CN114583684A

CN114583684A - Power generation, power transformation and grid connection method for clean energy field

Info

Publication number: CN114583684A
Application number: CN202210229411.2A
Authority: CN
Inventors: 张长增
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-03-09
Filing date: 2022-03-09
Publication date: 2022-06-03

Abstract

The invention discloses a power generation, power transformation and grid connection method of a clean energy field, which realizes the centralized and unified grid connection and remote power transmission of energy sources such as wind energy, solar energy, tidal energy and the like, realizes the conversion from mechanical energy of a fan to electric energy by a single-phase direct current generator, or realizes the conversion from light energy to electric energy by a solar battery pack, then converges to the same medium-high voltage buffer storage battery in a central converter substation, and converts and boosts the current into ultrahigh voltage direct current to be transmitted after the buffering and the smoothing of the buffer storage battery by an inverter. The method for collecting the unstable energy to a specific buffer area, saving the electric energy quality control in the power generation link of the generator position, and centralizing inversion and boosting to standard voltage grid connection realizes the low cost and the maximum efficiency of transmission of large-scale energy production.

Description

Power generation, power transformation and grid connection method for clean energy field

Technical Field

The invention discloses a power generation, power transformation and grid connection method for a clean energy field, belongs to the field of clean renewable energy power generation, and also belongs to the field of electromechanical equipment or machinery manufacturing.

Background

Improving the earth's atmospheric environment, reducing greenhouse gas emissions, advocating the use of wind and solar energy and limiting the use of fossil energy is the mainstream of contemporary energy technology. Therefore, the collection and utilization of natural resources such as wind power generation, solar power generation, tidal power generation and the like have practical significance and economic benefits.

However, wind power, solar energy and tidal energy are unstable energy sources and sometimes have complementarity, and a more economical method is needed for surfing the internet or storing the energy to mine and convert extremely discrete energy into electric energy and remotely consume or store the electric energy. The existing mining and utilizing technology is basically in the original discrete local area network application state, the wind driven generator also adopts three-phase control and requires and is aligned synchronously, the generator motion control and the power waveform control are quite complex, each generator set outputs 690V low voltage electricity, a 35kV transformer is arranged at the local position for boosting, a wind power plant is provided with countless small-capacity three-phase boosting transformers, then the three-phase electricity is converged to a central hub station for continuously boosting to an extra-high voltage, and therefore multiple power transformation, multiple loss, complex configuration, repeated construction, mutual influence and the like are not suitable for the economy of large-scale mining and utilization.

In the prior art, the largest waste is that the unnecessary high-quality three-phase electric energy is produced at the local position of the wind driven generator at high cost, and finally, the three-phase electric energy is converted into single-phase direct-current extra-high voltage output, so that the waveform, the phase, the frequency and the like of the voltage are not strictly managed in the middle process, but the traditional technical standard and the supply chain cause too much useless payment in the middle.

Disclosure of Invention

The term concept herein:

buffering the storage battery: a device capable of buffering voltage peaks and storing a certain amount of electricity.

Medium-high pressure: 1 kV-10 kV.

Ultra-high voltage: 100 kV-1000 kV.

The invention provides three basic points in the whole technical scheme of power generation, power transformation and power transmission, can improve the defects of the prior art and realize the economical efficiency of electric energy production and use.

Firstly, the conversion from mechanical energy to electric energy of wind power, tidal power resources and the like realized by a rotating motor through electromagnetic induction is realized, namely a generator is completed by adopting a relatively high-voltage single-phase motor, the single-phase pulsating direct current with relatively constant voltage is output after bridge rectification, and correspondingly changed current is output corresponding to different generating power at different wind speeds; however, the solar battery pack is different in that the solar battery pack outputs direct current but has low voltage, and the direct current needs to be integrated in series and parallel connection and generally needs to be inverted into single-phase medium-high voltage direct current;

secondly, configuring a buffer storage battery with a certain capacity in the whole energy field system, buffering pulsating direct current electric energy with inconstant current from all power generation units in the region, and collecting and storing the pulsating direct current electric energy, so that the electric energy is unified into a buffer storage battery voltage source with relatively constant voltage;

thirdly, an inversion and boosting device is arranged in a central load transformer substation of the whole energy field, and standard three-phase extra-high voltage alternating current or extra-high voltage direct current is obtained after the inversion of the single buffer storage battery is completed, so that the grid-connected output of electric power is realized.

Since the buffer storage battery performs the functions of buffering and smoothing, the capacity thereof does not need to be large, such as to reach the second-order capacity of the total load power, such as the level of 1s-10s, or more. Chemical batteries or super capacitors can be used as buffer storage batteries, or a combination of the chemical batteries and the super capacitors is adopted, and the combination scheme of the chemical batteries and the super capacitors is preferred.

Such buffer storage batteries and large-scale energy storage are not a concept. Even if large-scale energy storage is carried out, local energy storage in a local energy field is not advocated, and the energy storage are carried out in a wider area and at a consumption end, for example, a million KW pumped storage power station is arranged in a regional concept of 10 ten thousand square kilometers for peak regulation and dispatching of a large power grid, so that large-scale economic benefits are achieved, and the garbage electricity can be really changed into useful green electricity.

Thus, the entire energy farm primary energy source includes, but is not limited to, wind power and photovoltaic power generation.

Due to the great fluctuation of the primary energy, if the primary energy cannot be well scheduled for use, the generated electricity is 'garbage electricity'. Therefore, the energy field needs to have a transformer capable of reducing the current output, i.e., reducing the power output, under the premise of stabilizing the voltage, below the maximum power (or rated power). The output is expected to be continuous power adjustment and is not suitable for frequent switching or cutting of the high-voltage relay. The instantaneous power generation total power of the whole energy field can be identified through the voltage of the buffer storage battery, and the extra-high voltage output power of the clean energy field is controlled through the correlation between the inverter group control of the central hub station and the voltage change of the buffer storage battery. Of course, this is a power regulation strategy limited to the minute level. The power regulation at the small level needs to be coordinated with the thermal power energy of a large power grid. In addition, a remote pumped storage power station is the best interactive compensation mode.

Description of the figures and examples

Fig. 1 is an electrical schematic of the integrated architecture of the entire energy field.

In the figure, 1 is a wind turbine unit, 2 is a photovoltaic unit, 3 is a buffer storage battery, 4 is a boosting inversion group, Cpv1 is a capacitor group 1, Cpv2 is a capacitor group 2, and CR is a battery group.

FIG. 1 illustrates a case system of 10kV to + -400 kV.

Fig. 1 illustrates a wind turbine unit 1 and a photovoltaic unit 2, and in practice, a plurality of wind turbine units 1 and photovoltaic units 2 are converged on a 10kV bus, and then are charged and buffered to a buffer storage battery 3, and then are converted to ± 400kV through a boost inverter group 4 and sent out.

The wind turbine unit 1 is provided with a bridge rectifier circuit and directly outputs 10kV high-frequency single-phase pulsating direct current to converge to the buffer storage battery 3. The wind turbine generator is not connected with a three-phase step-up transformer used in the prior art (generally, 690V three-phase power is converted into 10kV or 35 kV).

The photovoltaic unit 2 is provided with a DC-DC booster circuit, and outputs 10kV high-frequency single-phase pulsating direct current after conversion to converge to the buffer storage battery 3.

In fig. 1, the buffer storage battery 3 has a structure that the capacities of the capacitors Cpv1 and Cpv2 are equal, the capacitors Cpv1 and Cpv2 are connected in series and then connected in parallel with the battery CR, a center tap is led out between the capacitor groups Cpv1 and Cpv2, and a three-wire two-level output is formed to the "DC-AC-DC" boost inverter group 4. The boost inverter group 4 may then be,inverter junction derived from H-bridge topology Structure of the organizationOrInverter architecture derived from NPC topology. The "DC-AC-DC" boost inverter group 4 may be a boost inverter with transformer isolation, or may be a non-isolated boost inverter without transformer. The addition of the battery CR being a function of the electricity of the batteryThe constant voltage source characteristic with relatively constant voltage compensates the defect that the capacitor has reduced capacity, i.e. voltage.

In fig. 1, the wind turbine unit 1 and the photovoltaic unit 2 are both injected into the buffer storage battery 3 after being isolated by diodes.

In fig. 1, a wind turbine unit 1 and a photovoltaic unit 2 are energy collection units distributed and configured in an energy field area, and are far away from each other and from a central load substation, and a buffer storage battery 3 and a boost inversion group 4 are devices configured together and are located in the central load substation.

The direct current with the same voltage grade is required to be sent into the buffer storage battery 3 by the wind turbine unit 1 and the photovoltaic unit 2, but the voltage (or current) attributes of the extra-high voltage direct current output by the wind turbine unit 1 and the photovoltaic unit 2 do not have any correlation except the voltage grade, namely, the constraint conditions of frequency, waveform, phase number, phase, power factor, synchronism and the like do not exist when the three are electrically connected. In other words, in the power generation link and the power collection link in the energy field, quality factors such as frequency, waveform, phase number, phase, power factor and the like of each power generation unit do not need to be considered and controlled to be matched with other parts, so that the regulation and control complexity of the power production process is greatly simplified, and the production cost is greatly saved.

Example one

The wind power generation set generates 1kV single-phase pulsating direct current which is sent to a central buffer storage battery of a local energy field, photovoltaic power generation is also adjusted to 1kV output direct current which is also sent to the central buffer storage battery of the local energy field, then an inversion boosting system inverts and boosts a 1kV power supply of the buffer storage battery into standard 35kV three-phase alternating current which is synchronous with a large power grid, the inversion boosting device comprises N sets of transformers, the capacities of the N sets of transformers are P, the N sets of 35kV three-phase alternating current are converged to a main transformer, the power of the main transformer is NP, and the voltage of the main transformer is boosted to 220kV through a three-phase transformer without inversion. And then incorporated into the backbone network through the relay. The total capacity of the energy field can reach the level of more than 100MW or even 1 GW. By doing so, it is good for power scheduling, and N35 kV three-phase becomes can be switched or cut one by one. Reducing the access impact on the backbone network.

This application is the power delivery mode through a three-phase extra-high voltage backbone network. The middle 35kv transformer has an isolation function.

Example two

The wind turbine directly generates 10kV single-phase pulsating direct current, the direct current is sent to a central buffer storage battery of the energy field, no three-phase step-up transformer is connected to the position of the wind turbine, the photovoltaic power generation voltage is relatively safe voltage, for example 100V, then the voltage is increased to 10kV through direct-alternating-direct, the voltage is single-phase variable current and direct current is output, and the direct current is also sent to a 10 kV-level buffer storage battery of the load center of the energy field. Then, the inversion system inverts the 10kV power supply direct current of the central buffer storage battery into a standard three-phase 220kV extra-high voltage synchronous with a large power grid, and then the three-phase 220kV extra-high voltage is merged into a backbone network through a relay. Or the direct current of the 10kV buffer storage battery at the load center of the energy field is inverted into a certain standard direct current extra-high voltage output of +/-100 kV to +/-1000 kV through a direct-alternating-direct inversion system. The total capacity of the energy field can reach more than 100MW or even 1GW level.

Obviously, the scheme is the most economic and valuable route from the regularization of discrete power generation units to the single-phase direct current 10kV buffer storage battery → +/-100 kV- +/-1000 kV direct current extra-high voltage output, and all links for controlling the quality of electric energy, including voltage, frequency, phase number, phase, waveform, power factor, three-phase imbalance control and the like, are omitted in the period, so that a large amount of power generation cost is saved. Therefore, the requirements on the wind driven generator are greatly reduced, only one single-phase high-voltage direct current generator is needed, pulsating direct current needing filtering is not needed, and the possibility is brought to the use of high-frequency power generation and power transformation technologies, for example, electromagnetic induction power generation or power transformation with the working frequency in the range of 1kHz-50kHz is used, and the size and the cost of the single-phase high-frequency high-voltage direct current generator are extremely low.

The invention has the advantages that, for example, in a coastal region, because the wind turbine in the intertidal zone and the wind turbine in the offshore zone are close to the central area of the electric load, a large amount of wind energy resources can be collected, and the offshore solar power generation also has the unique advantages that the photovoltaic power generation efficiency is high because the sand pollution is small, and the tidal power generation of sea waves is realized. But these resources have discrete and unstable characteristics. However, the three resources are all available in the area, and wind-solar complementation is also provided under certain conditions, so that the system is located in the same area, is intensively developed and shares a grid-connected power transmission and transformation system, compared with the prior art, a large number of intermediate transformers are saved, a large amount of investment can be saved, the power quality of a generator is not high, the fluctuation, the pulse frequency and the waveform of voltage are not high, after the buffer storage battery is injected through a diode, different machine position power supplies are isolated and do not interfere with each other, the motion control link of intermediate power generation equipment is greatly simplified, and the quality of output extra-high voltage power supply can be greatly improved. And the requirement of the power grid for low voltage ride through is easily met.

The above discussion is illustrated with reference to an energy farm for offshore power generation, and in fact this method is universal and can be used in land-based power systems and even share transmission lines with relatively stable hydroelectric power stations. For example, in a wind farm in the three north area of China, extra-high voltage direct current +/-1000 kV can be transmitted to the east area for use in a long distance. For example, the wind power of Dabancheng, Xinjiang and Gansu spring can be transmitted to the east China for consumption or pumped storage and energy storage through a +/-1000 kV line by adopting the method.

The foregoing is merely an illustration of specific embodiments of the invention and is not to be construed as limiting the scope of the invention.

Claims

1. A method for generating, transforming and connecting a grid of a clean energy field is characterized in that a system comprises a plurality of distributed generating units, corresponding primary energy sources are one or more of unstable natural resources such as solar energy, wind energy or tidal energy, and the like, quality attributes (including waveform, frequency, phase number, phase, power factor, synchronism and the like) of respective voltage or current between each generating unit and a backbone network are not related except voltage levels; firstly, the output form of each power generation unit is single-phase direct current with invariable power but the same voltage level, and different kinds of energy are set to the same medium-high voltage direct current voltage level; secondly, in a central load transformer substation of an energy field, a buffer storage battery with certain capacity is used for converging and buffering single-phase direct current electric energy from all power generation units, and the single-phase direct current electric energy is collected and stored at the same time, so that a buffer storage battery voltage source with relatively constant voltage is converged, and each converging branch circuit needs to be isolated by a diode and converged to the buffer storage battery; thirdly, an inversion and boosting device is arranged at a central load transformer substation of the energy field, and the extra-high voltage direct current or the standard three-phase extra-high voltage alternating current meeting the grid-connected condition is obtained from the inversion of the single buffer storage battery, so that the grid-connected output of the electric power is realized.

2. The method for generating, transforming and connecting the grid of a clean energy field according to claim 1, wherein the buffer storage battery is a chemical battery or a super capacitor or a combination of the two.

3. The power generation, transformation and grid connection method for the clean energy field according to claim 1 or 2, characterized in that the buffer storage battery 3 has the structure that the capacities of the capacitors Cpv1 and Cpv2 are equal, the capacitors Cpv1 and Cpv2 are connected in series and then connected in parallel with the battery CR, and the capacitor bank is led out through a center tap between Cpv1 and Cpv2 to form a three-wire two-level output to the "DC-AC-DC" boost inverter bank 4.

4. The power generation, transformation and grid connection method of the clean energy field according to claim 1, characterized in that the wind turbine generator is output by a single-phase medium-high voltage direct current generator, the voltage level is a set value in a range of 1kV to 10kV, the set value is directly collected into a buffer storage battery after bridge rectification, and no three-phase step-up transformer is connected to the wind turbine generator position; the photovoltaic battery pack is output at low voltage, is inverted and boosted to form single-phase direct current with the same voltage class as that of the wind generating set within the range of 1kV to 10kV, then is imported into the same buffer storage battery with the same rated voltage of a certain designed voltage class within the range of 1kV to 10kV, and finally is boosted to be converted into a certain extra-high voltage direct current within the range of +/-100 kV to +/-1000 kV through a direct-alternating-direct inverter to be sent out.

5. The method for generating, transforming and connecting the grid of a clean energy field according to claim 1, wherein the wind turbine generator in the energy field is a high frequency generator, the photovoltaic inverter is a high frequency magnetic circuit inverter, and the electricity supplied to the buffer storage battery is high frequency pulsating direct current.

6. The power generation, power transformation and grid connection method of the clean energy field according to claim 1, wherein the magnitude of the total instantaneous power generation power of the whole energy field is identified through the voltage level of the buffer storage battery, and the extra-high voltage output power of the clean energy field is controlled and scheduled through the correlation between the inverter control of the central hub station and the voltage change of the buffer storage battery.