CN105610182A - Tandem type microgrid structure of island operation and power control method of structure - Google Patents

Abstract

The invention relates to a tandem type microgrid structure of island operation. The structure comprises a DC power generation unit, a DC/AC conversion circuit and a sampling circuit, wherein the DC power generation unit comprises a DC bus capacitor, the DC/AC conversion circuit comprises a main power inversion circuit and a filter circuit, and the sampling circuit comprises a filter inductor current sampling circuit and a filter capacitor voltage sampling circuit. The invention also relates to a power control method of the microgrid structure. The structure and method have the advantages that a DC/DC boosting link in a traditional microgrid structure is omitted from the microgrid structure in the invention, the system cost is reduced, and the efficiency of a converter is improved.

Description

A kind of tandem type microgrid structure and Poewr control method thereof of islet operation

Technical field

The tandem type microgrid structure that the present invention relates to a kind of islet operation, also relates to a kind of above-mentioned stringThe Poewr control method of connection type microgrid structure.

Background technology

Microgrid is one to be possessed oneself and controls and the autonomous system of self-energy management, by DG withThe form access of microgrid, is generally considered the most effective mode of DG of utilizing. Microgrid can be withExternal electrical network is incorporated into the power networks, also can islet operation. Piconet island when operation, can improve pointThe receiving ability of the cloth formula energy; The power supply of guarantee critical load, improves user's power supply reliability;Solve the power supply difficult problem of user in remote districts, island and desert.

The DG unit of converters interface type is prevalent in micro-grid system, theyMainly access the points of common connection (PCC) of micro-electrical network and large electrical network with parallel way. For new energySource electricity generation system, as photovoltaic generating system, generally by organizing serial type photovoltaic panel through DC/DC changing ringJoint boosts to certain voltage range, then generates electricity by way of merging two or more grid systems through inversion. Due to systemIn a large amount of DC/DC converters that use, therefore, greatly improved the cost of system, also fall simultaneouslyThe low operational efficiency of DG system. If DG cell distribution is not concentrated, can pass through longer feedbackLine just can be incorporated to system PCC, and this will cause certain feed line impedance pressure drop loss. In order to reduceThe cost of communication and control system, droop control method is widely used in micro-grid system. ButThat traditional droop control method has certain limitation, has power division error.

Consider practical application and reduce costs, being badly in need of a kind of microgrid without DC/DC transform partStructure, the algorithm of simultaneously developing a kind of Simple And Practical accurately distributes power.

Summary of the invention

The technical problem to be solved in the present invention is to provide a kind of tandem type microgrid knot of islet operationStructure, and a kind of Poewr control method of tandem type microgrid structure.

For solving the problems of the technologies described above, technical scheme of the present invention is: a kind of string of islet operationConnection type microgrid structure, this microgrid structure is used for accessing the points of common connection of micro-electrical network and large electrical network,Its innovative point is: be made up of three distributed power source units in series, be respectively first distributedPower subsystem, the second distributed electrical source unit and the 3rd distributed electrical source unit, wherein first pointOutlet side one end of cloth formula power subsystem connects one end of common tie point, and the other end connects secondOne end of the outlet side of distributed electrical source unit, the outlet side of the second distributed electrical source unit anotherOne end connects one end of the outlet side of the 3rd distributed electrical source unit, the 3rd distributed electrical source unitThe other end of outlet side connect the other end of common tie point;

Described distributed electrical source unit comprises:

One direct current generator unit, described DC generation unit is by dc-link capacitance and group serial typePhotovoltaic panel is formed in parallel;

One AC/DC conversion circuit, this AC/DC conversion circuit comprises main power invertingCircuit and filter circuit, filter circuit is made up of filter inductance and filter capacitor, filtered electricalThe input of sense is connected with the output of main power inversion circuit, the output of filter inductanceBe connected with the input of filter capacitor, and access one end or another point of points of common connectionThe output of the filter capacitor of cloth formula power subsystem, the output of filter capacitor and anotherThe output of the filter inductance of distributed electrical source unit is connected or accesses the another of points of common connectionOne end;

One sample circuit, described sample circuit comprises the filter inductance of sampling filter inductive currentThe filter capacitor voltage sampling circuit of current sampling circuit and sampling filter capacitance voltage.

Further, described group of serial type photovoltaic panel is made up of multiple series-parallel photovoltaic modulies.

Further, described main power inversion circuit is bridge type inverse structure.

Further, described filter capacitor voltage sampling circuit is equipped with and adopts electric capacity or adopt electricityResistance.

A Poewr control method for tandem type microgrid structure, its innovative point is: step is:

A) first, measure filter inductance electric current, to obtain inductor current feedback signal I_o, surveyAmount filter capacitor voltage, to obtain capacitance voltage feedback signal V_c；

B) by inductor current feedback signal I_oWith capacitance voltage feedback signal V_c, obtain distributedThe instantaneous active power of power subsystem and reactive power, and calculate its power-factor cos (θ);

C) this power factor value as the input of power factor/frequency inverse dip control method because ofSon, is output as reference angle frequencies omega_DG, and then obtain voltage reference value V_ref, as follows:

ω_DG＝ω^*+D_PF·cos(θ)， $r_{ref}=\sqrt{2}Ecos\left({\mathrm{\ω}}_{DG}t\right)$

In formula, ω^*For specified angular frequency, D_PFFor inverse dip control coefrficient, E is rated voltageReference value;

D), for this voltage reference value, follow the tracks of dicyclo voltage with dicyclo voltage controllerThe outer ring controller quasi-resonance controller of controller, the transfer function of outer shroud is G_outer(s), outerRing output current reference value is I_ref; The transfer function of interior ring is G_Inner(s), interior ring is output as useIn the reference voltage level V of pulse width modulation_out, as follows:

$\begin{array}{c}{I}_{ref}=G_{Outer}\left(s\right)\·(V_{ref}-V_C)\\ =(k_p+\underset{h=1,3,\mathrm{....11}}{\Σ}\frac{2k_{i,h}{\mathrm{\ω}}_{c}s}{s^2+2{\mathrm{\ω}}_{c}s+{(h\·{\mathrm{\ω}}^{*})}^2})\·(V_{ref}-V_C)\end{array},\begin{array}{c}{V}_{out}=G_{Inner}\left(s\right)\·(I_{ref}-I_o)\\ =k_{inner}\·(I_{ref}-I_o)\end{array}$

In formula, k_p、k_innerBe respectively the proportional gain of outer shroud and interior ring control, h is harmonic wave rankNumber, k_i,hFor the proportional gain of h order harmonics, ω_cThe cut-off frequency of the resonant controller that is as the criterion.

The invention has the advantages that: the tandem type microgrid structure in the present invention is by multiple distributed electricalsSource unit connects by series system, is different from traditional grid-connected side of multiple distributed electrical source unitsFormula, this microgrid structure has been saved the DC/DC boosting inverter link in traditional microgrid structure, therebyReduce system cost, improved the operational efficiency of distributed electrical source unit.

The DC side input voltage class requirement of distributed electrical source unit is reduced, improved new energyThe utilization rate in source, has relatively reduced system Construction cost.

The output current of each distributed electrical source unit and output frequency are permanent to be equated, no longer examines simultaneouslyConsider the circulation problem between distributed electrical source unit.

In addition, for the micro-electric network composition of this tandem type, Poewr control method of the present invention, hasSimple and practical feature, only need to gather current signal He Yi road, a road voltage signal, noNeed the communication between distributed electrical source unit, also do not need to obtain the parameter of micro-grid system; SystemOutput voltage waveforms quality is high, and harmonic content obviously reduces; Realize distributed electrical source unitThe accurate distribution of meritorious and reactive power, thus the accurate power solving in traditional isolated microgrid dividesJoin a difficult problem.

Brief description of the drawings

Below in conjunction with the drawings and specific embodiments, the present invention is further detailed explanation.

Fig. 1 is traditional micro-electric network composition schematic diagram of parallel connection type.

Fig. 2 is the micro-electric network composition schematic diagram of tandem type of the present invention.

Fig. 3 is power factor/frequency inverse dip control algolithm flow chart of the present invention.

Fig. 4 is simulation waveform figure.

Detailed description of the invention

The following examples can make the present invention of professional and technical personnel's comprehend, but notTherefore limit the present invention among described scope of embodiments.

The tandem type microgrid structure of a kind of islet operation as shown in Figure 2 and Figure 3, by three pointsCloth formula power subsystem is composed in series, and is respectively the first distributed electrical source unit, the second distributed electricalSource unit and the 3rd distributed electrical source unit, the wherein outlet side one of the first distributed electrical source unitEnd connects one end of common tie point, and the other end connects the outlet side of the second distributed electrical source unitOne end, the other end of the outlet side of the second distributed electrical source unit connects the 3rd distributed power sourceOne end of the outlet side of unit, the other end of the outlet side of the 3rd distributed electrical source unit connects altogetherWith the other end of tie point.

Distributed electrical source unit comprises DC generation unit 1, AC/DC conversion circuit 2 and adoptsSample circuit 3.

DC generation unit 1 is formed in parallel by dc-link capacitance 12 and group serial type photovoltaic panel, groupSerial type photovoltaic panel is made up of multiple series-parallel photovoltaic modulies.

AC/DC conversion circuit 2 comprises main power inversion circuit 21 and filter circuit 22,Main power inversion circuit 21 is bridge type inverse structure, filter circuit 22 by filter inductance 221 andFilter capacitor 222 forms, the input of filter inductance 221 and main power inversion circuit 21Output is connected, and the output of filter inductance 221 is connected with the input of filter capacitor 222,And access the defeated of one end of points of common connection or the filter capacitor of another distributed electrical source unitGo out end, the filter inductance of the output of filter capacitor 222 and another distributed electrical source unitOutput be connected or access points of common connection the other end.

Sample circuit 3 comprise sampling filter inductive current filter inductance current sampling circuit 31 andThe filter capacitor voltage sampling circuit 32 of sampling filter capacitance voltage, filter capacitor voltage sampleCircuit is equipped with and adopts electric capacity or adopt resistance.

For a Poewr control method for above-mentioned tandem type microgrid structure, as shown in Figure 3,Its step is specific as follows:

The first step, measures filter inductance electric current, to obtain inductor current feedback signal I_o, measureFilter capacitor voltage, to obtain capacitance voltage feedback signal V_c。

Second step, by inductor current feedback signal I_oWith capacitance voltage feedback signal V_c, obtain pointInstantaneous active power and the reactive power of cloth formula power subsystem, and calculate its power-factor cos (θ).

The 3rd step, this power factor value is defeated as power factor/frequency inverse dip control methodEnter the factor, be output as reference angle frequencies omega_DG, and then obtain voltage reference value V_ref, as follows:

ω_DG＝ω^*+D_PF·cos(θ)， $r_{ref}=\sqrt{2}Ecos\left({\mathrm{\ω}}_{DG}t\right)$

In formula, ω^*For specified angular frequency, D_PFFor inverse dip control coefrficient, E is rated voltageReference value.

The 4th step, for this voltage reference value, follows the tracks of dicyclo with dicyclo voltage controllerThe outer ring controller quasi-resonance controller of voltage controller, the transfer function of outer shroud isG_outer(s), outer shroud output current reference value is I_ref; The transfer function of interior ring is G_Inner(s),Ring is output as the reference voltage level V for pulse width modulation (PWM)_out, as follows:

$\begin{array}{c}{I}_{ref}=G_{Outer}\left(s\right)\·(V_{ref}-V_C)\\ =(k_p+\underset{h=1,3,\mathrm{....11}}{\Σ}\frac{2k_{i,h}{\mathrm{\ω}}_{c}s}{s^2+2{\mathrm{\ω}}_{c}s+{(h\·{\mathrm{\ω}}^{*})}^2})\·(V_{ref}-V_C)\end{array},\begin{array}{c}{V}_{out}=G_{Inner}\left(s\right)\·(I_{ref}-I_o)\\ =k_{inner}\·(I_{ref}-I_o)\end{array}$

In formula, k_p、k_innerBe respectively the proportional gain of outer shroud and interior ring control, h is harmonic wave rankNumber, k_i,hFor the proportional gain of h order harmonics, ω_cThe cut-off frequency of the resonant controller that is as the criterion.

Simulation waveform as shown in Figure 4, uses traditional droop control before 1s, after 1s, startControl method of the present invention, the known meritorious and reactive power accurately that realized is distributed, and has verifiedThe correctness of the micro-electrical network of tandem type of the present invention and Poewr control method thereof.

The technical staff of the industry should understand, and the present invention is not restricted to the described embodiments, onState in embodiment and description, describe principle of the present invention is just described, do not departing from the present inventionUnder the prerequisite of spirit and scope, the present invention also has various changes and modifications, these variations and changingEnter and all fall in the claimed scope of the invention. The claimed scope of the present invention is by appended powerProfit claim and equivalent thereof define.

Claims (5)

1. a tandem type microgrid structure for islet operation, this microgrid structure be used for accessing micro-electrical network withThe points of common connection of large electrical network, is characterized in that: by three distributed power source units in seriesComposition, is respectively the first distributed electrical source unit, the second distributed electrical source unit and the 3rdDistributed electrical source unit, wherein outlet side one end of the first distributed electrical source unit connects altogetherWith one end of tie point, the other end connect the second distributed electrical source unit outlet side oneEnd, the other end of the outlet side of the second distributed electrical source unit connects the 3rd distributed power sourceOne end of the outlet side of unit, the other end of the outlet side of the 3rd distributed electrical source unit connectsConnect the other end of common tie point;

Described distributed electrical source unit comprises:

One direct current generator unit, described DC generation unit is by dc-link capacitance and group serial typePhotovoltaic panel is formed in parallel;

One AC/DC conversion circuit, this AC/DC conversion circuit comprises main power invertingCircuit and filter circuit, filter circuit is made up of filter inductance and filter capacitor, filtered electricalThe input of sense is connected with the output of main power inversion circuit, the output of filter inductanceBe connected with the input of filter capacitor, and access one end or another point of points of common connectionThe output of the filter capacitor of cloth formula power subsystem, the output of filter capacitor and anotherThe output of the filter inductance of distributed electrical source unit is connected or accesses the another of points of common connectionOne end;

One sample circuit, described sample circuit comprises the filter inductance of sampling filter inductive currentThe filter capacitor voltage sampling circuit of current sampling circuit and sampling filter capacitance voltage.

2. the tandem type microgrid structure of islet operation according to claim 1, is characterized in that:Described group of serial type photovoltaic panel is made up of multiple series-parallel photovoltaic modulies.

3. the tandem type microgrid structure of islet operation according to claim 1, is characterized in that:Described main power inversion circuit is bridge type inverse structure.

4. the tandem type microgrid structure of islet operation according to claim 1, is characterized in that:Described filter capacitor voltage sampling circuit is equipped with and adopts electric capacity or adopt resistance.

5. the power control for the tandem type microgrid structure of islet operation claimed in claim 1Method processed, is characterized in that: step is:

A) first, measure filter inductance electric current, to obtain inductor current feedback signal I_o, surveyAmount filter capacitor voltage, to obtain capacitance voltage feedback signal V_c；

B) by inductor current feedback signal I_oWith capacitance voltage feedback signal V_c, obtain distributedThe instantaneous active power of power subsystem and reactive power, and calculate its power-factor cos (θ);

C) this power factor value as the input of power factor/frequency inverse dip control method because ofSon, is output as reference angle frequencies omega_DG, and then obtain voltage reference value V_ref, as follows:

ω_DG＝ω^*+D_PF·cos(θ)，

In formula, ω^*For specified angular frequency, D_PFFor inverse dip control coefrficient, E is specified electricityPress reference value;

D), for this voltage reference value, follow the tracks of dicyclo electricity with dicyclo voltage controllerThe outer ring controller quasi-resonance controller of pressure controller, the transfer function of outer shroud is G_outer(s)，Outer shroud output current reference value is I_ref; The transfer function of interior ring is G_Inner(s), interior ring is output asFor the reference voltage level V of pulse width modulation (PWM)_out, as follows:

$\begin{array}{c}{I}_{ref}=G_{Outer}\left(s\right)\·\left(V_{ref}-V_C\right)\\ =\left(k_p+\underset{h=1,3,\mathrm{....11}}{\Σ}\frac{2k_{i,h}{\mathrm{\ω}}_{c}s}{s^2+2{\mathrm{\ω}}_{c}s+{\left(h\·{\mathrm{\ω}}^{*}\right)}^2}\right)\·\left(V_{ref}-V_C\right)\end{array},\begin{array}{c}{V}_{out}=G_{Inner}\left(s\right)\·\left(I_{ref}-I_o\right)\\ =k_{inner}\·\left(I_{ref}-I_o\right)\end{array}$

In formula, k_p、k_innerBe respectively the proportional gain of outer shroud and interior ring control, h is harmonic wave rankNumber, k_i,hFor the proportional gain of h order harmonics, ω_cThe cut-off frequency of the resonant controller that is as the criterion.