AC / DC bidirectional energy efficiency analysis method and analysis system applied to photovoltaic transformer area

Abstract

The invention relates to an AC / DC bidirectional energy efficiency analysis method and analysis system applied to a photovoltaic transformer area. The AC / DC bidirectional energy efficiency analysis method comprises the following steps: synchronously acquiring parameter information in an AC circuit and parameter information in a DC circuit; calculating the active power P1 in the AC circuit and the effective power P2 in the DC circuit according to the parameter information; calculating an electric energy input / output value E1 of the alternating current circuit in the period; and calculating an electric energy input / output value E2 of the direct-current circuit in the period. According to the invention, the bidirectional flow condition of alternating current and direct current electric energy is accurately and efficiently metered, and the metering and analysis result provides powerful support for efficient utilization and lean management of electric energy. By calculating the electric energy ratio, the efficiency and the performance of the system can be directly reflected, the economical efficiency and the reliability of the alternating current and direct current hybrid power distribution network planning scheme can be accurately evaluated, a basis is provided for optimizing system design and operation, and then safe operation of the alternating current and direct current hybrid power distribution network is better guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy metering, and in particular to an AC / DC bidirectional energy efficiency analysis method and analysis system applied to photovoltaic stations. Background Art

[0002] With the rapid development of power electronics technology, AC / DC hybrid systems are increasingly being used in the energy field. In AC / DC hybrid power systems, accurate measurement of the conversion and flow of AC / DC power, as well as accurate calculation of power ratios, are essential for achieving efficient utilization and lean management of photovoltaic power. However, the existing power data collection methods for AC / DC hybrid systems (such as charging piles, energy storage equipment and other operating equipment or systems) mainly measure a single type of power, that is, separate collection of AC and DC, and cannot be synchronized at the same time node. In AC / DC hybrid systems, due to the influence of differences in power supply methods, transmission losses, power fluctuations and other aspects, traditional collection methods will lead to inaccurate AC / DC power ratios, which in turn makes it impossible to accurately reflect, evaluate and analyze the energy efficiency characteristics of AC / DC hybrid systems. Summary of the invention

[0003] Based on this, it is necessary to provide an AC / DC bidirectional energy efficiency analysis method and analysis system for photovoltaic stations to address the problem that the existing AC / DC hybrid system cannot accurately analyze the energy efficiency characteristics of the AC / DC hybrid system.

[0004] An AC / DC bidirectional energy efficiency analysis method applied to a photovoltaic station area is used to measure the bidirectional flow of electric energy in an AC / DC hybrid system and perform energy efficiency analysis on the AC / DC hybrid system according to the bidirectional flow of electric energy. The AC / DC bidirectional energy efficiency analysis method comprises the following steps:

[0005] Synchronously collect parameter information in AC circuit and parameter information in DC circuit;

[0006] According to the parameter information, the active power P1 in the AC circuit and the effective power P2 in the DC circuit are calculated; the electric energy input / output value E1 of the AC circuit in a cycle is calculated, and the calculation formula is:

[0007] E1=P1*T

[0008] Calculate the electric energy input / output value E2 of the DC circuit within a cycle, and the calculation formula is:

[0009] E2=P2*T

[0010] In the formula, T is the cycle length;

[0011] Calculate the electric energy ratio η of the AC circuit and the DC circuit in the same cycle. The calculation formula is:

[0012] η=E1 / E2 or η=E2 / E1

[0013] Determine whether the electric energy ratio η is less than a set threshold; if the electric energy ratio η is less than the set threshold, it is considered that there is an energy waste point in the AC / DC hybrid system; if the electric energy ratio η is greater than or equal to the set threshold, it is considered that there is no energy waste point in the AC / DC hybrid system.

[0014] As a preferred example, the parameter information includes current, voltage and phase difference.

[0015] As a preferred example, the calculation formula of the active power P1 is:

[0016] P1=U1*I1*cosφ1

[0017] In the formula, U1 is the effective value of the voltage of the AC circuit, I1 is the effective value of the current of the AC circuit, and φ1 is the phase difference between U1 and I1;

[0018] The calculation formula of the effective power P2 is:

[0019] P2=U2*I2

[0020] Where U2 is the effective value of the voltage of the DC circuit, and I2 is the effective value of the current of the DC circuit.

[0021] As a preferred example, in an AC / DC hybrid system, if the DC circuit is the output end and the AC circuit is the input end, the energy efficiency ratio formula is used: η=E1 / E2; if the AC circuit is the output end and the DC circuit is the input end, the energy efficiency ratio formula is used: η=E2 / E1.

[0022] As a preferred example, the collected parameter information is preprocessed before calculation to remove noise and interference signals.

[0023] As a preferred example, if it is determined that there is energy waste in the AC / DC hybrid system, the operation and maintenance personnel will conduct an investigation.

[0024] An AC / DC bidirectional energy efficiency analysis system applied to a photovoltaic area uses the AC / DC bidirectional energy efficiency analysis method applied to a photovoltaic area as described above; the AC / DC bidirectional energy efficiency measurement system includes:

[0025] An acquisition module, which is used to synchronously acquire parameter information in the AC circuit and the DC circuit;

[0026] A data processing module, which is used to calculate the electric energy ratio η between the AC circuit and the DC circuit according to the parameter information;

[0027] The analysis module is used to determine whether there is an energy waste point in the AC / DC hybrid system according to the electric energy ratio η.

[0028] As a preferred example, the acquisition module includes:

[0029] A voltage sensor is used to synchronously collect the voltage in the AC circuit and the DC circuit;

[0030] A current sensor for synchronously collecting currents in an AC circuit and a DC circuit;

[0031] The AD converter is used to convert the signals collected by the voltage sensor and the current sensor into digital signals and output them to the data processing module.

[0032] As a preferred example, the acquisition module is calibrated at regular intervals; the calibration method comprises the following steps:

[0033] Connect the standard power supply to the input terminal of the acquisition module, and adjust the output parameters of the standard power supply to be equal to the preset calibration value;

[0034] Record the parameters actually measured by the acquisition module and compare them with the standard values; if there are differences, adjust the acquisition parameters of the acquisition module until the parameters measured by the acquisition module are equal to the standard values, and the calibration is completed.

[0035] As a preferred example, the acquisition module is set to have anti-interference in an AC / DC hybrid system, which is used to reduce the impact of environmental changes on the performance of the acquisition module.

[0036] The beneficial effects of the present invention are:

[0037] 1. The AC / DC bidirectional energy efficiency analysis method for photovoltaic stations provided by the present invention has the advantages of high accuracy, strong reliability, good real-time performance, etc. Previous power monitoring methods mostly measure a single type of power (AC or DC), and lack consideration and necessary measures in the accuracy calibration of monitoring equipment (sensors, etc.) and anti-interference technical support of the monitoring process, resulting in difficulty in ensuring the accuracy and real-time performance of the measurement results.

[0038] 2. The present invention provides strong support for the efficient use and lean management of electric energy by accurately and efficiently measuring the bidirectional flow of AC and DC electric energy, and measuring and analyzing the results. By calculating the electric energy ratio, the efficiency and performance of the system can be directly reflected, which is conducive to accurately evaluating the economy and reliability of the AC / DC hybrid distribution network planning scheme, providing a basis for optimizing system design and operation, and thus better ensuring the safe operation of the AC / DC hybrid distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The figure is a flow chart of the AC / DC bidirectional energy efficiency analysis method applied to photovoltaic areas. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "or / and" used herein includes any and all combinations of one or more of the related listed items.

[0042] Please refer to Figure 1 This embodiment provides an AC / DC bidirectional energy efficiency analysis method applied to a photovoltaic area, which is used to measure the bidirectional flow of electric energy in an AC / DC hybrid system and perform energy efficiency analysis on the AC / DC hybrid system according to the bidirectional flow of electric energy. Specifically, the AC / DC bidirectional energy efficiency analysis method includes the following steps:

[0043] S1. By configuring high-precision voltage sensors and current sensors, the AC circuit and DC circuit are monitored respectively, and the current, voltage, phase difference and other parameter information in the AC and DC circuits are collected synchronously. Accordingly, in order to ensure the accuracy of the subsequent analysis of the parameter information, the existing appropriate filtering algorithm is selected to remove noise and interference signals from the collected parameter information, and to enhance the useful signal and improve the signal-to-noise ratio. In addition, the amplitude of the useful signal can be enhanced and the signal-to-noise ratio can be improved through signal amplification and shaping, further reducing the impact of noise.

[0044] S2. Calculate the active power P1 in the AC circuit and the effective power P2 in the DC circuit according to the measured parameter information. The calculation formula of the active power P1 is:

[0045] P1=U1*I1*cosφ1

[0046] Where U1 is the effective value of the voltage of the AC circuit, I1 is the effective value of the current of the AC circuit, and φ1 is the phase difference between U1 and I1.

[0047] The calculation formula of effective power P2 is:

[0048] P2=U2*I2

[0049] Where U2 is the effective value of the voltage of the DC circuit, and I2 is the effective value of the current of the DC circuit.

[0050] S3. Calculate the power input / output of the AC circuit and the DC circuit. For the AC circuit, use the active power P1 to calculate the power input / output value within the cycle:

[0051] E1=P1*T

[0052] For DC circuits, the effective power P2 is used to calculate the energy input / output value within a cycle:

[0053] E2=P2*T

[0054] In the above formula, T is the cycle length.

[0055] S4. Calculate the electric energy ratio η of the AC circuit and the DC circuit in the AC / DC hybrid system in the same cycle. The calculation formula is:

[0056] η=E1 / E2 or η=E2 / E1

[0057] Among them, at this time, if the DC circuit is the output end and the AC circuit is the input end, the energy efficiency ratio formula is used: η = E1 / E2. If the AC circuit is the output end and the DC circuit is the input end, the energy efficiency ratio formula is used: η = E2 / E1.

[0058] S5. Perform analysis based on the electric energy ratio η obtained in the AC / DC hybrid system.

[0059] The energy ratio formula uses the input / output expression. Among them, the output indicates how much energy it provides, and the input indicates how much energy it actually uses. Since there will always be some other natural losses such as heat in the equipment or system, the energy ratio η will always be less than 1. The closer the energy ratio η is to 1, the higher the energy utilization efficiency of the equipment or system. In this embodiment, the analysis of the energy ratio needs to determine whether the energy ratio η is less than the set threshold (the set threshold <1, the set threshold is a value determined according to the actual situation and historical data). If the energy ratio η is less than the set threshold, it means that the AC / DC hybrid system is affected by a variety of negative factors, and it is believed that there are energy waste points in the AC / DC hybrid system. At this time, an internal alarm is required to notify the operation and maintenance personnel to investigate. If the energy ratio η is greater than or equal to the set threshold (the set threshold ≤ energy ratio η <1), it means that the AC / DC hybrid system is operating normally and efficiently, and it is believed that there are no energy waste points in the AC / DC hybrid system, and the monitoring of the AC / DC hybrid system can be maintained.

[0060] In another embodiment, an AC / DC bidirectional energy efficiency analysis system applied to a photovoltaic area is also proposed, which uses the AC / DC bidirectional energy efficiency analysis method applied to a photovoltaic area as described above. The AC / DC bidirectional energy efficiency analysis system includes an acquisition module, a data processing module and an analysis module. Among them, the acquisition module is used to synchronously acquire parameter information in the AC circuit and the DC circuit. Usually, the acquisition module includes a voltage sensor, a current sensor and an AD converter. Commercially available voltage sensors and current sensors can be used to collect analog signals such as current, voltage, phase difference, etc. in the corresponding circuit. The collected analog signal is input into the analog input port of the AD converter, and based on the sampling rate, resolution, reference voltage and other parameters of the AD converter configured in advance, the AD converter is started to perform data conversion, and finally the digital signal output by the AD converter is read through the data processing module and the data is analyzed to obtain parameter information such as circuit and current. In addition, in order to ensure the accuracy of the data collected by the acquisition module, the acquisition module can be calibrated at regular intervals. The calibration method includes the following steps:

[0061] Connect the standard power supply to the input end of the acquisition module to ensure that the connection is stable and reliable, and adjust the output parameters of the standard power supply to be equal to the preset calibration value. At the same time, observe the current waveform of the standard power supply through the oscilloscope of the measuring equipment to ensure the accuracy and stability of the waveform;

[0062] Record the parameters actually measured by the acquisition module and compare them with the standard values; if there are differences, adjust the acquisition parameters such as gain and compensation of the acquisition module until the parameters measured by the acquisition module are equal to the standard values, and the calibration is completed.

[0063] Furthermore, anti-interference settings can be made for the environment in which the acquisition module is installed in the AC / DC hybrid system. For example, a suitable working environment can be created, such as controlling factors such as temperature, humidity, pressure, and dust prevention to reduce the impact of environmental changes on the performance of the acquisition module.

[0064] The data processing module is used to calculate the power ratio η between the AC circuit and the DC circuit based on the parameter information. The analysis module can analyze and evaluate the power ratio η to determine whether there are other negative factors such as energy waste points in the AC / DC hybrid system.

[0065] The present invention has a wide range of applications. In a certain AC / DC hybrid microgrid system (such as an AC / DC distribution network containing a PET (power electronic transformer)), the management of electric energy needs to take into account the complementarity between different energy sources. There are differences between AC energy and DC energy in terms of power supply mode, transmission loss, etc. Therefore, in energy management, it is necessary to reasonably select the energy conversion and transmission mode to maximize the advantages of various energy sources. In the specific energy efficiency analysis process, the method of the present invention can be used to monitor and measure electric energy and electric energy ratio. First, high-precision current sensors and voltage sensors are installed to monitor the AC and DC lines respectively. The sensor transmits the collected parameters to the data processing module. The data processing module calculates the power value through a specific algorithm. Then, the energy transmission situation is determined according to the power value, and the electric energy ratio is calculated. In the actual operation process, the accuracy and reliability of the measurement results are ensured by calibrating and compensating the sensors, and adopting data filtering and anti-interference technology. Based on the energy efficiency analysis results, the energy utilization efficiency and power supply reliability of the AC / DC hybrid microgrid system can be improved by reasonably selecting the energy conversion and transmission mode, establishing a complementary relationship between energy sources, and real-time monitoring and analysis of the operating status of the system.

[0066] In another application aspect, the method of the present invention can also be applied in an electric vehicle charging system. When the electric vehicle is charging, the system measures the AC output and DC input electric energy. When the electric vehicle feeds back electric energy to the power grid, the system measures the DC output electric energy and the AC input electric energy. By calculating the AC and DC bidirectional electric energy ratio, the efficiency and performance of the charging system can be evaluated, providing a basis for optimizing the charging strategy.

[0067] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0068] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for analyzing AC and DC bidirectional energy efficiency applied to photovoltaic stations, characterized in that: It is used to measure the bidirectional flow of electric energy in an AC / DC hybrid system, and to perform energy efficiency analysis on the AC / DC hybrid system according to the bidirectional flow of electric energy; the AC / DC bidirectional energy efficiency analysis method comprises the following steps: Synchronously collect parameter information in AC circuit and parameter information in DC circuit; Calculate the active power P1 in the AC circuit and the effective power P2 in the DC circuit based on the parameter information; Calculate the electric energy input / output value E1 of the AC circuit during a cycle. The calculation formula is: E1=P1*T Calculate the electric energy input / output value E2 of the DC circuit within a cycle, and the calculation formula is: E2=P2*T In the formula, T is the cycle length; Calculate the electric energy ratio η of the AC circuit and the DC circuit in the same cycle. The calculation formula is: η=E1 / E2 or η=E2 / E1 Determine whether the electric energy ratio η is less than a set threshold; if the electric energy ratio η is less than the set threshold, it is considered that there is an energy waste point in the AC / DC hybrid system; if the electric energy ratio η is greater than or equal to the set threshold, it is considered that there is no energy waste point in the AC / DC hybrid system.

2. The AC / DC bidirectional energy efficiency analysis method applied to photovoltaic stations according to claim 1, characterized in that: The parameter information includes current, voltage and phase difference.

3. The AC / DC bidirectional energy efficiency analysis method applied to photovoltaic stations according to claim 1, characterized in that: The calculation formula of the active power P1 is: P1=U1*I1*cosφ1 In the formula, U1 is the effective value of the voltage of the AC circuit, I1 is the effective value of the current of the AC circuit, and φ1 is the phase difference between U1 and I1; The calculation formula of the effective power P2 is: P2=U2*I2 Where U2 is the effective value of the voltage of the DC circuit, and I2 is the effective value of the current of the DC circuit.

4. The AC / DC bidirectional energy efficiency analysis method applied to photovoltaic stations according to claim 1, characterized in that: In an AC / DC hybrid system, if the DC circuit is the output end and the AC circuit is the input end, the energy efficiency ratio formula is used: η=E1 / E2; if the AC circuit is the output end and the DC circuit is the input end, the energy efficiency ratio formula is used: η=E2 / E1.

5. The AC / DC bidirectional energy efficiency analysis method applied to photovoltaic stations according to claim 1, characterized in that: The collected parameter information is preprocessed before calculation to remove noise and interference signals.

6. The AC / DC bidirectional energy efficiency analysis method applied to photovoltaic stations according to claim 1, characterized in that: If it is determined that there are energy waste points in the AC / DC hybrid system, the operation and maintenance personnel will conduct an investigation.

7. An AC / DC bidirectional energy efficiency analysis system applied to photovoltaic stations, characterized in that: It uses the AC / DC bidirectional energy efficiency analysis method applied to a photovoltaic area as described in any one of claims 1 to 6; the AC / DC bidirectional energy efficiency measurement system comprises: An acquisition module, which is used to synchronously acquire parameter information in the AC circuit and the DC circuit; A data processing module, which is used to calculate the electric energy ratio η between the AC circuit and the DC circuit according to the parameter information; The analysis module is used to determine whether there is an energy waste point in the AC / DC hybrid system according to the electric energy ratio η.

8. The AC / DC bidirectional energy efficiency analysis system applied to photovoltaic stations according to claim 7, characterized in that: The acquisition module comprises: A voltage sensor is used to synchronously collect the voltage in the AC circuit and the DC circuit; A current sensor for synchronously collecting currents in an AC circuit and a DC circuit; The AD converter is used to convert the signals collected by the voltage sensor and the current sensor into digital signals and output them to the data processing module.

9. The AC / DC bidirectional energy efficiency analysis system applied to photovoltaic stations according to claim 7, characterized in that: The acquisition module is calibrated at regular intervals; the calibration method comprises the following steps: Connect the standard power supply to the input terminal of the acquisition module, and adjust the output parameters of the standard power supply to be equal to the preset calibration value; Record the parameters actually measured by the acquisition module and compare them with the standard values; if there are differences, adjust the acquisition parameters of the acquisition module until the parameters measured by the acquisition module are equal to the standard values, and the calibration is completed.

10. The AC / DC bidirectional energy efficiency analysis system applied to photovoltaic stations according to claim 7, characterized in that: The acquisition module is configured to resist interference in an AC / DC hybrid system, which is used to reduce the impact of environmental changes on the performance of the acquisition module.

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