Electric energy quality optimization method and system based on carrier modulation

Abstract

The invention discloses an electric energy quality optimization method and system based on carrier modulation, and relates to the field of electric energy quality optimization, and the method comprises the steps: obtaining bridge arm information of a distributed energy storage type electric energy quality controller, and determining a carrier amplitude adjustment strategy; determining a target zero-sequence component needing to be injected through carrier characteristics based on the carrier amplitude adjustment strategy; according to the target zero-sequence component, performing superposition on the original modulation wave to generate a target modulation wave; adjusting the power of the power grid based on the target modulating wave, and carrying out dynamic compensation on the capacitance voltage deviation; the harmonic suppression capability is improved, and the power distribution dynamic response efficiency is enhanced, so that the optimization of the electric energy quality is realized, and the problem that the real-time performance and the reliability of the electric energy quality regulation are reduced due to the limitation of harmonic compensation and the lack of real-time dynamic response in the conventional pulse width modulation method is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power quality optimization, in particular to a power quality optimization method and system based on carrier modulation. BACKGROUND

[0002] The conventional PWM (pulse width modulation) strategy generates a switching signal by comparing a fixed frequency triangular wave with a modulation wave. Due to the split capacitor voltage balancing on the DC side in the three-level converter used by the traditional UPQC, the two sets of triangular carriers are symmetrically distributed with respect to the zero axis, and their amplitudes are equal. In the distributed energy storage type power quality control device, the wide range of voltage at the low voltage port causes the carrier modulation strategy with equal amplitudes to result in an undesirable harmonic spectrum distribution, thereby causing an imbalance in the distribution of active power compensation. In addition, the distributed energy storage type power quality control device, as a system of MMC-BESS-UPQC fusion topology, involves multi-variable coupling such as bridge arm current, energy storage power, and capacitor voltage. The conventional PWM is not decoupled, and its use in MMC-BESS-UPQC will make the control complex, unable to dynamically adjust the modulation parameters, resulting in insufficient harmonic compensation, and thus affecting the power quality compensation effect. SUMMARY

[0003] The purpose of the present application is to solve the problem that the conventional pulse width modulation method has limitations in harmonic compensation and lacks real-time dynamic response, resulting in a decrease in the real-time performance and reliability of power quality regulation. The present application proposes a power quality optimization method and system based on carrier modulation, which obtains a target modulation wave by injecting a fusion carrier layer with zero sequence components, performs power distribution and capacitor voltage balancing control according to the target modulation wave, improves the harmonic suppression capability, and enhances the dynamic response efficiency of power distribution, thereby achieving power quality optimization and overcoming the problem that the conventional pulse width modulation method has limitations in harmonic compensation and lacks real-time dynamic response, resulting in a decrease in the real-time performance and reliability of power quality regulation.

[0004] To achieve the above-mentioned purpose, the technical solutions adopted by the embodiments of the present application are as follows: In a first aspect, the embodiments of the present application provide a power quality optimization method based on carrier modulation, which comprises: obtaining the bridge arm information of a distributed energy storage type power quality controller, determining a carrier amplitude adjustment strategy, determining the target zero sequence components to be injected based on the carrier amplitude adjustment strategy through carrier characteristics, superimposing the original modulation wave according to the target zero sequence components to generate a target modulation wave, and adjusting the grid power and dynamically compensating the capacitor voltage deviation based on the target modulation wave.

[0005] In the scheme, the real-time feedback of the capacitor voltage deviation through system state monitoring dynamically adjusts the carrier amplitude adjustment strategy, avoiding the hysteresis caused by fixed parameters; after superposition of the zero sequence component, the modulation wave extreme value range changes, indirectly adjusting the bridge arm switch duty cycle, thereby realizing dynamic distribution of active power among the sub-modules of the system, improving the harmonic suppression capability while enhancing the dynamic response.

[0006] Preferably, the determination of the zero sequence component limit to be injected according to the bridge arm power information of the distributed energy storage type power quality controller comprises: collecting real-time operation state information of the power system, calculating the voltage deviation of the power system; based on the voltage deviation and the high voltage port voltage value, obtaining the carrier amplitude of the distributed energy storage type power quality controller; establishing a carrier signal boundary line according to the carrier amplitude to determine the carrier amplitude adjustment strategy.

[0007] Preferably, the establishment of the carrier signal boundary line according to the carrier amplitude to determine the carrier amplitude adjustment strategy comprises: when the low voltage port voltage value is less than one half of the high voltage port voltage value, the negative current is suppressed; when the low voltage port voltage value is greater than one half of the high voltage port voltage value, the positive current is optimized.

[0008] Preferably, the determination of the target zero sequence component to be injected based on the carrier amplitude adjustment strategy through the carrier characteristics comprises: dividing the power frequency period of the distributed energy storage type power quality controller according to the polarity of the phase current, obtaining a plurality of regions with different phase current polarity combinations; based on the carrier amplitude adjustment strategy and the carrier characteristics of each region, determining the switch duty cycle of the connection midpoint of the bridge arm and the low voltage port of each phase of the level converter; based on the switch duty cycle, determining the target zero sequence component to be injected.

[0009] Preferably, the determination of the target zero sequence component to be injected based on the switch duty cycle comprises: constructing a boundary function of the zero sequence component according to the non-negative characteristic of the switch duty cycle; determining the target clamping of the switch duty cycle based on the carrier characteristics of each region; based on the target clamping of the switch duty cycle, calculating the target zero sequence component by using the boundary function of the zero sequence component.

[0010] Preferably, the superposition of the target zero sequence component on the original modulation wave to generate a target modulation wave comprises: obtaining the original modulation wave information of each phase of the level converter; superimposing the target zero sequence component corresponding to each region on the original modulation wave of each phase respectively to generate the target modulation wave.

[0011] Preferably, the adjusting grid power based on the target modulation wave and dynamically compensating the capacitor voltage deviation comprises: updating the switch duty cycle of the bridge arm midpoint low-voltage port based on the target modulation wave to obtain a target switch duty cycle; calculating the average current flowing through the low-voltage port according to the target switch duty cycle and the phase current, and dynamically adjusting the target zero sequence component to obtain the maximum average current to adjust the active power.

[0012] Preferably, the adjusting grid power based on the target modulation wave and dynamically compensating the capacitor voltage deviation further comprises: dynamically adjusting the target switch duty cycle based on the capacitor voltage deviation of the power system to achieve capacitor voltage sharing control; lowering the target switch duty cycle when the capacitor voltage deviation is greater than a capacitor voltage threshold; and increasing the target switch duty cycle when the capacitor voltage deviation is less than the capacitor voltage threshold.

[0013] Preferably, the method further comprises: distributing grid power according to the charge and discharge power of the energy storage system and the target zero sequence component; increasing the switch duty cycle of the bridge arm connected to the energy storage system to distribute the charging power by adjusting the target zero sequence component when the energy storage system needs to be charged; and reducing the switch duty cycle of the bridge arm connected to the energy storage system to release energy storage energy by adjusting the target zero sequence component when the energy storage system needs to be discharged.

[0014] In a second aspect, the embodiments of the present application provide an optimal power quality system based on carrier modulation, comprising: The acquisition module is configured to acquire the bridge arm information of the distributed energy storage type power quality controller and determine a carrier amplitude adjustment strategy; the calculation module is configured to determine the target zero sequence component to be injected through carrier characteristics based on the carrier amplitude adjustment strategy; the modulation wave module is configured to superimpose the target zero sequence component on an original modulation wave to generate a target modulation wave; and the optimization module is configured to adjust grid power based on the target modulation wave and dynamically compensate the capacitor voltage deviation.

[0015] The present application has the following beneficial effects: 1. The carrier amplitude normalization and asymmetric layering reduce the nonlinear overlapping area of the modulation wave and the carrier, making the output waveform closer to an ideal sine wave; dynamically adjusting the carrier amplitude can improve the utilization rate of the DC bus and avoid the problem of limited modulation degree caused by the fixed carrier amplitude in the traditional PWM; 2. Injecting specific zero sequence components through frequency cycle area division can block negative current and maximize the single-stage power transmission ratio, optimizing power distribution; after superimposing the zero sequence components, the modulation wave extreme value range changes, indirectly adjusting the bridge arm switch duty cycle to realize dynamic distribution of active power among submodules; through regional zero sequence component injection, power distribution can be quickly adjusted when the load suddenly changes, shortening the dynamic adjustment time and further enhancing the dynamic response; 3. The method adjusts the charging and discharging time of the high / low voltage sub-module by adjusting the duty cycle according to the capacitance voltage deviation, realizes dynamic balancing of the capacitance voltage, and solves the problem of capacitance imbalance; at the same time, the average current of the low voltage port connected through the bridge arm midpoint is realized, the active power is cooperatively distributed between the MMC and the BESS, the redundant power flow is reduced, and the overall efficiency of the MMC-BESS-UPQC is improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments, read in conjunction with the accompanying drawings. The drawings are only for the purpose of illustrating preferred embodiments and are not to be construed as limiting the application. Moreover, like reference numerals designate similar parts throughout the drawings.

[0017] Figure 1 A power quality optimization method based on carrier modulation is provided for the embodiments of the application.

[0018] Figure 2 A distribution diagram of the switch duty cycle in step S102 is provided for the embodiments of the application.

[0019] Figure 3 Another distribution diagram of the switch duty cycle in step S102 is provided for the embodiments of the application.

[0020] Figure 4 A power frequency cycle area division diagram is provided for the embodiments of the application.

[0021] Figure 5 A power quality optimization system module diagram based on carrier modulation is provided for the embodiments of the application. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the application more clear, the application will be further described in detail below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only the best mode of the application, which are used to explain the application and do not limit the protection scope of the application. All other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0023] Embodiment 1: as Figure 1As shown, in order to solve the problems mentioned in the background, according to an aspect of an embodiment of the present application, an embodiment of a carrier modulation-based power quality optimization method is provided, and it should be noted that the carrier modulation-based power quality optimization method provided in the embodiment of the present application is generally executed by a server and / or a terminal device, and the terminal device is generally an MMC-BESS-UPQC device, and a controller with data analysis and calculation is arranged in the MMC-BESS-UPQC device, and accordingly, the carrier modulation-based power quality optimization system is generally arranged in the server / terminal device. The carrier modulation-based power quality optimization method includes steps S101-S104, and the details are as follows: Step S101, acquiring the bridge arm information of the distributed energy storage type power quality controller, and determining the carrier amplitude adjustment strategy.

[0024] As an optional implementation, the above step S101 specifically includes: S1011, collecting real-time operation state information of the power system, and acquiring the carrier amplitude of the distributed energy storage type power quality controller; S1012, establishing a carrier signal boundary line according to the carrier amplitude, so as to determine the carrier amplitude adjustment strategy.

[0025] As an optional implementation, the above step S1013 specifically includes: When the low-voltage port voltage value is less than one-half of the high-voltage port voltage value, the negative current is inhibited; When the low-voltage port voltage value is greater than one-half of the high-voltage port voltage value, the positive current is optimized.

[0026] In some embodiments, the carrier amplitude of the distributed energy storage type power quality controller is proportional to the high-voltage port voltage and the low-voltage port voltage , and is normalized as: (1) (2) Wherein, and are the amplitudes of the two groups of carrier signals.

[0027] Further, the boundary line of the high-voltage port voltage and the low-voltage port voltage is calculated, and the carrier distribution is determined according to the position above and below the zero axis, and the details are as follows: the boundary line of the two groups of carrier signals can be derived from the above two carrier amplitudes as According to the different positions of the boundary line, the corresponding carrier amplitude adjustment strategy is formulated, including: The first carrier amplitude adjustment strategy: when When the boundary line is located on the zero coordinate axis, the amplitudes of the two groups of carrier signals are equal, and the CB-PWM strategy of the traditional three-level converter can be used; The second carrier amplitude adjustment strategy is as follows: When the boundary line is located below the zero coordinate axis, the upper carrier amplitude is greater than the lower carrier amplitude. The third carrier amplitude adjustment strategy is as follows: When the boundary line is located above the zero coordinate axis, the upper carrier amplitude is less than the lower carrier amplitude. The second carrier amplitude adjustment strategy and the third carrier amplitude adjustment strategy both obtain a target modulation wave by injecting a target zero sequence component for subsequent power adjustment and power quality optimization.

[0028] In some embodiments, the real-time operation state information of the power system includes key parameters such as grid voltage, load current, capacitor voltage, and energy storage battery of the energy storage system, providing dynamic input for subsequent control strategies.

[0029] In this embodiment, the carrier amplitude is dynamically adjusted through the high-voltage port voltage and the low-voltage port voltage, which can adapt to different working conditions; the control strategy is dynamically adjusted through real-time feedback of the capacitor voltage deviation, which avoids the hysteresis caused by fixed parameters, helps to shorten the response time, and improves the dynamic compensation capability.

[0030] Step S102, based on the carrier amplitude adjustment strategy, determining the target zero sequence component to be injected through the carrier characteristics.

[0031] As an optional implementation, the above step S102 specifically includes: S1021, dividing the power frequency period of the distributed energy storage type power quality controller according to the polarity of the phase current, and obtaining a plurality of regions with different phase current polarity combinations; S1022, based on the carrier amplitude adjustment strategy and the carrier characteristics of each region, determining the switching duty cycle of the connection midpoint of the bridge arm and the low-voltage port of the level converter; S1023, determining the target zero sequence component to be injected based on the switching duty cycle.

[0032] As an optional implementation, the above step S1023 specifically includes: According to the non-negative characteristic of the switching duty cycle, a boundary function of the zero sequence component is constructed; Based on the carrier characteristics of each region, the target clamping of the switching duty cycle is determined; Based on the target clamping of the switching duty cycle, the boundary function of the zero sequence component is used to calculate the target zero sequence component.

[0033] In some embodiments, in a switching cycle, the two sets of triangular carriers of the level converter intersect with the modulated wave signal to generate a switching signal, that is, the upper carrier or the lower carrier intersects with the modulated wave signal to generate a switching signal, thereby calculating the switching duty ratio of the connection midpoint between the bridge arm of each phase of the level converter and the low-voltage port. Figure 2 and Figure 3 As shown, in this embodiment, the intersection of the upper carrier or lower carrier and the modulated wave signal is considered in two cases, so as to obtain the corresponding switching duty cycle according to different cases. Figure 2 As shown, the first case is: , that is, the original modulation wave of a certain phase is greater than or equal to the boundary line of the two groups of carrier signals; Figure 3 As shown, the second case is: , that is, the original modulation wave of a phase is smaller than the boundary line of the two groups of carrier signals; the shaded part in the figure is the switch duty cycle when the midpoint of the bridge arm is connected to the low-voltage port. The switch duty cycle in the two cases can be obtained by graphical method. The calculation formula is as follows: (3) in, Indicates the switch duty cycle of the midpoint of the x-phase bridge arm connected to the low-voltage port, represents the original modulation wave of x phase, Indicates upper carrier, Indicates download wave.

[0034] In some possible implementations, when hour, Can be simplified to: .

[0035] Furthermore, in order to increase the single-stage power transfer ratio, it is assumed that the injected zero-sequence component is ,but It can be expressed as: (4) because is the switch duty cycle of the midpoint of a phase bridge arm connected to the low-voltage port, which is non-negative. Therefore, the zero-sequence component can be obtained The range of , that is, the boundary function, is expressed as follows: (5) in, , , represents the original modulation wave of phase a, represents the original modulation wave of phase b, Represents the original modulation wave of phase c.

[0036] Furthermore, the switching duty cycle is determined based on the carrier characteristics of each region. target zero-sequence component. For example, in order to maximize the single-stage power transfer ratio, the current average should be increased as much as possible, and the most direct method is to block the negative current flowing into the low-voltage port, i.e., when the current is less than 0, the switch duty cycle is clamped to 0, and the target zero-sequence component is calculated.

[0037] In some examples, as Figure 4 shown, one power frequency period is divided into 6 regions, i.e., regions S1-S6. In region S1, i.e., π / 6≤θ≤π / 2, the phase currents ia≥0, ib≥0, and ic<0 are satisfied. In this case, the phase currents iaand ibflow out of the low-voltage port, while the phase current icflows into the low-voltage port. In order to block the negative current ic, the ideal target zero-sequence component should clamp the switch duty cycle to 0, and thus the injected zero-sequence component is (-1-vc). After injecting the target zero-sequence component, the negative current in region S1 can be completely blocked.

[0038] In region S2, i.e., π / 2<θ≤5π / 6, ia≤0, ib>0, and ic≤0 are satisfied. In order to block the negative currents iaand icat the same time, the ideal zero-sequence component should clamp the switch duty cycle to 0 at the same time, which is obviously impossible.

[0039] According to the relationship of the three-phase sinusoidal modulation signals, region S2 can be further divided into two sub-regions S2 / 1 and S2 / 2. In sub-region S2 / 1, the phase angle relationship satisfies π / 2<θ≤2π / 3, and the original modulation wave vc≤va<vb is obtained, and thus . In order to make da0, the superimposed zero-sequence component v0is (-1-va), which exceeds the range defined by the boundary function. In contrast, in order to make dc0, the superimposed zero-sequence component is (-1-vc), which satisfies the defined range, and thus it can be determined that in sub-region S2 / 1, the injected zero-sequence component is (-1-vc), which means that although the negative current iaof the A-phase switch duty cycle cannot be clamped to 0 to completely block it, the action time of the negative current can still be effectively inhibited. Similarly, in sub-region S2 / 2, the phase angle relationship satisfies 2π / 3<θ≤5π / 6, and analysis obtains that the injected zero-sequence component is (-1-va), which completely blocks iaand suppresses ic. By obtaining the target zero-sequence component of each region, the superimposed zero-sequence component in one power frequency period can be summarized.

[0040] Step S103, superimposing the original modulation wave according to the target zero sequence component to generate a target modulation wave.

[0041] As an optional implementation, the step S103 specifically includes: obtaining original modulation wave information of each phase of the level converter; superimposing the target zero sequence component corresponding to each region on the original modulation wave of each phase respectively to generate the target modulation wave.

[0042] In some embodiments, the original three-phase modulation wave superimposes the target zero sequence component corresponding to each region to generate a new target modulation wave, and the target modulation wave is represented as follows: .

[0043] In the present embodiment, by dividing the power frequency cycle region and injecting a specific zero sequence component, the negative current is blocked and the single-stage power transmission ratio is maximized, the zero sequence component injection can expand the modulation degree range, reduce the high frequency harmonic component, and at the same time maintain the fundamental wave integrity; the extreme value range of the modulation wave changes after the superposition of the zero sequence component, which indirectly adjusts the bridge arm switch duty cycle, thereby realizing the dynamic distribution of active power among the sub-modules. And through the regional zero sequence component design, the power distribution can be quickly adjusted when the load is suddenly changed, the dynamic adjustment time is shortened, and the dynamic response is enhanced.

[0044] Step S104, adjusting the grid power based on the target modulation wave, and dynamically compensating the capacitor voltage deviation.

[0045] As an optional implementation, the step S104 specifically includes: updating the switch duty cycle of the low-voltage port connected to the bridge arm midpoint based on the target modulation wave to obtain a target switch duty cycle; calculating the average current flowing through the low-voltage port according to the target switch duty cycle and the phase current, and dynamically adjusting the target zero sequence component to maximize the average current to adjust the active power.

[0046] In some embodiments, the target switch duty cycle is represented as follows: (6) wherein, the target modulation wave is represented as, the target switch duty cycle is represented as.

[0047] Further, the average current flowing through the low-voltage port is calculated according to the target switch duty cycle and the phase current , and the formula is represented as follows: ​ (7) adjusting the target zero sequence component to maximize , optimizing the single-stage power transmission ratio.

[0048] In this embodiment, the average current of the low-voltage port connected to the bridge arm midpoint is used to achieve the cooperative distribution of active power between the MMC and the BESS, and then the power distribution is used to reduce the redundant power flow, thereby improving the overall efficiency of the MMC-BESS-UPQC system.

[0049] In some possible embodiments, the target switch duty cycle is signal-converted to obtain a switch pulse signal for controlling the action of the bridge arm switch.

[0050] Specifically, the on switch is determined by comparing the modulation wave and the carrier signal. The target modulation wave and the carrier signal amplitude are compared point by point using a digital comparator or an analog comparator, for example, when the upper bridge arm IGBT is turned on; when the lower bridge arm IGBT is turned on; and in the middle region, i.e. the low-voltage port connected to the bridge arm midpoint is connected.

[0051] Further, the target switch duty cycle is converted into a digital signal (such as a duty cycle value of 0-1) to drive the IGBT / MOSFET switch action of the corresponding bridge arm. At the same time, a dead time is added for time compensation to prevent short circuit, and the specific compensation value can be adjusted according to the characteristics of the device.

[0052] In this embodiment, the target switch duty cycle is adjusted according to the comparison result of the modulation wave and the carrier, to realize accurate control of the time of the low-voltage port connected to the bridge arm midpoint. By optimizing the target duty cycle distribution, the number of high-frequency switch operations can be reduced, and the switch loss can be reduced. In addition, the dynamic adjustment of the duty cycle can accurately adjust the charging and discharging time of each sub-module, thereby reducing the capacitor voltage fluctuation range and improving the capacitor voltage sharing accuracy.

[0053] As an optional implementation, the above step S104 specifically further includes: dynamically adjusting the target switch duty cycle based on the capacitor voltage deviation of the power system to realize capacitor voltage sharing control; in the case where the capacitor voltage deviation is greater than a capacitor voltage threshold, the target switch duty cycle is adjusted to be lower; in the case where the capacitor voltage deviation is less than the capacitor voltage threshold, the target switch duty cycle is adjusted to be higher.

[0054] In some embodiments, the capacitance voltage deviation of the system can be obtained by calculating the deviation of the capacitance voltage of each sub-module of the system from the reference voltage based on the real-time collected capacitance voltage of each sub-module of the system. The calculation formula is as follows: (8) In the formula, represents the capacitance voltage deviation, represents the capacitance voltage of the sub-module i, represents the voltage reference value.

[0055] Further, for the sub-modules with , the is reduced to reduce the charging and discharging time; for the sub-modules with , the is increased to improve the charging and discharging time, so as to dynamically adjust to compensate for the capacitance voltage deviation. Or, a capacitance voltage deviation threshold is preset, for the sub-modules with the capacitance voltage deviation greater than the capacitance voltage threshold, the is reduced to reduce the charging and discharging time, and for the sub-modules with the capacitance voltage deviation less than the capacitance voltage threshold, the is increased to increase the charging and discharging time, and at the same time, the target zero sequence component is dynamically adjusted to ensure that the capacitance voltage of all SMs converges to the capacitance voltage reference value .

[0056] In the embodiment, according to the capacitance voltage deviation, the charging and discharging time of the high / low voltage sub-modules is preferentially adjusted by adjusting the duty cycle, so as to dynamically balance the capacitance voltage and solve the capacitance imbalance problem.

[0057] As an optional implementation, the method further comprises: Step S105, performing power distribution of the power grid according to the power demand of the energy storage system in combination with the target zero sequence component; specifically comprising: When the energy storage system needs to be charged, the duty cycle of the switch of the bridge arm connected with the energy storage system is increased by adjusting the target zero sequence component to distribute the charging power; When the energy storage system needs to be discharged, the duty cycle of the switch of the bridge arm connected with the energy storage system is reduced by adjusting the target zero sequence component to release the energy storage energy.

[0058] In the embodiment, the charging and discharging power of the BESS can be set according to the battery, which is used as the reference value of the active power distribution, and is optimized in combination with the power distribution of the MMC, for example, when the BESS needs to be charged, the target zero sequence component is adjusted to increase the of the bridge arm connected with the BESS to improve the charging power; when the BESS needs to be discharged, the of the corresponding bridge arm is reduced to release the energy storage energy.

[0059] In the embodiment, the active power distribution target is dynamically adjusted according to the battery state of the BESS, the energy storage charging and discharging demand is preferentially met, and when the power grid is suddenly changed, the energy is quickly released by the BESS to assist the UPQC to complete instantaneous power compensation; the fast charging and discharging of the BESS can make up for the delay of the UPQC, improve the suppression ability of the system to the power grid disturbance, further realize the joint optimization of the energy storage system and the power quality compensation, and effectively solve the problems of difficulty in energy storage and compensation cooperation and insufficient dynamic response of the conventional PWM modulation method.

[0060] In the embodiment, the active power distribution target is dynamically adjusted according to the battery state of the BESS, the energy storage charging and discharging demand is preferentially met, and when the power grid is suddenly changed, the energy is quickly released by the BESS to assist the UPQC to complete instantaneous power compensation; the fast charging and discharging of the BESS can make up for the delay of the UPQC, improve the suppression ability of the system to the power grid disturbance, further realize the joint optimization of the energy storage system and the power quality compensation, and effectively solve the problems of difficulty in energy storage and compensation cooperation and insufficient dynamic response of the conventional PWM modulation method. Figure 5 As shown in the same inventive concept, the application embodiment also provides a carrier modulation-based power quality optimization system corresponding to the carrier modulation-based power quality optimization method, which comprises: The acquisition module 501 is configured to acquire the bridge arm information of the distributed energy storage type power quality controller, and determine a carrier amplitude adjustment strategy. The calculation module 502 is configured to determine a target zero sequence component to be injected based on the carrier amplitude adjustment strategy and carrier characteristics. The modulation wave module 503 is configured to superimpose the target zero sequence component on an original modulation wave to generate a target modulation wave. The optimization module 504 is configured to adjust power grid power and dynamically compensate for capacitor voltage deviation based on the target modulation wave.

[0061] As an optional implementation, the acquisition module 501 is specifically configured to: collect real-time operation state information of a power system, calculate voltage deviation of the power system, acquire a carrier amplitude of the distributed energy storage type power quality controller based on the voltage deviation and a high-voltage port voltage value, establish a carrier signal boundary line according to the carrier amplitude to determine a carrier amplitude adjustment strategy, suppress negative current when the low-voltage port voltage value is less than one half of the high-voltage port voltage value, and optimize positive current when the low-voltage port voltage value is greater than one half of the high-voltage port voltage value.

[0062] As an optional implementation, the calculation module 502 is specifically configured to: divide a power frequency period of the distributed energy storage type power quality controller according to polarity of phase current, acquire a plurality of regions with different phase current polarity combinations, determine a switching duty cycle of a connection midpoint of a bridge arm of each phase of the level converter and a low-voltage port based on the carrier amplitude adjustment strategy and carrier characteristics of each region, and determine a target zero sequence component to be injected based on the switching duty cycle.

[0063] Specifically, the calculation module 502 is further configured to: construct a boundary function of the zero sequence component according to the non-negative characteristic of the switch duty cycle; determine a target clamping of the switch duty cycle based on the carrier characteristic of each region; and calculate the target zero sequence component by using the boundary function of the zero sequence component based on the target clamping of the switch duty cycle.

[0064] As an optional implementation, the modulation wave module 503 is specifically configured to: obtain original modulation wave information of each phase of the level converter; and superimpose the target zero sequence component corresponding to each region on the original modulation wave of each phase respectively to generate the target modulation wave.

[0065] As an optional implementation, the optimization module 504 is specifically configured to: update the switch duty cycle of the low-voltage port connected to the bridge arm midpoint based on the target modulation wave to obtain a target switch duty cycle; calculate the average current flowing through the low-voltage port according to the target switch duty cycle and the phase current, and dynamically adjust the target zero sequence component to maximize the average current to regulate the active power.

[0066] As an optional implementation, the optimization module 504 is specifically configured to: dynamically adjust the target switch duty cycle based on the capacitor voltage deviation of the power system to achieve capacitor voltage sharing control; lower the target switch duty cycle when the capacitor voltage deviation is greater than a capacitor voltage threshold; and raise the target switch duty cycle when the capacitor voltage deviation is less than the capacitor voltage threshold.

[0067] As an optional implementation, the optimization module 504 is specifically configured to: perform power grid power distribution in combination with the target zero sequence component according to the power requirement of the energy storage system; increase the switch duty cycle of the bridge arm connected to the energy storage system by adjusting the target zero sequence component to distribute charging power when the energy storage system needs to be charged; and reduce the switch duty cycle of the bridge arm connected to the energy storage system by adjusting the target zero sequence component to release energy storage energy when the energy storage system needs to be discharged.

[0068] The above specific implementations are the preferred implementations of the present application, and the specific implementation range of the present application is not limited thereto. The scope of the present application includes but is not limited to the above specific implementations. Any equivalent changes made according to the shape, structure and method of the present application are within the protection scope of the present application.

Claims

1. A power quality optimization method based on carrier modulation, characterized by: The steps include: Obtain the bridge arm information of the distributed energy storage power quality controller and determine the carrier amplitude adjustment strategy; Based on the carrier amplitude adjustment strategy, determining the target zero-sequence component to be injected through carrier characteristics; Superimposing the original modulated wave according to the target zero-sequence component to generate a target modulated wave; The grid power is adjusted based on the target modulation wave, and the capacitor voltage deviation is dynamically compensated.

2. The power quality optimization method based on carrier modulation according to claim 1, characterized in that: The step of determining the zero-sequence component limit to be injected based on the bridge arm power information of the distributed energy storage power quality controller includes: Collect real-time operating status information of the power system and calculate the voltage deviation of the power system; Based on the voltage deviation and the high-voltage port voltage value, obtaining the carrier amplitude of the distributed energy storage type power quality controller; A carrier signal boundary line is established according to the carrier amplitude to determine a carrier amplitude adjustment strategy.

3. The power quality optimization method based on carrier modulation according to claim 2, characterized in that: The establishing of a carrier signal boundary line according to the carrier amplitude to determine a carrier amplitude adjustment strategy includes: When the voltage value of the low-voltage port is less than half of the voltage value of the high-voltage port, the negative current is suppressed; When the voltage value of the low-voltage port is greater than half of the voltage value of the high-voltage port, the forward current is optimized.

4. The power quality optimization method based on carrier modulation according to claim 1, characterized in that: The method of determining a target zero-sequence component to be injected based on carrier characteristics based on the carrier amplitude adjustment strategy includes: Dividing the power frequency cycle of the distributed energy storage type power quality controller according to the polarity of the phase current to obtain a plurality of regions with different phase current polarity combinations; Determining a switching duty cycle of a connection midpoint between a bridge arm of each phase of the level converter and the low-voltage port based on the carrier amplitude adjustment strategy and the carrier characteristics of each region; A target zero-sequence component to be injected is determined based on the switch duty cycle.

5. The power quality optimization method based on carrier modulation according to claim 4, characterized in that: The determining of a target zero-sequence component to be injected based on the switch duty cycle includes: Constructing a boundary function of a zero-sequence component according to the non-negative characteristic of the switch duty cycle; determining a target clamping value of the switching duty cycle based on carrier characteristics of each region; Based on the target clamping of the switching duty cycle, the target zero-sequence component is calculated using a boundary function of the zero-sequence component.

6. The power quality optimization method based on carrier modulation according to claim 4, characterized in that: The superimposing the original modulated wave according to the target zero-sequence component to generate the target modulated wave includes: Obtain the original modulation wave information of each phase of the level converter; The target zero-sequence component corresponding to each region is superimposed on the original modulation wave of each phase to generate the target modulation wave.

7. The power quality optimization method based on carrier modulation according to claim 6, characterized in that: The regulating the grid power based on the target modulation wave and dynamically compensating the capacitor voltage deviation include: updating the switch duty cycle of the bridge arm midpoint connected to the low-voltage port based on the target modulation wave to obtain a target switch duty cycle; The average current flowing through the low-voltage port is calculated according to the target switch duty cycle combined with the phase current, and the target zero-sequence component is dynamically adjusted to obtain the maximum average current to regulate the active power.

8. The power quality optimization method based on carrier modulation according to claim 7, characterized in that: The method of regulating the grid power based on the target modulation wave and dynamically compensating for the capacitor voltage deviation further includes: Dynamically adjust the target switch duty cycle based on the capacitor voltage deviation of the power system to achieve capacitor voltage balancing control; When the capacitor voltage deviation is greater than the capacitor voltage threshold, lowering the target switch duty cycle; When the capacitor voltage deviation is less than the capacitor voltage threshold, the target switch duty cycle is increased.

9. The power quality optimization method based on carrier modulation according to claim 1, characterized in that: The method further comprises: Performing grid power distribution based on the power demand of the energy storage system and the target zero-sequence component; When the energy storage system needs to be charged, the switching duty cycle of the energy storage system connecting bridge arm is increased by adjusting the target zero-sequence component to distribute the charging power; When the energy storage system needs to discharge, the target zero-sequence component is adjusted to reduce the switch duty cycle of the bridge arm connecting the energy storage system to release the stored energy.

10. The power quality optimization system based on carrier modulation is characterized by: The power quality optimization method based on carrier modulation according to any one of claims 1 to 9 above comprises: An acquisition module is used to obtain the bridge arm information of the distributed energy storage type power quality controller and determine the carrier amplitude adjustment strategy; A calculation module, configured to determine a target zero-sequence component to be injected based on carrier characteristics based on the carrier amplitude adjustment strategy; A modulation wave module, which superimposes the original modulation wave according to the target zero-sequence component to generate a target modulation wave; The optimization module adjusts the grid power based on the target modulation wave and dynamically compensates for the capacitor voltage deviation.

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