Power conversion apparatus, uninterruptible power supply, and photovoltaic inverter

Abstract

The embodiments of the present application relate to the technical field of power electronics, and disclose a power conversion apparatus, an uninterruptible power supply, and a photovoltaic inverter, which address the problem where large errors in sensing an alternating current capacitor current prevent accurate online measurement of a capacitance of the alternating current capacitor, resulting in the inability to accurately determine whether the alternating current capacitor is faulty. The specific solution provides a power conversion apparatus. The power conversion apparatus comprises an inverter circuit, an inductor, a capacitor, and a current sampling circuit. A positive input terminal of the inverter circuit is connected to a positive direct-current bus, a negative input terminal of the inverter circuit is connected to a negative direct-current bus, the inductor is arranged between an output terminal of the inverter circuit and an output terminal of the power conversion apparatus, and the capacitor and the current sampling circuit are arranged in series between the output terminal and a grounding terminal of the power conversion apparatus. The current sampling circuit is configured for sampling a current value of the capacitor.

Description

Power conversion device, uninterruptible power supply and photovoltaic inverter

[0001] The present application claims priority to the Chinese patent application No. 202422065473.1, filed on August 23, 2024, entitled "A power conversion device, uninterruptible power supply and photovoltaic inverter", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of power electronics, in particular to a power conversion device, uninterruptible power supply and photovoltaic inverter. BACKGROUND

[0003] An AC capacitor is included in an uninterruptible power supply (UPS) or a photovoltaic inverter, which is used for filtering, energy storage or harmonic suppression. When the AC capacitor bursts and generates smoke to trigger a smoke alarm, more stringent management measures or safety responses will be triggered, affecting normal operation and production.

[0004] When the capacitance of the AC capacitor decays, the risk of the AC capacitor bursting will increase, so the voltage, frequency and current of the AC capacitor can be detected, and the capacitance of the AC capacitor can be determined according to the voltage, frequency and current of the AC capacitor, and whether the AC capacitor fails can be determined according to the capacitance of the AC capacitor, so as to avoid the AC capacitor from bursting and generating smoke. At the same time, the uninterruptible power supply has high requirements for power supply continuity, so the capacitance of the AC capacitor needs to be detected by online capacitance detection.

[0005] However, there is a large error in detecting the current of the AC capacitor, which will result in inaccurate online detection of the capacitance of the AC capacitor and inaccurate determination of whether the AC capacitor fails.

[0006] Practical new type content

[0007] The present application provides a power conversion device, uninterruptible power supply and photovoltaic inverter, which solves the problem of large error in detecting the current of the AC capacitor, which will result in inaccurate online detection of the capacitance of the AC capacitor and inaccurate determination of whether the AC capacitor fails.

[0008] To achieve the above purpose, the embodiments of the present application adopt the following technical solutions:

[0009] In a first aspect of the embodiments of the present application, a power conversion device is provided, which includes an inverter circuit, an inductor, a capacitor and a current sampling circuit. The positive input terminal of the inverter circuit is connected with a positive DC bus, the negative input terminal of the inverter circuit is connected with a negative DC bus, the inductor is arranged between the output terminal of the inverter circuit and the output terminal of the power conversion device, and the capacitor and the current sampling circuit are arranged in series between the output terminal of the power conversion device and the ground terminal. The current sampling circuit is used to sample the current value of the capacitor.

[0010] In a possible embodiment, the current value of the capacitor is used to determine whether the capacitor is faulty, or the capacitance of the capacitor is determined according to the current value of the capacitor, and the capacitance of the capacitor is used to determine whether the capacitor is faulty.

[0011] In a possible embodiment, the inverter circuit is a two-level, three-level or multi-level inverter circuit, and the embodiments of the present application do not limit the inverter circuit.

[0012] In a possible embodiment, the type of the current sampling circuit includes a current transformer, a Hall effect sensor, a resistance current sensor, a capacitance current sensor or an electromagnetic induction sensor, and the embodiments of the present application do not limit the specific type of the current sampling circuit.

[0013] Based on the present solution, compared with sampling the current value of the inductor by one current transformer and sampling the current value of the output terminal of the power conversion device by another current transformer, and determining the current value of the capacitor according to the two current values, directly sampling the current value of the capacitor by the current sampling circuit can sample more accurate current value of the capacitor online, and then the current value of the capacitor can be used to more accurately determine whether the capacitor is faulty, or the capacitance of the capacitor can be more accurately determined online according to the current value of the capacitor, and whether the capacitor is faulty can be more accurately determined.

[0014] In combination with the first aspect, in a possible implementation, the current value of the capacitor is greater than or equal to the first range threshold of the current sampling circuit and less than or equal to the second range threshold of the current sampling circuit, and the first range threshold is less than the second range threshold.

[0015] Based on the present solution, the current value of the capacitor is greater than or equal to the first range threshold of the current sampling circuit and less than or equal to the second range threshold of the current sampling circuit, and the current value of the capacitor matches the range of the current sampling circuit, so that the measurement error of the current sampling circuit can be reduced. When the current sampling circuit samples the current value of the capacitor, more accurate current value of the capacitor can be sampled online, and then the current value of the capacitor can be used to more accurately determine whether the capacitor is faulty, or the capacitance of the capacitor can be more accurately determined online according to the current value of the capacitor, and whether the capacitor is faulty can be more accurately determined.

[0016] With reference to the first aspect, in a possible implementation manner, the uninterruptible power supply further includes a temperature sensor, and the temperature sensor is configured to sample the temperature of the capacitor.

[0017] Optionally, the temperature sensor can be a contact temperature sensor or a non-contact temperature sensor, and the embodiments of the present application do not limit the specific type of the temperature sensor.

[0018] According to the present solution, the temperature sensor is arranged to sample the temperature of the capacitor, so that whether the capacitor is faulty can be determined according to the temperature of the capacitor, and the accuracy of determining whether the capacitor is faulty can be further improved.

[0019] With reference to the first aspect, in a possible implementation manner, the uninterruptible power supply includes a plurality of inverter circuits and a plurality of inductors, the positive input end of each inverter circuit is connected with the positive DC bus, the negative input end of each inverter circuit is connected with the negative DC bus, and the plurality of inductors are respectively arranged between the output ends of the plurality of inverter circuits and the output end of the power conversion device.

[0020] According to the present solution, the plurality of inverter circuits and the plurality of inductors are arranged, so that the output power of the uninterruptible power supply can be improved. Meanwhile, the current sampling circuit directly samples the current value of the capacitor, so that when the uninterruptible power supply includes the plurality of inverter circuits and the plurality of inductors, and the load is a resistive load, a capacitive load or an inductive load, the current value of the capacitor can be more accurately sampled online, and then whether the capacitor is faulty can be more accurately determined according to the current value of the capacitor, or the capacitance of the capacitor can be more accurately determined online according to the current value of the capacitor, and whether the capacitor is faulty can be more accurately determined.

[0021] With reference to the first aspect, in a possible implementation manner, the inverter circuit is configured to implement an active power filter or a static var generator.

[0022] With reference to the first aspect, in a possible implementation manner, the power conversion device further includes a rectifier circuit, the input end of the rectifier circuit is connected with the input end of the power conversion device, the positive output end of the rectifier circuit is connected with the positive DC bus, and the negative output end of the rectifier circuit is connected with the negative DC bus.

[0023] The second aspect of the embodiments of the present application provides an uninterruptible power supply, which includes a power conversion device, the input end of the power conversion device is connected with the input end of the uninterruptible power supply, the output end of the power conversion device is connected with the output end of the uninterruptible power supply, the output end of the uninterruptible power supply is configured to be connected with a load, and the power conversion device is the power conversion device as described in the first aspect or any possible implementation manner of the first aspect.

[0024] In a third aspect, the present application provides a photovoltaic inverter, comprising a DC / DC conversion circuit and a power conversion device, the power conversion device being configured to convert direct current output by the DC / DC conversion circuit into alternating current, the power conversion device being as described in the first aspect or any possible implementation of the first aspect.

[0025] The second and third aspects of the present application can be described with reference to the detailed description of the first aspect, and the advantages of the second and third aspects can be described with reference to the advantages of the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0026] Fig. 1 is a schematic diagram of a circuit topology of an uninterruptible power supply;

[0027] Fig. 2 is a schematic diagram of a circuit topology of another uninterruptible power supply;

[0028] Fig. 3 is a schematic diagram of a circuit topology of a power conversion device according to an embodiment of the present application;

[0029] Fig. 4 is a schematic diagram of a circuit topology of another power conversion device according to an embodiment of the present application;

[0030] Fig. 5 is a schematic diagram of a circuit topology of yet another power conversion device according to an embodiment of the present application;

[0031] Fig. 6 is a schematic diagram of a circuit topology of still another power conversion device according to an embodiment of the present application;

[0032] Fig. 7 is a schematic diagram of a circuit topology of a photovoltaic inverter according to an embodiment of the present application. DETAILED DESCRIPTION

[0033] The making and using of various embodiments are discussed in detail below. It should be appreciated that the specific exemplary embodiments discussed are merely illustrative of the many applications of the present application and are not intended to limit the scope of the application. One having ordinary skill in the art will readily recognize from the disclosure herein possible alternative applications and uses of the application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0035] Circuits or other components can be described as or said to be "configured to" perform one or more tasks for convenience. In this context, a "configured to" passage does not necessarily imply that a circuit / component is directly / indirectly "configured" by a manufacturer or designer, but rather that the circuit / component is able to "perform" the task(s) due to its circuitry / componentry. Thus, the circuit / component can or can not be "configured" by a manufacturer or designer to perform the task(s), but the circuit / component is able to perform the task(s) due to its circuitry / componentry.

[0036] The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. In the embodiments of the present application, the terms "first", "second", etc. do not limit the quantity and order. In the present application, the words "exemplary" or "for example" are used to mean serving as an example, instance, or illustration. Any embodiment or design solution described as "exemplary" or "for example" in the present application should not be interpreted as being more preferred or advantageous than other embodiments or design solutions. Rather, the use of the words "exemplary" or "for example" is intended to present concepts in a particular manner.

[0037] Before introducing the embodiments of the present application, the technical terms and background art related to the present application are introduced first.

[0038] AC capacitor: refers to a capacitor used in an AC circuit. When the AC capacitor is connected at the output end of an inverter circuit, the AC capacitor can also be referred to as an inverter capacitor.

[0039] Capacitance: refers to the amount of free charge that a capacitor can store under a given potential difference (which can also be referred to as voltage).

[0040] Active power filter (APF): a new type of power electronic device for dynamically suppressing harmonics and compensating for reactive power, which can compensate for harmonics and reactive power that vary in size and frequency.

[0041] Static var generator (SVG): a device based on a free-commutation power semiconductor bridge converter. The static var generator is connected in parallel to the power grid through a bridge circuit, and can quickly absorb or emit reactive power according to the reactive power demand of the power grid.

[0042] Power factor correction (PFC): a circuit used to improve the power factor of a power system or power input. The power factor correction circuit adjusts the phase of the input current to synchronize it with the voltage, thereby reducing the reactive power.

[0043] An uninterruptible power supply is an uninterruptible power supply including an energy storage device (which can also be referred to as a battery), which is used to provide uninterrupted power supply to loads with high requirements for power supply stability. The uninterruptible power supply is widely used in data centers, medical equipment, industrial automation, communication equipment, etc., to provide stable and uninterrupted power supply for critical equipment.

[0044] As shown in FIG. 1 is a circuit topology diagram of an uninterruptible power supply 100. The uninterruptible power supply 100 includes an inverter circuit 110, an inductor L, a first current transformer (CT) CT1, an alternating current capacitor Ca, a second current transformer CT2, a switch K, and a load terminal H. The inductor L and the first current transformer CT1 are connected in series, and the series-connected inductor L and the first current transformer CT1 are arranged between an output terminal of the inverter circuit 110 and a node A. The alternating current capacitor Ca is arranged between the node A and a ground terminal (G). The second current transformer CT2 and the switch K are connected in series, and the series-connected second current transformer CT2 and the switch K are arranged between the node A and the load terminal H.

[0045] Referring to FIG. 1, the uninterruptible power supply 100 further includes a positive-negative bus capacitor arranged between a positive direct current bus BUS+ and a negative direct current bus BUS-. The positive-negative bus capacitor includes a first bus capacitor C1 and a second bus capacitor C2 connected in series. A connection point of the first bus capacitor C1 and the second bus capacitor C2 is connected to a neutral wire (N). The inverter circuit 110 includes a first switch tube Q1 and a second switch tube Q2 connected in series and arranged between the positive direct current bus BUS+ and the negative direct current bus BUS-. A connection point of the first switch tube Q1 and the second switch tube Q2 is an output terminal of the inverter circuit 110.

[0046] The inverter circuit 110 is configured to supply power to the load terminal H, which is configured to be connected to a load 200 to provide power to the load 200. The first current transformer CT1 is configured to sample a current value IL of the inductor L. The second current transformer CT2 is configured to sample a current value IO output by the load terminal H.

[0047] When the switch K is closed, a current value of the alternating current capacitor Ca is a function F(IL, IO) of the current value IL of the inductor L and the current value IO output by the load terminal H. The current value of the alternating current capacitor Ca satisfies the following formula:

[0048] ICa = IL - IO

[0049] wherein ICa represents the current value of the alternating current capacitor Ca.

[0050] A capacitance of the alternating current capacitor Ca is a function F(ICa, Uca, fCa) of the current value ICa, a voltage value UCa, and a frequency fCa of the alternating current capacitor Ca. The capacitance of the alternating current capacitor Ca satisfies the following formula:

[0051] wherein C represents the capacitance of the alternating current capacitor Ca.

[0052] By adopting the above manner, the capacitance C of the alternating current capacitor Ca is continuously detected, whether the capacitance C of the alternating current capacitor Ca is attenuated can be determined according to the detected capacitance C, and whether the alternating current capacitor Ca is faulty can be determined, so as to avoid the alternating current capacitor Ca from exploding to generate smoke.

[0053] However, when the first current transformer CT1 samples the current value IL of the inductor L, and when the second current transformer CT2 samples the current value IO output by the load end H, there are inevitable errors, the current value ICa of the alternating current capacitor Ca is a function F(IL, IO) of the current value IL of the inductor L and the current value IO output by the load end H, which will cause a large detection error of the current value ICa of the alternating current capacitor Ca, and further cause a large detection error of the capacitance C of the alternating current capacitor Ca.

[0054] At the same time, when the uninterruptible power supply 100 includes multiple inverter circuits 110, multiple inductors L and multiple first current transformers CT1, the detection error of the current value ICa of the alternating current capacitor Ca will be larger, and the detection error of the capacitance C of the alternating current capacitor Ca will be larger. Specifically, as shown in (a) of FIG. 2, it is another circuit topology schematic diagram of the uninterruptible power supply 100. The uninterruptible power supply 100 includes multiple inverter circuits 110, multiple inductors L and multiple first current transformers CT1, the positive input end of each inverter circuit 110 in the multiple inverter circuits 110 is connected with the positive direct current bus BUS+, the negative input end of each inverter circuit 110 in the multiple inverter circuits 110 is connected with the negative direct current bus BUS-, the multiple inductors L and the multiple first current transformers CT1 are respectively connected in series, and the series-connected multiple inductors L and the multiple first current transformers CT1 are respectively arranged between the output ends of the multiple inverter circuits 110 and the node A. When the uninterruptible power supply 100 includes multiple inverter circuits 110, multiple inductors L and multiple first current transformers CT1, the current value of the alternating current capacitor Ca is a function F(IL1, IL2, …, ILn, IO) of the current values IL of the multiple inductors L and the current value IO output by the load end H, n is a positive integer greater than or equal to 2, and the current value ICa of the alternating current capacitor Ca satisfies the following formula:

[0055] When the load 200 connected to the load end H is a resistive load, as shown in (b) of FIG. 2, the current vector diagram of the current value ICa of the AC capacitor Ca, the current value IO outputted by the load end H and the current value IL (IL1, IL2, IL3…ILn) of the plurality of inductors L, according to (b) of FIG. 2, it can be understood that since each of the plurality of first current transformers CT1 will introduce an error, it will cause the detection error of the current value ICa of the AC capacitor Ca to be larger, and further cause the capacitance C detection error of the AC capacitor Ca to be larger. When the load 200 connected to the load end H is an inductive load or a capacitive load, as shown in (c) of FIG. 2, the current vector diagram of the current value ICa of the AC capacitor Ca, the current value IO outputted by the load end H and the current value IL (IL1, IL2, IL3…ILn) of the plurality of inductors L, according to (c) of FIG. 2, it can be understood that when the load 200 connected to the load end H is an inductive load or a capacitive load, the current value IO outputted by the load end H and the current value IL of the plurality of inductors L will more directly affect the error of the current value ICa of the AC capacitor Ca, which will cause the detection error of the current value ICa of the AC capacitor Ca to be larger, and further cause the capacitance C detection error of the AC capacitor Ca to be larger.

[0056] Secondly, the current value IL of the inductor L and the current value IO outputted by the load end H are much larger than the current value ICa of the AC capacitor Ca, and the current value ICa of the AC capacitor Ca does not match the range of the first current transformer CT1 and the range of the second current transformer CT2, which will cause the detection error of the current value ICa of the AC capacitor Ca to be larger, and when the capacitance C of the AC capacitor Ca is calculated based on the above formula ICa=IL-IO, it will cause the capacitance C detection error of the AC capacitor Ca to be larger.

[0057] Finally, when the capacitance C of the AC capacitor Ca is detected in the above manner, the applicable range is narrow. Referring to FIG. 1, when the load 200 is heavy, the current value IL of the inductor L and the current value IO output by the load end H are both large, and when the current value ICa of the AC capacitor Ca is calculated based on the above formula ICa = IL-IO, the detection error of the current value ICa of the AC capacitor Ca is larger, and thus the detection error of the capacitance C of the AC capacitor Ca is larger. Therefore, the above manner can be used to detect the capacitance C of the AC capacitor Ca when the load 200 is light, but cannot be used to detect the capacitance C of the AC capacitor Ca when the load 200 is heavy. When the current flowing through the inductor L and the load end H includes a direct current component, the first current transformer CT1 and the second current transformer CT2 will not measure accurately, and the detection error of the current value ICa of the AC capacitor Ca is larger, and thus the detection error of the capacitance C of the AC capacitor Ca is larger. Therefore, the above manner can be used to detect the capacitance C of the AC capacitor Ca when the current flowing through the inductor L and the load end H does not include a direct current component, but cannot be used to detect the capacitance C of the AC capacitor Ca when the current flowing through the inductor L and the load end H includes a direct current component.

[0058] In summary, when the capacitance C of the AC capacitor Ca is detected on-line in the above manner, the detection error of the current value ICa of the AC capacitor Ca is large, which leads to a large detection error of the capacitance C of the AC capacitor Ca, and the applicable range is narrow. Based on this, the embodiments of the present application provide an uninterruptible power supply and a photovoltaic inverter, which directly sample the current value of the capacitor, so as to reduce the detection error of the current value of the capacitor, reduce the detection error of the capacitance of the capacitor, and have a wider applicable range.

[0059] As shown in FIG. 3, it is a circuit topology schematic diagram of a power conversion device 300 provided by an embodiment of the present application. The power conversion device 300 includes an inverter circuit 310, an inductor L, a capacitor Cb, and a current sampling circuit 320. The capacitor Cb can also be referred to as an AC capacitor.

[0060] The positive input end of the inverter circuit 310 is connected with the positive DC bus BUS+, the negative input end of the inverter circuit 310 is connected with the negative DC bus BUS-, the inductor L is arranged between the output end of the inverter circuit 310 and the output end of the power conversion device 300, the capacitor Cb and the current sampling circuit 320 are arranged in series between the output end of the power conversion device 300 and the ground end G, and the serial order of the capacitor Cb and the current sampling circuit 320 is not limited by the embodiments of the present application. The inverter circuit 310 is used to supply power to the output end of the power conversion device 300, and the output end of the power conversion device 300 is used to connect with the load 200 to provide power supply to the load 200. The current sampling circuit 320 is used to sample the current value of the capacitor Cb.

[0061] In a possible embodiment, the current value ICb of the capacitor Cb is used to determine whether the capacitor Cb fails, whether the current value ICb of the capacitor Cb is used to determine whether the capacitor Cb fails according to whether the current value ICb of the capacitor Cb decays, or the current value ICb of the capacitor Cb is used to determine the capacitance of the capacitor Cb, and the capacitance of the capacitor Cb is used to determine whether the capacitor Cb fails, whether the capacitance of the capacitor Cb decays is used to determine whether the capacitor Cb fails, which is not limited in the embodiments of the application. The embodiments of the application take the current value ICb of the capacitor Cb as an example to determine the capacitance of the capacitor Cb, and the capacitance of the capacitor Cb is used to determine whether the capacitor Cb fails.

[0062] Specifically, the capacitance of the capacitor Cb is a function F(ICb, Ucb, fCb) of the current value ICb, the voltage value Ucb and the frequency fCb of the capacitor Cb, and the capacitance of the capacitor Cb satisfies the following formula:

[0063] Wherein, C represents the capacitance of the capacitor Cb.

[0064] Compared with the method of detecting the capacitance C of the AC capacitor Ca in the uninterruptible power supply 100 shown in FIG. 1, the power conversion device 300 provided by the embodiments of the application directly samples the current value ICb of the capacitor Cb through the current sampling circuit 320, without determining the current value ICa of the AC capacitor Ca according to the current value IL of the inductor L sampled by the first current transformer CT1 and the current value IO output by the load end H sampled by the second current transformer CT2, which can avoid the measurement error of the first current transformer CT1 and the second current transformer CT2, thereby reducing the detection error, sampling more accurate current value ICb of the capacitor Cb, and further more accurately determining the capacitance C of the capacitor Cb and whether the capacitor Cb fails.

[0065] Secondly, when the load 200 is heavy, the current value IL of the inductor L and the current value IO output by the load end H are both large, which will result in a larger detection error of the current value ICa of the alternating capacitor Ca. The application directly samples the current value ICb of the capacitor Cb through the current sampling circuit 320, and can sample a more accurate current value ICb of the capacitor Cb when the load 200 is heavy or light. When the current flowing through the inductor L and the load end H includes a direct current component, the first current transformer CT1 and the second current transformer CT2 will not measure accurately, which will result in a larger detection error of the current value ICa of the alternating capacitor Ca. The application directly samples the current value ICb of the capacitor Cb through the current sampling circuit 320, and the current flowing through the capacitor Cb does not include a direct current component, so that a more accurate current value ICb of the capacitor Cb can be sampled. Therefore, the application has a wider application range for detecting the capacitance C of the capacitor Cb by directly sampling the current value ICb of the capacitor Cb through the current sampling circuit 320.

[0066] In a possible embodiment, the current value ICb of the capacitor Cb is greater than or equal to a first range threshold of the current sampling circuit 320 and less than or equal to a second range threshold of the current sampling circuit 320, and the first range threshold is less than the second range threshold. The application does not limit the specific values of the first range threshold and the second range threshold. Compared with the detection of the capacitance C of the alternating capacitor Ca in the uninterruptible power supply 100 shown in FIG. 1, the current value ICb of the capacitor Cb matches the range of the current sampling circuit 320, so that the measurement error of the current sampling circuit 320 can be reduced. The current sampling circuit 320 can sample a more accurate current value ICb of the capacitor Cb, and the capacitance C of the capacitor Cb can be determined more accurately online, and whether the capacitor Cb fails can be determined more accurately.

[0067] For example, taking the first range threshold as 1 / 3 of the range of the current sampling circuit 320 and the second range threshold as 2 / 3 of the range of the current sampling circuit 320 as an example, when the current value ICb of the capacitor Cb is greater than or equal to 1 / 3 of the range of the current sampling circuit 320 and less than or equal to 2 / 3 of the range of the current sampling circuit 320, the measurement error of the current sampling circuit 320 can be reduced. The current sampling circuit 320 can sample a more accurate current value ICb of the capacitor Cb online, and whether the capacitor Cb fails can be determined more accurately according to the current value ICb of the capacitor Cb, or the capacitance C of the capacitor Cb can be determined more accurately online according to the current value ICb of the capacitor Cb, and whether the capacitor Cb fails can be determined more accurately.

[0068] In a possible embodiment, the inverter circuit 310 can be used to implement an active power filter or a static var generator, which are not limited in the embodiments of the present application.

[0069] In a possible embodiment, the inverter circuit 310 is a two-level, three-level or multi-level inverter circuit, which are not limited in the embodiments of the present application.

[0070] For example, taking the two-level inverter circuit as an example. As shown in FIG. 3, the power conversion device 300 further includes a positive-negative bus capacitor arranged between the positive DC bus BUS+ and the negative DC bus BUS-, the positive-negative bus capacitor includes a first bus capacitor C1 and a second bus capacitor C2 connected in series, and a connection point of the first bus capacitor C1 and the second bus capacitor C2 is connected with the neutral line N. The inverter circuit 310 includes a first switch tube Q1 and a second switch tube Q2 arranged in series between the positive DC bus BUS+ and the negative DC bus BUS+, and a connection point of the first switch tube Q1 and the second switch tube Q2 is an output end of the inverter circuit 310.

[0071] For another example, taking the three-level inverter circuit as an example. As shown in FIG. 4, the power conversion device 300 further includes a positive-negative bus capacitor arranged between the positive DC bus BUS+ and the negative DC bus BUS-, the positive-negative bus capacitor includes a first bus capacitor C1 and a second bus capacitor C2 connected in series, and a connection point of the positive-negative bus capacitor is connected with the neutral line N. The inverter circuit 310 includes an upper bridge arm arranged between the positive DC bus BUS+ and an output end of the inverter circuit 310, and a lower bridge arm arranged between the negative DC bus BUS- and the output end of the inverter circuit 310, wherein the upper bridge arm includes a first switch tube Q1 and a second switch tube Q2 connected in series, the lower bridge arm includes a third switch tube Q3 and a fourth switch tube Q4 connected in series, the inverter circuit 310 further includes a first diode D1 and a second diode D2, a negative electrode of the first diode D1 is connected with a midpoint of the upper bridge arm, a positive electrode of the second diode D2 is connected with a midpoint of the lower bridge arm, and a positive electrode of the first diode D1 and a negative electrode of the second diode D2 are connected with the connection point of the positive-negative bus capacitor.

[0072] For another example, taking the inverter circuit 310 as a three-level inverter circuit as an example. As shown in FIG. 5, the power conversion device 300 further includes a positive-negative bus capacitor arranged between the positive DC bus BUS+ and the negative DC bus BUS-, the positive-negative bus capacitor includes a first bus capacitor C1 and a second bus capacitor C2 connected in series, and a connection point of the positive-negative bus capacitor is connected with the zero line N. The inverter circuit 310 includes a first switch tube Q1 and a second switch tube Q2 arranged in series between the positive DC bus BUS+ and the negative DC bus BUS+, a connection point of the first switch tube Q1 and the second switch tube Q2 is an output end of the inverter circuit 310, and the inverter circuit 310 further includes a switch tube bridge arm arranged between the output end of the inverter circuit 310 and the connection point of the positive-negative bus capacitor, the switch tube bridge arm includes a third switch tube Q3 and a fourth switch tube Q4 connected in series, and a drain or a collector of the third switch tube Q3 and a drain or a collector of the fourth switch tube Q4 are connected, so that the switch tube bridge arm can be completely turned off.

[0073] Optionally, each of the above-mentioned switch tubes can include a transistor or a transistor and a diode. Specifically, each of the switch tubes can include an insulate-gate bipolar transistor (IGBT) and a diode, a collector of the IGBT is connected with a negative electrode of the diode, and an emitter of the IGBT is connected with a positive electrode of the diode, or each of the switch tubes can include a metal-oxide-semiconductor field-effect transistor (MOSFET), which can also be referred to as a MOS tube, and each of the MOS tubes includes a reverse-biased body diode, and the embodiments of the present application do not limit the specific types of the switch tubes.

[0074] In a possible embodiment, the type of the current sampling circuit 320 includes a current transformer, a Hall effect sensor, a resistive current sensor, a capacitive current sensor or an electromagnetic induction sensor, and the embodiments of the present application do not limit the specific types of the current sampling circuit 320.

[0075] The power conversion device 300 provided by the embodiments of the present application does not need to determine the current value ICa of the alternating capacitor Ca according to the current value IL of the inductor L sampled by the first current transformer CT1 and the current value IO output by the load end H sampled by the second current transformer CT2, but directly samples the current value ICb of the capacitor Cb through the current sampling circuit 320, so that a more accurate current value ICb of the capacitor Cb can be sampled online, and then the capacitor Cb can be more accurately determined to be faulty according to the current value ICb of the capacitor Cb, or the capacitance of the capacitor Cb can be more accurately determined online according to the current value ICb of the capacitor Cb, so that whether the capacitor Cb is faulty can be more accurately determined.

[0076] In a possible implementation, as shown in FIG. 6, the power conversion device 300 further includes a temperature sensor 330 configured to sample the temperature of the capacitor Cb, so that whether the capacitor Cb fails can be determined according to the temperature of the capacitor Cb, and the accuracy of determining whether the capacitor Cb fails can be further improved.

[0077] Optionally, the temperature sensor 330 can be a contact temperature sensor or a non-contact temperature sensor, and the embodiments of the present application do not limit the specific type of the temperature sensor 330.

[0078] For example, when the temperature sensor 330 is a contact temperature sensor, the temperature sensor 330 can be a thermocouple temperature sensor or a thermal resistance temperature sensor, and when the temperature sensor 330 is a non-contact temperature sensor, the temperature sensor 330 can be an infrared temperature sensor or a thermistor, such as a negative temperature coefficient (NTC) thermistor or a positive temperature coefficient (PTC) thermistor.

[0079] The power conversion device 300 provided by the embodiments of the present application can sample the temperature of the capacitor Cb through the temperature sensor 330, so that whether the capacitor Cb fails can be determined according to the temperature of the capacitor Cb, and the accuracy of determining whether the capacitor Cb fails can be further improved.

[0080] In a possible implementation, as shown in FIG. 6, the power conversion device 300 includes a plurality of inverter circuits 310 and a plurality of inductors L, the positive input end of each inverter circuit 310 in the plurality of inverter circuits 310 is connected with the positive DC bus BUS+, the negative input end of each inverter circuit 310 in the plurality of inverter circuits 310 is connected with the negative DC bus BUS-, and the plurality of inductors L are respectively arranged between the output ends of the plurality of inverter circuits 310 and the output end of the power conversion device 300, so that the output power of the power conversion device 300 can be improved, and the embodiments of the present application do not limit the specific number of the inverter circuits 310 and the inductors L included in the power conversion device 300, and the embodiments of the present application are exemplarily described below taking the circuit topology of the inverter circuit 310 in FIG. 3 as an example.

[0081] Compared with the detection of the capacitance C of the AC capacitor Ca in the uninterruptible power supply 100 shown in FIG. 1, since each of the plurality of first current transformers CT1 will introduce errors, the detection error of the current value ICa of the AC capacitor Ca will be greater, and the detection error of the capacitance C of the AC capacitor Ca will be greater. In the application, the current value ICb of the capacitor Cb is directly sampled by the current sampling circuit 320, so that when the power conversion device 300 includes a plurality of inverter circuits 310 and a plurality of inductors L, and the load 200 is a resistive load, a capacitive load or an inductive load, a more accurate current value ICb of the capacitor Cb can be sampled, and the capacitance C of the capacitor Cb can be more accurately determined online, and whether the capacitor Cb fails can be more accurately determined.

[0082] In a possible embodiment, as shown in FIG. 6, the power conversion device 300 further includes a rectifier circuit 340, an input end of the rectifier circuit 340 is connected with an input end of the power conversion device 300, a positive output end of the rectifier circuit 340 is connected with the positive DC bus BUS+, and a negative output end of the rectifier circuit 340 is connected with the negative DC bus BUS-. At this time, the circuit composed of the rectifier circuit 340 and the inverter circuit 310 can be referred to as a power factor correction circuit.

[0083] In a possible embodiment, as shown in FIG. 6, the power conversion device 300 can further include an inductor current sampling circuit 350 and a switch K, the inductor current sampling circuit 350 is arranged between the connection point B of the inductor L and the capacitor Cb and the inductor L, and the switch K is arranged between the connection point B and an output end of the power conversion device 300. The number of the power conversion device 300 including the inductor current sampling circuit 350 is the same as the number of the power conversion device 300 including the inverter circuit 310. The inductor current sampling circuit 350 is used to sample the current value of the inductor L, which can be used to determine whether the power conversion device 300 fails, such as short circuit or overcurrent, so as to improve the reliability of the power conversion device 300. The switch K is used to control the conduction or disconnection between the connection point B of the inductor L and the capacitor Cb and the output end of the power conversion device 300, so as to control the power conversion device 300 to supply power to the load 200.

[0084] The power conversion device 300 provided by the embodiment of the present application can improve the output power of the power conversion device 300 by arranging multiple inverter circuits 310 and multiple inductors L. Meanwhile, the current sampling circuit 320 directly samples the current value ICb of the capacitor Cb, so that when the power conversion device 300 includes multiple inverter circuits 310 and multiple inductors L, and the load 200 is a resistive load, a capacitive load or an inductive load, the current value ICb of the capacitor Cb can be sampled more accurately online, and then the capacitor Cb can be determined more accurately whether it is faulty according to the current value ICb of the capacitor Cb, or the capacitance of the capacitor Cb can be determined more accurately online according to the current value ICb of the capacitor Cb, and the capacitor Cb can be determined more accurately whether it is faulty.

[0085] As shown in FIG. 6, the embodiment of the present application also provides an uninterruptible power supply 400, which includes the power conversion device 300, the input end of the power conversion device 300 is connected to the input end of the uninterruptible power supply 400, the output end of the power conversion device 300 is connected to the output end of the uninterruptible power supply 400, and the output end of the uninterruptible power supply 400 is used to connect the load 200. The circuit topology of the power conversion device 300 can be any one of the circuit topologies of the power conversion device 300 shown in FIGS. 3 to 6, and the embodiment of the present application does not make any limitation in this regard.

[0086] Based on this, as shown in FIG. 7, the embodiment of the present application also provides a photovoltaic inverter 500, which includes a direct current direct current (DCDC) conversion circuit 510 and the power conversion device 300 connected to the DCDC conversion circuit 510, the power conversion device 300 is used to convert the direct current output by the DCDC conversion circuit 510 into alternating current, and the circuit topology of the power conversion device 300 is any one of the circuit topologies of the power conversion device 300 shown in FIGS. 3 to 6, and the embodiment of the present application does not make any limitation in this regard. When the circuit topology of the power conversion device 300 is the circuit topology of the power conversion device 300 shown in FIG. 6, the power conversion device 300 does not include the rectifier circuit 340.

[0087] The above detailed description and beneficial effect analysis of the power conversion device 300 can be correspondingly referred to the uninterruptible power supply 400 and the photovoltaic inverter 500, and the embodiment of the present application will not be described here.

[0088] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited to this. Any change or replacement within the technical scope disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A power conversion device, characterized by, The power conversion device comprises an inverter circuit, an inductor, a capacitor and a current sampling circuit. The positive input end of the inverter circuit is connected with the positive DC bus, the negative input end of the inverter circuit is connected with the negative DC bus, the inductor is arranged between the output end of the inverter circuit and the output end of the power conversion device, and the capacitor and the current sampling circuit are arranged in series between the output end of the power conversion device and the ground end. The current sampling circuit is used for sampling the current value of the capacitor.

2. The power conversion device of claim 1, wherein, The current value of the capacitor is greater than or equal to the first range threshold of the current sampling circuit and less than or equal to the second range threshold of the current sampling circuit, and the first range threshold is less than the second range threshold.

3. The power conversion device of claim 2, wherein, The power conversion device further comprises a temperature sensor for sampling the temperature of the capacitor.

4. The power conversion device according to any one of claims 1 to 3, characterized by, The power conversion device comprises a plurality of inverter circuits and a plurality of inductors, the positive input end of each inverter circuit in the plurality of inverter circuits is connected with the positive DC bus, the negative input end of each inverter circuit in the plurality of inverter circuits is connected with the negative DC bus, and the plurality of inductors are arranged between the output ends of the plurality of inverter circuits and the output end of the power conversion device respectively.

5. The power conversion device of any one of claims 1-3, wherein, The inverter circuit is used for implementing an active power filter or a static var generator.

6. The power conversion device of any one of claims 1-3, wherein, The power conversion device further comprises a rectifier circuit, the input end of the rectifier circuit is connected with the input end of the power conversion device, the positive output end of the rectifier circuit is connected with the positive DC bus, and the negative output end of the rectifier circuit is connected with the negative DC bus.

7. An uninterruptible power supply, characterized by The uninterruptible power supply comprises a power conversion device, the input end of the power conversion device is connected with the input end of the uninterruptible power supply, the output end of the power conversion device is connected with the output end of the uninterruptible power supply, the output end of the uninterruptible power supply is used for connecting a load, and the power conversion device is the power conversion device as claimed in any one of claims 1-6.

8. A photovoltaic inverter, characterized by The photovoltaic inverter comprises a DCDC conversion circuit and the power conversion device as claimed in any one of claims 1-5, and the power conversion device is used for converting the DC power output by the DCDC conversion circuit into AC power.

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