Power converter and energy storage system

Abstract

The invention provides a power converter and an energy storage system, and belongs to the technical field of energy storage. A signal processing circuit in the power converter can adjust the amplitude of a zero-crossing reference signal from a first amplitude to a second amplitude according to a target rate after detecting that the power converter meets a target condition. The target rate is smaller than the change rate when the inductive current is changed from effective current to negative current. Therefore, even if the amplitude of the zero-crossing reference signal is adjusted after the inductive current crosses zero (namely after the inductive current is changed into negative current), the magnitude relationship between the negative current of the inductive current and the amplitude of the zero-crossing reference signal can be kept unchanged before and after the amplitude is adjusted. Correspondingly, the comparator can accurately detect whether the inductive current crosses zero or not based on the amplitude of the zero-crossing reference signal, and accurately output a zero-crossing comparison signal. The wave sending circuit can accurately trigger a new wave sending period based on the zero-crossing comparison signal.

Description

Technical Field

[0001] This application relates to the technical field of energy storage, and particularly to a power converter and an energy storage system. Background Art

[0002] A power converter generally includes a power conversion circuit and a controller. The power conversion circuit generally includes at least one switching tube and an inductor. The controller controls the output voltage or output current of the power conversion circuit by sending a waveform to the at least one switching tube.

[0003] The controller can trigger a new waveform period according to the zero-crossing comparison signal of the inductor current. Among them, the zero-crossing comparison signal is generated by a comparator comparing the amplitude of the inductor current and the amplitude of the zero-crossing reference signal. For example, when the amplitude of the inductor current is greater than the amplitude of the zero-crossing reference signal, the zero-crossing comparison signal output by the comparator is at a low level; when the amplitude of the inductor current is less than the amplitude of the zero-crossing reference signal, the zero-crossing comparison signal output by the comparator is at a high level.

[0004] When the power converter switches from light load to heavy load, the controller needs to adjust its waveform pattern. Correspondingly, the amplitude of the zero-crossing reference signal needs to be reduced. Generally, the power converter directly reduces the amplitude of the zero-crossing reference signal from the current value to the target value. However, if the power converter reduces the amplitude of the zero-crossing reference signal after the inductor current crosses zero (i.e., after the inductor current becomes a negative current), it may cause the amplitude of the adjusted zero-crossing reference signal to be less than the amplitude of the negative current of the inductor current. As a result, the zero-crossing comparison signal output by the comparator will be abnormal, and further the waveform of the controller will be abnormal. Summary of the Invention

[0005] This application provides a power converter and an energy storage system, which can solve the technical problem that abnormal waveform generation of the controller will occur when adjusting the amplitude of the zero-crossing reference signal after the inductor current crosses zero.

[0006] In a first aspect, a power converter is provided. The power converter includes: a controller and a power conversion circuit. The controller includes a signal processing circuit, a comparator, and a wave generating circuit. The power converter is used to charge or discharge a battery pack. The power conversion circuit includes an inductor and at least one switching transistor. The signal processing circuit is configured to output a zero-crossing reference signal to the comparator, and is further configured to adjust the amplitude of the zero-crossing reference signal from a first amplitude to a second amplitude at a target rate after detecting that the power converter meets a target condition. The comparator is configured to compare the amplitude of the zero-crossing reference signal with the amplitude of the inductor current, and output a zero-crossing comparison signal to the wave generating circuit. Herein, the inductor current refers to the current flowing through the inductor. The wave generating circuit is configured to determine a wave generation period according to the zero-crossing comparison signal, and send a wave to at least one switching transistor according to the wave generation period. The above-mentioned target rate is less than the change rate when the inductor current changes from an effective current to a negative current. The direction of the negative current is opposite to that of the effective current. Moreover, when the power converter charges the battery pack, the effective current refers to the current flowing into the battery pack through the inductor; when the power converter discharges the battery pack, the effective current refers to the current flowing out of the battery pack to the inductor.

[0007] In the solution provided in this application, after the power converter meets the target condition, the peak value of the negative current of the inductor current will change (for example, the absolute value of the peak value will increase). Therefore, it is necessary to correspondingly adjust the amplitude of the zero-crossing reference signal. Since the adjustment rate of the amplitude of the zero-crossing reference signal is less than the change rate when the inductor current changes from an effective current to a negative current, even if the amplitude of the zero-crossing reference signal is adjusted after the inductor current crosses zero (that is, after the inductor current becomes a negative current), it can be ensured that the magnitude relationship between the negative current of the inductor current and the amplitude of the zero-crossing reference signal remains unchanged. Based on this, the comparator can accurately detect whether the inductor current crosses zero based on the amplitude of the zero-crossing reference signal, and accurately output a zero-crossing comparison signal. Correspondingly, the wave generating circuit can accurately trigger a new wave generation period based on the zero-crossing comparison signal.

[0008] Optionally, the adjustment direction of the amplitude of the zero-crossing reference signal is the same as the change direction when the effective current changes to a negative current.

[0009] It can be understood that if the amplitude of the effective current is positive and the amplitude of the negative current is negative, then the second amplitude is less than the first amplitude, that is, the adjustment direction of the amplitude of the zero-crossing reference signal is the decreasing direction. In this scenario, when the peak value of the negative current of the inductor current decreases, the amplitude of the zero-crossing reference signal needs to be correspondingly decreased. If the amplitude of the zero-crossing reference signal decreases too fast, it may cause the inductor current to be greater than the amplitude of the zero-crossing reference signal after crossing zero, thereby causing an abnormality in the zero-crossing comparison signal output by the comparator. Therefore, it is necessary to gradually change the amplitude of the zero-crossing reference signal from the first amplitude to the second amplitude at the target rate to ensure that the comparator can accurately output a zero-crossing comparison signal.

[0010] If the amplitude of the effective current is negative and the amplitude of the negative current is positive, then the second amplitude is greater than the first amplitude, that is, the adjustment direction of the amplitude of the zero-crossing reference signal is the rising direction. In this scenario, when the peak value of the negative current of the inductor current increases, the amplitude of the zero-crossing reference signal needs to increase correspondingly. If the amplitude of the zero-crossing reference signal increases too fast, it may cause the inductor current to be less than the amplitude of the zero-crossing reference signal after passing through zero, thereby causing the zero-crossing comparison signal output by the comparator to be abnormal. Therefore, it is necessary to gradually change the amplitude of the zero-crossing reference signal from the first amplitude to the second amplitude at the target rate to ensure that the comparator accurately outputs the zero-crossing comparison signal.

[0011] Optionally, the waveform of the inductor current is a four-segment current waveform. In this four-segment current waveform, the inductor current in the first segment changes from negative current to effective current, the effective current in the second segment changes to the peak value, the third segment changes from effective current to negative current, and the fourth segment remains as negative current. Correspondingly, the above change rate may refer to the change rate of the inductor current in the third segment.

[0012] Optionally, the power converter meeting the target conditions includes at least one of the following: the power converter switches from light load to heavy load; the number of battery packs connected to the power converter increases; the battery pack connected to the power converter switches from the charging state to the discharging state, or from the discharging state to the charging state.

[0013] Among them, when the power converter switches from light load to heavy load, or when the number of battery packs connected to the power converter increases, the change rate of the inductor current changing from effective current to negative current will increase, and thus the absolute value of the peak value of the negative current of the inductor current will increase. Among them, if the amplitude of the negative current of the inductor current is negative, the peak value of the negative current of the inductor current will decrease. Correspondingly, the amplitude of the zero-crossing reference signal should also decrease correspondingly. If the amplitude of the negative current of the inductor current is positive, the peak value of the negative current of the inductor current will increase. Correspondingly, the amplitude of the zero-crossing reference signal should also increase correspondingly.

[0014] When the battery pack connected to the power converter switches from the charging state to the discharging state, or from the discharging state to the charging state, the current direction of the negative current of the inductor current will change, and the magnitude of the negative current will also change. For example, when switching from the charging state to the discharging state, the amplitude of the negative current will change from negative to positive, that is, the peak value of the negative current will increase. Correspondingly, the amplitude of the zero-crossing reference signal should also increase correspondingly. When switching from the discharging state to the charging state, the amplitude of the negative current will change from positive to negative, that is, the peak value of the negative current will decrease. Correspondingly, the amplitude of the zero-crossing reference signal should also decrease correspondingly.

[0015] Optionally, the wave generating circuit is further configured to adjust the wave generating mode when the power converter meets the target condition. The signal processing circuit is configured to adjust the amplitude of the zero-crossing reference signal from the first amplitude to the second amplitude at the target rate after the target duration after the wave generating mode is adjusted.

[0016] Wherein, the target duration is the duration required for the wave generating circuit to adjust the wave generating mode. Since the drive configuration parameters of different wave generating modes are different, the wave generating circuit needs to adjust its drive configuration parameters when switching the wave generating mode. The above target duration can be understood as the duration required for the adjusted drive configuration parameters to take effect. It can be seen that after this target duration, it can be ensured that the wave generating mode of the wave generating circuit is successfully switched, that is, the absolute value of the negative current peak of the inductor current will increase compared with that before the switch. At this time, the signal processing circuit adjusts the amplitude of the reference signal, which can ensure that the comparator accurately detects whether the inductor current passes through zero.

[0017] Optionally, the at least one switching tube includes a first main switching tube, a second main switching tube, a first freewheeling switching tube, and a second freewheeling switching tube. Wherein, the first main switching tube and the second freewheeling switching tube are connected in series between the positive and negative poles of the first end of the power conversion circuit, and the first freewheeling switching tube and the second main switching tube are connected in series between the positive and negative poles of the second end of the power conversion circuit. One end of the inductor is connected to the series node between the first main switching tube and the second freewheeling switching tube, and the other end of the inductor is connected to the series node between the first freewheeling switching tube and the second main switching tube. That is, the power conversion circuit can adopt a four-switch buck-boost circuit.

[0018] It can be understood that one of the first end and the second end of the power conversion circuit is used to connect to the battery pack, and the other end is used to connect to the DC bus. Wherein, the DC bus can be used to connect to a DC load and / or other DC power sources (such as photovoltaic modules), or the DC bus can also be connected to the power grid and / or AC load through a direct current / alternating current (DC / AC) converter.

[0019] Optionally, the wave generation circuit is configured to adjust the wave generation mode from a light load mode to a heavy load mode when the power converter switches from a light load to a heavy load. Each wave generation cycle in the light load mode includes a first wave generation period, a second wave generation period, and a third wave generation period. In the first wave generation period, the first main switch and the second main switch are turned on, and the first freewheeling switch and the second freewheeling switch are turned off. In the second wave generation period, the first main switch and the first freewheeling switch are turned on, and the second main switch and the second freewheeling switch are turned off. In the third wave generation period, the first main switch, the second main switch, the first freewheeling switch, and the second freewheeling switch are all turned off. Each wave generation cycle in the heavy load mode includes a fourth wave generation period, a fifth wave generation period, a sixth wave generation period, and a seventh wave generation period. In the fourth wave generation period, the first main switch and the second main switch are turned on, and the first freewheeling switch and the second freewheeling switch are turned off. In the fifth wave generation period, the first main switch and the first freewheeling switch are turned on, and the second main switch and the second freewheeling switch are turned off. In the sixth wave generation period, the first freewheeling switch and the second freewheeling switch are turned on, and the first main switch and the second main switch are turned off. In the seventh wave generation period, the first freewheeling switch is turned off, and the second freewheeling switch is turned on.

[0020] In the solution provided by the present application, during each wave generation cycle in the light load mode, two freewheeling switches are not turned on simultaneously, thereby effectively reducing the power consumption of the power converter in the light load mode.

[0021] Optionally, when the power converter charges the battery pack, the amplitude of the effective current of the inductor current is positive, and the amplitude of the negative current is negative. Correspondingly, the second amplitude is less than the first amplitude. When the power converter discharges the battery pack, the amplitude of the effective current of the inductor current is negative, and the amplitude of the negative current is positive. Correspondingly, the second amplitude is greater than the first amplitude. That is, the power converter can use the current direction during battery pack charging as the positive direction of the inductor current.

[0022] It can be understood that the current direction during battery pack discharge can also be used as the positive direction of the inductor current. Correspondingly, during battery pack charging, the amplitude of the effective current of the inductor current is negative, and the amplitude of the negative current is positive; during battery pack discharge, the amplitude of the effective current is positive, and the amplitude of the negative current is negative.

[0023] Optionally, the wave generation circuit is further configured to control the wave generation cycle to be greater than or equal to the switching cycle corresponding to the highest switching frequency of at least one switch in the power conversion circuit.

[0024] By controlling the wave generation cycle to be greater than or equal to the switching cycle corresponding to the highest switching frequency, it is possible to effectively prevent the switching frequency of the switch in the power conversion circuit from being higher than the highest switching frequency, thereby avoiding damage to the switch.

[0025] Optionally, during the process of the inductor current changing from the effective current to the negative current, if the amplitude of the inductor current reaches the amplitude of the zero-crossing reference signal, the zero-crossing comparison signal output by the comparator jumps from the first level to the second level. The wave generation circuit is further configured to generate a blanking signal, and trigger a new wave generation cycle when both the blanking signal and the zero-crossing comparison signal are at the second level. Wherein, the blanking signal is at the first level after the start of each wave generation cycle, and jumps to the second level after the duration of the first level reaches a target duration, and the target duration is greater than or equal to the above-mentioned switching period.

[0026] For example, if the second level is a high level, the wave generation circuit can perform a logical AND operation on the zero-crossing comparison signal and the blanking signal to generate a trigger signal, and can trigger a new wave generation cycle when the trigger signal is at a high level. Thus, it can not only ensure that the switching state of the switching tube is switched when the inductor current passes through zero to reduce the switching loss of the switching tube, but also effectively avoid damaging the switching tube due to too high a switching frequency of the switching tube.

[0027] Optionally, the second level is a high level relative to the first level. And, the wave generation circuit is configured to perform a logical AND operation on the blanking signal and the zero-crossing comparison signal to obtain a trigger signal, and is configured to trigger a new wave generation cycle when the trigger signal is at the second level.

[0028] For example, the wave generation circuit may include an AND gate circuit. Two input terminals of the AND gate circuit are respectively used to receive the blanking signal and the zero-crossing comparison signal, and the output terminal of the AND gate circuit is used to output the trigger signal. Based on the principle of the AND gate circuit, when both the blanking signal and the zero-crossing comparison signal are at a high level, the output trigger signal is at a high level.

[0029] In a second aspect, an energy storage system is provided, which includes at least one battery pack and a power converter as provided in the first aspect above. The DC terminal of the power converter is connected to at least one battery pack, and is configured to charge or discharge the at least one battery pack.

[0030] Wherein, the power converter may be a DC / DC converter. And, the power converter is configured to perform voltage conversion on the direct current provided by the at least one battery pack and then output it to a load or a DC / AC converter. The power converter is also configured to perform voltage conversion on the received direct current and then output it to the at least one battery pack to charge the at least one battery pack.

[0031] In summary, the present application provides a power converter and an energy storage system. The signal processing circuit in the power converter can adjust the amplitude of the zero-crossing reference signal from a first amplitude to a second amplitude at a target rate after detecting that the power converter meets the target conditions. Moreover, the target rate is less than the change rate when the inductor current changes from the effective current to the negative current. Therefore, even if the amplitude of the zero-crossing reference signal is adjusted after the inductor current passes through zero (i.e., after the inductor current becomes negative), it can be ensured that the magnitude relationship between the negative current of the inductor current and the amplitude of the zero-crossing reference signal remains unchanged before and after the amplitude adjustment. Correspondingly, the comparator can accurately detect whether the inductor current passes through zero based on the amplitude of the zero-crossing reference signal and accurately output a zero-crossing comparison signal. The wave generation circuit can then accurately trigger a new wave generation cycle based on the zero-crossing comparison signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 FIG. is a schematic diagram of a method for generating a zero-crossing comparison signal provided by an embodiment of the present application;

[0033] Figure 2 FIG. is a schematic diagram of the structure of an energy storage system provided by an embodiment of the present application;

[0034] Figure 3 FIG. is a schematic diagram of an abnormality of a zero-crossing comparison signal provided by an embodiment of the present application;

[0035] Figure 4 FIG. is a schematic diagram of the structure of a power converter provided by an embodiment of the present application;

[0036] Figure 5 FIG. is a schematic diagram of the structure of a power conversion circuit provided by an embodiment of the present application;

[0037] Figure 6 FIG. is a schematic diagram of adjusting the amplitude of a zero-crossing reference signal provided by an embodiment of the present application;

[0038] Figure 7 FIG. is another schematic diagram of adjusting the amplitude of a zero-crossing reference signal provided by an embodiment of the present application;

[0039] Figure 8 FIG. is still another schematic diagram of adjusting the amplitude of a zero-crossing reference signal provided by an embodiment of the present application;

[0040] Figure 9 FIG. is a schematic diagram of generating a trigger signal provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] The energy storage system provided by the embodiment of the present application will be introduced in detail below with reference to the drawings. First, the key terms involved in the embodiment of the present application will be introduced.

[0042] Zero-crossing comparison signal of inductor current: Also known as the zero-crossing signal or trigger zone (TZ) signal, it is used to start a new wave generation cycle and is generally generated by a comparator. For example, Figure 1 As shown, the two input terminals of the comparator can respectively receive the sampled signal of the inductor current and the zero-crossing reference signal (also known as the TZ reference signal). After comparing the signals received at its two input terminals, the comparator outputs the zero-crossing comparison signal, which can be used to indicate that the inductor current crosses zero. Among them, the logic of the comparator can be: when the inductor current is greater than the amplitude of the zero-crossing reference signal, a low level is output, that is, the zero-crossing comparison signal is at a low level; when the inductor current is less than the amplitude of the zero-crossing reference signal, the comparator outputs a high level, that is, the zero-crossing comparison signal is at a high level.

[0043] Blanking signal: Its main function is to temporarily turn off or eliminate some signals (such as the zero-crossing comparison signal), so that this part of the signal does not take effect. In the embodiments of the present application, the blanking signal is also called the frequency-limiting signal, which can be used to limit the length of the wave generation cycle, and further limit the switching frequency of the switching tube in the power conversion circuit to avoid damage due to too high a switching frequency of the switching tube. For example, the frequency of the blanking signal can be less than or equal to the maximum switching frequency that the switching tube can withstand.

[0044] Trigger signal: Also known as the new cycle trigger signal, it is used to trigger the controller to trigger a new wave generation cycle. This trigger signal can be generated by performing a logical AND operation on the zero-crossing comparison signal and the blanking information.

[0045] Effective current of inductor current: In the scenario where the power converter charges the battery pack, the effective current in the inductor current refers to the current flowing into the battery pack through the inductor. In the scenario where the power converter discharges the battery pack, the effective current in the inductor current refers to the current flowing out of the battery pack to the inductor.

[0046] Negative current of inductor current: It refers to the current with a direction opposite to the direction of the effective current in the inductor current. Among them, in the scenario where the power converter charges the battery pack, the negative current in the inductor current refers to the current flowing out of the battery pack to the inductor. In the scenario where the power converter discharges the battery pack, the negative current in the inductor current refers to the current flowing into the battery pack through the inductor.

[0047] Four-stage current waveform: It means that within one wave generation cycle, the waveform of the inductor current includes 4 stages. For example, the first stage is the rising stage, the second stage is the high-level holding stage, the third stage is the falling stage, and the fourth stage is the low-level holding stage. Or, the first stage is the falling stage, the second stage is the low-level holding stage, the third stage is the rising stage, and the fourth stage is the high-level holding stage. It can be understood that the inductor current in the above first and second stages is the effective current. In the third stage, the inductor current changes from the effective current to the negative current, and the inductor current in the fourth stage is the negative current.

[0048] Soft switch: It refers to that through specific control methods, the switching tube is turned off or on when the voltage or current passes through zero, so as to achieve approximate zero loss in the switching process.

[0049] Figure 2 It is a schematic structural diagram of an energy storage system provided by an embodiment of the present application. As Figure 2 shown, the energy storage system may include: a power converter 10 and at least one battery pack 20. Among them, the at least one battery pack 20 may refer to one battery pack 20, or multiple battery packs 20 connected in series. For example, Figure 2 taking the energy storage system including multiple battery packs 20 connected in series as an example for illustration. The power converter 10 is also called a power supply module, and it can be at least used to implement direct current / direct current (DC / DC) power conversion. Exemplarily, the power converter 10 may be a DC / DC converter, or may be a power conversion system (PCS). Among them, the power conversion system may include a DC / DC converter and a DC / AC converter.

[0050] Continue to refer to Figure 2 , one end of the power converter 10 is connected to at least one battery pack 20. If the power converter 10 is a DC / DC converter, the other end of the power converter 10 may be connected to a DC load and other DC power sources (such as photovoltaic modules). And, the DC / DC converter is used to convert the direct current of at least one battery pack 20 and then supply power to the DC load, and is used to convert the direct current provided by other DC power sources and then charge the at least one battery pack 20.

[0051] Or, the other end of the power converter 10 may be connected to the power grid and / or an AC load through a DC / AC converter. And, the DC / DC converter is used to convert the direct current of at least one battery pack 20 and then output it to the DC / AC converter, so that the DC / AC converter converts the direct current into alternating current and then outputs it to the power grid and / or the AC load. The DC / AC converter can also convert the alternating current of the power grid into direct current, and the DC / DC converter is also used to convert the direct current output by the DC / AC converter and then charge the at least one battery pack 20.

[0052] If the power converter 10 is a battery energy storage converter, the other end of the power converter 10 can be directly connected to the power grid and / or AC load. Moreover, the battery energy storage converter is configured to convert the direct current provided by at least one battery pack 20 into alternating current and output it to the power grid and / or AC load, and to convert the alternating current provided by the power grid into direct current and output it to the at least one battery pack 20 to charge the at least one battery pack 20.

[0053] It can be understood that the power converter 10 generally includes a controller and a power conversion circuit, and the power conversion circuit at least includes a DC / DC conversion circuit. The DC / DC conversion circuit includes at least one switching tube and an inductor. For example, the DC / DC conversion circuit can be a buck-boost circuit, and the buck-boost circuit can include 4 switching tubes and an inductor. The controller is configured to provide a PWM signal to at least one switching tube included in the DC / DC conversion circuit to control the on / off state of the at least one switching tube. Among them, the PWM signal is also called a PWM wave. Therefore, the controller providing a PWM signal to at least one switching tube can also be referred to as sending a wave to the at least one switching tube.

[0054] During the process of the controller sending a wave to the DC / DC conversion circuit, for example, during the triangular current mode (TCM) control process, a new wave generation cycle is usually triggered based on the zero-crossing comparison signal of the inductor current (i.e., the TZ signal). The zero-crossing comparison signal is crucial for implementing soft-switching control of power devices. Soft-switching technology can reduce switching losses and improve the efficiency and reliability of the power converter. For example, in the zero current switching (ZCS) technology, by means of an accurate zero-crossing detection technology of the inductor current, the switching tube can be controlled to turn off when the inductor current is zero. Thus, the current tail phenomenon during the turn-off of the switching tube can be avoided, and the turn-off loss of the switching tube can be significantly reduced.

[0055] In some embodiments, the power converter 10 further includes a comparator, which is capable of comparing the amplitude of the inductor current with the amplitude of the zero-crossing reference signal and outputting a zero-crossing comparison signal. Among them, the inductor current refers to the current flowing through the inductor in the power conversion circuit. And, as Figure 3 shown ( Figure 3 taking the four-segment current waveform as an example), when the amplitude of the inductor current is less than the amplitude of the zero-crossing reference signal, the zero-crossing comparison signal output by the comparator is at a high level to indicate that the inductor current crosses zero; when the amplitude of the inductor current is greater than the amplitude of the zero-crossing reference signal, the zero-crossing comparison signal output by the comparator is at a low level.

[0056] During the dynamic process of the power converter 10 switching from light load to heavy load, when the controller generates pulses for the switching devices in the power conversion circuit, the pulse generation mode needs to be changed from the light load mode to the heavy load mode. After the pulse generation mode is changed, the magnitude of the negative current of the inductor current will change (for example, the negative current will decrease), so the amplitude of the zero-crossing reference signal also needs to be changed correspondingly (for example, it needs to be decreased correspondingly) to ensure that the soft switching of the switching devices can be achieved. For example, in the light load mode, the negative current of the inductor current fluctuates around 0 A (such as ±4 A), and at this time, the amplitude of the zero-crossing reference signal is generally 7 A. In the heavy load mode, the negative current of the inductor current will decrease, for example, it will decrease to about -7 A, and at this time, the amplitude of the zero-crossing reference signal needs to be decreased to about 0 A. If the amplitude of the zero-crossing reference signal is directly adjusted, it may cause the inductor current to always be greater than the amplitude of the modified zero-crossing reference signal. Furthermore, it may cause the zero-crossing comparison signal output by the comparator to be abnormal and cause abnormal pulse generation by the controller.

[0057] For example, referring to Figure 3 , before time t1, the inductor current is greater than the amplitude TZ1 of the zero-crossing comparison signal, and the zero-crossing comparison signal output by the comparator is at a low level. At time t1, the inductor current crosses zero and enters the low-level holding stage, that is, enters the fourth stage. During this low-level holding stage, the inductor current is less than the amplitude TZ1 of the zero-crossing comparison signal, and the zero-crossing comparison signal output by the comparator jumps from a low level to a high level. At time t2, the blanking signal is at a high level. At this time, the trigger signal obtained by performing a logical AND operation on the zero-crossing comparison signal and the blanking signal is at a high level. Correspondingly, the controller can trigger a new pulse generation cycle based on the high level of this trigger signal. Among them, the blanking signal is at a low level after the start of each new pulse generation cycle, and jumps to a high level when the duration of the new pulse generation cycle reaches a preset duration. This preset duration is usually determined based on the highest switching frequency that the switching devices in the power conversion circuit can withstand. For example, assuming that the highest switching frequency that the switching devices can withstand is 22 kilohertz (KHz), then this preset duration can be the duration corresponding to 22 KHz, that is, 45 microseconds (us).

[0058] Continuing to refer to Figure 3, in the new wave transmission cycle, after the inductor current rises to a value greater than the amplitude TZ1 of the zero-crossing comparison signal, the zero-crossing comparison signal output by the comparator is at a low level. At time t3 in the new wave transmission cycle, the inductor current crosses zero again and enters the low-level holding stage. Correspondingly, the inductor current is less than the amplitude TZ1 of the zero-crossing comparison signal, and the zero-crossing comparison signal output by the comparator jumps from a low level to a high level. Assume that at time t4 after time t3, the power converter 10 switches from a light load to a heavy load, and the controller directly adjusts the amplitude of the zero-crossing reference signal from TZ1 to TZ2. At this time, although the inductor current is still in the low-level holding stage, that is, it is still in the fourth section, it will be greater than the amplitude TZ2 of the modified zero-crossing reference signal, that is, the inductor current (i.e., negative current) in the fourth section is greater than the amplitude TZ2 of the zero-crossing reference signal. Correspondingly, the level of the zero-crossing comparison signal output by the comparator will jump to a low level.

[0059] After time t4, when the duration of the new wave transmission cycle reaches the preset duration (for example, the duration corresponding to 22KHz), the blanking signal jumps to a high level. However, since the zero-crossing comparison signal is at a low level at this time, the trigger signal obtained after the blanking signal and the zero-crossing comparison signal are logically ANDed is a low level. That is, at the preset duration after time t2, the high level of the zero-crossing comparison signal is lost, resulting in the loss of the rising edge of the trigger signal, which in turn causes the controller to fail to trigger the next new wave transmission cycle. At time t5, when the counter counts the preset maximum cycle (for example, the duration of 100us corresponding to 10KHz), the controller will trigger the next new wave transmission cycle.

[0060] It is understandable that if Figure 3 As shown, after the inductor current passes through zero, the peak value of the negative flow of the inductor current (for example, the current value of the inductor current in the fourth section) can be maintained near the amplitude of the zero-crossing reference signal until a new wave-generating cycle is triggered. Therefore, if the amplitude of the zero-crossing reference signal is adjusted after the inductor current passes through zero, and the amplitude of the adjusted zero-crossing reference signal is less than the peak value of the negative flow of the inductor current, the high level of the zero-crossing comparison signal will be lost, which will lead to abnormal wave generation of the controller and abnormal inductor current.

[0061] It can also be understood that after the switching of the wave-generating mode is completed, if the amplitude of the zero-crossing reference signal can be adjusted before the inductor current crosses zero, it can be ensured that in the process of the inductor current changing from an effective current to a negative current, the comparator can directly detect whether the inductor current crosses zero based on the amplitude of the adjusted zero-crossing reference signal. However, since the frequency of the inductor current is variable, for example, its frequency may vary within a frequency range of 10KHz to 30KHz, it is difficult to ensure that the moment of adjusting the amplitude of the zero-crossing reference signal is definitely before the moment when the inductor current crosses zero.

[0062] An embodiment of the present application provides a power converter, which can solve the technical problem of abnormal wave generation of the controller caused by adjusting the amplitude of the zero-crossing reference signal after the inductor current crosses zero. As Figure 4 shown, the power converter 10 provided by the embodiment of the present application includes: a controller 11 and a power conversion circuit 12. Among them, the controller 11 includes a signal processing circuit 111, a comparator 112, and a wave generation circuit 113. The power converter 10 is used to charge or discharge the battery 20. For example, the power conversion circuit 12 in the power converter 10 is used to charge or discharge the battery 20. The power conversion circuit 12 includes an inductor and at least one switching tube. The power conversion circuit 12 can be a DC / DC conversion circuit. For example, referring to Figure 5 , the power conversion circuit 12 can be a buck-boost circuit, and the buck-boost circuit includes four switching tubes (Q1 to Q4) and an inductor L1.

[0063] Continuing to refer to Figure 4 , the signal processing circuit 111 is used to output a zero-crossing reference signal of the inductor current (also referred to as the TZ reference signal) to the comparator 112, and is used to adjust the amplitude of the zero-crossing reference signal from a first amplitude TZ1 to a second amplitude TZ2 at a target rate after detecting that the power converter 10 meets the target condition. That is, the signal processing circuit 111 is used to gradually change the amplitude of the zero-crossing reference signal from the first amplitude TZ1 to the second amplitude TZ2 at a target rate (also referred to as the target step).

[0064] The comparator 112 is used to compare the amplitude of the zero-crossing reference signal and the amplitude of the inductor current, and output a zero-crossing comparison signal (also referred to as the TZ signal) to the wave generation circuit 113. Among them, the inductor current refers to the current flowing through the inductor L1. And when the amplitude of the inductor current reaches (i.e., rises to or drops to) the amplitude of the zero-crossing reference signal, the level of the zero-crossing comparison signal output by the comparator 113 will jump.

[0065] In the embodiment of the present application, during the process of the inductor current changing from the effective current to the negative current, if the amplitude of the inductor current reaches the amplitude of the zero-crossing reference signal, the zero-crossing comparison signal output by the comparator 113 can jump from the first level to the second level. Among them, the first level can be referred to as the invalid level, and the second level can be referred to as the valid level. And the first level can be a high level or a low level relative to the second level. It can be seen that the jump edge of the zero-crossing reference signal jumping from the first level to the second level can indicate the zero-crossing of the inductor current.

[0066] A wave generating circuit 113 is configured to determine a wave generating period based on the zero-crossing comparison signal and send a wave to at least one switching transistor in the power conversion circuit 12 according to the wave generating period. Herein, the wave sent by the wave generating circuit 113 may refer to sending a pulse-width modulation (PWM) signal to the switching transistor, and this PWM signal is also called a PWM wave.

[0067] For example, the wave generating circuit 113 may trigger a new wave generating period when it determines that the inductor current crosses zero based on the zero-crossing comparison signal. Thus, it can be ensured that at least one switching transistor in the power conversion circuit 12 can switch its switching state when the inductor current crosses zero, thereby effectively reducing the switching loss of the switching transistor and improving the efficiency and reliability of the power converter.

[0068] In the embodiment of the present application, the above target rate is less than the change rate when the inductor current changes from the effective current to the negative current (hereinafter referred to as the reference rate). For example, in a four-segment current waveform, the reference rate may refer to the change rate of the inductor current in the third segment. The current direction of the negative current is opposite to that of the effective current. And when the power converter 10 charges the battery pack 20, the effective current refers to the current flowing into the battery pack 20 through the inductor L1, and when the power converter 10 discharges the battery pack 20, the effective current refers to the current flowing out of the battery pack 20 to the inductor L1.

[0069] In the embodiment of the present application, after the power converter 10 meets the target condition, the peak value of the negative current of the inductor current will change (for example, the absolute value of the peak value will increase), so it is necessary to correspondingly adjust the amplitude of the zero-crossing reference signal.

[0070] It can be understood that if the amplitude of the effective current is positive and the amplitude of the negative current is negative, then the amplitude of the effective current is greater than the amplitude of the negative current. Correspondingly, the above second amplitude is less than the first amplitude, that is, the target rate is the decreasing rate of the amplitude of the zero-crossing reference signal. And when the amplitude of the inductor current is less than the amplitude of the zero-crossing reference signal, the zero-crossing comparison signal output by the comparator is the second level (i.e., the effective level) to indicate that the inductor current crosses zero.

[0071] If the amplitude of the effective current is negative and the amplitude of the negative current is positive, then the amplitude of the effective current is less than the amplitude of the negative current. Correspondingly, the above second amplitude is greater than the first amplitude, that is, the target rate is the increasing rate of the amplitude of the zero-crossing reference signal. And when the amplitude of the inductor current is greater than the amplitude of the zero-crossing reference signal, the zero-crossing comparison signal output by the comparator is the second level (i.e., the effective level) to indicate that the inductor current crosses zero.

[0072] As described above, after the inductor current crosses zero, if the amplitude of the zero-crossing reference signal changes too fast, it may cause both the effective current and the negative current of the inductor current to be greater than (or both less than) the amplitude of the zero-crossing reference signal after the change. As a result, the comparator cannot accurately distinguish the effective current and the negative current of the inductor current based on the zero-crossing reference signal after the amplitude change, that is, it cannot accurately detect whether the inductor current crosses zero, and further causes the zero-crossing comparison signal output by the comparator to be abnormal. In the embodiment of the present application, since the adjustment rate of the amplitude of the zero-crossing reference signal (i.e., the target rate) is less than the change rate when the inductor current changes from the effective current to the negative current, it can be ensured that the comparator can accurately distinguish the effective current and the negative current of the inductor current based on the amplitude of the zero-crossing reference signal, that is, detect whether the inductor current crosses zero, and further ensure the reliability of the zero-crossing comparison signal output by the comparator. Correspondingly, the wave generation circuit can accurately trigger a new wave generation cycle based on the zero-crossing comparison signal.

[0073] Moreover, since the adjustment rate of the amplitude of the zero-crossing reference signal is less than the change rate when the inductor current changes from the effective current to the negative current, even if the signal processing current adjusts the amplitude of the zero-crossing reference signal after the inductor current crosses zero, it can be ensured that the magnitude relationship between the amplitude of the adjusted zero-crossing reference signal and the amplitude of the inductor current remains unchanged. For example, if the amplitude of the effective current is positive and the amplitude of the negative current is negative, after the inductor current crosses zero, since the decreasing rate of the amplitude of the zero-crossing reference signal is less than the decreasing rate of the negative current of the inductor current, it can be ensured that the amplitude of the zero-crossing reference signal is always greater than the amplitude of the negative current of the inductor current. If the amplitude of the effective current is negative and the amplitude of the negative current is positive, after the inductor current crosses zero, since the increasing rate of the amplitude of the zero-crossing reference signal is less than the increasing rate of the negative current of the inductor current, it can be ensured that the amplitude of the zero-crossing reference signal is always less than the amplitude of the negative current of the inductor current. Thus, it can be ensured that the comparator can accurately detect whether the inductor current crosses zero based on the amplitude of the zero-crossing reference signal, and further avoid the zero-crossing comparison signal output by the comparator from being abnormal.

[0074] Based on the above analysis, it can be seen that in the solution provided by the embodiment of the present application, the signal processing circuit can start to adjust the amplitude of the zero-crossing reference signal at any time after the power converter meets the target conditions. That is, the adjustment time of the amplitude of the zero-crossing reference signal is not limited by the zero-crossing time of the inductor current, thereby effectively improving the flexibility when adjusting the amplitude of the zero-crossing reference signal.

[0075] Optionally, the adjustment direction of the amplitude of the zero-crossing reference signal by the signal processing circuit 111 is the same as the change direction when the inductor current changes from the effective current to the negative current.

[0076] As a possible example, referring to Figure 6, assume a scenario where the power converter 10 charges the battery pack 20. The amplitude of the effective current of the inductor current is positive, and the amplitude of the negative current is negative. That is, the amplitude of the effective current of the inductor current is greater than 0, and the amplitude of the negative current is less than 0. In this example, within each wave generation cycle, after the amplitude of the effective current of the inductor current rises to the peak, it will decrease to the negative current at the reference rate. Correspondingly, when the amplitude of the zero-crossing reference signal needs to be reduced, the signal processing circuit 111 can reduce the amplitude of this zero-crossing reference signal at the target rate. That is, the above-mentioned second amplitude TZ2 is less than the first amplitude TZ1.

[0077] It can be understood that in this example, since the target rate is less than the reference rate, it can be ensured that within each wave generation cycle, the negative current of the inductor current (such as the fourth-segment inductor current) can always be less than the amplitude of the zero-crossing reference signal. Thus, it can be ensured that the comparator can accurately detect whether the inductor current crosses zero based on the amplitude of this zero-crossing reference signal, and further effectively avoid the abnormality of the zero-crossing comparison signal output by the comparator, ensuring the normal wave generation of the controller.

[0078] It can also be understood that in this example, if the amplitude of the zero-crossing reference signal needs to be increased, then since the amplitude of the zero-crossing reference signal will surely be greater than the amplitude of the negative current of the inductor current after the amplitude of the zero-crossing reference signal increases, the signal processing circuit 111 can directly increase the amplitude of this zero-crossing reference signal. That is, the amplitude of the zero-crossing reference signal can be directly increased from the current value to the target value without the need for adjustment in a slow-changing manner.

[0079] As another possible example, refer to Figure 7 , assume a scenario where the power converter 10 discharges the battery pack 20. The amplitude of the effective current of the inductor current is negative, and the amplitude of the negative current is positive. That is, the amplitude of the effective current of the inductor current is less than 0, and the amplitude of the negative current is greater than 0. In this example, within each wave generation cycle, after the amplitude of the effective current of the inductor current drops to the peak, it will rise to the negative current at the reference rate. Correspondingly, when the amplitude of the zero-crossing reference signal needs to be increased, the signal processing circuit 111 can increase the amplitude of this zero-crossing reference signal at the target rate. That is, the above-mentioned second amplitude TZ2 is greater than the first amplitude TZ1.

[0080] It can be understood that in this example, since the target rate is less than the reference rate, it can be ensured that within each wave generation cycle, the negative current of the inductor current (such as the fourth-segment inductor current) can always be greater than the amplitude of the zero-crossing reference signal. Thus, it can be ensured that the comparator can accurately detect whether the inductor current crosses zero based on the amplitude of this zero-crossing reference signal, and further effectively avoid the abnormality of the zero-crossing comparison signal output by the comparator, ensuring the normal wave generation of the controller.

[0081] It can also be understood that in this example, if the amplitude of the zero-crossing reference signal needs to be reduced, since the amplitude of the zero-crossing reference signal will surely be less than the amplitude of the negative current of the inductor current after the reduction, the signal processing circuit 111 can directly reduce the amplitude of the zero-crossing reference signal. That is to say, the amplitude of the zero-crossing reference signal can be directly reduced from the current value to the target value without adjustment by a slow-changing method.

[0082] The above is an illustration by taking the current direction of the effective current during the charging of the battery pack 20 as the positive direction, that is, an illustration with the effective current during charging as positive. It can be understood that the positive and negative of this effective current (i.e., the positive direction of the inductor current) can be flexibly set according to the requirements of the application scenario. For example, the current direction during the discharging of the battery pack 20 can also be used as the positive direction of the inductor current. Correspondingly, during the charging of the battery pack 20, the effective current of the inductor current is negative and the negative current is positive; during the discharging of the battery pack 20, the effective current of the inductor current is positive and the negative current is negative. The embodiments of the present application do not limit the positive direction of this inductor current.

[0083] Optionally, as Figure 4 shown, the controller 11 may further include a current detection circuit 114, and the current detection circuit 114 can detect the inductor current flowing through the inductor and output it to the comparator 112.

[0084] It can be understood that each component included in the controller 11 can be discrete components, that is, the above signal processing circuit 111, current detection circuit 114, comparator 112, and wave generation circuit 113 can be discretely arranged. Or, some components in the controller 11 can be integrally arranged. For example, the current detection circuit 114, signal processing circuit 111, and comparator 112 can be integrally arranged. Or, each component in the controller 11 can be integrated in one chip, that is, the controller 11 can be an integrated chip.

[0085] Exemplarily, the signal processing circuit 111 can be a digital signal processor (DSP) or a complex programmable logic device (CPLD). And, the signal processing circuit 111 can include a digital-to-analog converter (DAC), and the DAC can output a zero-crossing reference signal (i.e., the TZ reference signal). The current detection circuit 114 and the comparator 112 can be integrated in the signal processing circuit 111. The wave generation circuit 113 can be a micro-controller unit (MCU).

[0086] Optionally, the power converter 10 meeting the target condition may include at least one of the following:

[0087] The power converter 10 switches from light load to heavy load;

[0088] The number of battery packs 20 connected to the power converter 10 increases;

[0089] The battery pack 20 connected to the power converter 10 switches from the charging state to the discharging state, or from the discharging state to the charging state.

[0090] Among them, when the power converter 10 switches from light load to heavy load, the wave generating circuit 113 will adjust its wave generating mode from the light load mode to the heavy load mode. And, compared with the light load mode, when the power converter 10 is in the heavy load mode, the change rate of the inductor current from the effective current to the negative current will increase, which will further cause the absolute value of the peak value of the negative current to increase. Among them, if the amplitude of the negative current of the inductor current is negative, then in the heavy load mode, the peak value of the negative current of the inductor current will decrease compared with the light load mode. Correspondingly, the amplitude of the zero-crossing reference signal also needs to decrease correspondingly. If the amplitude of the negative current of the inductor current is positive, then in the heavy load mode, the peak value of the negative current of the inductor current will increase compared with the light load mode. Correspondingly, the amplitude of the zero-crossing reference signal also needs to increase correspondingly.

[0091] When the number of battery packs 20 connected to the power converter 10 increases, even if the wave generating mode of the wave generating circuit 113 remains unchanged, the output voltage of the power converter 10 will increase. Correspondingly, the absolute value of the peak value of the negative current of the inductor current will also increase. Among them, if the negative current of the inductor current is negative, then when the number of battery packs 20 increases, the peak value of the negative current of the inductor current will decrease. Correspondingly, the amplitude of the zero-crossing reference signal also needs to decrease correspondingly. If the negative current of the inductor current is positive, then when the number of battery packs 20 increases, the peak value of the negative current of the inductor current will increase. Correspondingly, the amplitude of the zero-crossing reference signal also needs to increase correspondingly.

[0092] It can be understood that when the battery pack 20 connected to the power converter 10 is in the charging state, the output voltage of the power converter 10 refers to the voltage output to the battery pack 20. When the battery pack 20 connected to the power converter 10 is in the discharging state, the output voltage of the power converter 10 refers to the voltage output to the DC bus (i.e., the load).

[0093] When the battery pack 20 connected to the power converter 10 switches from the charging state to the discharging state, or from the discharging state to the charging state, the wave generating circuit 113 will adjust its wave generating mode. And, the current direction of the effective current of the inductor current will change, that is, the current direction of the negative current will change. During the above charge-discharge conversion process, the magnitude of the negative current of the inductor current will also change. For example, refer to Figure 6 andFigure 7 When the charging state is switched to the discharging state, the amplitude of the negative current changes from negative to positive, that is, the negative current peak value increases. Correspondingly, the amplitude of the zero-crossing reference signal also needs to increase correspondingly. When the discharging state is switched to the charging state, the amplitude of the negative current changes from positive to negative, that is, the amplitude of the negative current decreases. Correspondingly, the amplitude of the zero-crossing reference signal also needs to decrease correspondingly.

[0094] Optionally, the wave generating circuit 113 is further configured to adjust the wave generating mode when the power converter 10 meets the target conditions. For example, when the power conversion circuit 12 switches from light load to heavy load, or when the battery pack 20 connected to the power conversion circuit 12 switches from the charging state to the discharging state, or when the battery pack 20 connected to the power conversion circuit 12 switches from the discharging state to the charging state, the wave generating circuit 113 can adjust its wave generating mode.

[0095] And, the signal processing circuit 111 is configured to reduce the amplitude of the zero-crossing reference signal from the first amplitude TZ1 to the second amplitude TZ2 at the target rate after the target duration after the wave generating mode is adjusted.

[0096] Wherein, the target duration can be pre-configured in the signal processing circuit 111, and the target duration can be the duration required for the wave generating circuit 113 to switch the wave generating mode. It can be understood that the wave generating circuit 113 needs to adjust its drive configuration parameters when switching the wave generating mode, and the above target duration can be understood as the duration required for the adjusted drive configuration parameters to take effect. Thus, it can be ensured that the wave generating mode of the wave generating circuit is successfully switched after the target duration, that is, the change rate of the inductor current from the effective current to the negative current will increase, and further the absolute value of the negative current peak will increase compared with that before the switch. At this time, the signal processing circuit adjusts the amplitude of the reference signal again, which can ensure that the comparator accurately detects whether the inductor current passes through zero.

[0097] Optionally, at least one switching transistor in the power conversion circuit 12 may include two main switching transistors and two freewheeling switching transistors. By way of example, such as Figure 5As shown, the power conversion circuit 12 can be a four-switch buck-boost circuit. The four-switch buck-boost circuit includes a total of 4 switching transistors Q1 to Q4. The 4 switching transistors include a first main switching transistor, a second main switching transistor, a first freewheeling switching transistor, and a second freewheeling switching transistor. Among them, the first main switching transistor and the second freewheeling switching transistor (such as Q1 and Q2) are connected in series between the positive and negative electrodes of the first end of the power conversion circuit 12, and the first freewheeling switching transistor and the second main switching transistor (such as Q3 and Q4) are connected in series between the positive and negative electrodes of the second end of the power conversion circuit 12. One end of the inductor L1 is connected to the series node between the first main switching transistor and the second freewheeling switching transistor, and the other end of the inductor L1 is connected to the series node between the first freewheeling switching transistor and the second main switching transistor.

[0098] It can be understood that, as Figure 5 shown, one of the first end and the second end of the power conversion circuit 12 is used to connect to the battery pack 20, and its voltage can be expressed as Vbat, and the other end is used to connect to the DC bus, and its voltage can be expressed as Vbus. It can also be understood that when the battery pack 20 connected to the power conversion circuit 12 is in the discharging state, the switching transistors Q1 and Q4 among the 4 switching transistors are the main switching transistors, and Q2 and Q3 are the freewheeling switching transistors. For example, the switching transistor Q1 is the first main switching transistor, the switching transistor Q4 is the second main switching transistor, the switching transistor Q3 is the first freewheeling switching transistor, and the switching transistor Q2 is the second freewheeling switching transistor. When the battery pack 20 connected to the power conversion circuit 12 is in the charging state, the switching transistors Q2 and Q3 among the 4 switching transistors are the main switching transistors, and Q1 and Q4 are the freewheeling switching transistors. For example, the switching transistor Q3 is the first main switching transistor, the switching transistor Q2 is the second main switching transistor, the switching transistor Q1 is the first freewheeling switching transistor, and the switching transistor Q4 is the second freewheeling switching transistor.

[0099] The following takes the case where the battery pack 20 is in the discharging state as an example for illustration. As Figure 8As shown, in the light load mode, each wave generation period includes a first wave generation period t11, a second wave generation period t12, and a third wave generation period t13. Among them, during the first wave generation period t11, two main switch tubes Q1 and Q4 are turned on, and two freewheeling switch tubes Q2 and Q3 are turned off. At this time, the inductor current gradually increases at a relatively fast rate. During the second wave generation period t12, the first main switch tube Q1 and the first freewheeling switch tube Q3 are turned on, and the second main switch tube Q4 and the second freewheeling switch tube Q2 are turned off. At this time, the inductor current continues to increase at a relatively slow rate. During the third wave generation period t13, all four switch tubes Q1 to Q4 are turned off. At this time, since the two freewheeling switch tubes Q2 and Q3 have parasitic diodes (also called body diodes), the inductor current can form a discharge loop through the parasitic diodes of the two freewheeling switch tubes Q2 and Q3, and the inductor current begins to decrease at the reference rate. After the inductor current drops to 0, since the freewheeling switch tubes Q2 and Q3 are not turned on, the inductor current resonates near the zero crossing point, that is, the inductor current will enter the low-level holding stage of the fourth segment.

[0100] In the embodiment of the present application, during each wave generation period in the light load mode, the two freewheeling switch tubes are not turned on simultaneously, so the power consumption of the power conversion circuit in the light load mode can be effectively reduced.

[0101] After the power converter 10 switches from light load to heavy load, the wave generation circuit 113 can generate waves according to the heavy load mode. And, continuing to refer to Figure 8 , each wave generation period in this heavy load mode may include a fourth wave generation period t14, a fifth wave generation period t15, a sixth wave generation period t16, and a seventh wave generation period t17. During the fourth wave generation period t14, two main switch tubes Q1 and Q4 are turned on, and two freewheeling switch tubes Q2 and Q3 are turned off. At this time, the inductor current gradually increases at a relatively fast rate. During the fifth wave generation period t15, the first main switch tube Q1 and the first freewheeling switch tube Q3 are turned on, and the second main switch tube Q4 and the second freewheeling switch tube Q2 are turned off. At this time, the inductor current continues to increase at a relatively slow rate. During the sixth wave generation period t16, the two freewheeling switch tubes Q2 and Q3 are turned on, and the two main switch tubes Q1 and Q4 are turned off. At this time, the inductor current gradually decreases to 0 at the reference rate, and after dropping to 0, it will continue to decrease to a negative value at the reference rate. During the seventh wave generation period t17, the first freewheeling switch tube Q3 is turned off, and the second freewheeling switch tube Q2 is turned on, and the inductor current is maintained at a negative value, that is, it enters the low-level holding stage of the fourth segment.

[0102] Exemplarily, such as Figure 8As shown in the figure, assume that at time T1, the power converter 10 switches from light load to heavy load. Then, the wave generating circuit 113 can switch the wave generating mode from the light load mode to the heavy load mode at this T1 moment, that is, switch from light load wave generation to heavy load wave generation. If the time required for the wave generating circuit 113 to switch the wave generating mode is 300 μs, that is, the target time is 300 μs, then the signal processing circuit 111 can start adjusting the amplitude of the zero-crossing reference signal at the target rate 300 μs after time T1, that is, at time T2. Thus, it can be ensured that when adjusting the amplitude of the zero-crossing reference signal, the heavy load wave generation (for example, wave generation for two freewheeling switching tubes Q2 and Q3) is successfully switched.

[0103] It can be understood that the power conversion circuit 12 can be other types of DC / DC conversion circuits in addition to the buck-boost circuit. For example, it can also be an LCC power conversion circuit. Here, L refers to inductor, and C refers to capacitor.

[0104] Optionally, one of the first amplitude TZ1 and the second amplitude TZ2 is positive, and the other is negative. And, the absolute values of the first amplitude TZ1 and the second amplitude TZ2 can be equal. For example, the first amplitude TZ1 can be 7 amperes (A), and the second amplitude TZ2 can be -7 A. Or, the first amplitude TZ1 can be -7 A, and the second amplitude TZ2 can be 7 A.

[0105] Or, one of the first amplitude TZ1 and the second amplitude TZ2 can be 0. Correspondingly, the other can be positive or negative. For example, one of the first amplitude TZ1 and the second amplitude TZ2 can be 0 A, and the other can be 7 A or -7 A.

[0106] Or, the first amplitude TZ1 and the second amplitude TZ2 can also be both positive or both negative, and the embodiments of the present application do not limit this.

[0107] It can be understood that the above reference rate can be calculated based on the hardware topology of the power conversion circuit 12. For example, based on the hardware topology of the power conversion circuit 12, the change rate of the inductor current from the effective current to the negative current under different working conditions can be calculated. And, if the change rate of the inductor current from the effective current to the negative current is different under different working conditions, the above target rate can be configured based on the minimum change rate, that is, the above target rate can be less than the minimum change rate. Thus, it can be ensured that under different working conditions, after adjusting the amplitude of the zero-crossing reference signal at the target rate, the comparator can accurately detect whether the inductor current passes through zero based on the adjusted zero-crossing reference signal, and further ensure the reliability of the zero-crossing comparison signal output by the comparator.

[0108] Optionally, the order of magnitude of the above target rate can be amperes per 100 microseconds (A / 100us). For example, as Figure 8 shown, the above target rate can be 1.4A / 100us. If the first amplitude TZ1 is 7A and the second amplitude TZ2 is -7A, the signal processing circuit 111 adjusts the amplitude of the zero-crossing reference signal at a rate of 1.4A / 100us. Correspondingly, the signal processing circuit 111 takes 1 millisecond (ms) to complete the gradual change of the amplitude of the zero-crossing reference signal. That is, Figure 8 the duration between time T3 and time T1 in Figure 8 can be 1ms. It can be understood that Figure 8 the number of wave generation cycles included between time T1 and time T2, and between time T2 and time T3 shown in

[0109] is only for illustration. In practical applications,

[0110] the number of wave generation cycles included between each moment in

[0111] can be flexibly adjusted according to the scenario requirements. Optionally, the wave generation circuit 113 can also be used to control the wave generation cycle to be greater than or equal to the switching cycle corresponding to the highest switching frequency of at least one switching tube in the power conversion circuit 12.

[0112] For example, assume that the highest switching frequency of at least one switching tube in the power conversion circuit 12 is 22KHz. Then the wave generation circuit 113 can control the wave generation cycle to be greater than or equal to the switching cycle corresponding to 22KHz, that is, 45us. By controlling the wave generation cycle to be greater than or equal to the above switching cycle, it can effectively prevent the switching frequency of the switching tube in the power conversion circuit 12 from being higher than the highest switching frequency, thereby avoiding damage to the switching tube. Figure 9 As

[0113] Assume that the second level is high relative to the first level. Then, the wave generating circuit 113 can perform a logical AND operation on the zero-crossing comparison signal and the blanking signal to generate a trigger signal. Moreover, the wave generating circuit 113 can trigger a new wave generating cycle when the trigger signal is high. Thus, not only can it ensure that the switching state of the switching transistor is switched when the inductor current passes through zero, so as to reduce the switching loss of the switching transistor, but also it can effectively prevent the switching frequency of the switching transistor from being too high and damaging the switching transistor.

[0114] Exemplarily, the wave generating circuit 113 may include an AND gate circuit. The two input terminals of the AND gate circuit are respectively used to receive the blanking signal and the zero-crossing comparison signal, and the output terminal of the AND gate circuit is used to output the trigger signal. Based on the principle of the AND gate circuit, it can be known that when both the blanking signal and the zero-crossing comparison signal are high, the output trigger signal is high.

[0115] Reference Figure 9 , for the scenario where the amplitude of the negative current of the inductor current is negative, the comparator 112 can output a high-level zero-crossing comparison signal when the amplitude of the inductor current is less than the amplitude of the zero-crossing reference signal, and can output a low-level zero-crossing comparison signal when the amplitude of the inductor current is greater than the amplitude of the zero-crossing reference signal. For the scenario where the amplitude of the negative current of the inductor current is positive, the comparator 112 can output a low-level zero-crossing comparison signal when the amplitude of the inductor current is less than the amplitude of the zero-crossing reference signal, and can output a high-level zero-crossing comparison signal when the amplitude of the inductor current is greater than the amplitude of the zero-crossing reference signal. Based on the above two scenarios, it can be known that the comparator 112 can output a high-level zero-crossing comparison signal when the inductor current passes through zero from the effective current and becomes a negative current.

[0116] Correspondingly, from Figure 9 it can be seen that the trigger signal generated by the wave generating circuit 113 is high when both the zero-crossing comparison signal and the blanking signal are high, and is low when any one of the zero-crossing comparison signal and the blanking signal is low. Moreover, the wave generating circuit 113 can trigger a new wave generating cycle when the trigger signal is high.

[0117] In summary, the embodiment of the present application provides a power converter. The signal processing circuit in the power converter can adjust the amplitude of the zero-crossing reference signal from a first amplitude to a second amplitude at a target rate after detecting that the power converter meets the target condition. Moreover, the target rate is less than the change rate when the inductor current changes from the effective current to the negative current. Therefore, even if the amplitude of the zero-crossing reference signal is adjusted after the inductor current passes through zero (i.e., after the inductor current becomes negative), it can be ensured that the magnitude relationship between the negative current of the inductor current and the amplitude of the zero-crossing reference signal remains unchanged before and after the amplitude adjustment. Correspondingly, the comparator can accurately detect whether the inductor current passes through zero based on the amplitude of the zero-crossing reference signal and accurately output a zero-crossing comparison signal. The wave generation circuit can then accurately trigger a new wave generation period based on the zero-crossing comparison signal.

[0118] The embodiment of the present application also provides an energy storage system, such as Figure 2 shown. The energy storage system includes at least one battery pack 20 and the power converter 10 provided in the above embodiment. The power converter 10 is connected to the at least one battery pack 20 and is used to charge or discharge the at least one battery pack 20. Wherein, the at least one battery pack 20 refers to one battery pack 20 or multiple battery packs 20 connected in series.

[0119] It can also be understood that the power converter 10 provided in the embodiment of the present application can be applied not only to the energy storage system but also to other fields. For example, the power converter 10 can also be applied to a charging pile.

[0120] In the embodiment of the present application, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. The term "at least one" means one or more, and "multiple" means two or more.

[0121] The term "and / or" in the embodiment of the present application is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0122] The above is only an alternative implementation mode of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A power converter, characterized in that: The power converter comprises: a controller and a power conversion circuit; the controller comprises a signal processing circuit, a comparator and a wave generating circuit; the power converter is used to charge or discharge the battery pack, and the power conversion circuit comprises an inductor and at least one switch tube; The signal processing circuit is used to output a zero-crossing reference signal to the comparator, and is used to adjust the amplitude of the zero-crossing reference signal from a first amplitude to a second amplitude according to a target rate after detecting that the power converter meets a target condition; The comparator is used to compare the amplitude of the zero-crossing reference signal with the amplitude of the inductor current, and output a zero-crossing comparison signal to the wave generating circuit, wherein the inductor current refers to the current flowing through the inductor; The wave-generating circuit is used to determine a wave-generating period according to the zero-crossing comparison signal, and to generate waves to the at least one switching tube according to the wave-generating period; Among them, the target rate is less than the change rate of the inductor current when it changes from an effective current to a negative current, and the current direction of the negative current is opposite to the current direction of the effective current; when the power converter charges the battery pack, the effective current refers to the current flowing into the battery pack through the inductor, and when the power converter discharges the battery pack, the effective current refers to the current flowing out of the battery pack to the inductor.

2. The power converter according to claim 1, characterized in that: The adjustment direction of the amplitude of the zero-crossing reference signal is the same as the change direction when the effective current changes to the negative current.

3. The power converter according to claim 1 or 2, characterized in that: The power converter satisfies the target condition including at least one of the following: The power converter switches from light load to heavy load; The number of battery packs connected to the power converter increases; The battery pack connected to the power converter switches from a charging state to a discharging state, or switches from a discharging state to a charging state.

4. The power converter according to any one of claims 1 to 3, characterized in that: The wave generating circuit is further used to adjust the wave generating mode when the wave is generated to the at least one switching tube when the power converter meets the target condition; The signal processing circuit is used to adjust the amplitude of the zero-crossing reference signal from the first amplitude to the second amplitude according to the target rate after the target duration after the wave transmission mode is adjusted.

5. The power converter according to any one of claims 1 to 4, characterized in that: The at least one switch tube comprises a first main switch tube, a second main switch tube, a first freewheeling switch tube and a second freewheeling switch tube; The first main switch tube and the second freewheeling switch tube are connected in series between the positive electrode and the negative electrode of the first end of the power conversion circuit, and the first freewheeling switch tube and the second main switch tube are connected in series between the positive electrode and the negative electrode of the second end of the power conversion circuit; One end of the inductor is connected to the series node between the first main switch tube and the second freewheeling switch tube, and the other end of the inductor is connected to the series node between the first freewheeling switch tube and the second main switch tube.

6. The power converter according to claim 5, characterized in that: The wave generating circuit is used to adjust the wave generating mode when transmitting waves to the at least one switching tube from the light load mode to the heavy load mode when the power converter is switched from the light load to the heavy load; In the light-load mode, each of the wave-generating cycles includes a first wave-generating period, a second wave-generating period, and a third wave-generating period. In the first wave-generating period, the first main switch tube and the second main switch tube are turned on, and the first freewheeling switch tube and the second freewheeling switch tube are turned off. In the second wave-generating period, the first main switch tube and the first freewheeling switch tube are turned on, and the second main switch tube and the second freewheeling switch tube are turned off. In the third wave-generating period, the first main switch tube, the second main switch tube, the first freewheeling switch tube, and the second freewheeling switch tube are all turned off. In the heavy load mode, each of the wave transmission cycles includes a fourth wave transmission period, a fifth wave transmission period, a sixth wave transmission period and a seventh wave transmission period. In the fourth wave transmission period, the first main switch tube and the second main switch tube are turned on, and the first freewheeling switch tube and the second freewheeling switch tube are turned off. In the fifth wave transmission period, the first main switch tube and the first freewheeling switch tube are turned on, and the second main switch tube and the second freewheeling switch tube are turned off. In the sixth wave transmission period, the first freewheeling switch tube and the second freewheeling switch tube are turned on, and the first main switch tube and the second main switch tube are turned off. In the seventh wave transmission period, the first freewheeling switch tube is turned off, and the second freewheeling switch tube is turned on.

7. The power converter according to any one of claims 1 to 6, characterized in that: When the power converter charges the battery pack, the amplitude of the effective current is positive, the amplitude of the negative current is negative, and the second amplitude is smaller than the first amplitude.

8. The power converter according to any one of claims 1 to 6, characterized in that: When the power converter discharges the battery pack, the amplitude of the effective current is negative, the amplitude of the negative current is positive, and the second amplitude is greater than the first amplitude.

9. The power converter according to any one of claims 1 to 8, characterized in that: The wave generating circuit is further used to control the wave generating period to be greater than or equal to the switching period corresponding to the highest switching frequency of the at least one switching tube.

10. The power converter according to claim 9, characterized in that: In the process that the inductor current changes from the effective current to the negative current, if the amplitude of the inductor current reaches the amplitude of the zero-crossing reference signal, the zero-crossing comparison signal output by the comparator jumps from the first level to the second level; The wave-generating circuit is further used to generate a blanking signal, and trigger a new wave-generating cycle when the blanking signal and the zero-crossing comparison signal are both at the second level; The blanking signal is at the first level after each of the wave transmission cycles begins, and changes to the second level after the duration of the first level reaches a target duration, and the target duration is greater than or equal to the switching cycle.

11. The power converter according to claim 10, characterized in that: The second level is a high level relative to the first level; The wave generation circuit is used for performing a logic AND operation on the blanking signal and the zero-crossing comparison signal to obtain a trigger signal, and is used for triggering a new wave generation cycle when the trigger signal is at the second level.

12. An energy storage system, characterized in that: The energy storage system includes at least one battery pack and a power converter as described in any one of claims 1 to 11, wherein the power converter is connected to the at least one battery pack and is used to charge or discharge the at least one battery pack.

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