Power converter, control method of power converter and energy storage system

Abstract

The embodiment of the invention discloses a power converter, a control method of the power converter and an energy storage system, relates to the technical field of energy, and solves the problem of how to reduce the complexity of a control circuit of DCDC power conversion circuits in the power converter under the condition that the power converter comprises a plurality of DCDC power conversion circuits which are connected in series. Specifically, the controller is used for sending a first pulse signal to control the first DCDC power conversion circuit to work and sending a second pulse signal to control the second DCDC power conversion circuit to work, so that the direct current bus charges the battery pack, or the battery pack discharges the direct current bus. Wherein the duty ratio of the first pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter; the second pulse signal has a fixed duty cycle and a fixed frequency.

Description

Technical Field

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

[0002] The energy storage system includes a power converter and a battery pack connected to one end of the power converter, and the other end of the power converter is used to connect to the DC bus. The power converter is used to adapt the voltage of the battery pack to the voltage of the DC bus and control the magnitude and direction of the current to realize the charging and discharging of the battery pack. The power converter can also be used to realize the balancing and protection functions of the battery pack, thereby improving the life and reliability of the battery pack.

[0003] Since each type of direct current to direct current (DCDC) power conversion circuit has its own advantages and disadvantages in terms of cost, volume, efficiency, operating range and electromagnetic interference, the power converter may include multiple different types of DCDC power conversion circuits connected in series, so that the advantages of multiple different types of DCDC power conversion circuits can be complemented. Alternatively, the power converter may also include multiple DCDC power conversion circuits of the same type connected in series, so that a higher voltage gain can be achieved.

[0004] However, when the power converter includes multiple DCDC power conversion circuits connected in series, each DCDC power conversion circuit uses the voltage and current at its two ends as feedback and control targets, and performs independent tracking control and protection, which will lead to a high complexity of the control circuit of the DCDC power conversion circuit in the power converter. How to reduce the complexity of the control circuit of the DCDC power conversion circuit in the power converter has become an urgent problem to be solved. Summary of the invention

[0005] The embodiments of the present application provide a power converter, a control method for the power converter, and an energy storage system, which solve the problem of how to reduce the complexity of the control circuit of the DCDC power conversion circuit in the power converter when the power converter includes multiple DCDC power conversion circuits connected in series.

[0006] In order to achieve the above purpose, the embodiment of the present application adopts the following technical solution:

[0007] In a first aspect of an embodiment of the present application, a power converter is provided, wherein a first end of the power converter is used to be connected to a DC bus, and a second end of the power converter is used to be connected to a battery pack. The power converter includes a first DCDC power conversion circuit, a second DCDC power conversion circuit, and a controller. One end of the first DCDC power conversion circuit is connected to the first end of the power converter, the other end of the first DCDC power conversion circuit is connected to one end of the second DCDC power conversion circuit, and the other end of the second DCDC power conversion circuit is connected to the second end of the power converter. The controller is used to send a first pulse signal to control the operation of the first DCDC power conversion circuit, and send a second pulse signal to control the operation of the second DCDC power conversion circuit, so that the DC bus charges the battery pack, or the battery pack discharges to the DC bus. Wherein, the duty cycle of the first pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter; the second pulse signal has a fixed duty cycle and a fixed frequency.

[0008] Based on this solution, the duty cycle of the first pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter, and the second pulse signal has a fixed duty cycle and a fixed frequency. The controller performs closed-loop control on the first DCDC power conversion circuit by sending the first pulse signal, and performs open-loop control on the second DCDC power conversion circuit by sending the second pulse signal, so that the DC bus charges the battery pack, or the battery pack discharges to the DC bus, without using the voltage and current at both ends of each DCDC power conversion circuit as feedback and control targets, and performing independent tracking control and protection. It is not necessary to set the voltage detection circuit and current detection circuit corresponding to each DCDC power conversion circuit, thereby reducing the complexity of the control circuit of the DCDC power conversion circuit in the power converter and reducing the cost of the power converter. Secondly, the controller performs closed-loop control on the first DCDC power conversion circuit through the first pulse signal, so as to control the voltage or current of any node in the loop composed of the DC bus, the first DCDC power conversion circuit, the second DCDC power conversion circuit and the battery pack, and improve the stability and safety of the voltage and current in the loop between the DC bus and the battery pack.

[0009] In combination with the first aspect, in a possible implementation, the DC bus includes a positive DC bus and a negative DC bus, and the first DCDC power conversion circuit includes: a first bridge arm and a second bridge arm connected between the positive DC bus and the negative DC bus, and a first inductor connecting the midpoint of the first bridge arm and the midpoint of the second bridge arm, the first bridge arm includes a first switch tube and a second switch tube connected in series, the second bridge arm includes a third switch tube and a fourth switch tube connected in series, the midpoint of the first bridge arm is the connection point of the first switch tube and the second switch tube, and the midpoint of the second bridge arm is the connection point of the third switch tube and the fourth switch tube. The second DCDC power conversion circuit includes: a first capacitor, a third bridge arm and a capacitor branch connected between the positive DC bus and the negative DC bus, the third bridge arm includes a fifth switch tube and a sixth switch tube connected in series, and the capacitor branch includes a second capacitor and a third capacitor connected in series. The primary coil of the transformer and the second inductor are connected in series and then connected between the midpoint of the third bridge arm and the midpoint of the capacitor branch. The third inductor is connected in parallel with the primary coil of the transformer. The midpoint of the third bridge arm is the connection point of the fifth switch tube and the sixth switch tube, and the midpoint of the capacitor branch is the connection point of the second capacitor and the third capacitor. The fourth bridge arm and the fifth bridge arm are used to be connected between the positive and negative electrodes of the battery pack. The fourth bridge arm includes the seventh switch tube and the eighth switch tube connected in series, and the fifth bridge arm includes the ninth switch tube and the tenth switch tube connected in series. The secondary coil of the transformer is connected between the midpoints of the fourth bridge arm and the fifth bridge arm. The midpoint of the fourth bridge arm is the connection point of the seventh switch tube and the eighth switch tube, and the midpoint of the fifth bridge arm is the connection point of the ninth switch tube and the tenth switch tube.

[0010] Based on this solution, the first DCDC power conversion circuit adopts the circuit topology of an H-bridge bidirectional DCDC power conversion circuit, and the second DCDC power conversion circuit adopts the circuit topology of a bidirectional LLC DCDC power conversion circuit, which can combine the advantages of a wide voltage regulation range of the H-bridge bidirectional DCDC power conversion circuit and the advantages of a large transformation ratio, high local working range efficiency and isolation of the bidirectional LLC DCDC power conversion circuit, thereby improving the working efficiency and dynamic response speed of the power converter.

[0011] In combination with the first aspect, in a possible implementation, the first pulse signal is used to control the fourth switch tube, and the second pulse signal is used to control the third bridge arm. The controller is also used to perform one of the following when the DC bus charges the battery pack and satisfies the first condition, the second condition, the third condition or the fourth condition: reduce the duty cycle of the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged; or stop sending the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, and send a third pulse signal to control the first switch tube, and the duty cycle of the third pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter. The first condition is that the current of the second end of the power converter is greater than the charging current threshold of the battery pack. The second condition is that the current of the first end of the power converter is greater than the discharge current threshold of the DC bus. The third condition is that the voltage of the first end of the power converter is less than the lower limit voltage threshold of the DC bus. The fourth condition is that the voltage of the second end of the power converter is greater than the upper limit voltage threshold of the battery pack.

[0012] Based on this solution, the controller generates a pulse signal to perform closed-loop control on the first DCDC power conversion circuit, thereby controlling the voltage or current of any node in the loop composed of the DC bus, the first DCDC power conversion circuit, the second DCDC power conversion circuit and the battery pack, which can improve the stability and safety of the voltage and current in the loop between the DC bus and the battery pack. At the same time, the controller generates a pulse signal to perform open-loop control on the second DCDC power conversion circuit, and there is no need to set the voltage detection circuit and current detection circuit corresponding to the second DCDC power conversion circuit, thereby reducing the complexity of the control circuit of the DCDC power conversion circuit in the power converter and reducing the cost of the power converter.

[0013] In combination with the first aspect, in a possible implementation, the controller is also used to stop sending the first pulse signal and the second pulse signal when the DC bus charges the battery pack, and the first condition, the second condition, the third condition or the fourth condition is met, and the fifth condition is met, and the fourth pulse signal is sent to control the second switch tube or the third switch tube, and the fifth pulse signal is sent to control the fourth bridge arm, so that the battery pack discharges to the DC bus, and the duty cycle of the fourth pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter, and the fifth pulse signal has a fixed duty cycle and a fixed frequency. The fifth condition is that the voltage of the first end of the power converter is less than the upper voltage threshold of the DC bus, the current of the first end of the power converter is less than or equal to the allowable discharge-to-charge current threshold of the DC bus, the voltage of the second end of the power converter is greater than the lower voltage threshold of the battery pack, and the current of the second end of the power converter is less than or equal to the allowable charge-to-discharge current threshold of the battery pack.

[0014] Based on this solution, the controller generates a pulse signal to perform closed-loop control on the first DCDC power conversion circuit, thereby controlling the voltage or current of any node in the loop composed of the DC bus, the first DCDC power conversion circuit, the second DCDC power conversion circuit and the battery pack, which can improve the stability and safety of the voltage and current in the loop between the DC bus and the battery pack. At the same time, the controller generates a pulse signal to perform open-loop control on the second DCDC power conversion circuit, and there is no need to set the voltage detection circuit and current detection circuit corresponding to the second DCDC power conversion circuit, thereby reducing the complexity of the control circuit of the DCDC power conversion circuit in the power converter and reducing the cost of the power converter.

[0015] In combination with the first aspect, in a possible implementation, the first pulse signal is used to control the first switch tube, and the second pulse signal is used to control the third bridge arm. The controller is also used to perform one of the following when the DC bus charges the battery pack and satisfies the first condition, the second condition, the third condition or the fourth condition: increase the duty cycle of the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged; or stop sending the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, and send a third pulse signal to control the fourth switch tube, and the duty cycle of the third pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter. The first condition is that the current of the second end of the power converter is less than the charging current threshold of the battery pack. The second condition is that the current of the first end of the power converter is less than the discharge current threshold of the DC bus. The third condition is that the voltage of the first end of the power converter is greater than the upper voltage threshold of the DC bus. The fourth condition is that the voltage of the second end of the power converter is less than the lower voltage threshold of the battery pack.

[0016] Based on this solution, the controller generates a pulse signal to perform closed-loop control on the first DCDC power conversion circuit, thereby controlling the voltage or current of any node in the loop composed of the DC bus, the first DCDC power conversion circuit, the second DCDC power conversion circuit and the battery pack, which can improve the stability and safety of the voltage and current in the loop between the DC bus and the battery pack. At the same time, the controller generates a pulse signal to perform open-loop control on the second DCDC power conversion circuit, and there is no need to set the voltage detection circuit and current detection circuit corresponding to the second DCDC power conversion circuit, thereby reducing the complexity of the control circuit of the DCDC power conversion circuit in the power converter and reducing the cost of the power converter.

[0017] In combination with the first aspect, in a possible implementation, the first pulse signal is used to control the second switch tube, and the second pulse signal is used to control the fourth bridge arm. The controller is also used to perform one of the following when the battery pack discharges to the DC bus and meets the first condition, the second condition, the third condition or the fourth condition: reduce the duty cycle of the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged; or stop sending the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, and send a third pulse signal to control the third switch tube, and the duty cycle of the third pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter. The first condition is that the current of the second end of the power converter is greater than the discharge current threshold of the battery pack. The second condition is that the current of the first end of the power converter is greater than the charging current threshold of the DC bus. The third condition is that the voltage of the first end of the power converter is greater than the upper voltage threshold of the DC bus. The fourth condition is that the voltage of the second end of the power converter is less than the lower voltage threshold of the battery pack.

[0018] Based on this solution, the controller generates a pulse signal to perform closed-loop control on the first DCDC power conversion circuit, thereby controlling the voltage or current of any node in the loop composed of the DC bus, the first DCDC power conversion circuit, the second DCDC power conversion circuit and the battery pack, which can improve the stability and safety of the voltage and current in the loop between the DC bus and the battery pack. At the same time, the controller generates a pulse signal to perform open-loop control on the second DCDC power conversion circuit, and there is no need to set the voltage detection circuit and current detection circuit corresponding to the second DCDC power conversion circuit, thereby reducing the complexity of the control circuit of the DCDC power conversion circuit in the power converter and reducing the cost of the power converter.

[0019] In combination with the first aspect, in a possible implementation, the controller is also used to stop sending the first pulse signal and the second pulse signal when the battery pack discharges to the DC bus, meets the first condition, the second condition, the third condition or the fourth condition, and meets the fifth condition, and sends a fourth pulse signal to control the first switch tube or the fourth switch tube, and sends a fifth pulse signal to control the third bridge arm, so that the DC bus charges the battery pack, and the duty cycle of the fourth pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter, and the fifth pulse signal has a fixed duty cycle and a fixed frequency. The fifth condition is that the voltage of the first end of the power converter is greater than the lower limit voltage threshold of the DC bus, the current of the first end of the power converter is less than or equal to the allowable charge-to-discharge current threshold of the DC bus, the voltage of the second end of the power converter is less than the upper limit voltage threshold of the battery pack, and the current of the second end of the power converter is less than or equal to the allowable discharge-to-charge current threshold of the battery pack.

[0020] Based on this solution, the controller generates a pulse signal to perform closed-loop control on the first DCDC power conversion circuit, thereby controlling the voltage or current of any node in the loop composed of the DC bus, the first DCDC power conversion circuit, the second DCDC power conversion circuit and the battery pack, which can improve the stability and safety of the voltage and current in the loop between the DC bus and the battery pack. At the same time, the controller generates a pulse signal to perform open-loop control on the second DCDC power conversion circuit, and there is no need to set the voltage detection circuit and current detection circuit corresponding to the second DCDC power conversion circuit, thereby reducing the complexity of the control circuit of the DCDC power conversion circuit in the power converter and reducing the cost of the power converter.

[0021] In combination with the first aspect, in a possible implementation, the first pulse signal is used to control the third switch tube, and the second pulse signal is used to control the fourth bridge arm. The controller is also used to perform one of the following when the battery pack discharges to the DC bus and meets the first condition, the second condition, the third condition or the fourth condition: increase the duty cycle of the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged; or stop sending the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, and send a third pulse signal to control the second switch tube, and the duty cycle of the third pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter. The first condition is that the current of the second end of the power converter is less than the discharge current threshold of the battery pack. The second condition is that the current of the first end of the power converter is less than the charging current threshold of the DC bus. The third condition is that the voltage of the first end of the power converter is less than the lower limit voltage threshold of the DC bus. The fourth condition is that the voltage of the second end of the power converter is greater than the upper limit voltage threshold of the battery pack.

[0022] Based on this solution, the controller generates a pulse signal to perform closed-loop control on the first DCDC power conversion circuit, thereby controlling the voltage or current of any node in the loop composed of the DC bus, the first DCDC power conversion circuit, the second DCDC power conversion circuit and the battery pack, which can improve the stability and safety of the voltage and current in the loop between the DC bus and the battery pack. At the same time, the controller generates a pulse signal to perform open-loop control on the second DCDC power conversion circuit, and there is no need to set the voltage detection circuit and current detection circuit corresponding to the second DCDC power conversion circuit, thereby reducing the complexity of the control circuit of the DCDC power conversion circuit in the power converter and reducing the cost of the power converter.

[0023] In combination with the first aspect, in a possible implementation, the controller is also used to control the first DCDC power conversion circuit to stop working when the voltage or current at the connection end of the first DCDC power conversion circuit and the second DCDC power conversion circuit, or the voltage or current at the second end of the power converter is greater than the first protection threshold. Alternatively, when the voltage or current at the connection end of the first DCDC power conversion circuit and the second DCDC power conversion circuit, or the voltage or current at the second end of the power converter is greater than the second protection threshold, the first DCDC power conversion circuit and the second DCDC power conversion circuit are controlled to stop working, and the second protection threshold is greater than the first protection threshold.

[0024] Based on this solution, when the voltage or current at the connection end of the first DCDC power conversion circuit and the second DCDC power conversion circuit, or the voltage or current at the second end of the power converter is greater than the protection threshold, the controller mainly controls the first DCDC power conversion circuit to stop working to achieve overcurrent or overvoltage protection. When selecting hardware, the first DCDC power conversion circuit selects a device with higher voltage and current resistance, and the second DCDC power conversion circuit can select a device with lower voltage and current resistance, without requiring both DCDC power conversion circuits to select devices with higher voltage and current resistance, thereby reducing the cost of the power converter. At the same time, by setting different protection thresholds, the power converter is protected in stages at different voltage or current levels, thereby improving the reliability and stability of the power converter.

[0025] In a second aspect of an embodiment of the present application, a control method for a power converter is provided, which is applied to a power converter, wherein a first end of the power converter is used to be connected to a DC bus, and a second end of the power converter is used to be connected to a battery pack. The power converter includes a first DCDC power conversion circuit, a second DCDC power conversion circuit, and a controller, wherein one end of the first DCDC power conversion circuit is connected to the first end of the power converter, the other end of the first DCDC power conversion circuit is connected to one end of the second DCDC power conversion circuit, and the other end of the second DCDC power conversion circuit is connected to the second end of the power converter. The method includes: sending a first pulse signal to control the operation of the first DCDC power conversion circuit, and sending a second pulse signal to control the operation of the second DCDC power conversion circuit, so that the DC bus charges the battery pack, or the battery pack discharges to the DC bus. The duty cycle of the first pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter; the second pulse signal has a fixed duty cycle and a fixed frequency.

[0026] In combination with the second aspect, in a possible implementation, the method further includes: when the voltage or current at the connection end of the first DCDC power conversion circuit and the second DCDC power conversion circuit, or the voltage or current at the second end of the power converter is greater than the first protection threshold, the first DCDC power conversion circuit is controlled to stop working. Alternatively, when the voltage or current at the connection end of the first DCDC power conversion circuit and the second DCDC power conversion circuit, or the voltage or current at the second end of the power converter is greater than the second protection threshold, the first DCDC power conversion circuit and the second DCDC power conversion circuit are controlled to stop working, and the second protection threshold is greater than the first protection threshold.

[0027] In a third aspect of the embodiments of the present application, there is provided an energy storage system, the energy storage system comprising a power converter and a battery pack connected to the power converter, the power converter being a power converter as described in the first aspect or any possible implementation of the first aspect. The power converter is used to perform power conversion on the voltage of a DC bus so that the DC bus charges the battery pack, or to perform power conversion on the voltage of the battery pack so that the battery pack discharges to the DC bus.

[0028] The description of the second to third aspects in this application can refer to the detailed description of the first aspect; and the beneficial effects of the second to third aspects can refer to the analysis of the beneficial effects of the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of a circuit topology for an application scenario of a power converter provided in an embodiment of the present application;

[0030] Figure 2 A schematic diagram of a circuit topology of a power converter provided in an embodiment of the present application;

[0031] Figure 3 A schematic diagram of another circuit topology of a power converter provided in an embodiment of the present application;

[0032] Figure 4 A circuit topology diagram of another power converter provided in an embodiment of the present application;

[0033] Figure 5 A schematic diagram of a circuit topology of another power converter provided in an embodiment of the present application;

[0034] Figure 6 A schematic diagram of a circuit topology of another power converter provided in an embodiment of the present application;

[0035] Figure 7 A schematic diagram of a waveform curve of an internal bus voltage provided in an embodiment of the present application;

[0036] Figure 8 A schematic diagram of another waveform curve of the internal bus voltage provided in an embodiment of the present application;

[0037] Fig. 9 A schematic diagram of a current curve waveform and a pulse signal waveform of a battery pack provided in an embodiment of the present application;

[0038] Fig.10 A schematic flow chart of a method for controlling a power converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0039] The following will discuss the making and use of various embodiments in detail. However, it should be understood that many applicable inventive concepts provided by this application can be implemented in a variety of specific environments. The specific embodiments discussed are only used to illustrate the specific ways to implement and use this description and this technology, and do not limit the scope of this application.

[0040] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.

[0041] Various circuits or other components may be described or referred to as being "configured to" perform one or more tasks. In this case, "configured to" is used to imply structure by indicating that the circuit / component includes structure (e.g., circuitry) that performs the one or more tasks during operation. Thus, even when the specified circuit / component is not currently operational (e.g., not turned on), the circuit / component may be referred to as being configured to perform the task. Circuits / components used with the phrase "configured to" include hardware, such as circuits that perform an operation, etc.

[0042] The technical scheme in the embodiment of the present application will be described below in conjunction with the accompanying drawings in the embodiment of the present application. In the present application, "at least one" refers to one or more, and "multiple" refers to two or more. "And / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or its similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can represent: a, b, c, a and b, a and c, b and c or a, b and c, where a, b and c can be single or multiple. In addition, in the embodiment of the present application, the words "first", "second" and the like do not limit the quantity and order.

[0043] In this application, the words "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the words "exemplary" or "for example" is intended to present the related concepts in a concrete way.

[0044] Before introducing the embodiments of the present application, the technical terms and background technologies involved in the present application are first introduced.

[0045] DCDC power conversion circuits can be divided into many types according to circuit topology, such as isolated, non-isolated, buck, boost, reverse, unidirectional and bidirectional. Each type of DCDC power conversion circuit has its own advantages and disadvantages in terms of cost, volume, efficiency, operating range and electromagnetic interference. For example, the isolated DCDC power conversion circuit has the disadvantages of more complex circuit topology, higher cost and larger volume due to the addition of a transformer, but also has the advantages of current isolation and higher safety.

[0046] In the energy storage system, the power converter may include multiple different types of DCDC power conversion circuits connected in series, so that the advantages of multiple different types of DCDC power conversion circuits can be complemented. Alternatively, the power converter may also include multiple DCDC power conversion circuits of the same type connected in series, so that a higher voltage gain can be achieved. However, in the case where the power converter includes multiple DCDC power conversion circuits connected in series, each DCDC power conversion circuit uses the voltage and current at both ends as feedback and control targets, and performs independent tracking control and protection, which will result in a higher complexity of the control circuit of the DCDC power conversion circuit in the power converter, and will result in a higher dynamic response delay of the power converter.

[0047] For example, taking a power converter including a first DCDC power conversion circuit and a second DCDC power conversion circuit connected in series, the first DCDC power conversion circuit is used to connect to a DC bus, and the second DCDC power conversion circuit is used to connect to a battery pack, in the process of the DC bus charging the battery pack through the power converter, or the battery pack discharging to the DC bus through the power converter, the first DCDC power conversion circuit is independently tracked, controlled and protected with the voltage and current at both ends of the circuit as feedback and control targets, and the second DCDC power conversion circuit is independently tracked, controlled and protected with the voltage and current at both ends of the circuit as feedback and control targets. The power converter needs to be provided with a detection circuit for detecting the voltage and current at both ends of the first DCDC power conversion circuit, and a detection circuit for detecting the voltage and current at both ends of the second DCDC power conversion circuit, which will result in a higher complexity of the control circuit in the power converter and a higher cost of the power converter. At the same time, since the first DCDC power conversion circuit and the second DCDC power conversion circuit are independently tracked, controlled and protected, in the process of the DC bus charging the battery pack through the power converter, the controller in the power converter needs to sequentially close-loop control the first DCDC power conversion circuit and the second DCDC power conversion circuit to realize the charging of the battery pack from the DC bus. In the process of the battery pack discharging from the DC bus through the power converter, the controller in the power converter needs to sequentially close-loop control the second DCDC power conversion circuit and the first DCDC power conversion circuit to realize the discharge of the battery pack from the DC bus, which will result in a higher dynamic response delay of the power converter.

[0048] Therefore, how to reduce the complexity of the control circuit of the DCDC power conversion circuit in the power converter and reduce the dynamic response delay of the power converter has become an urgent problem to be solved.

[0049] Based on this, an embodiment of the present application provides a power converter, in which a controller sends a first pulse signal to perform closed-loop control on a first DCDC power conversion circuit, and sends a second pulse signal to perform open-loop control on a second DCDC power conversion circuit, so that the DC bus charges the battery pack, or the battery pack discharges the DC bus, without independently tracking, controlling and protecting each DCDC power conversion circuit using the voltage and current at both ends of the circuit as feedback and control targets, thereby reducing the complexity of the control circuit of the DCDC power conversion circuit in the power converter and reducing the dynamic response delay of the power converter.

[0050] like Figure 1 FIG. 1 is a schematic diagram of a circuit topology of an application scenario of a power converter 100 provided in an embodiment of the present application. Figure 1The power converter 100 provided in the embodiment of the present application can be applied to an energy storage system 200, wherein a first end of the power converter 100 is used to be connected to a DC bus BUS, wherein the DC bus BUS includes a positive DC bus BUS+ and a negative DC bus BUS-, and the energy storage system 200 further includes a battery pack 300 connected to a second end of the power converter 100, wherein the battery pack 300 includes a positive electrode and a negative electrode.

[0051] In a possible embodiment, the type of the energy storage system 200 may include a photovoltaic energy storage system, a wind power generation energy storage system, or a power station energy storage system, which is not limited in this embodiment of the present application.

[0052] In a possible embodiment, the energy storage system 200 may be applied to a charging station.

[0053] In a possible embodiment, a battery pack 300 may include at least one battery module, and each battery module may include a plurality of battery cells, which is not limited in the embodiment of the present application.

[0054] In a possible embodiment, the power converter provided in the embodiment of the present application may also be applied to a photovoltaic inverter, an optimizer or an uninterruptible power supply (UPS), which is not limited in the embodiment of the present application.

[0055] Reference Figure 1 The power converter 100 provided in an embodiment of the present application includes a first DCDC power conversion circuit 110, a second DCDC power conversion circuit 120 and a controller 130, one end of the first DCDC power conversion circuit 110 is connected to a first end of the power converter 100, the other end of the first DCDC power conversion circuit 110 is connected to one end of the second DCDC power conversion circuit 120, and the other end of the second DCDC power conversion circuit 120 is connected to a second end of the power converter 100.

[0056] The controller 130 is used to send a first pulse signal to control the operation of the first DCDC power conversion circuit 110, and send a second pulse signal to control the operation of the second DCDC power conversion circuit 120, so that the DC bus BUS charges the battery pack 300, or the battery pack 300 discharges the DC bus BUS. The duty cycle of the first pulse signal is determined according to the voltage or current of the first end of the power converter 100 (also referred to as the voltage or current of the DC bus BUS), or the voltage or current of the second end of the power converter 100 (also referred to as the voltage or current of the battery pack 300); the second pulse signal has a fixed duty cycle and a fixed frequency, and the embodiment of the present application does not limit the specific values ​​of the duty cycle and frequency of the second pulse signal. The voltage or current of the first end of the power converter 100 is the voltage or current of the DC bus BUS, and the voltage or current of the second end of the power converter 100 is the voltage or current of the battery pack 300.

[0057] In a possible embodiment, the first pulse signal or the second pulse signal, and each pulse signal in the following embodiments include a pulse frequency modulation (PFM) or a pulse width modulation (PWM) signal, which is not limited in the embodiments of the present application.

[0058] It can be understood that the controller 130 performs closed-loop control on the first DCDC power conversion circuit 110 by sending a first pulse signal, and performs open-loop control on the second DCDC power conversion circuit 120 by sending a second pulse signal, so that the DC bus BUS charges the battery pack 300, or the battery pack 300 discharges to the DC bus BUS, instead of using the voltage and current at both ends of each DCDC power conversion circuit as feedback and control targets for independent tracking control and protection, and there is no need to set up a voltage detection circuit and a current detection circuit corresponding to each DCDC power conversion circuit, thereby reducing the complexity of the control circuit of the DCDC power conversion circuit in the power converter 100 and reducing the cost of the power converter 100. Secondly, the controller 130 performs closed-loop control on the first DCDC power conversion circuit 110 by sending the first pulse signal, so as to control the voltage or current of any node in the loop formed by the DC bus BUS, the first DCDC power conversion circuit 110, the second DCDC power conversion circuit 120 and the battery pack 300, and improve the stability and safety of the voltage and current in the loop between the DC bus BUS and the battery pack 300. Finally, compared with the closed-loop control of the second DCDC power conversion circuit 120 by the controller 130, the controller 130 performs open-loop control on the second DCDC power conversion circuit 120 by sending the second pulse signal, which can reduce the dynamic response delay of the power converter 100.

[0059] In a possible embodiment, the controller 130 is used to send a first pulse signal to control the operation of the first DCDC power conversion circuit 110 and send a second pulse signal to control the operation of the second DCDC power conversion circuit 120 when the voltage at the first end of the power converter 100 (also referred to as the voltage of the DC bus BUS) is greater than or equal to the DC bus voltage threshold and the voltage at the second end of the power converter 100 (also referred to as the voltage of the battery pack 300) is less than or equal to the battery pack voltage threshold, so that the DC bus BUS charges the battery pack 300. The embodiment of the present application does not limit the specific values ​​of the DC bus voltage threshold and the battery pack voltage threshold.

[0060] In a possible embodiment, the controller 130 is also used to send a first pulse signal to control the operation of the first DCDC power conversion circuit 110 and send a second pulse signal to control the operation of the second DCDC power conversion circuit 120 when the voltage at the first end of the power converter 100 (also referred to as the voltage of the DC bus BUS) is less than the DC bus voltage threshold and the voltage at the second end of the power converter 100 (also referred to as the voltage of the battery pack 300) is greater than the battery pack voltage threshold, so that the battery pack 300 discharges to the DC bus BUS.

[0061] In a possible embodiment, the type of the first DCDC power conversion circuit 110 or the type of the second DCDC power conversion circuit 120 includes an isolated type, a non-isolated type, a buck type, a boost type, a reverse type, a unidirectional type, and a bidirectional type, which is not limited in the embodiments of the present application. The type of the first DCDC power conversion circuit 110 and the type of the second DCDC power conversion circuit 120 may be the same, or may be different, which is not limited in the embodiments of the present application. In the following embodiments of the present application, an exemplary description is given by taking the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120 as bidirectional DCDC power conversion circuits as an example.

[0062] In a possible embodiment, Figure 2 , which is a schematic diagram of a circuit topology of a power converter 100 provided in an embodiment of the present application.

[0063] Reference Figure 2The first DCDC power conversion circuit 110 includes: a first bridge arm and a second bridge arm connected between the positive DC bus BUS+ and the negative DC bus BUS-, and a first inductor L1 connecting the midpoint of the first bridge arm and the midpoint of the second bridge arm, the first bridge arm includes a first switch tube Q1 and a second switch tube Q2 connected in series, the second bridge arm includes a third switch tube Q3 and a fourth switch tube Q4 connected in series, the midpoint of the first bridge arm is the connection point of the first switch tube Q1 and the second switch tube Q2, and the midpoint of the second bridge arm is the connection point of the third switch tube Q3 and the fourth switch tube Q4. The first DCDC power conversion circuit 110 can also be called an H-bridge type bidirectional DCDC power conversion circuit.

[0064] Continue to refer to Figure 2 The second DCDC power conversion circuit 120 includes: a first capacitor C1, a third bridge arm and a capacitor branch for connecting between the positive DC bus BUS+ and the negative DC bus BUS-, the third bridge arm includes a fifth switch tube Q5 and a sixth switch tube Q6 connected in series, and the capacitor branch includes a second capacitor C2 and a third capacitor C3 connected in series. The primary coil of the transformer T and the second inductor L2 are connected in series and then connected between the midpoint of the third bridge arm and the midpoint of the capacitor branch. The third inductor L3 is connected in parallel with the primary coil of the transformer T. The midpoint of the third bridge arm is the connection point of the fifth switch tube Q5 and the sixth switch tube Q6, and the midpoint of the capacitor branch is the connection point of the second capacitor C2 and the third capacitor C3. The fourth bridge arm and the fifth bridge arm are used to connect between the positive electrode and the negative electrode of the battery pack 300, the fourth bridge arm includes the seventh switch tube Q7 and the eighth switch tube Q8 connected in series, the fifth bridge arm includes the ninth switch tube Q9 and the tenth switch tube Q10 connected in series, the secondary coil of the transformer T is connected between the midpoints of the fourth bridge arm and the fifth bridge arm, the midpoint of the fourth bridge arm is the connection point of the seventh switch tube Q7 and the eighth switch tube Q8, and the midpoint of the fifth bridge arm is the connection point of the ninth switch tube Q9 and the tenth switch tube Q10. The second DCDC power conversion circuit 120 can be called a bidirectional LLC DCDC power conversion circuit, wherein the second capacitor C2 and the third capacitor C3 are resonant capacitors, the second inductor L2 is a resonant inductor, and the third inductor L3 is a magnetizing inductor. The resonant capacitor, the resonant inductor and the magnetizing inductor constitute a resonant circuit, which can also be called a resonant cavity.

[0065] Among them, the above-mentioned H-bridge type bidirectional DCDC power conversion circuit has the advantage of a wide voltage regulation range, and at the same time has the disadvantage of reduced efficiency when the voltage difference is large. The above-mentioned bidirectional LLC DCDC power conversion circuit has the advantages of a large transformation ratio, high efficiency in a local working range and isolation, and at the same time has the disadvantages of a fixed winding transformation ratio and a limited adjustment range. In the embodiment of the present application, the first DCDC power conversion circuit 110 adopts the circuit topology of an H-bridge type bidirectional DCDC power conversion circuit, and the second DCDC power conversion circuit 120 adopts the circuit topology of a bidirectional LLC DCDC power conversion circuit, which can combine the advantages of a wide voltage regulation range of an H-bridge type bidirectional DCDC power conversion circuit, and the advantages of a large transformation ratio, high efficiency in a local working range and isolation of a bidirectional LLC DCDC power conversion circuit, thereby improving the working efficiency and dynamic response speed of the power converter 100.

[0066] In a possible embodiment, each of the switch tubes may include a metal-oxide-semiconductor field-effect transistor (MOSFET), which may also be referred to as a MOS tube, and each MOS tube includes a reverse-biased body diode. Figure 2 Each switch tube may include an insulate-gate bipolar transistor (IGBT) and a diode D, wherein the collector of the IGBT is connected to the cathode of the diode D, and the emitter of the IGBT is connected to the anode of the diode D. For example, Figure 2 The first switch tube Q1 includes an IGBT and a diode D. In the following embodiments of the present application, each switch tube includes an IGBT and a diode D as an example for exemplary description.

[0067] In a possible embodiment, when the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120 are both bidirectional DCDC power conversion circuits, the power converter 100 can perform power conversion on the voltage of the DC bus BUS so that the DC bus BUS charges the battery pack 300, and the power converter 100 can also perform power conversion on the voltage of the battery pack 300 so that the battery pack 300 discharges to the DC bus BUS.

[0068] In a possible embodiment, Figure 3 FIG. 1 is a schematic diagram of a circuit topology of a power converter 100 provided in an embodiment of the present application. Figure 3The first DCDC power conversion circuit 110 may include multiple first sub-DCDC power conversion circuits 111, or the second DCDC power conversion circuit 120 may include multiple second sub-DCDC power conversion circuits 121. The embodiment of the present application does not limit the number of first sub-DCDC power conversion circuits 111 included in the first DCDC power conversion circuit 110, and the specific number of second sub-DCDC power conversion circuits 121 included in the second DCDC power conversion circuit 120.

[0069] In a possible embodiment, multiple first sub-DCDC power conversion circuits 111 in the first DCDC power conversion circuit 110, or multiple second sub-DCDC power conversion circuits 121 in the second DCDC power conversion circuit 120, can be connected in parallel, in series, or in a mixed connection, where the mixed connection means that part of the multiple sub-DCDC power conversion circuits are connected in series and the rest are connected in parallel, or one end of the multiple sub-DCDC power conversion circuits can be connected in series and the other end can be connected in parallel. The embodiment of the present application does not limit this.

[0070] For example, Figure 3 As shown, the multiple first sub-DCDC power conversion circuits 111 in the first DCDC power conversion circuit 110 can be connected in parallel, and the multiple second sub-DCDC power conversion circuits 121 in the second DCDC power conversion circuit 120 can be connected in parallel.

[0071] In a possible embodiment, the first DCDC power conversion circuit 110 adopts a circuit topology of an H-bridge bidirectional DCDC power conversion circuit. The circuit topology of the first DCDC power conversion circuit 110 is as described above. Figure 2 The circuit topology of the first DCDC power conversion circuit 110 shown in the figure, the second DCDC power conversion circuit 120 includes two second sub-DCDC power conversion circuits 121, each second sub-DCDC power conversion circuit 121 adopts the circuit topology of the bidirectional LLC DCDC power conversion circuit, and the circuit topology of each second sub-DCDC power conversion circuit 121 is as described above Figure 2 The circuit topology of the second DCDC power conversion circuit 120 shown in FIG. 1 is taken as an example. When the two second sub-DCDC power conversion circuits 121 are connected in parallel, the circuit topology of the power converter 100 is as follows: Figure 4 In the case where one end of the two second sub-DCDC power conversion circuits 121 is connected in series and the other end is connected in parallel, the circuit topology of the power converter 100 is as follows: Figure 5When the two second sub-DCDC power conversion circuits 121 are connected in series, the circuit topology of the power converter 100 is as follows: Figure 6 The circuit topology of the power converter 100 is shown.

[0072] In a possible embodiment, the controller 130 includes a digital signal processing (DSP) chip or a microcontroller unit (MCU), which may also be referred to as a single-chip microcomputer, and the embodiment of the present application does not limit this.

[0073] In the power converter 100 provided in the embodiment of the present application, the duty cycle of the first pulse signal is determined according to the voltage or current at the first end of the power converter 100, or the voltage or current at the second end of the power converter 100, and the second pulse signal has a fixed duty cycle and a fixed frequency. The controller 130 performs closed-loop control on the first DCDC power conversion circuit 110 by sending the first pulse signal, and performs open-loop control on the second DCDC power conversion circuit 120 by sending the second pulse signal, so that the DC bus BUS charges the battery pack 300, or the battery pack 300 discharges to the DC bus BUS, instead of performing independent tracking control and protection on each DCDC power conversion circuit using the voltage and current at its two ends as feedback and control targets, and there is no need to set a voltage detection circuit and a current detection circuit corresponding to each DCDC power conversion circuit, thereby reducing the complexity of the control circuit of the DCDC power conversion circuit in the power converter 100 and reducing the cost of the power converter 100. Secondly, the controller 130 performs closed-loop control on the first DCDC power conversion circuit 110 by sending the first pulse signal, so as to control the voltage or current of any node in the loop formed by the DC bus BUS, the first DCDC power conversion circuit 110, the second DCDC power conversion circuit 120 and the battery pack 300, and improve the stability and safety of the voltage and current in the loop between the DC bus BUS and the battery pack 300. Finally, compared with the closed-loop control of the second DCDC power conversion circuit 120 by the controller 130, the controller 130 performs open-loop control on the second DCDC power conversion circuit 120 by sending the second pulse signal, which can reduce the dynamic response delay of the power converter 100.

[0074] In a possible embodiment, the circuit topology of the power converter 100 in the following embodiments of the present application is as follows: Figure 2Taking the circuit topology of the power converter 100 shown in FIG. 1 as an example, the process of the controller 130 controlling the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120 through the pulse signal, and how to adjust the pulse signal to improve the stability and safety of the voltage and current in the loop between the DC bus BUS and the battery pack 300 are illustrated. When the circuit topology of the power converter 100 is as follows Figure 4 , Figure 5 or Figure 6 When the circuit topology of the power converter 100 shown in FIG. 1 is used, the circuit topology of the power converter 100 may be referred to as follows: Figure 2 The description of the circuit topology of the power converter 100 shown in the figure will not be repeated in the embodiment of the present application.

[0075] Reference Figure 2 The DC bus between the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120 can be called an inner DC bus or an inner bus, and the voltage of the inner bus can be called an inner bus voltage.

[0076] When the DC bus BUS charges the battery pack 300:

[0077] In one possible embodiment, referring to Figure 2 The first pulse signal control is used to control the fourth switch tube Q4, so that the first DCDC power conversion circuit 110 performs a boost power conversion on the voltage of the DC bus BUS to generate an internal bus voltage. The second pulse signal is used to control the third bridge arm (the fifth switch tube Q5 and the sixth switch tube Q6), so that the second DCDC power conversion circuit 120 performs a power conversion on the internal bus voltage, so that the DC bus BUS charges the battery pack 300. The specific power conversion process can refer to the prior art, and the embodiments of the present application will not be repeated here.

[0078] The controller 130 is also used to perform one of the following when the DC bus BUS charges the battery pack 300 and satisfies the first condition, the second condition, the third condition or the fourth condition: reduce the duty cycle of the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, so as to reduce the internal bus voltage; or stop sending the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, and send the third pulse signal to control the first switch tube Q1, so that the first DCDC power conversion circuit 110 performs a step-down power conversion on the voltage of the DC bus BUS to reduce the internal bus voltage. Thereby reducing the charging current of the battery pack 300 or the discharging current of the DC bus BUS, or increasing the voltage of the DC bus BUS, or slowing down the voltage rising trend of the battery pack 300, so as to improve the stability and safety of the voltage and current in the loop between the DC bus BUS and the battery pack 300. Among them, the duty cycle of the third pulse signal is determined according to the voltage or current of the first end of the power converter 100, or the voltage or current of the second end of the power converter 100. The first condition is that the current at the second end of the power converter 100 (also referred to as the charging current of the battery pack 300) is greater than the charging current threshold of the battery pack 300. The second condition is that the current at the first end of the power converter 100 (also referred to as the discharge current of the DC bus BUS) is greater than the discharge current threshold of the DC bus BUS. The third condition is that the voltage at the first end of the power converter 100 (also referred to as the voltage of the DC bus BUS) is less than the lower voltage threshold of the DC bus BUS. The fourth condition is that the voltage at the second end of the power converter 100 (also referred to as the voltage of the battery pack 300) is greater than the upper voltage threshold of the battery pack 300. The lower voltage threshold of the DC bus BUS is less than the above-mentioned DC bus voltage threshold, and the upper voltage threshold of the battery pack 300 is greater than the above-mentioned battery pack voltage threshold. The embodiment of the present application does not limit the specific values ​​of the charging current threshold of the battery pack 300, the discharge current threshold of the DC bus BUS, the lower voltage threshold of the DC bus BUS, and the upper voltage threshold of the battery pack 300.

[0079] In a possible embodiment, taking the case where the current at the second end of the power converter 100 (also referred to as the charging current of the battery pack 300) is greater than the charging current threshold of the battery pack 300 as an example, it may be in the following two possible embodiments that the current at the second end of the power converter 100 is greater than the charging current threshold of the battery pack 300. The case where the current at the first end of the power converter 100 (also referred to as the discharge current of the DC bus BUS) is greater than the discharge current threshold of the DC bus BUS, or the voltage at the first end of the power converter 100 (also referred to as the voltage of the DC bus BUS) is less than the lower limit voltage threshold of the DC bus BUS, or the voltage at the second end of the power converter 100 (also referred to as the voltage of the battery pack 300) is greater than the upper limit voltage threshold of the battery pack 300, as well as the remaining cases in the following embodiments, can refer to the following description, and the embodiments of the present application will not be repeated here.

[0080] In a first possible embodiment, Figure 7 The figure shows a waveform curve diagram of the internal bus voltage. Figure 7 When the internal bus voltage is greater than the charge-discharge boundary, the DC bus BUS charges the battery pack 300. When the internal bus voltage is less than the charge-discharge boundary, the battery pack 300 discharges to the DC bus BUS. When the voltage of the DC bus BUS fluctuates, the internal bus voltage will increase. The increase in the internal bus voltage will cause the charging current of the battery pack 300 to be greater than the charging current threshold of the battery pack 300. Figure 7 The controller 130 can reduce the internal bus voltage by reducing the duty cycle of the first pulse signal, or stop sending the first pulse signal and send a third pulse signal to control the first switch tube Q1, so that the charging current of the battery pack 300 can be restored to be equal to the charging current threshold of the battery pack 300. At this time, the internal bus voltage is greater than the charge and discharge boundary, and the DC bus BUS charges the battery pack 300.

[0081] In a second possible embodiment, when the host computer modifies the charging current threshold of the battery pack 300, or the controller 130 obtains a reference value as the charging current threshold of the battery pack 300, and the position where the controller 130 obtains the reference value changes, the charging current threshold of the battery pack 300 will change, which will cause the charging current of the battery pack 300 to be greater than the charging current threshold of the battery pack 300. For example, Figure 8(a) is a schematic diagram of another waveform curve of the internal bus voltage. When the upper computer modifies the charging current threshold of the battery pack 300, the charging current of the battery pack 300 will be greater than the charging current threshold of the battery pack 300. The controller 130 can reduce the internal bus voltage by reducing the duty cycle of the first pulse signal, or stop sending the first pulse signal, and send a third pulse signal to control the first switch tube Q1, so that the charging current of the battery pack 300 is restored to be equal to the charging current threshold of the battery pack 300. At this time, the internal bus voltage is greater than the charge and discharge boundary, and the DC bus BUS charges the battery pack 300. For another example, Figure 8 (b) is another schematic diagram of the waveform curve of the internal bus voltage. When the upper computer modifies the charging current threshold of the battery pack 300, the charging current of the battery pack 300 will be greater than the charging current threshold of the battery pack 300. The controller 130 can reduce the internal bus voltage by reducing the duty cycle of the first pulse signal, or stop sending the first pulse signal, and send a third pulse signal to control the first switch tube Q1, so that the charging current of the battery pack 300 is restored to be equal to the charging current threshold of the battery pack 300. At this time, the internal bus voltage is less than the charge and discharge boundary, and the battery pack 300 discharges to the DC bus BUS.

[0082] In a possible embodiment, the controller 130 is also used to stop sending the first pulse signal and the second pulse signal, and send the fourth pulse signal to control the second switch tube Q2 or the third switch tube Q3, and send the fifth pulse signal to control the fourth bridge arm (the seventh switch tube Q7 and the eighth switch tube Q8) when the DC bus BUS charges the battery pack 300 and the above-mentioned first condition, second condition, third condition or fourth condition is satisfied, and the fifth condition is satisfied, so that the battery pack 300 discharges to the DC bus BUS, reduces the internal bus voltage, thereby reducing the charging current of the battery pack 300 or the discharging current of the DC bus BUS, or, increases the voltage of the DC bus BUS, or reverses the rising trend of the voltage of the battery pack 300, thereby improving the stability and safety of the voltage and current in the loop between the DC bus BUS and the battery pack 300. Among them, the duty cycle of the fourth pulse signal is determined according to the voltage or current of the first end of the power converter 100, or the voltage or current of the second end of the power converter 100, and the fifth pulse signal has a fixed duty cycle and a fixed frequency. The embodiment of the present application does not limit the specific values ​​of the duty cycle and frequency of the fifth pulse signal. The fifth condition is that the voltage of the first end of the power converter 100 (also referred to as the voltage of the DC bus BUS) is less than the upper voltage threshold of the DC bus BUS, the current of the first end of the power converter 100 (also referred to as the discharge current of the DC bus BUS) is less than or equal to the allowable discharge-to-charge current threshold of the DC bus BUS, the voltage of the second end of the power converter BUS (also referred to as the voltage of the battery pack 300) is greater than the lower voltage threshold of the battery pack 300, and the current of the second end of the power converter 100 (also referred to as the charging current of the battery pack 300) is less than or equal to the allowable charge-to-discharge current threshold of the battery pack 300. The upper limit voltage threshold of the DC bus BUS is greater than the above-mentioned DC bus voltage threshold, and the lower limit voltage threshold of the battery pack 300 is less than the above-mentioned battery pack voltage threshold. The embodiment of the present application does not limit the specific values ​​of the allowable charge-to-discharge current threshold of the battery pack 300 and the allowable discharge-to-charge current threshold of the DC bus BUS.

[0083] In one possible embodiment, referring to Figure 2 The first pulse signal is used to control the first switch tube Q1, so that the first DCDC power conversion circuit 110 performs a step-down power conversion on the voltage of the DC bus BUS to generate an internal bus voltage. The second pulse signal is used to control the third bridge arm (the fifth switch tube Q5 and the sixth switch tube Q6), so that the second DCDC power conversion circuit 120 performs a power conversion on the internal bus voltage, so that the DC bus BUS charges the battery pack 300. The specific power conversion process can refer to the prior art, and the embodiments of the present application will not be repeated here.

[0084] The controller 130 is also used to perform one of the following when the DC bus BUS charges the battery pack 300 and satisfies the first condition, the second condition, the third condition or the fourth condition: increase the duty cycle of the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, so as to increase the internal bus voltage; or stop sending the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, and send the third pulse signal to control the fourth switch tube Q4 to increase the internal bus voltage. Thereby increasing the charging current of the battery pack 300 or the discharging current of the DC bus BUS, or reducing the voltage of the DC bus BUS, or accelerating the voltage rising trend of the battery pack 300, so as to improve the stability and safety of the voltage and current in the loop between the DC bus BUS and the battery pack 300. Among them, the duty cycle of the third pulse signal is determined according to the voltage or current of the first end of the power converter 100, or the voltage or current of the second end of the power converter 100. The first condition is that the current at the second end of the power converter 100 (also referred to as the charging current of the battery pack 300) is less than the charging current threshold of the battery pack 300. The second condition is that the current at the first end of the power converter 100 (also referred to as the discharge current of the DC bus BUS) is less than the discharge current threshold of the DC bus BUS. The third condition is that the voltage at the first end of the power converter 100 (the voltage of the DC bus BUS) is greater than the upper voltage threshold of the DC bus BUS. The fourth condition is that the voltage at the second end of the power converter 100 (the voltage of the battery pack 300) is less than the lower voltage threshold of the battery pack 300.

[0085] When the battery pack 300 discharges to the DC bus BUS:

[0086] In one possible embodiment, referring to Figure 2 The second pulse signal is used to control the fourth bridge arm (the seventh switch tube Q7 and the eighth switch tube Q8) so that the second DCDC power conversion circuit 120 converts the voltage of the battery pack 300 to generate an internal bus voltage. The first pulse signal is used to control the second switch tube Q2 so that the first DCDC power conversion circuit 110 performs a boost power conversion on the internal bus voltage so that the battery pack 300 discharges to the DC bus BUS. The specific power conversion process can refer to the prior art, and the embodiments of the present application will not be repeated here.

[0087] The controller 130 is also used to perform one of the following when the battery pack 300 discharges to the DC bus BUS and meets the first condition, the second condition, the third condition or the fourth condition: reduce the duty cycle of the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, so as to increase the internal bus voltage; or stop sending the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, and send a third pulse signal to control the third switch tube Q3, so that the first DCDC power conversion circuit 110 performs a step-down power conversion on the internal bus voltage to increase the internal bus voltage. Thereby reducing the discharge current of the battery pack 300 or the charging current of the DC bus BUS or the voltage of the DC bus BUS, or slowing down the voltage drop trend of the battery pack 300, so as to improve the stability and safety of the voltage and current in the loop between the DC bus BUS and the battery pack 300. Among them, the duty cycle of the third pulse signal is determined according to the voltage or current of the first end of the power converter 100, or the voltage or current of the second end of the power converter 100. The first condition is that the current at the second end of the power converter 100 (also referred to as the discharge current of the battery pack 300) is greater than the discharge current threshold of the battery pack 300. The second condition is that the current at the first end of the power converter 100 (also referred to as the charging current of the DC bus BUS) is greater than the charging current threshold of the DC bus BUS. The third condition is that the voltage at the first end of the power converter 100 (also referred to as the voltage of the DC bus BUS) is greater than the upper voltage threshold of the DC bus BUS. The fourth condition is that the voltage at the second end of the power converter 100 (also referred to as the voltage of the battery pack 300) is less than the lower voltage threshold of the battery pack 300. The embodiments of the present application do not limit the specific values ​​of the discharge current threshold of the battery pack 300 or the charging current threshold of the DC bus BUS.

[0088] In a possible embodiment, the controller 130 is also used to stop sending the first pulse signal and the second pulse signal, and send the fourth pulse signal to control the first switch tube Q1 or the fourth switch tube Q4, and send the fifth pulse signal to control the third bridge arm (the fifth switch tube Q5 and the sixth switch tube Q6) when the battery pack 300 discharges to the DC bus BUS and the above-mentioned first condition, second condition, third condition or fourth condition is met, and the fifth condition is met, so that the DC bus BUS charges the battery pack 300 and increases the internal bus voltage, thereby reducing the discharge current of the battery pack 300 or the charging current of the DC bus BUS or the voltage of the DC bus BUS, or reversing the voltage decrease trend of the battery pack 300, thereby improving the stability and safety of the voltage and current in the loop between the DC bus BUS and the battery pack 300. Among them, the duty cycle of the fourth pulse signal is determined according to the voltage or current of the first end of the power converter 100, or the voltage or current of the second end of the power converter 100, and the fifth pulse signal has a fixed duty cycle and a fixed frequency. The embodiment of the present application does not limit the specific values ​​of the duty cycle and frequency of the fifth pulse signal. The fifth condition is that the voltage of the first end of the power converter 100 (also referred to as the voltage of the DC bus BUS) is greater than the lower limit voltage threshold of the DC bus BUS, the current of the first end of the power converter 100 (also referred to as the charging current of the DC bus BUS) is less than or equal to the allowable charge-to-discharge current threshold of the DC bus BUS, the voltage of the second end of the power converter 100 (also referred to as the voltage of the battery pack 300) is less than the upper limit voltage threshold of the battery pack 300, and the current of the second end of the power converter 100 (also referred to as the discharge current of the battery pack 300) is less than or equal to the allowable discharge-to-charge current threshold of the battery pack 300. The embodiment of the present application does not limit the specific values ​​of the allowable charge-to-discharge current threshold of the DC bus BUS and the allowable discharge-to-charge current threshold of the battery pack 300.

[0089] In one possible embodiment, referring to Figure 2 The second pulse signal is used to control the seventh switch tube Q7 and the eighth switch tube Q8, so that the second DCDC power conversion circuit 120 converts the voltage of the battery pack 300 to generate an internal bus voltage. The first pulse signal is used to control the third switch tube Q3, so that the first DCDC power conversion circuit 110 performs a step-down power conversion on the internal bus voltage, so that the battery pack 300 discharges to the DC bus. The specific power conversion process can refer to the prior art, and the embodiments of the present application will not be repeated here.

[0090] The controller 130 is also used to perform one of the following when the battery pack 300 discharges to the DC bus BUS and meets the first condition, the second condition, the third condition or the fourth condition: increase the duty cycle of the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, so as to reduce the internal bus voltage; or stop sending the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, and send the third pulse signal to control the second switch tube Q2, so that the first DCDC power conversion circuit 110 performs a boost power conversion on the internal bus voltage to reduce the internal bus voltage. Thereby increasing the discharge current of the battery pack 300, the charging current of the DC bus BUS or the voltage of the DC bus BUS, or accelerating the voltage drop trend of the battery pack 300, so as to improve the stability and safety of the voltage and current in the loop between the DC bus BUS and the battery pack 300. Among them, the duty cycle of the third pulse signal is determined according to the voltage or current of the first end of the power converter 100, or the voltage or current of the second end of the power converter 100. The first condition is that the current at the second end of the power converter 100 (also referred to as the discharge current of the battery pack 300) is less than the discharge current threshold of the battery pack 300. The second condition is that the current at the first end of the power converter 100 (also referred to as the charging current of the DC bus BUS) is less than the charging current threshold of the DC bus BUS. The third condition is that the voltage at the first end of the power converter 100 (also referred to as the voltage of the DC bus BUS) is less than the lower limit voltage threshold of the DC bus BUS. The fourth condition is that the voltage at the second end of the power converter 100 (also referred to as the voltage of the battery pack 300) is greater than the upper limit voltage threshold of the battery pack 300.

[0091] In the power converter 100 provided in the embodiment of the present application, the controller 130 generates a pulse signal to perform closed-loop control on the first DCDC power conversion circuit 110, so as to control the voltage or current of any node in the loop composed of the DC bus BUS, the first DCDC power conversion circuit 110, the second DCDC power conversion circuit 120 and the battery pack 300, and improve the stability and safety of the voltage and current in the loop between the DC bus BUS and the battery pack 300. At the same time, the controller 130 generates a pulse signal to perform open-loop control on the second DCDC power conversion circuit 120, and there is no need to set the voltage detection circuit and current detection circuit corresponding to the second DCDC power conversion circuit 120, so as to reduce the complexity of the control circuit of the DCDC power conversion circuit in the power converter 100, and reduce the cost of the power converter 100.

[0092] In a possible embodiment, the controller 130 is also used to control the first DCDC power conversion circuit 110 to stop working when the voltage or current at the connection end of the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120, or the voltage or current at the second end of the power converter 100 is greater than the first protection threshold. Alternatively, when the voltage or current at the connection end of the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120, or the voltage or current at the second end of the power converter 100 is greater than the second protection threshold, the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120 are controlled to stop working, and the second protection threshold is greater than the first protection threshold. The embodiment of the present application does not limit the specific values ​​of the first protection threshold and the second protection threshold.

[0093] It can be understood that when the voltage or current at the connection end of the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120, or the voltage or current at the second end of the power converter 100 is greater than the protection threshold, the controller 130 mainly controls the first DCDC power conversion circuit 110 to stop working to achieve overcurrent or overvoltage protection. When selecting hardware, the first DCDC power conversion circuit 110 selects a device with higher withstand voltage and current, and the second DCDC power conversion circuit 120 can select a device with lower withstand voltage and current, without requiring both DCDC power conversion circuits to select devices with higher withstand voltage and current, thereby reducing the cost of the power converter 100. At the same time, by setting different protection thresholds, the power converter 100 is protected at different voltage or current levels, thereby improving the reliability and stability of the power converter 100.

[0094] For example, Fig. 9 , which is a schematic diagram of a current curve waveform and a pulse signal waveform of a battery pack 300. Fig. 9 When the current at the second end of the power converter 100 (also referred to as the current of the battery pack 300) is greater than the first protection threshold, the controller 130 stops sending a pulse signal to the first DCDC power conversion circuit 110 to control the first DCDC power conversion circuit 110 to stop working. Fig. 9 When the current at the second end of the power converter 100 (also referred to as the current of the battery pack 300) is greater than the second protection threshold, the controller 130 stops sending pulse signals to the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120 to control the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120 to stop working.

[0095] In a possible embodiment, the controller 130 is further used to control the first DCDC power conversion circuit 110 to stop working when the current of the resonant cavity in the second DCDC power conversion circuit 120 is greater than the first protection threshold. The controller 130 is also used to control the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120 to stop working when the current of the resonant cavity in the second DCDC power conversion circuit 120 is greater than the second protection threshold.

[0096] In the power converter 100 provided in the embodiment of the present application, when the voltage or current at the connection end of the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120, or the voltage or current at the second end of the power converter 100 is greater than the protection threshold, the controller 130 mainly controls the first DCDC power conversion circuit 110 to stop working to achieve overcurrent or overvoltage protection. When selecting hardware, the first DCDC power conversion circuit 110 selects a device with higher withstand voltage and current, and the second DCDC power conversion circuit 120 can select a device with lower withstand voltage and current, without requiring both DCDC power conversion circuits to select devices with higher withstand voltage and current, thereby reducing the cost of the power converter 100. At the same time, by setting different protection thresholds, the power converter 100 is protected in stages at different voltage or current levels, thereby improving the reliability and stability of the power converter 100.

[0097] like Fig.10 As shown, an embodiment of the present application further provides a control method for a power converter, which is applied to the above-mentioned power converter 100, and the method includes step S101.

[0098] S101, the controller 130 sends a first pulse signal to control the operation of the first DCDC power conversion circuit 110, and sends a second pulse signal to control the operation of the second DCDC power conversion circuit 120, so that the DC bus BUS charges the battery pack 300, or the battery pack 300 discharges to the DC bus BUS.

[0099] The duty cycle of the first pulse signal is determined according to the voltage or current at the first end of the power converter 100, or the voltage or current at the second end of the power converter 100. The second pulse signal has a fixed duty cycle and a fixed frequency, and the embodiment of the present application does not limit the specific values ​​of the duty cycle and frequency of the second pulse signal.

[0100] The process of the controller 130 controlling the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120 through a pulse signal, as well as how to adjust the pulse signal to improve the stability and safety of the voltage and current in the loop between the DC bus BUS and the battery pack 300, can be referred to the detailed description of the above-mentioned power converter 100, and the embodiments of the present application will not be repeated here.

[0101] In the control method of the power converter provided in the embodiment of the present application, the duty cycle of the first pulse signal is determined according to the voltage or current of the first end of the power converter 100, or the voltage or current of the second end of the power converter 100, and the second pulse signal has a fixed duty cycle and a fixed frequency. The controller 130 performs closed-loop control on the first DCDC power conversion circuit 110 by sending the first pulse signal, and performs open-loop control on the second DCDC power conversion circuit 120 by sending the second pulse signal, so that the DC bus BUS charges the battery pack 300, or the battery pack 300 discharges to the DC bus BUS, instead of performing independent tracking control and protection on each DCDC power conversion circuit using the voltage and current at both ends of the DCDC power conversion circuit as feedback and control targets, and there is no need to set a voltage detection circuit and a current detection circuit corresponding to each DCDC power conversion circuit, thereby reducing the complexity of the control circuit of the DCDC power conversion circuit in the power converter 100 and reducing the cost of the power converter 100. Secondly, the controller 130 performs closed-loop control on the first DCDC power conversion circuit 110 by sending the first pulse signal, so as to control the voltage or current of any node in the loop formed by the DC bus BUS, the first DCDC power conversion circuit 110, the second DCDC power conversion circuit 120 and the battery pack 300, and improve the stability and safety of the voltage and current in the loop between the DC bus BUS and the battery pack 300. Finally, compared with the closed-loop control of the second DCDC power conversion circuit 120 by the controller 130, the controller 130 performs open-loop control on the second DCDC power conversion circuit 120 by sending the second pulse signal, which can reduce the dynamic response delay of the power converter 100.

[0102] In a possible embodiment, Fig.10 As shown, the control method of the power converter provided in the embodiment of the present application further includes step S102, which can be performed after the above step S101.

[0103] S102, the controller 130 controls the first DCDC power conversion circuit 110 to stop working when the voltage or current at the connection end of the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120, or the voltage or current at the second end of the power converter 100 is greater than the first protection threshold. Alternatively, when the voltage or current at the connection end of the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120, or the voltage or current at the second end of the power converter 100 is greater than the second protection threshold, the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120 are controlled to stop working.

[0104] Among them, the second protection threshold is greater than the first protection threshold, and the embodiment of the present application does not limit the specific values ​​of the first protection threshold and the second protection threshold.

[0105] In the control method of the power converter provided by the embodiment of the present application, when the voltage or current at the connection end of the first DCDC power conversion circuit 110 and the second DCDC power conversion circuit 120, or the voltage or current at the second end of the power converter 100 is greater than the protection threshold, the controller 130 mainly controls the first DCDC power conversion circuit 110 to stop working to achieve overcurrent or overvoltage protection. When selecting hardware, the first DCDC power conversion circuit 110 selects a device with higher withstand voltage and current, and the second DCDC power conversion circuit 120 can select a device with lower withstand voltage and current, without requiring both DCDC power conversion circuits to select devices with higher withstand voltage and current, thereby reducing the cost of the power converter 100. At the same time, by setting different protection thresholds, the power converter 100 is protected in stages at different voltage or current levels, thereby improving the reliability and stability of the power converter 100.

[0106] Based on this, Figure 1 As shown, the embodiment of the present application also provides an energy storage system 200, which includes a power converter 100 and a battery pack 300 connected to the power converter 100. The power converter 100 is also used to connect to the DC bus BUS. The power converter 100 is used to perform power conversion on the voltage of the DC bus BUS so that the DC bus BUS charges the battery pack 300, or to perform power conversion on the voltage of the battery pack 300 so that the battery pack 300 discharges to the DC bus BUS. The circuit topology of the power converter 100 is as follows: Figures 1 to 6 The circuit topology of the power converter 100 shown in any of the figures.

[0107] The above detailed description of the power converter 100 and the analysis of the beneficial effects can be correspondingly referred to the control method of the power converter and the energy storage system 200, and the embodiments of the present application will not be repeated here.

[0108] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A power converter, characterized in that: The first end of the power converter is used to be connected to a DC bus, and the second end of the power converter is used to be connected to a battery pack. The power converter includes a first DCDC power conversion circuit, a second DCDC power conversion circuit and a controller. One end of the first DCDC power conversion circuit is connected to the first end of the power converter, the other end of the first DCDC power conversion circuit is connected to one end of the second DCDC power conversion circuit, and the other end of the second DCDC power conversion circuit is connected to the second end of the power converter; The controller is used to send a first pulse signal to control the operation of the first DCDC power conversion circuit, and send a second pulse signal to control the operation of the second DCDC power conversion circuit, so that the DC bus charges the battery pack, or the battery pack discharges to the DC bus; The duty cycle of the first pulse signal is determined according to the voltage or current at the first end of the power converter, or the voltage or current at the second end of the power converter; and the second pulse signal has a fixed duty cycle and a fixed frequency.

2. The power converter according to claim 1, characterized in that: The DC bus includes a positive DC bus and a negative DC bus, and the first DCDC power conversion circuit includes: A first bridge arm and a second bridge arm connected between the positive DC bus and the negative DC bus, and a first inductor connecting a midpoint of the first bridge arm and a midpoint of the second bridge arm, wherein the first bridge arm comprises a first switch tube and a second switch tube connected in series, the second bridge arm comprises a third switch tube and a fourth switch tube connected in series, the midpoint of the first bridge arm is a connection point between the first switch tube and the second switch tube, and the midpoint of the second bridge arm is a connection point between the third switch tube and the fourth switch tube; The second DCDC power conversion circuit comprises: A first capacitor, a third bridge arm and a capacitor branch connected between the positive DC bus and the negative DC bus, wherein the third bridge arm includes a fifth switch tube and a sixth switch tube connected in series, and the capacitor branch includes a second capacitor and a third capacitor connected in series; The primary coil of the transformer and the second inductor are connected in series and then connected between the midpoint of the third bridge arm and the midpoint of the capacitor branch. The third inductor is connected in parallel with the primary coil of the transformer. The midpoint of the third bridge arm is the connection point of the fifth switch tube and the sixth switch tube. The midpoint of the capacitor branch is the connection point of the second capacitor and the third capacitor. A fourth bridge arm and a fifth bridge arm are used to be connected between the positive pole and the negative pole of the battery pack, the fourth bridge arm includes a seventh switch tube and an eighth switch tube connected in series, the fifth bridge arm includes a ninth switch tube and a tenth switch tube connected in series, the secondary coil of the transformer is connected between the midpoints of the fourth bridge arm and the fifth bridge arm, the midpoint of the fourth bridge arm is the connection point of the seventh switch tube and the eighth switch tube, and the midpoint of the fifth bridge arm is the connection point of the ninth switch tube and the tenth switch tube.

3. The power converter according to claim 2, characterized in that: The first pulse signal is used to control the fourth switch tube, and the second pulse signal is used to control the third bridge arm; The controller is further configured to, when the DC bus charges the battery pack and the first condition, the second condition, the third condition or the fourth condition is met, perform one of the following: reducing the duty cycle of the first pulse signal and maintaining the duty cycle and frequency of the second pulse signal unchanged; Alternatively, stop sending the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, and send a third pulse signal to control the first switch tube, the duty cycle of the third pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter; The first condition is that the current at the second end of the power converter is greater than the charging current threshold of the battery pack; The second condition is that the current at the first end of the power converter is greater than the discharge current threshold of the DC bus; The third condition is that the voltage of the first terminal of the power converter is less than the lower voltage threshold of the DC bus; The fourth condition is that the voltage of the second terminal of the power converter is greater than an upper voltage threshold of the battery pack.

4. The power converter according to claim 3, characterized in that: The controller is further configured to stop sending the first pulse signal and the second pulse signal, and send a fourth pulse signal to control the second switch tube or the third switch tube, and send a fifth pulse signal to control the fourth bridge arm, so that the battery pack discharges to the DC bus, when the DC bus charges the battery pack and the first condition, the second condition, the third condition or the fourth condition is satisfied, and the fifth condition is satisfied, wherein the duty cycle of the fourth pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter, and the fifth pulse signal has a fixed duty cycle and a fixed frequency; The fifth condition is that the voltage of the first end of the power converter is less than the upper limit voltage threshold of the DC bus, the current of the first end of the power converter is less than or equal to the allowable discharge-to-charge current threshold of the DC bus, the voltage of the second end of the power converter is greater than the lower limit voltage threshold of the battery pack, and the current of the second end of the power converter is less than or equal to the allowable charge-to-discharge current threshold of the battery pack.

5. The power converter according to claim 2, characterized in that: The first pulse signal is used to control the first switch tube, and the second pulse signal is used to control the third bridge arm; The controller is further configured to, when the DC bus charges the battery pack and the first condition, the second condition, the third condition or the fourth condition is met, perform one of the following: Increasing the duty cycle of the first pulse signal and keeping the duty cycle and frequency of the second pulse signal unchanged; Alternatively, stop sending the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, and send a third pulse signal to control the fourth switch tube, the duty cycle of the third pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter; The first condition is that the current at the second end of the power converter is less than a charging current threshold of the battery pack; The second condition is that the current at the first end of the power converter is less than a discharge current threshold of the DC bus; The third condition is that the voltage at the first end of the power converter is greater than the upper voltage threshold of the DC bus; The fourth condition is that the voltage of the second end of the power converter is less than the lower voltage threshold of the battery pack.

6. The power converter according to claim 2, characterized in that: The first pulse signal is used to control the second switch tube, and the second pulse signal is used to control the fourth bridge arm; The controller is further configured to, when the battery pack discharges to the DC bus and the first condition, the second condition, the third condition or the fourth condition is met, perform one of the following: reducing the duty cycle of the first pulse signal and maintaining the duty cycle and frequency of the second pulse signal unchanged; Alternatively, stop sending the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, and send a third pulse signal to control the third switch tube, wherein the duty cycle of the third pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter; The first condition is that the current at the second end of the power converter is greater than the discharge current threshold of the battery pack; The second condition is that the current at the first end of the power converter is greater than a charging current threshold of the DC bus; The third condition is that the voltage at the first end of the power converter is greater than the upper voltage threshold of the DC bus; The fourth condition is that the voltage of the second end of the power converter is less than the lower voltage threshold of the battery pack.

7. The power converter according to claim 6, characterized in that: The controller is further configured to stop sending the first pulse signal and the second pulse signal, and send a fourth pulse signal to control the first switch tube or the fourth switch tube, and send a fifth pulse signal to control the third bridge arm, so that the DC bus charges the battery pack, when the battery pack discharges to the DC bus and the first condition, the second condition, the third condition or the fourth condition is satisfied, and the fifth condition is satisfied, wherein the duty cycle of the fourth pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter, and the fifth pulse signal has a fixed duty cycle and a fixed frequency; The fifth condition is that the voltage of the first end of the power converter is greater than the lower limit voltage threshold of the DC bus, the current of the first end of the power converter is less than or equal to the allowable charge-to-discharge current threshold of the DC bus, the voltage of the second end of the power converter is less than the upper limit voltage threshold of the battery pack, and the current of the second end of the power converter is less than or equal to the allowable discharge-to-charge current threshold of the battery pack.

8. The power converter according to claim 2, characterized in that: The first pulse signal is used to control the third switch tube, and the second pulse signal is used to control the fourth bridge arm; The controller is further configured to, when the battery pack discharges to the DC bus and the first condition, the second condition, the third condition or the fourth condition is met, perform one of the following: Increasing the duty cycle of the first pulse signal and keeping the duty cycle and frequency of the second pulse signal unchanged; Alternatively, stop sending the first pulse signal, keep the duty cycle and frequency of the second pulse signal unchanged, and send a third pulse signal to control the second switch tube, the duty cycle of the third pulse signal is determined according to the voltage or current of the first end of the power converter, or the voltage or current of the second end of the power converter; The first condition is that the current at the second end of the power converter is less than the discharge current threshold of the battery pack; The second condition is that the current at the first end of the power converter is less than a charging current threshold of the DC bus; The third condition is that the voltage of the first terminal of the power converter is less than the lower voltage threshold of the DC bus; The fourth condition is that the voltage of the second terminal of the power converter is greater than an upper voltage threshold of the battery pack.

9. The power converter according to any one of claims 1 to 8, characterized in that: The controller is further configured to control the first DCDC power conversion circuit to stop working when the voltage or current at the connection end of the first DCDC power conversion circuit and the second DCDC power conversion circuit, or the voltage or current at the second end of the power converter is greater than a first protection threshold; Alternatively, when the voltage or current at the connection end of the first DCDC power conversion circuit and the second DCDC power conversion circuit, or the voltage or current at the second end of the power converter is greater than a second protection threshold, the first DCDC power conversion circuit and the second DCDC power conversion circuit are controlled to stop working, and the second protection threshold is greater than the first protection threshold.

10. A method for controlling a power converter, characterized in that: Applied to a power converter, the first end of the power converter is used to be connected to a DC bus, the second end of the power converter is used to be connected to a battery pack, the power converter comprises a first DCDC power conversion circuit, a second DCDC power conversion circuit and a controller, one end of the first DCDC power conversion circuit is connected to the first end of the power converter, the other end of the first DCDC power conversion circuit is connected to one end of the second DCDC power conversion circuit, and the other end of the second DCDC power conversion circuit is connected to the second end of the power converter; the method comprises: Sending a first pulse signal to control the operation of the first DCDC power conversion circuit, and sending a second pulse signal to control the operation of the second DCDC power conversion circuit, so that the DC bus charges the battery pack, or the battery pack discharges to the DC bus; The duty cycle of the first pulse signal is determined according to the voltage or current at the first end of the power converter, or the voltage or current at the second end of the power converter; and the second pulse signal has a fixed duty cycle and a fixed frequency.

11. The method according to claim 10, characterized in that The method further comprises: When the voltage or current at the connection end of the first DCDC power conversion circuit and the second DCDC power conversion circuit, or the voltage or current at the second end of the power converter is greater than a first protection threshold, control the first DCDC power conversion circuit to stop working; Alternatively, when the voltage or current at the connection end of the first DCDC power conversion circuit and the second DCDC power conversion circuit, or the voltage or current at the second end of the power converter is greater than a second protection threshold, the first DCDC power conversion circuit and the second DCDC power conversion circuit are controlled to stop working, and the second protection threshold is greater than the first protection threshold.

12. An energy storage system, characterized in that: The energy storage system comprises a power converter according to any one of claims 1 to 9, and a battery pack connected to the power converter; The power converter is used to perform power conversion on the voltage of the DC bus so that the DC bus charges the battery pack, or to perform power conversion on the voltage of the battery pack so that the battery pack discharges to the DC bus.

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