CN109149660B - Reactive power control method and system for photovoltaic power generation system - Google Patents
Reactive power control method and system for photovoltaic power generation system Download PDFInfo
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Abstract
The invention relates to a reactive power control method and a system for a photovoltaic power generation system, which comprises a reactive power control mode based on a set photovoltaic power generation system model, and a reference value signal of the photovoltaic power generation system in the reactive power control mode is obtained; controlling the output of the converter according to the reference value signal; wherein the reactive control mode comprises: a voltage control mode, a reactive power control mode and a reactive voltage coordination control mode. According to the scheme, the photovoltaic power generation system can adapt to different reactive power regulation requirements of a power grid.
Description
Technical Field
The invention relates to the technical field of new energy power generation, in particular to a reactive power control method and system for a photovoltaic power generation system.
Background
With the problems of environmental pollution, the gradual depletion of petrochemical energy, the safety of energy supply and the like, the development and utilization of renewable energy are receiving more and more attention from the international society. Solar energy is a renewable clean energy source, and photovoltaic power generation is the main utilization form of the solar energy. Compared with the traditional power generation technology, the photovoltaic power generation has the advantages of sustainable energy, safety, environmental protection and the like, and is rapidly developed in recent years.
The photovoltaic system is incorporated into the electric wire netting, and when self capacity is less for the electric wire netting, the disturbance of its power can be neglected to electric wire netting safety and stability influence, and along with photovoltaic power generation's electric wire netting permeability constantly increases, photovoltaic power generation shows gradually to the influence of electric wire netting, and photovoltaic power generation also can bring the harm of security to the electric wire netting when providing active energy. With the continuous improvement of the grid-connected capacity of the photovoltaic grid-connected power generation, the problem is increasingly highlighted.
In order to ensure safe and stable operation of a power grid and reduce adverse effects of photovoltaic access on the power grid, china sets a series of standard and standard photovoltaic power generation grid-connected operation requirements, and the requirements are mainly focused on the following aspects: and (1) active power is independently controlled, and the frequency modulation characteristic is achieved. When the photovoltaic permeability is small, the influence of photovoltaic grid connection on a power grid is not large, and the photovoltaic power generation is mostly focused on the research on how to improve the power generation efficiency, namely the maximum power tracking technology; when the photovoltaic permeability is high, the influence of photovoltaic grid connection on the frequency modulation and peak shaving of the power grid gradually appears, so that the large photovoltaic power generation system has the independent control capability of active power. And (2) reactive power is independently controlled, and the voltage regulating characteristic is achieved. The photovoltaic power supply is connected to change the power distribution of a power grid, the grid-connected voltage is out of limit and fluctuates possibly, the photovoltaic power supply needs to participate in system voltage regulation control, and emergency reactive support is provided for the power grid when necessary. (3) In island protection, when a photovoltaic grid-connected power generation system is in an island operation state, serious consequences are generated to users, maintainers, power equipment and the like, and the island detection method and the protection measures are researched, so that the island protection method has very important realization significance for reducing the harm generated by an island to the minimum. (4) And low voltage ride through, wherein the low voltage ride through capability is a powerful support of the photovoltaic power generation system for grid fault recovery. (5) The grid-connected photovoltaic system has the advantages that the grid low-frequency oscillation is restrained, the grid low-frequency oscillation frequency is low, the period is long, the swept area is wide, great harm is brought to a power system, the low-frequency oscillation of each region of an interconnected grid easily causes the action of a tie line protection device to cause network disconnection, the low-frequency amplified oscillation even causes the breakdown of the whole system, and the grid-connected photovoltaic system has the function of participating in restraining the grid low-frequency oscillation along with the centralized grid-connected operation of a large photovoltaic power station. (6) The photovoltaic power station is adjusted as a whole, inverters of a large photovoltaic power station operate in parallel, the inverters are mutually influenced, and due to the existence of power grid impedance, the inverters are mutually coupled, so that when one inverter breaks down, the stable operation of other inverters is easily influenced. (7) The photovoltaic power generation system has the advantages that efficient conversion is achieved, better electric energy quality injection is achieved, the efficiency of the inverter is one of important indexes of the photovoltaic power generation system, the power of a single photovoltaic power generation system is low, a large photovoltaic power station is composed of a large number of photovoltaic power generation systems, the cluster control technology of the photovoltaic power generation systems is researched, and all power generation units in the power station work at efficient operation points as much as possible through a reasonable control strategy. The problem of power quality is well known, and aiming at the grid-connected operation of a large photovoltaic power station, the problems of power quality such as current harmonics in a low-frequency and weak power grid and superposition of the current harmonics in a simultaneous grid-connection process of a plurality of inverters, direct-current injection and the like are better suppressed.
Disclosure of Invention
In order to solve the defects of the prior art, the invention provides a reactive power control method and a reactive power control system for a photovoltaic power generation system.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
a reactive power control method for a photovoltaic power generation system, the method comprising:
acquiring a reference value signal of the photovoltaic power generation system in a reactive power control mode based on the set reactive power control mode of the photovoltaic power generation system model;
controlling the output of the converter according to the reference value signal;
wherein the reactive control mode comprises: a voltage control mode, a reactive power control mode and a reactive voltage coordination control mode.
Preferably, the setting of the reactive control mode of the photovoltaic power generation system model includes:
receiving a control instruction of the photovoltaic power generation system, and determining a reactive power control mode of a photovoltaic power generation system model based on the content of the control instruction;
modifying the value of the zone bit according to the reactive power control mode of the photovoltaic power generation system model;
the flag bits comprise a voltage flag bit Vflag and a reactive flag bit Qflag.
Further, the modifying the value of the flag bit according to the reactive control mode of the photovoltaic power generation system model includes:
when the voltage flag bit Vflag is 0 and the reactive flag bit Qflag is 1, the reactive control mode is a voltage control mode;
when the voltage flag bit Vflag is 0 or 1 and the reactive flag bit Qflag is 0, the reactive control mode is a reactive power control mode;
and when the voltage flag bit Vflag is 1 and the reactive flag bit Qflag is 1, the reactive control mode is a reactive voltage coordination control mode.
Preferably, the obtaining a reference value signal of the photovoltaic power generation system in the reactive control mode includes:
when the photovoltaic power generation system is in a voltage control mode, the deviation between the measured value of the terminal voltage and a predefined voltage reference value is input into a PI controller to output a first idle current reference value signal of the photovoltaic power generation system, and the first idle current reference value signal is limited to be in [ I ] qmin ,I qmax ]Within the range, obtaining a first inactive current reference value signal after clipping, wherein I qmin For the output current lower limit, I, of the PI controller qmax Outputting an upper current limit for the PI controller;
when the photovoltaic power generation system is in a reactive power control mode, inputting a terminal voltage measured value and a predefined reactive power reference value, performing delay processing through a delay link, and outputting a second reactive current reference value signal of the photovoltaic power generation system;
when the photovoltaic power generation system is in a reactive voltage coordination control mode, a predefined reactive power reference value and PI (proportional integral) control in a voltage control mode are used for controllingThe proportional coefficient and the differential coefficient of the device are input into a PI controller, and a voltage reference value signal is output; and limiting the voltage reference signal to [ V ] min ,V max ]Within the range, obtaining a clipped voltage reference signal, wherein V min For the output lower voltage limit, V, of the PI controller max Outputting an upper voltage limit for the PI controller; and inputting the deviation between the measured value of the voltage at the generator terminal and the voltage reference value signal after amplitude limiting into a PI controller, and outputting a third reactive current reference value signal of the photovoltaic power generation system.
Further, a first reactive current reference signal of the photovoltaic power generation system is determined by:
in the formula, V meas As a terminal voltage measurement value, V ref Is a predefined terminal voltage reference value, I qcmd Is the first reactive current reference signal, K vp And K vi Respectively representing the proportional coefficient and the differential coefficient of the PI controller in the voltage control mode, and S is a transfer function.
Further, a second reactive current reference value signal of the photovoltaic power generation system is determined by:
in the formula, T iq Time constant, Q, of the delay element ref For a predefined reference value of reactive power, V meas Is a terminal voltage measurement, I' qcmd For the second reactive current reference signal, S is a transfer function.
Further, a third reactive current reference signal of the photovoltaic power generation system is determined by:
in the formula, I " qcmd Is the third reactive current reference value signal, K qp And K qi Proportional coefficient and differential coefficient of PI device under the reactive voltage coordination control mode; k vp And K vi Proportional and differential coefficients, Q, of PI controller in voltage control mode meas For terminal reactive power measurement, Q cmd For a predefined reference value of reactive power, V cmd Is a voltage reference value, V meas For terminal voltage measurements, S is the transfer function.
Preferably, the controlling the output of the converter according to the reference value signal includes:
based on the type of a reactive power control mode, taking a measured value and a reference value of a generator end of the photovoltaic power generation system in the reactive power control mode as the input of a converter;
taking the current reference value signal in the corresponding reactive power control mode as a control parameter of the converter;
within a range based on a predefined limit value, the control parameters of the converter are adjusted by the proportional resonant regulator to change the output of the converter.
A reactive control system for a photovoltaic power generation system, comprising:
the acquisition module is used for acquiring a reference value signal of the photovoltaic power generation system in a reactive control mode based on the set reactive control mode of the photovoltaic power generation system model;
and the control module is used for controlling the output of the converter according to the reference value signal.
Preferably, the acquiring module comprises:
the receiving unit is used for receiving a control instruction of the photovoltaic power generation system and determining a reactive power control mode of a photovoltaic power generation system model based on the content of the control instruction;
and the conversion unit is used for modifying the value of the zone bit according to the reactive control mode of the photovoltaic power generation system model.
Further, the conversion unit includes:
the first setting subunit is used for setting the reactive control mode to be a voltage control mode when the voltage flag bit Vflag is 0 and the reactive flag bit Qflag is 1;
the second setting subunit is used for setting the reactive power control mode as a reactive power control mode when the voltage flag Vflag is 0 or 1 and the reactive flag Qflag is 0;
and the third setting subunit is used for setting the reactive control mode as a reactive voltage coordination control mode when the voltage flag bit Vflag is 1 and the reactive flag bit Qflag is 1.
Preferably, the obtaining module further includes:
a first obtaining unit, configured to input a deviation between a terminal voltage measurement value and a predefined voltage reference value into a PI controller when the photovoltaic power generation system is in a voltage control mode, output a first reactive current reference value signal of the photovoltaic power generation system, and limit the first reactive current reference value signal to [ I [ ] qmin ,I qmax ]Within the range, obtaining a first inactive current reference value signal after clipping, wherein I qmin For the output current lower limit, I, of the PI controller qmax Outputting an upper current limit for the PI controller;
the second acquisition unit is used for inputting a terminal voltage measured value and a predefined reactive power reference value, carrying out delay processing through a delay link and outputting a second reactive current reference value signal of the photovoltaic power generation system when the photovoltaic power generation system is in a reactive power control mode;
the third acquisition unit is used for inputting a predefined reactive power reference value and a proportional coefficient and a differential coefficient of the PI controller in the voltage control mode into the PI controller and outputting a voltage reference value signal when the photovoltaic power generation system is in the reactive voltage coordination control mode; and limiting the voltage reference signal to [ V ] min ,V max ]Within the range, obtaining a clipped voltage reference signal, wherein V min For the output lower voltage limit, V, of the PI controller max Is a PI controllerAn upper output voltage limit; and inputting the deviation between the measured value of the voltage at the generator terminal and the voltage reference value signal after amplitude limiting into a PI controller, and outputting a third reactive current reference value signal of the photovoltaic power generation system.
Further, the first acquisition unit includes: a first determining subunit for determining a first reactive current reference value signal of the photovoltaic power generation system by:
in the formula, V meas As a terminal voltage measurement value, V ref For a predefined terminal voltage reference value, I qcmd Is a first reactive current reference signal, K vp And K vi Respectively representing the proportional coefficient and the differential coefficient of the PI controller in the voltage control mode, and S is a transfer function.
Further, the second acquisition unit includes: a second determining subunit for determining a second reactive current reference value signal of the photovoltaic power generation system by:
in the formula, T iq Delay time constant, Q, of the delay element ref For a predefined reference value of reactive power, V meas Is a measured value of the terminal voltage, I' qcmd For the second reactive current reference signal, S is a transfer function.
Further, the third acquisition unit includes: a third determining subunit for determining a third reactive current reference value signal of the photovoltaic power generation system by:
in the formula, I " qcmd Is the third reactive current reference value signal, K qp And K qi Proportional coefficient and differential coefficient of PI device under the reactive voltage coordination control mode; k vp And K vi Proportional and differential coefficients, Q, of PI controller in voltage control mode meas For terminal reactive power measurement, Q cmd For a predefined reference value of reactive power, V cmd Is a voltage reference value, V meas For terminal voltage measurements, S is the transfer function.
Preferably, the control module includes:
the processing unit is used for taking an end measurement value and a reference value of the photovoltaic power generation system in the reactive power control mode as the input of the converter based on the type of the reactive power control mode; taking the current reference value signal in the corresponding reactive power control mode as a control parameter of the converter;
and the tracking adjusting unit is used for adjusting the control parameters of the converter through the proportional resonant regulator within a range based on a predefined limit value so as to change the output of the converter.
Compared with the closest prior art, the invention has the following beneficial effects:
the invention provides a reactive power control method and system for a photovoltaic power generation system, which comprises the following steps of firstly, obtaining a reference value signal of the photovoltaic power generation system in a reactive power control mode based on the set reactive power control mode of a photovoltaic power generation system model; wherein, the reactive control mode includes: a voltage control mode, a reactive power control mode and a reactive voltage coordination control mode.
And secondly, controlling the output of the converter according to the reference value signal. Different reactive power control modes are set, the operation dynamic of the photovoltaic power generation system reactive power control systems with different types and different capacities can be accurately reflected, and the adaptability of the models is strong. The modeling workload of the reactive power control of the photovoltaic power generation system is effectively reduced, and the models of different control modes are unified. The photovoltaic power generation system model structure containing the reactive control mode is easy to expand to renewable energy grid-connected reactive control systems such as wind power control systems, and has good universality and wide application prospect.
Drawings
Fig. 1 is a flow chart of a reactive power control method for a photovoltaic power generation system provided in an embodiment of the present invention;
FIG. 2 is a model structure of a photovoltaic power generation system provided in an embodiment of the present invention;
FIG. 3 is a diagram of a model architecture of a photovoltaic power generation system suitable for electromechanical transient simulation provided in an embodiment of the present invention;
fig. 4 is a photovoltaic power generation system model implemented based on a DIgSILENT PowerFactory platform provided in an embodiment of the present invention;
FIG. 5 is a simulation example photovoltaic power generation system access grid model provided in an embodiment of the present invention;
fig. 6 is a comparison curve of a voltage measurement value and a voltage command value of a photovoltaic power generation system when a photovoltaic power generation system changes a voltage reference value command in a voltage control mode according to a simulation example provided in an embodiment of the present invention, where (a) is the voltage reference value, and (b) is a reactive power operation curve of the photovoltaic power generation system (c) is the voltage reference value and the voltage measurement value.
Fig. 7 is a comparison curve of a reactive power measured value and a voltage command value of a photovoltaic power generation system when a reactive power reference value command is changed in a reactive power control mode adopted by the photovoltaic power generation system in the simulation example provided in the embodiment of the present invention;
FIG. 8 is a comparison curve of a reactive power measured value and a voltage command value of a photovoltaic power generation system when a reactive power reference value command is changed in a photovoltaic power generation system adopting a reactive voltage coordination control mode according to a simulation example provided in an embodiment of the present invention, in which (a) the reactive power reference value and the measured value, (b) the voltage reference value and the voltage measured value are compared in the reactive voltage coordination control mode and the reactive power control mode
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
In order to solve the adverse effect of a photovoltaic system on a power grid, the interactive effect of photovoltaic access on reactive voltage of the system is accurately analyzed. Firstly, an accurate photovoltaic power generation system model needs to be established, different reactive power control requirements of a power grid are met, and a model foundation is provided for further exerting the self reactive power quick regulation capability of the photovoltaic power generation system and supporting the voltage stability of the system.
In order to meet the above requirements, the present invention provides a reactive power control method and system for a photovoltaic power generation system. 1. The improvement is that:
(1) The specific model is realized as shown in fig. 2, different reactive power control modes including voltage control, reactive power control and reactive voltage coordination control can be realized simultaneously, the different reactive power control modes can be realized through different setting and combination of flag bits, the system structure is shown in fig. 3, the flag bits include a voltage flag bit (Vflag) and a reactive flag bit (Qflag), and the setting of the flag bits of the different reactive power control modes is shown in the following table.
TABLE 1 flag setting and reactive control mode
(2) The voltage control of the photovoltaic power generation system means that the photovoltaic power generation system controls the terminal voltage of the photovoltaic power generation system to meet the requirement of a voltage set value by adjusting the reactive power of a power generation unit, and when the photovoltaic power generation system adopts the voltage control, a reference signal S is input ref Is a voltage reference signal, denoted as V ref The method is concretely realized as follows: by measuring the value V of the current terminal voltage meas Terminal voltage set value V ref The deviation is calculated through a voltage deviation PI control link to obtain a reactive current reference value I of the photovoltaic power generation system qcmd As shown in fig. 2, the specific implementation is as follows:
in the formula: k vp And K vi And the proportional coefficient and the differential coefficient of a voltage deviation PI link.
In order to enable the reactive current reference value signal to meet the normal current operation range of the photovoltaic power generation system, an amplitude limiting link is added to a PI control link, and the reactive current reference value signal is limited to be in [ I ] qmin ,I qmax ]Within the interval, usually I qmin Set to-1,I qmax Is set to 1.
(3) The reactive power control of the photovoltaic power generation system refers to that the photovoltaic power generation system adjusts the reactive output of the system according to a reactive control instruction, and when the photovoltaic power generation system adopts a reactive power control mode, a reference signal S is input in the control mode ref Is a reactive power reference value, and is recorded as Q ref . The reactive power control is specifically realized as follows: according to the current reactive power setting value Q ref Divided by the terminal voltage measurement V meas And obtaining a reactive current reference value I of the photovoltaic power generation system through a time delay link qcmd The method is concretely realized as follows:
in the formula: t is iq Is the delay time constant of the delay link.
Time delay time constant T iq The method is used for reflecting reactive control response delay of the photovoltaic power generation system, and generally T is used due to the fact that the converter control system has high response speed iq Typical values of (a) may be 0.01 to 0.02s. In addition, in order to avoid the situation that the reactive current reference calculation value is too high due to too low terminal voltage of the photovoltaic generator, the minimum value of the terminal voltage measurement value signal is set to be 0.01pu.
(4) The photovoltaic power station reactive voltage coordination control means that a photovoltaic power generation system passes a reactive power reference signal through a voltage reference value signal V obtained by a PI control system cmd After obtaining the voltage reference value, entering the same control flow as the voltage control system to finally realize the reactive voltage coordination control of the photovoltaic power generation system, and inputting a reference signal S in the control mode ref Is a reactive power reference value, and is recorded as Q ref . The reactive voltage coordination control is realized as follows:
in the formula: k qp And K qi Proportional coefficient and differential coefficient of reactive deviation PI link; k vp And K vi The proportional coefficient and the differential coefficient of the voltage deviation PI link.
For obtaining a voltage reference signal V by a PI control system cmd In the normal working voltage range of the photovoltaic power generation system, an amplitude limiting link is additionally arranged in a voltage reference value signal PI control link to limit the voltage reference value signal to be V min ,V max ]Within the interval, usually V min Set to be 0.85-0.95V max The setting is 0.95-1.05.
2. The reactive power control method for the photovoltaic power generation system comprises the following specific steps: as shown in fig. 1.
S1, acquiring a reference value signal of a photovoltaic power generation system in a reactive control mode based on the set reactive control mode of a photovoltaic power generation system model;
and S2, controlling the output of the converter according to the reference value signal.
Wherein the reactive control mode comprises: a voltage control mode, a reactive power control mode and a reactive voltage coordination control mode. The voltage control of the photovoltaic power generation system means that the photovoltaic power generation system controls the terminal voltage of the photovoltaic power generation system by adjusting the reactive power of the power generation unit so as to meet the requirement of a voltage set value.
The reactive power control of the photovoltaic power generation system means that the photovoltaic power generation system meets the requirement of a reactive setting value by adjusting the reactive power output of the power generation system.
The reactive voltage control of the photovoltaic power generation system means that the photovoltaic power generation system meets the requirement of a reactive voltage curve (VQ curve) by adjusting the reactive power output of the power generation system.
Step S1, the set reactive power control mode of the photovoltaic power generation system model comprises the following steps:
step S1, the setting of the reactive power control mode of the photovoltaic power generation system model comprises the following steps:
a. receiving a control instruction of the photovoltaic power generation system, and determining a reactive power control mode of a photovoltaic power generation system model based on the content of the control instruction;
b. modifying the value of a zone bit according to the reactive power control mode of the photovoltaic power generation system model; and the reactive power control mode is converted by changing the value of the zone bit, so that the content of the reactive power control mode executed by the photovoltaic power generation system model is consistent with the content of the control instruction of the photovoltaic power generation system.
The flag bits comprise a voltage flag bit Vflag and a reactive flag bit Qflag.
In the step b, modifying the value of the zone bit according to the reactive power control mode of the photovoltaic power generation system model comprises:
when the voltage flag bit Vflag is 0 and the reactive flag bit Qflag is 1, the reactive control mode is a voltage control mode;
when the voltage flag bit Vflag is 0 or 1 and the reactive flag bit Qflag is 0, the reactive control mode is a reactive power control mode;
and when the voltage flag bit Vflag is 1 and the reactive flag bit Qflag is 1, the reactive control mode is a reactive voltage coordination control mode.
The step S1 of obtaining a reference value signal of the photovoltaic power generation system in the reactive power control mode includes:
a, when the photovoltaic power generation system is in a voltage control mode, inputting the deviation of a measured value of a terminal voltage and a predefined voltage reference value into a PI controller, outputting a first idle current reference value signal of the photovoltaic power generation system, carrying out amplitude limiting on the output of the PI controller, and limiting the first idle current reference value signal to be in [ I ] qmin ,I qmax ]Within the range, obtaining a first reactive current reference value signal after amplitude limiting;
the first reactive current reference signal of the photovoltaic power generation system is determined by:
in the formula, V meas As a terminal voltage measurement value, V ref For a predefined terminal voltage reference value, I qcmd Is a first reactive current reference signal, K vp And K vi Respectively representing the proportional coefficient and the differential coefficient of the PI controller in the voltage control mode.
b, when the photovoltaic power generation system is in a reactive power control mode, inputting a terminal voltage measured value and a predefined reactive power reference value, performing delay processing through a delay link, and outputting a second reactive current reference value signal of the photovoltaic power generation system;
the second reactive current reference value signal of the photovoltaic power generation system is determined by the following formula:
in the formula, T iq Time constant, Q, of the delay element ref For a predefined reference value of reactive power, V meas Is a measured value of the terminal voltage, I' qcmd Is the second reactive current reference value signal.
c, when the photovoltaic power generation system is in a reactive voltage coordination control mode, inputting a predefined reactive power reference value and a proportional coefficient and a differential coefficient of the PI controller in a voltage control mode into the PI controller, and outputting a voltage reference value signal; and limiting the amplitude of the voltage reference value signal output by the PI controller to limit the voltage reference value signal to [ V ] min ,V max ]Within the range, obtaining a clipped voltage reference signal, wherein V min For the output lower voltage limit, V, of the PI controller max Outputting an upper voltage limit for the PI controller;
and inputting the deviation between the measured value of the terminal voltage and the voltage reference value signal after amplitude limiting into a PI controller, and outputting a third reactive current reference value signal of the photovoltaic power generation system.
The third reactive current reference value signal of the photovoltaic power generation system is determined by the following formula:
in the formula, I' qcmd Is the third reactive current reference value signal, K qp And K qi Proportional coefficient and differential coefficient of PI device under the reactive voltage coordination control mode; k is vp And K vi Proportional and differential coefficients, Q, of PI controllers in voltage control mode meas For terminal reactive power measurement, Q cmd For a predefined reference value of reactive power, V cmd Is a voltage reference value, V meas Is a terminal voltage measurement.
Step S2, controlling the output of the converter according to the reference value signal comprises the following steps:
based on the type of a reactive power control mode, taking a measured value and a reference value of a machine end of the photovoltaic power generation system in the reactive power control mode as the input of a converter;
taking the current reference value signal in the corresponding reactive power control mode as a control parameter of the converter;
and adjusting the control parameters of the converter through the proportional resonant regulator within a range based on a predefined limit value to change the output of the converter.
Example (b):
two reactive power control zone bits Vflag and Qflag are set, three different control modes including reactive power control, voltage control and reactive voltage coordination control can be realized through the combination of different setting values of the zone bits, and the control modes corresponding to different zone bit values are shown in the following table.
TABLE 1 flag bit setting and reactive power control mode
| Control mode | Vflag | Qflag |
| |
0 or 1 | 0 |
| Voltage control | 0 | 1 |
| Reactive |
1 | 1 |
(1) Reactive power control mode: the photovoltaic power generation system receives a reactive power reference value Q ref And adjusting the reactive power output of the system to a reference value.
(2) Voltage control mode: and the photovoltaic power generation system adjusts the reactive power of the system according to the received voltage reference value signal so that the terminal voltage of the power generation system is adjusted to the voltage reference value signal.
(3) Reactive voltage coordination control: the photovoltaic power generation system receives the reactive power Q ref The reference value signal generates a voltage reference signal through a PI control system, a reactive voltage closed-loop control system is further formed according to the voltage reference value signal and an actual voltage measured value, and finally the reactive power of the photovoltaic power generation system is controlled to reach a reactive power reference value Q ref 。
Specifically, the reactive control modes are specifically realized as follows:
voltage control mode: by measuring the value V of the current terminal voltage meas Terminal voltage set value V ref The deviation is calculated through a voltage deviation PI control link to obtain a reactive current reference value I of the photovoltaic power generation system qcmd (as shown in fig. 2), the specific implementation is as follows:
in the formula: k vp And K vi The proportional coefficient and the differential coefficient of the voltage deviation PI link.
In order to enable the reactive current reference value signal to meet the normal current operation range of the photovoltaic power generation system, an amplitude limiting link is added to a PI control link, and the reactive current reference value signal is limited to be in [ I ] qmin ,I qmax ]Within the interval, usually I qmin Set to-1,I qmax Is set to 1.
Reactive power control mode: according to the current reactive power setting value Q ref Divided by the terminal voltage measurement V meas And obtaining a reactive current reference value I of the photovoltaic power generation system through a time delay link qcmd The method is concretely realized as follows:
in the formula: t is iq Is the delay time constant of the delay link.
Time delay time constant T iq The method is used for reflecting the reactive control response delay of the photovoltaic power generation system, and generally T is used due to the high response speed of a converter control system iq Typical values of (a) may be 0.01 to 0.02s. In addition, in order to avoid the situation that the reactive current reference calculation value is too high due to too low terminal voltage of the photovoltaic generator, the minimum value of the terminal voltage measurement value signal is set to be 0.01pu.
Reactive voltage coordination control mode: according to the measured value Q of the reactive power at the current machine end meas And a reactive power set point Q cmd The deviation is calculated by a reactive deviation PI control link to obtain a voltage reference value V cmd Further calculate the voltage reference value and the current terminal voltage measurement value V meas The deviation value is calculated through a voltage deviation PI control link to obtain a reactive current reference value signal I of the photovoltaic power generation system qcmd The method is concretely realized as follows:
in the formula: k qp And K qi Proportional coefficient and differential coefficient of reactive deviation PI link; k vp And K vi The proportional coefficient and the differential coefficient of the voltage deviation PI link.
For obtaining a voltage reference signal V by a PI control system cmd In the normal working voltage range of the photovoltaic power generation system, an amplitude limiting link is additionally arranged in a voltage reference value signal PI control link to limit the voltage reference value signal to be V min ,V max ]Within the interval, usually V min Is set to be 0.85 to 0.95 max The setting is 0.95-1.05.
Control parameter K related to each PI control link of photovoltaic power generation reactive power control system vp 、K vi 、K qp And K qi The photovoltaic power generation system can be set according to the specific model of the photovoltaic power generation system.
Taking a PowerFactory platform as an example, the method provided by the invention is adopted, and the established photovoltaic power generation system model is adopted, as shown in fig. 4: different reactive power control zone bits are respectively set to set different reactive power control modes, and whether the terminal voltage and the reactive power output value of the photovoltaic power generation system can respond to a reference value instruction or not is observed by changing a reference value signal so as to verify the accuracy of the established model.
In the simulation process, the capacity of a photovoltaic power station is set to be 110MWp, the photovoltaic power station consists of 220 photovoltaic inverters with the single-machine capacity of 500kW, and the photovoltaic power station access system is electrically connected as shown in FIG. 5, so that simulation verification of three different control modes, namely voltage control, reactive power control and reactive voltage coordination control, of a photovoltaic power generation system is respectively carried out.
(1) Voltage control mode
Under the control mode, the reactive control zone bits are set as follows: vflag is set to be 0, qflag is set to be 1, the voltage reference value signal is changed to observe the terminal voltage tracking condition of the photovoltaic power generation system and the reactive power output value of the photovoltaic power generation system, and the specific setting is as follows: t =3s, voltage reference value signal U ref To 0.98p.u.; t =7s, voltage reference value signal U ref Becomes 1.0p.u. Fig. 6 (a) shows a voltage tracking voltage reference signal curve at the terminal of the photovoltaic power generation system, fig. 6 (b) shows a reactive power operation curve of the photovoltaic power generation system, and fig. 6 (c) shows an operation curve of a voltage measurement value of the photovoltaic power generation system following a voltage reference value. It can be seen from the figure that when the voltage reference value signal changes, the reactive output of the photovoltaic power generation system changes along with the voltage command, when the voltage reference value signal decreases, the photovoltaic power generation system decreases the reactive power output to reduce the terminal voltage to satisfy the voltage reference value, when the voltage reference value signal increases, the photovoltaic power generation system increases the reactive power output to increase the terminal voltage to satisfy the voltage reference value, and the simulation result in fig. 6 (c) shows that when the photovoltaic power generation system reactive control adopts the voltage control mode, the terminal voltage can effectively track the voltage reference value signal, thereby verifying the correctness of the voltage control system modeling.
(2) Reactive power control mode
Under the control mode, the reactive control zone bits are set as follows: vflag is set to be 0 or 1, qflag is set to be 0, the reactive power output tracking condition of the photovoltaic power generation system is observed by changing a reactive power reference value signal, and the specific setting is as follows: t =3s, reactive power reference signal Q ref The sudden change is 0.2p.u., when t =7s, the reactive power reference value signal is suddenly changed to-0.1p.u., and the simulation result of fig. 7 shows that when the reactive power control mode is adopted for the reactive power control of the photovoltaic power generation system, the reactive power output value of the photovoltaic power generation system can quickly track the reactive power reference valueAnd (4) the value signal is considered, so that the correctness of the reactive power control system modeling is verified.
(3) Reactive voltage coordination control mode
Under the control mode, the reactive control zone bits are set as follows: vflag is set to be 1, qflag is set to be 1, the reactive power output tracking condition of the photovoltaic power generation system is observed by changing a reactive power reference value signal, and in order to fully reflect the supporting capacity of the photovoltaic power generation system to system voltage in a reactive voltage coordination control mode, the specific simulation setting is as follows: when t =3s, the reactive power reference value signal is suddenly changed to 0.2pu, and when t =7s, the reactive power reference value signal is suddenly changed to-0.1 s. The reactive voltage control mode and the reactive power control mode are compared, when the reactive reference value of the system is increased, the system needs the photovoltaic power station to send out reactive power to help the system voltage to rise, otherwise, when the reactive reference value of the system is reduced, the system needs the photovoltaic power station to reduce the reactive power to reduce the system voltage, and the simulation result shows that the photovoltaic power generation system can better support the voltage to meet the system requirement while quickly tracking the reactive power (as shown in figure 8), so that the accuracy of the voltage control system modeling is verified.
Based on the same inventive concept, the application also provides a reactive power control system for a photovoltaic power generation system, which comprises:
the acquisition module is used for acquiring a reference value signal of the photovoltaic power generation system in a reactive control mode based on the set reactive control mode of the photovoltaic power generation system model;
and the control module is used for controlling the output of the converter according to the reference value signal.
Wherein, the acquisition module includes:
the receiving unit is used for receiving a control instruction of the photovoltaic power generation system and determining a reactive power control mode of a photovoltaic power generation system model based on the content of the control instruction;
and the conversion unit is used for modifying the value of the zone bit according to the reactive power control mode of the photovoltaic power generation system model.
The conversion unit includes:
the first setting subunit is used for setting the reactive control mode to be a voltage control mode when the voltage flag bit Vflag is 0 and the reactive flag bit Qflag is 1;
the second setting subunit is used for setting the reactive power control mode as a reactive power control mode when the voltage flag bit Vflag is 0 or 1 and the reactive flag bit Qflag is 0;
and the third setting subunit is used for setting the reactive control mode as a reactive voltage coordination control mode when the voltage flag bit Vflag is 1 and the reactive flag bit Qflag is 1.
The acquisition module further comprises:
a first obtaining unit, configured to input a deviation between a terminal voltage measurement value and a predefined voltage reference value into a PI controller when the photovoltaic power generation system is in a voltage control mode, output a first reactive current reference value signal of the photovoltaic power generation system, and limit the first reactive current reference value signal to [ I [ ] qmin ,I qmax ]Within the range, obtaining a first inactive current reference value signal after clipping, wherein I qmin For the output current lower limit, I, of the PI controller qmax Outputting an upper current limit for the PI controller;
the second acquisition unit is used for inputting a terminal voltage measured value and a predefined reactive power reference value, carrying out delay processing through a delay link and outputting a second reactive current reference value signal of the photovoltaic power generation system when the photovoltaic power generation system is in a reactive power control mode;
the third acquisition unit is used for inputting a predefined reactive power reference value and a proportional coefficient and a differential coefficient of the PI controller in the voltage control mode into the PI controller and outputting a voltage reference value signal when the photovoltaic power generation system is in the reactive voltage coordination control mode; and limiting the voltage reference signal to [ V ] min ,V max ]Within the range, obtaining a clipped voltage reference signal, wherein V min For the output lower voltage limit, V, of the PI controller max Outputting an upper voltage limit for the PI controller; inputting the deviation between the measured value of the voltage at the generator terminal and the voltage reference value signal after amplitude limiting into a PI controller, and outputting the photovoltaic power generationA third reactive current reference signal of the system.
Wherein, the first acquisition unit includes: a first determining subunit for determining a first reactive current reference value signal of the photovoltaic power generation system by:
in the formula, V meas As a terminal voltage measurement value, V ref For a predefined terminal voltage reference value, I qcmd Is the first reactive current reference signal, K vp And K vi Respectively representing the proportional coefficient and the differential coefficient of the PI controller in the voltage control mode, and S is a transfer function.
The second acquisition unit includes: a second determining subunit for determining a second reactive current reference value signal of the photovoltaic power generation system by:
in the formula, T iq Time constant, Q, of the delay element ref For a predefined reference value of reactive power, V meas Is a measured value of the terminal voltage, I' qcmd For the second reactive current reference signal, S is a transfer function.
The third acquisition unit includes: a third determining subunit for determining a third reactive current reference value signal of the photovoltaic power generation system by:
in the formula, I' qcmd Is the third reactive current reference value signal, K qp And K qi Proportional coefficient and differential coefficient of PI device under the reactive voltage coordination control mode; k vp And K vi Proportional and differential coefficients, Q, of PI controller in voltage control mode meas For terminal reactive power measurement, Q cmd For a predefined reference value of reactive power, V cmd Is a voltage reference value, V meas For terminal voltage measurements, S is the transfer function.
The control module includes:
the processing unit is used for taking a measured value and a reference value of the machine end of the photovoltaic power generation system in the reactive control mode as the input of the converter based on the type of the reactive control mode; taking the current reference value signal in the corresponding reactive power control mode as a control parameter of the converter;
and the tracking adjusting unit is used for adjusting the control parameters of the converter through the proportional resonant regulator within a range based on a predefined limit value so as to change the output of the converter.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and so forth) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Claims (14)
1. A reactive power control method for a photovoltaic power generation system, the method comprising:
obtaining a reference value signal of the photovoltaic power generation system in a reactive power control mode based on a set reactive power control mode of the photovoltaic power generation system model;
controlling the output of the converter according to the reference value signal;
wherein the reactive control mode comprises: a voltage control mode, a reactive power control mode and a reactive voltage coordination control mode;
the obtaining of the reference value signal of the photovoltaic power generation system in the reactive power control mode comprises:
when the photovoltaic power generation system is in a voltage control mode, the deviation between the measured value of the terminal voltage and a predefined voltage reference value is input into a PI controller to output a first idle current reference value signal of the photovoltaic power generation system, and the first idle current reference value signal is limited to be in [ I ] qmin ,I qmax ]Within the range, obtaining a first passive current reference value signal after amplitude limiting,wherein, I qmin For the output current lower limit, I, of the PI controller qmax Outputting an upper current limit for the PI controller;
when the photovoltaic power generation system is in a reactive power control mode, inputting a terminal voltage measured value and a predefined reactive power reference value, performing delay processing through a delay link, and outputting a second reactive current reference value signal of the photovoltaic power generation system;
when the photovoltaic power generation system is in a reactive voltage coordination control mode, inputting a predefined reactive power reference value and a proportional coefficient and a differential coefficient of a PI controller in a voltage control mode into the PI controller, and outputting a voltage reference value signal; and limiting the voltage reference signal to [ V ] min ,V max ]Within the range, obtaining a clipped voltage reference signal, wherein V min For the output lower voltage limit, V, of the PI controller max Outputting an upper voltage limit for the PI controller; and inputting the deviation between the measured value of the voltage at the generator terminal and the voltage reference value signal after amplitude limiting into a PI controller, and outputting a third reactive current reference value signal of the photovoltaic power generation system.
2. The method of claim 1, wherein the setting of the reactive control mode of the photovoltaic power generation system model comprises:
receiving a control instruction of the photovoltaic power generation system, and determining a reactive power control mode of a photovoltaic power generation system model based on the content of the control instruction;
modifying the value of a zone bit according to the reactive power control mode of the photovoltaic power generation system model;
the flag bits comprise a voltage flag bit Vflag and a reactive flag bit Qflag.
3. The method of claim 2, wherein modifying the value of the flag bit according to the reactive control mode of the photovoltaic power generation system model comprises:
when the voltage flag bit Vflag is 0 and the reactive flag bit Qflag is 1, the reactive control mode is a voltage control mode;
when the voltage flag bit Vflag is 0 or 1 and the reactive flag bit Qflag is 0, the reactive control mode is a reactive power control mode;
and when the voltage flag bit Vflag is 1 and the reactive flag bit Qflag is 1, the reactive control mode is a reactive voltage coordination control mode.
4. The method of claim 1, wherein the first reactive current reference signal for the photovoltaic power generation system is determined by:
in the formula, V meas As a terminal voltage measurement value, V ref For a predefined terminal voltage reference value, I qcmd Is the first reactive current reference signal, K vp And K vi Respectively representing the proportional coefficient and the differential coefficient of the PI controller in the voltage control mode, and S is a transfer function.
5. The method of claim 1, wherein the second reactive current reference signal for the photovoltaic power generation system is determined by:
in the formula, T iq Time constant, Q, of the delay element ref For a predefined reference value of reactive power, V meas Is a measured value of the terminal voltage, I' qcmd For the second reactive current reference signal, S is a transfer function.
6. The method of claim 1, wherein the third reactive current reference signal for the photovoltaic power generation system is determined by:
in the formula, I " qcmd Is the third reactive current reference value signal, K qp And K qi Proportional coefficient and differential coefficient of PI device under the reactive voltage coordination control mode; k is vp And K vi Proportional and differential coefficients, Q, of PI controller in voltage control mode meas For terminal reactive power measurement, Q cmd For a predefined reference value of reactive power, V cmd Is a voltage reference value, V meas For terminal voltage measurements, S is the transfer function.
7. The method of claim 1, wherein said controlling the output of the converter based on the reference signal comprises:
based on the type of a reactive power control mode, taking a measured value and a reference value of a machine end of the photovoltaic power generation system in the reactive power control mode as the input of a converter;
taking the current reference value signal in the corresponding reactive power control mode as a control parameter of the converter;
within a range based on a predefined limit value, the control parameters of the converter are adjusted by the proportional resonant regulator to change the output of the converter.
8. A reactive control system for a photovoltaic power generation system, comprising:
the acquisition module is used for acquiring a reference value signal of the photovoltaic power generation system in a reactive control mode based on the set reactive control mode of the photovoltaic power generation system model;
the control module is used for controlling the output of the converter according to the reference value signal;
the acquisition module further comprises:
a first acquisition unit for serving as a photovoltaicWhen the power generation system is in a voltage control mode, the deviation of a terminal voltage measured value and a predefined voltage reference value is input into a PI controller, a first idle current reference value signal of the power generation system is output, and the first idle current reference value signal is limited to be in [ I ] qmin ,I qmax ]Within the range, obtaining a first passive current reference value signal after amplitude limiting, wherein I qmin For the output current lower limit, I, of the PI controller qmax Outputting an upper current limit for the PI controller;
the second acquisition unit is used for inputting a terminal voltage measured value and a predefined reactive power reference value, carrying out delay processing through a delay link and outputting a second reactive current reference value signal of the photovoltaic power generation system when the photovoltaic power generation system is in a reactive power control mode;
the third acquisition unit is used for inputting a predefined reactive power reference value and a proportional coefficient and a differential coefficient of the PI controller in the voltage control mode into the PI controller and outputting a voltage reference value signal when the photovoltaic power generation system is in the reactive voltage coordination control mode; and limiting the voltage reference signal to [ V ] min ,V max ]Within the range, obtaining a clipped voltage reference signal, wherein V min For the output lower voltage limit, V, of the PI controller max Outputting an upper voltage limit for the PI controller; and inputting the deviation between the measured value of the voltage at the generator terminal and the voltage reference value signal after amplitude limiting into a PI controller, and outputting a third reactive current reference value signal of the photovoltaic power generation system.
9. The system of claim 8, wherein the acquisition module comprises:
the receiving unit is used for receiving a control instruction of the photovoltaic power generation system and determining a reactive power control mode of a photovoltaic power generation system model based on the content of the control instruction;
and the conversion unit is used for modifying the value of the zone bit according to the reactive control mode of the photovoltaic power generation system model.
10. The system of claim 9, wherein the conversion unit comprises:
the first setting subunit is used for setting the reactive control mode to be a voltage control mode when the voltage flag bit Vflag is 0 and the reactive flag bit Qflag is 1;
the second setting subunit is used for setting the reactive power control mode as a reactive power control mode when the voltage flag bit Vflag is 0 or 1 and the reactive flag bit Qflag is 0;
and the third setting subunit is used for setting the reactive power control mode as a reactive power voltage coordination control mode when the voltage flag Vflag is 1 and the reactive power flag Qflag is 1.
11. The system of claim 8, wherein the first obtaining unit comprises: a first determining subunit for determining a first reactive current reference value signal of the photovoltaic power generation system by:
in the formula, V meas As a terminal voltage measurement value, V ref For a predefined terminal voltage reference value, I qcmd Is the first reactive current reference signal, K vp And K vi Respectively representing the proportional coefficient and the differential coefficient of the PI controller in the voltage control mode, and S is a transfer function.
12. The system of claim 8, wherein the second obtaining unit comprises: a second determining subunit for determining a second reactive current reference value signal of the photovoltaic power generation system by:
in the formula, T iq Time constant, Q, of the delay element ref For a predefined reference value of reactive power, V meas For the measurement of the terminal voltage,I' qcmd for the second reactive current reference signal, S is a transfer function.
13. The system of claim 8, wherein the third acquisition unit comprises: a third determining subunit for determining a third reactive current reference value signal of the photovoltaic power generation system by:
in the formula, I " qcmd Is the third reactive current reference value signal, K qp And K qi Proportional coefficient and differential coefficient of PI device under the reactive voltage coordination control mode; k vp And K vi Proportional and differential coefficients, Q, of PI controller in voltage control mode meas For terminal reactive power measurement, Q cmd For a predefined reference value of reactive power, V cmd Is a voltage reference value, V meas For terminal voltage measurements, S is the transfer function.
14. The system of claim 8, wherein the control module comprises:
the processing unit is used for taking an end measurement value and a reference value of the photovoltaic power generation system in the reactive power control mode as the input of the converter based on the type of the reactive power control mode; taking the current reference value signal in the corresponding reactive power control mode as a control parameter of the converter;
and the tracking adjusting unit is used for adjusting the control parameters of the converter through the proportional resonant regulator within a limit value range defined in advance so as to change the output of the converter.
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