CN115882514B - New energy power system and network construction integrated converter cluster aggregation control method - Google Patents
New energy power system and network construction integrated converter cluster aggregation control method Download PDFInfo
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Abstract
The invention provides a method for controlling aggregation of a network-following integrated converter cluster in a new energy power system, which comprises the following steps: obtaining an output power response curve of the synchronous generator according to the power characteristic of the synchronous generator; the output power of a power generation unit of the distributed energy system is equivalent, so that the response characteristic of the output power is equivalent to a virtual synchronous generator, and a swing equation of the virtual synchronous generator is obtained; constructing a power curve and distributing a power instruction; constructing a local and networking unified control method; and designing a power instruction distribution coefficient in the network construction integrated control method. According to the method, all power generation units are subjected to aggregation control, and an integrated control method with the advantages of the traditional networking and network following control strategies is constructed.
Description
Technical Field
The invention belongs to a power system, and particularly relates to a method for controlling aggregation of a grid-connected integrated converter cluster in a new energy power system.
Background
In order to reduce global energy crisis and irreversible climate change, renewable energy power generation technologies such as photovoltaic power generation have been rapidly developed in the past decade. The current new energy system is connected with the grid in a grid-following mode, namely, the output power is fixed according to the designated active and reactive power instruction, and the control is simple. However, since the grid-controlled inverter does not have inertia of the synchronous generator, the inertia is greatly affected by system load fluctuation and transition of the operation mode.
Fig. 1 depicts a typical distributed energy system structure, wherein a plurality of loads are distributed on an ac bus, a synchronous generator is connected to the ac bus, which is equivalent to G1, a power generation unit is connected in parallel with an energy storage unit, and is connected to the ac system through a voltage-source converter (VSC), and S1, S2, … Sn are the capacities of the units respectively. At present, each power generation unit can be connected into an alternating current power grid through two control methods of a follow-up grid type and a grid-structured grid type, and has relatively strong power tracking capability and network supporting capability respectively. However, when the ac system is weak, load fluctuation occurs, and it is difficult to maintain stable operation of the system with the grid-connected control method, and it is difficult to adjust the power output in time with the grid-connected control method.
Disclosure of Invention
Aiming at the problems, the invention provides a method for controlling aggregation of a network-following integrated converter cluster in a new energy power system. The method comprises the steps of firstly, aggregating power generation units in a distributed energy system, enabling an aggregated power output curve to be equivalent to a virtual synchronous generator, and simulating the external characteristics of the synchronous generator. On the basis, the integrated control method for constructing the network with the network is designed, and the functions of each power generation unit are actively regulated and controlled, so that the power generation units provide a power following function and a power grid supporting function according to requirements, and meanwhile, the power generation units are subjected to the scheduling of an equivalent power curve, so that the function switching of the power generation units following the network environment is realized, and the load of a power grid system is reduced.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a method for controlling aggregation of a network-following integrated converter cluster in a new energy power system comprises the following steps:
s1, according to synchronous generatorObtaining the output power response curve of the synchronous generator; equivalent power output by a power generation unit of the distributed energy system is carried out, so that the response characteristic of the power output is equivalent to a virtual synchronous generator model +.>And obtain a virtual synchronous generator model->Is a rocking equation of (2);
s2, constructing a power curve and distributing a power instruction;
s3, constructing a local networking unified control method;
s4, designing a power instruction distribution coefficient in the integrated control method of the network structure.
wherein ,the unit is rad/s for the mechanical angular velocity of the rotor; />For the moment of inertia of the rotor in +.>;/>For unbalanced torque acting on the rotor shaft, the unit is +.>I.e. the prime mover mechanical torque omitting windage friction etc losses +.>And generator electromagnetic torque>A difference between;
according to formula (1), the power generation units of the distributed energy system are aggregated and simplified into a virtual synchronous generator modelObtaining a virtual synchronous generator model->The rocking equation of (2) is:
wherein ,equivalent moment of inertia after aggregation for power generation units of a distributed energy system +.>Which is the equivalent unbalanced torque.
Further, in the step S2, when the load in the distributed energy system is disturbed, there are:
thereby obtaining a virtual synchronous generator modelIs +.>The output power response curve is +.>Weighting processing is carried out according to the capacity of each power generation unit to obtain a power instruction of each power generation unit;
assuming that S1, S2, … Sn are the capacities of the power generation units of the 1 st, 2 nd, … n th distributed energy systems, respectively, it willThe power command is decomposed into power commands of each period:
wherein ,、/>、…/>the power command values are the power command values of the power generation units of the 1 st, 2 nd and … n distributed energy systems, and the power command values are issued to the power generation units of the 1 st, 2 nd and … n distributed energy systems through the synchronous phasor measurement unit after the power command values are obtained;
if the power generation units of p distributed energy systems cannot accept the schedule, the sum of the capacities isThen the power command of the acceptable dispatch power generation units is reassigned according to equation (6):
Further, the step S3 includes: according to the power instructions of the power generation units of the distributed energy systems obtained in the step S2, a local control method integrated with the network structure is designed, and the following constraint relation is established:
by following the power reference value of the net type control moduleAnd a grid-formed control module power reference value +.>Calculating the current reference input value of the follow-net and net-structure control loop> and />:
Calculating a follow-up network and a network construction control loop voltage reference input value through kirchhoff's law:
wherein ,、/>output current and output voltage of the photovoltaic grid-connected converter respectively, R c +jL c Output filter impedance for converter, +.>、/>Virtual input currents for inputting the following net type control module GFL and the net construction type control module GFM; /> and />The control system is respectively a following net type control module GFL and a net structured control module GFMIs a virtual impedance of (a);control loop voltage reference input value for off-grid control, < >>The control loop voltage reference input value is controlled for the network.
Further, the step S4 includes: according to the output power instruction obtained in S2, when the power generation unit is in the pure grid-following mode, the grid-following control module is enabled to have a power reference valueDirectly distributing power instructions to each power generation unit; when the power generation unit is in the integrated mode of networking with the net, the power generation unit comprises: />
And adjusting the distribution coefficient of the network following and constructing power instructions according to the power instructions and the rated capacity of the power generation unit to execute control.
The beneficial effects are that:
the method for controlling the aggregation of the grid-connected integrated converter clusters in the new energy power system can control all power generation units in the distributed energy system in an aggregation mode, so that the output power curve of the aggregation system fits with the synchronous generator curve. Meanwhile, the integrated control method for networking is provided, so that the power generation unit has the power tracking capability, the frequency and voltage supporting capability of the two methods, and the application scene of the new energy power generation unit is expanded. According to the method, all power generation units are subjected to aggregation control, and an integrated control method with the advantages of the two power generation units is constructed on the basis of a traditional networking and network following control strategy. The invention reduces the complexity of the system, increases the stability of the system, can provide active supporting capability for a new energy power system with small inertia and weak damping, and provides important support for the development of a distributed energy system, thereby having wide market prospect.
Drawings
FIG. 1 is a block diagram of a typical distributed energy system;
FIG. 2 is a graph of synchronous generator output power response;
FIG. 3 is an equivalent structural diagram of a distributed energy system;
FIG. 4 is a simplified block diagram of a distributed energy system;
fig. 5 is a schematic diagram of a local control architecture integrated with a netbook.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
The invention relates to a cluster aggregation control method for a network-following integrated converter in a new energy power system, which comprises the following specific steps:
s1, according to the power characteristics of the synchronous generator, a synchronous generator output power response curve shown in fig. 2 can be obtained, wherein P is synchronous generator output power. According to fig. 2, the output power of the power generation unit of the distributed energy system is equivalent, so that the response characteristic of the output power is equivalent to a virtual synchronous generator, and a swing equation of the virtual synchronous generator is obtained. The equivalent distributed energy system structure is shown in fig. 3, G is an abbreviation of Generator, and represents a Generator.
wherein ,for rotor machinesAngular velocity (in rad/s); />For the moment of inertia of the rotor (unit->);For unbalanced torque acting on the rotor shaft (unit +.>) I.e. the prime mover mechanical torque omitting windage friction etc losses +.>And generator electromagnetic torque>And (3) a difference.
According to formula (1), the power generation units of the distributed energy system in fig. 3 are aggregated and simplified into a virtual synchronous generator modelA simplified distributed energy system is shown in fig. 4. Virtual synchronous generator model->The rocking equation of (2) is:
wherein ,equivalent moment of inertia after aggregation for power generation units of a distributed energy system +.>Which is the equivalent unbalanced torque.
S2, constructing a power curve and distributing a power instruction. When load disturbance occurs in the distributed energy system, there are:
wherein ,as the system power variation, by the simultaneous equations (1-3), it is possible to obtain:
thus, a virtual synchronous generator model can be obtainedIs +.>The output power response curve is +.>The power command of each power generation unit can be obtained by performing weighting processing according to the capacity of each power generation unit.
Assuming that S1, S2, … Sn are the capacities of the power generation units of the 1 st, 2 nd, … n th distributed energy systems, respectively, it willThe power command is decomposed into power commands of each period:
wherein ,、/>、…/>and the power command values are the power command values of the power generation units of the 1 st, 2 nd and … n distributed energy systems, and the power command values are issued to the power generation units of the 1 st, 2 nd and … n distributed energy systems through a synchronous phasor measurement unit (phasor measurement unit, PMU). />
If the power generation units of p distributed energy systems cannot accept the schedule, the sum of the capacities isThen the power command of the acceptable dispatch power generation units is reassigned according to equation (6):
S3, constructing a local networking unified control method. According to the power command of the power generation unit of each distributed energy system obtained in the step S2, the invention further designs a local control method integrated with the network structure, and the control structure is shown in figure 5.
In fig. 5, GFL and GFM are a heel-net type control module and a grid-built control module,、/>output current and output voltage of the photovoltaic grid-connected converter, respectively, +.>Output filter impedance for converter, +.>、/>Virtual input currents for inputting the following net type control module GFL and the net construction type control module GFM; /> and />Virtual impedance of the follow-net control module GFL and the net-constructed control module GFM respectively; /> and />The voltage is output by a following net type control module GFL and a net structured control module GFM; c is a system output capacitor, R is the internal resistance of the filter, and L is the inductance of the filter.
According to fig. 5, the following constraint relationship is established:
the converter is connected with the power grid, so that the output voltage of the photovoltaic grid-connected converterClamped by the system, whereby the module power reference value can be controlled by the quantity +.> and />Calculating the current reference input value of the follow-net and net-structure control loop> and />:
According to fig. 3, the following-net, net-build control loop voltage reference input value can be calculated by kirchhoff's law:
wherein ,control loop voltage reference input value for off-grid control, < >>The control loop voltage reference input value is controlled for the network. />
S4, designing a power instruction distribution coefficient in the integrated control method. According to the output power instruction obtained in S2, when the power generation unit is in the pure-heeled net mode, the power generation unit is started toDirectly distributing power instructions to each power generation unit; when the power generation unit is in the integrated mode of networking with the net, the power generation unit comprises:
and (5) performing control according to the power command and the rated capacity adjustment of the power generation unit and the network following/constructing ratio.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (1)
1. A method for controlling aggregation of a network-following integrated converter cluster in a new energy power system is characterized by comprising the following steps:
s1, according to synchronous generatorObtaining the output power response curve of the synchronous generator; equivalent power generation unit output power of the distributed energy system, so that the response characteristic of the power generation unit output power is equivalent to a virtual synchronous generator modelAnd obtain a virtual synchronous generator model->Is a rocking equation of (2); for synchronous generators->The rocking equation is as follows:
wherein ,the unit is rad/s for the mechanical angular velocity of the rotor; />For the moment of inertia of the rotor in +.>;For unbalanced torque acting on the rotor shaft, the unit is +.>I.e. prime mover mechanical torque omitting windage friction losses +.>And generator electromagnetic torque>A difference between;
according to formula (1), the power generation units of the distributed energy system are aggregated and simplified into a virtual synchronous generator modelObtaining a virtual synchronous generator model->The rocking equation of (2) is:
wherein ,equivalent moment of inertia after aggregation for power generation units of a distributed energy system +.>An imbalance torque equivalent thereto;
s2, constructing a power curve and distributing a power instruction; when load disturbance occurs in the distributed energy system, there are:
thereby obtaining a virtual synchronous generator modelIs +.>The output power response curve is +.>Weighting processing is carried out according to the capacity of each power generation unit to obtain a power instruction of each power generation unit;
assuming that S1, S2, … Sn are the capacities of the power generation units of the 1 st, 2 nd, … n th distributed energy systems, respectively, it willThe power command is decomposed into power commands of each period: />
wherein ,、/>、…/>the power command value of the power generation unit of the 1 st, 2 nd and … n distributed energy system is used for obtaining powerAfter the instruction, the instruction is issued to the power generation units of the 1 st, 2 nd and … n distributed energy systems through the synchronous phasor measurement unit;
if the power generation units of p distributed energy systems cannot accept the schedule, the sum of the capacities isThen the power command of the acceptable dispatch power generation units is reassigned according to equation (6):
s3, constructing a local networking unified control method; according to the power instructions of the power generation units of the distributed energy systems obtained in the step S2, a local control method integrated with the network structure is designed, and the following constraint relation is established:
by following the power reference value of the net type control moduleAnd a grid-formed control module power reference value +.>Calculating the current reference input value of the follow-net and net-structure control loop> and />:
Calculating a follow-up network and a network construction control loop voltage reference input value through kirchhoff's law:
wherein ,、/>output current and output voltage of the photovoltaic grid-connected converter, respectively, +.>Output filter impedance for converter, +.>、/>Virtual input currents for inputting the following net type control module GFL and the net construction type control module GFM; and />Virtual impedance of the follow-net control module GFL and the net-constructed control module GFM respectively; />For the voltage reference input value of the off-grid control loop, < >>A voltage reference input value for a networking control loop;
s4, designing a power instruction distribution coefficient in a unified control method of networking; according to the output power instruction obtained in S2, when the power generation unit is in the pure grid-following mode, the grid-following control module is enabled to have a power reference valueDirectly distributing power instructions to each power generation unit; when the power generation unit is in the integrated mode of networking with the net, the power generation unit comprises:
and adjusting the distribution coefficient of the network following and constructing power instructions according to the power instructions and the rated capacity of the power generation unit to execute control.
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