CN109672213B

CN109672213B - Power optimization system containing secondary optimization and optimization method thereof

Info

Publication number: CN109672213B
Application number: CN201710997312.8A
Authority: CN
Inventors: 张永; 胡晓磊
Original assignee: FONRICH NEW ENERGY TECHNOLOGY Ltd SHANGHAI
Current assignee: FONRICH NEW ENERGY TECHNOLOGY Ltd SHANGHAI
Priority date: 2017-10-17
Filing date: 2017-10-17
Publication date: 2023-02-28
Anticipated expiration: 2037-10-17
Also published as: CN109672213A

Abstract

The invention relates to a power optimization system with quadratic optimization and an optimization method thereof. The multi-stage voltage converter is connected in series, wherein each stage of voltage converter converts electric energy extracted from a corresponding direct current power supply into output power, the output voltages of the multi-stage voltage converters are superposed to be used as direct current bus voltage, each stage of voltage converter is used for setting the output current and the output voltage of the corresponding direct current power supply at the maximum power point, the energy source collecting device receives the output power provided by the multi-stage voltage converter, and the secondary optimization function of the energy source collecting device is used for setting the direct current bus voltage and the direct current bus current at the maximum power point.

Description

Power optimization system containing secondary optimization and optimization method thereof

Technical Field

The invention mainly relates to the field of photovoltaic power generation, in particular to a mechanism for executing secondary power optimization on a direct-current power supply in a power generation system containing a photovoltaic cell or other types of cells, and the optimization of the output power to the maximum extent is realized on the premise of ensuring the reliable operation of the direct-current power supply.

Background

The installation of the photovoltaic power generation system needs to pay early investment, and as the photovoltaic modules are not matched and have concealment, the owners of many solar power generation systems can neglect or do not know the mismatching problem of the photovoltaic modules, so that the investment recovery and profit are greatly reduced, and energy waste is caused. The reasons for the mismatch are manifold, the main mechanism is the mismatch of the combination of voltage and current, the cloud that is shaded and fluttered by local foreign objects, the shading of nearby objects, surface contamination, different installation tilt angles and installation orientations, aging and temperature variation, and other factors, and the mismatch of the photovoltaic module directly induces the unbalanced power loss of the photovoltaic module. The result is that the entire power generation system cannot operate at the maximum output power point.

In estimating the overall efficiency of a solar power system, it is generally assumed that the photovoltaic modules used all have the same irradiance, temperature, and performance parameters. However, in many cases, variations in factors such as partial shadowing, temperature imbalance, and mounting tilt may result in current and voltage mismatches between components and poor system performance. Power losses due to shadow occlusion have many forms, perhaps seasonal per year or several hours of the day, and power fluctuations that are not readily perceptible are difficult to predict accurately. The power optimization is merged into the design of the photovoltaic power generation system in advance, so that the overall power generation efficiency of the photovoltaic power station can be improved, the service life of the power station is prolonged, the return on investment is improved, the layout flexibility of photovoltaic components in the photovoltaic power station can be improved, and the limited space is utilized to the maximum extent.

The maximum power output by the photovoltaic module depends on the optimal working current multiplied by the optimal working voltage, and under any given working condition, a rule exists: there is a maximum power point for each photovoltaic module that corresponds to the maximum power output of the photovoltaic module. The maximum power point is approximately an exponential function with respect to voltage and current. The technical solution of maximum power tracking, such as the power optimization device disclosed in chinese patent application 201110097292.1, is used to monitor and optimize the power of each photovoltaic panel, so that even if any panel in the array has a mismatch problem, the other cells can still output the maximum power, thereby compensating the loss of power generation caused by the mismatch problem.

Disclosure of Invention

In an alternative embodiment, the present application discloses a power optimization system with quadratic optimization, comprising: a series connected multi-level voltage converter; each stage of voltage converter converts the electric energy extracted from the corresponding direct current power supply into output power; the respective output voltages of the multi-level voltage converters are superimposed to thereby serve as a DC bus voltage; each stage of voltage converter is used for setting the output current and the output voltage of one corresponding direct current power supply at the maximum power point; and the energy collecting device is used for receiving the output power provided by the multistage voltage converter, and a secondary optimization function configured by the energy collecting device is used for setting the direct-current bus voltage and the direct-current bus current at a maximum power point.

The power optimization system with quadratic optimization described above, wherein: the energy collecting device at least comprises an inverter or a charger for charging a storage battery.

The power optimization system with quadratic optimization described above, wherein: the energy harvesting device includes an inverter: when the secondary optimization function of the inverter is closed, the inverter is regarded as pure inverter equipment without maximum power tracking; or as an inverter device equipped with two-stage maximum power tracking when the secondary optimization function of the inverter is enabled.

The power optimization system with quadratic optimization described above, wherein: when the secondary optimization function of the inverter is turned off, each of the multi-level voltage converters sets the output current and the output voltage of one of the direct-current power supplies corresponding thereto at the maximum power point.

The power optimization system with quadratic optimization described above, wherein: defining a first class voltage converter and a second class voltage converter in the multi-stage voltage converter, wherein the first class voltage converter and the second class voltage converter respectively comprise a first input end and a second input end for capturing electric energy provided by a direct current power supply and a first output end and a second output end for providing self output power; when the secondary optimization function of the inverter is started, the following requirements are met: the first class of voltage converter couples the first input end of the first class of voltage converter to the positive pole of a direct current power supply corresponding to the first class of voltage converter, and the first input end is directly short-circuited and is directly connected to the first output end; and the second input end of the first type of voltage converter, which is coupled to the negative pole of the corresponding direct current power supply, is directly shorted and is directly conducted to the second output end.

The power optimization system with quadratic optimization described above, wherein: when the secondary optimization function of the inverter is started, the following conditions are also met: the second class of voltage converters are all used for setting the output current and the output voltage of one corresponding direct current power supply at the maximum power point.

The power optimization system with quadratic optimization described above, wherein: when the secondary optimization function of the inverter is started, the following conditions are also met: the voltage of the direct current bus is modulated in a voltage floating mode through the dynamic change voltage of the direct current power supply corresponding to each first class voltage converter.

The power optimization system with quadratic optimization described above, wherein: the types of direct current power sources include at least a fuel cell or a photovoltaic module, and the like.

The power optimization system with quadratic optimization described above, wherein: controlling the dynamically changing DC bus voltage by a voltage regulator coupled to the DC bus to be within a predetermined upper limit and lower limit range; the voltage regulator is provided separately to the dc bus or integrated in the energy collection device.

The power optimization system with quadratic optimization described above, wherein: when the power reduction event occurs to the direct current power supply corresponding to one or more first class voltage converters and causes the output voltage of one or more second class voltage converters to be forced to rise to the voltage tending to exceed the specified range, the second class voltage converters are controlled by the configured processor to limit the output voltage to an expected voltage value within the specified range.

The power optimization system with quadratic optimization described above, wherein: when the power reduction event occurs to the direct current power supply corresponding to the one or more first class voltage converters, the direct current power supply corresponding to the one or more second class voltage converters maintains the state of working at the maximum power point.

The power optimization system with quadratic optimization described above, wherein: when the direct current power supply corresponding to one or more first class voltage converters generates a power reduction event, the direct current power supply corresponding to one or more second class voltage converters is switched from a maximum power point state to a non-maximum power point state; the proportion of the external power output by the direct current power supply entering the non-maximum power point state in the sum of the total power provided by a series of direct current power supplies corresponding to the multi-stage voltage converter is reduced.

The power optimization system with quadratic optimization described above, wherein: limiting the voltage of the direct-current bus to float in a preset upper limit value range and a preset lower limit value range, and when the voltage of the direct-current bus falls to approach the lower limit value due to a power reduction event of a direct-current power supply corresponding to one or more first-class voltage converters; and switching the direct current power supplies corresponding to one or more second-class voltage converters from the maximum power point state to the non-maximum power point state, and forcing the total power provided by a series of direct current power supplies corresponding to the multistage voltage converter to be divided by the bus current calculated by the direct current bus voltage to be reduced.

The power optimization system with quadratic optimization described above, wherein: the voltage converter includes: first and second switches connected in series between first and second input terminals of a voltage source receiving a supply of DC power; third and fourth switches connected in series between first and second output terminals providing an output voltage; an inductive element is provided between the interconnection node between the first and second switches and the interconnection node between the third and fourth switches and a second input terminal is coupled to the second output terminal.

In an alternative embodiment, the present application discloses a power optimization method, comprising: connecting the multi-level voltage converters in series; capturing the electric energy of a corresponding photovoltaic module by each level of voltage converter and converting the electric energy into output power; superposing the output voltages of the multi-level voltage converters to form a total cascade voltage which is used as a direct current bus voltage; setting a photovoltaic component corresponding to each level of the voltage converter at the maximum power point; the output power provided by the multi-stage voltage converter is collected by an energy harvesting device configured with a secondary optimization function, and the energy harvesting device selects whether to set the dc bus voltage and the dc bus current at the maximum power point by selecting whether to enable the secondary optimization function.

The method described above, wherein: the energy collecting device at least comprises an inverter or a charger for charging a storage battery.

The method described above, wherein: the energy harvesting device includes an inverter, and the method further includes: the secondary optimization function of the inverter is closed, and the inverter is set to be pure inverter equipment without maximum power tracking; or starting a secondary optimization function of the inverter, and setting the inverter to be an inverter device provided with two-stage maximum power tracking.

The method described above, wherein: and (3) turning off the secondary optimization function of the inverter, so that each of the multistage voltage converters sets the output current and the output voltage of the photovoltaic module corresponding to the multistage voltage converter at the maximum power point through the maximum power tracking function of the multistage voltage converter.

The method described above, wherein: defining a first class of voltage converter and a second class of voltage converter in the multistage voltage converter, wherein each of the first class of voltage converter and the second class of voltage converter comprises a first input end and a second input end for capturing electric energy provided by the photovoltaic module and a first output end and a second output end for providing output power of the first input end and the second input end; enabling a secondary optimization function of the inverter, the method further comprising: the first class voltage converter is controlled by a processor configured with the first class voltage converter, and a first input end of the first class voltage converter, which is coupled to the anode of one photovoltaic module corresponding to the first class voltage converter, is directly shorted and directly communicated to a first output end; and the first type voltage converter is controlled by a processor configured to directly short and pass through a second input end coupled to the negative electrode of the photovoltaic component corresponding to the first type voltage converter to a second output end.

The method described above, wherein: enabling a secondary optimization function of the inverter, the method further comprising: the second type of voltage converter sets the output current and the output voltage of a corresponding photovoltaic module at the maximum power point through the maximum power tracking function of the voltage converter.

The method described above, wherein: enabling a secondary optimization function of the inverter, the method further comprising: the voltage of the direct current bus is modulated in a voltage floating mode through the dynamic change voltage output by the photovoltaic component corresponding to each first class voltage converter.

The method described above, wherein: arranging a voltage regulator on the direct current bus, wherein the voltage regulator is used for controlling the voltage of the dynamically changed direct current bus not to exceed the preset upper limit value and lower limit value ranges; the voltage regulator is provided separately to the dc bus or integrated directly into the inverter.

The method described above, wherein: when the power reduction event occurs to the photovoltaic component corresponding to the one or more first type voltage converters and causes the output voltage of the one or more second type voltage converters to be forced to rise to a value which tends to exceed a specified range; the processor that triggers the second type of voltage converter arrangement controls the output voltage of the second type of voltage converter to be limited to a desired voltage value within a prescribed range.

The method described above, wherein: when a power reduction event occurs to the photovoltaic component corresponding to the one or more first class voltage converters, the processor configured by the one or more second class voltage converters controls the one or more second class voltage converters to maintain the corresponding photovoltaic component to work in the maximum power point state.

The method described above, wherein: when a power reduction event occurs to the photovoltaic assembly corresponding to one or more first class voltage converters, triggering one or more second class voltage converters to configure the processor to control the one or more second class voltage converters to switch the corresponding photovoltaic assembly from a maximum power point state to a non-maximum power point state; the proportion of the external power output by the photovoltaic module entering the non-maximum power point state in the sum of the total power provided by a series of photovoltaic modules corresponding to the multi-level voltage converter is reduced.

The method described above, wherein: limiting the voltage of the direct-current bus to float within a preset upper limit value range and a preset lower limit value range, and when the direct-current bus voltage falls to approach the lower limit value due to a power reduction event of the direct-current power supply corresponding to one or more first-class voltage converters; accordingly, the processor triggering the one or more second type voltage converter configurations controls the one or more second type voltage converters to switch the corresponding dc power source from the maximum power point state to the non-maximum power point state, forcing the total power provided by the series of photovoltaic modules corresponding to the multi-level voltage converter at that time to be divided by the bus current calculated by the dc bus voltage to drop. Note that the voltage converter described in this application may also be replaced by the term power optimizer.

Drawings

In order that the above objects, features and advantages will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to the appended drawings, which are illustrated in the appended drawings.

Fig. 1 is a schematic diagram of photovoltaic modules connected in series and then in parallel to supply power to an inverter.

Fig. 2 is a schematic diagram of a series of multi-stage photovoltaic modules each configured with an optimizer.

Fig. 3 is a schematic diagram of power curves of a photovoltaic module under different illumination intensities.

Fig. 4 is an example of controlling the bus voltage using a voltage regulator in an alternative embodiment.

Fig. 5 is an example of a processor controlled power optimizer with an algorithm module that tracks the maximum power point.

Fig. 6 is a diagram with a portion of the power optimizer in the pass-through mode and another portion of the power optimizer in the power optimization mode.

Fig. 7 is a first example of controlling the power switch of the power optimizer to be turned off or on to enter the through mode.

Fig. 8 is a second example of controlling the power switch of the power optimizer to turn off or on to enter the through mode.

Detailed Description

The technical solutions of the present invention will be clearly and completely described below with reference to various embodiments, but the described embodiments are only used for describing and illustrating the present invention and not for describing all embodiments, and the solutions obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.

According to the output characteristic of the photovoltaic module, because the output voltage and the output current of the photovoltaic module are closely related to the environmental factors such as the sunlight radiation intensity and the working temperature, the maximum output power and the corresponding voltage of the maximum power point change along with the change of the environmental factors, and the photovoltaic module can not work in the maximum power point state due to the potential environmental change.

Referring to fig. 1, a photovoltaic module array is a basis for converting light energy into electric energy of a photovoltaic power generation system, and a plurality of battery strings are installed in the photovoltaic module array, and each battery string is formed by connecting a plurality of photovoltaic modules PV1 to PVN connected in series. Each photovoltaic module or photovoltaic cell is configured with a power optimizer that performs maximum power tracking calculation MPPT. The electric energy generated by the first-stage PV module PV1 in a certain string of battery cells is power-converted by the first-stage power optimizer CH1 to perform power optimization, the electric energy generated by the second-stage PV module PV2 is power-converted by the second-stage power optimizer CH2 to perform power optimization, and so on until the electric energy generated by the nth-stage PV module PVN is power-converted by the nth-stage power optimizer CHN to perform power optimization, N is a natural number not lower than 1. Power optimizers, also known as maximum power point trackers, typically use a particular type of topology circuit to search for a maximum power point and therebyAllowing the power optimizer to extract the maximum power possible from the photovoltaic module. First stage power optimizer CH1 output voltage V _O1 Second stage power optimizer CH2 output voltage V _O2 8230and so on, the Nth-stage power optimizer CHN outputs a voltage V _ON . So that the total string level voltage on any string of photovoltaic battery strings is about V through calculation _O1 +V _O2 +…V _ON =V _BUS . Different groups of battery packs are connected between the buses LA and LB in series-parallel mode: if the multistage power optimizers CH1-CHN are defined to form a certain link, different multiple links are connected in parallel between the buses LA and LB. The total electrical energy provided by the array of photovoltaic modules is transmitted by a dc bus to an energy harvesting device, which comprises at least the inverter INVT of fig. 1, which can invert dc power to ac power, or a charger, which charges a battery, etc. In fact, the photovoltaic module in fig. 1 is only a specific example as a dc power source, i.e. an optimized object, the power optimizer is not only compatible with a crystalline silicon solar panel, but also can be matched with a part of thin film batteries, the photovoltaic module can be replaced by a chemical battery, a storage battery, or the like, and the power optimizer has a broader meaning of performing power optimization on various types of dc power sources, even wind energy, fuel cells, or the like. Any scheme aiming at the maximum power tracking of the direct-current power supply in the prior art is also suitable for the power optimizer, and the most common maximum power tracking method comprises a constant voltage method, a conductance increment method, a disturbance observation method and the like.

Referring to fig. 1, the power optimizer is attributed to the power electronics, and the main purpose is to implement the function of maximum power point tracking of individual photovoltaic modules. The Buck Buck circuit, the Boost circuit, the Buck-Boost circuit, the other CuK converter circuit and the like are main circuit topologies suitable for the photovoltaic power optimizer. The main circuit topology can be found to belong to the category of a switching power supply system, and the switching power supply system usually adopts a power semiconductor device as a switching element, and controls the duty ratio of the switching element to adjust the output voltage through a periodic on-off switch. The power conversion realized by the switching power supply is a core part of the switching power supply, and in order to meet the requirement of high power density, the converter needs to work in a high-frequency state, and a switching transistor needs to adopt a power switch with high switching speed and short conduction and turn-off time, a power thyristor, a power field effect transistor, an insulated bipolar transistor and the like. The main control modes of the converter are pulse width modulation, pulse frequency modulation and the like, and a pulse width modulation scheme is commonly used. The power optimizer is embodied as a voltage converter for reducing or boosting direct current to direct current, and after the power optimizer optimizes the maximum power of the single component, the energy is transmitted to an inverter for processing direct current to alternating current and then is supplied to local use or power generation internet surfing. The inverter INVT may typically be a pure inverter device without maximum power tracking or an inverter device equipped with two-stage maximum power tracking.

Referring to fig. 2, for convenience of description, the entire photovoltaic power generation system is illustrated with ten photovoltaic modules PV1-PV10 and corresponding ten power optimizers CH1-CH10 and associated inverters INVT as examples. The power optimizer has an input coupled to the photovoltaic module and an output providing an output power. First input terminal IN of input side of first stage power optimizer CH1 ₁ Coupled to the positive pole of the first photovoltaic module PV1, a second input IN on the input side of the first power optimizer CH1 ₂ Coupled to the negative pole of the first photovoltaic module PV1, the electrical energy received on the input side is converted into a first output NO on the output side of the first power optimizer CH1 ₁ And a second output NO ₂ The output power of (c). The correspondence of the other photovoltaic modules PV2-PV10 and the power optimizers CH2-CH10 has been shown in the figure. The multistage power optimizers CH1-CH10 are connected in series according to the following rule: the second output terminal of any previous stage power optimizer is coupled to the first output terminal of the adjacent next stage power optimizer through a power line. Take the actual connection relationship as an example: second output terminal NO of first stage power optimizer CH1 ₂ A first output NO connected to the second stage power optimizer CH2 ₁ Second output NO of the second stage power optimizer CH2 ₂ First output terminal NO connected to third stage power optimizer CH3 ₁ And so on to the second output terminal NO of the ninth stage power optimizer CH9 ₂ Is connected toFirst output terminal NO of tenth stage power optimizer CH10 ₁ . It can be considered that: the cascade voltages provided by the cascade of multistage power optimizers CH1-CH10 equal to the superposition of their respective output voltages, the first output NO of the first stage power optimizer CH1 coupled to the bus LA ₁ And a second output NO of the last tenth stage power optimizer CH10 coupled to the bus LB ₂ A total cascade voltage V between which a plurality of power optimizers connected in series can be provided _BUS =V _O1 +V _O2 +…V _O10 . Also at the first input IN of any power optimizer ₁ And a second input terminal IN ₂ An input capacitor CI is connected between the first output end NO of any power optimizer ₁ And a second output NO ₂ An output capacitor CO is connected between the two.

Referring to fig. 2, meaning of power optimization: a certain power optimizer needs to set the output current and the output voltage of a dc power supply paired therewith to the maximum power point of the dc power supply, in other words, the power optimizer needs to set its own output current to have no direct correlation with the output current of the dc power supply paired therewith, and the power optimizer needs to set its own output voltage to have no direct correlation with the output voltage of the dc power supply paired therewith.

Referring to fig. 2, a conventional series type power optimizer adopts a fixed voltage design concept. The inverter confirms the voltage of a stable direct current bus according to the alternating current terminal voltage, summarizes the maximum power collected by each series power optimizer, further calculates the bus current and transmits the bus current to the power optimizer through wireless or power carrier signals. The voltage at the output of the power optimizer is equal to the power of the maximum power of the collected component divided by the bus current. If the maximum power collected by the multistage power optimizer CH1-CH10 is transmitted to the inverter INVT, the total power provided by the photovoltaic modules PV1-PV10 is divided by the fixed voltage of the DC bus of the inverter INVT to calculate the bus current I _BUS . And after the assembly is shielded, the corresponding power optimizer re-determines the maximum output power value according to the volt-ampere curve and transmits the maximum output power value to the inverter wirelessly or by carrier waves. In maintaining the DC busUnder the premise that the line voltage is unchanged, the bus current is recalculated, for example, reduced and fed back to each power optimizer. At this time, the power of the shielded component is reduced, and the corresponding power optimizer of the shielded component also reduces the voltage to confirm that the output current reaches the standard. The power optimizers of other unshielded components boost the voltage to achieve the standard output current, and the dynamic regulation is a voltage complement process, so that the bus voltage provided for the direct current end of the inverter is stabilized. It can be assumed that the blocking of the PV modules PV1-PV5 seriously causes the output voltage of each of the power optimizers CH1-CH5 to drop, and the power optimizers CH6-CH10 corresponding to the non-blocked PV modules PV6-PV10 must be boosted to compensate for the dropping of the power optimizers CH1-CH 5. The doubtful question is: the design concept of the fixed voltage easily causes that the output voltage of the power optimizer corresponding to the photovoltaic module which is not shielded may exceed the voltage tolerance range of the power optimizer, and the problem becomes more prominent when the shielding of part of the components is more serious. Clouds, buildings, tree shadows and the like which fly across the sky are all inducing factors of shading, whether seasonal shadows or transient shadows calculated in a plurality of hours, voltage out-of-range caused by power fluctuation is difficult to predict, and the defect that bus voltage is fixed is overcome.

Referring to fig. 2, the multi-stage power optimizers CH1-CH10 are configured with processors, and besides MPPT is performed by the PWM signals output by the processors, the processors and their configured peripheral hardware can also collect various target parameters of the dc power source or the power optimizer, which is equivalent to a data collector, because it is meaningful for the inverter INVT to capture these target parameter data, such as calculating the bus current and adjusting the bus voltage based on the total power of each battery string, and transmitting various data to the cloud server as backup or for recall. In an alternative embodiment, the peripheral hardware may collect a series of related specified target parameter information of voltage and current, power, temperature and power generation amount, and the like of the photovoltaic module, for example, the voltage parameter is collected by the voltage sensor, the current parameter is collected by the current sensor, and the temperature parameter is collected by the peripheral hardware such as the temperature sensor. The more kinds of peripheral hardware, the more kinds of parameters related to the photovoltaic module can be obtained by the processor, but the cost is increased, and the compromise is needed. The target parameters can also comprise peripheral environmental factor data of the photovoltaic module detected by an environmental monitor: the environment temperature, humidity, wind speed, illumination intensity, air pressure and the like, and the environment monitor is one of the data collectors. The power optimizers may communicate data with each other through wireless communication or carrier communication or the power optimizers and the inverter INVT may communicate data with each other through wireless communication or carrier communication.

Referring to fig. 3, the power voltage P of the photovoltaic module _CE -V _PV As shown in the graph, the output characteristic of the photovoltaic module is a nonlinear dc power supply. At the intensity of illumination LE ₁ -LE ₅ The power-voltage curves of the photovoltaic module under several radiation levels are different, and are summarized as follows: under the condition of inconsistent illumination intensity, the power-voltage curve of the photovoltaic module has the characteristic that the higher the radiation intensity is, the higher the output power of the photovoltaic cell is, and conversely, the lower the output power is. Light intensity LE ₁ -LE ₅ The corresponding power-voltage curve under each radiation level comprises a maximum power point, and the maximum power points of different power-voltage curves are connected to form a maximum power point combination curve P _MP When the maximum power point of the photovoltaic module is changed due to the change of illumination intensity such as shading, the power optimizer needs to be arranged on the combined curve P _MP And tracking the maximum power point. The photovoltaic module is also characterized in that the short-circuit current varies with the intensity of illumination, and the larger the short-circuit current, the larger the intensity of illumination, the slightly larger the open-circuit voltage but we can consider that the larger variation hardly occurs. The output characteristics of the photovoltaic cell are also temperature dependent, in that the short-circuit current becomes slightly larger as the temperature is higher, but the open-circuit voltage is lowered and the maximum output power becomes smaller.

Referring to fig. 3, one of the causes of the power reduction event of the photovoltaic module includes the conditions of shadow occlusion and the like, and also includes aging and the like, and if the shadow occlusion does not exist, the power reduction event is naturally released. If the aged DC power is replaced by a new non-defective good DC power, the power down event is also considered to be resolved. Observing power of any photovoltaic moduleVoltage P _CE -V _PV According to the curve, under the same environmental conditions, the photovoltaic module has a unique maximum output power point and is on the left side of the maximum power point, the output power of the photovoltaic module shows a linear rising trend along with the rising of the output voltage of the photovoltaic module, after the maximum power point is reached, the output power of the photovoltaic module rapidly drops, and the power dropping speed on the right side of the maximum power point is far higher than the rising speed on the left side of the maximum power point. The output voltage corresponding to the maximum power point of the photovoltaic module is approximately equal to about 78-80% of the open circuit voltage of the photovoltaic module.

Referring to fig. 4, it is assumed that a photovoltaic module PV1 corresponding to a certain power optimizer CH1 among the multi-stage power optimizers CH1-CH10 is shielded and a photovoltaic module PV10 corresponding to the power optimizer CH10 is not shielded, during which the rest of the entire multi-stage photovoltaic modules PV1-PV10 may be in a shielding state or in an unshielded state, which is only explained by taking the photovoltaic modules PV1 and PV10 as an example, and although the shielding is taken as an example, in practice, similar consequences may be caused by manufacturing variations of the dc power supply, even by aging degradation and other problems. Observing that the drastic reduction in power of the photovoltaic module PV1 in fig. 4 leads to the output voltage V of the power optimizer CH1 with which it is paired _O1 Step-down, and simultaneously, the power optimizer CH10 matched with the photovoltaic module PV10 raises the output voltage V _O10 The dynamic regulation process represented by the step-up or step-down of the output voltages of different power optimizers is to meet the requirement that the bus voltage is fixed. The power optimizer CH1 or CH10 employs the above mentioned main circuit topology suitable for photovoltaic power optimizers, thus the output voltage V _O1 Or V _O10 Must meet a prescribed range, i.e. within an operable voltage range, to a defined low predetermined value V _L And a high predetermined value V _H The voltage interval in between characterizes a specified range of power optimizer output voltages. However, the actual output voltage V of the power optimizer CH10 associated with the unshielded photovoltaic module PV10 _O10 The output voltage V may be caused by the photovoltaic module PV1 being shaded _O10 Is forced to exceed once or more timesHigh predetermined value V _H The lower the external power of the photovoltaic module PV1, the lower the output voltage V _O10 The greater the amplification of (a).

Referring to fig. 4, the basic idea of the present application is to avoid the abnormality that the output voltage of the power optimizer exceeds the specified range _BUS Is not fixed and is dynamically adjusted in a floating manner. The output power provided by the multi-level voltage converter is received by an energy harvesting device like an inverter, a secondary optimization function of the energy harvesting device configuration is used to set the dc bus voltage and the dc bus current at a maximum power point, and if the power optimizer performs power optimization on the photovoltaic module for the first time, the optimization of the energy harvesting device configuration is defined as secondary optimization relative to the first optimization. In conjunction with the scheme introduced in fig. 1 and described earlier in this application, the power optimization system with secondary optimization mainly includes: the series-connected multiple power optimizers CH1-CHN each convert the electrical energy extracted from its corresponding one of the dc power sources into output power, for example, the nth power optimizer CHN converts the electrical energy extracted from its corresponding one of the dc power sources, i.e., the pv module PVN, into output power. In a power optimization system, the output voltages of each of the multi-stage power optimizers CH1-CHN are superimposed to thereby serve as the voltage V of the DC bus _BUS In the multi-stage power optimizers CH1 to CHN, each stage of the power optimizer is configured to set the output current and the output voltage of the corresponding one of the dc power supplies at the maximum power point, and belongs to the first optimization, for example, the nth stage of the power optimizer CHN is configured to set the output current and the output voltage of the corresponding one of the dc power supplies, i.e., the photovoltaic module PVN, at the maximum power point. Additionally, the energy harvesting devices, such as the inverters INV, that receive the output power provided by each of the multi-stage power optimizers CH1-CHN are configured with a secondary optimization function that, if activated, can be used to set the dc bus voltage and the dc bus current at the maximum power point.

Referring to fig. 5, when the output voltage of the photovoltaic module PVK (natural number K is a number from 1 to N) is not equal to the voltage corresponding to the maximum power point, it is necessary to control the output voltage to approach the voltage corresponding to the maximum power point. As shown in the figure, the processor 300 configured by the photovoltaic assembly PVK samples the output voltage of the photovoltaic assembly PVK through the voltage sensor 111 and samples the output current of the photovoltaic assembly PVK through the current sensor 112, and the process that the analog quantity of the target parameter acquired by various sensors is converted into the digital quantity is omitted in the figure. Taking the disturbance observation method as an example, the processor 300 calculates whether the actual power falls on the left side or the right side of the maximum power point by multiplying the output voltage and the current of the photovoltaic module, and determines the voltage corresponding to the maximum power point of the photovoltaic module by the maximum power point tracking algorithm. The most common maximum power tracking algorithm is a constant voltage method, a conductance increment method, and the like in addition to the disturbance observation method. After the maximum power point tracking operation module 301 determines the voltage corresponding to the maximum power point, the processor 300 determines, according to the result of the determination, the voltage corresponding to the maximum power point at which the pv module PVK needs to operate, specifically, the processor 300 drives the power optimizer CHK through the output pulse modulation signal PWM to stabilize the output voltage of the pv module PVK at the voltage value corresponding to the maximum power point of the pv module PVK, and the processor 300 is provided with a pulse width modulator or a digital pulse width modulator 302, which is used to generate a pulse modulation signal and further drive or control the operation of the power optimizer CHK.

Referring to fig. 5, the processor 300 senses the output voltage of the power optimizer CHK through the voltage sensor 113 and senses the output current of the power optimizer CHK through the current sensor 114. In connection with the embodiments of fig. 4 and 5, a power down event of the photovoltaic module occurs, for example, at a time when the photovoltaic module PV1 is occluded but the photovoltaic module PVK is not occluded resulting in an output voltage V of the power optimizer CHK _OK Tends to exceed a predetermined value V which is too high _H The power optimizer CHK detects the output voltage V through the voltage sensor 113 _OK Output voltage V _OK Tends to exceed V _H The processor 300 directly drives the output voltage V of the power optimizer CHK through the pulse signal and according to the calculated maximum power point voltage _OK High-low predetermined value V falling in prescribed range _H -V _L And (4) the following steps. Controlling the power optimizer CHK to output a predetermined value V higher, for example, during the time phase when a power reduction event occurs in the photovoltaic module PV1 _H In this case, V tends to be higher than V originally _H Output voltage V of _OK Is clamped at a value not higher than V _H Resulting in a voltage V of the bus _BUS Dropping one or more of the serially connected multi-stage power optimizers to adjust the voltage V of the DC bus _BUS . The output voltage V of the power optimizer CHK due to the drop of the bus voltage _OK Is reduced or even not increased, means that the output voltage of the power optimizer CHK may fall within the specified range even in the face of a power reduction event of the photovoltaic module PV 1.

Referring to fig. 5, having introduced the main topology of the power optimizer, the photovoltaic module PVK utilizes the illustrated power optimizer CHK to generate the desired output voltage while performing maximum power point tracking. First input IN of input side of power optimizer CHK ₁ Coupled to the positive pole of the PV component PVK and the second input IN ₂ Coupled to the negative terminal of the photovoltaic module PVK. First output NO at the output side of the power optimizer CHK ₁ And a second output NO ₂ Between which an output voltage and a conversion power are provided, and an input capacitance CI is connected to the first input IN ₁ And a second input terminal IN ₂ And the output capacitor CO is connected to the first output terminal NO ₁ And a second output NO ₂ In between. The voltage conversion circuit or called power optimizer performs DC/DC voltage conversion on the DC power provided by the photovoltaic module and performs maximum power tracking calculation synchronously. The power switch S1 and the power switch S2 of the buck conversion circuit module IN the power optimizer CHK are connected IN series at the first input end IN ₁ And a second input terminal IN ₂ And also a power switch S3 and a power switch S4 of the boost converter circuit of the power optimizer CHK are connected in series at the first output NO ₁ And a second output NO ₂ In the meantime. The power switch S1 and the power switch S2 in the Buck conversion circuit module are connected to a first interconnection node NX1, the power switch S3 and the power switch S4 in the Boost conversion circuit module are connected to a second interconnection node NX2, and the first interconnection node NX is connected with the front power switch S1-S2 in the Buck-Boost circuit topology of the Buck-Boost circuit moduleA main inductive element L is arranged between a second interconnection node NX2, to which interconnection node NX1 and rear side power switches S3-S4 are connected, and a second output NO thereof ₂ And a second input terminal IN ₂ May be directly coupled together or set to substantially the same potential. The power optimizer configuration processor 300 may have several pulse modulation signals PWM generated by the pulse width modulator 302 for driving the power switches S1-S4, and may utilize a driver 400 to enhance the driving capability of the modulation signals, and several driving signals D1-D4 output by the driver 400 are respectively coupled to the gate control terminals of the switches S1-S4.

Referring to fig. 5, the power optimizer CHK comprises a dc-to-dc buck-boost type voltage converter at which the determined output voltage V is _OK When the voltage is higher than the voltage corresponding to the maximum power point of the corresponding photovoltaic module PVK, it is determined that the power optimizer CHK is controlled by the pulse width modulation signal PWM to operate in the boost mode, the boost converter circuit module boosts the voltage, and the power switch S1 of the buck converter circuit module is continuously turned on and the power switch S2 is continuously turned off. Output voltage V determined at power optimizer _OK When the voltage is lower than the voltage corresponding to the maximum power point of the photovoltaic module PVK, it is determined that the power optimizer CHK operates in the step-down mode under the control of the pulse width modulation signal PWM, the step-down conversion circuit module reduces the voltage, and the power switch S4 of the step-up conversion circuit module is continuously turned on and the power switch S3 is continuously turned off. Output voltage V determined at power optimizer _OK When the voltage is close to the voltage corresponding to the maximum power point of the pv module PVK, that is, the voltages of the two are approximately equal, the power optimizer CHK controls the Mixed mode operating in the Boost mode and the Buck mode by the pulse width modulation signal, and the Buck-Boost circuit operates in the Boost mode and the Buck mode, which belong to the known technologies, for example, the switches S1 to S3 are turned on, and then the switches S2 to S4 are turned on, and the cycle is performed. In addition as an alternative embodiment at the output voltage V _OK At a voltage approximately equal to the maximum power point, it may also be claimed that the power optimizer CHK control, which is used as a high frequency switched mode SMPS, operates in a pass-through mode, that is: coupled to a first input IN of the positive pole of the photovoltaic module ₁ Direct quiltConnected to a first output terminal NO providing an output voltage ₁ Such as switches S1-S4 being on and switches S2-S3 being off; a second input IN coupled additionally to the negative pole of the photovoltaic module ₂ Is directly connected to a second output terminal NO providing an output voltage ₂ (if the second input terminal IN ₂ And a second output NO ₂ Any switch coupled between must be turned on). The voltage regulation functions of boosting or reducing voltage and the like ensure the high-low adjustability of the output voltage.

Referring to fig. 5, since the processor 300 samples the output voltage of the pv module PVK through the voltage sensor 111 and samples the output current of the pv module PVK through the current sensor 112, the external power provided by the pv module PVK can be calculated. Whether the photovoltaic module generates a power reduction event or releases the power reduction event needs to monitor the external output power of the photovoltaic module, if the photovoltaic module is shielded and the like, the condition that the output power of the photovoltaic module is lower than a power threshold value indicates that the power reduction event is generated, and otherwise, if the output power of the photovoltaic module is not lower than the power threshold value, the condition that the power reduction event is released is indicated. And the processor configured by the power optimizer calculates the obtained external output power through the acquired output voltage and output current of the photovoltaic module and uses the calculated external output power as a basis for judging the occurrence or release of the power reduction event.

Referring to fig. 6, the energy harvesting device receiving the output power provided by the multi-stage power optimizers CH1-CH10 is an inverter INVT as shown, the secondary optimization function of the inverter INVT configuration being used to adapt the dc bus voltage V _BUS And a bus current I flowing through the DC bus _BUS Set at the maximum power point, i.e., the secondary MPPT function. The inverter INVT may also be replaced by a charger with or without secondary optimization. The secondary optimization function of the inverter INVT is considered as a pure inverter device without maximum power tracking when it is turned off, or as an inverter device equipped with secondary maximum power tracking when it is turned on. In an alternative embodiment, when the secondary optimization function of the inverter INVT is turned off, each of the multistage power optimizers CH1 to CH10 sets the output current and the output voltage of the corresponding one of the dc power sources to the maximum powerThe power optimization method comprises the following steps that a first-stage power optimizer CH1 controls a photovoltaic module PV1 to operate at a maximum power point, a tenth-stage power optimizer CH10 controls a photovoltaic module PV10 to operate at the maximum power point, and because a front-stage MPPT function of the power optimizer is started, a rear-stage MPPT function of an inverter is not needed to be started when all stages of direct current power supplies can achieve the optimal optimization effect, and meanwhile front-stage and rear-stage optimization conflict is prevented.

Referring to fig. 6, the multistage power optimizers CH1-CH10 are classified: a first class of power optimizers and a second class of power optimizers are defined in the multi-stage power optimizers, e.g. assuming that the first class of power optimizers comprises at least the power optimizers CH1-CH2 etc. as shown in the figure and assuming that the second class of power optimizers comprises at least the power optimizers CH10 etc. We define the first type of power optimizer to operate in the pass-through mode DIC-MOD, while we also define the second type of power optimizer to operate in the optimization mode MPP-MOD. The first type of power optimizer and the second type of power optimizer both comprise a first input end and a second input end for extracting electric energy provided by the photovoltaic module, and a first output end and a second output end for providing self output power. When the quadratic optimization function of the inverter INVT is enabled, the following steps are performed: the first type of power optimizer directly shorts and passes through a first input end which is coupled to the anode of one photovoltaic module corresponding to the first type of power optimizer to a first output end; meanwhile, the first-type power optimizer directly shorts and passes through a second input end, which is coupled to the negative electrode of the corresponding photovoltaic assembly, to a second output end. Such as: the power optimizer CH1 is coupled to a first input IN of the positive pole of the photovoltaic module PV1 ₁ Directly short-circuited and led through to a first output NO of a power optimizer CH1 ₁ The power optimizer CH1 is coupled to a second input IN of the negative pole of the photovoltaic module PV1 ₂ Directly short-circuited and conducted to a first output NO of a power optimizer CH1 ₂ This is also an example of limiting the power optimizer CH1 to operate in the direct mode DIC-MOD. When the secondary optimization function of the inverter INVT is enabled, the power optimizer CH10 may also be controlled to set the output current and the output voltage of the corresponding photovoltaic module PV10 at the maximum power point, which is an example of limiting the power optimizer CH10 to operate in the optimization mode MPP-MOD. First of allThe class power optimizer works in a direct mode DIC-MOD, a power margin capable of achieving maximum power tracking can be reserved for secondary MPPT of the inverter, and if the secondary MPPT lacks the power margin reserved by the multistage power optimizers CH1-CH10, the secondary MPPT of the inverter is difficult to locate the voltage and the current of the direct-current bus at the maximum power point and fails. In an alternative embodiment, the first type of power optimizer is more suitably paired with photovoltaic modules that often experience large power fluctuations, while the second type of power optimizer is more suitably paired with photovoltaic modules that are more power stable. Taking photovoltaic modules attached to a distributed residential building as an example, photovoltaic modules which are often subjected to large power fluctuations are generally those which are easily shaded by trees or other surrounding buildings, and photovoltaic modules which are relatively stable in power on a residence are generally those which are not easily shaded by a roof.

Referring to fig. 4, in some embodiments when faced with a power reduction event: one or more of the multi-stage power optimizers is in a specified range V of their own output voltage _L -V _H By selecting a desired voltage value, e.g. V _H This selected expected voltage value is slightly lower than the estimated voltage value of the output voltage of the power optimizer due to the power reduction event, thereby reducing the cascade voltage on the bus. For example, a power optimizer is forced to maintain its output voltage at about the estimated voltage greater than the predetermined high value due to a power down event, but is actually controlled to output a lower expected voltage value. It is mentioned above that the multi-stage power optimizers CH1-CH10 and the inverter INVT, etc. may communicate in a carrier or wireless manner, and the multi-stage power optimizers CH1-CH10 transmit data such as the respective output powers and output voltages to the inverter INVT, and as an alternative embodiment, the inverter INVT may configure the bus current according to these output voltage values and the output powers of the photovoltaic modules PV 1-PVN. Alternatively, a Voltage Regulator (Voltage Regulator) 250 provided to the dc bus may be coupled separately to the bus as a separate device or integrated into the inverter INVT as an integral part of the inverter. Although allowing the voltage V of the DC bus _BUS Rising or falling floats, but as an alternative, it is preferable to use voltage regulationThe node limits the voltage of the direct current bus to a preset upper limit value and a preset lower limit value V _UP -V _DW Floating within the range.

Referring to fig. 6, in the power optimization system with the quadratic optimization, the dc bus voltage is modulated in a voltage floating manner by dynamically changing the voltage of the photovoltaic modules PV1-PV2 corresponding to the first-class power optimizers, such as the power optimizers CH1-CH2, when the quadratic optimization function is enabled. The generation mechanism of the dynamically changing voltage of the photovoltaic modules PV1-PV2 can be multifaceted, and the output voltage and the output current of the photovoltaic modules can obviously fluctuate due to the high-low change or shading and temperature change of the illumination radiation. The first-class power optimizer works in a direct mode DIC-MOD, so that the dynamic change voltage output by the photovoltaic module corresponding to the first-class power optimizer is directly fed back to the bus.

Referring to FIG. 7, the first type of power optimizer operates in a pass-through mode DIC-MOD: if the power optimizer CHK is classified as a first type of power optimizer, and the power optimizer CHK is controlled or driven by the processor 300 configured to operate IN the pass-through mode, the power optimizer CHK is coupled to the first input IN of the positive pole of the pv module PVK ₁ Is directly connected to a first output terminal NO providing an output voltage ₁ For example, switches S1 and S4 are on and switches S2 and S3 are off, so that the input voltage of the voltage converter, i.e., the power optimizer CHK, as a high-frequency switching power supply is equal to the output voltage. A second input IN coupled to the negative pole of the PV module PVK ₂ Directly connected to a second output NO providing an output voltage ₂ 。

Referring to fig. 8, the power optimizer CHK no longer employs a buck-boost circuit, but rather a buck circuit topology. First input IN embodied on the input side of the step-down circuit ₁ Coupled to positive pole of PV component PVK and second input terminal IN ₂ Coupled to the negative terminal of the photovoltaic module PVK. First output NO of the output side of the step-down circuit ₁ And a second output NO ₂ Providing an output voltage and converting power. The power switch SW and the inductor L1 are connected IN series at the second input end IN of the voltage reduction circuit ₂ And a second output NO ₂ First input ofTerminal IN ₁ Directly coupled to the first output NO ₁ . One terminal and a second input terminal IN of a power switch SW ₂ The opposite end of the power switch SW is connected to the first input IN of the step-down circuit ₁ Having an anode connected to a node interconnecting the power switch SW and the inductor L1, and a cathode connected to the first input terminal IN ₁ . The pulse-width modulation signal PWM generated by the pulse-width modulator 302 of the processor 300 of the power optimizer configuration can be used to drive the power switch SW to be turned on/off, and the driving capability of the modulation signal can be enhanced by the driver 400 in the figure, and the driving signal D5 output by the driver 400 is applied to the gate control terminal of the power switch SW. Still, the first class of power optimizers working in the pass-through mode DIC-MOD is exemplified for illustration: the power optimizer CHK is classified as a first type of power optimizer, and when the power optimizer CHK is controlled or driven by the processor 300 configured to operate IN the pass-through mode, the power optimizer CHK enables the second input IN ₂ Directly connected to the second output NO ₂ For example, we control the power switch SW to be turned on, and the input voltage of the voltage converter as the high frequency switching power supply, i.e., the power optimizer CHK, is equal to the output voltage.

Referring to FIG. 6, a power reduction event occurs at one or more photovoltaic modules, e.g., photovoltaic modules PV1-PV2, corresponding to a first type of power optimizer, e.g., power optimizer CH1-CH2, and causes an output voltage V of one or more second type of power optimizer, e.g., power optimizer CH10 _O10 Is forced to rise to tend to exceed a specified range V _L -V _H When the second type of power optimizer, e.g., power optimizer CH10, is controlled by its configured processor 300 to output a voltage V _O10 Defining an expected voltage value within a specified range. If the output voltage V of the power optimizer CH10 is left _O10 Uncontrolled random fluctuations, power-down events of the photovoltaic modules PV1-PV2 may lead to an output voltage V _O10 Is forced to rise to be greater than a high predetermined value V _H To the output voltage V actively _O10 Controlled to clamp the output voltage V _O10 Practically equal to some lower expected powerPressure value and compliance with a specified range V _L -V _H 。

Referring to fig. 6, taking the photovoltaic modules PV1-PV10 and the power optimizers CH1-CH10 as examples, power fluctuation of the photovoltaic modules corresponding to one or more power optimizers of the first type causes the voltage V of the dc bus _BUS And (4) floating. At some point in time when the power reduction event occurs, photovoltaic module PV1 is occluded and photovoltaic module PV10 is not occluded, and one or more second type of power optimizers, such as power optimizer CH10, maintains the corresponding photovoltaic module, e.g., photovoltaic module PV10, operating at the maximum power point state. The pre-optimization mainly includes that the MPPT function of the processor 300 configured by the power optimizer CH10 and the like sets the output voltage and current of the photovoltaic module PV10 and the like at the maximum power point, and the activation of the secondary optimization function of the inverter mainly includes setting the voltage and current of the bus at the maximum power point. The series-connected photovoltaic modules PV1-PV10 can be made to produce as much output power as possible, maximizing the power delivered to the energy harvesting device, e.g. the inverter INVT.

Referring to FIG. 6, at some point in time when a power reduction event occurs, it is assumed that photovoltaic modules PV1-PV2 are occluded but photovoltaic modules PV3-PV10 are not. One or more of the remaining other photovoltaic modules PV3-PV10 for which no power reduction event has occurred are controlled by the corresponding power optimizers CH3-CH10 to switch from the maximum power point state to a non-maximum power point state. Assuming that the selected photovoltaic modules PV8-PV9 are in the non-maximum power point state, that is, the output voltage of the photovoltaic modules is lower than or higher than the voltage corresponding to the maximum power point, and still the sum of the total powers calculated by adding the respective external powers of the photovoltaic modules PV1-PV10, the photovoltaic modules PV8-PV9 are switched to the non-maximum power point state, the share of the external power output by the photovoltaic modules PV8-PV9 entering the non-maximum power point state in the sum of the total powers provided by the series of photovoltaic modules PV1-PV10 is reduced. In one embodiment, when a power reduction event occurs to one or more photovoltaic modules corresponding to the first type of voltage converter, such as photovoltaic modules PV1-PV2, the processor triggering the one or more second type of voltage converter configuration controls the one or more second type of voltage converter to convert the corresponding photovoltaic modules, such as photovoltaic modules PV8-PV9, from the maximumThe power point state switches to a non-maximum power point state. For example, the photovoltaic modules PV1-PV2 are shaded and the power reduction may cause the output voltages of the power optimizers CH8-CH9 to exceed V _H In this case: the proportion of the external power output by the photovoltaic modules PV8-PV9 entering the non-maximum power point state in the sum of the total power provided by the series of photovoltaic modules PV1-PV10 is reduced, so that the voltage output value V of the power optimizer CH8-CH9 corresponding to the photovoltaic modules PV8-PV9 entering the non-maximum power point state can be reduced ₈ Or V ₉ At a cascade voltage V ₁ +V ₂ …V ₁₀ To ensure that the output voltage of the respective power optimizers CH8-CH9 does not exceed specification V _L -V _H . This is a compromise to preserve the safety level of the power optimizer with an active loss of part of the power production. The power optimizer is controlled by a processor configured to determine whether the photovoltaic module is at a maximum power point or a non-maximum power point, the processor enables a maximum power point tracking calculation function to control the power optimizer to perform maximum power tracking, and the processor does not enable the maximum power point tracking calculation function but only uses ordinary voltage modulation to control the power optimizer to perform ordinary power conversion.

Referring to fig. 6, limiting the voltage V of the dc bus _BUS At a predetermined upper limit value V _UP And a lower limit value V _DW The range is dynamically floated, and at a certain time when the power reduction event occurs, the photovoltaic module PV1 is shielded and the photovoltaic module PV10 is not shielded. At the DC bus voltage V _BUS Drops to a value close to or equal to the lower limit value V _DW When the method is used: one or more of the remaining other photovoltaic components for which no power reduction event has occurred are controlled by the corresponding power optimizer to switch from a maximum power point state to a non-maximum power point state. For example, the photovoltaic modules PV10 are controlled by the power optimizer CH10 to switch from the maximum power point state to the non-maximum power point state, with the output voltage deviating from the voltage corresponding to the maximum power point, in order to force the bus current calculated by dividing the total power supplied by the series of photovoltaic modules PV1-PV10 at that moment by the current value of the dc bus voltage at that moment to drop. The bus current is decreasedMeans that: the bus current calculated when the photovoltaic module PV10 is in the non-maximum power point state is lower than the bus current calculated when the photovoltaic module PV10 is in the maximum power point state, which is obviously because the external output power of the photovoltaic module PV10 is necessarily reduced when the photovoltaic module PV10 is switched from the maximum power point state to the non-maximum power point state. In some embodiments, when a power reduction event occurs in the dc power source corresponding to the one or more first type of voltage converter, for example, the photovoltaic module PV1, and the dc bus voltage drops to approach the lower limit value, the processor triggering the one or more second type of voltage converter configuration controls the one or more second type of voltage converter to switch the corresponding dc power source, for example, the photovoltaic module PV10, from the maximum power point state to the non-maximum power point state. Is to consider: the reduction of the external power output by the photovoltaic modules entering the non-maximum power point state results in a reduction of the sum of the total powers provided by the series of photovoltaic modules PV1-PV10, so that the total power at this stage is divided by the bus current calculated from the actual voltage value (very close to or even equal to the lower limit value) of the dc bus voltage at that moment, for example because the power of the photovoltaic modules PV10 etc entering the non-maximum power point state is reduced. The actual voltage value of the dc bus voltage approaches the lower limit value, indicating that it has no more room for the spring to drop. The external power obtained by reducing the PV assembly PV10 entering the non-maximum power point state, divided by the reduced bus current, is approximately equal to the output voltage V of the power optimizer CH10 corresponding to the PV assembly PV10 entering the non-maximum power point state ₁₀ In this case, the output voltage V ₁₀ Easily controlled and limited specification range V _L -V _H And (4) the following steps. Conversely, if the photovoltaic module PV10 is still in the maximum power point state, the output voltage V of the power optimizer CH10 ₁₀ Is likely to be forced to rise far beyond the specified specification V _L -V _H Especially when the direct current bus voltage does not have any elastic space floating downwards, the more power the photovoltaic module PV1 and the like lose, the more the output voltage V ₁₀ The more voltages are to be compensated. Also, although there is a power loss, it is also a main factorAnd the way of dynamic loss of part of the generated energy is used for maintaining the compromise scheme of the safety level of the power optimizer.

While the foregoing specification teaches, with reference to the specific embodiments provided above, and illustrated in the accompanying drawings, certain embodiments of the present invention as disclosed herein are considered exemplary and not restrictive. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above description. Therefore, the appended claims should be construed to cover all such variations and modifications as fall within the true spirit and scope of the invention. Any and all equivalent ranges and contents within the scope of the claims should be considered to be within the intent and scope of the present invention.

Claims

1. A power optimization system including quadratic optimization, comprising:

a series connected multi-level voltage converter;

each stage of voltage converter converts the electric energy captured from a corresponding direct current power supply into output power;

the respective output voltages of the multi-level voltage converters are superimposed to thereby serve as a DC bus voltage;

each stage of voltage converter is used for setting the output current and the output voltage of one corresponding direct current power supply at the maximum power point;

the energy collecting device is used for receiving the output power provided by the multistage voltage converter, and the secondary optimization function configured by the energy collecting device is used for setting the direct-current bus voltage and the direct-current bus current at the maximum power point;

the energy collecting device comprises an inverter, wherein the inverter is regarded as an inverter device provided with secondary maximum power tracking when a secondary optimization function of the inverter is started;

defining a first class of voltage converter and a second class of voltage converter in the multistage voltage converter, wherein each of the first class of voltage converter and the second class of voltage converter comprises a first input end and a second input end for capturing electric energy provided by a direct current power supply and a first output end and a second output end for providing self output power;

when the secondary optimization function of the inverter is started, the following conditions are met:

the first class of voltage converters are coupled to a first input end of a positive pole of a corresponding direct current power supply to be directly short-circuited and directly communicated to a first output end, the first class of voltage converters are coupled to a second input end of a negative pole of the corresponding direct current power supply to be directly short-circuited and directly communicated to a second output end, the direct current bus voltage is modulated in a voltage floating mode through the dynamic change voltage of the direct current power supply corresponding to each first class of voltage converter, and the second class of voltage converters are all used for setting the output current and the output voltage of the corresponding direct current power supply at the maximum power point.

2. The power optimization system with quadratic optimization according to claim 1, characterized in that:

the type of dc power source includes at least a fuel cell or a photovoltaic module.

3. The power optimization system with quadratic optimization according to claim 1, wherein:

controlling the dynamically changing DC bus voltage by a voltage regulator coupled to the DC bus to be within a predetermined upper limit and lower limit;

the voltage regulator is provided separately to the dc bus or integrated in the energy collection device.

4. The power optimization system with quadratic optimization according to claim 1, characterized in that:

when the power reduction event occurs to the direct current power supply corresponding to one or more first class voltage converters and causes the output voltage of one or more second class voltage converters to be forced to rise to the voltage tending to exceed the specified range, the second class voltage converters are controlled by the configured processor to limit the output voltage to an expected voltage value within the specified range.

5. The power optimization system with quadratic optimization according to claim 1, characterized in that:

when the direct current power supply corresponding to one or more first-class voltage converters generates a power reduction event, the direct current power supply corresponding to one or more second-class voltage converters maintains the state of working at the maximum power point.

6. The power optimization system with quadratic optimization according to claim 1, wherein:

when the direct current power supply corresponding to one or more first class voltage converters generates a power reduction event, the direct current power supply corresponding to one or more second class voltage converters is switched from a maximum power point state to a non-maximum power point state;

the proportion of the external power output by the direct current power supply entering the non-maximum power point state in the sum of the total power provided by a series of direct current power supplies corresponding to the multi-stage voltage converter is reduced.

7. The power optimization system with quadratic optimization according to claim 1, characterized in that:

limiting the voltage of the direct-current bus to float in a preset upper limit value range and a preset lower limit value range, and when the voltage of the direct-current bus falls to approach the lower limit value due to a power reduction event of a direct-current power supply corresponding to one or more first-class voltage converters;

and the direct-current power supplies corresponding to one or more second-class voltage converters are switched to a non-maximum power point state from a maximum power point state, so that the total power provided by a series of direct-current power supplies corresponding to the multi-stage voltage converter at the moment is forced to be divided by the bus current calculated by the direct-current bus voltage to be reduced.

8. The power optimization system with quadratic optimization according to claim 1, wherein:

the voltage converter includes:

first and second switches connected in series between first and second input terminals of a voltage source receiving a supply of DC power;

third and fourth switches connected in series between first and second output terminals providing an output voltage;

an inductive element is provided between the interconnection node between the first and second switches and the interconnection node between the third and fourth switches and a second input terminal is coupled to the second output terminal.

9. A method of power optimization, comprising:

connecting the multi-level voltage converters in series;

capturing the electric energy of one corresponding photovoltaic module by each level of voltage converter and converting the electric energy into output power;

superposing the output voltages of the multi-level voltage converters to form a total cascade voltage which is used as a direct current bus voltage;

setting a photovoltaic component corresponding to each level of the voltage converter at a maximum power point;

collecting output power provided by the multi-stage voltage converter through an energy collecting device configured with a secondary optimization function, and selecting whether to set the direct-current bus voltage and the direct-current bus current at a maximum power point by selecting whether to start the secondary optimization function;

the energy harvesting device includes an inverter, and the method further includes: starting a secondary optimization function of the inverter, and setting the inverter to be an inverter device provided with secondary maximum power tracking;

defining a first class of voltage converter and a second class of voltage converter in the multistage voltage converter, wherein each of the first class of voltage converter and the second class of voltage converter comprises a first input end and a second input end for capturing electric energy provided by the photovoltaic module and a first output end and a second output end for providing output power of the first input end and the second input end;

enabling a secondary optimization function of the inverter, the method further comprising:

the first type of voltage converter is controlled by a processor configured with the first type of voltage converter to be coupled to a first input end of a positive pole of a photovoltaic component corresponding to the first type of voltage converter to be directly short-circuited and directly communicated to a first output end, the first type of voltage converter is controlled by the processor configured with the first type of voltage converter to be coupled to a second input end of a negative pole of the photovoltaic component corresponding to the first type of voltage converter to be directly short-circuited and directly communicated to a second output end, the direct current bus voltage is modulated in a voltage floating mode through the dynamic change voltage output by the photovoltaic component corresponding to each first type of voltage converter, and the second type of voltage converter is used for setting the output current and the output voltage of one photovoltaic component corresponding to the second type of voltage converter at a maximum power point through a maximum power tracking function.

10. The method of claim 9, wherein:

arranging a voltage regulator on the direct current bus, wherein the voltage regulator is used for controlling the voltage of the dynamically changed direct current bus not to exceed the range of a preset upper limit value and a preset lower limit value;

the voltage regulator is provided separately to the dc bus or integrated directly into the inverter.

11. The method of claim 9, wherein:

when the photovoltaic components corresponding to the one or more first type voltage converters generate power reduction events and cause the output voltages of the one or more second type voltage converters to be forced to rise to tend to exceed the specified range;

the processor that triggers the second type of voltage converter arrangement controls the output voltage of the second type of voltage converter to be limited to a desired voltage value within a prescribed range.

12. The method of claim 9, wherein:

when a power reduction event occurs to the photovoltaic component corresponding to the one or more first class voltage converters, the processor configured by the one or more second class voltage converters controls the one or more second class voltage converters to maintain the corresponding photovoltaic component to work in the maximum power point state.

13. The method of claim 9, wherein:

when a power reduction event occurs to a photovoltaic component corresponding to one or more first-type voltage converters, triggering a processor configured by one or more second-type voltage converters to control the one or more second-type voltage converters to switch the corresponding photovoltaic component from a maximum power point state to a non-maximum power point state;

the share of the external power output by the photovoltaic modules entering the non-maximum power point state in the sum of the total power provided by a series of photovoltaic modules corresponding to the multi-level voltage converter is reduced.

14. The method of claim 9, wherein:

limiting the direct current bus voltage to float in a preset upper limit value range and a preset lower limit value range, and when the direct current bus voltage falls to approach the lower limit value due to a power reduction event of the photovoltaic assembly corresponding to one or more first-type voltage converters;

and the processor triggering one or more second type voltage converter configurations controls one or more second type voltage converters to switch the corresponding photovoltaic assembly from the maximum power point state to the non-maximum power point state, so that the bus current calculated by dividing the total power provided by the series of photovoltaic assemblies corresponding to the multi-stage voltage converter by the direct-current bus voltage at the moment is reduced.