High-precision wide-band low-cost multiplication device for electric energy metering applications

Abstract

The application relates to the technical field of analog multipliers, and discloses a high-precision wide-bandwidth low-cost multiplication device for electric energy metering application. The topology comprises two absolute value operation circuits, two logarithmic amplification circuits and one anti-logarithmic amplification circuit. The input voltage is outputted as the absolute value after passing through the two absolute value operation circuits, and then the product of the logarithmic amplification circuit and the anti-logarithmic amplification circuit is outputted. The application can accurately meter the electric energy when the input voltage and current contain large harmonics, ensures the accuracy of electric charge metering, improves the metering precision, reduces the cost and increases the bandwidth.

Description

Technical Field

[0001] This invention relates to the field of analog multiplier technology, specifically to a high-precision, wide-bandwidth, low-cost multiplication device for electricity metering applications. Background Technology

[0002] Electricity metering is the basis for the economic accounting of the power grid, and the accuracy of electricity metering is related to the economic benefits of both electricity supply and demand. Currently, the commonly used electricity metering methods can be divided into three types: total electricity metering, fundamental frequency electricity metering, and harmonic electricity metering. Early digital electricity meters used the simplest dot product and electricity metering algorithms to achieve total electricity metering. However, due to the increasing number of electronic nonlinear loads connected to the power grid, a large number of harmonics, even interharmonics and DC attenuation components, appear in the grid voltage and current. Some of the harmonic sources in the grid voltage and current are generated by nonlinear loads, injecting harmonic currents into the grid in the opposite direction to the fundamental frequency current. The resulting harmonic active power offsets part of the fundamental frequency active power; while linear load users are harmed by harmonics, consuming both fundamental and harmonic energy. Therefore, researching how to accurately and reasonably perform electricity metering when voltage and current contain a large number of harmonic components has significant practical significance and value.

[0003] Multipliers are an indispensable component of electronic energy meters. Currently, the main type of electronic energy meter used in China is the time division multiplier (TDM). Some literature documents the establishment of simulation models for TDMs, and through calculation and simulation analysis, conclusions have been drawn that high harmonic content will have a significant impact on the energy measurement of electronic energy meters. Other literature, based on the working principle of the TDM, derives a theoretical expression for its measurement error under harmonic conditions, providing a theoretical basis for the quantitative analysis of metering system errors under harmonic conditions.

[0004] To address the issue of accurate energy metering in the presence of harmonics, some literature describes an energy metering model based on a time-division multiplier, designing an active power metering correction module adapted to the dynamic characteristics of distributed photovoltaic (PV) systems. This model combines the mathematical representation of PV grid-connected signals with an improved energy metering model, proposing an improved energy metering model adapted to the dynamic characteristics of distributed PV. Another literature designs an algorithm using wavelet transform to calculate the electrical energy consumption of nonlinear loads and verifies through examples that the algorithm's accuracy is significantly higher than other algorithms.

[0005] However, in general, existing traditional TDM multipliers have measurement deviations when the input voltage and current contain harmonics, resulting in large errors in actual power metering. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a high-precision, wide-bandwidth, low-cost multiplication arithmetic device for electricity metering applications. This device can accurately measure electrical energy even when the input voltage and current contain significant harmonics, ensuring the accuracy of electricity billing while improving metering precision and reducing costs. The technical solution is as follows:

[0007] A high-precision, wide-bandwidth, low-cost multiplication arithmetic device for electricity metering applications, the topology of which includes two absolute value arithmetic circuits, two logarithmic amplifier circuits, and one anti-logarithmic amplifier circuit.

[0008] The first absolute value operation circuit includes operational amplifiers A1 and A2, resistors R1, R2, R3 and R4, and diodes D1 and D2;

[0009] Input voltage v x The inverting input terminal of operational amplifier A1 is connected to the input terminal, the non-inverting input terminal of operational amplifier A1 is grounded, and the output terminal is connected to the cathode of diode D1 and the anode of diode D2.

[0010] The anode of diode D1 is connected to one end of resistors R1 and R2. The other end of resistor R1 is connected to the inverting input of operational amplifier A1. The other end of resistor R2 is connected to both the inverting input of operational amplifier A2 and one end of resistor R3. The other end of resistor R3 is connected to the output of operational amplifier A2.

[0011] The cathode of diode D2 is connected to both the non-inverting input of operational amplifier A2 and one end of resistor R4, while the other end of resistor R4 is connected to the inverting input of operational amplifier A1.

[0012] The output of operational amplifier A2 outputs the input voltage v. x absolute value |v x |;

[0013] The structure of the second absolute value operation circuit is the same as that of the first absolute value operation circuit, and the input voltage is v. y The absolute value |v is output through the second absolute value calculation circuit. y |;

[0014] The first logarithmic amplifier circuit includes resistors R9 and R10, operational amplifier A5, transistor T1, and diode D5;

[0015] Output absolute value | v xThe output of operational amplifier A2 is connected to the inverting input of operational amplifier A5 via resistor R9. The non-inverting input of operational amplifier A5 is grounded. The output is connected to the anode of diode D5 and the emitter of transistor T1 via resistor R10, as well as the anode of diode D7 and the emitter of transistor T3 in the anti-inverting circuit. The cathode of diode D5 is connected to the base of transistor T1, and the collector of transistor T1 is connected to the inverting input of operational amplifier A5.

[0016] The structure of the second logarithmic amplifier circuit is the same as that of the first logarithmic amplifier circuit, and the base of transistor T1 is connected to the emitter of transistor T2 in the second logarithmic amplifier circuit.

[0017] The anti-multiplexer amplifier circuit includes resistor R11, operational amplifier A6, transistor T3, and diode D7. Resistor R11 is connected between the inverting input and output of operational amplifier A6. The base of transistor T3 and the cathode of diode D7 are grounded. The collector of transistor T3 is connected to the inverting input of operational amplifier A6. The non-inverting input of operational amplifier A6 is grounded, and the output terminal outputs the output voltage v of the analog multiplier. p .

[0018] The beneficial effects of this invention are: it can accurately measure electrical energy even when the input voltage and current contain large harmonics, ensuring the accuracy of electricity billing, while improving metering accuracy, reducing costs, and increasing bandwidth. Attached Figure Description

[0019] Figure 1 This is a topology diagram of the high-precision, wide-bandwidth, low-cost multiplier of the present invention.

[0020] Figure 2 This is a simulation model for a high-precision, wide-bandwidth, low-cost multiplier.

[0021] Figure 3 The graph shows the comparison between simulated power and theoretical power (frequency 50Hz).

[0022] Figure 4 The graph shows the comparison between simulated electrical energy and theoretical electrical energy (frequency: 50Hz).

[0023] Figure 5 The graph shows the comparison between simulated power and theoretical power (frequency 300Hz).

[0024] Figure 6 The graph shows the comparison between simulated electrical energy and theoretical electrical energy (frequency 300Hz).

[0025] Figure 7 The graph shows the comparison between simulated power and theoretical power (frequency 500Hz).

[0026] Figure 8 The graph shows the comparison between simulated electrical energy and theoretical electrical energy (frequency: 500Hz). Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] 1. High-precision, wide-bandwidth, low-cost operational circuit topology and basic principles for electricity metering

[0029] To address the aforementioned problems of traditional TDM electronic energy meters, and considering that the input is AC voltage and current, resulting in both positive and negative signals, and that chips capable of processing reverse voltage and current signals are currently quite expensive, this invention employs discrete components to build an absolute value circuit to process the input voltage and current signals before implementing multiplication operations, such as... Figure 1 As shown, this invention proposes a high-precision, wide-bandwidth, low-cost operational circuit topology for electricity metering, wherein A1 to A4 are absolute value operation circuits, A5 and A7 operational amplifiers constitute logarithmic amplification, and A6 realizes anti-logarithmic amplification.

[0030] The specific structure of the two absolute value operation circuits, two logarithmic amplifier circuits, and one anti-logarithmic amplifier circuit is as follows:

[0031] The first absolute value operation circuit includes operational amplifiers A1 and A2, resistors R1, R2 and R3, and diodes D1 and D2.

[0032] Input voltage v x The input is connected to the inverting input of operational amplifier A1, the non-inverting input of operational amplifier A1 is grounded, and the output is connected to the cathode of diode D1 and the anode of diode D2.

[0033] The anode of diode D1 is connected to one end of resistors R1 and R2. The other end of resistor R1 is connected to the inverting input of operational amplifier A1. The other end of resistor R2 is connected to both the inverting input of operational amplifier A2 and one end of resistor R3. The other end of resistor R3 is connected to the output of operational amplifier A2.

[0034] The cathode of diode D2 is connected to both the non-inverting input of operational amplifier A2 and one end of resistor R4, while the other end of resistor R4 is connected to the inverting input of operational amplifier A1.

[0035] The output of operational amplifier A2 outputs the input voltage v. x absolute value |v x |

[0036] The structure of the second absolute value operation circuit is the same as that of the first absolute value operation circuit, and the input voltage is v. yThe absolute value |v is output through the second absolute value calculation circuit. y |

[0037] The first logarithmic amplifier circuit includes resistors R9 and R10, operational amplifier A5, transistor T1, and diode D5.

[0038] Enter |v x The input terminal of the circuit is connected to the inverting input terminal of operational amplifier A5 via resistor R9. The non-inverting input terminal of operational amplifier A5 is grounded. The output terminal is connected to the anode of diode D5 and the emitter of transistor T1 via resistor R10, as well as the anode of diode D7 and the emitter of transistor T3 in the anti-inverting circuit. The cathode of diode D5 is connected to the base of transistor T1, and the collector of transistor T1 is connected to the inverting input terminal of operational amplifier A5.

[0039] The structure of the second logarithmic amplifier circuit is the same as that of the first logarithmic amplifier circuit, and the base of transistor T1 is connected to the emitter of transistor T2 in the second logarithmic amplifier circuit.

[0040] The anti-multiplexer amplifier circuit includes resistor R11, operational amplifier A6, transistor T3, and diode D7. Resistor R11 is connected between the inverting input and output of operational amplifier A6. The base of transistor T3 and the cathode of diode D7 are grounded. The collector of transistor T3 is connected to the inverting input of operational amplifier A6. The non-inverting input of operational amplifier A6 is grounded, and the output terminal outputs the output voltage v of the analog multiplier. p .

[0041] Depend on Figure 1 We can obtain:

[0042] v be1 +v be2 =v be3 (1)

[0043] The base-emitter voltage v in a transistor operating in the amplification region ben With collector current i cn The relationship between them is logarithmic, where n = 1, 2, 3, that is:

[0044] v ben =V Tn ·ln(i cn / I sn (2)

[0045] Where V T It is the temperature-voltage equivalent of the transistor, I s It is its reverse saturation current.

[0046] Substituting equation (2) into equation (1), we get:

[0047] VT1 ·ln(i c1 / I s1 )+V T2 ·ln(i c2 / I s2 ) = V T3 ·ln(i c3 / I s3 (3)

[0048] If the three transistors are identical, then V T1 =V T2 =V T3 I s1 =I s2 =I s3 From the above formula, we can obtain:

[0049] i c1 ·i c2 =i c3 (4)

[0050] Combining the virtual short characteristic of operational amplifiers, the above equation can be used to deduce:

[0051] (|v x | / R1)·(|v y | / R2)=(v p / R3) (5)

[0052] If R1 = R2 = R3, then the output voltage v of the analog multiplier is... p for:

[0053] v p =|v x ||v y | (6)

[0054] 2. Simulation Verification of High-Precision, Wide-Bandwidth, Low-Cost Multiplier

[0055] like Figure 2 As shown, this invention builds a high-precision, wide-bandwidth, low-cost multiplication simulation model for power metering in PSIM software, which includes an input voltage and current sampling module and a logarithmic amplification module. This invention replaces the logarithmic amplification function of the transistor with a controlled current source and a logarithmic function module.

[0056] Figure 3 and Figure 4The simulation power and theoretical power comparison results and the simulation energy comparison results are given respectively when the voltage and current frequency is 50Hz. The solid curve is the simulation value and the dashed curve is the theoretical value. It can be clearly seen that the simulation curve and the theoretical curve are basically consistent. Therefore, it can be directly concluded that when the input voltage and current do not contain harmonics, the high-precision, wide-bandwidth, low-cost multiplier proposed in this invention has high calculation accuracy and precision.

[0057] Figure 5 and Figure 6 The simulation power and theoretical power comparison results, as well as the simulation electrical energy comparison results, are presented for a voltage and current frequency of 300Hz. The solid curve represents the simulation value, and the dashed curve represents the theoretical value. It can be clearly seen that the simulation curve and the theoretical curve are basically consistent. This indicates that the high-precision, wide-bandwidth, low-cost multiplier proposed in this invention has relatively high calculation accuracy and precision when the input voltage and current contain high-order harmonics.

[0058] To further verify this conclusion, Figure 7 and Figure 8 The simulation power and theoretical power, as well as the simulation energy and theoretical energy, are shown in graphs at a voltage, current, and frequency of 500Hz. Similarly, it is clear that the simulation curves and the theoretical curves are basically consistent.

[0059] Note: Figure 3 , Figure 5 , Figure 7 Because the proposed topology has extremely high accuracy, the curves in the figure completely overlap.

[0060] In summary, the high-precision, wide-bandwidth, low-cost multiplier proposed in this invention can accurately and precisely measure the actual power level under conditions where the input voltage and current are free of harmonics or contain high-order harmonics.

Claims

1. A high-precision, wide-bandwidth, low-cost multiplication arithmetic device for electricity metering applications, characterized in that, Its topology includes two absolute value operation circuits, two logarithmic amplifier circuits, and one anti-logarithmic amplifier circuit; The first absolute value operation circuit includes operational amplifiers A1 and A2, resistors R1, R2, R3 and R4, and diodes D1 and D2; Input voltage v x The inverting input terminal of operational amplifier A1 is connected to the input terminal, the non-inverting input terminal of operational amplifier A1 is grounded, and the output terminal is connected to the cathode of diode D1 and the anode of diode D2. The anode of diode D1 is connected to one end of resistors R1 and R2. The other end of resistor R1 is connected to the inverting input of operational amplifier A1. The other end of resistor R2 is connected to both the inverting input of operational amplifier A2 and one end of resistor R3. The other end of resistor R3 is connected to the output of operational amplifier A2. The cathode of diode D2 is connected to both the non-inverting input of operational amplifier A2 and one end of resistor R4, while the other end of resistor R4 is connected to the inverting input of operational amplifier A1. The output of operational amplifier A2 outputs the input voltage v. x absolute value |v x |; The structure of the second absolute value operation circuit is the same as that of the first absolute value operation circuit, and the input voltage is v. y The absolute value |v is output through the second absolute value calculation circuit. y |; The first logarithmic amplifier circuit includes resistors R9 and R10, operational amplifier A5, transistor T1, and diode D5; Output absolute value | v x The output of operational amplifier A2 is connected to the inverting input of operational amplifier A5 via resistor R9. The non-inverting input of operational amplifier A5 is grounded. The output is connected to the anode of diode D5 and the emitter of transistor T1 via resistor R10, as well as the anode of diode D7 and the emitter of transistor T3 in the anti-inverting circuit. The cathode of diode D5 is connected to the base of transistor T1, and the collector of transistor T1 is connected to the inverting input of operational amplifier A5. The structure of the second logarithmic amplifier circuit is the same as that of the first logarithmic amplifier circuit, and the base of transistor T1 is connected to the emitter of transistor T2 in the second logarithmic amplifier circuit. The anti-inverting amplifier circuit includes resistor R11, operational amplifier A6, transistor T3, and diode D7; resistor R11 is connected between the inverting input and output of operational amplifier A6, and the base of transistor T3 and the cathode of diode D7 are grounded. The collector of transistor T3 is connected to the inverting input of operational amplifier A6; the non-inverting input of operational amplifier A6 is grounded, and the output terminal outputs the output voltage v of the analog multiplier. p .

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