A kind of control method for being used for Three-Phase PWM Rectifier under unbalanced source voltage
Technical field
The invention belongs to power electronics control field, is related to a kind of control method of PWM rectifier, and especially one kind is used for
The control method of Three-Phase PWM Rectifier under unbalanced source voltage.
Background technology
With expanding economy, the increase of various electrical equipments, user proposes higher requirement to power network, then corresponding
Power network higher requirement also is proposed to the power-supply device of user.Half control diode rectification before, it is gradually whole by PWM
Stream device is substituted, and PWM rectifier can realize the sineization of current on line side, unity power factor, almost not any to power network
Pollution.
Three-Phase PWM Rectifier is in the case of three-phase power grid voltage is unbalanced, it may appear that the situation of various irregular operatings,
Fluctuation (this is also the substantive reason that current distortion rate becomes big) be present in three-phase current unbalance, busbar voltage.Some high-power
Occasion, switching frequency is relatively low, bandwidth is not high, also result in during imbalance of three-phase voltage bus can not voltage stabilizing, the feelings of overvoltage occur
Condition occurs.
In recent years, in the case of many scholars are to three-phase power grid voltage imbalance, the stabilization of PWM rectifier, high-performance operation
Studied, it is proposed that many methods.But many modes are summarized, all it is the angle in Automatic Control Theory, passes through
Improving the control characteristic of electric current loop improves performance.However, the switching frequency of an equipment is limited after all, bandwidth is limited, especially
At the relatively low scene of high power switch frequency, almost without what effect.
The content of the invention
The purpose of the present invention is in the stabilization of PWM rectifier, the control process of high-performance operation, is overcome because of facility switching
The limited adverse effect brought of frequency.The present invention has jumped out the thinking of conventional, propose it is a kind of it is not bandwidth limited, still may be used
To realize stable, high-performance operation method in the case of maximum three-phase power grid voltage degree of unbalancedness.
The solution of the present invention is as follows:
This is used for the control method of Three-Phase PWM Rectifier under unbalanced source voltage, including:
Detect in networking electric current because three-phase negative/positive electric current caused by three-phase power grid voltage imbalance;
Three-phase negative/positive electric current is controlled using the internal model principle of PR resonant controllers;The output of PR resonant controllers with
The active voltage stabilizing instruction superposition of three-phase gives as the instruction of electric current loop;
The electric current loop carries out closed loop to three pole reactor electric current, then by pi regulator, finally electric current loop is exported into
Row SPWM modulates to obtain driving pulse, drives the work of inverter.
Based on above scheme, the present invention preferably specific implementation process and optimization content is as follows:
The acquisition of the three-phase negative/positive electric current have passed through procedure below:
To three-phase networking current feedback, DQ axis informations are obtained first with negative-phase sequence ABC/DQ coordinate system transformations, by low pass
Filtering, DC component is obtained, recycle negative-phase sequence DQ/ABC coordinate system transformations to obtain three-phase negative/positive current component.
The LPF is realized using moving average filter.
The PR resonant controllers realize that three-phase negative/positive electric current to 0 control, i.e., first does the three-phase negative/positive electric current with 0
Difference, it is then fed into PR resonant controllers.
The acquisition of the active voltage stabilizing instruction of three-phase have passed through procedure below:
DC bus-bar voltage is detected, is made the difference with given busbar voltage, carries out no error following using pi regulator, and be superimposed one
Fixed voltage feed-forward control value, output are used as D axis components, and Q axis components are entered as 0, carry out positive phase sequence DQ/ABC coordinate systems
Conversion, obtain the active voltage stabilizing instruction of three-phase.
For the difference expression of pi regulator:
U (k)=KP*e(k)+KI* e (k)+u (k-1), wherein KPTake 2.5;KITake 0.3.
In each controlling cycle, soft-lock phase is carried out to the phase angle of three-phase power grid voltage first, for instantaneous power transform and
Current transformer controls.
The invention has the advantages that:
The present invention superposition instruction of de-regulation negative phase-sequence, avoids biography by the detection and control to networking electric current negative-sequence current
System control thinking continuous improvement electric current loop open-loop gain (and because bandwidth limits, especially high-power, open-loop gain lifting has
Limit) limitation, unbalanced power supply degree can be better adapted to, can adapt to worst degree of unbalancedness, have well application
Prospect.
Brief description of the drawings
Fig. 1 is a kind of control method for being used for Three-Phase PWM Rectifier under unbalanced source voltage that the present invention is introduced
Main circuit topological structure schematic diagram.
Fig. 2 is a kind of control method for being used for Three-Phase PWM Rectifier under unbalanced source voltage that the present invention is introduced
Control block diagram.
Embodiment
With reference to embodiment and accompanying drawing, the present invention is described in more detail:
It is as shown in Figure 1 PWM rectifier topological structure.3-phase power converter is three-phase voltage-type inverter, passes through three-phase electricity
Anti- to be attached with power network, there is storage capacitor in dc bus, realize voltage stabilizing by the switch motion of current transformer, reach specific work
Rate factor and current sinusoidal.
As shown in Fig. 2 this is used for the control method of Three-Phase PWM Rectifier under unbalanced source voltage, step is implemented
It is as follows:
A. traditional soft-lock phase algorithm is utilized, horizontal lock is entered to the phase angle of line voltage, for instantaneous power transform, is used for
Current transformer controls.
B. DC bus-bar voltage is detected, is made the difference with given busbar voltage, carries out no error following using pi regulator, and be superimposed
Fixed voltage feed-forward control value, for suppressing rush of current when starting.
Pi regulator can realize the indifference control to direct current;The difference expression of pi regulator is as follows:
U (k)=KP*e(k)+KI*e(k)+u(k-1)
Wherein KPFor 2.5;KI=0.3;
For dc-link capacitance, too quick discharge and recharge should not be carried out, so the response speed of busbar voltage ring needs
Reduce, typically the rank in several ms, will necessarily so bring operation starting PWM reorganizers the problem of dash current to be present,
So the present invention goes solve the problems, such as dash current by the way of one line voltage of superposition fixes feedforward value.
Component of the c.b output as D axles, Q axis components are entered as 0, carry out the conversion of positive phase sequence DQ/ABC coordinate systems, obtain
To three-phase active command Iap, Ibp, Icp.
Transformation for mula is as follows:
Wherein,
Wherein,
D., the extraction of negative phase-sequence reactive current active to three-phase networking electric current progress negative phase-sequence.Specifically:First with negative-phase sequence ABC/
DQ coordinate system transformations obtain DQ axis informations, are filtered using moving average filter, obtain DC component, recycle negative-phase sequence
DQ/ABC coordinate system transformations obtain three-phase negative/positive current component.
Transformation for mula such as c, extraction negative phase-sequence composition according to negative phase-sequence angle, it is necessary to carry out coordinate transform.
The extraction of DC component is carried out using moving average filter, moving average filter has fast response time, nothing
The advantages of overshoot, its difference expression are:
Wherein N is that sample frequency is counted with respect to corresponding to fundamental wave, and x (i) is the instantaneous value of D axles or Q axles.
Control information obtained by e.d, makes the difference with 0, carries out PR adjuster controls, obtains output information.
PR resonators are based on internal model principle, and integration is exactly the internal model of direct current.PR adjusters can realize well exchange into
The no error following of part.It is controlled here using PR resonators, realizes negative-sequence current to 0 control, the difference of PR adjusters
Expression formula is as follows;
Wherein:Molecule:a0=0.00004893758;a1=0;a2=0.00004893758;
Denominator:b0=1;b1=-1.988495047;b2=0.988000433;
Information obtained by f.e gives with information superposition obtained by c as the instruction of g electric current loops.
Information obtained by g.f makes the difference with three pole reactor electric current, is controlled using pi regulator, obtains modulating wave.It is limited to
System bandwidth, single P adjusters, PR adjusters, pi regulator can not all realize the tracing control of complete indifference, and comparatively PI is adjusted
Save device and be better than other two, therefore present invention selection pi regulator to the control effect of fundamental wave.The difference expression of pi regulator
And parameter is as follows:
U (k)=KP*e(k)+KI*e(k)+u(k-1)
Wherein KPFor 0.015;KI=0.0004;
Gained modulating wave obtains PWM driving pulse using SPWM modulation systems, drives the work of inverter.Realize voltage stabilizing,
Unity power factor, current sinusoidal.
New approaches mentioned by the present invention, using the mode for controlling adjust automatically negative phase-sequence to instruct, PWM changes can be substantially improved
Flow adaptability of the device to unbalanced power grid.With very big application prospect.