Two-stage module power supply with power fluctuation stabilizing function

Abstract

A direct-current power supply system has many advantages, but due to a large number of power electronic equipment in a pulse power supply mode, the pulse working mode of the power electronic equipment enables input power of a power supply side to fluctuate between a no-load state and a full-load state, and the stability and the service life of the power supply system and the power electronic power supply system are seriously affected. The invention provides a two-stage module power supply with a power fluctuation stabilizing function in order to solve the power fluctuation suppression problem of a power supply system under the pulse load condition of an inverter welding machine, a phased array radar and the like in a direct-current power supply system (such as a direct-current micro-grid and a small direct-current power distribution network). An advanced power fluctuation suppression algorithm is adopted, the stability and the service life of a direct current power supply system and a power electronic power supply system under the pulse load condition are greatly improved, and meanwhile the requirement for an energy storage capacitor is lowered.

Description

Technical Field

[0001] The invention belongs to the field of electrical engineering, and in particular relates to a two-stage module power supply with a power fluctuation smoothing function. Background Art

[0002] With the development of power electronics technology, the system power of power electronic equipment has gradually increased, and the working mode of pulse loads has become more complicated. In particular, pulse width loads such as inverter welding machines and weather radars cause large fluctuations in the input power of power electronic systems, which has a serious impact on the frequency and voltage stability of conventional AC power supply systems. The DC power supply system connects the power generation device, energy storage system, and load in the form of DC distribution. In terms of power quality, the DC power supply system does not have the problems of reactive circulating current and frequency deviation of the AC system, and has better power quality; in terms of operation control, the DC power supply system does not have to consider the synchronization problem between the power generation devices, and it is easier to achieve circulating current suppression and power balance. The DC power supply system has many advantages, but due to a large number of power electronic equipment in pulse power supply mode, its pulse working mode causes the input power on the power supply side to fluctuate between no-load and full-load, which seriously affects the stability and service life of the power supply system and the power electronic power supply system. Therefore, it is necessary to suppress the power fluctuation of the DC power supply system. Summary of the invention

[0003] In order to solve the problem of power fluctuation suppression of power supply systems under pulse load conditions such as inverter welding machines and phased array radars in DC power supply systems (such as DC microgrids and small DC distribution networks), the present invention proposes a two-stage modular power supply with power fluctuation suppression function. For the DC power supply system, a two-stage power supply architecture is used and an advanced power fluctuation suppression algorithm is adopted, which greatly improves the stability and service life of the DC power supply system and the power electronic power supply system under pulse load conditions, while reducing the demand for energy storage capacitors.

[0004] like Figure 1 As shown, the two-stage module power supply with power fluctuation smoothing function of the present invention adopts a two-stage module power supply architecture with power fluctuation suppression function, including DC power distribution, two-stage power supply module, intermediate bus energy storage capacitor C 1 , load side energy storage capacitor C 2 And the pulse load equivalent resistance R 1 The two-stage power module consists of an input-series output-parallel (ISOP) full-bridge converter with power fluctuation suppression function at the front stage and a BUCK converter with peak power supply at the back end. DC power can be provided by rectified AC mains power or directly by a DC microgrid composed of photovoltaics, batteries, etc. After passing through the two-stage power module, DC power provides a stable working voltage for pulse loads.

[0005] The ISOP full-bridge converter mainly consists of two parts: one is the hardware circuit part, including the main power part, signal conditioning circuit, protection circuit, ARM core circuit and drive signal level conversion circuit, etc. The main power part includes two cascaded full-bridge converters. Each full-bridge converter consists of a full-bridge inverter circuit, a DC blocking capacitor, a transformer, a full-wave rectifier circuit, a filter inductor, a filter capacitor, etc. Figure 2 As shown; the second is the program software part, including sampling value conversion, state judgment, software protection, soft start, power fluctuation suppression, current loop calculation, PWM update, working time reporting, power state reporting, remote control switch, current limit value setting, other communication functions, etc. The ISOP full-bridge converter software is composed of Figure 3 shown.

[0006] The main power part of the ISOP full-bridge converter consists of two identical full-bridge converters, each of which includes four switch tubes S 1 -S 4 , 1 DC blocking capacitor C g , 1 transformer T 1 , two rectifier diodes D 1 ~D 2 , a filter inductor L s , a filter capacitor C s . D s1 -D s4 They are switch tube S 1 -S 4 The body diode of 1 and S 3 The D pole of S is connected together with the positive pole of the input voltage. 2 and S 4 The S pole of the input voltage is connected together with the negative pole, S 1 The S pole is connected to S 2 The D pole, S 3 The S pole is connected to S 4 The D pole. 1 The S pole is connected to C g One side, C g The other side of the transformer is connected to the same-name terminal on the input side of the transformer, and the opposite-name terminal of the transformer is connected to S 3 The two windings of the transformer output, the opposite-name end of winding 1 and the same-name end of winding 2 are connected to the filter capacitor C s The negative pole, the same-name end of winding 1 and the opposite-name end of winding 2 are respectively connected through the rectifier diode D 1 , D 2 Then connect to the filter inductor L s , filter inductor L s The other end is connected to the filter capacitor C sPositive. The control part first detects the output voltage and output current of the main power part, and then sends the relevant information to the ARM core circuit through signal conditioning and hardware protection circuits. The software program in the ARM completes the control algorithm and outputs the PWM signal. The drive signal level conversion circuit mainly includes level conversion and isolation drive circuit, which converts the low-voltage and low-power PWM signal output by the ARM into the isolated and high-power drive signal required by the switch tube.

[0007] The ISOP full-bridge converter software is composed of the software written in ARM, including sampling value conversion, state judgment, software protection, soft start, power fluctuation suppression, current loop calculation, PWM update, working time reporting, power state reporting, remote control switch, current limit value setting, other communication functions, etc. The system configuration link completes the following tasks: connect the input end to the 25MHz clock signal of the external crystal oscillator, phase-lock and multiply it to the 168MHz system clock; configure the register parameters of peripherals such as timers, AD converters, and CAN communications; the sampling value conversion link in the PWM interrupt program converts the values ​​obtained by AD conversion into actual voltage, current and temperature parameters; the power fluctuation suppression link implements the power fluctuation suppression algorithm, the current loop calculation link completes the current loop calculation, generates a PWM duty cycle signal, and then the PWM update link writes the PWM duty cycle signal into the PWM register to complete the PWM waveform update.

[0008] like Figure 4 As shown in Figure 1, the hardware components of the BUCK converter include the input filter capacitor C f1 , switch tube S 1 and S 2 , filter inductor L f2 and output filter capacitor C f2 . D 1 -D 2 They are switch tube S 1 -S 2 The working principle is similar to that of ordinary Buck: the switch tube S 1 When conducting, S 2 As of the attached Figure 4 (b), current flows through the inductor L f2 , L f2 The upper current increases linearly, and the capacitance C f2 In the charging state, Vin provides power energy to the load; the switch tube S 1 At the end, S 2 Open, as attached Figure 4 (c) The current in the inductor decreases linearly, and the inductor current flows through S 2 In this stage, the energy storage capacitor C f2 Provides energy to the load.

[0009] The beneficial effects of the present invention are

[0010] 1. Reduce the output power fluctuation of the DC power supply system and improve the stability of the power supply system.

[0011] 2. Improve the service life of power electronic power supply system.

[0012] 3. Improve the service life of photovoltaic power generation devices and battery energy storage devices in DC power supply systems.

[0013] 4. Under the same pulse load condition, the two-stage module power supply technology with power fluctuation smoothing function can reduce the capacity of the energy storage capacitor and improve the external characteristics of the power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the power supply architecture for a two-stage power module.

[0015] Figure 2 This is the schematic diagram of the ISOP full-bridge converter.

[0016] Figure 3 This is the software composition diagram of the ISOP full-bridge converter.

[0017] Figure 4 This is the schematic diagram of the BUCK converter.

[0018] Figure 5 This is the control principle diagram of the power fluctuation suppression algorithm.

[0019] Figure 6 Bus voltage (top) and input current (bottom) waveforms.

[0020] Figure 7 This is a partial enlarged view of the bus voltage (top) and input current (bottom) waveforms. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example:

[0023] This embodiment adopts a two-stage module power supply architecture with power fluctuation suppression function, which consists of DC power distribution, two-stage power supply modules, and intermediate bus energy storage capacitor C 1 , load side energy storage capacitor C 2 And the pulse load equivalent resistance R 1The two-stage power module consists of an input-series output-parallel (ISOP) full-bridge converter with power fluctuation suppression function at the front stage and a BUCK converter with peak power supply at the back end. DC power can be provided by rectified AC mains power, or directly by a DC microgrid composed of photovoltaics, batteries, etc. After passing through the two-stage power module, DC power provides a stable working voltage for pulse loads.

[0024] The ISOP full-bridge converter mainly consists of two parts: one is the hardware circuit part, including the main power part, signal conditioning circuit, protection circuit, ARM core circuit and drive signal level conversion circuit, etc. The main power part includes two cascaded full-bridge converters. Each full-bridge converter consists of a full-bridge inverter circuit, a DC blocking capacitor, a transformer, a full-wave rectifier circuit, a filter inductor, a filter capacitor, etc. Figure 2 As shown; the second is the program software part, including sampling value conversion, state judgment, software protection, soft start, power fluctuation suppression, current loop calculation, PWM update, working time reporting, power state reporting, remote control switch, current limit value setting, other communication functions, etc. The ISOP full-bridge converter software is composed of Figure 3 shown.

[0025] like Figure 2 The hardware components of the ISOP full-bridge converter are shown in FIG. 1 , where the main power part consists of two identical full-bridge converters, each of which includes four switch tubes S 1 -S 4 , 1 DC blocking capacitor C g , 1 transformer T 1 , two rectifier diodes D 1 ~D 2 , a filter inductor L s , a filter capacitor C s . D s1 -D s4 They are switch tube S 1 -S 4 The body diode of 1 and S 3 The D pole of S is connected together with the positive pole of the input voltage. 2 and S 4 The S pole of the input voltage is connected together with the negative pole, S 1 The S pole is connected to S 2 The D pole, S 3 The S pole is connected to S 4 The D pole. 1 The S pole is connected to C g One side, C g The other side of the transformer is connected to the same-name terminal on the input side of the transformer, and the opposite-name terminal of the transformer is connected to S3 The two windings of the transformer output, the opposite-name end of winding 1 and the same-name end of winding 2 are connected to the filter capacitor C s The negative pole, the same-name end of winding 1 and the opposite-name end of winding 2 are respectively connected through the rectifier diode D 1 , D 2 Then connect to the filter inductor L s , filter inductor L s The other end is connected to the filter capacitor C s Positive. The control part first detects the output voltage and output current of the main power part, and then sends the relevant information to the ARM core circuit through signal conditioning and hardware protection circuits. The software program in the ARM completes the control algorithm and outputs the PWM signal. The drive signal level conversion circuit mainly includes level conversion and isolation drive circuit, which converts the low-voltage and low-power PWM signal output by the ARM into the isolated and high-power drive signal required by the switch tube.

[0026] like Figure 3 The ISOP full-bridge converter software shown in the figure is composed of software written in ARM, including sampling value conversion, state judgment, software protection, soft start, power fluctuation suppression, current loop calculation, PWM update, working time reporting, power state reporting, remote control on / off, current limit value setting, other communication functions, etc. The system configuration link completes the following tasks: connect the input end to the 25MHz clock signal of the external crystal oscillator, phase-lock and multiply it to the 168MHz system clock; configure the register parameters of peripherals such as timers, AD converters, and CAN communications; the sampling value conversion link in the PWM interrupt program converts the numerical value obtained by AD conversion into actual voltage, current and temperature parameters; the power fluctuation suppression link implements the power fluctuation suppression algorithm, the current loop calculation link completes the current loop calculation, generates a PWM duty cycle signal, and then the PWM update link writes the PWM duty cycle signal into the PWM register to complete the PWM waveform update.

[0027] like Figure 4 The hardware components of the BUCK converter shown in the figure include the input filter capacitor C f1 , switch tube S 1 and S 2 , filter inductor L f2 and output filter capacitor C f2 . D 1 -D 2 They are switch tube S 1 -S 2 The working principle is similar to that of ordinary Buck: the switch tube S 1 When conducting, S 2 As of the attached Figure 4 (b), current flows through the inductor L f2 , Lf2 The upper current increases linearly, and the capacitance C f2 In the charging state, Vin provides power energy to the load; the switch tube S 1 At the end, S 2 Open, as attached Figure 4 (c) The current in the inductor decreases linearly, and the inductor current flows through S 2 In this stage, the energy storage capacitor C f2 Provides energy to the load.

[0028] like Figure 5 The control principle diagram of the ISOP full-bridge converter shown in the figure includes an outer control loop for power fluctuation suppression, an inner current control loop and a PWM modulation module. ref is the voltage reference value, U o is the output voltage of the power fluctuation suppression device, ΔU is U ref with U o The difference, k up is the voltage control proportional coefficient, i ref is the calculated current reference value, i L is the actual value of the current of the output filter inductor Ls, Δi is i ref with i L The difference, k ip is the current control proportional coefficient, k ii is the current control integral coefficient, phase is the calculated phase shift angle, τ is the time constant, s indicates that the formula is in the time domain, P represents the proportional controller, and PI represents the proportional integral controller.

[0029] The control schematic diagram of the ISOP full-bridge converter is as follows: Figure 5 As shown, the power fluctuation suppression loop performs proportional control on the power supply output voltage, which is a static error system. The current set value generated by the voltage proportional control loop is smoothed by a digital low-pass filter to suppress the current fluctuation on the inductor. The control algorithm of the power fluctuation suppression module is as follows:

[0030]

[0031] The inductor current control loop uses a PI regulator, which mainly plays the role of loop compensation in the circuit to ensure that the power supply has good dynamic and steady-state characteristics. The current loop control algorithm is as follows:

[0032]

[0033] The low-pass filter of the power fluctuation suppression module is used to smooth the given value of the inductor current to achieve the effect of smoothing the input power fluctuation. z represents that the formula is in the frequency domain, and the digital filter adopts the forward numerical integration method, that is, s = (z-1) / T, and substitutes it into formula (1) to get:

[0034]

[0035] Where T is the filter sampling period. The z-transformed equation (3) is further converted into a discrete form executable by ARM, where k represents the current moment value and k+1 represents the next moment value.

[0036]

[0037] The digital PI regulator in the current control module mainly plays the role of loop compensation in the digital module power supply, ensuring that the power supply has good dynamic characteristics and steady-state characteristics. The current control loop adopts a position PI controller, and its control law is:

[0038]

[0039] The modulation signal generation module uses a 168MHz clock signal to output an 84kHz PWM signal. Each PWM cycle is accumulated by 2000 clock cycles. When the count value is 0, a new duty signal is loaded to update the PWM of the next cycle.

[0040] The effectiveness of the proposed two-stage module power supply technology with power fluctuation smoothing function is verified by experiments. When working under pulse load, the peak power is 4kW, the cycle is 8ms, and the duty cycle is 25%; the intermediate bus energy storage capacitor is 70000μF, and the filter time constant τ is 1 / 200. The experimental waveform is as follows Figure 6 As shown in the figure, the ISOP full-bridge converter with pulse load waveform: yellow is the input midpoint voltage, purple is the ISOP full-bridge converter output voltage, and green is the ISOP full-bridge converter input current. It can be seen from the test waveform that the power supply input current is stable, and the current fluctuation value is ≤ 20% of the input current.

[0041] Further test the ISOP full-bridge converter output voltage, BUCK converter output voltage and ISOP full-bridge converter input current. The experimental waveforms are as follows: Figure 7 As shown. The BUCK with pulse load waveform, yellow is the ISOP full-bridge converter output voltage; purple is the BUCK converter output voltage; green is the ISOP full-bridge converter input current. From the test waveform, it can be seen that when the pulse load is switched, the BUCK converter output voltage drop value is 0.8V, and the overshoot value is 0.6V; the ISOP full-bridge converter output voltage is a sawtooth wave, and the voltage drop is about 1V; the ISOP full-bridge converter input current is stable.

[0042] The present invention is not limited to the above specific implementations, and the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made to the above implementations based on the technical essence of the present invention shall be included in the protection scope of the present invention.

Claims

1. A two-stage module power supply with power fluctuation smoothing function, characterized in that: It includes DC power distribution, ISOP full-bridge converter, BUCK converter, intermediate bus energy storage capacitor C1, load-side energy storage capacitor C2 and pulse load equivalent resistor R1; wherein, DC power distribution is provided by industrial frequency AC mains after rectification, or directly provided by a DC microgrid composed of photovoltaic and battery, and the DC power is stepped down twice by cascading ISOP full-bridge converter and BUCK converter to provide a stable working voltage for the pulse load; ISOP full-bridge converter has power fluctuation suppression function, and BUCK converter adopts peak power supply mode; intermediate bus energy storage capacitor C1 is connected in parallel between ISOP full-bridge converter and BUCK converter, and load-side energy storage capacitor C2 is connected in parallel between BUCK converter and pulse load equivalent resistor R1.

2. A two-stage modular power supply with power fluctuation smoothing function as claimed in claim 1, characterized in that: The ISOP full-bridge converter includes a main power part and a control part; the main power part includes two cascaded full-bridge converters, each of which includes a full-bridge inverter circuit, a DC blocking capacitor, a transformer, a full-wave rectifier circuit, a filter inductor, and a filter capacitor; the control part includes a signal conditioning circuit, a protection circuit, an ARM core circuit, and a drive signal level conversion circuit.

3. A two-stage modular power supply with power fluctuation smoothing function as claimed in claim 2, characterized in that: The two full-bridge converters in the main power part of the ISOP full-bridge converter are exactly the same. Each full-bridge converter includes 4 switch tubes S1-S4 and 1 DC blocking capacitor C g , 1 transformer T1, two rectifier diodes D1~D2, a filter inductor L s , a filter capacitor C s , diode D s1 -D s4 They are the body diodes of the switch tubes S1-S4 respectively; among them, the D poles of S1 and S3 are connected to the positive pole of the input voltage together, the S poles of S2 and S4 are connected to the negative pole of the input voltage together, the S pole of S1 is connected to the D pole of S2, the S pole of S3 is connected to the D pole of S4; the S pole of S1 is connected to C g One side, C g The other side of the transformer is connected to the same-name terminal of the input side of the transformer T1, and the opposite-name terminal of the transformer T1 is connected to the S pole of S3; the transformer T1 includes two output windings, and the opposite-name terminal of winding 1 and the same-name terminal of winding 2 are connected to the filter capacitor C s The negative pole, the same-name end of winding 1 and the opposite-name end of winding 2 are connected to the filter inductor L through the rectifier diodes D1 and D2 respectively. s , filter inductor L s The other end is connected to the filter capacitor C s positive electrode.

4. A two-stage modular power supply with power fluctuation smoothing function as claimed in claim 2, characterized in that: One end of the signal conditioning circuit, protection circuit and drive signal level conversion circuit in the control part is connected to the main power part, and the other end is connected to the ARM core circuit; the control part first detects the output voltage and output current of the main power part, and then sends the information to the ARM core circuit through the signal conditioning circuit and protection circuit. The ARM core circuit outputs a low-voltage, low-power PWM signal. The drive signal level conversion circuit converts the low-voltage, low-power PWM signal output by the ARM into the isolation, high-power drive signal required by the switch tube, and sends it to the main power part.

5. A two-stage modular power supply with power fluctuation smoothing function as claimed in claim 1, characterized in that: The BUCK converter includes an input capacitor C f1 , switch tubes S1 and S2, filter inductor L f2 and capacitor C f2 , diodes D1-D2 are the body diodes of switch tubes S1-S2 respectively; when switch tube S1 is turned on, S2 is turned off, and the current flows through the filter inductor L f2 , L f2 The upper current increases linearly, and the capacitance C f2 In the charging state, Vin provides power energy to the load; when the switch tube S1 is turned off, S2 is turned on, and the filter inductor L f2 The upper current decreases linearly, and the inductor current continues to flow through the switch tube S2. At this stage, the capacitor C f2 Provides energy to the load.

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