An inverter loss calibration circuit and an inverter loss calibration method

Abstract

The present invention belongs to the technical field of power electronic modules, and particularly relates to an inverter loss calibration circuit and an inverter loss calibration method. When calibrating the inverter loss, only the output power of the DC power supply needs to be measured. By changing the connection status of each AC load device, the measurement of the output power of the DC power supply in three cases, namely, the series load of two load devices and the load of two single load devices, is completed. Finally, the loss of the inverter module is obtained through conversion. Using the above test method can simulate the real working conditions of the inverter as much as possible under low-cost conditions, and at the same time complete the calibration work of the inverter loss. The present invention greatly reduces the cost of calibrating the loss of the inverter module.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronic modules, and particularly relates to an inverter loss calibration circuit and an inverter loss calibration method. Background Art

[0002] The losses and efficiency of an inverter are important indicators for measuring product performance. Therefore, corresponding loss calibration experiments are required during product test and verification. To obtain accurate losses that can reflect the actual operating conditions, an adjustable DC power supply and the required load simulator are generally used in the experiment to simulate different operating conditions as much as possible. At the same time, a power analyzer is used to measure its input and output powers to calibrate the loss distribution of the inverter at this time. Simulating the actual operating conditions of the inverter generally requires high requirements for laboratory equipment. The laboratory needs to be equipped with corresponding load simulators and power analyzers, but these devices are often expensive. For small laboratories, it is not worth the cost in terms of both economic cost and time cost. To reduce the dependence on such devices and complete the calibration of the power module losses under low-cost conditions, a simple and feasible loss test and calibration method needs to be designed. Regarding the losses of the inverter, the most significant influencing factors are the DC input voltage and the fundamental current component flowing through the inverter. During test and calibration, only by first satisfying the simulation of these two parameters can the losses of the inverter be calibrated within an acceptable error range and used as a reference for subsequent iterative design. This simplified loss calibration method can greatly reduce the requirements for equipment, and only rely on commonly used equipment such as an adjustable DC power supply and a load reactor to complete the configuration work of the loss calibration experiment. However, since the load lacks equipment for consuming active power and cannot adjust the phase of the fundamental current, generally the method of connecting inverters in a back-to-back configuration is adopted to achieve full control of the fundamental current amplitude and phase.

[0003] The losses of the inverter can be obtained by subtracting the losses of the load reactor from the DC input power. The measurement of the DC input power is relatively easy, but the measurement of the losses of the load reactor is relatively difficult. On the one hand, the waveform on the load reactor changes at a high frequency. To measure it by electrical methods, voltage and current probes with sufficient bandwidth and completed delay correction must be used. On the other hand, the parasitic parameters of the measurement probes may resonate with the load reactor. Summary of the Invention

[0004] In view of this, the present invention provides an inverter loss calibration circuit. During loss calibration, only the output power of the DC power supply needs to be measured. By changing the connection status of each AC load device, the measurement of the output power of the DC power supply in three cases, namely, the series load of two load devices and the load of two single load devices, is completed. Finally, the loss of the inverter module is obtained through conversion. Using the above test method can simulate the real working conditions of the inverter as much as possible under low-cost conditions, and at the same time complete the calibration work of the inverter loss. The present invention greatly reduces the cost of calibrating the loss of the inverter module.

[0005] In order to achieve the above technical objectives, the specific technical solutions adopted by the present invention are as follows:

[0006] An inverter loss calibration circuit, comprising:

[0007] A DC voltage source;

[0008] A back-to-back system, including two inverter modules, with the DC side connected to the DC voltage source;

[0009] A measurement module, connected to the DC voltage source, for measuring the DC components of the voltage and current at the DC input end;

[0010] A calibration load module, connected to the AC side of the back-to-back system to form the load of the back-to-back system, including at least two groups of AC load devices, and each AC load device is set to be able to operate independently or in series with each other.

[0011] Further, the AC load device is a load reactor.

[0012] Further, when the inverter has a single-phase output at the AC end, each load reactor is a single-phase load reactor.

[0013] Further, the load reactors are connected in series.

[0014] Further, when the inverter has a three-phase output at the AC end, each load reactor is a three-phase load three-phase parallel reactor.

[0015] Further, the measurement points of the measurement module are distributed on the DC bus of the DC voltage source.

[0016] Further, the measurement module is an oscilloscope.

[0017] Further, the measurement module is a multimeter.

[0018] Further, the measurement module measures the fundamental wave of the current at the DC input end based on an isolated voltage probe and a toroidal current probe.

[0019] Meanwhile, the present invention also proposes an inverter loss calibration method based on the above inverter loss calibration circuit, which is as follows:

[0020] A calibration load module is set at the output end of the inverter; the calibration load module includes at least two load reactors;

[0021] Take the first load reactor on the back-to-back system as the AC-side load of the inverter, control the back-to-back system to output with a first current, and measure the input power at the DC input end of the inverter, denoted as P L1 ;

[0022] Take the second load reactor on the back-to-back system as the AC-side load of the inverter, control the back-to-back system to output with a first current, and measure the input power at the DC input end of the inverter, denoted as P L2 ;

[0023] Take the first load reactor and the second load reactor on the back-to-back system together as the AC-side load of the inverter, control the back-to-back system to output with a first current, and measure the input power at the DC input end of the inverter, denoted as P L12 ;

[0024] Calibrate the loss of the inverter when the DC voltage source operates with a first current as:

[0025] P 损 = P L1 + P L2 – P L12 .

[0026] Adopting the above technical solution, the present invention can bring the following beneficial effects:

[0027] (1) The present invention greatly reduces the dependence of the inverter module loss calibration experiment on experimental equipment. The loss calibration work can be completed by using the most common adjustable DC voltage source, load reactor, oscilloscope and multimeter, which can save the cost of purchasing additional equipment;

[0028] (2) Through the specially designed loss calibration test process, this aspect of the present invention omits the link of measuring the loss of the load reactor, only needs to measure the output power of the DC voltage source, reduces the difficulty of loss calibration, and can also improve the accuracy of the measurement result. Description of the Drawings

[0029] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the accompanying drawings required for the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0030] Figure 1 This is a circuit diagram for calibrating the losses of a single-phase output inverter at the AC end in a specific embodiment of the present invention;

[0031] Figure 2 This is a circuit diagram for calibrating the losses of a three-phase output inverter at the AC end in a specific embodiment of the present invention;

[0032] Wherein: 1. DC voltage source; 2. Isolated voltage probe; 3. Toroidal current probe; 4. Inverter module; 5. Calibration load module. Specific embodiments

[0033] The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0034] The following specific examples illustrate the embodiments of the present disclosure. Those skilled in the art can easily understand other advantages and effects of the present disclosure from the content disclosed in this specification. Obviously, the described embodiments are only some embodiments of the present disclosure, rather than all embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts belong to the scope of protection of the present disclosure.

[0035] It should be noted that the following describes various aspects of the embodiments within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is illustrative only. Based on the present disclosure, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement a device and / or practice a method. In addition, this device and / or this method can be implemented using other structures and / or functions in addition to one or more of the aspects described herein.

[0036] It should also be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present disclosure schematically. The diagrams only show the components related to the present disclosure, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0037] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0038] In an embodiment of the present invention, an inverter loss calibration method is proposed. The inverter loss calibration method is as follows:

[0039] Set a calibration load module 5 at the output end of the inverter; the calibration load module 5 includes at least two groups of load reactors;

[0040] Take the first load reactor on the calibration load module 5 as the AC-side load of the inverter, control the back-to-back system of the inverter to output with a first current, and measure the input power at the DC input end of the inverter, denoted as P L1 ;

[0041] Take the second load reactor on the back-to-back circuit 5 as the AC-side load of the inverter, control the back-to-back system of the inverter to output with a first current, and measure the input power at the DC input end of the inverter, denoted as P L2 ;

[0042] Take the first load reactor and the second load reactor on the back-to-back circuit 5 together as the AC-side load of the inverter, control the back-to-back system of the inverter to output with a first current, and measure the input power at the DC input end of the inverter, denoted as P L12 ;

[0043] Calibrate the loss of the inverter when the DC voltage source 1 operates with a first current as:

[0044] P 损 = P L1 + P L2 – P L12 。

[0045] At the same time, the back-to-back circuit 5 in this embodiment can use multiple groups of load reactors, and the individual operating power and overall power of two, more than two, or all of the load reactors can be extracted. After adding all the individual operating powers and finally subtracting the overall power, P 损 。

[0046] The DC input terminal of this embodiment can be configured accordingly in software to achieve full control of the fundamental current, making this component consistent with the actual working conditions. For the drag time, open-loop control or closed-loop control can be adopted. If open-loop control is selected, the modulation wave amplitude and phase difference of the two inverter modules need to be manually adjusted to control the fundamental current. If closed-loop control is selected, the required Id and Iq current values can be directly set. The two load reactors in this embodiment do not need to be exactly the same. According to the common Steinmetz magnetic core loss calculation formula P V = k·f α ·B m β , it can be seen that regardless of whether the reactors are connected in series or not, the magnetic core losses on them are basically the same. In addition, the copper losses of the reactors can also be considered to be basically the same. Therefore, the losses of the inverter module can be obtained through the conversion of the formula P L1 +P L2 -P L12 .

[0047] This embodiment omits the link of measuring the losses of the load reactors, improving the accuracy of the loss calibration result.

[0048] Based on the above inverter loss calibration method, an embodiment of the present invention also proposes an inverter loss calibration circuit, as shown in Figure 1 or Figure 2 , including:

[0049] DC voltage source 1;

[0050] Drag system, composed of two inverter modules 4, with the DC side connected to the DC voltage source 1 and the AC side connected to the calibration load module 5;

[0051] Measurement module, connected to the DC voltage source 1, for measuring the fundamental current of the DC input terminal; that is, P L1 、P L2 and P L12 .

[0052] Calibration load module 5, connected to the AC output terminal of the inverter module 4, forming the load of the drag system composed of the inverter module 4, including at least two groups of AC load devices, and each AC load device is set to be able to operate independently or simultaneously.

[0053] In this embodiment, the AC load device is a device that can consume alternating current, which is not limited in this embodiment, and is preferably a load reactor.

[0054] In one embodiment, when the inverter has single-phase output at the AC end, each load reactor is a single-phase load reactor.

[0055] In this embodiment, the load reactors are connected in series.

[0056] In one embodiment, when the inverter has three single-phase outputs on the AC side, each load reactor is a three-phase load three-phase reactor.

[0057] In this embodiment, the measurement points of the measurement module are distributed on the DC bus of the DC voltage source 1.

[0058] In some embodiments, the measurement module is an oscilloscope. The oscilloscope is used to measure the output voltage and output current of the DC source respectively by the oscilloscope, and obtain the output power of the DC source by integrating the voltage and current;

[0059] In some embodiments, the measurement module is a multimeter.

[0060] In some embodiments, the measurement module measures the fundamental wave of the current at the DC input end based on the isolation voltage probe 2 and the toroidal current probe 3. The toroidal current probe 3 can be a Rogowski coil or a Hall-type current probe 3.

[0061] As described above, the above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present disclosure should be covered by the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. An inverter loss calibration circuit, characterized in that Comprising: A DC voltage source; A back-to-back system, including two inverter modules, with the DC sides connected to the DC voltage source; A measurement module, connected to the DC voltage source, for measuring the DC components of the voltage and current at the DC input; A calibration load module, connected to the AC side of the back-to-back system to form the load of the back-to-back system, including at least two groups of AC load devices, and each of the AC load devices is set to be operable either individually or in series with each other.

2. The inverter loss calibration circuit according to claim 1, wherein The AC load device is a load reactor.

3. The inverter loss calibration circuit according to claim 2, characterized in that, When the inverter has a single-phase output at the AC end, each of the load reactors is a single-phase load reactor.

4. The inverter loss calibration circuit according to claim 2, wherein Each of the load reactors is arranged in series.

5. The inverter loss calibration circuit according to claim 2, wherein, When the inverter has a three-phase output at the AC end, each of the load reactors is a three-phase load three-phase shunt reactor.

6. The inverter loss calibration circuit according to claim 1, wherein The measurement points of the measurement module are distributed on the DC bus of the DC voltage source.

7. The inverter loss calibration circuit according to claim 1 or 6, characterized in that, The measurement module is an oscilloscope.

8. The inverter loss calibration circuit according to claim 1 or 6, characterized in that The measurement module is a multimeter.

9. The inverter loss calibration circuit according to claim 1, wherein, The measurement module measures the DC component of the current at the DC input based on an isolation voltage probe and a toroidal current probe.

10. A method for calibrating inverter losses of the inverter loss calibration circuit according to any one of claims 1-9, characterized in that, The inverter loss calibration method is as follows: Set a calibration load module at the output end of the inverter; the calibration load module includes at least two groups of load reactors; Take the first load reactor on the counter-rotating system as the AC terminal load of the inverter, control the counter-rotating system to output with a first current, and measure the input power at the DC input terminal of the inverter, denoted as P L1 ; Use the second load reactor on the counter-rotating system as the AC-side load of the inverter, control the counter-rotating system to output with a first current, and measure the input power at the DC input of the inverter, denoted as P L2 ; Take the first load reactor and the second load reactor on the counter-rotating system together as the AC terminal load of the inverter, control the counter-rotating system to output with a first current, and measure the input power at the DC input terminal of the inverter, denoted as P L12 ; Calibrate the loss of the inverter when the DC voltage source operates with a first current as: P 损 = P L1 + P L2 – P L12 .

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