TWI498705B - Method and system for selecting between centralized and distributed maximum power point tracking in an energy generating system - Google Patents

Method and system for selecting between centralized and distributed maximum power point tracking in an energy generating system Download PDF

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Publication number
TWI498705B
TWI498705B TW098115860A TW98115860A TWI498705B TW I498705 B TWI498705 B TW I498705B TW 098115860 A TW098115860 A TW 098115860A TW 98115860 A TW98115860 A TW 98115860A TW I498705 B TWI498705 B TW I498705B
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Taiwan
Prior art keywords
energy generating
system
panel
generating devices
mode
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TW098115860A
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Chinese (zh)
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TW201009534A (en
Inventor
Jianhui Zhang
Ali Djabbari
Gianpaolo Lisi
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Nat Semiconductor Corp
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Priority to US12/152,478 priority Critical patent/US9077206B2/en
Priority to US12/152,566 priority patent/US7991511B2/en
Application filed by Nat Semiconductor Corp filed Critical Nat Semiconductor Corp
Publication of TW201009534A publication Critical patent/TW201009534A/en
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Publication of TWI498705B publication Critical patent/TWI498705B/en

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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381Dispersed generators
    • H02J3/382Dispersed generators the generators exploiting renewable energy
    • H02J3/383Solar energy, e.g. photovoltaic energy
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05FSYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/66Regulating electric power
    • G05F1/67Regulating electric power to the maximum power available from a generator, e.g. from solar cell
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381Dispersed generators
    • H02J3/382Dispersed generators the generators exploiting renewable energy
    • H02J3/383Solar energy, e.g. photovoltaic energy
    • H02J3/385Maximum power point tracking control for photovoltaic sources
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02SGENERATION OF ELECTRIC POWER BY CONVERSION OF INFRA-RED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S50/00Monitoring or testing of PV systems, e.g. load balancing or fault identification
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy
    • Y02E10/56Power conversion electric or electronic aspects
    • Y02E10/563Power conversion electric or electronic aspects for grid-connected applications
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy
    • Y02E10/56Power conversion electric or electronic aspects
    • Y02E10/58Maximum power point tracking [MPPT] systems

Description

Method and system for selecting between centralized and decentralized maximum power point tracking in an energy generating system Cross-reference related application

The present invention is related to the following application: "METHOD AND SYSTEM FOR PROVIDING CENTRAL CONTROL IN AN ENERGY GENERATING SYSTEM", US Patent Application No. ___ (Attorney Docket No. P07166), name US Patent Application No. ___ (Attorney Docket No. P07168) of "METHOD AND SYSTEM FOR PROVIDING LOCAL CONVERTERS TO PROVIDE MAXIMUM POWER POINT TRACKING IN AN ENERGY GENERATING SYSTEM", and the name "METHOD AND SYSTEM FOR ACTIVATING" US Patent Application No. ___ (Attorney Docket No. P07169) of AND DEACTIVATING AN ENERGY GENERATING SYSTEM. The subject matter disclosed in each of these patent applications is hereby incorporated by reference in its entirety in its entirety in its entirety herein in its entirety herein.

The disclosure is broadly related to energy production systems. More specifically, the disclosure relates to methods and systems for selecting between centralized and decentralized maximum power point tracking in an energy generating system.

Solar and wind provide a renewable and non-polluting source of energy relative to conventional non-renewable, polluting sources of energy (such as coal or oil). Therefore, solar energy and wind power have become an increasingly important source of energy that can be converted into electrical energy. For solar energy, photovoltaic panels arranged in an array typically provide means for converting solar energy into electrical energy. Similar arrays can be used to collect wind or other natural sources of energy.

When operating a photovoltaic array, maximum power point tracking (MPPT) is typically used to automatically determine at which voltage or current the array should be operated to produce maximum power output at a particular temperature and solar radiation. Although the MPPT is fairly simple for the overall array when the array is in ideal conditions (i.e., for the same radiation, temperature, and electrical characteristics of the various panels in the array), when there is a mismatch or a partial In the case of shadowing, the MPPT for the overall array is more complicated. In this case, the MPPT technique does not provide accurate results because of the relatively optimal conditions of the multi-peak power versus voltage characteristics of the unmatched array. Therefore, only some of the array panels are ideal for operation. Because for an array containing rows of panels, the most inefficient panel determines the current and efficiency of the overall panel, which results in a dramatic drop in power generation.

Therefore, some photovoltaic systems provide a DC-DC converter for each panel in the array. Each of the DC-DC converters performs MPPT to find the maximum power point of its corresponding panel. However, the DC-DC converter in this system may be blinded to select a local maximum point to operate its panel instead of selecting the actual maximum power point of the panel. In addition, the use of multiple DC-DC converters in this system can result in electrical losses caused by operating the converter, thus reducing the overall system performance.

In this patent document, FIGS. 1 through 12, which are discussed below, and various embodiments for illustrating the principles of the present invention are merely illustrative and are not intended to limit the scope of the invention. It will be apparent to those skilled in the art that the principles of the present invention can be applied to any type of suitably arranged device or system.

1 is an energy generating system 100 that can be centrally controlled, in accordance with an embodiment of the disclosure. The energy generating system 100 includes a plurality of energy generating devices (EGDs) 102, each coupled to a corresponding one of the local converters 104, and together forming an energy generating array 106. For a particular embodiment, as disclosed, the energy generating system 100 can include a photovoltaic system, and the energy generating device 102 can include a photovoltaic (PV) panel. However, it should be appreciated that the energy generating system 100 can include any suitable type of energy generating system, such as a wind turbine system, a fuel cell, and the like. For such embodiments, the energy generating device 102 can include a wind turbine, a fuel cell, and the like.

The photovoltaic system 100 includes a central array controller 110 and may also include DC-AC converters 112 that are other suitable loads in response to the operation of system 100 as a cascading system. However, it should be appreciated that system 100 can operate as a stand-alone system by coupling array 106 to a battery charger or other suitable energy storage device instead of DC-AC converter 112.

The PV panels 102 in the array 106 are disposed in the string 114. For the illustrated embodiment, array 106 includes two strings 114, each string 114 including three panels 102. However, it should be appreciated that array 106 can include any suitable number of strings 114, and each string 114 can include any suitable number of panels 102. And for the illustrated embodiment, the panels 102 in each string 114 are arranged in series. Thus, the output voltage of each local converter 104 is still close to its input voltage, while the high voltage is supplied to the input port of the DC-AC converter 112, which for some embodiments is operable at an input voltage of 150V to 500V. between. Thus, transformer-based converters (e.g., users in a parallel configuration string) are not required, creating the ability to achieve high efficiency and low cost local converters 104.

Each PV panel 102 is capable of converting solar energy into electrical energy. Each local converter 104 is coupled to its corresponding panel 102 and can reshape the voltage versus current relationship of the input provided by panel 103 such that the electrical energy generated by panel 102 can be the load of array 106 (not shown in Figure 1). Use). The DC-AC converter 112 is coupled to the array 106 and is capable of converting direct current (DC) generated by the local converter 104 to alternating current (AC) for the load, which may be coupled to the DC-AC converter 112.

Maximum Power Point Tracking (MPPT) automatically determines the voltage or current that panel 102 should operate to produce maximum power output at a particular temperature and solar radiation. Performing a centralized MPPT is fairly straightforward for an overall array when the array is under ideal conditions (i.e., having the same radiation, temperature, and electrical characteristics for each panel in the array). However, performing MPPT for the overall array 106 is more complicated when there is, for example, a mismatch or a partial obscuration. In this case, the MPPT technique does not provide accurate results because of the relatively optimal conditions of the multi-peak power versus voltage characteristics of the mismatched array 106. Thus, only some of the panels 102 in the array 106 are ideally operated, resulting in a sharp drop in energy production. Therefore, to address this issue, each local converter 104 can provide a local MPPT to its corresponding panel 102. In this manner, each panel 102 can operate at its own maximum energy point (MPP), whether ideal or not matched or obscured. For embodiments in which the energy generating device 102 includes a wind turbine, the MPPT can be used to adjust the blade pitch of the wind turbine. It should also be appreciated that the MPPT can be used to optimize the system 100 including other types of energy generating devices 102.

The central array controller 110 is coupled to the array 106 and is capable of communicating with the array 106 via a wired connection (eg, a series or parallel bus bar) or a wireless connection. The central array controller 110 can include a diagnostic module 120 and/or a control module 125. The diagnostic module 120 can monitor the photovoltaic system 100, and the control module 125 can control the photovoltaic system 100.

Diagnostic module 120 can receive local converter data for local converter 104 and device data for panel 102 corresponding to local converter 104 from respective local converters 104 in array 106. The "device data" used herein means the output voltage, output current, temperature, radiation, output power, and the like of the panel 102. Similarly, "local converter data" indicates local converter output voltage, local converter output current, local converter output power, and the like.

The diagnostic module 120 is also capable of generating reports on the system 100 and providing reports to the operator. For example, the diagnostic module 120 can display some or all of the device data and local converter data for viewing by the operator. In addition, the diagnostic module 120 can provide some or all of the device data and local converter data to the control module 125. The diagnostic module 120 can also analyze the data in any suitable manner and provide the results of the analysis to the operator and/or control module 125. For example, the diagnostic module 120 can determine the statistics for each panel 102 based on any suitable time frame, such as hourly, daily, weekly, or monthly.

The diagnostic module 120 is also capable of providing error monitoring to the array 106. Based on the information received from the local converter 104, the diagnostic module 120 can identify one or more panels 102 having defects, such as a failed panel 102, a failed panel 102, a shaded panel 102, a dirty panel 102. Wait. The diagnostic module 120 can also notify the operator when the defective panel 102 should be replaced, repaired, or cleaned.

Control module 125 can actually control array 106 by transmitting control signals to one or more local converters 104. For example, control module 125 can transmit a detour control signal to a particular local converter 104 that corresponds to panel 102 failure. The bypass control signal causes local converter 104 to bypass panel 102 thereof, effectively removing panel 102 from array 106 without affecting the operation of other panels 102 (like bypassed panel 102) in the same string 114.

In addition, control module 125 can transmit control signals to one or more local converters 104 that direct local converters 104 to adjust their output voltages or currents. For some embodiments, the MPPT function of local converter 104 can be moved to central array controller 110. For the embodiments, the control module 125 can also calibrate the MPP of each panel 102 and transmit a conversion ratio command to each local converter 104 according to the calibration so that each panel 102 operates on its own MPP, such as The person determined by the control module 125.

The control module 125 can also receive commands from the operator and initiate commands. For example, the operator can direct the control module 125 system 100 to be inline or stand-alone, and the control module 125 can respond to the operator by setting the system 100 to be connected or independent of the system 100.

Thus, by utilizing the central array controller 110, the photovoltaic system 100 can provide better utilization on a per panel basis. Moreover, system 100 increases flexibility by mixing different sources. The central array controller 110 also provides better protection and data collection for the entire system 100.

2 is a diagram showing a local converter 204, in accordance with an embodiment of the disclosure. The local converter 204 can represent one of the local converters 104 of FIG. 1, however, it should be appreciated that the local converter 204 can be placed in the energy generating system in any suitable manner without departing from the scope of the disclosure. . In addition, although shown as being coupled to an energy generating device 202, referred to as a PV panel, it should be understood that the local converter 204 can be coupled to a single battery of a PV panel or a panel combination of photovoltaic arrays, or It is coupled to another energy generating device 202, such as a wind turbine, a fuel cell, or the like.

The local converter 204 includes a power stage 206 and a local controller 208, which further includes an MPPT module 210 and an optional communication interface 212. Power stage 206 can include a DC-DC converter that can receive panel voltage and current from PV panel 202 as an input and reshape the input voltage versus current relationship to produce an output voltage and current.

The communication interface 212 of the local controller 208 can provide a communication path between the local converter 204 and a central array controller (e.g., the central array controller 110 of FIG. 1). However, for embodiments in which local converter 204 is not in communication with the central array controller, communication interface 212 may be omitted.

The MPPT module 210 can receive panel voltages and currents from the panel 202 as inputs, and can receive output voltages and currents from the power stage 206 if needed by the algorithm used. Based on the inputs, the MPPT module 210 can provide signals to control the power stage 206. In this manner, the MPPT module 210 of the local controller 208 can provide an MPPT for the PV panel 202.

By providing an MPPT, the MPPT module 210 maintains the corresponding panel 202 at a substantially fixed operating point (i.e., a fixed voltage Vpan and current Ipan corresponding to the maximum power point of the panel 202). Thus, for a given fixed solar radiation, in the steady state, if the local converter 204 corresponds to the relative or absolute maximum power point of the panel 202, the input power of the local converter 204 is fixed (ie, P pan =V pan I pan ). In addition, the local converter 204 has a relatively high performance, and therefore, the output power is almost equal to the input power (i.e., P out ≒ P pan ).

FIG. 3 is a diagram showing details of local converter 204, in accordance with an embodiment of the disclosure. For this embodiment, the power stage 206 is implemented as a single inductor, four-switch synchronous lift switching regulator, and the MPPT module 210 includes a power stage regulator 302, an MPPT control block 304, and two analog to digital converters ( ADC) 306 and 308.

The ADC 306 is capable of scaling and quantizing the analog panel voltage Vpan and the analog panel current Ipan to produce a digital panel voltage and a digital panel current, respectively. It should be appreciated that although the panel voltage and panel current are, for any suitable energy generating device 202 (eg, wind turbine, fuel cell, etc.), V pan can be the output device voltage and I pan can be the output device current . The ADC 306 coupled to the MPPT control block 304 and the communication interface 212 can also provide digital panel voltage and current to the MPPT control block 304 and the communication interface 212. Similarly, the ADC 308 can scale and quantize the analog output voltage and the analog output current to produce a digital output voltage and a digital output current, respectively. The ADC 308, which is also coupled to the MPPT control block 304 and the communication interface 212, can provide digital output voltage and current signals to the MPPT control block 304 and the communication interface 212. The communication interface 212 can provide the digital panel voltage and current signals generated by the ADC 306 and the digital output voltage and current signals generated by the ADC 308 to the central array controller.

The MPPT control block 304 coupled to the power stage regulator 302 can receive the digital panel voltage and current from the ADC 306 and receive the digital output voltage and current from the ADC 308. Based on at least some of the digital signals. The MPPT control block 304 can generate a conversion ratio command for the power stage regulator 302. The conversion ratio command includes a conversion ratio for the power stage regulator 302 for use in operating the power stage 206. For embodiments in which the MPPT control block 304 can generate a conversion command based on the digital panel voltage and current (rather than the digital output voltage and current), the ADC 308 only provides the digital output voltage and current to the communication interface 212 instead of The MPPT control block 304 is reached.

For certain embodiments, power stage regulator 302 includes lift mode control logic and a digital pulse width adjuster. The power stage regulator 302 can operate the power stage 206 in different modes by generating a pulse width modulation (PWM) signal according to the conversion ratio provided by the MPPT control block 304, which can be calibrated for power. The conversion ratio of the PWM signal of stage 206.

The power stage regulator 302 is coupled to the power stage 206 and can operate the power stage 206 by using the duty cycle and a mode, and operates the power stage 206, the duty cycle, and a mode according to the conversion ratio generated by the MPPT control block 304. It is determined according to the conversion ratio. For embodiments in which power stage 206 is implemented as a buck converter, the possible modes of power stage 206 include a degraded mode, an upgrade mode, a lift mode, a bypass mode, and a stop mode.

For this embodiment, when the conversion ratio CR falls within the lift range, the power stage regulator 302 can operate the power stage 206 in the lift mode; when the conversion ratio CR is less than the lift range, the power stage adjuster 302 can be degraded The power stage 206 is operated in mode; when the conversion ratio CR is greater than the lift range, the power stage regulator 302 can operate the power stage 206 in the upgrade mode. The lift range contains a value substantially equal to one. For example, for a particular embodiment, the lift range includes 0.95 to 1.05. When the power stage 206 is in the degraded mode, if the CR is less than the maximum degraded conversion ratio CR buck,max , the power stage regulator 302 can fully operate the power stage 206 in a degraded configuration. Similarly, if CR is greater than the minimum upgrade conversion ratio CR boost,min , power stage regulator 302 can operate power stage 206 entirely in an upgrade configuration.

Finally, when the conversion ratio is greater than CR buck,max and less than CR boost,min , the power stage regulator 302 can alternately operate the power stage 206 in the degraded configuration and upgrade configuration. In this case, the power stage regulator 302 can implement time division multiplexing to alternate between the degraded configuration and the upgrade configuration. Therefore, when the conversion ratio is closer to CR buck,max , the power stage regulator 302 operates the power stage 206 in the degraded configuration more frequently than the operating power level 206 in the upgrade configuration. Similarly, when the conversion ratio is closer to CR boost,min , the power stage regulator 302 operates the power stage 206 in the upgrade configuration more frequently than the operational power level 206 in the degraded configuration. When the conversion ratio is near the intermediate point between CR buck,max and CR boost,min , the power stage regulator 302 operates in a degraded configuration with the power level 206 being comparable to the frequency of operating the power stage 206 in the upgrade configuration. For example, when the power stage 206 is in the hoist mode, the power stage regulator 302 can alternately operate the power stage 206 in a degraded configuration and upgrade configuration.

For the described embodiment, power stage 206 includes four switches 310a-d, and an inductor L and a capacitor C. For some embodiments, switch 310 can include an N-channel power MOSFET. For a particular embodiment, the transistors can include a gallium nitride device on the crucible. However, it should be understood that switch 310 can be implemented in other suitable manners without departing from the scope of the disclosure. Additionally, power stage 206 can include one or more drivers (not shown in FIG. 3) to drive switch 310 (eg, a gate of a transistor). For example, for a particular embodiment, the first driver can be coupled between the power stage regulator 302 and the transistors 310a and 310b to drive the gates of the transistors 310a and 310b, and the second driver can be coupled to the power. The stage regulator 302 is coupled between the transistors 310c and 310d to drive the gates of the transistors 310c and 310d. For this embodiment, the PWM signal generated by power stage regulator 302 is supplied to the driver, and the gates of its individual transistors 310 are driven in accordance with the signals.

For the described embodiment, in operating power stage 206, power stage regulator 302 can generate digital pulses to control switch 310 of power stage 206. For the embodiments described below, the switch comprises a transistor. For the degraded configuration, the power stage regulator 302 turns off the transistor 310c and turns on the transistor 310d. Then, the pulses alternately turn on and off the transistor 310a and the transistor 310b, causing the power stage 206 to operate as a degrading regulator. For this embodiment, the duty cycle of transistor 310a is equal to duty cycle D, which is included in the conversion ratio command generated by MPPT control block 304. For the upgrade mode, the power stage regulator 302 turns on the transistor 310a and turns off the transistor 310b. The pulses alternately turn on and off transistor 310c and transistor 310d to operate power stage 206 as an upgrade regulator. For this embodiment, the duty cycle of transistor 310 is equal to 1-D.

For the lift mode, the power stage regulator 302 performs time division multiplexing between the downgrade and upgrade configurations, as described above. Power stage regulator 302 generates control signals for the degraded switch pairs of transistors 310a and 310b, and control signals for the upgrade switch pairs of transistors 310c and 310d. The duty cycle of the transistor 310a is fixed to the duty cycle corresponding to CR buck,max , and the duty cycle of the transistor 310c is fixed to the duty cycle corresponding to CR boost,min . The ratio between the degraded composition and the upgrade constituent operations over a specified period of time is linearly proportional to D.

When the output voltage approaches the panel voltage, the power stage 206 operates in the lift mode. In this case, for the described embodiment, the stress caused by the inductor current chopping and voltage switching is much less than that of the SEPIC and conventional buck converters. Moreover, the power stage 206 can achieve higher performance than conventional lift converters.

For certain embodiments, as will be described in greater detail below with respect to FIG. 4, MPPT control block 304 can operate in one of four modes: sleep mode, tracking mode, hold mode, and bypass mode. When the panel voltage is less than a predetermined primary threshold voltage, the MPPT control block 304 can operate in a sleep mode. In sleep mode, MPPT control block 304 turns transistors 310a-d off. For example, for some embodiments, when MPPT control block 304 is in sleep mode, MPPT control block 304 can generate a conversion ratio command that causes power stage regulator 302 to turn off transistors 310a-d. Thus, power stage 206 is in stop mode and panel 202 is bypassed, thus effectively avoiding panel 202 from the photovoltaic system using panel 202.

When the panel voltage rises above the primary threshold voltage, the MPPT control block 304 operates in the tracking mode. In this mode, MPPT control block 304 performs maximum power point tracking on panel 202 to determine the optimal conversion ratio of power stage regulator 302. And in this mode, the power stage regulator 302 will place the power stage 206 in a degraded mode, an upgrade mode, or a lift mode depending on the currently generated conversion ratio command.

In addition, for some embodiments, the MPPT control block 304 may also include a stop register, which may be operated by a system operator or any suitable control program (eg, a control program located in the central array controller). The modification is to force the MPPT control block 304 to maintain the power stage 206 in the stop mode. For this embodiment, unless (i) the panel voltage exceeds the primary threshold voltage, and (ii) the stop register indicates that the MPPT control block 304 will move the power stage 206 out of the stop mode, the MPPT control block 304 will not Start working in tracking mode.

When the MPPT control block 304 finds the optimal conversion ratio, the MPPT control block 304 can operate in the hold mode for a predetermined period of time. In this mode, MPPT control block 304 may continue to provide the same conversion ratio to power stage adjuster 302 as determined in the tracking mode. And in this mode, as in the tracking mode, the power stage 206 is in the degraded mode, the upgrade mode, or the lift mode depending on the optimal conversion ratio provided by the conversion ratio command. After a predetermined period of time has elapsed, the MPPT control block 304 can be restored to the tracking mode to ensure that the optimal conversion ratio does not change, or if the conditions of the panel 202 change, a new optimal conversion ratio can be found.

As explained in more detail below with respect to Figures 5-8, the central array controller can set the MPPT control area when the various panels in the photovoltaic array (e.g., panel 202) are uniformly illuminated and there is no mismatch between the panels 202. Block 304 and power stage 206 are in a bypass mode. In the bypass mode, for some embodiments, transistors 310a and 310d are on, and transistors 310b and 310c are off so that the panel voltage is equal to the output voltage. For other embodiments, power stage 206 can include an optional switch 312 that can couple input 埠 to output 以 such that the output voltage is equal to the panel voltage. In this manner, local converter 204 can be substantially removed from the system when local MPPT is not required, thereby maximizing performance and increasing lifetime by reducing losses associated with local converter 204.

Thus, as described above, MPPT control block 304 can operate in a sleep mode and place power stage 206 in a stop mode that bypasses panel 202. The MPPT control block 304 can also operate in either a tracking mode or a hold mode. Regardless of the mode, the MPPT control block 304 can place the power stage 206 in one of the degraded mode, the upgrade mode, and the elevating mode. Finally, the MPPT control block 304 can operate in the bypass mode and place the power stage 206 in the bypass mode. In the bypass mode, the local converter 204 is bypassed, allowing the panel 202 to be directly coupled into the array. Other panels 202.

By operating the local converter 204 in this manner, the string current of the row of panels comprising the panel 202 is independent of the individual panel currents. Conversely, the string current is set by the string voltage and the total string power. In addition, the unmasked panel 202 can continue to operate at the highest power point without regard to the condition that portions of other panels in the string are obscured.

For an alternative embodiment, when the MPPT control block 304 finds the optimal conversion ratio, the MPPT control block 304 may not operate in the hold mode when the optimal conversion ratio corresponds to the lift mode of the power stage 206. It is operated in the bypass mode. In the lift mode, the output voltage is close to the panel voltage. Thus, panel 202 can operate close to its maximum power point by bypassing local converter 204, thus increasing performance. As with the previous embodiment, the MPPT control block 304 periodically reverts from the bypass mode to the tracking mode to verify that the optimal conversion ratio falls within the lift mode range.

For some embodiments, the MPPT control block 304 can gradually adjust the conversion ratio for the power stage regulator 302 instead of the general stepwise variation to avoid the transistors, inductors, and The stress of the capacitor. For some embodiments, the MPPT control block 304 can implement different MPPT techniques to adjust the panel voltage or conductivity rather than adjusting the conversion ratio. In addition, the MPPT control block 304 can adjust the reference voltage instead of adjusting the conversion ratio for dynamic input voltage regulation.

In addition, MPPT control block 304 can enable relatively fast and smooth transitions between the stop mode of power stage 206 and other modes. The MPPT control block 304 can include non-volatile memory that can store previous maximum power point states, such as conversion ratios and the like. For this embodiment, when the MPPT control block 304 transitions to the sleep mode, the maximum power point state is stored in this non-volatile memory. When the MPPT control block 304 subsequently returns to the tracking mode, the stored maximum power point state can be used as the initial maximum power point state. In this manner, for power stage 206, the transition time between stop and other modes can be significantly reduced.

For some embodiments, MPPT control block 304 can also provide over-power and/or over-voltage protection to local converter 204. Because signals Vpan and Ipan are forwarded to MPPT control block 304 via ADC 306, MPPT control block 304 attempts to draw maximum power. If the power stage 206 is output as an open circuit, the output voltage of the local converter 204 reaches a maximum value. Thus, for over power protection, the output current of local converter 204 can be used as a signal to turn MPPT control block 304 on and off. For this embodiment, if the output current drops too low, the conversion ratio can be set by the MPPT control block 304 such that the panel voltage is nearly equal to the output voltage.

For overvoltage protection, the MPPT control block 304 can have a maximum conversion ratio for the conversion ratio command that the MPPT control block 304 does not exceed. Therefore, if the conversion ratio continues to be higher than the maximum conversion ratio, the MPPT control block 304 limits the conversion ratio to the maximum value. This ensures that the output voltage does not increase beyond the corresponding maximum. The value of the maximum conversion ratio can be fixed or adaptive. For example, an adaptive conversion ratio limit can be achieved by sensing the panel voltage and calculating the estimated value of the output voltage corresponding to the next stylized value of the conversion ratio according to the conversion ratio of the power stage 206.

Moreover, for the described embodiment, power stage 206 includes an optional one-way switch 314. When the power stage 206 is in the stop mode, an optional switch 314 can be included to allow the panel 202 to be bypassed, thereby removing the panel 202 from the array and allowing the other panels 202 to continue operating. For a particular embodiment, the unidirectional switch 314 can include a diode. However, it should be understood that the unidirectional switch 314 can include any other suitable type of unidirectional switch, without departing from the scope of the disclosure.

4 is a diagram showing a method 400 of implementing MPPT in local converter 204, in accordance with an embodiment of the disclosure. The embodiment of method 400 is merely illustrative. Other embodiments of method 400 may be implemented without departing from the scope of the disclosure.

The method 400 begins with the MPPT control block 304 operating in the sleep mode (step 401). For example, MPPT control block 304 may generate a conversion ratio command to cause power stage regulator 302 to turn off transistors 310a-d of power stage 206, thereby placing power stage 206 in a stop mode and bypassing panel 202.

While in the sleep mode, the MPPT control block 304 monitors the panel voltage Vpan and compares the panel voltage to the primary threshold voltage Vth (step 402). For example, ADC 306 can convert the panel voltage from an analog signal to a digital signal and provide the digital panel voltage to MPPT control block 304, which stores a primary threshold voltage for comparison with the digital panel voltage.

As long as the panel voltage remains below the primary threshold voltage (step 402), the MPPT control block 304 continues to operate in the sleep mode. Further, as described above, when the stop register indicates that the power stage 206 remains in the stop mode, the MPPT control block 304 remains in the sleep mode. However, once the panel voltage exceeds the primary threshold voltage (step 402), the MPPT control block 304 generates a conversion ratio command to operate the power stage 206, the conversion ratio command including the initial conversion ratio (step 403). For example, for an embodiment, MPPT control block 304 begins with a conversion ratio of one. Alternatively, the MPPT control block 304 can store the optimal conversion ratio determined in the previous tracking mode. For this embodiment, MPPT control block 304 may initialize the conversion ratio to be the same as the previously determined optimal conversion ratio. Moreover, the conversion ratio command generated by the MPPT control block 304 is supplied to the power stage regulator 302, which operates the power stage 206 using the initial conversion ratio.

At this time, the MPPT control block 304 monitors the panel current I pan and the output current I out and compares the panel current and the output current with the threshold current I th (step 404). For example, the ADC 306 can convert the panel current from an analog signal to a digital signal and supply the digital panel current to the MPPT control block 304. The ADC 308 can convert the output current from an analog signal to a digital signal and supply the digital output current to the MPPT. Control block 304 stores a threshold current for comparison with the digital panel current and the digital output current. As long as at least one of the currents Ipan and Iout remains below the threshold current (step 404), the MPPT control block 304 continuously monitors the current level. However, once the currents exceed the threshold current (step 404), the MPPT control block 304 begins operating in the tracking mode, which includes initializing the set tracking variable T to one and initializing a counter (step 406).

Although not shown in the method 400 of FIG. 4, it should be appreciated that in the tracking mode, the MPPT control block 304 can continue to monitor the panel voltage and compare the panel voltage to a secondary threshold voltage that is less than the primary threshold voltage. . If the panel voltage is reduced below the secondary threshold voltage, the MPPT control block 304 reverts to the sleep mode. By using a secondary threshold voltage that is less than the primary threshold voltage, the MPPT control block 304 is immune to noise, thus preventing the MPPT control block 304 from frequently switching between sleep and tracking modes.

After setting the value of the tracking variable and initializing the counter, MPPT control block 304 calculates the initial power of panel 202 (step 408). For example, the ADC 306 can provide digital panel current and panel voltage signals ( Ipan and Vpan ) to the MPPT control block 304, after which the MPPT control block 304 multiplies the signals to determine the device (or panel). The initial value of power (I pan . V pan ).

After calculating the initial power, the MPPT control block 304 modifies the conversion ratio in a first direction and generates a conversion ratio command including the modified conversion ratio (step 410). For example, for certain embodiments, MPPT control block 304 may increase the conversion ratio. For other embodiments, MPPT control block 304 may reduce the conversion ratio. After the system has stabilized over time, the MPPT control block 304 calculates the current power of the panel 202 (step 412). For example, ADC 306 can provide digital panel current and panel voltage signals to MPPT control block 304, after which MPPT control block 304 multiplies these signals to determine the current value of panel power.

MPPT control block 304 then compares the now calculated power with the previously calculated power, which is the initial power (step 414). If the current power is greater than the previous power (step 414), the MPPT control block 304 modifies the conversion ratio in the same direction as the previous modification and generates an updated conversion ratio command (step 416). For some embodiments, the conversion ratio is modified to be higher or lower with an equal increase. For other embodiments, the conversion ratio can be modified to be higher or lower in linear or non-linear increments to optimize system response. For example, for some systems, if the conversion ratio is very different from the optimal value, then as you get closer to the optimal value, it is better to use a larger increment first, and then use a smaller increment.

The MPPT control block 304 also determines if the tracking variable T is equal to 1, indicating that the conversion ratio has changed in the same direction as the previous calculation because the conversion ratio has changed before the previous calculation (step 418). Therefore, when T is equal to 1, the panel power increases, which is the same direction as the previous change in the conversion ratio. In this case, after the system has been stabilized for a period of time, the MPPT control block 304 again calculates the current power of the panel 202 (step 412) and compares the current power with the previous power (step 414). However, if MPPT control block 304 determines that T is not equal to 1, indicating that the conversion ratio has changed in the opposite direction to the previous calculation (step 418) because the conversion ratio has changed before the previous calculation (step 418), then MPPT control block 304 sets T to 1, and increment the counter (step 420).

MPPT control block 304 then determines if the counter exceeds counter threshold Cth (step 422). If the current counter value does not exceed the counter threshold (step 422), after the system is stabilized for a period of time, the MPPT control block 304 again calculates the current power of the panel 202 (step 412) and compares the current power with the previous power. (Step 414) to determine if the panel power is increasing or decreasing.

If the MPPT control block 304 determines that the current power is not greater than the previous power (step 414), the MPPT control block 304 modifies the conversion ratio in the opposite direction to the previous modification and generates an updated conversion ratio command (step 424). The MPPT control block 304 also determines if the tracking variable T is equal to 2, and a T equal to 2 indicates that the conversion ratio has been modified in the opposite direction to the previous calculation because the conversion ratio has changed before the previous calculation (step 426). In this case, after the system has been stabilized for a period of time, the MPPT control block 304 again calculates the current power of the panel 202 (step 412) and compares the current power with the previous power (step 414).

However, if the MPPT control block 304 determines that T is not equal to 2, indicating that the conversion ratio has been changed in the same direction as the previous calculation (step 426) because the conversion ratio has been changed before the previous calculation, the MPPT control block sets T to 2. And increment the counter (step 428). The MPPT control block 304 then determines if the counter exceeds the counter threshold Cth (step 422), as described above.

If the counter does not exceed the counter threshold (step 422), it indicates that the conversion ratio has been changed several times in the first direction and the second direction, the number of times is greater than the counter threshold, and the MPPT control block 304 finds the corresponding panel. The optimal conversion ratio of the maximum power point of 202, and the MPPT control block 304 begins operating in the hold mode (step 430).

While in the hold mode, MPPT control block 304 can set a timer and reinitialize the counter (step 432). When the timer expires (step 434), the MPPT control block 304 can revert to the tracking mode (step 436) and calculate the current power (step 412) to compare the current power with the MPPT control block 304 in the tracking mode. Power (step 414). In this manner, MPPT control block 304 can ensure that the optimal conversion ratio is not changed, or that different optimal conversion ratios can be found when the conditions of panel 202 change.

Although FIG. 4 shows an example of a method 400 for tracking the maximum power point of the energy generating device 202, various changes can be made to the method 400. For example, although method 400 is described with reference to a photovoltaic panel, method 400 can be used with other energy generating devices 202, such as wind turbines, fuel cells, and the like. Still further, although the method 400 is described with reference to the MPPT control block 304 of FIG. 3, it should be appreciated that the method 400 can be used with any suitably arranged MPPT control block without departing from the scope of the disclosure. Moreover, for some embodiments, in step 430, if MPPT control block 304 determines that the optimal conversion ratio is equivalent to the lift mode of power stage 206, MPPT control block 304 can operate in a sleep mode rather than a hold mode. For these embodiments, after the sleep mode, the time of the timer period may be the same as or different from the time of the timer of the hold mode. Moreover, although shown in a series of steps, the steps in method 400 may overlap, occur in parallel, occur multiple times, or occur in a different order.

5 is a display energy generation system 500 that includes a plurality of energy generating devices 502 and a central array controller 510 that can be centralized or integrated with the energy generating system 100, in accordance with an embodiment of the disclosure. It is a decentralized MPPT. For the illustrated embodiment, the energy generating system is referred to as a photovoltaic system 500, and the photovoltaic system 500 includes an array of photovoltaic panels 502 each coupled to a corresponding local converter 504.

Each local converter 504 includes a power stage 506 and a local controller 508. Moreover, for some embodiments, each local converter 504 can be bypassed via an optional internal switch (e.g., switch 312). When bypassed, the output voltage of local converter 504 is substantially equal to its input voltage. In this manner, the loss associated with the operation of local converter 504 can be minimized or even eliminated (when local converter 504 is not needed).

In addition to the central array controller 510, embodiments of the system 500 also include a conversion stage 512, a square 514, and a data bus 516. The central array controller 510 includes a diagnostic module 520, a control module 525, and an optional conversion stage (CS) optimizer 530. Moreover, the described embodiment sets the global domain controller 540 to the conversion stage 512. However, it should be appreciated that the global controller 540 can be located in the central array controller 510 rather than in the conversion stage 512. Moreover, the CS optimizer 530 can be disposed in the conversion stage 512 instead of being disposed in the central array controller 510.

For some embodiments, panel 502 and local converter 504 represent panel 102 and local converter 104 of FIG. 1 and/or represent panel 202 and local converter 204 of FIG. 2 or 3, central array controller 510 can represent The central array controller 110 of FIG. 1 and/or the conversion stage 512 can represent the DC-to-AC converter 112 of FIG. In addition, the diagnostic module 520 and the control module 525 can respectively represent the diagnostic module 120 and the control module 125 of FIG. 1 . However, it should be appreciated that the components of system 500 can be implemented in any suitable manner. The conversion stage 512 can include a DC-AC converter, a battery charger, or other energy storage device, or any other suitable component. The grid 514 can include any suitable load that can operate in accordance with the energy produced by the photovoltaic system 500.

Each local controller 508 can provide data and local converter data for the corresponding panel device to the central array controller 510 via the data bus 516 or via a wireless connection. Based on this information, the diagnostic module 520 can determine whether the panel 502 is operating under quasi-ideal conditions, i.e., the panel 502 does not mismatch and is substantially uniformly illuminated. In this case, the diagnostic module 520 can cause the control module 525 to place the system 500 in a centralized MPPT (CMPPT) mode. To accomplish this state, control module 525 can transmit a stop signal to each local controller 508 via data bus 516 to stop local converter 504 by operating local converter 504 in a bypass mode. The control module 525 can also transmit an enable signal to the global controller 540.

In the bypass mode, the local controller 508 no longer implements the MPPT, and the output voltage of the power stage 506 is substantially equal to the panel voltage of the panel 502. Thus, the loss associated with operating the local converter 504 can be minimized and the performance of the system 500 can be maximized. When the local converter 504 is operating in the bypass mode, the global controller 540 can implement CMPPT on the array of panels 502.

The diagnostic module 520 can also determine if certain panels 502 are obscured or mismatched (i.e., certain panels 502 have different characteristics than other panels 502 in the array). In this case, the diagnostic module 520 can cause the control module 525 to place the system 500 in a decentralized MPPT (DMPPT) mode. To accomplish this, control module 525 can transmit an enable signal to each local controller 508 via data bus 516 to enable local converter 504 by allowing normal operation of local converter 504. Control module 525 can also transmit a stop signal to global controller 540.

When some of the panels 502 are obscured, the diagnostic module 520 can also determine that some of the shaded panels 502 are partially obscured. In this case, in addition to causing the control module 525 to place the system 500 in the DMPPT mode, the diagnostic module 410 can also perform a full diagnostic scan of the system 500 to ensure a partial controller 508 of the partially shielded panel 502. The true maximum power point can be found instead of the local maximum. For embodiments in which the energy generating device 502 includes a wind turbine, the diagnostic module 520 can determine whether certain wind turbines are caused by changing wind patterns, hills, or other wind blocking structures, or other conditions that affect wind conditions. Be obscured."

The case where the photovoltaic system 500 is partially shielded is illustrated in Figures 6 and 7A-C. Figure 6 shows a photovoltaic array 600 with portions partially obscured. 7A-C are graphs 700, 705, and 710 showing voltage versus power characteristics corresponding to the three photovoltaic panels of FIG.

The array has three strings 610 provided with photovoltaic panels. The three panels in string 610c are labeled Panel A, Panel B, and Panel C. It should be understood that such panels may represent panels 502 of Figure 5 or panels in any other suitably arranged photovoltaic system. Some of the panels are completely covered or partially covered by the obscured area 620.

In the illustrated example, panel A is fully illuminated, panel B is partially obscured by masked area 620, and panel C is completely obscured by masked area 620. The voltage versus power characteristics in graph 700 in FIG. 7A correspond to panel A, the voltage versus power characteristics of graph 705 in FIG. 7B correspond to panel B, and the voltage versus power characteristics of graph 710 in FIG. 7C correspond to panel C.

Thus, as shown in FIG. 705, the partially masked panel B has a local maximum 720 that is different from the actual maximum power point 725. The diagnostic module 520 of the central array controller 510 can determine that the panel B is partially obscured and perform a full diagnostic scan to ensure that panel B is operating at its actual maximum power point 725 for its local controller 508 rather than local maximum Point 720. Instead of operating at the actual maximum power point (e.g., point 725), panel 502 operating at a local maximum power point (e.g., point 720) is referred to as a "under-implemented" panel 502.

For a particular embodiment, the diagnostic module 520 can identify the partially obscured panel 502 as follows. First, the diagnostic module 520 assumes that the panels 1, ..., N are sub-combinations of the panels 502 in the array under consideration, which have the same characteristics, and assume that Ppan,i belongs to the combination [1,...,N] The output power of the i-th panel 502. therefore,

Where P pan,max is the output power of the best implementation panel 502, and P pan,min is the output power of the worst implementation panel 502.

The diagnostic module 520 also defines a variable ψ i by :

The probability that all or part of the i-th panel 502 is obscured can be expressed by the following formula:

Where k is a constant less than or equal to 1. Then is:

.

The diagnostic module 520 also defines ρ DMPPT as the minimum of the probability function ρ max , making DMPPT necessary. Therefore, if ρ max is greater than ρ DMPPT , DMPPT will be enabled. In addition, ρ diag is defined as the minimum of the probability function ρ max such that a diagnostic function is necessary to determine any panel 502 that is not partially obscured by the MPP. Therefore, if ρ max is greater than ρ diag , the diagnostic module 520 recognizes the panel 502 as partially obscured and performs a scan on the identified panel 502 .

Diagnostic module 520 can still enable DMPPT for a relatively small mismatch of panel 502, but for larger mismatches, diagnostic module 520 can also perform a full diagnostic scan. For its part, the value of ρ DMPPT is usually less than the value of ρ diag .

Thus, for certain embodiments, when ρ maxDMPPT , the diagnostic module 520 can determine that the system 500 should operate in the CMPPT mode, and when ρ DMPPTmaxdiag , the system 500 should operate in the DMPPT mode. Medium, and when ρ max > ρ diag , system 500 should operate in DMPPT mode along with a full diagnostic scan.

For such embodiments, the full diagnostic scan may include a complete scan of the voltage versus power characteristics of each panel j for ρ j > ρ diag . The diagnostic module 520 can individually scan the characteristics of each panel 502 according to the timing given by the central array controller 510. In this manner, the conversion stage 512 can continue to operate normally.

The CS optimizer 530 can optimize the operating point of the conversion stage 512 when the system 500 is operating in the DMPPT mode. For an embodiment, the operating point of the conversion stage 512 can be set to a constant. However, for embodiments using CS optimizer 530, the operating point of conversion stage 512 can be optimized by CS optimizer 530.

For a particular embodiment, CS optimizer 530 can determine the optimized operating point of conversion stage 512 as follows. For the ith power stage 506, its duty cycle is defined as D i and its conversion ratio is defined as M(D i ). Power stage 506 is designed to have a nominal conversion ratio M 0 . Thus, M 0 as close as possible to operate the power stage 506 can provide higher efficiency, reduced pressure, and to reduce the possibility of output voltage saturation. For power stage 506 that includes a step-up converter, M 0 can be one.

Therefore, the principle of optimization can be defined as follows:

Where Ipan,i is the input current of the i-th power stage 506, I out,i is the output current of the i-th power stage 506, η i is the efficiency of the i-th power stage 506, and I LOAD is the conversion stage 512 Input current. Therefore, the principle of optimization can be rewritten as follows:

The CS optimizer 530 can be optimized by using standard current mode control techniques at the input of the conversion stage 512, setting the input current of the conversion stage 512 to I LOAD .

FIG. 8 is a diagram showing a method 800 of selecting a centralized MPPT or a decentralized MPPT for an energy generating system 500, in accordance with an embodiment of the disclosure. The embodiment of method 800 is merely illustrative. Other embodiments of method 800 may be implemented without departing from the scope of the disclosure.

The method 800 begins with the diagnostic module 520 setting a timer (step 802). Diagnostic module 520 can trigger initialization of method 800 in a round-robin fashion using a timer. The diagnostic module 520 then analyzes the energy generating devices in system 500, such as panel 502 (step 804). For example, for some embodiments, the diagnostic module 520 can analyze the panel 502 by calculating the panel power P pan of each panel 502, and then determine a number of other values based on the calculated values of P pan , as described above. 5 stated. For example, the diagnostic module 520 can determine the maximum and minimum values of the calculated value P pan (P pan, max and P pan, min respectively ), and then use the maximum and minimum values to calculate that each panel 502 is completely The probability of being covered or partially obscured (ρ). The diagnostic module 520 can also determine the maximum value ρ max of the calculated probability.

After analyzing panel 502 (step 804), diagnostic module 520 can determine whether photovoltaic system 500 is operating under quasi-ideal conditions (step 806). For example, for some embodiments, the diagnostic module 520 can compare the calculated maximum probability (p max ) of the panel 502 to be masked with a predetermined DMPP (ρ DMPPT ). If ρ max is less than ρ DMPPT , the maximum output power and minimum output power of panel 502 are close enough so that the mismatch between panels 502 can be considered to be minimal and system 500 can be considered to operate under quasi-ideal conditions. If ρ max is not less than ρ DMPPT , the maximum output power and minimum output power of panel 502 are sufficiently different that the mismatch between panels 502 cannot be considered to be extremely small, and system 500 is deemed not to operate under quasi-ideal conditions.

If the diagnostic module 520 determines that the system 500 is not operating under a quasi-ideal condition (step 806), the control module 525 enables the local controller 508 (step 808) and stops the global controller 540 (step 810), thereby System 500 is located in DMPPT mode. Therefore, in this case, the local controller 508 implements MPPT for each panel 502.

Because the DMPPT mode is used for relatively small mismatches between the panels 502, the diagnostic module 520 can determine that the system 500 is inoperative even when the probability of the masked panel 502 is low (but not very low). Under quasi-ideal conditions. Therefore, after entering the DMPPT mode, the diagnostic module 520 determines if the probability of the shaded panel 502 is high (step 812). For example, the diagnostic module 520 can compare the maximum probability (p max ) at which the panel 502 is obscured with a predetermined diagnostic threshold (ρ diag ). If ρ max is greater than ρ diag , the maximum output power and the minimum output power of the panel 502 are sufficiently different, so that the probability of mismatch between the panels 502 is considered to be extremely high, and therefore, the probability that at least one panel 502 is shielded Very high.

If the probability of panel 502 being masked is high (step 812), diagnostic module 520 performs a full-feature scan for any panel 502 that may be obscured (step 814). For example, the diagnostic module 520 can identify the panel 502 that may be obscured by comparing the probability (p) and diagnostic threshold (ρ diag ) that the panel is obscured for each panel 502. If the ρ of the particular panel is greater than ρ diag , then the output power of the particular panel 502 is sufficiently different from the maximum output power of one of the panels 502 in the system 500, the probability that the particular panel 502 is at least partially shielded is relatively high.

When performing a full characteristic scan, the diagnostic module 520 can individually perform voltage versus power characteristic scans for each panel 502 that is likely to be masked according to the timing provided by the central array controller 510. In this manner, the conversion stage 512 can continue to operate normally during the scan.

If during the implementation of any full-feature scan, the diagnostic module 520 determines that any of the panels 502 are under-implemented (ie, operating at a local maximum power point (MPP), such as a local MPP 720, rather than an actual MPP, such as MPP725). The control module 525 can provide corrections for the less than implemented panels 502 (step 816).

At this time, or if the probability of the panel 502 being masked is not high (step 812), the diagnostic module 520 determines if the timer has expired (step 818), indicating that the method 800 must be initialized again. Once the timer expires (step 818), the diagnostic module 520 resets the timer (step 820) and begins analyzing the panel 502 again (step 804).

If the diagnostic module 520 determines that the system 500 is operating under a quasi-ideal condition (step 806), the control module 525 stops the local controller 508 (step 822) and enables the global controller 540 (step 824), thereby causing the system 500 Set in CMPPT mode. Thus, in this case, global controller 540 implements MPPT for the entire system 500.

At this point, the diagnostic module 520 determines if the timer has expired (step 818), indicating that the method 800 must be initialized again. Once the timer expires (step 818), the diagnostic module 520 resets the timer (step 820) and begins analyzing the panel 502 again (step 804).

Although FIG. 8 has shown an example of a method 800 of selecting between centralized and decentralized MPPTs, various changes can be made to method 800. For example, although method 800 is described in conjunction with a photovoltaic system, method 800 can be used with other energy production systems 500, such as wind turbine systems, fuel cell systems. Still further, although the method 800 is described in conjunction with the system 500 of FIG. 5, it should be appreciated that the method 800 can be used with any suitably arranged energy generating system without departing from the scope of the disclosure. Moreover, although shown as a series of steps, the steps in method 800 may overlap, occur in parallel, occur multiple times, or occur in a different order.

9 is a system 900 showing a local controller 908 for activating and deactivating a local converter 904 in an energy generating system, in accordance with an embodiment of the disclosure. System 900 includes an energy generating device 902 (referred to as a photovoltaic panel 902), and a local converter 904. Local converter 904 includes power stage 906, local controller 908, and initiator 910.

Local converter 904 may represent one of local converter 104 of FIG. 1, one of local converters 204 of FIG. 2 or 3, and/or one of local converters 504 of FIG. 5, however, it should be understood that Local converter 904 can be implemented in any suitable set of energy generating systems without departing from the scope of the disclosure. Accordingly, it should be appreciated that system 900 can be coupled in series and/or coupled in parallel to other similar systems 900 to form an energy generating array.

For the embodiment, the initiator 910 is coupled between the panel 902 and the local controller 908. For some embodiments, the initiator 910 can activate and deactivate the local controller 908 based on the output voltage of the panel 902. When the output voltage of panel 902 is too low, initiator 910 can provide a substantially zero supply voltage to local controller 908, thereby turning off local controller 908. When the output voltage of panel 902 is high, initiator 910 can provide a non-zero supply voltage to local controller 908 to cause local controller 908 to operate.

It should be appreciated that in addition to providing a supply voltage to the local controller 908, the initiator 910 can activate and deactivate the local controller 908 in any suitable manner. For example, for an alternative embodiment, the launcher 910 can set one or more pins of the local controller 908 to activate and deactivate the local controller 908. For another alternative embodiment, the initiator 910 can write the first predetermined value to the first register in the local controller 908 to activate the local controller 908 and the second predetermined value ( The first register or the second register in the local controller 908 can be written to the local register 908 to stop the local controller 908, depending on the particular implementation.

Thus, system 900 can cause local converter 904 to operate autonomously without the use of a battery or an external power source. When the solar radiation is high enough, the output panel voltage Vpan is increased to a level that causes the starter 910 to begin generating a non-zero supply voltage Vcc . At this point, the local controller 908 and/or the central array controller (not shown in Figure 9) can begin to implement the boot process, such as initialization of the scratchpad, preliminary voltage comparison between the panels 902, analog to digital converter calibration. , clock synchronization or clock insertion, synchronous start of power stage 906, and the like. Similarly, the stop procedure can be implemented prior to stopping the system 900, such as in a separate application scenario, synchronization with the backup unit, synchronization with the power stage 906, and the like. During these stop procedures, the initiator 910 can still keep itself activated.

Moreover, for certain embodiments, the initiator 910 can provide over power protection to the local converter 904. As described above in connection with FIG. 3, the MPPT control block 304, which is part of the local controller 208, can provide overpower protection. However, as an alternative embodiment of the system including the initiator 910, instead the initiator 910 can provide such a protection function. Thus, for this alternative embodiment, if the output current drops too low, the activator 910 may be closed MPPT function local controller 908 so that the panel voltage equals the output voltage V pan nearly V out.

10 is a diagram 920 of device voltage of display system 900 as a function of time, in accordance with an embodiment of the disclosure. For the photovoltaic panel 902, in the case where the solar radiation level oscillates near the voltage activation level (Vt -on ) of the initiator 910, the same voltage activation level is used as the voltage stop level ( Vt- Off ) will cause unwanted system 900 to start and stop multiple times. Therefore, as shown in FIG. 920, a lower voltage stop level is used to avoid this phenomenon. By using a lower voltage stop level, system 900 can maintain a consistent start until the solar radiation level is sufficiently lowered such that the panel voltage drops below the voltage start level. Therefore, frequent startup and stop can be avoided, and the system 900 is provided with noise immunity.

For some embodiments, after the panel voltage exceeds the voltage enable level at which the local controller 908 is activated, if the panel voltage drops below the voltage enable level, the local controller 908 begins to stop the program to be able to compare the panel. The voltage stops more quickly when it continues to fall below the voltage stop level. Moreover, for some embodiments, prior to reaching the voltage stop level, in some cases, local controller 908 can turn off initiator 910 and itself.

11 is a display launcher 910, in accordance with an embodiment of the disclosure. For this embodiment, the initiator 910 includes a power supply 930, a plurality of resistors R1, R2, R3, and a diode D. Resistors R1 and R2 are coupled in series between the input node (IN) of power supply 930 and the ground. The diode and the resistor R3 are coupled in series between the output node (OUT) of the power supply 930 and the node 940, and the resistors R1 and R2 are coupled at the node 940. In addition, the stop node (SD) of the power supply 930 is also coupled to the node 940.

The power supply 930 can receive the panel voltage Vpan at the input node and generate a supply voltage Vcc for the local controller 908 at the output node. If the voltage level of the stop node determined by the control circuit of the power supply 930 exceeds the specified voltage V 0 , the stop node of the power supply 930 enables the operation of the power supply 930, and if the voltage level of the stop node falls below the specified voltage. V 0 stops the operation of the node to stop the power supply 930.

When the power supply 930 is turned off, the diode does not conduct, and the voltage of the stop node is expressed by the following equation:

When the voltage V SDt-on exceeds the value V 0 , the diode begins to conduct and the voltage at the stop node becomes:

Where V d is the diode voltage drop, and . When the voltage V SD, t-off falls below V 0 , the power supply 930 is turned off. Therefore, the voltage threshold can be determined based on the resistance values of the resistors R1, R2, and R3.

FIG. 12 illustrates a method 1200 for activating and deactivating a local converter 904, in accordance with an embodiment of the disclosure. The embodiment of method 1200 is merely illustrative. Other embodiments of method 1200 can be implemented without departing from the scope of the disclosure.

The method 1200 begins with the energy generating device or panel 902 operating on an open circuit condition (step 1202). In this condition, the initiator 910 does not activate the local converter 908 because the panel voltage output by the panel 902 is too low. The initiator 910 monitors the panel voltage ( Vpan ) until the panel voltage exceeds the voltage enable level (Vt -on ) (step 1204).

Once the initiator 910 determines that the panel voltage has exceeded the voltage enable level (step 1204), the initiator 910 begins to activate the local converter 904 by turning on the local controller 908 (step 1206). For example, the initiator 910 can begin to activate the local converter 904 by generating a non-zero supply voltage Vcc for the local controller 908. For other embodiments, the initiator 910 can be configured by setting one or more pins of the local controller 908, or by writing the first predetermined value to the first register of the local controller 908. In the middle, the local converter 904 is started. The local controller 908 and/or the central array controller then implement a boot procedure for the local converter 904 (step 1208). For example, the boot process may include initialization of the scratchpad, preliminary voltage comparison between panel 902, analog to digital converter calibration, clock synchronization or insertion, synchronous start of a series of panels including power stage 906, and the like.

The local controller 908 operates the power stage 906 at a predetermined conversion ratio (step 1210) until the other power levels 906 in the string are operated (step 1212). Once the string each panel 902 having a power stage 906 (step 1212) an operation, the local controller 908 to the panel current (I pan) and the starting current level (I min) to be compared (step 1214). If the panel current is greater than the startup current level (step 1214), the local controller 908 begins normal operation (step 1216). Thus, local controller 908 begins to implement MPPT for power stage 906.

In this manner, the activation of all local controllers 908 in the energy generating system can be automatically synchronized. Moreover, if only a sub-combination of panels 902 in the photovoltaic system produces a voltage high enough to activate the initiator 910, a unidirectional switch (eg, switch 314) can be included in each power stage 906 to allow operation of the remaining panels. 902.

The local controller 908 continues to compare the panel current to the startup current level (step 1218). If the panel current is less than the startup current level (step 1218), the local controller 908 sets a stop timer (step 1220). The local controller 908 then operates the power stage 906 again at a predetermined conversion ratio (step 1222). The local controller 908 and/or the central array controller then implement a stop procedure for the local converter 904 (step 1224). For example, the stop procedure can be included in the case of a separate application, synchronization with the backup unit, synchronization with the power stage 906, and the like.

The local controller 908 then determines if the stop timer has expired (step 1226). This allows the panel current to rise above the start current level. Therefore, the local controller 908 prepares for the stop, but waits to ensure that the stop should actually be performed.

Thus, as long as the stop timer has not expired (step 1226), local controller 908 will still compare the panel current to the startup current level (step 1228). If the panel current continues to remain below the startup current level (step 1228), the local controller 908 continues to wait for the stop timer to expire (step 1226). If the panel current becomes greater than the startup current level prior to the timer period (step 1226) (step 1228), the local controller 908 can again operate normally by performing an MPPT on the power stage 906 (step 1216).

However, if the panel current is less than the startup current level (step 1228), the timer period is stopped (step 1226), then the local controller 908 turns off the power stage 906 and the local controller 908 and operates again under open conditions. Panel 902 (step 1230). For some embodiments, the initiator 910 can complete the stop of the local converter 904 by generating a zero supply voltage V CC to the local controller 908. For other embodiments, the initiator 910 can be set by writing one or more pins of the local controller 908, or by writing a second predetermined value to the first temporary storage in the local controller 908. The device is either the second register and the local converter 904 is stopped. At this time, the initiator 910 monitors the panel voltage again until the panel voltage exceeds the voltage enable level (step 1204), and reinitializes the startup process.

Although FIG. 12 shows an example of a method 1200 for starting and stopping local converter 904, various changes can be made to method 1200. For example, although the method 1200 is illustrated with a photovoltaic panel, the method 1200 can be used with other energy generating devices 902, such as wind turbines, fuel cells, and the like. Still further, although the method 1200 is described with respect to the local controller 908 and the initiator 910 of FIG. 9, it is understood that the local controller 908 and the initiator 910 can be used for any suitable configuration without departing from the scope of the disclosure. Energy generation system. Also, although a series of steps are shown, the steps in method 1200 may overlap, occur in parallel, occur multiple times, or occur in a different order.

Although the above description refers to a particular embodiment, it should be appreciated that certain of the components, systems, and methods described herein can be used in horizontal sub-cells, single cells, panels (ie, battery arrays), panel arrays. And / or a system of panel arrays. For example, although the local converters described above are each connected to a panel, a similar system can be implemented as a local converter connected to each battery in the panel, or a local converter connected to each row of panels. Moreover, some of the components, systems, and methods described above can be used with other energy generating devices other than photovoltaic devices, such as wind turbines, fuel cells, and the like.

The beneficial person is to propose a definition of certain words and phrases used in this patent document. The term "coupled" and its derivatives refer to either direct or indirect communication between two or more components, whether or not such components are in actual contact with each other. The terms "transfer", "receive", and "communication" and their derivatives include both direct and indirect communication. The terms "including" and "comprising" and their derivatives are intended to include, without limitation. The term "or" is inclusive, expressed and / or. The term "each" means each of at least one of the sub-combinations of the indicated items. The phrase "related to" and "related to" and its derivatives are intended to be included, included, interconnected, included, included, connected to or connected to, coupled to, or coupled to, Communication, cooperation with it, insertion, juxtaposition, proximity, bonding to or bonding, having, having certain characteristics, and the like.

Although the disclosure has been described in terms of specific embodiments and related methods, those skilled in the art can readily appreciate the substitution and combinations of the embodiments and methods. Therefore, the above description of the exemplary embodiments is not intended to define or limit the disclosure. Other changes, substitutions, and rotations are possible without departing from the spirit and scope of the disclosure, as defined by the scope of the appended claims.

100. . . Energy generation system

102. . . Energy generating device

104. . . Local converter

106. . . Energy generation array

110. . . Central array controller

112. . . DC-AC converter

120. . . Diagnostic module

125. . . Control module

202. . . Energy generating device

204. . . Local converter

206. . . Power level

208. . . Local controller

210. . . MPPT module

212. . . Communication interface

302. . . Power stage regulator

304. . . MPPT control block

306. . . Analog to digital converter

308. . . Analog to digital converter

310, 310a-d. . . switch

314. . . One-way switch

400. . . method

500. . . Energy generation system

502, 502a~502d. . . Energy generating device

504, 504a~504d. . . Local converter

506, 506a~506d. . . Energy generation array

508, 508a~508d. . . Local controller

510. . . Central array controller

512. . . Conversion level

514. . . Square

516. . . Data bus

520. . . Diagnostic module

525. . . Control module

530. . . Conversion level optimizer

540. . . Global controller

600. . . Array

610. . . string

620. . . Masked area

800. . . method

900. . . Energy generation system

902. . . Energy generating device

904. . . Local converter

906. . . Power level

908. . . Local controller

910. . . Launcher

930. . . power supply

940. . . node

1200. . . method

In order to provide a more complete understanding of the disclosure and its features, reference is made to the following description of the accompanying drawings in which:

1 is a diagram showing an energy generating system that can be centralized control, in accordance with an embodiment of the disclosure;

2 is a partial converter of FIG. 1 in accordance with an embodiment of the disclosure;

3 is a detail showing the local converter of FIG. 2 in accordance with an embodiment of the disclosure;

4 is a diagram showing a method of implementing maximum power point tracking (MPPT) in the local converter of FIG. 2, in accordance with an embodiment of the disclosure;

5 is a diagram showing an energy generating system including a central array controller capable of selecting between a centralized and decentralized MPPT in an energy generating system, in accordance with an embodiment of the disclosure;

6 is a diagram showing a case where the array of FIG. 5 is partially shielded according to an embodiment of the disclosure;

7A-C are diagrams showing voltage versus power characteristics corresponding to the three photovoltaic panels of FIG. 6 in accordance with an embodiment of the disclosure;

8 is a diagram showing a method for selecting between a centralized and decentralized MPPT of the energy generating system of FIG. 5, in accordance with an embodiment of the disclosure;

9 is a diagram showing a system for starting and stopping a local converter, in accordance with an embodiment of the disclosure;

10 is an illustration showing an example of device voltage variation over time in the system of FIG. 9 in accordance with an embodiment of the disclosure;

Figure 11 is a diagram showing the actuator of Figure 9 in accordance with an embodiment of the disclosure;

12 is a diagram showing a method for starting and stopping the local converter of FIG. 9 in accordance with an embodiment of the disclosure.

500. . . Energy generation system

502, 502a~502d. . . Energy generating device

504, 504a~504d. . . Local converter

506, 506a~506d. . . Energy generation array

508, 508a~508d. . . Local controller

510. . . Central array controller

512. . . Conversion level

514. . . Square

516. . . Data bus

520. . . Diagnostic module

525. . . Control module

530. . . Conversion level optimizer

540. . . Global controller

Claims (23)

  1. A method for selecting between centralized and decentralized maximum power point tracking in an energy generating system, the energy generating system comprising a plurality of energy generating devices, each of the energy generating devices being coupled to a corresponding local converter, each The local converter includes a local controller for the corresponding energy generating device, the method comprising: determining whether the energy generating devices are operating under quasi-ideal conditions; and operating the energy generating devices under quasi-ideal conditions Setting the energy generation system in a centralized maximum power point tracking (CMPPT) mode; and setting the energy generation system to a decentralized maximum power point when the energy generating devices are not operating under quasi-ideal conditions Tracking (DMPPT) mode.
  2. In the method of claim 1, the system is provided in the CMPPT mode to include the local controllers and enable a global controller.
  3. For example, in the method of claim 1, the system is provided in the DMPPT mode, including enabling the local controllers and disabling a global controller.
  4. The method of claim 1, further comprising determining whether the probability of at least one of the energy generating devices being masked is greater than a predetermined threshold when the system is in the DMPPT mode.
  5. The method of claim 4, further comprising determining that the probability that at least one of the energy generating devices is obscured is higher than the predetermined threshold Time: identifying at least one energy generating device that is likely to be obscured; and performing a full characteristic scan on each of the energy generating devices that are identified as likely to be obscured.
  6. The method of claim 5, further comprising: identifying at least one insufficiently performing energy generating device based on the complete characteristic scan; and providing a correction to each of the energy generating devices identified as being underexpressed.
  7. The method of claim 1, wherein determining whether the energy generating devices operate under quasi-ideal conditions comprises: for each of the energy generating devices, according to an output power value associated with each of the energy generating devices, Calculating a probability that the energy generating device is obscured; identifying a maximum value of the calculated probability; comparing the maximum value of the calculated probability with a DMPPT threshold; and when the calculated probability is the maximum value When less than the DMPPT threshold, it is determined that the energy generating devices are operated under quasi-ideal conditions.
  8. The method of claim 7, further comprising comparing the calculated maximum value to a diagnostic threshold when the system is in the DMPPT mode.
  9. The method of claim 8, further comprising: (i) each of the calculated probability is greater than the diagnostic threshold An energy generating device having a probability that the energy generating device is obscured by one of the occlusions greater than the diagnostic threshold is identified as an energy generating device that is likely to be obscured, and (ii) is identified as potentially obscured for each The energy generating device performs a full characteristic scan.
  10. The method of claim 9, further comprising (i) identifying at least one under-performing energy generating device based on the full characteristic scan, and (ii) providing a correction to each of the energy generating devices identified as underexpressing.
  11. The method of claim 1, wherein the energy generating device comprises a photovoltaic panel.
  12. A method for selecting between centralized and decentralized maximum power point tracking in an energy generating system, the energy generating system comprising a plurality of energy generating devices, each of the energy generating devices being coupled to a corresponding local converter, each The local converter includes a local controller for the corresponding energy generating device, the method comprising: calculating an output power value of each of the energy generating devices; for each of the energy generating devices, generating the energy according to the energy The output power values of the device calculate a probability that the energy generating device is obscured; identify a maximum value of the calculated probability; compare the maximum value of the calculated probability with a decentralized maximum power point tracking (DMPPT) a threshold value; when the calculated maximum value of the probability is less than the DMPPT threshold, the energy generating system is set in a centralized maximum power point tracking (CMPPT) mode; When the calculated maximum value of the probability is equal to or greater than the DMPPT threshold, the energy generating system is set in a DMPPT mode.
  13. The method of claim 12, further comprising determining whether a probability that at least one of the energy generating devices is obscured is greater than a predetermined threshold when the system is set in the DMPPT mode.
  14. In the method of claim 13, the determining whether the probability that at least one of the energy generating devices is obscured is greater than the predetermined threshold includes comparing the maximum of the calculated probability with a diagnostic threshold.
  15. The method of claim 14, further comprising: (i) calculating a probability that each of the energy generating devices is shaded is greater than when the calculated maximum value is greater than the diagnostic threshold. The diagnostic threshold energy generating device is identified as an energy generating device that is likely to be obscured, (ii) performing a complete characteristic scan on each of the energy generating devices that are identified as likely to be obscured, (iii) according to the integrity The characteristic scan identifies at least one under-performing energy generating device, and (iv) provides a correction to each of the energy generating devices that are identified as underexpressing.
  16. The method of claim 12, wherein the energy generating device comprises a photovoltaic panel.
  17. A central array controller capable of selecting between a centralized and decentralized maximum power point tracking of an energy generating system, the energy generating system including a plurality of energy generating devices, each of the energy generating devices coupled to a corresponding portion a converter, each of the local converters including a local controller for the corresponding energy generating device, the central array controller comprising: a diagnostic module capable of determining whether the energy generating devices are operated under quasi-ideal conditions; and a control module capable of setting the energy generating system in a concentration when the energy generating devices are operated under quasi-ideal conditions In the maximum power point tracking (CMPPT) mode, and when the energy generating devices are not operating under quasi-ideal conditions, the energy generating system is placed in a decentralized maximum power point tracking (DMPPT) mode.
  18. The central array controller of claim 17, wherein the control module is capable of setting the system in the CMPPT mode by deactivating the local controllers and enabling a global controller.
  19. For example, in the central array controller of claim 17, the control module can set the system in the DMPPT mode by enabling the local controllers and disabling a global controller.
  20. For example, in the central array controller of claim 17, when the system is in the DMPPT mode, the diagnostic module can further determine whether a probability that at least one of the energy generating devices is obscured is higher than a predetermined probability. Limit.
  21. The central array controller of claim 20, wherein the diagnostic module can further (i) identify at least one when determining that the probability that at least one of the energy generating devices is obscured is higher than the predetermined threshold An energy generating device that may be obscured, and (ii) performing a full characteristic scan of each of the energy generating devices that are identified as likely to be obscured.
  22. For example, in the central array controller of claim 21, the diagnostic module can further (i) identify at least one according to the complete characteristic scan. An insufficiently performing energy generating device, and (ii) providing a correction to each of the energy generating devices that are identified as underexpressing.
  23. A central array controller as claimed in claim 17, wherein the energy generating device comprises a photovoltaic panel.
TW098115860A 2008-05-14 2009-05-13 Method and system for selecting between centralized and distributed maximum power point tracking in an energy generating system TWI498705B (en)

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