Control method and device of energy storage converter

Abstract

The invention discloses a control method and device for an energy storage converter, and the method comprises the steps: controlling the energy storage converter to operate in an off-grid mode when a grid-connected mode of the energy storage converter is started; by controlling a voltage outer ring given value of the energy storage converter and / or calculating a sine value and a cosine value required by a modulation wave of the energy storage converter, the difference between the amplitude and the phase of the output voltage of the energy storage converter and the amplitude and the phase of the power grid voltage falls into a preset error range; after the difference between the amplitude and the phase of the output voltage of the energy storage converter and the amplitude and the phase of the power grid voltage falls into a preset error range, a grid-connected point switch closing instruction is sent out; and in response to the grid-connected point switch, completing a closing action according to the grid-connected point switch closing instruction, and controlling the energy storage converter to operate in a grid-connected mode.

Description

Technical Field

[0001] The present disclosure generally relates to the field of converters, and more specifically, to a control method and device for an energy storage converter. Background Art

[0002] During the grid-connected startup of the energy storage converter, due to the presence of AC filter capacitors and DC support capacitors, a large current shock will be generated when the grid-connected switch is closed, causing the energy storage converter to enter a protection state, resulting in startup failure, and in severe cases, damage to the power devices of the energy storage converter. At present, the current shock is often reduced by adding AC pre-charging resistance, but this method increases cost and has complex control logic. Summary of the invention

[0003] The embodiments of the present disclosure provide a control method and device for an energy storage converter, which can effectively solve the problem in the prior art of generating a large current shock when a grid-connected switch is closed.

[0004] In a general aspect, a control method for an energy storage inverter is provided, which is applied to a scenario where an off-grid mode is switched to a grid-connected mode, comprising: when the grid-connected mode of the energy storage inverter is started, controlling the energy storage inverter to operate in the off-grid mode; making the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage fall within a predetermined error range by controlling the voltage outer loop set value of the energy storage inverter and / or calculating the sine value and cosine value required for the modulation wave of the energy storage inverter; after the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within the predetermined error range, issuing a grid-connected point switch closing instruction; in response to the grid-connected point switch completing the closing action according to the grid-connected point switch closing instruction, controlling the energy storage inverter to operate in the grid-connected mode.

[0005] Optionally, by controlling the voltage outer loop set value of the energy storage inverter, the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range, including: by controlling the voltage outer loop set value of the energy storage inverter to be the amplitude of the grid voltage, the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range.

[0006] Optionally, controlling the voltage outer loop set value of the energy storage converter to be the amplitude of the grid voltage includes: controlling the voltage outer loop set value of the energy storage converter to gradually increase to the amplitude of the grid voltage.

[0007] Optionally, by controlling and calculating the sine value and cosine value required for the modulation wave of the energy storage inverter, the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range, including: obtaining the sine value and cosine value required for calculating the modulation wave of the energy storage inverter by phase-locking the grid voltage, so that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range.

[0008] Optionally, by controlling the voltage outer loop set value of the energy storage inverter and calculating the sine value and cosine value required for the modulation wave of the energy storage inverter, the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range, including: controlling the voltage outer loop set value of the energy storage inverter to be the amplitude of the grid voltage, and obtaining the sine value and cosine value required for calculating the modulation wave of the energy storage inverter by phase-locking the grid voltage, so that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range.

[0009] Optionally, before responding to the grid-connected point switch completing the closing action according to the grid-connected point switch closing instruction and controlling the energy storage converter to operate in the grid-connected mode, it also includes: keeping the output of the current inner loop of the energy storage converter unchanged.

[0010] Optionally, keeping the output of the inner current loop of the energy storage converter unchanged includes: keeping the output of the inner current loop of the energy storage converter as the output value of the previous cycle in the off-grid mode.

[0011] Optionally, the energy storage converter simultaneously samples the three-phase voltages at the front end and rear end of the grid connection point switch, wherein the front end of the grid connection point switch is located on the grid side and the rear end of the grid connection point switch is located on the energy storage converter side.

[0012] In another general aspect, a control device for an energy storage inverter is provided, which is applied to a scenario where an off-grid mode is switched to a grid-connected mode, and comprises: a mode control unit, configured to control the energy storage inverter to operate in an off-grid mode when the grid-connected mode of the energy storage inverter is started; a voltage control unit, configured to control a voltage outer loop given value of the energy storage inverter and / or calculate sine and cosine values ​​required for a modulation wave of the energy storage inverter so that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range; an instruction issuing unit, configured to issue a grid-connected point switch closing instruction after the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range; and an instruction execution unit, configured to control the energy storage inverter to operate in the grid-connected mode in response to the grid-connected point switch completing a closing action in accordance with the grid-connected point switch closing instruction.

[0013] Optionally, the voltage control unit is further configured to control the voltage outer loop set value of the energy storage inverter to be the amplitude of the grid voltage, so that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range.

[0014] Optionally, the voltage control unit is further configured to control the voltage outer loop set value of the energy storage converter to gradually increase to the amplitude of the grid voltage.

[0015] Optionally, the voltage control unit is also configured to obtain the sine value and cosine value required for calculating the modulation wave of the energy storage inverter by phase-locking the grid voltage, so that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range.

[0016] Optionally, the voltage control unit is also configured to control the voltage outer loop set value of the energy storage inverter to be the amplitude of the grid voltage, and obtain the sine value and cosine value required for calculating the modulation wave of the energy storage inverter by phase-locking the grid voltage, so that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range.

[0017] Optionally, the instruction execution unit is further configured to keep the output of the current inner loop of the energy storage converter unchanged before controlling the energy storage converter to operate in the grid-connected mode in response to the grid-connected point switch completing the closing action according to the grid-connected point switch closing instruction.

[0018] Optionally, the instruction execution unit is further configured to keep the output of the inner current loop of the energy storage converter as the output value of the previous cycle in the off-grid mode.

[0019] Optionally, the energy storage converter simultaneously samples the three-phase voltages at the front end and rear end of the grid connection point switch, wherein the front end of the grid connection point switch is located on the grid side and the rear end of the grid connection point switch is located on the energy storage converter side.

[0020] In another general aspect, a computer-readable storage medium storing instructions is provided, wherein when the instructions are executed by at least one computing device, the at least one computing device is prompted to execute any of the above-mentioned energy storage converter control methods.

[0021] In another general aspect, a system is provided that includes at least one computing device and at least one storage device storing instructions, wherein the instructions, when executed by the at least one computing device, cause the at least one computing device to execute any of the energy storage converter control methods described above.

[0022] According to the control method and device of the energy storage converter of the embodiment of the present disclosure, before issuing the grid connection point switch closing instruction, the energy storage converter is first controlled to operate in the off-grid mode, and by controlling the voltage outer loop set value of the energy storage converter and / or calculating the sine value and cosine value required for the modulation wave of the energy storage converter, the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within the predetermined error range, that is, the amplitude and phase of the output voltage of the energy storage converter are basically consistent with the grid voltage, so there is basically no current shock when the grid connection point switch is closed. Therefore, through the present disclosure, the problem of large current shock generated at the moment of grid connection point switch closing in the prior art can be effectively solved.

[0023] Additional aspects and / or advantages of the present general inventive concept will be set forth in part in the following description and in part will be apparent from the description or may be learned through practice of the present general inventive concept. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and other objects and features of the embodiments of the present disclosure will become more apparent through the following description in conjunction with the accompanying drawings showing the embodiments, in which:

[0025] Figure 1 is a flow chart showing a control method of an energy storage converter according to an embodiment of the present disclosure;

[0026] Figure 2 is a circuit schematic diagram showing a control method of an energy storage converter according to an embodiment of the present disclosure;

[0027] Figure 3 It is a control method showing the conversion of the energy storage converter from an off-grid mode to a grid-connected mode according to an embodiment of the present disclosure;

[0028] Figure 4 is a block diagram showing a control device of an energy storage converter disclosed in the present invention. DETAILED DESCRIPTION

[0029] The following specific embodiments are provided to help the reader obtain a comprehensive understanding of the methods, devices and / or systems described herein. However, after understanding the disclosure of the present application, various changes, modifications and equivalents of the methods, devices and / or systems described herein will be clear. For example, the order of operations described herein is only an example and is not limited to those orders set forth herein, but can be changed as will be clear after understanding the disclosure of the present application, except for operations that must occur in a specific order. In addition, for greater clarity and simplicity, the description of features known in the art may be omitted.

[0030] The features described herein can be implemented in different forms and should not be construed as being limited to the examples described herein. Rather, the examples described herein have been provided to illustrate only some of the many possible ways to implement the methods, devices, and / or systems described herein, which will be clear after understanding the disclosure of the present application.

[0031] As used herein, the term "and / or" includes any one of the associated listed items and any combination of any two or more.

[0032] Although terms such as "first", "second", and "third" may be used herein to describe various members, components, regions, layers, or portions, these members, components, regions, layers, or portions should not be limited by these terms. Instead, these terms are only used to distinguish one member, component, region, layer, or portion from another member, component, region, layer, or portion. Therefore, without departing from the teachings of the examples described herein, the first member, first component, first region, first layer, or first portion referred to in the examples may also be referred to as the second member, second component, second region, second layer, or second portion.

[0033] In the specification, when an element (such as a layer, a region, or a substrate) is described as being “on”, “connected to”, or “coupled to” another element, the element may be directly “on”, “connected to”, or “coupled to” another element, or one or more other elements may be present therebetween. Conversely, when an element is described as being “directly on”, “directly connected to”, or “directly coupled to” another element, there may be no other elements present therebetween.

[0034] The terms used herein are only used to describe various examples and are not intended to limit the disclosure. Unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. The terms "comprise", "include" and "have" indicate the presence of the described features, quantities, operations, components, elements and / or combinations thereof, but do not exclude the presence or addition of one or more other features, quantities, operations, components, elements and / or combinations thereof.

[0035] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by a person of ordinary skill in the art to which the present disclosure belongs after understanding the present disclosure. Unless explicitly defined as such herein, terms (such as those defined in a general dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the present disclosure, and should not be interpreted in an idealized or overly formal manner.

[0036] Furthermore, in the description of examples, when it is considered that a detailed description of a well-known related structure or function would cause vague interpretation of the present disclosure, such a detailed description will be omitted.

[0037] The present disclosure provides a control method and device for an energy storage converter, which can solve the above problems. The control method for the energy storage converter of the present disclosure can be applied to a separate server or to a controller on the energy storage converter, which is not limited by the present disclosure. The server, controller and energy storage converter can be connected wirelessly or by wire, which is not limited here. The above server can be a server, a server cluster composed of several servers, or a cloud computing platform or a virtualization center. The controller on the energy storage converter is used as an example for explanation below.

[0038] When the energy storage inverter is started in grid-connected mode, the controller controls the energy storage inverter to operate in off-grid mode; by controlling the voltage outer loop set value of the energy storage inverter and / or calculating the sine value and cosine value required for the modulation wave of the energy storage inverter, the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range; after the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within the predetermined error range, a grid-connected point switch closing instruction is issued; in response to the grid-connected point switch completing the closing action according to the grid-connected point switch closing instruction, the energy storage inverter is controlled to operate in grid-connected mode.

[0039] Before issuing the grid-connected point switch closing instruction, this embodiment first controls the energy storage converter to operate in the off-grid mode, and by controlling the voltage outer loop set value of the energy storage converter and / or calculating the sine value and cosine value required for the modulation wave of the energy storage converter, the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within the predetermined error range, that is, it is ensured that the amplitude and phase of the output voltage of the energy storage converter are basically consistent with the grid voltage, so there is basically no current shock when the grid-connected point switch is closed. Therefore, through the present disclosure, the problem of large current shock generated at the moment of grid-connected point switch closing in the prior art can be effectively solved.

[0040] The control method and device of the energy storage converter disclosed in the present invention are described in detail below with reference to the accompanying drawings.

[0041] The present invention proposes a control method for an energy storage converter. Figure 1 is a flow chart showing a control method of an energy storage converter according to an embodiment of the present disclosure. Figure 1 , the control method of the energy storage converter comprises the following steps:

[0042] In step S101, when the energy storage converter is started in grid-connected mode, the energy storage converter is controlled to operate in off-grid mode.

[0043] The application scenarios of the present disclosure may include, but are not limited to: a scenario of converting from an off-grid mode to a grid-connected mode, and a scenario of starting the grid-connected mode after power-on, which is not limited by the present disclosure.

[0044] The above-mentioned off-grid mode may adopt a single-loop control or a dual-loop control strategy of a voltage outer loop and a current inner loop, which is not limited in the present disclosure.

[0045] According to an embodiment of the present disclosure, the energy storage converter simultaneously samples the three-phase voltages at the front end and rear end of the grid-connected point switch, wherein the front end of the grid-connected point switch is located on the grid side and the rear end of the grid-connected point switch is located on the energy storage converter side.

[0046] As an example, the above-mentioned energy storage inverter generally has the ability to simultaneously sample the three-phase voltages at the front end (grid side) and the back end (energy storage inverter side) of the grid-connected point switch, which can ensure that the energy storage inverter can smoothly execute the solution of the present disclosure.

[0047] In step S102, by controlling the voltage outer loop set value of the energy storage inverter and / or calculating the sine value and cosine value required for the modulation wave of the energy storage inverter, the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range.

[0048] The above-mentioned method of controlling the voltage outer loop set value of the energy storage inverter can be to control the voltage outer loop set value of the energy storage inverter as a fixed value. The fixed value can be set by professionals based on experience according to needs, or it can be the amplitude of the grid voltage. Other methods can also be used, as long as the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage can fall within the predetermined error range, and the present disclosure is not limited to this.

[0049] The above-mentioned control method for calculating the sine value and cosine value required for the modulation wave of the energy storage inverter can be to obtain the sine value and cosine value required for the modulation wave of the energy storage inverter by locking the grid voltage into phase, or other methods can be used. As long as the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage can fall within a predetermined error range, the present disclosure is not limited to this.

[0050] According to an embodiment of the present disclosure, in step S102, by controlling the voltage outer loop set value of the energy storage converter, the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range, which may include but is not limited to: by controlling the voltage outer loop set value of the energy storage converter to be the amplitude of the grid voltage, the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range. Through this embodiment, the voltage outer loop set value of the off-grid mode before the grid-connected point switch is closed is taken from the grid voltage, which can conveniently and quickly synchronize the amplitude and phase of the output voltage of the energy storage converter with the amplitude and phase of the grid voltage, so as to reduce the current impact when the grid-connected point switch is closed.

[0051] As an example, when the grid-connected mode is started, the energy storage inverter is controlled to operate in the off-grid mode before the grid-connected point switch is closed, and after it is determined that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range by controlling the voltage outer loop set value of the energy storage inverter, the voltage outer loop set value of the energy storage inverter operating in the off-grid mode can adopt the amplitude of the grid voltage, so that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage can fall within the predetermined error range, which can facilitate and quickly synchronize the amplitude and phase of the output voltage of the energy storage inverter with the amplitude and phase of the grid voltage.

[0052] According to an embodiment of the present disclosure, controlling the voltage outer loop set value of the energy storage converter to be the amplitude of the grid voltage may include: controlling the voltage outer loop set value of the energy storage converter to gradually increase to the amplitude of the grid voltage. Through this embodiment, gradually increasing the voltage outer loop set value of the energy storage converter to the amplitude of the grid voltage can avoid the problem of irrational synchronization effect caused by increasing it to the grid voltage all at once.

[0053] As an example, after determining that the voltage outer loop set value of the energy storage inverter operating in off-grid mode adopts the amplitude of the grid voltage, the voltage outer loop set value can be slowly increased, such as gradually increasing the voltage outer loop set value to the amplitude of the grid voltage. The step size of the increase can be set as needed, and the present disclosure does not limit this. This can avoid the problem of irrational synchronization effect caused by a one-time increase to the grid voltage.

[0054] According to an embodiment of the present disclosure, in step S102, by controlling the sine value and cosine value required for calculating the modulation wave of the energy storage converter, the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range, which may include but is not limited to: obtaining the sine value and cosine value required for calculating the modulation wave of the energy storage converter by phase-locking the grid voltage, so that the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range. Through this embodiment, since the sine value and cosine value required for calculating the modulation wave of the energy storage converter in the off-grid mode are from the grid, the amplitude and phase of the output voltage of the energy storage converter can be quickly and conveniently synchronized with the amplitude and phase of the grid, so as to reduce the current impact when the grid connection point switch is closed, and the sine value and cosine value are obtained by phase-locking the grid voltage in the whole process, so there is no problem of switching between the phase adjustment and phase calculation methods, and the synchronization period is greatly shortened.

[0055] As an example, when the grid-connected mode is started, the energy storage inverter is controlled to operate in the off-grid mode before the grid-connected point switch is closed, and the sine value and cosine value required for the modulation wave of the energy storage inverter are determined and controlled to be calculated, so that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range. The sine value and cosine value required for calculating the modulation wave of the energy storage inverter can be obtained by locking the grid voltage into phase. In this way, since the sine value and cosine value required for calculating the modulation wave of the energy storage inverter in the off-grid mode are from the grid, the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid can be quickly and conveniently synchronized. In addition, this can also ensure that there is no switching between the off-grid mode before the grid-connected point switch is closed and the grid-connected mode after the grid-connected point switch is closed, and the phase and corresponding calculation method of the sine value and cosine value required for calculating the modulation wave of the energy storage inverter, and the synchronization period is greatly shortened.

[0056] According to an embodiment of the present disclosure, in step S102, by controlling the voltage outer loop set value of the energy storage inverter and calculating the sine value and cosine value of the modulation wave of the energy storage inverter, the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range. It may include but is not limited to: by controlling the voltage outer loop set value of the energy storage inverter to be the amplitude of the grid voltage, and by phase-locking the grid voltage to obtain the sine value and cosine value required for calculating the modulation wave of the energy storage inverter, the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range. Through this embodiment, since the energy storage inverter is in off-grid mode, the voltage outer loop given value and the sine value and cosine value required for calculating the modulation wave are all from the power grid, so the amplitude and phase of the output voltage of the energy storage inverter are highly consistent with the amplitude and phase of the power grid, and the synchronization effect is more accurate. Therefore, there is basically no impact on the current when the grid-connected point switch is closed, and there is no switching of phase adjustment and phase calculation methods in the whole process, and the synchronization period is greatly shortened.

[0057] As an example, when the grid-connected mode is started, the energy storage converter is controlled to operate in the off-grid mode before the grid-connected switch is closed, and the sine value and cosine value required for the modulation wave of the energy storage converter are determined, and the voltage outer loop set value of the energy storage converter is controlled to make the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage fall within a predetermined error range. The voltage outer loop set value of the energy storage converter operating in the off-grid mode can adopt the amplitude of the grid voltage, and the modulation wave required for calculating the energy storage converter can be obtained by phase-locking the grid voltage. The required sine and cosine values ​​are obtained by calculating the sine and cosine values ​​required for the modulation wave. In this way, since the given value of the voltage outer loop and the sine and cosine values ​​required for calculating the modulation wave are all from the power grid, the amplitude and phase of the output voltage of the energy storage inverter are highly consistent with the amplitude and phase of the power grid, and the synchronization effect is more accurate. Therefore, there is basically no impact on the current when the grid-connected point switch is closed. In addition, this can also ensure that in the off-grid mode before the grid-connected point switch is closed and the grid-connected mode after the grid-connected point switch is closed, there is no switching between the phase of the sine and cosine values ​​required for calculating the modulation wave of the energy storage inverter and the corresponding calculation method, and the synchronization period is greatly shortened.

[0058] In step S103, after the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range, a grid connection point switch closing instruction is issued.

[0059] In step S104, in response to the grid-connected point switch completing the closing action according to the grid-connected point switch closing instruction, the energy storage converter is controlled to operate in the grid-connected mode.

[0060] The grid-connected point switch completes the action indicated by the grid-connected point switch control instruction, and can control the energy storage converter to the grid-connected mode. At the same time, closed-loop control can be performed, that is, the output of the current inner loop of the energy storage converter is periodically obtained, and the current inner loop will have an output value in each cycle.

[0061] It should be noted that after issuing a grid-connected switch closing instruction, and in response to the grid-connected point switch completing the closing action according to the grid-connected point switch closing instruction, before controlling the energy storage inverter to operate in the grid-connected mode, the synchronization effect can be further increased and the current impact can be reduced, such as keeping the output of the current inner loop of the energy storage inverter unchanged, such as keeping the output of the current inner loop at a fixed value, which can be set by professionals based on experience according to needs, or can be the output of the current inner loop of the previous cycle, or can be the average value of the output of the current inner loop of the previous few cycles, and the present disclosure does not limit this.

[0062] According to an embodiment of the present disclosure, before the grid-connected point switch completes the closing action according to the grid-connected point switch closing instruction and controls the energy storage converter to operate in the grid-connected mode, the output of the current inner loop of the energy storage converter can also be kept unchanged. Through this embodiment, after the grid-connected point switch control instruction is issued and before the grid-connected point switch completes the closing action according to the grid-connected point switch closing instruction and controls the energy storage converter to operate in the grid-connected mode, the output of the current inner loop of the energy storage converter is kept unchanged, so that it is converted to open-loop control, and the amplitude and phase of the output voltage of the energy storage converter and the grid voltage are further guaranteed to be within the allowable error range, so that the current impact of the energy storage converter during the startup process between the grid-connected modes can be further reduced, so that the energy storage converter can successfully start the grid-connected mode.

[0063] As an example, when the grid-connected mode is started and a grid-connected point switch closing command is issued, the closed-loop control can be stopped, that is, the periodic calculation of the output of the current inner loop of the energy storage inverter is stopped, and the output of the current inner loop is kept unchanged. In this way, open-loop control can be entered, thereby ensuring that when switching between the grid-connected mode and the off-grid mode, the amplitude and phase of the output voltage of the energy storage inverter are basically consistent with the grid voltage. Therefore, the current impact of the energy storage inverter during the conversion between the grid-connected mode and the off-grid mode can be minimized, so that the energy storage inverter can successfully start the grid-connected mode.

[0064] According to an embodiment of the present disclosure, the above-mentioned maintaining the output of the current inner loop of the energy storage converter unchanged may include: maintaining the output of the current inner loop of the energy storage converter as the output value of the previous cycle in the off-grid mode. Through this embodiment, when the grid-connected point switch closing instruction is issued, the output of the current inner loop of the energy storage converter in the grid-connected mode can be maintained as the output value of the current inner loop of the previous cycle to perform open-loop control, and maintaining the output value of the current inner loop of the previous cycle can be more adapted to the output required in the control process, thereby reducing current shocks.

[0065] As an example, when the grid-connected mode is started and a grid-connected point switch closing instruction is issued, the output of the current inner loop of the energy storage converter in the off-grid mode can be kept at the output value of the current inner loop of the previous cycle for open-loop control.

[0066] It should be noted that, based on the above embodiments, in response to the grid-connected point switch completing the closing action according to the grid-connected point switch closing instruction, after controlling the energy storage converter to operate in the grid-connected mode, the output of the current inner loop of the energy storage converter can be periodically obtained.

[0067] According to an embodiment of the present disclosure, periodically obtaining the output of the inner current loop of the energy storage converter may include: in the first cycle, maintaining the output initial value of the inner current loop of the energy storage converter as the output value of the inner current loop before the grid-connected switch is closed; after the first cycle, continuing to obtain the output of the inner current loop of the energy storage converter by the calculation method in the grid-connected mode. Through this embodiment, in the first cycle when switching to closed-loop control, the output initial value of the inner current loop is assigned, rather than obtaining the output of the inner current loop by the previous calculation method in the corresponding second control mode, so as to make the output voltage of the energy storage converter more consistent with the grid voltage, and to further reduce the impact of current shocks, etc.

[0068] According to an embodiment of the present disclosure, in the first cycle, the initial value of the PI integral item of the current inner loop of the energy storage converter is also maintained as the output value of the current inner loop before the grid-connected switch is closed; wherein, after the first cycle, the output of the current inner loop continues to be obtained through the calculation method in the second control mode based on the initial value of the PI integral item. Through this embodiment, when switching to closed-loop control, the initial value of the PI integral item of the current inner loop is also assigned, and when the calculation starts after the first cycle, the initial value of the PI integral item used uses the assignment result, rather than starting the calculation from the initial value of the PI integral item of 0, so that the calculated result can ensure that the output voltage of the energy storage converter is more consistent with the grid voltage.

[0069] In order to better understand the present disclosure, Figure 2 A control method of the energy storage converter disclosed in the present invention is systematically described.

[0070] Figure 2The circuit diagram of the control method of the energy storage converter is shown. When the grid-connected mode is started, the energy storage converter is controlled to operate in the off-grid mode. In the off-grid mode, the voltage outer loop set value of the energy storage converter can adopt the amplitude of the grid voltage (U d_Grid , U q_Grid ), but the voltage outer loop given value can be gradually increased to the amplitude of the grid voltage. At the same time, the sine value (sinθ) and cosine value (cosθ) required for calculating the modulation wave can use the value obtained by phase locking the grid voltage (such as PLL module). When the phase and amplitude of the output voltage on the energy storage converter side are consistent with the phase and amplitude of the grid voltage or the error is within a predetermined range, a grid connection point switch closing instruction is issued. After the grid connection point switch completes the closing action according to the grid connection switch closing instruction, the energy storage converter can be controlled to operate in the grid connection mode. In this process, since the voltage outer loop given value of the energy storage converter in the off-grid mode and the sine value (sinθ) and cosine value (cosθ) required for calculating the modulation wave are all from the grid, the amplitude and phase of the output voltage of the energy storage converter are highly consistent with the amplitude and phase of the grid voltage. Therefore, when the grid connection point switch is closed, there is basically no impact on the current, and there is no switching of phase adjustment and phase calculation methods in the whole process, and the synchronization period is greatly shortened.

[0071] In addition, taking the grid-connected mode startup as an example to convert from off-grid mode to grid-connected mode, a solution is briefly described for keeping the output of the current inner loop of the energy storage converter unchanged when issuing a grid-connected point switch closing command. Figure 3 The control method of the energy storage converter from off-grid mode to grid-connected mode is demonstrated. Figure 3 As shown, the off-grid mode can adopt the control strategy of voltage outer loop plus current inner loop, where U d_Inv and U q_Inv is the voltage feedback of the energy storage converter output, I d_Inv and I q_Inv is the AC current feedback output by the energy storage converter, U d_Inv and I d_Inv Corresponding active component, U q_Inv and I q_Inv Corresponding to the reactive component, both the voltage outer loop and the current inner loop adopt PI control. It should be noted that for the grid-connected mode and the off-grid mode, the present disclosure is not limited to the control strategy of dual-loop control and PI control, wherein PI is a PI (proportional integral) loop control module, which compares the collected data with a set value to obtain a difference, and then uses the difference as feedback of the control result to calculate the new output value, so that the system data reaches or stabilizes near the set value.

[0072] When preparing to convert the energy storage inverter from the off-grid mode to the grid-connected mode, it is necessary to synchronously control the voltages of the front end (grid side) and the back end (converter side) of the grid-connected point switch of the energy storage inverter. When the amplitude and phase of the output voltage of the energy storage inverter are the same as the grid voltage or the error between the two is within a predetermined range, then a grid-connected point switch closing instruction is issued. At this time, the energy storage inverter still maintains the off-grid mode, and the output of the current inner loop of the energy storage inverter in the off-grid mode remains the output value of the previous cycle, realizing the transition from closed-loop control to open-loop control. When the grid-connected point switch is closed, the energy storage inverter is converted to the grid-connected mode. At this time, in the first cycle of conversion to the grid-connected mode, the initial value of the PI integral term and the initial value of the output of the current inner loop of the energy storage inverter both use the output value of the current inner loop of the energy storage inverter in the off-grid mode before the grid-connected point switch is closed. After the first cycle of switching to off-grid mode, the output of the inner current loop of the energy storage inverter continues to be obtained through the calculation method in the parallel control mode, and the initial value of the PI integral term used to obtain the output of the inner current loop through the previous calculation method in the grid-connected mode adopts the above-mentioned assignment result, that is, the output value of the inner current loop before the grid-connected point switch is closed, instead of starting the calculation from the initial value of the PI integral term of 0, so that the calculated result can ensure that the output voltage of the energy storage inverter is more consistent with the grid voltage.

[0073] In summary, when the energy storage inverter disclosed in the present invention is started in the grid-connected mode, it is necessary to first control the energy storage inverter to operate in the off-grid mode and perform synchronous control, such as gradually increasing the voltage outer loop setting of the energy storage inverter to the grid voltage, and obtaining the sine value and cosine value required for calculating the modulation wave of the energy storage inverter by phase-locking the grid voltage, so that the phase and amplitude of the off-grid output voltage of the energy storage inverter are consistent with the phase and amplitude of the grid voltage or within the allowable error range, and then close the grid-connected point switch to reduce the current impact when the grid-connected point switch is closed.

[0074] Therefore, the synchronization process disclosed in the present invention is simple, easy to control and has high control accuracy. The amplitude and phase of the output voltage of the energy storage inverter before the grid-connected point switch is closed have small errors with the amplitude and phase of the grid voltage, so as to ensure that when the grid-connected point switch is closed, the current impact on the energy storage inverter during the closing process of the grid-connected point switch can be minimized, so that the energy storage inverter can be successfully synchronized and controlled with high precision.

[0075] It should be noted that the method involving synchronous control of the energy storage inverter with the grid voltage when operating in off-grid mode, and the technical solution of controlling the amplitude and phase of the grid voltage during the synchronization process are all included in the solution of the present disclosure.

[0076] Figure 4 is a block diagram showing a control device of the energy storage converter disclosed in the present invention, such as Figure 4As shown, the device includes a mode control unit 40 , a voltage control unit 42 , an instruction issuing unit 44 and an instruction executing unit 46 .

[0077] The mode control unit 40 is configured to control the energy storage inverter to operate in the off-grid mode when the grid-connected mode of the energy storage inverter is started; the voltage control unit 42 is configured to control the voltage outer loop set value of the energy storage inverter and / or calculate the sine value and cosine value required for the modulation wave of the energy storage inverter, so that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range; the instruction issuing unit 44 is configured to issue a grid-connected point switch closing instruction after the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within the predetermined error range; the instruction execution unit 46 is configured to respond to the grid-connected point switch completing the closing action according to the grid-connected point switch closing instruction, and control the energy storage inverter to operate in the grid-connected mode.

[0078] According to an embodiment of the present disclosure, the voltage control unit 42 is also configured to control the voltage outer loop set value of the energy storage inverter to be the amplitude of the grid voltage, so that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range.

[0079] According to an embodiment of the present disclosure, the voltage control unit 42 is further configured to control the voltage outer loop set value of the energy storage converter to gradually increase to the amplitude of the grid voltage.

[0080] According to an embodiment of the present disclosure, the voltage control unit 42 is also configured to obtain the sine value and cosine value required for calculating the modulation wave of the energy storage inverter by phase-locking the grid voltage, so that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range.

[0081] According to an embodiment of the present disclosure, the voltage control unit 42 is also configured to control the voltage outer loop set value of the energy storage inverter to be the amplitude of the grid voltage, and obtain the sine value and cosine value required for calculating the modulation wave of the energy storage inverter by phase-locking the grid voltage, so that the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range.

[0082] According to an embodiment of the present disclosure, the instruction execution unit 46 is also configured to keep the output of the current inner loop of the energy storage converter unchanged before controlling the energy storage converter to operate in the grid-connected mode in response to the grid-connected point switch completing the closing action according to the grid-connected point switch closing instruction.

[0083] According to an embodiment of the present disclosure, the instruction execution unit 46 is further configured to keep the output of the inner current loop of the energy storage converter as the output value of the previous cycle in the off-grid mode.

[0084] According to an embodiment of the present disclosure, the energy storage converter simultaneously samples the three-phase voltages at the front end and rear end of the grid-connected point switch, wherein the front end of the grid-connected point switch is located on the grid side and the rear end of the grid-connected point switch is located on the energy storage converter side.

[0085] According to an embodiment of the present disclosure, a computer-readable storage medium storing instructions is provided, wherein when the instructions are executed by at least one computing device, the at least one computing device is prompted to execute a control method for an energy storage converter as described in any of the above embodiments.

[0086] According to an embodiment of the present disclosure, a system is provided including at least one computing device and at least one storage device storing instructions, wherein the instructions, when executed by the at least one computing device, prompt the at least one computing device to execute a control method for an energy storage converter as described in any of the above embodiments.

[0087] Although some embodiments of the present disclosure have been shown and described, it will be appreciated by those skilled in the art that modifications may be made to the embodiments without departing from the principles and spirit of the present disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. A control method for an energy storage converter, applied to a scenario where an off-grid mode is switched to a grid-connected mode, characterized in that: include: When the energy storage converter is started in grid-connected mode, the energy storage converter is controlled to operate in off-grid mode; By controlling the voltage outer loop given value of the energy storage converter and / or calculating the sine value and cosine value required for the modulation wave of the energy storage converter, the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range; After the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range, issuing a grid connection point switch closing instruction; In response to the grid-connected point switch completing a closing action according to the grid-connected point switch closing instruction, the energy storage converter is controlled to operate in the grid-connected mode.

2. The control method according to claim 1, characterized in that: The step of controlling the voltage outer loop given value of the energy storage converter so that the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range includes: By controlling the voltage outer loop set value of the energy storage converter to be the amplitude of the grid voltage, the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range.

3. The control method according to claim 2, characterized in that: The voltage outer loop setting value of the energy storage converter is the amplitude of the grid voltage, including: The voltage outer loop set value of the energy storage converter is controlled to gradually increase to the amplitude of the grid voltage.

4. The control method according to claim 1, characterized in that: The step of controlling and calculating the sine value and cosine value required for the modulation wave of the energy storage converter so that the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range includes: The sine value and cosine value required for the modulation wave of the energy storage converter are obtained by phase-locking the grid voltage, so that the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range.

5. The control method according to claim 1, characterized in that: The method controls the voltage outer loop given value of the energy storage converter and calculates the sine value and cosine value required by the modulation wave of the energy storage converter so that the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range, including: By controlling the voltage outer loop set value of the energy storage inverter to be the amplitude of the grid voltage, and by phase-locking the grid voltage to obtain the sine value and cosine value required for calculating the modulation wave of the energy storage inverter, the difference between the amplitude and phase of the output voltage of the energy storage inverter and the amplitude and phase of the grid voltage falls within a predetermined error range.

6. The control method according to claim 1, characterized in that: In response to the grid-connected point switch completing the closing action according to the grid-connected point switch closing instruction, before controlling the energy storage converter to operate in the grid-connected mode, the method further includes: The output of the inner current loop of the energy storage converter is kept unchanged.

7. The control method according to claim 6, characterized in that: The step of maintaining the output of the inner current loop of the energy storage converter unchanged comprises: The output of the inner current loop of the energy storage converter is maintained at the output value of the previous cycle in the off-grid mode.

8. The control method according to claim 1, characterized in that: The energy storage converter simultaneously samples the three-phase voltages at the front end and rear end of the grid-connected point switch, wherein the front end of the grid-connected point switch is located at the power grid side, and the rear end of the grid-connected point switch is located at the energy storage converter side.

9. A control device for an energy storage converter, applied to a scenario where an off-grid mode is switched to a grid-connected mode, characterized in that: include: A mode control unit is configured to control the energy storage converter to operate in an off-grid mode when the energy storage converter is started in a grid-connected mode; A voltage control unit is configured to control a voltage outer loop given value of the energy storage converter and / or calculate a sine value and a cosine value required for a modulation wave of the energy storage converter so that the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range; An instruction issuing unit is configured to issue a grid connection point switch closing instruction after the difference between the amplitude and phase of the output voltage of the energy storage converter and the amplitude and phase of the grid voltage falls within a predetermined error range; The instruction execution unit is configured to control the energy storage converter to operate in the grid-connected mode in response to the grid-connected point switch completing a closing action according to the grid-connected point switch closing instruction.

10. The control device according to claim 9, characterized in that The energy storage converter simultaneously samples the three-phase voltages at the front end and rear end of the grid-connected point switch, wherein the front end of the grid-connected point switch is located at the power grid side, and the rear end of the grid-connected point switch is located at the energy storage converter side.

11. A computer-readable storage medium storing instructions, characterized in that: When the instructions are executed by at least one computing device, the at least one computing device is prompted to execute the control method for the energy storage converter according to any one of claims 1 to 8.

12. A system comprising at least one computing device and at least one storage device storing instructions, characterized in that: When the instructions are executed by the at least one computing device, the at least one computing device is prompted to execute the control method for the energy storage converter according to any one of claims 1 to 8.

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