Single-phase voltage source dc-ac power converter and three-phase voltage source dc-ac power converter

Abstract

A single-phase voltage source DC-AC power converter includes (a) a single-phase voltage source DC-AC power converting circuit having a gate signal generator that detects a single-phase AC output current at an AC terminal and that generates gate signals for making values of a PWM command and the single-phase AC output current identical, and (b) target current producing means that produces the PWM command such that a DC component included in the single-phase AC output voltage at the AC terminal becomes zero.

What is claimed is: 
     
         1 . A single-phase voltage source DC-AC power converter comprising:
 a single-phase voltage source DC-AC power converting circuit that having a gate signal generator that detects a single-phase AC output current at an AC terminal and that generates gate signals for making values of a PWM command and the single-phase AC output current identical, and a single-phase voltage source DC-AC power converting unit converts power from a DC voltage source into single-phase AC power according to pulse width of the gate signals, and outputs the single-phase AC power from an AC terminal; and   target current producing means that includes a filter voltage command device and a voltage controller, the filter voltage command device generating a filter voltage command value that is a reference of the single-phase AC power output from the AC terminal, the single-phase AC output voltage at the AC terminal being input as an input signal to the voltage controller, the voltage controller including an integrator which integrates a difference between the filter voltage command value from the filter voltage command device and the single-phase AC output voltage at the AC terminal and specifies an internal equivalent impedance of the single-phase voltage source DC-AC power converting circuit, the target current producing means outputting the PWM command that is a current value such that a DC component included in the single-phase AC output voltage at the AC terminal becomes zero.   
     
     
         2 . The single-phase voltage source DC-AC power converter according to  claim 1 , further comprising an output current detecting circuit that detects the single-phase AC output current at the AC terminal to input the detected current value as an input signal to the target current producing means,
 wherein the target current producing means includes:   a filter current compensator that adds a current compensation value to the PWM command output from the voltage controller, the current compensation value being defined so as to compensate a current loss in a single-phase AC filter circuit of the single-phase voltage source DC-AC power converting circuit;   a PWM current deviation compensator that adds a current deviation compensation value to the PWM command output from the voltage controller, the current deviation compensation value being defined so as to compensate a current deviation of the single-phase AC output current from the single-phase voltage source DC-AC power converting circuit; and   a feedforward amplifier that amplifies the detected current value input from the output current detecting circuit with a predetermined gain, adds the detected current value to the PWM command output from the voltage controller, and compensates a fluctuation in single-phase AC output voltage caused by a change in single-phase AC output current at the AC terminal.   
     
     
         3 . The single-phase voltage source DC-AC power converter according to  claim 1 ,
 wherein the voltage controller includes an amplifier and the integrator, the amplifier and the integrator being connected in parallel, the difference between the filter voltage command value from the filter voltage command device and the single-phase AC output voltage at the AC terminal being input to the amplifier and the integrator, and   a transfer function is expressed as α(1+1/(T I ·S)), where α is a gain of the amplifier and T I  is an integration time constant of the integrator.   
     
     
         4 . The single-phase voltage source DC-AC power converter according to  claim 2 ,
 wherein the voltage controller includes an amplifier and the integrator, the amplifier and the integrator being connected in parallel, the difference between the filter voltage command value from the filter voltage command device and the single-phase AC output voltage at the AC terminal being input to the amplifier and the integrator, and   a transfer function is expressed as α(1+1/(T I ·S)), where α is a gain of the amplifier and T I  is an integration time constant of the integrator.   
     
     
         5 . The single-phase voltage source DC-AC power converter according to  claim 1 , wherein a transfer function of the integrator is expressed as a/(T I ·S), where T I  represents a time constant of the integrator which is determined by a resistance component Ri and an inductance component Li both of which constituting the internal equivalent impedance, and α represents a feedback gain. 
     
     
         6 . The single-phase voltage source DC-AC power converter according to  claim 2 , wherein a transfer function of the integrator is expressed as a/(T I ·S), where T I  represents a time constant of the integrator which is determined by a resistance component Ri and an inductance component Li both of which constituting the internal equivalent impedance, and α represents a feedback gain. 
     
     
         7 . The single-phase voltage source DC-AC power converter according to  claim 1 , wherein the voltage controller further includes:
 an adder that computes the difference between the filter voltage command value from the filter voltage command device and the single-phase AC output voltage at the AC terminal;   an amplifier which is connected in parallel to the integrator, and to which the difference is input from the adder similarly to the integrator; and   an adder that adds an output of the integrator and an output of the amplifier.   
     
     
         8 . A single-phase voltage source DC-AC power converting method comprising:
 detecting a single-phase AC output current at an AC terminal and generating gate signals for making values of a PWM command and the single-phase AC output current identical;   converting power from a DC voltage source into single-phase AC power according to pulse width of the gate signals;   generating a filter voltage command value that is a reference of the single-phase AC power output from the AC terminal;   inputting a difference between the filter voltage command value and the single-phase AC output voltage to an integrator that makes it possible to specify an internal equivalent impedance of a single-phase voltage source DC-AC power converting circuit configured to convert the power from the DC voltage source into single-phase AC power, and integrating the difference; and   outputting the PWM command that is a current value such that a DC component included in the single-phase AC output voltage at the AC terminal becomes zero.   
     
     
         9 . The single-phase voltage source DC-AC power converting method according to  claim 8 , further comprising:
 computing the difference between the filter voltage command value and the single-phase AC output voltage;   inputting the difference to both the integrator and an amplifier that is connected in parallel to the integrator;   amplifying the difference by the amplifier;   adding an output of the integrator and an output of the amplifier.