Voltage sag suppression method for diode energy-taking type dynamic voltage restorer

Abstract

The diode energy-taking type dynamic voltage restorer is mainly applied to a distributed voltage sag compensation scene. Because the diode energy-taking type dynamic voltage restorer is easy to generate power reverse transmission during the compensation voltage temporary rising period and further causes the pumping problem of a direct current bus, the device is difficult to apply to the compensation voltage temporary rising scene. According to the method provided by the invention, the defects of the device in the aspect of voltage sag are effectively overcome, and the application scene of the device is further expanded. Besides, according to the method provided by the invention, the device can be flexibly multiplexed to realize reactive power efficient regulation of the power grid in a quick fluctuation scene of a load power factor while realizing voltage sag suppression, so that the utilization rate of the equipment is greatly improved. According to the method, load current and voltage are obtained through a digital controller and a current and voltage sensor, and a load power factor is obtained through calculation. A specific compensation voltage reference is calculated according to the obtained power factor, an output voltage reference of the system is obtained through voltage and current double closed-loop control, and it is guaranteed that a direct-current bus does not pump up. According to the method, the problem that a traditional diode energy-taking type dynamic voltage restorer cannot deal with voltage sag is fundamentally eliminated, the problem of voltage sag caused by equipment switching, power flow reverse transmission and the like of an existing low-voltage power distribution network can be effectively solved, and the method has high applicability and generalization performance.

Description

TECHNICAL FIELD

[0001] The application is suitable for dealing with the harm caused by voltage sag and voltage swell to sensitive load in low-voltage distribution network, can be applied to the low-voltage distribution network scene of the low-cost diode energy type dynamic voltage restorer, and is an effective control strategy for inhibiting DC bus voltage pump-up and load voltage overvoltage. BACKGROUND

[0002] Due to the access of impulse load and fluctuating new energy power electronic equipment, the power system has brought many power quality problems, among which the harm caused by voltage sag and voltage swell to sensitive load is particularly significant. Traditionally, a dynamic voltage restorer containing a super capacitor is used, at this time, the transient energy in the compensation capacitor flows from the grid side to the device side, and is absorbed by the super capacitor. However, the device containing a super capacitor has high cost and poor reliability. Another method is to use a front-end uncontrolled diode rectifier without a super capacitor, but this voltage restorer can only compensate for voltage sag and cannot compensate for voltage swell because it does not have the ability to send energy back. In order to overcome this difficulty, the application proposes a voltage swell suppression strategy for a traditional uncontrolled diode energy type dynamic voltage restorer. SUMMARY

[0003] The diode energy type dynamic voltage restorer voltage swell suppression method provided by the application can prevent the DC bus voltage from being pumped up while meeting the normal power supply of the load voltage. At the same time of inhibiting voltage swell, the load power factor fluctuation scene is flexibly and quickly compensated.

[0004] The purpose of the application is achieved by the following technical solutions:

[0005] A diode energy type dynamic voltage restorer voltage swell suppression method, characterized in that it comprises: measuring the output current of the power conversion circuit according to the current sensor , measuring the thyristor current of the power conversion circuit according to the voltage sensor, measuring the grid voltage , and measuring the output voltage ; The controller is used for receiving current and voltage sensor information, and the grid voltage information is used to indicate whether the dynamic voltage restorer enters the controller voltage swell compensation stage; The controller obtains the load power factor P by a low-pass filter and a power factor calculator according to the measured power conversion circuit thyristor current and load voltage ; The controller obtains the load power factor PThe open-loop voltage reference calculator is used for calculating a compensation voltage reference corresponding to a power factor load ; The output voltage and the output current are measured, and a power converter output voltage P out The load voltage amplitude and the output current are respectively subjected to PI controllers, and a closed-loop compensation voltage reference is obtained through Park transformation ; The output current of the power conversion circuit is measured , and the output current reference compensated by the dynamic voltage restorer is obtained through the proportional-resonant controller ; The output voltage reference and the output current reference are calculated, and the modulation ratio required by the diode energy-taking dynamic voltage restorer to be compensated is obtained through the inner-loop controller ; The compensation voltage control signal of the diode energy-taking dynamic voltage restorer is obtained through the sinusoidal pulse width modulator based on the obtained modulation wave

[0006] The method prevents the DC bus voltage from being pumped up while meeting the normal power supply of the load voltage, and flexibly and quickly compensates the load power factor fluctuation scene while suppressing the voltage temporary rise. The method provides that the digital controller samples the load current and voltage, calculates the load power factor, calculates a specific compensation voltage reference according to the obtained power factor, and simultaneously compensates the power return problem caused by the power factor fluctuation through closed-loop control, thereby fundamentally eliminating the negative effects of the voltage temporary rise of the high-power sensitive load, further solving the problems caused by the voltage temporary rise of the current low-voltage power distribution network and leading to the failure of the power supply equipment, and having high applicability and generalization.

[0007] Compared with the prior art, the technical scheme of the application has the beneficial effects that: 1. The device scheme provided by the application can effectively enable the diode energy-taking dynamic voltage restorer to have the compensation voltage temporary rise capability, quickly compensate the voltage required for failure, and avoid the damage of the sensitive equipment.

[0008] 2. The voltage temporary rise suppression method of the diode energy-taking dynamic voltage restorer provided by the application can effectively cope with the scene of load power factor fluctuation.

[0009] 3. The diode power supply type dynamic voltage restorer voltage transient suppression method provided by the application can effectively suppress the DC bus voltage surge caused by power sending in reverse during compensation. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is an electrical connection structure of a diode power supply type dynamic voltage restorer provided by an embodiment of the application; Figure 2 is a voltage transient system flowchart of a diode power supply type dynamic voltage restorer provided by an embodiment of the application; Figure 3 is a controller block diagram of a diode power supply type dynamic voltage restorer voltage transient method provided by an embodiment of the application; Figure 4 is a flowchart of a diode power supply type dynamic voltage restorer voltage transient method provided by an embodiment of the application; Figure 5 is a voltage transient simulation running effect diagram of a diode power supply type dynamic voltage restorer provided by an embodiment of the application; Figure 6 is a module schematic diagram of a diode power supply type dynamic voltage restorer voltage transient embodiment provided by an embodiment of the application; Figure 7 is a diode power supply type dynamic voltage restorer voltage transient method device schematic diagram provided by an embodiment of the application. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be described in further detail below with reference to the drawings. The specific operation method in the method embodiment can also be applied to the device embodiment or the system embodiment. It should be noted that in the description of the present application, "at least one" means one or more, wherein more means two or more than two. Therefore, in the embodiments of the present application, "more" can also be understood as "at least two". "And / or", which describes the association relationship of the associated objects, means that there can be three relationships, for example, A and / or B, which means that there are three cases of A alone, A and B together, and B alone. In addition, the character " / ", if not specially stated, generally represents that the front and rear associated objects are in an "or" relationship. In addition, it should be understood that in the description of the present application, "first", "second", etc. are used only for the purpose of distinguishing the description, and cannot be understood as indicating or implying relative importance. The following will be further described in detail with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0012] The modular diode power supply type dynamic voltage restorer parallel method and system provided by the application comprises the following steps: Please refer to Figure 1, the electrical connection structure of the diode power supply type dynamic voltage restorer provided by the embodiment of the application comprises: Construct a circuit model as shown in Figure 1, including a controller, power conversion circuit, filter, current sensor, voltage sensor, and load; one end of the converter is connected to the controller, and the other end is connected to the filter through the current sensor and voltage sensor.

[0013] Please refer to Figure 2, a schematic diagram of the implementation process of the voltage spurious rise method for a diode-sourced dynamic voltage restorer, including: Step S201: Measure the grid voltage using the voltage sensor to determine whether a voltage spurt problem has occurred in the grid.

[0014] Step S202: If the system experiences a voltage spurt problem, the controller determines that the load power factor is measured using the load-side voltage and current sensors.

[0015] Step S203: Based on the controller and the measured power factor, the compensation voltage reference vector is calculated by the voltage calculation controller in step S301.

[0016] Please refer to Figure 3, a block diagram of a voltage spur method controller for a diode-sourced dynamic voltage restorer, including: Step S204: Calculate the output voltage and load voltage amplitude of the power converter based on the output current and output voltage received by the controller, and determine the fundamental voltage reference of the converter output through the closed-loop controller of S302.

[0017] Step S205: Based on the converter output voltage reference obtained by the controller and the compensation voltage reference vector obtained in S203, add them together to obtain the system's modulation wave voltage.

[0018] Optionally, step S203 can be implemented by using the thyristor current obtained from the controller. Combined with the measured grid voltage Selective switching determines the reference voltage of the power conversion circuit output fundamental frequency. As shown in equation (2): Step S207: Based on the modulation wave voltage obtained by the controller, the switching signal of the power converter is obtained through sinusoidal pulse width modulation.

[0019] (4) This invention is not limited to the embodiments described above. The above description of specific embodiments is intended to illustrate and explain the technical solutions of this invention. The specific embodiments described above are merely illustrative and not restrictive. Without departing from the spirit and scope of the claims, those skilled in the art can make many specific modifications based on the teachings of this invention, and these modifications all fall within the scope of protection of this invention.

[0020] It should be understood that the size of the step number in the above embodiment does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiment of the application.

[0021] Please refer to Figure 4, the diode energy type dynamic voltage restorer voltage transient method algorithm flow chart; Step one: the controller accepts the measured electrical quantity.

[0022] Step two: obtain the grid phase amplitude through the phase-locked loop algorithm of the second-order generalized integrator.

[0023] Step three: determine whether the amplitude is greater than 1.1pu, if true, go to step four, if not, return to step one.

[0024] Step four: determine the load power factor, if equal to 1, go to step five, if greater than 1, go to step six, if less than 1, go to step 7. Step five: as shown in Figure 3, resistive load control is performed, and open-loop and closed-loop voltage references are calculated.

[0025] Step six: as shown in Figure 3, resistive and inductive load control is performed, and open-loop and closed-loop voltage references are calculated.

[0026] Step seven: as shown in Figure 3, resistive and capacitive load control is performed, and open-loop and closed-loop voltage references are calculated.

[0027] Figure 5 is the actual simulation waveform of the diode energy type dynamic voltage restorer voltage transient, transient compensation under the condition of grid fault, wherein modules 501 to 504 are voltage transient simulation verification, and modules 505 to 508 are voltage transient simulation verification. As shown in module 501, the grid voltage transient occurs at 1.1s, and the voltage is 1.5 times the standard voltage. As shown in module 502, the method ensures the normal power supply of the load. Modules 503 and 504 verify that the method ensures that the DC bus voltage is not pumped up under the load power factor fluctuation scenario.

[0028] The embodiment module is shown in Figure 6, a diode energy type dynamic voltage restorer voltage transient method, comprising: A first obtaining module 601 is configured to obtain grid voltage, converter output current and converter output voltage, thyristor current, and DC bus voltage according to the sensor. A first determining module 602 is configured to obtain grid voltage real-time amplitude and phase angle through the phase-locked loop controller of the second-order generalized integrator according to the voltage sensor, and determine whether the grid voltage has a transient drop or a fault problem.

[0029] The second determination module 603 is configured to control the controller to send real-time power grid information to the upper computer. The second obtaining module 604 is configured to receive the thyristor current according to the controller, and perform thyristor turn-off control and wait for the controller thyristor turn-off signal through the legend 3 closed-loop controller.

[0030] The third determination module 605 is configured to determine the converter output voltage reference through the legend 3 closed-loop controller according to the thyristor current received by the controller.

[0031] The fourth determination module 606 is configured to determine the converter output fundamental current reference based on the converter output voltage measured by the legend 3 according to the converter output voltage reference obtained by the controller.

[0032] The fifth determination module 607 is configured to determine the modulation wave voltage of the converter through the current closed-loop controller according to the determination module 605, the obtaining module 601, and the determination module 606. The third obtaining module 608 is configured to obtain the switching signal of the power converter through the sine pulse width modulation according to the modulation wave voltage determined by the fifth determination module 607.

[0033] Please refer to Fig. 7, which is a hardware structure diagram of a multi-machine parallel compensation of a diode energy type dynamic voltage restorer.

[0034] The diode energy type dynamic voltage restorer can include, but is not limited to, an upper computer configuration screen 701, a controller 702, and a system power circuit 703. Figure 7 The diode energy type dynamic voltage restorer is only an example and does not constitute a limitation of the non-isolated transformer type diode energy type dynamic voltage restorer. It can include more or fewer components than the diagram, or combine certain components, or different components. For example, the service life evaluation terminal device of the power conversion circuit can also include input / output devices, network access devices, buses, etc.

[0035] Exemplarily, the controller 703, the controller 702 can be divided into one or more modules / units stored in the host computer 701 and executed by the controller 703, the controller 702 to complete the embodiments of the present application. The one or more modules / units can be a series of computer program instruction segments capable of completing a specific function, which are used to describe the execution process of the controller 703, the controller 702 in the multi-machine parallel compensation of the diode energy type dynamic voltage restorer. For example, the controller 703, the controller 702 can be divided into a first obtaining module, a first determining module, a second determining module, a second obtaining module, a third determining module, a fourth determining module, a fifth determining module, a third obtaining module, and the functions of each module are as follows: The first obtaining module 601 is configured to obtain the grid voltage, the converter output current and voltage, the thyristor current, and the DC bus voltage according to the sensor. The first determining module 602 is configured to obtain the real-time amplitude and phase angle of the grid voltage through the phase-locked loop controller of the second-order generalized integrator according to the voltage sensor, and determine whether the grid voltage has a temporary drop or a fault problem.

[0036] The second determining module 603 is configured to send the real-time grid information to the host computer by the controller. The second obtaining module 604 is configured to receive the thyristor current by the controller, and perform thyristor turn-off control through the figure 3 closed-loop controller and wait for the controller thyristor turn-off signal.

[0037] The third determining module 605 is configured to determine the converter output voltage reference through the figure 3 closed-loop controller according to the thyristor current received by the controller being 0.

[0038] The fourth determining module 606 is configured to determine the converter output fundamental current reference based on the converter output voltage measured by the figure 3 according to the converter output voltage reference obtained by the controller.

[0039] The fifth determining module 607 is configured to determine the modulation wave voltage of the converter through the current closed-loop controller according to the determining module 605, the obtaining module 601, and the determining module 606. The third obtaining module 608 is configured to obtain the switching signal of the power converter through the sine pulse width modulation according to the modulation wave voltage determined by the fifth determining module 607.

[0040] A hardware structure of a multi-machine parallel compensation of a diode energy type dynamic voltage restorer includes a host computer configuration screen 701, a controller 702, a controller 703, a power circuit 704, and a power circuit 705. Those skilled in the art can understand that Figure 7The hardware structure of the multi-machine parallel compensation of the diode power dynamic voltage restorer is only an example, and does not constitute a limitation of the multi-machine parallel device of the diode power dynamic voltage restorer, and can include more or fewer components than the diagram, or combine certain components, or different components, for example, the life evaluation terminal device of the power conversion circuit can also include an input / output device, a network access device, a bus, etc.

[0041] The controller 702, the controller 703 can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0042] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above-mentioned division of each functional unit and module is exemplified, and in actual application, the above-mentioned functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit, and the integrated unit can be realized in the form of hardware or in the form of software. In addition, the specific names of each functional unit and module are only for easy distinction, and do not limit the protection scope of the present application. The specific working process of the unit and module in the system can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0043] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in a certain embodiment can be referred to the related description of other embodiments.

[0044] Those skilled in the art can understand that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0045] In the embodiments provided by the present application, it should be understood that the disclosed apparatus / terminal device and method can be implemented in other ways. For example, the apparatus / terminal device embodiments described above are merely schematic, and the division of the modules or units is merely a logical function division, and there can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections between the units can be indirect couplings or communication connections through some interfaces, devices or units, and can be electrical, mechanical or in other forms.

[0046] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e. can be located in one place, or can be distributed on a plurality of network units. Some of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0047] In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can exist physically independently, or two or more units can be integrated into one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0048] The integrated module / unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. The computer program can implement the steps of each method embodiment when executed by a processor. The computer program includes computer program code, which can be in the form of source code, object code, executable files or some intermediate forms. The computer readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the contents included in the computer readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunication signals.

[0049] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method for voltage surge suppression in a diode-energized dynamic voltage restorer, characterized by, The application relates to a diode-powered dynamic voltage restorer, which comprises a controller, a power conversion circuit, a filter, a current sensor, a voltage sensor and a switching thyristor. The first end of the power conversion circuit is connected with the output end of the controller and a low-voltage distribution network, the second end of the power conversion circuit is connected with the first end of the current sensor, the second end of the current sensor is connected with the first end of the filter, the second end of the filter is connected with the first end of the switching thyristor, the second end of the switching thyristor is connected with the low-voltage distribution network, the dynamic voltage restorer is connected in series with the alternating-current distribution network, the voltage sensor is arranged at the output end of the power conversion circuit, the first end of the current sensor of the switching thyristor and the second end of the current sensor are connected to the sensitive load side. The application relates to a diode-powered dynamic voltage restorer, which comprises a controller, a power conversion circuit, a filter, a current sensor, a voltage sensor and a switching thyristor.

2. A method for voltage swell mitigation in a diode-energized dynamic voltage restorer, the method comprising: The controller is used for receiving current and voltage sensor information, and the grid voltage information is used for indicating whether the dynamic voltage restorer enters the controller temporary rise compensation stage. According to the current sensor, an output current of the power conversion circuit is measured , a thyristor current , according to the voltage sensor, a grid voltage is measured , an output voltage ; The controller obtains the compensation voltage control signal of the diode-powered dynamic voltage restorer through the sinusoidal pulse width modulator based on the obtained modulation waves. The controller is responsive to the measured power conversion circuit thyristor current , load voltage The load power factor is derived by a low pass filter and a power factor calculator P ; The controller calculates a compensation voltage reference corresponding to the measured power factor load through the open-loop voltage reference calculator P ;​ The output voltage is measured The output current is measured The power converter output voltage is calculated P out ; The load voltage amplitude is respectively passed through a PI controller, and a closed-loop compensation voltage reference is obtained through Park transformation ; The controller derives an output current reference for a dynamic voltage restorer compensation from the measured power conversion circuit output current , through the proportional-resonant controller ; The controller obtains the output voltage reference according to the calculation , and the calculated output current reference ; through the inner loop controller, obtains the modulation ratio that needs to be compensated by the diode energy-harvesting dynamic voltage restorer ; The system output voltage reference value is obtained based on the open-loop and closed-loop voltage references.

3. The method of claim 2, wherein the method further comprises: The controller calculates the open-loop voltage reference through the following formula (1) after judging that the grid voltage has a temporary rise The load voltage The load phase angle is calculated after low-pass filtering When the controller judges that the load is a purely resistive load, the open-loop voltage reference can be calculated through the following formula (1) : (1) wherein is the initial phase of the grid voltage, is the amplitude of the grid in normal state, is the current grid voltage amplitude, when the controller judges that the load is a resistive-inductive load, the open-loop voltage reference can be calculated by the following formula (2) (3) : (2) (3) wherein, DVR output voltage amplitude, when the controller determines that the load is a resistive-capacitive load, the open-loop voltage reference can be calculated by the following formula (4) : (4)。 4. The method of claim 2, wherein the method further comprises: The output voltage The output current The output voltage The output voltage The output voltage The output current The output voltage The output voltage (5) (6) wherein is the amplitude of the load voltage, are the load voltage controller and output power controller PI parameters, respectively, is the load voltage phase. ​ (7) Wherein are the open-loop and closed-loop voltage reference values of the above-mentioned method respectively. Meanwhile, in order to increase the system response speed, the is added to the double-loop controller as a feedforward. Finally, the system output modulation wave is obtained according to the double-loop controller.

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