Comprehensive electric energy quality regulation and control system and method for low-voltage transformer area

Abstract

The invention relates to the technical field of power systems, in particular to a comprehensive power quality regulation and control system and method for a low-voltage transformer area, the system comprises an information processing control platform, an information acquisition terminal and power regulation and control equipment, and the power regulation and control equipment comprises four information acquisition terminals, a phase converter and a reactive power compensation device. Data such as operation state and working state are collected, and the power quality abnormity reason is accurately positioned. Through issuing an area control strategy or a transformer area self-operation control strategy, when the power quality of a power grid is abnormal, voltage regulation, three-phase imbalance regulation and photovoltaic absorption are respectively carried out through power regulation and control equipment, and comprehensive treatment of the power quality is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power systems, and in particular to a low-voltage area comprehensive power quality control system and method. Background Art

[0002] With the rapid development of my country's power industry, the capacity of the power system has been further expanded to carry more power equipment, and with the development of distributed photovoltaics, the access coverage ratio of distributed photovoltaics has gradually increased. This has made the power quality problems of the public power grid increasingly serious, which can be divided into the following aspects: First, the terminal voltage stability is insufficient. Due to the relatively weak structure of the public transformer distribution network and the aging of transformer equipment, the access of photovoltaic power sources can easily lead to overvoltage at the end user during the day and low voltage at night. This not only causes unstable equipment operation, but may also cause equipment damage.

[0003] Second, the three-phase imbalance problem has intensified. Due to the large number of factory motors, welding machines and various types of equipment, coupled with the continuous emergence of village-run enterprises, the three-phase imbalance on the line has become more and more serious. This leads to insufficient voltage in the overloaded phase, making it difficult to start the equipment. At the same time, unstable voltage can also cause the motor to overheat when the equipment is running or starting, thus causing safety accidents.

[0004] The third is that the reactive power is too high. Due to the heavy line load and the continuous increase in nonlinear load, the active output is reduced and the reactive power increases accordingly, which in turn causes excessive line losses.

[0005] Fourth, there is the problem of reverse overload of photovoltaic power. Due to the characteristics of distributed photovoltaic power generation, such as dispersion, randomness and intermittency, and the limited capacity of the power grid terminal, after a large number of distributed photovoltaic power generation are connected to the power grid, the power grid flow direction will change, the local voltage will exceed the limit, and even cause the relay protection to malfunction. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a low-voltage area comprehensive power quality control system, including an information processing control platform, an information collection terminal and a power control device, wherein the power control device includes four information collection terminals, a phase converter and a reactive power compensation device; the information processing control platform is wirelessly connected to the information collection terminal, and the information collection terminal is electrically connected to the power control device; the four information collection terminals are used to be electrically connected to a photovoltaic energy storage system, and communicate with a photovoltaic inverter and an energy storage device of the photovoltaic energy storage system respectively; The information processing and control platform is used to receive the power data of the substation area uploaded by the information collection terminal and the abnormal power capacity information of the substation area reported, process the data, and issue the control strategy and corresponding control parameters; The information collection terminal is used to collect the power data of the substation area to judge the power capacity of the substation area and report the abnormal power capacity information of the substation area; and receive the control strategy issued by the information processing control platform to determine the required execution strategy and corresponding control parameters, and transmit them to the four information collection terminals, phase converters, and reactive power compensation devices respectively; A phase converter, used to adjust the three-phase load imbalance according to the control parameters sent by the information collection terminal; Reactive power compensation device, used to adjust reactive power according to the control parameters sent by the information collection terminal; Four information collection terminals are used to communicate with photovoltaic inverters and energy storage devices to collect the operating status of photovoltaic energy storage systems; photovoltaic consumption is carried out according to the control parameters issued by the information collection terminal.

[0007] In a specific implementation manner, the information collection terminal pre-stores initial control parameters of the station area self-operation control strategy.

[0008] The four information collection terminals store local protection strategies and protection parameters.

[0009] A low-voltage area integrated power quality control method is applied to the low-voltage area integrated power quality control system as described above, the method comprising: S1. The information collection terminal collects the power data of the substation area to determine the power capacity of the substation area. The specific operations are as follows: S1.1. Generate load power quality curve by collecting voltage, current, power and electric energy data of the substation area; S1.2. Determine the required regulation capacity of the power in the substation according to the load power quality curve, and calculate the capacity factor according to the required regulation capacity and adjustable capacity of the power in the substation; S1.3. Compare the calculated capacity factor with the normal threshold and capacity threshold respectively to determine the control strategy or report abnormal information on the power capacity of the substation; S2. The information processing control platform obtains the real-time collected power data of the substation based on the reported abnormal power capacity information of the substation, calculates the three-phase imbalance, power quality factor and photovoltaic return rate respectively, and compares them with the preset power quality indicators respectively, and determines the control strategy according to the comparison results, and the control strategy includes the substation self-operation strategy and the regional regulation strategy; S3, the information collection terminal obtains the determined control strategy, and determines the control strategy to be executed based on the priority of the control strategy; S4. The information collection terminal sends the executed control strategy to the power control device, and the power control device performs power quality control according to the control parameters.

[0010] The three-phase imbalance is the ratio of the effective value of the negative-sequence current effective value and the effective value of the zero-sequence current phase sum to the effective value of the positive-sequence current, and its calculation formula is: , , , , in, is the three-phase unbalance, is the negative sequence current effective value, is the positive sequence current effective value, is the effective value of zero-sequence current; is the rotation operator, ; I A , I B , I C Respectively represent the three-phase current values.

[0011] The specific method for determining the control strategy or reporting abnormal information of the power capacity of the substation in S1.3 is as follows: If the capacity factor is less than or equal to the normal threshold, no control strategy is issued; If the capacity factor is greater than the normal threshold and less than the capacity threshold, the pre-stored station area self-operation control strategy is determined and S3 is executed; If the capacity factor is greater than the capacity threshold, the abnormal information of the power capacity of the substation is reported and S2 is executed.

[0012] In S2, a control strategy is determined according to the comparison result, which is specifically: If the three-phase imbalance exceeds the preset power quality index value of the three-phase balance, the regional control mark is triggered; If the power quality factor falls into the preset power quality index range, the regional control flag is triggered; If the photovoltaic return rate exceeds the preset photovoltaic return power index value, the regional control mark will be triggered; According to the number of regional control identifications, if any regional control identification exists, it is determined as a regional control strategy; if the number of regional control identifications is zero, it is determined as a substation self-operation control strategy.

[0013] The information processing control platform is determined as a regional regulation strategy, and the control parameters of the regional regulation strategy are determined according to the calculated three-phase imbalance, the power quality factor of the substation area and the photovoltaic return rate.

[0014] In S3, the information collection terminal determines the control strategy to be executed based on the control strategy priority, specifically: If the information collection terminal obtains the determined control strategy as the regional control strategy, the regional control strategy and corresponding control parameters are issued; If the information collection terminal obtains the determined control strategy as the area self-operation control strategy, the area self-operation control strategy and initial control parameters are issued; If the information collection terminal does not obtain the control strategy determined by the information processing control platform, and has not determined the self-operation control strategy of the substation itself, the control strategy will not be issued.

[0015] The S3 also includes that when the information collection terminal does not send down the control strategy, the information collection terminal executes the stored local protection strategy and protection parameters.

[0016] The beneficial effect is that the present invention is a low-voltage substation comprehensive power quality control system and method, which is composed of a power control device consisting of four information collection terminals, a phase converter, and a reactive compensation device, and an information collection terminal and an information processing control platform to form a corresponding local-substation-regional three-layer control. Collect data such as operating status and working status to accurately locate the cause of abnormal power quality. By issuing regional control strategies or substation self-operation control strategies, when the power quality of the power grid is abnormal, the power control equipment is used to perform voltage regulation, three-phase unbalance regulation and photovoltaic absorption respectively, to achieve comprehensive power quality management and protect the safety of the power grid and the quality of power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural diagram of the integrated power quality control system for low-voltage substations; Figure 2 The figure is a flow chart of the comprehensive power quality control method for low voltage substations. DETAILED DESCRIPTION

[0018] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings.

[0019] See also Figure 1This embodiment provides a low-voltage substation integrated power quality control system, including an information processing control platform, an information collection terminal and a power control device, wherein the power control device includes four information collection terminals, a phase converter and a reactive power compensation device. The four information collection terminals are electrically connected to the photovoltaic energy storage system, and communicate with the photovoltaic inverter and the energy storage device of the photovoltaic energy storage system respectively. The information processing control platform is wirelessly connected to the information collection terminal, and the information collection terminal is electrically connected to the power control device. By installing the system on site, the various devices of the power control equipment are arranged and installed respectively, and the four information collection terminals are installed at the grid connection point of the photovoltaic inverter and inside the energy storage device respectively; the phase converter is installed at the electrical node of the substation load, and the reactive power compensation device is arranged next to the substation transformer; the information collection terminal collects the power data and operation data of each device of the power control equipment respectively, and uploads them to the information processing control platform.

[0020] Among them, the information processing control platform is used to receive the power data of the substation area uploaded by the information collection terminal and the abnormal power capacity information of the substation area reported, process the data, and issue the control strategy and corresponding control parameters; The information collection terminal is used to collect the power data of the substation area to judge the power capacity of the substation area and report the abnormal power capacity information of the substation area; and receive the control strategy issued by the information processing control platform to determine the required execution strategy and corresponding control parameters, and transmit them to the four information collection terminals, phase converters, and reactive power compensation devices respectively; The phase converter is used to adjust the three-phase load imbalance according to the control parameters sent by the information collection terminal; The reactive power compensation device is used to adjust reactive power according to the control parameters sent by the information collection terminal; The information collection terminal is used to communicate with the photovoltaic inverter and energy storage device to collect the operating status of the photovoltaic energy storage system; photovoltaic consumption is carried out according to the control parameters issued by the information collection terminal.

[0021] At the same time, the information collection terminal pre-stores the initial control parameters of the substation self-operation control strategy; when the information collection terminal does not report information, the four information collection terminals, the phase converter and the reactive compensation device are controlled based on the pre-stored initial control parameters to perform power quality regulation.

[0022] The four information collection terminals store local protection strategies and protection parameters. The protection parameters include the default grid protection parameters, voltage protection parameters, capacity protection parameters, island protection parameters, capacity control parameters and voltage control parameters. If the control strategy issued by the information processing control platform or the control strategy issued by the information collection terminal is not received, the local protection strategy is executed first.

[0023] In addition, this embodiment also provides a low-voltage area comprehensive power quality control method, see Figure 2 , applied to the low-voltage integrated power quality control system as described above, the specific implementation steps of the method are as follows: S1. The information collection terminal collects the power data of the substation area to determine the power capacity of the substation area. The specific operations are as follows: S1.1. Generate load power quality curve by collecting voltage, current, power and electric energy data of the substation area; S1.2. Determine the required regulation capacity of the power in the substation according to the load power quality curve, and calculate the capacity factor according to the required regulation capacity and adjustable capacity of the power in the substation; The capacity factor = (the required regulation capacity of the power of the substation - the adjustable capacity) / the required regulation capacity of the power of the substation; S1.3. Compare the calculated capacity factor with the normal threshold and capacity threshold respectively to determine the control strategy or report abnormal information on the power capacity of the substation; If the capacity factor is less than or equal to the normal threshold, no control strategy is issued; If the capacity factor is greater than the normal threshold and less than or equal to the capacity threshold, the pre-stored station area self-operation control strategy is determined and S3 is executed; If the capacity factor is greater than the capacity threshold, the abnormal information of the power capacity of the substation is reported and S2 is executed.

[0024] S2. The information processing control platform obtains the real-time collected power data of the substation based on the reported abnormal power capacity information of the substation, calculates the three-phase imbalance, power quality factor and photovoltaic return rate respectively, and compares them with the preset power quality indicators respectively, and determines the control strategy according to the comparison results, and the control strategy includes the substation self-operation strategy and the regional regulation strategy; The information processing and control platform calculates the three-phase imbalance, power quality factor and photovoltaic return rate based on the uploaded power data of the substation, including the power data and operation data of each device of the power control equipment in the substation, specifically the power generation, online power, photovoltaic output consumption data, reactive power processing data and three-phase power data.

[0025] The three-phase imbalance is the ratio of the effective value of the negative-sequence current effective value and the effective value of the zero-sequence current phase sum to the effective value of the positive-sequence current, and its calculation formula is: , , , , in, is the three-phase unbalance, is the negative sequence current effective value, is the positive sequence current effective value, is the effective value of zero-sequence current; is the rotation operator, ; I A , I B , I C Respectively represent the three-phase current values.

[0026] The power quality factor is the capacity factor, and the power quality factor = (the regulating capacity required for the power in the substation - the adjustable capacity) / the regulating capacity required for the power in the substation.

[0027] The photovoltaic return rate is the ratio of the real-time photovoltaic power minus the real-time load power and the station capacity.

[0028] The three-phase unbalance, power quality factor and photovoltaic return rate are compared with the preset power quality indicators, and the control strategy is determined according to the comparison results. The specific method is as follows: If the three-phase imbalance exceeds the preset power quality index value of the three-phase balance, the regional control mark is triggered; If the power quality factor falls into the preset power quality index range, the regional control flag is triggered; If the photovoltaic return rate exceeds the preset photovoltaic return power index value, the regional control mark will be triggered; According to the number of regional control identifications, if any regional control identification exists, it is determined as a regional control strategy; if the number of regional control identifications is zero, it is determined as a substation self-operation control strategy.

[0029] At the same time, when it is determined to be a regional regulation strategy, the information processing control platform also includes determining the control parameters of the regional regulation strategy based on the calculated three-phase imbalance, the power quality factor of the substation area and the photovoltaic return rate.

[0030] S3, the information collection terminal obtains the determined control strategy, and determines the control strategy to be executed based on the priority of the control strategy; The control strategy priority is regional regulation strategy > substation self-operation control strategy > local protection strategy.

[0031] The information collection terminal determines the control strategy to be executed based on the control strategy priority, specifically: If the information collection terminal obtains the determined control strategy as the regional control strategy, the regional control strategy and corresponding control parameters are issued; If the information collection terminal obtains the determined control strategy as the area self-operation control strategy, the area self-operation control strategy and initial control parameters are issued; If the information collection terminal does not obtain the control strategy determined by the information processing control platform, and has not determined the self-operation control strategy of the substation itself, the control strategy will not be issued.

[0032] The S3 also includes that when the information collection terminal does not send down the control strategy, the information collection terminal executes the stored local protection strategy and protection parameters.

[0033] S4. The information collection terminal sends the executed control strategy to the power control device, and the power control device controls the power quality according to the control parameters, specifically including: a, voltage regulation; Based on the fact that voltage is sensitive to reactive power changes but insensitive to active power changes, adjusting the voltage amplitude is to adjust reactive power supplementation; Based on the basic principle that voltage is more sensitive to reactive power changes but insensitive to active power changes, and voltage phase is sensitive to active power changes but insensitive to reactive power changes, the analysis is simplified by considering only the longitudinal component of voltage drop: ΔU=(PR+QX) / U, From the formula, we can see that voltage drop is related to both active power P and reactive power Q, but the reactance affects X>>R, so the component of QX in ΔU is larger, that is, adjusting the voltage amplitude is to adjust the reactive power.

[0034] The information collection terminal collects the voltage amplitude of the transformer in the substation area, compares the voltage amplitude with the preset voltage effective value interval, and if it is less than the lower limit of the preset voltage effective value interval, controls the reactive power compensation device to generate reactive power; if it is greater than the upper limit of the preset voltage effective value interval, controls the reactive power compensation device to absorb reactive power; In a specific embodiment, the preset voltage effective value range is 198V-242V, and a reactive power compensation device is used to generate or absorb reactive power to adjust the voltage amplitude. When the voltage exceeds the upper limit, the reactive power is reduced, and when the voltage falls below the lower limit, the reactive power is increased, so that the voltage is in a dynamic equilibrium state.

[0035] b. Three-phase unbalanced regulation; The information collection terminal communicates with the phase converter to obtain the surplus or shortage of each single-phase load in the three-phase four-wire phase converter, and controls the phase converter to automatically switch the load between phases; The information collection terminal calculates the three-phase imbalance based on the formula; compares the three-phase imbalance with the standard threshold, and if it is greater than or equal to the standard threshold, dynamically adjusts the load of each phase of the inverter until the three-phase imbalance is less than the standard threshold.

[0036] When the information collection terminal controls the inverter to perform three-phase unbalance adjustment, and the three-phase imbalance is still less than the standard threshold after the inverter is adjusted, the information collection terminal sends adjustments to the energy storage device through the four information collection terminals, and controls the energy storage device to charge and discharge to adjust the load, thereby achieving three-phase unbalance adjustment.

[0037] c, photovoltaic consumption; The information collection terminal determines the photovoltaic power generation adjustment power by calculating the photovoltaic return rate; the calculation formula of the photovoltaic power generation adjustment power is: (PV return rate - 0.8) * area capacity = PV power generation adjustment power; The information collection terminal sends the photovoltaic power generation adjustment power to the photovoltaic energy storage system through the four information collection terminals, and the photovoltaic energy storage system reduces the corresponding photovoltaic power generation power according to the photovoltaic power generation adjustment power.

[0038] The information collection terminal first controls several photovoltaic inverters in turn by issuing a control ratio (photovoltaic power generation ratio). If multiple photovoltaic inverters cannot adjust the photovoltaic power generation according to the control ratio, the photovoltaic power generation value is directly issued for control; If both the control ratio and the photovoltaic power value cannot be controlled, the current regulation control is abandoned and the event is reported, waiting for the next round of regulation control until the photovoltaic return rate is lower than 0.8. At the same time, when the output of the photovoltaic inverter decreases due to light, the information collection terminal increases the control ratio of the photovoltaic inverter that has adjusted the photovoltaic power until the photovoltaic power of each photovoltaic inverter is restored to 100%, achieving a dynamic balance of photovoltaic consumption.

Claims

1. A low voltage area comprehensive power quality control system, characterized in that: It includes an information processing control platform, an information collection terminal and a power control device, wherein the power control device includes an information collection terminal, a phase converter and a reactive power compensation device; the information processing control platform is connected to the information collection terminal via wireless communication, and the information collection terminal is electrically connected to the power control device; The four information collection terminals are used to be electrically connected to the photovoltaic energy storage system and communicate with the photovoltaic inverter and energy storage device of the photovoltaic energy storage system respectively; The information processing and control platform is used to receive the power data of the substation area uploaded by the information collection terminal and the abnormal power capacity information of the substation area reported, process the data, and issue the control strategy and corresponding control parameters; Information collection terminal, used to collect power data of the substation area to judge the power capacity of the substation area and report abnormal power capacity information of the substation area; And receive the control strategy issued by the information processing control platform to determine the required execution strategy and corresponding control parameters, and transmit them to the four information collection terminals, phase converters, and reactive power compensation devices respectively; A phase converter, used to adjust the three-phase load imbalance according to the control parameters sent by the information collection terminal; Reactive power compensation device, used to adjust reactive power according to the control parameters sent by the information collection terminal; Four information collection terminals are used to communicate with photovoltaic inverters and energy storage devices to collect the operating status of photovoltaic energy storage systems; photovoltaic consumption is carried out according to the control parameters issued by the information collection terminal.

2. The low voltage area comprehensive power quality control system according to claim 1 is characterized in that: The information collection terminal pre-stores initial control parameters of the station area self-operation control strategy.

3. The low voltage area comprehensive power quality control system according to claim 1 is characterized in that: The four information collection terminals store local protection strategies and protection parameters.

4. A low-voltage area integrated power quality control method, applied to the low-voltage area integrated power quality control system according to any one of claims 1 to 3, characterized in that: The method comprises: S1. The information collection terminal collects the power data of the substation area to determine the power capacity of the substation area. The specific operations are as follows: S1.

1. Generate load power quality curve by collecting voltage, current, power and electric energy data of the substation area; S1.

2. Determine the required regulation capacity of the power in the substation according to the load power quality curve, and calculate the capacity factor according to the required regulation capacity and adjustable capacity of the power in the substation; S1.

3. Compare the calculated capacity factor with the normal threshold and capacity threshold respectively to determine the control strategy or report abnormal information on the power capacity of the substation; S2. The information processing control platform obtains the real-time collected power data of the substation based on the reported abnormal power capacity information of the substation, calculates the three-phase imbalance, power quality factor and photovoltaic return rate respectively, and compares them with the preset power quality indicators respectively, and determines the control strategy according to the comparison results, and the control strategy includes the substation self-operation strategy and the regional regulation strategy; S3, the information collection terminal obtains the determined control strategy, and determines the control strategy to be executed based on the priority of the control strategy; S4. The information collection terminal sends the executed control strategy to the power control device, and the power control device performs power quality control according to the control parameters.

5. The low voltage area comprehensive power quality control method according to claim 4 is characterized in that: The three-phase imbalance is the ratio of the effective value of the negative-sequence current effective value and the effective value of the zero-sequence current phase sum to the effective value of the positive-sequence current, and its calculation formula is: ， ， ， ， in, is the three-phase unbalance, is the negative sequence current effective value, is the positive sequence current effective value, is the effective value of zero-sequence current; is the rotation operator, ; I A , I B , I C Respectively represent the three-phase current values.

6. The low voltage area comprehensive power quality control method according to claim 4 is characterized in that: The specific method for determining the control strategy or reporting abnormal information of the power capacity of the substation in S1.3 is as follows: If the capacity factor is less than or equal to the normal threshold, no control strategy is issued; If the capacity factor is greater than the normal threshold and less than or equal to the capacity threshold, the pre-stored station area self-operation control strategy is determined and S3 is executed; If the capacity factor is greater than the capacity threshold, the abnormal information of the power capacity of the substation is reported and S2 is executed.

7. The low voltage area comprehensive power quality control method according to claim 4 is characterized in that: In S2, a control strategy is determined according to the comparison result, which is specifically: If the three-phase imbalance exceeds the preset power quality index value of the three-phase balance, the regional control mark is triggered; If the power quality factor falls into the preset power quality index range, the regional control flag is triggered; If the photovoltaic return rate exceeds the preset photovoltaic return power index value, the regional control mark will be triggered; According to the number of regional control indicators, if any regional control indicator exists, it is determined as a regional control strategy; If the number of regional control identification is zero, the self-operation control strategy of the substation is determined.

8. The low voltage area comprehensive power quality control method according to claim 7 is characterized in that: It also includes the information processing control platform determining a regional regulation strategy, and determining control parameters of the regional regulation strategy according to the calculated three-phase imbalance, area power quality factor and photovoltaic return rate.

9. The low voltage area comprehensive power quality control method according to claim 4 is characterized in that: In S3, the information collection terminal determines the control strategy to be executed based on the control strategy priority, specifically: If the information collection terminal obtains the determined control strategy as the regional control strategy, the regional control strategy and corresponding control parameters are issued; If the information collection terminal obtains the determined control strategy as the area self-operation control strategy, the area self-operation control strategy and initial control parameters are issued; If the information collection terminal does not obtain the control strategy determined by the information processing control platform, and has not determined the self-operation control strategy of the substation itself, the control strategy will not be issued.

10. The low voltage area comprehensive power quality control method according to claim 9, characterized in that: The S3 also includes that when the information collection terminal does not send down the control strategy, the information collection terminal executes the stored local protection strategy and protection parameters.

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