Island micro-grid frequency control method and device based on virtual synchronous generator, and electronic equipment

Abstract

The invention discloses an island micro-grid frequency control method and device based on a virtual synchronous generator and electronic equipment. The island micro-grid frequency control method comprises the steps of obtaining three-phase voltage data and three-phase current data at an outlet of a micro-grid inverter; determining an unbalance degree matrix according to the three-phase voltage data and the three-phase current data; judging the running state of the micro-grid according to the unbalance degree matrix; if the micro-grid is in the symmetrical operation state, the detected three-phase total active power is substituted into a proportional-integral controller so as to realize frequency control of the island micro-grid; and if the micro-grid is in the asymmetric operation state, integral three-phase total active power is determined through an accumulation integral formula, and the integral three-phase total active power is substituted into a proportional integral controller to realize frequency control of the island micro-grid. When the frequency of the island micro-grid is adjusted, the fluctuation of the frequency is smaller, the frequency fluctuation time is shorter, and the frequency recovery capability is stronger after unbalanced disturbance disappears.

Description

Technical Field

[0001] The present invention relates to the technical field of microgrids, and in particular to a frequency control method, device and electronic equipment for an island microgrid based on a virtual synchronous generator. Background Art

[0002] At present, microgrids using renewable energy distributed generation are developing rapidly, but traditional inverters have problems such as small capacity, low output impedance, and lack of inertia, which pose great challenges to the safe and stable operation of the power grid. Among them, the Virtual Synchronous Generator (VSG) technology, which introduces the generator rotor motion equation into the inverter control algorithm to make it have the same external characteristics as the traditional rotating synchronous generator, thereby improving the frequency and voltage stability of the system, has attracted widespread attention.

[0003] There are two operating modes for microgrids based on virtual synchronous generator technology. If the microgrid is in grid-connected operation, its safe and stable operation is mainly supported by the large power grid, and the operating state is not easy to change, so there is no need for frequency control. If the microgrid is in island operation, when the microgrid is subject to load fluctuations or power output fluctuations, the system will produce corresponding frequency deviations, which will seriously endanger the safe and stable operation of the microgrid. Summary of the invention

[0004] The present invention provides an island microgrid frequency control method, device and electronic equipment based on a virtual synchronous generator, so that when adjusting the frequency of the island microgrid, the frequency volatility is smaller, the frequency fluctuation time is shorter, and the frequency recovery ability is stronger after the unbalanced disturbance disappears.

[0005] According to one aspect of the present invention, a frequency control method for an island microgrid based on a virtual synchronous generator is provided. The frequency control method for an island microgrid includes:

[0006] Obtain three-phase voltage data and three-phase current data at the outlet of the microgrid inverter;

[0007] Determine an imbalance matrix according to the three-phase voltage data and the three-phase current data; wherein the imbalance matrix is ​​a matrix for measuring whether the three-phase voltage and the three-phase current in the microgrid are unbalanced;

[0008] Determine the operating status of the microgrid based on the imbalance matrix;

[0009] If the microgrid is in a symmetrical operating state, the detected three-phase total active power is substituted into the proportional-integral controller to realize frequency control of the isolated island microgrid; if the microgrid is in an asymmetrical operating state, the integrated three-phase total active power is determined by the cumulative integral formula, and the integrated three-phase total active power is substituted into the proportional-integral controller to realize frequency control of the isolated island microgrid.

[0010] Furthermore, the cumulative integral formula is:

[0011]

[0012] Among them, P st is the integrated three-phase total active power, k is the serial number, and k is N is the total number of sampling times in one power frequency cycle; Δt is the sampling time interval between two samplings; u a_t-kΔt is the voltage data of phase a in the three-phase voltage data at time t-kΔt, u b_t-kΔt is the b-phase voltage data in the three-phase voltage data at time t-kΔt, u c_t-kΔt is the c-phase voltage data in the three-phase voltage data at time t-kΔt, i a_t-kΔt is the a-phase current data of the three-phase current data at time t-kΔt, i b_t-kΔt is the b-phase current data in the three-phase current data at time t-kΔt, i c_t-kΔt is the c-phase current data among the three-phase current data at time t-kΔt.

[0013] Further, determining the imbalance matrix according to the three-phase voltage data and the three-phase current data includes:

[0014] Determine the positive sequence voltage, negative sequence voltage and zero sequence voltage according to the three-phase voltage data;

[0015] Determine positive sequence current, negative sequence current and zero sequence current according to three-phase current data;

[0016] The unbalance matrix is ​​determined based on the positive sequence voltage, the negative sequence voltage, the zero sequence voltage, the positive sequence current, the negative sequence current and the zero sequence current.

[0017] Further, determining the positive sequence voltage, the negative sequence voltage and the zero sequence voltage according to the three-phase voltage data includes:

[0018] The positive sequence voltage, negative sequence voltage and zero sequence voltage are determined according to the following formula:

[0019]

[0020] Among them, U a is the voltage data of phase a in the three-phase voltage data, U b is the b-phase voltage data in the three-phase voltage data, U c is the c-phase voltage data in the three-phase voltage data, U1 is the positive-sequence voltage, U2 is the negative-sequence voltage, U0 is the zero-sequence voltage, and α is a complex operator.

[0021] Further, the positive sequence current, the negative sequence current and the zero sequence current are determined according to the three-phase current data, including:

[0022] The positive sequence current, negative sequence current and zero sequence current are determined according to the following formula:

[0023]

[0024] Among them, I a is the a-phase current data in the three-phase voltage data, I b is the b-phase current data in the three-phase voltage data, I c is the c-phase current data in the three-phase voltage data, I1 is the positive sequence current, I2 is the negative sequence current, I0 is the zero sequence current, and α is a complex operator.

[0025] Further, an unbalance matrix is ​​determined according to the positive sequence voltage, the negative sequence voltage, the zero sequence voltage, the positive sequence current, the negative sequence current and the zero sequence current, including:

[0026] The imbalance matrix is ​​determined according to the following formula:

[0027]

[0028] ε is the imbalance matrix, |U0| is the modulus of the zero-sequence voltage, |U1| is the modulus of the positive-sequence voltage, |U2| is the modulus of the negative-sequence voltage, |I1| is the modulus of the positive-sequence current, |I2| is the modulus of the negative-sequence current, and |I0| is the modulus of the zero-sequence current.

[0029] According to another aspect of the present invention, there is provided an island microgrid frequency control device based on a virtual synchronous generator, the island microgrid frequency control device comprising:

[0030] A three-phase data acquisition module is used to acquire three-phase voltage data and three-phase current data at the outlet of the microgrid inverter;

[0031] An imbalance matrix determination module is used to determine an imbalance matrix according to the three-phase voltage data and the three-phase current data; wherein the imbalance matrix is ​​a matrix for measuring whether the three-phase voltage and the three-phase current in the microgrid are unbalanced;

[0032] An operating state judgment module, used to judge the operating state of the microgrid according to the imbalance matrix;

[0033] The frequency control module is used to substitute the detected three-phase total active power into the proportional-integral controller when the microgrid is in a symmetrical operation state to realize frequency control of the isolated island microgrid; when the microgrid is in an asymmetrical operation state, determine the integrated three-phase total active power by the cumulative integral formula, and substitute the integrated three-phase total active power into the proportional-integral controller to realize frequency control of the isolated island microgrid.

[0034] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising:

[0035] at least one processor; and

[0036] a memory communicatively connected to the at least one processor; wherein,

[0037] The memory stores a computer program that can be executed by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the frequency control method of the island microgrid based on the virtual synchronous generator described in any embodiment of the present invention.

[0038] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to implement the frequency control method of an island microgrid based on a virtual synchronous generator described in any embodiment of the present invention when executed.

[0039] According to another aspect of the present invention, a computer program product is provided. The computer program product includes a computer program. When the computer program is executed by a processor, the frequency control method of an island microgrid based on a virtual synchronous generator according to any embodiment of the present invention is implemented.

[0040] The frequency control method of an isolated microgrid based on a virtual synchronous generator provided in an embodiment of the present invention obtains three-phase voltage data and three-phase current data at the outlet of the microgrid inverter, determines an imbalance matrix according to the three-phase voltage data and the three-phase current data, and judges the operating state of the microgrid according to the imbalance matrix. If the microgrid is in a symmetrical operating state, the detected three-phase total active power is substituted into a proportional-integral controller to realize frequency control of the isolated microgrid; if the microgrid is in an asymmetric operating state, the integrated three-phase total active power is determined by a cumulative integral formula, and the integrated three-phase total active power is substituted into a proportional-integral controller. The active power is substituted into a proportional-integral controller to realize frequency control of the isolated microgrid. Compared with the prior art, when the microgrid is in an asymmetric operation state, the total active power calculated by the active power of the microgrid is directly substituted into the proportional-integral controller to realize frequency control of the isolated microgrid. In the embodiment of the present invention, the integrated three-phase total active power is determined by a cumulative integral formula, and the integrated three-phase total active power is substituted into the proportional-integral controller, so that when adjusting the frequency of the isolated microgrid, the frequency volatility is smaller, the frequency fluctuation time is shorter, and the frequency recovery ability is stronger after the unbalanced disturbance disappears.

[0041] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 is a flow chart of a frequency control method for an island microgrid based on a virtual synchronous generator provided according to an embodiment of the present invention;

[0044] Figure 2 is a schematic diagram of the corresponding relationship between three-phase voltage amplitude and time in a microgrid provided according to an embodiment of the present invention;

[0045] Figure 3 is a schematic diagram of the corresponding relationship between the three-phase voltage phase and time in a microgrid provided according to an embodiment of the present invention;

[0046] Figure 4 is a schematic diagram of the corresponding relationship between the three-phase current amplitude and time in a microgrid provided according to an embodiment of the present invention;

[0047] Figure 5 is a schematic diagram of the corresponding relationship between the three-phase current amplitude and time in a microgrid provided according to an embodiment of the present invention;

[0048] Figure 6 is a schematic diagram of the corresponding relationship between the integrated three-phase total active power and time in an asymmetric operating state provided by an embodiment of the present invention;

[0049] Figure 7 is a schematic diagram of the corresponding relationship between frequency and time in an asymmetric operating state provided by an embodiment of the present invention;

[0050] Figure 8 is a structural schematic diagram of an island microgrid frequency control device based on a virtual synchronous generator provided according to an embodiment of the present invention;

[0051] Fig. 9 A schematic diagram showing the structure of an electronic device that can be used to implement an embodiment of the present invention is shown;

[0052] Fig.10 It is a schematic diagram of the corresponding relationship between the three-phase total active power and time under an asymmetric operating state in the prior art;

[0053] Fig.11 It is a schematic diagram of the corresponding relationship between frequency and time in an asymmetric operating state in the prior art. DETAILED DESCRIPTION

[0054] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0055] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0056] The embodiment of the present invention provides a frequency control method for an island microgrid based on a virtual synchronous generator. Figure 1 is a flowchart of a frequency control method for an island microgrid based on a virtual synchronous generator according to an embodiment of the present invention, with reference to Figure 1 , the frequency control method of the isolated microgrid includes:

[0057] S110, obtaining three-phase voltage data and three-phase current data at an inverter outlet of the microgrid.

[0058] Specifically, for an isolated microgrid controlled by a virtual synchronous generator, the three-phase voltage data and three-phase current data at the outlet of the main inverter of the isolated microgrid are measured by a signal detection device configured at the outlet of the main inverter of the isolated microgrid. For example, Figure 2 is a schematic diagram of the corresponding relationship between the three-phase voltage amplitude and time in a microgrid provided according to an embodiment of the present invention, Figure 3 is a schematic diagram of the corresponding relationship between the three-phase voltage phase and time in a microgrid provided according to an embodiment of the present invention, Figure 4 is a schematic diagram of the corresponding relationship between the three-phase current amplitude and time in a microgrid provided according to an embodiment of the present invention, Figure 5 is a schematic diagram of the corresponding relationship between the three-phase current amplitude and time in a microgrid provided according to an embodiment of the present invention, with reference to Figure 2-Figure 5 , the three-phase voltage data includes the a-phase voltage vector value Ua , that is, the voltage amplitude data of phase a and the voltage phase data of phase a, the voltage vector value U of phase b b , namely the b-phase voltage amplitude data and b-phase voltage phase data, and the c-phase voltage vector value U c , namely, the c-phase voltage amplitude data and the c-phase voltage phase data; the three-phase current data includes the a-phase current vector value I a , that is, the a-phase current amplitude data and the a-phase current phase data, the b-phase current vector value I b , i.e., the b-phase current amplitude data and the b-phase current phase data, and the c-phase current vector value I c , that is, the c-phase current amplitude data and the c-phase current phase data.

[0059] S120. Determine an imbalance matrix according to the three-phase voltage data and the three-phase current data; wherein the imbalance matrix is ​​a matrix for measuring whether the three-phase voltage and the three-phase current in the microgrid are unbalanced.

[0060] Specifically, the positive-sequence voltage, negative-sequence voltage and zero-sequence voltage can be determined according to the three-phase voltage data, and the positive-sequence current, negative-sequence current and zero-sequence current can be determined according to the three-phase current data. Finally, the unbalance matrix is ​​determined according to the positive-sequence voltage, negative-sequence voltage, zero-sequence voltage, positive-sequence current, negative-sequence current and zero-sequence current.

[0061] S130. Determine the operating state of the microgrid according to the imbalance matrix.

[0062] Specifically, the maximum value of the elements in the imbalance matrix is ​​compared with the set imbalance error threshold. If the maximum value of the elements in the imbalance matrix is ​​less than or equal to the imbalance error threshold, the operation state of the microgrid is determined to be a symmetrical operation state. If the maximum value of the elements in the imbalance matrix is ​​greater than the imbalance error threshold, the operation state of the microgrid is determined to be an asymmetric operation state. Exemplarily, if the maximum value of the elements in the imbalance matrix is ​​100.17% and the imbalance error threshold is 15%, at this time, the maximum value of the elements in the imbalance matrix is ​​greater than the imbalance error threshold, indicating that the operation state of the microgrid is an asymmetric operation state.

[0063] S140. If the microgrid is in a symmetrical operating state, the detected three-phase total active power is substituted into the proportional-integral controller to realize frequency control of the isolated island microgrid; if the microgrid is in an asymmetrical operating state, the integrated three-phase total active power is determined by the cumulative integral formula, and the integrated three-phase total active power is substituted into the proportional-integral controller to realize frequency control of the isolated island microgrid.

[0064] Specifically, if the microgrid is in a symmetrical operation state, the detected three-phase total active power can be substituted into the proportional integral controller to realize the frequency control of the isolated microgrid. The three-phase total active power can also be determined according to the general expression of the microgrid active power. For example, if the three-phase total active power is determined according to the general expression of the microgrid active power, the specific calculation process is described as follows:

[0065] First, according to the analytical formula of phase a voltage of the microgrid at time t The analytical formula of phase a current of the microgrid at time t is Determine the active power P of phase a of the microgrid at time t a_t :

[0066] P a_t =u a_t i a_t =U ma I ma [cosθ a_t -cos(2ωt+θ a_t )];

[0067] Among them, u a_t is the real-time value of phase a voltage of the microgrid at time t, i a_t is the real-time value of phase a current in the microgrid at time t, U ma is the effective value of phase a voltage when the microgrid is running, I ma is the effective value of phase a current when the microgrid is running, θ a_t is the phase difference between the voltage and current of phase a when the microgrid is running at time t, and time t can represent any time;

[0068] According to the analytical formula of phase b voltage of microgrid at time t And the analytical expression of phase b current of microgrid at time t Determine the active power P of phase b of the microgrid at time t b_t :

[0069] P b_t =u b_t i b_t =U mb I mb [cosθ b_t -cos(2ωt+240°+θ b_t )];

[0070] Among them, u b_t is the real-time value of phase b voltage of the microgrid at time t, i b_t is the real-time value of phase b current of the microgrid at time t, U mb is the effective value of phase b voltage when the microgrid is running, I mb is the effective value of phase b current when the microgrid is running, θ b_tis the phase difference between the voltage and current of phase b when the microgrid is running at time t;

[0071] According to the analytical formula of phase c voltage of microgrid at time t The analytical formula of phase c current of microgrid at time t is Determine the active power P of phase c of the microgrid at time t c_t :

[0072] P c_t =u c_t i c_t =U mc I mc [cosθ c_t -cos(2ωt-240°+θ c_t )];

[0073] Among them, u c_t is the real-time value of phase c voltage of the microgrid at time t, i c_t is the real-time value of phase c current in the microgrid at time t, U mc is the effective value of phase c voltage when the microgrid is running, I mc is the effective value of phase c current when the microgrid is running, θ c_t is the phase difference between the voltage and current of phase c when the microgrid is running at time t;

[0074] When the microgrid is in a symmetrical operation state, the three phases are symmetrical, U ma , U mb and U mc The same size, to simplify the formula, use the standard voltage value U m Unified representation, I ma ,I mb and I mc The size is the same. To simplify the formula, the standard voltage value I can also be used. m The total three-phase active power P of the microgrid at time t is expressed uniformly as t for:

[0075]

[0076] Therefore, when the microgrid is in a symmetrical operation state, the total active power P of the three-phase grid at time t is t At this time, the three-phase total active power determined according to the general expression of the microgrid active power is substituted into the proportional integral controller to realize the frequency control of the isolated microgrid, so that the angular frequency deviation of the microgrid tends to 0, that is:

[0077]

[0078] Among them, P refis the mechanical power output of the power grid prime mover simulated by the virtual synchronous generator; Δω is the angular frequency deviation of the power grid at time t. t When it is a constant value, it will eventually decay to 0 after time accumulation; parameter D is the rotational inertia of the virtual synchronous generator; J is the damping coefficient of the virtual synchronous generator; parameter k p is the active frequency deviation feedback coefficient of the virtual synchronous generator; ω0 is the rated value of the angular velocity of the virtual synchronous generator; k is the proportional integral control coefficient introduced by the virtual synchronous generator in the frequency regulation control link; s and s 2 is a variable.

[0079] When the microgrid is in an asymmetric operation state, the double frequency components in the active power of phase a, phase b, and phase c at time t cannot be offset after adding, so the total active power P of the three phases obtained by adding the active power of phase a, phase b, and phase c is t There is still a 2-fold frequency component in the three-phase total active power P t The 2-fold frequency component will continue to accumulate, that is, the three-phase total active power P t It is always in a changing state. Therefore, in the process of proportional-integral regulation by the proportional-integral controller, the angular frequency deviation of the microgrid cannot be made to approach 0. At this time, the integral three-phase total active power P can be determined by the cumulative integral formula. st ,Right now

[0080]

[0081] Among them, P st is the integrated three-phase total active power, k is the serial number, and k is N is the total number of sampling times in one power frequency cycle; Δt is the sampling time interval between two samplings; u a_t-kΔt is the voltage data of phase a in the three-phase voltage data at time t-kΔt, u b_t-kΔt is the b-phase voltage data in the three-phase voltage data at time t-kΔt, u c_t-kΔt is the c-phase voltage data in the three-phase voltage data at time t-kΔt, i a_t-kΔt is the a-phase current data of the three-phase current data at time t-kΔt, i b_t-kΔt is the b-phase current data in the three-phase current data at time t-kΔt, i c_t-kΔt is the c-phase current data among the three-phase current data at time t-kΔt.

[0082] The integrated three-phase total active power P determined by the cumulative integral formula st Substitute the angular frequency deviation calculation formula to replace the three-phase total active power P in the formula t , thus achieving effective control of the microgrid frequency. Figure 6is a schematic diagram of the corresponding relationship between the integrated three-phase total active power and time in an asymmetric operating state provided by an embodiment of the present invention, Fig.10 It is a schematic diagram of the corresponding relationship between the three-phase total active power and time under an asymmetric operating state in the prior art, such as Figure 6 and Fig.10 As shown, the integral three-phase total active power P is determined by the cumulative integral formula st The volatility is smaller, and the curve in the time period of 0.5s-1s is more stable; Figure 7 is a schematic diagram of the corresponding relationship between frequency and time in an asymmetric operating state provided by an embodiment of the present invention, Fig.11 It is a schematic diagram of the corresponding relationship between frequency and time under an asymmetric operating state in the prior art. When the frequency is adjusted by the isolated microgrid frequency control method determined by the embodiment of the present invention, the curve in the time period of 0.5s-1s is smoother, the frequency volatility is smaller, the frequency fluctuation time is shorter, and the frequency recovery ability is stronger after the unbalanced disturbance disappears.

[0083] The frequency control method of an isolated microgrid based on a virtual synchronous generator provided in an embodiment of the present invention obtains three-phase voltage data and three-phase current data at the outlet of the microgrid inverter, determines an imbalance matrix according to the three-phase voltage data and the three-phase current data, and judges the operating state of the microgrid according to the imbalance matrix. If the microgrid is in a symmetrical operating state, the detected three-phase total active power is substituted into a proportional-integral controller to realize frequency control of the isolated microgrid; if the microgrid is in an asymmetric operating state, the integrated three-phase total active power is determined by a cumulative integral formula, and the integrated three-phase total active power is substituted into a proportional-integral controller. The active power is substituted into a proportional-integral controller to realize frequency control of the isolated microgrid. Compared with the prior art, when the microgrid is in an asymmetric operation state, the total active power calculated by the active power of the microgrid is directly substituted into the proportional-integral controller to realize frequency control of the isolated microgrid. In the embodiment of the present invention, the integrated three-phase total active power is determined by the cumulative integral formula, and the integrated three-phase total active power is substituted into the proportional-integral controller to adjust the frequency of the isolated microgrid. The frequency volatility is smaller, the frequency fluctuation time is shorter, and the frequency recovery ability is stronger after the unbalanced disturbance disappears.

[0084] Furthermore, the cumulative integral formula is:

[0085]

[0086] Among them, P st is the integrated three-phase total active power, k is the serial number, and k is N is the total number of sampling times in one power frequency cycle; Δt is the sampling time interval between two samplings; u a_t-kΔt is the voltage data of phase a in the three-phase voltage data at time t-kΔt, ub_t-kΔt is the b-phase voltage data in the three-phase voltage data at time t-kΔt, u c_t-kΔt is the c-phase voltage data in the three-phase voltage data at time t-kΔt, i a_t-kΔt is the a-phase current data of the three-phase current data at time t-kΔt, i b_t-kΔt is the b-phase current data in the three-phase current data at time t-kΔt, i c_t-kΔt is the c-phase current data among the three-phase current data at time t-kΔt.

[0087] Specifically, the a-phase voltage data and the a-phase current data in each data collected within half a power frequency cycle can be multiplied, the b-phase voltage data and the b-phase current data can be multiplied, and the c-phase voltage data and the c-phase current data can be multiplied to determine the a-phase active power, the b-phase active power and the c-phase active power in each data collected within half a power frequency cycle, and the a-phase active power, the b-phase active power and the c-phase active power can be summed to determine the three-phase total active power corresponding to each data collected within half a power frequency cycle, and finally the three-phase total active power corresponding to each data collected within half a power frequency cycle can be summed and averaged to determine the integrated three-phase total active power P corresponding to the half power frequency cycle. st .

[0088] Further, determining the imbalance matrix according to the three-phase voltage data and the three-phase current data includes:

[0089] Determine the positive sequence voltage, negative sequence voltage and zero sequence voltage according to the three-phase voltage data;

[0090] Determine positive sequence current, negative sequence current and zero sequence current according to three-phase current data;

[0091] The unbalance matrix is ​​determined based on the positive sequence voltage, the negative sequence voltage, the zero sequence voltage, the positive sequence current, the negative sequence current and the zero sequence current.

[0092] Specifically, the positive sequence voltage, negative sequence voltage and zero sequence voltage can be determined according to the following formula:

[0093]

[0094] Among them, U a is the voltage data of phase a in the three-phase voltage data, U b is the b-phase voltage data in the three-phase voltage data, U c is the c-phase voltage data in the three-phase voltage data, U1 is the positive sequence voltage, U2 is the negative sequence voltage, U0 is the zero sequence voltage, and α is a complex operator;

[0095] And determine the positive sequence current, negative sequence current and zero sequence current according to the following formula:

[0096]

[0097] Among them, I a is the a-phase current data in the three-phase voltage data, I b is the b-phase current data in the three-phase voltage data, I c is the c-phase current data in the three-phase voltage data, I1 is the positive sequence current, I2 is the negative sequence current, I0 is the zero sequence current, and α is a complex operator;

[0098] Finally, the imbalance matrix is ​​determined according to the following formula:

[0099]

[0100] ε is the imbalance matrix, |U0| is the modulus of the zero-sequence voltage, |U1| is the modulus of the positive-sequence voltage, |U2| is the modulus of the negative-sequence voltage, |I1| is the modulus of the positive-sequence current, |I2| is the modulus of the negative-sequence current, and |I0| is the modulus of the zero-sequence current.

[0101] Further, determining the positive sequence voltage, the negative sequence voltage and the zero sequence voltage according to the three-phase voltage data includes:

[0102] The positive sequence voltage, negative sequence voltage and zero sequence voltage are determined according to the following formula:

[0103]

[0104] Among them, U a is the voltage data of phase a in the three-phase voltage data, U b is the b-phase voltage data in the three-phase voltage data, U c is the c-phase voltage data in the three-phase voltage data, U1 is the positive-sequence voltage, U2 is the negative-sequence voltage, U0 is the zero-sequence voltage, and α is a complex operator.

[0105] Among them, a vector multiplied by α indicates that the vector is rotated 120° counterclockwise based on the original direction. 2 This indicates that the vector is rotated 120° clockwise based on its original direction.

[0106] Specifically, U1=1 / 3*U a +1 / 3*α*U b +1 / 3*α 2 *U c , U2=1 / 3*U a +1 / 3*α 2 *U b +1 / 3*α*U c , U0=1 / 3*U a +1 / 3*U b +1 / 3*U c, for example, α*U b Indicates that in U b The indicated direction is rotated 120° counterclockwise, α 2 *U c Indicates that in U c The indicated direction is based on a 120° clockwise rotation.

[0107] For example, this embodiment will use the two-phase grounding fault of phase a and phase b to simulate the asymmetric operation state of the microgrid. Set the rated value of the active power of the microgrid virtual synchronous generator to 50kW and the rated frequency to 50Hz. At 0.5s, the asymmetric operation state of the two-phase grounding fault of phase a and phase b in the microgrid is simulated, and the data at 0.7s is taken for data calculation. The three-phase voltage data at this time is:

[0108]

[0109] The positive sequence voltage, negative sequence voltage and zero sequence voltage are determined by calculation as follows:

[0110]

[0111] Further, the positive sequence current, the negative sequence current and the zero sequence current are determined according to the three-phase current data, including:

[0112] The positive sequence current, negative sequence current and zero sequence current are determined according to the following formula:

[0113]

[0114] Among them, I a is the a-phase current data in the three-phase voltage data, I b is the b-phase current data in the three-phase voltage data, I c is the c-phase current data in the three-phase voltage data, I1 is the positive sequence current, I2 is the negative sequence current, I0 is the zero sequence current, and α is a complex operator.

[0115] Specifically, I1 = 1 / 3*I a +1 / 3*α*I b +1 / 3*α 2 *I c , I2=1 / 3*I a +1 / 3*α 2 *I b +1 / 3*α*I c , I0=1 / 3*I a +1 / 3*I b +1 / 3*I c , for example, α*I b Indicates that bThe indicated direction is rotated 120° counterclockwise, α 2 *I c Indicates that c The indicated direction is based on a 120° clockwise rotation.

[0116] For example, the data at 0.7s is taken for data calculation, and the three-phase current data at this time is:

[0117]

[0118] The positive sequence current, negative sequence current and zero sequence current are determined by calculation as follows:

[0119]

[0120] Further, an unbalance matrix is ​​determined according to the positive sequence voltage, the negative sequence voltage, the zero sequence voltage, the positive sequence current, the negative sequence current and the zero sequence current, including:

[0121] The imbalance matrix is ​​determined according to the following formula:

[0122]

[0123] ε is the imbalance matrix, |U0| is the modulus of the zero-sequence voltage, |U1| is the modulus of the positive-sequence voltage, |U2| is the modulus of the negative-sequence voltage, |I1| is the modulus of the positive-sequence current, |I2| is the modulus of the negative-sequence current, and |I0| is the modulus of the zero-sequence current.

[0124] Specifically, according to the positive-sequence voltage, the negative-sequence voltage, the zero-sequence voltage, the positive-sequence current, the negative-sequence current and the zero-sequence current, the modulus of the positive-sequence voltage, the modulus of the negative-sequence voltage, the modulus of the zero-sequence voltage, the modulus of the positive-sequence current, the modulus of the negative-sequence current and the modulus of the zero-sequence current are determined. Exemplarily, the data at 0.7s is taken for data calculation, and the modulus of the positive-sequence voltage, the modulus of the negative-sequence voltage, the modulus of the zero-sequence voltage, the modulus of the positive-sequence current, the modulus of the negative-sequence current and the modulus of the zero-sequence current are respectively:

[0125]

[0126] At this time, the obtained imbalance matrix ε of the microgrid is:

[0127]

[0128] The embodiment of the present invention provides an island microgrid frequency control device based on a virtual synchronous generator. Figure 8 is a structural schematic diagram of an island microgrid frequency control device based on a virtual synchronous generator according to an embodiment of the present invention, with reference to Figure 8 , the isolated microgrid frequency control device 200 comprises:

[0129] A three-phase data acquisition module 210 is used to acquire three-phase voltage data and three-phase current data at the outlet of the microgrid inverter;

[0130] The imbalance matrix determination module 220 is used to determine the imbalance matrix according to the three-phase voltage data and the three-phase current data; wherein the imbalance matrix is ​​a matrix for measuring whether the three-phase voltage and the three-phase current in the microgrid are unbalanced;

[0131] An operating state judgment module 230 is used to judge the operating state of the microgrid according to the imbalance matrix;

[0132] The frequency control module 240 is used to substitute the detected three-phase total active power into the proportional-integral controller when the microgrid is in a symmetrical operation state to realize frequency control of the isolated island microgrid; when the microgrid is in an asymmetrical operation state, the integrated three-phase total active power is determined by the cumulative integral formula, and the integrated three-phase total active power is substituted into the proportional-integral controller to realize frequency control of the isolated island microgrid.

[0133] Furthermore, the cumulative integral formula is:

[0134]

[0135] Among them, P st is the integrated three-phase total active power, k is the serial number, and k is N is the total number of sampling times in one power frequency cycle; Δt is the sampling time interval between two samplings; u a_t-kΔt is the voltage data of phase a in the three-phase voltage data at time t-kΔt, u b_t-kΔt is the b-phase voltage data in the three-phase voltage data at time t-kΔt, u c_t-kΔt is the c-phase voltage data in the three-phase voltage data at time t-kΔt, i a_t-kΔt is the a-phase current data of the three-phase current data at time t-kΔt, i b_t-kΔt is the b-phase current data in the three-phase current data at time t-kΔt, i c_t-kΔt is the c-phase current data among the three-phase current data at time t-kΔt.

[0136] Furthermore, the imbalance matrix determination module 220 includes:

[0137] A voltage data determination unit, used for determining a positive sequence voltage, a negative sequence voltage and a zero sequence voltage according to the three-phase voltage data;

[0138] A current data determination unit, used for determining a positive sequence current, a negative sequence current and a zero sequence current according to the three-phase current data;

[0139] The unbalance matrix determining unit is used to determine the unbalance matrix according to the positive sequence voltage, the negative sequence voltage, the zero sequence voltage, the positive sequence current, the negative sequence current and the zero sequence current.

[0140] Further, the voltage data determining unit includes:

[0141] The positive sequence voltage, negative sequence voltage and zero sequence voltage are determined according to the following formula:

[0142]

[0143] Among them, U a is the voltage data of phase a in the three-phase voltage data, U b is the b-phase voltage data in the three-phase voltage data, U c is the c-phase voltage data in the three-phase voltage data, U1 is the positive-sequence voltage, U2 is the negative-sequence voltage, U0 is the zero-sequence voltage, and α is a complex operator.

[0144] Further, the current data determining unit includes:

[0145] The positive sequence current, negative sequence current and zero sequence current are determined according to the following formula:

[0146]

[0147] Among them, I a is the a-phase current data in the three-phase voltage data, I b is the b-phase current data in the three-phase voltage data, I c is the c-phase current data in the three-phase voltage data, I1 is the positive-sequence current, I2 is the negative-sequence voltage, I0 is the zero-sequence voltage, and α is a complex operator.

[0148] Furthermore, the imbalance matrix determination unit includes:

[0149] The imbalance matrix is ​​determined according to the following formula:

[0150]

[0151] ε is the imbalance matrix, |U0| is the modulus of the zero-sequence voltage, |U1| is the modulus of the positive-sequence voltage, |U2| is the modulus of the negative-sequence voltage, |I1| is the modulus of the positive-sequence current, |I2| is the modulus of the negative-sequence current, and |I0| is the modulus of the zero-sequence current.

[0152] The isolated island microgrid frequency control device based on a virtual synchronous generator provided in an embodiment of the present invention can execute the isolated island microgrid frequency control method based on a virtual synchronous generator provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method.

[0153] Fig. 9A schematic diagram of an electronic device that can be used to implement an embodiment of the present invention is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device may also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices (such as helmets, glasses, watches, etc.) and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present invention described and / or required herein.

[0154] like Fig. 9 As shown, the electronic device 10 includes at least one processor 11, and a memory connected to the at least one processor 11, such as a read-only memory (ROM) 12, a random access memory (RAM) 13, etc., wherein the memory stores a computer program that can be executed by at least one processor, and the processor 11 can perform various appropriate actions and processes according to the computer program stored in the read-only memory (ROM) 12 or the computer program loaded from the storage unit 18 to the random access memory (RAM) 13. In the RAM 13, various programs and data required for the operation of the electronic device 10 can also be stored. The processor 11, the ROM 12, and the RAM 13 are connected to each other through a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0155] A number of components in the electronic device 10 are connected to the I / O interface 15, including: an input unit 16, such as a keyboard, a mouse, etc.; an output unit 17, such as various types of displays, speakers, etc.; a storage unit 18, such as a disk, an optical disk, etc.; and a communication unit 19, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 19 allows the electronic device 10 to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks.

[0156] The processor 11 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any appropriate processor, controller, microcontroller, etc. The processor 11 executes the various methods and processes described above, such as the frequency control method of an island microgrid based on a virtual synchronous generator.

[0157] In some embodiments, the frequency control method of an island microgrid based on a virtual synchronous generator may be implemented as a computer program, which is tangibly contained in a computer-readable storage medium, such as a storage unit 18. In some embodiments, part or all of the computer program may be loaded and / or installed on the electronic device 10 via the ROM 12 and / or the communication unit 19. When the computer program is loaded into the RAM 13 and executed by the processor 11, one or more steps of the frequency control method of an island microgrid based on a virtual synchronous generator described above may be performed. Alternatively, in other embodiments, the processor 11 may be configured to execute the frequency control method of an island microgrid based on a virtual synchronous generator in any other appropriate manner (e.g., by means of firmware).

[0158] Various implementations of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include: being implemented in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0159] Computer programs for implementing the methods of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when the computer program is executed by the processor, the functions / operations specified in the flow chart and / or block diagram are implemented. The computer program may be executed entirely on the machine, partially on the machine, partially on the machine and partially on a remote machine as a stand-alone software package, or entirely on a remote machine or server.

[0160] In the context of the present invention, a computer-readable storage medium may be a tangible medium that may contain or store a computer program for use by or in combination with an instruction execution system, device or equipment. A computer-readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices or equipment, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0161] To provide interaction with a user, the systems and techniques described herein may be implemented on an electronic device having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and a pointing device (e.g., a mouse or trackball) through which the user can provide input to the electronic device. Other types of devices may also be used to provide interaction with the user; for example, the feedback provided to the user may be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user may be received in any form (including acoustic input, voice input, or tactile input).

[0162] The systems and techniques described herein may be implemented in a computing system that includes backend components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes frontend components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such backend components, middleware components, or frontend components. The components of the system may be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: a local area network (LAN), a wide area network (WAN), a blockchain network, and the Internet.

[0163] A computing system may include a client and a server. The client and the server are generally remote from each other and usually interact through a communication network. The client and server relationship is generated by computer programs running on the corresponding computers and having a client-server relationship with each other. The server may be a cloud server, also known as a cloud computing server or cloud host, which is a host product in the cloud computing service system to solve the defects of difficult management and weak business scalability in traditional physical hosts and VPS services.

[0164] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0165] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A frequency control method for an island microgrid based on a virtual synchronous generator, characterized in that: include: Obtain three-phase voltage data and three-phase current data at the outlet of the microgrid inverter; Determine an imbalance matrix according to the three-phase voltage data and the three-phase current data; wherein the imbalance matrix is ​​a matrix for measuring whether the three-phase voltage and the three-phase current in the microgrid are unbalanced; Determining the operating state of the microgrid according to the imbalance matrix; If the microgrid is in a symmetrical operating state, the detected three-phase total active power is substituted into the proportional-integral controller to realize frequency control of the isolated island microgrid; if the microgrid is in an asymmetrical operating state, the integrated three-phase total active power is determined by the cumulative integral formula, and the integrated three-phase total active power is substituted into the proportional-integral controller to realize frequency control of the isolated island microgrid.

2. The frequency control method of the isolated island microgrid according to claim 1, characterized in that: The cumulative integral formula is: Among them, P st is the integrated three-phase total active power, k is the serial number, and k is 0, 1, 2, ..., N is the total number of sampling times in one power frequency cycle; Δt is the sampling time interval between two samplings; u a_t-kΔt is the voltage data of phase a in the three-phase voltage data at time t-kΔt, u b_t-kΔt is the b-phase voltage data in the three-phase voltage data at time t-kΔt, u c_t-kΔt is the c-phase voltage data in the three-phase voltage data at time t-kΔt, i a_t-kΔt is the a-phase current data of the three-phase current data at time t-kΔt, i b_t-kΔt is the b-phase current data in the three-phase current data at time t-kΔt, i c_t-kΔt is the c-phase current data among the three-phase current data at time t-kΔt.

3. The frequency control method of the isolated island microgrid according to claim 1, characterized in that: Determining an imbalance matrix according to the three-phase voltage data and the three-phase current data includes: Determine the positive sequence voltage, the negative sequence voltage and the zero sequence voltage according to the three-phase voltage data; Determine the positive sequence current, the negative sequence current and the zero sequence current according to the three-phase current data; The imbalance matrix is ​​determined according to the positive-sequence voltage, the negative-sequence voltage, the zero-sequence voltage, the positive-sequence current, the negative-sequence current and the zero-sequence current.

4. The frequency control method of the isolated island microgrid according to claim 1, characterized in that: The determining of the positive sequence voltage, the negative sequence voltage and the zero sequence voltage according to the three-phase voltage data comprises: The positive sequence voltage, the negative sequence voltage and the zero sequence voltage are determined according to the following formula: Among them, U a is the voltage data of phase a in the three-phase voltage data, U b is the b-phase voltage data in the three-phase voltage data, U c is the c-phase voltage data in the three-phase voltage data, U1 is the positive-sequence voltage, U2 is the negative-sequence voltage, U0 is the zero-sequence voltage, and α is a complex operator.

5. The frequency control method of the isolated island microgrid according to claim 4, characterized in that: The determining of the positive sequence current, the negative sequence current and the zero sequence current according to the three-phase current data comprises: The positive sequence current, the negative sequence current and the zero sequence current are determined according to the following formula: Among them, I a is the a-phase current data in the three-phase voltage data, I b is the b-phase current data in the three-phase voltage data, I c is the c-phase current data in the three-phase voltage data, I1 is the positive-sequence current, I2 is the negative-sequence voltage, I0 is the zero-sequence voltage, and α is a complex operator.

6. The frequency control method of the isolated island microgrid according to claim 5, characterized in that: The determining the imbalance matrix according to the positive-sequence voltage, the negative-sequence voltage, the zero-sequence voltage, the positive-sequence current, the negative-sequence current and the zero-sequence current comprises: The imbalance matrix is ​​determined according to the following formula: ε is the imbalance matrix, |U0| is the modulus of the zero-sequence voltage, |U1| is the modulus of the positive-sequence voltage, |U2| is the modulus of the negative-sequence voltage, |I1| is the modulus of the positive-sequence current, |I2| is the modulus of the negative-sequence current, and |I0| is the modulus of the zero-sequence current.

7. A frequency control device for an island microgrid based on a virtual synchronous generator, characterized in that: include: A three-phase data acquisition module is used to acquire three-phase voltage data and three-phase current data at the outlet of the microgrid inverter; An imbalance matrix determination module, used to determine an imbalance matrix according to the three-phase voltage data and the three-phase current data; wherein the imbalance matrix is ​​a matrix for measuring whether the three-phase voltage and the three-phase current in the microgrid are unbalanced; An operating state judgment module, used to judge the operating state of the microgrid according to the imbalance matrix; The frequency control module is used to substitute the detected three-phase total active power into the proportional-integral controller when the microgrid is in a symmetrical operation state to realize frequency control of the isolated island microgrid; when the microgrid is in an asymmetrical operation state, determine the integrated three-phase total active power by the cumulative integral formula, and substitute the integrated three-phase total active power into the proportional-integral controller to realize frequency control of the isolated island microgrid.

8. An electronic device, characterized in that: The electronic device comprises: at least one processor; and a memory communicatively connected to the at least one processor; wherein, The memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the frequency control method for an island microgrid based on a virtual synchronous generator as described in any one of claims 1-6.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to implement the frequency control method for an island microgrid based on a virtual synchronous generator according to any one of claims 1 to 6 when executed.

10. A computer program product, characterized in that The computer program product comprises a computer program, which, when executed by a processor, implements the frequency control method for an island microgrid based on a virtual synchronous generator according to any one of claims 1 to 6.

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