A coordinated control method for voltage and power angle stability of wind power grid-connected sending-end system

Abstract

This invention discloses a coordinated control method for voltage and power angle stability in a wind farm grid-connected sending-end system. First, after a fault is cleared, control is initiated to obtain real-time information about the wind turbine port voltage and the angular velocity of the wind farm's adjacent synchronous generators. Then, based on the acquired signals, additional control instructions for the wind turbine's active and reactive currents are determined. Finally, the generated additional control instructions for the wind turbine's active and reactive currents are superimposed on the control instructions during normal operation to adjust the wind turbine's active and reactive outputs. This method effectively suppresses power angle instability in the wind farm's adjacent synchronous generators while improving voltage safety in the wind farm's sending-end system, thus having significant significance in ensuring the safe and stable operation of power systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of synchronous stability control of wind power grid-connected systems, and in particular relates to a method for coordinated control of voltage and power angle stability of a wind power grid-connected sending-end system. Background Art

[0002] The large-scale integration of wind power into the grid has made the operating modes of renewable energy power systems more diverse and complex than those of traditional power systems, and their stability mechanisms have also changed. In traditional power systems dominated by synchronous generators, power angle desynchronization and voltage collapse often occur in a coupled manner, making the intermediate boundary difficult to define. With the accelerated pace of power electronics, the integration of wind power and its dynamics have led to fundamental changes in the system's power angle and voltage stability modes and mechanisms. Specifically, on the one hand, the injection of wind power alters the system's power angle and voltage stability margins. On the other hand, the diverse control methods of power electronic converters involve switching control strategies during short-circuit and short-circuit clearing events, as well as during power angle and voltage oscillations. This has complex and profound impacts on system power angle and voltage stability. Therefore, to ensure the safety and stability of power system power angle and voltage, it is necessary to design targeted control strategies for wind power transient output, ensuring the safe operation of wind power equipment while also participating in system stability regulation. Summary of the Invention

[0003] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a coordinated control method for the voltage and power angle stability of the wind power grid-connected sending-end system. The present invention adjusts the active and reactive output of the wind turbine in real time through feedback of the wind turbine terminal voltage and the angular velocity of the synchronous machine adjacent to the wind farm, thereby improving the transient stability of the new energy transmission system and solving the problem of transient power angle instability of the synchronous machine adjacent to the wind farm.

[0004] In order to achieve the above object, the technical solution adopted in the present invention is:

[0005] A method for coordinated control of voltage and power angle stability of a wind power grid-connected sending-end system comprises the following steps:

[0006] ① After the fault is cleared, the control starts to obtain the wind turbine terminal voltage and the angular velocity of the synchronous machine adjacent to the wind farm;

[0007] ② According to the signal obtained in step ①, determine the additional control instruction of the wind turbine reactive current and the additional control instruction of the wind turbine active current;

[0008] ③ Based on the principle of reactive output priority, the additional control instruction of the wind turbine active current generated in step ② is superimposed on the control instruction during normal operation of the wind turbine, and the active and reactive output of the wind turbine are adjusted. When the control time is greater than the active power recovery time limit requirement of the wind turbine, the control is exited.

[0009] In the step ②, the additional control instruction for the wind turbine reactive current is determined as:

[0010] I q =K1(U0-U)

[0011] Where, I q is the additional control instruction for the wind turbine reactive current; U and U0 are the measured value and expected value of the wind turbine terminal voltage respectively; K1 is the adjustment parameter, and K1>0;

[0012] The additional control instruction of the wind turbine active current is determined as

[0013] I p =-K2(ω-ω s )

[0014] Where ω and ω s are the angular velocity and synchronous speed of the synchronous machine respectively; K2 is the adjustment parameter, and K2>0. In the above step ③, the wind turbine reactive current control instruction is determined as

[0015] I q * =0-I q =-K1(U0-U)

[0016] Where, I q * It is the reactive current control instruction of the wind turbine;

[0017] The fan active current control command is determined as

[0018]

[0019] Where, I p * is the active current control instruction of the fan; I is the total current amplitude when the fan is operating normally.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This invention discloses a coordinated control method for voltage and power angle stability in a wind power grid-connected sending-end system. This method implements emergency control based on feedback drive after a fault is cleared. Compared to traditional synchronous generator transient power angle control strategies, such as setting according to a strategy table or shedding generators and loads, this method not only more effectively suppresses power angle instability in adjacent synchronous generators in a wind farm, but also offers greater adaptability to various fault and operating scenarios with lower cost. Furthermore, by fully utilizing the reactive power output potential of wind turbines, it improves the voltage safety of the renewable energy sending-end system, which is of great significance for ensuring the safe and stable operation of power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1It is a flow chart of the method of the present invention.

[0023] Figure 2 It is a control structure block diagram of the present invention.

[0024] Figure 3 It is the transmission system topology of the wind power grid-connected system.

[0025] Figure 4 It is a waveform diagram of the change of wind farm phase-shifting power angle over time under the traditional strategy of resuming normal operation after the end of low voltage ride-through and after adopting the control strategy of the present invention.

[0026] Figure 5 The waveform diagram shows the voltage change over time at the wind turbine grid connection point under the traditional strategy of resuming normal operation after the end of low voltage ride-through and after adopting the control strategy of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0028] like Figure 1 As shown, the present invention is a method for coordinated control of voltage and power angle stability of a wind power grid-connected system, comprising the following steps:

[0029] ① After the fault is cleared, the control starts, such as Figure 2 As shown, the voltage at the wind turbine terminal and the angular velocity of the synchronous machine adjacent to the wind farm are obtained;

[0030] ② If Figure 2 As shown, according to the signal obtained in step ①, the wind turbine reactive current additional control instruction and the wind turbine active current additional control instruction are determined; the wind turbine reactive current additional control instruction is determined as:

[0031] I q =K1(U0-U)

[0032] Where, I q is the additional control instruction for the wind turbine reactive current; U and U0 are the measured value and expected value of the wind turbine terminal voltage respectively; K1 is the adjustment parameter, and K1>0;

[0033] The additional control instruction of the wind turbine active current is determined as

[0034] I p =-K2(ω-ω s )

[0035] Where ω and ω s are the angular velocity and synchronous speed of the synchronous machine respectively; K2 is the adjustment parameter, and K2>0.

[0036] ③ Such as Figure 2As shown in the figure, based on the principle of reactive output priority, the wind turbine active current additional control instruction generated in step ② is superimposed on the control instruction during normal operation of the wind turbine to adjust the active and reactive output of the wind turbine. The wind turbine reactive current control instruction is determined as

[0037] I q * =0-I q =-K1(U0-U)

[0038] Where, I q * It is the reactive current control instruction of the wind turbine;

[0039] The fan active current control command is determined as

[0040]

[0041] Where, I p * is the active current control instruction of the fan; I is the total current amplitude when the fan is operating normally;

[0042] When the control time is greater than the wind turbine active power recovery time limit requirement, the control exits.

[0043] Preferably, the wind turbine active power recovery time limit requirement is 2s.

[0044] Example:

[0045] The method of the present invention is aimed at solving the problems of transient power angle stability and voltage safety of a wind power grid-connected sending-end system.

[0046] On the simulation platform, build Figure 3 The wind power grid-connected transmission system model shown was simulated and verified according to the following parameters:

[0047] The actual output of the direct-drive wind turbine is 420MW; the active output of the synchronous generator at the sending end is 300MVA; the receiving end is an infinite power grid. The regulation coefficients are: K1 = 2, K2 = 2.

[0048] At the first second, a three-phase permanent short circuit occurred in one circuit of the double-circuit line. After 200ms, the protection action disconnected the faulty line.

[0049] If the fan is operated in the traditional control mode, that is, the fan resumes normal operation immediately after the low voltage ride-through control ends, the effect of the design scheme of the present invention is compared with the effect of the traditional control mode. Figure 4 and Figure 5 shown. Figure 4 is the curve of the power angle of the sending-end synchronous generator changing with time, Figure 5 The voltage curve of the wind turbine grid connection point changes with time.

[0050] contrast Figure 4 and Figure 5 As can be seen, under traditional control, the system experienced power angle and voltage oscillations after the fault was cleared. However, after applying the control proposed in this invention, the system regained stability. Therefore, compared with immediately resuming normal control after the low-voltage breakover, the proposed method not only effectively improves the system's transient power angle stability but also ensures voltage safety at the wind farm's grid connection point.

Claims

1. A method for coordinated control of voltage and power angle stability of a wind power grid-connected sending-end system, characterized by: The following steps are involved: ① After the fault is cleared, the control starts to obtain the voltage at the wind turbine terminal and the angular velocity of the synchronous machines adjacent to the wind farm; ② According to the signal obtained in step ①, determine the additional control instruction of the wind turbine reactive current and the additional control instruction of the wind turbine active current; ③ Based on the principle of reactive power output priority, the additional control instruction for the wind turbine active current generated in step ② is superimposed on the control instruction during normal operation of the wind turbine to adjust the active and reactive output of the wind turbine. When the control time exceeds the required active power recovery time limit of the wind turbine, the control is exited; In step ②, the additional control instruction for the wind turbine reactive current is determined as: I q =K1(U0-U) Where, I q is the additional control instruction for the wind turbine reactive current; U and U0 are the measured value and expected value of the wind turbine terminal voltage respectively; K1 is the adjustment parameter, and K1>0; The additional control instruction of the wind turbine active current is determined as I p =-K2(ω-ω s ) Where ω and ω s are the angular velocity and synchronous speed of the synchronous machine respectively; K2 is the adjustment parameter, and K2>0; In the step ③, the wind turbine reactive current control instruction is determined as I q * =0-I q =-K1(U0-U) Where, I q * It is the reactive current control instruction of the wind turbine; The fan active current control command is determined as Where, I p * is the active current control instruction of the fan; I is the total current amplitude when the fan is operating normally.

2. The method for coordinated control of voltage and power angle stability of a wind power grid-connected sending-end system according to claim 1, characterized in that: The wind turbine active power recovery time limit requirement is 2s.

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