A unified power quality conditioner and method

Abstract

The present application belongs to the field of flexible AC transmission and distribution and power electronics, and discloses a unified power quality conditioner and method to achieve the goal of power quality management. The device comprises a DC bus and a compensation unit and a regulating unit connected thereto; the compensation unit comprises a series compensation subunit and a parallel compensation subunit; the series compensation subunit is used for compensating the load voltage; the DC bus is used for providing compensation energy for the series compensation subunit; the parallel compensation subunit is used for compensating the load harmonic, three-phase imbalance and reactive current, and also used for providing voltage support for the DC bus and energy for the series compensation subunit; the regulating unit comprises a parallel super capacitor energy storage system and a photovoltaic power generation system; 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. The present application solves the coupling problem of the series and parallel inverters of the device, and makes the DC side bus voltage stable.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of flexible alternating current transmission and distribution and power electronics, and particularly relates to a unified power quality conditioner and method. BACKGROUND

[0002] Distributed energy sources, such as solar energy and wind energy, have intermittent and uncertain power generation characteristics. This characteristic makes it easy to cause voltage fluctuation and frequency deviation after accessing the power grid, thereby interfering with the normal operation of user equipment and reducing power quality and system operation stability. With the increasing proportion of distributed energy sources, a series of power quality conditioners relying on modern power electronics technology have emerged, aiming to optimize the power quality of distribution networks and enhance the reliability of power supply. These conditioners, or compensation controllers, such as static var compensator (SVC), PWM switching static synchronous compensator (STATCOM), dynamic voltage restorer (DVR), and active power filter (APF), not only significantly improve the power quality of distribution networks, but also promote the further development of user power technology.

[0003] However, it is worth noting that the above-mentioned conditioners are relatively single in function and difficult to comprehensively cope with complex and variable power quality problems and achieve comprehensive compensation. Therefore, the unified power quality conditioner (UPQC) emerges as the times require, and its original intention is to comprehensively solve various power quality problems in power systems. UPQC is composed of two core parts: series active power filter (SAPF) and parallel active power filter (PAPF), and is closely connected through a shared DC bus. Through the integration of series and parallel compensation functions, UPQC can simultaneously correct voltage and current distortion, fluctuation, imbalance, and harmonic phenomena, ensuring that the user end enjoys high-quality power. However, it cannot be ignored that traditional UPQC faces challenges in actual application: there is a coupling phenomenon between the series and parallel side inverters, which easily leads to unstable DC side voltage fluctuation; and UPQC cannot provide active power support to the grid during operation, which cannot cope with situations that require active power regulation. Economic considerations or exacerbate the potential impact on the distribution network, making power quality problems more complex. Therefore, further improvement and optimization of UPQC are particularly necessary. SUMMARY

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

[0005] To achieve the above object, the present application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a unified power quality conditioner for regulating power quality between a load and a power supply, comprising a DC bus and a compensation unit and a regulating 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 for compensating load voltage; the DC bus is used for providing compensation energy for the series compensation subunit; the parallel compensation subunit is connected in parallel with the load for compensating load harmonics, three-phase imbalance and reactive current, and is also used for providing voltage support for the DC bus and energy for the series compensation subunit; the regulating unit comprises a parallel super capacitor energy storage system and a photovoltaic power generation system; the super capacitor energy storage system comprises a super capacitor and a first DC / DC converter, which is used for storing energy when the load consumes less power and providing energy when the load consumes more power; the first DC / DC converter is used for converting the voltage of the super capacitor energy storage system and transmitting power to the DC bus; the photovoltaic power generation system comprises a photovoltaic array and a second DC / DC converter, which is used for supplying power to the super capacitor energy storage system and the DC bus; the second DC / DC converter is used for converting the voltage of the photovoltaic power generation system and transmitting 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 voltage transformation subunit; the low-voltage source full-bridge subunit is arranged near the side of the super capacitor and / or the photovoltaic array; the high-voltage source full-bridge subunit is arranged near the side of the DC bus;

[0008] The voltage transformation subunit is used for transforming the voltage between the low-voltage source full-bridge subunit and the high-voltage source full-bridge subunit and transmitting power P from the low-voltage source full-bridge subunit to the high-voltage source full-bridge subunit.

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

[0010] In a second aspect, the present application provides a unified power quality conditioner method, based on the unified power quality conditioner of the first aspect, comprising the steps of: S1, obtaining the unified power quality conditioner; S2, obtaining a preset control strategy, and controlling the unified power quality conditioner based on the control strategy to adjust the power quality of the power grid and the load.

[0011] As a preferred solution, the step S1 of obtaining the unified power quality conditioner comprises the steps of: connecting the series compensator with the power grid through the coupled three-phase transformer between the DC bus and the power supply; connecting the parallel compensator with the power grid through the coupled three-phase transformer between the DC bus and the load; connecting the super capacitor energy storage system and the photovoltaic power generation system in parallel on the DC bus.

[0012] As a preferred solution, the control strategy comprises a series compensation subunit control strategy; controlling the unified power quality conditioner based on the series compensation subunit control strategy to adjust the power quality of the power grid and the load comprises the steps of: obtaining the system grid voltage, the load voltage and the system reference voltage; performing 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, obtaining a, b and c three-phase voltages through PI proportional integral control and then through park inverse transformation after the adjustment, generating SVPWM control signals to drive the series compensation subunit to provide power supply voltage for the load, thereby completing the power quality adjustment of the power grid.

[0013] As a preferred solution, the control strategy comprises a parallel compensation subunit control strategy; controlling the unified power quality conditioner based on the parallel compensation subunit control strategy to adjust the power quality of the load comprises the steps of: obtaining the system grid three-phase current; calculating the d-axis current component and the q-axis current component through the parallel side compensation amount detection unit; decoupling the d-axis current component and the q-axis current component, and performing park inverse transformation to obtain a voltage instruction signal and generate SVPWM control signals to drive the parallel compensation subunit to eliminate the influence of the load harmonic, three-phase imbalance and reactive current on the power grid, thereby completing the power quality adjustment of the load.

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

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

[0016] As a preferred solution, the control strategy includes a direct-current bus voltage stabilization control strategy of the photovoltaic power generation system; the unified power quality conditioner is controlled based on the direct-current 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; presetting the corresponding output voltage based on the maximum power point; controlling the photovoltaic power generation system based on the output voltage to stabilize the direct-current bus voltage and charge the supercapacitor energy storage system at the corresponding time, so as to complete the circuit power quality regulation.

[0017] As a preferred solution, the control strategy further includes a direct-current bus voltage stabilization control strategy of the supercapacitor energy storage system; the unified power quality conditioner is controlled based on the direct-current bus voltage stabilization control strategy to regulate 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 required energy of the circuit, the supercapacitor energy storage system is controlled based on the compensation voltage to stabilize the direct-current bus voltage, so as to complete the circuit power quality regulation.

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

[0019] 1. The series-parallel compensation subunits cooperate with each other to effectively suppress the temporary increase and temporary decrease of the current and / or voltage caused by the access of the distributed energy source, so that the direct-current side bus voltage is stable and easy to control.

[0020] 2. By arranging the supercapacitor energy storage system and the photovoltaic power generation system on the direct-current bus, the bidirectional flow of power on the direct-current bus is controlled, and the function of direct-current bus voltage control is completed, so that the direct-current side voltage remains stable and is not affected by the access of the distributed energy source.

[0021] Further or more detailed beneficial effects will be described in the specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description only only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0023] Figure 1 Figure 1 is a schematic diagram of the topology of the unified power quality conditioner according to the first embodiment of the present application.

[0024] Figure 2 Figure 2 is a schematic diagram of the topology of the first DC / DC converter and / or the second DC / DC converter according to the first embodiment of the present application.

[0025] Figure 3 Figure 3 is a schematic diagram of the control strategy of the series compensation subunit according to the second embodiment of the present application.

[0026] Figure 4 Figure 4 is a schematic diagram of the control strategy of the parallel compensation subunit according to the second embodiment of the present application.

[0027] Figure 5 Figure 5 is a schematic diagram of the power control strategy of the DC bus according to the second embodiment of the present application. DETAILED DESCRIPTION

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

[0029] In the following description, a plurality of embodiments of the present application are provided, and different embodiments can be replaced or combined, so that the present application can 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, the present application should also be considered to include one or more embodiments of all other possible combinations of A, B, C and D, even if the embodiment is not explicitly described in the following content.

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

[0031] In order to better understand the embodiments of the present application, the application scenarios thereof are described before the detailed description of the specific embodiments of the present application.

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

[0033] Embodiment one:

[0034] As shown in Figure 1 The present embodiment provides a unified power quality conditioner 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 for compensating 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 for compensating the load harmonics, three-phase imbalance and reactive current, and is also used to provide voltage support for the DC bus and energy for the series compensation subunit; the regulation unit comprises a parallel super capacitor energy storage system and a photovoltaic power generation system; the super capacitor energy storage system comprises a super capacitor and a first DC / DC converter for storing energy when the load consumes less power and providing energy when the load consumes more power; the first DC / DC converter is used to convert the voltage of the super capacitor energy storage system and transmit power to the DC bus; the photovoltaic power generation system comprises a photovoltaic array and a second DC / DC converter for supplying power to the super capacitor 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 can be understood that, due to the low rated voltage of the super capacitor, the super capacitor cannot be directly connected to the DC bus. Because the internal resistance of the super capacitor is relatively large, the output voltage of the super capacitor varies greatly, and the application is Figure 2The shown symmetrical full-bridge bidirectional DC / DC converter can keep the output voltage of the super capacitor stable and enable the direct current to flow bidirectionally. Generally, a photovoltaic cell energy storage system often uses a bidirectional Buck / Boost circuit to exchange energy between the photovoltaic cell and the battery. However, the super capacitor does not have a stable terminal voltage like the battery, so this time, the photovoltaic power generation system and the super capacitor 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, so as to fully utilize the power generation capacity of the photovoltaic system, and the charge and discharge control of the super capacitor energy storage system keeps the voltage of the DC bus stable.

[0036] It can be understood that, according to the access position, installation mode and internal topology structure of each compensation subunit, the following structures can be divided: left series-right parallel structure, left parallel-right series structure, two series structure, direct current isolation type structure and modular multilevel converter structure. The parallel compensation subunit of the left series-right parallel structure has a suppression effect on the harmonic current, so that the harmonic voltage is not generated on the parallel side, which is beneficial to the voltage quality of the compensation series subunit. The compensation on the parallel side also benefits from the compensation of the series side voltage, greatly facilitating the calculation of the harmonic current and being very beneficial to the design of the controller. Through comparison of advantages and disadvantages of these structures, the left series-right parallel structure is selected in the embodiment from aspects of volume, economic cost and control performance.

[0037] More specifically, the power supply in the embodiment is set to 380V. The main reason why the power supply in the embodiment is not set to a higher voltage level is that the purpose of the intelligent voltage regulation control device is to comprehensively regulate and control the power quality problems caused by the access of distributed energy. If a higher voltage level such as 10kV is designed, the cost will be too high and not economical. Because the most prominent and most significant place of power quality is 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, the embodiment provides a preferred implementation manner, 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 voltage transformation subunit; the low-voltage source full-bridge subunit is arranged on the side close to the super capacitor and / or the photovoltaic array; the high-voltage source full-bridge subunit is arranged on the side close to the DC bus; the voltage transformation subunit is used for transforming the voltage between the low-voltage source full-bridge subunit and the high-voltage source full-bridge subunit and completing the transmission of power P from the low-voltage source full-bridge subunit to the high-voltage source full-bridge subunit.

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

[0040] It can be understood that, by adjusting The amount of power flow of the converter can be adjusted, and by adjusting the power flow, active power can be exchanged between the super capacitor and the power system when the distributed energy source is accessed, and thus the function of voltage control can be completed, so that the DC side voltage of the super capacitor remains stable and is not affected by the access of the distributed energy source.

[0041] Embodiment two:

[0042] The embodiment provides a unified power quality regulation method based on the unified power quality regulation device in embodiment one, 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 regulate the power quality of the power grid and the load.

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

[0044] Specifically, the embodiment provides a preferred implementation manner, and the control strategy includes a series compensation subunit control strategy; the unified power quality regulation device is controlled based on the series compensation subunit control strategy to regulate the power quality of the power grid and the load, and includes the following steps: obtaining the system grid voltage, the load voltage and the system reference voltage; performing 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, generating SVPWM control signals by performing PI proportional integral control and then performing park inverse transformation to obtain a, b and c three-phase voltages, to drive the series compensation subunit to provide power supply voltage for the load, thereby completing power grid power quality regulation.

[0045] It can be understood that, the control of the series side has two strategies of direct control and indirect control, the direct control is to control the series converter to be a sinusoidal voltage source, and the indirect control is to control the series converter to be a sinusoidal current source. For example, Figure 3The embodiment shown adopts direct control, and the series inverter is controlled as a controlled voltage source to undertake voltage compensation function, so that the load side voltage becomes a set sinusoidal voltage. Considering uncontrollability of sudden access of the distributed energy and the fact that the series converter mainly suppresses voltage sag and rise, the response speed requirement is very high, and therefore the control strategy of voltage outer loop and current inner loop control is proposed for the problem. Figure 3 U ad U bd U cd is the difference between the system grid voltage and the load voltage, and the voltage components on the d-axis and the q-axis are obtained through park transformation, U ref is the system reference voltage, and the purpose is to reduce the regulation amplitude of the regulator, to accelerate the regulation through PI proportional integral control, to reduce the error, and to increase the stability. Then, the a, b and c three-phase voltages are obtained through park inverse transformation, and the SVPWM control signal is generated to drive the series active power filter. The single voltage loop control strategy can accelerate the response speed of voltage sag and rise compensation.

[0046] Specifically, the embodiment provides a preferred implementation, and the control strategy includes a parallel compensation subunit control strategy; the unified power quality conditioner is controlled based on the parallel compensation subunit control strategy to regulate the power quality of the grid and the load, including the steps that the system grid three-phase current is acquired; the d-axis current component and the q-axis current component are calculated through a parallel side compensation amount detection unit; the d-axis current component and the q-axis current component are decoupled, and park inverse transformation is performed to obtain a voltage instruction signal and generate an SVPWM control signal to drive the parallel compensation subunit to eliminate the influence of the load harmonic, three-phase imbalance and reactive current on the grid, so as to complete the load power quality regulation.

[0047] It can be understood that, considering that the parallel side has a relatively high requirement for steady-state error, the control strategy of voltage outer loop and current inner loop is proposed for the problem, as shown in Figure 4 The embodiment shown adopts the dq0 detection algorithm based on instantaneous reactive power to realize compensation of the harmonic current. Figure 4 In the embodiment, the DC side voltage outer loop adopts a PI regulator, so that the DC side voltage can be stabilized at the same voltage amplitude as the expected value. 1a i 1b i 1c is the system grid three-phase current, and the current components on the d-axis and the q-axis are obtained through a parallel side compensation amount detection unit, i d i qFor the system dq axis current, the compensation amount detection link inputs the superimposed signal of the fundamental positive sequence reactive power, the fundamental negative sequence and the harmonic component to the current inner loop, adopts the feedforward decoupling mode to decouple the rectifier d, q components, then carries out the park inverse transformation to obtain the voltage command signal and generates the SVPWM control signal to drive the parallel active power filter.

[0048] Specifically, the control strategy includes a DC bus power control strategy; the unified power quality conditioner is controlled based on the DC bus power control strategy to adjust the load power quality of the power grid, including the steps of: obtaining DC / DC converter parameters, the DC / DC converter parameters including low-voltage side voltage U1, switching angle frequency w, transformation ratio N, and leakage inductance L; obtaining load voltage U0; obtaining a preset angle of phase shift between the low-voltage side full-bridge of the DC / DC converter and the high-voltage side full-bridge based on the DC / DC converter parameters, load voltage U0 and the angle calculating the power P transmitted from the low-voltage side of the DC / DC converter to the high-voltage side, thereby completing the power quality adjustment of the circuit.

[0049] Specifically, the control strategy includes a DC bus power control strategy; the unified power quality conditioner is controlled based on the DC bus power control strategy to adjust the load power quality of the power grid, including the steps of: obtaining DC / DC converter parameters, the DC / DC converter parameters including low-voltage side voltage U1, switching angle frequency w, transformation ratio N, and leakage inductance L; obtaining load voltage U0; obtaining a preset angle of phase shift between the low-voltage side full-bridge of the DC / DC converter and the high-voltage side full-bridge

[0050] wherein U1 is the low-voltage source full-bridge subunit voltage, w is the switching angle frequency, U0 is the load voltage, N is the transformation ratio of the transformation unit, is the angle of phase shift 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, the control strategy includes a DC bus power control strategy; the unified power quality conditioner is controlled based on the DC bus power control strategy to adjust the load power quality of the power grid, including the steps of: obtaining DC / DC converter parameters, the DC / DC converter parameters including low-voltage side voltage U1, switching angle frequency w, transformation ratio N, and leakage inductance L; obtaining load voltage U0; obtaining a preset angle of phase shift between the low-voltage side full-bridge of the DC / DC converter and the high-voltage side full-bridge

[0052] Specifically, the embodiment provides a preferred implementation, and the control strategy further comprises a DC bus voltage stabilization control strategy of the super capacitor energy storage system; the unified power quality conditioner is controlled based on the DC bus voltage stabilization control strategy of the super capacitor energy storage system, so as to adjust the power quality of the power grid and the load, and the method comprises the following steps: presetting a compensation voltage; when the output of the photovoltaic power generation system is less than or equal to the required energy of the circuit, the super capacitor energy storage system is controlled based on the compensation voltage to stabilize the DC bus voltage, so as to complete the power quality adjustment of the circuit.

[0053] It can be understood that the super capacitor does not have a stable terminal voltage like a storage battery, and the terminal voltage of the super capacitor is shown in the following table. Figure 5 The embodiment shown in the figure connects the photovoltaic power generation system and the super capacitor energy storage system in parallel to the DC bus, controls the photovoltaic power generation system to work in the maximum power point tracking (MPPT) state, fully utilizes the power generation capacity of the photovoltaic system, and keeps the voltage of the DC bus stable by the charge and discharge control of the super capacitor energy storage system.

[0054] It should be noted that, for the foregoing method embodiments, in order to simply describe, they are all expressed as a series of action combinations, but those skilled in the art should know that the present application is not limited to the action sequence described, because according to the present application, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification all belong to preferred embodiments, and the actions and modules involved are not necessarily necessary for the present application.

[0055] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0056] The above are only exemplary embodiments of the present disclosure, and cannot limit the scope of the present disclosure. 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. Those skilled in the art will easily think of the embodiments of the present disclosure after considering the specification and practicing the disclosure herein. The present application is intended to cover any variations, uses or adaptive changes of the present disclosure, which follow the general principles of the present disclosure and include common knowledge or conventional technical means in the technical field not recorded in the present disclosure. The specification and examples are only considered as exemplary, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. A unified power quality conditioner, for regulating power quality between a load and a power supply, characterized in that: comprising a DC bus and a compensation unit and a regulating 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, for compensating load voltage; the DC bus is used for providing compensation energy for the series compensation subunit; the parallel compensation subunit is connected in parallel with the load, for compensating harmonics, three-phase imbalance and reactive current of the load, and for providing voltage support for the DC bus and energy for the series compensation subunit; the regulating unit comprises a super capacitor energy storage system and a photovoltaic power generation system connected in parallel; the super capacitor energy storage system comprises a super capacitor and a first DC / DC converter, for storing energy when the load consumes less power and providing energy when the load consumes more power; the first DC / DC converter is used for converting the voltage of the super capacitor energy storage system and transmitting power to the DC bus; the photovoltaic power generation system comprises a photovoltaic array and a second DC / DC converter, for supplying power to the super capacitor energy storage system and the DC bus; the second DC / DC converter is used for converting the voltage of the photovoltaic power generation system and transmitting power to the DC bus; 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 near the side of the super capacitor and / or the photovoltaic array; the high-voltage source full-bridge subunit is arranged near the side of the DC bus; comprising steps of: S1, obtaining the unified power quality conditioner; S2, obtaining a preset control strategy, and controlling the unified power quality conditioner based on the control strategy to regulate power quality of the power grid and the load. The step of obtaining the unified power quality conditioner in S1 comprises steps of: connecting the series compensator with the power grid through a coupled three-phase transformer between the DC bus and the power supply; connecting the parallel compensator with the power grid through a coupled three-phase transformer between the DC bus and the load; connecting the super capacitor energy storage system and the photovoltaic power generation system in parallel on the DC bus. 4.The unified power quality conditioning method according to claim 3, characterized in that: the control strategy comprises a series compensation subunit control strategy; controlling the unified power quality conditioner based on the series compensation subunit control strategy to regulate power quality of the power grid and the load comprises steps of: obtaining system grid voltage, load voltage and system reference voltage; calculating a voltage difference based on the system grid voltage and the load voltage; performing park transformation on the voltage difference to obtain a d-axis voltage component and a q-axis voltage component; ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The transformer unit is used for transforming the voltage between the low-voltage source full-bridge subunit and the high-voltage source full-bridge subunit, and completing the power transmission from the low-voltage source full-bridge subunit to the high-voltage source full-bridge subunit P ; The power transmitted by the transformer unit P Is: ， wherein, U 1 is the low voltage source full bridge subunit voltage, is the switching angle frequency, U 0 is the load voltage, N is the transformer subunit turns ratio, is the angle of phase shift between the low voltage source full bridge subunit and the high voltage source full bridge subunit, L is the leakage inductance of the transformer subunit.

2. A method of UPQC based on the UPQC device of claim 1, characterized in that, ​ ​ ​ 3. A unified power quality conditioner according to claim 2, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Based on the d-axis voltage component, q-axis voltage component and system reference voltage, the PI proportional integral control is used to accelerate the adjustment, and then the a, b and c three-phase voltages are obtained through the park inverse transformation to generate the SVPWM control signal, so as to drive the series compensation sub-unit to provide power supply voltage for the load, thereby completing the power quality regulation of the power grid.

5. The unified power quality conditioner method according to claim 3, wherein the control strategy comprises a parallel compensation sub-unit control strategy; and the power quality of the power grid and the load is regulated by controlling the unified power quality conditioner based on the parallel compensation sub-unit control strategy, including the steps of: obtaining three-phase current of the power grid; calculating d-axis current component and q-axis current component through a parallel side compensation amount 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 sub-unit to eliminate the influence of load harmonic, three-phase imbalance and reactive current on the power grid, thereby completing the load power quality regulation.

6. The unified power quality conditioner method according to claim 3, wherein the control strategy comprises a DC bus power control strategy; and the power quality of the power grid and the load is regulated by controlling the unified power quality conditioner based on the DC bus power control strategy, including the steps of: obtaining three-phase current of the power grid; calculating d-axis current component and q-axis current component through a parallel side compensation amount 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 sub-unit to eliminate the influence of load harmonic, three-phase imbalance and reactive current on the power grid, thereby completing the load power quality regulation.

7. The unified power quality conditioner method according to claim 3, wherein the control strategy comprises a DC bus voltage stabilization control strategy of a photovoltaic power generation system; and the power quality of the power grid and the load is regulated by controlling the unified power quality conditioner based on the DC bus voltage stabilization control strategy of the photovoltaic power generation system, including the steps of: obtaining a maximum power point of the photovoltaic power generation system; presetting a corresponding output voltage based on the maximum power point; and controlling the photovoltaic power generation system based on the output voltage to stabilize the DC bus voltage and charge the super capacitor energy storage system at a corresponding time, thereby completing the circuit power quality regulation.

8. The unified power quality conditioner method according to claim 7, wherein the control strategy further comprises a DC bus voltage stabilization control strategy of a super capacitor energy storage system; and the power quality of the power grid and the load is regulated by controlling the unified power quality conditioner based on the DC bus voltage stabilization control strategy of the super capacitor energy storage system, including the steps of: presetting a compensation voltage; and controlling the super capacitor energy storage system based on the compensation voltage to stabilize the DC bus voltage when the output of the photovoltaic power generation system is less than or equal to the required energy of the circuit, thereby completing the circuit power quality regulation. ​ ​ ​ ​ ​ obtaining DC / DC converter parameters, the DC / DC converter parameters including low side voltage U 1. switching angle frequency , transformation ratio N , leakage inductance L ; Acquiring load voltage U 0; 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 U 0 and angle , calculating the power transmitted from the low voltage side to the high voltage side of the dc / dc converter P , thus completing the circuit power quality regulation. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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