CN105356515A - Micro-grid inverter improved droop control method based on marginal cost - Google Patents

Abstract

The present invention discloses a micro-grid inverter improved droop control method based on a marginal cost. On the basis of traditional droop control, the marginal costs of different types of distributed power supplies are considered. According to the improved droop control, the marginal costs of the distributed units in parallel operation can be consistent, the distributed power supply with a high marginal cost makes less effort, the distributed power supply with a low marginal cost makes more effect, and thus the system power generation cost is reduced. Compared with the prior art, according to the method, the self-government control is employed, a communication network is not needed, the economic and optimized operation of a system is realized only through local information control, and the reliability and scalability are high.

Description

A kind of microgrid inverter based on marginal cost improves droop control method

Technical field

The invention belongs to micro-capacitance sensor and inverter control and optimisation technique field, be specifically related to a kind of microgrid inverter based on marginal cost and improve droop control method.

Background technology

Distributed power source generally by inverter parallel to improve the power supply reliability of system, distributed power source is of a great variety, its operating cost and efficiency are all different, traditional droop control distributes power according to rated capacity, do not consider the cost of electricity-generating of each power supply reality, easily cause system operation cost higher.

Consider the marginal cost of dissimilar distributed power source, the microgrid inverter proposed based on marginal cost improves droop control, reduces system total operating cost, improves the economy of micro-capacitance sensor, ensures that system is reliable, economical operation.

Summary of the invention

Goal of the invention: in order to overcome the cost of electricity-generating not considering each power supply reality of above-mentioned prior art and the problem easily causing system operation cost higher.

Technical scheme: the invention provides following technical scheme:

Microgrid inverter based on marginal cost improves a droop control method, comprises the following steps:

(1) based on the improvement P-V droop control of marginal cost, on the basis of conventional P-V droop control, the meritorious marginal cost of dissimilar distributed power source is considered.This control makes parallel running unit gain merit marginal cost unanimously, distributes active power with identical meritorious marginal cost, reduces system Active Generation cost, realizes systematic economy optimizing operation;

(2) based on the improvement Q-f droop control of marginal cost, on the basis of traditional Q-f droop control, the var marginal cost of different distributions formula power supply is considered.This control makes each unit var marginal cost of parallel running consistent, under identical var marginal cost, distribute reactive power, reduces reactive power generation cost, maintains system frequency and stablizes.

As optimization, the described improvement P-V droop control based on marginal cost as shown in the formula:

$U_{i,ref}=U_{max}-(U_{max}-U_{min})\·\frac{L_i\left(P_i\right)}{{\mathrm{\λ}}_{L,P}}---\left(1\right)$

In formula, U _max, U _minfor minimum and maximum permission voltage, P _ifor distributed unit i active power of output; L _i(P _i) be the meritorious marginal cost of distributed unit i, λ _l,Pfor meritorious sagging economic coefficient, each unit value is identical.

This improvement P-V droop control makes the meritorious marginal cost of parallel running distributed power source consistent, because the gain merit cost coefficient of marginal cost of each unit is different, therefore the unit that cost is high is exerted oneself less, and the unit that cost is low has more power, reaches the object reducing system operation cost.

As optimization, the described improvement Q-f droop control based on marginal cost as shown in the formula:

$f_{i,ref}=f_n+(f_{max}-f_n)\·\frac{L\left(Q_i\right)}{{\mathrm{\λ}}_{L,Q}}---\left(2\right)$

In formula, f _nfor the rated frequency of system, f _maxfor maximum tolerance frequency, Q _ifor distributed unit i output reactive power; L _i(Q _i) be the var marginal cost of distributed unit i, λ _l,Qfor idle sagging economic coefficient, each unit value is identical.

This improvement Q-f droop control makes parallel running unit unanimously exert oneself according to var marginal cost, because the cost coefficient of each unit var marginal cost is different, the unit that therefore cost is high is exerted oneself less, and the unit that cost is low has more power, reduce reactive power generation cost, maintain system frequency and stablize.

Beneficial effect: the present invention compared with prior art, has the following advantages:

The present invention is applicable to line impedance and mainly presents resistive interchange micro-capacitance sensor.

(1) the method considers the marginal cost of different distributions formula power supply, improves traditional droop control., can realize each unit marginal cost consistent, systems generate electricity cost is minimum, realizes micro-capacitance sensor economical operation while ensureing system stability.

(2) the method is autonomous control, only utilizes local information to control, and without the need to communication network, can realize " plug and play " of distributed power source, reliability and extensibility high.

(3) this improvement P-V droop control makes the meritorious marginal cost of the distributed power source of parallel running consistent, because the gain merit cost coefficient of marginal cost of each unit is different, therefore the unit that cost is high is exerted oneself less, and the unit that cost is low has more power, reaches the object reducing system operation cost.

(4) this improvement Q-f droop control makes each distributed power source of parallel running unanimously exert oneself according to var marginal cost, because the cost coefficient of each unit var marginal cost is different, therefore the unit that cost is high is exerted oneself less, the unit that cost is low has more power, reduce reactive power generation cost, maintain system frequency and stablize.

Accompanying drawing explanation

Fig. 1 is structural representation of the present invention;

Fig. 2 is for improving P-V droop control schematic diagram.

Embodiment

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is further described, illustrate the present invention further, these embodiments should be understood only be not used in for illustration of the present invention and limit the scope of the invention, after having read the present invention, the amendment of those skilled in the art to various equivalents of the present invention has all fallen within the application's claims limited range.

The invention discloses a kind of microgrid inverter based on marginal cost and improve droop control method, the present invention is applicable to line impedance and mainly presents resistive interchange micro-capacitance sensor.

(1) based on the improvement P-V droop control of marginal cost, consider the meritorious marginal cost of dissimilar distributed power source, improve conventional P-V droop control, make parallel running unit marginal cost of gaining merit consistent, the active power of each unit is distributed with identical meritorious marginal cost, reduce systems generate electricity cost, realize systematic economy optimizing operation.

(2) based on the improvement Q-f droop control of marginal cost, make parallel running unit var marginal cost consistent, distribute reactive power by identical var marginal cost, reduce reactive power generation cost, maintain system frequency and stablize.

The present invention proposes as follows based on the improvement P-V droop control of marginal cost:

$U_{i,ref}=U_{max}-(U_{max}-U_{min})\·\frac{L_i\left(P_i\right)}{{\mathrm{\λ}}_{L,P}}---\left(1\right)$

In formula, U _max, U _minfor minimum and maximum permission voltage, P _ifor the active power that distributed unit i exports, L _i(P _i) be the meritorious marginal cost of distributed unit i, be defined as formula (2).λ _l,Pfor meritorious sagging economic coefficient, each unit value is identical, need meet the condition of formula (4).

$L_i\left(P_i\right)=\frac{\∂C_i\left(P_i\right)}{\∂P_i}=2{\mathrm{\α}}_{i,P}{P}_i+{\mathrm{\β}}_{i,P},i=1,2,...n---\left(2\right)$

Wherein, Active Generation cost as shown in the formula:

$C_i\left(P_i\right)={\mathrm{\α}}_{i,P}{P}_i^2+{\mathrm{\β}}_{i,P}{P}_i+{\mathrm{\γ}}_{i,P},i=1,2,...n---\left(3\right)$

In formula, α _i,P, β _i,P, γ _i,Pfor the active power cost coefficient of distributed unit i.

${\mathrm{\ΔU}}_i=(U_{max}-U_{min})\·\frac{L_i\left(P_{i,max}\right)}{{\mathrm{\λ}}_{L,P}}\≤{\mathrm{\ΔU}}_{max},i=1,2...n---\left(4\right)$

Wherein, P _{i, max}for the maximum permission active power of output of distributed unit i, Δ U _maxfor maximum permissible voltage departure, be generally 5% of bus rated voltage.

System stable operation, when the marginal cost of each generator unit is consistent, the total operating cost of system is minimum.Improve P-V droop control principle as shown in Figure 2.This control method makes parallel running unit marginal cost consistent, as shown in U-L curve; Each unit distributes active power according to equal marginal cost, and exerted oneself by the generator unit that the known marginal cost of L-P curve is high few, low unit is exerted oneself many, can obtain U-P sagging curve comprehensively.Therefore, carry and improve the target that droop control can realize reducing systems generate electricity cost, realize microgrid economical operation.

The present invention proposes as follows based on the improvement Q-f droop control of marginal cost:

$f_{i,ref}=f_n+(f_{max}-f_n)\frac{L_i\left(Q_i\right)}{{\mathrm{\λ}}_{L,Q}}---\left(5\right)$

In formula, f _nfor the rated frequency of system, f _maxfor maximum tolerance frequency, Q _ifor distributed unit i output reactive power.L _i(Q _i) be the var marginal cost of distributed unit i, be defined as formula (6).λ _l,Qfor idle sagging economic coefficient, each unit value is identical, need meet the condition of formula (8).

$L_i\left(Q_i\right)=\frac{\∂C_i\left(Q_i\right)}{\∂Q_i}=2{\mathrm{\α}}_{i,Q}{Q}_i+{\mathrm{\β}}_{i,Q},i=1,2,...n---\left(6\right)$

Wherein, idle cost as shown in the formula:

$C_i\left(Q_i\right)={\mathrm{\α}}_{i,Q}{Q}_i^2+{\mathrm{\β}}_{i,Q}{Q}_i,i=1,2,...n---\left(7\right)$

In formula, α _i,Q, β _i,Qfor the idle cost coefficient of distributed unit i.

${\mathrm{\Δf}}_i=(f_{max}-f_n)\·\frac{L_i\left(Q_{i,max}\right)}{{\mathrm{\λ}}_{L,Q}}\≤{\mathrm{\Δf}}_{max},i=1,2...n---\left(8\right)$

In formula, Q _{i, max}for the maximum permission output reactive power of distributed unit i, Δ f _maxfor maximum tolerance frequency departure, be generally 0.5Hz.Improve Q-f droop control principle similar with improvement P-V droop control, do not repeat them here.

Claims (3)

1. the microgrid inverter based on marginal cost improves a droop control method, it is characterized in that: comprise the following steps:

(1) based on the improvement P-V droop control of marginal cost, on the basis of conventional P-V droop control, the meritorious marginal cost of dissimilar distributed power source is considered.This control makes parallel running unit gain merit marginal cost unanimously, distributes the active power of each unit with identical meritorious marginal cost, reduces system Active Generation cost, realizes systematic economy optimizing operation;

(2) based on the improvement Q-f droop control of marginal cost, on the basis of traditional Q-f droop control, the var marginal cost of different distributions formula power supply is considered.This control makes parallel running unit var marginal cost consistent, under identical var marginal cost, distribute reactive power, reduces reactive power generation cost, maintains system frequency and stablizes.

2. the microgrid inverter based on marginal cost according to claim 1 improves droop control method, it is characterized in that: the described improvement P-V droop control based on marginal cost as shown in the formula:

$U_{i,ref}=U_{max}-(U_{max}-U_{min})\·\frac{L_i\left(P_i\right)}{{\mathrm{\λ}}_{L,P}}---\left(1\right)$

In formula, U _max, U _minfor minimum and maximum permission voltage, P _ifor distributed unit i active power of output; L _i(P _i) be the meritorious marginal cost of distributed unit i, λ _l,Pfor meritorious sagging economic coefficient, each unit value is identical.

3. the microgrid inverter based on marginal cost according to claim 1 improves droop control method, it is characterized in that: the described improvement Q-f droop control based on marginal cost as shown in the formula:

$f_{i,ref}=f_n+(f_{max}-f_n)\·\frac{L_i\left(Q_i\right)}{{\mathrm{\λ}}_{L,Q}}---\left(2\right)$

In formula, f _nfor the rated frequency of system, f _maxfor maximum tolerance frequency, Q _ifor distributed unit i output reactive power; L _i(Q _i) be the var marginal cost of distributed unit i, λ _l,Qfor idle sagging economic coefficient, each unit value is identical.