CN112034261A - Method for monitoring ESR (equivalent series resistance) of DC bus capacitor of two-stage single-phase inverter - Google Patents

Abstract

The invention discloses an ESR (equivalent series resistance) monitoring method for a direct-current bus capacitor of a two-stage single-phase inverter, which comprises the following steps: first, the DC bus voltage v_busHigh-pass filtering is carried out to obtain the alternating current component v of the direct current bus voltage_{bus_ac}(ii) a Second, the AC component v of the DC bus voltage is compared_{bus_ac}And inverter inductance current i_L2Carrying out synchronous sampling; thirdly, sampling the AC component v of the DC bus voltage_{bus_ac}Inverter inductive current i_L2Denoising; fourthly, obtaining the inverter inductive current i after denoising_L2Peak value i of_{L2_peak}And the AC component v of the DC bus voltage at the corresponding time_{bus_ac}Voltage variation amount Δ v of_{bus_ac}(ii) a Fifthly, according to the obtained peak value i_{L2_peak}And the voltage variation amount delta v_{bus_ac}And calculating the ESR value of the direct current bus capacitor. The method provided by the invention does not need to increase extra sampling points, does not influence the normal work of the converter, is simple and easy to realize, and provides health monitoring for the capacitorAccording to the method.

Description

Method for monitoring ESR (equivalent series resistance) of DC bus capacitor of two-stage single-phase inverter

Technical Field

The invention belongs to the technical field of inverters, and relates to a health monitoring method for a direct-current bus capacitor of a two-stage single-phase inverter, in particular to a monitoring method for an ESR (equivalent series resistance) of the direct-current bus capacitor of the two-stage single-phase inverter.

Background

At present, in distributed power generation systems such as new energy, airplanes, electric automobiles and the like, the specifications of traditional low-voltage direct-current power supply systems are generally compatible, and direct-current power supplies such as 28V and 42V are still used. In order to obtain 115V or 220V ac power required by a load, a two-stage architecture is generally adopted, i.e., a front-stage dc-dc converter is used for completing input and output voltage matching and electrical isolation of an inverter, and a rear-stage inverter is used for completing dc-to-ac conversion and supplying power to a terminal load.

In the two-stage single-phase inverter, because the instantaneous output power of the inverter at the rear stage comprises the pulsating power with the frequency of twice the output voltage, the input current of the direct-current and direct-current converter at the front stage has the pulsation with the frequency of twice the output voltage. The second harmonic current not only increases the current stress of the switching tube, but also increases the conduction loss of the switching tube and the loss of the magnetic element, and can affect the soft switching of the switching tube, thereby being not beneficial to improving the efficiency of the converter. On the other hand, the double-frequency low-frequency ripple in the input current causes interference to the input source, affects the performance of the input source, and has a great influence on the service life of new energy sources such as a fuel cell, so that the input low-frequency ripple current of the conversion device is regulated by standards and must be controlled to be a small value. In order to suppress this ripple, a large electrolytic capacitor is generally connected in parallel to the dc bus. However, the electrolytic capacitor is the most inefficient power device in the power electronic converter. After the electrolytic capacitor is used for a period of time, the equivalent series resistance ESR of the capacitor can be increased, and when the ESR is increased to a certain extent, the capacitor can be considered to have failed, and the failure of the capacitor can cause the operation faults of the converter and the system. In industry, the equivalent series resistance of an electrolytic capacitor is an important index for measuring the health condition of the capacitor, so that monitoring the equivalent series resistance ESR of the capacitor on the direct current bus side of the two-stage single-phase inverter is important for evaluating the health condition of the capacitor. However, there is still a lack of effective health monitoring method for the electrolytic capacitor on the dc bus side.

Disclosure of Invention

The invention aims to solve the technical problem in the background art, and provides a method for monitoring the ESR of a two-stage single-phase inverter direct-current bus capacitor, which can monitor the ESR in real time on line and monitor the health state of an electrolytic capacitor, thereby providing a research basis for fault prediction of a power electronic circuit.

The invention adopts the following technical scheme for solving the technical problems:

a method for monitoring ESR of a DC bus capacitor of a two-stage single-phase inverter comprises an input power supply V_inDC-DC converter, inverter and load R_oInput power supply V_inIs connected to the input end of the DC-DC converter, the output end of the DC-DC converter is connected to the input end of the inverter, the output end of the inverter is connected to the load R_oThe monitoring method comprises the following steps:

step A), the voltage v of the direct current bus is converted into_busObtaining AC component v of DC bus voltage by high-pass filter unit_{bus_ac}；

Step B) for the alternating current component v of the direct current bus voltage_{bus_ac}And inverter inductance current i_L2Denoising after synchronous sampling;

step C), obtaining the inverter inductive current i after denoising_L2Peak value i of_{L2_peak}And the AC component v of the DC bus voltage at the corresponding time_{bus_ac}Voltage variation amount Δ v of_{bus_ac}；

Step D), calculating the value of ESR of the direct current bus capacitor according to the following formula,

by adopting the technical scheme, the invention has the following technical effects:

1. the invention needs less data to be sampled;

2. for a two-stage single-phase inverter with double-loop control of output voltage and current, no new sampling point is required to be introduced;

3. the circuit is simple, accurate monitoring of the ESR of the direct current bus capacitor can be achieved on the basis that electronic components are not added, and the method has important practical application value.

Drawings

Fig. 1 is a schematic diagram of an ESR value monitoring method for a dc bus capacitor of a two-stage single-phase inverter according to the present invention;

fig. 2 is a waveform diagram of the two-stage single-phase inverter according to the present invention.

Detailed Description

The technical scheme of the invention is further explained in detail by combining the attached drawings:

as shown in fig. 1, the invention discloses a method for monitoring ESR of a dc bus capacitor of a two-stage single-phase inverter, wherein the two-stage single-phase inverter comprises an input power source V_inDC-DC converter, inverter and load R_oInput power supply V_inIs connected to the input end of the DC-DC converter, the output end of the DC-DC converter is connected to the input end of the inverter, the output end of the inverter is connected to the load R_oThe method for monitoring the ESR of the DC bus capacitor of the two-stage single-phase inverter comprises the following steps:

step A), the voltage v of the direct current bus is converted into_busObtaining AC component v of DC bus voltage by high-pass filter unit_{bus_ac}；

Step B) for the alternating current component v of the direct current bus voltage_{bus_ac}And inverter inductance current i_L2Denoising after synchronous sampling;

step C), obtaining the inverter inductive current i after denoising_L2Peak value i of_{L2_peak}And the AC component v of the DC bus voltage at the corresponding time_{bus_ac}Voltage variation amount Δ v of_{bus_ac}；

Step D), according to the obtained peak value i_{L2_peak}And the voltage variation amount delta v_{bus_ac}And calculating the ESR value of the direct current bus capacitor according to the following formula:

FIG. 2 is a waveform diagram of the operation of the two-stage single-phase inverter of the present invention, in which FIG. 2(a) is an overall diagram and FIG. 2(b) is a partial diagram. The invention provides simulation of ESR monitoring of a DC bus capacitor, which comprises the steps of firstly simulating circuit operation, and acquiring an AC component v of a DC bus voltage after the operation is stopped_{bus_ac}With the inductor current i of the inverter_L2And introducing the current into Matlab Workspace for data processing to obtain the denoised inductive current i_L2Peak value i of_{L2_peak}And the AC component v of the DC bus voltage at the corresponding time_{bus_ac}Voltage variation amount Δ v of_{bus_ac}Will peak value i_{L2_peak}And a voltage variation amount Deltav_{bus_ac}Substitution formula

And (6) performing calculation. The simulation results under different ESR conditions are shown in Table 1, and therefore, the ESR monitoring method for the two-stage single-phase inverter direct-current bus capacitor provided by the invention has high tracking accuracy.

TABLE 1

Actual value of ESR/Ω	0.1	0.2	0.3	0.4
					Calculated ESR/Ω	0.0992	0.1963	0.2991	0.3992

The ESR monitoring method for the DC bus capacitor of the two-stage single-phase inverter has the advantages that no new measuring point is required to be introduced, the method is simple and easy to implement, and the identification precision is high.

It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only illustrative of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (1)

1. A method for monitoring ESR of a DC bus capacitor of a two-stage single-phase inverter comprises an input power supply V_inDC-DC converter, inverter and load R_oInput power supply V_inIs connected to the input end of the DC-DC converter, the output end of the DC-DC converter is connected to the input end of the inverter, the output end of the inverter is connected to the load R_oThe monitoring method is characterized by comprising the following steps:

step A), the voltage v of the direct current bus is converted into_busObtaining AC component v of DC bus voltage by high-pass filter unit_{bus_ac}；

Step B) for the alternating current component v of the direct current bus voltage_{bus_ac}And inverter inductance current i_L2Denoising after synchronous sampling;

step C), obtaining the inverter inductive current i after denoising_L2Peak value i of_{L2_peak}And the AC component v of the DC bus voltage at the corresponding time_{bus_ac}Voltage variation amount Δ v of_{bus_ac}；

Step D), calculating the value of ESR of the direct current bus capacitor according to the following formula,

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