Power grid system, control device of energy storage converter, control mode switching method and device of energy storage converter, and medium

Abstract

The invention discloses a power grid system, a control device of an energy storage converter, a control mode switching method and device of the energy storage converter and a medium, and the switching method comprises the steps: obtaining a first switching instruction in real time when the energy storage converter works in a grid following mode; the first switching instruction comprises an instruction for switching from a network following mode to a network construction mode; when a first switching instruction is obtained, determining a pre-synchronization signal of a network construction mode according to a first parameter of the energy storage converter in a network following mode; the first parameter at least comprises virtual impedance; the pre-synchronization signal at least comprises a synchronization angle, a current control ring reference initial value, a modulation voltage initial value and a voltage control ring reference initial value; and switching the working mode of the energy storage converter from a network following mode to a network construction mode according to the pre-synchronization signal. According to the technical scheme, the flexibility of loop design is improved, the electric energy quality in different modes is considered, the grid-connected stability is improved, the rapidity and stability of control mode switching are improved, and the power fluctuation in the switching process is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid control, and in particular to a power grid system, a control device for an energy storage converter, and a control mode switching method, device and medium for the energy storage converter. Background Art

[0002] An energy storage converter system is a device responsible for realizing the bidirectional energy conversion between a battery and a power grid, and plays a key role in application scenarios such as responding to power grid dispatching, suppressing power fluctuations, and off-grid power supply.

[0003] The control modes of the energy storage converter system are divided into grid-following control and grid-forming control. The grid-following control mode has stable characteristics under strong grid conditions, but has poor stability under weak grid conditions. The grid-forming control mode has stronger stability under weak grid conditions, but has disadvantages such as slow power regulation speed and poor stability under strong grid conditions. Therefore, the grid-following / grid-forming hybrid control mode will help to combine the advantages of both and improve the grid connection characteristics of the energy storage converter under different conditions.

[0004] However, the existing grid-following / grid-forming mode switching of the energy storage converter has the following problems: 1) When switching from the grid-following mode to the grid-forming mode, virtual impedance is not included, so the power coupling effect is large during grid-forming operation, which is not conducive to the stable operation of the power grid system; 2) The pre-synchronization scheme adopted in the existing technology needs to introduce an integrator and additionally adjust control parameters, resulting in a high complexity of the energy storage converter system. Summary of the Invention

[0005] The present invention provides a power grid system, a control device for an energy storage converter, and a control mode switching method, device and medium for the energy storage converter to solve the problems existing in the prior art, so that the grid-following and grid-forming modes adopt independent current control loops respectively, and virtual impedance is added during pre-synchronization, which helps to improve the flexibility of loop design, can take into account the power quality under different modes, and is also conducive to improving grid connection stability, thereby improving the rapidity and stability of control mode switching and reducing the power fluctuation during the switching process.

[0006] In a first aspect, the present invention provides a control mode switching method for an energy storage converter, including:

[0007] When the energy storage converter operates in the grid-following mode, a first switching instruction is obtained in real time; the first switching instruction includes an instruction to switch from the grid-following mode to the grid-forming mode;

[0008] When the first switching instruction is obtained, determine the pre-synchronization signal in the grid-forming mode according to the first parameters of the energy storage converter in the grid-following mode; the first parameters include at least virtual impedance; the pre-synchronization signal includes at least a synchronization angle, an initial value of the current control loop reference, an initial value of the modulation voltage, and an initial value of the voltage control loop reference;

[0009] According to the pre-synchronization signal, switch the operating mode of the energy storage converter from the grid-following mode to the grid-forming mode.

[0010] Optionally, determining the pre-synchronization signal in the grid-forming mode according to the first parameters of the energy storage converter in the grid-following mode includes:

[0011] According to the first parameters, determine the synchronization angle and the initial value of the current control loop reference in the grid-forming mode;

[0012] According to the first parameters and the synchronization angle, determine the initial value of the modulation voltage and the initial value of the voltage control loop reference.

[0013] Optionally, the first parameters further include the angle value of the grid-following phase-locked loop, the power command, and the grid-side voltage amplitude; according to the first parameters, determining the synchronization angle and the initial value of the current control loop reference includes:

[0014] According to the angle value of the grid-following phase-locked loop, determine the initial value of the synchronization angle;

[0015] According to the power command, the grid-side voltage, and the virtual impedance, determine the power angle and the grid-forming current reference in the grid-forming mode;

[0016] According to the initial value of the synchronization angle and the power angle in the grid-forming mode, determine the synchronization angle in the grid-forming mode;

[0017] According to the grid-forming current reference, determine the initial value of the current control loop reference.

[0018] Optionally, the first parameters further include the grid-side voltage amplitude and the modulation voltage of the grid-following phase-locked loop; according to the first parameters and the synchronization angle, determining the initial value of the modulation voltage and the initial value of the voltage control loop reference includes:

[0019] According to the synchronization angle and the grid-side voltage, determine the voltage feedforward value of the grid-forming current control loop;

[0020] According to the modulation voltage in the grid-following mode and the feedforward value of the grid-forming current control loop, determine the initial value of the modulation voltage;

[0021] According to the synchronization angle, determine the feedback value of the grid-forming current control loop;

[0022] Determine the initial reference value of the voltage control loop according to the feedback value of the grid-forming current control loop, the grid-side voltage, and the virtual impedance.

[0023] Optionally, the virtual impedance is determined according to the filter impedance of the energy storage converter and the strength of the power grid.

[0024] Optionally, according to the pre-synchronization signal, switching the operating mode of the energy storage converter from the grid-following mode to the grid-forming mode includes:

[0025] Switch the operating mode of the energy storage converter to the grid-forming mode, and use the pre-synchronization signal as the initial value of the grid-forming mode;

[0026] Control the grid-forming power synchronization control loop, the grid-forming voltage control loop, and the grid-forming current control loop to operate in a closed loop.

[0027] Optionally, the control mode switching method of the energy storage converter further includes:

[0028] When the energy storage converter operates in the grid-following mode, compensate for harmonic current and reactive power, and control the phase-locked loop and the grid-following current control loop to operate in a closed loop.

[0029] In a second aspect, the present invention provides a control mode switching device for an energy storage converter, including:

[0030] An instruction acquisition module, configured to, when the energy storage converter operates in the grid-following mode, acquire a first switching instruction in real time; the first switching instruction includes an instruction to switch from the grid-following mode to the grid-forming mode;

[0031] A pre-synchronization module, configured to, when the first switching instruction is acquired, determine a pre-synchronization signal for the grid-forming mode according to the first parameters of the energy storage converter in the grid-following mode; the first parameters at least include the virtual impedance; the pre-synchronization signal at least includes a synchronization angle, an initial reference value of the current control loop, an initial value of the modulation voltage, and an initial reference value of the voltage control loop;

[0032] A switching module, configured to switch the operating mode of the energy storage converter from the grid-following mode to the grid-forming mode according to the pre-synchronization signal.

[0033] In a third aspect, the present invention provides a control device for an energy storage converter, including: a grid-following control module, a grid-forming control module, a pre-synchronization module, and a switching module;

[0034] The pre-synchronization module is respectively connected to the grid-following control module and the switching module; the switching module is further connected to the grid-following control module and the grid-forming control module;

[0035] The grid-following control module is used to make the energy storage converter operate in the grid-following mode;

[0036] The grid-forming control module is used to make the energy storage converter operate in the grid-forming mode;

[0037] The pre-synchronization module is used to obtain a first parameter of the energy storage converter in the grid-following mode, and determine a pre-synchronization signal for the grid-forming mode according to the first parameter; the first parameter at least includes virtual impedance; the pre-synchronization signal at least includes a synchronization angle, an initial value of a current control loop reference, an initial value of a modulation voltage, and an initial value of a voltage control loop reference;

[0038] The switching module is used to obtain the pre-synchronization signal according to a first switching instruction, send the pre-synchronization signal to the grid-forming control module, and control the energy storage converter to operate in the grid-forming mode.

[0039] Optionally, the grid-following control module includes: a phase-locked loop and a grid-following current control loop.

[0040] Optionally, the grid-following control module further includes: a harmonic compensation loop and a reactive power compensation loop.

[0041] Optionally, the grid-forming control module includes: a power synchronization control loop, a voltage control loop, and a current control loop.

[0042] In a fourth aspect, the present invention provides a power grid system, including: a memory and a processor, the memory stores a computer program, and is characterized in that when the processor executes the computer program, the control mode switching method of the energy storage converter described in any one of the above is implemented.

[0043] In a fifth aspect, the present invention provides a computer-readable storage medium, the computer-readable storage medium stores computer instructions, and the computer instructions are used to implement the control mode switching method of the energy storage converter described in any one of the above when executed by a processor.

[0044] In the technical solution of the present invention, when the energy storage converter operates in the grid-following mode and obtains a first switching instruction including switching from the grid-following mode to the grid-forming mode, a pre-synchronization signal for the grid-forming mode is determined according to the first parameters of the energy storage converter in the grid-following mode, where the first parameters at least include virtual impedance, and the pre-synchronization signal at least includes a synchronization angle, an initial value of the current control loop reference, an initial value of the modulation voltage, and an initial value of the voltage control loop reference. And according to the pre-synchronization signal, the operating mode of the energy storage converter is switched from the grid-following mode to the grid-forming mode, so that the grid-following mode and the grid-forming mode of the energy storage converter adopt independent current control loops respectively, and virtual impedance is added during pre-synchronization, which helps to improve the flexibility of loop design, and can take into account the power quality in different modes, and at the same time is beneficial to improving grid connection stability, thereby improving the rapidity and stability of control mode switching and reducing the power fluctuation during the switching process.

[0045] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0047] Figure 1 It is a structural block diagram of an energy storage converter system;

[0048] Figure 2 It is a flowchart of a method for switching the control mode of an energy storage converter provided in Embodiment 1 of the present invention;

[0049] Figure 3 It is a flowchart of a method for switching the control mode of an energy storage converter provided in Embodiment 2 of the present invention;

[0050] Figure 4 It is a structural schematic diagram of an energy storage converter provided in an embodiment of the present invention;

[0051] Figure 5 It is a flowchart of a method for switching the control mode of an energy storage converter provided in Embodiment 3 of the present invention;

[0052] Figure 6 It is a structural schematic diagram of a device for switching the control mode of an energy storage converter provided in Embodiment 4 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0053] To enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0054] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here.

[0055] Figure 1 It is a structural block diagram of an energy storage converter system. Refer to Figure 1 As shown, the energy storage converter system mainly includes a battery system, a main circuit module, a power grid or a load (AC side), a control module (DSP controller), a filtering and protection circuit (including an LC filtering circuit, a circuit breaker, etc.), a communication and monitoring module (BMS / EMS interaction), etc. When the energy storage converter system is connected to the grid for operation, the control module can control the bidirectional flow of energy between the battery system (DC side) and the power grid system (AC side).

[0056] When the energy storage converter system is in the grid-following mode, it operates in the current source mode. It detects the grid voltage and frequency through a phase-locked loop and uses this as a reference to control the current injected into the grid to achieve power regulation. When the energy storage converter system is in the grid-forming mode, it operates in the voltage source mode. It autonomously generates a stable voltage and frequency through a power synchronization control loop, so that power supply can still be restored after the grid collapses. However, the grid-following control mode has poor stability under weak grid conditions, and the grid-forming mode has deficiencies such as slow power regulation speed and poor stability under strong grid conditions.

[0057] Currently, a grid-following / grid-forming hybrid control mode is adopted to solve the above problems. In the grid-following / grid-forming hybrid control mode, the switching type control is the simplest way. Its technical key points are: adopting the grid-following control method under strong grid conditions and the grid-forming control method under weak grid conditions, and switching different control methods according to the grid conditions to achieve complementary advantages.

[0058] However, there are many problems in the grid-following / grid-forming mode switching of the existing energy storage converters, resulting in unstable operation or complex structure of the energy storage converter system.

[0059] To solve the above problems, when the energy storage converter operates in the grid-following mode and obtains a first switching instruction including switching from the grid-following mode to the grid-forming mode, the energy storage converter determines a pre-synchronization signal for the grid-forming mode based on the first parameters in the grid-following mode. The first parameters at least include virtual impedance, and the synchronization signal at least includes a synchronization angle, an initial reference value of the current control loop, an initial value of the modulation voltage, and an initial reference value of the voltage control loop. According to the pre-synchronization signal, the operating mode of the energy storage converter is switched from the grid-following mode to the grid-forming mode, so that the grid-following mode and the grid-forming mode of the energy storage converter adopt independent current control loops, and virtual impedance is added during pre-synchronization, which helps to improve the flexibility of loop design, can take into account the power quality in different modes, and is beneficial to improving grid connection stability, thereby improving the rapidity and stability of control mode switching and reducing power fluctuations during the switching process.

[0060] The above is the core idea of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0061] Embodiment 1

[0062] Figure 2 The flowchart of a control mode switching method for an energy storage converter provided in Embodiment 1 of the present invention is applicable to the situation where the energy storage converter switches from the grid-following mode to the grid-forming mode. This method can be executed by a control mode switching device of the energy storage converter. The control mode switching device of the energy storage converter can be implemented in the form of hardware and / or software, and the control mode switching device of the energy storage converter can be configured in a controller of a power grid system. As Figure 2 shown, the method includes:

[0063] S110. When the energy storage converter operates in the grid-following mode, obtain a first switching instruction in real time.

[0064] Among them, the first switching instruction includes an instruction to switch from the grid-following mode to the grid-forming mode.

[0065] The operating modes of the energy storage converter provided in this embodiment include the grid-following mode and the grid-forming mode, and the operating mode of the energy storage converter can be switched between the grid-following mode and the grid-forming mode. Exemplarily, the grid-following mode is adopted under strong grid conditions, and the grid-forming mode is adopted under weak grid conditions, so as to achieve complementary advantages.

[0066] S120. When the first switching instruction is obtained, determine a pre-synchronization signal for the grid-forming mode according to the first parameters of the energy storage converter in the grid-following mode.

[0067] Among them, the first parameter includes at least a virtual impedance. The pre-synchronization signal refers to the initial values of each parameter in the grid-forming mode when the operating mode of the energy storage converter is switched to the grid-forming mode. The pre-synchronization signal includes at least a synchronization angle, an initial value of the current control loop reference, an initial value of the modulation voltage, and an initial value of the voltage control loop reference.

[0068] In an alternative embodiment, the virtual impedance can be determined according to the filter impedance of the energy storage converter and the strength of the power grid. In an exemplary embodiment, the range of the virtual impedance is between 0.5 mH and 2 mH.

[0069] In an alternative embodiment, the first parameter further includes other relevant parameters in the grid-following mode, such as the angle value of the grid-following phase-locked loop, the power command, and the grid-side voltage amplitude, etc. The initial values of each parameter when the operating mode of the energy storage converter is switched to the grid-forming mode are determined by the relevant parameters in the grid-following mode, so as to enable the rapidity and smoothness of the mode switching of the energy storage converter, reduce the power fluctuation during the mode switching process, and achieve seamless switching between the grid-following mode and the grid-forming mode.

[0070] In an alternative embodiment, the first parameter of the energy storage converter in the grid-following mode is obtained in real time. When the first switching instruction is obtained, the first parameter at the previous moment is called, and the pre-synchronization signal of the grid-forming mode is determined according to the first parameter, so as to make the switching of the operating mode of the energy storage converter faster. In another alternative embodiment, when the first switching instruction is obtained, the first parameter of the energy storage converter in the grid-following mode is obtained, and the pre-synchronization signal of the grid-forming mode is determined according to the obtained first parameter, so as to reduce the computing amount of the power grid system, which is beneficial to reducing the operating load of the power grid system itself.

[0071] S130. According to the pre-synchronization signal, switch the operating mode of the energy storage converter from the grid-following mode to the grid-forming mode.

[0072] Specifically, when the operating mode of the energy storage converter is switched from the grid-following mode to the grid-forming mode, the initial values of each parameter in the grid-forming mode are determined by the pre-synchronization signal.

[0073] In this embodiment, when the energy storage converter operates in the grid-following mode and obtains a first switching instruction including switching from the grid-following mode to the grid-forming mode, a pre-synchronization signal for the grid-forming mode is determined according to the first parameters of the energy storage converter in the grid-following mode, where the first parameters include at least virtual impedance, and the pre-synchronization signal includes at least a synchronization angle, an initial value of the reference of the current control loop, an initial value of the modulation voltage, and an initial value of the reference of the voltage control loop. And according to the pre-synchronization signal, the operating mode of the energy storage converter is switched from the grid-following mode to the grid-forming mode, so that the grid-following mode and the grid-forming mode of the energy storage converter adopt independent current control loops respectively, and virtual impedance is added during pre-synchronization, which helps to improve the flexibility of loop design, can take into account the power quality in different modes, and is beneficial to improving grid connection stability, thereby improving the rapidity and stability of control mode switching and reducing the power fluctuation during the switching process.

[0074] Embodiment 2

[0075] Figure 3 The flowchart of a control mode switching method for an energy storage converter provided in Embodiment 2 of the present invention is shown. On the basis of the above embodiment, this embodiment further adds steps of how to determine the pre-synchronization signal for the grid-forming mode according to the first parameters of the energy storage converter in the grid-following mode, and how to switch the operating mode of the energy storage converter from the grid-following mode to the grid-forming mode according to the pre-synchronization signal. Refer to Figure 3 As shown, the method specifically includes:

[0076] S210. When the energy storage converter operates in the grid-following mode, compensate for harmonic current and reactive power, and control the phase-locked loop and the grid-following current control loop to work in a closed loop.

[0077] Among them, the first switching instruction includes an instruction to switch from the grid-following mode to the grid-forming mode.

[0078] Figure 4 The structural schematic diagram of a control device for an energy storage converter provided in an embodiment of the present invention is shown. Refer to Figure 4 As shown, the grid-following control and grid-forming control of the energy storage converter are independent current control loops respectively. The grid-following control module for realizing grid-following control includes a phase-locked loop and a grid-following current control loop. The phase-locked loop outputs a phase-locked loop angle θ g,abc according to the grid-side voltage u PLL , and the grid-following current control loop outputs the modulation voltages u ref , Q ref , current compensation, and the phase-locked loop angle θ PLL injected into the grid, and outputs the modulation voltages u ma1 , u mb1 , u mc1, thus realizing the closed-loop control of the grid-following mode. The grid-forming control module for realizing the grid-forming mode includes a power synchronization control loop, a grid-forming voltage control loop, and a grid-forming current control loop. The power synchronization control loop outputs the electromotive force E and the synchronization angle θ according to the power command P ref 、Q ref and the grid-side power. The grid-forming voltage control loop outputs the current references I dref 、I qref according to the electromotive force E and the synchronization angle θ output by the power synchronization control loop. The grid-forming current control loop outputs the modulation voltages u ma2 、u mb2 、u mc2 injected into the power grid according to the synchronization angle θ and the current references I dref 、I qref , thus realizing the closed-loop control of the grid-forming mode; among them, the grid-side power is determined by the power calculation module according to the grid-side current i o,abc and the grid-side voltage u g,abc .

[0079] S220. Obtain the first switching instruction in real time.

[0080] Continue to refer to Figure 4 As shown, the energy storage converter further includes a pre-synchronization module. The pre-synchronization module determines the pre-synchronization signal according to the first parameter. Among them, the pre-synchronization signal includes the synchronization angle θ, the initial value I dref 、I qref of the current control loop reference, the initial values u ma 、u mb 、u mc of the modulation voltage, and the initial values U dref 、U qref of the voltage control loop reference.

[0081] In an optional embodiment, the energy storage converter further includes a switching module. The switching module is used to switch the working mode of the energy storage converter and output the modulation voltage output by the corresponding mode to the pulse width modulation module SVPWM, so that the pulse width modulation module SVPWM controls the on and off of each switch in the inverter module, thereby realizing the energy conversion between DC and AC.

[0082] S230. When the first switching instruction is obtained, determine the synchronization angle and the initial value of the current control loop reference according to the first parameter.

[0083] Among them, to ensure the stability of the power grid system during the switching process of the working mode of the energy storage converter, the angle value θ PLL of the grid-following phase-locked loop can be used as the initial value of the synchronization angle in the grid-forming mode. At the same time, since the power angle δ and the initial value of the current control loop reference in the grid-forming mode are related to the power command P ref 、the grid-side voltage amplitude U gm and the virtual impedance Lv related to the like, so that the synchronization angle and the initial reference value of the current control loop in the grid-forming mode can be determined according to the angle value θ of the grid-connected phase-locked loop PLL , power command P ref , grid-side voltage amplitude U gm and virtual impedance L v , and can determine the synchronization angle and the initial reference value of the current control loop in the grid-forming mode.

[0084] S240. Determine the initial value of the modulation voltage and the initial reference value of the voltage control loop according to the first parameter and the synchronization angle.

[0085] Specifically, when the energy storage converter operates in the grid-connected mode, it compensates for harmonic current and reactive power, and controls the phase-locked loop and the grid-connected current control loop to work in a closed loop. At the same time, it continuously obtains the first switching instruction. When the first switching instruction is obtained, according to the first parameter, it determines the synchronization angle and the initial reference value of the current control loop in the grid-forming mode, and according to the synchronization angle and the first parameter, it determines the initial value of the modulation voltage and the initial reference value of the voltage control loop, thereby improving the accuracy of the pre-synchronization signal.

[0086] S250. Switch the working mode of the energy storage converter to the grid-forming mode, and use the pre-synchronization signal as the initial value of the grid-forming mode.

[0087] S260. Control the grid-forming power synchronization control loop, the grid-forming voltage control loop, and the grid-forming current control loop to work in a closed loop.

[0088] In this embodiment, when the energy storage converter operates in the grid-connected mode, it compensates for harmonic current and reactive power, and controls the phase-locked loop and the grid-connected current control loop to work in a closed loop. At the same time, it continuously obtains the first switching instruction. When the first switching instruction is obtained, according to the first parameter, it determines the synchronization angle and the initial reference value of the current control loop in the grid-forming mode, and according to the synchronization angle and the first parameter, it determines the initial value of the modulation voltage and the initial reference value of the voltage control loop. Then, it switches the working mode of the energy storage converter to the grid-forming mode, and uses the pre-synchronization signal as the initial value of the grid-forming mode, and controls the grid-forming power synchronization control loop, the grid-forming voltage control loop, and the grid-forming current control loop to work in a closed loop, thereby improving the accuracy of the pre-synchronization signal, and further improving the stability of the working mode switching of the energy storage converter.

[0089] Embodiment III

[0090] Figure 5 The flowchart of a control mode switching method for an energy storage converter provided in Embodiment III of the present invention. On the basis of the above embodiment, this embodiment further adds steps of how to determine the synchronization angle and the initial reference value of the current control loop in the grid-forming mode according to the first parameter, and how to determine the initial value of the modulation voltage and the initial reference value of the voltage control loop according to the synchronization angle and the first parameter. Referring to Figure 5 as shown, the method specifically includes:

[0091] S310. When the energy storage converter operates in the grid-following mode, obtain the first switching instruction in real time.

[0092] Among them, the first switching instruction includes an instruction to switch from the grid-following mode to the grid-forming mode.

[0093] S320. When the first switching instruction is obtained, determine the initial value of the synchronization angle according to the angle value of the grid-following phase-locked loop.

[0094] In an alternative embodiment, the angle value θ of the grid-following phase-locked loop PLL is used as the initial value θ0 of the synchronization angle of the power synchronization control loop in the grid-forming mode.

[0095] S330. Determine the power angle and the grid-forming current reference in the grid-forming mode according to the power instruction, the grid-side voltage, and the virtual impedance.

[0096] In an alternative embodiment, according to the power instruction P ref , the grid-side voltage, and the virtual impedance L v , determine the power angle in the grid-forming mode from the first formula, where the first formula is as follows:

[0097]

[0098] Among them, U gm is the amplitude of the grid-side voltage, and ω is the angular frequency of the power grid system.

[0099] In an alternative embodiment, according to P ref , the grid-side voltage, and the virtual impedance L v , determine the grid-forming current reference from the second formula, where the second formula is as follows:

[0100]

[0101] S340. Determine the synchronization angle in the grid-forming mode according to the initial value of the synchronization angle and the power angle in the grid-forming mode.

[0102] In an alternative embodiment, the sum of the initial value of the synchronization angle θ0 and the power angle δ in the grid-forming mode is used as the synchronization angle θ in the grid-forming mode.

[0103] S350. Determine the initial value of the current control loop reference according to the grid-forming current reference.

[0104] Among them, the initial value of the current control loop reference is the initial value output by the grid-forming voltage control loop.

[0105] In an alternative embodiment, the grid-forming current references I dr , I qr are used as the initial value of the current control loop reference Idref0 、I qref0 。

[0106] S360. Determine the voltage feed - forward value of the grid - forming current control loop based on the synchronization angle θ and the grid - side voltage.

[0107] In an optional embodiment, based on the synchronization angle and the grid - side voltage, determine the voltage feed - forward value of the grid - forming current control loop according to the third formula, where the third formula is as follows:

[0108]

[0109] where, u gα and u gβ are the α - axis and β - axis components of the grid - side voltage respectively, u gd and u gq are the d - axis and q - axis components of the grid - side voltage respectively, U fd and U fq are the voltage feed - forward values of the grid - forming current control loop, K fd and K fq are the d - axis and q - axis voltage feed - forward coefficients respectively.

[0110] S370. Determine the initial value of the modulation voltage based on the modulation voltage in the grid - following mode and the feed - forward value of the grid - forming current control loop.

[0111] In an optional embodiment, based on the modulation voltage in the grid - following mode and the feed - forward value of the grid - forming current control loop, determine the initial value of the modulation voltage according to the fourth formula, where the fourth formula is as follows:

[0112]

[0113]

[0114] where, u ma1 、u mb1 、u mc1 are the three - phase modulation voltages in the grid - following mode respectively, u md1 、u mq1 are the components of the modulation voltage on the d - axis and q - axis, u fd1 、u fq1 are the voltage feed - forward values of the current control loop in the grid - following mode, u md2 、u mq2 are the components of the modulation voltage in the grid - forming mode on the d - axis and q - axis, u ma2 、u mb2 、u mc2 are the initial values of the three - phase modulation voltages in the grid - forming mode.

[0115] S380. Determine the feedback value of the grid - forming current control loop based on the synchronization angle.

[0116] In an optional embodiment, according to the synchronization angle θ, the feedback value i of the network-forming current control loop is determined by the fifth formula d 、i q , where the fifth formula is as follows:

[0117]

[0118] where i f,a 、i f,b 、i f,c are respectively the components of the inverter-side current on the a-axis, b-axis, and c-axis.

[0119] S390. Determine the reference initial value of the voltage control loop according to the feedback value of the network-forming current control loop, the grid-side voltage, and the virtual impedance.

[0120] In an optional embodiment, according to the feedback value of the network-forming current control loop, the grid-side voltage, and the virtual impedance, the reference initial value of the network-forming voltage control loop is determined by the sixth formula, where the sixth formula is as follows:

[0121]

[0122] S3100. Switch the working mode of the energy storage converter from the grid-following mode to the network-forming mode according to the pre-synchronization signal.

[0123] In this embodiment, when the first switching instruction is obtained, the initial value of the synchronization angle is determined according to the angle value of the grid-following phase-locked loop, the power angle and the reference of the network-forming current in the network-forming mode are determined according to the power instruction, the grid-side voltage, and the virtual impedance, so as to determine the synchronization angle in the network-forming mode according to the initial value of the synchronization angle and the power angle in the network-forming mode. At the same time, according to the reference of the network-forming current, the reference initial value of the current control loop is determined, and according to the synchronization angle θ and the grid-side voltage, the voltage feedforward value of the network-forming current control loop is determined, so as to determine the initial value of the modulation voltage according to the modulation voltage in the grid-following mode and the feedforward value of the network-forming current control loop. Finally, according to the pre-synchronization signal, the working mode of the energy storage converter is switched from the grid-following mode to the network-forming mode, thereby further improving the accuracy of the pre-synchronization signal, and at the same time facilitating ensuring the rapidity of the working mode switching of the energy storage converter, and further reducing the power fluctuation during the working mode switching.

[0124] Embodiment 4

[0125] This embodiment provides a control mode switching device for an energy storage converter, and this device can be implemented in the form of hardware and / or software. Figure 6 is the structural schematic diagram of the control mode switching device for the energy storage converter provided in Embodiment 4 of the present invention, as Figure 6 shown, this device includes:

[0126] An instruction acquisition module 410, configured to, when the energy storage converter operates in the grid-following mode, acquire a first switching instruction in real time; the first switching instruction includes an instruction to switch from the grid-following mode to the grid-forming mode.

[0127] A pre-synchronization module 420, configured to, when the first switching instruction is acquired, determine a pre-synchronization signal for the grid-forming mode based on first parameters of the energy storage converter in the grid-following mode; the first parameters at least include virtual impedance; the pre-synchronization signal at least includes a synchronization angle, an initial value of the current control loop reference, an initial value of the modulation voltage, and an initial value of the voltage control loop reference.

[0128] A switching module 430, configured to switch the operating mode of the energy storage converter from the grid-following mode to the grid-forming mode according to the pre-synchronization signal.

[0129] The control mode switching device of the energy storage converter provided by the embodiment of the present invention can execute the control mode switching method of the energy storage converter provided by any embodiment of the present invention, and has corresponding functional modules and beneficial effects for executing the method. The same parts can be referred to the above description.

[0130] Embodiment Five

[0131] The embodiment of the present invention provides a control device for an energy storage converter. Referring to Figure 4 as shown, the control device includes a grid-following control module, a grid-forming control module, a pre-synchronization module, and a switching module; the pre-synchronization module is respectively connected to the grid-following control module and the switching module; the switching module is further connected to the grid-following control module and the grid-forming control module; the grid-following control module is configured to make the energy storage converter operate in the grid-following mode; the grid-forming control module is configured to make the energy storage converter operate in the grid-forming mode; the pre-synchronization module is configured to acquire first parameters of the energy storage converter in the grid-following mode, and determine a pre-synchronization signal for the grid-forming mode according to the first parameters; the switching module is configured to acquire the pre-synchronization signal according to the first switching instruction, send the pre-synchronization signal to the grid-forming control module, and control the energy storage converter to operate in the grid-forming mode.

[0132] Wherein, the first parameters at least include virtual impedance; the pre-synchronization signal at least includes a synchronization angle, an initial value of the current control loop reference, an initial value of the modulation voltage, and an initial value of the voltage control loop reference.

[0133] In an optional embodiment, the first parameters further include an angle value of the grid-following phase-locked loop, a power command, a grid-side voltage amplitude, etc.

[0134] It should be noted that in this embodiment, the grid-following control module and the grid-forming control module work independently without a common loop, thereby improving the power quality in the grid-following mode and the grid-forming mode. In an alternative embodiment, the grid-following control module includes a phase-locked loop and a grid-following current control loop. Among them, the phase-locked loop outputs a phase-locked loop angle θPLL according to the grid-side voltage ug,abc, and the grid-following current control loop outputs the modulation voltages uma1, umb1, and umc1 injected into the grid according to the power commands Pref, Qref, current compensation, and the phase-locked loop angle θPLL, thereby realizing the closed-loop control of the grid-following mode. The grid-forming control module includes a power synchronization control loop, a voltage control loop, and a current control loop. Among them, the power synchronization control loop outputs an electromotive force E and a synchronization angle θ according to the power commands Pref, Qref, and the grid-side power. The grid-forming voltage control loop outputs current references Idref, Iqref according to the electromotive force E and the synchronization angle θ output by the power synchronization control loop. The grid-forming current control loop outputs the modulation voltages uma2, umb2, and umc2 injected into the grid according to the synchronization angle θ and the current references Idref, Iqref, thereby realizing the closed-loop control of the grid-forming mode; among them, the grid-side power is determined by the power calculation module according to the grid-side current io,abc and the grid-side voltage ug,abc.

[0135] In other embodiments, the grid-following control module further includes a harmonic compensation loop and a reactive power compensation loop to ensure the grid-connected power quality of the power grid system.

[0136] Specifically, in the grid-following control mode, the energy storage converter operates in the current source mode. In the grid-forming control mode, the energy storage converter operates in the voltage source mode. The pre-synchronization module is connected to the grid-following control module, so that the pre-synchronization module can obtain the first parameters of the energy storage converter in the grid-following mode and determine the pre-synchronization signal of the grid-forming mode according to the first parameters. At the same time, the pre-synchronization module is also connected to the switching module, so that the pre-synchronization module and the switching module can communicate, so that the switching module can obtain the pre-synchronization signal. The switching module is also connected to the grid-forming control module, so that the switching module can send the pre-synchronization signal to the grid-forming control module according to the first switching instruction, so that the grid-forming control module uses the pre-synchronization signal as the initial state of the grid-forming mode and controls the energy storage converter to operate in the grid-forming mode.

[0137] In this embodiment, by making the control device of the energy storage converter include a grid-following control module, a grid-forming control module, a pre-synchronization module, and a switching module, the pre-synchronization module is respectively connected to the grid-following control module and the switching module, the switching module is also connected to the grid-following control module and the grid-forming control module. The grid-following control module is used to make the energy storage converter operate in the grid-following mode, the grid-forming control module is used to make the energy storage converter operate in the grid-forming mode, the pre-synchronization module is used to obtain the first parameters of the energy storage converter in the grid-following mode, and determine the pre-synchronization signal of the grid-forming mode according to the first parameters. The switching module is used to obtain the pre-synchronization signal according to the first switching instruction, send the pre-synchronization signal to the grid-forming control module, and control the energy storage converter to operate in the grid-forming mode, thereby avoiding sharing the current loop of the energy storage converter in the grid-following mode and the grid-forming mode, which is beneficial to ensuring the power quality of the energy storage converter in the grid-following mode and the grid-forming mode. In addition, by the pre-synchronization module determining the pre-synchronization signal of the grid-forming mode according to the first parameters including the virtual impedance in the grid-following mode, and making the pre-synchronization signal be used as the initial state of the grid-forming mode when switching to the grid-forming mode, the power grid system can also operate stably during the mode switching process, which is beneficial to reducing the power fluctuation during the switching process and improving the grid connection stability of the power grid system.

[0138] Embodiment Six

[0139] An embodiment of the present invention provides a power grid system, which at least includes: a memory and a processor, and the memory stores a computer program; the processor may be integrated with the control mode switching device of the energy storage converter provided in any embodiment of the present invention. When the processor executes the computer program, it can implement the control mode switching method of the energy storage converter provided in any embodiment of the present invention.

[0140] Since the power grid system provided by the embodiment of the present invention includes the above-mentioned processor, and the processor can be integrated with the control mode switching device of the energy storage converter provided by the embodiment of the present invention and can execute the control mode switching method of the energy storage converter provided by the embodiment of the present invention, it can have the corresponding structure and features for executing the control mode switching method of the energy storage converter provided by the embodiment of the present invention, and can achieve the beneficial effects of the control mode switching method of the energy storage converter provided by the embodiment of the present invention. The same parts can be referred to the above description.

[0141] Embodiment Seven

[0142] Based on the same concept, an embodiment of the present invention further provides a computer-readable storage medium, which stores computer instructions for causing a processor to implement the method provided in any of the above embodiments when executed.

[0143] In the context of the present invention, a computer-readable storage medium can be a tangible medium that can contain or store a computer program for use by or in connection with an instruction execution system, apparatus, or device. The computer-readable storage medium can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. Alternatively, the computer-readable storage medium can be a machine-readable signal medium. More specific examples of the machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0144] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A control mode switching method for an energy storage converter, characterized in that, Including: When the energy storage converter operates in the grid - following mode, a first switching instruction is obtained in real - time; the first switching instruction includes an instruction to switch from the grid - following mode to the grid - forming mode; When the first switching instruction is obtained, according to the first parameters of the energy storage converter in the grid - following mode, a pre - synchronization signal for the grid - forming mode is determined; the first parameters at least include virtual impedance; the pre - synchronization signal at least includes a synchronization angle, an initial value of the current control loop reference, an initial value of the modulation voltage, and an initial value of the voltage control loop reference; According to the pre - synchronization signal, the operating mode of the energy storage converter is switched from the grid - following mode to the grid - forming mode.

2. The control mode switching method of the energy storage converter according to claim 1, characterized in that Determining the pre - synchronization signal for the grid - forming mode according to the first parameters of the energy storage converter in the grid - following mode includes: According to the first parameters, the synchronization angle and the initial value of the current control loop reference are determined; According to the first parameters and the synchronization angle, the initial value of the modulation voltage and the initial value of the voltage control loop reference are determined.

3. The control mode switching method of the energy storage converter according to claim 2, wherein The first parameters further include the angle value of the grid - following phase - locked loop, the power command, and the grid - side voltage amplitude; determining the synchronization angle and the initial value of the current control loop reference according to the first parameters includes: According to the angle value of the grid - following phase - locked loop, an initial value of the synchronization angle is determined; According to the power command, the grid - side voltage, and the virtual impedance, the power angle and the grid - forming current reference in the grid - forming mode are determined; According to the initial value of the synchronization angle and the power angle in the grid - forming mode, the synchronization angle in the grid - forming mode is determined; According to the grid - forming current reference, the initial value of the current control loop reference is determined.

4. The control mode switching method of the energy storage converter according to claim 2, characterized in that The first parameters further include the grid - side voltage amplitude and the modulation voltage of the grid - following phase - locked loop; determining the initial value of the modulation voltage and the initial value of the voltage control loop reference according to the first parameters and the synchronization angle includes: According to the synchronization angle and the grid - side voltage, the voltage feed - forward value of the grid - forming current control loop is determined; According to the modulation voltage in the grid - following mode and the feed - forward value of the grid - forming current control loop, the initial value of the modulation voltage is determined; According to the synchronization angle, the feedback value of the grid - forming current control loop is determined; According to the feedback value of the grid - forming current control loop, the grid - side voltage, and the virtual impedance, the initial value of the voltage control loop reference is determined.

5. The control mode switching method of the energy storage converter according to any one of claims 1-4, characterized in that The virtual impedance is determined according to the filter impedance of the energy storage converter and the strength of the power grid.

6. The control mode switching method of the energy storage converter according to claim 1, characterized in that Switching the operating mode of the energy storage converter from the grid - following mode to the grid - forming mode according to the pre - synchronization signal includes: Switching the operating mode of the energy storage converter to the grid - forming mode and using the pre - synchronization signal as the initial value of the grid - forming mode; Controlling the grid - forming power synchronization control loop, the grid - forming voltage control loop, and the grid - forming current control loop to work in a closed - loop manner.

7. The control mode switching method of the energy storage converter according to claim 1, wherein It further includes: When the energy storage converter operates in the grid - following mode, compensating for harmonic current and reactive power, and controlling the phase - locked loop and the grid - following current control loop to work in a closed - loop manner.

8. A control mode switching device for an energy storage converter, characterized in that Including: An instruction acquisition module, configured to, when the energy storage converter operates in the grid - following mode, obtain a first switching instruction in real - time; the first switching instruction includes an instruction to switch from the grid - following mode to the grid - forming mode; A pre-synchronization module, configured to determine a pre-synchronization signal for the grid-forming mode according to a first parameter of the energy storage converter in the grid-following mode when the first switching instruction is obtained; the first parameter includes at least virtual impedance; the pre-synchronization signal includes at least a synchronization angle, an initial reference value of the current control loop, an initial value of the modulation voltage, and an initial reference value of the voltage control loop; A switching module, configured to switch the working mode of the energy storage converter from the grid-following mode to the grid-forming mode according to the pre-synchronization signal.

9. A control device for an energy storage converter, characterized in that, Comprising: A grid-following control module, a grid-forming control module, a pre-synchronization module, and a switching module; The pre-synchronization module is respectively connected to the grid-following control module and the switching module; the switching module is further connected to the grid-following control module and the grid-forming control module; The grid-following control module is configured to make the energy storage converter work in the grid-following mode; The grid-forming control module is configured to make the energy storage converter work in the grid-forming mode; The pre-synchronization module is configured to obtain a first parameter of the energy storage converter in the grid-following mode and determine a pre-synchronization signal for the grid-forming mode according to the first parameter; the first parameter includes at least virtual impedance; the pre-synchronization signal includes at least a synchronization angle, an initial reference value of the current control loop, an initial value of the modulation voltage, and an initial reference value of the voltage control loop; The switching module is configured to obtain the pre-synchronization signal according to a first switching instruction, send the pre-synchronization signal to the grid-forming control module, and control the energy storage converter to work in the grid-forming mode.

10. The control device of the energy storage converter according to claim 9, characterized in that, The grid-following control module includes: a phase-locked loop and a grid-following current control loop.

11. The control device of the energy storage converter according to claim 10, characterized in that, The grid-following control module further includes: a harmonic compensation loop and a reactive power compensation loop.

12. The control device of the energy storage converter according to claim 9, characterized in that, The grid-forming control module includes: a power synchronization control loop, a voltage control loop, and a current control loop.

13. A power grid system, characterized in that, Comprising: A memory and a processor, the memory stores a computer program, wherein the processor, when executing the computer program, implements the control mode switching method of the energy storage converter according to any one of claims 1-7.

14. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions, and the computer instructions are used to make the processor implement the control mode switching method of the energy storage converter according to any one of claims 1-7 when executed.

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