TWI695986B - Analog power factor AC load system and method - Google Patents

Abstract

An AC load system and method for simulating power factor, including a load simulation circuit, including an adjustable resistance network, an adjustable inductance network, and an adjustable capacitance network, the load simulation circuit is connected to an AC power supply through a wire , Wherein the adjustable resistor network includes at least one resistor, the adjustable inductor network includes at least one inductor, and the adjustable capacitor network includes at least one capacitor. A path switching circuit is connected to the adjustable resistance network, the adjustable inductance network, and the adjustable capacitance network of the load simulation circuit. A control unit selectively selects the adjustable resistance network and the adjustable inductance network of the load simulation circuit through the path switching circuit according to the preset power factor values or resistance, inductance and capacitance values set by a setting unit 3. The adjustable capacitor network is connected to the AC power supply in a series parallel connection.

Description

Analog power factor AC load system and method

The invention relates to an AC electronic load, especially an AC load system and method for simulating power factor.

The AC load simulation device is used to simulate various actual loads in the AC circuit to understand and test the working state of the AC power supply device or power component under a specific load.

Inverter, uninterruptible power supply (UPS) and other actual electrical loads can be divided into resistive, capacitive, inductive, and rectifying loads. Among them, resistive and rectifying loads are the conventional AC electronic load products in the current market. It can be simulated, but the simulation of capacitive and inductive loads is still difficult.

The applicant of the present invention previously proposed an AC load simulation device (invention patent No. I540329) that uses a compensated power supply method to simulate inductive and capacitive loads, in order to solve the positive voltage negative current and negative voltage positive current of the PF power factor of the AC LC , The range of electronic components can not work. However, this method is costly, and is not applicable when the frequency of the power supply to be tested changes or the power supply voltage waveform is not a sine wave.

The main purpose of the present invention is to provide an AC load system that can simulate power factor. The invention adopts passive components and matched control circuits to achieve the purpose of simulating inductive and capacitive loads.

The technical method adopted by the present invention includes a load simulation circuit including an adjustable resistance network, an adjustable inductance network, and an adjustable capacitance network. The load simulation circuit is connected to an AC power supply through a wire, wherein the The adjustable resistor network includes at least one resistor, the adjustable inductor network includes at least one inductor, and the adjustable capacitor network includes at least one capacitor. A path switching circuit is connected to the adjustable resistance network, the adjustable inductance network, and the adjustable capacitance network of the load simulation circuit. A control unit is based on the preset power factor value and current value or resistance, inductance, and capacitance values set by a setting unit. The preset power factor value and current value are essentially the result of the load's resistance, inductance, and capacitance , The two are in an equivalent relationship. The path switching circuit selectively connects the adjustable resistance network, the adjustable inductance network, and the adjustable capacitance network of the load simulation circuit to the series in parallel AC power.

In a preferred embodiment, the present invention further includes a power factor detection circuit, connected between the AC power supply and the load simulation circuit, for detecting the voltage value of the AC power supply and the current value through the wire, and according to the voltage Value and current value to calculate a measured power factor value; a discrimination circuit connected to the power factor detection circuit for receiving and discriminating at least one error value between the measured power factor and the preset power factor value, and the at least one The error value is transmitted to the control unit. The control unit controls the plurality of switching units of the path switching circuit according to the error value to adjust the series-parallel type of the adjustable resistance network, the adjustable inductance network, and the adjustable capacitance network of the load simulation circuit To adjust the load simulation circuit to meet the preset power factor value.

In a preferred embodiment, the power factor detection circuit includes: a voltage detection circuit connected across the wire to detect the voltage value of the AC power supply; an analog-to-digital converter connected to the voltage detection circuit to generate A digital type of the voltage value; a current detection element connected in series to the wire; a current detection circuit connected to the current detection element to detect the current value passing through the wire; an analog-to-digital converter connected to The current detection circuit generates a digital type of the current value; a calculation unit is connected to the voltage detection circuit and the current detection circuit to calculate the measured power factor value according to the received digital type of the voltage value and the digital current value .

In a preferred embodiment, the at least one resistance in the adjustable resistance network includes at least one resistance element or one of electronic loads operating in a constant resistance mode or a constant current mode of the electronic load.

In terms of effect, the present invention can be widely used in various resistive, capacitive, and inductive tests. The invention is also applicable to the testing of rectifying loads (that is, components such as rectifying circuits, filter capacitors, etc. are included in the power circuit of electronic products). The invention is also applicable to various non-sine wave or frequency change (frequency conversion) test applications.

The specific technology adopted by the present invention will be further described by the following embodiments and accompanying drawings.

Please also refer to FIG. 1, which shows a circuit block diagram of the AC power load system and the analog power factor of the present invention. The analog power factor AC load system of the present invention includes a load simulation circuit 1, which is connected to an AC power source ACV via a pair of wires W1 and W2. The load simulation circuit 1 can be composed of an adjustable resistance network R, an adjustable inductance network L, and an adjustable capacitance network C.

A path switching circuit 2 includes a plurality of switching units connected to the adjustable resistance network R, the adjustable inductance network L, and the adjustable capacitance network C of the load simulation circuit 1, respectively.

A control unit 3 is connected to the adjustable resistance network R, the adjustable inductance network L, and the adjustable capacitance network C in the load simulation circuit 1 through the path switching circuit 2. A setting unit 4 is connected to the control unit 3 for the user to set a preset power factor value PF1, load current value I1 of the load simulation circuit 1 or resistance, inductance, and capacitance setting values.

The control unit 3 selectively selects the adjustable resistance network R and the adjustable inductance network of the load simulation circuit 1 through the path switching circuit 2 according to the preset power factor value PF1 and the load current value I1 set by the setting unit 4 L. The adjustable capacitor network C is connected to the AC power supply ACV in a series connection to form an AC load circuit that conforms to the preset power factor value PF1 and load current value I1.

A power factor detection circuit 5 is connected between the AC power source ACV and the load simulation circuit 1 for detecting the voltage value V between the wires W1 and W2 and the current value I passing through the wires W1 and W2, and according to the voltage value V, The current value I and the power value W of the AC power supply calculate a measured power factor value PF2, PF2=W/VI.

A discriminating circuit 6 can receive and discriminate the error value E between the measured power factor value PF2 measured by the power factor detection circuit 5 and the preset power factor value PF1 set by the setting unit 4, and transmit the error value E To control unit 3.

The control unit 3 selectively controls the adjustable resistance network R and the adjustable inductance network L of the load simulation circuit 1 through the path switching circuit 2 according to the preset power factor value PF1 and the load current value I1 set by the setting unit 4 In addition to the adjustable capacitor network C, the corresponding switching unit of the path switching circuit 2 is also controlled according to the error value E generated by the discrimination circuit 6 to adjust the adjustable resistance network R and the adjustable inductance network of the load simulation circuit 1 Series L and series of the adjustable capacitor network C, until the load simulation circuit 1 accurately matches the power factor value and load current value preset by the user.

In addition to inductance and capacitance, a series equivalent resistance Rs will be added as needed. The series equivalent resistance Rs is the equivalent resistance of the wire, fuse, switch, EMI filter and connector output from the AC power supply (such as UPS or Inverter) to the input of the electrical equipment in actual application. This series equivalent resistance Rs is the simulation Actual equivalent resistance value.

The aforementioned adjustable resistor network R can adopt an electric load simulated load operating in an electronic load in constant resistance mode (CR Mode) or constant current mode (CC Mode), and can also use one or more built-in resistance elements to form an adjustable resistance Network R. The adjustable inductance network L is the equivalent inductance value of the simulated actual load (such as motor, compressor, vacuum cleaner, air conditioner, washing machine, refrigerator, etc.). One or more inductance elements are built into the adjustable inductance network L. The adjustable capacitor network C is an equivalent capacitor that simulates the actual inductance load, because the actual load of the motor or compressor will change, and the power factor adjustment is adjusted to more than -0.8 or more when the load is heavy, so when the air is empty It will become capacitive when loaded or lightly loaded. At this time, the current will lead the voltage, so there is capacitive. One or more capacitive elements are built into the adjustable capacitor network C.

Basically, the range of inductance and capacitance impedance depends on the load, for example, inductive load or capacitive load is 50% of the load, and the other 50% is electronic load or resistive load. Such a power factor value of 45 degrees can reach approximately +0.707~ -0.707, to meet the actual capacitive and inductive load requirements. If you want a larger power factor range, you need to parallel resistance, inductance, and capacitance modules, which can be achieved.

In addition to the built-in one or more resistors, inductors, and capacitors, the load simulation circuit 1 can also add customer-defined parallel or series amplification inductors and capacitors. If it is insufficient, the required resistance can be amplified. , Inductance, capacitance module.

FIG. 2A shows an embodiment of the adjustable resistance network R in FIG. 1, which includes a plurality of resistors R1, R2, R3...Rn and a plurality of switching units S11, S12, S13...S1n. The switching units S11, S12, S13...S1n are respectively connected in series to the respective resistors R1, R2, R3...Rn. Therefore, when the closed and open circuits of the switching units S11, S12, S13...S1n are controlled, a plurality of resistors R1, R2, R3...Rn can be formed into an adjustable resistance network R having a desired resistance value. In the adjustable resistance network R, an amplification resistor pin Rext and an amplification switching unit S1ext can be reserved to facilitate the addition of the required amplification resistance.

FIG. 2B shows a schematic diagram of an embodiment of the adjustable resistance network R in FIG. 1 adopting a constant resistance mode of electronic load operation. FIG. 2C shows a schematic diagram of an embodiment of the adjustable resistor network R in FIG. 1 adopting a constant current mode of electronic load operation.

FIG. 3 shows an embodiment of the adjustable inductance network L in FIG. 1, which includes a plurality of inductors L1, L2, L3...Ln and a plurality of switching units S21, S22, S23...S2n. The switching units S21, S22, S23...S2n are connected in series to the inductors L1, L2, L3...Ln in series and then connected in parallel. Therefore, when the closed and open circuits of the switching units S21, S22, S23...S2n are controlled, a plurality of inductances L1, L2, L3...Ln can be formed into an adjustable inductance network L with a desired inductance value. An adjustable inductance pin Lext and an amplification switching unit S2ext can be reserved in the adjustable inductance network L, so as to add the required amplification inductance.

FIG. 4 shows an embodiment of the adjustable capacitor network C in FIG. 1, which includes a plurality of capacitors C1, C2, C3...Cn and a plurality of switching units S31, S32, S33...S3n. The switching units S31, S32, S33...S3n are connected in series to the respective capacitors C1, C2, C3...Cn and then connected in parallel. Therefore, when the closed and open circuits of the switching units S31, S32, S33...S3n are controlled, a plurality of capacitors C1, C2, C3...Cn can be formed to form an adjustable capacitor network L with a required capacitance value. In the adjustable capacitor network L, an amplification capacitor pin Cext and an amplification switching unit S3ext can be reserved to facilitate the addition of the required amplification capacitor.

FIG. 5 shows an embodiment of the series equivalent resistance Rs in FIG. 1, which includes a plurality of equivalent resistances Rs1, Rs2, Rs3...Rsn and a plurality of switching units S40, S41, S42, S43...S4n. Therefore, when the closed and open circuits of the switching units S41, S42, S43...S4n are controlled, the series equivalent resistance Rs of the required resistance value can be formed by a plurality of equivalent resistances Rs1, Rs2, Rs3...Rsn. When the switching unit S40 is closed, the series equivalent resistance Rs at this time is zero. An amplifier series equivalent resistance pin Rsext and an amplifier switching unit S4ext can be reserved in the series equivalent resistance Rs to facilitate the addition of the required amplifier series equivalent resistance.

The control unit 3 can calculate the required resistance value, inductance value, and capacitance value according to the load current value and the power factor value. Taking the power factor value PF=0.707 as an example, R=XC, PF=-0.707, R=XL, then according to the frequency and formula XL=2πfL, XC=1/2πfC, the inductance value, capacitance value and resistance value can be calculated .

The control unit 3 can control each switching unit S11, S12, S13...S1n, S21, S22, S23...S2n, S31, S32, S33... according to the calculated inductance value, capacitance value and resistance value The closed and open circuits of S3n, S41, S42, S43...S4n, thus the resistance R1, R2, R3...Rn, inductance L1, L2, L3...Ln, capacitor C1, C2, C3...Cn , Equivalent resistance Rs1, Rs2, Rs3...Rsn combined into various series and parallel circuits that meet the required resistance value, inductance value, capacitance value and power factor value, can achieve inductive and capacitive power simulation Factor AC load.

The aforementioned series-parallel circuit can be, for example, resistance and inductance in parallel, resistance and inductance in series, resistance and capacitance in parallel, resistance and capacitance in series, series equivalent resistance and inductance in series, then in parallel with resistance, series equivalent resistance and inductance and resistance Various types such as series, series equivalent resistance and capacitance are connected in series and then connected in parallel with resistance, series equivalent resistance and capacitance and resistance in series...etc.

The present invention is to combine the load of the electric analog load (or actual resistance element) with the adjustable inductance network L and the adjustable capacitance network C, and the power factor detection circuit to achieve the inductive load and the capacitive load Power factor simulation can be used to test and verify whether the output capacity of Inverter or UPS is stable, sufficient and can operate normally under the load conditions of different electrical equipment with different power factors.

6 shows a further circuit diagram of the power factor detection circuit 5 in FIG. 1, which includes a voltage detection circuit 51, an analog-to-digital converter 52, a calculation unit 53, a current detection element 54, a current detection circuit 55, an analog To digital converter 56. The voltage detection circuit 51 is connected across the AC power source ACV and can be used to detect the voltage value V between the wires W1 and W2. After the voltage value V is analogized to the digital converter 52, a digital voltage value is generated to the calculation unit 53. The current detection circuit 55 is connected across the two ends of the current detection element 54 and can be used to measure the magnitude of the load current value I. After the current value I is analogized to the digital converter 56, a digital current value is generated to the calculation unit 53.

After receiving the digital type voltage value V and current value I, the calculation unit 53 can calculate the apparent power VI and the average power W according to the voltage value V and the current value I, and then calculate the measured power factor value PF2 accordingly.

Figure 7 shows the control flow chart of the present invention. In conjunction with the circuit design shown in FIGS. 1 to 6, the control flow of the present invention is explained as follows. The control process of the present invention includes the following steps: Step 101: Build a load simulation circuit 1, and connect the load simulation circuit 1 to an alternating current power supply ACV through a wire. The load simulation circuit 1 includes an adjustable resistance network R, an adjustable inductance network L, and an adjustable capacitance network C; Step 102: Connect the load simulation circuit 1 to a control unit 3 through a path switching circuit 2 The path switching circuit 2 includes a plurality of switching units; Step 103: Set a preset power factor value PF1 and load current value I1 or resistance, inductance, capacitance value; Step 104: Control unit 3 according to the preset power factor value PF1 and load current value I1, through the path switching circuit 2 to selectively connect the adjustable resistance network R, the adjustable inductance network L, and the adjustable capacitance network C of the load simulation circuit 1 in series in parallel The type is connected to the AC power source ACV to form an AC load circuit that conforms to the preset power factor value PF1 and load current value I1. The control unit 3 calculates the required resistance value, inductance value, adjustable resistance network R, adjustable inductance network L, adjustable capacitance network C in the load simulation circuit 1 according to the load current value and power factor value Capacitance value. Step 105: Detect the voltage value V of the AC power supply ACV and the current value I through the wire, and calculate a measured power factor value PF2 based on the voltage value V and the current value I; Step 106: Receive and determine the preset power factor The error value E between the value PF1 and the measured power factor value PF2; Step 107: The control unit 3 passes the plurality of switching units of the path switching circuit 2 according to the error value E to adjust the adjustment of the load simulation circuit 1 The series-parallel type of the resistance network R, the adjustable inductance network L, and the adjustable capacitance network C until the measured power factor value PF2 is substantially equal to the preset power factor value PF1.

FIG. 7 shows the control flow chart of the present invention when performing the measurement of the measured power factor value PF2, which includes the following steps: Step 201: A voltage detection circuit 51 is used to detect the voltage value V between the wires W1 and W2; Step 202: The voltage value V generates a digital voltage value through the analog-to-digital converter 52; Step 203: Use a current detection circuit 54 to detect the current value I passing through the wires W1, W2; Step 204: Compare the current value I by analogy The digital-to-digital converter 56 generates a digital type of current value; Step 205: A voltage value and current value of the digital type are received by a computing unit 53, and the measured power factor value PF2 is calculated according to the voltage value and current value; Step 206 : Transmit the measured power factor value PF2 to the control unit 3.

The above-mentioned embodiments are only used to illustrate the present invention, not to limit the scope of the present invention. All other equivalent modifications or replacements completed without departing from the spirit of the present invention should be included in the scope of the patent application described later Inside.

[FIG. 1] A circuit block diagram showing an AC power load simulation system and method of the present invention. [FIG. 2A] An embodiment of the adjustable resistance network R in FIG. 1 is shown. [FIG. 2B] A schematic diagram showing an embodiment of the adjustable resistance network R in FIG. 1 adopting an operation mode of a constant resistance in an electronic load. [FIG. 2C] A schematic diagram of an embodiment of the adjustable resistance network R in FIG. 1 adopting an electronic load constant current mode. [FIG. 3] shows an embodiment of the adjustable inductance network L in FIG. 1. [FIG. 4] An embodiment of the adjustable capacitor network C in FIG. 1 is shown. [FIG. 5] An embodiment of the series equivalent resistance Rs in FIG. 1 is shown. [Figure 6] shows a further circuit diagram of the power factor detection circuit in FIG. [Figure 7] shows the control flow chart of the present invention.

Claims (9)

An AC load system simulating power factor includes: a load simulation circuit including an adjustable resistance network, an adjustable inductance network, and an adjustable capacitance network. The load simulation circuit is connected to an AC power supply through a wire, wherein The adjustable resistor network includes at least one resistor, the adjustable inductor network includes at least one inductor, and the adjustable capacitor network includes at least one capacitor; a path switching circuit, including a plurality of switching units, respectively connected to The adjustable resistance network, the adjustable inductance network and the adjustable capacitance network of the load simulation circuit; a control unit connected to the plurality of switching units in the path switching circuit; a setting unit connected to the The control unit is for the user to set a preset power factor value and load current value or resistance, inductance and capacitance value; wherein the control unit passes the path according to the preset power factor value and load current value set by the setting unit The switching circuit selectively connects the adjustable resistance network, the adjustable inductance network, and the adjustable capacitance network of the load simulation circuit to the AC power supply in a series parallel connection. According to the analog power factor AC load system described in item 1 of the patent application scope, it further includes: a power factor detection circuit connected between the AC power source and the load analog circuit to detect the voltage value of the AC power source and Calculate a measured power factor value based on the current value of the wire and the voltage and current values; a discrimination circuit connected to the power factor detection circuit for receiving and discriminating between the measured power factor and the preset power factor value At least one error value, and transmit the at least one error value to the control unit; the control unit controls the plurality of switching units of the path switching circuit according to the error value to adjust the adjustable resistance network of the load simulation circuit Circuit, the adjustable inductance network, and the series-parallel type of the adjustable capacitance network to adjust the load simulation circuit to meet the preset power factor value. According to the analog power factor AC load system described in item 2 of the patent application scope, wherein the power factor detection circuit includes: a voltage detection circuit connected across the wire to detect the voltage value of the AC power supply; an analogy A digital-to-digital converter connected to the voltage detection circuit to generate a digital version of the voltage value; a current detection element connected in series to the wire; and a current detection circuit connected to the current detection element to detect the voltage passing through the wire The current value; an analog-to-digital converter connected to the current detection circuit to generate a digital type of the current value; a calculation unit connected to the voltage detection circuit and the current detection circuit according to the received digital type of the voltage The value and the digital current value are calculated to obtain the measured power factor value. According to the analog power factor AC load system described in item 1 of the patent application scope, wherein the at least one resistor in the adjustable resistance network includes at least one resistive element or an electronic load operating in a fixed resistance mode of the electronic load or operation One of the electronic loads in constant current mode. According to the analog power factor AC load system described in item 1 of the patent application scope, wherein at least one amplifier resistor pin is reserved in the adjustable resistor network, and at least one amplifier inductor is reserved in the adjustable inductor network The pin position and at least one amplified capacitor pin position are reserved in the adjustable capacitor network. According to the analog power factor AC load system described in item 1 of the patent application scope, it further includes a series equivalent resistance, which is connected in series to the conductor. A method for simulating a power factor AC load, including the following steps: (a) Build a load simulation circuit including an adjustable resistance network, an adjustable inductance network, and an adjustable capacitance network, and load the load The analog circuit is connected to an AC power supply through a wire, wherein the adjustable resistor network includes at least one resistor, the adjustable inductor network includes at least one inductor, and the adjustable capacitor network includes at least one capacitor; (b) The load simulation circuit is connected to a control unit through a path switching circuit. The path switching circuit includes a plurality of switching units; (c) Set a preset power factor value and load current value or resistance, inductance, capacitance value; (d) According to the preset power factor value, the at least one resistance in the adjustable resistance network, the at least one inductance in the adjustable inductance network, and the adjustable capacitance network are selectively selected by the path switching circuit The at least one capacitor is connected to the AC power supply in a series parallel connection. According to the method of simulating power factor AC load as described in item 7 of the patent application scope, the following steps are further included after step (d): (e) Detect the voltage value of the AC power supply and the current value through the wire, and according to The voltage value and current value calculate a measured power factor value; (f) Receive and determine the error value between the preset power factor value and the measured power factor value; (g) According to the error value, the path switching circuit passes the A plurality of switching units to adjust the at least one resistance in the adjustable resistance network of the load simulation circuit, the at least one inductance in the adjustable inductance network, and the at least one capacitance in the adjustable capacitance network Until the measured power factor value is substantially equal to the preset power factor value. According to the method of simulating a power factor AC load as described in item 8 of the patent application scope, step (e) includes the following steps when calculating the measured power factor value: (e1) detecting the voltage between the wires with a voltage detection circuit Voltage value; (e2) A current detection circuit detects the current value passing through the wire; (e3) Calculate the measured power factor value based on the voltage value and the current value; (e4) Transmit the measured power factor value to The control unit.

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