Converter control method, controller and converter

Abstract

The invention provides a converter control method, a controller and a converter. The control method comprises the following steps: determining a first midpoint current value, a second midpoint current value and a third midpoint current value; based on the first midpoint current value, the second midpoint current value and the third midpoint current value, determining a zero-sequence voltage component used for realizing the midpoint potential balance of the converter; adjusting a three-phase modulation voltage value output by a pulse width modulation control system based on the zero sequence voltage component; controlling a three-phase bridge arm of the converter based on the adjusted three-phase modulation voltage value; wherein the first midpoint current value is a midpoint current value caused by DC positive and negative bus voltage fluctuation of the converter, and the second midpoint current value is a midpoint current value caused by a switching state of a three-phase bridge arm of the converter; the third midpoint current value is a midpoint current value caused by a three-phase modulation voltage value output by the pulse width modulation control system.

Description

Technical Field

[0001] The present disclosure generally relates to the field of converter technologies, and more particularly, to a control method, a controller, and a converter for a converter. Background Art

[0002] For a three-level converter, a neutral-point clamped topology is generally adopted. Taking the ANPC topology as an example, by controlling the on-off combinations of the IGBTs of each arm, three levels, namely +U dc / 2, 0, -U dc / 2, are output, thereby realizing three-level modulation.

[0003] During the actual operation of the three-level topology, due to the differences in hardware parameters involved and the power fluctuations caused by the level conversion, if neutral-point balance control is not adopted, the following effects will occur: the offset of the neutral-point potential causes uneven voltage sharing of the DC-side capacitors and the upper and lower IGBTs of the arm. In severe cases, it will lead to overvoltage failure of the device; the fluctuation of the neutral-point potential will increase the content of low-order harmonics, affecting the quality of the electric energy output by the converter; the fluctuation of the neutral-point potential reduces the control margin, affecting the stability of the control system. Summary of the Invention

[0004] An exemplary embodiment of the present disclosure is to provide a control method, a controller, and a controller for a converter, which can achieve neutral-point balance of a three-level converter under various working conditions and improve the control performance of the converter.

[0005] According to a first aspect of an embodiment of the present disclosure, a control method for a converter is provided. The control method includes: determining a first neutral-point current value, a second neutral-point current value, and a third neutral-point current value; determining a zero-sequence voltage component for achieving neutral-point potential balance of the converter based on the first neutral-point current value, the second neutral-point current value, and the third neutral-point current value; adjusting three-phase modulation voltage values output by a pulse-width modulation control system based on the zero-sequence voltage component; and controlling three-phase arms of the converter based on the adjusted three-phase modulation voltage values. Wherein, the first neutral-point current value is the neutral-point current value caused by the voltage fluctuations of the positive and negative DC buses of the converter, the second neutral-point current value is the neutral-point current value caused by the switching states of the three-phase arms of the converter, and the third neutral-point current value is the neutral-point current value caused by the three-phase modulation voltage values output by the pulse-width modulation control system.

[0006] Optionally, the step of determining the first midpoint current value includes: determining the first midpoint current value based on the capacitance value of the DC bus capacitor of the converter, and the deviation between the DC positive bus voltage value and the DC negative bus voltage value of the converter; wherein, the DC positive bus voltage value of the converter is the voltage value between the DC positive bus and the midpoint, and the DC negative bus voltage value of the converter is the voltage value between the midpoint and the DC negative bus.

[0007] Optionally, the converter includes a rectifier and an inverter. Wherein, the step of determining the second midpoint current value includes: determining the second midpoint current value for the inverter based on the switching states of the three-phase bridge arms in the inverter and the three-phase current values of the inverter, where the second midpoint current value for the inverter is the midpoint current value caused by the switching states of the three-phase bridge arms of the inverter; and / or, determining the second midpoint current value for the rectifier based on the switching states of the three-phase bridge arms in the rectifier and the three-phase current values of the rectifier, where the second midpoint current value for the rectifier is the midpoint current value caused by the switching states of the three-phase bridge arms of the rectifier.

[0008] Optionally, the converter includes a rectifier and an inverter. Wherein, the step of determining the third midpoint current value includes: determining the third midpoint current value for the inverter based on the three-phase modulation voltage values for the inverter output by the pulse width modulation control system and the three-phase current values of the inverter, where the third midpoint current value for the inverter is the midpoint current value caused by the three-phase modulation voltage values for the inverter; and / or, determining the third midpoint current value for the rectifier based on the three-phase modulation voltage values for the rectifier output by the pulse width modulation control system and the three-phase current values of the rectifier, where the third midpoint current value for the rectifier is the midpoint current value caused by the three-phase modulation voltage values for the rectifier.

[0009] Optionally, the converter includes a rectifier and an inverter; wherein, the step of determining a zero-sequence voltage component for achieving the neutral point potential balance of the converter based on the first neutral point current value, the second neutral point current value, and the third neutral point current value includes: determining the zero-sequence voltage component based on the first neutral point current value, the second neutral point current value for the inverter, and the third neutral point current value for the inverter; wherein, the step of adjusting the three-phase modulation voltage values output by the pulse width modulation control system based on the zero-sequence voltage component includes: superimposing the zero-sequence voltage component on the three-phase modulation voltage values for the inverter output by the pulse width modulation control system to obtain the adjusted three-phase modulation voltage values for the inverter; wherein, the step of controlling the three-phase bridge arms of the converter based on the adjusted three-phase modulation voltage values includes: controlling the switching states of the three-phase bridge arms of the inverter based on the adjusted three-phase modulation voltage values for the inverter; wherein, the second neutral point current value for the inverter is the neutral point current value caused by the switching states of the three-phase bridge arms of the inverter, and the third neutral point current value for the inverter is the neutral point current value caused by the three-phase modulation voltage values for the inverter.

[0010] Optionally, the converter includes a rectifier and an inverter; wherein, the step of determining a zero-sequence voltage component for achieving the neutral point potential balance of the converter based on the first neutral point current value, the second neutral point current value, and the third neutral point current value includes: determining the zero-sequence voltage component based on the first neutral point current value, the second neutral point current value for the rectifier, and the third neutral point current value for the rectifier; wherein, the step of adjusting the three-phase modulation voltage values output by the pulse width modulation control system based on the zero-sequence voltage component includes: superimposing the zero-sequence voltage component on the three-phase modulation voltage values for the rectifier output by the pulse width modulation control system to obtain the adjusted three-phase modulation voltage values for the rectifier; wherein, the step of controlling the three-phase bridge arms of the converter based on the adjusted three-phase modulation voltage values includes: controlling the switching states of the three-phase bridge arms of the rectifier based on the adjusted three-phase modulation voltage values for the rectifier; wherein, the second neutral point current value for the rectifier is the neutral point current value caused by the switching states of the three-phase bridge arms of the rectifier, and the third neutral point current value for the rectifier is the neutral point current value caused by the three-phase modulation voltage values for the rectifier.

[0011] Optionally, the converter includes a rectifier and an inverter. Among them, the steps of determining the zero-sequence voltage component for achieving the neutral point potential balance of the converter based on the first neutral point current value, the second neutral point current value, and the third neutral point current value include: determining a first zero-sequence voltage component for achieving the neutral point potential balance of the converter based on the first neutral point current value, the second neutral point current value of the inverter, and the third neutral point current value of the inverter; determining a second zero-sequence voltage component for achieving the neutral point potential balance of the converter based on the first neutral point current value, the second neutral point current value of the rectifier, and the third neutral point current value of the rectifier; where the second neutral point current value of the inverter is the neutral point current value caused by the switching states of the three-phase bridge arms of the inverter, the third neutral point current value of the inverter is the neutral point current value caused by the three-phase modulation voltage value of the inverter, the second neutral point current value of the rectifier is the neutral point current value caused by the switching states of the three-phase bridge arms of the rectifier, and the third neutral point current value of the rectifier is the neutral point current value caused by the three-phase modulation voltage value of the rectifier.

[0012] Optionally, the steps of adjusting the three-phase modulation voltage values output by the pulse width modulation control system based on the zero-sequence voltage component include: superimposing a first preset percentage of the first zero-sequence voltage component on the three-phase modulation voltage values of the inverter output by the pulse width modulation control system to obtain the adjusted three-phase modulation voltage values of the inverter; superimposing a second preset percentage of the second zero-sequence voltage component on the three-phase modulation voltage values of the rectifier output by the pulse width modulation control system to obtain the adjusted three-phase modulation voltage values of the rectifier; where the sum of the first preset percentage and the second preset percentage is 1.

[0013] According to a second aspect of the embodiments of the present disclosure, there is provided a computer-readable storage medium storing a computer program, which when executed by a processor, causes the processor to execute the control method of the converter as described above.

[0014] According to a third aspect of the embodiments of the present disclosure, there is provided a controller, which includes: a processor; a memory storing a computer program, which when executed by the processor, causes the processor to execute the control method of the converter as described above.

[0015] According to a fourth aspect of the embodiments of the present disclosure, there is provided a converter, which includes the controller as described above.

[0016] A control method, a controller, and a converter according to an exemplary embodiment of the present disclosure propose a control method for achieving neutral point potential balance of a three-level converter, realizing neutral point potential balance of the three-level converter under various working conditions, avoiding neutral point potential offset and fluctuation problems, effectively reducing the voltage stress of DC capacitors and power devices, improving the reliability of devices; effectively improving the quality of the electric energy output by the converter; effectively improving the stability of the converter control system, thereby improving the control performance of the converter.

[0017] In the following description, some aspects and / or advantages of the general concept of the present disclosure will be set forth, and some aspects and / or advantages will be learned from the following description or the implementation of the general concept of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] From the following detailed description of the embodiments of the present application in conjunction with the drawings, these and / or other aspects and advantages of the present application will become clearer and easier to understand, where:

[0019] Figure 1 A flowchart showing a control method of a converter according to a first exemplary embodiment of the present disclosure;

[0020] Figure 2 A flowchart showing a control method of a converter according to a second exemplary embodiment of the present disclosure;

[0021] Figure 3 A flowchart showing a control method of a converter according to a third exemplary embodiment of the present disclosure;

[0022] Figure 4 A flowchart showing a control method of a converter according to a fourth exemplary embodiment of the present disclosure;

[0023] Figure 5 A flowchart showing a control method of a converter according to a fifth exemplary embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein the same reference numerals always refer to the same components. The following embodiments will be described with reference to the accompanying drawings to explain the present disclosure.

[0025] It should be noted that the terms "first", "second", etc. in the description, claims and the above-mentioned drawings of the present disclosure are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present disclosure described here can be implemented in an order other than those illustrated or described here. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0026] It should be noted here that "at least one of several items" in the present disclosure all represents three parallel situations, including "any one of these several items", "a combination of any multiple of these several items", and "all of these several items". For example, "including at least one of A and B" includes the following three parallel situations: (1) including A; (2) including B; (3) including A and B. Another example, "performing at least one of step one and step two" means the following three parallel situations: (1) performing step one; (2) performing step two; (3) performing step one and step two.

[0027] Figure 1 A flowchart showing a control method of a converter according to a first exemplary embodiment of the present disclosure.

[0028] As an example, the control method of the converter according to the exemplary embodiment of the present disclosure can be executed by the controller of the converter.

[0029] As an example, the converter may include a rectifier and / or an inverter. As an example, the converter may be a converter of a wind power generation set, and it should be understood that it may also be a converter of other new energy power generation systems.

[0030] Referring to Figure 1 , in step S101, a first midpoint current value, a second midpoint current value, and a third midpoint current value are determined.

[0031] The first midpoint current value is the midpoint current value caused by the voltage fluctuations of the positive and negative DC busbars of the converter; the second midpoint current value is the midpoint current value caused by the switching states of the three-phase bridge arms of the converter; the third midpoint current value is the midpoint current value caused by the three-phase modulation voltage values output by the pulse width modulation control system.

[0032] As an example, the pulse width modulation control system may be one of a PWM control system, an SPWM control system, and an SVPWM control system. It should be understood that it may also be other types of pulse width modulation control systems, and the present disclosure does not limit this.

[0033] Exemplary embodiments regarding the first midpoint current value, the second midpoint current value, and the third midpoint current value are described separately below.

[0034] I. Regarding the first midpoint current value

[0035] As an example, the first midpoint current value can be determined based on the capacitance value of the DC bus capacitor of the converter, and the deviation between the DC positive bus voltage value and the DC negative bus voltage value of the converter.

[0036] The DC positive bus voltage value of the converter is the voltage value between the DC positive bus and the midpoint, and the DC negative bus voltage value of the converter is the voltage value between the midpoint and the DC negative bus.

[0037] As an example, the first midpoint current value can be calculated by the following formula:

[0038] C*d(U up -U un ) / dt(1)

[0039] where C represents the capacitance value of the DC bus capacitor; U up represents the DC positive bus voltage value; U un represents the DC negative bus voltage value.

[0040] II. Regarding the second midpoint current value

[0041] In one embodiment, the second midpoint current value for the inverter can be determined based on the switching states of the three-phase bridge arms in the inverter and the three-phase current values of the inverter.

[0042] The second midpoint current value for the inverter is the midpoint current value caused by the switching states of the three-phase bridge arms of the inverter.

[0043] As an example, the second midpoint current value for the inverter can be calculated by the following formula:

[0044] i switch1 =(1-|S a1 |)*i a1 +(1-|S b1 |)*i b1 +(1-|S c1 |)*i c1 (2)

[0045] where i switch1 represents the second midpoint current value for the inverter; S a1 、S b1 、S c1 represent the switching states of the a, b, and c three-phase bridge arms in the inverter, which are divided into three states: 1, 0, -1; i a1 、ib1 and i c1 represents the real-time values of the three-phase currents of the inverter.

[0046] In another embodiment, based on the switching states of the three-phase bridge arms in the rectifier and the three-phase current values of the rectifier, a second midpoint current value for the rectifier can be determined.

[0047] The second midpoint current value for the rectifier is the midpoint current value caused by the switching states of the three-phase bridge arms of the rectifier.

[0048] As an example, the second midpoint current value for the rectifier can be calculated by the following formula:

[0049] i switch2 = (1 - |S a2 ) * i a2 + (1 - |S b2 ) * i b2 + (1 - |S c2 ) * i c2 (3)

[0050] where i switch2 represents the second midpoint current value for the rectifier; S a2 , S b2 , S c2 represent the switching states of the a, b, and c phase bridge arms in the rectifier, respectively, which are divided into three states: 1, 0, and -1; i a2 , i b2 , i c2 represent the real-time values of the three-phase currents of the rectifier.

[0051] In the above embodiment, the switching states of the three-phase bridge arms can be the switching states of the three-phase bridge arms after the most recent switching operation.

[0052] Third, regarding the third midpoint current value

[0053] In one embodiment, based on the three-phase modulation voltage values for the inverter output by the pulse width modulation control system and the three-phase current values of the inverter, a third midpoint current value for the inverter can be determined.

[0054] The third midpoint current value for the inverter is the midpoint current value caused by the three-phase modulation voltage values for the inverter output by the pulse width modulation control system.

[0055] As an example, the third midpoint current value for the inverter can be calculated by the following formula:

[0056] i v1 = -sign(V a1 ) * i a1 - sign(V b1 ) * ib1 -sign(V c1 )*i c1 (4)

[0057] wherein, i v1 represents the third midpoint current value for the inverter; V a1 , V b1 , V c1 are the real-time values of the a, b, c phase modulation waves for the inverter output by the pulse width modulation control system, that is, the three-phase modulation voltage values to be adjusted in the subsequent step S103; Sign represents the sign function, if the variable is greater than 0, it returns 1, if the variable is less than 0, it returns -1; i a1 , i b1 , i c1 represent the real-time values of the three-phase currents of the inverter.

[0058] In another embodiment, based on the three-phase modulation voltage value for the rectifier and the three-phase current value of the rectifier output by the pulse width modulation control system, the third midpoint current value for the rectifier can be determined. The third midpoint current value for the rectifier is the midpoint current value caused by the three-phase modulation voltage value for the rectifier output by the pulse width modulation control system.

[0059] As an example, the third midpoint current value for the rectifier can be calculated by the following formula:

[0060] i v2 = -sign(V a2 )*i a2 -sign(V b2 )*i b2 -sign(V c2 )*i c2 (5)

[0061] wherein, i v2 represents the third midpoint current value for the rectifier; V a2 , V b2 , V c2 are the real-time values of the a, b, c phase modulation waves for the rectifier output by the pulse width modulation control system, that is, the three-phase modulation voltage values to be adjusted in the subsequent step S103; Sign represents the sign function, if the variable is greater than 0, it returns 1, if the variable is less than 0, it returns -1; i a2 , i b2 , i c2 represent the real-time values of the three-phase currents of the rectifier.

[0062] In step S102, based on the first midpoint current value, the second midpoint current value, and the third midpoint current value, determine the zero-sequence voltage component for achieving the midpoint potential balance of the converter.

[0063] As an example, step S102 may include: taking the above three current values as inputs and calculating the required zero-sequence voltage component V0 with the goal of keeping the midpoint charge unchanged. Keeping the midpoint charge unchanged can be understood as the inflow of positrons into the midpoint being equal to the outflow from the midpoint, and the inflow of negative electrons into the midpoint being equal to the outflow from the midpoint.

[0064] For example, the above three current values can be input into the zero-sequence voltage component calculation function. It should be understood that the present disclosure does not limit the specific form of the zero-sequence voltage component calculation function, and any zero-sequence voltage component calculation function that can meet the above conditions can be used to calculate the zero-sequence voltage component V0.

[0065] In step S103, based on the zero-sequence voltage component, the three-phase modulation voltage values output by the pulse width modulation control system are adjusted.

[0066] As an example, step S103 may include: superimposing the zero-sequence voltage component on the three-phase modulation voltage values output by the pulse width modulation control system to obtain the adjusted three-phase modulation voltage values.

[0067] As an example, in step S104, based on the adjusted three-phase modulation voltage values, the actions of the three-phase bridge arms of the converter are controlled.

[0068] As an example, based on the three-phase modulation waves and carriers corresponding to the adjusted three-phase modulation voltage values, the PWM waves for controlling the three-phase bridge arms of the converter can be determined to control the switching states of the three-phase bridge arms of the converter.

[0069] Figure 2 A flowchart showing a control method for a converter according to a second exemplary embodiment of the present disclosure.

[0070] Refer to Figure 2 , in step S201, a first midpoint current value, a second midpoint current value for the inverter, and a third midpoint current value for the inverter are determined.

[0071] In step S202, based on the first midpoint current value, the second midpoint current value for the inverter, and the third midpoint current value for the inverter, a zero-sequence voltage component for achieving the midpoint potential balance of the converter is determined.

[0072] In step S203, based on the zero-sequence voltage component, the three-phase modulation voltage values for the inverter output by the pulse width modulation control system are adjusted.

[0073] As an example, step S203 may include: superimposing the zero-sequence voltage component on the three-phase modulation voltage values for the inverter output by the pulse width modulation control system to obtain the adjusted three-phase modulation voltage values for the inverter.

[0074] In step S204, based on the adjusted three-phase modulation voltage values for the inverter, control the operations of the three-phase bridge arms of the inverter.

[0075] Figure 3 The flowchart showing the control method of the converter according to the third exemplary embodiment of the present disclosure.

[0076] Refer to Figure 3 , in step S301, determine the first neutral point current value, the second neutral point current value for the rectifier, and the third neutral point current value for the rectifier.

[0077] In step S302, based on the first neutral point current value, the second neutral point current value for the rectifier, and the third neutral point current value for the rectifier, determine the zero-sequence voltage component for achieving the neutral point potential balance of the converter.

[0078] In step S303, based on the zero-sequence voltage component, adjust the three-phase modulation voltage values for the rectifier output by the pulse width modulation control system.

[0079] As an example, step S303 may include: superimposing the zero-sequence voltage component on the three-phase modulation voltage values for the rectifier output by the pulse width modulation control system to obtain the adjusted three-phase modulation voltage values for the rectifier.

[0080] In step S304, based on the adjusted three-phase modulation voltage values for the rectifier, control the three-phase bridge arms of the rectifier.

[0081] Figure 4 The flowchart showing the control method of the converter according to the fourth exemplary embodiment of the present disclosure.

[0082] Refer to Figure 4 , in step S401, determine the first neutral point current value, the second neutral point current value for the inverter, the third neutral point current value for the inverter, the second neutral point current value for the rectifier, and the third neutral point current value for the rectifier.

[0083] In step S402, based on the first neutral point current value, the second neutral point current value for the inverter, and the third neutral point current value for the inverter, determine the first zero-sequence voltage component for achieving the neutral point potential balance of the converter; and based on the first neutral point current value, the second neutral point current value for the rectifier, and the third neutral point current value for the rectifier, determine the second zero-sequence voltage component for achieving the neutral point potential balance of the converter.

[0084] In step S403, a first zero-sequence voltage component of a first preset percentage is superimposed on the three-phase modulation voltage values for the inverter output by the pulse width modulation control system to obtain adjusted three-phase modulation voltage values for the inverter; and a second zero-sequence voltage component of a second preset percentage is superimposed on the three-phase modulation voltage values for the rectifier output by the pulse width modulation control system to obtain adjusted three-phase modulation voltage values for the rectifier.

[0085] The sum of the first preset percentage and the second preset percentage is 1.

[0086] In step S404, based on the adjusted three-phase modulation voltage values for the inverter, the three-phase bridge arms of the inverter are controlled; and based on the adjusted three-phase modulation voltage values for the rectifier, the three-phase bridge arms of the rectifier are controlled.

[0087] Figure 5 The flowchart shows a control method for a converter according to a fifth exemplary embodiment of the present disclosure.

[0088] Referring to Figure 5 , in step S501, the midpoint current i caused by the DC positive and negative bus voltage fluctuations is calculated cap .

[0089] In step S502, according to the IGBT switch states and the real-time values of the three-phase currents flowing out of the converter (rectifying or inverting), the midpoint current i formed by the three-phase switch states is calculated switch .

[0090] In step S503, according to the real-time values of the three-phase modulation voltages output by the control system and the real-time values of the three-phase currents flowing out of the converter (rectifying or inverting), the midpoint current i formed by the three-phase modulation voltages is calculated v .

[0091] In step S504, with the above three currents as inputs, the zero-sequence voltage component V0 to be injected is calculated to keep the midpoint potential charge unchanged.

[0092] In step S505, the zero-sequence voltage component V0 is superimposed on the three-phase modulation voltages output by the control system to form a synthesized modulation wave, which acts on the power devices of the converter to form midpoint balance control.

[0093] In view of the current situation of the midpoint potential imbalance in the three-level converter, the present disclosure proposes a control method for midpoint potential balance, which realizes the midpoint potential balance of the three-level converter, improves the operation reliability of the DC capacitor and the IGBT power unit, improves the quality of the electric energy output by the three-level converter, and improves the system stability of the three-level converter.

[0094] In a neutral-point clamped three-level converter, without using neutral-point balance control, when there are deviations in the DC capacitor values and during the action of small and medium vectors, neutral-point potential fluctuations will occur, manifested as neutral-point potential voltage offset and fluctuations, which will reduce the reliability of the main circuit devices, degrade the power quality of the converter output, and reduce the stability margin of the control system. The present disclosure proposes a control method for the neutral-point potential of a three-level converter to achieve neutral-point potential balance in a three-level converter (applicable to three-level topologies such as NPC, TPC, ANPC, etc.), which can minimize neutral-point potential offset and fluctuations, improve the reliability of the main circuit devices, enhance the power quality of the three-level converter output, and improve the system stability of the three-level converter.

[0095] An exemplary embodiment of the present disclosure provides a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to execute the control method of the converter as described in the above exemplary embodiment. The computer-readable storage medium is any data storage device capable of storing data readable by a computer system. Examples of computer-readable storage media include: read-only memory, random access memory, compact disc read-only memory, magnetic tape, floppy disk, optical data storage device, and carrier waves (such as data transmission via the Internet through wired or wireless transmission paths).

[0096] The controller according to an exemplary embodiment of the present disclosure includes: a processor (not shown) and a memory (not shown), wherein the memory stores a computer program, which, when executed by the processor, causes the processor to execute the control method of the converter as described in the above exemplary embodiment.

[0097] The converter according to an exemplary embodiment of the present disclosure includes: the controller as described in the above exemplary embodiment. As an example, the converter according to an exemplary embodiment of the present disclosure can be a converter for a new energy power generation system. For example, it can be a converter for a wind turbine generator set. It should be understood that the converter according to an exemplary embodiment of the present disclosure can also be applied in other scenarios, and the present disclosure does not limit this.

[0098] Although some exemplary embodiments of the present disclosure have been shown and described, those skilled in the art should understand that these embodiments can be modified without departing from the scope and spirit of the present disclosure defined by the claims and their equivalents.

Claims

1. A control method for an inverter, characterized in that, The control method includes: Determining a first midpoint current value, a second midpoint current value, and a third midpoint current value; Based on the first midpoint current value, the second midpoint current value, and the third midpoint current value, determining a zero-sequence voltage component for achieving midpoint potential balance of the converter; Based on the zero-sequence voltage component, adjusting three-phase modulation voltage values output by a pulse width modulation control system; Based on the adjusted three-phase modulation voltage values, controlling three-phase bridge arms of the converter; Wherein, the first midpoint current value is the midpoint current value caused by voltage fluctuations between the positive and negative DC bus voltages of the converter, the second midpoint current value is the midpoint current value caused by the switching states of three-phase bridge arms of the converter, and the third midpoint current value is the midpoint current value caused by the three-phase modulation voltage values output by the pulse width modulation control system.

2. The control method according to claim 1, wherein The step of determining the first midpoint current value includes: Based on the capacitance value of a DC bus capacitor of the converter and the deviation between the DC positive bus voltage value and the DC negative bus voltage value of the converter, determining the first midpoint current value; Wherein, the DC positive bus voltage value of the converter is the voltage value between the DC positive bus and the midpoint, and the DC negative bus voltage value of the converter is the voltage value between the midpoint and the DC negative bus.

3. The control method according to claim 1, wherein The converter includes a rectifier and an inverter. Wherein, the step of determining the second midpoint current value includes: Based on the switching states of three-phase bridge arms in the inverter and the three-phase current values of the inverter, determining a second midpoint current value for the inverter, where the second midpoint current value for the inverter is the midpoint current value caused by the switching states of three-phase bridge arms of the inverter; And / or, based on the switching states of three-phase bridge arms in the rectifier and the three-phase current values of the rectifier, determining a second midpoint current value for the rectifier, where the second midpoint current value for the rectifier is the midpoint current value caused by the switching states of three-phase bridge arms of the rectifier.

4. The control method according to claim 1, wherein The converter includes a rectifier and an inverter. Wherein, the step of determining the third midpoint current value includes: Based on the three-phase modulation voltage values for the inverter output by the pulse width modulation control system and the three-phase current values of the inverter, determining a third midpoint current value for the inverter, where the third midpoint current value for the inverter is the midpoint current value caused by the three-phase modulation voltage values for the inverter; And / or, based on the three-phase modulation voltage values for the rectifier output by the pulse width modulation control system and the three-phase current values of the rectifier, determining a third midpoint current value for the rectifier, where the third midpoint current value for the rectifier is the midpoint current value caused by the three-phase modulation voltage values for the rectifier.

5. The control method according to any one of claims 1 to 4, characterized in that The converter includes a rectifier and an inverter; Among them, the steps of determining the zero-sequence voltage component for achieving the neutral-point potential balance of the converter based on the first neutral-point current value, the second neutral-point current value, and the third neutral-point current value include: determining the zero-sequence voltage component based on the first neutral-point current value, the second neutral-point current value for the inverter, and the third neutral-point current value for the inverter; Among them, the steps of adjusting the three-phase modulation voltage values output by the pulse-width modulation control system based on the zero-sequence voltage component include: superimposing the zero-sequence voltage component on the three-phase modulation voltage values for the inverter output by the pulse-width modulation control system to obtain the adjusted three-phase modulation voltage values for the inverter; Among them, the steps of controlling the three-phase bridge arms of the converter based on the adjusted three-phase modulation voltage values include: controlling the switching states of the three-phase bridge arms of the inverter based on the adjusted three-phase modulation voltage values for the inverter; Among them, the second neutral-point current value for the inverter is the neutral-point current value caused by the switching states of the three-phase bridge arms of the inverter, and the third neutral-point current value for the inverter is the neutral-point current value caused by the three-phase modulation voltage values for the inverter.

6. The control method according to any one of claims 1 to 4, characterized in that, The converter includes a rectifier and an inverter; Among them, the steps of determining the zero-sequence voltage component for achieving the neutral-point potential balance of the converter based on the first neutral-point current value, the second neutral-point current value, and the third neutral-point current value include: determining the zero-sequence voltage component based on the first neutral-point current value, the second neutral-point current value for the rectifier, and the third neutral-point current value for the rectifier; Among them, the steps of adjusting the three-phase modulation voltage values output by the pulse-width modulation control system based on the zero-sequence voltage component include: superimposing the zero-sequence voltage component on the three-phase modulation voltage values for the rectifier output by the pulse-width modulation control system to obtain the adjusted three-phase modulation voltage values for the rectifier; Among them, the steps of controlling the three-phase bridge arms of the converter based on the adjusted three-phase modulation voltage values include: controlling the switching states of the three-phase bridge arms of the rectifier based on the adjusted three-phase modulation voltage values for the rectifier; Among them, the second neutral-point current value for the rectifier is the neutral-point current value caused by the switching states of the three-phase bridge arms of the rectifier, and the third neutral-point current value for the rectifier is the neutral-point current value caused by the three-phase modulation voltage values for the rectifier.

7. The control method according to any one of claims 1 to 4, characterized in that The converter includes a rectifier and an inverter. Among them, the steps of determining the zero-sequence voltage component for achieving the neutral-point potential balance of the converter based on the first neutral-point current value, the second neutral-point current value, and the third neutral-point current value include: Determining the first zero-sequence voltage component for achieving the neutral-point potential balance of the converter based on the first neutral-point current value, the second neutral-point current value for the inverter, and the third neutral-point current value for the inverter; Determine a second zero-sequence voltage component for achieving neutral-point potential balance of the converter based on the first neutral-point current value, a second neutral-point current value for the rectifier, and a third neutral-point current value for the rectifier; Wherein, the second neutral-point current value for the inverter is the neutral-point current value caused by the switching states of the three-phase bridge arms of the inverter, the third neutral-point current value for the inverter is the neutral-point current value caused by the three-phase modulation voltage values for the inverter, the second neutral-point current value for the rectifier is the neutral-point current value caused by the switching states of the three-phase bridge arms of the rectifier, and the third neutral-point current value for the rectifier is the neutral-point current value caused by the three-phase modulation voltage values for the rectifier.

8. The control method according to claim 7, wherein The steps of adjusting the three-phase modulation voltage values output by the pulse width modulation control system based on the zero-sequence voltage component include: Superimpose a first preset percentage of the first zero-sequence voltage component on the three-phase modulation voltage values for the inverter output by the pulse width modulation control system to obtain adjusted three-phase modulation voltage values for the inverter; Superimpose a second preset percentage of the second zero-sequence voltage component on the three-phase modulation voltage values for the rectifier output by the pulse width modulation control system to obtain adjusted three-phase modulation voltage values for the rectifier; Wherein, the sum of the first preset percentage and the second preset percentage is 1.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it causes the processor to execute the control method of the converter according to any one of claims 1 to 8.

10. A controller, characterized in that, The controller includes: A processor; A memory storing a computer program, when the computer program is executed by the processor, it causes the processor to execute the control method of the converter according to any one of claims 1 to 8.

11. A current converter, characterized in that, The converter includes the controller according to claim 10.

Images