Summary of the invention
In order to overcome the defect of prior art, the present invention proposes a kind of imbalance of three-phase voltage phase-locked loop of controlling based on decoupling zero, and positive sequence component, negative sequence component and the zero-sequence component of utilizing decoupling method to decomposite in three-phase imbalance voltage realize phase-locked function.
The present invention adopts following technical scheme to realize: a kind of imbalance of three-phase voltage phase-locked loop of controlling based on decoupling zero, and it comprises the first phase discriminator, the second phase discriminator, the 3rd phase discriminator, positive sequence voltage decoupling zero conversion computing module, negative sequence voltage decoupling zero conversion computing module at least, several are connected to low pass filter, full-wave integrator and the PI controller of positive sequence voltage decoupling zero conversion computing module output and negative sequence voltage decoupling zero conversion computing module output;
Described the first phase discriminator is used for three-phase voltage u
a, u
bAnd u
cCarry out the conversion of α β coordinate system, obtain positive sequence component and the negative sequence component component on α β coordinate system
With
Described the second phase discriminator is connected between the input of the output of described the first phase discriminator and positive sequence voltage decoupling zero conversion computing module, is used for the Output rusults of the first phase discriminator at forward dq coordinate system d
+q
+Carry out the synchronous conversion of forward, obtain
With
Described the 3rd phase discriminator is connected between the input of the output of described the first phase discriminator and negative sequence voltage decoupling zero conversion computing module, is used for the Output rusults of the first phase discriminator at negative sense dq coordinate system d
-q
-Carry out the synchronous conversion of negative sense, obtain
With
Described positive sequence voltage decoupling zero conversion computing module and described negative sequence voltage decoupling zero conversion computing module are respectively used to positive sequence voltage, negative sequence voltage are carried out the decoupling zero transformation calculations, utilize negative sense dq coordinate system d
-q
-Under transformation result eliminate forward dq coordinate system d
+q
+Two harmonics that produce during conversion;
Described PI controller is used for described positive sequence voltage decoupling zero conversion computing module is exported
Signal adopts closed-loop control to eliminate deviation;
Described full-wave integrator offers described the second phase discriminator, described the 3rd phase discriminator, described positive sequence voltage decoupling zero conversion computing module and described negative sequence voltage decoupling zero conversion computing module for generation of feedback phase θ '.
Wherein,
U
+For positive sequence fundamental voltage peak value, U
-For negative phase-sequence fundamental voltage peak value,
The starting phase angle of positive sequence fundamental voltage,
Be the starting phase angle of negative phase-sequence fundamental voltage, be the time.
Wherein, according to
With
The computing formula of described the second phase discriminator and described the 3rd phase discriminator Output rusults is:
Wherein, described positive sequence voltage decoupling zero conversion computing module carries out the decoupling zero transformation calculations to positive sequence voltage, obtains
With
Computing formula is:
Wherein, described negative sequence voltage decoupling zero conversion computing module carries out the decoupling zero transformation calculations to negative sequence voltage, obtains
With
Computing formula is:
Wherein, the transfer function of described full-wave integrator is 1/s, and s is laplace operator.
Compared with prior art, the present invention has following beneficial effect:
The present invention is based on the imbalance of three-phase voltage phase-locked loop that decoupling zero is controlled, realize with existing delay control method that positive-negative sequence is decomposed and compare, do not need to store the sampled point of line voltage, saved memory space, in addition, the result of decomposition is subjected to the impact of voltage ripple of power network little, and the decomposition effect is better.And,, owing to adopting closed-loop control, can obtain good phase-locked performance, under the condition of three-phase voltage balance, can obtain good effect, but when imbalance of three-phase voltage, the Phase Tracking effect is poor.Moreover the present invention can effectively follow the tracks of out its positive sequence component when three-phase signal is uneven, and the operand of this phase-locked loop is less, is more suitable for using in real-time control system.
Embodiment
The present invention proposes a kind of phase-locked loop of eliminating the impact of Voltage unbalance fully, based on two Synchronous Reference Frame Transforms and decoupling zero, calculate, also locking phase quickly and accurately under the failure conditions such as line voltage frequency discontinuity and single-phase earthing.
As shown in Figure 1, the phase-locked loop of the present invention's proposition comprises the first phase discriminator 11, the second phase discriminator 12, the 3rd phase discriminator 13, positive sequence voltage decoupling zero conversion computing module 14, negative sequence voltage decoupling zero conversion computing module 15, some low pass filters, full-wave integrator 16 and PI controller 17 at least.
The first phase discriminator is with three-phase voltage u
a, u
bAnd u
cCarry out the conversion of α β coordinate system, suppressed the impact of zero-sequence component and obtained positive sequence component and the component of negative sequence component on α β coordinate system
With
The decomposition of unbalance voltage vector under two reference synchronization coordinate systems, when the three phase network Voltage unbalance, according to symmetrical component method, the line voltage vector can be described as the synthetic of positive sequence, negative phase-sequence and zero-sequence component.Namely
In formula (1-1): U
+, U
-And U
0Respectively positive sequence fundamental voltage peak value, negative phase-sequence fundamental voltage peak value and zero sequence fundamental voltage peak value;
With
Respectively the starting phase angle of positive sequence fundamental voltage, the starting phase angle of negative phase-sequence fundamental voltage and the starting phase angle of zero sequence fundamental voltage.
Three-phase voltage u
a, u
bAnd u
cTransform to the two-phase rest frame, zero-sequence component is transformed to zero, thereby has suppressed the impact of zero-sequence component.The line voltage vector can be described as under α β coordinate system:
In formula (1-2)
Be respectively positive sequence component and the negative sequence component component on α β coordinate system.
(1-2) can find out from formula, and on α β coordinate system, voltage vector can be respectively the positive sequence voltage component U with the angular frequency rotation
+Negative sequence voltage component U with the rotation take angular frequency as-ω
-.As shown in Figure 2, it is comprised of 2 rotating coordinate systems: one is the d with the frequencies omega rotation
+q
+Coordinate system, the angle of rotation are θ ' (wherein θ ' is the feedback phase of full-wave integrator 16 outputs, and the transfer function of full-wave integrator 16 is 1/s, and s is laplace operator); Another is the d of the rotation take angular frequency as-ω
-q
-Coordinate system, the angle of rotation is-θ '.
By the Output rusults of 12 pairs of the first phase discriminators 11 of the second phase discriminator at forward dq coordinate system d
+q
+Carry out the synchronous conversion of forward, obtain
With
By the Output rusults of 13 pairs of the first phase discriminators 11 of the 3rd phase discriminator at negative sense dq coordinate system d
-q
-Carry out the synchronous conversion of negative sense, obtain
With
Formula (1-3)
According to two genlock principles, the rotation angle θ of the synchronous conversion of forward ' should be as far as possible close to
Namely have
Formula (1-3) is arranged:
(1-4) can find out by formula, at forward dq coordinate system d
+q
+Positive-going transition under, the positive sequence component of output voltage has become DC quantity, negative sequence component becomes the alternating current component of 2 ω frequencies; Equally, at negative sense dq coordinate system d
-q
-Negative going transition under, the negative sequence component of output voltage is DC quantity, and positive sequence component is the alternating current component of 2 ω frequencies.
Then, by 14 pairs of positive sequence voltages of positive sequence voltage decoupling zero conversion computing module, carry out the decoupling zero transformation calculations, obtain
With
Shown in (1-5); Carry out the decoupling zero transformation calculations by negative sequence voltage decoupling zero conversion computing module 15 negative sequence voltages, obtain
With
Shown in (1-6).
(1-4) is known by formula:
Known by formula (1-4) equally:
Then, by a plurality of output of positive sequence voltage decoupling zero conversion computing module 14, low pass filters pair of negative sequence voltage decoupling zero conversion computing module 15 outputs of being connected to
With
Carry out simultaneously low-pass filtering treatment, namely the result of formula (1-5) and formula (1-6) carried out low-pass filtering simultaneously and obtain:
Formula (1-7)
After phase-locked,
Substitution formula (1-6)
Formula (1-8) substitution formula (1-5) is obtained:
Formula (1-10)
And, the positive sequence voltage decoupling change is changed computing module 14 outputs
The closed-loop control of signal adopts PI controller 17 to eliminate deviation.When
The time, can realize that output phase synchronizes with electric network voltage phase., owing to adopting closed-loop control, can obtain good phase-locked performance.This algorithm under the condition of three-phase voltage balance, can be obtained good effect, but when imbalance of three-phase voltage, the Phase Tracking effect is poor.
Therefore, the present invention on the basis that is decomposed into positive sequence, negative phase-sequence and zero-sequence component, carries out three-phase voltage signal respectively the dq conversion under positive sequence, two reference axis of negative phase-sequence, and utilizes negative sense dq coordinate system d
-q
-Under transformation result eliminate forward dq coordinate system d
+q
+Two harmonics that produce during conversion, thus the impact of negative sequence component on phase-locked result suppressed.The present invention can effectively follow the tracks of out its positive sequence component when three-phase signal is uneven, and the operand of this phase-locked loop is less, is more suitable for using in real-time control system.
The foregoing is only preferred embodiment of the present invention,, not in order to limit the present invention, all any modifications of doing within the spirit and principles in the present invention, be equal to and replace and improvement etc., within all should being included in protection scope of the present invention.