CN112202208A - Small hydropower station micro-grid generator ad hoc network control method and system - Google Patents
Small hydropower station micro-grid generator ad hoc network control method and system Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
- H02J3/241—The oscillation concerning frequency
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
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Abstract
The embodiment of the invention discloses a small hydropower micro-grid generator ad hoc network control method and a system, wherein the method comprises the following steps: collecting the power grid frequency of the small hydropower microgrid, and taking the collected power grid frequency as a first frequency; determining whether to perform high-cycle tripping protection according to the first frequency; if the high-cycle tripping machine protection is carried out, tripping action of the high-cycle tripping machine is determined according to the change rate of the first frequency; collecting the power grid frequency of the small hydropower microgrid after the high-cycle generator tripping and taking the power grid frequency as a second frequency; and carrying out hierarchical frequency modulation control on the second frequency according to the output power and the reference frequency of the small hydropower microgrid after the high-frequency generator is switched off. According to the technical scheme provided by the embodiment of the invention, the action of the high-cycle generator tripping machine is determined according to the change rate of the first frequency, the capacity of the generator tripping machine can be prevented from being over-cut or under-cut, the frequency modulation control is carried out on the second frequency after the generator tripping machine, the second frequency output by the small hydropower microgrid in an island operation state can be quickly stabilized, and the second frequency is in a normal range.
Description
Technical Field
The embodiment of the invention relates to the technical field of microgrid control, in particular to a small hydropower station generator ad hoc network control method and system.
Background
The small hydropower microgrid can solve the problems that the power distribution and long-distance transmission of a large power grid are too concentrated, the recovery is slow, the fault is caused and the like after being influenced by an accident, and the power supply requirements of people are met.
The small hydropower microgrid conforms to the new sustainable development concept of economy and environmental protection, can supply power to a large power grid on the basis of zero-pollution power supply, and has high benefit and economy. However, the small hydropower microgrid does not have an automatic frequency modulation device, when the small hydropower microgrid is disconnected with a large power grid and runs in an island state, the frequency of the small hydropower microgrid suddenly rises to damage the power grid and user equipment, and meanwhile, due to the lack of a communication means meeting scheduling requirements, difficulties are brought to networking and frequency modulation control of the small hydropower microgrid.
Disclosure of Invention
The embodiment of the invention provides a small hydropower micro-grid generator ad hoc network control method and system, and aims to solve the problems of small hydropower micro-grid networking and frequency modulation control.
In a first aspect, an embodiment of the present invention provides an ad hoc network control method for a small hydropower micro-grid generator, including:
collecting the power grid frequency of the small hydropower microgrid, and taking the collected power grid frequency as a first frequency;
determining whether to perform high-cycle tripping protection according to the first frequency;
if the high-cycle cutting machine protection is carried out, the cutting machine action of the high-cycle cutting machine is determined according to the change rate of the first frequency;
collecting the power grid frequency of the small hydropower microgrid after the high-cycle generator tripping and taking the power grid frequency as a second frequency;
and carrying out hierarchical frequency modulation control on the second frequency according to the output power and the reference frequency of the small hydropower microgrid after the high-frequency generator is switched off.
Optionally, the determining whether to perform high cycle tripping protection according to the first frequency comprises:
if the first frequency is greater than or equal to a preset frequency and the duration time is greater than or equal to a preset time, protecting the high-frequency generator tripping machine; the preset frequency is the frequency of a first wheel cutter of the high-circumference cutter.
Optionally, if the high-cycle tripping protection is performed, the determining tripping action of the high-cycle tripping according to the change rate of the first frequency includes:
if the change rate of the first frequency is larger than the first change rate, starting a third wheel cutting machine;
if the change rate of the first frequency is greater than the second change rate and smaller than the first change rate, starting a second wheel cutting machine;
otherwise, the first wheel cutting machine is started.
Optionally, after the third wheel cutter is operated, the second wheel cutter and the first wheel cutter are performed in sequence.
Optionally, the cutting capacity of the high-circumference cutter is as follows in sequence from large to small: the device comprises a second wheel cutter, a third wheel cutter and a first wheel cutter, wherein the cutting capacity of the third wheel cutter is equal to that of the first wheel cutter.
Optionally, the hierarchical frequency modulation control comprises a primary frequency modulation control and a secondary frequency modulation control.
Optionally, the primary frequency modulation control comprises:
and adjusting the second frequency by adopting a droop control mode according to the output power of the small hydropower microgrid after the high-frequency generator is switched off.
Optionally, the secondary frequency modulation control comprises:
and adjusting the second frequency by adopting a closed loop PI control mode according to the reference frequency.
Optionally, if it is determined to perform high-cycle tripping protection according to the first frequency, before performing the high-cycle tripping protection, the method includes:
and calculating the change rate of the first frequency according to the power shortage of the small hydropower microgrid.
In a second aspect, the embodiment of the invention further provides a small hydropower micro-grid generator ad hoc network control system, which comprises the small hydropower micro-grid generator ad hoc network control method provided by any embodiment of the invention.
According to the technical scheme provided by the embodiment of the invention, whether high-cycle tripping protection is needed or not is determined according to the acquired first frequency of the small hydropower micro-grid, when the high-cycle tripping protection is determined, the action of the high-cycle tripping is determined according to the change rate of the first frequency, the phenomenon that the capacity of the small hydropower micro-grid is cut off too much or the capacity of the small hydropower micro-grid is cut off too little can be avoided, the second hydropower frequency output by the small hydropower micro-grid in an island operation state can be quickly and stably controlled by reasonably configuring the action of the high-cycle tripping and carrying out frequency modulation control in combination with the second frequency output by the small hydropower micro-grid after tripping, and the second frequency is in a normal range.
Drawings
Fig. 1 is a flowchart of an ad hoc network control method of a small hydropower station micro grid generator according to an embodiment of the invention;
fig. 2 is a schematic structural diagram of an equivalent circuit of a grid-connected hydroelectric generating set according to a first embodiment of the present invention;
fig. 3 is a flowchart of another ad hoc network control method of the small hydropower micro grid generator according to the second embodiment of the present invention;
fig. 4 is a flowchart of another ad hoc network control method of the small hydropower micro grid generator according to the second embodiment of the present invention;
fig. 5 is a schematic structural diagram of a hierarchical fm control according to a third embodiment of the present invention;
fig. 6 is a waveform diagram of an ad hoc network of a small hydropower micro grid generator provided by a third embodiment of the invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It is to be further noted that, for the convenience of description, only a part of the structure relating to the present invention is shown in the drawings, not the whole structure.
Example one
Fig. 1 is a flowchart of a small hydropower station generator ad hoc network control method according to an embodiment of the present invention, and referring to fig. 1, the small hydropower station generator ad hoc network control method according to the embodiment of the present invention includes:
s110, collecting the power grid frequency of the small hydropower microgrid, and taking the collected power grid frequency as a first frequency.
Specifically, the small hydropower stations can form a small power grid to independently operate or output electric energy to a large power grid, and when the frequency of the power grid where the small hydropower micro-grid is located is synchronous with the frequency of the large power grid, the small hydropower micro-grid can be connected to the power grid and can be connected with the large power grid to operate. When the little water and electricity microgrid breaks away from big electric wire netting, when supplying power to other consumer alone, be in island operating condition promptly, if little water and electricity microgrid island operation, can influence the power supply efficiency greatly, reduce the life of equipment easily, various electronic instrument also can cause certain harm. Little water and electricity is many to be distributed in remote mountain area, inserts distribution network 10kV feeder end more, has the characteristics that the capacity is little, the position dispersion, the regulation performance is poor, compares with networking power system, and the island is because various frequency modulation means limit and reactive compensation control means are not enough, and static stability and dynamic stability are all relatively poor, generally can recover through the power generation adjustment of longer time when active imbalance takes place, frequency collapse and voltage collapse phenomenon appear even. Because the operation state of the small hydropower microgrid is related to the frequency of the power grid where the small hydropower microgrid is located, the frequency of the power grid where the small hydropower microgrid is located can be detected by a hardware or software method, and the detected frequency of the power grid is used as the first frequency. For example, a hardware technology method such as a phase-locked loop or a counter can be adopted to detect the frequency of a power grid where the small hydropower station micro-grid is located, a closed loop formed by a phase comparator and an oscillator is used for realizing frequency tracking locking, the period of a signal is measured firstly, and the signal is converted into the frequency so as to improve the precision of frequency detection; and a software method for performing Fourier transform on the voltage and current output by the small hydropower microgrid can be adopted to obtain the frequency of the power grid where the small hydropower microgrid is located.
And S120, determining whether to perform high-cycle tripping protection according to the first frequency.
Specifically, after a plurality of small hydropower stations form a microgrid, the frequency of the small hydropower stations is controlled by adopting a V-F mode under a grid-connected mode; the frequency of the small hydropower station microgrid is controlled in a P-Q mode in an island mode, and the problem of frequency deviation caused by a large amount of unbalanced power generated due to disconnection of a connecting line between the microgrid and a large power grid is solved through an active power control strategy. The high-cycle generator tripping protection can ensure that the small hydropower microgrid can stably operate, and when the power system has active power surplus and the collected first frequency rises, the generator with proper capacity is cut off in time to ensure that the small hydropower microgrid formed by the surplus generator can quickly recover to the rated power to continue to operate.
S130, if the high-cycle cutting machine protection is carried out, the cutting machine action of the high-cycle cutting machine is determined according to the change rate of the first frequency.
Specifically, in order to reduce the influence of sudden rise of first frequency on a user or a hydroelectric generating set caused by the fact that an outgoing channel of the small hydropower microgrid is blocked, a high-frequency generator is adopted to protect a part of surplus generators which are cut off rapidly, so that the small hydropower microgrid in an island operation mode can maintain the stability of frequency. However, the protection of the high-frequency generator tripping machine is often insufficient or excessive due to the system capacity, so that the frequency of the small hydropower microgrid after the generator tripping is difficult to maintain at the rated power. Therefore, the technical solution provided by the embodiment of the present invention determines the action of the high-frequency cutting machine according to the change rate of the first frequency, wherein the action of the high-frequency cutting machine may include a multi-wheel cutting machine. For example, if the change rate of the first frequency is small, the first wheel cutting machine can be directly carried out to cut off less capacity of the generator set; if the change rate of the first frequency is large, the generator set can be cut off in multiple turns so as to prevent the over-cutting or under-cutting phenomenon.
Fig. 2 is a schematic structural diagram of an equivalent circuit for grid connection of a hydroelectric generating set according to an embodiment of the present invention, and referring to fig. 2, a difference between an output power of a synchronous generator SG and a consumption power of a load L may be balanced by a large power grid, so that a frequency of the entire system may be kept unchanged, that is, a small hydroelectric microgrid composed of the synchronous generator SG and the load L is in a grid-connected operation mode. When the electric power system breaks down, the outward transmission channel of the small hydropower station micro-grid is blocked, the circuit breaker CB is opened, the connection between the small hydropower station micro-grid and the large power grid is broken, the small hydropower station micro-grid is in an island operation mode, and the active power of the small hydropower station micro-grid is in an unbalanced state. Due to the fact that the small hydropower microgrid delivers power outwards at a high power, the frequency of the small hydropower microgrid in an island state suddenly rises due to surplus active power, namely the collected first frequency rises, and the first frequency dynamically changes. The relay ROOF can detect the speed of the change of the first frequency and determine the action of the high-cycle cutting machine based on the change rate of the first frequency. The relay ROCOF can sample a frequency signal of a terminal voltage of the synchronous generator SG and calculate a frequency change rate.
And S140, collecting the power grid frequency of the small hydropower microgrid after the high-frequency generator tripping and taking the power grid frequency as a second frequency.
S150, carrying out hierarchical frequency modulation control on the second frequency according to the output power and the reference frequency of the small hydropower microgrid after the high-cycle generator tripping.
Specifically, in order to keep the output frequency of the small hydropower microgrid subjected to high-cycle generator tripping protection stable, the frequency of the small hydropower microgrid in an island operation mode needs to be modulated. And acquiring the power grid frequency of the small hydropower microgrid after the generator is cut as a second frequency, and performing hierarchical frequency modulation control on the second frequency according to the power output by the small hydropower microgrid after the generator is cut and a reference frequency, wherein the hierarchical control can comprise primary frequency modulation control and secondary frequency modulation control, and the reference frequency is used for performing feedback regulation on the second frequency. The frequency modulation control is carried out on the small hydropower station micro-grid after the machine is switched under the island operation mode, so that the output frequency of the small hydropower station micro-grid is kept stable, and the small hydropower station micro-grid is quickly recovered to the rated power to continue to operate.
According to the self-networking control method of the small hydropower microgrid generator, whether high-frequency generator tripping protection needs to be carried out on the small hydropower microgrid is determined according to the collected first frequency of the small hydropower microgrid, when the high-frequency generator tripping protection is determined, the action of the high-frequency generator tripping is determined according to the change rate of the first frequency, the situation that the capacity of the small hydropower microgrid is cut off too much or too little can be avoided, the action of the high-frequency generator tripping is reasonably configured, frequency modulation control is carried out on the second frequency output by the small hydropower microgrid after the generator tripping, the second frequency output by the small hydropower microgrid in an island operation state can be rapidly and stably controlled, and the second frequency is in a normal range.
Example two
Fig. 3 is a flowchart of another ad hoc network control method of a small hydropower micro grid generator provided in the second embodiment of the present invention, and fig. 4 is a flowchart of another ad hoc network control method of a small hydropower micro grid generator provided in the second embodiment of the present invention, on the basis of the above embodiments, referring to fig. 3 and fig. 4, the ad hoc network control method of a small hydropower micro grid generator provided in the second embodiment of the present invention includes:
s210, collecting the power grid frequency of the small hydropower microgrid, and taking the collected power grid frequency as a first frequency.
S220, if the first frequency is greater than or equal to the preset frequency and the duration is greater than or equal to the preset time, the high-frequency generator tripping protection is carried out.
And S230, if the change rate of the first frequency is greater than the first change rate, starting the third wheel cutting machine.
S240, if the change rate of the first frequency is larger than the second change rate and smaller than the first change rate, the second wheel cutting machine is started.
And S250, otherwise, starting the first wheel cutting machine.
Specifically, preset frequency fop is the first round of cutter frequency of high cycle cutter, first frequency f1 when gathering surpasss preset frequency fop, and duration when surpassing the preset time, show that the outward channel of little water and electricity microgrid is obstructed, little water and electricity microgrid is in island operation mode, in order to avoid arousing the frequency surge because of the outward channel is obstructed, cause the influence to user equipment and hydroelectric generating set, can adopt high cycle cutter protection to cut off partial surplus generator fast, in order to ensure that generating set and user equipment can the safe and stable operation. At the moment, the small hydropower microgrid carries out high power, the frequency of the small hydropower microgrid in an island state suddenly rises due to surplus active power, namely the acquired first frequency f1 rises, and the first frequency f1 dynamically changes. The tripping action is determined from the rate of change df/dt of the first frequency, which may be calculated by the relay. Illustratively, if the rate of change df/dt of the first frequency is less than the second rate of change dop2, the first wheel cutter is directly activated, cutting off a portion of the generator; if the change rate df/dt of the first frequency is greater than the second change rate dop2 and less than the first change rate dop1, starting the second wheel cutting machine, and performing the first wheel cutting machine after the second wheel cutting machine is completed; and if the change rate df/dt of the first frequency is greater than the first change rate dop1, indicating that the frequency change amplitude of the small hydropower microgrid is large, and starting the third tripping machine. After the third round of cutting, the second round of cutting and the first round of cutting are carried out in sequence.
Optionally, the cutting capacity of the high-circumference cutting machine is as follows from large to small: the second wheel cutter, the third wheel cutter and the first wheel cutter, wherein the cutting capacity of the third wheel cutter is equal to the cutting capacity of the first wheel cutter.
Specifically, ablation capacity refers to the percentage of the total amount of load that can be ablated by each round of the cutter. When unbalanced power occurs in the small hydropower microgrid, the unbalanced power is firstly converted into kinetic energy through a generator rotor to influence the rotating speed and the frequency of the generator, and the frequency change of the generator can cause the frequency regulation effect of a prime mover, a speed regulator and a load to form power opposite to the input unbalanced power, and the power is fed back to the input unbalanced power. Therefore, the frequency adjusting capability of the system mainly depends on the rotation inertia of the generator set rotor, the adjusting effect of the prime motor and the speed regulator, the adjusting effect of the load and the like, when a part of the capacity of the generator is cut off, the rotation inertia of the generator set rotor, the adjusting effect of the prime motor and the speed regulator and the adjusting effect of the load are reduced in proportion, so that the frequency adjusting capability of the system is greatly reduced, and frequency oscillation is easily caused. It can be seen that the cutting capacity of the high-frequency cutting machine cannot be increased once, and in order to maintain the frequency regulation capability of the system, the total cutting capacity should be divided into a plurality of rounds of batch cutting, for example, the cutting capacity of each round can be determined according to the total cutting capacity and the setting value of the high-frequency cutting machine, the cutting capacity of the first round cutting machine is 30% of the total capacity, the cutting capacity of the second round cutting machine is 40% of the total capacity, and the cutting capacity of the third round cutting machine is 30% of the total capacity.
And S260, collecting the power grid frequency of the small hydropower microgrid after the high-frequency generator tripping and taking the power grid frequency as a second frequency.
And S270, carrying out hierarchical frequency modulation control on the second frequency according to the output power and the reference frequency of the small hydropower microgrid after the high-cycle generator tripping.
Alternatively, if it is determined that the high-cycle cutter protection is performed according to the first frequency f1, before performing the high-cycle cutter protection, the method includes: and calculating the change rate df/dt of the first frequency according to the power shortage of the small hydropower microgrid. Referring to fig. 2 and 4, in order to enable the relay ROCOF to operate reliably, the relay ROCOF needs to be set so that the second frequency f2 of the small hydropower station microgrid in the island operation mode is maintained at a desired frequency value, and the desired frequency value is set to 55Hz in order to avoid reconnection of the small hydropower station microgrid. Rate of change of first frequency
Wherein f isNThe rated frequency of the small hydropower micro-grid is set; t is any moment after the small hydropower microgrid has power shortage; delta PtThe power shortage of the small hydropower microgrid at the time t can be obtained from an empirical value; h is the inertia time constant after a plurality of generators of the small hydropower micro-grid are combined into one equivalent generator,
i is an integer greater than 1. The change rate df/dt of the first frequency can be calculated according to the formula, the action of the high-frequency tripping machine is determined according to the change rate df/dt of the first frequency, and the hierarchical frequency modulation control is performed on the second frequency f2 according to the output power of the small hydropower micro grid after the high-frequency tripping machine and the reference frequency, so that the second frequency output by the small hydropower micro grid in the island operation mode can be maintained at the expected frequency value, and the safe and stable operation of the small hydropower micro grid is further ensured.
EXAMPLE III
Fig. 5 is a schematic structural diagram of a hierarchical frequency modulation control according to a third embodiment of the present invention, and referring to fig. 4 and fig. 5, on the basis of the foregoing embodiments, the hierarchical control according to the third embodiment of the present invention includes a primary frequency modulation control and a secondary frequency modulation control. As the hydropower enrichment area is mostly located in a mountainous area, effective communication conditions are lacked, the conditions for centralized control through the microgrid dispatching center are immature, and then the hydropower enrichment area is put to a simple, flexible and cost-effective peer-to-peer control mode. The existing small hydroelectric generating sets do not all have frequency modulation capability, the regional positions of the hydroelectric generating sets are centralized, the reservoir capacity of the hydroelectric generating sets does not have economical difference, and the advantage of tertiary frequency modulation control for ensuring economical efficiency in classical frequency modulation control is not obvious, so that only primary frequency modulation control and secondary frequency modulation control are considered in the embodiment of the invention. The primary frequency modulation control comprises: and adjusting the second frequency f2 by adopting a droop control mode according to the output power of the small hydropower microgrid after the high-frequency generator is switched off. The secondary frequency modulation control comprises the following steps: the second frequency f2 is adjusted in a closed loop PI control manner based on the reference frequency. Referring to fig. 5, the linear droop control strategy is adopted in the primary frequency modulation control, and since the slope of the droop curve is constant, the load of the small hydropower microgrid can be distributed according to the rated power, so that the small hydropower microgrid is guaranteed to have good dynamic characteristics. The secondary frequency modulation control is realized by means of the second frequency f2 output by the small hydropower microgrid and directly adding a feedback link to maintain the second frequency f2 at a desired frequency value, so that the frequency deviation of the small hydropower microgrid during steady operation can be controlled to be small enough. As can be seen from fig. 5, the second frequency f2 output by the small hydropower microgrid is equal to the sum of the primary frequency modulation frequency and the secondary frequency modulation frequency, that is,
wherein the primary frequency is modulated
fminAnd fmaxMinimum and maximum values of dynamic frequency, T1And alpha are important parameters, such as proportional integral parameters, respectively, which influence the control effect. When the small hydropower network runs in a stable state, the power generation is carried outWhen the output power of the motor is a fixed value, the larger the value of alpha is, the smaller the frequency deviation is when the small hydropower microgrid operates in a steady state, that is, the closer the second frequency f2 is to the expected frequency value.
The embodiment of the invention takes a 35kV Hongling small hydropower station in Shaoguan region and a downstream line thereof as an example for specific description. The small hydropower station in red mountains is connected with a large power grid through a 35kV bus, and four 10kV lines are arranged in the station. The small hydropower station in the 10kV plum oblique line has sufficient storage capacity, and the unit can be used as a frequency modulation unit for 1000kW and can be responsible for the frequency modulation task of an island microgrid; generators of other lines are limited in regulating capacity of 250kW (small hydroelectric generating set 1, small hydroelectric generating set 2 and small hydroelectric generating set 3), and constant power control is adopted; all loads under the red ridge station are equivalent to a concentrated load. The generator and the load are connected into a power grid through a series connection structure. In order to avoid misoperation of the grid-connected circuit breaker, the island operation frequency of the small hydropower station microgrid is set to be 55 Hz. The frequency of a first wheel cutter of the high-cycle generator is 57Hz, the frequency of the small hydropower microgrid during grid-connected operation is 50Hz, and the frequency of the small hydropower microgrid during island operation is set to 55Hz, so that the frequency of the small hydropower microgrid in an island operation state fluctuates, and the frequency setting values of a second wheel cutter and a third wheel cutter are set to be larger than 55Hz, so that the generator set is prevented from being cut excessively. The scheme of the high-circumference cutting machine adopted by the embodiment of the invention is shown in the table 1.
TABLE 1
| Cutting machine action | Action signal | Cutting machine set | Delay/ms |
| First wheel cutting machine | f>57Hz | Small hydroelectric generating set 1 | 200 |
| Second wheel cutting machine | f>57Hz，df/dt>3Hz/s | Small hydroelectric generating set 2 | 200 |
| Third wheel cutter | f>57Hz，df/dt>5Hz/s | Small hydroelectric generating set 3 | 200 |
Fig. 6 is a waveform diagram of a generator tripping ad hoc network of a small hydropower station according to a third embodiment of the present invention, and specifically, fig. 6 is a waveform diagram of a second frequency f2 of the generator tripping ad hoc network when a power supply side fault of a small hydropower station in red mountains and an island microgrid load is 1000 kW. Referring to table 1 and fig. 6, in the case that the outward passage of the small hydropower station is blocked, the technical scheme provided by the embodiment of the invention can rapidly output the generator tripping signal according to the change rate of the first frequency, and can rapidly recover to the island operation frequency after cutting off a proper amount of generators, and stably operate. Referring to fig. 6, after the small hydropower microgrid forms an island, the load of the island is 1700kW, 300kW of load is removed at the moment of 4s, 100kW of load is put in at the moment of 9s, and 200kW of load is put in at the moment of 15s, and as can be seen from fig. 6, the maximum frequency fluctuation value of each generator set occurs at the moment of load switching and then tends to be stable within 3 seconds; the difference value between the dynamic process frequency and the island operation frequency set value of 55Hz does not exceed 0.2Hz, and the characteristic of primary frequency modulation control of a frequency modulation strategy is embodied; the frequency hardly fluctuates in a steady state, so that the requirement of a power grid on frequency stability under a normal working condition is met, and the characteristic of frequency modulation strategy secondary frequency modulation control is embodied. Compared with the prior art, the technical scheme provided by the embodiment of the invention can keep the frequency stability of the small hydropower microgrid after the high-cycle generator is protected, and when the load fluctuates, the frequency of each generator set can be quickly recovered to a stable state, thereby being beneficial to improving the reliability of the small hydropower microgrid.
Optionally, the embodiment of the invention also provides an ad hoc network control system of the small hydropower micro grid generator, which is controlled by the ad hoc network control method of the small hydropower micro grid generator provided by any embodiment of the invention.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions without departing from the scope of the invention. Therefore, although the present invention has been described in more detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A small hydropower station micro-grid generator ad hoc network control method is characterized by comprising the following steps:
collecting the power grid frequency of the small hydropower microgrid, and taking the collected power grid frequency as a first frequency;
determining whether to perform high-cycle tripping protection according to the first frequency;
if the high-cycle cutting machine protection is carried out, the cutting machine action of the high-cycle cutting machine is determined according to the change rate of the first frequency;
collecting the power grid frequency of the small hydropower microgrid after the high-cycle generator tripping and taking the power grid frequency as a second frequency;
and carrying out hierarchical frequency modulation control on the second frequency according to the output power and the reference frequency of the small hydropower microgrid after the high-frequency generator is switched off.
2. The small hydropower station microgrid tripping ad-hoc network control method of claim 1, wherein the determining whether to perform high-cycle tripping protection according to the first frequency comprises:
if the first frequency is greater than or equal to a preset frequency and the duration time is greater than or equal to a preset time, protecting the high-frequency generator tripping machine; the preset frequency is the frequency of a first wheel cutter of the high-circumference cutter.
3. The small hydropower station microgrid tripping self-networking control method of claim 1, wherein if high-cycle tripping protection is performed, the determining tripping action of the high-cycle tripping according to the change rate of the first frequency comprises:
if the change rate of the first frequency is larger than the first change rate, starting a third wheel cutting machine;
if the change rate of the first frequency is greater than the second change rate and smaller than the first change rate, starting a second wheel cutting machine;
otherwise, the first wheel cutting machine is started.
4. The small hydropower station microgrid generator ad hoc network control method according to claim 3, wherein the second wheel generator and the first wheel generator are sequentially performed after the third wheel generator is operated.
5. The small hydropower station microgrid generator ad hoc network control method according to claim 3, wherein the cutting capacities of the high-circumference generator generators are as follows from large to small: the device comprises a second wheel cutter, a third wheel cutter and a first wheel cutter, wherein the cutting capacity of the third wheel cutter is equal to that of the first wheel cutter.
6. The small hydropower station microgrid generator ad hoc network control method according to claim 1, wherein the hierarchical frequency modulation control comprises primary frequency modulation control and secondary frequency modulation control.
7. The small hydropower station microgrid generator ad hoc network control method according to claim 6, wherein the primary frequency modulation control comprises:
and adjusting the second frequency by adopting a droop control mode according to the output power of the small hydropower microgrid after the high-frequency generator is switched off.
8. The small hydropower station microgrid generator ad hoc network control method according to claim 6, wherein the secondary frequency modulation control comprises:
and adjusting the second frequency by adopting a closed loop PI control mode according to the reference frequency.
9. The small hydropower station microgrid tripping ad hoc network control method according to claim 1, wherein if high-cycle tripping protection is determined according to the first frequency, the method comprises the following steps before the high-cycle tripping protection is performed:
and calculating the change rate of the first frequency according to the power shortage of the small hydropower microgrid.
10. An ad hoc network control system of a small hydropower micro-grid generator, which is characterized by being controlled by the ad hoc network control method of the small hydropower micro-grid generator as claimed in any one of claims 1 to 9.
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