An inverter control method and device

Abstract

The embodiment of the present application provides a kind of inverter control method and device, when the grid state is normal, based on the first inverter power control signal generated according to the positive sequence current reference value, the sine value of positive sequence phase angle, the cosine value of positive sequence phase angle, positive sequence current and positive sequence voltage, the inverter is controlled.When the grid state is failure, the second inverter power control signal generated according to the positive sequence reactive current reference, the negative sequence reactive current reference, the positive sequence current, the negative sequence current, the positive sequence voltage and the negative sequence voltage are used to control the inverter.In the embodiment of the present application, positive sequence phase-locked loop and negative sequence phase-locked loop are not used, avoid the large amount of calculation caused by using positive sequence voltage phase-locked loop and negative sequence voltage phase-locked loop, and the problem of low inverter control efficiency caused by the slow response speed of negative sequence voltage phase-locked loop, effectively improve the inverter control efficiency.

Description

Technical Field

[0001] This application relates to the field of inverter and converter technology, and in particular to an inverter control method and apparatus. Background Technology

[0002] Asymmetrical faults in a power system refer to the damage or failure of one or more phases in a three-phase power system, causing the three-phase voltage, current, power, and other parameters to become unbalanced. Asymmetrical faults can lead to power system instability, and even equipment damage and system failure.

[0003] Currently, when an asymmetrical fault occurs, positive-sequence voltage phase-locked loops and negative-sequence voltage phase-locked loops can be used to calculate the positive-sequence reactive current and negative-sequence reactive current respectively. The inverter can restore the positive-sequence voltage based on the positive-sequence reactive current and suppress the rise of the negative-sequence voltage based on the negative-sequence reactive current, so as to solve the asymmetrical fault or reduce the impact of the asymmetrical fault on the power system.

[0004] Because both positive-sequence and negative-sequence reactive currents are calculated using both positive-sequence and negative-sequence voltage-locked loops, the computational load is large. Furthermore, the negative-sequence voltage-locked loop only starts after an asymmetrical fault occurs, resulting in a slow response speed and reduced inverter control efficiency. Summary of the Invention

[0005] To address the aforementioned issues, this application provides an inverter control method and apparatus.

[0006] The embodiments of this application disclose the following technical solutions:

[0007] First aspect: This application provides an inverter control method, including:

[0008] The three-phase voltages are separated into positive and negative sequence voltages to obtain positive and negative sequence voltages; the three-phase currents are also separated into positive and negative sequence currents to obtain positive and negative sequence currents.

[0009] The grid state is determined based on the effective values ​​of the positive-sequence voltage and the negative-sequence voltage.

[0010] When the power grid is in a normal state, the positive sequence power setpoint and the positive sequence power feedback value are input into the proportional-integral controller to obtain the positive sequence current reference value; the positive sequence power feedback value is calculated based on the positive sequence voltage and the positive sequence current.

[0011] The inverter is controlled based on a first inverter power control signal generated according to the positive sequence current reference value, the sine value of the positive sequence phase angle, the cosine value of the positive sequence phase angle, the positive sequence current, and the positive sequence voltage; the sine value and the cosine value of the positive sequence phase angle are calculated based on the positive sequence voltage.

[0012] When the power grid is in a fault state, based on the positive sequence voltage, negative sequence voltage, sine value of positive sequence phase angle, cosine value of positive sequence phase angle, sine value of negative sequence phase angle, and cosine value of negative sequence phase angle, reactive reference current is calculated to obtain positive sequence reactive reference current and negative sequence reactive reference current.

[0013] The inverter is controlled based on the second inverter power control signal generated according to the positive-sequence reactive reference current, negative-sequence reactive reference current, positive-sequence current, negative-sequence current, positive-sequence voltage, and negative-sequence voltage.

[0014] In one possible implementation, determining the grid state based on the effective values ​​of the positive-sequence voltage and the negative-sequence voltage includes:

[0015] When the effective value of the positive sequence voltage is within a first preset range and the effective value of the negative sequence voltage is within a second preset range, the power grid state is determined to be normal; otherwise, the power grid state is determined to be faulty.

[0016] In one possible implementation, when the power grid state is a fault, reactive power reference current is calculated based on the positive-sequence voltage, negative-sequence voltage, the sine of the positive-sequence phase angle, the cosine of the positive-sequence phase angle, the sine of the negative-sequence phase angle, and the cosine of the negative-sequence phase angle to obtain positive-sequence reactive power reference current and negative-sequence reactive power reference current, including:

[0017] When the power grid is in a fault state, calculate the ratio of the effective value of the positive sequence voltage to the rated value of the system voltage;

[0018] The product of the preset coefficient, the difference between the ratio, the first coefficient, the effective value of the positive sequence voltage, the cosine value of the positive sequence phase angle, and the rated current value of the equipment is determined as the α-axis component of the positive sequence reactive reference current; the product of the preset coefficient, the difference between the ratio, the first coefficient, the effective value of the positive sequence voltage, the sine value of the positive sequence phase angle, and the rated current value of the equipment is determined as the β-axis component of the positive sequence reactive reference current; the product of the cosine value of the negative sequence phase angle, the second coefficient, the effective value of the negative sequence voltage, and the rated current value of the equipment is determined as the α-axis component of the negative sequence reactive reference current; the product of the negative value of the sine of the negative sequence phase angle, the second coefficient, the effective value of the negative sequence voltage, and the rated current value of the equipment is determined as the β-axis component of the negative sequence reactive reference current.

[0019] In one possible implementation, controlling the inverter based on a second inverter power control signal generated according to the positive-sequence reactive power reference current, negative-sequence reactive power reference current, positive-sequence current, negative-sequence current, positive-sequence voltage, and negative-sequence voltage includes:

[0020] Based on the positive-sequence reactive reference current and the negative-sequence reactive reference current, the relationship between the current setpoint and time is calculated.

[0021] Based on the relationship between the current setpoint and time, the maximum value of the current setpoint is calculated within half a cycle;

[0022] The positive-sequence reactive reference current and the negative-sequence reactive reference current are limited based on the maximum value of the current setpoint to obtain the positive-sequence current setpoint and the negative-sequence current setpoint.

[0023] The inverter is controlled based on the second inverter power control signal generated by the positive sequence current setpoint, negative sequence current setpoint, positive sequence current, negative sequence current, positive sequence voltage, and negative sequence voltage.

[0024] In one possible implementation, when the power grid state is normal, inputting the positive-sequence power setpoint and the positive-sequence power feedback value into the proportional-integral controller to obtain the positive-sequence current reference value includes:

[0025] When the power grid is in normal condition, the positive sequence power setpoint and positive sequence power feedback value are input into the proportional-integral controller to obtain the positive sequence reference current, which is the product of the difference between the positive sequence power setpoint and the positive sequence power feedback value and the transfer function of the proportional-integral controller.

[0026] In one possible implementation, controlling the inverter based on a first inverter power control signal generated according to the positive sequence current reference value, the sine of the positive sequence phase angle, the cosine of the positive sequence phase angle, the positive sequence current, and the positive sequence voltage includes:

[0027] Based on the sine and cosine values ​​of the positive sequence phase angle, the positive sequence current reference value is subjected to Park transformation to obtain the positive sequence current setpoint.

[0028] The inverter is controlled based on the first inverter power control signal generated by the given positive sequence current, positive sequence current and positive sequence voltage.

[0029] In one possible implementation, controlling the inverter based on the first inverter power control signal generated according to the positive sequence current setpoint, the positive sequence current, and the positive sequence voltage includes:

[0030] The positive sequence current setpoint and the positive sequence current are input into the PR regulator to obtain the regulated positive sequence current;

[0031] The inverter is controlled based on the first inverter power control signal generated by the adjusted positive sequence current and positive sequence voltage.

[0032] Second aspect: Embodiments of this application provide an inverter control device, including:

[0033] The system includes a separation unit, a determination unit, a first input unit, a first control unit, a second input unit, and a second control unit.

[0034] The separation unit is used to separate the three-phase voltages into positive and negative sequence voltages to obtain positive and negative sequence voltages; and to separate the three-phase currents into positive and negative sequence currents to obtain positive and negative sequence currents.

[0035] The determining unit is used to determine the power grid state based on the effective values ​​of the positive-sequence voltage and the negative-sequence voltage.

[0036] The first input unit is used to input the positive sequence power setpoint and the positive sequence power feedback value into the proportional-integral controller when the power grid state is normal, so as to obtain the positive sequence current reference value; the positive sequence power feedback value is calculated based on the positive sequence voltage and the positive sequence current.

[0037] The first control unit is used to control the inverter based on a first inverter power control signal generated according to the positive sequence current reference value, the sine value of the positive sequence phase angle, the cosine value of the positive sequence phase angle, the positive sequence current, and the positive sequence voltage; the sine value and the cosine value of the positive sequence phase angle are calculated based on the positive sequence voltage.

[0038] The second input unit is used to calculate the reactive reference current based on the positive sequence voltage, negative sequence voltage, sine value of positive sequence phase angle, cosine value of positive sequence phase angle, sine value of negative sequence phase angle and cosine value of negative sequence phase angle when the power grid state is faulty, so as to obtain the positive sequence reactive reference current and the negative sequence reactive reference current.

[0039] The second control unit is used to control the inverter based on a second inverter power control signal generated according to the positive-sequence reactive power reference current, negative-sequence reactive power reference current, positive-sequence current, negative-sequence current, positive-sequence voltage, and negative-sequence voltage.

[0040] In one possible implementation, the determining unit is specifically used for:

[0041] When the effective value of the positive sequence voltage is within a first preset range and the effective value of the negative sequence voltage is within a second preset range, the power grid state is determined to be normal; otherwise, the power grid state is determined to be faulty.

[0042] In one possible implementation, the second input unit includes:

[0043] Calculate sub-units and determine sub-units;

[0044] The calculation subunit is used to calculate the ratio of the effective value of the positive sequence voltage to the rated value of the system voltage when the power grid state is a fault.

[0045] The determining subunit is used to determine the α-axis component of the positive-sequence reactive reference current by multiplying the difference between the preset coefficient and the ratio, the first coefficient, the effective value of the positive-sequence voltage, the cosine value of the positive-sequence phase angle, and the rated current value of the equipment; to determine the β-axis component of the positive-sequence reactive reference current by multiplying the difference between the preset coefficient and the ratio, the first coefficient, the effective value of the positive-sequence voltage, the sine value of the positive-sequence phase angle, and the rated current value of the equipment; to determine the α-axis component of the negative-sequence reactive reference current by multiplying the cosine value of the negative-sequence phase angle, the second coefficient, the effective value of the negative-sequence voltage, and the rated current value of the equipment; and to determine the β-axis component of the negative-sequence reactive reference current by multiplying the negative number of the sine value of the negative-sequence phase angle, the second coefficient, the effective value of the negative-sequence voltage, and the rated current value of the equipment.

[0046] Compared with the prior art, this application has the following beneficial effects:

[0047] This application provides an inverter control method and apparatus that can eliminate the need for positive-sequence and negative-sequence phase-locked loops. When the power grid is in a normal state, the positive-sequence power setpoint and positive-sequence power feedback value are input to a proportional-integral controller to obtain a positive-sequence current reference value. The inverter is controlled based on a first inverter power control signal generated from the positive-sequence current reference value, the sine and cosine values ​​of the positive-sequence phase angle, the positive-sequence current, and the positive-sequence voltage. The sine and cosine values ​​of the positive-sequence phase angle are calculated based on the positive-sequence voltage. When the power grid is in a fault state, reactive power reference current is calculated based on the positive-sequence voltage, negative-sequence voltage, the sine, cosine, and negative-sequence phase angles to obtain positive-sequence and negative-sequence reactive power reference currents. The inverter is controlled based on a second inverter power control signal generated from the positive-sequence reactive power reference current, negative-sequence reactive power reference current, positive-sequence current, negative-sequence current, positive-sequence voltage, and negative-sequence voltage. In this embodiment, positive-sequence and negative-sequence phase-locked loops are not used, thus avoiding the problems of high computational load and low inverter control efficiency caused by the slow response speed of the negative-sequence voltage phase-locked loop, effectively improving inverter control efficiency. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 An inverter electrical topology diagram is provided in this application embodiment;

[0050] Figure 2 A flowchart of an inverter control method provided in an embodiment of this application;

[0051] Figure 3 This is a schematic diagram illustrating the separation of positive and negative sequence voltages and currents provided in an embodiment of this application.

[0052] Figure 4 A power calculation schematic diagram provided for an embodiment of this application;

[0053] Figure 5 This application provides a schematic diagram of outer loop control when the power grid is in normal condition.

[0054] Figure 6 A schematic diagram illustrating the calculation of the sine and cosine values ​​of the positive sequence phase angle, provided for an embodiment of this application;

[0055] Figure 7 An inverter control diagram provided in an embodiment of this application;

[0056] Figure 8 A block diagram for calculating reactive reference current during a power grid fault, provided for an embodiment of this application;

[0057] Figure 9 This is a schematic diagram of the structure of an inverter control device provided in an embodiment of this application. Detailed Implementation

[0058] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0059] In the event of an asymmetrical fault during power grid operation, the output positive-sequence reactive current will lead the positive-sequence voltage by 90 degrees, while the absorbed negative-sequence reactive current will lag the negative-sequence voltage by 90 degrees. Therefore, to calculate the positive-sequence and negative-sequence reactive currents, it is necessary to first calculate the positive-sequence and negative-sequence voltages, as well as the positive-sequence and negative-sequence phase angles. The positive-sequence and negative-sequence phase angles need to be calculated based on positive-sequence and negative-sequence phase-locked loops (PLLs).

[0060] Currently, inverters use positive-sequence reactive current to restore positive-sequence voltage and negative-sequence reactive current to suppress negative-sequence voltage rise in order to solve asymmetrical faults or reduce their impact on the power system. However, the calculation of positive-sequence and negative-sequence reactive currents involves both positive-sequence and negative-sequence voltage phase-locked loops, resulting in a large computational load. Furthermore, the negative-sequence voltage phase-locked loop only starts after an asymmetrical fault occurs, leading to a slow response speed and reduced inverter control efficiency.

[0061] Based on this, embodiments of this application provide an inverter control method and apparatus that can eliminate the need for positive-sequence and negative-sequence phase-locked loops. When the grid state is normal, the positive-sequence power setpoint and positive-sequence power feedback value are input to a proportional-integral controller to obtain a positive-sequence current reference value. The inverter is controlled based on a first inverter power control signal generated from the positive-sequence current reference value, the sine and cosine values ​​of the positive-sequence phase angle, the positive-sequence current, and the positive-sequence voltage. The sine and cosine values ​​of the positive-sequence phase angle are calculated based on the positive-sequence voltage. When the grid state is faulty, reactive power reference current is calculated based on the positive-sequence voltage, negative-sequence voltage, the sine, cosine, and negative-sequence phase angles to obtain positive-sequence and negative-sequence reactive power reference currents. The inverter is controlled based on a second inverter power control signal generated from the positive-sequence reactive power reference current, negative-sequence reactive power reference current, positive-sequence current, negative-sequence current, positive-sequence voltage, and negative-sequence voltage. In this embodiment, positive-sequence and negative-sequence phase-locked loops are not used, thus avoiding the problems of high computational load and low inverter control efficiency caused by the slow response speed of the negative-sequence voltage phase-locked loop, effectively improving inverter control efficiency.

[0062] like Figure 1 As shown in the figure, this figure is an electrical topology diagram of an inverter provided in an embodiment of this application. The inverter consists of a battery pack, a power unit, a filter inductor (L), a filter capacitor (C), a line equivalent inductance (Lm), a voltage sensor, a current sensor, a grid-connected switch (QF), and a power grid.

[0063] Among them, the voltage sensor can be used to measure the grid connection point voltage, which is the three-phase voltage (U). abcThe current sensor can be used to measure the three-phase current (I) of the inverter. abc ).

[0064] like Figure 2 As shown, this figure is a flowchart of an inverter control method provided in an embodiment of this application.

[0065] S101. Separate the three-phase voltages into positive and negative sequence voltages to obtain positive and negative sequence voltages; separate the three-phase currents into positive and negative sequence currents to obtain positive and negative sequence currents.

[0066] like Figure 3 As shown in the figure, this is a schematic diagram of separating positive and negative sequence voltage and current according to an embodiment of this application. In this embodiment, the three-phase voltage can be processed by a positive and negative sequence separation algorithm to obtain positive sequence voltage and negative sequence voltage. The positive sequence voltage includes the α-axis component and the β-axis component of the positive sequence voltage, which can be represented as U, respectively. α+ and U β+ Negative-sequence voltage includes the α-axis component and the β-axis component, which can be represented as U... α- and U β- .

[0067] The three-phase current can be separated into positive-sequence current and negative-sequence current using a positive-sequence separation algorithm. The positive-sequence current includes the α-axis component and the β-axis component, which can be expressed as I... α+ and I β+ Negative sequence current includes the α-axis component and the β-axis component, which can be expressed as I, respectively. α- and I β- .

[0068] For example, positive and negative order separation algorithms can employ methods such as notch filter method, delay method, second-order generalized integrator method, and decoupling unit method.

[0069] S102. Determine the power grid state based on the effective values ​​of the positive sequence voltage and the negative sequence voltage.

[0070] In one possible implementation, when the effective value of the positive sequence voltage is within a first preset range and the effective value of the negative sequence voltage is within a second preset range, the power grid state is determined to be normal; otherwise, the power grid state is determined to be faulty.

[0071] In this embodiment of the application, the effective value of the positive sequence voltage (U) P The following can be expressed by equation (1):

[0072] (1)

[0073] The effective value of negative sequence voltage (U) N) can be expressed by equation (2) as follows:

[0074] (2)

[0075] When the power grid is in a normal state, the three-phase voltage has no negative sequence component, that is, the effective value of the negative sequence voltage is 0 or close to 0, and the effective value of the positive sequence voltage is within the first preset range; when the power grid is in a fault state, at least one of the effective values ​​of the negative sequence voltage and the effective value of the positive sequence voltage exceeds the corresponding normal range, that is, the effective value of the positive sequence voltage exceeds the first preset range, or the effective value of the negative sequence voltage exceeds the second preset range, or the effective value of the positive sequence voltage exceeds the first preset range and the effective value of the negative sequence voltage exceeds the second preset range.

[0076] Therefore, in the embodiments of this application, the power grid state can be determined based on the effective values ​​of the positive-sequence voltage and the negative-sequence voltage.

[0077] S103. When the power grid is in normal condition, the positive sequence power setpoint and positive sequence power feedback value are input into the proportional-integral controller to obtain the positive sequence current reference value.

[0078] The positive-sequence power feedback value is calculated based on the positive-sequence voltage and positive-sequence current, and includes positive-sequence active power and positive-sequence reactive power. The positive-sequence power setpoint includes positive-sequence active power setpoint and positive-sequence reactive power setpoint.

[0079] When the power grid is in normal condition, the three-phase voltages are symmetrical. Most of the active and reactive power is positive-sequence active and reactive power, while the negative-sequence power is relatively small. Therefore, the negative-sequence power can be ignored.

[0080] like Figure 4 As shown, this figure is a schematic diagram of power calculation provided in an embodiment of this application, based on U α+ U β+ I α+ and I β+ This allows us to obtain the positive-sequence active power and the positive-sequence reactive power.

[0081] According to the three-phase instantaneous power theory, the positive-sequence active power and positive-sequence reactive power of the inverter can be expressed by equation (3) as follows:

[0082] (3)

[0083] Among them, P + Q represents the positive-sequence active power; + This represents the positive-sequence reactive power.

[0084] Under normal grid conditions, the inverter mostly operates in constant power (PQ) mode. In the embodiments of this application, in PQ mode, the outer loop adopts power loop control, the inner loop adopts current loop control, the power loop adopts proportional-integral (PI) control, and the current loop adopts proportional-resonant (PR) control.

[0085] like Figure 5 As shown in the figure, this is a schematic diagram of outer loop control under normal grid conditions provided in an embodiment of this application. The positive sequence active power setpoint and the calculated positive sequence active power are controlled by a PI regulator, and the output of the PI regulator is the direct (d) axis component of the positive sequence reference current; the positive sequence reactive power setpoint and the calculated positive sequence reactive power are controlled by a PI regulator, and the output of the PI regulator is the quadrature (q) axis component of the positive sequence reference current.

[0086] The positive-sequence active power setpoint can be expressed as P + The direct-axis component of the positive-sequence reference current can be expressed as I. d+ The positive-sequence reactive power setpoint can be expressed as Q. + The quadrature-axis component of the positive-sequence reference current can be expressed as I. q+ .

[0087] The positive-sequence power setpoint and positive-sequence power feedback value are input to the proportional-integral controller to obtain I. d+ and I q+ The calculation process can be expressed by equation (4) as follows: when the power grid is in normal condition, the positive sequence power setpoint and the positive sequence power feedback value are input into the proportional-integral controller to obtain the positive sequence reference current, which is the product of the difference between the positive sequence power setpoint and the positive sequence power feedback value and the transfer function of the proportional-integral controller.

[0088] (4)

[0089] Where, k p k i These are the proportional and integral coefficients of the PI controller, respectively; (k p +k i ( / s) is the transfer function of the proportional-integral controller.

[0090] S104. The inverter is controlled based on the first inverter power control signal generated according to the positive sequence current reference value, the sine value of the positive sequence phase angle, the cosine value of the positive sequence phase angle, the positive sequence current, and the positive sequence voltage.

[0091] The sine and cosine values ​​of the positive sequence phase angle are calculated based on the positive sequence voltage.

[0092] In one possible implementation, the positive sequence current reference value is subjected to Parker transformation based on the sine and cosine values ​​of the positive sequence phase angle to obtain the positive sequence current setpoint; the inverter is controlled based on the positive sequence current setpoint, the positive sequence current, and the first inverter power control signal generated by the positive sequence voltage.

[0093] In this embodiment, a Park transformation is performed on the positive-sequence reference current based on the sine and cosine values ​​of the positive-sequence phase angle to obtain a given value for the positive-sequence reference current, including the α-axis component and the β-axis component of the positive-sequence reference current, which can be expressed as I. α+ ’ and I β+ ’ .

[0094] like Figure 5 As shown, for I d+ and I q+ Performing the Park transformation yields I. α+ ’ and I β+ ’ .

[0095] The Park transformation is a coordinate axis transformation method, which can be expressed by equation (5) as follows:

[0096] (5)

[0097] In this embodiment of the application, based on the sine and cosine values ​​of the positive sequence phase angle, I can be... d+ and I q+ Performing the Park transformation yields I. α+ ’ and I β+ ’ .

[0098] The sine of the positive sequence phase angle can be expressed as sinθ. P The cosine of the positive-sequence phase angle can be expressed as cosθ. P .

[0099] like Figure 6As shown, this figure is a schematic diagram illustrating the calculation of the sine and cosine values ​​of the positive sequence phase angle according to an embodiment of this application. Based on U α+ and U β+ By calculating the sine and cosine of the positive sequence phase angle, we can obtain sinθ. P and cosθ P .

[0100] Specifically, U α+ U β+、 U α- U β- It can be expressed by equation (6) as follows:

[0101] (6)

[0102] Substituting equations (1) and (2) into equation (6), we can obtain the sine, cosine, and negative phase angles, as shown in equation (7):

[0103] (7)

[0104] Where, sinθ N and cosθ N These are the sine and cosine values ​​of the negative phase angle, respectively.

[0105] In one possible implementation, the positive sequence current setpoint and the positive sequence current are input to the PR regulator to obtain the regulated positive sequence current; the inverter is controlled based on the first inverter power control signal generated by the regulated positive sequence current and the positive sequence voltage.

[0106] like Figure 7 As shown, this figure is an inverter control diagram provided in an embodiment of this application. When the grid state is normal, control switch S1 is selected as 1, and the α-axis component and β-axis component of the negative-sequence reference current of the current loop are 0, which can be represented as I respectively. α- ’ and I β- ’ I α+ ’ With the calculated I α+ After the PR regulator output, plus U α+ The α component (U) of the positive sequence voltage given value can be obtained. α+ ). I β+ ’ with I β+After the PR regulator output, plus U β+ The β component (U) of the positive sequence voltage given value can be obtained. β+ Similarly, the α component (U) of the negative sequence voltage given value can be calculated. α- ) and the β component of the negative sequence voltage given value (U β- ).

[0107] Under normal grid conditions, this can reduce the inverter's output negative sequence current to zero, thus suppressing negative sequence current. α+ Add U α- The modulation voltage U can be obtained α U β+ Add U β- The modulation voltage U can be obtained β U α and U β The first inverter power control signal can be generated by the SVPWM modulation algorithm. This first inverter power control signal can be a first pulse width modulation (PWM) signal, and the inverter is controlled based on this first inverter power control signal.

[0108] S105. When the power grid is in a fault state, based on the positive sequence voltage, negative sequence voltage, sine value of positive sequence phase angle, cosine value of positive sequence phase angle, sine value of negative sequence phase angle, and cosine value of negative sequence phase angle, the reactive reference current is calculated to obtain the positive sequence reactive reference current and the negative sequence reactive reference current.

[0109] In one possible implementation, S105 can be implemented in the following way:

[0110] When the power grid is in a fault state, the ratio of the effective value of the positive sequence voltage to the rated value of the system voltage is calculated. The product obtained by multiplying the preset coefficient by the difference of the ratio, the first coefficient, the effective value of the positive sequence voltage, the cosine value of the positive sequence phase angle, and the rated current value of the equipment is determined as the α-axis component of the positive sequence reactive power reference current. The product obtained by multiplying the preset coefficient by the difference of the ratio, the first coefficient, the effective value of the positive sequence voltage, the sine value of the positive sequence phase angle, and the rated current value of the equipment is determined as the β-axis component of the positive sequence reactive power reference current. The product obtained by multiplying the cosine value of the negative sequence phase angle, the second coefficient, the effective value of the negative sequence voltage, and the rated current value of the equipment is determined as the α-axis component of the negative sequence reactive power reference current. The product obtained by multiplying the negative number of the sine value of the negative sequence phase angle, the second coefficient, the effective value of the negative sequence voltage, and the rated current value of the equipment is determined as the β-axis component of the negative sequence reactive power reference current.

[0111] like Figure 8 As shown, this figure is a block diagram for calculating the reactive power reference current during a power grid fault, provided in an embodiment of this application. The calculation formula can be expressed by equation (8) as follows:

[0112] (8)

[0113] Where U represents the rated system voltage; the preset coefficient is 0.85; K2 + Indicates the first coefficient; K2 - This indicates the second coefficient.

[0114] In this embodiment, since the positive-sequence reactive current leads the positive-sequence voltage by 90 degrees, the calculation of the positive-sequence reactive current and the positive-sequence voltage is a cross-term calculation, i.e., I α+ Contains U β+ Calculation term, I β+ Contains U α+ Calculation terms. Negative-sequence reactive current lags behind negative-sequence voltage by 90 degrees, therefore the calculations for negative-sequence reactive current and negative-sequence voltage are cross-term calculations, i.e., I... α+ Contains U β+ Calculation term, I β+ Contains U α+ In the calculation, since the negative sequence current lags behind the negative sequence voltage by 90 degrees, the current needs to be negative.

[0115] S106. The inverter is controlled based on the second inverter power control signal generated according to the positive-sequence reactive reference current, negative-sequence reactive reference current, positive-sequence current, negative-sequence current, positive-sequence voltage, and negative-sequence voltage.

[0116] In a possible implementation, based on the positive-sequence reactive power reference current and the negative-sequence reactive power reference current, the relationship between the current set value and time can be calculated; based on the relationship between the current set value and time, the maximum value of the current set value within half a cycle is calculated.

[0117] The positive-sequence reactive power reference current and the negative-sequence reactive power reference current are limited according to the maximum value of the current set value to obtain a positive-sequence current set value and a negative-sequence current set value; the inverter is controlled based on a second inverter power control signal generated by the positive-sequence current set value, the negative-sequence current set value, the positive-sequence current, the negative-sequence current, the positive-sequence voltage, and the negative-sequence voltage.

[0118] In the embodiments of the present application, the voltage fault is an asymmetric fault, and the asymmetric fault includes single-phase grounding fault, double-phase grounding fault, and double-phase short-circuit fault. The asymmetric fault is characterized by the presence of positive-sequence and negative-sequence components in the voltage.

[0119] Taking the single-phase grounding fault of phase A as an example for introduction, ignoring the influence of phase jump, the three-phase voltages can be expressed by Equation (9) as follows:

[0120] (9)

[0121] where M is the depth of voltage dip, and 0 < M < 1; U a 、U b 、U c are the phase-A voltage, phase-B voltage, and phase-C voltage in the three-phase voltages, respectively.

[0122] The voltage α-axis component and β-axis component can be obtained by Clark transformation, as shown in Equation (10):

[0123]

[0124] (10)

[0125] In the case of a phase-A voltage fault, the instantaneous maximum value of the three-phase voltages (U MAX ) is the maximum value of the phase-B and phase-C voltages; when 0 < M < 0.5, the instantaneous maximum value of the α-axis and β-axis voltages U MAX ’ is the maximum value of U β ; when 0.5 < M < 1, the instantaneous maximum value of the α-axis and β-axis voltages U MAX ’ is the maximum value of U α .

[0126] From Equation (9) and Equation (10), the maximum value of the three-phase voltages U MAX =2 / 3 U MAX ’ Similarly, it can be deduced that when phase B and phase C fail, U... MAX =2 / 3 U MAX ’ .

[0127] Taking a BC phase fault as an example, ignoring the effect of phase jump, the three-phase voltage can be expressed by equation (11) as follows:

[0128] (11)

[0129] Similarly, the α-axis and β-axis components of the voltage can be obtained by Clark transformation, as shown in equation (12):

[0130]

[0131] (12)

[0132] In the event of a BC phase fault, U MAX It is the maximum value of phase A voltage, U MAX ’ It is in U α The maximum value of U can be obtained from equations (11) and (12). MAX =2 / 3 U MAX ’ Similarly, it can be deduced that when phases AB and CA are faulty, U MAX =2 / 3 U MAX ’ .

[0133] During an asymmetrical fault, the maximum value of the three-phase current occurs between the maximum values ​​of the α-axis and β-axis. The more severe the grid fault, or K2... + K2 - The larger the value, the larger the calculated positive-sequence reactive power reference current and negative-sequence reactive power reference current, and the larger the current flowing through the inverter, which may even exceed its maximum allowable value. Therefore, in this embodiment, a current limiter is used to limit the current flowing through the inverter within the allowable range.

[0134] In this embodiment of the application, θ can be obtained based on the above equations (6) and (7). P θ N U P and U N Substituting equations (6) and (7) into equation (8), we can obtain the positive-sequence reactive reference current and the negative-sequence reactive reference current, as shown in equation (13).

[0135] (13)

[0136] Among them, the positive-sequence reactive power reference current includes the α-component and the β-component of the positive-sequence reactive power reference current, which can be respectively expressed as I α+ , I β+ ; the negative-sequence reactive power reference current includes the α-component and the β-component of the negative-sequence reactive power reference current, which can be respectively expressed as I α- , I β- .

[0137] From I α+ and I α- , the α-axis component (I α ) of the reactive power reference current can be obtained; from I β+ and I β- , the β-axis component (I β ) of the reactive power reference current can be obtained, as shown in Equation (14).

[0138] (14)

[0139] The positive-sequence component rotates at an angular velocity ω, and the negative-sequence component rotates at an angular velocity -ω. From Equation (14), the relationship between the α-axis component, the β-axis component of the current set value and time is as shown in Equation (15).

[0140] (15)

[0141] The values of I α and I β exhibit sine and cosine characteristics, and there is only one maximum value within one cycle. To find its maximum value, only the maximum value of the absolute value in half a cycle needs to be calculated, that is, to find the maximum values of |I α | and |I β | in half a cycle. The maximum value of |I α | within the time of 0 < t <= 0.5T (T is the power frequency period) is denoted as I αMAX , and the maximum value of |I β | is denoted as I βMAX . Take I αMAX and IβMAX The maximum value is denoted as I. MAX .

[0142] If I MAX Greater than 1.05 times I N Divide the current reference value by I MAX This yields the current setpoint. If the maximum current I... MAX Less than 1.05 times I N The current reference value is the current setpoint.

[0143] Therefore, in this embodiment of the application, I α+ I β+ I α- I β- The current setpoint can be obtained after passing through the current limiter, including the positive sequence current setpoint and the negative sequence current setpoint. The positive sequence current setpoint includes the α component and the β component, denoted as I, respectively. α+ ’ I β+ ’ The negative sequence current setpoint includes the α component and the β component of the negative sequence current setpoint, denoted as I, respectively. α- ’ I β - ’ .

[0144] like Figure 7 As shown, when a power grid fault occurs, control switch S1 is selected as 2, I α+ ’ with I α+ After passing through the PR regulator output, plus U α+ U can be obtained α+ ;I β+ ’ With the calculated I β+ After passing through the PR regulator output, plus U β+ U can be obtained β+ Similarly, U can be calculated. α- and U β- U α+ Add Uα- Get U α U β+ Add U β- Get U β U α and U β A second inverter power control signal can be generated using the SVPWM modulation algorithm to control the inverter. This second inverter power control signal can be a second PWM signal.

[0145] In summary, the embodiments of this application do not employ positive-sequence phase-locked loops and negative-sequence phase-locked loops, thus avoiding the problems of large computational load caused by using positive-sequence and negative-sequence voltage phase-locked loops, and low inverter control efficiency caused by the slow response speed of negative-sequence voltage phase-locked loops, effectively improving inverter control efficiency.

[0146] This application provides an inverter control device, see [link]. Figure 9 The figure is a schematic diagram of the structure of an inverter control device provided in an embodiment of this application. Its specific implementation method is consistent with the implementation method and the technical effect achieved in the above-described method embodiment, and some contents will not be repeated.

[0147] An inverter control device 1100 includes:

[0148] The system includes a separation unit 1101, a determination unit 1102, a first input unit 1103, a first control unit 1104, a second input unit 1105, and a second control unit 1106.

[0149] The separation unit 1101 is used to separate the positive and negative sequence voltages of the three-phase voltages to obtain positive sequence voltages and negative sequence voltages; and to separate the positive and negative sequence currents of the three-phase currents to obtain positive sequence currents and negative sequence currents.

[0150] The determining unit 1102 is used to determine the power grid state based on the effective value of the positive sequence voltage and the effective value of the negative sequence voltage;

[0151] The first input unit 1103 is used to input the positive sequence power setpoint and the positive sequence power feedback value into the proportional-integral controller when the power grid state is normal, so as to obtain the positive sequence current reference value; the positive sequence power feedback value is calculated based on the positive sequence voltage and the positive sequence current.

[0152] The first control unit 1104 is used to control the inverter based on a first inverter power control signal generated according to the positive sequence current reference value, the sine value of the positive sequence phase angle, the cosine value of the positive sequence phase angle, the positive sequence current, and the positive sequence voltage; the sine value and the cosine value of the positive sequence phase angle are calculated based on the positive sequence voltage.

[0153] The second input unit 1105 is used to calculate the reactive reference current based on the positive sequence voltage, negative sequence voltage, sine value of positive sequence phase angle, cosine value of positive sequence phase angle, sine value of negative sequence phase angle, and cosine value of negative sequence phase angle when the power grid state is faulty, so as to obtain the positive sequence reactive reference current and the negative sequence reactive reference current. The negative sequence power feedback value is calculated based on the negative sequence voltage and the negative sequence current.

[0154] The second control unit 1106 is used to control the inverter based on the second inverter power control signal generated according to the positive-sequence reactive reference current, negative-sequence reactive reference current, positive-sequence current, negative-sequence current, positive-sequence voltage, and negative-sequence voltage.

[0155] In one possible implementation, the determining unit is specifically used for:

[0156] When the effective value of the positive sequence voltage is within a first preset range and the effective value of the negative sequence voltage is within a second preset range, the power grid state is determined to be normal; otherwise, the power grid state is determined to be faulty.

[0157] In one possible implementation, the second input unit includes:

[0158] Calculate sub-units and determine sub-units;

[0159] The calculation subunit is used to calculate the ratio of the effective value of the positive sequence voltage to the rated value of the system voltage when the power grid state is a fault.

[0160] The determining subunit is used to determine the α-axis component of the positive-sequence reactive reference current by multiplying the difference between the preset coefficient and the ratio, the first coefficient, the effective value of the positive-sequence voltage, the cosine value of the positive-sequence phase angle, and the rated current value of the equipment; to determine the β-axis component of the positive-sequence reactive reference current by multiplying the difference between the preset coefficient and the ratio, the first coefficient, the effective value of the positive-sequence voltage, the sine value of the positive-sequence phase angle, and the rated current value of the equipment; to determine the α-axis component of the negative-sequence reactive reference current by multiplying the cosine value of the negative-sequence phase angle, the second coefficient, the effective value of the negative-sequence voltage, and the rated current value of the equipment; and to determine the β-axis component of the negative-sequence reactive reference current by multiplying the negative number of the sine value of the negative-sequence phase angle, the second coefficient, the effective value of the negative-sequence voltage, and the rated current value of the equipment.

[0161] In one possible implementation, the second control unit is specifically used for:

[0162] Based on the positive-sequence reactive reference current and the negative-sequence reactive reference current, the relationship between the current setpoint and time is calculated.

[0163] Based on the relationship between the current setpoint and time, the maximum value of the current setpoint is calculated within half a cycle;

[0164] The positive-sequence reactive reference current and the negative-sequence reactive reference current are limited based on the maximum value of the current setpoint to obtain the positive-sequence current setpoint and the negative-sequence current setpoint.

[0165] The inverter is controlled based on the second inverter power control signal generated by the positive sequence current setpoint, negative sequence current setpoint, positive sequence current, negative sequence current, positive sequence voltage, and negative sequence voltage.

[0166] In one possible implementation, the first input unit is specifically used for:

[0167] When the power grid is in normal condition, the positive sequence power setpoint and positive sequence power feedback value are input into the proportional-integral controller to obtain the positive sequence reference current, which is the product of the difference between the positive sequence power setpoint and the positive sequence power feedback value and the transfer function of the proportional-integral controller.

[0168] In one possible implementation, the first control unit is specifically used for:

[0169] Based on the sine and cosine values ​​of the positive sequence phase angle, the positive sequence current reference value is subjected to Park transformation to obtain the positive sequence current setpoint.

[0170] The inverter is controlled based on the first inverter power control signal generated by the given positive sequence current, positive sequence current and positive sequence voltage.

[0171] In one possible implementation, the first control unit is specifically used for:

[0172] The positive sequence current setpoint and the positive sequence current are input into the PR regulator to obtain the regulated positive sequence current;

[0173] The inverter is controlled based on the first inverter power control signal generated by the adjusted positive sequence current and positive sequence voltage.

[0174] In summary, the embodiments of this application do not employ positive-sequence phase-locked loops and negative-sequence phase-locked loops, thus avoiding the problems of large computational load caused by using positive-sequence and negative-sequence voltage phase-locked loops, and low inverter control efficiency caused by the slow response speed of negative-sequence voltage phase-locked loops, effectively improving inverter control efficiency.

[0175] The above description is merely one specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An inverter control method, characterized in that, include: The three-phase voltages are separated into positive-sequence voltages and negative-sequence voltages; The three-phase currents are separated into positive-sequence current and negative-sequence current; The grid state is determined based on the effective values ​​of the positive-sequence voltage and the negative-sequence voltage. When the power grid is in normal condition, the positive sequence power setpoint and positive sequence power feedback value are input into the proportional-integral controller to obtain the positive sequence current reference value. The positive sequence power feedback value is calculated based on the positive sequence voltage and positive sequence current. The inverter is controlled based on a first inverter power control signal generated according to the positive sequence current reference value, the sine value of the positive sequence phase angle, the cosine value of the positive sequence phase angle, the positive sequence current, and the positive sequence voltage; the sine value and the cosine value of the positive sequence phase angle are calculated based on the positive sequence voltage. When the power grid is in a fault state, based on the positive sequence voltage, negative sequence voltage, sine value of positive sequence phase angle, cosine value of positive sequence phase angle, sine value of negative sequence phase angle, and cosine value of negative sequence phase angle, reactive reference current is calculated to obtain positive sequence reactive reference current and negative sequence reactive reference current. The inverter is controlled based on the second inverter power control signal generated according to the positive-sequence reactive reference current, negative-sequence reactive reference current, positive-sequence current, negative-sequence current, positive-sequence voltage, and negative-sequence voltage. When the power grid is in a fault state, based on the positive-sequence voltage, negative-sequence voltage, the sine of the positive-sequence phase angle, the cosine of the positive-sequence phase angle, the sine of the negative-sequence phase angle, and the cosine of the negative-sequence phase angle, a reactive power reference current is calculated to obtain the positive-sequence reactive power reference current and the negative-sequence reactive power reference current, including: When the power grid is in a fault state, calculate the ratio of the effective value of the positive sequence voltage to the rated value of the system voltage; The product of the preset coefficient, the difference between the ratio, the first coefficient, the effective value of the positive sequence voltage, the cosine value of the positive sequence phase angle, and the rated current value of the equipment is determined as the α-axis component of the positive sequence reactive reference current; the product of the preset coefficient, the difference between the ratio, the first coefficient, the effective value of the positive sequence voltage, the sine value of the positive sequence phase angle, and the rated current value of the equipment is determined as the β-axis component of the positive sequence reactive reference current; the product of the cosine value of the negative sequence phase angle, the second coefficient, the effective value of the negative sequence voltage, and the rated current value of the equipment is determined as the α-axis component of the negative sequence reactive reference current; the product of the negative value of the sine of the negative sequence phase angle, the second coefficient, the effective value of the negative sequence voltage, and the rated current value of the equipment is determined as the β-axis component of the negative sequence reactive reference current.

2. The method according to claim 1, characterized in that, The process of determining the power grid state based on the effective values ​​of the positive-sequence voltage and the negative-sequence voltage includes: When the effective value of the positive sequence voltage is within a first preset range and the effective value of the negative sequence voltage is within a second preset range, the power grid state is determined to be normal; otherwise, the power grid state is determined to be faulty.

3. The method according to claim 1, characterized in that, The control of the inverter based on the second inverter power control signal generated according to the positive-sequence reactive power reference current, negative-sequence reactive power reference current, positive-sequence current, negative-sequence current, positive-sequence voltage, and negative-sequence voltage includes: Based on the positive-sequence reactive reference current and the negative-sequence reactive reference current, the relationship between the current setpoint and time is calculated. Based on the relationship between the current setpoint and time, the maximum value of the current setpoint is calculated within half a cycle; The positive-sequence reactive reference current and the negative-sequence reactive reference current are limited based on the maximum value of the current setpoint to obtain the positive-sequence current setpoint and the negative-sequence current setpoint. The inverter is controlled based on the second inverter power control signal generated by the positive sequence current setpoint, negative sequence current setpoint, positive sequence current, negative sequence current, positive sequence voltage, and negative sequence voltage.

4. The method according to claim 1, characterized in that, When the power grid is in a normal state, the positive-sequence power setpoint and positive-sequence power feedback value are input to the proportional-integral controller to obtain the positive-sequence current reference value, including: When the power grid is in normal condition, the positive sequence power setpoint and positive sequence power feedback value are input into the proportional-integral controller to obtain the positive sequence reference current, which is the product of the difference between the positive sequence power setpoint and the positive sequence power feedback value and the transfer function of the proportional-integral controller.

5. The method according to claim 4, characterized in that, The control of the inverter based on a first inverter power control signal generated according to the positive sequence current reference value, the sine value of the positive sequence phase angle, the cosine value of the positive sequence phase angle, the positive sequence current, and the positive sequence voltage includes: Based on the sine and cosine values ​​of the positive sequence phase angle, the positive sequence current reference value is subjected to Park transformation to obtain the positive sequence current setpoint. The inverter is controlled based on the first inverter power control signal generated by the given positive sequence current, positive sequence current and positive sequence voltage.

6. The method according to claim 5, characterized in that, The first inverter power control signal, generated based on the positive sequence current setpoint, the positive sequence current, and the positive sequence voltage, controls the inverter, including: The positive sequence current setpoint and the positive sequence current are input into the PR regulator to obtain the regulated positive sequence current; The inverter is controlled based on the first inverter power control signal generated by the adjusted positive sequence current and positive sequence voltage.

7. An inverter control device, characterized in that, include: The system includes a separation unit, a determination unit, a first input unit, a first control unit, a second input unit, and a second control unit. The separation unit is used to separate the three-phase voltages into positive and negative sequence voltages to obtain positive and negative sequence voltages; and to separate the three-phase currents into positive and negative sequence currents to obtain positive and negative sequence currents. The determining unit is used to determine the power grid state based on the effective values ​​of the positive-sequence voltage and the negative-sequence voltage. The first input unit is used to input the positive sequence power setpoint and the positive sequence power feedback value into the proportional-integral controller when the power grid state is normal, so as to obtain the positive sequence current reference value. The positive sequence power feedback value is calculated based on the positive sequence voltage and positive sequence current. The first control unit is used to control the inverter based on a first inverter power control signal generated according to the positive sequence current reference value, the sine value of the positive sequence phase angle, the cosine value of the positive sequence phase angle, the positive sequence current, and the positive sequence voltage; the sine value and the cosine value of the positive sequence phase angle are calculated based on the positive sequence voltage. The second input unit is used to calculate the reactive reference current based on the positive sequence voltage, negative sequence voltage, sine value of positive sequence phase angle, cosine value of positive sequence phase angle, sine value of negative sequence phase angle and cosine value of negative sequence phase angle when the power grid state is faulty, so as to obtain the positive sequence reactive reference current and the negative sequence reactive reference current. The second control unit is used to control the inverter based on a second inverter power control signal generated according to the positive-sequence reactive reference current, negative-sequence reactive reference current, positive-sequence current, negative-sequence current, positive-sequence voltage, and negative-sequence voltage. The second input unit includes: Calculate sub-units and determine sub-units; The calculation subunit is used to calculate the ratio of the effective value of the positive sequence voltage to the rated value of the system voltage when the power grid state is a fault. The determining subunit is used to determine the α-axis component of the positive-sequence reactive reference current by multiplying the difference between the preset coefficient and the ratio, the first coefficient, the effective value of the positive-sequence voltage, the cosine value of the positive-sequence phase angle, and the rated current value of the equipment; to determine the β-axis component of the positive-sequence reactive reference current by multiplying the difference between the preset coefficient and the ratio, the first coefficient, the effective value of the positive-sequence voltage, the sine value of the positive-sequence phase angle, and the rated current value of the equipment; to determine the α-axis component of the negative-sequence reactive reference current by multiplying the cosine value of the negative-sequence phase angle, the second coefficient, the effective value of the negative-sequence voltage, and the rated current value of the equipment; and to determine the β-axis component of the negative-sequence reactive reference current by multiplying the negative number of the sine value of the negative-sequence phase angle, the second coefficient, the effective value of the negative-sequence voltage, and the rated current value of the equipment.

8. The apparatus according to claim 7, characterized in that, The determining unit is specifically used for: When the effective value of the positive sequence voltage is within a first preset range and the effective value of the negative sequence voltage is within a second preset range, the power grid state is determined to be normal; otherwise, the power grid state is determined to be faulty.

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