CN114530863A - Excitation control method for improving power grid stability of double-shaft excitation phase modulator - Google Patents

Abstract

The invention discloses an excitation control method for a dual-axis excitation control camera to improve the stability of the power grid. On the basis of a reactive power-voltage coordinated control strategy, the system side voltage is introduced as a feedback input. In the steady state, the reactive power is used as the control target to achieve slow regulation to meet the system's demand for reactive power; in the transient state, the system side voltage is used as the control target to achieve fast response, and when large disturbances or short-term faults occur in the system Fast and strong excitation to maintain the voltage stability of the system side. In addition, a PID correction circuit is introduced before the amplification link, thereby improving the stability of the excitation system and the rising speed of the excitation voltage during strong excitation. The excitation control method of the dual-axis excitation camera provided by the present invention starts from the input quantity of the excitation control system and the excitation system, which not only improves the stability of the excitation system and the excitation voltage rise speed during strong excitation, but also satisfies the grid's response to reactive power The power demand improves the grid voltage stability.

Description

An excitation control method for improving the stability of the power grid by a dual-axis excitation camera

technical field

The invention relates to an excitation control method for improving the stability of a power grid by a dual-axis excitation regulator, in particular to an excitation control method for maintaining the transient stability of a power system after the dual-axis excitation regulator is connected to the grid.

Background technique

With the development of new energy power generation technology and high-voltage direct current transmission technology, the power grid of the sending end of new energy power generation changes drastically in the face of faults such as DC system line failure, commutation failure at the receiving end, and DC blocking, and may even be disconnected from the grid. Affect the grid voltage stability. Compared with the traditional large-scale condensers built on the main grid side, the distributed condensers built near the new energy plant station can not only play the role of the system dynamic reactive power reserve, but also provide sub-transient and transient conditions for the new energy power station. , Steady-state whole process voltage support.

In addition, the traditional synchronous camera adopts single-axis excitation, which is affected by the motor parameters, and the phase-advance capability is not as good as the retardation capability, and cannot effectively suppress transient overvoltage. The traditional reactive power-voltage coordinated control strategy aims to maintain the stability of the machine terminal voltage. When the system side voltage drops, the camera sends out reactive power for adjustment. At this time, the machine terminal voltage is stable and the system side voltage drops. That is, when the terminal voltage is used as the control target, the system voltage cannot be guaranteed to be stable.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention provides an excitation control method for improving the stability of a power grid by a dual-axis excitation control camera, including:

1. Two-phase excitation windings that are perpendicular to each other are distributed on the rotor of the dual-axis excitation control camera. The structural parameters and excitation conditions of the two-phase excitation windings are the same. The size of the excitation current can be flexibly adjusted to change the excitation state of the camera. In the case of strong excitation, increase the excitation current so that the combined excitation electromotive force is greater than the machine terminal voltage, and the modulator emits reactive power. When under-excited, reduce the excitation current so that the combined excitation electromotive force is less than the machine terminal voltage, and the modulator absorbs reactive power;

2. Incorporate the dual-axis excitation camera into the power grid, and measure the camera terminal voltage, reactive power and system side voltage;

3. Calculate the difference between the actual value of the camera terminal voltage and the reference value of the camera, and act on the PID correction circuit to achieve fast forced excitation and maintain the stability of the terminal voltage;

4. Calculate the difference between the actual value of the reactive power of the camera and the reference value, and act on the PID correction circuit through the integral link to realize the fine-tuning of the excitation current and meet the system's demand for reactive power;

5. Calculate the difference between the actual value of the system side voltage and the reference value, and act on the PID correction circuit through amplification, phase compensation, and amplitude limiting links to improve the system voltage stability;

6. Further, the size of the excitation current of the two axes is the same, and the angle between the combined excitation current and the d-axis satisfies: θ=45°;

7. Further, the synthetic excitation electromotive force and the terminal voltage of the machine are in the same or opposite direction when the active power loss of the camera is not counted;

8. Further, when the total input of the PID correction circuit is equal to zero, the excitation is normal. When the total input of the PID correction circuit is greater than zero, the excitation currents of the d and q axes are reduced, and the phase-modulator runs in phase advance, which appears to absorb reactive power. When the total input of the PID correction circuit is less than zero, the excitation currents of the d and q axes are increased, and the phase-modulator runs late, which is manifested as generating reactive power;

9. Further, when the error rate of change input to the PID correction circuit is greater than zero, reduce the excitation currents of the d and q axes. When the error rate of change input to the PID correction circuit is less than zero, increase the excitation current of the d and q axes;

10. Further, the output of the PID correction circuit is amplified, limited, phase-shifted trigger, and rectified to obtain the excitation electromotive force.

As described above, the excitation control method for improving the stability of the power grid provided by the dual-axis excitation camera provided by the present invention has the following effects:

The two-phase excitation current of the dual-axis excitation controller is the same, which can reduce the heating of the rotor; the two-phase excitation winding adopts the same excitation control strategy, and a set of excitation system is used to supply power to the two-phase excitation winding, which is easy to operate and saves costs; and traditional synchronous regulation Compared with the camera, the dual-axis excitation modulated camera breaks through the limit of zero minimum excitation current, and can obtain the short-term phase advance capability equivalent to the retardation capability through reverse strong excitation, which can meet the system's demand for reactive power; the introduction of the system voltage As a feedback quantity, the grid voltage stability can be improved; the introduction of a PID correction circuit can improve the stability of the excitation system and the rising speed of the excitation voltage during strong excitation.

Description of drawings

Fig. 1 is the method flow chart of the present invention;

Figure 2 is a functional model of the excitation system of the present invention.

Detailed ways

Many specific details are set forth in the following description to facilitate a full understanding of the present invention. Obviously, the described embodiment is only an example of the present invention, and the present invention can also be implemented or applied by other different specific embodiments. Various details in this specification can also be modified or changed in various ways without departing from the spirit of the present invention based on different viewpoints and applications. Accordingly, the present invention is not limited by the specific implementations disclosed below.

As shown in FIG. 1 , the present invention provides an excitation control method for a dual-axis excitation camera to improve the stability of a power grid, and the method includes the following steps:

1. The 50Mvar hidden-pole distributed modulator is selected, and excitation windings are arranged on the d and q axes of the rotor. The two-phase excitation windings are perpendicular to each other and have the same parameters.

2. Use the same excitation control strategy for the two-phase excitation windings to ensure that the excitation voltage and excitation current of the two-phase excitation windings are the same, that is, u _fd =u _fq , _ifd = _ifq .

3. Incorporate the dual-axis excitation camera into the power grid through the step-up transformer, measure the camera terminal voltage, current and system side voltage, and calculate the reactive power emitted by the camera. Machine terminal voltage, reactive power and system side voltage, namely U _g , Q and U _s in Figure 2.

4. Calculate the difference between the actual value U _g of the camera terminal voltage and the reference value U _ref , and directly input it to the PID correction circuit. Calculate the difference between the actual value Q of the reactive power of the camera and the reference value Q _ref , and input it to the PID correction circuit through the integral link. Calculate the difference between the actual value U _s of the system voltage and the reference value U _sref , and input it to the PID correction circuit through amplification, phase compensation, and amplitude limiting. Add the 3 inputs to get the total input deviation.

5. The PID correction circuit uses a parallel proportional-integral-derivative correction circuit, and the expression is

中的放大倍数k_A＝50，时间常数T_A＝0.1s。限幅环节设置一个最大励磁电压和最小励磁电压，避免因强励过分引起励磁绕组过热或欠励过分引起调相机失步。整流电路

中的放大倍数k_z＝1，时间常数

6. The output of the PID correction circuit is amplified, limited, phase-shifted trigger, and rectified circuit, and finally the excitation electromotive force is output. Among them, the amplifier circuit

The magnification k _A =50 in , and the time constant T _A =0.1s. A maximum excitation voltage and a minimum excitation voltage are set in the limiter link to avoid overheating of the excitation winding or over-excitation caused by the over-excitation of the rectifier. Rectifier circuit

The magnification in k _z = 1, the time constant

The foregoing descriptions of embodiments of the present invention have been presented for purposes of illustration and description. The present invention may also have other various embodiments, and those skilled in the art can make various corresponding changes and modifications according to the present invention without departing from the spirit and essence of the present invention, but these corresponding changes and All modifications belong to the protection scope of the appended claims of the present invention. Therefore, it is to be understood that this invention is intended to cover all modifications and the like coming within the scope of the following claims.

Claims (4)

1. An excitation control method for a dual-axis excitation control camera to improve the stability of a power grid, the method comprising: excitation regulation of an excitation system acts on a two-phase excitation winding, so that the excitation currents of the two phases are equal in size, and the unbalance due to excitation current is reduced. Rotor heating caused by rotor heating; real-time acquisition of system side voltage, camera terminal voltage and reactive power; in steady state, reactive power control is the goal, and the actual value of reactive power changes with the reference value to meet the system’s demand for reactive power ;Target stable voltage in transient state, the actual value of the dual-axis excitation camera terminal voltage changes with the reference value, and the actual value of the system side voltage follows the reference value. Excitation to maintain the system side voltage stability; PID correction circuit compensates and corrects the input small deviation signal, so that the excitation system runs stably within the working range. 2. The excitation control method for improving the stability of the power grid for a dual-axis excitation camera according to claim 1, characterized in that: a reactive power control outer loop is introduced, and within the time when the system is running in a steady state, the reactive power The difference between the actual value and the reference value fine-tunes the field current. 3. The excitation control method for improving grid stability of a dual-axis excitation camera according to claim 1, characterized in that: on the basis that the excitation system of the dual-axis excitation camera is introduced into the machine terminal voltage as a feedback amount, an additional The system side voltage is used as the feedback value. When the busbar voltage on the system side is greatly reduced, the system side voltage deviation is introduced into the calculation, thereby improving the reactive power output of the dual-axis excitation camera and improving the system voltage stability. 4. The excitation control method for a dual-axis excitation control camera according to claim 1 to improve the stability of the power grid, characterized in that: the introduction of a PID correction circuit can both improve the stability of the excitation system and increase the speed of excitation voltage during strong excitation , and can reduce the steady-state error, thereby improving the static voltage regulation accuracy.

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