load voltage and active power are significantly reduced, and the adjustment time required after switching is also greatly reduced to 0.01s; at the moment of grid connection to off-grid in 0.45s, the drastic change in active power is eliminated, and only 0.02s of adjustment time is needed to reach steady state value, and the fluctuation of DC voltage and three-phase load voltage are also reduced.

[0087] In a specific implementation process, U dc The standard smooth switching strategy when the feeder connected to the Q port fails is as follows:

[0088] From 0 to 0.3 seconds, the feeder operates normally, and the FMSS control mode and active power reference value are as described in Table 1 above; from 0.3 to 0.5 seconds, a power failure occurs in the feeder connected to VSC1. At this time, VSC1 is switched from U... dc - Switch from Q mode to VF mode to supply power to critical loads on the feeder, and switch VSC2 from PA mode to VF mode. dc -Q mode is used to maintain DC voltage stability. In this mode, the active power reference value is adjusted to P1. ref =-25kW, P2 ref =65kW, P3 ref = -40kW. At this time, the FMSS operating status is as follows: Figure 7 As shown. The three-phase voltage waveform at the fault point is as follows. Figure 8 As shown. Figure 7 It's U dc - A diagram illustrating the FMSS operating mode when the feeder connected to the Q port fails and the network needs to be disconnected. Figure 8 yes Figure 7 A schematic diagram of the voltage waveform at the corresponding fault point.

[0089] Figure 9a The diagram shows the DC-side voltage waveform of the FMSS after mode switching based on the flexible multi-state switch control method of this invention. Figure 9bThis is the active power waveform of FMSS after mode switching based on the flexible multi-state switch control method of the present invention.

[0090] Depend on Figures 9a-9b It can be seen that the DC voltage fluctuation at the moment of switching is within ±5V, the active power does not fluctuate significantly, and the adjustment time is within 0.01s.

[0091] It should be noted that although the steps in the above embodiments are described in a specific order, those skilled in the art will understand that in order to achieve the effects of the present invention, different steps do not necessarily have to be executed in such an order. They can be executed simultaneously (in parallel) or in other orders, and these variations are all within the scope of protection of the present invention.

[0092] Figure 10 This is a schematic diagram of the structure of an embodiment of the multi-energy fusion system of the present invention, as shown below. Figure 10 The multi-energy fusion system described in this embodiment may include a flexible multi-state switch 101, a power generation station 102, an energy storage station 103, and a load 104;

[0093] The first power grid 1 to the Nth power grid N, the power plant, the energy storage station, and the load are respectively electrically connected to the flexible multi-state switch;

[0094] The flexible multi-state switch group operates under the control method of the flexible multi-state switch in the above embodiment.

[0095] In a specific implementation process, the constraints of the multi-energy fusion system include system power balance constraints, flexible multi-state switching power constraints, energy storage capacity constraints, energy storage charging and discharging power constraints, and energy storage state of charge constraints.

[0096] The system power balance constraints include:

[0097]

[0098] Among them, P PV (t) represents the power generation capacity of the power station at time t; P VSC1 (t) represents the power exchanged between the first port of the flexible multi-state switch and the corresponding feeder at time t; P represents the sum of the power exchanged between the (N-1)th port and its respective feeder in the flexible multi-state switch at time t; ESS (t) represents the power absorbed by the energy storage station at time t; P load (t) represents the load power at time t;

[0099] The power constraint conditions for the flexible multi-state switch include:

[0100] P VSCn_min (t)≤|P VSCn (t)|≤P VSCn_max (t), n = 1, 2...N

[0101] Among them, P VSCn_min (t) represents the lower limit of the power exchanged between the nth switch and the corresponding feeder. VSCn_max (t) represents the upper limit of the power exchanged between the nth switch and the corresponding feeder;

[0102] The energy storage capacity constraints include:

[0103] S ESS_min ≤S ESS ≤S ESS_max

[0104] Among them, S ESS Indicates energy storage capacity; S ESS_min S represents the lower limit of energy storage capacity. ESS_max Indicates the upper limit of energy storage capacity;

[0105] The energy storage charging and discharging power constraints include:

[0106]

[0107] Among them, P ESS_min P represents the lower limit of the charging and discharging power of energy storage devices. ESS_max This indicates the upper limit of the charging and discharging power of the energy storage device;

[0108] The energy storage state of charge constraints include:

[0109]

[0110] Among them, SOC[P ESS+ [(t)] represents the state of charge at the start of charging, SOC[P] ESS -(t)] indicates the state of charge at the end of discharge; SOC i State of charge (SOC) represents the state of charge of the battery at time i. (i-1) η represents the state of charge of the battery at time i-1; c η represents the charging efficiency of battery energy storage. d This represents the discharge efficiency of the battery energy storage; H represents the 0-1 function of energy storage charging / discharging, which is 1 during charging and 0 during discharging.

[0111] The above-described multi-energy fusion system is an embodiment of the control method for the flexible multi-state switch used to execute the above embodiments. The technical principles, technical problems solved, and technical effects of the two are similar. Those skilled in the art can clearly understand that, for the sake of convenience and brevity, the specific working process and related descriptions of the multi-energy fusion system can be referred to the content described in the embodiment of the control method for the flexible multi-state switch, and will not be repeated here.

[0112] Those skilled in the art will understand that all or part of the processes in the method of the above embodiment of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable storage medium can include any entity or device capable of carrying the computer program code, a medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory, a random access memory, an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc. It should be noted that the content included in the computer-readable storage medium can be appropriately added or removed 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 storage medium does not include electrical carrier signals and telecommunication signals.

[0113] Furthermore, it should be understood that since the various modules are only provided to illustrate the functional units of the device of the present invention, the physical devices corresponding to these modules may be the processor itself, or a part of the processor's software, hardware, or a combination of software and hardware. Therefore, the number of modules shown in the figures is merely illustrative.

[0114] Those skilled in the art will understand that the various modules in the device can be adaptively split or combined. Such splitting or combining of specific modules will not cause the technical solution to deviate from the principles of the present invention; therefore, the technical solutions after splitting or combining will fall within the protection scope of the present invention.

[0115] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A control method for a flexible multi-state switch, characterized in that, The flexible multi-state switch has no less than 2 ports; each port operates in a DC-DC voltage control mode under grid-connected operation, a current source mode under grid-connected operation, and a voltage source mode under off-grid operation; wherein the DC-DC voltage control mode and the current source mode share a first current inner loop, and the DC-DC voltage control mode has a corresponding first outer loop controller, the current source mode has a corresponding second outer loop controller; the voltage source mode has a corresponding third outer loop controller and a second current inner loop; when the flexible multi-state switch is operating normally, one port operates in the DC-DC voltage control mode, and all other ports operate in the current source mode; the method includes: When a feeder fault is detected at any port, the port with the feeder fault is switched from the current operating mode to the voltage source mode based on a preset smooth switching control method, so as to supply power to the important loads in the fault-free area. The preset smooth switching control method includes a state tracking control method based on adding an inertial element; The state tracking control method based on adding an inertial element includes: Based on the preset droop adjustment model, the dq axis input voltage of the third outer loop controller is obtained; Based on the third outer loop controller, the dq axis reference value of the control model of the second current inner loop is obtained, and under the control of the preset inertial control model, the dq axis reference value of the control model of the second current inner loop is input into the second current inner loop. Based on the control model of the second current inner loop, the dq axis output voltage of the voltage source mode is obtained; wherein, the dq axis output voltage of the voltage source mode is the same as the dq axis output voltage of the current operating mode.

2. The control method for a flexible multi-state switch according to claim 1, characterized in that, The preset smooth switching control method also includes a phase pre-synchronization control method; The phase pre-synchronization control method includes the following steps: Obtain the grid-side voltage phase angle on the normal feeder side obtained by the phase-locked loop and the reference phase angle obtained based on the droop adjustment model; The pre-synchronization phase angle is determined based on the grid-side voltage phase angle on the normal feeder side and the reference phase angle.

3. The control method for a flexible multi-state switch according to claim 2, characterized in that, The pre-synchronization phase angle is determined based on the grid-side voltage phase angle on the normal feeder side and the reference phase angle, including: The pre-synchronization phase angle is obtained by inputting the grid-side voltage phase angle of the normal feeder side and the reference phase angle into a preset phase angle calculation formula. The preset phase angle calculation formula is as follows: Where, θ 1,ref θ represents the pre-synchronization phase angle. 1,droop The reference phase angle is represented by θ0, which represents the grid-side voltage phase angle on the normal feeder side. K P,θ and K I,θ These are the proportional and integral coefficients of the pre-synchronous regulator, respectively, and θ1 represents the voltage phase angle of each port under grid-connected conditions.

4. The control method for a flexible multi-state switch according to claim 1, characterized in that, If the current operating mode is a constant DC side voltage control mode, the method further includes: By using a weighted adjustment method, any port that has not experienced a feeder fault is switched from current source mode to constant DC side voltage control mode.

5. The control method for a flexible multi-state switch according to claim 4, characterized in that, The formula for calculating the first current inner loop d-axis reference value corresponding to the weight adjustment method is as follows: Among them, I d,ref This represents the d-axis reference value of the first current inner loop. I represents the d-axis reference value of the constant DC voltage control section in the first outer loop controller. d,P represents the d-axis reference value of the constant active power control section in the second outer loop controller, and i represents the weight of the d-axis reference value of the constant active power control section in the second outer loop controller.

6. The control method for a flexible multi-state switch according to claim 5, characterized in that, i changes from 1 to 0 at a preset rate.

7. The control method for a flexible multi-state switch according to claim 1, characterized in that, The droop adjustment calculation formula corresponding to the droop adjustment model is: Where f represents the voltage frequency obtained from the droop adjustment formula, f0 represents the reference frequency, U represents the voltage amplitude obtained from the droop adjustment formula, U0 represents the reference voltage amplitude, P represents the active power of the input port converter, P0 represents the active power required by the critical load of the faulted feeder, Q represents the reactive power of the input port converter, and Q0 represents the reactive power required by the critical load of the faulted feeder; m and n are the droop adjustment coefficients, both of which are constants.

8. The control method for a flexible multi-state switch according to claim 7, characterized in that, The calculation formula for the third outer loop controller is: Among them, I cd,ref I represents the d-axis reference value of the control model for the second current inner loop. cq,ref This represents the q-axis reference value of the control model for the second current inner loop. This represents the d-axis input voltage of the third outer loop controller. I represents the q-axis input voltage of the third outer loop controller. d I represents the d-axis transformation value of the three-phase current measurement of the faulty feeder. q U represents the q-axis transformation value of the three-phase current measurement of the faulty feeder. d U represents the d-axis transformation value of the three-phase voltage measurement of the faulty feeder. q This represents the q-axis transformation value of the three-phase voltage measurements of the faulty feeder; k vp and k vI These are the proportional and integral coefficients of the outer loop PI regulator in voltage source mode, respectively.

9. A multi-energy integrated system, characterized in that, This includes flexible multi-state switches, power generation plants, energy storage stations, and loads; The power plant, the energy storage station, and the load are each electrically connected to the flexible multi-state switch. The flexible multi-state switch operates under the control method of the flexible multi-state switch as described in any one of claims 1-8.

10. The multi-energy fusion system according to claim 9, characterized in that, The constraints of the multi-energy integrated system include system power balance constraints, flexible multi-state switching power constraints, energy storage capacity constraints, energy storage charging and discharging power constraints, and energy storage state of charge constraints. The system power balance constraints include: Among them, P PV (t) represents the power generation capacity of the power station at time t; P VSC1 (t) represents the power exchanged between the first port of the flexible multi-state switch and the corresponding feeder at time t; P represents the sum of the power exchanged between the (N-1)th port and its respective feeder in the flexible multi-state switch at time t; ESS (t) represents the power absorbed by the energy storage station at time t; P load (t) represents the load power at time t; The power constraint conditions for the flexible multi-state switch include: P VSCn_min (t)≤|P VSCn (t)|≤P VSCn_max (t),n=1,2...N Among them, P VSCn_min (t) represents the lower limit of the power exchanged between the nth switch and the corresponding feeder, P VSCn_max (t) represents the upper limit of the power exchanged between the nth switch and the corresponding feeder; The energy storage capacity constraints include: S ESS_min ≤S ESS ≤S ESS_max Among them, S ESS Indicates energy storage capacity; S ESS_min S represents the lower limit of energy storage capacity. ESS_max Indicates the upper limit of energy storage capacity; The energy storage charging and discharging power constraints include: Among them, P ESS_min P represents the lower limit of the charging and discharging power of energy storage devices. ESS_max This indicates the upper limit of the charging and discharging power of the energy storage device; The energy storage state of charge constraints include: Among them, SOC[P ESS+ [(t)] represents the state of charge at the start of charging, SOC[P] ESS- [(t)] represents the state of charge at the end of discharge; SOC i State of charge (SOC) represents the state of charge of the battery at time i. (i-1) η represents the state of charge of the battery at time i-1; c η represents the charging efficiency of battery energy storage. d The value represents the discharge efficiency of the battery energy storage; H represents the 0-1 function of energy storage charging and discharging, which is 1 when charging and 0 when discharging.

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