WO2014026314A1

WO2014026314A1 - Method for coordinating and controlling primary ring and auxiliary ring of generator excited system

Info

Publication number: WO2014026314A1
Application number: PCT/CN2012/080013
Authority: WO
Inventors: 许其品; 邵宜祥; 徐蓉
Original assignee: 国电南瑞科技股份有限公司
Priority date: 2012-08-13
Filing date: 2012-08-13
Publication date: 2014-02-20

Abstract

A method for coordinating and controlling a primary ring and an auxiliary ring of a generator excited system. An auxiliary ring controller comprises a PSS, a low-excitation limiter, an over-excitation limiter, a stator current limiter, a V/F limiter, a maximum excitation current limiter, and a difference adjuster. The method selects a low-excitation limiter model having robustness. When a power grid has large disturbance, amplification factors of the low-excitation limiter and the PSS are increased, action time of the over-excitation limiter, the stator current limiter, the V/F limiter, the maximum excitation current limiter are delayed, hysteresis is set, and difference adjustment is blocked within a set time; when the power grid has small disturbance, an amplification factor of a primary ring is increased, and an amplification factor of the PSS is decreased. The coordination and controlling method can not only implement rapid excitation controlling during large disturbance, but also ensure stability in stable state.

Description

Main and auxiliary ring coordinated control method for generator excitation system

The invention relates to a coordinated control method between a primary ring and a secondary ring, a secondary ring and a secondary ring of a main control function of a generator excitation system, and belongs to the technical field of power system excitation control.

Background technique

With the continuous expansion of the power system, the problem of grid stability has become more and more prominent, and the safety of grid operation has attracted more and more attention. The grid dispatching has put forward higher and higher requirements for the excitation system, and gradually reinforced the grid. The requirements of the system are included in the scope of power grid management. The generator excitation system is no longer just the excitation of the power plant, but also the excitation of the power system, which plays a vital role in improving the stability of the power system.

The stability of the power system can be divided into small disturbance stability problems and large disturbance stability problems. Small disturbance refers to the fluctuation of the electrical quantity of the grid caused by the slow change of the grid load. There is no change as the stability point of the dynamic system; the large disturbance refers to the fluctuation of the electrical quantity of the grid caused by the rapid change of the grid load, and the stability point has changed significantly. That is, from the old stable point to the new stable point.

The excitation system is the core control component of the generator set. It is a real-time control system. Its performance directly affects the safety production of the power plant and the safety and stability of the power grid. Therefore, the excitation system not only needs to ensure the safe and stable operation of the power plant, but also must provide strong support for the stability of the power grid, not only the control performance requirements of the small disturbance of the power grid, but also the large disturbances such as short circuits. The requirements of the rapidity and stability of the control, for this reason, the excitation system not only needs to have the rapid adjustment of the large disturbance caused by the grid fault, but also has the stability of the regulation caused by the small load disturbance caused by the grid load variation. When the power grid is disturbed, not only the main loop of the excitation system is active, but also often accompanied by various auxiliary control links. In the excitation control system, in addition to maintaining the generator terminal voltage, achieving different generator sets In addition to the reasonable distribution of reactive power and the provision of transient and static stability of the generator set, it should also provide some protection to the generator. This requires the excitation system to have a main loop that functions in the normal control. It must also contain a number of auxiliary control links, such as PSS, under-excitation limits, to limit the various dynamic oscillations. Excitation limit, stator current limit, V/F limit, maximum field current limit, minimum field current limit, and so on. These limits have a more or less impact on the control performance of the primary loop, which affects grid stability. Due to the current international standard IEEE std

421, especially in the national standard GB/T 7409. 2 in the excitation system control model between the auxiliary link and the main control link between the superposition method and the high and low door mode, when using the high and low door form of the limiter, only need to separate Considering the choice of the main and auxiliary ring models and parameters, when using the superimposed excitation system model, it is necessary to consider not only the main and auxiliary ring models and parameters, but also the coordinated control. Since the excitation system using the high and low gate modes often has large disturbances during the switching process of limiting the action and exiting, the current excitation system uses the superposition mode more.

Summary of the invention

The technical problem to be solved by the present invention is: The existing genset excitation system usually only focuses on maintaining the stability of the terminal voltage of the genset, and lacks the necessary coordinated control strategy in the case of large disturbance or failure, resulting in the genset in this case. Failure to quickly return to a new stable point and disconnected from the grid will not only provide support for the stability of the grid, but may cause the grid to expand or the stability problem becomes more prominent. In order to solve the above technical problems, the present invention provides a coordinated control method for primary and secondary rings of a generator excitation system, and the secondary ring controller includes a PSS, a low excitation limiter, an overexcitation limiter, a stator current limiter, and a V/F limit. , maximum excitation current limiter and modulation, characterized by: Selecting a robust low-excitation limiter model, increasing the excitation of the low-excitation limiter and PSS when the grid is disturbed, delaying the over-excitation limiter, Stator current limiter, V/F limiter, maximum excitation current limiter operating time and set hysteresis, lock the adjustment within the set time; increase the main loop amplification when the grid is small disturbance, reduce the PSS Magnification.

The foregoing method for coordinating control of the main and auxiliary loops of the generator excitation system is characterized in that: when the power grid is smallly disturbed, the main loop amplification factor is increased to 1-2 times, and the PSS amplification factor is reduced by 0.1-0.8 times; When the large disturbance causes the auxiliary ring controller to operate, increase the amplification of the low excitation limiter and PSS to 1.2-15 times or allow the overexcitation limiter, stator current limiter, V/F limiter, and maximum excitation current. The action time of the limiter is delayed by 0.1-1 second and the hysteresis of the nominal value of 0.1%-1% is set, and the adjustment is closed within 0.2-5 seconds.

The foregoing method for coordinating control of main and auxiliary loops of a generator excitation system is characterized by: low excitation limit

l+T _QCl xs

K X—— 3£i _

In the device, the model of the low excitation limiter is selected as ^{1 + T} qc ₂ ^XS , and when the grid is smallly disturbed, the proportional magnification is ^K q . The value range is 5-15. In the case of large disturbance of the power grid, the range of the magnification factor ^ is 20-60, where ¹ ^ is the time link constant of the lead link, ^T is the time constant of the delay link, and s is the differential operator; When the active power low-frequency oscillation amplitude is greater than 5%, the amplification factor of the PSS is increased to 1-2 times. When the active power low-frequency oscillation amplitude is less than 0.5%, the amplification factor of the PSS is reduced to 0.2-0.5 times; When the over-excitation limiter, the stator current limiter, or the V/F limiter reaches the limit start value, the over-excitation limiter, the stator current limiter, or the V/F limiter is further delayed by 0.1-0.2 seconds, and When returning, set the rated value of 0. 2-0.5% hysteresis; when the maximum excitation current limiter is activated, the excitation system reduces the generator rotor current by directly outputting the inverter angle; In the range, the adjustment function of the locked excitation system is 1-5 seconds.

The invention provides a coordinated control method for main and auxiliary loops of a generator excitation system, abandoning the traditional fixed parameter control method, and adopting a variable parameter method to ensure that each auxiliary link of the excitation system has very good dynamic adjustment characteristics and can Close cooperation, effectively solve the contradiction between the rapid adjustment of excitation and the stability of excitation control under the condition of power system steady disturbance in the case of large disturbance of power system, satisfying the power system The need for stability under various working conditions.

DRAWINGS

Figure 1 is a block diagram of the coordinated control of the excitation system;

Figure 2 is a schematic diagram showing changes in reactive power and power angle under large disturbances when controlled by fixed parameters;

Figure 3 is a schematic diagram showing the changes of reactive power and power angle under large disturbances when adaptive variable parameter control is used.

Specific real 3⁄4 ^

The auxiliary loop controller includes PSS, underexcitation limit, overexcitation limit, rotor current limit, stator current limit, V/F limit, maximum field current limit, minimum field current limit, and trimming.

In the traditional control method, the coordination between the main and auxiliary rings is not considered. Although the excitation system can ensure the high precision of the generator terminal voltage in the case of small disturbance of the power grid, it can well meet the safe production of the power plant and the stable operation of the power grid. The need, but when the power grid is disturbed, the generator unit loses stability and the grid is de-listed due to the lack of the necessary coordinated control strategy of the main and auxiliary loops, which threatens the security and stability of the grid. In the present invention, the auxiliary loop controller includes a PSS, a low excitation limiter, an overexcitation limiter, a stator current limiter, a V/F limiter, a maximum field current limiter, and a harmonic adjustment, and a robust low excitation limit is selected. Model, when the grid is disturbed, increase the amplification of the low excitation limiter and PSS, delay the operation time of the overexcitation limiter, stator current limiter, V/F limiter, maximum excitation current limiter and set hysteresis. The adjustment is closed during the set time; when the grid is small, the main loop amplification is increased, and the amplification factor of the PSS is reduced.

1. Through the coordinated control strategy of the main and auxiliary loops, ensure that the excitation system can maintain the adjustment accuracy of the generator terminal voltage when the grid is smallly disturbed, and achieve rapid adjustment when the grid is disturbed, thereby improving the transient stability of the grid. Sexuality, achieving the uniformity of the rapidity and stability of the excitation system's regulation performance;

2. Coordination control method for main and auxiliary loops of generator excitation system, mainly by selecting appropriate auxiliary loop control model combined with variable parameter control means to coordinate the rapid adjustment of small disturbances in the grid and the adjustment of small disturbances Stability. Firstly, it is guaranteed that the auxiliary loop control model has excellent regulation performance and has very good robustness. Secondly, it ensures that the auxiliary loop control parameters can be automatically adjusted according to the change of working conditions to meet the rapid adjustment of large disturbances;

3. The coordinated control strategy solves the main contradictory transformation problem. For different auxiliary control functions, different control strategies are adopted to achieve:

i) When the low-frequency oscillation becomes the main contradiction of the grid stability, the excitation system quickly subsidizes the active power oscillation of the grid at the expense of the adjustment accuracy of the generator terminal voltage;

ϋ) When the generator set is deep into phase and the unit is running within the demagnetization protection impedance circle, the power angle stability of the generator set becomes the main contradiction. At this time, the accuracy of the terminal voltage regulation of the generator set is sacrificed, and even the active power oscillation amplitude of the power grid is At the cost, to ensure that the power angle of the generator set is stable;

Iii) Over-excitation limits, stator current limiters and V/F limiters need to be set to limiters with anti-time and hysteresis characteristics depending on the rotor or stator or core of the generator, the teeth and the thermal characteristics of the generator end. The frequent movement of the limiter instantaneously or at the boundary affects the normal regulation of the excitation system;

Iv) The maximum field current limiter shall ensure the safety of the generator rotor. When the rotor current of the generator exceeds its maximum allowable value, the excitation system will rapidly reduce the generator rotor current at the expense of other control performance;

V) The adjustment of the excitation system is to achieve a reasonable distribution of the reactive power of the generator set in parallel operation. It is a requirement of stable characteristics. When the transient or dynamic stability of the power grid or unit rises as the main contradiction, the adjustment link The role of other control links should not be weakened.

The core of the invention is a coordinated control method between the primary ring and the secondary ring, which solves the problem of the rapidity of the excitation control during large disturbances and the stability of the excitation control during small disturbances. In normal operation, the generator set excitation system should not only maintain the terminal voltage stability through the main loop control. It can also quickly start various auxiliary control links such as stability, limitation and protection in the case of large disturbances or faults, and cooperate with the main ring to provide support for the stability of the power grid. This patent conducts in-depth research on each auxiliary link of the excitation system, establishes a reasonable coordinated control strategy between the main ring and the auxiliary ring, and adopts the method of variable parameters, which not only ensures that the auxiliary links of the excitation system have very good dynamic adjustment characteristics. Moreover, it can closely cooperate to effectively solve the contradiction between the rapid regulation of excitation and the stability of excitation control under the condition of high power system disturbance, and meet the demand for stability under various working conditions of power system. In the low excitation limit function, the traditional fixed parameter control and the adaptive variable parameter control method are respectively used under the large disturbance. Fig. 2 and Fig. 3 are comparison diagrams of the test adjustment effects of the two. It can be seen from the figure that the adjustment speed of the adaptive variable parameter control is significantly faster than the fixed parameter control, and the adjustment time (reactive power is restored to the limit value) is shortened from 4.5 s to 1. 5s o The swing amplitude is reduced by about 4 degrees, and the power angle stability margin of the generator is significantly increased. The control of any auxiliary ring should first be able to coordinate with the main ring to ensure the stability of the generator set and the adjustment accuracy of the generator terminal voltage within the allowable range, and can provide support for the stability of the power grid, that is, when the low excitation limit action, Preventing the deep phase of the generator from causing the degeneration function of the generator group, the low excitation limiter should be able to quickly control the operating point of the generator set beyond the range of the demagnetization protection action of the generator and transformer group, without causing long-term oscillation; When low-frequency oscillation occurs, in order to prevent the amplitude of the oscillation from increasing and causing line overload, it should be able to provide sufficient positive damping to suppress low-frequency oscillation. When the generator rotor current exceeds the allowable long-term running current, the over-current limiter should be correct. According to the heat capacity of the generator rotor, the heat accumulation of the generator rotor is correctly calculated. When the heat generated by the generator rotor exceeds the set value, the overexcitation limiter can operate correctly, and the rotor current of the generator is quickly limited to the allowable current value of long-term operation. To ensure the safety of the rotor insulation of the generator; when the stator current of the generator Allowed values over time, adjusting the excitation The device can correctly calculate the cumulative capacity. When the accumulated heat reaches the allowable heat, it can automatically perform the magnetization or demagnetization control according to the generator operating conditions to ensure that the generator stator temperature is within the allowable range, and the generator stator insulation life is not If the generator V/F ratio exceeds the set value, in order to ensure the normal control adjustment of other links, V/F should not act immediately, but should make appropriate delay according to the size of the V/F ratio; When the generator rotor current exceeds the allowable strong excitation multiple, the channel switching can be performed; when the generator rotor current exceeds the top value current of the generator rotor, the protection trip can be started; the generator is adjusted to ensure parallel power generation. The units can be reasonably distributed, and according to the capacity of the unit, to determine the capacity of the unit with different capacity to support the grid reactive power, it is a steady-state distributor of reactive load, which should not be used in the transient process. Affect the role of other control links. Only the above-mentioned auxiliary links can realize coordinated control, and the excitation system can provide the most powerful support for the safe production of the unit and the safety and stability of the power grid. The above-mentioned embodiments are not intended to limit the technical solutions of the present invention in any way, and any technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

Claim

1. A primary and secondary loop coordinated control method for a generator excitation system, the secondary loop controller including a PSS, a low excitation limiter, an overexcitation limiter, a stator current limiter, a V/F limiter, a maximum field current limiter, and The adjustment is characterized by: Selecting a robust low-excitation limiter model to increase the amplification of the low-excitation limiter and PSS when the grid is disturbed, delay over-excitation limiter, stator current limiter, V/F The action time of the limiter and the maximum excitation current limiter is set and hysteresis is set, and the adjustment is blocked within the set time; when the grid is small, the main loop amplification is increased, and the amplification factor of the PSS is reduced.

2 . The method for coordinated control of main and auxiliary loops of a generator excitation system according to claim 1 , wherein: when the power grid is smallly disturbed, the primary loop amplification factor is increased to 1-2 times, and the amplification factor of the PSS is reduced. 0.1-0.8 times; When the auxiliary disturbance controller is operated by the large disturbance of the power grid, increase the amplification factor of the low excitation limiter and PSS to 1.2-15 times or let the overexcitation limiter, stator current limiter, V/ The limit time of the F limiter and the maximum field current limiter is 0.1-1 second and the hysteresis of the rated value is set to 0.1%-1%, and the adjustment is closed within 0.2-5 seconds.

3. The method for coordinated control of primary and secondary rings of an excitation system of a generator according to claims 1 and 2,

l+T _QCl xs

K X—— 3£i _

The sign is: In the low-excitation limiter, the model of the low-excitation limiter is ^ ^{1 + Τ} - ^{2 Χ} \ In the case of small disturbances in the grid, the scale of the magnification factor ^K is 5-15, when the grid is disturbed , Proportional magnification ^K q. The value range is 20-60, where ¹ ^ is the lead time constant, ^τ ^ is the time delay of the delay link, s is the differential operator; when the active power low frequency oscillation amplitude is greater than 5%, increase the amplification of PSS to The original 1-2 times, when the active power low frequency oscillation amplitude is less than 0.5%, reduce the PSS amplification factor to 0.2-0.5 times; when the overexcitation limiter, stator current limiter or V/F limiter reaches the limit When the starting value is set, let the over-excitation limiter, the stator current limiter or the V/F limiter delay 0. 1-0.2 seconds, and set the rated value of 0. 2-0.5% hysteresis when returning; Excitation system when the maximum excitation current limiter is activated The generator rotor current is reduced by directly outputting the inverter angle; when the generator operating point exceeds the safe working range, the adjustment function of the blocking excitation system is 1-5 seconds.