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A PLL Applicable to Grid Voltage Unbalance and Distortion State

A grid voltage, phase-locked loop technology, applied in the field of phase-locked loops, can solve the problems of phase-locked results discrete error, etc., and achieve the effects of fast dynamic response rate, small phase detection error, and small steady-state error.

Active Publication Date: 2018-08-14
DALIAN UNIV OF TECH
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Problems solved by technology

However, due to the non-ideal sampling frequency, this method may cause discrete errors in the phase-locked results

Method used

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  • A PLL Applicable to Grid Voltage Unbalance and Distortion State
  • A PLL Applicable to Grid Voltage Unbalance and Distortion State
  • A PLL Applicable to Grid Voltage Unbalance and Distortion State

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Embodiment 1

[0047] figure 1 It is the schematic diagram of the basic three-phase phase-locked loop. The three-phase grid voltage is transformed into the two-phase static coordinate system by using the Clark transformation, and the voltage U of the grid voltage in the two-phase static coordinate system is obtained. α and U β , and then use the Parker transformation to transform the voltage value of the grid voltage in the two-phase stationary coordinate system to the two-phase rotating coordinate system, and obtain the voltage U of the grid voltage in the two-phase rotating coordinate system d and U q , where the grid voltage component on the q-axis is:

[0048]

[0049] When the phase angle θ output by the PLL is close to the phase angle ωt of the actual grid voltage vector, that is to say (ωt-θ) is very small or close to zero, sin(ωt-θ) can be approximated as (ωt-θ) . Therefore, when the PLL is locked, the q-axis component of the grid voltage vector in the synchronous rotating coo...

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Abstract

The invention discloses a phase-locked loop applicable to power grid voltage unbalance and distortion states, and belongs to the related technical fields of power grid voltage phase signal detection and power grid load harmonic current extraction. The phase-locked loop provided by the invention aims to solve the problem as follows: the conventional synchronous rotating reference frame based three-phase digital phase-locked loop cannot accurately detect the phase value of the three-phase voltage fundamental wave positive-sequence component under power grid voltage unbalance and distortion states; consequently, the precision of a related harmonic current extraction algorithm is lowered, and the compensation effect of a harmonic compensation apparatus is weakened. The phase-locked loop provided by the invention improves the conventional three-phase digital phase-locked loop, and a repetition controller is introduced; the repetition controller is connected with a proportional integral controller in parallel to form a new controller, so that the excellent steady-state performance of the repetition controller is combined with the excellent dynamic performance of the proportional integral controller; and therefore, the phase-locked loop has the advantages of high dynamic response, high detection precision and the like. The phase-locked loop is mainly applied to voltage phase detection under power grid voltage unbalance and distortion states.

Description

technical field [0001] The invention relates to the related technical field of grid voltage phase signal detection and grid load harmonic current extraction, in particular to a phase-locked loop suitable for grid voltage unbalance and distortion state. Background technique [0002] PLL technology is widely used in power electronics and power systems and other fields. Common PLLs include single-phase PLL and three-phase PLL. Single-phase PLL is generally used in single-phase system and three-phase voltage balance system. When the three-phase voltage is unbalanced and distorted, single-phase PLL The phase loop cannot obtain the phase value of the positive sequence component of the fundamental wave of the three-phase voltage. The three-phase phase-locked loop can synthesize the three-phase voltage information, and use technical means such as coordinate transformation to obtain the phase difference signal. [0003] The traditional three-phase digital phase-locked loop based on...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/26G01R25/00
CPCY02E40/50
Inventor 张玉龙王志强王进君李国锋
Owner DALIAN UNIV OF TECH
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