High-safety and high-efficiency control methods and systems for photovoltaic energy storage systems

Abstract

This invention provides a highly safe and efficient control method and system for photovoltaic energy storage systems. It uses small positive and negative vectors with high common-mode voltage to synthesize a reference voltage vector, eliminating the focus on the vector's common-mode voltage value and instead limiting the range of common-mode voltage variation across all switching sequences. This reduces the system's common-mode voltage variation rate and leakage current, even when photovoltaic and battery voltages are variable. The use of small positive and negative vectors with high common-mode voltage provides more redundant switching states and sequences, facilitating power regulation of the photovoltaic-energy storage system. Switching sequences with medium-range vectors can also be used as independent control sequences for power regulation, achieving smooth power regulation between photovoltaic, battery, and grid components. This reduces the peak-to-valley load difference in the grid, bringing power generation and consumption closer to balance. Furthermore, the control algorithm is simple and easy to implement.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic energy storage system control technology, and in particular to a highly safe and efficient control method and system for photovoltaic energy storage systems. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Due to its advantages such as being green, environmentally friendly, and pollution-free, photovoltaic (PV) power generation has developed rapidly. However, PV power generation is limited by the environment, exhibiting significant intermittency and randomness. Power generation and load often fail to reach a balance, further affecting the stability of the entire power grid system. PV energy storage systems can store excess electricity generated by the PV system in batteries during off-peak hours to fill the load gap; and release the stored energy during peak hours to compensate for the power difference between the PV system and the load, thus reducing peak load. Because it can reduce the peak-to-valley load difference in the power grid and balance power generation and consumption, PV energy storage systems have broad application prospects.

[0004] In photovoltaic energy storage systems, dual-DC-port inverters can be used as a separate power conversion stage, with their DC side directly connected to the photovoltaic panels and batteries. However, the inventors discovered that because the photovoltaic voltage and battery voltage change with the external environment, this leads to an unstable high common-mode voltage, resulting in a larger common-mode current and affecting the normal operation of the system. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a highly safe and efficient control method and system for photovoltaic energy storage systems. It limits the variation range of vector common-mode voltage in all switching sequences, thereby reducing leakage current. The application of positive and negative small vectors with high common-mode voltage provides more redundant switching states and sequences. Switching sequences with medium vectors can also be used as independent control sequences to achieve power regulation of the photovoltaic energy storage system.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a highly safe and efficient control method for a photovoltaic energy storage system.

[0008] A highly safe and efficient control method for a photovoltaic energy storage system includes the following processes:

[0009] Obtain the reference voltage vector in the αβ coordinate system of the power grid, determine the large sector based on the phase angle of the reference voltage vector, and divide each large sector into the first part and the second part according to the position of the median vector.

[0010] Based on the photovoltaic voltage and the battery voltage, calculate the common-mode voltage of each vector, sort the common-mode voltages, and generate the vector order of the switching sequence;

[0011] Each large sector is divided into four smaller sectors in the first and second parts. Each smaller sector contains one or more charging and discharging sequences. In different switching sequences of different smaller sectors, a reference voltage vector is synthesized using three vectors for modulation, and the duration of the corresponding vector is calculated.

[0012] The photovoltaic power is calculated based on the photovoltaic voltage and photovoltaic current. The control parameters are generated by the DC power control loop through the PI regulator. The power control parameters are obtained by the limiting unit. The frequency of the charging sequence and the discharging sequence are adjusted in real time according to the power control parameters to achieve power regulation.

[0013] The operation of the inverter is controlled by controlling the on / off state of the power switching transistors in the dual DC port inverter based on the action time and switching sequence.

[0014] As a further limitation of the first aspect of the present invention, the common-mode voltage of each vector is calculated based on the photovoltaic voltage and the battery voltage, and the common-mode voltage is sorted, including:

[0015] Obtain photovoltaic voltage V PV and battery voltage V Bat The common-mode voltage of each vector is calculated. The vector corresponds to eight common-mode voltage values. Based on the different common-mode voltage values, they are divided into the first large vector, the second large vector, the medium vector, the first positive small vector, the second positive small vector, the first negative small vector, the second negative small vector, and the zero vector. The vectors are sorted from low to high common-mode voltage values.

[0016] When 2V Bat <V PV <3V Bat When the vectors are in order, they are: first negative small vector, second negative small vector, first large vector, zero vector, medium vector, first positive small vector, second large vector, and second positive small vector.

[0017] When V PV >3V Bat When the vectors are in order, they are: first negative small vector, second negative small vector, zero vector, first large vector, medium vector, first positive small vector, second large vector, and second positive small vector.

[0018] When 3V Bat / 2 <V PV <2V Bat When the vector is in the order of negative small vector, first large vector, second negative small vector, medium vector, zero vector, second large vector, first positive small vector, and second positive small vector;

[0019] When V PV <3V Bat When the value is 2, the order is as follows: first negative small vector, first large vector, second negative small vector, medium vector, second large vector, zero vector, first positive small vector, second positive small vector.

[0020] As a further limitation of the first aspect of the invention, based on the principle of minimizing the common-mode voltage variation range, the vector order for generating the switching sequence includes:

[0021] Based on the principle of minimizing the range of common-mode voltage variation, and according to the common-mode voltage sorting relationship, the switching interval between vectors is only allowed to be no more than one vector. The current sorting relationship is determined based on the photovoltaic voltage and the battery voltage, and the vector order of the switching sequence is changed in real time.

[0022] As a further limitation of the first aspect of the present invention, the first portion of the first large sector satisfies Based on the components of the voltage space vector on the α-axis, the components of the voltage space vector on the β-axis, the photovoltaic voltage, and the battery voltage, the first and second curves used to divide the four small sectors are obtained.

[0023] V α V represents the components of the voltage space vector along the α-coordinate axis. β V represents the components of the voltage space vector along the β-coordinate axis. PV V PV These are the photovoltaic voltage and the battery voltage, respectively.

[0024] When the reference voltage vector is above the first curve and below the second curve, it is determined that the reference voltage vector is located in the first small sector; when the reference voltage vector is below the first curve and below the second curve, it is determined that the reference voltage vector is located in the second small sector.

[0025] When the reference voltage vector is below the first curve and above the second curve, it is determined that the reference voltage vector is located in the third sub-sector; when the reference voltage vector is above the first curve and above the second curve, it is determined that the reference voltage vector is located in the fourth sub-sector.

[0026] As a further limitation of the first aspect of the invention, the second part of the first large sector satisfies Based on the components of the voltage space vector on the α-axis, the components of the voltage space vector on the β-axis, the photovoltaic voltage, and the battery voltage, the third and fourth curves used to divide the four small sectors are obtained.

[0027] When the reference voltage vector is below the third curve and to the left of the fourth curve, the reference voltage vector is determined to be located in the fifth sub-sector; when the reference voltage vector is below the third curve and to the right of the fourth curve, the reference voltage vector is determined to be located in the sixth sub-sector.

[0028] When the reference voltage vector is above the third curve and to the right of the fourth curve, the reference voltage vector is determined to be located in the seventh sub-sector; when the reference voltage vector is above the third curve and to the left of the fourth curve, the reference voltage vector is determined to be located in the eighth sub-sector.

[0029] The smaller sectors of other large sectors are obtained by rotation.

[0030] As a further limitation of the first aspect of the present invention, when the external light conditions are poor or the load increases, the photovoltaic power generation cannot meet the load demand. At this time, the power control parameters are reduced, and the frequency of use of the discharge sequence is increased in real time, so that the output power of the battery increases and makes up for the power difference between the photovoltaic power generation system and the load.

[0031] When the intensity of external sunlight increases or the load decreases, the photovoltaic power generation exceeds the load demand. At this time, the power control parameters are increased, and the frequency of use of the charging sequence is increased in real time to store the excess electrical energy output by the photovoltaic power generation system in the battery.

[0032] By adjusting the frequency of charging and discharging sequences in real time using power control parameters, power generation and consumption can be balanced, thus maintaining the stability of the entire power grid system.

[0033] Secondly, the present invention provides a high-safety and high-efficiency control system for a photovoltaic energy storage system.

[0034] A high-safety and high-efficiency control system for a photovoltaic energy storage system includes:

[0035] The reference voltage vector calculation module is configured to: obtain the reference voltage vector in the αβ coordinate system of the power grid, determine the large sector based on the phase angle of the reference voltage vector, and divide each large sector into a first part and a second part based on the position of the middle vector;

[0036] The vector common-mode voltage sorting module is configured to: calculate the common-mode voltage of each vector based on the photovoltaic voltage and the battery voltage, sort the common-mode voltages, and generate the vector order of the switching sequence based on the principle of minimizing the range of common-mode voltage variation;

[0037] The sector division module is configured to: based on the principle that each small sector has at least one small or medium vector that can be used for power regulation, divide each large sector into four small sectors in the first and second parts, and each small sector has one or more charging sequences and discharging sequences; in different switching sequences of different small sectors, the reference voltage vector is synthesized from three vectors for modulation, and the action time of the corresponding vector is calculated.

[0038] The power regulation module is configured to: calculate the photovoltaic power based on the photovoltaic voltage and photovoltaic current; generate control parameters by the DC power control loop through the PI regulator; obtain power control parameters ranging from 0 to 1 by the limiting unit; and adjust the usage frequency of the charging sequence and discharging sequence in real time according to the power control parameters to achieve power regulation.

[0039] The inverter control module is configured to control the switching of power switches in the dual DC port inverter based on the operating time and switching sequence, so as to control the operation of the inverter.

[0040] Thirdly, the present invention provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the steps in the high-safety and high-efficiency control method for a photovoltaic energy storage system as described in the first aspect of the present invention.

[0041] Fourthly, the present invention provides an electronic device, including a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps in the high-safety and high-efficiency control method for a photovoltaic energy storage system as described in the first aspect of the present invention.

[0042] Compared with the prior art, the beneficial effects of the present invention are:

[0043] 1. This invention uses small positive and negative vectors with high common-mode voltage to synthesize a reference voltage vector. Instead of focusing on the common-mode voltage value of the vector, it limits the range of common-mode voltage variation in all switching sequences. This reduces the common-mode voltage variation rate of the system and decreases leakage current when the photovoltaic voltage and battery voltage are variable.

[0044] 2. This invention employs positive and negative small vectors with high common-mode voltage, providing more redundant switching states and sequences, which is beneficial for power regulation of photovoltaic and energy storage systems. Traditional power regulation methods ignore the fact that medium vectors have the same role as small vectors in power control. In the scheme of this invention, the switching sequence with medium vectors can also be used as an independent control sequence to achieve power regulation, realizing smooth power regulation between photovoltaics, batteries and the grid, reducing the peak-valley difference of grid load, and making power generation and consumption tend to be balanced. The control algorithm is simple and easy to implement.

[0045] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0046] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0047] Figure 1 A schematic diagram of a typical photovoltaic energy storage system topology using a dual DC port inverter as a separate power conversion stage, provided in Embodiment 1 of the present invention;

[0048] Figure 2 The space vector state diagram of a typical photovoltaic energy storage system using a dual DC port inverter as a separate power conversion stage is provided in Embodiment 1 of the present invention.

[0049] Figure 3 This is a schematic diagram of the division of the first part of the first large sector in the spatial vector diagram of the photovoltaic energy storage system provided in Embodiment 1 of the present invention;

[0050] Figure 4 This is a schematic diagram of the division of the second part of the first large sector in the spatial vector diagram of the photovoltaic energy storage system provided in Embodiment 1 of the present invention;

[0051] Figure 5 This is a control block diagram of the common-mode voltage suppression and power control method for a photovoltaic energy storage system provided in Embodiment 1 of the present invention;

[0052] Figure 6 The simulation results are shown in the figure for the common-mode voltage suppression and power control method of the photovoltaic energy storage system provided in Embodiment 1 of the present invention. Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0054] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0055] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0056] Example 1:

[0057] This embodiment discloses a high-safety and high-efficiency control method for photovoltaic energy storage systems. This method is designed for photovoltaic energy storage systems and combines... Figure 1The diagram shows the topology of a photovoltaic energy storage system that uses a dual-DC-port inverter as a separate power conversion stage. The dual-DC-port inverter in this embodiment needs to operate under variable photovoltaic voltage and battery voltage conditions.

[0058] In each phase of a dual-DC-port inverter, S x1 S x2 S x3 and S x4 (x = a, b, c) are four power switching transistors. In this embodiment, IGBT transistors can be used as the switching transistors. Their DC sides are connected to the photovoltaic panel and the battery, respectively, and the midpoint of each phase bridge arm is connected to the power grid via filter L. The photovoltaic voltage and the battery voltage are denoted as V. PV and V Bat Each phase output is represented by one of three switching states: [h], [l], and [0]. These three different switching states can be achieved by controlling the on and off states of the power switching transistors, with output voltages of V respectively. PV V Bat With 0 and 0, the output phase voltage and switching state are shown in the following formula:

[0059]

[0060] Where x = a, b, c represents the three phases a, b, and c, u xo V represents the output voltage of each phase of the inverter. PV Represents photovoltaic voltage, V Bat This indicates the battery voltage.

[0061] The relationship between the output phase voltage and the conduction of the power switch is shown in Table 1 below.

[0062] Table 1: Relationship between output phase voltage and power switching transistor of dual DC port inverter.

[0063]

[0064] The three-phase current of the power grid is sampled, and after constant power control and coordinate transformation, the reference voltage vector V in the αβ coordinate system is obtained. ref The reference voltage vector V is determined based on its phase angle value. ref The spatial voltage vector region is divided into six large sectors, and each large sector is further divided into a first part and a second part based on the position of the median vector, resulting in a total of 27 vectors. When V PV -V Bat >V Bat The space vector state diagram of a photovoltaic energy storage system using a dual-DC-port inverter as a separate power conversion stage is shown below. Figure 2 As shown.

[0065] The spatial vector categories include zero vector, negative small vector, positive small vector, medium vector, and large vector. The zero vector includes (h, h, h), (l, l, l), and (0, 0, 0). The negative small vector includes (l, 0, 0), (0, l, 0), (0, 0, l), (l, l, 0), (0, l, l), and (l, 0, l). The positive small vector includes (h, l, l), (l, h, l), (l, l, h), (h, h, l), (l, h, h), and (h, l, h). The medium vector includes (h, l, 0), (0, h, l), (l, 0, h), (l, h, 0), (0, l, h), and (h, 0, l). The large vector includes (h, 0, 0), (0, h, 0), (0, 0, h), (h, h, 0), (0, h, h), and (h, 0, h). Based on the different common-mode voltage values, large vectors, positive small vectors, and negative small vectors are further divided into large vector-1 (i.e., the first large vector), large vector-2 (i.e., the second large vector), positive small vector-1 (i.e., the first positive small vector), positive small vector-2 (i.e., the second positive small vector), negative small vector-1 (i.e., the first negative small vector), and negative small vector-2 (i.e., the second negative small vector).

[0066] Common-mode voltage v CM Defined as the average value of the three-phase output phase voltages of a dual-DC-port inverter:

[0067]

[0068] Among them, u xo (x = a, b, c) represents the output voltage of each phase of the inverter.

[0069] Based on the above formula, the common-mode voltages of all vectors can be obtained, as shown in Table 2 below:

[0070] Table 2: Common-mode voltages of all vectors in a dual-DC-port inverter.

[0071]

[0072]

[0073] Unlike traditional common-mode voltage suppression methods, this embodiment uses small positive and negative vectors with high common-mode voltages to synthesize a reference voltage vector V. ref This embodiment no longer focuses on the common-mode voltage value of the vector, but rather on the range of common-mode voltage variation across all switching sequences. The application of small positive and negative vectors with high common-mode voltages provides more redundant switching states and sequences, which is beneficial for power regulation in photovoltaic-storage systems. Traditional power regulation methods neglect the fact that medium vectors play the same role as small vectors in power control; switching sequences with medium vectors can also be used as independent control sequences to achieve power regulation.

[0074] The high-safety and high-efficiency control method for the photovoltaic energy storage system in this embodiment specifically includes the following process:

[0075] S1: Sample the three-phase current of the power grid, and after constant power control and coordinate transformation, obtain the reference voltage vector V in the αβ coordinate system. ref The reference voltage vector V is determined based on its phase angle value. ref The large sector it belongs to, and based on the position of the median vector, each large sector is divided into two parts, 1 and 2;

[0076] S2: Obtain the photovoltaic voltage and battery voltage, calculate the common-mode voltage of each vector, sort them, and arrange the vector order of the switching sequence based on the principle of minimizing the range of common-mode voltage variation;

[0077] S3: Based on the principle that each small sector has at least one small or medium vector that can be used for power regulation, four small sectors are divided into the first and second parts of each large sector. Each small sector has one or more charging sequences and discharging sequences. In practical engineering applications, the discharging / charging sequence can be selected according to the required power regulation speed.

[0078] S4: Based on the use of three vector synthesized reference voltage vectors V in different switching sequences of different small sectors. ref Based on the modulation principle, the action time of the corresponding vector is calculated;

[0079] S5: Obtain photovoltaic voltage and photovoltaic current, calculate photovoltaic power, and generate control parameter k from the DC power control loop via a PI regulator. This control parameter k is then passed through a limiting unit to obtain a power control parameter k ranging from 0 to 1. c Based on the power control parameter k c Power regulation is achieved by adjusting the frequency of charging and discharging sequences in real time.

[0080] S6: Controls the switching of power switches in the dual DC port inverter based on the action time and switching sequence to control the operation of the inverter.

[0081] Specifically, this implementation also uses the small positive and negative vectors of the high common-mode voltage to synthesize the reference voltage vector V. ref Instead of focusing on the common-mode voltage value of the vector, we focus on the range of common-mode voltage variations across all switching sequences. Specifically, when V... PV =2V Bat At the same time, ensure that the common-mode voltage variation range of each switching sequence is equal to V. PV / 6. This embodiment limits the range of common-mode voltage variation so that when V PV =2V BatAt this time, the common-mode voltage variation range of each switching sequence is reduced to one-sixth of the photovoltaic voltage, further reducing leakage current. When V PV >2V Bat or V PV <2V Bat At the same time, the range of common-mode voltage variation is also reduced, and the leakage current is also reduced.

[0082] Obtain the photovoltaic voltage and battery voltage, and calculate the common-mode voltage of each vector, as shown in Table 1.

[0083] It can be seen that, except for the zero vector (h, h, h) and (l, l, l), the other vectors correspond to eight common-mode voltage values, and the vectors are sorted from low to high according to the common-mode voltage values.

[0084] Sort (1), when 2V Bat <V PV <3V Bat hour,

[0085] Negative small vector -1 < Negative small vector -2 < Large vector -1 < Zero vector < Medium vector < Positive small vector -1 < Large vector -2 < Positive small vector -2;

[0086] Sort (2), when V PV >3V Bat hour,

[0087] Negative small vector -1 < Negative small vector -2 < Zero vector < Large vector -1 < Medium vector < Positive small vector -1 < Large vector -2 < Positive small vector -2;

[0088] Sort (3), when 3V Bat / 2 <V PV <2V Bat hour,

[0089] Negative small vector -1 < Large vector -1 < Negative small vector -2 < Medium vector < Zero vector < Large vector -2 < Positive small vector -1 < Positive small vector -2;

[0090] Sort (4), when V PV <3V Bat / 2 o'clock,

[0091] Negative small vector -1 < Large vector -1 < Negative small vector -2 < Medium vector < Large vector -2 < Zero vector < Positive small vector -1 < Positive small vector -2.

[0092] Based on the principle of minimizing the common-mode voltage variation range, when designing the switching sequence, according to the above sorting relationship, the switching interval between vectors is only allowed to be no more than one vector. For example, sorting (1): when 2V Bat <V PV <3V BatAt this time, switching between the zero vector and the negative small vector -2 is allowed, but switching between the zero vector and the negative small vector -1 is not allowed. Simultaneously, the current sorting relationship needs to be determined based on the photovoltaic voltage and the battery voltage, and the vector order of the switching sequence needs to be changed in real time.

[0093] The three-phase current is sampled, and after constant power control and coordinate transformation, the reference voltage V in the αβ coordinate system is obtained. ref The reference voltage vector V is determined based on its phase angle value. ref The large sector is denoted as I-VI, and each large sector is divided into a first part and a second part according to the position of the median vector. Due to the similarity of the sectors, taking the first large sector as an example, the other large sectors can be obtained by rotation.

[0094] In this embodiment, before determining the sector distribution location of the reference vector, it is necessary to first divide the vector space corresponding to the voltage space vector into sectors. The process of dividing the first part I-1 of the first large sector into 4 smaller sectors is as follows:

[0095] The first part of the first sector, I-1, satisfies The expressions for the two curves used to divide the four small sectors are as follows:

[0096]

[0097] Among them, V α V represents the components of the voltage space vector along the α-coordinate axis. β V represents the components of the voltage space vector along the β-coordinate axis. PV V PV These are the photovoltaic voltage and the battery voltage, respectively. When the reference voltage vector V... ref When it is above B1 and below B2, determine V. ref Located in small sector S1; when the reference voltage vector V ref When it is below B1 and below B2, determine V. ref Located in small sector S2; when the reference voltage vector V ref When it is below B1 and above B2, determine V. ref Located in small sector S3; when the reference voltage vector V ref When it is above B1 and above B2, determine V. ref Located in sector S4.

[0098] Figure 3 For V PV -V Bat >V Bat At that time, the schematic diagram of the first part of the first sector I-1 of the spatial vector diagram of the photovoltaic energy storage system is a representation of the three-phase output voltage V of the dual DC port inverter in the αβ coordinate system. aV b V c Modeling is performed where, based on the two-phase voltages in the αβ coordinate system, the reference voltage vector can be defined as: V ref =V α +jV β .

[0099] The process of dividing the second part I-2 of the first large sector into 4 smaller sectors is as follows: The second part I-2 of the first large sector satisfies The expressions for the two curves used to divide the four small sectors are as follows:

[0100]

[0101] Among them, V α V represents the components of the voltage space vector along the α-coordinate axis. β V represents the components of the voltage space vector along the β-coordinate axis. PV V PV These are the photovoltaic voltage and the battery voltage, respectively. When the reference voltage vector V... ref When it is below B3 and to the left of B4, determine V. ref Located in small sector S5; when the reference voltage vector V ref When it is located below B3 and to the right of B4, determine V. ref Located in sector S6; when the reference voltage vector V ref When it is above B3 and to the right of B4, determine V. ref Located in sector S7; when the reference voltage vector V ref When it is above B3 and to the left of B4, determine V. ref Located in sector S8.

[0102] Figure 4 This is a schematic diagram of the second part of the first sector of the spatial vector diagram of a photovoltaic energy storage system, showing the division of the three-phase output voltage V of the dual-DC-port inverter in the αβ coordinate system. a V b V c Modeling is performed where, based on the two-phase voltages in the αβ coordinate system, the reference voltage vector can be defined as: V ref =V α +jV β .

[0103] In this embodiment, three vectors are used to synthesize the reference voltage vector V in different small sectors. ref The three vectors each act for a period of time according to their respective proportions, which is equivalent to one sampling period T. S Internal reference voltage vector V ref Its effects.

[0104]

[0105] Among them, V iα and V iβ (i = 1, 2, 3) are the coordinates of the selected nearest voltage vector Vi in the αβ coordinate system, T i It is the duration of action of the corresponding vector.

[0106] In this embodiment, during the synthesis of the reference vector, to limit the range of common-mode voltage variation, based on the vector common-mode voltage sorting relationship, the switching interval between vectors in the same switching sequence is not allowed to exceed one vector. Sort by (1): 2V Bat <V PV <3V Bat For example, the switching sequence of the first part I1 of the first large sector designed in this embodiment is shown in Table 3.

[0107] Table 3. I1 Switch Sequence of the First Major Sector, Part 1, and Corresponding Battery Current and Control Capability

[0108]

[0109]

[0110] Traditional power regulation methods neglect the fact that the medium vector plays the same role as the small vector in power control. A switching sequence with a medium vector can also be used as an independent control sequence for power regulation. In each small sector, at least one charging / discharging sequence exists for power regulation. A control capability "↑" indicates a discharging sequence, releasing stored energy during peak load periods to compensate for the power difference between the photovoltaic system and the load, thus reducing peak load. A control capability "↓" indicates a charging sequence, storing excess energy from the photovoltaic system in batteries during off-peak load periods to fill the load gap. Furthermore, "↑↑" or "↓↓" indicates that the corresponding discharging / charging sequence has a better power regulation capability than a single "↑" or "↓" sequence. In practical engineering applications, the discharging / charging sequence can be selected based on the required power regulation speed.

[0111] Similarly, sorted by (1): 2V Bat <V PV <3V Bat For example, the switching sequence of the second part I2 of the first large sector designed in this embodiment is shown in Table 4.

[0112] Table 4: The I2 switch sequence of the first part of the first major sector and its corresponding battery current and control capability.

[0113]

[0114]

[0115] In the first part I2 of the first major sector, each sub-sector also contains one or more discharge / charge sequences. In practical engineering applications, the discharge / charge sequence can be selected according to the required power adjustment speed.

[0116] When the external environment changes, the photovoltaic voltage and battery voltage change accordingly. At this time, it is necessary to determine the current sequencing relationship and adjust the vector order of the switching sequence in real time. For example, when the light intensity increases, the photovoltaic voltage increases from 2V. Bat <V PV <3V Bat Increase to V PV >3V Bat At this point, the sorting relationship is switched from sorting (1) to sorting (2). The original S1 charging sequence (l, l, l)-(h, l, l)-(h, l, 0)-(h, l, l)-(l, l, l) has the zero vector and the positive small vector -1 switching between each other. Under sorting (2), the zero vector and the positive small vector -1 are separated by two vectors, which does not satisfy the principle that the switching between vectors is only allowed to be at an interval of no more than one vector. Therefore, the switching sequence needs to be rearranged. The S1 charging sequence in sorting (2) is (l, l, l)-(h, l, 0)-(h, l, l)-(h, l, 0)-(l, l, l). At this time, the switching sequence satisfies the principle that the switching between vectors is only allowed to be at an interval of no more than one vector.

[0117] The photovoltaic voltage and current are obtained, and the photovoltaic power is calculated. The control parameter k is generated by the DC power control loop through the PI regulator. The control parameter k is then passed through the limiting unit to obtain the power control parameter k in the range of 0 to 1. c Based on the power control parameter k c The frequency of use of charging and discharging sequences is adjusted in real time to achieve power regulation between photovoltaics, energy storage and the grid.

[0118] When external sunlight conditions are poor or the load increases, the photovoltaic power generation cannot meet the load demand. At this time, the power control parameter k c The frequency of the discharge sequence is increased in real time to increase the battery output power and compensate for the power difference between the photovoltaic power generation system and the load. When the external light intensity increases or the load decreases, the photovoltaic power generation exceeds the load demand, and at this time the power control parameter k... c Increase the frequency of the charging sequence in real time to store excess electrical energy from the photovoltaic power generation system in batteries. This is achieved through the power control parameter k. c The frequency of charging and discharging sequences is adjusted in real time to balance power generation and consumption, thus maintaining the stability of the entire power grid system.

[0119] Figure 5 The control block diagram of the high-safety and high-efficiency control method of the photovoltaic energy storage system in this embodiment mainly consists of four major functions: DC-side power control, AC-side power control, calculation of the action time, and design of the charging / discharging sequence, which work together to generate the PWM signal to drive the power transistor.

[0120] In terms of DC-side power control, the power between the photovoltaic panels and the battery is regulated. To ensure the normal operation of the dual-DC-port inverter, different operating modes need to be switched. Therefore, a photovoltaic maximum power point tracking (MPPT) strategy or other power point tracking strategies must be adopted. The reference photovoltaic power P*PV can be determined using the MPPT algorithm. After the photovoltaic power outputs control parameter k via the MPPT algorithm, the power control parameter k is then output via the limiting unit. c , where k c The range is 0≤k c ≤1, used to adjust the frequency of charging and discharging sequences. For AC side power control, a constant power control strategy is adopted to ensure the system operates at a predetermined power. Where P... ref and Q ref These are the reference active power and reference reactive power, respectively, and i*d and i*q are the reference d-axis and q-axis AC currents, respectively.

[0121] Figure 6 This is a simulation result diagram of the high-safety and high-efficiency control method of the photovoltaic energy storage system in this embodiment. From top to bottom, the simulated waveforms of photovoltaic power, battery power, three-phase current, line voltage, common-mode voltage, and leakage current are recorded. The main parameters are as follows: Photovoltaic voltage V... PV =100V; Battery voltage V Bat =40V; AC side mains voltage u abc =30V; AC side reference active power P ref =500W, reference reactive power Q ref =0var; Switching frequency f s =10kHz; Filter inductance L = 3.5mH; Leakage capacitance C PV =100nF. As shown in the figure, when the AC side rated power is 500W and the photovoltaic MPPT power is 580W, 80W of excess energy output from the photovoltaic power generation is stored in the battery, achieving power regulation between the photovoltaic system, battery, and grid, thus verifying the effectiveness of the control method of this invention. The proposed method has a common-mode voltage amplitude of -26.6V to 40V, but the range of common-mode voltage variation is reduced, and the leakage current i CM The effective value is only 152mA.

[0122] Example 2:

[0123] Embodiment 2 of the present invention provides a high-safety and high-efficiency control system for a photovoltaic energy storage system, comprising:

[0124] The reference voltage vector calculation module is configured to: obtain the reference voltage vector in the αβ coordinate system of the power grid, determine the large sector based on the phase angle of the reference voltage vector, and divide each large sector into a first part and a second part based on the position of the middle vector;

[0125] The vector common-mode voltage sorting module is configured to: calculate the common-mode voltage of each vector based on the photovoltaic voltage and the battery voltage, sort the common-mode voltages, and generate the vector order of the switching sequence based on the principle of minimizing the range of common-mode voltage variation;

[0126] The sector division module is configured to: based on the principle that each small sector has at least one small or medium vector that can be used for power regulation, divide each large sector into four small sectors in the first and second parts, and each small sector has one or more charging sequences and discharging sequences; in different switching sequences of different small sectors, the reference voltage vector is synthesized from three vectors for modulation, and the action time of the corresponding vector is calculated.

[0127] The power regulation module is configured to: calculate the photovoltaic power based on the photovoltaic voltage and photovoltaic current; generate control parameters by the DC power control loop through the PI regulator; obtain power control parameters ranging from 0 to 1 by the limiting unit; and adjust the usage frequency of the charging sequence and discharging sequence in real time according to the power control parameters to achieve power regulation.

[0128] The inverter control module is configured to control the switching of power switches in the dual DC port inverter based on the operating time and switching sequence, so as to control the operation of the inverter.

[0129] The operating methods of each module of the system are the same as the high-safety and high-efficiency control method of the photovoltaic energy storage system provided in Example 1, and will not be repeated here.

[0130] Example 3:

[0131] Embodiment 3 of the present invention provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the steps in the high-safety and high-efficiency control method for a photovoltaic energy storage system as described in Embodiment 1 of the present invention.

[0132] Example 4:

[0133] Embodiment 4 of the present invention provides an electronic device, including a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the high-safety and high-efficiency control method of the photovoltaic energy storage system as described in Embodiment 1 of the present invention.

[0134] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A highly safe and efficient control method for a photovoltaic energy storage system, characterized in that, The process includes the following: Obtaining power grid αβ The reference voltage vector in the coordinate system is used to determine the large sector based on the phase angle of the reference voltage vector. Each large sector is then divided into a first part and a second part based on the position of the median vector. Based on the photovoltaic voltage and the battery voltage, calculate the common-mode voltage of each vector, sort the common-mode voltages, and generate the vector order of the switching sequence; Each large sector is divided into four smaller sectors in the first and second parts. Each smaller sector contains one or more charging and discharging sequences. In different switching sequences of different smaller sectors, a reference voltage vector is synthesized using three vectors for modulation, and the duration of the corresponding vector is calculated. The photovoltaic power is calculated based on the photovoltaic voltage and photovoltaic current. The control parameters are generated by the DC power control loop through the PI regulator. The power control parameters are obtained by the limiting unit. The frequency of the charging sequence and the discharging sequence is adjusted in real time according to the power control parameters. The operation of the inverter is controlled by controlling the on / off state of the power switching transistors in the dual DC port inverter based on the action time and switching sequence. Based on the photovoltaic voltage and battery voltage, calculate the common-mode voltage of each vector, and sort the common-mode voltages, including: Obtain photovoltaic voltage V PV and battery voltage V Bat The common-mode voltage of each vector is calculated. The vector corresponds to eight common-mode voltage values. Based on the different common-mode voltage values, they are divided into the first large vector, the second large vector, the medium vector, the first positive small vector, the second positive small vector, the first negative small vector, the second negative small vector, and the zero vector. The vectors are sorted from low to high common-mode voltage values. When 2 V Bat <V PV < 3 V Bat At that time, the order is as follows: the first negative small vector 、 Second negative small vector 、 First largest vector 、 Zero vector 、 Medium vector 、 First positive small vector 、 Second largest vector 、 The second positive smallest vector; when V PV > 3 V Bat At that time, the order is as follows: the first negative small vector 、 Second negative small vector 、 Zero vector 、 First largest vector 、 Medium vector 、 First positive small vector 、 Second largest vector 、 The second positive smallest vector; When 3 V Bat / 2 <V PV < 2 V Bat At that time, the order is as follows: the first negative small vector 、 First largest vector 、 Second negative small vector 、 Medium vector 、 Zero vector 、 Second largest vector 、 First positive small vector 、 The second positive smallest vector; when V PV <3V Bat / 2 At that time, the order is as follows: the first negative small vector 、 First largest vector 、 Second negative small vector 、 Medium vector 、 Second largest vector 、 Zero vector 、 First positive small vector 、 The second positive small vector.

2. The high-safety and high-efficiency control method for a photovoltaic energy storage system as described in claim 1, characterized in that, Based on the principle of minimizing the common-mode voltage variation range, the vector order of the switching sequence is generated, including: Based on the principle of minimizing the range of common-mode voltage variation, and according to the common-mode voltage sorting relationship, the switching interval between vectors is only allowed to be no more than one vector. The current sorting relationship is determined based on the photovoltaic voltage and the battery voltage, and the vector order of the switching sequence is changed in real time.

3. The high-safety and high-efficiency control method for a photovoltaic energy storage system as described in claim 1, characterized in that, The first part of the first major sector satisfies According to the voltage space vector in α The components of the coordinate axes and the voltage space vector are in β The components of the coordinate axes, photovoltaic voltage, and battery voltage are used to obtain the first and second curves for dividing the four small sectors; V α For voltage space vector in α Components of the coordinate axes V β For voltage space vector in β Components of the coordinate axes V PV , V PV These are the photovoltaic voltage and the battery voltage, respectively. When the reference voltage vector is above the first curve and below the second curve, it is determined that the reference voltage vector is located in the first small sector; when the reference voltage vector is below the first curve and below the second curve, it is determined that the reference voltage vector is located in the second small sector. When the reference voltage vector is below the first curve and above the second curve, it is determined that the reference voltage vector is located in the third sub-sector; when the reference voltage vector is above the first curve and above the second curve, it is determined that the reference voltage vector is located in the fourth sub-sector.

4. The high-safety and high-efficiency control method for a photovoltaic energy storage system as described in claim 3, characterized in that, The second part of the first major sector satisfies According to the voltage space vector in α The components of the coordinate axes and the voltage space vector are in β The components of the coordinate axes, photovoltaic voltage, and battery voltage are used to obtain the third and fourth curves used to divide the four small sectors; When the reference voltage vector is below the third curve and to the left of the fourth curve, the reference voltage vector is determined to be located in the fifth sub-sector; when the reference voltage vector is below the third curve and to the right of the fourth curve, the reference voltage vector is determined to be located in the sixth sub-sector. When the reference voltage vector is above the third curve and to the right of the fourth curve, the reference voltage vector is determined to be located in the seventh sub-sector; when the reference voltage vector is above the third curve and to the left of the fourth curve, the reference voltage vector is determined to be located in the eighth sub-sector. The smaller sectors of other large sectors are obtained by rotation.

5. The high-safety and high-efficiency control method for a photovoltaic energy storage system as described in any one of claims 1-4, characterized in that, In different sectors, a three-vector composite reference voltage vector is used for modulation, and the duration of the corresponding vector is calculated, specifically: , , ;in, V α Reference voltage vector V ref exist α Components of the coordinate axes V β Reference voltage vector V ref exist β Components of the coordinate axes; V iα and V iβ ( i = 1, 2, 3) is the selected nearest voltage vector V i exist αβ Coordinates in a coordinate system T i It is the duration of action of the corresponding vector. T S The sampling period.

6. The high-safety and high-efficiency control method for a photovoltaic energy storage system as described in any one of claims 1-4, characterized in that, When external lighting conditions are poor or the load increases, the photovoltaic power generation cannot meet the load demand. At this time, the power control parameters are reduced, and the frequency of use of the discharge sequence is increased in real time, so that the output power of the battery increases to make up for the power difference between the photovoltaic power generation system and the load. When the intensity of external sunlight increases or the load decreases, the photovoltaic power generation exceeds the load demand. At this time, the power control parameters are increased, and the frequency of use of the charging sequence is increased in real time. The excess electrical energy output by the photovoltaic power generation system is stored in the battery. The frequency of use of the charging and discharging sequences is adjusted in real time through the power control parameters.

7. A high-safety and high-efficiency control system for a photovoltaic energy storage system, characterized in that, include: The reference voltage vector calculation module is configured to: obtain the power grid αβ The reference voltage vector in the coordinate system is used to determine the large sector based on the phase angle of the reference voltage vector. Each large sector is then divided into a first part and a second part based on the position of the median vector. The vector common-mode voltage sorting module is configured to: calculate the common-mode voltage of each vector based on the photovoltaic voltage and the battery voltage, sort the common-mode voltages, and generate the vector order of the switching sequence; The sector division module is configured to divide each large sector into four smaller sectors in the first and second parts, with each smaller sector containing one or more charging and discharging sequences; in different switching sequences of different smaller sectors, a reference voltage vector is synthesized using three vectors for modulation, and the duration of the corresponding vector is calculated. The power regulation module is configured to: calculate the photovoltaic power based on the photovoltaic voltage and photovoltaic current; generate control parameters by the DC power control loop through the PI regulator; obtain power control parameters by the limiting unit through the control parameters; and adjust the usage frequency of the charging sequence and discharging sequence in real time according to the power control parameters. The inverter control module is configured to control the switching of the power switching transistors in the dual DC port inverter based on the action time and switching sequence, so as to control the operation of the inverter. Based on the photovoltaic voltage and battery voltage, calculate the common-mode voltage of each vector, and sort the common-mode voltages, including: Obtain photovoltaic voltage V PV and battery voltage V Bat The common-mode voltage of each vector is calculated. The vector corresponds to eight common-mode voltage values. Based on the different common-mode voltage values, they are divided into the first large vector, the second large vector, the medium vector, the first positive small vector, the second positive small vector, the first negative small vector, the second negative small vector, and the zero vector. The vectors are sorted from low to high common-mode voltage values. When 2 V Bat <V PV < 3 V Bat At that time, the order is as follows: the first negative small vector 、 Second negative small vector 、 First largest vector 、 Zero vector 、 Medium vector 、 First positive small vector 、 Second largest vector 、 The second positive smallest vector; when V PV > 3 V Bat At that time, the order is as follows: the first negative small vector 、 Second negative small vector 、 Zero vector 、 First largest vector 、 Medium vector 、 First positive small vector 、 Second largest vector 、 The second positive smallest vector; When 3 V Bat / 2 <V PV < 2 V Bat At that time, the order is as follows: the first negative small vector 、 First largest vector 、 Second negative small vector 、 Medium vector 、 Zero vector 、 Second largest vector 、 First positive small vector 、 The second positive smallest vector; when V PV <3V Bat / 2 At that time, the order is as follows: the first negative small vector 、 First largest vector 、 Second negative small vector 、 Medium vector 、 Second largest vector 、 Zero vector 、 First positive small vector 、 The second positive small vector.

8. A computer-readable storage medium having a program stored thereon, characterized in that, When executed by the processor, the program implements the steps in the high-safety and high-efficiency control method for the photovoltaic energy storage system as described in any one of claims 1-6.

9. An electronic device comprising a memory, a processor, and a program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the high-safety and high-efficiency control method for the photovoltaic energy storage system as described in any one of claims 1-6.

Images