CN102969928A - Output power adjustment method for resonance type converter - Google Patents

Abstract

Output power regulation method of resonant converter. According to the requirements of the output power of the resonant converter, in the method, when the effective value of the fundamental wave of the output voltage of the inverter is less than or equal to the maximum value of the effective value of the kth harmonic, the maximum k value that meets the requirements is selected, so that The switching frequency is reduced to 1/k of the resonant frequency, so that the k-order harmonic works in a resonant state, and the duty cycle of the output voltage is controlled to adjust the effective value of the k-order harmonic to adjust the output power. The wave component transmits power, and k is a positive odd number. The invention does not need to change the hardware circuit, has a wider power regulation range than the common resonant converter, has smaller switch loss and lower electromagnetic interference.

Description

Output Power Regulation Method of Resonant Converter

technical field

The invention relates to a method for adjusting the output power of a resonant converter.

Background technique

The resonant inverter is the core component of the resonant converter. The resonant inverter relies on the resonance of the inductor and capacitor to make the switching device easy to work under soft switching conditions. Among them, the full-bridge phase-shifted resonant inverter has been widely used in the high-power field. By introducing resonance into the phase-shifted full-bridge converter The inductance, resonant capacitance and dead time enable the switching device to realize zero-voltage turn-on, and have a good regulation effect when the load is heavy. However, under light load conditions that require a small output power, due to the large phase shift angle, it is difficult to achieve zero-voltage turn-on, and the switching loss is large, resulting in a resonant inverter with a wide range of load changes and a wide range of power supply voltage fluctuations. Large occasion performance is greatly affected.

Patent 201110078847.8 discloses a method and device for reducing the switching loss of a phase-shifted full-bridge converter. By providing the best dead time, the switching loss is reduced to a minimum and the soft switching frequency range is expanded. However, the loss at light load is still relatively low. big.

Patent 200610061264.3 discloses a control method of a phase-shifted full-bridge circuit, which enables the circuit to adjust the switching frequency of the inverter through the drive circuit under different loads or make the drive circuit work intermittently to reduce the switching loss at light load. Although the loss is reduced, it does not indicate how to adjust the frequency. At the same time, due to the intermittent operation of the circuit, the load voltage fluctuates greatly.

The problems existing in the existing phase shifting resonant inverter control method are: (1) at light load, the phase shift angle is very large, it is difficult to realize soft switching, and the switching loss is high; (2) at light load, if the drive Circuit gap operation will increase the load voltage fluctuation; (3) At light load, the harmonic content in the inverter output voltage is greater than the fundamental wave content, and the harmonic content in the resonant current is large.

Contents of the invention

The purpose of the present invention is to solve the problems of high loss, large load voltage fluctuation and high harmonic content in the existing high-frequency resonant inverter at light load, and propose a pulse width modulation method using harmonic phase shifting, which can be used in light load When loading, reduce the fundamental frequency of the inverter output voltage, control the harmonic components in the inverter output voltage to work in a resonant state to transmit power, and adjust the output power by controlling the harmonic effective value. The invention is particularly suitable for high-frequency resonant inverter circuits in the field of wireless energy transmission.

The frequency of the output voltage of a typical resonant inverter is the same as the switching frequency of the inverter, and there are abundant harmonics in the output voltage of the inverter, and as the pulse width and frequency of the output voltage of the inverter decrease, the harmonic content accounts for The proportion increased significantly.

The technical solution adopted by the present invention to solve technical problems is as follows:

The present invention does not change the topology structure of the existing main circuit, and adopts a power regulation method. According to the size of the output power, different harmonics in the output voltage of the resonant inverter are respectively operated in the resonant state, and the effective value of the harmonic is controlled to Adjust output power.

The output power adjustment steps are as follows:

1) First, according to the given output power of the resonant inverter, the per-unit value G _k of the fundamental wave and the effective value of each harmonic in the output voltage when the fundamental wave of the output voltage of the resonant inverter works in the resonance state is obtained, k =1, 3, 5, 7..., the per unit value is a reference value based on the effective value of the fundamental wave in the case of a 50% duty cycle of the output voltage waveform of the resonant inverter, and the maximum value of G _k is 1/k; k is a positive odd number;

(k＝1，3，5，7…)，则将开关频率变为谐振频率的1/k，使k次谐波工作在谐振状态；对于半桥式谐振型逆变器，通过调节变流器开关器件驱动脉冲的占空比来调节输出功率，在开关频率为谐振频率时，若占空比小于参考占空比

(k＝1，3，5，7…)，则将开关频率变为谐振频率的1/k，使k次谐波工作在谐振状态；2) When G ₁ ≤ 1/k, k=1, 3, 5, 7..., find the maximum k value that meets the requirements, and control the switching frequency of the resonant inverter to 1/k of the resonant frequency, so that k Subharmonics work in a state of resonance. For a full-bridge phase-shift resonant inverter, the output power is adjusted by adjusting the phase-shift angle of the driving pulse of the diagonal switching device of the converter. When the switching frequency is the resonant frequency, if the phase-shift angle is greater than the reference phase-shift angle

(k=1, 3, 5, 7...), then change the switching frequency to 1/k of the resonant frequency, so that the kth harmonic works in the resonant state; for the half-bridge resonant inverter, by adjusting the current The duty cycle of the driving pulse of the switch device is used to adjust the output power. When the switching frequency is the resonant frequency, if the duty cycle is less than the reference duty cycle

(k=1, 3, 5, 7...), then change the switching frequency to 1/k of the resonant frequency, so that the kth harmonic works in the resonant state;

(k＝1，3，5，7…)。3) When the kth harmonic is working in a resonant state, if G _k ≤ 1/(k+2), k=1, 3, 5, 7..., so that the switching frequency is reduced to 1/(k+ 2) Make the (k+2) harmonic work in a resonant state. For the full-bridge phase-shifting resonant inverter, the range of the reference phase-shifting angle when the kth harmonic is in the resonant state is (k=1, 3, 5, 7...); for the half-bridge resonant inverter, the reference duty ratio range when the kth harmonic works in the resonant state is

(k=1, 3, 5, 7...).

The resonant inverter has a dead time. For the full-bridge phase-shifting resonant inverter, the dead time is equivalent to a certain phase shift angle, and the reference phase shift angle of the kth harmonic should be subtracted from the dead time zone time equivalent phase shift angle; for the half-bridge resonant inverter, the dead zone time is equivalent to the duty cycle of the switching device drive pulse, and the reference duty cycle of the kth harmonic should be subtracted from the dead zone Time equivalent duty cycle;

The power regulation method of the present invention is to reduce the switching frequency of the resonant inverter so that the kth harmonic in the output voltage waveform of the resonant inverter works in a resonant state, that is, the kth harmonic frequency is approximately equal to the resonance Frequency, by controlling the duty ratio of the output voltage waveform of the resonant inverter to adjust the harmonic RMS value of the output voltage waveform of the resonant inverter to realize the adjustment of the output power.

Compared with existing methods, the power regulation method of the present invention has the following characteristics:

1. It can significantly reduce the switching frequency of the inverter, that is, the switching frequency is only 1/k of the original, and the switching loss is greatly reduced;

2. Using harmonic transmission power, under the same output power, the phase shift angle range or duty cycle adjustment range is larger, and the power adjustment accuracy is higher;

3. Using harmonic transmission power, its phase shift angle is smaller, it is easier to work in the soft switching state, and the loss is less;

4. Using harmonic transmission power, the frequency of each harmonic component is also significantly reduced, and the electromagnetic interference is reduced;

5. The driving pulse is continuous, and the load voltage fluctuation is small.

The invention can be applied to various electric energy wireless transmission, induction heating and other possible high-frequency electric energy conversion fields.

Description of drawings

Figure 1 is a topological block diagram of a full-bridge phase-shifting resonant converter;

Figure 2 is a topological block diagram of a half-bridge resonant converter;

Figure 3 is a distribution diagram of the harmonic content of the output voltage of the full-bridge phase-shifting resonant inverter at different phase-shifting angles;

Fig. 4 is a flow chart of a power regulation method for a full-bridge phase-shifting resonant converter;

Figure 5 is the experimental waveform of the output voltage and output current of the inverter when the third harmonic is working in the resonant state with a phase shift of 1.9 degrees;

In the figure, 1 DC power supply, 2 resonant inverter, 3 inverter output sensor, 4 resonant capacitor, 5 inductor, 6 load input sensor, 7 load, 8 drive circuit, 9 frequency and phase detection module, 10 main controller.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Embodiment 1 is a full-bridge phase-shifting resonant inverter structure.

Figure 1 shows the topological block diagram of the full-bridge phase-shifting resonant converter, and its basic composition and connection methods are as follows.

The full-bridge phase-shifting resonant inverter includes: DC power supply 1, resonant inverter 2, inverter output sensor 3, resonant capacitor 4, inductance 5, load input sensor 6, load 7, drive circuit 8 , frequency and phase detection module 9, main controller, etc. 10.

The positive and negative terminals of the DC power supply 1 are respectively connected to the DC input terminals of the resonant inverter 2; the resonant inverter 2 outputs a high-frequency voltage, and the resonant inverter 2 is connected to the two terminals of the resonant capacitor 4 in series or in parallel; The two terminals of the capacitor 4 are connected in series or in parallel with the inductor 5 , and the two terminals of the inductor 5 are connected with the load 7 . An inverter output sensor 3 is provided between the output terminal of the resonant inverter 2 and the resonant capacitor 4. The inverter output sensor 3 includes a voltage sensor and a current sensor, and detects the output voltage and the current sensor of the inverter 2 respectively. Output current. The inverter output voltage and current signals detected by the inverter output sensor 3 are sent to the frequency and phase detection module 9, and the frequency and phase detection module 9 will obtain the frequency signal of the inverter output current and the inverter output voltage The phase difference signal between the output current of the inverter and the output current of the inverter is sent to the main controller 10 . All the signals detected by the inverter output sensor 3 are sent to the main controller 10 . Between the inductance 5 and the load 7 is a load input sensor 6 , including a voltage sensor and a current sensor, which respectively send the detected output voltage and output current signals of the load 7 to the main controller 10 . The main controller 10 sends an inverter driving pulse signal to the driving circuit 8, and the driving circuit 8 is connected to the driving terminals of each switching device of the inverter.

The DC power source 1 may be a DC source obtained by rectifying an AC power source, or may be a DC source such as a storage battery or a capacitor. The DC power supply can be a voltage source or a current source, respectively corresponding to a voltage source inverter and a current source inverter. The structure of the resonant inverter 2 will be described below taking the voltage source inverter as an example.

The resonant inverter 2 has a full-bridge topology, and each switch group in each set of inverter units can be a single device, or multiple devices connected in series or in parallel. The power device in the frequency multiplication circuit of the inverter can be a full-control device such as MOSFET, IGBT, IGCT, etc., and the device can have an anti-parallel freewheeling diode, or an antiparallel freewheeling diode can be added.

The inverter output sensor 3 includes an inverter output voltage sensor and an inverter 2 output current sensor. The inverter output voltage sensor is connected to two output terminals of the inverter 2; the inverter output current sensor is connected in series to one output line of the inverter.

The resonant capacitor 4 can be composed of a single or multiple capacitors; the resonant capacitor 4 can be connected in series, in parallel or in parallel with the inductance 5 .

The inductance 5 may be a single inductance, leakage inductance of a transformer, or equivalent inductance of other circuit structures.

The load input sensor 6 includes a load output voltage sensor and a load output current sensor. The load output voltage sensor is connected to the two output terminals of the resonant inverter 2; the load output current sensor is connected in series to one input line of the load.

The load 7 may be an actual load, or may pass through an equivalent load of other circuit structures.

After the drive circuit 8 processes the drive pulse signal sent by the main controller 10, the output of the drive circuit is connected to each switching device drive terminal of the inverter frequency multiplication circuit to drive each switch of the inverter frequency multiplication circuit device.

The frequency and phase detection module 9 calculates the frequency of the inverter output current and the phase difference between the inverter output voltage and the output current according to the inverter output voltage and output current obtained by the inverter output sensor 3 and Send it to the main controller 10 to realize the closed-loop control of the frequency and phase difference.

The main controller 10 calculates the current output power according to the signals sent by the load input sensor 6 and the inverter output sensor 3, and adjusts the phase shift angle of the resonant inverter. Then judge the phase shift angle and switching frequency. If it is unreasonable, change the switching frequency and calculate the required phase shift angle under the same output power. After dead zone control, a driving pulse signal is formed and sent to the driving circuit 8 .

The steps of the method for adjusting the output power of the full-bridge phase-shifting resonant inverter are as follows:

(k=1,3,5,7...)其中，U_pk为k次谐波电压有效值，U_dc是直流输入侧电压，α为移相角，不同移相角α下的G_k分布如图3所示，因篇幅所限图3中仅显示到9次谐波，其中，“1次”所示的为谐振型逆变器输出电压基波成分有效值的标幺值随移相角的变化，“3次”、“5次”、“7次”和“9次”所示的分别为谐振型逆变器输出电压的3次谐波成分、5次谐波成分、7次谐波成分和9次谐波成分有效值的标幺值随移相角的变化。1) First, according to the given output power of the resonant inverter, the per unit value G _k of the fundamental wave and the effective value of each harmonic in the output voltage when the fundamental component of the output voltage of the resonant inverter works in the resonance state is obtained , k=1,3,5,7..., the per unit value is the reference value of the fundamental effective value under the condition of 50% duty cycle of the output voltage waveform of the resonant inverter, and the maximum value of G _k is 1/ k. _Gk is defined as

(k=1,3,5,7...) Among them, U _pk is the effective value of the kth harmonic voltage, U _dc is the DC input side voltage, α is the phase shift angle, G _k under different phase shift angle α The distribution is shown in Figure 3. Due to space limitations, only the 9th harmonic is shown in Figure 3, where "1st" shows the per unit value of the effective value of the fundamental wave component of the output voltage of the resonant inverter. The change of the phase angle, "3rd", "5th", "7th" and "9th" are respectively the 3rd harmonic component, 5th harmonic component, 7th harmonic component of the output voltage of the resonant inverter The per unit value of the effective value of the sub-harmonic component and the 9th harmonic component varies with the phase shift angle.

(k=1,3,5,7...)，则将开关频率变为谐振频率的1/k，使k次谐波工作在谐振状态。2) When G ₁ ≤ 1/k, k=1, 3, 5, 7..., find the maximum k value that meets the requirements, and control the switching frequency of the resonant inverter to 1/k of the resonant frequency, so that k The subharmonic works in the resonant state, and the output power can be adjusted by adjusting the phase shift angle of the driving pulse of the diagonal switching device of the converter. When the switching frequency is the resonant frequency, if the phase shift angle is greater than the reference phase shift angle

(k=1,3,5,7...), then change the switching frequency to 1/k of the resonant frequency, so that the kth harmonic works in the resonant state.

(k=1,3,5,7...)。3) When the kth harmonic is working in a resonant state, if G _k ≤ 1/(k+2), the switching frequency is reduced to 1/(k+2) of the resonant frequency, so that the (k+2) harmonic The wave works in the resonant state, and the phase shift angle is controlled to adjust the output power. The reference phase shift angle range when the kth harmonic works in the resonant state is

(k=1,3,5,7...).

Embodiment 2: Topological structure of a half-bridge resonant converter.

Fig. 2 is a topological block diagram of a half-bridge resonant converter, which differs from the first embodiment in that: (1) the resonant inverter 2 in the second embodiment is a half-bridge resonant inverter; (2 ) The half-bridge resonant inverter adjusts the output power by adjusting the duty cycle of the driving pulse of the switching device, while the first embodiment adjusts the output power by adjusting the phase shift angle of the resonant inverter.

The steps of the method for adjusting the output power of the half-bridge resonant inverter are as follows:

1) First, according to the given output power of the resonant inverter, the per unit value G _k of the fundamental wave and the effective value of each harmonic in the output voltage when the fundamental component of the output voltage of the resonant inverter works in the resonance state is obtained , k=1,3,5,7..., the per unit value is the reference value of the fundamental effective value under the condition of 50% duty cycle of the output voltage waveform of the resonant inverter, and the maximum value of G _k is 1/ k.

(k=1,3,5,7...)，则将开关频率变为谐振频率的1/k，使k次谐波工作在谐振状态。2) When G ₁ ≤ 1/k, k=1, 3, 5, 7..., find the maximum k value that meets the requirements, and control the switching frequency of the resonant inverter to 1/k of the resonant frequency, so that k The sub-harmonic works in the resonant state, and the output power can be adjusted by adjusting the duty cycle of the driving pulse of the switching device of the converter. When the switching frequency is the resonant frequency, if the duty cycle is less than the reference duty cycle

(k=1,3,5,7...), then change the switching frequency to 1/k of the resonant frequency, so that the kth harmonic works in the resonant state.

(k=1,3,5,7...)。3) When the kth harmonic is working in a resonant state, if G _k ≤ 1/(k+2), the switching frequency is reduced to 1/(k+2) of the resonant frequency, so that the (k+2) harmonic The wave works in the resonant state, and the output power can be adjusted by adjusting the duty cycle of the driving pulse of the switching device. The reference duty cycle range when the kth harmonic works in the resonant state is

(k=1,3,5,7...).

In order to illustrate the output power adjustment process of the present invention, the flow chart of the power adjustment method of the full-bridge phase-shifting resonant inverter shown in Figure 4 is given, and the power adjustment method flow chart of the half-bridge resonant inverter is similar to Figure 4, It is no longer given here.

As shown in Figure 4, first determine the required output power of the inverter, and calculate the phase shift angle required when the fundamental wave of the output voltage of the resonant inverter works in a resonant state. If the fundamental wave amplitude at this phase shift angle is greater than k times The maximum value of the harmonic RMS value will form a phase-shift pulse signal controlled by the dead zone; if the fundamental wave amplitude under the phase-shift angle is less than or equal to the maximum value of the k-order harmonic RMS value, calculate and adjust the switching frequency and shift The phase angle forms a phase-shifting pulse signal controlled by the dead zone, and finally outputs it through the driving circuit.

Fig. 5 is the experimental waveform of the full-bridge phase-shifting resonant converter power regulation method in the present invention, inverter output voltage and output current waveform (voltage: 125V/grid, electric current: 34A) when the third harmonic phase shifts 1.9 ° /grid).

The above-mentioned reference phase shift angle and reference duty cycle may have a certain range of variation according to actual conditions.

Claims (5)

1. A method for adjusting the output power of a resonant converter, characterized in that the method for adjusting the output power is to reduce the switching frequency of the resonant inverter so that a certain value in the output voltage waveform of the resonant inverter The sub-harmonic works in the resonant state. By controlling the duty ratio of the output voltage of the resonant inverter to adjust the effective value of a certain harmonic of the output voltage of the resonant inverter, the adjustment of the output power is realized. 2. The method for adjusting the output power of the resonant converter according to claim 1, wherein the step of adjusting the output power is as follows: 1) First, according to the given output power of the resonant inverter, the per-unit value G _k of the fundamental wave and the effective value of each harmonic in the output voltage when the fundamental wave of the output voltage of the resonant inverter is in the resonance state is obtained, k = 1, 3, 5, 7..., the per unit value is based on the fundamental effective value of the output voltage waveform of the resonant inverter with a 50% duty cycle as a reference value, and the maximum value of G _k is 1/k; k is a positive odd number; 2) When G ₁ ≤ 1/k, k=1, 3, 5, 7..., find the maximum k value that meets the requirements, and control the switching frequency of the resonant inverter to 1/k of the resonant frequency, so that k The sub-harmonic works in the resonant state, and adjusts the effective value of the k-th harmonic in the output voltage of the resonant inverter by controlling the duty ratio of the output voltage of the resonant inverter to realize the adjustment of the output power; 3) When the kth harmonic is working in a resonant state, if G _k ≤ 1/(k+2), k=1, 3, 5, 7..., then the control switching frequency is reduced to 1/(k of the resonant frequency +2), make the (k+2) harmonic work in the resonant state, and adjust the output voltage of the resonant inverter by controlling the duty ratio of the output voltage of the resonant inverter (k+2). value to adjust the output power. 3. The resonant converter power regulation method according to claim 2, characterized in that, for a full-bridge phase-shifting resonant inverter, by adjusting the phase shift angle of the drive pulse of the converter diagonal switching device to adjust the output power; in the output power adjustment step 2), when the switching frequency is the resonant frequency, if the phase shift angle is greater than the reference phase shift angle (k=1,3,5,7...), then change the switching frequency to 1/k of the resonant frequency, so that the k-th harmonic works in the resonant state; in the output power adjustment step 3), k The range of the reference phase shift angle when the subharmonic works in the resonant state is

(k=1,3,5,7...). 4. The resonant converter power regulation method according to claim 2, characterized in that, for the half-bridge resonant inverter, the output power is regulated by adjusting the duty cycle of the drive pulse of the converter switching device, In the output power adjustment step 2), when the switching frequency is the resonant frequency, if the duty cycle is less than the reference duty cycle

(k=1,3,5,7...) then change the switching frequency to 1/k of the resonant frequency, so that the k-order harmonic works in the resonant state; in the above-mentioned output power adjustment step 3), the k-order The reference duty cycle range when the harmonics work in the resonant state is

(k=1,3,5,7...). 5. The resonant converter power regulation method according to claim 1, characterized in that, the resonant inverter has a dead time, and for a full-bridge phase-shifting resonant inverter, the dead time Equivalent to a certain phase shift angle, the reference phase shift angle of the kth harmonic should be subtracted from the dead time equivalent phase shift angle; for the half-bridge resonant inverter, the dead time is equivalent to the switch The duty ratio of the device driving pulse, the reference duty ratio of the kth harmonic should be subtracted from the equivalent duty ratio of the dead time.

Images