CN115473273A - Self-synchronization low-voltage ride-through control method for new energy power generation unit under extremely weak grid - Google Patents
Self-synchronization low-voltage ride-through control method for new energy power generation unit under extremely weak grid Download PDFInfo
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- H—ELECTRICITY
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- H—ELECTRICITY
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract
The invention discloses a self-synchronization low-voltage ride through control method for a new energy power generation unit under an extremely weak grid, and belongs to the field of power control. The control method comprises the following steps: under the condition of steady-state operation, the device has the capability of actively supporting the voltage and the frequency of a power grid, and simultaneously has better current control capability; during the voltage drop, the current peak value at the initial stage of the voltage drop can be reduced by amplitude synchronous control; during the low-voltage-through stable operation period, the power instruction switching can enable the system to preferentially send out reactive power to help the voltage of the power grid to recover; during the voltage recovery period, the phase angle synchronous control can prevent the sudden change of the phase angle caused by voltage drop and prevent overcurrent and overvoltage. According to the control method, low-voltage ride through can be realized without switching control modes, the control is relatively simple, errors are not prone to occurring, and the stability and the power grid adaptability of the new energy grid-connected system are improved.
Description
Technical Field
The invention relates to a self-synchronizing low-voltage ride-through control method for a new energy power generation unit, in particular to a transient and steady state control method for a self-synchronizing voltage source of the new energy power generation unit under an extremely weak power grid, and belongs to the field of power control.
Background
With the introduction of the "dual-carbon" target, the country pays more attention to the development of new energy technology, and the construction of a new generation of power system mainly based on clean energy becomes a hot spot of current research. However, when a disturbance occurs under weak grid conditions, the voltage and frequency of the new energy system are prone to destabilization. Therefore, further research on an active support technology and a system stable operation control method under high-proportion penetration of new energy has great significance for realizing the aim of 'double carbon'.
In recent years, experts and scholars at home and abroad research the active support and stability problems of a new energy system from various angles, and self-synchronous voltage source control methods such as a virtual synchronous generator and the like are continuously applied. The virtual synchronous generator control method has certain inertia and damping by simulating the rotor motion equation of the traditional generator, and has the capability of actively supporting a power grid. However, the conventional virtual synchronous generator control method has no low voltage ride through capability, and is very easy to cause system overcurrent, overvoltage and system breakdown during grid voltage sag. In addition, the interaction problem of the new energy system under the weak network or the ultra-weak network is complex, and the system stability is greatly reduced.
In order to solve the problems, experts and scholars at home and abroad provide methods which mainly comprise the following steps:
chinese patent application specification (CN 113595147A) entitled "virtual synchronous generator control method based on model prediction control" provides a control method in which an optimal switching sequence is directly applied to an inverter by a model prediction method, which can effectively improve system stability under power fluctuation, and has active support capability, but lacks current control capability, and is prone to overcurrent when grid voltage drops.
In the technical scheme disclosed in the chinese patent application specification (CN 108092308A) entitled "a distributed virtual synchronous generator low voltage ride through control method", a comprehensive control method for accelerating the reactive power loop response speed, introducing virtual impedance, and changing power instructions during faults is provided, the control method has a certain low voltage ride through capability, and improves the stability of a new energy system under faults, however, the interaction condition is severe under weak networks or extremely weak networks, and the stability of the method is greatly reduced.
The chinese patent application specification (CN 108718097A) entitled "seamless switching system suitable for virtual synchronous generator low voltage ride through" provides a mode seamless switching control method based on VSG control of amplitude and phase pre-synchronization and traditional LVRT control, which has a good low voltage ride through capability, but the control method is complex and is prone to errors in practical application.
In a word, in the face of grid voltage drop, the existing virtual synchronous generator control method has the problems of overvoltage, overcurrent and system breakdown under the condition of a weak grid or an extremely weak grid, and the power angle of a system is easy to be unstable after the grid voltage drop, so that low-voltage ride through is difficult to realize.
Disclosure of Invention
The invention aims to overcome the limitations of various technical schemes, and provides a self-synchronizing low-voltage ride-through control method of a new energy power generation unit under an extremely weak grid, aiming at the problems that the traditional virtual synchronous generator control method under the weak grid is poor in current control capability, and overcurrent, overvoltage, power angle instability, system breakdown and the like are easy to occur under the voltage drop of a power grid.
The object of the invention is thus achieved. The invention provides a self-synchronizing low-voltage ride-through control method of a new energy power generation unit under an extremely weak grid, wherein the topology of the new energy power generation unit comprises direct currentSource U dc DC side filter capacitor C dc Three-phase full-bridge inverter circuit, filter inductor L and filter capacitor C 1 Passive damping resistor R C Grid-connected equivalent resistor R g Grid-connected equivalent inductor L g And a three-phase network e a 、e b 、e c Filter capacitor C at DC side dc Connected in parallel with a direct current source U dc And a three-phase full-bridge inverter circuit connected in series with the DC side power supply U dc And a filter capacitor C between the filter inductor L 1 First series passive damping resistor R C Then connected in parallel with the filter inductor L and the grid-connected equivalent resistor R g Equivalent inductance L between and connected to grid g Serially connected with a grid-connected equivalent resistor R g And a three-phase network e a 、e b 、e c To (c) to (d);
the control method comprises the following steps:
step 1, sampling and coordinate transformation;
the sampling includes collecting the following data: voltage of grid-connected point of new energy power generation unit is recorded as grid-connected voltage u oa ，u ob ，u oc And the current of the grid-connected point of the new energy power generation unit is recorded as grid-connected current i oa ，i ob ，i oc And the current at the filter inductor L of the new energy power generation unit is recorded as bridge arm side inductor current i La ，i Lb ，i Lc And the grid voltage of the new energy power generation unit is recorded as grid voltage u ga ，u gb ，u gc ；
The coordinate transformation includes coordinate transformation of: for grid-connected voltage u oa ，u ob ，u oc Grid-connected current i oa ，i ob ，i oc Bridge arm side induction current i La ，i Lb ，i Lc Grid voltage u ga ，u gb ，u gc Respectively carrying out single synchronous rotation coordinate transformation to obtain grid-connected voltage dq component U od ，U oq Grid-connected current dq component I od ，I oq Bridge arm side inductor current dq component I Ld ，I Lq Grid voltage dq component U gd ，U gq ；
Step 2, obtaining an average active power P and an average reactive power Q by using an active power calculation equation and a reactive power calculation equation, wherein the active power calculation equation and the reactive power calculation equation are respectively as follows:
P＝1.5(U oq I oq +U od I od )
Q＝1.5(U od I oq -U aq I od )
wherein, ω is 0 Giving an active power instruction P for the new energy power generation unit 0 The method comprises the following steps that (1) the rated angular frequency of time, m is a power angle control droop coefficient, J is the virtual rotational inertia of a simulation synchronous generator set, and s is a Laplace operator;
carrying out phase angle synchronous control at the voltage drop ending moment, and meanwhile, integrating the angular frequency omega of the self-synchronous control to obtain an output phase angle theta of the self-synchronous control; the phase angle synchronization control of the voltage drop ending time is the compensation of the output phase difference delta theta, and delta theta = theta g0 -θ n Wherein θ g0 For the output phase angle, theta, of the network voltage at the end of the voltage sag 0 For the output phase angle of the self-synchronization control at the voltage drop ending time, the expression of the output phase angle θ of the self-synchronization control is as follows:
The reactive power control equation and the instruction synthesis equation are expressed as follows:
E * ＝U 0 +n(Q 0 -Q)
wherein, U 0 Giving reactive power instruction Q for new energy power generation unit 0 Rated voltage of the time, n is a reactive-voltage droop coefficient;
wherein R is v Is a virtual resistance, L v Is a virtual inductor;
for current command signal
Performing single synchronous rotation coordinate transformation to obtain a dq component of a current command signal
the expressions of the power grid voltage amplitude calculation equation and the voltage drop calculation equation are respectively as follows:
step 7, obtaining a q-axis instruction of a current loop when the voltage of the power grid drops according to a reactive compensation control equation in the low voltage ride through standard
Obtaining d-axis instruction of current loop when grid voltage drops through limiting control equation of power device current stress
The reactive compensation control equation and the limiting control equation of the current stress of the power device are respectively as follows:
wherein, K m As a reactive compensation coefficient, I N The rated current amplitude of the new energy power generation unit is obtained;
step 8, according to the d-axis instruction of the current loop when the grid voltage drops, obtained in the step 7
And a current loop q-axis instruction when the voltage of a power grid drops
Obtaining an active power instruction under the fault through a fault power instruction calculation equation
And reactive power command
The fault power command calculation equation is as follows:
step 9, obtaining the voltage drop depth of the grid-connected point according to the step 6D, obtaining a voltage instruction under the fault through a fault voltage instruction calculation equation
The fault voltage command calculation equation is as follows:
step 10, performing power instruction switching and amplitude synchronous control according to the grid-connected point voltage drop depth D obtained in the step 6, specifically, setting a power switching instruction as P ref The reactive power switching command is Q ref The voltage switching command is U ref ：
(1) In the stable operation stage, D is more than or equal to 0.9 ref ＝P 0 ，Q ref ＝Q 0 ，U ref ＝U 0 ；
(2) In the voltage drop stage of the power grid, D is less than 0.9,
(3) Grid voltage recovery phase, P ref ＝P 0 ，Q ref ＝Q 0 ，
Step 11, according to the current command signal dq component obtained in step 5
And the bridge arm side induction current dq component I obtained in the step 1 Ld ，I Lq Obtaining a control signal U by a current control equation d ，U q The current governing equation is:
wherein, K pi Is a current loop proportional control coefficient, K ii Is a current loop integral control coefficient;
the obtained control signal U d ，U q Obtaining a control signal U of the new energy power generation unit through single synchronous rotation coordinate inverse transformation a ，U b ，U c Then according to the control signal U a ，U b ，U c And generating PWM control signals for the three-phase full-bridge inverter circuit.
Compared with the prior art, the invention has the following advantages for the new energy power generation system:
1. the balance current control can effectively inhibit harmonic waves under small disturbance, and the current control capability is improved.
2. The amplitude synchronous control can effectively reduce the current peak during the voltage drop, the phase angle synchronous control can effectively reduce the current peak during the voltage recovery, and the stability and the power grid adaptability of the new energy grid-connected system are improved.
3. The low-voltage ride through can be realized without switching control strategies when the voltage of the power grid drops, the control is relatively simple, and errors are not easy to occur.
Drawings
Fig. 1 is a grid-connected inverter topology of a new energy power generation unit of the present invention.
Fig. 2 is a control block diagram of the self-synchronous low-voltage ride-through control method of the new energy power generation unit according to the invention.
Fig. 3 is a waveform diagram of grid-connected voltage simulation when the grid voltage drops by 50% in the embodiment of the invention.
Fig. 4 is a waveform diagram of grid-connected current simulation when the grid voltage drops by 50% in the embodiment of the invention.
Fig. 5 is a simulation waveform diagram of d-axis component of bridge arm side inductive current when the grid voltage drops by 50% in the embodiment of the invention.
Fig. 6 is a waveform diagram of an output active power simulation when the voltage of the power grid drops by 50% in the embodiment of the invention.
Detailed Description
The preferred embodiments of the present invention will be described in further detail with reference to the accompanying drawings.
Fig. 1 is a topology of a new energy grid-connected inverter according to an embodiment of the present invention. As can be seen from the figure, the topology of the new energy power generation unit comprises a direct current power supply U dc DC side filter capacitor C dc Three-phase full-bridge inverter circuit, filter inductor L and filter capacitor C 1 Passive damping resistor R C And a grid-connected equivalent resistor R g Grid-connected equivalent inductor L g And a three-phase network e a 、e b 、e c Filter capacitor C on the DC side dc Connected in parallel to a direct current source U dc And a three-phase full-bridge inverter circuit connected in series with the DC side power supply U dc A filter capacitor C between the filter inductor L and the filter capacitor 1 First series passive damping resistor R C Then connected in parallel with the filter inductor L and the grid-connected equivalent resistor R g Equivalent inductance L of grid connection g Serially connected with a grid-connected equivalent resistor R g And a three-phase network e a 、e b 、e c In the meantime. In addition, PCC on fig. 1 is a grid-tie point.
Specifically, the parameters in this embodiment are as follows: the effective value of the output alternating current line voltage is 380V/50Hz, the rated capacity is 100kW, the inductance value of the filter inductance L is 0.3mH, and the filter capacitance C 1 The capacity value of (2) is 200 mu F, and the sampling frequency F of the new energy power generation unit s Is 10kHz, so the sampling period T s ＝100μs。
Fig. 2 is a control block diagram of the control method of the present invention, and as can be seen from fig. 2, the steps of the self-synchronization low-voltage ride through control method of the new energy power generation unit under the very weak grid of the present invention are as follows:
step 1, sampling and coordinate transformation.
The sampling includes collecting the following data: voltage of grid-connected point of new energy power generation unit is recorded as grid-connected voltage u oa ，u ob ，u oc And the current of the grid-connected point of the new energy power generation unit is recorded as grid-connected current i oa ，i ob ，i oc New energy power generation unitThe current at the filter inductor L is recorded as bridge arm side inductor current i La ，i Lb ，i Lc And the grid voltage of the new energy power generation unit is recorded as grid voltage u ga ，u gb ，u gc 。
The coordinate transformation includes coordinate transformation of: to grid-connected voltage u oa ，u ob ，u oc Grid-connected current i oa ，i ob ，i oc Bridge arm side inductive current i La ，i Lb ，i Lc Grid voltage u ga ，u gb ，u gc Respectively carrying out single synchronous rotation coordinate transformation to obtain grid-connected voltage dq component U od ，U oq Grid-connected current dq component I od ，I oq Bridge arm side inductor current dq component I Ld ，I Lq Grid voltage dq component U gd ，U gq 。
Step 2, obtaining an average active power P and an average reactive power Q by using an active power calculation equation and a reactive power calculation equation, wherein the active power calculation equation and the reactive power calculation equation are respectively as follows:
P＝1.5(U oq I oq +U od I od )
Q＝1.5(U od I oq -U oq I od )
wherein, ω is 0 Giving an active power instruction P for the new energy power generation unit 0 And m is a power angle control droop coefficient, J is the virtual rotational inertia of the simulated synchronous generator set, and s is a Laplace operator.
At the end of voltage dropPhase angle synchronous control, namely integrating the angular frequency omega of the self-synchronous control to obtain an output phase angle theta of the self-synchronous control; the phase angle synchronization control of the voltage drop ending time is the compensation of the output phase difference delta theta, and delta theta = theta g0 -θ 0 Wherein theta g0 The phase angle, theta, of the output of the grid voltage at the end of the voltage sag 0 For the output phase angle of the self-synchronization control at the voltage drop ending moment, the expression of the output phase angle theta of the self-synchronization control is as follows:
the power angle control equation shows the droop curve relationship and the virtual inertia of the active power of the new energy power generation unit. The virtual inertia indicates the change rate of the system frequency, and a larger virtual inertia is needed to ensure the stable change of the system frequency; however, the virtual inertia is equivalent to adding a first-order inertia element in the system, and too large virtual inertia may cause instability of the system. The parameter selection thus requires a compromise. The inertia time constant is in the range of tau to ensure the stability of the system virtual ＝Jω 0 m≤2e -3 And s. The active power droop curve relationship in the power angle control equation comprises three coefficients, the power angle control droop coefficient m represents the slope of the droop curve, and the value principle is that when the active power changes by 100%, the frequency changes within 0.5 Hz; given active power command P 0 And corresponding nominal angular frequency omega 0 The position relation of a droop curve is represented, and the active power output by the new energy grid-connected inverter is mainly considered to be P 0 The output frequency is large or small.
In this embodiment, the power angle control droop coefficient takes the value of
Taking tau according to the principle of the value of inertia time constant virtual ＝Jω 0 m＝1.5e -3 s, can yield J =0.154kg · m 2 Giving the value of the active power instruction as P 0 =100kW, the corresponding rated angular frequency is ω 0 ＝314.16rad/s。
The expressions of the reactive power control equation and the instruction synthesis equation are respectively as follows:
E * ＝U 0 +n(Q 0 -Q)
wherein, U 0 Giving a reactive power instruction Q for a new energy power generation unit 0 The rated voltage of the time, n, is the reactive-voltage droop coefficient.
In the present embodiment of the present invention,
Q 0 =0, corresponding U 0 ＝311.13V。
wherein R is v Is a virtual resistance, L v Is a virtual inductor.
For current command signal
Performing single synchronous rotation coordinate transformation to obtain a current command signal dq component
In this example, R v ＝0.05Ω，L v ＝0.52mH。
The expressions of the power grid voltage amplitude calculation equation and the voltage drop calculation equation are respectively as follows:
in the present embodiment, it is preferred that,
step 7, obtaining a q-axis instruction of a current loop when the voltage of the power grid drops according to a reactive compensation control equation in the low voltage ride through standard
Obtaining a d-axis instruction of a current loop when the voltage of a power grid drops through a limiting control equation of the current stress of a power device
The reactive compensation control equation and the limiting control equation of the current stress of the power device are respectively as follows:
wherein, K m As a reactive compensation coefficient, I N And the current amplitude is the rated current amplitude of the new energy power generation unit.
In this embodiment, K m ＝-1.5，
Step 8, according to the d-axis instruction of the current loop when the grid voltage drops, obtained in the step 7
And a current loop q-axis instruction when the voltage of a power grid drops
Obtaining an active power instruction under the fault through a fault power instruction calculation equation
And reactive power command
The fault power instruction calculation equation is as follows:
step 9, obtaining a voltage instruction under the fault through a fault voltage instruction calculation equation according to the grid-connected point voltage drop depth D obtained in the step 6
The fault voltage command calculation equation is as follows:
step 10, performing power instruction switching and amplitude synchronous control according to the voltage drop depth D of the grid-connected point obtained in the step 6, specifically, setting a power switching instruction as P ref The reactive power switching command is Q ref The voltage switching command is U ref ：
(1) In the stable operation stage, D is more than or equal to 0.9 ref ＝P 0 ，Q ref ＝Q 0 ，U ref ＝U 0 ；
(2) In the voltage drop stage of the power grid, D is less than 0.9,
(3) Grid voltage recovery phase, P ref ＝P 0 ，Q ref ＝Q 0 ，
As seen from step 10, in the stable operation stage, the active power command and the voltage command are not switched; in the phase of recovering the voltage of the power grid, only the switching of the voltage command is carried out.
Step 11, according to the dq component of the current command signal obtained in step 5
And the bridge arm side induction current dq component I obtained in the step 1 Ld ，I Lq Obtaining a control signal U by a current control equation d ，U q The current control equation is:
wherein, K pi As a current loop proportional control coefficient, K ii The control coefficient is integrated for the current loop.
The obtained control signal U is d ，U q Control signal U of new energy power generation unit is obtained through single synchronous rotation coordinate inverse transformation a ，U b ，U c Then according to the control signal U a ，U b ，U c And generating PWM control signals for the three-phase full-bridge inverter circuit.
In this embodiment, K pi ＝1.0，K ii ＝15。
In order to prove the technical effect of the invention, the invention is simulated.
Fig. 3, 4, 5, and 6 are a grid-connected voltage waveform, a grid-connected current waveform, a bridge arm side inductance current d-axis component waveform, and an active power waveform of the new energy power generation unit when the grid voltage drops by 50% in the case of an extremely weak grid (short-circuit ratio SCR = 1.2), respectively. As can be seen from fig. 3 and 4, the self-synchronization low-voltage ride through control method for the new energy power generation unit under the extremely weak grid provided by the invention can ensure rated operation of grid-connected voltage and grid-connected current in a normal operation stage, can ensure operation of the grid-connected voltage and the grid-connected current in a rated range in a voltage drop stage, and can recover to a stable operation state after transient oscillation in a voltage recovery stage. As can be seen from fig. 5 and 6, according to the self-synchronization low-voltage ride-through control method for the new energy power generation unit under the extremely weak grid, when the voltage of the power grid drops, the system reduces active output and helps the voltage of the power grid to recover, so that low-voltage ride-through is realized and the stability of the system is improved.
Claims (1)
1. A self-synchronization low-voltage ride-through control method for a new energy power generation unit under an extremely weak grid is disclosed, wherein the topology of the new energy power generation unit comprises a direct-current power supply U dc DC side filter capacitor C dc Three-phase full-bridge inverter circuit, filter inductor L and filter capacitor C 1 Passive damping resistor R C And a grid-connected equivalent resistor R g Grid-connected equivalent inductor L g And a three-phase network e a 、e b 、e c Filter capacitor C on the DC side dc Connected in parallel to a direct current source U dc And a three-phase full-bridge inverter circuit connected in series with the DC side power supply U dc A filter capacitor C between the filter inductor L and the filter capacitor 1 First series passive damping resistor R C And then connected in parallel with the filter inductor L and the grid-connected equivalent resistor R g Equivalent inductance L of grid connection g Connected in series with a grid-connected equivalent resistor R g And a three-phase network e a 、e b 、e c To (c) to (d);
the control method is characterized by comprising the following steps:
step 1, sampling and coordinate transformation;
the sampling includes collecting the following data: newVoltage of grid-connected point of energy power generation unit is recorded as grid-connected voltage u oa ，u ob ，u oc And the current of the grid-connected point of the new energy power generation unit is recorded as grid-connected current i oa ，i ob ，i oc And the current at the filter inductor L of the new energy power generation unit is recorded as bridge arm side inductor current i La ，i Lb ，i Lc And the grid voltage of the new energy power generation unit is recorded as grid voltage u ga ，u gb ，u gc ；
The coordinate transformation includes coordinate transformation of: for grid-connected voltage u oa ，u ob ，u oc Grid-connected current i oa ，i ob ，i oc Bridge arm side inductive current i La ，i Lb ，i Lc Grid voltage u ga ，u gb ，u gc Respectively carrying out single synchronous rotation coordinate transformation to obtain grid-connected voltage dq component U od ，U oq Grid-connected current dq component I od ，I oq Bridge arm side inductor current dq component I Ld ，I Lq Grid voltage dq component U gd ，U gq ；
Step 2, obtaining an average active power P and an average reactive power Q by using an active power calculation equation and a reactive power calculation equation, wherein the active power calculation equation and the reactive power calculation equation are respectively as follows:
P＝1.5(U oq I oq +U od I od )
Q＝1.5(U od I oq -U oq I od )
step 3, according to the average active power P obtained in the step 2 and an active power instruction P given by the new energy power generation unit 0 Obtaining an angular frequency omega of self-synchronization control through a power angle control equation, wherein the expression of the power angle control equation is as follows:
wherein, ω is 0 Generating sheet for new energyMeta given active power instruction P 0 The method comprises the following steps that (1) m is a power angle control droop coefficient, J is the virtual rotational inertia of a simulated synchronous generator set, and s is a Laplace operator;
carrying out phase angle synchronous control at the voltage drop ending moment, and meanwhile, integrating the angular frequency omega of the self-synchronous control to obtain an output phase angle theta of the self-synchronous control; the phase angle synchronization control of the voltage drop ending time is the compensation of the output phase difference delta theta, and delta theta = theta g0 -θ 0 Wherein theta g0 For the output phase angle, theta, of the network voltage at the end of the voltage sag 0 For the output phase angle of the self-synchronization control at the voltage drop ending time, the expression of the output phase angle θ of the self-synchronization control is as follows:
step 4, according to the average reactive power Q obtained in the step 2 and a reactive power instruction Q given by the new energy power generation unit 0 Obtaining a self-synchronous control terminal voltage amplitude instruction E through a reactive power control equation * And then according to the self-synchronous control output phase angle theta and the terminal voltage amplitude instruction E obtained in the step 3 * Obtaining self-synchronous control three-phase terminal voltage instruction through instruction synthesis equation
The expressions of the reactive power control equation and the instruction synthesis equation are respectively as follows:
E * ＝U 0 +n(Q 0 -Q)
wherein, U 0 Giving a reactive power instruction Q for a new energy power generation unit 0 The rated voltage of the transformer, n is a reactive-voltage droop coefficient;
step 5, according to the three-phase terminal voltage instruction obtained in the step 4
And the grid-connected voltage u obtained in the step 1 oa ，u ob ，u oc Obtaining a current command signal by a virtual impedance control equation
The expression of the virtual impedance control equation is as follows:
wherein R is v Is a virtual resistance, L v Is a virtual inductor;
for current command signal
Performing single synchronous rotation coordinate transformation to obtain a current command signal dq component
Step (ii) of6, according to the grid voltage dq component U obtained in the step 1 gd ，U gq Obtaining the grid voltage amplitude U through a grid voltage amplitude calculation equation g According to the obtained voltage amplitude U of the power grid g With a given grid voltage amplitude command U ref Determining the voltage drop depth D of the grid-connected point through a voltage drop calculation equation;
the expressions of the power grid voltage amplitude calculation equation and the voltage drop calculation equation are respectively as follows:
step 7, obtaining a q-axis instruction of a current loop when the voltage of the power grid drops according to a reactive compensation control equation in the low voltage ride through standard
Obtaining a d-axis instruction of a current loop when the voltage of a power grid drops through a limiting control equation of the current stress of a power device
The reactive compensation control equation and the limiting control equation of the current stress of the power device are respectively as follows:
wherein, K m Is a reactive compensation coefficient, I N Generating list for new energyThe nominal current amplitude of the element;
step 8, according to the d-axis instruction of the current loop when the grid voltage drops, obtained in the step 7
And a q-axis instruction of a current loop when the voltage of a power grid drops
Obtaining an active power instruction under the fault through a fault power instruction calculation equation
And reactive power command
The fault power command calculation equation is as follows:
step 9, according to the grid-connected point voltage drop depth D obtained in the step 6, obtaining a voltage instruction under the fault through a fault voltage instruction calculation equation
The fault voltage command calculation equation is as follows:
step 10, performing power instruction switching and amplitude synchronous control according to the grid-connected point voltage drop depth D obtained in the step 6, specifically, setting a power switching instructionIs P ref The reactive power switching command is Q ref The voltage switching command is U ref ：
(1) In the stable operation stage, D is more than or equal to 0.9 ref ＝P 0 ，Q ref ＝Q 0 ，U ref ＝U 0 ；
(2) In the voltage drop stage of the power grid, D is less than 0.9,
(3) Grid voltage recovery phase, P ref ＝P 0 ，Q ref ＝Q 0 ，
Step 11, according to the dq component of the current command signal obtained in step 5
And the bridge arm side induction current dq component I obtained in the step 1 Ld ，I Lq Obtaining the control signal U by a current control equation d ，U q The current governing equation is:
wherein, K pi As a current loop proportional control coefficient, K ii Is a current loop integral control coefficient;
the obtained control signal U d ，U q Control for obtaining new energy power generation unit through single synchronous rotation coordinate inverse transformationSignal U a ，U b ，U c Then according to the control signal U a ，U b ，U c And generating PWM control signals for the three-phase full-bridge inverter circuit.
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| CN105978042A (en) * | 2016-06-14 | 2016-09-28 | 东南大学 | Fault protection and ride-through control system and method for virtual synchronous machine |
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| CN114865711A (en) * | 2022-04-01 | 2022-08-05 | 国网湖北省电力有限公司电力科学研究院 | Dual-mode switching control method and system for new energy grid-connected inverter |
| CN115021317A (en) * | 2022-06-24 | 2022-09-06 | 合肥工业大学 | Low voltage ride through control method for new energy self-synchronizing grid-connected inverter |
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| CN105978042A (en) * | 2016-06-14 | 2016-09-28 | 东南大学 | Fault protection and ride-through control system and method for virtual synchronous machine |
| US20200335978A1 (en) * | 2019-04-16 | 2020-10-22 | Xi'an University Of Technology | Adaptive Control Method for Output Feedback of Virtual Synchronous Generator |
| CN114865711A (en) * | 2022-04-01 | 2022-08-05 | 国网湖北省电力有限公司电力科学研究院 | Dual-mode switching control method and system for new energy grid-connected inverter |
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