Direct-current bus midpoint potential balance control method and device, electronic equipment, medium and product

Abstract

The application provides a direct-current bus midpoint potential balance control method and device, electronic equipment, medium and product. It relates to the technical field of power electronic converter control. The method comprises the following steps: obtaining an active current instruction value and a reactive current instruction value output by a grid-connected control loop; obtaining a continuous polarity target coefficient based on the active current instruction value and the reactive current instruction value; performing filtering processing on the continuous polarity target coefficient to obtain a smoothed continuous polarity target coefficient; determining a midpoint voltage deviation of a direct-current bus; processing the midpoint voltage deviation and the smoothed continuous polarity target coefficient through a proportional-integral controller to obtain a target adjustment amount; and performing balance control on the direct-current bus midpoint potential based on the target adjustment amount. Based on the method provided in the application, the balance accuracy and dynamic stability of the ANPC three-level converter midpoint potential can be improved.

Description

Technical Field

[0001] This application relates to the field of power electronic converter control technology, and in particular to a DC bus midpoint potential balance control method, device, electronic equipment, medium and product. Background Technology

[0002] In modern power electronic systems, the Active Neutral-Point Clamped (ANPC) three-level topology is widely used in high-power power conversion systems (PCS), photovoltaic inverters, wind power converters, active power filters, and static var generators due to its high power density, low switching losses, and low output voltage harmonic content. This type of system typically includes a grid-connected control loop, a DC bus, a voltage detection unit, and a modulation and control unit, and needs to maintain a stable DC bus neutral point potential under continuous active and reactive power regulation conditions.

[0003] Currently, the solutions for the neutral point potential balance problem of ANPC three-level converters are mostly fixed-deviation proportional-integral regulation, operating condition judgment switching, or hardware-assisted equalization. When the power factor changes continuously, the regulation direction is prone to mismatch, making it difficult to balance the neutral point potential balance accuracy and dynamic stability of ANPC three-level converters. Summary of the Invention

[0004] This application provides a DC bus midpoint potential balance control method, device, electronic equipment, medium, and product, which can improve the balance accuracy and dynamic stability of the midpoint potential of an ANPC three-level converter.

[0005] In a first aspect, embodiments of this application provide a DC bus midpoint potential balance control method, including:

[0006] Obtain the active current command value and reactive current command value output by the grid-connected control loop;

[0007] The continuous polarity target coefficient is obtained based on the active current command value and the reactive current command value;

[0008] Filtering is performed on the continuous polarity target coefficients to obtain smooth continuous polarity target coefficients;

[0009] Determine the midpoint voltage deviation of the DC bus;

[0010] The target adjustment amount is obtained by processing the midpoint voltage deviation and the smooth continuous polarity target coefficient through a proportional-integral controller.

[0011] Balance control of the DC bus midpoint potential is performed based on the target adjustment amount.

[0012] In one possible embodiment, the continuous polarity target coefficient is obtained based on the active current command value and the reactive current command value, including:

[0013] Determine the pure active power gain value and the pure reactive power gain value;

[0014] Based on the active current command value and the reactive current command value, determine the proportion of the reactive current command value.

[0015] Based on the proportion of reactive current command value, a linear difference is performed between the pure active gain value and the pure reactive gain value to obtain the continuous polarity target coefficient.

[0016] In one possible embodiment, the DC bus includes a positive DC bus and a negative DC bus;

[0017] Accordingly, the midpoint voltage deviation of the DC bus is determined, including:

[0018] Determine the first voltage corresponding to the positive DC bus and the second voltage corresponding to the negative DC bus;

[0019] Determine the voltage difference between the first voltage and the second voltage;

[0020] The voltage difference is limited based on preset upper and lower voltage limits to obtain the midpoint voltage deviation.

[0021] In one possible embodiment, the target adjustment amount is obtained by processing the midpoint voltage deviation and the smooth continuous polarity target coefficient through a proportional-integral controller, including:

[0022] Determine the proportional and integral coefficients corresponding to the proportional-integral controller;

[0023] Determine the first product of the midpoint voltage deviation and the proportional coefficient, and the second product of the midpoint voltage deviation and the integral coefficient;

[0024] The second product is subjected to amplitude limiting based on the preset upper and lower limits of integration to obtain the target integral value;

[0025] Determine the sum between the first product and the target integral value;

[0026] The sum is limited based on the preset upper and lower limits of the adjustment amount to obtain the initial adjustment amount;

[0027] Determine the third product of the smooth continuous polarity target coefficient and the initial adjustment amount;

[0028] The negative of the third product is determined as the target adjustment amount.

[0029] In one possible embodiment, the target adjustment amount is obtained by processing the midpoint voltage deviation and the smooth continuous polarity target coefficient through a proportional-integral controller, including:

[0030] Determine the proportional and integral coefficients corresponding to the proportional-integral controller;

[0031] Determine the fourth product of the midpoint voltage deviation and the negative of the smooth continuous polarity target coefficient;

[0032] Determine the fifth product of the fourth product and the proportionality coefficient, and the sixth product of the fourth product and the integral coefficient;

[0033] The sixth product is subjected to amplitude limiting based on the preset upper and lower limits of integration to obtain the target integral value;

[0034] The sum of the fifth product and the target integral value is determined as the initial adjustment amount;

[0035] The initial adjustment amount is limited based on the preset upper and lower limits of the adjustment amount to obtain the target adjustment amount.

[0036] In one possible embodiment, balancing control of the DC bus neutral point potential based on a target adjustment amount includes:

[0037] Collect the instantaneous values ​​and current amplitudes of each phase current in the DC bus;

[0038] The target adjustment amount, the instantaneous values ​​of the current in each phase, and the current amplitude are processed using a preset first formula to determine the zero-sequence component of the current in each phase. The first formula is:

[0039]

[0040] Among them, u final For the target adjustment, I x I is the instantaneous value of the phase current. amp V is the amplitude of the phase current. x0 This is the zero-sequence component of the phase current;

[0041] The DC bus midpoint potential is balanced and controlled based on the zero-sequence component corresponding to each phase current.

[0042] In one possible embodiment, when the current amplitude is lower than a preset ratio of the rated current, the integral term and target adjustment of the proportional-integral controller are set to zero.

[0043] In one possible embodiment, the step of suspending the DC bus midpoint potential balance control is performed within a preset time window after the grid voltage zero-crossing phase calibration is completed.

[0044] Secondly, embodiments of this application provide a DC bus neutral point potential balance control device, comprising:

[0045] The acquisition module is used to acquire the active current command value and reactive current command value output by the grid-connected control loop;

[0046] The processing module is used to obtain the continuous polarity target coefficient based on the active current command value and the reactive current command value;

[0047] The processing module is also used to filter the continuous polarity target coefficients to obtain smooth continuous polarity target coefficients;

[0048] The processing module is also used to determine the midpoint voltage deviation of the DC bus;

[0049] The processing module is also used to process the midpoint voltage deviation and the smooth continuous polarity target coefficient through the proportional-integral controller to obtain the target adjustment amount;

[0050] The processing module is also used to balance the DC bus midpoint potential based on the target adjustment amount.

[0051] In one possible embodiment, the processing module is specifically used to determine the pure active power gain value and the pure reactive power gain value;

[0052] The processing module is also specifically used to determine the proportion of the reactive current command value based on the active current command value and the reactive current command value.

[0053] The processing module is also used to perform linear difference processing between the pure active gain value and the pure reactive gain value based on the proportion of reactive current command value, so as to obtain the continuous polarity target coefficient.

[0054] In one possible embodiment, the DC bus includes a positive DC bus and a negative DC bus;

[0055] Accordingly, the processing module is also specifically used to determine the first voltage corresponding to the positive DC bus and the second voltage corresponding to the negative DC bus;

[0056] The processing module is also specifically used to determine the voltage difference between the first voltage and the second voltage;

[0057] The processing module is also used to limit the voltage difference based on preset upper and lower voltage limits to obtain the midpoint voltage deviation.

[0058] In one possible embodiment, the processing module is further configured to determine the proportional coefficient and integral coefficient corresponding to the proportional-integral controller.

[0059] The processing module is also specifically used to determine the first product of the midpoint voltage deviation and the proportional coefficient, and the second product of the midpoint voltage deviation and the integral coefficient;

[0060] The processing module is also specifically used to perform amplitude limiting on the second product based on preset upper and lower limits of integration to obtain the target integral value;

[0061] The processing module is also specifically used to determine the sum between the first product and the target integral value;

[0062] The processing module is also specifically used to limit the sum value based on the preset upper and lower limits of the adjustment amount to obtain the initial adjustment amount;

[0063] The processing module is also specifically used to determine the third product of the smooth continuous polarity target coefficient and the initial adjustment amount;

[0064] The processing module is also specifically used to determine the opposite of the third product as the target adjustment amount.

[0065] In one possible embodiment, the processing module is further configured to determine the proportional coefficient and integral coefficient corresponding to the proportional-integral controller.

[0066] The processing module is also specifically used to determine the fourth product of the midpoint voltage deviation and the opposite of the smooth continuous polarity target coefficient;

[0067] The processing module is also specifically used to determine the fifth product of the fourth product and the proportional coefficient, and the sixth product of the fourth product and the integral coefficient;

[0068] The processing module is also specifically used to perform amplitude limiting on the sixth product based on preset upper and lower limits of integration to obtain the target integral value;

[0069] The processing module is also specifically used to determine the sum between the fifth product and the target integral value as the initial adjustment amount;

[0070] The processing module is also used to limit the initial adjustment amount based on the preset upper and lower limits of the adjustment amount to obtain the target adjustment amount.

[0071] In one possible embodiment, the processing module is further configured to acquire the instantaneous value and current amplitude of each phase current in the DC bus;

[0072] The processing module is further configured to process the target adjustment amount, the instantaneous values ​​of the current in each phase, and the current amplitude using a preset first formula to determine the zero-sequence component of the current in each phase. The first formula is:

[0073]

[0074] Among them, u final For the target adjustment, I x I is the instantaneous value of the phase current. amp V is the amplitude of the phase current. x0 This is the zero-sequence component of the phase current;

[0075] The processing module is also used to balance the DC bus midpoint potential based on the zero-sequence component corresponding to each phase current.

[0076] In one possible embodiment, the processing module is further configured to set the integral term and target adjustment amount of the proportional-integral controller to zero when the current amplitude is lower than the preset ratio of the rated current.

[0077] In one possible embodiment, the processing module is further configured to suspend the execution of the DC bus midpoint potential balance control step within a preset time window after the grid voltage zero-crossing phase calibration is completed.

[0078] Thirdly, embodiments of this application provide an electronic device, including: a processor, and a memory communicatively connected to the processor;

[0079] The memory stores the instructions that the computer executes;

[0080] The processor executes computer execution instructions stored in memory to implement the DC bus midpoint potential balance control method provided above.

[0081] Fourthly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the DC bus midpoint potential balance control method provided above.

[0082] Fifthly, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements the DC bus midpoint potential balance control method described above.

[0083] The DC bus midpoint potential balance control method, device, electronic equipment, medium, and product provided in this application acquire the active current command value and reactive current command value output by the grid-connected control loop, obtain the continuous polarity target coefficient based on the two, and filter the continuous polarity target coefficient. At the same time, the target adjustment amount is obtained by combining the DC bus midpoint voltage deviation with the proportional-integral controller. This enables the adjustment direction of the midpoint potential balance control to be consistent with the power factor change trend, and improves the continuity and smoothness of the adjustment process. In turn, it improves the balance accuracy and dynamic stability of the ANPC three-level converter under continuous power factor changes and complex operating conditions. Attached Figure Description

[0084] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0085] Figure 1 Flowchart of the DC bus midpoint potential balance control method provided in this application Figure 1 ;

[0086] Figure 2 Flowchart of the DC bus midpoint potential balance control method provided in this application Figure 2 ;

[0087] Figure 3 Flowchart of the DC bus midpoint potential balance control method provided in this application Figure 3 ;

[0088] Figure 4 Flowchart of the DC bus midpoint potential balance control method provided in this application Figure 4 ;

[0089] Figure 5 Flowchart of the DC bus midpoint potential balance control method provided in this application Figure 5 ;

[0090] Figure 6 Flowchart of the DC bus midpoint potential balance control method provided in this application Figure 6 ;

[0091] Figure 7 A schematic diagram of the DC bus midpoint potential balance control device provided in this application;

[0092] Figure 8 A schematic diagram of the structure of the electronic device provided in this application.

[0093] The accompanying drawings have illustrated specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0094] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0095] It should be noted that in the embodiments of this application, certain software, components, models and other existing solutions in the industry may be mentioned. These should be regarded as exemplary and are only intended to illustrate the feasibility of implementing the technical solution of this application. However, it does not mean that the applicant has used or necessarily used the solution.

[0096] ANPC three-level converter neutral point potential balance control technology belongs to the field of power electronic converter control technology. It is mainly applied in systems that adopt DC bus structures, such as energy storage converters, photovoltaic inverters, wind power grid-connected converters, and reactive power compensation devices. These systems typically include a grid-connected control loop, a DC bus, a voltage detection unit, and a modulation and control unit, and need to maintain a stable DC bus neutral point potential under continuous adjustment of active and reactive power.

[0097] Existing midpoint potential balance control schemes mostly employ a fixed-deviation proportional-integral (PI) regulation method, or switch the deviation definition and regulation direction according to operating conditions. Some schemes also achieve midpoint voltage correction through additional equalization circuits. The basic idea is to detect the DC bus midpoint voltage deviation, then generate an adjustment amount based on the deviation, and apply compensation to the modulation process to change the midpoint current distribution and achieve midpoint potential return. However, under operating conditions with continuously changing power factor and simultaneous active and reactive power output, the above schemes cannot guarantee that the regulation direction is always consistent with the actual midpoint current regulation requirements. Fixed-deviation control is prone to polarity mismatch under certain operating conditions, and operating condition switching methods are prone to sudden changes, oscillations, or regulation steady-state errors at critical states, making it difficult to simultaneously achieve the balance accuracy and dynamic stability of the ANPC three-level converter's midpoint potential.

[0098] In view of this, this application provides a DC bus midpoint potential balance control method. By acquiring the active current command value and reactive current command value output by the grid-connected control loop, a continuous polarity target coefficient is obtained based on the two values. The continuous polarity target coefficient is then filtered, and the target adjustment amount is obtained by combining the DC bus midpoint voltage deviation with a proportional-integral controller. This method enables the adjustment direction of the midpoint potential balance control to be consistent with the power factor change trend, and improves the continuity and smoothness of the adjustment process. In turn, it enhances the balance accuracy and dynamic stability of the ANPC three-level converter under continuous power factor changes and complex operating conditions.

[0099] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0100] Figure 1Flowchart of the DC bus midpoint potential balance control method provided in this application Figure 1 ,like Figure 1 As shown, it includes:

[0101] S101. Obtain the active current command value and reactive current command value output by the grid-connected control loop.

[0102] For example, the active current command value is used to characterize the current reference quantity corresponding to the active power that the system currently needs to output, and the reactive current command value is used to characterize the current reference quantity corresponding to the reactive power that the system currently needs to output. The grid-connected control loop is used to output the above two command quantities during grid-connected operation based on the external power input, bus status, and grid-side control objectives, as the operating condition input for subsequently generating continuous polarity target coefficients. In this example, the acquisition process is executed by the controller within a fixed sampling period, which is consistent with the current command refresh period of the grid-connected control loop. The controller can be a digital signal processor, microcontroller, control core in a programmable logic device, or other computing unit capable of running control algorithms in real time.

[0103] S102. Obtain the continuous polarity target coefficient based on the active current command value and the reactive current command value.

[0104] For example, the continuous polarity target coefficient is used to construct a continuously changing adjustment direction coefficient based on the current active and reactive component relationship, so that the midpoint potential balance control maintains directional consistency when the power factor changes continuously.

[0105] Optional, Figure 2 Flowchart of the DC bus midpoint potential balance control method provided in this application Figure 2 ,like Figure 2 As shown, S102 includes:

[0106] S201. Determine the pure active gain value and the pure reactive gain value.

[0107] For example, the active current command value and reactive current command value output by the grid-connected control loop can be sent to the coefficient calibration module respectively. The coefficient calibration module pre-stores the pure active gain value and pure reactive gain value corresponding to the midpoint current coupling characteristics of the target topology, and writes them into a lookup table or parameter register.

[0108] S202. Based on the active current command value and the reactive current command value, determine the proportion of the reactive current command value.

[0109] For example, the percentage of reactive current command value can be obtained using the following formula:

[0110]

[0111] Among them, fQratio D represents the proportion of the reactive current command value. ref Q is the active current command value. ref Here, ε is the reactive current command value, and ε is a preset minimum positive number whose magnitude can be any value. ε is used to prevent the denominator from being zero.

[0112] S203. Based on the proportion of reactive current command value, perform linear difference processing between pure active gain value and pure reactive gain value to obtain continuous polarity target coefficient.

[0113] For example, the continuous polarity target coefficient can be obtained using the following formula:

[0114] f TargetCoeff =GA+(GR-GA)×f Qratio

[0115] Among them, f TargetCoeff GA is the continuous polarity target coefficient, GR is the pure active gain value, and GR is the pure reactive gain value. GA and GR are opposites of each other and can be given by the internal parameter table of the controller. Normally, GA=1 and GR=-1, while at low modulation ratios, GR can be adjusted to other values ​​in the range of -0.8 to -1.2.

[0116] Under pure active power conditions, the reactive current command value is zero, so the proportion of the reactive current command value is zero, and the continuous polarity target coefficient is equal to 1. Under pure reactive power conditions, the active current command value is zero, so the proportion of the reactive current command value is approximately equal to 1, and the continuous polarity target coefficient is equal to -1. Under mixed power conditions, the proportion of the reactive current command value is between 0 and 1, so the continuous polarity target coefficient varies continuously between -1.0 and 1.0.

[0117] S103. Filter the continuous polarity target coefficients to obtain smooth continuous polarity target coefficients.

[0118] For example, filtering is used to suppress rapid changes in the continuous polarity target coefficient caused by changes in external power commands, grid regulation switching, or transient responses in the grid-connected control loop, while smoothing the continuous polarity target coefficient serves as the joint input to the subsequent proportional-integral controller.

[0119] The following method, employing first-order exponential smoothing, can be used to filter the coefficients of continuous polarity targets:

[0120] S PolarityCoeff =S PolarityCoeff ×(1-α)+f TargetCoeff ×α

[0121] Among them, S PolarityCoeffTo smooth the continuous polarity target coefficients, α is the filtering coefficient, which is usually α=0.05.

[0122] Alternatively, first-order, second-order, or higher-order digital filters can be used to filter the coefficients of continuous polarity targets. Or, smoothing algorithms such as moving average and Kalman filtering can be used to filter the coefficients of continuous polarity targets.

[0123] S104. Determine the midpoint voltage deviation of the DC bus.

[0124] For example, the midpoint voltage deviation is used to characterize the degree to which the DC bus midpoint potential deviates from the equilibrium state, and serves as the feedback basis for the proportional-integral controller to generate the target adjustment amount.

[0125] Optional, Figure 3 Flowchart of the DC bus midpoint potential balance control method provided in this application Figure 3 The DC bus includes a positive DC bus and a negative DC bus; correspondingly, such as Figure 3 As shown, it includes:

[0126] S301. Determine the first voltage corresponding to the positive DC bus and the second voltage corresponding to the negative DC bus.

[0127] For example, the first voltage can be defined as Vp, and the second voltage can be defined as Vn.

[0128] S302. Determine the voltage difference between the first voltage and the second voltage.

[0129] For example, after acquiring the first voltage and the second voltage, the controller performs a difference calculation between the two to obtain a voltage difference value that reflects the degree of imbalance in the midpoint potential. This voltage difference value serves as an intermediate quantity for the midpoint voltage state, and its numerical direction reflects the offset trend of the voltages on both sides of the bus.

[0130] In a real machine system scenario, the voltage difference can be obtained through Vp-Vn; in a simulation platform scenario, the voltage difference can be obtained through Vn-Vp.

[0131] S303. Based on the preset upper and lower voltage limits, the voltage difference is limited to obtain the midpoint voltage deviation.

[0132] For example, the upper and lower voltage limits can be determined based on the actual situation. If the voltage difference is greater than the upper voltage limit, the upper voltage limit is determined as the midpoint voltage deviation. If the voltage difference is less than the lower voltage limit, the lower voltage limit is determined as the midpoint voltage deviation. If the voltage difference is between the upper and lower voltage limits, the voltage difference is directly determined as the midpoint voltage deviation.

[0133] S105. The target adjustment amount is obtained by processing the midpoint voltage deviation and the smooth continuous polarity target coefficient through the proportional-integral controller.

[0134] For example, a proportional-integral controller is used to convert the midpoint voltage deviation into a basic regulation with amplitude information, a smoothing continuous polarity target coefficient is used to apply a conditional direction correction to this basic regulation, and the target regulation is then used as the midpoint balance control quantity finally injected into the modulation control unit.

[0135] Optional, Figure 4 Flowchart of the DC bus midpoint potential balance control method provided in this application Figure 4 ,like Figure 4 As shown, S105 includes:

[0136] S401. Determine the proportional coefficient and integral coefficient corresponding to the proportional-integral controller.

[0137] For example, the proportional coefficient can be defined as Kp, and the integral coefficient can be defined as Ki.

[0138] S402. Determine the first product of the midpoint voltage deviation and the proportional coefficient, and the second product of the midpoint voltage deviation and the integral coefficient.

[0139] For example, the midpoint voltage deviation can be defined as e, so the first product is: e × Kp, and the second product is: e × Ki.

[0140] S403. Based on the preset upper and lower limits of integration, the second product is subjected to amplitude limiting to obtain the target integral value.

[0141] For example, the upper and lower limits of integration can be determined based on the actual situation. If the second product is greater than the upper limit, then the upper limit is set as the target integration value. If the second product is less than the lower limit, then the lower limit is set as the target integration value. If the second product is between the upper and lower limits, then the second product is directly set as the target integration value.

[0142] S404. Determine the sum between the first product and the target integral value.

[0143] For example, the sum is obtained by adding e×Kp and the target integral value.

[0144] S405. The sum value is limited based on the preset upper and lower limits of the adjustment amount to obtain the initial adjustment amount.

[0145] For example, the upper and lower limits of the adjustment amount can be determined according to the actual situation. If the sum is greater than the upper limit, the upper limit is determined as the initial adjustment amount. If the sum is less than the lower limit, the lower limit is determined as the initial adjustment amount. If the sum is between the upper and lower limits, the sum is directly determined as the initial integral value.

[0146] S406. Determine the third product of the smooth continuous polarity target coefficient and the initial adjustment amount.

[0147] For example, multiplying the smooth continuous polarity target coefficient by the initial adjustment amount yields the third product, so the third product is: S PolarityCoeff ×U raw , among which, U raw This is the initial adjustment amount.

[0148] S407. The negative of the third product is determined as the target adjustment amount.

[0149] For example, the negative of the third product is determined as the target adjustment, so the target adjustment is: -S PolarityCoeff ×U raw .

[0150] This processing method enables the proportional term, integral term, and polarity coefficient to work together, and the target adjustment amount can simultaneously reflect the magnitude of the midpoint voltage deviation and the adjustment direction of the current operating condition. Furthermore, by limiting the integral amplitude and the adjustment amount, it suppresses the abnormal accumulation of output, thereby making the midpoint potential adjustment more stable.

[0151] Optional, Figure 5 Flowchart of the DC bus midpoint potential balance control method provided in this application Figure 5 ,like Figure 5 As shown, S105 includes:

[0152] S501. Determine the proportional coefficient and integral coefficient corresponding to the proportional-integral controller.

[0153] For example, the proportional coefficient can be defined as Kp, and the integral coefficient can be defined as Ki.

[0154] S502. Determine the fourth product of the midpoint voltage deviation and the opposite of the smooth continuous polarity target coefficient.

[0155] For example, the midpoint voltage deviation can be defined as e, so the fourth product is: -e×S PolarityCoeff .

[0156] S503. Determine the fifth product of the fourth product and the proportionality coefficient, and the sixth product of the fourth product and the integral coefficient.

[0157] For example, the fifth product is: -e×SPolarityCoeff ×Kp, the sixth product is: -e×S PolarityCoeff ×Ki.

[0158] S504. Based on the preset upper and lower limits of integration, the sixth product is subjected to amplitude limiting to obtain the target integral value.

[0159] For example, the upper and lower limits of integration can be determined based on the actual situation. If the sixth product is greater than the upper limit, then the upper limit is set as the target integration value. If the sixth product is less than the lower limit, then the lower limit is set as the target integration value. If the sixth product is between the upper and lower limits, then the sixth product is directly set as the target integration value.

[0160] S505. The sum of the fifth product and the target integral value is determined as the initial adjustment amount.

[0161] For example, the initial adjustment is obtained by summing the fifth product with the target integral value.

[0162] S506. The initial adjustment amount is limited based on the preset upper and lower limits of the adjustment amount to obtain the target adjustment amount.

[0163] For example, the upper and lower limits of the adjustment range can be determined based on the actual situation. If the initial adjustment range is greater than the upper limit, then the upper limit is determined as the target adjustment range. If the total initial adjustment range is less than the lower limit, then the lower limit is determined as the target adjustment range. If the initial adjustment range is between the upper and lower limits, then the initial adjustment range is directly determined as the target integral value.

[0164] This processing method uses the midpoint voltage deviation and the opposite of the smooth continuous polarity target coefficient as inputs for proportional-integral calculation, so that the adjustment direction is consistent with the current balance requirement. At the same time, the control quantity is constrained by integral limiting and output limiting, so that the target adjustment quantity maintains continuity and stability when the operating conditions change.

[0165] S106. Balance control of the DC bus midpoint potential based on the target adjustment amount.

[0166] For example, the target adjustment is used to directly affect the modulation control process of the ANPC three-level converter, so as to bring the DC bus neutral point potential back to the equilibrium state by changing the neutral point current distribution.

[0167] Optional, Figure 6 Flowchart of the DC bus midpoint potential balance control method provided in this application Figure 6 ,like Figure 6 As shown, S106 includes:

[0168] S601. Collect the instantaneous value and current amplitude of each phase current in the DC bus.

[0169] For example, the sampling unit synchronously acquires the three-phase current in the DC bus to obtain the instantaneous value Ix of each phase current, and extracts the amplitude I of each phase current through the current detection module. amp ,

[0170] S602. The target adjustment amount, the instantaneous value of each phase current, and the current amplitude are processed using a preset first formula to determine the zero-sequence component of each phase current. The first formula is:

[0171]

[0172] Among them, u final For the target adjustment, I x I is the instantaneous value of the phase current. amp V is the amplitude of the phase current. x0 This represents the zero-sequence component of the phase current.

[0173] For example, for each phase current, the zero-sequence component of each phase current is calculated using the first formula mentioned above.

[0174] S603. Balance control of the DC bus midpoint potential based on the zero-sequence component corresponding to each phase current.

[0175] The zero-sequence component is used during modulation to correct the direction of the midpoint current flow, ensuring that the current distribution entering the DC bus midpoint matches the current potential deviation, thereby driving the midpoint potential to converge towards an equilibrium state. Since this zero-sequence component is directly determined by the target adjustment amount and the current state of each phase, it enables synchronous linkage between the midpoint potential adjustment and the actual operating current.

[0176] Based on the method provided in this example, the target regulation quantity can be converted into a zero-sequence component according to the instantaneous state of each phase current and participate in modulation control, thereby achieving continuous balance regulation of the neutral point potential. This control method reduces the polarity mismatch problem caused by fixed deviation and maintains the continuity and smoothness of the neutral point potential regulation under different current conditions, thereby improving the balance accuracy and dynamic stability of the ANPC three-level converter under continuous power factor changes and complex operating conditions.

[0177] Optionally, it also includes: when the current amplitude is lower than the preset ratio of the rated current, setting the integral term and target adjustment of the proportional-integral controller to zero.

[0178] For example, when the current amplitude is less than the preset ratio of the rated current, such as 5%, the integral term, that is, the sixth product or the second product, can be cleared to zero, as well as the target adjustment amount can be cleared to prevent the adjustment channel noise from amplifying and causing oscillation when the signal is weak.

[0179] Optionally, it also includes: pausing the DC bus midpoint potential balance control step within a preset time window after the grid voltage zero-crossing phase calibration is completed.

[0180] For example, when the grid voltage zero-crossing phase calibration is just completed, midpoint potential balance control is not performed within a preset time period to avoid regulation shock caused by phase calibration jump.

[0181] Figure 7 This is a schematic diagram of the DC bus midpoint potential balance control device provided in this application, as shown below. Figure 7 As shown, it includes:

[0182] The acquisition module 71 is used to acquire the active current command value and reactive current command value output by the grid-connected control loop;

[0183] Processing module 72 is used to obtain the continuous polarity target coefficient based on the active current command value and the reactive current command value;

[0184] The processing module 72 is also used to filter the continuous polarity target coefficients to obtain smooth continuous polarity target coefficients;

[0185] Processing module 72 is also used to determine the midpoint voltage deviation of the DC bus;

[0186] The processing module 72 is also used to process the midpoint voltage deviation and the smooth continuous polarity target coefficient through the proportional-integral controller to obtain the target adjustment amount;

[0187] The processing module 72 is also used to balance the DC bus midpoint potential based on the target adjustment amount.

[0188] Optionally, processing module 72 is specifically used to determine the pure active gain value and the pure reactive gain value;

[0189] The processing module 72 is further used to determine the proportion of the reactive current command value based on the active current command value and the reactive current command value.

[0190] The processing module 72 is also used to perform linear difference processing between the pure active gain value and the pure reactive gain value based on the proportion of the reactive current command value, so as to obtain the continuous polarity target coefficient.

[0191] Optionally, the DC bus includes a positive DC bus and a negative DC bus;

[0192] Accordingly, the processing module 72 is also specifically used to determine the first voltage corresponding to the positive DC bus and the second voltage corresponding to the negative DC bus;

[0193] The processing module 72 is further used to determine the voltage difference between the first voltage and the second voltage;

[0194] The processing module is further used to perform amplitude limiting processing on the voltage difference based on the preset upper and lower voltage limits 72, so as to obtain the midpoint voltage deviation.

[0195] Optionally, the processing module 72 is further used to determine the proportional coefficient and integral coefficient corresponding to the proportional-integral controller;

[0196] The processing module 72 is further used to determine the first product of the midpoint voltage deviation and the proportional coefficient, and the second product of the midpoint voltage deviation and the integral coefficient.

[0197] The processing module 72 is further used to perform amplitude limiting processing on the second product based on the preset upper limit and lower limit of integration to obtain the target integral value;

[0198] Processing module 72 is further used to determine the sum between the first product and the target integral value;

[0199] The processing module 72 is further used to limit the sum value based on the preset upper limit and lower limit of the adjustment amount to obtain the initial adjustment amount;

[0200] Processing module 72 is further used to determine the third product of the smooth continuous polarity target coefficient and the initial adjustment amount;

[0201] The processing module 72 is further used to determine the opposite of the third product as the target adjustment amount.

[0202] Optionally, the processing module 72 is further used to determine the proportional coefficient and integral coefficient corresponding to the proportional-integral controller;

[0203] Processing module 72 is also specifically used to determine the fourth product of the midpoint voltage deviation and the opposite of the smooth continuous polarity target coefficient;

[0204] The processing module 72 is also specifically used to determine the fifth product of the fourth product and the proportionality coefficient, and the sixth product of the fourth product and the integral coefficient;

[0205] The processing module 72 is further used to perform amplitude limiting processing on the sixth product based on the preset upper limit and lower limit of integration to obtain the target integral value;

[0206] The processing module 72 is further configured to determine the sum between the fifth product and the target integral value as the initial adjustment amount;

[0207] The processing module 72 is further used to limit the initial adjustment amount based on the preset upper and lower limits of the adjustment amount to obtain the target adjustment amount.

[0208] Optionally, the processing module 72 is also used to collect the instantaneous value and current amplitude of each phase current in the DC bus;

[0209] Processing module 72 is further configured to process the target adjustment amount, the instantaneous values ​​of the currents in each phase, and the current amplitudes using a preset first formula to determine the zero-sequence components of the currents in each phase. The first formula is:

[0210]

[0211] Among them, u final For the target adjustment, I x I is the instantaneous value of the phase current. amp V is the amplitude of the phase current. x0 This is the zero-sequence component of the phase current;

[0212] The processing module 72 is also used to balance the DC bus midpoint potential based on the zero-sequence component corresponding to each phase current.

[0213] Optionally, the processing module 72 is also used to set the integral term and target adjustment of the proportional-integral controller to zero when the current amplitude is lower than the preset ratio of the rated current.

[0214] Optionally, the processing module 72 is also used to pause the execution of the DC bus midpoint potential balance control step within a preset time window after the grid voltage zero-crossing phase calibration is completed.

[0215] The DC bus midpoint potential balance control device provided in this embodiment can execute the DC bus midpoint potential balance control method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0216] Figure 8 A schematic diagram of the structure of the electronic device provided in this application. Figure 8 As shown, the electronic device 50 provided in this embodiment includes at least one processor 501 and a memory 502. Optionally, the electronic device 50 further includes a communication component 503. The processor 501, memory 502, and communication component 503 are connected via a bus.

[0217] In a specific implementation, at least one processor 501 executes computer execution instructions stored in memory 502, causing at least one processor 501 to perform the above-described method.

[0218] The specific implementation process of processor 501 can be found in the above method embodiments, and its implementation principle and technical effect are similar. It will not be repeated here.

[0219] In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.

[0220] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.

[0221] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0222] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0223] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0224] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory, electrically erasable programmable read-only memory, erasable programmable read-only memory, programmable read-only memory, read-only memory, magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0225] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0226] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0227] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0228] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0229] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to related technologies, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0230] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0231] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for controlling the potential balance at the midpoint of a DC bus, characterized in that, include: Obtain the active current command value and reactive current command value output by the grid-connected control loop; The continuous polarity target coefficient is obtained based on the active current command value and the reactive current command value; The continuous polarity target coefficients are filtered to obtain smooth continuous polarity target coefficients; Determine the midpoint voltage deviation of the DC bus; The target adjustment amount is obtained by processing the midpoint voltage deviation and the smooth continuous polarity target coefficient through a proportional-integral controller. The DC bus midpoint potential is balanced and controlled based on the target adjustment amount.

2. The method according to claim 1, characterized in that, The method of obtaining the continuous polarity target coefficient based on the active current command value and the reactive current command value includes: Determine the pure active power gain value and the pure reactive power gain value; Based on the active current command value and the reactive current command value, determine the proportion of the reactive current command value; Based on the proportion of the reactive current command value, a linear difference is performed between the pure active gain value and the pure reactive gain value to obtain the continuous polarity target coefficient.

3. The method according to claim 1, characterized in that, The DC bus includes a positive DC bus and a negative DC bus; Accordingly, determining the midpoint voltage deviation of the DC bus includes: Determine and collect the first voltage corresponding to the positive DC bus and the second voltage corresponding to the negative DC bus; Determine the voltage difference between the first voltage and the second voltage; The voltage difference is limited based on preset upper and lower voltage limits to obtain the midpoint voltage deviation.

4. The method according to claim 1, characterized in that, The process of processing the midpoint voltage deviation and the smooth continuous polarity target coefficient through a proportional-integral controller to obtain the target adjustment amount includes: Determine the proportional coefficient and integral coefficient corresponding to the proportional-integral controller; Determine the first product of the midpoint voltage deviation and the proportional coefficient, and the second product of the midpoint voltage deviation and the integral coefficient; The second product is subjected to amplitude limiting based on the preset upper and lower limits of integration to obtain the target integral value; Determine the sum between the first product and the target integral value; The sum value is limited based on the preset upper and lower limits of the adjustment amount to obtain the initial adjustment amount; Determine the third product of the smooth continuous polarity target coefficient and the initial adjustment amount; The negative of the third product is determined as the target adjustment amount.

5. The method according to claim 1, characterized in that, The process of processing the midpoint voltage deviation and the smooth continuous polarity target coefficient through a proportional-integral controller to obtain the target adjustment amount includes: Determine the proportional coefficient and integral coefficient corresponding to the proportional-integral controller; Determine the fourth product of the midpoint voltage deviation and the negative of the smooth continuous polarity target coefficient; Determine the fifth product of the fourth product and the proportionality coefficient, and the sixth product of the fourth product and the integral coefficient; The sixth product is subjected to amplitude limiting based on the preset upper and lower limits of integration to obtain the target integral value; The sum between the fifth product and the target integral value is determined as the initial adjustment amount; The initial adjustment amount is limited based on the preset upper and lower limits of the adjustment amount to obtain the target adjustment amount.

6. The method according to claim 1, characterized in that, The step of balancing the DC bus midpoint potential based on the target adjustment amount includes: Collect the instantaneous values ​​and current amplitudes of each phase current in the DC bus; The target adjustment amount, the instantaneous values ​​of the current in each phase, and the current amplitude are processed using a preset first formula to determine the zero-sequence component of the current in each phase. The first formula is: Among them, u final For the target adjustment, I x I is the instantaneous value of the phase current. amp V is the amplitude of the phase current. x0 This is the zero-sequence component of the phase current; The DC bus midpoint potential is balanced and controlled based on the zero-sequence component corresponding to each phase current.

7. The method according to claim 6, characterized in that, Also includes: When the current amplitude is lower than the preset ratio of the rated current, the integral term of the proportional-integral controller and the target adjustment amount are set to zero.

8. The method according to claim 1, characterized in that, Also includes: Within a preset time window after the grid voltage zero-crossing phase calibration is completed, the step of executing the DC bus midpoint potential balance control is paused.

9. A DC bus midpoint potential balance control device, characterized in that, include: The acquisition module is used to acquire the active current command value and reactive current command value output by the grid-connected control loop; The processing module is used to obtain the continuous polarity target coefficient based on the active current command value and the reactive current command value; The processing module is also used to filter the continuous polarity target coefficients to obtain smooth continuous polarity target coefficients; The processing module is also used to determine the midpoint voltage deviation of the DC bus; The processing module is also used to process the midpoint voltage deviation and the smooth continuous polarity target coefficient through a proportional-integral controller to obtain the target adjustment amount; The processing module is also used to perform balance control on the DC bus midpoint potential based on the target adjustment amount.

10. An electronic device, characterized in that, include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executed instructions; The processor executes computer execution instructions stored in the memory to implement the DC bus midpoint potential balance control method as described in any one of claims 1-8.

11. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the DC bus midpoint potential balance control method as described in any one of claims 1-8.

12. A computer program product, characterized in that, It includes a computer program that, when executed by a processor, implements the DC bus midpoint potential balance control method as described in any one of claims 1-8.

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