CN103346570A - Solar photovoltaic power generation dynamic voltage compensator with energy storage function - Google Patents

Abstract

The invention discloses a solar photovoltaic power generation dynamic voltage compensator with an energy storage function. The solar photovoltaic power generation dynamic voltage compensator comprises a solar photovoltaic cell panel, a direct-current boost unit, an inversion unit, an energy storage unit and a transformer. The solar photovoltaic cell panel converts solar energy to electric energy to be output, two input ends of the direct-current boost unit are connected with two output ends of the solar photovoltaic cell panel, two input ends of the inversion unit are connected with two output ends of the direct-current boost unit, the two ends of the energy storage unit are respectively connected to a connecting electric wire between the direct-current boost unit and the inversion unit, a primary coil of the transformer is connected with an output end of the inversion unit, and a secondary coil of the transformer is used for being connected in series to a power grid in series. The solar photovoltaic power generation dynamic voltage compensator with the energy storage function can carry out voltage compensation when the voltage of the power grid drops.

Description

Dynamic voltage compensator with energy storage function for solar photovoltaic power generation

Technical Field

The invention relates to a voltage compensation device, in particular to a voltage compensation device for solar photovoltaic power generation.

Background

With the rapid development of high-tech industry in China, the requirement of users on the power quality level is higher and higher, the power quality problem not only can bring great economic loss to the industry, such as increasing production cost caused by shutdown and restart, damaging sensitive reaction equipment, scrapping semi-finished products, reducing product quality, causing marketing difficulty and damaging company image and good business relation with users, but also can bring harm to equipment of important power utilization departments such as medical treatment and the like, and causing serious production and operation accidents.

Among the power quality problems, voltage sag is one of the most important problems, and the voltage sag not only causes the voltage quality problem of the power system, but also endangers the safe operation of the electric equipment. The voltage drop caused by the faults of the power system, the starting of a large motor, the short circuit of a branch circuit and the like can cause the voltage drop, although the voltage drop time is short, the voltage drop can cause the interruption or the shutdown of the industrial process, and the shutdown time of the industrial process is far longer than the time of the voltage drop accident, so the loss caused by the voltage drop accident is large. The voltage drop is characterized in that the voltage of the power grid suddenly drops to a normal voltage value of 10-90% and lasts for 0.5-50 cycles, the voltage variation amplitude of most of the voltage drop is within 50%, and the duration time is not more than 500 milliseconds.

Some existing devices, such as voltage regulators, do not solve the voltage sag problem, and UPS devices, although they do, are very expensive.

Disclosure of Invention

The invention aims to provide a solar photovoltaic power generation dynamic voltage compensator with an energy storage function, which utilizes solar power generation to compensate voltage drop in a power grid, can convert solar energy into electric energy for storage when the power grid is normal, and outputs voltage to compensate the difference of the power grid voltage when the voltage drop occurs in the power grid, thereby ensuring that the load voltage is not changed and further protecting the load.

In order to achieve the above object, the present invention provides a dynamic voltage compensator for solar photovoltaic power generation having an energy storage function, comprising:

the solar photovoltaic cell panel is used for converting solar energy into electric energy to be output;

two input ends of the direct current boosting unit are connected with two output ends of the solar photovoltaic cell panel;

the two input ends of the inversion unit are connected with the two output ends of the direct current boosting unit;

the two ends of the energy storage unit are respectively connected to the connecting wires between the direct current boosting unit and the inversion unit;

and a transformer, the primary coil of which is connected with the output end of the inversion unit, and the secondary coil of which is connected in series in the power grid so as to be respectively connected with the public end and the load end of the power grid.

In the above dynamic voltage compensator with energy storage function for solar photovoltaic power generation, the capacity S of the inverter unit_r，lSatisfies the following conditions:

$S_{r,l}\≥\sqrt{P_i^2+Q_i^2}$

in the formula, P_iRepresenting the active power, Q, of the output of a dynamic voltage compensator_iRepresenting the reactive power output by the dynamic voltage compensator.

Suppose the grid voltage is

A load voltage of

Then the dynamic voltage compensator according to the present technical solution injects voltage into the power grid

To the network voltage

And load voltage

The relationship between them is shown as follows:

${\stackrel{\‾}{V}}_L={\stackrel{\‾}{V}}_i+{\stackrel{\‾}{E}}_S-{\stackrel{\‾}{Z}}_S{\stackrel{\‾}{I}}_i---\left(1\right)$

wherein,

is the equivalent impedance of the power supply of the power grid,

for the current injected by the dynamic voltage compensator into the grid, "a" represents the vector sign.

If the load is expressed as: (wherein P is_LAnd Q_LActive and reactive power representing load respectively)

${\stackrel{\‾}{S}}_L=P_L+j{Q}_L---\left(2\right)$

If it isRepresents the load current, then

${\stackrel{\‾}{V}}_L\·{\stackrel{\‾}{I}}_L^{*}=P_L+j{Q}_L---\left(3\right)$

${\stackrel{\‾}{V}}_i\·{\stackrel{\‾}{I}}_i^{*}=P_i+j{Q}_i---\left(4\right)$

In the above formula, the first and second carbon atoms are,

is composed of

The value of the conjugate of (a) is,

is composed of

The conjugate value of (c).

The load current and the injection current of the dynamic voltage compensator to the power grid are respectively as follows:

${\stackrel{\‾}{I}}_L=\frac{P_L-j{Q}_L}{{\stackrel{\‾}{V}}_L^{*}}---\left(5\right)$

${\stackrel{\‾}{I}}_i=\frac{P_i-j{Q}_i}{{\stackrel{\‾}{V}}_i^{*}}---\left(6\right)$

because the dynamic voltage compensator is connected in series in the power grid, the current injected into the power grid by the dynamic voltage compensator

Should be matched with the load current

Are equal, i.e.

According to the above two formulas (5) and (6), the compound (I) can be obtained

${\stackrel{\‾}{V}}_i=\frac{P_i+j{Q}_i}{P_L+j{Q}_L}{\stackrel{\‾}{V}}_L---\left(7\right)$

By substituting the above formula (7) into (1), the compound can be obtained

$V_L^2[(P_L-P_i)+j(Q_L-Q_i)]={\stackrel{\‾}{E}}_S{\stackrel{\‾}{V}}_L^{*}(P_L+j{Q}_L)-{\stackrel{\‾}{Z}}_S{S}_L^2---\left(8\right)$

The real part and the imaginary part of the equation (8) are respectively equal to obtain:

$\left.\begin{array}{c}{V}_L^2(P_L-P_i)+(-E_S{P}_L{V}_L\mathrm{Cos\θ}-E_S{Q}_L{V}_L\mathrm{Sin\θ})+R_S{S}_L^2=0\\ V_L^2(Q_L-Q_i)+(-E_S{Q}_L{V}_L\mathrm{Cos\θ}+E_S{P}_L{V}_L\mathrm{Sin\θ})+X_S{S}_L^2=0\end{array}\right\}---\left(9\right)$

wherein, theta is a load voltage phase angle, V_LIs the load voltage amplitude, R_SAnd X_SRespectively, the line equivalent resistance and the reactance.

Formula (9) indicates that: by regulating the active power P output by the dynamic voltage compensator_iAnd reactive power Q_iThe phase angle and amplitude of the load voltage can be kept unchanged.

Further, in the above dynamic voltage compensator with energy storage function for solar photovoltaic power generation, the energy storage unit includes a battery, and the electric energy is stored in the battery.

As an embodiment, the energy storage unit in the present technical solution includes: the battery, the inductance, the IGBT, diode and direct current capacitance, wherein, the anodal projecting pole with the IGBT of battery links to each other, the negative pole of battery links to each other with energy storage unit's the anodal output of voltage, the collecting electrode of IGBT, the negative pole of diode and the one end of inductance link together, the positive pole of diode links to each other with energy storage unit's the anodal output of voltage, the other end of inductance is connected with energy storage unit's the anodal output of voltage, direct current capacitance connects in parallel between energy storage unit's the anodal output of voltage and the negative output of voltage, energy storage unit's the anodal output of voltage and the negative output of voltage connect respectively on the connecting wire between direct current booster unit and.

The energy storage unit in the technical scheme can further comprise a super capacitor, and the super capacitor is used for storing electric energy.

As another embodiment, the energy storage unit in this technical solution includes: super capacitor, inductance, IGBT, diode and direct current capacitance, wherein, super capacitor's positive pole links to each other with IGBT's projecting pole, super capacitor's negative pole links to each other with energy storage unit's the anodal output of voltage, IGBT's collecting electrode, diode's negative pole and the one end of inductance link together, diode's positive pole links to each other with energy storage unit's the anodal output of voltage, the other end of inductance is connected with energy storage unit's the anodal output of voltage, direct current capacitance connects in parallel between energy storage unit's the anodal output of voltage and voltage negative pole output, energy storage unit's the anodal output of voltage and voltage negative pole output are connected respectively on the connecting wire between direct current booster unit and the contravariant.

Further, in the above dynamic voltage compensator for solar photovoltaic power generation having an energy storage function, the dc boost unit includes: the direct current boost unit comprises a direct current boost inductor, an IGBT, a diode and a direct current capacitor, wherein the voltage positive input end of the direct current boost unit is connected with one end of the direct current boost inductor, the voltage negative input end of the direct current boost unit is connected with the collector of the IGBT, the emitter of the IGBT, the other end of the direct current boost inductor and the anode of the diode are connected together, the cathode of the diode is connected with the positive output end of the direct current boost unit, the collector of the IGBT is connected with the negative output end of the direct current boost unit, and the direct current capacitor is connected between the positive output end and the negative output end of the direct current boost unit in.

Further, in the above dynamic voltage compensator with energy storage function for solar photovoltaic power generation, the inverter unit includes three phases, each phase is an H-bridge structure, each H-bridge structure includes four IGBTs, the dc input end of each H-bridge is connected to two output ends of the dc voltage boost unit, and the ac output end of each H-bridge is connected to two ends of the primary coil of the transformer.

Compared with the prior art, the solar photovoltaic power generation dynamic voltage compensator with the energy storage function has the following advantages:

1) solar energy is effectively utilized;

2) the problem of voltage drop of a power grid can be effectively solved, so that the load is protected;

3) when no voltage drop occurs, energy can be stored.

Drawings

Fig. 1 is a schematic structural diagram of a solar photovoltaic power generation dynamic voltage compensator with an energy storage function according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of the voltage compensation principle of the dynamic voltage compensator with energy storage function for solar photovoltaic power generation according to the present invention.

Fig. 3 is a voltage compensation simulation diagram of the solar photovoltaic power generation dynamic voltage compensator with the energy storage function in voltage drop.

Fig. 4 is a simulation diagram of the active power and reactive power output of the dynamic voltage compensator with energy storage function for solar photovoltaic power generation in voltage drop.

Fig. 5 is a topology structure diagram of a DC/DC boost unit in an embodiment of the dynamic voltage compensator for solar photovoltaic power generation with energy storage function according to the present invention.

Fig. 6 is a topology diagram of an energy storage unit of the solar photovoltaic power generation dynamic voltage compensator with energy storage function according to an embodiment of the present invention.

Fig. 7 is a topology structure diagram of an energy storage unit in another embodiment of the dynamic voltage compensator with energy storage function for solar photovoltaic power generation according to the present invention.

Fig. 8 is a topology diagram of one phase of the inversion unit DC/AC in one embodiment of the dynamic voltage compensator with energy storage function for solar photovoltaic power generation according to the present invention.

Detailed Description

The dynamic voltage compensator for solar photovoltaic power generation with energy storage function according to the present invention will be further described with reference to the following specific embodiments and the accompanying drawings, but the description is not to be construed as limiting the invention.

Fig. 1 shows an embodiment of the dynamic voltage compensator for solar photovoltaic power generation with energy storage function according to the present invention.

As shown in fig. 1, the dynamic voltage compensator includes: solar photovoltaic panel PV for converting solar energy into electric energy P_PVOutputting the voltage to a direct current boosting unit DC/DC; two input ends of the DC/DC boosting unit are connected with two output ends of the solar photovoltaic cell panel PV, and two output ends of the DC/DC boosting unit are connected with two input ends of the DC/AC inverting unit; the energy storage unit ESS is connected in parallel between two input ends of the inverter unit DC/AC (namely two output lines of the direct current boosting unit); the output end of the inversion unit DC/AC is connected with the primary coil of the transformer in series, and the secondary coil of the transformer is connected in series in the power grid and is respectively connected with the public end and the load end of the power grid.

It should be noted that, a person skilled in the art should know that the ac transformer has three phases, and therefore, the output end of the inverter unit in this embodiment is connected to the primary coil of the transformer, which means that the output end of each phase in the inverter unit is correspondingly connected to the primary coil of each phase of the transformer.

In FIG. 1, the grid voltage of the grid is

A load voltage of

This exampleThe dynamic voltage compensator in the transformer injects voltage into the power grid

To the network voltage

And load voltageThe relationship between them is shown as follows:

${\stackrel{\‾}{V}}_L={\stackrel{\‾}{V}}_i+{\stackrel{\‾}{E}}_S-{\stackrel{\‾}{Z}}_S{\stackrel{\‾}{I}}_i---\left(1\right)$

wherein,

is the equivalent impedance of the power supply of the power grid,

the current injected into the grid for the dynamic voltage compensator.

If the load is expressed as: (wherein P is_LAnd Q_LActive and reactive power representing load respectively)

${\stackrel{\‾}{S}}_L=P_L+j{Q}_L---\left(2\right)$

If it is

Represents the load current, then

${\stackrel{\‾}{V}}_L\·{\stackrel{\‾}{I}}_L^{*}=P_L+j{Q}_L---\left(3\right)$

${\stackrel{\‾}{V}}_i\·{\stackrel{\‾}{I}}_i^{*}=P_i+j{Q}_i---\left(4\right)$

Wherein,

is composed of

The value of the conjugate of (a) is,

is composed ofThe conjugate value of (1), P_iRepresenting the active power, Q, of the output of a dynamic voltage compensator_iRepresenting the reactive power output by the dynamic voltage compensator.

The load current and the injection current of the dynamic voltage compensator to the power grid are respectively as follows:

${\stackrel{\‾}{I}}_L=\frac{P_L-j{Q}_L}{{\stackrel{\‾}{V}}_L^{*}}---\left(5\right)$

${\stackrel{\‾}{I}}_i=\frac{P_i-j{Q}_i}{{\stackrel{\‾}{V}}_i^{*}}---\left(6\right)$

because the dynamic voltage compensator is connected in series in the power grid, the current injected into the power grid by the dynamic voltage compensator

Should be matched with the load current

Are equal, i.e.

According to the above two formulas (5) and (6), the compound (I) can be obtained

${\stackrel{\‾}{V}}_i=\frac{P_i+j{Q}_i}{P_L+j{Q}_L}{\stackrel{\‾}{V}}_L---\left(7\right)$

By substituting the above formula (7) into (1), the compound can be obtained

$V_L^2[(P_L-P_i)+j(Q_L-Q_i)]={\stackrel{\‾}{E}}_S{\stackrel{\‾}{V}}_L^{*}(P_L+j{Q}_L)-{\stackrel{\‾}{Z}}_S{S}_L^2---\left(8\right)$

The real part and the imaginary part of the equation (8) are respectively equal to obtain:

$\left.\begin{array}{c}{V}_L^2(P_L-P_i)+(-E_S{P}_L{V}_L\mathrm{Cos\θ}-E_S{Q}_L{V}_L\mathrm{Sin\θ})+R_S{S}_L^2=0\\ V_L^2(Q_L-Q_i)+(-E_S{Q}_L{V}_L\mathrm{Cos\θ}+E_S{P}_L{V}_L\mathrm{Sin\θ})+X_S{S}_L^2=0\end{array}\right\}---\left(9\right)$

wherein, theta is a load voltage phase angle, V_LIs the load voltage amplitude, R_SAnd X_SRespectively, the line equivalent resistance and the reactance.

Equation (9) shows that the active power P output by the dynamic voltage compensator is adjusted_iAnd reactive power Q_iThe phase angle and amplitude of the load voltage can be kept unchanged.

In the present embodiment, the capacity S of the inverter unit_r，lSatisfies the following conditions:

fig. 2 shows a schematic diagram of the voltage compensation principle of the dynamic voltage compensator. FIG. 2 is a schematic view ofThe injection voltage is plotted for reference

Common point PCC bus voltage in fig. 1

Load voltage

Load current

The relationship between the equal vectors, as can be seen from fig. 2, depends on the grid voltage

The dynamic voltage compensator of the invention injects voltage into the power gridObtain the voltage required by the load

FIG. 3 is a simulation diagram of a grid voltage sag, when the grid voltage sag is caused by a grid fault, the dynamic voltage compensator of the present invention injects the grid voltage

Make the amplitude and phase angle of the load voltage not affected by the grid fault, haveDuring solar energy, the voltage of the direct current bus is not affected, and when the solar energy is insufficient or the power grid breaks down at night and needs to protect the load, the energy storage of the energy storage unit is needed.

FIG. 4 shows the output active power P of the dynamic voltage compensator according to the invention in case of a voltage drop_iAnd reactive power Q_iThe waveform of (2).

Fig. 5 is a topological structure diagram showing a DC/DC boost unit DC/DC of the solar photovoltaic power generation dynamic voltage compensator with energy storage function according to an embodiment of the present invention.

As shown in fig. 5, in this embodiment, the dc boost unit includes: the direct current boost unit comprises a direct current boost inductor, an IGBT, a diode and a direct current capacitor, wherein the voltage positive input end of the direct current boost unit is connected with one end of the direct current boost inductor, the voltage negative input end of the direct current boost unit is connected with the collector of the IGBT, the emitter of the IGBT, the other end of the direct current boost inductor and the anode of the diode are connected together, the cathode of the diode is connected with the positive output end of the direct current boost unit, the collector of the IGBT is connected with the negative output end of the direct current boost unit, and the direct current capacitor is connected between the positive output end and the negative output end of the direct current boost unit.

Fig. 6 shows a topology diagram of an energy storage unit of the dynamic voltage compensator with energy storage function for solar photovoltaic power generation according to an embodiment of the invention.

As shown in fig. 6, in this embodiment, the energy storage unit includes: the battery, the inductance, the IGBT, diode and direct current capacitance, the anodal projecting pole with the IGBT of battery links to each other, the negative pole of battery links to each other with energy storage unit's the anodal output of voltage, the collecting electrode of IGBT, the negative pole of diode and the one end of inductance link together, the positive pole of diode links to each other with energy storage unit's the voltage negative pole output, the other end of inductance is connected with energy storage unit's the anodal output of voltage, direct current capacitance connects in parallel between energy storage unit's the anodal output of voltage and the voltage negative pole output, energy storage unit's the anodal output of voltage and voltage negative pole output connect respectively on the connecting wire between direct current unit and the contravariant.

Fig. 7 shows a topology diagram of an energy storage unit in another embodiment of the dynamic voltage compensator with energy storage function for solar photovoltaic power generation according to the present invention. As shown in fig. 7, in this embodiment, the structure of the energy storage unit is not greatly different from that shown in fig. 6, except that the battery is replaced with a super capacitor.

Fig. 8 shows a topology diagram of one phase of the inversion unit DC/AC in one embodiment of the dynamic voltage compensator with energy storage function for solar photovoltaic power generation according to the present invention. As shown in fig. 8, each phase of the inverter unit is an H-bridge structure formed by four IGBTs.

It should be noted that the above-mentioned embodiments are only specific embodiments of the present invention. It is apparent that the present invention is not limited to the above embodiments and similar changes or modifications can be easily made by those skilled in the art from the disclosure of the present invention and shall fall within the scope of the present invention.

Claims (8)

1. A dynamic voltage compensator with energy storage function for solar photovoltaic power generation comprises:

the solar photovoltaic cell panel is used for converting solar energy into electric energy to be output;

two input ends of the direct current boosting unit are connected with two output ends of the solar photovoltaic cell panel;

the two input ends of the inversion unit are connected with the two output ends of the direct current boosting unit;

the two ends of the energy storage unit are respectively connected to the connecting wires between the direct current boosting unit and the inversion unit;

and a primary coil of the transformer is connected with the output end of the inversion unit, and a secondary coil of the transformer is connected in series in a power grid.

2. The dynamic voltage compensator of claim 1, wherein the capacity S of the inverting unit_r，lSatisfies the following conditions:

$S_{r,l}\≥\sqrt{P_i^2+Q_i^2}$

in the formula, P_iRepresenting the active power, Q, of the output of a dynamic voltage compensator_iRepresenting the reactive power output by the dynamic voltage compensator.

3. The dynamic voltage compensator of claim 1, wherein the energy storage unit comprises a battery.

4. The dynamic voltage compensator of claim 3, wherein the energy storage unit further comprises: inductance, IGBT, diode and direct current capacitance, wherein, the positive pole of battery links to each other with IGBT's projecting pole, and battery's negative pole links to each other with energy storage unit's the anodal output of voltage, and IGBT's collecting electrode, diode's negative pole and the one end of inductance link together, and diode's positive pole links to each other with energy storage unit's the anodal output of voltage, and the other end of inductance is connected with energy storage unit's the anodal output of voltage, and direct current capacitance connects in parallel between energy storage unit's the anodal output of voltage and the output of voltage negative pole, energy storage unit's the anodal output of voltage and the output of voltage negative pole are connected respectively on the connecting wire between.

5. The dynamic voltage compensator of claim 1, wherein the energy storage unit comprises a super capacitor.

6. The dynamic voltage compensator of claim 5, wherein the energy storage unit further comprises: the direct current power supply comprises an inductor, an IGBT, a diode and a direct current capacitor, wherein the anode of a super capacitor is connected with the emitting electrode of the IGBT, the cathode of the super capacitor is connected with the voltage anode output end of an energy storage unit, the collector of the IGBT, the cathode of the diode and one end of the inductor are connected together, the anode of the diode is connected with the voltage cathode output end of the energy storage unit, the other end of the inductor is connected with the voltage anode output end of the energy storage unit, the direct current capacitor is connected between the voltage anode output end and the voltage cathode output end of the energy storage unit in parallel, and the voltage anode output end and the voltage cathode output end of the energy storage unit are respectively connected onto a connecting wire between the direct.

7. The dynamic voltage compensator of claim 1, wherein the dc boost unit comprises: the direct current boost unit comprises a direct current boost inductor, an IGBT, a diode and a direct current capacitor, wherein the voltage positive input end of the direct current boost unit is connected with one end of the direct current boost inductor, the voltage negative input end of the direct current boost unit is connected with the collector of the IGBT, the emitter of the IGBT, the other end of the direct current boost inductor and the anode of the diode are connected together, the cathode of the diode is connected with the positive output end of the direct current boost unit, the collector of the IGBT is connected with the negative output end of the direct current boost unit, and the direct current capacitor is connected between the positive output end and the negative output end of the direct current boost unit in.

8. The dynamic voltage compensator of claim 1, wherein the inverter unit comprises three phases, each phase is an H-bridge structure, each H-bridge structure comprises four IGBTs, the dc input terminals of each H-bridge are connected to two output terminals of the dc boost unit, and the ac output terminals of each H-bridge are connected to two ends of the primary coil of the transformer.

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