Virtual impedance and inertia compensation-based pre-synchronization control method for network construction type energy storage converter

Abstract

The invention belongs to the technical field of energy storage converter control, and discloses a network construction type energy storage converter pre-synchronization control method based on virtual impedance and inertia compensation, and the method comprises the following steps: 1, obtaining parameters; 2, virtual instantaneous reactive power Qv is calculated; 3, calculating an energy storage grid-connected pre-synchronization frequency compensation amount omega v; 4, calculating the voltage amplitudes of the two sides of the bus-side circuit breaker BRK1; step 5, calculating the pre-synchronization voltage compensation amount of the network construction type energy storage grid connection; 6, frequency and voltage compensation feed-in control is carried out; step 7, determining a network construction type energy storage grid-connected condition; step 8, designing a first-order inertial link to slow down jump; and step 9, quitting pre-synchronization. After the pre-synchronization control method provided by the invention is adopted, when a line has a fault, rapid and stable grid connection of network construction type energy storage can be realized, and the reliability of grid connection after the fault is recovered and the transient stability of the system are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage converter control, and in particular relates to a pre-synchronization control method for a grid-type energy storage converter based on virtual impedance and inertia compensation. Background Art

[0002] With the rapid development of renewable energy generation and the advancement of intelligent grids, energy storage systems are playing an increasingly important role in power systems. Grid-connected energy storage systems, with their ability to proactively support grid voltage and frequency, have become an indispensable key technology for scenarios with a high proportion of renewable energy access.

[0003] Traditional grid-connected energy storage pre-synchronization control methods typically assume a direct connection between the energy storage system and the grid. For voltage amplitude pre-synchronization, they fail to consider the voltage amplitude transformation caused by transformers in actual projects, resulting in systematic deviations in the voltage amplitude compensation calculated by traditional methods. For phase pre-synchronization, traditional pre-synchronization methods rely on a phase-locked loop (PLL) to track the grid phase in real time. However, in transformer-coupled scenarios, their dynamic response lag and phase step jump issues are more pronounced. When the energy storage meets grid connection requirements, traditional methods directly switch the voltage amplitude and frequency compensation to 0. The lack of a transition mechanism leads to significant jumps in the phase adjustment process, exacerbating voltage oscillations during the grid connection process and making it difficult to meet the grid connection condition determination threshold, resulting in grid connection difficulties. Summary of the Invention

[0004] The object of the present invention is to provide a pre-synchronization control method for a grid-type energy storage converter based on virtual impedance and inertia compensation to solve the above-mentioned technical problems.

[0005] To solve the above technical problems, the specific technical solution of the pre-synchronization control method of a grid-type energy storage converter based on virtual impedance and inertia compensation of the present invention is as follows:

[0006] A pre-synchronization control method for a grid-type energy storage converter based on virtual impedance and inertia compensation is based on a grid-type energy storage grid-connected architecture, which includes an energy storage DC voltage source U dc , inverter, LC filter, AC bus Bus, transformer, load Load, bus side circuit breaker BRK1, grid side circuit breaker BRK2 and line Line, the energy storage DC voltage source U dc Through an inverter and an LC filter, after being transformed by a transformer, the AC bus is connected to the power grid through a bus-side circuit breaker BRK1, a line Line, and a grid-side circuit breaker BRK2. The middle of the line is a fault point Fault. The method includes the following steps:

[0007] Step 1: parameter acquisition;

[0008] Step 2: Calculate the virtual instantaneous reactive power Q v ;

[0009] Step 3: Calculate the energy storage grid-connected pre-synchronization frequency compensation △ω v ;

[0010] Step 4: Calculate the voltage amplitude on both sides of busbar circuit breaker BRK1;

[0011] Step 5: Calculate the pre-synchronization voltage compensation for grid-connected energy storage;

[0012] Step 6: Frequency and voltage compensation feed control;

[0013] Step 7: Determine grid connection conditions for grid-connected energy storage;

[0014] Step 8: Design a first-order inertia link to slow down the jump;

[0015] Step 9: Exit pre-sync.

[0016] Furthermore, the step 1 includes the following steps:

[0017] After the fault point Fault occurs, the bus side circuit breaker BRK1 and the grid side circuit breaker BRK2 are disconnected. After a period of time, when it is detected that the fault has been completely eliminated, the grid side circuit breaker BRK2 is closed, and the instantaneous value of the phase voltage on both sides of the three-phase bus side circuit breaker BRK1 is measured using a voltmeter. The three-phase voltages on the left side of the bus side circuit breaker BRK1 are recorded as v a ,v b ,v c , the three-phase voltages on the right side of busbar circuit breaker BRK1 are recorded as v ga ,v gb ,v gc .

[0018] Furthermore, the step 2 includes the following steps:

[0019] Based on the voltage difference on both sides of busbar circuit breaker BRK1, set the virtual impedance and calculate the instantaneous value of virtual reactive power according to the following formula:

[0020]

[0021] Where R v is a virtual resistor.

[0022] Furthermore, the step 3 includes the following steps:

[0023] The -Q calculated in step 2 v The frequency compensation value Δω of the grid-connected pre-synchronization is generated by the PI controller. v , the calculation formula is as follows

[0024]

[0025] Where k p1 is the proportional coefficient of the PI controller, k i1 is the integral coefficient of the PI controller, and s is the Laplace operator.

[0026] Furthermore, step 4 includes the following steps:

[0027] Using the phase voltage value, calculate the voltage amplitude. The calculation formula is:

[0028]

[0029] Where, U is the voltage amplitude on the left side of busbar circuit breaker BRK1, U g is the voltage amplitude on the right side of busbar circuit breaker BRK1.

[0030] Furthermore, the step 5 includes the following steps:

[0031] First, calculate the voltage amplitude difference △U1 on both sides of the busbar circuit breaker BRK1 obtained in step 3:

[0032] ΔU1=UU g

[0033] Normalize △U1 to the grid-connected point voltage of the grid-connected energy storage inverter, and the normalized voltage amplitude difference ΔU2 is calculated as follows:

[0034] ΔU2=ΔU1×K1×K2

[0035] Where K1 and K2 are the transformation ratios of the transformer on the right side of the busbar and the transformer on the left side respectively. ΔU2 is fed into the PI controller to obtain the voltage regulation ΔU of the grid-connected pre-synchronization. v , the calculation formula is as follows

[0036]

[0037] Where k p2 is the proportional coefficient of the PI controller, k i2 is the integral coefficient of the PI controller, and s is the Laplace operator.

[0038] Furthermore, the step 6 includes the following steps:

[0039] Δω v and ΔU v They are respectively injected into the active-frequency loop and reactive-voltage loop of the energy storage network to achieve voltage and frequency regulation of the energy storage.

[0040] Furthermore, the step 7 includes the following steps:

[0041] The amplitude difference ΔU, phase angle difference Δθ, and frequency difference Δf of the voltage on both sides of the busbar circuit breaker BRK1 are monitored in real time. When they meet the grid connection threshold, the first-order inertia regulation link is entered.

[0042] Furthermore, the step 8 includes the following steps:

[0043] The compensation Δω at the last moment before grid connection is achieved through the first-order inertia link v , ΔU v For smooth transition, the frequency and voltage compensation in the last period before grid connection are recorded as Δω v ', ΔU v ', the calculation formula is as follows:

[0044]

[0045] Where T is the first-order inertia constant.

[0046] Furthermore, the step 9 includes the following steps:

[0047] After the pre-synchronization is completed, the frequency and voltage compensation Δω v , ΔU v Set to 0.

[0048] The pre-synchronization control method of a grid-type energy storage converter based on virtual impedance and inertia compensation of the present invention has the following advantages:

[0049] The present invention provides a pre-synchronization control method for a grid-type energy storage converter based on virtual impedance and inertia compensation. When calculating the voltage amplitude compensation amount, the transformer ratio is used to reduce the voltage amplitude, thereby eliminating the voltage amplitude deviation caused by the transformer ratio. By designing virtual impedance, calculating instantaneous virtual reactive power, and controlling virtual reactive power, phase pre-synchronization is achieved. This method can achieve dynamic rapid response without relying on a phase-locked loop, and smoothly transitions the frequency and voltage amplitude compensation amounts before grid connection through a first-order inertia link, effectively suppressing phase jumps, and enabling the energy storage system to achieve impact-free grid connection in a transformer connection scenario. The grid connection impact current is reduced to less than 1.05 times the rated value, significantly improving the reliability of grid connection after fault recovery and the transient stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a topological diagram of the grid-connected energy storage;

[0051] Figure 2 This is a pre-synchronization flow chart of the present invention;

[0052] Figure 3 This is a diagram of a grid-connected energy storage model according to an embodiment of the present invention;

[0053] Figure 4 This is a schematic diagram of a grid-type energy storage system;

[0054] Figure 5 This is the grid-connected pre-synchronization control block diagram for the grid-connected energy storage system;

[0055] Figure 6 This is the active power-frequency modulation loop control block diagram;

[0056] Figure 7 This is the control block diagram of the reactive-voltage regulation loop;

[0057] Figure 8 is the grid-connected point voltage U for grid-connected energy storage pcc Phase A simulation result diagram;

[0058] Figure 9 is the grid-connected point current of the grid-connected energy storage I pcc Phase A simulation result diagram;

[0059] Figure 10 Output active power for grid-type energy storage;

[0060] Figure 11 is the voltage on both sides of BRK1 v a ,v ga Phase A simulation result diagram;

[0061] Figure 12 This is the simulation result diagram of the voltage phase angle on both sides of BRK1. DETAILED DESCRIPTION

[0062] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a pre-synchronization control method of a grid-type energy storage converter based on virtual impedance and inertia compensation of the present invention in conjunction with the accompanying drawings.

[0063] like Figure 1 As shown in the figure, the typical grid-connected architecture of grid-type energy storage includes the energy storage DC voltage source U dc , inverter, LC filter, AC bus Bus, transformer, load Load, bus side circuit breaker BRK1, grid side circuit breaker BRK2 and line Line, energy storage DC voltage source U dc Through the inverter and LC filter, after transformer transformation, it is connected to the AC bus Bus, and the AC bus Bus is transformed by the transformer and connected to the grid through the bus side circuit breaker BRK1, line Line and grid side circuit breaker BRK2. dc is the energy storage DC voltage; L g 、C gBus is the AC bus; Load is the load; BRK1 and BRK2 are the bus side circuit breaker and grid side circuit breaker respectively; Line is the line, and Fault is the line fault point.

[0064] The present invention proposes a pre-synchronization control method for a grid-type energy storage converter based on virtual impedance and inertia compensation. When calculating the voltage amplitude compensation amount, the transformer ratio is used to reduce the voltage amplitude to eliminate the voltage amplitude deviation caused by the transformer ratio; at the same time, the nonlinear relationship between virtual reactive power and frequency is used to convert phase pre-synchronization into a frequency dynamic adjustment problem, thereby indirectly achieving phase synchronization. On this basis, the compensation amount is smoothly transitioned through a first-order inertia link, so that the adjustment process at the moment of grid connection is transformed from sudden change to gradual convergence, completely solving the transient shock problem caused by the jump of compensation amount in traditional methods. This method does not rely on complex phase tracking algorithms, and can achieve rapid and smooth grid connection of the energy storage system in transformer connection scenarios, significantly improving the power supply reliability in fault recovery scenarios.

[0065] The flowchart of pre-synchronization is as follows Figure 2 As shown, the specific steps include:

[0066] Step 1: Obtain parameters

[0067] After the fault point Fault of line Line occurs, the bus side circuit breaker BRK1 and the grid side circuit breaker BRK2 are disconnected. After a period of time, when it is detected that the fault has been completely eliminated, the grid side circuit breaker BRK2 is closed, and the instantaneous value of the phase voltage on both sides of the three-phase bus side circuit breaker BRK1 is measured using a voltmeter. The three-phase voltage on the left side of the bus side circuit breaker BRK1 (respectively recorded as v a ,v b ,v c ), the three-phase voltage on the right side of busbar circuit breaker BRK1 (respectively denoted as v ga ,v gb ,v gc ).

[0068] Step 2: Calculate the virtual instantaneous reactive power Q v

[0069] Based on the voltage difference on both sides of busbar circuit breaker BRK1, set the virtual impedance and calculate the instantaneous value of virtual reactive power according to the following formula:

[0070]

[0071] Where R v is a virtual resistor, which can be set to 1Ω for ease of calculation;

[0072] Step 3: Calculate the energy storage grid-connected pre-synchronization frequency compensation △ω v

[0073] The -Q calculated in step 2 v The frequency compensation value Δω of the grid-connected pre-synchronization is generated by the PI controller. v , the calculation formula is as follows

[0074]

[0075] Where k p1 is the proportional coefficient of the PI controller, k i1 is the integral coefficient of the PI controller, and s is the Laplace operator.

[0076] Step 4: Calculate the voltage amplitude on both sides of busbar circuit breaker BRK1

[0077] Using the phase voltage value, calculate the voltage amplitude. The calculation formula is:

[0078]

[0079] Where, U is the voltage amplitude on the left side of busbar circuit breaker BRK1, U g is the voltage amplitude on the right side of busbar circuit breaker BRK1.

[0080] Step 5: Calculate the pre-synchronization voltage compensation for grid-connected energy storage

[0081] First, calculate the voltage amplitude difference △U1 on both sides of the busbar circuit breaker BRK1 obtained in step 3:

[0082] ΔU1=UU g

[0083] Considering that the two transformers will transform the voltage amplitude, it is necessary to normalize △U1 to the grid-connected point voltage of the grid-connected energy storage inverter. The calculation formula for the normalized voltage amplitude difference ΔU2 is as follows:

[0084] ΔU2=ΔU1×K1×K2

[0085] Where K1 and K2 are the transformation ratios of the transformer on the right side of the busbar and the transformer on the left side respectively. ΔU2 is fed into the PI controller to obtain the voltage regulation ΔU of the grid-connected pre-synchronization. v , the calculation formula is as follows

[0086]

[0087] Where k p2 is the proportional coefficient of the PI controller, k i2 is the integral coefficient of the PI controller, and s is the Laplace operator.

[0088] Step 6: Frequency and Voltage Compensation Feedback Control

[0089] Δω v and ΔU v They are respectively injected into the active-frequency loop and reactive-voltage loop of the energy storage network to achieve voltage and frequency regulation of the energy storage.

[0090] Step 7: Determine grid-connected conditions for grid-connected energy storage

[0091] The amplitude difference ΔU, phase angle difference Δθ, and frequency difference Δf of the voltage on both sides of the busbar circuit breaker BRK1 are monitored in real time. When they meet the grid connection threshold (such as ΔU < 7%, Δθ < 10°, Δf < 0.2Hz), the first-order inertia regulation link is entered.

[0092] Step 8: Design a first-order inertia link to slow down the jump

[0093] The compensation amount (Δω) at the last moment before grid connection is calculated by the first-order inertia link. v , ΔU v ) for smooth transition, and the frequency and voltage compensation in the last period before grid connection are respectively recorded as Δω v ', ΔU v ', the calculation formula is as follows.

[0094]

[0095] Where T is the first-order inertia constant.

[0096] Step 9: Exit Pre-Sync

[0097] After the pre-synchronization is completed, the frequency and voltage compensation Δω v , ΔU v Set to 0.

[0098] Example:

[0099] To illustrate the application example of the present invention, the following simulation example is constructed based on the PSCAD / EMTDC simulation platform: Figure 3 The grid-connected energy storage system model is shown in Figure 1. Figure 4 The grid-connected pre-synchronization control block diagram of the grid-connected energy storage system is shown in Figure 5 As shown, the VSG active power-frequency loop control block diagram is as follows Figure 6 As shown, the VSG reactive-voltage loop is as follows Figure 7 The main parameters of the simulation model are shown in Table 1.

[0100] Table 1 Simulation parameters of grid-connected energy storage model

[0101]

[0102] During the initial two seconds, the grid-connected energy storage system maintained stable grid-connected operation using a virtual synchronous generator (VSG) control strategy, outputting 100kW of active power. At t = 2.0s, a three-phase short-circuit fault (fault resistance 2Ω) occurred on the busbar side and persisted for 150ms before clearing. At t = 2.13s, the protection system triggered the opening of BRK1 and BRK2 (the circuit breaker has an inherent opening time of 100ms, and the protection action delay is 30ms), transitioning the energy storage system to off-grid island operation. At t = 2.5s, BRK2 was closed to reconnect the grid, and at t = 2.52s, the grid-connected control system received the pre-synchronization command. The switches of the grid-type active-frequency loop and reactive-voltage loop are switched from (1) to (2) for pre-synchronization. The voltage amplitude and phase angle at both ends of BRK1 are adjusted to keep synchronization. At t = 2.59s, after the voltage amplitude and phase angle difference on both sides of BRK1 reaches the grid-connected standard, the energy storage receives the grid-connected signal, and the active loop and reactive loop switches are switched from (2) to (3) to perform first-order inertia compensation output. After the grid-connected signal is sent for 4T (T = 0.015s), since the frequency and voltage compensation amounts are only less than 20% of the frequency compensation amount before grid connection, which is already small enough, t = 2.65, BRK1 is closed, the s switch is switched back to the position (1), and the pre-synchronization ends.

[0103] Energy storage grid connection point (grid connection point such as Figure 4 PCC shows the voltage U pcc A phase Figure 8 As shown, the grid-connected current I pcc A phase Figure 9 As shown, the energy storage output active power is as follows Figure 10 As shown, the voltage across BRK1 is phase A v a ,v ga like Figure 11 As shown, the phase angles A and A at both ends of BRK1 are g like Figure 12 As shown, the grid side phase angle A is kept at 0.

[0104] Depend on Figure 8 and Figure 9 It can be seen that when a three-phase short-circuit fault occurs at t = 2.0s, the fault current increases rapidly, causing the voltage to drop. At t = 2.13s, due to the disconnection of circuit breakers BRK1 and BRK2, the grid-connected control system switches from grid-connected operation to off-grid operation, and the grid-connected point voltage recovers to 0.99pu within 20ms. The grid-connected point current decays from the fault state to the off-grid steady state. At t = 2.52s, pre-synchronization begins, and the grid-connected point voltage and current remain stable. At t = 2.65s, BRK1 closes, and the energy storage system transitions from off-grid to grid-connected. The voltage remains stable, and the current increases smoothly from the off-grid steady-state value to the grid-connected steady-state value, verifying the present invention's ability to suppress transient overvoltage and overcurrent surges.

[0105] Depend on Figure 10 It can be seen that during the grid-connected steady-state phase (t = 0-2.0s), the energy storage continuously outputs 100kW of rated active power. After BRK1 is disconnected, the active power gradually decreases from 100kW to 50kW. At 2.13s, the moment BRK1 is disconnected, the active power briefly fluctuates before returning to the steady-state value of 50kW, which persists for a period of time. After pre-synchronization is completed, the energy storage transitions from off-grid to grid-connected, and the output active power gradually increases from 50kW to 100kW. At 2.65s, BRK1 is closed, resulting in a brief fluctuation before gradually rising to the steady-state value of 100kW.

[0106] Depend on Figure 11 and Figure 12 It can be seen that after the pre-synchronization algorithm starts at t=2.52s, the voltage v on the left side of BRK1 abc Gradually with the right voltage v gabc The voltage on the bus side of BRK1 is basically consistent with the voltage on the grid side at around 2.58s. The phase angle difference on both sides of BRK1 gradually decreases from 50° before pre-synchronization to 0, verifying the effectiveness of the present invention in phase regulation.

[0107] In summary, after adopting the pre-synchronization control method proposed in the present invention, when a line fault occurs, the grid-connected energy storage can be quickly and stably connected to the grid.

[0108] It will be understood that the present invention is described by way of some embodiments, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A pre-synchronization control method for a grid-type energy storage converter based on virtual impedance and inertia compensation, based on a grid-type energy storage grid-connected architecture, the architecture includes an energy storage DC voltage source U dc , inverter, LC filter, AC bus Bus, transformer, load Load, bus side circuit breaker BRK1, grid side circuit breaker BRK2 and line Line, the energy storage DC voltage source U dc Through the inverter and LC filter, after transformer transformation, it is connected to the AC bus Bus, and the AC bus Bus is connected to the grid through the bus side circuit breaker BRK1, line Line and grid side circuit breaker BRK2 after transformer transformation. The characteristics are: The method comprises the following steps: Step 1: parameter acquisition; Step 2: Calculate the virtual instantaneous reactive power Q v ; Step 3: Calculate the energy storage grid-connected pre-synchronization frequency compensation △ω v ; Step 4: Calculate the voltage amplitude on both sides of busbar circuit breaker BRK1; Step 5: Calculate the pre-synchronization voltage compensation for grid-connected energy storage; Step 6: Frequency and voltage compensation feed control; Step 7: Determine grid connection conditions for grid-connected energy storage; Step 8: Design a first-order inertia link to slow down the jump; Step 9: Exit pre-sync.

2. The pre-synchronization control method of a grid-type energy storage converter based on virtual impedance and inertia compensation according to claim 1 is characterized in that: The step 1 comprises the following steps: After the fault point Fault of line Line occurs, the bus side circuit breaker BRK1 and the grid side circuit breaker BRK2 are disconnected. After a period of time, when it is detected that the fault has been completely eliminated, the grid side circuit breaker BRK2 is closed, and the instantaneous value of the phase voltage on both sides of the three-phase bus side circuit breaker BRK1 is measured using a voltmeter. The three-phase voltages on the left side of the bus side circuit breaker BRK1 are recorded as v a ,v b ,v c , the three-phase voltages on the right side of busbar circuit breaker BRK1 are recorded as v ga ,v gb ,v gc .

3. The pre-synchronization control method of a grid-type energy storage converter based on virtual impedance and inertia compensation according to claim 1 is characterized in that: The step 2 comprises the following steps: Based on the voltage difference on both sides of busbar circuit breaker BRK1, set the virtual impedance and calculate the instantaneous value of virtual reactive power according to the following formula: Where R v is a virtual resistor.

4. The pre-synchronization control method of a grid-type energy storage converter based on virtual impedance and inertia compensation according to claim 1 is characterized in that: The step 3 comprises the following steps: The -Q calculated in step 2 v The frequency compensation value Δω of the grid-connected pre-synchronization is generated by the PI controller. v , the calculation formula is as follows Where k p1 is the proportional coefficient of the PI controller, k i1 is the integral coefficient of the PI controller, and s is the Laplace operator.

5. The pre-synchronization control method of a grid-type energy storage converter based on virtual impedance and inertia compensation according to claim 1 is characterized in that: The step 4 comprises the following steps: Using the phase voltage value, calculate the voltage amplitude. The calculation formula is: Where, U is the voltage amplitude on the left side of busbar circuit breaker BRK1, U g is the voltage amplitude on the right side of busbar circuit breaker BRK1.

6. The pre-synchronization control method of a grid-type energy storage converter based on virtual impedance and inertia compensation according to claim 1 is characterized in that: The step 5 comprises the following steps: First, calculate the voltage amplitude difference △U1 on both sides of the busbar circuit breaker BRK1 obtained in step 3: ΔU1=UU g Normalize △U1 to the grid-connected point voltage of the grid-connected energy storage inverter, and the normalized voltage amplitude difference ΔU2 is calculated as follows: ΔU2=ΔU1×K1×K2 Where K1 and K2 are the transformation ratios of the transformer on the right side of the busbar and the transformer on the left side respectively. ΔU2 is fed into the PI controller to obtain the voltage regulation ΔU of the grid-connected pre-synchronization. v , the calculation formula is as follows Where k p2 is the proportional coefficient of the PI controller, k i2 is the integral coefficient of the PI controller, and s is the Laplace operator.

7. The pre-synchronization control method of a grid-type energy storage converter based on virtual impedance and inertia compensation according to claim 1 is characterized in that: The step 6 comprises the following steps: Δω v and ΔU v They are respectively injected into the active-frequency loop and reactive-voltage loop of the energy storage network to achieve voltage and frequency regulation of the energy storage.

8. The pre-synchronization control method of a grid-type energy storage converter based on virtual impedance and inertia compensation according to claim 1 is characterized in that: The step 7 comprises the following steps: The amplitude difference ΔU, phase angle difference Δθ, and frequency difference Δf of the voltage on both sides of the busbar circuit breaker BRK1 are monitored in real time. When they meet the grid connection threshold, the first-order inertia regulation link is entered.

9. The pre-synchronization control method of a grid-type energy storage converter based on virtual impedance and inertia compensation according to claim 1, characterized in that: The step 8 comprises the following steps: The compensation Δω at the last moment before grid connection is achieved through the first-order inertia link v , ΔU v For smooth transition, the frequency and voltage compensation in the last period before grid connection are recorded as Δω v ', ΔU v ', the calculation formula is as follows: Where T is the first-order inertia constant.

10. The pre-synchronization control method of a grid-type energy storage converter based on virtual impedance and inertia compensation according to claim 1, characterized in that: The step 9 comprises the following steps: After the pre-synchronization is completed, the frequency and voltage compensation Δω v , ΔU v Set to 0.

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