CN115579872A - Current tracking control method for virtual synchronous machine - Google Patents
Current tracking control method for virtual synchronous machine Download PDFInfo
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- CN115579872A CN115579872A CN202211252783.3A CN202211252783A CN115579872A CN 115579872 A CN115579872 A CN 115579872A CN 202211252783 A CN202211252783 A CN 202211252783A CN 115579872 A CN115579872 A CN 115579872A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/48—Controlling the sharing of the in-phase component
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
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- Control Of Eletrric Generators (AREA)
Abstract
The invention discloses a virtual synchronous machine current tracking control method, which is characterized in that a reactive current set value of a virtual synchronous machine and an actual reactive current of the virtual synchronous machine are subjected to difference to obtain a reactive current difference, and the reactive current difference is used as G QR Inputting links, and then summing the voltage modulus of the grid-connected point to obtain the internal potential amplitude, the internal potential angle and the internal potential amplitude f Obtaining the output voltage of the virtual synchronous machine directly through coordinate transformation; or the internal potential angle, the internal potential amplitude and the grid-connected point voltage are measured by G VAC The method can directly control the current of the virtual synchronous machine, ensure that the virtual synchronous machine can accurately control active and reactive currents during fault ride-through, and ensure that the fault ride-through characteristic of the virtual synchronous machine is compatible with the existing power grid fault ride-throughThe standard requirement effectively limits the output current of the synchronous machine and reduces the overcurrent risk of the virtual synchronous machine.
Description
Technical Field
The invention relates to the technical field of grid connection, in particular to a current tracking control method for a virtual synchronous machine.
Background
In order to build new power systems powered by a high proportion of renewable energy sources, even a proportion of 100%, as interface devices between renewable energy sources and the power grid, power electronic converters must take over more and more functions of synchronous machines. The virtual synchronization technology simulates the operation mode of the synchronous machine, and naturally inherits many characteristics of the synchronous machine, so that the virtual synchronization technology becomes a research hotspot.
The existing virtual synchronous machine control mostly adopts a voltage source type control mode. And the active part in the power ring refers to a rotor swing equation of the synchronous machine, and the real-time active power of the virtual synchronous machine is used as feedback to obtain the internal potential angle of the virtual synchronous machine. And (4) in the reactive part, referring to the excitation control of the synchronous machine, and taking the real-time reactive power of the virtual synchronous machine as feedback to obtain the virtual synchronous internal potential amplitude. And directly controlling the output voltage of the virtual synchronous machine according to the amplitude and the phase of the internal potential obtained by the power loop. Although the voltage source type virtual synchronous machine can directly control the voltage of the virtual synchronous machine, the voltage source type virtual synchronous machine has the advantage of stronger small disturbance stability. However, because the current cannot be directly controlled, the overcurrent problem is easy to occur when the disturbance such as grid voltage drop, load sudden change, grid voltage unbalance and the like is encountered.
The virtual synchronous machine current tracking control method has the advantages that the power loop of the original voltage source type virtual synchronous machine is transformed into the active current loop and the reactive current loop, the active current and the reactive current of the virtual synchronous machine are used as feedback, the direct control of the output current of the virtual synchronous machine is realized under the condition that the voltage source control mode of the virtual synchronous machine is not changed, the current of a power electronic device can be controlled more accurately, the risk of overcurrent in the fault process is reduced, and the requirement of the power grid standard is better met.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a virtual synchronous machine current tracking control method, which can directly control the current of a virtual synchronous machine, ensure that the virtual synchronous machine can accurately control active and reactive currents during fault ride-through without changing the motion equation of the existing virtual synchronous machine, ensure that the fault ride-through characteristic of the virtual synchronous machine is compatible with the existing power grid fault ride-through standard requirement, effectively limit the output current of the synchronous machine and reduce the overcurrent risk of the virtual synchronous machine.
In order to solve the technical problem, the invention provides a current tracking control method of a virtual synchronous machine; the method comprises the following steps when controlling the active current and the reactive current of the virtual synchronous machine:
and subtracting the active current set value of the virtual synchronous machine from the active current of the virtual synchronous machine, and taking the active current difference as the mechanical active input of the rotor motion equation link of the synchronous machine.
Constructing a synchronous machine rotor motion equation, and passing the obtained active current difference through one integration link 1/T j s is a forward channel, a closed loop link taking an output signal as a negative feedback channel through a proportion link D, and then the sum of the output signal and the rated angular frequency is obtained, and an internal potential power angle is obtained through a unit integration link.
And subtracting the reactive current set value of the virtual synchronous machine from the reactive current of the virtual synchronous machine, taking the reactive current difference as the input of a PI link, and summing the reactive current difference with the output voltage modulus of the virtual synchronous machine to obtain the internal potential amplitude.
Preferably, in a steady state, the active current set value of the virtual synchronous machine port is calculated from the active power set value of the virtual synchronous machine and the voltage modulus of the grid-connected point. The reactive current setpoint of the virtual synchronous machine port is directly given a value of 0.
Preferably, when a fault passes through, the reactive current set value of the virtual synchronization port is calculated by the voltage modulus of the grid-connected point according to the grid-connected requirement. The active current set value of the virtual synchronous machine port is calculated from the active power set value and the grid-connected point voltage modulus of the virtual synchronous machine and is limited by the reactive current set value. The sum of the active current set value and the reactive current set value of the virtual synchronous machine port does not exceed the virtual synchronous machine current upper limit.
Preferably, the network-access active current and the network-access reactive current are active current and reactive current which are actually injected into the power grid by the virtual synchronous machine port.
Preferably, in the method for constructing the equation of motion link of the rotor of the synchronous machine, the forward channel 1/Js corresponds to a rotational inertia link of the rotor, and the proportional negative feedback link D corresponds to a damping link of the rotor.
Preferably, the PI controller is a proportional plus integral regulator, and can eliminate the direct current given error.
Preferably, the internal potential amplitude is obtained by feedforward of a voltage modulus of a grid-connected point and output of a reactive current deviation PI controller, so that the given tracking speed of the reactive current and the tracking precision of the reactive current are both considered.
Preferably, the internal potential amplitude and the rotor angle can be directly subjected to coordinate transformation as input of the PWM wave generator. Or the difference between the voltage of the PWM wave generator and the voltage of the grid-connected point can be obtained, and the difference is used as the input of the PWM wave generator through a PI controller and the addition of voltage feedforward. So as to obtain faster and more accurate output voltage control of the virtual synchronous machine.
After the method is adopted, the virtual synchronous machine current tracking control method is characterized in that the difference is made between the active current set value of the virtual synchronous machine and the active current of the virtual synchronous machine, and the active current difference is used as the mechanical active input of a synchronous machine rotor motion equation link. And constructing a synchronous machine rotor motion equation, and carrying out summation on the obtained active current difference and rated angular frequency through a closed loop link which takes an integral link as a forward channel and takes an output signal as a negative feedback channel through a proportional link D, so as to obtain an internal potential power angle through a unit integral link. The reactive current set value of the virtual synchronous machine is differenced with the reactive current of the virtual synchronous machine, the reactive current difference is used as the input of a PI link, and then the difference is summed with the output voltage modulus of the virtual synchronous machine to obtain an internal potential amplitude; the virtual synchronous machine current tracking control method can directly control the output current of the virtual synchronous machine, so that the current controllability of the virtual synchronous machine is enhanced, the output current of the synchronous machine can be effectively limited when a voltage drop fault occurs in a power grid, the overcurrent risk of the virtual synchronous machine is reduced, the current can be controlled according to the existing new energy power grid fault ride-through standard when the power grid fails, and the fault ride-through characteristic of the virtual synchronous machine is compatible with the existing power grid fault ride-through standard requirements.
Drawings
FIG. 1 is an overall system diagram of the virtual synchronous machine current tracking control method of the present invention;
fig. 2 is an active current control diagram of a virtual synchronous machine current tracking control method according to a first embodiment of the present invention;
fig. 3 is a reactive current control diagram of a virtual synchronous machine current tracking control method according to a first embodiment of the present invention;
fig. 4 is an active current and reactive current obtaining diagram of a virtual synchronous machine current tracking control method according to a second embodiment of the present invention;
fig. 5 is a diagram illustrating an output voltage e of a virtual synchronous machine obtained in a current tracking control method of the virtual synchronous machine according to an embodiment of the present invention vscref_α And e vscref_β Control chart of the first mode;
fig. 6 is a diagram illustrating an output voltage e of a virtual synchronous machine obtained in a current tracking control method of the virtual synchronous machine according to an embodiment of the present invention vscref_α And e vscref_β Control of mode two.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example one
Please refer to fig. 1, fig. 2 and fig. 3; fig. 1 is an overall system diagram of a current tracking control method of a virtual synchronous machine according to the present invention, fig. 2 is an active current control diagram of the current tracking control method of the virtual synchronous machine according to the first embodiment of the present invention, and fig. 3 is a reactive current control diagram of the current tracking control method of the virtual synchronous machine according to the first embodiment of the present invention;
the embodiment discloses a current tracking control method of a virtual synchronous machine, which comprises the following steps:
setting the active current set value I of the virtual synchronous machine pref Actual active current I with virtual synchronous machine p Performing difference to obtain an active current difference, and using the active current difference as mechanical active input of a virtual synchronous machine rotor motion equation;
constructing a virtual synchronous machine rotor motion equation, enabling the mechanical active input to pass through a closed loop link which takes an integral link 1/Js as a forward channel and an output signal to pass through a proportional link D as a negative feedback channel, and then mixing the mechanical active input with a rated angular frequency omega g Making a sum, and obtaining an internal potential angle theta through a unit integration link vsc ；
Setting the reactive current set value I of the virtual synchronous machine qref Actual reactive current I with virtual synchronous machine q Obtaining a reactive current difference by difference making, and taking the reactive current difference as G QR Inputting link, and then summing point voltage modulus U om Making and obtaining the internal potential amplitude E ref Wherein G is QR The link is a PI controller;
referring to FIG. 5, the internal potential angle θ vsc And the magnitude of the internal potential E ref Directly obtaining the output voltage e of the virtual synchronous machine through coordinate transformation vscref_α And e vscref_β ；
Alternatively, referring to FIG. 6, the internal potential angle θ vsc And the magnitude of the internal potential E ref And the voltage u of the grid connection point od And u oq Make a difference, jing G VAC Obtaining the output voltage e of the virtual synchronous machine by the link and adding the voltage feedforward vscref_α And e vscref_β Wherein G is VAC The link is a PI controller.
Example two
Referring to fig. 4, fig. 4 is a diagram for obtaining an active current and a reactive current of a virtual synchronous machine current tracking control method according to a second embodiment of the present invention;
in this embodiment, based on the first embodiment, in a steady state, the active current setting value I of the virtual synchronous machine pref Active power setpoint P by virtual synchronous machine ref And grid point voltage modulus U om The division calculation is carried out to obtain the reactive current set value I of the virtual synchronous machine qref Directly given as 0.
EXAMPLE III
In this embodiment, based on the first embodiment, the virtual synchronous reactive current setting value I is set during fault crossing qref From the voltage modulus U of the grid-connected point om Calculating to obtain an active current set value I of the virtual synchronous machine according to grid connection requirements pref Active power setpoint P by virtual synchronous machine ref And the voltage modulus U of the grid-connected point om The division calculation is carried out; active current set value I of the virtual synchronous machine qref And a reactive current setpoint value I qref Does not exceed the virtual synchronous machine current upper limit.
Example four
The present embodiment is based on the first embodiment, and in the present embodiment, the actual active current I pq The active current of the power grid is actually injected into the virtual synchronous machine, and the actual reactive current I q The reactive current of the power grid is actually injected into the virtual synchronous machine;
when a virtual synchronous machine rotor motion equation is constructed, the integral link 1/Js is taken as a rotational inertia link corresponding to a virtual synchronous machine rotor in a forward channel, and the closed loop link taking an output signal as a negative feedback channel through a proportional link D is taken as a damping link corresponding to the virtual synchronous machine rotor;
the PI controller is a proportional plus integral regulator, and can eliminate the error given by direct current.
EXAMPLE five
The present embodiment is based on the first embodiment, and in the present embodiment, the internal potential amplitude E ref Voltage modulus U through point of connection om And the output of the reactive current deviation PI controller is added to obtain the output so as to give consideration to the given tracking speed of the reactive current and the tracking precision of the reactive current.
EXAMPLE six
The present embodiment is based on the first embodiment, and in the present embodiment, the internal potential amplitude E ref And internal potential angle theta vsc Can be directly subjected to coordinate transformation and used as the input of a PWM wave generator. Or making difference with the voltage of the grid-connected point, using the voltage feedforward through the PI controller as the input of the PWM wave generator, the method can control more quickly and accuratelyThe virtual synchronous machine voltage, and all control loops are working during fault ride through.
Claims (8)
1. A virtual synchronous machine current tracking control method is characterized by comprising the following steps:
setting the active current of the virtual synchronous machine to be I pref Actual active current I with virtual synchronous machine p Performing difference to obtain an active current difference, and taking the active current difference as mechanical active input of a virtual synchronous machine rotor motion equation;
constructing a virtual synchronous machine rotor motion equation, enabling the mechanical active input to pass through a closed loop link which takes an integral link 1/Js as a forward channel and an output signal to pass through a proportional link D as a negative feedback channel, and then mixing the mechanical active input with a rated angular frequency omega g Making a sum, and obtaining an internal potential angle theta through a unit integration link vsc ；
Setting the reactive current of the virtual synchronous machine to be I qref Actual reactive current I with virtual synchronous machine q Obtaining a reactive current difference by difference making, and taking the reactive current difference as G QR Inputting link, and then summing point voltage modulus U om Making and obtaining the internal potential amplitude E ref Wherein G is QR The link is a PI controller;
the internal potential angle theta vsc And the magnitude of the internal potential E ref Directly obtaining the output voltage e of the virtual synchronous machine through coordinate transformation vscref_α And e vscref_β (ii) a Or the internal potential angle theta vsc And the magnitude of the internal potential E ref And the voltage u of the grid connection point od And u oq Make a difference, jing G VAC Obtaining the output voltage e of the virtual synchronous machine by the link and adding the voltage feedforward vscref_α And e vscref_β Wherein G is VAC The link is a PI controller.
2. The method according to claim 1, wherein the active current setting value I of the virtual synchronous machine is set at a steady state pref Active power setpoint by virtual synchronous machineP ref And grid point voltage modulus U om The division calculation is carried out to obtain the reactive current set value I of the virtual synchronous machine qref Directly given as 0.
3. The virtual synchronous machine current tracking control method according to claim 1, wherein the virtual synchronous reactive current setpoint I is set at a fault crossing qref From the voltage modulus U of the grid-connected point om Calculating to obtain an active current set value I of the virtual synchronous machine according to grid connection requirements pref Active power setpoint P by virtual synchronous machine ref And grid point voltage modulus U om The division calculation is carried out; active current set value I of the virtual synchronous machine qref And a reactive current setpoint value I qref Does not exceed the virtual synchronous machine current upper limit.
4. The virtual synchronous machine current tracking control method according to claim 1, wherein the actual active current I pq The active current of the power grid is actually injected into the virtual synchronous machine, and the actual reactive current I q And actually injecting reactive current of the power grid into the virtual synchronous machine.
5. The method according to claim 1, wherein when constructing the equation of motion of the virtual synchronous machine rotor, the integral element 1/Js is used as a rotational inertia element of the virtual synchronous machine rotor corresponding to a forward channel, and the closed loop element using the output signal as a negative feedback channel through the proportional element D is used as a damping element of the virtual synchronous machine rotor.
6. The virtual synchronous machine current tracking control method according to claim 1, wherein the PI controller is a proportional-integral regulator.
7. The virtual synchronous machine current tracking control method according to claim 1, wherein the internal potential amplitude E is ref Through a point of connectionVoltage modulus U om And adding the output of the reactive current deviation PI controller to obtain the reactive current deviation.
8. The method for controlling current tracking of the virtual synchronous machine according to claim 1, wherein the virtual synchronous machine outputs a voltage e vscref_α And e vscref_β As input to a PWM wave generator.
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