KR102376838B1 - photovoltaic power plant - Google Patents

Abstract

A photovoltaic (PV) power plant includes at least one AC power generating unit. The AC power generating unit includes an energy store that is supplied with DC energy from a DC power generator such as PV panels. The energy storage is used as a buffer for storing energy, improving the efficiency of PV power plants. Irrespective of whether energy storage is used or not, the separation devices can be used to prevent power dissipation, which can reduce the amount of power delivered to the grid by the power plant. In the system integration of PV power plants, it can be seen that the published ratings of DC/AC converters in the power grid convention should not be considered as power conversion capabilities.

Description

photovoltaic power plant

Photovoltaic (PV) power plants generate electricity by converting solar energy into electricity. The generated electricity is then provided to the power grid. A solar energy source (ie received sun rays) is characterized as having a time varying intensity. Accordingly, PV power generators within these PV power plants include a power generation optimization device (also referred to as an “optimizer”). One type of optimizer is termed a “Maximum Power Point Tracker (MPPT)” (or “MPPT Device”), which tracks the instantaneous maximum power production point (MPPP) voltage that the MPPT device uses to control the operation of the PV power plant. This practice is referred to herein as "blind MPPT form". MPPT devices are typically software or firmware; Tracks the time-varying voltage that results in maximum power production from a time-varying solar energy source.

The subject matter claimed herein is not limited to embodiments that work only in circumstances as described above or that solve any disadvantages. Rather, this background is merely provided to illustrate one exemplary area of technology in which some embodiments described herein may be practiced.

Embodiments described herein relate to a photovoltaic (PV) power plant comprising at least one AC power generating unit. According to an embodiment of the PV power state, each AC power generating unit includes a DC power generator, a first DC/AC three-phase converter(s), an energy store, and a second DC/AC three-phase converter(s). do. The DC power generator consists of x MW solar strings, where x is positive. The first DC/AC three-phase converter(s) has a total published power rating of y MW. The first DC/AC three-phase converter(s) receives DC power provided by the DC power generator, converts the received DC power into AC power, and provides the converted AC power to the power grid through a transformer. The energy store receives at least a portion of the remainder of the DC power generated by the DC power generator. The second DC/AC three-phase converter(s) has a total published power rating of z MW, where z is positive and the sum of y and z is greater than x. The second DC/AC three-phase converter(s) receives DC power from the energy store, converts the DC power received from the energy store into AC power, and provides the converted AC power to the power grid through a transformer. Since the sum of y and z is greater than x, the power plant according to this embodiment delivers more power to the power grid.

According to another embodiment described herein, each AC power generating unit is a DC power generator consisting of x MW solar strings, an energy storage, and a DC/AC three-phase converter having a total published power rating of z MW. , and z is greater than x. The energy store receives at least a portion of the remainder of the DC power generated by the DC power generator. The DC/AC three-phase converter(s) receives DC power from the energy storage, converts the DC power received from the energy storage into AC power, and provides the converted AC power to the power grid through a transformer. Since z is greater than x, the power plant according to this embodiment delivers more power to the power grid.

According to another embodiment described herein, each AC power generating unit comprises a DC power generator composed of solar strings. The DC/AC three-phase converter(s) receives DC power from a DC power generator through a separator, converts the received DC power into AC power, and provides the converted AC power to the power grid through a transformer. The use of a separator increases the amount of power a power plant can deliver to the grid by avoiding the problems the inventors have found with regard to power dissipation.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be an aid in determining the scope of the claimed subject matter.

In order to explain how the above and other advantages and features may be obtained, a more specific description of various embodiments will be provided with reference to the accompanying drawings. Accordingly, embodiments will be described with further specificity and detail through the use of the accompanying drawings, with the understanding that these drawings represent only sample embodiments and are not to be considered limiting of the scope of the present invention.
1A-1C show block diagrams of various power plants in which decoupling devices are used in conjunction with energy storage;
2A shows a block diagram of a power plant set up in an experiment, with two AC power generating units typically set up, with power and energy meters measuring the output of each power generating unit; ;
FIG. 2B shows a block diagram of the power plant of FIG. 2A after modification to include separation devices and energy storage, which is used to verify improved energy output to the grid;
Fig. 3 shows a block diagram of a power plant with two power delivery channels, one channel calling the use of energy storage and the other not calling users of the energy storage;
Fig. 4 shows a block diagram of a power plant representing the broader embodiment of Fig. 3;
5 shows a block diagram of a power plant in which power is delivered through the use of energy storage;
Fig. 6 shows a block diagram of a power plant representing the broader embodiment of Fig. 5;
7 shows a block diagram of a power plant;
8 shows a block diagram of a Maximum Energy Utilization Point Tracking (MEUPT) controller in accordance with the principles described herein;
Fig. 9 shows a block diagram of the MEUPT controller of Fig. 8 in relation to a power plant;

Patent publications US2016/0036232 and US2017/0149250 A1, the contents of which are incorporated herein by reference, disclose that PV energy systems implementing blind MPPT configuration achieve sub-optimal electricity provided to the grid. These patent publications teach that in order to efficiently and efficiently extract electricity for energy use, the characteristics of the energy extraction device must be matched in order to effectively and efficiently extract the generated electrical energy. In addition, these patent applications teach that the related devices must also be matched to modulate and/or deliver the extracted electricity for efficient energy use.

These patent publications further emphasize the fact that energy utilization efficiency is inextricably dependent on electricity demand in addition to electricity production. They also teach that in any energy system, typical power consumption is not necessarily equal to power production, even when the laws of conservation of energy and charge are met.

Instead of using the MPPT device as an optimizer for solar power plants, the referenced patent publications propose to use a “maximum energy utilization point tracker” or “MEUPT device” as a PV power plant optimizer. Such an optimizer will be referred to herein as a "MEUPT optimizer". According to the referenced patent publications, the MEUPT optimizer is designed to capture what is referred to as "surplus energy", which is defined as electrical energy that is generated but not extracted and/or delivered to the power grid for use. The definition of “surplus energy” is also used herein.

The MEUPT optimizer is also designed to temporarily store the captured surplus energy in an energy store; This electrical energy is then prepared and delivered to the power grid for use. Thus, when integrating the MEUPT optimizer, the PV power plant's electricity sales revenue can be improved.

Section 1: Features of the MEUPT optimizer

According to the principles described in US2016/0036232 and US2017/0149250 A1 (“referenced patent publications”), the MEUPT optimizer of one embodiment disclosed herein comprises a surplus energy extractor, an energy store, and a MEUPT controller. The MEUPT controller works in concert with energy extractors and DC/AC converters. The terms "power" and "energy" (though not exactly the same) are used interchangeably in the art. Accordingly, unless otherwise specified, each term has the same meaning.

An energy extractor extracts an initial oscillation power train from the generated DC power source. The extracted initial power chain conforms to the AC power grid requirements of the power grid. In other words, the extracted initial power chain has a time-varying sinusoidal voltage with a peak voltage that conforms to the power grid voltage range. Also, electrical power (proportional to the square of the voltage) takes the form (sin ² (ωt) or cos ² (ωt)) synchronized with the power grid (with the same phase and the same frequency).

Meanwhile, the surplus energy extractor subtracts the initial oscillation power train from the generated DC power and extracts the remaining oscillation power train. In other words, this remaining oscillating power train is a left-over oscillating power train that remains after providing the initial oscillating power train to the power grid. The remaining oscillating power train has a 90° phase shift compared to the initial oscillating power train provided to the power grid. Due to the 90° phase shift, this remaining oscillating power train cannot be immediately converted to AC power to provide on the same power grid. Thus, an energy store is used to temporarily store the surplus energy of the remaining oscillating power train. Thereafter, the stored energy is supplied to a DC/AC converter; The stored surplus energy can be converted to AC power synchronized to the same power grid (same phase and frequency).

The MEUPT controller measures the energy level of the reservoir; estimate the amount of energy in the reservoir that can be extracted; This information is communicated to the relevant DC/AC converter(s) so that this amount of energy can be extracted by the DC/AC converter(s). The DC/AC converter(s) then extracts the stored energy from the storage for conversion to AC power in the form of an appropriate pulsating power train and provides the AC power to the power grid. Thus, PV power plants can provide almost all of the generated electrical energy to the power grid when integrating the MEUPT optimizer. In contrast, without the MEUPT optimizer, a PV power plant according to the referenced patent publications can only provide less than half of the power/energy generated to the power grid.

Section 2: Retrofitting conventional PV power plants with MEUPT

Solar power plants are often rated in terms of a certain number of megawatts (MW). Typically, when a solar power plant is declared rated at x MW (where x is some positive number), this means that the sum of the DC power generation ratings of all solar strings is x MW. These conventional solar power plants also have three-phase DC/AC converters, which have a total manufacturer published DC/AC conversion capacity of no greater than x MW. This principle summarizes the operations of a conventional power plant according to a conventional MPPT implementation.

In other words, a conventional PV power plant rated x MW consists of a string of x MW PV solar panels that convert solar energy into DC electricity. Next, the generated DC electricity is extracted and converted by three-phase DC/AC converters to appropriate AC power complying with all AC power requirements of the power grid, and then provided to the power grid. This AC electrical power provided to the power grid is also referred to herein as an “initial oscillation power train”. Recall that the total manufacturer published DC/AC conversion capacity of DC/AC converters is not greater than x MW, which is the total amount of DC generating capacity of installed solar panels published by the solar panel industry.

According to the description of the referenced patent publications US2016/0036232 and US2017/0149250 A1, the remainder resulting from subtracting the initial oscillation power train (extracted by the energy extractor) from the total DC power generated by the solar panel strings. An oscillating power train exists. In other words, this power train is the remaining oscillating power grid with about 90° phase difference from the initial oscillating power train extracted by the energy extractor and provided to the power grid.

Because the remaining oscillating power train is about 90° out of phase from the power grid, this remaining oscillating power train cannot be directly conditioned and converted to AC power and provided to the same power grid. According to the principles disclosed in the referenced patent publications, the energy storage temporarily stores the energy contained in the remaining oscillating power train out of phase by 90° (when storing the indicated surplus energy). After this surplus energy is stored in the energy store, the surplus energy can function as DC energy that can be supplied to a DC/AC converter. This surplus energy can then be converted into AC power complying with all power grid requirements (including synchronization with the power grid), so that the resulting AC power can be provided to the same grid.

Section 3: Preventing Energy Leakage from Energy Storage

Before detailing energy storage design considerations for the MEUPT optimizer, an important issue is first addressed herein. Specifically, solar panel strings can have very high resistance at sunset, but solar panel strings can conduct significant current in either direction when the sun is strong at noon. Thus, electrical energy stored in the reservoir can leak and heat up through the solar panels during the day. Thus, isolation diodes are added to each of the solar panel strings so that electrical energy can flow from each solar panel string to charge the reservoir, but the energy in the reservoir cannot flow back into the solar panel strings from the reservoir. Various energy storage systems that achieve this separation will now be described with respect to FIGS. 1A , 1B and 1C .

Section 4: Design Considerations for Energy Storage

1A shows the power stream generated from a set of solar strings 1100A that subtracts the power drawn by DC/AC converter 1200A when DC/AC converter 1200A converts that power to AC power. A block diagram depicting an energy storage 1300A designed to temporarily store surplus power is shown. AC power is provided to AC power grid 1600A via transformer 1500A. Reservoir 1300A receives the remaining oscillating power train via isolation diode set 1400A. In one example, this energy storage 1300A is designed to temporarily store the surplus energy of a 1 MW PV power plant for two minutes.

By way of example only, assume that the primary energy source is capable of maintaining a constant intensity for 2 minutes (and the power production of the PV strings 1100A is maintained to allow for a constant 1 MW generator power production). For the following analysis, both the initial and remaining oscillating power trains have the same repetition shapes, but with a 90 degree phase difference. First, we examine how energy storage can be designed using brute forces. Keep in mind that the purpose of energy storage is to temporarily store surplus energy so that DC/AC converters can convert this stored energy later.

As discussed in the referenced patent publications, the estimated ratio of surplus energy to generated DC electrical energy exceeds 0.5 for a typical conventional PV power plant. For analysis, a PV power plant has 1 MW PV solar panel strings; Assume that DC power is converted to AC power and provided to the grid, which is 50 hertz and line voltage 380 V _AC 3-phase AC power. In this case, the duration of one power cycle is equal to about 0.01 seconds and the total phase current is at most 1,000,000/(380/1.732), where 1.732 is the square root of 3. This ratio is the ratio of peak voltage to line voltage (line-to-phase voltage, or “phase voltage” in three-phase AC power). Storing the charge associated with the surplus energy in the power cycle for this power plant would require an equivalent charge capacity of approximately 8 V Faradays (0.5*0.01*1,000,000/(380/1.732)), where "V" is the designed storage before and after charging. is the voltage difference between

To maximize the energy utilization of this PV plant, in some embodiments, the operating voltage of the MEUPT optimizer is within 75% of the PV maximum power production voltage. In other words, a voltage range of 75% maximum power production should be observed in that embodiment of the MEUPT optimizer. Measured I-V data typically indicate that this range is about 80 volts. When this voltage range is selected as the charge/discharge voltage range for the energy store (i.e., V=80 volts), the charge capacity of the energy store is about 0.1 Faradays per MW, per power cycle (if the power cycle lasts 0.01 seconds). .

If design considerations store the maximum amount of this surplus energy accumulated over two (2) minutes, the required equivalent charge capacity is equivalent to 1200 Faradays (100*120*0.1) of a 1 MW PV power plant. This required equivalent charge capacity is referred to as the "full maximum charge capacity," and the associated amount of storage storage energy is referred to herein as "full maximum energy storage capacity", or "full maximum surplus energy."

If only thin film capacitors are used to meet this required charging capacity, the set of thin film capacitors required to achieve the charging capacity will be prohibitively bulky and expensive. Therefore, it is not practical to design such an energy store that consists only of thin film capacitors.

As a variation on this brute force design, Faraday devices (such as batteries) can be incorporated into the design to reduce volume and size. The inventors' careful analyzes reveal that the required charge capacitance is in fact technically manageable for energy storage with thin film capacitors and Faraday devices. However, the cost of such storage is still too high to be advantageous if the price of the battery cannot be dropped by at least three times while maintaining the same performance.

The use of electrolytic capacitors can substantially reduce the required capital cost. However, such would increase the operating cost due to the relatively short lifetime of these capacitors. Therefore, at present, the use of electrolytic capacitors is not practical. Thus, brute force does not achieve economically advantageous designs with the required full maximum energy storage capacity.

The principles described herein make use of the following facts observed by the inventors to solve this problem:

(1) most existing DC/AC converters can easily power up or down 3% in 1 second; In addition, existing 500kW DC/AC converters can easily ramp up or down in excess of 10kW within 1 second during operation.

(2) As a rough observation, a typical 1 MW PV power plant starts generating power from zero power every morning, and rarely ramps up its power production faster than 10 kW/sec in its normal routine and operation.

(3) MW class PV plants (rated above 1 MW) may occasionally experience ramp-up rates greater than 10 kW per second during short bursts of power. However, the energy contained in these short bursts (or even more than 100 kW bursts per second) is insignificant compared to the total daily energy produced by a MW-class power plant.

From these three facts, the inventors found that (1) the power production in each of the solar panel strings starts at zero every morning; (2) It was determined that the PV generator does not instantaneously generate full power. Thus, the remaining oscillating power train does not immediately ramp up to its maximum. In other words, the rest of the oscillating power train typically increases much sharper than the ramp-up rate of DC/AC converters. Also, the amount of energy in any short ramp up burst is not a significant issue in the energy collection of PV plants rated above 1 MW.

Thus, instead of designing an energy storage capable of storing the maximum total amount of surplus energy, the principles described herein are based on the difference between the surplus energy input into the storage and the energy extracted from the storage by the DC/AC converter(s). It is proposed to design the reservoir to store the same net amount of energy (more than 2 minutes). This amount of energy is referred to herein as “maximum differential surplus energy”. The amount of this maximum differential surplus energy is much smaller than the maximum total surplus energy. Therefore, it is easier to design such a smaller energy store; It is technically manageable and also cost effective.

1B is a block diagram symbolically illustrating an energy storage 1300B that stores surplus power resulting from a power stream produced from a set of solar strings 1100B minus the power drawn by the DC/AC converter 1201B. shows the figure. At the same time, the other DC/AC converter 1202B is instructed by the MEUPT controller 1310B to receive approximately the same amount of DC energy from the energy store 1300B (including the surplus power). Both DC/AC converters 1201B and 1202B simultaneously convert the received DC energy to AC power and provide that AC power to the same grid 1600B via the same transformer 1500B. In doing so, the net energy storage burden on storage 1300B can be reduced to a very small capacity compared to that of storage 1300A shown in FIG. 1A .

Fig. 1C shows a configuration modified from the configuration shown in Fig. 1B, but having almost the same performance as the configuration shown in Fig. 1B. 1C , energy storage 1300C stores the DC power stream produced by PV solar strings 1100C via diode set 1400C. The two DC/AC converters 1201C and 1202C combine approximately the same total DC power from energy storage 1300C in approximately the same amount as the DC energy input produced by the PV string by MEUPT controller 1310C (all together). receive Accordingly, there is only a very small net power input balance at the inputs and outputs of storage 1300C. Both 1201C and 1202C simultaneously convert received DC power to AC power provided to the same grid 1600B via the same transformer 1500C.

In summary, as shown in FIG. 1B (when properly separated), the energy storage stores the remaining DC power after it has been extracted by the energy extractor (which may be incorporated as a module of DC/AC converter 1201B). The surplus energy can be extracted and stored in the form of the remaining oscillating power train. Another DC/AC converter 1201B is designed to extract approximately the same amount of energy out of energy storage 1300B to reduce the net amount of surplus energy stored in the storage. Therefore, a relatively small reservoir is suitable.

As also shown in FIG. 1C , energy storage 1300C (when properly separated) may receive all of the DC power produced from PV strings 1100C. Next, the oscillating power train is extracted by DC/AC converters 1201C and 1202C, while the surplus energy (remaining power) is also in energy store 1300C in the form of the remaining oscillating power train out of phase by 90° stored implicitly. As can be seen, this surplus energy is also implicitly automatically extracted and stored in storage 1300C.

Applying either design shown in FIG. 1B (or FIG. 1C ), the designed energy storage can serve as an energy storage for the MEUPT optimizer; It temporarily stores a small amount of net surplus energy that is 90° out of phase. The difficult task of energy storage design is now shifted to designing an appropriate MEUPT controller.

Section 5: Necessary functions of the MEUPT controller

The controller should be able to direct the associated DC/AC converter(s) to consistently draw an appropriate amount of energy from the storage substantially equal to the amount of surplus power being charged into the storage. In doing so, it is possible to minimize the net amount of energy storage into the reservoir; Maintaining properly balanced energy storage within the reservoir can stabilize system operation. In doing so, the energy store only needs to store (or provide) the energy difference between the surplus power charged and the power drawn by the DC/AC converter(s) within a small duration.

With a competent controller, the energy difference can be designed to be manageably small. the duration is long enough for the DC/AC converter(s) to ramp up or down in matching the surplus energy; It can be designed to be short enough to significantly reduce the capacity of the storage while maintaining stable system operation. Thus, the estimated storage capacity can be reduced to less than 0.001 times the maximum total surplus energy. This capacity is less than 2 Faradays per 1 MW PV plant; It is a manageable charge capacity even when thin film capacitors are used. Examples of suitable MEUPT controllers will be described below in connection with Sections 12 to 14 below.

Section 6: Capacitor/Battery Combined Energy Storage

Another problem is that a good thin film capacitor can last for 10 to 15 years while still retaining more than 80% of its original capacitance, whereas a good battery can last less than 5 years and after that time it is approximately 70% of its charge capacity. is to have Therefore, a careful design balance is proposed to optimize economic cost. Also, the amount of energy in the reservoir should always be large enough to stabilize operation. Design simulations show that, with current thin film capacitor and battery prices, a typical 20-year optimal energy storage design for a 1 MW PV power plant is 0.1 to 1 Faraday thin film capacitor combined with an approximately 50 amp-hour automatic battery string with an appropriate operating voltage. It shows that the design has

Section 7: Avoiding Mutual Power Dissipation in PV Strings

As noted above, the separation technique applied in FIGS. 1B and 1C allows strings of solar panels to charge an energy store; Prevents power from flowing back into the PV solar strings from storage. When properly applied with a set of isolation diodes, this technique can prevent energy leakage from storage through PV solar panel strings, as well as a phenomenon discovered by the inventors. This phenomenon is referred to herein as "mutual power dissipation during PV string phenomenon", "mutual power dissipation phenomenon" or "power dissipation phenomenon".

This phenomenon occurs when several PV strings connected in parallel collect the generated power. This phenomenon is particularly noticeable when parallel connected PV strings have very different I-V characteristics, photoelectric conversion efficiencies, and/or maximum power production voltages.

For example, when fewer than all the solar panels are cast in shadows, the strings in the shadow will have a lower photoelectric conversion efficiency than those outside the shadow. In other words, these solar strings will have very different I-V characteristics even at the same time of day due to the different casting of shadows. When these solar strings are connected in parallel, the high-efficiency strings can discharge some of their generated power to the lower-efficiency solar strings, disrupting power production in the PV solar strings. The present inventors confirmed this phenomenon experimentally. Experiments also show that this phenomenon can be prevented when PV solar strings are properly separated.

Power dissipation may also occur when parallel connected PV strings have very different maximum power production voltages. For example, suppose you have two strings of solar panels connected in parallel, one with 15 stringed solar panels and the other with 19 stringed solar panels. The power produced in the string with 19 panels will flow clearly through the string with 15 panels, and power dissipation occurs. Experiments show that the power received from the two strings connected in parallel can be reduced to less than half that produced by a string with 19 panels alone. When properly separated, the power received from the two parallel-connected strings can recover up to about 1.53 times that produced by the 19-panel string alone. The experiment shows that (a) there is a mutual power dissipation phenomenon; (b) show that appropriate separation techniques can prevent the phenomenon;

In one other experiment, the PV plant was arranged to have two power generating units; Each unit consists of 85 solar panels of the same make and model. Each of the two power generating units consisted of five (5) parallel connected PV strings to collect the generated DC energy. The two PV strings consisted of 15 panels connected in series, two strings with 17 panels connected in series, and another string with 21 panels connected in series. When the maximum power production voltages of these ten strings are individually measured at noon on a clear sky, the maximum power production voltages range from a low of 420 volts to a high of 610 volts. Thus, these parallel connected PV solar strings have very different maximum power production voltages under the same clear sky.

Each of the power generating units converts the collected DC power into AC power through a different DC/AC converter. To measure the energy and power generated in each production unit, a kilowatt meter and a wattmeter were connected to the AC output of each of the DC/AC converters of each production unit. Next, these units were connected to a transformer to provide AC power to the grid. With 72 identical readings of the two wattmeters over a 36-day period, and the same readings of the 2-kilo watt-hour meter at the end of the 36-day period, All elements are found to be substantially identical.

Next, one power generating unit is modified to consist of 4 strings of 21 panels (and 1 panel not being used); The other power generating unit remained unchanged from the above five strings. The measured power generation of the modified power generating unit was typically 4.1 times greater than other power generating units at noon and clear skies. Next, the measured sixty (60) days of accumulated energy, derived from the readings of the two kilowatt hour meter, were presented. The modified power generating unit provided energy to the grid 3.38 times that of the unmodified power generating unit. The experiment shows that the mutual power dissipation phenomenon actually exists in parallel-connected PV strings; In particular, it has been clearly and unambiguously demonstrated that the strings have very different I-V characteristics or very different maximum power voltages.

In conclusion, a suitable separation technique in accordance with the principles described herein can prevent energy leakage from energy storage through solar strings; It also avoids the mutual power dissipation found between PV strings.

Section 8: Experiments to prove the existence of surplus energy

Before describing the designs of the MEUPT optimizer, this section describes experiments to clearly prove the existence of surplus energy in these PV power plants; This is predicted by the referenced patent publications, US2016/0036232 and US2017/0149250 A1. In other words, the referenced patent publications define electrical energy that is generated but not extracted and/or utilized prior to conversion of surplus energy into heat. Specifically, in a PV power plant, “surplus energy” includes the electrical energy remaining after the generated DC energy is extracted and converted into AC power by three-phase DC/AC converters. The MEUPT optimizer can be designed to capture/use this remaining electrical energy, the surplus energy. The following describes the experimental setups and step-by-step runs of the experiment.

2A shows a starting setup of a PV power plant 2000A including two AC power generating units 2100A and 2200A. Each of the AC power generating units 2100A and 2200A implements a blind MPPT form; Provides three-phase AC power to the power grid 2600A. The AC power generating unit 2100A is composed of a DC power generator 2110A and a three-phase DC/AC (15 kW) converter 2130A. The AC power generating unit 2200A is composed of a DC power generator 2220A and a three-phase DC/AC (15 kW) converter 2230A. Power generator 2110A generates DC electricity using two parallel connected PV strings 2111A and 2112A. Power generator 2220A uses the other two parallel connected solar strings 2221A and 2222A to generate DC electricity. Each of the four PV strings consists of 25 series connected solar panels; Each panel can produce 250W of power at noon and clear skies.

DC power generator 2110A supplies DC power to 3-phase DC/AC converter 2130A; The DC power generator 2220A supplies DC power to the three-phase DC/AC converter 2230A. These two converters 2130A and 2230A then convert the supplied DC power into three-phase AC power. In the experiment, the AC output power of the power generating units 2100A and 2200A was measured by two three-phase AC wattmeters (kW) 2351A and 2352A, respectively. The AC energy generation (kW*hour) of these two power generating units 2100A and 2200A was also measured by two kW hour meters 2361A and 2362A, respectively. Next, the generated three-phase AC power was provided to grid 2600A via transformer 2500A. The PV plant has been put into operation; The energy production of two AC power generating units 2100A and 2200A was measured for 7 days.

The readings of the two kW hour meters showed the same values every day during this time period. This provides high confidence that all elements of these two power generating units 2100A and 2200A (including two sets of instruments for measurement) are substantially identical. After this step, one of the two AC power generating units 2200A remained unchanged, while the other AC power generating unit 2100A was modified to a different configuration 2100B as shown on the left side of FIG. 2B . .

The power generating unit 2200B of FIG. 2B is the unmodified power generating unit 2200A of FIG. 2A . Also, elements 2351B, 2361B, 2352B, 2362B, 2500B, and 2600B of FIG. 2B are identical to elements 2351A, 2361A, 2352A, 2362A, 2500A, and 2600A of FIG. 2A , respectively. In addition, although the configuration of the power generating unit 2100B is different from the power generating unit 2100A of FIG. 2A in FIG. 2B , some of the elements of the power generating unit 2100B of FIG. 2B are the power generating unit 2100A of FIG. 2A . ) are the same as those contained within. For example, PV strings 2111B and 2112B of FIG. 2 are identical to PV strings 2111A and 2112A of FIG. 2A , respectively. Likewise, the DC/AC converter 2130B of FIG. 2B is the same as the DC/AC converter 2130A of FIG. 2A .

The following six (6) steps describe how the power generation unit 2100A has been modified to the configuration of 2100B, and is described with respect to the left side of FIG. 2B. Step 1 is to add a set of isolation diodes 2311B between the solar strings 2111B and 2112B and the three-phase DC/AC converter 2130B, implementing the blind MPPT configuration. Step 2 is to add energy storage 2410B to the configuration. Step 3 is to connect energy store 2410B to the DC terminals of DC/AC converter 2130B via another set of isolation diodes 2312B and via switch SW1. Step 4 is to add another three-phase DC/AC converter 2130S (20 kW) to the configuration, which converter 2130S was operated according to the direction of the designed MEUPT controller 2420B. Step 5 is to connect DC/AC converter 2130S to energy storage 2410B via another set of isolation diodes 2313B and via switch SW2. Step 6 is to connect the output terminals of converter 2130S to power and energy measuring instrument sets 2351B and 2361B via switch SW3. Note that the referenced "isolated diode set" may be diodes referred to in the art as "blocking diodes". In addition, switches SW1, SW2, and SW3 are added as shown in FIG. 1B so that the relevant devices can be introduced into (or removed from) the experiments at the appropriate time in the designed experiment execution steps described below. take note of

on the first night after the fertilization was made; SW1 was turned on while switches SW2 and SW3 were turned off. Converters 2130B and 2230B started running early the next morning. Power meters 2351B and 2352B measuring the two outputs of power generating units 2100B and 2200B showed the same reading. Reservoir 2410B also begins charging as indicated by the measurement of the high terminal voltage of reservoir 2410B. The system operated as described throughout the day. The measured energy provided from the two power generating units 2100B and 2200B is; The readings of the kW hour meters 2361B and 2362B were identical as shown. This experimental step demonstrated that the added isolation diode sets 2311B and storage 2410B did not alter the power and energy productions of the power generation unit 2100B.

Switches SW1, SW2, and SW3 were turned on the night (second night) after the first operation. Converters 2130B and 2230B started running early in the morning (day 2), while converter 2130S started running at a lower power conversion level about 15 minutes after converters 2130B and 2230B started running. started to become Thereafter, converter 2130 increased its converted power level about every two minutes; This is consistent with the controller design and increments of the storage energy level. The reading of wattmeter 2351B (for unit 2100B) is approximately twice the reading of wattmeter 2352B (for unit 2200B) for the entire day of the week until nearly sunset. At the end of the second day, the energy provided from the two power generating units 2100B and 2200B was derived from the readings of the 2 kW hour meter. The results showed that the energy provided from the modified power generating unit 2100B was more than twice the energy provided from the unmodified power generating unit 2200B. For the next 6 consecutive days, switches SW1 , SW2 and SW3 were left on, and the energy provided from the modified power generating unit 2100B was consistently more than twice that of the power generating unit 2200B every day.

The next night, switches SW2 and SW3 were turned off. The measured energy provided from the power generating units 2100B and 2200B returned to the same level for the next 5 consecutive days while the switches SW2 and SW3 were off. The next night, switches SW2 and SW3 were turned on again. The measured energy production of power generating unit 2100B again exceeded twice that of power generating unit 2200B every day for the next five consecutive days with switches SW2 and SW3 in the on state.

As mentioned above, the step-by-step execution of these experiments clearly demonstrates the existence of the referenced surplus energy in the PV power plant, as predicted by the patent publications US2016/0036232 and US2017/0149250 A1. Specifically, in a PV power plant when the generated DC energy is extracted by a three-phase DC/AC converter, there is still energy left over. The MEUPT optimizer can capture and use this surplus energy to increase the electricity provided to the power grid.

Section 9: Components of the designed MEUPT optimizer

The modified power generation unit 2100B (as described above and shown in FIG. 2B ) may serve as an example of a PV power generation unit that includes a MEUPT optimizer. In this case, the MEUPT optimizer consists of three sets of isolation diodes 2311B, 2312B, 2313B; a storage 2140B, and a MEUPT controller 2320B. Note that the isolation diode set is hereinafter referred to as the “isolation device”.

The connection of the MEUPT optimizer module is shown in Figure 2b and described above. Note that the surplus energy is passively extracted by the energy store 2410B in this embodiment. Another power extractor is included as a module in the three-phase DC/AC inverter 2130S that extracts the surplus energy stored in the reservoir 2410B. The AC power conversion level of converter 2130S is regulated by MEUPT controller 2320B such that the power charges into energy store 2410B approximately balance the power discharged from energy store 2410B. Thus, the “net” power charged into the storage within a period can be as small as desired. The smaller net power charge has the advantage of allowing a smaller energy store 2410B at the expense of tighter control by the MEUPT controller 2320B.

Another embodiment is shown in FIG. 3 . This embodiment illustrates the configuration of a PV power plant 3000 comprising a MEUPT optimizer comprising only one AC power generation unit 3100 that converts solar power to DC power using 500 kW solar panels 3110 . In other words, the AC power generating unit 3100 is composed of a DC power generator 3110 and a three-phase DC/AC (500 kW) converter 3130 . Power generator 3110 generates DC electricity using 80 parallel connected solar strings. Each of the 80 solar strings consists of 25 series connected solar panels; Each panel is declared to have a 250W DC power production capacity at noon and clear skies. This DC generator 3110 is referred to as a 500 kW electrical power generator (80*25*250W=500kW); Note that this PV plant is referred to as a 500 kW PV plant.

As shown in FIG. 3 , the power generator 3110 supplies DC power to a three-phase DC/AC converter 3130 (published at 500 kW) via a separation device 3311 . The generator 3110 also provides DC power to the energy store 3410 via the disconnect device 3312 , and serves as a DC energy source to charge the energy store 3410 . Thus, the surplus energy is passively extracted by the reservoir 3410 . Reservoir 3410 then supplies (or discharges) DC power to another three-phase DC/AC converter 3130S (published at 500 kW) via decoupling device 3313 . Converter 3130 operates as an MPPT optimizer, while converter 3130S operates as a MEUPT controller. The converters 3130 and 3130S convert separately supplied DC power into three-phase AC power, and supply power to the grid 3600 through the same transformer 3500 .

The DC/AC converters used in the above description can be classified into two types; That is, it is noted that one type receives its DC power directly from the PV solar strings, and the other type receives its DC power from the energy store. Where a converter type distinction is required in this disclosure and in the detailed description below, receiving DC power from PV solar strings is also referred to as a “PS DC/AC converter”; Others that receive DC power from an energy store are also referred to herein as “ER DC/AC converters”. When a distinction is needed when using three-phase DC/AC converters in the present disclosure, the converters are also classified and referred to herein as "PS three-phase DC/AC converter" and "ER three-phase DC/AC converter", respectively, respectively will be

to repeat on a wider level; As shown in the configuration shown in FIG. 4 , this MEUPT optimizer provides optimization services to an x MW PV power plant with properly arranged solar panel strings having a rated x MW power production capacity. The generated DC power is extracted by the manufacturer published y MW “PS 3-phase DC/AC converter” 4130 via a separation device 4311 . The remaining power is charged into the energy storage 4410 via another separation device 4312; The surplus energy is extracted and stored accordingly. Then, the stored surplus energy is converted by another manufacturer's published z MW "ER three-phase DC/AC converter" (4130S) through another separation device. One of the converters 4130 is regulated by the MPPT optimizer, while the other converter 4130S is regulated by the MEUPT controller. Both converters convert an appropriate amount of DC power to three-phase AC power; Provides three-phase AC power to the power grid 4600 via the same transformer 4500 . Note that x=y=z=0.5 in this configuration.

5 shows another embodiment of integrating a MEUPT optimizer in a large PV power plant. The power plant is equipped with rated 0.5 MW solar panel strings 5110 and two published 500 kW three-phase DC/AC converters 5130 and 5130S. This embodiment illustrates another configuration for the MEUPT optimizer. The PV power plant 5000 may be considered to include one AC power generating unit (hereinafter also referred to as “AC power generating unit 5100 ”). The AC power generation unit 5100 consists of a DC power generator 5110 consisting of rated 500 kW solar panels, and two three-phase DC/AC converters 5130 and 5130S (published at 500 kW each). Power generator 5110 uses 80 parallel connected solar strings to generate DC electricity. Each of the 80 solar strings consists of 25 series connected solar panels; Each solar panel is rated to have a 250W power production capacity. Energy store 5410 receives DC power from generator 5110 via separation device 5311 . The two three-phase DC/AC converters 5130 and 5130S are stored through two separate separation devices including a separation device 5312 for converter 5130 and a separation device 5313 for converter 5130S. Receive DC power from 5410 . Converters 5130 and 5130S are regulated by the MEUPT controller to draw the appropriate amount of power from storage 5410 and convert DC power to three-phase AC power to power grid 5600 via transformer 5500. to provide.

To describe the configuration shown in Figure 5 in more broadly detailed detail: The MEUPT optimizer provides optimization services to x MW PV power plants. This PV power plant has one AC power generating unit with solar panel strings with total rated DC power generating capacity x MW. The DC generator charges the energy store through a disconnect device. The energy store supplies DC electricity to the two three-phase DC/AC converters via two separate sets of separation devices. The total manufacturer published conversion capacity of two "ER three-phase DC/AC converters" is z ₁ +z ₂ =z MW. The two converters are regulated by the MEUPT controller to convert an appropriate amount of DC power to three-phase AC power. The electricity generated by the two converters is provided to the power grid through the same transformer. The above-described configuration is shown with modification in FIG. 6 . Note that x=0.5, y=0, z=1 in this configuration.

This description will now compare the two configurations shown in FIGS. 4 and 6 . In the configuration shown in Fig. 4, the DC generator supplies DC power to the "PS three-phase DC/AC converter" having a capacity of y MW published by the manufacturer; The remaining power is charged into the energy storage. In FIG. 4 , the energy store supplies DC power to the “ER three-phase DC/AC converter” with a manufacturer published capacity of z MW. In the absence of a “PS three-phase DC/AC converter” in the configuration shown in FIG. 6 (ie y=0), all generated DC power charges are charged into the energy store through the separation device; The energy storage supplies DC electricity into the two “ER three-phase DC/AC converters” via two separate sets of separation devices. Thus, in the configuration of Fig. 3, x=y=z=0.5; In the configuration of FIG. 6, x=0.5, y=0, and z=1. In one further embodiment of FIG. 6 , energy storage 6410 is not present. Instead, the solar strings 6110 provide DC power to the converters 6130 via a separation device 6311 .

Now, the only remaining design problem for the MEUPT optimizer is to identify the optimal power matching relationship between the converters and parameters representing the rated capability of the solar strings. Specifically, the task is to identify the relationship between the values of x, y and z in an optimal situation. In other words, the value of the sum y+z is not greater than the value x in a conventional PV power plant as described in section 2.

Also, a value x is specified for the MW value of the rated DC power-producing capacity of the PV strings; Whereas the value y is specified for the total MW value of the maker-published ability of the “PS three-phase DC/AC converter” to convert the DC energy supplied by the PV strings; Note that the value z is specified for the total MW value of the manufacturer published ability of the “ER three-phase DC/AC converter” to convert the DC energy supplied by the energy store.

For example, in Figure 6, x is equal to the published total PV capacity of the 0.5 and 0.5 MW manufacturers; y is equal to 0 meaning "PS 3-phase DC/AC converter" is not installed; z equals 1, meaning that the declared capacity of the 1 MW gun maker of two "ER three-phase DC/AC converters" includes receiving DC power from an energy store and converting DC energy to three-phase AC power. Do. Note that the value of y+z is at least twice the value of x in both of the foregoing configurations. The term “capability” is also referred to as the “power rating” of a device; Unless otherwise indicated, the following may be modified.

Section 10: Optimal Power Matching Relationships

Due to different fields (industries), the definition of power rating for solar panels is different from that of DC/AC converters. The power rating of solar panels is defined as the maximum DC power the solar panel can generate at noon on a clear sky. The solar panel manufacturing industry uses a predetermined type of lighting lamp (referred to herein as a “standard lamp”) to simulate a clear sky; Noon is simulated by illuminating a light flux vertically through the solar panel surface. Thus, the manufacturer's declared power production capacity can be very close to that of an actual DC generator. Experiments performed by the inventors also confirm the above statement. Accordingly, the total DC power generating capacity of the PV solar strings is determined to be reliable; The title “maker published capability” herein is omitted when describing the power ratings of solar strings. On the other hand, the DC/AC converter manufacturing industry defines the power rating of DC/AC converters according to a convention of the power grid industry referred to herein as a "power grid convention". The definition of this convention and DC/AC converter capability is detailed as follows.

The AC power grid industry enforces protocols (referred to as power grid codes) to ensure that a configured three-phase AC power grid can meet its published power delivery capabilities. A three-phase AC power grid consists of three or four power lines capable of carrying time-varying sinusoidal functions of voltage and current in one phase in each pair of power lines. The power grid convention defines the voltage published in the specification as the “standard” maximum voltage that power lines can withstand (referred to as the “line voltage”). Likewise, the specific maximum current published in the specification is the maximum current that power lines can carry (referred to as “maximum phase current”). When a device is manufactured to comply with power grid regulations, the voltage published in the device's specifications is the maximum voltage that all related components must withstand. Likewise, the maximum current published in the specification is the maximum current carrying capacity for all relevant components of a phase, connected to a pair of power lines. The time-varying functions of the voltage and current of the device also need to conform to the sinusoidal function of each phase in the AC power grid.

In other words, the specific voltage of a three-phase DC/AC converter is defined as the line voltage of three-phase power; The specific maximum current is defined as the maximum current carrying capacity of a pair of power lines for each phase; The specific maximum power is defined as the sum of the maximum power capabilities that the three phases can withstand. In other words, according to the power grid convention, the power lines and connected power devices of each phase must be able to transmit one-third (1/3) of a certain maximum power to the state in another way, three-phase DC The "maker published power rating" of an /AC converter is 3*U*I, where U is the phase voltage and I is the phase current. Each pair of power lines can carry U*I power, or can be 1/3 of the “maker published power rating”; In accordance with power grid conventions, each module connected to a pair of power lines is also required to carry or deliver one-third of the specified published power rating.

For example, AC voltage=315 VAC; max current=916 amps; An example is a three-phase DC/AC converter that specifies "maximum power output = 500 kW". The specification "AC voltage = 315 VAC" should read as "The output line voltage of this converter is 315 volts". Alternatively, if three phase When balanced, the phase voltages U of all phases are U=315/1.732=181.9 volts, where 1.732 is the square root of 3, which is the ratio of line voltage to phase voltage. It should be read that the power lines and all components in each phase are designed to ensure a current carrying capacity of I = 916 amps The specified "maximum power output = 500 kW" is for each DC/AC conversion stage = U* It should be understood as the maximum power conversion and transfer capability of all components of I=181.9*916=500/3 KW; the total maximum power conversion and transfer capability of the relevant modules in three conversion stages is the sum of their respective phases, 3* U*I=3*181.9*916=500kW, which is the “maker published power rating”=3*U*I defined when following the power grid convention mentioned in the previous paragraph.

In a three-phase DC/AC converter, the three phases are strictly correlated to be 120° out of phase. In other words, a pair of power lines (phase) carries a time-varying power of U*I sin ² (ωt); the second phase carries a time-varying power of U*I sin ² (ωt+120°); The third phase carries a time-varying power of U*I sin ² (ωt-120°). Each pair of power lines of three phases carries three oscillating AC power trains related to each other with tight correlation. Note that the power conversion capacity P(t) is not equal to the defined “maker published power rating”. The power conversion capacity P(t) is expressed as a function of time and is derived according to defined three-phase AC power limits.

In other words, the DC/AC power conversion capacity P(t) has a strictly correlated phase difference of 120°; derived from the sum of three phase time-varying power outputs with power waveforms conforming to square sine wave oscillations of sin ² (ωt) or cos ² (ωt); The angular frequency ω is synchronized with the power grid (same phase and frequency) held constant.

Now, the time-varying power conversion capacity P(t) of the three-phase DC/AC converter is derived. The power conversion capacity of a three-phase DC/AC converter as a function of time is P(t)=U*I*(sin ² (ωt)+sin ² (ωt+120°)+sin ² (ωt+120°)) . As defined above, U is the phase voltage, I is the phase current, and ω is the constant angular frequency of the power grid. Also, it can be seen that sin ² (ωt+120°)+sin ² (ωt-120°)=cos ² (ωt)+1/2. Thus, the power conversion capacity P(t) of a three-phase DC/AC converter as a function of time is P(t)=U*I*(sin ² (ωt)+sin ² (ωt+120°)+sin ² (ωt) -120°))=U*I*(sin ² (ωt)+cos ² (ωt)+1/2)=U*I*(1+1/2)=3/2(U*I).

In other words, the sum of these tightly correlated three oscillation power trains in three phases is a constant. In other words, the total power transfer of these three pairs of power lines is constant. or the sum of the three modules associated with the three phases is a constant. However, this constant is equal to half (1/2) of the "published power capability". This is the relationship between the power conversion capacity of a three-phase DC/AC converter and the defined “published power capability” according to the power grid convention.

As described above, it is recalled that the "manufacturer published power rating" or referenced "maker published power capability" of a three-phase DC/AC converter is 3*U*I, when according to the power grid convention. Comparing this with the derived power conversion capacity, P(t)=3/2(U*I); It is clear that the derived DC/AC power conversion capacity of a three-phase DC/AC converter is only half of the "manufacturer published power capacity".

For example, "AC voltage=315 VAC"; max phase current=916 amps; and the above-mentioned three-phase DC/AC converter specifying "maximum power output=500 kW". Actually, the DC/AC power conversion capacity of this three-phase DC/AC converter is only 250 kW. To draw the above conclusion , first confirmed that the published maximum power of 500 kW is actually equal to 3*U*I, where U is the phase voltage derived from the specified line voltage, I is the published maximum current; the power conversion capacity of this converter is Equivalent to 3/2*U*I=250kW.

The optimal power matching relationship for the parameters x, y, and z (as defined) is that the value of (y+z) will not be less than 2x. If the relevant PV plant consists of x MW PV solar strings; “PS three-phase DC/AC converters” have a total “maker published power capability” of y MW; “ER three-phase DC/AC converters” have a total “maker published power capability” of z MW. “PS three-phase DC/AC converters” and “ER three-phase DC/AC converters” may be operated by one or more MPPT controllers, or by one or more MEUPT controllers. In order to implement the MEUPT optimization, it is desirable to operate all DC/AC converters by the MEUPT controller(s).

Section 11: Summary

7 abstractly shows the configuration of a PV solar power plant 7000 . The power plant includes a full x MW solar panel arranged in solar strings 7100 . The DC power generated in the solar strings 7100 provides DC power input to the group of three-phase DC/AC converters 7301 through a separation device 7201 ; The surplus power is charged into the storage 7400 via a disconnect device 7202 . Energy storage 7400 provides DC power input to the group of three-phase DC/AC converters 7302 via a separation device 7203 . Both three-phase DC/AC converters 7301 and 7302 provide converted three-phase AC power to the power grid 7600 via a transformer 7500 . The total “maker published capacity” of converters 7301 is y MW. The total “maker published capacity” of converters 7302 is z MW. The value of the sum (y+z) is not less than the value of 2x. Recall that when using a similar configuration to describe a conventional PV power plant as described in section 2, the value of (y+z) is not greater than the value of x. Thus, if a design with a value of (y+z) is greater than x or even 1.1 times better than x, this means that some of the surplus energy can be captured to improve the electrical energy provided to the power grid.

Converters 7301 and 7302 can both be operated by the aforementioned MEUPT controller(s). In some embodiments, some or one of the converters are operated by the MEUPT controller, or none of them are operated by the MEUPT controller. Also, in some embodiments, one or some of the separation devices 7201 , 7202 , and 7203 may be omitted from configuration. PV solar strings 7100 provide DC power input to converter 7301 . Accordingly, they are referred to as "PS converters" in this specification. Energy storage 7400 provides DC power input to converters 7302 . Accordingly, they are referred to herein as “ER converters”. The terms full "maker published power rating" and full "maker published power capability" will be abbreviated herein as "published power".

To repeat the description of the configuration shown in FIG. 7 : PV power plant 7000 includes x MW solar strings 7100 as DC power generator. DC power generator 7100 provides an input with "published power" of y MW to "PS converters" 7301 via separation device 7201 ; Remaining power is charged to the storage 7400 via another separation device 7202 . Reservoir 7400 provides an input with "published power" of z MW to "ER converters" 7302 via separation device 7203 . All three-phase DC/AC converters 7301 and 7302 provide converted three-phase AC power via transformer 7500 to power grid 7600 . In some embodiments, the value of (y+z) is not less than the value of 2x. However, when the value of (y+z) is greater than the value of x, the design may benefit in part to improve electrical energy sales to the power grid.

A MEUPT optimizer according to the principles described herein may provide a small or large PV power plant comprising one or more AC power generating unit(s). In addition, by means of a properly designed separation device, energy leakage from the energy storage through the PV solar strings can be prevented. Also, with a properly designed separation device, the discovered "mutual power dissipation" phenomenon can be avoided. Also, the energy storage can be used to receive only the surplus energy after energy extraction of the "PS converter", or to receive all the generated DC energy before any extraction. Finally, the MEUPT optimizer can also provide services for PV power plants with single phase DC/AC converter(s).

Section 12: Design Constraints of the MEUPT Controller

8 shows a MEUPT controller 8000 (also referred to as a “system controller”) representing an example of the MEUPT controller 2320B of FIG. 2B . The MEUPT controller 8000 includes three executable components: a detection component 8100 , a decision component 8200 , and a delivery component 8300 .

The detection component 8100 measures the energy level stored in the storage 8400 . Examples of storage include storage 2410B of FIG. 2B , energy storage 3410 of FIG. 3 , energy storage 4410 of FIG. 4 , energy storage 5410 of FIG. 5 , energy storage 6410 of FIG. 6 , and FIG. 7 energy storage 7410 .

Determining component 8200 determines an appropriate power drawing level to approximately balance the charge provided to and discharged from energy store 8400 .

The forwarding component 8300 forwards the coded message of the determined appropriate power draw level to the surplus DC/AC converter(s) 8500 . The converters interpret the coded message and comply with the coded message so that the converter(s) continues to operate at the indicated power level, whereby the in-charging energy is approximately balanced. can do. Examples of converters 8500 withdrawn from storage 8400 are converters 2130S of FIG. 2B , converters 3130S of FIG. 3 , converters 4130S of FIG. 4 , and converters 5130S of FIG. 5 . , the converters 6130S of FIG. 6 , and the converters 7302 of FIG. 3 .

In order to derive the MEUPT economic benefit optimizer, the design of the MEUPT controller depends on the following parameters and variables: (1) the capacity of the energy store 8400; (2) ramping up/down speed of DC/AC converters 8500; (3) I-V characteristics of solar strings; (4) the climate at the location of the PV plant; and (5) the ability of the MEUPT controller to operate so that the surplus DC/AC converter minimizes the difference (or balance) between the amount of charge provided to the energy store and the amount of charge drawn from the energy store. A simple design can be derived when applying a custom designed controller for each and every PV power plant, only taking these parameters and variables into account.

SECTION 13: MEUPT CONTROLLER DESIGN

It is impractical to custom design a MEUPT controller for each and every one PV plant that uses a MEUPT controller. On the other hand, pursuing a simple design for the required MEUPT controller; Especially when custom design controllers are not allowed, it is very difficult. However, the terminal voltage of the energy store can be viewed as a measurement influenced by each of the five parameters and variables. Accordingly, the above five design constraints can be broken down into two parts when the terminal voltage of the MEUPT energy store is selected as the determining parameter.

when comparing the measured terminal voltage to a set of site-specific "standard voltage intervals"; It became apparent to the inventors that the level of power extraction and transformation currently running by the system can be quantized, as the power extraction level is (1) too low, (2) too high, or (3) just right. Thus, the MEUPT controller design task can be separated into 1) a typical industrial controller, plus 2) a custom configured site-specific “standard voltage intervals” table (referred to herein as a “ voltage interval table ”).

If a site-specific voltage interval table is configured for a PV plant; The voltage interval table can work in concert with the industrial controller to achieve the necessary MEUPT controller functions. Then, the industrial controller is composed of a detecting component, a determining component, and a forwarding component, as also shown in FIG. 8 . However, in this case, the detection component 8100 measures the terminal voltage of the energy store 8400 . The determining component 8200 compares the measured voltage to a voltage interval table; Determining the appropriate power draw to roughly balance the internal-charge energy. The forwarding component 8300 again forwards the coded message of the determined appropriate power draw level to the surplus DC/AC converter(s); Allows the converter(s) to operate continuously at the indicated power level to approximately balance the incoming and outgoing charge of the energy store 8400 .

In one embodiment, the detection component 8100 of the MEUPT controller 8000 measures the terminal voltage of the surplus energy store 8400 in real time. Nevertheless, the determining component 8200 may still perform the comparison (of the measured voltage to the voltage interface table) every designated time interval comparison. This comparison can lead to one of three situations:

(1) If the comparison of the measured voltage with the voltage interval table indicates that the power level is too low, the controller 8000 (via the transfer component 8300) determines that the three-phase DC/AC converter 8500 may request to be increased by one level of power extraction and conversion to ;

(2) If the comparison of the measured voltage with the voltage interval table indicates that the power level is too high, the controller 8000 (via the transfer component 8300) determines that the three-phase DC/AC converter 8500 is at the next specified time interval. may request to be reduced by one level of power extraction and conversion;

(3) If the comparison of the measured voltage with the voltage interval table indicates that the power level is just right, then the controller 8000 indicates that the three-phase DC/AC converter 8500 will have at least the next comparison during the next specified time interval. You can ask them to stay at the same power extraction level until they happen.

When the power extraction/conversion regulation level of the DC/AC converter is small enough, the design is suitable for all kinds of energy storage capacity; For up/down ramping speed of all kinds of DC/AC converters; for the I-V characteristics of all kinds of solar strings; and all climates of the PV site. Therefore, it is important that the controller be able to direct small adjustment steps to the three-phase DC/AC converter that draws power from the energy store.

Typical conventional centralized three-phase DC/AC converters can operate in very small adjustment steps when directed. However, an equipped communication channel, referred to in the art as a “ dry connection box ” (and referred to herein), typically has only 6-bit communication channels via optical messages. To command more than six power extraction levels through the dry junction box, an encoding-decoding technique is employed. This technique allows passing up to 2 ⁶ =64 messages to command power extraction levels. With up to 64 coordinated power extraction levels, the near-zero net balancing required for the incoming and outgoing energy of the storage can be technically achieved.

Section 14: PV power plants incorporating the MEUPT optimizer

As shown in FIG. 9 , the PV power plant 9000 includes a MEUPT optimizer 9200 configured as a MEUPT controller 9210 . MEUPT controller 9200 includes three executable components; That is, a detection component 9211 that measures the terminal voltage of the surplus energy store 9400; a determining component 9212 for comparing the measured voltage to a voltage interval table of the PV power plant; and a forwarding component 9213 for notifying the three-phase DC/AC converter 4502 via the forwarding component 4213 to boot-up, drop-down, or keep the same. Components 9211 , 9212 and 9213 of FIG. 9 are examples of components 8100 , 8200 and 8300 of FIG. 8 , respectively. The energy storage 9400 of FIG. 9 is an example of the energy storage 8400 of FIG. 8 . Converters 9502 are examples of converters 8500 of FIG. 8 .

The PV power plant 9000 also includes PV solar strings 9100 . Solar strings 9100 convert solar energy into electricity; The generated DC power is transferred to the surplus energy storage 9400 via a separation device 9320 . The three-phase DC/AC converter 9502 receives DC power input from the surplus energy storage 9400 via a separation device 9330 . The solar strings 9100 of FIG. 9 are a DC energy source for collectively charging an energy store, the solar strings 2111A and 2111B of FIG. 2B , the solar string 3110 of FIG. 3 , the solar string of FIG. 4 . 4110 , the solar string 5110 of FIG. 5 , the solar string 6110 of FIG. 6 , and the solar string 7110 of FIG. 7 are examples. The separation device 9320 of FIG. 9 is the separation device 2312B of FIG. 2B , the separation device 3312 of FIG. 3 , the separation device 4312 of FIG. 4 , the separation device 5311 of FIG. 5 , and the separation device of FIG. 6 . 6311 , and an example of the separation device 7202 of FIG. 7 . The separation device 9330 of FIG. 9 is the separation device 2313B of FIG. 2B , the separation device 3313 of FIG. 3 , the separation device 4313 of FIG. 4 , the separation device 5313 of FIG. 5 , and the separation device of FIG. 6 . 6313 , and an example of the separation device 7203 of FIG. 7 .

As noted above, the MEUPT controller 9210 directs the three-phase DC/AC converter 9502 to draw an appropriate amount of energy from the energy store 9400 to balance the input energy charge from the solar strings 9100 . and; As a result, it appears that near zero energy is either in-charged or out-withdrawn to the reservoir 9400 . Thus, the small energy storage 9400 is suitable for a PV power plant. The converted AC power from the DC/AC converter is provided to a connected power grid 9700 via a transformer 9600 .

As used herein, the term “executable component” is used in connection with FIGS. 8 and 9 . The term “executable component” is a name for a structure that can be well understood by those skilled in the art as a structure that may be software, hardware, firmware, or a combination thereof in the computing field. For example, when implemented in software, those of ordinary skill in the art will recognize that the structure of an executable component is software objects, routines, methods in which it may be executed on a computing system, and that such an executable component is implemented on the computing system's heap ( heap), or whether the executable component resides on a computer-readable storage medium.

In this case, one of ordinary skill in the art will recognize that the structure of executable components is on a computer-readable medium such that, when interpreted by one or more processors (by processor threads) of the computing system, the computing system performs functions. will recognize that it exists. This structure may be directly computer readable by processors (such as when the executable component is a binary number). Alternatively, the structure may be structured to be interpretable and/or compiled (either in a single stage or in multiple stages) to produce such a binary number that is directly interpretable by processors. This understanding of the example structures of an executable component is within the understanding of one of ordinary skill in the art of computing when using the term “executable component”.

The term “executable component” is also used by those of ordinary skill in the art to exclusively or substantially It is understood to include exclusively implemented structures. Accordingly, the term “executable component” is a term for a structure well understood by those skilled in the art of computing, whether implemented in software, hardware, or a combination.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only for purposes of illustration and without limitation. Accordingly, the scope of the invention is indicated by the appended claims rather than by the foregoing description. All modifications made within the meaning and scope of equivalents to the claims are embraced within their scope.

Claims (20)

A PV power plant comprising at least one AC power generating unit, comprising:
Each of the one or more of the at least one AC power generating unit comprises:
DC power generator consisting of x MW solar strings -x is positive-;
one or more first DC/AC three-phase converters having a total published power rating of y MW, wherein the first DC/AC three-phase converter(s) receives DC power provided by the DC power generator and convert DC power to AC power and provide the converted AC power to a power grid through a transformer;
an energy store, the energy store configured to receive at an input of the energy store at least a portion of a remaining portion of the DC power generated by the DC power generator;
at least one second DC/AC three-phase converter having a total published power rating of z MW -z is positive, and wherein the second DC/AC three-phase converter(s) is the one or more second DC/AC three-phase converters receive DC power from the energy store at an input of , convert the received DC power from the energy store to AC power, and provide the converted AC power to the power grid via the transformer; and
turn the input of the energy store and the input of the at least one second DC/AC three-phase converter such that the input of the energy store and the input of the at least one second DC/AC three-phase converter are not turned on at the same time a switching mechanism configured to be on and off;
A PV plant where the sum of y and z is greater than x. According to claim 1,
A PV power plant wherein the sum of y and z is greater than twice x. According to claim 1,
wherein the sum of y and z is between 1.1 and 2 times x. According to claim 1,
y is a PV plant less than x. According to claim 1,
z is a PV plant greater than x. According to claim 1,
wherein the at least one AC power generating unit is a plurality of AC power generating units, and a ratio of (y+z)/x is substantially the same for each of the plurality of AC power generating units. According to claim 1,
a first separation device, wherein the DC power generator provides DC power to the first DC/AC three-phase converter(s) via the first separation device;
a second separation device, wherein the DC power generator provides DC power to the energy store via the second separation device; and
The PV power plant further comprising at least one of a third separation device, wherein the energy storage provides DC power to the second DC/AC three-phase converter(s) via the third separation device. According to claim 1,
a first separation device, wherein the DC power generator provides DC power to the first DC/AC three-phase converter(s) via the first separation device;
a second separation device, wherein the DC power generator provides DC power to the energy store via the second separation device; and
The PV power plant further comprising at least two of a third separation device, wherein the energy storage provides DC power to the second DC/AC three-phase converter(s) via the third separation device. According to claim 1,
a first separation device, wherein the DC power generator provides DC power to the first DC/AC three-phase converter(s) via the first separation device;
a second separation device, wherein the DC power generator provides DC power to the energy store via the second separation device; and
The PV power plant further comprising a third separation device, wherein the energy storage provides DC power to the second DC/AC three-phase converter(s) via the third separation device. According to claim 1,
The first DC/AC three-phase converter(s) is a PV power plant operating using a MEUPT controller. 11. The method of claim 10,
The second DC/AC three-phase converter(s) also operate using a MEUPT controller. According to claim 1,
wherein the second DC/AC three-phase converter(s) operates using a MEUPT controller. According to claim 1,
the PV power plant comprises a first set of one or more isolation diodes and a second set of one or more isolation diodes, the second set of one or more isolation diodes different from the first set of one or more isolation diodes;
wherein the one or more isolation diodes in the first set each have a forward direction away from the DC power generator, each of the x MW solar strings being associated with a corresponding one of the one or more isolation diodes in the first set;
The one or more isolation diodes in the second set also have a forward direction away from the DC power generator and are further positioned between the energy store and the DC power generator. According to claim 1,
The switching mechanism alternately turns on and off the input of the energy store and the input of the one or more second DC/AC three-phase converters so that when the input of the energy store is on, the one or more second DC a PV power plant, configured to cause the input of the at least one second DC/AC three-phase converter to be on when the input of the /AC three-phase converter is off and the input of the energy store is off. 15. The method of claim 14,
The switching mechanism is:
a first switch controlling the input of the energy store;
a second switch controlling the input of the at least one second DC/AC three-phase converter;
a duty factor adjuster (DFA) configured to control the first switch to be on and off at a predetermined frequency; and
an out-of-phase locking module configured to invert the phase of the DFA and control the second switch to be off and on at the predetermined frequency;
The duty factor adjuster and the abnormal synchronization module cause the first switch and the second switch to be turned on and off alternately, so that when the first switch is on, the second switch is turned off, and the first switch is turned off A PV power plant that causes the second switch to be on when off. delete delete delete delete delete

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