DE19716909A1 - Method of synchronising a phase control loop e.g. for energy network of AC rail traction - Google Patents

Abstract

The method involves deriving a correlation signal (KSY) from an input signal (S) by multiplying it with a cosinusoidal, phase synchronous target parameter (SY) and finally smoothing the product. The correlation signal is proportional to the correlation between the input signal and target parameter. A phase correlation signal derived from the correlation signal by proportional amplification and integration is used as a reference phase signal. A sinusoidal, phase synchronous target parameter (SX) and the cosinusoidal, phase synchronous target parameter (SY) are derived from the reference phase signal.

Description

The invention relates to a method and an apparatus for Synchronization of a phase locked loop.

In many technical applications, e.g. B. Railway and Industry drives, is an exact syn with regard to phase and frequency chronization on an input signal is required, the Input signal in practice significant distortion components may contain. Such distortion components come from the third and fifth harmonics ago, z. B. by equal other consumers currently operating on the network, such as B. train vehicles and industrial drives with leading edge control, be generated. A phase re determines for synchronization gelkreis, also known as phase locked loop (PLL), at least least the frequency and possibly the phase position of the on output signal. From this one can then become the fundamental vibration of the Input signal frequency synchronous and possibly phase synchronous system of sine or cosine vibrations generated will. This frequency and, if necessary, phase synchronous System is briefly referred to below as the phase reference system net.

As application examples for phase locked loops are in the range Power technology, network-controlled and self-commutated converters, in the field of traffic engineering four quadrant controllers from AC  Railway vehicles and in the area of measurement and control technology synchro to call function generators.

Frequency synchronization at least requires knowledge the frequency corresponding to the change in phase over time speaks. For the possible phase synchro is only the initial value of the phase position the fundamental of the input signal. Phase re gel circles based on zero crossing detection are z. B. in the book "semiconductor circuit technology" by U. Tietze and Ch. Schenk, Springer-Verlag, Berlin-Heidelberg, im Section "26.4. Follow-up synchronization (PLL)" is described. These synchronization methods attempt zero passages of the input signal and the one to be synchronized Detect signal and from the time interval of the Zero crossings provide information about the phase relationship of both To get signals. Such synchronization methods are problematic with relatively distorted input signal, because then basically several zero crossings per period of the on can occur. Signaloff also falsify sets the phase information strong.

Furthermore, phase locked loops are known which are based on sawtooth shaped phase signals are based. With these synchronizations Differentiation becomes a virtual imagination Närteil to the single-phase input signal formed, d. H. it z. B. formed the cosine to the sine. From the entrance signal and the virtual imaginary part of the input signal can then the associated pointer and from it the phase position of the Input signal can be determined. The phase signal corresponds  a sawtooth, the period of which is that of Corresponds to the input signal and its instantaneous value corresponds to the au corresponds to the current phase position of the input signal. The Reference phase system is usually called sine wave and Cosine vibration of a likewise sawtooth-shaped reference phase sensignals formed, which then by a controller on the Pha position of the input signal is synchronized. Problema In this process, the algebraic sign is particularly important change of the control deviation between the phase position of the on output signal and the sawtooth-shaped reference phase signal, the always occurs when the phase of the input signal or the sawtooth-shaped reference phase signal has the value 180 ° is enough and then jumps to -180 °. The syn chronization with a strongly distorted input signal Pro bleme, so by bandpass filtering first the reason vibration of the input signal must be determined. Because of the principally variable frequency of the input signal must the bandpass parameters are adjusted depending on the frequency, which greatly increases the implementation effort.

The object of the present invention is therefore to provide a simple ches procedure for the synchronization of a phase locked loop and to specify a suitable device for this.

The task is invented for a phase-synchronous control accordingly solved by a method according to claim 1. A Device for carrying out the method according to claim 1 is the subject of claim 5. For a phase and fre The task according to the invention is synchronous control  solved by a method according to claim 2. One for this suitable device is described in claim 6.

In the method of claim 1, which is a phase synchronous Control describes is from an input signal by Mul tiplication with a cosine, phase synchronous target size and subsequent smoothing a correlation signal averages that is proportional to the correlation between the on output signal and the target variable. The formation of the correlati onssignals occurs according to claim 5 in a phase error end tector, the smoothing of the correlation signal in front partially done by a low-pass filter. From the Correlation signal is through proportional gain and In tegration generates a phase correction signal. The phase regulator the device according to claim 5 points to this purpose have a PI controller.

In the method according to claim 1, the phase correction signal used as a reference phase signal. According to an ex staltung of the method according to claim 3, the reference phase sensignal from a phase pilot signal and the phase cor rectified signal determined, from the known nominal frequency of the input signal by integrating a phase precontrol gnal is formed.

If the method according to claim 3 with the device according to Claim 7 performed, then the integration of Nominal frequency of the input signal in an integrator, before preferably in a sawtooth generator, and that is formed from it te phase pilot signal is together with the phase correction  tursignal fed to an adder to the corrected Pha to receive pilot control signal.

The reference phase signal is used in the method according to An saying 1 a sinusoidal, phase-synchronous target variable as well a cosine-shaped, phase-synchronous target variable is formed. The Both phase-synchronous target variables are formed in accordance with An saying 5 in a sine / cosine generator, where the cosine shaped target, which is used to form the correlation signal is used, is returned to the phase error detector.

In the inventive method according to claim 2, the one describes phase and frequency synchronous control if from an input signal by multiplication by one cosine-shaped, phase-synchronized target variable and subsequent Smoothing a correlation signal that is proportional for the correlation between the input signal and the target variable is. If the method according to claim 2 with a Vorrich tion performed according to claim 6, then serves for education a phase error detector of the correlation signal, which in turn preferably uses a low-pass filter for smoothing having.

The correlation signal becomes proportional gain generates a phase correction signal. According to claim 2 he Required proportional gain occurs with a pre Direction according to claim 6 in the phase controller, the one for this P controller or a PI controller.  

In the method according to claim 2, the phase correction signal through proportional gain and integration Frequency correction signal generated and from the frequency correction tursignal formed a frequency pilot signal as a target. If the device according to claim 6 for performing the Method used according to claim 2, then the Bil the frequency pilot signal in a frequency controller, the one PI controller for proportional gain and integra tion of the phase correction signal contains, from the Fre frequency correction signal is a frequency precontrol signal as the target variable esse is formed.

According to an embodiment of the method according to claim 4 the frequency precontrol signal from the frequency correction signal and the known nominal frequency of the input signal will. Is for the method according to claim 4 with the front direction carried out according to claim 8, then is in the fre Sequence controller from the phase correction signal through proportional amplification and integration of a frequency correction signal testifies and from the frequency correction signal and the known The nominal frequency of the input signal becomes a frequency feedforward signal formed as a target.

In the method according to claim 2, the Frequency pilot signal by integrating a phase pilot first signal generated. From the phase pilot signal and the Pha correction signal is then a reference phase signal telt. The generation of the phase pilot signal from the Fre pre-control signal and the determination of the reference phase i gnals takes place in the device according to claim 6 in one  Phase pre-control, the integration of the frequency pre control signal in an integrator, preferably in a Sä tooth generator, and to determine the reference phases signals from the phase pilot signal and the phase correction tursignal serves an adder.

From the phase pilot signal is a si according to claim 2 nus-shaped, phase and frequency synchronous target as well as egg ne cosine-shaped, phase and frequency synchronous target variable educated. Is used to carry out the procedure according to An saying 2 uses the device according to claim 6, then he follows the formation of the two phase and frequency synchronous Target values in a sine / cosine generator.

In the method according to claim 2, the reference phases signal also a cosine-shaped, phase-synchronous target variable formed, which is used to form the correlation signal. The The cosine-shaped, phase-synchronous target is used for the pre direction according to claim 6 in a cosine generator telt and returned to the phase error detector.

Both in the method according to claim 1 and in the A method according to claim 2 gives a phase control, with the smoothing effect of the correlation calculation safe even with a strongly distorted input signal synchronized to the fundamental of the input signal becomes. Because of the simplicity of the two methods, you can in principle, this is implemented both analog and digital will. In addition, both are methods according to the invention due to its simplicity both as a software solution and  can also be implemented as a hardware solution. The procedure according to Claim 1 represents a direct phase control, which against over a phase and frequency regulation faster and is more stable. The method according to claim 2 additionally has for direct phase control also a control of the phase the frequency on. The dynamic properties of this ver driving correspond to those of the direct phase control, the sinusoidal phase and frequency synchronous target values as well the cosine, phase and frequency synchronous target size Beyond that, even with a strongly distorted input signals and quickly set phase controllers almost ideal distortion free.

The control method according to claims 3 and 4 indicate there by that from the known nominal frequency of the input signal a phase or frequency pilot signal is formed, ge compared to the method of claim 1 and 2 an improved Dynamic on.

To further explain the invention, reference is made to the drawing Reference is made in the two embodiments of a front Direction for performing the synchronization process a phase locked loop are explained. Show it:

Fig. 1 shows a vector diagram of the phase reference system at the beginning of the synchronization,

FIG. 2 shows a vector diagram of the phase reference system according to FIG. 1 after synchronization has ended,

Fig. 3 shows a device for carrying out the method according to an embodiment according to claim 1,

Fig. 4 shows a device for performing the method according to an embodiment according to claim 2.

In Fig. 1, the starting situation at the beginning of the synchronization is shown. The phase reference system of an input signal S, consisting of the sinusoidal oscillation S _x and the cosine oscillation S _y (shown in FIG. 1 as well as the input signal S as a pointer), generally has a different frequency and phase position than the input signal S. Target one Synchronization is to regulate the phase error angle ε between the input signal S and the sinusoidal, phase-synchronous target variable S _x to zero, which results in the pointer image shown in FIG. 2. The sinusoidal oscillation S _x is then in phase with the fundamental oscillation of the input signal S and the cosine oscillation S _{y leads} the fundamental oscillation of the input signal S by 90 °, so it is also in phase with the fundamental oscillation of the input signal S and is orthogonal to the fundamental oscillation of the input signal S.

The device according to FIG. 3, which enables the method according to claim 3 to be carried out, comprises a phase error detector 1 , a phase controller 2 and a phase pre-control 3 and a sine / cosine generator 4 .

An input signal S and a cosine-shaped, phase-synchronous target variable S _{y are} fed to the phase error detector 1 . In the phase error detector 1 , the input signal S is multiplied by the cosine-shaped, phase-synchronous target variable S _y in a multiplier 11 . The input signal S is multiplied by a cosine-shaped variable because the input signal S is a sinusoidal variable which is generally subject to harmonics. The product of the input signal S and that of the cosine-shaped, phase-synchronous target variable S _y is then fed to a low-pass filter 12 for smoothing. At the output of the phase error detector 1 is therefore a smoothed product, which is formed from the input signal S and the cosine-shaped, phase-synchronous target variable S _y , which is orthogonal to the input signal S. The smoothed product is referred to as the correlation signal K _sy and is proportional to the correlation between the input signal S and the cosine-phase-synchronous target variable S _y . Due to its proportionality to the phase error, the correlation signal K _sy is a measure of the phase error and thus of the phase error angle ε. The correlation becomes zero if and only if the cosine-shaped target variable S _{y is} orthogonal to the input signal S.

The correlation signal K _sy is then fed to the phase controller 2 . In phase controller 2 , a phase correction signal Δϕ _{PLL is} generated by proportional amplification and integration by a PI controller 21 . This phase correction signal Δϕ _PLL is fed to the phase pre-control 3 .

In the embodiment shown in FIG. 3, the phase precontrol 3 is also advantageously supplied with the known nominal frequency f _{nominal of} the input signal S. In the phase precontrol 3 , a sawtooth-shaped phase pilot signal ignal _{PLL is} formed from the nominal frequency f _nominal by integration in an integrator 31 , which is preferably designed as a sawtooth generator. The phase pilot signal ϕ _PLL is supplied to an adder 32 together with the phase correction signal Δϕ _PLL . In the adder 32 is obtained from the _PLL Phasenvorsteu ersignal φ and the phase correcting signal Δφ _PLL a reference phase signal φ _PLL formed. This correction of the phase pre-control signal ϕ _PLL by the phase correction signal Δϕ _PLL in the phase pre-control 3 leads to the reference phase signal ϕ ' _{PLL being} phase-synchronous with the input signal S.

The reference phase signal ϕ ' _PLL , which has the value zero at the start of the synchronization, is fed to the downstream sine / cosine generator 4 . The sine / cosine generator 4 consists essentially of a sine generator 41 and egg nem arranged parallel to this cosine generator 42nd In the sine generator 41 , the formation of the sinusoidal, phase-synchronous target variables S _{x takes place} , whereas in the cosine generator 42 the cosine-shaped, phase-synchronous target variable S _y ge is formed. The two target variables S _x and S _y describe the phase reference system sought. The cosine-shaped, phase-synchronous target variable S _{y also} serves to form the correlation signal K _sy and is supplied to the multiplier 11 of the phase error detector 1 for this purpose.

The cosine-shaped target variable S _y is a cosine oscillation which is initially not in phase with the input signal S and which also has a different frequency than the input signal S. At the start of the control process - the reference phase signal ϕ ' _PLL has the value zero at this point in time - the target variable S _{x has} the value zero and the target variable S _{y has} the value one.

The phase correction signal Δϕ _PLL determined in the phase controller 2 has the value zero if the frequency f _{s of} the input signal S is equal to the known nominal frequency f _{nominal of} the input signal S. If the frequency f _{s is} not equal to the frequency f _nominal , then the phase correction signal Δϕ _PLL is also not equal to zero.

The device shown in Fig. 3 thus enables a direct phase control, which is faster and more stable than a control of the phase via the frequency.

The apparatus according to the can be used for carrying out of the procedure according to claim 4 Fig. 4, comprises a phase error detector 1, a phase shifter 2, a phase precontrol 3, a frequency controller 5, and a sine / cosine generator 6, and a cosine generator 7 .

The phase error detector 1 of the device according to FIG. 4 corresponds to the phase error detector shown in FIG. 3. The correlation signal K _sy is thus formed as in the device described in FIG. 3. The correlation signal K _sy formed in the phase error detector 1 is fed to a phase controller 2 , which this time, however, only comprises one P controller 22 . In phase controller 2 , a phase correction signal Δϕ _PLL is thus generated from the correlation signal K _sy by proportional amplification. This phase correction signal Δϕ _PLL represents the measure of the frequency deviation and contains the control stroke of the phase controller 2 . The phase correction signal Δϕ _PLL is given on the one hand to the phase precontrol 3 and on the other hand to the frequency controller 5 .

A frequency correction signal Δf _{PLL is} generated in the frequency controller 5 from the phase correction signal Δϕ _PLL by proportional amplification and integration into a PI controller 51 . This frequency correction signal Δf _PLL is fed to an adder 52 . In this embodiment of the invention, the adder 52 is also advantageously supplied with the known nominal frequency f _{nominal of} the input signal S. A frequency pilot signal f _{PLL is} formed in the adder 52 from the frequency correction signal Δf _PLL and the known nominal frequency f _{nominal of} the input signal S. The frequency pilot signal f _PLL is one of the target variables and is therefore coupled accordingly, on the other hand, the frequency pilot signal f _{PLL is} supplied to the phase pilot 3 .

The frequency pre-control signal f _PLL generated in the frequency controller 5 corresponds in the adjusted state, which is characterized in that the phase correction signal Δϕ _PLL generated in the phase controller 2 becomes zero, to the sought frequency f _{s of} the input signal S.

In the phase pre-control 3 is from the Frequenzvorsteuersi gnal f _PLL by an integrator, the saw tooth generator is preferably configured as a saw-tooth phase pilot signal φ _PLL formed, on the one hand in the phase 3 to an adder 32 and the feedforward control on the other hand a sine / cosine -Generator 6 is supplied.

A reference phase signal ein ' _PLL is formed in the adder 32 from the phase pilot signal ϕ _PLL and the phase correction signal Δϕ _PLL .

In the sine / cosine generator 6 , a sinusoidal, phase and frequency synchronous target variable S ' _x and a cosine, phase and frequency synchronous target variable S' _{y are} formed from the phase pilot signal ϕ _PLL . The sinusoidal target variable S ' _x has the value zero at the start of the control process, whereas the cosine-shaped target variable S' _{y has} the value one at the start of the control process.

In the case of a strongly distorted input signal S, the correlation signal K _sy also contains a certain amount of distortion, which is disruptively reproduced in the cosine-shaped, phase-synchronous target variable S _y via the P channel of the phase controller 2 . Therefore, the phase and frequency synchronous target variables S ' _x and S' _{y are formed} from the phase pilot signal ϕ _PLL , which was coupled out of the phase pilot 3 after integration in the integrator 31 . The phase pilot signal ϕ _PLL is chosen because it contains the distortion component of the correlation signal K _sy only to a greatly weakened extent. The target variables S ' _x and S' _y are therefore almost ideally sinusoidal or cosine-shaped, the target variables S ' _x and S' _{y being} in phase with the fundamental oscillation of the input signal S and the target variable S ' _y also being orthogonal to the fundamental oscillation of the input signal S. is.

In the device according to FIG. 4, the phase controller 2 initially only ensures that the desired target variable S ' _{x is} sinusoidal and is in phase with the fundamental oscillation of the input signal S (see FIG. 2). The phase precontrol signal ϕ _PLL is then not necessarily the same as the frequency f _{s of} the input signal S which is also sought. The difference between the frequency precontrol signal f _PLL and the frequency f _{s of} the input signal S can, however, be seen from the phase correction signal Δϕ _PLL , which is is a permanent manipulated variable of the phase controller 2 .

The reference phase signal ϕ ' _PLL formed in the phase precontrol 3 , which has the value zero at the beginning of the synchronization, is supplied to the cosine generator 7 to form a cosine-phase-synchronous target variable S _y . The ko sinusoidal, phase-synchronous target variable S _y is used to form the correlation signal K _sy and is supplied to the multiplier 11 of the phase error detector 1 for this purpose.

The device according to FIG. 4 thus additionally enables the phase to be regulated via the frequency. Such a method achieves the dynamic properties of the direct phase control, the sinusoidal phase and frequency synchronous target variable S ' _x and the cosine, phase and frequency synchronous target variables S' _y are even with a strongly distorted input signal and a quickly set phase controller 2 almost ideally distortion-free.

Claims (8)

1. A method for synchronizing a phase-locked loop, which comprises the following features:

• - From an input signal (S) by multiplication with a cosine-shaped, phase-synchronous target variable (S _y ) and subsequent smoothing, a correlation signal (K _sy ) is determined, which is proportional to the correlation between the input signal (S) and the cosine-shaped, phase-synchronous target variable ( S _y ) is
• a phase correction signal (Δϕ _PLL ) is generated from the correlation signal (K _sy ) by proportional amplification and integration,
• - The phase correction signal (Δϕ _PLL ) is used as the reference phase signal (ϕ ' _PLL ),
• - From the reference phase signal (ϕ ' _PLL ) a sinusoidal, phase-synchronous target variable (S _x ) and a cosine-shaped, phase-synchronous target variable (S _y ) are formed, the cosine-shaped, phase-synchronous target variable (S _y ) being used to form the correlation signal (K _sy ) .

2. A method for synchronizing a phase-locked loop, which comprises the following features:

• - From an input signal (S) by multiplication with a cosine-shaped, phase-synchronous target variable (S _y ) and subsequent smoothing, a correlation signal (K _sy ) is determined, which is proportional to the correlation between the input signal (S) and the cosine-shaped, phase-synchronous target variable ( S _y ) is
• a phase correction signal (Δϕ _PLL ) is generated from the correlation signal (K _sy ) by proportional amplification and integration,
• - A frequency correction signal (Δf _PLL ) is generated from the phase correction signal (Δϕ _PLL ) by proportional amplification and integration,
• a frequency precontrol signal (f _PLL ) is formed as a target variable from the frequency correction signal (Δf _PLL ),
• a phase pilot signal (ϕ _PLL ) is still generated from the frequency _pilot signal (f _PLL ) by integration,
• - a reference phase signal (ϕ ' _PL L) is determined from the phase pilot signal (ϕ _PLL ) and the phase correction signal (Δϕ _PLL ),
• - From the phase pilot signal (ϕ _PLL ) a sinusoidal, phase and frequency synchronous target variable (S ' _x ) and a cosine, phase and frequency synchronous target variable (S' _y ) are formed and
• - From the reference phase signal (ϕ ' _PLL ) a cosine-shaped, phase-synchronous target variable (S _y ) is formed, which is used to form the correlation signal (K _sy ).

3. A method for synchronizing a phase-locked loop according to claim 1, comprising the following features:

• - The reference phase signal (ϕ ' _PL L) is determined from a phase control signal (ϕ _PLL ) and the phase correction signal (Δϕ _PLL ), wherein
• - From the known nominal frequency (f _nominal ) of the input signal (S) by integration, a phase pilot signal (ϕ _PLL ) is formed.

4. A method for synchronizing a phase-locked loop according to claim 2, comprising the following feature:

• - The frequency _precontrol signal (f _PLL ) is formed from the frequency correction signal (Δf _PLL ) and the known nominal frequency (f _nominal ) of the input signal (S).

5. Apparatus for performing the method according to claim 1, comprising the following features:

• - A phase error detector ( 1 ) in which a correlation signal (K _sy ) is determined from an input signal (S) by multiplication with a cosine-shaped, phase-synchronous target variable (S _y ) and subsequent smoothing, which is proportional to the correlation between the input signal (S ) and the cosine-shaped, phase-synchronous target variable (S _y ),
• - A phase controller ( 2 ) in which a phase correction signal (Δϕ _PLL ) is generated from the correlation signal (K _sy ) by proportional amplification and integration, which serves as a reference phase signal (ϕ ' _PLL ),
• - A sine / cosine generator ( 4 ), in which a sinusoidal, phase-synchronous target variable (S _x ) and a cosine-shaped, phase-synchronous target variable (S _y ) is formed from the reference phase signal (ϕ ' _PLL ), the cosine-shaped phase-synchronous target variable ( S _y ) to form the correlation signal (K _sy ) the phase error detector ( 1 ) is supplied.

6. Apparatus for performing the method according to claim 2, comprising the following features:

• - A phase error detector ( 1 ) in which a correlation signal (K _sy ) is determined from an input signal (S) by multiplication with a cosine-shaped, phase-synchronous target variable (S _y ) and subsequent smoothing, which is proportional to the correlation between the input signal (S ) and the cosine-shaped, phase-synchronous target variable (S _y ),
• - A phase controller ( 2 ) in which a phase correction signal (Δϕ _PLL ) is generated from the correlation signal (K _sy ) by proportional amplification,
• - a frequency controller (5), in the signal from the phase correction (Δφ _PLL) by proportional amplification and integration of a frequency correction signal (.DELTA.f _PLL) is generated, and is formed in the from the frequency correction signal (.DELTA.f _PLL) a Frequenzvor control signal (f _PLL) as the target size ,
• - A phase feedforward control ( 3 ) in which a phase feedforward control signal (ϕ _PLL ) is generated by integration from the frequency feedforward control signal (f _PLL ) and in which a reference phase signal (ϕ.) from the phase feedforward control signal (ϕ _PLL ) and the phase correction signal (Δϕ _PLL ) ' _PLL ) is determined
• - A sine / cosine generator ( 6 ) in which a sinusoidal, phase and frequency-synchronous target variable (S ' _x ) and a cosine, phase and frequency-synchronous target variable (S' _y ) are formed from the phase pilot signal (ϕ _PLL ) becomes,
• - A cosine generator ( 7 ) in which a cosine-shaped, phase-synchronous target variable (S _y ) is formed from the reference phase signal (ϕ ' _PLL ), which is fed to the phase detector ( 1 ).

7. The apparatus of claim 5, comprising:

• - A phase precontrol ( 3 ) in which a phase precontrol signal (L _PLL ) is formed from the known nominal frequency (f _nominal ) of the input signal (S) by integration and in which the phase precontrol signal (ϕ _PLL ) and the phase correction signal (Δϕ _PLL ) a reference phase signal (ϕ ' _PLL ) is determined.

8. The apparatus of claim 6, comprising:

• - In the frequency controller ( 5 ), a frequency correction signal (Δf _PLL ) is generated from the phase correction signal (Δϕ _PLL ) by proportional amplification and integration, and the frequency correction signal (Δf _PLL ) and the known nominal frequency (f _nominal ) of the input signal (S) becomes a frequency precontrol signal (f _PLL ) as a target.