A design method of wind storage combined frequency modulation based on VSG control

Abstract

The present application belongs to the technical field of power system stability control, and particularly relates to a wind storage combined frequency modulation design method based on VSG control. The present application comprises: the rotor field oriented vector control strategy is adopted for the machine side converter, the actual value and the given value of voltage are taken as input signals, the voltage control signal is synthesized, so that the bus voltage is constant; the VSG control strategy is adopted for the grid side converter control, so that the control of the converter is realized; the energy storage system is added at the DC bus, the double closed loop strategy of power outer ring and current inner ring is adopted, the charging and discharging of the storage battery is controlled, and the compensation of frequency secondary drop is realized. The present application not only overcomes the defect that VSG can only participate in the primary frequency modulation of the power grid, but also makes up for the frequency drop problem generated during the speed recovery of the wind turbine, solves the problem of insufficient active reserve of the wind turbine, and improves the system frequency stability. The constant DC bus voltage is realized, and the output power and the input power of the two side converters are maintained.

Description

Technical Field

[0001] This invention belongs to the field of power system stability control technology, and particularly relates to a wind-storage joint frequency regulation design method based on VSG control. Background Technology

[0002] With the formation of the "dual-high" characteristics of high proportion of new energy and high proportion of power electronic equipment, the traditional power system dominated by thermal power generation is gradually transforming into a new type of power system with new energy as the main body. However, under general control methods, new energy units cannot participate in system frequency regulation, resulting in a "low inertia" characteristic of the power system, which leads to prominent stability problems in the "dual-high" power system.

[0003] In existing technologies, VSG can enable wind turbines to have primary frequency regulation capabilities. However, when the power system experiences significant disturbances, relying solely on the system's primary frequency regulation without coordinating with the system's secondary frequency regulation can only alleviate the frequency decline trend and cannot achieve error-free frequency regulation. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, this invention provides a wind-storage joint frequency regulation design method based on VSG control. Its purpose is to compensate for the deficiencies of VSG in secondary frequency regulation, mitigate the frequency drop problem caused during wind turbine speed recovery, and ultimately improve the stability of the power system.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0006] A wind-storage joint frequency regulation design method based on VSG control includes the following steps:

[0007] Step 1. The machine-side converter adopts a rotor field-oriented vector control strategy, using the actual voltage value and the setpoint as input signals to synthesize a voltage control signal, so that the bus voltage is constant;

[0008] Step 2. The grid-side converter control adopts the VSG control strategy to achieve converter control;

[0009] Step 3. Add an energy storage system at the DC bus to enable secondary frequency drop and VSG participation in secondary frequency regulation. Use a dual closed-loop strategy of power outer loop and current inner loop to control battery charging and discharging, thereby compensating for secondary frequency drop.

[0010] Furthermore, in the rotor magnetic field orientation vector control strategy, .

[0011] Furthermore, in the rotor magnetic field orientation vector control strategy, At that time, the formula for the generator stator phase voltage is:

[0012] In the formula, s represents the complex variable used in the Laplace transform. This refers to the stator phase voltage of the generator. For synchronous angular velocity; L sq L sd The stator winding inductances for the q-axis and d-axis are respectively, i sq i sd These are the stator currents along the q-axis and d-axis, respectively. For stator flux linkage.

[0013] Furthermore, in the rotor magnetic field orientation vector control strategy, At that time, the machine-side converter control system is a dual-loop control system under the joint control of voltage and current. The outer loop is the DC bus voltage loop, which compares the actual voltage value with the setpoint value, and the deviation is passed through a PI regulator to obtain the output as the quadrature-axis setpoint current i. sqref The given value of the direct-axis current i sdref =0, through current inner loop control, the electromagnetic power is changed, and finally the machine-side converter achieves constant DC bus voltage; the voltage equation is transformed from a three-phase stationary coordinate system to a two-phase rotating coordinate system as follows:

[0014] In the formula, s represents the complex variable used in the Laplace transform, u sd u sq The voltages are the voltages on the direct axis and the quadrature axis. For synchronous angular velocity, R s It is the stator resistance, L sq L sd The stator winding inductances for the q-axis and d-axis are respectively, i sq i sd These are the stator currents along the q-axis and d-axis, respectively. Let d be the stator flux linkage, and d / dt be the differential operator.

[0015] Furthermore, the grid-side converter control adopts the VSG control strategy, which uses the phase information and voltage amplitude information generated by the active-frequency controller and reactive-voltage controller in the VSG control to synthesize a voltage control signal, thereby controlling the converter.

[0016] Furthermore, the VSG control strategy is modeled using a second-order model, with the following equations:

[0017] In the formula, E is the magnetizing electromotive force, U is the armature voltage, and I is the armature current. , , It is expressed in vector form, where J is the moment of inertia and D is the damping coefficient. Let J be the electrical angle, j be the imaginary part, and P be the electrical angle. m P e These are the mechanical power output by the prime mover and the electromagnetic power output by the generator, respectively. The rated angular frequency, For virtual angular frequency, ω g Let d be the reference angular frequency, t be time, and d / dt be the differential operator. The difference between the reference angular frequency and the virtual angular frequency, For armature resistance, It is a synchronous reactance.

[0018] Furthermore, the addition of an energy storage system at the DC bus is based on the actual power P input to the grid. g and grid demand command P agc The difference is the input signal.

[0019] Furthermore, when the actual power P input to the power grid... g and grid demand command P agc When the difference is the input signal, the physical constraint equations of the energy storage system are as follows:

[0020] In the formula, s is the complex variable used in the Laplace transform, and P ES For energy storage discharge power, J and Here, E represents the inertia coefficient and damping coefficient of the VSG, respectively; E represents the VSG voltage amplitude; and U represents the turbine terminal voltage. For VSG mechanical angular velocity, Where L is the grid synchronization angular velocity, and L is the filter inductance. This represents the power fluctuation value.

[0021] A computer device includes a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor. When the processor executes the computer program, it implements the steps of the wind-storage joint frequency regulation design method based on VSG control.

[0022] A computer storage medium storing a computer program, wherein when the computer program is executed by a processor, the steps of the wind-storage joint frequency regulation design method based on VSG control are implemented.

[0023] The present invention has the following beneficial effects and advantages:

[0024] This invention provides a wind-storage combined frequency regulation design method based on VSG control. The method employs a wind-storage combined frequency regulation design, with the PMSG generator-side converter control using i... dA vector control strategy with a rotor field orientation of 0 is employed. By comparing the actual voltage value with the setpoint, the bus voltage is kept constant, maintaining the output power of both converters equal to the input power. The grid-side converter control uses a VSG control strategy. Phase information from the active-frequency controller and reactive-voltage controller within the VSG is combined with voltage amplitude information to synthesize a voltage control signal, thereby controlling the converter, providing inertia and damping support, and thus adjusting the grid frequency in a timely manner. An energy storage system is added at the DC bus to input the actual power P into the grid. g and grid demand command P agc The difference is used as the input signal. A dual closed-loop strategy of power outer loop and current inner loop is adopted to control the charging and discharging of the battery, thereby achieving the purpose of compensating for the secondary frequency drop. This invention overcomes the defect that VSG can only participate in the primary frequency regulation of the power grid, makes up for the frequency drop problem caused during the wind turbine speed recovery period, solves the problem of insufficient active power reserve of wind turbines, and improves the frequency stability of the system.

[0025] (1) This invention addresses the characteristic that VSG can only enable wind turbines to have primary frequency regulation capability by adding an energy storage system at the DC bus to input the actual power P to the grid. g and grid demand command P agc The difference is used as the input signal. A dual closed-loop strategy of power outer loop and current inner loop is adopted to control the charging and discharging of the battery, so that the wind turbine has the ability to regulate the frequency twice, thereby achieving the purpose of compensating for the second frequency drop.

[0026] (2) An energy storage system is added at the DC bus of the present invention. The physical constraints of the energy storage system are usually related to the rotational inertia J and damping coefficient D of the VSG. p Relatedly, VSG will adjust the charging and discharging power P of the energy storage system. ES P ES When positive, the energy storage system discharges, P ES When the value is negative, the energy storage system is charging.

[0027] (3) The machine-side converter control of this invention adopts i d The rotor field-oriented vector control strategy with a value of 0 is adopted. When this control method is used, the electromagnetic torque is relatively easy to control because the electromagnetic torque and current have a linear relationship. By comparing the actual voltage value with the given value, the DC bus voltage is kept constant through the rectification control of the machine-side converter, and the output power of the two converters is kept equal to the input power. Attached Figure Description

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0029] Figure 1This is a schematic diagram of the VSG-controlled wind and energy storage combined structure according to an embodiment of the present invention;

[0030] Figure 2 The i-type converter used in this embodiment of the invention d A schematic diagram of vector control for rotor magnetic field orientation when it is 0;

[0031] Figure 3 This is a schematic diagram of the VSG grid-connected system structure according to an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of the control structure of a battery energy storage system according to an embodiment of the present invention;

[0033] Figure 5 This diagram shows a comparison of active power output between wind and energy storage frequency regulation controlled by VSG and wind power frequency regulation with only VSG involved, according to an embodiment of the present invention. Detailed Implementation

[0034] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0035] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0036] The following reference Figures 1-5 The technical solutions of some embodiments of the present invention are described below.

[0037] Example 1

[0038] This invention provides an embodiment of a wind-storage joint frequency regulation design method based on VSG control. For example... Figure 1 As shown, Figure 1 This is a schematic diagram of the VSG-controlled wind and energy storage combined structure according to an embodiment of the present invention.

[0039] Step 1. The machine-side converter adopts i d The rotor field-oriented vector control strategy with a value of 0 uses the actual voltage value and the setpoint as input signals to synthesize a voltage control signal, thereby keeping the bus voltage constant.

[0040] The main function of the generator-side converter is to maintain a constant bus voltage, and its control method is as follows: A rotor field-oriented vector control strategy is employed. When using this control method, the electromagnetic torque is relatively easy to control because the electromagnetic torque and current have a linear relationship, and the direct-axis armature reaction does not demagnetize the permanent magnet. The control block diagram for controlling the machine-side converter using this rotor field-oriented vector control strategy is shown below. Figure 2 As shown. The general expression for the generator stator phase voltage formula is:

[0041] ;

[0042] In the formula, s represents the complex variable used in the Laplace transform. This refers to the stator phase voltage of the generator. For synchronous angular velocity; L sq L sd The stator winding inductances for the q-axis and d-axis are respectively, i sq i sd These are the stator currents along the q-axis and d-axis, respectively. For stator flux linkage.

[0043] The generator-side converter control system is a dual-loop control system under combined voltage and current control. Its outer loop is the DC bus voltage loop, which compares the actual voltage value with the setpoint, and the deviation is processed by a PI regulator to obtain the quadrature-axis setpoint current i. sqref Under this control method, the given value i of the direct-axis current sdref =0. At this point, the electromagnetic power is changed through the inner current loop control, ultimately achieving a constant DC bus voltage in the machine-side converter. The voltage equation, when transformed from a three-phase stationary coordinate system to a two-phase rotating coordinate system, is as follows:

[0044] ;

[0045] In the formula, s represents the complex variable used in the Laplace transform, u sd u sq The voltages are the voltages on the direct axis and the quadrature axis. For synchronous angular velocity, R s It is the stator resistance, L sq L sd The stator winding inductances for the q-axis and d-axis are respectively, i sq i sd These are the stator currents along the q-axis and d-axis, respectively. Let d be the stator flux linkage, and d / dt be the differential operator.

[0046] Step 2. The grid-side converter control adopts the VSG control strategy. The phase information and voltage amplitude information generated by the active-frequency controller and reactive-voltage controller in the VSG control are combined to form a voltage control signal to control the converter.

[0047] To enable new energy power sources to possess inertia, damping, frequency regulation, and voltage regulation characteristics similar to synchronous generators, the grid-side converter of this invention employs VSG control, such as... Figure 1 As shown. The VSG rotor motion equation and the control structure diagram of the virtual excitation regulator are as follows. Figure 3 As shown. Step 2 characterizes the synchronous generator characteristics. The VSG control strategy is modeled using a second-order model, and the modeling equations for the VSG control strategy are as follows:

[0048] ;

[0049] In the formula, E is the magnetizing electromotive force, U is the armature voltage, and I is the armature current. , , It is expressed in vector form, where J is the moment of inertia and D is the damping coefficient. Let J be the electrical angle, j be the imaginary part, and P be the electrical angle. m P e These are the mechanical power output by the prime mover and the electromagnetic power output by the generator, respectively. The rated angular frequency, For virtual angular frequency, ω g Let d be the reference angular frequency, t be time, and d / dt be the differential operator. The difference between the reference angular frequency and the virtual angular frequency, For armature resistance, It is a synchronous reactance.

[0050] Step 3. Add an energy storage system at the DC bus to enable secondary frequency sag and VSG participation in secondary frequency regulation, so that the actual power P input to the grid can be adjusted. g and grid demand command P agc The difference is used as the input signal. A dual closed-loop strategy of power outer loop and current inner loop is adopted to control the charging and discharging of the battery, thereby achieving the purpose of compensating for the secondary frequency drop.

[0051] After the VSG provides inertial support, the turbine enters the speed recovery phase, and the electromagnetic power drops instantaneously, causing a secondary frequency sag in the grid. When the inertial response time of the wind turbine is too long and the proportion of renewable energy in the system is high, the magnitude of the secondary frequency sag is generally much greater than the depth of the primary sag. To solve the problems of secondary frequency sag and the inability of the VSG to participate in secondary frequency regulation, an energy storage system is added at the DC bus to input the actual power P into the grid. g and grid demand command P agc The difference is used as the input signal, and a dual closed-loop strategy of power outer loop and current inner loop is adopted to control the charging and discharging of the battery. Its control structure is as follows: Figure 4 As shown, the physical constraint equations of the energy storage system are as follows:

[0052] ;

[0053] In the formula, s is the complex variable used in the Laplace transform, and P ES For energy storage discharge power, J and Here, E represents the inertia coefficient and damping coefficient of the VSG, respectively; E represents the VSG voltage amplitude; and U represents the turbine terminal voltage. For VSG mechanical angular velocity, Where L is the grid synchronization angular velocity, and L is the filter inductance. This represents the power fluctuation value.

[0054] The wind-storage joint frequency regulation method based on VSG control of the present invention can effectively improve the stability of new energy power generation systems and provides certain theoretical support and technical guarantee for grid-connected operation control of new energy power generation systems using VSG and energy storage.

[0055] Example 2

[0056] This invention provides another embodiment, which is a wind-storage joint frequency regulation design method based on VSG control, comprising:

[0057] The improvement effect of the VSG-controlled wind-storage joint frequency regulation design method in this embodiment of the invention is as follows: Figure 5 As shown. Figure 5 The curves show the comparison of active power when VSG control is used, with and without energy storage. Figure 5 It was designed based on the MATLAB / Simulink simulation platform. In this embodiment, a frequency drop of 0.1 Hz was set at t=1s, and the output power of the VSG before and after energy storage was observed.

[0058] Depend on Figure 5 It can be seen that the active power remains stable at 2MW during normal system operation. After t=1s, the active power contribution without energy storage is relatively small, and the response speed is slow. When connected to the traditional power grid, it is more prone to frequency instability. In contrast, the active power contribution of wind and energy storage joint frequency regulation based on VSG control is larger and the response is faster, proving the effectiveness of the wind and energy storage joint control method based on VSG control for frequency regulation.

[0059] Example 3

[0060] Based on the same inventive concept, embodiments of the present invention also provide a computer device, including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor. When the processor executes the computer program, it implements the steps of any of the wind-storage joint frequency regulation design methods based on VSG control described in Embodiment 1 or 2.

[0061] Example 4

[0062] Based on the same inventive concept, this embodiment of the invention also provides a computer storage medium storing a computer program, which, when executed by a processor, implements the steps of any of the wind-storage joint frequency regulation design methods based on VSG control described in embodiment 1 or 2.

[0063] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0064] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0065] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0066] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0067] In the description of this specification, the terms "one embodiment," "some embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A wind-storage joint frequency regulation design method based on VSG control, characterized by: Includes the following steps: Step 1. The machine-side converter adopts a rotor field-oriented vector control strategy, using the actual voltage value and the setpoint as input signals to synthesize a voltage control signal, thereby keeping the bus voltage constant; in the rotor field-oriented vector control strategy, ; In a rotor field-oriented vector control strategy, At that time, the formula for the generator stator phase voltage is: In the formula, s represents the complex variable used in the Laplace transform. This refers to the stator phase voltage of the generator. For synchronous angular velocity; L sq L sd The stator winding inductances for the q-axis and d-axis are respectively, i sq i sd These are the stator currents along the q-axis and d-axis, respectively. For stator flux linkage; in the vector control strategy for rotor magnetic field orientation, At that time, the machine-side converter control system is a dual-loop control system under the joint control of voltage and current. The outer loop is the DC bus voltage loop, which compares the actual voltage value with the setpoint value, and the deviation is passed through a PI regulator to obtain the output as the quadrature-axis setpoint current i. sqref The given value of the direct-axis current i sdref =0, through current inner loop control, the electromagnetic power is changed, and finally the machine-side converter achieves constant DC bus voltage; the voltage equation is transformed from a three-phase stationary coordinate system to a two-phase rotating coordinate system as follows: In the formula, s represents the complex variable used in the Laplace transform, u sd u sq The voltages are the voltages on the direct axis and the quadrature axis. For synchronous angular velocity, R s It is the stator resistance, L sq L sd The stator winding inductances for the q-axis and d-axis are respectively, i sq i sd These are the stator currents along the q-axis and d-axis, respectively. Here, d is the stator flux linkage, and d / dt is the differential operator; Step 2. The grid-side converter control adopts the VSG control strategy to control the converter. The VSG control strategy is achieved by synthesizing the voltage control signal from the phase information and voltage amplitude information generated by the active-frequency controller and reactive-voltage controller in the VSG control, thereby controlling the converter. The VSG control strategy is modeled using a second-order model, and the equations are as follows: In the formula, E is the magnetizing electromotive force, U is the armature voltage, and I is the armature current. , , It is expressed in vector form, where J is the moment of inertia and D is the damping coefficient. Let J be the electrical angle, j be the imaginary part, and P be the electrical angle. m P e These are the mechanical power output by the prime mover and the electromagnetic power output by the generator, respectively. The rated angular frequency, For virtual angular frequency, ω g Let d be the reference angular frequency, t be time, and d / dt be the differential operator. The difference between the reference angular frequency and the virtual angular frequency, For armature resistance, Synchronous reactance; Step 3. Add an energy storage system at the DC bus to compensate for the secondary frequency sag and the participation of the VSG in secondary frequency regulation. A dual closed-loop strategy of power outer loop and current inner loop is used to control battery charging and discharging, thus achieving compensation for the secondary frequency sag. The energy storage system added to the DC bus is based on the actual power P input to the grid. g and grid demand command P agc The difference is the input signal; at this time, the physical constraint equations of the energy storage system are as follows: In the formula, s is the complex variable used in the Laplace transform, and P ES For energy storage discharge power, J and Here, E represents the inertia coefficient and damping coefficient of the VSG, respectively; E represents the VSG voltage amplitude; and U represents the turbine terminal voltage. For VSG mechanical angular velocity, Where L is the grid synchronization angular velocity, and L is the filter inductance. This represents the power fluctuation value.

2. A computer device, characterized by: It includes a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor. When the processor executes the computer program, it implements the steps of the wind-storage joint frequency regulation design method based on VSG control as described in claim 1.

3. A computer storage medium, characterized in that: The computer storage medium contains a computer program, which, when executed by a processor, implements the steps of the wind-storage joint frequency regulation design method based on VSG control as described in claim 1.

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