Network-constructed energy storage converter and control method thereof

Abstract

This application discloses a grid-connected energy storage converter and its control method. The method includes: outputting a grid impedance value based on the grid connection point voltage amplitude, active current, and reactive current in multiple operating points; calculating a PWM modulation voltage command based on the output voltage phase, output voltage reference value, grid connection point voltage, grid connection point current, and the grid impedance value; and performing space vector modulation on the PWM modulation voltage command to generate a drive signal for controlling the grid-connected converter. By introducing grid impedance measurement, this application can actively sense changes in the grid without affecting the normal operation of the energy storage converter, thereby automatically adjusting control parameters to adapt to different grid scenarios. Furthermore, it simplifies the design of the converter's control strategy and parameters, and reduces the workload of product maintenance during application while ensuring its grid adaptability and support.

Description

Technical Field

[0001] This application relates to the field of energy storage converter technology, and in particular to a grid-type energy storage converter and its control method. Background Technology

[0002] Building a new power system with renewable energy as the mainstay is a major trend in achieving the ambitious goals of "carbon peaking and carbon neutrality." Traditional renewable energy generating units operate in grid-connected mode, essentially as controlled current sources. Large-scale integration reduces grid resilience and poses significant challenges to the frequency and voltage stability of the power system. As the proportion of renewable energy generating units in the power system increases, the regulation capacity of the synchronous machines that the power system can rely on will gradually become insufficient, threatening the stability of the power system and, in turn, hindering the development of renewable energy.

[0003] Connecting energy storage to support the power grid can enhance grid resilience and safeguard the large-scale integration of new energy sources. Centralized energy storage, due to its simple topology, large single-unit capacity, and relatively easy-to-implement converter control schemes, has been widely used in grid services. The grid support capability of energy storage is mainly achieved through the control of the energy storage converter. This control can employ either the relatively mature grid-following control or the more recently developed grid-based control. Compared to grid-following control, grid-based technology allows the energy storage to operate in a manner similar to a synchronous machine. When the grid is disturbed, it can proactively respond to disturbance suppression needs, much like a synchronous machine in a traditional power system. This enhances the energy storage's adaptability to the grid while further improving its grid support capability.

[0004] However, while grid-based control systems have strong adaptability to weak power grids, their adaptability to strong power grids is poor. In practical applications, it is still necessary to adjust the control parameters of the grid-based energy storage converter according to the actual power grid scenario to ensure the output performance under the current power grid environment. As new power plants are put into the grid in batches, the power grid environment often changes significantly. The grid-based control parameters adapted to the initial power grid environment may not be suitable for the new environment, requiring manual parameter adjustments and increasing the workload of product maintenance. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a grid-type energy storage converter and its control method to solve the problem that existing grid-type energy storage converters have poor adaptability to changes in power grid scenarios and require manual adjustment of parameters according to different power grid scenarios to ensure output performance.

[0006] The technical solution adopted in this application to solve the above-mentioned technical problems is as follows:

[0007] This application provides a control method for a grid-type energy storage converter, the method comprising:

[0008] Based on the grid connection point voltage amplitude, active current, and reactive current in multiple operating points, output the grid impedance value;

[0009] The PWM modulation voltage command is calculated based on the output voltage phase, output voltage reference value, grid connection point voltage, grid connection point current, and grid impedance value.

[0010] The PWM modulated voltage command is space vector modulated to generate a drive signal for controlling the grid-type energy storage converter.

[0011] Another aspect of this application provides a grid-type energy storage converter, wherein the DC side of the grid-type energy storage converter is connected to an energy storage battery, and the AC side of the grid-type energy storage converter is connected to the power grid; the grid-type energy storage converter also includes a control unit configured to execute a control method for the grid-type energy storage converter.

[0012] The grid-type energy storage converter and its control method provided in this application, by introducing the measurement of grid impedance, can actively sense changes in the grid link without affecting the normal operation of the grid-type energy storage converter, thereby automatically adjusting the control parameters to adapt to different grid scenarios; in addition, it can simplify the design of the control strategy and parameters of the grid-type energy storage converter, and reduce the workload of converter product maintenance in application while ensuring its grid adaptability and support. Attached Figure Description

[0013] Figure 1 A block diagram illustrating the grid-type energy storage system and its control principle provided in the embodiments of this application;

[0014] Figure 2 This is a block diagram illustrating the control principle of the voltage and current control module provided in an embodiment of this application.

[0015] Figure 3 Another control principle block diagram of the voltage and current control module provided in the embodiments of this application;

[0016] Figure 4 A schematic diagram of the control method for a grid-type energy storage converter provided in an embodiment of this application.

[0017] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer and more understandable, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0019] The variables and their definitions involved in the embodiments of this application are as follows:

[0020] u oabc : Grid connection point voltage;

[0021] i oabc : Grid connection point current;

[0022] u om : Grid connection point voltage amplitude

[0023] i op Active current;

[0024] i oq Reactive current;

[0025] i Labc : Grid-side inductor current;

[0026] L g Inductance in the power grid impedance;

[0027] R g Resistance in the power grid impedance;

[0028] L pfc : The filter inductor of the converter;

[0029] C f AC filter capacitors for the converter;

[0030] P vsc Q vsc : Measured values ​​of active power and reactive power output by the converter;

[0031] θ vsc Output voltage phase;

[0032] E ref : Output voltage reference value;

[0033] e αβ_ref : The vector of the transmitted voltage command on the αβ axis;

[0034] u dc DC voltage;

[0035] C dc DC side capacitor.

[0036] Operating point: Represents the operating state of the grid connection point. A set of grid connection point voltage amplitude, active current and reactive current at a certain point in time is recorded as a set of operating points.

[0037] Figure 1 A block diagram illustrating the grid-type energy storage system and its control principle provided in the embodiments of this application.

[0038] like Figure 1 As shown, the energy storage system includes a grid-type energy storage converter Q1 and an energy storage battery C1. The DC side of the grid-type energy storage converter Q1 is connected to the energy storage battery C1, and the AC side of the grid-type energy storage converter Q1 is connected to the power grid.

[0039] The control section of a grid-type energy storage system includes active and reactive power control modules, power and current calculation modules, grid impedance measurement modules, voltage and current control modules, and PWM (Pulse Width Modulation) modulation modules.

[0040] The output of the power current calculation module is connected to the input of the grid impedance measurement module. The active and reactive power control module and the grid impedance measurement module are connected to the input of the voltage and current control module. The output of the voltage and current control module is connected to the PWM modulation module. The PWM drive signal output by the PWM modulation module is used to drive the grid-type energy storage converter Q1.

[0041] In one example, the inputs to the active and reactive power control modules include the grid connection point voltage u. oabc , grid connection point current i oabc Active power command P ref and reactive power command Q ref The output of the active and reactive power control module includes the output voltage phase θ. vsc and output voltage reference value E ref .

[0042] The active and reactive power control module is configured to collect grid-side parameter values; based on the grid-connected point voltage u in the grid-side parameter values... oabc and grid connection point current i oabc The active power P output by the energy storage converter is calculated. vsc and reactive power Q vsc .

[0043] For active power command P ref With active power P vsc The deviation is adjusted to obtain the output voltage phase θ. vsc This is to achieve control over active power.

[0044] Output voltage phase θ vsc It can be expressed as equation (1):

[0045] In the formula, G PR For an active power regulator, its frequency domain characteristics can be expressed as equation (2): Where J and D are the virtual moment of inertia and damping coefficient, respectively.

[0046] ω fwThis is a frequency feedforward quantity, which can be the grid's rated frequency ω0 or the measured frequency ω. g .

[0047] For reactive power command Q ref With reactive power Q vsc The deviation is adjusted to obtain the output voltage reference value E. ref This is to achieve control over reactive power.

[0048] Output voltage reference value E ref It can be expressed as equation (3): E ref =G QR (Q ref -Q vsc )+U fw .

[0049] In the formula, G QR and U fw These are a reactive power regulator and a voltage feedforward quantity, respectively. The former can be a PI regulator, while the latter can be the grid's rated voltage U0 or the measured voltage U. g .

[0050] In one example, the input to the power current calculation module includes active power P. vsc Reactive power Q vsc and grid connection point voltage u oabc The output of the power current calculation module includes the grid connection point voltage amplitude u. om Active current i op and reactive current i oq .

[0051] The power current calculation module is configured to calculate based on the grid connection point voltage u. oabc Calculate the voltage amplitude u at the grid connection point. om According to the active power P vsc and grid connection point voltage amplitude u om Calculate the active current i op According to reactive power Q vsc and grid connection point voltage amplitude u om Calculate the reactive current i oq .

[0052] Among them, the active current i op It can be expressed as equation (4): i op =P vsc / u om Reactive current i oq It can be expressed as equation (5): i oq =-Q vsc / u om .

[0053] Repeat the above steps to obtain three linearly independent operating points 1(u). om1 i op1 i oq1 Working point 2 (u) om2 i op2 i oq2 Working point 3 (u) om3 i op3 i oq3 ).

[0054] In one example, the inputs to the grid impedance measurement module include operating point 1 (u om1 i op1 i oq1 Working point 2 (u) om2 i op2 i oq2 Working point 3 (u) om3 i op3 i oq3 ), that is, the grid connection point voltage amplitude u of operating point 1. om1 Active current i op1 and reactive current i oq1 The grid connection voltage amplitude u at operating point 2 om2 Active current i op2 and reactive current i oq2 The grid connection voltage amplitude u at operating point 3 om3 Active current i op3 and reactive current i oq3 The output of the power grid impedance measurement module includes the resistance R in the power grid impedance. g and the reactance ω0L in the grid impedance g .

[0055] The grid impedance measurement module is configured to measure the voltage amplitude u at the grid connection point of operating point 1. om1 Active current i op1 and reactive current i oq1 The derived parameters a1, b1, c1 and d1 of working point 1 are calculated.

[0056] Among them, the derived parameter a1 of working point 1 can be expressed as equation (6): a1=(U om1 ) 2 The derived parameter b1 of operating point 1 can be expressed as equation (7): b1 = u om1 *i op1 The derived parameter c1 of operating point 1 can be expressed as equation (8): c1 = u om1 *i oq1 The derived parameter d1 of operating point 1 can be expressed as equation (9):

[0057] d1=(i op1 ) 2 +(i oq1 ) 2 .

[0058] Repeat the above steps to calculate the derived parameters a2, b2, c2, d2 for operating point 2 and the derived parameters a3, b3, c3, d3 for operating point 3.

[0059] Based on the derived parameters a1~a3, b1~b3, c1~c3, d1~d3 and the preset parameter e, the resistance R in the power grid impedance is calculated. g Reactance ω0L in the power grid impedance g and the test parameter K;

[0060] Among them, the resistance R in the power grid impedance g It can be expressed as equation (10):

[0061]

[0062] Reactance ω0L in the power grid impedance g It can be expressed as equation (11):

[0063]

[0064] The test parameter K can be expressed as equation (12):

[0065]

[0066] Based on the resistance R in the power grid impedance g Reactance ω0L in the power grid impedance g And the test parameter K, calculate the power grid impedance deviation ΔZ g ;

[0067] Among them, the network impedance deviation ΔZ g It can be expressed as equation (13):

[0068] The grid impedance deviation ΔZ g Deviation from the set value △Z of the grid impedance set Compare;

[0069] If the grid impedance deviation ΔZ g Less than the set value of grid impedance deviation △Z set Then the resistance R in the output mains impedance g Reactance ω0L in the power grid impedance g ;

[0070] If the grid impedance deviation ΔZ g Greater than the set value of grid impedance deviation △Zset If the impedance calculation fails, the operating points 1, 2, and 3 need to be collected again for recalculation.

[0071] In one example, the inputs to the voltage and current control module include the output voltage phase θ. vsc Output voltage reference value E ref Grid connection point voltage u oabc , grid connection point current i oabc Grid impedance Z g The output of the voltage and current control module includes PWM modulated voltage commands e αβ_ref .

[0072] The total impedance of the grid to which the pre-configured grid-connected energy storage converter is connected is Z. T =R T +jω0L T

[0073] The voltage and current control module is configured as follows:

[0074] Based on the output voltage phase θ vsc Output voltage reference value E ref The output voltage command u is obtained. dq_ref Among them, the output voltage command u dq_ref It can be expressed as equation (14): u dq_ref =E ref +j0.

[0075] Based on the grid connection point voltage u oabc , grid connection point current i oabc and output voltage phase θ vsc The grid connection point voltage u oabc , grid connection point current i oabc Transform to the dq coordinate system according to equations (15) and (16) respectively.

[0076] Formula (15): u odq =T 3s / 2r u oabc , Formula (16): i dq =T 3s / 2r i oabc .

[0077] Among them, T 3s / 2r The coordinate transformation matrix is ​​expressed as equation (17):

[0078]

[0079] The total impedance Z of the grid connected to the pre-configured energy storage converter is used. T Subtract the input grid impedance Z g The virtual impedance value Z is obtained.VR =jω0L VR +R VR ;

[0080] The virtual admittance parameters in the voltage regulator are updated according to the rules of equations (18) and (19) to obtain the updated voltage regulator.

[0081]

[0082] In the formula, L vmin and R vmin These are the lower limits of the inductive and resistive components in the virtual admittance parameters required to ensure the normal, controlled, and stable operation of the energy storage converter.

[0083] Output voltage command u dq_ref Grid connection point voltage u oabc The quantity u in the dq coordinate system odq The input is fed into the updated voltage regulator to obtain the grid-side current base command value i. dqV_ref .

[0084] like Figure 2 As shown, when the voltage regulator is implemented using a virtual admittance regulator, the grid-side current basic command value i dqV_ref It can be obtained from the following equation (20):

[0085] like Figure 3 As shown, when the voltage regulator is implemented using a PI regulator + virtual impedance method, the grid-side current basic command value i dqV_ref It can be obtained from the following equation (21): In the formula, It is a PI controller.

[0086] The grid-side current basic command value i dqV_ref and the disturbance current setpoint i for measuring grid impedance dq_Inj By superimposing the values, the grid-side current command value i is obtained. dq_ref It should be noted that the disturbance current setting value i for measuring the grid impedance is... dq_Inj The frequency is f h .

[0087] The grid-side current command value i dq_ref , grid connection point current i oabc The quantity i in the dq coordinate system dq and grid connection point voltage u oabc The quantity u in the dq coordinate system odq The input is given to the current regulator to obtain the quantity e of the PWM modulated voltage command in the dq coordinate system. dq_ref As shown in equation (22): e dq_ref=G CR (i dq_ref -i dq )+u odq In the formula, G CR For a current regulator, a standard PI converter will suffice.

[0088] Based on the output voltage phase θ vsc The quantity e of the PWM modulation voltage command in the dq coordinate system dq_ref The PWM modulation voltage command e is calculated. αβ_ref As shown in equation (23):

[0089] In one example, the PWM modulated voltage command e αβ_ref The input PWM modulation module performs space vector modulation to generate the drive signal required for the control of the grid-type energy storage converter, thereby realizing the grid-type control of the energy storage converter.

[0090] Figure 4 A schematic diagram of the control method for a grid-type energy storage converter provided in an embodiment of this application.

[0091] like Figure 4 As shown, the method includes the following steps:

[0092] S11. Output the grid impedance value based on the grid connection point voltage amplitude, active current and reactive current in multiple operating points;

[0093] S12. Calculate the PWM modulation voltage command based on the output voltage phase, output voltage reference value, grid connection point voltage, grid connection point current, and the grid impedance value.

[0094] S13. Perform space vector modulation on the PWM modulation voltage command to generate a drive signal for controlling the grid-type energy storage converter.

[0095] In one example, the step of outputting the grid impedance value based on the grid connection point voltage amplitude, active current, and reactive current in multiple sets of operating points includes:

[0096] Calculate the values ​​of multiple derived parameters corresponding to each set of working points;

[0097] Based on the preset parameter values ​​and all derived parameter values ​​corresponding to all group working points, the resistance, reactance, and test parameters in the power grid impedance are calculated.

[0098] The power grid impedance deviation is calculated based on the resistance in the power grid impedance, the reactance in the power grid impedance, and the test parameters.

[0099] The grid impedance value is output based on the grid impedance deviation setting value and the grid impedance deviation.

[0100] In one example, the derived parameter value includes at least one of the following:

[0101] It is calculated solely from the voltage amplitude at the grid connection point;

[0102] It is calculated from the voltage amplitude at the grid connection point and the active current;

[0103] It is calculated from the voltage amplitude and reactive current at the grid connection point;

[0104] It is calculated from active current and reactive current.

[0105] In one example, outputting the grid impedance value based on the grid impedance deviation setpoint and the grid impedance deviation includes:

[0106] Compare the set value of the power grid impedance deviation with the power grid impedance deviation;

[0107] If the grid impedance deviation is less than the grid impedance deviation set value, then the grid impedance value is output.

[0108] In one example, the step of calculating the PWM modulation voltage command based on the output voltage phase, output voltage reference value, grid connection point voltage, grid connection point current, and grid impedance value includes:

[0109] The parameters of the voltage regulator are adjusted according to the grid impedance value to obtain an updated voltage regulator;

[0110] The output voltage command is obtained based on the output voltage phase and the output voltage reference value;

[0111] The output voltage command and the grid connection point voltage in the preset coordinate system are input into the updated voltage regulator to obtain the grid-side current basic command value.

[0112] The grid-side current command value is obtained by superimposing the grid-side current base command value with the disturbance current setting value for measuring grid impedance.

[0113] The grid-side current command value, the grid connection point voltage in the preset coordinate system, and the grid connection point current in the preset coordinate system are input to the current regulator to obtain the PWM modulation voltage command in the preset coordinate system.

[0114] The PWM modulation voltage command is calculated based on the output voltage phase and the value of the PWM modulation voltage command in a preset coordinate system.

[0115] In one example, adjusting the parameters of the voltage regulator based on the grid impedance value to obtain an updated voltage regulator includes:

[0116] The virtual impedance value is obtained by subtracting the grid impedance value from the total grid impedance value to which the pre-configured grid-type energy storage converter is connected.

[0117] The virtual admittance parameter of the voltage regulator is updated using the virtual impedance value to obtain the updated voltage regulator.

[0118] In one example, updating the virtual admittance parameter of the voltage regulator with the virtual impedance value includes:

[0119] When the virtual impedance value contains the virtual inductance L VR The inductive component L in the virtual admittance parameter is greater than v The lower limit L vmin Take L at time v =L VR Conversely, take L. v =L vmin ;

[0120] When the virtual impedance value includes the virtual resistance R VR Greater than the resistive component R in the virtual admittance v The lower limit R vmin Take R at time v =R VR Conversely, take R. v =R vmin .

[0121] In one example, a set of working points is obtained in the following way:

[0122] Based on the grid connection point voltage, the grid connection point voltage amplitude in a set of operating points is calculated;

[0123] The active current in the set of operating points is calculated based on the active power and the voltage amplitude of the grid connection point in the set of operating points.

[0124] The reactive current in the set of operating points is calculated based on the reactive power and the voltage amplitude of the grid connection point in the set of operating points.

[0125] In one example, the active power and the reactive power are obtained in the following way:

[0126] Collect the grid connection point voltage and the grid connection point current;

[0127] Based on the collected grid connection point voltage and grid connection point current, the active power and reactive power are calculated.

[0128] It should be noted that the content not elaborated in detail in the above examples can be found by referring to [the relevant documentation / reference]. Figures 1-3 And its corresponding description.

[0129] The preferred embodiments of this application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and spirit of this application shall be within the scope of the claims.

Claims

1. A control method for a grid-type energy storage converter, characterized in that, The method includes: Based on the grid connection point voltage amplitude, active current, and reactive current in multiple operating points, output the grid impedance value; The PWM modulation voltage command is calculated based on the output voltage phase, output voltage reference value, grid connection point voltage, grid connection point current, and the grid impedance value. The PWM modulation voltage command is space vector modulated to generate a drive signal for controlling the grid-type energy storage converter.

2. The control method according to claim 1, characterized in that, The step of outputting the grid impedance value based on the grid connection point voltage amplitude, active current, and reactive current in multiple operating points includes: Based on the grid connection point voltage amplitude, active current, and reactive current in multiple operating points, calculate multiple derived parameter values ​​corresponding to each operating point. Based on the preset parameter values ​​and all derived parameter values ​​corresponding to all group working points, the resistance, reactance, and test parameters in the power grid impedance are calculated. The power grid impedance deviation is calculated based on the resistance in the power grid impedance, the reactance in the power grid impedance, and the test parameters. The grid impedance value is output based on the grid impedance deviation setting value and the grid impedance deviation.

3. The control method according to claim 2, characterized in that, The derived parameter value includes at least one of the following: It is calculated solely from the voltage amplitude at the grid connection point; It is calculated from the voltage amplitude at the grid connection point and the active current; It is calculated from the voltage amplitude and reactive current at the grid connection point; It is calculated from active current and reactive current.

4. The control method according to claim 2, characterized in that, The step of outputting the grid impedance value based on the grid impedance deviation setpoint and the grid impedance deviation includes: Compare the set value of the power grid impedance deviation with the power grid impedance deviation; If the grid impedance deviation is less than the grid impedance deviation set value, then the grid impedance value is output.

5. The control method according to claim 1, characterized in that, The step of calculating the PWM modulation voltage command based on the output voltage phase, output voltage reference value, grid connection point voltage, grid connection point current, and grid impedance value includes: The parameters of the voltage regulator are adjusted according to the grid impedance value to obtain an updated voltage regulator; The output voltage command is obtained based on the output voltage phase and the output voltage reference value; The output voltage command and the grid connection point voltage in the preset coordinate system are input into the updated voltage regulator to obtain the grid-side current basic command value. The grid-side current command value is obtained by superimposing the grid-side current base command value with the disturbance current setting value for measuring grid impedance. The grid-side current command value, the grid connection point voltage in the preset coordinate system, and the grid connection point current in the preset coordinate system are input to the current regulator to obtain the PWM modulation voltage command in the preset coordinate system. The PWM modulation voltage command is calculated based on the output voltage phase and the value of the PWM modulation voltage command in a preset coordinate system.

6. The control method according to claim 5, characterized in that, The step of adjusting the parameters of the voltage regulator according to the grid impedance value to obtain an updated voltage regulator includes: The virtual impedance value is obtained by subtracting the grid impedance value from the total grid impedance value to which the pre-configured grid-type energy storage converter is connected. The virtual admittance parameter of the voltage regulator is updated using the virtual impedance value to obtain the updated voltage regulator.

7. The control method according to claim 6, characterized in that, The step of updating the virtual admittance parameter of the voltage regulator using the virtual impedance value includes: When the virtual impedance value contains the virtual inductance L VR The inductive component L in the virtual admittance parameter is greater than v The lower limit L vmin Take L at time v =L VR Conversely, take L. v =L vmin ; When the virtual impedance value includes the virtual resistance R VR Greater than the resistive component R in the virtual admittance v The lower limit R vmin Take R at time v =R VR Conversely, take R. v =R vmin .

8. The control method according to claim 1, characterized in that, A set of operating points is obtained in the following way: Based on the grid connection point voltage, the grid connection point voltage amplitude in a set of operating points is calculated; The active current in the set of operating points is calculated based on the active power and the voltage amplitude of the grid connection point in the set of operating points. The reactive current in the set of operating points is calculated based on the reactive power and the voltage amplitude of the grid connection point in the set of operating points.

9. The control method according to claim 8, characterized in that, The active power and the reactive power are obtained in the following ways: Collect the grid connection point voltage and the grid connection point current; Based on the collected grid connection point voltage and grid connection point current, the active power and reactive power are calculated.

10. A grid-type energy storage converter, characterized in that, The DC side of the grid-type energy storage converter is connected to the energy storage battery, and the AC side of the grid-type energy storage converter is connected to the power grid; the grid-type energy storage converter also includes a control unit configured to execute the control method according to any one of claims 1-9.

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