An apparatus and method for simulating different power grid flicker environments

Abstract

The device for simulating different power grid flicker environments of the present invention includes a measurement module, an impedance module, and a reactive power generation module. The three-phase output terminals of the impedance module are connected to the power grid. The reactive power generation module acquires voltage and current signals at the connection point with the power grid via the measurement module. The reactive power generation module generates an inrush current through a power unit, and the impedance module converts the inrush current into an inrush voltage and applies it to its connection point with the power grid. The simulation method of the present invention includes: a) giving a reactive power command; b) calculating and feeding back reactive power; c) reactive power PI regulation; d) active power PI regulation; e) 2 / 3 conversion; g) generating reactive power inrush voltage; h) power grid flicker feedback and adjustment. The device and method for simulating different power grid flicker environments of the present invention can controllably and adjustably issue the required power grid flicker value without affecting the operation of other load equipment under the same power grid.

Description

Technical Field

[0001] This invention relates to an apparatus and method for simulating different power grid flicker environments, and more specifically, to an apparatus and method for simulating different power grid flicker environments that do not affect the power grid and are controllable and adjustable in generating power grid flicker. Background Technology

[0002] With rapid economic development and higher requirements for environmental protection, the reuse of scrap steel has become particularly important. As a result, a large number of nonlinear high-power devices such as electric arc furnaces have entered the power grid, causing various types of power quality pollution, including flicker, during production. This has led to the inability of other electrical load equipment to operate normally, making the issue of power management urgent.

[0003] For relevant power quality management companies, their management equipment usually has to be installed on-site for actual use before its effectiveness in controlling flicker can be observed. If the management effect is poor or even impossible, both users and power generation companies will face incalculable losses. Therefore, if a real-world flicker scenario can be simulated during the early research and development process, the management effect can be better optimized.

[0004] If different flicker values ​​are actually generated on the power grid, it usually requires equipment with a large capacity. In addition, it will also cause great harm to other equipment operating on the power grid. Therefore, simulating a power grid flicker background similar to that of a normal power grid can more intuitively demonstrate the effectiveness of flicker mitigation equipment. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned technical problems, the present invention provides an apparatus and method for simulating different power grid flicker environments.

[0006] The present invention provides a device for simulating different power grid flicker environments, comprising a measurement module, an impedance module, and a reactive power generation module. The three-phase output terminals of the impedance module are connected to the power grid. The measurement module is used to measure the current and voltage signals at the connection point between the impedance module and the power grid. The device is characterized in that: the reactive power generation module consists of a reactive power generation control system and power units, with multiple power units connected in series to form one phase output of the reactive power generation module; the reactive power generation control system is connected to the measurement module via a signal line to obtain the voltage and current signals at the connection point between the impedance module and the power grid; the output terminal of the reactive power generation control system is connected to the control terminal of the power unit to control the power unit to generate an inrush current; the three-phase output terminals of the reactive power generation module are connected to the input terminals of the impedance module, and the impedance module is used to convert the inrush current output by the reactive power generation module into an inrush voltage applied to its connection point with the power grid to simulate different power grid flicker environments.

[0007] The device for simulating different power grid flicker environments of the present invention includes a measurement module consisting of three voltage sensors (PT) and a current sensor (CT).

[0008] The device for simulating different power grid flicker environments of the present invention includes an impedance module that is a three-phase inductor with a certain impedance.

[0009] The present invention provides a device for simulating different power grid flicker environments. The reactive power generation module is equipped with a reactor, and the reactive power generation control system is equipped with a main control DSP chip and a touch screen connected to the main control DSP chip.

[0010] The simulation method for different power grid flicker environments of the present invention is characterized by the following steps:

[0011] a) Given a reactive power command, the tester, based on the grid flicker value to be simulated, gives the reactive power command QrefOut via the touchscreen;

[0012] b) Calculate the feedback reactive power, and the reactive power generation control system obtains its actual output reactive power Q_out;

[0013] c) Reactive power PI regulation: The reactive power command QrefOut is subtracted from the feedback output reactive power Q_out and then PI regulation is performed. The value after PI regulation is multiplied by the reciprocal of the product of the grid voltage acquisition value Vrms and 1.732 to obtain the reactive current command Iq.

[0014] d) Active power PI regulation: For the reactive power generation module to operate normally, it is necessary to control the DC bus voltage of each power unit. Assume that the target value of the DC bus voltage of the given power unit is Cell_Vdc_Ref, and the actual collected value of the DC bus voltage of the power unit is Cell_Vdc. First, the difference between Cell_Vdc_Ref and Cell_Vdc is calculated, and then PI regulation is performed. The value after PI regulation is multiplied by the reciprocal of the product of the grid voltage collected value Vrms and 1.732 to obtain the active current command Ip.

[0015] e). 2 / 3 transformation: Perform the 2 / 3 transformation of reactive current command Iq and active current command Ip as shown in formulas (1) to (5) to obtain the instantaneous values ​​of three-phase current commands Ia_ref, Ib_ref ​​and Ic_ref;

[0016] Alpha = Ip * Cosφ - Iq * Sinβ (1)

[0017] Beta = Iq * Cosφ + Ip * Sinβ (2)

[0018] Ia_ref = Alpha (3)

[0019] Ib_ref ​​= -Alpha * sin (30) + Beta * cos (30) (4)

[0020] Ic_ref = -Alpha * sin (30) - Beta * cos (30) (5)

[0021] Where Alpha and Beta are temporary variables, and φ and β are the angles of the phase-locked loop output;

[0022] f) Reactive current is generated. The reactive current generation control system controls the power unit to generate reactive current of different amplitudes at a specific frequency according to the calculated three-phase current commands Ia_ref, Ib_ref ​​and Ic_ref, and outputs it to the impedance module.

[0023] g) Generate reactive impulse voltage. The impedance module converts the reactive current into voltage fluctuations and inputs them to the power grid to simulate different grid flicker.

[0024] h) Grid flicker feedback and adjustment: The voltage sensor PT and current sensor CT in the measurement module collect voltage and current signals and transmit them to the main control DSP chip in the reactive power generation module. After receiving the voltage and current signals, the main control DSP chip calculates the grid flicker value and transmits it to the touch screen for display. By observing the flicker value displayed on the touch screen, the operator can modify the impact amplitude of the reactive current as needed to adjust and generate different flicker values.

[0025] The beneficial effects of this invention are as follows: The apparatus and method for simulating different power grid flicker environments of this invention are equipped with a measurement module, an impedance module, and a reactive power generation module. The reactive power generation module generates a reactive current with a controllable amplitude at a specific frequency, which is then input to the impedance module. The impedance module converts the input surge current into a surge voltage and inputs it to the power grid to simulate different power grid flicker environments. By manufacturing power grid flicker, the apparatus and method of this invention can actually simulate a power grid flicker background that meets the requirements. At the same time, for different power grid flicker, the corresponding required power grid flicker value can be generated in a controllable and adjustable manner. Furthermore, due to the adjustment of the impedance value in its impedance module, it is not necessary for the reactive power generation module to generate a very large reactive current, and the required equipment size and cost are also lower. In this process, there is no other impact on the power grid actually connected to the device, and it will not affect the operation of other load equipment under the same power grid. Attached Figure Description

[0026] Figure 1 This is a schematic block diagram of the device for simulating different power grid flicker environments according to the present invention;

[0027] Figure 2 This is a circuit diagram of the device for simulating different power grid flicker environments according to the present invention;

[0028] Figure 3 This is a circuit diagram of the power unit in this invention;

[0029] Figure 4 This is a schematic diagram of the PWM drive waveform of a single power unit in this invention;

[0030] Figure 5 This is a schematic diagram of the voltage flicker generation control of the present invention;

[0031] Figure 6 This is a schematic diagram of the reactive power generation mode control of the present invention;

[0032] In the diagram: 1 Measurement module, 2 Impedance module, 3 Reactive power generation module, 4 Power grid, 5 Signal line, 6 Voltage sensor PT and current sensor CT, 7 Three-phase inductor, 8 Reactive power generation control system, 9 Power unit, 10 Reactor. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] This invention proposes a device for simulating different power grid flicker environments. Its feature is that it generates different voltage fluctuations to create impact disturbances at the connection point between the device and the power grid, making the power grid flicker value at the connection point controllable and adjustable. It creates a power grid background similar to the site where the power quality management equipment needs to be treated, so as to generate power grid flicker in a controllable and adjustable manner without affecting the power grid. The device can then be used to observe whether the power quality management effect of the equipment meets the requirements.

[0035] like Figure 1 and Figure 2 As shown, the schematic block diagram and circuit diagram of the device for simulating different power grid flicker environments of the present invention are given respectively. It consists of a measurement module 1, an impedance module 2, and a reactive power generation module 3. The reactive power generation module 3 is used to generate reactive power. The output terminal of the reactive power generation module 3 is connected to the input terminal of the impedance module 2, and the output terminal of the impedance module 2 is connected to the power grid 4. The measurement module 1 is located on the connection line between the impedance module 2 and the power grid 4, and is used to measure the voltage and current signals at the connection point between the impedance module 2 and the power grid 4. The output terminal of the measurement module 1 is connected to the signal acquisition terminal of the reactive power generation module 3 via a signal line 5, so that the reactive power generation module 3 can detect the voltage and current at the connection point between the impedance module 2 and the power grid 4.

[0036] The measurement module 1 shown consists of three sets of voltage sensors (PTs) and current sensors (CTs). The voltage transformers (PTs) convert voltages such as 10,000 volts into 100 volts for use in the voltage coil of a power meter, while the current transformers (CTs) convert large load currents into small currents of less than 5 amps for use in the current coil of a power meter. The reactive power generation module 3 shown consists of a reactive power generation control system 8, a reactor 10, a touch screen, and multiple power units 9. The reactive power generation control system 8 contains a main control DSP chip and is used to acquire the output signals of the voltage sensors (PTs) and current sensors (CTs), and to control the power units 9 to invert and generate the required reactive power (reactive current). The impedance module 2 shown is a three-phase inductor 7 with a certain impedance. The reactive current with a controllable amplitude and frequency output from the reactive power generation module 3 is converted into reactive voltage by the impedance module 2 and input to the power grid 4, simulating different flicker values ​​of the power grid.

[0037] Impedance module 2 is a three-phase inductor with a certain impedance. Impedance module 2 converts the reactive power inrush current generated by the reactive power generator into a voltage inrush, thereby generating different grid flicker values ​​at the connection point between impedance module 2 and grid 1. Reactive power generator module 3 is a device that provides reactive power inrush current at a specific frequency. Reactive power generator module 3 transmits the current to impedance module 2 by emitting inrush current at different rates at a specific frequency, generating different grid flicker values ​​at the connection point of grid 4.

[0038] like Figure 3 As shown, the circuit diagram of the power unit in this invention is given, as follows: Figure 4 The diagram shows a schematic of the PWM drive waveform of a single power unit in this invention. The controllable element in the power unit 9 shown generates the required reactive power output under the action of the pulse signal output by the reactive power generation control system 8.

[0039] like Figure 5 The diagram shown illustrates the voltage flicker generation control of the present invention. Figure 6 A schematic diagram of reactive power generation mode control according to the present invention is provided. The simulation method of the device for simulating different power grid flicker environments according to the present invention is implemented through the following steps:

[0040] a) Given a reactive power command, the tester, based on the grid flicker value to be simulated, gives the reactive power command QrefOut via the touchscreen;

[0041] b) Calculate the feedback reactive power, and the reactive power generation control system obtains its actual output reactive power Q_out;

[0042] c) Reactive power PI regulation: The reactive power command QrefOut is subtracted from the feedback output reactive power Q_out and then PI regulation is performed. The value after PI regulation is multiplied by the reciprocal of the product of the grid voltage acquisition value Vrms and 1.732 to obtain the reactive current command Iq.

[0043] d) Active power PI regulation: For the reactive power generation module to operate normally, it is necessary to control the DC bus voltage of each power unit. Assume that the target value of the DC bus voltage of the given power unit is Cell_Vdc_Ref, and the actual collected value of the DC bus voltage of the power unit is Cell_Vdc. First, the difference between Cell_Vdc_Ref and Cell_Vdc is calculated, and then PI regulation is performed. The value after PI regulation is multiplied by the reciprocal of the product of the grid voltage collected value Vrms and 1.732 to obtain the active current command Ip.

[0044] e). 2 / 3 transformation: Perform the 2 / 3 transformation of reactive current command Iq and active current command Ip as shown in formulas (1) to (5) to obtain the instantaneous values ​​of three-phase current commands Ia_ref, Ib_ref ​​and Ic_ref;

[0045] Alpha = Ip * Cosφ - Iq * Sinβ (1)

[0046] Beta = Iq * Cosφ + Ip * Sinβ (2)

[0047] Ia_ref = Alpha (3)

[0048] Ib_ref ​​= -Alpha * sin (30) + Beta * cos (30) (4)

[0049] Ic_ref = -Alpha * sin (30) - Beta * cos (30) (5)

[0050] Where Alpha and Beta are temporary variables, and φ and β are the angles of the phase-locked loop output;

[0051] f) Reactive current is generated. The reactive current generation control system controls the power unit to generate reactive current of different amplitudes at a specific frequency according to the calculated three-phase current commands Ia_ref, Ib_ref ​​and Ic_ref, and outputs it to the impedance module.

[0052] g) Generate reactive impulse voltage. The impedance module converts the reactive current into voltage fluctuations and inputs them to the power grid to simulate different grid flicker.

[0053] h) Grid flicker feedback and adjustment: The voltage sensor PT and current sensor CT in the measurement module collect voltage and current signals and transmit them to the main control DSP chip in the reactive power generation module. After receiving the voltage and current signals, the main control DSP chip calculates the grid flicker value and transmits it to the touch screen for display. By observing the flicker value displayed on the touch screen, the operator can modify the impact amplitude of the reactive current as needed to adjust and generate different flicker values.

Claims

1. A simulation method for a device simulating different power grid flicker environments, the device simulating different power grid flicker environments includes a measurement module (1), an impedance module (2), and a reactive power generation module (3). The three-phase output terminal of the impedance module is connected to the power grid (4). The measurement module is used to measure the current and voltage signals at the connection point between the impedance module and the power grid. The reactive power generation module is composed of a reactive power generation control system (8) and a power unit (9). Multiple power units are connected in series to form one phase output of the reactive power generation module. The reactive power generation control system is connected to the measurement module via a signal line (5) to obtain the voltage and current signals at the connection point between the impedance module and the power grid. The output terminal of the reactive power generation control system is connected to the control terminal of the power unit to control the power unit to generate an inrush current. The three-phase output terminal of the reactive power generation module is connected to the input terminal of the impedance module. The impedance module is used to convert the inrush current output by the reactive power generation module into an inrush voltage and apply it to the connection point between the module and the power grid to realize different flicker simulations of the power grid. The measurement module (1) consists of three voltage sensors PT and a current sensor CT (6). The reactive power generation module (3) is equipped with a reactor (10), and the reactive power generation control system (8) is equipped with a main control DSP chip and a touch screen connected to the main control DSP chip. Its features are, The simulation method for devices simulating different power grid flicker environments is achieved through the following steps: a) Given a reactive power command, the tester, based on the grid flicker value to be simulated, gives the reactive power command QrefOut via the touchscreen; b) Calculate the feedback reactive power, and the reactive power generation control system obtains its actual output reactive power Q_out; c) Reactive power PI regulation: The reactive power command QrefOut is subtracted from the feedback output reactive power Q_out and then PI regulation is performed. The value after PI regulation is multiplied by the reciprocal of the product of the grid voltage acquisition value Vrms and 1.732 to obtain the reactive current command Iq. d) Active power PI regulation: The reactive power generation module needs to control the DC bus voltage of each power unit to operate normally. Suppose the target value of the DC bus voltage of the given power unit is Cell_Vdc_Ref, and the actual collected value of the DC bus voltage of the power unit is Cell_Vdc. First, the difference between Cell_Vdc_Ref and Cell_Vdc is calculated, and then PI regulation is performed. The value after PI regulation is multiplied by the reciprocal of the product of the grid voltage collected value Vrms and 1.732 to obtain the active current command Ip. e). 2 / 3 transformation: Perform the 2 / 3 transformation of reactive current command Iq and active current command Ip as shown in formulas (1) to (5) to obtain the instantaneous values ​​of three-phase current commands Ia_ref, Ib_ref ​​and Ic_ref; Alpha = Ip * Cosφ - Iq * Sinβ (1) Beta = Iq * Cosφ + Ip * Sinβ (2) Ia_ref = Alpha (3) Ib_ref ​​= -Alpha * sin (30) + Beta * cos (30) (4) Ic_ref = -Alpha * sin (30) - Beta * cos (30) (5) Where Alpha and Beta are temporary variables, and φ and β are the angles of the phase-locked loop output; f) Reactive current is generated. The reactive current generation control system controls the power unit to generate reactive current of different amplitudes at a specific frequency according to the calculated three-phase current commands Ia_ref, Ib_ref ​​and Ic_ref, and outputs it to the impedance module. g) Generate reactive impulse voltage. The impedance module converts the reactive current into voltage fluctuations and inputs them to the power grid to simulate different grid flicker. h). Grid flicker feedback and adjustment: The voltage sensor PT and current sensor CT in the measurement module will collect the voltage and current signals and transmit them to the main control DSP chip in the reactive power generation module. The main control DSP chip calculates the grid flicker value after receiving voltage and current signals and transmits it to the touch screen for display. By observing the flicker value displayed on the touch screen by the reactive power generation module, the operator can modify the impact amplitude of the reactive current as needed to adjust the generation of different flicker values.

2. The simulation method of the device for simulating different power grid flicker environments according to claim 1, characterized in that: The impedance module (2) is a three-phase inductor (7) with a certain impedance.

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