CN201797326U - Multifunctional power network simulator - Google Patents

Abstract

The utility model discloses a multifunctional power network simulator. The simulator is characterized in that: the main circuit structure of the simulator is provided with three independent back-to-back systems, wherein an input side is provided with a three-phase pulse-width modulation (PWM) rectifier; an output side is provided with a single-phase PWM inverter with a controllable output voltage; a mains supply is isolated by a three-phase transformer and connected to the three-phase PWM rectifier; and the single-phase PWM inverter outputs voltages through an inductance-capacitance (LC) filter. Taken as a power network voltage generating device in a distributed power generation synchronization research, the simulator can be used for simulating the output of standard power network voltage and the like, provides a power network environment as true as possible for the distributed power generation synchronization research and meets the requirements of a distributed power generation research.

Description

Multi-functional electrical network simulator

Technical field

The utility model relates to a kind of line voltage generating means, and it is a kind of in the distributed research of generating electricity by way of merging two or more grid systems more specifically to say so, and the generating means of power grid environment is provided for system.

Background technology

Being incorporated into the power networks to be known as by the many energy in the world and electric power expert of grid-connected power generation system such as solar energy photovoltaic generator, wind power generation plant can be reduced investment outlay, cut down the consumption of energy, improves power system reliability and flexibility, is the important directions of 21 century power industry development.In order to ensure the safety of system's setter and the reliability service of electrical network, distributed generation system must satisfy the specification requirement of being incorporated into the power networks, along with increasing distributed generation system inserts electrical network, various countries' grid company has all proposed strict requirement to being incorporated into the power networks of distributed power generation.

Because various malfunctions such as electrical network may occur that voltage magnitude falls, electric voltage frequency skew, imbalance of three-phase voltage and harmonic voltage distortion, therefore in the process of distributed power generation research, the service behaviour under these malfunctions that the consideration electrical network may occur and research system nonserviceable is very important.

The voltage that electrical network provides is the standard sine voltage of low harmonic wave, and electric network fault has contingency and uncontrollability, when the research of distributed power generation and system testing, only can't simulate various malfunctions by electrical network itself.Therefore, need simulate the failure condition of electrical network by some special equipment.

Low-voltage for wind power generation is passed through test, existing special realization voltage falling generator VSG, i.e. Voltage Sag Generator.Specifically comprise:, be to realize electric voltage dropping by parallel connection in main circuit or series resistance/reactance based on the VSG that the impedance form realizes; Based on the VSG of transformer, be that the no-load voltage ratio by transformer realizes falling of line voltage; Based on the VSG of Technics of Power Electronic Conversion, utilize falling of realization voltages such as alternating electromotive force control circuit, ac/ac frequency converter and friendship orthogonal converter.But this analogue means function is single relatively, can't simulate various electric network faults, therefore can not satisfy the test request of distributed generation system fully.

The utility model content

The utility model is for avoiding above-mentioned existing in prior technology weak point, a kind of multi-functional electrical network simulator is provided, as distributed power generation be incorporated into the power networks research in the line voltage generating means, simulation outputting standard line voltage, failure conditions such as simulation electrical network voltage magnitude falls, the frequency shift (FS) of line voltage frequency, imbalance of three-phase voltage and voltage voltage distortion, for being incorporated into the power networks to study, distributed generation system provides real as far as possible power grid environment, to satisfy the demand of distributed power generation research.

The utility model is following technology technical scheme for the technical solution problem adopts:

The characteristics of the multi-functional electrical network simulator of the utility model are that the main circuit structure of described simulator is: three separate back-to-back system (CCC-0) are set, the version of described separate back-to-back system (CCC-0) is: input side is a Three-Phase PWM Rectifier, and outlet side is set to the controlled single-phase PWM inverter of output voltage; Civil power inserts Three-Phase PWM Rectifier after three-phase transformer is isolated; Described single-phase PWM inverter is exported through the LC filter.

The control method of the multi-functional electrical network simulator of the utility model is the difference according to output voltage, and the mode of operation of simulator is divided into first-harmonic mode of operation and harmonic wave mode of operation; The line voltage of outputting standard under described first-harmonic mode of operation, and simulation electrical network voltage magnitude falls, the electric network fault of line voltage frequency shift (FS), imbalance of three-phase voltage; Control mode under the described first-harmonic workman pattern is two closed-loop controls of exporting control signal with output voltage as the outer shroud feedback variable, with the electric current of inductance in the described LC filter as interior ring feedback variable, to the PWM inverter; Simulation Voltage Harmonic distortion fault under described harmonic operation pattern; Control mode under the described harmonic operation pattern is that the voltage of 50Hz fundamental frequency is carried out the effective value FEEDBACK CONTROL, higher harmonic voltage is carried out open loop control.

Compared with the prior art, the utility model beneficial effect is embodied in:

1, the utility model main circuit is made up of three single-phase subsystems, and three single phase systems can realize can simulating electrical network synchronously by communication between the three-phase respectively as the single phase system operation, and flexible working mode is easy to modularization.

2, the utility model can be divided into first-harmonic mode of operation and harmonic wave mode of operation with simulator according to the difference of output voltage.Two closed-loop controls are adopted in system's control under the first-harmonic mode of operation; System's control has been adopted the voltage of 50Hz fundamental frequency is carried out the effective value FEEDBACK CONTROL, higher harmonic voltage is carried out the control mode that open loop is controlled under the harmonic operation pattern.This control mode has guaranteed the line voltage of the exportable standard of simulator and has accurately reappeared the electric network fault that distorts such as electric network electric voltage drop, electric voltage frequency skew, three-phase imbalance and harmonic voltage.

Description of drawings

Fig. 1 is the utility model simulator main circuit diagram.

Fig. 2 is the utility model first-harmonic modular system control block diagram.

Fig. 3 is the utility model harmonic mode system control block diagram.

Embodiment

Referring to Fig. 1, in the present embodiment, main circuit adopts three single phase systems to simulate A, B, the C three-phase of electrical network respectively, and each single phase system is back to back structure, makes that simulator can four quadrant running, realizes the feedback of energy to electrical network G.The voltage that electrical network G provides is follow-up rectification link power supply after three-phase transformer is isolated, the rectification link adopts Three-Phase PWM Rectifier M1, and Three-Phase PWM Rectifier M1 provides stable DC side and can realize the energy feedback for late-class circuit.Compare the single-phase PWM rectifier, three-phase rectifier can effectively reduce the secondary ripple of DC side, and dc voltage is more steady, and the three-phase rectifier AC side powered by three phase mains, and load capacity is bigger, more is applicable to powerful occasion.Three-Phase PWM Rectifier M1 output dc voltage carries out voltage stabilizing through capacitor C d; Direct voltage is the output AC voltage signal after single-phase PWM inverter inversion output PWM voltage, PWM voltage are by the LC filter filtering; In the present embodiment, the inversion link adopts PWM inverter M2, simulate three-phase output respectively with three single-phase PWM inverters, and DC side is separate, is provided respectively by three PWM rectifiers.

Control circuit adopts the numerical control system based on DSP in the present embodiment, and main circuit voltage, current parameters form closed-loop control system by transducer and numerical control system.According to the difference of output voltage, simulator is divided into first-harmonic mode of operation and harmonic wave mode of operation.The line voltage of outputting standard under the first-harmonic mode of operation, and simulation electrical network voltage magnitude falls, the electric network fault of line voltage frequency shift (FS), imbalance of three-phase voltage, simulation Voltage Harmonic distortion fault under the harmonic operation pattern.

Referring to Fig. 2, two closed-loop controls are adopted in system's control under the first-harmonic mode of operation, and output voltage outer ring can be improved the quality of waveform, and ring can be accelerated the inverter dynamic response in the inductive current, makes system's nonlinear load adaptive capacity strengthen.Inverter output voltage obtains output voltage signal u behind sensor measurement _oDeliver to the DSP control system, with given voltage signal u _o ^*Compare, error is regulated through pi regulator, and output is given as interior ring control.Electric current on the inductance L is through measuring inductor current signal I _L, comparing with the given signal of interior ring, error is regulated through proportional controller, and regulator output signal is used for the break-make of control inverter switch.

Referring to Fig. 3, system's control has been adopted the voltage of 50Hz fundamental frequency is carried out the effective value FEEDBACK CONTROL, higher harmonic voltage is carried out the control mode that open loop is controlled under the harmonic operation pattern, make the effective value of output voltage keep stable, harmonic wave is given to be equivalent to the open loop stack, can not suppressed by closed loop.Inverter output voltage obtains output voltage signal u behind sensor measurement _o, through filtering link G _Filter(s) carry out filtering after, filtered signal carries out the effective value U that effective value RMS computing obtains output voltage _o, with given voltage effective value U _o ^*Compare, error is regulated through pi regulator.The given u of harmonic voltage _n ^*With the output signal stack of effective value FEEDBACK CONTROL, the total signal that obtains is used for the break-make of control inverter switch.

Under the harmonic operation pattern, main circuit can have amplification to the amplitude of higher harmonic voltage, in order to suppress the influence of main circuit to the output higher harmonic voltage, in higher harmonic voltage open loop control, increased compensation tache to the higher harmonic voltage amplitude, in the compensation tache, penalty coefficient is relevant with the frequency of filter parameter and harmonic voltage, G _K(s) | _{S=j ω}=1-LC ω ²L is the inductance value in the filter, and C is the capacitance in the filter, and ω is the frequency of higher harmonic voltage.

Under the harmonic operation pattern, output voltage is that 50Hz fundamental voltage and higher harmonic voltage are formed by stacking, so output voltage amplitude can increase to some extent, thereby needs bigger DC voltage control gain.Present embodiment is a foundation with the relevant harmonic standard of IEC, calculates according to lagrange's method of multipliers, the direct voltage that Three-Phase PWM Rectifier provides has been made requirement, when outlet side fundamental voltage effective value is U ₁, the direct voltage voltage U that Three-Phase PWM Rectifier provides _DcNeed to satisfy

Guarantee that with this transducer gain can export any harmonic wave.

Utilize lagrange's method of multipliers design dc voltage principle

1.1 electrical network simulator harmonic standard

(1) the electrical network simulator can be simulated any harmonic wave in 40 times, based on odd harmonic

(2) harmonic wave total content THDuTHDu≤14%

1.2 case study

Regulation according in 1.1 makes the following assumptions:

(1) only consider odd harmonic:

6k-3：3，9，15，21，27，33，39

6k-1：5，11，17，23，29，35

6k+1：7，13，19，25，31，37

Totally 19 kinds of harmonic waves

(2) harmonic content is according to the highest design, and the effective value of establishing each component of degree n n is U ₁, U _6k-3, U _6k-1, U _6k+1

$\mathrm{THDu}=\frac{\sqrt{\underset{k\&Element;(\mathrm{1,2},...,7)}{\mathrm{\&Sigma;}}{U}_{6k-3}^2+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k-1}^2+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k+1}^2}}{{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1}=14\%$ That is:

$\underset{k\&Element;(\mathrm{1,2}...,7)}{\mathrm{\&Sigma;}}{U}_{6k-3}^2+\underset{k\&Element;(\mathrm{1,2}...,6)}{\mathrm{\&Sigma;}}{U}_{6k-1}^2+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k+1}^2=0.0196{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1^2---\left(1\right)$

(3) output of electrical network simulator simulation harmonic wave

1.3 the desirable output waveform analysis of electrical network simulator

By formula (2) as can be seen, when each harmonic content amplitude and angle not simultaneously, the simulator output waveform will be different.

From the angle of converter alternating current-direct current modulation, the needed DC side modulation voltage of the output waveform u of different amplitudes is different.Need to obtain the maximum of u for this reason.

1.3.1 each harmonic is with respect to the influence to amplitude of the angle of first-harmonic

According to the requirement in 2.1, each harmonic can superpose arbitrarily, so the amplitude of each harmonic and angle are variablees independently in the formula (2).

No matter the amplitude size of each harmonic is how, can draw as drawing a conclusion:

When each harmonic is obtained peak value simultaneously, the amplitude maximum of u, that is:

$\mathrm{\&omega;t}=\frac{\mathrm{\&pi;}}{2}$

Abbreviation gets,

$u_{\max }^{\&prime;}=\sqrt{2}({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1+\underset{k\&Element;(\mathrm{1,2},...,7)}{\mathrm{\&Sigma;}}{U}_{6k-3}+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k-1}+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k+1})---\left(3\right)$

Proof: adopt reduction to absurdity, suppose

So

$\sqrt{2}({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1+\underset{k\&Element;(\mathrm{1,2},...,7)}{\mathrm{\&Sigma;}}{U}_{6k-3}+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k-1}+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k+1})<\sqrt{2}({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1\sin \mathrm{\&omega;t}+)$

$<0$

Because

Therefore, suppose to be false.

1.3.2 simulator output maximum

Through above derivation, simulator output maximum becomes the extreme-value problem of the function of many variables, promptly

$u_{\max }^{\&prime;}=\sqrt{2}({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1+\underset{k\&Element;(\mathrm{1,2},...,7)}{\mathrm{\&Sigma;}}{U}_{6k-3}+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k-1}+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k+1}),$

When

Extreme-value problem.

Order

According to lagrange's method of multipliers [1], can get

$=\sqrt{2}({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1+\underset{k\&Element;(\mathrm{1,2},...,7)}{\mathrm{\&Sigma;}}{U}_{6k-3}+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k-1}+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k+1})+$

$\mathrm{\&lambda;}(\underset{k\&Element;(\mathrm{1,2},...,7)}{\mathrm{\&Sigma;}}{U}_{6k-3}^2+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k-1}^2+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k+1}^2-0.0196{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1^2)$

$L_{6k-3}=\sqrt{2}+2\mathrm{\&lambda;}{U}_{6k-3}=0,k\&Element;(\mathrm{1,2},...,7)$

$L_{6k-1}=\sqrt{2}+2\mathrm{\&lambda;}{U}_{6k-1}=0,k\&Element;(\mathrm{1,2},...,7)$

$L_{6k+1}=\sqrt{2}+2\mathrm{\&lambda;}{U}_{6k+1}=0,k\&Element;(\mathrm{1,2},...,7)$

$\underset{k\&Element;(\mathrm{1,2},...,7)}{\mathrm{\&Sigma;}}{U}_{6k-3}^2+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k-1}^2+\underset{k\&Element;(\mathrm{1,2},...,6)}{\mathrm{\&Sigma;}}{U}_{6k+1}^2=0.0196{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1^2$

Therefore, $\underset{k\&Element;(\mathrm{1,2},...,7)}{U_{6k-3}}=\underset{k\&Element;(\mathrm{1,2},...,6)}{U_{6k-1}}=\underset{k\&Element;(\mathrm{1,2},...,6)}{U_{6k+1}}=\frac{1}{\sqrt{k^{\&prime;}}}0.14{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1$

Then, $u_{\max }=\sqrt{2}({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1+0.14\sqrt{k^{\&prime;}}{U}_1)$

Conclusion

When k '=19, simulator can send 3～39 times odd harmonic, according to above-mentioned analysis,

When each harmonic satisfies:

(1) amplitude equates

$\mathrm{\&omega;t}=\frac{\mathrm{\&pi;}}{2}$

(2) phase place obtains sinusoidal wave peak value simultaneously

Simulator output peak value maximum.

$u_{\max }=\sqrt{2}({\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1+0.14\sqrt{k^{\&prime;}}{U}_1)=1.61\sqrt{2}{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1$

For single-phase inverter, converter dc voltage U _Dc〉=u _Max

Promptly $U_{\mathrm{dc}}\&GreaterEqual;1.61\sqrt{2}{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000287427200021.png,HSA00000287427200022.png"\; state="\{\{state\}\}">U</figure-callout>}}_1.$

Claims (1)

1. multi-functional electrical network simulator, the main circuit structure that it is characterized in that described simulator is: three separate back-to-back system (CCC-0) are set, the version of described separate back-to-back system (CCC-0) is: input side is a Three-Phase PWM Rectifier, and outlet side is set to the controlled single-phase PWM inverter of output voltage; Civil power inserts Three-Phase PWM Rectifier after three-phase transformer is isolated; Described single-phase PWM inverter is exported through the LC filter.

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