CN103236709A - Method for coordinating and optimizing small-interference and large-disturbance damping of alternating-current and direct-current sending-end unit - Google Patents

Abstract

The present invention provides a small-disturbance and large-disturbance damping coordination optimization method for AC/DC sending-end units, including the following steps: (1). Constructing a stability analysis model of AC-DC hybrid sending-end power grid; (2). Quantitatively evaluating hybrid Oscillation damping characteristics of small disturbance and large disturbance in power grid; (3). Determine the adjustable range of PSS parameters that meet the requirements of small disturbance oscillation damping; (4). Analysis of the suppression effect of PSS parameters on large disturbance oscillation; (5) Small disturbance and large disturbance PSS type selection and parameter optimization for coordinated disturbance oscillation damping. The PSS coordination optimization method for the small disturbance and large disturbance oscillation damping of the AC/DC hybrid sending-end unit provided by the present invention can improve the ability of the DC sending-end system to withstand the impact of faults, and improve the safe and stable operation level of the power grid.

Description

Coordinated optimization method for small disturbance and large disturbance damping of AC/DC sending-end units

technical field

The invention belongs to the field of electric power systems, and in particular relates to a small-disturbance and large-disturbance damping coordination optimization method for an AC/DC transmission unit.

Background technique

my country's primary energy and load centers are distributed in reverse, and water energy resources are mainly distributed in the southwest region; coal resources are mainly distributed in Shanxi, Shaanxi and Xinjiang and other northwest regions; wind and solar energy resources are mainly distributed in Gansu, Qinghai, Xinjiang and other regions. In order to meet the continuously growing energy demand of load centers in the central and eastern regions, to build a "resource-saving and environment-friendly" society, and to realize the optimal allocation of resources across regions, the development of UHV DC large-capacity transmission technology is an inevitable choice.

Centralized development of energy bases, and direct transmission of power to load centers through UHV DC, is a cost-effective way of energy development and transmission. In order to improve the stable operation capability of the sending-end unit, the energy base is usually connected to the sending-end AC main network through a weak AC channel. According to the requirements of the "State Grid Corporation of Power System Safety and Stability Calculation Regulations", the small disturbance oscillation damping of the sending unit should be greater than 0.03, and the large disturbance oscillation damping should be greater than 0.015, so as to ensure that the power grid is under disturbances of different degrees such as load fluctuations and short-circuit fault impacts. Able to quickly restore stable operation. The generator at the sending end is equipped with a power system stabilizer PSS, which is an effective means to enhance the oscillation damping of the disturbed unit, and the relevant requirements of oscillation damping can be met through reasonable parameter setting.

Since UHVDC has the characteristics of large power transmission capacity, strong nonlinearity, and high degree of AC-DC coupling correlation, under the impact of large disturbance faults such as short circuits, the oscillation damping of the AC-DC hybrid sending unit will have a large difference from the small disturbance oscillation damping. difference. Therefore, the PSS parameter configuration should not only meet the requirements of small disturbance oscillation damping, but also be able to effectively suppress the adverse effects of AC and DC interaction on the subsequent oscillation damping of large disturbances, and ensure that the oscillation damping of large disturbances is greater than 0.015.

Contents of the invention

In order to overcome the above defects, the present invention provides a coordinated optimization method for the small disturbance and large disturbance damping of the AC/DC sending-end unit. From the perspectives of the small disturbance and large disturbance damping of the AC-DC hybrid sending unit, the PSS selection of the unit is coordinated and optimized. The model and parameters can improve the stable operation capability of the sending power grid and ensure the smooth implementation of the optimal allocation of cross-regional resources.

In order to achieve the above object, the present invention provides a PSS optimization method for coordinating small disturbance and large disturbance oscillation damping of the AC/DC hybrid sending unit. The improvement is that the method includes the following steps:

(1). Construct the stability analysis model of the AC-DC hybrid transmission grid;

(2). Quantitatively evaluate the small disturbance and large disturbance oscillation damping characteristics of the hybrid power grid;

(3). Determine the adjustable range of PSS parameters that meet the small disturbance oscillation damping requirements;

(4). Analysis of the suppression effect of PSS parameters on large disturbance oscillations;

(5) PSS type selection and parameter optimization for coordinated oscillation damping of small disturbances and large disturbances.

In the preferred technical solution provided by the present invention, in the step 1, data is collected, and a model adapted to the small disturbance and large disturbance stability analysis of the AC/DC hybrid transmission grid is constructed.

In the second preferred technical solution provided by the present invention, the data includes: AC-DC hybrid sending end grid structure, AC-DC channel transmission power, load level, generator and its exciter and governor, DC transmission system and control system The data.

In the third preferred technical solution provided by the present invention, in the step 2, various typical normal operation modes of the AC/DC hybrid transmission grid are established; the frequency-domain characteristic root scan program with small interference is used to calculate the mixed Oscillation damping of small disturbances in the sending-end unit of the connected grid; using the transient time-domain simulation program to calculate the transient time-domain response of the hybrid power grid under large disturbances.

In the fourth preferred technical solution provided by the present invention, the normal operation mode includes summer heavy load mode, summer small load mode, winter heavy load mode, winter small load mode, and equipment maintenance mode.

In the fifth preferred technical solution provided by the present invention, the AC electrical quantity fluctuates greatly under large disturbances, and the DC dynamic characteristics will show strong nonlinearity. Due to the nonlinear factor of DC, the large disturbance damping will significantly reduce the small disturbance damping.

If under different operating modes, the small disturbance oscillation damping of the AC/DC hybrid sending unit is greater than 0.03, and the oscillation damping after various large disturbance faults is greater than 0.015, both meet the requirements, and there is no need to optimize the PSS type and parameters; Otherwise, optimize the PSS type and parameters, so that the small disturbance and large disturbance oscillation damping can meet the requirements at the same time.

In the sixth preferred technical solution provided by the present invention, in the step 3, the gain coefficient, phase lead and lag parameters of the PSS are adjusted in equal proportions respectively, and the characteristic root change track of the small disturbance oscillation of the sending unit is drawn, and determined according to the change track The parameter adjustable range meets the requirement that the damping ratio is greater than 0.03.

In the seventh preferred technical solution provided by the present invention, in the step 4, within the adjustable range of PSS parameters, the gain coefficient, phase lead and lag parameter combinations are selected at equal intervals to verify the improvement of the large disturbance oscillation damping characteristics; if The large-disturbance oscillation damping can be increased to 0.015, then the PSS parameter is the PSS coordinated optimization scheme for the small-disturbance and large-disturbance oscillation damping of the AC/DC hybrid sending unit.

In the eighth preferred technical solution provided by the present invention, in step 5, if the large disturbance oscillation damping cannot be increased to 0.015 within the adjustable range of PSS parameters, the type of PSS needs to be optimized; for the newly selected PSS , repeat steps 2 to 4, optimize the gain coefficient, phase lead and lag parameters of the PSS, so that the small disturbance damping ratio is greater than 0.03 and the large disturbance oscillation damping is greater than 0.015; if the damping ratio can be satisfied at the same time, then the PSS type and parameter, that is, the PSS coordinated optimization scheme for the small disturbance and large disturbance oscillation damping of the AC/DC hybrid sending unit; if the damping ratio requirement still cannot be met, select the large disturbance within the parameter adjustable range where the small disturbance damping ratio is greater than 0.03 A set of parameters with relatively large oscillation damping is used as a coordinated optimization scheme, and corresponding machine cut-off measures are configured in the AC system to cooperate with suppressing the oscillation of the sending-end unit after a large disturbance fault.

In the ninth preferred technical solution provided by the present invention, the preferred PSS type includes: input signal type and transfer function logic structure.

Compared with the prior art, the present invention provides a coordinated optimization method for the small disturbance and large disturbance damping of the AC/DC sending unit, which can effectively suppress the large disturbance UHV DC abnormality while the sending unit has strong small disturbance damping. Linear dynamics have an unfavorable effect on oscillation damping, speeding up oscillation subsidence. The proposed method is used to improve the safe and stable operation level of the UHV DC sending-end power grid and the UHV large-capacity stable power transmission capability.

Description of drawings

Figure 1 shows the PSS optimization process for coordinating the small disturbance and large disturbance damping of the AC/DC hybrid sending unit.

Figure 2 shows the SG type PSS with generator electromagnetic power deviation as input.

Figure 3 shows the divergent oscillation response of the Fufeng UHVDC sending end under large disturbances.

Figure 4 shows the effect of the SG gain coefficient on the root locus.

Figure 5 shows the effect of SG-type lead parameters on the root locus.

Figure 6 shows the effect of SG-type lag parameters on the root locus.

Figure 7 shows the effect of SG type lag parameters on the root locus.

Figure 8 shows the S1 type PSS which takes the combination of generator electromagnetic power deviation and rotational speed deviation as input.

Figure 9 shows the effect of the S1 type PSS gain coefficient on the root locus.

Figure 10 shows the effect of the S1 type PSS gain on the transient response to large disturbances.

Detailed ways

A coordinated optimization method for small-disturbance and large-disturbance damping of AC/DC sending-end units, which is used to suppress the adverse effects of DC nonlinear characteristics on large-disturbance oscillation damping, and improve the stable operation level of UHV DC sending-end units in large-capacity energy bases.

As shown in Figure 1, a coordinated optimization method for small disturbance and large disturbance damping of AC/DC sending-end units, under the condition of ensuring strong damping of small disturbances, suppresses the adverse effects of DC nonlinear dynamic characteristics on large disturbance oscillation damping. The method includes the following steps:

(1). Construct the stability analysis model of the AC-DC hybrid transmission grid;

(2). Quantitatively evaluate the small disturbance and large disturbance oscillation damping characteristics of the hybrid power grid;

(3). Determine the adjustable range of PSS parameters that meet the small disturbance oscillation damping requirements;

(4). Analysis of the suppression effect of PSS parameters on large disturbance oscillations;

(5) PSS type selection and parameter optimization for coordinated oscillation damping of small disturbances and large disturbances.

In the above step 1, collect the relevant data of AC-DC hybrid transmission end grid structure, AC-DC channel transmission power, load level, generator and its regulator, DC transmission system and control system, and construct an adaptive AC-DC hybrid A model for the stability analysis of small and large disturbances in the sending-end power grid.

In the step 2, various typical normal operation modes of the AC/DC hybrid sending end power grid are established, including summer heavy load mode, summer small load mode, winter heavy load mode and winter small load mode, and equipment maintenance mode. Using the small disturbance frequency domain characteristic root scanning program, calculate the small disturbance oscillation damping of the sending unit of the hybrid power grid under different operating modes; use the transient time domain simulation program to calculate the transient time domain response of the hybrid power grid under large disturbances.

Under large disturbances, the AC electrical quantity fluctuates greatly, and the DC dynamic characteristics will show strong nonlinearity. The analysis results of the small disturbance damping characteristics are quite different from the large disturbance oscillation damping. Usually, due to the nonlinear factors of DC, the large disturbance damping will be slower. Significantly lower damping of small disturbances.

If under different operating modes, the small disturbance oscillation damping of the AC/DC hybrid sending unit is greater than 0.03, and the oscillation damping after various large disturbance faults is greater than 0.015, then both of them meet the "State Grid Corporation of Power System Safety and Stability Calculation Regulations" , there is no need to optimize the PSS type and parameters. Otherwise, it is necessary to further optimize the PSS type and parameters, so that the small disturbance and large disturbance oscillation damping can meet the requirements at the same time.

In the step 3, adjust the gain coefficient, phase lead and lag parameters of the PSS in equal proportions respectively, draw the change trajectory of the characteristic root of the small disturbance characteristic oscillation of the sending unit, and determine the adjustable parameters that meet the requirement that the damping ratio is greater than 0.03 according to the change trajectory scope.

In the step 4, within the adjustable range of PSS parameters, the gain coefficient, phase lead and lag parameter combinations are selected at equal intervals to verify the improvement of the large disturbance oscillation damping characteristics. If the large-disturbance oscillation damping can be increased to 0.015, then this parameter is the PSS coordinated optimization scheme for the small-disturbance and large-disturbance oscillation damping of the AC/DC hybrid sending unit.

In the step 5, if the large disturbance oscillation damping cannot be increased to 0.015 within the adjustable range of the PSS parameters, it is necessary to optimize the type of PSS, including the input signal type and the logic structure of the transfer function. For the newly selected PSS, repeat steps 2 to 4 to optimize the gain coefficient, phase lead and lag parameters of the PSS, so that the small disturbance damping ratio is greater than 0.03 and the large disturbance oscillation damping is greater than 0.015. If the damping ratio can be satisfied at the same time, the PSS type and parameters at this time are the PSS coordinated optimization scheme for the small disturbance and large disturbance oscillation damping of the AC/DC hybrid sending unit. If the damping ratio can be satisfied at the same time, the PSS type and parameters at this time are the PSS coordinated optimization scheme for the small disturbance and large disturbance oscillation damping of the AC/DC hybrid sending unit; Within the adjustable range of parameters with a damping ratio greater than 0.03, select a set of parameters with relatively large large disturbance oscillation damping as the coordinated optimization scheme, and configure corresponding cut-off measures in the AC system to cooperate with the transmission end after suppressing large disturbance faults. Unit oscillates.

The specific embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

(1).Construct the stability analysis model of AC/DC hybrid power grid

Taking the UHV DC transmission system in Sichuan in 2013 as an example, collect data such as the network source construction sequence of the Sichuan AC-DC hybrid grid, the level of load development, and the model of the generator and its excitation and speed regulation systems, and construct the interconnection system of the Sichuan and Central China main grid. Power flow calculation model and stability calculation model.

According to the forecast of power flow in the wet season, the power of each main power transmission channel or section is arranged as follows: Sichuan-Chongqing AC section 4000MW, western Sichuan transmission 2000MW, Xiangjiaba-Shanghai UHV DC 6400MW, Jinping-Sunan UHV DC 7200MW , Changzhi-Nanyang-Jingmen AC UHV channel "South Power to North Transmission" 5000MW.

Due to the difference in network source construction timing, the units of Xiluodu Power Station will be put into operation ahead of Xiluodu-Zhexi UHVDC. In order to reduce the capacity of hydropower nests, Xiluodu Power Station will connect with the main network through the Xiluodu-Fulong-Luzhou long-distance AC radial channel in 2013. Interconnection, the electrical connection is relatively weak.

(2). Quantitative evaluation of small disturbance and large disturbance oscillation damping characteristics of hybrid power grid

The Xiluodu and Xiangjiaba units at the sending end of the Xiangjiaba-Shanghai UHVDC hybrid power grid adopt the SG-type PSS with the generator electromagnetic power deviation as the input signal as shown in Figure 2, and the parameter configuration is shown in Table 1.

Table 1 Xiangjiaba and Xiluodu SG type PSS parameter settings

parameter _QUR K _{Q QUR QPSS Q1} T _{Q1,, Q2} T _{Q2,, Q3} T _Q3,, V _SMAXPSS Settings 5 4.17 5 5 8 2 0.1 0.5 0.01 0.24 0.05

Using the small disturbance frequency domain characteristic root scanning program, calculate the small disturbance damping characteristics of the relative oscillation between the Xiluodu and Xiangjiaba generating units at the sending end and the Sichuan main grid, and the attenuation characteristics of the power angle oscillation between the sending end generating units and the main grid under the condition of large disturbances, They are shown in Table 2 and Figure 3 respectively. It can be seen from the calculation results that the small disturbance oscillation has a very large damping ratio, but in the case of large fluctuations in the electrical quantity after the impact of a large disturbance and severe fault, due to the interaction of AC and DC, the distance between the sending unit and the main grid will increase oscillating trend.

Table 2 Oscillation mode of AC/DC hybrid sending units in Duanxi Luodu, Xiangjiaba and main grid (unit: Hz)

oscillation mode characteristic root Oscillation frequency Damping ratio Xiluodu, Xiangjiaba and Main Network Oscillation -0.6591+i3.4733 0.5528 0.1864

According to the calculation results, it can be seen that the characteristics of super-strong damping for small disturbances and negative damping for large disturbances determine that the PSS of the sending unit should be optimized from the perspective of coordinating the damping characteristics of the two, so as to improve the stable operation of the sending unit under the impact of large disturbances.

(3). Determine the adjustable range of PSS parameters that meet the small disturbance oscillation damping requirements

The root locus method is used to calculate the change trajectory of the characteristic root of the AC/DC hybrid sending unit and the main grid oscillation when the gain coefficient, phase lead and lag parameters increase and decrease proportionally, and the corresponding gain, lead parameters and lag parameters change The root loci of are shown in Figures 4, 5 and 6, respectively.

It can be seen from the figure that when the gain is less than 10, the damping ratio of interference increases as the value increases; when the gain is between 10 and 20, the damping ratio decreases when the gain increases; the damping ratio decreases when the leading parameter increases. If the value is small, the increase of the hysteresis parameter will have little effect on the damping ratio. However, it can be generally seen that the parameter changes will not cause the small interference damping ratio to drop below 0.03. Therefore, when investigating the effect of PSS parameter adjustment on the damping characteristics of large disturbance oscillations, the gain coefficient, phase lead and lag parameters can be selected in a wide range.

(4). Analysis of the suppression effect of PSS parameters on large disturbance oscillation

Under the conditions of PSS gain coefficient, phase lead and lag parameter changes, the power angle oscillation characteristics of large-disturbance AC-DC hybrid power grid units are evaluated. The calculation shows that the gain coefficient has no obvious effect on large-disturbance damping, and the increase of phase lead parameters will Further worsening the large disturbance oscillation damping, increasing the phase lag parameter will help to improve the large disturbance oscillation damping and speed up the oscillation subsidence, as shown in Figure 7. However, replacing the location of the short-circuit fault point further increases the impact of the fault on the AC-DC hybrid grid, and the optimized PSS parameters still cannot restore the stability of the subsequent oscillation after the large disturbance.

Therefore, it is necessary to further optimize its effect on the large-disturbance oscillation damping from the two aspects of PSS type and parameters.

(5) PSS type selection and parameter optimization for coordinated oscillation damping of small disturbances and large disturbances

The SG-type PSS, which only uses the generator electromagnetic power deviation as the input signal, has relatively weak control ability, and optimizing the gain coefficient and phase adjustment parameters is not enough to achieve the purpose of suppressing large disturbance oscillations. For this reason, the combined signal of generator electromagnetic power deviation and speed deviation is used as the PSS input, that is, the S1 type PSS is used, as shown in Figure 8 and parameter setting table 3.

Table 3 Xiangjiaba and Xiluodu S1 type PSS parameter setting

parameter T _R T ₅ T ₆ T ₇ K _{R TRP} T _{W W1 W2} K _S T ₉ T ₁₀ T ₁₁

Settings 0.02 5 5 5 0.01444 0.02 5 5 5 1 0.6 0.12 0.12 parameter K _P T ₁ T ₂ T ₁₃ T ₁₄ T3 T4 V _SMAX V _SMIN Settings 15 2 8 0.5 0.1 0.02 0.02 0.1 -0.1

The calculation results show that only using the S1 type PSS can further improve the oscillation damping characteristics of the large-disturbance AC-DC hybrid power grid, but the oscillation still tends to be of equal amplitude and cannot be rapidly attenuated. Therefore, it is necessary to further optimize the relevant parameters of PSS.

Xiangjiaba and Xiluodu units are equipped with S1 type PSS, and the effect of gain coefficient adjustment on the change trajectory of small disturbance characteristic root is shown in Figure 9. It can be seen that the characteristic root moves to the left with increasing gain, and the damping of small disturbance oscillations further increases. The comparison of large disturbance transient response under different gain values is shown in Figure 10. It can be seen from the figure that increasing the gain can also enhance large disturbance oscillation damping at the same time, that is, the gain adjustment direction of enhancing small disturbance and large disturbance oscillation damping is the same.

Comprehensively analyzing the calculation results, the PSS optimization scheme for coordinating the small disturbance and large disturbance damping of the Xiluodu and Xiangjiaba units at the sending end of the AC/DC hybrid connection is as follows: use the S1-type PSS with the combined signal of the generator electromagnetic power deviation and speed deviation as input, and Configure parameters as shown in Table 3, where the gain value is adjusted to 18.

It should be declared that the contents and specific implementation methods of the present invention are intended to prove the practical application of the technical solutions provided by the present invention, and should not be construed as limiting the protection scope of the present invention. Those skilled in the art may make various modifications, equivalent replacements, or improvements under the inspiration of the spirit and principles of the present invention. But these changes or modifications are all within the protection scope of the pending application.

Claims (10)

1. the little interference of an alternating current-direct current sending end unit and big disturbance damping coordination optimizing method is characterized in that, said method comprising the steps of:

(1). make up alternating current-direct current series-parallel connection sending end grid stability analytical model;

(2). the little interference of qualitative assessment series-parallel connection electrical network and big disturbance oscillation damping characteristic;

(3). determine to satisfy the PSS parameter adjustable extent of small interference oscillatory damping requirement;

(4) the .PSS parameter is to the inhibition analysis of big disturbance vibration;

(5) PSS type selecting and the parameter optimization of little interference and big disturbance oscillation damping coordination.

2. method according to claim 1 is characterized in that, in described step 1, collects data, makes up the model that the little interference of adaptation alternating current-direct current series-parallel connection sending end electrical network and big stability for disturbance are analyzed.

3. method according to claim 2 is characterized in that, data comprise: the data that alternating current-direct current series-parallel connection sending end grid structure, alternating current-direct current passage send electrical power, load level, generator and exciter thereof and speed regulator, DC power transmission system to unify control system.

4. method according to claim 1 is characterized in that, in described step 2, sets up the various typical normal operating modes of alternating current-direct current series-parallel connection sending end electrical network; Utilize little interference frequency domain character root scanning imaging system, calculate the small interference oscillatory damping of series-parallel connection electrical network sending end unit under the different running method; Utilize transient state time-domain-simulation program, calculate the transient state time-domain response under the big disturbance of series-parallel connection electrical network.

5. method according to claim 4 is characterized in that, normal operating mode, comprise little load method of big load method in summer, summer, winter big load method and winter little load method, and overhaul of the equipments mode.

6. method according to claim 4, it is characterized in that, the big AC electric quantity fluctuation down of disturbing, the direct current dynamic characteristic will present strong nonlinearity, differing greatly between little interference damping characteristic analysis result and big disturbance oscillation damping, usually owing to the non-linear factor of direct current, the big less interference damping of disturbance damping meeting significantly reduces.

If under the different running method, the damping of alternating current-direct current series-parallel connection sending end unit small interference oscillatory is greater than 0.03, and the oscillation damping after the various big disturbance fault is all greater than 0.015, and then both all meet the demands, and need not PSS pattern and parameter are optimized; Otherwise carry out PSS pattern and Parameter Optimization, make little interference and big disturbance oscillation damping meet the demands simultaneously.

7. method according to claim 1, it is characterized in that, in described step 3, equal proportion is regulated gain coefficient, the phase place lead and lag parameter of PSS respectively, draw the characteristic root variation track of sending end unit small interference oscillatory, determine to satisfy damping ratio greater than the 0.03 parameter adjustable extent that requires according to variation track.

8. method according to claim 1 is characterized in that, in described step 4, in PSS parameter adjustable extent, uniformly-spaced selects gain coefficient, phase place lead and lag parameter combinations, verifies the improvement situation of big disturbance oscillation damping characteristic; If big disturbance oscillation damping can be promoted to 0.015, then this PSS parameter is the PSS coordination optimization scheme of the little interference of alternating current-direct current series-parallel connection sending end unit and big disturbance oscillation damping.

9. method according to claim 1 is characterized in that, in described step 5, if in PSS parameter adjustable extent, still big disturbance oscillation damping can't be promoted to 0.015, then needs the pattern of preferred PSS; At the PSS of new selection, repeating step 2 is to step 4, optimizes gain coefficient, the phase place lead and lag parameter of PSS, make little interference damping ratio greater than 0.03 and big disturbance oscillation damping be higher than 0.015; If the damping specific energy satisfies simultaneously, Ci Shi PSS pattern and parameter then is the little interference of alternating current-direct current series-parallel connection sending end unit and the PSS coordination optimization scheme of disturbance oscillation damping greatly; If still can't satisfy the damping ratio requirement, then little interference damping ratio greater than 0.03 parameter adjustable extent in, select one group of relatively large parameter of big disturbance oscillation damping as the coordination optimization scheme, and the corresponding cutter measure of configuration in AC system, with the sending end unit vibration after the big disturbance fault of cooperation inhibition.

10. method according to claim 9 is characterized in that, the pattern of preferred PSS comprises: input signal types and transfer function logical construction.

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