CN107887909B - Time delay matching power system stabilizer and design method thereof - Google Patents

Abstract

The invention discloses a time delay matching power system stabilizer which is formed by sequentially connecting a blocking filter module W, a feedback gain module K, a time delay matching module T and an output amplitude limiting module B in series, wherein an input signal of the time delay matching module T is from a Phasor Measurement Unit (PMU) of a power system, and an output signal of the time delay matching module T is input into a power system stability regulation and control device. The invention also relates to a design method of the time delay matching power system stabilizer, which can determine the parameters of the time delay matching power system stabilizer according to the characteristic root of the controlled oscillation mode, the amplitude and the phase of the corresponding residue of the characteristic root and the actual time delay of the control loop, and the total time delay of the feedback loop reaches the optimal value through the time delay matching, thereby obtaining the optimal stable control effect.

Description

Time delay matching power system stabilizer and design method thereof

Technical Field

The invention relates to the technical field of power system stabilization and control, in particular to a novel time delay matching power system stabilizer and a design method thereof.

Background

With the integration of renewable energy sources such as solar energy, wind energy, biomass energy and the like, and more electric vehicles and energy storage elements, the scale of modern power systems is continuously enlarged in order to meet the requirements of energy transmission and efficiency improvement. In order to solve the stability problem of a large-scale power System, it is necessary to apply a Wide-area measurement System (WAMS) in power System stability control. However, in the engineering application of Wide-area power system Stabilizer (WAPSS), the inherent delay of WAMS is an unavoidable problem, and the influence of the delay needs to be considered when designing PSS. If the controller is designed based on the assumption of no time delay, the time delay in the system will affect the stability of the system, so in recent years, many researchers have adopted some control theories with time delay to design the WAPSS, and it is expected that a better damping effect is obtained. In addition, researchers think that compensating for the time delay before adopting a control method without time delay is also a feasible research idea. However, if this method is adopted, the number of compensation modules increases with the increase of the time lag, and the control structure becomes more complicated. Furthermore, if there is a large delay in the closed-loop control, it becomes difficult to accurately predict the feedback control signal of the Phasor Measurement Unit (PMU).

In fact, the delay does not have a completely negative impact on the system stability. The phase lag caused by the signal delay is substantially the same as the phase offset in the system transfer function, and both will generate a phase difference between the input signal and the output signal, and even have some complementarity when the system phase deviation is advanced. In the control theory, if the matched time delay is added to the input signal, the effect of improving the system stability can be achieved, and the method is widely applied to the system damping control.

Disclosure of Invention

The present invention overcomes the above-mentioned shortcomings in the prior art, and provides a time delay matching power system stabilizer and a design method thereof.

The invention designs a novel Delay-matched power System Stabilizer DMPSS (Delay-MatchingPower System Stabilizer), which can overcome the defects of complex structure and complicated control method of the conventional PSS controller. The main differences between this new DMPSS and the classical PSS are: the delay matching module replaces a lead-lag module in a classical structure, additional delay is introduced into a controller through the delay matching module, so that the total delay of a control loop is optimal, and the damping effect is obviously improved under the condition that feedback gain is determined.

In order to achieve the technical aim, the technical scheme provided by the invention is as follows:

a time delay matching power system stabilizer DMPSS is characterized in that: the device is formed by sequentially connecting a blocking filter module W, a feedback gain module K, a time delay matching module T and an output amplitude limiting module B in series, wherein an input signal of the blocking filter module W is from a Phasor Measurement Unit (PMU) of the power system, and an output signal of the blocking filter module K is input into a stable regulation and control device of the power system; the transfer function T(s) of the delay matching module T is as shown in formula (1):

T(s)＝e^-sΔτ(1)

in the formula, s represents a complex variable, Δ τ represents a matching delay, and needs to be calculated and determined according to an actual system operation mode and a real-time delay of a control loop.

The design method of the time delay matching power system stabilizer comprises the following steps:

step 1: screening a control loop in a power system, wherein the screening comprises the steps of determining a Phasor Measurement Unit (PMU) signal input into a DMPSS, selecting a proper stable control actuator, and determining the actual Measurement time delay tau of the control loop under the normal working condition;

step 2: determining a dominant oscillation mode of the system, the characteristic root of which is lambda_jAnd calculating the corresponding residue R of the oscillation mode_jAmplitude of (2) | R_jAnd its phase angle ∠ R_jAnd ∠ R_jAt [0, 2 π]Within the range;

and step 3: setting the matching time delay delta tau of a time delay matching module T and a gain value K of a feedback gain module K in the DMPSS, wherein the specific mode is as follows:

step 31, determining a target value ξ of the damping coefficient, and calculating a characteristic value lambda of the oscillation mode according to the formula (2)_jAmount of change of

Δλ_j：

Δλ_j≈-ξω_j-σ_j(2)

Wherein sigma_jAnd ω_jAre each lambda_jThe real and imaginary parts of (c);

step 32: setting the matching time delay delta tau and the feedback gain value K, wherein the calculation method is as the following formulas (3) to (4):

if 2k pi is less than or equal to ∠ R_j-ω_jτ < (2k +1) π, then

If (2k +1) pi is less than or equal to ∠ R_j-ω_jτ < (2k +2) π, then

Wherein k is 0 or 1

And 4, step 4: further fine-tuning the matching time delay delta tau calculated in the step 3 to obtain an optimal damping effect;

and 5: and determining the parameters of the blocking filter module W and the output amplitude limiting module B according to a conventional method.

The invention has the advantages that: the time delay matching module replaces a lead-lag module in a classical structure, so that the structure of the controller and the design method thereof can be effectively simplified, the damping effect and the robustness of the system are improved, and the low-frequency oscillation can be effectively inhibited.

Drawings

Fig. 1 is a block diagram of a new england power system to which the time delay matched power system stabilizer of the present invention is applied.

Fig. 2 is a structural diagram of the delay matching power system stabilizer DMPSS of the present invention.

FIGS. 3a to 3b are dynamic characteristic change curves of the system before and after different control loops are connected to the DMPSS, wherein FIG. 3a is the active power (P) of the line L16-17_L17-16) Fig. 3b is the relative power angle (Δ δ) between the generators G5 and G10_5-10) A dynamic variation curve.

FIGS. 4 a-4 b illustrate the relative power angle (Δ δ) between generators G5 and G10 for different matching delays Δ τ_5-10) The comparison of the dynamic responses, fig. 4a and 4b, correspond to control loop 1 and control loop 3, respectively.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited to these examples. The present embodiment adopts a new england power system for simulation, the system includes 10 units, 39 buses and 46 lines, and the specific structure is shown in fig. 1. The system is used as a test standard and widely applied to small interference stability analysis and research of inter-area low-frequency oscillation. The effect of the method is tested by carrying out simulation analysis on the new England power system.

According to the technical scheme provided by the text, a structural framework of the DMPSS is determined and established, and the structure is formed by transfer functions

A dc blocking filter module W, a feedback gain module K with a transfer function of h(s) K, and a transfer function of t(s) e^-sΔτThe delay matching module T and the upper and lower output amplitude limiting modules B are connected in series in sequence, as shown in fig. 2.

According to the structural framework of the built DMPSS, a novel DMPSS for a new England power system is designed, and the method comprises the following specific steps:

step 1: a suitable control loop is screened in the power system of this embodiment, and the DMPSS design basic information in this embodiment is shown in table 1. Table 1 lists the basic information required for DMPSS design with three different control loops. Taking control loop 1 as an example, PMU signal is active power P of line between bus 5 and bus 8_L5-8The stable regulating device is a Static Var Compensator (SVC), and the time delay delta tau is under the normal working condition of the system₁＝0.15s。

TABLE 1 DMPSS design basis information

Control loop	PMU signals	Stable regulation and control device	Time delay(s)
				1	PL5-8	SVC	0.15
2	PL5-8	EXC4	0.25
				3	Δδ5-10	SVC	0.7

Step 2: through linearization and characteristic value analysis of the power system in the embodiment under the standard operation state, the characteristic root lambda of the dominant oscillation mode of the system can be determined_j-0.1679 ± 4.1683i, a damping coefficient of 0.0403, and an oscillation frequency of 0.66 Hz; calculating the transfer function of the linearized power system by small signal analysis, taking control loop 1 as an example, the residue R corresponding to the oscillation mode_jAmplitude of (2) | R_j10.50, its phase angle ∠ R_j＝1.49rad。

And step 3: according to the selected control loop, setting the matching time delay delta tau and the feedback gain value K of the DMPSS, taking the control loop 1 as an example, the specific implementation mode is as follows:

(a) calculating the variation Delta lambda of the characteristic value_jHere, the target damping coefficient ξ is 0.17, σ_jAnd ω_jAre each lambda_jReal and imaginary parts of:

Δλ_j≈-ξω_j-σ_j＝-0.17×4.1683+0.1679＝-0.3728

(b) according to the equations (3) to (4), the matching time delay Delta tau of the control loop 1 is set₁And a feedback gain value K, where_∑1To control the total delay, τ, of loop 1₁For the measured delay of the system:

Δτ₁＝τ_∑1-τ₁＝(∠R_j)/ω_j-τ₁＝0.21(s)

and 4, step 4: the parameters of the blocking filter block W and the output clipping block B are determined according to conventional methods, in this embodiment, the time constant T is determined_WThe clipping value is ± 0.05p.u, 5 s.

After the design of the DMPSS using the control loop 1 is completed, the parameters of the DMPSS corresponding to the control loops 2 and 3 can be calculated in the same manner according to the parameter tuning mode of the control loop 1, and are listed in table 2. On this basis, better damping is obtained by matching the fine tuning of the time delay Δ τ, the fine tuning values of Δ τ also being listed in table 2. And accessing the designed DMPSS into the power system, and detecting the control effect of the DMPSS. Specific parameters of DMPSS under different control loops and its control effect are shown in table 2. As can be seen from table 2, after the DMPSS designed by the control loop 1 and the control loop 3 is accessed into the system, the damping coefficient is significantly improved, and the control effect is better. With the control loop 2, the system damping coefficient is improved even if limited by the system stability.

TABLE 2 parameter tuning and control Effect of different control loops DMPSS

Control loop	τ(s)	Calculated value of Δ τ(s)	Delta tau trim value(s)	K	ξ	f(Hz)
							1	0.15	0.21	0.15	-0.04	0.1700	0.65
2	0.25	0.11	0.10	0.60	0.0821	0.66
							3	0.70	0.40	0.35	0.10	0.1654	0.52

In order to verify the effectiveness of the invention, the stability analysis of the power system after the DMPSS is accessed is also needed. The simulation embodiment tests the damping effect of the DMPSS in the control loop 1 and the control loop 3. Setting in simulation: when t is 1s, a three-phase short-circuit fault occurs in one line between the bus 16 and the bus 17, and the fault line is cut off after 0.1 s. FIGS. 3 a-3 b show the dynamic characteristic change of the system before and after different control loops are accessed to the DMPSSAnd (5) comparing the graph. After the fault is cut off, the active power P of another fault-free line between the bus 16 and the bus 17_L17-16Becomes 2 times the original power and the power oscillates significantly as shown in figure 3 a. As can be seen from fig. 3a to 3b, before DMPSS access, the line L is connected_16-17Active power P of_L17-16And the relative power angle (Δ δ) between generators G5 and G10_5-10) All oscillations of (2) exceed 15 s; after the DMPSS designed by the invention is accessed, the oscillation can be obviously inhibited within 5s, and the result of the simulation embodiment fully shows the effectiveness of the DMPSS designed by the invention.

Influence of matching time delay delta tau on system dynamic response as shown in fig. 4 a-4 b, when delta tau is different, relative power angle (delta) between generators G5 and G10_5-10) The oscillation curves are clearly different. After the control loop 1 is accessed to the designed DMPSS in fig. 4a, when Δ τ is set to 0.15s, i.e. the optimal value of the matching delay of the control loop 1, the damping effect of the DMPSS is the best; when the delta tau is 0.00s or 0.35s, the DMPSS still has better damping effect. Fig. 4b shows that when Δ τ is 0.00s, i.e. deviates far from its optimal value of 0.35s, the system will lose stability after control loop 3 accesses the designed DMPSS. Fig. 4a to 4b further illustrate the effectiveness and accuracy of the matching delay Δ τ set by the method.

The invention designs a novel time delay matching power system stabilizer, replaces a lead-lag module in a classical structure with a time delay matching module, and provides a method for complementary design of feedback gain and matching time delay, thereby not only effectively simplifying the structure of a controller and the design method thereof, but also improving the damping effect and the robustness of a system. The invention is applied to a new England power system in a simulation way, and the result shows that the invention has better inhibiting effect on the active power of the power system and the low-frequency oscillation of the relative power angle of the generator.

The embodiments described in this specification are merely illustrative of implementations of the inventive concept and the scope of the present invention should not be considered limited to the specific forms set forth in the embodiments but rather by the equivalents thereof as may occur to those skilled in the art upon consideration of the present inventive concept.

Claims (1)

1. The design method of the time delay matching power system stabilizer comprises the steps that input signals of the time delay matching power system stabilizer are from a Phasor Measurement Unit (PMU) of a power system, output signals of the time delay matching power system stabilizer are input into a power system stability regulation and control device, and the time delay matching power system stabilizer is formed by sequentially connecting a DC blocking filter module W, a feedback gain module K, a time delay matching module T and an output amplitude limiting module B in series; the transfer function T(s) of the delay matching module T is as shown in formula (1):

T(s)＝e^-s△τ(1)

wherein s represents a complex variable, and Δ τ represents a matching time delay, which needs to be calculated and determined according to an actual system operation mode and a control loop real-time delay;

the method is characterized in that: the method comprises the following steps:

step 1: screening a control loop in a power system, wherein the screening comprises the steps of determining a Phasor Measurement Unit (PMU) signal input into a DMPSS, selecting a proper stable control actuator, and determining the actual measurement time delay tau of the control loop under the normal working condition;

step 2: determining a dominant oscillation mode of the system, the characteristic root of which is lambda_jAnd calculating the corresponding residue R of the oscillation mode_jAmplitude of (2) | R_jAnd its phase angle ∠ R_jAnd ∠ R_jAt [0, 2 π]Within the range;

and step 3: setting the matching time delay delta tau of a time delay matching module T in the DMPSS and a gain value K of a feedback gain module (K), wherein the specific mode is as follows:

step 31, determining a target value ξ of the damping coefficient, and calculating a characteristic value lambda of the oscillation mode according to the formula (2)_jChange amount of (a) λ_j：

△λ_j≈-ξω_j-σ_j(2)

Wherein sigma_jAnd ω_jAre each lambda_jThe real and imaginary parts of (c);

step 32: setting the matching time delay delta tau and the feedback gain value K, wherein the calculation method is as the following formulas (3) to (4):

if 2k pi is less than or equal to ∠ R_j-ω_jτ<(2k +1) pi, then

If (2k +1) pi is less than or equal to ∠ R_j-ω_jτ<(2k +2) pi, then

Wherein k is 0 or 1

And 4, step 4: further fine-tuning the matching time delay delta tau calculated in the step 3 to obtain an optimal damping effect;

and 5: and determining parameters of the blocking filtering module W and the output amplitude limiting module B.

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