CN104638634B - Direct current micro-grid oscillation suppression method based on band-pass filter in master-slave mode - Google Patents

Abstract

The invention relates to a direct current micro-grid oscillation suppression method based on a band-pass filter in a master-slave mode. The direct current bus voltage is controlled by a main power supply, a voltage and current dual-loop control mode is adopted, the method aims at two kinds of oscillation modes possibly occurring in a direct current micro-grid, a control system of the main power supply is improved, a feedback channel using output voltage and output current as the feedback quantity is newly added, two groups of corresponding oscillation suppression links are formed, and in a high-frequency component oscillation suppression link, the output voltage of a feedback quantity direct current bus is used as the compensation quantity to be added to the reference voltage of the main power supply control system after passing through a high-frequency band-pass filter; in a low-frequency component oscillation suppression link, the output current of the feedback quantity main power supply is used as the compensation quantity to be added onto the reference voltage of the main power supply control system after passing through a low-frequency band-pass filter. The direct current micro-grid oscillation suppression method has the advantages that the stable operation of the system can be ensured, the realization is simple, and the reliability is higher.

Description

Direct-current grid oscillation suppression method based on band filter under master slave mode

Technical field

The present invention is a kind of control method of energy suppression system Unstable oscillation in direct-current grid, belongs to distributed power generation micro- Network technology field.

Background technology

With user, the attention rate of power supply reliability and the quality of power supply is improved constantly and the various shape such as solar energy, wind energy The regenerative resource of formula utilizes in a large number, and the effective way that micro-capacitance sensor accesses electrical network as distributed power source has obtained Chinese scholars Extensive concern.Micro-capacitance sensor generally refers to connect multiple distributed power sources, energy storage device and load by power electronic equipment The small grids form got up, can be incorporated into the power networks, and traditional bulk power grid positive energy exchange, but can independent operating, become an energy The isolated blob of stable operation.

For exchange micro-capacitance sensor, direct-current grid has a lot of marked featurees.First, most distributed electrical Source, such as photovoltaic cell, wind-driven generator etc., are essentially all output unidirectional current (or there is the intermediate link of direct current)；And it is many Many household electrical appliance and office equipment inherently need DC source ability normal work.If they are connected to DC micro-electric In net, conversion link can be reduced, improve energy utilization rate.Meanwhile, do not have in direct-current grid the stationary problem of equipment room with And reactive power flowing is so that the coordination control between current transformer is more easy.

It mostly is distributed AC servo system currently for the oscillation suppression method in direct-current grid, that is, need institute in improvement system There is the control loop of parallel power electronic device.But when the structure of system changes, such as put into new power supply or cut Except DC load, these distributed damping controller parameters are required for accordingly being adjusted, otherwise may impact system just Often run.This also brings difficulty to real world applications.

Content of the invention

It is an object of the invention to overcoming the above-mentioned deficiency of prior art, providing and under a kind of master slave mode, being based on bandpass filtering The direct-current grid oscillation suppression method of device.Technical scheme is as follows:

Under a kind of master slave mode, the direct-current grid oscillation suppression method based on band filter, controls direct current by main power source Busbar voltage, using voltage x current double -loop control mode it is characterised in that the method is directed in direct-current grid is likely to occur Two kinds of oscillation modes, by improving the control system of main power source, increase newly with output voltage v_dcWith output current i_oFor feedback quantity Feedback channel, forms two groups of corresponding vibration suppression links, and is added to the reference voltage of main power source control system as compensation dosage v_dcrefOn, the higher-order of oscillation and low-frequency oscillation that two groups of vibration suppression links can be likely to occur in suppression system respectively, wherein,

High fdrequency components vibration suppression link is by feedback quantity DC bus-bar voltage v_dcConduct after high freguency bandpass filter Compensation dosage is added on the reference voltage of main power source control system, thus the higher-order of oscillation that suppression is likely to occur, the transmission being adopted Function is:

$g_{\mathrm{com}1}\left(s\right)=k_1\frac{2{\mathrm{\ξ}}_1{\mathrm{\ω}}_{1}s}{s^2+2{\mathrm{\ξ}}_1{\mathrm{\ω}}_{1}s+{{\mathrm{\ω}}_1}^2}$

Wherein ω₁Take main power source closed loop control transmission function △ v_dc/△v_dcrefResonant frequency；ξ₁For high-frequency band pass filtering The bandwidth of device, value is 1；k₁It is used for coordinating the relation of system damping and system stability as proportional gain, according to system Characteristic root scattergram chooses more excellent parameter, span 0.3-0.7；

Low frequency component vibration suppression link is by output current i of feedback quantity main power source_oAfter low frequency bandpass filter It is added on the reference voltage of main power source control system as compensation dosage, thus the low-frequency oscillation that suppression is likely to occur, adopted Transmission function is:

$g_{\mathrm{com}2}\left(s\right)=k_2\frac{2{\mathrm{\ξ}}_2{\mathrm{\ω}}_{2}s}{s^2+2{\mathrm{\ξ}}_2{\mathrm{\ω}}_{2}s+{{\mathrm{\ω}}_2}^2}$

Wherein ω₂Take the resonant frequency of constant power load entrance side lc wave filter；ξ₂For the bandwidth of low frequency bandpass filter, Value is 0.2；k₂Characteristic root scattergram according to system chooses more excellent parameter, span 0.3-0.7.

Preferably, described direct-current grid oscillation suppression method, main power source closed loop control transmission function For:

$\frac{{\mathrm{\δv}}_{\mathrm{dc}}}{{\mathrm{\δv}}_{\mathrm{ref}}}=\frac{(1-d)v_{\mathrm{dc}}{g}_i{g}_v-(\mathrm{sl}+r_l)i_l{g}_i{g}_v}{(\mathrm{sl}+r_l+v_{\mathrm{dc}}{g}_i)(\mathrm{sc}-i_l{g}_i{g}_v)+(1-d+i_l{g}_i)(1-d+v_{\mathrm{dc}}{g}_i{g}_v)}$

Wherein c, l/r_l, d be respectively the electric capacity of voltage regulation of main power source current transformer, filter inductance and equivalent resistance and switching tube Dutycycle, g_i、g_vIt is respectively the transmission function of inner and outer ring pi controller, Bode diagram is drawn by this transmission function, high-frequency band pass filters The ω of device₁Take the frequency corresponding to resonance spikes.

The present invention adopts centralized damping control strategy, using main power source as the damping controller of straight-flow system it is only necessary to Using the local information of main power source, the hardware circuits such as extra sensor need not be increased, without using communication.By improving main electricity The control loop in source, with the voltage x current of primary power outlet side for feeding back signal, introduces additional oscillation suppressor, just can suppress The oscillatory occurences of the different frequency being likely to occur in straight-flow system is it is ensured that the stable operation of system.The method realizes simple, reliability Property is higher.

Brief description

Fig. 1 is DC micro power grid system structure chart under the master slave mode of the present invention；

Fig. 2 is DC micro power grid system characteristic root scattergram of the present invention；

Fig. 3 is main power source closed loop control transmission function △ v of the present invention_dc/△v_dcrefBode diagram；

Fig. 4 is main power source small-signal control block diagram of the present invention；

Fig. 5 is main power source equivalent output impedance z of the present invention_{out_cl}(s) frequency characteristic figure；

Fig. 6 is main power source oscillation suppression method control loop block diagram of the present invention；

Fig. 7 adds oscillation suppressor post-simulation oscillogram for DC micro power grid system of the present invention.

Specific embodiment

Below according to Figure of description, introduce technical scheme in detail.

Under typical master slave mode, the structure of DC micro power grid system is as shown in Figure 1.This direct-current grid is mainly by a master Power supply, several constitute from power supply and DC load, wherein each distributed power source, energy storage etc. are all equivalent to preferable unidirectional current Potential source, DC load is all represented with resistance.With a certain distance from having from load in view of distributed power source in side circuit, this direct current In micro-capacitance sensor from power supply all by one section of connection to dc bus.Dc-dc current transformer in micro-capacitance sensor is opened up using boost type Flutter structure, main power source is voltage x current double -loop control, to maintain DC bus-bar voltage constant, adopts current control from power supply, is Load provides required power.

The stability analyses conclusion based on DC micro power grid system for the present invention.As shown in Fig. 2 can by small-signal analysis , there are two groups of unstable characteristic roots in system, wherein eigenvalue 1 is higher-order of oscillation component, and characteristic root 2 divides for low-frequency oscillation Amount.When eigenvalue 1 or 2 enters z domain unit circle outside, DC micro power grid system Unstable oscillation.

The present invention proposes a kind of direct-current grid oscillation suppression method based on band filter, using main power source as collection The damping controller of Chinese style, using local data acquisition information, improves the control loop of main power source, realizes suppression system vibration Function.Concrete grammar is as follows:

1) capacitance voltage value v of main power source outlet side when starting in each sampling period, is gathered using a/d sample circuit_dc、 Output current value i_oInductor current value i with dc-dc current transformer_l, and the digital quantity after conversion is sent to the control mould of current transformer Block.

2) utilize digital algorithm by capacitance voltage value v_dcObtain Voltage Reference after higher-order of oscillation component filters are processed Compensation component v_com1.This high fdrequency components oscillation suppressor is substantially to be made up of a band filter and proportional compensation device, Its transmission function can be expressed as

$g_{\mathrm{com}1}\left(s\right)=k_1\frac{2{\mathrm{\ξ}}_1{\mathrm{\ω}}_{1}s}{s^2+2{\mathrm{\ξ}}_1{\mathrm{\ω}}_{1}s+{{\mathrm{\ω}}_1}^2}$

Wherein ω₁Take main power source closed loop control transmission function △ v_dc/△v_dcrefResonant frequency；ξ₁For band filter Bandwidth, generally can be with value for 1；k₁It is used for coordinating the relation of system damping and system stability, Ke Yigen as proportional gain Characteristic root scattergram according to system chooses more excellent parameter, generally 0.3-0.7.

Solid line in Fig. 3 is main power source closed loop control transmission function △ v_dc/△v_dcrefBode diagram, its expression formula is as follows

$\frac{{\mathrm{\δv}}_{\mathrm{dc}}}{{\mathrm{\δv}}_{\mathrm{ref}}}=\frac{(1-d)v_{\mathrm{dc}}{g}_i{g}_v-(\mathrm{sl}+r_l)i_l{g}_i{g}_v}{(\mathrm{sl}+r_l+v_{\mathrm{dc}}{g}_i)(\mathrm{sc}-i_l{g}_i{g}_v)+(1-d+i_l{g}_i)(1-d+v_{\mathrm{dc}}{g}_i{g}_v)}$

Wherein c, l/r_l, d be respectively the electric capacity of voltage regulation of main power source current transformer, filter inductance and equivalent resistance and switching tube Dutycycle, g_i、g_vIt is respectively the transmission function of inner and outer ring pi controller.In Fig. 3, the resonance spikes of solid line are to produce unstability characteristic root The ω of 1 basic reason, therefore band filter₁Need to take the frequency corresponding to resonance spikes.The dotted line of Fig. 3 represents and increases surely Frequency characteristic after voltage capacitance c, finds that resonance peak is obviously reduced.When the value of holding capacitor c is constant, high fdrequency components vibration suppression Device puts into operation, and shown in Fig. 3 dotted line, this controller can play and increase capacitance identical effect.

3) utilize digital algorithm by main power source output current i_oObtain voltage after low-frequency oscillation component filters are processed The compensation component v of reference_com2.This low frequency component oscillation suppressor is substantially by a band filter and proportional compensation device structure Become, its transmission function can be expressed as

$g_{\mathrm{com}2}\left(s\right)=k_2\frac{2{\mathrm{\ξ}}_2{\mathrm{\ω}}_{2}s}{s^2+2{\mathrm{\ξ}}_2{\mathrm{\ω}}_{2}s+{{\mathrm{\ω}}_2}^2}$

Wherein ω₂Take the resonant frequency of constant power load entrance side lc wave filter；ξ₂For the bandwidth of band filter, in order to Reduce influencing each other and high freguency bandpass filter between, generally can be with value for 0.2；k₂Determine main electricity under this resonant frequency The size of source equivalent output impedance, can choose more excellent parameter, generally 0.3-0.7 according to the characteristic root scattergram of system.

In order to verify the ability of this oscillation suppressor regulation main power source equiva lent impedance, main power source under small-signal of having derived below Equivalent output impedance method for solving.

Fig. 4 is main power source small-signal control block diagram, and dotted portion is additional low frequency component vibration suppression control loop, can Obtain the equivalent output impedance z of main power source_{out_cl}S () is

$z_{\mathrm{out}\_\mathrm{cl}}\left(s\right)=-\frac{{\mathrm{\δv}}_{\mathrm{dc}}\left(s\right)}{{\mathrm{\δi}}_o\left(s\right)}{|}_{{\mathrm{\δv}}_i\left(s\right)=0}=\frac{z_{\mathrm{out}}+z_{\mathrm{out}}{g}_{\mathrm{id}}{g}_i-a_{\mathrm{io}}{g}_{\mathrm{vd}}{g}_i}{1+g_{\mathrm{id}}{g}_i+g_{\mathrm{vd}}{g}_v{g}_i}$

Wherein open-loop voltage gain a_voS () is

$a_{\mathrm{vo}}\left(s\right)=\frac{{\mathrm{\δv}}_{\mathrm{dc}}\left(s\right)}{{\mathrm{\δv}}_i\left(s\right)}{|}_{{\mathrm{\δi}}_o\left(s\right),\mathrm{\δd}\left(s\right)=0}=\frac{1-d}{{\mathrm{lcs}}^2+r_l\mathrm{cs}+{(1-d)}^2}$

Open-loop output impedance z_outS () is

$z_{\mathrm{out}}\left(s\right)=-\frac{{\mathrm{\δv}}_{\mathrm{dc}}\left(s\right)}{{\mathrm{\δi}}_o\left(s\right)}{|}_{{\mathrm{\δv}}_i\left(s\right),\mathrm{\δd}\left(s\right)=0}=\frac{\mathrm{ls}+r_l}{{\mathrm{lcs}}^2+r_l\mathrm{cs}+{(1-d)}^2}$

Control dutycycle-output voltage transmission function g_vdS () is

$g_{\mathrm{vd}}\left(s\right)=\frac{{\mathrm{\δv}}_{\mathrm{dc}}\left(s\right)}{\mathrm{\δd}\left(s\right)}{|}_{{\mathrm{\δv}}_i\left(s\right),{\mathrm{\δi}}_o\left(s\right)=0}=\frac{-{\mathrm{li}}_{l}s-r_l{i}_l+v_i}{{\mathrm{lcs}}^2+r_l\mathrm{cs}+{(1-d)}^2}$

Open loop input admittance y_ioS () is

$y_{\mathrm{io}}\left(s\right)=\frac{{\mathrm{\δi}}_l\left(s\right)}{{\mathrm{\δv}}_i\left(s\right)}{|}_{{\mathrm{\δi}}_o\left(s\right),\mathrm{\δd}\left(s\right)=0}=\frac{\mathrm{cs}}{{\mathrm{lcs}}^2+r_l\mathrm{cs}+{(1-d)}^2}$

Input current-inductive current transmission function a_ioS () is

$a_{\mathrm{io}}\left(s\right)=-\frac{{\mathrm{\δi}}_l\left(s\right)}{{\mathrm{\δi}}_o\left(s\right)}{|}_{{\mathrm{\δv}}_i\left(s\right),\mathrm{\δd}\left(s\right)=0}=\frac{-(1-d)}{{\mathrm{lcs}}^2+r_l\mathrm{cs}+{(1-d)}^2}$

Control dutycycle-inductive current transmission function g_idS () is

$g_{\mathrm{id}}\left(s\right)=\frac{{\mathrm{\δi}}_l\left(s\right)}{\mathrm{\δd}\left(s\right)}{|}_{{\mathrm{\δv}}_i\left(s\right),{\mathrm{\δi}}_o\left(s\right)=0}=\frac{{\mathrm{cv}}_{\mathrm{dc}}s+i_l(1-d)}{{\mathrm{lcs}}^2+r_l\mathrm{cs}+{(1-d)}^2}$

Fig. 5 is the equivalent output impedance z of main power source_{out_cl}S the frequency characteristic of (), the solid line of in figure and dotted line represent respectively The equivalent output impedance of main power source before and after addition low frequency component oscillation suppressor.It is easy to get by figure, when this oscillation suppressor puts into fortune After row, equivalent output impedance at design resonant frequency for the main power source increases, therefore can be in the base not increasing system excess loss Suppression system resonance on plinth.

4) the reference v of main power voltage outer shroud_refBy DC voltage with reference to v_dcref, offset voltage component v_com1And v_com2Three Part combines.Outer voltage is by current transformer outlet side electric capacity of voltage regulation voltage v_dcWith pi controller composition, it is that current inner loop carries For current reference i_ref.Current inner loop is by inductive current i_lWith pi controller composition, ultimately produce boost type dc-dc current transformer Modulation wave signal d.

5) modulation wave signal and triangular wave are compared, and obtain the duty cycle signals of switching tube, thus controlling current transformer to open Close opening and turning off of pipe.

Fig. 6 is main power source oscillation suppression method control loop block diagram.

Fig. 7 adds the simulation waveform after oscillation suppressor for DC micro power grid system, and Fig. 7 (a), (b) represent directly respectively Stream busbar voltage v_dcWith main power source output current i_oInstantaneous value waveform.Build emulation as shown in Figure 1 with matlab/simulink Model, the t=2.5s moment loads and puts into operation, now occurs in that the oscillating component of two kinds of frequencies, system oscillation in straight-flow system Unstability.T=2.7s, 2.8s moment high and low frequency component oscillation suppressor priority comes into operation.As seen from the figure: during 2.7s In straight-flow system, the oscillating component of relative high frequency disappears, and unstability eigenvalue 1 comes back to inside the unit circle of z domain；2.8s moment phase The oscillating component amplitude of low frequency is gradually reduced, after 3.1s, busbar voltage and output current recover stable again, and system just returns to Often running status.Direct-current grid vibration suppression based on band filter under a kind of master slave mode therefore proposed by the invention Method is practical, can effectively increase system damping, and the periodic swinging occurring in suppression system is it is ensured that system stable operation.

Claims (2)

1. the direct-current grid oscillation suppression method based on band filter under a kind of master slave mode, controls direct current female by main power source Line voltage, using voltage x current double -loop control mode it is characterised in that the method is directed to two be likely to occur in direct-current grid Plant oscillation mode, by improving the control system of main power source, increase newly with output voltage v_dcWith output current i_oAnti- for feedback quantity Feedthrough road, forms two groups of corresponding vibration suppression links, and is added to the reference voltage of main power source control system as compensation dosage v_dcrefOn, the higher-order of oscillation and low-frequency oscillation that two groups of vibration suppression links can be likely to occur in suppression system respectively, wherein, high frequency Component vibration suppression link is by feedback quantity DC bus-bar voltage v_dcIt is added to master as compensation dosage after high freguency bandpass filter On the reference voltage of power control system, thus the higher-order of oscillation that suppression is likely to occur, the transmission function being adopted is:

$g_{com1}\left(s\right)=k_1\frac{2{\mathrm{\ξ}}_1{\mathrm{\ω}}_{1}s}{s^2+2{\mathrm{\ξ}}_1{\mathrm{\ω}}_{1}s+{{\mathrm{\ω}}_1}^2}$

Wherein ω₁Take main power source closed loop control transmission function △ v_dc/△v_dcrefResonant frequency, wherein △ v_dcIt is dc bus electricity The microvariations amount of pressure, △ v_dcrefBased on power control system reference voltage microvariations amount；ξ₁For high freguency bandpass filter Bandwidth, value is 1；k₁It is used for coordinating the relation of system damping and system stability as proportional gain, according to the feature of system Root scattergram chooses more excellent parameter, span 0.3-0.7；

Low frequency component vibration suppression link is by output current i of feedback quantity main power source_oAs benefit after low frequency bandpass filter The amount of repaying is added on the reference voltage of main power source control system, thus the low-frequency oscillation that suppression is likely to occur, the transmission letter being adopted Number is:

$g_{com2}\left(s\right)=k_2\frac{2{\mathrm{\ξ}}_2{\mathrm{\ω}}_{2}s}{s^2+2{\mathrm{\ξ}}_2{\mathrm{\ω}}_{2}s+{{\mathrm{\ω}}_2}^2}$

Wherein ω₂Take the resonant frequency of constant power load entrance side lc wave filter；ξ₂For the bandwidth of low frequency bandpass filter, value For 0.2；k₂Characteristic root scattergram according to system chooses more excellent parameter, span 0.3-0.7.

2. direct-current grid oscillation suppression method according to claim 1 is it is characterised in that main power source closed loop control is transmitted Function is:

$\frac{{\mathrm{\δv}}_{dc}}{{\mathrm{\δv}}_{dcref}}=\frac{(1-d)v_{dc}{g}_i{g}_v-(sl+r_l)i_l{g}_i{g}_v}{(sl+r_l+v_{dc}{g}_i)(sc-i_l{g}_i{g}_v)+(1-d+i_l{g}_i)(1-d+v_{dc}{g}_i{g}_v)}$

Wherein c, l, r_l, d be respectively main power source current transformer electric capacity of voltage regulation, filter inductance and equivalent resistance and switching tube duty Ratio g_i、g_vIt is respectively the transmission function of inner and outer ring pi controller, Bode diagram is drawn by this transmission function, high freguency bandpass filter ω₁Take the frequency corresponding to resonance spikes.