CN107623338A - The independent excitation control method of three-phase four-arm virtual synchronous generator - Google Patents
The independent excitation control method of three-phase four-arm virtual synchronous generator Download PDFInfo
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Abstract
The present invention relates to a kind of independent excitation control method of three-phase four-arm virtual synchronous generator, belong to power electronics transformation of electrical energy control technology field.This method comprises the following steps：（1）Active environmental protection is held work(phase angle and is uniformly controlled, and active torque and torque difference signal is calculated in systematic sampling, and system angular frequency and phase angle are obtained through inertia control；（2）Idle ring changes virtual excitation mode, and independent sample respectively obtains each phase excitation coefficient per phase voltage amplitude, reactive power after idle link；（3）Unified phase angle signal, frequency signal and each phase excitation coefficient are passed through into virtual synchronous generator modulating wave formula, calculates and generates each phase modulation wave signal；（4）Three-phase modulations ripple signal generates triple-frequency harmonics by calculating, and by each phase modulation wave signal of third-harmonic zero-sequence voltage to modulate first three bridge arm, while triple-frequency harmonics is individually modulating four bridge legs.The virtual synchronous generator of the invention that effectively solves is unbalanced load powerup issue when off-network works.
Description
Technical field
The present invention relates to a kind of independent excitation control method of three-phase four-arm virtual synchronous generator, belong to power electronics
Transformation of electrical energy control technology field.
Background technology
With the sustained and rapid development of social economy, after China's energy development faces the increasing of energy supply and demand breach, oil
Standby inadequate resource, the problems such as environmental pollution is serious.For reply energy crisis and problem of environmental pollution, sustainable development path is walked,
The utilization of the renewable and clean energy resources such as wind energy, solar energy turn into the strategic choice of most countries in the world, global energy
Structure is undergoing great reform.It is contemplated that proportion of the generated energy of following regenerative resource in global generating total amount
It can improve constantly, renewable and clean energy resource will play the part of vital role in human social development.
The electric energy that renewable and clean energy resource is sent generally is connected by power electronic equipments such as inverters with power network, these electricity
Power electronic equipment uses Digital Circuit Control mostly, and when being disturbed, fast response time is intrinsic without typical power system
Inertia, the characteristic such as damping, also do not possess and participate in power system frequency modulation, the ability of pressure regulation.When the distributed power source of access power network
Capacity it is smaller when, the influence to power system is smaller, power network can be relied on to provide stable Voltage Reference and frequency reference.But
Under high permeability power network or under micro-capacitance sensor, the capacity of the distributed power source higher ratio of occupation ratio in power system total capacity
Example, the characteristic of power system there occurs huge change, the rotary inertia of whole power system and the relative reduction of damping action,
Cause the increase of power grid frequency modulation pressure regulation difficulty, or even influence the stable operation of power system.
In order to ensure the stabilization of high permeability power system frequency and voltage, inverter is allowed to simulate the outer spy of synchronous generator
Property is a kind of solution route received significant attention.Based on above-mentioned thought, there is the concept that scholar proposes virtual synchronous generator,
One of which typical virtual synchronous generator control block diagram is as shown in Figure 3.
Virtual synchronous generator, which generally has, to be incorporated into the power networks and two kinds of mode of operations of off-grid operation, needs to have during off-grid operation
The standby ability with unbalanced load.The control method of existing virtual synchronous generator can be made in off-grid operation band unbalanced load
Into the imbalance of three-phase output voltage, the quality of power supply under unbalanced load can not be ensured.
The content of the invention
In view of the above-mentioned problems, the present invention proposes a kind of independent excitation controlling party of three-phase four-arm virtual synchronous generator
Method, it is unbalanced load powerup issue when off-network works effectively to solve virtual synchronous generator.
The present invention adopts the following technical scheme that to solve its technical problem：
A kind of independent excitation control method of three-phase four-arm virtual synchronous generator, comprises the following steps：
(1) active environmental protection is held work(phase angle and is uniformly controlled, sampling input active power, active power divided by system frequency,
Active torque is obtained, system angle difference on the frequency obtains torque difference signal through sagging link；Active dtc signal passes through with torque difference signal
Inertia control obtains active ring output system angular frequency and phase angle；
(2) idle ring changes virtual excitation mode, and independent sample is per phase voltage amplitude, reactive power, each phase voltage amplitude
After sagging link, synthesized with reactive power, each phase excitation coefficient is respectively obtained after idle inertia coeffeicent link；
(3) unified phase angle signal, frequency signal obtained by active ring are passed through into virtual synchronous with each phase excitation coefficient of idle ring
Generator modulating wave calculation formula, calculate and generate each phase modulation wave signal；
(4) three-phase modulations ripple signal generates triple-frequency harmonics by calculating, and each phase modulation wave signal of third-harmonic zero-sequence voltage is used
To modulate first three bridge arm, while triple-frequency harmonics is individually modulating four bridge legs.
It is specific as follows that the method that work(phase angle is uniformly controlled is held in step (1) the active environmental protection：
Keep three-phase to be uniformly controlled, sample the total active power of output of virtual synchronous generator three-phase as active phase square ring
The value of feedback on road, the angle values of system operation are generated with this, then this angle values is symmetrically added and subtracted 120 °, form symmetrical three-phase phase
Angle value.
Step (2) the idle ring changes virtual excitation mode, and independent sample is per phase voltage amplitude, the specific mistake of reactive power
Journey is as follows：
Each phase voltage is individually regulated and controled, each road magnitude of voltage is sampled, after its square value is filtered out into second harmonic with trapper
Evolution feeds back as the voltage magnitude of loop, while each phase reactive power of sampling three-phase, as the reactive power in this phase loop
Feedback.
Beneficial effects of the present invention are as follows：
1st, method of the invention, the full decoupled independence of three-phase is different from into single-phase control, it only will in idle excitation link
Three-phase is independently separately controlled, and active phase angle link is uniformly controlled for three-phase, is so not only controlled containing independent control but also containing unified
The mode of system is the substantive characteristics of this independent excitation control technology.
2nd, the present invention proposes a kind of decoupling control method of three-phase independent excitation, by individually being adjusted to each phase voltage
Control so that the reactive power/voltage control between three-phase is full decoupled, so as to significantly more efficient reply load asymmetry problem.
3rd, the decoupling control method of three-phase independent excitation, although reactive power/voltage control is independent, active Phase angle control is protected
Hold and be uniformly controlled, form symmetrical three-phase phase angle, such uniformity control, ensure that the symmetrical of three-phase system three-phase phase angle,
It ensure that the symmetry of virtual synchronous generator three-phase operation.
4th, the decoupling control method of three-phase independent excitation of the present invention uses digital control realization, and algorithm is simple and convenient, without
Increase any other hardware cost, you can improve virtual synchronous generator band unbalanced load ability.
Brief description of the drawings
Fig. 1 is three-phase four-arm virtual synchronous generator topological diagram.
Fig. 2 is three-phase four-arm virtual synchronous generator large-signal model figure.
Fig. 3 is the three-phase four-arm virtual synchronous generator control block diagram of unified excitation.
Fig. 4 is the idle ring control block diagram of unified excitation.
Fig. 5 is the three-phase four-arm virtual synchronous generator control block diagram of independent excitation.
Embodiment
The invention is described in further details below in conjunction with the accompanying drawings.
To cause virtual synchronous generator for unbalanced load power supply when, remain to output balance three-phase voltage, need pair
Main circuit topology takes corrective measure, generally has following two measures available：
1) DC side supply voltage midpoint is connected with load neutral point.In the band unbalanced load of virtual synchronous generator
When, to ensure the balance of output voltage, three pole reactor electric current and can not be necessarily 0, by DC side supply voltage midpoint with it is negative
Carry neutral point to be connected, can circulate out-of-balance current on line, and split capacitor formula inverter topology is thus derivation.
2) be not connected to DC side supply voltage midpoint and load neutral point, and inverter topology newly add one it is controllable
Electric current item.Increase four bridge legs in the bridge arm virtual synchronous generator topology of three-phase three, by load neutral point and four bridge legs
Point is connected, and forms three-phase four-arm topology.One bridge arm of increase can directly control neutral point voltage, and the injustice that can circulate
Weigh electric current, which increases one degree of freedom so that and three-phase four-arm virtual synchronous generator can export the voltage of three-phase independence,
The balance of output voltage can be maintained under the conditions of unbalanced load.
1. the control of three-phase four-arm virtual synchronous generator
The topological diagram of three-phase four-arm virtual synchronous generator is as shown in Figure 1.Its four bridge legs midpoint n passes through inductance LNWith
Load neutral point N is connected, iNFor neutral current, inductance LNFor suppressing neutral current switching harmonics, inductance value is smaller, ignores
Its equivalent resistance.ia、ib、icFor three pole reactor electric current, ua、ub、ucFor three-phase output voltage, it is assumed that virtual synchronous generator LC is filtered
Ripple device is identical per phase parameter, filter inductance value L, ignores inductance equivalent resistance, filtering capacitance C.The upper, lower tube of inverter bridge
The Pulse Width Control upper tube for cutting gained, its anti-phase control down tube are handed over for complementary conducting, modulated signal and triangular wave.
According to average modeling, it is big under three-phase static coordinate system that three-phase four-arm virtual synchronous generator can be obtained
Signal model, as shown in Figure 2.
ioa、iob、iocRespectively threephase load electric current, the zero-sequence component of threephase load electric current is denoted as ioz, three-phase is exported
The zero-sequence component of voltage is denoted as uzIf pass through suitable control so that the zero-sequence component of load current returns to mother through four bridge legs
On line, only have electric current positive-sequence component to pass through on three-phase filter capacitor, then the zero-sequence component u of three-phase output voltagezFor 0, so as to
Can be by first three bridge arm and four bridge legs independent control of four bridge legs virtual synchronous generator.Three-phase four-arm virtual synchronous generator
Three single-phase virtual synchronous generators can be equivalent to, therefore it remains to the three-phase electricity of output balance under the conditions of laod unbalance
Pressure.
The control method of three-phase four-leg inverter includes symmetrical component method, hysteretic loop current control, SVPWM (space vectors
Pulsewidth modulation) control and PWM (pulsewidth modulation) controls etc..Three-phase output voltage is resolved into positive sequence, negative phase-sequence, zero by symmetrical component method
Order components, design negative phase-sequence, zero sequence controller are controlled to the negative phase-sequence and zero-sequence component of output voltage respectively, so as to ensure to export
Voltage remains to keep balance under the conditions of unbalanced load, but this method amount of calculation is huge, and control is complicated；Hysteresis Current control
System calculates the Error Absolute Value of three pole reactor electric current and current reference value respectively, comes on the basis of that phase maximum by Error Absolute Value
The state of four bridge arm switching tubes is determined, this method needs real-time comparison error signal, adds the complexity of computing；
SVPWM control method is synthesized and floating voltage reference vector with one group of limited switching vector selector so that the three-phase voltage of output
Can floating voltage reference, and the amplitude of voltage reference vector is correspondingly changed according to the situation of load and input voltage, so as to
Reach the purpose of pressure regulation, although control is flexible, DC voltage utilization rate is high, and THD (total harmonic distortion factor) is low, efficiency high, fortune
It is sufficiently complex.
Assuming that tri- bridge arms of four bridge legs virtual synchronous generator abc are modulated using SPWM, four bridge legs use is fixed 0.5 and accounted for
Sky works than mode, then it is up to u that it, which exports phase voltage amplitude,dc/ 2, DC voltage utilization rate is relatively low.
, can be by changing modulating wave in order to improve DC voltage utilization rate so that in the case of output voltage is constant,
Abc three-phase bridge arms mid-point voltage reduces.Abc three-phase bridge arm mid-point voltages can be changed by changing four bridge legs mid-point voltage.
If the modulated signal of four bridge arms is sa、sb、sc、sn, m is modulation ratio, and k is triple-frequency harmonics coefficient, in practical application
In, to take into account influence of the triple-frequency harmonics coefficient to harmonic wave of output voltage and DC voltage utilization rate, 0.15≤k≤0.2 is generally taken,
The amplitude of modulating wave is less than the amplitude of triangular wave, is not in ovennodulation phenomenon.
When taking m=1, during k=1/6, with ω0T is that independent variable carries out derivation to a phase bridge arm mid-point voltages expression formula, and is allowed
Derivative is 0, can obtain ω0T=60 °, substituted into a phase bridge arm mid-point voltage expression formulas, can obtain its maximum isTogether
Sample also can be in the hope of the maximum of b, c phase bridge arm mid-point voltageIllustrate DC bus-bar voltage from udcIt is reduced toThe requirement of virtual synchronous generator operation can still be met.
Ignore pressure drop on inductance, the output voltage of virtual synchronous generator can be obtained, it was found from above-mentioned analysis, in the bridge of three-phase four
Inject triple-frequency harmonics in the modulated signal of the abc three-phases of the virtual synchronous generator of arm, and be used as the 4th bridge by the use of this triple-frequency harmonics
The modulating wave of arm, abc three-phases can be not only independently controlled, it is exported three-phase equilibrium voltage, but also will be straight
Stream voltage utilization is brought up to from 1/2Improve 15%.
Using the complete control block diagram of three-phase four-arm virtual synchronous generator such as Fig. 3 institutes of third-harmonic zero-sequence voltage modulator approach
Show, active ring, idle ring control loop are consistent with three bridge arm virtual synchronous generators in figure；ea、eb、ecIt is that virtual synchronous generates electricity
The output of the power ring of the original control method of machine, it is sinusoidal quantity, is the modulating wave of original control method, after it injects triple-frequency harmonics
Modulating wave as first three bridge arm of four bridge legs virtual synchronous generator；The generation of triple-frequency harmonics is realized using digital method, is calculated
Method is simple, repeats no more.
2. the independent excitation control of three-phase four-arm virtual synchronous generator
Three-phase modulations ripple e in the original control of virtual synchronous generatora、eb、ecAmplitude it is related to the output of idle ring,
Virtual excitation i.e. with virtual synchronous generator has close ties, will analyze the excitation con-trol of virtual synchronous generator below.
Fig. 4 is virtual synchronous generator reactive ring control block diagram, and its virtual excitation mode is unified excitation.
It is hereby achieved that three-phase modulations ripple ea、eb、ecExpression formula.Understand that virtual synchronous generator is uniformly encouraged by expression formula
Magnetic control method, it is not that each phase voltage is individually regulated and controled.The modulating wave of a phases is not only relevant with a phase output voltages, also with b,
C phase output voltages are relevant, and b, c phase are similarly.Due to the unique control loop of virtual synchronous generator, three-phase four-arm it is virtual same
Still there is coupling between step generator three-phase, using the three-phase four-arm virtual synchronous generator of unified excitation con-trol to injustice
During weighing apparatus load supplying, the three-phase voltage degree of balance of output has the space for continuing to improve.
For more effective reply unbalanced load, the degree of balance of output voltage is improved, considers to change virtual excitation mode, proposes
The control mode of three-phase independent excitation, each phase voltage is individually regulated and controled, the reactive power feedback in loop is also this phase
Reactive power so that full decoupled between three-phase four-arm virtual synchronous generator, control block diagram is as shown in Figure 5.
V in control block diagrama、Vb、VcThe respectively amplitude of a, b, c three-phase output voltage, by by ua、ub、ucSquare it
Obtained after filtering out second harmonic with trapper again afterwards；Qa、Qb、QcThe respectively reactive power of a, b, c three-phase, it is only electric with this phase
Current voltage is relevant.
Above analysis shows, be between the three-phase four-arm virtual synchronous generator three-phase of independent excitation it is full decoupled,
In the case of laod unbalance, three-phase equilibrium voltage can be exported.Three-phase independent excitation is idle loop parameter and unified excitation control
The parameter of system is identical.
Described above is embodiments of the present invention, and its description is more specific and detailed, but can not be therefore interpreted as
Limitation of the scope of the invention.It should be pointed out that for the person of ordinary skill of the art, structure of the present invention is not being departed from
On the premise of think of, various modifications and improvements can be made, these belong to protection scope of the present invention.The specific guarantor of the present invention
Shield scope is determined by the appended claims.
Claims (3)
1. a kind of independent excitation control method of three-phase four-arm virtual synchronous generator, it is characterised in that comprise the following steps：
（1）Active environmental protection is held work(phase angle and is uniformly controlled, sampling input active power, active power divided by system frequency, obtains
Active torque, system angle difference on the frequency obtain torque difference signal through sagging link；Active dtc signal is with torque difference signal through inertia
Control obtains active ring output system angular frequency and phase angle；
（2）Idle ring changes virtual excitation mode, and independent sample is per phase voltage amplitude, reactive power, under each phase voltage amplitude warp
After tabs section, synthesized with reactive power, each phase excitation coefficient is respectively obtained after idle inertia coeffeicent link；
（3）Unified phase angle signal, frequency signal obtained by active ring are generated electricity with each phase excitation coefficient of idle ring by virtual synchronous
Machine modulating wave calculation formula, calculate and generate each phase modulation wave signal；
（4）Three-phase modulations ripple signal generates triple-frequency harmonics by calculating, by each phase modulation wave signal of third-harmonic zero-sequence voltage adjusting
Make first three bridge arm, while triple-frequency harmonics is individually modulating four bridge legs.
2. the independent excitation control method of the three-phase four-arm virtual synchronous generator according to claim 1, its feature exist
In step（1）It is specific as follows that the method that work(phase angle is uniformly controlled is held in the active environmental protection：
Keep three-phase to be uniformly controlled, sample the total active power of output of virtual synchronous generator three-phase as active phase angle loop
Value of feedback, the angle values of system operation are generated with this, then this angle values is symmetrically added and subtracted 120 °, form symmetrical three-phase phase angle
Value.
3. the independent excitation control method of three-phase four-arm virtual synchronous generator according to claim 1, its feature exist
In step（2）The idle ring changes virtual excitation mode, and the every phase voltage amplitude of independent sample, reactive power detailed process are such as
Under：
Each phase voltage is individually regulated and controled, samples each road magnitude of voltage, evolution after its square value is filtered out into second harmonic with trapper
Voltage magnitude as loop feeds back, while each phase reactive power of sampling three-phase, as the reactive power feedback in this phase loop.
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| CN108493966A (en) * | 2018-04-24 | 2018-09-04 | 东北大学 | A kind of micro-capacitance sensor uncompensated load control method and device based on virtual synchronous technology |
| CN109713928A (en) * | 2018-12-30 | 2019-05-03 | 东北电力大学 | Four bridge legs dual output inverter SVPWM method under unbalanced load |
| CN110048582A (en) * | 2019-05-23 | 2019-07-23 | 华北电力大学 | A kind of MMC submodule capacitor voltage fluctuation suppressing method of Harmonic coupling injection |
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| CN110048582A (en) * | 2019-05-23 | 2019-07-23 | 华北电力大学 | A kind of MMC submodule capacitor voltage fluctuation suppressing method of Harmonic coupling injection |
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