Unified power quality adjusting device and method

Abstract

The invention belongs to the technical field of flexible alternating-current power transmission and distribution and power electronics, and discloses a unified power quality adjusting device and method so as to achieve the purpose of power quality control. The device comprises a direct current bus, a compensation unit and an adjusting unit, the compensation unit comprises a series compensation subunit and a parallel compensation subunit; the series compensation subunit is used for compensating load voltage; the direct-current bus is used for providing compensation energy for the series compensation subunit; the parallel compensation subunit is used for compensating harmonic waves, three-phase imbalance and reactive current of a load, and is also used for providing voltage support for a direct-current bus and providing energy for the series compensation subunit; the adjusting unit comprises a super capacitor energy storage system and a photovoltaic power generation system which are connected in parallel; the super capacitor energy storage system comprises a super capacitor and a first DC / DC converter; the photovoltaic power generation system comprises a photovoltaic array and a second DC / DC converter. According to the invention, the coupling problem of series-parallel inverters of the device is solved, so that the voltage of the direct-current side bus is stable.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible AC power transmission and distribution and power electronics, and specifically relates to a unified power quality regulation device and method. Background Art

[0002] Distributed energy, such as solar energy and wind energy, has intermittent and uncertain power generation characteristics. This feature makes it easy to cause voltage fluctuations and frequency deviations after connecting to the power grid, thereby interfering with the normal operation of user equipment and reducing the power quality and stability of system operation. With the increase in the proportion of distributed energy, a series of power quality regulators based on modern power electronics technology have emerged, aiming to optimize the power quality of the distribution network and enhance its power supply reliability. These regulators, or compensation controllers, such as reactive power compensators (SVCs), PWM switching static synchronous compensators (STATCOMs), dynamic voltage restorers (DVRs) and active power filters (APFs), have not only significantly improved the power quality of the distribution network, but also promoted the further development of user power technology.

[0003] However, it is worth noting that the above-mentioned regulators are relatively simple in function and it is difficult to fully cope with complex and changeable power quality problems and achieve comprehensive compensation. For this reason, the unified power quality conditioner (UPQC) has emerged, and its original design intention is to comprehensively solve various power quality problems in the power system. UPQC consists of two core parts: a series active power filter (SAPF) and a parallel active power filter (PAPF), which are closely connected through a shared DC bus. By integrating the dual functions of series and parallel compensation, UPQC can synchronously correct the distortion, fluctuation, imbalance and harmonic phenomena in voltage and current to ensure that users enjoy high-quality electricity. However, it cannot be ignored that traditional UPQC faces challenges in practical applications: there is a coupling phenomenon between the series and parallel side inverters, which easily leads to unstable voltage fluctuations on the DC side; and UPQC cannot provide active power support to the power grid during operation, and cannot cope with occasions where active power needs to be regulated. Under economic considerations, it may aggravate the potential impact on the distribution network and make the power quality problem more complicated. Therefore, further improvement and optimization of UPQC is particularly necessary. Summary of the invention

[0004] Based on the above-mentioned shortcomings and deficiencies in the prior art, one of the objects of the present invention is to solve at least one or more of the above-mentioned problems in the prior art. In other words, one of the objects of the present invention is to provide a unified power quality regulation device and method that meets one or more of the aforementioned needs, so as to achieve the power quality management goal while effectively solving the mutual coupling of the series and parallel side inverters of the unified power quality conditioner, so that the DC side bus voltage is stable and easy to control.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a unified power quality regulation device for regulating the power quality between a load and a power supply, comprising a DC bus and a compensation unit and a regulation unit connected thereto; the compensation unit comprises a series compensation subunit and a parallel compensation subunit; the series compensation subunit is connected between the power supply and the load, and is used to compensate for the load voltage; the DC bus is used to provide compensation energy for the series compensation subunit; the parallel compensation subunit is connected in parallel with the load, and is used to compensate for the harmonics, three-phase imbalance and reactive current of the load, and is also used to provide voltage support for the DC bus and provide energy for the series compensation subunit; the regulation The solar cell includes a supercapacitor energy storage system and a photovoltaic power generation system connected in parallel; the supercapacitor energy storage system includes a supercapacitor and a first DC / DC converter, which is used to store energy when the load consumes less power and provide energy when the load consumes more power; the first DC / DC converter is used to convert the voltage of the supercapacitor energy storage system and transmit power to the DC bus; the photovoltaic power generation system includes a photovoltaic array and a second DC / DC converter, which is used to supply power to the supercapacitor energy storage system and the DC bus; the second DC / DC converter is used to convert the voltage of the photovoltaic power generation system and transmit power to the DC bus.

[0007] As a preferred solution, the first DC / DC converter and / or the second DC / DC converter comprises a low voltage source full bridge subunit, a high voltage source full bridge subunit and a transformer subunit; the low voltage source full bridge subunit is arranged on a side close to the super capacitor and / or the photovoltaic array; the high voltage source full bridge subunit is arranged on a side close to the DC bus;

[0008] The transformer unit is used to transform the voltage between the low-voltage source full-bridge unit and the high-voltage source full-bridge unit, and complete the transmission of power P from the low-voltage source full-bridge unit to the high-voltage source full-bridge unit.

[0009] As a preferred solution, the power P transmitted by the transformer subunit is: Wherein, U1 is the voltage of the full-bridge subunit of the low-voltage source, w is the switching angular frequency, U0 is the load voltage, N is the transformation ratio of the transformer subunit, is the phase shift angle between the low voltage source full bridge subunit and the high voltage source full bridge subunit, and L is the leakage inductance of the transformer subunit.

[0010] In a second aspect, the present invention provides a unified power quality regulation method, based on a unified power quality regulation device described in the first aspect, comprising the steps of: S1, obtaining the unified power quality regulation device; S2, obtaining a preset control strategy, and controlling the unified power quality regulation device based on the control strategy to regulate the power quality of the power grid and the load.

[0011] As a preferred solution, the unified power quality regulation device is obtained in step S1, including the steps of: connecting the series compensator to the grid through a coupled three-phase transformer between the DC bus and the power supply; connecting the parallel compensator to the grid through a coupled three-phase transformer between the DC bus and the load; and connecting a supercapacitor energy storage system and a photovoltaic power generation system in parallel on the DC bus.

[0012] As a preferred solution, the control strategy includes a series compensation subunit control strategy; based on the series compensation subunit control strategy, the unified power quality regulation device is controlled to regulate the power quality of the power grid and the load, including the steps of: obtaining the system power grid voltage, the load voltage and the system reference voltage; performing difference calculation based on the system power grid voltage and the load voltage to obtain the voltage difference; performing park transformation on the voltage difference to obtain the d-axis voltage component and the q-axis voltage component; based on the d-axis voltage component, the q-axis voltage component and the system reference voltage, accelerating the regulation through PI proportional integral control and then obtaining the a, b, c three-phase voltages through park inverse transformation, generating an SVPWM control signal to drive the series compensation subunit to provide the load with a power supply voltage, thereby completing the power grid power quality regulation.

[0013] As a preferred solution, the control strategy includes a parallel compensation subunit control strategy; based on the parallel compensation subunit control strategy, the unified power quality regulation device is controlled to adjust the load power quality, including the steps of: obtaining the three-phase current of the system power grid; calculating the d-axis current component and the q-axis current component through the parallel side compensation detection unit; decoupling the d-axis current component and the q-axis current component, and performing park inverse transformation to obtain a voltage command signal and generate an SVPWM control signal to drive the parallel compensation subunit to eliminate the influence of load harmonics, three-phase imbalance and reactive current on the power grid, thereby completing the load power quality regulation.

[0014] As a preferred solution, the control strategy includes a DC bus power control strategy; based on the DC bus power control strategy, the unified power quality regulation device is controlled to regulate the power quality of the power grid and the load, including the steps of: obtaining DC / DC converter parameters, the DC / DC converter parameters including the low-voltage side voltage U1, the switching angular frequency w, the transformation ratio N, and the leakage inductance L; obtaining the load voltage U0; obtaining the phase shift angle between the low-voltage side full bridge and the high-voltage side full bridge of the preset DC / DC converter Based on the DC / DC converter parameters, load voltage U0 and angle The power P transmitted from the low-voltage side to the high-voltage side of the DC / DC converter is calculated to complete the circuit power quality regulation.

[0015] As a preferred solution, the calculation formula for the power P transmitted from the low-voltage side to the high-voltage side of the DC / DC converter is: Wherein, U1 is the voltage of the full-bridge subunit of the low-voltage source, w is the switching angular frequency, U0 is the load voltage, N is the transformation ratio of the transformer unit, is the phase shift angle between the low voltage source full bridge subunit and the high voltage source full bridge subunit, and L is the leakage inductance of the transformer subunit.

[0016] As a preferred solution, the control strategy includes a DC bus voltage stabilization control strategy for a photovoltaic power generation system; based on the DC bus voltage stabilization control strategy for the photovoltaic power generation system, the unified power quality regulation device is controlled to adjust the power quality of the power grid and the load, including the steps of: obtaining the maximum power point of the photovoltaic power generation system; based on the maximum power point, presetting the corresponding output voltage; based on the output voltage, controlling the photovoltaic power generation system to stabilize the DC bus voltage, and charging the supercapacitor energy storage system at the corresponding time, thereby completing the circuit power quality regulation.

[0017] As a preferred solution, the control strategy also includes a DC bus voltage stabilization control strategy for a supercapacitor energy storage system; based on the DC bus voltage stabilization control strategy, the unified power quality regulation device is controlled to adjust the power quality of the power grid and the load, including the steps of: presetting a compensation voltage; when the output of the photovoltaic power generation system is less than or equal to the energy required by the circuit, controlling the supercapacitor energy storage system based on the compensation voltage to stabilize the DC bus voltage, thereby completing the circuit power quality regulation.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The series-parallel compensation sub-units work together to effectively suppress the temporary increase and decrease of current and / or voltage caused by the access of distributed energy, making the DC side bus voltage stable and easy to control.

[0020] 2. By setting up a supercapacitor energy storage system and a photovoltaic power generation system on the DC bus, the bidirectional flow of power in the DC bus can be controlled, thereby completing the function of DC bus voltage control, so that the DC side voltage is not affected by the access of distributed energy and remains stable.

[0021] Further or more detailed beneficial effects will be described in detail in conjunction with specific examples in the specific implementation manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 It is a schematic diagram of the topological structure of the unified power quality regulation device described in Example 1 of the present invention.

[0024] Figure 2 It is a schematic diagram of the topological structure of the first DC / DC converter and / or the second DC / DC converter according to the first embodiment of the present invention.

[0025] Figure 3 It is a schematic diagram of the series compensation subunit control strategy described in the second embodiment of the present invention.

[0026] Figure 4 It is a schematic diagram of the parallel compensation subunit control strategy described in the second embodiment of the present invention.

[0027] Figure 5 It is a schematic diagram of the DC bus power control strategy described in the second embodiment of the present invention. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0029] In the following description, multiple embodiments of the present invention are provided, and different embodiments may be replaced or combined, so the present invention may also be considered to include all possible combinations of the same and / or different embodiments described. Therefore, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then the present invention should also be considered to include embodiments containing one or more of A, B, C, and D, all other possible combinations, even though the embodiment may not be clearly described in the following text.

[0030] The following description provides examples and does not limit the scope, applicability or examples set forth in the claims. Changes may be made to the functions and arrangements of the elements described without departing from the scope of the present invention. Various processes or components may be appropriately omitted, substituted or added to each example. For example, the described method may be performed in an order different from the described order, and various steps may be added, omitted or combined. In addition, the features described in some examples may be combined in other examples.

[0031] In order to facilitate a better understanding of the embodiments of the present invention, before explaining the specific implementation modes of the present invention in detail, its application scenarios are first described.

[0032] The unified power quality regulation device and method described in the embodiments of this specification are applied to a variety of power transmission and distribution processes. In these scenarios, the application of the unified power quality regulation device and method is intended to effectively control grid voltage and current fluctuations, thereby significantly improving power quality, reducing equipment failures and downtime caused by power quality problems, and providing high-quality user experience and reliable performance.

[0033] Embodiment 1:

[0034] like Figure 1 As shown, this embodiment provides a unified power quality regulation device for regulating the power quality between a load and a power supply, including a DC bus and a compensation unit and a regulation unit connected thereto; the compensation unit includes a series compensation subunit and a parallel compensation subunit; the series compensation subunit is connected between the power supply and the load, and is used to compensate for the load voltage; the DC bus is used to provide compensation energy for the series compensation subunit; the parallel compensation subunit is connected in parallel with the load, and is used to compensate for the harmonics, three-phase imbalance and reactive current of the load, and is also used to provide voltage support for the DC bus and provide energy for the series compensation subunit; the The regulating unit includes a supercapacitor energy storage system and a photovoltaic power generation system connected in parallel; the supercapacitor energy storage system includes a supercapacitor and a first DC / DC converter, which is used to store energy when the load consumes less power and provide energy when the load consumes more power; the first DC / DC converter is used to convert the voltage of the supercapacitor energy storage system and transmit power to the DC bus; the photovoltaic power generation system includes a photovoltaic array and a second DC / DC converter, which is used to supply power to the supercapacitor energy storage system and the DC bus; the second DC / DC converter is used to convert the voltage of the photovoltaic power generation system and transmit power to the DC bus.

[0035] It is understandable that due to the low rated voltage of supercapacitors, it is not possible to directly connect supercapacitors to the DC bus. Because the internal resistance of supercapacitors is relatively large, the voltage variation range of its output terminal is very large. Figure 2The symmetrical full-bridge bidirectional DC / DC converter shown in the figure can keep the output voltage of the supercapacitor stable and enable bidirectional flow of DC power. General photovoltaic battery energy storage systems often use bidirectional Buck / Boost circuits to exchange energy between photovoltaic cells and batteries. However, supercapacitors do not have stable terminal voltages like batteries, so this time the photovoltaic power generation system and the supercapacitor energy storage system are connected in parallel to the DC bus, and the photovoltaic power generation system is controlled to work in the maximum power point tracking (MPPT) state, making full use of the photovoltaic system's power generation capacity, and the supercapacitor energy storage system's charge and discharge control maintains a stable voltage on the DC bus.

[0036] It is understandable that, according to the different access positions, installation methods, and internal topological structures of each compensation subunit, it can be divided into the following structures: left-series and right-parallel structure, left-parallel and right-series structure, two-series structure, DC isolation structure, and modular multi-level converter structure. The parallel compensation subunits of the left-series and right-parallel structure have a suppressive effect on harmonic currents, so no harmonic voltage will be generated on the parallel side, which is beneficial to the voltage quality of the compensation series subunits. The compensation on the parallel side will also benefit from the compensation of the voltage on the series side, which greatly facilitates the calculation of harmonic currents and is very beneficial to the design of the controller. By comparing the advantages and disadvantages of these types of structures, from the aspects of volume, economic cost, and control performance, this embodiment selects the left-series and right-parallel structure.

[0037] More specifically, the power supply in this embodiment is set to 380V. The main reason why the power supply in this embodiment is not set to a higher voltage level is that the purpose of the intelligent voltage regulation control device is to comprehensively regulate the power quality problems caused by the access of distributed energy. If a higher voltage level is designed, such as 10kV, the cost will be too high and uneconomical. Because the most prominent and most significant impact of power quality is mainly in the low-voltage power grid, the lowest 380V that can meet the requirements is selected as the voltage level of the power grid.

[0038] Specifically, this embodiment provides a preferred implementation manner, wherein the first DC / DC converter and / or the second DC / DC converter includes a low-voltage source full-bridge subunit, a high-voltage source full-bridge subunit and a transformer subunit; the low-voltage source full-bridge subunit is arranged on a side close to the supercapacitor and / or the photovoltaic array; the high-voltage source full-bridge subunit is arranged on a side close to the DC bus; the transformer subunit is used to transform the voltage between the low-voltage source full-bridge unit and the high-voltage source full-bridge unit, and complete the transmission of power P from the low-voltage source full-bridge unit to the high-voltage source full-bridge unit.

[0039] Specifically, this embodiment provides a preferred implementation mode, the power P transmitted by the transformer subunit is: Wherein, U1 is the voltage of the full-bridge subunit of the low-voltage source, w is the switching angular frequency, U0 is the load voltage, N is the transformation ratio of the transformer subunit, is the phase shift angle between the low voltage source full bridge subunit and the high voltage source full bridge subunit, and L is the leakage inductance of the transformer subunit.

[0040] It is understandable that by adjusting The amount of power flowing in the converter can be adjusted. By adjusting the power flow, active power can be exchanged between the supercapacitor and the power system when distributed energy is connected to the power system, thereby completing the voltage control function and keeping the DC side voltage of the supercapacitor stable without being affected by the access of distributed energy.

[0041] Embodiment 2:

[0042] The present embodiment provides a unified power quality regulation method, which is based on a unified power quality regulation device described in Embodiment 1, and includes the following steps: S1, obtaining the unified power quality regulation device; S2, obtaining a preset control strategy, and controlling the unified power quality regulation device based on the control strategy to thereby regulate the power quality of the power grid and the load.

[0043] Specifically, this embodiment provides a preferred implementation of step S1, wherein obtaining the unified power quality regulation device includes the steps of: connecting the series compensator to the grid through a coupled three-phase transformer between the DC bus and the power supply; connecting the parallel compensator to the grid through a coupled three-phase transformer between the DC bus and the load; and connecting a supercapacitor energy storage system and a photovoltaic power generation system in parallel on the DC bus.

[0044] Specifically, this embodiment provides a preferred implementation method, wherein the control strategy includes a series compensation subunit control strategy; based on the series compensation subunit control strategy, the unified power quality regulation device is controlled to regulate the power quality of the power grid and the load, including the steps of: obtaining the system power grid voltage, the load voltage and the system reference voltage; performing difference calculation based on the system power grid voltage and the load voltage to obtain the voltage difference; performing park transformation on the voltage difference to obtain the d-axis voltage component and the q-axis voltage component; based on the d-axis voltage component, the q-axis voltage component and the system reference voltage, accelerating the regulation through PI proportional integral control and then obtaining the a, b, c three-phase voltages through park inverse transformation, generating an SVPWM control signal to drive the series compensation subunit to provide the load with a power supply voltage, thereby completing the power grid power quality regulation.

[0045] It can be understood that there are two strategies for controlling the series side: direct control and indirect control. Direct control is achieved by controlling the series converter as a sinusoidal voltage source, and indirect control is achieved by controlling the series converter as a sinusoidal current source. Figure 3The embodiment shown adopts direct control, and the series inverter is controlled as a controlled voltage source, which assumes the voltage compensation function and makes the load side voltage become the set sinusoidal voltage. Considering the uncontrollability of the sudden access of distributed energy and the fact that the series inverter mainly suppresses voltage sag and rise, the reaction speed requirement is very high. Therefore, a control strategy of voltage outer loop and current inner loop control is proposed for this problem. Figure 3 Middle,U ad , U bd , U cd is the difference between the system grid voltage and the load voltage. The voltage components of the d-axis and q-axis are obtained through Park transformation. ref The system reference voltage is used to reduce the adjustment range of the regulator, speed up the adjustment through PI proportional integral control, reduce the error and increase the stability. Then the three-phase voltages a, b and c are obtained through the park inverse transformation to generate the SVPWM control signal to drive the series active power filter. The single voltage loop control strategy can speed up the response speed of voltage sag and swell compensation.

[0046] Specifically, this embodiment provides a preferred implementation method, wherein the control strategy includes a parallel compensation subunit control strategy; based on the parallel compensation subunit control strategy, the unified power quality regulation device is controlled to adjust the power quality of the power grid and the load, including the steps of: obtaining the three-phase current of the system power grid; calculating the d-axis current component and the q-axis current component through the parallel side compensation detection unit; decoupling the d-axis current component and the q-axis current component, and performing park inverse transformation to obtain a voltage command signal and generate an SVPWM control signal to drive the parallel compensation subunit to eliminate the influence of load harmonics, three-phase imbalance and reactive current on the power grid, thereby completing the load power quality regulation.

[0047] It is understandable that considering the relatively high requirements for the steady-state error on the parallel side, a control strategy of the voltage outer loop and the current inner loop is proposed for this problem, such as Figure 4 The embodiment shown adopts a dq0 detection algorithm based on instantaneous reactive power to achieve compensation of harmonic current. Figure 4 In the DC side voltage outer loop, a PI regulator is used to stabilize the DC side voltage at the same voltage amplitude as the expected value. 1a 、i 1b 、i 1c is the three-phase current of the system power grid, and the current components of the d-axis and q-axis are obtained through the parallel side compensation detection unit, i d 、i qThe compensation detection link inputs the superposition signal of fundamental positive sequence reactive power, fundamental negative sequence and harmonic components into the current inner loop for the system dq axis current. The feedforward decoupling method is used to decouple the rectifier d and q components. Then, the park inverse transformation is performed to obtain the voltage command signal and generate the SVPWM control signal to drive the parallel active power filter.

[0048] Specifically, this embodiment provides a preferred implementation method, wherein the control strategy includes a DC bus power control strategy; based on the DC bus power control strategy, the unified power quality regulation device is controlled to regulate the load power quality of the power grid, including the steps of: obtaining DC / DC converter parameters, wherein the DC / DC converter parameters include a low-voltage side voltage U1, a switching angular frequency w, a transformation ratio N, and a leakage inductance L; obtaining a load voltage U0; obtaining a preset phase shift angle between a low-voltage side full bridge and a high-voltage side full bridge of a DC / DC converter; Based on the DC / DC converter parameters, load voltage U0 and angle The power P transmitted from the low-voltage side to the high-voltage side of the DC / DC converter is calculated to complete the circuit power quality regulation.

[0049] Specifically, this embodiment provides a preferred implementation mode, the calculation formula of the power P transmitted from the low voltage side to the high voltage side of the DC / DC converter is:

[0050] Wherein, U1 is the voltage of the full-bridge subunit of the low-voltage source, w is the switching angular frequency, U0 is the load voltage, N is the transformation ratio of the transformer unit, is the phase shift angle between the low voltage source full bridge subunit and the high voltage source full bridge subunit, and L is the leakage inductance of the DC / DC converter.

[0051] Specifically, this embodiment provides a preferred implementation method, wherein the control strategy includes a DC bus voltage stabilization control strategy for a photovoltaic power generation system; based on the DC bus voltage stabilization control strategy for the photovoltaic power generation system, the unified power quality regulation device is controlled to adjust the power quality of the power grid and the load, including the steps of: obtaining the maximum power point of the photovoltaic power generation system; based on the maximum power point, presetting the corresponding output voltage; based on the output voltage, controlling the photovoltaic power generation system to stabilize the DC bus voltage, and charging the supercapacitor energy storage system at the corresponding time, thereby completing the circuit power quality regulation.

[0052] Specifically, this embodiment provides a preferred implementation method, wherein the control strategy also includes a DC bus voltage stabilization control strategy of a supercapacitor energy storage system; based on the DC bus voltage stabilization control strategy of the supercapacitor energy storage system, the unified power quality regulation device is controlled to adjust the power quality of the power grid and the load, including the steps of: presetting a compensation voltage; when the output of the photovoltaic power generation system is less than or equal to the energy required by the circuit, controlling the supercapacitor energy storage system based on the compensation voltage to stabilize the DC bus voltage, thereby completing the circuit power quality regulation.

[0053] It is understandable that supercapacitors do not have the same stable terminal voltage as batteries, such as Figure 5 The embodiment shown connects the photovoltaic power generation system and the supercapacitor energy storage system in parallel to the DC bus, and controls the photovoltaic power generation system to operate in the maximum power point tracking (MPPT) state, fully utilizing the power generation capacity of the photovoltaic system, and maintaining a stable voltage of the DC bus by the charge and discharge control of the supercapacitor energy storage system.

[0054] It should be noted that, for the above-mentioned method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present invention.

[0055] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0056] The above is only an exemplary embodiment of the present disclosure, and the scope of the present disclosure cannot be limited thereto. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure here, those skilled in the art will easily think of the implementation scheme of the present disclosure. The present invention is intended to cover any variation, use or adaptive change of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the technical field not recorded in the present disclosure. The description and examples are regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. A unified power quality regulating device for regulating the power quality between a load and a power source, characterized in that: It includes a DC bus and a compensation unit and a regulating unit connected thereto; The compensation unit includes a series compensation subunit and a parallel compensation subunit; The series compensation subunit is connected between the power supply and the load to compensate for the load voltage; The DC bus is used to provide compensation energy for the series compensation subunit; The parallel compensation subunit is connected in parallel with the load, and is used to compensate for the harmonics, three-phase imbalance and reactive current of the load, and is also used to provide voltage support for the DC bus and provide energy for the series supplement subunit; The regulating unit includes a supercapacitor energy storage system and a photovoltaic power generation system connected in parallel; The supercapacitor energy storage system includes a supercapacitor and a first DC / DC converter, which is used to store energy when the load uses less power and provide energy when the load uses more power; The first DC / DC converter is used to convert the voltage of the supercapacitor energy storage system and transmit power to the DC bus; The photovoltaic power generation system includes a photovoltaic array and a second DC / DC converter, which are used to supply power to the supercapacitor energy storage system and the DC bus; The second DC / DC converter is used to convert the voltage of the photovoltaic power generation system and transmit power to the DC bus.

2. A unified power quality control device according to claim 1, characterized in that: The first DC / DC converter and / or the second DC / DC converter comprises a low voltage source full bridge subunit, a high voltage source full bridge subunit and a voltage transformation subunit; The low voltage source full bridge subunit is arranged close to the super capacitor and / or the photovoltaic array; The high-voltage source full-bridge subunit is arranged on a side close to the DC bus; The transformer unit is used to transform the voltage between the low-voltage source full-bridge unit and the high-voltage source full-bridge unit, and complete the transmission of power P from the low-voltage source full-bridge unit to the high-voltage source full-bridge unit.

3. A unified power quality control device according to claim 2, characterized in that: The power P transmitted by the transformer subunit is: Wherein, U1 is the voltage of the full-bridge subunit of the low-voltage source, w is the switching angular frequency, U0 is the load voltage, N is the transformation ratio of the transformer subunit, is the phase shift angle between the low voltage source full bridge subunit and the high voltage source full bridge subunit, and L is the leakage inductance of the transformer subunit.

4. A unified power quality regulation method, based on the unified power quality regulation device according to claim 3, characterized in that: Includes steps: S1. Obtaining the unified power quality regulation device; S2. Obtain a preset control strategy, and control the unified power quality regulation device based on the control strategy to regulate the power quality of the power grid and the load.

5. A unified power quality regulation method according to claim 4, characterized in that: The step S1 of obtaining the unified power quality regulation device comprises the following steps: The series compensator is connected to the grid via a coupled three-phase transformer between the DC bus and the power supply; The shunt compensator is connected to the grid via a coupled three-phase transformer between the DC bus and the load; A supercapacitor energy storage system and a photovoltaic power generation system are connected in parallel on the DC bus.

6. A unified power quality regulation method according to claim 5, characterized in that: The control strategy includes a series compensation subunit control strategy; Based on the series compensation subunit control strategy, the unified power quality regulation device is controlled to regulate the power quality of the power grid and the load, including the steps of: Obtain system grid voltage, load voltage and system reference voltage; Performing a difference calculation based on the system grid voltage and the load voltage to obtain a voltage difference; Performing park transformation on the voltage difference to obtain a d-axis voltage component and a q-axis voltage component; Based on the d-axis voltage component, the q-axis voltage component and the system reference voltage, the a, b, and c three-phase voltages are obtained by accelerating the regulation through PI proportional integral control and then through park inverse transformation, and an SVPWM control signal is generated to drive the series compensation subunit to provide the load with a power supply voltage, thereby completing the power quality regulation of the power grid.

7. A unified power quality regulation method according to claim 5, characterized in that: The control strategy includes a parallel compensation subunit control strategy; Based on the parallel compensation subunit control strategy, the unified power quality regulation device is controlled to regulate the power quality of the power grid and the load, including the steps of: Obtain the three-phase current of the system power grid; The d-axis current component and the q-axis current component are calculated by the parallel side compensation detection unit; The d-axis current component and the q-axis current component are decoupled, and a park inverse transformation is performed to obtain a voltage command signal and generate an SVPWM control signal to drive the parallel compensation subunit to eliminate the influence of load harmonics, three-phase imbalance and reactive current on the power grid, thereby completing load power quality regulation.

8. A unified power quality regulation method according to claim 5, characterized in that: The control strategy includes a DC bus power control strategy; Controlling the unified power quality regulation device based on the DC bus power control strategy to regulate the power quality of the power grid and the load comprises the following steps: Obtaining DC / DC converter parameters, wherein the DC / DC converter parameters include low-voltage side voltage U1, switching angular frequency w, transformation ratio N, and leakage inductance L; Get the load voltage U0; Get the phase shift angle between the low-voltage side full bridge and the high-voltage side full bridge of the preset DC / DC converter Based on the DC / DC converter parameters, load voltage U0 and angle The power P transmitted from the low-voltage side to the high-voltage side of the DC / DC converter is calculated to complete the circuit power quality regulation.

9. A unified power quality regulation method according to claim 5, characterized in that: The control strategy includes a DC bus voltage stabilization control strategy for a photovoltaic power generation system; The unified power quality regulating device is controlled based on the DC bus voltage stabilization control strategy of the photovoltaic power generation system to regulate the power quality of the power grid and the load, including the steps of: Obtaining the maximum power point of the photovoltaic power generation system; Based on the maximum power point, preset a corresponding output voltage; The photovoltaic power generation system is controlled based on the output voltage to stabilize the DC bus voltage, and the supercapacitor energy storage system is charged at a corresponding time, thereby completing circuit power quality regulation.

10. A unified power quality regulation method according to claim 9, characterized in that: The control strategy also includes a DC bus voltage stabilization control strategy for a supercapacitor energy storage system; The unified power quality regulation device is controlled based on the DC bus voltage stabilization control strategy of the supercapacitor energy storage system to regulate the power quality of the power grid and the load, including the steps of: Preset compensation voltage; When the output of the photovoltaic power generation system is less than or equal to the energy required by the circuit, the supercapacitor energy storage system is controlled based on the compensation voltage to stabilize the DC bus voltage, thereby completing circuit power quality regulation.

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