TWI449320B - Parallel utility power supply system with phase interleaved and parallel converters - Google Patents

Description

Mains parallel power supply system with phase-interleaved parallel converter

The invention relates to a commercial parallel power supply system with a phase-interleaved parallel converter, in particular to a phase-interleaved parallel converter method which shifts the pulse width modulation by an angle to offset current ripple, thereby reducing The current output of the inverter is chopped and effectively reduces the influence of excessive switching frequency on electromagnetic interference (EMI) caused by the entire power system.

According to the independent power supply system, it is mainly used in areas where the market power such as outlying islands and mountainous areas cannot be supplied or the demand for electricity is small. This system usually needs to install a battery, the system DC power supply to the load and charge the battery, and the battery is supplied to the load at night to achieve independent power supply.

The advantage of this system is independent power generation, which does not affect other systems; the disadvantage is that it requires continuous supply of large-capacity batteries, so the overall system takes up a lot of space and construction costs.

The mains parallel power supply system is a system that supplies power to the DC power supply and the mains supply. When the input power of the converter is greater than the load required, the system will feed the excess power into the mains, and the system must achieve the best parallel efficiency of the unit power. When the input power of the inverter is not enough to supply the load, The mains supply to provide insufficient power to the load.

The existing parallel power supply system for commercial power is divided into three forms, which are respectively based on the architecture form, the transformer isolation method and the device capacity. Among them: the mains parallel type system is divided according to the structure, which can be divided into single-stage and two-stage. Single-stage systems typically have higher conversion efficiencies than two-stage. Because it is a single-stage converter, in addition to having to maintain the basic functions of the converter, it must also perform DC charging and discharging and parallel control of the mains at the same time, so the single-stage control strategy will be much more complicated. The two-stage type is usually one level lower than the single-stage type, so the efficiency is usually lower than the single-stage type. The main function of the pre-stage of this architecture is to increase the output voltage and DC charge and discharge. The post-stage converter only needs to be responsible for the mains parallel function. The advantage of the two-stage single-stage is that the control strategy is simpler, the controller has a lower computational amount, and the lower-order controller is used to complete.

According to the transformer isolation form, the mains parallel system can be divided into a transformerless and transformer isolated design. The transformerless isolation type has a higher overall conversion efficiency and therefore a lower system cost because the loss of the primary transformer is less. The output of the transformer isolated type converter is isolated by a transformer. The low frequency transformer is bulky, heavy, and the system cost is relatively improved, but it can ensure the isolation and protect the safety of maintenance personnel.

If the mains parallel system is divided by the device capacity, it can be divided into a central-inverter, a multi-string-inverter and a modular inverter. Module-inverter). Large systems above 5 kW are called centralized converters, which have lower system cost but higher efficiency. The serial module application range is between 500W and 5kW, and the modular inverter system capacity is mostly below 500W. Because of its architecture, each module is equipped with individual converters, and the output terminal is directly connected with the mains. Also because more components and controllers have to be used at the same wattage, the cost is much higher than the centralized one.

In order to make the inverter parallel system more stable, many literatures have proposed ways to operate the inverter in parallel, including direct coupling of inductors, instantaneous current control, N+1 margin control, combined voltage control and current control, and concentration. Control method, master servant control method and decentralized logic control method.

Inductive direct coupling, when there is a circulating current in the voltage or phase difference across the inductor. The inductor can be used as a conductor, so that the converter will not be damaged due to excessive circulating current. The advantage is that it is more flexible and low in cost. The disadvantage is that there is a difference between the module converters, so the characteristics cannot be grasped.

When the instantaneous current control method operates on inverters of different capacities, there may be an overload or underload condition. Therefore, it is only suitable for parallel operation of converters of the same capacity. The N+1 margin control method uses one more inverter to be connected in parallel to the system to increase the stability of the system.

Combined with the voltage control and current control method, the voltage source is used as a voltage reference. All of the output voltages of the converters that are added in parallel operation follow the voltage source converter, and the current distribution part is completed by the load current distribution center, and the load current is equally divided to other inverters. Therefore, there is no phase difference. Since the current load distribution center needs to distribute the load current, the cost is high.

The centralized control method can be divided into two types: (1) direct centralized control method (2) indirect centralized control method; parallel control unit uniformly sends synchronous signals to the inverter, and the voltage phase is synchronized with the synchronous signal of the output frequency, so that each change The current is accurately distributed between the flow devices. The disadvantage is that if the centralized control system fails, the entire system will collapse.

As for the master-servant control method, it can overcome the shortcomings of the centralized control unit, and is automatically set by the switch or the software. One group of converters is used as the master module to generate the voltage adjustment signal for the shunt control signal correction to simultaneously adjust. Voltage and control shunt.

The main object of the present invention is to provide a commercial parallel power supply system with a phase-interleaved parallel converter, which can reduce the current ripple of the converter output and effectively reduce the switching frequency to cause electromagnetic interference (EMI) to the entire power system. ) the impact to provide good power quality output.

The main object of the present invention is achieved by the following technology: a commercial parallel power supply system with a phase-interleaved parallel converter, comprising a two-digit signal processor, two feedback circuit modules, two driving circuits, and two converters. And a second filter circuit; the digital signal processor obtains a current signal and a voltage signal that is fed back by the feedback circuit module, and uses the zero point detection circuit in the feedback circuit module as a voltage base in parallel with the commercial power, and Outputting a control signal that is modulated by the pulse width and staggered by an angle to the driving circuit to achieve the synchronous output of the two converters by means of an external interrupt, and to make the two commutation The output current waveform of the device is completely shifted by 180 degrees. When the two converters are connected in parallel, the part of the current chopping will be cancelled to achieve the purpose of reducing the current chopping of the converter output.

The commercial parallel power supply system with phase-interleaved parallel converter of the present invention has the following advantages:

(1) The staggered phase shift mode is realized, and the inverter is operated synchronously to parallel the mains. The synchronous signal is sent out by its digital signal processor to solve the problem of inverter output voltage and phase synchronization.

(2) The voltage feedback circuit and the current feedback circuit are used in the feedback circuit module, which can effectively and accurately control the output power.

(3) The cost of the filter capacitor and the filter inductor is greatly reduced, and the switching frequency is reduced to the electromagnetic pollution of the power system.

(4) The output power of the parallel module is used to achieve the burden of the distributed power system, reducing the influence of harmonics on the transformer, and reducing the current ripple of the output when the converter is connected in parallel.

(1)‧‧‧Digital Signal Processor

(2)‧‧‧Responsible circuit module

(21)‧‧‧PLL lock-in circuit

(22)‧‧‧Voltage feedback circuit

(23) ‧‧‧ Current feedback circuit

(3) ‧‧‧Drive Circuit

(4) ‧‧‧ Full Bridge Inverter

(5) ‧‧‧Filter circuit

(6) ‧ ‧ load

(7) ‧‧‧Power

The first figure: the overall hardware architecture of the present invention; the second picture: the phase sequence diagram of the phase interleaving and the power crystal switch; the third picture: the overall architecture diagram of the system; the fourth picture: the output system of the converter is connected to the power system; Figure: Converter output current is reduced to 0.4A; Figure 6: Single converter output current 1A; seventh picture: single converter output current 1.5A; eighth picture: dual module converter synchronous output preliminary parallel power network current output waveform; ninth: double Module converter synchronous parallel power network current output 0.5A waveform; 10th picture: dual module converter synchronous parallel power network current output 3A waveform; 11th: dual module converter interleaved phase shift preliminary Parallel power network current output waveform; Figure 12: Dual-module converter interleaved phase-shift parallel power network total current output 0.5A waveform; Figure 13: Dual-module converter interleaved phase-shift parallel power network Total current output 3A waveform; Figure 14: Single converter connected to power system current waveform; Figure 15: Module 1 and module 2 synchronous output converter connected to power system current waveform; Figure 16: Mode The group one and the module two interleaved converters are connected to the output current waveform of the power system.

For a more complete and clear disclosure of the technical content, the purpose of the invention and the effects thereof achieved by the present invention, it will be explained in detail below, and Please refer to the illustrated figure and figure number: please refer to the first figure. The mains parallel power supply system with phase-interleaved parallel converter of the present invention includes: two-digit signal processor (1), two times The circuit module (2), the two driving circuit (3), the two full-bridge converter (4) and the two filtering circuit (5); wherein: the output terminals of the two-digit signal processor (1) are respectively connected to a driving The circuit (3), the two driving circuits (3) are respectively connected to a full bridge converter (4), and the output ends of the two full bridge converters (4) are respectively connected to a filter circuit (5) Then connected to the load (6) and the mains (7), and the voltage signal, current signal and phase signal of the mains (7) are fed back to the second feedback circuit module (2), and the second feedback circuit module ( 2) Each includes a PLL phase lock circuit (21), a voltage feedback circuit (22), a current feedback circuit (23), and a PLL phase lock circuit (21) of the second feedback circuit module (2), voltage back The circuit (22) and the current feedback circuit (23) are respectively connected to the two-digit signal processor (1); and the timing counter of the digital signal processor (1) is not shown in the figure. Connected to it The trigger terminal is connected to the negative edge trigger end of the other digital signal processor (1), thereby enabling the two-digit signal processor (1) to achieve synchronous operation; wherein the digital signal processing The device (1) uses the TMS302F2812.

The digital signal processor (1) obtains the voltage feedback circuit (22) and the current feedback circuit (23) feedback control of the feedback circuit module (2) After compensating the current signal and voltage signal, before the full-bridge converter (4) is connected in parallel with the mains (7), it must be determined whether the output of the full-bridge inverter (4) is in phase with the mains (7). The output voltage of the bridge converter (4) runs simultaneously with the mains (7). As the reference value of the output current, the timing is put in, so that the mains (7) and the current are in phase, so that the current and voltage are in real power output; therefore, the PLL is locked. The circuit (21) detects the mains (7) zero crossing point and sends the signal to the digital signal processor (1), so that the digital signal processor (1) performs the feedback based on the current signal, the voltage signal and the zero crossing point. The processing is processed, and the output pulse width is shifted by an angle of the control signal to the driving circuit (3) to drive the two full-bridge converters (4) in an interleaved manner, so that the two full-bridge converters (4) The output current waveform is completely shifted by 180 degrees, and then the high-frequency harmonic component of the output current of the full-bridge converter (4) is filtered out by the filter circuit (5). When the two full-bridge converters (4) are connected in parallel, the current 涟The part of the wave will be offset to achieve the purpose of reducing the current ripple of the output of the full-bridge inverter (4) [please refer to the second Figure].

<Example>

The feasibility of the commercial parallel system of the present invention will be verified by experimental waveforms below. Among them, the overall architecture of the verification system is shown in the third figure. The system is divided into a single module converter, parallel connection of commercial power supply, and dual-module inverter synchronous parallel mains parallel output, dual-module inverter phase-interleaved synchronous parallel mains parallel output. .

[Single module inverter commercial parallel output]

When the system is connected in parallel with a single module, in order to make the current and voltage in phase, as shown in the fourth figure, the system starts to be connected in parallel with the mains. Because the mains itself has harmonic component waveform distortion, the voltage phase is different, resulting in the output current falling behind the voltage phase. . The inverter output current command zero current is approximately 0.4A, as shown in Figure 5. The output is corrected by the proportional control current; the current command is 1.0A, as shown in the sixth figure. The current command is 1.5A, as shown in the seventh figure.

[Double Module Inverter Synchronous Parallel Mains Parallel Output]

This system uses two modular inverters in parallel with each other and outputs synchronous inverters. Before paralleling the mains, pay attention to the same frequency and phase of the output voltage of the two converters and the voltage of the mains system, and conduct current control to ensure the output. The current approximates the sine wave fed into the city grid.

Since the test circuit is connected in parallel with the mains, the output voltage of the inverter has been locked to 110V by the mains voltage. The output current of the inverter is controlled by the current to follow the mains phase. The output AC current and voltage are in phase and the actual power can be output to the mains system. .

The eighth figure shows the dual-module converter synchronous initial parallel power network current output waveform, TPV1 is the mains waveform. TPC1 is an inductor-inductor current. TPC2 is the inverter two inductor current. TPC3 is connected in parallel to each other and finally output to the mains. Since the current ripple is relatively increased, it can be observed from the figure that the mains waveform is affected.

The ninth figure shows the current output waveform of the synchronous parallel power network of the dual module converter, and TPV1 is the mains waveform. TPC1 is 0.3A for the inverter Current command. TPC2 gives the inverter 2 a 0.2A current command. TPC3 is connected in parallel with each other and finally outputs 0.5A to the main output of the mains waveform.

The tenth figure shows the current output waveform of the synchronous parallel power network of the dual module converter, and TPV1 is the mains waveform. TPC1 is a 1.5A current command for the inverter. The TPC2 is a 1.5A current command for the inverter 2. TPC3 is connected in parallel with each other and finally outputs to the main output of the mains waveform 3A.

[Double module inverter phase interleaved synchronous parallel mains parallel output]

The eleventh figure shows the preliminary current output waveform of the two-module inverter staggered phase-displacement parallel power network, and TPV1 is the mains waveform. TPC1 is an inverter-inductor current waveform. TPC2 is the inverter two inductor current. TPC3 is connected in parallel to each other and finally output to the mains waveform. The influence of the harmonics of the converter on the mains terminal is also significantly reduced, and the TPV1 waveform observation in the figure is obviously unaffected.

The twelfth figure shows the current output waveform of the inter-parallel phase-displacement parallel power network of the dual-module converter, and TPV1 is the mains waveform. TPC1 is a current command of 0.3A for the inverter. TPC2 gives the inverter 2 a 0.2A current command. TPC3 is connected in parallel with each other and finally outputs 0.5A to the main output of the mains waveform.

The thirteenth picture shows the current output waveform of the inter-parallel phase-shift parallel power network of the dual-module converter, and TPV1 is the mains waveform. TPC1 is a 1.5A current command for the inverter. The TPC2 is a 1.5A current command for the inverter 2. TPC3 is connected in parallel with each other and finally outputs to the main output of the mains waveform 3A. The influence of the harmonics of the converter on the mains terminal is also significantly reduced, which is obvious from the TPV1 waveform in the figure. Not affected.

Current chopping comparison is then performed for the above three states. Figure 14 shows the current waveform of a single converter connected to the power system. TPC1 is the output current of a single converter, and TPC3 is the output of the mains. The fifteenth figure is the external interrupt synchronous output connection power system current waveform, TPC1 is the module one converter one output inductor current, TPC2 is the module two converter two output inductor current, TPC3 is connected in parallel to the mains 3.0A current Waveform. The sixteenth figure is the external interrupt interleaved phase-shift output connected to the power system current waveform, TPC1 is the module-converter-output inductor current, TPC2 is the module two converter two output inductor current, TPC3 is connected in parallel to the mains 3.0A current waveform.

Through the experimental results of the above-mentioned commercial parallel mode, it can be seen that the inverter through current control strategy is connected in parallel with the staggered phase shift converter. The staggered angle between the modules causes the output currents to cancel each other, and the same capacity output is better. The power quality output, and can reduce the harmonic distortion current of the sine wave into the mains.

The above is only a part of the embodiments of the present invention, and is not intended to limit the present invention. It is intended to be included in the scope of the present invention.

In summary, this case is not only innovative in terms of space type, but also can enhance the above-mentioned multiple functions compared with conventional articles. It should fully comply with the statutory invention patent requirements of novelty and progressiveness, and apply for it according to law. Approved this invention patent application, in order to invent invention, to the sense of virtue.

(1)‧‧‧Digital Signal Processor

(2)‧‧‧Responsible circuit module

(21)‧‧‧PLL lock-in circuit

(22)‧‧‧Voltage feedback circuit

(23) ‧‧‧ Current feedback circuit

(3) ‧‧‧Drive Circuit

(4) ‧‧‧ Full Bridge Inverter

(5) ‧‧‧Filter circuit

(6) ‧ ‧ load

(7) ‧‧‧Power

Claims (1)

The utility model relates to a commercial parallel power supply system with a phase-interleaved parallel converter, which comprises: a two-digit signal processor, wherein the output ends of the two-digit signal processor are respectively connected to a driving circuit; and the timing counter of the digital signal processor thereof is positive The edge output is connected to its own trigger terminal, and the negative edge output terminal is connected to the negative edge trigger terminal of another digital signal processor, thereby enabling the two-digit signal processor to achieve synchronous operation; the second drive circuit, the second The drive circuits are respectively connected to a full bridge converter; the two full bridge converters, the output ends of the two full bridge converters are respectively connected to a filter circuit and then connected to the load and the mains, and the voltage of the mains The signal, the current signal and the phase signal are fed back to the second feedback circuit module; the second feedback circuit module includes a PLL phase lock circuit, a voltage feedback circuit, and a current feedback circuit, and The PLL phase lock circuit, the voltage feedback circuit and the current feedback circuit of the second feedback circuit module are respectively connected with the two-digit signal processor; and the second filter circuit is used for filtering the full bridge commutation The high-frequency harmonic component of the output current; the digital signal processor obtains the voltage feedback circuit of the feedback circuit module and the current feedback circuit to feedback the current signal and the voltage signal after the compensation, due to the full-bridge converter and Before the mains supply is connected in parallel, the full bridge converter must be determined. Whether the output is in phase with the mains, the output voltage of the full-bridge inverter can be operated simultaneously with the mains. As the reference value of the output current, the timing is put into the phase, so that the mains and the current are in phase, so that the current and the voltage are in real power output; therefore, the PLL lock is utilized. The phase circuit detects the zero crossing point of the mains and sends the signal to the digital signal processor, so that the digital signal processor performs arithmetic processing according to the feedback current signal, the voltage signal and the zero crossing point, and the output pulse width modulation is staggered. An angle control signal to the driving circuit enables the two full-bridge converters to be driven in an interleaved manner, so that the output current waveform of the two full-bridge converters is completely shifted by 180 degrees, and then the full-bridge converter output is filtered by the filter circuit. The high-frequency harmonic component of the current, when the two full-bridge converters are connected in parallel, the part of the current chopping will be cancelled, and the purpose of reducing the current chopping of the output of the full-bridge converter is achieved.