Single power analyzer

Abstract

The invention discloses a single power analyzer which comprises a power management circuit, the power management circuit is connected with an alternating current sampling module, a key / display module and a signal conditioning and processor system, the alternating current sampling module is connected with the signal conditioning and processor system, and the key / display module is connected with the signal conditioning and processor system. According to the technical scheme, power consumption is extremely low, operation is easy and convenient, meanwhile, a single lithium battery is adopted for power supply, and dependence on a fixed power source is avoided; measurement of AC voltage, AC current, harmonic voltage, harmonic current, current total harmonic coefficient, active power and power factor is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of intelligent electric energy metering, and in particular relates to a single-item power analyzer. Background Art

[0002] In the field of smart energy metering, single-item power analyzers are key tools for monitoring and optimizing electricity consumption, and are widely used in industrial equipment monitoring, household energy management, and power measurement. However, traditional power analyzers are often limited by their large size, high power consumption, and complex wiring, and are not suitable for scenarios that require high portability, flexibility, and low power consumption. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a single-item power analyzer with extremely low power consumption, simple operation, and power supply by a single lithium battery, thus avoiding dependence on a fixed power supply; and to realize the measurement of AC voltage, AC current, harmonic voltage and harmonic current, total harmonic coefficient of current, active power, and power factor.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] A single-item power analyzer includes a power management circuit, which is connected to an AC sampling module, a key / display module, a signal conditioning and processor system, the AC sampling module is connected to the signal conditioning and processor system, and the key / display module is connected to the signal conditioning and processor system.

[0006] Preferably, the power management circuit consists of a battery box, a switch, and a power indicator light, and is powered by a single lithium battery.

[0007] Preferably, the AC sampling module is composed of a voltage transformer, an AC current transformer, a DC bias circuit, a differential circuit, and a follower circuit, and the AC current transformer is an open transformer.

[0008] Preferably, the button / display module is composed of a 0.96-inch OLED screen and buttons, and the measurement mode is switched by pressing the buttons to display the measurement data.

[0009] Preferably, the signal conditioning and processor system is controlled by the MSP30F5529LP single chip microcomputer as the core.

[0010] As a preferred embodiment, the MSP30F5529LP single-chip microcomputer realizes the measurement of AC voltage, AC current, harmonic voltage and harmonic current, total harmonic coefficient of current, active power and power factor according to the collected AC current and voltage.

[0011] As a preferred method, the MSP30F5529LP microcontroller uses a timer to trigger the ADC to collect AC current and voltage in real time according to the set sampling frequency; the ADC collects a half-cycle voltage and current value and transfers it through the DMA. During the calculation, the ADC sampling and the corresponding timer are turned off, and both are turned on again after the calculation ends a cycle; the root mean square value algorithm and the FFT algorithm are used to calculate the effective value of the voltage and current, the active power and the power factor, and then the FFT algorithm is used to calculate the THD value and the 10th harmonic current value.

[0012] The present invention can directly measure the electrical equipment on the socket without additional wiring, and can accurately measure the key parameters of the load such as voltage, current, power factor and active power. It is powered by a single lithium battery, which is simple and avoids dependence on fixed power sources. This design significantly improves the portability and flexibility of the instrument, while greatly reducing power consumption and extending battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0014] Figure 1 This is a schematic diagram of the structure of a single-phase power analyzer according to an embodiment of the present invention;

[0015] Figure 2 Schematic diagram of power supply for lithium battery;

[0016] Figure 3 is a schematic diagram of a DC bias circuit;

[0017] Figure 4 is a schematic diagram of an AC voltage detection circuit;

[0018] Figure 5 is a schematic diagram of an AC current detection circuit;

[0019] Figure 6 This is the working flow chart of a single power analyzer. DETAILED DESCRIPTION

[0020] 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.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Embodiment 1:

[0023] like Figure 1 As shown, the present invention provides a single-phase power analyzer, including: a power management circuit, the power management circuit is connected to an AC sampling module, a button / display module, a signal conditioning and processor system, the AC sampling module is connected to the signal conditioning and processor system, and the button / display module is connected to the signal conditioning and processor system.

[0024] The power management circuit consists of a battery box and a switch. It is powered by a single lithium battery to realize the power supply of the entire system. It has a simple structure and low system power consumption. The AC sampling module is composed of an AC voltage transformer, an AC current transformer, a DC bias circuit, a differential circuit, and a follower circuit. The AC current transformer uses an open transformer, which can improve its sensitivity by using the original multi-turn winding method, and can set the turn ratio in the system to achieve accurate collection of a wide range of currents. The button / display module consists of a 0.96-inch OLED screen and buttons. The measurement mode is switched by pressing the buttons to realize the function of displaying the measurement data in the system. The signal conditioning and processor system is controlled by the MSP30F5529LP microcontroller as the control core. The MSP30F5529LP microcontroller has lower power consumption. After the microcontroller collects the voltage output by the AC sampling module, it calculates and realizes the measurement of AC voltage, AC current, harmonic voltage and harmonic current, total harmonic coefficient of current, active power, and power factor by the system.

[0025] like Figure 2 As shown, a single 3.7V lithium battery is used to power the entire system, and the battery voltage is directly output to power the OLED screen, microcontroller, and AC sampling module.

[0026] like Figure 3 As shown, the LM4040 reference source is powered by a lithium battery, outputting a 2.04V DC voltage, raising the AC signal to above zero level for collection by the microcontroller.

[0027] like Figure 4 As shown, the AC voltage generates current through R1, and the main winding of the voltage transformer receives the current input signal; a magnetic field is generated through the main winding and transmitted to the secondary winding; an induced current is generated in the secondary winding, and its magnitude is proportional to the mutual inductance ratio of the current on the main winding side; the secondary winding outputs a current signal, and an AC voltage is generated on R2, which is raised by the DC bias circuit and sent to the microcontroller through the differential circuit and the follower circuit.

[0028] like Figure 5As shown, the AC voltage generates current through the electrical equipment, and the secondary winding of the current transformer generates an induced current through the AC current on the main winding, and its magnitude is proportional to the mutual inductance ratio with the current on the main winding side; and outputs a current signal to generate an AC voltage on R8, which is raised by the DC bias circuit and sent to the microcontroller through the differential circuit and the follower circuit.

[0029] After the single chip microcomputer collects the AC voltage signal, it performs FFT calculation on the voltage signal to obtain the effective value U of the 1st to 10th harmonic components of the voltage n , where U n Indicates the effective value of the nth harmonic voltage.

[0030] After the single chip microcomputer collects the AC current signal, it performs FFT calculation on the current signal to obtain the effective value of the 1st to 10th harmonic components of the current I n , where I n Indicates the effective value of the nth harmonic current.

[0031] Get the effective value of the current 1-10 harmonic components I n After that, the total harmonic coefficient of current can be obtained:

[0032]

[0033] After the single chip microcomputer collects the AC voltage and current signals, it performs FFT calculation on the voltage and current signals to obtain the 1st to 10th harmonic component values ​​and phase differences of the voltage and current, and calculates the active power of each harmonic:

[0034]

[0035] Among them, P n represents the nth harmonic active power, Indicates the phase angle difference of the nth harmonic voltage and current.

[0036] The total active power P is obtained as follows:

[0037]

[0038] After the single chip microcomputer collects the AC voltage and current signals, it obtains the voltage effective value u and the current effective value i. From this, the apparent power P is obtained. S :

[0039] P S =u×i

[0040] The power factor PF is obtained as follows:

[0041]

[0042] like Figure 6As shown, the working process of the single-phase power analyzer in the embodiment of the present invention is as follows:

[0043] 1. Plug the electrical equipment into the socket. After the power analyzer is powered on, the voltage and current amplitude, frequency and phase of the electrical equipment are sent to the microcontroller through the AC sampling module.

[0044] 2. The single-chip computer uses the timer to trigger the ADC to collect AC current and voltage in real time and accurately according to the set sampling frequency; the ADC collects the voltage and current values ​​of one and a half cycles and transfers them through the DMA. The ADC sampling and the corresponding timer are turned off during the calculation, and they are turned on again after the calculation is completed for one cycle to reduce the power consumption of some parts of the system. Considering the performance of MSP430, the system functions are operated in time-sharing mode. The RMS value algorithm and FFT algorithm are first used to calculate the effective value of voltage and current, active power and power factor, and then the FFT algorithm is used to calculate the THD value and the 10th harmonic current value, and the two are executed back and forth.

[0045] 3. Press the button to select the number of transformer turns, switch the voltage and current correction coefficients, and switch the displayed parameters.

[0046] 4. When the voltage and current exceed the set input threshold, the microcontroller indicator light displays red, otherwise it displays green.

[0047] The single power analyzer of the present invention can measure the AC voltage, AC current, harmonic voltage and current, total harmonic coefficient of current, active power and power factor. The following is the test plan and test results.

[0048] Instruments and models used for testing

[0049] Power Analyzer: PA1000

[0050] Test plan and results

[0051] AC voltage relative error absolute value test

[0052] Fixed the input AC voltage, adjusted the load so that the load current changes from 0A to 4A, and measured the load voltage. The results are recorded in Table 1. Compared with the voltage measured by the power analyzer, the absolute value of the relative error of the AC voltage calculated by formula (7) is 0.47%.

[0053] Table 1

[0054]

[0055]

[0056] AC current relative error absolute value test

[0057] Fixed the input AC voltage, adjusted the load so that the load current changes from 0A to 4A, and measured the load current. The results are recorded in Table 2. Compared with the current measured by the power analyzer, the absolute value of the relative error of the AC current calculated by formula (8) is 0.62%.

[0058] Table 2

[0059]

[0060]

[0061] Power factor relative error absolute value test

[0062] The input AC voltage is fixed, the load current is 3A, the electronic load and DC power supply are connected, the energy consumption of the instrument is changed, and the load power factor is measured. The results are recorded in Table 3. Compared with the power factor measured by the power analyzer, the absolute value of the relative error of the power factor calculated by formula (9) is 0.44%.

[0063] Table 3

[0064]

[0065]

[0066] Active power relative error absolute value test

[0067] The input AC voltage is fixed, the load current is 3A, the electronic load and DC power supply are connected, the energy consumption of the instrument is changed, and the load active power is measured. The results are recorded in Table 4. Compared with the active power measured by the power analyzer, the absolute value of the relative error of the active power calculated by formula (10) is 0.65%.

[0068] Table 4

[0069]

[0070]

[0071] Harmonic current relative error absolute value test

[0072] Fixed input AC voltage, adjusted the load so that the load current changes from 0A to 4A, and measured the load harmonic current. Compared with the harmonic current measured by the power analyzer, the absolute value of the relative error of the current harmonics was 0.52%.

[0073] Current harmonic coefficient error absolute value test

[0074] Fixed input AC voltage, adjusted load so that load current changes from 0A to 4A, measured 10th harmonic current coefficient of load each time. Compared with the harmonic current coefficient measured by power analyzer, the absolute value of relative error of harmonic current coefficient is 0.57%.

[0075] Power consumption test when the system is working

[0076] The voltage and current output by the battery are measured and multiplied to obtain the system power consumption, which is 46mW.

[0077] Test results analysis

[0078] (1) The waveforms collected by the voltage and current transformers are not obviously distorted and are sent to the microcontroller for calculation.

[0079] (2) The voltage, current, power factor and other measurement values ​​calculated by the system are highly accurate.

[0080] (3) The screen measurement data display is intuitive, the button switching data type is convenient, and the human-computer interaction is good.

[0081] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A single-phase power analyzer, characterized in that: It includes a power management circuit, which is connected to an AC sampling module, a key / display module, a signal conditioning and processor system, the AC sampling module is connected to the signal conditioning and processor system, and the key / display module is connected to the signal conditioning and processor system.

2. The single-phase power analyzer according to claim 1, characterized in that: The power management circuit consists of a battery box, a switch, and a power indicator light, and is powered by a single lithium battery.

3. The single-phase power analyzer according to claim 2, characterized in that: The AC sampling module is composed of a voltage transformer, an AC current transformer, a DC bias circuit, a differential circuit, and a follower circuit. The AC current transformer adopts an open transformer.

4. The single-phase power analyzer according to claim 3, characterized in that: The button / display module consists of a 0.96-inch OLED screen and buttons. The measurement mode is switched by pressing the buttons to display the measurement data.

5. The single-phase power analyzer according to claim 4, characterized in that: The signal conditioning and processor system is controlled by the MSP30F5529LP microcontroller.

6. The single-phase power analyzer according to claim 5, characterized in that: The MSP30F5529LP single-chip microcomputer realizes the measurement of AC voltage, AC current, harmonic voltage and harmonic current, total harmonic coefficient of current, active power and power factor according to the collected AC current and voltage.

7. The single-phase power analyzer according to claim 6, characterized in that: The MSP30F5529LP microcontroller uses a timer to trigger the ADC to collect AC current and voltage in real time according to the set sampling frequency; The ADC collects the voltage and current values ​​for one and a half cycles and transfers them through DMA. The ADC sampling and corresponding timer are turned off during the calculation, and both are turned on again after one cycle of calculation is completed. The RMS value algorithm and FFT algorithm are used to calculate the effective value of voltage and current, active power and power factor, and then the FFT algorithm is used to calculate the THD value and 10th harmonic current value.

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