Current harmonic control method, device, system and computer readable storage medium

Abstract

This invention discloses a current harmonic control method, apparatus, system, and computer-readable storage medium. The method includes: when the grid imbalance meets preset conditions, acquiring the bus capacitor voltage value of the grid-connected inverter, and determining a target fundamental frequency harmonic based on the bus capacitor voltage value; determining an input current based on the target fundamental frequency harmonic, and inputting the input current into the grid-connected inverter to obtain an output current. This invention, by determining the target fundamental frequency harmonic based on the bus capacitor voltage value of the grid-connected inverter when the grid imbalance meets preset conditions, and then determining the input current based on the target fundamental frequency harmonic, suppresses the harmonics of the input current of the grid-connected inverter, thereby reducing the harmonic distortion of the output current of the grid-connected inverter and ensuring that the harmonic distortion of the output current meets the standards.

Description

Technical Field

[0001] This invention relates to the field of power grid control technology, and in particular to current harmonic control methods, devices, systems and computer-readable storage media. Background Technology

[0002] Uneven distribution of three-phase loads and impedance imbalance in transmission lines can lead to grid voltage imbalance. Under grid imbalance, the inverter's output current becomes distorted. Due to cost reduction requirements, the DC bus capacitors in existing inverters are generally small, making them more susceptible to grid imbalance fluctuations. This results in severe harmonic distortion in the inverter's output current, which can even burn out the entire device. Therefore, reducing harmonic distortion in the inverter's output current is an urgent problem to solve. Summary of the Invention

[0003] The main objective of this invention is to provide a current harmonic control method, apparatus, system, and computer-readable storage medium, aiming to solve the problem of how to reduce the harmonic distortion of the inverter's output current.

[0004] To achieve the above objectives, the present invention provides a current harmonic control method, which includes the following steps:

[0005] When the grid imbalance meets the preset conditions, the bus capacitor voltage value of the grid-connected inverter is obtained, and the target fundamental frequency harmonic is determined based on the bus capacitor voltage value.

[0006] The input current is determined based on the target fundamental frequency harmonics, and the input current is input into the grid-connected inverter to obtain the output current.

[0007] Optionally, before the step of obtaining the bus capacitor voltage value of the grid-connected inverter and determining the target fundamental frequency harmonic based on the bus capacitor voltage value when the grid imbalance meets the preset conditions, the method includes:

[0008] The u-phase voltage, v-phase voltage, and w-phase voltage of the power grid are obtained, and the effective value of the balance degree is calculated based on the u-phase voltage, the v-phase voltage, and the w-phase voltage.

[0009] The grid imbalance is calculated based on the effective value of the balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage.

[0010] Based on the power grid imbalance degree and the preset imbalance threshold, determine whether the power grid imbalance degree meets the preset conditions.

[0011] Optionally, the step of calculating the grid imbalance based on the effective value of the balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage includes:

[0012] Based on the effective value of the balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage, the u-phase voltage unbalance, the v-phase voltage unbalance, and the w-phase voltage unbalance are calculated respectively.

[0013] The voltage imbalance of phase u, phase v, and phase w are compared to determine the maximum imbalance, and the power grid imbalance is determined based on the maximum imbalance.

[0014] Optionally, the bus capacitor voltage value includes a positive bus capacitor voltage value and a negative bus capacitor voltage value. The step of obtaining the bus capacitor voltage value of the grid-connected inverter and determining the target fundamental frequency harmonic based on the bus capacitor voltage value includes:

[0015] Obtain the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter, and calculate the difference between the positive bus capacitor voltage value and the negative bus capacitor voltage value;

[0016] The difference is input into the controller of the grid-connected inverter, and the controller outputs the target fundamental frequency harmonic based on the difference.

[0017] Optionally, the step of obtaining the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter includes:

[0018] Obtain the capacitance values ​​of the positive bus capacitor and the negative bus capacitor of the grid-connected inverter;

[0019] The impedance value of the positive bus capacitor is determined based on the capacitance value of the positive bus capacitor, and the voltage value of the positive bus capacitor is determined based on the impedance value of the positive bus capacitor.

[0020] The impedance value of the negative bus capacitor is determined based on its capacitance value, and the voltage value of the negative bus capacitor is determined based on its impedance value.

[0021] Optionally, the step of outputting the target fundamental frequency harmonic by the controller based on the difference includes:

[0022] The controller acquires the initial fundamental frequency harmonics, and adjusts the amplitude and phase of the initial fundamental frequency harmonics according to the difference, thereby obtaining and outputting the target fundamental frequency harmonics.

[0023] Optionally, the step of determining the input current based on the target fundamental frequency harmonics includes:

[0024] The target voltage value is determined based on the target fundamental frequency harmonics, and the pre-input current is determined based on the target voltage value;

[0025] Obtain a preset suppression current, and determine the input current based on the preset suppression current and the preset input current.

[0026] Optionally, the step of determining the pre-input current based on the target voltage value includes:

[0027] The target voltage value is input into the conversion module of the grid-connected inverter, and the conversion module calculates the pre-input current based on the target voltage value and the preset transfer function.

[0028] Optionally, after determining the input current based on the target fundamental frequency harmonics and inputting the input current into the grid-connected inverter to obtain the output current, the process includes:

[0029] The output voltage value is determined based on the output current, and the utilization rate of the output voltage is calculated.

[0030] If the utilization rate of the output voltage is lower than the preset utilization rate threshold, the bus capacitor voltage value is adjusted according to the preset rules.

[0031] Furthermore, to achieve the above objectives, the present invention also provides a current harmonic control device, the current harmonic control device comprising:

[0032] The determination module is used to obtain the bus capacitor voltage value of the grid-connected inverter when the grid imbalance meets the preset conditions, and determine the target fundamental frequency harmonic based on the bus capacitor voltage value.

[0033] The input module is used to determine the input current based on the target fundamental frequency harmonics and input the input current into the grid-connected inverter to obtain the output current.

[0034] Furthermore, the determining module is also used for:

[0035] The u-phase voltage, v-phase voltage, and w-phase voltage of the power grid are obtained, and the effective value of the balance degree is calculated based on the u-phase voltage, the v-phase voltage, and the w-phase voltage.

[0036] The grid imbalance is calculated based on the effective value of the balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage.

[0037] Based on the power grid imbalance degree and the preset imbalance threshold, determine whether the power grid imbalance degree meets the preset conditions.

[0038] Furthermore, the determining module is also used for:

[0039] Based on the effective value of the balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage, the u-phase voltage unbalance, the v-phase voltage unbalance, and the w-phase voltage unbalance are calculated respectively.

[0040] The voltage imbalance of phase u, phase v, and phase w are compared to determine the maximum imbalance, and the power grid imbalance is determined based on the maximum imbalance.

[0041] Furthermore, the determining module is also used for:

[0042] Obtain the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter, and calculate the difference between the positive bus capacitor voltage value and the negative bus capacitor voltage value;

[0043] The difference is input into the controller of the grid-connected inverter, and the controller outputs the target fundamental frequency harmonic based on the difference.

[0044] Furthermore, the determining module is also used for:

[0045] Obtain the capacitance values ​​of the positive bus capacitor and the negative bus capacitor of the grid-connected inverter;

[0046] The impedance value of the positive bus capacitor is determined based on the capacitance value of the positive bus capacitor, and the voltage value of the positive bus capacitor is determined based on the impedance value of the positive bus capacitor.

[0047] The impedance value of the negative bus capacitor is determined based on its capacitance value, and the voltage value of the negative bus capacitor is determined based on its impedance value.

[0048] Furthermore, the determining module is also used for:

[0049] The controller acquires the initial fundamental frequency harmonics, and adjusts the amplitude and phase of the initial fundamental frequency harmonics according to the difference, thereby obtaining and outputting the target fundamental frequency harmonics.

[0050] Furthermore, the input module is also used for:

[0051] The target voltage value is determined based on the target fundamental frequency harmonics, and the pre-input current is determined based on the target voltage value;

[0052] Obtain a preset suppression current, and determine the input current based on the preset suppression current and the preset input current.

[0053] Furthermore, the input module is also used for:

[0054] The target voltage value is input into the conversion module of the grid-connected inverter, and the conversion module calculates the pre-input current based on the target voltage value and the preset transfer function.

[0055] Furthermore, the input module also includes an adjustment module, which is used for:

[0056] The output voltage value is determined based on the output current, and the utilization rate of the output voltage is calculated.

[0057] If the utilization rate of the output voltage is lower than the preset utilization rate threshold, the bus capacitor voltage value is adjusted according to the preset rules.

[0058] In addition, to achieve the above objectives, the present invention also provides a current harmonic control system, which includes: a memory, a processor, and a current harmonic control program stored in the memory and executable on the processor. When the current harmonic control program is executed by the processor, it implements the steps of the current harmonic control method as described above.

[0059] In addition, to achieve the above objectives, the present invention also provides a computer-readable storage medium storing a current harmonic control program, which, when executed by a processor, implements the steps of the current harmonic control method as described above.

[0060] The current harmonic control method proposed in this invention, when determining that the grid imbalance meets preset conditions, acquires the bus capacitor voltage value of the grid-connected inverter and determines the target fundamental frequency harmonics based on the bus capacitor voltage value; determines the input current based on the target fundamental frequency harmonics, and inputs the input current into the grid-connected inverter to obtain the output current. This invention, by determining the target fundamental frequency harmonics based on the bus capacitor voltage value of the grid-connected inverter when the grid imbalance meets preset conditions, and then determining the input current based on the target fundamental frequency harmonics, suppresses the harmonics of the input current of the grid-connected inverter, thereby reducing the harmonic distortion of the output current of the grid-connected inverter and ensuring that the harmonic distortion of the output current meets the standards. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of the device structure of the hardware operating environment involved in the embodiments of the present invention;

[0062] Figure 2 This is a flowchart illustrating the first embodiment of the current harmonic control method of the present invention;

[0063] Figure 3 This is a schematic diagram of the three-phase multi-level grid-connected inverter structure of the present invention;

[0064] Figure 4 This is a schematic diagram of the current harmonic control process of the present invention;

[0065] Figure 5 This is a flowchart illustrating the second embodiment of the current harmonic control method of the present invention;

[0066] Figure 6 This is a flowchart illustrating the third embodiment of the current harmonic control method of the present invention;

[0067] Figure 7 This is a schematic diagram of the current harmonic control device of the present invention.

[0068] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0069] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0070] like Figure 1 As shown, Figure 1 This is a schematic diagram of the device structure of the hardware operating environment involved in the embodiments of the present invention.

[0071] The device in this embodiment of the invention can be a PC or a server.

[0072] like Figure 1 As shown, the device may include: a processor 1001, such as a CPU; a network interface 1004; a user interface 1003; a memory 1005; and a communication bus 1002. The communication bus 1002 is used to enable communication between these components. The user interface 1003 may include a display screen or an input unit such as a keyboard; optionally, the user interface 1003 may also include a standard wired interface or a wireless interface. The network interface 1004 may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface). The memory 1005 may be high-speed RAM or non-volatile memory, such as a disk drive. Optionally, the memory 1005 may also be a storage device independent of the aforementioned processor 1001.

[0073] Those skilled in the art will understand that Figure 1 The device structure shown does not constitute a limitation on the device and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0074] like Figure 1 As shown, the memory 1005, which serves as a computer storage medium, may include an operating system, a network communication module, a user interface module, and a current harmonic control program.

[0075] The operating system is a program that manages and controls portable storage devices and software resources, and supports the operation of the network communication module, user interface module, current harmonic control program, and other programs or software; the network communication module is used to manage and control the network interface 1002; and the user interface module is used to manage and control the user interface 1003.

[0076] exist Figure 1 In the storage device shown, the storage device calls the current harmonic control program stored in the memory 1005 through the processor 1001 and executes the operations in the various embodiments of the current harmonic control method described below.

[0077] Based on the above hardware structure, an embodiment of the current harmonic control method of the present invention is proposed.

[0078] Reference Figure 2 , Figure 2 This is a flowchart illustrating the first embodiment of the current harmonic control method of the present invention, the method comprising:

[0079] Step S10: When it is determined that the grid imbalance meets the preset conditions, the bus capacitor voltage value of the grid-connected inverter is obtained, and the target fundamental frequency harmonic is determined based on the bus capacitor voltage value.

[0080] Step S20: Determine the input current based on the target fundamental frequency harmonics, and input the input current into the grid-connected inverter to obtain the output current.

[0081] This embodiment of the current harmonic control method is applied to a current harmonic control system in a power grid. This current harmonic control system can be applied to intelligent devices such as terminal devices and PC terminals. For ease of description, a current harmonic control system is used as an example. During the operation of the grid-connected inverter, the current harmonic control system determines whether the grid imbalance corresponding to the grid connected to the grid-connected inverter meets the preset conditions. When it is determined that the grid imbalance meets the preset conditions, the system obtains the bus capacitor voltage value of the grid-connected inverter. The bus capacitor voltage value includes the positive bus capacitor voltage value and the negative bus capacitor voltage value, and calculates the difference between the positive bus capacitor voltage value and the negative bus capacitor voltage value. The current harmonic control system inputs the difference value into the controller of the grid-connected inverter, and the controller outputs the target fundamental frequency harmonic based on the difference value. The current harmonic control system determines the target voltage value based on the target fundamental frequency harmonic, and determines the pre-input current based on the target voltage value. The current harmonic control system obtains the preset suppression current, and determines the input current based on the preset suppression current and the pre-input current, and then inputs the input current into the grid-connected inverter, so that the grid-connected inverter obtains the output current based on the input current.

[0082] The current harmonic control method in this embodiment, when determining that the grid imbalance meets preset conditions, acquires the bus capacitor voltage value of the grid-connected inverter and determines the target fundamental frequency harmonics based on the bus capacitor voltage value; determines the input current based on the target fundamental frequency harmonics, and inputs the input current into the grid-connected inverter to obtain the output current. This invention, by determining the target fundamental frequency harmonics based on the bus capacitor voltage value of the grid-connected inverter when the grid imbalance meets preset conditions, and then determining the input current based on the target fundamental frequency harmonics, suppresses the harmonics of the input current of the grid-connected inverter, thereby reducing the harmonic distortion of the output current of the grid-connected inverter and ensuring that the harmonic distortion of the output current meets the standards.

[0083] The following will provide a detailed explanation of each step:

[0084] Step S10: When it is determined that the grid imbalance meets the preset conditions, the bus capacitor voltage value of the grid-connected inverter is obtained, and the target fundamental frequency harmonic is determined based on the bus capacitor voltage value.

[0085] In this embodiment, during the operation of the grid-connected inverter, the current harmonic control system acquires the three-phase voltage corresponding to the grid connected to the inverter, determines the grid imbalance based on the three-phase voltage, and judges whether the grid imbalance meets a preset condition. When the current harmonic control system determines that the grid imbalance meets the preset condition, it acquires the bus capacitor voltage value of the grid-connected inverter and determines the target fundamental frequency harmonic based on the bus capacitor voltage value. It should be noted that the preset condition is that the grid imbalance is greater than the imbalance threshold, which can be determined according to the actual situation and is not limited here. When the current harmonic control system determines that the grid imbalance does not meet the preset condition, it inputs the input current to the grid-connected inverter according to normal logic to obtain the output current.

[0086] Specifically, the steps of obtaining the bus capacitor voltage value of the grid-connected inverter and determining the target fundamental frequency harmonics based on the bus capacitor voltage value include:

[0087] Step S101: Obtain the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter, and calculate the difference between the positive bus capacitor voltage value and the negative bus capacitor voltage value.

[0088] In this step, when the current harmonic control system determines that the grid imbalance meets the preset conditions, it acquires the bus capacitor voltage value of the grid-connected inverter. The bus capacitor voltage value includes both the positive and negative bus capacitor voltage values, and calculates the difference between the positive and negative bus capacitor voltage values. Figure 3 As shown, Figure 3The diagram shows the structure of a three-phase multi-level grid-connected inverter. The positive bus capacitor voltage and negative bus capacitor voltage obtained by the current harmonic control system are the voltage values ​​of capacitors C1 and C2 in the figure, respectively. Then, according to the formula: Verr=VC1-VC2, the difference between the positive bus capacitor voltage and the negative bus capacitor voltage is calculated, where Verr is the difference, VC1 is the voltage value of capacitor C1, and VC2 is the voltage value of capacitor C2.

[0089] Further, the steps for obtaining the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter include:

[0090] Step S1011: Obtain the capacitance value of the positive bus capacitor and the capacitance value of the negative bus capacitor of the grid-connected inverter.

[0091] Step S1012: Determine the impedance value of the positive bus capacitor based on the capacitance value of the positive bus capacitor, and determine the voltage value of the positive bus capacitor based on the impedance value of the positive bus capacitor.

[0092] Step S1013: Determine the impedance value of the negative bus capacitor based on the capacitance value of the negative bus capacitor, and determine the voltage value of the negative bus capacitor based on the impedance value of the negative bus capacitor.

[0093] In steps S1011 to S1013, the current harmonic control system acquires the capacitance values ​​of the positive bus capacitor and the negative bus capacitor of the grid-connected inverter, such as... Figure 3 As shown, the capacitance values ​​of the positive bus capacitor and the negative bus capacitor are the capacitance values ​​of capacitor C1 and capacitor C2, respectively. The current harmonic control system acquires the current values ​​flowing through the positive and negative bus capacitors, determines the impedance value of the positive bus capacitor based on its capacitance value, and determines the voltage value of the positive bus capacitor based on the current value flowing through it and its impedance value. Similarly, it determines the impedance value of the negative bus capacitor based on its capacitance value, and determines the voltage value of the negative bus capacitor based on the current value flowing through it and its impedance value. Figure 4 As shown, the formula for calculating the impedance of a capacitor is: 1 / Cs, where C is the capacitance value and s is a complex unit.

[0094] Step S102: Input the difference value into the controller of the grid-connected inverter, and output the target fundamental frequency harmonic based on the difference value.

[0095] In this step, after calculating the difference between the positive bus capacitor voltage and the negative bus capacitor voltage, the current harmonic control system inputs the difference into the controller of the grid-connected inverter. The controller then outputs the target fundamental frequency harmonic based on the difference. Figure 4As shown, the current harmonic control system obtains the absolute value of the difference Verr by adding or subtracting it from zero. This absolute value is then input into the controller, which outputs the target fundamental frequency harmonic. The controller is typically a proportional resonant (PR) controller, with its resonant frequency being the fundamental frequency.

[0096] Furthermore, the step of outputting the target fundamental frequency harmonic by the controller based on the difference includes:

[0097] Step S1021: Obtain the initial fundamental frequency harmonics through the controller, and adjust the amplitude and phase of the initial fundamental frequency harmonics according to the difference to obtain and output the target fundamental frequency harmonics.

[0098] In this step, the current harmonic control system obtains the initial fundamental frequency harmonics of the current to be input to the grid-connected inverter through the controller. These initial fundamental frequency harmonics are mainly caused by grid imbalance. The controller adjusts the amplitude and phase of the initial fundamental frequency harmonics according to the difference to obtain and output the target fundamental frequency harmonics. It should be noted that the adjustment of the amplitude and phase of the initial fundamental frequency harmonics is to ensure that the harmonic distortion of the final target fundamental frequency harmonics meets the national standard for THD (Total Harmonic Distortion).

[0099] Step S20: Determine the input current based on the target fundamental frequency harmonics, and input the input current into the grid-connected inverter to obtain the output current.

[0100] In this embodiment, after the current harmonic control system outputs the target fundamental frequency harmonic through the controller, it determines the input current based on the target fundamental frequency harmonic and inputs the input current into the grid-connected inverter to obtain the output current.

[0101] Specifically, the step of determining the input current based on the target fundamental frequency harmonics includes:

[0102] Step S201: Determine the target voltage value based on the target fundamental frequency harmonics, and determine the pre-input current based on the target voltage value;

[0103] Step S202: Obtain the preset suppression current, and determine the input current based on the preset suppression current and the preset input current.

[0104] In steps S201 to S202, the current harmonic control system calculates the target voltage value based on the target fundamental frequency harmonics and a preset calculation rule, and then calculates the pre-input current based on the target voltage value; the current harmonic control system obtains a preset suppression current and determines the input current based on the preset suppression current and the pre-input current; specifically, as follows... Figure 4 As shown, the current harmonic control system calculates the pre-input current based on the target voltage value through the G(s) conversion module, and obtains the preset suppression current I. M1 The preset suppression current I M1 The input current I is obtained by performing a preset calculation with the pre-input current. M .

[0105] Further, the step of determining the pre-input current based on the target voltage value includes:

[0106] Step S2011: Input the target voltage value into the conversion module of the grid-connected inverter, and calculate the pre-input current through the conversion module based on the target voltage value and the preset transfer function.

[0107] In this step, such as Figure 4 As shown, the current harmonic control system inputs the target voltage value into the conversion module (G(s)) of the grid-connected inverter, and calculates the pre-input current through the conversion module based on the target voltage value and the preset transfer function. The preset transfer function, G(s), is determined and set in the conversion module in advance according to the actual situation of the grid-connected inverter.

[0108] In this embodiment, the current harmonic control system determines whether the grid imbalance corresponding to the grid connected to the inverter meets preset conditions during the operation of the grid-connected inverter. When it is determined that the grid imbalance meets the preset conditions, it acquires the bus capacitor voltage value of the grid-connected inverter, which includes the positive bus capacitor voltage value and the negative bus capacitor voltage value, and calculates the difference between the positive bus capacitor voltage value and the negative bus capacitor voltage value. The current harmonic control system inputs the difference value into the controller of the grid-connected inverter, and the controller outputs the target fundamental frequency harmonic based on the difference value. The current harmonic control system determines the target voltage value based on the target fundamental frequency harmonic, and determines the pre-input current based on the target voltage value. The current harmonic control system acquires the preset suppression current, and determines the input current based on the preset suppression current and the pre-input current, and then inputs the input current into the grid-connected inverter, so that the grid-connected inverter obtains the output current based on the input current. When the grid imbalance meets the preset conditions, the target fundamental frequency harmonics are determined based on the bus capacitor voltage value of the grid-connected inverter. Then, the input current is determined based on the target fundamental frequency harmonics, so that the harmonics of the input current of the grid-connected inverter can be suppressed, thereby reducing the harmonic distortion of the output current of the grid-connected inverter and ensuring that the harmonic distortion of the output current meets the standards.

[0109] Further, refer to Figure 5The second embodiment of the present invention is proposed. The difference between the second embodiment and the first embodiment is that, before the step of obtaining the bus capacitor voltage value of the grid-connected inverter and determining the target fundamental frequency harmonic based on the bus capacitor voltage value after determining that the grid imbalance meets preset conditions, the method includes:

[0110] Step a: Obtain the u-phase voltage, v-phase voltage, and w-phase voltage of the power grid, and calculate the effective value of the balance degree based on the u-phase voltage, v-phase voltage, and w-phase voltage;

[0111] Step b: Calculate the grid imbalance based on the effective value of the balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage;

[0112] Step c: Determine whether the power grid imbalance meets the preset conditions based on the power grid imbalance degree and the preset imbalance threshold.

[0113] In this embodiment, the current harmonic control system acquires the u-phase voltage, v-phase voltage, and w-phase voltage of the power grid, and calculates the effective value of the balance degree based on these voltages. The system then calculates the u-phase voltage unbalance, v-phase voltage unbalance, and w-phase voltage unbalance degree based on the effective value of the balance degree, the u-phase voltage, the v-phase voltage, and the w-phase voltage, respectively. These unbalance degrees are compared to determine the maximum unbalance degree, and the power grid unbalance degree is determined based on this maximum unbalance degree. Finally, the system determines whether the power grid unbalance degree meets preset conditions based on the power grid unbalance degree and a preset unbalance threshold. It should be noted that the power grid is generally a three-phase power grid, where the u-phase voltage, v-phase voltage, and w-phase voltage are the voltage values ​​corresponding to the three live wires of the three-phase power grid.

[0114] The current harmonic control system in this embodiment can determine in advance whether the grid imbalance meets the preset conditions, and then take corresponding current harmonic control measures according to the grid imbalance, thereby reducing the harmonic distortion of the output current of the grid-connected inverter, ensuring that the harmonic distortion of the output current meets the standard, and at the same time ensuring the capacitor life and inverter efficiency.

[0115] The following is a detailed explanation of each step:

[0116] Step a: Obtain the u-phase voltage, v-phase voltage, and w-phase voltage of the power grid, and calculate the effective value of the balance degree based on the u-phase voltage, v-phase voltage, and w-phase voltage;

[0117] In this step, the current harmonic control system can directly obtain the u-phase voltage, v-phase voltage, and w-phase voltage of the power grid based on the electrical characteristics of the power grid, and calculate the effective value of the balance degree based on the u-phase voltage, v-phase voltage, and w-phase voltage. Specifically, the formula for calculating the effective value of the balance degree based on the u-phase voltage, v-phase voltage, and w-phase voltage is: Vave=(Vu+Vv+Vw) / 3, where Vave is the effective value of the balance degree, Vu is the u-phase voltage, Vv is the v-phase voltage, and Vw is the w-phase voltage.

[0118] Step b: Calculate the grid imbalance based on the effective value of the balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage;

[0119] Specifically, step b includes:

[0120] Step b1: Calculate the unbalance of phase u, phase v, and phase w based on the effective value of the balance, the phase u voltage, the phase v voltage, and the phase w voltage, respectively.

[0121] In this step, after calculating the effective value of the balance, the current harmonic control system calculates the voltage unbalance of phase u based on the effective value of the balance and the phase u voltage, calculates the voltage unbalance of phase v based on the effective value of the balance and the phase v voltage, and calculates the voltage unbalance of phase w based on the effective value of the balance and the phase w voltage. Specifically, the formula for calculating the voltage unbalance of phase u is: H1=|(Vu-Vave)| / Vave, where H1 is the voltage unbalance of phase u and Vave is the effective value of the balance; the formula for calculating the voltage unbalance of phase v is: H2=|(Vv-Vave)| / Vave, where H2 is the voltage unbalance of phase v and Vave is the effective value of the balance; the formula for calculating the voltage unbalance of phase w is: H3=|(Vw-Vave)| / Vave, where H3 is the voltage unbalance of phase w and Vave is the effective value of the balance.

[0122] Step b2: Compare the voltage imbalance of phase u, phase v, and phase w to determine the maximum imbalance, and determine the grid imbalance based on the maximum imbalance.

[0123] In this step, after calculating the voltage imbalance of phase u, phase v, and phase w, the current harmonic control system compares these voltage imbalances to determine the maximum imbalance, and then determines the grid imbalance based on the maximum imbalance. Specifically, the formula for calculating the grid imbalance is: Hmax = max(H1, H2, H3), where Hmax is the grid imbalance, max represents the maximum value, H1 is the voltage imbalance of phase u, H2 is the voltage imbalance of phase v, and H3 is the voltage imbalance of phase w.

[0124] Step c: Determine whether the power grid imbalance meets the preset conditions based on the power grid imbalance degree and the preset imbalance threshold.

[0125] In this step, after obtaining the grid imbalance, the current harmonic control system acquires a preset imbalance threshold and compares the grid imbalance with the preset imbalance threshold to determine whether the grid imbalance meets the preset conditions. Specifically, the preset imbalance threshold is generally 3%. The current harmonic control system compares the grid imbalance with the preset imbalance threshold. If it is determined that the grid imbalance is greater than the preset imbalance threshold, it determines whether the grid imbalance meets the preset conditions and requires corresponding current harmonic control measures. If it is determined that the grid imbalance is not greater than the preset imbalance threshold, it determines whether the grid imbalance does not meet the preset conditions and does not require corresponding current harmonic control measures. The input current can be determined according to normal logic and input to the grid-connected inverter.

[0126] The current harmonic control system in this embodiment acquires the u-phase voltage, v-phase voltage, and w-phase voltage of the power grid, and calculates the effective value of the balance degree based on these voltages. The system then calculates the unbalance degrees of the u-phase voltage, v-phase voltage, and w-phase voltage, respectively, and compares these values ​​to determine the maximum unbalance degree. Based on this maximum unbalance degree, the system determines the overall grid unbalance degree. Finally, the system determines whether the grid unbalance degree meets preset conditions based on the grid unbalance degree and a preset unbalance threshold. This system can predict whether the grid unbalance degree meets preset conditions in advance, and then take corresponding current harmonic control measures accordingly. This reduces the harmonic distortion of the output current of the grid-connected inverter, ensuring that the harmonic distortion meets standards, while also guaranteeing capacitor lifespan and inverter efficiency.

[0127] Further, refer to Figure 6The present invention proposes a third embodiment, which differs from the first and second embodiments in that, after the step of determining the input current based on the target fundamental frequency harmonics and inputting the input current into the grid-connected inverter to obtain the output current, the third embodiment includes:

[0128] Step d: Determine the output voltage value based on the output current and calculate the utilization rate of the output voltage;

[0129] Step e: If the utilization rate of the output voltage is lower than the preset utilization rate threshold, the bus capacitor voltage value is adjusted according to the preset rule.

[0130] In this embodiment, since the amplitude and phase of the fundamental frequency harmonics of the input current are changed, the amplitude and phase of the fundamental frequency harmonics of the output current will also change accordingly, which may lead to a decrease in the utilization rate of the output voltage. The current harmonic control system determines the output voltage value based on the output current and calculates the utilization rate of the output voltage. If the utilization rate of the output voltage is lower than the preset utilization rate threshold, the bus capacitor voltage value is appropriately increased according to the preset rules so that the utilization rate of the output voltage is greater than the preset utilization rate threshold.

[0131] The current harmonic control system in this embodiment adjusts the bus capacitor voltage value appropriately according to the utilization rate of the output voltage, so that the utilization rate of the output voltage is greater than the preset utilization rate threshold, thereby improving the efficiency of the inverter.

[0132] like Figure 7 As shown, the present invention also provides a current harmonic control device. The current harmonic control device of the present invention includes:

[0133] The determination module 101 is used to obtain the bus capacitor voltage value of the grid-connected inverter when the grid imbalance meets the preset conditions, and determine the target fundamental frequency harmonic based on the bus capacitor voltage value.

[0134] The input module 102 is used to determine the input current based on the target fundamental frequency harmonics and input the input current into the grid-connected inverter to obtain the output current.

[0135] Furthermore, the determining module is also used for:

[0136] The u-phase voltage, v-phase voltage, and w-phase voltage of the power grid are obtained, and the effective value of the balance degree is calculated based on the u-phase voltage, the v-phase voltage, and the w-phase voltage.

[0137] The grid imbalance is calculated based on the effective value of the balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage.

[0138] Based on the power grid imbalance degree and the preset imbalance threshold, determine whether the power grid imbalance degree meets the preset conditions.

[0139] Furthermore, the determining module is also used for:

[0140] Based on the effective value of the balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage, the u-phase voltage unbalance, the v-phase voltage unbalance, and the w-phase voltage unbalance are calculated respectively.

[0141] The voltage imbalance of phase u, phase v, and phase w are compared to determine the maximum imbalance, and the power grid imbalance is determined based on the maximum imbalance.

[0142] Furthermore, the determining module is also used for:

[0143] Obtain the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter, and calculate the difference between the positive bus capacitor voltage value and the negative bus capacitor voltage value;

[0144] The difference is input into the controller of the grid-connected inverter, and the controller outputs the target fundamental frequency harmonic based on the difference.

[0145] Furthermore, the determining module is also used for:

[0146] Obtain the capacitance values ​​of the positive bus capacitor and the negative bus capacitor of the grid-connected inverter;

[0147] The impedance value of the positive bus capacitor is determined based on the capacitance value of the positive bus capacitor, and the voltage value of the positive bus capacitor is determined based on the impedance value of the positive bus capacitor.

[0148] The impedance value of the negative bus capacitor is determined based on its capacitance value, and the voltage value of the negative bus capacitor is determined based on its impedance value.

[0149] Furthermore, the determining module is also used for:

[0150] The controller acquires the initial fundamental frequency harmonics, and adjusts the amplitude and phase of the initial fundamental frequency harmonics according to the difference, thereby obtaining and outputting the target fundamental frequency harmonics.

[0151] Furthermore, the input module is also used for:

[0152] The target voltage value is determined based on the target fundamental frequency harmonics, and the pre-input current is determined based on the target voltage value;

[0153] Obtain a preset suppression current, and determine the input current based on the preset suppression current and the preset input current.

[0154] Furthermore, the input module is also used for:

[0155] The target voltage value is input into the conversion module of the grid-connected inverter, and the conversion module calculates the pre-input current based on the target voltage value and the preset transfer function.

[0156] Furthermore, the input module also includes an adjustment module, which is used for:

[0157] The output voltage value is determined based on the output current, and the utilization rate of the output voltage is calculated.

[0158] If the utilization rate of the output voltage is lower than the preset utilization rate threshold, the bus capacitor voltage value is adjusted according to the preset rules.

[0159] The present invention also provides a current harmonic control system.

[0160] The current harmonic control system includes: a memory, a processor, and a current harmonic control program stored in the memory and executable on the processor. When the current harmonic control program is executed by the processor, it implements the steps of the current harmonic control method as described above.

[0161] The method implemented when the current harmonic control program running on the processor is executed can be referred to in various embodiments of the current harmonic control method of the present invention, and will not be repeated here.

[0162] The present invention also provides a computer-readable storage medium.

[0163] The computer-readable storage medium stores a current harmonic control program, which, when executed by a processor, implements the steps of the current harmonic control method as described above.

[0164] The method implemented when the current harmonic control program running on the processor is executed can be referred to in various embodiments of the current harmonic control method of the present invention, and will not be repeated here.

[0165] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0166] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0167] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0168] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A current harmonic control method, characterized by, The current harmonic control method includes the following steps: When the grid imbalance meets the preset conditions, the bus capacitor voltage value of the grid-connected inverter is obtained, and the target fundamental frequency harmonic is determined based on the bus capacitor voltage value. The input current is determined based on the target fundamental frequency harmonics, and the input current is input into the grid-connected inverter to obtain the output current; The bus capacitor voltage value includes a positive bus capacitor voltage value and a negative bus capacitor voltage value. The step of obtaining the bus capacitor voltage value of the grid-connected inverter and determining the target fundamental frequency harmonic based on the bus capacitor voltage value includes: Obtain the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter, and calculate the difference between the positive bus capacitor voltage value and the negative bus capacitor voltage value; The difference is input into the controller of the grid-connected inverter, the initial fundamental frequency harmonic is obtained through the controller, and the amplitude and phase of the initial fundamental frequency harmonic are adjusted according to the difference to obtain and output the target fundamental frequency harmonic. The step of determining the input current based on the target fundamental frequency harmonics includes: The target voltage value is determined based on the target fundamental frequency harmonics, and the pre-input current is determined based on the target voltage value; Obtain a preset suppression current, and determine the input current based on the preset suppression current and the preset input current.

2. The current harmonic control method of claim 1, wherein, Before the step of obtaining the bus capacitor voltage value of the grid-connected inverter and determining the target fundamental frequency harmonic based on the bus capacitor voltage value when the grid imbalance meets the preset conditions, the method includes: The u-phase voltage, v-phase voltage, and w-phase voltage of the power grid are obtained, and the effective value of the balance degree is calculated based on the u-phase voltage, the v-phase voltage, and the w-phase voltage. The grid imbalance is calculated based on the effective value of the balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage. Based on the power grid imbalance degree and the preset imbalance threshold, determine whether the power grid imbalance degree meets the preset conditions.

3. The current harmonic control method of claim 2, wherein, The step of calculating the grid imbalance based on the effective value of the balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage includes: Based on the effective value of the balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage, the u-phase voltage unbalance, the v-phase voltage unbalance, and the w-phase voltage unbalance are calculated respectively. The voltage imbalance of phase u, phase v, and phase w are compared to determine the maximum imbalance, and the power grid imbalance is determined based on the maximum imbalance.

4. The current harmonic control method of claim 1, wherein, The steps for obtaining the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter include: Obtain the capacitance values ​​of the positive bus capacitor and the negative bus capacitor of the grid-connected inverter; The impedance value of the positive bus capacitor is determined based on the capacitance value of the positive bus capacitor, and the voltage value of the positive bus capacitor is determined based on the impedance value of the positive bus capacitor. The impedance value of the negative bus capacitor is determined based on its capacitance value, and the voltage value of the negative bus capacitor is determined based on its impedance value.

5. The current harmonic control method of claim 1, wherein, The step of determining the pre-input current based on the target voltage value includes: The target voltage value is input into the conversion module of the grid-connected inverter, and the conversion module calculates the pre-input current based on the target voltage value and the preset transfer function.

6. The current harmonic control method of claim 1, wherein, After the step of determining the input current based on the target fundamental frequency harmonics and inputting the input current into the grid-connected inverter to obtain the output current, the method includes: The output voltage value is determined based on the output current, and the utilization rate of the output voltage is calculated. If the utilization rate of the output voltage is lower than the preset utilization rate threshold, the bus capacitor voltage value is adjusted according to the preset rules.

7. A current harmonic control device, characterized by comprising: The current harmonic control device includes: The determination module is used to obtain the bus capacitor voltage value of the grid-connected inverter when the grid imbalance meets the preset conditions, and determine the target fundamental frequency harmonic based on the bus capacitor voltage value. The input module is used to determine the input current based on the target fundamental frequency harmonics and input the input current into the grid-connected inverter to obtain the output current; The bus capacitor voltage value includes a positive bus capacitor voltage value and a negative bus capacitor voltage value. The determining module is further used for: Obtain the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter, and calculate the difference between the positive bus capacitor voltage value and the negative bus capacitor voltage value; The difference is input into the controller of the grid-connected inverter, the initial fundamental frequency harmonic is obtained through the controller, and the amplitude and phase of the initial fundamental frequency harmonic are adjusted according to the difference to obtain and output the target fundamental frequency harmonic. The input module is also used for: The target voltage value is determined based on the target fundamental frequency harmonics, and the pre-input current is determined based on the target voltage value; Obtain a preset suppression current, and determine the input current based on the preset suppression current and the preset input current.

8. A current harmonic control system characterized by, The current harmonic control system includes: a memory, a processor, and a current harmonic control program stored in the memory and executable on the processor. When the current harmonic control program is executed by the processor, it implements the steps of the current harmonic control method as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a current harmonic control program, which, when executed by a processor, implements the steps of the current harmonic control method as described in any one of claims 1 to 6.

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