A multi-branch power system stabilizer suitable for a wind and thermal bundling system

Abstract

The application discloses a kind of multi-branch power system stabilizer suitable for wind and fire bundling system, the stabilizer uses the collaborative control structure of low-frequency branch and subsynchronous branch parallel, pass through the second-order filter of low-frequency branch, direct current compensation and lead-lag module inhibits the low-frequency oscillation of 0.1Hz-4Hz frequency band, and subsynchronous branch extracts subsynchronous risk mode based on the inverse transformation matrix of generator shaft system torsional vibration mode quantity, combined with phase compensation module, and damping signal is injected directionally to inhibit the subsynchronous oscillation of 10Hz-50Hz frequency band.Parallel output module is connected to excitation regulator after the superposition of multi-branch signal is limited, and electromagnetic torque is dynamically adjusted, to realize wide frequency domain oscillation suppression.The application is controlled by mode quantity direction, parameter self-adaptive setting and multi-branch dynamic decoupling, solves the problem, such as the insufficient suppression ability of multiple frequency bands of traditional power system stabilizer in wind and fire coupling system, parameter mismatch and controller conflict, significantly improves the stability and robustness of new energy high penetration rate power grid.

Description

Technical Field

[0001] This invention belongs to the field of power system automatic control, and specifically relates to a multi-branch power system stabilizer suitable for wind and fire bundled systems. Background Technology

[0002] With the rapid development of new energy power generation technologies, wind power and other renewable energy sources are being integrated into the power grid on a large scale. The "wind-thermal bundled" system, operating in conjunction with thermal power units, is gradually becoming an important model in the power sector. However, due to the significant differences in the dynamic characteristics of wind turbines and thermal power units, the problem of low-frequency oscillations in the power system is becoming increasingly prominent. The strong randomness and weak inertia of wind power, combined with the dynamic response characteristics of the synchronous machines in thermal power units, makes the system prone to inducing multi-frequency oscillation modes under disturbances, seriously threatening the safe and stable operation of the power grid.

[0003] Traditional power system stabilizers (PSS) are primarily designed for thermal synchronous generator units, suppressing local or regional oscillation modes by introducing additional damping control. However, in wind-thermal bundled systems, the dynamic coupling characteristics of wind power connected to the grid via converters and thermal power connected to the grid via synchronous generators are complex. Traditional single-branch PSSs struggle to meet the broadband oscillation suppression requirements under multi-energy interaction. Furthermore, existing PSS parameters are typically tuned based on a single operating point, failing to adapt to system operating condition changes caused by random fluctuations in wind and thermal power output. This can lead to parameter mismatch issues and even exacerbate oscillation risks.

[0004] In recent years, research has attempted to improve the stability of multi-energy power systems by coordinating multiple power system controllers (PSS) or combining wind turbine additional damping control. However, these methods still have limitations: First, the coupling mechanism of multiple branches (such as the shaft system mode of thermal power units, resonance of wind farm collection networks, and AC / DC tie-line oscillation) in the wind-thermal bundled system has not been fully analyzed, resulting in insufficient targeting of control strategies. Second, the lack of dynamic coordination mechanism among multiple controllers can easily lead to control conflicts or response lags. Third, existing technologies rely heavily on accurate models, which are difficult to adapt to the strong uncertainty and time-varying nature caused by the high proportion of new energy access. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by proposing a multi-branch power system stabilizer suitable for wind-thermal power bundled systems. It aims to significantly improve the stability of systems with a high proportion of wind and thermal power through multi-branch collaborative control, wide-frequency adaptive adjustment, and dynamic characteristic decoupling technology. This overcomes the problems of insufficient multi-frequency oscillation suppression, poor parameter robustness, and difficulties in coordinating multiple controllers inherent in traditional power system stabilizers (PSS) in wind-thermal power bundled systems.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] This invention discloses a multi-branch power system stabilizer applicable to a wind-fire bundled system. The wind-fire bundled system includes: an equivalent wind turbine multiplied by n wind turbines, an equivalent generator multiplied by n generators, a series compensation transmission line, and an AC power grid. The equivalent generator includes an excitation system and a six-mass block equivalent model. The equivalent wind turbine and the equivalent synchronous machine are connected in parallel via transformers and then connected to the AC power grid through the series compensation transmission line. The invention is characterized by the multi-branch power system stabilizer further comprising: a low-frequency branch, a sub-synchronous branch, and a parallel output module. The low-frequency branch and the sub-synchronous branch are connected in parallel, then connected in series with the parallel output module, and connected to the additional control port of the excitation regulator in the excitation system.

[0008] The low-frequency branch includes: a first input channel and a second input channel;

[0009] The first input channel sequentially includes: a second-order bandpass filter module, a first DC blocking module, a second DC blocking module, a lead-lag compensation module, and a first gain module, and is used to adjust the electromagnetic power deviation of the input equivalent generator. The signal is processed and output as a low-frequency damping signal.

[0010] The second input channel sequentially includes: a first-order high-pass filter, a second-order band-pass filter, a time constant compensation module, and a second gain module, and processes the speed deviation of the input equivalent generator. The signal is processed and output as a sub-low frequency damping signal.

[0011] The subsynchronous branch sequentially includes: a DC blocking module, a phase compensation module, and a third gain module, and measures the shaft torsional vibration mode quantity pq under the i-th subsynchronous oscillation risk mode of the equivalent generator. i Process the signal to generate the i-th additional damping control signal;

[0012] The parallel output module superimposes and limits the output signals of the low-frequency branch and the subsynchronous branch to obtain the stabilizer output signal U. PSS It is also connected to the additional control port of the excitation regulator, so that the excitation regulator can adjust the output signal U of the stabilizer. PSS The excitation voltage of the equivalent generator is adjusted to change its electromagnetic torque, thereby suppressing the wideband oscillation of the equivalent generator.

[0013] The multi-branch power system stabilizer described in this invention is also characterized by the shaft torsional vibration mode quantity pq under the i-th subsynchronous oscillation risk mode of the equivalent generator. i It is obtained using equation (1):

[0014] (1)

[0015] In equation (1), These are the six constants obtained through the inverse modal transformation matrix P; This represents the electrical angular velocity of each mass block in the equivalent six-mass model relative to the synchronously rotating reference axis.

[0016] Furthermore, the lead-lag compensation module of the first input channel is composed of a first lead element and a first lag element connected in series, used to compensate for the phase lag of the excitation system in the frequency band of 0.1Hz to 4Hz; the time constant compensation module of the second input channel is composed of a second lead element and a second lag element connected in series, used to suppress high-frequency interference of its own input signal.

[0017] Furthermore, the feature is that the phase compensation link of the subsynchronous branch is composed of a third leading link and a third lagging link connected in series, which is used to compensate for the phase lag of the subsynchronous frequency band of the excitation system.

[0018] Furthermore, the upper limit amplitude of the output of the parallel output module is V. max and output lower limit amplitude V min It is used to constrain the amplitude range of the superimposed control signal to prevent over-adjustment of the excitation system.

[0019] Furthermore, the parameters of the low-frequency branch are tuned according to the following steps:

[0020] Step 1: Obtain the phase lag characteristics of the excitation system using the test signal method, and use them to design the parameters of the lead-lag compensation link to match the phase requirements of the target low frequency band.

[0021] Step 2: Determine the total gain of the low-frequency branch using the critical gain method:

[0022] In a single-machine infinite bus system, the gain coefficient of the multi-branch power system stabilizer is gradually increased until the output of the excitation regulator in the excitation system or the rotor voltage of the equivalent generator oscillates, thereby obtaining the critical gain. Then, 1 / 3 to 1 / 5 of the critical gain is used as the total gain of the power system stabilizer.

[0023] Furthermore, the parameters of the secondary synchronization branch are tuned according to the following steps:

[0024] Step a: Identify the secondary synchronous oscillation risk mode in the wind and fire bundling system using eigenvalue analysis.

[0025] Step b, construct the inverse mode transformation matrix P=K -1 T jmWhere K is the stiffness coefficient K of the two adjacent mass blocks of the six mass blocks of the equivalent generator in the wind-fire bundling system. 12 , K 23 ,…, K 56 The matrix formed, T jm It is determined by the inertial time constant T of each mass block of the equivalent generator. jm1 , T jm2 ,…, T jm6 The resulting diagonal matrix has the following properties:

[0026] (2)

[0027] (3)

[0028] Step c: Calculate the shaft torsional vibration mode quantity under the i-th subsynchronous oscillation risk mode of the equivalent generator. ,in, Let represent the i-th row vector of the inverse modal transform matrix, and , Let represent the column vector consisting of the electrical angular velocities of each mass block relative to the synchronously rotating reference axis in the equivalent model of the six mass blocks, and T represents transpose;

[0029] Step d: Based on the transfer function and modal damping requirements of the excitation system, calculate the gain coefficient K of the subsynchronous branch using equation (4). G :

[0030]

[0031] In equation (4), Q is the damping coefficient under the i-th subsynchronous oscillation risk mode; 5i Let P be the element in the fifth row and i-th column of the mode transformation matrix Q, and Q = P. -1 V mi Let M be the mode frequency under the i-th subsynchronous oscillation risk mode. mi and D mi Let be the modal inertia and modal damping under the i-th subsynchronous oscillation risk mode, respectively. This is the transfer function of the excitation system before phase compensation. This represents the transfer function of the excitation system after phase compensation. The additional damping torque coefficient for the electromagnetic torque of the subsynchronous branch of the multi-branch power system stabilizer under the i-th subsynchronous oscillation risk mode; is the additional damping torque coefficient of the subsynchronous branch of the multi-branch power system stabilizer under the i-th subsynchronous oscillation risk mode; j represents the complex unit.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. This invention realizes multi-band coordinated damping control: through the parallel structure of the low-frequency branch and the subsynchronous branch, directional damping compensation is provided for the oscillation modes of different frequency bands, which effectively suppresses the oscillation risk in a wide frequency range, and in particular solves the defect of traditional PSS that cannot take into account both low-frequency and subsynchronous oscillations.

[0034] 2. This invention employs modal quantity directional control: the subsynchronous branch is based on the accurate calculation of the torsional vibration mode of the generator shaft system, and extracts specific subsynchronous oscillation risk modes through the inverse modal transformation matrix, thereby realizing the accurate injection of damping signals and avoiding control conflicts caused by multimodal coupling.

[0035] 3. The application of this invention will significantly improve the stable operation capability of the wind-fire bundling system in scenarios with high penetration of new energy sources, provide technical support for power grid security, and provide a new solution for the stable control of multi-energy power systems. Attached Figure Description

[0036] Figure 1 A structural diagram of the wind and fire bundling system;

[0037] Figure 2 This is a diagram of a multi-branch PSS structure.

[0038] Figure 3 This is a phase lag curve of the excitation system;

[0039] Figure 4 Simulation waveforms of critical gain and tuning gain for multi-branch PSS;

[0040] Figure 5 The output power response diagram of the synchronous machine when the mechanical power changes by 10%;

[0041] Figure 6 The output power response diagram of the synchronous machine when the excitation reference voltage changes by 5%;

[0042] Figure 7 The synchronous motor speed response diagram under wind farm power fluctuations;

[0043] Figure 8 The synchronous motor speed spectrum under power fluctuations in a wind farm;

[0044] Figure 9 The output power and speed response of the synchronous machine under a three-phase short-circuit fault are shown in the diagram.

[0045] Figure 10 The diagram shows the torque response of the synchronous motor shaft system under a three-phase short-circuit fault.

[0046] Figure 11This is a spectrum diagram of the synchronous machine speed under a three-phase short-circuit fault. Detailed Implementation

[0047] In this embodiment, a power system stabilization device capable of adapting to the multi-branch dynamic characteristics of a wind-fire bundled system, possessing strong robustness and adaptability, is provided to solve key technical challenges such as multi-band oscillation suppression, multi-controller coordination optimization, and adaptability to complex operating conditions, ensuring the safe and stable operation of the new power system. Specifically, the multi-branch power system stabilizer applicable to the wind-fire bundled system includes: an equivalent wind turbine multiplied by n wind turbines, an equivalent generator multiplied by n generators, a series compensation transmission line, and an AC power grid. The equivalent generator includes an excitation system and a six-mass block equivalent model. The equivalent wind turbine and equivalent synchronous machine are connected in parallel via transformers and then connected to the AC power grid through the series compensation transmission line. A detailed structural diagram of the wind-fire bundled system is shown below. Figure 1 .

[0048] The equivalent generator also includes a multi-branch power system stabilizer, comprising: a low-frequency branch, a sub-synchronous branch, and a parallel output module. The low-frequency branch is connected in parallel with the sub-synchronous branch, then in series with the parallel output module, and connected to the additional control port of the excitation regulator in the excitation system. The power system stability structure diagram is shown below. Figure 2 .

[0049] The low-frequency branch includes: a first input channel and a second input channel;

[0050] The first input channel includes, in sequence: a second-order bandpass filter module. First DC blocking module Second DC blocking module Lead-lag compensation module and and the first gain module And the electromagnetic power deviation of the input equivalent generator. The signal is processed and output as a low-frequency damped signal.

[0051] In this embodiment, the lead-lag compensation module of the first input channel is composed of a first lead element and a first lag element connected in series, and is used to compensate for the phase lag of the excitation system in the frequency band of 0.1Hz to 4Hz; the time constant compensation module of the second input channel is composed of a second lead element and a second lag element connected in series, and is used to suppress high-frequency interference of its own input signal.

[0052] The second input channel includes, in sequence: a first-order high-pass filter. Second-order bandpass filter Third DC blocking module Time constant compensation module and the second gain module And the speed deviation of the input equivalent generator. The signal is processed and output as a sub-low frequency damping signal.

[0053] In practice, the parameters of the low-frequency branch are tuned according to the following steps:

[0054] Step 1: Obtain the phase lag characteristics of the excitation system using the test signal method, and use them to design the parameters of the lead-lag compensation circuit to match the phase requirements of the target low-frequency band.

[0055] Step 1.1 First, provide the reference voltage U to the generator's excitation regulator. ref Apply a series of very small sinusoidal perturbations, applying one perturbation every 0.1 Hz in the range of 0.1 to 3 Hz, and one perturbation every 1 Hz in the range of 3 to 50 Hz;

[0056] Step 1.2 Taking the output response of the generator terminal voltage in steady state For the common cycle and Perform Fourier decomposition to obtain the values ​​at different frequencies. and The phasors are then calculated. Frequency characteristics;

[0057] Step 1.3 Plot the frequency-hysteresis phase curve of the excitation system, find the phase jump point, and determine the targeted compensation frequency point;

[0058] Step 2: Determine the total gain of the low-frequency branch using the critical gain method:

[0059] In a single-machine infinite bus system, the gain coefficient of the multi-branch power system stabilizer is gradually increased until the output of the excitation regulator in the excitation system or the rotor voltage of the equivalent generator oscillates, thereby obtaining the critical gain. Then, 1 / 3 to 1 / 5 of the critical gain is used as the total gain of the power system stabilizer.

[0060] The secondary synchronization branch includes, in sequence: DC blocking module Phase compensation module and the third gain module And the shaft torsional vibration mode quantity pq under the i-th subsynchronous oscillation risk mode of the equivalent generator. i The signal is processed to generate the i-th additional damping control signal.

[0061] In specific implementation, the shaft torsional vibration mode quantity pq under the i-th subsynchronous oscillation risk mode of the equivalent generator i It is obtained using equation (1):

[0062] (1)

[0063] In equation (1), These are the six constants obtained through the inverse modal transformation matrix P; This represents the electrical angular velocity of each mass block in the equivalent six-mass model relative to the synchronously rotating reference axis.

[0064] The phase compensation stage of the secondary synchronization branch consists of a third leading stage and a third lagging stage connected in series, used to compensate for the phase lag of the secondary synchronization frequency band of the excitation system.

[0065] In this embodiment, the parameters of the secondary synchronization branch are tuned according to the following steps:

[0066] Step a: Identify the risk mode of subsynchronous oscillation in the wind and fire bundling system using eigenvalue analysis.

[0067] (1) Establishing the dynamic model of the system: The wind-fire bundled system includes an equivalent wind turbine, an equivalent synchronous generator (six-mass block shaft system model), a series compensation transmission line, and an AC power grid. The mathematical models of each module in the system are linearized to obtain the state-space models of each sub-module:

[0068]

[0069] In the formula, the subscript k represents each submodule; X k U k Y k These are the state variable matrix, input variable matrix, and output variable matrix of submodule k, respectively; A k B k C k D k These are the coefficient matrix, input matrix, output matrix, and transfer matrix of the k-th submodule, respectively. The elements in each matrix are obtained from the steady state of the system.

[0070] By simultaneously solving the linearized equations of each module, we obtain the small-signal model of the entire system:

[0071]

[0072] In the formula, These are the state variables of the submodule; The input matrix consists of the system control setpoints and becomes a zero matrix after the system is closed.

[0073] (2) Linearize the above system at a certain equilibrium point using Taylor expansion to obtain

[0074]

[0075] Where A represents the state matrix, through To study the key factors of small-disturbance stability of power systems, we solve for all eigenvalues ​​of matrix A to analyze the stability of the power system. Let the eigenvalues ​​be... The eigenvalues ​​of A reflect the oscillation modes that the power system may produce, i.e. Therefore This reflects the attenuation performance. It reflects the oscillation frequency; The system becomes unstable due to oscillations caused by increased amplitude. To reduce oscillations, the system is stable; It is a constant amplitude oscillation, a critical state.

[0076] (3) Subsynchronous oscillation mode screening: According to the definition of subsynchronous oscillation, select characteristic values ​​that meet the following conditions: frequency range between 10Hz and 50Hz, damping ratio (A value close to zero or negative) indicates poor modal stability.

[0077] Step b, construct the inverse mode transformation matrix P=K -1 T jm Where K is the stiffness coefficient K of the two adjacent mass blocks of the six mass blocks of the equivalent generator in the wind-fire bundling system. 12 , K 23 ,…, K 56 The matrix formed, T jm It is determined by the inertial time constant T of each mass block of the equivalent generator. jm1 , T jm2 ,…, T jm6 The resulting diagonal matrix has the following properties:

[0078] (2)

[0079] (3)

[0080] Step c: Calculate the shaft torsional vibration mode quantity under the i-th subsynchronous oscillation risk mode of the equivalent generator. ,in, Let represent the i-th row vector of the inverse modal transform matrix, and , Let represent the column vector consisting of the electrical angular velocities of each mass block relative to the synchronously rotating reference axis in the equivalent model of the six mass blocks, and T represents transpose;

[0081] Step d: Based on the transfer function and modal damping requirements of the excitation system, calculate the gain coefficient K of the subsynchronous branch using equation (4). G :

[0082]

[0083] In equation (4), Q is the damping coefficient under the i-th subsynchronous oscillation risk mode; 5i Let P be the element in the fifth row and i-th column of the mode transformation matrix Q, and Q = P. -1 V mi Let M be the mode frequency under the i-th subsynchronous oscillation risk mode. mi and D mi Let be the modal inertia and modal damping under the i-th subsynchronous oscillation risk mode, respectively. This is the transfer function of the excitation system before phase compensation. This represents the transfer function of the excitation system after phase compensation. The additional damping torque coefficient for the electromagnetic torque of the subsynchronous branch of the multi-branch power system stabilizer under the i-th subsynchronous oscillation risk mode; is the additional damping torque coefficient of the subsynchronous branch of the multi-branch power system stabilizer under the i-th subsynchronous oscillation risk mode; j represents the complex unit.

[0084] The parallel output module superimposes and limits the output signals of the low-frequency branch and the subsynchronous branch to obtain the stabilizer output signal U. PSS It is also connected to the additional control port of the excitation regulator, so that the excitation regulator can adjust the output signal U of the stabilizer. PSS The excitation voltage of the equivalent generator is adjusted to change its electromagnetic torque, thereby suppressing the wideband oscillation of the equivalent generator.

[0085] In practical implementation, the upper limit amplitude of the parallel output module is V. max and output lower limit amplitude V min It is used to constrain the amplitude range of the superimposed control signal to prevent over-adjustment of the excitation system.

[0086] Example:

[0087] 1. Create in PSCAD / EMTDC Figure 1 The wind and fire bundling system in the middle (see Tables 1 to 5 for specific parameters).

[0088] Table 1 shows the generator parameters.

[0089]

[0090] Table 2 shows the inertial time constants for each mass segment of the generator;

[0091]

[0092] Table 3 shows the elastic coefficients of each shaft section of the generator;

[0093]

[0094] Table 4 shows the excitation system parameters;

[0095]

[0096] Table 5 shows the main topology parameters;

[0097]

[0098] 2. The phase lag characteristic curve of the excitation system is calculated using the test signal method, such as... Figure 3 As shown, find the frequencies corresponding to the phase transition points: 1Hz and 32Hz.

[0099] 3. Construct a single-machine infinite bus model, and build an excitation model and PSS for simulation calculation and analysis, gradually increasing the gain of the low-frequency branch. and This continues until the generator excitation voltage begins to diverge and oscillate. and This is the critical gain. (From...) Figure 4 It can be seen that the critical gain obtained from the simulation is K. P =98, K ω =0.5, set the gain to K P =21, K ω When the phase lag curve is 0.1, the generator's excitation voltage can be stabilized at around 1 pu, meeting the tuning requirements. Then, based on the excitation system phase lag curve, the low-frequency branch parameters are tuned as shown in Table 6.

[0100] Table 6 shows the parameter tuning results.

[0101]

[0102] 4. Using the relevant parameters of the synchronizer, the corresponding inverse mode transformation matrix is ​​calculated as shown in Table 7.

[0103] Table 7 shows the inverse modal transformation matrix.

[0104]

[0105] 5. Regarding Figure 1 The eigenvalue analysis of the wind-fire bundling system was performed, and the results are shown in Table 8. The results indicate that the system has the risk of oscillation at mode 4 frequency (32.27Hz). Therefore, the mode quantity was selected. As the input signal for the secondary synchronization branch.

[0106] Table 8 shows the results of the eigenvalue analysis.

[0107]

[0108] 6. For mode 4, let the damping coefficient be... =0.01, and the subsynchronous branch is obtained as follows based on the inverse modal transformation matrix and equation (4):

[0109]

[0110] =-0.4106 +0.2276 -0.5891 +0.1319 -0.0484 +0.0045

[0111] 7. Test the effect of multi-branch PSS on the equivalent synchronous machine's mechanical power under a 10% sudden change in power over 15 seconds. The generator output power is as follows: Figure 5 As shown, after installing a multi-branch PSS, the stabilization time and peak oscillation of the synchronous machine output power are both shorter than those with PSS1A installed and without PSS. The multi-branch PSS has a better damping effect on low-frequency oscillations than the traditional PSS.

[0112] 8. Test the effect of the multi-branch PSS on the equivalent synchronous machine excitation reference voltage under the condition of a 10% sudden change in voltage over 10 seconds. The generator output power is as follows: Figure 6 As shown, after installing a multi-branch PSS, the stabilization time and peak oscillation of the synchronous machine output power are both shorter than those with PSS1A installed and without PSS. The multi-branch PSS has a better damping effect on low-frequency oscillations than the traditional PSS.

[0113] 9. Set the power reference value of the wind farm to fluctuate periodically, and test the effect of the multi-branch PSS in suppressing forced oscillations. The generator speed and spectrum are shown in the figure. Figure 7 and Figure 8 As shown, after installing a multi-branch PSS, the oscillation amplitude of the synchronous machine speed is reduced by nearly 25%, and the low-frequency component in the system is reduced from 0.03 pu to almost zero, with a significant effect on suppressing forced oscillation.

[0114] 10. A three-phase short-circuit fault is simulated to induce low-frequency oscillations in the generator. The generator output power is as follows: Figure 9 As shown, after installing a multi-branch PSS, the oscillation amplitude of the synchronous machine's output power and speed under a three-phase short-circuit fault is greatly reduced, and the speed at which it recovers to a steady state is also greatly accelerated.

[0115] 11. Adjust the series compensation circuit parameters, set a three-phase short-circuit fault, and excite the generator's subsynchronous oscillation. The generator's shaft torque and spectrum diagram are shown below. Figure 10 and Figure 11As shown, after configuring a multi-branch PSS, the oscillation amplitude of the synchronous machine shaft torque is reduced by more than 90%, and the subsynchronous component in the system can be almost ignored, which greatly suppresses the torsional oscillation of the generator shaft.

Claims

1. A multi-branch power system stabilizer suitable for use in a wind-thermal bundling system, the wind-thermal bundling system comprising: An equivalent fan multiplied by n fans, an equivalent generator multiplied by n generators, series compensation outgoing line, AC power grid, wherein the equivalent generator contains an excitation system and a six-mass equivalent model; the equivalent fan and the equivalent synchronous machine are connected in parallel through transformers and connected to the AC power grid through the series compensation outgoing line; characterized in that the multi-branch power system stabilizer is further arranged in the equivalent generator and comprises a low-frequency branch, a subsynchronous branch and a parallel output module, the low-frequency branch and the subsynchronous branch are connected in parallel and connected in series with the parallel output module and connected to an additional control port of an excitation regulator in the excitation system; The low-frequency branch comprises a first input channel and a second input channel. The first input channel sequentially comprises a second-order band-pass filter module, a first direct-current elimination module, a second direct-current elimination module, a lead-lag compensation module and a first gain module, and is used for processing the input electromagnetic power deviation of the equivalent generator and outputting a low-frequency damping signal. The second input channel sequentially comprises a first-order high-pass filter, a second-order band-pass filter, a time constant compensation module and a second gain module, and is used for processing the input equivalent generator speed deviation and outputting a sub-low-frequency damping signal. The subsynchronous branch comprises a direct-current isolation module, a phase compensation module and a third gain module in sequence, and is used for processing the shaft torsional vibration modal quantity pq of the equivalent generator under the i th subsynchronous oscillation risk modal i generating the i th additional damping control signal; The parallel output module superimposes and limits the output signals of the low-frequency branch and the subsynchronous branch to obtain the stabilizer output signal U. PSS It is also connected to the additional control port of the excitation regulator, so that the excitation regulator can adjust the output signal U of the stabilizer. PSS The excitation voltage of the equivalent generator is adjusted to change its electromagnetic torque, thereby suppressing the wideband oscillation of the equivalent generator.

2. The multi-pole power system stabilizer according to claim 1, characterized by a shaft torsional mode quantity pq of the equivalent generator in an i-th subsynchronous oscillation risk mode i is obtained using equation (1): (1) In formula (1), are 6 constants obtained by the modal inverse transformation matrix P; are the electrical angular velocities of each mass of the six-mass equivalent model with respect to the synchronously rotating reference axis.

3. The multi-pole power system stabilizer of claim 1, wherein The lead-lag compensation module of the first input channel is connected in series by a first lead element and a first lag element, for compensating the phase lag of the excitation system in the frequency band of 0.1 Hz to 4 Hz; the time constant compensation module of the second input channel is connected in series by a second lead element and a second lag element, for suppressing the high-frequency interference of the input signal.

4. The multi-pole power system stabilizer of claim 1, wherein The phase compensation element of the subsynchronous branch is connected in series by a third lead element and a third lag element, for compensating the phase lag of the excitation system in the subsynchronous frequency band.

5. The multi-pole power system stabilizer of claim 1, wherein, The upper limit amplitude of the output of the parallel output module is V max and the lower limit amplitude of the output is V min , for restraining the amplitude range of the superimposed control signal to prevent over-regulation of the excitation system.

6. The multi-pole power system stabilizer of claim 1, wherein The parameters of the low-frequency branch are set as follows: Step 1, the phase lag characteristic of the excitation system is obtained by using the test signal method, for designing the parameters of the lead-lag compensation element to match the phase requirement of the target low-frequency band; Step 2, the total gain of the low-frequency branch is determined by using the critical gain method: In the single-machine infinite system, the gain coefficient of the multi-branch power system stabilizer is gradually increased until the output of the excitation regulator in the excitation system or the rotor voltage of the equivalent generator oscillates, so as to obtain the critical gain, and 1 / 3 to 1 / 5 of the critical gain is used as the total gain of the power system stabilizer.

7. The multi-pole power system stabilizer of claim 1, wherein The parameters of the subsynchronous branch are set as follows: Step a, the subsynchronous oscillation risk mode in the wind-fire bundled system is identified by the eigenvalue analysis method; Step b, construct modal inverse transformation matrix P = K -1 T jm , where K is a matrix composed of stiffness coefficients K 12 , K 23 ,…, K 56 of adjacent two mass blocks of six mass blocks of the equivalent generator in the wind-fire bundling system, T jm is a diagonal matrix composed of inertia time constants T jm1 , T jm2 ,…, T jm6 of each mass block of the equivalent generator, and has: (2) (3) Step c, calculating the shaft torsional mode quantity of the equivalent generator in the i-th subsynchronous oscillation risk mode wherein denotes the i-th row vector of the modal inverse transformation matrix, and , denotes a column vector of the electrical angular velocity components of each mass block in the six-mass equivalent model with respect to the synchronous rotating reference axis, and T denotes the transpose; Step d, the gain coefficient K of the subsynchronous branch is calculated using equation (4) based on the transfer function of the excitation system and the modal damping requirement G : (4) in formula (4), is the damping coefficient under the i-th subsynchronous oscillation risk mode; Q 5i represents the element of the modal transformation matrix Q in the fifth row and the i-th column, and Q = P -1 , V mi is the modal frequency under the i-th subsynchronous oscillation risk mode, M mi and D mi are the modal inertia and the modal damping under the i-th subsynchronous oscillation risk mode, respectively, is the transfer function of the excitation system before phase compensation, represents the transfer function of the excitation system after phase compensation, is the additional damping torque coefficient of the subsynchronous branch electromagnetic torque of the multi-branch power system stabilizer under the i-th subsynchronous oscillation risk mode; is the additional damping torque coefficient of the subsynchronous branch of the multi-branch power system stabilizer under the i-th subsynchronous oscillation risk mode; j represents the complex number unit.

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