Amplitude limiting method and system for peak current of constructed energy storage power grid

Abstract

The invention belongs to the field of network construction energy storage, and particularly relates to a peak current amplitude limiting method and system for a network construction type energy storage power grid. The method comprises the steps that according to a dq-axis current instruction output by a network construction control model, an abc-axis three-phase current instruction is obtained through conversion; obtaining a three-phase virtual beta-axis current instruction according to the abc-axis three-phase current instruction; according to the abc-axis three-phase current instruction and the three-phase virtual beta-axis current instruction, the amplitude of the three-phase current instruction is obtained; obtaining a peak current instruction according to the maximum value in the amplitudes of the three-phase current instruction; and when the peak current instruction is greater than a set amplitude limiting value, dividing the current instruction of the network construction control model by the peak current instruction to obtain a current instruction after amplitude limiting so as to perform network construction control. The method can ensure that the peak current can be accurately limited within the set amplitude limiting value during the grid construction energy storage low-voltage ride-through period, is not influenced by a three-phase current imbalance strategy, is high in applicability, does not need to wait for at least one current period, and is higher in amplitude limiting speed.

Description

Technical Field

[0001] This invention belongs to the field of grid-based energy storage, specifically relating to a peak current limiting method and system for grid-based energy storage grids. Background Technology

[0002] In the field of grid-based energy storage, it is usually necessary to limit the output three-phase current during low-voltage ride-through. Existing current-limiting methods for grid-based energy storage mainly include the following:

[0003] 1) Power command current limiting method: This method indirectly limits the output current by limiting the power command. However, this method has the problem of slow dynamic response, which means that the current cannot be limited to the set value for a period of time after a grid fault. It can only be used for three-phase current balance strategy, not for three-phase current imbalance strategy.

[0004] 2) Circular current limiting method: This method calculates the amplitude of the dq-axis current command. When the amplitude exceeds a set value, the dq-axis current command is divided by the amplitude and then multiplied by a set overload factor to limit the current to the set value. This method does not have a response speed issue, but it can only be used for three-phase current balance strategies and not for three-phase current imbalance strategies.

[0005] 3) Virtual impedance current limiting method: During the low-voltage period, the transient current is limited by the input of virtual impedance. This scheme does not have the problem of response speed, but it can only be used for three-phase current balance strategy and cannot be used for three-phase current imbalance strategy.

[0006] For example, Chinese invention patent application CN115579944A provides a grid-connected energy storage control system and method with self-current limiting protection. This system includes a current measurement module, a voltage measurement module, an actual power calculation module, a PLL phase-locked loop module, a grid-connected control strategy and modulation wave generation module, a grid-following control strategy and modulation wave generation module, a current comparison module, and a selection and modulation module. This invention enables the grid-connected inverter to operate stably in both normal and three-phase fault states, employing different control strategies for each state. This effectively prevents excessive line current from affecting system stability, and its two switching modes ensure stable, safe, and reliable system operation during switching. Under normal operation, the effective value of the three-phase current on the line is less than the limited current, and the three-phase inverter is controlled by the grid-connected control strategy. After a three-phase fault occurs on the line, the system needs to switch to a grid-following control strategy. The pre-synchronization of the PLL phase-locked loop phase ensures that the phase is seamless after the switch, and the current reference values ​​of the dq axis in the grid-following current control module are switched to the corresponding current limit values ​​to prevent the line current from being too large. Summary of the Invention

[0007] The purpose of this invention is to provide a peak current limiting method and system for grid-type energy storage grids, which solves the problem that existing peak current limiting methods for grid-type energy storage grids are difficult to apply to strategies for three-phase current imbalance.

[0008] To achieve the above objectives, the present invention provides a peak current limiting method for a grid-based energy storage network, comprising:

[0009] Based on the dq-axis current command output by the network control model, the abc-axis three-phase current command is obtained.

[0010] Based on the three-phase current command, a three-phase virtual β-axis current command is obtained; then, based on the three-phase current command and the three-phase virtual β-axis current command, the amplitude of the three-phase current command is obtained.

[0011] The peak current command is obtained based on the maximum value among the amplitudes of the three-phase current commands. When the peak current command is greater than the set limit value, the current command of the grid control model is divided by the peak current command to obtain the current command after limiting, so as to perform grid control.

[0012] Furthermore, it also includes:

[0013] The reactive power limit value is obtained by multiplying the positive sequence voltage amplitude of the grid-type energy storage network by the set limit value, and is used to limit the reactive power command of the grid-type energy storage network.

[0014] Furthermore, it also includes:

[0015] The square root of the difference between the positive sequence voltage amplitude of the grid-type energy storage network multiplied by the set limit value and the square root of the reactive power command of the grid-type energy storage network after the limit is obtained, and the active power limit value is used to limit the active power command of the grid-type energy storage network.

[0016] Furthermore, the method for obtaining the three-phase virtual β-axis current command based on the three-phase current command includes: obtaining the three-phase virtual β-axis current command based on the result of a 90° phase shift of the three-phase current command.

[0017] Furthermore, the method for obtaining the amplitude of the three-phase current command based on the three-phase current command and the three-phase virtual β-axis current command includes: calculating the root mean square of the current command of each phase in the three-phase current command and the virtual β-axis current command of the corresponding phase in the three-phase virtual β-axis current command respectively, to obtain the amplitude of the three-phase current command.

[0018] Furthermore, the set limit value is determined based on the upper limit of the output current of the grid-type energy storage network during the low-voltage ride-through period of the grid-type energy storage.

[0019] Furthermore, the method of dividing the current command of the network control model by the peak current command to obtain the current command after limiting includes: dividing the current command in the dq coordinate system of the network control model by the peak current command to obtain the current command in the dq coordinate system after limiting.

[0020] Furthermore, the three-phase current commands are phase-shifted by 90° respectively through an all-pass filter.

[0021] The beneficial effects of the above-described peak current limiting method for grid-type energy storage power grids of the present invention include:

[0022] This method fully considers the phenomenon that when the grid voltage is unbalanced and drops, the peak current of the three-phase current command output by the grid-type control strategy, when transformed into the three-phase abc coordinate system, will inevitably exceed the limit. By using the maximum amplitude obtained from the abc axis three-phase current command and the three-phase virtual β axis current command, it is determined whether there is a risk of the peak current exceeding the set limit. Once such a current over-limit risk exists, the current command is directly divided by the maximum amplitude to limit the current command of the grid-type control model. This ensures that during the low-voltage ride-through of grid-type energy storage, the peak current can be accurately limited to within the set limit, unaffected by the three-phase current imbalance strategy. It has strong applicability, and the amplitude of the three-phase current command is calculated using the three-phase virtual β axis current command. Compared with the existing technology that calculates the amplitude through the effective value, it does not require waiting for at least one current cycle, resulting in faster limiting speed.

[0023] The present invention also provides a peak current limiting system for a grid-based energy storage grid, comprising a processor storing executable program instructions, which are executed to implement the above-described peak current limiting method for a grid-based energy storage grid, including:

[0024] Based on the dq-axis current command output by the network control model, the abc-axis three-phase current command is obtained.

[0025] Based on the three-phase current command, a three-phase virtual β-axis current command is obtained; then, based on the three-phase current command and the three-phase virtual β-axis current command, the amplitude of the three-phase current command is obtained.

[0026] The peak current command is obtained based on the maximum value among the amplitudes of the three-phase current commands. When the peak current command is greater than the set limit value, the current command of the grid control model is divided by the peak current command to obtain the current command after limiting, so as to perform grid control.

[0027] Furthermore, it also includes:

[0028] The reactive power limit value is obtained by multiplying the positive sequence voltage amplitude of the grid-type energy storage network by the set limit value, and is used to limit the reactive power command of the grid-type energy storage network.

[0029] Furthermore, it also includes:

[0030] The square root of the difference between the positive sequence voltage amplitude of the grid-type energy storage network multiplied by the set limit value and the square root of the reactive power command of the grid-type energy storage network after the limit is obtained, and the active power limit value is used to limit the active power command of the grid-type energy storage network.

[0031] Furthermore, the method for obtaining the three-phase virtual β-axis current command based on the three-phase current command includes: obtaining the three-phase virtual β-axis current command based on the result of a 90° phase shift of the three-phase current command.

[0032] Furthermore, the method for obtaining the amplitude of the three-phase current command based on the three-phase current command and the three-phase virtual β-axis current command includes: calculating the root mean square of the current command of each phase in the three-phase current command and the virtual β-axis current command of the corresponding phase in the three-phase virtual β-axis current command respectively, to obtain the amplitude of the three-phase current command.

[0033] Furthermore, the set limit value is determined based on the upper limit of the output current of the grid-type energy storage network during the low-voltage ride-through period of the grid-type energy storage.

[0034] Furthermore, the method of dividing the current command of the network control model by the peak current command to obtain the current command after limiting includes: dividing the current command in the dq coordinate system of the network control model by the peak current command to obtain the current command in the dq coordinate system after limiting.

[0035] Furthermore, the three-phase current commands are phase-shifted by 90° respectively through an all-pass filter.

[0036] The technical solution of the peak current limiting system for grid-type energy storage grid described above can achieve the same beneficial effects as the peak current limiting method for grid-type energy storage grid described above. Attached Figure Description

[0037] Figure 1 This is an example diagram of the main circuit topology of the grid-type energy storage system to which the peak current limiting method of the grid-type energy storage network of the present invention is applicable;

[0038] Figure 2 This is a block diagram of the grid-type control strategy applicable to the peak current limiting method of the energy storage grid in the implementation of the peak current limiting method of the grid-type energy storage grid of the present invention;

[0039] Figure 3This is a principle block diagram of the peak current limiting method for grid-type energy storage grids in the implementation of the present invention.

[0040] Figure 4a This is an example diagram of the output voltage and grid-connected current waveforms obtained from the simulation of the peak current limiting method for grid-connected energy storage grids in the implementation method of the present invention.

[0041] Figure 4b This is an example diagram of the locally expanded waveform during a grid voltage fault obtained from the simulation of the peak current limiting method for the grid-type energy storage network in the implementation method of the present invention.

[0042] Figure 4c This is an example diagram of the three-phase current command waveform output by the VSG model obtained from the simulation of the peak current limiting method for grid-type energy storage grids in the implementation of the peak current limiting method for grid-type energy storage grids of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0044] Implementation Method of Peak Current Limiting Method for Grid-Based Energy Storage Network

[0045] This embodiment presents a technical solution for peak current limiting in a grid-type energy storage grid. This method uses abc-axis three-phase current commands and three-phase virtual β-axis current commands to directly limit the current commands of the grid control model. It is not affected by the three-phase current imbalance strategy, has strong applicability, and does not require waiting for at least one current cycle, resulting in fast limiting speed.

[0046] The method includes:

[0047] According to the dq-axis current command i output by the network control model d_ref and i q_ref The transformation yields the three-phase current command i for the abc axis. a_ref i b_ref and i c_ref ;

[0048] According to the three-phase current command i of axis abc a_ref i b_ref and i c_ref The three-phase virtual β-axis current command i is obtained. a_ref_β i b_ref_β and i c_ref_β Then, according to the three-phase current command i of the abc axis... a_ref i b_ref and i c_refand the three-phase virtual β-axis current command i a_ref_β i b_ref_β and i c_ref_β The amplitude i of the three-phase current command is obtained. am_ref i bm_ref i cm_ref ;

[0049] Based on the amplitude i of the three-phase current command am_ref i bm_ref i cm_ref The maximum value in the range is used to obtain the peak current command i. abcm_ref_max Peak current command i abcm_ref_max When the current command exceeds the set limit, the current command of the network control model is divided by the peak current command to obtain the current command after limiting, so as to perform network control.

[0050] Therefore, this method fully considers the phenomenon that when the grid voltage imbalance drops, the peak current of the three-phase current command output by the grid-type control strategy, when transformed into the three-phase abc coordinate system, will inevitably exceed the limit value (for example, during the low-voltage ride-through of grid-type energy storage, it is usually necessary to ensure that the output current during the fault does not exceed 3 times the rated value, so the limit value is set to 3 times the rated current value). By using the maximum amplitude obtained from the abc axis three-phase current command and the three-phase virtual β axis current command, it is determined whether there is a risk of the peak current exceeding the set limit value (i.e., the peak current command is greater than the set limit value). Once such a current over-limit risk exists, the current command is directly divided by the limit value of the maximum amplitude value to limit the current command of the grid-type control model, thereby ensuring that the peak current can be accurately limited to within the set limit value during the low-voltage ride-through of grid-type energy storage, unaffected by the three-phase current imbalance strategy. It has strong applicability, and the amplitude of the three-phase current command is calculated using the three-phase virtual β axis current command. Compared with the existing technology that calculates the amplitude through the effective value, it does not require waiting for at least one current cycle, and the limiting speed is faster.

[0051] In this embodiment, the set limit value is determined based on the upper limit of the output current of the grid-type energy storage network during the low-voltage ride-through period. The grid-type energy storage main circuit topology to which this method is applicable is referenced. Figure 1 The block diagram for network-type control strategies is as follows: Figure 2 It adopts virtual synchronous machine control; Figure 2 In this context, ω represents the angular velocity of the virtual synchronous generator; ω0 represents the rated angular velocity of the virtual synchronous generator; ω g ω represents the grid voltage angular velocity; J represents the moment of inertia of the virtual synchronous generator; T represents the moment of inertia of the generator. m T e These represent the mechanical torque and electromagnetic torque of the virtual synchronous generator, respectively; D is the damping coefficient; R and L are the stator resistance and stator inductance of the virtual synchronous generator, respectively; Ed E q u d u q i d i q These represent the three-phase internal electromotive force, terminal voltage, and stator current dq-axis components of the virtual synchronous generator, respectively; θ is the output electrical angle of the virtual synchronous generator.

[0052] In one specific embodiment, the upper limit of the output current of the grid-type energy storage network is three times the rated current value. Therefore, the set limit value is the upper limit of the output current of the grid-type energy storage network, which is three times the rated current value, to ensure that the fault protection is not triggered.

[0053] Furthermore, in this embodiment, the method for obtaining the three-phase virtual β-axis current command based on the abc-axis three-phase current command includes: obtaining the three-phase virtual β-axis current command based on the result of a 90° phase shift of each of the abc-axis three-phase current commands. Specifically, the three-phase current command i a_ref i b_ref i c_ref Phase shift by 90° respectively to obtain i a_ref_β i b_ref_β i c_ref_β This can be achieved using an all-pass filter, as shown in the following example:

[0054]

[0055] In the formula, ω0 is the rated angular velocity of the virtual synchronous generator; s is the Laplace variable.

[0056] The methods for obtaining the amplitude of the three-phase current command based on the abc-axis three-phase current command and the three-phase virtual β-axis current command include: calculating the current command i for each phase in the abc-axis three-phase current command. a_ref i b_ref i c_ref The virtual β-axis current command i corresponding to the phase in the three-phase virtual β-axis current command respectively a_ref_β i b_ref_β i c_ref_β The root mean square of i is obtained by finding i respectively. a_ref and i a_ref_β Root mean square, i b_ref and i b_ref_β Root mean square, i c_ref and i c_ref_β The root mean square of the three-phase current command, i, is obtained. am_ref i bm_ref i cm_ref .

[0057] The method of dividing the current command of the grid control model by the peak current command to obtain the limited current command includes: dividing the current command i in the dq coordinate system of the grid control model... d_ref i q_ref Divide by the peak current command i respectively abcm_ref_max The current command i in the dq coordinate system after limiting is obtained. d_ref_lim i q_ref_lim .

[0058] In other implementations, the current command i in the abc coordinate system of the network control model can also be used. a_ref i b_ref i c_ref Divide by the peak current command i respectively abcm_ref_max The current command i in the abc coordinate system after limiting is obtained. a_ref_lim i b_ref_lim i c_ref_lim This is used to obtain the current command after limiting, and the principle is the same as limiting the current command in the dq coordinate system, so it will not be elaborated here.

[0059] The limit value is set to 3 times the rated current value, i.e., 3I. n Then when i abcm_ref_max >3I n At that time, the current command i in the dq coordinate system will be... d_ref i q_ref Divide by the peak current command i respectively abcm_ref_max This will give you the current command i in the dq coordinate system after the amplitude is limited. d_ref_lim i q_ref_lim :

[0060]

[0061] The block diagram for the above peak current limiting control is shown below. Figure 3 . Figure 3 in,i a_ref i b_ref and i c_ref For three-phase current command; i a_ref_β i b_ref_β and i c_ref_β To obtain the virtual β-axis current command through the all-pass filter aPF; i am_ref i bm_ref i cm_ref The amplitude of the three-phase current command; i abcm_ref_max This represents the maximum value of the three-phase current command, i.e., the peak current command; i d_ref i q_ref The VSG model outputs current commands in the dq coordinate system; d_ref_lim i q_ref_limOutput the current command in the dq coordinate system for the limited VSG model.

[0062] In addition, in this embodiment, to achieve rapid reactive power tracking, the method further includes:

[0063] The reactive power limit value Q is obtained by multiplying the positive sequence voltage amplitude of the grid-type energy storage network by the set limit value. _ref_lim This is used to limit the reactive power command of the grid-type energy storage network. A specific expression example is as follows:

[0064]

[0065] In the formula I n For the rated current, u pm This represents the positive sequence amplitude of the grid voltage.

[0066] Similarly, considering the rapid tracking of active power, this method also includes:

[0067] The result of multiplying the positive sequence voltage amplitude of the grid-type energy storage network by the set limit value and the reactive power command Q of the grid-type energy storage network after the limit is obtained. ref The square difference is then taken as the square root to obtain the active power limiting value. This is used to limit the active power command of the grid-type energy storage network. A specific expression example is as follows:

[0068]

[0069] in, This means that the positive sequence voltage amplitude of the grid-type energy storage network is multiplied by the set limit value.

[0070] With the above-mentioned reactive and active power limiting methods, as long as the active and reactive power can be tracked quickly, it can be ensured that the network will still be in operation during the low-voltage period.

[0071] Figures 4a-4c The figure shows the simulation results of the peak current limiting method for grid-type energy storage grids in this embodiment. Figure 4a The waveforms are output voltage and grid-connected current, with time on the horizontal axis. Figure 4b The waveform during a power grid voltage fault is shown in partial expansion. The vertical axis is in V and the horizontal axis is time. Figure 4c Output the three-phase current command waveform for the VSG model, with the vertical axis in units of pu and the horizontal axis representing time. The simulation conditions are: grid-connected energy storage rated power of 50kW, grid short-circuit ratio SCR=3, a 1pu active power command is given at 0.2s, the impedance between phases A and B drops to 0.16pu between 0.5-0.7s, and the impedance is removed at 0.7s. Figure 4a , 4bIt can be seen that, except for the current exceeding 3pu (306A) during the low-voltage breakdown instant, the peak current during the fault steady-state period is 3pu. Figure 4c It is evident that the peak value of the three-phase current command output by the VSG model was consistently limited to 3 pu throughout the entire fault period.

[0072] Implementation of Peak Current Limiting System for Grid-Based Energy Storage Networks

[0073] This embodiment provides a technical solution for a peak current limiting system for a grid-based energy storage network, including a processor containing executable program instructions. These instructions are used to execute a peak current limiting method for a grid-based energy storage network, which includes:

[0074] According to the dq-axis current command i output by the network control model d_ref and i q_ref The transformation yields the three-phase current command i for the abc axis. a_ref i b_ref and i c_ref ;

[0075] According to the three-phase current command i of axis abc a_ref i b_ref and i c_ref The three-phase virtual β-axis current command i is obtained. a_ref_β i b_ref_β and i c_ref_β Then, according to the three-phase current command i of the abc axis... a_ref i b_ref and i c_ref and the three-phase virtual β-axis current command i a_ref_β i b_ref_β and i c_ref_β The amplitude i of the three-phase current command is obtained. am_ref i bm_ref i cm_ref ;

[0076] Based on the amplitude i of the three-phase current command am_ref i bm_ref i cm_ref The maximum value in the range is used to obtain the peak current command i. abcm_ref_max Peak current command i abcm_ref_max When the current command exceeds the set limit, the current command of the network control model is divided by the peak current command to obtain the current command after limiting, so as to perform network control.

[0077] Therefore, this method fully considers the phenomenon that when the grid voltage imbalance drops, the peak current of the three-phase current command output by the grid-type control strategy, when transformed into the three-phase abc coordinate system, will inevitably exceed the limit value (for example, during the low-voltage ride-through of grid-type energy storage, it is usually necessary to ensure that the output current during the fault does not exceed 3 times the rated value, so the limit value is set to 3 times the rated current value). By using the maximum amplitude obtained from the abc axis three-phase current command and the three-phase virtual β axis current command, it is determined whether there is a risk of the peak current exceeding the set limit value (i.e., the peak current command is greater than the set limit value). Once such a current over-limit risk exists, the current command is directly divided by the limit value of the maximum amplitude value to limit the current command of the grid-type control model, thereby ensuring that the peak current can be accurately limited to within the set limit value during the low-voltage ride-through of grid-type energy storage, unaffected by the three-phase current imbalance strategy. It has strong applicability, and the amplitude of the three-phase current command is calculated using the three-phase virtual β axis current command. Compared with the existing technology that calculates the amplitude through the effective value, it does not require waiting for at least one current cycle, and the limiting speed is faster.

[0078] In this embodiment, the set limit value is determined based on the upper limit of the output current of the grid-type energy storage network during the low-voltage ride-through period. The grid-type control strategy applicable to this method for grid-type energy storage employs virtual synchronous machine control. In a specific embodiment, the upper limit of the output current of the grid-type energy storage network is three times the rated current value. Therefore, the set limit value is taken as the upper limit of the output current of the grid-type energy storage network, i.e., three times the rated current value, to ensure that fault protection is not triggered.

[0079] Furthermore, in this embodiment, the method for obtaining the three-phase virtual β-axis current command based on the abc-axis three-phase current command includes: obtaining the three-phase virtual β-axis current command based on the result of a 90° phase shift of each of the abc-axis three-phase current commands. Specifically, the three-phase current command i a_ref i b_ref i c_ref Phase shift by 90° respectively to obtain i a_ref_β i b_ref_β i c_ref_β This can be achieved using an all-pass filter, as shown in the following example:

[0080]

[0081] In the formula, ω0 is the rated angular velocity of the virtual synchronous generator; s is the Laplace variable.

[0082] The methods for obtaining the amplitude of the three-phase current command based on the abc-axis three-phase current command and the three-phase virtual β-axis current command include: calculating the current command i for each phase in the abc-axis three-phase current command. a_ref i b_refi c_ref The virtual β-axis current command i corresponding to the phase in the three-phase virtual β-axis current command respectively a_ref_β i b_ref_β i c_ref_β The root mean square of i is obtained by finding i respectively. a_ref and i a_ref_β Root mean square, i b_ref and i b_ref_β Root mean square, i c_ref and i c_ref_β The root mean square of the three-phase current command, i, is obtained. am_ref i bm_ref i cm_ref .

[0083] The method of dividing the current command of the grid control model by the peak current command to obtain the limited current command includes: dividing the current command i in the dq coordinate system of the grid control model... d_ref i q_ref Divide by the peak current command i respectively abcm_ref_max The current command i in the dq coordinate system after limiting is obtained. d_ref_lim i q_ref_lim .

[0084] In other implementations, the current command i in the abc coordinate system of the network control model can also be used. a_ref i b_ref i c_ref Divide by the peak current command i respectively abcm_ref_max The current command i in the abc coordinate system after limiting is obtained. a_ref_lim i b_ref_lim i c_ref_lim This is used to obtain the current command after limiting, and the principle is the same as limiting the current command in the dq coordinate system, so it will not be elaborated here.

[0085] The limit value is set to 3 times the rated current value, i.e., 3I. n Then when i abcm_ref_max >3I n At that time, the current command i in the dq coordinate system will be... d_ref i q_ref Divide by the peak current command i respectively abcm_ref_max This will give you the current command i in the dq coordinate system after the amplitude is limited. d_ref_lim i q_ref_lim :

[0086]

[0087] In addition, in this embodiment, to achieve rapid reactive power tracking, the method further includes:

[0088] The reactive power limit value Q is obtained by multiplying the positive sequence voltage amplitude of the grid-type energy storage network by the set limit value. _ref_lim This is used to limit the reactive power command of the grid-type energy storage network. A specific expression example is as follows:

[0089]

[0090] In the formula I n For the rated current, u pm This represents the positive sequence amplitude of the grid voltage.

[0091] Similarly, considering the rapid tracking of active power, this method also includes:

[0092] The result of multiplying the positive sequence voltage amplitude of the grid-type energy storage network by the set limit value and the reactive power command Q of the grid-type energy storage network after the limit is obtained. ref The square difference is then taken as the square root to obtain the active power limiting value. This is used to limit the active power command of the grid-type energy storage network. A specific expression example is as follows:

[0093]

[0094] in, This means that the positive sequence voltage amplitude of the grid-type energy storage network is multiplied by the set limit value.

[0095] With the above-mentioned reactive and active power limiting methods, as long as the active and reactive power can be tracked quickly, it can be ensured that the network will still be in operation during the low-voltage period.

[0096] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or explanatory of the principles of the present invention, and do not constitute a limitation thereof.

Claims

1. A method for peak current limiting in a grid-type energy storage power grid, characterized in that, include: According to the output of the network control model dq Axis current command, transformed to obtain abc Shaft three-phase current command; According to the three-phase current command ， Obtain three-phase virtual β Shaft current command; then based on the aforementioned three-phase current command and three-phase virtual... β The shaft current command is used to obtain the amplitude of the three-phase current command. The peak current command is obtained based on the maximum value among the amplitudes of the three-phase current commands. When the peak current command is greater than the set limit value, the current command of the grid control model is divided by the peak current command to obtain the current command after limiting, so as to perform grid control.

2. The peak current limiting method for grid-type energy storage power grids according to claim 1, characterized in that, Also includes: The reactive power limit value is obtained by multiplying the positive sequence voltage amplitude of the grid-type energy storage network by the set limit value, and is used to limit the reactive power command of the grid-type energy storage network.

3. The peak current limiting method for grid-type energy storage power grids according to claim 2, characterized in that, Also includes: The square root of the difference between the positive sequence voltage amplitude of the grid-type energy storage network multiplied by the set limit value and the square root of the reactive power command of the grid-type energy storage network after the limit is obtained, and the active power limit value is used to limit the active power command of the grid-type energy storage network.

4. The peak current limiting method for grid-type energy storage power grids according to any one of claims 1-3, characterized in that, Based on the three-phase current command, a three-phase virtual three-phase current is obtained. β The method of shaft current command includes: obtaining three-phase virtual current commands by shifting each phase by 90° based on the three-phase current commands. β Shaft current command.

5. The peak current limiting method for grid-type energy storage power grids according to any one of claims 1-3, characterized in that, Based on the three-phase current command and the three-phase virtual β The methods for obtaining the amplitude of the three-phase current command include: calculating the current command of each phase in the three-phase current command and the three-phase virtual current command separately. β Virtual phase corresponding to the shaft current command β The root mean square of the shaft current command is used to obtain the amplitude of the three-phase current command.

6. The peak current limiting method for grid-type energy storage power grids according to any one of claims 1-3, characterized in that, The set limit value is determined based on the upper limit of the output current of the grid-type energy storage network during the low voltage ride-through period of the grid-type energy storage.

7. The peak current limiting method for grid-type energy storage power grids according to any one of claims 1-3, characterized in that, The method of dividing the current command of the network control model by the peak current command to obtain the current command after limiting includes: dividing the current command in the dq coordinate system of the network control model by the peak current command to obtain the current command in the dq coordinate system after limiting.

8. The peak current limiting method for grid-type energy storage power grids according to claim 4, characterized in that, The three-phase current commands are phase-shifted by 90° respectively and implemented through an all-pass filter.

9. A peak current limiting system for a grid-based energy storage network, comprising a processor, wherein the processor stores executable program instructions, characterized in that, The executable program instructions are executed to implement the peak current limiting method for grid-type energy storage grids as described in any one of claims 1-8.

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