CN104917417B - ISOP inverter system interconnection-free voltage-sharing control method - Google Patents

Abstract

The invention discloses an ISOP inverter system non-interconnected voltage equalization control method, comprising the following steps: Step 1) is based on the droop of the output reference voltage amplitude V _i and the reactive power Q _i of each inverter module The characteristic curve calculates the output reference voltage amplitude V _i , step 2) is to calculate the output reference voltage frequency f _i according to the upturned characteristic curve between the frequency f _i of each inverter module and the input voltage V _ini , and step 3) is to obtain the output Reference voltage V _refi , step 4) is to obtain the output reference current I _refi , step 5) is to subtract the output reference current I _refi from the filter inductor current I _Lfi , and generate a PWM wave through the PI regulator and the output voltage regulator to drive Switching device of the inverter module. The invention realizes beneficial effects such as no interconnection among modules, high modularization degree, strong expandability and the like.

Description

An ISOP inverter system without interconnection voltage equalization control method

technical field

The invention relates to an ISOP inverter system non-interconnection voltage equalization control method, in particular to an ISOP inverter system non-interconnection voltage equalization control method.

Background technique

With the rapid development of power electronic technology, power electronic devices are developing in the direction of high frequency, modularization and integration. Multiple standardized converter modules are combined in series and parallel to form various power electronic devices that meet different needs. A research hotspot of electronic system integration technology. Input-Series Output-parallel (ISOP) combined converter, as a type of multi-module series-parallel combined converter, is very suitable for high-voltage input, low-voltage and high-current output applications.

Inverter power supplies in industrial applications often have high input voltages and high output power, so the choice of switching devices is limited. Therefore, the input terminals of multiple inverter modules can be connected in series and the output terminals in parallel to form an ISOP combination form, so that the input voltage and output current of each inverter module will be reduced to 1/N of the original (N is the series module number), thereby reducing the voltage and current stress of the switching devices required for each module and improving the performance of the overall system.

For the ISOP inverter combination system, the key issue is to ensure that each module is equalized in voltage on the input side and current on the output side. At present, many scholars have conducted a lot of research on the non-interconnection control technology of the IPOP converter parallel combination system. The research shows that the output active power can be controlled by changing the frequency of the inverter output voltage, and by changing the frequency of the inverter output voltage. The amplitude is used to control the output reactive power, which is also the theoretical basis for the frequency voltage amplitude droop method to be used for the non-interconnection control of the inverter parallel system. However, there are relatively few studies on the non-interconnected voltage equalization control of the ISOP inverter combination system at present. The patent application number is CN201010567190.7, which proposes a "stable current control method for input series output parallel type high frequency inverter module". This method controls the input series output parallel inverter system of N modules. Strategically, the output current cross-feedback method is used to realize the input voltage equalization and power sharing among the modules. However, in this control method, there are cross-connections between the modules, the system modularity is not high, and the scalability is limited.

Contents of the invention

Purpose of the invention: The purpose of the invention is to provide a non-interconnected voltage equalization control method for ISOP inverter systems based on the frequency upturn characteristic and the voltage amplitude droop characteristic without interconnection between modules, high degree of modularization, and strong scalability.

Technical scheme: in order to achieve this goal, the present invention adopts following technical scheme:

An ISOP inverter system non-interconnected voltage equalization control method according to the present invention comprises the following steps:

Step 1): Sampling the filter inductor current I _Lfi and output voltage V _oi of each inverter module, calculating the reactive power Q _i output by each inverter module through the power calculation unit, and then according to each inverter Calculate the output reference voltage amplitude V _i from the droop characteristic curve of the output reference voltage amplitude V _i and the reactive power Q _i of the converter module;

Step 2): Sampling the input voltage V _ini of each inverter module, and then calculating the output reference voltage frequency f _i according to the upturned characteristic curve between the frequency f _i of each inverter module and the input voltage V _ini ;

Step 3): Synthesizing the output reference voltage amplitude V _i obtained in step 1) and the output reference voltage frequency f _i obtained in step 2), to obtain the output reference voltage V _refi ;

Step 4): Subtract the output reference voltage V _refi obtained in step 3) from the output voltage V _oi obtained in step 1), and obtain the output reference current I _refi through the PI regulator;

Step 5): Subtract the output reference current I _refi obtained in step 4) from the filter inductor current I _Lfi obtained in step 1), and generate a PWM wave through the PI regulator and the output voltage regulator to drive the switch of the inverter module device;

i=1, 2, . . . , N in the above steps, where N≥1.

Further, the expression of the droop characteristic curve of the output reference voltage amplitude V _i and the reactive power Q _i of each inverter module in the step 1) is:

V _i ＝V' _0i -K _i Q _i (1)

Wherein, K _i is the voltage amplitude droop coefficient, V' _0i is the no-load voltage amplitude, i=1,2,...,N, N≥1.

Further, the expression of the upturned characteristic curve between the frequency fi and the input voltage _{V ini} of each inverter module in the step 2) is:

f _i ＝f' _0i +M _i V _ini (2)

Wherein, M _i is the frequency upwarping coefficient, f' _0i is the no-load frequency, i=1,2,...,N, N≥1.

Further, the step 3) synthesizes the output reference voltage amplitude V _i and the output reference voltage frequency f _i according to the following formula to obtain the output reference voltage V _refi :

V _refi ＝V _i sin(2πf _i ·t+α _i ) (3)

Wherein, α _i is the initial phase angle, t is the time variable, i=1,2,...,N, N≥1.

Further, the inverter module includes a two-stage structure, wherein the front stage is a DC converter, and the latter stage is an inverter.

Further, the inverter module is a single-stage high-frequency inverter.

Beneficial effects: In the present invention, each inverter module only detects its own input and output information, which avoids interconnection and communication in control, and each module only inputs and outputs information according to itself, without any mutual information exchange conditions In this way, completely independent and equivalent control is realized, and the modular design of the ISOP inverter combination system is truly realized, which has high system reliability; in addition, the present invention has a high degree of modularization and strong scalability.

Description of drawings

Fig. 1 is the block diagram of the system that the inventive method is aimed at;

Figure 2 is a schematic diagram of an ISOP inverter system with two modules;

Figure 3 is the frequency upturning characteristic curve of the two modules;

Fig. 4 is the voltage amplitude droop characteristic curve of two modules;

Figure 5 is the system input voltage waveform of the ISOP inverter system composed of two modules;

Figure 6 shows the respective input voltage waveforms of the two modules of the ISOP inverter system when the system input voltage jumps;

Figure 7 shows the respective output active power waveforms of the two modules of the ISOP inverter system when the system input voltage jumps;

Fig. 8 shows the respective output reactive power waveforms of the two modules of the ISOP inverter system when the system input voltage jumps.

detailed description

The technical solution of the present invention will be further introduced below in combination with specific embodiments.

The system aimed at by the method of the present invention is shown in Figure 1, which includes an input series output parallel circuit composed of at least two inverter modules, each inverter module has its own independent and identical control circuit, and there is no connection between each control circuit. Any exchange of information, i.e. no interconnection.

The inventive method comprises the steps:

Step 1): Sampling the filter inductor current I _Lfi and output voltage V _oi of each inverter module, calculating the reactive power Q _i output by each inverter module through the power calculation unit, and then according to each inverter Calculate the output reference voltage amplitude V _i from the droop characteristic curve of the output reference voltage amplitude V _i and the reactive power Q _i of the converter module;

Step 2): Sampling the input voltage V _ini of each inverter module, and then calculating the output reference voltage frequency f _i according to the upturned characteristic curve between the frequency f _i of each inverter module and the input voltage V _ini ;

Step 3): Synthesizing the output reference voltage amplitude V _i obtained in step 1) and the output reference voltage frequency f _i obtained in step 2), to obtain the output reference voltage V _refi ;

Step 4): Subtract the output reference voltage V _refi obtained in step 3) from the output voltage V _oi obtained in step 1), and obtain the output reference current I _refi through the PI regulator;

Step 5): Subtract the output reference current I _refi obtained in step 4) from the filter inductor current I _Lfi obtained in step 1), and generate a PWM wave through the PI regulator and the output voltage regulator to drive the switch of the inverter module device;

i=1, 2, . . . , N in the above steps, where N≥1.

Wherein, the expression of the droop characteristic curve of the output reference voltage amplitude V _i and the reactive power Q _i of each inverter module in step 1) is:

V _i ＝V' _0i -K _i Q _i (1)

Wherein, K _i is the voltage amplitude droop coefficient, V' _0i is the no-load voltage amplitude, i=1,2,...,N, N≥1.

The expression of the upturned characteristic curve between frequency f _i and input voltage V _ini of each inverter module in step 2) is:

f _i ＝f' _0i +M _i V _ini (2)

Wherein, M _i is the frequency upwarping coefficient, f' _0i is the no-load frequency, i=1,2,...,N, N≥1.

Step 3) Combining the output reference voltage amplitude V _i and the output reference voltage frequency f _i according to the following formula to obtain the output reference voltage V _refi :

V _refi ＝V _i sin(2πf _i ·t+α _i ) (3)

Wherein, α _i is the initial phase angle, t is the time variable, i=1,2,...,N, N≥1.

In addition, the inverter module may include a two-stage structure, that is, the former stage is a DC converter, and the latter stage is an inverter. The inverter module can also be a single-stage high-frequency inverter.

The technical solution of the present invention is described below with a specific embodiment.

In order to simplify the analysis of the ISOP inverter system, the ISOP inverter system composed of two inverter modules is introduced here, as shown in Figure 2. The two inverter modules have the same frequency upturn characteristic and voltage amplitude droop characteristic, as shown in Fig. 3 and Fig. 4 . Assuming that the ISOP inverter system works stably and the output voltage remains constant, the input voltage of the two inverter modules is disturbed, for example, V _in1 rises and V _in2 drops, that is, V _in1 >V _in /2>V _in2 . For the 1# inverter module, when V _in1 rises, due to the frequency upturn characteristic, the frequency f _oA of its given reference voltage will be higher than the voltage frequency f _oO detected during steady-state operation, and through the PI regulator After connecting with the PWM driver, the output frequency of the 1# inverter module will increase (that is, the phase is advanced), that is, the 1# inverter module will output more active power, and the power conservation will make the 1# inverter module I _in1 increases, I _cd1 decreases, and its input voltage V _in1 decreases; similarly, for the 2# inverter module, when V _in2 decreases, due to the frequency upturn characteristic, the frequency of its given reference voltage f _oB will be lower than the voltage frequency f _oO detected during steady-state operation, after passing through the PI regulator and PWM driver, the output frequency of the 2# inverter module will decrease (that is, the phase is advanced), that is, the 2# inverter module It will output less active power. According to power conservation, the I _in2 of the 2# inverter module decreases, and the I _cd2 increases, so that its input voltage V _in2 increases, and finally the system returns to the steady state.

In fact, it can be seen from the principle of power conservation that since the input of each inverter module is connected in series, the input voltage of the inverter module is controlled, that is, the output active power balance of each inverter module is controlled. Since the input voltage equalization of each inverter module can only make the output active power balance, but has no constraint on the output reactive power, the output reactive power balance still adopts the traditional voltage amplitude droop characteristic.

In the embodiment, an ISOP inverter simulation system composed of two inverter modules is built. The main circuit of each inverter module has a two-stage structure, that is, the front stage is a DC converter, which is used to realize electrical isolation and voltage conversion. function, its output stable voltage is the input of the subsequent inverter. Figure 5 describes the system input voltage waveform of the ISOP inverter system composed of two modules. When t = 1s, the system input voltage jumps from 1000V to 1200V. Figure 6 describes the respective input voltage waveforms of the two modules when the system input voltage jumps, where V _in1 is the input voltage of the 1# module, and V _in2 is the input voltage of the 2# module. It can be seen from the figure that in the system The system remains stable before and after a jump in the input voltage, and both modules share the input voltage of the system well. Figure 7 describes the respective output active power waveforms of the two modules when the system input voltage jumps. It can be seen from the figure that the output active power of the two modules is the same before and after the system input voltage jumps. Figure 8 describes the respective output reactive power waveforms of the two modules when the system input voltage jumps. It can be seen from the figure that the output reactive power of the two modules is the same before and after the system input voltage jumps. In a word, it can be seen from Fig. 5 to Fig. 8 that before and after the system input voltage jumps, the ISOP inverter system can better realize the equalization of the input voltage and output power of each module. It can be seen that the control strategy proposed by the present invention can make the system stable and have high reliability.

Claims (6)

1. a kind of ISOP inverter systems are without interconnection pressure equalizing control method, it is characterised in that：Including the steps：

Step 1)：Filter inductance electric current I to each inverter module_LfiWith output voltage V_oiSampled, by power calculation Unit calculates the reactive power Q of each inverter module output_i, the then output reference voltage width according to each inverter module Value V_iWith reactive power Q_iDroop characteristic calculate output reference voltage amplitude V_i；

Step 2)：Input voltage V to each inverter module_iniSampled, then the output according to each inverter module Reference voltage frequency f_iWith input voltage V_iniBending upwards curve calculate output reference voltage frequency f_i；

Step 3)：By step 1) output reference voltage amplitude V that obtains_iWith step 2) output reference voltage frequency f that obtains_iEnter Row synthesis, obtains output reference voltage V_refi；

Step 4)：By step 3) the output reference voltage V that obtains_refiWith step 1) the output voltage V that obtains_oiSubtract each other, through PI Actuator obtains exporting reference current I_refi；

Step 5)：By step 4) the output reference current I that obtains_refiWith step 1) the filter inductance electric current I that obtains_LfiSubtract each other, lead to Cross pi regulator and PWM generation module produces PWM ripples, drive the switching device of inverter module；

More than i=1 in each step, 2 ..., N, N >=1.

2. ISOP inverter systems according to claim 1 are without interconnection pressure equalizing control method, it is characterised in that：The step 1) output reference voltage amplitude V of each inverter module in_iWith reactive power Q_iThe expression formula of droop characteristic be：

V_i=V'_0i-K_iQ_i (1)

Wherein, K_iFor the sagging coefficient of voltage magnitude, V'_0iFor floating voltage amplitude, i=1,2 ..., N, N >=1.

3. ISOP inverter systems according to claim 1 are without interconnection pressure equalizing control method, it is characterised in that：The step 2) output reference voltage frequency f of each inverter module in_iWith input voltage V_iniBending upwards curve expression formula For：

f_i=f'_0i+M_iV_ini (2)

Wherein, M_iCoefficient, f' are upwarped for frequency_0iFor idling frequency, i=1,2 ..., N, N >=1.

4. ISOP inverter systems according to claim 1 are without interconnection pressure equalizing control method, it is characterised in that：The step 3) output reference voltage amplitude V is carried out according to formula below_iWith output reference voltage frequency f_iSynthesis, obtain output reference Voltage V_refi：

V_refi=V_isin(2πf_i·t+α_i) (3)

Wherein, α_iFor initial phase angle, t is time variable, i=1,2 ..., N, N >=1.

5. ISOP inverter systems according to claim 1 are without interconnection pressure equalizing control method, it is characterised in that：The inversion Device module includes two-layer configuration, wherein, prime is DC converter, and rear class is inverter.

6. ISOP inverter systems according to claim 1 are without interconnection pressure equalizing control method, it is characterised in that：The inversion Device module is single stage type high-frequency chain inverter.