CN115755826A - Method and system for testing primary frequency modulation function of micro-grid virtual synchronous machine - Google Patents
Method and system for testing primary frequency modulation function of micro-grid virtual synchronous machine Download PDFInfo
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Abstract
The invention provides a method and a system for testing a primary frequency modulation function of a micro-grid virtual synchronous machine, wherein the method comprises the following steps: setting a main controller to adopt constant-voltage constant-frequency control; setting the charging and discharging state of the main controller, and the voltage and frequency controlled by the constant voltage and the constant frequency according to different test working conditions; the micro-grid system is switched from a grid-connected mode to an off-grid mode, and the main controller is switched from constant-power control to constant-voltage constant-frequency control; testing the bus voltage and the line current of the virtual synchronous machine to be tested; and analyzing the primary frequency modulation function index of the virtual synchronous machine by using the test result. The invention fully utilizes the mode conversion functions of PQ control and VF control in the grid-connected and off-grid switching process of the micro-grid system, realizes frequency step, and has the advantages of no power outage, no influence on the normal work of the virtual synchronous machine, simple wiring and the like.
Description
Technical Field
The invention belongs to the technical field of new energy power generation, and particularly relates to a method and a system for testing a primary frequency modulation function of a microgrid virtual synchronous machine.
Background
Because photovoltaic and wind power generation have intermittency and volatility, the quality and stability of electric energy of a power system are influenced by directly connecting a large amount of distributed power supplies to a main power grid through a micro-grid, partial distributed energy can be consumed on site, loss in electric energy transmission is omitted, and the rest electric energy after being consumed on site can also be transmitted to the main power grid. Meanwhile, the micro-grid system contains various power electronic devices, various devices in the system can be flexibly and quickly controlled, and rapidity and flexibility of the micro-grid are embodied. The energy of many forms in the little electric wire netting, rational planning can optimize energy management, promotes the complementary efficiency of multipotency.
Meanwhile, with large-scale distributed power generation grid connection, the stability of a power grid cannot be maintained only by a synchronous generator, and the distributed power supply can also have inertia and damping characteristics like a synchronous machine by applying a virtual synchronous machine control technology to the control of a distributed power supply grid-connected inverter. The distributed power supply can participate in maintaining the stability of a power grid system while providing power for a power grid, and the problem that large-scale distributed power generation cannot be grid-connected due to the stability is solved.
The primary frequency modulation function is a basic function of a distributed power supply virtual synchronous machine, namely when the frequency of an electric power system deviates from a target frequency, a generator set adjusts active power output through automatic reaction of a control system to reduce frequency deviation, the primary frequency modulation capability of the generator set is a first important barrier for maintaining power balance and safety and stability of a power grid, the adjustment performance of the primary frequency modulation capability plays an important role in dynamic stability of the power grid, and the performance of the primary frequency modulation capability needs to pass detection and verification.
In the prior art, the method for detecting the primary frequency modulation of the microgrid virtual synchronous machine is divided into 2 types:
(1) And (3) power shortage is generated by rapidly switching loads to cause frequency deviation, a frequency response curve of the virtual synchronous machine is recorded, and indexes such as lag time, response time, adjusting time and adjusting precision are further analyzed. According to the method, the frequency deviation is generated by rapidly switching the load, the problem that the numerical value of the frequency deviation is uncontrollable exists, the fluctuation of a micro-grid system can be caused, even the power failure can be caused, and the power supply reliability is reduced. In the prior art, a PMU phasor data concentrator is used for forwarding a primary frequency modulation instruction between an active primary frequency modulation master station and an active primary frequency modulation slave station, and primary frequency modulation phasor, analog quantity and switching quantity are sent to the active primary frequency modulation slave station at regular time, so that the test of primary frequency modulation performance can be rapidly realized on the premise of not influencing the normal operation of the existing real-time dynamic monitoring system. However, the virtual signal is transmitted by the primary frequency modulation master station, which can only be used for judging whether the logic strategy of the primary frequency modulation system is correct or not, and monitoring the secondary station primary frequency modulation system, and cannot detect the real response characteristics of the system, such as adjustment time, control precision and the like.
(2) The virtual synchronous machine frequency acquisition module needs to acquire grid-connected point frequency, a collection loop of the virtual synchronous machine frequency acquisition module is disconnected, a frequency disturbance signal is injected through a frequency modulation and voltage regulation signal source to generate frequency deviation, and indexes such as lag time, response time, regulation time and regulation precision are further analyzed. The method needs to disconnect a frequency acquisition loop, the implementation of the virtual synchronous machine is difficult, the frequency acquisition and the synchronous phase locking of part of the virtual synchronous machine are the same loop, and the virtual synchronous machine cannot work after being disconnected. In the prior art, a frequency generation device is connected between a wind power plant step-up transformer and a wind turbine generator step-up transformer, the frequency generation device is adjusted according to frequency change test points, a tested wind turbine generator is tested, test data of each collection point in the tested wind turbine generator are collected, results of all the test data are integrated to perform judgment and analysis, and primary frequency modulation capability of the tested wind turbine generator is obtained. However, the frequency generation device is connected between the wind power plant step-up transformer and the wind turbine generator step-up transformer, so that the problems of difficult wiring, personal safety hazard, influence on normal work of the wind turbine generator and the like exist.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a method and a system for testing the primary frequency modulation function of a micro-grid virtual synchronous machine.
The invention adopts the following technical scheme.
The invention provides a method for testing the primary frequency modulation function of a micro-grid virtual synchronous machine on the one hand, which comprises the following steps:
step 1, setting a main controller to adopt constant-voltage constant-frequency control;
step 2, setting the charging and discharging state of the main controller, and the voltage and frequency controlled by the constant voltage and the constant frequency according to different test working conditions; wherein, the test operating mode includes: the frequency of the charging state of the main controller is disturbed upwards, the frequency of the discharging state of the main controller is disturbed upwards, the frequency of the charging state of the main controller is disturbed downwards, and the frequency of the discharging state of the main controller is disturbed downwards;
step 3, switching the micro-grid system from a grid-connected mode to an off-grid mode, and switching the main controller from constant-power control to constant-voltage constant-frequency control; testing the bus voltage and the line current of the virtual synchronous machine to be tested;
step 4, analyzing the primary frequency modulation function index of the virtual synchronous machine by using the test result of the step 3; the indexes include: lag time, response time, adjustment accuracy.
Preferably, step 1 comprises:
when the micro-grid is in grid-connected operation, the main controller is set to operate in constant power control, and the frequency of the micro-grid is consistent with the frequency of the power grid and is both 50Hz;
when the microgrid is in off-grid operation, the main controller is set to operate in constant voltage and constant frequency control, and the control frequency is set to be unequal to 50Hz.
Preferably, in step 2, the method for testing the frequency interference of the charging state of the main controller includes: the main controller is set to be in a charging state, the voltage controlled by the main controller in a constant voltage and constant frequency mode is set to be the rated voltage of a power grid, and the frequency value range is greater than or equal to 50.05Hz and less than or equal to 50.15Hz.
Preferably, in step 2, the method for testing the frequency rise of the discharge state of the main controller includes: the main controller is set to be in a discharging state, the voltage controlled by the main controller through constant voltage and constant frequency is set to be the rated voltage of a power grid, and the frequency range is greater than or equal to 50.05Hz and less than or equal to 50.15Hz.
Preferably, in step 2, the method for testing disturbance of the main controller under the charging state frequency includes: the main controller is set to be in a charging state, the voltage controlled by the main controller in a constant voltage and constant frequency mode is set to be the rated voltage of a power grid, and the frequency value range is smaller than or equal to 49.95Hz and larger than or equal to 49.85Hz.
Preferably, in step 2, the method for testing disturbance under the discharge state frequency of the main controller includes: and setting the main controller to be in a discharging state, and setting the voltage controlled by the VF of the main controller to be the rated voltage of the power grid, wherein the value range of the frequency is less than or equal to 49.95Hz and more than or equal to 49.85Hz.
Preferably, the micro-grid system is switched from a grid-connected mode to an off-grid mode, and the bus voltage and the line current of the virtual synchronous machine to be tested are recorded by the electric quantity recording analyzer.
Preferably, step 3 comprises:
step 3.1, setting a fixed value of a frequency deviation dead zone by a primary frequency modulation control system;
step 3.2, when the frequency of the microgrid deviates from the target frequency, the generator set adjusts the active power output through the control system;
step 3.3, when the frequency deviation crosses the dead zone, the primary frequency modulation system is realized based on an active power-frequency droop characteristic curve function, and the function meets the following relational expression:
in the formula (I), the compound is shown in the specification,
f is the frequency of the virtual synchronous machine,
f d in order to respond to the dead zone for the primary frequency modulation,
f n in order to provide a nominal frequency for the system,
P n in order to provide the rated power for the virtual synchronous machine,
delta% is the response rate of the primary frequency modulation of the virtual synchronous machine,
P 0 the initial value of the active power of the virtual synchronous machine is obtained;
3.4, the electric quantity recording analyzer records data of at least 30 seconds before the frequency deviation crosses the dead zone and data of at least 30 seconds later; the data comprises voltage, current, active and reactive data;
and 3.5, calculating the lag time, the response time, the adjusting time and the adjusting precision of the primary frequency modulation system through the data.
Preferably, in step 3.5, the lag time is the time required by the microgrid to switch from the grid-connected mode to the off-grid mode until the power variation of the virtual synchronizer reaches 10%;
the response time is the time required by the micro-grid from the moment when the grid-connected mode is switched to the off-grid mode to the moment when the power variation of the virtual synchronizer is 90%;
the adjusting time is the shortest time from the moment when the micro-grid is switched from a grid-connected mode to an off-grid mode to the moment when the absolute value of the power and the final steady-state value of the virtual synchronizer does not exceed 5% of variation;
the adjustment precision is the deviation of the power and the target value when the virtual synchronous machine is stabilized.
Preferably, the primary frequency modulation response up-regulation power limit coefficient k is determined according to an active-frequency droop characteristic curve function 1 A primary frequency modulation response down-regulation power limit coefficient k 2 And a primary frequency modulation response adjustment total power lower limit coefficient k min 。
The invention also provides a system for testing the primary frequency modulation function of the micro-grid virtual synchronous machine, which comprises the following components: the system comprises an acquisition module, a working condition testing module and a primary frequency modulation function analysis module;
the acquisition module is used for acquiring bus voltage and line current of the virtual synchronous machine to be detected when the micro-grid system is switched from a grid-connected mode to an off-grid mode;
the operating mode test module includes: the working condition setting unit is connected with the off-grid switching unit; the working condition setting unit is used for setting the charging and discharging state of the main controller, and the voltage and frequency of constant voltage and constant frequency control according to different test working conditions; the grid-connected and off-grid switching unit is used for switching the micro-grid system from a grid-connected mode to an off-grid mode;
the primary frequency modulation function analysis module is used for analyzing primary frequency modulation function indexes of the virtual synchronous machine by using the test result acquired by the acquisition module; the indexes include: lag time, response time, adjustment time, and adjustment accuracy.
The collection module includes: the system comprises a voltage transformer, a current transformer and an electric quantity recording analyzer, wherein the voltage transformer is connected to a bus; the voltage transformer is used for collecting voltage signals of a bus when the micro-grid system is switched from a grid-connected mode to an off-grid mode, and the current transformer is used for collecting current signals of a virtual synchronous machine line to be detected when the micro-grid system is switched from the grid-connected mode to the off-grid mode; and the voltage signal and the current signal are transmitted to the electric quantity recording analyzer together.
The operating mode setting unit includes: the master controller state setting unit and the master controller voltage and frequency setting unit;
the main controller state setting unit sets the main controller to be in a charging state, and the main controller voltage and frequency setting unit sets the main controller to be in a main controller charging state frequency upper disturbance test mode when the voltage controlled by the constant voltage and constant frequency of the main controller is the rated voltage of a power grid and the frequency is 50.05Hz-50.15Hz;
the main controller state setting unit sets the main controller to be in a discharging state, and the main controller voltage and frequency setting unit sets the main controller to be in a frequency up-disturbance testing mode in the discharging state when the voltage controlled by the main controller at constant voltage and constant frequency is the rated voltage of a power grid and the frequency is 50.05Hz-50.15Hz;
the master controller state setting unit sets the master controller to be in a charging state, and the master controller voltage and frequency setting unit sets the master controller to be in a disturbance test mode under the charging state frequency of the master controller when the voltage controlled by the constant voltage and constant frequency of the master controller is the rated voltage of a power grid and the frequency is 49.95Hz-49.85Hz;
the main controller state setting unit sets the main controller to be in a discharging state, and the main controller voltage and frequency setting unit sets the main controller to be in a disturbance test mode under the frequency of the discharging state when the voltage controlled by the main controller in a constant voltage and constant frequency mode is the rated voltage of a power grid and the frequency is 49.95Hz-49.85Hz.
Compared with the prior art, the method for testing the primary frequency modulation function of the micro-grid virtual synchronous machine has the advantages that under the grid-connected operation of the micro-grid system, each power electronic device (including the main controller) operates in a PQ control mode, and the system frequency is kept consistent with the grid frequency and is 50Hz. The method comprises the steps of carrying out parallel-connection and off-grid seamless switching by utilizing a micro-grid system main controller, converting the micro-grid system from a grid-connection mode to an off-grid mode, switching PQ control of the main controller to VF control, setting the frequency of the VF control mode of the main controller to be slightly more than or less than 50Hz in the switching process, and realizing the new frequency step of the micro-grid system from 50Hz, thereby detecting the primary frequency modulation function of the virtual synchronous machine and analyzing indexes of lag time, response time, regulation precision and the like.
The invention solves the problems of uncontrollable deviation, system fluctuation, reduced power supply reliability and the like in the primary frequency modulation function test by adopting a rapid load switching method, and solves the problems of difficult wiring, influence on the work of a virtual synchronous machine and the like in the primary frequency modulation function test by adopting a method of injecting a disturbing signal into a frequency acquisition module.
The invention fully utilizes the conversion function of PQ control and VF control modes in the parallel-grid and off-grid switching process of the micro-grid system, realizes frequency step, and has the advantages of no power outage, no influence on the normal work of the virtual synchronous machine, simple wiring and the like.
The detection of the primary frequency modulation function of the virtual synchronous machine is important for verifying the grid-connected performance of the virtual synchronous machine, reasonably standardizes and monitors the primary frequency modulation parameters and performance of a unit, and has important significance for safe and stable operation of a power grid and optimal scheduling in the future smart power grid environment.
Drawings
Fig. 1 is a flowchart of a method for testing a primary frequency modulation function of a virtual synchronous machine of a micro-grid according to the present invention;
FIG. 2 is a schematic diagram of detection wiring of a primary frequency modulation function of a virtual synchronous machine in a typical micro-grid system in the embodiment of the invention;
fig. 3 is a schematic diagram of an active-frequency droop characteristic of the primary frequency modulation function in the embodiment of the present invention;
FIG. 4 is a diagram illustrating the results of a disturb test on the frequency of the main controller's state of charge in accordance with an embodiment of the present invention;
FIG. 5 is a graph illustrating the results of the frequency up-disturb test of the main controller in the discharging state of the embodiment of the present invention;
FIG. 6 is a diagram illustrating the results of a disturb test at the frequency of the main controller's charging state in an embodiment of the present invention;
FIG. 7 is a diagram illustrating the results of the disturb test at the main controller discharge state frequency in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described clearly and completely in the following with reference to the accompanying drawings in the embodiments of the present invention. The embodiments described herein are only some embodiments of the invention, and not all embodiments. All other embodiments obtained by a person skilled in the art without making any inventive step on the basis of the spirit of the present invention are within the scope of protection of the present invention.
Example 1.
The invention provides a method for testing a primary frequency modulation function of a micro-grid virtual synchronous machine on the one hand, which comprises the following steps of:
step 1, setting a main controller to adopt constant-voltage constant-frequency control.
In a microgrid system, a grid-connected operation mode and an off-grid operation mode are mainly adopted.
(1) During normal operation, an alternating current bus of the microgrid is connected with a power distribution network through a Point of Common Coupling (PCC), the system operates in a grid-connected mode, electric energy scheduling is performed according to a system instruction, and the power electronic equipment operates in a constant power control (PQ control) mode. At the moment, the output voltage is consistent with the voltage of the power grid, the system voltage and the frequency are both provided by the power grid, the power electronic equipment works in constant power output, only the output power value needs to be set in the control mode, and the equipment operates according to the given power value;
(2) When a system fault occurs in the power distribution network, the PCC nodes of the micro power grid and the power distribution network can be quickly disconnected by the controller, the control mode is changed, and the micro power grid system works in an off-grid mode and works in a constant-voltage constant-frequency control (VF control) mode at the moment. When master-slave control is generally adopted in an island microgrid, a master control power supply adopting a VF control strategy needs to provide voltage and frequency reference for the island microgrid, and the rest distributed power supplies serving as slave controllers generally adopt PQ control. The main controller adopting VF control needs to be able to track the change of load in time, and all the surplus power in the microgrid needs to be borne by the main control power supply, so an energy storage unit with stable and controllable power or a large-capacity distributed power supply with configured energy storage is generally adopted as the main controller.
A typical microgrid system architecture is shown in fig. 2. In fig. 2, a line 1 is connected to a main controller (generally, an energy storage), lines 2 and 3 are both connected to a distributed power virtual synchronous machine, and other lines are both connected to a load.
The micro-grid system in fig. 2 is operated in a grid-connected mode, electric energy scheduling is carried out according to system instructions, each power electronic device (including a main controller) works in a PQ control mode, at the moment, the frequency of the micro-grid system is kept consistent with the 50Hz frequency of a power grid, the output voltage is consistent with the voltage of the power grid, the system voltage and the frequency are both provided by the power grid, the power electronic device works in constant power output, only an output power value needs to be set in the control mode, and the device operates according to a power given value.
In fig. 2, the microgrid system operates in an off-grid mode, a main control power supply adopting a VF control strategy needs to provide voltage and frequency references for an off-grid island microgrid, the voltage and frequency can be manually preset, the frequency of the VF control mode of the main controller is preset to be slightly larger than or smaller than 50Hz, the remaining distributed power supplies serving as slave controllers generally adopt PQ control, and usually, an energy storage unit with stable and controllable power or a large-capacity distributed power supply with energy storage configuration is adopted as a main controller.
And 2, setting the charge-discharge state of the main controller, and the voltage and frequency controlled by the constant voltage and the constant frequency according to different test working conditions.
The detection of the primary frequency modulation function of the virtual synchronous machine comprises 4 working condition tests: the frequency disturbance of the charging state of the main controller is (1) up disturbed, (2) up disturbed, (3) down disturbed, and (4) down disturbed.
The method for testing the frequency upper disturbance of the charging state of the main controller comprises the following steps: setting a main controller to be in a charging state, and setting the voltage controlled by a VF (variable frequency) of the main controller to be the rated voltage of a power grid and the frequency of 50.05Hz-50.15Hz;
the main controller is set to be in a discharging state, and the VF control voltage of the main controller is set to be the rated voltage of a power grid, and the frequency of the VF control voltage is set to be 50.05Hz-50.15Hz;
the disturbance testing method under the main controller charging state frequency comprises the following steps of setting a main controller to be in a charging state, and setting a VF control voltage of the main controller to be a rated voltage of a power grid and the frequency of the VF control voltage to be 49.95Hz-49.85Hz;
the method for testing the disturbance of the main controller under the discharge state frequency comprises the following steps of setting the main controller to be in a discharge state, and setting the voltage controlled by the VF of the main controller to be the rated voltage of a power grid and the frequency of the VF of the main controller to be 49.95Hz-49.85Hz.
The invention fully utilizes the conversion function of PQ control and VF control modes in the parallel-grid and off-grid switching process of the micro-grid system, realizes frequency step, and has the advantages of no power outage, no influence on the normal work of the virtual synchronous machine, simple wiring and the like. The invention solves the problems of uncontrollable deviation, system fluctuation, reduced power supply reliability and the like in the primary frequency modulation function test by adopting a rapid load switching method, and solves the problems of difficult wiring, influence on the work of a virtual synchronous machine and the like in the primary frequency modulation function test by adopting a method of injecting a disturbing signal into a frequency acquisition module.
And 3, switching the micro-grid system from a grid-connected mode to an off-grid mode, and testing the bus voltage and the line current of the virtual synchronous machine to be tested.
In embodiment 1, the microgrid system is switched from a grid-connected mode to an off-grid mode, and the bus voltage and the line current of the virtual synchronous machine to be measured are recorded by using the electric quantity recording analyzer. As shown in fig. 2, a voltage transformer PT connected to the bus collects a voltage signal of the bus, and a current transformer CT connected to the bus side of the line 2 collects a current signal of the line of the virtual synchronous machine to be tested; and the voltage signal and the current signal are transmitted to the electric quantity recording analyzer together.
Through the grid-connected and off-grid seamless switching, the micro-grid system is switched from a grid-connected mode to an off-grid mode, the main controller is switched from PQ control to VF control, the frequency of the micro-grid system is stepped from 50Hz to new frequency, and the primary frequency modulation function of the virtual synchronous machine is detected. In fig. 2, the off-grid seamless switching means that when the operation state of the microgrid system is switched, the control strategy of the main controller converter is also switched between constant voltage and constant frequency control and constant power control. When adopting PQ control, the main controller converter adopts a current inner loop control mode. When the VF control is adopted, the current loop reference current of the converter of the main controller is calculated by the voltage outer loop according to the voltage reference signal.
The primary frequency modulation function of the virtual synchronous generator in fig. 3 is realized as follows: when the frequency of the power system deviates from the target frequency, the generator set adjusts the active output to reduce the frequency deviation through the automatic reaction of the control system, the primary frequency modulation control system sets a frequency deviation dead zone fixed value, and when the frequency deviation crosses a dead zone, the primary frequency modulation function is realized by setting a frequency and active power broken line function (active-frequency droop characteristic curve function), namely:
in the formula (I), the compound is shown in the specification,
f is the frequency of the virtual synchronous machine, and the unit is as follows: the frequency of the mixed gas is 50Hz,
f d is a primary frequency modulation response dead zone, unit: the frequency of the Hz,
f n is the system rated frequency, unit: at a frequency of 50Hz,
P n rated power of the virtual synchronous machine, unit: the weight ratio of the light beams in the MW,
delta% is the response rate of the primary frequency modulation of the virtual synchronous machine,
P 0 the method is characterized in that the method is an initial value of active power of a virtual synchronous machine, and the unit is as follows: MW.
The functional-frequency droop characteristic curve of the primary frequency modulation function is shown in fig. 2, k 1 For the primary frequency modulation response to the power limit coefficient, k 2 For the primary frequency modulation response down-regulation of the power limit coefficient, k min A total power lower limit coefficient is adjusted for the primary frequency modulation response.
Step 4, analyzing the primary frequency modulation function index of the virtual synchronous machine by using the test result of the step 3; the indexes include: lag time, response time, adjustment accuracy.
The lag time is the time required by the micro-grid from the moment when the grid-connected mode is switched to the off-grid mode to the moment when the power variation of the virtual synchronous machine is 10%.
The response time is the time required by the moment when the micro-grid is switched from the grid-connected mode to the off-grid mode to the moment when the power variation of the virtual synchronous machine is 90%.
The adjusting time is the shortest time from the moment when the micro-grid is switched from a grid-connected mode to an off-grid mode to the moment when the absolute value of the power and the final steady-state value of the virtual synchronizer does not exceed 5% of the variation.
The adjustment precision is the deviation of the power and the target value when the virtual synchronous machine is stabilized.
Example 2.
Taking a certain 10kV microgrid system as an example, the structure of the 10kV microgrid system is shown in FIG. 2. The distributed power supply virtual synchronous machine of the line 2 has the rated capacity of 10MW, the primary frequency modulation dead zone is 0.05Hz, the primary frequency modulation difference rate is 2%, the primary frequency modulation power regulation limit coefficient is 10%, and the primary frequency modulation regulation total power lower limit coefficient is 20%; the voltage set by the VF control mode of the main controller is 10.5kV, and the up-down interference test frequency of the primary frequency modulation function is respectively set to be 50.15Hz and 49.85Hz.
(1) And (3) testing the frequency interference of the charging state of the main controller:
under the grid-connected operation of the micro-grid system, each power electronic device (including a main controller) operates in a PQ control mode, and the system frequency is consistent with the grid frequency of 50Hz. And performing parallel-connection and off-grid seamless switching by using the micro-grid system main controller, switching the micro-grid system main controller from PQ control to VF control, and changing the frequency to 50.15Hz, wherein the test result is shown in figure 4.
The main controller charging state frequency upper interference test result shows that the lag time, the response time, the adjusting time and the adjusting precision are shown in the table 1:
TABLE 1 master controller State of Charge frequency Up-disturb test results
(2) And (3) testing the frequency up-disturbance of the discharge state of the main controller:
under the grid-connected operation of the micro-grid system, each power electronic device (including a main controller) operates in a PQ control mode, and the system frequency is consistent with the grid frequency of 50Hz. And performing parallel-connection and off-grid seamless switching by using the micro-grid system main controller, switching the micro-grid system main controller from PQ control to VF control, and changing the frequency to 50.15Hz, wherein the test result is shown in figure 5.
The main controller discharge state frequency up-disturbance test result shows that the lag time, the response time, the adjusting time and the adjusting precision are shown in the table 2:
TABLE 2 frequency up-disturb test results for master controller discharge state
(3) Disturbance test under the main controller charging state frequency:
under the grid-connected operation of the microgrid system, each power electronic device (including a main controller) operates in a PQ control mode, and the system frequency is kept consistent with the grid frequency of 50Hz. And performing parallel-connection and off-grid seamless switching by using the micro-grid system main controller, switching the micro-grid system main controller from PQ control to VF control, and changing the frequency to 49.85Hz, wherein the test result is shown in FIG. 6.
The disturbance test result of the main controller in the charging state frequency shows that the lag time, the response time, the adjusting time and the adjusting precision are shown in the table 3:
TABLE 3 master controller charging State frequency disturbance test results
(4) And (3) disturbance test of the main controller under the discharge state frequency:
under the grid-connected operation of the micro-grid system, each power electronic device (including a main controller) operates in a PQ control mode, and the system frequency is consistent with the grid frequency of 50Hz. And performing parallel-connection and off-grid seamless switching by using the micro-grid system main controller, switching the micro-grid system main controller from PQ control to VF control, and changing the frequency to 49.85Hz, wherein the test result is shown in FIG. 7.
The disturbance test result of the main controller under the discharge state frequency shows that the lag time, the response time, the regulation time and the regulation precision are shown in the table 4:
TABLE 4 disturbance test result under frequency of main controller in discharge state
And 4 working condition detection results of the primary frequency modulation function of the virtual synchronous machine meet standard requirements, and the primary frequency modulation function test of the virtual synchronous machine of the microgrid is completed.
The invention also provides a primary frequency modulation function test of the micro-grid virtual synchronous machine, which comprises the following steps: the device comprises an acquisition module, a working condition testing module and a primary frequency modulation function analysis module.
The collection module includes: the system comprises a voltage transformer, a current transformer and an electric quantity recording analyzer, wherein the voltage transformer is connected to a bus; the voltage transformer is used for collecting voltage signals of a bus when the micro-grid system is switched from a grid-connected mode to an off-grid mode, and the current transformer is used for collecting current signals of a virtual synchronous machine line to be detected when the micro-grid system is switched from the grid-connected mode to the off-grid mode; and the voltage signal and the current signal are transmitted to the electric quantity recording analyzer together. And the voltage signal and the current signal are restored to be primary values through the setting of the transformation ratio, and the voltage frequency and the virtual synchronous machine power are calculated through the electric quantity recording analyzer.
The operating mode test module includes: the working condition setting unit is connected with the off-grid switching unit; the working condition setting unit is used for setting the charging and discharging state of the main controller, and the voltage and frequency of constant voltage and constant frequency control according to different test working conditions; wherein, the test operating mode includes: the frequency of the charging state of the main controller is disturbed upwards, the frequency of the discharging state of the main controller is disturbed upwards, the frequency of the charging state of the main controller is disturbed downwards, and the frequency of the discharging state of the main controller is disturbed downwards; the grid-connected and off-grid switching unit is used for switching the micro-grid system from a grid-connected mode to an off-grid mode;
the primary frequency modulation function analysis module is used for analyzing primary frequency modulation function indexes of the virtual synchronous machine by using the test result acquired by the acquisition module; the indexes include: lag time, response time, adjustment time, and adjustment accuracy. The function analysis module calculates the time required for outputting the active power variable quantity to reach 10% of the difference between the active power target value and the initial value from the time when the frequency exceeds the primary frequency modulation dead zone, namely the lag time; the function analysis module calculates the time required for outputting the active power variable quantity to reach 90% of the difference between the active power target value and the initial value from the time when the frequency exceeds the primary frequency modulation dead zone, and the time is the response time; the function analysis module calculates the shortest time that the absolute value of the difference between the output active power and the active target value always does not exceed the allowable deviation from the time when the frequency exceeds the primary frequency modulation dead zone, namely the regulation time; and the function analysis module calculates the percentage of the deviation of the actual active power and the target active power in the rated active power when the primary frequency modulation is stabilized, namely the regulation precision.
The present disclosure may be systems, methods, and/or computer program products. The computer program product may include a computer-readable storage medium having computer-readable program instructions embodied thereon for causing a processor to implement various aspects of the present disclosure.
The computer-readable storage medium may be a tangible device that can hold and store the instructions for use by the instruction execution device. The computer readable storage medium may be, for example, but not limited to, an electronic memory device, a magnetic memory device, an optical memory device, an electromagnetic memory device, a semiconductor memory device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a Static Random Access Memory (SRAM), a portable compact disc read-only memory (CD-ROM), a Digital Versatile Disc (DVD), a memory stick, a floppy disk, a mechanical coding device, such as a punch card or an in-groove protruding structure with instructions stored thereon, and any suitable combination of the foregoing. Computer-readable storage media as used herein is not to be construed as transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission medium (e.g., optical pulses through a fiber optic cable), or electrical signals transmitted through electrical wires.
The computer-readable program instructions described herein may be downloaded from a computer-readable storage medium to a respective computing/processing device, or to an external computer or external storage device over a network, such as the internet, a local area network, a wide area network, and/or a wireless network. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. The network adapter card or network interface in each computing/processing device receives computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium in the respective computing/processing device.
The computer program instructions for carrying out operations of the present disclosure may be assembler instructions, instruction Set Architecture (ISA) instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C + + or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet service provider). In some embodiments, the electronic circuitry that can execute the computer-readable program instructions implements aspects of the present disclosure by utilizing the state information of the computer-readable program instructions to personalize the electronic circuitry, such as a programmable logic circuit, a Field Programmable Gate Array (FPGA), or a Programmable Logic Array (PLA).
Various aspects of the present disclosure are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer-readable program instructions.
These computer-readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, 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/acts specified in the flowchart and/or block diagram block or blocks. These computer-readable program instructions may also be stored in a computer-readable storage medium that can direct a computer, programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer-readable medium storing the instructions comprises an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.
The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer, other programmable apparatus or other devices implement the functions/acts specified in the flowchart and/or block diagram block or blocks.
The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (13)
1. A method for testing a primary frequency modulation function of a micro-grid virtual synchronous machine is characterized by comprising the following steps:
step 1, setting a main controller to adopt constant-voltage constant-frequency control;
step 2, setting the charging and discharging state of the main controller, and the voltage and frequency controlled by the constant voltage and the constant frequency according to different test working conditions; wherein, the test operating mode includes: the frequency of the charging state of the main controller is disturbed upwards, the frequency of the discharging state of the main controller is disturbed upwards, the frequency of the charging state of the main controller is disturbed downwards, and the frequency of the discharging state of the main controller is disturbed downwards;
step 3, switching the micro-grid system from a grid-connected mode to an off-grid mode, and switching the main controller from constant-power control to constant-voltage constant-frequency control; testing the bus voltage and the line current of the virtual synchronous machine to be tested;
step 4, analyzing the primary frequency modulation function index of the virtual synchronous machine by using the test result of the step 3; the indexes include: lag time, response time, adjustment accuracy.
2. The method for testing the primary frequency modulation function of the microgrid virtual synchronous machine according to claim 1,
the step 1 comprises the following steps:
when the micro-grid is connected to the power grid, the main controller is set to operate in constant power control, and the frequency of the micro-grid is consistent with the frequency of the power grid and is 50Hz;
when the micro-grid runs off the grid, the main controller is set to run in constant-voltage constant-frequency control, and the control frequency is not equal to 50Hz.
3. The method for testing the primary frequency modulation function of the microgrid virtual synchronous machine according to claim 1,
in step 2, the method for testing the frequency interference of the charging state of the main controller comprises the following steps: the main controller is set to be in a charging state, the voltage controlled by the main controller through constant voltage and constant frequency is set to be the rated voltage of a power grid, and the frequency range is greater than or equal to 50.05Hz and less than or equal to 50.15Hz.
4. The method for testing the primary frequency modulation function of the microgrid virtual synchronous machine according to claim 1,
in step 2, the method for testing the frequency upper disturbance of the discharge state of the main controller comprises the following steps: setting a main controller to be in a discharging state, setting the voltage controlled by the main controller at constant voltage and constant frequency to be the rated voltage of a power grid, and setting the value range of the frequency to be more than or equal to 50.05Hz and less than or equal to 50.15Hz.
5. The method for testing the primary frequency modulation function of the microgrid virtual synchronous machine according to claim 1,
in step 2, the disturbance testing method under the charging state frequency of the main controller comprises the following steps: the main controller is set to be in a charging state, the voltage controlled by the main controller through constant voltage and constant frequency is set to be the rated voltage of a power grid, and the frequency range is smaller than or equal to 49.95Hz and larger than or equal to 49.85Hz.
6. The method for testing the primary frequency modulation function of the microgrid virtual synchronous machine according to claim 1,
in step 2, the disturbance testing method under the frequency of the discharge state of the main controller comprises the following steps: and setting the main controller to be in a discharging state, and setting the voltage controlled by the VF of the main controller to be the rated voltage of the power grid, wherein the value range of the frequency is less than or equal to 49.95Hz and more than or equal to 49.85Hz.
7. The method for testing the primary frequency modulation function of the microgrid virtual synchronous machine according to claim 1,
the micro-grid system is switched from a grid-connected mode to an off-grid mode, and the bus voltage and the line current of the virtual synchronous machine to be detected are recorded by the electric quantity recording analyzer.
8. The method for testing the primary frequency modulation function of the microgrid virtual synchronous machine according to claim 1,
the step 3 comprises the following steps:
step 3.1, setting a fixed value of a frequency deviation dead zone by a primary frequency modulation control system;
step 3.2, when the frequency of the microgrid deviates from the target frequency, the generator set adjusts the active power output through the control system;
and 3.3, when the frequency deviation crosses the dead zone, the primary frequency modulation system is realized based on an active-frequency droop characteristic curve function, and the function meets the following relational expression:
in the formula (I), the compound is shown in the specification,
f is the frequency of the virtual synchronous machine,
f d in order to respond to the dead zone for the primary frequency modulation,
f n in order to be the nominal frequency of the system,
P n in order to provide the rated power for the virtual synchronous machine,
delta% is the response rate of the primary frequency modulation of the virtual synchronous machine,
P 0 setting an initial value of active power of the virtual synchronous machine;
3.4, the electric quantity recording analyzer records data of at least 30 seconds before the frequency deviation crosses the dead zone and data of at least 30 seconds later; the data comprises voltage, current, active and reactive data;
and 3.5, calculating the lag time, response time, adjusting time and adjusting precision of the primary frequency modulation system through the data.
9. The method for testing the primary frequency modulation function of the microgrid virtual synchronous machine according to claim 8,
in the step 3.5, the lag time is the time required by the moment when the micro-grid is switched from the grid-connected mode to the off-grid mode to the power variation of the virtual synchronizer being 10%;
the response time is the time required by the micro-grid from the moment when the grid-connected mode is switched to the off-grid mode to the moment when the power variation of the virtual synchronizer is 90%;
the adjusting time is the shortest time from the moment when the micro-grid is switched from a grid-connected mode to an off-grid mode to the moment when the absolute value of the power and the final steady-state value of the virtual synchronizer does not exceed 5% of the variation;
the adjustment precision is the deviation of the power and the target value when the virtual synchronous machine is stabilized.
10. The method for testing the primary frequency modulation function of the microgrid virtual synchronous machine according to claim 8,
determining a primary frequency modulation response upper regulation power limit value coefficient k according to an active-frequency droop characteristic curve function 1 And a primary frequency modulation response down-regulation power limit coefficient k 2 And a primary frequency modulation response adjustment total power lower limit coefficient k min 。
11. A micro-grid virtual synchronous machine primary frequency modulation function test system using the method of any one of claims 1 to 10,
the system comprises: the system comprises an acquisition module, a working condition testing module and a primary frequency modulation function analysis module;
the acquisition module is used for acquiring bus voltage and line current of the virtual synchronous machine to be detected when the micro-grid system is switched from a grid-connected mode to an off-grid mode;
the operating mode test module includes: the working condition setting unit is connected with the off-grid switching unit; the working condition setting unit is used for setting the charging and discharging state of the main controller, and the voltage and frequency of constant voltage and constant frequency control according to different test working conditions; the grid-connected and off-grid switching unit is used for switching the micro-grid system from a grid-connected mode to an off-grid mode;
the primary frequency modulation function analysis module is used for analyzing primary frequency modulation function indexes of the virtual synchronous machine by utilizing the test result acquired by the acquisition module; the indexes include: lag time, response time, adjustment time, and adjustment accuracy.
12. The microgrid virtual synchronous machine primary frequency modulation function test system of claim 10,
the collection module includes: the system comprises a voltage transformer, a current transformer and an electric quantity recording analyzer, wherein the voltage transformer is connected to a bus; the voltage transformer is used for collecting voltage signals of a bus when the micro-grid system is switched from a grid-connected mode to an off-grid mode, and the current transformer is used for collecting current signals of a virtual synchronous machine line to be detected when the micro-grid system is switched from the grid-connected mode to the off-grid mode; and the voltage signal and the current signal are transmitted to the electric quantity recording analyzer together.
13. The microgrid virtual synchronous machine primary frequency modulation function test system of claim 10,
the operating mode setting unit includes: the master controller state setting unit and the master controller voltage and frequency setting unit;
the main controller state setting unit sets the main controller to be in a charging state, and the main controller voltage and frequency setting unit sets the main controller to be in a main controller charging state frequency upper interference test mode when the voltage controlled by the constant voltage and constant frequency of the main controller is the rated voltage of a power grid and the frequency is 50.05Hz-50.15Hz;
the main controller state setting unit sets the main controller to be in a discharging state, and the main controller voltage and frequency setting unit sets the main controller to be in a frequency up-disturbance testing mode in the discharging state when the voltage controlled by the main controller at constant voltage and constant frequency is the rated voltage of a power grid and the frequency is 50.05Hz-50.15Hz;
the master controller state setting unit sets the master controller to be in a charging state, and the master controller voltage and frequency setting unit sets the master controller to be in a disturbance test mode under the charging state frequency of the master controller when the voltage controlled by the constant voltage and constant frequency of the master controller is the rated voltage of a power grid and the frequency is 49.95Hz-49.85Hz;
the master controller state setting unit sets the master controller to be in a discharging state, and the master controller voltage and frequency setting unit sets the master controller to be in a disturbance testing mode under the discharging state frequency when the voltage controlled by the constant voltage and constant frequency of the master controller is the rated voltage of a power grid and the frequency is 49.95Hz-49.85Hz.
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