High-frequency AC power measurement method and system with phase difference compensation

Abstract

The present invention proposes a high-frequency AC power measurement method and system with phase difference compensation. An inductance-free resistor is introduced into the measurement circuit, and by measuring the voltage and current of the inductance-free resistor and the device under test, the compensation for the measurement error of the phase difference between the voltage and current of the device under test is realized. The present invention combines the actual AC power formula of the inductance-free resistor and the device under test, and solves to obtain an AC power formula that is independent of the phase difference measurement error, so that the new measurement method can achieve the measurement of AC power under high-frequency conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of measurement and metrology of AC power and losses, and particularly to a high-frequency AC power measurement method and system based on phase difference compensation. Background Art

[0002] The AC power measurement method (hereinafter simply referred to as the AC method) is a widely used measurement method in the field of power and loss measurement. This method obtains the power of the device under test by sampling the AC voltage and current parameters of the device under test, and its measurement accuracy is related to the measurement accuracy of voltage, current, and phase difference. According to the error source formula of the AC method, the main error of the AC method comes from the measurement error of the phase difference. In particular, when measuring high-frequency AC power or the impedance angle of the device under test is very large, a very small measurement error of the phase difference can cause a large error. The measurement error of the phase difference is caused by the inconsistency of the two measurement channels of the AC voltage and current. In an actual measurement system or measurement instrument, the voltage and current sampling circuits, conditioning circuits, and signal processing circuits cannot be completely consistent, making the measurement of the phase difference inevitably have errors and cannot be avoided. As the measurement frequency increases, especially for high-frequency low-loss magnetic components, their impedance angles are very large, close to 90°, and the measurement error may reach several times or even dozens of times, restricting the application of the AC method in the field of high-frequency power measurement.

[0003] Currently, the power systems, common switch-mode power supplies, power systems, lighting systems, and new energy vehicle systems used in the national defense field, ship equipment, and aerospace equipment are all closely related to power converters, which involve the accurate measurement of AC power; the loss evaluation of components such as semiconductor devices, high-frequency magnetic components, high-frequency capacitors, and resistors is also closely related to the measurement of AC power. As the main measurement method for the power of electrical equipment and the loss of devices, the AC method is restricted in high-frequency applications due to the influence of its measurement error on the phase difference parameter. With the development of technology, the application of third-generation semiconductor devices is increasing, and the frequency of devices in power converters is continuously increasing. The evaluation of their efficiency, thermal design, and device loss is one of the key technologies of power converters. Therefore, the research on the AC power measurement method at high frequencies is of great significance for the above-mentioned electrical systems, power converters, and high-frequency components. Existing AC power measurement methods include the three-parameter method, binomial squaring method, time-division method, analog sampling method, numerical sampling method, etc. These AC power measurement methods are widely used in engineering measurement and metrology fields, and these methods do not deal with the influence of the measurement error of the phase difference in the AC method, so the measurement frequency is not high.

[0004] Among the numerous methods of power measurement, the AC power measurement method, as a simple and fast measurement method, obtains the loss or power of the DUT by collecting the voltage u(t) and current i(t) of the DUT and according to formula (1*), where T is the period of the voltage and current. Therefore, in the field of low-frequency power and loss measurement, the AC method has been widely used. However, due to the influence of the phase difference measurement error, the application of this method in the high-frequency field is limited. Its phase error formula is formula (2*), where U and I are the effective values of the voltage and current of the DUT, ΔU and ΔI are the measurement error values of the voltage and current respectively, is the phase difference between the voltage and the current, is the measurement error of the phase difference.

[0005]

[0006]

[0007] It can be seen from the error formula (2) of the AC method that the error sources of the AC method mainly consist of three parts: AC voltage, current and phase. High-precision voltage and current measurement equipment or voltage and current sampling circuits using high-precision components can achieve accurate measurement of voltage and current. The traceability of the phase difference has always been a difficult point in the industry's measurement of electrical parameters and is also the key factor for the AC method to be difficult to measure high-frequency power. It can be seen from the third part of formula (2*) that the larger the phase difference between the voltage and the current or the larger the measurement error of the phase difference, the larger the error of the AC method. When the phase difference is close to 90°, a very small phase difference error will result in a large error. In high-frequency applications, as the measurement frequency continues to increase, the phase difference error also continues to increase. Especially for high-frequency magnetic components and capacitors, their impedance angles reach seventy or eighty degrees, or even close to 90°. And there are inconsistencies between the two channels and their components during the acquisition and processing of voltage and current parameters, which will inevitably lead to different sampling time delays of voltage and current during the measurement process, that is, there is an inherent phase difference measurement error Generally, the higher the frequency the larger it is, resulting in the AC method being unable to accurately measure the power and loss at high frequencies. Even when measuring magnetic components close to 90°, even with a very high-precision power meter, the measurement result is negative. That is, if the phase difference or phase difference error in the traditional AC method is not processed, the AC method cannot be used at all in the field of high-frequency power measurement. Summary of the Invention

[0008] In view of the defects and deficiencies existing in the prior art, the present invention proposes a high-frequency AC power measurement method and system with phase difference compensation. By analyzing the error sources of the AC method, it is found that the most important factor affecting the power measurement accuracy under high-frequency conditions is the measurement error of the voltage and current phase difference, and the phase difference measurement error comes from the different delays of the two measurement channels of voltage and current. Therefore, the present invention introduces a non-inductive resistor into the measurement circuit, and by measuring the voltage and current of the non-inductive resistor and the device under test, the compensation of the measurement error of the phase difference between the voltage and current of the device under test is realized. The present invention combines the actual AC power formula of the non-inductive resistor and the device under test, and obtains an AC power formula independent of the phase difference measurement error, so that the new measurement method can realize the measurement of AC power under high-frequency conditions. By deeply analyzing the error characteristics of the AC method, a non-inductive resistor is used to calibrate the phase difference or delay of the measurement channel, and the phase difference between the voltage and current of the device under test is compensated to realize the measurement of AC power or loss under high frequency.

[0009] Specifically, the following technical solutions are adopted:

[0010] A high-frequency AC power measurement method with phase difference compensation, characterized in that:

[0011] The device under test Z and the non-inductive resistor R are connected in parallel, and the currents flowing through the device under test and the non-inductive resistor and the voltages at both ends are measured respectively; the voltage is measured directly by leading out measurement terminals from both ends of the non-inductive resistor and the device under test.

[0012] The AC power formula is adopted as: for calculation;

[0013] wherein, is the phase angle, By measuring the voltage U R 、current I R and the phase difference are calculated and obtained; an impedance measuring instrument is used to obtain the resistance values of the non-inductive resistor at different frequencies, and then according to the obtained resistance value of the non-inductive resistor and the current I R flowing through the non-inductive resistor, the power of the non-inductive resistor under the working condition is obtained. Combining the obtained voltage U R 、current I R 、phase difference and k1, the AC power formula is calibrated to obtain the parameter k2;

[0014] Since for the same measurement circuit, the measurement error of the phase difference between the non-inductive resistor and the magnetic component under test under sinusoidal excitation is the same, according to the obtained k1 and k2 coefficients at different frequencies, and the formula (1), the AC power of the device under test in the frequency range is calculated.

[0015] Further, the measurement process includes the following steps:

[0016] Step S1: Use an impedance analyzer to obtain the resistance values of the non-inductive resistor at different frequencies;

[0017] Step S2: Measure the effective values of the voltage and current of the non-inductive resistor and the phase difference, and calculate the parameter k1 in formula (1);

[0018] Step S3: According to the resistance value of the non-inductive resistor obtained in Step S1 and the current flowing through the non-inductive resistor, obtain the power of the non-inductive resistor under the working condition, and combine the parameter k1 calculated by formula (1) and Step S2 to calculate the value of parameter k2;

[0019] Step S4: Calculate the AC power of the DUT Z according to the obtained parameters k1 and k2 and formula (1).

[0020] And, a high-frequency AC power measurement system with phase difference compensation, based on the above high-frequency AC power measurement method with phase difference compensation:

[0021] It includes: a high-frequency excitation source, a non-inductive resistor R, a switching switch S, a voltage sensor, and a current sensor. The measurement of the voltage of the non-inductive resistor and the DUT is to lead out a test wire from the terminals of the non-inductive resistor R and the DUT and connect it to the voltage test terminal through the switching switch S; the high-frequency excitation source is composed of a signal generator and a power amplifier.

[0022] Compared with the prior art, the present invention and its preferred solutions deeply analyze the error sources of the AC measurement method, study the influence of the key parameter phase difference error on the measurement result, compensate and calibrate the measurement error of the phase difference in the measurement system through a non-inductive resistor, and combine the AC power formula of the non-inductive resistor and the DUT to derive an AC power formula without phase difference measurement error, which can realize the measurement of AC power or loss at high frequencies. The measurement circuit is relatively simple, and the measurement is convenient, fast, and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The following further details the present invention in conjunction with the drawings and specific embodiments:

[0024] Figure 1 It is a schematic diagram of the basic principle of an embodiment of the present invention;

[0025] Figure 2 It is a reference schematic diagram of the experimental circuit of an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] To make the features and advantages of this patent more obvious and understandable, the following specific embodiments are given in conjunction with the drawings and described in detail as follows:

[0027] First, in order to minimize the error of the AC method under high-frequency measurements, an embodiment of the present invention proposes a high-frequency AC power measurement method for compensating the phase difference by introducing a parallel-connected non-inductive resistor into the measurement circuit to calibrate the phase difference of the voltage and current measurement channels, so as to eliminate the measurement error of the phase difference on the AC method, and obtain the high-frequency power or loss of the device under test at high frequencies.

[0028] The AC power measurement formulas for the non-inductive resistor and the device under test are shown in Equations (2) and (3).

[0029]

[0030]

[0031] Where P Rt and P Ct are the AC measurement powers of the non-inductive resistor and the device under test, U R and U C are the effective values of the voltages across the non-inductive resistor and the device under test, I R and I C are the effective values of the currents flowing through the non-inductive resistor and the device under test, is the phase difference between the voltage and current of the device under test, is the measurement error of the phase difference. Let k1 = P Rt / (U R I R ). Combining Equations (3) and (4), a quadratic equation for the true value of the AC power or loss P c is obtained as follows:

[0032]

[0033] Solving it gives the formula for the AC power or loss of the device under test as:

[0034]

[0035] After analysis, it can be seen that the two ± root values of the equation respectively correspond to and two cases. In the actual measurement process of the loss value of the device under test, in addition to the error caused by inconsistent measurement channels in the measurement error of the phase difference, there is still a certain amount of inductance value in the non-inductive resistor, and the calculation error in the phase difference processing process cannot be ignored. Therefore, the present invention further introduces an influence factor k2 to obtain the formula for the AC power or loss of the device under test as Equation (7) to eliminate the influence of other phase difference influencing factors on the AC power measurement.

[0036]

[0037] To obtain the values of k1 and k2 in Equation (7), first, the resistance values of the non-inductive resistor at different frequencies are obtained through a precise impedance measuring instrument. The voltage, current, and impedance angle of the non-inductive resistor are obtained through a power measuring instrument. The value of k1 is obtained according to the formula of k1. Further, considering that the non-inductive resistor itself has a certain inductance value and other influencing factors, the power of the non-inductive resistor under the working condition is obtained by using the resistance value of the non-inductive resistor obtained by the impedance analyzer and the measured current, and the formula (7) is calibrated to obtain the k2 coefficient.

[0038] For the same measurement circuit, the measurement error of the phase difference between the non-inductive resistor and the magnetic component under test under sine wave excitation is the same. Therefore, the coefficients k1 and k2 obtained by using the non-inductive resistor are used to further measure and obtain the high-frequency AC power or loss of the component under test under the same working condition.

[0039] Based on the above design, the following further introduces the solution of the present invention in combination with specific examples:

[0040] The method of the present invention is based on the AC power measurement method. A non-inductive resistor branch is connected in parallel in the measurement circuit, and the phase difference measurement error in the AC power measurement method is compensated and calibrated through the non-inductive resistor. The content of the present invention is introduced in detail with reference to the accompanying drawings:

[0041] Figure 1 This is an application case of the present invention, mainly for measuring the power or loss of the component under test Z. The hardware platform mainly includes a high-frequency excitation source, voltage and current sensors, a voltage, current effective value, phase angle measurement and processing module, and a non-inductive resistor R. Among them, the current sensors are respectively used to measure the currents flowing through the component under test and the non-inductive resistor, and the voltage sensor is used to measure the voltages across the component under test Z and the non-inductive resistor R. The voltage is measured directly by leading out measurement terminals from both ends of the non-inductive resistor and the component under test to avoid the influence of the inductance of the line on the measurement result. Among them, the voltage and current sensors can be the voltage and current probes of an oscilloscope or a specially designed voltage and current measurement circuit. The voltage, current, and phase angle processing and calculation module is used to obtain the voltage, current effective values of the component under test Z and the non-inductive resistor R, and the phase difference between the two. The power calculation module obtains the AC power or loss of the component under test according to formula (7).

[0042]

[0043] Among them, k1 = P Rt / (U R I R ), by measuring the voltage U R 、I R of the non-inductive resistor and the phase difference between the voltage and the current k1 can be obtained. Further, considering that the sense resistor itself has a certain inductance value and other influencing factors, the power of the sense resistor under the working condition is obtained by using the resistance value of the sense resistor obtained by the impedance analyzer and the measured current, and the formula (7) is calibrated to obtain the k2 coefficient.

[0044] For the same measurement circuit, the measurement error of the phase difference between the sense resistor and the magnetic component under test under sine wave excitation is the same. According to the above process, the k1 and k2 coefficients of the measurement system at different frequencies can be obtained, and then the AC power or loss of different DUTs in this frequency range can be obtained according to formula (7).

[0045] In a test experiment, first, a test board is designed, which includes the input terminals of the excitation source, the terminals of the DUT, the sense resistor R, the switch S, the voltage measurement terminals, and the current measurement terminals. The measurement of the voltage of the sense resistor and the DUT is to lead out the test wires from the pins of the sense resistor R and the DUT terminals and connect them to the voltage measurement terminals through the switch S. The test circuits for the sense resistor and the DUT on the test board should be basically the same. The specific test system is as Figure 2 shown. The high-frequency excitation source is composed of a signal generator and a power amplifier and is connected to the input end of the test board. The sampling of voltage and current is realized by the voltage and current probes of the oscilloscope / power meter. The voltage probe is connected to the voltage measurement terminal of the test board, and the current probe is connected to the current measurement terminal of the test board.

[0046] The process of realizing high-frequency power measurement is as follows:

[0047] (1) Use a precision impedance analyzer to obtain the resistance values of the sense resistor at different frequencies.

[0048] (2) Connect according to the Figure 2 test system, obtain the effective values of voltage and current and the phase difference through the oscilloscope / power meter, and obtain the parameter k1 according to the formula of the parameter k1 in formula (1).

[0049] (3) According to the resistance value of the sense resistor in the first step and the current flowing through the sense resistor, the power of the sense resistor under the working condition can be obtained. Combining formula (1) and the parameter k1 in the second step, the parameter k2 can be obtained.

[0050] (4) According to the obtained parameters k1 and k2 and formula (1), the measurement of the AC power or loss of the DUT Z can be realized.

[0051] According to the above design, it can be summarized that the general scheme for compensating the phase difference error of the measurement circuit by measuring the electrical parameters of the sense resistor includes:

[0052] Combine the AC power formula of the non-inductive resistor and the device under test to solve a new AC power formula that is independent of the phase difference error. It includes the following detailed steps:

[0053] (1) According to the AC power formula:

[0054] in, Parameter k1 reflects the influence of phase difference error, and parameter k2 reflects the existence of certain inductance value and other influencing factors of the non-inductive resistor itself.

[0055] (2) Use a measuring instrument or measuring circuit to obtain the voltage U of the non-inductive resistor R 、Current I R And the phase difference The k1 value is obtained through the k1 formula.

[0056] (3) Use a precise impedance meter to obtain the resistance value of the non-inductive resistor at different frequencies. Based on the obtained non-inductive resistor value and the current I flowing through the non-inductive resistor R Get the non-inductive resistance power under working conditions, combined with the obtained voltage U R 、Current I R , Phase difference and k1, calibrate the AC power formula to obtain parameter k2.

[0057] (4) Based on the obtained parameters k1 and k2 and formula (1), the AC power or loss of the device under test Z can be measured.

[0058] To achieve the measurement of high-frequency AC power, the measurement platform generally includes a high-frequency excitation source, a test board, an AC voltage and current sampling circuit module, an AC voltage, current and phase difference processing circuit module, and a power calculation module.

[0059] Preferably, the high-frequency excitation source can be generated by a signal generator and a power amplifier to generate the excitation source required for the test, or the excitation source required by the actual device under test can be used.

[0060] Preferably, the test board includes an excitation source input terminal, a non-inductive resistor R, a device under test input terminal, a switch S, a voltage measurement terminal, and a current measurement terminal. The measurement circuit in the test board is consistent in design, and the voltage measurement of the non-inductive resistor and the device under test is directly derived from the non-inductive resistor and the device under test pin terminal to prevent the high-frequency parameters of the line from affecting the measurement results. When one voltage measurement channel is used in the test circuit, the switch S is used to switch the voltage measurement of the non-inductive resistor and the device under test. When two voltage measurement channels are used, the switch S is not required.

[0061] Preferably, the three parts of the AC voltage and current sampling circuit module, the AC voltage, current and phase difference processing circuit module and the power calculation module can use voltage and current sensors, conditioning circuits and data processing circuits to achieve high-frequency AC power measurement, or use an oscilloscope or power analyzer to obtain the three electrical parameters of the non-inductive resistor and the device under test, namely voltage, current and phase difference, and then use a new formula to obtain the AC power of the device under test.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

[0063] This patent is not limited to the above-mentioned optimal implementation mode. Anyone can derive other forms of high-frequency AC power measurement methods and systems with phase difference compensation under the inspiration of this patent. All equal changes and modifications made according to the scope of the patent application of the present invention should be covered by this patent.

Claims

1. A high-frequency AC power measurement method with phase difference compensation, characterized in that: The device under test Z and the non-inductive resistor R are connected in parallel, and the currents flowing through the device under test and the non-inductive resistor and the voltage across them are measured respectively; the voltage is measured directly by leading out measurement terminals from both ends of the non-inductive resistor and the device under test. The AC power formula used is: for calculation; Among them, is the phase angle, By measuring the voltage U of the non-inductive resistor R , current I R and the phase difference it is calculated; the resistance value of the non-inductive resistor at different frequencies is obtained by using an impedance measuring instrument, and then according to the obtained resistance value of the non-inductive resistor and the current I flowing through the non-inductive resistor R the power of the non-inductive resistor under the working condition is obtained. Combining the already obtained voltage U R , current I R , phase difference and k1, the AC power formula is calibrated to obtain the parameter k2; Since for the same measurement circuit, the measurement errors of the phase differences of the non-inductive resistor and the magnetic component under test under sinusoidal excitation are the same, the AC power of the device under test in the frequency range is calculated according to the obtained k1 and k2 coefficients at different frequencies and formula (1).

2. The high-frequency AC power measurement method for phase difference compensation according to claim 1, characterized in that: The measurement process includes the following steps: Step S1: Use an impedance analyzer to obtain the resistance values of the non-inductive resistor at different frequencies. Step S2: Measure the effective values and phase differences of the voltage and current of the non-inductive resistor, and calculate the parameter k1 in formula (1). Step S3: According to the resistance value of the non-inductive resistor obtained in Step S1 and the current flowing through the non-inductive resistor, obtain the power of the non-inductive resistor under the working condition, and combine formula (1) and the parameter k1 calculated in Step S2 to calculate the value of the parameter k2. Step S4: Calculate the AC power of the device under test Z according to the obtained parameters k1 and k2 and formula (1).

3. A high-frequency AC power measurement system with phase difference compensation, characterized in that, Based on the high-frequency AC power measurement method with phase difference compensation as described in claim 1: It includes: a high-frequency excitation source, a non-inductive resistor R, a switching switch S, a voltage sensor, and a current sensor. The measurement of the voltage of the non-inductive resistor and the device under test is to lead out a test line from the terminal pins of the non-inductive resistor R and the device under test and connect it to the voltage test terminal through the switching switch S; the high-frequency excitation source is composed of a signal generator and a power amplifier.

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