Power conversion device and uninterruptible power supply

Abstract

The embodiment of the invention discloses a power conversion device and an uninterruptible power supply, relates to the field of power electronics, and solves the problem of inaccurate detection when the current value of the output end of the uninterruptible power supply or a photovoltaic inverter is detected at present. The power conversion device comprises an inductor and a first current sampling circuit which are connected in series between the output end of an inverter circuit and the output end of the power conversion device, and a first capacitor and a second current sampling circuit which are connected in series between the output end of the power conversion device and a grounding end. The first current sampling circuit is used for sampling the current value of the inductor, the second current sampling circuit is used for sampling the current value of the first capacitor, and the operational amplifier circuit is used for receiving the current value of the inductor and the current value of the first capacitor and calculating the current value of the output end of the power conversion device.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a power conversion device and an uninterruptible power supply. Background Art

[0002] Uninterruptible power supply (UPS) or photovoltaic inverter adopts dual-loop control to improve the dynamic response and stability of the system while ensuring the quality of the output voltage. The dual-loop control includes voltage outer loop control and current inner loop control. The voltage outer loop control is used to ensure the stability and accuracy of the output voltage, and the current inner loop control is used to quickly respond to load changes and accurately control the current.

[0003] Taking the uninterruptible power supply as an example, the uninterruptible power supply includes an inverter circuit, an inductor arranged between the output end of the inverter circuit and the output end of the uninterruptible power supply, and a capacitor arranged between the output end of the uninterruptible power supply and the ground end. In the case where the uninterruptible power supply adopts the current inner loop control, the current value of the inductor is used as feedback to improve the dynamic performance of the inverter circuit, but it will cause the load regulation rate of the output voltage of the uninterruptible power supply to be too high. The current value at the output end of the uninterruptible power supply can be used as feedforward to compensate for the problem that the load regulation rate of the output voltage of the uninterruptible power supply is too high when the current value of the inductor is used as feedback, and the current value at the output end of the uninterruptible power supply can be used for parallel current sharing feedback.

[0004] However, currently, when detecting the current value at the output end of an uninterruptible power supply or a photovoltaic inverter, there is a problem of inaccurate detection, which will not effectively improve the dynamic response and stability of the system. Summary of the invention

[0005] The embodiments of the present application provide a power conversion device and an uninterruptible power supply, which solve the problem of inaccurate detection when detecting the current value at the output end of an uninterruptible power supply or a photovoltaic inverter, and can effectively improve the dynamic response and stability of the system.

[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 conversion device is provided, which includes an inverter circuit, an inductor, a first capacitor, a first current sampling circuit, a second current sampling circuit, and an operational amplifier circuit. The positive input terminal of the inverter circuit is connected to the positive DC bus, the negative input terminal of the inverter circuit is connected to the negative DC bus, the inductor and the first current sampling circuit are arranged in series between the output terminal of the inverter circuit and the output terminal of the power conversion device, and the first capacitor and the second current sampling circuit are arranged in series between the output terminal of the power conversion device and the ground terminal. The first current sampling circuit is used to sample the current value of the inductor, the second current sampling circuit is used to sample the current value of the first capacitor, and the operational amplifier circuit is used to receive the current value of the inductor and the current value of the first capacitor, and calculate the current value of the output terminal of the power conversion device.

[0008] Based on this solution, the first current sampling circuit is used to sample the current value of the inductor, the second current sampling circuit is used to sample the current value of the first capacitor, and the operational amplifier circuit is used to receive the current value of the inductor and the current value of the first capacitor to calculate the current value of the output end of the power conversion device. Since the first capacitor can isolate the DC component, the current value of the first capacitor can be detected more accurately. The operational amplifier circuit can more accurately calculate the current value of the output end of the power conversion device based on the current value of the inductor and the current value of the first capacitor. The current value of the output end of the power conversion device is used as feedforward, thereby effectively improving the dynamic response and stability of the power conversion device.

[0009] In combination with the first aspect, in one possible implementation, the operational amplifier circuit includes a subtraction circuit, and the current value at the output end of the power conversion device is the difference between the current value of the inductor and the current value of the first capacitor, or the operational amplifier circuit includes an addition circuit, and the current value at the output end of the power conversion device is the sum of the current value of the inductor and the current value of the first capacitor.

[0010] In combination with the first aspect, in a possible implementation, the power conversion device further includes a current limiting threshold generating circuit, a comparison circuit and a controller. The input end of the current limiting threshold generating circuit is connected to the output end of the operational amplifier circuit, the output end of the current limiting threshold generating circuit and the sampling output end of the first current sampling circuit are respectively connected to the two input ends of the comparison circuit, the output end of the comparison circuit is connected to the input end of the controller, and the current value of the inductor is used to indicate the current value of the switch tube in the inverter circuit. The current limiting threshold generating circuit is used to output a variable current limiting threshold when the voltage value output by the operational amplifier circuit is greater than the positive first voltage threshold or less than the negative first voltage threshold. The comparison circuit is used to output a current limiting enable signal when the variable current limiting threshold is greater than the current value of the switch tube in the inverter circuit. The controller is used to control the switch tube in the inverter circuit to turn off when receiving the current limiting enable signal.

[0011] Based on this solution, the operational amplifier circuit can determine a more accurate current value at the output end of the power conversion device according to the current value of the inductor and the current value of the first capacitor. The voltage value output by the operational amplifier circuit is used to indicate the current value at the output end of the power conversion device. The current limiting threshold generating circuit outputs a variable current limiting threshold according to the voltage value output by the operational amplifier circuit. The comparison circuit outputs a current limiting enable signal when the variable current limiting threshold is greater than the current value of the switch tube in the inverter circuit. When receiving the current limiting enable signal, the controller controls the switch tube in the inverter circuit to turn off. Therefore, when a nonlinear load is suddenly added to the output end of the power conversion device (generating a load shock) and the current at the output end of the power conversion device suddenly increases, the switch tube in the inverter circuit can be controlled to turn off, which can improve the safety and reliability of the power conversion device.

[0012] In combination with the first aspect, in a possible implementation, the power conversion device further includes a current limiting threshold generating circuit, a comparison circuit and a controller. The input end of the current limiting threshold generating circuit is connected to the sampling output end of the second current sampling circuit, the output end of the current limiting threshold generating circuit and the sampling output end of the first current sampling circuit are respectively connected to the two input ends of the comparison circuit, the output end of the comparison circuit is connected to the input end of the controller, and the current value of the inductor is used to indicate the current value of the switch tube in the inverter circuit. The current limiting threshold generating circuit is used to output a variable current limiting threshold when the voltage value output by the second current sampling circuit is greater than the positive second voltage threshold or less than the negative second voltage threshold. The comparison circuit is used to output a current limiting enable signal when the variable current limiting threshold is greater than the current value of the switch tube in the inverter circuit. The controller is used to control the switch tube in the inverter circuit to turn off when receiving the current limiting enable signal.

[0013] Based on this solution, since the first capacitor can cut off the DC component, the current value of the first capacitor can be detected more accurately, the voltage value output by the second current sampling circuit is used to indicate the current value of the first capacitor, and the current limiting threshold generating circuit outputs a variable current limiting threshold according to the voltage value output by the second current sampling circuit. The comparison circuit outputs a current limiting enable signal when the variable current limiting threshold is greater than the current value of the switch tube in the inverter circuit. When the controller receives the current limiting enable signal, it controls the switch tube in the inverter circuit to turn off. Thus, when a nonlinear load is suddenly added to the output end of the power conversion device (generating a load shock) and the current at the output end of the power conversion device suddenly increases, the switch tube in the inverter circuit can be controlled to turn off, which can improve the safety and reliability of the power conversion device. At the same time, since the current value at the output end of the power conversion device is determined according to the current value of the inductor and the current value of the first capacitor, compared with the current value at the output end of the power conversion device, the current value of the first capacitor is more accurate, which can more significantly improve the safety and reliability of the power conversion device.

[0014] In combination with the first aspect, in a possible implementation, the current limiting threshold generating circuit includes: an inverting input terminal of a first comparator and a non-inverting input terminal of a second comparator are connected to an input terminal of the current limiting threshold generating circuit, the non-inverting input terminal of the first comparator is used to receive a positive voltage threshold, and the inverting input terminal of the second comparator is used to receive a negative voltage threshold. The output terminal of the first comparator and the output terminal of the second comparator are connected to one end of a first resistor, the other end of the first resistor and one end of the second resistor are connected to a controlled end of a first switch tube, the first end of the first switch tube is connected to one end of a third resistor and one end of a fourth resistor, the other end of the third resistor and one end of a fifth resistor are used to receive a reference voltage, the other end of the fourth resistor and one end of a sixth resistor are connected to the controlled end of the second switch tube, the first end of the second switch tube is connected to one end of a seventh resistor, the other end of the fifth resistor, the other end of the seventh resistor, and one end of the second capacitor are connected to the output terminal of the current limiting threshold generating circuit, and the other end of the second resistor, the second end of the first switch tube, the other end of the sixth resistor, the second end of the second switch tube, and the other end of the second capacitor are connected to the ground terminal.

[0015] In a second aspect of the embodiments of the present application, an uninterruptible power supply is provided, the uninterruptible power supply includes a main circuit, a bypass and a load end, the main circuit and the bypass are both used to supply power to the load end. A rectifier circuit and a power conversion device are provided on the main circuit, the input end of the rectifier circuit is connected to the input end of the uninterruptible power supply, the output end of the rectifier circuit is connected to the input end of the power conversion device, the output end of the power conversion device is connected to the load end, the load end is used to connect the load, and the power conversion device is the power conversion device as described in the first aspect or any possible implementation of the first aspect.

[0016] The description of the second aspect in this application can refer to the detailed description of the first aspect; and the beneficial effects of the second aspect can refer to the analysis of the beneficial effects of the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A circuit topology diagram of an uninterruptible power supply;

[0018] Figure 2 A control flow diagram of an uninterruptible power supply using dual-loop control;

[0019] Figure 3 A schematic diagram of a circuit topology of a power conversion device provided in an embodiment of the present application;

[0020] Figure 4 A schematic diagram of a circuit topology of another power conversion device provided in an embodiment of the present application;

[0021] Figure 5 A circuit topology diagram of another power conversion device provided in an embodiment of the present application;

[0022] Figure 6 A schematic diagram of a circuit topology of another power conversion device provided in an embodiment of the present application;

[0023] Figure 7 A schematic diagram of a circuit topology of another power conversion device provided in an embodiment of the present application;

[0024] Figure 8 A schematic diagram of a circuit topology of another power conversion device provided in an embodiment of the present application;

[0025] Fig. 9 A schematic diagram of a circuit topology of another power conversion device provided in an embodiment of the present application;

[0026] Fig.10 A schematic diagram of a circuit topology of another power conversion device provided in an embodiment of the present application;

[0027] Fig.11 A schematic diagram of a change curve of a variable current limiting threshold provided in an embodiment of the present application;

[0028] Fig.12 A schematic diagram of a circuit topology of another power conversion device provided in an embodiment of the present application;

[0029] Fig.13 A schematic diagram of a circuit topology of a photovoltaic inverter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] The following will discuss the making and use of each embodiment 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.

[0031] 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.

[0032] 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.

[0033] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. In the embodiments of the present application, words such as "first" and "second" do not limit the quantity and order. In the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplary" or "for example" in the present application should not be interpreted as being more preferred or more advantageous than other embodiments or design. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way.

[0034] Before introducing the embodiments of the present application, the technical terms and background technologies involved in the present application are first introduced.

[0035] Load regulation: It is an important indicator to measure the performance of power supply (uninterruptible power supply or photovoltaic inverter), reflecting the stability of power supply output voltage when the load changes. Specifically, load regulation refers to the change of output voltage of power supply when it is no-load (no load current) and full-load (reaching the rated maximum load current), usually expressed as a percentage. Load regulation = (output voltage when no load - output voltage when full load) / output voltage when full load * 100%.

[0036] Parallel current sharing feedback: refers to when multiple power supplies (uninterruptible power supplies or photovoltaic inverters) work in parallel, a certain control strategy is used to ensure that each power supply can evenly share the load current, avoid overloading of some power supplies due to excessive current, and prevent other power supplies from working in a non-optimal state due to insufficient current.

[0037] Uninterruptible power supplies are used to provide uninterrupted power to loads that require high power stability. This uninterruptible power supply is widely used in data centers, medical equipment, industrial automation, communication equipment and other fields to provide stable and uninterrupted power supply for key equipment.

[0038] like Figure 1The figure shows a circuit topology diagram of an uninterruptible power supply 100. The uninterruptible power supply 100 includes a main circuit 110, a bypass circuit 120 and a load end. The main circuit 110 is used to connect to a first input power source 210, and the bypass circuit 120 is used to connect to a second input power source 220. Both the main circuit 110 and the bypass circuit 120 are used to supply power to the load end, and the load end is used to connect to a load 300 to supply power to the load 300. The main circuit 110 is provided with a rectifier circuit 111, an inverter circuit 112, an inductor L, a hall current sensor H, a current transformer (CT) and a capacitor C. The input end of the rectifier circuit 111 is used to connect to the first input power supply 210, the output end of the rectifier circuit 111 is connected to the positive DC bus BUS+ and the negative DC bus BUS-, the positive input end of the inverter circuit 112 is connected to the positive DC bus BUS+, the negative input end of the inverter circuit 112 is connected to the negative DC bus BUS-, the output end of the inverter circuit 112 is connected to one end of the inductor L, the other end of the inductor L is connected to the first end of the Hall current sensor H, the current transformer CT is arranged between the second end of the Hall current sensor H and the load end, and the capacitor C is arranged between the second end of the Hall current sensor H and the ground end (ground, G).

[0039] Reference Figure 1 The main circuit 110 in the uninterruptible power supply 100 also includes positive and negative bus capacitors arranged between the positive DC bus BUS+ and the negative DC bus BUS-, and the positive and negative bus capacitors include a first bus capacitor Ca and a second bus capacitor Cb connected in series. The connection point of the first bus capacitor Ca and the second bus capacitor Cb is connected to the neutral wire (neutral wire, N). The inverter circuit 112 includes a first switch tube Q1 and a second switch tube Q2 connected in series between the positive DC bus BUS+ and the negative DC bus BUS-, and the connection point of the first switch tube Q1 and the second switch tube Q2 is the output end of the inverter circuit 112.

[0040] Continue to refer to Figure 1 The Hall current sensor H is used to sample the current value of the inductor L, and the current value of the inductor L is used as feedback to improve the dynamic performance of the inverter circuit 112, but it will cause the load regulation rate of the output voltage of the uninterruptible power supply 100 to be too high. The current transformer CT is used to sample the current value at the load end, and the current value at the load end is used as feedforward to compensate for the problem that the load regulation rate of the output voltage of the uninterruptible power supply 100 is too high when the current value of the inductor L is used as feedback, and the current value at the load end can be used for parallel current sharing feedback.

[0041] Specifically, Figure 2As shown, it is a control flow diagram of the uninterruptible power supply 100 using dual-loop control. Among them, the current value of the inductor L and the current value of the load end are both used as feedback signals to adjust the reference voltage to adjust the pulse signal sent to the inverter circuit 112 (INV), thereby adjusting the output voltage of the uninterruptible power supply 100. Since the current value of the inductor L and the current value of the load end have different functions, the current value of the inductor L is used to correct the output voltage of the uninterruptible power supply 100 after the output voltage of the uninterruptible power supply 100 is affected. Therefore, the process of using the current value of the inductor L as a feedback signal for feedback adjustment is called the current value of the inductor L as feedback, and the current value of the load end is used to correct the output voltage of the uninterruptible power supply 100 before the output voltage of the uninterruptible power supply 100 is disturbed. Therefore, the process of using the current value of the load end as a feedback signal for feedback adjustment is called the current value of the load end as feedforward. Figure 2 The meanings of the remaining parameters and the control process can refer to the prior art, and the embodiments of the present application will not be repeated here.

[0042] However, when the current outputted from the load end includes a DC component, the current transformer CT may be saturated, resulting in the current transformer CT being unable to accurately detect the current value at the load end, and the dynamic response and stability of the system cannot be effectively improved. In addition, in order to avoid the problem that the short-circuit current flows through the current transformer CT in the case of a short circuit at the load end, resulting in the saturation of the current transformer CT and the low detection accuracy of the current transformer CT, the volume and weight of the current transformer CT need to be increased, which will increase the volume and weight of the uninterruptible power supply 100.

[0043] Based on this, the embodiment of the present application provides a power conversion device, which can be applied to an uninterruptible power supply or a photovoltaic inverter. Since the capacitor can cut off the DC component, the current value of the capacitor can be detected more accurately. According to the current value of the inductor and the current value of the capacitor, a more accurate current value of the output end of the power conversion device can be determined, which can effectively improve the dynamic response and stability of the system. At the same time, there is no need for a current transformer to directly detect the current value of the output end of the power conversion device, and there is no need to use a current transformer with a large volume and weight, which can avoid the increase of the volume and weight of the power conversion device.

[0044] like Figure 3 , which is a schematic diagram of a circuit topology of a power conversion device 400 provided in an embodiment of the present application. The power conversion device 400 includes an inverter circuit 410, an inductor L, a first capacitor C1, a first current sampling circuit 420, a second current sampling circuit 430 and an operational amplifier circuit 440.

[0045] Among them, the positive input terminal of the inverter circuit 410 is connected to the positive DC bus BUS+, the negative input terminal of the inverter circuit 410 is connected to the negative DC bus BUS-, the inductor L and the first current sampling circuit 420 are arranged in series between the output terminal of the inverter circuit 410 and the output terminal of the power conversion device 400, the first capacitor C1 and the second current sampling circuit 430 are arranged in series between the output terminal of the power conversion device 400 and the ground terminal G, and the sampling output terminal of the first current sampling circuit 420 and the sampling output terminal of the second current sampling circuit 430 are connected to the input terminal of the operational amplifier circuit 440 through a signal line.

[0046] In one possible embodiment, referring to Figure 3 The power conversion device 400 provided in the embodiment of the present application further includes a controller 450 , and the output end of the operational amplifier circuit 440 is connected to the controller 450 via a signal line.

[0047] The first current sampling circuit 420 is used to sample the current value IL of the inductor L, the second current sampling circuit 430 is used to sample the current value IC of the first capacitor C1, the operational amplifier circuit 440 is used to receive the current value IL of the inductor L and the current value IC of the first capacitor C1, and calculate the current value IO of the output end of the power conversion device 400. The current value IO of the output end of the power conversion device 400 is used as a feedforward, and the controller 450 is used to control the inverter circuit 410 according to the current value IO of the output end of the power conversion device 400, so as to improve the dynamic response and stability of the power conversion device 400. Among them, the voltage value output by the first current sampling circuit 420 is used to indicate the current value IL of the inductor L, the voltage value output by the second current sampling circuit 430 is used to indicate the current value IC of the first capacitor C1, and the voltage value output by the operational amplifier circuit 440 is used to indicate the current value IO of the output end of the power conversion device 400.

[0048] Understandably, Figure 1 In the uninterruptible power supply 100 shown, when the current output from the load end includes a DC component, it may cause the current transformer CT to be saturated, resulting in the current transformer CT being unable to accurately detect the current value at the load end. Compared with the first capacitor C1, which can block the DC component, the current value IC of the first capacitor C1 can be more accurately detected. The operational amplifier circuit 440 receives the current value IL of the inductor L and the current value IC of the first capacitor C1, calculates the current value IO of the output end of the power conversion device 400, and can determine a more accurate current value IO of the output end of the power conversion device 400. The current value IO of the output end of the power conversion device 400 is used as a feedforward, thereby effectively improving the dynamic response and stability of the power conversion device 400. At the same time, compared with the above Figure 1In the uninterruptible power supply 100 shown, in order to avoid the problem that the short-circuit current flows through the current transformer CT when the load end is short-circuited, causing the current transformer CT to be saturated and the detection accuracy of the current transformer CT to be too low, the volume and weight of the current transformer CT need to be increased. In the power conversion device 400, there is no need for the current transformer CT to directly detect the current value IO at the output end of the power conversion device 400, and there is no need to use a current transformer with a larger volume and weight, which can avoid increasing the volume and weight of the power conversion device 400.

[0049] In a possible embodiment, the inverter circuit 410 is a two-level, three-level or multi-level inverter circuit, which is not limited in the embodiment of the present application.

[0050] For example, the inverter circuit 410 is a two-level inverter circuit. Figure 3 As shown, the power conversion device 400 further includes positive and negative bus capacitors arranged between the positive DC bus BUS+ and the negative DC bus BUS-, and the positive and negative bus capacitors include a first bus capacitor Ca and a second bus capacitor Cb connected in series, and the connection point of the first bus capacitor Ca and the second bus capacitor Cb is connected to the neutral line N. The inverter circuit 410 includes a first switch tube Q1 and a second switch tube Q2 connected in series between the positive DC bus BUS+ and the negative DC bus BUS-, and the connection point of the first switch tube Q1 and the second switch tube Q2 is the output end of the inverter circuit 410.

[0051] For another example, take the inverter circuit 410 as a three-level inverter circuit. Figure 4 As shown, the power conversion device 400 also includes positive and negative bus capacitors arranged between the positive DC bus BUS+ and the negative DC bus BUS-, the positive and negative bus capacitors include a first bus capacitor Ca and a second bus capacitor Cb connected in series, and the connection point of the positive and negative bus capacitors is connected to the neutral line N. The inverter circuit 410 includes an upper bridge arm arranged between the positive DC bus BUS+ and the output end of the inverter circuit 410, and a lower bridge arm arranged between the negative DC bus BUS- and the output end of the inverter circuit 410, wherein the upper bridge arm includes a first switch tube Q1 and a second switch tube Q2 connected in series, and the lower bridge arm includes a third switch tube Q3 and a fourth switch tube Q4 connected in series, and the inverter circuit 410 also includes a first diode D1 and a second diode D2, the cathode of the first diode D1 is connected to the midpoint of the upper bridge arm, the anode of the second diode D2 is connected to the midpoint of the lower bridge arm, and the anode of the first diode D1 and the cathode of the second diode D2 are connected to the connection point of the positive and negative bus capacitors.

[0052] Optionally, each switch tube in the embodiment of the present application includes a triode, an insulate-gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET), which is not limited in the embodiment of the present application.

[0053] Optionally, the first current sampling circuit 420 or the second current sampling circuit 430, as well as other current sampling circuits in the following embodiments, may include a Hall current sensor or a current transformer, which is not limited in the embodiments of the present application.

[0054] In a possible embodiment, when the first current sampling circuit 420 or the second current sampling circuit 430, as well as other current sampling circuits in the following embodiments, include a Hall current sensor, the Hall current sensor may be a voltage-type Hall current sensor, or may be a current-type Hall current sensor, which is not limited in this embodiment of the present application.

[0055] For example, the first current sampling circuit 420 is taken as an example. When the first current sampling circuit 420 includes a voltage-type Hall current sensor H1, the circuit topology of the first current sampling circuit 420 is as follows: Figure 5 When the first current sampling circuit 420 includes a current type Hall current sensor H2, the circuit topology of the first current sampling circuit 420 is as follows: Figure 5 As shown in (b) of FIG. 1 , the current type Hall current sensor H2 includes a voltage type Hall current sensor H1 and a first resistor R1 disposed between the ground terminal and the sampling output terminal of the voltage type Hall current sensor H1. When the first current sampling circuit 420 includes a current transformer CT, the circuit topology of the first current sampling circuit 420 is as follows: Figure 5 As shown in (c) in FIG. 8 , the current transformer CT includes a primary winding K1 and a secondary winding K2.

[0056] In a possible embodiment, the first current sampling circuit 420 or the second current sampling circuit 430, as well as other current sampling circuits in the following embodiments, in addition to including a Hall current sensor or a current transformer, may also include at least one operational amplifier circuit connected to the output end of the Hall current sensor or the current transformer. The embodiment of the present application does not limit the specific number of operational amplifier circuits in the first current sampling circuit 420 or the second current sampling circuit 430, as well as other current sampling circuits in the following embodiments.

[0057] In a possible embodiment, when the first current sampling circuit 420 or the second current sampling circuit 430, as well as other current sampling circuits in the following embodiments, include an operational amplifier circuit, the operational amplifier circuit may be a common-phase operational amplifier circuit, or may be an inverting operational amplifier circuit, which is not limited in the embodiments of the present application. When the first current sampling circuit 420 or the second current sampling circuit 430, as well as other current sampling circuits in the following embodiments, include multiple operational amplifier circuits, the multiple operational amplifier circuits are connected in series, and the multiple operational amplifier circuits may include multiple common-phase operational amplifier circuits, or may include multiple inverting operational amplifier circuits, or may include some common-phase operational amplifier circuits and some inverting operational amplifier circuits, which is not limited in the embodiments of the present application.

[0058] For example, take the first current sampling circuit 420 as an example. When the first current sampling circuit 420 includes an operational amplifier circuit, and the operational amplifier circuit is a common-phase operational amplifier circuit, the circuit topology of the first current sampling circuit 420 is as follows: Figure 5 As shown in (a) in . For details, refer to Figure 5 As shown in (a), the first current sampling circuit 420 includes a voltage-type Hall current sensor H1 and a common-phase operational amplifier circuit 421, and the common-phase operational amplifier circuit 421 includes an operational amplifier (OP), a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4. One end of the first resistor R1 and one end of the second resistor R2 are connected to the common-phase input terminal of the operational amplifier OP, the other end of the first resistor R1 is connected to the sampling output terminal of the voltage-type Hall current sensor H1, the other end of the second resistor R2 is connected to the output terminal of the operational amplifier OP, and the output terminal of the operational amplifier OP is the sampling output terminal of the first current sampling circuit 420, one end of the third resistor R3 and one end of the fourth resistor R4 are connected to the inverting input terminal of the operational amplifier OP, the other end of the third resistor R3 and the ground terminal of the voltage-type Hall current sensor H1 are connected to the ground terminal G, and the other end of the fourth resistor R4 is connected to the ground terminal G.

[0059] For another example, take the first current sampling circuit 420 as an example. When the first current sampling circuit 420 includes an operational amplifier circuit, and the operational amplifier circuit is an inverting operational amplifier circuit, the circuit topology of the first current sampling circuit 420 is as follows: Figure 5 As shown in (b) in the figure. For details, refer to Figure 5As shown in (b), the first current sampling circuit 420 includes a current type Hall current sensor H2 and an inverting operational amplifier circuit 422. The current type Hall current sensor H2 includes a voltage type Hall current sensor H1 and a first resistor R1 arranged between the ground terminal and the sampling output terminal of the voltage type Hall current sensor H1. The inverting operational amplifier circuit 422 includes an operational amplifier OP, a second resistor R2, a third resistor R3, a fourth resistor R4 and a fifth resistor R5. One end of the second resistor R2 and one end of the third resistor R3 are connected to the inverting input terminal of the operational amplifier OP, the other end of the second resistor R2 is connected to the sampling output terminal of the current type Hall current sensor H2, the other end of the third resistor R3 is connected to the ground terminal G, one end of the fourth resistor R4 and one end of the fifth resistor R5 are connected to the non-inverting input terminal of the operational amplifier OP, the other end of the fourth resistor R4 and the ground terminal of the current type Hall current sensor H2 are connected to the ground terminal G, and the other end of the fifth resistor R5 is connected to the output terminal of the operational amplifier OP. The output terminal of the operational amplifier OP is the sampling output terminal of the first current sampling circuit 420.

[0060] For another example, take the first current sampling circuit 420 as an example. When the first current sampling circuit 420 includes a plurality of operational amplifier circuits, and the plurality of operational amplifier circuits include some in-phase operational amplifier circuits and some inverting operational amplifier circuits, the circuit topology of the first current sampling circuit 420 is as follows: Figure 5 As shown in (c) in the figure. For details, refer to Figure 5In (c), the first current sampling circuit 420 may include a current transformer CT, a first resistor R1, an inverting operational amplifier circuit 423 and a non-inverting operational amplifier circuit 424, the inverting operational amplifier circuit 423 includes a first operational amplifier OP1, a second resistor R2 to a fifth resistor R5, and the non-inverting operational amplifier circuit 424 includes a second operational amplifier OP2, a sixth resistor R6 to an eighth resistor R8. The first resistor R1 is arranged between the two ends of the secondary winding K2 in the current transformer CT, one end of the second resistor R2 and one end of the third resistor R3 are connected to the inverting input terminal of the first operational amplifier OP1, the other end of the second resistor R2 is connected to one end of the first resistor R1, the other end of the third resistor R3 is connected to the ground terminal G, one end of the fourth resistor R4 and one end of the fifth resistor R5 are connected to the non-inverting input terminal of the first operational amplifier OP1, the other end of the fourth resistor R4 and the other end of the first resistor R1 are connected to the ground terminal G, the other end of the fifth resistor R5 is connected to the output terminal of the first operational amplifier OP1, one end of the sixth resistor R6 is connected to the inverting input terminal of the second operational amplifier OP2, the other end of the sixth resistor R6 is connected to the ground terminal G, one end of the seventh resistor R7 and one end of the eighth resistor R8 are connected to the non-inverting input terminal of the second operational amplifier OP2, the other end of the seventh resistor R7 is connected to the output terminal of the first operational amplifier OP1, the other end of the eighth resistor R8 is connected to the output terminal of the second operational amplifier OP2, and the output terminal of the second operational amplifier OP2 is the sampling output terminal of the first current sampling circuit 420. When the first current sampling circuit 420 includes a plurality of operational amplifier circuits, and the plurality of operational amplifier circuits include a plurality of in-phase operational amplifier circuits, or include a plurality of inverting operational amplifier circuits, the circuit topology of the first current sampling circuit 420 can refer to Figure 5 (a) to Figure 5 (c) and the prior art in the present application will not be described in detail herein.

[0061] In a possible embodiment, the operational amplifier circuit 440 includes a subtraction circuit, and the current value IO at the output end of the power conversion device 400 is the difference between the current value IL of the inductor L and the current value IC of the first capacitor C1, or, the operational amplifier circuit 440 includes an addition circuit, and the current value IO at the output end of the power conversion device 400 is the sum of the current value IL of the inductor L and the current value IC of the first capacitor C1.

[0062] Specifically, since the Hall current sensor or current transformer can detect the direction of the current, the positive or negative value of the voltage output by the Hall current sensor or current transformer is used to indicate the direction of the current in the circuit, and the positive voltage value is used to indicate the positive direction of the current in the circuit. In the first current sampling circuit 420 or the second current sampling circuit 430, by changing the connection mode of the Hall current sensor or current transformer, or changing the number or type of operational amplifier circuits connected to the Hall current sensor or current transformer, the positive or negative value of the output voltage of the first current sampling circuit 420 or the second current sampling circuit 430 can be changed, so that the positive voltage value indicates the positive direction change of the current. For details, reference can be made to the prior art, and the embodiments of the present application are not repeated here. When the first current sampling circuit 420 or the second current sampling circuit 430 outputs a positive voltage value indicating the positive direction change of the current, and the current value IO at the output end of the power conversion device 400 defines different positive directions of the current, it is necessary to use an operational amplifier circuit 440 with a different circuit topology to determine the current value IO at the output end of the power conversion device 400.

[0063] For example, Figure 6 As shown in (a), when the positive voltage value output by the first current sampling circuit 420 indicates that the positive direction of the current flowing through the inductor L is from the inductor L to the output end of the power conversion device 400, and the positive voltage value output by the second current sampling circuit 430 indicates that the positive direction of the current flowing through the first capacitor C1 is from the output end of the power conversion device 400 to the first capacitor C1, the positive direction of the current value IO at the output end of the power conversion device 400 is defined as the inductor L to the output end of the power conversion device 400, or, as Figure 6 As shown in (b), when the positive voltage value output by the first current sampling circuit 420 indicates that the positive direction of the current flowing through the inductor L is from the output end of the power conversion device 400 to the inductor L, and the positive voltage value output by the second current sampling circuit 430 indicates that the positive direction of the current flowing through the first capacitor C1 is from the first capacitor C1 to the output end of the power conversion device 400, and the positive direction of the current value IO at the output end of the power conversion device 400 is defined as from the output end of the power conversion device 400 to the inductor L, the operational amplifier circuit 440 includes a subtraction circuit. Specifically, as Figure 6As shown in (c), the operational amplifier circuit 440 includes an operational amplifier OP and a first resistor R1 to a fourth resistor R4, one end of the first resistor R1 and one end of the second resistor R2 are connected to the inverting input terminal of the operational amplifier OP, the other end of the first resistor R1 is connected to the sampling output terminal of the second current sampling circuit 430, the other end of the second resistor R2 is connected to the output terminal of the operational amplifier OP, the output terminal of the operational amplifier OP is the output terminal of the operational amplifier circuit 440, one end of the third resistor R3 and one end of the fourth resistor R4 are connected to the non-inverting input terminal of the operational amplifier OP, the other end of the third resistor R3 is connected to the sampling output terminal of the first current sampling circuit 420, and the other end of the fourth resistor R4 is connected to the ground terminal G.

[0064] For example, Figure 7 As shown in (a), when the positive voltage value output by the first current sampling circuit 420 indicates that the positive direction of the current flowing through the inductor L is from the inductor L to the output end of the power conversion device 400, and the positive voltage value output by the second current sampling circuit 430 indicates that the positive direction of the current flowing through the first capacitor C1 is from the output end of the power conversion device 400 to the first capacitor C1, the positive direction of the current value IO at the output end of the power conversion device 400 is defined as the output end of the power conversion device 400 to the inductor L, or, as Figure 7 As shown in (b), when the positive voltage value output by the first current sampling circuit 420 indicates that the positive direction of the current flowing through the inductor L is from the output end of the power conversion device 400 to the inductor L, and the positive voltage value output by the second current sampling circuit 430 indicates that the positive direction of the current flowing through the first capacitor C1 is from the first capacitor C1 to the output end of the power conversion device 400, and the positive direction of the current value IO at the output end of the power conversion device 400 is defined as from the inductor L to the output end of the power conversion device 400, the operational amplifier 340 includes a subtraction circuit. Specifically, as Figure 7 As shown in (c), the operational amplifier circuit 440 includes an operational amplifier OP and a first resistor R1 to a fourth resistor R4, one end of the first resistor R1 and one end of the second resistor R2 are connected to the inverting input terminal of the operational amplifier OP, the other end of the first resistor R1 is connected to the sampling output terminal of the first current sampling circuit 420, the other end of the second resistor R2 is connected to the output terminal of the operational amplifier OP, the output terminal of the operational amplifier OP is the output terminal of the operational amplifier circuit 440, one end of the third resistor R3 and one end of the fourth resistor R4 are connected to the non-inverting input terminal of the operational amplifier OP, the other end of the third resistor R3 is connected to the sampling output terminal of the second current sampling circuit 430, and the other end of the fourth resistor R4 is connected to the ground terminal G.

[0065] For example, Figure 8As shown in (a), when the positive voltage value output by the first current sampling circuit 420 indicates that the positive direction of the current flowing through the inductor L is from the inductor L to the output end of the power conversion device 400, and the positive voltage value output by the second current sampling circuit 430 indicates that the positive direction of the current flowing through the first capacitor C1 is from the first capacitor C1 to the output end of the power conversion device 400, the positive direction of the current value IO at the output end of the power conversion device 400 is defined as the inductor L to the output end of the power conversion device 400, or, as Figure 8 As shown in (b), when the positive voltage value output by the first current sampling circuit 420 indicates that the positive direction of the current flowing through the inductor L is from the output end of the power conversion device 400 to the inductor L, and the positive voltage value output by the second current sampling circuit 430 indicates that the positive direction of the current flowing through the first capacitor C1 is from the output end of the power conversion device 400 to the first capacitor C1, and the positive direction of the current value IO at the output end of the power conversion device 400 is defined as from the output end of the power conversion device 400 to the inductor L, the operational amplifier circuit 440 includes an adding circuit. Specifically, as Figure 8 As shown in (c), the operational amplifier circuit 440 includes an operational amplifier OP and a first resistor R1 to a fourth resistor R4, one end of the first resistor R1 and one end of the second resistor R2 are connected to the inverting input terminal of the operational amplifier OP, the other end of the first resistor R1 is connected to the ground terminal G, the other end of the second resistor R2 is connected to the output terminal of the operational amplifier OP, the output terminal of the operational amplifier OP is the output terminal of the operational amplifier circuit 440, one end of the third resistor R3 and one end of the fourth resistor R4 are connected to the non-inverting input terminal of the operational amplifier OP, the other end of the third resistor R3 is connected to the sampling output terminal of the second current sampling circuit 430, and the other end of the fourth resistor R4 is connected to the sampling output terminal of the first current sampling circuit 420.

[0066] For example, Fig. 9 As shown in (a), when the positive voltage value output by the first current sampling circuit 420 indicates that the positive direction of the current flowing through the inductor L is from the inductor L to the output end of the power conversion device 400, the positive voltage value output by the second current sampling circuit 430 indicates that the positive direction of the current flowing through the first capacitor C1 is from the first capacitor C1 to the output end of the power conversion device 400, the positive direction of the current value IO at the output end of the power conversion device 400 is defined as the output end of the power conversion device 400 to the inductor L, or, as Fig. 9As shown in (b), when the positive voltage value output by the first current sampling circuit 420 indicates that the positive direction of the current flowing through the inductor L is from the output end of the power conversion device 400 to the inductor L, and the positive voltage value output by the second current sampling circuit 430 indicates that the positive direction of the current flowing through the first capacitor C1 is from the output end of the power conversion device 400 to the first capacitor C1, and the positive direction of the current value IO at the output end of the power conversion device 400 is defined as from the inductor L to the output end of the power conversion device 400, the operational amplifier circuit 440 includes an adding circuit. Specifically, as Fig. 9 As shown in (c), the operational amplifier circuit 440 includes an operational amplifier OP and a first resistor R1 to a fourth resistor R4, one end of the first resistor R1 is connected to the non-inverting input terminal of the operational amplifier OP, the other end of the first resistor R1 is connected to the ground terminal G, one end of the second resistor R2, one end of the third resistor R3 and one end of the fourth resistor R4 are connected to the inverting input terminal of the operational amplifier OP, the other end of the second resistor R2 is connected to the sampling output terminal of the second current sampling circuit 430, the other end of the third resistor R3 is connected to the sampling output terminal of the first current sampling circuit 420, and the other end of the fourth resistor R4 is connected to the output terminal of the operational amplifier OP, and the output terminal of the operational amplifier OP is the output terminal of the operational amplifier circuit 440.

[0067] In a possible embodiment, the operational amplifier circuit 440 may include, in addition to an addition circuit or a subtraction circuit, at least one in-phase operational amplifier circuit and / or at least one inverting operational amplifier circuit connected to the output end of the addition circuit or the subtraction circuit. The embodiment of the present application does not limit the specific number of in-phase operational amplifier circuits or inverting operational amplifier circuits included in the operational amplifier circuit 440.

[0068] Exemplarily, the operational amplifier circuit 440 may include a common-phase operational amplifier circuit connected to the output end of the addition circuit or the subtraction circuit, or an inverting operational amplifier circuit, or a plurality of common-phase operational amplifier circuits connected in series, or a plurality of inverting operational amplifier circuits connected in series, or some common-phase operational amplifier circuits and some inverting operational amplifier circuits connected in series, which are not limited in the embodiments of the present application.

[0069] In the power conversion device 400 provided in the embodiment of the present application, the first current sampling circuit 420 is used to sample the current value IL of the inductor L, the second current sampling circuit 430 is used to sample the current value IC of the first capacitor C1, and the operational amplifier circuit 440 is used to receive the current value IL of the inductor L and the current value IC of the first capacitor C1 to calculate the current value IO of the output end of the power conversion device 400. It can be understood that, with the above Figure 1In the uninterruptible power supply 100 shown, when the current output from the load end includes a DC component, it may cause the current transformer CT to be saturated, resulting in the current transformer CT being unable to accurately detect the current value at the load end. Compared with the first capacitor C1, which can block the DC component, the current value IC of the first capacitor C1 can be more accurately detected. The operational amplifier circuit 440 receives the current value IL of the inductor L and the current value IC of the first capacitor C1, calculates the current value IO of the output end of the power conversion device 400, and can determine a more accurate current value IO of the output end of the power conversion device 400. The current value IO of the output end of the power conversion device 400 is used as a feedforward, thereby effectively improving the dynamic response and stability of the power conversion device 400. At the same time, compared with the above Figure 1 In the uninterruptible power supply 100 shown, in order to avoid the problem that the short-circuit current flows through the current transformer CT when the load end is short-circuited, causing the current transformer CT to be saturated and the detection accuracy of the current transformer CT to be too low, the volume and weight of the current transformer CT need to be increased. In the power conversion device 400, there is no need for the current transformer CT to directly detect the current value IO at the output end of the power conversion device 400, and there is no need to use a current transformer with a larger volume and weight, which can avoid increasing the volume and weight of the power conversion device 400.

[0070] In one possible embodiment, referring to Fig.10 When the output end of the power conversion device 400 supplies power to the load 300, the first capacitor C1 discharges to the load 300, and the current value IO at the output end of the power conversion device 400 increases rapidly. Due to the self-inductance characteristics of the inductor L, the increase of the current value IL of the inductor L will lag behind the current value IO at the output end of the power conversion device 400. Therefore, when a nonlinear load is suddenly added to the output end of the power conversion device 400 (generating a load impact), the current value IO at the output end of the power conversion device 400 can be used to predict the sudden increase of the current value IL of the inductor L. The sudden increase of the current value IL of the inductor L can indicate the sudden increase of the current value of the switch tube in the inverter circuit 410. According to the current value IO at the output end of the power conversion device 400, the switch tube in the inverter circuit 410 is controlled to be turned off, and the current value of the switch tube in the inverter circuit 410 is limited, thereby improving the safety and reliability of the power conversion device 400.

[0071] Specifically, refer to Fig.10The power conversion device 400 provided in the embodiment of the present application further includes a current limiting threshold generating circuit 460 and a comparison circuit 470. The input end of the current limiting threshold generating circuit 460 is connected to the output end of the operational amplifier circuit 440 through a signal line, the output end of the current limiting threshold generating circuit 460 and the sampling output end of the first current sampling circuit 420 are respectively connected to the two input ends of the comparison circuit 470 through signal lines, the output end of the comparison circuit 470 is connected to the input end of the controller 450 through a signal line, and the current value IL of the inductor L is used to indicate the current value of the switch tube in the inverter circuit 410.

[0072] The voltage value output by the operational amplifier circuit 440 is used to indicate the current value IO at the output end of the power conversion device 400. The current limiting threshold generating circuit 460 is used to output a variable current limiting threshold when the voltage value output by the operational amplifier circuit 440 is greater than the positive first voltage threshold or less than the negative first voltage threshold. The embodiment of the present application does not limit the specific value of the first voltage threshold and the specific value of the variable current limiting threshold.

[0073] For example, Fig.11 (a) in FIG. 4 is a schematic diagram showing a curve diagram of a voltage value output by the operational amplifier circuit 440. Fig.11 (b) in FIG. 1 is a schematic diagram of the change curve of the variable current limiting threshold. Fig.11 As shown in (a) of FIG. 1 , from time t1 to time t2, when the voltage value output by the operational amplifier circuit 440 is greater than the positive first voltage threshold, as shown in FIG. Fig.11 As shown in (b) of FIG. 4 , the variable current limiting threshold output by the current limiting threshold generating circuit 460 is reduced from IX1 to IX2 and stabilized at IX2. Fig.11 As shown in (a) in FIG. 1 , after time t2, the voltage value output by the operational amplifier circuit 440 is less than the positive first voltage threshold and not less than the negative first voltage threshold. Fig.11 As shown in (b) in FIG. 1 , the variable current limiting threshold output by the current limiting threshold generating circuit 460 gradually recovers from IX2 to IX1.

[0074] The comparison circuit 470 is used to output a current limiting enable signal when the variable current limiting threshold is greater than the current value of the switch tube in the inverter circuit 410. The controller 450 is used to control the switch tube in the inverter circuit 410 to turn off when receiving the current limiting enable signal. Therefore, when a nonlinear load is suddenly added to the output end of the power conversion device 400 (generating a load shock) and the current at the output end of the power conversion device 400 suddenly increases, the switch tube in the inverter circuit 410 can be controlled to turn off, thereby improving the safety and reliability of the power conversion device 400.

[0075] In a possible embodiment, Fig.10As shown, the current limiting threshold generating circuit 460 includes: the inverting input terminal of the first comparator 461 and the non-inverting input terminal of the second comparator 462 are connected to the input terminal of the current limiting threshold generating circuit 460, the non-inverting input terminal of the first comparator 461 is used to receive the positive first voltage threshold, and the inverting input terminal of the second comparator 462 is used to receive the negative first voltage threshold. The output end of the first comparator 461 and the output end of the second comparator 462 are connected to one end of the first resistor R1, the other end of the first resistor R1 and one end of the second resistor R2 are connected to the controlled end of the first switch tube Q1, the first end of the first switch tube Q1 is connected to one end of the third resistor R3 and one end of the fourth resistor R4, the other end of the third resistor R3 and one end of the fifth resistor R5 are used to receive a reference voltage (voltage reference, Vref), the other end of the fourth resistor R4 and one end of the sixth resistor R6 are connected to the controlled end of the second switch tube Q2, the first end of the second switch tube Q2 is connected to one end of the seventh resistor R7, the other end of the fifth resistor R5, the other end of the seventh resistor R7, and one end of the second capacitor C2 are connected to the output end of the current limiting threshold generating circuit 460, and the other end of the second resistor R2, the second end of the first switch tube Q1, the other end of the sixth resistor R6, the second end of the second switch tube Q2, and the other end of the second capacitor C2 are connected to the ground terminal G.

[0076] By adjusting the resistance values ​​of the fifth resistor R5 and the seventh resistor R7, the charging and discharging time of the second capacitor C2 can be controlled. Fig.11 (b) in the figure, the variable current limiting threshold output by the current limiting threshold generating circuit 460 can be adjusted, and the time for the current limiting threshold to be restored from IX2 to IX1 after time t2.

[0077] In a possible embodiment, the controller 450 may be a microcontroller unit (MCU) or a digital signal processor (DSP), which is not limited in the embodiment of the present application.

[0078] In the power conversion device 400 provided in the embodiment of the present application, the operational amplifier circuit 440 receives the current value IL of the inductor L and the current value IC of the first capacitor C1, calculates the current value IO of the output end of the power conversion device 400, and can determine a more accurate current value IO of the output end of the power conversion device 400. The voltage value output by the operational amplifier circuit 440 is used to indicate the current value IO of the output end of the power conversion device 400. The current limit threshold generating circuit 460 outputs a variable current limit threshold according to the voltage value output by the operational amplifier circuit 440. The comparison circuit 470 outputs a current limit enable signal when the variable current limit threshold is greater than the current value of the switch tube in the inverter circuit 410. The controller 450 controls the switch tube in the inverter circuit 410 to turn off when receiving the current limit enable signal. Therefore, when a nonlinear load is suddenly added to the output end of the power conversion device 400 (generating a load impact), the current at the output end of the power conversion device 400 suddenly increases, and the switch tube in the inverter circuit 410 is controlled to turn off, which can improve the safety and reliability of the power conversion device 400.

[0079] In a possible embodiment, Fig.12 As shown, the input end of the current limiting threshold generating circuit 460 is connected to the sampling output end of the second current sampling circuit 430 through a signal line, the output end of the current limiting threshold generating circuit 460 and the sampling output end of the first current sampling circuit 420 are respectively connected to the two input ends of the comparison circuit 470 through signal lines, the output end of the comparison circuit 470 is connected to the input end of the controller 450 through a signal line, and the current value IL of the inductor L is used to indicate the current value of the switch tube in the inverter circuit 410.

[0080] The voltage value output by the second current sampling circuit 430 is used to indicate the current value IC of the first capacitor C1. The current limiting threshold generating circuit 460 is used to output a variable current limiting threshold when the voltage value output by the second current sampling circuit 430 is greater than the positive second voltage threshold or less than the negative second voltage threshold. The embodiment of the present application does not limit the specific values ​​of the positive second voltage threshold and the negative second voltage threshold. The functions of the remaining circuits can refer to the above Fig.10 The functions of each circuit in the power conversion device 400 are not described in detail in the embodiment of the present application.

[0081] Reference Fig.10 ,like Fig.12 As shown, the circuit topology of the current limiting threshold generating circuit 460 is unchanged, except that the non-inverting input terminal of the first comparator 461 is used to receive the positive second voltage threshold, and the inverting input terminal of the second comparator 462 is used to receive the negative second voltage threshold. For the specific circuit topology of the current limiting threshold generating circuit 460, reference can be made to the above Fig.10 The description in the embodiments of the present application will not be repeated here.

[0082] In the power conversion device 400 provided in the embodiment of the present application, since the first capacitor C1 can cut off the DC component, the current value IC of the first capacitor C1 can be detected more accurately, the voltage value output by the second current sampling circuit 430 is used to indicate the current value IC of the first capacitor C1, and the current limiting threshold generating circuit 460 outputs a variable current limiting threshold according to the voltage value output by the second current sampling circuit 430. When the variable current limiting threshold is greater than the current value of the switch tube in the inverter circuit 410, the comparison circuit 470 outputs a current limiting enable signal. When the controller 450 receives the current limiting enable signal, it controls the switch tube in the inverter circuit 410 to turn off. Thus, when a nonlinear load is suddenly added to the output end of the power conversion device 400 (generating a load impact), and the current at the output end of the power conversion device 400 suddenly increases, the switch tube in the inverter circuit 410 is controlled to turn off, which can improve the safety and reliability of the power conversion device 400. At the same time, since the current value IO of the output end of the power conversion device 400 is determined based on the current value IL of the inductor L and the current value of the first capacitor C1, compared with the current value IO of the output end of the power conversion device 400, the current value of the first capacitor C1 is more accurate, which can significantly improve the safety and reliability of the power conversion device 400.

[0083] like Fig.10 or Fig.12 As shown, the embodiment of the present application further provides an uninterruptible power supply 500, which includes a main circuit 510, a bypass circuit 520 and a load end. The main circuit 510 is used to connect to the first input power supply 210, and the bypass circuit 520 is used to connect to the second input power supply 220. The main circuit 510 and the bypass circuit 520 are both used to supply power to the load end, and the load end is used to connect to the load 300 to supply power to the load 300. A rectifier circuit 511 and a power conversion device 400 are provided on the main circuit. The input end of the rectifier circuit 511 is used to connect to the first input power supply 210, and the output end of the rectifier circuit 511 is connected to the positive DC bus BUS+ and the negative DC bus BUS-. The input end of the power conversion device 400 is connected to the positive DC bus BUS+ and the negative DC bus BUS-. The output end of the power conversion device 400 is connected to the load end. The circuit topology of the power conversion device 400 can be Figures 3 to 10 or Fig.12 The circuit topology of any power conversion device 400 shown in the figure is not limited in the embodiments of the present application.

[0084] Based on this, Fig.13As shown, the embodiment of the present application also provides a photovoltaic inverter 600, which includes a direct current direct current (DCDC) conversion circuit 610 and a power conversion device 400 connected to the DCDC conversion circuit 610. The power conversion device 400 is used to convert the direct current output by the DCDC conversion circuit 610 into alternating current. The circuit topology of the power conversion device 400 is as follows: Figures 3 to 10 or Fig.12 The circuit topology of any power conversion device 400 shown in the figure is not limited in the embodiments of the present application.

[0085] The above detailed description of the power conversion device 400 and the analysis of the beneficial effects can be correspondingly referred to the uninterruptible power supply 500 and the photovoltaic inverter 600, and the embodiments of the present application will not be repeated here.

[0086] 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 conversion device, characterized in that: The power conversion device includes an inverter circuit, an inductor, a first capacitor, a first current sampling circuit, a second current sampling circuit and an operational amplifier circuit; The positive input terminal of the inverter circuit is connected to the positive DC bus, the negative input terminal of the inverter circuit is connected to the negative DC bus, the inductor and the first current sampling circuit are arranged in series between the output terminal of the inverter circuit and the output terminal of the power conversion device, and the first capacitor and the second current sampling circuit are arranged in series between the output terminal of the power conversion device and the ground terminal; The first current sampling circuit is used to sample the current value of the inductor, the second current sampling circuit is used to sample the current value of the first capacitor, and the operational amplifier circuit is used to receive the current value of the inductor and the current value of the first capacitor to calculate the current value of the output end of the power conversion device.

2. The power conversion device according to claim 1, characterized in that: The operational amplifier circuit includes a subtraction circuit, and the current value of the output end of the power conversion device is the difference between the current value of the inductor and the current value of the first capacitor; Alternatively, the operational amplifier circuit includes an adding circuit, and the current value at the output end of the power conversion device is the sum of the current value of the inductor and the current value of the first capacitor.

3. The power conversion device according to claim 2, characterized in that: The power conversion device also includes a current limiting threshold generation circuit, a comparison circuit and a controller; The input end of the current limiting threshold generating circuit is connected to the output end of the operational amplifier circuit, the output end of the current limiting threshold generating circuit and the sampling output end of the first current sampling circuit are respectively connected to the two input ends of the comparison circuit, the output end of the comparison circuit is connected to the input end of the controller, and the current value of the inductor is used to indicate the current value of the switch tube in the inverter circuit; The current limiting threshold generating circuit is used to output a variable current limiting threshold when the voltage value output by the operational amplifier circuit is greater than the positive first voltage threshold or less than the negative first voltage threshold; The comparison circuit is used to output a current limiting enable signal when the variable current limiting threshold is greater than the current value of the switch tube in the inverter circuit; The controller is used to control the switch tube in the inverter circuit to turn off when receiving the current limiting enable signal.

4. The power conversion device according to claim 2, characterized in that: The power conversion device also includes a current limiting threshold generation circuit, a comparison circuit and a controller; The input end of the current limiting threshold generating circuit is connected to the sampling output end of the second current sampling circuit, the output end of the current limiting threshold generating circuit and the sampling output end of the first current sampling circuit are respectively connected to the two input ends of the comparison circuit, the output end of the comparison circuit is connected to the input end of the controller, and the current value of the inductor is used to indicate the current value of the switch tube in the inverter circuit; The current limiting threshold generating circuit is used to output a variable current limiting threshold when the voltage value output by the second current sampling circuit is greater than the positive second voltage threshold or less than the negative second voltage threshold; The comparison circuit is used to output a current limiting enable signal when the variable current limiting threshold is greater than the current value of the switch tube in the inverter circuit; The controller is used to control the switch tube in the inverter circuit to turn off when receiving the current limiting enable signal.

5. The power conversion device according to claim 3 or 4, characterized in that: The current limiting threshold generating circuit comprises: An inverting input terminal of a first comparator and a non-inverting input terminal of a second comparator are connected to an input terminal of the current limiting threshold generating circuit, the non-inverting input terminal of the first comparator is used to receive the positive voltage threshold, and the inverting input terminal of the second comparator is used to receive the negative voltage threshold; The output end of the first comparator and the output end of the second comparator are connected to one end of the first resistor, the other end of the first resistor and one end of the second resistor are connected to the controlled end of the first switch tube, the first end of the first switch tube is connected to one end of the third resistor and one end of the fourth resistor, the other end of the third resistor and one end of the fifth resistor are used to receive a reference voltage, the other end of the fourth resistor and one end of the sixth resistor are connected to the controlled end of the second switch tube, the first end of the second switch tube is connected to one end of the seventh resistor, the other end of the fifth resistor, the other end of the seventh resistor, and one end of the second capacitor are connected to the output end of the current limiting threshold generating circuit, and the other end of the second resistor, the second end of the first switch tube, the other end of the sixth resistor, the second end of the second switch tube, and the other end of the second capacitor are connected to the ground end.

6. An uninterruptible power supply, characterized in that: The uninterruptible power supply comprises a main circuit, a bypass circuit and a load end, and both the main circuit and the bypass circuit are used to supply power to the load end; A rectifier circuit and a power conversion device are provided on the main line, the input end of the rectifier circuit is connected to the input end of the uninterruptible power supply, the output end of the rectifier circuit is connected to the input end of the power conversion device, the output end of the power conversion device is connected to the load end, the load end is used to connect a load, and the power conversion device is a power conversion device as described in any one of claims 1-5.

Images