Power parameter correction method and module of circuit breaker and circuit breaker

Abstract

The invention discloses a power parameter correction method of a circuit breaker. The method specifically comprises the following steps: calculating a phase angle difference of a power factor measurement value relative to a corresponding standard power factor according to the power factor measurement value of a power parameter measurement module under a standard power factor input condition in advance; in the power parameter measurement process, firstly, a phase angle measurement value is calculated according to a power factor measurement value, then the phase angle measurement value is corrected by using the phase angle difference, and then a corrected power factor is calculated by using the corrected phase angle measurement value. And finally, other corrected power parameters are calculated according to the corrected power factor and the apparent power measurement value. The invention further discloses a power parameter correction module of the circuit breaker and the circuit breaker. According to the invention, a phase-shifting capacitor or other complex power parameter correction circuits are not needed, and high-precision correction of power parameters can be realized at low cost.

Description

Technical Field

[0001] The invention relates to a power parameter correction method for a circuit breaker, and belongs to the technical field of electrical parameter measurement. Background Art

[0002] With the development of intelligent and networked circuit breakers, circuit breakers are no longer just simple functions of cutting off and connecting load circuits. Users have begun to pay attention to circuit breakers with power measurement functions, which can measure and calculate power parameters such as power factor, active power and reactive power. Considering the cost and installation size, existing circuit breakers generally use low-cost microprocessors and current transformers with integrated measurement and protection functions. The ADC sampling module of the low-cost microprocessor is generally a successive approximation ADC, with a multi-channel sequential conversion mode, which has the characteristics of high accuracy, moderate resolution and speed, and short sampling delay. It has the advantage of low cost, but there is a problem of low frequency of collecting voltage and current, and there is a phase difference in the voltage and current sampling signals, which will result in poor accuracy in real-time calculation of power factor, active power, reactive power and apparent power. The output accuracy of the current transformer with integrated microprocessor measurement and protection functions is also low, which affects the measurement accuracy of power factor, active power and reactive power. This requires correction of the power parameters measured and calculated in real time.

[0003] The conventional existing correction method is to perform hardware circuit correction on the collected voltage phase. The mainstream method is to use a capacitor to shift the phase of the voltage signal. When the AC signal passes through the capacitor, the charge in the capacitor will change with the change of the signal, causing the voltage of the capacitor to change. Since there is a certain phase difference between the current and voltage in the capacitor, the capacitor can shift the phase of the signal, thereby correcting the phase angle difference between the voltage signal and the current signal, thereby achieving power parameter correction. However, this method has high requirements for the capacitors used, and the capacitance of the capacitor also has a great influence on the phase shift angle, requiring high-precision capacitance requirements. Due to process limitations, the accuracy of general capacitors is poor, and the cost is also high. In addition, due to the inconsistency of circuit parameters, the solution using capacitors cannot achieve high-precision power parameter correction. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a power parameter correction method for a circuit breaker, which does not require a phase-shifting capacitor or other complex power parameter correction circuits and can achieve high-precision power parameter correction at low cost through software.

[0005] The present invention specifically adopts the following technical solutions to solve the above technical problems:

[0006] A power parameter correction method for a circuit breaker, the circuit breaker having a power parameter measurement module for measuring power parameters including power factor; the power parameter correction method is specifically as follows: according to the power factor measurement value of the power parameter measurement module under the standard power factor input condition, the phase angle difference of the power factor measurement value of the power parameter measurement module relative to the corresponding standard power factor is calculated in advance; in the power parameter measurement process, the phase angle measurement value is first calculated according to the power factor measurement value of the power parameter measurement module, and then the phase angle measurement value is corrected by using the phase angle difference, and then the corrected phase angle measurement value is used to calculate the corrected power factor, and finally the corrected other power parameters are calculated according to the corrected power factor and the apparent power measurement value.

[0007] Preferably, the other power parameters include active power and reactive power.

[0008] Based on the same inventive concept, the following technical solutions can also be obtained:

[0009] A power parameter correction module for a circuit breaker, the circuit breaker having a power parameter measurement module for measuring power parameters including power factor; the power parameter correction module stores a phase angle difference of the power factor measurement value of the power parameter measurement module relative to the corresponding standard power factor, which is calculated in advance based on the power factor measurement value of the power parameter measurement module under standard power factor input conditions; during the power parameter measurement process, the power parameter correction module first calculates a phase angle measurement value based on the power factor measurement value of the power parameter measurement module, then uses the phase angle difference to correct the phase angle measurement value, then uses the corrected phase angle measurement value to calculate the corrected power factor, and finally calculates other corrected power parameters based on the corrected power factor and apparent power measurement value.

[0010] Preferably, the other power parameters include active power and reactive power.

[0011] A circuit breaker comprises a power parameter measurement module for measuring power parameters including power factor, and a power parameter correction module for correcting the power parameter measurement value output by the power parameter measurement module; the power parameter correction module is the power parameter correction module described in any of the above technical solutions.

[0012] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0013] The present invention utilizes the power factor measurement value of the power parameter measurement module under the standard power factor input condition to calculate the phase angle difference of the power factor measurement value of the power parameter measurement module relative to the corresponding standard power factor, and realizes the digital phase shift correction of the power parameter by software, without the need for high-precision phase shift capacitors or other complex correction circuits, and without the need for high-cost microprocessors and current transformers. High-precision correction of power parameters can be achieved at low cost, and the invention has good application prospects. DETAILED DESCRIPTION

[0014] In view of the deficiencies in the prior art, the solution of the present invention is to use the phase angle difference of the power factor measurement value of the power parameter measurement module calculated in advance based on the power factor measurement value of the power parameter measurement module under standard power factor input conditions relative to the corresponding standard power factor to perform digital phase shift correction on the power parameter measurement value of the power parameter measurement module, so as to achieve high-precision correction of the power parameters at low cost.

[0015] The present invention specifically adopts the following technical solutions to solve the above technical problems:

[0016] A power parameter correction method for a circuit breaker, the circuit breaker having a power parameter measurement module for measuring power parameters including power factor; the power parameter correction method is specifically as follows: according to the power factor measurement value of the power parameter measurement module under the standard power factor input condition, the phase angle difference of the power factor measurement value of the power parameter measurement module relative to the corresponding standard power factor is calculated in advance; in the power parameter measurement process, the phase angle measurement value is first calculated according to the power factor measurement value of the power parameter measurement module, and then the phase angle measurement value is corrected by using the phase angle difference, and then the corrected phase angle measurement value is used to calculate the corrected power factor, and finally the corrected other power parameters are calculated according to the corrected power factor and the apparent power measurement value.

[0017] A power parameter correction module for a circuit breaker, the circuit breaker having a power parameter measurement module for measuring power parameters including power factor; the power parameter correction module stores a phase angle difference of the power factor measurement value of the power parameter measurement module relative to the corresponding standard power factor, which is calculated in advance based on the power factor measurement value of the power parameter measurement module under standard power factor input conditions; during the power parameter measurement process, the power parameter correction module first calculates a phase angle measurement value based on the power factor measurement value of the power parameter measurement module, then uses the phase angle difference to correct the phase angle measurement value, then uses the corrected phase angle measurement value to calculate the corrected power factor, and finally calculates other corrected power parameters based on the corrected power factor and apparent power measurement value.

[0018] A circuit breaker comprises a power parameter measurement module for measuring power parameters including power factor, and a power parameter correction module for correcting the power parameter measurement value output by the power parameter measurement module; the power parameter correction module is the power parameter correction module described in any of the above technical solutions.

[0019] In order to facilitate public understanding, the technical solution of the present invention is described in detail below through a specific embodiment:

[0020] The circuit breaker of this embodiment includes: a voltage conditioning module, a current conditioning module, a microprocessor module and a human-machine interface module; the voltage conditioning module and the current conditioning module are used to convert the collected voltage and current signals of the circuit where the circuit breaker is located into a voltage signal within a predetermined range, the voltage conditioning module includes a voltage sampling circuit and a signal conditioning circuit, and converts the high voltage signal into a voltage signal within a predetermined range of low voltage; the current conditioning module includes a current transformer, a current sampling current, and a signal conditioning current, and converts the current signal into a voltage signal within a predetermined range of low voltage, for example, the voltage signal within the predetermined range is a voltage signal within 0 to 3V. The microprocessor module includes: a sampling module, which is used to sample the voltage signal within the predetermined range; a power calculation module, which calculates the signal sampled by the sampling module to calculate power parameters such as power factor, active power, reactive power and apparent power; a power correction module, which is implemented through software programming and is used to correct the power parameters calculated by the power calculation module to obtain the actual power parameters of the circuit; and a human-machine interface module is used for users to view the measured values ​​and corrected values ​​of power parameters such as power factor, active power, reactive power, apparent power, etc., and to realize data exchange between the circuit breaker controller and the user.

[0021] The sampling module in this embodiment uses the ADC sampling module inside the microprocessor to sample the voltage signals output by the voltage conditioning module and the current conditioning module at a fixed frequency, convert them into digital signals for calculation by the power calculation module, and sample the voltage signals output by the voltage conditioning module and the current conditioning module at a fixed frequency, and the sampling frequencies of the two voltages are the same.

[0022] The microprocessor can sample n points in one cycle, and the sampling interval is 360° / n. Limited by the performance of the microprocessor and the complexity of software design, the ADC sampling module in this embodiment samples 64 points per cycle; the power calculation module calculates the active power, reactive power and apparent power of the circuit according to the active power, reactive power and apparent power calculation method, and calculates the power factor of the circuit according to the power factor calculation method.

[0023] In an AC circuit, active power P refers to the average value of the integral of the instantaneous power emitted or consumed by the load within a period T, so it is also called average power. The calculation formula for active power P is as follows:

[0024]

[0025] Wherein, n is the number of sampling points, I is the actual current value corresponding to the current conditioning module at the corresponding sampling point, and U is the actual voltage value corresponding to the voltage conditioning module at the corresponding sampling point. The microprocessor can calculate the actual current value and the actual voltage value based on the pre-stored proportional coefficients of the output voltage of the current conditioning module and the output voltage of the voltage conditioning module.

[0026] In a circuit with energy storage elements such as inductors and capacitors, the energy storage elements convert the power supply energy into magnetic field (or electric field) energy in half a cycle and store it, and return the stored magnetic field (or electric field) energy to the power supply in the other half a cycle. Since this part of the energy is only exchanged between the energy storage element and the power supply and is not actually consumed, it is called reactive power Q. The reactive power Q can be calculated by first shifting the voltage phase by 90° and based on the formula:

[0027]

[0028] Wherein, n is the number of sampling points, I is the actual current value corresponding to the output voltage of the current conditioning module at the corresponding sampling point, and U is the actual voltage value corresponding to the output voltage of the voltage conditioning module at the corresponding sampling point after the output voltage of the voltage conditioning module is phase shifted by 90°.

[0029] Apparent power S is calculated by active power P and reactive power Q:

[0030]

[0031] The power factor cosΦ is calculated by the active power P and the apparent power S:

[0032] cosΦ=P / S

[0033] The above are all existing mature technologies, and will not be described in detail for the sake of saving space. The following is an explanation of the implementation process and principle of the power correction module:

[0034] According to the definition of power factor cosΦ, where Φ is the phase difference between voltage and current. A standard power factor cosΦ1, such as 0.5, is input to the circuit breaker controller using a standard tester in advance; the power factor calculation module measures the corresponding power factor measurement value cosΦ2; Φ1 and Φ2 are calculated according to the inverse trigonometric function arccos, thereby calculating the phase angle difference Φ'=Φ1-Φ2 of the power factor measurement value relative to the corresponding standard power factor input.

[0035] In the actual power parameter measurement process, the phase angle difference Φ' is used to correct the power parameters output by the power factor calculation module, as follows:

[0036] (1) According to the power factor measurement value cosΦ output by the power factor calculation module, the phase angle measurement value Φ is calculated using the inverse trigonometric function arccos;

[0037] (2) The phase angle measurement value Φ is corrected using the phase angle difference Φ', and the corrected actual phase angle Φ3 = Φ + Φ' is calculated;

[0039] (3) Calculate the corrected power factor cosΦ3 using the corrected phase angle Φ3;

[0040] (4) Based on the corrected power factor cosΦ3 and the apparent power measurement value S output by the power factor calculation module, the corrected active power P = S*cosΦ3 and reactive power Q = S*sinΦ3 are calculated.

[0041] According to the above steps, the power parameter calibration can be completed.

Claims

1. A method for correcting power parameters of a circuit breaker, wherein the circuit breaker has a power parameter measurement module for measuring power parameters including power factor; characterized in that: The power parameter correction method is specifically as follows: the phase angle difference of the power factor measurement value of the power parameter measurement module relative to the corresponding standard power factor is calculated in advance according to the power factor measurement value of the power parameter measurement module under the standard power factor input condition; during the power parameter measurement process, the phase angle measurement value is first calculated according to the power factor measurement value of the power parameter measurement module, and then the phase angle measurement value is corrected using the phase angle difference, and then the corrected phase angle measurement value is used to calculate the corrected power factor, and finally the corrected other power parameters are calculated based on the corrected power factor and the apparent power measurement value.

2. The power parameter calibration method of a circuit breaker according to claim 1, characterized in that: The other power parameters include active power and reactive power.

3. A power parameter correction module for a circuit breaker, the circuit breaker having a power parameter measurement module for measuring power parameters including power factor; characterized in that: The power parameter correction module stores the phase angle difference of the power factor measurement value of the power parameter measurement module relative to the corresponding standard power factor, which is calculated in advance based on the power factor measurement value of the power parameter measurement module under the standard power factor input condition; during the power parameter measurement process, the power parameter correction module first calculates the phase angle measurement value based on the power factor measurement value of the power parameter measurement module, then uses the phase angle difference to correct the phase angle measurement value, then uses the corrected phase angle measurement value to calculate the corrected power factor, and finally calculates the corrected other power parameters based on the corrected power factor and the apparent power measurement value.

4. The power parameter correction module of the circuit breaker according to claim 3, characterized in that: The other power parameters include active power and reactive power.

5. A circuit breaker, comprising a power parameter measurement module for measuring power parameters including power factor, and a power parameter correction module for correcting the power parameter measurement value output by the power parameter measurement module; characterized in that: The power parameter correction module is the power parameter correction module as claimed in claim 3 or 4.

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