Converter control method, system and storage medium

Abstract

The present application discloses a control method, system and storage medium for a converter, and belongs to the field of renewable energy power generation. The method includes: a converter control device obtains a three-phase modulation wave voltage based on the three-phase current, d-axis current given value and q-axis current given value at the AC end of the converter module at the time corresponding to the inflection point of the most recent predetermined carrier, and obtains the three-phase modulation wave increment voltage of each converter module according to the three-phase current at the AC end of the converter module at the time corresponding to the inflection point of the most recent predetermined carrier, and generates a pulse control signal corresponding to each converter module based on the three-phase modulation wave voltage and the three-phase modulation wave increment voltage of each converter module when the three-phase modulation wave voltage and the inflection point voltage of the predetermined carrier meet the balanced adjustment condition, and uses the pulse control signal to control the corresponding converter module. According to the embodiment of the present application, the current balance of the converter modules in parallel in the converter can be improved.

Description

Technical Field

[0001] The present application relates to the field of renewable energy power generation, and in particular to a control method, system and storage medium for a converter. Background Art

[0002] With the promotion of renewable energy, the capacity demand of energy conversion equipment for renewable energy is increasing. As an important component of energy conversion equipment, the converter also has the demand for capacity improvement. The converter can adopt modular design and realize the capacity improvement of the converter by parallel connection of converter modules. In order to improve the control accuracy of the converter module, each converter module in the converter can be controlled separately. The control unit for executing the control algorithm assumes the control algorithm of multiple converter modules and sends down the modulation waves of multiple converter modules. The current of multiple converter modules is prone to current mutation at the commutation point, resulting in uneven current of multiple converter modules, and may also trigger converter faults, reducing the safety of the converter. Summary of the invention

[0003] Embodiments of the present application provide a control method, system, and storage medium for a converter, which can improve the current balance of converter modules connected in parallel in the converter.

[0004] In a first aspect, an embodiment of the present application provides a control method for a converter, wherein the converter includes N converter modules connected in parallel, where N is an integer greater than 1, and the converter module has an AC end. The method includes: a converter control device obtains a three-phase modulation wave voltage based on the three-phase current, a d-axis current given value, and a q-axis current given value of the AC end of the converter module at a time corresponding to a most recently passed inflection point of a predetermined carrier; the converter control device obtains a three-phase modulation wave incremental voltage of each converter module based on the three-phase current of the AC end of the converter module at a time corresponding to a most recently passed inflection point of a predetermined carrier; when the three-phase modulation wave voltage and the voltage at the inflection point of the predetermined carrier meet a balanced adjustment condition, the converter control device generates a pulse control signal corresponding to each converter module based on the three-phase modulation wave voltage and the three-phase modulation wave incremental voltage of each converter module, and controls the corresponding converter module using the pulse control signal.

[0005] In a second aspect, an embodiment of the present application provides a control system for a converter, comprising: a converter, comprising N converter modules connected in parallel, N being an integer greater than 1, and the converter module having an AC end; a converter control device, configured to obtain a three-phase modulated wave voltage based on the three-phase current, a d-axis current given value, and a q-axis current given value from the AC end of the converter module at a time corresponding to a most recently passed inflection point of a predetermined carrier; and, obtaining a three-phase modulated wave incremental voltage of each converter module according to the three-phase current at the AC end of the converter module at a time corresponding to a most recently passed inflection point of a predetermined carrier; and, in a case where the three-phase modulated wave voltage and the voltage at the inflection point of the predetermined carrier meet a balanced adjustment condition, generate a pulse control signal corresponding to each converter module based on the three-phase modulated wave voltage and the three-phase modulated wave incremental voltage of each converter module, and use the pulse control signal to control the corresponding converter module.

[0006] In a third aspect, an embodiment of the present application provides a computer-readable storage medium having computer program instructions stored thereon. When the computer program instructions are executed by a processor, the control method of the converter of the first aspect is implemented.

[0007] The embodiment of the present application provides a control method, system and storage medium of a converter, wherein the converter control device can obtain a three-phase modulation wave voltage based on the three-phase current of the AC end of each converter module at the time corresponding to the inflection point of the predetermined carrier that has passed most recently, and obtain the three-phase modulation wave increment voltage of each AC module according to the three-phase current of the AC end of each converter module at the time corresponding to the inflection point of the predetermined carrier. When the three-phase modulation wave voltage and the voltage at the inflection point of the predetermined carrier meet the balanced adjustment condition, a pulse control signal can be generated according to the three-phase modulation wave increment voltage and the three-phase modulation wave voltage, the three-phase modulation wave increment voltage can make up for the current difference between the parallel converter modules, and the three-phase modulation wave voltage and the voltage at the inflection point of the predetermined carrier meet the balanced adjustment condition, the three-phase modulation wave voltage after being processed by the three-phase modulation wave increment voltage will not exceed the voltage range of the predetermined carrier, the difference in the current of the parallel converter modules controlled by the generated pulse control signal is reduced, and the current of the converter module at the commutation point will not suddenly change, thereby improving the current balance of the converter module, and thus improving the safety of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the technical solution of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0009] Figure 1 A schematic diagram of an example of a converter provided in an embodiment of the present application;

[0010] Figure 2 A flow chart of a method for controlling a converter provided in one embodiment of the present application;

[0011] Figure 3 A schematic diagram of an example of current of a converter module that is not controlled by the converter control method provided in the embodiment of the present application;

[0012] Figure 4 A schematic diagram of an example of the current of a converter module controlled by the converter control method provided in an embodiment of the present application;

[0013] Figure 5 A schematic diagram of another example of the current of a converter module that is not controlled by the converter control method provided in the embodiment of the present application;

[0014] Figure 6 A schematic diagram of another example of the current of a converter module controlled by the converter control method provided in an embodiment of the present application;

[0015] Figure 7 A flowchart of a method for controlling a converter provided by another embodiment of the present application;

[0016] Figure 8 A logic diagram of an example of obtaining the average value of the d-axis current provided in an embodiment of the present application;

[0017] Fig. 9 A logic diagram of an example of obtaining the average value of the q-axis current provided in an embodiment of the present application;

[0018] Fig.10 A logic diagram of an example of obtaining a three-phase modulated wave voltage provided in an embodiment of the present application;

[0019] Fig.11 A logic diagram of an example of obtaining a current difference provided in an embodiment of the present application;

[0020] Fig.12 A schematic diagram of an example of control logic for a converter provided in an embodiment of the present application;

[0021] Fig.13 A schematic diagram of the structure of a control system of a converter provided in one embodiment of the present application. DETAILED DESCRIPTION

[0022] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by illustrating the examples of the present application.

[0023] With the promotion of renewable energy, the capacity demand of energy conversion equipment for renewable energy is increasing. As an important component of energy conversion equipment, the converter also has the demand for capacity improvement. The converter can adopt modular design and realize the capacity improvement of the converter by parallel connection of converter modules. In order to improve the control accuracy of the converter module, each converter module in the converter can be controlled separately. The control unit for executing the control algorithm assumes the control algorithm of multiple converter modules and sends down the modulation waves of multiple converter modules. The current of multiple converter modules is prone to current mutation at the commutation point, resulting in uneven current of multiple converter modules, and may also trigger converter faults, reducing the safety of the converter.

[0024] In an embodiment of the present application, the converter may include but is not limited to a photovoltaic converter matched with a photovoltaic device, a wind power converter matched with a wind turbine generator set, and the like. The type of converter is not limited here either. For example, the converter may include but is not limited to a doubly-fed converter, a full-power converter, and the like. The converter includes N converter modules connected in parallel, where N is an integer greater than 1. The converter module has an AC end, and the AC end can input or output three-phase current. In some examples, the converter module may include a machine-side rectifier module or a grid-side inverter module. The machine-side rectifier module is a converter module electrically connected to the power generation structure of the energy conversion device, and can convert the AC power generated by the power generation structure in the energy conversion device into DC power. Specifically, the AC end of the machine-side rectifier module can be electrically connected to the power generation structure of the energy conversion device. The grid-side inverter module is a conversion module electrically connected to the grid side. The grid-side inverter module is electrically connected to the machine-side rectifier module and can convert the DC power output by the machine-side rectifier module into AC power for transmission to the grid. Specifically, the AC end of the grid-side inverter module can be electrically connected to the grid side.

[0025] For example, Figure 1 A schematic diagram of an example of a converter provided in an embodiment of the present application is shown as follows: Figure 1 As shown, the converter 11 may include a machine-side rectifier module 111 and a grid-side inverter module 112 , and the machine-side rectifier module 111 may be electrically connected to the grid-side inverter module 112 via a DC bus. Figure 1The converter shown includes two parallel machine-side rectifier modules 111, each of which is electrically connected to the power generation structure 12 via a filter reactor L1 and a filter reactor L2. The grid-side inverter module 112 is connected to the power grid 14 via a filter L3 and a transformer 13. The machine-side rectifier module 111 and the grid-side inverter module 112 can share a current conversion control device, that is, the machine-side rectifier module 111 and the grid-side inverter module 112 are controlled by the same current conversion control device.

[0026] The converter module in the converter can be connected to a filter reactor, such as the machine-side rectifier module in the converter can be electrically connected to the power generation structure through the filter reactor, and the grid-side inverter module in the converter can be electrically connected to the grid side through the filter reactor. Under ideal conditions, in multiple converter modules connected in parallel, the parameters such as the filter reactors connected to different converter modules and the reactance of the circuit where the converter modules are located should be the same, so that a control algorithm and a modulation wave can be used to ensure the consistency of the current of multiple converter modules in parallel. However, due to the error of the manufacturing process, in multiple converter modules connected in parallel, the filter reactors connected to different converter modules will have inductance differences, the reactance of the circuits where different converter modules are located will have differences, and the control circuits of different converter modules will also have different control delays. These differences will cause differences in current between the converter modules in parallel, that is, the current of the parallel AC modules is uneven, resulting in current mutations, and the current mutation is also very easy to trigger the current safety boundary of the converter module, thereby affecting the service life of the power devices in the converter module, and even triggering a fault to cause the shutdown of the energy conversion equipment. For example, a sudden change in current at the commutation point is likely to cause the converter module to shut down, resulting in a fault.

[0027] The control method, system and storage medium of the converter provided in the embodiment of the present application can be applied to the scenario of N machine-side rectifier modules connected in parallel in the converter, and can also be applied to the scenario of N grid-side inverter modules connected in parallel in the converter, and are not limited here. If the converter includes N machine-side rectifier modules connected in parallel and N grid-side inverter modules connected in parallel, the control method of the converter provided in the embodiment of the present application can be used for the N machine-side rectifier modules connected in parallel, and the control method of the converter provided in the embodiment of the present application can be used for the N grid-side inverter modules connected in parallel. In the embodiment of the present application, the converter modules connected in parallel share a three-phase modulation wave voltage, and each converter module has a corresponding three-phase modulation wave incremental voltage. When the balanced adjustment conditions are met, the three-phase modulation wave voltage is reduced by the three-phase modulation wave incremental voltage, and then a pulse control signal corresponding to each converter module is generated. The three-phase modulated wave incremental voltage is generated for each AC module. The pulse control signal generated by the three-phase modulated wave voltage together can reduce the difference between the currents of the parallel AC modules, improve the current balance of the parallel AC modules, avoid voltage mutations in the AC modules, and improve the safety of the converter.

[0028] The control method of the converter provided in the embodiment of the present application can be performed by a converter control device. The converter control device may include a general converter controller, which can be used to collect data, run control algorithms, perform fault protection, control converter modules, and upload status information of the converter controller. The general converter controller can control power devices such as insulated gate bipolar transistors (IGBT) in the converter module by outputting pulse control signals, such as pulse width modulation (PWM) signals, to control the converter module. The general converter controller may include a control unit and a computing unit, the control unit may be implemented as but not limited to a microcontroller unit (MCU), and the computing unit may be implemented as but not limited to a field programmable gate array (FPGA). The converter control device may also include a power interface unit and a drive control unit, the power interface unit and the drive control unit may be implemented as an integrated circuit board, but not limited thereto. The power interface unit can convert the pulse control signal output by the universal current converter controller into a drive signal suitable for the current converter module, and can also convert the status signal of the current converter module, such as fault signal, thermal signal, etc., into a signal suitable for the universal current converter controller. The power interface unit can also isolate the current converter module from the universal current converter controller to improve the anti-interference ability of the current converter control device and improve the reliability of the current converter control device. The drive control unit can convert and process the drive signal output by the power interface unit. The drive signal output by the drive control unit can be used to drive the power device in the current converter module. The drive control unit can also perform short-circuit monitoring on the power device in the current converter module, and upload the temperature information of the power device in the current converter module to the universal current converter controller.

[0029] The control method, system and storage medium of the converter provided in the present application are described below respectively.

[0030] A first aspect of the present application provides a control method for a converter, which can be executed by a converter control device to control N converter modules connected in parallel in the above embodiment. Figure 2 This is a flow chart of a method for controlling a converter provided in one embodiment of the present application, such as Figure 2 As shown, the control method of the converter may include steps S201 to S203.

[0031] In step S201, the current conversion control device obtains a three-phase modulated wave voltage based on the three-phase current, the d-axis current given value and the q-axis current given value at the AC end of the current conversion module at the time corresponding to the inflection point of the most recently passed predetermined carrier.

[0032] The predetermined carrier is a pre-set carrier with periodicity. The predetermined carrier and the modulated wave work together to obtain a pulse control signal, the maximum value of the modulated wave acting together is less than or equal to the maximum value of the predetermined carrier, and the minimum value of the modulated wave acting together is greater than or equal to the minimum value of the predetermined carrier. In some examples, the maximum value of the modulated wave can be equal to the maximum value of the predetermined carrier, and the minimum value of the modulated wave can be equal to the minimum value of the predetermined carrier. The predetermined carrier can be set according to the scene, demand, experience, etc. For example, the predetermined carrier may include a triangular wave. The inflection point of the predetermined carrier may include a peak point and a valley point, the peak point of the predetermined carrier is the maximum value of the predetermined carrier, and the valley point of the predetermined carrier is the minimum value of the predetermined carrier. The three-phase current at the AC end of the converter module at the time corresponding to the inflection point of the most recently passed predetermined carrier may be the three-phase voltage at the AC end of the AC module at the time corresponding to the inflection point in the predetermined carrier closest to the current moment. For example, the predetermined carrier wave is a triangular wave. If the current time is at the rising edge of the predetermined carrier wave, the inflection point of the predetermined carrier wave that has passed most recently is the valley point, and the three-phase current used is the three-phase current of the AC end of the AC module at the time of the valley point of the predetermined carrier wave; if the current time is at the falling edge of the predetermined carrier wave, the inflection point of the predetermined carrier wave that has passed most recently is the peak point, and the three-phase current used is the three-phase current of the AC end of the AC module at the time of the peak point of the predetermined carrier wave. The current conversion control device can latch the three-phase current of the current conversion module at the peak point and the valley point of the predetermined carrier wave, so as to obtain the three-phase modulated wave voltage by using the latched three-phase current of the current conversion module, the d-axis current given value, and the q-axis current given value. In the embodiment of the present application, it is necessary to obtain the three-phase current of the AC end of each current conversion module in the N parallel current conversion modules at the time corresponding to the inflection point of the predetermined carrier wave that has passed most recently. For example, if the converter includes two converter modules connected in parallel, the two converter modules connected in parallel are converter module 1 and converter module 2, then the three-phase current i of the AC end of converter module 1 at the time corresponding to the inflection point of the most recently passed predetermined carrier is obtained. 1a,1b,1c , obtain the three-phase current i of the AC end of the conversion module 2 at the time corresponding to the inflection point of the most recently passed predetermined carrier 2a,2b,2c .

[0033] The d-axis current given value is the d-axis reference current given in the two-phase rotating coordinate system, and the q-axis current given value is the q-axis reference current given in the two-phase rotating coordinate system. The specific settings can be based on scenarios, requirements, experience, etc., and are not limited here.

[0034] The three-phase current of the AC end of each converter module at the time corresponding to the inflection point of the most recently passed predetermined carrier can be first converted into the d-axis current and the q-axis current in the two-phase rotating coordinate system, and then processed according to the d-axis current, the q-axis current, the d-axis current given value and the q-axis current given value to obtain the three-phase modulation wave voltage. The three-phase modulation wave voltage can characterize the modulation wave.

[0035] In step S202, the converter control device obtains the three-phase modulation wave incremental voltage of each converter module according to the three-phase current at the AC end of the converter module at the time corresponding to the inflection point of the most recently passed predetermined carrier.

[0036] The current conversion control device can latch the three-phase current of the current conversion module at the peak point and the valley point of the predetermined carrier wave to obtain the three-phase modulation wave incremental voltage.

[0037] The three-phase modulation wave increment voltage of each of the N converter modules can be obtained according to the average value of the three-phase current of the AC end of the N converter modules connected in parallel at the time corresponding to the inflection point of the most recently passed predetermined carrier and the three-phase current of each of the AC end of the N converter modules at the time corresponding to the inflection point of the most recently passed predetermined carrier, and through proportional integral (PI) processing, etc. The three-phase modulation wave increment voltage of the converter module can make up for the current difference between the converter module and other converter modules connected in parallel with the converter module.

[0038] In step S203, when the voltage of the three-phase modulation wave voltage and the inflection point of the predetermined carrier satisfy the balanced adjustment condition, the converter control device generates a pulse control signal corresponding to each converter module based on the three-phase modulation wave voltage and the three-phase modulation wave incremental voltage of each converter module, and uses the pulse control signal to control the corresponding converter module.

[0039] The three-phase modulation wave voltage and the three-phase modulation wave incremental voltage cannot work together unconditionally. If the three-phase modulation wave voltage and the three-phase modulation wave incremental voltage work together unconditionally, the three-phase modulation wave voltage after the three-phase modulation wave incremental voltage processing is easy to exceed the voltage range of the predetermined carrier at the peak and valley points (i.e., the phase switching point) of the three-phase modulation wave, so that some converter modules have pulse signals and some converter modules do not have pulse signals, resulting in current mutations and current imbalance in multiple converter modules in parallel. Therefore, the three-phase modulation wave voltage after the three-phase modulation wave incremental voltage processing cannot exceed the voltage range of the predetermined carrier. The balanced adjustment condition includes the condition that the three-phase modulation wave voltage and the three-phase modulation wave incremental voltage can work together. If the voltage of the three-phase modulation wave voltage and the inflection point of the predetermined carrier meets the balanced adjustment condition, the three-phase modulation wave voltage after the three-phase modulation wave incremental voltage processing will not exceed the voltage range of the predetermined carrier, which can ensure that the current of the converter module at the phase switching point will not suddenly change, thereby ensuring the safety of the converter module. The three-phase modulation wave voltage can be processed by using the three-phase modulation wave increment voltage of each converter module to obtain a new three-phase modulation wave voltage corresponding to each converter module, and a pulse control signal corresponding to each converter module is generated based on the new three-phase modulation wave voltage to control the corresponding converter module. The difference between the currents of the converter modules controlled by the pulse control signal is reduced, and the current balance of the N converter modules connected in parallel is improved.

[0040] When the voltage at the inflection point of the three-phase modulated wave voltage and the predetermined carrier does not meet the balanced adjustment condition, a pulse control signal corresponding to the converter module is generated based on the three-phase modulated wave voltage. In this case, the three-phase modulated wave incremental voltage does not participate in the generation of the pulse control signal to avoid the three-phase modulated wave voltage after being processed by the three-phase modulated wave incremental voltage exceeding the voltage range of the predetermined carrier, and to avoid a sudden change in the current of the converter module at the commutation point.

[0041] In the embodiment of the present application, the current conversion control device can obtain the three-phase modulation wave voltage based on the three-phase current of the AC end of each current conversion module at the time corresponding to the inflection point of the predetermined carrier that has passed most recently, and obtain the three-phase modulation wave incremental voltage of each AC module according to the three-phase current of the AC end of each current conversion module at the time corresponding to the inflection point of the predetermined carrier. In the case that the three-phase modulation wave voltage and the voltage at the inflection point of the predetermined carrier meet the balanced adjustment condition, a pulse control signal can be generated according to the three-phase modulation wave incremental voltage and the three-phase modulation wave voltage, the three-phase modulation wave incremental voltage can make up for the current difference between the parallel current conversion modules, and the three-phase modulation wave voltage and the voltage at the inflection point of the predetermined carrier meet the balanced adjustment condition, the three-phase modulation wave voltage after being processed by the three-phase modulation wave incremental voltage will not exceed the voltage range of the predetermined carrier, the difference in the current of the parallel current conversion modules controlled by the generated pulse control signal is reduced, and the current of the current conversion module at the commutation point will not suddenly change, thereby improving the current balance of the current conversion module and thus improving the safety of the converter.

[0042] Figure 3 is a schematic diagram of an example of the current of a converter module that is not controlled by the converter control method provided in the embodiment of the present application, Figure 4 The present invention is a schematic diagram of an example of the current of a converter module controlled by the converter control method provided in an embodiment of the present application. Figure 3 and Figure 4 The experimental conditions of the current conversion modules shown are the same.

[0043] Figure 3 The two colored curves in the figure represent the currents of the two parallel-connected converter modules in the converter. Figure 3 It can be seen that if the control method of the converter provided in the embodiment of the present application is not adopted, it is very easy for some converter modules to have pulse signals and some converter modules to have no pulse signals at the switching points of the modulation wave, that is, the peak points and valley points. The currents of the two parallel converter modules suddenly change in the peak area, resulting in a large difference in the currents of the two parallel converter modules at this point, resulting in the following phenomenon: Figure 3 The waveform shown is a sudden change in current imbalance.

[0044] Figure 4 The two colored curves in the figure represent the currents of the two parallel-connected converter modules in the converter. Figure 4 It can be seen that, by adopting the control method of the converter provided in the embodiment of the present application, the current of the converter module basically does not change suddenly, and the current balance of the two converter modules is better.

[0045] Figure 5 is a schematic diagram of another example of the current of the converter module that is not controlled by the converter control method provided in the embodiment of the present application, Figure 6A schematic diagram of another example of the current of a converter module controlled by the converter control method provided in an embodiment of the present application. Figure 5 and Figure 6 The experimental conditions of the current conversion module are the same as shown. Figure 5 and Figure 3 The experimental conditions for the current of the converter modules shown are different. Figure 5 The two colored curves in the figure represent the currents of the two parallel-connected converter modules in the converter. Figure 5 It can be seen that if the control method for the converter provided in the embodiment of the present application is not adopted, the current of the converter module will suddenly change in the peak area, and the current difference between the two converter modules here will be relatively large. Figure 6 The two colored curves in the figure represent the currents of the two parallel-connected converter modules in the converter. Figure 6 It can be seen that, by adopting the control method of the converter provided in the embodiment of the present application, the current of the converter module basically does not change suddenly, and the current balance of the two converter modules is better.

[0046] It can be seen from the current schematic diagram of the above-mentioned converter module that the control method of the converter provided in the embodiment of the present application can avoid sudden changes in the current of the converter modules connected in parallel in the converter, thereby improving the balance of the current of the converter modules connected in parallel.

[0047] Figure 7 This is a flow chart of a method for controlling a converter provided in another embodiment of the present application. Figure 7 and Figure 2 The difference is that Figure 2 Step S201 in the above example can be specifically broken down into Figure 7 Steps S2011 to S2013 in Figure 2 Step S202 in the above example can be specifically broken down into Figure 7 Steps S2021 and S2022 in Figure 2 Step S203 in the above example can be specifically broken down into Figure 7 Step S2031 and step S2032 in .

[0048] In step S2011, the d-axis current and q-axis current of each converter module in a two-phase rotating coordinate system are converted according to the three-phase current of the converter module at the time corresponding to the inflection point of the most recently passed predetermined carrier.

[0049] The three-phase current here is the three-phase current in the three-phase stationary coordinate system. The three-phase current at the AC end of each converter module at the time corresponding to the inflection point of the most recently passed predetermined carrier can be converted into the d-axis current and q-axis current of each converter module by transforming the three-phase stationary coordinate system and the two-phase rotating coordinate system. The N converter modules connected in parallel each have their own d-axis current and q-axis current.

[0050] In step S2012, the average d-axis current and the average q-axis current of the N converter modules are obtained according to the d-axis current and the q-axis current of each converter module in the two-phase rotating coordinate system.

[0051] The average d-axis current is the average of the d-axis currents of the N converter modules. The average q-axis current is the average of the q-axis currents of the N converter modules. For example, Figure 8 and Fig. 9 The present invention provides a logic schematic diagram of an example of obtaining the average value of the d-axis current and a logic schematic diagram of an example of obtaining the average value of the q-axis current, respectively. The converter includes two parallel converter modules, the two parallel converter modules are converter module 1 and converter module 2, and the d-axis current i of converter module 1 is 1d and the d-axis current of converter module 2 is i 2d The average value of the d-axis current i is obtained by superimposing and averaging. df ; The q-axis current i of the converter module 1 1q and the q-axis current of the converter module 2 is i 2q The average value of the q-axis current i is obtained by superimposing and averaging. qf .

[0052] In step S2013, a three-phase modulated wave voltage is obtained according to the d-axis current average value, the q-axis current average value, the d-axis current given value and the q-axis current given value.

[0053] The d-axis reference voltage can be obtained according to the given value of the d-axis current and the average value of the d-axis current. The q-axis reference voltage can be obtained according to the given value of the q-axis current and the average value of the q-axis current. The d-axis reference voltage and the q-axis reference voltage are subjected to coordinate system transformation and space vector pulse width modulation (SVPWM) processing to obtain a three-phase modulated wave voltage. The three-phase modulated wave voltage is common to N parallel AC modules.

[0054] For example, Fig.10 A logic diagram of an example of obtaining a three-phase modulated wave voltage provided in an embodiment of the present application is as follows: Fig.10 As shown, the d-axis current is given a value i dr * and the average d-axis current i df The difference is processed by proportional integral (PI) and limiting to obtain the d-axis reference voltage V dr *; Set the q-axis current to a given value i qr * and the average value of q-axis current i qf The difference is processed by proportional integration and limiting to obtain the q-axis reference voltage V qr *. For d-axis reference voltage V dr * and q-axis reference voltage Vqr *Perform Park inverse transformation to obtain the α-axis reference voltage V in the two-phase stationary coordinate system α * and β-axis reference voltage V β *. Reference voltage V for α axis α * and β-axis reference voltage V β *Perform SVPWM processing to obtain the three-phase modulation wave voltage V xmod , where x can take the values ​​of a, b and c, representing phase a, phase b and phase c.

[0055] In step S2021, the average three-phase current of N converter modules is obtained according to the three-phase current of the AC end of the converter module at the time corresponding to the inflection point of the most recently passed predetermined carrier.

[0056] The three-phase current here adopts the three-phase current of the conversion end of the conversion module latched by the conversion control device at the time corresponding to the inflection point of the predetermined carrier. The average value of the three-phase current of the AC end of the N conversion modules at the time corresponding to the inflection point of the predetermined carrier that has passed most recently can be used as a reference current to be used in subsequent steps to act on the three-phase current of the AC end of each conversion module at the time corresponding to the inflection point of the predetermined carrier that has passed most recently.

[0057] In step S2022, based on the current difference between the three-phase current of each converter module and the average value of the three-phase current, a three-phase modulation wave incremental voltage of each converter module is obtained through proportional integration processing.

[0058] The current difference between the three-phase current at the AC end of each converter module at the time corresponding to the inflection point of the predetermined carrier that has passed most recently and the average value of the three-phase current can reflect the difference between the current of each converter module and the reference current. Each converter module has a corresponding current difference. For example, Fig.11 A logic diagram of an example of obtaining a current difference provided in an embodiment of the present application, if the converter includes two parallel converter modules, the two parallel converter modules are converter module 1 and converter module 2; the three-phase current i of the AC end of converter module 1 at the time corresponding to the inflection point of the predetermined carrier most recently passed is 1a,1b,1c The three-phase current i of the AC end of the converter module 2 at the time corresponding to the inflection point of the predetermined carrier that has passed most recently 2a,2b,2c After superposition, the average processing is performed to obtain the average value of the three-phase current; the three-phase current i of the conversion module 1 1a,1b,1c Divide the current difference i of the converter module 1 by the average value of the three-phase current 1xdiff ; The three-phase current i of the converter module 2 2a,2b,2c Differ from the average value of the three-phase current to obtain the current difference i of the converter module 2 2xdiff .

[0059] After the current difference is processed by proportional integration, it can also be limited to obtain the three-phase modulation wave incremental voltage of the conversion module.

[0060] In step S2031, when the three-phase modulation wave voltage and the voltage of the inflection point of the predetermined carrier satisfy the balanced adjustment condition, the modulation wave voltage difference between the three-phase modulation wave voltage and the three-phase modulation wave incremental voltage of each conversion module is calculated respectively.

[0061] The inflection point includes a peak point and a valley point, and the equalization adjustment condition may include: the voltage difference between the peak point of the predetermined carrier and the voltage of the three-phase modulation wave voltage is greater than or equal to the preset adjustment threshold, and the voltage difference between the three-phase modulation wave voltage and the valley point of the predetermined carrier is greater than or equal to the preset adjustment threshold. The preset adjustment threshold is a threshold value at which the three-phase modulation wave voltage processed by the three-phase modulation wave incremental voltage does not exceed the maximum value of the predetermined carrier, which can be set according to the scene, demand, experience, etc., and is not limited here. Correspondingly, if the voltage difference between the peak point of the predetermined carrier and the voltage of the three-phase modulation wave voltage is less than the preset adjustment threshold, or the difference between the three-phase modulation wave voltage and the valley point of the predetermined carrier is less than the preset adjustment threshold, then the three-phase modulation wave incremental voltage does not participate in the generation of the pulse control signal.

[0062] Each current conversion module corresponds to a modulation wave voltage difference value. The modulation wave voltage difference value corresponding to a current conversion module is the difference between the three-phase modulation wave voltage and the three-phase modulation wave incremental voltage of the current conversion module.

[0063] In step S2032, pulse conversion processing is performed on the modulation wave voltage difference of each converter module to generate a pulse control signal corresponding to each converter module, and the pulse control signal is used to control the corresponding converter module.

[0064] The modulation wave voltage difference of the converter module can be input into the PWM generator, and the signal output by the PWM generator can be used as a pulse control signal. The pulse control signal can be used to control the corresponding converter module. In some examples, the modulation wave voltage difference corresponding to different converter modules may be different. If the modulation wave voltage difference is different, the pulse width in the pulse control signal corresponding to the converter module will be different. In this case, when the converter module is controlled by the pulse control signal, the power devices in different converter modules need to be turned on at the same time, that is, the turn-on edge of the pulse control signal of different converter modules corresponds to the same time, and the turn-on edge of the pulse control signal is the starting edge of the signal that controls the turn-on of the power device in the converter module. The turn-on edge of the pulse control signal of different converter modules corresponds to the same time, and the pulse width of the pulse control signal of different converter modules may be different. Then, the turn-off edge of the pulse control signal of different converter modules may correspond to different times, which is equivalent to adjustment at the end time of the pulse control signal.

[0065] For example, Fig.12A schematic diagram of an example of the control logic of the converter provided in an embodiment of the present application, taking the converter including two parallel converter modules as an example, the two parallel converter modules are converter module 1 and converter module 2, and the logic part of the three-phase modulated wave voltage is obtained and Fig.10 The logic part of the voltage difference is consistent with Fig.11 The contents shown are consistent, and the logic of obtaining the three-phase modulation wave voltage and the logic of obtaining the voltage difference will not be repeated here. Fig.12 As shown, the current difference i corresponding to the converter module 1 1xdiff Perform PI processing and amplitude limiting processing to obtain the three-phase modulation wave increment voltage of the converter module 1; the current difference i corresponding to the converter module 2 2xdiff Perform PI processing and amplitude limiting processing to obtain the three-phase modulation wave increment voltage of the converter module 2. Subtract the three-phase modulation wave voltage from the three-phase modulation wave increment voltage of the converter module 1 to obtain the modulation wave voltage difference corresponding to the converter module 1. The modulation wave voltage difference corresponding to the converter module 1 is input into the PWM generator 1 to obtain the pulse control signal output by the PWM generator 1. The converter module 1 is controlled by the pulse control signal. The three-phase current i at the AC end of the controlled converter module 1 at the time corresponding to the inflection point of the most recently passed predetermined carrier wave is 1a,1b,1c Perform coordinate system transformation to obtain the d-axis current i 1d and q-axis current i 1q , participate in the next round of converter control. The three-phase modulation wave voltage is subtracted from the three-phase modulation wave increment voltage of the converter module 2 to obtain the modulation wave voltage difference corresponding to the converter module 2. The modulation wave voltage difference corresponding to the converter module 2 is input into the PWM generator 2 to obtain the pulse control signal output by the PWM generator 2. The converter module 2 is controlled by the pulse control signal. The three-phase current i at the AC end of the controlled converter module 2 at the time corresponding to the inflection point of the most recently passed predetermined carrier 2a,2b,2c Perform coordinate system transformation to obtain the d-axis current i 2d and q-axis current i 2q , participate in the next round of converter control.

[0066] In some embodiments, the current conversion control device includes a control unit and a calculation unit, the control unit can be implemented as but not limited to an MCU, and the calculation unit can be implemented as but not limited to an FPGA. The process of obtaining a three-phase modulated wave voltage based on data such as three-phase current can be executed by the control unit, that is, the control unit obtains the three-phase modulated wave voltage based on the three-phase current, the d-axis current given value, and the q-axis current given value. The process of obtaining a three-phase modulated wave incremental voltage and generating a pulse control signal according to the three-phase current can be executed by the calculation unit, that is, the calculation unit obtains the three-phase modulated wave incremental voltage of each current conversion module according to the three-phase current, and the calculation unit generates a pulse control signal based on the three-phase modulated wave voltage and the three-phase modulated wave incremental voltage of each current conversion module, and uses the pulse control signal to control the corresponding current conversion module.

[0067] Compared with the technical solution that each of the N parallel converter modules adopts a set of control algorithms, in the embodiment of the present application, the control unit executes the process of obtaining the three-phase modulation wave voltage, and the three-phase modulation wave voltage is common to the N parallel converter modules, that is, for the N parallel converter modules, the control unit only needs to execute a set of control algorithms, obtain the three-phase modulation wave incremental voltage through the calculation unit, and adjust the pulse control signal driving pulse level through the three-phase modulation wave incremental voltage and the three-phase modulation wave voltage to achieve the current equalization control of the current of the N parallel converter modules. Implementing the current equalization control algorithm through the calculation unit has a faster response, and can avoid the situation where the control unit bears the control algorithms of multiple converter modules, release the resources of the control unit, reduce the load of the control unit, and avoid the situation where the control unit is overloaded.

[0068] A second aspect of the present application provides a control system for a converter. Fig.13 A schematic diagram of the structure of a control system of a converter provided in an embodiment of the present application, such as Fig.13 As shown, the control system of the converter may include a converter 31 and a converter control device 32 .

[0069] The converter 31 may include N converter modules 311 connected in parallel, where N is an integer greater than 1. The converter module 311 has an AC end, and the AC end of the converter module 311 can input or output a three-phase current.

[0070] The converter control device 32 can be configured to obtain a three-phase modulated wave voltage based on the three-phase current, d-axis current given value and q-axis current given value at the AC end of the converter module at the time corresponding to the inflection point of the most recently passed predetermined carrier; and, obtain a three-phase modulated wave incremental voltage of each converter module according to the three-phase current at the AC end of the converter module at the time corresponding to the inflection point of the most recently passed predetermined carrier; and, when the three-phase modulated wave voltage and the voltage at the inflection point of the predetermined carrier meet the balanced adjustment condition, generate a pulse control signal corresponding to each converter module based on the three-phase modulated wave voltage and the three-phase modulated wave incremental voltage of each converter module, and use the pulse control signal to control the corresponding converter module.

[0071] The converter control device 32 may be configured to execute the converter control method in the above embodiment. For details, please refer to the relevant contents in the above embodiment, which will not be described again.

[0072] In some examples, the variable flow control device 32 may include a control unit 321 and a calculation unit 322 .

[0073] The control unit 321 may be configured to obtain the three-phase modulated wave voltage based on the three-phase current, d-axis current given value, and q-axis current given value at the AC end of the conversion module at the time corresponding to the inflection point of the most recent predetermined carrier. Similarly, the control unit may also be configured to execute the detailed steps of obtaining the three-phase modulated wave voltage based on the three-phase current, d-axis current given value, and q-axis current given value at the AC end of the conversion module at the time corresponding to the inflection point of the most recent predetermined carrier, which may be specifically referred to the relevant contents in the above embodiments, and will not be repeated here.

[0074] The calculation unit 322 can be configured to obtain the three-phase modulation wave increment voltage of each conversion module according to the three-phase current at the AC end of the conversion module at the time corresponding to the inflection point of the predetermined carrier that has passed most recently; and, when the three-phase modulation wave voltage and the voltage at the inflection point of the predetermined carrier meet the balanced adjustment condition, based on the three-phase modulation wave voltage and the three-phase modulation wave increment voltage of each conversion module, generate a pulse control signal corresponding to each conversion module, and use the pulse control signal to control the corresponding conversion module. Similarly, the control unit can also be configured to perform a detailed step of obtaining the three-phase modulation wave increment voltage of each conversion module according to the three-phase current at the AC end of the conversion module at the time corresponding to the inflection point of the closest predetermined carrier, and is configured to perform a detailed step of generating the pulse control signal corresponding to each conversion module based on the three-phase modulation wave voltage and the three-phase modulation wave increment voltage of each conversion module, and using the pulse control signal to control the corresponding conversion module when the three-phase modulation wave voltage and the voltage at the inflection point of the predetermined carrier meet the balanced adjustment condition. For details, please refer to the relevant content in the above embodiment, which will not be repeated here.

[0075] The third aspect of the present application provides a computer-readable storage medium, on which a computer program instruction is stored, and when the computer program instruction is executed by a processor, the control method of the converter in the above embodiment can be implemented, and the same technical effect can be achieved. To avoid repetition, it is not repeated here. Among them, the above-mentioned computer-readable storage medium may include a non-transitory computer-readable storage medium, such as a read-only memory (Read-Only Memory, referred to as ROM), a random access memory (Random Access Memory, referred to as RAM), a disk or an optical disk, etc., which is not limited here.

[0076] An embodiment of the present application provides a computer program product, which includes a computer program. When the computer program is executed by a processor, it implements the control method of the converter in the above embodiment and can achieve the same technical effect. To avoid repetition, it will not be repeated here.

[0077] It should be clear that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. For system embodiments, computer-readable storage medium embodiments, and computer program products, the relevant parts can refer to the description part of the method embodiment. The present application is not limited to the specific steps and structures described above and shown in the figures. Those skilled in the art can make various changes, modifications and additions, or change the order between the steps after understanding the spirit of the present application. In addition, for the sake of brevity, a detailed description of known method technologies is omitted here.

[0078] The above reference is according to the method of the embodiment of the present application, the flow chart of the device (system) and the computer program product and / or the block diagram described various aspects of the present application.It should be understood that each square box in the flow chart and / or the block diagram and the combination of each square box in the flow chart and / or the block diagram can be realized by computer program instructions.These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer or other programmable data processing device to produce a machine so that these instructions executed by the processor of the computer or other programmable data processing device enable the realization of the function / action specified in one or more square boxes of the flow chart and / or the block diagram.Such a processor can be but is not limited to a general-purpose processor, a special-purpose processor, a special application processor or a field programmable logic circuit.It can also be understood that each square box in the block diagram and / or the flow chart and the combination of the square boxes in the block diagram and / or the flow chart can also be realized by the dedicated hardware that performs the specified function or action, or can be realized by the combination of dedicated hardware and computer instructions.

[0079] Those skilled in the art should understand that the above embodiments are exemplary rather than restrictive. Different technical features appearing in different embodiments can be combined to achieve beneficial effects. Based on the study of the drawings, the specification and the claims, those skilled in the art should be able to understand and implement other variations of the disclosed embodiments. In the claims, the term "comprising" does not exclude other devices or steps; the quantifier "one" does not exclude multiple; the terms "first" and "second" are used to indicate names rather than to indicate any specific order. Any figure marks in the claims should not be understood as limiting the scope of protection. The functions of multiple parts appearing in the claims can be implemented by a single hardware or software module. The appearance of certain technical features in different dependent claims does not mean that these technical features cannot be combined to achieve beneficial effects.

Claims

1. A method for controlling a converter, characterized in that: The converter includes N converter modules connected in parallel, where N is an integer greater than 1, and the converter module has an AC terminal. The method includes: The current conversion control device obtains a three-phase modulated wave voltage based on the three-phase current, the d-axis current given value and the q-axis current given value of the AC end of the current conversion module at the time corresponding to the inflection point of the most recently passed predetermined carrier, wherein the inflection point includes a peak point and a valley point; The current conversion control device obtains the three-phase modulation wave incremental voltage of each current conversion module according to the three-phase current at the AC end of the current conversion module at the time corresponding to the inflection point of the most recently passed predetermined carrier; When the three-phase modulation wave voltage and the voltage of the inflection point of the predetermined carrier satisfy the balanced adjustment condition, the current conversion control device generates a pulse control signal corresponding to each current conversion module based on the three-phase modulation wave voltage and the three-phase modulation wave incremental voltage of each current conversion module, and uses the pulse control signal to control the corresponding current conversion module.

2. The method according to claim 1, characterized in that The method of obtaining the three-phase modulation wave incremental voltage of each of the conversion modules according to the three-phase current at the AC end of the conversion module at the time corresponding to the inflection point of the predetermined carrier that has passed most recently comprises: Obtaining an average value of the three-phase currents of N of the conversion modules according to the three-phase currents at the AC end of the conversion module at a time corresponding to an inflection point of a predetermined carrier that has passed most recently; Based on the current difference between the three-phase current of each of the conversion modules and the three-phase current average value, the three-phase modulation wave incremental voltage of each of the conversion modules is obtained through proportional integration processing.

3. The method according to claim 1, characterized in that The balance adjustment conditions include: The voltage difference between the peak point of the predetermined carrier and the voltage of the three-phase modulation wave voltage is greater than or equal to a preset adjustment threshold, and the voltage difference between the three-phase modulation wave voltage and the valley point of the predetermined carrier is greater than or equal to the preset adjustment threshold.

4. The method according to claim 1, characterized in that: The step of generating a pulse control signal corresponding to each of the conversion modules based on the three-phase modulation wave voltage and the three-phase modulation wave incremental voltage of each of the conversion modules comprises: respectively calculating the modulation wave voltage difference between the three-phase modulation wave voltage and the three-phase modulation wave incremental voltage of each of the conversion modules; The modulation wave voltage difference of each of the conversion modules is subjected to pulse conversion processing to generate the pulse control signal corresponding to each of the conversion modules.

5. The method according to claim 1, characterized in that The time corresponding to the conduction edge of the pulse control signal of different converter modules is the same.

6. The method according to claim 1, characterized in that The method of obtaining a three-phase modulated wave voltage based on the three-phase current, the d-axis current given value, and the q-axis current given value at the time corresponding to the inflection point of the most recently passed predetermined carrier at the AC end of the converter module comprises: According to the three-phase current of the AC end of the conversion module at the time corresponding to the inflection point of the most recently passed predetermined carrier, converting to obtain the d-axis current and q-axis current of each of the conversion modules in the two-phase rotating coordinate system; Obtaining an average d-axis current and an average q-axis current of N converter modules according to a d-axis current and a q-axis current of each converter module in a two-phase rotating coordinate system; A three-phase modulated wave voltage is obtained according to the d-axis current average value, the q-axis current average value, the d-axis current given value and the q-axis current given value.

7. The method according to claim 1, characterized in that The variable current control device comprises a control unit and a calculation unit; The current conversion control device obtains a three-phase modulated wave voltage based on the three-phase current, the d-axis current given value, and the q-axis current given value at the time corresponding to the inflection point of the most recently passed predetermined carrier from the AC end of the current conversion module, including: The control unit obtains the three-phase modulation wave voltage based on the three-phase current, the d-axis current given value and the q-axis current given value; The current conversion control device obtains the three-phase modulation wave incremental voltage of each of the current conversion modules according to the three-phase current at the AC end of the current conversion module at the time corresponding to the inflection point of the most recently passed predetermined carrier, including: The calculation unit obtains the three-phase modulation wave incremental voltage of each of the conversion modules according to the three-phase current; The current conversion control device generates a pulse control signal corresponding to each current conversion module based on the three-phase modulation wave voltage and the three-phase modulation wave incremental voltage of each current conversion module, and controls the corresponding current conversion module using the pulse control signal, including: The calculation unit generates the pulse control signal based on the three-phase modulation wave voltage and the three-phase modulation wave incremental voltage of each of the conversion modules, and uses the pulse control signal to control the corresponding conversion module.

8. The method according to claim 1, characterized in that The conversion module includes a machine-side rectifier module or a grid-side inverter module.

9. A control system for a converter, characterized in that: include: A converter, comprising N converter modules connected in parallel, where N is an integer greater than 1, and the converter modules have an AC terminal; The converter control device is configured to obtain a three-phase modulated wave voltage based on the three-phase current, a d-axis current given value and a q-axis current given value at the AC end of the converter module at a time corresponding to an inflection point of a predetermined carrier that has passed most recently, wherein the inflection point includes a peak point and a valley point; and, according to the three-phase current at the AC end of the converter module at a time corresponding to an inflection point of a predetermined carrier that is closest to the AC end of the converter module, obtain a three-phase modulated wave incremental voltage of each converter module; and, when the three-phase modulated wave voltage and the voltage at the inflection point of the predetermined carrier satisfy a balanced adjustment condition, generate a pulse control signal corresponding to each converter module based on the three-phase modulated wave voltage and the three-phase modulated wave incremental voltage of each converter module, and use the pulse control signal to control the corresponding converter module.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer program instructions, and when the computer program instructions are executed by a processor, the method for controlling the converter according to any one of claims 1 to 8 is implemented.

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