Power converter, driving control method thereof and energy storage system

Abstract

The invention provides a power converter, a driving control method thereof and an energy storage system, after the power converter enters a burst wave sending mode, M power conversion circuits synchronously output waveforms in a first time period in response to the fact that the target voltage or target current of the output ends of the power conversion circuits is smaller than a first threshold value, in this way, it can be guaranteed that voltage or current is stably output in multiple continuous first time periods, ripple jitter of the output voltage and the output current of the power converter is reduced, so that ripples are smoother, the other power conversion circuits are controlled not to output waveforms in the first time periods, the requirement for outputting low voltage or low current can be met, and the power conversion efficiency is improved. Wherein M is a positive integer, and M is determined according to the target voltage or the target current.

Description

Technical Field

[0001] The present application relates to the field of energy technology, and in particular to a power converter, a drive control method thereof, and an energy storage system. Background Art

[0002] At present, with the increase in demand for energy, power converters are generally required to have large output power and high power density. In order to improve the efficiency of the power converter, a plurality of power conversion circuits are often used in parallel in the power converter to meet the requirements of outputting high voltage and high current. When the power converter is required to output low voltage and low current, the power conversion circuit is required to adopt an intermittent (burst) wave mode. When the burst wave mode is adopted, all power conversion circuits in the power converter output power synchronously and turn off the drive synchronously. Although the burst wave mode can meet the requirements of low output voltage or current, it will cause the ripple of the output voltage and output current to be large, and the battery connected to the power converter will be damaged. Therefore, how to solve the problem of large output voltage and output current ripple of the power converter with a plurality of power conversion circuits in parallel is a technical problem that needs to be solved in this field. Summary of the invention

[0003] The present application provides a power converter, a drive control method thereof and an energy storage system, which are used to reduce the output voltage and output current ripple of the power converter.

[0004] In a first aspect, an embodiment of the present application provides a power converter, comprising at least three power conversion circuits. The input ends of the at least three power conversion circuits are connected to the output ends of the energy storage device, i.e., the battery, and the output ends of the at least three power conversion circuits are connected to the DC bus, which can be connected to a load or other next-level conversion circuits. The at least three power conversion circuits are generally connected in parallel, and the at least three power conversion circuits can also be connected in series. The at least three power conversion circuits are used to adjust the output voltage of the energy storage device, that is, the battery voltage provided by the battery is converted by power and then output to the DC bus. The bus voltage is output.

[0005] The power converter may also include a controller, each power conversion circuit includes a plurality of switch tubes, and the controller is used to control the on-off state of the switch tubes in each power conversion circuit to control the output waveform of the power conversion circuit. By controlling the various parameters of the output waveform (including the peak value, duty cycle, frequency and other parameters of the output waveform), the output voltage and output current of the output end of the power conversion circuit can be controlled. The controller can determine whether the intermittent (burst) wave conditions are met based on the output voltage and output current of the power converter. Specifically, the output voltage and output current of the power converter can be compared with the set intermittent wave threshold. When it is determined that the output voltage and output current are less than the intermittent wave threshold, it is determined that the power converter needs to enter the burst wave mode.

[0006] After entering the burst wave mode, the controller will determine whether the target voltage or target current of the total output end of at least three power conversion circuits needs to be less than the first threshold value according to the operation mode of the power converter. When it is determined that the target voltage or target current needs to be less than the first threshold value, M power conversion circuits synchronously output waveforms within the first time period, and the remaining power conversion circuits do not output waveforms, that is, the controller controls the power converter to enter the staggered wave mode. M is a positive integer, and M is determined according to the target voltage or target current. The first time period is the duration of the power conversion circuit outputting one or multiple consecutive output waveforms.

[0007] In the present application, after the controller controls the power converter to enter the staggered wave generation mode, unlike the traditional burst wave generation mode, part of the power conversion circuits synchronously output waveforms in each first time period, so as to ensure a stable output voltage or output current in multiple consecutive first time periods, so as to reduce the output voltage and output current ripple jitter of the power converter to make the ripple smoother, and in each first time period, there is a power conversion circuit that does not output a waveform, which can meet the demand for outputting low voltage or low current. Since there are at least three power conversion circuits in the power converter, one or more power conversion circuits can be more flexibly selected according to the target current or target voltage, and switch between outputting waveforms and not outputting waveforms to more finely control the changes in output current or output voltage.

[0008] In some embodiments of the present application, in response to the target voltage or target current of the power converter being greater than a second threshold, all power conversion circuits can synchronously output waveforms within a second time period, that is, the power converter can be controlled to exit the interlaced wave generation mode to meet the demand for increasing the output voltage or output current.

[0009] In some embodiments of the present application, the second threshold may be different from the first threshold. For example, the second threshold may be slightly higher than the first threshold, so that there is a hysteresis between the two thresholds to prevent frequent switching of the wave generation mechanism at the critical point of the judgment condition.

[0010] In an embodiment of the present application, when the target voltage or the target current exceeds the second threshold value, after the power converter exits the interlaced wave generation mode, the power converter may still remain in the burst wave generation mode, such as by adopting a mechanism in which all power conversion circuits synchronously output waveforms or do not output waveforms. Alternatively, the power converter may directly exit the burst wave generation mode, that is, directly enter a working mode in which all power conversion circuits synchronously output waveforms in each second time period.

[0011] In some embodiments of the present application, in response to a target voltage or a target current being less than a first threshold value, in two consecutive first time periods, the power conversion circuits that do not output waveforms are different, so that each power conversion circuit is alternately non-operating to extend the overall service life of the power converter.

[0012] In some embodiments of the present application, within multiple consecutive first time periods, the number of first time periods of the output waveform of each power conversion circuit is the same, so as to ensure that the operating time of each power conversion circuit is relatively consistent and extend the overall service life of the power converter.

[0013] In some embodiments of the present application, in a third time period different from the first time period, N power conversion circuits synchronously output waveforms, and the remaining power conversion circuits do not output waveforms. Wherein, the voltage or current of the total output end of at least three power conversion circuits in the third time period is greater than the voltage or current of the total output end of at least three power conversion circuits in the first time period, and N is greater than M; or, the voltage or current of the total output end of at least three power conversion circuits in the third time period is less than the voltage or current of the total output end of at least three power conversion circuits in the first time period, and N is less than M.

[0014] In some embodiments of the present application, the controller is used to: in response to a target voltage or a target current being less than a first threshold, determine the M value based on the target voltage or the target current, and control M power conversion circuits to synchronously output waveforms within a first time period, and control the remaining power conversion circuits not to output waveforms, so as to meet the demand of outputting a lower voltage or current.

[0015] In the second aspect, the present application provides an energy storage system, which may include any power converter and energy storage device of any possible design in the first aspect, the total input end of at least three power conversion circuits in the power converter is connected to the output end of the energy storage device, and the total output end of at least three power conversion circuits is used to connect to the DC bus, and the power converter can output the bus voltage after the battery voltage provided by the energy storage device is converted by power. When the DC bus is lightly loaded, after the power converter enters the burst wave mode, part of the power conversion circuits synchronously output waveforms in the first time period, so that the output voltage or output current can be ensured to be stable in multiple consecutive first time periods, so as to reduce the output voltage and output current ripple jitter of the power converter to make the ripple smoother, and there is a power conversion circuit that does not output waveforms in the first time period, which can meet the demand of outputting low voltage or low current. Since there are at least three power conversion circuits in the power converter, one or more power conversion circuits can be selected more flexibly according to the target current or target voltage, and switched between output waveforms and non-output waveforms to more finely control the changes in output current or output voltage.

[0016] In a third aspect, the present application provides a drive control method for a power converter, which can be executed by a controller, and the drive control method includes: in response to a target voltage or a target current at a total output end of at least three power conversion circuits being less than a first threshold, controlling at least one power conversion circuit to synchronously output a waveform within a first time period, and controlling the remaining power conversion circuits not to output a waveform. Wherein, M is a positive integer, and M is determined according to the target voltage or the target current.

[0017] In the present application, after the power converter enters the staggered wave generation mode, unlike the traditional burst wave generation mode, when the target voltage or target current is less than the first threshold value, part of the power conversion circuits synchronously output waveforms in the first time period, so as to ensure a stable output voltage or output current in a plurality of consecutive first time periods, so as to reduce the output voltage and output current ripple jitter of the power converter to make the ripple smoother, and in the first time period, there is a power conversion circuit that does not output a waveform, which can meet the demand for outputting low voltage or low current. Since there are at least three power conversion circuits in the power converter, one or more power conversion circuits can be more flexibly selected according to the target current or target voltage, and switched between outputting waveforms and not outputting waveforms, so as to more finely control the changes in output current or output voltage.

[0018] In some embodiments of the present application, the control method also includes: in response to the target voltage or target current being greater than a second threshold, controlling all power conversion circuits to synchronously output waveforms within a second time period, that is, the power converter can be controlled to exit the staggered wave generation mode to meet the demand for increasing the output voltage or output current.

[0019] In some embodiments of the present application, the second threshold may be different from the first threshold. For example, the second threshold may be slightly higher than the first threshold, so that there is a hysteresis between the two thresholds to prevent frequent switching of the wave generation mechanism at the critical point of the judgment condition.

[0020] In an embodiment of the present application, when the target voltage or the target current exceeds the second threshold value, after the power converter exits the interlaced wave generation mode, the power converter may still remain in the burst wave generation mode, such as by adopting a mechanism in which all power conversion circuits synchronously output waveforms or do not output waveforms. Alternatively, the power converter may directly exit the burst wave generation mode, that is, directly enter a working mode in which all power conversion circuits synchronously output waveforms in each second time period.

[0021] In some embodiments of the present application, the control method also includes: in response to the target voltage or target current being less than a first threshold value, in two consecutive first time periods, controlling different power conversion circuits that do not output waveforms so that each power conversion circuit is alternately non-operating to extend the overall service life of the power converter.

[0022] In some embodiments of the present application, the control method also includes: within multiple consecutive first time periods, controlling the number of first time periods of the output waveform of each power conversion circuit to be the same, so as to ensure that the operating time of each power conversion circuit is relatively consistent and extend the overall service life of the power converter.

[0023] In some embodiments of the present application, the control method further includes: in a third time period, controlling N power conversion circuits to synchronously output waveforms, and controlling the remaining power conversion circuits not to output waveforms. Wherein, the voltage or current of the total output end of at least three power conversion circuits in the third time period is greater than the voltage or current of the total output end of at least three power conversion circuits in the first time period, and N is greater than M; or, the voltage or current of the total output end of at least three power conversion circuits in the third time period is less than the voltage or current of the total output end of at least three power conversion circuits in the first time period, and N is less than M.

[0024] The technical effects that can be achieved by any possible design in the second and third aspects can be referred to the technical effects that can be achieved by any possible design in the first aspect, and will not be repeated here. These or other aspects of the present application will be more concise and easy to understand in the description of the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the background technology, the drawings required for use in the embodiments of the present application or the background technology will be described below.

[0026] Figure 1 A schematic diagram of the structure of an energy storage system;

[0027] Figure 2 This is a schematic diagram of the output waveform of the burst wave mode;

[0028] Figure 3 A schematic diagram of the structure of a power converter provided in an embodiment of the present application;

[0029] Figure 4 A schematic diagram of an output waveform of a power converter provided in an embodiment of the present application;

[0030] Figure 5 A schematic diagram of the structure of a power converter provided in Example 1;

[0031] Figure 6a A schematic diagram of an output waveform of a power converter provided in Embodiment 1;

[0032] Figure 6b Another output waveform schematic diagram of the power converter provided in the first embodiment;

[0033] Figure 6c Another output waveform schematic diagram of the power converter provided in the first embodiment;

[0034] Figure 6d Another output waveform schematic diagram of the power converter provided in the first embodiment;

[0035] Figure 7 A schematic diagram of the structure of a power converter provided in Embodiment 2;

[0036] Figure 8a A schematic diagram of an output waveform of a power converter provided in Embodiment 2;

[0037] Figure 8b Another output waveform diagram of the power converter provided in the second embodiment;

[0038] Figure 8c This is another output waveform schematic diagram of the power converter provided in the second embodiment. DETAILED DESCRIPTION

[0039] In order to make the objectives, 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.

[0040] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be limiting of the present application. As used in the specification and appended claims of the present application, the singular expressions "a", "an", "said", "above", "the" and "this" are intended to also include expressions such as "one or more", unless there is a clear contrary indication in the context.

[0041] References to "one embodiment" or "some embodiments" etc. described in this specification mean that a particular feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the phrases "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear at different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0042] In addition, the same reference numerals in the figures represent the same or similar structures, and thus their repeated description will be omitted. The words expressing positions and directions described in this application are all explained with reference to the drawings as examples, but they can be changed as needed, and the changes are all included in the protection scope of this application. The drawings of this application are only used to illustrate the relative position relationship and do not represent the true proportion.

[0043] Reference Figure 1 The energy storage system includes an energy storage device and a power converter. The input end of the power converter is connected to the output end of the energy storage device. The energy storage device includes one or more batteries. To improve the output efficiency of the power converter, the power converter generally includes multiple power conversion circuits ( Figure 1 Taking n as an example) and a controller. The input end of each power conversion circuit is connected to the output end of the battery, and the output end of each power conversion circuit is connected to the DC bus. The DC bus can be connected to a load or other next-stage conversion circuits. The power conversion circuit is used to convert the battery voltage Vbat provided by the energy storage device into a bus voltage Vbus to the DC bus. The output ends of each power conversion circuit can be arranged in parallel, or the output ends of each power conversion circuit can also be arranged in series. Each power conversion circuit includes a plurality of switching tubes, and the controller is used to control the on and off states of the switching tubes in each power conversion circuit to control the output voltage and output current of the power converter. When high voltage or high current needs to be output, the controller is used to control all power conversion circuits in the power converter to output waveforms at the same time to meet the demand for high output power. Refer to Figure 2When low voltage or low current needs to be output, the controller is used to control the power converter to enter the intermittent (burst) wave mode, that is, all power conversion circuits synchronously output waveforms in one or multiple consecutive time periods, and all power conversion circuits do not output waveforms in the next or next multiple consecutive time periods to achieve lower output voltage or current. Since all power conversion circuits output power at the same time in the burst wave mode, the output power is large when the output voltage is low and the load is light, and the output voltage and output current have more overshoots. At the same time, after the waveform is not output, the output voltage and output current drop greatly, resulting in a large ripple peak in the burst wave mode, which causes greater battery loss.

[0044] In order to overcome the problem of large ripple in the above-mentioned burst wave mode, the present application provides a power converter, a drive control method thereof and an energy storage system, which adopts a new wave control method. When low voltage or low current needs to be output, part of the power conversion circuit can be controlled to synchronously output waveforms in each time period to ensure stable output voltage or output current in multiple consecutive time periods, so as to reduce the output voltage and output current ripple of the power converter, and the remaining power conversion circuits are controlled not to output waveforms in each time period to meet the demand of outputting low voltage or low current.

[0045] The power converter, its drive control method and energy storage system provided by the present application are described in detail below with reference to the accompanying drawings.

[0046] Figure 3 The schematic diagram of the structure of the power converter provided by the embodiment of the present application is exemplarily shown. Figure 4 The output waveform diagram of the power converter provided in the embodiment of the present application is exemplified.

[0047] Reference Figure 3 and Figure 4 In the embodiment of the present application, the power converter includes at least three power conversion circuits. Figure 3n power conversion circuits are schematically shown in the figure. The total input end of at least three power conversion circuits is connected to the output end of the energy storage device, i.e., the battery. The total output end of at least three power conversion circuits is connected to the DC bus. The DC bus can be connected to a load or other next-level conversion circuits. At least three power conversion circuits are generally connected in parallel. At least three power conversion circuits are used to adjust the output voltage of the energy storage device, i.e., the battery voltage Vbat provided by the battery is output to the DC bus after power conversion. The power converter may also include a controller. Each power conversion circuit includes a plurality of switch tubes. The controller is used to control the on-off state of the switch tubes in each power conversion circuit to control the output waveform of the power conversion circuit. By controlling the various parameters of the output waveform (including the peak value, duty cycle, frequency and other parameters of the output waveform), the output voltage and output current of the output end of the power conversion circuit can be controlled. The switch tube used in the power conversion circuit needs to be a switch tube that can switch the on and off state at high frequency. For example, the switch tube can be a metal oxide semiconductor field effect transistor (metal oxide semiconductor field effect transistor, MOSFET), a bipolar junction transistor (bipolar junction transistor, BJT), an insulated gate bipolar transistor (insulated gate bipolar transistor, IGBT) and other types of switch tubes. One or more of these are not listed one by one in the embodiments of the present application. Exemplarily, the controller can be any one of a microprocessor (microcontroller unit, MCU), a general-purpose central processing unit (central processing unit, CPU), a general-purpose processor, a digital signal processing (digital signal processing, DSP), an application specific integrated circuit (application specific integrated circuits, ASIC), a field programmable gate array (field programmable gate array, FPGA), etc., or it can be any one or more combinations of other programmable logic devices, transistor logic devices, and hardware components.

[0048] In the present application, the controller can determine whether the intermittent (burst) wave condition is met according to the output voltage and output current of the power converter. Specifically, the output voltage and output current of the power converter can be compared with the set intermittent wave threshold, and when it is determined that the output voltage and output current are less than the intermittent wave threshold, it is determined that the power converter needs to enter the burst wave mode. Specifically, different intermittent wave thresholds can be set according to different operating modes of the power converter. Specifically, when the power converter is running in a current limiting state, the intermittent wave threshold of the corresponding value can be set for different output voltages, corresponding to the output current, and the higher the output voltage, the smaller the intermittent wave threshold is relatively. For example, when the output voltage is 200V, the intermittent wave threshold can be set to 30A, that is, when the output current is less than 30A, the burst wave mode needs to be entered; when the output voltage is 500V, the intermittent wave threshold can be set to 10A, that is, when the output current is less than 10A, the burst wave mode needs to be entered. Specifically, when the power converter operates in a constant voltage state, an intermittent wave generation threshold value of a corresponding value can be set for the output voltage according to different output current conditions, and the larger the output current, the smaller the intermittent wave generation threshold value. For example, when the output current is 30A, the intermittent wave generation threshold value can be set to 200V, that is, when the output voltage is less than 200V, it is necessary to enter the burst wave generation mode; when the output current is 10A, the intermittent wave generation threshold value can be set to 500V, that is, when the output voltage is less than 500V, it is necessary to enter the burst wave generation mode.

[0049] In the present application, after entering the burst wave mode, the controller will determine whether the target voltage or target current at the total output end of at least three power conversion circuits is less than a first threshold value according to the operating mode of the power converter. The target voltage is the target value to which the output voltage of the power conversion circuit needs to be adjusted in the end, and the target current is the target value to which the output current of the power conversion circuit needs to be adjusted in the end. When it is determined that the target voltage or target current is less than the first threshold value, M power conversion circuits are controlled to output waveforms synchronously within a first time period, where M is a positive integer and is determined based on the target voltage or target current; and the remaining power conversion circuits are controlled not to output waveforms within the first time period, that is, the controller controls the power converter to enter the staggered wave mode. Among them, the first time period is the duration of the power conversion circuit outputting one or multiple consecutive output waveforms, Figure 4In the example, each first time period includes three continuous output waveforms. Specifically, when the power converter is running in the current limiting state, the first threshold value of the corresponding value can be set for the target current according to the different output voltage conditions, and the higher the output voltage, the smaller the first threshold value is. For example, when the output voltage is 200V, the first threshold value can be set to 20A, that is, when the target current is less than 20A, it is necessary to enter the staggered wave mode; when the output voltage is 500V, the first threshold value can be set to 5A, that is, when the target current is less than 5A, it is necessary to enter the partial wave mode. Specifically, when the power converter is running in the constant voltage state, the first threshold value of the corresponding value can be set for the target voltage according to the different output current conditions, and the larger the output current, the smaller the first threshold value is. For example, when the output current is 30A, the first threshold value can be set to 150V, that is, when the target voltage is less than 150V, it is necessary to enter the staggered wave mode; when the output current is 10A, the first threshold value can be set to 400V, that is, when the target voltage is less than 400V, it is necessary to enter the staggered wave mode.

[0050] In the present application, after the controller controls the power converter to enter the staggered wave generation mode, unlike the traditional burst wave generation mode, part of the power conversion circuits synchronously output waveforms in each first time period, so as to ensure a stable output voltage or output current in multiple consecutive first time periods, so as to reduce the output voltage and output current ripple jitter of the power converter to make the ripple smoother, and in each first time period, there is a power conversion circuit that does not output a waveform, which can meet the demand for outputting low voltage or low current. Since there are at least three power conversion circuits in the power converter, one or more power conversion circuits can be more flexibly selected according to the target current or target voltage, and switch between outputting waveforms and not outputting waveforms to more finely control the changes in output current or output voltage.

[0051] In some embodiments of the present application, in order to extend the service life of the power conversion circuit, after the power converter enters the staggered wave generation mode, that is, in response to the target voltage or the target current being less than the first threshold value, in two consecutive first time periods, the power conversion circuits that are controlled not to output waveforms are different, wherein the power converters that do not output waveforms are different means that there are one or more different power converters that do not output waveforms, so that each power conversion circuit is alternately non-operating, to ensure that each power conversion circuit does not work continuously for a long time, thereby extending the service life of the power converter.

[0052] Furthermore, in some embodiments of the present application, the number of first time periods of each power conversion circuit outputting a waveform may be controlled to be the same within a plurality of consecutive first time periods, so as to ensure that the operating time of each power conversion circuit is relatively consistent, thereby extending the overall service life of the power converter. Figure 4When the target voltage or the target current is less than the first threshold value, for example, three output waveforms can be used as a time period to replace the power conversion circuit of the output waveform and the power conversion circuit that is not working. In a first time period formed by the first three output waveforms, power conversion circuit 1 and power conversion circuit 2 synchronously output waveforms and power conversion circuit n does not output waveforms; in the next first time period, power conversion circuit 2 and power conversion circuit n synchronously output waveforms and power conversion circuit 1 does not output waveforms, and so on.

[0053] In some embodiments of the present application, after the controller controls the power converter to enter the staggered wave generation mode, in order to meet the demand of outputting a lower voltage or current, the controller determines the M value according to the operating mode of the power converter and the target voltage or target current, where M is the number of power conversion circuits that output the waveform. Then, within a first time period, the M power conversion circuits are controlled to output the waveform synchronously and the remaining power conversion circuits are controlled not to output the waveform.

[0054] In some embodiments of the present application, after the controller controls the power converter to enter the staggered wave generation mode, in order to meet the requirements of different output voltages or currents, the controller will adjust the number of power conversion circuits that synchronously output waveforms in the third time period after the first time period in response to changes in the target voltage or target current according to the operating mode of the power converter, and the number of power conversion circuits that do not output waveforms. Specifically, in the third time period, N power conversion circuits are controlled to synchronously output waveforms, and the remaining power conversion circuits do not output waveforms. If N is greater than M, the voltage or current of the total output end of at least three power conversion circuits in the third time period is greater than the voltage or current of the total output end of at least three power conversion circuits in the first time period. If N is less than M, the voltage or current of the total output end of at least three power conversion circuits in the third time period is less than the voltage or current of the total output end of at least three power conversion circuits in the first time period.

[0055] Specifically, when the power converter operates in a current limiting state, the number of power conversion circuits that synchronously output waveforms within the third time period and the number of power conversion circuits that do not output waveforms can be adjusted according to the target current. Exemplarily, if it is necessary to reduce the output current of the power converter, that is, to lower the target current, the controller can reduce the number of power conversion circuits that synchronously output waveforms within the third time period, and correspondingly increase the number of power conversion circuits that do not output waveforms; if it is necessary to increase the output current of the power converter, that is, to increase the target current, the controller can increase the number of power conversion circuits that synchronously output waveforms within the third time period, and reduce the number of power conversion circuits that do not output waveforms. Refer to Figure 4, after entering the staggered wave generation mode, the number of power conversion circuits that synchronously output waveforms in each time period may be n-1, and the number of power conversion circuits that do not output waveforms is one. Referring to the direction of the arrow, as the target current of the power converter decreases, the number of power conversion circuits that synchronously output waveforms in each time period may be n-2, and the number of power conversion circuits that do not output waveforms is two, and so on.

[0056] Specifically, when the power converter operates in a constant voltage state, the number of power conversion circuits that synchronously output waveforms within the third time period and the number of power conversion circuits that do not output waveforms can be adjusted according to the target voltage. Exemplarily, if it is necessary to reduce the output voltage of the power converter, that is, to lower the target voltage, the controller can reduce the number of power conversion circuits that synchronously output waveforms within the third time period, and correspondingly increase the number of power conversion circuits that do not output waveforms; if it is necessary to increase the output voltage of the power converter, that is, to increase the target voltage, the controller can increase the number of power conversion circuits that synchronously output waveforms within the third time period, and reduce the number of power conversion circuits that do not output waveforms. Refer to Figure 4 , after entering the staggered wave generation mode, the number of power conversion circuits that synchronously output waveforms in each time period may be n-1, and the number of power conversion circuits that do not output waveforms is one. Referring to the direction of the arrow, as the target voltage of the power converter decreases, the number of power conversion circuits that synchronously output waveforms in each time period may be n-2, and the number of power conversion circuits that do not output waveforms is two, and so on.

[0057] In some embodiments of the present application, after the controller controls the power converter to enter the burst wave mode and before entering the staggered wave mode, the controller can control each power conversion circuit in the power converter to first output the waveform synchronously for a period of time, and then not output the waveform, that is, shut down for a period of time, so as to control the output voltage or output current of the power converter and achieve a lower output voltage or output current. After that, the output voltage or output current is detected, and when it is determined that the target voltage or target current needs to be lower than the first threshold, it is switched to the staggered wave mode.

[0058] Reference Figure 4In some embodiments of the present application, as the output voltage or output current demand changes, when the controller determines that the target voltage or target current needs to be greater than the second threshold value according to the operation mode of the power converter, the power converter can be controlled to exit the staggered wave mode, and all power conversion circuits can be controlled to output waveforms synchronously in the second time period to meet the demand for increasing the output voltage or output current. Exemplarily, the second threshold value can be different from the first threshold value, for example, the second threshold value can be slightly higher than the first threshold value, so that there is a hysteresis between the two threshold values ​​to prevent frequent switching of the wave mechanism at the critical point of the judgment condition. Specifically, when the power converter is running in the current limiting state, the second threshold value of the corresponding value can be set for the target current according to the different output voltage conditions, and the higher the output voltage, the smaller the second threshold value is. For example, when the output voltage is 200V, the second threshold value can be set to 25A, that is, when the target current is greater than 25A, the staggered wave mode needs to be exited; when the output voltage is 500V, the second threshold value can be set to 8A, that is, when the target current is greater than 8A, the partial wave mode needs to be exited. Specifically, when the power converter operates in a constant voltage state, a second threshold value of a corresponding value can be set corresponding to the target voltage for different output currents, and the larger the output current, the smaller the second threshold value. For example, when the output current is 30A, the second threshold value can be set to 180V, that is, when the target voltage is greater than 180V, it is necessary to exit the interlaced wave mode; when the output current is 10A, the second threshold value can be set to 450V, that is, when the target voltage is greater than 450V, it is necessary to exit the interlaced wave mode.

[0059] In an embodiment of the present application, when the target voltage or the target current exceeds the second threshold value, after the controller controls the power converter to exit the staggered wave generation mode, the power converter may still remain in the burst wave generation mode, such as by adopting a mechanism in which all power conversion circuits synchronously output waveforms or do not output waveforms. Alternatively, the power converter may directly exit the burst wave generation mode, that is, directly enter a working mode in which all power conversion circuits synchronously output waveforms in each second time period.

[0060] The following two specific embodiments are used to illustrate the switching process of the power mode of the power converter provided by the present application.

[0061] Embodiment 1:

[0062] Figure 5 The schematic diagram of the structure of the power converter provided by the first embodiment is shown as an example. Figure 6a An output waveform diagram of a power converter provided in the first embodiment is exemplarily shown. Figure 6b Another output waveform diagram of the power converter provided in the first embodiment is exemplarily shown. Figure 6c Another output waveform diagram of the power converter provided in the first embodiment is exemplarily shown. Figure 6d Another output waveform diagram of the power converter provided in the first embodiment is exemplarily shown.

[0063] Reference Figure 5 The power converter includes four power conversion circuits arranged in parallel, and the controller can independently control each power conversion circuit to switch between output waveform (wave generation) and non-output waveform (wave blocking). The output end of the power conversion circuit can be connected to a resistive load through a DC bus, and the power converter can output the bus voltage after power conversion of the battery voltage provided by the battery and discharge it to the resistive load.

[0064] During the discharge process when the power converter is running in the current limiting state, as the discharge current output by the power converter decreases, when the discharge current is less than the intermittent wave threshold, the controller switches the power converter to the burst wave mode. For example, when the discharge current output by the power converter is less than 50A, the controller switches the power converter to the burst wave mode. Figure 6a In the burst wave mode, all power conversion circuits synchronously output waveforms within the time of three consecutive output waveforms, and all power conversion circuits do not output waveforms within the time of the next three consecutive output waveforms to achieve a lower output discharge current.

[0065] As the target current of the power converter decreases, when the target current is less than the first threshold, the controller switches the power converter to the staggered wave generation mode. For example, when the target current of the power converter is less than 40A, the controller switches the power converter to the staggered wave generation mode. In the staggered wave generation mode, the number of power conversion circuits that synchronously output waveforms in each time period can be adjusted accordingly according to the change of the target current.

[0066] For example, when the target current is between 30A and 40A, the controller can control the three power conversion circuits to synchronously output waveforms in each time period, and control the remaining one power conversion circuit not to output waveforms in each time period. Figure 6b , the controller can follow Figure 6b The four wave generation modes A, B, C and D are fully or partially cycled to control different power conversion circuits to not output waveforms.

[0067] For example, when the target current is between 20A and 30A, the controller can control the two power conversion circuits to synchronously output waveforms in each time period, and control the remaining two power conversion circuits not to output waveforms in each time period. Figure 6c , the controller can follow Figure 6c The four wave generation modes A, B, C and D are fully or partially cycled to control different power conversion circuits to not output waveforms.

[0068] For example, when the target current is less than 20A, the controller can control one power conversion circuit to synchronously output a waveform in each time period, and control the remaining three power conversion circuits not to output a waveform in each time period. Figure 6d , the controller can follow Figure 6d The four wave generation modes A, B, C and D are fully or partially cycled to control different power conversion circuits to not output waveforms.

[0069] Similarly, during the discharge process when the power converter is running in a constant voltage state, as the discharge voltage output by the power converter decreases, when the discharge voltage is less than the intermittent wave threshold, the controller switches the power converter to the burst wave mode. For example, when the discharge voltage output by the power converter is less than 800V, the controller switches the power converter to the burst wave mode. Figure 6a In the burst wave mode, all power conversion circuits synchronously output waveforms within the time of three consecutive output waveforms, and all power conversion circuits do not output waveforms within the time of the next three consecutive output waveforms to achieve a lower output discharge voltage.

[0070] As the target voltage of the power converter decreases, when the target voltage is less than the first threshold, the controller switches the power converter to the staggered wave generation mode. For example, when the target voltage of the power converter is less than 700V, the controller switches the power converter to the staggered wave generation mode. In the staggered wave generation mode, the number of power conversion circuits that synchronously output waveforms in each time period can be adjusted accordingly according to the change of the target voltage.

[0071] For example, when the target voltage is between 600V and 700V, the controller can control the three power conversion circuits to synchronously output waveforms in each time period, and control the remaining one power conversion circuit not to output waveforms in each time period. Figure 6b , the controller can follow Figure 6b The four wave generation modes A, B, C and D are fully or partially cycled to control different power conversion circuits to not output waveforms.

[0072] For example, when the target voltage is between 500V and 600V, the controller can control the two power conversion circuits to synchronously output waveforms in each time period, and control the remaining two power conversion circuits not to output waveforms in each time period. Figure 6c , the controller can follow Figure 6c The four wave generation modes A, B, C and D are fully or partially cycled to control different power conversion circuits to not output waveforms.

[0073] For example, when the target voltage is less than 500V, the controller can control one power conversion circuit to synchronously output a waveform in each time period, and control the remaining three power conversion circuits not to output a waveform in each time period. Figure 6d , the controller can follow Figure 6d The four wave generation modes A, B, C and D are fully or partially cycled to control different power conversion circuits to not output waveforms.

[0074] Embodiment 2:

[0075] Figure 7 The schematic diagram of the structure of the power converter provided by the second embodiment is exemplarily shown. Figure 8a An output waveform diagram of a power converter provided in the second embodiment is exemplarily shown. Figure 8b Another output waveform diagram of the power converter provided in the second embodiment is exemplarily shown. Figure 8c Another output waveform diagram of the power converter provided in the second embodiment is exemplarily shown.

[0076] Reference Figure 7 The power converter includes three power conversion circuits arranged in parallel. The controller can independently control each power conversion circuit to switch between output waveform (wave generation) and non-output waveform (wave blocking). The output end of the power conversion circuit can be connected to a resistive load through a DC bus. The power converter can output the bus voltage after power conversion of the battery voltage provided by the battery and discharge it to the resistive load.

[0077] During the discharge process when the power converter is running in the current limiting state, as the discharge current output by the power converter decreases, when the discharge current is less than the intermittent wave threshold, the controller switches the power converter to the burst wave mode. For example, when the discharge current output by the power converter is less than 50A, the controller switches the power converter to the burst wave mode. Figure 8a In the burst wave mode, all power conversion circuits synchronously output waveforms within the time of three consecutive output waveforms, and all power conversion circuits do not output waveforms within the time of the next three consecutive output waveforms to achieve a lower output discharge current.

[0078] As the target current of the power converter decreases, when the target current is less than the first threshold, the controller switches the power converter to the staggered wave generation mode. For example, when the target current of the power converter is less than 40A, the controller switches the power converter to the staggered wave generation mode. In the staggered wave generation mode, the number of power conversion circuits that synchronously output waveforms in each time period can be adjusted accordingly according to the change of the target current.

[0079] For example, when the target current is between 20A and 40A, the controller can control the two power conversion circuits to synchronously output waveforms in each time period, and control the remaining power conversion circuit not to output waveforms in each time period. Figure 8b , the controller can follow Figure 8b The three wave generation modes A, B and C are fully or partially cycled to control different power conversion circuits to not output waveforms.

[0080] For example, when the target current is less than 20A, the controller can control one power conversion circuit to synchronously output a waveform in each time period, and control the other two power conversion circuits not to output a waveform in each time period. Figure 8c , the controller can follow Figure 8c The three wave generation modes A, B and C are fully or partially cycled to control different power conversion circuits to not output waveforms.

[0081] Similarly, during the discharge process when the power converter is running in a constant voltage state, as the discharge voltage output by the power converter decreases, when the discharge voltage is less than the intermittent wave threshold, the controller switches the power converter to the burst wave mode. For example, when the discharge voltage output by the power converter is less than 800V, the controller switches the power converter to the burst wave mode. Figure 8a In the burst wave mode, all power conversion circuits synchronously output waveforms in three consecutive time periods, and all power conversion circuits do not output waveforms in the next three consecutive time periods to achieve a lower output discharge voltage.

[0082] As the target voltage of the power converter decreases, when the target voltage is less than the first threshold, the controller switches the power converter to the staggered wave generation mode. For example, when the target voltage of the power converter is less than 700V, the controller switches the power converter to the staggered wave generation mode. In the staggered wave generation mode, the number of power conversion circuits that synchronously output waveforms in each time period can be adjusted accordingly according to the change of the target voltage.

[0083] For example, when the target voltage is between 500V and 700V, the controller can control the two power conversion circuits to synchronously output waveforms in each time period, and control the remaining power conversion circuit not to output waveforms in each time period. Figure 8b , the controller can follow Figure 8b The three wave generation modes A, B and C are fully or partially cycled to control different power conversion circuits to not output waveforms.

[0084] For example, when the target voltage is less than 500V, the controller can control one power conversion circuit to synchronously output a waveform in each time period, and control the other two power conversion circuits not to output a waveform in each time period. Figure 8c , the controller can follow Figure 8c The three wave generation modes A, B and C are fully or partially cycled to control different power conversion circuits to not output waveforms.

[0085] The above two embodiments are only to illustrate how the power converter provided by the present application reduces the output voltage or output current ripple when lightly loaded, taking the power converter including three or four power conversion circuits as an example. The power converter may also include more power conversion circuits, which is not limited here.

[0086] The above-mentioned power converter provided in the embodiment of the present application can be widely used in energy storage systems such as household energy storage, industrial and commercial energy storage or power station energy storage. Based on this, the present application also provides an energy storage system, including the above-mentioned power converter and an energy storage device, the total input end of at least three power conversion circuits in the power converter is connected to the output end of the energy storage device, the total output end of at least three power conversion circuits is used to connect to the DC bus, and at least three power conversion circuits can output the bus voltage after power conversion of the battery voltage provided by the energy storage device. When the DC bus is lightly loaded, after the power converter enters the burst wave mode, the controller controls that part of the power conversion circuit synchronously outputs the waveform in each time period, so that the output voltage or output current can be ensured to be stable in multiple consecutive time periods, so as to reduce the output voltage and output current ripple jitter of the power converter to make the ripple smoother, and in each time period, there is a power conversion circuit that does not output the waveform, which can meet the demand of outputting low voltage or low current. Since there are at least three power conversion circuits in the power converter, one or more power conversion circuits can be selected more flexibly according to the target current or target voltage, and switch between outputting a waveform and not outputting a waveform to more finely control the change of the output current or output voltage.

[0087] Based on the same inventive concept, an embodiment of the present application also provides a drive control method for a power converter, which can be executed by a controller. The drive control method includes: in response to a target voltage or target current at the total output end of at least three power conversion circuits being less than a first threshold, within a first time period, controlling M power conversion circuits to output waveforms synchronously, and controlling the remaining power conversion circuits not to output waveforms; wherein M is a positive integer, and M is determined based on the target voltage or target current.

[0088] In the present application, after the power converter enters the staggered wave generation mode, unlike the traditional burst wave generation mode, when the target voltage or target current at the output end of the power conversion circuit is less than the first threshold value, part of the power conversion circuit synchronously outputs the waveform in the first time period, so as to ensure the stable output voltage or output current in multiple consecutive first time periods, so as to reduce the output voltage and output current ripple jitter of the power converter to make the ripple smoother, and the power conversion circuit does not output the waveform in the first time period, which can meet the demand of outputting low voltage or low current. Since there are at least three power conversion circuits in the power converter, one or more power conversion circuits can be selected more flexibly according to the target current or target voltage, and switch between outputting the waveform and not outputting the waveform, so as to more finely control the change of the output current or output voltage.

[0089] In some embodiments of the present application, the control method also includes: in response to the target voltage or target current being greater than a second threshold, controlling all power conversion circuits to synchronously output waveforms within a second time period, that is, the power converter can be controlled to exit the staggered wave generation mode to meet the demand for increasing the output voltage or output current.

[0090] In some embodiments of the present application, the second threshold may be different from the first threshold. For example, the second threshold may be slightly higher than the first threshold, so that there is a hysteresis between the two thresholds to prevent frequent switching of the wave generation mechanism at the critical point of the judgment condition.

[0091] In an embodiment of the present application, when the target voltage or the target current exceeds the second threshold value, after the power converter exits the interlaced wave generation mode, the power converter may still remain in the burst wave generation mode, such as by adopting a mechanism in which all power conversion circuits synchronously output waveforms or do not output waveforms. Alternatively, the power converter may directly exit the burst wave generation mode, that is, directly enter a working mode in which all power conversion circuits synchronously output waveforms in each second time period.

[0092] In some embodiments of the present application, the control method also includes: in response to the target voltage or target current being less than a first threshold value, controlling different power conversion circuits that do not output waveforms in two consecutive first time periods so that each power conversion circuit is alternately non-operating to extend the overall service life of the power converter.

[0093] In some embodiments of the present application, the control method also includes: within multiple consecutive first time periods, controlling the number of first time periods of the output waveform of each power conversion circuit to be the same, so as to ensure that the operating time of each power conversion circuit is relatively consistent and extend the overall service life of the power converter.

[0094] In some embodiments of the present application, the control method further includes: in order to meet the requirements of different output voltages or currents, in a third time period, controlling N power conversion circuits to synchronously output waveforms, and controlling the remaining power conversion circuits not to output waveforms. Wherein, the voltage or current of the total output end of at least three power conversion circuits in the third time period is greater than the voltage or current of the total output end of at least three power conversion circuits in the first time period, and N is greater than M; or, the voltage or current of the total output end of at least three power conversion circuits in the third time period is less than the voltage or current of the total output end of at least three power conversion circuits in the first time period, and N is less than M.

[0095] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A power converter, characterized in that: include: At least three power conversion circuits; the at least three power conversion circuits are connected in parallel or in series, the total input end of the at least three power conversion circuits is used to connect the output end of the energy storage device, the total output end of the at least three power conversion circuits is used to connect the DC bus, and the at least three power conversion circuits are used to adjust the output voltage of the energy storage device; In response to the target voltage or target current of the total output end of the at least three power conversion circuits being less than a first threshold, within a first time period, M of the power conversion circuits synchronously output waveforms, and the remaining power conversion circuits do not output waveforms, where M is determined based on the target voltage or the target current; M is a positive integer.

2. The power converter according to claim 1, characterized in that In response to the target voltage or the target current at the total output end of the at least three power conversion circuits being greater than a second threshold, all of the power conversion circuits synchronously output waveforms within a second time period.

3. The power converter according to claim 2, characterized in that: The second threshold is greater than the first threshold.

4. The power converter according to any one of claims 1 to 3, characterized in that: In response to the target voltage or the target current at the total output end of the at least three power conversion circuits being less than the first threshold, the power conversion circuits that do not output waveforms are different in two consecutive first time periods.

5. The power converter according to any one of claims 1 to 4, characterized in that: In a plurality of consecutive first time periods, the number of first time periods of the waveform output by each of the power conversion circuits is the same.

6. The power converter according to any one of claims 1 to 5, characterized in that: In a third time period, N of the power conversion circuits synchronously output waveforms, and the remaining power conversion circuits do not output waveforms; The voltage or current at the total output end of the at least three power conversion circuits in the third time period is greater than the voltage or current at the total output end of the at least three power conversion circuits in the first time period, and N is greater than M; or, The voltage or current at the total output end of the at least three power conversion circuits in the third time period is less than the voltage or current at the total output end of the at least three power conversion circuits in the first time period, and N is less than M.

7. The power converter according to any one of claims 1 to 5, characterized in that: Also included is a controller, the controller being configured to: In response to the target voltage or the target current at the total output end of the at least three power conversion circuits being less than the first threshold, M is determined according to the target voltage or the target current at the total output end of the at least three power conversion circuits, and the M power conversion circuits are controlled to synchronously output waveforms during the first time period, and the remaining power conversion circuits are controlled not to output waveforms.

8. A drive control method for a power converter, characterized in that: The power converter includes at least three power conversion circuits, and the control method includes: In response to a target voltage or a target current at the total output end of the at least three power conversion circuits being less than a first threshold, within a first time period, M of the power conversion circuits are controlled to synchronously output waveforms, and the remaining power conversion circuits are controlled not to output waveforms; wherein M is a positive integer, and M is determined based on the target voltage or the target current.

9. The driving control method according to claim 8, characterized in that: The control method further comprises: In response to the target voltage or the target current at the total output end of the at least three power conversion circuits being greater than a second threshold, all of the power conversion circuits are controlled to synchronously output waveforms within a second time period.

10. The driving control method according to claim 9, characterized in that: The second threshold is greater than the first threshold.

11. The driving control method according to any one of claims 8 to 10, characterized in that: The control method further comprises: In response to the target voltage or the target current at the total output end of the at least three power conversion circuits being less than the first threshold, in two consecutive first time periods, the power conversion circuits that are controlled not to output waveforms are different.

12. The driving control method according to any one of claims 8 to 11, characterized in that: The control method further comprises: In a plurality of consecutive first time periods, the number of first time periods for controlling each power conversion circuit to output a waveform is the same.

13. The driving control method according to any one of claims 8 to 12, characterized in that: The control method further comprises: In a third time period, controlling N of the power conversion circuits to synchronously output waveforms, and controlling the remaining power conversion circuits not to output waveforms; The voltage or current at the total output end of the at least three power conversion circuits in the third time period is greater than the voltage or current at the total output end of the at least three power conversion circuits in the first time period, and N is greater than M; or, The voltage or current at the total output end of the at least three power conversion circuits in the third time period is less than the voltage or current at the total output end of the at least three power conversion circuits in the first time period, and N is less than M.

14. An energy storage system, characterized in that: include: An energy storage device and a power converter as described in any one of claims 1 to 7, wherein the total input end of at least three power conversion circuits in the power converter is connected to the output end of the energy storage device, and the total output end of the at least three power conversion circuits is used to be connected to a DC bus.

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