CN106356838A - Negative-sequence real-time optimized compensation method of RPC (railway power conditioner) - Google Patents

Abstract

The invention discloses a negative-sequence real-time optimized compensation method of an RPC (railway power conditioner). A function expression between lambda and omega is obtained by establishing function relations between active transfer current delta Ip and lambda and between reactive compensation current delta Iq and omega; a three-phase voltage unbalance degree set value is taken as a constraint condition, and the optimal active compensation coefficient and the optimal negative-sequence reactive compensation angle are calculated with a steepest descent method, so that the optimal negative-sequence compensation current set value under the real-time working condition is obtained. The method is small in calculation amount, the optimal compensation power set value can be calculated accurately online in real time, and negative sequence and reactive real-time optimization treatment of electrified railways can be realized; negative sequence and reactive comprehensive treatment of a traction substation can be realized, the minimum operation of the compensation power of the RPC can be realized, so that the operation current and loss of the RPC are reduced, the long-term operation capacity of the RPC can be improved, and the method has good industrial application prospect.

Description

Negative sequence real-time optimization compensation method for railway power regulator

Technical Field

The invention relates to the technical field of electrified railways, in particular to a negative sequence real-time optimization compensation method for a railway power regulator.

Background

With the construction of a high-speed railway network, heavy load and high speed are key points of railway development in China, and the negative sequence problem in the electrified railway is more prominent due to the increase of the traction power of the high-speed railway. The electrified railway is a typical single-phase load, and when a three-phase power system supplies power to the electrified railway, negative-sequence current is generated, which influences the safe and stable operation of a traction power supply system and a power system. The railway power Regulator (RPC) has obvious effects on balancing system voltage, improving power factor, inhibiting voltage fluctuation and filtering harmonic waves, and is an effective comprehensive treatment means. From the RPC treatment effect, the method can be divided into complete compensation and optimized compensation. The optimized compensation mode can effectively reduce the RPC capacity and the working current under the condition of meeting the national standard requirement of the power quality, and has good application prospect.

On the RPC optimization compensation problem, the literature 'research on the electric energy quality comprehensive compensation technology of the electrified railway power supply system' analyzes the relation between negative sequence current and compensation power, but does not carry out optimization design aiming at the national standard requirement of the negative sequence; the document 'hybrid electric energy quality compensation research based on a V/V traction power supply system' provides a negative sequence optimization compensation strategy, but the method is only suitable for calculating the minimum installation capacity under the condition of one-arm heavy load and one-arm no-load working condition, and cannot calculate the optimal compensation quantity in real time under the condition of traction load fluctuation; in the literature, "railway power regulator capacity allocation and energy optimization compensation strategy based on V/V wiring transformer" adopts particle swarm optimization algorithm to calculate RPC minimum compensation power, but the method sets the traction load as a certain step length, and then adopts an offline optimization calculation method to obtain an optimized solution, so that the method cannot be applied to real-time calculation under the condition of traction load fluctuation, and under the condition of too large step length, the compensation accuracy is not ideal enough, and the problems of under-compensation or compensation exist. Therefore, a simple method for accurately calculating the optimal compensation power in real time on line under the condition of fluctuating load does not exist at present.

Disclosure of Invention

In order to solve the problems, the invention aims to provide a real-time optimization compensation method for a negative sequence of a railway power regulator, which can accurately calculate an optimal compensation power set value on line in real time and realize real-time optimization management of the negative sequence and reactive power of an electrified railway so as to meet the requirements of railway companies and power departments.

A negative sequence real-time optimization compensation method for a railway power regulator comprises the following data:

step 1: sampling voltage and current of a two-phase feeder line at the traction side of a traction transformer;

step 2, obtaining α arm load active current I by using the data obtained by sampling in the step 1 and adopting a fast Fourier algorithm and an instantaneous power algorithm_αLpAnd a load reactive current I_αLqβ arm load active current I_βLpAnd a load reactive current I_βLqRatio of active current to load K_IAnd an active compensation coefficient λ;

and step 3: calculating the active transfer current Delta I_pFunction relation delta I between active compensation coefficient lambda_pF (λ), and a reactive compensation current Δ I_qAngle of reactive compensation with negative sequenceFunctional relationship between

And 4, step 4: given value by three-phase voltage unbalance^* _u1.2% as constraint with Δ I_pF (λ) andobtaining an active compensation coefficient lambda and a negative sequence reactive compensation angleFunctional relationship betweenAnd an optimization algorithm is adopted to calculate the optimal active compensation coefficient lambda when the compensation current is minimum₀And an optimal negative sequence reactive compensation angle

The quality of electric energy requires unbalanced three-phase voltage (GB/T15543-2008) and unbalanced three-phase voltage_uShould be less than 1.2%;

and 5: using the optimal active power compensation coefficient lambda₀And an optimal negative sequence reactive compensation angleFor the purpose, α arm compensation power given value active component I is calculated_αcpAnd a reactive component I_αcqAnd β arm compensates for power setpoint power componentI_βcpAnd a reactive component I_βcq；

Step 6: and (5) inputting the given value of the compensation power obtained in the step (5) into an alpha converter and a beta converter of the railway power regulator, controlling the operation of the railway power regulator and realizing negative sequence and reactive power optimization control of the traction substation.

The load active current ratio K_IThe ratio of the magnitude of active current of the α arm and the β arm is indicated when the power factor of the α arm and β arm locomotives of the traction transformer is 1.

The active transfer current Delta I_pFunction relation delta I between active compensation coefficient lambda_pA specific expression of ═ f (λ) is:

${\mathrm{\ΔI}}_P=f\left(\mathrm{\λ}\right)=\frac{1}{2}\mathrm{\λ}(I_{\mathrm{\α}Lp}-I_{\mathrm{\β}Lp})=\frac{1}{2}\mathrm{\λ}(1-K_I)I_{\mathrm{\α}Lp};$

the reactive compensation current Delta I_qAngle of reactive compensation with negative sequenceFunctional relationship betweenThe specific expression of (A) is as follows:

wherein, Delta I_qαAnd Δ I_qβRespectively, a reactive compensation current DeltaI_qα arm component and β arm component.

The active compensation coefficient lambda and the negative sequence reactive compensation angleFunctional relationship betweenThe expression of (a) is as follows:

wherein, ^* _ufor given value of unbalance of three-phase voltage, S_LFor loading apparent power, S_dIs the system short circuit capacity.

In solving forWhen the three-phase voltage is unbalanced, the given value is^* _uAs a constraint, corresponding

According to the national standard definition, the formula of the three-phase voltage unbalance is as follows:

${\mathrm{\ϵ}}_U={\mathrm{\ϵ}}_I\frac{S_L}{S_d}$

due to apparent power S of the load_LAnd system short circuit capacity S_dBoth of these parameters are constants; while_IThe three-phase current unbalance degree is expressed as follows:

in formula (II)'_αTo compensate for a post α arm current value, I'_βTo compensate for the post β arm current value.

To obtainExpression of (c), I 'needs to be found'_αAnd l'_βAnd λ andthe relationship of (1):

the voltage-current vector relation of the primary side and the secondary side of the V/V transformer can be known as follows:

substituting the voltage-current vector relation formula of the primary side and the secondary side of the V/V transformer into a three-phase current unbalance formula, and then carrying out three-phase voltage unbalanceDegree formula to obtainIs described in (1).

The optimization algorithm adopted in the step 4 is a steepest descent method, a Newton iteration method or a conjugate direction method.

α arm compensation power given value active component I in step 5_αcpAnd a reactive component I_αcqAnd β arm compensation power setpoint power component I_βcpAnd a reactive component I_βcqRespectively as follows:

$I_{\mathrm{\α}cp}=I_{\mathrm{\β}cp}=\frac{1}{2}L(I_{\mathrm{\α}Lp}-I_{\mathrm{\β}Lp})$

advantageous effects

The invention provides a negative sequence real-time optimization compensation of a railway power regulatorMethod by establishing an active transfer current Δ I_pAnd between lambda and the reactive compensation current delta I_qAndis functionally related to each other, thereby obtaining λ anda functional expression therebetween; and calculating to obtain an optimal active compensation coefficient and an optimal negative sequence reactive compensation angle by taking the given value of the three-phase voltage unbalance as a constraint condition and adopting a steepest descent method, so as to obtain an optimal negative sequence compensation current given value under a real-time working condition. The method of the invention takes the three-phase voltage unbalance as a constraint condition, provides an expression based on the three-phase current unbalance through the analysis of the three-phase voltage unbalance, and creatively analyzes the active compensation coefficient lambda and the negative sequence reactive compensation angleThe function relationship between the compensation current and the negative sequence reactive compensation angle is accurately obtained when the compensation current reaches the minimumAnd the optimal active compensation coefficient lambda₀(ii) a The method has small calculation amount, can accurately calculate the optimal compensation power given value on line in real time, and realizes the real-time optimization treatment of negative sequence and reactive power of the electrified railway; the comprehensive control of the negative sequence and the reactive power of the traction substation can be realized, and the minimum operation of the RPC compensation power can also be realized, so that the RPC operation current and the loss are reduced, the long-term operation capability of the RPC can be improved, and the method has a good industrial application prospect; and the method is suitable for real-time online calculation of the fluctuating load, and has practical application value.

Drawings

Fig. 1 is an implementation schematic diagram of a negative sequence real-time optimization compensation method for a railway power regulator according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail below with reference to specific embodiments and with reference to the attached drawings.

As shown in fig. 1, the present invention provides a negative sequence real-time optimization compensation method for a railway power regulator, which comprises the following steps:

step 1, at the initial point of each sampling period, a voltage measuring circuit and a current measuring circuit are used for measuring the voltage u of a two-phase feeder line at the traction side of a traction transformer_α、u_βAnd two-phase feeder current i_Lα、i_LβRespectively sampling, and inputting sampling data into a parameter calculation module;

step 2, in the parameter calculation module, adopting a fast Fourier algorithm and an instantaneous power algorithm to obtain α arm load active current I_αLpAnd a load reactive current I_αLqβ arm load active current I_βLpAnd a load reactive current I_βLqRatio of active current to load K_IAnd an active compensation coefficient λ;

step 3, combining the given value of the unbalance degree of the three-phase voltage^* _uCalculating the parameters by the parameter calculation module to obtain I_αLp、I_αLq、I_βLp、I_βLq、K_IAnd lambda, calculating the active transfer current delta I_pA functional relationship Δ I with said λ_pF (λ), and a reactive compensation current Δ I_qAngle of reactive compensation with negative sequenceFunctional relationship between

ΔI_pF (λ), specifically:

${\mathrm{\ΔI}}_P=\frac{1}{2}\mathrm{\λ}(I_{\mathrm{\α}Lp}-I_{\mathrm{\β}Lp})=\frac{1}{2}\mathrm{\λ}(1-K_I)I_{\mathrm{\α}Lp}---\left(1\right)$

functional relationshipThe method specifically comprises the following steps:

in the formula,. DELTA.I_qαAnd Δ I_qβRespectively, a reactive compensation current DeltaI_qα arm component and β arm component.

Then the total compensation current Δ I of the two arms is:

step 4, setting the three-phase voltage unbalance degree^* _u1.2% as constraint with Δ I_pF (λ) andobtaining an active compensation coefficient lambda and a negative sequence reactive compensation angleFunctional relationship betweenAnd when the compensation current is minimum, the optimal active compensation coefficient lambda is calculated by adopting an optimization algorithm₀And an optimal negative sequence reactive compensation angle

The quality of electric energy requires unbalanced three-phase voltage (GB/T15543-2008) and unbalanced three-phase voltage_uShould be less than 1.2%;

in order to meet the national standard requirement (namely three-phase voltage unbalance degree)^* _u1.2%), reducing the compensation current Δ I as much as possible requires setting the value for the imbalance of the three-phase voltages to a value given by the three-phase voltage^* _uAnd solving the optimal value of the compensation current delta I as a constraint condition.

In the formula (3), K_IAnd I_αLPIs constant, the compensation current Δ I is formed by the variables λ andand (6) determining. Although λ may be in [0,1 ]]，Can be in the range of [ - π/3, π/3]Can be arbitrarily chosen within the range of (1), but in order to meet the national standard requirement of three-phase voltage unbalance (namely_u1.2%) we found that lambda andcannot take any value at all_uUnder the constraint of (2), λ andmust satisfy a certain functional relationship, i.e.

The following analysisThe specific expression of (A):

according to the national standard definition, the formula of the three-phase voltage unbalance is as follows:

${\mathrm{\ϵ}}_U={\mathrm{\ϵ}}_I\frac{S_L}{S_d}---\left(4\right)$

in the formula (4), S_LFor loading apparent power, S_dBoth of these parameters are constant for system short circuit capacity._IThe three-phase current unbalance degree is expressed as follows:

in formula (II)'_αTo compensate for a post α arm current value, I'_βTo compensate for the post β arm current value to obtainOf l, we need to find out'_αAnd l'_βAnd λ andthe relationship of (1):

the voltage-current vector relation of the primary side and the secondary side of the V/V transformer can be known as follows:

substituting the formula (6) into the formula (5) and then substituting the formula (4) to obtain the final productThe expression of (a) is:

$\mathrm{\λ}=1-\sqrt{1+4\×\[K_I-\frac{{(1+K_I)}^2}{v+2}\]/{(1-K_I)}^2}---\left(7\right)$

in the formula,thus, in the formula (7), the satisfaction is obtained_uLambda and of the constraintThe relational expression (c) of (c).

In satisfying_uUnder the constraint condition, in order to obtain the minimum compensation current, the sum of λ and is constrained by the formula (7)The minimum value of the compensation current Δ I is calculated by equation (3). Therefore, equation (7) can be substituted into equation (3) to establishΔ I expression for independent variables:

for the formula (8), the minimum value delta I of the compensation current is calculated by adopting a steepest descent method, a Newton iteration method or a conjugate direction method₀Optimal negative sequence reactive compensation angleAnd the optimal active compensation coefficient lambda₀。

Step 5, using the optimal active power compensation coefficient lambda₀And an optimal negative sequence reactive compensation angleConditional on calculating α arm compensation power given value active component I_αcpAnd a reactive component I_αcqAnd calculating β arm compensation power given value active component I_βcpAnd do not haveWork component I_βcq；

And 6, inputting the given value of the compensation power into an alpha converter and a beta converter of the railway power regulator to control the operation of the railway power regulator and realize negative sequence and reactive power optimization control of the traction substation.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (6)

1. A negative sequence real-time optimization compensation method for a railway power regulator is characterized by comprising the following data:

step 1: sampling voltage and current of a two-phase feeder line at the traction side of a traction transformer;

step 2, obtaining α arm load active current I by using the data obtained by sampling in the step 1 and adopting a fast Fourier algorithm and an instantaneous power algorithm_αLpAnd a load reactive current I_αLqβ arm load active current I_βLpAnd a load reactive current I_βLqRatio of active current to load K_IAnd an active compensation coefficient λ;

and step 3: calculating the active transfer current Delta I_pFunction relation delta I between active compensation coefficient lambda_pF (λ), and a reactive compensation current Δ I_qAngle of reactive compensation with negative sequenceFunctional relationship between

And 4, step 4: given value by three-phase voltage unbalance^* _u1.2% as constraint with Δ I_pF (λ) andobtaining an active compensation coefficient lambda and a negative sequence reactive compensation angleFunctional relationship betweenAnd an optimization algorithm is adopted to calculate the optimal active compensation coefficient lambda when the compensation current is minimum₀And an optimal negative sequence reactive compensation angle

And 5: using the optimal active power compensation coefficient lambda₀And an optimal negative sequence reactive compensation angleFor the purpose, α arm compensation power given value active component I is calculated_αcpAnd a reactive component I_αcqAnd β arm compensation power setpoint power component I_βcpAnd a reactive component I_βcq；

Step 6: and (5) inputting the given value of the compensation power obtained in the step (5) into an alpha converter and a beta converter of the railway power regulator, controlling the operation of the railway power regulator and realizing negative sequence and reactive power optimization control of the traction substation.

2. The method of claim 1, wherein the load active current ratio K_IThe ratio of the magnitude of active current of the α arm and the β arm is indicated when the power factor of the α arm and β arm locomotives of the traction transformer is 1.

3. Method according to claim 2, characterized in that the active transfer current Δ I_pFunction relation delta I between active compensation coefficient lambda_pA specific expression of ═ f (λ) is:

the reactive compensation current Delta I_qAngle of reactive compensation with negative sequenceFunctional relationship betweenThe specific expression of (A) is as follows:

wherein, Delta I_qαAnd Δ I_qβRespectively, a reactive compensation current DeltaI_qα arm component and β arm component.

4. A method according to any of claims 1-3, characterized in that the active compensation coefficient λ and the negative sequence reactive compensation angleFunctional relationship betweenThe expression of (a) is as follows:

wherein, ^* _ufor given value of unbalance of three-phase voltage, S_LFor loading apparent power, S_dIs the system short circuit capacity.

5. The method according to claim 4, wherein the optimization algorithm adopted in the step 4 is a steepest descent method, a Newton iteration method or a conjugate direction method.

6. Method according to claim 5, characterized in that in step 5 α arm compensation power setpoint power component I_αcpAnd a reactive component I_αcqAnd β arm compensation power setpoint power component I_βcpAnd a reactive component I_βcqRespectively as follows:

$I_{\mathrm{\α}cp}=I_{\mathrm{\β}cp}=\frac{1}{2}{\mathrm{\λ}}_0(I_{\mathrm{\α}Lp}-I_{\mathrm{\β}Lp})$