CN109494762B - Photovoltaic power station primary frequency modulation control method and system based on multi-master station coordinated control - Google Patents
Photovoltaic power station primary frequency modulation control method and system based on multi-master station coordinated control Download PDFInfo
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Abstract
The invention discloses a primary frequency modulation control method and a primary frequency modulation control system of a photovoltaic power station based on multi-master station coordinated control
Active power P at the moment of load shedding levelref. When the frequency of the power grid exceeds the disturbance of the primary frequency modulation artificial dead zone DB, the PFC control system calculates the active power variation delta P after the frequency fluctuation, and the active power given target value P which needs to be issued to the inverter groupset＝PrefAnd + delta P, so that the active power of the photovoltaic power station is changed, and the effect of primary frequency modulation is achieved. According to the scheme, algorithm upgrading is only needed to be carried out on conventional photovoltaic power station inverter control software, and a PFC master station coordination mechanism is added on the basis of the existing AGC function of the power station, so that AGC and PFC multi-master station coordination control is realized, the cost can be reduced to the maximum extent, the primary frequency modulation function of the photovoltaic power station is exerted, and the power grid frequency recovery speed is accelerated.
Description
Technical Field
The invention belongs to the technical field of grid connection of photovoltaic power station inverters, and particularly relates to a photovoltaic power station primary frequency modulation control method and system based on multi-master-station coordination control.
Background
Solar energy is a new energy source for sustainable development, and due to its non-pollution and renewable properties, it is increasingly paid more attention by countries in the world. In recent years, the photovoltaic power generation industry in China is rapidly developed, the installed capacity of photovoltaic power stations is continuously improved, and as more and more high-capacity photovoltaic power stations are directly merged into a power grid, the mutual influence between a photovoltaic power generation system and the power grid is more and more complicated.
In the solar power generation technology, a photovoltaic cell power generation system is widely used at present. The grid-connected photovoltaic power generation system is characterized in that a photovoltaic module converts received solar radiation energy into high-voltage direct current after high-frequency direct current conversion, and sinusoidal alternating current with the same phase and frequency as the voltage and current of a power grid is output to the power grid after inversion of an inverter.
Nowadays, frequency control of photovoltaic power stations has been paid attention to by more and more electric power companies and has proposed relevant technical requirements, and photovoltaic power stations themselves have frequency modulation ability, participate in frequency adjustment of power grids, and are one of the important characteristics of power grid-friendly photovoltaic power stations.
At present, a photovoltaic power station has no example application participating in primary frequency modulation of a power grid, and the rotary inertia and equivalent scale of the power grid are continuously reduced due to the fact that a new energy unit does not have the rotary inertia characteristic of a conventional unit, and the structural difficulty of power grid frequency control is gradually obvious. With the large production of extra-high voltage direct current transmission projects, the system power balance and frequency modulation difficulty is increased continuously, direct current high-power locking (sequential locking) poses serious threats to the frequency safety of a power grid, a new energy unit is urgently needed to participate in the rapid frequency response of the power grid, and the safety level of the frequency of the large power grid is improved.
Disclosure of Invention
In order to solve the problems, the invention provides a primary frequency modulation control method of a photovoltaic power station based on multi-master-station coordination control, so as to realize the function of the photovoltaic power station participating in rapid frequency modulation response of a power grid.
In order to achieve the purpose, the primary frequency modulation control method of the photovoltaic power station based on multi-master-station coordination control comprises the following steps:
step 1, multi-master station control is realized by establishing a PFC control system which is coordinated and parallel with an AGC control system; the PFC control system collects three-phase alternating current voltage and three-phase alternating current at the high-voltage side of a main transformer of a grid-connected point of the photovoltaic power station through an alternating current sampling module of a main controller, and monitors active power and grid frequency f of the grid-connected point of the photovoltaic power station in real time;
step 3, the PFC control system puts into the primary frequency modulation function and sends a primary frequency modulation putting flag bit to the AGC control system, and the AGC receives the primary frequency modulation putting flag bit to determine that the PFC control system is normal; when the power grid frequency f exceeds the set primary frequency modulation artificial dead zone DB, the PFC control system sends a primary frequency modulation action flag bit to the AGC control system, and the AGC control system automatically locks after receiving the action flag bit; the PFC control system replaces an AGC control system to calculate the active power target value P of the photovoltaic power station in the primary frequency modulation processsetThe calculated active power target value P of the photovoltaic power stationsetAveragely distributing the active power to each controlled inverter, controlling the corresponding photovoltaic sub-array to output the active power to a target value by each inverter according to the instruction, and controlling and regulating the active power through a PID algorithmThe speed and the response time are saved, and the integral primary frequency modulation function of the photovoltaic power station is realized;
step 4, after the primary frequency modulation action is finished, the PFC control system sends a primary frequency modulation action quit flag bit to the AGC control system, the AGC control system releases the locking, and the AGC control system enables the photovoltaic power station active power target value P given by the current dispatching center to be given by the AGC control systemAGCSending the target value P to a PFC control system, and enabling the PFC control system to quit the active power target value P of the photovoltaic power station after primary frequency modulationAGCAnd averagely distributing the active power to each controlled inverter, controlling and adjusting the output active power of the corresponding photovoltaic sub-array to a target value by each inverter according to the instruction, exiting the function of the PFC control system, controlling all the inverters by the AGC control system, and recovering the normal power generation working state of the photovoltaic power station.
Further, in step 2, the load shedding operation of the photovoltaic power station is controlled through an AGC system, and the load shedding level is used
Showing that the current maximum available active power of the photovoltaic power station is PMax，PNFor the rated total power of a photovoltaic power station, the photovoltaic power station is provided with
The active power of the grid-connected point at the deloading level is Pref，
Further, in the above-mentioned case,
values greater than 0 and less than 20%.
Further, in step 3, the primary frequency modulation active power target value Pset＝Pref+ Δ P, difference f between grid frequency f and nominal frequencybAnd when the frequency exceeds the primary frequency modulation artificial dead zone DB, the active power of the inverter is adjusted according to the active-frequency droop characteristic curve, and a PID algorithm is set to realize the function of quickly stabilizing the frequency.
Further, in the step 3, the control strategy is that the change of the power grid frequency exceeds a primary frequency modulation artificial dead zone DB, and the active power of the photovoltaic power station is more than 10% PNIn the process, the photovoltaic power station automatically increases or decreases active power according to an active-frequency droop characteristic curve and participates in primary frequency modulation of the system; when the active power of the photovoltaic power station is less than 10 percent PNDuring the operation, the droop control is not activated, and the specific method for adjusting the active power of the inverter according to the active-frequency droop characteristic curve is as follows:
when the frequency f is within the control dead zone fd-fd +, the photovoltaic power station does not participate in primary frequency modulation, normally operates, and reserves the rated power under the current illumination intensity
Spare capacity of (a);
when the frequency f drops to fd-When the power supply voltage is lower than the preset value, the photovoltaic power station increases the active power variation delta P, and the frequency modulation droop coefficient is epThe calculation formula of the increased active power variation Δ P is as follows:
wherein, Delta P is less than or equal to 10 percent of PN；
When the frequency f rises to fd+In the above, the photovoltaic power station reduces the active power variation delta P, and the frequency modulation droop coefficient is epWhen the system frequency continues to rise to above 51.5Hz, the power supply to the power grid is stopped, and the calculation formula of the reduced active power variation quantity delta P is as follows:
wherein epThe value range of (A) is 1-10%.
Further, in step 1, the frequency measurement precision is not lower than 0.001Hz, and the frequency measurement period is less than or equal to 20 ms.
A photovoltaic power station primary frequency modulation control system based on multi-master station coordinated control comprises a photovoltaic power station AGC control system and a photovoltaic power station PFC control system, wherein the photovoltaic power station AGC control system and the photovoltaic power station PFC control system are in communication connection through an Ethernet TCP/IP interface, and are both in communication connection with an inverter group;
the photovoltaic power station AGC control system is used for tracking an instruction issued by power scheduling and adjusting the active power of the photovoltaic power station in real time according to a set adjusting rate so as to meet the requirements of power system frequency and tie line power control; meanwhile, the system has the function of coordinating with a PFC control system of the photovoltaic power station to control the active power reserve capacity of the photovoltaic power station;
the photovoltaic power station PFC control system is used for realizing active power output of a photovoltaic inverter through an active-frequency droop characteristic curve in a primary frequency modulation process; a PID algorithm is set, so that the frequency stability of the power grid is quickly realized, and the safe and reliable operation of the power grid is ensured;
the inverter group is used for receiving control instructions of the AGC control system and the PFC control system of the photovoltaic power station, controlling the active power output of the photovoltaic subarray group according to the received control instructions, and transmitting electric energy generated by the photovoltaic subarray to a power grid through inversion.
Further, the photovoltaic power station PFC control system comprises a communication controller group consisting of a main controller and a plurality of communication controllers, and is connected with a photoelectric converter at the side of the AGC control system through a communication line consisting of an Ethernet switch, the photoelectric converter and a communication cable to realize network communication;
the main controller is used for collecting grid-connected point three-phase alternating current voltage current and power grid frequency and calculating a primary frequency modulation active power target value P according to a control strategysetAnd the network communication is carried out with the human-computer interface and the communication controller group through the exchanger; and the communication controller group is used for receiving the adjusting instruction of the main controller and sending the adjusting instruction to the inverter group.
Compared with the prior art, the method has at least the following beneficial technical effects that the active power of the grid-connected point of the photovoltaic power station is collected in real time, the power reserve capacity is reserved for the photovoltaic power station due to AGC load shedding control, and the active power of the grid-connected point of the photovoltaic power station is the photovoltaic power station
Active power P at the moment of load shedding levelrefI.e. by
When the grid frequency exceeds the artificial dead zone disturbance, the PFC control system records the active power of the grid-connected point of the photovoltaic power station at the disturbance moment, calculates the active power variation delta P after the frequency fluctuation, and sends the active power given target value P to the inverter groupset＝PrefAnd + delta P, so that the active power of the photovoltaic power station is changed, and the effect of primary frequency modulation is achieved. The primary frequency modulation has the advantages that the primary frequency modulation active power target value is sent out simultaneously, the simultaneous response of the photovoltaic power station and the whole station is met, the effect of quick frequency response is achieved, and the dual response capability of frequency up-disturbance and frequency down-disturbance is achieved.
Further, the frequency difference f after delta P is fluctuated by the power gridbAnd frequency modulation droop coefficient epDetermining and adding a PID algorithm to obtain an active power given target value Pset. Setting PID algorithm to control active power given target value PsetThe given speed can realize primary frequency modulation of the photovoltaic power station according to the set speed.
Drawings
FIG. 1 is a block diagram of a primary frequency modulation topology of a photovoltaic power plant;
FIG. 2 is a functional block diagram of a primary frequency modulation function of a photovoltaic power station with multiple master stations;
FIG. 3 is a primary frequency modulation droop characteristic curve of a photovoltaic power station;
FIG. 4 is a primary frequency modulation coordination control block diagram of a photovoltaic power station;
FIG. 5a is a diagram of a primary frequency modulation process of a photovoltaic power station in frequency up-time interference;
fig. 5b is a primary frequency modulation process diagram of the photovoltaic power station under frequency disturbance.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
In the description of the present invention, it is to be understood that, in the description of the present invention, the meaning of "a plurality" is two or more unless otherwise specified. In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Referring to fig. 1, the primary frequency modulation system of the photovoltaic power station comprises a photovoltaic power station AGC control system and a photovoltaic power station PFC control system, the photovoltaic power station AGC control system and the photovoltaic power station PFC control system establish network communication connection through an ethernet TCP/IP interface, the photovoltaic power station AGC control system and the photovoltaic power station PFC control system both establish network communication connection with an inverter group through an ethernet switch, the inverter group receives a coordination instruction of the AGC control system and the PFC control system, controls the photovoltaic subarray group to output active power, and the active power is transmitted to the inverter group and sent to a power grid through an inversion process, so that a power generation control process of the photovoltaic power station is completed.
The photovoltaic power station AGC control system is used for tracking an instruction issued by power dispatching in the normal operation process of the photovoltaic power station and adjusting the active power of the photovoltaic power station in real time so as to meet the requirements of power system frequency and tie line power control; meanwhile, the method has the function of coordinating with a PFC control system of the photovoltaic power station to control the active power reserve capacity of the photovoltaic power station.
The PFC control system of the photovoltaic power station is used for realizing the active power output of a photovoltaic inverter through an active-frequency droop characteristic curve in the primary frequency modulation process, setting a PID algorithm, adjusting the active power of the photovoltaic power station according to a set adjusting rate, realizing quick frequency response, stabilizing the frequency of a power grid and ensuring the safe and reliable operation of the power grid.
The inverter group is used for receiving control instructions of the AGC control system and the PFC control system of the photovoltaic power station, controlling the active power output of the photovoltaic subarray group, and transmitting electric energy generated by the photovoltaic subarray to a power grid through inversion.
The photovoltaic subarray group is used for converting light energy into electric energy under the condition of illumination, finishing energy conversion and adjusting active power output according to control of the inverter group.
Referring to fig. 2, the primary frequency modulation function of the photovoltaic power station is realized by coordination control of an AGC control system of the photovoltaic power station and a PFC control system of the photovoltaic power station. The photovoltaic power station primary frequency modulation system comprises a photovoltaic power station AGC control system and a photovoltaic power station PFC control system, wherein the AGC control system receives an active power regulation instruction issued by a power station dispatching server under the condition that the power grid frequency is normal, the instruction is issued to an inverter group through a communication line established by an Ethernet switch, a photoelectric converter and a communication optical cable, and the inverter group receives the instruction to control the active power output of a photovoltaic sub-array group, so that the active power control of the photovoltaic power station is realized. When the frequency of a power grid is disturbed and exceeds an artificial frequency dead zone, a PFC control system sends a primary frequency modulation input and a primary frequency modulation action zone bit to an AGC control system, the AGC control system automatically locks after receiving the action zone bit, the PFC control system establishes network communication between an internal main controller, a communication server and an inverter group through an Ethernet switch, and sends a primary frequency modulation active power target value instruction to the inverter group, and the inverter group receives the instruction to control the active power output of a photovoltaic subarray group, so that the primary frequency modulation function of a photovoltaic power station is realized.
The PFC control system of the photovoltaic power station comprises a main controller and a communication controller group consisting of a plurality of communication controllers, and network communication is realized by establishing connection between a communication line consisting of an Ethernet switch, a photoelectric converter and a communication cable and the photoelectric converter at the side of an AGC control system.
The main controller (X201584) is used for collecting three-phase alternating current voltage and current of a grid-connected point and grid frequency, further comprises subsequent control strategy calculation work, and is in network communication with the human-computer interface and the communication controller group through the switch.
And the communication controller group (X201381) is used for receiving the adjusting instruction of the main controller and sending the instruction to the inverter group for establishing communication connection, so that the function of network communication expanded connection is achieved.
The Ethernet switch is used for a switch for transmitting data through Ethernet, and can be simultaneously communicated with a plurality of pairs of ports, so that each pair of hosts which are communicated with each other can transmit data without conflict like exclusive communication media.
The photoelectric converter is used for converting Ethernet electric signals into optical signals or converting the optical signals into photoelectric conversion equipment of the Ethernet electric signals, and the transmission quantity of network information is enhanced.
Referring to fig. 4, the photovoltaic power station primary frequency modulation control method based on multi-master station coordination control comprises the following steps:
step 1, monitoring the frequency f of a grid-connected point of a photovoltaic power station in real time, wherein the frequency measurement precision is required to be not lower than 0.001Hz and the frequency measurement period is not more than 20ms in order to ensure the control effect;
step 3, setting a PID algorithm in the PFC control system, and setting KP、KI、KDParameter, accounting for frequency difference f after frequency disturbancebThe power response rate control after exceeding the primary frequency modulation artificial dead zone DB can continuously send active power variation delta P to the inverter, and the purpose of issuing a primary frequency modulation active power target value P to the inverter is realizedsetAnd (4) precise control. Wherein, KP、KI、KDThe value range is between 0 and 20, T1VThe differential constant is generally about 0.5, and S is a laplace operator.
And 4, modifying the control logic of the photovoltaic inverter, and increasing an active-frequency droop characteristic curve to realize the rapid frequency response function of the photovoltaic inverter.
In step 2, for a power control module of the photovoltaic power station, the signal input quantity comprises a power grid dispatching instruction, illumination of the photovoltaic power station, temperature of the photovoltaic power station and the like, and the control target is to output active power according to the power grid requirement. For the photovoltaic power station which actually operates at present, the maximum power tracking is adopted for controlling the active power (MPPT), utilizing the illumination resources as much as possible. When the photovoltaic power station adopts maximum power tracking control, the power output can be reduced at any time, but the power output cannot be increased to participate in frequency adjustment, so that the photovoltaic power station firstly needs to operate in a power difference mode to reserve a certain active standby for frequency adjustment if the photovoltaic power station needs to participate in primary frequency adjustment of a system. When the power difference control mode is operated, the active power and the maximum power P which can be generated of the photovoltaic power stationMaxBy maintaining a fixed ratio difference between them, i.e. leaving a fixed ratio
The ratio is determined by the photovoltaic plant operating derating level. In order to ensure that the photovoltaic power station has a certain standby frequency modulation capacity, the load shedding operation control of the photovoltaic power station needs to be carried out through an AGC system. For relieving load
The invention defines that the load shedding level refers to that the active frequency modulation reserve capacity accounts for the rated total power P of the photovoltaic power stationNThe ratio of (a) to (b).
Under a certain fixed illumination intensity S and temperature T, the maximum possible active power of the photovoltaic power station is PMaxThe photovoltaic power station is provided with
Has a power P at the relief levelrefThe calculation formula is as follows:
in the formula: pMaxIs the current maximum available power, P, of the photovoltaic power stationNIs the rated total power of the photovoltaic power plant,
and setting according to a power grid plan curve, wherein the value is between 0 and 20 percent.
In step 4, droop control, in order to better exert the rapid frequency response capability of the photovoltaic inverter, the droop characteristic curve of the photovoltaic inverter is set by imitating the parameters of the primary frequency modulation dead zone of the conventional water and thermal power generating unit and combining the change condition of the power grid frequency during the test, and the droop characteristic curve is as shown in fig. 3.
Droop control is a steady state process that is used primarily to reduce system frequency deviations. Disturbance occurs in the frequency of the power grid, the frequency difference exceeds a primary frequency modulation artificial dead zone DB, and the active power of the photovoltaic power station is more than 10 percent PN(PNRated total power of the photovoltaic power station), the photovoltaic power station adjusts the active power of the inverter according to a preset active-frequency droop characteristic curve to participate in primary frequency modulation of the system; when the active power of the photovoltaic power station is less than 10 percent PNWhen the droop control is activated, the droop control is not activated.
The droop characteristic curve of the photovoltaic power station, which is made according to the control purpose, is shown in figure 3.
1) When the grid frequency f is controlled at fd-～fd+Within the range, the photovoltaic power station does not participate in primary frequency modulation, normally operates, and reserves rated power under the current illumination intensity
Spare capacity of (2), general, fd-＝49.4Hz，fd+＝50.6Hz。
2) Referring to FIG. 5b, when the frequency f drops to fd-When the power supply voltage is lower than the preset value, the photovoltaic power station increases the active power variation delta P, and the frequency modulation droop coefficient is epThe upper limit of the increased active power variation quantity delta P is the reserved power reserve capacity and the minimum frequency f of the frequency lower interferenceMinThe calculation formula of the added active power variation delta P for the small calculated value of the time primary frequency modulation power is as follows:
wherein, Delta P is less than or equal to 10 percent of PN，epThe value range is 1% -10%;
3) referring to FIG. 5a, when the frequency f rises to fd+In the above, the photovoltaic power station reduces the active power variation delta P, and the frequency modulation droop coefficient is epThe lower limit of the reduced active power variation is the maximum frequency f of the frequency up-disturbanceMaxAnd when the system frequency continues to rise to above 51.5Hz, stopping supplying power to the power grid, wherein the reduced active power variation delta P is calculated according to the following formula:
wherein, Delta P is less than or equal to 10 percent of PN，epThe value range of (A) is 1-10%.
The frequency f in the three cases refers to the frequency f of the photovoltaic power station grid-connected point collected in the step 1.
In the invention, in all formulas: pNThe rated total power of the photovoltaic power station; Δ P is the active power variation; e.g. of the typepIs the frequency-modulated sag factor, ep＝3％；fNFor grid frequency reference value, fN＝50Hz；fd-Is a value of the disturbance area under frequency, fd+Is a frequency upper dead zone value, fd-＝49.4Hz，fd+＝50.6Hz。
A primary frequency modulation control method of a photovoltaic power station based on multi-master-station coordinated control realizes multi-master-station control by establishing a PFC control system (a rapid frequency response measurement and control system) coordinated and parallel with an AGC control system. The method comprises the steps of connecting a PT voltage U on a main transformer high-voltage side of a grid-connected system and a CT current I into a PFC control system, monitoring the active power of a grid-connected point and the grid frequency f in real time, putting into a primary frequency modulation function, and sending a primary frequency modulation putting-in flag bit to an AGC control system. When the power grid frequency f exceeds a set primary frequency modulation dead zone, the PFC control system sends a primary frequency modulation action flag bit to the AGC control system, the AGC control system receives the action flag bit to automatically lock, the PFC control system replaces the AGC control system, and the active power target value P of the photovoltaic power station in the primary frequency modulation process is calculated according to a control strategysetI.e. Pset＝Pref+ delta P, calculating the obtained active power target value P of the photovoltaic power stationsetThe active power is averagely distributed to each controlled inverter, each inverter controls the corresponding photovoltaic sub-array to output the active power to a target value according to the instruction, and a PID algorithm is set to control the regulation rate and the response time, so that the integral primary frequency modulation function of the photovoltaic power station is realized, and the requirement of a power grid system on the frequency modulation function is met. The principle of average distribution is a preferred method under the existing control mode of collecting the total power, if the power value of each inverter is collected, the proportional distribution mode can be realized, the data transmission quantity can be increased, and the reliability and stability can be influenced on the premise of not increasing equipment or expanding the capacity. Wherein, the primary frequency modulation active power target value PsetAnd calculating through a control strategy, and when the frequency exceeds the dead zone, adjusting the active power of the inverter according to an active-frequency droop characteristic curve, and setting a PID algorithm to realize the function of quickly stabilizing the frequency. According to the scheme, algorithm upgrading is only needed to be carried out on conventional photovoltaic power station inverter control software, and a PFC master station coordination mechanism is added on the basis of the existing AGC function of the power station, so that AGC and PFC multi-master station coordination control is realized, upgrading cost can be reduced to the maximum extent, the primary frequency modulation function of the photovoltaic power station is exerted, and the power grid frequency recovery speed is accelerated.
When the primary frequency modulation action is finished, the PFC control system judges fd-≤f≤fd+If yes, finishing the primary frequency modulation action, otherwise, continuing the primary frequency modulation action; when the frequency returns to the normal range, the PFC control system sends a primary frequency modulation action quit flag bit to the AGC control system, the AGC control system releases the locking and dispatches a given active power target value PAGCSending the instruction to a PFC control system, wherein the instruction is the active power target value P of the photovoltaic power station after the primary frequency modulation exitsAGC。
And the PFC control system distributes the active power target value to each controlled inverter according to an average distribution principle, each inverter controls the corresponding photovoltaic subarray to output active power to the target value according to the instruction, the PFC control system exits, and the AGC control system controls all the inverters to recover the normal power generation working state of the photovoltaic power station.
Primary frequency modulation active power targetValue of
The PFC control system calculates through a control strategy, and when the frequency exceeds the dead zone, the active power output by the photovoltaic sub-array group is increased or reduced within a specified time according to a set rate, so that the function of rapidly stabilizing the frequency is realized.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (8)
1. A photovoltaic power station primary frequency modulation control method based on multi-master station coordination control is characterized by comprising the following steps:
step 1, multi-master station control is realized by establishing a PFC control system which is coordinated and parallel with an AGC control system; the PFC control system collects three-phase alternating current voltage and three-phase alternating current at the high-voltage side of a main transformer of a grid-connected point of the photovoltaic power station through an alternating current sampling module of a main controller, and monitors active power and grid frequency f of the grid-connected point of the photovoltaic power station in real time;
step 2, ensuring the control of the active power reserve capacity through load shedding;
step 3, the PFC control system puts into the primary frequency modulation function and sends a primary frequency modulation putting flag bit to the AGC control system, and the AGC receives the primary frequency modulation putting flag bit to determine that the PFC control system is normal; when the power grid frequency f exceeds the set primary frequency modulation artificial dead zone DB, the PFC control system sends a primary frequency modulation action flag bit to the AGC control system, and the AGC control system automatically locks after receiving the action flag bit; the PFC control system replaces an AGC control system to calculate the active power target value P of the photovoltaic power station in the primary frequency modulation processsetThe calculated active power target value P of the photovoltaic power stationsetAveragely distributing the active power to each controlled inverter, controlling the corresponding photovoltaic sub-array to output the active power to a target value by each inverter according to the instruction, and controlling and regulating the speed and the response time by a PID algorithm to realize the integral photovoltaic power stationPrimary frequency modulation function;
step 4, after the primary frequency modulation action is finished, the PFC control system sends a primary frequency modulation action quit flag bit to the AGC control system, the AGC control system releases the locking, and the AGC control system enables the photovoltaic power station active power target value P given by the current dispatching center to be given by the AGC control systemAGCSending the target value P to a PFC control system, and enabling the PFC control system to quit the active power target value P of the photovoltaic power station after primary frequency modulationAGCAnd averagely distributing the active power to each controlled inverter, controlling and adjusting the output active power of the corresponding photovoltaic sub-array to a target value by each inverter according to the instruction, exiting the function of the PFC control system, controlling all the inverters by the AGC control system, and recovering the normal power generation working state of the photovoltaic power station.
2. The photovoltaic power station primary frequency modulation control method based on multi-master station coordination control as claimed in claim 1, wherein in step 2, the photovoltaic power station is subjected to load shedding operation control through an AGC system, and the load shedding level is used
Showing that the current maximum available active power of the photovoltaic power station is PMax，PNFor the rated total power of a photovoltaic power station, the photovoltaic power station is provided with
The active power of the grid-connected point at the deloading level is Pref，
3. The photovoltaic power station primary frequency modulation control method based on multi-master station coordination control as claimed in claim 2,
values greater than 0 and less than 20%.
4. The photovoltaic power station primary frequency modulation control method based on multi-master-station coordinated control as claimed in claim 2, wherein in step 3, the primary frequency modulation active power target value Pset＝Pref+ Δ P, difference f between grid frequency f and nominal frequencybAnd when the frequency exceeds the primary frequency modulation artificial dead zone DB, the active power of the inverter is adjusted according to the active-frequency droop characteristic curve, and a PID algorithm is set to realize the function of quickly stabilizing the frequency.
5. The photovoltaic power station primary frequency modulation control method based on multi-master-station coordinated control as claimed in claim 4, wherein in step 3, the control strategy is that the grid frequency variation exceeds the primary frequency modulation artificial dead zone DB, and the active power of the photovoltaic power station is greater than 10% PNIn the process, the photovoltaic power station automatically increases or decreases active power according to an active-frequency droop characteristic curve and participates in primary frequency modulation of the system; when the active power of the photovoltaic power station is less than 10 percent PNDuring the operation, the droop control is not activated, and the specific method for adjusting the active power of the inverter according to the active-frequency droop characteristic curve is as follows:
when the frequency f is within the control dead zone fd-fd +, the photovoltaic power station does not participate in primary frequency modulation, normally operates, and reserves the rated power under the current illumination intensity
Spare capacity of (a);
when the frequency f drops to fd-When the power supply voltage is lower than the preset value, the photovoltaic power station increases the active power variation delta P, and the frequency modulation droop coefficient is epThe calculation formula of the increased active power variation Δ P is as follows:
wherein, Delta P is less than or equal to 10 percent of PN；
When the frequency f rises to fd+In the above, the photovoltaic power station reduces the active power variation delta P, and the frequency modulation droop coefficient is epWhen the system frequency continues to rise above 51.5Hz, the power supply to the power grid is stopped, and the active power change is reducedThe quantity Δ P is calculated as:
wherein epThe value range of (A) is 1-10%.
6. The photovoltaic power station primary frequency modulation control method based on multi-master-station coordinated control according to claim 1, wherein in step 1, the frequency measurement precision is not lower than 0.001Hz, and the frequency measurement period is not more than 20 ms.
7. The photovoltaic power station primary frequency modulation control method based on multi-master station coordinated control according to claim 1, characterized by being executed by a primary frequency modulation control system, wherein the primary frequency modulation control system comprises a photovoltaic power station AGC control system and a photovoltaic power station PFC control system, the photovoltaic power station AGC control system and the photovoltaic power station PFC control system are in communication connection through an Ethernet TCP/IP interface, and the photovoltaic power station AGC control system and the photovoltaic power station PFC control system are both in communication connection with an inverter group;
the photovoltaic power station AGC control system is used for tracking an instruction issued by power scheduling and adjusting the active power of the photovoltaic power station in real time according to a set adjusting rate so as to meet the requirements of power system frequency and tie line power control; meanwhile, the system has the function of coordinating with a PFC control system of the photovoltaic power station to control the active power reserve capacity of the photovoltaic power station;
the photovoltaic power station PFC control system is used for realizing active power output of a photovoltaic inverter through an active-frequency droop characteristic curve in a primary frequency modulation process; a PID algorithm is set, so that the frequency stability of the power grid is quickly realized, and the safe and reliable operation of the power grid is ensured;
the inverter group is used for receiving control instructions of the AGC control system and the PFC control system of the photovoltaic power station, controlling the active power output of the photovoltaic subarray group according to the received control instructions, and transmitting electric energy generated by the photovoltaic subarray to a power grid through inversion.
8. The primary frequency modulation control method of the photovoltaic power station based on the multi-master station coordinated control as claimed in claim 7, wherein the PFC control system of the photovoltaic power station comprises a communication controller group consisting of a main controller and a plurality of communication controllers, and the PFC control system of the photovoltaic power station is connected with a photoelectric converter at the side of the AGC control system through a communication line consisting of an Ethernet switch, the photoelectric converter and a communication cable to realize network communication;
the main controller is used for collecting grid-connected point three-phase alternating current voltage current and power grid frequency and calculating a primary frequency modulation active power target value P according to a control strategysetAnd the network communication is carried out with the human-computer interface and the communication controller group through the exchanger;
and the communication controller group is used for receiving the adjusting instruction of the main controller and sending the adjusting instruction to the inverter group.
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