CN109831093B - Current generating device for realizing power factor compensation in circuit breaker test - Google Patents
Current generating device for realizing power factor compensation in circuit breaker test Download PDFInfo
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Abstract
The invention provides a current generating device for realizing power factor compensation in a breaker test, which comprises a rectifier bridge circuit, a power factor correction circuit, a full-bridge inverter circuit, an LCR filter circuit, a transformer, a double closed-loop PI control circuit and a PID control circuit. The rectifier bridge circuit converts commercial power into direct current; the power factor correction circuit sets the current input by the rectifier bridge circuit to be sinusoidal and have the same phase with the voltage through the double closed loop PI control circuit, and outputs direct current with stable amplitude and small voltage ripple; the PID control circuit acquires sinusoidal current feedback of the circuit breaker as a driving signal; the full-bridge inverter circuit is driven to be conducted through the driving signal to convert the direct current output by the power factor correction circuit into alternating current, and the alternating current is processed by the LCR filter circuit and the transformer to obtain the required power frequency sinusoidal current. By implementing the invention, the input waveform of the rectifier bridge circuit is controlled under the condition of ensuring controllable output current precision, and the power factor compensation control is realized.
Description
Technical Field
The invention relates to the technical field of circuit breaker protection characteristic testing, in particular to a current generating device for realizing power factor compensation in circuit breaker testing.
Background
The circuit breaker is widely applied to system protection, and is the most important device for breaking control and preventing faults such as overload, short circuit, override and the like. When the short circuit condition occurs in the circuit, the circuit breaker generates instantaneous tripping action (disconnection), and the circuit is reliably cut off to protect the safety of the power distribution system. When the circuit is running normally, the main contact is reliably connected with the circuit, and the release of the main contact does not malfunction. The malfunction and the rejection of the circuit breaker can have a great influence on the lines and equipment and even on the personal safety. Therefore, in order to ensure the reliability of the protection characteristics of the circuit breaker, strict protection characteristic detection and verification are required before the circuit breaker is shipped.
The circuit breaker is subjected to protection characteristic test, high precision and instantaneous large current are required, and parameters such as transient response time, transient non-periodic components, waveform distortion and the like of the current generation device need to be accurately controllable. However, due to the influence of factors such as power grid voltage fluctuation, power grid higher harmonic distortion, dynamic test loop impedance change and the like, the generation and control of high-precision instantaneous large current have great challenges.
In the test of current circuit breaker, current generator adopts the solution of autotransformer cooperation step-down transformer mostly, this scheme can obtain the power frequency sinusoidal current of thousands of amperes, but when carrying out instantaneous protection characteristic test, because there is the uncertain problem of closing a floodgate phase angle, make the change of the instantaneous action current value of closing a floodgate at every turn change greatly, the switching-on process in test loop passes through mechanical switch and realizes, the phase angle is undulant great, therefore very easily cause the existence of instantaneous action current non-periodic component, transient response time is long, and current distortion and ripple are great, lead to the malfunction among the circuit breaker testing process easily. In addition, the large-current generator adopting the autotransformer has large volume, is easily influenced by factors such as power grid voltage fluctuation, power grid harmonic waves and the like, and has long current generation time, low detection efficiency and poor equipment robustness.
The method is one of the common methods for detecting the protection characteristic of the circuit breaker by using a discharge circuit or power supply equipment to generate large current, generally, the method utilizes a power electronic technology and designs a corresponding circuit breaker detection power supply as a circuit breaker protection characteristic test device through power conversion, the generated instantaneous current value has no overshoot, small ripple, high precision, short transition time and strong anti-interference performance, and can ensure that the circuit breaker is quickly, accurately and reliably detected. Due to the existence of the rectification link, the input current is seriously distorted and contains a large number of harmonic waves, and the harmonic waves reversely flow into the power grid, so that a large number of reactive power circulation currents appear in the power grid, serious harmonic pollution is caused, the electric energy utilization efficiency is greatly reduced, and the power factor is reduced to 0.5-0.65.
Therefore, the current and power factor combined compensation control method is adopted in the detection process of the protection characteristic of the circuit breaker, the power factor compensation is realized while the accuracy of the test current is guaranteed, and the method has great significance for improving the detection efficiency, accuracy and reliability of the circuit breaker.
Disclosure of Invention
The technical problem to be solved by the embodiments of the present invention is to provide a current generating device for realizing power factor compensation in a circuit breaker test, which can control an input waveform of a rectifier bridge circuit under the condition of ensuring controllable output current precision, so as to achieve the purpose of power factor compensation control.
In order to solve the above technical problems, an embodiment of the present invention provides a current generating device for implementing power factor compensation in a circuit breaker test, which is disposed between an ac voltage source and a circuit breaker, and includes a rectifier bridge circuit, a power factor correction circuit, a full-bridge inverter circuit, an LCR filter circuit, a transformer, a dual closed-loop PI control circuit, and a PID control circuit; wherein,
the rectifier bridge circuit, the power factor correction circuit, the full-bridge inverter circuit, the LCR filter circuit and the transformer are sequentially connected in series, the rectifier bridge circuit is further connected with the alternating current voltage source, and the transformer is further connected with the circuit breaker; the first end and the second end of the double closed loop PI control circuit are connected between the rectifier bridge circuit and the power factor correction circuit, the third end of the double closed loop PI control circuit is connected between the power factor correction circuit and the full-bridge inverter circuit, and the fourth end of the double closed loop PI control circuit is connected with the power factor correction circuit; the PID control circuit is connected with the full-bridge inverter circuit and is also connected between the transformer and the circuit breaker;
the rectifier bridge circuit is used for converting power frequency commercial power input by the alternating current voltage source into direct current and outputting the direct current;
the double closed loop PI control circuit is used for carrying out voltage PI setting on the voltage phase and amplitude of the direct current output by the rectifier bridge circuit and carrying out current PI setting on the current phase and waveform of the direct current output by the rectifier bridge circuit, so that the voltage amplitude of the direct current output by the rectifier bridge circuit is stable and the ripple is small, the current of the alternating current input by the rectifier bridge circuit is a sine wave, the phase of the alternating current is the same as the power frequency commercial power phase of the alternating current voltage source, and the double closed loop PI control circuit is used for controlling and reducing the harmonic wave of the current waveform entering the power factor correction circuit;
the power factor correction circuit is used for correcting the steamed bread wave current output by the rectifier bridge circuit controlled by the double closed-loop PI control circuit to obtain direct current with stable amplitude and small voltage ripple;
the PID control circuit is used for sampling the current sinusoidal current of the circuit breaker and setting the current sinusoidal current to be expected current, and then the current sinusoidal current is used as a driving signal for the full-bridge inverter circuit to be conducted;
the full-bridge inverter circuit is used for converting the direct current output by the power factor correction circuit into alternating current and outputting the alternating current after the full-bridge inverter circuit is driven to be conducted by the driving signal of the PID control circuit;
the LCR filter circuit is used for filtering the alternating current output by the full-bridge inverter circuit to obtain power frequency alternating current required by the transformer;
and the transformer is used for isolating and outputting the obtained power frequency alternating current as power frequency sinusoidal current required by the detection of the protection characteristic of the circuit breaker.
The power factor correction circuit comprises a booster circuit formed by connecting an inductor L1 and a capacitor C1 in parallel, a diode VD and a MOS tube VT; wherein,
one end of the inductor L1 is connected with the positive output end of the rectifier bridge circuit and the second end of the double closed-loop PI control circuit, and the other end of the inductor L1 is connected with the anode of the diode VD and the drain of the MOS transistor VT; one end of the capacitor C1 is connected to the negative electrode of the diode VD, the positive input end of the full-bridge inverter circuit and the third end of the double-closed-loop PI control circuit, and the other end is connected to the source electrode of the MOS transistor VT, the first end of the double-closed-loop PI control circuit, the negative output end of the rectifier bridge circuit and the negative input end of the full-bridge inverter circuit; the grid electrode of the MOS tube VT is connected with the fourth end of the double closed loop PI control circuit;
the double closed loop PI control circuit comprises a voltage error amplifier M1, a multiplier M2, a current error amplifier M3 and a comparator M4; wherein,
one input end of the voltage error amplifier M1 is connected to the negative electrode of the diode VD in the pfc circuit, one end of the capacitor C1, and the positive input end of the full-bridge inverter circuit, and the other input end is connected to a reference voltage source, and the output end is connected to one input end of the multiplier M2; the other input end of the multiplier M2 is connected to one end of the inductor L1 in the power factor correction circuit and the positive output end of the rectifier bridge circuit, and the output end is connected to one input end of the current error amplifier M3; the other input end of the current error amplifier M3 is connected to the source of the MOS transistor VT, one end of the capacitor C1, the negative output end of the rectifier bridge circuit, and the negative input end of the full-bridge inverter circuit, and the output end is connected to one input end of the comparator M4; the other input end of the comparator M4 is connected with a sawtooth wave signal source, and the output end is connected with the grid electrode of the MOS tube VT in the power factor correction circuit.
The alternating voltage source is 220V, and the phase is 0 degree; the output voltage of the power factor correction circuit is 311V, the inductance of the inductor L1 is 0.7mH, and the capacitance of the capacitor C1 is 4.5 mF.
The full-bridge inverter circuit is a double-bridge arm circuit formed by four MOS tubes VT 1-VT 4.
The embodiment of the invention has the following beneficial effects:
the invention introduces the power factor correction circuit controlled by the double closed loop PI control circuit, on one hand, the direct current voltage ripple output by the rectifier bridge circuit is smaller, the amplitude is more stable, on the other hand, the alternating current input by the rectifier bridge circuit is sinusoidal and has the same phase with the input voltage, so that the harmonic wave is reduced, the power factor is improved, the input waveform of the rectifier bridge circuit can be controlled under the condition of ensuring the controllable precision of the output current, and the purpose of power factor compensation control is achieved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.
Fig. 1 is a system structural diagram of a current generating device for implementing power factor compensation in a circuit breaker test according to an embodiment of the present invention;
fig. 2 is a structural connection diagram of a power factor correction circuit and a dual closed-loop PI control circuit in a current generation apparatus for implementing power factor compensation in a circuit breaker test according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the operation of the dual closed loop PI control circuit of FIG. 2;
FIG. 4 is a circuit topology diagram of the power factor correction circuit of FIG. 2;
FIG. 5 is a schematic diagram of the PID control circuit of FIG. 1;
fig. 6 is an application scenario diagram of a current generating apparatus for implementing power factor compensation in a circuit breaker test according to an embodiment of the present invention;
FIG. 7 is a waveform diagram of a peak current of a rectifier bridge circuit in a current generating device without a power factor correction circuit;
FIG. 8 is a diagram of a harmonic waveform carried by a peak current of a rectifier bridge circuit in a conventional current generator without a PFC circuit;
fig. 9 is a graph comparing the same phase waveform of the current and the ac voltage source of the rectifier bridge circuit in the current generating apparatus for power factor compensation in the circuit breaker test according to the embodiment of the present invention;
fig. 10 is a waveform diagram of a harmonic carried by a peak current of a rectifier bridge circuit in a current generating device for implementing power factor compensation in a circuit breaker test according to an embodiment of the present invention after the harmonic is corrected by a power factor correction circuit.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, in the embodiment of the present invention, a current generating device for implementing power factor compensation in a circuit breaker test is disposed between an AC voltage source AC and a circuit breaker T, and includes a rectifier bridge circuit 1, a power factor correction circuit 2, a full-bridge inverter circuit 3, an LCR filter circuit 4, a transformer 5, a dual-closed loop PI control circuit 6, and a PID control circuit 7; wherein,
the rectifier bridge circuit 1, the power factor correction circuit 2, the full-bridge inverter circuit 3, the LCR filter circuit 4 and the transformer 5 are sequentially connected in series, the rectifier bridge circuit 1 is further connected with an alternating current voltage source AC, and the transformer 5 is further connected with a circuit breaker T; a first end a1 and a second end a2 of the double-closed-loop PI control circuit 6 are connected between the rectifier bridge circuit 1 and the power factor correction circuit 2, a third end a3 is connected between the power factor correction circuit 2 and the full-bridge inverter circuit 3, and a fourth end a4 is connected with the power factor correction circuit 2; the PID control circuit 7 is connected with the full-bridge inverter circuit 3 and is also connected between the transformer 5 and the breaker T;
the rectifier bridge circuit 1 is used for converting power frequency commercial power input by an alternating current voltage source AC into direct current and outputting the direct current;
the double closed loop PI control circuit 6 is used for performing voltage PI setting on the voltage phase and amplitude of the direct current output by the rectifier bridge circuit 1 and performing current PI setting on the current phase and waveform of the direct current output by the rectifier bridge circuit 1, so that the voltage amplitude of the direct current output by the rectifier bridge circuit 1 is stable and has small ripple, the current of the alternating current input by the rectifier bridge circuit 1 is a sine wave, the phase of the alternating current is the same as the power frequency commercial power phase of an alternating current voltage source AC, and the double closed loop PI control circuit is used for controlling the current waveform entering the power factor correction circuit 2 and reducing harmonic waves;
the power factor correction circuit 2 is used for controlling the steamed bread wave current output by the rectifier bridge circuit 1 according to the double closed loop PI control circuit 6 to correct and obtain direct current with stable amplitude and small voltage ripple;
the PID control circuit 7 is used for sampling the current sinusoidal current of the circuit breaker T and setting the current sinusoidal current as an expected current to be used as a drive signal for the conduction of the full-bridge inverter circuit 3;
the full-bridge inverter circuit 3 is used for converting the direct current output by the power factor correction circuit 2 into alternating current and outputting the alternating current after being driven and conducted by a driving signal of the PID control circuit 7;
the LCR filter circuit 4 is used for filtering the alternating current output by the full-bridge inverter circuit 3 to obtain the power frequency alternating current required by the transformer 5;
and the transformer 5 is used for isolating and outputting the obtained power frequency alternating current as power frequency sinusoidal current required by the detection of the protection characteristic of the circuit breaker.
It should be noted that the first end a1 and the second end a2 of the double closed-loop PI control circuit 6 are both connected between the rectifier bridge circuit 1 and the power factor correction circuit 2, and are mainly used for collecting the voltage and the current of the direct current output by the rectifier bridge circuit 1 and performing PI setting.
It can be understood that, when the rectifier bridge circuit 1 is externally connected with an AC voltage source AC and then supplies power to the circuit, the rectifier bridge circuit 1 converts the input power frequency commercial power into direct current through an uncontrolled rectifier bridge, and through the power factor correction circuit 2, on one hand, the rectifier bridge circuit 1 converts the direct current output by the rectifier bridge into direct current with smaller ripple and more stable amplitude, and on the other hand, the current of the alternating current input by the rectifier bridge circuit 1 is sinusoidal and has the same phase with the AC input voltage of the AC voltage source, so as to reduce harmonic waves and improve the power factor; the full-bridge inverter circuit 3 converts the direct current output by the power factor correction circuit 2 into alternating current, and finally obtains the required power frequency alternating current at the primary side of the transformer 5 through the LCR filter circuit 4. And the secondary side of the transformer 5 can obtain power frequency sinusoidal large current for detecting the protection characteristic of the circuit breaker by isolating and outputting the power frequency sinusoidal large current through the transformer 5.
In the embodiment of the present invention, the power factor correction circuit 2 reduces the harmonic of the current and improves the power factor by using the dual-closed-loop PI control, that is, the dual-closed-loop PI control circuit 6. At this time, the power factor correction circuit 2 adopts a boost output type circuit structure, the boost output type is used for simple current type control, has the advantages of high PF value, small total harmonic distortion rate and high efficiency, is suitable for power factor correction application occasions in a power range of 75-2000W, and is most widely applied. The control method of the power factor correction circuit 2 is classified into an average current mode, a hysteresis current mode, a peak current mode, and a voltage control mode according to the operation principle of controlling the input current, and the control of the average current mode is finally selected according to the characteristics that the operation frequency of the designed circuit is fixed and the input current is continuous.
In one example, as shown in fig. 2, the power factor correction circuit 2 includes a boost circuit formed by connecting an inductor L1 and a capacitor C1 in parallel, a diode VD, and a MOS transistor VT; wherein,
one end of the inductor L1 is connected with the positive output end of the rectifier bridge circuit 1 and the second end a2 of the double closed loop PI control circuit 6, and the other end is connected with the anode of the diode VD and the drain D of the MOS transistor VT; one end of the capacitor C1 is connected with the cathode of the diode VD, the positive input end of the full-bridge inverter circuit 3 and the third end a3 of the double-closed-loop PI control circuit 6, and the other end is connected with the source S of the MOS transistor VT, the first end a1 of the double-closed-loop PI control circuit 6, the negative output end of the rectifier bridge circuit 1 and the negative input end of the full-bridge inverter circuit 3; the grid G of the MOS tube VT is connected with the fourth end a4 of the double closed loop PI control circuit 6;
the double closed loop PI control circuit 6 comprises a voltage error amplifier M1, a multiplier M2, a current error amplifier M3 and a comparator M4; wherein,
one input end of the voltage error amplifier M1 is connected to the cathode of the diode VD in the power factor correction circuit 2, one end of the capacitor C1 and the full bridge inverter circuit 3,another input terminal and a reference voltage source U0(e.g., 5V) and the output terminal is connected to an input terminal of the multiplier M2; the other input end of the multiplier M2 is connected to both one end of the inductor L1 in the power factor correction circuit 2 and the positive output end of the rectifier bridge circuit 1, and the output end is connected to one input end of the current error amplifier M3; the other input end of the current error amplifier M3 is connected with the source S of the MOS transistor VT, one end of the capacitor C1, the negative output end of the rectifier bridge circuit 1 and the negative input end of the full-bridge inverter circuit 3, and the output end is connected with one input end of the comparator M4; the other input terminal of the comparator M4 and a sawtooth wave signal source I0(e.g. 50mA,100KHz) and the output terminal is connected with the grid G of the MOS transistor VT in the power factor correction circuit 2.
As shown in fig. 3, the control operation principle of the double closed loop PI control circuit 6 that realizes the average current mode will be explained. Specifically, the circuit output voltage is collected as output voltage feedback UoWith a given reference voltage U*Comparing, adjusting the error by PI controller, and comparing the output value with the output voltage U of the rectifier bridge circuitinThe multiplication is performed by a multiplier. The output of the multiplier has the same shape and phase as the input voltage, and is used as the reference value of the direct current of the rectifier bridge circuit to output current I to the rectifier bridge circuitinThe acquisition is carried out and compared with a current reference value, the error value of the acquisition is set by a PI controller and then compared with a sawtooth wave signal so as to output a PWM signal, and the on-off of a power semiconductor switch can be controlled by changing the duty ratio of output pulses of a PWM modulator and passing through a driving circuit, so that the purposes of stabilizing output voltage, making input current sinusoidal and having the same phase with the input voltage are achieved, and the power factor correction is realized.
Meanwhile, as shown in fig. 4, the power factor correction circuit 2 is subjected to the following design requirements:
(1) the power factor correction circuit can be determined according to the input and output voltages and the power of the current generating device:
a. input voltage (220 +/-10%) V and output voltage (311 +/-10%) V; the power is 1500W; the input power frequency is 50HZ, and the working frequency is 100 kHZ.
(2) The magnitude of the inductor L1 will determine the magnitude of the ripple current, so it is related to the peak value of the incoming current supply. In the case of equal input and output power, the peak current maximum is:
the ripple current is typically 20% of the peak current, then
ΔI＝0.2×IL(pk)
Calculating the maximum duty cycle of the circuit:
the value of the boost inductance is then:
(3) the capacitor C1 is designed mainly considering the rated power, the voltage ripple requirement and the output required holding time. The length of the required maintaining time of the system depends on the situation, and the maintaining time of the general output voltage is selected from 15ms to 50ms, which is obtained according to the energy conservation:
where Δ t is the sustain time and α is the output voltage output sustain factor. Then, from the above equation:
in the embodiment of the invention, the full-bridge inverter circuit 3 is a double-bridge arm circuit formed by four MOS transistors VT 1-VT 4, and the output current of the full-bridge inverter circuit 3 is controlled by PID, namely realized by a PID control circuit 7,
as shown in fig. 5, the control operation principle of the PID control circuit 7 for realizing the electric energy conversion will be explained. Specifically, the current sinusoidal current of the circuit breaker is sampled and compared with a given sinusoidal reference current I*And comparing, and setting the error of the two by using a PID controller to obtain a PID control signal. The PID control signal is compared with the sawtooth wave signal to obtain an SPWM signal for controlling the full-bridge inverter circuit 3 to be conducted by four MOS tubes VT 1-VT 4, and the signal enables two pairs of bridge arms of the full-bridge inverter circuit 3 to be conducted alternately through a driving circuit to realize the conversion of electric energy.
In fig. 5, n (t) is a set expected current reference value, y (t) is a current output value of the circuit breaker testing system, e (t) is a deviation signal input to the controller, i.e. a difference value between an actual current output and the current reference value, u (t) is an output control quantity of the controller, and the PID control formula is as follows:
kp, Ti and Td are respectively a proportional coefficient, an integral time constant and a differential time constant.
Fig. 6 is a diagram illustrating an application scenario of a current generating apparatus for implementing power factor compensation in a circuit breaker test according to an embodiment of the present invention. At this time, the AC voltage source AC is 220V, and the phase is 0 °; the output voltage of the power factor correction circuit 2 is 311V, the inductance of the inductor L1 is 0.7mH, and the capacitance of the capacitor C1 is 4.5 mF.
In the embodiment of the present invention, as shown in fig. 7 to 10, a current generating device for power factor compensation in a circuit breaker test in the embodiment of the present invention is compared with an existing current generating device without introducing a power factor correction circuit.
In fig. 7, the current waveform is subjected to spectrum analysis for the input peak current of the rectifier bridge circuit when no power factor correction circuit is introduced, and the current harmonic content is as shown in fig. 8, and it can be seen from fig. 8 that the harmonic content is large.
FIG. 9 shows an AC power supply voltage V when a power factor correction circuit is introduced in the embodiment of the present inventionacWith input current I of rectifier bridge circuitacAfter the system is operated for 0.1s, the input current waveform is close to a sine wave and is the same as the input voltage waveform. The current waveform at this time was subjected to spectrum analysis, and the input current harmonic content graph is shown in fig. 10, which is a significant improvement over fig. 8, and the current fundamental component is the largest, and the measured THD was 5.04%, based on the results
Get PF 0.99, see that the simulated system has a higher power factor.
The embodiment of the invention has the following beneficial effects:
the invention introduces the power factor correction circuit controlled by the double closed loop PI control circuit, on one hand, the direct current voltage ripple output by the rectifier bridge circuit is smaller, the amplitude is more stable, on the other hand, the alternating current input by the rectifier bridge circuit is sinusoidal and has the same phase with the input voltage, so that the harmonic wave is reduced, the power factor is improved, the input waveform of the rectifier bridge circuit can be controlled under the condition of ensuring the controllable precision of the output current, and the purpose of power factor compensation control is achieved.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (3)
1. A current generating device for realizing power factor compensation in a breaker test is characterized by being arranged between an alternating current voltage source and a breaker and comprising a rectifier bridge circuit, a power factor correction circuit, a full-bridge inverter circuit, an LCR filter circuit, a transformer, a double closed-loop PI control circuit and a PID control circuit; wherein,
the rectifier bridge circuit, the power factor correction circuit, the full-bridge inverter circuit, the LCR filter circuit and the transformer are sequentially connected in series, the rectifier bridge circuit is further connected with the alternating current voltage source, and the transformer is further connected with the circuit breaker; the first end and the second end of the double closed loop PI control circuit are connected between the rectifier bridge circuit and the power factor correction circuit, the third end of the double closed loop PI control circuit is connected between the power factor correction circuit and the full-bridge inverter circuit, and the fourth end of the double closed loop PI control circuit is connected with the power factor correction circuit; the PID control circuit is connected with the full-bridge inverter circuit and is also connected between the transformer and the circuit breaker;
the rectifier bridge circuit is used for converting power frequency commercial power input by the alternating current voltage source into direct current and outputting the direct current;
the double closed loop PI control circuit is used for carrying out voltage PI setting on the voltage phase and amplitude of the direct current output by the rectifier bridge circuit and carrying out current PI setting on the current phase and waveform of the direct current output by the rectifier bridge circuit, so that the voltage amplitude of the direct current output by the rectifier bridge circuit is stable and the ripple is small, the current of the alternating current input by the rectifier bridge circuit is a sine wave, the phase of the alternating current is the same as the power frequency commercial power phase of the alternating current voltage source, and the double closed loop PI control circuit is used for controlling and reducing the harmonic wave of the current waveform entering the power factor correction circuit;
the power factor correction circuit is used for correcting the steamed bread wave current output by the rectifier bridge circuit controlled by the double closed-loop PI control circuit to obtain direct current with stable amplitude and small voltage ripple;
the PID control circuit is used for sampling the current sinusoidal current of the circuit breaker and setting the current sinusoidal current to be expected current, and then the current sinusoidal current is used as a driving signal for the full-bridge inverter circuit to be conducted;
the full-bridge inverter circuit is used for converting the direct current output by the power factor correction circuit into alternating current and outputting the alternating current after the full-bridge inverter circuit is driven to be conducted by the driving signal of the PID control circuit;
the LCR filter circuit is used for filtering the alternating current output by the full-bridge inverter circuit to obtain power frequency alternating current required by the transformer;
the transformer is used for isolating and outputting the obtained power frequency alternating current as power frequency sinusoidal current required by the detection of the protection characteristic of the circuit breaker;
the power factor correction circuit comprises a booster circuit formed by connecting an inductor L1 and a capacitor C1 in parallel, a diode VD and an MOS tube VT; wherein,
one end of the inductor L1 is connected with the positive output end of the rectifier bridge circuit and the second end of the double closed-loop PI control circuit, and the other end of the inductor L1 is connected with the anode of the diode VD and the drain of the MOS transistor VT; one end of the capacitor C1 is connected to the negative electrode of the diode VD, the positive input end of the full-bridge inverter circuit and the third end of the double-closed-loop PI control circuit, and the other end is connected to the source electrode of the MOS transistor VT, the first end of the double-closed-loop PI control circuit, the negative output end of the rectifier bridge circuit and the negative input end of the full-bridge inverter circuit; the grid electrode of the MOS tube VT is connected with the fourth end of the double closed loop PI control circuit;
the double closed loop PI control circuit comprises a voltage error amplifier M1, a multiplier M2, a current error amplifier M3 and a comparator M4; wherein,
one input end of the voltage error amplifier M1 is connected to the negative electrode of the diode VD in the pfc circuit, one end of the capacitor C1, and the positive input end of the full-bridge inverter circuit, and the other input end is connected to a reference voltage source, and the output end is connected to one input end of the multiplier M2; the other input end of the multiplier M2 is connected to one end of the inductor L1 in the power factor correction circuit and the positive output end of the rectifier bridge circuit, and the output end is connected to one input end of the current error amplifier M3; the other input end of the current error amplifier M3 is connected to the source of the MOS transistor VT, one end of the capacitor C1, the negative output end of the rectifier bridge circuit, and the negative input end of the full-bridge inverter circuit, and the output end is connected to one input end of the comparator M4; the other input end of the comparator M4 is connected with a sawtooth wave signal source, and the output end of the comparator M4 is connected with the grid electrode of the MOS tube VT in the power factor correction circuit;
the MOS tube VT is a P-channel enhanced MOS tube;
e (t) is a deviation signal input into the controller, i.e. the difference between the current actual output and the current reference value, u (t) is the output control quantity of the controller, and the control formula of PID is:
kp, Ti and Td are respectively a proportional coefficient, an integral time constant and a differential time constant.
2. The current generating apparatus for compensating power factor in testing the circuit breaker according to claim 1, wherein the ac voltage source is 220V and has a phase of 0 °; the output voltage of the power factor correction circuit is 311V, the inductance of the inductor L1 is 0.7mH, and the capacitance of the capacitor C1 is 4.5 mF.
3. The current generating apparatus for compensating power factor in testing circuit breaker according to claim 1, wherein the full bridge inverter circuit is a double arm circuit formed by four MOS transistors VT 1-VT 4.
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| CN111239598B (en) * | 2020-01-16 | 2022-07-29 | 温州大学乐清工业研究院 | Device for carrying out online test on protection characteristic of circuit breaker |
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Application publication date: 20190531 Assignee: Shanghai Red Sandalwood Intelligent Technology Co.,Ltd. Assignor: Wenzhou University Contract record no.: X2022330000630 Denomination of invention: A Current Generator for Power Factor Compensation in Circuit Breaker Testing Granted publication date: 20210706 License type: Common License Record date: 20221025 |
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