CN111366796A - Phase sequence detection method of three-phase alternating current power supply - Google Patents

Abstract

A phase sequence detection method of a three-phase alternating current power supply solves the problems that the phase sequence detection difficulty is high, the operation is complex and the phase sequence cannot be judged quickly under the distortion condition of the voltage or the line current of the existing power grid, and belongs to the technical field of phase sequence testing in a power system. The method comprises the following steps: s1, collecting the line voltage or line current of BC phase and AB phase of three-phase AC power supply, and recording the collection time; s2: extracting sine values and cosine values of an AB phase initial phase angle and a BC phase initial phase angle according to the line voltage or line current of the BC phase and the AB phase and the acquisition time; and S3, judging the angle of the voltage or the current of the AB phase line ahead of the voltage or the current of the BC phase line according to the sine value and the cosine value of the initial phase angle of the AB phase and the initial phase angle of the BC phase to finish the phase sequence detection, wherein the three-phase alternating current power supply is a three-phase three-wire power supply, the positive sequence angle range of the three-phase three-wire power supply is 110.3-129.7 degrees, and the power frequency is 49-51 Hz.

Description

Phase sequence detection method of three-phase alternating current power supply

Technical Field

The invention relates to a phase sequence detection method of a three-phase alternating current power supply, and belongs to the technical field of phase sequence testing in an electric power system.

Background

In a three-phase power system, "phase" is the most basic unit in the system, which is called A, B, C, and "sequence" is the arrangement order of "phase", that is, the order of the rotating direction of the rotating magnetic field, where a positive sequence is changed to a positive sequence and a negative sequence is changed to a negative sequence, and it is a zero sequence that cannot form the rotating magnetic field. In a three-phase power system, there is a problem that a phase sequence of an access electric device is wrong due to various reasons, but the difficulty of phase sequence detection is large and the accuracy is low due to the fact that the power grid voltage or the line current is distorted. The three-phase sequence is required to be detected in a specific occasion, and the correctness of the three-phase sequence plays a crucial role in control.

Disclosure of Invention

The invention provides a method for rapidly detecting a phase sequence of a three-phase alternating current power supply, which aims to solve the problems that the phase sequence detection difficulty is high, the operation is complex and the phase sequence cannot be rapidly judged under the distortion condition of the voltage or the line current of the conventional power grid.

The invention discloses a phase sequence detection method of a three-phase alternating current power supply, which comprises the following steps:

s1, collecting the line voltage or line current of BC phase and AB phase of three-phase AC power supply, and recording the collection time;

s2: extracting cos phi 1, sin phi 1, cos phi 2 and sin phi 2 according to the line voltage or line current of the BC phase and the AB phase and the acquisition time, wherein phi 1 represents an AB phase initial phase angle, and phi 2 represents a BC phase initial phase angle;

s3, if sin (Φ 1- Φ 2) ═ sin Φ 1 · cos Φ 2-cos Φ 1 · sin Φ 2 > 0, the AB phase line voltage or line current of the three-phase ac power supply leads the BC phase line voltage or line current θ; theta represents a positive sequence angle of the three-phase alternating current power supply;

if sin (phi 1-phi 2) ═ sin phi 1 · cos phi 2-cos phi 1 · sin phi 2 < 0, the AB phase line voltage or line current leads the BC phase line voltage or line current-theta;

the three-phase alternating current power supply is a three-phase three-wire power supply, the positive sequence angle theta of the three-phase three-wire power supply ranges from 110.3 degrees to 129.7 degrees, and the power frequency ranges from 49 Hz to 51 Hz.

Preferably, in S2, the cos Φ 1, sin Φ 1, cos Φ 2, and sin Φ 2 are extracted according to the voltages or line currents of the BC phase and the AB phase and the acquisition time, and specifically:

extracting sin phi 1, cos phi 1, sin phi 2 and cos phi 2 according to the formulas I to IV respectively;

wherein x is_ABRepresenting AB phase line voltage or line current, x_{m_AB}Representing maximum value of AB phase line voltage or line current, x_{m_BC}Representing the maximum value of the voltage or current of the BC phase line, ω representing the frequency of the three-phase AC source, t representing time, x_BCRepresenting the BC phase line voltage or line current and T representing the sampling period.

The invention has the advantages that aiming at the condition that the initial phase angle is not influenced by the distortion of the power grid voltage or the line current under the distortion condition of the existing power grid voltage or the existing line current, the sine value and the cosine value of the AB phase initial phase angle and the BC phase initial phase angle are extracted by using the detected line voltage and the line current and the data of the acquisition time, and the angle that the AB phase line voltage or the line current leads the BC phase line voltage or the line current is judged according to the sine value and the cosine value of the AB phase initial phase angle and the BC phase initial phase angle, so that the phase sequence detection is completed.

Drawings

FIG. 1 is a flow chart of the present invention.

Detailed Description

Referring to fig. 1, the method for detecting the phase sequence of the three-phase ac power supply according to the present embodiment includes the following steps:

s1, acquiring voltage or line current of a BC phase line and voltage or line current of an AB phase line of a three-phase alternating-current power supply in real time by using the existing voltage and current detection circuit, and recording acquisition time;

s2, extracting sine values and cosine values of the AB phase initial phase angle and the BC phase initial phase angle according to the voltage or line current of the BC phase line, the voltage or line current of the AB phase line and the acquisition time: cos phi 1, sin phi 1, cos phi 2 and sin phi 2, wherein phi 1 represents an AB phase initial phase angle, and phi 2 represents a BC phase initial phase angle;

s3, if sin (Φ 1- Φ 2) ═ sin Φ 1 · cos Φ 2-cos Φ 1 · sin Φ 2 > 0, the AB phase line voltage or line current of the three-phase ac power supply leads the BC phase line voltage or line current θ; theta represents a positive sequence angle of the three-phase alternating current power supply;

if sin (φ 1- φ 2) ═ sin φ 1 · cos φ 2-cos φ 1 · sin φ 2 < 0, the AB phase line voltage or line current leads the BC phase line voltage or line current- θ.

Because the initial phase angle is not influenced by the distortion of the power grid voltage or the line current, the sine value and the cosine value of the AB phase initial phase angle and the BC phase initial phase angle are obtained according to the line voltage and the line current which are collected in real time and the collecting time, and the angle of the AB phase line voltage or the line current which is ahead of the BC phase line voltage or the line current is judged according to the sine value and the cosine value of the AB phase initial phase angle and the BC phase initial phase angle, so that the phase sequence detection is completed, the detection method is simple, and the detection result is accurate.

The embodiment is suitable for a three-phase three-wire power supply, the positive sequence angle theta of the three-phase power supply ranges from 110.3 degrees to 129.7 degrees, and the power frequency ranges from 49 Hz to 51 Hz.

The fundamental wave separation algorithm can be extracted by adopting a fundamental wave separation variable method through BC and AB phase voltage and acquisition time, and has the following principle:

u_AB(t)＝u_{m_AB}sin(ωt+φ1)

the same can be obtained:

and the following steps:

u(t)_BC·cosωt＝u_{m_BC}(sinωt·cosφ2+cosωt·sinφ2)·cosωt

＝u_{m_BC}sinωt·cosωt·cosφ2+u_{m_BC}(cosωt)²·sinφ2

the same can be obtained:

the AB phase initial phase angle is obtained by the method

Cos and sin values of, BC phase initial phase angle

Cos and sin values of;

method for extracting variable through BC and AB phase line current and acquisition time by adopting fundamental wave separation method

Sum of cos and sin values of

The principle of cos and sin values of (c) is the same as above; the formula is processed to obtain an algorithm which can be executed by two singlechips of the embodiment 1 and the embodiment 2;

example 1:

s1, the three-phase alternating current power supply is a three-phase three-wire power supply, the positive sequence angle is 120 degrees, the power frequency is 49-51Hz, and the line voltage signal u is obtained in real time through the existing voltage detection circuit_AB，u_BCAnd acquiring line voltage time t;

s2, collecting the line voltage u_ABMultiplying sin ω t and cos ω t at corresponding time t to obtain u_ABSin ω t and u_ABCos ω t, multiplying sin ω t and cos ω t at a time t corresponding to the collected line voltage UBC to obtain u_BCSin ω t and u_BC·cosωt；

All u in one sampling period T_AB·sinωt，u_AB·cos(ωt)，u_BC·sinωt，u_BCCos ω t is added and summed to ∑ u_AB·sinωt，∑u_AB·cosωt，∑u_BC·sinωt，∑u_BC·cosωt；

Will u_AB·sinωt，∑u_AB·cos(ωt)，∑u_BC·sin(ωt)，∑u_BCDividing cos ω T by the number of samples N in the sampling period T to obtain u_ABInitial phase angle

Cos value, sin value of; u. of_BCInitial phase angle

Cos value, sin value of; namely, it is

S3, calculating cos phi 1, sin phi 1, cos phi 2 and sin phi 2 according to the formula

When the calculation value of the formula is larger than 0, the line voltage u is calculated_ABLead u_BCAbout 120 °; when the formula calculation value is less than 0, the line voltage u is_ABLead u_BCAbout-120.

Example 2:

s1, the three-phase AC power supply is a three-phase three-wire power supply, the positive sequence angle is 120 degrees, the power frequency is 49-51Hz, and a wire current signal i is obtained in real time through the existing current detection circuit_AB，i_BCAnd obtaining a line current time t;

s2 line current i to be collected_ABMultiplying sin ω t and cos ω t at corresponding time t to obtain i_ABSin ω t and u_ABCos ω t, i is obtained by multiplying sin ω t and cos ω t) at a time t corresponding to the acquired line current UBC_BCSin ω t and i_BC·cosωt；

All i in one sampling period T_AB·sinωt，i_AB·cos(ωt)，i_BC·sinωt，i_BCCos ω t is added and summed to ∑ i_AB·sinωt，∑i_AB·cosωt，∑i_BC·sinωt，∑i_BC·cosωt；

Will i_AB·sinωt，∑i_AB·cos(ωt)，∑i_BC·sin(ωt)，∑i_BCDividing cos ω T by the number of samples N in the sampling period T to obtain i_ABInitial phase angle

Cos value, sin value of; i.e. i_BCInitial phase angle

Cos value, sin value of; namely, it is

S3, calculating cos phi 1, sin phi 1, cos phi 2 and sin phi 2 according to the formula

When the calculated value of the formula is larger than 0, the line current i is calculated_ABLead i_BCAbout 120 °; line current i when the formula calculation value is less than 0_ABLead i_BCAbout-120.

Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that features described in different dependent claims and herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.

Claims (2)

1. A method for detecting a phase sequence of a three-phase alternating current power supply, the method comprising:

s1, collecting the line voltage or line current of BC phase and AB phase of three-phase AC power supply, and recording the collection time;

s2, extracting cos phi 1, sin phi 1, cos phi 2 and sin phi 2 according to the line voltage or line current of the BC phase and the AB phase and the acquisition time, wherein phi 1 represents an AB phase initial phase angle, and phi 2 represents a BC phase initial phase angle;

s3, if sin (Φ 1- Φ 2) ═ sin Φ 1 · cos Φ 2-cos Φ 1 · sin Φ 2 > 0, the AB phase line voltage or line current of the three-phase ac power supply leads the BC phase line voltage or line current θ; theta represents a positive sequence angle of the three-phase alternating current power supply;

if sin (phi 1-phi 2) ═ sin phi 1 · cos phi 2-cos phi 1 · sin phi 2 < 0, the AB phase line voltage or line current leads the BC phase line voltage or line current-theta;

the three-phase alternating current power supply is a three-phase three-wire power supply, the positive sequence angle theta of the three-phase three-wire power supply ranges from 110.3 degrees to 129.7 degrees, and the power frequency ranges from 49 Hz to 51 Hz.

2. The method according to claim 1, wherein in S2, cos Φ 1, sin Φ 1, cos Φ 2, sin Φ 2 are extracted according to the voltages or line currents of the BC phase and the AB phase and the acquisition time, specifically:

extracting sin phi 1, cos phi 1, sin phi 2 and cos phi 2 according to the formulas I to IV respectively;

wherein x is_ABRepresenting AB phase line voltage or line current, x_{m_AB}Representing maximum value of AB phase line voltage or line current, x_{m_BC}Representing the maximum value of the voltage or current of the BC phase line, ω representing the frequency of the three-phase AC source, t representing time, x_BCRepresenting the BC phase line voltage or line current and T representing the sampling period.

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